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Sample records for increased monolayer permeability

  1. Hypoxia/reoxygenation increases the permeability of endothelial cell monolayers: Role of oxygen radicals

    Inauen, W.; Payne, D.K.; Kvietys, P.R.; Granger, D.N.

    1990-01-01

    We assessed the effect of hypoxia/reoxygenation on 14C-albumin flux across endothelial monolayers. Cultured bovine pulmonary artery endothelial cells were grown to confluence on nitrocellulose filters (pore size 12 microns). The endothelialized filters were mounted in Ussing-type chambers which were filled with cell culture medium (M 199). Equimolar amounts (33 nM) of 14C-labeled and unlabeled albumin were added to the hot and cold chambers, respectively. The monolayers were then exposed to successive periods (90 min) of normoxia (pO2 145 mmHg), hypoxia (pO2 20 mmHg), and reoxygenation (pO2 145 mmHg). A gas bubbling system was used to control media pO2 and to ensure adequate mixing. Four aliquots of culture media were taken during each period in order to calculate the 14C-albumin permeability across the endothelialized filter. In some experiments, either the xanthine oxidase inhibitor, oxypurinol (10 microM), or superoxide dismutase (600 U/mL), was added to the media immediately prior to the experiments. As compared to the normoxic control period, albumin permeability was 1.5 times higher during hypoxia (p less than 0.01) and 2.3 times higher during reoxygenation (p less than 0.01). The reoxygenation-induced increase in albumin permeability was prevented by either oxypurinol or superoxide dismutase. These data indicate that xanthine oxidase-derived oxygen radicals contribute to the hypoxia/reoxygenation-induced endothelial cell dysfunction. The altered endothelial barrier function induced by hypoxia/reoxygenation is consistent with the microvascular dysfunction observed following reperfusion of ischemic tissues

  2. Permeability of surface modified polyamidoamine (PAMAM) dendrimers across Caco-2 cell monolayers

    Yellepeddi, Venkata K.; Pisal, Dipak S.; Kumar, Ajay; Kaushik, Radhey S.; Hildreth, Michael B.; Guan, Xiangming; Palakurthi, Srinath

    2007-01-01

    Aim of this study was to prepare polyamine-conjugated PAMAM dendrimers and study their permeability across Caco-2 cell monolayers. Polyamines, namely, arginine and ornithine were conjugated to the amine terminals of the G4 PAMAM dendrimers by Fmoc synthesis. The apical-to-basolateral (AB) and basolateral-to-apical (BA) apparent permeability coefficients (Papp) for the PAMAM dendrimers increased by conjugating the dendrimers with both of the polyamines. The enhancement in permeability was depe...

  3. Regulation of endothelial cell shape and monolayer permeability by atrial natriuretic peptide

    Lofton-Day, C.E.

    1989-01-01

    Atrial natriuretic peptide (ANP), considered to be an important regulator of intravascular fluid volume, binds specifically to receptors on endothelial cells. In this study, the role of ANP-specific binding was investigated by examining the effect of ANP on the morphology and macromolecular permeability of monolayer cultures of bovine aortic endothelial cells. ANP alone had no observable effect on the monolayers. However, incubation of monolayers with ANP antagonized thrombin- or glucose oxidase-induced cell shape changes and intercellular gap formation. ANP pretreatment also opposed the effect of thrombin and glucose oxidase on actin filament distribution as observed by rhodamine-phalloidin staining and digital image analysis of F0actin staining. In addition, ANP reversed cell shape changes and cytoskeletal alterations induced by thrombin treatment but did not reverse alternations induced by glucose oxidase treatment. ANP significantly reduced increases in monolayer permeability to albumin resulting from thrombin or glucose oxidases treatment. Thrombin caused a 2-fold increase in monolayer permeability to 125 I-labeled albumin, which was abolished by 10 -8 -10 -6 M ANP pretreatment. Glucose oxidase caused similar increases in permeability and was inhibited by ANP at slightly shorter time periods

  4. Connexin 26-mediated gap junctional intercellular communication suppresses paracellular permeability of human intestinal epithelial cell monolayers

    Morita, Hidekazu; Katsuno, Tatsuro; Hoshimoto, Aihiro; Hirano, Noriaki; Saito, Yasushi; Suzuki, Yasuo

    2004-01-01

    In some cell types, gap junctional intercellular communication (GJIC) is associated with tight junctions. The present study was performed to determine the roles of GJIC in regulation of the barrier function of tight junctions. Caco-2 human colonic cells were used as a monolayer model, and barrier function was monitored by measuring mannitol permeability and transepithelial electrical resistance (TER). The monolayers were chemically disrupted by treatment with oleic acid and taurocholic acid. Western blotting analyses were performed to evaluate the protein levels of connexins, which are components of gap junctional intercellular channels. Cx26 expression was detected in preconfluent Caco-2 cells, and its level increased gradually after the monolayer reached confluency. These results prompted us to examine whether overexpression of Cx26 affects barrier function. Monolayers of Caco-2 cells stably expressing Cx26 showed significantly lower mannitol permeability and higher TER than mock transfectants when the monolayers were chemically disrupted. The levels of claudin-4, an important component of tight junctions, were significantly increased in the stable Cx26 transfectant. These results suggest that Cx26-mediated GJIC may play a crucial role in enhancing the barrier function of Caco-2 cell monolayers

  5. Acamprosate permeability across Caco-2 cell monolayer is predominantly paracellular

    Antonescu, Irina-Elena; Steffansen, Bente

    support area, thickness, and porosity). Results. The mean (± SD) Papp, exp of acamprosate and [14C]-mannitol across Caco-2 cell monolayers was measured as 0.19 ± 0.07 x 10-6 cm/s (n = 2, N = 3) and 0.35 ± 0.17 x 10-6 cm/s (n = 3, N = 4), respectively. Acamprosate PUBL and Pf were estimated as 200 - 3150 x...... role in acamprosate permeability, as only a very low fraction of acamprosate is in the neutral form at pH 7.4. The estimated acamprosate Ppara accounts for nearly 100% of the mathematically determined acamprosate Papp, calc (0.20 ± 0.10 x 10-6 cm/s), which matches well with the experimentally...... to the overall acamprosate apparent permeability. Methods. Acamprosate apparent permeability (Papp, exp) was determined across Caco-2 monolayers in the apical-to-basolateral transport direction using a buffer pH of 7.4 and several cell passages (N). Acamprosate concentrations were quantified by LC...

  6. The effect of novel surfactants and Solutol HS 15 on paclitaxel aqueous solubility and permeability across a Caco-2 monolayer.

    Alani, Adam W G; Rao, Deepa A; Seidel, Ron; Wang, Jian; Jiao, Jim; Kwon, Glen S

    2010-08-01

    The effect of novel surfactants on the aqueous solubility and the permeability of paclitaxel across a Caco-2 cell monolayer were examined in this work. The solubility and permeability of paclitaxel was evaluated in the presence of four soft surfactants (SS) KXN441, KXN424, KXN437, and KXN 337 and Solutol HS15. All surfactants increased the aqueous solubility of paclitaxel. Caco-2 cell membrane integrity in the presence of SS and Solutol HS15 was assessed by mannitol permeability and LDH release. All surfactants were tested at 0.5x CMC, 5x CMC and 1.5 mM concentrations. The effect of SSs on paclitaxel permeability was concentration dependent. At all concentrations tested, KXN 441 and Solutol HS 15 showed partially inhibition of drug efflux with no discernable change in mannitol permeability or cytotoxicity as observed with LDH release. At these concentrations, other SSs exhibited some partial efflux inhibition along with compromised membrane integrity and increasing mannitol permeability. In conclusion, all SSs were able to increase the aqueous solubility and permeability of paclitaxel across Caco-2 cells monolayer. However, KXN441 and Solutol HS15 were able to enhance paclitaxel permeability across Caco-2 monolayer without cytotoxicity. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  7. Radiation Effects on the Cytoskeleton of Endothelial Cells and Endothelial Monolayer Permeability

    Gabrys, Dorota; Greco, Olga; Patel, Gaurang; Prise, Kevin M.; Tozer, Gillian M.; Kanthou, Chryso

    2007-01-01

    Purpose: To investigate the effects of radiation on the endothelial cytoskeleton and endothelial monolayer permeability and to evaluate associated signaling pathways, which could reveal potential mechanisms of known vascular effects of radiation. Methods and Materials: Cultured endothelial cells were X-ray irradiated, and actin filaments, microtubules, intermediate filaments, and vascular endothelial (VE)-cadherin junctions were examined by immunofluorescence. Permeability was determined by the passage of fluorescent dextran through cell monolayers. Signal transduction pathways were analyzed using RhoA, Rho kinase, and stress-activated protein kinase-p38 (SAPK2/p38) inhibitors by guanosine triphosphate-RhoA activation assay and transfection with RhoAT19N. The levels of junction protein expression and phosphorylation of myosin light chain and SAPK2/p38 were assessed by Western blotting. The radiation effects on cell death were verified by clonogenic assays. Results: Radiation induced rapid and persistent actin stress fiber formation and redistribution of VE-cadherin junctions in microvascular, but not umbilical vein endothelial cells, and microtubules and intermediate filaments remained unaffected. Radiation also caused a rapid and persistent increase in microvascular permeability. RhoA-guanosine triphosphatase and Rho kinase were activated by radiation and caused phosphorylation of downstream myosin light chain and the observed cytoskeletal and permeability changes. SAPK2/p38 was activated by radiation but did not influence either the cytoskeleton or permeability. Conclusion: This study is the first to show rapid activation of the RhoA/Rho kinase by radiation in endothelial cells and has demonstrated a link between this pathway and cytoskeletal remodeling and permeability. The results also suggest that the RhoA pathway might be a useful target for modulating the permeability and other effects of radiation for therapeutic gain

  8. Reversible alterations in cultured pulmonary artery endothelial cell monolayer morphology and albumin permeability induced by ionizing radiation

    Friedman, M.; Ryan, U.S.; Davenport, W.C.; Chaney, E.L.; Strickland, D.L.; Kwock, L.

    1986-01-01

    The effects of ionizing irradiation (0, 600, 1500, or 3000 rads) on the permeability of pulmonary endothelial monolayers to albumin were studied. Pulmonary endothelial cells were grown to confluence on gelatin-coated polycarbonate filters, placed in serum-free medium, and exposed to a 60 Co source. The monolayers were placed in modified flux chambers 24 hours after irradiation; 125 I-albumin was added to the upper well, and both the upper and lower wells were serially sampled over 4 hours. The amount of albumin transferred from the upper well/hour over the period of steady-state clearance (90-240 min after addition of 125 I-albumin) was 2.8 +/- 0.2% in control monolayers and was increased in monolayers exposed to 1500 or 3000 rads (increase of 63 +/- 10% and 61 +/- 10%, respectively, P less than 0.01). No increase was found in monolayers exposed to 600 rads. The increases in endothelial albumin transfer rates were associated with morphologic evidence of monolayer disruption and endothelial injury which paralleled the changes in albumin permeability. Dose-dependent alterations in endothelial actin filament organization were also found. Incubation of the monolayers exposed to 3000 rads with medium supplemented with 10% fetal calf serum for 24 hours resulted in normalization of albumin permeability, improvement in morphologic appearance of the monolayers, and reorganization of the actin filament structure. These studies demonstrate that ionizing radiation is an active principle in the reversible disorganization of cultured pulmonary endothelial cell monolayers without the need of other cell types or serum components

  9. Chitosan-modified porous silicon microparticles for enhanced permeability of insulin across intestinal cell monolayers.

    Shrestha, Neha; Shahbazi, Mohammad-Ali; Araújo, Francisca; Zhang, Hongbo; Mäkilä, Ermei M; Kauppila, Jussi; Sarmento, Bruno; Salonen, Jarno J; Hirvonen, Jouni T; Santos, Hélder A

    2014-08-01

    Porous silicon (PSi) based particulate systems are emerging as an important drug delivery system due to its advantageous properties such as biocompatibility, biodegradability and ability to tailor the particles' physicochemical properties. Here, annealed thermally hydrocarbonized PSi (AnnTHCPSi) and undecylenic acid modified AnnTHCPSi (AnnUnTHCPSi) microparticles were developed as a PSi-based platform for oral delivery of insulin. Chitosan (CS) was used to modify the AnnUnTHCPSi microparticles to enhance the intestinal permeation of insulin. Surface modification with CS led to significant increase in the interaction of PSi microparticles with Caco-2/HT-29 cell co-culture monolayers. Compared to pure insulin, the CS-conjugated microparticles significantly improved the permeation of insulin across the Caco-2/HT-29 cell monolayers, with ca. 20-fold increase in the amount of insulin permeated and ca. 7-fold increase in the apparent permeability (P(app)) value. Moreover, among all the investigated particles, the CS-conjugated microparticles also showed the highest amount of insulin associated with the mucus layer and the intestinal Caco-2 cells and mucus secreting HT-29 cells. Our results demonstrate that CS-conjugated AnnUnTHCPSi microparticles can efficiently enhance the insulin absorption across intestinal cells, and thus, they are promising microsystems for the oral delivery of proteins and peptides across the intestinal cell membrane. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Thrombin-induced increase in albumin permeability across the endothelium

    Garcia, J.G.; Siflinger-Birnboim, A.; Bizios, R.; Del Vecchio, P.J.; Fenton, J.W. II; Malik, A.B.

    1986-01-01

    We studied the effect of thrombin on albumin permeability across the endothelial monolayer in vitro. Bovine pulmonary artery endothelial cells were grown on micropore membranes. Morphologic analysis confirmed the presence of a confluent monolayer with interendothelial junctions. Albumin permeability was measured by the clearance of 125I-albumin across the endothelial monolayer. The control 125I-albumin clearance was 0.273 +/- 0.02 microliter/min. The native enzyme, alpha-thrombin (10(-6) to 10(-10) M), added to the luminal side of the endothelium produced concentration-dependent increases in albumin clearance (maximum clearance of 0.586 +/- 0.08 microliter/min at 10(-6) M). Gamma (gamma) thrombin (10(-6) M and 10(-8) M), which lacks the fibrinogen recognition site, also produced a concentration-dependent increase in albumin clearance similar to that observed with alpha-thrombin. Moreover, the two proteolytically inactive forms of the native enzyme, i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin, increased the 125I-albumin clearance (0.610 +/- 0.09 microliter/min and 0.609 +/- 0.02 microliter/min for i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin at 10(-6) M, respectively). Since the modified forms of thrombin lack the fibrinogen recognition and active serine protease sites, the results indicate that neither site is required for increased albumin permeability. The increase in albumin clearance with alpha-thrombin was not secondary to endothelial cell lysis because lactate dehydrogenase concentration in the medium following thrombin was not significantly different from baseline values. There was also no morphological evidence of cell lysis. Moreover, the increase in 125I-albumin clearance induced by alpha-thrombin was reversible by washing thrombin from the endothelium

  11. Atrial natriuretic factor increases vascular permeability

    Lockette, W.; Brennaman, B.

    1990-01-01

    An increase in central blood volume in microgravity may result in increased plasma levels of atrial natriuretic factor (ANF). Since elevations in plasma ANF are found in clinical syndromes associated with edema, and since space motion sickness induced by microgravity is associated with an increase in central blood volume and facial edema, we determined whether ANF increases capillary permeability to plasma protein. Conscious, bilaterally nephrectomized male rats were infused with either saline, ANF + saline, or hexamethonium + saline over 2 h following bolus injections of 125I-albumin and 14C-dextran of similar molecular size. Blood pressure was monitored and serial determinations of hematocrits were made. Animals infused with 1.0 micrograms.kg-1.min-1 ANF had significantly higher hematocrits than animals infused with saline vehicle. Infusion of ANF increased the extravasation of 125I-albumin, but not 14C-dextran from the intravascular compartment. ANF also induced a depressor response in rats, but the change in blood pressure did not account for changes in capillary permeability to albumin; similar depressor responses induced by hexamethonium were not accompanied by increased extravasation of albumin from the intravascular compartment. ANF may decrease plasma volume by increasing permeability to albumin, and this effect of ANF may account for some of the signs and symptoms of space motion sickness

  12. LDL-Cholesterol Increases the Transcytosis of Molecules through Endothelial Monolayers.

    Magalhaes, Ana; Matias, Inês; Palmela, Inês; Brito, Maria Alexandra; Dias, Sérgio

    2016-01-01

    Cholesterol has been identified as a causative factor in numerous pathologies including atherosclerosis and cancer. One of the frequent effects of elevated cholesterol levels in humans is the compromise of endothelial function due to activation of pro-inflammatory signalling pathways. While the mechanisms involved in endothelial activation by cholesterol during an inflammatory response are well established, less is known about the mechanisms by which cholesterol may affect endothelial barrier function, which were the subject of the present study. Here we show that low density lipoprotein (LDL) increases the permeability of endothelial monolayers to high molecular weight dextrans in an LDL receptor and cholesterol-dependent manner. The increased permeability seen upon LDL treatment was not caused by disruption of cell-to-cell junctions as determined by a normal localization of VE-Cadherin and ZO-1 proteins, and no major alterations in transendothelial electrical resistance or permeability to fluorescein. We show instead that LDL increases the level of high molecular weight transcytosis and that this occurs in an LDL receptor, cholesterol and caveolae-dependent way. Our findings contribute to our understanding of the systemic pathological effects of elevated cholesterol and the transport of cargo through endothelial monolayers.

  13. Enhanced Intestinal Permeability of Bufalin by a Novel Bufalin-Peptide-Dendrimer Inclusion through Caco-2 Cell Monolayer

    Chi-on Chan

    2017-11-01

    Full Text Available Bufalin (BFL has excellent physiological activities such as defending tumors, improving cardiac function, and so on. However, due to its poor water-solubility and bioavailability, the clinical application of BFL remains limited. In order to improve bioavailability of BFL, in our previous research, a novel peptide-dendrimer (PD was synthesized and applied to encapsulate BFL. In the present study, we investigate the absorption property and mechanism of BFL in free form and BFL-peptide-dendrimer inclusion (BPDI delivery system by using the Caco-2 cell monolayer model in vitro. The apparent permeability coefficient (Papp values of BFL in free or BPDI form were over 1.0 × 10−6 cm/s. Meanwhile, their almost equal bi-directional transport and linear transport percentage with time and concentration course indicated that BFL in both forms was absorbed mainly through passive diffusion. The most important result is that the Papp values of BFL increased about three-fold more BPDI than those of its free form, which indicated the intestinal permeability of BFL could be improved while BFL was encapsulated in BPDI form. Therefore, PD encapsulation may be a potential delivery system to increase the bioavailability of BFL.

  14. Evaluation of the intestinal permeability of rosemary (Rosmarinus officinalis L. extract polyphenols and terpenoids in Caco-2 cell monolayers.

    Almudena Pérez-Sánchez

    Full Text Available Rosemary (Rosmarinus officinalis is grown throughout the world and is widely used as a medicinal herb and to season and preserve food. Rosemary polyphenols and terpenoids have attracted great interest due to their potential health benefits. However, complete information regarding their absorption and bioavailability in Caco-2 cell model is scarce. The permeation properties of the bioactive compounds (flavonoids, diterpenes, triterpenes and phenylpropanoids of a rosemary extract (RE, obtained by supercritical fluid extraction, was studied in Caco-2 cell monolayer model, both in a free form or liposomed. Compounds were identified and quantitated by liquid chromatography coupled to quadrupole time-of-flight with electrospray ionization mass spectrometry analysis (HPLC-ESI-QTOF-MS, and the apparent permeability values (Papp were determined, for the first time in the extract, for 24 compounds in both directions across cell monolayer. For some compounds, such as triterpenoids and some flavonoids, Papp values found were reported for the first time in Caco-2 cells.Our results indicate that most compounds are scarcely absorbed, and passive diffusion is suggested to be the primary mechanism of absorption. The use of liposomes to vehiculize the extract resulted in reduced permeability for most compounds. Finally, the biopharmaceutical classification (BCS of all the compounds was achieved according to their permeability and solubility data for bioequivalence purposes. BCS study reveal that most of the RE compounds could be classified as classes III and IV (low permeability; therefore, RE itself should also be classified into this category.

  15. Evaluation of the intestinal permeability of rosemary (Rosmarinus officinalis L.) extract polyphenols and terpenoids in Caco-2 cell monolayers

    Arráez-Román, David; González-Álvarez, Isabel; Ibáñez, Elena; Segura-Carretero, Antonio; Bermejo, Marival; Micol, Vicente

    2017-01-01

    Rosemary (Rosmarinus officinalis) is grown throughout the world and is widely used as a medicinal herb and to season and preserve food. Rosemary polyphenols and terpenoids have attracted great interest due to their potential health benefits. However, complete information regarding their absorption and bioavailability in Caco-2 cell model is scarce. The permeation properties of the bioactive compounds (flavonoids, diterpenes, triterpenes and phenylpropanoids) of a rosemary extract (RE), obtained by supercritical fluid extraction, was studied in Caco-2 cell monolayer model, both in a free form or liposomed. Compounds were identified and quantitated by liquid chromatography coupled to quadrupole time-of-flight with electrospray ionization mass spectrometry analysis (HPLC-ESI-QTOF-MS), and the apparent permeability values (Papp) were determined, for the first time in the extract, for 24 compounds in both directions across cell monolayer. For some compounds, such as triterpenoids and some flavonoids, Papp values found were reported for the first time in Caco-2 cells.Our results indicate that most compounds are scarcely absorbed, and passive diffusion is suggested to be the primary mechanism of absorption. The use of liposomes to vehiculize the extract resulted in reduced permeability for most compounds. Finally, the biopharmaceutical classification (BCS) of all the compounds was achieved according to their permeability and solubility data for bioequivalence purposes. BCS study reveal that most of the RE compounds could be classified as classes III and IV (low permeability); therefore, RE itself should also be classified into this category. PMID:28234919

  16. Permeability, transport, and metabolism of solutes in Caco-2 cell monolayers: a theoretical study.

    Sun, Huadong; Pang, K Sandy

    2008-01-01

    We explored the properties of a catenary model that includes the basolateral (B), apical (A), and cellular compartments via simulations under linear and nonlinear conditions to understand the asymmetric observations arising from transporters, enzymes, and permeability in Caco-2 cells. The efflux ratio (EfR; P(app,B-->A)/P(app,A-->B)), obtained from the effective permeability from the A-->B and B-->A direction under linear conditions, was unity for passively permeable drugs whose transport does not involve transporters; the value was unaffected by cellular binding or metabolism, but increased with apical efflux. Metabolism was asymmetric, showing lesser metabolite accrual for the B-->A than A-->B direction because of inherent differences in the volumes for A and B. Moreover, the net flux (total - passive permeation) due to saturable apical efflux, absorption, or metabolism showed nonconformity to simple Michaelis-Menten kinetics against C(D,0), the loading donor concentration. EfR values differed with saturable apical efflux and metabolism (>1), as well as apical absorption (EfRs transport and metabolic data in Caco-2 cells.

  17. Tumor necrosis factor alpha increases epithelial barrier permeability by disrupting tight junctions in Caco-2 cells

    W. Cui

    2010-04-01

    Full Text Available The objectives of this study were to determine the effect of tumor necrosis factor alpha (TNF-α on intestinal epithelial cell permeability and the expression of tight junction proteins. Caco-2 cells were plated onto Transwell® microporous filters and treated with TNF-α (10 or 100 ng/mL for 0, 4, 8, 16, or 24 h. The transepithelial electrical resistance and the mucosal-to-serosal flux rates of the established paracellular marker Lucifer yellow were measured in filter-grown monolayers of Caco-2 intestinal cells. The localization and expression of the tight junction protein occludin were detected by immunofluorescence and Western blot analysis, respectively. SYBR-Green-based real-time PCR was used to measure the expression of occludin mRNA. TNF-α treatment produced concentration- and time-dependent decreases in Caco-2 transepithelial resistance and increases in transepithelial permeability to the paracellular marker Lucifer yellow. Western blot results indicated that TNF-α decreased the expression of phosphorylated occludin in detergent-insoluble fractions but did not affect the expression of non-phosphorylated occludin protein. Real-time RT-PCR data showed that TNF-α did not affect the expression of occludin mRNA. Taken together, our data demonstrate that TNF-α increases Caco-2 monolayer permeability, decreases occludin protein expression and disturbs intercellular junctions.

  18. Silver nanoparticles interact with the cell membrane and increase endothelial permeability by promoting VE-cadherin internalization

    Sun, Xia; Shi, Junpeng; Zou, Xiaoyan; Wang, Chengcheng; Yang, Yi; Zhang, Hongwu, E-mail: hwzhang@iue.ac.cn

    2016-11-05

    Highlights: • Short-term exposure to AgNPs at low doses induces increase HUVECs monolayer permeability. • AgNPs interact with the cell membrane and increase endothelial permeability by promoting VE-Cadherin internalization. • Particle effect is a major factor leading to endothelial dysfunction. - Abstract: The toxicological risks of silver nanoparticles (AgNPs) have attracted widespread attention, and many studies have been published that have contributed to understanding AgNPs-induced toxicity. However, little attention has been paid to the low-dose effects of AgNPs and the related toxicological mechanism is still unclear. Here, we show that short-term exposure to AgNPs at low doses induces a substantial increase in human umbilical vein endothelial cells (HUVECs) monolayer permeability, whereas Ag ions at low doses do not induce an observable increase in monolayer permeability. This effect is independent of oxidative stress and apoptosis. Scanning electron microscopy confirms that AgNPs adhere to the cell membrane after 1 h exposure. Furthermore, adhesion of AgNPs to the cell membrane can trigger vascular endothelial (VE)-cadherin phosphorylation at Y658 followed by VE-cadherin internalization, which lead to the increase in endothelial monolayer permeability. Our data show that surface interactions of AgNPs with the cell membrane, in other words, the particle effect, is a major factor leading to endothelial dysfunction following low-dose and short-term exposure. Our findings will contribute to understanding the health effects and the toxicological mechanisms of AgNPs.

  19. Bovine Colostrum Supplementation During Running Training Increases Intestinal Permeability

    Grant D. Brinkworth

    2009-12-01

    Full Text Available 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 < 0.05 and CON (−7 ± 13%, P < 0.02. The increase in intestinal permeability with BC may have been due to BC inducing greater leakiness of tight junctions between enterocytes or by increasing macromolecular transport as it does in neonatal gut. Further research should investigate the potential for BC to increase intestinal macromolecular transport in adults.

  20. Particulate matter air pollution causes oxidant-mediated increase in gut permeability in mice

    Keshavarzian Ali

    2011-06-01

    Full Text Available Abstract Background Exposure to particulate matter (PM air pollution may be an important environmental factor leading to exacerbations of inflammatory illnesses in the GI tract. PM can gain access to the gastrointestinal (GI tract via swallowing of air or secretions from the upper airways or mucociliary clearance of inhaled particles. Methods We measured PM-induced cell death and mitochondrial ROS generation in Caco-2 cells stably expressing oxidant sensitive GFP localized to mitochondria in the absence or presence of an antioxidant. C57BL/6 mice were exposed to a very high dose of urban PM from Washington, DC (200 μg/mouse or saline via gastric gavage and small bowel and colonic tissue were harvested for histologic evaluation, and RNA isolation up to 48 hours. Permeability to 4kD dextran was measured at 48 hours. Results PM induced mitochondrial ROS generation and cell death in Caco-2 cells. PM also caused oxidant-dependent NF-κB activation, disruption of tight junctions and increased permeability of Caco-2 monolayers. Mice exposed to PM had increased intestinal permeability compared with PBS treated mice. In the small bowel, colocalization of the tight junction protein, ZO-1 was lower in the PM treated animals. In the small bowel and colon, PM exposed mice had higher levels of IL-6 mRNA and reduced levels of ZO-1 mRNA. Increased apoptosis was observed in the colon of PM exposed mice. Conclusions Exposure to high doses of urban PM causes oxidant dependent GI epithelial cell death, disruption of tight junction proteins, inflammation and increased permeability in the gut in vitro and in vivo. These PM-induced changes may contribute to exacerbations of inflammatory disorders of the gut.

  1. Endothelial glycocalyx dysfunction in disease: albuminuria and increased microvascular permeability.

    Salmon, Andrew H J; Satchell, Simon C

    2012-03-01

    Appreciation of the glomerular microcirculation as a specialized microcirculatory bed, rather than as an entirely separate entity, affords important insights into both glomerular and systemic microvascular pathophysiology. In this review we compare regulation of permeability in systemic and glomerular microcirculations, focusing particularly on the role of the endothelial glycocalyx, and consider the implications for disease processes. The luminal surface of vascular endothelium throughout the body is covered with endothelial glycocalyx, comprising surface-anchored proteoglycans, supplemented with adsorbed soluble proteoglycans, glycosaminoglycans and plasma constituents. In both continuous and fenestrated microvessels, this endothelial glycocalyx provides resistance to the transcapillary escape of water and macromolecules, acting as an integral component of the multilayered barrier provided by the walls of these microvessels (ie acting in concert with clefts or fenestrae across endothelial cell layers, basement membranes and pericytes). Dysfunction of any of these capillary wall components, including the endothelial glycocalyx, can disrupt normal microvascular permeability. Because of its ubiquitous nature, damage to the endothelial glycocalyx alters the permeability of multiple capillary beds: in the glomerulus this is clinically apparent as albuminuria. Generalized damage to the endothelial glycocalyx can therefore manifest as both albuminuria and increased systemic microvascular permeability. This triad of altered endothelial glycocalyx, albuminuria and increased systemic microvascular permeability occurs in a number of important diseases, such as diabetes, with accumulating evidence for a similar phenomenon in ischaemia-reperfusion injury and infectious disease. The detection of albuminuria therefore has implications for the function of the microcirculation as a whole. The importance of the endothelial glycocalyx for other aspects of vascular function

  2. Acute cigarette smoke exposure increases alveolar permeability in rabbits

    Witten, M.L.; Lemen, R.J.; Quan, S.F.; Sobonya, R.E.; Roseberry, H.; Stevenson, J.L.; Clayton, J.

    1985-01-01

    The authors measured lung clearance of aerosolized technetium-labeled diethylenetriamine pentaacetic acid (/sup 99m/TcDTPA) as an index of alveolar epithelial permeability in rabbits exposed to cigarette smoke. Eighteen rabbits were randomly assigned to 3 equal-size groups: control, all smoke exposure (ASE), and limited smoke exposure (LSE). Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 20-min counting period between each subset of breaths to determine /sup 99m/TcDTPA biologic half-life (T 1 / 2 ). Mean T 1 / 2 minimum was significantly lower for ASE and LSE rabbits than by control rabbits. They observed a significant difference at 20 and 30 breath exposures between the control and ASE group mean values for T 1 / 2 , arterial blood pressure, and peak airway pressure. A combination of light and electron microscopy showed focal alveolar edema and hemorrhage in the ASE and LSE groups but no alveolar-capillary membrane damage. In summary, acute cigarette smoke exposure increases alveolar permeability as measured by /sup 99m/TcDTPA clearance, but there was no detectable ultrastructural alteration of the alveolar-capillary membrane

  3. Ozone exposure increases respiratory epithelial permeability in humans

    Kehrl, H.R.; Vincent, L.M.; Kowalsky, R.J.; Horstman, D.H.; O'Neil, J.J.; McCartney, W.H.; Bromberg, P.A.

    1987-01-01

    Ozone is a respiratory irritant that has been shown to cause an increase in the permeability of the respiratory epithelium in animals. We used inhaled aerosolized /sup 99m/Tc-labeled diethylene triamine pentacetic acid (/sup 99m/Tc-DTPA) to investigate whether human respiratory epithelial permeability is similarly affected by exposure to ozone. In a randomized, crossover double-blinded study, 8 healthy, nonsmoking young men were exposed for 2 h to purified air and 0.4 ppm ozone while performing intermittent high intensity treadmill exercise (minute ventilation = 66.8 L/min). SRaw and FVC were measured before and at the end of exposures. Seventy-five minutes after the exposures, the pulmonary clearance of /sup 99m/Tc-DTPA was measured by sequential posterior lung imaging with a computer-assisted gamma camera. Ozone exposure caused respiratory symptoms in all 8 subjects and was associated with a 14 +/- 2.8% (mean +/- SEM) decrement in FVC (p less than 0.001) and a 71 +/- 22% increase in SRaw (p = 0.04). Compared with the air exposure day, 7 of the 8 subjects showed increased /sup 99m/Tc-DTPA clearance after the ozone exposure, with the mean value increasing from 0.59 +/- 0.08 to 1.75 +/- 0.43%/min (p = 0.03). These data show that ozone exposure sufficient to produce decrements in the pulmonary function of human subjects also causes an increase in /sup 99m/Tc-DTPA clearance

  4. Blood-brain barrier permeability and neuroprotective effects of three main alkaloids from the fruits of Euodia rutaecarpa with MDCK-pHaMDR cell monolayer and PC12 cell line.

    Zhang, Yi-Nan; Yang, Yan-Fang; Yang, Xiu-Wei

    2018-02-01

    The fruits of Euodia rutaecarpa (Euodiae Fructus, EF), the widely used traditional Chinese medicine, have various central nervous system effects. Alkaloids following as evodiamine (EDM), rutaecarpine (RCP) and dehydroevodiamine (DEDM) are the major substances in EF. The MDCK-pHaMDR cell monolayer model was utilized as a blood-brain barrier (BBB) surrogate model to study their BBB permeability. The transport samples were analyzed by high performance liquid chromatography and the apparent permeability coefficients (P app ) were calculated. EDM and RCP showed high permeability through BBB by passive diffusion, while DEDM showed moderate permeability with efflux mechanism related to P-glycoprotein (P-gp). EDM and RCP could also reduce the efflux of DEDM probably by inhibiting P-gp. The neuroprotective effects of the three alkaloids were then studied on the PC12 cell line injured by 1-methyl-4-phenylpyridinium ion (MPP + ) or hydrogen peroxide (H 2 O 2 ). EDM could significantly reduce MPP + or H 2 O 2 -induced cell injury dose-dependently. RCP could increase the cell viability in MPP + treated group while DEDM showed a protective effect against H 2 O 2 injury. This study predicted the permeability of EDM, RCP and DEDM through BBB and discovered the neuroprotective substance basis of EF as a potential encephalopathy drug. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  5. Increasing the permeability of Escherichia coli using MAC13243

    Muheim, Claudio; Götzke, Hansjörg; Eriksson, Anna U.

    2017-01-01

    molecules that make the outer membrane of Escherichia coli more permeable. We identified MAC13243, an inhibitor of the periplasmic chaperone LolA that traffics lipoproteins from the inner to the outer membrane. We observed that cells were (1) more permeable to the fluorescent probe 1-N...

  6. The Blood-Brain Barrier Permeability of Six Indole Alkaloids from Uncariae Ramulus Cum Uncis in the MDCK-pHaMDR Cell Monolayer Model

    Yi-Nan Zhang

    2017-11-01

    Full Text Available Uncariae Ramulus Cum Uncis (URCU is a widely used traditional Chinese medicine, and is reported to have various central nervous system effects. Alkaloids have been demonstrated to be the predominant pharmacological active components of URCU. In order to evaluate the blood-brain barrier (BBB permeability and transport mechanism of six typical indole alkaloids from URCU, the MDCK-pHaMDR cell monolayer model was used as an in vitro surrogate model for BBB. The samples were analyzed by high-performance liquid chromatography, and the apparent permeability coefficients (Papp were calculated. Among the six alkaloids, isorhynchophylline (2, isocorynoxeine (4, hirsutine (5 and hirsuteine (6 showed high permeability, with Papp values at 10−5 cm/s level in bidirectional transport. For rhynchophylline (1 and corynoxeine (3, they showed moderate permeability, with Papp values from the apical (AP side to the basolateral (BL side at 10−6 cm/s level and efflux ratio (Papp BL→AP/Papp AP→BL above 2. The time- and concentration-dependency experiments indicated that the main mechanism for 2, 4, 5 and 6 through BBB was passive diffusion. The efflux mechanism involved in the transports of compounds 1 and 3 could be reduced significantly by verapamil, and molecular docking screening also showed that 1 and 3 had strong bindings to P-glycoprotein. This study provides useful information for predicting the BBB permeability for 1–6, as well as better understanding of their central nervous system pharmacological activities.

  7. Pathophysiology of increased intestinal permeability in obstructive jaundice

    Assimakopoulos, Stelios F; Scopa, Chrisoula D; Vagianos, Constantine E

    2007-01-01

    Despite advances in preoperative evaluation and postoperative care, intervention, especially surgery, for relief of obstructive jaundice still carries high morbidity and mortality rates, mainly due to sepsis and renal dysfunction. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. This breakage of the gut barrier in obstructive jaundice is multi-factorial, involving disruption of the immunologic, biological and mechanical barrier. Experimental and clinical studies have shown that obstructive jaundice results in increased intestinal permeability. The mechanisms implicated in this phenomenon remain unresolved, but growing research interest during the last decade has shed light in our knowledge in the field. This review summarizes the current concepts in the pathophysiology of obstructive jaundice-induced gut barrier dysfunction, analyzing pivotal factors, such as altered intestinal tight junctions expression, oxidative stress and imbalance of enterocyte proliferation and apoptosis. Clinicians handling patients with obstructive jaundice should not neglect protecting the intestinal barrier function before, during and after intervention for the relief of this condition, which may improve their patients’ outcome. PMID:18161914

  8. Bactericidal Permeability-Increasing Proteins Shape Host-Microbe Interactions

    Fangmin Chen

    2017-04-01

    Full Text Available We characterized bactericidal permeability-increasing proteins (BPIs of the squid Euprymna scolopes, EsBPI2 and EsBPI4. They have molecular characteristics typical of other animal BPIs, are closely related to one another, and nest phylogenetically among invertebrate BPIs. Purified EsBPIs had antimicrobial activity against the squid’s symbiont, Vibrio fischeri, which colonizes light organ crypt epithelia. Activity of both proteins was abrogated by heat treatment and coincubation with specific antibodies. Pretreatment under acidic conditions similar to those during symbiosis initiation rendered V. fischeri more resistant to the antimicrobial activity of the proteins. Immunocytochemistry localized EsBPIs to the symbiotic organ and other epithelial surfaces interacting with ambient seawater. The proteins differed in intracellular distribution. Further, whereas EsBPI4 was restricted to epithelia, EsBPI2 also occurred in blood and in a transient juvenile organ that mediates hatching. The data provide evidence that these BPIs play different defensive roles early in the life of E. scolopes, modulating interactions with the symbiont.

  9. Increased gut permeability in cancer cachexia: mechanisms and clinical relevance.

    Bindels, Laure B; Neyrinck, Audrey M; Loumaye, Audrey; Catry, Emilie; Walgrave, Hannah; Cherbuy, Claire; Leclercq, Sophie; Van Hul, Matthias; Plovier, Hubert; Pachikian, Barbara; Bermúdez-Humarán, Luis G; Langella, Philippe; Cani, Patrice D; Thissen, Jean-Paul; Delzenne, Nathalie M

    2018-04-06

    Intestinal disorders often occur in cancer patients, in association with body weight loss, and this alteration is commonly attributed to the chemotherapy. Here, using a mouse model of cancer cachexia induced by ectopic transplantation of C26 cancer cells, we discovered a profound alteration in the gut functions (gut permeability, epithelial turnover, gut immunity, microbial dysbiosis) independently of any chemotherapy. These alterations occurred independently of anorexia and were driven by interleukin 6. Gut dysfunction was found to be resistant to treatments with an anti-inflammatory bacterium ( Faecalibacterium prausnitzii ) or with gut peptides involved in intestinal cell renewal (teduglutide, a glucagon-like peptide 2 analogue). The translational value of our findings was evaluated in 152 colorectal and lung cancer patients with or without cachexia. The serum level of the lipopolysaccharide-binding protein, often presented as a reflection of the bacterial antigen load, was not only increased in cachectic mice and cancer patients, but also strongly correlated with the serum IL-6 level and predictive of death and cachexia occurrence in these patients. Altogether, our data highlight profound alterations of the intestinal homeostasis in cancer cachexia occurring independently of any chemotherapy and food intake reduction, with potential relevance in humans. In addition, we point out the lipopolysaccharide-binding protein as a new biomarker of cancer cachexia related to gut dysbiosis.

  10. Endothelial cell permeability during hantavirus infection involves factor XII-dependent increased activation of the kallikrein-kinin system.

    Shannon L Taylor

    Full Text Available Hemorrhagic fever with renal syndrome (HFRS and hantavirus pulmonary syndrome (HPS are diseases caused by hantavirus infections and are characterized by vascular leakage due to alterations of the endothelial barrier. Hantavirus-infected endothelial cells (EC display no overt cytopathology; consequently, pathogenesis models have focused either on the influx of immune cells and release of cytokines or on increased degradation of the adherens junction protein, vascular endothelial (VE-cadherin, due to hantavirus-mediated hypersensitization of EC to vascular endothelial growth factor (VEGF. To examine endothelial leakage in a relevant in vitro system, we co-cultured endothelial and vascular smooth muscle cells (vSMC to generate capillary blood vessel-like structures. In contrast to results obtained in monolayers of cultured EC, we found that despite viral replication in both cell types as well as the presence of VEGF, infected in vitro vessels neither lost integrity nor displayed evidence of VE-cadherin degradation. Here, we present evidence for a novel mechanism of hantavirus-induced vascular leakage involving activation of the plasma kallikrein-kinin system (KKS. We show that incubation of factor XII (FXII, prekallikrein (PK, and high molecular weight kininogen (HK plasma proteins with hantavirus-infected EC results in increased cleavage of HK, higher enzymatic activities of FXIIa/kallikrein (KAL and increased liberation of bradykinin (BK. Measuring cell permeability in real-time using electric cell-substrate impedance sensing (ECIS, we identified dramatic increases in endothelial cell permeability after KKS activation and liberation of BK. Furthermore, the alterations in permeability could be prevented using inhibitors that directly block BK binding, the activity of FXIIa, or the activity of KAL. Lastly, FXII binding and autoactivation is increased on the surface of hantavirus-infected EC. These data are the first to demonstrate KKS activation

  11. Vascular permeability-increasing effect of the leaf essential oil of ...

    African Journal of Traditional, Complementary and Alternative Medicines ... Analysis of the differences in vascular permeability between treatment groups showed that, Ocimum oil, in intensity and duration, was significantly (p < 0.05) more effective in increasing cutaneous capillary permeability over a 24h period after ...

  12. Dietary fat and bile juice, but not obesity, are responsible for the increase in small intestinal permeability induced through the suppression of tight junction protein expression in LETO and OLETF rats

    Suzuki Takuya

    2010-03-01

    Full Text Available Abstract Background An increase in the intestinal permeability is considered to be associated with the inflammatory tone and development in the obesity and diabetes, however, the pathogenesis of the increase in the intestinal permeability is poorly understood. The present study was performed to determine the influence of obesity itself as well as dietary fat on the increase in intestinal permeability. Methods An obese rat strain, Otsuka Long Evans Tokushima Fatty (OLETF, and the lean counter strain, Long Evans Tokushima Otsuka (LETO, were fed standard or high fat diets for 16 weeks. Glucose tolerance, intestinal permeability, intestinal tight junction (TJ proteins expression, plasma bile acids concentration were evaluated. In addition, the effects of rat bile juice and dietary fat, possible mediators of the increase in the intestinal permeability in the obesity, on TJ permeability were explored in human intestinal Caco-2 cells. Results The OLETF rats showed higher glucose intolerance than did the LETO rats, which became more marked with the prolonged feeding of the high fat diet. Intestinal permeability in the OLETF rats evaluated by the urinary excretion of intestinal permeability markers (Cr-EDTA and phenolsulfonphthalein was comparable to that in the LETO rats. Feeding the high fat diet increased intestinal permeability in both the OLETF and LETO rats, and the increases correlated with decreases in TJ proteins (claudin-1, claudin-3, occludin and junctional adhesion molecule-1 expression in the small, but not in the large intestine (cecum or colon. The plasma bile acids concentration was higher in rats fed the high fat diet. Exposure to bile juice and the fat emulsion increased TJ permeability with concomitant reductions in TJ protein expression (claudin-1, claudin-3, and junctional adhesion molecule-1 in the Caco-2 cell monolayers. Conclusion Excessive dietary fat and/or increased levels of luminal bile juice, but not genetic obesity, are

  13. The permeability characteristics and interaction of main components from Si-Ni-San in a MDCK epithelial cell monolayer model.

    Chen, Ruonan; Shen, Chenlin; Xu, Qingqing; Liu, Yaru; Li, Bo; Huang, Cheng; Ma, Taotao; Meng, Xiaoming; Wu, Maomao; Li, Jun

    2017-07-26

    1. Si-Ni-San (SNS) possesses extensive therapeutic effects, however, the extent to which main components are absorbed and the mechanisms involved are controversial. 2. In this study, MDCK cell model was used to determine the permeability characteristics and interaction between the major components of Si-Ni-San, including saikosaponin a, paeoniflorin, naringin and glycyrrhizic acid. 3. The transport of the major components was concentration-dependent in both directions. Moreover, the transport of paeoniflorin, naringin and glycyrrhizic acid was significantly reduced at 4°C or in the presence of NaN3. Additionally, the efflux of paeoniflorin and naringin were apparently reduced in the presence of P-gp inhibitor verapamil. The transport of glycyrrhizic acid was clearly inhibited by the inhibitors of MRP2, indicating that MRP2 may be involved in the transport of glycyrrhizic acid. However, the results indicated that saikosaponin a was absorbed mainly by passive diffusion. Furthermore, the combined incubation of four major components had a powerful sorbefacient effect than a single drug used alone which may be regulated by tight junctions. 4. Taken together, our study provides useful information for pharmacological applications of Si-Ni-San and offers new insights into this ancient decoction for further researches, especially in drug synergism.

  14. Synchronization modulation increases transepithelial potentials in MDCK monolayers through Na/K pumps.

    Vu Tran

    Full Text Available Transepithelial potential (TEP is the voltage across a polarized epithelium. In epithelia that have active transport functions, the force for transmembrane flux of an ion is dictated by the electrochemical gradient in which TEP plays an essential role. In epithelial injury, disruption of the epithelial barrier collapses the TEP at the wound edge, resulting in the establishment of an endogenous wound electric field (∼100 mV/mm that is directed towards the center of the wound. This endogenous electric field is implicated to enhance wound healing by guiding cell migration. We thus seek techniques to enhance the TEP, which may increase the wound electric fields and enhance wound healing. We report a novel technique, termed synchronization modulation (SM using a train of electric pulses to synchronize the Na/K pump activity, and then modulating the pumping cycles to increase the efficiency of the Na/K pumps. Kidney epithelial monolayers (MDCK cells maintain a stable TEP and transepithelial resistance (TER. SM significantly increased TEP over four fold. Either ouabain or digoxin, which block Na/K pump, abolished SM-induced TEP increases. In addition to the pump activity, basolateral distribution of Na/K pumps is essential for an increase in TEP. Our study for the first time developed an electrical approach to significantly increase the TEP. This technique targeting the Na/K pump may be used to modulate TEP, and may have implication in wound healing and in diseases where TEP needs to be modulated.

  15. Phosphatidylcholine Reverses Ethanol-Induced Increase in Transepithelial Endotoxin Permeability and Abolishes Transepithelial Leukocyte Activation

    Mitzscherling, Katja; Volynets, Valentina; Parlesak, Alexandr

    2009-01-01

    Chronic alcohol abuse increases both intestinal bacterial overgrowth and intestinal permeability to macromolecules. Intestinal permeability of endotoxin, a component of the outer cell membrane of Gram-negative bacteria, plays a crucial role in the development of alcohol-induced liver disease (ALD......). As impaired bile flow leads to endotoxemia and the bile component phosphatidylcholine (PC) is therapeutically active in ALD, we tested the hypothesis that conjugated primary bile salts (CPBS) and PC inhibit ethanol-enhanced transepithelial permeability of endotoxin and the subsequent transepithelial...... activation of human leukocytes. For this purpose, we used a model in which intestinal epithelial cells (Caco-2) were basolaterally cocultivated with mononuclear leukocytes. Cells were challenged apically with endotoxin from Escherichia coli K12 and were incubated with or without the addition of CPBS (1.5 m...

  16. Phosphatidylcholine reverses ethanol-induced increase in transepithelial endotoxin permeability and abolishes transepithelial leukocyte activation

    Mitscherling, K.; Volynets, V.; Parlesak, Alexandr

    2009-01-01

    BACKGROUND: Chronic alcohol abuse increases both intestinal bacterial overgrowth and intestinal permeability to macromolecules. Intestinal permeability of endotoxin, a component of the outer cell membrane of Gram-negative bacteria, plays a crucial role in the development of alcohol-induced liver...... disease (ALD). As impaired bile flow leads to endotoxemia and the bile component phosphatidylcholine (PC) is therapeutically active in ALD, we tested the hypothesis that conjugated primary bile salts (CPBS) and PC inhibit ethanol-enhanced transepithelial permeability of endotoxin and the subsequent...... transepithelial activation of human leukocytes. METHODS: For this purpose, we used a model in which intestinal epithelial cells (Caco-2) were basolaterally cocultivated with mononuclear leukocytes. Cells were challenged apically with endotoxin from Escherichia coli K12 and were incubated with or without...

  17. Subchronic mild noise stress increases HRP permeability in rat small intestine in vitro

    Bijlsma, P. B.; van Raaij, M. T.; Dobbe, C. J.; Timmerman, A.; Kiliaan, A. J.; Taminiau, J. A.; Groot, J. A.

    2001-01-01

    Recently we reported an increased trans- and paracellular protein permeability in rat small intestine after acute cold restraint stress. In the present study, we applied randomized 95- or 105-dB white noise pulses during 45 min/h, 12 h/day, duration 8 days, as a milder, but more chronic stressor to

  18. Suppressions of Serotonin-Induced Increased Vascular Permeability and Leukocyte Infiltration by Bixa orellana Leaf Extract

    Yoke Keong Yong

    2013-01-01

    Full Text Available The aim of the present study was to evaluate the anti-inflammatory activities of aqueous extract of Bixa orellana (AEBO leaves and its possible mechanisms in animal models. The anti-inflammatory activity of the extract was evaluated using serotonin-induced rat paw edema, increased peritoneal vascular permeability, and leukocyte infiltrations in an air-pouch model. Nitric oxide (NO, indicated by the sum of nitrites and nitrates, and vascular growth endothelial growth factor (VEGF were measured in paw tissues of rats to determine their involvement in the regulation of increased permeability. Pretreatments with AEBO (50 and 150 mg kg−1 prior to serotonin inductions resulted in maximum inhibitions of 56.2% of paw volume, 45.7% of Evans blue dye leakage in the peritoneal vascular permeability model, and 83.9% of leukocyte infiltration in the air-pouch model. 57.2% maximum inhibition of NO and 27% of VEGF formations in rats’ paws were observed with AEBO at the dose of 150 mg kg−1. Pharmacological screening of the extract showed significant (P<0.05 anti-inflammatory activity, indicated by the suppressions of increased vascular permeability and leukocyte infiltration. The inhibitions of these inflammatory events are probably mediated via inhibition of NO and VEGF formation and release.

  19. Simple clinical means of documenting increased pulmonary endothelial permeability to protein

    Mishkin, F.S.; Niden, A.; Kumar, A.; Thomas, A.; Reese, I.C.; Vasinrapee, P.

    1987-01-01

    The authors investigated a simple method that can be used at the bedside for documenting the net accumulation of albumin in the lung. The technique employs measurement with a computer-linked gamma camera of the activity ratio in an area of the right lung compared with the same-sized area in the heart at 20 minutes and three hours following intravenous injection of technetium Tc 99m albumin. They applied this measurement to three groups of patients: a control group and patients with roentgenographic evidence of edema classified according to clinically available criteria as either hydrostatic edema or permeability edema to see if they could document differences among these groups. In control patients this ratio did not increase by more than seven units between the 20-minute and three-hour measurements. Of 18 patients classified by other routine clinical means as having hydrostatic pulmonary edema, 89% showed no increase in lung albumin accumulation. In 29 patients with permeability edema associated with the so-called adult respiratory distress syndrome, 31% showed evidence of net pulmonary albumin accumulation. These findings suggest that some patients otherwise classified as having hydrostatic edema have concomitant permeability changes in the microvasculature and that permeability edema represents a spectrum of endothelial damage

  20. Simple clinical means of documenting increased pulmonary endothelial permeability to protein

    Mishkin, F.S.; Niden, A.; Kumar, A.; Thomas, A.; Reese, I.C.; Vasinrapee, P.

    1987-02-20

    The authors investigated a simple method that can be used at the bedside for documenting the net accumulation of albumin in the lung. The technique employs measurement with a computer-linked gamma camera of the activity ratio in an area of the right lung compared with the same-sized area in the heart at 20 minutes and three hours following intravenous injection of technetium Tc 99m albumin. They applied this measurement to three groups of patients: a control group and patients with roentgenographic evidence of edema classified according to clinically available criteria as either hydrostatic edema or permeability edema to see if they could document differences among these groups. In control patients this ratio did not increase by more than seven units between the 20-minute and three-hour measurements. Of 18 patients classified by other routine clinical means as having hydrostatic pulmonary edema, 89% showed no increase in lung albumin accumulation. In 29 patients with permeability edema associated with the so-called adult respiratory distress syndrome, 31% showed evidence of net pulmonary albumin accumulation. These findings suggest that some patients otherwise classified as having hydrostatic edema have concomitant permeability changes in the microvasculature and that permeability edema represents a spectrum of endothelial damage.

  1. Thromboxane A2 increases endothelial permeability through upregulation of interleukin-8

    Kim, Su-Ryun; Bae, Soo-Kyung; Park, Hyun-Joo; Kim, Mi-Kyoung; Kim, Koanhoi; Park, Shi-Young; Jang, Hye-Ock; Yun, Il; Kim, Yung-Jin; Yoo, Mi-Ae; Bae, Moon-Kyoung

    2010-01-01

    Thromboxane A 2 (TXA 2 ), a major prostanoid formed from prostaglandin H 2 by thromboxane synthase, is involved in the pathogenesis of a variety of vascular diseases. In this study, we report that TXA 2 mimetic U46619 significantly increases the endothelial permeability both in vitro and in vivo. U46619 enhanced the expression and secretion of interleukin-8 (IL-8), a major inducer of vascular permeability, in endothelial cells. Promoter analysis showed that the U46619-induced expression of IL-8 was mainly regulated by nuclear factor-κB (NF-κB). U46619 induced the activation of NF-κB through IκB kinase (IKK) activation, IκB phosphorylation and NF-κB nuclear translocation. Furthermore, the inhibition of IL-8 or blockade of the IL-8 receptor attenuated the U46619-induced endothelial cell permeability by modulating the cell-cell junctions. Overall, these results suggest that U46619 promotes vascular permeability through the production of IL-8 via NF-κB activation in endothelial cells.

