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Sample records for channels enabling permeability

  1. Symmetry-Breaking Metamaterials Enabling Broadband Negative Permeability

    Science.gov (United States)

    Trang, Pham Thi; Nguyen, Bui Huu; Tiep, Dinh Hong; Thuy, Le Minh; Lam, Vu Dinh; Tung, Nguyen Thanh

    2016-05-01

    Looking for a metamaterial, which can operate over a broad frequency band, has been indispensable towards promising applications. In this report, we propose a simple approach, allowing enlargement of the negative permeability band by breaking the structural symmetry in conventional cut-wire-pair metamaterials. Equivalent LC circuit and finite integration simulations are performed to explain underlying physics of the band expansion. Microwave samples are also prepared and measured to verify the proposed idea.

  2. Transient Receptor Potential Channel 1 (TRPC1) Reduces Calcium Permeability in Heteromeric Channel Complexes

    Science.gov (United States)

    Storch, Ursula; Forst, Anna-Lena; Philipp, Maximilian; Gudermann, Thomas; Mederos y Schnitzler, Michael

    2012-01-01

    Specific biological roles of the classical transient receptor potential channel 1 (TRPC1) are still largely elusive. To investigate the function of TRPC1 proteins in cell physiology, we studied heterologously expressed TRPC1 channels and found that recombinant TRPC1 subunits do not form functional homomeric channels. Instead, by electrophysiological analysis TRPC1 was shown to form functional heteromeric, receptor-operated channel complexes with TRPC3, -4, -5, -6, and -7 indicating that TRPC1 proteins can co-assemble with all members of the TRPC subfamily. In all TRPC1-containing heteromers, TRPC1 subunits significantly decreased calcium permeation. The exchange of select amino acids in the putative pore-forming region of TRPC1 further reduced calcium permeability, suggesting that TRPC1 subunits contribute to the channel pore. In immortalized immature gonadotropin-releasing hormone neurons endogenously expressing TRPC1, -2, -5, and -6, down-regulation of TRPC1 resulted in increased calcium permeability and elevated basal cytosolic calcium concentrations. We did not observe any involvement of TRPC1 in store-operated cation influx. Notably, TRPC1 suppressed the migration of gonadotropin-releasing hormone neurons without affecting cell proliferation. Conversely, in TRPC1 knockdown neurons, specific migratory properties like distance covered, locomotion speed, and directionality were increased. These findings suggest a novel regulatory mechanism relying on the expression of TRPC1 and the subsequent formation of heteromeric TRPC channel complexes with reduced calcium permeability, thereby fine-tuning neuronal migration. PMID:22157757

  3. Potentially Conductive Channels in Fracture Cements of Low Permeability Rocks

    Science.gov (United States)

    Wright, E.; Landry, C. J.; Eichhubl, P.

    2015-12-01

    Natural fractures in shale reservoirs are frequently filled with mineral cement that lacks any residual fracture porosity that is visible under the petrographic microscope. These fully cemented fractures are generally interpreted to be impermeable for fluid flow. Scanning electron microscopy of calcite, dolomite, and barite fracture cements from a variety of shale reservoirs, prepared using broad ion beam milling, provides evidence of open to partially healed elongate pores that are on the order of hundreds of nanometers in aperture. In calcite fracture cement, these pores have consistent apertures of about 100 nm. In dolomite and barite, apertures are up to 500 nm. These pores have been previously overlooked because traditional thin sectioning and polishing destroys sub-micron details of the fracture cement pore structure. Ion milling preserves these details with a minimum of sample damage during sample preparation. Electron backscatter diffraction shows that these pores occur along grain boundaries within the blocky or columnar fracture cement. While partially healed, these pores, arranged along grain boundaries, are frequently sufficiently well connected acting as channels for fluid flow along and across fully cemented natural fractures. In shale reservoirs of ultra-low matrix permeability, these grain boundary channels may thus provide fracture permeability significantly contributing to reservoir production where intersected or indirectly reactivated by hydraulic fractures.

  4. Highly permeable artificial water channels that can self-assemble into two-dimensional arrays.

    Science.gov (United States)

    Shen, Yue-Xiao; Si, Wen; Erbakan, Mustafa; Decker, Karl; De Zorzi, Rita; Saboe, Patrick O; Kang, You Jung; Majd, Sheereen; Butler, Peter J; Walz, Thomas; Aksimentiev, Aleksei; Hou, Jun-li; Kumar, Manish

    2015-08-11

    Bioinspired artificial water channels aim to combine the high permeability and selectivity of biological aquaporin (AQP) water channels with chemical stability. Here, we carefully characterized a class of artificial water channels, peptide-appended pillar[5]arenes (PAPs). The average single-channel osmotic water permeability for PAPs is 1.0(± 0.3) × 10(-14) cm(3)/s or 3.5(± 1.0) × 10(8) water molecules per s, which is in the range of AQPs (3.4 ∼ 40.3 × 10(8) water molecules per s) and their current synthetic analogs, carbon nanotubes (CNTs, 9.0 × 10(8) water molecules per s). This permeability is an order of magnitude higher than first-generation artificial water channels (20 to ∼ 10(7) water molecules per s). Furthermore, within lipid bilayers, PAP channels can self-assemble into 2D arrays. Relevant to permeable membrane design, the pore density of PAP channel arrays (∼ 2.6 × 10(5) pores per μm(2)) is two orders of magnitude higher than that of CNT membranes (0.1 ∼ 2.5 × 10(3) pores per μm(2)). PAP channels thus combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis, chemical stability, and propensity to form arrays. PMID:26216964

  5. Exploring the biophysical evidence that mammalian two-pore channels are NAADP-activated calcium-permeable channels.

    Science.gov (United States)

    Pitt, Samantha J; Reilly-O'Donnell, Benedict; Sitsapesan, Rebecca

    2016-08-01

    Nicotinic acid adenine dinucleotide phosphate (NAADP) potently releases Ca(2+) from acidic intracellular endolysosomal Ca(2+) stores. It is widely accepted that two types of two-pore channels, termed TPC1 and TPC2, are responsible for the NAADP-mediated Ca(2+) release but the underlying mechanisms regulating their gating appear to be different. For example, although both TPC1 and TPC2 are activated by NAADP, TPC1 appears to be additionally regulated by cytosolic Ca(2+) . Ion conduction and permeability also differ markedly. TPC1 and TPC2 are permeable to a range of cations although biophysical experiments suggest that TPC2 is slightly more selective for Ca(2+) over K(+) than TPC1 and hence capable of releasing greater quantities of Ca(2+) from acidic stores. TPC1 is also permeable to H(+) and therefore may play a role in regulating lysosomal and cytosolic pH, possibly creating localised acidic domains. The significantly different gating and ion conducting properties of TPC1 and TPC2 suggest that these two ion channels may play complementary physiological roles as Ca(2+) -release channels of the endolysosomal system. PMID:26872338

  6. Mexico : New Technology-Enabled Channels to Scale Up Financial Access

    OpenAIRE

    International Monetary Fund; World Bank

    2013-01-01

    This is a technical note for the 2011 the Financial Sector Assessment Program (FSAP) carried out in Mexico. The focus of this document is the new technology-enabled channels to scale up financial access being employed. Key issues such as a pro-inclusion policy environment and harnessing technology for financial inclusion are discussed. Issues relevant to enabling policy framework, such as ...

  7. Methane oxidation in permeable sediments at hydrocarbon seeps in the Santa Barbara Channel, California

    OpenAIRE

    T. Treude; W. Ziebis

    2010-01-01

    A shallow-water area in the Santa Barbara Channel, California, known collectively as the Coal Oil Point seep field, is one of the largest natural submarine hydrocarbon emission areas in the world. Both gas and oil are seeping constantly through a predominantly sandy seabed into the ocean. This study focused on the methanotrophic activity within the surface sediments (0–15 cm) of the permeable seabed in the so-called Brian Seep area at a water depth of ∼10 m. Detailed investigations of...

  8. Methane oxidation in permeable sediments at hydrocarbon seeps in the Santa Barbara Channel, California

    OpenAIRE

    T. Treude; W. Ziebis

    2010-01-01

    A shallow-water area in the Santa Barbara Channel (California), known collectively as the Coal Oil Point seep field, is one the largest natural submarine oil and gas emission areas in the world. Both gas and oil are seeping constantly through a predominantly sandy seabed into the ocean. This study focused on the methanotrophic activity within the surface sediments (0–15 cm) of the permeable seabed in the so-called Brian Seep area at a water depth ~10 m. Detailed investigations of biogeochemic...

  9. Calcium-permeable ion channels involved in glutamate receptor-independent ischemic brain injury

    Institute of Scientific and Technical Information of China (English)

    Ming-hua LI; Koichi INOUE; Hong-fang SI; Zhi-gang XIONG

    2011-01-01

    Brain ischemia is a leading cause of death and long-term disabilities worldwide. Unfortunately, current treatment is limited to thrombolysis, which has limited success and a potential side effect of intracerebral hemorrhage. Searching for new cell injury mechanisms and therapeutic interventions has become a major challenge in the field. It has been recognized for many years that intracellular Ca2+overload in neurons is essential for neuronal injury associated with brain ischemia. However, the exact pathway(s) underlying the toxic Ca2+ loading remained elusive. This review discusses the role of two Ca2+-permeable cation channels, TRPM7 and acid-sensing channels, in glutamate-independent Ca2+ toxicity associated with brain ischemia.

  10. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  11. The permeability transition pore as a Ca2+ release channel: New answers to an old question

    Science.gov (United States)

    Bernardi, Paolo; von Stockum, Sophia

    2012-01-01

    Mitochondria possess a sophisticated array of Ca2+ transport systems reflecting their key role in physiological Ca2+ homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca2+ uptake, the ruthenium red (RR)-sensitive mitochondrial Ca2+ uniporter (MCU); and one main mechanism for Ca2+ release, the RR-insensitive 3Na+–Ca2+ antiporter. An additional mechanism for Ca2+ release is provided by a Na+ and RR-insensitive release mechanism, the putative 3H+–Ca2+ antiporter. A potential kinetic imbalance is present, however, because the Vmax of the MCU is of the order of 1400 nmol Ca2+ mg−1 protein min−1 while the combined Vmax of the efflux pathways is about 20 nmol Ca2+ mg−1 protein min−1. This arrangement exposes mitochondria to the hazards of Ca2+ overload when the rate of Ca2+ uptake exceeds that of the combined efflux pathways, e.g. for sharp increases of cytosolic [Ca2+]. In this short review we discuss the hypothesis that transient opening of the Ca2+-dependent permeability transition pore may provide mitocondria with a fast Ca2+ release channel preventing Ca2+ overload. We also address the relevance of a mitochondrial Ca2+ release channel recently discovered in Drosophila melanogaster, which possesses intermediate features between the permeability transition pore of yeast and mammals. PMID:22513364

  12. The permeability transition pore as a Ca(2+) release channel: new answers to an old question.

    Science.gov (United States)

    Bernardi, Paolo; von Stockum, Sophia

    2012-07-01

    Mitochondria possess a sophisticated array of Ca(2+) transport systems reflecting their key role in physiological Ca(2+) homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca(2+) uptake, the ruthenium red (RR)-sensitive mitochondrial Ca(2+) uniporter (MCU); and one main mechanism for Ca(2+) release, the RR-insensitive 3Na(+)-Ca(2+) antiporter. An additional mechanism for Ca(2+) release is provided by a Na(+) and RR-insensitive release mechanism, the putative 3H(+)-Ca(2+) antiporter. A potential kinetic imbalance is present, however, because the V(max) of the MCU is of the order of 1400nmol Ca(2+)mg(-1) proteinmin(-1) while the combined V(max) of the efflux pathways is about 20nmol Ca(2+)mg(-1) proteinmin(-1). This arrangement exposes mitochondria to the hazards of Ca(2+) overload when the rate of Ca(2+) uptake exceeds that of the combined efflux pathways, e.g. for sharp increases of cytosolic [Ca(2+)]. In this short review we discuss the hypothesis that transient opening of the Ca(2+)-dependent permeability transition pore may provide mitocondria with a fast Ca(2+) release channel preventing Ca(2+) overload. We also address the relevance of a mitochondrial Ca(2+) release channel recently discovered in Drosophila melanogaster, which possesses intermediate features between the permeability transition pore of yeast and mammals. PMID:22513364

  13. Structure and permeability of ion-channels by integrated AFM and waveguide TIRF microscopy.

    Science.gov (United States)

    Ramachandran, Srinivasan; Arce, Fernando Teran; Patel, Nirav R; Quist, Arjan P; Cohen, Daniel A; Lal, Ratnesh

    2014-01-01

    Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal reflection fluorescence microscopy (TIRFM) for high resolution imaging and molecular transport measurement. Significantly, membranes over the nanopore were stable for repeated AFM imaging. We studied structure-activity relationship of gap junction hemichannels reconstituted in lipid bilayers. Individual hemichannels in the membrane overlying the nanopore were resolved and transport of hemichannel-permeant LY dye was visualized when the hemichannel was opened by lowering calcium in the medium. This integrated technique will allow direct structure-permeability relationship of many ion channels and receptors. PMID:24651823

  14. Straight line methods for estimating permeability or width for a two-zone composite channelized reservoir

    International Nuclear Information System (INIS)

    Some well pressure tests conducted in channelized systems which result from either fluvial deposition or faulting, cannot be completely interpreted by conventional techniques, since variation in facies or reservoir width are not normally recognized yet in the oil literature. In this case, the corresponding equations traditionally used for single linear flow will provide inaccurate results. Therefore, they must be corrected. In this study, new equations to be used in conventional analysis for the linear flow (pseudo linear) regime formed during the acting of the anomaly - reservoir width or permeability - are introduced to the oil literature. The equations do not consider the simultaneous variation of both parameters. The proposed equations were validated by applying them to synthetic and field examples.

  15. Reconstitution of CO2 Regulation of SLAC1 Anion Channel and Function of CO2-Permeable PIP2;1 Aquaporin as CARBONIC ANHYDRASE4 Interactor.

    Science.gov (United States)

    Wang, Cun; Hu, Honghong; Qin, Xue; Zeise, Brian; Xu, Danyun; Rappel, Wouter-Jan; Boron, Walter F; Schroeder, Julian I

    2016-02-01

    Dark respiration causes an increase in leaf CO2 concentration (Ci), and the continuing increases in atmospheric [CO2] further increases Ci. Elevated leaf CO2 concentration causes stomatal pores to close. Here, we demonstrate that high intracellular CO2/HCO3 (-) enhances currents mediated by the Arabidopsis thaliana guard cell S-type anion channel SLAC1 upon coexpression of any one of the Arabidopsis protein kinases OST1, CPK6, or CPK23 in Xenopus laevis oocytes. Split-ubiquitin screening identified the PIP2;1 aquaporin as an interactor of the βCA4 carbonic anhydrase, which was confirmed in split luciferase, bimolecular fluorescence complementation, and coimmunoprecipitation experiments. PIP2;1 exhibited CO2 permeability. Mutation of PIP2;1 in planta alone was insufficient to impair CO2- and abscisic acid-induced stomatal closing, likely due to redundancy. Interestingly, coexpression of βCA4 and PIP2;1 with OST1-SLAC1 or CPK6/23-SLAC1 in oocytes enabled extracellular CO2 enhancement of SLAC1 anion channel activity. An inactive PIP2;1 point mutation was identified that abrogated water and CO2 permeability and extracellular CO2 regulation of SLAC1 activity. These findings identify the CO2-permeable PIP2;1 as key interactor of βCA4 and demonstrate functional reconstitution of extracellular CO2 signaling to ion channel regulation upon coexpression of PIP2;1, βCA4, SLAC1, and protein kinases. These data further implicate SLAC1 as a bicarbonate-responsive protein contributing to CO2 regulation of S-type anion channels. PMID:26764375

  16. Temporal decorrelation by SK channels enables efficient neural coding and perception of natural stimuli

    Science.gov (United States)

    Huang, Chengjie G.; Zhang, Zhubo D.; Chacron, Maurice J.

    2016-01-01

    It is commonly assumed that neural systems efficiently process natural sensory input. However, the mechanisms by which such efficient processing is achieved, and the consequences for perception and behaviour remain poorly understood. Here we show that small conductance calcium-activated potassium (SK) channels enable efficient neural processing and perception of natural stimuli. Specifically, these channels allow for the high-pass filtering of sensory input, thereby removing temporal correlations or, equivalently, whitening frequency response power. Varying the degree of adaptation through pharmacological manipulation of SK channels reduced efficiency of coding of natural stimuli, which in turn gave rise to predictable changes in behavioural responses that were no longer matched to natural stimulus statistics. Our results thus demonstrate a novel mechanism by which the nervous system can implement efficient processing and perception of natural sensory input that is likely to be shared across systems and species. PMID:27088670

  17. Up-Regulation of Pressure-activated Ca2+-permeable Cation Channel in Intact Vascular Endothelium of Hypertensive Rats

    Science.gov (United States)

    Hoyer, J.; Kohler, R.; Haase, W.; Distler, A.

    1996-10-01

    In endothelial cells, stretch-activated cation channels have been proposed to act as mechanosensors for changes in hemodynamic forces. We have identified a novel mechanosensitive pressure-activated channel in intact endothelium from rat aorta and mesenteric artery. The 18-pS cation channel responded with a multifold increase in channel activity when positive pressure was applied to the luminal cell surface with the patch pipette and inactivated at negative pipette pressure. Channel permeability ratio for K+, Na+, and Ca2+ ions was 1:0.98:0.23. Ca2+ influx through the channel was sufficient to activate a neighboring Ca2+-dependent K+ channel. Hemodynamic forces are chronically disturbed in arterial hypertension. Endothelial cell dysfunction has been implicated in the pathogenesis of arterial hypertension. In two comparative studies, density of the pressure-activated channel was found to be significantly higher in spontaneously hypertensive rats and renovascular hypertensive rats compared with their respective normotensive controls. Channel activity presumably leads to mechanosensitive Ca2+ influx and induces cell hyperpolarization by K+ channel activity. Both Ca2+ influx and hyperpolarization are known to induce a vasodilatory endothelial response by stimulating endothelial nitric oxide (NO) production. Up-regulation of channel density in hypertension could, therefore, represent a counterregulatory mechanism of vascular endothelium.

  18. Specific permeability and selective formation of gap junction channels in connexin-transfected HeLa cells

    OpenAIRE

    1995-01-01

    DNAs coding for seven murine connexins (Cx) (Cx26, Cx31, Cx32, Cx37, Cx40, Cx43, and Cx45) are functionally expressed in human HeLa cells that were deficient in gap junctional communication. We compare the permeabilities of gap junctions comprised of different connexins to iontophoretically injected tracer molecules. Our results show that Lucifer yellow can pass through all connexin channels analyzed. On the other hand, propidium iodide and ethidium bromide penetrate very poorly or not at all...

  19. Molecular Mechanisms Contributing to TARP Regulation of Channel Conductance and Polyamine Block of Calcium-Permeable AMPA Receptors

    Science.gov (United States)

    Coombs, Ian D.; Gratacòs-Batlle, Esther

    2014-01-01

    Many properties of fast synaptic transmission in the brain are influenced by transmembrane AMPAR regulatory proteins (TARPs) that modulate the pharmacology and gating of AMPA-type glutamate receptors (AMPARs). Although much is known about TARP influence on AMPAR pharmacology and kinetics through their modulation of the extracellular ligand-binding domain (LBD), less is known about their regulation of the ion channel region. TARP-induced modifications in AMPAR channel behavior include increased single-channel conductance and weakened block of calcium-permeable AMPARs (CP-AMPARs) by endogenous intracellular polyamines. To investigate how TARPs modify ion flux and channel block, we examined the action of γ-2 (stargazin) on GluA1 and GluA4 CP-AMPARs. First, we compared the permeation of organic cations of different sizes. We found that γ-2 increased the permeability of several cations but not the estimated AMPAR pore size, suggesting that TARP-induced relief of polyamine block does not reflect altered pore diameter. Second, to determine whether residues in the TARP intracellular C-tail regulate polyamine block and channel conductance, we examined various γ-2 C-tail mutants. We identified the membrane proximal region of the C terminus as crucial for full TARP-attenuation of polyamine block, whereas complete deletion of the C-tail markedly enhanced the TARP-induced increase in channel conductance; thus, the TARP C-tail influences ion permeation. Third, we identified a site in the pore-lining region of the AMPAR, close to its Q/R site, that is crucial in determining the TARP-induced changes in single-channel conductance. This conserved residue represents a site of TARP action, independent of the AMPAR LBD. PMID:25164663

  20. Small intestinal efflux mediated by MRP2 and BCRP shifts sulfasalazine intestinal permeability from high to low, enabling its colonic targeting.

    Science.gov (United States)

    Dahan, Arik; Amidon, Gordon L

    2009-08-01

    Sulfasalazine is characterized by low intestinal absorption, which essentially enables its colonic targeting and therapeutic action. The mechanisms behind this low absorption have not yet been elucidated. The purpose of this study was to investigate the role of efflux transporters in the intestinal absorption of sulfasalazine as a potential mechanism for its low small-intestinal absorption and colonic targeting following oral administration. The effects of P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2), and breast cancer resistance protein (BCRP) inhibitors on sulfasalazine bidirectional permeability were studied across Caco-2 cell monolayers, including dose-response analysis. Sulfasalazine in vivo permeability was then investigated in the rat jejunum by single-pass perfusion, in the presence vs. absence of inhibitors. Sulfasalazine exhibited 19-fold higher basolateral-to-apical (BL-AP) than apical-to-basolateral (AP-BL) Caco-2 permeability, indicative of net mucosal secretion. MRP2 inhibitors (MK-571 and indomethacin) and BCRP inhibitors [fumitremorgin C (FTC) and pantoprazole] significantly increased AP-BL and decreased BL-AP sulfasalazine Caco-2 transport in a concentration-dependent manner. No effect was observed with the P-gp inhibitors verapamil and quinidine. The IC50 values of the specific MRP2 and BCRP inhibitors MK-571 and FTC on sulfasalazine secretion were 21.5 and 2.0 microM, respectively. Simultaneous inhibition of MRP2 and BCRP completely abolished sulfasalazine Caco-2 efflux. Without inhibitors, sulfasalazine displayed low (vs. metoprolol) in vivo intestinal permeability in the rat model. MK-571 or FTC significantly increased sulfasalazine permeability, bringing it to the low-high permeability boundary. With both MK-571 and FTC present, sulfasalazine displayed high permeability. In conclusion, efflux transport mediated by MRP2 and BCRP, but not P-gp, shifts sulfasalazine permeability from high to low, thereby enabling its

  1. Transepithelial water permeability in microperfused distal airways. Evidence for channel-mediated water transport.

    OpenAIRE

    Folkesson, H G; Matthay, M. A.; Frigeri, A.; Verkman, A.S.

    1996-01-01

    Water movement across the airway epithelium is important for regulation of the volume and composition of airspace fluid. A novel approach is reported here to measure osmotic and diffusional water permeability in intact airways. Small airways (100-200 microns diameter, 1-2 mm length) from guinea pig lung were microdissected and perfused in vitro using concentric glass holding and perfusion pipettes. For measurement of osmotic water permeability (Pf), the airway lumen was perfused wit PBS (300 ...

  2. Magnetic resonance image enhancement by reducing receptors' effective size and enabling multiple channel acquisition.

    Science.gov (United States)

    Yepes-Calderon, Fernando; Velasquez, Adriana; Lepore, Natasha; Beuf, Olivier

    2014-01-01

    Magnetic resonance imaging is empowered by parallel reading, which reduces acquisition time dramatically. The time saved by parallelization can be used to increase image quality or to enable specialized scanning protocols in clinical and research environments. In small animals, the sizing constraints render the use of multi-channeled approaches even more necessary, as they help to improve the typically low spatial resolution and lesser signal-to-noise ratio; however, the use of multiple channels also generates mutual induction (MI) effects that impairs imaging creation. Here, we created coils and used the shared capacitor technique to diminish first degree MI effects and pre-amplifiers to deal with higher order MI-related image deterioration. The constructed devices are tested by imaging phantoms that contain identical solutions; thus, creating the conditions for several statistical comparisons. We confirm that the shared capacitor strategy can recover the receptor capacity in compounded coils when working at the dimensions imposed by small animal imaging. Additionally, we demonstrate that the use of pre-amplifiers does not significantly reduce the quality of the images. Moreover, in light of our results, the two MI-avoiding techniques can be used together, therefore establishing the practical feasibility of flexible array coils populated with multiple loops for small animal imaging. PMID:25570478

  3. Sodium Permeability of a Cloned Small-Conductance Calcium-Activated Potassium Channel

    OpenAIRE

    Shin, Narae; Soh, Heun; Chang, Sunghoe; Kim, Do Han; Park, Chul-Seung

    2005-01-01

    Small-conductance Ca2+-activated potassium channels (SKCa channels) are heteromeric complexes of pore-forming main subunits and constitutively bound calmodulin. SKCa channels in neuronal cells are activated by intracellular Ca2+ that increases during action potentials, and their ionic currents have been considered to underlie neuronal afterhyperpolarization. However, the ion selectivity of neuronal SKCa channels has not been rigorously investigated. In this study, we determined the monovalent...

  4. Activation, Permeability, and Inhibition of Astrocytic and Neuronal Large Pore (Hemi)channels

    DEFF Research Database (Denmark)

    Hansen, Daniel Bloch; Ye, Zu-Cheng; Calloe, Kirstine;

    2014-01-01

    overlapping sensitivity to the inhibitors Brilliant Blue, gadolinium, and carbenoxolone. These results demonstrated isoform-specific characteristics among the large pore membrane channels; an open (hemi)channel is not a nonselective channel. With these isoform-specific properties in mind, we characterized the...

  5. Control of the Aquaporin-4 Channel Water Permeability by Structural Dynamics of Aromatic/Arginine Selectivity Filter Residues.

    Science.gov (United States)

    Kitchen, Philip; Conner, Alex C

    2015-11-17

    The aquaporins (AQPs) make up a family of integral membrane proteins that control cellular water flow. Gating of the water channel by conformational changes induced by phosphorylation or protein-protein interactions is an established regulatory mechanism for AQPs. Recent in silico and crystallographic analyses of the structural biology of AQPs suggest that the rate of water flow can also be controlled by small movements of single-amino acid side chains lining the water pore. Here we use measurements of the membrane water permeability of mammalian cells expressing AQP4 mutants to provide the first in vitro evidence in support of this hypothesis. PMID:26512424

  6. Structure and Permeability of Ion-channels by Integrated AFM and Waveguide TIRF Microscopy

    OpenAIRE

    Srinivasan Ramachandran; Fernando Teran Arce; Patel, Nirav R.; Quist, Arjan P.; Cohen, Daniel A.; Ratnesh Lal

    2014-01-01

    Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal refle...

  7. Interaction of H2S with Calcium Permeable Channels and Transporters

    Directory of Open Access Journals (Sweden)

    Weihua Zhang

    2015-01-01

    Full Text Available A growing amount of evidence has suggested that hydrogen sulfide (H2S, as a gasotransmitter, is involved in intensive physiological and pathological processes. More and more research groups have found that H2S mediates diverse cellular biological functions related to regulating intracellular calcium concentration. These groups have demonstrated the reciprocal interaction between H2S and calcium ion channels and transporters, such as L-type calcium channels (LTCC, T-type calcium channels (TTCC, sodium/calcium exchangers (NCX, transient receptor potential (TRP channels, β-adrenergic receptors, and N-methyl-D-aspartate receptors (NMDAR in different cells. However, the understanding of the molecular targets and mechanisms is incomplete. Recently, some research groups demonstrated that H2S modulates the activity of calcium ion channels through protein S-sulfhydration and polysulfide reactions. In this review, we elucidate that H2S controls intracellular calcium homeostasis and the underlying mechanisms.

  8. Gap-Junctional Single-Channel Permeability for Fluorescent Tracers in Mammalian Cell Cultures

    OpenAIRE

    Eckert, Reiner

    2006-01-01

    We have developed a simple dye transfer method that allows quantification of the gap-junction permeability of small cultured cells. Fluorescent dyes (calcein and Lucifer yellow) were perfused into one cell of an isolated cell pair using a patch-type micropipette in the tight-seal whole cell configuration. Dye spreading into the neighboring cells was monitored using a low-light charge-coupled device camera. Permeation rates for calcein and Lucifer yellow were then estimated by fitting the time...

  9. Cosegregation of Permeability and Single-Channel Conductance in Chimeric Connexins

    OpenAIRE

    Ma, Meiyun; Dahl, Gerhard

    2005-01-01

    The physiological function of gap junction channels goes well beyond their initially discovered role in electrical synchronization of excitable cells. In most tissues, gap junction cells facilitate the exchange of second messengers and metabolites between cells. To test which parts of the channels formed by connexins determine the exclusion limit for the transit of molecules in the size range of second messengers and metabolites a domain exchange approach was used in combination with an acces...

  10. Enabling Technology for the Exploration of the Arctic Ocean - Multi Channel Seismic Reflection data acquisition

    Science.gov (United States)

    Coakley, B.; Anderson, R.; Chayes, D. N.; Goemmer, S.; Oursler, M.

    2009-12-01

    Great advances in mapping the Arctic Ocean have recently been made through the relatively routine acquisition of multibeam data from icebreakers operating on various cruise. The USCGC Healy, the German icebreaker Polarstern, the Canadian icebreaker Amundsen and the Swedish icebreaker Oden all routinely collect multibeam data, even while in heavy ice pack. This increase in data has substantially improved our knowledge of the form of the Arctic Ocean seafloor. Unfortunately, it is not possible to routinely collect Multi Channel Seismic Reflection (MCS) data while underway in the ice pack. Our inability to simply collect these data restricts how we understand many of the features that segment the basin by depriving us of the historical information that can be obtained by imaging the stratigraphy. Without these data, scientific ocean drilling, the ultimate ground truth for Marine Geology, cannot be done. The technology and expertise to collect MCS must be adapted for the particular circumstances of the Arctic Ocean. While MCS data have been collected in the Arctic Ocean, the procedures have relied on icebreakers towing equipment. Since icebreakers follow the path of least resistance through the pack, data are acquired in locations that are not scientifically optimal and rarely in the relatively straight lines necessary for optimal processing. Towing in the ice pack is also difficult, inefficient and puts this equipment at substantial risk of crushing or loss. While icebreakers are one means to collect these data, it is time to conduct a systematic evaluation of the costs and benefits of different platforms for MCS data acquisition. This evaluation should enable collection of high-quality data set at selected locations to solve scientific problems. Substantial uncertainties exist about the relative capabilities, costs and limitations for acquisition of MCS data from various platforms in the Arctic Ocean. For example; - Is it possible to collect multi-channel seismic

  11. In pursuit of small molecule chemistry for calcium-permeable non-selective TRPC channels -- mirage or pot of gold?

    Science.gov (United States)

    Bon, Robin S; Beech, David J

    2013-10-01

    The primary purpose of this review is to address the progress towards small molecule modulators of human Transient Receptor Potential Canonical proteins (TRPC1, TRPC3, TRPC4, TRPC5, TRPC6 and TRPC7). These proteins generate channels for calcium and sodium ion entry. They are relevant to many mammalian cell types including acinar gland cells, adipocytes, astrocytes, cardiac myocytes, cochlea hair cells, endothelial cells, epithelial cells, fibroblasts, hepatocytes, keratinocytes, leukocytes, mast cells, mesangial cells, neurones, osteoblasts, osteoclasts, platelets, podocytes, smooth muscle cells, skeletal muscle and tumour cells. There are broad-ranging positive roles of the channels in cell adhesion, migration, proliferation, survival and turning, vascular permeability, hypertrophy, wound-healing, hypo-adiponectinaemia, angiogenesis, neointimal hyperplasia, oedema, thrombosis, muscle endurance, lung hyper-responsiveness, glomerular filtration, gastrointestinal motility, pancreatitis, seizure, innate fear, motor coordination, saliva secretion, mast cell degranulation, cancer cell drug resistance, survival after myocardial infarction, efferocytosis, hypo-matrix metalloproteinase, vasoconstriction and vasodilatation. Known small molecule stimulators of the channels include hyperforin, genistein and rosiglitazone, but there is more progress with inhibitors, some of which have promising potency and selectivity. The inhibitors include 2-aminoethoxydiphenyl borate, 2-aminoquinolines, 2-aminothiazoles, fatty acids, isothiourea derivatives, naphthalene sulfonamides, N-phenylanthranilic acids, phenylethylimidazoles, piperazine/piperidine analogues, polyphenols, pyrazoles and steroids. A few of these agents are starting to be useful as tools for determining the physiological and pathophysiological functions of TRPC channels. We suggest that the pursuit of small molecule modulators for TRPC channels is important but that it requires substantial additional effort and

  12. Na+-permeable channels of human sperm membrane re- assembled into giant liposome

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Previous data showed that a Na+-transmembrane flux was accompanied with acrosome reaction of sperm. However, the electrophysiological recording and characterization of Na+ current in human sperm membrane have not been yet reported. In the present investigation, membrane proteins extracted from human sperms were reassembled into liposome bilayer, and then the liposomes were fused by dehydration-rehydration into giant liposomes with the diameter of more than 10 mm. By patch clamping the giant liposomes two kinds of single channel currents were recorded in a NaCl solution system. Both of them were Na+-carried, TTX-sensitive and strongly rectifying, but with different unit conductance and open probability. Moreover, bursting activity and channel-substates as well as two open time constants were observed in the larger channel.

  13. Channel Decision in Cognitive Radio Enabled Sensor Networks: A Reinforcement Learning Approach

    Directory of Open Access Journals (Sweden)

    Joshua Abolarinwa

    2015-08-01

    Full Text Available Recent advancements in the field of cognitive radio technology have paved way for cognitive radio-based wireless sensor networks. This has been tipped to be the next generation sensor. Spectrum sensing and energy efficient channel access are two important operations in this network. In this paper, we propose the use of machine learning and decision making capability of reinforcement learning to address the problem of energy efficiency associated with channel access in cognitive radio aided sensor networks. A simple learning algorithm was developed to improve network parameters such as secondary user throughput, channel availability in relation to the sensing time. Comparing the results obtained from simulations with other channel access without intelligent learning such as random channel assignment and dynamic channel assignment, the learning algorithm produced better performance in terms of throughput, energy efficiency and other quality of service requirement of the network application.

  14. Tilted Magnetic Levitation Enables Measurement of the Complete Range of Densities of Materials with Low Magnetic Permeability.

    Science.gov (United States)

    Nemiroski, Alex; Soh, Siowling; Kwok, Sen Wai; Yu, Hai-Dong; Whitesides, George M

    2016-02-01

    Magnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic field gradient provides a simple method to measure the density of small samples of solids or liquids. One major limitation of this method, thus far, has been an inability to measure or manipulate materials outside of a narrow range of densities (0.8 g/cm(3) densities that can be levitated magnetically. Tilting the MagLev device relative to the gravitational vector enables the magnetic force to be decreased (relative to the magnetic force) along the axis of measurement. This approach enables many practical measurements over the entire range of densities observed in matter at ambient conditions-from air bubbles (ρ ≈ 0) to osmium and iridium (ρ ≈ 23 g/cm(3)). The ability to levitate, simultaneously, objects with a broad range of different densities provides an operationally simple method that may find application to forensic science (e.g., for identifying the composition of miscellaneous objects or powders), industrial manufacturing (e.g., for quality control of parts), or resource-limited settings (e.g., for identifying and separating small particles of metals and alloys). PMID:26722977

  15. A Charge Separation Study to Enable the Design of a Complete Muon Cooling Channel

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, C. [Muons, Inc.; Ankenbrandt, Charles M. [Muons, Inc.; Johnson, Rolland P. [Muons, Inc.; Derbenev, Yaroslav [JLAB; Morozov, Vasiliy [JLAB; Neuffer, David [FNAL; Yonehara, K. [FNAL

    2013-12-01

    The most promising designs for 6D muon cooling channels operate on a specific sign of electric charge. In particular, the Helical Cooling Channel (HCC) and Rectilinear RFOFO designs are the leading candidates to become the baseline 6D cooling channel in the Muon Accelerator Program (MAP). Time constraints prevented the design of a realistic charge separator, so a simplified study was performed to emulate the effects of charge separation on muons exiting the front end of a muon collider. The output of the study provides particle distributions that the competing designs will use as input into their cooling channels. We report here on the study of the charge separator that created the simulated particles.

  16. Inhibition of TRPV1 channels enables long-term potentiation in the entorhinal cortex.

    Science.gov (United States)

    Banke, Tue G

    2016-04-01

    The transient receptor potential vanilloid 1 (TRPV1) channel is a non-selective cation channel that is mainly found in nociceptive neurons of the peripheral nervous system; however, these channels have also been located within the CNS, including the entorhinal cortex. Whole-cell patch-clamp recordings of principal entorhinal cortex (EC) layers II/III neurons revealed that evoked inhibitory postsynaptic currents were depressed by application of the TRPV1 agonist capsaicin (CAP), accompanied by a change in the pair-pulse ratio (PPR). In addition, recordings of miniature inhibitory postsynaptic currents (mIPSCs) revealed that inter-event intervals but not amplitude were decreased in wild-type (WT) after application of CAP. This suggests that TRPV1 channels are functional in the entorhinal cortex and are located on inhibitory neurons with their axonal arborization within layers II/III. In order to study TRPV1 channels and their involvement in long-term potentiation (LTP) induction in a more intact circuit, extracellular field potential recordings were performed in EC layers II/III. It was found that activated TRPV1 channels preclude induction of long-term potentiation. In sharp contrast, clear LTP was observed when antagonizing TRPV1 channels or recording from TRPV1 knock-out mice. Thus, these results suggests that signaling through activating inhibitory presynaptic TRPV1 channels represents a novel mechanism by which a shift in feed-forward inhibition of layers II/III cortical principal neurons prompt changes in synaptic strength and thereby contribute to a change of information storage within the brain. PMID:26729265

  17. Prefrontal Cortex HCN1 Channels Enable Intrinsic Persistent Neural Firing and Executive Memory Function

    OpenAIRE

    Thuault, Sébastien J.; Malleret, Gaël; Constantinople, Christine M.; Nicholls, Russell; Chen, Irene; Zhu, Judy; Panteleyev, Andrey; Vronskaya, Svetlana; Nolan, Matthew F; Bruno, Randy; Siegelbaum, Steven A.; Kandel, Eric R.

    2013-01-01

    In many cortical neurons, HCN1 channels are the major contributors to Ih, the hyperpolarization-activated current, which regulates the intrinsic properties of neurons and shapes their integration of synaptic inputs, paces rhythmic activity, and regulates synaptic plasticity. Here, we examine the physiological role of Ih in deep layer pyramidal neurons in mouse prefrontal cortex (PFC), focusing on persistent activity, a form of sustained firing thought to be important for the behavioral functi...

  18. Reactive derivatives of gramicidin enable light- and ion-modulated ion channels

    Science.gov (United States)

    Macrae, Michael X.; Blake, Steven; Mayer, Thomas; Mayer, Michael; Yang, Jerry

    2009-08-01

    Detection of chemical processes on a single molecule scale is the ultimate goal of sensitive analytical assays. We have explored methods to detect chemical analytes in solution using synthetic derivatives of gramicidin A (gA). We exploited the functional properties of an ion channel-forming peptideg--gA--to report changes in the local environment near the opening of these semi-synthetic nanopores upon exposure to specific external stimuli. These peptide-based nanosensors detect reaction-induced changes in the chemical or physical properties of functional groups presented at the opening of the pore. This paper discusses the development of gA-based sensors for detecting external factors such as metal ions in solution or for detecting specific wavelengths of light. We propose that gA-based ion channel sensors offer tremendous potential for ultra sensitive functional detection since a single chemical modification of each individual sensing element can lead to readily detectable changes in channel conductance.

  19. Wirelessly powered micro-tracer enabled by miniaturized antenna and microfluidic channel

    Science.gov (United States)

    Duan, G.; Zhao, X.; Seren, H. R.; Chen, C.; Zhang, X.

    2015-12-01

    A miniaturized antenna, 380μm by 380μm in size, was fabricated and integrated with a commercialized passive RFID chip to form a micro-tracer, whose size was 2mm by 1mm in total. The micro-tracer was wirelessly powered and interrogated by a single layer spiral reader antenna through near field coupling. To maximize the working distance, the resonant frequency of micro-tracer and reader antenna were matched at 840MHz. Due to the ultra small size of the tracer antenna, power transfer efficiency decreased dramatically as the distance between tracer antenna and reader antenna increased, thus the working distance of the microtracer was limited within 1mm. To achieve massive operation of the micro-tracer, a microfluidic platform was fabricated with in channel focusing and separation. Acrylic sheets were laser cut to define the channel and cover structure, then bonded together layer by layer with a glass substrate, on which reader antenna was integrated. Pump oil was used as the fluidic media carrying the micro-tracer flowing inside the microfluidic channel. The wireless power transfer and real-time communication was demonstrated with the micro-tracer flowing above the reader antenna, as the ID of the micro-tracer was retrieved and displayed on a computer screen.

  20. Voltage dependent anion channel-1 regulates death receptor mediated apoptosis by enabling cleavage of caspase-8

    International Nuclear Information System (INIS)

    Activation of the extrinsic apoptosis pathway by tumour necrosis factor related apoptosis inducing ligand (TRAIL) is a novel therapeutic strategy for treating cancer that is currently under clinical evaluation. Identification of molecular biomarkers of resistance is likely to play an important role in predicting clinical anti tumour activity. The involvement of the mitochondrial type 1 voltage dependent anion channel (VDAC1) in regulating apoptosis has been highly debated. To date, a functional role in regulating the extrinsic apoptosis pathway has not been formally excluded. We carried out stable and transient RNAi knockdowns of VDAC1 in non-small cell lung cancer cells, and stimulated the extrinsic apoptotic pathway principally by incubating cells with the death ligand TRAIL. We used in-vitro apoptotic and cell viability assays, as well as western blot for markers of apoptosis, to demonstrate that TRAIL-induced toxicity is VDAC1 dependant. Confocal microscopy and mitochondrial fractionation were used to determine the importance of mitochondria for caspase-8 activation. Here we show that either stable or transient knockdown of VDAC1 is sufficient to antagonize TRAIL mediated apoptosis in non-small cell lung cancer (NSCLC) cells. Specifically, VDAC1 is required for processing of procaspase-8 to its fully active p18 form at the mitochondria. Loss of VDAC1 does not alter mitochondrial sensitivity to exogenous caspase-8-cleaved BID induced mitochondrial depolarization, even though VDAC1 expression is essential for TRAIL dependent activation of the intrinsic apoptosis pathway. Furthermore, expression of exogenous VDAC1 restores the apoptotic response to TRAIL in cells in which endogenous VDAC1 has been selectively silenced. Expression of VDAC1 is required for full processing and activation of caspase-8 and supports a role for mitochondria in regulating apoptosis signaling via the death receptor pathway

  1. Channelling science into policy: enabling best practices from research on land degradation and sustainable land management in dryland Africa.

    Science.gov (United States)

    Stringer, Lindsay C; Dougill, Andrew J

    2013-01-15

    Demands are increasing for scientific research to be explicitly and demonstrably policy relevant. Research funders are requiring greater returns on their investments and scientists are expected to demonstrate clearly how their research can inform policy and regulation to deliver positive consequences for societal, economic and environmental wellbeing. Within the co-evolving context of environmental management research in dryland Africa and the policy approaches designed to mitigate land degradation, few academic analyses have deconstructed the practical 'bottom-up' actions that can help to channel scientific research into national decision-making and policy. Similarly, while international platforms developed by the United Nations Convention to Combat Desertification have started to facilitate greater knowledge exchange between scientists and policymakers, analyses have failed to consider the powerful informal actions that scientists can take to allow their research to inform evidence-based international policy. Drawing on examples in the literature from research on land degradation and sustainable land management across sub-Saharan African drylands, we identify key enabling activities that help make scientific research more visible, accessible to, and compatible with, policy processes at local, national and international levels. We argue that these enablers are applicable to other environmental research areas beyond land degradation, and suggest that improved understanding of science into policy processes that look across multiple scales and levels will help researchers and policy-makers to better match information supply and demand to the mutual benefit of both groups. PMID:23158525

  2. Developments in permeable and low permeability barriers

    International Nuclear Information System (INIS)

    The concept of the reactive treatment zone whereby pollutants are attenuated as they move along a pathway in the ground has enabled a re-thinking of many of the concepts of containment. In particular it offers the potential for the control of the flux from a contaminated area by controlling the contaminant concentration in the pathway(s) as well as or instead of using a low permeability barrier. The paper outlines the basic concepts of the reactive treatment zone and the use of permeable and low permeability reactive systems. The paper then gives a case history of the installation of a permeable barrier using an in-situ reaction chamber

  3. Effects of Levetiracetam, Carbamazepine, Phenytoin, Valproate, Lamotrigine, Oxcarbazepine, Topiramate, Vinpocetine and Sertraline on Presynaptic Hippocampal Na(+) and Ca(2+) Channels Permeability.

    Science.gov (United States)

    Sitges, María; Chiu, Luz María; Reed, Ronald C

    2016-04-01

    Ion channels are targets of various antiepileptic drugs. In cerebral presynaptic nerve endings Na(+) and Ca(2+) channels are particularly abundant, as they control neurotransmitter release, including the release of glutamate (Glu), the most concentrated excitatory amino acid neurotransmitter in the brain. Several pre-synaptic channels are implicated in the mechanism of action of the pro-convulsive agent, 4-aminopyridine (4-AP). In the present study the effects of levetiracetam and other established and newer (vinpocetine) anti-epileptic drugs, as well as of the anti-depressant, sertraline on the increase in Ca(2+) induced by 4-AP in hippocampal isolated nerve endings were investigated. Also the effects of some of the anti-seizure drugs on the selective increase in Ca(2+) induced by high K(+), or on the selective increase in Na(+) induced by veratridine were tested. Sertraline and vinpocetine effectively inhibited the rise in Ca(2+) induced by 4-AP, which was dependent on the out-in Na(+) gradient and tetrodotoxin sensitive. Carbamazepine, phenytoin, lamotrigine and oxcarbazepine inhibited the rise in Ca(2+) induced by 4-AP too, but at higher concentrations than sertraline and vinpocetine, whereas levetiracetam, valproic acid and topiramate did not. The three latter antiepileptic drugs also failed in modifying other responses mediated by the activation of brain presynaptic Na(+) or Ca(2+) channels, including Glu release. This indicates that levetiracetam, valproic acid and topiramate mechanisms of action are unrelated with a decrease in presynaptic Na(+) or Ca(2+) channels permeability. It is concluded that depolarized cerebral isolated nerve endings represent a useful tool to unmask potential antiepileptic drugs targeting presynaptic Na(+) and/or Ca(2+) channels in the brain; such as vinpocetine or the anti-depressant sertraline, which high effectiveness to control seizures in the animal in vivo has been demonstrated. PMID:26542150

  4. Low Permeability Polyimide Insulation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Resodyn Technologies proposes a new technology that enables the application of polyimide based cryogenic insulation with low hydrogen permeability. This effort...

  5. Alternative translation initiation in rat brain yields K2P2.1 potassium channels permeable to sodium

    OpenAIRE

    Thomas, Dierk; Plant, Leigh D.; Wilkens, Christina M.; McCrossan, Zoe A.; Goldstein, Steve A. N.

    2008-01-01

    K2P channels mediate potassium background currents essential to central nervous system function, controlling excitability by stabilizing membrane potential below firing threshold and expediting repolarization. Here, we show that alternative translation initiation (ATI) regulates function of K2P2.1 (TREK-1) via a novel strategy. Full length K2P2.1 and an isoform lacking the first 56 residues of the intracellular N-terminus (K2P2.1 Δ1-56) are produced differentially in a regional and developmen...

  6. A Putative Calcium-Permeable Cyclic Nucleotide-Gated Channel, CNGC18, Regulates Polarized Pollen Tube Growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A tip-focused Ca2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca2+ are required for this process. However the molecular identity and regulation of the potential Ca2+ channels remains elusive.The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca2+]ex). CNGC18-yellow fluorescence protein (YFP)was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes.The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator)blocked the PM localization. These results support a role for PM-localized CNGC18 in the regulation of polarized pollen tube growth through Its potential function in the modulation of calcium influxes.

  7. Broad neutralization of calcium-permeable amyloid pore channels with a chimeric Alzheimer/Parkinson peptide targeting brain gangliosides.

    Science.gov (United States)

    Di Scala, Coralie; Yahi, Nouara; Flores, Alessandra; Boutemeur, Sonia; Kourdougli, Nazim; Chahinian, Henri; Fantini, Jacques

    2016-02-01

    Growing evidence supports a role for brain gangliosides in the pathogenesis of neurodegenerative diseases including Alzheimer's and Parkinson's. Recently we deciphered the ganglioside-recognition code controlling specific ganglioside binding to Alzheimer's β-amyloid (Aβ1-42) peptide and Parkinson's disease-associated protein α-synuclein. Cracking this code allowed us to engineer a short chimeric Aβ/α-synuclein peptide that recognizes all brain gangliosides. Here we show that ganglioside-deprived neural cells do no longer sustain the formation of zinc-sensitive amyloid pore channels induced by either Aβ1-42 or α-synuclein, as assessed by single-cell Ca(2+) fluorescence microscopy. Thus, amyloid channel formation, now considered a key step in neurodegeneration, is a ganglioside-dependent process. Nanomolar concentrations of chimeric peptide competitively inhibited amyloid pore formation induced by Aβ1-42 or α-synuclein in cultured neural cells. Moreover, this peptide abrogated the intracellular calcium increases induced by Parkinson's-associated mutant forms of α-synuclein (A30P, E46K and A53T). The chimeric peptide also prevented the deleterious effects of Aβ1-42 on synaptic vesicle trafficking and decreased the Aβ1-42-induced impairment of spontaneous activity in rat hippocampal slices. Taken together, these data show that the chimeric peptide has broad anti-amyloid pore activity, suggesting that a common therapeutic strategy based on the prevention of amyloid-ganglioside interactions is a reachable goal for both Alzheimer's and Parkinson's diseases. PMID:26655601

  8. Non-Linear Oberbeck Convection in Chiral Fluid through a Vertical Permeable Channel in the Presence of a Transverse Magnetic Field

    Directory of Open Access Journals (Sweden)

    N. Rudraiah

    2014-01-01

    Full Text Available Nonlinear oberbeck convection in a chiral incompressible Boussinesq fluid flowing through a vertical channel bounded by rigid permeable isothermal boundaries kept at different temperatures is investigated in this paper in the presence of a uniform transverse magnetic field, under the influence of viscous dissipation. The nonlinear-coupled momentum and energy equations are solved analytically using a regular perturbation method valid for small values of buoyancy parameter N. To validate the results obtained from the analytical solutions of the non-linear equations, which are also solved numerically using a finite difference method supplemented with the successive over recreation (SOR technique. The velocity, temperature, skin friction, mass flow rate and the rate of heat transfer are computed for various values of electromagnetic thermal number Wemt, buoyancy parameter N, and suction Reynolds Number Re. The results obtained are represented graphically and found that an increase in Wemt, increases the velocity and temperature. Physically, we attributes this to setting up of small scale turbulence by magnetic filed. The effect of perturbation parameter N is shown to increases the skin friction, heat transfer and the mass flow rate.

  9. Determination Permeability Coefficient from Piezocone

    Directory of Open Access Journals (Sweden)

    Qiang Wang

    2014-01-01

    Full Text Available The permeability coefficient of soil profile is one of the problems concerned by engineers, and the determination of permeability coefficient method mainly relies on the laboratory permeability test and field pumping test, but these tests are time-consuming and inefficient, and especially the permeability coefficient of soil under the condition of partial drainage was difficult to determine; in this paper, the modern digital CPTU technology was used. Dimensional permeability KT was defined by using the dimensionless normalized cone tip resistance Qt, friction factor Fr, and pore pressure ratio Bq, these parameters enable plots of Bq-Qt, Fr-Qt, Bq-Fr to be contoured KT and hence for permeability coefficient. The relationship has been applied to Nanjing 4th Yangtze river bridge, and compared with laboratory penetration test. The results indicate that the method can accurately determine the permeability coefficient of soil under partial drainage condition and provide the theoretical basis for engineering application.

  10. Use of prototype two-channel endoscope with elevator enables larger lift-and-snare endoscopic mucosal resection in a porcine model

    OpenAIRE

    Atkinson, Matthew; Chukwumah, Chike; Marks, Jeffrey; Chak, Amitabh

    2014-01-01

    Background: Flat and depressed lesions are becoming increasingly recognized in the esophagus, stomach, and colon. Various techniques have been described for endoscopic mucosal resection (EMR) of these lesions. Aims: To evaluate the efficacy of lift-grasp-cut EMR using a prototype dual-channel forward-viewing endoscope with an instrument elevator in one accessory channel (dual-channel elevator scope) as compared to standard dual-channel endoscopes. Methods: EMR was performed using a lift-grasp...

  11. Relative permeability through fractures

    Energy Technology Data Exchange (ETDEWEB)

    Diomampo, Gracel, P.

    2001-08-01

    The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.

  12. Stainless Steel Permeability

    Energy Technology Data Exchange (ETDEWEB)

    Buchenauer, Dean A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Karnesky, Richard A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  13. Ca2+ and Na+ permeability of high-threshold Ca2+ channels and their voltage-dependent block by Mg2+ ions in chick sensory neurones.

    Science.gov (United States)

    Carbone, E; Lux, H D; Carabelli, V; Aicardi, G; Zucker, H

    1997-10-01

    1. The Mg2+ block of Na+ and Ca2+ currents through high-voltage activated (HVA; L- and N-type) Ca2+ channels was studied in chick dorsal root ganglion neurones. 2. In low extracellular [Ca2+] ( 1.45 x 10(8) M-1 S-1 when Na+ is the permeating ion and a rate approximately 3 orders of magnitude smaller for Ca2+. 6. Mg2+ unblock of HVA Na+ currents at +100 mV was independent of the size of outward currents, whether Na+, Cs+ or NMG+ were the main internal cations. 7. Consistent with the idea of a high-affinity binding site for Ca2+ inside the channel, micromolar amounts of Ca2+ caused a strong depression of Na+ currents between -40 and 0 mV, which was effectively relieved with more positive as well as with negative potentials (KD = 0.7 microM in 120 mM Na+ at -20 mV). In this case, the kinetics of re-block could be resolved and gave rates of entry and exit for Ca2+ of 1.4 x 10(8) M-1 S-1 and 2.95 x 10(2) s-1, respectively. 8. The strong voltage dependence and weak current dependence of HVA channel block by divalent cations and the markedly different KD values of Na+ and Ca2+ current block by Mg2+ can be well described by a previously proposed model for Ca2+ channel permeation based on interactions between the permeating ion and the negative charges forming the high-affinity binding site for Ca2+ inside the pore (Lux, Carbone & Zucker, 1990). PMID:9350613

  14. The gain-of-function enhancement of IP3-receptor channel gating by familial Alzheimer's disease-linked presenilin mutants increases the open probability of mitochondrial permeability transition pore.

    Science.gov (United States)

    Toglia, Patrick; Ullah, Ghanim

    2016-07-01

    Mutants in presenilins (PS1 or PS2) are the major cause of familial Alzheimer's disease (FAD). They affect intracellular Ca(2+) homeostasis by increasing the open probability (Po) of inositol 1,4,5-trisposphate (IP3) receptor (IP3R) Ca(2+) release channel located on the endoplasmic reticulum (ER) leading to exaggerated Ca(2+) release into a cytoplasmic microdomain formed by neighboring cluster of a few IP3R channels and mitochondrial Ca(2+) uniporter (MCU). Ca(2+) concentration in the microdomain ( [Formula: see text] ) depends on the distance between the cluster and MCU (r); the number of IP3R in the cluster releasing Ca(2+) to the cytoplasm ( [Formula: see text] ), and Po of IP3R. Using experimental whole-cell IP3R-mediated cytosolic Ca(2+) data, in conjunction with a computational model of cell bioenergetics, a data-driven Markov chain model for IP3R gating, and a model for the dynamics of the mitochondrial permeability transition pore (PTP), we explore differences in mitochondrial Ca(2+) uptake in cells expressing wild type (PS1-WT) and FAD-causing mutant (PS1-M146L) PS. We find that increased mitochondrial [Formula: see text] due to the gain-of-function enhancement of IP3R channels in the cells expressing PS1-M146L leads to the opening of PTP in high conductance state (PTPh), where the latency of opening is inversely correlated with r and proportional to [Formula: see text] . Furthermore, we observe diminished inner mitochondrial membrane potential (ΔΨm), [NADH], [Formula: see text] , and [ATP] when PTP opens. Additionally, we explore how parameters such as the pH gradient, inorganic phosphate concentration, and the rate of the Na(+)/Ca(2+)-exchanger affect the latency of PTP to open in PTPh. PMID:27184076

  15. Grouting technology of tunnelling construction in submarine developing belt of permeable channel%海底透水通道发育带隧道施工注浆技术研究

    Institute of Scientific and Technical Information of China (English)

    王永红; 马栋; 凌树云; 陈鹰

    2011-01-01

    With the analysis of characteristics of subsea permeable channels, the pre-grouting and additional grouting in fracture grouting methods are successfully used to solve the problem of water off during tunnel construction. It has provided a guarantee for the construction safety, and proposed the principle, parameters, equipment, processes, materials and grouting effect of grouting methods for subsea cracks. The methods are also successfully applied to Jiaozhou bay subsea tunnel through the fracture zones. The results provide a reference for similar engineering.%通过对海底透水通道的特征分析,采用裂隙超前预注浆和裂隙补充注浆方法成功地解决了裂隙注浆堵水难题,为海底隧道安全施工提供了保障.提出了适于海水条件下的裂隙注浆原则、参数、设备、方法、工艺、材料及注浆效果检查方法,并成功地应用于胶州湾海底隧道穿越断裂破碎带时裂隙岩体注浆实践,其研究结果可为类似工程提供参考.

