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Sample records for main transport mechanism

  1. MEGARA main optics opto-mechanics

    Science.gov (United States)

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

    2014-08-01

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

  2. Nucleocytoplasmic transport: factors and mechanisms.

    Science.gov (United States)

    Simos, G; Hurt, E C

    1995-08-01

    In the past two years, our knowledge concerning the mechanisms of nucleocytoplasmic transport through the nuclear pore complex (NPC) has considerably expanded. The application of in vitro systems that reconstitute nuclear protein import has allowed the identification of cytosolic factors that are required for the import process. Microinjection into Xenopus oocytes and yeast genetic systems have provided interesting candidates for RNA export mediators. Functional and structural analysis of nucleoporins has demonstrated the involvement of NPC components in the transport process. Finally, new concepts have emerged such as the integration of the mechanisms of the nuclear protein import and RNA export reactions and the assembly of the transport machinery at specialised domains of the NPC. PMID:7543863

  3. Membranes, mechanics, and intracellular transport

    Science.gov (United States)

    Parthasarathy, Raghuveer

    2012-10-01

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

  4. Dynamic analysis of the mechanical systems vibrating transversally in transportation

    OpenAIRE

    Buchacz, A.; Z?o??kiewski, S.

    2007-01-01

    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...

  5. Mechanical oscillation measurement of cERL main cavity

    International Nuclear Information System (INIS)

    Compact ERL(cERL) has been constructed from 2012 to 2013. The main linac of cERL has two superconducting cavities, for which high power test at low temperature were carried out in December 2012. In general, the RF resonant frequency of accelerating cavity is determined by the geometrical shape. Q value of superconducting cavity is so high that the instability of RF operation could be happened when mechanical oscillation make superconducting cavity deform. Mechanical oscillation mode of superconducting cavity was investigated in the term of the cERL construction in 2012. (author)

  6. The Equivalence Postulate of Quantum Mechanics: Main Theorems

    CERN Document Server

    Faraggi, Alon E

    2009-01-01

    We consider the two main theorems in the derivation of the Quantum Hamilton--Jacobi Equation from the Equivalence Postulate (EP) of quantum mechanics. The first one concerns a basic cocycle condition, which holds in any dimension with Euclidean or Minkowski metrics and implies a global conformal symmetry underlying the Quantum Hamilton--Jacobi Equation. In one dimension such a condition fixes the Schwarzian equation. The second theorem concerns energy quantization which follows rigorously from consistency of the equivalence postulate.

  7. The Equivalence Postulate of Quantum Mechanics: Main Theorems

    OpenAIRE

    Faraggi, Alon E.; Matone, Marco

    2009-01-01

    We consider the two main theorems in the derivation of the Quantum Hamilton--Jacobi Equation from the Equivalence Postulate (EP) of quantum mechanics. The first one concerns a basic cocycle condition, which holds in any dimension with Euclidean or Minkowski metrics and implies a global conformal symmetry underlying the Quantum Hamilton--Jacobi Equation. In one dimension such a condition fixes the Schwarzian equation. The second theorem concerns energy quantization which foll...

  8. Common folds and transport mechanisms of secondary active transporters.

    Science.gov (United States)

    Shi, Yigong

    2013-01-01

    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. PMID:23654302

  9. Investigation into mechanical properties of bone and its main constituents

    Science.gov (United States)

    Evdokimenko, Ekaterina

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

  10. Main academic institutions conducting research in the public transport area

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-12-01

    The international exchange of knowledge is becoming increasingly important for all activities. Within Europe, the need for simple reviews of institutions within one and the same subject area has become more tangible since the European Union started its public transport research program. The survey has been carried out in two stages. First a questionnaire was sent to those institutions, public transport authorities, public transport associations and individuals within the subject area that were known to the Department. In this questionnaire we asked for the names and addresses of institutions at colleges and universities where significant research on public transport is carried out. In a second stage, a list was compiled of the 48 institutions that were named in the results of the first questionnaire. This list was sent to these institutions with the request for a brief presentation of their research within the public transport sector and information on any institution they felt were missing in the list. We found further interesting institutions on the Internet. The final list contains more than 60 institutions outside the Nordic area. Within the Nordic countries we have exclusively followed our own address list of institutions with long-term research work within the subject area

  11. Mechanisms of intracellular protein transport

    Science.gov (United States)

    Rothman, James E.

    1994-11-01

    Recent advances have uncovered the general protein apparatus used by all eukaryotes for intracellular transport, including secretion and endocytosis, and for triggered exocytosis of hormones and neurotransmitters. Membranes are shaped into vesicles by cytoplasmic coats which then dissociate upon GTP hydrolysis. Both vesicles and their acceptor membranes carry targeting proteins which interact specifically to initiate docking. A general apparatus then assembles at the docking site and fuses the vesicle with its target.

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

    CERN Document Server

    Ludwig, H G; Hauschildt, P H

    2006-01-01

    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...

  13. Molecular Mechanism of Biological Proton Transport

    Energy Technology Data Exchange (ETDEWEB)

    Pomes, R.

    1998-09-01

    Proton transport across lipid membranes is a fundamental aspect of biological energy transduction (metabolism). This function is mediated by a Grotthuss mechanism involving proton hopping along hydrogen-bonded networks embedded in membrane-spanning proteins. Using molecular simulations, the authors have explored the structural, dynamic, and thermodynamic properties giving rise to long-range proton translocation in hydrogen-bonded networks involving water molecules, or water wires, which are emerging as ubiquitous H{sup +}-transport devices in biological systems.

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

    International Nuclear Information System (INIS)

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

  15. Mechanism for alternating access in neurotransmitter transporters

    OpenAIRE

    Forrest, Lucy R.; Zhang, Yuan-wei; Jacobs, Miriam T.; Gesmonde, Joan; Xie, Li; Honig, Barry H.; Rudnick, Gary

    2008-01-01

    Crystal structures of LeuT, a bacterial homologue of mammalian neurotransmitter transporters, show a molecule of bound substrate that is essentially exposed to the extracellular space but occluded from the cytoplasm. Thus, there must exist an alternate conformation for LeuT in which the substrate is accessible to the cytoplasm and a corresponding mechanism that switches accessibility from one side of the membrane to the other. Here, we identify the cytoplasmic accessibility pathway of the alt...

  16. Invasive home mechanical ventilation, mainly focused on neuromuscular disorders

    Directory of Open Access Journals (Sweden)

    Börger, Sandra

    2010-01-01

    Full Text Available Introduction and background: Invasive home mechanical ventilation is used for patients with chronic respiratory insufficiency. This elaborate and technology-dependent ventilation is carried out via an artificial airway (tracheal cannula to the trachea. Exact numbers about the incidence of home mechanical ventilation are not available. Patients with neuromuscular diseases represent a large portion of it. Research questions: Specific research questions are formulated and answered concerning the dimensions of medicine/nursing, economics, social, ethical and legal aspects. Beyond the technical aspect of the invasive home, mechanical ventilation, medical questions also deal with the patient’s symptoms and clinical signs as well as the frequency of complications. Economic questions pertain to the composition of costs and the differences to other ways of homecare concerning costs and quality of care. Questions regarding social aspects consider the health-related quality of life of patients and caregivers. Additionally, the ethical aspects connected to the decision of home mechanical ventilation are viewed. Finally, legal aspects of financing invasive home mechanical ventilation are discussed. Methods: Based on a systematic literature search in 2008 in a total of 31 relevant databases current literature is viewed and selected by means of fixed criteria. Randomized controlled studies, systematic reviews and HTA reports (health technology assessment, clinical studies with patient numbers above ten, health-economic evaluations, primary studies with particular cost analyses and quality-of-life studies related to the research questions are included in the analysis. Results and discussion: Invasive mechanical ventilation may improve symptoms of hypoventilation, as the analysis of the literature shows. An increase in life expectancy is likely, but for ethical reasons it is not confirmed by premium-quality studies. Complications (e. g. pneumonia are rare. Mobile home ventilators are available for the implementation of the ventilation. Their technical performance however, differs regrettably. Studies comparing the economic aspects of ventilation in a hospital to outpatient ventilation, describe home ventilation as a more cost-effective alternative to in-patient care in an intensive care unit, however, more expensive in comparison to a noninvasive (via mask ventilation. Higher expenses arise due to the necessary equipment and the high expenditure of time for the partial 24-hour care of the affected patients through highly qualified personnel. However, none of the studies applies to the German provisionary conditions. The calculated costs strongly depend on national medical fees and wages of caregivers, which barely allows a transmission of the results. The results of quality-of-life studies are mostly qualitative. The patient’s quality of life using mechanical ventilation is predominantly considered well. Caregivers of ventilated patients report positive as well as negative ratings. Regarding the ethical questions, it was researched which aspects of ventilation implementation will have to be considered. From a legal point of view the financing of home ventilation, especially invasive mechanical ventilation, requiring specialised technical nursing is regulated in the code of social law (Sozialgesetzbuch V. The absorption of costs is distributed to different insurance carriers, who often, due to cost pressures within the health care system, insurance carriers, who consider others and not themselves as responsible. Therefore in practice, the necessity to enforce a claim of cost absorption often arises in order to exercise the basic right of free choice of location. Conclusion: Positive effects of the invasive mechanical ventilation (overall survival and symptomatic are highly probable based on the analysed literature, although with a low level of evidence. An establishment of a home ventilation registry and health care research to ascertain valid data to improve outpatient structures is necessary. Gathering specific G

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

    International Nuclear Information System (INIS)

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

  18. Evaporation as the transport mechanism of metals in arid regions.

    Science.gov (United States)

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

    2014-09-01

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

  19. As if Kyoto mattered: The clean development mechanism and transportation

    International Nuclear Information System (INIS)

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

  20. Molecular Mechanism of Ochratoxin A Transport in the Kidney

    Directory of Open Access Journals (Sweden)

    Naohiko Anzai

    2010-06-01

    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.

  1. Mechanisms of calcium transport across the placenta: Review

    Directory of Open Access Journals (Sweden)

    Catarina Tivane

    2013-01-01

    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.

  2. Molecular Mechanism of Ochratoxin A Transport in the Kidney

    OpenAIRE

    Naohiko Anzai; Promsuk Jutabha; Hitoshi Endou

    2010-01-01

    The mycotoxin, ochratoxin A (OTA), is thought to be responsible for Balkan endemic nephropathy. OTA accumulates in several tissues, especially in the kidneys and liver. The excretion of OTA into urine is thought to be mainly by tubular secretion, presumably via the organic anion transport system. Recently, several families of multispecific organic anion transporters have been identified: organic anion transporters (OATs), organic anion-transporting polypeptides (OATPs), oligopeptide transport...

  3. 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

  4. Chemical and mechanical control of corrosion product transport

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-01

    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)

  5. Longitudinal vibrations of mechanical systems with the transportation effect

    Directory of Open Access Journals (Sweden)

    A. Buchacz

    2009-01-01

    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.

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

    OpenAIRE

    Ludwig, H. -g; Allard, F.; Hauschildt, P. H.

    2006-01-01

    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 particu...

  7. Mechanism of ochratoxin A transport in kidney

    International Nuclear Information System (INIS)

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

  8. Membrane transport mechanism 3D structure and beyond

    CERN Document Server

    Ziegler, Christine

    2014-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

  12. Walking mechanism of the intracellular cargo transporter myosin V

    International Nuclear Information System (INIS)

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

  13. Charge transport mechanism in thin cuticles holding nandi flame seeds.

    Science.gov (United States)

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

    2009-01-01

    Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4 mum thick Nandi flame [Spathodea campanulata P. Beauv.] seed cuticles. J-V characteristics showed ohmic conduction at low fields and space charge limited current at high fields. Charge mobility in ohmic region was 4.06 x 10(-5) (m(2)V(-1)s(-1)). Temperature-dependent conductivity measurements have been carried out in the temperature range 320 K 450 K. Activation energy within a temperature of 320 K-440 K was about 0.86 eV. Variable range hopping (VRH) is the main current transport mechanism at the range of 330-440 K. The VRH mechanism was analyzed based on Mott theory and the Mott parameters: density of localized states near the Fermi-level N(E(F)) approximately 9.04 x 10(19) (eV(-1)cm(-3)) and hopping distance R approximately 1.44 x 10(-7) cm, while the hopping energy (W) was in the range of 0.72 eV-0.98 eV. PMID:20130799

  14. Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds

    Directory of Open Access Journals (Sweden)

    Wycliffe K. Kipnusu

    2009-01-01

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

  15. 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...

  16. A Study on the Main Steam Safety Valve Opening Mechanism by Flashing on NPPs

    International Nuclear Information System (INIS)

    A safety injection event happened by opening of the Main Steam Safety Valve at Kori unit 1 on April 16, 2005. The safety valves were opened at the lower system pressure than the valve opening set point due to rapid system pressure drop by opening of the Power Operated Relief Valve installed at the upstream of the Main Steam System. But the opening mechanism of safety valve at the lower set point pressure was not explained exactly. So, it needs to be understood about the safety valve opening mechanism to prevent a recurrence of this kind of event at a similar system of Nuclear Power Plant. This study is aimed to suggest the hydrodynamic mechanism for the safety valve opening at the lower set point pressure and the possibility of the recurrence at similar system conditions through document reviewing for the related previous studies and Kori unit 1 event

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

    Science.gov (United States)

    Zhou, Yanhua; Xie, Fugui; Liu, Xinjun

    2013-09-01

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

  18. Electron Transport Mechanism in Cobalt Polymethacrylate (CoPMA)

    Science.gov (United States)

    Chohan, M. H.; Khalid, A. H.; Zulfiqar, M.; Butt, P. K.; Khan, Farah; Hussain, Rizwan

    Electron transport mechanisms in cobalt polymethacrylate have been investigated. The electrical measurements made on the polymer, show that the current-voltage relationship at lower voltages (V<300 V) is ohmic whereas at higher voltages it is exponential. The strong temperature dependence of current on voltage indicates the dominance of a Poole-Frenkel mechanism and the existence of trapping levels. Low activation energy values suggest an electronic conduction mechanism.

  19. Transport mechanisms in nanopores and nanochannels: can we mimic nature?

    Directory of Open Access Journals (Sweden)

    Mario Tagliazucchi

    2015-04-01

    Full Text Available The last few years have witnessed major advancements in the synthesis, modification, characterization and modeling of nanometer-size solid-state channels and pores. Future applications in sensing, energy conversion and purification technologies will critically rely on qualitative improvements in the control over the selectivity, directionality and responsiveness of these nanochannels and nanopores. It is not surprising, therefore, that researchers in the field seek inspiration in biological ion channels and ion pumps, paradigmatic examples of transport selectivity. This work reviews our current fundamental understanding of the mechanisms of transport of ions and larger cargoes through nanopores and nanochannels by examining recent experimental and theoretical work. It is argued that that structure and transport in biological channels and polyelectrolyte-modified synthetic nanopores are strongly coupled: the structure dictates transport and transport affects the structure. We compare synthetic and biological systems throughout this review to conclude that while they present interesting similarities, they also have striking differences.

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

    International Nuclear Information System (INIS)

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

  1. 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

  2. X-ray structure of dopamine transporter elucidates antidepressant mechanism.

    Science.gov (United States)

    Penmatsa, Aravind; Wang, Kevin H; Gouaux, Eric

    2013-11-01

    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. PMID:24037379

  3. Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets

    CERN Document Server

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

    1998-01-01

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

  4. Neuropathy-induced spinal GAP-43 expression is not a main player in the onset of mechanical pain hypersensitivity.

    Science.gov (United States)

    Jaken, Robby J; van Gorp, Sebastiaan; Joosten, Elbert A; Losen, Mario; Martínez-Martínez, Pilar; De Baets, Marc; Marcus, Marco A; Deumens, Ronald

    2011-12-01

    Structural plasticity within the spinal nociceptive network may be fundamental to the chronic nature of neuropathic pain. In the present study, the spatiotemporal expression of growth-associated protein-43 (GAP-43), a protein which has been traditionally implicated in nerve fiber growth and sprouting, was investigated in relation to mechanical pain hypersensitivity. An L5 spinal nerve transection model was validated by the presence of mechanical pain hypersensitivity and an increase in the early neuronal activation marker cFos within the superficial spinal dorsal horn upon innocuous hindpaw stimulation. Spinal GAP-43 was found to be upregulated in the superficial L5 dorsal horn from 5 up to 10 days after injury. GAP-43 was co-localized with calcitonin-gene related peptide (CGRP), but not vesicular glutamate transporter-1 (VGLUT-1), IB4, or protein kinase-? (PKC-?), suggesting the regulation of GAP-43 in peptidergic nociceptive afferents. These GAP-43/CGRP fibers may be indicative of sprouting peptidergic fibers. Fiber sprouting largely depends on growth factors, which are typically associated with neuro-inflammatory processes. The putative role of neuropathy-induced GAP-43 expression in the development of mechanical pain hypersensitivity was investigated using the immune modulator propentofylline. Propentofylline treatment strongly attenuated the development of mechanical pain hypersensitivity and glial responses to nerve injury as measured by microglial and astroglial markers, but did not affect neuropathy-induced levels of spinal GAP-43 or GAP-43 regulation in CGRP fibers. We conclude that nerve injury induces structural plasticity in fibers expressing CGRP, which is regarded as a main player in central sensitization. Our data do not, however, support a major role of these structural changes in the onset of mechanical pain hypersensitivity. PMID:21671799

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

    Science.gov (United States)

    Jaken, Robby J.; van Gorp, Sebastiaan; Joosten, Elbert A.; Losen, Mario; Martínez-Martínez, Pilar; De Baets, Marc; Marcus, Marco A.

    2011-01-01

    Abstract Structural plasticity within the spinal nociceptive network may be fundamental to the chronic nature of neuropathic pain. In the present study, the spatiotemporal expression of growth-associated protein-43 (GAP-43), a protein which has been traditionally implicated in nerve fiber growth and sprouting, was investigated in relation to mechanical pain hypersensitivity. An L5 spinal nerve transection model was validated by the presence of mechanical pain hypersensitivity and an increase in the early neuronal activation marker cFos within the superficial spinal dorsal horn upon innocuous hindpaw stimulation. Spinal GAP-43 was found to be upregulated in the superficial L5 dorsal horn from 5 up to 10 days after injury. GAP-43 was co-localized with calcitonin-gene related peptide (CGRP), but not vesicular glutamate transporter-1 (VGLUT-1), IB4, or protein kinase-? (PKC-?), suggesting the regulation of GAP-43 in peptidergic nociceptive afferents. These GAP-43/CGRP fibers may be indicative of sprouting peptidergic fibers. Fiber sprouting largely depends on growth factors, which are typically associated with neuro-inflammatory processes. The putative role of neuropathy-induced GAP-43 expression in the development of mechanical pain hypersensitivity was investigated using the immune modulator propentofylline. Propentofylline treatment strongly attenuated the development of mechanical pain hypersensitivity and glial responses to nerve injury as measured by microglial and astroglial markers, but did not affect neuropathy-induced levels of spinal GAP-43 or GAP-43 regulation in CGRP fibers. We conclude that nerve injury induces structural plasticity in fibers expressing CGRP, which is regarded as a main player in central sensitization. Our data do not, however, support a major role of these structural changes in the onset of mechanical pain hypersensitivity. PMID:21671799

  6. Cultural diffusion was the main driving mechanism of the Neolithic transition in southern Africa.

    Science.gov (United States)

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

    2014-01-01

    It is well known that the Neolithic transition spread across Europe at a speed of about 1 km/yr. This result has been previously interpreted as a range expansion of the Neolithic driven mainly by demic diffusion (whereas cultural diffusion played a secondary role). However, a long-standing problem is whether this value (1 km/yr) and its interpretation (mainly demic diffusion) are characteristic only of Europe or universal (i.e. intrinsic features of Neolithic transitions all over the world). So far Neolithic spread rates outside Europe have been barely measured, and Neolithic spread rates substantially faster than 1 km/yr have not been previously reported. Here we show that the transition from hunting and gathering into herding in southern Africa spread at a rate of about 2.4 km/yr, i.e. about twice faster than the European Neolithic transition. Thus the value 1 km/yr is not a universal feature of Neolithic transitions in the world. Resorting to a recent demic-cultural wave-of-advance model, we also find that the main mechanism at work in the southern African Neolithic spread was cultural diffusion (whereas demic diffusion played a secondary role). This is in sharp contrast to the European Neolithic. Our results further suggest that Neolithic spread rates could be mainly driven by cultural diffusion in cases where the final state of this transition is herding/pastoralism (such as in southern Africa) rather than farming and stockbreeding (as in Europe). PMID:25517968

  7. Directional auxin transport mechanisms in early diverging land plants.

    Science.gov (United States)

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

    2014-12-01

    The emergence and radiation of multicellular land plants was driven by crucial innovations to their body plans. The directional transport of the phytohormone auxin represents a key, plant-specific mechanism for polarization and patterning in complex seed plants. Here, we show that already in the early diverging land plant lineage, as exemplified by the moss Physcomitrella patens, auxin transport by PIN transporters is operational and diversified into ER-localized and plasma membrane-localized PIN proteins. Gain-of-function and loss-of-function analyses revealed that PIN-dependent intercellular auxin transport in Physcomitrella mediates crucial developmental transitions in tip-growing filaments and waves of polarization and differentiation in leaf-like structures. Plasma membrane PIN proteins localize in a polar manner to the tips of moss filaments, revealing an unexpected relation between polarization mechanisms in moss tip-growing cells and multicellular tissues of seed plants. Our results trace the origins of polarization and auxin-mediated patterning mechanisms and highlight the crucial role of polarized auxin transport during the evolution of multicellular land plants. PMID:25448004

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

    CERN Document Server

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

    2012-01-01

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

  9. Issues in tokamak/stellarator transport and confinement enhancement mechanisms

    International Nuclear Information System (INIS)

    At present, the mechanism for anomalous energy transport in low-? toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E x B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs

  10. Modeling Transport and Flow Regulatory Mechanisms of the Kidney

    Science.gov (United States)

    Layton, Anita T.

    2013-01-01

    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. PMID:23914303

  11. Mechanism of Transport through Wood Cell Wall Polymers

    Directory of Open Access Journals (Sweden)

    Joseph E Jakes

    2013-11-01

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

  12. Controllable Lubrication for Main Engine Bearings Using Mechanical and Piezoelectric Actuators

    DEFF Research Database (Denmark)

    Estupinan, Edgar; Santos, Ilmar

    2012-01-01

    Although mechatronic systems are nowadays implemented in a large number of systems in vehicles, active lubrication systems are still incipient in industrial applications. This study is an attempt to extend the active lubrication concept to combustion engines and gives a theoretical contribution to this field. One refers to active lubrication when conventional hydrodynamic lubrication is combined with dynamically modified hydrostatic lubrication. In this study, two different schemes for the oil injection system in actively lubricated main engine bearings are presented. The use of active lubrication in journal bearings helps to enhance the hydrodynamic fluid film by increasing the fluid film thickness and consequently reducing viscous friction losses and vibrations. In this study, the hydrostatic lubrication is modified by injecting oil at controllable pressures through orifices circumferentially located around the bearing surface. The main equations that govern the dynamics of the injection for a piezo-actuated oil injector and a mechanical-actuated oil injector are presented. It is shown how the dynamics of the oil injection system is coupled to the dynamics of the bearing fluid film through equations. The global system is numerically solved using as a case study a single-cylinder combustion engine, where the conventional lubrication of the main bearing is modified by applying radial oil injection using piezo-actuated injection. The performance of such a hybrid bearing is compared to an equivalent conventional lubricated bearing in terms of the maximum fluid film pressures, minimum fluid film thicknesses, and reduction of viscous friction losses.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-11-01

    The purpose of this project is to develop tools to model and simulate the processes of self-assembly and growth in biological systems from the molecular to the continuum length scales. The model biological system chosen for the study is the tendon fiber which is composed mainly of Type I collagen fibrils. The macroscopic processes of self-assembly and growth at the fiber scale arise from microscopic processes at the fibrillar and molecular length scales. At these nano-scopic length scales, we employed molecular modeling and simulation method to characterize the mechanical behavior and stability of the collagen triple helix and the collagen fibril. To obtain the physical parameters governing mass transport in the tendon fiber we performed direct numerical simulations of fluid flow and solute transport through an idealized fibrillar microstructure. At the continuum scale, we developed a mixture theory approach for modeling the coupled processes of mechanical deformation, transport, and species inter-conversion involved in growth. In the mixture theory approach, the microstructure of the tissue is represented by the species concentration and transport and material parameters, obtained from fibril and molecular scale calculations, while the mechanical deformation, transport, and growth processes are governed by balance laws and constitutive relations developed within a thermodynamically consistent framework.

  14. Structure and mechanism of ATP-dependent phospholipid transporters

    DEFF Research Database (Denmark)

    Lopez Marques, Rosa Laura; Poulsen, Lisbeth Rosager

    2015-01-01

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

  15. Directed transport as a mechanism for protein folding in vivo

    CERN Document Server

    Gonzalez-Candela, Ernesto

    2009-01-01

    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.

  16. Comparative Localization and Functional Activity of the Main Hepatobiliary Transporters in HepaRG Cells and Primary Human Hepatocytes.

    Science.gov (United States)

    Bachour-El Azzi, Pamela; Sharanek, Ahmad; Burban, Audrey; Li, Ruoya; Guével, Rémy Le; Abdel-Razzak, Ziad; Stieger, Bruno; Guguen-Guillouzo, Christiane; Guillouzo, André

    2015-05-01

    The role of hepatobiliary transporters in drug-induced liver injury remains poorly understood. Various in vivo and in vitro biological approaches are currently used for studying hepatic transporters; however, appropriate localization and functional activity of these transporters are essential for normal biliary flow and drug transport. Human hepatocytes (HHs) are considered as the most suitable in vitro cell model but erratic availability and inter-donor functional variations limit their use. In this work, we aimed to compare localization of influx and efflux transporters and their functional activity in differentiated human HepaRG hepatocytes with fresh HHs in conventional (CCHH) and sandwich (SCHH) cultures. All tested influx and efflux transporters were correctly localized to canalicular [bile salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2), multidrug resistance protein 1 (MDR1), and MDR3] or basolateral [Na(+)-taurocholate co-transporting polypeptide (NTCP) and MRP3] membrane domains and were functional in all models. Contrary to other transporters, NTCP and BSEP were less abundant and active in HepaRG cells, cellular uptake of taurocholate was 2.2- and 1.4-fold and bile excretion index 2.8- and 2.6-fold lower, than in SCHHs and CCHHs, respectively. However, when taurocholate canalicular efflux was evaluated in standard and divalent cation-free conditions in buffers or cell lysates, the difference between the three models did not exceed 9.3%. Interestingly, cell imaging showed higher bile canaliculi contraction/relaxation activity in HepaRG hepatocytes and larger bile canaliculi networks in SCHHs. Altogether, our results bring new insights in mechanisms involved in bile acids accumulation and excretion in HHs and suggest that HepaRG cells represent a suitable model for studying hepatobiliary transporters and drug-induced cholestasis. PMID:25690737

  17. Mechanical systems vibrating longitudinally with the transportation effect

    OpenAIRE

    Z?o??kiewski, S.; Buchacz, A.

    2007-01-01

    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,...

  18. Transport mechanisms and enhanced confinement studies in RFX

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

    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

    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.

  20. Insights into transport mechanism from LeuT engineered to transport tryptophan

    OpenAIRE

    Piscitelli, Chayne L.; Gouaux, Eric

    2011-01-01

    LeuT is a model protein for studying the structure and mechanism of the neurotransmitter/sodium symporter family. This study reveals how the ability of a ligand to promote the structural transition to the occluded state modulates transport specificity.

  1. A general mechanism for helium blistering involving displaced atom transport

    International Nuclear Information System (INIS)

    A mechanism developed to account for formation of vertically elongated blisters in high displacement environments produced by 252Cf alpha particles and fission fragments has been extended to formation of dome-shaped blisters in the low displacement environments produced by simple helium ion beams. In this mechanism, transport of displaced atoms to relieve compressive stresses in the helium-implanted layer allows interconnections of small, subsurface bubbles to form the blister cavity. The same transport may cause thickening of the blister caps at low implantation energies. The transition from dome-shaped to vertically elongated blistering occurs between the 300 and 3000 displacements per helium atom produced by simple helium ions and 252Cf radiations, respectively. (orig.)

  2. General mechanism for helium blistering involving displaced atom transport

    International Nuclear Information System (INIS)

    A mechanism developed to account for formation of vertically elongated blisters in high displacement environments produced by 252Cf alpha particles and fission fragments has been extended to formation of done-shaped blisters in the low displacement environments produced by simple helium ion beams. In this mechanism, transport of displaced atoms to relieve compressive stresses in the helium-implanted layer allows interconnections of small, subsurface bubbles to form the blister cavity. The same transport may cause thickening of the blister caps at low implantation energies. The transition from dome-shaped to vertically elongated blistering occurs between the 300 and 3000 displacements per helium atom produced by simple helium ions and 252Cf radiations respectively

  3. Microscopic chaos, fractals and transport in nonequilibrium statistical mechanics

    CERN Document Server

    Klages, Rainer

    2007-01-01

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

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

    OpenAIRE

    I. W. M. Pothof

    2011-01-01

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

  5. Increased coordination in public transport – which mechanisms are available?

    DEFF Research Database (Denmark)

    SØrensen, Claus Hedegaard; Longva, Frode

    2011-01-01

    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.

  6. MIRI-JWST spectrometer main optics opto-mechanical design and prototyping

    Science.gov (United States)

    Kroes, Gabby; Oudenhuysen, Ad; Meijers, Michael; Pel, Jan-Willem

    2005-08-01

    In December 2004 the European Consortium that develops the optical bench assembly for MIRI successfully passed the Preliminary Design Review. MIRI is the combined imager and integral field spectrometer for the 5-28 micron wavelength range under development for the JWST. After this PDR milestone the optical design of the MIRI spectrometer is now implemented in a compact, modular mechanical design that puts all optical elements in place within the required tolerances. Many aspects of this design are based on the heritage of previous instruments developed at ASTRON, in particular the cryogenic optics for the mid-IR VLT instruments VISIR and MIDI, but several adjustments to this design philosophy were made to develop the necessary space-qualified light-weighted components. Prototyping of these components has now started. This paper describes trade-offs and solutions for the opto-mechanical design of the optics (gratings, mirrors and their mountings) and of the main structure of the spectrometer, taking into account optical performance, manufacturability, cost and lead times. It also addresses the complex interface management in a large international consortium and reports first prototype results.

  7. Cytoplasmic HIV-1 RNA is mainly transported by diffusion in the presence or absence of Gag protein

    Science.gov (United States)

    Chen, Jianbo; Grunwald, David; Sardo, Luca; Galli, Andrea; Plisov, Sergey; Nikolaitchik, Olga A.; Chen, De; Lockett, Stephen; Larson, Daniel R.; Pathak, Vinay K.; Hu, Wei-Shau

    2014-01-01

    Full-length HIV-1 RNA plays a central role in viral replication by serving as the mRNA for essential viral proteins and as the genome packaged into infectious virions. Proper RNA trafficking is required for the functions of RNA and its encoded proteins; however, the mechanism by which HIV-1 RNA is transported within the cytoplasm remains undefined. Full-length HIV-1 RNA transport is further complicated when group-specific antigen (Gag) protein is expressed, because a significant portion of HIV-1 RNA may be transported as Gag–RNA complexes, whose properties could differ greatly from Gag-free RNA. In this report, we visualized HIV-1 RNA and monitored its movement in the cytoplasm by using single-molecule tracking. We observed that most of the HIV-1 RNA molecules move in a nondirectional, random-walk manner, which does not require an intact cytoskeletal structure, and that the mean-squared distance traveled by the RNA increases linearly with time, indicative of diffusive movement. We also observed that a single HIV-1 RNA molecule can move at various speeds when traveling through the cytoplasm, indicating that its movement is strongly affected by the immediate environment. To examine the effect of Gag protein on HIV-1 RNA transport, we analyzed the cytoplasmic HIV-1 RNA movement in the presence of sufficient Gag for virion assembly and found that HIV-1 RNA is still transported by diffusion with mobility similar to the mobility of RNAs unable to express functional Gag. These studies define a major mechanism of HIV-1 gene expression and resolve the long-standing question of how the RNA genome is transported to the assembly site. PMID:25404326

  8. The ion transport mechanism of lithium polymer electrolytes

    Science.gov (United States)

    Dai, Hongli

    Lithium polymer electrolytes are of great interest for use in polymer-electrolyte rechargeable batteries. However, the lithium transport mechanism in the polymer electrolyte has not been fully understood, due partly to the lack of a means to characterize a key lithium transport property, the transference number, correctly and efficiently. This research pioneered the use of the electrophoretic nuclear magnetic resonance technique to measure the lithium transference number (TsbLi) of polymer electrolytes. The development of this technique is described. It is shown that the technique is strictly valid regardless of the degree of dissociation of the electrolyte and the measurement protocol is relatively straightforward. As a result, the accuracy of the technique is high compared to existing techniques. The lithium transport mechanism in polymer gel electrolytes are investigated systematically with complementary techniques including vibrational spectroscopy (Raman scattering), nuclear magnetic resonance, and a.c. impedance spectroscopy. The characteristic lithium transport behavior as a function of the temperature, the salt concentration, the anion type, and the polymer matrices is established. Perfluoroimide and perfluoromethide lithium salts always lead to a larger lithium transference number compared to conventional lithium salts. In poly(vinylidene fluororide-hexfloropropylene) based gel electrolytes, the perfluoroimide anion, (CFsb3SOsb3)sb2Nsp-, results in a nearly invariant TsbLi over a wide salt concentration range. In contrast, the CFsb3SOsb3sp- anion results in TsbLi decreasing monotonically with increasing salt concentration. In poly(acrylonitrile), which binds with Lisp+, the TsbLi versus LiCFsb3SOsb3 concentration curve is nearly parabolic. A qualitative model is proposed which defines the important molecular interactions underlying the lithium transport behavior and extends the Fuoss and Onsager theory to systems with extensive ion complexation.

  9. Insights into transport mechanism from LeuT engineered to transport tryptophan

    Energy Technology Data Exchange (ETDEWEB)

    Piscitelli, Chayne L.; Gouaux, Eric (Oregon HSU)

    2012-01-10

    LeuT is a bacterial homologue of the neurotransmitter:sodium symporter (NSS) family and, being the only NSS member to have been structurally characterized by X-ray crystallography, is a model protein for studying transporter structure and mechanism. Transport activity in LeuT was hypothesized to require structural transitions between open-to-out and occluded conformations dependent upon protein:ligand binding complementarity. Here, using crystallographic and functional analysis, we show that binding site modification produces changes in both structure and activity that are consistent with complementarity-dependent structural transitions to the occluded state. The mutation I359Q converts the activity of tryptophan from inhibitor to transportable substrate. This mutation changes the local environment of the binding site, inducing the bound tryptophan to adopt a different conformer than in the wild-type complex. Instead of trapping the transporter open, tryptophan binding now allows the formation of an occluded state. Thus, transport activity is correlated to the ability of the ligand to promote the structural transition to the occluded state, a step in the transport cycle that is dependent on protein:ligand complementarity in the central binding site.