  2. Stress induces endotoxemia and low-grade inflammation by increasing barrier permeability

    Karin ede Punder

    2015-05-01

    Full Text Available Chronic non-communicable diseases (NCDs are the leading causes of work absence, disability and mortality worldwide. Most of these diseases are associated with low-grade inflammation. Here we hypothesize that stresses (defined as homeostatic disturbances can induce low-grade inflammation by increasing the availability of water, sodium and energy-rich substances to meet the increased metabolic demand induced by the stressor. One way of triggering low-grade inflammation is by increasing intestinal barrier permeability through activation of various components of the stress system. Although beneficial to meet the demands necessary during stress, increased intestinal barrier permeability also raises the possibility of the translocation of bacteria and their toxins across the intestinal lumen into the blood circulation. In combination with modern life-style factors, the increase in bacteria/bacterial toxin translocation arising from a more permeable intestinal wall causes a low-grade inflammatory state. We support this hypothesis with numerous studies finding associations with NCDs and markers of endotoxemia, suggesting that this process plays a pivotal and perhaps even a causal role in the development of low-grade inflammation and its related diseases.

  3. Gadolinium prevents high airway pressure-induced permeability increases in isolated rat lungs.

    Parker, J C; Ivey, C L; Tucker, J A

    1998-04-01

    To determine the initial signaling event in the vascular permeability increase after high airway pressure injury, we compared groups of lungs ventilated at different peak inflation pressures (PIPs) with (gadolinium group) and without (control group) infusion of 20 microM gadolinium chloride, an inhibitor of endothelial stretch-activated cation channels. Microvascular permeability was assessed by using the capillary filtration coefficient (Kfc), a measure of capillary hydraulic conductivity. Kfc was measured after ventilation for 30-min periods with 7, 20, and 30 cmH2O PIP with 3 cmH2O positive end-expiratory pressure and with 35 cmH2O PIP with 8 cmH2O positive end-expiratory pressure. In control lungs, Kfc increased significantly to 1.8 and 3.7 times baseline after 30 and 35 cmH2O PIP, respectively. In the gadolinium group, Kfc was unchanged from baseline (0.060 +/- 0.010 ml . min-1 . cmH2O-1 . 100 g-1) after any PIP ventilation period. Pulmonary vascular resistance increased significantly from baseline in both groups before the last Kfc measurement but was not different between groups. These results suggest that microvascular permeability is actively modulated by a cellular response to mechanical injury and that stretch-activated cation channels may initiate this response through increases in intracellular calcium concentration.

  4. Increased paracellular permeability in intrahepatic cholestasis induced by carmustine (BCNU) in rats

    Krell, H.; Fromm, H.; Larson, R.E.

    1991-01-01

    Carmustine [i.e., 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU)] is a drug with cholestatic potency both in experimental animals and in humans. To study the mechanisms involved in the development of the hepatic lesions, early changes in liver function in rats pretreated with the drug were investigated. Dosages and sampling times that did not result in hepatocellular injury, as indicated by release of marker enzymes, were applied. In isolated perfused livers from pretreated rats, bile flow and maximal secretion rate of taurocholate were decreased. An increase in biliary 14 Csucrose clearance suggested enhanced permeability of the bile tract and was correlated with increased inorganic phosphate concentration in bile. To assess the contribution of paracellular and transcellular pathways of sucrose, 14 Csucrose access into bile was analyzed by biliary off-kinetics after omission of the radioactive marker from the perfusion medium. An improved method was developed to quantitate the permeability of the bile tract by applying the classical flow equation to the paracellular portion of biliary sucrose clearance. With this method it was shown that pretreatment of rats with BCNU resulted in an increase in both diffusion and convection of paracellular sucrose from perfusate into bile. Accordingly, the fast access of horseradish peroxidase from perfusate into bile was facilitated in isolated perfused livers of BCNU-treated rats. The results indicate that an increase in paracellular permeability is an early alteration that may contribute to the development of hepatotoxic lesions caused by BCNU. It is shown that inert solute clearance can be used to assess paracellular permeability if the paracellular fraction is determined

  5. Glutathione metabolism in Bangladeshi children with increased small bowel permeability and impaired growth

    Kumar Roy, Swapan; Tomkins, A.; Johnson, A.

    2000-01-01

    Objectives: To determine whether intestinal permeability during diarrhoea is associated with increased requirement of Sulphur Containing Amino Acid (SCAA); Changes in SCAA metabolism are associated with decreased urinary sulphate and increased excretion of proline from collagen; Rates of turnover SCAA would change as intestinal permeability improves during different dietary levels of SCAA in nutritional regimes. Hypothesis: Supplementation of a standard diet with sulphur containing amino acids is necessary to meet requirements for sulphur under conditions of growth faltering, diarrhoea and increased intestinal permeability. Subjects: Children with persistent diarrhoea aged between 4 months to 18 months and height for age less than 95%. Study site: International Centre for Diarrhoeal Disease Research Bangladesh. Methods: At the baseline, children will be classified into low and normal ISE (Inorganic Sulphar excretion) then each group will be divided into two subgroups. A total of 40 children will be studied (20 in each group). One group will receive a dietary supplement of SCAA and another group will receive an isonitrogenous standard diet for six weeks. Children will be assessed for intestinal permeability at baseline and after two weeks of admission. Before and at six weeks of admission the children will receive a regular drink containing 15 N Glyceine at the rate of 2ml/kg/hr. Blood and urine samples will be collected at baseline and at the end of the supplementation i.e. at 6 weeks. Incorporation of 15 N Glyceine, plasma and red cell glutathione will be assessed by isotope rationing. Urine will be assessed for 15 N enrichment of urea and ammonia, which will used as an assessment of body protein turnover Folate status of these patients will be determined before and after supplementation with SCAA. Benefit of the study: The results of the study will provide specific information on the requirement of Sulphur containing amino acid during malnutrition and persistent

  6. Increased pulmonary vascular permeability as a cause of re-expansion edema in rabbits

    Pavlin, D.J.; Nessly, M.L.; Cheney, F.W.

    1981-01-01

    In order to study the mechanism(s) underlying re-expansion edema, we measured the concentration of labeled albumin (RISA) in the extravascular, extracellular water (EVECW) of the lung as a measure of pulmonary vascular permeability. Re-expansion edema was first induced by rapid re-expansion of rabbit lungs that had been collapsed for 1 wk by pneumothorax. The RISA in EVECW was expressed as a fraction of its plasma concentration: (RISA)L/(RISA)PL. The volume of EVECW (ml/gm dry lung) was measured using a 24 Na indicator. Results in re-expansion edema were compared with normal control lungs and with oleic acid edema as a model of permeability edema. In re-expanded lungs, EVECW (3.41 +/- SD 1.24 ml/g) and (RISA)L/(RISA)PL 0.84 +/- SD 0.15) were significantly increased when compared with normal control lungs (2.25 +/- 0.41 ml/g and 0.51 +/- 0.20, respectively). Results in oleic acid edema (5.66 +/- 2.23 ml/g and 0.84 +/- 0.23) were similar to re-expansion edema. This suggested that re-expansion edema is due to increased pulmonary vascular permeability caused by mechanical stresses applied to the lung during re-expansion

  7. Resistance of essential fatty acid-deficient rats to endotoxin-induced increases in vascular permeability

    Li, E.J.; Cook, J.A.; Spicer, K.M.; Wise, W.C.; Rokach, J.; Halushka, P.V.

    1990-01-01

    Resistance to endotoxin in essential fatty acid-deficient (EFAD) rats is associated with reduced synthesis of certain arachidonic acid metabolites. It was hypothesized that EFAD rats would manifest decreased vascular permeability changes during endotoxemia as a consequence of reduced arachidonic acid metabolism. To test this hypothesis, changes in hematocrit (HCT) and mesenteric localization rate of technetium-labeled human serum albumin (99mTc-HSA) and red blood cells (99mTc-RBC) were assessed in EFAD and normal rats using gamma-camera imaging. Thirty minutes after Salmonella enteritidis endotoxin, EFAD rats exhibited less hemoconcentration as determined by % HCT than normal rats. Endotoxin caused a less severe change in permeability index in the splanchnic region in EFAD rats than in normal rats (1.2 +/- 0.6 x 10(-3)min-1 vs. 4.9 +/- 1.7 x 10(-3)min-1 respectively, P less than 0.05). In contrast to 99mTc-HSA, mesenteric localization of 99mTc-RBC was not changed by endotoxin in control or EFAD rats. Supplementation with ethyl-arachidonic acid did not enhance susceptibility of EFAD rats to endotoxin-induced splanchnic permeability to 99mTc-HSA. Leukotrienes have been implicated as mediators of increased vascular permeability in endotoxin shock. Since LTC3 formation has been reported to be increased in EFA deficiency, we hypothesized that LTC3 may be less potent than LTC4. Thus the effect of LTC3 on mean arterial pressure and permeability was compared to LTC4 in normal rats. LTC3-induced increases in peak mean arterial pressure were less than LTC4 at 10 micrograms/kg (39 +/- 5 mm Hg vs. 58 +/- 4 mm Hg respectively, P less than 0.05) and at 20 micrograms/kg (56 +/- 4 mm Hg vs. 75 +/- 2 mm Hg respectively, P less than 0.05). LY171883 (30 mg/kg), an LTD4/E4 receptor antagonist, attenuated the pressor effect of LTC4, LTD4, and LTC3

  8. Relationship of pleural effusions to increased permeability pulmonary edema in anesthetized sheep.

    Wiener-Kronish, J P; Broaddus, V C; Albertine, K H; Gropper, M A; Matthay, M A; Staub, N C

    1988-01-01

    We studied anesthetized sheep to determine the relationship between increased permeability pulmonary edema and the development and mechanism of pleural effusion formation. In 12 sheep with intact, closed thoraces, we studied the time course of pleural liquid formation after 0.12 ml/kg i.v. oleic acid. After 1 h, there were no pleural effusions, even though extravascular lung water increased 50% to 6.0 +/- 0.7 g/g dry lung. By 3 h pleural effusions had formed, they reached a maximum at 5 h (48...

  9. Bile salt-induced increases in duodenal brush-border membrane proton permeability, fluidity, and fragility

    Zhao, D.L.; Hirst, B.H.

    1990-01-01

    Rabbit duodenal brush-border membrane vesicles were treated in vitro with deoxycholate, glycodeoxycholate, or taurodeoxycholate. Intravesicular [14C]glucose space at equilibrium, 0.54 microliters/mg protein, was reduced by exposure to the three bile salts in a concentration (0.1-5.0 mM)-dependent manner, equatable with increased membrane fragility. Net proton permeability (Pnet), determined by acridine orange fluorescence quenching, was increased from 6.3 x 10(-4) cm/sec in untreated vesicles, by approximately 120, 150, and 170%, by treatment with bile salts at 0.1, 0.5 and 1.0 mM, respectively. The three bile salts were equipotent. The increases in membrane fragility and Pnet were not accompanied by significant increases in membrane fluidity, as assessed from steady-state and time-resolved diphenylhexatriene fluorescence anisotropy. The data demonstrate direct effects of bile salts on duodenal apical membrane fragility and proton permeability that are likely to be early events in bile salt-induced mucosal damage

  10. Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

    Payne, Allison H; Hawryluk, Gregory W; Anzai, Yoshimi; Odéen, Henrik; Ostlie, Megan A; Reichert, Ethan C; Stump, Amanda J; Minoshima, Satoshi; Cross, Donna J

    2017-12-01

    Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

  11. Clostridium sordellii lethal toxin kills mice by inducing a major increase in lung vascular permeability.

    Geny, Blandine; Khun, Huot; Fitting, Catherine; Zarantonelli, Leticia; Mazuet, Christelle; Cayet, Nadège; Szatanik, Marek; Prevost, Marie-Christine; Cavaillon, Jean-Marc; Huerre, Michel; Popoff, Michel R

    2007-03-01

    When intraperitoneally injected into Swiss mice, Clostridium sordellii lethal toxin reproduces the fatal toxic shock syndrome observed in humans and animals after natural infection. This animal model was used to study the mechanism of lethal toxin-induced death. Histopathological and biochemical analyses identified lung and heart as preferential organs targeted by lethal toxin. Massive extravasation of blood fluid in the thoracic cage, resulting from an increase in lung vascular permeability, generated profound modifications such as animal dehydration, increase in hematocrit, hypoxia, and finally, cardiorespiratory failure. Vascular permeability increase induced by lethal toxin resulted from modifications of lung endothelial cells as evidenced by electron microscopy. Immunohistochemical analysis demonstrated that VE-cadherin, a protein participating in intercellular adherens junctions, was redistributed from membrane to cytosol in lung endothelial cells. No major sign of lethal toxin-induced inflammation was observed that could participate in the toxic shock syndrome. The main effect of the lethal toxin is the glucosylation-dependent inactivation of small GTPases, in particular Rac, which is involved in actin polymerization occurring in vivo in lungs leading to E-cadherin junction destabilization. We conclude that the cells most susceptible to lethal toxin are lung vascular endothelial cells, the adherens junctions of which were altered after intoxication.

  12. Mitochondrial permeability transition pore (MPTP) desensitization increases sea urchin spermatozoa fertilization rate.

    Torrezan-Nitao, Elis; Boni, Raianna; Marques-Santos, Luis Fernando

    2016-10-01

    Mitochondrial permeability transition pore (MPTP) is a protein complex whose opening promotes an abrupt increase in mitochondrial inner membrane permeability. Calcium signaling pathways are described in gametes and are involved in the fertilization process. Although mitochondria may act as Ca(2+) store and have a fast calcium-releasing mechanism through MPTP, its contribution to fertilization remains unclear. The work aimed to investigate the MPTP phenomenon in sea urchin spermatozoa and its role on the fertilization. Several pharmacological tools were used to evaluate the MPTP's physiology. Our results demonstrated that MPTP occurs in male gametes in a Ca(2+) - and voltage-dependent manner and it is sensitive to cyclosporine A. Additionally, our data show that MPTP opening does not alter ROS generation in sperm cells. Inhibition of MPTP in spermatozoa strongly improved the fertilization rate, which may involve mechanisms that increase the spermatozoa lifespan. The present work is the first report of the presence of a voltage- and Ca(2+) -dependent MPTP in gametes of invertebrates and indicates MPTP opening as another evolutionary feature shared by sea urchins and mammals. Studies about MPTP in sea urchin male gametes may contribute to the elucidation of several mechanisms involved in sperm infertility. © 2016 International Federation for Cell Biology.

  13. Multi scale impacts of a (Mg,Ca)-Pb exchange on the permeability increase of a bentonite

    Jozja, N.; Baillif, P.; Touray, J.C.; Pons, Ch.H.; Muller, F.; Burgevin, C.

    2003-01-01

    The article addresses the structural effects of solutions of lead nitrate on a suspended or compacted bentonite. A permeability increase is observed on compacted clay. Investigating the composition of output solution, using X-Rays Diffusion at Small Angles and Scanning Electron Microscopy, this permeability increase is explained from structural variations at nano-metric (reduction of particle size) and micrometric scales (micro-fissuration of aggregates). (authors)

  14. Subchronic mild noise stress increases HRP permeability in rat small intestine in vitro.

    Bijlsma, P B; van Raaij, M T; Dobbe, C J; Timmerman, A; Kiliaan, A J; Taminiau, J A; Groot, J A

    2001-05-01

    Recently we reported an increased trans- and paracellular protein permeability in rat small intestine after acute cold restraint stress. In the present study, we applied randomized 95- or 105-dB white noise pulses during 45 min/h, 12 h/day, duration 8 days, as a milder, but more chronic stressor to male rats. At 8 days before the noise experiments, 50% of the animals were cannulated in the vena cava for blood sampling during the experimental period. The other 50% of the animals were sacrificed at Day 9, segments of ileum were mounted in Ussing chambers and perfused at 37 degrees C. Horseradish peroxidase (HRP) was added mucosally, serosal appearance was detected enzymatically and tissues were fixed for electron microscopy. In the animals exposed to 95-dB noise, plasma corticosterone levels were enhanced twofold compared to controls, and ileal HRP flux was enhanced twofold. Electron micrographs of tissue from stressed or control animals showed no detectable paracellular staining of HRP. Quantification of HRP-containing endosomes in enterocytes revealed a twofold increase in endosome number in the animals exposed to 95-db noise indicating that the increased HRP permeability was primarily due to increased endocytosis. In contrast to the animals exposed to 95-dB noise, rats exposed to 105-dB noise showed no increase in corticosterone levels and ileal HRP fluxes were not significantly different from controls. We conclude that mild subchronic noise stress may cause a decrease in intestinal barrier function by increased transcytosis of luminal antigens.

  15. Biomimetic carriers mimicking leukocyte plasma membrane to increase tumor vasculature permeability

    Palomba, R.; Parodi, A.; Evangelopoulos, M.; Acciardo, S.; Corbo, C.; De Rosa, E.; Yazdi, I. K.; Scaria, S.; Molinaro, R.; Furman, N. E. Toledano; You, J.; Ferrari, M.; Salvatore, F.; Tasciotti, E.

    2016-10-01

    Recent advances in the field of nanomedicine have demonstrated that biomimicry can further improve targeting properties of current nanotechnologies while simultaneously enable carriers with a biological identity to better interact with the biological environment. Immune cells for example employ membrane proteins to target inflamed vasculature, locally increase vascular permeability, and extravasate across inflamed endothelium. Inspired by the physiology of immune cells, we recently developed a procedure to transfer leukocyte membranes onto nanoporous silicon particles (NPS), yielding Leukolike Vectors (LLV). LLV are composed of a surface coating containing multiple receptors that are critical in the cross-talk with the endothelium, mediating cellular accumulation in the tumor microenvironment while decreasing vascular barrier function. We previously demonstrated that lymphocyte function-associated antigen (LFA-1) transferred onto LLV was able to trigger the clustering of intercellular adhesion molecule 1 (ICAM-1) on endothelial cells. Herein, we provide a more comprehensive analysis of the working mechanism of LLV in vitro in activating this pathway and in vivo in enhancing vascular permeability. Our results suggest the biological activity of the leukocyte membrane can be retained upon transplant onto NPS and is critical in providing the particles with complex biological functions towards tumor vasculature.

  16. NO2 decreases paracellular resistance to ion and solute flow in alveolar epithelial monolayers

    Cheek, J.M.; Kim, K.J.; Crandall, E.D.

    1990-01-01

    Primary cultured monolayers of rat alveolar epithelial cells grown on tissue culture-treated Nuclepore filters were exposed to 2.5 ppm nitrogen dioxide NO 2 for 2-20 min. Changes in monolayer bioelectric properties and solute permeabilities were subsequently measured. Exposure to NO 2 produced a dose-dependent decrease in monolayer transepithelial electrical resistance (Rt), whereas monolayer short-circuit current was unaffected. Post-exposure monolayer permeability to 14 C-sucrose (which primarily crosses alveolar epithelium via the paracellular pathway) increased markedly. That for 3 H-glycerol (which permeates through both paracellular and transcellular pathways) increased to a lesser extent. Partial recovery of Rt and solute permeabilities was noted by 48-h post-exposure. The time courses of the decrease in Rt and increase in solute permeabilities were similar. These results suggest that NO 2 primarily impairs passive alveolar epithelial barrier functions in vitro, probably by altering intercellular junctions, and does not appear to directly affect cell membrane active ion transport processes. When correlated with results obtained from experimental approaches, studies of in vitro alveolar epithelial monolayers may facilitate investigations of dosimetry, sites, and mechanisms of oxidant injury in the lung

  17. Transcranial direct current stimulation transiently increases the blood-brain barrier solute permeability in vivo

    Shin, Da Wi; Khadka, Niranjan; Fan, Jie; Bikson, Marom; Fu, Bingmei M.

    2016-03-01

    Transcranial Direct Current Stimulation (tDCS) is a non-invasive electrical stimulation technique investigated for a broad range of medical and performance indications. Whereas prior studies have focused exclusively on direct neuron polarization, our hypothesis is that tDCS directly modulates endothelial cells leading to transient changes in blood-brain-barrier (BBB) permeability (P) that are highly meaningful for neuronal activity. For this, we developed state-of-the-art imaging and animal models to quantify P to various sized solutes after tDCS treatment. tDCS was administered using a constant current stimulator to deliver a 1mA current to the right frontal cortex of rat (approximately 2 mm posterior to bregma and 2 mm right to sagittal suture) to obtain similar physiological outcome as that in the human tDCS application studies. Sodium fluorescein (MW=376), or FITC-dextrans (20K and 70K), in 1% BSA mammalian Ringer was injected into the rat (SD, 250-300g) cerebral circulation via the ipsilateral carotid artery by a syringe pump at a constant rate of ~3 ml/min. To determine P, multiphoton microscopy with 800-850 nm wavelength laser was applied to take the images from the region of interest (ROI) with proper microvessels, which are 100-200 micron below the pia mater. It shows that the relative increase in P is about 8-fold for small solute, sodium fluorescein, ~35-fold for both intermediate sized (Dex-20k) and large (Dex-70k) solutes, 10 min after 20 min tDCS pretreatment. All of the increased permeability returns to the control after 20 min post treatment. The results confirmed our hypothesis.

  18. Isoproterenol attenuates high vascular pressure-induced permeability increases in isolated rat lungs.

    Parker, J C; Ivey, C L

    1997-12-01

    To separate the contributions of cellular and basement membrane components of the alveolar capillary barrier to the increased microvascular permeability induced by high pulmonary venous pressures (Ppv), we subjected isolated rat lungs to increases in Ppv, which increased capillary filtration coefficient (Kfc) without significant hemorrhage (31 cmH2O) and with obvious extravasation of red blood cells (43 cmH2O). Isoproterenol (20 microM) was infused in one group (Iso) to identify a reversible cellular component of injury, and residual blood volumes were measured to assess extravasation of red blood cells through ruptured basement membranes. In untreated lungs (High Ppv group), Kfc increased 6.2 +/- 1.3 and 38.3 +/- 15.2 times baseline during the 31 and 43 cmH2O Ppv states. In Iso lungs, Kfc was 36.2% (P Kfc increases at moderate Ppv, possibly because of an endothelial effect, but it did not affect red cell extravasation at higher vascular pressures.

  19. Increasing plasmid transformation efficiency of natural spizizen method in Bacillus Subtilis by a cell permeable peptide

    Mehrdad Moosazadeh Moghaddam

    2013-01-01

    Full Text Available Introduction: Some of bacterial species are able to uptake DNA molecule from environment, the yield of this process depends on some conditions such as plasmid size and host type. In the case of Bacillus subtilis, DNA uptake has low efficacy. Using Spizizen minimal medium is common method in plasmid transformation into B. subtilis, but rate of this process is not suitable and noteworthy. The aim of this study was investigation of novel method for improvement of DNA transformation into B. subtilis based on CM11 cationic peptide as a membrane permeable agent.Materials and methods: In this study, for optimization of pWB980 plasmid transformation into B. subtilis, the CM11 cationic peptide was used. For this purpose, B. subtilis competent cell preparation in the present of different concentration of peptide was implemented by two methods. In the first method, after treatment of bacteria with different amount of peptide for 14h, plasmid was added. In the second method, several concentration of peptide with plasmid was exposed to bacteria simultaneously. Bacteria that uptake DNA were screened on LB agar medium containing kanamycin. The total transformed bacteria per microgram of DNA was calculated and compared with the control.Results: Plasmid transformation in best conditions was 6.5 folds higher than the control. This result was statistically significant (P value <0.001.Discussion and conclusion: This study showed that CM11 cationic peptide as a membrane permeable agent was able to increase plasmid transformation rate into B. subtilis. This property was useful for resolution of low transformation efficacy.

  20. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

    2010-04-01

    Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.

  1. Zonulin upregulation is associated with increased gut permeability in subjects with type 1 diabetes and their relatives.

    Sapone, Anna; de Magistris, Laura; Pietzak, Michelle; Clemente, Maria G; Tripathi, Amit; Cucca, Francesco; Lampis, Rosanna; Kryszak, Deborah; Cartenì, Maria; Generoso, Maddalena; Iafusco, Dario; Prisco, Francesco; Laghi, Francesca; Riegler, Gabriele; Carratu, Romano; Counts, Debra; Fasano, Alessio

    2006-05-01

    Zonulin, a protein that modulates intestinal permeability, is upregulated in several autoimmune diseases and is involved in the pathogenesis of autoimmune diabetes in the BB/Wor animal model of the disease. To verify the association between serum zonulin levels and in vivo intestinal permeability in patients with type 1 diabetes, both parameters were investigated in different stages of the autoimmune process. Forty-two percent (141 of 339) of the patients had abnormal serum zonulin levels, as compared with age-matched control subjects. The increased zonulin levels correlated with increased intestinal permeability in vivo and changes in claudin-1, claudin-2, and myosin IXB genes expression, while no changes were detected in ZO1 and occludin genes expression. When tested in serum samples collected during the pre-type 1 diabetes phase, elevated serum zonulin was detected in 70% of subjects and preceded by 3.5 +/- 0.9 years the onset of the disease in those patients who went on to develop type 1 diabetes. Combined, these results suggest that zonulin upregulation is associated with increased intestinal permeability in a subgroup of type 1 diabetic patients. Zonulin upregulation seems to precede the onset of the disease, providing a possible link between increased intestinal permeability, environmental exposure to non-self antigens, and the development of autoimmunity in genetically susceptible individuals.

  2. Epithelial Cell Damage Activates Bactericidal/Permeability Increasing-Protein (BPI Expression in Intestinal Epithelium

    Arjun Balakrishnan

    2017-08-01

    Full Text Available As the first line of defense against invading pathogen, intestinal epithelium produces various antimicrobial proteins (AMP that help in clearance of pathogen. Bactericidal/permeability-increasing protein (BPI is a 55 kDa AMP that is expressed in intestinal epithelium. Dysregulation of BPI in intestinal epithelium is associated with various inflammatory diseases like Crohn’s Disease, Ulcerative colitis, and Infectious enteritis’s. In this paper, we report a direct correlation between intestinal damage and BPI expression. In Caco-2 cells, we see a significant increase in BPI levels upon membrane damage mediated by S. aureus infection and pore-forming toxins (Streptolysin and Listeriolysin. Cells detect changes in potassium level as a Danger-associated molecular pattern associated with cell damage and induce BPI expression in a p38 dependent manner. These results are further supported by in vivo findings that the BPI expression in murine intestinal epithelium is induced upon infection with bacteria which cause intestinal damage (Salmonella Typhimurium and Shigella flexneri whereas mutants that do not cause intestinal damage (STM ΔfliC and STM ΔinvC did not induce BPI expression. Our results suggest that epithelial damage associated with infection act as a signal to induce BPI expression.

  3. Acute high-intensity interval running increases markers of gastrointestinal damage and permeability but not gastrointestinal symptoms.

    Pugh, Jamie N; Impey, Samuel G; Doran, Dominic A; Fleming, Simon C; Morton, James P; Close, Graeme L

    2017-09-01

    The purpose of this study was to investigate the effects of high-intensity interval running on markers of gastrointestinal (GI) damage and permeability alongside subjective symptoms of GI discomfort. Eleven male runners completed an acute bout of high-intensity interval training (HIIT) (eighteen 400-m runs at 120% maximal oxygen uptake) where markers of GI permeability, intestinal damage, and GI discomfort symptoms were assessed and compared with resting conditions. Compared with rest, HIIT significantly increased serum lactulose/rhamnose ratio (0.051 ± 0.016 vs. 0.031 ± 0.021, p = 0.0047; 95% confidence interval (CI) = 0.006 to 0.036) and sucrose concentrations (0.388 ± 0.217 vs. 0.137 ± 0.148 mg·L -1 ; p HIIT and resting conditions. Plasma intestinal-fatty acid binding protein (I-FABP) was significantly increased (p HIIT whereas no changes were observed during rest. Mild symptoms of GI discomfort were reported immediately and at 24 h post-HIIT, although these symptoms did not correlate to GI permeability or I-FABP. In conclusion, acute HIIT increased GI permeability and intestinal I-FABP release, although these do not correlate with symptoms of GI discomfort. Furthermore, by using serum sampling, we provide data showing that it is possible to detect changes in intestinal permeability that is not observed using urinary sampling over a shorter time-period.

  4. Diagnosis of hydrostatic versus increased permeability pulmonary edema with chest radiographic criteria in critically ILL patients

    Aberle, D.R.; Wiener-Kronish, J.P.; Webb, W.R.; Matthay, M.A.

    1987-01-01

    To evaluate chest radiographic criteria in distinguishing mechanisms of pulmonary edema, the authors studied 45 intubated patients with extensive edema. Edema type was clinically classified by the ratio of alveolar edema-to-plasma protein concentration in association with compatible clinical/hemodynamic parameters. Chest films were scored as hydrostatic, permeability, or mixed by three readers in blinded fashion based on cardiac size, vascular pedicle width, distribution of edema, effusions, peribronchial cuffs, septal lines, or air bronchograms. Overall radiographic score accurately identified 87% of patients with hydrostatic edema but only 60% of those with permeability edema. Edema distribution was most discriminating, with a patchy peripheral pattern relatively specific for clinical permeability edema. Hydrostatic features on chest radiograph were common with permeability edema, including effusions (36%), widened pedicle (56%), cuffs (72%), or septa (40%). The authors conclude that the chest radiograph is limited in distinguishing edema mechanism in the face of extensive pulmonary edema

  5. Reversibility of increased intestinal permeability to 51Cr-EDTA in patients with gastrointestinal inflammatory diseases

    Jenkins, R.T.; Jones, D.B.; Goodacre, R.L.; Collins, S.M.; Coates, G.; Hunt, R.H.; Bienenstock, J.

    1987-01-01

    Intestinal permeability in adults with inflammatory gastrointestinal diseases was investigated by measuring the 24-h urinary excretion of orally administered 51 Cr-EDTA. Eighty controls along with 100 patients with Crohn's disease, 46 patients with ulcerative colitis, 20 patients with gluten-sensitive enteropathy, and 18 patients with other diseases were studied. In controls, the median 24-h excretion was 1.34%/24 h of the oral dose. Patients with Crohn's disease (median 2.96%/24 h), ulcerative colitis (median 2.12%/24 h), and untreated gluten-sensitive enteropathy (median 3.56%/24 h) had significantly elevated urinary excretion of the probe compared to controls (p less than 0.0001). Increased 24-h urinary excretion of 51 Cr-EDTA had a high association with intestinal inflammation (p less than 0.0001). Test specificity and sensitivity were 96% and 57%, respectively. A positive test has a 96% probability of correctly diagnosing the presence of intestinal inflammation, whereas a negative test has a 50% probability of predicting the absence of disease

  6. Relative rates of albumin equilibration in the skin interstitium and lymph during increased permeability

    Powers, M.R.; Wallace, J.R.; Bell, D.R.

    1986-01-01

    The initial equilibration of 125 I-labelled albumin between the vascular and extravascular compartments was studied in hindpaw heel skin of anesthetized rabbits. Bradykinin (0.3 μg/min) was infused into a small branch of the femoral artery. A second group of rabbits served as control. Following bradykinin, prenodal popliteal lymph flow was 4 times control flow. The lymph-to-plasma concentration ratios for total protein and albumin were, respectively, 60% and 50% larger than control. Tissue albumin concentration was twice control. After reaching a steady, elevated lymph flow, tracer albumin was infused to maintain plasma activity constant for 3 hrs. The plasma volume in tissue samples was measured using 131 I-labeled albumin injected 10 min before ending the experiment. Endogenous albumin was measured in plasma, lymph, and tissue samples using rocket electroimmunoassay. After 3 hrs of tracer infusion, lymph specific activity was 3 times greater than control. In the control group, plasma albumin equilibrated more rapidly with lymph than with tissue (p < 0.05). Following bradykinin, extravascular specific activity was 4 times control, resulting in lymph and tissue equilibrating with plasma at similar rates. Thus, increasing capillary permeability causes the extravascular albumin mass to behave as if distributed in a single compartment

  7. Permeability enhancers dramatically increase zanamivir absolute bioavailability in rats: implications for an orally bioavailable influenza treatment.

    Eric H Holmes

    Full Text Available We have demonstrated that simple formulations composed of the parent drug in combination with generally regarded as safe (GRAS permeability enhancers are capable of dramatically increasing the absolute bioavailability of zanamivir. This has the advantage of not requiring modification of the drug structure to promote absorption, thus reducing the regulatory challenges involved in conversion of an inhaled to oral route of administration of an approved drug. Absolute bioavailability increases of up to 24-fold were observed when Capmul MCM L8 (composed of mono- and diglycerides of caprylic/capric acids in glycerol was mixed with 1.5 mg of zanamivir and administered intraduodenally to rats. Rapid uptake (t(max of 5 min and a C(max of over 7200 ng/mL was achieved. Variation of the drug load or amount of enhancer demonstrated a generally linear variation in absorption, indicating an ability to optimize a formulation for a desired outcome such as a targeted C(max for enzyme saturation. No absorption enhancement was observed when the enhancer was given 2 hr prior to drug administration, indicating, in combination with the observed tmax, that absorption enhancement is temporary. This property is significant and aligns well with therapeutic applications to limit undesirable drug-drug interactions, potentially due to the presence of other poorly absorbed polar drugs. These results suggest that optimal human oral dosage forms of zanamivir should be enteric-coated gelcaps or softgels for intraduodenal release. There continues to be a strong need and market for multiple neuraminidase inhibitors for influenza treatment. Creation of orally available formulations of inhibitor drugs that are currently administered intravenously or by inhalation would provide a significant improvement in treatment of influenza. The very simple GRAS formulation components and anticipated dosage forms would require low manufacturing costs and yield enhanced convenience. These results

  8. Interferon-β lipofection I. Increased efficacy of chemotherapeutic drugs on human tumor cells derived monolayers and spheroids.

    Villaverde, M S; Gil-Cardeza, M L; Glikin, G C; Finocchiaro, L M E

    2012-07-01

    We evaluated the effect of hIFNβ gene transfer alone or in combination with different antineoplastic drugs commonly used in cancer treatment. Five human tumor-derived cell lines were cultured as monolayers and spheroids. Four cell lines (Ewing sarcomas EW7 and COH, melanoma M8 and mammary carcinoma MCF-7) were sensitive to hIFNβ gene lipofection. Although this effect appeared in both culture configurations, spheroids showed a relative multicellular resistance (insensitive colon carcinoma HT-29 excluded). EW7 and M8 hIFNβ-expressing cells were exposed to different concentrations of bleomycin, bortezomib, carboplatin, doxorubicin, etoposide, methotrexate, paclitaxel and vincristine in both configuration models. In chemotherapy-sensitive EW7 monolayers, the combination of hIFNβ gene and antineoplastic drugs displayed only additive or counteractive (methotrexate) effects, suggesting that cytotoxic mechanisms triggered by hIFNβ gene lipofection could be saturating the signaling pathways. Conversely, in chemotherapy-resistant EW7 spheroids or M8 cells, the combination of hIFNβ with drugs that mainly operate at the genotoxic level (doxorubicin, methotrexate and paclitaxel) presented only additive effects. However, drugs that also increase pro-oxidant species can complement the antitumor efficacy of the hIFNβ gene and clearly caused potentiated effects (bleomycin, bortezomib, carboplatin, etoposide and vincristine). The great bystander effect induced by hIFNβ gene lipofection could be among the main causes of its effectiveness, because only 1 or 2% of EW7 or M8 hIFNβ-expressing cells killed more than 60 or 80% of cell population, respectively.

  9. New biomarkers for increased intestinal permeability induced by dextran sodium sulphate and fasting in chickens.

    Gilani, S; Howarth, G S; Kitessa, S M; Tran, C D; Forder, R E A; Hughes, R J

    2017-10-01

    Increased intestinal permeability (IP) can lead to compromised health in chickens. As there is limited literature on in vivo biomarkers to assess increased IP in chickens, the objective of this study was to identify a reliable biomarker of IP using DSS ingestion and fasting models. Male Ross chickens (n = 48) were reared until day 14 on the floor pen in an animal care facility, randomized into the following groups: control, DSS and fasting (each with n = 16), and then placed in metabolism cages. DSS was administered in drinking water at 0.75% from days 16 to 21, while controls and fasted groups received water. All birds had free access to feed and water except the birds in the fasting group that were denied feed for 19.5 h on day 20. On day 21, all chickens were given two separate oral gavages comprising fluorescein isothiocyanate dextran (FITC-d, 2.2 mg in 1 ml/bird) at time zero and lactulose, mannitol and rhamnose (LMR) sugars (0.25 g L, 0.05 g M and 0.05 g R in 2 ml/bird) at 60 min. Whole blood was collected from the brachial vein in a syringe 90 min post-LMR sugar gavage. Serum FITC-d and plasma LMR sugar concentrations were measured by spectrophotometry and high-performance ion chromatography respectively. Plasma concentrations of intestinal fatty acid binding protein, diamine oxidase, tight junction protein (TJP), d-lactate and faecal α-antitrypsin inhibitor concentration were also analysed by ELISA. FITC-d increased significantly (p fasting compared with control. L/M and L/R ratios for fasting and L/M ratio for DSS increased compared with control chickens (p fasting but not DSS treatment, compared with controls. Other tests did not indicate changes in IP (p > 0.05). We concluded that FITC-d and LMR sugar tests can be used in chickens to assess changes in IP. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

  10. Rapid increases in permeability and porosity of bentonite-sand mixtures due to alteration by water vapor

    Couture, R.A.

    1984-01-01

    Packed columns of canister packing material containing 25% bentonite and 75% quartz or basalt sand, were exposed to water vapor at temperatures up t 260 0 C. The permeabilities of the columns were subsequently measured after complete saturation with liquid water in a pressurized system. Exposure to water vapor caused irreversible increases in permeability by factors of up to 10 5 . After saturation with liquid water, the permeability was nearly independent of temperature. The increases in permeability were due to a large decrease in the ability of the bentonite to swell in water. Calculations suggest that swelling of bentonite altered at 250 0 C was not sufficient to fill the pore spaces. If the pore spaces are filled, the mixture will form an effective barrier against flow, diffusion, and transport of colloids. The results suggest that if bentonite-based canister packing material is exposed even briefly to water vapor at high temperatures in a high-level nuclear waste repository, its performance will be seriously impaired. The problem is less severe if the proportion of bentonite is high and the material is highly compacted. Previous results show significant degradation of bentonite by water vapor at temperatures as low as 150 0 C. This suggests that in some repositories, backfill in tunnels and drifts may also be affected. 9 references, 5 figures, 1 table

  11. Leaky gut and mycotoxins: Aflatoxin B1 does not increase gut permeability in broiler chickens

    Rosario eGalarza-Seeber

    2016-02-01

    Full Text Available Previous studies conducted in our laboratory have demonstrated that intestinal barrier function can be adversely affected by diet ingredients or feed restriction, resulting in increased intestinal inflammation-associated permeability. Two experiments were conducted in broilers to evaluate the effect of 3 concentrations of Aflatoxin B1 (AFB1; 2, 1.5 or 1 ppm on gastrointestinal leakage and liver bacterial translocation (BT. In Exp 1, 240 day-of-hatch male broilers were allocated in two groups, each group had six replicates of 20 chickens (n = 120/group: Control feed or feed + 2 ppm AFB1. In Exp 2, 240 day-of-hatch male broilers were allocated in three groups, each group had 5 replicates of 16 chickens (n = 80/group: Control feed; feed + 1 ppm AFB1; or feed + 1.5 ppm AFB1. In both experiments, chickens were fed starter (d1-d7 and grower diets (d8-d21 ad libitum and performance parameters were evaluated every week. At day 21, all chicks received an oral gavage dose of FITC-d (4.16 mg/kg 2.5h before collecting blood samples to evaluate gastrointestinal leakage of FITC-d. In Exp 2 a hematologic analysis was also performed. Liver sections were aseptically collected and cultured using TSA plates to determine BT. Cecal contents were collected to determine total cfu/g of Gram-negative bacteria; lactic acid bacteria (LAB or anaerobes by plating on selective media. In Exp 2, liver, spleen and bursa of Fabricius were removed to determine organ weight ratio, and also intestinal samples were obtained for morphometric analysis. Performance parameters, organ weight ratio and morphometric measurements were significantly different between control and AFB1 groups in both experiments. Gut leakage of FITC-d was not affected by the three concentrations of AFB1 evaluated (P > 0.05. Interestingly, a significant reduction in BT was observed in chickens that received 2 and 1 ppm AFB1. An increase (P < 0.05 in total aerobic bacteria, total Gram negatives, and total LAB

  12. Increased Serum Zonulin Levels as an Intestinal Permeability Marker in Autistic Subjects.

    Esnafoglu, Erman; Cırrık, Selma; Ayyıldız, Sema Nur; Erdil, Abdullah; Ertürk, Emine Yurdakul; Daglı, Abdullah; Noyan, Tevfik

    2017-09-01

    To evaluate the serum levels of zonulin, which regulates tight junctions between enterocytes and is a physiological modulator controlling intestinal permeability, in patients with autism spectrum disorders (ASDs). Serum zonulin levels were determined in 32 patients with ASD and 33 healthy controls using an enzyme-linked immunosorbent assay. The severity of ASD symptoms was assessed with the Childhood Autism Rating Scale. Serum zonulin levels were significantly higher in the patients with ASD (122.3 ± 98.46 ng/mL) compared with the healthy controls (41.89 ± 45.83 ng/mL). There was a positive correlation between zonulin levels and Childhood Autism Rating Scale score when all subjects were assessed (r = 0.523; P zonulin, which regulates intestinal permeability, plays a role in the development of symptoms of ASD. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Cortactin deficiency is associated with reduced neutrophil recruitment but increased vascular permeability in vivo.

    Schnoor, Michael; Lai, Frank P L; Zarbock, Alexander; Kläver, Ruth; Polaschegg, Christian; Schulte, Dörte; Weich, Herbert A; Oelkers, J Margit; Rottner, Klemens; Vestweber, Dietmar

    2011-08-01

    Neutrophil extravasation and the regulation of vascular permeability require dynamic actin rearrangements in the endothelium. In this study, we analyzed in vivo whether these processes require the function of the actin nucleation-promoting factor cortactin. Basal vascular permeability for high molecular weight substances was enhanced in cortactin-deficient mice. Despite this leakiness, neutrophil extravasation in the tumor necrosis factor-stimulated cremaster was inhibited by the loss of cortactin. The permeability defect was caused by reduced levels of activated Rap1 (Ras-related protein 1) in endothelial cells and could be rescued by activating Rap1 via the guanosine triphosphatase (GTPase) exchange factor EPAC (exchange protein directly activated by cAMP). The defect in neutrophil extravasation was caused by enhanced rolling velocity and reduced adhesion in postcapillary venules. Impaired rolling interactions were linked to contributions of β(2)-integrin ligands, and firm adhesion was compromised by reduced ICAM-1 (intercellular adhesion molecule 1) clustering around neutrophils. A signaling process known to be critical for the formation of ICAM-1-enriched contact areas and for transendothelial migration, the ICAM-1-mediated activation of the GTPase RhoG was blocked in cortactin-deficient endothelial cells. Our results represent the first physiological evidence that cortactin is crucial for orchestrating the molecular events leading to proper endothelial barrier function and leukocyte recruitment in vivo.

  14. Intact penetratin metabolite permeates across Caco-2 monolayers

    Birch, Ditlev; Christensen, Malene Vinther; Stærk, Dan

    . Previous studies have demonstrated that cell-penetrating peptides (CPPs) may be used as carriers in order to improve the bioavailability of a therapeutic cargo like insulin after oral administration. Penetratin, a commonly used CPP, has been shown to increase the uptake of insulin across Caco-2 cell......-2 cells cultured on permeable filter inserts and in cell lysates, respectively. The epithelial permeation of penetratin and the formed metabolites was assessed by using Caco-2 monolayers cultured on permeable filter inserts. Results Preliminary data revealed that at least one specific metabolite...... is formed upon both intracellular and extracellular degradation of penetratin (figure 1A). Following incubation with epithelium for 4 hours, the metabolite permeated the Caco-2 monolayer and the concentration increased approximately 10-fold when compared to a sample collected following 15 minutes...

  15. Effect of acute, slightly increased intra-abdominal pressure on intestinal permeability and oxidative stress in a rat model.

    Yuxin Leng

    Full Text Available INTRODUCTION: Intra-abdominal hypertension (IAH is known as a common, serious complication in critically ill patients. Bacterial translocation and permeability changes are considered the pathophysiological bases for IAH-induced enterogenic endotoxemia and subsequent multiorgan failure. Nevertheless, the effects of slightly elevated intra-abdominal pressures (IAPs on the intestinal mucosa and the associated mechanisms remain unclear. METHODS: To investigate the acute effects of different nitrogen pneumoperitoneum grades on colonic mucosa, male Sprague-Dawley rats were assigned to six groups with different IAPs (0 [control], 4, 8, 12, 16, and 20 mmHg, n = 6/group. During 90 min of exposure, we dynamically monitored the heart rate and noninvasive hemodynamic parameters. After gradual decompression, arterial blood gas analyses were conducted. Thereafter, structural injuries to the colonic mucosa were identified using light microscopy. Colon permeability was determined using the expression of tight junction proteins, combined with fluorescein isothiocyanate dextran (FD-4 absorption. The pro-oxidant-antioxidant balance was determined based on the levels of malondialdehyde (MDA and antioxidant enzymes. RESULTS: IAH significantly affected the histological scores of the colonic mucosa, tight junction protein expression, mucosal permeability, and pro-oxidant-antioxidant balance. Interestingly, elevations of IAP that were lower than the threshold for IAH also showed a similar, undesirable effect. In the 8 mmHg group, mild hyponatremia, hypocalcemia, and hypoxemia occurred, accompanied by reduced blood and abdominal perfusion pressures. Mild microscopic inflammatory infiltration and increased MDA levels were also detected. Moreover, an 8-mm Hg IAP markedly inhibited the expression of tight junction proteins, although no significant differences in FD-4 permeability were observed between the 0- and 8-mmHg groups. CONCLUSIONS: Acute exposure to slightly

  16. Effects of Streptomycin Administration on Increases in Skeletal Muscle Fiber Permeability and Size Following Eccentric Muscle Contractions.

    Hayao, Keishi; Tamaki, Hiroyuki; Nakagawa, Kouki; Tamakoshi, Keigo; Takahashi, Hideaki; Yotani, Kengo; Ogita, Futoshi; Yamamoto, Noriaki; Onishi, Hideaki

    2018-06-01

    The purpose of this study was to investigate the preventive effect of streptomycin (Str) administration on changes in membrane permeability and the histomorphological characteristics of damaged muscle fibers following eccentric contraction (ECC ). Eighteen 7-week-old male Fischer 344 rats were randomly assigned to three groups: control (Cont), ECC, and ECC with Str (ECC + Str). The tibialis anterior (TA) muscles in both ECC groups were stimulated electrically and exhibited ECC. Evans blue dye (EBD), a marker of muscle fiber damage associated with increased membrane permeability, was injected 24 hr before TA muscle sampling. The number of EBD-positive fibers, muscle fiber cross-sectional area (CSA), and roundness were determined via histomorphological analysis. The ECC intervention resulted in an increased fraction of EBD-positive fibers, a larger CSA, and decreased roundness. The fraction of EBD-positive fibers was 79% lower in the ECC + Str group than in the ECC group. However, there was no difference in the CSA and roundness of the EBD-positive fibers between the two ECC groups. These results suggest that Str administration can reduce the number of myofibers that increase membrane permeability following ECC, but does not ameliorate the extent of fiber swelling in extant EBD-positive fibers. Anat Rec, 301:1096-1102, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

  17. Gliadin induces an increase in intestinal permeability and zonulin release by binding to the chemokine receptor CXCR3.

    Lammers, Karen M; Lu, Ruliang; Brownley, Julie; Lu, Bao; Gerard, Craig; Thomas, Karen; Rallabhandi, Prasad; Shea-Donohue, Terez; Tamiz, Amir; Alkan, Sefik; Netzel-Arnett, Sarah; Antalis, Toni; Vogel, Stefanie N; Fasano, Alessio

    2008-07-01

    Celiac disease is an immune-mediated enteropathy triggered by gliadin, a component of the grain protein gluten. Gliadin induces an MyD88-dependent zonulin release that leads to increased intestinal permeability, a postulated early element in the pathogenesis of celiac disease. We aimed to establish the molecular basis of gliadin interaction with intestinal mucosa leading to intestinal barrier impairment. Alpha-gliadin affinity column was loaded with intestinal mucosal membrane lysates to identify the putative gliadin-binding moiety. In vitro experiments with chemokine receptor CXCR3 transfectants were performed to confirm binding of gliadin and/or 26 overlapping 20mer alpha-gliadin synthetic peptides to the receptor. CXCR3 protein and gene expression were studied in intestinal epithelial cell lines and human biopsy specimens. Gliadin-CXCR3 interaction was further analyzed by immunofluorescence microscopy, laser capture microscopy, real-time reverse-transcription polymerase chain reaction, and immunoprecipitation/Western blot analysis. Ex vivo experiments were performed using C57BL/6 wild-type and CXCR3(-/-) mouse small intestines to measure intestinal permeability and zonulin release. Affinity column and colocalization experiments showed that gliadin binds to CXCR3 and that at least 2 alpha-gliadin 20mer synthetic peptides are involved in this binding. CXCR3 is expressed in mouse and human intestinal epithelia and lamina propria. Mucosal CXCR3 expression was elevated in active celiac disease but returned to baseline levels following implementation of a gluten-free diet. Gliadin induced physical association between CXCR3 and MyD88 in enterocytes. Gliadin increased zonulin release and intestinal permeability in wild-type but not CXCR3(-/-) mouse small intestine. Gliadin binds to CXCR3 and leads to MyD88-dependent zonulin release and increased intestinal permeability.

  18. Glycerol and urea can be used to increase skin permeability in reduced hydration conditions.

    Björklund, Sebastian; Engblom, Johan; Thuresson, Krister; Sparr, Emma

    2013-12-18

    The natural moisturizing factor (NMF) is a group of hygroscopic molecules that is naturally present in skin and protects from severe drying. Glycerol and urea are two examples of NMF components that are also used in skin care applications. In the present study, we investigate the influence of glycerol and urea on the permeability of a model drug (metronidazole, Mz) across excised pig skin membranes at different hydrating conditions. The degree of skin hydration is regulated by the gradient in water activity across the membrane, which in turn depends on the water activity of the formulation in contact with the skin membrane. Here, we determine the water activity of all formulations employed using an isothermal calorimetric method. Thus, the gradient in water activity is controlled by a novel experimental set-up with well-defined boundary conditions on both sides of the skin membrane. The results demonstrate that glycerol and urea can retain high steady state flux of Mz across skin membranes at dehydrating conditions, which otherwise would decrease the permeability due to dehydration. X-ray diffraction measurements are performed to give insight into the effects of glycerol and urea on SC molecular organization. The novel steady state flux results can be related to the observation that water, glycerol, and urea all affect the structural features of the SC molecular components in a similar manner. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  19. Increased intestinal permeability, measured by serum zonulin, is associated with metabolic risk markers in overweight pregnant women.

    Mokkala, Kati; Pellonperä, Outi; Röytiö, Henna; Pussinen, Pirkko; Rönnemaa, Tapani; Laitinen, Kirsi

    2017-04-01

    Increased intestinal permeability with subsequent metabolic endotoxemia, i.e., elevated circulating levels of bacterial lipopolysaccharide, LPS, has been introduced as a novel initiator of obesity related metabolic disturbances in non-pregnant individuals. The objective was to investigate the extent to which intestinal permeability, measured by serum zonulin concentration, is related to metabolic endotoxemia and metabolic risk markers in overweight pregnant women. This was a cross-sectional study including 100 pregnant overweight women in early pregnancy. Serum zonulin was analyzed using ELISA, and markers for metabolic endotoxemia (LPS), inflammation (high-sensitive C-reactive protein and glycoprotein acetylation GlyA), glucose metabolism (fasting glucose and insulin), and lipid metabolism were measured. Higher serum zonulin concentration associated positively with LPS (P=0.02), inflammatory markers (Pzonulin quartiles). All the observed associations were confirmed (Pzonulin concentration, i.e., increased intestinal permeability, contributes to metabolic endotoxemia, systemic inflammation, and insulin resistance in overweight pregnant women. By reinforcing intestinal barrier, it may be possible to manipulate maternal metabolism during pregnancy with subsequent health benefits. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Silver ions increase plasma membrane permeability through modulation of intracellular calcium levels in tobacco BY-2 cells.

    Klíma, Petr; Laňková, Martina; Vandenbussche, Filip; Van Der Straeten, Dominique; Petrášek, Jan

    2018-05-01

    Silver ions increase plasma membrane permeability for water and small organic compounds through their stimulatory effect on plasma membrane calcium channels, with subsequent modulation of intracellular calcium levels and ion homeostasis. The action of silver ions at the plant plasma membrane is largely connected with the inhibition of ethylene signalling thanks to the ability of silver ion to replace the copper cofactor in the ethylene receptor. A link coupling the action of silver ions and cellular auxin efflux has been suggested earlier by their possible direct interaction with auxin efflux carriers or by influencing plasma membrane permeability. Using tobacco BY-2 cells, we demonstrate here that besides a dramatic increase of efflux of synthetic auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthalene acetic acid (NAA), treatment with AgNO 3 resulted in enhanced efflux of the cytokinin trans-zeatin (tZ) as well as the auxin structural analogues tryptophan (Trp) and benzoic acid (BA). The application of AgNO 3 was accompanied by gradual water loss and plasmolysis. The observed effects were dependent on the availability of extracellular calcium ions (Ca 2+ ) as shown by comparison of transport assays in Ca 2+ -rich and Ca 2+ -free buffers and upon treatment with inhibitors of plasma membrane Ca 2+ -permeable channels Al 3+ and ruthenium red, both abolishing the effect of AgNO 3 . Confocal microscopy of Ca 2+ -sensitive fluorescence indicator Fluo-4FF, acetoxymethyl (AM) ester suggested that the extracellular Ca 2+ availability is necessary to trigger the response to silver ions and that the intracellular Ca 2+ pool alone is not sufficient for this effect. Altogether, our data suggest that in plant cells the effects of silver ions originate from the primal modification of the internal calcium levels, possibly by their interaction with Ca 2+ -permeable channels at the plasma membrane.