  16. Experimental Measurements for the Velocity Distribution of Turbulent Open-channel Flow over a Permeable Rough Bed%粗糙透水床面明渠水流垂线流速分布的试验研究

    Institute of Scientific and Technical Information of China (English)

    陈兴伟; 林木生; 林炳青

    2012-01-01

    A laboratory experimental research is reported, which considered effects of bed permeabili- ty on the velocity distribution of turbulent open-channel flow. The experiment was conducted in a glass-sided flume that was 20 m long, 0.8 m wide and 0. 6 m deep, and its bed was glued a layer of uniform marbles with a diameter of 1 cm. Located at a distance of 10 m from the upstream end of the flume was a rectangular recess that was 1.65 m long and 0. 7 m wide. The permeable bed is simulated in the recess where is well packed with eleven layers of the same marble. The velocity measurements were carried out using a laser Doppler velocimeter ( LDV, DANTEC) and the probe of the LDV was installed by a high resolution traversing system. The measurements were conducted under three flow conditions. Velocity distribution at 2 locations for impermeable bed and 3 for permeable bed were measured. The results show that the velocity distribution for impermeable bed follows the law of the wall when the reference level is lowered to 0. 25-diameter of the marble top. For permeable bed, its distribution is similar to that over impermeable bed, but with larger shear velocity and smaller integra- tion constant. Still, how the shear velocity and integration constant vary need further investigation.%冲积河流的粗颗粒河床,具有较大的渗透性,河床渗透对明渠水流运动特性的影响不可忽视.通过水槽试验,研究了河床渗透对垂线流速分布的影响.距试验玻璃水槽进口10m处,设计一个长1.65m、宽0.7m的收缩段,由12层直径1cm的玻璃珠紧密有规则铺成,以模拟粗糙透水床面.其上下游铺上1层相同玻璃珠,形成粗糙度相同但不透水的床面.垂线流速分布通过激光多普勒测速仪及配套的高精度坐标架系统测量.试验施放了3种流量,分别在不透水和透水床面进行垂线流速分布测量.试验结果表明:1)不透水床面的垂线流速分布符合

  17. Permeability Calculation in a Fracture Network - 12197

    International Nuclear Information System (INIS)

    Laminar flow of a viscous fluid in the pore space of a saturated fractured rock medium is considered to calculate the effective permeability of the medium. The effective permeability is determined from the flow field which is calculated numerically by using the finite element method. The computation of permeability components is carried out with a few different discretizations for a number of fracture arrangements. Various features such as flow field in the fracture channels, the convergence of permeability, and the variation of permeability among different fracture networks are discussed. The longitudinal permeability in general appears greater than the transverse ones. The former shows minor variations with fracture arrangement whereas the latter appears to be more sensitive to the arrangement. From the calculations of the permeability in a rock medium with a fracture network (two parallel fractures aligned in the direction of 45-deg counterclockwise from the horizontal and two connecting fractures(narrowing, parallel and widening) the following conclusions are drawn. 1. The permeability of fractured medium not only depends on the primary orientation of the main fractures but also is noticeably influenced by the connecting fractures in the medium. 2. The transverse permeability (the permeability in the direction normal to the direction of the externally imposed macro-scale pressure gradient) is only a fraction of the longitudinal one, but is sensitive to the arrangement of the connecting fractures. 3. It is important to figure out the pattern of the fractures that connect (or cross) the main fractures for reliable calculation of the transverse permeability. (authors)

  18. Gramicidin Channels: Versatile Tools

    Science.gov (United States)

    Andersen, Olaf S.; Koeppe, Roger E., II; Roux, Benoît

    Gramicidin channels are miniproteins in which two tryptophan-rich subunits associate by means of transbilayer dimerization to form the conducting channels. That is, in contrast to other ion channels, gramicidin channels do not open and close; they appear and disappear. Each subunit in the bilayer-spanning channel is tied to the bilayer/solution interface through hydrogen bonds that involve the indole NH groups as donors andwater or the phospholipid backbone as acceptors. The channel's permeability characteristics are well-defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the plethora of available experimental information—for not only the wild-type channels but also for channels formed by amino acid-substituted gramicidin analogues—gramicidin channels continue to provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For similar reasons, gramicidin channels constitute a system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the more complex channels formed by integral membrane proteins.

  19. Chemical dissolution-front instability associated with water-rock reactions in groundwater hydrology: Analyses of porosity-permeability relationship effects

    Science.gov (United States)

    Zhao, Chongbin; Hobbs, B. E.; Ord, A.

    2016-09-01

    Because dissolution of rocks may create and enhance groundwater flow channels, the chemical dissolution-front instability (CDFI) can control the quality of groundwater. This paper presents the theoretical analyses of porosity-permeability relationship effects on the CDFI in water-saturated porous rocks. Since the CDFI in a water-rock reaction system can be assessed by comparing the comprehensive dimensionless dynamic characteristic (CDDC) number with the corresponding critical CDDC number of the geochemical dissolution system, it is necessary to investigate theoretically how different porosity-permeability relationships can affect the CDDC number and critical CDDC number of a water-rock reaction system. With the commonly-used Kozeny-Carman (KC) formula taken as a reference porosity-permeability formula, the permeability variation indicator (PVI), which is defined as the ratio of the permeability obtained from any porosity-permeability formula to that obtained from the KC formula, is proposed to reflect the effect of the porosity-permeability formula on the CDFI in a water-rock reaction system. The theoretical results demonstrated that: (1) since the porosity-permeability formula with a higher PVI can result in a stronger Darcy flow velocity, it may have a significant influence on the CDFI in the water-rock reaction system. (2) With an increase in the PVI of a porosity-permeability formula, there is a decrease in the critical CDDC number of the water-rock reaction system. This means that the porous rock with a higher PVI can enable the CDFI to take place much easier in the water-rock reaction system. (3) The use of the porosity-permeability formula with a higher PVI can also cause an increase in both the dimensionless growth rate of a perturbation and the propagation speed of the chemical dissolution front in the water-rock reaction system.

  20. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium channel blockers are a type of medicine used ...

  1. Flow unit modeling and fine-scale predicted permeability validation in Atokan sandstones: Norcan East Kansas

    Science.gov (United States)

    Bhattacharya, S.; Byrnes, A.P.; Watney, W.L.; Doveton, J.H.

    2008-01-01

    Characterizing the reservoir interval into flow units is an effective way to subdivide the net-pay zone into layers for reservoir simulation. Commonly used flow unit identification techniques require a reliable estimate of permeability in the net pay on a foot-by-foot basis. Most of the wells do not have cores, and the literature is replete with different kinds of correlations, transforms, and prediction methods for profiling permeability in pay. However, for robust flow unit determination, predicted permeability at noncored wells requires validation and, if necessary, refinement. This study outlines the use o f a spreadsheet-based permeability validation technique to characterize flow units in wells from the Norcan East field, Clark County, Kansas, that produce from Atokan aged fine- to very fine-grained quartzarenite sandstones interpreted to have been deposited in brackish-water, tidally dominated restricted tidal-flat, tidal-channel, tidal-bar, and estuary bay environments within a small incised-valley-fill system. The methodology outlined enables the identification of fieldwide free-water level and validates and refines predicted permeability at 0.5-ft (0.15-m) intervals by iteratively reconciling differences in water saturation calculated from wire-line log and a capillary-pressure formulation that models fine- to very fine-grained sandstone with diagenetic clay and silt or shale laminae. The effectiveness of this methodology was confirmed by successfully matching primary and secondary production histories using a flow unit-based reservoir model of the Norcan East field without permeability modifications. The methodologies discussed should prove useful for robust flow unit characterization of different kinds of reservoirs. Copyright ?? 2008. The American Association of Petroleum Geologists. All rights reserved.

  2. Permeability of Dentine

    OpenAIRE

    Ghazali, Farid Bin Che

    2003-01-01

    This is an update on the present integrated knowledge regarding dentine permeability that assumed a role in dentine sensitivity and contribute clinically to the effective bonding properties of restorative dental materials. This paper will attempt to refer to in vivo and in vitro studies of dentine permeability and the various interrelated factors governing it.

  3. Permeable Pavements at Purdue

    OpenAIRE

    Knapp, Jim

    2013-01-01

    Two case studies will be presented describing sustainable drainage alternatives. The processes used for the 2nd Street project in Seymour will provide a comparison of the design processes for conventional and green infrastructure solutions. Purdue University will discuss a number of permeable pavement installations on campus and provide a map for viewing. Asphalt, concrete, and permeable paver options will be discussed.

  4. Permeability prediction in chalks

    DEFF Research Database (Denmark)

    Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Prasad, Manika

    2011-01-01

    The velocity of elastic waves is the primary datum available for acquiring information about subsurface characteristics such as lithology and porosity. Cheap and quick (spatial coverage, ease of measurement) information of permeability can be achieved, if sonic velocity is used for permeability...... prediction, so we have investigated the use of velocity data to predict permeability. The compressional velocity fromwireline logs and core plugs of the chalk reservoir in the South Arne field, North Sea, has been used for this study. We compared various methods of permeability prediction from velocities....... The relationships between permeability and porosity from core data were first examined using Kozeny’s equation. The data were analyzed for any correlations to the specific surface of the grain, Sg, and to the hydraulic property defined as the flow zone indicator (FZI). These two methods use two...

  5. Visualizing Dermal Permeation of Sodium Channel Modulators by Mass Spectrometric Imaging

    OpenAIRE

    Eberlin, Livia S; Mulcahy, John V.; Tzabazis, Alexander; Zhang, Jialing; Liu, Huwei; Logan, Matthew M.; Roberts, Heather J.; Lee, Gordon K.; Yeomans, David C.; Du Bois, Justin; Zare, Richard N.

    2014-01-01

    Determining permeability of a given compound through human skin is a principal challenge owing to the highly complex nature of dermal tissue. We describe the application of an ambient mass spectrometry imaging method for visualizing skin penetration of sodium channel modulators, including novel synthetic analogs of natural neurotoxic alkaloids, topically applied ex vivo to human skin. Our simple and label-free approach enables successful mapping of the transverse and lateral diffusion of smal...

  6. Dynamical Properties of Potassium Ion Channels with a Hierarchical Model

    Institute of Scientific and Technical Information of China (English)

    ZHAN Yong; AN Hai-Long; YU Hui; ZHANG Su-Hua; HAN Ying-Rong

    2006-01-01

    @@ It is well known that potassium ion channels have higher permeability than K ions, and the permeable rate of a single K ion channel is about 108 ions per second. We develop a hierarchical model of potassium ion channel permeation involving ab initio quantum calculations and Brownian dynamics simulations, which can consistently explain a range of channel dynamics. The results show that the average velocity of K ions, the mean permeable time of K ions and the permeable rate of single channel are about 0.92nm/ns, 4.35ns and 2.30×108 ions/s,respectively.

  7. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(2+) concentration ([Ca(2+)]o). In the presence of physiological [Ca(2+)]o (∼1.5 mM), CALHM1 and CLHM-1 are closed at resting membrane potentials but can be opened by strong depolarizations. Reducing [Ca(2+)]o increases channel open probability, enabling channel activation at negative membrane potentials. Together, voltage and Ca(2+) o allosterically regulate CALHM channel gating. Through convergent evolution, CALHM has structural features that are reminiscent of connexins and pannexins/innexins/LRRC8 (volume-regulated anion channel (VRAC)) gene families, including four transmembrane helices with cytoplasmic amino and carboxyl termini. A CALHM1 channel is a hexamer of CALHM1 monomers with a functional pore diameter of ∼14 Å. CALHM channels discriminate poorly among cations and anions, with signaling molecules including Ca(2+) and ATP able to permeate through its pore. CALHM1 is expressed in the brain where it plays an important role in cortical neuron excitability induced by low [Ca(2+)]o and in type II taste bud cells in the tongue that sense sweet, bitter, and umami tastes where it functions as an essential ATP release channel to mediate nonsynaptic neurotransmitter release. CLHM-1 is expressed in C. elegans sensory neurons and body wall muscles, and its genetic deletion causes locomotion defects. Thus, CALHM is a voltage- and Ca(2+) o-gated ion channel, permeable to large cations and anions, that plays important roles in physiology. PMID:26603282

  8. Adaptive evolution of voltage-gated sodium channels: The first 800 million years

    OpenAIRE

    Zakon, Harold H.

    2012-01-01

    Voltage-gated Na+-permeable (Nav) channels form the basis for electrical excitability in animals. Nav channels evolved from Ca2+ channels and were present in the common ancestor of choanoflagellates and animals, although this channel was likely permeable to both Na+ and Ca2+. Thus, like many other neuronal channels and receptors, Nav channels predated neurons. Invertebrates possess two Nav channels (Nav1 and Nav2), whereas vertebrate Nav channels are of the Nav1 family. Approximately 500 Mya ...

  9. Seismic waves increase permeability.

    Science.gov (United States)

    Elkhoury, Jean E; Brodsky, Emily E; Agnew, Duncan C

    2006-06-29

    Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Piñon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, the permeability at the site increases by a factor as high as three. The permeability increase depends roughly linearly on the amplitude of seismic-wave peak ground velocity in the range of 0.21-2.1 cm s(-1). Such permeability increases are of interest to hydrologists and oil reservoir engineers as they affect fluid flow and might determine long-term evolution of hydrological and oil-bearing systems. They may also be interesting to seismologists, as the resulting pore pressure changes can affect earthquakes by changing normal stresses on faults. PMID:16810253

  10. The putative P-gp inhibitor telmisartan does not affect the transcellular permeability and cellular uptake of the calcium channel antagonist verapamil in the P-glycoprotein expressing cell line MDCK II MDR1

    DEFF Research Database (Denmark)

    Saaby, Lasse; Tfelt-Hansen, Peer; Brodin, Birger

    2015-01-01

    Verapamil is used in high doses for the treatment of cluster headache. Verapamil has been described as a P-glycoprotein (P-gp, ABCB1) substrate. We wished to evaluate in vitro whether co administration of a P-gp inhibitor with verapamil could be a feasible strategy for increasing CNS uptake of...... verapamil. Fluxes of radiolabelled verapamil across MDCK II MDR1 monolayers were measured in the absence and presence of the putative P-gp inhibitor telmisartan (a clinically approved drug compound). Verapamil displayed a vectorial basolateral-toapical transepithelial efflux across the MDCK II MDR1...... monolayers with a permeability of 5.7 9 105 cm sec1 compared to an apical to basolateral permeability of 1.3 9 105 cm sec-1. The efflux could be inhibited with the P-gp inhibitor zosuquidar. Zosuquidar (0.4 lmol/L) reduced the efflux ratio (PB-A/PA-B) for verapamil 4.6–1.6. The presence of telmisartan...

  11. Timescales for permeability reduction and strength recovery in densifying magma

    Science.gov (United States)

    Heap, M. J.; Farquharson, J. I.; Wadsworth, F. B.; Kolzenburg, S.; Russell, J. K.

    2015-11-01

    Transitions between effusive and explosive behaviour are routine for many active volcanoes. The permeability of the system, thought to help regulate eruption style, is likely therefore in a state of constant change. Viscous densification of conduit magma during effusive periods, resulting in physical and textural property modifications, may reduce permeability to that preparatory for an explosive eruption. We present here a study designed to estimate timescales of permeability reduction and strength recovery during viscous magma densification by coupling measurements of permeability and strength (using samples from a suite of variably welded, yet compositionally identical, volcanic deposits) with a rheological model for viscous compaction and a micromechanical model, respectively. Bayesian Information Criterion analysis confirms that our porosity-permeability data are best described by two power laws that intersect at a porosity of 0.155 (the "changepoint" porosity). Above and below this changepoint, the permeability-porosity relationship has a power law exponent of 8.8 and 1.0, respectively. Quantitative pore size analysis and micromechanical modelling highlight that the high exponent above the changepoint is due to the closure of wide (∼200-300 μm) inter-granular flow channels during viscous densification and that, below the changepoint, the fluid pathway is restricted to narrow (∼50 μm) channels. The large number of such narrow channels allows porosity loss without considerable permeability reduction, explaining the switch to a lower exponent. Using these data, our modelling predicts a permeability reduction of four orders of magnitude (for volcanically relevant temperatures and depths) and a strength increase of a factor of six on the order of days to weeks. This discrepancy suggests that, while the viscous densification of conduit magma will inhibit outgassing efficiency over time, the regions of the conduit prone to fracturing, such as the margins, will

  12. Permeability measuremens of brazilian Eucalyptus

    OpenAIRE

    Marcio Rogério da Silva; Gilmara de Oliveira Machado; Jay Deiner; Carlito Calil Junior

    2010-01-01

    The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as t...

  13. ICT-enabled Service Design Suitable for Museums – The Case of the iPalace Channel of the National Palace Museum in Taipei 適用於博物館的資通訊化服務設計─以故宮iPalace 頻道為例

    OpenAIRE

    黃馨瑩、趙依庭、蔡瑞煌 Shin-Ying Huang, Yiting Chao, Rua-Huan Tsaih

    2013-01-01

    In the service economy, the information and communication technologies (ICT) have become more popular and the service of the National Palace Museum (NPM) is evolving to be customer-oriented, innovative, and ICT-enabled. This study takes the case of iPalace channel of NPM to explore the suitable communication tool for designing such new ICT-enabled services. This study integrates approaches from the disciplines of service and system engineering to derive such a communication tool for the iPala...

  14. Permeability of cork for water and ethanol.

    Science.gov (United States)

    Fonseca, Ana Luisa; Brazinha, Carla; Pereira, Helena; Crespo, Joao G; Teodoro, Orlando M N D

    2013-10-01

    Transport properties of natural (noncompressed) cork were evaluated for water and ethanol in both vapor and liquid phases. The permeability for these permeants has been measured, as well as the sorption and diffusion coefficients. This paper focuses on the differences between the transport of gases' relevant vapors and their liquids (water and ethanol) through cork. A transport mechanism of vapors and liquids is proposed. Experimental evidence shows that both vapors and liquids permeate not only through the small channels across the cells (plasmodesmata), as in the permeation of gases, but also through the walls of cork cells by sorption and diffusion as in dense membranes. The present study also shows that cork permeability for gases was irreversibly and drastically decreased after cork samples were exposed to ethanol or water in liquid phase. PMID:24001097

  15. Biodiesel permeability in polyethylene

    OpenAIRE

    RICHAUD, Emmanuel; FLACONNÈCHE, Bruno; Verdu, Jacques

    2012-01-01

    This paper reports solubility and diffusivity data for soy and rapeseed methyl esters in polyethylene together with comparisons with methyl oleate and linoleate. These data showed that there is no significant difference in diffusivity and solubility between all these penetrants. Data were used to discuss the reliability of predictive models for diffusion and solubility of additive type molecules into semi-crystalline thermoplastic polymers. Permeability data were monitored by a new device, th...

  16. Optimal reservoir conditions for fluid extraction through permeable walls in the viscous limit

    CERN Document Server

    Herschlag, Gregory; Layton, Anita T

    2015-01-01

    In biological transport mechanisms such as insect respiration and renal filtration, fluid travels along a leaky channel allowing exchange with systems exterior the the channel. The channels in these systems may undergo peristaltic pumping which is thought to enhance the material exchange. To date, little analytic work has been done to study the effect of pumping on material extraction across the channel walls. In this paper, we examine a fluid extraction model in which fluid flowing through a leaky channel is exchanged with fluid in a reservoir. The channel walls are allowed to contract and expand uniformly, simulating a pumping mechanism. In order to efficiently determine solutions of the model, we derive a formal power series solution for the Stokes equations in a finite channel with uniformly contracting/expanding permeable walls. This flow has been well studied in the case of weakly permeable channel walls in which the normal velocity at the channel walls is proportional to the wall velocity. In contrast ...

  17. Endocannabinoids modulate human blood–brain barrier permeability in vitro

    Science.gov (United States)

    Hind, William H; Tufarelli, Cristina; Neophytou, Maria; Anderson, Susan I; England, Timothy J; O'Sullivan, Saoirse E

    2015-01-01

    Background and Purpose Endocannabinoids alter permeability at various epithelial barriers, and cannabinoid receptors and endocannabinoid levels are elevated by stroke, with potential neuroprotective effects. We therefore explored the role of endocannabinoids in modulating blood–brain barrier (BBB) permeability in normal conditions and in an ischaemia/reperfusion model. Experimental Approach Human brain microvascular endothelial cell and astrocyte co-cultures modelled the BBB. Ischaemia was modelled by oxygen-glucose deprivation (OGD) and permeability was measured by transepithelial electrical resistance. Endocannabinoids or endocannabinoid-like compounds were assessed for their ability to modulate baseline permeability or OGD-induced hyperpermeability. Target sites of action were investigated using receptor antagonists and subsequently identified with real-time PCR. Key Results Anandamide (10 μM) and oleoylethanolamide (OEA, 10 μM) decreased BBB permeability (i.e. increased resistance). This was mediated by cannabinoid CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) channels, calcitonin gene-regulated peptide (CGRP) receptor (anandamide only) and PPARα (OEA only). Application of OEA, palmitoylethanolamide (both PPARα mediated) or virodhamine (all 10 μM) decreased the OGD-induced increase in permeability during reperfusion. 2-Arachidonoyl glycerol, noladin ether and oleamide did not affect BBB permeability in normal or OGD conditions. N-arachidonoyl-dopamine increased permeability through a cytotoxic mechanism. PPARα and γ, CB1 receptors, TRPV1 channels and CGRP receptors were expressed in both cell types, but mRNA for CB2 receptors was only present in astrocytes. Conclusion and Implication The endocannabinoids may play an important modulatory role in normal BBB physiology, and also afford protection to the BBB during ischaemic stroke, through a number of target sites. PMID:25651941

  18. Permeability measuremens of brazilian Eucalyptus

    Directory of Open Access Journals (Sweden)

    Marcio Rogério da Silva

    2010-09-01

    Full Text Available The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as the liquid phase permeability. No radial permeability was observed for either wood. The permeability of air and water through the sapwood of Eucalyptus grandis was greater than that through the sapwood of Eucalyptus citriodora. The permeability of neen oil preservative through the sapwood of Eucalyptus grandis was also greater than through the sapwood of E. Citradora, but the difference was not statistically significant. Scanning Electron Microscopy images showed that the distribution and obstruction in the vessels could be correlated with observed permeability properties. Irrespective of the causes of differences in permeability between the species, the fluid phase flux through the sapwood of both species was significant, indicating that both Eucalyptus grandis and Eucalyptus citriodora could be successfully treated with wood preservative.

  19. Artificial water channels--incipient innovative developments.

    Science.gov (United States)

    Barboiu, Mihail

    2016-04-28

    Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) water molecules per s per channel), with complete proton/ion exclusion. Few synthetic channels have been designed to mimic this high water permeability and to reject ions at a significant level. This Feature Article will discuss the incipient developments of the first artificial water channel systems. PMID:27046217

  20. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs.......The TRP ("transient receptor potential") family of ion channels now comprises more than 30 cation channels, most of which are permeable for Ca2+, and some also for Mg2+. On the basis of sequence homology, the TRP family can be divided in seven main subfamilies: the TRPC ('Canonical') family, the...... TRPV ('Vanilloid') family, the TRPM ('Melastatin') family, the TRPP ('Polycystin') family, the TRPML ('Mucolipin') family, the TRPA ('Ankyrin') family, and the TRPN ('NOMPC') family. The cloning and characterization of members of this cation channel family has exploded during recent years, leading to a...

  1. On partially entanglement breaking channels

    OpenAIRE

    Chruściński, Dariusz; Kossakowski, Andrzej

    2005-01-01

    Using well known duality between quantum maps and states of composite systems we introduce the notion of Schmidt number of a quantum channel. It enables one to define classes of quantum channels which partially break quantum entanglement. These classes generalize the well known class of entanglement breaking channels.

  2. Regulation of AQP0 water permeability is enhanced by cooperativity.

    Science.gov (United States)

    Németh-Cahalan, Karin L; Clemens, Daniel M; Hall, James E

    2013-03-01

    Aquaporin 0 (AQP0), essential for lens clarity, is a tetrameric protein composed of four identical monomers, each of which has its own water pore. The water permeability of AQP0 expressed in Xenopus laevis oocytes can be approximately doubled by changes in calcium concentration or pH. Although each monomer pore functions as a water channel, under certain conditions the pores act cooperatively. In other words, the tetramer is the functional unit. In this paper, we show that changes in external pH and calcium can induce an increase in water permeability that exhibits either a positive cooperativity switch-like increase in water permeability or an increase in water permeability in which each monomer acts independently and additively. Because the concentrations of calcium and hydrogen ions increase toward the center of the lens, a concentration signal could trigger a regulatory change in AQP0 water permeability. It thus seems plausible that the cooperative modes of water permeability regulation by AQP0 tetramers mediated by decreased pH and elevated calcium are the physiologically important ones in the living lens. PMID:23440275

  3. Electrokinetic effects and fluid permeability

    Science.gov (United States)

    G. Berryman, James

    2003-10-01

    Fluid permeability of porous media depends mainly on connectivity of the pore space and two physical parameters: porosity and a pertinent length-scale parameter. Electrical imaging methods typically establish connectivity and directly measure electrical conductivity, which can then often be related to porosity by Archie's law. When electrical phase measurements are made in addition to the amplitude measurements, information about the pertinent length scale can then be obtained. Since fluid permeability controls the ability to flush unwanted fluid contaminants from the subsurface, inexpensive maps of permeability could improve planning strategies for remediation efforts. Detailed knowledge of fluid permeability is also important for oil field exploitation, where knowledge of permeability distribution in three dimensions is a common requirement for petroleum reservoir simulation and analysis, as well as for estimates on the economics of recovery.

  4. Design/Construction of a Permeable Pavement Demonstration Site at the Edison Environmental Center (EEC)

    Science.gov (United States)

    This project will provide a scientifically defensible estimate of the performance of the three permeable surfaces: porous concrete, porous asphalt, and interlocking concrete pavers. The U.S. Environmental Protection Agency (EPA) can provide the results to municipalities enabling...

  5. The temperature dependence of lipid membrane permeability, its quantized nature, and the influence of anesthetics

    CERN Document Server

    Blicher, Andreas; Fidorra, Matthias; Winterhalter, Mathias; Heimburg, Thomas

    2008-01-01

    We investigate the permeability of lipid membranes for fluorescence dyes and ions. We find that permeability reaches a maximum close to the chain melting transition of the membranes. Close to transitions, fluctuations in area and compressibility are high, leading to an increased likelihood of spontaneous lipid pore formation. Fluorescence Correlation Spectroscopy (FCS) reveals the permeability for rhodamine dyes across 100 nm vesicles. Using FCS, we find that the permeability of vesicle membranes for fluorescence dyes is within error proportional to the excess heat capacity. To estimate defect size we measure the conductance of solvent-free planar lipid bilayer. Microscopically, we show that permeation events appear as quantized current events. Further, we demonstrate that anesthetics lead to a change in membrane permeability that can be predicted from their effect on heat capacity profiles. Depending on temperature, the permeability can be enhanced or reduced. We demonstrate that anesthetics decrease channel...

  6. Water permeability of elastomers.

    Science.gov (United States)

    Held, H R; Landi, S

    1977-01-01

    In a previous study it has been shown that the free moisture content in freeze-dried BCG vaccine dispensed in vials sealed with rubber stoppers increased during storage. The search for the source of this increase led us to explore the possibility that this additional moisture could originate from the rubber stoppers themselves. Therefore, the water permeability of various rubber stoppers has been studied, and the water content of grey butyl stoppers during some operations (autoclaving, oven-drying, freeze-drying, storage) used in the manufacturing of BCG vaccine has been determined. Our experiments showed: rapid water uptake during steam-autoclaving and rapid water release during subsequent oven-drying of the stoppers; a slow water uptake of the stoppers during freeze-drying and a slow water permeation through the stoppers when vials containing Indicating Drierite were stored in a water-saturated atmosphere. Among 12 types of rubber stoppers tested, the grey butyl stoppers and the silicone stoppers showed the lowest water uptake. Moisture-resistant wrappings decreased significantly the moisture uptake of Drierite. To delay moisture from reaching the vaccine it is recommended that the stoppers employed be as dry as possible. PMID:881425

  7. The permeability and consolidation of deep-sea sediments

    International Nuclear Information System (INIS)

    This report presents permeability and consolidation data for a wide range of sediment types. Permeability is one of the two parameters which are needed to directly quantify pore water advection in deep sea sediments and which are being investigated in high-level radioactive waste study areas. While it is desirable that these parameters should be measured in situ it is argued that values of permeability can be measured sufficiently accurately in the laboratory from core samples. Consequently, an apparatus has been developed which enables sediment permeability to be measured at decreasing void ratios during a back-pressured consolidation test. Data presented in this report from over 60 samples have established the major differences in permeability between various sediment types and how permeability changes as a function of burial depth and void ratio. Samples from two study areas in the North Atlantic Ocean, King's Trough Flank (KTF) and Great Meteor East (GME), have been compared with samples of Red Clay (RC) obtained from the NW Pacific Ocean. Results are presented and discussed. (author)

  8. Permeability testing of biomaterial membranes

    Energy Technology Data Exchange (ETDEWEB)

    Dreesmann, L; Hajosch, R; Nuernberger, J Vaz; Schlosshauer, B [NMI Natural and Medical Sciences Institute at University Tuebingen, Markwiesenstr. 55, D-72770 Reutlingen (Germany); Ahlers, M [GELITA AG, Gammelsbacher Str. 2, D-69412 Eberbach (Germany)], E-mail: schlosshauer@nmi.de

    2008-09-01

    The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts. Cytochemical evaluation after cryosectioning of the membranes was used to ascertain whether fibroblasts had infiltrated the membrane inside. Zymography was used to investigate the potential release of proteases from fibroblasts, which are known to degrade collagen derivatives such as gelatin. Our data show that the diffusion equilibrium of a low molecular weight dye across the selected gelatin membrane is approached after about 6-8 h. Fibroblasts increase the permeability due to cavity formation in the membrane inside without penetrating the membrane for an extended time period (>21 days in vitro). Zymography indicates that cavity formation is most likely due to the secretion of matrix metalloproteinases. In summary, the combination of the depicted methods promises to facilitate a more rational development of biomaterials, because it provides a rapid means of determining permeability characteristics and bridges the gap between descriptive methodology and the mechanistic understanding of permeability alterations due to biological degradation.

  9. Permeability testing of biomaterial membranes

    International Nuclear Information System (INIS)

    The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts. Cytochemical evaluation after cryosectioning of the membranes was used to ascertain whether fibroblasts had infiltrated the membrane inside. Zymography was used to investigate the potential release of proteases from fibroblasts, which are known to degrade collagen derivatives such as gelatin. Our data show that the diffusion equilibrium of a low molecular weight dye across the selected gelatin membrane is approached after about 6-8 h. Fibroblasts increase the permeability due to cavity formation in the membrane inside without penetrating the membrane for an extended time period (>21 days in vitro). Zymography indicates that cavity formation is most likely due to the secretion of matrix metalloproteinases. In summary, the combination of the depicted methods promises to facilitate a more rational development of biomaterials, because it provides a rapid means of determining permeability characteristics and bridges the gap between descriptive methodology and the mechanistic understanding of permeability alterations due to biological degradation

  10. Relative Permeability of Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  11. Vulnerability of hydraulic networks to channel clogging

    Science.gov (United States)

    Rognon, P.; Russo, D.; Griffani, D.; Einav, I.

    2016-01-01

    This study focuses on the loss of permeability and connectivity of hydraulic networks induced by channel clogging. Five network attack scenarios are considered that consist of clogging an increasing number of channels, selected according to their pressure drop and flow rate. By simulating the flow in the network before and after each attack, we show that some strategies only marginally affect the permeability and lead to a loss of connectivity only after a large proportion of channels are clogged. By contrast, other strategies strongly decrease the permeability and lead to a loss of connectivity after a small proportion of channels are clogged. These findings, interpreted in terms of change in porosity and network tortuosity, should help the prediction of the effect of network attacks in biological systems, hydrogeology and microfluidics.

  12. Hydrogeological Characterization of Low-permeability Clayey Tills

    DEFF Research Database (Denmark)

    Kessler, Timo Christian

    further constitute conductive facies within low-permeability tills and are suspected to affect hydraulic conductivity fields and subsurface transport behaviour. The purpose of the study is to characterize sand lenses in terms of occurrence, geometry and connectivity and to assess their importance for...... enhance the horizontal spreading of contaminants without a significant increase of the equivalent permeability in the till. Overall, sand lenses occur in all types of glacial sediments and with a broad range of shapes and hydraulic properties. Geometric characterization enabled classification of the most...

  13. TRIP database 2.0: a manually curated information hub for accessing TRP channel interaction network.

    Directory of Open Access Journals (Sweden)

    Young-Cheul Shin

    Full Text Available Transient receptor potential (TRP channels are a family of Ca(2+-permeable cation channels that play a crucial role in biological and disease processes. To advance TRP channel research, we previously created the TRIP (TRansient receptor potential channel-Interacting Protein Database, a manually curated database that compiles scattered information on TRP channel protein-protein interactions (PPIs. However, the database needs to be improved for information accessibility and data utilization. Here, we present the TRIP Database 2.0 (http://www.trpchannel.org in which many helpful, user-friendly web interfaces have been developed to facilitate knowledge acquisition and inspire new approaches to studying TRP channel functions: 1 the PPI information found in the supplementary data of referred articles was curated; 2 the PPI summary matrix enables users to intuitively grasp overall PPI information; 3 the search capability has been expanded to retrieve information from 'PubMed' and 'PIE the search' (a specialized search engine for PPI-related articles; and 4 the PPI data are available as sif files for network visualization and analysis using 'Cytoscape'. Therefore, our TRIP Database 2.0 is an information hub that works toward advancing data-driven TRP channel research.

  14. Geothermal Permeability Enhancement - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Joe Beall; Mark Walters

    2009-06-30

    The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.

  15. Permeability of soils in Mississippi

    Science.gov (United States)

    O'Hara, Charles G.

    1994-01-01

    The permeability of soils in Mississippi was determined and mapped using a geographic information system (GIS). Soil permeabilities in Mississippi were determined to range in value from nearly 0.0 to values exceeding 5.0 inches per hour. The U.S. Soil Conservation Service's State Soil Geographic Data Base (STATSGO) was used as the primary source of data for the determination of area-weighted soil permeability. STATSGO provides soil layer properties that are spatially referenced to mapped areas. These mapped areas are referred to as polygons in the GIS. The polygons arc boundaries of soils mapped as a group and are given unique Map Unit Identifiers (MUIDs). The data describing the physical characteristics of the soils within each polygon are stored in a tabular data base format and are referred to as attributes. The U.S. Soil Conservation Service developed STATSGO to be primarily used as a guide for regional resource planning, management, and monitoring. STATSGO was designed so that soil information could be extracted from properties tables at the layer level, combined by component, and statistically expanded to cover the entire map unit. The results of this study provide a mapped value for permeability which is representative of the vertical permeability of soils in that area. The resultant permeability map provides a representative vertical soil permeability for a given area sufficient for county, multi- county, and area planning, and will be used as the soil permeability data component in the evaluation of the susceptibility of major aquifers to contami- nation in Mississippi.

  16. Permeability within basaltic oceanic crust

    Science.gov (United States)

    Fisher, Andrew T.

    1998-05-01

    Water-rock interactions within the seafloor are responsible for significant energy and solute fluxes between basaltic oceanic crust and the overlying ocean. Permeability is the primary hydrologic property controlling the form, intensity, and duration of seafloor fluid circulation, but after several decades of characterizing shallow oceanic basement, we are still learning how permeability is created and distributed and how it changes as the crust ages. Core-scale measurements of basaltic oceanic crust yield permeabilities that are quite low (generally 10-22 to 10-17 m²), while in situ measurements in boreholes suggest an overlapping range of values extending several orders of magnitude higher (10-18 to 10-13 m²). Additional indirect estimates include calculations made from borehole temperature and flow meter logs (10-16 to 10-11 m²), numerical models of coupled heat and fluid flow at the ridge crest and within ridge flanks (10-16 to 10-9 m²), and several other methods. Qualitative indications of permeability within the basaltic oceanic crust come from an improved understanding of crustal stratigraphy and patterns of alteration and tectonic modification seen in ophiolites, seafloor samples and boreholes. Difficulties in reconciling the wide range of estimated permeabilities arise from differences in experimental scale and critical assumptions regarding the nature and distribution of fluid flow. Many observations and experimental and modeling results are consistent with permeability varying with depth into basement and with primary basement lithology. Permeability also seems to be highly heterogeneous and anisotropic throughout much of the basaltic crust, as within crystalline rocks in general. A series of focused experiments is required to resolve permeability in shallow oceanic basement and to directly couple upper crustal hydrogeology to magmatic, tectonic, and geochemical crustal evolution.

  17. Morphodynamics of Floodplain Chute Channels

    Science.gov (United States)

    David, S. R.; Edmonds, D. A.

    2015-12-01

    Floodplain chute channel formation is a key process that can enable rivers to transition from single-thread to multi-thread planform geometries. Floodplain chute channels are usually incisional channels connecting topographic lows across point bars and in the floodplain. Surprisingly, it is still not clear what conditions promote chute channel formation and what governs their morphodynamic behavior. Towards this end we have initiated an empirical and theoretical study of floodplain chute channels in Indiana, USA. Using elevation models and satellite imagery we mapped 3064 km2 of floodplain in Indiana, and find that 37.3% of mapped floodplains in Indiana have extensive chute channel networks. These chute channel networks consist of two types of channel segments: meander cutoffs of the main channel and chute channels linking the cutoffs together. To understand how these chute channels link meander cutoffs together and eventually create floodplain channel networks we use Delft3D to explore floodplain morphodynamics. Our first modeling experiment starts from a generic floodplain prepopulated with meander cutoffs to test under what conditions chute channels form.We find that chute channel formation is optimized at an intermediate flood discharge. If the flood discharge is too large the meander cutoffs erosively diffuse, whereas if the floodwave is too small the cutoffs fill with sediment. A moderately sized floodwave reworks the sediment surrounding the topographic lows, enhancing the development of floodplain chute channels. Our second modeling experiments explore how floodplain chute channels evolve on the West Fork of the White River, Indiana, USA. We find that the floodplain chute channels are capable of conveying the entire 10 yr floodwave (Q=1330m3/s) leaving the inter-channel areas dry. Moreover, the chute channels can incise into the floodplain while the margins of channels are aggrading, creating levees. Our results suggest that under the right conditions

  18. ICT-enabled Service Design Suitable for Museums – The Case of the iPalace Channel of the National Palace Museum in Taipei 適用於博物館的資通訊化服務設計─以故宮iPalace 頻道為例

    Directory of Open Access Journals (Sweden)

    黃馨瑩、趙依庭、蔡瑞煌 Shin-Ying Huang, Yiting Chao, Rua-Huan Tsaih

    2013-09-01

    Full Text Available In the service economy, the information and communication technologies (ICT have become more popular and the service of the National Palace Museum (NPM is evolving to be customer-oriented, innovative, and ICT-enabled. This study takes the case of iPalace channel of NPM to explore the suitable communication tool for designing such new ICT-enabled services. This study integrates approaches from the disciplines of service and system engineering to derive such a communication tool for the iPalace channel. Specifically, the proposed communication tool helps the designer comprehensively describe the following three parts: the ICT-enabled service blueprint, the interface table of ICT-enabled service encounter, and the pseudo code of the middle-office and back-office activities that cross the intra -organizational business processes and the inter-organizational workflows. Application results confirm that the proposed communication tool for the iPalace channel can be accepted by the senior managers of NPM, and can effectively and efficiently facilitate the prototype implementation of iPalace channel. pp. 90-105在服務經濟的時代, 由於資通訊科技(Information and Communication Technologies, ICT)的蓬勃發展,國立故宮博物院(以下簡稱故宮)的服務正逐步朝向顧客導向的、創新的、資通訊化的(ICT-enabled)方向發展。本研究以故宮的一個躍進的(radical)資通訊化服務創新─故宮頻道(iPalace channel)─為實例,來說明適用於開發此類型之資通訊化服務,且兼具概���與操作指引的溝通工具設計。本研究整合服務學門與資訊系統學門的設計理論,提出下列之溝通工具:(1)資通訊化服務藍圖(ICT-enabled service blueprint),以顯示服務體系中有關資通訊科技應用的部分之設計藍圖;(2)服務介面表(Interface table of service encounter),以顯示服務體系中有關資通訊

  19. Haemophilia, AIDS and lung epithelial permeability

    International Nuclear Information System (INIS)

    Lung 99mTc DTPA transfer was measured in HIV antibodypositive haemophiliacs (11 smokers, 26 nonsmokers, 5 patients with Pneumocystis carinii pneumonia (PCP)). Lung 99mTc DTPA transfer as a marker of lung epithelial permeability was measured as the half time of transfer (from airspace into blood). This half time was faster in smokers compred to nonsmokers and the transfer curve was monoexponential. In nonsmokers no difference was observed between asymptomatic HIV-positive haemophiliacs and normal subjects, with the exception of the lung bases. At the lung basis in HIV-positive haemophiliac nonsmokers the transfer was faster than in normal individuals, implying increased alveolar permeability. Pneumocystis carinii pneumonia resulted in a rapid transfer of 99mTc DTPA (mean T50 of 2 minutes) and the transfer curve was biphasic, confirming previous observations in homosexual HIV antibody-positive patients with PCP. These changes returned to a monoexponential profile by 6 weeks following successful treatment. The DTPA lung transfer study may enable clinicians to instigate therapy for PCP without the need for initial bronchoscopy and provide a noninvasive method for the reassessment of patients should further respiratory signs or symptoms develop. This method is considered to be highly cost-effective in that it obviates the use of factor VIII concentrates required to cover bronchoscopic procedures and, with its early application and ease of use as a follow-up investigation, permits the evaluation of patients on an outpatient basis, thus reducing hospital costs. (au)

  20. Haemophilia, AIDS and lung epithelial permeability

    Energy Technology Data Exchange (ETDEWEB)

    O' Doherty, M.J.; Page, C.J.; Harrington, C.; Nunan, T.; Savidge, G. (Haemophilia Centre and Coagulation Research Unit, Department of Nuclear Medicine, Rayne Institute, St. Thomas' Hospital, London (United Kingdom))

    1990-01-01

    Lung {sup 99m}Tc DTPA transfer was measured in HIV antibodypositive haemophiliacs (11 smokers, 26 nonsmokers, 5 patients with Pneumocystis carinii pneumonia (PCP)). Lung {sup 99m}Tc DTPA transfer as a marker of lung epithelial permeability was measured as the half time of transfer (from airspace into blood). This half time was faster in smokers compred to nonsmokers and the transfer curve was monoexponential. In nonsmokers no difference was observed between asymptomatic HIV-positive haemophiliacs and normal subjects, with the exception of the lung bases. At the lung basis in HIV-positive haemophiliac nonsmokers the transfer was faster than in normal individuals, implying increased alveolar permeability. Pneumocystis carinii pneumonia resulted in a rapid transfer of {sup 99m}Tc DTPA (mean T50 of 2 minutes) and the transfer curve was biphasic, confirming previous observations in homosexual HIV antibody-positive patients with PCP. These changes returned to a monoexponential profile by 6 weeks following successful treatment. The DTPA lung transfer study may enable clinicians to instigate therapy for PCP without the need for initial bronchoscopy and provide a noninvasive method for the reassessment of patients should further respiratory signs or symptoms develop. This method is considered to be highly cost-effective in that it obviates the use of factor VIII concentrates required to cover bronchoscopic procedures and, with its early application and ease of use as a follow-up investigation, permits the evaluation of patients on an outpatient basis, thus reducing hospital costs. (au).

  1. Organising to Enable Innovation

    DEFF Research Database (Denmark)

    Brink, Tove

    2016-01-01

    . The findings reveal a continous organising process between individual/ team creativity and organisational structures/control to enable innovation at firm level. Organising provides a dynamic approach and contains the integrated reconstruction of creativity, structures and boundaries for enhanced balance......The purpose of this conceptual paper is to reveal how organising can enable innovation across organisational layers and organisational units. This approach calls for a cross-disciplinary literature review. The aim is to provide an integrated understanding of innovation in an organisational approach...... of explorative and exploitative learning in uncertain environments. Shedding light on the cross-disciplinary theories to organise innovation provides a contribution at the firm level to enable innovation....

  2. Venus Flytrap HKT1-Type Channel Provides for Prey Sodium Uptake into Carnivorous Plant Without Conflicting with Electrical Excitability

    Science.gov (United States)

    Böhm, J.; Scherzer, S.; Shabala, S.; Krol, E.; Neher, E.; Mueller, T.D.; Hedrich, R.

    2016-01-01

    The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na+- and K+-permeable mutants function as ion channels rather than K+ transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na+-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap. PMID:26455461

  3. Venus Flytrap HKT1-Type Channel Provides for Prey Sodium Uptake into Carnivorous Plant Without Conflicting with Electrical Excitability.

    Science.gov (United States)

    Böhm, J; Scherzer, S; Shabala, S; Krol, E; Neher, E; Mueller, T D; Hedrich, R

    2016-03-01

    The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na(+)- and K(+)-permeable mutants function as ion channels rather than K(+) transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na(+)-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap. PMID:26455461

  4. Air permeability of polyester nonwoven fabrics

    OpenAIRE

    Zhu Guocheng; Kremenakova Dana; Wang Yan; Militky Jiri

    2015-01-01

    Air permeability is one of the most important properties of non-woven fabrics in many applications. This paper aims to investigate the effects of thickness, porosity and density on the air permeability of needle-punched non-woven fabrics and compare the experimental values with two models which are based on hydraulic radius theory and drag theory, respectively. The air permeability of the samples was measured by an air permeability tester FX3300. The results showed that the air permeability o...

  5. Synergistic Malaria Parasite Killing by Two Types of Plasmodial Surface Anion Channel Inhibitors.

    Directory of Open Access Journals (Sweden)

    Margaret Pain

    Full Text Available Malaria parasites increase their host erythrocyte's permeability to a broad range of ions and organic solutes. The plasmodial surface anion channel (PSAC mediates this uptake and is an established drug target. Development of therapies targeting this channel is limited by several problems including interactions between known inhibitors and permeating solutes that lead to incomplete channel block. Here, we designed and executed a high-throughput screen to identify a novel class of PSAC inhibitors that overcome this solute-inhibitor interaction. These new inhibitors differ from existing blockers and have distinct effects on channel-mediated transport, supporting a model of two separate routes for solute permeation though PSAC. Combinations of inhibitors specific for the two routes had strong synergistic action against in vitro parasite propagation, whereas combinations acting on a single route produced only additive effects. The magnitude of synergism depended on external nutrient concentrations, consistent with an essential role of the channel in parasite nutrient acquisition. The identified inhibitors will enable a better understanding of the channel's structure-function and may be starting points for novel combination therapies that produce synergistic parasite killing.

  6. Enabling distributed collaborative science

    DEFF Research Database (Denmark)

    Hudson, T.; Sonnenwald, Diane H.; Maglaughlin, K.;

    2000-01-01

    To enable collaboration over distance, a collaborative environment that uses a specialized scientific instrument called a nanoManipulator is evaluated. The nanoManipulator incorporates visualization and force feedback technology to allow scientists to see, feel, and modify biological samples being...

  7. The Nordic Housing Enabler

    DEFF Research Database (Denmark)

    Helle, T.; Nygren, C.; Slaug, B.;

    2014-01-01

    This study addresses development of a content-valid cross-Nordic version of the Housing Enabler and investigation of its inter-rater reliability when used in occupational therapy rating situations, involving occupational therapists, clients, and their home environments. The instrument was...

  8. Pilot project as enabler?

    DEFF Research Database (Denmark)

    Neisig, Margit; Glimø, Helle; Holm, Catrine Granzow;

    This article deals with a systemic perspective on transition. The field of study addressed is a pilot project as enabler of transition in a highly complex polycentric context. From a Luhmannian systemic approach, a framework is created to understand and address barriers of change occurred using...

  9. Mitochondrial Ion Channels

    Science.gov (United States)

    O’Rourke, Brian

    2009-01-01

    In work spanning more than a century, mitochondria have been recognized for their multifunctional roles in metabolism, energy transduction, ion transport, inheritance, signaling, and cell death. Foremost among these tasks is the continuous production of ATP through oxidative phosphorylation, which requires a large electrochemical driving force for protons across the mitochondrial inner membrane. This process requires a membrane with relatively low permeability to ions to minimize energy dissipation. However, a wealth of evidence now indicates that both selective and nonselective ion channels are present in the mitochondrial inner membrane, along with several known channels on the outer membrane. Some of these channels are active under physiological conditions, and others may be activated under pathophysiological conditions to act as the major determinants of cell life and death. This review summarizes research on mitochondrial ion channels and efforts to identify their molecular correlates. Except in a few cases, our understanding of the structure of mitochondrial ion channels is limited, indicating the need for focused discovery in this area. PMID:17059356

  10. Reservoir characteristics of low-permeability sandstones in the Rocky Mountains

    Energy Technology Data Exchange (ETDEWEB)

    Byrnes, A.P.

    1997-01-01

    Understanding gas production from low-permeability sandstones requires an understanding of the in situ porosity, brine saturation, and effective gas permeability at reservoir brine saturation. Diagenesis in these sandstones commonly resulted in the destruction of much of the original intergranular porosity and left dissolved grains, clay-filled pores, and sheet-like connecting intergranular pore throats. Pore throats or channels that connect larger pores typically range in size from 1 to 0.1 micron and represent only a small portion of the total porosity. In most low-permeability sandstones, porosity is not significantly changed by confining stress changes, but in situ effective gas permeabilities range from 10 to 1,000 times less than routine air permeability. The influence of confining stress on permeability can be attributed primarily to the decrease in size of the thin, tabular pore throats that connect the larger pores. Under stress, pore throats decrease in diameter by up to 50% to 70% resulting in permeability decreases of 10 to 40 times. Gas effective permeabilities also decrease rapidly to less than 1% of absolute values at water saturations above approximately 40% to 50%. {open_quotes}Irreducible{close_quotes} water saturations increase with decreasing porosity and permeability, and, in sandstones with less than 0.01 md permeability, {open_quotes}irreducible{close_quotes} water saturations increase dramatically. Cumulative flow and storage capacity plots indicate that very thin higher permeability intervals typically yield a large percentage of the cumulative flow capacity. Increased water saturations due to drilling or stimulation result in lower effective gas permeabilities and can unknowingly be stabilized by capillary pressure forces if pore pressures are decreased. This type of formation damage can be remedied by increasing the gas pore pressure to displace mobile water.

  11. Permeability enhancement by shock cooling

    Science.gov (United States)

    Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean

    2015-04-01

    The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of

  12. Capillary permeability in adipose tissue

    DEFF Research Database (Denmark)

    Paaske, W P; Nielsen, S L

    1976-01-01

    A method for measurement of capillary permeability using external registration of gamma emitting isotopes after close arterial bolus injection was applied to the isolated inguinal fat pad in slightly fasting rabbits. An average extraction of 26 per cent for 51Cr-EDTA was found at a plasma flow of...... about 7 ml/100 g-min. This corresponds to a capillary diffusion capacity of 2.0 ml/100 g-min which is half the value reported for vasodilated skeletal muscle having approximately twice as great capillary surface area. Thus, adipose tissue has about the same capillary permeability during slight metabolic...

  13. RFI channels

    Science.gov (United States)

    Mceliece, R. J.

    1980-01-01

    A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels.

  14. Lipid Ion Channels

    CERN Document Server

    Heimburg, Thomas

    2010-01-01

    The interpretation electrical phenomena in biomembranes is usually based on the assumption that the experimentally found discrete ion conduction events are due to a particular class of proteins called ion channels while the lipid membrane is considered being an inert electrical insulator. The particular protein structure is thought to be related to ion specificity, specific recognition of drugs by receptors and to macroscopic phenomena as nerve pulse propagation. However, lipid membranes in their chain melting regime are known to be highly permeable to ions, water and small molecules, and are therefore not always inert. In voltage-clamp experiments one finds quantized conduction events through protein-free membranes in their melting regime similar to or even undistinguishable from those attributed to proteins. This constitutes a conceptual problem for the interpretation of electrophysiological data obtained from biological membrane preparations. Here, we review the experimental evidence for lipid ion channels...

  15. Microfluidic Fabrication of Pluronic Vesicles with Controlled Permeability.

    Science.gov (United States)

    do Nascimento, Débora F; Arriaga, Laura R; Eggersdorfer, Max; Ziblat, Roy; Marques, Maria de Fátima V; Reynaud, Franceline; Koehler, Stephan A; Weitz, David A

    2016-05-31

    Block copolymers with a low hydrophilic-to-lipophilic balance form membranes that are highly permeable to hydrophilic molecules. Polymersomes with this type of membrane enable the controllable release of molecules without membrane rupture. However, these polymersomes are difficult to assemble because of their low hydrophobicity. Here, we report a microfluidic approach to the production of these polymersomes using double-emulsion drops with ultrathin shells as templates. The small thickness of the middle oil phase enables the attraction of the hydrophobic blocks of the polymers adsorbed at each of the oil/water interfaces of the double emulsions; this results in the dewetting of the oil from the surface of the innermost water drops of the double emulsions and the ultimate formation of the polymersome. This approach to polymersome fabrication enables control of the vesicle size and results in the efficient encapsulation of hydrophilic ingredients that can be released through the polymer membrane without membrane rupture. We apply our approach to the fabrication of Pluronic L121 vesicles and characterize the permeability of their membranes. Furthermore, we show that membrane permeability can be tuned by blending different Pluronic polymers. Our work thus describes a route to producing Pluronic vesicles that are useful for the controlled release of hydrophilic ingredients. PMID:27192611

  16. Permeability heterogeneity of the Palm Spring formation, Mecca Hills, California: Implications for fluvial-deltaic reservoir characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kelty, T.K.; Yin, An [Univ. of California, Los Angeles, CA (United States)

    1996-12-31

    Excellent exposures of the nonmarine, Pliocene to Pleistocene Palm Spring Formation allow the investigation of the spatial permeability variations. By sampling with a field permeameter, the permeability variations between and within sedimentary lithofacies, as well as effects of a major intraformational, angular unconformity on the permeability structure of the lower Palm Spring Formation are characterized. A systematic permeability distribution of the major lithofacies within the lower Palm Spring Formation is revealed by this work. The highest mean permeability is found in the coarse-grained matrix of conglomerates and the horizontally laminated and cross-bedded sandstones. The massive and rippled sandstones exhibit the lowest mean permeability. The three lithofacies that show the greatest variability about the mean are the conglomerates, horizontally laminated sandstones and massive sandstones. This study indicates that field observations of sedimentary features can be correlated with permeability variations in the Palm Spring Formation. Permeability data are utilized to estimate the correlation ranges over a horizontal distance of 500 meters within a sandstone bed. This analysis and field observations indicate that the correlation distance of permeability corresponds with the width of channels in the sandstone bed. Sampling of the Palm Spring Formation adjacent to an intraformational unconformity demonstrates that there is a decrease in permeability directly beneath the unconformity. This permeability reduction is due to secondary mineralization localized along the unconformity that possibly occurred during subaerial exposure.

  17. Nordic Housing Enabler

    DEFF Research Database (Denmark)

    Helle, Tina; Brandt, Åse

    2009-01-01

    Development and reliability testing of the Nordic Housing Enabler – an instrument for accessibility assessment of the physical housing. Tina Helle & Åse Brandt University of Lund, Health Sciences, Faculty of Medicine (SE) and University College Northern Jutland, Occupational Therapy department (DK......, however, the built environment shows serious deficits when it comes to accessibility. This study addresses development of a content valid cross-Nordic version of the Housing Enabler and investigation of inter-rater reliability, when used in occupational therapy practice. The instrument was translated from...... the original Swedish version and adapted according to accessibility norms and guidelines for housing design in Sweden, Denmark, Iceland and Finland. This iterative process involved occupational therapists, architects, building engineers and professional translators, resulting in the Nordic Housing...

  18. Spatially enabled land administration

    DEFF Research Database (Denmark)

    Enemark, Stig

    2006-01-01

    other words: Good governance and sustainable development is not attainable without sound land administration or - more broadly – sound land management. The paper presents a land management vision that incorporates the benefits of ICT enabled land administration functions. The idea is that spatial......Good governance is a qualitative term or an ideal which may be difficult to achieve. Different people, organisations, and government authorities will define “good governance” according to their own experience and interests. In any case, almost all kind of government includes a spatial component. In...... enabling of land administration systems managing tenure, valuation, planning, and development will allow the information generated by these activities to be much more useful. Also, the services available to private and public sectors and to community organisations should commensurably improve. Knowledge...