  10. Insights into transport mechanism from LeuT engineered to transport tryptophan.

    Science.gov (United States)

    Piscitelli, Chayne L; Gouaux, Eric

    2012-01-01

    LeuT is a bacterial homologue of the neurotransmitter:sodium symporter (NSS) family and, being the only NSS member to have been structurally characterized by X-ray crystallography, is a model protein for studying transporter structure and mechanism. Transport activity in LeuT was hypothesized to require structural transitions between open-to-out and occluded conformations dependent upon protein:ligand binding complementarity. Here, using crystallographic and functional analysis, we show that binding site modification produces changes in both structure and activity that are consistent with complementarity-dependent structural transitions to the occluded state. The mutation I359Q converts the activity of tryptophan from inhibitor to transportable substrate. This mutation changes the local environment of the binding site, inducing the bound tryptophan to adopt a different conformer than in the wild-type complex. Instead of trapping the transporter open, tryptophan binding now allows the formation of an occluded state. Thus, transport activity is correlated to the ability of the ligand to promote the structural transition to the occluded state, a step in the transport cycle that is dependent on protein:ligand complementarity in the central binding site. PMID:21952050

  11. A mutation affecting gluconate catabolism in Escherichia coli: the locus for the main high affinity transport.

    Science.gov (United States)

    De Rekarte, U D; Istúriz, T

    1994-01-01

    The bioH-malA region of the E. coli chromosome (min 75.5) includes the gntT gene which encodes a high affinity transport for gluconate. Other gnt loci have not been characterized in this region; nevertheless, because lesions in it affect severely the utilization of gluconate, it has been suggested as being more complex. This region was investigated with respect to gluconate catabolism through the characterization of suitable E. coli strains lysogenized with a specialized transducing phage carrying the bioH-malA region of the bacterial chromosome (lambda cI857st68h80d2bioH-malA). It was found that the region transduced by this phage while includes the gntT gene lacks other gnt loci that might code additional activities for transport of gluconate or its phosphorylation. Moreover, the pleiotropic lesion gntM2, previously mapped into this region and suggested as altering gntT or a presumptive regulator gene that might be involved in this catabolism, resulted recessive in lysogens (partial diploids) containing the defective prophage. The results obtained supported the idea that gntM2 is an allele of gntT; consequently those results suggested the precise position of this gene on the cromosomic map and the central role that its product might have in the initial incorporation of gluconate in E. coli. PMID:8731292

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

    International Nuclear Information System (INIS)

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

  13. Structural insights into thyroid hormone transport mechanisms of the L-type amino Acid transporter 2.

    Science.gov (United States)

    Hinz, Katrin M; Meyer, Katja; Kinne, Anita; Schülein, Ralf; Köhrle, Josef; Krause, Gerd

    2015-06-01

    Thyroid hormones (THs) are transported across cell membranes by different transmembrane transporter proteins. In previous studies, we showed marked 3,3'-diiodothyronine (3,3'-T2) but moderate T3 uptake by the L-type amino acid transporter 2 (Lat2). We have now studied the structure-function relationships of this transporter and TH-like molecules. Our Lat2 homology model is based on 2 crystal structures of the homologous 12-transmembrane helix transporters arginine/agmatine antiporter and amino acid/polyamine/organocation transporter. Model-driven mutagenesis of residues lining an extracellular recognition site and a TH-traversing channel identified 9 sensitive residues. Using Xenopus laevis oocytes as expression system, we found that side chain shortening (N51S, N133S, N248S, and Y130A) expanded the channel and increased 3,3'-T2 transport. Side chain enlargements (T140F, Y130R, and I137M) decreased 3,3'-T2 uptake, indicating channel obstructions. The opposite results with mutations maintaining (F242W) or impairing (F242V) uptake suggest that F242 may have a gating function. Competitive inhibition studies of 14 TH-like compounds revealed that recognition by Lat2 requires amino and carboxylic acid groups. The size of the adjacent hydrophobic group is restricted. Bulky substituents in positions 3 and 5 of the tyrosine ring are allowed. The phenolic ring may be enlarged, provided that the whole molecule is flexible enough to fit into the distinctly shaped TH-traversing channel of Lat2. Taken together, the next Lat2 features were identified 1) TH recognition site; 2) TH-traversing channel in the center of Lat2; and 3) switch site that potentially facilitates intracellular substrate release. Together with identified substrate features, these data help to elucidate the molecular mechanisms and role of Lat2 in T2 transport. PMID:25945809

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

    International Nuclear Information System (INIS)

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

  15. Nonlinear charge transport mechanism in periodic and disordered DNA

    CERN Document Server

    Hennig, D; Agarwal, J P

    2003-01-01

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

  16. Transport mechanisms for Mg/Zn3P2 junctions

    International Nuclear Information System (INIS)

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

  17. 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

  18. Analysis of River – Sea Transport in the Direction of the Danube – Black Sea and the Danube Rhine River River Main

    Directory of Open Access Journals (Sweden)

    S. Šo?kic

    2014-12-01

    Full Text Available Development of the river sea transport is directly related to the characteristics of waterway network which enables navigation between river basins and seas. Inland waterways in Serbia belong to the Danube navigational system. There are two navigational directions: Danube East and Danube West. River-sea transport can be directly established in these directions between the Serbian international ports on the Danube (Apatin, Novi Sad, Belgrade, Pan?evo, Smederevo and Prahovo. Development of the Pan-European Corridor VII and the River Danube-Black Sea and Danube-Rhine-Main region would allow not only in Serbia but also in neighbouring states and all over Europe connection with the sea. In this paper the technical and exploitation characteristics of the river Danube will be analysed in terms of the navigation of various river and sea vessels with different exploitation characteristics.

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

    Directory of Open Access Journals (Sweden)

    Satoshi Kameyama

    2013-01-01

    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.

  20. Mechanism of travelling-wave transport of particles

    International Nuclear Information System (INIS)

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

  1. 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)

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

    Science.gov (United States)

    Bair, E. K.

    1987-01-01

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

  3. Double internal transport barrier triggering mechanism in tokamak plasmas

    International Nuclear Information System (INIS)

    Sheared flow layers created by energy released in magnetic reconnection processes are studied with the magneto hydrodynamics (MHD), aimed at internal transport barrier (ITB) dynamics. The double tearing mode induced by electron viscosity is investigated and proposed as a triggering mechanism for double internal transport barrier (DITB) observed in tokamak plasmas with non-monotonic safety factor profiles. The quasi-linear development of the mode is simulated and the emphasis is placed on the structure of sheared poloidal flow layers formed in the vicinity of the magnetic islands. For viscosity double tearing modes, it is shown that the sheared flows induced by the mode may reach the level required by the condition for ITB formation. Especially, the flow layers are found to form just outside the magnetic islands. The scaling of the generated velocity with plasma parameters is given. Possible explanation for the experimental observations that the preferential formation of transport barriers in the proximity of low order rational surface is discussed. (author)

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

    International Nuclear Information System (INIS)

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

  5. Calcium transport mechanism in molting crayfish revealed by microanalysis

    International Nuclear Information System (INIS)

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

  6. Mass transport mechanisms during excimer laser nitriding of aluminum

    International Nuclear Information System (INIS)

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

  7. Kinesin-1/Hsc70-dependent mechanism of slow axonal transport and its relation to fast axonal transport.

    Science.gov (United States)

    Terada, Sumio; Kinjo, Masataka; Aihara, Makoto; Takei, Yosuke; Hirokawa, Nobutaka

    2010-02-17

    Cytoplasmic protein transport in axons ('slow axonal transport') is essential for neuronal homeostasis, and involves Kinesin-1, the same motor for membranous organelle transport ('fast axonal transport'). However, both molecular mechanisms of slow axonal transport and difference in usage of Kinesin-1 between slow and fast axonal transport have been elusive. Here, we show that slow axonal transport depends on the interaction between the DnaJ-like domain of the kinesin light chain in the Kinesin-1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin-1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein transport and reinforced membranous organelle transport, indicating that this domain might have a function as a switchover system between slow and fast transport by Hsc70. Transgenic mice overexpressing a dominant-negative form of the domain showed delayed slow transport, accelerated fast transport and optic axonopathy. These findings provide a basis for the regulatory mechanism of intracellular transport and its intriguing implication in neuronal dysfunction. PMID:20111006

  8. Cellular Transport Mechanisms of Cytotoxic Metallodrugs: An Overview beyond Cisplatin

    Directory of Open Access Journals (Sweden)

    Sarah Spreckelmeyer

    2014-09-01

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

  9. 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

  10. Mechanism of Hydrogen Trapping and Transport in Carbon Materials

    Science.gov (United States)

    Atsumi, H.

    Bulk hydrogen retention and hydrogen diffusion in graphite and carbon materials have been studied to estimate hydrogen recycling and tritium inventory in a fusion reactor environment. Hydrogen may permeate into a filler grain in the form of a hydrogen molecule, diffuse through crystallite boundaries and finally be trapped as hydrogen atoms at the edge surface of a crystallite. In the estimation of hydrogen transport, the activation energy of hydrogen diffusion can be determined from absorption experiments, and the activation energy of detrapping can be obtained from desorption experiments. The activation energies of hydrogen trapping are 2.6 eV in ordinary graphite and 4.4 eV for irradiated or mechanically milled graphite samples.

  11. Flexible Mechanical Conveyors for Regolith Extraction and Transport

    Science.gov (United States)

    Walton, Otis R.; Vollmer, Hubert J.

    2013-01-01

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

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

    Science.gov (United States)

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

    2014-12-01

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

  13. Mechanical reliability of geometrically imperfect tubular oxygen transport membranes

    DEFF Research Database (Denmark)

    Kwok, Kawai; Frandsen, Henrik Lund

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-07-01

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

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

    Science.gov (United States)

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

    2014-07-01

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

  16. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    Science.gov (United States)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.

  17. CLUB FORMATION MECHANISM FOR TRANSPORT-COMMUNITY CREDIT CARDS

    Science.gov (United States)

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

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

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

    Czech Academy of Sciences Publication Activity Database

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

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

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

    Science.gov (United States)

    Penmatsa, Aravind; Gouaux, Eric

    2014-03-01

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

  20. Integration of computational modeling with membrane transport studies reveals new insights into amino acid exchange transport mechanisms.

    Science.gov (United States)

    Widdows, Kate L; Panitchob, Nuttanont; Crocker, Ian P; Please, Colin P; Hanson, Mark A; Sibley, Colin P; Johnstone, Edward D; Sengers, Bram G; Lewis, Rohan M; Glazier, Jocelyn D

    2015-06-01

    Uptake of system L amino acid substrates into isolated placental plasma membrane vesicles in the absence of opposing side amino acid (zero-trans uptake) is incompatible with the concept of obligatory exchange, where influx of amino acid is coupled to efflux. We therefore hypothesized that system L amino acid exchange transporters are not fully obligatory and/or that amino acids are initially present inside the vesicles. To address this, we combined computational modeling with vesicle transport assays and transporter localization studies to investigate the mechanisms mediating [(14)C]l-serine (a system L substrate) transport into human placental microvillous plasma membrane (MVM) vesicles. The carrier model provided a quantitative framework to test the 2 hypotheses that l-serine transport occurs by either obligate exchange or nonobligate exchange coupled with facilitated transport (mixed transport model). The computational model could only account for experimental [(14)C]l-serine uptake data when the transporter was not exclusively in exchange mode, best described by the mixed transport model. MVM vesicle isolates contained endogenous amino acids allowing for potential contribution to zero-trans uptake. Both L-type amino acid transporter (LAT)1 and LAT2 subtypes of system L were distributed to MVM, with l-serine transport attributed to LAT2. These findings suggest that exchange transporters do not function exclusively as obligate exchangers.-Widdows, K. L., Panitchob, N., Crocker, I. P., Please, C. P., Hanson, M. A., Sibley, C. P., Johnstone, E. D., Sengers, B. G., Lewis, R. M., Glazier, J. D. Integration of computational modeling with membrane transport studies reveals new insights into amino acid exchange transport mechanisms. PMID:25761365

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

    OpenAIRE

    M Sekuli?; Z. Jurkovi?; M. Hadžistevi?; M. Gostimirovi?

    2010-01-01

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

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

    CERN Document Server

    Ramos, D

    2012-01-01

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

  3. Main mechanical and thermal problems in the vacuum vessel of the FTU Tokamak machine

    International Nuclear Information System (INIS)

    The FTU Tokamak, in order to reach the expected performance has to operate steadily at high magnetic fields. Its vacuum chamber would undergo very high stresses due to thermal and electromagnetic loads for a large number of shots. In order to assess the feasibility of this component, numerical codes to compute current, magnetic field and temperature distributions and extensive three dimensional finite element stress analysis have been developed. The main results obtained are illustrated

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

    Directory of Open Access Journals (Sweden)

    M. Sekuli?

    2010-10-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

  6. Tunnelling effect enhanced by lattice screening as main cold fusion mechanism: An brief theoretical overview

    International Nuclear Information System (INIS)

    In this paper are illustrated the main features of tunneling traveling between two deuterons within a lattice. Considering the screening effect due lattice electrons we compare the d-d fusion rate evaluated from different authors assuming different screening efficiency and different d-d potentials. Then, we propose a effective potential which describe very well the attractive contribute due to plasmon exchange between two deuterons and by means of it we will compute the d-d fusion rates for different energy values. Finally the good agreement between theoretical and experimental results proves the reality of cold fusion phenomena and the reliability of our model

  7. An Ekman Transport Mechanism for the Atlantic Multidecadal Oscillation

    Science.gov (United States)

    Pratt, V. R.

    2014-12-01

    Multidecadal global climate since 1850 consists of the expected greenhouse warming and two cycles of a fluctuation commonly associated with the AMO that so far has not been satisfactorily explained. In GC53C-06 at AGUFM13 we compared land and sea temperatures during the global warmings of 1860-1880 and 1910-1940 and inferred that heat flowed sea to land, ruling out aerosol-based external forcings and indicating an internal source such as an instability in the AMOC. Length of day during the past century has varied by ~4 ms inversely with the AMO. Noting that the ocean floor is some five times thinner than the continental crust, we propose here that Earth's rotation regulates heat flux through the ocean floor. One mechanism for this is centrifugal force pulling plates apart, particularly along the Mid-Atlantic Ridge and around the Ring of Fire, increasing flux by an amount that would easily pass unnoticed in the 1930s. Another mechanism, perhaps less strong, is stress from rotational acceleration increasing the thermal conductivity of the young rocks comprising the ocean floor. A difficulty is that the ocean would absorb the fluctuations before reaching the surface. We overcome this difficulty via Ekman transport. This mechanism acts on a 50 m deep layer at the surface to drive it polewards from the ITCZ at 3 cm/sec or 1000 km/yr, orders of magnitude faster than the MOC which therefore cannot interfere. This creates a suction at the ITCZ and a downwards pumping action at 30°. In order to close this cycle there must be a flow equal in volume rate towards the ITCZ at depth. We propose that the heat entering the ocean bottom between 30° S and 30° N enters these two "Ekman cells", which carry it to the surface via the ITCZ. To evaluate feasibility, take the area of the participating 50m surface layer to be 1014 m2, making the volume of the top and bottom layers 1016 m3. Only 1022 J of heat is needed to warm or cool this by 1/3.85 = 0.26 °C. Over the 30 years 1910-1940 or 109seconds, this represents 10 TW of warming, raising Earth's total geothermal release from a cold 40 TW to 50 TW (80 to 100 mW/m2), subsequently declining to today's 45-47 TW, an entirely feasible amount. An additional 10 TW to warm the whole OML is still plausible. If this mechanism is correct, varying LOD would forecast varying AMO several years in advance.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-05-15

    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)

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

    International Nuclear Information System (INIS)

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

  10. Fluka and thermo-mechanical studies for the CLIC main dump

    CERN Document Server

    Mereghetti, Alessio; Vlachoudis, Vasilis

    2011-01-01

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

  11. Supernova explosion mechanism taking into account large-scale convection and neutrino transport

    Science.gov (United States)

    Aksenov, A. G.; Chechetkin, V. M.

    2014-07-01

    Two types of supernovae are considered: thermonuclear supernovae, whose explosions are due to thermonuclear energy, and core-collapse supernovae, whose explosions are due to the gravitational energy of collapsing stars released in the form of neutrinos. Numerical models of supernovae are discussed. Themain problem in devising supernova explosion mechanisms is producing the energy required to disperse the envelope. In theoretical models, it is necessary to solve multi-dimensional problems involving complex physics (3D gas dynamics, neutrino transport, large-scale convective instability, and other important physical processes). In recent years, the development of large-scale convection during supernova explosions has been reconsidered. Self-consistent problems problems in three-dimensional, gas-dynamical instability have been considered. Two-dimensional gas-dynamical calculations taking into account neutrino absorption in the envelope have been performed. The spherically symmetric collapse and neutrino transport were calculated including all reactions, leading to a new understanding of possible paths for the development of supernova theory. The main emphasis is placed on the neutrino transport and the basis for promising multidimensional models taking into account large-scale convective instability.

  12. The transport mechanism DC arcs in advanced spectroanalysis

    International Nuclear Information System (INIS)

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

  13. Mechanical transport and porous media equivalence in anisotropic fracture networks

    International Nuclear Information System (INIS)

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

  14. Mechanical manipulations on electronic transport of graphene nanoribbons.

    Science.gov (United States)

    Wang, Jing; Zhang, Guiping; Ye, Fei; Wang, Xiaoqun

    2015-06-10

    We study the effects of uniaxial strains on the transport properties of graphene nanoribbons (GNRs) connected with two metallic leads in heterojunctions, using the transfer matrix method. Two typical GNRs with zigzag and armchair boundaries are considered and the tension is applied either parallel or perpendicular to the ribbon axis. It turns out that the electron-hole symmetry is missing in the gate voltage dependence of the conductance data of the armchair GNRs, while it persists in the zigzag ribbons under any strains. For an armchair GNR with a vertical tension applied, a sharp drop of conductance is found near the critical value of the strain inducing a quantum phase transition, which allows one to determine the critical strain accurately via measuring the conductance. In the zigzag ribbon, there exists a range of gate voltage around zero, where the conductance is insensitive to the small horizontal strains. The band structures and low-energy properties are calculated to elucidate the mechanism on the strain effects in GNRs. We expect that our results can be useful in developing graphene-based strain sensors. PMID:25985040

  15. Mechanical manipulations on electronic transport of graphene nanoribbons

    Science.gov (United States)

    Wang, Jing; Zhang, Guiping; Ye, Fei; Wang, Xiaoqun

    2015-06-01

    We study the effects of uniaxial strains on the transport properties of graphene nanoribbons (GNRs) connected with two metallic leads in heterojunctions, using the transfer matrix method. Two typical GNRs with zigzag and armchair boundaries are considered and the tension is applied either parallel or perpendicular to the ribbon axis. It turns out that the electron–hole symmetry is missing in the gate voltage dependence of the conductance data of the armchair GNRs, while it persists in the zigzag ribbons under any strains. For an armchair GNR with a vertical tension applied, a sharp drop of conductance is found near the critical value of the strain inducing a quantum phase transition, which allows one to determine the critical strain accurately via measuring the conductance. In the zigzag ribbon, there exists a range of gate voltage around zero, where the conductance is insensitive to the small horizontal strains. The band structures and low-energy properties are calculated to elucidate the mechanism on the strain effects in GNRs. We expect that our results can be useful in developing graphene-based strain sensors.

  16. Mechanical transport and porous media equivalence in anisotropic fracture networks

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Bair, E. K.

    1986-01-01

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

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

    Science.gov (United States)

    Lucy R. Forrest (Max Planck Institute for Biophysics)

    2009-12-01

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

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

    OpenAIRE

    Forrest, Lucy R.; Rudnick, Gary

    2009-01-01

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

  20. The molecular mechanism of ion-dependent gating in secondary transporters.

    Science.gov (United States)

    Zhao, Chunfeng; Noskov, Sergei Yu

    2013-10-01

    LeuT-like fold Na-dependent secondary active transporters form a large family of integral membrane proteins that transport various substrates against their concentration gradient across lipid membranes, using the free energy stored in the downhill concentration gradient of sodium ions. These transporters play an active role in synaptic transmission, the delivery of key nutrients, and the maintenance of osmotic pressure inside the cell. It is generally believed that binding of an ion and/or a substrate drives the conformational dynamics of the transporter. However, the exact mechanism for converting ion binding into useful work has yet to be established. Using a multi-dimensional path sampling (string-method) followed by all-atom free energy simulations, we established the principal thermodynamic and kinetic components governing the ion-dependent conformational dynamics of a LeuT-like fold transporter, the sodium/benzyl-hydantoin symporter Mhp1, for an entire conformational cycle. We found that inward-facing and outward-facing states of Mhp1 display nearly the same free energies with an ion absent from the Na2 site conserved across the LeuT-like fold transporters. The barrier separating an apo-state from inward-facing or outward-facing states of the transporter is very low, suggesting stochastic gating in the absence of ion/substrate bound. In contrast, the binding of a Na2 ion shifts the free energy stabilizing the outward-facing state and promoting substrate binding. Our results indicate that ion binding to the Na2 site may also play a key role in the intracellular thin gate dynamics modulation by altering its interactions with the transmembrane helix 5 (TM5). The Potential of Mean Force (PMF) computations for a substrate entrance displays two energy minima that correspond to the locations of the main binding site S1 and proposed allosteric S2 binding site. However, it was found that substrate's binds to the site S1 ?5 kcal/mol more favorable than that to the site S2 for all studied bound combinations of ions and a substrate. PMID:24204233

  1. Center for low-gravity fluid mechanics and transport phenomena

    Science.gov (United States)

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

    1991-01-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

  3. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    Science.gov (United States)

    Ren, Jian; Yan, Dawei; Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng

    2015-04-01

    Lattice-matched Pt/Au-In0.17Al0.83N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  4. Electrolytes and sodium transport mechanism in diabetes mellitus.

    Science.gov (United States)

    Shahid, Syed Mohammad; Rafique, Roomana; Mahboob, Tabassum

    2005-04-01

    The metabolic derangements and disturbances and their consequences in diabetes mellitus are well known more or less in details too. However, knowledge on the diabetic disorders in membrane functions and transport mechanisms is limited which is an essential factor in progression of the disease. Serum electrolytes were measured by flame photometer (Corning 410) and spectrophotometer (Spectro SC) in 60 diabetic patients with stable glycemic control (aged 38 +/- 2.5 years) and in 60 age-matched normal subjects with no known history of hyperglycemia as control. Erythrocytes were isolated from samples, washed and used for the estimation of sodium and potassium concentrations using flame photometer. Erythrocyte membranes were prepared for the estimation of Na+-K+-ATPase activity in terms of inorganic phosphate released/mg protein/hour. Na+-K+-ATPase activity, Intra-erythrocyte potassium and serum magnesium levels were significantly low in diabetic patients than in the controls. Serum and intra-erythrocyte sodium and serum potassium levels were increased significantly in patients as compared to control subjects. A significant effect of sex and interaction was observed on serum sodium, potassium and magnesium. A significant effect of sex, disease and interaction on red cell sodium, potassium and Na+-K+-ATPase activity was observed in male and female subjects. Na+-K+-ATPase dysfunction and changes in intra-erythrocyte and serum sodium, potassium and magnesium induced by diabetes may be implicated in the pathogenesis of neuropathy, nephropathy and vascular diseases in humans. It is suggested that male diabetic patients are at high risk of diabetic complications than females. PMID:16431390

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Ilchenko Svetlana V.

    2012-01-01

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

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

    OpenAIRE

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

    2013-01-01

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

  8. CO2-ECBM related coupled physical and mechanical transport processes

    Science.gov (United States)

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

    2013-04-01

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

  9. 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)

  10. FEATURES FOR TRANSPORT AND AIR MECHANICAL SYSTEMS OF DANGEROUS GOODS

    Directory of Open Access Journals (Sweden)

    Eugen Dumitru BUSA

    2012-05-01

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

  11. Basic mechanisms for recognition and transport of synaptic cargos

    OpenAIRE

    Schlager Max A; Hoogenraad Casper C

    2009-01-01

    Abstract Synaptic cargo trafficking is essential for synapse formation, function and plasticity. In order to transport synaptic cargo, such as synaptic vesicle precursors, mitochondria, neurotransmitter receptors and signaling proteins to their site of action, neurons make use of molecular motor proteins. These motors operate on the microtubule and actin cytoskeleton and are highly regulated so that different cargos can be transported to distinct synaptic specializations at both pre- and post...

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

    Science.gov (United States)

    Scully, Shawn Ryan

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

  13. Glutamate forward and reverse transport: From molecular mechanism to transporter-mediated release after ischemia

    OpenAIRE

    Grewer, Christof; Gameiro, Armanda; Zhang, Zhou; Tao, Zhen; Braams, Simono; Rauen, Thomas

    2008-01-01

    Glutamate transporters remove the excitatory neurotransmitter glutamate from the extracellular space after neurotransmission is complete, by taking glutamate up into neurons and glia cells. As thermodynamic machines, these transporters can also run in reverse, releasing glutamate into the extracellular space. Because glutamate is excitotoxic, this transporter-mediated release is detrimental to the health of neurons and axons, and it, thus, contributes to the brain damage that typically follow...

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

    OpenAIRE

    Thiele, Uwe; John, Karin

    2010-01-01

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

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

    DEFF Research Database (Denmark)

    Zeuthen, Thomas; Alsterfjord, Magnus

    2013-01-01

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

  16. Differences in acidity of apples are probably mainly caused by a malic acid transporter gene on LG16

    OpenAIRE

    S.A. Khan; Beekwilder, J.; Schaart, J.G.; Mumm, R.; Soriano, J. M.; Jacobsen, E.; Schouten, H J

    2013-01-01

    Acidity has profound effects on the taste of apples (Malus × domestica). Malic acid is the predominant organic acid in apples. Differences in malic acid content are caused by differences in accumulation of malic acid in the vacuole. This accumulation may be caused by a gene that is responsible for transport of malic acid from the cytosol into the vacuole. Here, we provide evidence that a malic acid transporter gene at the top of chromosome 16 caused significant differences in malic acid conce...

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

    OpenAIRE

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

    2009-01-01

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

  18. Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

    CERN Document Server

    Appert-Rolland, Cecile; Santen, Ludger

    2015-01-01

    Cells are strongly out-of-equilibrium systems driven by continuous energy supply. They carry out many vital functions requiring active transport of various ingredients and organelles, some being small, others being large. The cytoskeleton, composed of three types of filaments, determines the shape of the cell and plays a role in cell motion. It also serves as a road network for the so-called cytoskeletal motors. These molecules can attach to a cytoskeletal filament, perform directed motion, possibly carrying along some cargo, and then detach. It is a central issue to understand how intracellular transport driven by molecular motors is regulated, in particular because its breakdown is one of the signatures of some neuronal diseases like the Alzheimer. We give a survey of the current knowledge on microtubule based intracellular transport. We first review some biological facts obtained from experiments, and present some modeling attempts based on cellular automata. We start with background knowledge on the origi...

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

    International Nuclear Information System (INIS)

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

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

    OpenAIRE

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

    2009-01-01

    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...

  1. Price Analysis of Railway Freight Transport under Marketing Mechanism

    Science.gov (United States)

    Shi, Ying; Fang, Xiaoping; Chen, Zhiya

    Regarding the problems in the reform of the railway tariff system and the pricing of the transport, by means of assaying the influence of the price elasticity on the artifice used for price, this article proposed multiple regressive model which analyzed price elasticity quantitatively. This model conclude multi-factors which influences on the price elasticity, such as the averagely railway freight charge, the averagely freight haulage of proximate supersede transportation mode, the GDP per capita in the point of origin, and a series of dummy variable which can reflect the features of some productive and consume demesne. It can calculate the price elasticity of different classes in different domains, and predict the freight traffic volume on different rate levels. It can calculate confidence-level, and evaluate the relevance of each parameter to get rid of irrelevant or little relevant variables. It supplied a good theoretical basis for directing the pricing of transport enterprises in market economic conditions, which is suitable for railway freight, passenger traffic and other transportation manner as well. SPSS (Statistical Package for the Social Science) software was used to calculate and analysis the example. This article realized the calculation by HYFX system(Ministry of Railways fund).

  2. Structure and transport mechanism of the bacterial oxalate transporter OxlT.

    Science.gov (United States)

    Hirai, Teruhisa; Subramaniam, Sriram

    2004-11-01

    Membrane proteins that belong to the major facilitator superfamily (MFS) are found in organisms across the evolutionary spectrum and mediate the transport of a variety of substrates ranging from small metabolites to neurotransmitters. The oxalate transporter (OxlT) is a representative MFS protein, and exchanges formate for oxalate across the cytoplasmic membrane of the organism Oxalobacter formigenes. Here, we present a structural model for the protein conformational changes that occur during oxalate transport by combining a three-dimensional map of the oxalate-bound, "closed" state of OxlT at 6.5 A determined by cryo-electron microscopy with a model of the "open" state of OxlT based on the atomic structures of the related transporters, glycerol-3-phosphate transporter (GlpT) and lactose permease (LacY). We demonstrate that the principal structural change associated with substrate transport is a concerted rocking movement of the two structurally similar halves of the protein relative to each other. Our structural model places two positively charged residues, Arg-272 and Lys-355 in the central cavity, suggesting that electrostatic interactions between these residues and the oxalate anion is a key step in generating the conformational change between the open and closed states of the transporter. PMID:15339805

  3. Transport mechanism of macromolecules on hydrophilic bio-polymeric matrices : diffusion of protein-based compounds from chitosan films

    OpenAIRE

    A.C. Pinheiro; Bourbon, A. I.; Vicente, A.A.; Mafalda A.C. Quintas

    2013-01-01

    The transport mechanism of protein-based bioactive compounds (a peptide fraction from whey protein concentrate, glycomacropeptide and lactoferrin), from chitosan films to liquid medium, was studied. Mathematical models were used to discuss the transport mechanism. Data from release experiments was successfully described by a model which accounts for both Fick and Case II transport – the linear superimposition model. Results show that the mechanism of transport and the effect of temperature ...

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

    Science.gov (United States)

    Thiele, Uwe; John, Karin

    2010-10-01

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

  5. Elastic tunneling charge transport mechanisms in silicon quantum dots / Si O 2 thin films and superlattices

    Science.gov (United States)

    Illera, S.; Prades, J. D.; Cirera, A.

    2015-05-01

    The role of different charge transport mechanisms in Si / Si O 2 structures has been studied. A theoretical model based on the Transfer Hamiltonian Formalism has been developed to explain experimental current trends in terms of three different elastic tunneling processes: (1) trap assisted tunneling; (2) transport through an intermediate quantum dot; and (3) direct tunneling between leads. In general, at low fields carrier transport is dominated by the quantum dots whereas, for moderate and high fields, transport through deep traps inherent to the SiO2 is the most relevant process. Besides, current trends in Si / Si O 2 superlattice structure have been properly reproduced.

  6. Benchmark calculations for mechanical stresses upon a transport cask

    International Nuclear Information System (INIS)

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

  7. Structure and Transport Mechanism of the Bacterial Oxalate Transporter OxlT

    OpenAIRE

    Hirai, Teruhisa; Subramaniam, Sriram

    2004-01-01

    Membrane proteins that belong to the major facilitator superfamily (MFS) are found in organisms across the evolutionary spectrum and mediate the transport of a variety of substrates ranging from small metabolites to neurotransmitters. The oxalate transporter (OxlT) is a representative MFS protein, and exchanges formate for oxalate across the cytoplasmic membrane of the organism Oxalobacter formigenes. Here, we present a structural model for the protein conformational changes that occur during...

  8. Modeling Transport and Flow Regulatory Mechanisms of the Kidney

    OpenAIRE

    Layton, Anita T.

    2012-01-01

    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 mechan...

  9. Analysis of mechanical systems with transversal vibrations in transportation

    OpenAIRE

    Buchacz, A.; Z?o??kiewski, S.

    2008-01-01

    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...

  10. Salmonella infection inhibits intestinal biotin transport: cellular and molecular mechanisms.

    Science.gov (United States)

    Ghosal, Abhisek; Jellbauer, Stefan; Kapadia, Rubina; Raffatellu, Manuela; Said, Hamid M

    2015-07-15

    Infection with the nontyphoidal Salmonella is a common cause of food-borne disease that leads to acute gastroenteritis/diarrhea. Severe/prolonged cases of Salmonella infection could also impact host nutritional status, but little is known about its effect on intestinal absorption of vitamins, including biotin. We examined the effect of Salmonella enterica serovar Typhimurium (S. typhimurium) infection on intestinal biotin uptake using in vivo (streptomycin-pretreated mice) and in vitro [mouse (YAMC) and human (NCM460) colonic epithelial cells, and human intestinal epithelial Caco-2 cells] models. The results showed that infecting mice with wild-type S. typhimurium, but not with its nonpathogenic isogenic invA spiB mutant, leads to a significant inhibition in jejunal/colonic biotin uptake and in level of expression of the biotin transporter, sodium-dependent multivitamin transporter. In contrast, infecting YAMC, NCM460, and Caco-2 cells with S. typhimurium did not affect biotin uptake. These findings suggest that the effect of S. typhimurium infection is indirect and is likely mediated by proinflammatory cytokines, the levels of which were markedly induced in the intestine of S. typhimurium-infected mice. Consistent with this hypothesis, exposure of NCM460 cells to the proinflammatory cytokines TNF-? and IFN-? led to a significant inhibition of biotin uptake, sodium-dependent multivitamin transporter expression, and activity of the SLC5A6 promoter. The latter effects appear to be mediated, at least in part, via the NF-?B signaling pathway. These results demonstrate that S. typhimurium infection inhibits intestinal biotin uptake, and that the inhibition is mediated via the action of proinflammatory cytokines. PMID:25999427

  11. Decoupling of mass transport mechanisms in the stagewise swelling of multiple emulsions.

    Science.gov (United States)

    Bahtz, Jana; Gunes, Deniz Z; Hughes, Eric; Pokorny, Lea; Riesch, Francesca; Syrbe, Axel; Fischer, Peter; Windhab, Erich J

    2015-05-19

    This contribution reports on the mass transport kinetics of osmotically imbalanced water-in-oil-in-water (W1/O/W2) emulsions. Although frequently studied, the control of mass transport in W1/O/W2 emulsions is still challenging. We describe a microfluidics-based method to systematically investigate the impact of various parameters, such as osmotic pressure gradient, oil phase viscosity, and temperature, on the mass transport. Combined with optical microscopy analyses, we are able to identify and decouple the various mechanisms, which control the dynamic droplet size of osmotically imbalanced W1/O/W2 emulsions. So, swelling kinetics curves with a very high accuracy are generated, giving a basis for quantifying the kinetic aspects of transport. Two sequential swelling stages, i.e., a lag stage and an osmotically dominated stage, with different mass transport mechanisms are identified. The determination and interpretation of the different stages are the prerequisite to control and trigger the swelling process. We show evidence that both mass transport mechanisms can be decoupled from each other. Rapid osmotically driven mass transport only takes place in a second stage induced by structural changes of the oil phase in a lag stage, which allow an osmotic exchange between both water phases. Such structural changes are strongly facilitated by spontaneous water-in-oil emulsification. The duration of the lag stage is pressure-independent but significantly influenced by the oil phase viscosity and temperature. PMID:25919942

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

    Directory of Open Access Journals (Sweden)

    James Baker-Jarvis

    2009-11-01

    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.