  1. Problems of increasing of thermostability of highly permeable Ni-Zn ferrites and relative materials for telecommunications

    Gonchar, A. E-mail: letyuk@mail.ru; Andreev, V.; Letyuk, L.; Shishkanov, A.; Maiorov, V

    2003-01-01

    The work considers ways of increasing of thermostability of ferrites of the basic systems NiO-ZnO-Fe{sub 2}O{sub 3} and MgO-ZnO-Fe{sub 2}O{sub 3} and relative materials for telecommunication. Sufficient results in increasing of the thermostability were achieved by doping Cu ions and controlling rejection of Fe{sub 2}O{sub 3} content from equimolar composition. These results allow to increase the Curie temperature to 130-140 deg. C for Ni-Zn ferrites with initial permeability 2000.

  2. Self-assembled monolayers of n-alkanethiols suppress hydrogen evolution and increase the efficiency of rechargeable iron battery electrodes.

    Malkhandi, Souradip; Yang, Bo; Manohar, Aswin K; Prakash, G K Surya; Narayanan, S R

    2013-01-09

    Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

  3. Self-Assembled Monolayers of n-Alkanethiols Suppress Hydrogen Evolution and Increase the Efficiency of Rechargeable Iron Battery Electrodes

    Malkhandi, S; Yang, B; Manohar, AK; Prakash, GKS; Narayanan, SR

    2013-01-09

    Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

  4. Chronic air-flow limitation does not increase respiratory epithelial permeability assessed by aerosolized solute, but smoking does

    Huchon, G.J.; Russell, J.A.; Barritault, L.G.; Lipavsky, A.; Murray, J.F.

    1984-01-01

    To determine the separate influences of smoking and severe air-flow limitation on aerosol deposition and respiratory epithelial permeability, we studied 26 normal nonsmokers, 12 smokers without airway obstruction, 12 nonsmokers with chronic obstructive pulmonary disease (COPD), and 11 smokers with COPD. We aerosolized 99mTc-labeled diethylene triamine pentaacetic acid to particles approximately 1 micron activity median aerodynamic diameter. Levels of radioactivity were plotted semilogarithmically against time to calculate clearance as percent per minute. The distribution of radioactivity was homogeneous in control subjects and in smokers, but patchy in both groups with COPD. No difference was found between clearances of the control group (1.18 +/- 0.31% min-1), and nonsmoker COPD group (1.37 +/- 0.82% min-1), whereas values in smokers without COPD (4.00 +/- 1.70% min-1) and smokers with COPD (3.62 +/- 2.88% min-1) were significantly greater than in both nonsmoking groups. We conclude that (1) small particles appear to deposit peripherally, even with severe COPD; (2) respiratory epithelial permeability is normal in nonsmokers with COPD; (3) smoking increases permeability by a mechanism unrelated to air-flow limitation

  5. Are self-reported gastrointestinal symptoms among older adults associated with increased intestinal permeability and psychological distress?

    Ganda Mall, John-Peter; Östlund-Lagerström, Lina; Lindqvist, Carl Mårten; Algilani, Samal; Rasoal, Dara; Repsilber, Dirk; Brummer, Robert J; V Keita, Åsa; Schoultz, Ida

    2018-03-20

    Despite the substantial number of older adults suffering from gastrointestinal (GI) symptoms little is known regarding the character of these complaints and whether they are associated with an altered intestinal barrier function and psychological distress. Our aim was to explore the relationship between self-reported gut health, intestinal permeability and psychological distress among older adults. Three study populations were included: 1) older adults with GI symptoms (n = 24), 2) a group of older adults representing the general elderly population in Sweden (n = 22) and 3) senior orienteering athletes as a potential model of healthy ageing (n = 27). Questionnaire data on gut-health, psychological distress and level of physical activity were collected. Intestinal permeability was measured by quantifying zonulin in plasma. The level of systemic and local inflammation was monitored by measuring C-reactive protein (CRP), hydrogen peroxide in plasma and calprotectin in stool samples. The relationship between biomarkers and questionnaire data in the different study populations was illustrated using a Principal Component Analysis (PCA). Older adults with GI symptoms displayed significantly higher levels of both zonulin and psychological distress than both general older adults and senior orienteering athletes. The PCA analysis revealed a separation between senior orienteering athletes and older adults with GI symptoms and showed an association between GI symptoms, psychological distress and zonulin. Older adults with GI symptoms express increased plasma levels of zonulin, which might reflect an augmented intestinal permeability. In addition, this group suffer from higher psychological distress compared to general older adults and senior orienteering athletes. This relationship was further confirmed by a PCA plot, which illustrated an association between GI symptoms, psychological distress and intestinal permeability.

  6. Advantageous Solubility-Permeability Interplay When Using Amorphous Solid Dispersion (ASD) Formulation for the BCS Class IV P-gp Substrate Rifaximin: Simultaneous Increase of Both the Solubility and the Permeability.

    Beig, Avital; Fine-Shamir, Noa; Lindley, David; Miller, Jonathan M; Dahan, Arik

    2017-05-01

    Rifaximin is a BCS class IV (low-solubility, low-permeability) drug and also a P-gp substrate. The aims of this work were to assess the efficiency of different rifaximin amorphous solid dispersion (ASDs) formulations in achieving and maintaining supersaturation and to investigate the consequent solubility-permeability interplay. Spray-dried rifaximin ASDs were prepared with different hydrophilic polymers and their ability to achieve and maintain supersaturation was assessed. Then, rifaximin's apparent intestinal permeability was investigated as a function of increasing supersaturation both in vitro using the parallel artificial membrane permeability assay (PAMPA) and in vivo using the single-pass rat intestinal perfusion (SPIP) model. The efficiency of the different ASDs to achieve and maintain supersaturation of rifaximin was found to be highly polymer dependent, and the copovidone/HPC-SL formulation was found to be superior to the other two, allowing supersaturation of 200× that of the crystalline solubility for 20 h. In vitro, rifaximin flux was increased and the apparent permeability was constant as a function of increasing supersaturation level. In vivo, on the other hand, absorption rate coefficient (k a ) was first constant as a function of increasing supersaturation, but at 250×, the crystalline solubility k a was doubled, similar to the k a in the presence of the strong P-gp inhibitor GF120918. In conclusion, a new and favorable nature of solubility-permeability interplay was revealed in this work: delivering high supersaturation level of the BCS class IV drug rifaximin via ASD, thereby saturating the drugs' P-gp-mediated efflux transport, led to the favorable unique win-win situation, where both the solubility and the permeability increased simultaneously.

  7. Polyhydroxybutyrate Targets Mammalian Mitochondria and Increases Permeability of Plasmalemmal and Mitochondrial Membranes

    Elustondo, Pia A.; Angelova, Plamena R.; Kawalec, Michał; Michalak, Michał; Kurcok, Piotr; Abramov, Andrey Y.; Pavlov, Evgeny V.

    2013-01-01

    Poly(3-hydroxybutyrate) (PHB) is a polyester of 3-hydroxybutyric acid (HB) that is ubiquitously present in all organisms. In higher eukaryotes PHB is found in the length of 10 to 100 HB units and can be present in free form as well as in association with proteins and inorganic polyphosphate. It has been proposed that PHB can mediate ion transport across lipid bilayer membranes. We investigated the ability of PHB to interact with living cells and isolated mitochondria and the effects of these interactions on membrane ion transport. We performed experiments using a fluorescein derivative of PHB (fluo-PHB). We found that fluo-PHB preferentially accumulated inside the mitochondria of HeLa cells. Accumulation of fluo-PHB induced mitochondrial membrane depolarization. This membrane depolarization was significantly delayed by the inhibitor of the mitochondrial permeability transition pore - Cyclosporin A. Further experiments using intact cells as well as isolated mitochondria confirmed that the effects of PHB directly linked to its ability to facilitate ion transport, including calcium, across the membranes. We conclude that PHB demonstrates ionophoretic properties in biological membranes and this effect is most profound in mitochondria due to the selective accumulation of the polymer in this organelle. PMID:24086638

  8. Lipopolysaccharide precipitates hepatic encephalopathy and increases blood-brain barrier permeability in mice with acute liver failure.

    Chastre, Anne; Bélanger, Mireille; Nguyen, Bich N; Butterworth, Roger F

    2014-03-01

    Acute liver failure (ALF) is frequently complicated by infection leading to precipitation of central nervous system complications such as hepatic encephalopathy (HE) and increased mortality. There is evidence to suggest that when infection occurs in ALF patients, the resulting pro-inflammatory mechanisms may be amplified that could, in turn, have a major impact on blood-brain barrier (BBB) function. The aim of this study was to investigate the role of endotoxemia on the progression of encephalopathy in relation to BBB permeability during ALF. Adult male C57-BL6 mice with ALF resulting from azoxymethane-induced toxic liver injury were administered trace amounts of the endotoxin component lipopolysaccharide (LPS). Effects on the magnitude of the systemic inflammatory response, liver pathology and BBB integrity were measured as a function of progression of HE, defined as time to loss of corneal reflex (coma). Lipopolysaccharide caused additional two- to seven-fold (P liver pathology and associated increases of circulating transaminases as well as increased hyperammonaemia consistent with a further loss of viable hepatocytes. LPS treatment of ALF mice led to a rapid precipitation of hepatic coma and the BBB became permeable to the 25-kDa protein immunoglobulin G (IgG). This extravasation of IgG was accompanied by ignificant up-regulation of matrix metalloproteinase-9 (MMP-9), an endopeptidase known to modulate opening of the BBB in a wide range of neurological disorders. These findings represent the first direct evidence of inflammation-related BBB permeability changes in ALF. © 2013 John Wiley & Sons A/S. Publishing by John Wiley & Sons Ltd.

  9. Comparison of extravascular lung water volume with radiographic findings in dogs with experimentally increased permeability pulmonary edema

    Takeda, A.; Okumura, S.; Miyamoto, T.; Hagio, M.; Fujinaga, T.

    1995-01-01

    The relationship between extravascular lung water volume (ELWV) and chest radiographical findings was studied in general-anesthetized beagles. The dogs were experimentally injected with oleic acid to increase pulmonary vascular permeability. When the ELWV value in the dogs increased more than approximately 37% from the control value, their chest radiographs began to show signs of pulmonary edema. At this time, the chest X-ray density increased to 10% above the control level. PaO2 decreased, and PaCO2 increased after the administration of oleic acid. This clearly showed that the pulmonary gas exchange function was reduced following increasing ELWV. This comparison showed that probably the thermal-sodium double indicator dilution measurement of ELWV can detect slight hyperpermeability pulmonary edema that does not show on chest radiographs. The chest radiograph was therefore not suitable for the detection of slight pulmonary edema, because it did not show any changes in the early stages in hyperpermeability pulmonary edema

  10. Medroxyprogesterone acetate and levonorgestrel increase genital mucosal permeability and enhance susceptibility to genital herpes simplex virus type 2 infection.

    Quispe Calla, N E; Vicetti Miguel, R D; Boyaka, P N; Hall-Stoodley, L; Kaur, B; Trout, W; Pavelko, S D; Cherpes, T L

    2016-11-01

    Depot-medroxyprogesterone acetate (DMPA) is a hormonal contraceptive especially popular in areas with high prevalence of HIV and other sexually transmitted infections (STI). Although observational studies identify DMPA as an important STI risk factor, mechanisms underlying this connection are undefined. Levonorgestrel (LNG) is another progestin used for hormonal contraception, but its effect on STI susceptibility is much less explored. Using a mouse model of genital herpes simplex virus type 2 (HSV-2) infection, we herein found that DMPA and LNG similarly reduced genital expression of the desmosomal cadherin desmoglein-1α (DSG1α), enhanced access of inflammatory cells to genital tissue by increasing mucosal epithelial permeability, and increased susceptibility to viral infection. Additional studies with uninfected mice revealed that DMPA-mediated increases in mucosal permeability promoted tissue inflammation by facilitating endogenous vaginal microbiota invasion. Conversely, concomitant treatment of mice with DMPA and intravaginal estrogen restored mucosal barrier function and prevented HSV-2 infection. Evaluating ectocervical biopsy tissue from women before and 1 month after initiating DMPA remarkably revealed that inflammation and barrier protection were altered by treatment identically to changes seen in progestin-treated mice. Together, our work reveals DMPA and LNG diminish the genital mucosal barrier; a first-line defense against all STI, but may offer foundation for new contraceptive strategies less compromising of barrier protection.

  11. Measurement of the filtration coefficient (Kfc) in the lung of Gallus domesticus and the effects of increased microvascular permeability.

    Weidner, W Jeffrey; Waddell, David S; Furlow, J David

    2006-08-01

    The filtration coefficient (Kfc) is a sensitive measure of microvascular hydraulic conductivity and has been reported for the alveolar lungs of many mammalian species, but not for the parabronchial avian lung. This study reports the Kfc in the isolated lungs of normal chickens and in the lungs of chickens given the edemogenic agents oleic acid (OA) or dimethyl amiloride (DMA). The control Kfc =0.04+/-0.01 ml min(-1) kPa(-1) g(-1). This parameter increased significantly following the administration of both OA (0.12+/-0.02 ml min(-1) kPa(-1) g(-1)) and DMA (0.07+/-0.01 ml min kPa(-1) g(-1)). As endothelial cadherins are thought to play a role in the dynamic response to acute lung injury, we utilized Western blot analysis to assess lung cadherin content and Northern blot analysis to assess pulmonary vascular endothelial (VE) cadherin expression following drug administration. Lung cadherin content decreases markedly following DMA, but not OA administration. VE cadherin expression increases as a result of DMA treatment, but is unchanged following OA. Our results suggest that the permeability characteristics of the avian lung are more closely consistent with those of the mammalian rather than the reptilian lung, and, that cadherins may play a significant role in the response to acute increases in avian pulmonary microvascular permeability.

  12. Circulating zonulin, a marker of intestinal permeability, is increased in association with obesity-associated insulin resistance.

    José María Moreno-Navarrete

    Full Text Available Zonulin is the only physiological mediator known to regulate intestinal permeability reversibly by modulating intercellular tight junctions. To investigate the relationship between intestinal permeability and obesity-associated metabolic disturbances in humans, we aimed to study circulating zonulin according to obesity and insulin resistance. Circulating zonulin (ELISA was measured in 123 caucasian men in association with inflammatory and metabolic parameters (including minimal model-measured insulin sensitivity. Circulating zonulin increased with body mass index (BMI, waist to hip ratio (WHR, fasting insulin, fasting triglycerides, uric acid and IL-6, and negatively correlated with HDL-cholesterol and insulin sensitivity. In multiple regression analysis, insulin sensitivity (p = 0.002 contributed independently to circulating zonulin variance, after controlling for the effects of BMI, fasting triglycerides and age. When circulating IL-6 was added to this model, only BMI (p = 0.01 contributed independently to circulating zonulin variance. In conclusion, the relationship between insulin sensitivity and circulating zonulin might be mediated through the obesity-related circulating IL-6 increase.

  13. Circulating zonulin, a marker of intestinal permeability, is increased in association with obesity-associated insulin resistance.

    Moreno-Navarrete, José María; Sabater, Mònica; Ortega, Francisco; Ricart, Wifredo; Fernández-Real, José Manuel

    2012-01-01

    Zonulin is the only physiological mediator known to regulate intestinal permeability reversibly by modulating intercellular tight junctions. To investigate the relationship between intestinal permeability and obesity-associated metabolic disturbances in humans, we aimed to study circulating zonulin according to obesity and insulin resistance. Circulating zonulin (ELISA) was measured in 123 caucasian men in association with inflammatory and metabolic parameters (including minimal model-measured insulin sensitivity). Circulating zonulin increased with body mass index (BMI), waist to hip ratio (WHR), fasting insulin, fasting triglycerides, uric acid and IL-6, and negatively correlated with HDL-cholesterol and insulin sensitivity. In multiple regression analysis, insulin sensitivity (p = 0.002) contributed independently to circulating zonulin variance, after controlling for the effects of BMI, fasting triglycerides and age. When circulating IL-6 was added to this model, only BMI (p = 0.01) contributed independently to circulating zonulin variance. In conclusion, the relationship between insulin sensitivity and circulating zonulin might be mediated through the obesity-related circulating IL-6 increase.

  14. Role of platelets in maintenance of pulmonary vascular permeability to protein

    Lo, S.K.; Burhop, K.E.; Kaplan, J.E.; Malik, A.B.

    1988-01-01

    The authors examined the role of platelets in maintenance of pulmonary vascular integrity by inducing thrombocytopenia in sheep using antiplatelet serum (APS). A causal relationship between thrombocytopenia and increase in pulmonary vascular permeability was established by platelet repletion using platelet-rich plasma (PRP). Sheep were chronically instrumented and lung lymph fistulas prepared to monitor pulmonary lymph flow (Q lym ). A balloon catheter was positioned in the left atrium to assess pulmonary vascular permeability to protein after raising the left atrial pressure (P la ). Thrombocytopenia was maintained for 3 days by daily intramuscular APS injections. In studies using cultured bovine pulmonary artery endothelial monolayers, transendothelia permeability of 125 I-labeled albumin was reduced 50 and 95%, respectively, when 2.5 x 10 7 or 5 x 10 7 platelets were added onto endothelial monolayers. However, addition of 5 x 10 6 platelets or 5 x 10 7 red blood cells did not reduce endothelial monolayer albumin permeability. Results indicate that platelets are required for the maintenance of pulmonary vascular permeability. Reduction in permeability appears to involve an interaction of platelets with the endothelium

  15. Studies on the increase of capillary permeability in rat skin under the action of pyridoxal 5' phosphate

    Garcia Agudo, N.L. del M. de.

    1979-01-01

    The activity of pyridoxal 5'-phosphate (PLP) is described on the vascular permeability response, measured in the abdominal wall of rats from the amount of extravased Evans blue labelled with radioactive iodine 125 or 131. The PLP effect is related to histamine release as it has been showed by tha use of antihistaminics. An attempt has been made in order to correlate structure and biological activity by using PLP analogs. The intact molecule of PLP seems to be the proper active substance. The critical role of calcium in histamine release is discussed in relation to our observations. In the presence of high concentrations of calcium and lantanium, PLP fails to increase the vascular permeability; magnesium does not show any influence. The calcium mobilization produced by theophylline results in inhibition of the response. The course of the reaction between PLP and histamine in vitro was followed; the synthetic cyclic product is deprived of activity and does not interfere with the intrinsic effects of PLP and histamine. (Author) [pt

  16. Increase of radiation damage to potassium-ion permeability in E. coli cells with decrease in membrane fluidity

    Suzuki, S.

    1980-01-01

    Membrane lipids of an auxotroph of E. coli requiring unsaturated fatty acid were manipulated by supplementing the growth medium with unsaturated fatty acids of different chain lengths and/or configurations, and the radiation damage to K + -permeability of the resulting modified cells was investigated in relation with factors influencing membrane fluidity, such as temperature and procaine. Radiation had greater effects on membranes supplemented with unsaturated fatty acids of the trans configuration with a longer chain than on those of the cis configuration with a shorter chain. Radiation damage also increased with decrease in temperature. Furthermore, procaine-treated membranes showed increased resistance to radiation. All these results indicate that the damage was affected by the physical character of membrane lipids and that it was greater in membranes with decreased fluidity. (author)

  17. The exhibition to ozone diminishes the adherence and increases the membrane permeability of macrophages alveolar of rate

    Garcia, J.

    2000-01-01

    Ozone gas is generated photochemically in areas with high levels of automotive or industrial emissions, and causes irritation and inflammation of the airways if inhaled. Rat alveolar macrophages were obtained by lung lavage from male Sprague Dawley rats and used as a model to assess ozone induced cell damage (0,594 ppm for up to 60 minutes). Ozone exposure caused loss of cell adherence to a polystyrene substrate and increased membrane permeability, as noted by increases in specific 51 Cr release and citoplasmic calcium levels. The results indicate that the cell membrane is a target for ozone damage. Elevations of cytoplasmic calcium could mediate other macrophage responses to ozone , including eicosanoid and nitric oxide production, with concomitant decreases in phagocytic ability and superoxide production. (Author) [es

  18. The Effect of Excipients on the Permeability of BCS Class III Compounds and Implications for Biowaivers.

    Parr, Alan; Hidalgo, Ismael J; Bode, Chris; Brown, William; Yazdanian, Mehran; Gonzalez, Mario A; Sagawa, Kazuko; Miller, Kevin; Jiang, Wenlei; Stippler, Erika S

    2016-01-01

    Currently, the FDA allows biowaivers for Class I (high solubility and high permeability) and Class III (high solubility and low permeability) compounds of the Biopharmaceutics Classification System (BCS). Scientific evidence should be provided to support biowaivers for BCS Class I and Class III (high solubility and low permeability) compounds. Data on the effects of excipients on drug permeability are needed to demonstrate that commonly used excipients do not affect the permeability of BCS Class III compounds, which would support the application of biowaivers to Class III compounds. This study was designed to generate such data by assessing the permeability of four BCS Class III compounds and one Class I compound in the presence and absence of five commonly used excipients. The permeability of each of the compounds was assessed, at three to five concentrations, with each excipient in two different models: Caco-2 cell monolayers, and in situ rat intestinal perfusion. No substantial increases in the permeability of any of the compounds were observed in the presence of any of the tested excipients in either of the models, with the exception of disruption of Caco-2 cell monolayer integrity by sodium lauryl sulfate at 0.1 mg/ml and higher. The results suggest that the absorption of these four BCS Class III compounds would not be greatly affected by the tested excipients. This may have implications in supporting biowaivers for BCS Class III compounds in general.

  19. Glutathione metabolism in Bangladeshi children with increased small bowel permeability and impaired growth

    Roy, S.K.; Tomkins, A.; Johson, A.

    1994-01-01

    In addition to requiring an increased concentration of protein, dietary treatments for children during convalescence from malnutrition may require additions of selected amino acids to meet increased requirements. However, relatively little is known about the quantities of amino acids to use in the supplements. This project will test the hypothesis that requirements for sulphur-containing amino acids (SCAA) are increased during malnutrition and diarrhea. The primary mechanism by which requirements for SCAA might be increased under these conditions are that SCAA may be restricted at the growth plates in bones through shunting of the available sulphur to other biological processes with higher physiological priority. In this study, evidence of the SCAA being diverted to other uses will be increased rates of turnover of glutathione (GSH), a sulphur-containing tripeptide with functions including stimulation of lymphocyte production and immune function. Further evidence of the diversion of SCAA to GSH and away from the larger metabolic pool will be decreased urinary inorganic sulphate excretion (ISE), and increased urinary concentrations of proline peptides which arise from collagen breakdown. It is expected that appropriate supplementation of a standard recovery diet will meet the requirement for GSH synthesis, thereby freeing the SCAA for growth plates, increasing the incorporation of proline into collage, and will have the overall effect of stimulating growth. (author). 29 refs, 3 tabs

  20. Glutathione metabolism in Bangladeshi children with increased small bowel permeability and impaired growth

    Roy, S K [International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDRB) (India); Tomkins, A; Johson, A [Centre for International Child Health (CICH), London (United Kingdom)

    1994-12-31

    In addition to requiring an increased concentration of protein, dietary treatments for children during convalescence from malnutrition may require additions of selected amino acids to meet increased requirements. However, relatively little is known about the quantities of amino acids to use in the supplements. This project will test the hypothesis that requirements for sulphur-containing amino acids (SCAA) are increased during malnutrition and diarrhea. The primary mechanism by which requirements for SCAA might be increased under these conditions are that SCAA may be restricted at the growth plates in bones through shunting of the available sulphur to other biological processes with higher physiological priority. In this study, evidence of the SCAA being diverted to other uses will be increased rates of turnover of glutathione (GSH), a sulphur-containing tripeptide with functions including stimulation of lymphocyte production and immune function. Further evidence of the diversion of SCAA to GSH and away from the larger metabolic pool will be decreased urinary inorganic sulphate excretion (ISE), and increased urinary concentrations of proline peptides which arise from collagen breakdown. It is expected that appropriate supplementation of a standard recovery diet will meet the requirement for GSH synthesis, thereby freeing the SCAA for growth plates, increasing the incorporation of proline into collage, and will have the overall effect of stimulating growth. (author). 29 refs, 3 tabs.

  1. [Biological availability of ophthalmic drugs. 1. Increasing drug permeability in the cornea].

    Masteiková, R; Chalupová, Z; Savickiene, N

    2004-03-01

    Most eye diseases are treated by topical administration of ophthalmic preparations. Low ophthalmic bioavailability is due to a number of physiological and physicochemical factors. The main obstacle to the penetration of active ingredients to the eye is the layered character of the cornea. Formulation of ophthalmic preparations enabling easier penetration of this biological barrier thus ranks among the most effective ways of improving bioavailability. Penetrability of the cornea can be increased by the following methods: a) adjustment of the actual acidity in such a way that pH of the preparation makes it possible to produce the optimal portion of non-ionized particles; b) incorporation of absorption enhancers (non-ionic tensides, salts of bile acids, some antimicrobial substances, EDTA, cyclodextrins, etc.) into the composition of the preparation, and c) production of prodrugs or ionic pairs.

  2. Increased permeability-oedema and atelectasis in pulmonary dysfunction after trauma and surgery: a prospective cohort study

    Groeneveld AB Johan

    2007-07-01

    Full Text Available Abstract Background Trauma and surgery may be complicated by pulmonary dysfunction, acute lung injury (ALI and acute respiratory distress syndrome (ARDS, but the mechanisms are incompletely understood. Methods We evaluated lung capillary protein permeability non-invasively with help of the 67Ga-transferrin pulmonary leak index (PLI technique and extravascular lung water (EVLW by the transpulmonary thermal-dye dilution technique in consecutive, mechanically ventilated patients in the intensive care unit within 24 h of direct, blunt thoracic trauma (n = 5, 2 with ARDS, and within 12 h of indirect trauma by transhiatal oesophagectomy (n = 8, abdominal surgery for cancer (n = 6 and bone surgery (n = 4. We studied transfusion history, haemodynamics, oxygenation and mechanics of the lungs. The lung injury score (LIS, 0–4 was calculated. Plain radiography was also done to judge densities and atelectasis. Results The PLI and EVLW were elevated above normal in 61 and 30% of patients, respectively, and the PLI directly related to the number of red cell concentrates given (rs = 0.69, P s = 0.55, P = 0.007. Thoracic trauma patients had a worse oxygenation requiring higher airway pressures and thus higher LIS than the other patient groups, unrelated to PLI and EVLW but attributable to a higher cardiac output and thereby venous admixture. Finally, patients with radiographic signs of atelectasis had more impaired oxygenation and more densities than those without. Conclusion The oxygenation defect and radiographic densities in mechanically ventilated patients with pulmonary dysfunction and ALI/ARDS after trauma and surgery are likely caused by atelectasis rather than by increased permeability-oedema related to red cell transfusion.

  3. Porosity and permeability evolution of vesicular basalt reservoirs with increasing depth: constraints from the Big Island of Hawai'i

    Millett, John; Haskins, Eric; Thomas, Donald; Jerram, Dougal; Planke, Sverre; Healy, Dave; Kück, Jochem; Rossetti, Lucas; Farrell, Natalie; Pierdominici, Simona

    2017-04-01

    Volcanic reservoirs are becoming increasingly important in the targeting of petroleum, geothermal and water resources globally. However, key areas of uncertainty in relation to volcanic reservoir properties during burial in different settings remain. In this contribution, we present results from borehole logging and sampling operations within two fully cored c. 1.5 km deep boreholes, PTA2 and KMA1, from the Humúula saddle region on the Big Island of Hawai'i. The boreholes were drilled as part of the Humu'ula Groundwater Research Project (HGRP) between 2013-2016 and provide unique insights into the evolution of pore structure with increasing burial in a basaltic dominated lava sequence. The boreholes encounter mixed sequences of 'a'ā, pāhoehoe and transitional lava flows along with subsidiary intrusions and sediments from the shield to post-shield phases of Mauna Kea. Borehole wireline data including sonic, spectral gamma and Televiewer imagery were collected along with density, porosity, permeability and ultrasonic velocity laboratory measurements from core samples. A range of intra-facies were sampled for analysis from various depths within the two boreholes. By comparison with core data, the potential for high resolution Televiewer imaging to reveal spectacular intra-facies features including individual vesicles, vesicle segregations, 'a'ā rubble zones, intrusive contacts, and intricate pāhoehoe lava flow lobe morphologies is demonstrated. High quality core data enables the calibration of Televiewer facies enabling improved interpretation of volcanic reservoir features in the more common exploration scenario where core is absent. Laboratory results record the ability of natural vesicular basalt samples to host very high porosity (>50%) and permeability (>10 darcies) within lava flow top facies which we demonstrate are associated with vesicle coalescence and not micro-fractures. These properties may be maintained to depths of c. 1.5 km in regions of limited

  4. Simvastatin Ameliorates Matrix Stiffness-Mediated Endothelial Monolayer Disruption.

    Marsha C Lampi

    Full Text Available Arterial stiffening accompanies both aging and atherosclerosis, and age-related stiffening of the arterial intima increases RhoA activity and cell contractility contributing to increased endothelium permeability. Notably, statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase inhibitors whose pleiotropic effects include disrupting small GTPase activity; therefore, we hypothesized the statin simvastatin could be used to attenuate RhoA activity and inhibit the deleterious effects of increased age-related matrix stiffness on endothelial barrier function. Using polyacrylamide gels with stiffnesses of 2.5, 5, and 10 kPa to mimic the physiological stiffness of young and aged arteries, endothelial cells were grown to confluence and treated with simvastatin. Our data indicate that RhoA and phosphorylated myosin light chain activity increase with matrix stiffness but are attenuated when treated with the statin. Increases in cell contractility, cell-cell junction size, and indirect measurements of intercellular tension that increase with matrix stiffness, and are correlated with matrix stiffness-dependent increases in monolayer permeability, also decrease with statin treatment. Furthermore, we report that simvastatin increases activated Rac1 levels that contribute to endothelial barrier enhancing cytoskeletal reorganization. Simvastatin, which is prescribed clinically due to its ability to lower cholesterol, alters the endothelial cell response to increased matrix stiffness to restore endothelial monolayer barrier function, and therefore, presents a possible therapeutic intervention to prevent atherogenesis initiated by age-related arterial stiffening.

  5. Bactericidal/Permeability-increasing protein fold-containing family member A1 in airway host protection and respiratory disease.

    Britto, Clemente J; Cohn, Lauren

    2015-05-01

    Bactericidal/permeability-increasing protein fold-containing family member A1 (BPIFA1), formerly known as SPLUNC1, is one of the most abundant proteins in respiratory secretions and has been identified with increasing frequency in studies of pulmonary disease. Its expression is largely restricted to the respiratory tract, being highly concentrated in the upper airways and proximal trachea. BPIFA1 is highly responsive to airborne pathogens, allergens, and irritants. BPIFA1 actively participates in host protection through antimicrobial, surfactant, airway surface liquid regulation, and immunomodulatory properties. Its expression is modulated in multiple lung diseases, including cystic fibrosis, chronic obstructive pulmonary disease, respiratory malignancies, and idiopathic pulmonary fibrosis. However, the role of BPIFA1 in pulmonary pathogenesis remains to be elucidated. This review highlights the versatile properties of BPIFA1 in antimicrobial protection and its roles as a sensor of environmental exposure and regulator of immune cell function. A greater understanding of the contribution of BPIFA1 to disease pathogenesis and activity may clarify if BPIFA1 is a biomarker and potential drug target in pulmonary disease.

  6. Circulating Zonulin, a Marker of Intestinal Permeability, Is Increased in Association with Obesity-Associated Insulin Resistance

    Moreno-Navarrete, José María; Sabater, Mònica; Ortega, Francisco; Ricart, Wifredo; Fernández-Real, José Manuel

    2012-01-01

    Zonulin is the only physiological mediator known to regulate intestinal permeability reversibly by modulating intercellular tight junctions. To investigate the relationship between intestinal permeability and obesity-associated metabolic disturbances in humans, we aimed to study circulating zonulin according to obesity and insulin resistance. Circulating zonulin (ELISA) was measured in 123 caucasian men in association with inflammatory and metabolic parameters (including minimal model-measure...

  7. Leucocyte depletion attenuates the early increase in myocardial capillary permeability to small hydrophilic solutes following ischaemia and reperfusion

    Svendsen, Jesper Hastrup; Hansen, P R; Ali, S

    1993-01-01

    The aim was to assess the significance of polymorphonuclear leucocytes on the myocardial capillary permeability to a small hydrophilic indicator, on the vascular tone of the resistance vessels, and on contractile function following ischaemia and reperfusion.......The aim was to assess the significance of polymorphonuclear leucocytes on the myocardial capillary permeability to a small hydrophilic indicator, on the vascular tone of the resistance vessels, and on contractile function following ischaemia and reperfusion....

  8. Zonulin transgenic mice show altered gut permeability and increased morbidity/mortality in the DSS colitis model.

    Sturgeon, Craig; Lan, Jinggang; Fasano, Alessio

    2017-06-01

    Increased small intestinal permeability (IP) has been proposed to be an integral element, along with genetic makeup and environmental triggers, in the pathogenies of chronic inflammatory diseases (CIDs). We identified zonulin as a master regular of intercellular tight junctions linked to the development of several CIDs. We aim to study the role of zonulin-mediated IP in the pathogenesis of CIDs. Zonulin transgenic Hp2 mice (Ztm) were subjected to dextran sodium sulfate (DSS) treatment for 7 days, followed by 4-7 days' recovery and compared to C57Bl/6 (wild-type (WT)) mice. IP was measured in vivo and ex vivo, and weight, histology, and survival were monitored. To mechanistically link zonulin-dependent impairment of small intestinal barrier function with clinical outcome, Ztm were treated with the zonulin inhibitor AT1001 added to drinking water in addition to DSS. We observed increased morbidity (more pronounced weight loss and colitis) and mortality (40-70% compared with 0% in WT) at 11 days post-DSS treatment in Ztm compared with WT mice. Both in vivo and ex vivo measurements showed an increased IP at baseline in Ztm compared to WT mice, which was exacerbated by DSS treatment and was associated with upregulation of zonulin gene expression (fourfold in the duodenum, sixfold in the jejunum). Treatment with AT1001 prevented the DSS-induced increased IP both in vivo and ex vivo without changing zonulin gene expression and completely reverted morbidity and mortality in Ztm. Our data show that zonulin-dependent small intestinal barrier impairment is an early step leading to the break of tolerance with subsequent development of CIDs. © 2017 New York Academy of Sciences.

  9. Importance of the terminal α-amino group of bradykinin and some kynins on capillary permeability increase

    Sugavara, S.

    1979-01-01

    A simple and reliable method is described for the quantitative evaluation of vascular permeability increase induced by vasoactive drugs with Evans blue labelled with iodine-125 or 131. By using this method the importance of α-amino group of bradykinin (Bk), kallidin (Kd) and methionyl-kallidin (Met-Kd) on the biological activity were studied after reacting the kinins with pyridoxal 5'-phosphate followed by reduction with sodium borohydride. Phosphopyridoxyl-kinins were formed leaving free the guanidino groups. Aminoacid analysis of phosphopyridoxyl-kinin showed that the efficiency of the reaction was extremely good in the blockage of α-amino groups [phosphopyridoxyl-bradikinin (PP-Bk) = 98,8%, phosphopyridoxyl-kallidin (PP-Kd) = 95,2%, phosphopyridoxyl-methionyl-kallidin (PP-Met-Kd) = 98,0%. Log dose-response curves were obtained for Bk, Kd, Met-Kd, acetyl-bradykinin (Ac-Bk), PP-Bk, PP-Kd and PP-Met-Kd and the relative potencies calculated through the Lineweaver-Burk plots. The relative potencies were: PP-Bk about 16% the activity of Bk, Ac-Bk about 31% the activity of Bk, PP-Kd about 17% the activity of Kd, PP-Met-Kd about 12% the activity of Met-Kd. The results show that the terminal α-amino group of kinins is important in the mechanisms of biological activity. (Author) [pt

  10. Zonulin level, a marker of intestinal permeability, is increased in association with liver enzymes in young adolescents.

    Kim, Ji Hee; Heo, Ju Sun; Baek, Kyung Suk; Kim, Soo-Yeon; Kim, Jung Hyun; Baek, Kwang-Hyun; Kim, Ki Eun; Sheen, Youn Ho

    2018-06-01

    Zonulin is acknowledged as the only physiological mediator established to reversibly regulate intestinal permeability through modulation of intercellular tight junctions. We aimed to determine whether there are differences in zonulin levels between 74 subjects with overweight or obesity and 76 with normal-weight and to assess correlations of circulating zonulin levels with anthropometric measures and obesity-related biomarkers. We assessed anthropometric and laboratory measures, including body mass index (BMI) z-score, blood pressure, liver enzymes, lipid profiles, and insulin resistance. Serum zonulin levels were measured using an enzyme-linked immunosorbent assay. The mean age of the participants was 12.8 ± 1.5 years. Circulating serum zonulin levels were significantly increased in subjects with overweight/obesity compared with those of normal-weight (P = 0.03). Zonulin levels were significantly and positively associated with BMI z-score, alanine aminotransferase levels, triglyceride, fasting insulin, and insulin resistance as indicated by the homeostatic model assessment of insulin resistance (HOMA-IR) (all P zonulin levels in adolescents with overweight or obesity (P zonulin levels in this subgroup analysis (P = 0.06). Serum zonulin is a biomarker associated with hepatic metabolic disturbances in young adolescents with overweight or obesity. The positive relationship suggests a potentially relevant pathophysiological mechanism linking zonulin to hepatic metabolism in this age group of young adolescents with overweight or obesity. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Phase transitions in surfactant monolayers

    Casson, B.D.

    1998-01-01

    Two-dimensional phase transitions have been studied in surfactant monolayers at the air/water interface by sum-frequency spectroscopy and ellipsometry. In equilibrium monolayers of medium-chain alcohols C n H 2n+1 OH (n = 9-14) a transition from a two-dimensional crystalline phase to a liquid was observed at temperatures above the bulk melting point. The small population of gauche defects in the solid phase increased only slightly at the phase transition. A model of the hydrocarbon chains as freely rotating rigid rods allowed the area per molecule and chain tilt in the liquid phase to be determined. The area per molecule, chain tilt and density of the liquid phase all increased with increasing chain length, but for each chain length the density was higher than in a bulk liquid hydrocarbon. In a monolayer of decanol adsorbed at the air/water interface a transition from a two-dimensional liquid to a gas was observed. A clear discontinuity in the coefficient of ellipticity as a function of temperature showed that the transition is first-order. This result suggests that liquid-gas phase transitions in surfactant monolayers may be more widespread than once thought. A solid-liquid phase transition has also been studied in mixed monolayers of dodecanol with an anionic surfactant (sodium dodecyl sulphate) and with a homologous series of cationic surfactants (alkyltrimethylammonium bromides: C n TABs, n = 12, 14, 16). The composition and structure of the mixed monolayers was studied above and below the phase transition. At low temperatures the mixed monolayers were as densely packed as a monolayer of pure dodecanol in its solid phase. At a fixed temperature the monolayers under-went a first-order phase transition to form a phase that was less dense and more conformationally disordered. The proportion of ionic surfactant in the mixed monolayer was greatest in the high temperature phase. As the chain length of the C n TAB increased the number of conformational defects

  12. Sodium butyrate attenuates soybean oil-based lipid emulsion-induced increase in intestinal permeability of lipopolysaccharide by modulation of P-glycoprotein in Caco-2 cells

    Yan, Jun-Kai; Gong, Zi-Zhen; Zhang, Tian; Cai, Wei

    2017-01-01

    Down-regulation of intestinal P-glycoprotein (P-gp) by soybean oil-based lipid emulsion (SOLE) may cause elevated intestinal permeability of lipopolysaccharide (LPS) in patients with total parenteral nutrition, but the appropriate preventative treatment is currently limited. Recently, sodium butyrate (NaBut) has been demonstrated to regulate the expression of P-gp. Therefore, this study aimed to address whether treatment with NaBut could attenuate SOLE-induced increase in intestinal permeability of LPS by modulation of P-gp in vitro. Caco-2 cells were exposed to SOLE with or without NaBut. SOLE-induced down-regulation of P-gp was significantly attenuated by co-incubation with NaBut. Nuclear recruitment of FOXO 3a in response to NaBut was involved in P-gp regulation. Transport studies revealed that SOLE-induced increase in permeability of LPS was significantly attenuated by co-incubation with NaBut. Collectively, our results suggested that NaBut may be a potentially useful medication to prevent SOLE-induced increase in intestinal permeability of LPS. - Highlights: • Caco-2 cells were used as models for studying parenteral nutrition in vitro. • NaBut restored SOLE-induced down-regulation of P-gp in Caco-2 cells. • Regulation of P-gp by NaBut was mediated via nuclear recruitment of FOXO 3a. • NaBut modulated the permeability of LPS by P-gp function, not barrier function.

  13. Crustal permeability

    Gleeson, Tom; Ingebritsen, Steven E.

    2016-01-01

    Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures.  The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration.  Although there are thousands of research papers on crustal permeability, this is the first book-length treatment.  This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. 

  14. Conductivity Evolution of Fracture Proppant in Partial Monolayers and Multilayers

    Fan, M.; Han, Y.; McClure, J. E.; Chen, C.

    2017-12-01

    Proppant is a granular material, typically sand, coated sand, or man-made ceramic materials, which is widely used in hydraulic fracturing to keep the induced fractures open. Optimization of proppant placement in a hydraulic fracture, as well as its role on the fracture's conductivity, is vital for effective and economical production of petroleum hydrocarbons. In this research, a numerical modeling approach, combining Discrete Element Method (DEM) with lattice Boltzmann (LB) method, was adopted to advance the understanding of fracture conductivity as function of proppant concentration under various effective stresses. DEM was used to simulate effective stress increase and the resultant proppant particle compaction and rearrangement during the process of reservoir depletion due to hydrocarbon extraction. DEM-simulated pore structure was extracted and imported into the LB simulator as boundary conditions to calculate the time-dependent permeability of the proppant pack. We first validated the DEM-LB coupling workflow; the simulated proppant pack permeabilities as functions of effective stress were in good agreement with laboratory measurements. Next, several proppant packs were generated with various proppant concentrations, ranging from partial-monolayer to multilayer structures. Proppant concentration is defined as proppant mass per unit fracture face area. Fracture conductivity as function of proppant concentration was measured in LB simulations. It was found that a partial-monolayer proppant pack with large-diameter particles was optimal in maintaining sufficient conductivity while lowering production costs. Three proppant packs with the same average diameter but different diameter distributions were generated. Specifically, we used the coefficient of variation (COV) of diameter, defined as the ratio of standard deviation of diameter to mean diameter, to characterize the heterogeneity in particle size. We obtained proppant pack porosity, permeability, and fracture

  15. Retinal pathology is associated with increased blood-retina barrier permeability in a diabetic and hypercholesterolaemic pig model: Beneficial effects of the LpPLA2 inhibitor Darapladib.

    Acharya, Nimish K; Qi, Xin; Goldwaser, Eric L; Godsey, George A; Wu, Hao; Kosciuk, Mary C; Freeman, Theresa A; Macphee, Colin H; Wilensky, Robert L; Venkataraman, Venkat; Nagele, Robert G

    2017-05-01

    Using a porcine model of diabetes mellitus and hypercholesterolaemia, we previously showed that diabetes mellitus and hypercholesterolaemia is associated with a chronic increase in blood-brain barrier permeability in the cerebral cortex, leading to selective binding of immunoglobulin G and deposition of amyloid-beta 1-42 peptide in pyramidal neurons. Treatment with Darapladib (GlaxoSmithKline, SB480848), an inhibitor of lipoprotein-associated phospholipase-A2, alleviated these effects. Here, investigation of the effects of chronic diabetes mellitus and hypercholesterolaemia on the pig retina revealed a corresponding increased permeability of the blood-retina barrier coupled with a leak of plasma components into the retina, alterations in retinal architecture, selective IgG binding to neurons in the ganglion cell layer, thinning of retinal layers due to cell loss and increased glial fibrillary acidic protein expression in Müller cells, all of which were curtailed by treatment with Darapladib. These findings suggest that chronic diabetes mellitus and hypercholesterolaemia induces increased blood-retina barrier permeability that may be linked to altered expression of blood-retina barrier-associated tight junction proteins, claudin and occludin, leading to structural changes in the retina consistent with diabetic retinopathy. Additionally, results suggest that drugs with vascular anti-inflammatory properties, such as Darapladib, may have beneficial effects on eye diseases strongly linked to vascular abnormalities such as diabetic retinopathy and age-related macular degeneration.

  16. Notional Permeability

    Kik, R.; Van den Bos, J.P.; Maertens, J.; Verhagen, H.J.; Van der Meer, J.W.

    2012-01-01

    Different layer design of a rock slope and under layers has a large effect on the strengths on the rock slope itself. In the stability formula developed of VAN DER MEER [1988] this effect is represented by the term Notional Permeability with symbol P. A more open, or permeable, structure underneath

  17. Measurement of the increase in the capillary permeability in skin with Evans blue labelled with iodine-125 or 131

    Sugarava, S.; Goncalves, J.M.

    1976-01-01

    The quantitative evaluation of bradykinin and histamine with Evans blue labelled with iodine -125 or 131 is described. The activity upon vascular permeability was performed in the abdominal wall of rats injecting intravenously solution of labelled Evans blue and 0,1 ml of vasoactive drugs solution intradermally. Skin discs were cut with circular punch for external counting, quantitative results being compared with control discs. By using this method, satisfactory log dose-reponse curves were obtained for bradykinin and histamine that followed the general trend of S - shaped curves [pt

  18. Human Lysozyme Synergistically Enhances Bactericidal Dynamics and Lowers the Resistant Mutant Prevention Concentration for Metronidazole to Helicobacter pylori by Increasing Cell Permeability

    Xiaolin Zhang

    2016-10-01

    Full Text Available Metronidazole (MNZ is an effective agent that has been employed to eradicate Helicobacter pylori (H. pylori. The emergence of broad MNZ resistance in H. pylori has affected the efficacy of this therapeutic agent. The concentration of MNZ, especially the mutant prevention concentration (MPC, plays an important role in selecting or enriching resistant mutants and regulating therapeutic effects. A strategy to reduce the MPC that can not only effectively treat H. pylori but also prevent resistance mutations is needed. H. pylori is highly resistant to lysozyme. Lysozyme possesses a hydrolytic bacterial cell wall peptidoglycan and a cationic dependent mode. These effects can increase the permeability of bacterial cells and promote antibiotic absorption into bacterial cells. In this study, human lysozyme (hLYS was used to probe its effects on the integrity of the H. pylori outer and inner membranes using as fluorescent probe hydrophobic 1-N-phenyl-naphthylamine (NPN and the release of aspartate aminotransferase. Further studies using a propidium iodide staining method assessed whether hLYS could increase cell permeability and promote cell absorption. Finally, we determined the effects of hLYS on the bactericidal dynamics and MPC of MNZ in H. pylori. Our findings indicate that hLYS could dramatically increase cell permeability, reduce the MPC of MNZ for H. pylori, and enhance its bactericidal dynamic activity, demonstrating that hLYS could reduce the probability of MNZ inducing resistance mutations.

  19. Sicilian pistachio (Pistacia vera L.) nut inhibits expression and release of inflammatory mediators and reverts the increase of paracellular permeability in IL-1β-exposed human intestinal epithelial cells.

    Gentile, C; Perrone, A; Attanzio, A; Tesoriere, L; Livrea, M A

    2015-08-01

    Dietary approaches to control inflammatory bowel diseases (IBD) may include proanthocyanidin-rich foods. Our previous research showed that a hydrophilic extract from Sicilian pistachio nut (HPE) contains substantial amounts of proanthocyanidins and possesses anti-inflammatory activities. We studied the effects of HPE and of its polymeric proanthocyanidin fraction (PPF) in a cell model that simulated some conditions of IBD, consisting of interleukin (IL)-1β-stimulated Caco-2 cells. HPE was prepared by Pistacia vera L. nuts, and PPF was isolated from HPE by adsorbance chromatography. Proanthocyanidins were quantified as anthocyanidins after acidic hydrolysis. Differentiated Caco-2 cells were pre-incubated with HPE or PPF and then were exposed to IL-1β. Cell viability and parameters associated with nuclear factor-κB (NF-κB) activation were assayed. Adsorption of polymeric proanthocyanidins to the cell membrane was investigated by transepithelial electrical resistance (TEER) measurements. HPE decreased prostaglandin (PG)E2 production, IL-6 and IL-8 release, and cyclooxygenase (COX)-2 expression. HPE also inhibited the increase in paracellular permeability and reduced NF-κB activation. Polymeric proanthocyanidins, tested at a concentration comparable with their content in HPE, produced effects comparable to HPE. Finally, cell exposure to PPF increases TEER of the epithelial monolayers. Our results provide evidence that pistachio nut components inhibit inflammatory response of intestinal epithelial cells in vitro and indicate polymeric proanthocyanidins as the major bioactive nut components. The protection implies inhibition of NF-κB activation and occurs in parallel with the adsorption of polymeric proanthocyanidins to cell membrane. Our findings suggest that intake of small amounts of pistachio nut can exert beneficial effects to gastrointestinal pathophysiology.

  20. Dietary soya saponins increase gut permeability and play a key role in the onset of soyabean-induced enteritis in Atlantic salmon ( Salmo salar L.).

    Knudsen, David; Jutfelt, Fredrik; Sundh, Henrik; Sundell, Kristina; Koppe, Wolfgang; Frøkiaer, Hanne

    2008-07-01

    Saponins are naturally occurring amphiphilic molecules and have been associated with many biological activities. The aim of the present study was to investigate whether soya saponins trigger the onset of soyabean-induced enteritis in Atlantic salmon (Salmo salar L.), and to examine if dietary soya saponins increase the epithelial permeability of the distal intestine in Atlantic salmon. Seven experimental diets containing different levels of soya saponins were fed to seawater-adapted Atlantic salmon for 53 d. The diets included a fishmeal-based control diet, two fishmeal-based diets with different levels of added soya saponins, one diet containing 25% lupin kernel meal, two diets based on 25% lupin kernel meal with different levels of added soya saponins, and one diet containing 25% defatted soyabean meal. The effect on intestinal morphology, intestinal epithelial permeability and faecal DM content was examined. Fish fed 25% defatted soyabean meal displayed severe enteritis, whereas fish fed 25% lupin kernel meal had normal intestinal morphology. The combination of soya saponins and fishmeal did not induce morphological changes but fish fed soya saponins in combination with lupin kernel meal displayed significant enteritis. Increased epithelial permeability was observed in fish fed 25% defatted soyabean meal and in fish fed soya saponin concentrate independent of the protein source in the feed. The study demonstrates that soya saponins, in combination with one or several unidentified components present in legumes, induce an inflammatory reaction in the distal intestine of Atlantic salmon. Soya saponins increase the intestinal epithelial permeability but do not, per se, induce enteritis.

  1. Minoxidil sulfate induced the increase in blood-brain tumor barrier permeability through ROS/RhoA/PI3K/PKB signaling pathway.

    Gu, Yan-ting; Xue, Yi-xue; Wang, Yan-feng; Wang, Jin-hui; Chen, Xia; ShangGuan, Qian-ru; Lian, Yan; Zhong, Lei; Meng, Ying-nan

    2013-12-01

    Adenosine 5'-triphosphate-sensitive potassium channel (KATP channel) activator, minoxidil sulfate (MS), can selectively increase the permeability of the blood-tumor barrier (BTB); however, the mechanism by which this occurs is still under investigation. Using a rat brain glioma (C6) model, we first examined the expression levels of occludin and claudin-5 at different time points after intracarotid infusion of MS (30 μg/kg/min) by western blotting. Compared to MS treatment for 0 min group, the protein expression levels of occludin and claudin-5 in brain tumor tissue of rats showed no changes within 1 h and began to decrease significantly after 2 h of MS infusion. Based on these findings, we then used an in vitro BTB model and selective inhibitors of diverse signaling pathways to investigate whether reactive oxygen species (ROS)/RhoA/PI3K/PKB pathway play a key role in the process of the increase of BTB permeability induced by MS. The inhibitor of ROS or RhoA or PI3K or PKB significantly attenuated the expression of tight junction (TJ) protein and the increase of the BTB permeability after 2 h of MS treatment. In addition, the significant increases in RhoA activity and PKB phosphorylation after MS administration were observed, which were partly inhibited by N-2-mercaptopropionyl glycine (MPG) or C3 exoenzyme or LY294002 pretreatment. The present study indicates that the activation of signaling cascades involving ROS/RhoA/PI3K/PKB in BTB was required for the increase of BTB permeability induced by MS. Taken together, all of these results suggested that MS might increase BTB permeability in a time-dependent manner by down-regulating TJ protein expression and this effect could be related to ROS/RhoA/PI3K/PKB signal pathway. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Dietary soya saponins increase gut permeability and play a key role in the onset of soyabean-induced enteritis in Atlantic salmon (Salmo salar L.)

    Knudsen, Sven David Lausten; Jutfelt, Fredrik; Sundh, Henrik

    2008-01-01

    are naturally occurring amphiphilic molecules and have been associated with many biological activities. The aim of the present study was to investigate whether soya saponins trigger the onset of soyabean-induced enteritis in Atlantic salmon (Salmo salar L.), and to examine if dietary soya saponins...... increase the epithelial permeability of the distal intestine in Atlantic salmon. Seven experimental diets containing different levels of soya saponins were fed to seawater-adapted Atlantic salmon for 53 d. The diets included a fishmeal-based control diet, two fishmeal-based diets with different levels...... of added soya saponins, one diet containing 25 % lupin kernel meal, two diets based on 25 % lupin kernel meal with different levels of added soya saponins, and one diet containing 25 % defatted soyabean meal. The effect on intestinal morphology, intestinal epithelial permeability and faecal DM content...