  19. Enabling Wind Power Nationwide

    Energy Technology Data Exchange (ETDEWEB)

    Jose Zayas, Michael Derby, Patrick Gilman and Shreyas Ananthan,

    2015-05-01

    Leveraging this experience, the U.S. Department of Energy’s (DOE’s) Wind and Water Power Technologies Office has evaluated the potential for wind power to generate electricity in all 50 states. This report analyzes and quantifies the geographic expansion that could be enabled by accessing higher above ground heights for wind turbines and considers the means by which this new potential could be responsibly developed.

  20. Innovative reactor technologies - Enabling success

    International Nuclear Information System (INIS)

    Many innovative reactors are being discussed, offering advantages in economics, sustainability, environmental impact, versatility and efficiency. To be successful, however, innovative reactors must meet the requirements for a successful build project. This requires achieving the mixture of innovation and proveness required to meet the first-of-a-kind hurdle. Based on the successful CANDU 6 reactor, a design still being built today, the ACR adds specific innovations in key areas chosen to achieve a balanced design. Capital cost has been significantly reduced by optimising the reactor-core design and simplifying systems. Key changes in this area include a move from a heavy water coolant to a light water coolant, and the adoption of SEU fuel. Construction times have also been reduced by using a modular design that takes advantage of modern construction techniques. Operating performance has been enhanced through improvements in system materials, equipment layout and component specifications. In parallel with these priorities, design adaptations have been applied so as to increase safety margins and defence-in-depth, again adding to the confidence in ACR licensability. The ACR development plan includes early review by regulators to reduce licensing risk, with international regulatory review having commenced. Overall, this places the ACR in a good position to meet the first-of-a-kind challenge, a necessary condition to enabling the success of an innovative reactor. AECL sees a logical evolution from the ACR, via increasing temperature and pressure capability, to the SCWR (Supercritical Water Reactor). AECL's CANDU-X program is already looking at designs for this concept. Inherent features of both ACR and the fuel channel SCWR lend themselves to different fuel cycles for the future. One of the prominent characteristics of the heavy-water moderated fuel channel reactor approach is the high potential for innovation. The evolutionary path allows innovation in practical steps

  1. High membrane permeability for melatonin.

    Science.gov (United States)

    Yu, Haijie; Dickson, Eamonn J; Jung, Seung-Ryoung; Koh, Duk-Su; Hille, Bertil

    2016-01-01

    The pineal gland, an endocrine organ in the brain, synthesizes and secretes the circulating night hormone melatonin throughout the night. The literature states that this hormone is secreted by simple diffusion across the pinealocyte plasma membrane, but a direct quantitative measurement of membrane permeability has not been made. Experiments were designed to compare the cell membrane permeability to three indoleamines: melatonin and its precursors N-acetylserotonin (NAS) and serotonin (5-HT). The three experimental approaches were (1) to measure the concentration of effluxing indoleamines amperometrically in the bath while cells were being dialyzed internally by a patch pipette, (2) to measure the rise of intracellular indoleamine fluorescence as the compound was perfused in the bath, and (3) to measure the rate of quenching of intracellular fura-2 dye fluorescence as indoleamines were perfused in the bath. These measures showed that permeabilities of melatonin and NAS are high (both are uncharged molecules), whereas that for 5-HT (mostly charged) is much lower. Comparisons were made with predictions of solubility-diffusion theory and compounds of known permeability, and a diffusion model was made to simulate all of the measurements. In short, extracellular melatonin equilibrates with the cytoplasm in 3.5 s, has a membrane permeability of ∼1.7 µm/s, and could not be retained in secretory vesicles. Thus, it and NAS will be "secreted" from pineal cells by membrane diffusion. Circumstances are suggested when 5-HT and possibly catecholamines may also appear in the extracellular space passively by membrane diffusion. PMID:26712850

  2. Permeability and effective slip in confined flows transverse to wall slippage patterns

    Science.gov (United States)

    Kumar, Avinash; Datta, Subhra; Kalyanasundaram, Dinesh

    2016-08-01

    The pressure-driven Stokes flow through a plane channel with arbitrary wall separation having a continuous pattern of sinusoidally varying slippage of arbitrary wavelength and amplitude on one/both walls is modelled semi-analytically. The patterning direction is transverse to the flow. In the special situations of thin and thick channels, respectively, the predictions of the model are found to be consistent with lubrication theory and results from the literature pertaining to free shear flow. For the same pattern-averaged slip length, the hydraulic permeability relative to a channel with no-slip walls increases as the pattern wave-number, amplitude, and channel size are decreased. Unlike discontinuous wall patterns of stick-slip zones studied elsewhere in the literature, the effective slip length of a sinusoidally patterned wall in a confined flow continues to scale with both channel size and the pattern-averaged slip length even in the limit of thin channel size to pattern wavelength ratio. As a consequence, for sufficiently small channel sizes, the permeability of a channel with sinusoidal wall slip patterns will always exceed that of an otherwise similar channel with discontinuous patterns on corresponding walls. For a channel with one no-slip wall and one patterned wall, the permeability relative to that of an unpatterned reference channel of same pattern-averaged slip length exhibits non-monotonic behaviour with channel size, with a minimum appearing at intermediate channel sizes. Approximate closed-form estimates for finding the location and size of this minimum are provided in the limit of large and small pattern wavelengths. For example, if the pattern wavelength is much larger than the channel thickness, exact results from lubrication theory indicate that a worst case permeability penalty relative to the reference channel of ˜23% arises when the average slip of the patterned wall is ˜2.7 times the channel size. The results from the current study should

  3. Optimizing water permeability through the hourglass shape of aquaporins.

    Science.gov (United States)

    Gravelle, Simon; Joly, Laurent; Detcheverry, François; Ybert, Christophe; Cottin-Bizonne, Cécile; Bocquet, Lydéric

    2013-10-01

    The ubiquitous aquaporin channels are able to conduct water across cell membranes, combining the seemingly antagonist functions of a very high selectivity with a remarkable permeability. Whereas molecular details are obvious keys to perform these tasks, the overall efficiency of transport in such nanopores is also strongly limited by viscous dissipation arising at the connection between the nanoconstriction and the nearby bulk reservoirs. In this contribution, we focus on these so-called entrance effects and specifically examine whether the characteristic hourglass shape of aquaporins may arise from a geometrical optimum for such hydrodynamic dissipation. Using a combination of finite-element calculations and analytical modeling, we show that conical entrances with suitable opening angle can indeed provide a large increase of the overall channel permeability. Moreover, the optimal opening angles that maximize the permeability are found to compare well with the angles measured in a large variety of aquaporins. This suggests that the hourglass shape of aquaporins could be the result of a natural selection process toward optimal hydrodynamic transport. Finally, in a biomimetic perspective, these results provide guidelines to design artificial nanopores with optimal performances. PMID:24067650

  4. Sensing with Ion Channels

    CERN Document Server

    Martinac, Boris

    2008-01-01

    All living cells are able to detect and translate environmental stimuli into biologically meaningful signals. Sensations of touch, hearing, sight, taste, smell or pain are essential to the survival of all living organisms. The importance of sensory input for the existence of life thus justifies the effort made to understand its molecular origins. Sensing with Ion Channels focuses on ion channels as key molecules enabling biological systems to sense and process the physical and chemical stimuli that act upon cells in their living environment. Its aim is to serve as a reference to ion channel specialists and as a source of new information to non specialists who want to learn about the structural and functional diversity of ion channels and their role in sensory physiology.

  5. Chloride channels in toad skin

    DEFF Research Database (Denmark)

    Larsen, Erik Hviid; Rasmussen, B E

    1982-01-01

    A study of the voltage and time dependence of a transepithelial Cl- current in toad skin (Bufo bufo) by the voltage-clamp method leads to the conclusion that potential has a dual role for Cl- transport. One is to control the permeability of an apical membrane Cl-pathway, the other is to drive Cl-...... that Cl- transport through open channels does not obey the constant-field equation....

  6. Anisotropic flow in striped superhydrophobic channels

    CERN Document Server

    Zhou, Jiajia; Schmid, Friederike; Vinogradova, Olga I

    2012-01-01

    We report results of dissipative particle dynamics simulations and develop a semi-analytical theory and of an anisotropic flow in a parallel-plate channel with two superhydrophobic striped walls. Our approach is valid for any local slip at the gas sectors and an arbitrary distance between the plates, ranging from a thick to a thin channel. It allows us to optimize area fractions, slip lengths, channel thickness and texture orientation to maximize a transverse flow. Our results may be useful for extracting effective slip tensors from global measurements, such as the permeability of a channel, in experiments or simulations, and may also find applications in passive microfluidic mixing.

  7. Enabling Global Collaboration

    DEFF Research Database (Denmark)

    Brix, Anders; de Gier, Nicolai

    2014-01-01

    Traditional crafts still in existence and daily use in less industrialized countries, but to a great extend either extinct or deprived of meaning in the technologically 'developed' parts of the world, have an important role to play in creating the ’quality economy’ (Fry 2009). This involves...... recognizing the value of incremental refinement of tradition and sustainability obtained through cultivation of the culturally and visually sustainable. As a contribution to this development, we propose: 1) The notion of tectonics as a core concept enabling a mutual, cross-cultural design discourse, a...

  8. CtOS Enabler

    OpenAIRE

    Crespo Cepeda, Rodrigo; El Yamri El Khatibi, Meriem; Carrera García, Juan Manuel

    2015-01-01

    Las Smart Cities son, indudablemente, el futuro próximo de la tecnología al que nos acercamos cada día, lo que se puede observar en la abundancia de dispositivos móviles entre la población, que informatizan la vida cotidiana mediante el uso de la geolocalización y la información. Pretendemos unir estos dos ámbitos con CtOS Enabler para crear un estándar de uso que englobe todos los sistemas de Smart Cities y facilite a los desarrolladores de dicho software la creación de nuevas herramientas. ...

  9. Enabling Digital Literacy

    DEFF Research Database (Denmark)

    Ryberg, Thomas; Georgsen, Marianne

    2010-01-01

    There are some tensions between high-level policy definitions of “digital literacy” and actual teaching practice. We need to find workable definitions of digital literacy; obtain a better understanding of what digital literacy might look like in practice; and identify pedagogical approaches, which...... support teachers in designing digital literacy learning. We suggest that frameworks such as Problem Based Learning (PBL) are approaches that enable digital literacy learning because they provide good settings for engaging with digital literacy. We illustrate this through analysis of a case. Furthermore......, these operate on a meso-level mediating between high-level concepts of digital literacy and classroom practice....

  10. The air permeability of gypsum insulating structures

    Energy Technology Data Exchange (ETDEWEB)

    Krikunenko, V.K.; Denisova, G.F.; Omelchenko, A.S.

    1980-01-01

    The air permeability of materials made from gypsum binders used to build insulation and blast-resistant crosspieces is studied, and it is established that the materials tested provided reliable insulation due to the low air permeability factor.

  11. Permeable Pavement Research - Edison, New Jersey

    Science.gov (United States)

    This presentation provides the background and summary of results collected at the permeable pavement parking lot monitored at the EPA facility in Edison, NJ. This parking lot is surfaced with permeable interlocking concrete pavers (PICP), pervious concrete, and porous asphalt. ...

  12. DMD-enabled confocal microendoscopy

    Science.gov (United States)

    Lane, Pierre M.; Dlugan, Andrew L. P.; MacAulay, Calum E.

    2001-05-01

    Conventional endoscopy is limited to imaging macroscopic views of tissue. The British Columbia Cancer Research Center, in collaboration with Digital Optical Imaging Corp., is developing a fiber-bundle based microendoscopy system to enable in vivo confocal imaging of cells and tissue structure through the biopsy channel of an endoscope, hypodermic needle, or catheter. The feasibility of imaging individual cells and tissue architecture will be presented using both reflectance and tissue auto-fluorescence modes of imaging. The system consists of a coherent fiber bundle, low-magnification high-NA objective lens, Digital Micromirror DeviceTM(DMD), light source, and CCD camera. The novel approach is the precise control and manipulation of light flow into and out of individual optical fibers. This control is achieved by employing a DMD to illuminate and detect light from selected fibers such that only the core of each fiber is illuminated or detected. The objective of the research is to develop a low-cost, clinically viable microendoscopy system for a range of detection, diagnostic, localization and differentiation uses associated with cancer and pre-cancerous conditions. Currently, multi-wavelength reflectance confocal images with 1 micrometers lateral resolution and 1.6 micrometers axial resolution have been achieved using a 0.95 mm bundle with 30,000 fibers.

  13. Altered conductance and permeability of Cx40 mutations associated with atrial fibrillation.

    Science.gov (United States)

    Santa Cruz, Ana; Meşe, Gülistan; Valiuniene, Laima; Brink, Peter R; White, Thomas W; Valiunas, Virginijus

    2015-11-01

    Gap junctions ensure the rapid propagation of the action potential throughout the myocardium. Three mutant forms of connexin40 (Cx40; A96S, M163V, and G38D), the primary component of the atrial gap junction channel, are associated with atrial fibrillation and retain the ability to form functional channels. We determined the biophysical properties of these mutant gap junctions in transiently transfected HeLa and N2A cells. All three mutants showed macroscopic junctional conductances over the range of 0.5 to 40 nS, and voltage dependences comparable to those of wild-type (WT) Cx40. However, the unitary conductance of G38D channels was ∼1.6-fold higher than that of WT Cx40 channels (∼220 vs. ∼135 pS), whereas the unitary conductances of the A96S and M163V mutants were similar to that of WT Cx40. Furthermore, the M163V and G38D channels exhibited approximately two- and approximately fivefold higher permeability to the anionic dye Lucifer yellow (LY) relative to K+ (LY/K+) compared with that of WT Cx40, whereas A96S LY transfer was similar to that of WT (G38D > M163V > A96S ≈ Cx40WT). In contrast, G38D channels were almost impermeable to cationic ethidium bromide (EtBr), suggesting that G38D alters channel selectivity. Conversely, A96S and M163V channels showed enhanced EtBr permeability relative to WT Cx40, with the following permeability order: M163V > A96S > Cx40WT > G38D. Altered conductive and permeability properties of mutant channels suggest an essential role for Cx40-mediated biochemical and electrical coupling in cardiac tissues. The altered properties of the three single-base substitution mutants may play a role in mechanisms of reentry arrhythmias. PMID:26503720

  14. Enable, mediate, advocate.

    Science.gov (United States)

    Saan, Hans; Wise, Marilyn

    2011-12-01

    The authors of the Ottawa Charter selected the words enable, mediate and advocate to describe the core activities in what was, in 1986, the new Public Health. This article considers these concepts and the values and ideas upon which they were based. We discuss their relevance in the current context within which health promotion is being conducted, and discuss the implications of changes in the health agenda, media and globalization for practice. We consider developments within health promotion since 1986: its central role in policy rhetoric, the increasing understanding of complexities and the interlinkage with many other societal processes. So the three core activities are reviewed: they still fit well with the main health promotion challenges, but should be refreshed by new ideas and values. As the role of health promotion in the political arena has grown we have become part of the policy establishment and that is a mixed blessing. Making way for community advocates is now our challenge. Enabling requires greater sensitivity to power relations involved and an understanding of the role of health literacy. Mediating keeps its central role as it bridges vital interests of parties. We conclude that these core concepts in the Ottawa Charter need no serious revision. There are, however, lessons from the last 25 years that point to ways to address present and future challenges with greater sensitivity and effectiveness. We invite the next generation to avoid canonizing this text: as is true of every heritage, the heirs must decide on its use. PMID:22080073

  15. Smart Grid Enabled EVSE

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2014-10-15

    The combined team of GE Global Research, Federal Express, National Renewable Energy Laboratory, and Consolidated Edison has successfully achieved the established goals contained within the Department of Energy’s Smart Grid Capable Electric Vehicle Supply Equipment funding opportunity. The final program product, shown charging two vehicles in Figure 1, reduces by nearly 50% the total installed system cost of the electric vehicle supply equipment (EVSE) as well as enabling a host of new Smart Grid enabled features. These include bi-directional communications, load control, utility message exchange and transaction management information. Using the new charging system, Utilities or energy service providers will now be able to monitor transportation related electrical loads on their distribution networks, send load control commands or preferences to individual systems, and then see measured responses. Installation owners will be able to authorize usage of the stations, monitor operations, and optimally control their electricity consumption. These features and cost reductions have been developed through a total system design solution.

  16. Quantifying porosity, compressibility and permeability in Shale

    DEFF Research Database (Denmark)

    Mbia, Ernest Ncha; Fabricius, Ida Lykke; Frykman, Peter;

    strain data. We found that Kozeny's modelled permeability fall in the same order of magnitude with measured permeability for shale rich in kaolinite but overestimates permeability by two to three orders of magnitudes for shale with high content of smectite. The empirical Yang and Aplin model gives good...... permeability estimate comparable to the measured one for shale rich in smectite. This is probably because Yang and Aplin model was calibrated in London clay which is rich in smectite....

  17. RESEARCH REGARDING AIR PERMEABILITY OF KNITTED FABRIC

    OpenAIRE

    Alina Coldea; Dorin Vlad

    2011-01-01

    This paper presents a study on the air permeability of knitted fabric manufactured using the yarns of different raw materials. The air permeability of plain pure knits wool, cotton and wool was investigated. The variation in air permeability depending on the area density, linear density, loop length and thickness of yarns.

  18. The kinetics of denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.

    2013-01-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to...... environment experienced in permeable sediments. In contrast to previous studies, we did not observe any significant rates of oxic denitrification....

  19. Development of Pressure-Sensitive Channel Chip for Micro Gas Flows

    Science.gov (United States)

    Matsuda, Yu; Yamaguchi, Hiroki; Niimi, Tomohide

    2012-05-01

    Optical measurement techniques are useful for experimental studies on micro gas flows, which enable us to non-intrusively measure the flows with a high spatial resolution. The pressure-sensitive paint (PSP) technique, which is based on the emission of photons from luminophore, is a potential diagnostic tool for pressure measurement of micro gas flows. However, measurements by conventional PSPs are limited to the sub-millimeter order spatial resolution of ca. 200 μm, indicating the difficulty of the micro scale measurements. The present study proposes pressure-sensitive channel chip (PSCC) which is a micro channel with the capability of measuring pressure. We focused on the poly (dimethylsiloxane) (PDMS) micro-molding technique, which is one of the most popular techniques to fabricate a micro channel easily. Moreover, PDMS is a polymer used as a binder in PSP because of high optical transparency, gas permeability, and gas diffusivity. Thus, we developed a micro channel by the PDMS micro-molding technique with mixing a pressure-sensitive luminophore into PDMS: i.e. a micro channel fabricated by PSP, which is named PSCC. A flow through a micro converging-diverging nozzle with the throat width of 120 μm was demonstrated. The pressure distribution on the nozzle surface was successfully obtained by PSCC.

  20. Development of Pressure-Sensitive Channel Chip for Micro Gas Flows

    International Nuclear Information System (INIS)

    Optical measurement techniques are useful for experimental studies on micro gas flows, which enable us to non-intrusively measure the flows with a high spatial resolution. The pressure-sensitive paint (PSP) technique, which is based on the emission of photons from luminophore, is a potential diagnostic tool for pressure measurement of micro gas flows. However, measurements by conventional PSPs are limited to the sub-millimeter order spatial resolution of ca. 200 μm, indicating the difficulty of the micro scale measurements. The present study proposes pressure-sensitive channel chip (PSCC) which is a micro channel with the capability of measuring pressure. We focused on the poly (dimethylsiloxane) (PDMS) micro-molding technique, which is one of the most popular techniques to fabricate a micro channel easily. Moreover, PDMS is a polymer used as a binder in PSP because of high optical transparency, gas permeability, and gas diffusivity. Thus, we developed a micro channel by the PDMS micro-molding technique with mixing a pressure-sensitive luminophore into PDMS: i.e. a micro channel fabricated by PSP, which is named PSCC. A flow through a micro converging-diverging nozzle with the throat width of 120 μm was demonstrated. The pressure distribution on the nozzle surface was successfully obtained by PSCC.

  1. Sanding process and permeability change

    Energy Technology Data Exchange (ETDEWEB)

    Xue, S. [Petroleum Univ., Beijing (China); Yuan, Y.

    2004-07-01

    Sand production is a major problem in the petroleum industry, particularly with operators aggressive production schedules. Sand production occurs when the well fluid under high pumping rate dislodges part of the formation solids causing a continuous flux of formation solids. It increases completion costs, plus it erodes casings, pipes and pumps. However, sand production can also effectively increase well productivity in heavy oil and light oil reservoirs.The challenge in understanding the sanding process lies in developing a mathematical model which can predict the amount of sand production. A quantitative model would allow engineers to understand the unique phenomena and evaluate the impact of sand production on reservoir enhancement. Measures could then be taken to reduce unnecessary costs during field operations. In order to develop such a model, the complicated sanding process equations was divided into a fluid flow and sand transport equation, and into a porous solid matrix deforming and stress concentration or failure function equation. The two types of sand production mechanisms that were presented in this paper were the production of coarse sands under mechanical failure and the production of fine sands under hydro-dynamical erosion. The behaviour of sandstone deformation was examined using the Drucker-Prager constitutive law with cap hardening criterion. The governing equation system was solved using the finite element method. The model was validated using field data for sand production and permeability change obtained from 10 wells in Gudong, China. It was shown that permeability can be modified at any time during the sanding process of a well. Permeability can be reduced by up to 60 per cent of the initial level under depletion production. It was determined that the best way to control permeability decline is to balance the pore pressure. 9 refs., 1 tab., 7 figs.

  2. Enabling graphene nanoelectronics.

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Wei; Ohta, Taisuke; Biedermann, Laura Butler; Gutierrez, Carlos; Nolen, C. M.; Howell, Stephen Wayne; Beechem Iii, Thomas Edwin; McCarty, Kevin F.; Ross, Anthony Joseph, III

    2011-09-01

    Recent work has shown that graphene, a 2D electronic material amenable to the planar semiconductor fabrication processing, possesses tunable electronic material properties potentially far superior to metals and other standard semiconductors. Despite its phenomenal electronic properties, focused research is still required to develop techniques for depositing and synthesizing graphene over large areas, thereby enabling the reproducible mass-fabrication of graphene-based devices. To address these issues, we combined an array of growth approaches and characterization resources to investigate several innovative and synergistic approaches for the synthesis of high quality graphene films on technologically relevant substrate (SiC and metals). Our work focused on developing the fundamental scientific understanding necessary to generate large-area graphene films that exhibit highly uniform electronic properties and record carrier mobility, as well as developing techniques to transfer graphene onto other substrates.

  3. Aspects of tensor permeability in reservoir simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, C.F.

    2002-04-01

    A number of simulation grids relevant to reservoir engineering practice are studied. The impact of neglecting correct local flux and pressure continuity at the grid cell interfaces is assessed. It is shown that the correct local interface conditions with increased discretisation support lead to improved solutions on non-orthogonal grids with the generation of a full permeability tensor. A full tensor permeability arises even when the permeability is non-isotropic on orthogonal grids. The approach described efficiently includes the permeability tensor contributions from the geometric grid structure, but also implies the importance of modelling the full permeability tensor pressure equation in the reservoir simulation up-scaling process. (orig.)

  4. The molecular basis of selective permeability of connexins is complex and includes both size and charge

    OpenAIRE

    Nicholson B.J.; Weber P.A.; Cao F; Chang H.-C.; Lampe P.; Goldberg G.

    2000-01-01

    Although gap junction channels are still widely viewed as large, non-specific pores connecting cells, the diversity in the connexin family has led more attention to be focused on their permeability characteristics. We summarize here the current status of these investigations, both published and on-going, that reveal both charge and size selectivity between gap junction channels composed of different connexins. In particular, this review will focus on quantitative approaches that monitor the e...

  5. On the permeability of fractal tube bundles

    CERN Document Server

    Zinovik, I

    2011-01-01

    The permeability of a porous medium is strongly affected by its local geometry and connectivity, the size distribution of the solid inclusions and the pores available for flow. Since direct measurements of the permeability are time consuming and require experiments that are not always possible, the reliable theoretical assessment of the permeability based on the medium structural characteristics alone is of importance. When the porosity approaches unity, the permeability-porosity relationships represented by the Kozeny-Carman equations and Archie's law predict that permeability tends to infinity and thus they yield unrealistic results if specific area of the porous media does not tend to zero. The goal of this paper is an evaluation of the relationships between porosity and permeability for a set of fractal models with porosity approaching unity and a finite permeability. It is shown that the two-dimensional foams generated by finite iterations of the corresponding geometric fractals can be used to model poro...

  6. Ammonia and urea permeability of mammalian aquaporins

    DEFF Research Database (Denmark)

    Litman, Thomas; Søgaard, Rikke; Zeuthen, Thomas

    2009-01-01

    /arginine region, and an exclusively water-permeable aquaporin can be transformed into an ammonia-permeable aquaporin by single point mutations in this region. The ammonia-permeable aquaporins fall into two groups: those that are permeable (AQP3, 7, 9, 10) and those that are impermeable (AQP8) to glycerol. The two......The human aquaporins,AQP3,AQP7, AQP8,AQP9, and possibly AQP10, are permeable to ammonia, and AQP7, AQP9, and possibly AQP3, are permeable to urea. In humans, these aquaporins supplement the ammonia transport of the Rhesus (Rh) proteins and the urea transporters (UTs). The mechanism by which...... significant at alkaline pH. It is debated whether the H(+) ion passes via the aquaporin or by some external route; the investigation of this problem requires the aquaporin-expressing cell to be voltage-clamped. The ammonia-permeable aquaporins differ from other aquaporins by having a less restrictive aromatic...

  7. Second law violations, continuum mechanics, and permeability

    Science.gov (United States)

    Ostoja-Starzewski, Martin

    2016-03-01

    The violations of the second law are relevant as the length and/or time scales become very small. The second law then needs to be replaced by the fluctuation theorem and mathematically, the irreversible entropy is a submartingale. First, we discuss the consequences of these results for the axioms of continuum mechanics, arguing in favor of a framework relying on stochastic functionals of energy and entropy. We next determine a Lyapunov function for diffusion-type problems governed by stochastic rather than deterministic functionals of internal energy and entropy, where the random field coefficients of diffusion are not required to satisfy the positive definiteness everywhere. Next, a formulation of micropolar fluid mechanics is developed, accounting for the lack of symmetry of stress tensor on molecular scales. This framework is then applied to employed to show that spontaneous random fluctuations of the microrotation field will arise in Couette—and Poiseuille-type flows in the absence of random (turbulence-like) fluctuations of the classical velocity field. Finally, while the permeability is classically modeled by the Darcy law or its modifications, besides considering the violations of the second law, one also needs to account for the spatial randomness of the channel network, implying a modification of the hierarchy of scale-dependent bounds on the macroscopic property of the network.

  8. Enabling distributed petascale science

    International Nuclear Information System (INIS)

    Petascale science is an end-to-end endeavour, involving not only the creation of massive datasets at supercomputers or experimental facilities, but the subsequent analysis of that data by a user community that may be distributed across many laboratories and universities. The new SciDAC Center for Enabling Distributed Petascale Science (CEDPS) is developing tools to support this end-to-end process. These tools include data placement services for the reliable, high-performance, secure, and policy-driven placement of data within a distributed science environment; tools and techniques for the construction, operation, and provisioning of scalable science services; and tools for the detection and diagnosis of failures in end-to-end data placement and distributed application hosting configurations. In each area, we build on a strong base of existing technology and have made useful progress in the first year of the project. For example, we have recently achieved order-of-magnitude improvements in transfer times (for lots of small files) and implemented asynchronous data staging capabilities; demonstrated dynamic deployment of complex application stacks for the STAR experiment; and designed and deployed end-to-end troubleshooting services. We look forward to working with SciDAC application and technology projects to realize the promise of petascale science

  9. Enabling immersive simulation.

    Energy Technology Data Exchange (ETDEWEB)

    McCoy, Josh (University of California Santa Cruz, Santa Cruz, CA); Mateas, Michael (University of California Santa Cruz, Santa Cruz, CA); Hart, Derek H.; Whetzel, Jonathan; Basilico, Justin Derrick; Glickman, Matthew R.; Abbott, Robert G.

    2009-02-01

    The object of the 'Enabling Immersive Simulation for Complex Systems Analysis and Training' LDRD has been to research, design, and engineer a capability to develop simulations which (1) provide a rich, immersive interface for participation by real humans (exploiting existing high-performance game-engine technology wherever possible), and (2) can leverage Sandia's substantial investment in high-fidelity physical and cognitive models implemented in the Umbra simulation framework. We report here on these efforts. First, we describe the integration of Sandia's Umbra modular simulation framework with the open-source Delta3D game engine. Next, we report on Umbra's integration with Sandia's Cognitive Foundry, specifically to provide for learning behaviors for 'virtual teammates' directly from observed human behavior. Finally, we describe the integration of Delta3D with the ABL behavior engine, and report on research into establishing the theoretical framework that will be required to make use of tools like ABL to scale up to increasingly rich and realistic virtual characters.

  10. Structural permeability of complex networks to control signals

    Science.gov (United States)

    Lo Iudice, Francesco; Garofalo, Franco; Sorrentino, Francesco

    2015-09-01

    Many biological, social and technological systems can be described as complex networks. The goal of affecting their behaviour has motivated recent work focusing on the relationship between the network structure and its propensity to be controlled. While this work has provided insight into several relevant problems, a comprehensive approach to address partial and complete controllability of networks is still lacking. Here, we bridge this gap by developing a framework to maximize the diffusion of the control signals through a network, while taking into account physical and economic constraints that inevitably arise in applications. This approach allows us to introduce the network permeability, a unified metric of the propensity of a network to be controllable. The analysis of the permeability of several synthetic and real networks enables us to extract some structural features that deepen our quantitative understanding of the ease with which specific controllability requirements can be met.

  11. A calcium-permeable cGMP-activated cation conductance in hippocampal neurons

    Science.gov (United States)

    Leinders-Zufall, T.; Rosenboom, H.; Barnstable, C. J.; Shepherd, G. M.; Zufall, F.

    1995-01-01

    Whole-cell patch clamp recordings detected a previously unidentified cGMP-activated membrane conductance in cultured rat hippocampal neurons. This conductance is nonselectively permeable for cations and is completely but reversibly blocked by external Cd2+. The Ca2+ permeability of the hippocampal cGMP-activated conductance was examined in detail, indicating that the underlying ion channels display a high relative permeability for Ca2+. The results indicate that hippocampal neurons contain a cGMP-activated membrane conductance that has some properties similar to the cyclic nucleotide-gated channels previously shown in sensory receptor cells and retinal neurons. In hippocampal neurons this conductance similarly could mediate membrane depolarization and Ca2+ fluxes in response to intracellular cGMP elevation.

  12. A permeability and compliance contrast measured hydrogeologically on the San Andreas Fault

    Science.gov (United States)

    Xue, Lian; Brodsky, Emily E.; Erskine, Jon; Fulton, Patrick M.; Carter, Reed

    2016-03-01

    Hydrogeologic properties of fault zones are critical to faulting processes; however, they are not well understood and difficult to measure in situ, particularly in low-permeability fractured bedrock formations. Analysis of continuous water level response to Earth tides in monitoring wells provides a method to measure the in situ hydrogeologic properties. We utilize four monitoring wells within the San Andreas Fault zone near Logan Quarry to study the fault zone hydrogeologic architecture by measuring the water level tidal response. The specific storage and permeability inferred from the tidal response suggest that there is a difference in properties at different distances from the fault. The sites closer to the fault have higher specific storage and higher permeability than farther from the fault. This difference of properties might be related to the fault zone fracture distribution decreasing away from the fault. Although permeability channels near faults have been documented before, the difference in specific storage near the fault is a new observation. The inferred compliance contrast is consistent with prior estimates of elastic moduli in the near-fault environment, but the direct measurements are new. The combination of measured permeability and storage yields a diffusivity of about 10-2 m2/s at all the sites both near and far from the fault as a result of the competing effects of permeability and specific storage. This uniform diffusivity structure suggests that the permeability contrast might not efficiently trap fluids during the interseismic period.

  13. Enabling cleanup technology transfer

    International Nuclear Information System (INIS)

    Technology transfer in the environmental restoration, or cleanup, area has been challenging. While there is little doubt that innovative technologies are needed to reduce the times, risks, and costs associated with the cleanup of federal sites, particularly those of the Departments of Energy (DOE) and Defense, the use of such technologies in actual cleanups has been relatively limited. There are, of course, many reasons why technologies do not reach the implementation phase or do not get transferred from developing entities to the user community. For example, many past cleanup contracts provided few incentives for performance that would compel a contractor to seek improvement via technology applications. While performance-based contracts are becoming more common, they alone will not drive increased technology applications. This paper focuses on some applications of cleanup methodologies and technologies that have been successful and are illustrative of a more general principle. The principle is at once obvious and not widely practiced. It is that, with few exceptions, innovative cleanup technologies are rarely implemented successfully alone but rather are implemented in the context of enabling processes and methodologies. And, since cleanup is conducted in a regulatory environment, the stage is better set for technology transfer when the context includes substantive interactions with the relevant stakeholders. Examples of this principle are drawn from Argonne National Laboratory's experiences in Adaptive Sampling and Analysis Programs (ASAPs), Precise Excavation, and the DOE Technology Connection (TechCon) Program. The lessons learned may be applicable to the continuing challenges posed by the cleanup and long-term stewardship of radioactive contaminants and unexploded ordnance (UXO) at federal sites

  14. Effects of temperature, mechanical loading and of their interactions on the permeability of structural concrete

    International Nuclear Information System (INIS)

    Concrete permeability may influence the durability of structures indirectly by controlling the penetration rate of aggressive agents, but also directly if the structure has a confinement role, like containment vessels of nuclear power plants for instance. In the industrial background on the safety of these structures, the objective of this study is to characterize the evolution of concrete permeability under the effects of temperature and mechanical loading. The permeability tests are performed on hollow concrete cylinders, subjected to temperature up to 150 C and compressive loading up to failure. Experimental results reveal that the effects of temperature and damage may be decoupled for the estimation of permeability and enable us to propose a relation between permeability, damage and temperature. However, this relation may only be applied in the pre-peak phase as concrete remains micro-cracked. In order to overcome this limit to be able to model also permeability increase in the post-peak phase, another parameter, which is crack opening, is introduced in the relation between permeability and damage. This problem, investigated by modelling, is exploited according to two approaches. The first one is based on the definition of a matching law between existing relations of permeability evolution with damage and with crack opening. With this approach the tendencies are similar to the observed ones on the experimental results. The second approach consists in linking from a mechanical point of view damage with crack opening in order to apply the Poiseuille's law for permeability determination. Experimental validation of this approach, emerging towards a continuous model capable to reproduce permeability variations of a concrete structure, constitutes a major perspective of this work. (author)

  15. A new method of building permeability model in low-permeability reservoir numerical simulation

    OpenAIRE

    Lei Su; Lin-Song Cheng; Yong-Chao Xue

    2010-01-01

    Aiming at solving the problem that big differ-ence exists between logging permeability and true permeability of micro-fractured low-permeability sand reservoir, this paper puts forward a new method to revise logging per-meability by using primiparity data of oil field. This method has been successfully applied to revise logging permeability of micro-fractured low-permeability sand reservoir in Baiyushan area of Jing’An oil field, which shows that the method is reliable because the geological ...

  16. Steam-water relative permeability

    Energy Technology Data Exchange (ETDEWEB)

    Ambusso, W.; Satik, C.; Home, R.N. [Stanford Univ., CA (United States)

    1997-12-31

    A set of relative permeability relations for simultaneous flow of steam and water in porous media have been measured in steady state experiments conducted under the conditions that eliminate most errors associated with saturation and pressure measurements. These relations show that the relative permeabilities for steam-water flow in porous media vary approximately linearly with saturation. This departure from the nitrogen/water behavior indicates that there are fundamental differences between steam/water and nitrogen/water flows. The saturations in these experiments were measured by using a high resolution X-ray computer tomography (CT) scanner. In addition the pressure gradients were obtained from the measurements of liquid phase pressure over the portions with flat saturation profiles. These two aspects constitute a major improvement in the experimental method compared to those used in the past. Comparison of the saturation profiles measured by the X-ray CT scanner during the experiments shows a good agreement with those predicted by numerical simulations. To obtain results that are applicable to general flow of steam and water in porous media similar experiments will be conducted at higher temperature and with porous rocks of different wetting characteristics and porosity distribution.

  17. Predicting permeability and electrical conductivity of sedimentary rocks from microgeometry

    International Nuclear Information System (INIS)

    The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab

  18. FOILFEST :community enabled security.

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Judy Hennessey; Johnson, Curtis Martin; Whitley, John B.; Drayer, Darryl Donald; Cummings, John C., Jr. (.,; .)

    2005-09-01

    The Advanced Concepts Group of Sandia National Laboratories hosted a workshop, ''FOILFest: Community Enabled Security'', on July 18-21, 2005, in Albuquerque, NM. This was a far-reaching look into the future of physical protection consisting of a series of structured brainstorming sessions focused on preventing and foiling attacks on public places and soft targets such as airports, shopping malls, hotels, and public events. These facilities are difficult to protect using traditional security devices since they could easily be pushed out of business through the addition of arduous and expensive security measures. The idea behind this Fest was to explore how the public, which is vital to the function of these institutions, can be leveraged as part of a physical protection system. The workshop considered procedures, space design, and approaches for building community through technology. The workshop explored ways to make the ''good guys'' in public places feel safe and be vigilant while making potential perpetrators of harm feel exposed and convinced that they will not succeed. Participants in the Fest included operators of public places, social scientists, technology experts, representatives of government agencies including DHS and the intelligence community, writers and media experts. Many innovative ideas were explored during the fest with most of the time spent on airports, including consideration of the local airport, the Albuquerque Sunport. Some provocative ideas included: (1) sniffers installed in passage areas like revolving door, escalators, (2) a ''jumbotron'' showing current camera shots in the public space, (3) transparent portal screeners allowing viewing of the screening, (4) a layered open/funnel/open/funnel design where open spaces are used to encourage a sense of ''communitas'' and take advantage of citizen ''sensing'' and funnels are technological

  19. Effect of temperature on sandstone permeability

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Kjøller, Claus

    Hot water injection in geothermal sandstone aquifers is considered for seasonal energy storage in Denmark. However, an increase in the aquifer temperature might reduce permeability, and thereby increase production costs. An understanding of the factors that control permeability is required in order...... to address the effects of temperature on permeability. Therefore, different aspects of sandstone permeability are investigated in this research project. Data from a range of sources including: published literature; a database containing over 120 tight gas sandstone samples; new flow...... permeability to sandstone texture. The simple physically based Kozeny (1927) equation, relates permeability to porosity and specific surface per pore volume, or equivalent pore size, for a homogeneous porous medium with a uniform pore size. As pore sizes in sandstones can range from nanometres to micrometres...

  20. Modelling of water permeability in cementitious materials

    DEFF Research Database (Denmark)

    Guang, Ye; Lura, Pietro; van Breugel, K.

    2006-01-01

    This paper presents a network model to predict the permeability of cement paste from a numerical simulation of its microstructure. Based on a linked list pore network structure, the effective hydraulic conductivity is estimated and the fluid flow is calculated according to the Hagen-Poiseuille law....... The pressure gradient at all nodes is calculated with the Gauss elimination method and the absolute permeability of the pore network is calculated directly from Darcy's law. Finally, the permeability model is validated by comparison with direct water permeability measurements. According to this model......, the predicted permeability of hydrating cement pastes is extremely sensitive to the particle size distribution of the cement and especially to the minimum size of the cement particles. Both in simulations and experiments, the permeability of cement pastes is mainly determined by the critical diameter...

  1. Pannexin 1 channels in skeletal muscles

    OpenAIRE

    Cea, Luis A.; Riquelme, Manuel A.; Vargas, Anibal A.; Urrutia, Carolina; Sáez, Juan C.

    2014-01-01

    Normal myotubes and adult innervated skeletal myofibers express the glycoprotein pannexin1 (Panx1). Six of them form a “gap junction hemichannel-like” structure that connects the cytoplasm with the extracellular space; here they will be called Panx1 channels. These are poorly selective channels permeable to ions, small metabolic substrate, and signaling molecules. So far little is known about the role of Panx1 channels in muscles but skeletal muscles of Panx1−/− mice do not show an evident ph...

  2. Water vapour permeability of clay bricks

    OpenAIRE

    Dondi, M.; Principi, P.; Raimondo, M.; Zanarini, G.

    2003-01-01

    The water vapour permeability of clay bricks has been experimentally measured in order to draw a representative outline of industrial products without pore-forming additives. The correlations between water vapour permeability and the main compositional and microstructural parameters of both bricks and clay bodies have been investigated. A statistical model was set up in order to predict with reasonable precision and reliability, the water vapour permeability on the basis of open porosity, bul...

  3. Zinc modulation of water permeability reveals that aquaporin 0 functions as a cooperative tetramer.

    Science.gov (United States)

    Németh-Cahalan, Karin L; Kalman, Katalin; Froger, Alexandrine; Hall, James E

    2007-11-01

    We previously showed that the water permeability of AQP0, the water channel of the lens, increases with acid pH and that His40 is required (Németh-Cahalan, K.L., and J.E. Hall. 2000. J. Biol. Chem. 275:6777-6782; Németh-Cahalan, K.L., K. Kalman, and J.E. Hall. 2004. J. Gen. Physiol. 123:573-580). We have now investigated the effect of zinc (and other transition metals) on the water permeability of AQP0 expressed in Xenopus oocytes and determined the amino acid residues that facilitate zinc modulation. Zinc (1 mM) increased AQP0 water permeability by a factor of two and prevented any additional increase induced by acid pH. Zinc had no effect on water permeability of AQP1, AQP4 or MIPfun (AQP0 from killifish), or on mutants of AQP1 and MIPfun with added external histidines. Nickel, but not copper, had the same effect on AQP0 water permeability as zinc. A fit of the concentration dependence of the zinc effect to the Hill equation gives a coefficient greater than three, suggesting that binding of more than one zinc ion is necessary to enhance water permeability. His40 and His122 are necessary for zinc modulation of AQP0 water permeability, implying structural constraints for zinc binding and functional modulation. The change in water permeability was highly sensitive to a coinjected zinc-insensitive mutant and a single insensitive monomer completely abolished zinc modulation. Our results suggest a model in which positive cooperativity among subunits of the AQP0 tetramer is required for zinc modulation, implying that the tetramer is the functional unit. The results also offer the possibility of a pharmacological approach to manipulate the water permeability and transparency of the lens. PMID:17938229

  4. Permeability Tests on Eastern Scheldt Sand

    DEFF Research Database (Denmark)

    Jakobsen, Kim Parsberg

    The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends on the...... characteristics of the soil matrix, the permeability is determined for different void ratios. All tests are performed on reconstituted specimens of Eastern Scheldt Sand. The permeability is determined by use of a falling head apparatus. Finally the test results are briefly summarised and a relationship between...... void ratio and permeability is established....

  5. Permeability of Electrospun Superhydrophobic Nanofiber Mats

    Directory of Open Access Journals (Sweden)

    Sarfaraz U. Patel

    2012-01-01

    Full Text Available This paper discusses the fabrication and characterization of electrospun nanofiber mats made up of poly(4-methyl-1-pentene polymer. The polymer was electrospun in different weight concentrations. The mats were characterized by their basis weight, fiber diameter distribution, contact angles, contact angle hysteresis, and air permeability. All of the electrospun nonwoven fiber mats had water contact angles greater than 150 degrees making them superhydrophobic. The permeabilities of the mats were empirically fitted to the mat basis weight by a linear relation. The experimentally measured air permeabilities were significantly larger than the permeabilities predicted by the Kuwabara model for fibrous media.

  6. Characterization of printable cellular micro-fluidic channels for tissue engineering

    International Nuclear Information System (INIS)

    Tissue engineering has been a promising field of research, offering hope of bridging the gap between organ shortage and transplantation needs. However, building three-dimensional (3D) vascularized organs remains the main technological barrier to be overcome. One of the major challenges is the inclusion of a vascular network to support cell viability in terms of nutrients and oxygen perfusion. This paper introduces a new approach to the fabrication of vessel-like microfluidic channels that has the potential to be used in thick tissue or organ fabrication in the future. In this research, we investigate the manufacturability of printable micro-fluidic channels, where micro-fluidic channels support mechanical integrity as well as enable fluid transport in 3D. A pressure-assisted solid freeform fabrication platform is developed with a coaxial needle dispenser unit to print hollow hydrogel filaments. The dispensing rheology is studied, and effects of material properties on structural formation of hollow filaments are analyzed. Sample structures are printed through the developed computer-controlled system. In addition, cell viability and gene expression studies are presented in this paper. Cell viability shows that cartilage progenitor cells (CPCs) maintained their viability right after bioprinting and during prolonged in vitro culture. Real-time PCR analysis yielded a relatively higher expression of cartilage-specific genes in alginate hollow filament encapsulating CPCs, compared with monolayer cultured CPCs, which revealed that printable semi-permeable micro-fluidic channels provided an ideal environment for cell growth and function. (paper)

  7. Characterization of printable cellular micro-fluidic channels for tissue engineering.

    Science.gov (United States)

    Zhang, Yahui; Yu, Yin; Chen, Howard; Ozbolat, Ibrahim T

    2013-06-01

    Tissue engineering has been a promising field of research, offering hope of bridging the gap between organ shortage and transplantation needs. However, building three-dimensional (3D) vascularized organs remains the main technological barrier to be overcome. One of the major challenges is the inclusion of a vascular network to support cell viability in terms of nutrients and oxygen perfusion. This paper introduces a new approach to the fabrication of vessel-like microfluidic channels that has the potential to be used in thick tissue or organ fabrication in the future. In this research, we investigate the manufacturability of printable micro-fluidic channels, where micro-fluidic channels support mechanical integrity as well as enable fluid transport in 3D. A pressure-assisted solid freeform fabrication platform is developed with a coaxial needle dispenser unit to print hollow hydrogel filaments. The dispensing rheology is studied, and effects of material properties on structural formation of hollow filaments are analyzed. Sample structures are printed through the developed computer-controlled system. In addition, cell viability and gene expression studies are presented in this paper. Cell viability shows that cartilage progenitor cells (CPCs) maintained their viability right after bioprinting and during prolonged in vitro culture. Real-time PCR analysis yielded a relatively higher expression of cartilage-specific genes in alginate hollow filament encapsulating CPCs, compared with monolayer cultured CPCs, which revealed that printable semi-permeable micro-fluidic channels provided an ideal environment for cell growth and function. PMID:23458889

  8. TRIP Database 2.0: A Manually Curated Information Hub for Accessing TRP Channel Interaction Network

    OpenAIRE

    Young-Cheul Shin; Soo-Yong Shin; Jung Nyeo Chun; Hyeon Sung Cho; Jin Muk Lim; Hong-Gee Kim; Insuk So; Dongseop Kwon; Ju-Hong Jeon

    2012-01-01

    Transient receptor potential (TRP) channels are a family of Ca(2+)-permeable cation channels that play a crucial role in biological and disease processes. To advance TRP channel research, we previously created the TRIP (TRansient receptor potential channel-Interacting Protein) Database, a manually curated database that compiles scattered information on TRP channel protein-protein interactions (PPIs). However, the database needs to be improved for information accessibility and data utilization...

  9. Molecular dynamics insights into human aquaporin 2 water channel.

    Science.gov (United States)

    Binesh, A R; Kamali, R

    2015-12-01

    In this study, the first molecular dynamics simulation of the human aquaporin 2 is performed and for a better understanding of the aquaporin 2 permeability performance, the characteristics of water transport in this protein channel and key biophysical parameters of AQP2 tetramer including osmotic and diffusive permeability constants and the pore radius are investigated. For this purpose, recently recovered high resolution X-ray crystal structure of` the human aquaporin 2 is used to perform twenty nanosecond molecular dynamics simulation of fully hydrated tetramer of this protein embedded in a lipid bilayer. The resulting water permeability characteristics of this protein channel showed that the water permeability of the human AQP2 is in a mean range in comparison with other human aquaporins family. Finally, the results reported in this research demonstrate that molecular dynamics simulation of human AQP2 provided useful insights into the mechanisms of water permeation and urine concentration in the human kidney. PMID:26489820

  10. Method to quantify the notional permeability

    NARCIS (Netherlands)

    Verhagen, H.J.; Jumelet, D.; Vilaplana Domingo, A.; Van Broekhoven, P.

    2011-01-01

    In de Van der Meer formulas for armour stability the Notional Permeability is used as a parameter. Unfortunately the physical basis of this parameter is weak. It is therefore suggested to use a relation between the Notional Permeability P and the reduction of wave run-up due to infiltration into the

  11. Accurate determination of characteristic relative permeability curves

    Science.gov (United States)

    Krause, Michael H.; Benson, Sally M.

    2015-09-01

    A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.

  12. Small-bowel permeability in collagenous colitis

    DEFF Research Database (Denmark)

    Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J

    2006-01-01

    , indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal permeability....

  13. Intercomparison on measurement of water vapour permeability

    DEFF Research Database (Denmark)

    Hansen, Kurt Kielsgaard

    Three different materials are tested - hard woodfibre board - damp proof course - underlay for roofing The water vapour permeability has been measured according to EN ISO 12572 (2001).......Three different materials are tested - hard woodfibre board - damp proof course - underlay for roofing The water vapour permeability has been measured according to EN ISO 12572 (2001)....

  14. Estimation of bone permeability considering the morphology of lacuno-canalicular porosity.

    Science.gov (United States)

    Kameo, Yoshitaka; Adachi, Taiji; Sato, Narumichi; Hojo, Masaki

    2010-04-01

    Load-induced interstitial fluid flow in lacuno-canalicular porosity is believed to play an important role in cellular activities regulating adaptive bone remodeling. To investigate interstitial fluid behavior based on poroelasticity, it is important to determine the anisotropic permeability tensor reflecting the morphological features of the lacuno-canalicular porosity as fluid channels. In this study, we presented an estimation method of trabecular permeability by describing the analytical relationship between the volume orientation (VO) fabric tensor, which represents the canalicular orientation, and the permeability tensor. The relationship showed that the trabecular permeability tensor is proportional to the product of the volume fraction of the interstitial fluid and the VO fabric tensor of the canaliculi. We applied the proposed method to a two-dimensional fluorescent image of a trabecular cross section to quantify the canalicular anisotropy and the trabecular permeability tensor. The results indicated that the canaliculi are predominantly oriented in the radial direction of the trabecula, and the permeability depends strongly on the canalicular morphology. PMID:20142108

  15. General slip regime permeability model for gas flow through porous media

    Science.gov (United States)

    Zhou, Bo; Jiang, Peixue; Xu, Ruina; Ouyang, Xiaolong

    2016-07-01

    A theoretical effective gas permeability model was developed for rarefied gas flow in porous media, which holds over the entire slip regime with the permeability derived as a function of the Knudsen number. This general slip regime model (GSR model) is derived from the pore-scale Navier-Stokes equations subject to the first-order wall slip boundary condition using the volume-averaging method. The local closure problem for the volume-averaged equations is studied analytically and numerically using a periodic sphere array geometry. The GSR model includes a rational fraction function of the Knudsen number which leads to a limit effective permeability as the Knudsen number increases. The mechanism for this behavior is the viscous fluid inner friction caused by converging-diverging flow channels in porous media. A linearization of the GSR model leads to the Klinkenberg equation for slightly rarefied gas flows. Finite element simulations show that the Klinkenberg model overestimates the effective permeability by as much as 33% when a flow approaches the transition regime. The GSR model reduces to the unified permeability model [F. Civan, "Effective correlation of apparent gas permeability in tight porous media," Transp. Porous Media 82, 375 (2010)] for the flow in the slip regime and clarifies the physical significance of the empirical parameter b in the unified model.

  16. Optimization of Permeability Tensor Characteristics of Anisotropic Reservoir and Well Pattern Parameters

    Institute of Scientific and Technical Information of China (English)

    计秉玉; 兰玉波

    2003-01-01

    The problems of well pattern arrangement, well array direction, and well array spacing ratios for anisotropic reservoirs were studied using tensor analysis. The problems were formulated as a bilevel programming model which was solved using a genetic algorithm. The results show that if the permeability in one direction is much higher than in another direction, the wells should be aligned along the high permeability direction. The analysis provides a theoretical foundation for well pattern arrangement in fractured reservoirs as well as in channel sand reservoirs.

  17. The mitochondrial permeability transition pore: Molecular nature and role as a target in cardioprotection

    OpenAIRE

    Bernardi, Paolo; Di Lisa, Fabio

    2015-01-01

    The mitochondrial permeability transition (PT) – an abrupt increase permeability of the inner membrane to solutes – is a causative event in ischemia–reperfusion injury of the heart, and the focus of intense research in cardioprotection. The PT is due to opening of the PT pore (PTP), a high conductance channel that is critically regulated by a variety of pathophysiological effectors. Very recent work indicates that the PTP forms from the F-ATP synthase, which would switch from an energy-conser...

  18. Different Methods of Predicting Permeability in Shale

    DEFF Research Database (Denmark)

    Mbia, Ernest Ncha; Fabricius, Ida Lykke; Krogsbøll, Anette

    Permeability is often very difficult to measure or predict in shale lithology. In this work we are determining shale permeability from consolidation tests data using Wissa et al., (1971) approach and comparing the results with predicted permeability from Kozeny’s model. Core and cuttings materials...... were obtained from Fjerritslev shale Formation in Juassic interval of Stenlille and Vedsted on-shore wells of Danish basin. The calculated permeability from specific surface and porosity vary from 0.09 to 48.53 μD while that calculated from consolidation tests data vary from 1000 μD at a low vertical...... effective stress to 9 μD at high vertical effective stress of 100 MPa. The indirect permeability calculated from consolidation tests falls in the same magnitude at higher vertical effective stress, above 40 MPa, as that of the Kozeny model for shale samples with high non-clay content ≥ 70% but are higher by...

  19. Ion permeation of AQP6 water channel protein. Single channel recordings after Hg2+ activation.

    Science.gov (United States)

    Hazama, Akihiro; Kozono, David; Guggino, William B; Agre, Peter; Yasui, Masato

    2002-08-01

    Aquaporin-6 (AQP6) has recently been identified as an intracellular vesicle water channel with anion permeability that is activated by low pH or HgCl2. Here we present direct evidence of AQP6 channel gating using patch clamp techniques. Cell-attached patch recordings of AQP6 expressed in Xenopus laevis oocytes indicated that AQP6 is a gated channel with intermediate conductance (49 picosiemens in 100 mm NaCl) induced by 10 microm HgCl2. Current-voltage relationships were linear, and open probability was fairly constant at any given voltage, indicating that Hg2+-induced AQP6 conductance is voltage-independent. The excised outside-out patch recording revealed rapid activation of AQP6 channels immediately after application of 10 microm HgCl2. Reduction of both Na+ and Cl- concentrations from 100 to 30 mm did not shift the reversal potential of the Hg2+-induced AQP6 current, suggesting that Na+ is as permeable as Cl-. The Na+ permeability of Hg2+-induced AQP6 current was further demonstrated by 22Na+ influx measurements. Site-directed mutagenesis identified Cys-155 and Cys-190 residues as the sites of Hg2+ activation both for water permeability and ion conductance. The Hill coefficient from the concentration-response curve for Hg2+-induced conductance was 1.1 +/- 0.3. These data provide the first evidence of AQP6 channel gating at a single-channel level and suggest that each monomer contains the pore region for ions based on the number of Hg2+-binding sites and the kinetics of Hg2+-activation of the channel. PMID:12034750

  20. 46 CFR 172.240 - Permeability of spaces.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Permeability of spaces. 172.240 Section 172.240 Shipping... Permeability of spaces. When doing the calculations required in § 172.225, (a) The permeability of a floodable... space permeability of 85% unless the use of an assumed permeability of less than 85% is justified...

  1. Gas and Water Permeability of Concrete

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Martin, P. L.; Romero, F. J.; Gutierrez-Rodirgo, V.; Barcala, J. M.

    2012-11-01

    The gas pressure of concrete samples was measured in an unsteady-state equipment working under low injection pressures and in a newly fine tuned steady-state setup working under different pressures. These measurements allowed the estimation of the intrinsic and relative gas permeability of the concrete and of the effect of boundary conditions on them. Permeability decreased with water content, but it was also greatly affected by the hydraulic history of concrete, i.e. if it had been previously dried or wetted. In particular, and for a given degree of saturation, the gas permeability of concrete previously saturated was lower than if the concrete had been just air dried or saturated after air drying. In any case, the gas permeability was about two orders of magnitude higher than the liquid water permeability (10-16 vs. 10-18 m2), probably due to the chemical reactions taking place during saturation (carbonation). The relative gas permeability of concrete increased sharply for water degrees of saturation smaller than 50%. The boundary conditions also affected the gas permeability, which seemed to be mostly conditioned by the back pressure and the confining pressure, increasing as the former increased and decreasing as the latter increased, i.e. decreasing as the effective pressure increased. Overall the increase of pressure head or injection pressure implied a decrease in gas permeability. External,microcracking during air-drying could not be ruled out as responsible for the decrease of permeability with confining pressure. The apparent permeability obtained applying the Klinkenberg method for a given effective pressure was only slightly smaller than the average of all the values measured for the same confining pressure range. For this reason it is considered that the Klinkenberg effect was not relevant in the range of pressures applied. (Author) 37 refs.