  13. Mechanical properties used for the qualification of transport casks

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-01-01

    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.

  15. Turbulence elasticity—A new mechanism for transport barrier dynamics

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-15

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

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

    Science.gov (United States)

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

    2009-04-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

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

    International Nuclear Information System (INIS)

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

  19. Tape-transport mechanisms of systems for image processing from bubble chambers

    International Nuclear Information System (INIS)

    Main requirements are formulated for film traction mechanisms of systems for developing big bubble chamber pictures. An account of known film-traction mechanisms and methods of controlling film movement is given. Rapid operation and degree of automation are considered to be the main characteristics of film-traction mechanisms. The best of known mechanisms provide film rewinding speed from 2 to 5 m/s, a picture therewith is positioned in a window with an accuracy of +- 0.5 mm, or better. Depending on a number of film windows, all the film-traction mechanisms may be classified into two types. The first type includes mechanisms with two or more film windows; mechanisms with one window may be referred to the second type. Consideration is given to working out a universal module of a film-traction mechanism, based on the second type

  20. Structure and permeation mechanism of a mammalian urea transporter

    Science.gov (United States)

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

    2012-01-01

    As an adaptation to infrequent access to water, terrestrial mammals produce urine that is hyperosmotic to plasma. To prevent osmotic diuresis by the large quantity of urea generated by protein catabolism, the kidney epithelia contain facilitative urea transporters (UTs) that allow rapid equilibration between the urinary space and the hyperosmotic interstitium. Here we report the first X-ray crystal structure of a mammalian UT, UT-B, at a resolution of 2.36 ?. UT-B is a homotrimer and each protomer contains a urea conduction pore with a narrow selectivity filter. Structural analyses and molecular dynamics simulations showed that the selectivity filter has two urea binding sites separated by an approximately 5.0 kcal/mol energy barrier. Functional studies showed that the rate of urea conduction in UT-B is increased by hypoosmotic stress, and that the site of osmoregulation coincides with the location of the energy barrier. PMID:22733730

  1. Kinetics and mechanism of proton transport across membrane nanopores

    OpenAIRE

    Dellago, Christoph; Hummer, Gerhard

    2006-01-01

    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 ...

  2. Longitudinal vibrations of mechanical systems with the transportation effect

    OpenAIRE

    Buchacz, A.; Z?o??kiewski, S.

    2009-01-01

    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 moti...

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    C.-Y. Lin

    2009-10-01

    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.

  5. Kinetics and mechanism of proton transport across membrane nanopores

    CERN Document Server

    Dellago, C; Dellago, Christoph; Hummer, Gerhard

    2006-01-01

    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.

  6. A structural mechanism for calcium transporter headpiece closure.

    Science.gov (United States)

    Smolin, Nikolai; Robia, Seth L

    2015-01-29

    To characterize the conformational dynamics of sarcoplasmic reticulum (SR) calcium pump (SERCA) we performed molecular dynamics simulations beginning with several different high-resolution structures. We quantified differences in structural disorder and dynamics for an open conformation of SERCA versus closed structures and observed that dynamic motions of SERCA cytoplasmic domains decreased with decreasing domain-domain separation distance. The results are useful for interpretation of recent intramolecular Förster resonance energy transfer (FRET) distance measurements obtained for SERCA fused to fluorescent protein tags. Those previous physical measurements revealed several discrete structural substates and suggested open conformations of SERCA are more dynamic than compact conformations. The present simulations support this hypothesis and provide additional details of SERCA molecular mechanisms. Specifically, all-atoms simulations revealed large-scale translational and rotational motions of the SERCA N-domain relative to the A- and P-domains during the transition from an open to a closed headpiece conformation over the course of a 400 ns trajectory. The open-to-closed structural transition was accompanied by a disorder-to-order transition mediated by an initial interaction of an N-domain loop (N?5-?6, residues 426-436) with residues 133-139 of the A-domain. Mutation of three negatively charged N-domain loop residues abolished the disorder-to-order transition and prevented the initial domain-domain interaction and subsequent closure of the cytoplasmic headpiece. Coarse-grained molecular dynamics simulations were in harmony with all-atoms simulations and physical measurements and revealed a close communication between fluorescent protein tags and the domain to which they were fused. The data indicate that previous intramolecular FRET distance measurements report SERCA structure changes with high fidelity and suggest a structural mechanism that facilitates the closure of the SERCA cytoplasmic headpiece. PMID:25531267

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-11-01

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

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

    Science.gov (United States)

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

    2014-08-01

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

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

    International Nuclear Information System (INIS)

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

  10. 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)

    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

    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.)

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

    OpenAIRE

    González-Guerrero, Manuel; Argüello, José M

    2008-01-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    OpenAIRE

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

    2012-01-01

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

  14. Long-term carbon transport and fuel retention in gaps of the main toroidal limiter in TEXTOR

    International Nuclear Information System (INIS)

    The 1.1–1.5 mm wide gaps between tiles of the main toroidal belt limiter in TEXTOR were utilized to study the long-term impurity deposition and fuel retention in gaps. The tiles were exposed during a full tokamak campaign of 9365 s of plasma to various discharge conditions and wall conditioning, accumulating of up to 30 ?m thick layers at the gap entrance. It was found that (i) gaps trap impurities twice as efficient as the top surface, (ii) the deposition in the toroidal gaps is twice as high as in the poloidal, (iii) carbon deposition decays with a fall-off length of about 0.7 mm towards the gap bottom, (iv) deposition on the bottom is significantly higher than on the adjacent side walls of gaps, and (v) the amount of deuterium scales with the amount of carbon with D/C varying from 3% to 30% depending on the surface temperature

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

    Science.gov (United States)

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

    2012-12-01

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

  16. 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

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

    Science.gov (United States)

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

    2013-02-01

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

  18. Effects of temperature and electric field on the transport mechanisms in the porous microstructure

    Science.gov (United States)

    Koseoglu, K.; Karaduman, I.; Demir, M.; Ozer, M.; Acar, S.; Salamov, B. G.

    2015-05-01

    The electrical characterizations of nanoporous zeolite and transport mechanisms were studied for the first time in a wide operating temperature range (28-800 K) and electric field strength (60-200 kV/cm) at room temperature. The influence of temperature, electric field and cell types on the dc conductivity was described. The resistivity decreased from 2.34 × 1010 to 2.17 × 108 ? m whiles the temperature increased from 28 to 800 K which is associated with the ionic mobility. The existence of water in the channels and pores is the decisive parameter in the ionic transport and it depends strongly on the electric field. When a high voltage was applied to gas discharge gap and porous structure, ionization phenomena increased. In this stage, electronic conduction also contributed to zeolite dc conduction. Therefore, the ionic and electronic transport mechanisms and their interactions are essential in enhancing applications in microdischarge devices with nanoporous zeolite cathodes.

  19. Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs

    International Nuclear Information System (INIS)

    Using self-consistent calculations of million-atom Schrödinger-Poisson equations, we investigate the I–V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor held effect transistors (MOSFET) based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I–V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8 mA/?m when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage Vt. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al

  20. 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)

    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

    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

  1. 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

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

    Directory of Open Access Journals (Sweden)

    Yerlan MYRZAKHMETOV

    2012-01-01

    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.

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

    OpenAIRE

    Yerlan MYRZAKHMETOV; Aleksander S?ADKOWSKI

    2012-01-01

    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.

  4. Reform of refined oil product pricing mechanism and energy rebound effect for passenger transportation in China

    International Nuclear Information System (INIS)

    Improving energy efficiency is the primary method adopted by the Chinese government in an effort to achieve energy conservation target in the transport sector. However, the offsetting effect of energy rebound would greatly reduce its real energy-saving potentials. We set up a Linear Approximation of the Almost Ideal Demand System Model (LA-AIDS model) to estimate the rebound effect for passenger transportation in China. Real energy conservation effect of improving energy efficiency can also be obtained in the process. The result shows that the rebound effect is approximately 107.2%. This figure signifies the existence of ‘backfire effect’, indicating that efficiency improvement in practice does not always lead to energy-saving. We conclude that one important factor leading to the rebound effect, is the refined oil pricing mechanism. China's refined oil pricing mechanism has been subjected to criticism in recent years. The results of simulation analysis show that the rebound could be reduced to approximately 90.7% if the refined oil pricing mechanism is reformed. In this regard, we suggest further reforms in the current refined oil pricing mechanism. - Highlights: ? We set up the LA-AIDS model to estimate traffic service demand for urban residents. ? The size of the rebound effect for passenger transportation in China is evaluated. ? The rebound effect for passenger transportation in China is 107.2%. ? Reform of oil pricing could reduced the rebound to 90.7%. ? Reform of oil pricing might be an effective method for mitigating rebound effect

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

    International Nuclear Information System (INIS)

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

  6. A fully resolved active musculo-mechanical model for esophageal transport

    CERN Document Server

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

    2015-01-01

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

  7. Seat Belt Usage in Injured Car Occupants: Injury Patterns, Severity and Outcome After Two Main Car Accident Mechanisms in Kashan, Iran, 2012

    Science.gov (United States)

    Mohammadzadeh, Mahdi; Paravar, Mohammad; Mirzadeh, Azadeh Sadat; Mohammadzadeh, Javad; Mahdian, Soroush

    2015-01-01

    Background: Road traffic accidents (RTAs) are the main public health problems in Iran. The seat belts, which are vehicle safety devices, are imperative to reduce the risk of severe injuries and mortality. Objectives: The aim of the study was to evaluate injury patterns, severity and outcome among belted and unbelted car occupants who were injured in car accidents. Patients and Methods: This cross-sectional prospective study was performed on all car occupants injured in RTAs (n = 822) who were transported to hospital and hospitalized for more than 24 hours from March 2012 to March 2013. Demographic profile of the patients, including age, gender, position in the vehicle, the use of seat belts, type of car crashes, injured body regions, revised trauma score (RTS), Glasgow coma score (GCS), duration of hospital stay and mortality rate were analyzed by descriptive analysis, chi-square and independent t-test. P head, abdomen and multiple injuries (P = 0.01, P = 0.01 and P = 0.009, respectively). Also, these patients had significantly lower GCS and elongated hospitalization and higher death rate (P = 0.001, P = 0.001 and P = 0.05, respectively). Tendency of severe head trauma and low RTS and death were increased in unbelted occupants in car rollover accident mechanisms (P = 0.001, P = 0.01 and P = 0.008, respectively). Conclusions: During car crashes, especially car rollover, unbelted occupants are more likely to sustain multiple severe injuries and death. Law enforcement of the seat belt usage for all occupants (front and rear seat) is obligatory to reduce severe injuries sustained as a result of car accidents, especially in vehicles with low safety.

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

    International Nuclear Information System (INIS)

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

  9. OPTIMIZATION OF REGULATORY MECHANISMS AS A CONDITION OF COMPETITIVE TRANSPORT COMPLEX

    Directory of Open Access Journals (Sweden)

    S. Ilchenko

    2012-06-01

    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.

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

    Science.gov (United States)

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

    2013-12-01

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

  11. Structure and mechanism of ATP-dependent phospholipid transporters : Biochim Biophys Acta

    DEFF Research Database (Denmark)

    Lopez-Marques, R. L.; Poulsen, L. R.

    2014-01-01

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

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

    Science.gov (United States)

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

    2013-05-01

    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

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

    Science.gov (United States)

    Farmer, James R.

    1986-01-01

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

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

    Science.gov (United States)

    Agar, Ertan

    Vanadium redox flow batteries (VRFBs) are an emerging energy storage technology that offers unique advantages for grid-scale energy storage due to their flexible design and decoupled power/energy feature. Despite their popularity, a series of technical challenges hinder their widespread implementation. Among these, capacity loss (i.e., loss of energy storage capability) due to the undesired species crossover across the membrane has been identified as the key issue limiting the longevity of these systems. This issue is primarily governed by the properties of the membrane and can be mitigated by using proper membrane architectures with desired features. Presently, identifying proper membrane architectures for VRFB systems is hampered by the lack of a fundamental understanding of the nature of species transport mechanisms and how they are related to the membrane properties and key operating conditions. This Ph.D. study seeks to address this critical challenge by exploring the fundamental mechanisms responsible for species transport within the membrane. The overall objective of this dissertation study is to establish a fundamental understanding of the multi-ionic transport in VRFB membranes by investigating the ionic transport mechanisms responsible for crossover, and utilize this understanding to reveal the role of membrane properties and operating conditions on the capacity loss. To achieve these goals, a combined experimental and computational study was designed. An experimentally validated, 2-D, transient VRFB model that can track the vanadium crossover and capture the related capacity loss was developed. In addition to the model, several electrochemical techniques were used to characterize different types of membrane and study the effects of various operating conditions on the species crossover. Using these computational and experimental tools, an in-depth understanding of the species transport mechanisms within the membrane and how they are related to membrane properties and operating conditions of VRFBs has been obtained. Finally, this understanding was utilized to identify effective mitigation strategies to minimize the capacity fade and improve the long-term performance of these systems.

  15. Dynamic Length-Scale Characterization and Nonequilibrium Statistical Mechanics of Transport in Open-Cell Foams

    Science.gov (United States)

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

    2009-11-01

    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.

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

    Science.gov (United States)

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

    2010-01-01

    There is a need for effective sample handling tools to deliver and sort particles for analytical instruments that are planned for use in future NASA missions. Specifically, a need exists for a compact mechanism that allows transporting and sieving particle sizes of powdered cuttings and soil grains that may be acquired by sampling tools such as a robotic scoop or drill. The required tool needs to be low mass and compact to operate from such platforms as a lander or rover. This technology also would be applicable to sample handling when transporting samples to analyzers and sorting particles by size.

  17. Transport mechanisms in doped LaMnO3: Evidence for polaron formation

    International Nuclear Information System (INIS)

    We report electrical transport experiments on the colossal magnetoresistance compound (La,Ca)MnO3 over a wide range of composition and temperature. Comparison of thermopower and electrical resistivity measurements above the metal-insulator transition indicate a transport mechanism not dominated by spin disorder, but by small polaron formation. Additionally, we find that in the high-temperature limit the thermopower corresponds to backflow of spin entropy, expected from motion of positively charged particles in a rigid S=2 system, showing a remarkable independence of S=3/2 particle density. copyright 1997 The American Physical Society

  18. Alternating-access mechanism in conformationally asymmetric trimers of the betaine transporter BetP.

    Science.gov (United States)

    Perez, Camilo; Koshy, Caroline; Yildiz, Ozkan; Ziegler, Christine

    2012-10-01

    Betaine and Na(+) symport has been extensively studied in the osmotically regulated transporter BetP from Corynebacterium glutamicum, a member of the betaine/choline/carnitine transporter family, which shares the conserved LeuT-like fold of two inverted structural repeats. BetP adjusts its transport activity by sensing the cytoplasmic K(+) concentration as a measure for hyperosmotic stress via the osmosensing carboxy-terminal domain. BetP needs to be in a trimeric state for communication between individual protomers through several intratrimeric interaction sites. Recently, crystal structures of inward-facing BetP trimers have contributed to our understanding of activity regulation on a molecular level. Here we report new crystal structures, which reveal two conformationally asymmetric BetP trimers, capturing among them three distinct transport states. We observe a total of four new conformations at once: an outward-open apo and an outward-occluded apo state, and two closed transition states--one in complex with betaine and one substrate-free. On the basis of these new structures, we identified local and global conformational changes in BetP that underlie the molecular transport mechanism, which partially resemble structural changes observed in other sodium-coupled LeuT-like fold transporters, but show differences we attribute to the osmolytic nature of betaine, the exclusive substrate specificity and the regulatory properties of BetP. PMID:22940865

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

    Science.gov (United States)

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

    2014-10-01

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

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

    Science.gov (United States)

    Liang, Qing

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

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

    International Nuclear Information System (INIS)

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

  2. Neutrino-driven supernovae Boltzmann neutrino transport and the explosion mechanism

    CERN Document Server

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

    1998-01-01

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

  3. 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.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  6. Work mechanization schemej used during the main building construction of the second phase of the Chernobylsk NPP

    International Nuclear Information System (INIS)

    The scheme of crane arrangement at different stages of the main building construction of the second phase of the Chernobylsk NPP was described. Application of this scheme allowed one to provide the ahead construction of the underground building part and to concentrate necessary number of cranes in the reactor section, due to which duration and labor content of constructional works were reduced

  7. Mechanisms of energy transport in solar flares and their associated radiation signatures

    International Nuclear Information System (INIS)

    A series of papers including theoretical modelling of energy transport mechanisms and their application to observations of solar flares in the extreme ultraviolet and X-ray region is presented. The first two papers deal with the interpretation of the hard X-ray bursts observed during large solar flares. The next two develop the theory relating to the dynamics of an electron beam injected downwards into the solar chromosphere. Then the observed EUV and X-ray bursts which occur during solar flares are interpreted. Finally, the theoretical interpretation of the strong temperature enhancements produced at great depths in solar flares is presented. It is concluded that currently accepted mechanisms of energy transport do not explain the observations and it is suggested that in situ energy release also occurs in the flare process. (U.K.)

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2004-01-01

    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 ...

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2015-02-01

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

  15. 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

  16. Intestinal absorption mechanisms of ginsenoside Rh2: stereoselectivity and involvement of ABC transporters.

    Science.gov (United States)

    Gu, Y; Wang, G-J; Wu, X-L; Zheng, Y-T; Zhang, J-W; Ai, H; Sun, J-G; Jia, Y-W

    2010-09-01

    This study investigated the absorption mechanism of ginsenoside Rh2 to clarify the reasons for its poor absorption. Transepithelial transport across Caco-2 cell monolayers, cellular uptake, and in situ rat intestinal perfusion were examined. Cellular uptake of Rh2 was linear from 1 to 50 ?M at 4°C, whereas it was saturated when the concentration exceeded 10 ?M at 37°C. At 37°C, the uptake at 10 ?M was linear in 60 min. Intracellular exposure in 240 min was 2173.70 and 979.38 ng·min/?g for S and R isomers, respectively. Transepithelial permeability of Rh2 was about 10?? to 10?? cm/s. Efflux ratios were above 1.5. Sodium dodecyl sulfate, sodium citrate, and sodium deoxycholate had no effect on Rh2 permeability. After intestinal perfusion for 3 h, 9.1% of 20(R)-Rh2 and 15.7% of 20(S)-Rh2 were absorbed. Cyclosporine, quercetin, and probenecid could improve the cellular uptake, absorptive permeability, and intestinal absorption. Carrier-mediated transport was the major absorption mechanism. Rh2 was a substrate of ABC transporters. The ABC-transporter-mediated efflux and the poor permeability were the major reasons for Rh2 poor absorption. The stereoselective absorption was significant. R isomer exhibited lower absorption profiles in all the experiments, possibly due to more potent efflux. PMID:20608841

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

    Directory of Open Access Journals (Sweden)

    P. Zunino

    2013-10-01

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

  18. Electron Transport Mechanism in GaN/AlGaN HEMT Structures

    OpenAIRE

    Go?kden, Sibel

    2003-01-01

    The electron transport mechanism in GaN/AlGaN HEMT (High Electron Mobility Transistors) structures grown with MBE on sapphire substrate was investigated by using the temperature dependence of the Hall coefficient, resistivity, carrier density and Hall mobility. Hall measurements were carried out using Van der Pauw geometry. From the LO-phonon-scattering-limited component of the mobility, we obtain LO phonon energy \\hbar w \\approx 90 meV and the momentum relaxation time of tm \\approx ...

  19. Mechanically reinforced MgB2 wires and tapes with high transport currents

    OpenAIRE

    Nast, R; Schlachter, S. I.; Zimmer, S; Reiner, H.; Goldacker, W.

    2001-01-01

    Monofilamentary MgB2-wires with a 2- or 3-component sheath containing mechanical reinforcing stainless steel (SS) were prepared and characterized. In direct contact to the superconductor Nb, Ta or Fe was used. For a selection of samples with a Fe and Fe/SS sheath, we investigated the transport critical current behaviour in magnetic fields changing systematically the geometrical shape from a round wire to a flat tape. A strong increase of the current densities in flat tapes w...

  20. Identification of P-Glycoprotein and Transport Mechanism of Paclitaxel in Syncytiotrophoblast Cells

    OpenAIRE

    Lee, Na-young; Lee, Ha-eun; Kang, Young-sook

    2014-01-01

    When chemotherapy is administered during pregnancy, it is important to consider the fetus chemotherapy exposure, because it may lead to fetal consequences. Paclitaxel has become widely used in the metastatic and adjuvant settings for woman with cancer including breast and ovarian cancer. Therefore, we attempted to clarify the transport mechanisms of paclitaxel through blood-placenta barrier using rat conditionally immortalized syncytiotrophoblast cell lines (TR-TBTs). The uptake of paclitaxel...

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

    International Nuclear Information System (INIS)

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

  2. In situ investigation of the mechanisms of the transport to tissues of polycyclic aromatic hydrocarbons adsorbed onto the root surface of Kandelia obovata seedlings.

    Science.gov (United States)

    Li, Ruilong; Zhu, Yaxian; Zhang, Yong

    2015-06-01

    A novel method for in situ determination of the polycyclic aromatic hydrocarbons (PAHs) adsorbed onto the root surface of Kandelia obovata seedlings was established using laser-induced time-resolved nanosecond fluorescence spectroscopy (LITRF). The linear dynamic ranges for the established method were 1.5-1240ng/spot for phenanthrene, 1.0-1360ng/spot for pyrene and 5.0-1220ng/spot for benzo[a]pyrene. Then, the mechanisms of PAHs transport from the Ko root surface to tissues were investigated. The three-phase model including fast, slow and very slow fractions was superior to the single or dual-phase model to describe the PAHs transport processes. Moreover, the fast fraction of PAHs transport process was mainly due to passive movement, while the slow and very slow fractions were not. Passive movement was the main process of B[a]P adsorbed onto Ko root surface transport to tissues. In addition, the extent of the PAHs transport to Ko root tissues at different salinity were evaluated. PMID:25779208

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

    Science.gov (United States)

    McNair, James N; Newbold, J Denis

    2012-05-01

    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. PMID:22281520

  4. 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)

    Nakonechnaya Darina Yu.

    2013-05-01

    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.? ?????? ??????????? ????????? ??????? ?????? ? ??????? ???????????? ???????? ? ????????? ??????? «??????-??????». ?????????? ????????????? ??????????? ??????? «??????-?????? ?????????????????? ???????????», ??????? ????????? ????????? ??????? «??????-??????» ? ??????????? ??????? ??????? ? ????????? ????? ??????. ???????????? ??????? ?????? ???????????? ? ???????????? ????????????? ?????? ??????-??????. ???????????????? ? ???????????????? ?? ???????? ??????????? ?????????? ??? ???????????? ???????????, ? ??? ?????, ????????????? ????????????? ???????, ???????? ????????: ???????? ???????????? ???????????; ??????????? ????????? ??? ?????????????; ??????? ??????? ????????????????; ??????????? ???????????? ?????????????? ???????????? ??????????? ?? ???? ????????? ???????????????????; ???????? ?????????? ?????????????????; ?????????? ??????? ????????????????; ??????? ???????????????????; ??????? ???????????? ?????????? ?????????????????; ??????? ?????????? ?????????????????; ?????????? ???????????????? ? ?????????? ??. ?????????? ? ??????? ??????????? ????? ????????????? ???????????? ????????????, ? ????? ??????? ?????? ? ??????? ??????.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  7. 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

  8. [Heavy metal absorption, transportation and accumulation mechanisms in hyperaccumulator Thlaspi caerulescens].

    Science.gov (United States)

    Liu, Geyu; Chai, Tuanyao; Sun, Tao

    2010-05-01

    Thlaspi caerulescens, the famous model plant of heavy-metal hyperaccumulator, can uptake and accumulate large amount of heavy metals in its above-ground part of the plants. However, the very low biomass in Thlaspi caerulescens makes this plant unfit for direct application in phytoremediation. In recent years, there are many reports about the physiological and molecular characterization of Thlaspi caerulescens under heavy metals stresses, including absorption, transport and intracellular detoxification processes (e.g., chelation and compartmentation). Research teams have conducted many studies of chelators in plants, such as organ acid, amino acid, phytochelatins, metallothioneins and nicotianamine, and so on. Several transport protein families, such as Zinc Regulated Protein, Cation Diffusion Facilitator, Natural Resistance and Macrophage Protein and Heavy Metal ATPase, play important role in short/long distance transport in the plant. In this review, we summarize the current knowledge of the physiological and molecular mechanisms of heavy metals accumulation in Thlaspi caerulescens, with particular emphasis on the roles of transporters and chelatins in modulating plant heave-metal-stress responses. PMID:20684297

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

    International Nuclear Information System (INIS)

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

  10. 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.)

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

    Scientific Electronic Library Online (English)

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

    2014-04-01

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

  12. 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)

    A.M.Ponomaryov

    2011-12-01

    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.

  13. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Ince, C.

    2015-06-01

    Full Text Available The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs on water transport kinetics and mechanical properties of hydrated lime (CL90 and Portland cement (PC mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.El objetivo de este artículo es investigar el papel de los materiales cementantes suplementarios (SCMs en la cinética de transporte del agua y en las propiedades mecánicas de los morteros de cal hidratada (CL90 y cemento Portland. Las propiedades de la cal hidratada son significativamente diferentes a las del cemento y por lo tanto el control de las propiedades de los morteros frescos y endurecidos es fundamental en la optimización mortero/substrato en albañilería. Los parámetros estudiados en este trabajo son a menudo las principales barreras para el uso de la cal hidratada en la práctica de la construcción. Los resultados indican que la absortividad y el tiempo necesario para deshidratar morteros de cal hidratada recién mezclados pueden ser controlados cuando el conglomerante es parcialmente remplazado por SCMs. La resistencia a compresión de los morteros CL90 aumenta sistemáticamente con el nivel de sustitución de SCM. Las imágenes microestructurales realizadas, confirman estos resultados. La posibilidad de manipular la cinética de transporte de agua y las propiedades mecánicas permite la compatibilidad entre el mortero y la unidad de sustrato en albañilería.

  14. 210Pb and 210Po as tracers of particle transport mechanisms on continental margins

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    This document presents an investigation of the safety impact resulting from mechanical- and maintenance-induced reactor coolant pump (RCP) seal failures in nuclear power plants. A data survey of the pump seal failures for existing nuclear power plants in the US from several available sources was performed. The annual frequency of pump seal failures in a nuclear power plant was estimated based on the concept of hazard rate and dependency evaluation. The conditional probability of various sizes of leak rates given seal failures was then evaluated. The safety impact of RCP seal failures, in terms of contribution to plant core-melt frequency, was also evaluated for three nuclear power plants. For leak rates below the normal makeup capacity and the impact of plant safety were discussed qualitatively, whereas for leak rates beyond the normal make up capacity, formal PRA methodologies were applied. 22 refs., 17 figs., 19 tabs

  16. Mechanism of enhanced plasma transport of vacuum arc plasma through curved magnetic ducts

    International Nuclear Information System (INIS)

    The mechanism of the enhanced transport efficiency in a vacuum arc plasma source equipped with a curved magnetic filter is investigated. The relationship between the transported ion current and the cathodic arc current is determined, and our results suggest that the outer and inner walls of the duct interact with the plasma independently. The plasma flux is composed of two components: a diffusion flux in the transverse direction due to particle collisions, and a drift flux due to the ion inertia. The inner wall of the magnetic duct sees only the diffusion flux while the outer wall receives both fluxes. Thus, applying a positive potential to the outer duct wall reflects the ions and increases the output current. Our experimental data also show that biasing both sides of the duct is more effective than biasing the outer wall alone. copyright 1999 American Vacuum Society

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

    CERN Document Server

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2015-02-01

    Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

  19. Phonon limited transport in graphene nanoribbon field effect transistors using full three dimensional quantum mechanical simulation

    Science.gov (United States)

    Akhavan, Nima Dehdashti; Jolley, Gregory; Umana-Membreno, Gilberto A.; Antoszewski, Jarek; Faraone, Lorenzo

    2012-11-01

    This paper present a study of carrier transport in graphene nanoribbon (GNR) transistors using three-dimensional quantum mechanical simulations based on a real-space approach of the non-equilibrium Green's function formalism in the ballistic and dissipative limit. The carrier transport parameters are determined in the presence of electron-phonon scattering, and its influence on carrier mobility including both optical phonons (OPs) and acoustic phonons (APs). The performances of GNR field effect transistors (GNRFETs) are investigated in detail considering the third nearest neighbour tight-binding approximation. The low-field mobility is extracted in the presence of AP and OP as a function of nanoribbon width and length, from which the diffusive/ballistic limit of operation in GNRFETs is determined.

  20. Transport mechanisms and rates for the long-lived Chernobyl deposits

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-08-01

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

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

    DEFF Research Database (Denmark)

    Liddelow, Shane A; Temple, Sally

    2012-01-01

    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.

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Jansy Passiflora Sarathy

    2012-11-01

    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.

  5. Intestinal ammonia transport in freshwater and seawater acclimated rainbow trout (Oncorhynchus mykiss): Evidence for a Na(+) coupled uptake mechanism.

    Science.gov (United States)

    Rubino, Julian G; Zimmer, Alex M; Wood, Chris M

    2015-05-01

    In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na(+) treatment indicated a Na(+) linked transport mechanism. Mucosal bumetanide (10(-4)M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4(+) substitution for K(+) on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na(+) uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na(+) and ammonia for transport. Finally, [(14)C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5mmoll(-1)) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport. PMID:25545914

  6. Lattice thermal transport through atomically defined systems in a quantum mechanical description.

    Science.gov (United States)

    Mingo, Natalio

    2007-03-01

    There are different theoretical approaches to describe lattice thermal transport through nano-sized solid structures. From those approaches, atomistic calculations represent the smallest level of description, and provide a straight route towards fully understanding the phonon transport process across nanomaterials and interfaces. Within the atomistic descriptions themselves, there are several categories: 1-``classical,'' such as molecular dynamics, 2-``semi-classical,'' such as the Boltzmann-Peierls equation, and 3-``quantum-mechanical,'' such as Green's functions techniques. In this talk we will focus on quantum mechanical effects on nanoscale thermal transport, with specific examples in nanowires, nanotubes, and molecular junctions. Thus, we will discuss specific theoretical techniques from categories 2 and 3 above. We will start from the simplest of these approaches [1], which gives a good account of experimental measurements in semiconductor nanowires. Then we will discuss the more complex problem of thermal conduction in single walled carbon nanotubes, graphene, and graphite. We will see how the character of the 3-phonon scattering process in these systems results in long phonon mean free paths and thermal conductivities [2]. Subsequent experimental results have confirmed findings from the theoretical study [3]. Then, we will discuss a newer technique, based on non-equilibrium Green's functions, that allows to study the quantum mechanical many-body problem of interacting phonons flowing through generic, atomically described, anharmonic structures [4]. This technique is applied to investigate a simple model molecular junction. We will show some strictly quantum mechanical effects that take place in the anharmonic scattering process. Finally, we will present new results on first-principles calculations of phonon conduction across nitrogen impurities in carbon nanotubes [5]. [1] N. Mingo, Phys. Rev. B 68, 113308 (2003); N. Mingo and D. A. Broido, Phys. Rev. Lett. 93, 246106 (2004). [2] N. Mingo and D. A. Broido, Nano Letters 5, 1221-1225 (2005); N. Mingo and D. A. Broido, Phys. Rev. Lett. 95, 096105 (2005). [3] C. Yu, L. Shi, Z. Yao, D. Li, A. Majumdar, Nano. Lett., Vol. 5, 1842-1846 (2005); E. Pop, D. Mann, Q. Wang, K. E. Goodson and H. Dai, Nano Letters, 6, 96 (2006). [4] N. Mingo, Phys. Rev. B, 74, 125402 (2006). [5] N. Mingo, D. A. Stewart, D. A. Broido, and D. Srivastava, Nanoscale phonon transport from First-Principles (to be published).

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

    Science.gov (United States)

    Connolly, J.; Podladchikov, Y.

    2009-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-04

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

  9. Recent fracture mechanics results from NASA research related to the aging commercial transport fleet

    Science.gov (United States)

    Harris, Charles E.

    1991-01-01

    NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development to predict the fatigue crack growth in complex built-up shell structures. Innovative nondestructive examination technologies are also under development to provide large area inspection capability to detect corrosion, disbonds, and fatigue cracks. Recent fracture mechanics results applicable to predicting the growth of cracks initiating at the rivets of fuselage splice joints are reviewed.

  10. 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)

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

    2009-07-15

    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)

  11. Low temperature electron transport spectroscopy of mechanically templated carbon nanotube single electron transistors

    Science.gov (United States)

    Stokes, Paul; Islam, Muhammad R.; Khondaker, Saiful I.

    2013-08-01

    We report electronic transport investigations of mechanically templated carbon nanotube single electron transistors (SETs). The devices were fabricated on a Si/SiO2 substrate by controllably placing individual single walled carbon nanotubes (SWNTs) between the source and drain electrodes via dielectrophoresis with a 100 nm wide local Al/Al2O3 bottom gate in the middle. From the low temperature electronic transport measurements, we show that a quantum dot is formed whose charging energy can be tuned from 10 to 90 meV by varying both the local gate and Si backgate. The temperature dependent measurements show that the Coulomb oscillations persist up to 250 K. The transport properties can be explained by a simple potential configuration, which suggests that two tunnel barriers are formed due to the bending of the SWNT at the local gate edges and that the size of the dot and tunnel barrier transparency can be tuned by the gates allowing the operation of SET in a wide temperature range and thereby realizing a controllable and tunable SET. Our simple fabrication technique and its tunability over a large temperature range could facilitate large scale fabrication of SET for practical applications.

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

    Science.gov (United States)

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

    2014-10-14

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

  13. Evaluation of the film formation and the charge transport mechanism of indium tin oxide nanoparticle films

    International Nuclear Information System (INIS)

    The structure formation and charge transfer of thin nanoparticulate indium tin oxide (ITO) films prepared by dip-coating was studied as a function of stabilizer before and after annealing at different temperatures. The analysis of the film structure by optical methods revealed that it is a function of the stability. Suspensions containing an optimum stabilizer concentration of 0.1 mol/l resulted in densely packed films with a peak specific conductivity of 8.3 S cm-1 after annealing at 550 oC for 1 h in air and 121 S cm-1 after annealing in forming gas at 250 oC for 1 h, respectively. Furthermore, for the densely packed films fluctuation-induced tunnelling was found to be the dominant charge transport mechanism, whereas for the low density films a thermally activated charge transport was observed. That the films of maximum density showed a metallic charge transport behaviour at temperatures above 300 K indicated the optimal contact between ITO particles had been achieved.