  3. Transport of surface engineered polyamidoamine (PAMAM) dendrimers across IPEC-J2 cell monolayers.

    Pisal, Dipak S; Yellepeddi, Venkata K; Kumar, Ajay; Palakurthi, Srinath

    2008-11-01

    The aim of our study was to prepare arginine-and ornithine-conjugated Polyamidoamine (PAMAM) dendrimers and study their permeability across IPEC-J2 cell monolayers, a new intestinal cell line model for drug absorption studies. Arginine and ornithine were conjugated to the amine terminals of the PAMAM(G4) dendrimers by Fmoc synthesis. The apical-to-basolateral (AB) and basolateral-to-apical (BA) apparent permeability coefficients (P(app)) for the PAMAM dendrimers increased by conjugating the dendrimers with both of these polyamines. The enhancement in permeability was dependent on the dendrimer concentration and duration of incubation. Correlation between monolayer permeability and the decrease in transepithelial electrical resistance (TEER) with the PAMAM dendrimers and the polyamine-conjugated dendrimers suggests that paracellular transport is one of the mechanisms of transport across the epithelial cells. Cytotoxicity of these surface-modified dendrimers was evaluated in IPEC-J2 cells by MTT (methylthiazoletetrazolium) assay. Arginine-conjugated dendrimers were insignificantly more toxic than PAMAM dendrimer as well as ornithine-conjugated dendrimers. Though investigations on the possible involvement of other transport mechanisms are in progress, results of the present study suggest the potential of dendrimer-polyamine conjugates as the carriers for antigen/drug delivery through the oral mucosa.

  4. Concentrations of lipopolysaccharide-binding protein, bactericidal/permeability-increasing protein, soluble CD14 and plasma lipids in relation to endotoxaemia in patients with alcoholic liver disease

    Schäfer, C.; Parlesak, Alexandr; Schütt, C.

    2002-01-01

    of endotoxin on its target cells (LPS-binding protein and sCD14) were increased. Endotoxin antagonists, such as bactericidal/permeability-increasing protein and high-density lipoprotein, were increased in the pre-cirrhotic stages, whereas a significant reduction of the latter was observed in cirrhosis. Low......-density lipoprotein remained unchanged. The elevation of binding factors in the pre-cirrhotic stages of alcoholic liver disease might attenuate the effects of endotoxaemia, whereas in cirrhosis the reduction of high density lipoprotein, to which large quantities of endotoxin bind, may contribute to its pro...

  5. Indicaxanthin inhibits NADPH oxidase (NOX)-1 activation and NF-κB-dependent release of inflammatory mediators and prevents the increase of epithelial permeability in IL-1β-exposed Caco-2 cells.

    Tesoriere, L; Attanzio, A; Allegra, M; Gentile, C; Livrea, M A

    2014-02-01

    Dietary redox-active/antioxidant phytochemicals may help control or mitigate the inflammatory response in chronic inflammatory bowel disease (IBD). In the present study, the anti-inflammatory activity of indicaxanthin (Ind), a pigment from the edible fruit of cactus pear (Opuntia ficus-indica, L.), was shown in an IBD model consisting of a human intestinal epithelial cell line (Caco-2 cells) stimulated by IL-1β, a cytokine known to play a major role in the initiation and amplification of inflammatory activity in IBD. The exposure of Caco-2 cells to IL-1β brought about the activation of NADPH oxidase (NOX-1) and the generation of reactive oxygen species (ROS) to activate intracellular signalling leading to the activation of NF-κB, with the over-expression of inflammatory enzymes and release of pro-inflammatory mediators. The co-incubation of the cells with Ind, at a nutritionally relevant concentration (5-25 μM), and IL-1β prevented the release of the pro-inflammatory cytokines IL-6 and IL-8, PGE2 and NO, the formation of ROS and the loss of thiols in a dose-dependent manner. The co-incubation of the cells with Ind and IL-1β also prevented the IL-1β-induced increase of epithelial permeability. It was also shown that the activation of NOX-1 and NF-κB was prevented by Ind and the expression of COX-2 and inducible NO synthase was reduced. The uptake of Ind in Caco-2 cell monolayers appeared to be unaffected by the inflamed state of the cells. In conclusion, our findings suggest that the dietary pigment Ind may have the potential to modulate inflammatory processes at the intestinal level.

  6. Permeable pavement study (Edison)

    U.S. Environmental Protection Agency — While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types...

  7. Alpha-Melanocyte Stimulating Hormone Protects against Cytokine-Induced Barrier Damage in Caco-2 Intestinal Epithelial Monolayers.

    Judit Váradi

    Full Text Available Alpha-melanocyte-stimulating hormone (α-MSH is a potent anti-inflammatory peptide with cytoprotective effect in various tissues. The present investigation demonstrates the ability of α-MSH to interact with intestinal epithelial cell monolayers and mitigate inflammatory processes of the epithelial barrier. The protective effect of α-MSH was studied on Caco-2 human intestinal epithelial monolayers, which were disrupted by exposure to tumor necrosis factor-α and interleukin-1β. The barrier integrity was assessed by measuring transepithelial electric resistance (TEER and permeability for marker molecules. Caco-2 monolayers were evaluated by immunohistochemistry for expression of melanocortin-1 receptor and tight junction proteins ZO-1 and claudin-4. The activation of nuclear factor kappa beta (NF-κB was detected by fluorescence microscopy and inflammatory cytokine expression was assessed by flow cytometric bead array cytokine assay. Exposure of Caco-2 monolayers to proinflammatory cytokines lowered TEER and increased permeability for fluorescein and albumin, which was accompanied by changes in ZO-1 and claudin-4 immunostaining. α-MSH was able to prevent inflammation-associated decrease of TEER in a dose-dependent manner and reduce the increased permeability for paracellular marker fluorescein. Further immunohistochemistry analysis revealed proinflammatory cytokine induced translocation of the NF-κB p65 subunit into Caco-2 cell nuclei, which was inhibited by α-MSH. As a result the IL-6 and IL-8 production of Caco-2 monolayers were also decreased with different patterns by the addition of α-MSH to the culture medium. In conclusion, Caco-2 cells showed a positive immunostaining for melanocortin-1 receptor and α-MSH protected Caco-2 cells against inflammatory barrier dysfunction and inflammatory activation induced by tumor necrosis factor-α and interleukin-1β cytokines.

  8. Methamphetamine transiently increases the blood-brain barrier permeability in the hippocampus: role of tight junction proteins and matrix metalloproteinase-9.

    Martins, Tânia; Baptista, Sofia; Gonçalves, Joana; Leal, Ermelindo; Milhazes, Nuno; Borges, Fernanda; Ribeiro, Carlos F; Quintela, Oscar; Lendoiro, Elena; López-Rivadulla, Manuel; Ambrósio, António F; Silva, Ana P

    2011-09-09

    Methamphetamine (METH) is a powerful stimulant drug of abuse that has steadily gained popularity worldwide. It is known that METH is highly neurotoxic and causes irreversible damage of brain cells leading to neurological and psychiatric abnormalities. Recent studies suggested that METH-induced neurotoxicity might also result from its ability to compromise blood-brain barrier (BBB) function. Due to the crucial role of BBB in the maintenance of brain homeostasis and protection against toxic molecules and pathogenic organisms, its dysfunction could have severe consequences. In this study, we investigated the effect of an acute high dose of METH (30mg/kg) on BBB permeability after different time points and in different brain regions. For that, young adult mice were sacrificed 1h, 24h or 72h post-METH administration. METH increased BBB permeability, but this effect was detected only at 24h after administration, being therefore a transitory effect. Interestingly, we also found that the hippocampus was the most susceptible brain region to METH, comparing to frontal cortex and striatum. Moreover, in an attempt to identify the key players in METH-induced BBB dysfunction we further investigated potential alterations in tight junction (TJ) proteins and matrix metalloproteinase-9 (MMP-9). METH was able to decrease the protein levels of zonula occludens (ZO)-1, claudin-5 and occludin in the hippocampus 24h post-injection, and increased the activity and immunoreactivity of MMP-9. The pre-treatment with BB-94 (30mg/kg), a matrix metalloproteinase inhibitor, prevented the METH-induced increase in MMP-9 immunoreactivity in the hippocampus. Overall, the present data demonstrate that METH transiently increases the BBB permeability in the hippocampus, which can be explained by alterations on TJ proteins and MMP-9. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Permeability of porour rhyolite

    Cashman, K.; Rust, A.; Wright, H.; Roberge, J.

    2003-04-01

    The development of permeability in bubble-bearing magmas determines the efficiency of volatile escape during their ascent through volcanic conduits, which, in turn, controls their explosive potential. As permeability requires bubble connectivity, relationships between permeability and porosity in silicic magmas must be controlled by the formation, growth, deformation and coalescence of their constituent bubbles. Although permeability data on porous volcanic pyroclasts are limited, the database can be greatly extended by including data for ceramic and metallic foams1. Several studies indicate that a single number does not adequately describe the permeability of a foam because inertial effects, which predominate at high flow rates, cause deviations from Darcy's law. These studies suggest that permeability is best modeled using the Forschheimer equation to determine both the Darcy permeability (k1) and the non-Darcian (k2) permeability. Importantly, at the high porosities of ceramic foams (75-95%), both k1 and k2 are strongly dependent on pore size and geometry, suggesting that measurement of these parameters provides important information on foam structure. We determined both the connected porosity (by He-pycnometry) and the permeability (k1 and k2) of rhyolitic samples having a wide range in porosity (22-85%) and vesicle textures. In general, these data support previous observations of a power law relationship between connected porosity and Darcy permeability2. In detail, variations in k1 increase at higher porosities. Similarly, k2 generally increases in both mean and standard deviation with increasing porosity. Measurements made on three mutually perpendicular cores from individual pumice clasts suggest that some of the variability can be explained by anisotropy in the vesicle structure. By comparison with ceramic foams, we suggest that the remaining variability results from differences either in average vesicle size or, more likely, in the size of apertures

  10. Research and application of multi-hydrogen acidizing technology of low-permeability reservoirs for increasing water injection

    Ning, Mengmeng; Che, Hang; Kong, Weizhong; Wang, Peng; Liu, Bingxiao; Xu, Zhengdong; Wang, Xiaochao; Long, Changjun; Zhang, Bin; Wu, Youmei

    2017-12-01

    The physical characteristics of Xiliu 10 Block reservoir is poor, it has strong reservoir inhomogeneity between layers and high kaolinite content of the reservoir, the scaling trend of fluid is serious, causing high block injection well pressure and difficulty in achieving injection requirements. In the past acidizing process, the reaction speed with mineral is fast, the effective distance is shorter and It is also easier to lead to secondary sedimentation in conventional mud acid system. On this point, we raised multi-hydrogen acid technology, multi-hydrogen acid release hydrogen ions by multistage ionization which could react with pore blockage, fillings and skeletal effects with less secondary pollution. Multi-hydrogen acid system has advantages as moderate speed, deep penetration, clay low corrosion rate, wet water and restrains precipitation, etc. It can reach the goal of plug removal in deep stratum. The field application result shows that multi-hydrogen acid plug removal method has good effects on application in low permeability reservoir in Block Xiliu 10.

  11. Intestinal Permeability: The Basics

    Ingvar Bjarnason

    1995-01-01

    Full Text Available The authors review some of the more fundamental principles underlying the noninvasive assessment of intestinal permeability in humans, the choice of test markers and their analyses, and the practical aspects of test dose composition and how these can be changed to allow the specific assessment of regional permeability changes and other intestinal functions. The implications of increased intestinal permeability in the pathogenesis of human disease is discussed in relation to findings in patients with Crohn’s disease. A common feature of increased intestinal permeability is the development of a low grade enteropathy, and while quantitatively similar changes may be found in Crohn’s disease these seem to predict relapse of disease. Moreover, factors associated with relapse of Crohn’s disease have in common an action to increase intestinal permeability. While increased intestinal permeability does not seem to be important in the etiology of Crohn’s disease it may be a central mechanism in the clinical relapse of disease.

  12. MiR-144 Increases Intestinal Permeability in IBS-D Rats by Targeting OCLN and ZO1

    Qiuke Hou

    2017-12-01

    Full Text Available Background/Aims: Irritable bowel syndrome with diarrhoea (IBS-D is a chronic, functional bowel disorder characterized by abdominal pain or diarrhoea and altered bowel habits, which correlate with intestinal hyperpermeability. MicroRNAs (miRNAs are involved in regulating intestinal permeability in IBS-D. However, the role of miRNAs in regulating intestinal permeability and protecting the epithelial barrier remains unclear. Our goals were to (i identify differential expression of miRNAs and their targets in the distal colon of IBS-D rats; (ii verify in vitro whether occludin (OCLN and zonula occludens 1 (ZO1/TJP1 were direct targets of miR-144 and were down-regulated in IBS-D rats; and (iii determine whether down-regulation of miR-144 in vitro could reverse the pathological hallmarks of intestinal hyperpermeability via targeting OCLN and ZO1. Methods: The IBS-D rat model was established using 4% acetic acid and evaluated by haematoxylin-eosin (HE staining. The distal colon was obtained in order to perform miRNA microarray analysis and to isolate and culture colonic epithelial cells. When differential expression of miRNA was found, the results were verified by qRT-PCR, and the target genes were further explored by bioinformatics analysis. Correlation analyses were carried out to compare the expression of miRNA and target genes. Then, mutants, miRNA mimics and inhibitors of the target genes were constructed and transfected to colonic epithelial cells. qRT-PCR, western blotting, enzyme-linked immunosorbent assays (ELISAs and dual-luciferase assays were used to investigate the expression of miR-144 and OCLN, ZO1 in IBS-D rats. Results: There were 8 up-regulated and 18 down-regulated miRNAs identified in the IBS-D rat model. Of these, miR-144 was markedly up-regulated and resulted in the down-regulation of OCLN and ZO1 expression. Overexpression of miR-144 by transfection of miR-144 precursor markedly inhibited the expression of OCLN and ZO1. Further

  13. Preparation and Photoluminescence of Tungsten Disulfide Monolayer

    Yanfei Lv

    2018-05-01

    Full Text Available Tungsten disulfide (WS2 monolayer is a direct band gap semiconductor. The growth of WS2 monolayer hinders the progress of its investigation. In this paper, we prepared the WS2 monolayer through chemical vapor transport deposition. This method makes it easier for the growth of WS2 monolayer through the heterogeneous nucleation-and-growth process. The crystal defects introduced by the heterogeneous nucleation could promote the photoluminescence (PL emission. We observed the strong photoluminescence emission in the WS2 monolayer, as well as thermal quenching, and the PL energy redshift as the temperature increases. We attribute the thermal quenching to the energy or charge transfer of the excitons. The redshift is related to the dipole moment of WS2.

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

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

    2015-01-05

    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

  15. Ischemia and reperfusion of the lung tissues induced increase of lung permeability and lung edema is attenuated by dimethylthiourea (PP69).

    Chen, K H; Chao, D; Liu, C F; Chen, C F; Wang, D

    2010-04-01

    This study sought to determine whether oxygen radical scavengers of dimethylthiourea (DMTU), superoxide dismutase (SOD), or catalase (CAT) pretreatment attenuated ischemia-reperfusion (I/R)-induced lung injury. After isolation from a Sprague-Dawley rat, the lungs were perfused through the pulmonary artery cannula with rat whole blood diluted 1:1 with a physiological salt solution. An acute lung injury was induced by 10 minutes of hypoxia with 5% CO2-95% N2 followed by 65 minutes of ischemia and then 65 minutes of reperfusion. I/R significantly increased microvascular permeability as measured by the capillary filtration coefficient (Kfc), lung weight-to-body weight ratio (LW/BW), and protein concentration in bronchoalveolar lavage fluid (PCBAL). DMTU pretreatment significantly attenuated the acute lung injury. The capillary filtration coefficient (P<.01), LW/BW (P<.01) and PCBAL (P<.05) were significantly lower among the DMTU-treated rats than hosts pretreated with SOD or CAT. The possible mechanisms of the protective effect of DMTU in I/R-induced lung injury may relate to the permeability of the agent allowing it to scavenge intracellular hydroxyl radicals. However, whether superoxide dismutase or catalase antioxidants showed protective effects possibly due to their impermeability of the cell membrane not allowing scavenging of intracellular oxygen radicals. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  16. Role of permissive hypotension, hypertonic resuscitation and the global increased permeability syndrome in patients with severe hemorrhage: adjuncts to damage control resuscitation to prevent intra-abdominal hypertension.

    Duchesne, Juan C; Kaplan, Lewis J; Balogh, Zsolt J; Malbrain, Manu L N G

    2015-01-01

    Secondary intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are closely related to fluid resuscitation. IAH causes major deterioration of the cardiac function by affecting preload, contractility and afterload. The aim of this review is to discuss the different interactions between IAH, ACS and resuscitation, and to explore a new hypothesis with regard to damage control resuscitation, permissive hypotension and global increased permeability syndrome. Review of the relevant literature via PubMed search. The recognition of the association between the development of ACS and resuscitation urged the need for new approach in traumatic shock management. Over a decade after wide spread application of damage control surgery damage control resuscitation was developed. DCR differs from previous resuscitation approaches by attempting an earlier and more aggressive correction of coagulopathy, as well as metabolic derangements like acidosis and hypothermia, often referred to as the 'deadly triad' or the 'bloody vicious cycle'. Permissive hypotension involves keeping the blood pressure low enough to avoid exacerbating uncontrolled haemorrhage while maintaining perfusion to vital end organs. The potential detrimental mechanisms of early, aggressive crystalloid resuscitation have been described. Limitation of fluid intake by using colloids, hypertonic saline (HTS) or hyperoncotic albumin solutions have been associated with favourable effects. HTS allows not only for rapid restoration of circulating intravascular volume with less administered fluid, but also attenuates post-injury oedema at the microcirculatory level and may improve microvascular perfusion. Capillary leak represents the maladaptive, often excessive, and undesirable loss of fluid and electrolytes with or without protein into the interstitium that generates oedema. The global increased permeability syndrome (GIPS) has been articulated in patients with persistent systemic inflammation failing

  17. Miscibility of dl-α-tocopherol β-glucoside in DPPC monolayer at air/water and air/solid interfaces

    Neunert, G. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Makowiecki, J.; Piosik, E.; Hertmanowski, R. [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland); Polewski, K. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Martynski, T., E-mail: tomasz.martynski@put.poznan.pl [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland)

    2016-10-01

    The role of newly synthesized tocopherol glycosidic derivative in modifying molecular organization and phase transitions of phospholipid monolayer at the air/water interface has been investigated. Two-component Langmuir films of dl-α-tocopheryl β-D-glucopyranoside (BG) mixed with dipalmitoyl phosphatidylcholine (DPPC) in the whole range of mole fractions were formed at the water surface. An analysis of surface pressure versus mean molecular area (π-A) isotherms and Brewster angle microscope images showed that the presence of BG molecules changes the structure and packing of the DPPC monolayer in a BG concentration dependent manner. BG molecules incorporated into DPPC monolayer inhibit its liquid expanded to liquid condensed phase transition proportionally to the BG concentration. The monolayers were also transferred onto solid substrates and visualized using an atomic force microscope. The results obtained indicate almost complete miscibility of BG and DPPC in the monolayers at surface pressures present in the biological cell membrane (30-35·10{sup -3} N·m{sup -1}) for a BG mole fraction as high as 0.3. This makes the monolayer less packed and more disordered, leading to an increased permeability. The results support our previous molecular dynamics simulation data. - Highlights: • Langmuir films of α-tocopherol derivative with DPPC was studied thermodynamically. • Mixed DPPC/BG films were transferred onto mica substrates for topography imaging by using AFM. • Miscibility of BG/DPPC films at surface pressures present in membranes was observed up to MF = 0.3.

  18. 3-Dimensional culture systems for anti-cancer compound profiling and high-throughput screening reveal increases in EGFR inhibitor-mediated cytotoxicity compared to monolayer culture systems.

    Howes, Amy L; Richardson, Robyn D; Finlay, Darren; Vuori, Kristiina

    2014-01-01

    3-dimensional (3D) culture models have the potential to bridge the gap between monolayer cell culture and in vivo studies. To benefit anti-cancer drug discovery from 3D models, new techniques are needed that enable their use in high-throughput (HT) screening amenable formats. We have established miniaturized 3D culture methods robust enough for automated HT screens. We have applied these methods to evaluate the sensitivity of normal and tumorigenic breast epithelial cell lines against a panel of oncology drugs when cultured as monolayers (2D) and spheroids (3D). We have identified two classes of compounds that exhibit preferential cytotoxicity against cancer cells over normal cells when cultured as 3D spheroids: microtubule-targeting agents and epidermal growth factor receptor (EGFR) inhibitors. Further improving upon our 3D model, superior differentiation of EC50 values in the proof-of-concept screens was obtained by co-culturing the breast cancer cells with normal human fibroblasts and endothelial cells. Further, the selective sensitivity of the cancer cells towards chemotherapeutics was observed in 3D co-culture conditions, rather than as 2D co-culture monolayers, highlighting the importance of 3D cultures. Finally, we examined the putative mechanisms that drive the differing potency displayed by EGFR inhibitors. In summary, our studies establish robust 3D culture models of human cells for HT assessment of tumor cell-selective agents. This methodology is anticipated to provide a useful tool for the study of biological differences within 2D and 3D culture conditions in HT format, and an important platform for novel anti-cancer drug discovery.

  19. Lung function declines in patients with pulmonary sarcoidosis and increased respiratory epithelial permeability to 99mTc-DTPA

    Chinet, T.; Dusser, D.; Labrune, S.; Collignon, M.A.; Chretien, J.; Huchon, G.J.

    1990-01-01

    Respiratory epithelial clearance of 99m Tc-DTPA (RC-Tc-DTPA) and pulmonary function tests (PFT) were determined at intervals of 6 or 12 months in 37 untreated, nonsmoking patients with sarcoidosis over a period of 6 to 36 months. PFT included the measurements of total lung capacity (TLC), vital capacity (VC), FEV1, and diffusing capacity for carbon monoxide. No difference was found between the respiratory clearance of 113m In-DTPA (2.25 +/- 1.00%/min) and RC-Tc-DTPA (2.29 +/- 1.11%/min) in eight patients with pulmonary sarcoidosis. Pulmonary function decreased 15% or more in at least 2 function tests during 11 follow-up periods, but it remained stable during 47 follow-up periods. In patients whose lung function deteriorated, RC-Tc-DTPA increased to 3.51 +/- 1.55%/min; in contrast, in patients whose lung function remained stable, regardless of the initial values, RC-Tc-DTPA was normal (1.00 +/- 0.50%/min; p less than 0.001). In eight patients who were treated with corticosteroids, RC-Tc-DTPA decreased from 3.48 +/- 1.31%/min to 1.56 +/- 0.64%/min (p less than 0.001), and PFT improved. We conclude that in nonsmokers with pulmonary sarcoidosis, increased RC-Tc-DTPA is not related to dissociation of 99mTc from DTPA, RC-Tc-DTPA is increased when pulmonary function decreases, and, when increased, RC-Tc-DTPA decreases with corticosteroid therapy

  20. Reduced cerebral glucose metabolism and increased brain capillary permeability following high-dose methotrexate chemotherapy: a positron emission tomographic study

    Phillips, P.C.; Dhawan, V.; Strother, S.C.; Sidtis, J.J.; Evans, A.C.; Allen, J.C.; Rottenberg, D.A.

    1987-01-01

    Regional glucose metabolic rate constants and blood-to-brain transport of rubidium were estimated using positron emission tomography in an adolescent patient with a brain tumor, before and after chemotherapy with intravenous high-dose methotrexate. Widespread depression of cerebral glucose metabolism was apparent 24 hours after drug administration, which may reflect reduced glucose phosphorylation, and the influx rate constant for 82 Rb was increased, indicating a drug-induced alteration in blood-brain barrier function. Associated changes in neuropsychological performance, electroencephalogram, and plasma amino acid concentration were identified in the absence of evidence of systemic methotrexate toxicity, suggesting primary methotrexate neurotoxicity

  1. Bovine colostrum increases pore-forming claudin-2 protein expression but paradoxically not ion permeability possibly by a change of the intestinal cytokine milieu.

    Peggy Bodammer

    Full Text Available An impaired intestinal barrier function is involved in the pathogenesis of inflammatory bowel disease (IBD. Several nutritional factors are supposed to be effective in IBD treatment but scientific data about the effects on the intestinal integrity remain scarce. Bovine colostrum was shown to exert beneficial effects in DSS-induced murine colitis, and the present study was undertaken to explore the underlying molecular mechanisms. Western blot revealed increased claudin-2 expression in the distal ileum of healthy mice after feeding with colostrum for 14 days, whereas other tight junction proteins (claudin-3, 4, 10, 15 remained unchanged. The colostrum-induced claudin-2 induction was confirmed in differentiated Caco-2 cells after culture with colostrum for 48 h. Paradoxically, the elevation of claudin-2, which forms a cation-selective pore, was neither accompanied by increased ion permeability nor impaired barrier function. In an in situ perfusion model, 1 h exposure of the colonic mucosa to colostrum induced significantly increased mRNA levels of barrier-strengthening cytokine transforming growth factor-β, while interleukine-2, interleukine-6, interleukine-10, interleukine-13, and tumor-necrosis factor-α remained unchanged. Thus, modulation of the intestinal transforming growth factor-β expression might have compensated the claudin-2 increase and contributed to the observed barrier strengthening effects of colostrum in vivo and in vitro.

  2. Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin.

    Kuck, Jamie L; Bastarache, Julie A; Shaver, Ciara M; Fessel, Joshua P; Dikalov, Sergey I; May, James M; Ware, Lorraine B

    2018-01-01

    Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity. Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of 14 C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC. CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability. CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Diamondoid monolayers as electron emitters

    Yang, Wanli [El Cerrito, CA; Fabbri, Jason D [San Francisco, CA; Melosh, Nicholas A [Menlo Park, CA; Hussain, Zahid [Orinda, CA; Shen, Zhi-Xun [Stanford, CA

    2012-04-10

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  4. Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines.

    Drago, Sandro; El Asmar, Ramzi; Di Pierro, Mariarosaria; Grazia Clemente, Maria; Tripathi, Amit; Sapone, Anna; Thakar, Manjusha; Iacono, Giuseppe; Carroccio, Antonio; D'Agate, Cinzia; Not, Tarcisio; Zampini, Lucia; Catassi, Carlo; Fasano, Alessio

    2006-04-01

    Little is known about the interaction of gliadin with intestinal epithelial cells and the mechanism(s) through which gliadin crosses the intestinal epithelial barrier. We investigated whether gliadin has any immediate effect on zonulin release and signaling. Both ex vivo human small intestines and intestinal cell monolayers were exposed to gliadin, and zonulin release and changes in paracellular permeability were monitored in the presence and absence of zonulin antagonism. Zonulin binding, cytoskeletal rearrangement, and zonula occludens-1 (ZO-1) redistribution were evaluated by immunofluorescence microscopy. Tight junction occludin and ZO-1 gene expression was evaluated by real-time polymerase chain reaction (PCR). When exposed to gliadin, zonulin receptor-positive IEC6 and Caco2 cells released zonulin in the cell medium with subsequent zonulin binding to the cell surface, rearrangement of the cell cytoskeleton, loss of occludin-ZO1 protein-protein interaction, and increased monolayer permeability. Pretreatment with the zonulin antagonist FZI/0 blocked these changes without affecting zonulin release. When exposed to luminal gliadin, intestinal biopsies from celiac patients in remission expressed a sustained luminal zonulin release and increase in intestinal permeability that was blocked by FZI/0 pretreatment. Conversely, biopsies from non-celiac patients demonstrated a limited, transient zonulin release which was paralleled by an increase in intestinal permeability that never reached the level of permeability seen in celiac disease (CD) tissues. Chronic gliadin exposure caused down-regulation of both ZO-1 and occludin gene expression. Based on our results, we concluded that gliadin activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.

  5. Polymeric nanoparticles for increased oral bioavailability and rapid absorption using celecoxib as a model of a low-solubility, high-permeability drug.

    Morgen, Michael; Bloom, Corey; Beyerinck, Ron; Bello, Akintunde; Song, Wei; Wilkinson, Karen; Steenwyk, Rick; Shamblin, Sheri

    2012-02-01

    To demonstrate drug/polymer nanoparticles can increase the rate and extent of oral absorption of a low-solubility, high-permeability drug. Amorphous drug/polymer nanoparticles containing celecoxib were prepared using ethyl cellulose and either sodium caseinate or bile salt. Nanoparticles were characterized using dynamic light scattering, transmission and scanning electron microscopy, and differential scanning calorimetry. Drug release and resuspension studies were performed using high-performance liquid chromatography. Pharmacokinetic studies were performed in dogs and humans. A physical model is presented describing the nanoparticle state of matter and release performance. Nanoparticles dosed orally in aqueous suspensions provided higher systemic exposure and faster attainment of peak plasma concentrations than commercial capsules, with median time to maximum drug concentration (Tmax) of 0.75 h in humans for nanoparticles vs. 3 h for commercial capsules. Nanoparticles released celecoxib rapidly and provided higher dissolved-drug concentrations than micronized crystalline drug. Nanoparticle suspensions are stable for several days and can be spray-dried to form dry powders that resuspend in water. Drug/polymer nanoparticles are well suited for providing rapid oral absorption and increased bioavailability of BCS Class II drugs.

  6. Monolayer atomic crystal molecular superlattices

    Wang, Chen; He, Qiyuan; Halim, Udayabagya; Liu, Yuanyue; Zhu, Enbo; Lin, Zhaoyang; Xiao, Hai; Duan, Xidong; Feng, Ziying; Cheng, Rui; Weiss, Nathan O.; Ye, Guojun; Huang, Yun-Chiao; Wu, Hao; Cheng, Hung-Chieh; Shakir, Imran; Liao, Lei; Chen, Xianhui; Goddard, William A., III; Huang, Yu; Duan, Xiangfeng

    2018-03-01

    Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.

  7. Contrasting suspended covers reveal the impact of an artificial monolayer on heat transfer processes at the interfacial boundary layer.

    Pittaway, P; Martínez-Alvarez, V; Hancock, N

    2015-01-01

    The highly variable performance of artificial monolayers in reducing evaporation from water storages has been attributed to wind speed and wave turbulence. Other factors operating at the interfacial boundary layer have seldom been considered. In this paper, two physical shade covers differing in porosity and reflectivity were suspended over 10 m diameter water tanks to attenuate wind and wave turbulence. The monolayer octadecanol was applied to one of the covered tanks, and micrometeorological conditions above and below the covers were monitored to characterise diurnal variation in the energy balance. A high downward (air-to-water) convective heat flux developed under the black cover during the day, whereas diurnal variation in the heat flux under the more reflective, wind-permeable white cover was much less. Hourly air and water temperature profiles under the covers over 3 days when forced convection was minimal (low wind speed) were selected for analysis. Monolayer application reduced temperature gain in surface water under a downward convective heat flux, and conversely reduced temperature loss under an upward convective heat flux. This 'dual property' may explain why repeat application of an artificial monolayer to retard evaporative loss (reducing latent heat loss) does not inevitably increase water temperature.

  8. Foam film permeability: theory and experiment.

    Farajzadeh, R; Krastev, R; Zitha, Pacelli L J

    2008-02-28

    The mass transfer of gas through foam films is a prototype of various industrial and biological processes. The aim of this paper is to give a perspective and critical overview of studies carried out to date on the mass transfer of gas through foam films. Contemporary experimental data are summarized, and a comprehensive overview of the theoretical models used to explain the observed effects is given. A detailed description of the processes that occur when a gas molecule passes through each layer that forms a foam film is shown. The permeability of the film-building surfactant monolayers plays an important role for the whole permeability process. It can be successfully described by the models used to explain the permeability of surfactant monolayers on aqueous sub-phase. For this reason, the present paper briefly discusses the surfactant-induced resistance to mass transfer of gases through gas-liquid interface. One part of the paper discusses the experimental and theoretical aspects of the foam film permeability in a train of foam films in a matrix or a cylinder. This special case is important to explain the gas transfer in porous media or in foams. Finally, this paper will highlight the gaps and challenges and sketch possible directions for future research.

  9. Permeability Increase with Deep Borehole Controlled Pre-cracking Blasting Technology in Low Permeability and High Gassy Seam"%低透气性高瓦斯煤层深孔控制预裂爆破增透技术

    弓美疆; 池鹏; 张明杰

    2012-01-01

    为了解决低透气性高瓦斯煤层难抽采问题,运用RFPA2D数值模拟软件,建立了2种深孔控制预裂爆破力学模型,通过对模拟结果进行对比分析,得出一套适用于鹤煤八矿底板抽采的爆破参数,并进行了现场试验,爆破后煤层透气性系数平均值达到了2.23 m2/(MPa2.d),比爆破前测定的煤层原始透气性平均值提高了近3.05倍,说明该技术可以明显提高钻孔周围煤体裂隙发育程度,煤体透气性增加,达到了提高煤层瓦斯抽采量和抽采率的目的。%In order to solve the difficult gas drainage problem in low permeability and high gassy seam, the RFPA2D numerical simulation software was applied to establish two deep borehole controlled pre-cracking blasting mechanics models. With the comparison and analysis on the simulation results, a set of blasting parameters obtained which were suitable for floor gas drainage in No. 8 mine of Hegang Coal Mining and the site trial with the parameters was conducted. The results showed that after the blasting, the average value of the seam per- meability coefficient reached at 2. 23 m2/ ( MPa2 ·d) and 3.05 times higher than the average value of the seam in-situ permeability be- fore the blasting conducted. Thus the technology could obviously improve the cracking development degree of coal around the borehole and could improve the permeability of the seam. The target to improve the seam gas drainage value and the gas drainage rate could be reached.

  10. Increased intestinal permeability to macromolecules and endotoxemia in patients with chronic alcohol abuse in different stages of alcohol-induced liver disease

    Parlesak, Alexandr; Schäfer, C.; Schütz, Tanja

    2000-01-01

    BACKGROUND/AIMS: No information is yet available about the influence of alcohol abuse on the translocation of larger molecules (Mr>1200) through the intestinal mucosa in man. The present study aimed to determine the intestinal permeability to macromolecules in patients with chronic alcohol abuse...... and mild to more advanced stages of liver disease, and to measure the concentration of endotoxins in the plasma, as these compounds derive from the intestinal flora and are suspected to contribute to the development of alcoholic liver disease (ALD). METHODS: The permeability to polyethylene glycol Mr 400......, Mr 1500, Mr 4000, and Mr 10,000 and endotoxin plasma concentrations were measured in 54 patients with alcoholic liver disease, 19 of them with cirrhosis, and in 30 non-alcoholic healthy controls. RESULTS: Permeability to polyethylene glycol Mr 400 was found to be unchanged in patients with ALD...

  11. Effect of permeability enhancers on paracellular permeability of acyclovir.

    Ates, Muge; Kaynak, Mustafa Sinan; Sahin, Selma

    2016-06-01

    According to Biopharmaceutics Classification System (BCS), acyclovir is a class III (high solubility, low permeability) compound, and it is transported through paracellular route by passive diffusion. The aim of this study was to investigate the effect of various pharmaceutical excipients on the intestinal permeability of acyclovir. The single-pass in-situ intestinal perfusion (SPIP) method was used to estimate the permeability values of acyclovir and metoprolol across different intestinal segments (jejunum, ileum and colon). Permeability coefficient (Peff ) of acyclovir was determined in the absence and presence of a permeation enhancer such as dimethyl β-cyclodextrin (DM-β-CD), sodium lauryl sulfate (SLS), sodium caprate (Cap-Na) and chitosan chloride. All enhancers increased the permeability of paracellularly transported acyclovir. Although Cap-Na has the highest permeability-enhancing effect in all segments, permeation-enhancing effect of chitosan and SLS was only significant in ileum. On the other hand, DM-β-CD slightly decreased the permeability in all intestinal segments. These findings have potential implication concerning the enhancement of absorption of paracellularly transported compounds with limited oral bioavailability. In the case of acyclovir, Cap-Na either alone or in combination with SLS or chitosan has the potential to improve its absorption and bioavailability and has yet to be explored. © 2016 Royal Pharmaceutical Society.

  12. Rhubarb Antagonizes Matrix Metalloproteinase-9-induced Vascular Endothelial Permeability

    Yun-Liang Cui

    2016-01-01

    Conclusions: The rhubarb mixture of emodin, 3,8-dihydroxy-1-methyl-anthraquinone-2-carboxylic acid, 1-O-caffeoyl-2-(4-hydroxyl-O-cinnamoyl-β-D-glucose, daucosterol linoleate, and rhein, at a low concentration, antagonized the MMP9-induced HUVEC monolayer permeability by promoting HUVEC proliferation and reducing extracellular VE-cadherin concentrations.

  13. Effect of Salt Forms of Chitosan on In Vitro Permeability ...

    Purpose: To investigate the effect of chitosan (CS) salt forms and pH condition on the transepithelial electrical resistance (TEER) of Caco-2 cell monolayer for enhanced permeability. Methods: Solutions (2 %w/v) of four different salt forms of CS-aspartate (CS-A), CS-ethylene diamine tetraacetate (CS-EDTA), ...

  14. WSe2 Monolayer

    Zhang, Shuai; Wang, Chen-Guang; Li, Ming-yang; Huang, Di; Li, Lain-Jong; Ji, Wei; Wu, Shiwei

    2017-01-01

    dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work

  15. Permeability testing of biomaterial membranes

    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.

  16. Permeability testing of biomaterial membranes

    Dreesmann, L; Hajosch, R; Nuernberger, J Vaz; Schlosshauer, B; Ahlers, M

    2008-01-01

    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

  17. Developments in permeable and low permeability barriers

    Jefferis, S.A.; Norris, G.H.; Thomas, A.O.

    1997-01-01

    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

  18. Beneficial Effects of Anti-Interleukin-6 Antibodies on Impaired Gastrointestinal Motility, Inflammation and Increased Colonic Permeability in a Murine Model of Sepsis Are Most Pronounced When Administered in a Preventive Setup.

    Sara Nullens

    Full Text Available During sepsis, gastrointestinal ileus, mucosal barrier dysfunction and bacterial translocation are accepted to be important triggers that can maintain or exacerbate the septic state. In the caecal ligation and puncture animal model of sepsis, we demonstrated that systemic and colonic interleukin-6 levels are significantly increased coinciding with an impaired colonic barrier function. We therefore aimed to study the effect of therapeutic or curative administration of anti-IL6 antibodies on overall GI motility, colonic permeability and translocation of intestinal bacteria in blood and mesenteric lymph nodes in the mouse caecal ligation and puncture model.OF-1 mice were randomized to either the preventive or curative protocol, in which they received 1 mg/kg of antibodies to interleukin-6, or its IgG isotype control solution. They subsequently underwent either the caecal ligation and puncture procedure, or sham-surgery. GI motility was assessed 48 h following the procedure, as well as colonic permeability, serum and colon cytokines, colonic tight junction proteins at the mRNA level; cultures of blood and mesenteric lymph nodes were performed.Preventive administration of anti-interleukin-6 antibodies successfully counteracted the gastrointestinal motility disturbances and impaired colonic barrier function that could be observed in vehicle-treated septic animals. Serum and colonic levels of proinflammatory cytokines were significantly lower when animals were preventively treated with anti-interleukin-6 antibodies. A repetitive injection 24 h later resulted in the most pronounced effects. Curative treatment significantly lowered systemic and colonic inflammation markers while the effects on transit and permeability were unfortunately no longer significant.Caecal ligation and puncture resulted in septic ileus with an increased colonic permeability. Antibodies to interleukin-6 were able to ameliorate gastro-intestinal motility, suppress inflammation and

  19. Automation of cell-based drug absorption assays in 96-well format using permeable support systems.

    Larson, Brad; Banks, Peter; Sherman, Hilary; Rothenberg, Mark

    2012-06-01

    Cell-based drug absorption assays, such as Caco-2 and MDCK-MDR1, are an essential component of lead compound ADME/Tox testing. The permeability and transport data they provide can determine whether a compound continues in the drug discovery process. Current methods typically incorporate 24-well microplates and are performed manually. Yet the need to generate absorption data earlier in the drug discovery process, on an increasing number of compounds, is driving the use of higher density plates. A simple, more efficient process that incorporates 96-well permeable supports and proper instrumentation in an automated process provides more reproducible data compared to manual methods. Here we demonstrate the ability to perform drug permeability and transport assays using Caco-2 or MDCKII-MDR1 cells. The assay procedure was automated in a 96-well format, including cell seeding, media and buffer exchanges, compound dispense, and sample removal using simple robotic instrumentation. Cell monolayer integrity was confirmed via transepithelial electrical resistance and Lucifer yellow measurements. Proper cell function was validated by analyzing apical-to-basolateral and basolateral-to-apical movement of rhodamine 123, a known P-glycoprotein substrate. Apparent permeability and efflux data demonstrate how the automated procedure provides a less variable method than manual processing, and delivers a more accurate assessment of a compound's absorption characteristics.

  20. Pressure-dependent optical and vibrational properties of monolayer molybdenum disulfide

    Nayak, Avinash P.; Pandey, Tribhuwan; Voiry, Damien; Liu, Jin; Moran, Samuel T.; Sharma, Ankit; Tan, Cheng; Chen, Changhsiao; Li, Lain-Jong; Chhowalla, Manish U.; Lin, Jungfu; Singh, Abhishek Kumar; Akinwande, Deji

    2015-01-01

    vibrational dynamics of the distorted monolayer 1T-MoS2 (1T′) and the monolayer 2H-MoS2 via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS2 increases by 11.7% from 1.85 to 2.08 e

  1. Importance of Terminal Amino Acid Residues to the Transport of Oligopeptides across the Caco-2 Cell Monolayer.

    Ding, Long; Wang, Liying; Yu, Zhipeng; Ma, Sitong; Du, Zhiyang; Zhang, Ting; Liu, Jingbo

    2017-09-06

    The objective of this paper was to investigate the effects of terminal amino acids on the transport of oligopeptides across the Caco-2 cell monolayer. Ala-based tetra- and pentapeptides were designed, and the N- or C-terminal amino acid residues were replaced by different amino acids. The results showed that the oligopeptides had a wide range of transport permeability across the Caco-2 cell monolayer and could be divided into four categories: non-/poor permeability, low permeability, intermediate permeability, and good permeability. Tetrapeptides with N-terminal Leu, Pro, Ile, Cys, Met, and Val or C-terminal Val showed the highest permeability, with apparent permeability coefficient (P app ) values over 10 × 10 -6 cm/s (p transport of tetrapeptides. Pentapeptides with N- or C-terminal Tyr also showed high permeability levels, with P app values of about 10 × 10 -6 cm/s. The amino acids Glu, Asn, and Thr at the N terminus or Lys, Asp, and Arg at the C terminus were also beneficial for the transport of tetra- and pentapeptides, with P app values ranging from 1 × 10 -6 to 10 × 10 -6 cm/s. In addition, peptides with amino acids replaced at the N terminus generally showed higher permeability than those with amino acids replaced at the C terminus (p transport of oligopeptides across the Caco-2 cell monolayer.

  2. Protonation of octadecylamine Langmuir monolayer by adsorption of halide counterions

    Sung, Woongmo; Avazbaeva, Zaure; Lee, Jonggwan; Kim, Doseok

    Langmuir monolayer consisting of octadecylamine (C18H37NH2, ODA) was investigated by heterodyne vibrational sum-frequency generation (HD-VSFG) spectroscopy in conjunction with surface pressure-area (π- A) isotherm, and the result was compared with that from cationic-lipid (DPTAP) Langmuir monolayer. In case of ODA monolayer on pure water, both SF intensity of water OH band and the surface pressure were significantly smaller than those of the DPTAP monolayer implying that only small portion of the amine groups (-NH3+ is protonated in the monolayer. In the presence of sodium halides (NaCl and NaI) in the subphase water, it was found that the sign of Imχ (2) of water OH band remained the same as that of the ODA monolayer on pure water, but there was a substantial increase in the SF amplitude. From this, we propose that surface excess of the halide counterions (Cl- and I-) makes the solution condition near the ODA monolayer/water interface more acidic so that ODA molecules in the monolayer are more positively charged, which works to align the water dipoles at the interface.

  3. The Role of miR-330-3p/PKC-α Signaling Pathway in Low-Dose Endothelial-Monocyte Activating Polypeptide-II Increasing the Permeability of Blood-Tumor Barrier

    Jiahui Liu

    2017-12-01

    Full Text Available This study was performed to determine whether EMAP II increases the permeability of the blood-tumor barrier (BTB by affecting the expression of miR-330-3p as well as its possible mechanisms. We determined the over-expression of miR-330-3p in glioma microvascular endothelial cells (GECs by Real-time PCR. Endothelial monocyte-activating polypeptide-II (EMAP-II significantly decreased the expression of miR-330-3p in GECs. Pre-miR-330-3p markedly decreased the permeability of BTB and increased the expression of tight junction (TJ related proteins ZO-1, occludin and claudin-5, however, anti-miR-330-3p had the opposite effects. Anti-miR-330-3p could enhance the effect of EMAP-II on increasing the permeability of BTB, however, pre-miR-330-3p partly reversed the effect of EMAP-II on that. Similarly, anti-miR-330-3p improved the effects of EMAP-II on increasing the expression levels of PKC-α and p-PKC-α in GECs and pre-miR-330-3p partly reversed the effects. MiR-330-3p could target bind to the 3′UTR of PKC-α. The results of in vivo experiments were similar to those of in vitro experiments. These suggested that EMAP-II could increase the permeability of BTB through inhibiting miR-330-3p which target negative regulation of PKC-α. Pre-miR-330-3p and PKC-α inhibitor decreased the BTB permeability and up-regulated the expression levels of ZO-1, occludin and claudin-5 while anti-miR-330-3p and PKC-α activator brought the reverse effects. Compared with EMAP-II, anti-miR-330-3p and PKC-α activator alone, the combination of the three combinations significantly increased the BTB permeability. EMAP-II combined with anti-miR-330-3p and PKCα activator could enhance the DOX’s effects on inhibiting the cell viabilities and increasing the apoptosis of U87 glioma cells. Our studies suggest that low-dose EMAP-II up-regulates the expression of PKC-α and increases the activity of PKC-α by inhibiting the expression of miR-330-3p, reduces the expression of ZO-1

  4. Water sorption and water permeability properties of edible film made from potato peel waste

    Siti Hajar OTHMAN

    Full Text Available Abstract The water sorption and permeability properties of edible film produced from potato peel waste was investigated under different levels of relative humidity (23, 33, 43, 57, 75% RH and temperatures (5, 30, 50 °C. The water sorption behaviour and isotherms of the film were investigated by fitting water sorption data to the Peleg model and the Guggenheim, Anderson de Boer model (GAB model. The amount of moisture content, time required for the moisture content of the film to reach equilibrium, water sorption rate, and water sorption capacity increased when the relative humidity increased. The effect of temperature on moisture content, water sorption rate, water sorption capacity, and monolayer moisture content is complex and related to the water activity as well as the moisture content. Based on R2 and RMSE values, the Peleg and GAB models were respectively determined as excellent models to predict the water sorption properties of the films, thus supporting the reliability of water sorption behaviour prediction. The water vapour transmission rate and water vapour permeability increased with an increase in relative humidity and temperature. The sorption and permeability properties of the film are worth investigation since the final application of the film as food packaging is ultimately dependent on these behaviours.

  5. Film Permeability Determination Using Static Permeability Cells

    The permeability of tarps to soil fumigant pesticides varies depending on the active ingredient chemical: dimethyl disulfide (DMDS), methyl bromide, chloropicrin, or other. The diffusion rate can be represented by the mass transfer coefficient (MTC).

  6. Fabrication of high permeability non-oriented electrical steels by increasing 〈0 0 1〉 recrystallization texture using compacted strip casting processes

    Liu, Hai-Tao, E-mail: liuht@ral.neu.edu.cn [State Key Laboratory of Rolling and Automation, Northeastern University, PO Box 105, Shenyang 110819 (China); Institute of Research of Iron and Steel, Shasteel, Zhangjiagang 215625, Jiangsu (China); Schneider, J. [Institut für Metallformung, Technische Universität Bergakademie Freiberg, Bernhard-von-Cotta-Str. 4, D-09596 Freiberg (Germany); Li, Hua-Long [Institute of Research of Iron and Steel, Shasteel, Zhangjiagang 215625, Jiangsu (China); Sun, Yu; Gao, Fei; Lu, Hui-Hu; Song, Hong-Yu [State Key Laboratory of Rolling and Automation, Northeastern University, PO Box 105, Shenyang 110819 (China); Li, Lei; Geng, Dian-Qiao [Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Liu, Zhen-Yu; Wang, Guo-Dong [State Key Laboratory of Rolling and Automation, Northeastern University, PO Box 105, Shenyang 110819 (China)

    2015-01-15

    In this paper we will report on the application of the twin-roll casting technique to get a 2 mm thick material of Fe-3.2%Si alloy, which was finally hot rolled, cold rolled and annealed. After a mild hot rolling to a thickness of 1 mm and a mild cold rolling to a thickness of 0.35 mm, we obtained a high intensity of λ-fiber (〈0 0 1〉|| ND) and η-fiber (〈0 0 1〉|| RD) texture concentrated on cube ({0 0 1}〈0 1 0〉) component and a diminishing intensity of the γ-fiber (〈1 1 1〉|| ND) texture, and a large average grain size in the final processed material. The experimental results for the evolution of the microstructure and texture along the used processing routes were described within the paper in detail. The formation mechanism for the desired recrystallization textures were explained in terms of oriented nucleation, micro-growth selection, accumulated deformation stored energy, geometric softening and orientation pinning. It will be demonstrated that this new processing route using the compact strip casting offers the possibility to fabricate high permeability non-oriented electrical steels without additional fabrication steps like hot band annealing or two step cold rolling with intermediate annealing as in the case of conventional processing route. - Highlights: • High permeability non-oriented electrical steel was fabricated by strip casting processes. • Hot band annealing or two step cold rolling with intermediate annealing was eliminated. • Prevailing of 〈0 0 1〉|| ND and 〈0 0 1〉|| RD textures over diminishing 〈1 1 1〉|| ND texture was realized. • Evolution of microstructure and texture along the used processing routes were described.

  7. Monolayer Superconductivity in WS2

    Zheliuk, Oleksandr; Lu, Jianming; Yang, Jie; Ye, Jianting

    Superconductivity in monolayer tungsten disulfide (2H-WS2) is achieved by strong electrostatic electron doping of an electric double-layer transistor (EDLT). Single crystals of WS2 are grown by a scalable method - chemical vapor deposition (CVD) on standard Si/SiO2 substrate. The monolayers are

  8. Clogging in permeable concrete: A review.

    Kia, Alalea; Wong, Hong S; Cheeseman, Christopher R

    2017-05-15

    Permeable concrete (or "pervious concrete" in North America) is used to reduce local flooding in urban areas and is an important sustainable urban drainage system. However, permeable concrete exhibits reduction in permeability due to clogging by particulates, which severely limits service life. This paper reviews the clogging mechanism and current mitigating strategies in order to inform future research needs. The pore structure of permeable concrete and characteristics of flowing particulates influence clogging, which occurs when particles build-up and block connected porosity. Permeable concrete requires regular maintenance by vacuum sweeping and pressure washing, but the effectiveness and viability of these methods is questionable. The potential for clogging is related to the tortuosity of the connected porosity, with greater tortuosity resulting in increased potential for clogging. Research is required to develop permeable concrete that can be poured on-site, which produces a pore structure with significantly reduced tortuosity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Different Methods of Predicting Permeability in Shale

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

    by two to five orders of magnitudes at lower vertical effective stress below 40 MPa as the content of clay minerals increases causing heterogeneity in shale material. Indirect permeability from consolidation can give maximum and minimum values of shale permeability needed in simulating fluid flow......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...... 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...

  10. Bentonite Permeability at Elevated Temperature

    Katherine A. Daniels

    2017-01-01

    Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.

  11. Paracellular transport of avidin saturated or not with biotinylated cobalamin through Caco-2 cell epithelium monolayer.

    Guy, M; Pons, L; Namour, F; de Nonancourt, M; Michalski, J C; Hatier, R; Guéant, J L

    2001-01-01

    The cationic charge of molecules may promote their uptake across epithelia, which are rich in brush border anionic sites. The transport of unsaturated avidin and avidin saturated with a biotinylated compound was investigated across Caco-2 adenocarcinoma cell with fetal enterocyte phenotype. The unsaturated avidin and avidin saturated with either biotin or a biotinyl-cobalamin conjugate (biotinyl-Cbl) were iodinated to follow their transport through the cell monolayer. Their apparent permeability coefficient (Papp) and transepithelial pathway were determined and compared to those for control radiolabeled markers [3H]-mannitol, [125I]-beta-lactoglobulin and [57Co]-cobalamin/intrinsic factor (Cbl/IF). The Papp of [125I]-avidin estimated at 2.8 x 10(-7) +/- 0.08 cm/s was close to that for mannitol that uses paracellular pathway. The binding of biotin or biotin conjugate to avidin enhanced its tetrameric conformation. The Papp for [125I]-avidin/biotin and [125I]- avidin/biotinyl-Cbl were respectively increased by 2-fold, compared to that for [125I]-avidin and 4-fold, compared to that for [125I]-beta-lactoglobulin and [54Co]-Cbl/IF. The protein was not accumulated in the cell and was found in intact form in the basolateral side, after its transport across the monolayer. Chloroquine (0.66 micromol/ml) did not significantly decrease the Papp for [125I]-avidin/biotinyl-Cbl. Conversely it decreased by 80% the Papp for Cbl/IF, that uses transepithelial pathway. Avidin (either saturated or not with biotin and biotinyl-Cbl) was able to cross the monolayer of Caco-2 cell line through a paracellular pathway. This study pointed out the interest for using this protein as a shuttle for increasing the transport rate of biotinylated compounds through fetal epithelial barriers. Copyright 2001 S. Karger AG, Basel

  12. Permeability enhancement by shock cooling

    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

  13. Permeability prediction in chalks

    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 p...... significantly using the effective specific surface as the fluid-flow concept. The FZI unit is appropriate for highly permeable sedimentary rocks such as sandstones and limestones that have small surface areas....

  14. Gas and Water Permeability of Concrete

    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.