  2. Compact rock material gas permeability properties

    International Nuclear Information System (INIS)

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO2, shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10−19 m2; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10−17 m2; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens’ permeability evolution is related to the relative particle movements and microcrack closure

  3. Compact rock material gas permeability properties

    Science.gov (United States)

    Wang, Huanling; Xu, Weiya; Zuo, Jing

    2014-09-01

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO2, shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10-19 m2; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10-17 m2; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens' permeability evolution is related to the relative particle movements and microcrack closure.

  4. Effects of phase transformation of steam-water relative permeabilities

    Energy Technology Data Exchange (ETDEWEB)

    Verma, A.K.

    1986-03-01

    A combined theoretical and experimental study of steam-water relative permeabilities (RPs) was carried out. First, an experimental study of two-phase concurrent flow of steam and water was conducted and a set of RP curves was obtained. These curves were compared with semi-empirical and experimental results obtained by other investigators for two-phase, two-component flow (oil/gas; gas/water; gas/oil). It was found that while the wetting phase RPs were in good agreement, RPs for the steam phase were considerably higher than the non-wetting phase RPs in two-component systems. This enhancement of steam RP is attributed to phase transformation effects at the pore level in flow channels. The effects of phase transformation were studied theoretically. This study indicates that there are two separate mechanisms by which phase transformation affects RP curves: (1) Phase transformation is converging-diverging flow channels can cause an enhancement of steam phase RP. In a channel dominated by steam a fraction of the flowing steam condenses upstream from the constriction, depositing its latent heat of condensation. This heat is conducted through the solid grains around the pore throat, and evaporation takes place downstream from it. Therefore, for a given bulk flow quality; a smaller fraction of steam actually flows through the throat segments. This pore-level effect manifests itself as relative permeability enhancement on a macroscopic level; and (2) phase transformation along the interface of a stagnant phase and the phase flowing around it controls the irreducible phase saturation. Therefore, the irreducible phase saturation in steam-water flow will depend, among other factors, on the boundary conditions of the flow.

  5. Geo-Enabled, Mobile Services

    DEFF Research Database (Denmark)

    Jensen, Christian Søndergaard

    2006-01-01

    We are witnessing the emergence of a global infrastructure that enables the widespread deployment of geo-enabled, mobile services in practice. At the same time, the research community has also paid increasing attention to data management aspects of mobile services. This paper offers me an...

  6. Measuring the extent of seepage losses occuring from unlined channels

    International Nuclear Information System (INIS)

    The problem of seepage losses is one of the major problems encountered in the irrigation channels. Radioisotope iodine-131 was used as the tracer for measuring the seepage losses from unlined channels. The method is based on determining the time of travel of the tracer along the outermost streamline from one borehole to the other drilled on the banks of a canal. The permeability of the soil was calculated from the velocity of the tracer. The shape of the outermost streamline was determined from the water levels in the boreholes. Knowing permeability, hydraulic gradient and the geometry of the channels, seepage losses were calculated. The technique has many advantages over the other conventional methods of measuring seepage losses. It directly gives the position of the outermost streamline and can also be used effectively for determining the permeability of soils in situ. (author)

  7. A Poroelastic Description of Permeability Evolution

    Science.gov (United States)

    Hassanzadegan, Alireza; Zimmermann, Günter

    2014-07-01

    Pore pressure changes in a geothermal reservoir, as a result of injection and/or production of water, result in changes of stress acting on the reservoir rock and, consequently, changes in the mechanical and transport properties of the rock. Bulk modulus and permeability were measured at different pressures and temperatures. An outcropping equivalent of Rotliegend reservoir rock in the North German Basin (Flechtinger sandstone) was used to perform hydrostatic tests and steady state fluid flow tests. Permeability measurements were conducted while cycling confining pressure; the dependence of permeability on stress was determined at a constant downstream pressure of 1 MPa. Also, temperature was increased stepwise from 30 to 140 °C and crack porosity was calculated at different temperatures. Although changes in the volumes of cracks are not significant, the cracks control fluid flow pathways and, consequently, the permeability of the rock. A new model was derived which relates microstructure of porosity, the stress-strain curve, and permeability. Porosity change was described by the first derivative of the stress-strain curve. Permeability evolution was ascribed to crack closure and was related to the second derivative of the stress-strain curve. The porosity and permeability of Flechtinger sandstone were reduced by increasing the effective pressure and decreased after each pressure cycle.

  8. Permeability profiles -- key to reservoir management

    Energy Technology Data Exchange (ETDEWEB)

    Georgi, D.; Kasap, E.; Tang, X.; Cheng, A.

    1998-06-01

    Three-dimensional seismic data being collected routinely today offer those responsible for reservoir management a detailed picture of the configuration of the subsurface. Often, the porosity of reservoir rocks can also be deduced. However, knowing porosity exists, i.e., that there is pore space and vugs for the storage of hydrocarbons, is important but valueless if hydrocarbons cannot be made to flow into wells. Permeability is the quantity that measures flow capability. Having a permeability profile is the key to reservoir management. Accurate values can be obtained from cores taken during drilling; however, cutting cores is expensive and cores taken to the surface may be damaged or not representative of the reservoir rock of interest. Rotary coring can provide limited permeability data but, generally, insufficient data are available to develop a permeability profile. Here, the authors are concerned with measuring permeability with instruments placed in a well or used for logging a well. They shall discuss permeability-measuring methods available from Western Atlas Logging Services (WALS). Together, they make it possible to obtain continuous permeability in any well without coring or extensive well testing.

  9. Aquaporin 4 as a NH3 Channel.

    Science.gov (United States)

    Assentoft, Mette; Kaptan, Shreyas; Schneider, Hans-Peter; Deitmer, Joachim W; de Groot, Bert L; MacAulay, Nanna

    2016-09-01

    Ammonia is a biologically potent molecule, and the regulation of ammonia levels in the mammalian body is, therefore, strictly controlled. The molecular paths of ammonia permeation across plasma membranes remain ill-defined, but the structural similarity of water and NH3 has pointed to the aquaporins as putative NH3-permeable pores. Accordingly, a range of aquaporins from mammals, plants, fungi, and protozoans demonstrates ammonia permeability. Aquaporin 4 (AQP4) is highly expressed at perivascular glia end-feet in the mammalian brain and may, with this prominent localization at the blood-brain-interface, participate in the exchange of ammonia, which is required to sustain the glutamate-glutamine cycle. Here we observe that AQP4-expressing Xenopus oocytes display a reflection coefficient permeable water channels. PMID:27435677

  10. [Model of the selective calcium channel of characean algae].

    Science.gov (United States)

    Lunevskiĭ, V Z; Zherelova, O M; Aleksandrov, A A; Vinokurov, M G; Berestovskiĭ, G N

    1980-01-01

    The present work was intended to further investigate the selective filter of calcium channel on both a cell membrane and reconstructed channels. For the studies on cell membranes, an inhibitor of chloride channels was chosen (ethacrynic acid) to pass currents only through the calcium channels. On both the cells and reconstructed channels, permeability of ions of different crystal radii and valencies was investigated. The obtained results suggest that the channel represents a wide water pore with a diameter larger than 8 A into which ions go together with the nearest water shell. The values of the maximal currents are given by electrostatic interaction of the ions with the anion center of the channel. A phenomenological two-barrier model of the channel is given which describes the movement of all the ions studied. PMID:6251921

  11. A Negative Permeability Material at Red Light

    DEFF Research Database (Denmark)

    Yuan, Hsiao-Kuan; Chettiar, Uday K.; Cai, Wenshan;

    2007-01-01

    A negative permeability in a periodic array of pairs of thin silver strips is demonstrated experimentally for two distinct samples. The effect of the strip surface roughness on negative permeability is evaluated. The first sample, Sample A, is fabricated of thinner strips with a root mean square...... roughness of 7 nm, while Sample B is made of thicker strips with 3-nm roughness. The real part of permeability, μ ′ , is −1 at a wavelength of 770 nm in Sample A and −1.7 at 725 nm in Sample B. Relative to prototypes simulated with ideal strips, larger strip roughness acts to decrease μ ′ by a factor of 7...

  12. Permeability of rock salt - theory and experiment

    International Nuclear Information System (INIS)

    For the nuclear repository Morsleben (ERAM), Germany, various sealing system have been designed. One element of these sealing concepts is the sealing of the shafts of the repository. An essential condition for the design of an effective shaft seal is the knowledge of the permeability in the disturbed rock zone that has developed around the shafts. For this purpose, permeability tests have been conducted in situ. This article deals with the test equipment and its investigation in the laboratory, with the theoretic basis of the interpretation of test results as well as with the carrying out and interpretation of selected in-situ-permeability tests. (orig.)

  13. The solubility-permeability interplay in using cyclodextrins as pharmaceutical solubilizers: mechanistic modeling and application to progesterone.

    Science.gov (United States)

    Dahan, Arik; Miller, Jonathan M; Hoffman, Amnon; Amidon, Gregory E; Amidon, Gordon L

    2010-06-01

    A quasi-equilibrium mass transport analysis has been developed to quantitatively explain the solubility-permeability interplay that exists when using cyclodextrins as pharmaceutical solubilizers. The model considers the effects of cyclodextrins on the membrane permeability (P(m)) as well as the unstirred water layer (UWL) permeability (P(aq)), to predict the overall effective permeability (P(eff)) dependence on cyclodextrin concentration (C(CD)). The analysis reveals that: (1) UWL permeability markedly increases with increasing C(CD) since the effective UWL thickness quickly decreases with increasing C(CD); (2) membrane permeability decreases with increasing C(CD), as a result of the decrease in the free fraction of drug; and (3) since P(aq) increases and P(m) decreases with increasing C(CD), the UWL is effectively eliminated and the overall P(eff) tends toward membrane control, that is, P(eff) approximately P(m) above a critical C(CD). Application of this transport model enabled excellent quantitative prediction of progesterone P(eff) as a function of HP beta CD concentrations in PAMPA assay, Caco-2 transepithelial studies, and in situ rat jejunal-perfusion model. This work demonstrates that when using cyclodextrins as pharmaceutical solubilizers, a trade-off exists between solubility increase and permeability decrease that must not be overlooked; the transport model presented here can aid in striking the appropriate solubility-permeability balance in order to achieve optimal overall absorption. PMID:20039391

  14. River channel response to runoff variability

    OpenAIRE

    Kargapolova, I.

    2008-01-01

    The focus of this study was to determine river runoff impacts on channel evolution during the last centuries. Comparing a number of maps from the 18th–21th centuries and space images in concert with hydrological data we estimated natural trends, cycles and the intensity of channel formation for periods of high and low runoff. Our analysis for a long period of time enable us assessing mean and maximum rates of erosion and accumulation of river channels and bank dynamics under differe...

  15. Thermodynamic impact of aquifer permeability on the performance of a compressed air energy storage plant

    International Nuclear Information System (INIS)

    Highlights: • Design procedure of an aquifer compressed air energy storage system was proposed. • An approach to select aquifers with adequate permeability was presented. • Applied an exergy analysis to exam the impact of permeability on plant economics. • The exergy destruction in the aquifer was reduced as the permeability increased. - Abstract: Economic, large-scale energy storage technology plays a key role in enabling the utility industry to integrate more renewable energy sources into the grid. Compressed air energy storage in porous geological formations has the potential to become one of the principal energy storage technologies in the future. Storing pressurized air in aquifers has several advantages, including large storage capacity, geologically widespread availability, relatively constant pressure, and relatively low construction cost. The performance of a compressed air energy storage plant is influenced by the subsurface reservoir properties. In this paper, the design criteria, calculation procedure, and exergy analysis approach to quantify the influence of aquifer permeability on compressed air energy storage plants are proposed. A case-study model was built to simulate a compressed air energy storage plant using aquifers with porosities of 30% and different permeabilities (0.01–1.0 darcies). The exergy destruction rates and exergy and thermal efficiencies were calculated. The results indicated that as the permeability increased, the exergy destruction due to a pressure drop of working fluid in an aquifer decreased; as the permeability increased, both thermal and exergy efficiencies increased, and the net output of the plant increased. The benefits are more obvious when the permeability increased from low (⩽0.05 darcies) to medium–high values (⩾0.25 darcies)

  16. Metasurface-Enabled Remote Quantum Interference.

    Science.gov (United States)

    Jha, Pankaj K; Ni, Xingjie; Wu, Chihhui; Wang, Yuan; Zhang, Xiang

    2015-07-10

    An anisotropic quantum vacuum (AQV) opens novel pathways for controlling light-matter interaction in quantum optics, condensed matter physics, etc. Here, we theoretically demonstrate a strong AQV over macroscopic distances enabled by a judiciously designed array of subwavelength-scale nanoantennas-a metasurface. We harness the phase-control ability and the polarization-dependent response of the metasurface to achieve strong anisotropy in the decay rate of a quantum emitter located over distances of hundreds of wavelengths. Such an AQV induces quantum interference among radiative decay channels in an atom with orthogonal transitions. Quantum vacuum engineering with metasurfaces holds promise for exploring new paradigms of long-range light-matter interaction for atom optics, solid-state quantum optics, quantum information processing, etc. PMID:26207477

  17. Taxonomy Enabled Discovery (TED) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposal addresses the NASA's need to enable scientific discovery and the topic's requirements for: processing large volumes of data, commonly available on the...

  18. Population shift between the open and closed states changes the water permeability of an Aquaporin Z mutant.

    Science.gov (United States)

    Xin, Lin; Hélix-Nielsen, Claus; Su, Haibin; Torres, Jaume; Tang, Chuyang; Wang, Rong; Fane, Anthony Gordon; Mu, Yuguang

    2012-07-18

    Aquaporins are tetrameric transmembrane channels permeable to water and other small solutes. Wild-type (WT) and mutant Aquaporin Z (AqpZ) have been widely studied and multiple factors have been found to affect their water permeability. In this study, molecular dynamics simulations have been performed for the tetrameric AqpZ F43W/H174G/T183F mutant. It displayed ∼10% average water permeability compared to WT AqpZ, which had been attributed to the increased channel lumen hydrophobicity. Our simulations, however, show a ring stacking between W43 and F183 acting as a secondary steric gate in the triple mutant with R189 as the primary steric gate in both mutant and WT AqpZ. The double gates (R189 and W43-F183) result in a high population of the closed conformation in the mutant. Occasionally an open state, with diffusive water permeability very close to that of WT AqpZ, was observed. Taken together, our results show that the double-gate mechanism is sufficient to explain the reduced water permeability in the mutant without invoking effects arising from increased hydrophobicity of the channel lumen. Our findings provide insights into how aquaporin-mediated water transport can be modulated and may further point to how aquaporin function can be optimized for biomimetic membrane applications. PMID:22853898

  19. Variability of permeability with diameter of conduit

    Indian Academy of Sciences (India)

    J A Adegoke; J A Olowofela

    2008-05-01

    An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related.

  20. Permeability of rayon based polymer composites

    Science.gov (United States)

    Stokes, E. H.

    1992-01-01

    Several types of anomalous rayon based phenolic behavior have been observed in post-fired nozzles and exit cones. Many of these events have been shown to be related to the development of internal gas pressure within the material. The development of internal gas pressure is a function of the amount of gas produced within the material and the rate at which that gas is allowed to escape. The latter property of the material is referred to as the material's permeability. The permeability of two dimensional carbonized rayon based phenolic composites is a function of material direction, temperature, and stress/strain state. Recently significant differences in the permeability of these materials has been uncovered which may explain their inconsistent performance. This paper summarizes what is known about the permeability of these materials to date and gives possible implications of these finding to the performance of these materials in an ablative environment.

  1. Permeability Tests on Silkeborg Sand No. 0000

    DEFF Research Database (Denmark)

    Lund, Willy; Jakobsen, Kim Parsberg

    The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends on the...... characteristics of the soil matrix, the permeability is determined for different void ratios. All tests are performed on reconstituted specimens of Silkeborg Sand No. 0000. The permeability is determined by use of a falling head apparatus. The apparatus, test procedures and the analysis method are described in...... the succeeding sections. Finally the test results are briefly summarised and a relationship between void ratio l and permeability is established....

  2. Small-bowel permeability in collagenous colitis

    DEFF Research Database (Denmark)

    Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J

    2006-01-01

    -intestinal biopsies, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal...... permeability. MATERIAL AND METHODS: Ten patients with CC and chronic diarrhoea participated in the study. Coeliac disease was excluded by small-bowel biopsy and/or serology. Intestinal permeability was assessed as urinary excretion (ratios) 2, 4 and 6 h after ingestion of 14C-labelled mannitol (14C......: No alterations in intestinal permeability in patients with CC could be demonstrated. Impairment of the integrity of the mucosa of the small bowel and the presence of a general dysfunction of the small intestine in patients with CC seem unlikely....

  3. Gyroid Nanoporous Membranes with Tunable Permeability

    DEFF Research Database (Denmark)

    Li, Li; Schulte, Lars; Clausen, Lydia D.;

    2011-01-01

    Understanding the relevant permeability properties of ultrafiltration membranes is facilitated by using materials and procedures that allow a high degree of control on morphology and chemical composition. Here we present the first study on diffusion permeability through gyroid nanoporous cross...... chemistry of 1,2-PB nanoporous membranes can be controlled, for example, by hydrophilic patterning of the originally hydrophobic membranes, which allows for different active porosity toward aqueous solutions and, therefore, different permeability. The membrane selectivity is evaluated by comparing the...... effective diffusion coefficients of a series of antibiotics, proteins, and other biomolecules; solute permeation is discussed in terms of hindered diffusion. The combination of uniform bulk morphology, isotropically percolating porosity, controlled surface chemistry, and tunable permeability is distinctive...

  4. The Water Permeability and Pore Entrance Structure of Aquaporin-4 Depend on Lipid Bilayer Thickness.

    Science.gov (United States)

    Tong, Jihong; Wu, Zhe; Briggs, Margaret M; Schulten, Klaus; McIntosh, Thomas J

    2016-07-12

    Aquaporin-4 (AQP4), the primary water channel in glial cells of the mammalian brain, plays a critical role in water transport in the central nervous system. Previous experiments have shown that the water permeability of AQP4 depends on the cholesterol content in the lipid bilayer, but it was not clear whether changes in permeability were due to direct cholesterol-AQP4 interactions or to indirect effects caused by cholesterol-induced changes in bilayer elasticity or bilayer thickness. To determine the effects resulting only from bilayer thickness, here we use a combination of experiments and simulations to analyze AQP4 in cholesterol-free phospholipid bilayers with similar elastic properties but different hydrocarbon core thicknesses previously determined by x-ray diffraction. The channel (unit) water permeabilities of AQP4 measured by osmotic-gradient experiments were 3.5 ± 0.2 × 10(-13) cm(3)/s (mean ± SE), 3.0 ± 0.3 × 10(-13) cm(3)/s, 2.5 ± 0.2 × 10(-13) cm(3)/s, and 0.9 ± 0.1 × 10(-13) cm(3)/s in bilayers containing (C22:1)(C22:1)PC, (C20:1)(C20:1)PC, (C16:0)(C18:1)PC, and (C13:0)(C13:0)PC, respectively. Channel permeabilities obtained by molecular dynamics (MD) simulations were 3.3 ± 0.1 × 10(-13) cm(3)/s and 2.5 ± 0.1 × 10(-13) cm(3)/s in (C22:1)(C22:1)PC and (C14:0)(C14:0)PC bilayers, respectively. Both the osmotic-gradient and MD-simulation results indicated that AQP4 channel permeability decreased with decreasing bilayer hydrocarbon thickness. The MD simulations also suggested structural modifications in AQP4 in response to changes in bilayer thickness. Although the simulations showed no appreciable changes to the radius of the pore located in the hydrocarbon region of the bilayers, the simulations indicated that there were changes in both pore length and α-helix organization near the cytoplasmic vestibule of the channel. These structural changes, caused by mismatch between the hydrophobic length of AQP4 and the bilayer hydrocarbon

  5. Testing Research on the Coal Specimen Permeability

    OpenAIRE

    Peide Sun

    2006-01-01

    The three-dimensional compression tests to coal specimen containing methane gas were carried out with various confining pressures and pore pressures in this study. The rule for three-dimensional compression deformation on the gas permeability of the coal specimens was systematically studied by the tests. The new empiric equations for the gas permeability of the coal specimens were formulated by the numerical fit of the test data and they were successfully used in the visual numerical simulati...

  6. Electrostatically gated membrane permeability in inorganic protocells

    OpenAIRE

    Li, Mei; Harbron, Rachel; Weaver, Jonathan; Binks, Bernard; Mann, Stephen.

    2013-01-01

    Although several strategies are now available to produce functional microcompartments analogous to primitive cell-like structures, little progress has been made in generating protocell constructs with self-controlled membrane permeability. Here we describe the preparation of water-dispersible colloidosomes based on silica nanoparticles and delineated by a continuous semipermeable inorganic membrane capable of self-activated, electrostatically gated permeability. We use crosslinking and covale...

  7. Pneumatic fracturing of low permeability media

    Energy Technology Data Exchange (ETDEWEB)

    Schuring, J.R. [New Jersey Institute of Technology, Newark, NJ (United States)

    1996-08-01

    Pneumatic fracturing of soils to enhance the removal and treatment of dense nonaqueous phase liquids is described. The process involves gas injection at a pressure exceeding the natural stresses and at a flow rate exceeding the permeability of the formation. The paper outlines geologic considerations, advantages and disadvantages, general technology considerations, low permeability media considerations, commercial availability, efficiency, and costs. Five case histories of remediation using pneumatic fracturing are briefly summarized. 11 refs., 2 figs., 1 tab.

  8. Subnanometer Two-Dimensional Graphene Oxide Channels for Ultrafast Gas Sieving.

    Science.gov (United States)

    Shen, Jie; Liu, Gongping; Huang, Kang; Chu, Zhenyu; Jin, Wanqin; Xu, Nanping

    2016-03-22

    Two-dimensional (2D) materials with atomic thickness and extraordinary physicochemical properties exhibit unique mass transport behaviors, enabling them as emerging nanobuilding blocks for separation membranes. Engineering 2D materials into membrane with subnanometer apertures for precise molecular sieving remains a great challenge. Here, we report rational-designing external forces to precisely manipulate nanoarchitecture of graphene oxide (GO)-assembled 2D channels with interlayer height of ∼0.4 nm for fast transporting and selective sieving gases. The external forces are synergistic to direct the GO nanosheets stacking so as to realize delicate size-tailoring of in-plane slit-like pores and plane-to-plane interlayer-galleries. The 2D channels endow GO membrane with excellent molecular-sieving characteristics that offer 2-3 orders of magnitude higher H2 permeability and 3-fold enhancement in H2/CO2 selectivity compared with commercial membranes. Formation mechanism of 2D channels is proposed on the basis of the driving forces, nanostructures, and transport behaviors. PMID:26866661

  9. Durability Evaluation in Concrete Using Cracked Permeability and Chloride Permeability Tests

    OpenAIRE

    V. M. Sounthararajan; A. Sivakumar

    2013-01-01

    The objective of this study is to identify the possibilities of utilizing the quarry dust in concrete to obtain an improved strength and durability properties of concrete. In the present study, the addition of quarry dust as alternative for natural sand has been investigated, and the durability properties of concrete were evaluated systematically by means of cracked water permeability and rapid chloride permeability tests. The permeability of concrete was assessed with initial stress applied ...

  10. The Berea Sandstone -- a shallow, low permeable gas reservoir in Dickenson County, Virginia

    Energy Technology Data Exchange (ETDEWEB)

    Nolde, J.E. (Virginia Dept. of Mines, Minerals and Energy, Charlottesville, VA (United States))

    The Berea Sandstone is a major resource of natural gas in a low permeability, low pressure reservoir at depths of less than 5,000 feet in Dickenson County. The sandstone lies between the underlying Devonian shale sequence and the overlying Sunbury Shale. Thickness of the Berea ranges from 20 to 150 feet. Gas associated with the Berea is the product of the immature stage of hydrocarbon generation (biogenic gas). Trend surface analysis of thickness data delineates a prominent nearshore bar complex and associated facies extending northerly across the central-portion of the county. These nearshore marine bar sediments are cut locally by shallow marine channel deposits of the Virginia-Carolina delta. The marine bar facies is a coarsening-upward sequence consisting of very-fine-grained sandstone. The channel facies grades upward from medium-to percent, with permeabilities of 0.003-0.008 millidarcies.

  11. Altered plasmodial surface anion channel activity and in vitro resistance to permeating antimalarial compounds

    OpenAIRE

    Lisk, Godfrey; Pain, Margaret; Sellers, Morgan; Gurnev, Philip A.; Pillai, Ajay D.; Bezrukov, Sergey M.; Desai, Sanjay A.

    2010-01-01

    Erythrocytes infected with malaria parasites have increased permeability to various solutes. These changes may be mediated by an unusual small conductance ion channel known as the plasmodial surface anion channel (PSAC). While channel activity benefits the parasite by permitting nutrient acquisition, it can also be detrimental because water-soluble antimalarials may more readily access their parasite targets via this channel. Recently, two such toxins, blasticidin S and leupeptin, were used t...

  12. Simulating Perforation Permeability Damage and Cleanup; TOPICAL

    International Nuclear Information System (INIS)

    Completion of cased and cemented wells by shaped charge perforation causes its own damage to the formation, potentially reducing well productivity. In practice it is found that underbalance conditions clean up the damaged zone to some extent, however, the mechanisms of these processes are poorly understood. Most hydrocodes typically used to simulate rock response to shaped charge penetration do not provide permeability estimates. Furthermore, the time scales for formation clean up are potentially much longer than the period of jet penetration. We have developed a simple, yet accurate model for the evolution of porosity and permeability which can easily be incorporated into existing hydrocodes using information from the history of each cell. In addition, we have developed a code that efficiently simulates fines migration during the post-shot surge period using initial conditions taken directly from hydrocode simulations of jet penetration. Results from a one-dimensional model simulation are in excellent agreement with measured fines and permeability distributions. We also present two-dimensional numerical results which qualitatively reproduce experimentally obtained permeability maps for different values of underbalance. Although initial results have been promising, further comparison with experiment is essential to tune the coupling between the hydrocode and fines migration simulator. Currently the permeability model is most appropriate for high permeability sandstones (such as Berea), but with little effort, the model can be extended to other rock types, given sufficient experimental data

  13. Relations Between Permeability and Structure of Wood

    Institute of Scientific and Technical Information of China (English)

    Bao Fucheng; Zhao Youke; Lü Jianxiong

    2003-01-01

    The permeability and the structure of heartwood and sapwood of the solvent-exchange dried and the air-dried green-wood of Chinese-fir (Cunninghamia lanceolata (Lamb.) Hook.) and masson pine (Pinus massoniana Lamb.) were measured inorder to study the relations between the permeability and the structure. The results showed that the permeability of sapwood of boththe air-dried and the solvent-exchange dried wood was higher than that of heartwood, and the permeability of the solvent-exchangeddried heartwood and sapwood was higher than that of the air-dried. A higher permeability of wood was attributed to, on the one hand,a bigger number of flow path per unit area of the wood perpendicular to the flow direction resulted from a bigger number ofunaspirated pits per unit area and a bigger number of effective pit openings per membrane, and on the other hand, a smaller numberof tracheid in series connection per unit length parallel to flow direction resulted from a longer tracheid length and an effectivetracheid length for permeability.

  14. Crystal Structure of an Ammonia-Permeable Aquaporin.

    Science.gov (United States)

    Kirscht, Andreas; Kaptan, Shreyas S; Bienert, Gerd Patrick; Chaumont, François; Nissen, Poul; de Groot, Bert L; Kjellbom, Per; Gourdon, Pontus; Johanson, Urban

    2016-03-01

    Aquaporins of the TIP subfamily (Tonoplast Intrinsic Proteins) have been suggested to facilitate permeation of water and ammonia across the vacuolar membrane of plants, allowing the vacuole to efficiently sequester ammonium ions and counteract cytosolic fluctuations of ammonia. Here, we report the structure determined at 1.18 Å resolution from twinned crystals of Arabidopsis thaliana aquaporin AtTIP2;1 and confirm water and ammonia permeability of the purified protein reconstituted in proteoliposomes as further substantiated by molecular dynamics simulations. The structure of AtTIP2;1 reveals an extended selectivity filter with the conserved arginine of the filter adopting a unique unpredicted position. The relatively wide pore and the polar nature of the selectivity filter clarify the ammonia permeability. By mutational studies, we show that the identified determinants in the extended selectivity filter region are sufficient to convert a strictly water-specific human aquaporin into an AtTIP2;1-like ammonia channel. A flexible histidine and a novel water-filled side pore are speculated to deprotonate ammonium ions, thereby possibly increasing permeation of ammonia. The molecular understanding of how aquaporins facilitate ammonia flux across membranes could potentially be used to modulate ammonia losses over the plasma membrane to the atmosphere, e.g., during photorespiration, and thereby to modify the nitrogen use efficiency of plants. PMID:27028365

  15. Gels correct in-depth reservoir permeability variation

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J.E.; Mack, J.C. [Tiorco Inc., Denver, CO (United States)

    1997-01-06

    Continuous, long-term injection of an environmentally sound colloidal dispersion gel (CDG) provides a solution to in-depth, away from the well bore, channeling and crossflow problems inherent with waterflooding. This unique in-depth permeability modification process has been applied in 37 field projects over the last 11 years. In the 29 successful projects, the gels increased oil production at lower water/oil ratios. The colloidal dispersion gel was successfully placed at reservoir temperatures up to 202 F. Oil viscosities were often high, from 10 cps to more than 20 cps at the reservoir bottom hole temperature. The paper discusses CDG technology, laboratory work, the gels, field development, initial field results, unsuccessful projects, marginal projects, and successful projects.

  16. Crystal Structure of an Ammonia-Permeable Aquaporin

    DEFF Research Database (Denmark)

    Kirscht, Andreas; Kaptan, Shreyas S; Bienert, Gerd Patrick;

    2016-01-01

    the structure determined at 1.18 Å resolution from twinned crystals of Arabidopsis thaliana aquaporin AtTIP2;1 and confirm water and ammonia permeability of the purified protein reconstituted in proteoliposomes as further substantiated by molecular dynamics simulations. The structure of AtTIP2;1 reveals......Aquaporins of the TIP subfamily (Tonoplast Intrinsic Proteins) have been suggested to facilitate permeation of water and ammonia across the vacuolar membrane of plants, allowing the vacuole to efficiently sequester ammonium ions and counteract cytosolic fluctuations of ammonia. Here, we report...... filter region are sufficient to convert a strictly water-specific human aquaporin into an AtTIP2;1-like ammonia channel. A flexible histidine and a novel water-filled side pore are speculated to deprotonate ammonium ions, thereby possibly increasing permeation of ammonia. The molecular understanding...

  17. Permeability properties of erythrocyte ghosts.

    Science.gov (United States)

    TEORELL, T

    1952-05-01

    1. Erythrocyte ghosts from human blood were produced by gentle water hemolysis. The ghost-containing hemolysate (about 20 mN) was added to media of different composition (KCl, NaCl, glucose, sucrose, etc.) and varying concentration ranging from 8 to 840 mN. The volume changes of the ghost cells were followed by a light absorption method. The potassium and sodium concentrations were also analyzed in some representative cases. 2. The ghosts shrank, or swelled, in two stages. An initial phase with a momentary expulsion, or uptake, of water leading to an osmotic equilibrium, was followed by a second phase in which a slow swelling or shrinking proceeded toward a final constant volume. 3. The ghosts were semipermeable in the sense that water always passed rapidly in either direction so as to maintain isotonicity with the external medium. The relation between ghost cell volumes (V) and the total concentration (C(e)) of the suspension medium can be expressed by a modified van't Hoff-Mariotte law: (C(e) + a)(V - b) = constant. Here a is a term correcting for an internal pressure and b is the non-solvent volume of the ghost cells. This means that the ghosts behave as perfect osmometers. 4. On the other hand appreciable concentration differences of the K and Na ions could be maintained across the intact ghost cell membranes for long periods. Whether this phenomenon is due simply to very low cation permeability or to active transport processes cannot be decided, although the first assumption appears more probable. 5. When the ghosts were treated with small concentrations of a lytic substance like Na oleate, the alkali ion transfer was greatly increased. This seems to be a simple exchange diffusion process with simultaneous, continued maintenance of osmotic equilibrium (= the second phase). A simplified theory is also given for the kinetics of the volume variations and ion exchange during the second phase (cf. the Appendix). 6. Miscellaneous observations on the effects of p

  18. Comparative field permeability measurement of permeable pavements using ASTM C1701 and NCAT permeameter methods.

    Science.gov (United States)

    Li, Hui; Kayhanian, Masoud; Harvey, John T

    2013-03-30

    Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability. PMID:23434738

  19. Innovative reactor technologies - Enabling success

    International Nuclear Information System (INIS)

    Full text: 1. Introduction. AECL has been pursuing innovation in reactor design using an evolutionary approach. The Advanced CANDU Reactor, or ACR design is the logical next step in the CANDU fuel-channel reactor design process, and achieves major improvements in economics while expanding safety margins. ACR technology is also the start of the long-term development path for CANDU fuel channel reactors. This path fits in with the long-term development directions identified in initiatives such as the Generation IV International Forum (GIF) and INPRO. AECL sees the product evolution from the ACR to the Supercritical Water-costed Reactor (SCWR), one of the concepts identified by GIF for further development. One of the prominent characteristics of the heavy-water moderated fuel channel reactor approach is the high potential for innovation. 2. Background to Development Strategy. As part of the pressurized water reactor family, CANDU's share many characteristics with other light water reactors, while retaining a set of distinctive features: High pressure water coolant in individual fuel channels, with low-pressure, low temperature moderator; Horizontal fuel channel design with on-power refuelling; Simple, easily-fabricated fuel bundle design; Use of heavy water to improve neutron efficiency. Since the original CANDU reactors were first built, the advent of deregulated, competitive energy markets has strongly emphasized the importance of low capital cost and short construction time. The ACR design innovations are chosen to respond to this evolution of energy markets, while retaining the proven features of the CANDU line. 3. Innovative CANDU Product Designs. The ACR-700 design is an evolutionary development of familiar CANDU technology, adding a carefully chosen set of innovations to the major improvements in economics, operations and safety margins: Slightly enriched uranium fuel contained in CANFLEX bundles; Light water replacing heavy water as the reactor coolant; More

  20. Erythropoietin modulation of astrocyte water permeability as a component of neuroprotection

    OpenAIRE

    Gunnarson, Eli; Song, Yutong; Kowalewski, Jacob M.; Brismar, Hjalmar; Brines, Michael; Cerami, Anthony; Andersson, Ulf; Zelenina, Marina; Aperia, Anita

    2009-01-01

    Disturbed brain water homeostasis with swelling of astroglial cells is a common complication in stroke, trauma, and meningitis and is considered to be a major cause of permanent brain damage. Astroglial cells possess the water channel aquaporin 4 (AQP4). Recent studies from our laboratory have shown that glutamate, acting on group I metabotropic glutamate receptors (mGluRs), increases the permeability of astrocyte AQP4, which, in situations of hypoxia-ischemia, will increase astrocyte water u...

  1. Gas permeability of nuclear membranes as a function of pore diameter

    International Nuclear Information System (INIS)

    Measurements of He, Xe, Ar, N2 permeability of polyethylene terephthalate (PETP), which pore diameters varied within 1.5-10 nm range by means of loading-unloading cycles, are carried out. For descritpion of experimental data a theoretical model based on solution of a system of interrelated kinetic equations for distribution functions of free and adsorbed gas molecules in a channel is suggested

  2. High Ca2+ permeability of a peptide-gated DEG/ENaC from Hydra

    Science.gov (United States)

    Dürrnagel, Stefan; Falkenburger, Björn H.

    2012-01-01

    Degenerin/epithelial Na+ channels (DEG/ENaCs) are Na+ channels that are blocked by the diuretic amiloride. In general, they are impermeable for Ca2+ or have a very low permeability for Ca2+. We describe here, however, that a DEG/ENaC from the cnidarian Hydra magnipapillata, the Hydra Na+ channel (HyNaC), is highly permeable for Ca2+ (PCa/PNa = 3.8). HyNaC is directly gated by Hydra neuropeptides, and in Xenopus laevis oocytes expressing HyNaCs, RFamides elicit currents with biphasic kinetics, with a fast transient component and a slower sustained component. Although it was previously reported that the sustained component is unselective for monovalent cations, the selectivity of the transient component had remained unknown. Here, we show that the transient current component arises from secondary activation of the Ca2+-activated Cl− channel (CaCC) of Xenopus oocytes. Inhibiting the activation of the CaCC leads to a simple on–off response of peptide-activated currents with no apparent desensitization. In addition, we identify a conserved ring of negative charges at the outer entrance of the HyNaC pore that is crucial for the high Ca2+ permeability, presumably by attracting divalent cations to the pore. At more positive membrane potentials, the binding of Ca2+ to the ring of negative charges increasingly blocks HyNaC currents. Thus, HyNaC is the first member of the DEG/ENaC gene family with a high Ca2+ permeability. PMID:23008433

  3. TRPM2 channel regulates endothelial barrier function.

    Science.gov (United States)

    Hecquet, Claudie M; Ahmmed, Gias U; Malik, Asrar B

    2010-01-01

    Oxidative [Au1]stress, through the production of oxygen metabolites such as hydrogen peroxide[Au2] (H(2)O(2)), increases vascular endothelial permeability and plays a crucial role in several lung diseases. The transient receptor potential (melastatin) 2 (TRPM2) is an oxidant-sensitive, nonselective cation channel that is widely expressed in mammalian tissues, including the vascular endothelium. We have demonstrated the involvement of TRPM2 in mediating oxidant-induced calcium entry and endothelial hyperpermeability in cultured pulmonary artery endothelial cells. Here, we provide evidence that neutrophil activation-dependent increase in endothelial permeability and neutrophil extravasation requires TRPM2 in cultured endothelial cells. In addition, protein kinase Calpha (PKCalpha) that rapidly colocalizes with the short (nonconducting) TRPM2 isoform after exposure to hydrogen peroxide positively regulates calcium entry through the functional TRPM2 channel. Thus, increase in lung microvessel permeability and neutrophil sequestration depends on the activation of endothelial TRPM2 by neutrophilic oxidants and on PKCalpha regulation of TRPM2 channel activity. Manipulating TRPM2 function in the endothelium may represent a novel strategy aimed to prevent oxidative stress-related vascular dysfunction. PMID:20204729

  4. Insight into Enabling Adaptive Management

    Directory of Open Access Journals (Sweden)

    Lorne A. Greig

    2013-09-01

    Full Text Available The U.S. National Commission on Science for Sustainable Forestry recognized a need for effective adaptive management to support management for biological diversity. However, difficulties in implementing adaptive management in the U.S. Northwest Forest Plan led the Commission to wonder if comparisons across multiple adaptive management trials in the forest sector could provide insight into the factors that serve to enable or inhibit adaptive management. This comparison and the resulting discussions among a group of seasoned practitioners, with adaptive management experience at a variety of scales and levels of complexity, led to insights into a hierarchy of ten factors that can serve to either enable or inhibit implementation. Doing high quality adaptive management is about doing good science to enable learning from management experience. Enabling adaptive management though is about working with people to understand their concerns, to develop a common understanding and an environment of trust that allows adaptive management to proceed. Careful attention to enabling factors is critical to fulfilling the promise of adaptive management.

  5. Black holes as bosonic Gaussian channels

    CERN Document Server

    Bradler, Kamil

    2014-01-01

    We identify the quantum channels corresponding to the interaction of a Gaussian quantum state with an already formed Schwarzschild black hole. Using recent advances in the classification of one-mode bosonic Gaussian channels we find that (with one exception) the black hole Gaussian channels lie in the non-entanglement breaking subset of the lossy channels $\\mathcal{C}({\\rm loss})$, amplifying channels $\\mathcal{C}({\\rm amp})$ and classical-noise channels $\\mathcal{B}_2$. We show that the channel parameters depend on the black hole mass and the properties of the potential barrier surrounding it. This classification enables us to calculate the classical and quantum capacity of the black hole and to estimate the quantum capacity where no tractable quantum capacity expression exists today. We discuss these findings in the light of the black hole quantum information loss problem.

  6. Method of positioning channel box

    International Nuclear Information System (INIS)

    Upon measuring the dimension of a channel box by disposing ultrasonic sensors to the uppermost portion of a measuring device main body, the deviation of the channel box from the center of the device main body is detected by measuring the distance betwen the sensors at the uppermost portion of the device main body and the lower end of the channel box for four surfaces simultaneously. The direction and the distance for moving the channel box to the center of the device main body are calculated based on the results to feedback tham for the operation of a fuel exchanger, thereby positioning the channel box upon insertion to the device main body. That is, a fuel assembly loaded with the channel box is gradually brought down being suspended from a crane and the position of the channel box is recognized by the ultrasonic sensors, thereafter, the position of the center is corrected and it is brought down again and the outer dimension is measured. Accurate positioning in a short periodof time is enabled and operator's burden can be mitigated to prevent the danger of indury. (N.H.)

  7. 46 CFR 174.090 - Permeability of spaces.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Permeability of spaces. 174.090 Section 174.090 Shipping... Permeability of spaces. When doing the calculations required in § 174.065— (a) The permeability of a floodable... machinery space is treated as a floodable space must be based on an assumed machinery space permeability...

  8. Relative permeability in dual porosity porous media

    Energy Technology Data Exchange (ETDEWEB)

    Deghmoum, A. [SONATRACH CRD, Boumerdes (Algeria); Tiab, D. [Oklahoma Univ., Norman, OK (United States); Mazouzi, A. [SONATRACH PED (Algeria)

    2000-06-01

    One of the important factors in the field of reservoir simulation of dual-porosity systems is reliable relative permeability data. Laboratory limitations hinder measurements. The real behaviour of naturally fractures reservoirs is not reflected in the reservoir core samples, which as a rule originate from zones without induced or natural fractures. Therefore, it is commonly assumed that the relative permeability of a naturally fractured system is a straight line, which can cause errors. The authors undertook to conduct special core analyses on Berea outcrop core samples, to simulate fracture opening through the cutting of the samples to get different fracture apertures, to study the effects of dual porosity on the shape of capillary pressure curves, and to evaluate absolute and relative permeability, as they are affected by fracture opening. The correlation obtained between absolute permeability and fracture aperture was good, and capillary pressure curves permitted the observation of the effect of dual porosity. High residual oil saturation was present in the matrix, since the fractures became the easiest route for water flow, and this situation prevented the use of unsteady-state tests to measure relative permeability on the samples. Instead, the centrifuge technique was successfully used. A naturally fractured reservoir (NFR), the Tin Fouye Tabankort (TFT) reservoir in Algeria was selected to extend the findings. The site was principally selected due to the availability of naturally fractured cores and published data. Core observations, well test analysis and borehole imager tools were all TFT natural fracture indicators presented in the paper. Representative data of relative permeability was obtained by conducting a displacement test on a full diameter core to solve the laboratory limitations. The correlation between permeability and fracture opening was used to estimate the aperture of natural fractures in TFT reservoir. 17 refs., 2 tabs., 24 figs.

  9. Nanoscale grain boundary channels in fracture cement enhance flow in mudrocks

    Science.gov (United States)

    Landry, Christopher J.; Eichhubl, Peter; Prodanović, Maša.; Wilkins, Scott

    2016-05-01

    Hydrocarbon production from mudrock or shale reservoirs typically exceeds estimates based on mudrock laboratory permeability measurements, with the difference attributed to natural fractures. However, natural fractures in these reservoirs are frequently completely cemented and thus assumed not to contribute to flow. We quantify the permeability of nanoscale grain boundary channels with mean apertures of 50-130 nm in otherwise completely cemented natural fractures of the Eagle Ford Formation and estimate their contribution to production. Using scanning electron imaging of grain boundary channel network geometry and a digital rock physics workflow of image reconstruction and direct flow modeling, we estimate cement permeability to be 38-750 nd, higher than reported permeability of Eagle Ford host rock (~2 nd) based on laboratory measurements. Our results suggest that effective fracture-parallel mudrock permeability can exceed laboratory values by upward of 1 order of magnitude in shale reservoirs of high macroscopic cemented fracture volume fraction.

  10. Fluid extraction across pumping and permeable walls in the viscous limit

    Science.gov (United States)

    Herschlag, G.; Liu, J.-G.; Layton, A. T.

    2016-04-01

    In biological transport mechanisms such as insect respiration and renal filtration, fluid travels along a leaky channel allowing material exchange with systems exterior to the channel. The channels in these systems may undergo peristaltic pumping which is thought to enhance the material exchange. To date, little analytic work has been done to study the effect of pumping on material extraction across the channel walls. In this paper, we examine a fluid extraction model in which fluid flowing through a leaky channel is exchanged with fluid in a reservoir. The channel walls are allowed to contract and expand uniformly, simulating a pumping mechanism. In order to efficiently determine solutions of the model, we derive a formal power series solution for the Stokes equations in a finite channel with uniformly contracting/expanding permeable walls. This flow has been well studied in the case in which the normal velocity at the channel walls is proportional to the wall velocity. In contrast we do not assume flow that is proportional to the wall velocity, but flow that is driven by hydrostatic pressure, and we use Darcy's law to close our system for normal wall velocity. We incorporate our flow solution into a model that tracks the material pressure exterior to the channel. We use this model to examine flux across the channel-reservoir barrier and demonstrate that pumping can either enhance or impede fluid extraction across channel walls. We find that associated with each set of physical flow and pumping parameters, there are optimal reservoir conditions that maximize the amount of material flowing from the channel into the reservoir.

  11. Quasi-superactivation for the classical capacity of quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Gyongyosi, Laszlo, E-mail: gyongyosi@hit.bme.hu [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117, Hungary and Information Systems Research Group, Mathematics and Natural Sciences, Hungarian Ac (Hungary); Imre, Sandor [Quantum Technologies Laboratory, Department of Telecommunications, Budapest University of Technology and Economics, 2 Magyar tudosok krt, Budapest, H-1117 (Hungary)

    2014-12-04

    The superactivation effect has its roots in the extreme violation of additivity of the channel capacity and enables to reliably transmit quantum information over zero-capacity quantum channels. In this work we demonstrate a similar effect for the classical capacity of a quantum channel which previously was thought to be impossible.

  12. Quantitative Permeability Prediction for Anisotropic Porous Media

    Science.gov (United States)

    Sheng, Q.; Thompson, K. E.

    2012-12-01

    Pore-scale modeling as a predictive tool has become an integral to both research and commercial simulation in recent years. Permeability is one of the most important of the many properties that can be simulated. Traditionally, permeability is determined using Darcy's law, based on the assumption that the pressure gradient is aligned with the principal flow direction. However, a wide variety of porous media exhibit anisotropic permeability due to particle orientation or laminated structure. In these types of materials, the direction of fluid flow is not aligned with the pressure gradient (except along the principal directions). Thus, it is desirable to predict the full permeability tensor for anisotropic materials using a first-principles pore-scale approach. In this work, we present a fast method to determine the full permeability tensor and the principal directions using a novel network modeling algorithm. We also test the ability of network modeling (which is an approximate method) to detect anisotropy in various structures. Both computational fluid dynamics (CFD) methods and network modeling have emerged as effective techniques to predict rock properties. CFD models are more rigorous but computationally expensive. Network modeling involves significant approximations but can be orders-of-magnitude more efficient computationally, which is important for both speed and the ability to model larger scales. This work uses network modeling, with simulations performed on two types of anisotropic materials: laminated packings (with layers of different sized particles) and oriented packings (containing particles with preferential orientation). Pore network models are created from the porous media data, and a novel method is used to determine the permeability tensor and principal flow direction using pore network modeling. The method is verified by comparing the calculated principal directions with the known anisotropy and also by comparing permeability with values from CFD

  13. Permeability Evolution and Rock Brittle Failure

    Directory of Open Access Journals (Sweden)

    Sun Qiang

    2015-08-01

    Full Text Available This paper reports an experimental study of the evolution of permeability during rock brittle failure and a theoretical analysis of rock critical stress level. It is assumed that the rock is a strain-softening medium whose strength can be described by Weibull’s distribution. Based on the two-dimensional renormalization group theory, it is found that the stress level λ c (the ratio of the stress at the critical point to the peak stress depends mainly on the homogeneity index or shape parameter m in the Weibull’s distribution for the rock. Experimental results show that the evolution of permeability is closely related to rock deformation stages: the permeability has a rapid increase with the growth of cracks and their surface areas (i.e., onset of fracture coalescence point, and reaches the maximum at rock failure. Both the experimental and analytical results show that this point of rapid increase in permeability on the permeabilitypressure curve corresponds to the critical point on the stress-strain curve; for rock compression, the stress at this point is approximately 80% of the peak strength. Thus, monitoring the evolution of permeability may provide a new means of identifying the critical point of rock brittle fracture

  14. Vascular permeability in cerebral cavernous malformations

    DEFF Research Database (Denmark)

    Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao;

    2015-01-01

    Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observ......Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case......-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability...... correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive...

  15. Permeability variation of bentonite-sand mixture due to shear strain

    International Nuclear Information System (INIS)

    The objective of this study is to investigate the permeability variation of the compacted bentonite-sand mixture, a candidate material to be used in low level radioactive nuclear waste geotechnical disposal facility, due to shear deformation which might occur in the mixture caused by the earthquake and/or the nonuniform deformation in its long term performance. To execute the study systematically, a coupled shear and permeability testing apparatus was firstly developed in which a hollow cylindric specimen and the constant flow pump was adopted. It enabled the authors to measure the permeability along the shear plane in the specimen successfully and rapidly. The result of this study revealed that the permeability of the compacted bentonite-sand mixture with 15% of bentonite was not significantly influenced by the shear deformation. This has tentatively shown the effectiveness of both the new coupled shear and permeability testing apparatus and the bentonite-sand mixture to be used for retarding the radionuclide migration around the radioactive waste repository accompanying water movement

  16. Non-invasive optical modulation of local vascular permeability

    Science.gov (United States)

    Choi, Myunghwan; Choi, Chulhee

    2011-03-01

    For a systemically administered drug to act, it first needs to cross the vascular wall. This step represents a bottleneck for drug development, especially in the brain or retina, where tight junctions between endothelial cells form physiological barriers. Here, we demonstrate that femtosecond pulsed laser irradiation focused on the blood vessel wall induces transient permeabilization of plasma. Nonlinear absorption of the pulsed laser enabled the noninvasive modulation of vascular permeability with high spatial selectivity in three dimensions. By combining this method with systemic injection, we could locally deliver molecular probes in various tissues, such as brain cortex, meninges, ear, striated muscle, and bone. We suggest this method as a novel delivery tool for molecular probes or drugs.

  17. Channel Networks

    Science.gov (United States)

    Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio; Rigon, Riccardo

    This review proceeds from Luna Leopold's and Ronald Shreve's lasting accomplishments dealing with the study of random-walk and topologically random channel networks. According to the random perspective, which has had a profound influence on the interpretation of natural landforms, nature's resiliency in producing recurrent networks and landforms was interpreted to be the consequence of chance. In fact, central to models of topologically random networks is the assumption of equal likelihood of any tree-like configuration. However, a general framework of analysis exists that argues that all possible network configurations draining a fixed area are not necessarily equally likely. Rather, a probability P(s) is assigned to a particular spanning tree configuration, say s, which can be generally assumed to obey a Boltzmann distribution: P(s) % e^-H(s)/T, where T is a parameter and H(s) is a global property of the network configuration s related to energetic characters, i.e. its Hamiltonian. One extreme case is the random topology model where all trees are equally likely, i.e. the limit case for T6 4 . The other extreme case is T 6 0, and this corresponds to network configurations that tend to minimize their total energy dissipation to improve their likelihood. Networks obtained in this manner are termed optimal channel networks (OCNs). Observational evidence suggests that the characters of real river networks are reproduced extremely well by OCNs. Scaling properties of energy and entropy of OCNs suggest that large network development is likely to effectively occur at zero temperature (i.e. minimizing its Hamiltonian). We suggest a corollary of dynamic accessibility of a network configuration and speculate towards a thermodynamics of critical self-organization. We thus conclude that both chance and necessity are equally important ingredients for the dynamic origin of channel networks---and perhaps of the geometry of nature.

  18. A novel approach to characterization of effective permeability for naturally fractured reservoirs

    Science.gov (United States)

    Jin, G.

    2013-12-01

    measurements, and/or well log interpretations. Since the fracture size properties has been taken into account in calculating effective permeability, the proposed approach has the advantage of automatic scaling ability with respect to the element size of the domain. For example, the effective permeability for smaller element size with respect to fracture size reveals higher fluctuation of values, suggesting higher heterogeneity of reservoir property will be modeled. The effective permeability for larger element size respect to average fracture size tends to model the more homogeneous but anisotropic behavior of fluid flow. This approach allows for rapid automated characterization of effective fracture permeability which enables us to stochastically evaluate the existence of equivalent permeability of the fracture network through multiple realizations of DFN modes. Thus by studying the relationships between the calculated effective permeability and average fracture size, one is able to determine the appropriate size of domain to discretize in order to model either the heterogeneity or the average homogeneous behavior of a reservoir. The proposed approach has been applied to modeling the fractured Cambrian-Ordovician Knox dolomite group in the Black Warrior basin in Alabama and the predicted fracture permeability and well injectivities have been supported by the historical well test data.

  19. Hydrogen permeability of nitrided stainless steel

    International Nuclear Information System (INIS)

    The surface of a 316 stainless steel (316SS) specimen was nitrided by an electrochemical treatment in molten fluoride salt. Its hydrogen permeability was evaluated and compared with that of bare 316SS at temperature from 450degC to 650degC. When it was exposed to hydrogen pressure of 1.0 kPa from 450degC to 650degC, its permeability was 7.2×10-11 to 6.4×10-12 mol/sec.m.Pa1/2. The permeation flux was increased with temperature and the permeability is deviated from Sieverts' law around 450degC. It followed Sieverts' law and was similar to that of bare 316SS at elevated temperatures. This result suggested the surface nitriding increases solubility at low temperatures around 450degC. (author)

  20. Food Packaging Permeability Behaviour: A Report

    Directory of Open Access Journals (Sweden)

    Valentina Siracusa

    2012-01-01

    Full Text Available The use of polymer materials in food packaging field is one of the largest growing market area. Actually the optimization behaviour of packaging permeability is of crucial importance, in order to extend the food shelf-life and to reach the best engineering solution. Studying the permeability characterization of the different polymer material (homogeneous and heterogeneous polymer system to the different packaging gases, in different environmental condition, is crucial to understand if the selected material is adapted to the chosen food contact field. Temperature and humidity parameters are of crucial importance for food quality preservation, especially in real life situations, like food market, and house long-life use. The aim of this report was to collect information about the state of the art on the permeability characteristics of the polymer packages used on food field.

  1. Permeability of Hollow Microspherical Membranes to Helium

    Science.gov (United States)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  2. Preventive administration of cromakalim reduces aquaporin-4 expression and blood-brain barrier permeability in a rat model of cerebral ischemia/reperfusion injury

    Institute of Scientific and Technical Information of China (English)

    Shilei Wang; Yanting Wang; Yan Jiang; Qingxian Chang; Peng Wang; Shiduan Wang

    2011-01-01

    Cromakalim, an adenosine triphosphate-sensitive potassium channel opener, exhibits protective effects on cerebral ischemia/reperfusion injury. However, there is controversy as to whether this effect is associated with aquaporin-4 and blood-brain barrier permeability. Immunohistochemistry results show that preventive administration of cromakalim decreased aquaporin-4 and IgG protein expression in rats with ischemia/reperfusion injury; it also reduced blood-brain barrier permeability, and alleviated brain edema, ultimately providing neuroprotection.

  3. Effect of detergents on corneal permeability

    International Nuclear Information System (INIS)

    Changes of corneal permeability for 22Na caused by benzalkonium chloride (BAC) and the Czechoslovak detergent Jar were tested in vitro as well as in vivo. Experiments in vitro were performed on corneas of bovine eyes incubated at 37 degC. During a 10 min span the corneal surface was wetted with nine drops of aqueous solutions of BAC (0.001%, 0.01%, 0.1%, 1% and 10.0%, resp.) and Jar (0.01%, 0.1%, 1.0%, 10.0% and 100.0%, i.e., commercialy available compound, resp.). Changes of corneal permeability caused by detergents were demonstrated by an increaseJ uptake of 22Na transferred from the paper strips stretched over the corneal surface. For the controls, saline was used instead of detergents. The corneal permeability for 22Na increased with increasing detergent concentration. Significant changes of corneal permeability were caused by Jar diluted to 0.01%. Experiments in vivo were carried out on rabbits. Both detergents were tested in above mentioned concetrations using always two drops during a 1 min exposure. The eyes were observed for 6 days. Heavy keratitis with corneal edema, purulent conjunctival discharge and blepharitis was caused by 10% BAC and to a lesser degree also by 1% BAC or undiluted Jar. On the seventh day the permeability of the rabbit corneas was tested applying the paper strips soaked with 22Na. After 30 min the rabbits were dissected and the radioactivity of the isolated tissues and aqueous has been evaluated. After the six days delay the functional changes of the epithelial barrier were still observable manifesting itself by changed permeability and ocular distribution of 22Na. (author)

  4. Density and permeability of a loess soil

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Schjønning, Per; Møldrup, Per;

    2013-01-01

    Pa). Investigated indicators for compression resistance included compression index, precompression stress, and resistance and resilience indices based on measured soil physical properties (bulk density, air-filled porosity, air permeability, and void ratio). Soil resilience was assessed following exposure of...... and air permeability was observed following exposure to FT and WD cycles, with the latter cycle showing higher recovery levels. The OC and ρbi significantly influenced the magnitude of recovery following FT cycles, with ρbi showing contrasting trends on void ratio after both WD and FT cycles. It was...