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2011-12-01

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

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

    Directory of Open Access Journals (Sweden)

    B. Guenet

    2013-04-01

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

  17. The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes

    Science.gov (United States)

    Shi, Yanuo; Bork, Alexander Hansen; Schweiger, Sebastian; Rupp, Jennifer Lilia Marguerite

    2015-07-01

    Understanding `electro-chemo-mechanics’ in oxygen ion conducting membranes represents a foundational step towards new energy devices such as micro fuel cells and oxygen or fuel separation membranes. For ionic transport in macro crystalline electrolytes, doping is conventionally used to affect oxygen ionic association/migration energies. Recently, tuning ionic transport in films through lattice strain conveyed by substrates or heterostructures has generated much interest. However, reliable manipulation of strain states to twist the ionic conduction in real micro energy devices remains intractable. Here, we demonstrate that the oxygen ionic conductivity clearly correlates with the compressive strain energy acting on the near order of the electrolyte lattices by comparing thin-film ceria-based membrane devices against substrate-supported flat structures. It is possible to capitalize on this phenomenon with a smart choice of strain patterns achieved through microelectrode design. We highlight the importance of electro-chemo-mechanics in the electrolyte material for the next generation of solid-state energy conversion microdevices.

  18. Fractional occurrence of defects in membranes and mechanically driven interleaflet phospholipid transport.

    Science.gov (United States)

    Raphael, R M; Waugh, R E; Svetina, S; Zeks, B

    2001-11-01

    The picture of biological membranes as uniform, homogeneous bileaflet structures has been revised in recent times due to the growing recognition that these structures can undergo significant fluctuations both in local curvature and in thickness. In particular, evidence has been obtained that a temporary, localized disordering of the lipid bilayer structure (defects) may serve as a principal pathway for movement of lipid molecules from one leaflet of the membrane to the other. How frequently these defects occur and how long they remain open are important unresolved questions. In this report, we calculate the rate of molecular transport through a transient defect in the membrane and compare this result to measurements of the net transbilayer flux of lipid molecules measured in an experiment in which the lipid flux is driven by differences between the mechanical stress in the two leaflets of the membrane bilayer. Based on this comparison, we estimate the frequency of defect occurrence in the membrane. The occurrence of defects is rare: the probability of finding a defect in 1.0 microm2 of a lecithin membrane is estimated to be approximately 6.0x10(-6). Based on this fractional occurrence of defects, the free energy of defect formation is estimated to be approximately 1.0x10(-19) J. The calculations provide support for a model in which interleaflet transport in membranes is accelerated by mechanically driven lipid flow. PMID:11735974

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-08-15

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

  20. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    Science.gov (United States)

    Altuntas, Halit; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi

    2015-04-01

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2-21.5 MV/m), Schottky emission (23.6-39.5 MV/m), Frenkel-Poole emission (63.8-211.8 MV/m), trap-assisted tunneling (226-280 MV/m), and Fowler-Nordheim tunneling (290-447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-04-01

    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.

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

    Science.gov (United States)

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

    1988-06-01

    The design of a Lunar Bulk Material Transport Vehicle (LBMTV) is discussed. Goals set in the project include a payload of 50 cubic feet of lunar soil with a lunar of approximately 800 moon-pounds, a speed of 15 mph, and the ability to handle a grade of 20 percent. Thermal control, an articulated steering mechanism, a dump mechanism, a self-righting mechanism, viable power sources, and a probable control panel are analyzed. The thermal control system involves the use of small strip heaters to heat the housing of electronic equipment in the absence of sufficient solar radiation and multi-layer insulation during periods of intense solar radiation. The entire system uses only 10 W and weighs about 60 pounds, or 10 moon-pounds. The steering mechanism is an articulated steering joint at the center of the vehicle. It utilizes two actuators and yields a turning radius of 10.3 feet. The dump mechanism rotates the bulk material container through an angle of 100 degree using one actuator. The self-righting mechanism consists of two four bar linkages, each of which is powered by the same size actuator as the other linkages. The LBMTV is powered by rechargeable batteries. A running time of at least two hours is attained under a worst case analysis. The weight of the batteries is 100 pounds. A control panel consisting of feedback and control instruments is described. The panel includes all critical information necessary to control the vehicle remotely. The LBMTV is capable of handling many types of cargo. It is able to interface with many types of removable bulk material containers. These containers are made to interface with the three-legged walker, SKITTER. The overall vehicle is about 15 feet in length and has a weight of about 1000 pounds, or 170 lunar pounds.

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

    Science.gov (United States)

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

    2014-10-01

    Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem. PMID:25375520

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

    DEFF Research Database (Denmark)

    Dölger, Julia; Rademaker, Hanna

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-10-01

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

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

    DEFF Research Database (Denmark)

    Dölger, Julia; Rademaker, Hanna

    2014-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  9. Main Facilities

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Isabella Van Rooyen

    2014-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-30

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Monika S?omi?ska-Wojewódzka

    2013-04-01

    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.

  15. 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.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

    Hong, J; Hong, Jongbae; Woo, Wonmyung

    2007-01-01

    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.

  19. Dynamical Heterogeneities in Glasses from Fluctuating Mobility Generation and Transport: Two Equilibration Mechanisms in Glasses

    Science.gov (United States)

    Wisitsorasak, Apiwat; Wolynes, Peter G.

    2014-03-01

    In the random first order transition theory, fluctuating mobility generation and transport are explored from an extended mode coupling theory of the glass transition that includes activated events. We numerically solve the continuum equations of mobility and temperature fields and find that the fluctuations which account for spatiotemporal structure in aging and rejuvenating glasses lead for dynamical heterogeneity in glass. Non-Gaussian distribution of free energy, stretch exponent ?, and growing characteristic length are presented along with the four-point correlation function. Our results demonstrate that two equilibration mechanisms that have been observed in aged polymer glasses are the results of the heterogeneity and out-of-equilibrium behavior of glasses below the glass transition temperature. Numerical results of distribution of relaxation time agree with experimental observations.

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

    Science.gov (United States)

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

    2015-01-01

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

  1. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    Science.gov (United States)

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

    2014-06-01

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

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

    Science.gov (United States)

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

    2014-12-23

    The interface between the metal and dielectric is an indispensable part in various electronic devices. The migration of metallic species into the dielectric can adversely affect the reliability of the insulating dielectric and can also form a functional solid-state electrolyte device. In this work, we insert graphene between Cu and SiO2 as a barrier layer and investigate the mass transport mechanism of Cu species through the graphene barrier using density functional theory calculations, second-ion mass spectroscopy (SIMS), capacitance-voltage measurement, and cyclic voltammetry. Our theoretical calculations suggest that the major migration path for Cu species to penetrate through the multiple-layered graphene is the overlapped defects larger than 0.25 nm2. The depth-profile SIMS characterizations indicate that the "critical" thickness of the graphene barrier for completely blocking the Cu migration is 5 times smaller than that of the conventional TaN barrier. Capacitance-voltage and cyclic voltammetry measurement reveal that the electrochemical reactions at the Cu/SiO2 interface become a rate-limiting factor during the bias-temperature stressing process with the use of a graphene barrier. These studies provide a distinct roadmap for designing controllable mass transport in solid-state electrolyte devices with the use of a graphene barrier. PMID:25423484

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

    Science.gov (United States)

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

    2013-12-01

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

  4. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    International Nuclear Information System (INIS)

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

  5. 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

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

    Science.gov (United States)

    Kreuter, Jörg

    2013-01-01

    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. PMID:22676632

  7. Maine Ingredients

    Science.gov (United States)

    Waters, John K.

    2009-01-01

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

  8. 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...

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

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1993-01-01

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

  10. Study on a self-similar traffic shaping mechanism with QoS in transport networks

    Science.gov (United States)

    Bo, Mingxia; Lee, Peiyuan; Pan, Xiaofei; Gu, Wanyi

    2005-11-01

    Due to easy realization and high bandwidth utilization, SDH/WDM technology becomes the important way to carry IP traffic over the backbone network. On the other hand, the feature of the data traffic which is much different from the voice traffic is dynamic, burst and self-similar, and many proofs show that the self-similar traffic can lead to some adverse effects on the network performance due to the property of long-range dependence (LRD). For this reason it is widely recognized that self-similarity of the traffic is a significant problem as far as network engineering is concerned. So any reduction in the degree of self-similarity will be greatly beneficial. One possible strategy for mitigating the deleterious effects of the self-similarity is to reduce the burstiness of the input traffic through traffic shaping function at the edge nodes. According to this scheme, in this paper, we present a new self-similar traffic shaping mechanism with QoS in transport networks, called double threshold algorithm (DTA). Simulation results show that the proposed mechanism can effectively reduce the degree of input self-similar traffic, and performs better in the terms of network packet-loss rate and blocking probability than the non-traffic shaping schemes. At the same time it guarantees good quality of service.

  11. Serotonin transporter deficiency protects mice from mechanical allodynia and heat hyperalgesia in vincristine neuropathy.

    Science.gov (United States)

    Hansen, Niels; Uçeyler, Nurcan; Palm, Florian; Zelenka, Marek; Biko, Lydia; Lesch, Klaus-Peter; Gerlach, Manfred; Sommer, Claudia

    2011-05-16

    Painful vincristine (VCR) neuropathy is a frequent and dose-limiting problem in cancer treatment. Here, we investigated how pain behavior is modulated in mice lacking the serotonin transporter (5-HTT-/- mice) after inducing neuropathy by intraperitoneal injections of VCR. We used standard tests for evoked pain, high performance liquid chromatography to measure serotonin (5-HT), and immunohistochemistry of L4/5 dorsal root ganglia (DRG) to assess neuronal injury and inflammation. After injections of VCR, 5-HTT-/- mice did not develop hypersensitivity to heat, in contrast to their wildtype (wt) littermates (p<0.05). Also, 5-HTT-/- mice recovered faster from mechanical hypersensitivity than wt mice (p<0.05). 5-HT levels were lower in the peripheral and central nervous tissue of vehicle or VCR-treated 5-HTT-/- mice compared to wt mice. VCR-treated mice had higher numbers of injured neurons as identified by immunostaining for activating transcription factor 3, and more immunoreactive macrophages in the L4/5 DRG than vehicle-treated mice. There was no difference between genotypes. Thus the 5-HTT-/- genotype did not protect mice from VCR-induced neuronal injury and macrophage infiltration in the DRG. Our results suggest that the reduced peripheral 5-HT levels of 5-HTT-/- mice in VCR neuropathy underlie the lack of heat hyperalgesia. Conversely, attenuation of mechanical allodynia in 5-HTT-/- mice may indicate reduced 5-HT-mediated facilitation in the central nervous system. PMID:21419830

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

    International Nuclear Information System (INIS)

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

  13. Effect of temperature and UV illumination on charge transport mechanisms in DNA

    Science.gov (United States)

    Narenji, Alaleh G.; Goshi, Noah; Bui, Chris; Mokili, John; Kassegne, Sam

    2015-04-01

    Research into the use of DNA molecules as building blocks for nanoelectronics as well as nanosystems continues. Recently, our group has reported significant electrical conductivity in ?-DNA through direct and in-direct measurements involving high-aspect ratio electrodes that eliminate the effect of the substrate. Our results demonstrate that, at moderate to high frequencies, ?-DNA molecular wires show low impedance. In addition, to prove that the conductivity is indeed from DNA bridge, we studied the effect of temperature and UV irradiation on DNA molecular wires. The temperature results indicate that ?-DNA molecular wires have differing impedance responses at two temperature regimes: impedance increases between 4°C - 40°C, then decreases from 40°C to the melting point (~110°C) at which ?-DNA denatures resulting in a complete loss of current transduction. This hysteric and bi-model behavior makes DNA a candidate for nanoelectronics components such as thermal transistors and switches. The data from UV exposure experiments indicates decreased conductivity of ?-DNA molecular wires after UV exposure, due to damage to GC base pairs and phosphate groups reducing the path available for both charge hopping and short-range electron tunneling mechanisms. The lessons learned from these conductivity experiments along with our knowledge of different charge transport mechanisms within DNA can be applied to the design of synthetic molecular wires for the construction of nanoelectronic devices.

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

    Directory of Open Access Journals (Sweden)

    Li Feiran

    2012-01-01

    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.

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

    Science.gov (United States)

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

    2014-12-01

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

  16. 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

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

    Directory of Open Access Journals (Sweden)

    PEDRO LOPES DE MELO

    2000-08-01

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

  18. Application of sediment characteristics and transport conditions to resource management in selected main-stem reaches of the Upper Colorado River, Colorado and Utah, 1965-2007

    Science.gov (United States)

    Williams, Cory A.; Schaffrath, Keelin R.; Elliott, John G.; Richards, Rodney J.

    2013-01-01

    The Colorado River Basin provides habitat for 14 native fish, including 4 endangered species protected under the Federal Endangered Species Act of 1973. These endangered fish species once thrived in the Colorado River system, but water-resource development, including the building of numerous diversion dams and several large reservoirs, and the introduction of non-native fish, resulted in large reductions in the numbers and range of the four species through loss of habitat and stream function. Understanding how stream conditions and habitat change in response to alterations in streamflow is important for water administrators and wildlife managers and can be determined from an understanding of sediment transport. Characterization of the processes that are controlling sediment transport is an important first step in identifying flow regimes needed for restored channel morphology and the sustained recovery of endangered fishes within these river systems. The U.S. Geological Survey, in cooperation with the Upper Colorado River Endangered Fish Recovery Program, Bureau of Reclamation, U.S. Fish and Wildlife Service, Argonne National Laboratory, Western Area Power Administration, and Wyoming State Engineer’s Office, began a study in 2004 to characterize sediment transport at selected locations on the Colorado, Gunnison, and Green Rivers to begin addressing gaps in existing datasets and conceptual models of the river systems. This report identifies and characterizes the relation between streamflow (magnitude and timing) and sediment transport and presents the findings through discussions of (1) suspended-sediment transport, (2) incipient motion of streambed material, and (3) a case study of sediment-transport conditions for a reach of the Green River identified as a razorback sucker spawning habitat (See report for full abstract).

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-15

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

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

    Science.gov (United States)

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

    2015-01-01

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

  1. Study on transportation and accumulation mechanisms of cesium in Camellia sinensis by SR-XRF imaging

    International Nuclear Information System (INIS)

    After the tragedy in Fukushima, soil and food pollution by radionuclides has become a serious problem. Cs can be uptaken by many plants due to its chemical similarities with K. So, removal of radioactive Cs from the soils can be carried out using the phytoremediation technology. However, the development of phytoremediation techniques require the knowledge on the interactions between the plants and soils. Although the competitive relation between K and Cs to enter the plant is known, few works were dedicated to the visual localization of Cs in the plant and its relation to potassium. In this study, we have used synchrotron radiation X-ray fluorescence (SR-XRF) imaging in order to reveal accumulation of Cs with a cellular spatial resolution. The Cs L? intensity measured in the XRF imaging were transformed into the Cs concentration based on the calibration curves prepared using in house standard samples of known Cs concentrations. It is remarkable that after exposure to 10 ppm Cs solution for 4 weeks Camellia sinensis accumulated Cs up to 300 ppm (expressed in dry weight) in the body. XRF imaging of the root show that Cs was located mainly at the epidermis. On the other hand, K was located mainly at endodermis and the cell wall. A correlation coefficient(R) between XRF intensity of K and that of Cs in the root was about R=0.5. This suggest that Cs is hardly absorbed from roots of Camellia sinensis compared with K, due to its large ionic radius. In the case of stem, distribution of Cs was similar to that of K. They were located at the exodermis, epidermis and the cell wall. Their correlation coefficient was about R=0.8. These results suggest that Cs was transported through the same pathway as that of K in the stem. (author)

  2. Mechanism of lipid mobilization by the small intestine after transport blockade

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-11-18

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Strauß, Olaf

    2014-03-01

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

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

    OpenAIRE

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

    2008-01-01

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

  7. A possible mechanism for enhanced magnetic quantum oscillations in the mixed state of layered superconductors with incoherent electronic transport

    International Nuclear Information System (INIS)

    We present a new mechanism for the scattering rate in the mixed state of layered superconductors. This mechanism acts through the modification of the layer-stacking factor which suppresses magnetic quantum oscillations if the interlayer electron hopping is incoherent. In the superconducting state, the interlayer incoherence restores and gives a negative contribution to the interlayer quasiparticle scattering rate. The mechanism may explain recent findings of enhanced magnetic quantum-oscillation amplitudes in the superconducting state of a layered organic conductor which displays an incoherent electronic transport across the layers

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

    Science.gov (United States)

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

    2008-03-01

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

  9. Bimodal drug release achieved with multi-layer matrix tablets: transport mechanisms and device design.

    Science.gov (United States)

    Streubel, A; Siepmann, J; Peppas, N A; Bodmeier, R

    2000-12-01

    The aim of this study was to develop new multi-layer matrix tablets to achieve bimodal drug release profiles (fast release/slow release/fast release). Hydroxypropyl methylcellulose acetate succinate (HPMCAS, type MF) was chosen as a matrix former, because it is water-insoluble at low, and water-soluble at high pH values. Studies focused on the elucidation of the drug release mechanisms from HPMCAS-MF:drug tablets. In 0.1 N HCl the resulting release kinetics can be described using Fick's second law of diffusion, taking into account axial and radial mass transfer in cylindrical geometry. As the diffusion coefficients are found to be constant and the boundary conditions to be stationary, these systems are purely drug diffusion-controlled. In contrast, the dominating mass transport phenomena in phosphate buffer pH 7.4 are more complex. Due to polymer dissolution the resulting matrix structure is time-variant, leading to increasing drug diffusion coefficients and decreasing tablet dimensions, and thus moving boundary conditions. Drug release is affected by water imbibition, drug diffusion and polymer dissolution and is faster compared to 0.1 N HCl. With knowledge of these underlying release mechanisms, multi-layer matrix tablets were developed to achieve bimodal drug release. HPMCAS-MF:drug mixtures were used as tablet cores. As expected, changing the release medium from 0.1 N HCl to phosphate buffer pH 7. 4 after 2 h, lead to a significant increase in drug release. The abruptness of this rate change could be enhanced by adding two drug-free HPMCAS-MF barrier layers (one on each side) to the system. The addition of a fourth, drug-containing and fast disintegrating initial dose layer yielded the desired bimodal drug release patterns. The process and formulation parameters affecting the resulting release rates were investigated using theophylline and acetaminophen as model drugs. PMID:11102685

  10. Evaluation of potential sources and transport mechanisms of fecal indicator bacteria to beach water, Murphy Park Beach, Door County, Wisconsin

    Science.gov (United States)

    Juckem, Paul F.; Corsi, Steven R.; McDermott, Colleen; Kleinheinz, Gregory; Fogarty, Lisa R.; Haack, Sheridan K.; Johnson, Heather E.

    2013-01-01

    Fecal Indicator Bacteria (FIB) concentrations in beach water have been used for many years as a criterion for closing beaches due to potential health concerns. Yet, current understanding of sources and transport mechanisms that drive FIB occurrence remains insufficient for accurate prediction of closures at many beaches. Murphy Park Beach, a relatively pristine beach on Green Bay in Door County, Wis., was selected for a study to evaluate FIB sources and transport mechanisms. Although the relatively pristine nature of the beach yielded no detection of pathogenic bacterial genes and relatively low FIB concentrations during the study period compared with other Great Lakes Beaches, its selection limited the number of confounding FIB sources and associated transport mechanisms. The primary sources of FIB appear to be internal to the beach rather than external sources such as rivers, storm sewer outfalls, and industrial discharges. Three potential FIB sources were identified: sand, swash-zone groundwater, and Cladophora mats. Modest correlations between FIB concentrations in these potential source reservoirs and FIB concentrations at the beach from the same day illustrate the importance of understanding transport mechanisms between FIB sources and the water column. One likely mechanism for transport and dispersion of FIB from sand and Cladophora sources appears to be agitation of Cladophora mats and erosion of beach sand due to storm activity, as inferred from storm indicators including turbidity, wave height, current speed, wind speed, sky visibility, 24-hour precipitation, and suspended particulate concentration. FIB concentrations in beach water had a statistically significant relation (p-value ‹0.05) with the magnitude of these storm indicators. In addition, transport of FIB in swash-zone groundwater into beach water appears to be driven by groundwater recharge associated with multiday precipitation and corresponding increased swash-zone groundwater discharge at the beach, as indicated by an increase in the specific conductance of beach water. Understanding the dynamics of FIB sources (sand, swash-zone groundwater, and Cladophora) and transport mechanisms (dispersion and erosion from storm energy, and swash-zone groundwater discharge) is important for improving predictions of potential health risks from FIB in beach water.

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

    International Nuclear Information System (INIS)

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

  12. Glutathione conjugation as a mechanism for the transport of reactive metabolites.

    Science.gov (United States)

    Monks, T J; Lau, S S

    1994-01-01

    From this and other chapters in this volume, it should be clear that GSH conjugation no longer represents a mechanism for the detoxication of xenobiotics or their metabolites. Although the majority of conjugations with GSH do facilitate the efficient excretion of xenobiotics from the body, many examples now exist where this process results in enhanced biological reactivity (Monks et al., 1990a; Monks and Lau, 1992, 1994). The number of examples in which GSH conjugation plays an important role in the generation of biologically reactive intermediates is expanding rapidly and GSH-dependent toxicity is manifested in many diverse ways. As emphasized in this chapter, GSH can act as a transport form for reactive metabolites, permitting the delivery of such metabolites to target tissues distal to the site of the initial conjugation. This type of GSH conjugate may be important in the mutagenic, carcinogenic, nephrotoxic, embryotoxic, cataractogenic, methemoglobinemic, and neurotoxic properties of a variety of redox active compounds (Monks and Lau, 1992). PMID:7915133

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

    International Nuclear Information System (INIS)

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

  14. 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)

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

    2000-01-01

    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.

  15. A multi-scale approach of mechanical and transport properties of cementitious materials under rises of temperature

    International Nuclear Information System (INIS)

    The modern industrial activities (storage of nuclear waste, geothermal wells, nuclear power plants,...) can submit cementitious materials to some extreme conditions, for example at temperatures above 200 C. This level of temperature will induce phenomena of dehydration in the cement paste, particularly impacting the CSH hydrates which led to the mechanical cohesion. The effects of these temperatures on the mechanical and transport properties have been the subject of this thesis.To understand these effects, we need to take into account the heterogeneous, porous, multi-scale aspects of these materials. To do this, micro-mechanics and homogenization tools based on the Eshelby problem's solution were used. Moreover, to support this multi-scale modeling, mechanical testing based on the theory of porous media were conducted. The measurements of modulus compressibility, permeability and porosity under confining pressure were used to investigate the mechanisms of degradation of these materials during thermal loads up to 400 C. (author)

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

    OpenAIRE

    Clausen, Thomas; Leistiko, Otto

    1993-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  19. Structure and mechanism of a Na+independent amino acid transporter

    OpenAIRE

    Shaffer, Paul L.; Goehring, April; Shankaranarayanan, Aruna; Gouaux, Eric

    2009-01-01

    Amino acid, polyamine, and organocation (APC) transporters are secondary transporters that play essential roles in nutrient uptake, neurotransmitter recycling, ionic homeostasis, and regulation of cell volume. Here we present the crystal structure of apo-ApcT, a proton-coupled broad-specificity amino acid transporter, at 2.35 Å resolution. The structure contains 12 transmembrane helices, with the first 10 consisting of an inverted structural repeat of 5 transmembrane helices like LeuT. The A...

  20. 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)

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

    Science.gov (United States)

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

    2014-12-01

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

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

    Science.gov (United States)

    Seggewiss, G.; Dickson, S. E.

    2013-12-01

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

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

    International Nuclear Information System (INIS)

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

  4. Characterizing rates and mechanisms of soil transport using tephra as a tracer: Charwell River, South Island, New Zealand

    Science.gov (United States)

    Roering, J. J.; Almond, P.; Tonkin, P.; McKean, J.

    2001-12-01

    Downslope transport of soil in the absence of overland flow has been attributed to numerous mechanisms, including particle-by-particle rheologic creep and disturbances associated with biological activity. Process stochasticity and difficulties associated with field measurement have obscured the characterization of long-term soil transport rates and mechanisms. Most modeling studies represent soil transport as a slope and/or soil depth-dependent process, although field evidence is sparse. At our study site along incised fluvial terraces of the Charwell River, South Island, New Zealand, we documented vertical profiles of tephra concentration along a hillslope transect to quantify soil transport. Near the relatively undissected hilltop, we observed a 10 cm thick primary tephra layer (ca 22.6 kyr) within loess deposits approximately 80 cm below the landscape surface. In the downslope direction, the depth to the highly concentrated tephra layer decreases, coincident with an increase in hillslope convexity (which is proportional to erosion rate if soil flux varies linearly with hillslope gradient). Exhumation of the spike in tephra concentration results from landscape lowering due to soil transport processes as evidence for overland flow erosion is lacking. Approximately 20 m downslope of the hilltop, where the depth to the tephra spike declines to 40-50 cm, peak concentrations decrease by a factor of 4 and tephra is distributed uniformly within the upper 40 cm of soil. Further downslope near the valley margin, we observed low and relatively uniform tephra concentrations in the upper soil. The transition from a thin, highly concentrated tephra layer at depth to sparse, widely distributed tephra within the upper soil column may result from soil mixing and transport by tree and plant root activity. The depth of this transition is approximately 50 cm along our transect, coincident with the rooting depth of Podocarpus trees that populated the area through much of the Holocene. Our observations can be used to calibrate the linear transport model and suggest that over geomorphic timescales stochastic cycles of root growth and tree throw may generate a well-mixed and actively transporting soil layer, the depth of which is primarily determined by plant physiology, as opposed to mechanical properties of soil.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2013-10-01

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

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

    OpenAIRE

    Zhang, Lisha; Huang, Min; Harsay, Edina

    2009-01-01

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

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

    OpenAIRE

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

    2010-01-01

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

  9. Lithium Ion Transport Mechanism in Ternary Polymer Electrolyte-Ionic Liquid Mixtures - A Molecular Dynamics Simulation Study

    OpenAIRE

    Diddens, Diddo; Heuer, Andreas

    2012-01-01

    The lithium transport mechanism in ternary polymer electrolytes, consisting of PEO/LiTFSI and various fractions of the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethane)sulfonimide, are investigated by means of MD simulations. This is motivated by recent experimental findings [Passerini et al., Electrochim. Acta 2012, 86, 330-338], which demonstrated that these materials display an enhanced lithium mobility relative to their binary counterpart PEO/LiTFSI. In o...

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

    Energy Technology Data Exchange (ETDEWEB)

    Vikhrenko, V.S. E-mail: vvikhre@bstu.unibel.by; Bokun, G.S.; Groda, Ya.G

    2003-07-01

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

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

    Weyand, Simone; Shimamura, Tatsuro

    2008-01-01

    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.

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

    International Nuclear Information System (INIS)

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

  14. A simple modeling approach to elucidate the main transport processes and predict invasive spread: River-mediated invasion of Ageratina adenophora in China

    Science.gov (United States)

    Horvitz, Nir; Wang, Rui; Zhu, Min; Wan, Fang-Hao; Nathan, Ran

    2014-12-01

    A constantly increasing number of alien species invade novel environments and cause enormous damage to both biodiversity and economics worldwide. This global problem is calling for better understanding of the different mechanisms driving invasive spread, hence quantification of a range of dispersal vectors. Yet, methods for elucidating the mechanisms underlying large-scale invasive spread from empirical patterns have not yet been developed. Here we propose a new computationally efficient method to quantify the contribution of different dispersal vectors to the spread rate of invasive plants. Using data collected over 30 years regarding the invasive species Ageratina adenophora since its detection at the Sichuan province, we explored its spread by wind and animals, rivers, and roads into 153 subcounties in the Sichuan, Chongqingshi, and Hubei provinces of China. We found that rivers are the most plausible vector for the rapid invasion of this species in the study area. Model explorations revealed robustness to changes in key assumptions and configuration. Future predictions of this ongoing invasion process project that the species will quickly spread along the Yangtze River and colonize large areas within a few years. Further model developments would provide a much needed tool to mechanistically and realistically describe large-scale invasive spread, providing insights into the underlying mechanisms and an ability to predict future spatial invasive dynamics.

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

    Science.gov (United States)

    Bair, E. K.

    1986-01-01

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

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

    Science.gov (United States)

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

    2014-09-01

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

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

    CERN Document Server

    Vikhrenko, V S; Groda, Y G

    2003-01-01

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

  18. 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...

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

    Directory of Open Access Journals (Sweden)

    Choi Cheol-Hee

    2005-10-01

    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.

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

    OpenAIRE

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

    2009-01-01

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

  1. Mechanism of L-glutamate transport in membrane vesicles from Bacillus stearothermophilus.

    OpenAIRE

    de Vrij, W; Bulthuis, R A; van Iwaarden, P R; Konings, W. N.

    1989-01-01

    In the presence of electrochemical energy, several branched-chain neutral and acidic amino acids were found to accumulate in membrane vesicles of Bacillus stearothermophilus. The membrane vesicles contained a stereo-specific transport system for the acidic amino acids L-glutamate and L-aspartate, which could not translocate their respective amines, L-glutamine and L-asparagine. The transport system was thermostable (Ti = 70 degrees C) and showed highest activities at elevated temperatures (60...

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

    OpenAIRE

    Tanford, C.

    1983-01-01

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

  3. Mechanisms of equinatoxin II-induced transport through the membrane of a giant phospholipid vesicle.

    OpenAIRE

    Mally, M.; Majhenc, J.; Svetina, S.; Zeks, B.

    2002-01-01

    Protein equinatoxin II from sea anemone Actinia equina L. was used to form pores in phospholipid membranes. We studied the effect of these pores on the net transmembrane transport of sucrose and glucose by observing single giant (cell-size) vesicles under the phase contrast microscope. Sugar composition in the vesicle was determined by measuring the width of the halo, which appears around the vesicle in the phase contrast image. The transport of sugars was induced when a vesicle, filled with ...

  4. Single molecule charge transport: from a quantum mechanical to a classical description:

    OpenAIRE

    Kocherzhenko, A. A.; Grozema, F. C.; Siebbeles, L. D. A.

    2010-01-01

    This paper explores charge transport at the single molecule level. The conductive properties of both small organic molecules and conjugated polymers (molecular wires) are considered. In particular, the reasons for the transition from fully coherent to incoherent charge transport and the approaches that can be taken to describe this transition are addressed in some detail. The effects of molecular orbital symmetry, quantum interference, static disorder and molecular vibrations on c...

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

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Sylow, Lykke

    2014-01-01

    Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca(2+) release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

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

    Directory of Open Access Journals (Sweden)

    Thomas E. Jensen

    2014-10-01

    Full Text Available Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca2+ as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca2+ release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca2+ centric paradigm.

  7. Linking valve closure behavior and sodium transport mechanism in freshwater clam Corbicula fluminea in response to copper

    International Nuclear Information System (INIS)

    The purpose of this study is to develop a mechanistic model to describe a conceptually new 'flux-biological response' approach based on biotic ligand model (BLM) and Michaelis-Menten (M-M) kinetics to allow the linkage between valve closure behavior and sodium (Na) transport mechanism in freshwater clam Corbicula fluminea in response to waterborne copper (Cu). We test the proposed model against published data regarding Na uptake kinetics in rainbow trout and Na uptake profile in C. fluminea, confirming that the predictive model is robust. Here, we show that the predicted M-M maximum Cu internalization flux in C. fluminea is 0.369 ?mol g-1 h-1 with a half-saturation affinity constant of 7.87 x 10-3 ?M. Dynamics of Na uptake and valve closure daily rhythm driven by external Cu can also be predicted simultaneously. We suggest that this 'Na transport-valve closure behavior' approach might provide the basis of a future design of biomonitoring tool. - A new flux-biological response model can link valve closure and sodium transport mechanisms in freshwater clam in response to copper

  8. Effect of PANI rate percentage on morphology, structure and charge transport mechanism in PANI–PVDF composites above percolation threshold

    International Nuclear Information System (INIS)

    Polyaniline–Poly(vinylidene) fluoride (PANI–PVDF) composites were prepared by adding PANI to the PVDF by different weight percentages p % (p = 0, 5, 10, 20, … until 100%). The dc and ac electrical conductivity were studied as a function of PANI percentage in the temperature range 303–453 K. The percolation threshold was found to be equal to 2.95%. When the amount of PANI varies from 5 to 30%, the charge transport mechanism was found to be governed by Mott's three-dimensional variable range hopping model and the dc conductivity decreases within this range. For p > 30%, the conductivity increases and the charge transport mechanism are better fitted by a fluctuation induced tunnelling model (FIT). By calculating the distance ‘s’ between two successive clusters (the distance between two active imines centres (=N+H–) of PANI) from the FIT model, we deduce that electron charge transfer is done by inter-chain hopping for the range [p = 40 to 60%] and by intra-chain hopping for p = 70 to 90%. Some insights about the contribution of the ionic charge transport for PANI concentrations in the interval 5% < p < 30% were obtained using impedance measurements at different frequencies. X-ray diffraction measurements, Fourier transform infrared spectroscopy and scanning electron microscopy were used to investigate the effect of PANI on the structure and morphology of composites. (paper)

  9. Molecular Mechanism of Ion-Ion and Ion-Substrate Coupling in the Na+-Dependent Leucine Transporter LeuT

    OpenAIRE

    Caplan, David A.; Subbotina, Julia O.; Noskov, Sergei Yu

    2008-01-01

    Ion-coupled transport of neurotransmitter molecules by neurotransmitter:sodium symporters (NSS) play an important role in the regulation of neuronal signaling. One of the major events in the transport cycle is ion-substrate coupling and formation of the high-affinity occluded state with bound ions and substrate. Molecular mechanisms of ion-substrate coupling and the corresponding ion-substrate stoichiometry in NSS transporters has yet to be understood. The recent determination of a high-resol...

  10. The molecular mechanism of "ecstasy" [3,4-methylenedioxy-methamphetamine (MDMA)]: serotonin transporters are targets for MDMA-induced serotonin release.

    OpenAIRE

    Rudnick, G.; Wall, S. C.

    1992-01-01

    MDMA ("ecstasy") has been widely reported as a drug of abuse and as a neurotoxin. This report describes the mechanism of MDMA action at serotonin transporters from plasma membranes and secretory vesicles. MDMA stimulates serotonin efflux from both types of membrane vesicle. In plasma membrane vesicles isolated from human platelets, MDMA inhibits serotonin transport and [3H]imipramine binding by direct interaction with the Na(+)-dependent serotonin transporter. MDMA stimulates radiolabel efflu...

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

    International Nuclear Information System (INIS)

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-05-12

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

  13. Main roads to melanoma

    OpenAIRE

    Sini Maria; Casula Milena; Stroncek David F; Gentilcore Giusy; Ascierto Maria; Capone Mariaelena; Palmieri Giuseppe; Palla Marco; Mozzillo Nicola; Ascierto Paolo A

    2009-01-01

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

  14. The theoretical basis of state control mechanisms by national oil and gas transport systems

    Directory of Open Access Journals (Sweden)

    ????? ?????????? ??????