  15. Effect of temperature on sandstone permeability

    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...... and the Klinkenberg procedure showed the expected correlation between the two measures, however, differences could be around one order of magnitude. In tight gas sandstones, permeability is often sensitive to net stress, which might change due to the pore pressure change in the Klinkenberg procedure. Besides...... affecting the Klinkenberg procedure, the combined effect of slip and changes in permeability would affect production during pressure depletion in tight gas sandstone reservoirs; therefore effects of gas slip and net stress on permeability were combined in a model based on the Klinkenberg equation. A lower...

  16. Arctigenin from Fructus Arctii (Seed of Burdock) Reinforces Intestinal Barrier Function in Caco-2 Cell Monolayers

    Shin, Hee Soon; Jung, Sun Young; Back, Su Yeon; Do, Jeong-Ryong; Shon, Dong-Hwa

    2015-01-01

    Fructus Arctii is used as a traditional herbal medicine to treat inflammatory diseases in oriental countries. This study aimed to investigate effect of F. Arctii extract on intestinal barrier function in human intestinal epithelial Caco-2 cells and to reveal the active component of F. Arctii. We measured transepithelial electrical resistance (TEER) value (as an index of barrier function) and ovalbumin (OVA) permeation (as an index of permeability) to observe the changes of intestinal barrier function. The treatment of F. Arctii increased TEER value and decreased OVA influx on Caco-2 cell monolayers. Furthermore, we found that arctigenin as an active component of F. Arctii increased TEER value and reduced permeability of OVA from apical to the basolateral side but not arctiin. In the present study, we revealed that F. Arctii could enhance intestinal barrier function, and its active component was an arctigenin on the functionality. We expect that the arctigenin from F. Arctii could contribute to prevention of inflammatory, allergic, and infectious diseases by reinforcing intestinal barrier function. PMID:26550018

  17. Arctigenin from Fructus Arctii (Seed of Burdock Reinforces Intestinal Barrier Function in Caco-2 Cell Monolayers

    Hee Soon Shin

    2015-01-01

    Full Text Available Fructus Arctii is used as a traditional herbal medicine to treat inflammatory diseases in oriental countries. This study aimed to investigate effect of F. Arctii extract on intestinal barrier function in human intestinal epithelial Caco-2 cells and to reveal the active component of F. Arctii. We measured transepithelial electrical resistance (TEER value (as an index of barrier function and ovalbumin (OVA permeation (as an index of permeability to observe the changes of intestinal barrier function. The treatment of F. Arctii increased TEER value and decreased OVA influx on Caco-2 cell monolayers. Furthermore, we found that arctigenin as an active component of F. Arctii increased TEER value and reduced permeability of OVA from apical to the basolateral side but not arctiin. In the present study, we revealed that F. Arctii could enhance intestinal barrier function, and its active component was an arctigenin on the functionality. We expect that the arctigenin from F. Arctii could contribute to prevention of inflammatory, allergic, and infectious diseases by reinforcing intestinal barrier function.

  18. Microfluidic passive permeability assay using nanoliter droplet interface lipid bilayers.

    Nisisako, Takasi; Portonovo, Shiva A; Schmidt, Jacob J

    2013-11-21

    Membrane permeability assays play an important role in assessing drug transport activities across biological membranes. However, in conventional parallel artificial membrane permeability assays (PAMPA), the membrane model used is dissimilar to biological membranes physically and chemically. Here, we describe a microfluidic passive permeability assay using droplet interface bilayers (DIBs). In a microfluidic network, nanoliter-sized donor and acceptor aqueous droplets are alternately formed in cross-flowing oil containing phospholipids. Subsequently, selective removal of oil through hydrophobic pseudo-porous sidewalls induces the contact of the lipid monolayers, creating arrayed planar DIBs between the donor and acceptor droplets. Permeation of fluorescein from the donor to the acceptor droplets was fluorometrically measured. From the measured data and a simple diffusion model we calculated the effective permeabilities of 5.1 × 10(-6) cm s(-1), 60.0 × 10(-6) cm s(-1), and 87.6 × 10(-6) cm s(-1) with donor droplets at pH values of 7.5, 6.4 and 5.4, respectively. The intrinsic permeabilities of specific monoanionic and neutral fluorescein species were obtained similarly. We also measured the permeation of caffeine in 10 min using UV microspectroscopy, obtaining a permeability of 20.8 × 10(-6) cm s(-1). With the small solution volumes, short measurement time, and ability to measure a wide range of compounds, this device has considerable potential as a platform for high-throughput drug permeability assays.

  19. Proton and hydrogen transport through two-dimensional monolayers

    Seel, Max; Pandey, Ravindra

    2016-01-01

    Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS 2 ) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS 2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS 2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene. (paper)

  20. Proton and hydrogen transport through two-dimensional monolayers

    Seel, Max; Pandey, Ravindra

    2016-06-01

    Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS2) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene.

  1. Absorption mechanism of whey-protein-delivered curcumin using Caco-2 cell monolayers.

    Li, Ming; Cui, Jie; Ngadi, Michael O; Ma, Ying

    2015-08-01

    Curcumin (CCM) is a bioactive polyphenolic compound that suffers a low bioavailability because of its low water solubility. In this work β-lactoglobulin (β-Lg) and nanoemulsion were used as carriers to deliver curcumin. The pH stability of β-Lg-CCM was investigated. The digestion of β-Lg-CCM and the nanoemulsion was studied using an in vitro gastrointestinal model. The effect of different carriers on the permeability of curcumin was assessed using the Caco-2 cell monolayer model. The results revealed that the water solubility and the pH stability of curcumin significantly increased by binding with β-Lg. In SDS-PAGE experiments the β-Lg-CCM complex and nanoemulsion were found to be resistant to pepsin digestion but sensitive to trypsin. In the permeability experiment it was shown that the digested nanoemulsion and β-Lg-CCM improved significantly the permeation rate of curcumin. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Permeability During Magma Expansion and Compaction

    Gonnermann, Helge. M.; Giachetti, Thomas; Fliedner, Céline; Nguyen, Chinh T.; Houghton, Bruce F.; Crozier, Joshua A.; Carey, Rebecca J.

    2017-12-01

    Plinian lapilli from the 1060 Common Era Glass Mountain rhyolitic eruption of Medicine Lake Volcano, California, were collected and analyzed for vesicularity and permeability. A subset of the samples were deformed at a temperature of 975°, under shear and normal stress, and postdeformation porosities and permeabilities were measured. Almost all undeformed samples fall within a narrow range of vesicularity (0.7-0.9), encompassing permeabilities between approximately 10-15 m2 and 10-10 m2. A percolation threshold of approximately 0.7 is required to fit the data by a power law, whereas a percolation threshold of approximately 0.5 is estimated by fitting connected and total vesicularity using percolation modeling. The Glass Mountain samples completely overlap with a range of explosively erupted silicic samples, and it remains unclear whether the erupting magmas became permeable at porosities of approximately 0.7 or at lower values. Sample deformation resulted in compaction and vesicle connectivity either increased or decreased. At small strains permeability of some samples increased, but at higher strains permeability decreased. Samples remain permeable down to vesicularities of less than 0.2, consistent with a potential hysteresis in permeability-porosity between expansion (vesiculation) and compaction (outgassing). We attribute this to retention of vesicle interconnectivity, albeit at reduced vesicle size, as well as bubble coalescence during shear deformation. We provide an equation that approximates the change in permeability during compaction. Based on a comparison with data from effusively erupted silicic samples, we propose that this equation can be used to model the change in permeability during compaction of effusively erupting magmas.

  3. Subcellular topological effect of particle monolayers on cell shapes and functions.

    Miura, Manabu; Fujimoto, Keiji

    2006-12-01

    We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir-Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell-cell adhesion became stronger than cell-substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm(-2), some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and

  4. Quasi-equilibrium analysis of the ion-pair mediated membrane transport of low-permeability drugs.

    Miller, Jonathan M; Dahan, Arik; Gupta, Deepak; Varghese, Sheeba; Amidon, Gordon L

    2009-07-01

    The aim of this research was to gain a mechanistic understanding of ion-pair mediated membrane transport of low-permeability drugs. Quasi-equilibrium mass transport analyses were developed to describe the ion-pair mediated octanol-buffer partitioning and hydrophobic membrane permeation of the model basic drug phenformin. Three lipophilic counterions were employed: p-toluenesulfonic acid, 2-naphthalenesulfonic acid, and 1-hydroxy-2-naphthoic acid (HNAP). Association constants and intrinsic octanol-buffer partition coefficients (Log P(AB)) of the ion-pairs were obtained by fitting a transport model to double reciprocal plots of apparent octanol-buffer distribution coefficients versus counterion concentration. All three counterions enhanced the lipophilicity of phenformin, with HNAP providing the greatest increase in Log P(AB), 3.7 units over phenformin alone. HNAP also enhanced the apparent membrane permeability of phenformin, 27-fold in the PAMPA model, and 4.9-fold across Caco-2 cell monolayers. As predicted from a quasi-equilibrium analysis of ion-pair mediated membrane transport, an order of magnitude increase in phenformin flux was observed per log increase in counterion concentration, such that log-log plots of phenformin flux versus HNAP concentration gave linear relationships. These results provide increased understanding of the underlying mechanisms of ion-pair mediated membrane transport, emphasizing the potential of this approach to enable oral delivery of low-permeability drugs.

  5. Soils - Mean Permeability

    Kansas Data Access and Support Center — This digital spatial data set provides information on the magnitude and spatial pattern of depth-weighted, mean soil permeability throughout the State of Kansas. The...

  6. Hydrogen permeability through metals

    Pisarev, A.A.; Tsvetkov, I.V.; Marenkov, E.D.; Yarko, S.S.

    2011-01-01

    The mechanisms of hydrogen permeability through one-layer and multi-layer membranes are considered. The effect of surface roughness, crystal defects, cracks and pores is described. Mathematical description of the processes is given [ru

  7. Evolution of permeability in diatomaceous rocks mediated by pressure solution

    Yasuhara, Hideaki; Kinoshita, Naoki; Kurikami, Hiroshi; Kishida, Kiyoshi

    2007-01-01

    A conceptual model is presented to follow the evolution of permeability in diatomaceous rocks mediated by pressure solution. The progress of compaction and the evolution of permeability may be followed with time. Specifically, the main minerals of diatomaceous rocks that are quartz, cristobalite, and amorphous silica, are focused to examine differences of the permeability evolutions among them at effective stresses of 5, and 10 MPa, and temperatures of 20 and 90degC. The rates and magnitudes of permeability reduction increase with increase of the dissolution rate constants. Ultimate permeabilities reduce to the order of 90% at the completion of dissolution-mediated compaction. (author)

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

    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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Permeability After Impact Testing of Composite Laminates

    Nettles, Alan T.

    2003-01-01

    Since composite laminates are beginning to be identified for use in reusable launch vehicle propulsion systems, an understanding of their permeance is needed. A foreign object impact event can cause a localized area of permeability (leakage) in a polymer matrix composite and it is the aim of this study to assess a method of quantifying permeability-after-impact results. A simple test apparatus is presented and variables that could affect the measured values of permeability-after-impact were assessed. Once it was determined that valid numbers were being measured, a fiber/resin system was impacted at various impact levels and the resulting permeability measured, first with a leak check solution (qualitative) then using the new apparatus (quantitative). The results showed that as the impact level increased, so did the measured leakage. As the pressure to the specimen was increased, the leak rate was seen to increase in a non-linear fashion for almost all of the specimens tested.

  10. Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro

    Holden, W.E.; Maier, J.M.; Malinow, M.R.

    1989-01-01

    Cigarette smoking causes lung inflammation, and a characteristic of inflammation is an increase in vascular permeability. To determine if cigarette smoke could alter endothelial permeability, we studied flux of radiolabeled albumin across monolayers of porcine pulmonary artery endothelium grown in culture on microporous membranes. Extracts (in either dimethylsulfoxide or phosphate-buffered saline) of cigarette smoke in a range estimate of concentrations simulating cigarette smoke exposure to the lungs in vivo caused a dose-dependent increase in albumin flux that was dependent on extracellular divalent cations and associated with polymerization of cellular actin. The effect was reversible, independent of the surface of endothelial cells exposed (either luminal or abluminal), and due primarily to components of the vapor phase of smoke. The effects occurred without evidence of cell damage, but subtle morphological changes were produced by exposure to the smoke extracts. These findings suggest that cigarette smoke can alter permeability of the lung endothelium through effects on cytoskeletal elements

  11. Protective Effects of Bifidobacterium on Intestinal Barrier Function in LPS-Induced Enterocyte Barrier Injury of Caco-2 Monolayers and in a Rat NEC Model.

    Ling, Xiang; Linglong, Peng; Weixia, Du; Hong, Wei

    2016-01-01

    Zonulin protein is a newly discovered modulator which modulates the permeability of the intestinal epithelial barrier by disassembling intercellular tight junctions (TJ). Disruption of TJ is associated with neonatal necrotizing enterocolitis (NEC). It has been shown bifidobacterium could protect the intestinal barrier function and prophylactical administration of bifidobacterium has beneficial effects in NEC patients and animals. However, it is still unknown whether the zonulin is involved in the gut barrier dysfunction of NEC, and the protective mechanisms of bifidobacterium on intestinal barrier function are also not well understood. The present study aims to investigate the effects of bifidobacterium on intestinal barrier function, zonulin regulation, and TJ integrity both in LPS-induced enterocyte barrier injury of Caco-2 monolayers and in a rat NEC model. Our results showed bifidobacterium markedly attenuated the decrease in transepithelial electrical resistance and the increase in paracellular permeability in the Caco-2 monolayers treated with LPS (P zonulin release (P zonulin (P zonulin protein release and improvement of intestinal TJ integrity.

  12. Orientational epitaxy in adsorbed monolayers

    Novaco, A.D.; McTague, J.P.

    1977-01-01

    The ground state for adsorbed monolayers on crystalline substrates is shown to involve a definite relative orientation of the substrate and adsorbate crystal axes, even when the relative lattice parameters are incommensurate. The rotation angle which defines the structure of the monolayer-substrate system is determined by the competition between adsorbate-substrate and adsorbate-adsorbate energy terms, and is generally not a symmetry angle. Numerical predictions are presented for the rare gas-graphite systems, whose interaction potentials are rather well known. Recent LEED data for some of these systems appear to corroborate these predictions

  13. Erbium:YAG laser resurfacing increases skin permeability and the risk of excessive absorption of antibiotics and sunscreens: the influence of skin recovery on drug absorption.

    Lee, Woan-Ruoh; Shen, Shing-Chuan; Al-Suwayeh, Saleh A; Li, Yi-Ching; Fang, Jia-You

    2012-06-01

    While laser skin resurfacing is expected to result in reduced barrier function and increased risk of drug absorption, the extent of the increment has not yet been systematically investigated. We aimed to establish the skin permeation profiles of tetracycline and sunscreens after exposure to the erbium:yttrium-aluminum-garnet (Er:YAG) laser during postoperative periods. Physiological and histopathological examinations were carried out for 5 days after laser treatment on nude mice. Percutaneous absorption of the permeants was determined by an in vitro Franz cell. Ablation depths varied in reaching the stratum corneum (10 μm, 2.5 J/cm²) to approach the epidermis (25 μm, 6.25 J/cm²) and upper dermis (40 μm, 10 J/cm²). Reepithelialization evaluated by transepidermal water loss was complete within 2-4 days and depended on the ablation depth. Epidermal hyperplasia was observed in the 40-μm-treated group. The laser was sufficient to disrupt the skin barrier and allow the transport of the permeants into and across the skin. The laser fluence was found to play an important role in modulating skin absorption. A 25-μm ablation depth increased tetracycline flux 84-fold. A much smaller enhancement (3.3-fold) was detected for tetracycline accumulation within the skin. The laser with different fluences produced enhancement of oxybenzone skin deposition of 3.4-6.4-fold relative to the untreated group. No penetration across the skin was shown regardless of whether titanium dioxide was applied to intact or laser-treated skin. However, laser resurfacing increased the skin deposition of titanium dioxide from 46 to 109-188 ng/g. Tetracycline absorption had recovered to the level of intact skin after 5 days, while more time was required for oxybenzone absorption. The in vivo skin accumulation and plasma concentration revealed that the laser could increase tetracycline absorption 2-3-fold. The experimental results indicated that clinicians should be cautious when determining the

  14. A trough for improved SFG spectroscopy of lipid monolayers

    Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

    2017-05-01

    Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

  15. Viscous fingering with permeability heterogeneity

    Tan, C.; Homsy, G.M.

    1992-01-01

    Viscous fingering in miscible displacements in the presence of permeability heterogeneities is studied using two-dimensional simulations. The heterogeneities are modeled as stationary random functions of space with finite correlation scale. Both the variance and scale of the heterogeneities are varied over modest ranges. It is found that the fingered zone grows linearly in time in a fashion analogous to that found in homogeneous media by Tan and Homsy [Phys. Fluids 31, 1330 (1988)], indicating a close coupling between viscous fingering on the one hand and flow through preferentially more permeable paths on the other. The growth rate of the mixing zone increases monotonically with the variance of the heterogeneity, as expected, but shows a maximum as the correlation scale is varied. The latter is explained as a ''resonance'' between the natural scale of fingers in homogeneous media and the correlation scale

  16. Transport properties in monolayer-bilayer-monolayer graphene planar junctions

    Kai-Long Chu; Zi-Bo Wang; Jiao-Jiao Zhou; Hua Jiang

    2017-01-01

    The transport study of graphene based junctions has become one of the focuses in graphene research.There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions.One is the two monolayer graphene contacting the same side of the bilayer graphene,and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene.In this paper,according to the Landauer-Büttiker formula,we study the transport properties of these two configurations.The influences of the local gate potential in each part,the bias potential in bilayer graphene,the disorder and external magnetic field on conductance are obtained.We find the conductances of the two configurations can be manipulated by all of these effects.Especially,one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene.The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.

  17. Solution-processable septithiophene monolayer transistor

    Defaux, M.; Gholamrezaie, F.; Wang, J.; Kreyes, A.; Ziener, U.; Anokhin, D.V.; Ivanov, D.A.; Moser, A.; Neuhold, A.; Salzmann, I.; Resel, R.; Leeuw, de D.M.; Meskers, S.C.J.; Moeller, M.; Mourran, A.

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  18. Solution-Processable Septithiophene Monolayer Transistor

    Defaux, Matthieu; Gholamrezaie, Fatemeh; Wang, Jingbo; Kreyes, Andreas; Ziener, Ulrich; Anokhin, Denis V.; Ivanov, Dimitri A.; Moser, Armin; Neuhold, Alfred; Salzmann, Ingo; Resel, Roland; de Leeuw, Dago M.; Meskers, Stefan C. J.; Moeller, Martin; Mourran, Ahmed

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  19. Borehole stoneley waves and permeability: Laboratory results

    Winkler, K.W.; Plona, T.J.; Froelich, B.; Liu, H.L.

    1987-01-01

    Recent interest in full waveform sonic logging has created the need for full waveform laboratory experiments on model boreholes. Of particular interest is the investigation of Stoneley waves and their interaction with permeable formations. The authors describe experimental results that show how Stoneley wave slowness and attenuation are affected by formation permeability. Both slowness and attenuation (1/Q) are observed to increase with formation permeability. This increase is frequency dependent, being greatest at low frequencies. The presence of simulated mudcakes on the borehole wall reduces the permeability effect on Stoneley waves, but does not eliminate it. The mudcake effect is frequency dependent, being greatest at low frequencies. In our experiments on rocks, the laboratory data is in qualitative agreement with theoretical predictions. In a very well characterized synthetic porous material, theory and experiment are in good quantitative agreement

  20. Permeability of gypsum samples dehydrated in air

    Milsch, Harald; Priegnitz, Mike; Blöcher, Guido

    2011-09-01

    We report on changes in rock permeability induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air (dry) for up to 800 h at ambient pressure and temperatures between 378 and 423 K. Subsequently, the reaction kinetics, so induced changes in porosity, and the concurrent evolution of sample permeability were constrained. Weighing the heated samples in predefined time intervals yielded the reaction progress where the stoichiometric mass balance indicated an ultimate and complete dehydration to anhydrite regardless of temperature. Porosity showed to continuously increase with reaction progress from approximately 2% to 30%, whilst the initial bulk volume remained unchanged. Within these limits permeability significantly increased with porosity by almost three orders of magnitude from approximately 7 × 10-19 m2 to 3 × 10-16 m2. We show that - when mechanical and hydraulic feedbacks can be excluded - permeability, reaction progress, and porosity are related unequivocally.

  1. Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions.

    Lechuga, Susana; Baranwal, Somesh; Ivanov, Andrei I

    2015-05-01

    Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis. Copyright © 2015 the American Physiological Society.

  2. A Chitin-binding Protein Purified from Moringa oleifera Seeds Presents Anticandidal Activity by Increasing Cell Membrane Permeability and Reactive Oxygen Species Production

    João X.S. Neto

    2017-06-01

    Full Text Available Candida species are opportunistic pathogens that infect immunocompromised and/or immunosuppressed patients, particularly in hospital facilities, that besides representing a significant threat to health increase the risk of mortality. Apart from echinocandins and triazoles, which are well tolerated, most of the antifungal drugs used for candidiasis treatment can cause side effects and lead to the development of resistant strains. A promising alternative to the conventional treatments is the use of plant proteins. M. oleifera Lam. is a plant with valuable medicinal properties, including antimicrobial activity. This work aimed to purify a chitin-binding protein from M. oleifera seeds and to evaluate its antifungal properties against Candida species. The purified protein, named Mo-CBP2, represented about 0.2% of the total seed protein and appeared as a single band on native PAGE. By mass spectrometry, Mo-CBP2 presented 13,309 Da. However, by SDS-PAGE, Mo-CBP2 migrated as a single band with an apparent molecular mass of 23,400 Da. Tricine-SDS-PAGE of Mo-CBP2 under reduced conditions revealed two protein bands with apparent molecular masses of 7,900 and 4,600 Da. Altogether, these results suggest that Mo-CBP2 exists in different oligomeric forms. Moreover, Mo-CBP2 is a basic glycoprotein (pI 10.9 with 4.1% (m/m sugar and it did not display hemagglutinating and hemolytic activities upon rabbit and human erythrocytes. A comparative analysis of the sequence of triptic peptides from Mo-CBP2 in solution, after LC-ESI-MS/MS, revealed similarity with other M. oleifera proteins, as the 2S albumin Mo-CBP3 and flocculating proteins, and 2S albumins from different species. Mo-CBP2 possesses in vitro antifungal activity against Candida albicans, C. parapsilosis, C. krusei, and C. tropicalis, with MIC50 and MIC90 values ranging between 9.45–37.90 and 155.84–260.29 μM, respectively. In addition, Mo-CBP2 (18.90 μM increased the cell membrane permeabilization

  3. Transport of curcumin derivatives in Caco-2 cell monolayers.

    Zeng, Zhen; Shen, Zhe L; Zhai, Shuo; Xu, Jia L; Liang, Hui; Shen, Qin; Li, Qing Y

    2017-08-01

    Curcumin (Cur) is a strong natural antioxidant, who can prevent multiple diseases such as anti-cancer, anti-inflammatory, have a resistance to alzheimer's disease and various malignant diseases. But it has poor oral bioavailability due to its poor aqueous solubility, as well as instability. While its novel derivatives (CB and FE), showed better anti-tumor activity, better anti-oxidant activity and better stability than the original drug (Cur). The aim of this study was to study the intestinal transport of Cur, CB and FE using an in vitro Caco-2 cell monolayer model. The results showed that Cur had a lower permeability coefficient (1.13×10 -6 ±0.11×10 -6 cm/s) for apical-to-basolated (AP-BL) transport at 25μM, while the transport rate for AP to BL flux of CB (3.18×10 -6 ±0.31×10 -6 cm/s) and FE (5.28×10 -6 ±0.83×10 -6 cm/s) were significantly greater than that of Cur. The efflux ratio (ER) value at the concentration of 25μM was 1.31 for Cur, 1.26 for CB and 1.33 for FE, suggesting there was no active efflux involved in the translocation across the Caco-2 cell monolayers for the three compounds. Furthermore, the transport flux of CB and FE was in a concentration dependent manner, suggesting the intestinal transport mechanism in them was passive transport. In summary, the results demonstrated that both the intestinal permeability of CB and FE across Caco-2 cell monolayers was significantly improved compare to Cur. Thus they might show a higher oral bioavailability in vivo, and show the potential application in clinic or nutraceutical. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Structures and shear response of lipid monolayers

    Dutta, P.; Ketterson, J.B.

    1993-02-01

    This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

  5. Endothelial Proliferation and Increased Blood - Brain Barrier Permeability in the Basal Ganglia in a Rat Model of 3,4-Dihydrozyphenyl-L-Alanine-Induced Dyskinesia

    Westin, Jenny E.; Lindgren, Hanna S.; Gardi, Jonathan Eyal

    2006-01-01

    3,4-Dihydroxyphenyl-L-alanine (L-DOPA)-induced dyskinesia is associated with molecular and synaptic plasticity in the basal ganglia, but the occurrence of structural remodeling through cell genesis has not been explored. In this study, rats with 6-hydroxydopamine lesions received injections of th...... of angiogenesis and blood-brain barrier dysfunction in an experimental model of L-DOPA-induced dyskinesia. These microvascular changes are likely to affect the kinetics of L-DOPA entry into the brain, favoring the occurrence of motor complications....... dyskinesia. The vast majority (60-80%) of the newborn cells stained positively for endothelial markers. This endothelial proliferation was associated with an upregulation of immature endothelial markers (nestin) and a downregulation of endothelial barrier antigen on blood vessel walls. In addition......, dyskinetic rats exhibited a significant increase in total blood vessel length and a visible extravasation of serum albumin in the two structures in which endothelial proliferation was most pronounced (substantia nigra pars reticulata and entopeduncular nucleus). The present study provides the first evidence...

  6. Exosomes from metastatic cancer cells transfer amoeboid phenotype to non-metastatic cells and increase endothelial permeability: their emerging role in tumor heterogeneity.

    Schillaci, Odessa; Fontana, Simona; Monteleone, Francesca; Taverna, Simona; Di Bella, Maria Antonietta; Di Vizio, Dolores; Alessandro, Riccardo

    2017-07-05

    The goal of this study was to understand if exosomes derived from high-metastatic cells may influence the behavior of less aggressive cancer cells and the properties of the endothelium. We found that metastatic colon cancer cells are able to transfer their amoeboid phenotype to isogenic primary cancer cells through exosomes, and that this morphological transition is associated with the acquisition of a more aggressive behavior. Moreover, exosomes from the metastatic line (SW620Exos) exhibited higher ability to cause endothelial hyperpermeability than exosomes from the non metastatic line (SW480Exos). SWATH-based quantitative proteomic analysis highlighted that SW620Exos are significantly enriched in cytoskeletal-associated proteins including proteins activating the RhoA/ROCK pathway, known to induce amoeboid properties and destabilization of endothelial junctions. In particular, thrombin was identified as a key mediator of the effects induced by SW620Exos in target cells, in which we also found a significant increase of RhoA activity. Overall, our results demonstrate that in a heterogeneous context exosomes released by aggressive sub-clones can contribute to accelerate tumor progression by spreading malignant properties that affect both the tumor cell plasticity and the endothelial cell behavior.

  7. Transepithelial transport of aliphatic carboxylic acids studied in Madin Darby canine kidney (MDCK) cell monolayers

    Cho, M.J.; Adson, A.; Kezdy, F.J.

    1990-01-01

    Transport of 14C-labeled acetic, propionic (PA), butyric, valeric, heptanoic (HA), and octanoic (OA) acids across the Madin Darby canine kidney (MDCK) epithelial cell monolayer grown on a porous polycarbonate membrane was studied in Hanks' balanced salt solution (HBSS) at 37 degrees C in both apical-to-basolateral and basolateral-to-apical directions. At micromolar concentrations of solutes, metabolic decomposition was significant as evidenced by [14C]CO2 production during the OA transport. The apparent permeability (Pe) indicates that as lipophilicity increases, diffusion across the unstirred boundary layer becomes rate limiting. In support of this notion, transport of OA and HA was enhanced by agitation, showed an activation energy of 3.7 kcal/mol for OA, and resulted in identical Pe values for both transport directions. Analysis of Pe changes with varying alkyl chain length resulted in a delta G of -0.68 +/- 0.09 kcal/mol for -CH2-group transfer from an aqueous phase to the MDCK cells. When the intercellular tight junctions were opened by the divalent chelator EGTA in Ca2+/Mg2(+)-free HBSS, transport of the fluid-phase marker Lucifer yellow greatly increased because of paracellular leakage. PA transport also showed a significant increase, but OA transport was independent of EGTA. Although albumin also undergoes paracellular transport in the presence of EGTA and OA binds strongly to albumin, OA transport in EGTA solution was unchanged by albumin. These observations indicate that transmembrane transport is the major mechanism for lipophilic substances. The present study, together with earlier work on the transport of polar substances, shows that the MDCK cell monolayer is an excellent model of the transepithelial transport barrier

  8. Acrolein Disrupts Tight Junction Proteins and Causes Endoplasmic Reticulum Stress-Mediated Epithelial Cell Death Leading to Intestinal Barrier Dysfunction and Permeability.

    Chen, Wei-Yang; Wang, Min; Zhang, Jingwen; Barve, Shirish S; McClain, Craig J; Joshi-Barve, Swati

    2017-12-01

    Increasing evidence suggests that environmental and dietary factors can affect intestinal epithelial integrity leading to gut permeability and bacterial translocation. Intestinal barrier dysfunction is a pathogenic process associated with many chronic disorders. Acrolein is an environmental and dietary pollutant and a lipid-derived endogenous metabolite. The impact of acrolein on the intestine has not been investigated before and is evaluated in this study, both in vitro and in vivo. Our data demonstrate that oral acrolein exposure in mice caused damage to the intestinal epithelial barrier, resulting in increased permeability and subsequently translocation of bacterial endotoxin-lipopolysaccharide into the blood. Similar results were seen in vitro using established Caco-2 cell monolayers wherein acrolein decreased barrier function and increased permeability. Acrolein also caused the down-regulation and/or redistribution of three representative tight junction proteins (ie, zonula occludens-1, Occludin, Claudin-1) that critically regulate epithelial paracellular permeability. In addition, acrolein induced endoplasmic reticulum stress-mediated death of epithelial cells, which is an important mechanism contributing to intestinal barrier damage/dysfunction, and gut permeability. Overall, we demonstrate that exposure to acrolein affects the intestinal epithelium by decrease/redistribution of tight junction proteins and endoplasmic reticulum stress-mediated epithelial cell death, thereby resulting in loss of barrier integrity and function. Our findings highlight the adverse consequences of environmental and dietary pollutants on intestinal barrier integrity/function with relevance to gut permeability and the development of disease. Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  9. Phase transitions in polymer monolayers

    Deschênes, Louise; Lyklema, J.; Danis, Claude; Saint-Germain, François

    2015-01-01

    In this paper we investigate the application of the two-dimensional Clapeyron law to polymer monolayers. This is a largely unexplored area of research. The main problems are (1) establishing if equilibrium is reached and (2) if so, identifying and defining phases as functions of the temperature.

  10. Biostable glucose permeable polymer

    2017-01-01

    A new biostable glucose permeable polymer has been developed which is useful, for example, in implantable glucose sensors. This biostable glucose permeable polymer has a number of advantageous characteristics and, for example, does not undergo hydrolytic cleavage and degradation, thereby providing...... a composition that facilitates long term sensor stability in vivo. The versatile characteristics of this polymer allow it to be used in a variety of contexts, for example to form the body of an implantable glucose sensor. The invention includes the polymer composition, sensor systems formed from this polymer...

  11. The food contaminant deoxynivalenol, decreases intestinal barrier permeability and reduces claudin expression

    Pinton, Philippe; Nougayrede, Jean-Philippe; Del Rio, Juan-Carlos; Moreno, Carolina; Marin, Daniela E.; Ferrier, Laurent; Bracarense, Ana-Paula; Kolf-Clauw, Martine; Oswald, Isabelle P.

    2009-01-01

    'The gastrointestinal tract represents the first barrier against food contaminants as well as the first target for these toxicants. Deoxynivalenol (DON) is a mycotoxin that commonly contaminates cereals and causes various toxicological effects. Through consumption of contaminated cereals and cereal products, human and pigs are exposed to this mycotoxin. Using in vitro, ex vivo and in vivo approaches, we investigated the effects of DON on the intestinal epithelium. We demonstrated that, in intestinal epithelial cell lines from porcine (IPEC-1) or human (Caco-2) origin, DON decreases trans-epithelial electrical resistance (TEER) and increases in a time and dose-dependent manner the paracellular permeability to 4 kDa dextran and to pathogenic Escherichia coli across intestinal cell monolayers. In pig explants treated with DON, we also observed an increased permeability of intestinal tissue. These alterations of barrier function were associated with a specific reduction in the expression of claudins, which was also seen in vivo in the jejunum of piglets exposed to DON-contaminated feed. In conclusion, DON alters claudin expression and decreases the barrier function of the intestinal epithelium. Considering that high levels of DON may be present in food or feed, consumption of DON-contaminated food/feed may induce intestinal damage and has consequences for human and animal health.

  12. Drug-permeability and transporter assays in Caco-2 and MDCK cell lines.

    Volpe, Donna A

    2011-12-01

    The human colon adenocarcinoma Caco-2 and Madin-Darby canine kidney epithelial cell lines provide in vitro tools to assess a drug's permeability and transporter interactions during discovery and development. The cells, when cultured on semiporous filters, form confluent monolayers that model the intestinal epithelial barrier for permeability, transporter and drug-interaction assays. The applications of these assays in pharmaceutical research include qualitative prediction and ranking of absorption, determining mechanism(s) of permeability, formulation effects on drug permeability, and the potential for transporter-mediated drug-drug interactions. This review focuses on recent examples of Caco-2 and Madin-Darby canine kidney cells assays for drug permeability including transfected and knock-down cells, miniaturization and automation, and assay combinations to better understand and predict intestinal drug absorption.

  13. Cell permeability beyond the rule of 5.

    Matsson, Pär; Doak, Bradley C; Over, Björn; Kihlberg, Jan

    2016-06-01

    Drug discovery for difficult targets that have large and flat binding sites is often better suited to compounds beyond the "rule of 5" (bRo5). However, such compounds carry higher pharmacokinetic risks, such as low solubility and permeability, and increased efflux and metabolism. Interestingly, recent drug approvals and studies suggest that cell permeable and orally bioavailable drugs can be discovered far into bRo5 space. Tactics such as reduction or shielding of polarity by N-methylation, bulky side chains and intramolecular hydrogen bonds may be used to increase cell permeability in this space, but often results in decreased solubility. Conformationally flexible compounds can, however, combine high permeability and solubility, properties that are keys for cell permeability and intestinal absorption. Recent developments in computational conformational analysis will aid design of such compounds and hence prediction of cell permeability. Transporter mediated efflux occurs for most investigated drugs in bRo5 space, however it is commonly overcome by high local intestinal concentrations on oral administration. In contrast, there is little data to support significant impact of transporter-mediated intestinal absorption in bRo5 space. Current knowledge of compound properties that govern transporter effects of bRo5 drugs is limited and requires further fundamental and comprehensive studies. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Airborne acrolein induces keratin-8 (Ser-73) hyperphosphorylation and intermediate filament ubiquitination in bronchiolar lung cell monolayers.

    Burcham, Philip C; Raso, Albert; Henry, Peter J

    2014-05-07

    The combustion product acrolein is a key mediator of pulmonary edema in victims of smoke inhalation injury. Since studying acrolein toxicity in conventional in vitro systems is complicated by reactivity with nucleophilic culture media constituents, we explored an exposure system which delivers airborne acrolein directly to lung cell monolayers at the air-liquid interface. Calu-3 lung adenocarcinoma cells were maintained on membrane inserts such that the basal surface was bathed in nucleophile-free media while the upper surface remained in contact with acrolein-containing air. Cells were exposed to airborne acrolein for 30 min before they were allowed to recover in fresh media, with cell sampling at defined time points to allow evaluation of toxicity and protein damage. After prior exposure to acrolein, cell ATP levels remained close to controls for 4h but decreased in an exposure-dependent manner by 24h. A loss of transepithelial electrical resistance and increased permeability to fluorescein isothiocyanate-labeled dextran preceded ATP loss. Use of antibody arrays to monitor protein expression in exposed monolayers identified strong upregulation of phospho-keratin-8 (Ser(73)) as an early consequence of acrolein exposure. These changes were accompanied by chemical damage to keratin-8 and other intermediate filament family members, while acrolein exposure also resulted in controlled ubiquitination of high mass proteins within the intermediate filament extracts. These findings confirm the usefulness of systems allowing delivery of airborne smoke constituents to lung cell monolayers during studies of the molecular basis for acute smoke intoxication injury. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  15. Controlling DC permeability in cast steels

    Sumner, Aaran; Gerada, Chris; Brown, Neil; Clare, Adam

    2017-01-01

    Annealing (at multiple cooling rates) and quenching (with tempering) was performed on specimens of cast steel of varying composition. The aim was to devise a method for selecting the steel with the highest permeability, from any given range of steels, and then increasing the permeability by heat treatment. Metallographic samples were imaged using optical microscopy to show the effect of the applied heat treatments on the microstructure. Commonly cast steels can have DC permeability altered by the careful selection of a heat treatment. Increases of up to 381% were achieved by annealing using a cooling rate of 6.0 °C/min. Annealing was found to cause the carbon present in the steel to migrate from grain boundaries and from within ferrite crystals into adjacent pearlite crystals. The migration of the carbon resulted in less carbon at grain boundaries and within ferrite crystals reducing the number of pinning sites between magnetic domains. This gives rise to a higher permeability. Quenching then tempering was found to cause the formation of small ferrite crystals with the carbon content of the steel predominately held in the martensitic crystal structures. The results show that with any given range of steel compositions the highest baseline DC permeability will be found with the steel that has the highest iron content and the lowest carbon content. For the samples tested in this paper a cooling rate of 4.5 °C/min resulted in the relative permeability of the sample with the highest baseline permeability, AS4, increasing from 783 to 1479 at 0.5 T. This paper shows how heat treatments commonly applied to hypoeutectoid cast steels, to improve their mechanical performance, can be used to also enhance electromagnetic properties of these alloys. The use of cast steels allows the creation of DC components for electrical machines not possible by the widely used method of stacking of electrical grade sheet steels. - Highlights: • A range of structural steels had their

  16. Controlling DC permeability in cast steels

    Sumner, Aaran, E-mail: aaran.sumner@nottingham.ac.uk [University of Nottingham, Nottingham University Park Campus, Nottingham NG7 2RD, England (United Kingdom); Gerada, Chris, E-mail: chris.gerada@nottingham.ac.uk [Electrical Machines, University of Nottingham, Tower Building, Nottingham NG7 2RD, England (United Kingdom); Brown, Neil, E-mail: neil.brown@cummins.com [Advanced Electrical Machines Research and Technology at Cummins Power Generation, Peterborough PE2 6FZ, England (United Kingdom); Clare, Adam, E-mail: adam.clare@nottingham.ac.uk [Advanced Manufacturing, University of Nottingham, University Park Campus, Nottingham NG7 2RD, England (United Kingdom)

    2017-05-01

    Annealing (at multiple cooling rates) and quenching (with tempering) was performed on specimens of cast steel of varying composition. The aim was to devise a method for selecting the steel with the highest permeability, from any given range of steels, and then increasing the permeability by heat treatment. Metallographic samples were imaged using optical microscopy to show the effect of the applied heat treatments on the microstructure. Commonly cast steels can have DC permeability altered by the careful selection of a heat treatment. Increases of up to 381% were achieved by annealing using a cooling rate of 6.0 °C/min. Annealing was found to cause the carbon present in the steel to migrate from grain boundaries and from within ferrite crystals into adjacent pearlite crystals. The migration of the carbon resulted in less carbon at grain boundaries and within ferrite crystals reducing the number of pinning sites between magnetic domains. This gives rise to a higher permeability. Quenching then tempering was found to cause the formation of small ferrite crystals with the carbon content of the steel predominately held in the martensitic crystal structures. The results show that with any given range of steel compositions the highest baseline DC permeability will be found with the steel that has the highest iron content and the lowest carbon content. For the samples tested in this paper a cooling rate of 4.5 °C/min resulted in the relative permeability of the sample with the highest baseline permeability, AS4, increasing from 783 to 1479 at 0.5 T. This paper shows how heat treatments commonly applied to hypoeutectoid cast steels, to improve their mechanical performance, can be used to also enhance electromagnetic properties of these alloys. The use of cast steels allows the creation of DC components for electrical machines not possible by the widely used method of stacking of electrical grade sheet steels. - Highlights: • A range of structural steels had their

  17. Do the recommended standards for in vitro biopharmaceutic classification of drug permeability meet the "passive transport" criterion for biowaivers?

    Žakelj, Simon; Berginc, Katja; Roškar, Robert; Kraljič, Bor; Kristl, Albin

    2013-01-01

    BCS based biowaivers are recognized by major regulatory agencies. An application for a biowaiver can be supported by or even based on "in vitro" measurements of drug permeability. However, guidelines limit the application of biowaivers to drug substances that are transported only by passive mechanisms. Regarding published permeability data as well as measurements obtained in our institution, one can rarely observe drug substances that conform to this very strict criterion. Therefore, we measured the apparent permeability coefficients of 13 drugs recommended by FDA's Guidance to be used as standards for "in vitro" permeability classification. The asymmetry of permeability data determined for both directions (mucosal-to-serosal and serosalto- mucosal) through the rat small intestine revealed significant active transport for four out of the nine high-permeability standards and for all four low-permeability standard drugs. As could be expected, this asymmetry was abolished at 4°C on rat intestine. The permeability of all nine high-permeability, but none of the low permeability standards, was also much lower when measured with intestinal tissue, Caco-2 cell monolayers or artificial membranes at 4°C compared to standard conditions (37°C). Additionally, concurrent testing of several standard drugs revealed that membrane transport can be affected by the use of internal permeability standards. The implications of the results are discussed regarding the regulatory aspects of biopharmaceutical classification, good practice in drug permeability evaluation and regarding the general relevance of transport proteins with broad specificity in drug absorption.

  18. Transient impedance changes in venous endothelial monolayers as a biological radiation dosimetry response

    Erik Fossum Young

    2012-10-01

    Full Text Available In March of 2011, a magnitude 9.0 earthquake and subsequent 14 m-high tsunami caused major damage to the Fukushima Daiichi nuclear power plant in Japan.  While cancer incidence in the radiation-exposed population is a logical concern, the complex effects of radiation on the heart and cardiovascular system are also of interest.  Immediate and early vascular radiation effects could be exploited as a dosimetry modality.  To test whether non-coronary vasculature exhibited transient perturbation in barrier function, video microscopy studies and Electric Cell Substrate Impedance Sensing technology were used to probe very subtle changes in primary human vascular endothelium.  Human umbilical vein endothelial cell (HUVEC monolayers exhibit a transient, statistically significant decrease (P = 0.017 in monolayer resistance 3 h after irradiation with 5.0 Gy of g rays.  Radiation induced perturbations in HUVEC monolayer permeability are similar in magnitude and kinetics to those observed in coronary arterial endothelium.  Therefore, at least two types of vasculature respond to radiation on ECIS arrays with an early transient disruption in permeability.  The finding supports the use of early passage HUVECs for use in bioelectric dosimetry studies of vasculature and suggests that permeability of vessels could potentially serve as a biological dosimetry tool.

  19. Infrared spectroscopy of self-assembled monolayer films on silicon

    Rowell, N. L.; Tay, Lilin; Boukherroub, R.; Lockwood, D. J.

    2007-07-01

    Infrared vibrational spectroscopy in an attenuated total reflection (ATR) geometry has been employed to investigate the presence of organic thin layers on Si-wafer surfaces. The phenomena have been simulated to show there can be a field enhancement with the presented single-reflection ATR (SR-ATR) approach which is substantially larger than for conventional ATR or specular reflection. In SR-ATR, a discontinuity of the field normal to the film contributes a field enhancement in the lower index thin film causing a two order of magnitude increase in sensitivity. SR-ATR was employed to characterize a single monolayer of undecylenic acid self-assembled on Si(1 1 1) and to investigate a two monolayer system obtained by adding a monolayer of bovine serum albumin protein.

  20. Recombinant albumin monolayers on latex particles.

    Sofińska, Kamila; Adamczyk, Zbigniew; Kujda, Marta; Nattich-Rak, Małgorzata

    2014-01-14

    The adsorption of recombinant human serum albumin (rHSA) on negatively charged polystyrene latex micro-particles was studied at pH 3.5 and the NaCl concentration range of 10(-3) to 0.15 M. The electrophoretic mobility of latex monotonically increased with the albumin concentration in the suspension. The coverage of adsorbed albumin was quantitatively determined using the depletion method, where the residual protein concentration was determined by electrokinetic measurements and AFM imaging. It was shown that albumin adsorption was irreversible. Its maximum coverage on latex varied between 0.7 mg m(-2) for 10(-3) M NaCl to 1.3 mg m(-2) for 0.15 M NaCl. The latter value matches the maximum coverage previously determined for human serum albumin on mica using the streaming potential method. The increase in the maximum coverage was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. These facts confirm that albumin adsorption at pH 3.5 is governed by electrostatic interactions and proceeds analogously to colloid particle deposition. The stability of albumin monolayers was measured in additional experiments where changes in the latex electrophoretic mobility and the concentration of free albumin in solutions were monitored over prolonged time periods. Based on these experimental data, a robust procedure of preparing albumin monolayers on latex particles of well-controlled coverage and molecule distribution was proposed.

  1. Repair during multifraction exposures: spheroids versus monolayers

    Durand, R.E.

    1984-01-01

    Many type of mammalian cells, when grown in culture as multicell spheroids, display an increased ability to accumulate and repair sublethal radiation damage which has been called the ''contact effect''. Since this effect has the potential to markedly modify the multifraction radiation response of cells in V79 spheroids relative to cells in monolayer cultures, an investigation was made of regimens ranging from 1 to 100 fractions. Effective dose rates were chosen near 1 Gy h -1 to inhibit cell progression and thus simplify analysis of the results. As expected, larger doses per fraction produced more net cell killing in both systems than lower doses per fraction. Additionally, less killing of spheroid cells was observed in all regimens, in accord with their greater potential for repair. However, when the data were expressed as isoeffect curves, the spheroid and monolayer curves converged as the number of fractions increased. Thus, quite similar inherent sensitivity and repair capabilities would be predicted for ultra-low doses per fraction. High precision techniques for defining survival after doses of radiation from 0.2 to 1 Gy were, however, still able to demonstrate a survival advantage for cells grown as spheroids. (author)

  2. Study on road surface source pollution controlled by permeable pavement

    Zheng, Chaocheng

    2018-06-01

    The increase of impermeable pavement in urban construction not only increases the runoff of the pavement, but also produces a large number of Non-Point Source Pollution. In the process of controlling road surface runoff by permeable pavement, a large number of particulate matter will be withheld when rainwater is being infiltrated, so as to control the source pollution at the source. In this experiment, we determined the effect of permeable road surface to remove heavy pollutants in the laboratory and discussed the related factors that affect the non-point pollution of permeable pavement, so as to provide a theoretical basis for the application of permeable pavement.

  3. Calculation of Permeability inside the Basket including one Fuel Assembly

    Yu, Seung Hwan; Bang, Kyung Sik; Lee, Ju an; Choi, Woo Seok [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In general, the porous media model and the effective thermal conductivity were used to simply the fuel assembly. The methods of calculating permeability were compared considering the flow inside a basket which includes a nuclear fuel. Detailed fuel assembly was a computational modeling and the flow characteristics were investigated. The flow inside the basket which included a fuel assembly is analyzed by CFD. As the height of the fuel assembly increases, the pressure drop linearly increased. The inertia resistance could be neglected. Three methods to calculate the permeability were compared. The permeability by the friction factor is 50% less than the permeability by wall shear stress and pressure drop.

  4. Effect of β-cyclodextrin derivatives on the diosgenin absorption in Caco-2 cell monolayer and rats.

    Okawara, Masaki; Tokudome, Yoshihiro; Todo, Hiroaki; Sugibayashi, Kenji; Hashimoto, Fumie

    2014-01-01

    Orally administrated diosgenin, a steroidal saponin found in the roots of Dioscorea villosa, improves reduced skin thickness in ovariectomized mice, and plays an important role in the treatment of hyperlipidemia. Diosgenin has been noticed as an active element in cosmeceutical and dietary supplements. We have already elucidated that the absolute oral bioavailability of diosgenin is very low; however, a high skin distribution of diosgenin was also observed. The aim of the present study was to examine and compare the effects of β-cyclodextrin (β-CD) and 3 kinds of its derivatives such as hydroxypropyl β-CD on the diosgenin permeability using a Caco-2 model and rat jejunal perfusion. These derivatives of β-CD greatly improved the low solubility of diosgenin. No significant increase was observed in the lactate dehydrogenase leakage from Caco-2 cell, while a slight decrease was found on the transepithelial electrical resistance by diosgenin and β-CD derivatives. However, β-CD derivatives, especially hydroxyethyl β-CD and hydroxypropyl β-CD, markedly enhanced diosgenin permeability across the Caco-2 monolayer and rat jejunum. The bioavailability of diosgenin in the presence of β-CD derivatives were about 4 to 11 fold higher than diosgenin suspension. The mechanisms of these enhancement effects may be due to improvements in solubility and tight junction opening.

  5. Active intestinal drug absorption and the solubility-permeability interplay.

    Porat, Daniel; Dahan, Arik

    2018-02-15

    The solubility-permeability interplay deals with the question: what is the concomitant effect on the drug's apparent permeability when increasing the apparent solubility with a solubility-enabling formulation? The solubility and the permeability are closely related, exhibit certain interplay between them, and ongoing research throughout the past decade shows that treating the one irrespectively of the other may be insufficient. The aim of this article is to provide an overview of the current knowledge on the solubility-permeability interplay when using solubility-enabling formulations for oral lipophilic drugs, highlighting active permeability aspects. A solubility-enabling formulation may affect the permeability in opposite directions; the passive permeability may decrease as a result of the apparent solubility increase, according to the solubility-permeability tradeoff, but at the same time, certain components of the formulation may inhibit/saturate efflux transporters (when relevant), resulting in significant apparent permeability increase. In these cases, excipients with both solubilizing and e.g. P-gp inhibitory properties may lead to concomitant increase of both the solubility and the permeability. Intelligent development of such formulation will account for the simultaneous effects of the excipients' nature/concentrations on the two arms composing the overall permeability: the passive and the active arms. Overall, thorough mechanistic understanding of the various factors involved in the solubility-permeability interplay may allow developing better solubility-enabling formulations, thereby exploiting the advantages analyzed in this article, offering oral delivery solution even for BCS class IV drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Permeability-Porosity Relationships of Subduction Zone Sediments

    Gamage, K.; Screaton, E.; Bekins, B.; Aiello, I.

    2008-12-01

    Permeability-porosity relationships for sediments from Northern Barbados, Costa Rica, Nankai, and Peru subduction zones were examined based on their sediment type and grain size distribution. Greater correlation was observed between permeability and porosity for siliciclastic sediments, diatom oozes, and nannofossil chalk than for nannofossil oozes. For siliciclastic sediments, grouping of sediments by clay content yields relationships that are generally consistent with results from other marine settings and suggest decreasing permeability for a given porosity as clay content increases. Correction of measured porosities for smectite content generally improves the quality of permeability-porosity relationships. The relationship between permeability and porosity for diatom oozes may be controlled by the amount of clay present in the ooze, causing diatom oozes to behave similarly to siliciclastic sediments. For a given porosity the nannofossil oozes have higher permeability values by 1.5 orders of magnitude than the siliciclastic sediments. However, the use of a permeability-porosity relation may not be appropriate for unconsolidated carbonates such as nannofossil oozes. This study provided insight to the effects of porosity correction for smectite, variations in lithology and grain size in permeability-porosity relationships. However, further progress in delineating controls on permeability will require more careful and better documented permeability tests on characterized samples.

  7. Theory of lithium islands and monolayers: Electronic structure and stability

    Quassowski, S.; Hermann, K.

    1995-01-01

    Systematic calculations on planar clusters and monolayers of lithium are performed to study geometries and stabilities of the clusters as well as their convergence behavior with increasing cluster size. The calculations are based on ab initio methods using density-functional theory within the local-spin-density approximation for exchange and correlation. The optimized nearest-neighbor distances d NN of the Li n clusters, n=1,...,25, of both hexagonal and square geometry increase with cluster size, converging quite rapidly towards the monolayer results. Further, the cluster cohesive energies E c increase with cluster size and converge towards the respective monolayer values that form upper bounds. Clusters of hexagonal geometry are found to be more stable than square clusters of comparable size, consistent with the monolayer results. The size dependence of the cluster cohesive energies can be described approximately by a coordination model based on the concept of pairwise additive nearest-neighbor binding. This indicates that the average binding in the Li n clusters and their relative stabilities can be explained by simple geometric effects which derive from the nearest-neighbor coordination

  8. Chain Stretching and Order-Disorder Transitions in Block Copolymer Monolayers and Multilayers

    Kramer, Edward J.; Mishra, Vindhya; Stein, Gila E.; Sohn, Karen E.; Hur, Sumi; Fredrickson, Glenn H.; Cochran, Eric W.

    2009-03-01

    Both monolayers of block copolymer cylinders and spheres undergo order to disorder transitions (ODT) at temperatures well below those of the bulk. Monolayers of PS-b-P2VP cylinders undergo a ``nematic'' to ``isotropic'' transition at temperatures about 20 K below the bulk ODT while monolayers of PS-b-P2VP with P2VP spheres undergo a 2D crystal to hexatic transition at least 10 K below the bulk ODT. Bilayers of each structure disorder at temperatures well above that of the monolayers. While one is tempted to attribute all of the difference to the fact that ordered monolayers are quasi 2 dimensional while bilayers are not, an alternative explanation exists. In the cylinder monolayer the corona PS chains must stretch to fill a nearly square cross-section domain rather than a hexagonal one in the bulk, while the corona PS chains in a sphere monolayer must stretch to fill a hexagonal prism rather than an octahedron in the bulk. The more non-uniform stretching of the chains in the monolayer should increase its free energy and decrease its order-disorder temperature.