  5. The Permeability of Rubble Mound Breakwaters

    DEFF Research Database (Denmark)

    Williams, A.F.; Burcharth, H. F.; Adel, H. den

    1992-01-01

    The results of an extensive series of permeability experiments originally analysed by Shih (1990) are reinterpreted in the light of new experiments. It is proposed that the Forchheimer equation might not fully describe flow at the high Reynolds numbers found in the interior of rubble material. A...... new series of tests designed to test for deviations from the Forchheimer equation and investigate the effects of material shape are described. While no evidence can be found to indicate a deviation from the Forchheimer equation a dependency of permeability and the surface roughness the material is...

  6. Ontogeny of rabbit proximal tubule urea permeability

    OpenAIRE

    Quigley, Raymond; LISEC, AMBER; Baum, Michel

    2001-01-01

    Urea transport in the proximal tubule is passive and is dependent on the epithelial permeability. The present study examined the maturation of urea permeability (Purea) in in vitro perfused proximal convoluted tubules (PCT) and basolateral membrane vesicles (BLMV) from rabbit renal cortex. Urea transport was lower in neonatal than adult PCT at both 37 and 25°C. The PCT Purea was also lower in the neonates than the adults (37°C: 45.4 ± 10.8 vs. 88.5 ± 15.2 × 10−6 cm/s, P < 0.05; 25°C: 28.5 ± 6...

  7. Clostridium perfringens Epsilon-Toxin Increases Permeability of Single Perfused Microvessels of Rat Mesentery

    OpenAIRE

    Adamson, R. H.; Ly, J. C.; Fernandez-Miyakawa, M.; Ochi, S; Sakurai, J.; Uzal, F.; Curry, F. E.

    2005-01-01

    Epsilon-toxin, the primary virulence factor of Clostridium perfringens type D, causes mortality in livestock, particularly sheep and goats, in which it induces an often-fatal enterotoxemia. It is believed to compromise the intestinal barrier and then enter the gut vasculature, from which it is carried systemically, causing widespread vascular endothelial damage and edema. Here we used single perfused venular microvessels in rat mesentery, which enabled direct observation of permeability prope...

  8. Nanomaterial-enabled neural stimulation

    OpenAIRE

    Yongchen eWang; Liang eGuo

    2016-01-01

    Neural stimulation is a critical technique in treating neurological diseases and investigating brain functions. Traditional electrical stimulation uses electrodes to directly create intervening electric fields in the immediate vicinity of neural tissues. Second-generation stimulation techniques directly use light, magnetic fields or ultrasound in a non-contact manner. An emerging generation of non- or minimally invasive neural stimulation techniques is enabled by nanotechnology to achieve a h...

  9. Nanomaterial-Enabled Neural Stimulation

    OpenAIRE

    Wang, Yongchen; Guo, Liang

    2016-01-01

    Neural stimulation is a critical technique in treating neurological diseases and investigating brain functions. Traditional electrical stimulation uses electrodes to directly create intervening electric fields in the immediate vicinity of neural tissues. Second-generation stimulation techniques directly use light, magnetic fields or ultrasound in a non-contact manner. An emerging generation of non- or minimally invasive neural stimulation techniques is enabled by nanotechnology to achieve a h...

  10. 'Ethos' Enabling Organisational Knowledge Creation

    Science.gov (United States)

    Matsudaira, Yoshito

    This paper examines knowledge creation in relation to improvements on the production line in the manufacturing department of Nissan Motor Company and aims to clarify embodied knowledge observed in the actions of organisational members who enable knowledge creation will be clarified. For that purpose, this study adopts an approach that adds a first, second, and third-person's viewpoint to the theory of knowledge creation. Embodied knowledge, observed in the actions of organisational members who enable knowledge creation, is the continued practice of 'ethos' (in Greek) founded in Nissan Production Way as an ethical basis. Ethos is knowledge (intangible) assets for knowledge creating companies. Substantiated analysis classifies ethos into three categories: the individual, team and organisation. This indicates the precise actions of the organisational members in each category during the knowledge creation process. This research will be successful in its role of showing the indispensability of ethos - the new concept of knowledge assets, which enables knowledge creation -for future knowledge-based management in the knowledge society.

  11. Current insights into the physiology of the epithelial calcium and magnesium channels

    NARCIS (Netherlands)

    Topala, C.N.

    2008-01-01

    Ion channels are specialized proteins that span the plasma membrane of living cells allowing ion fluxes through this essentially impermeable barrier. Most ion channels show selectivity in that their pores are more permeable to some ions than to others. The development of the patch-clamp technique en

  12. Near-surface permeability in a supraglacial drainage basin on the Llewellyn glacier, Juneau Ice Field, British Columbia

    Directory of Open Access Journals (Sweden)

    L. Karlstrom

    2013-11-01

    Full Text Available Supraglacial channel networks link time varying solar forcing and melt water routing on temperate glaciers. We present measurements of supraglacial channel spacing and network properties on the Juneau Icefield, subsurface water table height, and time variation of hydraulic characteristics including diurnal variability in water temperature. We combine these data with modeling of porous flow in weathered ice to infer near-surface permeability. Estimates are based on an observed phase lag between diurnal water temperature variations and discharge, and independently on measurement of water table surface elevation away from a stream. Both methods predict ice permeability on a 1–10 m scale in the range of 10–10–10–11 m2. These estimates are considerably smaller than common parameterizations of surface water flow on bare ice in the literature, as well as smaller than estimates of snowpack permeability. For supraglacial environments in which porosity/permeability creation in the subsurface is balanced by porous flow of melt water, our methods provide an estimate of microscale hydraulic properties from macroscale, remote observations of supraglacial channel spacing.

  13. High-permeability criterion for BCS classification: segmental/pH dependent permeability considerations.

    Science.gov (United States)

    Dahan, Arik; Miller, Jonathan M; Hilfinger, John M; Yamashita, Shinji; Yu, Lawrence X; Lennernäs, Hans; Amidon, Gordon L

    2010-10-01

    The FDA classifies a drug substance as high-permeability when the fraction of dose absorbed (F(abs)) in humans is 90% or higher. This direct correlation between human permeability and F(abs) has been recently controversial, since the β-blocker sotalol showed high F(abs) (90%) and low Caco-2 permeability. The purpose of this study was to investigate the scientific basis for this disparity between permeability and F(abs). The effective permeabilities (P(eff)) of sotalol and metoprolol, a FDA standard for the low/high P(eff) class boundary, were investigated in the rat perfusion model, in three different intestinal segments with pHs corresponding to the physiological pH in each region: (1) proximal jejunum, pH 6.5; (2) mid small intestine, pH 7.0; and (3) distal ileum, pH 7.5. Both metoprolol and sotalol showed pH-dependent permeability, with higher P(eff) at higher pH. At any given pH, sotalol showed lower permeability than metoprolol; however, the permeability of sotalol determined at pH 7.5 exceeded/matched metoprolol's at pH 6.5 and 7.0, respectively. Physicochemical analysis based on ionization, pK(a) and partitioning of these drugs predicted the same trend and clarified the mechanism behind these observed results. Experimental octanol-buffer partitioning experiments confirmed the theoretical curves. An oral dose of metoprolol has been reported to be completely absorbed in the upper small intestine; it follows, hence, that metoprolol's P(eff) value at pH 7.5 is not likely physiologically relevant for an immediate release dosage form, and the permeability at pH 6.5 represents the actual relevant value for the low/high permeability class boundary. Although sotalol's permeability is low at pH 6.5 and 7.0, at pH 7.5 it exceeds/matches the threshold of metoprolol at pH 6.5 and 7.0, most likely responsible for its high F(abs). In conclusion, we have shown that, in fact, there is no discrepancy between P(eff) and F(abs) in sotalol's absorption; the data emphasize that

  14. Contribution of the Steady State Method to Water Permeability Measurement in Very Low Permeability Porous Media

    OpenAIRE

    Boulin P.F.; Bretonnier P.; Gland N.; Lombard J.M.

    2012-01-01

    Very low permeability geomaterials (order of nanoDarcy (10-21 m2)), such as clay rocks, are of interest for many industrial applications including production from unconventional reserves of oil and gas, CO2 geological storage and deep geological disposal of high-level long-lived radioactive waste. In these last two applications, the efficiency of clay, as a barrier, relies on their very low permeability. Yet, laboratory measurement of low permeability to water (below 100 nD (10-19 m2)) remain...

  15. Channeling experiment

    International Nuclear Information System (INIS)

    Channeling of water flow and tracer transport in real fractures in a granite body at Stripa have been investigated experimentally. The experimental site was located 360 m below the ground level. Two kinds of experiments were performed. In the single hole experiments, 20 cm diameter holes were drilled about 2.5 m into the rock in the plane of the fracture. Specially designed packers were used to inject water into the fracture in 5 cm intervals all along the fracture trace in the hole. The variation of the injection flowrates along the fracture were used to determine the transmissivity variations in the fracture plane. Detailed photographs were taken from inside the hole and the visual fracture aperture was compared with the injection flowrates in the same locations. Geostatistical methods were used to evaluate the results. Five holes were measured in great detail. In addition 7 holes were drilled and scanned by simpler packer systems. A double hole experiment was performed where two parallel holes were drilled in the same fracture plane at nearly 2 m distance. Pressure pulse tests were made between the holes in both directions. Tracers were injected in 5 locations in one hole and monitored for in many locations in the other hole. The single hole experiment and the double hole experiment show that most of the fracture planes are tight but that there are open sections which form connected channels over distances of at least 2 meters. It was also found in the double hole experiment that the investigated fracture was intersected by at least one fracture between the two holes which diverted a large amount of the injected tracers to several distant locations at the tunnel wall. (authours)

  16. Permeable pavement research – Edison, New Jersey

    Science.gov (United States)

    These are the slides for the New York City Concrete Promotional Council Pervious Concrete Seminar presentation. The basis for the project, the monitoring design and some preliminary monitoring data from the permeable pavement parking lot at the Edison Environmental Center are pre...

  17. Altered permeability barrier structure in cholesteatoma matrix

    DEFF Research Database (Denmark)

    Svane-Knudsen, Viggo; Halkier-Sørensen, Lars; Rasmussen, Gurli;

    2002-01-01

    The stratum corneum of the cholesteatoma epithelium comprises the greater part of the cholesteatoma matrix. The permeability barrier that militates against diffusion and penetration of infectious and toxic agents into and through the epithelium is situated here. The multiple long sheets of lamellar...

  18. Tunable permeability of magnetic wires at microwaves

    Energy Technology Data Exchange (ETDEWEB)

    Panina, L.V., E-mail: lpanina@plymouth.ac.uk [National University of Science and Technology, MISiS, Moscow (Russian Federation); Institute for Design Problems in Microelectronics, RAN, Moscow (Russian Federation); Makhnovskiy, D.P. [School of Computing and Mathematics, University of Plymouth (United Kingdom); Morchenko, A.T.; Kostishin, V.G. [National University of Science and Technology, MISiS, Moscow (Russian Federation)

    2015-06-01

    This paper presents the analysis into microwave magnetic properties of magnetic microwires and their composites in the context of applications in wireless sensors and tunable microwave materials. It is demonstrated that the intrinsic permeability of wires has a wide frequency dispersion with relatively large values in the GHz band. In the case of a specific magnetic anisotropy this results in a tunable microwave impedance which could be used for distributed wireless sensing networks in functional composites. The other range of applications is related with developing the artificial magnetic dielectrics with large and tunable permeability. The composites with magnetic wires with a circumferential anisotropy have the effective permeability which differs substantially from unity for a relatively low concentration (less than 10%). This can make it possible to design the wire media with a negative and tunable index of refraction utilising natural magnetic properties of wires. - Highlights: • Applications of magnetic microwires for functional composites and distributed sensor networks are proposed. • Diluted composites with magnetic microwires can demonstrate tunable left-handed properties. • Large microwave permeability combined with a specific magnetic structure lead to a large and sensitive microwave magnetoimpedance. • Microwave magnetoimpedance highly sensitive to temperature is demonstrated.

  19. Programs for the calculi of blocks permeabilities

    International Nuclear Information System (INIS)

    This report studies the stochastic analysis of radionuclide transport. The permeability values of blocks are necessary to do a numeric model for the flux and transport problems in ground soils. The determination of block value by function on grill value is the objective of this program

  20. Magnetic levitation induced by negative permeability

    OpenAIRE

    Rangelov, A. A.

    2011-01-01

    In this paper we study the interaction between a point magnetic dipole and a semi-infinite metamaterial using the method of images. We obtain analytical expressions for the levitation force for an arbitrarily oriented dipole. Surprisingly the maximal levitation force for negative permeability is found to be stronger compared to the case when the dipole is above a superconductor.

  1. Pump and treat in low permeability media

    Energy Technology Data Exchange (ETDEWEB)

    Mackay, D.M. [Univ. of Waterloo, Ontario (Canada)

    1996-08-01

    Pump and Treat (P&T) is a commonly applied technology whose primary promise for the low permeability environments of interest to these technology reviews is almost certainly containment of the problem. Conventional P&T would be expected to offer little promise of complete restoration in such environments, unless very long time frames (decades or centuries) are considered. A variety of approaches have been proposed to enhance the efficiency of P&T; some appear to offer little promise in low or mixed permeability environments, while others may offer more promise (e.g. hydro- or pneumatic-fracturing, which are described elsewhere in this document, and application of vacuum to the extraction well(s), which is a proprietary technology whose promise is currently difficult to assess objectively). Understanding the potential advantages and means of optimizing these enhancement approaches requires more understanding of the basic processes limiting P&T performance in low or mixed permeability media. These efforts are probably also necessary to understand the advantages and means of optimizing many of the very different remedial technologies that may be applicable to low or mixed permeability environments. Finally, since a reasonably certain capability of P&T is containment (i.e. prevention of further migration of contaminants), P&T may generally be required as a sort of safety net around sites at which the alternative technologies are being tested or applied. 23 refs.

  2. Transverse flow in thin superhydrophobic channels

    CERN Document Server

    Feuillebois, Francois; Vinogradova, Olga I

    2010-01-01

    We provide some general theoretical results to guide the optimization of transverse hydrodynamic phenomena in superhydrophobic channels. Our focus is on the canonical micro- and nanofluidic geometry of a parallel-plate channel with an arbitrary two-component (low-slip and high-slip) coarse texture, varying on scales larger than the channel thickness. By analyzing rigorous bounds on the permeability, over all possible patterns, we optimize the area fractions, slip lengths, geometry and orientation of the surface texture to maximize transverse flow. In the case of two aligned striped surfaces, very strong transverse flows are possible. Optimized superhydrophobic surfaces may find applications in passive microfluidic mixing and amplification of transverse electrokinetic phenomena.

  3. Optimized microsystems-enabled photovoltaics

    Science.gov (United States)

    Cruz-Campa, Jose Luis; Nielson, Gregory N.; Young, Ralph W.; Resnick, Paul J.; Okandan, Murat; Gupta, Vipin P.

    2015-09-22

    Technologies pertaining to designing microsystems-enabled photovoltaic (MEPV) cells are described herein. A first restriction for a first parameter of an MEPV cell is received. Subsequently, a selection of a second parameter of the MEPV cell is received. Values for a plurality of parameters of the MEPV cell are computed such that the MEPV cell is optimized with respect to the second parameter, wherein the values for the plurality of parameters are computed based at least in part upon the restriction for the first parameter.

  4. Cosmological science enabled by Planck

    OpenAIRE

    White, Martin

    2006-01-01

    Planck will be the first mission to map the entire cosmic microwave background (CMB) sky with mJy sensitivity and resolution better than 10'. The science enabled by such a mission spans many areas of astrophysics and cosmology. In particular it will lead to a revolution in our understanding of primary and secondary CMB anisotropies, the constraints on many key cosmological parameters will be improved by almost an order of magnitude (to sub-percent levels) and the shape and amplitude of the ma...

  5. Deviation of permeable coarse-grained boundary resistance from Nikuradse's observations

    Science.gov (United States)

    Cheng, Nian-Sheng; Liu, Xingnian; Chen, Xingwei; Qiao, Changkai

    2016-02-01

    Nikuradse's (1933) rough pipe study is enormously influential in the understanding of flow resistance over a sediment bed. However, the rough boundary employed in Nikuradse's study differs from permeable sediment beds in rivers. This implies that the results derived from the rough pipe experiments may not be applicable for flows over a permeable coarse-grained bed. The present study aimed to explore to what extent the flow resistance of a permeable coarse-grained boundary deviates from the Nikuradse's observations. Experiments were conducted with rough pipes, which were prepared by overlaying the inner wall with one to four layers of spherical beads. The single layer roughness resembles the experimental setup reported in Nikuradse's study, while the multilayer of grains allows significant flow to pass through the porous roughness layer. In addition, the ratio of grain diameter, k, to pipe diameter, d, was chosen to be one to two orders greater than the range (0.001 open channel resistance in the presence of large-scale roughness. The measurements also suggest the existence of a laminar flow regime, in which the friction factor is inversely proportional to the Reynolds number. The observed variations in the flow resistance are attributed to both wall permeability and large-scale roughness.

  6. Regulation of Aquaporin Z osmotic permeability in ABA tri-block copolymer

    Directory of Open Access Journals (Sweden)

    Wenyuan Xie

    2015-08-01

    Full Text Available Aquaporins are transmembrane water channel proteins present in biological plasma membranes that aid in biological water filtration processes by transporting water molecules through at high speeds, while selectively blocking out other kinds of solutes. Aquaporin Z incorporated biomimetic membranes are envisaged to overcome the problem of high pressure needed, and holds great potential for use in water purification processes, giving high flux while keeping energy consumption low. The functionality of aquaporin Z in terms of osmotic permeability might be regulated by factors such as pH, temperature, crosslinking and hydrophobic thickness of the reconstituted bilayers. Hence, we reconstituted aquaporin Z into vesicles that are made from a series of amphiphilic block copolymers PMOXA-PDMS-PMOXAs with various hydrophobic molecular weights. The osmotic permeability of aquaporin Z in these vesicles was determined through a stopped-flow spectroscopy. In addition, the temperature and pH value of the vesicle solutions were adjusted within wide ranges to investigate the regulation of osmotic permeability of aquaporin Z through external conditions. Our results show that aquaporin Z permeability was enhanced by hydrophobic mismatch. In addition, the water filtration mechanism of aquaporin Z is significantly affected by the concentration of H+ and OH- ions.

  7. Identification of the outer membrane porin of Thermus thermophilus HB8: the channel-forming complex has an unusually high molecular mass and an extremely large single-channel conductance.

    Science.gov (United States)

    Maier, E; Polleichtner, G; Boeck, B; Schinzel, R; Benz, R

    2001-01-01

    The outer membrane of the thermophilic bacterium Thermus thermophilus was isolated using sucrose step gradient centrifugation. Its detergent extracts contained an ion-permeable channel with an extremely high single-channel conductance of 20 nS in 1 M KCl. The channel protein was purified by preparative sodium dodecyl sulfate (SDS)-polyacylamide gel electrophoresis. It has a high molecular mass of 185 kDa, and its channel-forming ability resists boiling in SDS for 10 min. PMID:11133980

  8. Identification of the Outer Membrane Porin of Thermus thermophilus HB8: the Channel-Forming Complex Has an Unusually High Molecular Mass and an Extremely Large Single-Channel Conductance

    OpenAIRE

    Maier, Elke; Polleichtner, Georg; Boeck, Birgit; Schinzel, Reinhard; Benz, Roland

    2001-01-01

    The outer membrane of the thermophilic bacterium Thermus thermophilus was isolated using sucrose step gradient centrifugation. Its detergent extracts contained an ion-permeable channel with an extremely high single-channel conductance of 20 nS in 1 M KCl. The channel protein was purified by preparative sodium dodecyl sulfate (SDS)-polyacylamide gel electrophoresis. It has a high molecular mass of 185 kDa, and its channel-forming ability resists boiling in SDS for 10 min.

  9. A Novel Empirical Equation for Relative Permeability in Low Permeability Reservoirs☆

    Institute of Scientific and Technical Information of China (English)

    Yulei Ge; Shurong Li; Kexin Qu

    2014-01-01

    In this paper, a novel empirical equation is proposed to calculate the relative permeability of low permeability res-ervoir. An improved item is introduced on the basis of Rose empirical formula and Al-Fattah empirical formula, with one simple model to describe oil/water relative permeability. The position displacement idea of bare bones particle swarm optimization is applied to change the mutation operator to improve the RNA genetic algorithm. The param-eters of the new empirical equation are optimized with the hybrid RNA genetic algorithm (HRGA) based on the ex-perimental data. The data is obtained from a typical low permeability reservoir wel 54 core 27-1 in GuDong by unsteady method. We carry out matlab programming simulation with HRGA. The comparison and error analysis show that the empirical equation proposed is more accurate than the Rose empirical formula and the exponential model. The generalization of the empirical equation is also verified.

  10. Nanomaterial-Enabled Neural Stimulation.

    Science.gov (United States)

    Wang, Yongchen; Guo, Liang

    2016-01-01

    Neural stimulation is a critical technique in treating neurological diseases and investigating brain functions. Traditional electrical stimulation uses electrodes to directly create intervening electric fields in the immediate vicinity of neural tissues. Second-generation stimulation techniques directly use light, magnetic fields or ultrasound in a non-contact manner. An emerging generation of non- or minimally invasive neural stimulation techniques is enabled by nanotechnology to achieve a high spatial resolution and cell-type specificity. In these techniques, a nanomaterial converts a remotely transmitted primary stimulus such as a light, magnetic or ultrasonic signal to a localized secondary stimulus such as an electric field or heat to stimulate neurons. The ease of surface modification and bio-conjugation of nanomaterials facilitates cell-type-specific targeting, designated placement and highly localized membrane activation. This review focuses on nanomaterial-enabled neural stimulation techniques primarily involving opto-electric, opto-thermal, magneto-electric, magneto-thermal and acousto-electric transduction mechanisms. Stimulation techniques based on other possible transduction schemes and general consideration for these emerging neurotechnologies are also discussed. PMID:27013938

  11. Nanomaterial-enabled neural stimulation

    Directory of Open Access Journals (Sweden)

    Yongchen eWang

    2016-03-01

    Full Text Available Neural stimulation is a critical technique in treating neurological diseases and investigating brain functions. Traditional electrical stimulation uses electrodes to directly create intervening electric fields in the immediate vicinity of neural tissues. Second-generation stimulation techniques directly use light, magnetic fields or ultrasound in a non-contact manner. An emerging generation of non- or minimally invasive neural stimulation techniques is enabled by nanotechnology to achieve a high spatial resolution and cell-type specificity. In these techniques, a nanomaterial converts a remotely transmitted primary stimulus such as a light, magnetic or ultrasonic signal to a localized secondary stimulus such as an electric field or heat to stimulate neurons. The ease of surface modification and bio-conjugation of nanomaterials facilitates cell-type-specific targeting, designated placement and highly localized membrane activation. This review focuses on nanomaterial-enabled neural stimulation techniques primarily involving opto-electric, opto-thermal, magneto-electric, magneto-thermal and acousto-electric transduction mechanisms. Stimulation techniques based on other possible transduction schemes and general consideration for these emerging neurotechnologies are also discussed.

  12. Enabling Exploration Through Docking Standards

    Science.gov (United States)

    Hatfield, Caris A.

    2012-01-01

    Human exploration missions beyond low earth orbit will likely require international cooperation in order to leverage limited resources. International standards can help enable cooperative missions by providing well understood, predefined interfaces allowing compatibility between unique spacecraft and systems. The International Space Station (ISS) partnership has developed a publicly available International Docking System Standard (IDSS) that provides a solution to one of these key interfaces by defining a common docking interface. The docking interface provides a way for even dissimilar spacecraft to dock for exchange of crew and cargo, as well as enabling the assembly of large space systems. This paper provides an overview of the key attributes of the IDSS, an overview of the NASA Docking System (NDS), and the plans for updating the ISS with IDSS compatible interfaces. The NDS provides a state of the art, low impact docking system that will initially be made available to commercial crew and cargo providers. The ISS will be used to demonstrate the operational utility of the IDSS interface as a foundational technology for cooperative exploration.

  13. A relative permeability modifier for water control of gas wells in a low-permeability reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Chen Tielong; Zhao Yong; Peng Kezong; Pu Wanfeng

    1996-08-01

    Water control in gas wells is a major measure to enhance gas recovery. The work is concentrated on finding a highly selective polymer to reduce water production without affecting gas production from gas wells in low-permeability reservoirs. This paper presents the conceptions of residual resistance factors (RRF`s) to both wetting and non-wetting phases and the laboratory experimental and field trial results of relative permeability modifiers for water control in gas wells.

  14. Considerations about the internodal permeability evaluation in reservoir simulation

    Energy Technology Data Exchange (ETDEWEB)

    Cordazzo, Jonas; Maliska, Clovis R. [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. Computacional de Dinamica dos Fluidos]. E-mails: jonas@sinmec.ufsc.br; maliska@sinmec.ufsc.br; Romeu, Regis K. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas]. E-mail: regis@cenpes.petrobras.com.br

    2003-07-01

    This work reports some numerical problems caused by the using of harmonic average in the inter nodal permeability calculation during the petroleum reservoir simulation. This paper begins with a brief review, showing, in the sequence the approach used by commercial simulators in interpreting the permeability map. Then, the results of using harmonic averaging to determine the inter nodal permeability are presented by solving the 2D chessboard problem. Finally, the Element-based Finite Volume Method (EbFVM) is analyzed considering the permeability evaluation. It is demonstrated that this method, besides dealing with triangular and quadrilateral elements, can also deal with the permeability map without averaging. The two possibilities of storing the physical properties and their implications in the permeability evaluation are addressed. The permeability storage in the center of the elements, instead of in the center of control volumes, avoids the need of weighting the permeability values in the interfaces of the control volumes. (author)

  15. Moisture Durability of Vapor Permeable Insulating Sheathing (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2013-10-01

    In this project, Building America team Building Science Corporation researched some of the ramifications of using exterior, vapor permeable insulation on retrofit walls with vapor permeable cavity insulation. Retrofit strategies are a key factor in reducing exterior building stock consumption.

  16. Quantitative Prediction of Structural Fractures in Low Permeability Reservoir

    Institute of Scientific and Technical Information of China (English)

    Zeng Lianbo; Tian Chonglu

    1996-01-01

    @@ Low -permeability fractured reservoirs will become increasingly prominent along with the enhanced exploration extent and the emerging moderate-high water content in most of the moderate-high permeability reservoirs of the oil fields in eastern China.

  17. TRP Channels in Respiratory Pathophysiology: The Role of Oxidative, Chemical Irritant and Temperature Stimuli

    OpenAIRE

    Zholos, Alexander V.

    2015-01-01

    There is rapidly growing evidence indicating multiple and important roles of Ca2+-permeable cation TRP channels in the airways, both under normal and disease conditions. The aim of this review was to summarize the current knowledge of TRP channels in sensing oxidative, chemical irritant and temperature stimuli by discussing expression and function of several TRP channels in relevant cell types within the respiratory tract, ranging from sensory neurons to airway smooth muscle and epithelial ce...

  18. The SecY complex forms a channel capable of ionic discrimination

    OpenAIRE

    Dalal, Kush; Duong, Franck

    2009-01-01

    Protein translocation across the bacterial membrane occurs at the SecY complex or channel. The resting SecY channel is impermeable to small molecules owing to a plug domain that creates a seal. Here, we report that a channel loosely sealed, or with a plug locked open, does not, however, lead to general membrane permeability. Instead, strong selectivity towards small monovalent anions, especially chloride, is observed. Mutations in the pore ring-structure increase both the translocation activi...

  19. Sex differences in neuroprotection provided by inhibition of TRPM2 channels following experimental stroke

    OpenAIRE

    Jia, Jia; Verma, Saurabh; Nakayama, Shin; Quillinan, Nidia; Grafe, Marjorie R; Hurn, Patricia D.; Herson, Paco S.

    2011-01-01

    The calcium-permeable transient receptor potential M2 (TRPM2) ion channel is activated following oxidative stress and has been implicated in ischemic damage; however, little experimental evidence exists linking TRPM2 channel activation to damage following cerebral ischemia. We directly assessed the involvement of TRPM2 channels in ischemic brain injury using pharmacological inhibitors and short-hairpin RNA (shRNA)-mediated knockdown of TRPM2 expression. Each of the four TRPM2 inhibitors teste...

  20. Pannexin 1 channels in skeletal muscles

    Science.gov (United States)

    Cea, Luis A.; Riquelme, Manuel A.; Vargas, Anibal A.; Urrutia, Carolina; Sáez, Juan C.

    2014-01-01

    Normal myotubes and adult innervated skeletal myofibers express the glycoprotein pannexin1 (Panx1). Six of them form a “gap junction hemichannel-like” structure that connects the cytoplasm with the extracellular space; here they will be called Panx1 channels. These are poorly selective channels permeable to ions, small metabolic substrate, and signaling molecules. So far little is known about the role of Panx1 channels in muscles but skeletal muscles of Panx1−/− mice do not show an evident phenotype. Innervated adult fast and slow skeletal myofibers show Panx1 reactivity in close proximity to dihydropyridine receptors in the sarcolemma of T-tubules. These Panx1 channels are activated by electrical stimulation and extracellular ATP. Panx1 channels play a relevant role in potentiation of muscle contraction because they allow release of ATP and uptake of glucose, two molecules required for this response. In support of this notion, the absence of Panx1 abrogates the potentiation of muscle contraction elicited by repetitive electrical stimulation, which is reversed by exogenously applied ATP. Phosphorylation of Panx1 Thr and Ser residues might be involved in Panx1 channel activation since it is enhanced during potentiation of muscle contraction. Under denervation, Panx1 levels are upregulated and this partially explains the reduction in electrochemical gradient, however its absence does not prevent denervation-induced atrophy but prevents the higher oxidative state. Panx1 also forms functional channels at the cell surface of myotubes and their functional state has been associated with intracellular Ca2+ signals and regulation of myotube plasticity evoked by electrical stimulation. We proposed that Panx1 channels participate as ATP channels and help to keep a normal oxidative state in skeletal muscles. PMID:24782784

  1. Context-Enabled Business Intelligence

    Energy Technology Data Exchange (ETDEWEB)

    Troy Hiltbrand

    2012-04-01

    To truly understand context and apply it in business intelligence, it is vital to understand what context is and how it can be applied in addressing organizational needs. Context describes the facets of the environment that impact the way that end users interact with the system. Context includes aspects of location, chronology, access method, demographics, social influence/ relationships, end-user attitude/ emotional state, behavior/ past behavior, and presence. To be successful in making Business Intelligence content enabled, it is important to be able to capture the context of use user. With advances in technology, there are a number of ways in which this user based information can be gathered and exposed to enhance the overall end user experience.

  2. Transmembrane dynamics of the Thr-5 phosphorylated sarcolipin pentameric channel.

    Science.gov (United States)

    Cao, Yipeng; Wu, Xue; Wang, Xinyu; Sun, Haiying; Lee, Imshik

    2016-08-15

    Sarcolipin (SLN), an important membrane protein expressed in the sarcoplasmic reticulum (SR), regulates muscle contractions in cardiac and skeletal muscle. The phosphorylation at amino acid Thr5 of the SLN protein modulates the amount of Ca(2+) that passes through the SR. Using molecular dynamics simulation, we evaluated the phosphorylation at Thr5 of pentameric SLN (phospho-SLN) channel's energy barrier and pore characteristics by calculating the potential of mean force (PMF) along the channel pore and determining the diffusion coefficient. The results indicate that pentameric phospho-SLN promotes penetration of monovalent and divalent ions through the channel. The analysis of PMF, pore radius and diffusion coefficient indicates that Leu21 is the hydrophobic gate of the pentameric SLN channel. In the channel, water molecules near the Leu21 pore demonstrated a clear hydrated-dehydrated transition; however, the mutation of Leu21 to an Alanine (L21A) destroyed the hydrated-dehydrated transitions. These water-dynamic behaviors and PMF confirm that Leu21 is the key residue that regulates the ion permeability of the pentameric SLN channel. These results provide the structural-basis insights and molecular-dynamic information that are needed to understand the regulatory mechanisms of ion permeability in the pentameric SLN channel. PMID:27378083

  3. Theoretical and computational studies of microscopic water channels

    Science.gov (United States)

    Zhu, Fangqiang

    Water channels are ubiquitous in all life forms. A notable example is aquaporins (AQPs), a family of proteins which mainly function as passive water channels in cell membranes. The availability of the crystal structures of several AQPs in recent years allowed us to study them in atomic details. We performed molecular dynamics (MD) simulations on AQPs in lipid bilayers to study water permeation through these channels. We also simulated water conduction in carbon nanotubes, serving as simplified models for biological channels. We developed theories and methodologies aimed to reproduce and predict important experimental quantities of water channels from simulations. We showed that the diffusion permeability (pd), which is measured by tracer diffusion in experiments, can be calculated from equilibrium MD simulations. In order to calculate the osmotic permeability (p f), which is experimentally measured in the presence of a solute concentration difference, we developed a method to induce a hydrostatic pressure difference across the membrane under periodic boundary conditions. We calculated the osmotic permeability for aquaporin-1 using this method, which agrees with experiments. Using a continuous-time random-walk model, we showed that for single-file water channels, the ratio of p f to pd is roughly equal to the number of water molecules in the channel. Proton transfer through single water file was studied theoretically using network thermodynamics. Finally, we proposed a new model for general water channels, which gives a quantitative relationship between water permeations under equilibrium and non-equilibrium conditions, and therefore allows one to calculate pf from equilibrium MD simulations.

  4. 21 CFR 876.5860 - High permeability hemodialysis system.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false High permeability hemodialysis system. 876.5860... (CONTINUED) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Therapeutic Devices § 876.5860 High permeability hemodialysis system. (a) Identification. A high permeability hemodialysis system is a device intended for...

  5. 46 CFR 172.185 - Permeability of spaces.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Permeability of spaces. 172.185 Section 172.185 Shipping... Under Subchapter O of This Chapter § 172.185 Permeability of spaces. (a) When doing the calculations required in § 172.170, the permeability of a floodable space other than a machinery space must be as...

  6. Determination of permeability using fractal method for porous media

    Institute of Scientific and Technical Information of China (English)

    施明恒; 陈永平

    2001-01-01

    A theoretical formulation was developed to express permeability as a function of different fractal dimensions and other scales for porous media . The effective fractal void ratio, the spectral dimension and the fractal dimension of particle mass distribution were introduced. The permeabilities for different soils in China are calculated. The predicted permeability for rice soil was compared with the measured data available in literature.

  7. 46 CFR 172.140 - Permeability of spaces.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Permeability of spaces. 172.140 Section 172.140 Shipping... Subchapter O of This Chapter § 172.140 Permeability of spaces. (a) When doing the calculations required in § 172.130, the permeability of a floodable space other than a machinery space must be as listed in...

  8. Degradation of permeability resistance of high strength concrete after combustion

    Institute of Scientific and Technical Information of China (English)

    Min LI; Hongtao KAO; Chunxiang QIAN

    2008-01-01

    To evaluate the remaining durability of con-crete materials after combustion, the permeability of high strength concrete (HSC) after combustion was studied. The transport behavior of chloride ion, water and air in concrete after combustion and the effect of temperature, strength grade, and aggregation on the permeability of HSC after combustion are investigated by chloride ion permeability coefficient (Dc), water permeability coef-ficient (Dw) and air permeability coefficient (Da). The experiment results show that all three permeability coeffi-cients commendably reflect changes of permeability. The permeability coefficient increases with the evaluation tem-perature. After the same temperature, the permeability coefficient of HSC is lower than that of normal strength concrete (NSC). However, the degree of degradation of permeability coefficient of HSC is greater than that of NSC. The permeability resistance of HSC containing limestone is better than that of HSC containing basalt. Combining changes of compressive strength and per-meability, the remaining durability of concrete materials after combustion is appropriately evaluated.

  9. Tuning PAK Activity to Rescue Abnormal Myelin Permeability in HNPP.

    Science.gov (United States)

    Hu, Bo; Arpag, Sezgi; Zhang, Xuebao; Möbius, Wiebke; Werner, Hauke; Sosinsky, Gina; Ellisman, Mark; Zhang, Yang; Hamilton, Audra; Chernoff, Jonathan; Li, Jun

    2016-09-01

    Schwann cells in the peripheral nervous systems extend their membranes to wrap axons concentrically and form the insulating sheath, called myelin. The spaces between layers of myelin are sealed by myelin junctions. This tight insulation enables rapid conduction of electric impulses (action potentials) through axons. Demyelination (stripping off the insulating sheath) has been widely regarded as one of the most important mechanisms altering the action potential propagation in many neurological diseases. However, the effective nerve conduction is also thought to require a proper myelin seal through myelin junctions such as tight junctions and adherens junctions. In the present study, we have demonstrated the disruption of myelin junctions in a mouse model (Pmp22+/-) of hereditary neuropathy with liability to pressure palsies (HNPP) with heterozygous deletion of Pmp22 gene. We observed a robust increase of F-actin in Pmp22+/- nerve regions where myelin junctions were disrupted, leading to increased myelin permeability. These abnormalities were present long before segmental demyelination at the late phase of Pmp22+/- mice. Moreover, the increase of F-actin levels correlated with an enhanced activity of p21-activated kinase (PAK1), a molecule known to regulate actin polymerization. Pharmacological inhibition of PAK normalized levels of F-actin, and completely prevented the progression of the myelin junction disruption and nerve conduction failure in Pmp22+/- mice. Our findings explain how abnormal myelin permeability is caused in HNPP, leading to impaired action potential propagation in the absence of demyelination. We call it "functional demyelination", a novel mechanism upstream to the actual stripping of myelin that is relevant to many demyelinating diseases. This observation also provides a potential therapeutic approach for HNPP. PMID:27583434

  10. Permittivity and permeability tensors for cloaking applications

    CERN Document Server

    Choudhury, Balamati; Jha, Rakesh Mohan

    2016-01-01

    This book is focused on derivations of analytical expressions for stealth and cloaking applications. An optimal version of electromagnetic (EM) stealth is the design of invisibility cloak of arbitrary shapes in which the EM waves can be controlled within the cloaking shell by introducing a prescribed spatial variation in the constitutive parameters. The promising challenge in design of invisibility cloaks lies in the determination of permittivity and permeability tensors for all the layers. This book provides the detailed derivation of analytical expressions of the permittivity and permeability tensors for various quadric surfaces within the eleven Eisenhart co-ordinate systems. These include the cylinders and the surfaces of revolutions. The analytical modeling and spatial metric for each of these surfaces are provided along with their tensors. This mathematical formulation will help the EM designers to analyze and design of various quadratics and their hybrids, which can eventually lead to design of cloakin...

  11. Permeability of protective coatings to tritium

    International Nuclear Information System (INIS)

    The permeability of four protective coatings to tritium gas and tritiated water was investigated. The coatings, including two epoxies, one vinyl and one urethane, were selected for their suitability in CANDU plant service in Ontario Hydro. Sorption rates of tritium gas into the coatings were considerably larger than for tritiated water, by as much as three to four orders of magnitude. However, as a result of the very large solubility of tritiated water in the coatings, the overall permeability to tritium gas and tritiated water is comparable. Marked differences were also evident among the four coatings, the vinyl exhibiting an abnormally high retention of free water because of a highly porous surface structure. It appears that epoxy coatings having a high pigment-to-binder ratio are most suited for coating concrete in tritium handling facilities

  12. Electrostatically gated membrane permeability in inorganic protocells

    Science.gov (United States)

    Li, Mei; Harbron, Rachel L.; Weaver, Jonathan V. M.; Binks, Bernard P.; Mann, Stephen

    2013-06-01

    Although several strategies are now available to produce functional microcompartments analogous to primitive cell-like structures, little progress has been made in generating protocell constructs with self-controlled membrane permeability. Here we describe the preparation of water-dispersible colloidosomes based on silica nanoparticles and delineated by a continuous semipermeable inorganic membrane capable of self-activated, electrostatically gated permeability. We use crosslinking and covalent grafting of a pH-responsive copolymer to generate an ultrathin elastic membrane that exhibits selective release and uptake of small molecules. This behaviour, which depends on the charge of the copolymer coronal layer, serves to trigger enzymatic dephosphorylation reactions specifically within the protocell aqueous interior. This system represents a step towards the design and construction of alternative types of artificial chemical cells and protocell models based on spontaneous processes of inorganic self-organization.

  13. Permeability imaging in pediatric brain tumors

    OpenAIRE

    Lam, Sandi; Lin, Yimo; Warnke, Peter C.

    2014-01-01

    While traditional computed tomography (CT) and magnetic resonance (MR) imaging illustrate the structural morphology of brain pathology, newer, dynamic imaging techniques are able to show the movement of contrast throughout the brain parenchyma and across the blood-brain barrier (BBB). These data, in combination with pharmacokinetic models, can be used to investigate BBB permeability, which has wide-ranging applications in the diagnosis and management of central nervous system (CNS) tumors in ...

  14. Effective Permeability of Hydrofractured Sedimentary Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Wangen, Magnus

    2002-02-01

    Natural hydrofracturing is studied numerically with a 1-D model where overpressure build-up is due to expulsion of fluids from porosity reduction. The porosity is assumed given as a function of depth. This assumption covers compaction processes controlled by temperature. It is therefore nothing in the model, except for hydrofracturing, that prevents the fluid pressure flow exceeding the lithostatic pressure because there is no feedback from the pressure on the compaction. Three aspects of the hydrofracture process are accounted for in the model: 1) a fracture criterion 2) permeability enhancement, 3) fracture sealing. The hydrofracturing is triggered when the fluid pressure exceeds a given fraction of the lithostatic pressure. Hydrofracturing is modeled by increasing the bulk permeability of the rock by a given factor, (the fracture factor). Sealing of the fractures is modeled by letting the fracture factor decay towards 1 by a given half life. Hydrofracturing is studied with three cases which are different with respect to the maximum fracture factor and the half life for fracture healing. The cases show that a large maximum fracture factor gives less amplitude in the oscillatory fluid pressure than a smaller maximum fracture factor. A long half life is shown to produce smaller amplitudes in the pressure oscillations than a short half life, because the permeability enhancement lasts longer. An important result in this study is that the fluid pressure is intermittent during hydrofracturing, but not the fluid flow. This is a direct consequence of the compaction model used, where the porosity is controlled by depth. The numerical case studies show that hydrofractured depth intervals are characterized by a gravity number close to 1. This observation is used to derive an estimate for the permeability of hydrofractured sediments. (author)

  15. Nonlinear effective pressure law for permeability

    Science.gov (United States)

    Li, M.; Xiao, W.-L.; Bernabé, Y.; Zhao, J.-Z.

    2014-01-01

    The permeability k of porous rocks is known to vary with confining pressure pc and pore fluid pressure pf. But it is, in principle, possible to replace the two-variable function k(pf, pc) by a function k(peff) of a single variable, peff(pf, pc), called the effective pressure. Our goal in this paper is to establish an experimental method for determining a possibly nonlinear, effective pressure law (EPL) for permeability, i.e., find the function κs(pf, pc) such that the effective pressure is given by peff = pc - κs(pf, pc) pf. We applied this method to a set of 26 sandstone cores from various hydrocarbon reservoirs in China. We found that κs greatly varied, from sample to sample, in magnitude and range, sometimes even reaching theoretically prohibited values (i.e., greater than 1 or lower than porosity). One interesting feature of κs(pf, pc) is that it could be approximately described in all rocks but one as a decreasing function κs(pc - pf) of Terzaghi's differential pressure. We also investigated the dependence of permeability on peff for each of our samples. Three models from the literature, i.e., exponential (E), power law (P), and the Walsh model (W), were tested. The (W) model was more likely to fit the experimental data of cores with a high pressure dependence of permeability whereas (E) occurred more frequently in low-pressure-sensitive rocks. Finally, we made various types of two- and three-dimensional microstructural observations that generally supported the trend mentioned above.

  16. Thermal cycling: impact on bentonite permeability

    OpenAIRE

    Zihms, S.G.; Harrington, J. F.

    2015-01-01

    Due to its favourable properties, in particular, low permeability and swelling capacity, bentonite has been favoured as an engineered-barrier and backfill material for the geological storage of radioactive waste. To ensure its safe long-term performance it is important to understand any changes in these properties when the material is subject to heat-emitting waste. As such, this study investigates the hydraulic response of bentonite under multi-step thermal loading subject to a constant-volu...

  17. A Reconciliation of Packed Column Permeability Data: Column Permeability as a Function of Particle Porosity

    Directory of Open Access Journals (Sweden)

    Hubert M. Quinn

    2014-01-01

    Full Text Available In his textbook teaching of packed bed permeability, Georges Guiochon uses mobile phase velocity as the fluid velocity term in his elaboration of the Darcy permeability equation. Although this velocity frame makes a lot of sense from a thermodynamic point of view, it is valid only with respect to permeability at a single theoretical boundary condition. In his more recent writings, however, Guiochon has departed from his long-standing mode of discussing permeability in terms of the Darcy equation and has embraced the well-known Kozeny-Blake equation. In this paper, his teaching pertaining to the constant in the Kozeny-Blake equation is examined and, as a result, a new correlation coefficient is identified and defined herein based on the velocity frame used in his teaching. This coefficient correlates pressure drop and fluid velocity as a function of particle porosity. We show that in their experimental protocols, Guiochon et al. have not adhered to a strict material balance of permeability which creates a mismatch of particle porosity and leads to erroneous conclusions regarding the value of the permeability coefficient in the Kozeny-Blake equation. By correcting the experimental data to properly reflect particle porosity we reconcile the experimental results of Guiochon and Giddings, resulting in a permeability reference chart which is presented here for the first time. This reference chart demonstrates that Guiochon’s experimental data, when properly normalized for particle porosity and other related discrepancies, corroborates the value of 267 for the constant in the Kozeny-Blake equation which was derived by Giddings in 1965.

  18. General teleportation as a quantum channel

    International Nuclear Information System (INIS)

    Teleportation is viewed as a quantum channel. We present an explicit expression for the general teleportation channel in the Kraus decomposition form. We then analyse optimal teleportation procedures for a noisy entangled resource, Bell measurement by the sender and arbitrary operations by the receiver. Our general result allows us to derive the corresponding quantum channel and fidelity, thereby enabling us to formulate the fidelity-based optimization problem and to conclude that this is a problem of semidefinite programming. We offer an alternative viewpoint on optimal teleportation, namely one can perform corrective operations at the receiver's side instead of first manipulating entanglement, and we give an optimal teleportation strategy

  19. Permeability restoration in underground disposal reservoirs

    International Nuclear Information System (INIS)

    The aim of the research performed was to explore methods of permeability restoration in underground disposal reservoirs that may improve the receptive capacity of a well to a level that will allow continued use of the disposal zone without resorting to elevated injection pressures. The laboratory investigation employed a simulated open-hole completion in a disposal well wherein the entire formation face is exposed to the well bore. Cylindrical core samples from representative reservoir rocks through which a central vertical opening or borehole had been drilled were injected with a liquid waste obtained from a chemical manufacturing plant. This particular waste material was found to have a moderate plugging effect when injected into samples of reservoir rocks in a prior study. A review was made of the chemical considerations that might account for the reduction of permeability in waste injection. Purpose of this study was to ascertain the conditions under which the precipitation of certain compounds might occur in the injection of the particular waste liquid employed. A summary of chemical calculations is contained in Appendix B. The data may be useful in the treatment of wastes prior to injection and in the design of restoration procedures where analyses of waste liquids and interstitial materials are available. The results of permeability restoration tests were analyzed mathematically by curve-fitting techniques performed by a digital computer. A summary of the analyses is set forth in the discussion of test results and examples of computer printouts are included in Appendix A

  20. The solubility-permeability interplay: mechanistic modeling and predictive application of the impact of micellar solubilization on intestinal permeation.

    Science.gov (United States)

    Miller, Jonathan M; Beig, Avital; Krieg, Brian J; Carr, Robert A; Borchardt, Thomas B; Amidon, Gregory E; Amidon, Gordon L; Dahan, Arik

    2011-10-01

    Surfactants are routinely employed to increase the apparent aqueous solubility of poorly soluble drugs. Yet the impact of micellar solubilization on the intestinal membrane permeability of a lipophilic drug is often overlooked and poorly understood. In this work, the interplay between the apparent solubility increase and intestinal membrane permeability decrease that exists when surfactants are used as drug solubility enhancers is described. A quasi-equilibrium mechanistic mass transport analysis was developed and employed to describe the effect of micellar solubilization by sodium taurocholate (STC) and sodium lauryl sulfate (SLS) on the intestinal membrane permeability of the lipophilic drug progesterone. The model considers the effects of micellar solubilization on both the membrane permeability (P(m)) and the unstirred water layer (UWL) permeability (P(aq)), to predict the overall effective permeability (P(eff)) dependence on surfactant concentration (C(S)). The analysis reveals that (1) the effective UWL thickness (h(aq)) quickly decreases with increasing C(S) above the critical micelle concentration (CMC), such that P(aq) markedly increases with increasing C(S); (2) the free fraction of drug available for membrane permeation decreases with increasing C(S) above CMC, such that P(m) decreases with increasing C(S); and (3) P(aq) increases and P(m) decreases with increasing C(S) above CMC, consequently the UWL is effectively shorted out and the overall P(eff) tends toward membrane control with increasing C(S). The model enabled excellent quantitative prediction of the progesterone P(eff) as a function of C(S) in the rat jejunal perfusion model. This work demonstrates that a trade-off exists between micellar apparent solubility increase and permeability decrease that must be taken into account to strike the optimal solubility-permeability balance. The model presented in this work offers the formulation scientist a simple method for a priori prediction of this

  1. A Micromechanical RF Channelizer

    Science.gov (United States)

    Akgul, Mehmet

    this work is quite enabling, since it provides a much less expensive method than microwave CVD based alternatives for depositing doped CVD diamond over large wafers (e.g., 8") for batch fabrication. The first three methods described so far focus on a single vibrating disk resonator and improve its electrical equivalent modeling, C x/Co, and Q. Once we craft the resonator that meets the challenging design requirements of RF channel-select filters, the last method presents a design hierarchy that achieves the desired filter response with a specific center frequency, bandwidth, and filter termination resistance. The design procedure culminates in specific values for all mechanical geometry variables necessary for the filter layout, such as disk radii, and beam widths; and process design variables such as resonator material thickness and capacitive actuation gap spacing. Finally, the experimental results introduce a 39nm-gap capacitive transducer, voltage-controlled frequency tuning, and a stress relieving coupled array design that enable a 0.09% bandwidth 223.4 MHz channel-select filter with only 2.7dB of in-band insertion loss and 50dB rejection of out-of-band interferers. This amount of rejection is more than 23dB better than previous capacitive-gap transduced filter designs that did not benefit from sub-50nm gaps. It also comes in tandem with a 20dB shape factor of 2.7 realized by a hierarchical mechanical circuit design utilizing 206 micromechanical circuit elements, all contained in an area footprint of only 600mumx420mum. The key to such low insertion loss for this tiny percent bandwidth is Q's>8,800 supplied by polysilicon disk resonators employing for the first time capacitive transducer gaps small enough to generate coupling strengths of C x/Co ˜0.1%, which is a 6.1x improvement over previous efforts. The filter structure utilizes electrical tuning to correct frequency mismatches due to process variations, where a dc tuning voltage of 12.1 V improves the filter

  2. Channel strategy adaptation

    OpenAIRE

    Rangan, V. Kasturi; Nueno, Jose L

    1999-01-01

    Using transaction cost theory, considerable research in marketing has focused on the conditions under which firms would use direct or vertically integrated versus indirect or arms length channels of distribution. Data from the field, however, indicate that channel configurations are more varied and complex, with multiple channels and composite channels being just as common as direct and indirect channels. In an attempt to explain this variety, this paper revisits the influence on channel stru...

  3. Enabling technology for human collaboration.

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Tim Andrew (MindTel, LLC, Syracuse, NY); Jones, Wendell Bruce; Warner, David Jay (MindTel, LLC, Syracuse, NY); Doser, Adele Beatrice; Johnson, Curtis Martin; Merkle, Peter Benedict

    2003-11-01

    This report summarizes the results of a five-month LDRD late start project which explored the potential of enabling technology to improve the performance of small groups. The purpose was to investigate and develop new methods to assist groups working in high consequence, high stress, ambiguous and time critical situations, especially those for which it is impractical to adequately train or prepare. A testbed was constructed for exploratory analysis of a small group engaged in tasks with high cognitive and communication performance requirements. The system consisted of five computer stations, four with special devices equipped to collect physiologic, somatic, audio and video data. Test subjects were recruited and engaged in a cooperative video game. Each team member was provided with a sensor array for physiologic and somatic data collection while playing the video game. We explored the potential for real-time signal analysis to provide information that enables emergent and desirable group behavior and improved task performance. The data collected in this study included audio, video, game scores, physiological, somatic, keystroke, and mouse movement data. The use of self-organizing maps (SOMs) was explored to search for emergent trends in the physiological data as it correlated with the video, audio and game scores. This exploration resulted in the development of two approaches for analysis, to be used concurrently, an individual SOM and a group SOM. The individual SOM was trained using the unique data of each person, and was used to monitor the effectiveness and stress level of each member of the group. The group SOM was trained using the data of the entire group, and was used to monitor the group effectiveness and dynamics. Results suggested that both types of SOMs were required to adequately track evolutions and shifts in group effectiveness. Four subjects were used in the data collection and development of these tools. This report documents a proof of concept

  4. Enabling Participation In Exoplanet Science

    Science.gov (United States)

    Taylor, Stuart F.

    2015-08-01

    Determining the distribution of exoplanets has required the contributions of a community of astronomers, who all require the support of colleagues to finish their projects in a manner to enable them to enter new collaborations to continue to contribute to understanding exoplanet science.The contributions of each member of the astronomy community are to be encouraged and must never be intentionally obstructed.We present a member’s long pursuit to be a contributing part of the exoplanet community through doing transit photometry as a means of commissioning the telescopes for a new observatory, followed by pursuit of interpreting the distributions in exoplanet parameter data.We present how the photometry projects have been presented as successful by the others who have claimed to have completed them, but how by requiring its employees to present results while omitting one member has been obstructive against members working together and has prevented the results from being published in what can genuinely be called a peer-reviewed fashion.We present how by tolerating one group to obstruct one member from finishing participation and then falsely denying credit is counterproductive to doing science.We show how expecting one member to attempt to go around an ostracizing group by starting something different is destructive to the entire profession. We repeat previously published appeals to help ostracized members to “go around the observatory” by calling for discussion on how the community must act to reverse cases of shunning, bullying, and other abuses. Without better recourse and support from the community, actions that do not meet standard good collegial behavior end up forcing good members from the community. The most important actions are to enable an ostracized member to have recourse to participating in group papers by either working through other authors or through the journal. All journals and authors must expect that no co-author is keeping out a major

  5. ICEPO: the ion channel electrophysiology ontology.

    Science.gov (United States)

    Hinard, V; Britan, A; Rougier, J S; Bairoch, A; Abriel, H; Gaudet, P

    2016-01-01

    Ion channels are transmembrane proteins that selectively allow ions to flow across the plasma membrane and play key roles in diverse biological processes. A multitude of diseases, called channelopathies, such as epilepsies, muscle paralysis, pain syndromes, cardiac arrhythmias or hypoglycemia are due to ion channel mutations. A wide corpus of literature is available on ion channels, covering both their functions and their roles in disease. The research community needs to access this data in a user-friendly, yet systematic manner. However, extraction and integration of this increasing amount of data have been proven to be difficult because of the lack of a standardized vocabulary that describes the properties of ion channels at the molecular level. To address this, we have developed Ion Channel ElectroPhysiology Ontology (ICEPO), an ontology that allows one to annotate the electrophysiological parameters of the voltage-gated class of ion channels. This ontology is based on a three-state model of ion channel gating describing the three conformations/states that an ion channel can adopt: closed, open and inactivated. This ontology supports the capture of voltage-gated ion channel electrophysiological data from the literature in a structured manner and thus enables other applications such as querying and reasoning tools. Here, we present ICEPO (ICEPO ftp site:ftp://ftp.nextprot.org/pub/current_release/controlled_vocabularies/), as well as examples of its use. PMID:27055825

  6. Local Cubic Law Simulation of Stress-dependent Aperture-based Permeability

    Science.gov (United States)

    Huo, D.; Benson, S. M.