    2014-12-01

    Full Text Available The information materials and state control experience in oil and gas pipeline transport systems were analyzed in the context of globalization and European integration. The theoretical basis for organization the effective functioning of national oil and gas transport systems were developed. Elementary business process was interpreted as a typical section of cross-functional coherence. Dimensional model the pareto-optimal point searching of the economically efficient market interaction between participants of the business process was constructed. The scheme of multilateral international private partnership was developed.

  15. The dynamical response of the plasma as a tool for investigating transport mechanisms

    International Nuclear Information System (INIS)

    The dynamical response of the soft X-ray emission profile to different external perturbations - gas feed, impurity injection, RF power, surface loop voltage - has been studied on the TCA tokamak and analysed using the same techniques. The frequency dependence of the response has been exploited to distinguish between the dominant transport processes. Remarkably similar phase response profiles were obtained with the different stimuli; they show a link with the sawtooth activity. The model which most plausibly explains these experimental observations requires diffusive transport with the diffusive coefficient locally modulated by the perturbation. (author) 15 figs., 27 refs

  16. Observations of Intertidal Bars Welding to the Shoreline: Examining the Mechanisms of Onshore Sediment Transport and Beach Recovery

    Science.gov (United States)

    Cohn, N.; Anderson, D. L.; Susa, T.; Ruggiero, P.; Honegger, D.; Haller, M. C.

    2014-12-01

    Many coastlines throughout the world are in a net erosional state due to factors such as climate change and anthropogenic activities. While most coastal erosion occurs episodically during major storms, beaches recover during extended periods of low wave energy. Despite the importance of beach recovery on limiting coastal vulnerability, the mechanisms driving onshore sediment transport are much less well understood than those of storm-driven offshore transport. Intertidal bar (i.e., swash bar) welding to the shoreline is one proposed mechanism of sediment delivery from the nearshore to the backshore. However, studies of swash bars and their contribution to beach building have been scarce because of the sporadic nature of these events and difficulty measuring sediment fluxes in the intertidal zone. Several beaches in the US Pacific Northwest are prograding rapidly in part due to highly dissipative conditions and an abundant sediment supply. For example, at South Beach State Park (SBSP) in Newport, OR the shoreline accreted at an average of 6 m/yr from 1960 to 2002. To explore the role of intertidal bar welding on supplying sediment to this dynamic backshore, we recently completed a boutique field experiment at SBSP. Topographic and bathymetric surveys carried out over 9 months document the short term (intertidal bar welding on supplying sediment to the backshore as well as the environmental conditions and physical mechanisms that promote onshore delivery of sediment.

  17. Evidence for Operation of the Direct Zinc Ligand Exchange Mechanism for Trafficking, Transport, and Reactivity of Zinc in Mammalian Cells

    Science.gov (United States)

    Costello, Leslie C.; Fenselau, Catherine C.; Franklin, Renty B.

    2011-01-01

    In addition to its critical role in normal cell function, growth, and metabolism, zinc is implicated as a major factor in the development and progression of many pathological conditions and diseases. Despite this importance of zinc, many important factors, processes, and mechanisms of the physiology, biochemistry, and molecular biology of zinc remain unknown. Especially important is the unresolved issue regarding the mechanism and process of the trafficking, transport, and reactivity of zinc in cells; especially in mammalian cells. This presentation focuses on the concept that, due to the existence of a negligible pool of free Zn2+ ions in the mammalian cell environment, the trafficking, transport and reactivity of zinc occurs via a direct exchange of zinc from donor Zn-Ligands to acceptor ligands. This Zn exchange process occurs without the requirement for production of free Zn2+ ions. The direct evidence from mammalian cell studies is presented in support of the operation of the direct Zn-Ligand exchange mechanism. The paper also provides important information and conditions that should be considered and employed in the conduct of studies regarding the role and effects of zinc in biological/biomedical research; and in its clinical interpretation and application. PMID:21440525

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

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, Glenn C.

    1999-12-01

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

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

    Scientific Electronic Library Online (English)

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

    2010-12-01

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

  20. Development of intestinal ion-transporting mechanisms during smoltification and seawater acclimation in Atlantic salmon Salmo salar

    Science.gov (United States)

    Sundh, Henrik; Nilsen, Tom O.; Lindström, Jenny; Hasselberg-Frank, Linda; Stefansson, Sigurd O.; McCormick, Stephen D.; Sundell, K.

    2014-01-01

    This study investigated the expression of ion transporters involved in intestinal fluid absorption and presents evidence for developmental changes in abundance and tissue distribution of these transporters during smoltification and seawater (SW) acclimation of Atlantic salmonSalmo salar. Emphasis was placed on Na+, K+-ATPase (NKA) and Na+, K+, Cl? co-transporter (NKCC) isoforms, at both transcriptional and protein levels, together with transcription of chloride channel genes. The nka ?1c was the dominant isoform at the transcript level in both proximal and distal intestines; also, it was the most abundant isoform expressed in the basolateral membrane of enterocytes in the proximal intestine. This isoform was also abundantly expressed in the distal intestine in the lower part of the mucosal folds. The protein expression of intestinal Nka?1c increased during smoltification. Immunostaining was localized to the basal membrane of the enterocytes in freshwater (FW) fish, and re-distributed to a lateral position after SW entry. Two other Nka isoforms, ?1a and ?1b, were expressed in the intestine but were not regulated to the same extent during smoltification and subsequent SW transfer. Their localization in the intestinal wall indicates a house-keeping function in excitatory tissues. The absorptive form of the NKCC-like isoform (sub-apically located NKCC2 and/or Na+, Cl?co-transporter) increased during smoltification and further after SW transfer. The cellular distribution changed from a diffuse expression in the sub-apical regions during smoltification to clustering of the transporters closer to the apical membrane after entry to SW. Furthermore, transcript abundance indicates that the mechanisms necessary for exit of chloride ions across the basolateral membrane and into the lateral intercellular space are present in the form of one or more of three different chloride channels: cystic fibrosis transmembrane conductance regulator I and II and chloride channel 3.

  1. Lead transport in intra-oceanic subduction zones: 2D geochemical-thermo-mechanical modeling of isotopic signatures

    Science.gov (United States)

    Baitsch-Ghirardello, Bettina; Stracke, Andreas; Connolly, James A. D.; Nikolaeva, Ksenia M.; Gerya, Taras V.

    2014-11-01

    Understanding the physical-chemical mechanisms and pathways of geochemical transport in subduction zones remains a long-standing goal of subduction-related research. In this study, we perform fully coupled geochemical-thermo-mechanical (GcTM) numerical simulations to investigate Pb isotopic signatures of the two key "outputs" of subduction zones: (A) serpentinite mélanges and (B) arc basalts. With this approach we analyze three different geodynamic regimes of intra-oceanic subduction systems: (1) retreating subduction with backarc spreading, (2) stable subduction with high fluid-related weakening, and (3) stable subduction with low fluid-related weakening. Numerical results suggest a three-stage Pb geochemical transport in subduction zones: (I) from subducting sediments and oceanic crust to serpentinite mélanges, (II) from subducting serpentinite mélanges to subarc asthenospheric wedge and (III) from the mantle wedge to arc volcanics. Mechanical mixing and fluid-assisted geochemical transport above slabs result in spatially and temporarily variable Pb concentrations in the serpentinized forearc mantle as well as in arc basalts. The Pb isotopic ratios are strongly heterogeneous and show five types of geochemical mixing trends: (i) binary mantle-MORB, (i) binary MORB-sediments, (iii) double binary MORB-mantle and MORB-sediments, (iv) double binary MORB-mantle and mantle-sediments and (v) triple MORB-sediment-mantle. Double binary and triple mixing trends are transient and characterize relatively early stages of subduction. In contrast, steady-state binary mantle-MORB and MORB-sediments trends are typical for mature subduction zones with respectively low and high intensity of sedimentary melange subduction. Predictions from our GcTM models are in agreement with Pb isotopic data from some natural subduction zones.

  2. Mechanisms of energetic efficiency in the transportation sector: environmental impacts and reflections in final energy consumption: PNE 2030; Mecanismos de eficiencia energetica no setor de transportes: impactos ambientais e os reflexos no consumo final de energia: PNE 2030

    Energy Technology Data Exchange (ETDEWEB)

    Berni, Mauro Donizeti [Universidade Estadual de Campinas (NIPE/UNICAMP), SP (Brazil). Nucleo Interdisciplinar de Planejamento Energetico], email: mauro_berni@nipeunicamp.org.br; Dorileo, Ivo Leandro [Universidade Federal do Mato Grosso (NIEPE/UFMT), Cuiaba, MT (Brazil). Nucleo Interdisciplinar de Estudos em Planejamento Energetico; Perez, Andrea Juliana Ortiz [Universidade Estadual de Campinas (DE/FEM/UNICAMP), SP (Brazil). Dept. de Energia. Fac. de Engenharia Mecanica; Paccola, Jose Angelo; Silva Junior, Herculano Xavier da; Bernardes, Cyro Barbosa [MCPAR Engenharia, Campinas, SP (Brazil)

    2010-07-01

    This work presents an energy efficiency mechanisms analysis in the Brazilian transport sector. Significant energy savings can be made in this sector and rely on urgent widespread implementation of mechanisms. The experience of the developed countries serves as base for the critical evaluation of the Brazilian situation, considering the current technological period, the investments and initiatives to reduce CO{sub 2} emissions. (author)

  3. Transport Characteristics in Mechanically Agitated Gas–Liquid Dispersion with Higher Viscosity.

    Czech Academy of Sciences Publication Activity Database

    Zedníková, Mária; Linek, V.; Moucha, T.

    Bratislava : Slovak University of Technology, 2003 - (Markoš, J.; Štefuca, V.), s. 20 ISBN 80-227-1889-0. [30 International Conference of Slovak Society of Chemical Engineering. Tatranské Matliare (SK), 26.05.2003-30.05.2003] Institutional research plan: CEZ:AV0Z4072921 Keywords : gas liquid dispersion * transport characteristics Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  4. Panorama 2013 - Air transport and the problem of CO2: ETS mechanisms and bio-jet fuels

    International Nuclear Information System (INIS)

    Air transport currently accounts for only 2% (?600 Mt/year) of global CO2 emissions from human activity. Despite this 2% level, this industry is targeted by governments - especially European Union - and initiatives targeting zero growth in carbon from 2020 onwards, and a 50% reduction by 2050. Over and above aircraft technical innovations and the way in which air traffic is organised, the introduction of ETS (Emissions Trading System) mechanisms and the development of bio-jet fuels are the options most commonly cited in discussions on how to achieve that target. (author)

  5. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis. In prokaryotes and photosynthetic eukaryotes, Zn(2+)-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn(2+) and related elements. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2·Pi) of ZntA from Shigella sonnei, determined at 3.2 Å and 2.7 Å resolution, respectively. The structures reveal a similar fold to Cu(+)-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn(2+) ions by the transporter. The E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including C392, C394 and D714. The pathway closes in the E2·Pi state, in which D714 interacts with the conserved residue K693, which possibly stimulates Zn(2+) release as a built-in counter ion, as has been proposed for H(+)-ATPases. Indeed, transport studies in liposomes provide experimental support for ZntA activity without counter transport. These findings suggest a mechanistic link between PIB-type Zn(2+)-ATPases and PIII-type H(+)-ATPases and at the same time show structural features of the extracellular release pathway that resemble PII-type ATPases such as the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+), K(+)-ATPase. These findings considerably increase our understanding of zinc transport in cells and represent new possibilities for biotechnology and biomedicine.

  6. Structure and mechanism of Zn(2+)-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis. In prokaryotes and photosynthetic eukaryotes, Zn(2+)-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn(2+) and related elements. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2·Pi) of ZntA from Shigella sonnei, determined at 3.2 Å and 2.7 Å resolution, respectively. The structures reveal a similar fold to Cu(+)-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn(2+) ions by the transporter. The E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including C392, C394 and D714. The pathway closes in the E2·Pi state, in which D714 interacts with the conserved residue K693, which possibly stimulates Zn(2+) release as a built-in counter ion, as has been proposed for H(+)-ATPases. Indeed, transport studies in liposomes provide experimental support for ZntA activity without counter transport. These findings suggest a mechanistic link between PIB-type Zn(2+)-ATPases and PIII-type H(+)-ATPases and at the same time show structural features of the extracellular release pathway that resemble PII-type ATPases such as the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+), K(+)-ATPase. These findings considerably increase our understanding of zinc transport in cells and represent new possibilities for biotechnology and biomedicine.

  7. A novel micro transportation system with fast movement of a micro container based on electrostatic actuation and a ratchet mechanism

    International Nuclear Information System (INIS)

    This paper presents a novel micro transportation system (MTS), which can drive micro containers in both straight and curved paths based on an electrostatic comb actuator and a ratchet mechanism. The micro container, which has four driving wings and four anti-reverse wings attached to its central 'backbone', is driven to move forward only by an electrostatic actuator. While the driving wings act as the legs of a water strider to push the container forward, the anti-reverse wings work as a ratchet mechanism to prevent the container from moving backward. The container with a length, width and thickness of 500 µm, 250 µm and 30 µm, respectively, moves unidirectionally with a desirable velocity up to 1000 µm s?1 in straight and curved paths. The velocity can be changed by varying the frequency and/or amplitude of the driving voltage. The MTS has been fabricated from SOI (silicon on insulator) wafer utilizing silicon micromachining technology with only one mask

  8. Mechanical analysis of a transportation accident involving empty shipping casks for radioactive materials near Hilda, South Carolina, in November 1982

    International Nuclear Information System (INIS)

    An accident involving a passenger automobile and a tractor-trailer carrying two empty shipping casks for transporting low-level radioactive materials occurred on November 3, 1982, near Hilda, SC. The purpose of this report is to document the mechanical circumstances of the accident, and to assess the types and magnitudes of accident environments to which the casks were subjected. The report contains two major parts. The first concerns the accident description, which includes fact-finding and the inferred accident scenario. The second part deals with the mechanical analysis of the accident, consisting of estimates of the impact loads and an assessment of the response of the casks and their tie-down systems. Discussions of results and recommendations are also included. 10 references, 25 figures, 1 table

  9. Concerted hydrogen-bond dynamics in the transport mechanism of the hydrated proton: a first-principles molecular dynamics study.

    Science.gov (United States)

    Berkelbach, Timothy C; Lee, Hee-Seung; Tuckerman, Mark E

    2009-12-01

    First-principles molecular dynamics calculations performed in a fully converged basis set are used to reveal new details about the mechanism of the anomalous proton-transport process in water, a fundamental question dating back over 200 years. By separating actual structural diffusion from simple rattling events, wherein a proton shuttles forth and back in a hydrogen bond, it is found that the former are driven by a concerted mechanism in which hydronium begins to accept a hydrogen bond from a donor water molecule while the proton-receiving water molecule simultaneously loses one of its acceptor hydrogen bonds. The kinetics of the process are found to be in good agreement with recent experiments. PMID:20366181

  10. Material investigations on the dynamic, fracture mechanical behavior of nodular-graphite iron for transport and storage casks type CASTOR

    International Nuclear Information System (INIS)

    In the frame of the transport and storage cask type CASTOR design strain rate dependent static and dynamic loads are considered based on the IAEA accident scenarios. The fracture mechanical evaluation of the structural integrity is performed assuming crack-like defects. For nodular-graphite iron a validated data base of materials' static data is available, but the dynamic materials characteristics of cast iron materials available in literature are not sufficient. There are only few approaches for the experimental determination of dynamical fracture toughness, therefore an extensive program was started to investigate the dynamic fracture mechanical properties of 28 grades of nodular graphite iron at temperatures of -40 C. The crack resistance curve according to the J-integral concept was determined using small samples (10x10x55 mm).

  11. Transport suppression by diamagnetic phase shift as a possible mechanism to the L to H transition

    International Nuclear Information System (INIS)

    In the presence of a pressure gradient, the phase velocity of drift-wave or ITG-mode turbulence is different from the poloidal ExB rotation velocity of guiding centers. This results in an ExB turbulent particle diffusion being suppressed by the phase shift due to the diamagnetic rotation velocity ?? = (c/enB)dP/dr. This shift cannot be eliminated by a frame change and affects the plasma transport. For ?? well above the turbulent velocity v = -c??xB/B2, the radial diffusivity is suppressed as D ? ??-3. This results in a non-monotonous particle flux ?(?n) ? -D0?n[1+?(?n)2]3/2 such as the transport can develop a bifurcation at a realistic density gradient

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

    International Nuclear Information System (INIS)

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

  13. Noise as a turbulent decorrelation mechanism in Reaction-Diffusion equation like transport models

    Science.gov (United States)

    Samaddar, Debasmita; Newman, D. E.; Broussard, John

    2006-10-01

    Simple dynamical models of transport have been able to capture much of the dynamics of the transport barriers found in many devices. However, these models, which have many similarities with the classic reaction-diffusion equations, have wave like structures that can propagate in certain regimes near transition points. This propagation, while being realistic in a reaction diffusion model, is probably limited in a turbulent plasma due to the turbulent decorrelation. In order to investigate methods for correcting this, noise is added to the system to simulate the intrinsic decorrelations. The wave propagation characteristics are studied as a function of the noise amplitude and compared to similar studies in reaction diffusion systems in which propagation can actually increase in the presence of noise.

  14. An Iris-Like Mechanism of Pore Dilation in the CorA Magnesium Transport System

    OpenAIRE

    Chakrabarti, Nilmadhab; Neale, Chris; Payandeh, Jian; Pai, Emil F.; Pomès, Régis

    2010-01-01

    Magnesium translocation across cell membranes is essential for numerous physiological processes. Three recently reported crystal structures of the CorA magnesium transport system revealed a surprising architecture, with a bundle of giant ?-helices forming a 60-Å-long pore that extends beyond the membrane before widening into a funnel-shaped cytosolic domain. The presence of divalent cations in putative intracellular regulation sites suggests that these structures correspond to the closed conf...

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

    OpenAIRE

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

    1998-01-01

    The accumulation of quaternary ammonium compounds in Lactobacillus plantarum is mediated via a single transport system with a high affinity for glycine betaine (apparent Km of 18 ?M) and carnitine and a low affinity for proline (apparent Km of 950 ?M) and other analogues. Mutants defective in the uptake of glycine betaine were generated by UV irradiation and selected on the basis of resistance to dehydroproline (DHP), a toxic proline analogue. Three independent DHP-resistant mutants showed ...

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

    OpenAIRE

    Yang, J.

    2009-01-01

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

  17. Description of Transport Mechanism in Polymeric Membrane via Sorption in Steady State.

    Czech Academy of Sciences Publication Activity Database

    Fialová, Kate?ina

    Geesthacht : GKSS Research Centre, 2004 - (Castano, M.; Schipolowski, T.; Siegert, M.), s. 82-83 [Network Young Membrains 6th Meeting. Hamburg (DE), 22.09.2004-24.09.2004] R&D Projects: GA ?R GD203/03/H140; GA AV ?R IAA4072402 Institutional research plan: CEZ:AV0Z4072921 Keywords : vapor permeation * pervaporation * membrane transport Subject RIV: CI - Industrial Chemistry, Chemical Engineering

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

    OpenAIRE

    Colonna, M.; Baran, V.; Di Toro, M.; Frecus, B.; Zhang, Y. X.

    2012-01-01

    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 b...

  19. Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers.

    Science.gov (United States)

    Moerman, D; Sebaihi, N; Kaviyil, S E; Leclère, P; Lazzaroni, R; Douhéret, O

    2014-09-21

    In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime. PMID:25079791

  20. Real-time transport in open quantum systems from PT-symmetric quantum mechanics

    Science.gov (United States)

    Elenewski, Justin E.; Chen, Hanning

    2014-08-01

    Nanoscale electronic transport is of intense technological interest, with applications ranging from semiconducting devices and molecular junctions to charge migration in biological systems. Most explicit theoretical approaches treat transport using a combination of density functional theory (DFT) and nonequilibrium Green's functions. This is a static formalism, with dynamic response properties accommodated only through complicated extensions. To circumvent this limitation, the carrier density may be propagated using real-time time-dependent DFT (RT-TDDFT), with boundary conditions corresponding to an open quantum system. Complex absorbing potentials can emulate outgoing particles at the simulation boundary, although these do not account for introduction of charge density. It is demonstrated that the desired positive particle flux is afforded by a class of PT-symmetric generating potentials that are characterized by anisotropic transmission resonances. These potentials add density every time a particle traverses the cell boundary, and may be used to engineer a continuous pulse train for incident packets. This is a first step toward developing a complete transport formalism unique to RT-TDDFT.

  1. The influence of particle shape on structure, mechanics, and transport in granular materials

    Science.gov (United States)

    Smith, Kyle C.

    The development of materials with tailored transport properties is essential to energy conversion and storage applications. Utilization of heterogeneous composite materials composed of discrete particles (i.e., granular materials) represents a promising approach to sustainable, scalable materials production. The so-called jamming point, which represents the transition between fluid-like and solid-like regimes of granular materials, has been the subject of recent fundamental studies. Prior studies have incorporated highly simplified grain shapes that do not reflect the diversity commonly observed in advanced composite materials (e.g., nanomaterials). In the present work, the coupling of heat and charge transport to the level of order in jammed microstructures composed of faceted 3D grains is explored. The systems investigated include lithium ion battery cathodes composed of LiFePO4 nanoparticles, solid state H2 storage in packed beds composed of metal hydride particles, and the Platonic solids. Empirical and theoretical representations of particle shape are determined with single crystal growth models, statistical geometric models, and experimental measurements. An energy-based structural optimization method for the jamming of such arbitrary polyhedral grains is developed to model the mesoscopic structure of heterogeneous materials. Diffusion through the resulting microstructures is simulated with the finite volume method. In LiFePO4 systems a strong dependence of jamming on particle shapes is observed, in which columnar structures aligned with the [010] direction inhibit diffusion along [010] in anisotropic LiFePO4. Transport limitations are induced by [010] columnar order and lead to catastrophic performance degradation in anisotropic LiFePO4 cathodes. Further, judicious mixing of nanoplatelets with additive nanoparticles can frustrate columnar ordering and thereby enhance the rate capability of LiFePO4 electrodes by nearly an order of magnitude. In contrast, metal hydride particles (and all Platonic solids except cubes) jam into highly disordered structures, as a result of anisotropic shape and size distribution. Such systems exhibit fundamentally different pathways of heat transport than that of packed spheres and consequently display close agreement with granular effective medium theory predictions. Also, despite possessing rigidity percolation at the jamming point, conductivity percolation does not occur at the jamming point. From these initial studies it is clear that knowledge of particle shape effects on structure and transport provide a pathway for scalable, bottom-up design of materials.

  2. Non-equilibrium statistical mechanics: From a paradigmatic model to biological transport

    OpenAIRE

    Chou, T.; Mallick, K.; Zia, R. K. P.

    2011-01-01

    Unlike equilibrium statistical mechanics, with its well-established foundations, a similar widely-accepted framework for non-equilibrium statistical mechanics (NESM) remains elusive. Here, we review some of the many recent activities on NESM, focusing on some of the fundamental issues and general aspects. Using the language of stochastic Markov processes, we emphasize general properties of the evolution of configurational probabilities, as described by master equations. Of p...

  3. Forward Current Transport Mechanisms of Ni/Au—InAlN/AlN/GaN Schottky Diodes

    Science.gov (United States)

    Wang, Xiao-Feng; Shao, Zhen-Guang; Chen, Dun-Jun; Lu, Hai; Zhang, Rong; Zheng, You-Dou

    2014-05-01

    We fabricate two Ni/Au-In0.17Al0.83N/AlN/GaN Schottky diodes on substrates of sapphire and Si, respectively, and investigate their forward-bias current transport mechanisms by temperature-dependent current-voltage measurements. In the temperature range of 300-485 K, the Schottky barrier heights (SBHs) calculated by using the conventional thermionic-emission (TE) model are strongly positively dependent on temperature, which is in contrast to the negative-temperature-dependent characteristic of traditional semiconductor Schottky diodes. By fitting the forward-bias I-V characteristics using different current transport models, we find that the tunneling current model can describe generally the I-V behaviors in the entire measured range of temperature. Under the high forward bias, the traditional TE mechanism also gives a good fit to the measured I-V data, and the actual barrier heights calculated according to the fitting TE curve are 1.434 and 1.413 eV at 300K for InAlN/AlN/GaN Schottky diodes on Si and the sapphire substrate, respectively, and the barrier height shows a slightly negative temperature coefficient. In addition, a formula is given to estimate SBHs of Ni/Au—InAlN/AlN/GaN Schottky diodes taking the Fermi-level pinning effect into account.

  4. Forward Current Transport Mechanism and Schottky Barrier Characteristics of a Ni/Au Contact on n-GaN

    International Nuclear Information System (INIS)

    The forward current transport mechanism and Schottky barrier characteristics of a Ni/Au contact on n-GaN are studied by using temperature-dependent current-voltage (T—I—V) and capacitance-voltage (C—V) measurements. The low-forward-bias I-V curve of the Schottky junction is found to be dominated by trap-assisted tunneling below 400 K, and thus can not be used to deduce the Schottky barrier height (SBH) based on the thermionic emission (TE) model. On the other hand, TE transport mechanism dominates the high-forward-bias region and a modified I—V method is adopted to deduce the effective barrier height. It is found that the estimated SBH (?0.95 eV at 300K) by the I—V method is ?0.20 eV lower than that obtained by the C—V method, which is explained by a barrier inhomogeneity model over the Schottky contact area. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Uranium series geochemistry in aquifers: quantification of transport mechanisms of uranium and daughter products: the chalk aquifer (Champagne, France)

    International Nuclear Information System (INIS)

    With the increase of contaminant flux of radionuclides in surface environment (soil, river, aquifer...), there is a need to understand and model the processes that control the distribution of uranium and its daughter products during transport within aquifers. We have used U-series disequilibria as an analogue for the transport of uranium and its daughter products in aquifer to understand such mechanisms. The measurements of uranium (234U et 238U), thorium (230Th et 232Th), 226Ra and 222Rn isotopes in the solid and liquid phases of the chalk aquifer in Champagne (East of France) allows us to understand the processes responsible for fractionation within the uranium decay chain. Fractionations are induced by physical and chemical properties of the elements (leaching, adsorption) but also by radioactive properties (recoil effect during ?-decay). For the first time a comprehensive sampling of the solid phase has been performed, allowing quantifying mechanisms responsible for the long term evolution of the aquifer. A non steady state 1D model has been developed which takes into account leaching, adsorption processes as well as radioactive filiation and ?-recoil effect. Retardation coefficients have been calculated for uranium, thorium and radium. The aquifer is characterised by a double porosity, and the contribution of fracture and matrix porosity on the water/rock interaction processes has been estimated. (author)

  6. 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

  7. Mechanisms of meridional transport processes in the tropical Atlantic; Mechanismen meridionaler Transportprozesse im tropischen Atlantik

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, J.

    2001-07-01

    Meridional transport processes of water masses and tracers in the subtropical and tropical Atlantic are investigated using a regional eddy resolving model of the wind driven and thermohaline circulation. Analytical emphasis is on float simulations in the model which, complementary to Eulerian means, represent the Lagrangian view and give further insight into the spreading and pathways of characteristic water masses in this area. In the tropics and subtropics shallow 3-dimensional circulation cells are superimposed on the northward warm water transfer within the deep reaching thermohaline overturning cell (MOC) as part of the global ''Conveyor Belt''. Under present-day climate conditions the model shows that the equatorial thermocline is exclusively ventilated by subsurface flow within the tropical-subtropical cell (STC) of the South Atlantic. Only with a prescribed ''Conveyor-off''-Mode the STC of the North Atlantic contributes to this ventilation process with equal amounts. Throughout the year the interhemispheric transport of surface and central water masses of South Atlantic origin into the Caribbean Sea is dominated by zonal detours to the east as a consequence of the interplay of several retroflection events occuring in the North Atlantic. The eulerian mean flow field in the deep layer postulates the interhemispheric mass transport into the South Atlantic to be confined entirely to the western boundary, whereas Lagrangian means indicate intermittent eastward excursions along the equator, related to seasonally alternating zonal currents due to long Rossby waves. It was suggested that the observed characteristic eastward maximum of tracer concentrations along the equator is a consequence of rectifying effects of single or interacting equatorial waves. The model does not validate this hypothesis. The response to transport anomalies of subpolar origin and long periodicity is subject to different time-scales in both hemispheres. The fast response is confined to the northern hemisphere and dominates the first two years because of the mediating waves which at first propagate only around the North Atlantic basin. After 8 to 10 years the changes in the overturning are not restricted to the North anymore but are apparent in both hemispheres. (orig.)

  8. Results of the thermomechanical and fracture mechanical analysis of pipeline tee-junction break under conditions of interaction between hot sodium jet and main cold sodium flow

    International Nuclear Information System (INIS)

    Benchmark problem is considered associated with determination of thermo-mechanical stresses in the region of a tee where the interaction of hot sodium jet with cold sodium flow occurs. Using the results of a thermo-hydraulic analysis swings and frequencies of temperature pulsations on the wall of the pipeline are determined. The analysis of stresses, cyclic strength calculation and analysis of cracks progress under specified initial defect for the pipeline element were performed using the obtained data. (author)

  9. Main: FEA5 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA5 Structural biology on efflux transport machineries to understand multi-drug resistance Effl ... ness of a drug such as an antimicrobial or an anti-cancer ... drug, is the main cause of hospital-acquired infec ... ness of a drug such as an antimicrobial or an anti-cancer ... drug, is an emerging threat worldwide. One of the ...

  10. Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers

    Science.gov (United States)

    Moerman, D.; Sebaihi, N.; Kaviyil, S. E.; Leclère, P.; Lazzaroni, R.; Douhéret, O.

    2014-08-01

    In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime.In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime. Electronic supplementary information (ESI) available: SI-1: tapping mode AFM image of fibrillar P3HT. SI-2: current-distance profile of a high aspect ratio channel exhibiting both the contact and transport resistance dominating regimes. SI-3: full analytical derivation of the Mott-Gurney law, describing the SCLC regime in a point probe geometrical configuration for C-AFM measurements. See DOI: 10.1039/c4nr02577f

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

    Science.gov (United States)

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

    1999-01-01

    Two major routes of preprotein targeting into mitochondria are known. Preproteins carrying amino-terminal signals mainly use Tom20, the general import pore (GIP) complex and the Tim23–Tim17 complex. Preproteins with internal signals such as inner membrane carriers use Tom70, the GIP complex, and the special Tim pathway, involving small Tims of the intermembrane space and Tim22–Tim54 of the inner membrane. Little is known about the biogenesis and assembly of the Tim proteins of this carrier pathway. We report that import of the preprotein of Tim22 requires Tom20, although it uses the carrier Tim route. In contrast, the preprotein of Tim54 mainly uses Tom70, yet it follows the Tim23–Tim17 pathway. The positively charged amino-terminal region of Tim54 is required for membrane translocation but not for targeting to Tom70. In addition, we identify two novel homologues of the small Tim proteins and show that targeting of the small Tims follows a third new route where surface receptors are dispensable, yet Tom5 of the GIP complex is crucial. We conclude that the biogenesis of Tim proteins of the carrier pathway cannot be described by either one of the two major import routes, but involves new types of import pathways composed of various features of the hitherto known routes, including crossing over at the level of the GIP. PMID:10397776

  12. Theoretical preconditions and technical substantiation for mechanical compressed air drying method application on the railway transport

    OpenAIRE

    Ripol’-saragosi, Tatiana; Ripol’-saragosi, Leonid

    2009-01-01

    The article is related to the compressed air purification for the rolling stock problems. The mechanical method is described as a potential way of the compressed air cooling and purificating. The temperature field at the heat conducting surface engineer function equation is given in the article as well.

  13. DC electronic transport mechanisms in some manganese-oxide insulator thin films grown on Si substrates

    International Nuclear Information System (INIS)

    Thin films of crystalline of Mn2O3, MnO, and their mixture have been prepared on Si(P) substrates by evaporation of MnO2 powder followed by calcination in air and in vacuum. The structure of the prepared oxide films was studied by X-ray diffraction (XRD). For electrical studies, the samples were constructed in the form of Al/oxide/Si MOS structures. Those MOS devices have been electrically characterised by the measurement of their capacitance as a function of gate voltage. The MOS capacitors exhibited the charge regimes of accumulation, depletion, and inversion. The net surface charge density was measured to be in the range of 1014 to 1015 m-2. The dc current-voltage characteristic measurements at room temperature and in the temperature range (290-370 K) show that the mechanisms controlling the current flow in those oxides were the Richardson-Schottky (RS) mechanism and the trap-charge-limited space-charge-limited conductivity (TSCLC) mechanism characterised by exponential distribution of traps, depending on the film structure and hence the preparation conditions. The temperature dependence of leakage current in films of ?-Mn2O3 and MnO has interesting property that higher temperatures reduce the current. This may be important in the application in circuits that operate under extreme conditions. The parameters of those mechanisms like the activation energy of electrical conductionctivation energy of electrical conduction, dynamic relative permittivity, and traps concentration were determined

  14. Transepithelial transport of a natural cholinesterase inhibitor, huperzine A, along the gastrointestinal tract: the role of ionization on absorption mechanism.

    Science.gov (United States)

    Burshtein, Gregory; Friedman, Michael; Greenberg, Sarit; Hoffman, Amnon

    2013-03-01

    During recent years there has been increasing interest in the Lycopodium alkaloid huperzine A as a potential therapeutic agent for neurodegenerative diseases. This study aimed to characterize huperzine A's permeability across the enterocyte barrier along the gastrointestinal tract with an emphasis on the effect of ionization on the drug absorption. Intestinal permeability of huperzine A was evaluated by in vitro Caco-2 and parallel artificial membrane permeation assay models and by the ex vivo Ussing chamber model. The permeability rate was strongly dependent on the degree of ionization and increased with elevation of the donor medium pH in all studied models. The transport of the unionized fraction was similar to the permeability of the markers for passive transcellular diffusion. Addition of the paracellular permeability modulator palmitoylcarnitine in the Caco-2 model led to significant enhancement in the permeability of the ionized huperzine A fraction. No evidence of active transport of huperzine A was detected in this study. The Ussing chamber model experiments showed similar drug permeability along the entire rat intestine. In conclusion, huperzine A permeates the intestinal border mainly by passive transcellular diffusion whereas some fraction, dependent on the degree of huperzine A ionization, is absorbed by the paracellular route. Huperzine A's permeability characteristics pave the way to the development of its oral extended release dosage form. The specific population of the potential users of huperzine A and the high potency of this molecule support the rationale for such a delivery. PMID:23345165

  15. Transport and charging mechanisms in Ta2O5 thin films for capacitive RF MEMS switches application

    International Nuclear Information System (INIS)

    The potential of sputtered Ta2O5 thin films to be used as dielectric layers in capacitive radio frequency microelectromechanical system switches is evaluated by investigating two factors of crucial importance for the performance of these devices which are the transport mechanisms and the charging effects in the dielectric layer. We find that Ta2O5 films show good electrical and dielectrical properties for the considered application in terms of a low leakage current density of 4 nA/cm2 for E=1 MV/cm, a high breakdown field of 4 MV/cm and a high dielectric constant of 32. For electric fields lower than 1 MV/cm the conduction mechanism is found to be variable-range hopping in the temperature range 300-400 K, while nearest-neighbor hopping is observed at higher temperatures. For fields in the range 1-4 MV/cm Poole-Frenkel becomes the dominant conduction mechanism. Current and capacitance transients used to investigate the charging effects show a decay which is well described by the stretched-exponential law, thus providing further insights on capture and emission processes.