  9. In vivo human buccal permeability of nicotine

    Adrian, Charlotte L; Olin, Helle B D; Dalhoff, Kim

    2006-01-01

    The aim was to examine the in vivo buccal pH-dependent permeability of nicotine in humans and furthermore compare the in vivo permeability of nicotine to previous in vitro permeability data. The buccal permeability of nicotine was examined in a three-way cross-over study in eight healthy non......-smokers using a buccal perfusion cell. The disappearance of nicotine from perfusion solutions with pH 6.0, 7.4, and 8.1 was studied for 3h. The apparent permeability of nicotine (P(app)) was determined at each pH value. Parotid saliva was collected in an attempt to assess systemic levels of nicotine....... The disappearance rate of nicotine increased significantly as the pH increased, which resulted in P(app) values of 0.57+/-0.55 x 10(-4), 2.10+/-0.23 x 10(-4), and 3.96+/-0.54 x 10(-4)cms(-1) (mean+/-S.D.) at pH 6.0, 7.4, and 8.1, respectively. A linear relationship (R(2)=0.993) was obtained between the P...

  10. A strain-controlled C2N monolayer membrane for gas separation in PEMFC application

    Deng, Shengwei; Hu, Hui; Zhuang, Guilin; Zhong, Xing; Wang, Jianguo

    2018-05-01

    Ultrathin membranes with controllable pore sizes have great potential to realize high-selectivity gas separation at low energy cost, especially for those mixtures with narrow size distributions. Using a combination of van der Waals-corrected density functional theory (DFT) calculations and molecular dynamics (MD) simulation, we examine the separation ability of biaxial stretched monolayer C2N nanosheets which is applied to the O2 separation from CO/CO2/O2 mixtures in the cathode of proton exchange membrane fuel cells (PEMFC). The DFT calculations show that the diffusion energy barrier for molecules passing through the membrane followed by CO, CO2 and O2 in descending order, and an overall decrease of energy barriers due to the widen the pore size is observed with the increase of applied strains. Furthermore, MD results show that the nanosheet can effectively purify O2 from CO2 and CO with a strain from 8% to 10%. It confirms that the selectivity is determined by the electronic structure related interaction in addition to the kinetic diameter of individual molecules. The O2 permeability is improved progressively with further increase of strain, and small amount of CO2 begins to permeate through the nanosheet at relatively large strain, while the excellent CO isolation is not compromised until the theoretical maximum strain.

  11. Packing of ganglioside-phospholipid monolayers

    Majewski, J.; Kuhl, T.L.; Kjær, K.

    2001-01-01

    Using synchrotron grazing-incidence x-ray diffraction (GIXD) and reflectivity, the in-plane and out-of-plane structure of mixed ganglioside-phospholipid monolayers was investigated at the air-water interface. Mixed monolayers of 0, 5, 10, 20, and 100 mol% ganglioside GM, and the phospholipid...... monolayers did not affect hydrocarbon tail packing (fluidization or condensation of the hydrocarbon region). This is in contrast to previous investigations of lipopolymer-lipid mixtures, where the packing structure of phospholipid monolayers was greatly altered by the inclusion of lipids bearing hydrophilic...

  12. Structure and shear response of lipid monolayers

    Dutta, P.; Ketterson, J.B.

    1990-02-01

    Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this Progress Report, we describe our X-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of monolayer mechanical properties using a simple but effective technique available to anyone using the Wilhelmy method to measure surface tension

  13. Therapeutic benefits of enhancing permeability barrier for atopic eczema

    George Man

    2015-06-01

    Full Text Available The regulatory role of epidermal permeability barrier function in cutaneous inflammation has been well appreciated. While barrier disruption induces cutaneous inflammation, improvement of permeability barrier function alleviates inflammation. Studies have demonstrated that improvement of epidermal permeability barrier function not only prevents the development of atopic eczema, but also delays the relapse of these diseases. Moreover, enhancing the epidermal permeability barrier also alleviates atopic eczema. Furthermore, co-applications of barrier enhancing products with glucocorticoids can increase the therapeutic efficacy and reduce the adverse effects of glucocorticoids in the treatment of atopic eczema. Therefore, utilization of permeability barrier enhancing products alone or in combination with glucocorticoids could be a valuable approach in the treatment of atopic eczema. In this review, we discuss the benefits of improving the epidermal permeability barrier in the management of atopic eczema.

  14. Transepithelial transport of flavanone in intestinal Caco-2 cell monolayers

    Kobayashi, Shoko; Konishi, Yutaka

    2008-01-01

    Our recent study [S. Kobayashi, S. Tanabe, M. Sugiyama, Y. Konishi, Transepithelial transport of hesperetin and hesperidin in intestinal Caco-2 cell monolayers, Biochim. Biophys. Acta, 1778 (2008) 33-41] shows that the mechanism of absorption of hesperetin involves both proton-coupled active transport and transcellular passive diffusion. Here, as well as analyzing the cell permeability of hesperetin, we also study the transport of other flavanones, naringenin and eriodictyol, using Caco-2 cell monolayers. Similar to hesperetin mentioned, naringenin and eriodictyol showed proton-coupled polarized transport in apical-to-basolateral direction in non-saturable manner, constant permeation in the apical-to-basolateral direction (J ap→bl ) irrespective of the transepithelial electrical resistance (TER), and preferable distribution into the basolateral side after apical loading in the presence of a proton gradient. Furthermore, the proton-coupled J ap→bl of hesperetin, naringenin and eriodictyol, were inhibited by substrates of the monocarboxylic acid transporter (MCT), such as benzoic acid, but not by ferulic acid. In contrast, both benzoic and ferulic acids have no stimulatory effect on J ap→bl of each flavanone by trans-stimulation analysis. These results indicates that proton-driven active transport is commonly participated in the absorption of flavanone in general, and that its transport is presumed to be unique other than MCT-mediated transport for absorption of phenolic acids (PAs), sodium-dependent MCT (SMCT) nor anion exchanger-mediated transport

  15. Permeability measuremens of brazilian Eucalyptus

    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.

  16. Transcytosis Involvement in Transport System and Endothelial Permeability of Vascular Leakage during Dengue Virus Infection

    Chanettee Chanthick

    2018-02-01

    Full Text Available The major role of endothelial cells is to maintain homeostasis of vascular permeability and to preserve the integrity of vascular vessels to prevent fluid leakage. Properly functioning endothelial cells promote physiological balance and stability for blood circulation and fluid components. A monolayer of endothelial cells has the ability to regulate paracellular and transcellular pathways for transport proteins, solutes, and fluid. In addition to the paracellular pathway, the transcellular pathway is another route of endothelial permeability that mediates vascular permeability under physiologic conditions. The transcellular pathway was found to be associated with an assortment of disease pathogeneses. The clinical manifestation of severe dengue infection in humans is vascular leakage and hemorrhagic diatheses. This review explores and describes the transcellular pathway, which is an alternate route of vascular permeability during dengue infection that corresponds with the pathologic finding of intact tight junction. This pathway may be the route of albumin transport that causes endothelial dysfunction during dengue virus infection.

  17. Antibiotic interaction with phospholipid monolayers

    Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G.

    2002-01-01

    We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids

  18. Antibiotic interaction with phospholipid monolayers

    Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G

    2002-12-01

    We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids.

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

    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

  20. Effect of low levels of lipid oxidation on the curvature, dynamics, and permeability of lipid bilayers and their interactions with cationic nanoparticles

    Lee, Hwankyu; Malmstadt, Noah

    2018-04-01

    Lipid bilayers composed of saturated and unsaturated lipids, oxidized lipids, and cholesterol at concentrations of 0–18 mol% oxidized lipid were simulated, showing that the presence of oxidized lipid increases bilayer disorder, curvature, and lateral dynamics at low oxidized-lipid concentrations of 18 mol% or less. The aldehyde terminal of a shortened oxidized-lipid tail tends to interact with water and thus bends toward the bilayer-water interface, in agreement with previous experiments and simulations. In particular, water molecules pass through the oxidized bilayer without pore formation, implying passive permeability. A single nanoparticle, which consists of 300 polystyrene (PS) chains with cationic terminals, added to this bilayer simulation induces negative bilayer curvature and inserts to the bilayer, regardless of the oxidized-lipid concentration. Hydrophobic monomers and cationic terminals of the PS particle interact respectively with lipid tails and headgroups, leading to the wrapping of either lipid monolayer or bilayer along the particle surface. These results indicate that lipid oxidation increases membrane curvature and permeability even at such a low concentration of oxidized lipid, which supports the experimental observations regarding the passive permeability of oxidized bilayer, and also that oxidized lipids of low concentration do not significantly influence the insertion of a cationic PS particle to the bilayer.

  1. Lateral pressure profiles in lipid monolayers

    Baoukina, Svetlana; Marrink, Siewert J.; Tieleman, D. Peter

    2010-01-01

    We have used molecular dynamics simulations with coarse-grained and atomistic models to study the lateral pressure profiles in lipid monolayers. We first consider simple oil/air and oil/water interfaces, and then proceed to lipid monolayers at air/water and oil/water interfaces. The results are

  2. Overcrowding drives the unjamming transition of gap-free monolayers

    Lan, Ganhui; Su, Tao

    Collective cell motility plays central roles in various biological phenomena such as wound healing, cancer metastasis and embryogenesis. These are demonstrations of the unjamming transition in biology. However, contradictory to the typical density-driven jamming in particulate assemblies, cellular systems often get unjammed in highly packed, sometimes overcrowding environments. Here, we investigate monolayers' collective behaviors when cell number changes under the gap-free constraint. We report that overcrowding can unjam gap-free monolayers through increasing isotropic compression. We show that the transition boundary is determined by the isotropic compression and the cell-cell adhesion. Furthermore, we construct the free energy landscape for the T1 topological transition during monolayer rearrangement, and discover that the landscape evolves from single-barrier W shape to double-barrier M shape during the unjamming process. We also discover a distributed-to-disordered morphological transition of cells' geometry, coinciding with the unjamming transition. Our analyses reveal that the overcrowding and adhesion induced unjamming reflects the mechanical yielding of the highly deformable monolayer, suggesting an alternative mechanism that cells may robustly gain collective mobility through proliferation in confined environments, which differs from those caused by loosing up a packed particulate assembly. This work is supported by the GWU College Facilitating Funds.

  3. Vascular permeability in cerebral cavernous malformations

    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...

  4. Permeability of crust is key to crispness retention

    Hirte, A.; Hamer, R.J.; Meinders, M.B.J.; Primo-Martin, C.

    2010-01-01

    Bread loses crispness rapidly after baking because water originating from the wet crumb accumulates in the dry crust. This water accumulation might be increased by the dense and low permeable character of the bread crust. Our objective was to investigate the influence of permeability of the crust on

  5. Frictional stability-permeability relationships for fractures in shales

    Fang, Yi; Elsworth, Derek; Wang, Chaoyi; Ishibashi, Takuya; Fitts, Jeffrey P.

    2017-03-01

    There is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO2 sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction-stability-permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate-rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate-rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction-stability-permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.

  6. A class of monolayer metal halogenides MX{sub 2}: Electronic structures and band alignments

    Lu, Feng; Wang, Weichao; Luo, Xiaoguang; Cheng, Yahui; Dong, Hong; Liu, Hui; Wang, Wei-Hua, E-mail: whwangnk@nankai.edu.cn [Department of Electronics and Tianjin Key Laboratory of Photo-Electronic Thin Film Device and Technology, Nankai University, Tianjin 300071 (China); Xie, Xinjian [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2016-03-28

    With systematic first principles calculations, a class of monolayer metal halogenides MX{sub 2} (M = Mg, Ca, Zn, Cd, Ge, Pb; M = Cl, Br, I) has been proposed. Our study indicates that these monolayer materials are semiconductors with the band gaps ranging from 2.03 eV of ZnI{sub 2} to 6.08 eV of MgCl{sub 2}. Overall, the band gap increases with the increase of the electronegativity of the X atom or the atomic number of the metal M. Meanwhile, the band gaps of monolayer MgX{sub 2} (X = Cl, Br) are direct while those of other monolayers are indirect. Based on the band edge curvatures, the derived electron (m{sub e}) and hole (m{sub h}) effective masses of MX{sub 2} monolayers are close to their corresponding bulk values except that the m{sub e} of CdI{sub 2} is three times larger and the m{sub h} for PbI{sub 2} is twice larger. Finally, the band alignments of all the studied MX{sub 2} monolayers are provided using the vacuum level as energy reference. These theoretical results may not only introduce the monolayer metal halogenides family MX{sub 2} into the emerging two-dimensional materials, but also provide insights into the applications of MX{sub 2} in future electronic, visible and ultraviolet optoelectronic devices.

  7. Acid monolayer functionalized iron oxide nanoparticle catalysts

    Ikenberry, Myles

    Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide

  8. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide

    Sun, Xiaoli; Wang, Zhiguo; Fu, Yong Qing

    2015-01-01

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristin...

  9. Permeability, storage and hydraulic diffusivity controlled by earthquakes

    Brodsky, E. E.; Fulton, P. M.; Xue, L.

    2016-12-01

    Earthquakes can increase permeability in fractured rocks. In the farfield, such permeability increases are attributed to seismic waves and can last for months after the initial earthquake. Laboratory studies suggest that unclogging of fractures by the transient flow driven by seismic waves is a viable mechanism. These dynamic permeability increases may contribute to permeability enhancement in the seismic clouds accompanying hydraulic fracking. Permeability enhancement by seismic waves could potentially be engineered and the experiments suggest the process will be most effective at a preferred frequency. We have recently observed similar processes inside active fault zones after major earthquakes. A borehole observatory in the fault that generated the M9.0 2011 Tohoku earthquake reveals a sequence of temperature pulses during the secondary aftershock sequence of an M7.3 aftershock. The pulses are attributed to fluid advection by a flow through a zone of transiently increased permeability. Directly after the M7.3 earthquake, the newly damaged fault zone is highly susceptible to further permeability enhancement, but ultimately heals within a month and becomes no longer as sensitive. The observation suggests that the newly damaged fault zone is more prone to fluid pulsing than would be expected based on the long-term permeability structure. Even longer term healing is seen inside the fault zone of the 2008 M7.9 Wenchuan earthquake. The competition between damage and healing (or clogging and unclogging) results in dynamically controlled permeability, storage and hydraulic diffusivity. Recent measurements of in situ fault zone architecture at the 1-10 meter scale suggest that active fault zones often have hydraulic diffusivities near 10-2 m2/s. This uniformity is true even within the damage zone of the San Andreas fault where permeability and storage increases balance each other to achieve this value of diffusivity over a 400 m wide region. We speculate that fault zones

  10. Electrokinetic effects and fluid permeability

    Berryman, J.G.

    2003-01-01

    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

  11. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    Zheng, Yu Jie; Huang, Yu Li; Chen, Yifeng; Zhao, Weijie; Eda, Goki; Spataru, Catalin D.; Zhang, Wenjing; Chang, Yung-Huang; Li, Lain-Jong; Chi, Dongzhi; Quek, Su Ying; Wee, Andrew Thye Shen

    2016-01-01

    © 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.

  12. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    Zheng, Yu Jie

    2016-01-21

    © 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.

  13. Enhanced photoresponse of monolayer molybdenum disulfide (MoS2) based on microcavity structure

    Lu, Yanan; Yang, Guofeng; Wang, Fuxue; Lu, Naiyan

    2018-05-01

    There is an increasing interest in using monolayer molybdenum disulfide (MoS2) for optoelectronic devices because of its inherent direct band gap characteristics. However, the weak absorption of monolayer MoS2 restricts its applications, novel concepts need to be developed to address the weakness. In this work, monolayer MoS2 monolithically integrates with plane microcavity structure, which is formed by the top and bottom chirped distributed Bragg reflector (DBR), is demonstrated to improve the absorption of MoS2. The optical absorption is 17-fold enhanced, reaching values over 70% at work wavelength. Moreover, the monolayer MoS2-based photodetector device with microcavity presents a significantly increased photoresponse, demonstrating its promising prospects in MoS2-based optoelectronic devices.

  14. Molecular printboards: monolayers of beta-cyclodextrins on silicon oxide surfaces.

    Onclin, Steffen; Mulder, Alart; Huskens, Jurriaan; Ravoo, Bart Jan; Reinhoudt, David N

    2004-06-22

    Monolayers of beta-cyclodextrin host molecules have been prepared on SiO2 surfaces. An ordered and stable cyano-terminated monolayer was modified in three consecutive surface reactions. First, the cyanide groups were reduced to their corresponding free amines using Red Al as a reducing agent. Second, 1,4-phenylene diisothiocyanate was used to react with the amine monolayer where it acts as a linking molecule, exposing isothiocyanates that can be derivatized further. Finally, per-6-amino beta-cyclodextrin was reacted with these isothiocyanate functions to yield a monolayer exposing beta-cyclodextrin. All monolayers were characterized by contact angle measurements, ellipsometric thickness measurements, Brewster angle Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry, which indicate the formation of a densely packed cyclodextrin surface. It was demonstrated that the beta-cyclodextrin monolayer could bind suitable guest molecules in a reversible manner. A fluorescent molecule (1), equipped with two adamantyl groups for complexation, was adsorbed onto the host monolayer from solution to form a monolayer of guest molecules. Subsequently, the guest molecules were desorbed from the surface by competition with increasing beta-cyclodextrin concentration in solution. The data were fitted using a model. An intrinsic binding constant of 3.3 +/- 1 x 10(5) M(-1) was obtained, which corresponds well to previously obtained results with a divalent guest molecule on beta-cyclodextrin monolayers on gold. In addition, the number of guest molecules bound to the host surface was determined, and a surface coverage of ca. 30% was found.

  15. Inhibition of insulin-stimulated hydrogen peroxide production prevents stimulation of sodium transport in A6 cell monolayers.

    Markadieu, N.Y.G.; Crutzen, R.; Boom, A.; Erneux, C.; Beauwens, R.

    2009-01-01

    Insulin-stimulated sodium transport across A6 cell (derived from amphibian distal nephron) monolayers involves the activation of a phosphatidylinositol (PI) 3-kinase. We previously demonstrated that exogenous addition of H2O2 to the incubation medium of A6 cell monolayers provokes an increase in PI

  16. Channel formation in single-monolayer pentacene thin film transistors

    Park, B-N; Seo, Soonjoo; Evans, Paul G

    2007-01-01

    The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport

  17. Expression and functional activity of P-glycoprotein in passaged primary human nasal epithelial cell monolayers cultured by the air-liquid interface method for nasal drug transport study.

    Cho, Hyun-Jong; Choi, Min-Koo; Lin, Hongxia; Kim, Jung Sun; Chung, Suk-Jae; Shim, Chang-Koo; Kim, Dae-Duk

    2011-03-01

    P-glycoprotein (P-gp) is an efflux transporter encoded by the multidrug resistance gene (MDR1), which is also known as the human ABCB1 gene (ATP-binding cassette, subfamily-B). The objectives of this study were to investigate the expression of P-gp in passaged primary human nasal epithelial (HNE) cell monolayer, cultured by the air-liquid interface (ALI) method, and to evaluate its feasibility as an in-vitro model for cellular uptake and transport studies of P-gp substrates. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to verify the expression of the MDR1 gene. Transport and cellular uptake studies with P-gp substrate (rhodamine123) and P-gp inhibitors (verapamil and cyclosporin A) were conducted to assess the functional activity of P-gp in HNE cell monolayers cultured by the ALI method. MDR1 gene expression in primary HNE cell monolayers cultured by ALI method was confirmed by RT-PCR. The apparent permeability coefficient (P(app) ) of the P-gp substrate (rhodamine123) in the basolateral to apical (B to A) direction was 6.9 times higher than that in the apical to basolateral (A to B) direction. B to A transport was saturated at high rhodamine123 concentration, and the treatment of P-gp inhibitors increased cellular uptake of rhodamine123 in a time- and concentration-dependent manner. These results support the MDR1 gene expression and the functional activity of P-gp in primary HNE cell monolayers cultured by the ALI method. © 2011 The Authors. JPP © 2011 Royal Pharmaceutical Society.

  18. Radionuclide assessment of pulmonary microvascular permeability

    Groeneveld, A.B.J. [Medical Intensive Care Unit, Department of Internal Medicine, Free University Hospital, De Boelelaan 1117, 1081 HV Amsterdam (Netherlands)

    1997-04-01

    The literature has been reviewed to evaluate the technique and clinical value of radionuclide measurements of microvascular permeability and oedema formation in the lungs. Methodology, modelling and interpretation vary widely among studies. Nevertheless, most studies agree on the fact that the measurement of permeability via pulmonary radioactivity measurements of intravenously injected radiolabelled proteins versus that in the blood pool, the so-called pulmonary protein transport rate (PTR), can assist the clinician in discriminating between permeability oedema of the lungs associated with the adult respiratory distress syndrome (ARDS) and oedema caused by an increased filtration pressure, for instance in the course of cardiac disease, i.e. pressure-induced pulmonary oedema. Some of the techniques used to measure PTR are also able to detect subclinical forms of lung microvascular injury not yet complicated by permeability oedema. This may occur after cardiopulmonary bypass and major vascular surgery, for instance. By paralleling the clinical severity and course of the ARDS, the PTR method may also serve as a tool to evaluate new therapies for the syndrome. Taken together, the currently available radionuclide methods, which are applicable at the bedside in the intensive care unit, may provide a gold standard for detecting minor and major forms of acute microvascular lung injury, and for evaluating the severity, course and response to treatment. (orig.). With 2 tabs.

  19. Activation of protein kinase C and disruption of endothelial monolayer integrity by sodium arsenite-Potential mechanism in the development of atherosclerosis

    Pereira, Flavia E.; Coffin, J. Douglas; Beall, Howard D.

    2007-01-01

    Arsenic exposure has been shown to exacerbate atherosclerosis, beginning with activation of the endothelium that lines the vessel wall. Endothelial barrier integrity is maintained by proteins of the adherens junction (AJ) such as vascular endothelial cadherin (VE-cadherin) and β-catenin and their association with the actin cytoskeleton. In the present study, human aortic endothelial cells (HAECs) were exposed to 1, 5 and 10 μM sodium arsenite [As(III)] for 1, 6, 12 and 24 h, and the effects on endothelial barrier integrity were determined. Immunofluorescence studies revealed formation of actin stress fibers and non-uniform VE-cadherin and β-catenin staining at cell-cell junctions that were concentration- and time-dependent. Intercellular gaps were observed with a measured increase in endothelial permeability. In addition, concentration-dependent increases in tyrosine phosphorylation (PY) of β-catenin and activation of protein kinase Cα (PKCα) were observed. Inhibition of PKCα restored VE-cadherin and β-catenin staining at cell-cell junctions and abolished the As(III)-induced formation of actin stress fibers and intercellular gaps. Endothelial permeability and PY of β-catenin were also reduced to basal levels. These results demonstrate that As(III) induces activation of PKCα, which leads to increased PY of β-catenin downstream of PKCα activation. Phosphorylation of β-catenin plausibly severs the association of VE-cadherin and β-catenin, which along with formation of actin stress fibers, results in intercellular gap formation and increased endothelial permeability. To the best of our knowledge, this is the first report demonstrating that As(III) causes a loss of endothelial monolayer integrity, which potentially could contribute to the development of atherosclerosis

  20. Prediction of permeability changes in an excavation response zone

    Kinoshita, Naoto; Ishii, Takashi; Kuroda, Hidetaka; Tada, Hiroyuki

    1992-01-01

    In geologic disposal of radioactive wastes, stress changes due to cavern excavation may expand the existing fractures and create possible bypasses for groundwater. This paper proposes a simple method for predicting permeability changes in the excavation response zones. Numerical analyses using this method predict that the response zones created by cavern excavation would differ greatly in thickness and permeability depending on the depth of the cavern site and the initial in-situ stress, that when the cavern site is deeper, response zones would expand more and permeability would increases more, and that if the ratio of horizontal to vertical in-situ stress is small, extensive permeable zones at the crown and the bottom would occur, whereas if the ratio is large, extensive permeable zones would occur in the side walls. (orig.)

  1. 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

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

    2015-01-01

    monolayers with a permeability of 5.7 × 10−5 cm sec−1 compared to an apical to basolateral permeability of 1.3 × 10−5 cm sec-1. The efflux could be inhibited with the P-gp inhibitor zosuquidar. Zosuquidar (0.4 μmol/L) reduced the efflux ratio (PB-A/PA-B) for verapamil 4.6–1.6. The presence of telmisartan......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-to-apical transepithelial efflux across the MDCK II MDR1...

  2. A drainage data-based calculation method for coalbed permeability

    Lai, Feng-peng; Li, Zhi-ping; Fu, Ying-kun; Yang, Zhi-hao

    2013-01-01

    This paper establishes a drainage data-based calculation method for coalbed permeability. The method combines material balance and production equations. We use a material balance equation to derive the average pressure of the coalbed in the production process. The dimensionless water production index is introduced into the production equation for the water production stage. In the subsequent stage, which uses both gas and water, the gas and water production ratio is introduced to eliminate the effect of flush-flow radius, skin factor, and other uncertain factors in the calculation of coalbed methane permeability. The relationship between permeability and surface cumulative liquid production can be described as a single-variable cubic equation by derivation. The trend shows that the permeability initially declines and then increases after ten wells in the southern Qinshui coalbed methane field. The results show an exponential relationship between permeability and cumulative water production. The relationship between permeability and cumulative gas production is represented by a linear curve and that between permeability and surface cumulative liquid production is represented by a cubic polynomial curve. The regression result of the permeability and surface cumulative liquid production agrees with the theoretical mathematical relationship. (paper)

  3. Relative Permeability of Fractured Rock

    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.

  4. Large Friction Anisotropy of a Polydiacetylene Monolayer

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-01-01

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  5. Molecular diffusion in monolayer and submonolayer nitrogen

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2001-01-01

    The orientational and translational motions in a monolayer fluid of physisorbed molecular nitrogen are treated using molecular dynamics simulations. Dynamical response functions and several approximations to the coefficient of translational diffusion are determined for adsorption on the basal plane...

  6. Dark excitations in monolayer transition metal dichalcogenides

    Deilmann, Thorsten; Thygesen, Kristian Sommer

    2017-01-01

    Monolayers of transition metal dichalcogenides (TMDCs) possess unique optoelectronic properties, including strongly bound excitons and trions. To date, most studies have focused on optically active excitations, but recent experiments have highlighted the existence of dark states, which are equally...

  7. Method to synthesize metal chalcogenide monolayer nanomaterials

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  8. Janus Monolayer Transition-Metal Dichalcogenides.

    Zhang, Jing; Jia, Shuai; Kholmanov, Iskandar; Dong, Liang; Er, Dequan; Chen, Weibing; Guo, Hua; Jin, Zehua; Shenoy, Vivek B; Shi, Li; Lou, Jun

    2017-08-22

    The crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe 2 , the top layer of selenium atoms is substituted by sulfur atoms, while the bottom selenium layer remains intact. The structure of this material is systematically investigated by Raman, photoluminescence, transmission electron microscopy, and X-ray photoelectron spectroscopy and confirmed by time-of-flight secondary ion mass spectrometry. Density functional theory (DFT) calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction activity is discovered for the Janus monolayer, and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.

  9. Nanotubes based on monolayer blue phosphorus

    Montes Muñ oz, Enrique; Schwingenschlö gl, Udo

    2016-01-01

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube

  10. Optical absorption in disordered monolayer molybdenum disulfide

    Ekuma, C. E.; Gunlycke, D.

    2018-05-01

    We explore the combined impact of sulfur vacancies and electronic interactions on the optical properties of monolayer MoS2. First, we present a generalized Anderson-Hubbard Hamiltonian that accounts for both randomly distributed sulfur vacancies and the presence of dielectric screening within the material. Second, we parametrize this energy-dependent Hamiltonian from first-principles calculations based on density functional theory and the Green's function and screened Coulomb (GW) method. Third, we apply a first-principles-based many-body typical medium method to determine the single-particle electronic structure. Fourth, we solve the Bethe-Salpeter equation to obtain the charge susceptibility χ with its imaginary part being related to the absorbance A . Our results show that an increased vacancy concentration leads to decreased absorption both in the band continuum and from exciton states within the band gap. We also observe increased absorption below the band-gap threshold and present an expression, which describes Lifshitz tails, in excellent qualitative agreement with our numerical calculations. This latter increased absorption in the 1.0 -2.5 eV range makes defect engineering of potential interest for solar cell applications.

  11. Exciton Binding Energy of Monolayer WS2

    Zhu, Bairen; Chen, Xi; Cui, Xiaodong

    2015-03-01

    The optical properties of monolayer transition metal dichalcogenides (TMDC) feature prominent excitonic natures. Here we report an experimental approach to measuring the exciton binding energy of monolayer WS2 with linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE). TP-PLE measurements show the exciton binding energy of 0.71 +/- 0.01 eV around K valley in the Brillouin zone.

  12. Effect of confining pressure on permeability behavior of Beishan granite

    Ma Like; Li Yunfeng; Zhao Xingguang; Tan Guohuan

    2012-01-01

    By using of the Electro-Hydraulic Servo-controlled Rock Mechanics Testing System (MTS 815.04) in the University of Hong Kong, a series of permeability tests were performed on specimens of Beishan granite at different confining pressures. The result indicates that: (1) there is a decrease of permeability due to progressive closure of initial microcracks and the corresponding volumetric strain is compressive when the confining pressures increase from 2.5 MPa to 15 MPa, (2) when the confining pressures decrease from 15 MPa to 2.5 MPa, there is an increase of permeability in this stage in relation with the volumetric dilation. (authors)

  13. Molecular Monolayers for Electrical Passivation and Functionalization of Silicon-Based Solar Energy Devices.

    Veerbeek, Janneke; Firet, Nienke J; Vijselaar, Wouter; Elbersen, Rick; Gardeniers, Han; Huskens, Jurriaan

    2017-01-11

    Silicon-based solar fuel devices require passivation for optimal performance yet at the same time need functionalization with (photo)catalysts for efficient solar fuel production. Here, we use molecular monolayers to enable electrical passivation and simultaneous functionalization of silicon-based solar cells. Organic monolayers were coupled to silicon surfaces by hydrosilylation in order to avoid an insulating silicon oxide layer at the surface. Monolayers of 1-tetradecyne were shown to passivate silicon micropillar-based solar cells with radial junctions, by which the efficiency increased from 8.7% to 9.9% for n + /p junctions and from 7.8% to 8.8% for p + /n junctions. This electrical passivation of the surface, most likely by removal of dangling bonds, is reflected in a higher shunt resistance in the J-V measurements. Monolayers of 1,8-nonadiyne were still reactive for click chemistry with a model catalyst, thus enabling simultaneous passivation and future catalyst coupling.

  14. Platinum monolayer electrocatalysts for oxygen reduction: effect of substrates, and long-term stability

    J. ZHANG

    2005-03-01

    Full Text Available We describe a novel concept for a Ptmonolayer electrocatalyst and present the results of our electrochemical, X-ray absorption spectroscopy, and scanning tunneling microscopy studies. The electrocatalysts were prepared by a new method for depositing Pt monolayers involving the galvanic displacement by Pt of an underpotentially deposited Cu monolayer on substrates of Au (111, Ir(111, Pd(111, Rh(111 and Ru(0001 single crylstals, and Pd nanoparticles. The kinetics of O2 reduction showed significant enhancement with Pt monolayers on Pd(111 and Pd nanoparticle surfaces in comparisonwith the reaction on Pt(111 and Pt nanoparticles, respectively. This increase in catalytic activity is attributed partly to the decreased formation of PtOH, as shown by in situ X-ray absorption spectroscopy. The results illustrate that placing a Pt monolayer on a suitable substrate of metal nanoparticles is an attractive way of designing better O2 reduction electrocatalysts with very low Pt contents.

  15. DNA excision repair in permeable human fibroblasts

    Kaufmann, W.K.; Bodell, W.J.; Cleaver, J.E.

    1983-01-01

    U.v. irradiation of confluent human fibroblasts activated DNA repair, aspects of which were characterized in the cells after they were permeabilized. Incubation of intact cells for 20 min between irradiation and harvesting was necessary to obtain a maximum rate of reparative DNA synthesis. Cells harvested immediately after irradiation before repair was initiated displayed only a small stimulation of DNA synthesis, indicating that permeable cells have a reduced capacity to recognize pyrimidine dimers and activate repair. The distribution of sizes of DNA strands labeled during 10 min of reparative DNA synthesis resembled that of parental DNA. However, during a 60-min incubation of permeable cells at 37 degrees C, parental DNA and DNA labeled by reparative DNA synthesis were both cleaved to smaller sizes. Cleavage also occurred in unirradiated cells, indicating that endogenous nuclease was active during incubation. Repair patches synthesized in permeable cells displayed increased sensitivity to digestion by micrococcal nuclease. However, the change in sensitivity during a chase with unlabeled DNA precursors was small, suggesting that reassembly of nucleosome structure at sites of repair was impaired. To examine whether this deficiency was due to a preponderance of incomplete or unligated repair patches, 3H-labeled (repaired) DNA was purified, then digested with exonuclease III and nuclease S1 to probe for free 3' ends and single-stranded regions. About 85% of the [3H]DNA synthesized during a 10-min pulse resisted digestion, suggesting that a major fraction of the repair patches that were filled were also ligated. U.v. light-activated DNA synthesis in permeable cells, therefore, appears to represent the continuation of reparative gap-filling at sites of excision repair activated within intact cells. Gap-filling and ligation were comparatively efficient processes in permeable cells

  16. Plasmonic light-sensitive skins of nanocrystal monolayers

    Akhavan, Shahab; Gungor, Kivanc; Mutlugun, Evren; Demir, Hilmi Volkan

    2013-04-01

    We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.

  17. Geothermal Permeability Enhancement - Final Report

    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.

  18. Protective Effects of Bifidobacterium on Intestinal Barrier Function in LPS-Induced Enterocyte Barrier Injury of Caco-2 Monolayers and in a Rat NEC Model.

    Xiang Ling

    Full Text Available Zonulin protein is a newly discovered modulator which modulates the permeability of the intestinal epithelial barrier by disassembling intercellular tight junctions (TJ. Disruption of TJ is associated with neonatal necrotizing enterocolitis (NEC. It has been shown bifidobacterium could protect the intestinal barrier function and prophylactical administration of bifidobacterium has beneficial effects in NEC patients and animals. However, it is still unknown whether the zonulin is involved in the gut barrier dysfunction of NEC, and the protective mechanisms of bifidobacterium on intestinal barrier function are also not well understood. The present study aims to investigate the effects of bifidobacterium on intestinal barrier function, zonulin regulation, and TJ integrity both in LPS-induced enterocyte barrier injury of Caco-2 monolayers and in a rat NEC model. Our results showed bifidobacterium markedly attenuated the decrease in transepithelial electrical resistance and the increase in paracellular permeability in the Caco-2 monolayers treated with LPS (P < 0.01. Compared with the LPS group, bifidobacterium significantly decreased the production of IL-6 and TNF-α (P < 0.01 and suppressed zonulin release (P < 0.05. In addition, bifidobacterium pretreatment up-regulated occludin, claudin-3 and ZO-1 expression (P < 0.01 and also preserved these proteins localization at TJ compared with the LPS group. In the in vivo study, bifidobacterium decreased the incidence of NEC from 88 to 47% (P < 0.05 and reduced the severity in the NEC model. Increased levels of IL-6 and TNF-α in the ileum of NEC rats were normalized in bifidobacterium treated rats (P < 0.05. Moreover, administration of bifidobacterium attenuated the increase in intestinal permeability (P < 0.01, decreased the levels of serum zonulin (P < 0.05, normalized the expression and localization of TJ proteins in the ileum compared with animals with NEC. We concluded that bifidobacterium may

  19. Permeability of cork to gases.

    Faria, David P; Fonseca, Ana L; Pereira, Helen; Teodoro, Orlando M N D

    2011-04-27

    The permeability of gases through uncompressed cork was investigated. More than 100 samples were assessed from different plank qualities to provide a picture of the permeability distribution. A novel technique based on a mass spectrometer leak detector was used to directly measure the helium flow through the central area of small disks 10 mm in diameter and 2 mm thick. The permeability for nitrogen, oxygen, and other gases was measured by the pressure rise technique. Boiled and nonboiled cork samples from different sections were evaluated. An asymmetric frequency distribution ranging 3 orders of magnitude (roughly from 1 to 1000 μmol/(cm·atm·day)) for selected samples without macroscopic defects was found, having a peak below 100 μmol/(cm·atm·day). Correlation was found between density and permeability: higher density samples tend to show lower permeability. However, boiled cork showed a mean lower permeability despite having a lower density. The transport mechanism of gases through cork was also examined. Calculations suggest that gases permeate uncompressed cork mainly through small channels between cells under a molecular flow regime. The diameter of such channels was estimated to be in the range of 100 nm, in agreement with the plasmodesmata size in the cork cell walls.

  20. Compression characteristics and permeability of saturated Gaomiaozi ca-bentonite

    Sun Wenjing; Sun De'an; Fang Lei

    2012-01-01

    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/cm 3 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)

  1. Catalase and superoxide dismutase conjugated with platelet-endothelial cell adhesion molecule antibody distinctly alleviate abnormal endothelial permeability caused by exogenous reactive oxygen species and vascular endothelial growth factor.

    Han, Jingyan; Shuvaev, Vladimir V; Muzykantov, Vladimir R

    2011-07-01

    Reactive oxygen species (ROS) superoxide anion (O(2)()) and hydrogen peroxide (H(2)O(2)) produced by activated leukocytes and endothelial cells in sites of inflammation or ischemia cause endothelial barrier dysfunction that may lead to tissue edema. Antioxidant enzymes (AOEs) catalase and superoxide dismutase (SOD) conjugated with antibodies to platelet-endothelial cell adhesion molecule-1 (PECAM-1) specifically bind to endothelium, quench the corresponding ROS, and alleviate vascular oxidative stress and inflammation. In the present work, we studied the effects of anti-PECAM/catalase and anti-PECAM/SOD conjugates on the abnormal permeability manifested by transendothelial electrical resistance decline, increased fluorescein isothiocyanate-dextran influx, and redistribution of vascular endothelial-cadherin in human umbilical vein endothelial cell (HUVEC) monolayers. Anti-PECAM/catalase protected HUVEC monolayers against H(2)O(2)-induced endothelial barrier dysfunction. Polyethylene glycol-conjugated catalase exerted orders of magnitude lower endothelial uptake and no protective effect, similarly to IgG/catalase. Anti-PECAM/catalase, but not anti-PECAM/SOD, alleviated endothelial hyperpermeability caused by exposure to hypoxanthine/xanthine oxidase, implicating primarily H(2)O(2) in the disruption of the endothelial barrier in this model. Thrombin-induced endothelial permeability was not affected by treatment with anti-PECAM/AOEs or the NADPH oxidase inhibitor apocynin or overexpression of AOEs, indicating that the endogenous ROS play no key role in thrombin-mediated endothelial barrier dysfunction. In contrast, anti-PECAM/SOD, but not anti-PECAM/catalase, inhibited a vascular endothelial growth factor (VEGF)-induced increase in endothelial permeability, identifying a key role of endogenous O(2)() in the VEGF-mediated regulation of endothelial barrier function. Therefore, AOEs targeted to endothelial cells provide versatile molecular tools for testing the roles of

  2. Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols.

    Li, Meng; Liu, Ping; Adzic, Radoslav R

    2012-12-06

    The slow, incomplete oxidation of methanol and ethanol on platinum-based anodes as well as the high price and limited reserves of Pt has hampered the practical application of direct alcohol fuel cells. We describe the electrocatalysts consisting of one Pt monolayer (one atom thick layer) placed on extended or nanoparticle surfaces having the activity and selectivity for the oxidation of alcohol molecules that can be controlled with platinum-support interaction. The suitably expanded Pt monolayer (i.e., Pt/Au(111)) exhibits a factor of 7 activity increase in catalyzing methanol electrooxidation relative to Pt(111). Sizable enhancement is also observed for ethanol electrooxidation. Furthermore, a correlation between substrate-induced lateral strain in a Pt monolayer and its activity/selectivity is established and rationalized by experimental and theoretical studies. The knowledge we gained with single-crystal model catalysts was successfully applied in designing real nanocatalysts. These findings for alcohols are likely to be applicable for the oxidation of other classes of organic molecules.

  3. Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

    Peter T. Bähler

    2016-07-01

    Full Text Available Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

  4. Monolayer MoS{sub 2} self-switching diodes

    Al-Dirini, Feras, E-mail: alf@unimelb.edu.au; Hossain, Md Sharafat [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Victorian Research Laboratory, National ICT Australia, West Melbourne, Victoria (Australia); Hossain, Faruque M.; Skafidas, Efstratios [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Mohammed, Mahmood A. [Princess Sumaya University for Technology, Amman (Jordan); Nirmalathas, Ampalavanapillai [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Melbourne Networked Society Institute (MNSI), University of Melbourne, Victoria (Australia)

    2016-01-28

    This paper presents a new molybdenum disulphide (MoS{sub 2}) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS{sub 2} monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS{sub 2} results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  5. Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer

    Zhang Lei; Hao Changchun; Feng Ying; Gao Feng; Lu Xiaolong; Li Junhua; Sun Runguang

    2016-01-01

    Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure–area ( π – A ) and pressure–time ( π – T ) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value. (special topic)

  6. Technique for etching monolayer and multilayer materials

    Bouet, Nathalie C. D.; Conley, Raymond P.; Divan, Ralu; Macrander, Albert

    2015-10-06

    A process is disclosed for sectioning by etching of monolayers and multilayers using an RIE technique with fluorine-based chemistry. In one embodiment, the process uses Reactive Ion Etching (RIE) alone or in combination with Inductively Coupled Plasma (ICP) using fluorine-based chemistry alone and using sufficient power to provide high ion energy to increase the etching rate and to obtain deeper anisotropic etching. In a second embodiment, a process is provided for sectioning of WSi.sub.2/Si multilayers using RIE in combination with ICP using a combination of fluorine-based and chlorine-based chemistries and using RF power and ICP power. According to the second embodiment, a high level of vertical anisotropy is achieved by a ratio of three gases; namely, CHF.sub.3, Cl.sub.2, and O.sub.2 with RF and ICP. Additionally, in conjunction with the second embodiment, a passivation layer can be formed on the surface of the multilayer which aids in anisotropic profile generation.

  7. Nanomechanics and sodium permeability of endothelial surface layer modulated by hawthorn extract WS 1442.

    Wladimir Peters

    Full Text Available The endothelial glycocalyx (eGC plays a pivotal role in the physiology of the vasculature. By binding plasma proteins, the eGC forms the endothelial surface layer (ESL which acts as an interface between bloodstream and endothelial cell surface. The functions of the eGC include mechanosensing of blood flow induced shear stress and thus flow dependent vasodilation. There are indications that levels of plasma sodium concentrations in the upper range of normal and beyond impair flow dependent regulation of blood pressure and may therefore increase the risk for hypertension. Substances, therefore, that prevent sodium induced endothelial dysfunction may be attractive for the treatment of cardiovascular disease. By means of combined atomic force-epifluorescence microscopy we studied the impact of the hawthorn (Crataegus spp. extract WS 1442, a herbal therapeutic with unknown mechanism of action, on the mechanics of the ESL of ex vivo murine aortae. Furthermore, we measured the impact of WS 1442 on the sodium permeability of endothelial EA.hy 926 cell monolayer. The data show that (i the ESL contributes by about 11% to the total endothelial barrier resistance for sodium and (ii WS 1442 strengthens the ESL resistance for sodium up to about 45%. This mechanism may explain some of the vasoprotective actions of this herbal therapeutic.

  8. Nanoemulsions of cancer chemopreventive agent benzyl isothiocyanate display enhanced solubility, dissolution, and permeability.

    Qhattal, Hussaini Syed Sha; Wang, Shu; Salihima, Tri; Srivastava, Sanjay K; Liu, Xinli

    2011-12-14

    Benzyl isothiocyanate (BITC), a compound found in cruciferous vegetables, is an effective chemopreventive agent. The objective of this study was to develop nanoemulsion formulations for the oral delivery of BITC. Optimized oil-in-water BITC nanoemulsions were prepared by a spontaneous self-nanoemulsification method and a homogenization-sonication method. Both nanoemulsions entrapped high amounts of BITC (15-17 mg/mL), with low polydispersity and good colloidal stability. The BITC nanoemulsions showed enhanced solubility and dissolution compared to pure BITC. These formulations markedly increased the apical to basolateral transport of BITC in Caco-2 cell monolayers. The apparent permeability values were 3.6 × 10(-6) cm/s for pure BITC and (1.1-1.3) × 10(-5) cm/s for BITC nanoemulsions. The nanoemulsions were easily taken up by human cancer cells A549 and SKOV-3 and inhibited tumor growth in vitro. This work shows for the first time that BITC can be formulated into nanoemulsions and may show promise in enhancing absorption and bioavailability.

  9. Modification of permeability of frog perineurium to [14C]-sucrose by stretch and hypertonicity

    Weerasuriya, A.; Rapoport, S.I.; Taylor, R.E.

    1979-01-01

    An in vitro method has been developed to determine quantitatively the permeability of the perineurium to radiotracers at room temperature. The permeability to [ 14 C]sucrose of the isolated perineurium of the sciatic nerve of the frog, Rana pipiens, was measured at rest length, when the perineurium was stretched and after the perineurium had been subjected to hypertonic treatment. Mean permeability at rest length was calculated to be 5.6 +- 0.27 (S.E.M., n=45)x10 -7 cm/sec, and both stretch and hypertonic treatment increased the permeability. A 10% stretch increased permeability reversibly, whereas a 20% stretch or immersion of the perineurium in a hypertonic bath increased permeability irreversibly. Altered permeability under these conditions might be related to changes in the ultrastructure of tight junctions in the perineurium. (Auth.)

  10. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide.

    Sun, Xiaoli; Wang, Zhiguo; Fu, Y Q

    2015-12-22

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25-0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries.

  11. The kinetics of denitrification in permeable sediments

    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...... 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 K...... in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O-2 consumption to V-max was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. As a consequence, models implemented...

  12. 钻孔割缝网络化增透机制及其在底板穿层钻孔瓦斯抽采中的应用%Permeability-increasing mechanism of network slotting boreholes and application in crossing borehole gas drainage

    林柏泉; 张其智; 沈春明; 杨威

    2012-01-01

    For the pressure relief inadequacy problem of bottom road boreholes, based on the method of combination of theoretical analysis and field tests, the permeability-increasing mechanism of network slotting boreholes was studied, and the permeability-increasing technology of network slotted boreholes crossing from floor was proposed. Filed test show that the technology can improve the extraction effect significantly,the permeability can be increased by 122 times in average, while the extraction flow increases 3.5 times and the gas concentration increases 2.3 times, and the stand- ard time of gas pre-pumping decreases more than 50%.%针对底板穿层瓦斯抽采钻孔卸压不充分的主要问题,采用理论分析与现场试验相结合的方法,研究了钻孔割缝网络化卸压增透机制,提出了底板穿层钻孔割缝网络化增透技术,并且在国内相关矿井进行了现场应用。应用结果表明:采用该技术措施后,平均透气性系数提高了122倍,瓦斯抽采流量提高了3.5倍,瓦斯抽采浓度提高了2.3倍,预抽达标时间缩短50%以上。

  13. Permeability of WIPP Salt During Damage Evolution and Healing

    BODNER, SOL R.; CHAN, KWAI S.; MUNSON, DARRELL E.

    1999-01-01

    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

  14. Stress dependence of permeability of intact and fractured shale cores.

    van Noort, Reinier; Yarushina, Viktoriya

    2016-04-01

    Whether a shale acts as a caprock, source rock, or reservoir, understanding fluid flow through shale is of major importance for understanding fluid flow in geological systems. Because of the low permeability of shale, flow is thought to be largely confined to fractures and similar features. In fracking operations, fractures are induced specifically to allow for hydrocarbon exploration. We have constructed an experimental setup to measure core permeabilities, using constant flow or a transient pulse. In this setup, we have measured the permeability of intact and fractured shale core samples, using either water or supercritical CO2 as the transporting fluid. Our measurements show decreasing permeability with increasing confining pressure, mainly due to time-dependent creep. Furthermore, our measurements show that for a simple splitting fracture, time-dependent creep will also eliminate any significant effect of this fracture on permeability. This effect of confinement on fracture permeability can have important implications regarding the effects of fracturing on shale permeability, and hence for operations depending on that.

  15. Diagenetic effect on permeabilities of geothermal sandstone reservoirs

    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...

  16. Water permeability is a measure of severity in acute appendicitis.

    Pini, Nicola; Pfeifle, Viktoria A; Kym, Urs; Keck, Simone; Galati, Virginie; Holland-Cunz, Stefan; Gros, Stephanie J

    2017-12-01

    Acute appendicitis is the most common indication for pediatric abdominal emergency surgery. Determination of the severity of appendicitis on clinical grounds is challenging. Complicated appendicitis presenting with perforation, abscess or diffuse peritonitis is not uncommon. The question remains why and when acute appendicitis progresses to perforation. The aim of this study was to assess the impact of water permeability on the severity of appendicitis. We show that AQP1 expression and water permeability in appendicitis correlate with the stage of inflammation and systemic infection parameters, leading eventually to perforation of the appendix. AQP1 is also expressed within the ganglia of the enteric nervous system and ganglia count increases with inflammation. Severity of appendicitis can be correlated with water permeability measured by AQP1 protein expression and increase of ganglia count in a progressive manner. This introduces the question if regulation of water permeability can present novel curative or ameliorating therapeutic options.

  17. Acamprosate has no impact on the permeability of paracellular markers across Caco-2 cells

    Antonescu, Irina; Steffansen, Bente; Neuhoff, Sibylle

    of the paracellular markers, mannitol and Lucifer Yellow (LY), was investigated. Methods: Ppara of LY and [14C]-mannitol was investigated across filter grown human epithelial colorectal adenocarcinoma (Caco-2) cell monolayers. Changes in the transepithelial electrical resistance (TEER) across the monolayers were...... the [14C]-mannitol, Papp values of 0.71±0.2x10-6 and 0.51±0.17x10-6 cm/s were obtained. TEER values at the end of all experiments were in the range of 426-444 ohm*cm2. Summary/Conclusion: Acamprosate has no impact on the paracellular pathway across Caco-2 cell monolayers of LY and mannitol, or on the TEER......Backgrounds: The oral bioavailability of poorly permeable and non-metabolised acamprosate (BCS III) is 11%. It is controversial whether the intestinal effective permeability of the fully an-ionized acamprosate (pKa 1.83; MW 181.2 g/mol) is predominantly paracellular (Ppara) or transcellular...

  18. Permeability, zonulin production, and enteropathy in dermatitis herpetiformis.

    Smecuol, Edgardo; Sugai, Emilia; Niveloni, Sonia; Vázquez, Horacio; Pedreira, Silvia; Mazure, Roberto; Moreno, María Laura; Label, Marcelo; Mauriño, Eduardo; Fasano, Alessio; Meddings, Jon; Bai, Julio César

    2005-04-01

    Dermatitis herpetiformis (DH) is characterized by variable degrees of enteropathy and increased intestinal permeability. Zonulin, a regulator of tight junctions, seems to play a key role in the altered intestinal permeability that characterizes the early phase of celiac disease. Our aim was to assess both intestinal permeability and serum zonulin levels in a group of patients with DH having variable grades of enteropathy. We studied 18 DH patients diagnosed on the basis of characteristic immunoglobulin (Ig)A granular deposits in the dermal papillae of noninvolved skin. Results were compared with those of classic celiac patients, patients with linear IgA dermatosis, and healthy controls. According to Marsh's classification, 5 patients had no evidence of enteropathy (type 0), 4 patients had type II, 2 patients had type IIIb damage, and 7 patients had a more severe lesion (type IIIc). Intestinal permeability (lactulose/mannitol ratio [lac/man]) was abnormal in all patients with DH. Patients with more severe enteropathy had significantly greater permeability ( P zonulin concentration (enzyme-linked immunosorbent assay) for patients with DH was 2.1 +/- .3 ng/mg with 14 of 16 (87.5%) patients having abnormally increased values. In contrast, patients with linear IgA dermatosis had normal histology, normal intestinal permeability, and negative celiac serology. Increased intestinal permeability and zonulin up-regulation are common and concomitant findings among patients with DH, likely involved in pathogenesis. Increased permeability can be observed even in patients with no evidence of histologic damage in biopsy specimens. Patients with linear IgA dermatosis appear to be a distinct population with no evidence of gluten sensitivity.

  19. Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells

    Artursson, P.; Karlsson, J.

    1991-01-01

    Monolayers of a well differentiated human intestinal epithelial cell line, Caco-2, were used as a model to study passive drug absorption across the intestinal epithelium. Absorption rate constants (expressed as apparent permeability coefficients) were determined for 20 drugs and peptides with different structural properties. The permeability coefficients ranged from approximately 5 x 10 - 8 to 5 x 10 - 5 cm/s. A good correlation was obtained between data on oral absorption in humans and the results in the Caco-2 model. Drugs that are completely absorbed in humans had permeability coefficients greater than 1 x 10 - 6 cm/s. Drugs that are absorbed to greater than 1% but less than 100% had permeability coefficients of 0.1-1.0 x 10 - 6 cm/s while drugs and peptides that are absorbed to less than 1% had permeability coefficients of less than or equal to 1 x 10 - 7 cm/s. The results indicate that Caco-2 monolayers can be used as a model for studies on intestinal drug absorption

  20. Thermal ripples in model molybdenum disulfide monolayers

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Changes in permeability caused by transient stresses: field observations, experiments, and mechanisms

    Manga, Michael; Beresnev, Igor; Brodsky, Emily E.; Elkhoury, Jean E.; Elsworth, Derek; Ingebritsen, Steve E.; Mays, David C.; Wang, Chi-Yuen

    2012-01-01

    Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10–6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to prestimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the prestimulated value is governed by the time to reblock pores, or for geochemical processes to seal pores. Monitoring permeability in geothermal systems where there is abundant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution.

  2. Influence of demagnetizing field on the permeability of soft magnetic composites

    Lin, G.Q.; Li, Z.W.; Chen, Linfeng; Wu, Y.P.; Ong, C.K.