    2014-12-01

    Research on calculating fracture permeability has been undergoing for decades (Witherspoon, 1980). Local Cubic Law (LCL) has been proposed to be one feasible way to simulate the fracture permeability with variable aperture changes (Brown, 1987). The purpose of this research is to present an evaluation of LCL based on a set of experimental results of permeability, aperture distribution and effective stress. We concurrently measure fracture permeability and fracture aperture distribution changes (using X-Ray CT) with cycling stress. Fractured Berea sandstone and Zenifim sandstone are measured, representing rough and smooth rock fracture surfaces. Using thin section data, we evaluate the grain size and apply Stokes fluid flow simulation in a synthetic field to estimate the stagnant fluid level between rock grains. By accounting for the stagnant fluid level, LCL simulation provides a reliable prediction for fracture permeability. Comparing with previous research (Konzuk and Kueper, 2004), we propose that LCL simulation requires detailed information about local grain arrangement. The experiment shows that permeability change is greater than expected from mean aperture change at different stress levels. LCL simulation demonstrates that this is mainly due to the change of fluid flow pattern with stress, which is caused by aperture distribution change. LCL simulation also exhibits that channeling behavior plays an important role in fluid flow in fractures, and sometimes a small number of channels dominate the flow. In the experiment, we apply different flow rates to assess the LCL simulation at different Reynolds number. The simulation results show that fluid flow rate (1.24 < Re < 15.28) does not have a large impact on LCL predictability in the highly tortuous and rough rock fractures, which agrees with the results of Konzuk and Kueper (2004). References: Brown, S. R., 1987, Fluid flow through rock joints: The effect of surface roughness, J. Geophys. Res., 92(B2), 1337

  7. Multiple—tube Permeable Element for Combined Blowing Converter

    Institute of Scientific and Technical Information of China (English)

    YANGWen-yuan; XUWei-hua; 等

    1994-01-01

    The method consisting of cold test and hot simulating has been proved to be reliable for designing permeable ele-ments.The carbon-magnesia multiple-tube permeable ele-ments which are formed by isostatical pressure have higher density,high heat resistance and good thermoshock resis-tance,The brickwork ,maintenance and erosion meha-nism of permeable elements were studied.The tehnology of combined blowing wa established based on the peculiari-ties of semi-steel refining at Panzhihua Irom& Steel Co.(PZISC).The service life of permeable elements reahed 600 heats,that means the permeable elements can work synchronitially with converter lining.

  8. Substrate specificity within a family of outer membrane carboxylate channels.

    Directory of Open Access Journals (Sweden)

    Elif Eren

    2012-01-01

    Full Text Available Many Gram-negative bacteria, including human pathogens such as Pseudomonas aeruginosa, do not have large-channel porins. This results in an outer membrane (OM that is highly impermeable to small polar molecules, making the bacteria intrinsically resistant towards many antibiotics. In such microorganisms, the majority of small molecules are taken up by members of the OprD outer membrane protein family. Here we show that OprD channels require a carboxyl group in the substrate for efficient transport, and based on this we have renamed the family Occ, for outer membrane carboxylate channels. We further show that Occ channels can be divided into two subfamilies, based on their very different substrate specificities. Our results rationalize how certain bacteria can efficiently take up a variety of substrates under nutrient-poor conditions without compromising membrane permeability. In addition, they explain how channel inactivation in response to antibiotics can cause resistance but does not lead to decreased fitness.

  9. EDZ and permeability in clayey rocks

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Deep geological layers are being considered as potential host rocks for the high level radioactivity waste disposals. During drilling in host rocks, an excavated damaged zone - EDZ is created. The fluid transmissivity may be modified in this damaged zone. This paper deals with the permeability evolution in relation with diffuse and/or localized crack propagation in the material. We mainly focus on argillaceous rocks and on some underground laboratories: Mol URL in Boom clay, Bure URL in Callovo-Oxfordian clay and Mont-Terri URL in Opalinus clay. First, observations of damage around galleries are summarized. Structure of damage in localized zone or in fracture has been observed at underground gallery scale within the excavation damaged zone (EDZ). The first challenge for a correct understanding of all the processes occurring within the EDZ is the characterization at the laboratory scale of the damage and localization processes. The observation of the initiation and propagation of the localized zones needs for advanced techniques. X-ray tomography is a non-destructive imaging technique that allows quantification of internal features of an object in 3D. If mechanical loading of a specimen is applied inside a X-ray CT apparatus, successive 3D images at different loading steps show the evolution of the specimen. However, in general volumetric strain in a shear band is small compared to the shear strain and, unfortunately, in tomographic images grey level is mainly sensitive to the local mass density field. Such a limitation has been recently overcome by complementing X-ray tomography with 3D Volumetric Digital Image Correlation (V-DIC) which allows the determination of the full strain tensor field. Then it is possible to further explore the progression of localized deformation in the specimen. The second challenge is the robust modelling of the strain localized process. In fact, modelling the damage process with finite

  10. Evaluating Permeability Enchancement Using Electrical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    John W. Pritchett

    2008-09-01

    Enhanced Geothermal Systems (EGS) development projects involve the artificial stimulation of relatively impermeable high-temperature underground regions (at depths of 2-4 kilometers or more) to create sufficient permeability to permit underground fluid circulation, so that hot water can be withdrawn from production wells and used to generate electric power. Several major research projects of this general type have been undertaken in the past in New Mexico (Fenton Hill), Europe, Japan and Australia. Recent U.S. activities along these lines focus mainly on stimulating peripheral areas of existing operating hydrothermal fields rather than on fresh 'greenfield' sites, but the long-term objective of the Department of Energy's EGS program is the development of large-scale power projects based on EGS technology (MIT, 2006; NREL, 2008). Usually, stimulation is accomplished by injecting water into a well at high pressure, enhancing permeability by the creation and propagation of fractures in the surrounding rock (a process known as 'hydrofracturing'). Beyond just a motivation, low initial system permeability is also an essential prerequisite to hydrofracturing. If the formation permeability is too high, excessive fluid losses will preclude the buildup of sufficient pressure to fracture rock. In practical situations, the actual result of injection is frequently to re-open pre-existing hydrothermally-mineralized fractures, rather than to create completely new fractures by rupturing intact rock. Pre-existing fractures can often be opened using injection pressures in the range 5-20 MPa. Creation of completely new fractures will usually require pressures that are several times higher. It is preferable to undertake development projects of this type in regions where tectonic conditions are conducive to shear failure, so that when pre-existing fractures are pressurized they will fail by shearing laterally. If this happens, the fracture will often stay open

  11. Pressure-induced water transport in membrane channels studied by molecular dynamics.

    OpenAIRE

    Zhu, Fangqiang; Tajkhorshid, Emad; Schulten, Klaus

    2002-01-01

    A method is proposed to measure the water permeability of membrane channels by means of molecular dynamics simulations. By applying a constant force to the bulk water molecules and a counter force on the complementary system, a hydrostatic pressure difference across the membrane can be established, producing a net directional water flow. The hydraulic or osmotic permeability can then be determined by the ratio of the water flux and the pressure difference. The method is applied and tested on ...

  12. Permeability-controlled optical modulator with Tri-gate metamaterial: control of permeability on InP-based photonic integration platform.

    Science.gov (United States)

    Amemiya, Tomohiro; Ishikawa, Atsushi; Kanazawa, Toru; Kang, JoonHyung; Nishiyama, Nobuhiko; Miyamoto, Yasuyuki; Tanaka, Takuo; Arai, Shigehisa

    2015-01-01

    Metamaterials are artificially structured materials that can produce innovative optical functionalities such as negative refractive index, invisibility cloaking, and super-resolution imaging. Combining metamaterials with semiconductors enables us to develop novel optoelectronic devices based on the new concept of operation. Here we report the first experimental demonstration of a permeability-controlled waveguide optical modulator consisting of an InGaAsP/InP Mach-Zehnder interferometer with 'tri-gate' metamaterial attached on its arms. The tri-gate metamaterial consists of metal resonator arrays and triple-gate field effect elements. It changes its permeability with a change in the controlling gate voltage, thereby changing the refractive index of the interferometer arm to switch the modulator with an extinction ratio of 6.9 dB at a wavelength of 1.55 μm. The result shows the feasibility of InP-based photonic integrated devices that can produce new functions by controlling their permeability as well as their permittivity. PMID:25797041

  13. Shear dilatancy in unconsolidated laboratory samples improves relative permeability performance

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Hasnain A.; Olson, Jon E. [Society of Petroleum Engineers (Canada); Holder, Jon [University of Texas at Austin (United States)

    2011-07-01

    Dilatant shear failure can occur in unconsolidated heavy oil reservoirs as a result of steam assisted gravity drainage (SAGD). This paper discusses the changes induced by dilatant shear failure in absolute permeability, relative permeability to oil and water and residual saturations. Synthetic specimens 2 inches in diameter made from lower fine to medium grain size Ottawa sand were tested. Triaxial compression and radial extension loading paths were used. During deformation, volumetric and axial strains were measured directly. The relative permeability was determined using the unsteady state method. Shearing strongly affects relative permeabilities. The effect is slightly greater for finer grain than for medium grain. During triaxial testing, it was seen that absolute permeability increased with shearing at 50 psi stress. But at 200 psi, absolute permeability decreased, even though the volumetric strain was still dilatant. From both triaxial and radial extension tests, it was evident that oil and water relative permeability is affected by stresses acting on the sand pack.

  14. Upscaling of permeability field of fractured rock system: Numerical examples

    KAUST Repository

    Bao, K.

    2012-01-01

    When the permeability field of a given porous medium domain is heterogeneous by the existence of randomly distributed fractures such that numerical investigation becomes cumbersome, another level of upscaling may be required. That is such complex permeability field could be relaxed (i.e., smoothed) by constructing an effective permeability field. The effective permeability field is an approximation to the real permeability field that preserves certain quantities and provides an overall acceptable description of the flow field. In this work, the effective permeability for a fractured rock system is obtained for different coarsening scenarios starting from very coarse mesh all the way towards the fine mesh simulation. In all these scenarios, the effective permeability as well as the pressure at each cell is obtained. The total flux at the exit boundary is calculated in all these cases, and very good agreement is obtained.

  15. Water block effects in low permeability gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, N. G. [Core Laboratories Canada Ltd, Calgary, AB (Canada)

    1996-09-01

    The mechanism of permeability reduction as a result of extraneous fluid invasion was studied. Laboratory data showed that for water-wet reservoirs, areas of porosity where bound water exists, contribute little to permeability. Even in extremely low permeability cores, the effect of irreducible water saturation on gas permeability was only a 20 per cent reduction. These results led to the conclusion that permeability damage is only slightly worse in dessicated gas reservoirs than in gas reservoirs controlled by capillary pressure. Similarly, it was concluded that the primary mechanism of permeability loss due to water block is the blocking of macro pores; microporosity contributes little if any to permeability. 11 refs., 1 tab., 12 figs.

  16. Less water permeable concrete structure for radioactive wastes disposal field

    International Nuclear Information System (INIS)

    A less water permeable concrete structure comprises three gas permeable concrete layers each having a predetermined thickness and less water permeable and high gas permeable fibrous layers each put between the gas permeable concrete layers. The fibrous layer used is an extremely thin film-like material, and having a fine open cell structure, for example, polytetrafluoroethylene which is chemically and thermally stable and excellent in weather resistance. The outer circumferential shell for the radioactive waste disposal field is formed by using the less water permeable concrete structure having such a constitution. The gases inside pass through the gas permeable concrete layers and the fibrous layers and released to the outside. Water intruded from the outside is blocked by the fibrous layers and can not reach the inside of the structure. (I.N.)

  17. The Accelerated Test of Chloride Permeability of Concrete

    Institute of Scientific and Technical Information of China (English)

    TAN Ke-feng; ODD E Gjφrv

    2003-01-01

    The availability of accelerated chloride permeability test and the effect of w/c ratio, incorporation of silica fume, maximum aggregate size and aggregate type on the chloride permeability were studied. The mathematic analysis certifies that there is a linear relationship between accelerated test and natural diffusion. Test results show that the chloride permeability of concrete increases as w/c ratio increases whilst a limited amount of replacement of cement with silica fume, the chloride permeability decreases dramatically. The maximum aggregate size in the range of 8 to 25 mm seems also affect chloride permeability but with a much less significant level. The chloride permeability of silica fume lightweight aggregate concrete is very low, especially the concrete made with dry lightweight concrete. The chloride permeability can be evaluated by this accelerated test method.

  18. Population Shift between the Open and Closed States Changes the Water Permeability of an Aquaporin Z Mutant

    DEFF Research Database (Denmark)

    Xin, Lin; Helix Nielsen, Claus; Su, Haibin;

    2012-01-01

    Aquaporins are tetrameric transmembrane channels permeable to water and other small solutes. Wild-type (WT) and mutant Aquaporin Z (AqpZ) have been widely studied and multiple factors have been found to affect their water permeability. In this study, molecular dynamics simulations have been...... performed for the tetrameric AqpZ F43W/H174G/T183F mutant. It displayed similar to 10% average water permeability compared to WT AqpZ, which had been attributed to the increased channel lumen hydrophobicity. Our simulations, however, show a ring stacking between W43 and F183 acting as a secondary steric...... gate in the triple mutant with R189 as the primary steric gate in both mutant and WT AqpZ. The double gates (R189 and W43-F183) result in a high population of the closed conformation in the mutant. Occasionally an open state, with diffusive water permeability very close to that of WT AqpZ, was observed...

  19. Micro-Channel Embedded Pulsating Heat Pipes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  20. Role of physiological ClC-1 Cl- ion channel regulation for the excitability and function of working skeletal muscle

    DEFF Research Database (Denmark)

    Pedersen, Thomas Holm; Riisager, Anders; de Paoli, Frank Vincenzo;

    2016-01-01

    permeability for Cl- ions. Thus, in resting human muscle, ClC-1 Cl- ion channels account for ∼80% of the membrane conductance, and because active Cl- transport is limited in muscle fibers, the equilibrium potential for Cl- lies close to the resting membrane potential. These conditions—high membrane conductance...... and passive distribution—enable ClC-1 to conduct membrane current that inhibits muscle excitability. This depressing effect of ClC-1 current on muscle excitability has mostly been associated with skeletal muscle hyperexcitability in myotonia congenita, which arises from loss-of-function mutations in...... the CLCN1 gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with...

  1. Propagation behavior of permeability reduction in heterogeneous porous media due to particulate transport

    Science.gov (United States)

    Xu, Jianping

    2016-04-01

    In this letter we explore the propagation behavior of permeability reduction due to particulate transport in heterogeneous porous media. By simulating an advection-dispersion–based model we find that an attenuating sequence exists in terms of the propagation of particle concentration, permeability reduction and heterogeneity perturbation. The advancing speed of the fronts of the mentioned physical quantities attenuates successively from const to \\text{const}(1/n)1/t1-1/n to \\text{const}1/t (where n > 1 and t denotes time) regardless of the heterogeneity patterns. Then we move on to discuss the micro-dynamics of the propagation sequence, involving how it originates and how it connects with the macroscopic results. Moreover, exploiting the propagation mechanism enables us to know the condition under which we can apply the hypothesis of media homogeneity to describe the behavior of the particulate transport system in porous media.

  2. Ultrathin Gas Permeable Oxide Membranes for Chemical Sensing: Nanoporous Ta2O5 Test Study

    Directory of Open Access Journals (Sweden)

    Alexander Imbault

    2015-09-01

    Full Text Available Conductometric gas sensors made of gas permeable metal oxide ultrathin membranes can combine the functions of a selective filter, preconcentrator, and sensing element and thus can be particularly promising for the active sampling of diluted analytes. Here we report a case study of the electron transport and gas sensing properties of such a membrane made of nanoporous Ta2O5. These membranes demonstrated a noticeable chemical sensitivity toward ammonia, ethanol, and acetone at high temperatures above 400 °C. Different from traditional thin films, such gas permeable, ultrathin gas sensing elements can be made suspended enabling advanced architectures of ultrasensitive analytical systems operating at high temperatures and in harsh environments.

  3. Genetic Manipulation of The Cardiac Mitochondrial Phosphate Carrier does not affect Permeability Transition

    OpenAIRE

    Gutiérrez-Aguilar, Manuel; Douglas, Diana L.; Gibson, Anne K.; Domeier, Timothy L.; Molkentin, Jeffery D.; Baines, Christopher P.

    2014-01-01

    The Mitochondrial Permeability Transition (MPT) pore is a voltage-sensitive unselective channel known to instigate necrotic cell death during cardiac disease. Recent models suggest that the isomerase cyclophilin D (CypD) regulates the MPT pore by binding to either the F0F1-ATP synthase lateral stalk or the mitochondrial phosphate carrier (PiC). Here we confirm that CypD, through its N-terminus, can directly bind PiC. We then generated cardiac-specific mouse strains overexpressing or with decr...

  4. Exploring the scale-dependent permeability of fractured andesite

    Science.gov (United States)

    Heap, Michael J.; Kennedy, Ben M.

    2016-08-01

    Extension fractures in volcanic systems exist on all scales, from microscopic fractures to large fissures. They play a fundamental role in the movement of fluids and distribution of pore pressure, and therefore exert considerable influence over volcanic eruption recurrence. We present here laboratory permeability measurements for porous (porosity = 0.03-0.6) andesites before (i.e., intact) and after failure in tension (i.e., the samples host a throughgoing tensile fracture). The permeability of the intact andesites increases with increasing porosity, from 2 ×10-17 to 5 ×10-11 m2. Following fracture formation, the permeability of the samples (the equivalent permeability) falls within a narrow range, 2- 6 ×10-11 m2, regardless of their initial porosity. However, laboratory measurements on fractured samples likely overestimate the equivalent permeability due to the inherent scale-dependence of permeability. To explore this scale-dependence, we first determined the permeability of the tensile fractures using a two-dimensional model that considers flow in parallel layers. Our calculations highlight that tensile fractures in low-porosity samples are more permeable (as high as 3.5 ×10-9 m2) than those in high-porosity samples (as low as 4.1 ×10-10 m2), a difference that can be explained by an increase in fracture tortuosity with porosity. We then use our fracture permeability data to model the equivalent permeability of fractured rock (with different host rock permeabilities, from 10-17 to 10-11 m2) with increasing lengthscale. We highlight that our modelling approach can be used to estimate the equivalent permeability of numerous scenarios at andesitic stratovolcanoes in which the fracture density and width and host rock porosity or permeability are known. The model shows that the equivalent permeability of fractured andesite depends heavily on the initial host rock permeability and the scale of interest. At a given lengthscale, the equivalent permeability of high-permeability

  5. Permeability of the Lucky Strike deep-sea hydrothermal system: Constraints from the poroelastic response to ocean tidal loading

    Science.gov (United States)

    Barreyre, Thibaut; Escartin, Javier; Sohn, Robert; Cannat, Mathilde

    2014-12-01

    We use the time delay between tidal loading and the induced subsurface flow response to constrain the poroelastic behavior and permeability of the Lucky Strike hydrothermal field on the Mid-Atlantic Ridge. We demonstrate that high-temperature (T > 200 °C) exit-fluid discharge records from four hydrothermal sites across the field are highly coherent with contemporaneously acquired bottom pressure records at tidal periods, with the thermal response lagging pressure by ˜155° (5.3 h) on average across all sites for the semi-diurnal (M2) frequency over a three-year observation period. In a one-dimensional poroelastic model of ocean tidal loading this phase lag corresponds to a high-permeability system where pore pressure perturbations at the seafloor rapidly propagate downward from the seafloor interface until they encounter a permeability boundary. Our results suggest that at the Lucky Strike field this tidal pumping is largely restricted to the ˜600 m thick extrusive layer (i.e., seismic layer 2A). Under a plausible set of matrix elastic parameters, the ˜5.3 h lag between pressure and exit-fluid temperature is consistent with an effective matrix permeability of ˜10-10 m2 and an average vertical flow velocity of ˜0.02 m/s within the extrusive layer. Our results argue against tidal pumping of the entire crustal section between the seafloor and the axial magma chamber (at ˜3.4 kmbsf) because this scenario requires unrealistically high effective permeabilities (˜10-9 m2) and average vertical flow velocities (˜0.15 m/s) over this depth range. Our effective permeability estimate for the extrusive layer is broadly consistent with previous results, and indicates that flow must be channeled in discrete permeable pathways (e.g., faults, fissures) that cut through the extrusive volcanic layer.

  6. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  7. Connexin channels and phospholipids: association and modulation

    Directory of Open Access Journals (Sweden)

    Harris Andrew L

    2009-08-01

    Full Text Available Abstract Background For membrane proteins, lipids provide a structural framework and means to modulate function. Paired connexin hemichannels form the intercellular channels that compose gap junction plaques while unpaired hemichannels have regulated functions in non-junctional plasma membrane. The importance of interactions between connexin channels and phospholipids is poorly understood. Results Endogenous phospholipids most tightly associated with purified connexin26 or connexin32 hemichannels or with junctional plaques in cell membranes, those likely to have structural and/or modulatory effects, were identified by tandem electrospray ionization-mass spectrometry using class-specific interpretative methods. Phospholipids were characterized by headgroup class, charge, glycerol-alkyl chain linkage and by acyl chain length and saturation. The results indicate that specific endogenous phospholipids are uniquely associated with either connexin26 or connexin32 channels, and some phospholipids are associated with both. Functional effects of the major phospholipid classes on connexin channel activity were assessed by molecular permeability of hemichannels reconstituted into liposomes. Changes to phospholipid composition(s of the liposome membrane altered the activity of connexin channels in a manner reflecting changes to the surface charge/potential of the membrane and, secondarily, to cholesterol content. Together, the data show that connexin26 and connexin32 channels have a preference for tight association with unique anionic phospholipids, and that these, independent of headgroup, have a positive effect on the activity of both connexin26 and connexin32 channels. Additionally, the data suggest that the likely in vivo phospholipid modulators of connexin channel structure-function that are connexin isoform-specific are found in the cytoplasmic leaflet. A modulatory role for phospholipids that promote negative curvature is also inferred. Conclusion

  8. Key Enabling Physical Layer Technologies for LTE-Advanced

    Science.gov (United States)

    Jiang, Meilong; Prasad, Narayan; Xin, Yan; Yue, Guosen; Khojastepour, Amir; Liu, Le; Inoue, Takamichi; Koyanagi, Kenji; Kakura, Yoshikazu

    The 3GPP Long Term Evolution Advanced (LTE-A) system, as compared to the LTE system, is anticipated to include several new features and enhancements, such as the usage of channel bandwidth beyond 20MHz (up 100MHz), higher order multiple input multiple output (MIMO) for both downlink and uplink transmissions, larger capacity especially for cell edge user equipment, and voice over IP (VoIP) users, and wider coverage and etc. This paper presents some key enabling technologies including flexible uplink access schemes, advanced uplink MIMO receiver designs, cell search, adaptive hybrid ARQ, and multi-resolution MIMO precoding, for the LTE-A system.

  9. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  10. Clamshell excavation of a permeable reactive barrier

    Science.gov (United States)

    Molfetta, Antonio Di; Sethi, Rajandrea

    2006-06-01

    Nowadays, permeable reactive barriers (PRB) are one of the most widespread techniques for the remediation of contaminated aquifers. Over the past 10 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC in: Permeable reactive barriers: lessons learned/new directions. The Interstate Technology and Regulatory Council, Permeable Reactive Barriers Team 2005). Although, a variety of excavation methods have been developed, backhoe excavators are often used for the construction of PRBs. The aim of this study is to describe the emplacement of a full-scale PRB and the benefits deriving from the use of a crawler crane equipped with a hydraulic grab (also known as clamshell excavator) in the excavation phases. The studied PRB was designed to remediate a chlorinated hydrocarbons plume at an old industrial landfill site, in Avigliana, near the city of Torino, in Italy. The continuous reactive barrier was designed to be 120 m long, 13 m deep, and 0.6 m thick. The installation of the barrier was accomplished using a clamshell for the excavation of the trench and a guar-gum slurry to support the walls. The performance of this technique was outstanding and allowed the installation of the PRB in 7 days. The degree of precision of the excavation was very high because of the intrinsic characteristics of this excavation tool and of the use of a concrete curb to guide the hydraulic grab. Moreover, the adopted technique permitted a saving of bioslurry thus minimizing the amount of biocide required.

  11. The kinetics of denitrification in permeable sediments

    Science.gov (United States)

    Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.

    2013-04-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to study experimentally. The realistic implementation of such models requires reliable experimentally derived data on the kinetics of denitrification. Here we undertook measurements of denitrification kinetics as a function of nitrate concentration and in the presence and absence of oxygen, in carefully controlled flow through reactor experiments on sediments taken from six shallow coastal sites in Port Phillip Bay, Victoria, Australia. The results showed that denitrification commenced rapidly (within 30 min) after the onset of anoxia and the kinetics could be well described by Michaelis-Menten kinetics with half saturation constants (apparent Km) ranging between 1.5 and 19.8 μM, and maximum denitrification rate (Vmax) were in the range of 0.9-7.5 nmol mL-1 h-1. The production of N2 through anaerobic ammonium oxidation (anammox) was generally found to be less than 10% that of denitrification. Vmax were in the same range as previously reported in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O2 consumption to Vmax was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. The most likely explanation for this is that the microbial community is not able to instantaneously shift or optimally use a particular electron acceptor in the highly dynamic redox environment experienced in permeable sediments. Consistent with this explanation, subsequent longer-term experiments over 5 days showed that denitrification rates increased by a factor of 10 within 3 days of the permanent onset of anoxia. In contrast to previous studies, we did not observe any significant

  12. PERMEABILITY OF SALTSTONE MEASUREMENT BY BEAM BENDING

    International Nuclear Information System (INIS)

    One of the goals of the Saltstone variability study is to identify (and, quantify the impact of) the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. A performance property for Saltstone mixes that is important but not routinely measured is the liquid permeability or saturated hydraulic conductivity of the cured Saltstone mix. The value for the saturated hydraulic conductivity is an input into the Performance Assessment for the SRS Z-Area vaults. Therefore, it is important to have a method available that allows for an accurate and reproducible measurement of permeability quickly and inexpensively. One such method that could potentially meet these requirements for the measurement of saturated hydraulic conductivity is the technique of beam bending, developed by Professor George Scherer at Princeton University. In order to determine the feasibility of this technique for Saltstone mixes, a summer student, David Feliciano, was hired to work at Princeton under the direction of George Scherer. This report details the results of this study which demonstrated the feasibility and applicability of the beam bending method to measurement of permeability of Saltstone samples. This research effort used samples made at Princeton from a Modular Caustic side solvent extraction Unit based simulant (MCU) and premix at a water to premix ratio of 0.60. The saturated hydraulic conductivities for these mixes were measured by the beam bending technique and the values determined were of the order of 1.4 to 3.4 x 10-9 cm/sec. These values of hydraulic conductivity are consistent with independently measured values of this property on similar MCU based mixes by Dixon and Phifer. These values are also consistent with the hydraulic conductivity of a generic Saltstone mix measured by Langton in 1985. The high water to premix ratio used for Saltstone along with the relatively low degree of hydration for MCU

  13. Channel nut tool

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Marvin

    2016-01-12

    A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.

  14. Two Types of Bureaucracy: Enabling and Coercive.

    Science.gov (United States)

    Adler, Paul S.; Borys, Bryan

    1996-01-01

    Proposes a conceptualization of workflow formalization that helps reconcile contrasting assessments of bureaucracy as alienating or enabling to employees. Uses research on equipment technology design to identify enabling and coercive types of formalization. Identifies some forces tending to discourage an enabling orientation and some persistent…

  15. Recent Genetic Discoveries Implicating Ion Channels in Human Cardiovascular Diseases

    OpenAIRE

    George, Alfred L.

    2013-01-01

    The term channelopathy refers to human genetic disorders caused by mutations in genes encoding ion channels or their interacting proteins. Recent advances in this field have been enabled by next-generation DNA sequencing strategies such as whole exome sequencing with several intriguing and unexpected discoveries. This review highlights important discoveries implicating ion channels or ion channel modulators in cardiovascular disorders including cardiac arrhythmia susceptibility, cardiac condu...

  16. Enhancing the nail permeability of topically applied drugs.

    Science.gov (United States)

    Murdan, Sudaxshina

    2008-11-01

    The topical therapy of nail diseases, especially of onychomycosis, and to a smaller extent, of nail psoriasis, is desirable to avoid the side effects associated with their systemic therapy, to increase patient compliance and reduce the cost of treatment. Systemic therapy is however the mainstay of treatment due to the poor permeability of the nail plate to topically applied drugs. For effective topical therapy, ungual drug permeation must be enhanced. This can be achieved by disrupting the nail plate using physical techniques or chemical agents. Alternatively, drug permeation into the intact nail plate may be encouraged, for example, by iontophoresis or by formulating the drug within a vehicle which enables high drug partition out of the vehicle and into the nail plate. The physical techniques (manual and electrical nail abrasion, acid etching, ablation by lasers, microporation, application of low-frequency ultrasound and electric currents) and chemicals (thiols, sulphites, hydrogen peroxide, urea, water, enzymes) that have shown ungual enhancer activity are discussed in this review. Optimal drug formulation, while crucial to ungual drug delivery, is only briefly reviewed due to the limited literature. PMID:18976136

  17. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    International Nuclear Information System (INIS)

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress

  18. Vortex Ring Interaction with Multiple Permeable Screens

    Science.gov (United States)

    Musta, Mustafa N.; Krueger, Paul S.

    2008-11-01

    Previous experiments on the interaction of a vortex ring impinging on single thin permeable screen demonstrated the formation of secondary vortices and a transmitted vortex ring. The present work concerns experimental investigation of the interaction of a vortex ring with multiple permeable screens. Vortex rings are formed by piston-cylinder type vortex ring generator and impinge on an array of parallel, transparent screens. The screens have an open ratio of 84% and the spacing between screens is variable. The vortex rings were formed with an approximate jet Reynolds number of 1300 and a piston stroke-to-jet diameter ratio (L/D) of approximately 4. Dye visualization of the vortex rings shows that they break into multiple vortices after impinging on first screen The vortices subsequently disintegrate, but the total distance required for disintegration is relatively unaffected by the number of screens through with the vortices pass due to the regular structure of the screens. It is also observed that the location of the initial vortex ring axis relative to the screen rods has a significant effect on the vortex breakup and disintegration process.

  19. Reservoir permeability from seismic attribute analysis

    Energy Technology Data Exchange (ETDEWEB)

    Silin, Dmitriy; Goloshubin, G.; Silin, D.; Vingalov, V.; Takkand, G.; Latfullin, M.

    2008-02-15

    In case of porous fluid-saturated medium the Biot's poroelasticity theory predicts a movement of the pore fluid relative to the skeleton on seismic wave propagation through the medium. This phenomenon opens an opportunity for investigation of the flow properties of the hydrocarbon-saturated reservoirs. It is well known that relative fluid movement becomes negligible at seismic frequencies if porous material is homogeneous and well cemented. In this case the theory predicts an underestimated seismic wave velocity dispersion and attenuation. Based on Biot's theory, Helle et al. (2003) have numerically demonstrated the substantial effects on both velocity and attenuation by heterogeneous permeability and saturation in the rocks. Besides fluid flow effect, the effects of scattering (Gurevich, et al., 1997) play very important role in case of finely layered porous rocks and heterogeneous fluid saturation. We have used both fluid flow and scattering effects to derive a frequency-dependent seismic attribute which is proportional to fluid mobility and applied it for analysis of reservoir permeability.

  20. Permeability of protective coatings to tritium

    International Nuclear Information System (INIS)

    The permeability of four protective coatings to tritium gas and tritiated water was investigated. The coatings, including two epoxies, one vinyl and one urethane, were selected for their suitability in CANDU plant service in Ontario Hydro. Sorption rates of tritium gas into the coatings were considerably larger than for tritiated water, by as much as three to four orders of magnitude. However, as a result of the very large solubility of tritiated water in the coatings, the overall permeability to tritium gas and tritiated water are comparable, being somewhat larger for HTO. Marked differences were also evident among the four coatings, the vinyl proving to be unique in behaviour and morphology. Because of a highly porous surface structure water condensation takes place at high relative humidities, leading to an abnormally high retention of free water. Desorption rates from the four coatings were otherwise quite similar. Of practical importance was the observation that more effective desorption of tritiated water could be carried out at relatively high humidities, in this case 60%. It was believed that isotopic exchange was responsible for this phenomenon. It appears that epoxy coatings having a high pigment-to-binder ratio are most suited for coating concrete in tritium handling facilities

  1. Air sparging in low permeability soils

    Energy Technology Data Exchange (ETDEWEB)

    Marley, M.C. [Envirogen, Inc., Canton, MA (United States)

    1996-08-01

    Sparging technology is rapidly growing as a preferred, low cost remediation technique of choice at sites across the United States. The technology is considered to be commercially available and relatively mature. However, the maturity is based on the number of applications of the technology as opposed to the degree of understanding of the mechanisms governing the sparging process. Few well documented case studies exist on the long term operation of the technology. Sparging has generally been applied using modified monitoring well designs in uniform, coarse grained soils. The applicability of sparging for the remediation of DNAPLs in low permeability media has not been significantly explored. Models for projecting the performance of sparging systems in either soils condition are generally simplistic but can be used to provide general insight into the effects of significant changes in soil and fluid properties. The most promising sparging approaches for the remediation of DNAPLs in low permeability media are variations or enhancements to the core technology. Recirculatory sparging systems, sparging/biosparging trenches or curtains and heating or induced fracturing techniques appear to be the most promising technology variants for this type of soil. 21 refs., 9 figs.

  2. Permeability of asthenospheric mantle and melt extraction rates at mid-ocean ridges.

    Science.gov (United States)

    Connolly, James A D; Schmidt, Max W; Solferino, Giulio; Bagdassarov, Nikolai

    2009-11-12

    Magmatic production on Earth is dominated by asthenospheric melts of basaltic composition that have mostly erupted at mid-ocean ridges. The timescale for segregation and transport of these melts, which are ultimately responsible for formation of the Earth's crust, is critically dependent on the permeability of the partly molten asthenospheric mantle, yet this permeability is known mainly from semi-empirical and analogue models. Here we use a high-pressure, high-temperature centrifuge, at accelerations of 400g-700g, to measure the rate of basalt melt flow in olivine aggregates with porosities of 5-12 per cent. The resulting permeabilities are consistent with a microscopic model in which melt is completely connected, and are one to two orders of magnitude larger than predicted by current parameterizations. Extrapolation of the measurements to conditions characteristic of asthenosphere below mid-ocean ridges yields proportionally higher transport speeds. Application of these results in a model of porous-media channelling instabilities yields melt transport times of approximately 1-2.5 kyr across the entire asthenosphere, which is sufficient to preserve the observed (230)Th excess of mid-ocean-ridge basalts and the mantle signatures of even shorter-lived isotopes such as (226)Ra (refs 5,11-14). PMID:19907492

  3. NH3 and NH4+ permeability in aquaporin-expressing Xenopus oocytes

    DEFF Research Database (Denmark)

    Holm, Lars M.; Jahn, Thomas Paul; Møller, Anders Laurell Blom;

    2005-01-01

    We have shown recently, in a yeast expression system, that some aquaporins are permeable to ammonia. In the present study, we expressed the mammalian aquaporins AQP8, AQQP9, AQP3, AQP1 and a plant aquaporin TIP2;1 in Xenopus oocytes to study the transport of ammonia (NH3) and ammonium (NH4+) under...... opencircuit and voltage-clamped conditions. TIP2;1 was tested as the wild-type and in a mutated version (tip2;1) in which the water permeability is intact. When AQP8-, AQP9-, AQP3- and TIP2;1-expressing oocytes were placed in a well-stirred bathing medium of low buffer capacity, NH3 permeability was evident...... oocytes as well as AQP1 and tip2;1-expressing oocytes showed small currents that were associated with small and even negative volume changes. We conclude that AQP8, AQP9, AQP3, and TIP2;1, apart from being water channels, also support significant fluxes of NH3. These aquaporins could support NH4...

  4. EFFECTS OF CAPTOPRIL, DILTIAZEM AND DOBUTAMINE ON PERMEABILITY OF RAT AORTIC ENDOTHELIAL CELL MONOLAYERS

    Institute of Scientific and Technical Information of China (English)

    王晓峰; 由广旭; 皮绍文; 秦永文

    2001-01-01

    To investigate the effects of angiotensin converting enzyme inhibitor captopril, calcium channel blocker diltiazem and β-adrenoceptor antagonist dobutamine on the permeability of rat aortic endothelial monolayers.Methods Trauma-free isolation by Chen et al was adopted in the culture of rat aortic endothelial cells. Rat aortic endothelial cells were seeded on the nitrocellulose microporous filters. Eight days after seeding, the monolayers could be used for measuring the permeability. Before being perfused, monolayers were treated with captopril, diltiazem and dobutamine for 4 hours successively. The prepared filters were mounted on the Boydon chambers and perfused with hyperlipemia containing FITC-labeled albumin. The fluid filtering through the monolayers and the filter was collected and the albumin concentration was measured. At the same time, cholesterol, triglyceride, lipoprotein A and lipoprotein B concentrations of the collected fluid were also measured by ELISA.Results The above three drugs decreased the permeability of aortic endothelial cell monolayers to water, cholesterol, triglyceride lipoprotein A and lipoprotein B significantly. Dobutamine had more significant effects than the other two drugs. But diltiazem worked well in the clearance of albumin, while the other two drugs had no obvious effect.Conclusion Captopril, diltiazem and dobutamine may decrease the infiltration of lipids and lipoproteins into the subendothelial space, thus they can be used to prevent and ameliorate atherosclerosis.

  5. Structural Determinants of Oligomerization of the Aquaporin-4 Channel.

    Science.gov (United States)

    Kitchen, Philip; Conner, Matthew T; Bill, Roslyn M; Conner, Alex C

    2016-03-25

    The aquaporin (AQP) family of integral membrane protein channels mediate cellular water and solute flow. Although qualitative and quantitative differences in channel permeability, selectivity, subcellular localization, and trafficking responses have been observed for different members of the AQP family, the signature homotetrameric quaternary structure is conserved. Using a variety of biophysical techniques, we show that mutations to an intracellular loop (loop D) of human AQP4 reduce oligomerization. Non-tetrameric AQP4 mutants are unable to relocalize to the plasma membrane in response to changes in extracellular tonicity, despite equivalent constitutive surface expression levels and water permeability to wild-type AQP4. A network of AQP4 loop D hydrogen bonding interactions, identified using molecular dynamics simulations and based on a comparative mutagenic analysis of AQPs 1, 3, and 4, suggest that loop D interactions may provide a general structural framework for tetrameric assembly within the AQP family. PMID:26786101

  6. Experimental Investigation on Sandstone Rock Permeability of Pakistan Gas Fields

    Science.gov (United States)

    Raza, Arshad; Bing, Chua Han; Nagarajan, Ramasamy; Hamid, Mohamed Ali

    2015-04-01

    Permeability is the ability of formation to produce hydrocarbon which is affected by compaction, pore size, sorting, cementation, layering and clay swelling. The effect of texture on permeability in term of grain size, sorting, sphericity, degree of cementing has been reported in literature. Also, the effect of permeability on capillary pressure, irreducible water saturation, displacement pressure and pore geometry constant has been studied separately. This preliminary study presents the experimental results of eight samples to understand the effect of similar factors of texture on permeability. With the knowledge of the results, it can be said that the effect of grain size, cementation, texture material, sphericity, and porosity can't be observed on permeability except sorting when less than ten samples are considered from different depositional environment. The results also show the impact of permeability on capillary pressure, irreducible water saturation, and displacement pressure and pore geometry index as similar as published in the literature.

  7. Calculation of large scale relative permeabilities from stochastic properties of the permeability field and fluid properties

    Energy Technology Data Exchange (ETDEWEB)

    Lenormand, R.; Thiele, M.R. [Institut Francais du Petrole, Rueil Malmaison (France)

    1997-08-01

    The paper describes the method and presents preliminary results for the calculation of homogenized relative permeabilities using stochastic properties of the permeability field. In heterogeneous media, the spreading of an injected fluid is mainly sue to the permeability heterogeneity and viscosity fingering. At large scale, when the heterogeneous medium is replaced by a homogeneous one, we need to introduce a homogenized (or pseudo) relative permeability to obtain the same spreading. Generally, is derived by using fine-grid numerical simulations (Kyte and Berry). However, this operation is time consuming and cannot be performed for all the meshes of the reservoir. We propose an alternate method which uses the information given by the stochastic properties of the field without any numerical simulation. The method is based on recent developments on homogenized transport equations (the {open_quotes}MHD{close_quotes} equation, Lenormand SPE 30797). The MHD equation accounts for the three basic mechanisms of spreading of the injected fluid: (1) Dispersive spreading due to small scale randomness, characterized by a macrodispersion coefficient D. (2) Convective spreading due to large scale heterogeneities (layers) characterized by a heterogeneity factor H. (3) Viscous fingering characterized by an apparent viscosity ration M. In the paper, we first derive the parameters D and H as functions of variance and correlation length of the permeability field. The results are shown to be in good agreement with fine-grid simulations. The are then derived a function of D, H and M. The main result is that this approach lead to a time dependent . Finally, the calculated are compared to the values derived by history matching using fine-grid numerical simulations.

  8. The Earliest Ion Channels

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.; Wei, C.

    2009-12-01

    Supplying protocells with ions required assistance from channels spanning their membrane walls. The earliest channels were most likely short proteins that formed transmembrane helical bundles surrounding a water-filled pore. These simple aggregates were capable of transporting ions with efficiencies comparable to those of complex, contemporary ion channels. Channels with wide pores exhibited little ion selectivity but also imposed only modest constraints on amino acid sequences of channel-forming proteins. Channels with small pores could have been selective but also might have required a more precisely defined sequence of amino acids. In contrast to modern channels, their protocellular ancestors had only limited capabilities to regulate ion flux. It is postulated that subsequent evolution of ion channels progressed primarily to acquire precise regulation, and not high efficiency or selectivity. It is further proposed that channels and the surrounding membranes co-evolved.

  9. Permeability Properties of Enac Selectivity Filter Mutants

    OpenAIRE

    Kellenberger, Stephan; Auberson, Muriel; Gautschi, Ivan; Schneeberger, Estelle; Schild, Laurent

    2001-01-01

    The epithelial Na+ channel (ENaC), located in the apical membrane of tight epithelia, allows vectorial Na+ absorption. The amiloride-sensitive ENaC is highly selective for Na+ and Li+ ions. There is growing evidence that the short stretch of amino acid residues (preM2) preceding the putative second transmembrane domain M2 forms the outer channel pore with the amiloride binding site and the narrow ion-selective region of the pore. We have shown previously that mutations of the αS589 residue in...

  10. Multi-Channel Retailing

    Directory of Open Access Journals (Sweden)

    Dirk Morschett, Dr.,

    2005-01-01

    Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.

  11. Increased pulmonary and intestinal permeability in Crohn's disease.

    OpenAIRE

    Adenis, A; Colombel, J.F.; Lecouffe, P; Wallaert, B.; Hecquet, B.; Marchandise, X; Cortot, A

    1992-01-01

    We tested the hypothesis that an increased epithelial permeability may affect sites other than the intestine in patients with Crohn's disease by simultaneously evaluating their pulmonary and intestinal permeability. Pulmonary and intestinal permeability were measured by clearance of inhaled technetium-99m diethylene triamine pentacetate (99mTc-DTPA) and by urinary recovery of chromium-51 ethylene diamine tetracetate respectively in 22 patients with Crohn's disease. The half time clearance of ...

  12. Permeable Concrete Block Paving Applications in the United Arab Emirates

    OpenAIRE

    James Eyre; Prakash Bhalchandra

    2014-01-01

    Permeable Concrete Block Paving (CBP) solutions are well established and widely implemented throughout the USA and Europe, although only recently applied in the Middle East and Asia. The concept of permeable CBP originated in Germany in the early 1980’s and has seen rapidly increasing acceptance by engineers and landscapers globally (see [1] for further details). Permeable CBP is a Construction Industry Research and Information Association (CIRIA) recognised source control component of Sustai...

  13. Determination of relevant parameters influencing gas permeability of motars

    OpenAIRE

    CARE, Sabine; Derkx, François

    2011-01-01

    This paper is devoted to the study of the influence of the microstructure of cementitious materials on their gas permeability. For that purpose, cement pastes with four water to cement ratios W/C and mortar specimens with two aggregate volume contents have been cast. On the one hand gas permeability tests with a low pressure device have been carried out on desaturated materials and on the other hand porosity features have been determined by mercury porosimetry measurements. Gas permeability d...

  14. Noble gas permeability of polymer films and coatings

    International Nuclear Information System (INIS)

    Permeabilities of noble gases, particularly argon, krypton, and xenon, were measured through a number of polymer films and coatings. Extrapolation of the log of the permeation coefficient versus the square of the gas molecular diameter was used to estimate radon permeability. An equation has been developed that can predict permeability to these noble gases as a function of the base polymer structure of the coating

  15. Bovine Colostrum Supplementation During Running Training Increases Intestinal Permeability

    OpenAIRE

    Brinkworth, Grant D.; Emma Southcott; Buckley, Jonathan D.; Butler, Ross N.

    2009-01-01

    Endurance exercise training can increase intestinal permeability which may contribute to the development of gastrointestinal symptoms in some athletes. Bovine colostrum (BC) supplementation reduces intestinal permeability induced by non-steroidal anti-inflammatory drugs. This study aimed to determine whether BC could also reduce intestinal permeability induced by endurance exercise. Thirty healthy adult males (25.0 ± 4.7 yr; mean ± SD) completed eight weeks of running three times per week for...

  16. An Experimental Study of Micron-Size Zero-Valent Iron Emplacement in Permeable Porous Media Using Polymer-Enhanced Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A.; Vermeul, Vince R.

    2005-12-22

    At the Hanford Site, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. One possible cause for premature chromate breakthrough is associated with the presence of high-permeability zones in the aquifer. In these zones, groundwater moves relatively fast and is able to oxidize iron more rapidly. There is also a possibility that the high-permeability flow paths are deficient in reducing equivalents (e.g. reactive iron), required for barrier performance. One way enhancement of the current barrier reductive capacity can be achieved is by the addition of micron-scale zero-valent iron to the high-permeability zones within the aquifer. The potential emplacement of zero-valent iron (Fe0) into high-permeability Hanford sediments (Ringold Unit E gravels) using shear-thinning fluids containing polymers was investigated in three-dimensional wedge-shaped aquifer models. Polymers were used to create a suspension viscous enough to keep the Fe0 in solution for extended time periods to improve colloid movement into the porous media without causing a permanent detrimental decrease in hydraulic conductivity. Porous media were packed in the wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone in between two low-permeability zones or a high-permeability channel surrounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments.

  17. Intestinal permeability study of minoxidil: assessment of minoxidil as a high permeability reference drug for biopharmaceutics classification.

    Science.gov (United States)

    Ozawa, Makoto; Tsume, Yasuhiro; Zur, Moran; Dahan, Arik; Amidon, Gordon L

    2015-01-01

    The purpose of this study was to evaluate minoxidil as a high permeability reference drug for Biopharmaceutics Classification System (BCS). The permeability of minoxidil was determined in in situ intestinal perfusion studies in rodents and permeability studies across Caco-2 cell monolayers. The permeability of minoxidil was compared with that of metoprolol, an FDA reference drug for BCS classification. In rat perfusion studies, the permeability of minoxidil was somewhat higher than that of metoprolol in the jejunum, while minoxidil showed lower permeability than metoprolol in the ileum. The permeability of minoxidil was independent of intestinal segment, while the permeability of metoprolol was region-dependent. Similarly, in mouse perfusion study, the jejunal permeability of minoxidil was 2.5-fold higher than that of metoprolol. Minoxidil and metoprolol showed similar permeability in Caco-2 study at apical pH of 6.5 and basolateral pH of 7.4. The permeability of minoxidil was independent of pH, while metoprolol showed pH-dependent transport in Caco-2 study. Minoxidil exhibited similar permeability in the absorptive direction (AP-BL) in comparison with secretory direction (BL-AP), while metoprolol had higher efflux ratio (ER > 2) at apical pH of 6.5 and basolateral pH of 7.4. No concentration-dependent transport was observed for either minoxidil or metoprolol transport in Caco-2 study. Verapamil did not alter the transport of either compounds across Caco-2 cell monolayers. The permeability of minoxidil was independent of both pH and intestinal segment in intestinal perfusion studies and Caco-2 studies. Caco-2 studies also showed no involvement of carrier mediated transport in the absorption process of minoxidil. These results suggest that minoxidil may be an acceptable reference drug for BCS high permeability classification. However, minoxidil exhibited higher jejunal permeability than metoprolol and thus to use minoxidil as a reference drug would raise the

  18. Channel estimation for MIMO-OFDM systems in wireless mobile channels

    Institute of Scientific and Technical Information of China (English)

    Lu Zhen; Ge Jianhua

    2008-01-01

    New training sequences and frame structure are proposed to estimate time-varying channel for multiple-input multiple-output and orthogonal frequency division multiplexing (MIMO-OFDM) systems. The training sequences are modulatable orthogonal polyphase sequences, which have both good autocorrelations and cross-correlations. The channel impulse response (CIR) can be obtained by measuring the correlation between the received training sequence and the locally generated training sequence. The training sequences are used as guard interval instead of cyclic prefix, which not only improve the transmission efficiency but also enable the channel estimator to track time-varying channel. The simulation results show that the proposed method has about 2dB SNR gain over conventional methods in fast time-varying channel.

  19. Buoyancy Effect on MHD Flow Past a Permeable Bed

    OpenAIRE

    S. Venkataramana; D. Bathaiah

    1986-01-01

    In this paper, the effect of buoyancy force on the parallel flows bounded above by a rigid permeable plate which may be moving or stationary and below, by a permeable bed has been investigated. To discuss the solution, the flow region is divided into two zones. In Zone 1, the flow is laminar and is governed by the Navier-Stokes equations from the impermeable upper rigid plate to the permeable bed. In Zone 2, the flow is governed by the Darcy law in the permeable bed below the nominal surface....

  20. Experiment Study on Permeability of Solidified Dianchi Peaty Soil

    Directory of Open Access Journals (Sweden)

    Wang Mingshan

    2015-01-01

    Full Text Available In this paper, the permeability of Dianchi solidified peaty soil was studied by laboratory tests. The peaty soil was solidified by addicting cement, ardealite, lime, fly ash and their combination, and the coeffi-cient of permeability under different curing stages were measured through the variable head method. Results showed that the coefficient of permeability of solidified peaty soil increased with the growth of the dosage of curing stagent and reduced with the growth of the stage. When the determined dosage in the deep mixing pile is used, it would be meet the permeability the need of the engineering.

  1. Wetting phase permeability in a partially saturated horizontal fracture

    International Nuclear Information System (INIS)

    A major obstacle to understanding of unsaturated fracture flow is the paucity of physical data on both fracture aperture structure and the effects of phase structure on permeability. An experimental procedure is developed for collecting detailed data on aperture and phase structure from a transparent analog fracture. Stable phase structures of varying complexity are creating within the horizontal analog fracture. Wetting phase permeability is measured under steady-state conditions. A process based model for wetting phase relative permeability is explored. Average distribution of the wetting phase is shown to provide insufficient information for modeling relative permeability; descriptive models must account for spatial structure of the phases

  2. Permeability of continental crust influenced by internal and external forcing

    Science.gov (United States)

    Rojstaczer, S.A.; Ingebritsen, S.E.; Hayba, D.O.

    2008-01-01

    The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability-depth relations) on a very large scale? Here we argue that large-scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing - fluxes induced by metamorphism, magmatism, and mantle degassing - is dominant, whereas in the shallow crust, external forcing - the vigor of the hydrologic cycle - is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near-lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near-hydrostatic fluid pressures are the norm. We use first-order calculations and numerical modeling to explore the hypothesis that upper-crustal permeability is influenced by the magnitude of external fluid sources, much as lower-crustal permeability is influenced by the magnitude of internal fluid sources. We compare model-generated permeability structures with various observations of crustal permeability. ?? 2008 The Authors Journal compilation ?? 2008 Blackwell Publishing Ltd.

  3. Neural Approach for Calculating Permeability of Porous Medium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ji-Cheng; LIU Li; SONG Kao-Ping

    2006-01-01

    @@ Permeability is one of the most important properties of porous media. It is considerably difficult to calculate reservoir permeability precisely by using single well-logging response and simple formula because reservoir is of serious heterogeneity, and well-logging response curves are badly affected by many complicated factors underground. We propose a neural network method to calculate permeability of porous media. By improving the algorithm of the back-propagation neural network, convergence speed is enhanced and better results can be achieved. A four-layer back-propagation network is constructed to effectively calculate permeability from well log data.

  4. Permeability of Electro spun Super hydrophobic Nano fiber Mats

    International Nuclear Information System (INIS)

    This paper discusses the fabrication and characterization of electro spun nano fiber mats made up of poly(4-methyl-1-pentene) polymer. The polymer was electro spun in different weight concentrations. The mats were characterized by their basis weight, fiber diameter distribution, contact angles, contact angle hysteresis, and air permeability. All of the electro spun nonwoven fiber mats had water contact angles greater than 150 degrees making them super hydrophobic. The permeabilities of the mats were empirically fitted to the mat basis weight by a linear relation. The experimentally measured air permeabilities were significantly larger than the permeabilities predicted by the Kuwabara model for fibrous media.

  5. Identification of channel-forming activity in the cell wall of Corynebacterium glutamicum.

    OpenAIRE

    Niederweis, M.; Maier, E. (Eva Maria); Lichtinger, T; Benz, R; Krämer, R

    1995-01-01

    The cell wall of the gram-positive Corynebacterium glutamicum was prepared. It contained an ion-permeable channel with a single-channel conductance of about 6 nS in 1 M KCl. The mobility sequence of the ions in the channel is similar to that in the aqueous phase, suggesting that it is a water-filled channel wide enough to allow unhindered diffusion of ions. The results indicate that we have identified the hydrophilic pathway through the mycolic acid layer of C. glutamicum.

  6. Water transportation across narrow channel of nanometer dimension

    Science.gov (United States)

    Wan, Rongzheng; Fang, Haiping

    2010-06-01

    Since the discovery of the carbon nanotube and aquaporin, the study of the transportation of water across nanochannels has become one of the hot subjects. When the radius of a nanochannel is only about one nanometer or a little larger, water confined in those nanoscale channels usually exhibits dynamics different from those in bulk system, such as the wet-dry transition due to the confinement, concerted hydrogen-bond orientations and flipping, concerted motion of water molecules, and strong interactions with external charges. Those dynamics correlate with the unique behavior of the water transportation across the channels, such as the extra-high permeability, excellent on-off gating behavior with response to the external mechanical and electrical signals and noises, enhancement by structure outside the channel, directional transportation driven by charges close to a channel or electric field. In this article, we review some of the recent progress on the study of the water molecules inside those narrow nanochannels.

  7. Sodium permeability of frog skeletal muscle in absence and presence of veratridine

    International Nuclear Information System (INIS)

    The effect of veratridine on the Na permeability of frog sartorius muscle was studied by means of ion flux measurements using radiolabeled sodium. Veratridine increases Na influx in a dose-dependent manner. The increase can be completely inhibited by tetrodoxotin (TTX) indicating that all veratridine-induced Na influx occurs via sodium channels. The time constant for the rate of onset of veratridine action is 1 h. Raising external pH one unit to 8.3 causes the rate of action of veratridine and the final level of Na influx to increase. The apparent K/sub d/ for veratridine depends on membrane voltage. Veratridine-induced Na influx obeys the Goldman constant field flux equation and when veratridine concentration is 1 mM, sodium permeability is 1.5 x 10-7 cm/s. This is much less than the maximum P/sub Na/ (1.6 x 10-3 cm/s) obtained from voltage-clamp measurements of peak Na conductance. Mg (52 mM) inhibits veratridine-induced influx by about half. Aspects of resting Na influx in the absence of veratridine were also characterized. Steady-state Na influx is unaffected by tetrodoxotin over the voltage range -90-0 mV, suggesting that no sodium channels are open in the resting state. Na influx is also insensitive to curare. It is linearly dependent on external sodium and larger at more negative membrane potentials

  8. On the structural basis for ionic selectivity among Na+, K+, and Ca2+ in the voltage-gated sodium channel.

    OpenAIRE

    Favre, I; Moczydlowski, E; Schild, L

    1996-01-01

    Voltage-sensitive sodium channels and calcium channels are homologous proteins with distinctly different selectivity for permeation of inorganic cations. This difference in function is specified by amino acid residues located within P-region segments that link presumed transmembrane elements S5 and S6 in each of four repetitive Domains I, II, III, and IV. By analyzing the selective permeability of Na+, K+, and Ca2+ in various mutants of the mu 1 rat muscle sodium channel, the results in this ...