  16. Mechanized Verification of Security Properties of Transport Layer Security 1.2 Protocol with Crypto Verif in Computational Model

    Directory of Open Access Journals (Sweden)

    Bo Meng

    2014-01-01

    Full Text Available In modern society, many transactions have been processed through web-based applications. In order to protect those critical applications against attacks, Transport Layer Security (TLS protocol has been implemented and widely deployed. The related literatures show that security analysis of TLS 1.2 protocol where cipher suite is RSA encryption has not been implemented with mechanized tool in computational model. Hence in this study, Blanchet calculus is used to analyze TLS 1.2 protocol where cipher suite is RSA encryption with mechanized tool crypto verif in computational model. The term, process and correspondence are used to model authentication in TLS 1.2 protocol where cipher suite is RSA encryption. The result shows that TLS 1.2 protocol where Cipher suite is RSA encryption has the pre master key confidentiality and authentication from server to client. The first mechanized analysis on TLS 1.2 protocol where Cipher suite is RSA encryption is implemented in computational model with active adversary in this study.

  17. Atypical Dopamine Uptake Inhibitors that Provide Clues About Cocaine's Mechanism at the Dopamine Transporter

    Science.gov (United States)

    Hauck Newman, Amy; Katz, Jonathan L.

    The dopamine transporter (DAT) has been a primary target for cocaine abuse/addiction medication discovery. However predicted addiction liability and limited clinical evaluation has provided a formidable challenge for development of these agents for human use. The unique and atypical pharmacological profile of the benztropine (BZT) class of dopamine uptake inhibitors, in preclinical models of cocaine effects and abuse, has encouraged further development of these agents. Moreover, in vivo studies have challenged the original DAT hypothesis and demonstrated that DAT occupancy and subsequent increases in dopamine produced by BZT analogues are significantly delayed and long lasting, as compared to cocaine. These important and distinctive elements are critical to the lack of abuse liability among BZT analogues, and improve their potential for development as treatments for cocaine abuse and possibly other neuropsychiatric disorders.

  18. Transport mechanisms in Plasmodium-infected erythrocytes: lipid rafts and a tubovesicular network.

    Science.gov (United States)

    Haldar, K; Samuel, B U; Mohandas, N; Harrison, T; Hiller, N L

    2001-10-01

    The mature human erythrocyte is a simple cell that is devoid of intracellular organelles and does not show endocytic or phagocytic activity at the plasma membrane. However, following infection by Plasmodium, the erythrocyte undergoes several morphological and functional changes. Parasite-derived proteins are exported into the erythrocyte cytoplasm and to the membrane, while several proteins are localised to the parasitophorous vacuolar membrane and to the tubovesicular membranous network structures surrounding the parasite. Recent evidence indicates that multiple host proteins, independent of the type of their membrane anchor, that exist in detergent-resistant membrane (DRM) rafts or microdomains enter this apicomplexan vacuole. The internalised host components along with the parasite-encoded transmembrane protein PfEXP1 can be detected as DRM rafts in the vacuole. It appears that in Plasmodium-infected erythrocytes lipid rafts may play a role in endovacuolation and macromolecular transport. PMID:11566306

  19. Numerical simulation of dynamic deformation of a spent nuclear fuel transport package in accidental mechanical impacts

    International Nuclear Information System (INIS)

    Numerical simulation results and their analysis are presented for dynamic deformations of the TUK-117 package, intended for the transport of spent nuclear fuel from nuclear power plants, subjected to accidental 9 m drops on to an unyielding surface at different angles. This paper focuses on the analysis of the deformation behaviour of container shock limiters. It is demonstrated that maximum loading affects the package during a side drop. For a side drop, the maximum strain levels are determined for the different construction elements, including the cask's body and the bolts securing the sealing lid. Dynamic simulation of the behaviour of the construction elements was carried out using the LS-DYNA code, version 970. (author)

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

    International Nuclear Information System (INIS)

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

  1. Transport mechanisms and rates for long lived Chernobyl deposits in mid-Wales

    International Nuclear Information System (INIS)

    The deposition and transport of 134Cs and 137Cs derived from Chernobyl within 3 upland catchments in mid-Wales (Upper Severn, Wye and Rheidol) has been examined between 1987-1989. An increase in the pre-existing inventory of 137Cs of 15% was observed. During the study period all fluvial outputs of 134Cs and 137Cs were in association with suspended and bedload sediments with no radiocaesium being detectable in solute form. The major source of 137Cs on suspended sediments was ''old'' 137Cs originating from fallout due to nuclear weapons testing. Mineral magnetic measurements combined with radiometric data suggest that the Chernobyl component in association with suspended sediments originates from top-soil sediment sources whilst the fine particulate material in association with bedload is supplied from subsurface and channel sources. Outputs of Chernobyl-labelled sediments from the catchments indicated by river and lake sampling were low. In 1988 ?0.08% of the soil inventory of Chernobyl derived radiocaesium was removed from the Wye and Severn catchments via fluvial transport, whilst between January and August 1989 ?0.04% was removed. Lake sediment inventories in Llyn Llygad Rheidol also suggest that rates of transfer across the upper Rheidol catchment are low. Sampling of the Hafren Forest indicates ?0.01 GBq of 137Cs and ?0.006 GBq of 134Cs deposited due to the C134Cs deposited due to the Chernobyl accident is stored in the canopy of the forest. Losses to the forest floor from a Norway Spruce canopy were 13% and 15% of the activity contained in the overlying canopy in 1988 and 1989 and 16.5% and 9% in 1988 and 1989 under Sitka Spruce. (author)

  2. Biosynthetic mechanism for L-Gulose in main polar lipids of Thermoplasma acidophilum and possible resemblance to plant ascorbic acid biosynthesis.

    Science.gov (United States)

    Yamauchi, Noriaki; Nakayama, Yusuke

    2013-01-01

    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. PMID:24096672

  3. 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)

    Bruce A. Roberts

    2011-03-01

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

  4. Autotransporters: The Cellular Environment Reshapes a Folding Mechanism to Promote Protein Transport

    OpenAIRE

    Braselmann, Esther; Clark, Patricia L.

    2012-01-01

    We know very little about how the cellular environment affects protein folding mechanisms. Here, we focus on one unique aspect of that environment that is difficult to recapitulate in the test tube: the effect of a folding vector. When protein folding is initiated at one end of the polypeptide chain, folding starts from a much smaller ensemble of conformations than during refolding of a full-length polypeptide chain. But to what extent can vectorial folding affect protein folding kinetics and...

  5. Further assessment of houseflies (Musca domestica) as vectors for the mechanical transport and transmission of porcine reproductive and respiratory syndrome virus under field conditions

    OpenAIRE

    Pitkin, Andrea; Deen, John; Otake, Satoshi; Moon, Roger; Dee, Scott

    2009-01-01

    The purpose of this study was to evaluate the potential for houseflies (Musca domestica) to mechanically transport and transmit porcine reproductive and respiratory syndrome virus (PRRSV) between pig populations under controlled field conditions. The study employed swine housed in commercial livestock facilities and a release-recapture protocol involving marked (ochre-eyed) houseflies. To assess whether transport of PRRSV by insects occurred, ochre-eyed houseflies were released and collected ...

  6. Ammonia excretion in Caenorhabditis elegans: mechanism and evidence of ammonia transport of the Rhesus protein CeRhr-1.

    Science.gov (United States)

    Adlimoghaddam, Aida; Boeckstaens, Mélanie; Marini, Anna-Maria; Treberg, Jason R; Brassinga, Ann-Karen C; Weihrauch, Dirk

    2015-03-01

    The soil-dwelling nematode Caenorhabditis elegans is a bacteriovorous animal, excreting the vast majority of its nitrogenous waste as ammonia (25.3±1.2?µmol gFW(-1) day(-1)) and very little urea (0.21±0.004?µmol gFW(-1) day(-1)). Although these roundworms have been used for decades as genetic model systems, very little is known about their strategy to eliminate the toxic waste product ammonia from their bodies into the environment. The current study provides evidence that ammonia is at least partially excreted via the hypodermis. Starvation reduced the ammonia excretion rates by more than half, whereas mRNA expression levels of the Rhesus protein CeRhr-2, V-type H(+)-ATPase (subunit A) and Na(+)/K(+)-ATPase (?-subunit) decreased correspondingly. Moreover, ammonia excretion rates were enhanced in media buffered to pH 5 and decreased at pH 9.5. Inhibitor experiments, combined with enzyme activity measurements and mRNA expression analyses, further suggested that the excretion mechanism involves the participation of the V-type H(+)-ATPase, carbonic anhydrase, Na(+)/K(+)-ATPase, and a functional microtubule network. These findings indicate that ammonia is excreted, not only by apical ammonia trapping, but also via vesicular transport and exocytosis. Exposure to 1?mmol l(-1) NH4Cl caused a 10-fold increase in body ammonia and a tripling of ammonia excretion rates. Gene expression levels of CeRhr-1 and CeRhr-2, V-ATPase and Na(+)/K(+)-ATPase also increased significantly in response to 1?mmol l(-1) NH4Cl. Importantly, a functional expression analysis showed, for the first time, ammonia transport capabilities for CeRhr-1 in a phylogenetically ancient invertebrate system, identifying these proteins as potential functional precursors to the vertebrate ammonia-transporting Rh-glycoproteins. PMID:25740900

  7. Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

    Science.gov (United States)

    Crossman, J.; Futter, M. N.; Whitehead, P. G.; Stainsby, E.; Baulch, H. M.; Jin, L.; Oni, S. K.; Wilby, R. L.; Dillon, P. J.

    2014-07-01

    Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which is expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of Global Climate Model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the Integrated Catchment Model of Phosphorus Dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968-1997) to two future periods: 2020-2049 and 2060-2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivity) were highly varied. Sensitivity was governed by soil type (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy-loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

  8. Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

    Directory of Open Access Journals (Sweden)

    J. Crossman

    2014-07-01

    Full Text Available Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities to climate change, which is expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE, derived from a series of Global Climate Model (GCM variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the Integrated Catchment Model of Phosphorus Dynamics (INCA-P, we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968–1997 to two future periods: 2020–2049 and 2060–2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivity were highly varied. Sensitivity was governed by soil type (influencing flow pathways and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy-loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

  9. Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

    Science.gov (United States)

    Crossman, J.; Futter, M. N.; Whitehead, P. G.; Stainsby, E.; Baulch, H. M.; Jin, L.; Oni, S. K.; Wilby, R. L.; Dillon, P. J.

    2014-12-01

    Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which are expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as it is to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of global climate model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the INtegrated CAtchment model of Phosphorus dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968-1997) to two future periods: 2020-2049 and 2060-2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivities) were highly varied. Sensitivity was governed by quaternary geology (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

  10. Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation

    Directory of Open Access Journals (Sweden)

    Isabella Farella

    2013-07-01

    Full Text Available Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden.

  11. On the electronic transport mechanism in thin films of some new poly(azomethine sulfone)s

    International Nuclear Information System (INIS)

    The studied polymers, poly(azomethine sulfone)s, were prepared by the reaction of bis(4-chlorophenyl)sulfone with a mixture of bisphenols: 2,2-bis(p-hydroxyphenyl)propane (bisphenol A) and 4,4'-bis(4-hydroxybenzylideneiminophenoxy)biphenyl in various molar ratios. The temperature dependences of the electrical conductivity and Seebeck coefficient of polymers were investigated using thin-film samples deposited from chloroform solutions (spin coating method) onto glass substrates. It was found that the respective polymers show typical semiconducting properties. Some correlations between these properties and the chemical structures of the polymers were established. The mechanism of electronic transport in the films studied is discussed. The study of optical absorption (in spectral range, 300-1400 nm) evidenced direct bandgaps ranged between 1.30 and 1.80 eV

  12. Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

    Energy Technology Data Exchange (ETDEWEB)

    Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying; Neaton, J. B.; Salmeron, Miquel

    2007-11-12

    The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of {approx} 1 {angstrom}{sup -1} found when the separation is changed by changing the length of the alkanethiol molecules. Calculations indicate that for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.

  13. Complex metabolic network of 1,3-propanediol transport mechanisms and its system identification via biological robustness.

    Science.gov (United States)

    Guo, Yanjie; Feng, Enmin; Wang, Lei; Xiu, Zhilong

    2014-04-01

    The bioconversion of glycerol to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae (K. pneumoniae) can be characterized by an intricate metabolic network of interactions among biochemical fluxes, metabolic compounds, key enzymes and genetic regulation. Since there are some uncertain factors in the fermentation, especially the transport mechanisms of 1,3-PD across cell membrane, the metabolic network contains multiple possible metabolic systems. Considering the genetic regulation of dha regulon and inhibition of 3-hydroxypropionaldehyde to the growth of cells, we establish a 14-dimensional nonlinear hybrid dynamical system aiming to determine the most possible metabolic system and the corresponding optimal parameter. The existence, uniqueness and continuity of solutions are discussed. Taking the robustness index of the intracellular substances together as a performance index, a system identification model is proposed, in which 1,395 continuous variables and 90 discrete variables are involved. The identification problem is decomposed into two subproblems and a parallel particle swarm optimization procedure is constructed to solve them. Numerical results show that it is most possible that 1,3-PD passes the cell membrane by active transport coupled with passive diffusion. PMID:24002752

  14. Mechanisms of calcium transport in small intestine. Overall review of the contract, September 1, 1972--March 1, 1975

    International Nuclear Information System (INIS)

    During the past three years considerable advance has been registered in our understanding of the mechanism of intestinal calcium transport, which is activated in response to 1,25-(OH)2D3, the active form of the vitamin in the system. In brush borders isolated from vitamin D-deficient chicks, a 200,000 molecular weight protein has been found by disc gel electrophoresis which is not present in chicks given vitamin D. This protein does not bind calcium and does not possess calcium dependent adenosine triphosphatase activity. Following the administration of 1,25-(OH)2D3 to the deficient chicks this protein disappears from the disc gel profiles and a protein of molecular weight 220,000 appears in the gel profiles. This protein has been isolated and shown to possess calcium adenosine triphosphatase activity, alkaline phosphatase activity and it binds calcium. Work is progressing on the purification of these proteins with the ultimate aim of discerning what role they have in intestinal calcium transport. (U.S.)

  15. Endocytosis of ABCG2 drug transporter caused by binding of 5D3 antibody: trafficking mechanisms and intracellular fate.

    Science.gov (United States)

    Studzian, Maciej; Bartosz, Grzegorz; Pulaski, Lukasz

    2015-08-01

    ABCG2, a metabolite and xenobiotic transporter located at the plasma membrane (predominantly in barrier tissues and progenitor cells), undergoes a direct progressive endocytosis process from plasma membrane to intracellular compartments upon binding of 5D3 monoclonal antibody. This antibody is specific to an external epitope on the protein molecule and locks it in a discrete conformation within its activity cycle, presumably providing a structural trigger for the observed internalization phenomenon. Using routine and novel assays, we show that ABCG2 is endocytosed by a mixed mechanism: partially via a rapid, clathrin-dependent pathway and partially in a cholesterol-dependent, caveolin-independent manner. While the internalization process is entirely dynamin-dependent and converges initially at the early endosome, subsequent intracellular fate of ABCG2 is again twofold: endocytosis leads to only partial lysosomal degradation, while a significant fraction of the protein is retained in a post-endosomal compartment with the possibility of at least partial recycling back to the cell surface. This externally triggered, conformation-related trafficking pathway may serve as a general regulatory paradigm for membrane transporters, and its discovery was made possible thanks to consistent application of quantitative methods. PMID:25918011

  16. Determination of micro-mechanical parameters of primary heat transport piping material of Pressurised Heavy Water Reactor

    International Nuclear Information System (INIS)

    Models being developed for numerical simulation of ductile fracture require a number of input parameters, which are known as micro-mechanical parameters. The micro-mechanical parameters of the primary heat transport (PHT) piping material of pressurised heavy water reactor (PHWR) are not known. A study has been carried out to understand the micro-void development and to determine the three important micro-mechanical parameters of this material namely, initial void volume fraction (fo), critical void volume fraction (fc) and void volume fraction at final failure (fF). Initial void volume fraction (fo) was determined by measuring inclusion volume fraction by quantitative image analysis of photomicrographs taken on the as polished surface of the samples cut of PHT piping piece. Micro-void development in the material was studied using scanning electron microscope (SEM) on specimens sectioned from the tensile tested specimens. For this purpose, nine smooth round bar tensile testing specimens were subjected to uniaxial tension test. Six samples underwent interrupted test while three were loaded till fracture occurred. The critical void volume fraction (fc) and the void volume fraction at fracture (fF) were estimated from the fracture surfaces of the tensile specimens. The study of sections from the interrupted tests showed that voids were present in the material around inclusions when the diameter reduction during tension test was 10.5% or more. However, no micro-voids were seen in the specimens in which the diameter reduction was 4.5%. The mean values of the three micro-mechanical parameters fo, fc and fF from the study were found to be 0.0011, 0.118 and 0.368, respectively. The average void volume fraction at a location where the diameter reduction was 44% was found to be 0.00463 which is more than four times the initial void volume fraction. (author)

  17. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    Science.gov (United States)

    Das, Kallol; Freund, Jonathan B.; Johnson, Harley T.

    2015-02-01

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.

  18. A mass-transportation approach to a one dimensional fluid mechanics model with nonlocal velocity

    CERN Document Server

    Carrillo, J A; Precioso, J C

    2011-01-01

    We consider a one dimensional transport model with nonlocal velocity given by the Hilbert transform and develop a global well-posedness theory of probability measure solutions. Both the viscous and non-viscous cases are analyzed. Both in original and in self-similar variables, we express the corresponding equations as gradient flows with respect to a free energy functional including a singular logarithmic interaction potential. Existence, uniqueness, self-similar asymptotic behavior and inviscid limit of solutions are obtained in the space $\\mathcal{P}_{2}(\\mathbb{R})$ of probability measures with finite second moments, without any smallness condition. Our results are based on the abstract gradient flow theory developed in \\cite{Ambrosio}. An important byproduct of our results is that there is a unique, up to invariance and translations, global in time self-similar solution with initial data in $\\mathcal{P}_{2}(\\mathbb{R})$, which was already obtained in \\textrm{\\cite{Deslippe,Biler-Karch}} by different metho...

  19. Modelling and pathway identification involving the transport mechanism of a complex metabolic system in batch culture

    Science.gov (United States)

    Yuan, Jinlong; Zhang, Xu; Zhu, Xi; Feng, Enmin; Yin, Hongchao; Xiu, Zhilong

    2014-06-01

    The bio-dissimilation of glycerol to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae (K. pneumoniae) can be characterized by a complex metabolic system of interactions among biochemical fluxes, metabolic compounds, key enzymes and genetic regulation. In this paper, in consideration of the fact that the transport ways of 1,3-PD and glycerol with different weights across cell membrane are still unclear in batch culture, we consider 121 possible metabolic pathways and establish a novel mathematical model which is represented by a complex metabolic system. Taking into account the difficulty in accurately measuring the concentration of intracellular substances and the absence of equilibrium point for the metabolic system of batch culture, the novel approach used here is to define quantitatively biological robustness of the intracellular substance concentrations for the overall process of batch culture. To determine the most possible metabolic pathway, we take the defined biological robustness as cost function and establish an identification model, in which 1452 system parameters and 484 pathway parameters are involved. Simultaneously, the identification model is subject to the metabolic system, continuous state constraints and parameter constraints. As such, solving the identification model by a serial program is a very complicated task. We propose a parallel migration particle swarm optimization algorithm (MPSO) capable of solving the identification model in conjunction with the constraint transcription and smoothing approximation techniques. Numerical results show that the most possible metabolic pathway and the corresponding metabolic system can reasonably describe the process of batch culture.

  20. Hydro-mechanical and gas transport properties of bentonite blocks - role of interfaces

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The long-term safety of the disposal of nuclear waste is an important issue in all countries with a significant nuclear programme. Repositories for the disposal of high-level and long-lived radioactive waste generally rely on a multi-barrier system to isolate the waste from the biosphere. The multi-barrier system typically comprises the natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system (EBS), i.e. the backfilling and sealing of shafts and galleries to block any preferential path for radioactive contaminants. Because gas will be created in a radioactive waste repository performance assessment requires quantification of the relevancy of various potential pathways. Referring to the sealing plugs it is expected that in addition to the matrix properties of the sealing material conductive discrete interfaces inside the sealing elements itself and to the host rock may act not only as mechanical weakness planes but also as preferential gas pathways (Popp, 2009). For instance despite the assumed self sealing capacity of bentonite inherent existing interfaces may be reopened during gas injection. Our lab investigations are aiming on a comprehensive hydro-mechanical characterization of interfaces in bentonite buffers, i.e. (1) between prefabricated bentonite blocks itself and (2) on mechanical contacts of bentonite blocks and concrete to various host rocks, i.e.s and concrete to various host rocks, i.e. granite. We used as reference material pre-compacted bentonite blocks consisting of a sand clay-bentonite mixture but the variety of bentonite-based buffer materials has to be taken in mind. The blocks were manufactured in the frame work of the so-called dam - project 'Sondershausen', i.e. a German research project performed between 1997 and 2002. The blocks have a standard size of (250 x 125 x 62.5) mm. Approximately 500 t of such bentonite blocks have been produced and assembled in underground drift sealing elements. The investigations consist of: - long-term water injection tests in a new designed oedometer cell with different sample constellations under well controlled stress and swelling conditions to provide data about - time dependent interface 'permeability' changes during long-term compaction and fluid injection - gas entry pressures and relative gas permeability changes during pressure dependent gas injection; - shear tests to quantify mechanical interface properties of pre-saturated bentonite blocks under well controlled shear forces or displacements. As initial characterization both, triaxial and direct strength tests were performed, which allow to separate between matrix and interface properties. The investigations are being performed in the framework of the pan-European project FORGE project which aims on the generation and movement of repository gases. Results and interpretation The performed lab investigations cover a wide field of hydro-mechanical properties of bentonite blocks, which represent a favorable option for constructing sealing plugs in different host rock environments. Based on the experimental results the following conclusions can be drawn: - At dry conditions gas flow along interfaces is at least 4 orders higher than through the matrix. Increase of confinement significantly lowers the gas flow but the effect is more pronounced for interfaces ? crack sealing. - Saturation of bentonite block assembly, i.e. blocks with a common interface, is not affected by the interfaces and only weakly by the acting confining pressure. - During gas injection a significant effect is only observed if the minimal stress is passed resulting in some minor gas flow. - The gas break through results in stationary inflow but no significant effect on the total stress is measured, probably due to the central gas injection. - The measured gas threshold pressures under constant volume conditions significantly exceed the sum of the swelling pressure and externally-applied pore water pressure - drained conditions. An

  1. Thermo-Hydro-Mechanical Evolution of Transport Properties in Porous Media: From Laboratory to the Groß-Schönebeck Geothermal Reservoir.

    Science.gov (United States)

    Jacquey, Antoine; Cacace, Mauro; Blöcher, Guido; Watanabe, Norihiro; Scheck-Wenderoth, Magadalena

    2015-04-01

    Quantifying variations of transport properties of porous material, which are porosity and permeability is of special interest for geothermal applications. Variations of these properties result from the coupling between rock deformation and thermal processes. Significant pore pressure and temperature changes can occur during injection and production of fluid. Such changes have a direct impact on the stress-field affecting the geothermal reservoir performance. Understanding the coupling between deformation of the porous material and variation of its properties for mass and energy transfer is therefore a major focus for any geothermal operations. Deformation of a porous material filled with fluid is based on variations of bulk and pore volumes and affects therefore the basic transport properties of the rock. Variations of the transport properties can be expressed by theoretical formulations based on experimental observations and then integrated into numerical models which can be used to predict reservoir performance at the field scale. The aim of this study is to develop a complete poro- and thermoelastic formulation capable of explaining and quantifying fluid-rock interactions in a context of geothermal applications. In a first step, formulations to quantify porosity variations are tested with the open-source finite element method based software OpenGeoSys (Kolditz et al. 2012) and compared to laboratory experiments to constrain the parameters involved. Numerical description of the physical phenomena involved for such behavior requires to account for the coupling between deformation, thermal and hydraulic processes and the relations between different scales. Three different formulations with H-M coupling are studied which are based on the theories of poroelasticity and crack closure (Zimmerman 1991, Blöcher et al. 2013 and Chin et al. 2000). These three formulations are tested on two different kinds of sandstones (Flechtinger and Bentheimer sandstones) by comparing simulations to experimental results. It is then possible to constrain some parameters involved in these porosity formulations. One formulation with T-M coupling is also investigated (Ghabezloo et al. 2008) which is based on thermoelasticity and a fluid volume balance. Then, this theoretical background has been applied to the field scale to study the performance of the Groß-Schönebeck geothermal reservoir situated in the North-East German Basin. Current results on numerical simulations of Thermo-Hydro-Mechanical coupled processes involving transport properties evolution will be presented.

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

    Scientific Electronic Library Online (English)

    Helena Z. W., Grotto.

    2008-10-01

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

  3. Virus in Groundwater: Characterization of transport mechanisms and impacts on an agricultural area in Uruguay

    Science.gov (United States)

    Gamazo, P. A.; Colina, R.; Victoria, M.; Alvareda, E.; Burutaran, L.; Ramos, J.; Lopez, F.; Soler, J.

    2014-12-01

    In many areas of Uruguay groundwater is the only source of water for human consumption and for industrial-agricultural economic activities. Traditionally considered as a safe source, due to the "natural filter" that occurs in porous media, groundwater is commonly used without any treatment. The Uruguayan law requires bacteriological analysis for most water uses, but virological analyses are not mentioned in the legislation. In the Salto district, where groundwater is used for human consumption and for agricultural activities, bacterial contamination has been detected in several wells but no viruses analysis have been performed. The Republic University (UDELAR), with the support of the National Agency for Research and Innovation (ANII), is studying the incidence of virus in groundwater on an intensive agriculture area of the Salto district. In this area water is pumped from the "Salto Aquifer", a free sedimentary aquifer. Below this sedimentary deposit is the "Arapey" basaltic formation, which is also exploited for water productions on its fractured zones. A screening campaign has been performed searching for bacterial and viral contamination. Total and fecal coliforms have been found on several wells and Rotavirus and Adenovirus have been detected. A subgroup of the screening wells has been selected for an annual survey. On this subgroup, besides bacteria and viruses analysis, a standard physical and chemical characterization was performed. Results show a significant seasonal variation on microbiological contamination. In addition to field studies, rotavirus circulation experiments on columns are being performed. The objective of this experiments is to determinate the parameters that control virus transport in porous media. The results of the study are expected to provide an insight into the impacts of groundwater on Salto's viral gastroenterocolitis outbreaks.

  4. Giant shot noise due to mechanical transportation of spin-polarized electrons.

    Energy Technology Data Exchange (ETDEWEB)

    Gorelik, L. Y.; Kulinich, S. I.; Shekhter, R. I.; Jonson, M.; Vinokur, V. M.; Materials Science Division; Chalmers Univ. of Technology; Univ.of Goteborg; B.I. Verkin Inst. for Low Temperature Physics and Engineering; Goteborg Univ.; Heriot-Watt Univ.

    2008-05-01

    We show that single-electron 'shuttling' of electrons in a magnetic nanoelectromechanical single-electron transistor device can be an efficient tool for studying electron spin-flip relaxation on quantum dots. The reason is traced to a spin blockade of the mechanically aided shuttle current that occurs in devices with highly polarized and collinearly magnetized leads. This results in giant peaks in the shot-noise spectral function, wherein the peak heights are only limited by the rate of electronic spin flips. Therefore, we show that nanomechanical spectroscopy of the spin-flip rate is possible, allowing spin-flip relaxation times as long as 10 {micro}s to be detected.

  5. Auxin apical control of the auxin polar transport and its oscillation - a suggested cellular transduction mechanism

    Directory of Open Access Journals (Sweden)

    Tomasz J. Wodzicki

    2014-02-01

    Full Text Available The proposed hypothesis concerns the transduction of auxin molecular signals arriving from the apoplast at the plasma membrane or recognized by the proteineous receptors of the responding cell, to the concentration gradients oscillating in the supracellular space, associated usually with the specific plant growth and differentiation. Acting as an agonist from outside the target cell auxin stimulates in this cell: (1 the liberation of auxin from the cytosolic pool of its conjugates directly into the basipetal efflux; (2 the synthesis of new auxin which restores the cytosolic reserve of auxin conjugates. The functioning of such a system may be effective in a series of processes initiated by the changing concentration of cytosolic calcium. The hypothesis suggests a molecular mechanism for the development and effective operation of the morphogenetic field in the supracellular space of the plant body, such as the field resulting from auxin waves discovered in cambium.

  6. Charge transport in C60-based dumbbell-type molecules: mechanically induced switching between two distinct conductance states.

    Science.gov (United States)

    Moreno-García, Pavel; La Rosa, Andrea; Kolivoška, Viliam; Bermejo, Daniel; Hong, Wenjing; Yoshida, Koji; Baghernejad, Masoud; Filippone, Salvatore; Broekmann, Peter; Wandlowski, Thomas; Martín, Nazario

    2015-02-18

    Single molecule charge transport characteristics of buckminsterfullerene-capped symmetric fluorene-based dumbbell-type compound 1 were investigated by scanning tunneling microscopy break junction (STM-BJ), current sensing atomic force microscopy break junction (CS-AFM-BJ), and mechanically controlled break junction (MCBJ) techniques, under ambient conditions. We also show that compound 1 is able to form highly organized defect-free surface adlayers, allowing the molecules on the surface to be addressed specifically. Two distinct single molecule conductance states (called high G(H)(1) and low G(L)(1)) were observed, depending on the pressure exerted by the probe on the junction, thus allowing molecule 1 to function as a mechanically driven molecular switch. These two distinct conductance states were attributed to the electron tunneling through the buckminsterfullerene anchoring group and fully extended molecule 1, respectively. The assignment of conductance features to these configurations was further confirmed by control experiments with asymmetrically designed buckminsterfullerene derivative 2 as well as pristine buckminsterfullerene 3, both lacking the G(L) feature. PMID:25651069

  7. Theoretical study on mechanical and electron-transport properties of conjugated molecular junctions with carboxylic or methyl sulfide links

    International Nuclear Information System (INIS)

    The mechanical and electronic transport properties of 4-(methylthio)benzoic acid (M1), 1,4-bis(methylthio) benzene (M2) and methyl 4-(methylthio)benzoate (M3) molecular junctions are studied employing density functional theory and elastic scattering Green's function method. The numerical results show that the rupture force of M1 and M2 junctions are both about 0.6±0.1 nN as experiment probed, which is much smaller than the force to break COO?–Au bond. The COO? group strongly influenced on M1 molecular junction and further strengthened SMe–Au bond at the other end of the junction. The M3 junction is less stable because the CH3 group linked to COO group destroyed the mechanical stability of COO–Au connection. The conductance of M2 junction is about an order larger than that of M1 junction as the experiment probed. The less stable feature of M3 junction leads the absence of conductive peak.

  8. Molecular mechanisms of reduced glutathione transport: role of the MRP/CFTR/ABCC and OATP/SLC21A families of membrane proteins

    International Nuclear Information System (INIS)

    The initial step in reduced glutathione (GSH) turnover in all mammalian cells is its transport across the plasma membrane into the extracellular space; however, the mechanisms of GSH transport are not clearly defined. GSH export is required for the delivery of its constituent amino acids to other tissues, detoxification of drugs, metals, and other reactive compounds of both endogenous and exogenous origin, protection against oxidant stress, and secretion of hepatic bile. Recent studies indicate that some members of the multidrug resistance-associated protein (MRP/CFTR or ABCC) family of ATP-binding cassette (ABC) proteins, as well as some members of the organic anion transporting polypeptide (OATP or SLC21A) family of transporters contribute to this process. In particular, five of the 12 members of the MRP/CFTR family appear to mediate GSH export from cells namely, MRP1, MRP2, MRP4, MRP5, and CFTR. Additionally, two members of the OATP family, rat Oatp1 and Oatp2, have been identified as GSH transporters. For the Oatp1 transporter, efflux of GSH may provide the driving force for the uptake of extracellular substrates. In humans, OATP-B and OATP8 do not appear to transport GSH; however, other members of this family have yet to be characterized in regards to GSH transport. In yeast, the ABC proteins Ycf1p and Bpt1p transport GSH from the cytosol into the vacuole, whereas Hgt1p mediates GSH uptake across the plasma membrane. Because transport is a key step in GSH homeostuse transport is a key step in GSH homeostasis and is intimately linked to its biological functions, GSH export proteins are likely to modulate essential cellular functions

  9. Altered ion transport by thyroid epithelia from CFTR(-/-) pigs suggests mechanisms for hypothyroidism in cystic fibrosis.