    2006-01-01

    The influence of demagnetizing field on the effective permeability of magnetic composites has been investigated. A theoretical expression of the effective permeability has been obtained and discussed according to four typical composites with spheres, needles, flakes, and aligned prolate ellipsoidal particles. The results indicate that the demagnetizing field within the particles can reduce the effective permeability significantly. In order to increase the effective permeability, it is necessary to decrease the demagnetizing field within the particles. A linear relationship between effective permeability and volume fraction is also observed for composites filled with spherical particles at low volume fraction

  3. Monolayer-by-monolayer growth of platinum films on complex carbon fiber paper structure

    Pang, Liuqing; Zhang, Yunxia [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Liu, Shengzhong, E-mail: szliu@dicp.ac.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Dalian National Laboratory for Clean Energy, iChEM, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2017-06-15

    Graphical abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer strategy. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. - Highlights: • Developed a controlled monolayer-by-monolayer Pt deposition using a dual buffer strategy. • The present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. • This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. - Abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer (Au/Ni) strategy. The X-ray diffraction, electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value.

  4. Long-term bioventing performance in low-permeability soils

    Phelps, M.B.; Stanin, F.T.; Downey, D.C.

    1995-01-01

    Short-term and long-term bioventing treatability testing has shown that in situ air injection and extraction is a practical method for sustaining increased oxygen levels and enhancing aerobic biodegradation of petroleum hydrocarbons in low-permeability soils. At several test sites, initial physical parameter analysis of soils and air permeability tests indicated that impacted soils (fine sandy silts and clays) had low air permeabilities. Measurements of depleted soil-gas oxygen levels and increased soil-gas carbon dioxide levels indicated that the natural process of aerobic biodegradation of petroleum hydrocarbons was oxygen-limited. Initial treatability testing consisted of air permeability tests to measure the permeability of the soils to air and in situ respiration tests to measure the rates at which native microorganisms could biodegrade the contaminants when provided with sufficient oxygen. During the long-term treatment period, active air injection or extraction systems were operated for 1 year or longer. Soil gas was periodically monitored within the treatment zone to evaluate the success of the bioventing systems in increasing soil-gas oxygen levels in the low-permeability soils. Follow-up respiration tests and soil and soil-gas sampling were conducted to evaluate changes in respiration rates and contaminant concentrations with time

  5. Potential of amino acid/dipeptide monoester prodrugs of floxuridine in facilitating enhanced delivery of active drug to interior sites of tumors: a two-tier monolayer in vitro study.

    Tsume, Yasuhiro; Hilfinger, John M; Amidon, Gordon L

    2011-10-01

    To evaluate the advantages of amino acid/dipeptide monoester prodrugs for cancer treatments by assessing the uptake and cytotoxic effects of floxuridine prodrugs in a secondary cancer cell monolayer following permeation across a primary cancer cell monolayer. The first Capan-2 monolayer was grown on membrane transwell inserts; the second monolayer was grown at the bottom of a plate. The permeation of floxuridine and its prodrugs across the first monolayer and the uptake and cell proliferation assay on secondary layer were sequentially determined. All floxuridine prodrugs exhibited greater permeation across the first Capan-2 monolayer than the parent drug. The correlation between uptake and growth inhibition in the second monolayer with intact prodrug permeating the first monolayer suggests that permeability and enzymatic stability are essential for sustained action of prodrugs in deeper layers of tumors. The correlation of uptake and growth inhibition were vastly superior for dipeptide prodrugs to those obtained with mono amino acid prodrugs. Although a tentative general overall correlation between intact prodrug and uptake or cytotoxic action was obtained, it appears that a mixture of floxuridine prodrugs with varying beneficial characteristics may be more effective in treating tumors.

  6. Intestinal Permeability of β-Lapachone and Its Cyclodextrin Complexes and Physical Mixtures.

    Mangas-Sanjuan, Victor; Gutiérrez-Nieto, Jorge; Echezarreta-López, Magdalena; González-Álvarez, Isabel; González-Álvarez, Marta; Casabó, Vicente-Germán; Bermejo, Marival; Landin, Mariana

    2016-12-01

    β-Lapachone (βLAP) is a promising, poorly soluble, antitumoral drug. βLAP combination with cyclodextrins (CDs) improves its solubility and dissolution but there is not enough information about the impact of cyclodextrins on βLAP intestinal permeability. The objectives of this work were to characterize βLAP intestinal permeability and to elucidate cyclodextrins effect on the dissolution properties and on the intestinal permeability. The final goal was to evaluate CDs influence on the oral absorption of βLAP. Binary systems (physical mixtures and inclusion complexes) including βLAP and CDs (β-cyclodextrin: βCD, random-methyl-β-cyclodextrin: RMβCD and sulfobutylether-β-cyclodextrin: SBEβCD) have been prepared and analysed by differential scanning calorimetry. βLAP (and its combinations with CDs) absorption rate coefficients and effective permeability values have been determined in vitro in MDCK or MDCK-Mdr1 monolayers and in situ in rat by a closed loop perfusion technique. DSC results confirmed the formation of the inclusion complexes. βLAP-CDs inclusion complexes improve drug solubility and dissolution rate in comparison with physical mixtures. βLAP presented a high permeability value which can provide complete oral absorption. Its oral absorption is limited by its low solubility and dissolution rate. Cyclodextrin (both as physical mixtures and inclusion complexes) showed a positive effect on the intestinal permeability of βLAP. Complexation with CDs does not reduce βLAP intestinal permeability in spite of the potential negative effect of the reduction in free fraction of the drug. The use of RMβCD or SBEβCD inclusion complexes could benefit βLAP oral absorption by enhancing its solubility, dissolution rate and permeability.

  7. Electrochemical behavior of monolayer and bilayer graphene.

    Valota, Anna T; Kinloch, Ian A; Novoselov, Kostya S; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W; Dryfe, Robert A W

    2011-11-22

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as a masking coating in order to expose a stable, well-defined area of graphene. Both multilayer and monolayer graphene microelectrodes showed quasi-reversible behavior during voltammetric measurements in potassium ferricyanide. However, the standard heterogeneous charge transfer rate constant, k°, was estimated to be higher for monolayer graphene flakes. © 2011 American Chemical Society

  8. Sub-THz Characterisation of Monolayer Graphene

    Ehsan Dadrasnia

    2014-01-01

    Full Text Available We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325–500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range.

  9. Low temperature photoresponse of monolayer tungsten disulphide

    Bingchen Cao

    2014-11-01

    Full Text Available High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup, while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  10. Nonlinear optical studies of organic monolayers

    Shen, Y.R.

    1988-02-01

    Second-order nonlinear optical effects are forbidden in a medium with inversion symmetry, but are necessarily allowed at a surface where the inversion summary is broken. They are often sufficiently strong so that a submonolayer perturbation of the surface can be readily detected. They can therefore be used as effective tools to study monolayers adsorbed at various interfaces. We discuss here a number of recent experiments in which optical second harmonic generation (SHG) and sum-frequency generation (SFG) are employed to probe and characterize organic monolayers. 15 refs., 5 figs

  11. Ammonia gas permeability of meat packaging materials.

    Karim, Faris; Hijaz, Faraj; Kastner, Curtis L; Smith, J Scott

    2011-03-01

    Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.

  12. Fluorescein transport properties across artificial lipid membranes, Caco-2 cell monolayers and rat jejunum.

    Berginc, Katja; Zakelj, Simon; Levstik, Lea; Ursic, Darko; Kristl, Albin

    2007-05-01

    Membrane transport characteristics of a paracellular permeability marker fluorescein were evaluated using artificial membrane, Caco-2 cell monolayers and rat jejunum, all mounted in side-by-side diffusion cells. Modified Ringer buffers with varied pH values were applied as incubation salines on both sides of artificial membrane, cell culture monolayers or rat jejunum. Passive transport according to pH partition theory was determined using all three permeability models. In addition to that, active transport of fluorescein in the M-S (mucosal-to-serosal) direction through rat jejunum was observed. The highest M-S P(app) values regarding the active transport through the rat jejunum were observed in incubation saline with pH 6.5. Fluorescein transport through the rat jejunum was inhibited by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) and alpha-CHC (alpha-cyano-4-hydroxycinnamic acid). Thus, we assume that two pH-dependent influx transporters could be involved in the fluorescein membrane transport through the intestinal (jejunal) epithelium. One is very likely an MCT (monocarboxylic acid cotransporter) isoform, inhibited by specific MCT inhibitor alpha-CHC, while the involvement of the second one with overlapping substrate/inhibitor specificities (most probably a member of the organic anion-transporting polypeptide family, inhibited at least partially by DIDS) could not be excluded.

  13. Translocation of SiO2-NPs across in vitro human bronchial epithelial monolayer

    George, I; Vranic, S; Boland, S; Borot, M C; Marano, F; Baeza-Squiban, A

    2013-01-01

    Safe development and application of nanotechnologies in many fields require better knowledge about their potential adverse effects on human health. Evidence of abilities of nanoparticles (NPs) to cross epithelial barriers and reach secondary organs via the bloodstream led us to investigate the translocation of SiO 2 NPs of 50 nm (50 nm-SiO 2 -NPs) across human bronchial epithelial cells that are primary targets after exposure to inhaled NPs. We quantified the translocation of fluorescently labelled SiO 2 NPs at non-cytotoxic concentrations (5 and 10 μg/cm 2 ) across Calu-3 epithelial monolayer. After 14 days in culture Calu-3 cells seeded onto 3 μm-polycarbonate Transwell membranes formed an efficient bronchial barrier assessed by measurement of the transepithelial electric resistance and quantification of the permeability of the monolayer. After 24 hours of exposure, we observed a significant translocation of NPs that was more important when the initial NP concentration decreased. Confocal microscopy observations revealed NP uptake by cells and an important NP retention inside the porous membrane. In conclusion, 50 nm-SiO 2 -NPs can cross the human bronchial epithelial barrier without affecting the integrity of the epithelial cell monolayer.

  14. Highly permeable, cement-bounded backfilling mortars for SMA repositories

    Jacobs, F.; Mayer, G.; Wittmann, F.H.

    1994-03-01

    In low- and intermediate-level waste repositories, gas is produced due e.g. to corrosion. This gas must be able to escape from the repository in order to prevent damage to the repository structure. A cement-based backfill should take over this function. For this purpose, the composition of cement-based materials was varied to study their influence on porosity and permeability. In parallel to this study the behaviour of fresh concrete, the liberation of the heat of hydration and the hardened concrete properties were investigated. To characterize the permeability of cement-based materials the following parameters are important: 1) composition of the material (pore fabric), 2) storage conditions (degree of saturation), 3) degree of hydration (age), 4) measuring fluid. A change in the composition of cement-based materials can vary the permeability by ten orders of magnitude. It is shown that, by using dense aggregates, the transport of the fluid takes place through the matrix and along the aggregate/matrix interface. By using porous aggregates the permeability can be increased by two orders of magnitude. In the case of a dense matrix, porous aggregates do not alter the permeability. Increasing the matrix content or interface content increases permeability. Hence light weight mortars are an obvious choice. Like-grained mixes showed higher permeabilities in combination with better mechanical properties but, in comparison to normal mixes, they showed worse flow properties. With the composition cement-: water-: aggregate content 1:0.4:5.33 the likegrained mix with aggregates ranging from 2 to 3 mm proved to be a suitable material. With a low compaction after 28 days this mix reaches a permeability of 4.10 -12 m 2 and an uniaxial cylinder compressive strength of 16 N/mm 2 . (author) 58 figs., 23 tabs., refs

  15. Investigation of negative permeability metamaterials for wireless power transfer

    Wenhui Xin

    2017-11-01

    Full Text Available In order to enhance the transmission efficiency of wireless power transfer (WPT, a negative permeability metamaterials (NPM with a structure of honeycomb composed by units of hexagon-shaped spirals copper is proposed in this paper. The unit parameters of the NPM are optimized, to make sure the negative permeability at the special frequency. The S-parameters of the designed NPM are measured by a network analyzer and the permeability is extracted, it shows the honeycomb NPM has a negative permeability at 6.43 MHz. A two-coil WPT is setup and the transmission efficiency of WPT embedded with NPM at the different position and with different structure are investigated. The measured results show that the 2-slab honeycomb NPM have a good perform compared with the 1-slab NPM, and the efficiency can be increased up to 51%. The results show that honeycomb NPM embedded in the WPT help to improve the transmission efficiency remarkable.

  16. Investigation of negative permeability metamaterials for wireless power transfer

    Xin, Wenhui; Mi, Chunting Chris; He, Fei; Jiang, Meng; Hua, Dengxin

    2017-11-01

    In order to enhance the transmission efficiency of wireless power transfer (WPT), a negative permeability metamaterials (NPM) with a structure of honeycomb composed by units of hexagon-shaped spirals copper is proposed in this paper. The unit parameters of the NPM are optimized, to make sure the negative permeability at the special frequency. The S-parameters of the designed NPM are measured by a network analyzer and the permeability is extracted, it shows the honeycomb NPM has a negative permeability at 6.43 MHz. A two-coil WPT is setup and the transmission efficiency of WPT embedded with NPM at the different position and with different structure are investigated. The measured results show that the 2-slab honeycomb NPM have a good perform compared with the 1-slab NPM, and the efficiency can be increased up to 51%. The results show that honeycomb NPM embedded in the WPT help to improve the transmission efficiency remarkable.

  17. Quantifying tidally driven benthic oxygen exchange across permeable sediments

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

    2014-01-01

    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...... 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 variable sediment O-2 penetration depth (from approximate to 3 to 8 mm) and the concurrent turbulence-driven 25-fold variation in the benthic sediment O-2 uptake. The O-2 flux and variability were reproduced using a simple 1-D model linking the benthic turbulence to the sediment pore water exchange...

  18. Study on Surface Permeability of Concrete under Immersion.

    Liu, Jun; Xing, Feng; Dong, Biqin; Ma, Hongyan; Pan, Dong

    2014-01-28

    In this paper, concrete specimens are immersed in ultrapure water, to study the evolutions of surface permeability, pore structure and paste microstructure following the prolonging of immersion period. According to the results, after 30-day immersion, the surface permeability of concrete becomes higher as compared with the value before immersion. However, further immersion makes the surface permeability decrease, so that the value measured after 150-day immersion is only half that measured after 30-day immersion. The early increase in surface permeability should be mainly attributed to the leaching of calcium hydroxide, while the later decrease to the refinement of pore structure due to hydration. The two effects work simultaneously and compete throughout the immersion period. The proposed mechanisms get support from microscopic measurements and observations.

  19. Segmental dependent transport of low permeability compounds along the small intestine due to P-glycoprotein: the role of efflux transport in the oral absorption of BCS class III drugs.

    Dahan, Arik; Amidon, Gordon L

    2009-01-01

    The purpose of this study was to investigate the role of P-gp efflux in the in vivo intestinal absorption process of BCS class III P-gp substrates, i.e. high-solubility low-permeability drugs. The in vivo permeability of two H (2)-antagonists, cimetidine and famotidine, was determined by the single-pass intestinal perfusion model in different regions of the rat small intestine, in the presence or absence of the P-gp inhibitor verapamil. The apical to basolateral (AP-BL) and the BL-AP transport of the compounds in the presence or absence of various efflux transporters inhibitors (verapamil, erythromycin, quinidine, MK-571 and fumitremorgin C) was investigated across Caco-2 cell monolayers. P-gp expression levels in the different intestinal segments were confirmed by immunoblotting. Cimetidine and famotidine exhibited segmental dependent permeability through the gut wall, with decreased P(eff) in the distal ileum in comparison to the proximal regions of the intestine. Coperfusion of verapamil with the drugs significantly increased the permeability in the ileum, while no significant change in the jejunal permeability was observed. Both drugs exhibited significantly greater BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. Concentration dependent decrease of this secretion was obtained by the P-gp inhibitors verapamil, erythromycin and quinidine, while no effect was evident by the MRP2 inhibitor MK-571 and the BCRP inhibitor FTC, indicating that P-gp is the transporter mediates the intestinal efflux of cimetidine and famotidine. P-gp levels throughout the intestine were inversely related to the in vivo permeability of the drugs from the different segments. The data demonstrate that for these high-solubility low-permeability P-gp substrates, P-gp limits in vivo intestinal absorption in the distal segments of the small intestine; however P-gp plays a minimal role in the proximal intestinal segments due to significant lower P-gp expression levels

  20. Strain and electric field induced metallization in the GaX (X = N, P, As & Sb) monolayer

    Bahuguna, Bhagwati Prasad; Saini, L. K.; Sharma, Rajesh O.; Tiwari, Brajesh

    2018-05-01

    We investigate the strain and electric field dependent electronic properties of two dimensional Ga-based group III-V monolayer from the first-principles approach within density functional theory. The energy bandgap of GaX monolayer increases upto the certain value of compressive strain and then decreases. On the other hand, the energy bandgap of GaX monolayer is monotonically decreased with increasing tensile strain and become metallic at the higher value. Furthermore, the perpendicular electric field decreases the energy band gap of unstrained GaX monolayer and shows semiconductor to metal transition. These results suggest that the nature of energy bands and value of energy bandgap in GaX monolayer can be tuned by the biaxial mechanical strain or perpendicular electrical field. Additionally, we have also studied the optical response of unstrained GaX monolayer in term of optical conductivity. These findings may provide valuable information to develop the Ga-based optoelectronic devices and further the understanding of the GaX monolayer.

  1. First-Principles Investigation of Phase Stability, Electronic Structure and Optical Properties of MgZnO Monolayer

    Changlong Tan

    2016-10-01

    Full Text Available MgZnO bulk has attracted much attention as candidates for application in optoelectronic devices in the blue and ultraviolet region. However, there has been no reported study regarding two-dimensional MgZnO monolayer in spite of its unique properties due to quantum confinement effect. Here, using density functional theory calculations, we investigated the phase stability, electronic structure and optical properties of MgxZn1−xO monolayer with Mg concentration x range from 0 to 1. Our calculations show that MgZnO monolayer remains the graphene-like structure with various Mg concentrations. The phase segregation occurring in bulk systems has not been observed in the monolayer due to size effect, which is advantageous for application. Moreover, MgZnO monolayer exhibits interesting tuning of electronic structure and optical properties with Mg concentration. The band gap increases with increasing Mg concentration. More interestingly, a direct to indirect band gap transition is observed for MgZnO monolayer when Mg concentration is higher than 75 at %. We also predict that Mg doping leads to a blue shift of the optical absorption peaks. Our results may provide guidance for designing the growth process and potential application of MgZnO monolayer.

  2. Photoluminescence inhomogeneity and excitons in CVD-grown monolayer WS2

    Ren, Dan-Dan; Qin, Jing-Kai; Li, Yang; Miao, Peng; Sun, Zhao-Yuan; Xu, Ping; Zhen, Liang; Xu, Cheng-Yan

    2018-06-01

    Transition metal dichalcogenides two-dimensional materials are of great importance for future electronic and optoelectronic applications. In this work, triangular WS2 monolayers with size up to 130 μm were prepared via chemical vapor deposition method. WS2 monolayers presented uniform Raman intensity, while quenched photoluminescence (PL) was observed in the center. The PL quenching in the central part of WS2 monolayer flakes was attributed to the gradually increasing sulfur vacancies toward the center. The proportion of negative trion (X-) in PL spectrum increases with increasing sulfur vacancies in WS2. The enhanced binding energy of X- suggests higher Fermi level and n-doping level with larger sulfur vacancy concentration. Our findings may be beneficial to the development of integrated devices, and also explore the defect-induced optical and electrical properties for nanophotonics.

  3. Transverse Chemotactic Migration of Bacteria from High to Low Permeability Regions in a Dual Permeability Porous Microfluidic Device

    Singh, R.; Olson, M. S.

    2011-12-01

    to decrease at 9.8 mm and 19.6 mm cross-sections in low permeability regions due to dilution with the injectate from the non-porous channel (Figure 1). However, relative bacterial counts increased in the low permeability region at both downstream cross-sections under chemotactic conditions. A large increase in relative bacterial count in the pore throats just outside the low permeability region was also observed at both cross-sections (Figure 1). The bacterial chemotactic response was observed to decrease linearly with increasing Darcy velocity and at flow rate 0.220 mm/s the chemotactic effect was offset by the advective flow in the porous channel.

  4. Imidazolide monolayers for versatile reactive microcontact printing

    Hsu, S.H.; Reinhoudt, David; Huskens, Jurriaan; Velders, Aldrik

    2008-01-01

    Imidazolide monolayers prepared from the reaction of amino SAMs with N,N-carbonyldiimidazole (CDI) are used as a versatile platform for surface patterning with amino-, carboxyl- and alcohol-containing compounds through reactive microcontact printing (µCP). To demonstrate the surface reactivity of

  5. Nanotubes based on monolayer blue phosphorus

    Montes Muñoz, Enrique

    2016-07-08

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube diameter and axial strain. The nanotubes are found to be semiconductors with a sensitive indirect band gap that allows flexible tuning.

  6. Integrated circuits based on conjugated polymer monolayer.

    Li, Mengmeng; Mangalore, Deepthi Kamath; Zhao, Jingbo; Carpenter, Joshua H; Yan, Hongping; Ade, Harald; Yan, He; Müllen, Klaus; Blom, Paul W M; Pisula, Wojciech; de Leeuw, Dago M; Asadi, Kamal

    2018-01-31

    It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm 2  V -1  s -1 . The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.

  7. Shadow mask evaporation through monolayer modified nanostencils

    Kolbel, M.; Tjerkstra, R.W.; Brugger, J.P.; van Rijn, C.J.M.; Nijdam, W.; Huskens, Jurriaan; Reinhoudt, David

    2002-01-01

    Gradual clogging of the apertures of nanostencils used as miniature shadow masks in metal evaporations can be reduced by coating the stencil with self-assembled monolayers (SAM). This is quantified by the dimensions (height and volume) of gold features obtained by nanostencil evaporation as measured

  8. Fullerene monolayer formation by spray coating

    Cervenka, J.; Flipse, C.F.J.

    2010-01-01

    Many large molecular complexes are limited in thin film applications by their insufficient thermal stability, which excludes deposition via commonly used vapour phase deposition methods. Here we demonstrate an alternative way of monolayer formation of large molecules by a simple spray coating method

  9. Semiconductor monolayer assemblies with oriented crystal faces

    Ma, Guijun; Takata, Tsuyoshi; Katayama, Masao; Zhang, Fuxiang; Moriya, Yosuke; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  10. Fullerene monolayer formation by spray coating

    Červenka, Jiří; Flipse, C.F.J.

    2010-01-01

    Roč. 21, č. 6 (2010), 065302/1-065302/7 ISSN 0957-4484 Institutional research plan: CEZ:AV0Z10100521 Keywords : monolayer * spray coating * fullerene * atomic force microscopy * scanning tunnelling microscopy * electronic structure * graphite * gold Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.644, year: 2010

  11. Onset wear in self-assembled monolayers

    D'Acunto, Mario

    2006-01-01

    Self-assembled monolayers (SAMs) are very useful for the systematic modification of the physical, chemical and structural properties of a surface by varying the chain length, tail group and composition. Many of these properties can be studied making use of atomic force microscopy (AFM), and the interaction between the AFM probe tip and the SAMs can also be considered an excellent reference to study the fundamental properties of dissipation phenomena and onset wear for viscoelastic materials on the nanoscale. We have performed a numerical study showing that the fundamental mechanism for the onset wear is a process of nucleation of domains starting from initial defects. An SAM surface repeatedly sheared by an AFM probe tip with enough applied loads shows the formation of progressive damages nucleating in domains. The AFM induced surface damages involve primarily the formation of radicals from the carbon chain backbones, but the deformations of the chains resulting in changes of period lattice also have to be taken into consideration. The nucleation of the wear domains generally starts at the initial surface defects where the energy cohesion between chains is lower. Moreover, the presence of surface defects is consistent with the changes in lateral force increasing the probability of the activation for the removal of carbon debris from the chain backbone. The quantification of the progressive worn area is performed making use of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for phase transition kinetic processes. The advantage of knowing the general conditions for onset wear on the SAM surfaces can help in studying the fundamental mechanisms for the tribological properties of viscoelastic materials, in solid lubrication applications and biopolymer mechanics

  12. Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Lee, Mi Jung; Park, Bae Ho; Lee, Changgu; Yoon, Duhee; Cheong, Hyeonsik; Lee, Ki Ho; Son, Young-Woo; Park, Jeong Young; Salmeron, Miquel

    2011-07-29

    Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

  13. Kinetics of monolayer graphene growth by segregation on Pd(111)

    Mok, H. S.; Murata, Y.; Kodambaka, S., E-mail: kodambaka@ucla.edu [Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095 (United States); Ebnonnasir, A.; Ciobanu, C. V. [Department of Mechanical Engineering and Materials Science Program, Colorado School of Mines, Golden, Colorado 80401 (United States); Nie, S.; McCarty, K. F. [Sandia National Laboratories, Livermore, California 94550 (United States)

    2014-03-10

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface.

  14. Kinetics of monolayer graphene growth by segregation on Pd(111)

    Mok, H. S.; Murata, Y.; Kodambaka, S.; Ebnonnasir, A.; Ciobanu, C. V.; Nie, S.; McCarty, K. F.

    2014-01-01

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface

  15. Conduction quantization in monolayer MoS2

    Li, T. S.

    2016-10-01

    We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.

  16. EDZ and permeability in clayey rocks

    Levasseur, Severine; Collin, Frederic; Charlier, Robert; Besuelle, Pierre; Chambon, Rene; Viggiani, Cino

    2010-01-01

    element codes is not trivial. Strain localisation in classical solid mechanics leads to nonobjective (mesh dependent) results for such process. Enriched continuum theories (like second gradient models who introduce an internal length scale) are needed to overcome this drawback. However even if these methods provide objective results, it is recalled that they don't restore uniqueness: multiple solutions are always possible. It is shown that it is possible to model strain localization as a precursor of fractures. Advantages and drawbacks of different refinement in the FE modelling are discussed. Permeability depends on strain and on fracture opening. Field observations indicate an increase of permeability of some orders of magnitude within the EDZ. How can be modelled the observed permeability increase? It depends on the kind of FE model used for the solid mechanics part of the problem. Solutions of coupled problems occurring during drilling can be proposed based on direct relations between EDZ damage processes and permeability variations as shown for the modelling of lab tests by Dizier et al. (2009) or for the modelling of field experiments by Levasseur et al. (2009a). It provides a global evolution of the permeability tensor in EDZ. But, explicit strain localizations can also be considered by means of second gradient modelling or the definition of crack media with interface elements. It permits to modify permeability tensor only in localization bands as shown for the modelling of field experiments by Levasseur et al. (2009b). (authors)

  17. Damage-induced permeability changes around underground excavations

    Coll, C.

    2005-07-01

    The storage of nuclear waste in deep geological formations is now considered more and more as a potential solution. During excavation, a disturbed zone develops in which damaging can be important and which can lead eventually to the failure of the rock. Fluid flow and permeability in the rock mass can be significantly modified producing a possible security risk. Our work consisted in an experimental study of the hydro-mechanical coupling of two argillaceous rocks: Boom clay (Mol, Belgium) and Opalinus clay (Mont-Terri, Switzerland). Triaxial tests were performed in a saturated state to study the permeability evolution of both clays with isotropic and deviatoric stresses. Argillaceous rocks are geo-materials with complex behaviour governed by numerous coupled processes. Strong physico-chemical interactions between the fluid and the solid particles and their very low permeability required the modification of the experimental set up. Moreover, specific procedures were developed to measure permeability and to detect strain localisation in shear bands. We show that for Boom Clay, permeability is not significantly influenced by strain localisation. For Opalinus clay, fracturing can induce an increase of the permeability at low confining pressure. (author)

  18. Synthetic Rock Analogue for Permeability Studies of Rock Salt with Mudstone

    Hongwu Yin

    2017-09-01

    Full Text Available Knowledge about the permeability of surrounding rock (salt rock and mudstone interlayer is an important topic, which acts as a key parameter to characterize the tightness of gas storage. The goal of experiments that test the permeability of gas storage facilities in rock salt is to develop a synthetic analogue to use as a permeability model. To address the permeability of a mudstone/salt layered and mixed rock mass in Jintan, Jiangsu Province, synthetic mixed and layered specimens using the mudstone and the salt were fabricated for permeability testing. Because of the gas “slippage effect”, test results are corrected by the Klinkenberg method, and the permeability of specimens is obtained by regression fitting. The results show that the permeability of synthetic pure rock salt is 6.9 × 10−20 m2, and its porosity is 3.8%. The permeability of synthetic mudstone rock is 2.97 × 10−18 m2, with a porosity 17.8%. These results are close to those obtained from intact natural specimens. We also find that with the same mudstone content, the permeability of mixed specimens is about 40% higher than for the layered specimens, and with an increase in the mudstone content, the Klinkenberg permeability increases for both types of specimens. The permeability and mudstone content have a strong exponential relationship. When the mudstone content is below 40%, the permeability increases only slightly with mudstone content, whereas above this threshold, the permeability increases rapidly with mudstone content. The results of the study are of use in the assessment of the tightness of natural gas storage facilities in mudstone-rich rock salt formations in China.

  19. Tunable band gap and optical properties of surface functionalized Sc2C monolayer

    Wang Shun; Du Yu-Lei; Liao Wen-He

    2017-01-01

    Using the density functional theory, we have investigated the electronic and optical properties of two-dimensional Sc 2 C monolayer with OH, F, or O chemical groups. The electronic structures reveal that the functionalized Sc 2 C monolayers are semiconductors with a band gap of 0.44–1.55 eV. The band gap dependent optical parameters, like dielectric function, absorption coefficients, reflectivity, loss function, and refraction index were also calculated for photon energy up to 20 eV. At the low-energy region, each optical parameter shifts to red, and the peak increases obviously with the increase of the energy gap. Consequently, Sc 2 C monolayer with a tunable band gap by changing the type of surface chemical groups is a promising 2D material for optoelectronic devices. (paper)

  20. Quantifying Evaporation in a Permeable Pavement System

    Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. Th...

  1. Permeable Pavement Research - Edison, New Jersey

    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. ...

  2. Quantifying porosity, compressibility and permeability in Shale

    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....

  3. Comparative evaluation of nano-CuO crossing Caco-2 cell monolayers and cellular uptake

    Chen, Gao; Lianqin, Zhu; Fenghua, Zhu; Fang, Zheng; Mingming, Song; Kai, Huang

    2015-01-01

    Different concentrations of CuSO 4 , micro-CuO, and nano-CuO were added to Caco-2 cell monolayers to study the absorption and transport characteristics in this epithelial cell model. Nano-CuO nanoparticles had a diameter of 10–20 nm. Inhibitors of endocytosis were used to explore whether nano-CuO could enter the Caco-2 cell in the form of nanoparticles, and to ascertain the endocytotic pathway that is involved in the transport process. The apparent permeability coefficient (P app ) of CuSO 4 and nano-CuO increased with the Cu concentration in the culture medium (p < 0.05). The micro-CuO of different concentrations had no significant impact on the P app value of Caco-2 cells (p > 0.05). When the Cu concentration in the culture medium was in the range 31.25–500 μM, the P app value of Caco-2 cells incubated with nano-CuO was significantly higher than that obtained with CuSO 4 . The latter was also significantly higher than that when cells were incubated with micro-CuO (p < 0.05). The amount of Cu transport increased with the increase of CuSO 4 concentration in the culture medium. After 90 min, the amount of transport began to saturate, and the transport rate of Cu declined with the increase of CuSO 4 concentration. For the cells incubated with nano-CuO, the amount of Cu transport increased with the increase of nano-CuO concentration, but did not show an obvious saturation with the extension of transport time. Nano-CuO could enter the Caco-2 cell in the form of nanoparticles, and were found in the cytoplasm, vesicles, lysosomes, and cell nuclei. Several inhibitors of endocytosis effectively prevented the entry of nano-CuO into the Caco-2 cells. It was concluded that nano-CuO particles can enter the Caco-2 cells through several cellular endocytotic pathways

  4. Comparative evaluation of nano-CuO crossing Caco-2 cell monolayers and cellular uptake

    Chen, Gao; Lianqin, Zhu, E-mail: lianqinz1963@163.com; Fenghua, Zhu [Qingdao Agricultural University, College of Animal Science and Veterinary Medicine (China); Fang, Zheng [Dezhou University, College of Agriculture (China); Mingming, Song; Kai, Huang [Qingdao Agricultural University, College of Animal Science and Veterinary Medicine (China)

    2015-04-15

    Different concentrations of CuSO{sub 4}, micro-CuO, and nano-CuO were added to Caco-2 cell monolayers to study the absorption and transport characteristics in this epithelial cell model. Nano-CuO nanoparticles had a diameter of 10–20 nm. Inhibitors of endocytosis were used to explore whether nano-CuO could enter the Caco-2 cell in the form of nanoparticles, and to ascertain the endocytotic pathway that is involved in the transport process. The apparent permeability coefficient (P{sub app}) of CuSO{sub 4} and nano-CuO increased with the Cu concentration in the culture medium (p < 0.05). The micro-CuO of different concentrations had no significant impact on the P{sub app} value of Caco-2 cells (p > 0.05). When the Cu concentration in the culture medium was in the range 31.25–500 μM, the P{sub app} value of Caco-2 cells incubated with nano-CuO was significantly higher than that obtained with CuSO{sub 4}. The latter was also significantly higher than that when cells were incubated with micro-CuO (p < 0.05). The amount of Cu transport increased with the increase of CuSO{sub 4} concentration in the culture medium. After 90 min, the amount of transport began to saturate, and the transport rate of Cu declined with the increase of CuSO{sub 4} concentration. For the cells incubated with nano-CuO, the amount of Cu transport increased with the increase of nano-CuO concentration, but did not show an obvious saturation with the extension of transport time. Nano-CuO could enter the Caco-2 cell in the form of nanoparticles, and were found in the cytoplasm, vesicles, lysosomes, and cell nuclei. Several inhibitors of endocytosis effectively prevented the entry of nano-CuO into the Caco-2 cells. It was concluded that nano-CuO particles can enter the Caco-2 cells through several cellular endocytotic pathways.

  5. A plate reader-based method for cell water permeability measurement

    Fenton, Robert A.; Moeller, H B; Nielsen, S

    2010-01-01

    Cell volume and water permeability measurements in cultured mammalian cells are typically conducted under a light microscope. Many of the employed approaches are time consuming and not applicable to a study of confluent epithelial cell monolayers. We present here an adaptation of a calcein......: AQP2-S256D > AQP2 wild-type > AQP2-S256A. We propose that the method can be applied to study AQP function and more generally to study cell volume changes in adherent cell lines. Furthermore, it should be adaptable for AQP inhibitor screening in chemical compound libraries....

  6. Pressure-dependent optical and vibrational properties of monolayer molybdenum disulfide

    Nayak, Avinash P.

    2015-01-14

    Controlling the band gap by tuning the lattice structure through pressure engineering is a relatively new route for tailoring the optoelectronic properties of two-dimensional (2D) materials. Here, we investigate the electronic structure and lattice vibrational dynamics of the distorted monolayer 1T-MoS2 (1T′) and the monolayer 2H-MoS2 via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS2 increases by 11.7% from 1.85 to 2.08 eV, which is the highest reported for a 2D transition metal dichalcogenide (TMD) material. DFT calculations reveal a subsequent decrease in the band gap with eventual metallization of the monolayer 2H-MoS2, an overall complex structure-property relation due to the rich band structure of MoS2. Remarkably, the metastable 1T′-MoS2 metallic state remains invariant with pressure, with the J2, A1g, and E2g modes becoming dominant at high pressures. This substantial reversible tunability of the electronic and vibrational properties of the MoS2 family can be extended to other 2D TMDs. These results present an important advance toward controlling the band structure and optoelectronic properties of monolayer MoS2 via pressure, which has vital implications for enhanced device applications.

  7. Thermal stability and molecular ordering of organic semiconductor monolayers: effect of an anchor group.

    Jones, Andrew O F; Knauer, Philipp; Resel, Roland; Ringk, Andreas; Strohriegl, Peter; Werzer, Oliver; Sferrazza, Michele

    2015-06-08

    The thermal stability and molecular order in monolayers of two organic semiconductors, PBI-PA and PBI-alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI-PA, are reported. In situ X-ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI-PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI-alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Strictly monolayer large continuous MoS2 films on diverse substrates and their luminescence properties

    Mohapatra, P. K.; Deb, S.; Singh, B. P.; Vasa, P.; Dhar, S.

    2016-01-01

    Despite a tremendous interest on molybdenum disulfide as a thinnest direct band gap semiconductor, single step synthesis of a large area purely monolayer MoS 2 film has not yet been reported. Here, we report a CVD route to synthesize a continuous film of strictly monolayer MoS 2 covering an area as large as a few cm 2 on a variety of different substrates without using any seeding material or any elaborate pretreatment of the substrate. This is achieved by allowing the growth to take place in the naturally formed gap between a piece of SiO 2 coated Si wafer and the substrate, when the latter is placed on top of the former inside a CVD reactor. We propose a qualitative model to explain why the MoS 2 films are always strictly monolayer in this method. The photoluminescence study of these monolayers shows the characteristic excitonic and trionic features associated with monolayer MoS 2 . In addition, a broad defect related luminescence band appears at ∼1.7 eV. As temperature decreases, the intensity of this broad feature increases, while the band edge luminescence reduces

  9. Crystallization of calcium oxalate monohydrate at dipalmitoylphosphatidylcholine monolayers in the presence of chondroitin sulfate A

    Ouyang, Jian-Ming; Deng, Sui-Ping; Zhong, Jiu-Ping; Tieke, Bernd; Yu, Shu-Hong

    2004-10-01

    The growth and aggregation of calcium oxalate monohydrate (COM) crystals beneath dipalmitoylphosphatidylcholine (DPPC) monolayers in the presence of chondroitin sulfate A (C4S) was systematically examined under different surface pressure. The results indicated that the addition of C4S can inhibit the crystal growth and prevent the aggregation of COM crystals. Under a DPPC monolayer, well-defined three-dimensional hexagonal prisms and three-dimensional rhombus prisms with sharply angled tips were obtained. The DPPC monolayer at a surface pressure of 10 mN/m can match the Ca2+ distance of the (1 bar 0 1) face of COM better than at 20 mN/m. The addition of C4S could cooperatively modulate the interaction strength between the monolayer (or itself) with the specific morphology determining faces such as (1 bar 0 1) and (0 2 0), and thus results in remarkable stabilization of the (1 bar 0 1) faces. The dramatic changes in morphological details were due to the strong electrostatic interactions between the Ca2+-rich (1 bar 0 1) crystal faces of COM and the polyanionic polysaccharide C4S together with the negatively charged sites of the zwitterionic DPPC monolayers. The increase of the concentration of C4S can further enhance the stabilization of the (1 bar 0 1) face.

  10. Effect of temperature on the permeability of gas adsorbed coal under triaxial stress conditions

    Li, Xiangchen; Yan, Xiaopeng; Kang, Yili

    2018-04-01

    The combined effects of gas sorption, stress and temperature play a significant role in the changing behavior of gas permeability in coal seams. The effect of temperature on nitrogen and methane permeability of naturally fractured coal is investigated. Coal permeability, P-wave velocity and axial strain were simultaneously measured under two effective stresses and six different temperatures. The results showed that the behavior of nitrogen and methane permeability presented nonmonotonic changes with increasing temperature. The variation in the P-wave velocity and axial strain showed a good correspondence with coal permeability. A higher effective stress limited the bigger deformation and caused the small change in permeability. Methane adsorption and desorption significantly influence the mechanical properties of coal and play an important role in the variations in coal permeability. The result of coal permeability during a complete stress-strain process showed that the variation in permeability is determined by the evolution of the internal structure. The increase in the temperature of the gas saturated coal causes the complex interaction between matrix swelling, matrix shrinkage and micro-fracture generation, which leads to the complex changes in coal structure and permeability. These results are helpful to understand the gas transport mechanism for exploiting coal methane by heat injection.

  11. Polycyclic aromatic hydrocarbons in model bacterial membranes - Langmuir monolayer studies.

    Broniatowski, Marcin; Binczycka, Martyna; Wójcik, Aneta; Flasiński, Michał; Wydro, Paweł

    2017-12-01

    High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are persistent organic pollutants which due to their limited biodegradability accumulate in soils where their increased presence can lead to the impoverishment of the decomposer organisms. As very hydrophobic PAHs easily penetrate cellular membranes of soil bacteria and can be incorporated therein, changing the membrane fluidity and other functions which in consequence can lead to the death of the organism. The structure and size of PAH molecule can be crucial for its membrane activity; however the correlation between PAH structure and its interaction with phospholipids have not been investigated so far. In our studies we applied phospholipid Langmuir monolayers as model bacterial membranes and investigated how the incorporation of six structurally different PAH molecules change the membrane texture and physical properties. In our studies we registered surface pressure and surface potential isotherms upon the monolayer compression, visualized the monolayer texture with the application of Brewster angle microscopy and searched the ordering of the film-forming molecules with molecular resolution with the application of grazing incidence X-ray diffraction (GIXD) method. It turned out that the phospholipid-PAH interactions are strictly structure dependent. Four and five-ring PAHs of the angular or cluster geometry can be incorporated into the model membranes changing profoundly their textures and fluidity; whereas linear or large cluster PAHs cannot be incorporated and separate from the lipid matrix. The observed phenomena were explained based on structural similarities of the applied PAHs with membrane steroids and hopanoids. Copyright © 2017. Published by Elsevier B.V.

  12. Apparent permeability of electrical steel under PWM magnetisation

    Moses, A.J.; Leicht, J.; Anderson, P.

    2006-01-01

    In recent years much attention has been paid to material performance under pulse width modulation (PWM) excitation conditions, which is of increasing importance to motor applications particularly in energy efficient variable speed drive systems. It is well known that in general, losses increase significantly with reducing modulation index, the increase depending on parameters such as silicon contents, thickness and grain size. The effect of the PWM waveform on permeability has attracted little attention until now. So in this paper its influence on the permeability of electrical steel is analysed and characterised. A prediction approach based on the permeability under sine wave excitation and total harmonic distortion is introduced which results in errors below 10% for non-electrical steel at 1.5 T

  13. Reduction in cardiolipin decreases mitochondrial spare respiratory capacity and increases glucose transport into and across human brain cerebral microvascular endothelial cells.

    Nguyen, Hieu M; Mejia, Edgard M; Chang, Wenguang; Wang, Ying; Watson, Emily; On, Ngoc; Miller, Donald W; Hatch, Grant M

    2016-10-01

    Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. Cardiolipin is a mitochondrial phospholipid required for function of the electron transport chain and ATP generation. We examined the role of cardiolipin in maintaining mitochondrial function necessary to support barrier properties of brain microvessel endothelial cells. Knockdown of the terminal enzyme of cardiolipin synthesis, cardiolipin synthase, in hCMEC/D3 cells resulted in decreased cellular cardiolipin levels compared to controls. The reduction in cardiolipin resulted in decreased mitochondrial spare respiratory capacity, increased pyruvate kinase activity, and increased 2-deoxy-[(3) H]glucose uptake and glucose transporter-1 expression and localization to membranes in hCMEC/D3 cells compared to controls. The mechanism for the increase in glucose uptake was an increase in adenosine-5'-monophosphate kinase and protein kinase B activity and decreased glycogen synthase kinase 3 beta activity. Knockdown of cardiolipin synthase did not affect permeability of fluorescent dextran across confluent hCMEC/D3 monolayers grown on Transwell(®) inserts. In contrast, knockdown of cardiolipin synthase resulted in an increase in 2-deoxy-[(3) H]glucose transport across these monolayers compared to controls. The data indicate that in hCMEC/D3 cells, spare respiratory capacity is dependent on cardiolipin. In addition, reduction in cardiolipin in these cells alters their cellular energy status and this results in increased glucose transport into and across hCMEC/D3 monolayers. Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. In human adult brain endothelial cell hCMEC/D3 monolayers cultured on Transwell(®) plates, knockdown of cardiolipin synthase results in decrease in mitochondrial

  14. The effect of offset on fracture permeability of rocks from the Southern Andes Volcanic Zone, Chile

    Pérez-Flores, P.; Wang, G.; Mitchell, T. M.; Meredith, P. G.; Nara, Y.; Sarkar, V.; Cembrano, J.

    2017-11-01

    The Southern Andes Volcanic Zone (SVZ) represents one of the largest undeveloped geothermal provinces in the world. Development of the geothermal potential requires a detailed understanding of fluid transport properties of its main lithologies. The permeability of SVZ rocks is altered by the presence of fracture damage zones produced by the Liquiñe-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF). We have therefore measured the permeability of four representative lithologies from the volcanic basement in this area: crystalline tuff, andesitic dike, altered andesite and granodiorite. For comparative purposes, we have also measured the permeability of samples of Seljadalur basalt, an Icelandic rock with widely studied and reported hydraulic properties. Specifically, we present the results of a systematic study of the effect of fractures and fracture offsets on permeability as a function of increasing effective pressure. Baseline measurements on intact samples of SVZ rocks show that the granodiorite has a permeability (10-18 m2), two orders of magnitude higher than that of the volcanic rocks (10-20 m2). The presence of throughgoing mated macro-fractures increases permeability by between four and six orders of magnitude, with the highest permeability recorded for the crystalline tuff. Increasing fracture offset to produce unmated fractures results in large increases in permeability up to some characteristic value of offset, beyond which permeability changes only marginally. The increase in permeability with offset appears to depend on fracture roughness and aperture, and these are different for each lithology. Overall, fractured SVZ rocks with finite offsets record permeability values consistent with those commonly found in geothermal reservoirs (>10-16 m2), which potentially allow convective/advective flow to develop. Hence, our results demonstrate that the fracture damage zones developed within the SVZ produce permeable regions, especially within the

  15. Evolution of permeability in siliceous rocks induced by mineral dissolution and precipitation

    Yasuhara, Hideaki; Kinoshita, Naoki; Kurikami, Hiroshi; Nakashima, Shinichiro; Kishida, Kiyoshi

    2007-01-01

    A conceptual model is presented to follow the evolution of permeability in siliceous rocks mediated by pressure solution. Specifically, the main minerals of siliceous rocks that are quartz, cristobalite, and amorphous silica, are focused to examine differences of the permeability evolutions among them at effective pressures of 1, 5, and 10 MPa, and temperatures of 20 and 90degC. The rates and magnitudes of permeability reduction increase with increases of the pressures and temperatures applied. Ultimate permeabilities reduced by the order of 90 % at the completion of dissolution-mediated compaction at 10 MPa and 90degC. Precipitation may augment more degradation of flow transport in time. (author)

  16. Temperature-dependent surface density of alkylthiol monolayers on gold nanocrystals

    Liu, Xuepeng; Lu, Pin; Zhai, Hua; Wu, Yucheng

    2018-03-01

    Atomistic molecular dynamics (MD) simulations are performed to study the surface density of passivating monolayers of alkylthiol chains on gold nanocrystals at temperatures ranging from 1 to 800 K. The results show that the surface density of alkylthiol monolayer reaches a maximum value at near room temperature (200-300 K), while significantly decreases with increasing temperature in the higher temperature region (> 300 {{K}}), and slightly decreases with decreasing temperature at low temperature (< 200 {{K}}). We find that the temperature dependence of surface ligand density in the higher temperature region is attributed to the substantial ligand desorption induced by the thermal fluctuation, while that at low temperature results from the reduction in entropy caused by the change in the ordering of passivating monolayer. These results are expected helpful to understand the temperature-dependent surface coverage of gold nanocrystals.

  17. Strain engineering on electronic structure and carrier mobility in monolayer GeP3

    Zeng, Bowen; Long, Mengqiu; Zhang, Xiaojiao; Dong, Yulan; Li, Mingjun; Yi, Yougen; Duan, Haiming

    2018-06-01

    Using density functional theory coupled with the Boltzmann transport equation with relaxation time approximation, we have studied the strain effect on the electronic structure and carrier mobility of two-dimensional monolayer GeP3. We find that the energies of valence band maximum and conduction band minimum are nearly linearly shifted with a biaxial strain in the range of  ‑4% to 6%, and the band structure experiences a remarkable transition from semiconductor to metal with the appropriate compression (‑5% strain). Under biaxial strain, the mobility of the electron and hole in monolayer GeP3 reduces and increases by more than one order of magnitude, respectively. It is suggested that it is possible to perform successive transitions from an n-type semiconductor (‑4% strain) to a good performance p-semiconductor (+6% strain) by applying strain in monolayer GeP3, which is potentially useful for flexible electronics and nanosized mechanical sensors.

  18. Unsaturated fatty acids lactose esters: cytotoxicity, permeability enhancement and antimicrobial activity.

    Lucarini, Simone; Fagioli, Laura; Campana, Raffaella; Cole, Hannah; Duranti, Andrea; Baffone, Wally; Vllasaliu, Driton; Casettari, Luca

    2016-10-01

    Sugar based surfactants conjugated with fatty acid chains are an emerging broad group of highly biocompatible and biodegradable compounds with established and potential future applications in the pharmaceutical, cosmetic and food industries. In this work, we investigated absorption enhancing and antimicrobial properties of disaccharide lactose, monoesterified with unsaturated fatty acids through an enzymatic synthetic approach. After chemical and cytotoxicity characterizations, their permeability enhancing activity was demonstrated using intestinal Caco-2 monolayers through transepithelial electrical resistance (TEER) and permeability studies. The synthesized compounds, namely lactose palmitoleate (URB1076) and lactose nervonate (URB1077), were shown to exhibit antimicrobial activity versus eight pathogenic species belonging to Gram-positive, Gram-negative microorganisms and fungi. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Performance of monolayer graphene nanomechanical resonators with electrical readout.

    Chen, Changyao; Rosenblatt, Sami; Bolotin, Kirill I; Kalb, William; Kim, Philip; Kymissis, Ioannis; Stormer, Horst L; Heinz, Tony F; Hone, James

    2009-12-01

    The enormous stiffness and low density of graphene make it an ideal material for nanoelectromechanical applications. Here, we demonstrate the fabrication and electrical readout of monolayer graphene resonators, and test their response to changes in mass and temperature. The devices show resonances in the megahertz range, and the strong dependence of resonant frequency on applied gate voltage can be fitted to a membrane model to yield the mass density and built-in strain of the graphene. Following the removal and addition of mass, changes in both density and strain are observed, indicating that adsorbates impart tension to the graphene. On cooling, the frequency increases, and the shift rate can be used to measure the unusual negative thermal expansion coefficient of graphene. The quality factor increases with decreasing temperature, reaching approximately 1 x 10(4) at 5 K. By establishing many of the basic attributes of monolayer graphene resonators, the groundwork for applications of these devices, including high-sensitivity mass detectors, is put in place.

  20. Molecular tilt on monolayer-protected nanoparticles

    Giomi, L.

    2012-02-01

    The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

  1. Epitaxial growth by monolayer restricted galvanic displacement

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  2. Collective cell motion in endothelial monolayers

    Szabó, A; Ünnep, R; Méhes, E; Czirók, A; Twal, W O; Argraves, W S; Cao, Y

    2010-01-01

    Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior

  3. Molecular tilt on monolayer-protected nanoparticles

    Giomi, L.; Bowick, M. J.; Ma, X.; Majumdar, A.

    2012-01-01

    The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

  4. Electrochemical behaviour of monolayer and bilayer graphene

    Valota, Anna T.; Kinloch, Ian A.; Novoselov, Kostya S.; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W.; Dryfe, Robert A. W.

    2011-01-01

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as masking coating in order to expose a stable, well defined area of graphene. Both multilayer and monolayer graphene microe...

  5. Conformation, orientation and interaction in molecular monolayers

    Superfine, R.; Huang, J.Y.; Shen, Y.R.

    1989-01-01

    Knowledge of the conformation and ordering of molecular monolayers is essential for a detailed understanding of a wide variety of surface and interfacial phenomena. Over the past several years, surface second harmonic generation (SHG) has proven to be a valuable and versatile probe of monolayer systems. Our group has recently extended the technique to infrared-visible sum frequency generation (SFG) which has unique capabilities for surface vibrational spectroscopy. Like second harmonic generation, SFG is highly surface specific with submonolayer sensitivity at all interfaces accessible by light. The orientation of individual groups within an adsorbate molecule can be deduced by a polarization analysis of the SFG signal from the vibrational modes of the groups. The authors have used SHG and SFG to study orientations and conformations of surfactant and liquid crystal (LC) monolayers and their interaction on a substrate. The interfacial properties of LC are of great interest to many researchers for both basic science understanding and practical application to LC devices. It is well known that the bulk alignment of a liquid crystal in a cell is strongly affected by the surface treatment of the cell walls. The reason behind it is not yet clear. The theoretical background and experimental arrangement of SHG and SFG have been described elsewhere. In the setup, a 30 psec. Nd:YAG mode-locked laser system together with nonlinear accessories generates a visible beam at .532μm and an infrared beam tunable about 3.4μm. Both beams are focused to a common spot of 300μm dia. The typical signal off the surface from a compact ordered alkyl chain monolayer is ∼500 photons per pulse, easily detected with a photomultiplier tube

  6. Structure of cholesterol/ceramide monolayer mixtures

    Scheffer, L.; Solomonov, I.; Weygand, M.J.

    2005-01-01

    The structure of monolayers of cholesterol/ ceramide mixtures was investigated using grazing incidence x-ray diffraction, immunofluorescence, and atomic force microscopy techniques. Grazing incidence x-ray diffraction measurements showed the existence of a crystalline mixed phase of the two....... As ceramide incorporates the lipid backbone common to all sphingolipids, this arrangement may be relevant to the understanding of the molecular organization of lipid rafts....

  7. A systematic evaluation of solubility enhancing excipients to enable the generation of permeability data for poorly soluble compounds in Caco-2 model.