  9. Enhanced CO2 permeability of membranes by incorporating polyzwitterion@CNT composite particles into polyimide matrix.

    Science.gov (United States)

    Liu, Ye; Peng, Dongdong; He, Guangwei; Wang, Shaofei; Li, Yifan; Wu, Hong; Jiang, Zhongyi

    2014-08-13

    In this study, polyzwitterion is introduced into a CO2 separation membrane. Composite particles of polyzwitterion coated carbon nanotubes (SBMA@CNT) are prepared via a precipitation polymerization method. Hybrid membranes are fabricated by incorporating SBMA@CNT in polyimide matrix and utilized for CO2 separation. The prepared composite particles and hybrid membranes are characterized by transmission electron microscopy (TEM) with element mapping, field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC) and an electronic tensile machine. Water uptake and water state of membranes are measured to probe the relationship among water uptake, water state and CO2 transport behavior. Hybrid membranes show significantly enhanced CO2 permeability compared to an unfilled polyimide membrane at a humidified state. A hybrid membrane with 5 wt % SBMA@CNT exhibits the maximum CO2 permeability of 103 Barrer with a CO2/CH4 selectivity of 36. The increase of CO2 permeability is attributed to the incorporation of the SBMA@CNT composite particles. First, SBMA@CNT form interconnected channels for CO2 transport due to the facilitated transport effect of the quaternary ammonium in repeat unit of pSBMA. Second, SBMA@CNT improve water uptake and adjust water state of membrane, which further increases CO2 permeability. Meanwhile, the variation of CO2/CH4 selectivity is dependent on the bound water portion in the membrane. A gas permeation test at a dry state and a pressure test are conducted to further probe the membrane separation performance. PMID:25068977

  10. Interaction of free fatty acids with mitochondria: coupling, uncoupling and permeability transition.

    Science.gov (United States)

    Di Paola, Marco; Lorusso, Michele

    2006-01-01

    Long chain free fatty acids (FFA) exert, according to their actual concentration, different effects on the energy conserving system of mitochondria. Sub-micromolar concentrations of arachidonic acid (AA) rescue DeltapH-dependent depression of the proton pumping activity of the bc1 complex. This effect appears to be due to a direct interaction of AA with the proton-input mouth of the pump. At micromolar concentrations FFA increase the proton conductance of the inner membrane acting as protonophores. FFA can act as natural uncouplers, causing a mild uncoupling, which prevents reactive oxygen species production in the respiratory resting state. When Ca(2+)-loaded mitochondria are exposed to micromolar concentrations of FFA, the permeability of the inner membrane increases, resulting in matrix swelling, rupture of the outer membrane and release of intermembrane pro-apoptotic proteins. The characteristics of AA-induced swelling appear markedly different in mitochondria isolated from heart or liver. While in the latter it presents the canonical features of the classical permeability transition (PT), in heart mitochondria substantial differences are observed concerning CsA sensitivity, DeltaPsi dependence, reversibility by BSA and specificity for the activating divalent cation. In heart mitochondria, the AA-dependent increase of the inner membrane permeability is affected by ANT ligands such as adenine nucleotides and atractyloside. AA apparently causes a Ca2+-mediated conversion of ANT from a translocator to a channel system. Upon diamide treatment of heart mitochondria, the Ca2+/AA-induced CsA insensitive channel is converted into the classical PT pore. The relevance of these observations in terms of tissue-specific components of the putative PTP and heart ischemic and post-ischemic process is discussed. PMID:16697347

  11. Cadmium substituted high permeability lithium ferrite

    Indian Academy of Sciences (India)

    S S Bellad; S C Watawe; A M Shaikh; B K Chougule

    2000-04-01

    Polycrystalline Li0.5–/2 Cd Fe2.5–/2O4 ferrites where = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 were prepared by a double sintering ceramic technique and characterized by X-ray diffraction and scanning electron microscopy (SEM). The lattice parameter is found to increase monotonically with the cadmium content. It is explained in terms of the sizes of component ions. The grain size of the samples increases up to = 0.3 and then it decreases for higher values of . A similar trend is observed in the variation of Ms with Cd2+ content. The initial permeability () is however found to increase continuously with . The increase in is attributed to decrease of anisotropy constant K1 and higher grain size of the samples.

  12. Fluid permeability measurement system and method

    Science.gov (United States)

    Hallman, Jr., Russell Louis; Renner, Michael John

    2008-02-05

    A system for measuring the permeance of a material. The permeability of the material may also be derived. The system provides a liquid or high concentration fluid bath on one side of a material test sample, and a gas flow across the opposing side of the material test sample. The mass flow rate of permeated fluid as a fraction of the combined mass flow rate of gas and permeated fluid is used to calculate the permeance of the material. The material test sample may be a sheet, a tube, or a solid shape. Operational test conditions may be varied, including concentration of the fluid, temperature of the fluid, strain profile of the material test sample, and differential pressure across the material test sample.

  13. Composite Crew Module (CCM) Permeability Characterization

    Science.gov (United States)

    Kirsch, Michael T.

    2013-01-01

    In January 2007, the NASA Administrator chartered the NASA Engineering and Safety Center (NESC) to form an Agency team to design and build a composite crew module in 18 months in order to gain hands-on experience in anticipation that future exploration systems may be made of composite materials. One of the conclusions from this Composite Crew Module Primary Structure assessment was that there was a lack of understanding regarding the ability for composite pressure shells to contain consumable gases, which posed a technical risk relative to the use of a metallic design. After the completion of the Composite Crew Module test program, the test article was used in a new program to assess the overall leakage/permeability and identify specific features associated with high leak rates. This document contains the outcome of the leakage assessment.

  14. Helium gas permeability of Kapton polyimide film

    International Nuclear Information System (INIS)

    In a beam line for radioactive samples of a large-scale synchrotron radiation facility, it is necessary to protect the storage ring from contamination in a case of accident in a measurement chamber. For the purpose it has been proposed to separate the beam line from the storage ring using two sheets of polyimide film (Kapton), between which helium gas is introduced; the damage in the sheets could be detected by continuous helium gas leak monitoring. To examine whether this method is effective or not, helium permeation rate was measured for Kapton sheets of 25, 12.5 and 7.9 μm thickness at room temperatures. The obtained permeability was (7∼8)x10-16 mol·m-1·Pa-1·s-1, which is so high that the small defects in the sheets cannot be detected. Accordingly another detection method should be considered when Kapton is used as the separator. (author)

  15. Water permeability in human airway epithelium

    DEFF Research Database (Denmark)

    Pedersen, Peter Steen; Procida, Kristina; Larsen, Per Leganger;

    2005-01-01

    Osmotic water permeability (P(f)) was studied in spheroid-shaped human airway epithelia explants derived from nasal polyps by the use of a new improved tissue collection and isolation procedure. The fluid-filled spheroids were lined with a single cell layer with the ciliated apical cell membrane......(f), determined by the changes of the apical solution osmolarity, was not influenced by the presence of glucose, Na(+), or Na(+)/glucose-cotransport inhibitors in the bath, but was sensitive to the aquaporin (AQP) inhibitor HgCl(2). The measured P(f) levels and the values of activation energy were in the range...... of those seen in AQP-associated water transport. Together, these results indicate the presence of an AQP in the apical membrane of the spheroids. Notably, identical values for P(f) were found in CF and non-CF airway preparations, as was the case also for the calculated spontaneous fluid absorption rates....

  16. Composite binders for concrete with reduced permeability

    Science.gov (United States)

    Fediuk, R.; Yushin, A.

    2016-02-01

    Composite binder consisting of cement (55%), acid fly ash (40%) and limestone (5%) has been designed. It is obtained by co-milling to a specific surface of 550 kg/m2, it has an activity of 77.3 MPa and can produce a more dense cement stone structure. Integrated study revealed that the concrete on the composite binder basis provides an effective diffusion coefficient D. So we can conclude that the concrete layer protects buildings from toxic effects of expanded polystyrene. Low water absorption of the material (2.5% by weight) is due to the structure of its cement stone pore space. Besides lime powder prevents the penetration of moisture, reduces water saturation of the coverage that has a positive effect on useful life period. It also explains rather low water vapor permeability of the material - 0.021 mg/(m- hour-Pa).

  17. Consolidation and permeability of salt in brine

    Energy Technology Data Exchange (ETDEWEB)

    Shor, A.J.; Baes, C.F. Jr.; Canonico, C.M.

    1981-07-01

    The consolidation and loss of permeability of salt crystal aggregates, important in assessing the effects of water in salt repositories, has been studied as a function of several variables. The kinetic behavior was similar to that often observed in sintering and suggested the following expression for the time dependence of the void fraction: phi(t) = phi(0) - (A/B)ln(1 + Bt/z(0)/sup 3/), where A and B are rate constants and z(0) is initial average particle size. With brine present, A and phi(0) varied linearly with stress. The initial void fraction was also dependent to some extent on the particle size distribution. The rate of consolidation was most rapid in brine and least rapid in the presence of only air as the fluid. A brine containing 5 m MgCl/sub 2/ showed an intermediate rate, presumably because of the greatly reduced solubility of NaCl. A substantial wall effect was indicated by an observed increase in the void fraction of consolidated columns with distance from the top where the stress was applied and by a dependence of consolidation rate on the column height and radius. The distance through which the stress fell by a factor of phi was estimated to change inversely as the fourth power of the column diameter. With increasing temperature (to 85/sup 0/C), consolidation proceeded somewhat more rapidly and the wall effect was reduced. The permeability of the columns dropped rapidly with consolidation, decreasing with about the sixth power of the void fraction. In general, extrapolation of the results to repository conditions confirms the self-sealing properties of bedded salt as a storage medium for radioactive waste.

  18. Remediation of DNAPLs in Low Permeability Soils. Innovative Technology Summary Report

    International Nuclear Information System (INIS)

    Dense, non-aqueous phase liquid (DNAPL) compounds like trichloroethene (TCE) and perchloroethene (PCE) are prevalent at U. S. Department of Energy (DOE), other government, and industrial sites. Their widespread presence in low permeability media (LPM) poses severe challenges for assessment of their behavior and implementation of effective remediation technologies. Most remedial methods that involve fluid flow perform poorly in LPM. Hydraulic fracturing can improve the performance of remediation methods such as vapor extraction, free-product recovery, soil flushing, steam stripping, bioremediation, bioventing, and air sparging in LPM by enhancing formation permeability through the creation of fractures filled with high-permeability materials, such as sand. Hydraulic fracturing can improve the performance of other remediation methods such as oxidation, reductive dechlorination, and bioaugmentation by enhancing delivery of reactive agents to the subsurface. Hydraulic fractures are typically created using a 2-in. steel casing and a drive point pushed into the subsurface by a pneumatic hammer. Hydraulic fracturing has been widely used for more than 50 years to stimulate the yield of wells recovering oil from rock at great depth and has recently been shown to stimulate the yield of wells recovering contaminated liquids and vapors from LPM at shallow depths. Hydraulic fracturing is an enabling technology for improving the performance of some remedial methods and is a key element in the implementation of other methods. This document contains information on the above-mentioned technology, including description, applicability, cost, and performance data

  19. Zn- and Cu-substituted Co2Y hexagonal ferrites: Sintering behavior and permeability

    Science.gov (United States)

    Bierlich, S.; Töpfer, J.

    2012-05-01

    Y-type polycrystalline hexagonal ferrites Ba2Co2-x-yZnxCuyFe12O22 with 0≤x≤2 and 0≤y≤0.8 were prepared by the mixed-oxide route. Single phase Y-type ferrite powders were obtained after calcinations at 1000 °C. Samples sintered at 1200 °C show a permeability that increases with the substitution of Zn for Co and display maximum permeability of μ‧=35 at 1 MHz for x=1.6 and y=0.4. A resonance frequency fr=500 MHz is observed for Zn-rich ferrites with y=0 and 0.4. The saturation magnetization increases with substitution of Zn for Co. Addition of Bi2O3 shifts the temperature of maximum shrinkage down to T≤950 °C. Moreover, an increase of the Cu-concentration further lowers the sintering temperature to T≤900 °C, enabling co-firing of the ferrites with Ag metallization for multilayer technologies. However, low-temperature firing reduces the permeability to μ‧=10 and the resonance frequency is shifted to 1 GHz. Thus substituted hexagonal Y-type ferrites can be used as soft magnetic materials for multilayer inductors for high frequency applications.

  20. Effect of lung injuries on [14C]urea permeability-surface area product in dogs

    International Nuclear Information System (INIS)

    To determine whether [14C]urea permeability-surface area product (PS) is a reliable indicator of changes in permeability in various injuries and its relationship to indicator-dilution and gravimetric lung water contents, we studied six groups of anesthetized, paralyzed, and mechanically ventilated dogs (5 animals each). The groups consisted of control dogs, those injured by intravenous alloxan, oleic acid, or glass beads, and those exposed to acute hypoxia or increased left atrial pressure from volume loading (Pla). Interanimal variation of PS was large (3.0-15.0 ml/s), but successive hourly values in individual animals were stable for 2 h in experimental groups and for 4 h in controls. The PS increased after alloxan, elevated Pla, and 2 h of hypoxia; PS decreased after oleic acid and micremboli. The gravimetric lung water increased after alloxan, oleic acid, and microemboli, and indicator-dilution lung water increased only after alloxan. We conclude (1) that intersubject variability requires normalization to enable detection of significant deviation from base line, and (2) that decreased PS after oleic acid and microvascular injury occurred because vascular obstruction, which decreased surface area, masked probable coexisting increases in capillary permeability

  1. Hydraulic Permeability of Resorcinol-Formaldehyde Resin

    International Nuclear Information System (INIS)

    An ion exchange process using spherical resorcinol-formaldehyde (RF) resin is the baseline process for removing cesium from the dissolved salt solution in the high-level waste tanks at the Hanford Site, using large scale columns as part of the Waste Treatment Plant (WTP). The RF resin is also being evaluated for use in the proposed small column ion exchange (SCIX) system, which is an alternative treatment option at Hanford and at the Savannah River Site (SRS). A recirculating test loop with a small ion exchange column was used to measure the effect of oxygen uptake and radiation exposure on the permeability of a packed bed of the RF resin. The lab-scale column was designed to be prototypic of the proposed Hanford columns at the WTP. Although the test equipment was designed to model the Hanford ion exchange columns, the data on changes in the hydraulic permeability of the resin will also be valuable for determining potential pressure drops through the proposed SCIX system. The superficial fluid velocity in the lab-scale test (3.4-5.7 cm/s) was much higher than is planned for the full-scale Hanford columns to generate the maximum pressure drop expected in those columns (9.7 psig). The frictional drag from this high velocity produced forces on the resin in the lab-scale tests that matched the design basis of the full-scale Hanford column. Any changes in the resin caused by the radiation exposure and oxygen uptake were monitored by measuring the pressure drop through the lab-scale column and the physical properties of the resin. Three hydraulic test runs were completed, the first using fresh RF resin at 25 C, the second using irradiated resin at 25 C, and the third using irradiated resin at 45 C. A Hanford AP-101 simulant solution was recirculated through a test column containing 500 mL of Na-form RF resin. Known amounts of oxygen were introduced into the primary recirculation loop by saturating measured volumes of the simulant solution with oxygen and reintroducing

  2. Hydraulic Permeability of Resorcinol-Formaldehyde Resin

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Paul Allen [ORNL

    2010-01-01

    An ion exchange process using spherical resorcinol-formaldehyde (RF) resin is the baseline process for removing cesium from the dissolved salt solution in the high-level waste tanks at the Hanford Site, using large scale columns as part of the Waste Treatment Plant (WTP). The RF resin is also being evaluated for use in the proposed small column ion exchange (SCIX) system, which is an alternative treatment option at Hanford and at the Savannah River Site (SRS). A recirculating test loop with a small ion exchange column was used to measure the effect of oxygen uptake and radiation exposure on the permeability of a packed bed of the RF resin. The lab-scale column was designed to be prototypic of the proposed Hanford columns at the WTP. Although the test equipment was designed to model the Hanford ion exchange columns, the data on changes in the hydraulic permeability of the resin will also be valuable for determining potential pressure drops through the proposed SCIX system. The superficial fluid velocity in the lab-scale test (3.4-5.7 cm/s) was much higher than is planned for the full-scale Hanford columns to generate the maximum pressure drop expected in those columns (9.7 psig). The frictional drag from this high velocity produced forces on the resin in the lab-scale tests that matched the design basis of the full-scale Hanford column. Any changes in the resin caused by the radiation exposure and oxygen uptake were monitored by measuring the pressure drop through the lab-scale column and the physical properties of the resin. Three hydraulic test runs were completed, the first using fresh RF resin at 25 C, the second using irradiated resin at 25 C, and the third using irradiated resin at 45 C. A Hanford AP-101 simulant solution was recirculated through a test column containing 500 mL of Na-form RF resin. Known amounts of oxygen were introduced into the primary recirculation loop by saturating measured volumes of the simulant solution with oxygen and reintroducing

  3. An Internet enabled impact limiter material database

    International Nuclear Information System (INIS)

    This paper presents a detailed explanation of the construction of an interest enabled database, also known as a database driven web site. The data contained in the internet enabled database are impact limiter material and seal properties. The technique used in constructing the internet enabled database presented in this paper are applicable when information that is changing in content needs to be disseminated to a wide audience

  4. Dynamic channel allocation

    OpenAIRE

    Kaminsky, Andrew D.

    2003-01-01

    Approved for public release; distribution in unlimited. Dynamic Channel Allocation (DCA) offers the possibility of capturing unused channel capacity by allocating unused resources between competing network nodes. This can reduce or possibly eliminate channels sitting idle while information awaits transmission. This holds potential for increasing throughput on bandwidth constrained networks. The purpose of this thesis is to examine the techniques used to allocate channels on demand and acc...

  5. Potassium channels and vascular reactivity in genetically hypertensive rats.

    Science.gov (United States)

    Furspan, P B; Webb, R C

    1990-06-01

    In hypertension, membrane potassium permeability and vascular reactivity are increased. This study characterizes a potassium-selective channel and contractions to barium, a potassium channel inhibitor, in vascular smooth muscle (tail artery) from spontaneously hypertensive stroke-prone rats (SHRSP) and normotensive Wistar-Kyoto (WKY) rats. Smooth muscle cells were isolated by enzymatic digestion, and potassium channel activity was characterized by using patch-clamp technique (inside-out configuration). Isometric contractile activity was evaluated in helically cut arterial strips by using standard muscle bath methodology. In membrane patches, a voltage-gated, calcium-insensitive, potassium-selective channel of large conductance (200 picosiemens) was observed. The channel did not conduct sodium or rubidium. Barium (10(-6) to 10(-4) M) produced a dose-dependent blockade of channel activity. These channel characteristics did not differ in SHRSP and WKY rat cells. After treatment with 35 mM KCl, barium (10(-5) to 10(-3) M) caused greater contractions in SHRSP arteries compared with arteries in WKY rats. The contractions to barium were markedly attenuated in calcium-free solution, and nifedipine and verapamil abolished contractions induced by barium in depolarizing solution. We conclude that increased vascular reactivity to barium in SHRSP arteries is not due to an alteration in the biophysical properties of the potassium channel studied. PMID:2351424

  6. Semantic Sensor Web Enablement for COAST Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Sensor Web Enablement (SWE) is an Open Geospatial Consortium (OGC) standard Service Oriented Architecture (SOA) that facilitates discovery and integration of...

  7. Critical assessment of OmpF channel selectivity: merging information from different experimental protocols

    International Nuclear Information System (INIS)

    The ion selectivity of a channel can be quantified in several ways by using different experimental protocols. A wide, mesoscopic channel, the OmpF porin of the outer membrane of E. coli, serves as a case study for comparing and analysing several measures of the channel cation-anion permeability in chlorides of alkali metals (LiCl, NaCl, KCl, CsCl). We show how different insights can be gained and integrated to rationalize the global image of channel selectivity. To this end, reversal potential, channel conductance and bi-ionic potential (two different salts with a common anion on each side of the channel but with the same concentration) experiments are discussed in light of an electrodiffusion model based on the Poisson-Nernst-Planck formalism. Measurements and calculations based on the atomic crystal structure of the channel show that each protocol displays a particular balance between the different sources of selectivity.

  8. Apical Na+ permeability of frog skin during serosal Cl- replacement.

    Science.gov (United States)

    Leibowich, S; DeLong, J; Civan, M M

    1988-05-01

    Gluconate substitution for serosal Cl- reduces the transepithelial short-circuit current (Isc) and depolarizes short-circuited frog skins. These effects could result either from inhibition of basolateral K+ conductance, or from two actions to inhibit both apical Na+ permeability (PapNa) and basolateral pump activity. We have addressed this question by studying whole-and split-thickness frog skins. Intracellular Na+ concentration (CcNa) and PapNa have been monitored by measuring the current-voltage relationship for apical Na+ entry. This analysis was conducted by applying trains of voltage pulses, with pulse durations of 16 to 32 msec. Estimates of PapNa and CcNa were not detectably dependent on pulse duration over the range 16 to 80 msec. Serosal Cl- replacement uniformly depolarized short-circuited tissues. The depolarization was associated with inhibition of Isc across each split skin, but only occasionally across the whole-thickness preparations. This difference may reflect the better ionic exchange between the bulk medium and the extracellular fluid in contact with the basolateral membranes, following removal of the underlying dermis in the split-skin preparations. PapNa was either unchanged or increased, and CcNa either unchanged or reduced after the anionic replacement. These data are incompatible with the concept that serosal Cl- replacement inhibits PapNa and Na,K-pump activity. Gluconate substitution likely reduces cell volume, triggering inhibition of the basolateral K+ channels, consistent with the data and conclusions of S.A. Lewis, A.G. Butt, M.J. Bowler, J.P. Leader and A.D.C. Macknight (J. Membrane Biol. 83:119-137, 1985) for toad bladder. The resulting depolarization reduces the electrical force favoring apical Na+ entry. The volume-conductance coupling serves to conserve volume by reducing K+ solute loss. Its molecular basis remains to be identified. PMID:2458472

  9. Receptor-mediated glutamate release from volume sensitive channels in astrocytes

    Science.gov (United States)

    Takano, Takahiro; Kang, Jian; Jaiswal, Jyoti K.; Simon, Sanford M.; Lin, Jane H.-C.; Yu, Yufei; Li, Yuxing; Yang, Jay; Dienel, Gerald; Zielke, H. Ronald; Nedergaard, Maiken

    2005-11-01

    Several lines of work have shown that astrocytes release glutamate in response to receptor activation, which results in a modulation of local synaptic activity. Astrocytic glutamate release is Ca2+-dependent and occurs in conjunction with exocytosis of glutamate containing vesicles. However, astrocytes contain a millimolar concentration of cytosolic glutamate and express channels permeable to small anions, such as glutamate. Here, we tested the idea that astrocytes respond to receptor stimulation by dynamic changes in cell volume, resulting in volume-sensitive channel activation, and efflux of cytosolic glutamate. Confocal imaging and whole-cell recordings demonstrated that astrocytes exhibited a transient Ca2+-dependent cell volume increase, which activated glutamate permeable channels. HPLC analysis revealed that glutamate was released in conjunction with other amino acid osmolytes. Our observations indicate that volume-sensitive channel may constitute a previously uncharacterized target for modulation of astrocyte-neuronal interactions. electrophysiology | exocytosis | neurotransmitters | osmolarity | synapses

  10. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  11. Quantum Channels With Memory

    International Nuclear Information System (INIS)

    Quantum memory channels represent a very general, yet simple and comprehensible model for causal processes. As such they have attracted considerable research interest, mostly aimed on their transfer capabilities and structure properties. Most notably it was shown that memory channels can be implemented via physically naturally motivated collision models. We also define the concept of repeatable channels and show that only unital channels can be implemented repeat ably with pure memory channels. In the special case of qubit channels we also show that every unital qubit channel has a repeatable implementation. We also briefly explore the possibilities of stroboscopical simulation of channels and show that all random unitary channels can be stroboscopically simulated. Particularly in qubit case, all indivisible qubit channels are also random unitary, hence for qubit all indivisible channels can be stroboscopically simulated. Memory channels also naturally capture the framework of correlated experiments. We develop methods to gather and interpret data obtained in such setting and in detail examine the two qubit case. We also show that for control unitary interactions the measured data will never contradict a simple unitary evolution. Thus no memory effects can be spotted then. (author)

  12. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  13. Desynched channels on IRCnet

    CERN Document Server

    Hansen, Michael

    2008-01-01

    In this paper we describe what a desynchronised channel on IRC is. We give procedures on how to create such a channel and how to remove desynchronisation. We explain which types of desynchronisation there are, what properties desynchronised channels have, and which properties can be exploited.

  14. Permeability of R6G across C×43 hemichannels through a novel combination of patch clamp and surface enhanced Raman spectroscopy

    Indian Academy of Sciences (India)

    C madhavan Nair; C Sabna; K V G K Murty; S V Ramanan

    2005-10-01

    We have measured the permeability of rhodamine-6G across C×43 hemichannels reconstituted on a pipette tip. C×43 hemichannels were overexpressed in Sf9 cells, and affinity-purified. The hemichannels were reconstituted in a lipid bilayer on a pipette tip by the tip-dip method. R6G in the pipette permeated across the channels into the bath. The permeability of R6G was quantified by measuring R6G concentration in the bath after several hours by surface enhanced Raman spectroscopy (SERS) with 100 nm silver colloid particles. The ratio of the permeability of dye to salt, as extracted by this combined electrical-SERS technique, is compatible with similar ratios for other dyes across whole gap junction channels. The results for the permeability ratio were further compared to fluorescence measurements. The novel combination of patch and SERS techniques can be extended to quantifying the transport of biologically significant non-fluorescent molecules, such as cAMP and IP3, across 1 nm sized pores, such as the gap junction channel.

  15. Current-voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

    DEFF Research Database (Denmark)

    Fuchs, W; Larsen, Erik Hviid; Lindemann, B

    1977-01-01

    1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na-selective membrane.2. In this state, the transepithelial voltage (V) was...

  16. The permeability transition pore as a Ca2+ release channel: New answers to an old question

    OpenAIRE

    Bernardi, Paolo; von Stockum, Sophia

    2012-01-01

    Mitochondria possess a sophisticated array of Ca2+ transport systems reflecting their key role in physiological Ca2+ homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca2+ uptake, the ruthenium red (RR)-sensitive mitochondrial Ca2+ uniporter (MCU); and one main mechanism for Ca2+ release, the RR-insensitive 3Na+–Ca2+ antiporter. An additional mechanism for Ca2+ release is provided by a Na+ and RR-insensitive re...

  17. The effects of the Histone Deacetylase (HDAC Inhibitor 4-Phenylbutyrate on gap junction conductance and permeability

    Directory of Open Access Journals (Sweden)

    PeterBrink

    2013-09-01

    Full Text Available Longitudinal resistance is a key factor in determining cardiac action potential propagation. Action potential conduction velocity has been shown to be proportional to the square root of longitudinal resistance. A major determinant of longitudinal resistance in myocardium is the gap junction channel, comprised of connexin proteins. Within the ventricular myocardium connexin 43 (Cx43 is the dominantly expressed connexin. Reduced numbers of gap junction channels will result in an increase in longitudinal resistance creating the possibility of slowed conduction velocity while increased numbers of channels would potentially result in an increase in conduction velocity. We sought to determine if inhibition of histone deacetylase (HDAC by 4-phenylbutyrate (4-PB, a known inhibitor of HDAC resulted in an increase in junctional conductance and permeability, which is not the result of changes in single channel unitary conductance. These experiments were performed using HEK-293 cells and HeLa cells stably transfected with Cx43. Following treatment with increasing concentrations of 4-PB up-regulation of Cx43 was observed via Western blot analysis. Junctional (gj conductance and unitary single channel conductance were measured via whole-cell patch clamp. In addition intercellular transfer of Lucifer Yellow (LY was determined by fluorescence microscopy. The data in this study indicates that 4-PB is able to enhance functional Cx43 gap junction coupling as indicated by LY dye transfer and multichannel and single channel data along with Western blot analysis. As a corollary, pharmacological agents such as 4-PB have the potential, by increasing intercellular coupling, to reduce the effect of ischemia. It remains to be seen whether drugs like 4-PB will be effective in preventing cardiac maladies.

  18. Boiling crisis during liquid motion at high mass rate and underheating in channels

    International Nuclear Information System (INIS)

    One describes a physical model of liquid boiling crisis in smooth wall channels for high values of underheating and of mass rate of flow. One worded a condition ensuring crisis initiation. Paper presents the calculated ratio for the critical density of thermal flow in channels enabling to analyze the effect of channel diameter, of underheating and of mass rate on it

  19. Low complexity source and channel coding for mm-wave hybrid fiber-wireless links

    DEFF Research Database (Denmark)

    Lebedev, Alexander; Vegas Olmos, Juan José; Pang, Xiaodan;

    2014-01-01

    performance of several encoded high-definition video sequences constrained by the channel bitrate and the packet size. We argue that light video compression and low complexity channel coding for the W-band fiber-wireless link enable low-delay multiple channel 1080p wireless HD video transmission....

  20. Permeable Textual Discussion in Tracked Language Arts Classrooms

    Science.gov (United States)

    Gritter, Kristine

    2012-01-01

    Permeable textual discussion occurs when the unofficial texts and discursive practices and personal histories that are already recognized and valued in students' cultures are scaffolds to academically sanctioned literacies. Ideally, permeable textual discussions are safe havens where students' identities (racial, gender, world views) are…

  1. 21 CFR 886.5916 - Rigid gas permeable contact lens.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rigid gas permeable contact lens. 886.5916 Section... lens. (a) Identification. A rigid gas permeable contact lens is a device intended to be worn directly against the cornea of the eye to correct vision conditions. The device is made of various materials,...

  2. Nanochannel flow past permeable walls via molecular dynamics

    Science.gov (United States)

    Xie, Jian-Fei; Cao, Bing-Yang

    2016-07-01

    The nanochannel flow past permeable walls with nanopores is investigated by molecular dynamics (MD) simulations, including the density distribution, velocity field, molecular penetration mechanism and surface friction coefficient. A low density distribution has been found at the gas-wall interface demonstrating the low pressure region. In addition, there exists a jump of the gas density on the permeable surface, which indicates the discontinuity of the density distribution across the permeable surface. On the other hand, the nanoscale vortices are observed in nanopores of the permeable wall, and the reduced mass flux of the flow in nanopores results in a shifted hydrodynamic boundary above the permeable surface. Particularly the slip length of the gas flow on the permeable surface is pronounced a non-linear function of the molecular mean free path, which produces a large value of the tangential momentum accommodation coefficient (TMAC) and a big portion of the diffusive refection. Moreover, the gas-gas interaction and multi-collision among gas molecules may take place in nanopores, which contribute to large values of TMAC. Consequently the boundary friction coefficient on the permeable surface is increased because of the energy dissipation consumed by the nanoscale vortices in nanopores. The molecular boundary condition provides us with a new picture of the nanochannel flow past the permeable wall with nanopores.

  3. Duration of ultrasound-mediated enhanced plasma membrane permeability

    NARCIS (Netherlands)

    Lammertink, Bart; Deckers, RHR; Storm, Gert; Moonen, Chrit; Bos, Clemens

    2015-01-01

    Ultrasound (US) induced cavitation can be used to enhance the intracellular delivery of drugs by transiently increasing the cell membrane permeability. The duration of this increased permeability, termed temporal window, has not been fully elucidated. In this study, the temporal window was investiga

  4. Nitrogen Transformations in Three Types of Permeable Pavement

    Science.gov (United States)

    In 2009, USEPA constructed a 0.4-ha (1-ac) parking lot at the Edison Environmental Center in Edison, NJ, that incorporated three different permeable pavement types - permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). The driving lanes...

  5. Recovery of Porosity and Permeability for High Plasticity Clays

    DEFF Research Database (Denmark)

    Krogsbøll, Anette; Foged, Niels Nielsen

    Clays, which have been loaded to a high stress level, will under certain conditions keep low porosity and permeability due to the high degree of compression. In some situations it seems that porosity and permeability will recover to a very high extent when the clay is unloaded. This seems to be the...

  6. Mapping permeability over the surface of the Earth

    Science.gov (United States)

    Gleeson, Tom; Smith, Leslie; Moosdorf, Nils; Hartmann, Jens; Durr, Hans H.; Manning, Andrew H.; van Beek, Ludovicus P. H.; Jellinek, A. Mark

    2011-01-01

    Permeability, the ease of fluid flow through porous rocks and soils, is a fundamental but often poorly quantified component in the analysis of regional-scale water fluxes. Permeability is difficult to quantify because it varies over more than 13 orders of magnitude and is heterogeneous and dependent on flow direction. Indeed, at the regional scale, maps of permeability only exist for soil to depths of 1-2 m. Here we use an extensive compilation of results from hydrogeologic models to show that regional-scale (>5 km) permeability of consolidated and unconsolidated geologic units below soil horizons (hydrolithologies) can be characterized in a statistically meaningful way. The representative permeabilities of these hydrolithologies are used to map the distribution of near-surface (on the order of 100 m depth) permeability globally and over North America. The distribution of each hydrolithology is generally scale independent. The near-surface mean permeability is of the order of -5 x 10-14 m2. The results provide the first global picture of near-surface permeability and will be of particular value for evaluating global water resources and modeling the influence of climate-surface-subsurface interactions on global climate change.

  7. Influence of Core Permeability on Accropode Armour Layer Stability

    DEFF Research Database (Denmark)

    Burcharth, H. F.; Christensen, M.; Jensen, T.;

    1998-01-01

    Hedar and van der Meer studied the influence of core permeability on the stability of two layer rock armour. In both cases a significant influence was found. However, it is to be expected that for single layer armour there will be an even larger influence on the core permeability. This is because...

  8. Unsaturated and Saturated Permeabilities of Fiber Reinforcement: Critics and Suggestions

    Directory of Open Access Journals (Sweden)

    Chung Hae ePARK

    2015-04-01

    Full Text Available In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

  9. Sodium channel selectivity and conduction: Prokaryotes have devised their own molecular strategy

    OpenAIRE

    Finol-Urdaneta, Rocio K.; Wang, Yibo; Al-Sabi, Ahmed; Zhao, Chunfeng; Noskov, Sergei Y.; French, Robert J.

    2014-01-01

    Striking structural differences between voltage-gated sodium (Nav) channels from prokaryotes (homotetramers) and eukaryotes (asymmetric, four-domain proteins) suggest the likelihood of different molecular mechanisms for common functions. For these two channel families, our data show similar selectivity sequences among alkali cations (relative permeability, Pion/PNa) and asymmetric, bi-ionic reversal potentials when the Na/K gradient is reversed. We performed coordinated experimental and compu...

  10. Capacities of Grassmann channels

    CERN Document Server

    Bradler, Kamil; Jauregui, Rocio

    2010-01-01

    A new class of quantum channels called Grassmann channels is introduced and their classical and quantum capacity is calculated. The channel class appears in a study of the two-mode squeezing operator constructed from operators satisfying the fermionic algebra. We compare Grassmann channels with the channels induced by the bosonic two-mode squeezing operator. Among other results, we challenge the relevance of calculating entanglement measures to assess or compare the ability of bosonic and fermionic states to send quantum information to uniformly accelerated frames.

  11. Topology optimization of Channel flow problems

    DEFF Research Database (Denmark)

    Gersborg-Hansen, Allan; Sigmund, Ole; Haber, R. B.

    2005-01-01

    ]. Further, the inclusion of inertia effects significantly alters the physics, enabling solutions of new classes of optimization problems, such as velocity--driven switches, that are not addressed by the earlier method. Specifically, we determine optimal layouts of channel flows that extremize a cost...... sensitivities. Our target application is optimal layout design of channels in fluid network systems. Using concepts borrowed from topology optimization of compliant mechanisms in solid mechanics, we introduce a method for the synthesis of fluidic components, such as switches, diodes, etc....

  12. A theoretical model for gas permeability in a composite membrane

    International Nuclear Information System (INIS)

    We present in this work an analytical expression for permeability in a two-layer composite membrane, which was derived assuming the same hypothesis as those of Adzumi model for permeability in a homogeneous membrane. Whereas in Adzumi model permeability shows a linear dependence on the mean pressure, our model for a composite membrane related permeability to pressure through a rather complex expression, which covers the whole range of flow, from molecular-Knudsen to viscous-Poiseuille regimes. The expression obtained for permeability contained information of membrane structural properties as pore size, porosity and thickness of each layer, as well as gas nature and operational conditions. Our two-layer-model expression turns into Adzumi formula when the structure of the layers approach to each other.

  13. Two-phase relative permeability models in reservoir engineering calculations

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, S.; Hicks, P.J.; Ertekin, T.

    1999-01-15

    A comparison of ten two-phase relative permeability models is conducted using experimental, semianalytical and numerical approaches. Model predicted relative permeabilities are compared with data from 12 steady-state experiments on Berea and Brown sandstones using combinations of three white mineral oils and 2% CaCl1 brine. The model results are compared against the experimental data using three different criteria. The models are found to predict the relative permeability to oil, relative permeability to water and fractional flow of water with varying degrees of success. Relative permeability data from four of the experimental runs are used to predict the displacement performance under Buckley-Leverett conditions and the results are compared against those predicted by the models. Finally, waterflooding performances predicted by the models are analyzed at three different viscosity ratios using a two-dimensional, two-phase numerical reservoir simulator. (author)

  14. Coal reservoir permeability and its controlled factors in China

    Energy Technology Data Exchange (ETDEWEB)

    Ye, J.; Shi, B.; Zhang, C. [China Administration Bureau of Coal Geology (China). Exploration Branch No. 1

    1999-04-01

    Based on most of the well-testing data in China since the 1990's, the permeability of the coal reservoir and the controlling factors in the major CBM-accumulating districts and zones were objectively evaluated. It was found that the coal reservoir's permeability in China is generally lower than that in America and there is a certain regional distribution rules. The permeability is lower in the eastern part of North China CBM-accumulating province than that in the west, and is lower in Northeast China's and South China's CBM-accumulating provinces than that in North China. Ground stress is the major factor which influences the coal reservoir's permeability. The distribution of the permeability with the burial depth of the coal reservoirs seems to be the function of the stress. 5 refs., 6 figs.

  15. Wisely apply relative permeability data to reservoir management study

    Energy Technology Data Exchange (ETDEWEB)

    Du, Y.; Bai, B. [New Mexico Inst. of Mining and Technology, NM (United States); Guan, L. [Chevron Texaco Energy Technology Co., San Fransisco, CA (United States)

    2004-07-01

    Darcy's law is the basis for most fluid flow calculations within a hydrocarbon reservoir. The relative permeability of the reservoir rock to each of the fluid phases must be known in order to apply the law. The challenge lies in measuring and calculating relative permeabilities. It can be obtained by measuring core samples in the laboratory or from correlations from nearby reservoirs in the same formation. Each of these methods have some advantages and disadvantages. This paper described the limitations of lab data, as well as the limitations of analogy methods and correlation methods. It was emphasized that since relative permeability is such an important parameter in understanding the interaction of fluids and porous media at the microscopic level, better methods are needed to evaluate and generate relative permeability data in reservoir management studies. The authors present some recommendations for applying relative permeability data to reservoir management. 19 refs.

  16. Stress-induced permeability anisotropy in fractured reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.; Wong, R.C.K. [Calgary Univ., AB (Canada)

    2002-07-01

    The approach generally used to analyze the anisotropy of a heterogeneous, naturally fractured reservoirs was examined to verify if the approach is appropriate. Most reservoir simulations account for permeability anisotropy in fractured reservoirs through 3 principal permeabilities and 3 mutually orthogonal principal axes. It is demonstrated that the deformation of the fractures from changes in stress could result in an offset of the permeability tensor. This would result in an error in well interpretation because the conventional simple anisotropy model does not consider the cross permeability effect. The stress displacement behaviour of the fracture was also examined in this study through a non-linear model that can be used to describe the closure process of the fracture under varying stresses. The authors propose a comprehensive coupled model for geomechanical reservoir analysis. The advantage of the newly proposed model is that it takes into account the full permeability tensor and non-linear deformation properties of the fracture. 10 refs., 8 figs.

  17. Quantifying tidally driven benthic oxygen exchange across permeable sediments

    DEFF Research Database (Denmark)

    McGinnis, Daniel F.; Sommer, Stefan; Lorke, Andreas;

    2014-01-01

    of permeable sediments and has been identified as increasingly at risk for developing hypoxia. Therefore, we investigate the benthic O-2 exchange across the permeable North Sea sediments using a combination of in situ microprofiles, a benthic chamber, and aquatic eddy correlation. Tidal bottom currents drive....... The high O-2 flux variability results from deeper sediment O-2 penetration depths and increased O-2 storage during high velocities, which is then utilized during low-flow periods. The study reveals that the benthic hydrodynamics, sediment permeability, and pore water redox oscillations are all intimately......Continental shelves are predominately (approximate to 70%) covered with permeable, sandy sediments. While identified as critical sites for intense oxygen, carbon, and nutrient turnover, constituent exchange across permeable sediments remains poorly quantified. The central North Sea largely consists...

  18. Steady flow in voids and closed cracks in permeable media

    International Nuclear Information System (INIS)

    This paper considers what happens when a steady flow in a permeable medium meets two concentric spheres which have different permeabilities. This can form a first stage model for water flow near an engineered cavity in rock or a concreted waste package placed in filler material as in a nuclear waste repository. Results are obtained in terms of the simplest spherical harmonics, which lets them be used easily. Included are the well-known result that a highly permeable sphere will see only a few times the flux which would occur if it had the permeability of its surroundings, and the less well-known result, though unsurprising, that a spherical region surrounded by a highly permeable shell will see almost no flow, as it will almost all by-pass. A companion paper will include more geometrical effects by replacing the spheres by ellipsoids. (author)

  19. Evaluation methodology of gas permeable characterization in a polymer-based microfluidic device by confocal fluorescence imaging

    Science.gov (United States)

    Ichiyanagi, Mitsuhisa; Sakai, Keita; Kidani, Shinya; Kakinuma, Yasuhiro; Sato, Yohei; Hishida, Koichi

    2012-06-01

    The evaluation technique of gas permeable characterization has been developed for an increased efficiency of gas-liquid chemical reactions and high accuracy of environmental diagnosis. This technique enables us to measure spatial distributions of velocity and dissolved gas concentration by utilizing confocal micron-resolution particle image velocimetry combined with a laser-induced fluorescence technique. Microfluidic devices with gas permeability through polymer membranes are composed of a cover glass and a polydimethylsiloxane (PDMS) chip with the ability to permeate various gases, since PDMS is an elastomeric material. In the chip, microchannels are manufactured using a cryogenic micromachining system. The gas permeation is dominated by several factors, such as the gas and liquid flow rates, the membrane thickness between the gas and liquid flow, and the surface area of the membranes. The advantage of the present device is to realize the control of gas permeability by changing the surface roughness of PDMS, because the cryogenic micromachining enables us to control the surface roughness of microchannels and an increase in roughness yields an increase in the surface area of membranes. The experiments were performed under several conditions with a change in the gas flow rate, the PDMS membrane thickness and the surface roughness, which affect the gas permeation phenomena. The spatial distributions of velocity and dissolved gas concentration were measured in the liquid flow fields. The results indicate that the velocity-vector distributions have similar patterns under all experimental conditions, while the dissolved gas concentration distributions have different patterns. It was observed that the gas permeability through PDMS membranes increased with an increase in gas flow rates and surface roughness and with a decrease in membrane thicknesses, which is in qualitative agreement with membrane theory. The important conclusion is that the proposed technique is

  20. Evaluation methodology of gas permeable characterization in a polymer-based microfluidic device by confocal fluorescence imaging

    International Nuclear Information System (INIS)

    The evaluation technique of gas permeable characterization has been developed for an increased efficiency of gas–liquid chemical reactions and high accuracy of environmental diagnosis. This technique enables us to measure spatial distributions of velocity and dissolved gas concentration by utilizing confocal micron-resolution particle image velocimetry combined with a laser-induced fluorescence technique. Microfluidic devices with gas permeability through polymer membranes are composed of a cover glass and a polydimethylsiloxane (PDMS) chip with the ability to permeate various gases, since PDMS is an elastomeric material. In the chip, microchannels are manufactured using a cryogenic micromachining system. The gas permeation is dominated by several factors, such as the gas and liquid flow rates, the membrane thickness between the gas and liquid flow, and the surface area of the membranes. The advantage of the present device is to realize the control of gas permeability by changing the surface roughness of PDMS, because the cryogenic micromachining enables us to control the surface roughness of microchannels and an increase in roughness yields an increase in the surface area of membranes. The experiments were performed under several conditions with a change in the gas flow rate, the PDMS membrane thickness and the surface roughness, which affect the gas permeation phenomena. The spatial distributions of velocity and dissolved gas concentration were measured in the liquid flow fields. The results indicate that the velocity-vector distributions have similar patterns under all experimental conditions, while the dissolved gas concentration distributions have different patterns. It was observed that the gas permeability through PDMS membranes increased with an increase in gas flow rates and surface roughness and with a decrease in membrane thicknesses, which is in qualitative agreement with membrane theory. The important conclusion is that the proposed technique is

  1. Source and Channel Coding for Correlated Sources Over Multiuser Channels

    OpenAIRE

    Gunduz, Deniz; Erkip, Elza; Goldsmith, Andrea; Poor, H. Vincent

    2008-01-01

    Source and channel coding over multiuser channels in which receivers have access to correlated source side information is considered. For several multiuser channel models necessary and sufficient conditions for optimal separation of the source and channel codes are obtained. In particular, the multiple access channel, the compound multiple access channel, the interference channel and the two-way channel with correlated sources and correlated receiver side information are considered, and the o...

  2. A new pH-sensitive rectifying potassium channel in mitochondria from the embryonic rat hippocampus.

    Science.gov (United States)

    Kajma, Anna; Szewczyk, Adam

    2012-10-01

    Patch-clamp single-channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of two different potassium ion channels: a large-conductance (288±4pS) calcium-activated potassium channel and second potassium channel with outwardly rectifying activity under symmetric conditions (150/150mM KCl). At positive voltages, this channel displayed a conductance of 67.84pS and a strong voltage dependence at holding potentials from -80mV to +80mV. The open probability was higher at positive than at negative voltages. Patch-clamp studies at the mitoplast-attached mode showed that the channel was not sensitive to activators and inhibitors of mitochondrial potassium channels but was regulated by pH. Moreover, we demonstrated that the channel activity was not affected by the application of lidocaine, an inhibitor of two-pore domain potassium channels, or by tertiapin, an inhibitor of inwardly rectifying potassium channels. In summary, based on the single-channel recordings, we characterised for the first time mitochondrial pH-sensitive ion channel that is selective for cations, permeable to potassium ions, displays voltage sensitivity and does not correspond to any previously described potassium ion channels in the inner mitochondrial membrane. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). PMID:22406520

  3. Effects of anisotropic permeability and electrical conductivity of gas diffusion layers on the performance of proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Highlights: ► The in-plane electrical conductivity of the GDL must be captured numerically. ► Fuel cell performance is insensitive to the anisotropy in the permeability of GDL. ► The anisotropy in the in-plane electrical conductivity of the GDL can be neglected. ► For the reported conditions, the U-bend has no effect on the fuel cell performance. -- Abstract: A 3-dimensional model for an in-house proton exchange membrane (PEM) fuel cell with serpentine channels has been developed in order to investigate the sensitivity of the fuel cell performance to the anisotropic gas permeability and electrical conductivity of gas diffusion layers (GDLs). For a realistic range of transport properties being investigated, the fuel cell performance was found to be very sensitive to the electrical conductivity but almost insensitive to the gas permeability of the GDL. For the given operating conditions, the current density was found to be a maximum in the vicinity of the edge between the flow channel and the rib of the current collector. Since the most common GDL materials present a rather significant anisotropy in the in-plane directions, the effects of such anisotropy has been evaluated. Given that the through-plane conductivity is maintained constant for all the cases investigated, for a realistic range of the in-plane electrical conductivity, the fuel cell performance was found to be almost insensitive to this parameter. Therefore such anisotropy can be practically ignored. Finally, for single phase operating conditions, the U-bend in the serpentine channel has no effect on the overall performance of the fuel cell. Hence, only a straight channel of the fuel cell may be modelled and used as a quick performance indicator.

  4. Does the hourglass shape of aquaporins optimize water permeability This research was supported by the ERC program, project Micromegas.

    Science.gov (United States)

    Gravelle, Simon; Joly, Laurent; Detcheverry, François; Ybert, Christophe; Cottin-Bizonne, Cecile; Bocquet, Lyderic; Liquide et interfaces Team

    2013-11-01

    The ubiquitous aquaporin channels are able to conduct water across cell membranes, combining the seemingly antagonist functions of a very high selectivity with a remarkable permeability. While molecular details are obvious keys to perform these tasks, the overall efficiency of transport in such nanopores is also strongly limited by viscous dissipation arising at the connection between the nanoconstriction and the nearby bulk reservoirs. In this contribution, we focus on these so-called entrance effects and specifically examine whether the characteristic hourglass shape of aquaporins may arise from a geometrical optimum for such hydrodynamic dissipation. Using a combination of finite element calculations and analytical modeling, we show that conical entrances with suitable opening angle can indeed provide a large increase of the overall channel permeability. Moreover, the optimal opening angles that maximize the permeability are found to compare well with the angles measured in a large variety of aquaporins. This suggests that the hourglass shape of aquaporins could be the result of a natural selection process toward optimal hydrodynamic transport. Finally, in a biomimetic perspective, these results provide guidelines to design artificial nanopores with optimal performances.

  5. Predicting skin permeability from complex chemical mixtures

    International Nuclear Information System (INIS)

    Occupational and environmental exposure to topical chemicals is usually in the form of complex chemical mixtures, yet risk assessment is based on experimentally derived data from individual chemical exposures from a single, usually aqueous vehicle, or from computed physiochemical properties. We present an approach using hybrid quantitative structure permeation relationships (QSPeR) models where absorption through porcine skin flow-through diffusion cells is well predicted using a QSPeR model describing the individual penetrants, coupled with a mixture factor (MF) that accounts for physicochemical properties of the vehicle/mixture components. The baseline equation is log k p = c + mMF + aΣα 2H + bΣβ 2H + sπ 2H + rR 2 + vV x where Σα 2H is the hydrogen-bond donor acidity, Σβ 2H is the hydrogen-bond acceptor basicity, π 2H is the dipolarity/polarizability, R 2 represents the excess molar refractivity, and V x is the McGowan volume of the penetrants of interest; c, m, a, b, s, r, and v are strength coefficients coupling these descriptors to skin permeability (k p) of 12 penetrants (atrazine, chlorpyrifos, ethylparathion, fenthion, methylparathion, nonylphenol, ρ-nitrophenol, pentachlorophenol, phenol, propazine, simazine, and triazine) in 24 mixtures. Mixtures consisted of full factorial combinations of vehicles (water, ethanol, propylene glycol) and additives (sodium lauryl sulfate, methyl nicotinate). An additional set of 4 penetrants (DEET, SDS, permethrin, ricinoleic acid) in different mixtures were included to assess applicability of this approach. This resulted in a dataset of 16 compounds administered in 344 treatment combinations. Across all exposures with no MF, R2 for absorption was 0.62. With the MF, correlations increased up to 0.78. Parameters correlated to the MF include refractive index, polarizability and log (1/Henry's Law Constant) of the mixture components. These factors should not be considered final as the focus of these studies was

  6. Electromagnetic imaging of lithosphere permeable zones

    Science.gov (United States)

    Litvinova, Tamara; Petrova Petrova, Alevtina; Petrishchev Petrishchev, Maxim

    2014-05-01

    By way of strong minima of magnetic anomalies studies we are investigated the features of the lithosphere structure by magnetic and gravity data. Exploration methods included the application of existing and open source near-surface aeromagnetic (WDMAM) with satellite data both at 100 km and 400 km in altitude (CHAMP) and gravity satellite data (GRACE). Aeromagnetic data have been used for the 2D geomagnetic model for a depth range from 3 to 50 km plotting. Gravity data has allowed to study the 2D density model for a depth range from 5 to 200 km plotting. At the heart of the geomagnetic and density model plotting lies the technique of the spectral-spatial representation of a geomagnetic field converted in a deep geomagnetic model. The technique of the spectral-spatial analysis (SPAN) is used to differentiate the weakly magnetic heterogeneities within the basement. In this paper we have studied the structure of the lithosphere in the area of deep magnetic minima in the vicinity of the eastern part of the Fennoscandian Shield, Central Europe and the northern part of South America. We have found powerful (more than 10 km) permeable feeble magnetic zones in the middle crust (20-30 km in depth) that are detected as feebly magnetic layer using the geomagnetic data. The magnetic minimum at 100 and 400 km in altitude corresponds to this feeble magnetic layer. It stands out as the low density layer at depth 20-35 km and, after the break, at depth 60-100 km. Ground-based magnetotelluric survey has allowed to allocate the high-conductivity layer at depth 15-30 and 60-110 km. It suggests that the detected layers can be rheological weak. The same is for the regions of Central Europe and South America. The powerful feebly magnetic layers have been detected in the middle and bottom crust (30-50 km for the Central Europe and 30-40 km for South America). The low density layers have been found for 20-35 km and 50-80 km in depth. The ground based measurement has confirmed the presence

  7. Tracer kinetic modelling in MRI: estimating perfusion and capillary permeability

    International Nuclear Information System (INIS)

    The tracer-kinetic models developed in the early 1990s for dynamic contrast-enhanced MRI (DCE-MRI) have since become a standard in numerous applications. At the same time, the development of MRI hardware has led to increases in image quality and temporal resolution that reveal the limitations of the early models. This in turn has stimulated an interest in the development and application of a second generation of modelling approaches. They are designed to overcome these limitations and produce additional and more accurate information on tissue status. In particular, models of the second generation enable separate estimates of perfusion and capillary permeability rather than a single parameter Ktrans that represents a combination of the two. A variety of such models has been proposed in the literature, and development in the field has been constrained by a lack of transparency regarding terminology, notations and physiological assumptions. In this review, we provide an overview of these models in a manner that is both physically intuitive and mathematically rigourous. All are derived from common first principles, using concepts and notations from general tracer-kinetic theory. Explicit links to their historical origins are included to allow for a transfer of experience obtained in other fields (PET, SPECT, CT). A classification is presented that reveals the links between all models, and with the models of the first generation. Detailed formulae for all solutions are provided to facilitate implementation. Our aim is to encourage the application of these tools to DCE-MRI by offering researchers a clearer understanding of their assumptions and requirements. (topical review)

  8. Phosphorylation of rat aquaporin-4 at Ser(111) is not required for channel gating

    DEFF Research Database (Denmark)

    Assentoft, Mette; Kaptan, Shreyas; Fenton, Robert A;

    2013-01-01

    is therefore of therapeutic interest. Phosphorylation of some aquaporins has been proposed to regulate their water permeability via gating of the channel itself. Protein kinase (PK)-dependent phosphorylation of Ser(111) has been reported to increase the water permeability of AQP4 expressed in an astrocytic......Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. AQP4 has been described as an important entry and exit site for water during formation of brain edema and regulation of AQP4...... cell line. This possibility was, however, questioned based on the crystal structure of the human AQP4. Our study aimed to resolve if Ser(111) was indeed a site involved in phosphorylation-mediated gating of AQP4. The water permeability of AQP4-expressing Xenopus oocytes was not altered by a range...

  9. Expression profiles of seven channel catfish antimicrobial peptides in response to Edwardsiella ictaluri infection

    Science.gov (United States)

    Using quantitative PCR technique, the relative transcriptional levels of seven channel catfish antimicrobial peptide (AMP) genes [NK-lysin type 1, NK-lysin type 2, NK-lysin type 3, bactericidal permeability-increasing protein (BPI), cathepsin D, hepcidin, and liver-expressed antimicrobial peptide 2 ...

  10. Electronic Health Record Application Support Service Enablers.

    Science.gov (United States)

    Neofytou, M S; Neokleous, K; Aristodemou, A; Constantinou, I; Antoniou, Z; Schiza, E C; Pattichis, C S; Schizas, C N

    2015-08-01

    There is a huge need for open source software solutions in the healthcare domain, given the flexibility, interoperability and resource savings characteristics they offer. In this context, this paper presents the development of three open source libraries - Specific Enablers (SEs) for eHealth applications that were developed under the European project titled "Future Internet Social and Technological Alignment Research" (FI-STAR) funded under the "Future Internet Public Private Partnership" (FI-PPP) program. The three SEs developed under the Electronic Health Record Application Support Service Enablers (EHR-EN) correspond to: a) an Electronic Health Record enabler (EHR SE), b) a patient summary enabler based on the EU project "European patient Summary Open Source services" (epSOS SE) supporting patient mobility and the offering of interoperable services, and c) a Picture Archiving and Communications System (PACS) enabler (PACS SE) based on the dcm4che open source system for the support of medical imaging functionality. The EHR SE follows the HL7 Clinical Document Architecture (CDA) V2.0 and supports the Integrating the Healthcare Enterprise (IHE) profiles (recently awarded in Connectathon 2015). These three FI-STAR platform enablers are designed to facilitate the deployment of innovative applications and value added services in the health care sector. They can be downloaded from the FI-STAR cataloque website. Work in progress focuses in the validation and evaluation scenarios for the proving and demonstration of the usability, applicability and adaptability of the proposed enablers. PMID:26736531

  11. Betti reaction enables efficient synthesis of 8-hydroxyquinoline inhibitors of 2-oxoglutarate oxygenases.

    Science.gov (United States)

    Thinnes, C C; Tumber, A; Yapp, C; Scozzafava, G; Yeh, T; Chan, M C; Tran, T A; Hsu, K; Tarhonskaya, H; Walport, L J; Wilkins, S E; Martinez, E D; Müller, S; Pugh, C W; Ratcliffe, P J; Brennan, P E; Kawamura, A; Schofield, C J

    2015-10-28

    There is interest in developing potent, selective, and cell-permeable inhibitors of human ferrous iron and 2-oxoglutarate (2OG) oxygenases for use in functional and target validation studies. The 3-component Betti reaction enables efficient one-step C-7 functionalisation of modified 8-hydroxyquinolines (8HQs) to produce cell-active inhibitors of KDM4 histone demethylases and other 2OG oxygenases; the work exemplifies how a template-based metallo-enzyme inhibitor approach can be used to give biologically active compounds. PMID:26345662

  12. An exact analytical solution for steady seepage from a perched Aquifer to a low-permeable sublayer: Kirkham-Brock's legacy revisited

    Science.gov (United States)

    Kacimov, A. R.; Obnosov, Yu. V.