    Science.gov (United States)

    Li, Hui; Ganta, Suhasini; Fong, Peying

    2010-12-01

    Subclinical hypothyroidism has been linked to cystic fibrosis, and the cystic fibrosis transmembrane conductance regulator (CFTR) shown to be expressed in the thyroid. The thyroid epithelium secretes Cl? and absorbs Na(+) in response to cAMP. Chloride secretion may provide a counter-ion for the SLC26A4 (pendrin)-mediated I? secretion which is required for the first step of thyroid hormonogenesis, thyroglobulin iodination. In contrast, few models exist to explain a role for Na(+) absorption. Whether CFTR mediates the secretory Cl? current in thyroid epithelium has not been directly addressed. We used thyroids from a novel pig CFTR(-/-) model, generated primary pig thyroid epithelial cell cultures (pThECs), analysed these cultures for preservation of thyroid-specific transcripts and proteins, and monitored the following parameters: (1) the Cl? secretory response to the cAMP agonist, isoprenaline; and (2) the amiloride-sensitive Na(+) current. Baseline short-circuit current (I(sc)) did not differ between CFTR(+/+) and CFTR(-/-) cultures. Serosal isoprenaline increased I(sc) in CFTR(+/+), but not CFTR(-/-), monolayers. Compared with CFTR(+/+) thyroid cultures, amiloride-sensitive Na(+) absorption measured in CFTR(-/-) pThECs represented a greater fraction of the resting I(sc). However, levels of transcripts encoding epithelial sodium channel (ENaC) subunits did not differ between CFTR(+/+) and CFTR(-/-) pThECs. Immunoblot analysis verified ENaC subunit protein expression, but quantification indicated no difference in expression levels. Our studies definitively demonstrate that CFTR mediates cAMP-stimulated Cl? secretion in a well-differentiated thyroid culture model and that knockout of CFTR promotes increased Na(+) absorption by a mechanism other than increased ENaC expression. These findings suggest several models for the mechanism of cystic fibrosis-associated hypothyroidism. PMID:20729267

  10. Kidins220/ARMS is transported by a kinesin-1-based mechanism likely to be involved in neuronal differentiation.

    Science.gov (United States)

    Bracale, Aurora; Cesca, Fabrizia; Neubrand, Veronika E; Newsome, Timothy P; Way, Michael; Schiavo, Giampietro

    2007-01-01

    Kinase D-interacting substrate of 220 kDa/ankyrin repeat-rich membrane spanning (Kidins220/ARMS) is a conserved membrane protein mainly expressed in brain and neuroendocrine cells, which is a downstream target of the signaling cascades initiated by neurotrophins and ephrins. We identified kinesin light chain 1 (KLC1) as a binding partner for Kidins220/ARMS by a yeast two-hybrid screen. The interaction between Kidins220/ARMS and the kinesin-1 motor complex was confirmed by glutathione S-transferase-pull-down and coimmunoprecipitation experiments. In addition, Kidins220/ARMS and kinesin-1 were shown to colocalize in nerve growth factor (NGF)-differentiated PC12 cells. Using Kidins220/ARMS and KLC1 mutants, we mapped the regions responsible for the binding to a short sequence of Kidins220/ARMS, termed KLC-interacting motif (KIM), which is sufficient for the interaction with KLC1. Optimal binding of KIM requires a region of KLC1 spanning both the tetratricopeptide repeats and the heptad repeats, previously not involved in cargo recognition. Overexpression of KIM in differentiating PC12 cells impairs the formation and transport of EGFP-Kidins220/ARMS carriers to the tips of growing neurites, leaving other kinesin-1 dependent processes unaffected. Furthermore, KIM overexpression interferes with the activation of the mitogen-activated protein kinase signaling and neurite outgrowth in NGF-treated PC12 cells. Our results suggest that Kidins220/ARMS-positive carriers undergo a kinesin-1-dependent transport linked to neurotrophin action. PMID:17079733

  11. Electronic parameters and carrier transport mechanism of high-barrier Se Schottky contacts to n-type GaN

    Science.gov (United States)

    Rajagopal Reddy, V.; Janardhanam, V.; Ju, Jin-Woo; Yun, Hyung-Joong; Choi, Chel-Jong

    2014-02-01

    The electrical properties and current conduction mechanism of high-barrier Se/n-GaN Schottky diode have been investigated for the first time by current-voltage (I-V) and capacitance-voltage (C-V) measurements. High resolution transmission electron microscopy (HRTEM) results confirmed that no reaction occurs between Se film and the GaN substrate during Se deposition. Investigations reveal that the contact exhibited an excellent rectification behavior. The estimated barrier height of Se/n-GaN Schottky contact is 0.92 eV (I-V) and 1.27 eV (C-V) with the ideality factor of 1.10. The barrier height and series resistance are extracted by Cheung's functions. It is observed that the series resistance values obtained from Cheung's functions is in good agreement with each other. Further, capacitance-voltage measurements of the Se/n-GaN Schottky diode are carried out at different frequencies. The discrepancy between Schottky barrier heights obtained from I-V and C-V measurements is also explained. The AFM results showed that the surface morphology of the Se Schottky contacts on n-GaN is fairly smooth. The forward bias current transport mechanism of the Se/n-type GaN Schottky diode is determined by the log-log plot of I-V characteristics. Investigations reveal that the Schottky emission mechanism is found to be dominant in the reverse bias region of Se/n-GaN Schottky diode.

  12. Adiabatic and diabatic aerosol transport to the Jungfraujoch

    Energy Technology Data Exchange (ETDEWEB)

    Lugauer, M.; Baltensperger, U.; Furger, M.; Jost, D.T.; Schwikowski, M.; Gaeggeler, H.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Synoptic scale vertical motion, here detected by the geopotential height of the 500 hPa surface, mainly accounts for the aerosol transport to the Jungfraujoch in winter. In summer, diabatic convection provides the dominant vertical transport mechanism. Nevertheless, synoptic scale adiabatic motion still determines whether diabatic convection can develop. (author) 2 figs., 2 refs.

  13. Aqueous HPMCAS coatings: effects of formulation and processing parameters on drug release and mass transport mechanisms.

    Science.gov (United States)

    Siepmann, Florence; Siepmann, Juergen; Walther, Mathias; MacRae, Ross; Bodmeier, Roland

    2006-07-01

    The major aim of the present work was to study the effects of various formulation and processing parameters on the resulting drug release kinetics from theophylline matrix pellets coated with aqueous hydroxypropyl methylcellulose acetate succinate (HPMCAS) dispersions. The plasticizer content, coating level and curing conditions significantly affected the release patterns in 0.1 M HCl, whereas no major effects were observed in phosphate buffer, pH 7.4. Due to the significant size of the HPMCAS particles (being in the micrometer range), their coalescence was particularly crucial and not complete upon coating. Consequently, at low coating levels continuous water-filled channels connected the bead cores with the release medium through which the drug could rapidly diffuse, resulting in high release rates even at low pH. In contrast, at high coating levels such continuous connections did not exist (due to the increased number of polymer particle layers), and drug release was controlled by diffusion through the macromolecular network resulting in much lower release rates in 0.1 M HCl. Importantly, pellet curing at elevated temperature and ambient relative humidity or exposure to elevated relative humidity at room temperature did not significantly alter the microstructure of the coatings, leading to only slightly decreased drug release rates. In contrast, pellet curing at elevated temperature combined with elevated relative humidity induced significant further polymer particle coalescence, resulting in a change of the underlying drug release mechanism and significantly reduced drug release rates. PMID:16621484

  14. Mechanical properties of 1%B-A6061-T6/T651 and A6061-T6/T651 used for basket of transport and storage cask

    International Nuclear Information System (INIS)

    Basket material of transport and storage cask is required to have not only a structural strength during transport and storage conditions, neutron absorbing function but also heat removal function. The basket material is also preferable to be light in order to reduce the weight of cask because it is very important to improve the efficiency of transport and storage by increasing the number of fuel assemblies loaded in cask. Aluminum alloy is suitable base material for basket due to its low density and high thermal conductivity. Enriched borated aluminum alloys have been developed, suitable for application to baskets in transport and storage casks for spent fuels. This borated aluminum alloy is 1% borated in A6061-T6/T651 alloy. In order to use this material for cask basket, it is necessary to be registered to the 'Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)' by the Japanese Society of Mechanical Engineers. Therefore, various mechanical properties such as tensile strength at elevated temperature with or without long term aging, creep properties and fracture toughness, etc.. And the allowable stresses of 1%B-A6061-T6/T651 have been evaluated according to the 'Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)'. (author)

  15. Transport mechanisms in carbon nitride CNx (0.16=x=0.25) materials

    International Nuclear Information System (INIS)

    Full text.The electronic properties in pulsed laser deposited unhydrogenated amorphous carbon nitride thin films are studied by dc conductivity measurements using the four-point probe method. At room temperature, the value of the electrical conductivity, ?, was found to grow by more than one order of magnitude, going from 0.33 to 17 (?.cm)-1, as nitrogen incorporation in teh films is decreased from 25 to 16 % atomic. Temperature dependent conductivity measurements show that two different conduction regimes could take place over the investigated temperature range, from T=90 to 400 K. In the low temperature range, up to about 270 K, the logarithm of the conductivity, log(?) varies linearly with T-1/4, thus indicating some hopping mechanism of the charge carries. A correlation between the temperature coefficient T? and the pre-exponential factor ?? of the temperature dependent conductivity is evidenced, as both were found to increase with increasing nitrogen content. In the high temperature range, a linear relationship between log(?) an d1/T provided a better fit of the experimental data. the activation energy, obtained fron the Arrhenius-type dependence of the conductivity on temperature, was also found to increase with nitrogen incorporation in the films. It is argued that the presence of nitrogen in the layers alters the structure of the sp2 regions thus inducing the observed changes in conductivity from onved changes in conductivity from one film to another. This analysis will be discussed in the light of the Electron Spin Resonance and Raman Spectroscopy signatures of such ?-bonded domains

  16. Effect of triorganotin compounds on calcium transport mechanisms in rat cardiac sarcoplasmic reticulum

    International Nuclear Information System (INIS)

    Although organotin compounds, in general, are neurotoxicants, recent studies indicate that these tin compounds affect heme metabolism as well as cardiovascular system. Sarcoplasmic reticulum (SR) calcium pump together with phosphorylation of phospholamban has an important role in myocardial contraction and relaxation. Since organotin compounds interfere with cardiovascular system, we have studied the in vitro as well as in vivo effects of tributyltin bromide (TBT), triethyltin bromide (TET) and trimethyltin chloride (TMT) on cardiac SR Ca2+-pump activity, in order to know the relative potency of these tin compounds. SR was isolated from heart ventricles of male Sprague-Dawley rats and used for in vitro studies. For in vivo studies, rats were treated orally in corn oil for 6 days with different doses of TET (0.5, 1.0 and 1.5 mg/kg/d), TMT (0.75, 1.5 and 2.5 mg/kg/d) and TBT (0.75, 1.5 and 2.5 mg/kg/d). Rats were sacrificed 24 hr after the last dosage and cardiac SR was prepared. Cardiac SR Ca2+-ATPase and 45Ca-uptake were measured. All the three tin compounds inhibited Ca2+-ATPase and 45Ca-uptake in vitro in a concentration dependent manner. The order of potency for Ca2+-ATPase as determined IC50, is TBT (2 uM) > TET (63 uM) > TMT (280 uM). For 45Ca-uptake, if followed the same order i.e., TBT (0.35 uM) > TET (10 uM) > TMT (440 uM). In agreement with in vitro results, both SR Ca2+-ATPase and 45Ca-uptake were significantly inhibited in rats treated with these tin compounds. These studies indicate that triorganotin compounds affect Ca2+-pumping mechanisms and thereby alter cardiac contraction-relaxation process

  17. Understanding the differential nitrogen sensing mechanism in rice genotypes through expression analysis of high and low affinity ammonium transporter genes.

    Science.gov (United States)

    Gaur, Vikram Singh; Singh, U S; Gupta, Atul K; Kumar, Anil

    2012-03-01

    Two rice genotypes, Kalanamak 3119 (KN3119) and Pusa Basmati 1(PB1) differing in their optimum nitrogen requirements (30 and 120 kg/ha, respectively) were undertaken to study the expression of both high and low affinity ammonium transporter genes responsible for ammonium uptake. Exposing the roots of the seedlings of both the genotypes to increasing (NH(4))(2)SO(4) concentrations revealed that all the three families of rice AMT genes are expressed, some of which get altered in a genotype and concentration specific manner. This indicates that individual ammonium transporter genes have defined contributions for ammonium uptake and plant growth. Interestingly, in response to increasing nitrogen concentrations, a root specific high affinity gene, AMT1;3, was repressed in the roots of KN3119 but not in PB1 indicating the existence of a differential ammonium sensing mechanism. This also indicates that not only AMT1;3 is involved not only in ammonium uptake but may also in ammonium sensing. Further, if it can differentiate and could be used as a biomarker for nitrogen responsiveness. Expression analysis of low affinity AMT genes showed that, both AMT2;1 and AMT2;2 have high levels of expression in both roots and shoots and in KN3119 are induced at low ammonium concentrations. Expressions of AMT3 family genes were higher shoots than in the roots indicating that these genes are probably involved in the translocation and distribution of ammonium ions in leaves. The expression of the only high affinity AMT gene, AMT1;1, along with six low affinity AMT genes in the shoots suggests that low affinity AMTs in the shoots leaves are involved in supporting AMT1;1 to carry out its activities/function efficiently. PMID:21678052

  18. Geoinformatics for intelligent transportation

    CERN Document Server

    Ivan, Igor; Jiang, Bin; Horák, Jirí; Haworth, James; Inspektor, Tomas

    2014-01-01

    The aim of the book is to present and discuss new methods, issues and challenges involved in geoinformatics' contribution to making transportation more intelligent, efficient and human-friendly. It covers a wide range of topics related to transportation and geoinformatics. The themes are divided into four main sections: Transport modeling, Sensor data and services, Intelligent transport systems, and Transport planning and accessibility.

  19. Avaliação de danos mecânicos causados em banana "Nanicão" durante as etapas de beneficiamento, transporte e embalagem" Mechanical damages caused in banana "Nanicão" in the improvement process, packing and transport

    Directory of Open Access Journals (Sweden)

    Juliana Sanches

    2004-04-01

    Full Text Available Este estudo teve como objetivo a avaliação de danos mecânicos ocorridos na banana "Nanicão" durante o processo de beneficiamento, transporte, embalagem e distribuição, identificando os prováveis pontos críticos. Avaliaram-se os danos mecânicos causados após o transporte, despistilagem e primeira despenca; limpeza e classificação; acondicionamento nas embalagens e transporte, e amadurecimento. As embalagens estudadas foram: embalagem de madeira torito (18 kg, madeira tipo ½ caixa (13 kg e papelão (18 kg. Verificou-se que, na etapa de acondicionamento e transporte das frutas até o centro de distribuição, duplicaram os defeitos leves e os defeitos graves quintuplicaram, causando podridões após a climatização. A embalagem de papelão não suportou o empilhamento e apresentou deformações, que resultaram no amassamento das frutas que estavam nas embalagens inferiores e no aumento significativo dos defeitos graves. As frutas acondicionadas nas embalagens envolvidas pelo plástico bolha apresentaram menos danos graves quando comparadas às demais embalagens, sem o plástico.This study had as objective the evaluation of mechanical damages occurred in banana "Nanicão" during the improvement process, packing and distribution, identifying the probable critical points. The mechanical damages caused by transport, first cleaning; cleanness and sorting; preservation in the packing, transport, and mature were evaluated. The studied packing had been: torito wooden packing (18 kg, wood type ½ box, (13 kg and cardboard (18 kg. The stage of preservation and transport of the fruits to the distribution center duplicated the light defects and quintupled the serious defects, causing rottenness after the acclimatization. The cardboard packing did not support the piling up and presented deformations, that resulted in the kneading the fruits of the inferior packing, causing a significant increase of the serious defects. The fruits conditioned in the involved packing of plastic bubble had presented an inferior number of serious damages when compared with the others packing, without the plastic.

  20. Avaliação de danos mecânicos causados em banana "Nanicão" durante as etapas de beneficiamento, transporte e embalagem" / Mechanical damages caused in banana "Nanicão" in the improvement process, packing and transport

    Scientific Electronic Library Online (English)

    Juliana, Sanches; Paulo A. M., Leal; José H., Saravali; Silvia, Antoniali.

    2004-04-01

    Full Text Available Este estudo teve como objetivo a avaliação de danos mecânicos ocorridos na banana "Nanicão" durante o processo de beneficiamento, transporte, embalagem e distribuição, identificando os prováveis pontos críticos. Avaliaram-se os danos mecânicos causados após o transporte, despistilagem e primeira des [...] penca; limpeza e classificação; acondicionamento nas embalagens e transporte, e amadurecimento. As embalagens estudadas foram: embalagem de madeira torito (18 kg), madeira tipo ½ caixa (13 kg) e papelão (18 kg). Verificou-se que, na etapa de acondicionamento e transporte das frutas até o centro de distribuição, duplicaram os defeitos leves e os defeitos graves quintuplicaram, causando podridões após a climatização. A embalagem de papelão não suportou o empilhamento e apresentou deformações, que resultaram no amassamento das frutas que estavam nas embalagens inferiores e no aumento significativo dos defeitos graves. As frutas acondicionadas nas embalagens envolvidas pelo plástico bolha apresentaram menos danos graves quando comparadas às demais embalagens, sem o plástico. Abstract in english This study had as objective the evaluation of mechanical damages occurred in banana "Nanicão" during the improvement process, packing and distribution, identifying the probable critical points. The mechanical damages caused by transport, first cleaning; cleanness and sorting; preservation in the pac [...] king, transport, and mature were evaluated. The studied packing had been: torito wooden packing (18 kg), wood type ½ box, (13 kg) and cardboard (18 kg). The stage of preservation and transport of the fruits to the distribution center duplicated the light defects and quintupled the serious defects, causing rottenness after the acclimatization. The cardboard packing did not support the piling up and presented deformations, that resulted in the kneading the fruits of the inferior packing, causing a significant increase of the serious defects. The fruits conditioned in the involved packing of plastic bubble had presented an inferior number of serious damages when compared with the others packing, without the plastic.

  1. Analysis and development of fracture mechanical failure concepts on the basis of research results from the field of component safety engineering. Points of main interest: J-integral concept, crack resistance curves, dynamic parameters

    International Nuclear Information System (INIS)

    On the basis of results and data obtained within the framework of reactor safety research, activities for the development and application of fracture mechanical failure concepts for assessing the behaviour of structural members and components have been carried out in the years 1980 through 1985 in close co-operation with the FhIWM at Freiburg, the IEHK of Aachen University, and the BAM, Berlin. The work performed by the FhIWM are theoretical numerical and experimental investigations centering on the following subjects: Application, verification and development of continuum-mechanical strength and failure concepts on the basis of the J-integral, and analysis of dynamic loads and load characteristics. The results obtained are presented in this report in the three main sections entitled 'Loads', 'Materials characteristics', and 'Applicability'. (orig.). With 62 figs., 3 tabs., 73 refs

  2. Structure and Mechanism of Proton Transport Through the Transmembrane Tetrameric M2 Protein Bundle of the Influenza A Virus

    Energy Technology Data Exchange (ETDEWEB)

    R Acharya; V Carnevale; G Fiorin; B Levine; A Polishchuk; V Balannick; I Samish; R Lamb; L Pinto; et al.

    2011-12-31

    The M2 proton channel from influenza A virus is an essential protein that mediates transport of protons across the viral envelope. This protein has a single transmembrane helix, which tetramerizes into the active channel. At the heart of the conduction mechanism is the exchange of protons between the His37 imidazole moieties of M2 and waters confined to the M2 bundle interior. Protons are conducted as the total charge of the four His37 side chains passes through 2{sup +} and 3{sup +} with a pK{sub a} near 6. A 1.65 {angstrom} resolution X-ray structure of the transmembrane protein (residues 25-46), crystallized at pH 6.5, reveals a pore that is lined by alternating layers of sidechains and well-ordered water clusters, which offer a pathway for proton conduction. The His37 residues form a box-like structure, bounded on either side by water clusters with well-ordered oxygen atoms at close distance. The conformation of the protein, which is intermediate between structures previously solved at higher and lower pH, suggests a mechanism by which conformational changes might facilitate asymmetric diffusion through the channel in the presence of a proton gradient. Moreover, protons diffusing through the channel need not be localized to a single His37 imidazole, but instead may be delocalized over the entire His-box and associated water clusters. Thus, the new crystal structure provides a possible unification of the discrete site versus continuum conduction models.

  3. Charge transport mechanism in CdTe-based p-n junction detectors formed by laser irradiation

    Science.gov (United States)

    Aoki, T.; Gnatyuk, V. A.; Kosyachenko, L. A.; Maslyanchuk, O. L.; Grushko, E. V.

    2010-08-01

    Charge transport mechanism responsible for leakage current in X/?-ray detectors with a p-n junction formed in semi-insulating p-like CdTe single crystals by laser-induced doping is studied. The In/CdTe/Au diodes showed high rectification and good spectral response to high-energy radiation, however samples were suffering from an increase in leakage current and deterioration of the characteristics with time. The proposed energy diagram allows to explain the reverse I-V characteristic of the diodes. At low voltages, the Sah-Noyce-Shockley theory describes well both the shape of the I-V characteristic and its temperature changes. At higher voltages, measured currents deviate from the theoretically calculated values toward increasing. An additional current increase is attributed to injection of electrons from the "near-ohmic" Au/CdTe contact and their diffusion to the p-n junction. When the current increases, the drift component is also included in injection of electrons. This leads to a rapid rise in the current contribution with increasing bias voltage and limits possibility to extend the detector active region by increasing the applied voltage.

  4. Chloride/formate exchange with formic acid recycling: a mechanism of active chloride transport across epithelial membranes

    International Nuclear Information System (INIS)

    The pathways for transport of Cl- and formate in microvillus membrane vesicles isolated from rabbit renal cortex were evaluated. An outward formate gradient stimulated the uptake of 36Cl-, and an outward 36Cl- gradient stimulated the uptake of formate, indicating Cl-/formate exchange. In addition, an inside alkaline pH gradient induced the accumulation of formate, consistent with nonionic diffusion of formic acid. Although an inward Na+ gradient also stimulated uphill formate accumulation, this effect was abolished when ionophores were used to prevent the generation of a transmembrane pH gradient. An inside alkaline pH gradient only minimally stimulated the uptake of 82Br-, used as tracer for Cl-, confirming the absence of appreciable Cl-/OH- exchange. However, the same pH gradient in the presence of a physiologic formate concentration (0.2 mM) markedly stimulated 82Br- influx. These data suggest that Cl-/formate exchange with recycling of formic acid by nonionic diffusion is a potential mechanism for active Cl- absorption across the luminal membrane in the proximal tubule and perhaps in other epithelia

  5. Hydro-mechanical coupling and transport in Meuse/Haute-Marne argillite: experimental and multi-scale approaches

    International Nuclear Information System (INIS)

    This thesis deals with the hydro-mechanical behaviour of argillite. Classical Biot theory is shown to be badly adapted to the case of argillite. An original state equation is then built by use of homogenization tools, and takes into account the microstructure of argillite as well as physical phenomena happening inside the material, like the swelling overpressure inside the clay particles or the capillary effects in the porous network. This state equation explains some experiments which were not by the classical Biot theory. It is then improved by integrating the experimental data that are the dependency of the elasticity tensor with the saturation degree and the existence of a porosity surrounding the inclusions. Combined with the monitoring of length variation under hydric loading, this relevant state equation permits one to determine the Biot tensor of argillite. Since this state equation is coupled with the hydric state of the material, one is interested in modelling the variation of the saturation degree during a drying process. Two transport models are studied and compared, then a model for the porous network is proposed in order to explain the unusual permeability measurements. (author)

  6. Investigation of temperature dependent dc current transport mechanism on Au/poly(4-vinyl phenol)/p-Si device

    International Nuclear Information System (INIS)

    In this study, temperature dependent current-voltage (I-V) measurements and investigation of the dc current transport mechanism of Au/poly(4-vinyl phenol)/p-Si device have been performed. While the series resistance value displayed nearly temperature independent behaviour, the ideality factor varied between 7.26 and 2.76 in the temperature range 100-300 K. There is a linear relationship between the barrier height and the ideality factor which is attributed to barrier height inhomogeneities in the Au/poly(4-vinyl phenol)/p-Si device. The temperature dependent ideality factor behaviour shows that thermionic field emission theory is valid rather than thermionic emission theory and the characteristic tunnelling energy is calculated as 65 meV. It is concluded that poly(4-vinyl phenol) is a preferable organic insulator layer with low interface state density because the temperature dependent interface state density calculations give values of the order of 1012 eV-1 cm-2.

  7. Transport Phenomena.

    Science.gov (United States)

    McCready, Mark J.; Leighton, David T.

    1987-01-01

    Discusses the problems created in graduate chemical engineering programs when students enter with a wide diversity of understandings of transport phenomena. Describes a two-semester graduate transport course sequence at the University of Notre Dame which focuses on fluid mechanics and heat and mass transfer. (TW)

  8. Tissue Nonspecific Alkaline Phosphatase Is Activated via a Two-step Mechanism by Zinc Transport Complexes in the Early Secretory Pathway*

    OpenAIRE

    Fukunaka, Ayako; Kurokawa, Yayoi; Teranishi, Fumie; Sekler, Israel; Oda, Kimimitsu; Ackland, M. Leigh; Faundez, Victor; Hiromura, Makoto; Masuda, Seiji; Nagao, Masaya; Enomoto, Shuichi; Kambe, Taiho

    2011-01-01

    A number of enzymes become functional by binding to zinc during their journey through the early secretory pathway. The zinc transporters (ZnTs) located there play important roles in this step. We have previously shown that two zinc transport complexes, ZnT5/ZnT6 heterodimers and ZnT7 homo-oligomers, are required for the activation of alkaline phosphatases, by converting them from the apo- to the holo-form. Here, we investigated the molecular mechanisms of this activation. ZnT1 and ZnT4 expres...

  9. Sistemas primários de transporte de prótons integram os mecanismos de desintoxicação do mesotrione em plantas de milho / Proton transport primary systems used as mechanisms of mesotrione detoxification in corn plants

    Scientific Electronic Library Online (English)

    J., Ogliari; S.P., Freitas; A.C., Ramos; R.E., Bressan Smith; A.R., Façanha.

    Full Text Available O mesotrione é um dos mais efetivos herbicidas desenvolvidos para o controle de uma ampla gama de plantas daninhas que infestam campos de milho (Zea mays). Todavia, as bases bioquímicas e moleculares da tolerância das plantas de milho a esse herbicida ainda não foram estabelecidas. Para compreender [...] os mecanismos de desintoxicação do mesotrione em plantas de milho, foram analisadas as atividades dos principais sistemas primários de transporte de prótons (íons H+) das membranas plasmática e vacuolar (H+-ATPases do tipo P e V e H+-PPases) de células de diferentes tecidos de plantas tratadas após aplicação do herbicida em pós-emergência. Para isso, foram realizados procedimentos de fracionamento celular, de tecidos radiculares, foliares e do caule, por centrifugação diferencial e purificação de vesículas membranares em gradiente de densidade de sacarose. Os ensaios enzimáticos das atividades hidrolíticas das três bombas de H+ foram realizados aplicando-se um método colorimétrico para medir o fosfato liberado das hidrólises dos substratos: adenosina-5'-trifosfato (ATP) e pirofosfato (PPi). Parâmetros fotossintéticos foram analisados como marcadores fisiológicos dos diferentes estádios da desintoxicação das plantas. Essa análise demonstrou que o tratamento com mesotrione promoveu uma redução na taxa fotossintética e na relação Fv/Fm no terceiro dia após aplicação (DAA), mas não afetou significativamente a fotossíntese a partir do quinto DAA. Nos três tecidos analisados, raiz, folha e caule, aos 3 DAA, foi observado forte estímulo da atividade da H+-PPase vacuolar, a qual variou de cerca de 100 a 600%. Essa forte ativação foi reduzida significativamente aos 7 DAA, mas permaneceu pelo menos duas vezes maior com relação ao controle. Por sua vez, as H+-ATPases das membranas plasmática e vacuolar foram bem menos moduladas pelo tratamento com o herbicida, apresentando estimulações e inibições que não variaram mais do que 20 a 60% das atividades obtidas em vesículas de membranas oriundas de plantas não tratadas (controle). Os resultados demonstraram que o mesotrione promove uma ativação diferencial dos principais sistemas primários de transporte de H+, indicando que essas bombas iônicas são enzimas transportadoras essenciais aos mecanismos relacionados com o processo de desintoxicação das plantas de milho, possivelmente ao energizar a compartimentalização das moléculas do herbicida mesotrione no vacúolo ou a exceção celular através das membranas plasmáticas. Abstract in english The herbicide Mesotrione herbicides are very effective in the control of a wide range of weeds that infest corn (Zea mays) fields. However, the biochemical and molecular bases of corn seedling tolerance to this herbicide have not been established so far. To understand the mechanisms of mesotrione de [...] toxification in corn plants, the activities of the main primary proton (H+ ion) transport systems of the vacuolar and plasma membranes (H+-ATPases V- and P-types, and H+-PPase) of the cells from different tissues were analyzed, after post-emergence herbicide application. Thus, cell fractionation procedures on root, leaf and mesocotyl tissues were performed using differential membrane vesicle centrifugation and purification in sucrose density gradient. Hydrolytic activities of the proton pumps were measured by using a colorimetric method for phosphate released through enzymatic hydrolysis of the substrates adenosine-5'-triphosphate (ATP) and pyrophosphate (PPi). Photosynthetic parameters were analyzed as physiological markers of the different stages of plant detoxification. Such analysis demonstrated that, three days after herbicide application (DAA), mesotrione induced a reduction in the photosynthetic rate and Fv/Fm ratio, but no significant effect could be found after the fifth DAA. These data suggest that the treatment with mesotrione promoted a spatial and temporal regulation of the H+ pump activities. In all the root, leaf and mesocotyl tisues analyzed, at

  10. Conformational rearrangements to the intracellular open states of the LeuT and ApcT transporters are modulated by common mechanisms.

    Science.gov (United States)

    Shi, Lei; Weinstein, Harel

    2010-12-15

    Recent crystallographic studies revealed that five transporter families without much sequence similarities among them have similar structure folds to LeuT, a bacterial neurotransmitter:sodium symporter homolog. The LeuT fold is characterized by an internal twofold structural pseudosymmetry. The transport cycle of some members of each of these families is dependent on a sodium gradient across the membrane, whereas in some others the role of sodium is mimicked by proton. We report on the identification of common structure-dynamics elements of the transporters with LeuT fold, which are recognizable in the conformational transitions related to function. The findings from comparative computational modeling and simulation studies of LeuT, and ApcT from the amino acid-polyamine-organocation transporter family define the intramolecular mechanisms by which Na+ binding couples to the transport process, and single out the lead/active role of TM1a in the transition to inward-open conformation. These mechanistic insights are derived in the context of collaborative investigations of LeuT dynamics with both single-molecule fluorescence and simulations that have produced excellent agreement of the dynamic details, and are found to be generalizable across the transporter families and to transcend sequence and motif similarities. PMID:21156121

  11. Neutron transport

    International Nuclear Information System (INIS)

    This bibliographical note presents a reference book which addresses the study of neutron transport in matter, the study of conditions for a chain reaction and the study of modifications of matter composition due to nuclear reactions. This book presents the main nuclear data, their measurement, assessment and processing, and the spallation. It proposes an overview of methods applied for the study of neutron transport: basic equations and their derived forms, deterministic methods and Monte Carlo method of resolution of the Boltzmann equation, methods of resolution of generalized Bateman equations, methods of time resolution of space kinetics coupled equations. It presents the main calculation codes, discusses the qualification and experimental aspects, and gives an overview of neutron transport applications: neutron transport calculation of reactors, neutron transport coupled with other disciplines, physics of fuel cycle, criticality

  12. Reactive Transport Modelling of CO2 Storage in Saline Aquifers to Elucidate Fundamental Processes, Trapping Mechanisms, and Sequestration Partitioning

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J W; Nitao, J J; Knauss, K G

    2004-07-26

    The ultimate fate of CO{sub 2} injected into saline aquifers for environmental isolation is governed by three interdependent yet conceptually distinct processes: CO{sub 2} migration as a buoyant immiscible fluid phase, direct chemical interaction of this rising plume with ambient saline waters, and its indirect chemical interaction with aquifer and cap-rock minerals through the aqueous wetting phase. Each process is directly linked to a corresponding trapping mechanism: immiscible plume migration to hydrodynamic trapping, plume-water interaction to solubility trapping, and plume-mineral interaction to mineral trapping. In this study, reactive transport modeling of CO{sub 2} storage in a shale-capped sandstone aquifer at Sleipner has elucidated and established key parametric dependencies of these fundamental processes, the associated trapping mechanisms, and sequestration partitioning among them during consecutive 10-year prograde (active-injection) and retrograde (post-injection) regimes. Intra-aquifer permeability structure controls the path of immiscible CO{sub 2} migration, thereby establishing the spatial framework of plume-aquifer interaction and the potential effectiveness of solubility and mineral trapping. Inter-bedded thin shales--which occur at Sleipner--retard vertical and promote lateral plume migration, thereby significantly expanding this framework and enhancing this potential. Actual efficacy of these trapping mechanisms is determined by compositional characteristics of the aquifer and cap rock: the degree of solubility trapping decreases with increasing formation-water salinity, while that of mineral trapping is proportional to the bulk concentration of carbonate-forming elements--principally Fe, Mg, Ca, Na, and Al. In the near-field environment of Sleipner-like settings, 80-85% by mass of injected CO{sub 2} remains and migrates as an immiscible fluid phase, 15-20% dissolves into formation waters, and less than 1% precipitates as carbonate minerals. This partitioning defines the relative effectiveness of hydrodynamic, solubility, and mineral trapping on a mass basis. Seemingly inconsequential, mineral trapping has enormous strategic significance: it maintains injectivity, delineates the storage volume, and improves cap-rock integrity. We have identified four distinct mechanisms: dawsonite [NaAlCO{sub 3}(OH){sub 2}] cementation occurs throughout the intra-aquifer plume, while calcite-group carbonates [principally, (Fe,Mg,Ca)CO{sub 3}] precipitate via disparate processes along lateral and upper plume margins, and by yet another process within inter-bedded and cap-rock shales. The coupled mineral dissolution/precipitation reaction associated with each mechanism reduces local porosity and permeability. For Sleipner-like settings, the magnitude of such reduction for dawsonite cementation is near negligible; hence, this process effectively maintains initial CO{sub 2} injectivity. Of similarly small magnitude is the reduction associated with formation of carbonate rind along upper and lateral plume boundaries; these processes effectively delineate the CO{sub 2} storage volume, and for saline aquifers anomalously rich in Fe-Mg-Ca may partially self-seal the plume. Porosity and permeability reduction is most extreme within shales, because their clay-rich mineralogy defines bulk Fe-Mg concentrations much greater than those of saline aquifers. In the basal cap-rock shale of our models, these reductions amount to 4.5 and 13%, respectively, after the prograde regime. During the retrograde phase, residual saturation of immiscible CO{sub 2} maintains the prograde extent of solubility trapping while continuously enhancing that of mineral trapping. At the close of our 20-year simulations, initial porosity and permeability of the basal cap-rock shale have been reduced by 8 and 22%, respectively. Extrapolating to hypothetical complete consumption of Fe-Mg-bearing shale minerals (here, 10 vol.% Mg-chlorite) yields an ultimate reduction of about 52 and 90%, respectively, after 130 years. Hence, the most crucial strategic impa

  13. Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

    Science.gov (United States)

    Marshall, John R.

    1999-09-01

    Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a dense saltation population of many tens or hundreds of grains for each single high-speed saltation percussion of the bed. Impact cascading will lead to near-surface distortion of the boundary layer, and choked flow formed by a dense "slurry" of sand, with the majority of grains mobilized by repercussive forces rather than by aerodynamic lift. This proceeds until a fully-matured transport layer imposes self- limitations as grain-population density constrains the free-path motion of individual grains.

  14. The Mechanism of the Tyrosine Transporter TyrP Supports a Proton Motive Tyrosine Decarboxylation Pathway in Lactobacillus brevis

    OpenAIRE

    Wolken, Wout A. M.; Lucas, Patrick M.; Lonvaud-Funel, Aline; Lolkema, Juke S.

    2006-01-01

    The tyrosine decarboxylase operon of Lactobacillus brevis IOEB9809 contains, adjacent to the tyrosine decarboxylase gene, a gene for TyrP, a putative tyrosine transporter. The two genes potentially form a proton motive tyrosine decarboxylation pathway. The putative tyrosine transporter gene of L. brevis was expressed in Lactococcus lactis and functionally characterized using right-side-out membranes. The transporter very efficiently catalyzes homologous tyrosine-tyrosine exchange and heterolo...

  15. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers: A Case Study of Regional Entrepreneurship in Finland

    OpenAIRE

    Teijo Palander; Mika Vainikka; Antti Yletyinen

    2012-01-01

    The objectives of this study were to investigate how to increase co-operation in the regional entrepreneurship approach of wood transportation and facilitate the ongoing outsourcing of wood-procurement responsibilities in the Finnish forest industry. We examined co-operation between transportation entrepreneurs (suppliers) and between suppliers and the forest industry (customers). A questionnaire was sent to wood transportation entrepreneurs working in the wood-procurement network of the cust...

  16. Ballistic transport in planetary ring systems due to particle erosion mechanisms. I - Theory, numerical methods, and illustrative examples

    Science.gov (United States)

    Durisen, Richard H.; Murphy, Brian W.; Cramer, Nichael Lynn; Cuzzi, Jeffrey N.; Mullikin, Thomas L.

    1989-01-01

    Ballistic transport, defined as the net radial transport of mass and angular momentum due to exchanges of meteoroid hypersonic-impact ejecta by neighboring planetary ring regions on time-scales orders-of-magnitude shorter than the age of the solar system, is presently considered as a problem in mathematical physics. The preliminary results of a numerical scheme for following the combined effects of ballistic transport and viscous diffusion demonstrate that ballistic transport generates structure near sharp edges already present in the ring-mass distribution; the entire ring system ultimately develops an undulatory structure whose length scale is typically of the order of the radial excursion of the impact ejecta.

  17. Large-scale atomistic and quantum-mechanical simulations of a Nafion membrane: Morphology, proton solvation and charge transport

    Directory of Open Access Journals (Sweden)

    Pavel V. Komarov

    2013-09-01

    Full Text Available Atomistic and first-principles molecular dynamics simulations are employed to investigate the structure formation in a hydrated Nafion membrane and the solvation and transport of protons in the water channel of the membrane. For the water/Nafion systems containing more than 4 million atoms, it is found that the observed microphase-segregated morphology can be classified as bicontinuous: both majority (hydrophobic and minority (hydrophilic subphases are 3D continuous and organized in an irregular ordered pattern, which is largely similar to that known for a bicontinuous double-diamond structure. The characteristic size of the connected hydrophilic channels is about 25–50 Å, depending on the water content. A thermodynamic decomposition of the potential of mean force and the calculated spectral densities of the hindered translational motions of cations reveal that ion association observed with decreasing temperature is largely an entropic effect related to the loss of low-frequency modes. Based on the results from the atomistic simulation of the morphology of Nafion, we developed a realistic model of ion-conducting hydrophilic channel within the Nafion membrane and studied it with quantum molecular dynamics. The extensive 120 ps-long density functional theory (DFT-based simulations of charge migration in the 1200-atom model of the nanochannel consisting of Nafion chains and water molecules allowed us to observe the bimodality of the van Hove autocorrelation function, which provides the direct evidence of the Grotthuss bond-exchange (hopping mechanism as a significant contributor to the proton conductivity.

  18. Functional characterization of the vertebrate primary ureter: Structure and ion transport mechanisms of the pronephric duct in axolotl larvae (Amphibia

    Directory of Open Access Journals (Sweden)

    Prehn Lea R

    2010-05-01

    Full Text Available Abstract Background Three kidney systems appear during vertebrate development: the pronephroi, mesonephroi and metanephroi. The pronephric duct is the first or primary ureter of these kidney systems. Its role as a key player in the induction of nephrogenic mesenchyme is well established. Here we investigate whether the duct is involved in urine modification using larvae of the freshwater amphibian Ambystoma mexicanum (axolotl as model. Results We investigated structural as well as physiological properties of the pronephric duct. The key elements of our methodology were: using histology, light and transmission electron microscopy as well as confocal laser scanning microscopy on fixed tissue and applying the microperfusion technique on isolated pronephric ducts in combination with single cell microelectrode impalements. Our data show that the fully differentiated pronephric duct is composed of a single layered epithelium consisting of one cell type comparable to the principal cell of the renal collecting duct system. The cells are characterized by a prominent basolateral labyrinth and a relatively smooth apical surface with one central cilium. Cellular impalements demonstrate the presence of apical Na+ and K+ conductances, as well as a large K+ conductance in the basolateral cell membrane. Immunolabeling experiments indicate heavy expression of Na+/K+-ATPase in the basolateral labyrinth. Conclusions We propose that the pronephric duct is important for the subsequent modification of urine produced by the pronephros. Our results indicate that it reabsorbs sodium and secretes potassium via channels present in the apical cell membrane with the driving force for ion movement provided by the Na+/K+ pump. This is to our knowledge the first characterization of the pronephric duct, the precursor of the collecting duct system, which provides a model of cell structure and basic mechanisms for ion transport. Such information may be important in understanding the evolution of vertebrate kidney systems and human diseases associated with congenital malformations.

  19. 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)

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

    2011-04-01

    Full Text Available 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 corrient [...] e vs voltaje en función de la temperatura. El análisis de los resultados muestra que a bajos voltajes de polarización 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 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.

  20. Mechanics

    CERN Document Server

    Hartog, J P Den

    2013-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  1. Mechanism of efavirenz influence on methadone pharmacokinetics and pharmacodynamics II: Hepatic and intestinal CYP2B6, CYP3A and transporter activities

    OpenAIRE

    Kharasch, Evan D.; Campbell, Scott; Stubbert, Kristi; Crafford, Amanda; London, Amy; Kim, Thomas; Whittington, Dale; Ensign, Dustin; Hoffer, Christine; Bedynek, Pamela Sheffels

    2012-01-01

    Efavirenz diminishes methadone plasma concentrations, an effect attributed to CYP3A induction, but actual mechanisms are unknown. This investigation determined the effects of two weeks of efavirenz (600 mg daily) on hepatic and intestinal CYP3A4/5 (probed with intravenous and oral alfentanil), hepatic CYP2B6 (oral efavirenz hydroxylation) and intestinal transporter (oral fexofenadine) activities, and on methadone pharmacokinetics and pharmacodynamics in healthy volunteers. It also assessed ef...

  2. Inhibition Mechanism of the Intracellular Transporter Ca2+-Pump from Sarco-Endoplasmic Reticulum by the Antitumor Agent Dimethyl-Celecoxib

    OpenAIRE

    Coca, Ramo?n; Soler, Fernando; Corte?s-castell, Ernesto; Gil-guille?n, Vicente; Ferna?ndez-belda, Francisco

    2014-01-01

    Dimethyl-celecoxib is a celecoxib analog that lacks the capacity as cyclo-oxygenase-2 inhibitor and therefore the life-threatening effects but retains the antineoplastic properties. The action mechanism at the molecular level is unclear. Our in vitro assays using a sarcoplasmic reticulum preparation from rabbit skeletal muscle demonstrate that dimethyl-celecoxib inhibits Ca2+-ATPase activity and ATP-dependent Ca2+ transport in a concentration-dependent manner. Celecoxib was a more potent inhi...

  3. Mechanism of basolateral membrane H+/OH-/HCO-3 transport in the rat proximal convoluted tubule. A sodium-coupled electrogenic process

    OpenAIRE

    1985-01-01

    In order to examine the mechanism of basolateral membrane H+/OH-/HCO-3 transport, a method was developed for the measurement of cell pH in the vivo doubly microperfused rat proximal convoluted tubule. A pH- sensitive fluorescein derivative, (2',7')-bis(carboxyethyl)-(5,6)- carboxyfluorescein, was loaded into cells and relative changes in fluorescence at two excitation wavelengths were followed. Calibration was accomplished using nigericin with high extracellular potassium concentrations. When...

  4. Análise comparativa entre os mecanismos de trauma, as lesões e o perfil de gravidade das vítimas, em Catanduva - SP / Mechanisms of trauma, main injuries and severity of patients’ conditions in Catanduva - SP

    Scientific Electronic Library Online (English)

    Sandra Elisa Adami, Batista; Juliana Govoni, Baccani; Raquel Amarante de Paula e, Silva; Kamila de Paula Ferlin, Gualda; Raul José de Andrade, Vianna Jr..

    2006-02-01

    Full Text Available OBJETIVO: Realizar uma análise comparativa entre os principais mecanismos de trauma, a gravidade das vítimas e os principais ferimentos que proporcionaram. MÉTODO: Estudo randomizado de 1486 fichas de vítimas traumatizadas atendidas pela Unidade de Resgate do Corpo de Bombeiros em Catanduva - SP, no [...] período de janeiro/1997 a dezembro/2003. Foi realizada uma avaliação a partir dos itens ferimentos, Revised Trauma Score e mecanismos de trauma, cujas variáveis foram expressas em porcentagens e correlacionadas pelo Teste X². RESULTADOS: Houve predomínio de acidentes motociclísticos com 42,2% dos traumas. As regiões corpóreas mais acometidas foram os membros inferiores/cintura pélvica (32,2%). Os ferimentos superficiais acometeram 88% das vítimas. Para todos os eventos, prevaleceram vítimas com RTS=6 excetuando-se os acidentes envolvendo veículos pesados em que 25% das vítimas obtiveram RTS Abstract in english BACKGROUND: To compare main trauma mechanisms, main injuries and severity of patients’ conditions. METHODS: A retrospective study of 1486 records of trauma patients treated at the Firefighters’ Rescue Unit in Catanduva, Sao Paulo, from January 1997 to December 2003. Assessment was based on the follo [...] wing criteria: injuries, Revised Trauma Score, and trauma mechanisms. The variables were expressed in percentages and evaluated by X² Test. RESULTS: The most frequent accidents were motorcycle related (42% of the total). The most affected segments were the lower limbs and pelvis (32%). 88% of the patients had superficial injuries. Most patients had RTS6 for all types of accidents except for those related to large truck, in which 25% of the victims had RTS

  5. Quantum transport and electroweak baryogenesis

    International Nuclear Information System (INIS)

    We review the mechanism of electroweak baryogenesis. The main focus of the review lies on the development of quantum transport equations from first principles in the Kadanoff-Baym framework. We emphasize the importance of the semi-classical force that leads to reliable predictions in most cases. Besides, we discuss the status of electroweak baryogenesis in the light of recent electric dipole moment probes and collider experiments in a variety of models.

  6. Quantum transport and electroweak baryogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Konstandin, Thomas

    2013-02-15

    We review the mechanism of electroweak baryogenesis. The main focus of the review lies on the development of quantum transport equations from first principles in the Kadanoff-Baym framework. We emphasize the importance of the semi-classical force that leads to reliable predictions in most cases. Besides, we discuss the status of electroweak baryogenesis in the light of recent electric dipole moment probes and collider experiments in a variety of models.

  7. A Study of e- Transport through Li2O2, the Main Discharge Product in the Li-O2 Battery

    DEFF Research Database (Denmark)

    Knudsen, Kristian Bastholm; Jensen, SØren HØjgaard

    2015-01-01

    In the field of energy storage devices the pursuit for cheap, high energy density, reliable secondary batteries is at the top of the agenda. The Li-O2battery is one of the possible technologies that, in theory, should be able to close the gap, which exists between the present state-of-the-art Li-ion technologies and the demand placed on batteries by technologies such as electrical vehicles [1]. However, the Li-O2 battery still suffers greatly from high overpotentials during oxygen reduction and evolution reactions (discharge and charge, respectively), poor rechargeability, and decomposition of salts and solvents etc. [2] [3]. In order to improve the electrochemical performance of the Li-O2batteries; it is crucial to understand the fundamental mechanisms that governs and limits the system during electrochemical operation. Here we present a redox probing study of the charge transfer across the deposition product lithium peroxide, Li2O2, using outer-sphere redox shuttles: cobaltocene, ferrocene, and decamethylferrocene. The change in heterogeneous electron transfer exchange rate as a function of the potential and the Li2O2 layer thickness (~state of charge) was determined using electrochemical impedance spectroscopy. The attenuation of the electron transfer exchange rate with film thickness is dependent on the probing potential, indicating that hole tunneling is the dominant process for charge transfer through Li2O2supporting previous work by Luntz et al. [4]. Additionally, this work includes the determination of diffusion coefficients and concentrations of the redox shuttles and the superoxide ion, in a 1,2-dimethoxyethane based electrolyte. References [1] S. A. Freunberger, P. G. Bruce, L. J. Hardwick et J.-M. Tarascon, «Li-O2 and Li-S batteries with high energy storage,» Nature Materials, vol. 11, pp. 19-29, 2012. [2] B. D. McCloskey, A. Valery, A. C. Luntz, S. R. Gowda, G. M. Wallraff, J. M. Garcia, T. Mori et L. E. Krupp, «Combining Accurate O2 and Li2O2 Assays to Separate Discharge and Charge stability Limitations in Nonaqueous Li-O2 Batteries,» J. Phys. Chem. Lett., vol. 4, pp. 2989-2993, 2013. [3] R. Younesi, M. Hahlin, F. Björefors, P. Johansson et K. Edström, «Li-O2 Battery Degradation by Lithium Peroxide (Li2O2): A Model Study,» Chem. Mater., vol. 25, pp. 77-84, 2013. [4] A. C. Luntz, V. Viswanathan, J. Voss, J. B. Varley, J. K. Nørskov, R. Scheffler and A. Speidel, "Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries," J. Phys. Chem. Lett., vol. 4, pp. 3494-3499, 2013.

  8. (abstract) Fundamental Mechanisms of Electrode Kinetics and Alkali Metal Atom Transport at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    Science.gov (United States)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S. K.

    1993-01-01

    The mechanisms of electrode kinetics and mass transport of alkali metal oxidation and alkali metal cation reduction at the solid electrolyte/porous electrode boundary as well as alkali metal transport through porous metal electrodes has important applications in optimizing device performance in alkali metal thermal to electric converter (AMTEC) cells which are high temperature, high current density electrochemical cells. Basic studies of these processes also affords the opportunity to investigate a very basic electrochemical reaction over a wide range of conditions; and a variety of mass transport modes at high temperatures via electrochemical techniques. The temperature range of these investigations covers 700K to 1240K; the alkali metal vapor pressures range from about 10(sup -2) to 10(sup 2) Pa; and electrodes studied have included Mo, W, Mo/Na(sub 2)MoO(sub 4), W/Na(sub 2)WO(sub 4), WPt(sub x), and WRh(sub x) (1.0 alkali metal vapor and alkali metal vapor/solid electrolyte/vapor cells have been used to characterize the reaction and transport processes. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes.

  9. Review on mechanisms and continuum models of multi-phase transport phenomena in porous structures of non-aqueous Li-Air batteries

    Science.gov (United States)

    Yuan, Jinliang; Yu, Jong-Sung; Sundén, Bengt

    2015-03-01

    During recent years intensive research activities involving both experimental and modeling approaches have appeared for different aspects of Lithium-air (Li-air) battery. Multi-phase transport phenomena including dissolved oxygen and lithium ions (Li+) in the liquid electrolyte, as well as electrons in the solid materials, are strongly coupled with the porous structures and various reactions, particularly the solid product grown in the porous cathode during battery discharge. Understanding the mechanisms of transport phenomena and accurate evaluation of effective transport properties are significant for improving the battery capacities and design, especially at high rate conditions. In this paper, the transport governing equations commonly used for macroscopic continuum models at porous-average level are outlined and highlighted, with a purpose to provide a general overview of the validity and the limitation of these approaches. The most often used models in the open literature are reviewed and discussed focusing on the effective properties involving tortuosity factors, solid product morphologies, as well as effects on the void space clogging, surface area reduction and passivation. Comments and suggestions are also provided for better understanding of multi-phase transport phenomena and implementation of the detailed models for solid product generation and morphology growth in Li-air battery cathodes.

  10. Atomic transport mechanisms in thin oxide films grown on zirconium by thermal oxidation, as-derived from 18O-tracer experiments

    International Nuclear Information System (INIS)

    Two-stage oxidation experiments using 16O and 18O isotopes were performed to reveal the governing atomic transport mechanism(s) in thin (thickness ¯0) single-crystalline surfaces were prepared under ultra-high vacuum conditions by a cyclic treatment of alternating ion-sputtering and in vacuo annealing steps. Next, the bare Zr surfaces were oxidized at 450 K and at pO2 = 1 × 10?4 Pa, first in 16O2(g) and subsequently in 18O2(g). The 18O-tracer depth distributions in the oxide films were recorded by time-of-flight secondary ion mass spectrometry. It was concluded that the early stage of the oxidation process is governed by oxygen transport to the metal/oxide interface through the lattice and along the grain boundaries of the nanosized oxide grains whereas, on continuing oxidation, only oxygen lattice transport controls the oxidation process. An oxide-film growth mechanism is proposed.

  11. Exploring the mechanics of water flow and bedload sediment transport and their interplay with river topography using seismic observations acquired along the 'Les Bossons' river (France)

    Science.gov (United States)

    Gimbert, F.; Tsai, V. C.; Lamb, M. P.; Guillon, H.; Mugnier, J. L.

    2013-12-01

    Seismic observations near rivers may be used to infer bedload sediment flux rates, a quantity that is particularly challenging to measure continuously through other means. However, there remain difficulties in applying the seismic technique, including understanding the correct mechanical interpretation for the various observations. This work aims at improving estimates of sediment bedload fluxes using seismic noise by developing appropriate mechanical descriptions of river mechanics such as bedload transport and water flow, and their connections with river morphology such as slope, roughness and degree of channelization. We conducted a field experiment at the Les Bossons river, a small mountain stream fed by a large Alpine glacier in the Mont-Blanc area (France). This river exhibits a wide range of bed roughness and average slopes, which vary from 1 to about 30 degrees. These features make the Les Bossons river an ideal place to test theoretical assumptions on seismic noise induced by both water flow and bedload transport. For water flow, we propose a mechanical description of noise induced by water flowing down large riverbed steps that decrease in size in the downstream direction. Our analysis is supported by in-situ measurements of riverbed roughness, topography, water discharge and water flow velocities, that were measured over scales of several tens of meters and also locally in plunge pools. To constrain the granular bed mechanics, we investigate the motion of individual sediment particles by isolating individual impact events from the seismic signal. We investigate the grain impacts and their mechanical properties such as grain size, impact velocity and impact directionality, which can be obtained by evaluating the ratio of Rayleigh versus Love waves. This information provides useful constraints that allow us to improve upon the mechanical model recently proposed by Tsai et al. (2012). Finally, we apply the theoretical concepts described above to analyze a flood event that induced a complete re-channelization of the river. Sediment transport and grain displacements were estimated by measuring river profiles before and after the event, and by analyzing PIT-tag grain trajectories. These estimates are compared with the sediment flux rates obtained from the seismic noise records. REFERENCES V.C. Tsai, B. Minchew, M. P. Lamb and J-P. Ampuero (2012), A physical model for seismic noise generation from sediment transport in rivers, Geophys. Res. Lett., 39, L02404, doi:10.1029/2011GL050255.

  12. Análise comparativa entre os mecanismos de trauma, as lesões e o perfil de gravidade das vítimas, em Catanduva - SP Mechanisms of trauma, main injuries and severity of patients’ conditions in Catanduva - SP

    Directory of Open Access Journals (Sweden)

    Sandra Elisa Adami Batista

    2006-02-01

    Full Text Available OBJETIVO: Realizar uma análise comparativa entre os principais mecanismos de trauma, a gravidade das vítimas e os principais ferimentos que proporcionaram. MÉTODO: Estudo randomizado de 1486 fichas de vítimas traumatizadas atendidas pela Unidade de Resgate do Corpo de Bombeiros em Catanduva - SP, no período de janeiro/1997 a dezembro/2003. Foi realizada uma avaliação a partir dos itens ferimentos, Revised Trauma Score e mecanismos de trauma, cujas variáveis foram expressas em porcentagens e correlacionadas pelo Teste X². RESULTADOS: Houve predomínio de acidentes motociclísticos com 42,2% dos traumas. As regiões corpóreas mais acometidas foram os membros inferiores/cintura pélvica (32,2%. Os ferimentos superficiais acometeram 88% das vítimas. Para todos os eventos, prevaleceram vítimas com RTS=6 excetuando-se os acidentes envolvendo veículos pesados em que 25% das vítimas obtiveram RTSBACKGROUND: To compare main trauma mechanisms, main injuries and severity of patients’ conditions. METHODS: A retrospective study of 1486 records of trauma patients treated at the Firefighters’ Rescue Unit in Catanduva, Sao Paulo, from January 1997 to December 2003. Assessment was based on the following criteria: injuries, Revised Trauma Score, and trauma mechanisms. The variables were expressed in percentages and evaluated by X² Test. RESULTS: The most frequent accidents were motorcycle related (42% of the total. The most affected segments were the lower limbs and pelvis (32%. 88% of the patients had superficial injuries. Most patients had RTS6 for all types of accidents except for those related to large truck, in which 25% of the victims had RTS<2. If we ignore motor vehicle accidents, 63.4% were falls. There was association between trauma mechanisms and injured segment of the body (p <0.01. The lower limbs/pelvis were the most affected body parts in accidents involving people hit by cars and motorcycle accidents. The head/neck were injured in agressions, falls, and accidents involving large trucks and cars. Cyclists had similar head/neck and lower patients limb/pelvis injuries. CONCLUSION: The majority of trauma patients in Catanduva were victims of motorcycle accidents. The part of the body most frequently injured was the the lower limbs/pelvis. Most patients had superficial injuries characterized as mild trauma.

  13. Mechanics of the foot Part 2: A coupled solid-fluid model to investigate blood transport in the pathologic foot.

    Science.gov (United States)

    Mithraratne, K; Ho, H; Hunter, P J; Fernandez, J W

    2012-10-01

    A coupled computational model of the foot consisting of a three-dimensional soft tissue continuum and a one-dimensional (1D) transient blood flow network is presented in this article. The primary aim of the model is to investigate the blood flow in major arteries of the pathologic foot where the soft tissue stiffening occurs. It has been reported in the literature that there could be up to about five-fold increase in the mechanical stiffness of the plantar soft tissues in pathologic (e.g. diabetic) feet compared with healthy ones. The increased stiffness results in higher tissue hydrostatic pressure within the plantar area of the foot when loaded. The hydrostatic pressure acts on the external surface of blood vessels and tend to reduce the flow cross-section area and hence the blood supply. The soft tissue continuum model of the foot was modelled as a tricubic Hermite finite element mesh representing all the muscles, skin and fat of the foot and treated as incompressible with transversely isotropic properties. The details of the mechanical model of soft tissue are presented in the companion paper, Part 1. The deformed state of the soft tissue continuum because of the applied ground reaction force at three foot positions (heel-strike, midstance and toe-off) was obtained by solving the Cauchy equations based on the theory of finite elasticity using the Galerkin finite element method. The geometry of the main arterial network in the foot was represented using a 1D Hermite cubic finite element mesh. The flow model consists of 1D Navier-Stokes equations and a nonlinear constitutive equation to describe vessel radius-transmural pressure relation. The latter was defined as the difference between the fluid and soft tissue hydrostatic pressure. Transient flow governing equations were numerically solved using the two-step Lax-Wendroff finite difference method. The geometry of both the soft tissue continuum and arterial network is anatomically-based and was developed using the data derived from visible human images and magnetic resonance images of a healthy male volunteer. Simulation results reveal that a two-fold increase in tissue stiffness leads to about 28% reduction in blood flow to the affected region. PMID:23027636

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

    Directory of Open Access Journals (Sweden)

    M. Lin

    2008-12-01

    Full Text Available Mechanisms controlling surface ozone (O3 over East Asia are examined using the regional Community Multiscale Air Quality (CMAQ model at two horizontal scales: 81 km and 27 km. Through sensitivity studies and comparison with recently available satellite data and surface measurements in China and Japan, we find that the O3 budget over East Asia shows complex interactions among photochemical production, regional transport, meteorological conditions, burning of agricultural residues, and global inflows. For example, wintertime surface O3 over northern domain is sensitive to boundary conditions derived from the MOZART (Model for Ozone and Related Tracers global model, whereas summertime O3 budget is controlled by the competitive processes between photochemical production and monsoonal intrusion of low-O3 marine air masses from tropical Pacific. We find that simulated surface O3 for 2001 does not exhibit the same sharp drop in July and August concentrations that is observed at two mountaintop sites (Tai and Hua for 2004 and Beijing for 1995–2005. CMAQ sensitivity tests with two widely used photochemical schemes demonstrate that over the industrial areas in East Asia north of 30° N, SAPRC99 produces higher values of mean summertime O3 than CBIV, amounting to a difference of 10 ppb. In addition, analysis of NCEP winds and geopotential heights suggests that southwesterly monsoonal intrusion in central east China is weakened in August 2001 as compared with the climatologically mean for 1980–2005. Further examination of the O3 diurnal cycle at nine Japanese sites shows that boundary layer evolution has an important effect on the vertical mixing of ground-level O3, and error in near surface meteorology might contribute to overprediction of nighttime O3 in urban and rural areas. In conclusion, the uncertainties in simulating cloud activities and convection mixing, Asian monsoon circulation, photochemical production, and nighttime cooling explain why CMAQ with 81 km horizontal scale overpredicts the observed surface O3 in July and August over central east China and central Japan by 5–15 ppb (CBIV and 15–25 ppb (SAPRC99. The results suggest clear benefits in evaluating atmospheric chemistry over Asia with high resolution regional model.

  15. Cement reactivity in CO2 saturated brines: use of a reactive transport code to highlight key degradation mechanisms

    International Nuclear Information System (INIS)

    A modular reactive transport code is proposed to analyze the reactivity of cement in CO2 saturated brine. The coupling of the transport module and the geochemical module within DynaflowTM is derived. Both modules are coupled in a sequential iterative approach to accurately model: (1) mineral dissolution/precipitation and (2) porosity dependent transport properties. Results of the model reproduce qualitatively the dissolution of cement hydrates (C-H, C-S-H, AFm, AFt) and intermediate products (CaCO3) into the brine. Slight discrepancies between modeling and experimental results were found concerning the dynamics of the mineral zoning. Results suggest that the power law relationship to model effective transport properties from porosity values is not accurate for very reactive case. (authors)

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

    OpenAIRE

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

    2000-01-01

    Herpes simplex virus type I (HSV) typically enters peripheral nerve terminals and then travels back along the nerve to reach the neuronal cell body, where it replicates or enters latency. To monitor axoplasmic transport of HSV, we used the giant axon of the squid, Loligo pealei, a well known system for the study of axoplasmic transport. To deliver HSV into the axoplasm, viral particles stripped of their envelopes by detergent were injected into the giant axon, thereby bypassing the infective ...

  17. Electrogenic glutamate transporters in the CNS: Molecular mechanism, pre-steady-state kinetics, and their impact on synaptic signaling

    OpenAIRE

    Grewer, Christof; Rauen, Thomas

    2005-01-01

    Glutamate is the major excitatory neurotransmitter in the mammalian CNS. The spatiotemporal profile of the glutamate concentration in the synapse is critical for excitatory synaptic signalling. The control of this spatiotemporal concentration profile requires the presence of large numbers of synaptically localized glutamate transporters that remove pre-synaptically released glutamate by uptake into neurons and adjacent glia cells. These glutamate transporters are electrogenic and utilize ener...

  18. 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, Technical University of Denmark, 17 - 18 March 2009

    DEFF Research Database (Denmark)

    2009-01-01

    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 green house 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.

  19. Inhibition of the OCTN2 carnitine transporter by HgCl2 and methylmercury in the proteoliposome experimental model: insights in the mechanism of toxicity.

    Science.gov (United States)

    Pochini, Lorena; Peta, Valentina; Indiveri, Cesare

    2013-02-01

    Mercury causes toxic effects in many tissues interacting with protein cysteine (Cys) thiols. Transport systems represent critical targets of mercurials. Indeed, the majority of transport systems of higher eukaryotes contain several Cys residues. One of the most up to date method of studying transport is the reconstitution of transporters in proteoliposomes. This method has been used as a useful approach to test the effect of HgCl(2) and methylmercury (MeHg) on the carnitine (OCTN2) transporter. OCTN2, extracted from kidney brush border membranes with 3% octaethylene glycol monododecyl ether (C(12)E(8)), was reconstituted in liposomes by removing the detergent with hydrophobic chromatography columns. Transport was measured as [(3)H]carnitine uptake into proteoliposomes containing carnitine (antiport reaction). Mercurials strongly inhibited the antiport. Inhibition was reversed by 1,4-dithioerythritol, L-cysteine (Cys), and N-acetyl-L-cysteine (NAC) indicating that it was caused by covalent reaction of mercurials with Cys residue(s). The IC(50) for HgCl(2), and MeHg were 2.5 and 7.4 µM, respectively. Kinetic studies showed non competitive or mixed inhibition for HgCl(2) or MeHg with Ki of 4.2 and 13 µM, respectively. The presence of substrate prevented the inhibition indicating that the mercurial binding residue (Cys) is in the substrate binding site. Efflux of carnitine from proteoliposomes was trans-stimulated, not inhibited, by higher concentrations (500 µM) of extraliposomal MeHg and HgCl(2). Differently, no effects on uptake of carnitine were exerted by mercurials present in the internal compartment of the proteoliposomes. The results allowed gaining new insights in the molecular mechanism of inhibition and of mercurial toxicity. PMID:22900493

  20. CIEMAT results in the frame of the european project Mechanisms governing the behaviour and transport of transuranics (analogues) and other radionuclides in marine ecosystems

    International Nuclear Information System (INIS)

    This report summarises the objectives and more relevant conclusions obtained by CIEMAT in the frame of the project Mechanisms governing the behaviour and transport of transuranics (analogues) and other radionuclides in marine ecosystems. The overall objective of this project was to identify the basic mechanisms and define the key parameters governing the physico-chemical speciation, vertical and horizontal mobility, biological magnification, incorporation to seabed sediments and ultimate fate of transuranium and other long-lived radionuclides in the marine environment, with a view to providing high-quality data of a universal character for use in the development and validation of predictive models based on fundamental mechanisms rather than the simpler box-model approach. This research was carried out in different European marine ecosystems: those directly affected by controlled releases from Nuclear Industries and/or accidents and those characterized by being preferent radionuclides accumulation sites (submarine canyons, estuaries, etc.). (Author)

  1. Teaching Main Idea Comprehension.

    Science.gov (United States)

    Baumann, James F., Ed.

    Intended to help classroom teachers, curriculum developers, and researchers, this book provides current information on theoretical and instructional aspects of main idea comprehension. Titles and authors are as follows: "The Confused World of Main Idea" (James W. Cunningham and David W. Moore); "The Comprehension of Important Information in…

  2. Gulf of Maine: Weather

    Science.gov (United States)

    Lessons and activities from the Gulf of Maine Research Institute (formerly Gulf of Maine Aquarium), focused on hurricanes, El Nino, fog, and volcanic eruptions. Emphasis on important hurricanes of the past. Resources include lessons, guides for simple experiments, and a student weather network. Downloadable materials and additional webpages also provided.

  3. The Maine Event

    Science.gov (United States)

    McHale, Tom

    2007-01-01

    In this article, the author describes the successful laptop program employed at Mt. Abram High School in Strong, Maine. Through the Maine Learning Technology Initiative, the school has issued laptops to all 36,000 teachers and students in grades 7-8. This program has helped level the playing field for a student population that is 50 percent to 55…

  4. Comparative physiology and architecture associated with the mammalian urine concentrating mechanism: role of inner medullary water and urea transport pathways in the rodent medulla.

    Science.gov (United States)

    Pannabecker, Thomas L

    2013-04-01

    Comparative studies of renal structure and function have potential to provide insights into the urine-concentrating mechanism of the mammalian kidney. This review focuses on the tubular transport pathways for water and urea that play key roles in fluid and solute movements between various compartments of the rodent renal inner medulla. Information on aquaporin water channel and urea transporter expression has increased our understanding of functional segmentation of medullary thin limbs of Henle's loops, collecting ducts, and vasa recta. A more complete understanding of membrane transporters and medullary architecture has identified new and potentially significant interactions between these structures and the interstitium. These interactions are now being introduced into our concept of how the inner medullary urine-concentrating mechanism works. A variety of regulatory pathways lead directly or indirectly to variable patterns of fluid and solute movements among the interstitial and tissue compartments. Animals with the ability to produce highly concentrated urine, such as desert species, are considered to exemplify tubular structure and function that optimize urine concentration. These species may provide unique insights into the urine-concentrating process.(1) PMID:23364530

  5. Universal quantifier derived from AFM analysis links cellular mechanical properties and cell-surface integration forces with microbial deposition and transport behavior.

    Science.gov (United States)

    Li, Yueyun; Wang, Xin; Onnis-Hayden, Annalisa; Wan, Kai-tak; Gu, April Z

    2014-02-01

    In this study, we employed AFM analysis combined with mathematical modeling for quantifying cell-surface contact mechanics and magnitude and range of cell-surface interaction forces for seven bacterial strains with a wide range of cell morphology, dimension, and surface characteristics. Comprehensive cell-surface characterization including surface charge, extracellular polymeric substance content, hydrophobicity, and cell-cell aggregation analyses were performed. Flow-through column tests were employed to determine the attachment efficiency and deposition-transport behavior of these bacterial strains. No statistically significant correlation between attachment efficiency and any single-cell surface property was identified. Single-cell characterization by atomic force microscopy (AFM) yielded the mechanical deformation and elastic modulus, penetration resistance to AFM probe penetration by cellular surface substances (CSS), range and magnitude of the repulsive-attractive intersurface forces, and geometry of each strain. We proposed and derived a universal dimensionless modified Tabor's parameter to integrate all these properties that account for their collective behavior. Results showed that the Tabor parameter derived from AFM analysis correlated well with experimentally determined attachment efficiency (?), which therefore is able to link microscale cell-surface properties with macroscale bacterial transport behavior. Results suggested that the AFM tests performed between a single cell and a surface captured the key quantities of the interactions between the cell and the surface that dictate overall cell attachment behavior. Tabor's parameter therefore can be potentially incorporated into the microbial transport model. PMID:24450282

  6. Maine Folklife Center

    Science.gov (United States)

    Located at the University of Maine, the Maine Folklife Center is committed to documenting and understanding the folklore, folklife, and history of Maine and Atlantic Canada. Along with its various scholarly activities, the Center sponsors a number of festivals, lectures, and like-minded programs that encourage appreciation of the diverse cultural traditions within the region. The site will be useful to researchers with a penchant in these fields, as it contains information about the collections, including a rather extensive oral history collection (with work that documenting the cranberry culture of Massachusetts and the traditional music of Maine). There is also material on the public programs and exhibits sponsored by the center, and a set of external links that lead to other sites dealing with oral history, folklore, and Maine. While the Center's site does not have a great deal of online material for consideration, the center has transcribed the sixth volume of Northeast Folklore (originally published in 1964) and placed them online.

  7. Electronic transport and conduction mechanism transition in La{sub 1?3}Sr{sub 2?3}FeO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Devlin, R. C.; Krick, A. L.; Sichel-Tissot, R. J.; Xie, Y. J.; May, S. J., E-mail: smay@coe.drexel.edu [Departm