    2015-05-01

    An analytical solution is obtained for steady 2-D potential seepage flow from a nonclogged and nonlined soil channel into a highly permeable porous layer, with phreatic surfaces tapering toward a horizontal interface with a subjacent low-permeable formation. Along this boundary, a vertical component of the Darcian velocity vector equals the formation saturated hydraulic conductivity. The image of the physical flow domain in the hodograph plane is a circular polygon, a triangle or digon in a limiting case of a "phreatic jet" impinging on the low-permeable substratum. The polygon is mapped onto an auxiliary half plane, where the complex physical coordinate and complex potential are reconstructed by the Polubarinova-Kochina method, i.e., by solution of a Riemann BVP. The seepage flow rate from the channel, free surfaces, and a saturated (water-logged) area are found for different thicknesses of the top layer, channel widths, and conductivity ratios of the two strata. In particular, the earlier results of Brock, Kirkham, and Youngs, which are based on a numerical solution, Dupuit-Forchheimer (DF) approximation, and approximate potential model, are confirmed in the full 2-D models. Sufficiently far from the channel, the phreatic surface and interface make a wedge. For a sufficiently deep substratum, three zones are analytically distinguished: an almost vertical 1-D descending flow, an almost wedge-configured 1-D flow, and an essentially 2-D zone in between, where neither a standard infiltration theory nor DF analysis are valid.

  13. Drainage hydraulics of permeable friction courses

    Science.gov (United States)

    Charbeneau, Randall J.; Barrett, Michael E.

    2008-04-01

    This paper describes solutions to the hydraulic equations that govern flow in permeable friction courses (PFC). PFC is a layer of porous asphalt approximately 50 mm thick that is placed as an overlay on top of an existing conventional concrete or asphalt road surface to help control splash and hydroplaning, reduce noise, and enhance quality of storm water runoff. The primary objective of this manuscript is to present an analytical system of equations that can be used in design and analysis of PFC systems. The primary assumptions used in this analysis are that the flow can be modeled as one-dimensional, steady state Darcy-type flow and that slopes are sufficiently small so that the Dupuit-Forchheimer assumptions apply. Solutions are derived for cases where storm water drainage is confined to the PFC bed and for conditions where the PFC drainage capacity is exceeded and ponded sheet flow occurs across the pavement surface. The mathematical solutions provide the drainage characteristics (depth and residence time) as a function of rainfall intensity, PFC hydraulic conductivity, pavement slope, and maximum drainage path length.

  14. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Shlomo Shamai (Shitz

    2009-01-01

    Full Text Available This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom (s.d.o.f. are derived for the degraded case with one receiver. Schemes to achieve the s.d.o.f. for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable s.d.o.f. is given for the general case.

  15. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Kramer Gerhard

    2009-01-01

    Full Text Available Abstract This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom ( are derived for the degraded case with one receiver. Schemes to achieve the for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable is given for the general case.

  16. Human AQP1 is a constitutively open channel that closes by a membrane-tension-mediated mechanism.

    Science.gov (United States)

    Ozu, Marcelo; Dorr, Ricardo A; Gutiérrez, Facundo; Politi, M Teresa; Toriano, Roxana

    2013-01-01

    This work presents experimental results combined with model-dependent predictions regarding the osmotic-permeability regulation of human aquaporin 1 (hAQP1) expressed in Xenopus oocyte membranes. Membrane elastic properties were studied under fully controlled conditions to obtain a function that relates internal volume and pressure. This function was used to design a model in which osmotic permeability could be studied as a pressure-dependent variable. The model states that hAQP1 closes with membrane-tension increments. It is important to emphasize that the only parameter of the model is the initial osmotic permeability coefficient, which was obtained by model-dependent fitting. The model was contrasted with experimental records from emptied-out Xenopus laevis oocytes expressing hAQP1. Simulated results reproduce and predict volume changes in high-water-permeability membranes under hypoosmotic gradients of different magnitude, as well as under consecutive hypo- and hyperosmotic conditions. In all cases, the simulated permeability coefficients are similar to experimental values. Predicted pressure, volume, and permeability changes indicate that hAQP1 water channels can transit from a high-water-permeability state to a closed state. This behavior is reversible and occurs in a cooperative manner among monomers. We conclude that hAQP1 is a constitutively open channel that closes mediated by membrane-tension increments. PMID:23332061

  17. The dynamics of coherent flow structures within a submerged permeable bed

    Science.gov (United States)

    Blois, G.; Best, J.; Sambrook Smith, G.; Hardy, R. J.; Lead, J.

    2009-12-01

    The existence of complex 3D coherent vortical structures in turbulent boundary layers has been widely reported from experimental observations (Adrian et al., 2007, Christensen and Adrian, 2001) and investigations of natural open channel flows (e.g. Kostaschuk and Church, 1993; Best, 2005). The interaction between these flow structures and the solid boundary that is responsible for their generation is also receiving increasing attention due to the central role played by turbulence in governing erosion-deposition processes. Yet, for the majority of studies, the bed roughness has been represented using rough impermeable surfaces. While not inherently acknowledged, most research in this area is thus only strictly applicable to those natural river beds composed either of bedrock or clay, or that have armoured, impermeable, surfaces. Recently, many researchers have noted the need to account for the role of bed permeability in order to accurately reproduce the true nature of flow over permeable gravel-bed rivers. For these cases, the near-bed flow is inherently and mutually linked to the interstitial-flow occurring in the porous solid matrix. This interaction is established through turbulence mechanisms occurring across the interface that may be important for influencing the incipient motion of cohesionless sediment. However, the nature of this turbulence and the formation of coherent structures within such permeable beds remain substantially unresolved due to the technical challenges of collecting direct data in this region. In this paper, we detail the existence and dynamic nature of coherent vortical structures within the individual pore spaces of a permeable bed submerged by a free stream flow. Laboratory experiments are reported in which a permeable flume bed was constructed using spheres packed in an offset cubic arrangement. We applied a high resolution E-PIV (Endoscopic Particle Image Velocimetry) approach in order to fully resolve the instantaneous structure of

  18. Compression characteristics and permeability of saturated Gaomiaozi ca-bentonite

    International Nuclear Information System (INIS)

    The compression characteristics and permeability of compacted Gaomiaozi Ca-bentonite saturated by the water uptake tests are studied by conducting a series of one-dimension compression tests. The permeability coefficient can be calculated by the Terzaghi's one-dimensional consolidation theory after the consolidation coefficient is obtained by the square root of time method. It is found that the compression curves of compacted specimens saturated by the water uptake tests tend to be consistent in the relatively high stress range. The compression indexes show a linear decrease with increasing dry density and the swelling index is a constant. The permeability coefficient decreases with increasing compression stress, and they show the linear relationship in double logarithmic coordinates. Meanwhile, the permeability coefficient shows a linear decrease with decreasing void ratio, which has no relationship with initial states, stress states and stress paths. The permeability coefficient k of GMZ Ca-bentonite at dry density Pd of 1.75 g/cm3 can be calculated as 2.0 × 10-11 cm/s by the linear relationship between Pd and log k. It is closed to the permeability coefficient of GMZ Ca-bentonite with the same dry density published in literature, which testifies that the method calculating the permeability coefficient is feasible from the consolidation coefficient obtained by the consolidation test. (authors)

  19. Vertical and horizontal permeability measurements in organic soils

    Directory of Open Access Journals (Sweden)

    Malinowska Edyta E.

    2015-06-01

    Full Text Available The paper is referring to vertical and horizontal laboratory permeability measurements in soft organic soils. The estimation of anisotropic permeability in soft organic soils, as peats, requires to use a special apparatus and the knowledge of proper analysis of the test results. During loading the void ratio decreases substantially that causes the changeability of the permeability. The change of permeability during the compression is very important because of the influence of the consolidation co-efficient. Initial strain in soft organic soils appears very quickly, just after loading, and brings immediately the decrease of permeability. In most of the estimations, it is assumed that during the consolidation process the water flows just in the vertical direction. In soft organic soils, like peats, the consolidation theory should consider the changes of mechanical and physical properties in consolidation period, in both directions. The direct measurement of vertical and horizontal permeability of organic soil and the non-Darcian flow theory may be of considerable importance in estimating pore water pressure dissipation, and settlement rates in the consolidation model. In the paper, the method of investigation and the test results of the vertical and horizontal permeability are presented. The Modified Rowe Cell Set for obtaining consolidation and flow characteristics in different directions is used.

  20. Permeability of WIPP Salt During Damage Evolution and Healing

    International Nuclear Information System (INIS)

    The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering

  1. Characterization and estimation of permeability correlation structure from performance data

    Energy Technology Data Exchange (ETDEWEB)

    Ershaghi, I.; Al-Qahtani, M. [Univ. of Southern California, Los Angeles, CA (United States)

    1997-08-01

    In this study, the influence of permeability structure and correlation length on the system effective permeability and recovery factors of 2-D cross-sectional reservoir models, under waterflood, is investigated. Reservoirs with identical statistical representation of permeability attributes are shown to exhibit different system effective permeability and production characteristics which can be expressed by a mean and variance. The mean and variance are shown to be significantly influenced by the correlation length. Detailed quantification of the influence of horizontal and vertical correlation lengths for different permeability distributions is presented. The effect of capillary pressure, P{sub c1} on the production characteristics and saturation profiles at different correlation lengths is also investigated. It is observed that neglecting P{sub c} causes considerable error at large horizontal and short vertical correlation lengths. The effect of using constant as opposed to variable relative permeability attributes is also investigated at different correlation lengths. Next we studied the influence of correlation anisotropy in 2-D reservoir models. For a reservoir under five-spot waterflood pattern, it is shown that the ratios of breakthrough times and recovery factors of the wells in each direction of correlation are greatly influenced by the degree of anisotropy. In fully developed fields, performance data can aid in the recognition of reservoir anisotropy. Finally, a procedure for estimating the spatial correlation length from performance data is presented. Both the production performance data and the system`s effective permeability are required in estimating the correlation length.

  2. A novel fluorescence-based cellular permeability assay.

    Science.gov (United States)

    Chandra, Ankur; Barillas, Samuel; Suliman, Ahmed; Angle, Niren

    2007-04-10

    Vascular permeability is a pathologic process in many disease states ranging from metastatic progression of malignancies to ischemia-reperfusion injury. In order to more precisely study tissue, and more specifically cell layer permeability, our goal was to create a fluorescence-based assay which could quantify permeability without radioactivity or electrical impedance measurements. Human aortic endothelial cells were grown in monolayer culture on Costar-Transwell clear polyester membrane 6-well cell culture inserts. After monolayer integrity was confirmed, vascular endothelial growth factor (VEGF(165)) at varying concentrations with a fixed concentration of yellow-green fluorescent 0.04 microm carboxylate-modified FluoSpheres microspheres were placed in the luminal chamber and incubated for 24 h. When stimulated with VEGF(165) at 20, 40, 80, and 100 ng/ml, this assay system was able to detect increases in trans-layer flux of 8.2+/-2.4%, 16.0+/-3.7%, 41.5+/-4.9%, and 58.6+/-10.1% for each concentration, respectively. This represents the first fluorescence-based permeability assay with the sensitivity to detect changes in the permeability of a cell layer to fluid flux independent of protein flux; as well as being simpler and safer than previous radioactive-and impedance-based permeability assays. With the application of this in vitro assay to a variety of pathologic conditions, both the dynamics and physiology relating to cellular permeability can be more fully investigated. PMID:16962665

  3. Scale Dependence of Equivalent Permeability Tensor in Naturally Fractured Reservoirs

    Science.gov (United States)

    Azizmohammadi, S.; Matthäi, S. K.; Paul, J. D.

    2012-04-01

    Fracture geometries in naturally fractured reservoirs are usually inferred from sparse subsurface observations from well logs or cores. Since the largest fractures tend to be the least frequent, they are often undersampled. Therefore, interpretations based on samples taken at any scale smaller than that of interest contain a bias, misrepresenting the true characteristics of the fracture system. This bias may lead to the incorrect characterisation of the reservoir, upscaling and gridding. In this work, we investigate the variation of the equivalent permeability and its anisotropy in naturally fractured rocks as a function of sample size. We use a two dimensional linear elastic model of fracture aperture, taking into account the far-field stresses in conjunction with the parallel plate model, to determine fracture permeability. These apertures are applied to fractured reservoir analogues mapped in the field to numerically estimate permeability. We then employ a finite element scheme to compute equivalent permeability tensors for random samples of the fractured porous medium at specific length scales. We find that the distribution of the principle component of equivalent permeability tensor computed at each scale size appears to be dependent upon the underlying attributes of the fracture networks. We notice a clear trend between the mean equivalent permeability and sample size. Our findings suggest that fracture geometries in naturally fractured reservoirs should be sampled at the scales of interest; if not, the equivalent permeability of such reservoirs might be significantly underestimated.

  4. Diverting acid into low permeability reservoir using foam for stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Talabani, S.; Islam, M.R.

    1999-07-01

    A very difficult problem in oil well recovery is the displacement of oil in the low permeability zones in a heterogeneous reservoir. The presence of foam helps reduce the liquid mobility in the high permeability layers. The reduction in mobility causes the diversion of most of the liquid to low permeability layers. There are three factors that characterize a surfactant's ability to divert acid into the low permeability layers: the true mobility reduction factor, the foam injectivity index, and the early diversion factor. They are very practical to use in the field, and some surfactants destabilize the clays in the core that might swell. Other surfactants displace most of the oil in the core, hence generating a more stable foam later. Because most of the oil stays in the low permeability core, it will later cause the distraction of the foam in the core if it is generated. Surfactants that cause the wash of oil in the high permeability core will later generate a stable foam, which produces acid diversion into the lower permeability core. 8 refs., 10 figs.

  5. Permeability of WIPP Salt During Damage Evolution and Healing

    Energy Technology Data Exchange (ETDEWEB)

    BODNER,SOL R.; CHAN,KWAI S.; MUNSON,DARRELL E.

    1999-12-03

    The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering.

  6. Wave transmission over permeable submerged breakwaters; Transmision del oleaje en rompeolas sumergidos permeables

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-y-Zurvia-Flores, Jaime Roberto; Fragoso-Sandoval, Lucio [Instituto Politecnico Nacional(Mexico)

    2008-10-15

    The permeable submerged breakwaters represent a coastal protection alternative, where some degree of wave energy transmission is acceptable. Such would be the case of tourist beach protection in Mexico. In previous researches, like those performed by D'Angremond et al. (1996), Seabrook and Hall (1998), and Briganti et al. (2003), the empirical formulas developed, give only some limited information over the spatial distribution of wave energy over the structure. Therefore, a decision was made to conduct a study on a reduced physical model of a permeable submerged breakwater based on the results presented by those researchers and with possible applications. Therefore this paper presents the development of a study of wave transmission over permeable submerged breakwaters performed in a reduced physical model of different sections of a submerged rockfill breakwater of the trapezoidal type. This was done in a narrow wave flume with a hydraulic irregular wave generator controlled by a computer that was used to generate and to reproduce different types of irregular waves to be used in the tests. It also has a wave meter with four sensors, and they are connected to a computer in order to process the wave data. The main objective of the study was to determine in an experimental way the influence of the several parameters of submerged breakwater over the wave transmission coefficient. Our experimental results were comparable to those obtained by D'Angremond et al. (1996) and Seabrook and Hall (1998). The results show that the sumerged breakwater parameters of most influence over the wave transmission coefficient were relative submergence and the relative width crest of the sumerged breakwater, and that the formula by Seabrook and Hall correlates best with our results. [Spanish] Los rompeolas sumergidos permeables representan actualmente una alternativa de proteccion de costas, donde un cierto grado de transmision de energia del oleaje es aceptable, como seria el

  7. A Fast Channel Switching Method in EPON System for IPTV Service

    Science.gov (United States)

    Nie, Yaling; Yoshiuchi, Hideya

    This paper presents a fast channel switching method in Ethernet Passive Optical Network (EPON) system for IPTV service. Fast channel switching is one of the important features of successful IPTV systems. Users surely prefer IPTV systems with small channel switching time rather than a longer one. Thus a channel switching control module and a channel/permission list in EPON system’s ONU or OLT is designed. When EPON system receives channel switching message from IPTV end user, the channel switching control module will catch the message and search the channel list and permission list maintained in EPON system, then got the matching parameter of EPON for the new channel. The new channel’s data transmission will be enabled by directly updating the optical filter of the ONU that end user connected. By using this method in EPON system, it provides a solution for dealing with channel switching delays in IPTV service.

  8. Channel capacity and error exponents of variable rate adaptive channel coding for Rayleigh fading channels

    OpenAIRE

    Lau, KN

    1999-01-01

    We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the err...

  9. Channel Sounding for the Masses: Low Complexity GNU 802.11b Channel Impulse Response Estimation

    CERN Document Server

    Firooz, Mohammad H; Zhang, Junxing; Patwari, Neal; Kasera, Sneha K

    2010-01-01

    New techniques in cross-layer wireless networks are building demand for ubiquitous channel sounding, that is, the capability to measure channel impulse response (CIR) with any standard wireless network and node. Towards that goal, we present a software-defined IEEE 802.11b receiver and CIR estimation system with little additional computational complexity compared to 802.11b reception alone. The system implementation, using the universal software radio peripheral (USRP) and GNU Radio, is described and compared to previous work. By overcoming computational limitations and performing direct-sequence spread-spectrum (DS-SS) matched filtering on the USRP, we enable high-quality yet inexpensive CIR estimation. We validate the channel sounder and present a drive test campaign which measures hundreds of channels between WiFi access points and an in-vehicle receiver in urban and suburban areas.

  10. Quantum broadcast channels

    CERN Document Server

    Yard, J; Devetak, I; Yard, Jon; Hayden, Patrick; Devetak, Igor

    2006-01-01

    We analyze quantum broadcast channels, which are quantum channels with a single sender and many receivers. Focusing on channels with two receivers for simplicity, we generalize a number of results from the network Shannon theory literature which give the rates at which two senders can receive a common message, while a personalized one is sent to one of them. Our first collection of results applies to channels with a classical input and quantum outputs. The second class of theorems we prove concern sending a common classical message over a quantum broadcast channel, while sending quantum information to one of the receivers. The third group of results we obtain concern communication over an isometry, giving the rates at quantum information can be sent to one receiver, while common quantum information is sent to both, in the sense that tripartite GHZ entanglement is established. For each scenario, we provide an additivity proof for an appropriate class of channels, yielding single-letter characterizations of the...

  11. Enabling Technology for Small Satellite Launch Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Access to space for Small Satellites is enabled by the use of excess launch capacity on existing launch vehicles. A range of sizes, form factors and masses need to...

  12. Enabling Technology for Small Satellite Launch Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Access to space for Small Satellites is enabled by the use of excess launch capacity on existing launch vehicles. A range of sizes, form factors and masses of small...

  13. iMarine - data infrastructure enabling software ?

    OpenAIRE

    Simi, Manuele

    2012-01-01

    iMarine Data Infrastructure Enabling Software contains the description of software and pointers to the documentation and artifacts of the related components that comprise the e-Infrstructure Management suite delivered from M7 to M10 ?

  14. iMarine - data infrastructure enabling software ?

    OpenAIRE

    Simi, Manuele; Farantatos, Gerasimos

    2012-01-01

    iMarine Data Infrastructure Enabling Software contains the description of software and pointers to the related documentation and artifacts of the components that comprise the e-Infrastructure Management suite delivered up to M6. ? ? ? ?

  15. On "enabling systems - A strategic review"

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, M.R.

    Enabling Systems is a formal strategic planning exercise that sets its direction in an organization for the 21st century. Information technology (IT), Computer Centre (CC) and Analytical Laboratory (AnLab) are identified as three important...

  16. Utility Energy Services Contracts: Enabling Documents

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-05-01

    Utility Energy Services Contracts: Enabling Documents provides materials that clarify the authority for Federal agencies to enter into utility energy services contracts (UESCs), as well as sample documents and resources to ease utility partnership contracting.

  17. Altered expression of two-pore domain potassium (K2P) channels in cancer

    OpenAIRE

    Williams, Sarah; Bateman, Andrew; O'Kelly, Ita

    2013-01-01

    Potassium channels have become a focus in cancer biology as they play roles in cell behaviours associated with cancer progression, including proliferation, migration and apoptosis. Two-pore domain (K2P) potassium channels are background channels which enable the leak of potassium ions from cells. As these channels are open at rest they have a profound effect on cellular membrane potential and subsequently the electrical activity and behaviour of cells in which they are expressed. The K2P fami...

  18. Permeability anisotropy of serpentinite and fluid migration in subduction zones

    Science.gov (United States)

    Kawano, S.; Katayama, I.; Okazaki, K.

    2010-12-01

    Subduction zones are the place where water is transported into the Earth's interior and causes arc volcanism and seismic activities. Subducting slabs release most of the water to the mantle wedge by the dehydration reactions, and the expelled water reacts with mantle rocks, forming serpentinite at the plate interface. The existence of hydrous layer has been detected by low- velocity anomaly and high-Poison's ratio in several subduction zones (Kamiya and Kobayashi 2000 ; Brocher et al. 2003). The migration of water is generally considered to move upward by buoyancy in the mantle. However, if the hydrous layer is extensively deformed, the migration of water can be controlled by the deformation plane within such layer. In order to test this hypothesis, we analyzed the permeability anisotropy of serpentinite with a strongly-developed schistosity and discuss fluid migration in the subduction systems. Serpentinite samples were collected from Nishisonogi metamorphic terrane in Nagasaki, which schistosity is well-defined developed. Two types of experimental samples were prepared: one is parallel to schistosity and the other is perpendicular. We used intra-vessel deformation and fluid- flow apparatus (IVA) in Hiroshima University to measure the permeability. In this study, we measured gas permeability using nitrogen gas and water permeability under isotropic pressure. Gas permeability was measured using the constant flow method, and water permeability was similar to gas and the transient pulse method was also used. The experiments were conducted at confining pressures up to 50 MPa, pore pressures up to 8 MPa at room temperature. We converted gas permeability to intrinsic permeability with Klinkenberg effect. The permeability decreased with increasing confining pressure, and intrinsic permeability of samples parallel to schistosity were about 10^-20 m2 at confining pressure of 50 MPa. We observed two types of pressure effect: one is significant decline due to crack filling

  19. The Effect of Bacteria Penetration on Chalk Permeability

    DEFF Research Database (Denmark)

    Halim, Amalia Yunita; Shapiro, Alexander; Nielsen, Sidsel Marie;

    , the spore forming Bacillus licheniformis 421 and the non-spore forming Pseudomonas putida K12, were used. The core plugs were Stevns Klint outcrop with initial permeability at 2-4 mD. The results revealed that bacteria were able to penetrate and to be transported through the chalk. Furthermore, a...... higher number of B. licheniformis was detected on the effluent compared with P. putida. However, in the experiment with B. licheniformis mainly spores were detected in the effluent. The core permeability decreased rapidly during injection of bacteria and a starvation period of 12 days did not allow the...... permeability to return to initial condition....

  20. Experimental and numerical evaluation of the permeability of silica sol

    International Nuclear Information System (INIS)

    The permeability of silica sol to narrow rock fracture and low permeable sand layer was studied by means of laboratory tests and numerical analysis. Parallel plate tests and sand column tests were conducted to evaluate penetrability of silica sol. Particle size distribution tests revealed that the silica sol was comprised of particles which were larger than the aperture of the rock fracture or the void diameter of sand, and clogging may have reduced the penetration length of silica sol. The measured penetration lengths were properly reproduced by the flow analysis which took into account the variations in the viscosity over time and the permeability reduction by clogging of grout particles. (author)

  1. Compressible fluid flow through rocks of variable permeability

    International Nuclear Information System (INIS)

    The effectiveness of course-grained igneous rocks as shelters for burying radioactive waste can be assessed by determining the rock permeabilities at their in situ pressures and stresses. Analytical and numerical methods were used to solve differential equations of one-dimensional fluid flow through rocks with permeabilities from 104 to 1 nD. In these calculations, upstream and downstream reservoir volumes of 5, 50, and 500 cm3 were used. The optimal size combinations of the two reservoirs were determined for measurements of permeability, stress, strain, acoustic velocity, and electrical conductivity on low-porosity, coarse-grained igneous rocks

  2. One of parameters reflecting coal reservoir permeability - block coal rate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. [China Coal Research Institute, Xian (China)

    2001-12-01

    The permeability of coal reservoir depends to a large extent on the coal body texture. The coal body texture determines the block coal rate derived from sieve experiment. Hence the block coal rate can reflect the permeability of the coal reservoir as a whole. In the mining areas of the central part of Liaoning, the block coal rate is found to have a direct relationship with coal permeability. This has provided an example that block coal rate can be used as one of the parameters for evaluating coal reservoir. 6 refs., 3 tabs.

  3. Open-channel hydraulics

    International Nuclear Information System (INIS)

    This text discusses the following: concepts of fluid flow; the momentum principle; computation of uniform flow; design of channels; and turbulent diffusion and dispersion in steady open-channel flow. Emphasis is concerned only with the flow of water in channels where the water is not transporting significant quantities of air or sediment. The text contains quite a few examples demonstrating the application of the presented principles

  4. Bank Liabilities Channel

    OpenAIRE

    Quadrini, Vincenzo

    2014-01-01

    The financial intermediation sector is important not only for channeling resources from agents in excess of funds to agents in need of funds (lending channel). By issuing liabilities it also creates financial assets held by other sectors of the economy for insurance purpose. When the intermediation sector creates less liabilities or their value falls, agents are less willing to engage in activities that are individually risky but desirable in aggregate (bank liabilities channel). The paper st...

  5. Bank Liabilities Channel

    OpenAIRE

    Vincenzo Quadrini

    2015-01-01

    The financial intermediation sector is important not only for channeling resources from agents in excess of funds to agents in need of funds (lending channel). By issuing liabilities it also creates financial assets held by other sectors of the economy for insurance purpose. When the intermediation sector creates less liabilities or their value falls, agents are less willing to engage in activities that are individually risky but desirable in aggregate (bank liabilities channel). The paper st...

  6. HIPPI and Fibre Channel

    International Nuclear Information System (INIS)

    The High-Performance Parallel Interface (HIPPI) and Fibre Channel are near-gigabit per second data communications interfaces being developed in ANSI standards Task Group X3T9.3. HIPPI is the current interface of choice in the high-end and supercomputer arena, and Fibre Channel is a follow-on effort. HIPPI came from a local area network background, and Fibre Channel came from a mainframe to peripheral interface background

  7. An Architecture to Enable Future Sensor Webs

    Science.gov (United States)

    Mandl, Dan; Caffrey, Robert; Frye, Stu; Grosvenor, Sandra; Hess, Melissa; Chien, Steve; Sherwood, Rob; Davies, Ashley; Hayden, Sandra; Sweet, Adam

    2004-01-01

    A sensor web is a coherent set of distributed 'nodes', interconnected by a communications fabric, that collectively behave as a single dynamic observing system. A 'plug and play' mission architecture enables progressive mission autonomy and rapid assembly and thereby enables sensor webs. This viewgraph presentation addresses: Target mission messaging architecture; Strategy to establish architecture; Progressive autonomy with onboard sensor web; EO-1; Adaptive array antennas (smart antennas) for satellite ground stations.

  8. Transmission ion channeling images of crystal defects

    International Nuclear Information System (INIS)

    This paper demonstrates how images of crystal defects can be produced using ion channeling. A focused, scanned beam of MeV protons from the University of Oxford Nuclear Microprobe has been used. With the beam aligned with a channeling direction of the crystal, protons transmitted through the thinned samples are detected and images produced showing the mean transmitted proton energy loss. Regions where dechanneling is occurring owing to the presence of a defect are revealed. Images of groups of misfit dislocations in epitaxial Si1-xGex on Si provide evidence of the lattice plane rotation produced by these defects. Stacking faults have also been imaged, and the choice of the planar channeling direction enables information on the fault translation vector to be obtained. (orig.)

  9. Symmetrization for redundant channels

    Science.gov (United States)

    Tulplue, Bhalchandra R. (Inventor); Collins, Robert E. (Inventor)

    1988-01-01

    A plurality of redundant channels in a system each contain a global image of all the configuration data bases in each of the channels in the system. Each global image is updated periodically from each of the other channels via cross channel data links. The global images of the local configuration data bases in each channel are separately symmetrized using a voting process to generate a system signal configuration data base which is not written into by any other routine and is available for indicating the status of the system within each channel. Equalization may be imposed on a suspect signal and a number of chances for that signal to heal itself are provided before excluding it from future votes. Reconfiguration is accomplished upon detecting a channel which is deemed invalid. A reset function is provided which permits an externally generated reset signal to permit a previously excluded channel to be reincluded within the system. The updating of global images and/or the symmetrization process may be accomplished at substantially the same time within a synchronized time frame common to all channels.

  10. A method of determining the permeability coefficient of coal seam based on the permeability of loaded coal

    Institute of Scientific and Technical Information of China (English)

    Li Bo; Wei Jianping; Wang Kai; Li Peng; Wang Ke

    2014-01-01

    This study developed the equipment for thermo-fluid-solid coupling of methane-containing coal, and investigated the seepage character of loaded coal under different working conditions. Regarding the effective pressure as a variable, the variation characteristics of the gas permeability of loaded meth-ane-containing coal has been studied under the conditions of different confining pressures and pore pres-sures. The qualitative and quantitative relationship between effective stress and permeability of loaded methane-containing coal has been established, considering the adsorption of deformation, amount of pore gas compression and temperature variation. The results show that the permeability of coal samples decreases along with the increasing effective stress. Based on the Darcy law, the correlation equation between the effective stress and permeability coefficient of coal seam has been established by combining the permeability coefficient of loaded coal and effective stress. On the basis of experimental data, this equation is used for calculation, and the results are in accordance with the measured gas permeability coefficient of coal seam. In conclusion, this method can be accurate and convenient to determine the gas permeability coefficient of coal seam, and provide evidence for forecasting that of the deep coal seam.

  11. Composites with tuned effective magnetic permeability

    Science.gov (United States)

    Amirkhizi, Alireza V.; Nemat-Nasser, Sia

    2007-07-01

    Pendry et al. [J. B. Pendry, A. J. Holden, D. J. Robbins, and W. J. Stewart, IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and Smith et al. [D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, Phys. Rev. Lett. 84, 4184 (2000)] have shown that the effective magnetic permeability, μ, of free space can be rendered negative over a certain frequency range by a periodic arrangement of very thin conductors with suitable magnetic resonance properties, the so-called split-ring resonators. Because of its rather bulky architecture, this structure does not lend itself to a proper integration into a reasonably thin real composite structural panel. To remedy this fundamental barrier, we invented a new magnetic resonator consisting of very thin folded plates that are suitably nested within one another to form folded-doubled resonators (FDRs) that can be integrated into an actual composite panel. Measurements, using a focused beam electromagnetic characterization system combined with time-domain numerical simulations of the reflection and transmission coefficients of such a composite slab have revealed that indeed the composite has a negative μ over a frequency range of about 9.1-9.35 GHz [S. Nemat-Nasser, S. C. Nemat-Nasser, T. A. Plaisted, A. Starr, and A. Vakil Amirkhizi, in Biomimetics: Biologically Inspired Technologies, edited by Y. Bar Cohen (CRC Press, Boca Raton, FL, 2006)]. Thus, it has become possible to construct a structural composite panel with negative index of refraction by simultaneously creating negative effective ɛ and μ [V. G. Veselago, Sov. Phys. Usp. 10, 509 (1968); R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001); A. F. Starr, P. M. Rye, D. R. Smith, and S. Nemat-Nasser, Phys. Rev. B 70, 113102 (2004)].

  12. Enabling Awareness Driven Differentiated data service in IOT

    Directory of Open Access Journals (Sweden)

    Haoming Guo

    2011-11-01

    Full Text Available IOT needs to organize sensor resources to monitor events in real world for all time. As result, huge number of data will be concentrated in the system. Due to difference of sensors’ awareness on event, the concentrated data’s qualities are different. The data process task’s performance will be affected without discrimination of data’s quality. This paper introduced an approach, called Awareness Driven Schedule (ADS that enables involved sensor resources to provide differentiated data service by their awareness, to address the issue. In the approach, higher a sensor resource’s awareness on the event is, more detailed data service it should provide. Requirement that specify relation of sensors’ awareness and rules of data collect job will be submitted initially. Constant and continuous data channels are created to organize sensors. In accordance of their awareness and task initial requirement, sensor resources are scheduled to collect data and aggregate to task through the channels. Sensor resource’s involvement and service depend on it’s awareness and task’s requirement.  Upon ADS, a middleware is built for CEA’s(China Earthquake Administration SPON(Seismological Precursors Observation Net and applied for China’s earthquake research applications. In the applications, Dull data of low awareness sensors could be banned out, applications may by more efficient.

  13. Understanding Sodium Channel Function and Modulation Using Atomistic Simulations of Bacterial Channel Structures.

    Science.gov (United States)

    Boiteux, C; Allen, T W

    2016-01-01

    Sodium channels are chief proteins involved in electrical signaling in the nervous system, enabling critical functions like heartbeat and brain activity. New high-resolution X-ray structures for bacterial sodium channels have created an opportunity to see how these proteins operate at the molecular level. An important challenge to overcome is establishing relationships between the structures and functions of mammalian and bacterial channels. Bacterial sodium channels are known to exhibit the main structural features of their mammalian counterparts, as well as several key functional characteristics, including selective ion conduction, voltage-dependent gating, pore-based inactivation and modulation by local anesthetic, antiarrhythmic and antiepileptic drugs. Simulations have begun to shed light on each of these features in the past few years. Despite deviations in selectivity signatures for bacterial and mammalian channels, simulations have uncovered the nature of the multiion conduction mechanism associated with Na(+) binding to a high-field strength site established by charged glutamate side chains. Simulations demonstrated a surprising level of flexibility of the protein, showing that these side chains are active participants in the permeation process. They have also uncovered changes in protein structure, leading to asymmetrical collapses of the activation gate that have been proposed to correspond to inactivated structures. These observations offer the potential to examine the mechanisms of state-dependent drug activity, focusing on pore-blocking and pore-based slow inactivation in bacterial channels, without the complexities of inactivation on multiple timescales seen in eukaryotic channels. Simulations have provided molecular views of the interactions of drugs, consistent with sites predicted in mammalian channels, as well as a wealth of other sites as potential new drug targets. In this chapter, we survey the new insights into sodium channel function that

  14. Linear Stability Analysis of Compressible Channel Flow with Porous Walls

    CERN Document Server

    Rahbari, Iman

    2015-01-01

    We have investigated the effects of permeable walls, modeled by linear acoustic impedance with zero reactance, on compressible channel flow via linear stability analysis (LSA). Base flow profiles are taken from impermeable isothermal-wall laminar and turbulent channel flow simulations at bulk Reynolds number, $Re_b$= 6900 and Mach numbers, $M_b$ = 0.2, 0.5, 0.85. For a sufficiently high value of permeability, two dominant modes are excited: a bulk pressure mode, causing symmetric expulsion and suction of mass from the porous walls (Mode 0); a standing-wave-like mode, with a pressure node at the centerline (Mode 1). In the case of turbulent mean flow profiles, both modes generate additional Reynolds shear stresses augmenting the (base) turbulent ones, but concentrated in the viscous sublayer region; the trajectories of the two modes in the complex phase velocity space follow each other very closely for values of wall permeability spanning two orders of magnitude, suggesting their coexistence. The transition fr...

  15. Adaptive Channel Allocation for Enabling Target SINR Achievability in Power-Controlled Wireless Networks

    Czech Academy of Sciences Publication Activity Database

    Kučera, Štěpán; Aissa, S.; Yoshida, S.

    2010-01-01

    Roč. 9, č. 2 (2010), s. 833-843. ISSN 1536-1276 R&D Projects: GA ČR GA102/09/1795 Institutional research plan: CEZ:AV0Z20670512 Keywords : ALGORITHMS * RADIO SYSTEMS Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.152, year: 2010

  16. Probing permeability and microstructure: Unravelling the role of a low-permeability dome on the explosivity of Merapi (Indonesia)

    Science.gov (United States)

    Kushnir, Alexandra R. L.; Martel, Caroline; Bourdier, Jean-Louis; Heap, Michael J.; Reuschlé, Thierry; Erdmann, Saskia; Komorowski, Jean-Christophe; Cholik, Noer

    2016-04-01

    Low permeability dome rocks may contribute to conduit overpressure development in volcanic systems, indirectly abetting explosive activity. The permeability of dome-forming rocks is primarily controlled by the volume, type (vesicles and/or microcracks), and connectivity of the void space present. Here we investigate the permeability-porosity relationship of dome-forming rocks and pumice clasts from Merapi's 1888 to 2013 eruptions and assess their possible role in eruptive processes, with particular emphasis on the 2010 paroxysmal eruption. Rocks are divided into three simple field classifications common to all eruptions: Type 1 samples have low bulk density and are pumiceous in texture; Type 2 samples, ubiquitous to the 2010 eruption, are dark grey to black in hand sample and vary greatly in vesicularity; and Type 3 samples are weakly vesicular, light grey in hand sample, and are the only samples that contain cristobalite. Type 2 and Type 3 rocks are present in all eruptions and their permeability and porosity data define similar power law relationships, whereas data for Type 1 samples are clearly discontinuous from these trends. A compilation of permeability and porosity data for andesites and basaltic andesites with published values highlights two microstructural transitions that exert control on permeability, confirmed by modified Bayesian Information Criterion (BIC) analysis. Permeability is microcrack- and diktytaxitic-controlled at connected porosities, φc, 31 vol.%. Type 3 basaltic andesites, the least permeable of the measured samples and therefore the most likely to have originated in the uppermost low-permeability dome, are identified as relicts of terminal domes (the last dome extruded prior to quiescence). Cristobalite commonly found in the voids of Type 3 blocks may not contribute significantly to the reduction of the permeability of these samples, mainly because it is associated with an extensive microporous, diktytaxitic texture. Indeed, the low

  17. Measurement of relative permeability of fuel cell diffusion media

    KAUST Repository

    Hussaini, I.S.

    2010-06-01

    Gas diffusion layer (GDL) in PEM fuel cells plays a pivotal role in water management. Modeling of liquid water transport through the GDL relies on knowledge of relative permeability functions in the in-plane and through-plane directions. In the present work, air and water relative permeabilities are experimentally determined as functions of saturation for typical GDL materials such as Toray-060, -090, -120 carbon paper and E-Tek carbon cloth materials in their plain, untreated forms. Saturation is measured using an ex situ gravimetric method. Absolute and relative permeability functions in the two directions of interest are presented and new correlations for in-plane relative permeability of water and air are established. © 2010 Elsevier B.V. All rights reserved.

  18. Bovine colostrum supplementation during running training increases intestinal permeability.

    Science.gov (United States)

    Buckley, Jonathan D; Butler, Ross N; Southcott, Emma; Brinkworth, Grant D

    2009-02-01

    Endurance exercise training can increase intestinal permeability which may contribute to the development of gastrointestinal symptoms in some athletes. Bovine colostrum (BC) supplementation reduces intestinal permeability induced by non-steroidal anti-inflammatory drugs. This study aimed to determine whether BC could also reduce intestinal permeability induced by endurance exercise. Thirty healthy adult males (25.0 ± 4.7 yr; mean ± SD) completed eight weeks of running three times per week for 45 minutes at their lactate threshold while consuming 60 g/day of BC, whey protein (WP) or control (CON). Intestinal permeability was assessed at baseline and after eight weeks by measuring the ratio of urinary lactulose (L) and rhamnose (R) excretion. After eight weeks the L/R ratio increased significantly more in volunteers consuming BC (251 ± 140%) compared with WP (21 ± 35%, P gut. Further research should investigate the potential for BC to increase intestinal macromolecular transport in adults. PMID:22253980

  19. Porosity, permeability, and their relationship in granite, basalt, and tuff

    International Nuclear Information System (INIS)

    This report discusses the porosity, storage, and permeability of fractured (mainly crystalline) rock types proposed as host rock for nuclear waste repositories. The emphasis is on the inter-relationships of these properties, but a number of reported measurements are included as well. The porosity of rock is shown to consist of fracture porosity and matrix porosity; techniques are described for determining the total interconnected porosity through both laboratory and field measurement. Permeability coefficient, as obtained by experiments ranging from laboratory to crustal scale, is discussed. Finally, the problem of determining the relationship between porosity and permeability is discussed. There is no simple, all encompassing relationship that describes the dependence of permeability upon porosity. However, two particular cases have been successfully analyzed: flow through a single rough fracture, and flow through isotropic porous rock. These two cases are discussed in this report

  20. CHLORIDE ION PERMEABILITY STUDIES OF METAKAOLIN BASED HIGH PERFORMANCE CONCRETE

    Directory of Open Access Journals (Sweden)

    Dr.Vaishali. G.Ghorpade,

    2011-02-01

    Full Text Available To increase the applications of HPC in India, greater under standing of HPC produced with locally available materials and indigenously produced mineral admixtures is essential. In the present investigation, HPC has been produced with locally available aggregates and metakaolin as the mineral admixture. Various metakaolin based HPC mixes were attained by absolute volume method. Cubes of 150X150X150 mm size were cast and cured for 28 days and then tested for compressive strength. Chloride ion permeability test as per ASTM C 1202 has been conducted on various HPC mixes to measure the permeability values of HPC produced with metakaolin. The experimental results indicate that metakaolin has the ability to considerably reduce the permeability of high performance concrete. The various details about the chloride ion permeability test have been presented in this paper.

  1. Gas permeability measurement in polyethylene and its copolymer films

    International Nuclear Information System (INIS)

    In this research, low density polyethylene (LDPE) and poly(ethylene-co-vinyl acetate) (EVA) were used as polymeric materials. The methods used to produce LDPE and EVA was film blowing and thermal-dry phase inversion. The amount of permeability, diffusivity and solubility of O2 and CO2 through above polymers were obtained and also the effect of temperature, pressure and film thickness for LDPE was measured. To study film cross-section morphology in EVA, scanning electron microscopy (SEM) was applied. The results showed that the amount of permeability and solubility were decreased by increasing film thickness but diffusivity was increased. However, by increasing temperature, permeability, solubility, and diffusivity were increased. From the results for EVA, adding 28% of vinyl acetate groups to polyethylene chain increased permeability of O2 and CO2 through the film. Scanning electron microscopy (SEM) microphotograph for EVA film verified that the film cross-section structure was as dense as for polyethylene

  2. A topology optimization method for design of negative permeability metamaterials

    DEFF Research Database (Denmark)

    Diaz, A. R.; Sigmund, Ole

    2010-01-01

    A methodology based on topology optimization for the design of metamaterials with negative permeability is presented. The formulation is based on the design of a thin layer of copper printed on a dielectric, rectangular plate of fixed dimensions. An effective media theory is used to estimate the...... effective permeability, obtained after solving Maxwell's equations on a representative cell of a periodic arrangement using a full 3D finite element model. The effective permeability depends on the layout of copper, and the subject of the topology optimization problem is to find layouts that result in...... negative (real) permeability at a prescribed frequency. A SIMP-like model is invoked to represent the conductivity of regions of intermediate density. A number of different filtering strategies are invoked to facilitate convergence to binary solutions. Examples of designs for S-band applications are...

  3. AXISYMMETRIC FLOW THROUGH A PERMEABLE NEAR-SPHERE

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    An analytical approach is described for the axisymmetric flow through a permeable near-sphere with a modification to boundary conditions in order to account permeability. The Stokes equation was solved by a regular perturbation technique up to the second order correction in epsilon representing the deviation from the radius of nondeformed sphere. The drag and the flow rate were calculated and the results were evaluated from the point of geometry and the permeability of the surface. An attempt also was made to apply the theory to the filter feeding problem. The filter appendages of small ecologically important aquatic organisms were modeled as axisymmetric permeable bodies, therefore a rough model for this problem was considered here as an oblate spheroid or near-sphere.

  4. Effect of Lactobacilli on Paracellular Permeability in the Gut

    Directory of Open Access Journals (Sweden)

    Marie-Louise Johansson Hagslatt

    2011-01-01

    Full Text Available Paracellular permeability is determined by the complex structures of junctions that are located between the epithelial cells. Already in 1996, it was shown that the human probiotic strain Lactobacillus plantarum 299v and the rat-originating strain Lactobacillus reuteri R2LC could reduce this permeability in a methotrexate-induced colitis model in the rat. Subsequently, many animal models and cell culture systems have shown indications that lactobacilli are able to counteract increased paracellular permeability evoked by cytokines, chemicals, infections, or stress. There have been few human studies focusing on the effect of lactobacilli on intestinal paracellular permeability but recently it has been shown that they could influence the tight junctions. More precisely, short-term administration of L. plantarum WCSF1 to healthy volunteers increased the relocation of occludin and ZO-1 into the tight junction area between duodenal epithelial cells.

  5. Quantifying tight-gas sandstone permeability via critical path analysis

    Science.gov (United States)

    Ghanbarian, Behzad; Torres-Verdín, Carlos; Skaggs, Todd H.

    2016-06-01

    Rock permeability has been actively investigated over the past several decades by the geosciences community. However, its accurate estimation still presents significant technical challenges, particularly in spatially complex rocks. In this short communication, we apply critical path analysis (CPA) to estimate permeability in porous rocks from measured mercury intrusion porosimetry and electrical conductivity data. Theoretical estimations of various CPA-based models are then compared to experimental measurements using eighteen tight-gas sandstones. Except for two of the samples, we find permeability estimations performed with the Skaggs model (assuming pore diameter independent of its length) more accurate than other models, within a factor of two of the measured permeabilities. We discuss some plausible sources of the uncertainties.

  6. Buoyancy Effect on MHD Flow Past a Permeable Bed

    Directory of Open Access Journals (Sweden)

    S. Venkataramana

    1986-10-01

    Full Text Available In this paper, the effect of buoyancy force on the parallel flows bounded above by a rigid permeable plate which may be moving or stationary and below, by a permeable bed has been investigated. To discuss the solution, the flow region is divided into two zones. In Zone 1, the flow is laminar and is governed by the Navier-Stokes equations from the impermeable upper rigid plate to the permeable bed. In Zone 2, the flow is governed by the Darcy law in the permeable bed below the nominal surface. The expressions for velocity and temparature distributions, Slip velocity, slip temperature, mass flow rate and the rates of heat transfer coefficients are obtained. The effects of magnetic, porous, slip and buoyancy parameters and Biot number on the above physical quantities are investigated. The thickness of the boundary layer in Zone 2 has been evaluated.

  7. Xenon NMR measurements of permeability and tortuosity in reservoir rocks.

    Science.gov (United States)

    Wang, Ruopeng; Pavlin, Tina; Rosen, Matthew Scott; Mair, Ross William; Cory, David G; Walsworth, Ronald Lee

    2005-02-01

    In this work we present measurements of permeability, effective porosity and tortuosity on a variety of rock samples using NMR/MRI of thermal and laser-polarized gas. Permeability and effective porosity are measured simultaneously using MRI to monitor the inflow of laser-polarized xenon into the rock core. Tortuosity is determined from measurements of the time-dependent diffusion coefficient using thermal xenon in sealed samples. The initial results from a limited number of rocks indicate inverse correlations between tortuosity and both effective porosity and permeability. Further studies to widen the number of types of rocks studied may eventually aid in explaining the poorly understood connection between permeability and tortuosity of rock cores. PMID:15833638

  8. Lightweight, Low Permeability, Cryogenic Thoraeus RubberTM Inflatables Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NanoSonic has developed a candidate state-of-the-art inflatable as a novel bladder material for life critical, space habitats that maintains low air permeability...

  9. Differential water permeability and regulation of three aquaporin 4 isoforms

    DEFF Research Database (Denmark)

    Fenton, Robert A.; Moeller, Hanne B; Zelenina, Marina;

    2010-01-01

    Aquaporin 4 (AQP4) is expressed in the perivascular glial endfeet and is an important pathway for water during formation and resolution of brain edema. In this study, we examined the functional properties and relative unit water permeability of three functional isoforms of AQP4 expressed...... in the brain (M1, M23, Mz). The M23 isoform gave rise to square arrays when expressed in Xenopus laevis oocytes. The relative unit water permeability differed significantly between the isoforms in the order of M1 > Mz > M23. None of the three isoforms were permeable to small osmolytes nor were they affected...... by changes in external K(+) concentration. Upon protein kinase C (PKC) activation, oocytes expressing the three isoforms demonstrated rapid reduction of water permeability, which correlated with AQP4 internalization. The M23 isoform was more sensitive to PKC regulation than the longer isoforms...

  10. Diagenetic effect on permeabilities of geothermal sandstone reservoirs

    DEFF Research Database (Denmark)

    Weibel, Rikke; Olivarius, Mette; Kristensen, Lars;

    The Danish subsurface contains abundant sedimentary deposits, which can be utilized for geothermal heating. The Upper Triassic – Lower Jurassic continental-marine sandstones of the Gassum Formation has been utilised as a geothermal reservoir for the Thisted Geothermal Plant since 1984 extracting...... and permeability is caused by increased diagenetic changes of the sandstones due to increased burial depth and temperatures. Therefore, the highest water temperatures typically correspond with the lowest porosities and permeabilities. Especially the permeability is crucial for the performance of the geothermal......-line fractures. Continuous thin chlorite coatings results in less porosity- and permeability-reduction with burial than the general reduction with burial, unless carbonate cemented. Therefore, localities of sandstones characterized by these continuous chlorite coatings may represent fine geothermal reservoirs...

  11. Effect Of Hot Water Injection On Sandstone Permeability

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Fabricius, Ida Lykke

    2012-01-01

    of published results regarding the effect of temperature on sandstone permeability. These tests are performed with mineral oil, nitrogen gas, distilled water and solutions of NaCl, KCl, CaCl2 as well as brines that contain a mixture of salts. Thirteen sandstone formations, ranging from quartz arenites....... Heating causes thermal expansion, which results in porosity reduction if the sandstone is confined. The maximum effect of porosity reduction as a result of thermal expansion on permeability is modelled and compared the change in specific surface that is computed from the reported data. This does...... not account for all the permeability reductions observed. Permeablity reduction occurs both when distilled water is the saturating fluid as well as in tests with NaCl, KCl or CaCl2 solutions, however, this is not the case in tests with mineral oil or nitrogen gas. The formation of a filter cake or influx...

  12. A thin permeable-membrane device for single-molecule manipulation

    Science.gov (United States)

    Park, Chang-Young; Jacobson, David R.; Nguyen, Dan T.; Willardson, Sam; Saleh, Omar A.

    2016-01-01

    Single-molecule manipulation instruments have unparalleled abilities to interrogate the structure and elasticity of single biomolecules. Key insights are derived by measuring the system response in varying solution conditions; yet, typical solution control strategies require imposing a direct fluid flow on the measured biomolecule that perturbs the high-sensitivity measurement and/or removes interacting molecules by advection. An alternate approach is to fabricate devices that permit solution changes by diffusion of the introduced species through permeable membranes, rather than by direct solution flow through the sensing region. Prior implementations of permeable-membrane devices are relatively thick, disallowing their use in apparatus that require the simultaneous close approach of external instrumentation from two sides, as occurs in single-molecule manipulation devices like the magnetic tweezer. Here, we describe the construction and use of a thin microfluidic device appropriate for single-molecule studies. We create a flow cell of only ˜500 μm total thickness by sandwiching glass coverslips around a thin plastic gasket and then create permeable walls between laterally separated channels in situ through photo-induced cross-linking of poly(ethylene glycol) diacrylate hydrogels. We show that these membranes permit passage of ions and small molecules (thus permitting solution equilibration in the absence of direct flow), but the membranes block the passage of larger biomolecules (thus retaining precious samples). Finally, we demonstrate the suitability of the device for high-resolution magnetic-tweezer experiments by measuring the salt-dependent folding of a single RNA hairpin under force.

  13. Calcium-Mediated Mitochondrial Permeability Transition Involved in Hydrogen Peroxide-Induced Apoptosis in Tobacco Protoplasts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In the present study, we focused on whether intracellular free Ca2+ ([Ca2+]i) regulates the formation of mitochondrial permeability transition pore (MPTP) in H2O2-induced apoptosis in tobacco protoplasts. It was shown that the decrease in mitochondrial membrane potential (△Ψm) preceded the appearance of H2O2-induced apoptosis;pretreatment with the specific MPTP inhibitor cyclosporine A, which also inhibits Ca2+ cycling by the mitochondria,effectively retarded apoptosis and the decrease in △Ψm. Apoptosis and decreased △Ψm were exacerbated by CaCl2, whereas the plasma membrane voltage-dependent Ca2+ channel blocker lanthanum chloride (LaCl3)attentuated these responses. Chelation of extracellular Ca2+ with EGTA almost totally inhibited apoptosis and the decrease in △Ψm induced by H2O2. The time-course of changes in [Ca2+]i in apoptosis was detected using the Ca2+ probe Fluo-3 AM. These studies showed that [Ca2+]i was increased at the very early stage of H2O2-induced apoptosis. The EGTA evidently inhibited the increase in [Ca2+]i induced by H2O2, whereas it was only partially inhibited by LaCl3. The results suggest that H2O2 may elevate cytoplasmic free Ca2+ concentrations in tobacco protoplasts, which mainly results from the entry of extracellular Ca2+, to regulate mitochondrial permeability transition. The signaling pathway of [Ca2+]i-mediated mitochondrial permeability transition was associated with H2O2-induced apoptosis in tobacco protoplasts.

  14. Repercussions on concrete permeability due to recycled concrete aggregate

    OpenAIRE

    Gómez Soberón, José Manuel Vicente; Agulló Fité, Luís; Vázquez Ramonich, Enric

    2001-01-01

    This paper presents an experimental analysis of recycled concrete (RC) in which the natural aggregates are replaced by recycled concrete aggregates (RCA). This experimental program covers the specifications of the aggregates employed, together with that of the concrete that is manufactured with them. The considerable effect on the permeability of RC that is produced by the use of RCA is described and discussed. Tests reveal considerable increase in permeability of RC in compari...

  15. An Asymptotic Model of Seismic Reflection from a Permeable Layer

    OpenAIRE

    Silin, Dmitriy; Goloshubin, Gennady

    2010-01-01

    Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot’s model of poroelasticity. A review of t...

  16. The system of thermoelectric air conditioning based on permeable thermoelements

    OpenAIRE

    Cherkez R. G.

    2009-01-01

    There is thermoelectric air conditioner unit on the basis of permeable cooling thermoelements presented. In thermoelectric air conditioner unit the thermoelectric effects and the Joule–Thomson effect have been used for the air stream cooling. There have been described the method of temperature distribution analysis, the determinations of energy conversion power characteristics and design style of permeable thermoelement with maximum coefficient of performance described. The results of compute...

  17. Permeability of rapid prototyped artificial bone scaffold structures

    OpenAIRE

    Lipowiecki, Marcin; Ryvolava, Marketa; Tottosi, Akos; Naher, Sumsun; Brabazon, Dermot

    2012-01-01

    Fluid flow through a bone scaffold structure is an important factor in its ability to build up a living tissue. Permeability is often used as a measure of a structure's ability to allow for flow of nutrients and waste products related to the growth of new tissue. These structures also need to meet conflicting mechanical strength requirements to allow for load bearing. In this work, the effect of different bone structure morphologies on permeability were examined both numerically and experimen...

  18. Thyroid hormone modulates rabbit proximal straight tubule paracellular permeability

    OpenAIRE

    Baum, Michel; Quigley, Raymond

    2003-01-01

    Proximal straight tubules (PST) from both neonatal and hypothyroid adult rabbits have a lower rate of passive volume absorption when perfused with a high-chloride solution simulating late proximal tubular fluid than adult rabbit PST. We hypothesized that the maturational increase in serum thyroid hormone levels mediates the developmental changes in PST paracellular permeability. Neonatal tubules had lower chloride permeability, higher transepithelial resistance, but comparable mannitol permea...

  19. Development of Low Permeability Oilfields in Shengli Oil Province

    Institute of Scientific and Technical Information of China (English)

    Wang Binhai; Fan Naifu

    1995-01-01

    @@ Shengli oil province,complicated in geology and rich in resources, is the second largest oil production basin of China. Except for some big/medium sized oil/gas field with high and medium permeability which have already been put into production. There are 11oil fields at great depth with low permeability of less than 50 ×10-3 μm2 have been discovered with 12. 2% of the total proved original oil in place.

  20. Abnormal small bowel permeability and duodenitis in recurrent abdominal pain.

    OpenAIRE

    Meer, S.B.; Forget, P P; Arends, J.W.

    1990-01-01

    Thirty nine children with recurrent abdominal pain aged between 5.5 and 12 years, underwent endoscopic duodenal biopsy to find out if there were any duodenal inflammatory changes, and if there was a relationship between duodenal inflammation and intestinal permeability to 51Cr-EDTA. Duodenal inflammation was graded by the duodenitis scale of Whitehead et al (grade 0, 1, 2, and 3). In 13 out of 39 patients (33%) definite signs of inflammation were found (grade 2 and 3). Intestinal permeability...