    Shah, Devang; Paruchury, Sundeep; Matta, Muralikrishna; Chowan, Gajendra; Subramanian, Murali; Saxena, Ajay; Soars, Matthew G; Herbst, John; Haskell, Roy; Marathe, Punit; Mandlekar, Sandhya

    2014-01-01

    The study presented here identified and utilized a panel of solubility enhancing excipients to enable the generation of flux data in the Human colon carcinoma (Caco-2) system for compounds with poor solubility. Solubility enhancing excipients Dimethyl acetamide (DMA) 1 % v/v, polyethylene glycol (PEG) 400 1% v/v, povidone 1% w/v, poloxamer 188 2.5% w/v and bovine serum albumin (BSA) 4% w/v did not compromise Caco-2 monolayer integrity as assessed by trans-epithelial resistance measurement (TEER) and Lucifer yellow (LY) permeation. Further, these excipients did not affect P-glycoprotein (P-gp) mediated bidirectional transport of digoxin, permeabilities of high (propranolol) or low permeability (atenolol) compounds, and were found to be inert to Breast cancer resistant protein (BCRP) mediated transport of cladribine. This approach was validated further using poorly soluble tool compounds, atazanavir (poloxamer 188 2.5% w/v) and cyclosporine A (BSA 4% w/v) and also applied to new chemical entity (NCE) BMS-A in BSA 4% w/v, for which Caco-2 data could not be generated using the traditional methodology due to poor solubility (solubility of atazanavir by >8 fold whereas BSA 4% w/v increased the solubility of cyclosporine A and BMS-A by >2-4 fold thereby enabling permeability as well as efflux liability estimation in the Caco-2 model with reasonable recovery values. To conclude, addition of excipients such as poloxamer 188 2.5% w/v and BSA 4% w/v to HBSS leads to a significant improvement in the solubility of the poorly soluble compounds resulting in enhanced recoveries without modulating transporter-mediated efflux, expanding the applicability of Caco-2 assays to poorly soluble compounds.

  8. Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

    Mary Vergheese, T.; Berchmans, Sheela

    2004-02-15

    In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China){sub 6}]{sup 4-}, [Ru(NH{sub 3}){sub 6}]{sup 2+} and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK{sub a}pH{sub medium} reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH{sub 3}){sub 6}]{sup 2+/3+}. Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH.

  9. Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

    Mary Vergheese, T.; Berchmans, Sheela

    2004-01-01

    In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China) 6 ] 4- , [Ru(NH 3 ) 6 ] 2+ and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK a medium and at pK a >pH medium reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH 3 ) 6 ] 2+/3+ . Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH

  10. Investigation on gallium ions impacting monolayer graphene

    Wu, Xin; Zhao, Haiyan, E-mail: hyzhao@tsinghua.edu.cn; Yan, Dong; Pei, Jiayun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. Chinaand Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  11. Janus monolayers of transition metal dichalcogenides

    Lu, Ang-Yu

    2017-05-15

    Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

  12. Exploring atomic defects in molybdenum disulphide monolayers

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm '2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  13. Exploring atomic defects in molybdenum disulphide monolayers

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  14. Affinity of serum apolipoproteins for lipid monolayers

    Ibdah, J.A.

    1987-01-01

    The effects of lipid composition and packing as well as the structure of the protein on the affinities of apolipoproteins for lipid monolayers have been investigated. The adsorption of 14 C-reductively methylated human apolipoproteins A-I and A-II at saturating subphase concentrations to monolayers prepared with synthetic lipids or lipoprotein surface lipids spread at various initial surface pressures has been studied. The adsorption of apolipoproteins is monitored by following the surface radioactivity using a gas flow counter and Wilhelmy plate, respectively. The physical states of the lipid monolayers are evaluated by measurement of the surface pressure-molecular area isotherms using a Langmuir-Adam surface balance. The probable helical regions in various apolipoproteins have been predicted using a secondary structure analysis computer program. The mean residue hydrophobicity and mean residue hydrophobic moment for the predicted helical segments have been calculated. The surface properties of synthetic peptides which are amphipathic helix analogs have been investigated at the air-water and lipid-water interfaces

  15. Pb2+ Modulates Ca2+ Membrane Permeability In Paramecium

    Bernal-Martínez, Juan; Ortega Soto, Arturo

    2004-09-01

    Intracellular recording experiments in current clamp configuration were done to evaluate whether Pb2+ modulates ionic membrane permeability in the fresh water Paramecium tetraurelia. It was found that Pb2+ triggers in a dose-dependent manner, a burst of spontaneous action potentials followed by a robust and sustained after hyper-polarization. In addition, Pb2+ increased the frequency of firing the spontaneous Ca2+-Action Potential and also, the duration of Ca2+-Action Potential, in a dose and reversibly-dependent manner. These results suggest that Pb2+ increases calcium membrane permeability of Paramecium and probably activates a calcium-dependent-potassium conductance in the ciliate.

  16. Effect of aggregate grain size distribution on properties of permeable ...

    ) ratio on the mechanical properties of permeable concrete is investigated. The aim of this study is to prepare permeable concrete mixture with optimum properties in terms of strength and permeability. For this purpose, five different permeable ...

  17. The structure and dynamics of Nano Particles encapsulated by the SDS monolayer collapse at the water/TCE interface

    Shi, Wenxiong

    2016-11-01

    The super-saturated surfactant monolayer collapses with the nanoparticles (NPs) at the water/trichloroethylene (TCE) interface are investigated using molecular dynamics (MD) simulations. The results show that sodium alkyl sulfate (SDS) monolayer collapse is initiated by buckling and followed primarily by budding and the bud encapsulating the NPs and oil molecules. The developed bud detaches from the monolayer into a water phase and forms the swollen micelle emulsion with NPs and oil molecules. We investigate the wavelength of the initial budding and the theoretical description of the budding process. The wavelength of the monolayer increases with bending modulus. The energy barrier of the budding can be easily overcome by thermal fluctuation energy, which indicates that budding process proceeds rapidly.

  18. Zonulin, a newly discovered modulator of intestinal permeability, and its expression in coeliac disease.

    Fasano, A; Not, T; Wang, W; Uzzau, S; Berti, I; Tommasini, A; Goldblum, S E

    2000-04-29

    We identified zonulin, a novel human protein analogue to the Vibrio cholerae derived Zonula occludens toxin, which induces tight junction disassembly and a subsequent increase in intestinal permeability in non-human primate intestinal epithelia. Zonulin expression was raised in intestinal tissues during the acute phase of coeliac disease, a clinical condition in which tight junctions are opened and permeability is increased.

  19. Fullerene nanostructures, monolayers and thin films

    Cotier, B.N.

    2000-10-01

    The interaction of submonolayer, monolayer and multilayer coverages of C 60 with the Ag/Si(111)-(√3x√3)R30 deg. (√3Ag/Si) and Si(111)-7x7 surfaces has been investigated using atomic force microscopy (AFM), photoelectron spectroscopy (PES) and ultra high vacuum scanning tunneling microscopy (UHV-STM). It is shown that it is possible to preserve the √3Ag/Si surface, normally corrupted by exposure to air, in ambient conditions when immersed beneath a few layers of C 60 molecules. Upon removal of the fullerene layers in the UHV-STM some corruption is observed which is linked to the morphology of the fullerene film (defined by the nature of the interaction of C 60 with √3Ag/Si). This technique opens up the possibility of performing experiments on the clean √3Ag/Si surface outside of UHV conditions. With the discovery of techniques whereby structures may be formed that are composed of only a few atoms/molecules, there is a need to perform electrical measurements in order to probe the fascinating properties of these 'nano-scale' devices. Using AFM, PES and STM evaporated metals and ion implantation have been investigated as materials for use in forming sub-micron scale contacts to nanostructures. It is found that ion implantation is a more promising approach after studying the response to annealing of treated surfaces. Electrical measurements between open/short circuited contacts and through Ag films clearly demonstrate the validity of the method, further confirmed by a PES study which probes the chemical nature of the near surface region of ion-implanted samples. Attempts have been made to form nanostructure templates between sub-micron scale contacts as a possible precursor to forming nanostructures. The bonding state of C 60 molecules on the Si(111)-7x7 surface has been in dispute for many years. To properly understand the system a comprehensive AFM, PES and STM study has been performed. PES results indicate covalent bond formation, with the number of bonds

  20. Endodontic sealers: Intratubular penetration and permeability to Enterococcus faecalis

    Bortolini Maria Cecilia

    2010-01-01

    Full Text Available Aim : Evaluate in vitro the intratubular penetration and permeability of endodontic sealers in teeth contaminated with Enterococcus faecalis. Materials and Methods : Human canines were filled with AHPlus ® , Endo CPM-sealer ® or EndoRez ® sealers. To evaluate permeability, the coronary portion of each tooth was contaminated with E. faecalis, then the apical portion was immersed in brain heart infusion (BHI broth, and medium turbidity was observed for thirty days. Scanning electron microscope (SEM was used to evaluate the intratubular penetration of each sealer at the cervical, middle, and apical thirds of the tooth. Results : Only one tooth from the Endo CPM-sealer ® group presented broth contamination. EndoRez ® showed increased intratubular penetration compared to AHPlus ® and Endo CPM-sealer ® . Conclusions : Endo CPM-sealer ® showed greater permeability to E. faecalis and EndoRez ® showed increased intratubular penetration.

  1. The permeability of concrete for reactor containment vessels

    Mills, R.H.

    1983-07-01

    Review of the literature pertaining to water, water vapour and gas transmission through concrete revealed conflicting views on the mechanisms involved and the influence of mix design parameters such as initial porosities and water/cement ratio. Consideration of the effects of ageing and of construction defects in field concrete were totally neglected in published work. Permeability data from three published papers were compared with permeability calculated according to Powers. The ratio of calculated to observed permeability varied from 40 x 10 -3 to 860 x 10 -3 for one group: from 0.17 x 10 3 to 8.6 x 10 3 in the second; and from 24 x 10 3 to 142 x 10 3 for the third. There were therefore wide discrepancies within each group of data and between groups. A bibliography was prepared and an exploratory experimental programme was mounted to determine the relative importance of key parameters such as cement type, porosity and water/cement ratio. Contrary to frequently cited references it was found that permeability of concrete was not significantly influenced by water/cement ratio when the starting porosity was constant. If water/cement ratio was held constant, however, the permeability was strongly influenced by starting porosity. It was also found that with constant water/cement ratio permeability increased with cement content. The value of fly ash and blast furnace slag in partial substitution for Portland cement is neglected in the literature but it is important since such substitutions alleviate alkali-silicate reactions. Permeability of concrete was significantly decreased by partial substitution of Portland cement with fly ash but there was no benefit in the use of blast furnace slag

  2. Rectification of current responds to incorporation of fullerenes into mixed-monolayers of alkanethiolates in tunneling junctions.

    Qiu, Li; Zhang, Yanxi; Krijger, Theodorus L; Qiu, Xinkai; Hof, Patrick Van't; Hummelen, Jan C; Chiechi, Ryan C

    2017-03-01

    This paper describes the rectification of current through molecular junctions comprising self-assembled monolayers of decanethiolate through the incorporation of C 60 fullerene moieties bearing undecanethiol groups in junctions using eutectic Ga-In (EGaIn) and Au conducting probe AFM (CP-AFM) top-contacts. The degree of rectification increases with increasing exposure of the decanethiolate monolayers to the fullerene moieties, going through a maximum after 24 h. We ascribe this observation to the resulting mixed-monolayer achieving an optimal packing density of fullerene cages sitting above the alkane monolayer. Thus, the degree of rectification is controlled by the amount of fullerene present in the mixed-monolayer. The voltage dependence of R varies with the composition of the top-contact and the force applied to the junction and the energy of the lowest unoccupied π-state determined from photoelectron spectroscopy is consistent with the direction of rectification. The maximum value of rectification R = | J (+)/ J (-)| = 940 at ±1 V or 617 at ±0.95 V is in agreement with previous studies on pure monolayers relating the degree of rectification to the volume of the head-group on which the frontier orbitals are localized.

  3. Biotransformation of hydralazine (HDZ) in monolayer cultures of rabbit hepatocytes

    McQueen, C.A.; Rosado, R.R.

    1990-01-01

    Adverse reactions to HDZ have been associated with the acetylator polymorphism; slow acetylators are more likely to develop HDZ-induced lupus erythematosus. In studying the role of this polymorphism in susceptibility to HDZ toxicity, the biotransformation of HDZ was investigated in rabbit hepatocytes. New Zealand white rabbits, like humans, are classified as rapid or slow acetylators. Heptocytes were isolated from rapid acetylator rabbits by collagenase perfusion. Monolayer cultures were initiated and exposed to 14 C-HDZ. Since HDZ is unstable at neutral pH, parallel incubations were done in the absence of cells. Metabolites in the media were determined by reverse phase HPLC. Phthalazine (P), phthalazinone (PZ), triazoloph-thalazine (TP), methyl TP (MTP) and 3-hydroxy MTP were identified. In the absence of cells, more TP was formed than MTP, probably resulting from reaction of HDZ with components in the medium. In the presence of cells, there was a three-fold increase in MTP, while the amount of TP was relatively constant. Only trace amounts of P, PZ 3-hydroxy MTP were detected. These data indicate that monolayer cultures of rapid acetylator rabbit hepatocytes were capable of metabolizing HDZ with acetylation playing a major role. These studies are being extended to cells from slow acetylator rabbits

  4. Fabrication and surface transformation of FePt nanoparticle monolayer

    Wang Ying; Ding Baojun; Li Hua; Zhang Xiaoyan; Cai Bingchu; Zhang Yafei

    2007-01-01

    The monolayer of FePt nanoparticles with the mean size of ∼4 nm was fabricated on a glass substrate by the Langmuir--Blodgett (LB) technology. The monolayer of FePt nanoparticles has a smooth surface and a high density structure as shown by the AFM image. The array structure of FePt nanoparticles on the surface of the film is clearly with a cubic symmetry in appropriate condition. Small-angle X-ray diffraction (SXRD) measurement of multilayer structure for the FePt nanoparticles has indicated that the superlattices consist of well-defined smooth layers. The transfer of nanoparticle layers onto a solid substrate surface was quite efficient for the first few layers, exhibiting a proportional increase of optical absorption in the UV-vis range. This results potentially opens up a new approach to the long-range ordered array of FePt nanoparticles capped by organic molecules on substrate and provide a promising thin film, which may exhibit the excellent ultra-high density magnetic recording properties

  5. Electron transport nonlocality in monolayer graphene modified with hydrogen silsesquioxane polymerization

    Kaverzin, A. A.; van Wees, B. J.

    2015-01-01

    A number of practical and fundamental applications of graphene requires modification of some of its properties. In this paper we study the effect of polymerization of a hydrogen silsesquioxane film on top of monolayer graphene with the intent to increase the strength of the spin-orbit interaction.

  6. Air permeability for a concrete shear wall after a damaging seismic load simulation cycle

    Girrens, S.P.; Farrar, C.R.

    1991-01-01

    A study was initiated to estimate air leakage, driven by wind-generated pressure gradients, from a seismically damaged concrete structure. This paper describes an experiment performed to measure the air permeability in a reinforced concrete shear wall, both before and after simulated seismic loading. Static load-cycle testing was used to simulate earthquake loading. Permeability measurements were made by pressurizing one side of the shear wall above atmospheric conditions and recording the transient-pressure decay. Air permeability measurements made on the shear wall before loading fell within the range of values for concrete permeability published in the literature. As long as the structure exhibited linear load-displacement response, no variation in the air permeability was detected. However, experimental results indicate that the air permeability in the shear wall increased by a factor of 40 after the wall had been damaged (cracked)

  7. Haemophilia, AIDS and lung epithelial permeability

    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).

  8. Haemophilia, AIDS and lung epithelial permeability

    O'Doherty, M.J.; Page, C.J.; Harrington, C.; Nunan, T.; Savidge, G.

    1990-01-01

    Lung 99m Tc DTPA transfer was measured in HIV antibodypositive haemophiliacs (11 smokers, 26 nonsmokers, 5 patients with Pneumocystis carinii pneumonia (PCP)). Lung 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 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)

  9. Salt-saturated concrete strength and permeability

    Pfeifle, T.W.; Hansen, F.D.; Knowles, M.K.

    1996-01-01

    Laboratory-scale experiments applicable to the use of salt-saturated concrete as a seal material for a transuranic waste repository have been completed. Nitrogen gas permeability measurements were made using a flexible-wall permeameter, a confining pressure of 1 MPa, and gas pressure gradients ranging from 0.3 MPa to 0.75 MPa. Results show that salt-saturated concrete has very low intrinsic permeability with values ranging from 9.4 x 10 -22 m 2 to 9.7 x 10 -17 m 2 . Strength and deformation characteristics were investigated under conditions of triaxial compression with confining pressures ranging from 0 to 15 MPa using either axial strain-rate or axial stress-rate control and show that the failure strength of concrete increases with confining pressure which can be adequately described through pressure-sensitive failure criteria. Axial, radial, and volumetric strains were also measured during each test and these data were used to determine elastic properties. Experimental results are applicable in the design and analysis of scale-related functions and apply to other concrete structures subjected to compressive loadings such as dams and prestressed structural members

  10. Permeability of highly compacted bentonite

    Pusch, R.

    1980-12-01

    The object of the study was the water flow through the bentonite which is caused by hydraulic gradients. The study comprised laboratory tests and theoretical considerations. It was found that high bulk densities reduced the permeability to very low values. It was concluded that practically impervious conditions prevail when the gradients are low. Thus with a regional gradient of 10 -2 and a premeability of 10 -13 m/s the flow rate will not be higher than approximately 1 mm in 30 000 years. (G.B.)

  11. The effects of heavy metal ions on the chlorophyll content and cell membrane permeability of charophytes

    Fu Hualong; Chen Hao; Dong Bin; Qing Renwei

    2001-01-01

    The authors studied the effects of several heavy metal ions in different concentrations (Cd 2+ , Hg 2+ , Pb 2+ , Cr 6+ ) on the chlorophyll content and cell membrane permeability of Chara vulgaris L. It was discovered that the effects of heavy metal ions on the chlorophyll content and cell membrane permeability of Chara vulgaris L. changed with their different concentration. The trend was that the chlorophyll content and cell membrane permeability were decreased with the increase of the heavy metal ions. The degree of chlorophyll content affected was Cr 6+ , Cd 2+ , Hg 2+ , Pb 2+ , and that of cell membrane permeability affected was Cd 2+ , Cr 6+ , Hg 2+ , Pb 2+

  12. Hydrogeology of rocks of low permeability: region studies

    Llamas, M.R.

    1985-01-01

    Hydrogeological regional studies on low permeability rocks are rather scarce in comparison to similar studies on normal permeability rocks. Economic and technological difficulties to develop ground water from these terrains may be the main cause of this scarcity. Several facts may indicate that these studies will increase in the near future. First, the need to supply water to the people living in underdeveloped arid zones over extensive areas of low permeability rocks. Second, the relevant role that some low permeability large groundwater basins may play in conjunctive ground and surface-water use. And last but not least the feasibility of some low permeability rock areas as sites for nuclear waste repositories. Some specific difficulties in these regional studies may be: a) intrinsic difficulties in obtaining representative water samples and measuring hydraulic heads; b) scarcity of observation and/or pumping wells; c) important hydraulic head and chemical properties variations in a vertical direction; d) old groundwater ages; this may require paleohydrological considerations to understand certain apparent anomalies. In most of these regional studies hydrogeochemical methods and modelling (flow and mass transport) may be very valuable tools. 77 references, 7 figures

  13. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    Qi, Junjie; Lan, Yann-Wen; Stieg, Adam Z.; Chen, Jyun-Hong; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Zhang, Yue; Wang, Kang L.

    2015-01-01

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices. PMID:26109177

  14. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    Qi, Junjie

    2015-06-25

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices.

  15. Determining the thickness of aliphatic alcohol monolayers covalently attached to silicon oxide surfaces using angle-resolved X-ray photoelectron spectroscopy

    Lee, Austin W. H.; Kim, Dongho; Gates, Byron D.

    2018-04-01

    The thickness of alcohol based monolayers on silicon oxide surfaces were investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS). Advantages of using alcohols as building blocks for the formation of monolayers include their widespread availability, ease of handling, and stability against side reactions. Recent progress in microwave assisted reactions demonstrated the ease of forming uniform monolayers with alcohol based reagents. The studies shown herein provide a detailed investigation of the thickness of monolayers prepared from a series of aliphatic alcohols of different chain lengths. Monolayers of 1-butanol, 1-hexanol, 1-octanol, 1-decanol, and 1-dodecanol were each successfully formed through microwave assisted reactions and characterized by ARXPS techniques. The thickness of these monolayers consistently increased by ∼1.0 Å for every additional methylene (CH2) within the hydrocarbon chain of the reagents. Tilt angles of the molecules covalently attached to silicon oxide surfaces were estimated to be ∼35° for each type of reagent. These results were consistent with the observations reported for thiol based or silane based monolayers on either gold or silicon oxide surfaces, respectively. The results of this study also suggest that the alcohol based monolayers are uniform at a molecular level.

  16. Gap junction protein connexin43 exacerbates lung vascular permeability.

    James J O'Donnell

    Full Text Available Increased vascular permeability causes pulmonary edema that impairs arterial oxygenation and thus contributes to morbidity and mortality associated with Acute Respiratory Distress Syndrome and sepsis. Although components of intercellular adhesive and tight junctions are critical for maintaining the endothelial barrier, there has been limited study of the roles of gap junctions and their component proteins (connexins. Since connexins can modulate inflammatory signaling in other systems, we hypothesized that connexins may also regulate pulmonary endothelial permeability. The relationships between connexins and the permeability response to inflammatory stimuli were studied in cultured human pulmonary endothelial cells. Prolonged treatment with thrombin, lipopolysaccharide, or pathological cyclic stretch increased levels of mRNA and protein for the major connexin, connexin43 (Cx43. Thrombin and lipopolysaccharide both increased intercellular communication assayed by transfer of microinjected Lucifer yellow. Although thrombin decreased transendothelial resistance in these cells, the response was attenuated by pretreatment with the connexin inhibitor carbenoxolone. Additionally, the decreases of transendothelial resistance produced by either thrombin or lipopolysaccharide were attenuated by reducing Cx43 expression by siRNA knockdown. Both carbenoxolone and Cx43 knockdown also abrogated thrombin-induced phosphorylation of myosin light chain. Taken together, these data suggest that increased lung vascular permeability induced by inflammatory conditions may be amplified via increased expression of Cx43 and intercellular communication among pulmonary endothelial cells.

  17. Steam-water relative permeability

    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.

  18. Moisture diffusion and permeability characteristics of hydroxypropylmethylcellulose and hard gelatin capsules.

    Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

    2015-01-30

    The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Permeability of granular beds emplaced in vertical drill holes

    Griffiths, S.K.; Morrison, F.A. Jr.

    1979-01-01

    To determine the permeabilities of granular materials emplaced in vertical drill holes used for underground nuclear tests, an experiment at the USDOE Nevada Test Site (NTS) was conducted. As the hole is being filled, falling material increases pressure above and within the granular beds beneath. When the filling operation starts or stops, a transient pressure response occurs within the beds; measurements of this response in beds of various compositions were made. The permeabilities after emplacement were found by matching analytical predictions of the response to these data. This information is useful in assuring the containment of nuclear tests conducted in such drill holes

  20. Bronchoalveolar permeability changes in rats inhaling gas/particle combinations during rest or exercise

    Bhalla, D.K.; Phalen, R.F.; Mannix, R.C.; Lavan, S.M.; Crocker, T.T.

    1986-01-01

    Bronchoalveolar (BA) injury in rats exposed at rest or exercise to air pollutants was studied by changes in epithelial permeability. Rats exposed to air, single gases or pollutant combinations were anesthetized, tracheostomized, and placed on an incline. /sup 99m/Tc-DTPA was delivered directly to a major bronchus. Radioactivity measurements were made on blood samples collected during first 10 min. Exposure of resting rats to 0.6 ppm O 3 increased BA permeability just after exposure, but it was normal 24 hrs later; in exercising rats the increase was greater than in rats exposed at rest, and it persisted up to 24 hrs. NO 2 at 6 ppm did not affect permeability. Exposure of resting rats to 2.5 ppm NO 2 + 0.6 ppm O 3 only increased permeability right after the exposure, but in exercising rats this exposure resulted in a greater permeability which remained elevated up to 24 hrs. Exposure of exercising rats to 0.8 ppm O 3 + 10 ppm HCHO increased permeability. Exposure of resting rats to an atmosphere of 0.6 ppm O 3 + 2.5 ppm NO 2 + 5 ppm SO 2 + 1 mg/m 3 sulfates of ferric, ammonium and manganese also produced an increase in permeability that persisted up to 24 hrs. The results suggest potentiation of the pollutant effects by exercise, but there is no indication of synergistic effect of pollutant combinations on BA permeability

  1. Zitterbewegung in monolayer silicene in a magnetic field

    Romera, E.; Roldán, J.B.; Santos, F. de los

    2014-01-01

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS 2 . - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS 2 )

  2. Zitterbewegung in monolayer silicene in a magnetic field

    Romera, E. [Departamento de Física Atómica, Molecular y Nuclear and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Roldán, J.B. [Departamento de Electrónica y Tecnología de Computadores and CITIC, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Santos, F. de los [Departamento de Electromagnetismo y Física de la Materia, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2014-07-04

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS{sub 2}. - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS{sub 2})

  3. Testing the effectiveness of monolayers under wind and wave conditions.

    Palada, C; Schouten, P; Lemckert, C

    2012-01-01

    Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

  4. Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer

    Zhang, Lei; Hao, Changchun; Feng, Ying; Gao, Feng; Lu, Xiaolong; Li, Junhua; Sun, Runguang

    2016-09-01

    Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure-area (π-A) and pressure-time (π-T) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value. Project supported by the National Natural Science Foundation of China (Grant Nos. 21402114 and 11544009), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JM2010), the Fundamental Research Funds for the Central

  5. Nutrient Infiltrate Concentrations from Three Permeable Pavement Types

    While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types have on nutrient concentrations present in stormwater runoff are limited. In 2009, the U.S. EPA constructed a 0.4-ha...

  6. Sensing of Vascular Permeability in Inflamed Vessel of Live Animal

    Sang A Park

    2018-01-01

    Full Text Available Increase in vascular permeability is a conclusive response in the progress of inflammation. Under controlled conditions, leukocytes are known to migrate across the vascular barriers to the sites of inflammation without severe vascular rupture. However, when inflammatory state becomes excessive, the leakage of blood components may occur and can be lethal. Basically, vascular permeability can be analyzed based on the intensity of blood outflow. To evaluate the amount and rate of leakage in live mice, we performed cremaster muscle exteriorization to visualize blood flow and neutrophil migration. Using two-photon intravital microscopy of the exteriorized cremaster muscle venules, we found that vascular barrier function is transiently and locally disrupted in the early stage of inflammatory condition induced by N-formylmethionyl-leucyl-phenylalanine (fMLP. Measurement of the concentration of intravenously (i.v. injected Texas Red dextran inside and outside the vessels resulted in clear visualization of real-time increases in transient and local vascular permeability increase in real-time manner. We successfully demonstrated repeated leakage from a target site on a blood vessel in association with increasing severity of inflammation. Therefore, compared to other methods, two-photon intravital microscopy more accurately visualizes and quantifies vascular permeability even in a small part of blood vessels in live animals in real time.

  7. Permeability of salt-crystal interfaces to brine

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

    1982-06-01

    To investigate the movement of brine along grain boundaries in polycrystalline salt, measurements have been made of the radial flow of brine through the interface between cylindrical salt crystals under axial stresses to 140 bar and temperatures to 80 0 C. For constant conditions, the total flow of brine showed a linear dependence on the logarithm of time, and the reciprocal permeability increased linearly with time. Loss of salt from the interface by pressure solution effects was more than enough to account for the decrease in the apparent thickness of the interface (i.e., that which may be estimated for an interface of the same permeability formed by plane parallel surfaces). This apparent thickness, initially as large as 10 μm, decreased to as little as 0.2 μm with exposure to stress and flowing brine. It decreased quickly with sudden increases in axial stress and usually increased, though not reversibly, with decreases in stress. The rate of increase in the reciprocal permeability with time was roughly proportional to the stress and to the square of the hydraulic pressure drop. Assuming similar apparent thicknesses for the grain boundaries in polycrystalline salt, permeabilities are predicted that are quite consistent with the low values reported for stressed core specimens

  8. Optimizing solubility and permeability of a biopharmaceutics classification system (BCS) class 4 antibiotic drug using lipophilic fragments disturbing the crystal lattice.

    Tehler, Ulrika; Fagerberg, Jonas H; Svensson, Richard; Larhed, Mats; Artursson, Per; Bergström, Christel A S

    2013-03-28

    Esterification was used to simultaneously increase solubility and permeability of ciprofloxacin, a biopharmaceutics classification system (BCS) class 4 drug (low solubility/low permeability) with solid-state limited solubility. Molecular flexibility was increased to disturb the crystal lattice, lower the melting point, and thereby improve the solubility, whereas lipophilicity was increased to enhance the intestinal permeability. These structural changes resulted in BCS class 1 analogues (high solubility/high permeability) emphasizing that simple medicinal chemistry may improve both these properties.

  9. Template-Directed Self-Assembly of Alkanethiol Monolayers: Selective Growth on Preexisting Monolayer Edges

    Sharpe, R.B.A.; Burdinski, Dirk; Huskens, Jurriaan; Zandvliet, Henricus J.W.; Reinhoudt, David; Poelsema, Bene

    2007-01-01

    Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time.

  10. Mixed DPPC/POPC Monolayers: All-atom Molecular Dynamics Simulations and Langmuir Monolayer Experiments

    Olžyńska, Agnieszka; Zubek, M.; Roeselová, Martina; Korchowiec, J.; Cwiklik, Lukasz

    2016-01-01

    Roč. 1858, č. 12 (2016), s. 3120-3130 ISSN 0005-2736 R&D Projects: GA ČR GA15-14292S Institutional support: RVO:61388955 ; RVO:61388963 Keywords : phospholipid monolayers * Lung surfactant * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.498, year: 2016

  11. Electric field enhanced adsorption and diffusion of adatoms in MoS{sub 2} monolayer

    Shi, Wenwu [School of Physical Electronics, Center for Public Security Information and Equipment Integration Technology, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Wang, Zhiguo, E-mail: zgwang@uestc.edu.cn [School of Physical Electronics, Center for Public Security Information and Equipment Integration Technology, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Li, Zhijie [School of Physical Electronics, Center for Public Security Information and Equipment Integration Technology, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Fu, Y.Q., E-mail: richard.fu@northumbria.ac.uk [School of Physical Electronics, Center for Public Security Information and Equipment Integration Technology, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Faculty of Engineering and Environment, University of Northumbria, Newcastle upon Tyne, NE1 8ST (United Kingdom)

    2016-11-01

    A new phenomenon, electric field enhanced adsorption and diffusion of lithium, magnesium and aluminum ions in a MoS{sub 2} monolayer, was investigated using density functional theory in this study. With the electric field increased from 0 to 0.8 V/Å, the adsorption energies of the Li, Mg and Al atoms in the MoS{sub 2} monolayer were decreased from −2.01 to −2.49 eV, from −0.80 to −1.28 eV, and −2.71 to −3.01 eV, respectively. The corresponding diffusion barriers were simultaneously decreased from 0.23 to 0.08 eV, from 0.15 to 0.10 eV, and 0.24 to 0.21 eV for the Li, Mg and Al ions, respectively. We concluded that the external electric field can increase the charging speed of rechargeable ion batteries based on the MoS{sub 2} anode materials. - Highlights: • Effect of electric field on the adsorption and diffusion were investigated. • Adsorption energies of the adatoms in the MoS{sub 2} monolayer were enhanced. • Diffusion barriers of the adatoms in the MoS{sub 2} monolayer were decreased. • Electric field can be used to realize a fast charging rate of rechargeable ion batteries.

  12. Low Permeability Polyimide Insulation, Phase I

    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...

  13. Modelling of water permeability in cementitious materials

    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...

  14. Preliminary study of the irradiation-induced modification of skin permeability

    Coelho, R.; Istin, M.

    1978-01-01

    Irradiation of the skin of an animal leads immediately to a strong increase in vascular permeability. If a dye is at once injected intraveinously it diffuses very rapidly in the irradiated zone, this becomes highly coloured and the colour intensity measurement gives a clue to the severity of the lesions produced. This phenomenon has been used in the past as a pharmacological test to study vascular permeability and is employed in this work to observe the effect of diosmine-titrated flavonoids on vascular permeability in inflammatory diseases. The capillary permeability increase due to local γ irradiation of rabbit skin has been accurately determined by measurement of the colouration observed after injection of Geigy Blue. Diosmine, injected intraperitoneally, protects the vascular system against increased permeability due to ionising radiations [fr

  15. Fabrication of P3HT/gold nanoparticle LB films by P3HT templating Langmuir monolayer

    Chen, Liang-Huei; Hsu, Wen-Ping; Chan, Han-Wen; Lee, Yuh-Lang

    2014-01-01

    Highlights: • Addition of ODA into the P3HT monolayer can significantly improve the dispersion ability of P3HT molecules. • The adsorption ability of the P3HT monolayer to the dispersed AuNPs can also be enhanced by the presence of ODA. - Abstract: Regioregular poly(3-hexyl thiophene) (rr-P3HT) and mixed P3HT/octadecyl amine (ODA) were used as template monolayers to adsorb the gold nanoparticles (AuNPs) dispersed in subphase. The behaviors of P3HT and P3HT/ODA monolayers were investigated by surface pressure area per molecule (π–A) isotherms, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The experimental results show that P3HT does not form a homogeneous film and tends to aggregate at the air/water interface. Meanwhile, the amount of AuNPs adsorbed by the P3HT monolayers is low, attributable to the weak interaction between AuNPs and P3HT. By introduction of ODA molecules into the P3HT monolayer, the spreading of P3HT molecules at the air/water interface is improved and the aggregation of P3HT is significantly inhibited. A nearly uniform and homogeneously mixed P3HT/ODA monolayer can be obtained when 50% of ODA is introduced. It is also found that the introduction of ODA can significantly increase the adsorption of AuNPs. For the mixed monolayer with low ratio of ODA (P3HT/ODA = 1/0.2), a higher concentration of adsorbed AuNPs was observed on the corresponding monolayer. However, when the ODA/P3HT ratio increases to 1/1, the AuNPs tend to form three-dimensional (3D) aggregates and the AuNPs cannot distribute well as a homogeneous monolayer. This result is ascribed to the increasing hydrophobicity of the adsorbed AuNPs because of capping of more ODA molecules

  16. Modeling stress/strain-dependent permeability changes for deep geoenergy applications

    Rinaldi, Antonio Pio; Rutqvist, Jonny

    2016-04-01

    Rock permeability is a key parameter in deep geoenergy systems. Stress and strain changes induced at depth by fluid injection or extraction may substantially alter the rock permeability in an irreversible way. With regard to the geoenergies, some applications require the permeability to be enhanced to improve productivity. The rock permeability is generally enhanced by shearing process of faults and fractures (e.g. hydroshearing for Enhanced and Deep Geothermal Systems), or the creation of new fractures (e.g. hydrofracturing for shale gas). However, such processes may, at the same time, produce seismicity that can be felt by the local population. Moreover, the increased permeability due to fault reactivation may pose at risk the sealing capacity of a storage site (e.g. carbon sequestration or nuclear waste disposal), providing then a preferential pathway for the stored fluids to escape at shallow depth. In this work we present a review of some recent applications aimed at understanding the coupling between stress (or strain) and permeability. Examples of geoenergy applications include both EGS and CO2 sequestration. To investigate both "wanted" and "unwanted" effects, THM simulations have been carried out with the TOUGH-FLAC simulator. Our studies include constitutive equations relating the permeability to mean effective stress, effective normal stress, volumetric strain, as well as accounting for permeability variation as related to fault/fracture reactivation. Results show that the geomechanical effects have a large role in changing the permeability, hence affecting fluids leakage, reservoir enhancement, as well as the induced seismicity.

  17. Consolidation and permeability of salt in brine

    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) 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 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 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. Cavity plasmon polaritons in monolayer graphene

    Kotov, O.V.; Lozovik, Yu.E.

    2011-01-01

    Plasmon polaritons in a new system, a monolayer doped graphene embedded in optical microcavity, are studied here. The dispersion law for lower and upper cavity plasmon polaritons is obtained. Peculiarities of Rabi splitting for the system are analyzed; particularly, role of Dirac-like spinor (envelope) wave functions in graphene and corresponding angle factors are considered. Typical Rabi frequencies for maximal (acceptable for Dirac-like electron spectra) Fermi energy and frequencies of polaritons near polariton gap are estimated. The plasmon polaritons in considered system can be used for high-speed information transfer in the THz region. -- Highlights: → Plasmon polaritons in a monolayer doped graphene embedded in optical microcavity, are studied here. → The dispersion law for lower and upper cavity plasmon polaritons is obtained. → Peculiarities of Rabi splitting for the system are analyzed. → Role of Dirac-like wave functions in graphene and corresponding angle factors are considered. → Typical Rabi frequencies and frequencies of polaritons near polariton gap are estimated.

  19. The effects of a multispecies probiotic on migraine and markers of intestinal permeability-results of a randomized placebo-controlled study

    Roos, De N.M.; Hemert, Van S.; Rovers, J.M.P.; Smits, M.G.; Witteman, B.J.M.

    2017-01-01

    Background/Objectives:Migraine, associated with several gastrointestinal disorders, may result from increased intestinal permeability, allowing endotoxins to enter the bloodstream. We tested whether probiotics could reduce migraine through an effect on intestinal permeability and

  20. Improved permeability of acyclovir: optimization of mucoadhesive liposomes using the phospholipid vesicle-based permeation assay.

    Naderkhani, Elenaz; Erber, Astrid; Škalko-Basnet, Nataša; Flaten, Gøril Eide

    2014-02-01

    The antiviral drug acyclovir (ACV) suffers from poor solubility both in lipophilic and hydrophilic environment, leading to low and highly variable bioavailability. To overcome these limitations, this study aimed at designing mucoadhesive ACV-containing liposomes to improve its permeability. Liposomes were prepared from egg phosphatidylcholine (E-PC) and E-PC/egg phosphatidylglycerol (E-PC/E-PG) and their surfaces coated with Carbopol. All liposomal formulations were fully characterized and for the first time the phospholipid vesicle-based permeation assay (PVPA) was used for testing in vitro permeability of drug from mucoadhesive liposome formulations. The negatively charged E-PC/E-PG liposomes could encapsulate more ACV than neutral E-PC liposomes. Coating with Carbopol increased the entrapment in the neutral E-PC liposomes. The incorporation of ACV into liposomes exhibited significant increase in its in vitro permeability, compared with its aqueous solution. The neutral E-PC liposomal formulations exhibited higher ACV permeability values compared with charged E-PC/E-PG formulations. Coating with Carbopol significantly enhanced the permeability from the E-PC/E-PG liposomes, as well as sonicated E-PC liposomes, which showed the highest permeability of all tested formulations. The increased permeability was according to the formulations' mucoadhesive properties. This indicates that the PVPA is suitable to distinguish between permeability of ACV from different mucoadhesive liposome formulations developed for various routes of administration. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  1. Bacterial infections in cirrhosis: Role of proton pump inhibitors and intestinal permeability

    L.G. van Vlerken (Lotte); E.J. Huisman (Ellen); B. van Hoek (Bart); W. Renooij (W.); F.W.M. de Rooij (Felix); P.D. Siersema (Peter); K.J. van Erpecum (Karel)

    2012-01-01

    textabstractBackground Cirrhotic patients are at considerable risk for bacterial infections, possibly through increased intestinal permeability and bacterial overgrowth. Proton pump inhibitors (PPIs) may increase infection risk. We aimed to explore the potential association between PPI use and

  2. Examination of fluorination effect on physical properties of saturated long-chain alcohols by DSC and Langmuir monolayer.

    Nakahara, Hiromichi; Nakamura, Shohei; Okahashi, Yoshinori; Kitaguchi, Daisuke; Kawabata, Noritake; Sakamoto, Seiichi; Shibata, Osamu

    2013-02-01

    Partially fluorinated long-chain alcohols have been newly synthesized from a radical reaction, which is followed by a reductive reaction. The fluorinated alcohols have been investigated by differential scanning calorimetry (DSC) and compression isotherms in a Langmuir monolayer state. Their melting points increase with an increase in chain length due to elongation of methylene groups. However, the melting points for the alcohols containing shorter fluorinated moieties are lower than those for the typical hydrogenated fatty alcohols. Using the Langmuir monolayer technique, surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of monolayers of the fluorinated alcohols have been measured in the temperature range from 281.2 to 303.2K. In addition, a compressibility modulus (Cs(-1)) is calculated from the π-A isotherms. Four kinds of the alcohol monolayers show a phase transition (π(eq)) from a disordered to an ordered state upon lateral compression. The π(eq) values increase linearly with increasing temperatures. A slope of π(eq) against temperature for the alcohols with shorter fluorocarbons is unexpectedly larger than that for the corresponding fatty alcohols. Generally, fluorinated amphiphiles have a greater thermal stability (or resistance), which is a characteristic of highly fluorinated or perfluorinated compounds. Herein, however, the alcohols containing perfluorobutylated and perfluorohexylated chains show the irregular thermal behavior in both the solid and monolayer states. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Coulomb Blockade in a Two-Dimensional Conductive Polymer Monolayer.

    Akai-Kasaya, M; Okuaki, Y; Nagano, S; Mitani, T; Kuwahara, Y

    2015-11-06

    Electronic transport was investigated in poly(3-hexylthiophene-2,5-diyl) monolayers. At low temperatures, nonlinear behavior was observed in the current-voltage characteristics, and a nonzero threshold voltage appeared that increased with decreasing temperature. The current-voltage characteristics could be best fitted using a power law. These results suggest that the nonlinear conductivity can be explained using a Coulomb blockade (CB) mechanism. A model is proposed in which an isotropic extended charge state exists, as predicted by quantum calculations, and percolative charge transport occurs within an array of small conductive islands. Using quantitatively evaluated capacitance values for the islands, this model was found to be capable of explaining the observed experimental data. It is, therefore, suggested that percolative charge transport based on the CB effect is a significant factor giving rise to nonlinear conductivity in organic materials.

  4. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    Arbeitman, Claudia R.; Grosso, Mariela F. del [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Behar, Moni [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); García Bermúdez, Gerardo, E-mail: ggb@tandar.cnea.gov.ar [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Escuela de Ciencia y Tecnología, UNSAM (Argentina)

    2013-11-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology.

  5. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    Arbeitman, Claudia R.; Grosso, Mariela F. del; Behar, Moni; García Bermúdez, Gerardo

    2013-01-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology

  6. Anisotropic charged impurity-limited carrier mobility in monolayer phosphorene

    Ong, Zhun-Yong; Zhang, Gang; Zhang, Yong Wei

    2014-01-01

    The room temperature carrier mobility in atomically thin 2D materials is usually far below the intrinsic limit imposed by phonon scattering as a result of scattering by remote charged impurities in its environment. We simulate the charged impurity-limited carrier mobility μ in bare and encapsulated monolayer phosphorene. We find a significant temperature dependence in the carrier mobilities (μ ∝ T −γ ) that results from the temperature variability of the charge screening and varies with the crystal orientation. The anisotropy in the effective mass leads to an anisotropic carrier mobility, with the mobility in the armchair direction about one order of magnitude larger than in the zigzag direction. In particular, this mobility anisotropy is enhanced at low temperatures and high carrier densities. Under encapsulation with a high-κ overlayer, the mobility increases by up to an order of magnitude although its temperature dependence and its anisotropy are reduced

  7. Monolayer phosphorene under time-dependent magnetic field

    Nascimento, J. P. G.; Aguiar, V.; Guedes, I.

    2018-02-01

    We obtain the exact wave function of a monolayer phosphorene under a low-intensity time-dependent magnetic field using the dynamical invariant method. We calculate the quantum-mechanical energy expectation value and the transition probability for a constant and an oscillatory magnetic field. For the former we observe that the Landau level energy varies linearly with the quantum numbers n and m and the magnetic field intensity B0. No transition takes place. For the latter, we observe that the energy oscillates in time, increasing linearly with the Landau level n and m and nonlinearly with the magnetic field. The (k , l) →(n , m) transitions take place only for l = m. We investigate the (0,0) →(n , 0) and (1 , l) and (2 , l) probability transitions.

  8. Anisotropic charged impurity-limited carrier mobility in monolayer phosphorene

    Ong, Zhun-Yong; Zhang, Gang; Zhang, Yong Wei [Institute of High Performance Computing, A*STAR, Singapore 138632 (Singapore)

    2014-12-07

    The room temperature carrier mobility in atomically thin 2D materials is usually far below the intrinsic limit imposed by phonon scattering as a result of scattering by remote charged impurities in its environment. We simulate the charged impurity-limited carrier mobility μ in bare and encapsulated monolayer phosphorene. We find a significant temperature dependence in the carrier mobilities (μ ∝ T{sup −γ}) that results from the temperature variability of the charge screening and varies with the crystal orientation. The anisotropy in the effective mass leads to an anisotropic carrier mobility, with the mobility in the armchair direction about one order of magnitude larger than in the zigzag direction. In particular, this mobility anisotropy is enhanced at low temperatures and high carrier densities. Under encapsulation with a high-κ overlayer, the mobility increases by up to an order of magnitude although its temperature dependence and its anisotropy are reduced.

  9. [Effect of β-cyclodextrin inclusion complex on transport of major components of Xiangfu Siwu decoction essential oil in Caco-2 cell monolayer model].

    Xi, Jun-zuan; Qian, Da-wei; Duan, Jin-ao; Liu, Pei; Zhu, Yue; Zhu, Zhen-hua; Zhang, Li

    2015-08-01

    Although the essential oil of Xiangfu Siwu decoction (XFSWD) has strong pharmacological activity, its special physical and chemical properties restrict the clinical application and curative effect. In this paper, Xiangfu Siwu decoction essential oil (XFS-WO) was prepared by forming inclusion complex with β-cyclodextrin (β-CD). The present study is to investigate the effect of β-CD inclusion complex on the transport of major components of XFSWO using Caco-2 cell monolayer model, thus to research the effect of this formation on the absorption of drugs with low solubility and high permeability, which belong to class 2 in biopharmaceutics classification system. A sensitive and rapid UPLC-MS/MS method was developed for simultaneous quantification of senkyunolide A, 3-n-butylphthalide, Z-ligustilide, dehydrocostus lactone and α-cyperone, which are active compounds in XFSWO. The transport parameters were analyzed and compared in free oil and its β-CD inclusion complex. The result revealed that the formation of XFSWO/β-CD inclusion complex has significantly increased the transportation and absorption of major active ingredients than free oil. Accordingly, it can be speculated that cyclodextrin inclusion complex can improve bioavailability of poorly water-soluble drugs. Above all these mentioned researches, it provided foundation and basis for physiological disposition and pharmaceutical study of XFSWD.

  10. Enhancement and inhibition effects on the corneal permeability of timolol maleate: Polymers, cyclodextrins and chelating agents.

    Rodríguez, Isabel; Vázquez, José Antonio; Pastrana, Lorenzo; Khutoryanskiy, Vitaliy V

    2017-08-30

    This study investigates how both bioadhesive polymers (chitosan, hyaluronic acid and alginate) and permeability enhancers (ethylene glycol- bis(2-aminoethylether)- N, N, N', N'- tetraacetic acid (EGTA) and hydroxypropyl-ß-cyclodextrin) influence the permeability of the anti-glaucoma drug timolol maleate through ex vivo bovine corneas. Our results showed that only the permeability enhancers alone were able to increase drug permeability, whereas the polymers significantly reduced drug permeation, and however, they increased the pre-corneal residence of timolol. Ternary systems (polymer-enhancer-drug) showed a reduced drug permeability compared to the polymers alone. Fluorescence microscopy analysis of the epithelium surface confirmed there was no evidence of epithelial disruption caused by these formulations, suggesting that polymer-enhancer interactions reduce drug solubilization and counteract the disruptive effect of the permeability enhancers on the surface of the cornea. Further mucoadhesive tests, revealed a stable interaction of chitosan and hyaluronic acid with the epithelium, while alginate showed poor mucoadhesive properties. The differences in mucoadhesion correlated with the permeability of timolol maleate observed, i.e. formulations containing mucoadhesive polymers showed lower drug permeabilities. The results of the present study indicate polymers acting as an additional barrier towards drug permeability which is even more evident in the presence of permeability enhancers like EGTA and hydroxypropyl-ß-cyclodextrin. Then, this study highlights the need to adequately select additives intended for ocular applications since interactions between them can have opposite results to what expected in terms of drug permeability. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold.

    Petoral, Rodrigo M; Björefors, Fredrik; Uvdal, Kajsa

    2006-11-23

    Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

  12. A MOLECULAR-DYNAMICS STUDY OF LECITHIN MONOLAYERS

    AHLSTROM, P; BERENDSEN, HJC

    1993-01-01

    Two monolayers of didecanoyllecithin at the air-water interface have been studied using molecular dynamics simulations. The model system consisted of two monolayers of 42 lecithin molecules each separated by a roughly 4 nm thick slab of SPC water. The area per lecithin molecule was 0.78 nm(2)

  13. Characterization of self-assembled monolayers on a ruthenium surface

    Shaheen, Amrozia; Sturm, Jacobus Marinus; Ricciardi, R.; Huskens, Jurriaan; Lee, Christopher James; Bijkerk, Frederik

    2017-01-01

    We have modified and stabilized the ruthenium surface by depositing a self-assembled monolayer (SAM) of 1-hexadecanethiol on a polycrystalline ruthenium thin film. The growth mechanism, dynamics, and stability of these monolayers were studied. SAMs, deposited under ambient conditions, on

  14. Langmuir monolayer formation of metal complexes from polymerizable amphiphilic ligands

    Werkman, P.J; Schouten, A.J.

    1996-01-01

    The monolayer behaviour of 4-(10,12-pentacosadiynoicamidomethyl)-pyridine at the air-water interface was studied by measuring the surface pressure-area isotherms. The amphiphile formed stable monolayers with a clear liquid-expanded (LE) to liquid-condensed phase transition at various temperatures.

  15. Mechanical and electronic properties of Janus monolayer transition metal dichalcogenides

    Shi, Wenwu; Wang, Zhiguo

    2018-05-01

    The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y  =  S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16–1.91 and 0.94–1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M  =  Ti, Zr and Hf). The monolayers MXY (M  =  V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M  =  Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m‑1. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.

  16. Exciton center-of-mass localization and dielectric environment effect in monolayer WS2

    Hichri, Aïda; Ben Amara, Imen; Ayari, Sabrine; Jaziri, Sihem

    2017-06-01

    The ultrathin transition metal dichalcogenides (TMDs) have emerged as promising materials for various applications using two dimensional semiconductors. They have attracted increasing attention due to their unique optical properties originate from neutral and charged excitons. In this paper, we study the strong localization of exciton center-of-mass motion within random potential fluctuations caused by the monolayer defects. Here, we report negatively charged exciton formation in monolayer TMDs, notably tungsten disulfide WS2. Our theory is based on an effective mass model of neutral and charged excitons, parameterized by ab-initio calculations. Taking into the account the strong correlation between the monolayer WS2 and the surrounding dielectric environment, our theoretical results are in good agreement with one-photon photoluminescence (PL) and reflectivity measurements. We also show that the exciton state with p-symmetry, experimentally observed by two-photon PL emission, is energetically below the 2s-state. We use the equilibrium mass action law, to quantify the relative weight of exciton and trion PL. We show that exciton and trion emission can be tuned and controlled by external parameters like temperature, pumping, and injection electrons. Finally, in comparison with experimental measurements, we show that exciton emission in monolayer tungsten dichalcogenides is substantially reduced. This feature suggests that free exciton can be trapped in disordered potential wells to form a localized exciton and therefore offers a route toward novel optical properties.

  17. Cation effects on phosphatidic acid monolayers at various pH conditions.

    Zhang, Ting; Cathcart, Matthew G; Vidalis, Andrew S; Allen, Heather C

    2016-10-01

    The impact of pH and cations on phase behavior, stability, and surface morphology for dipalmitoylphosphatidic acid (DPPA) monolayers was investigated. At pHCations are found to expand and stabilize the monolayer in the following order of increasing magnitude at pH 5.6: Na + >K + ∼Mg 2+ >Ca 2+ . Additionally, cation complexation is tied to the pH and protonation state of DPPA, which are the primary factors controlling the monolayer surface behavior. The binding affinity of cations to the headgroup and thus deprotonation capability of the cation, ranked in the order of Ca 2+ >Mg 2+ >Na + >K + , is found to be well explained by the law of matching water affinities. Nucleation of surface 3D lipid structures is observed from Ca 2+ , Mg 2+ , and Na + , but not from K + , consistent with the lowest binding affinity of K + . Unraveling cation and pH effects on DPPA monolayers is useful in further understanding the surface properties of complex systems such as organic-coated marine aerosols where organic films are directly influenced by the pH and ionic composition of the underlying aqueous phase. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  18. Novel top-contact monolayer pentacene-based thin-film transistor for ammonia gas detection.

    Mirza, Misbah; Wang, Jiawei; Li, Dexing; Arabi, S Atika; Jiang, Chao

    2014-04-23

    We report on the fabrication of an organic field-effect transistor (OFET) of a monolayer pentacene thin film with top-contact electrodes for the aim of ammonia (NH3) gas detection by monitoring changes in its drain current. A top-contact configuration, in which source and drain electrodes on a flexible stamp [poly(dimethylsiloxane)] were directly contacted with the monolayer pentacene film, was applied to maintain pentacene arrangement ordering and enhance the monolayer OFET detection performance. After exposure to NH3 gas, the carrier mobility at the monolayer OFET channel decreased down to one-third of its original value, leading to a several orders of magnitude decrease in the drain current, which tremendously enhanced the gas detection sensitivity. This sensitivity enhancement to a limit of the 10 ppm level was attributed to an increase of charge trapping in the carrier channel, and the amount of trapped states was experimentally evaluated by the threshold voltage shift induced by the absorbed NH3 molecular analyte. In contrast, a conventional device with a 50-nm-thick pentacene layer displayed much higher mobility but lower response to NH3 gas, arising from the impediment of analyte penetrating into the conductive channel, owing to the thick pentacene film.

  19. Investigation on the Permeability Evolution of Gypsum Interlayer Under High Temperature and Triaxial Pressure

    Tao, Meng; Yechao, You; Jie, Chen; Yaoqing, Hu

    2017-08-01

    The permeability of the surrounding rock is a critical parameter for the designing and assessment of radioactive waste disposal repositories in the rock salt. Generally, in the locations that are chosen for radioactive waste storage, the bedded rock salt is a sedimentary rock that contains NaCl and Na2SO4. Most likely, there are also layers of gypsum ( {CaSO}_{ 4} \\cdot 2 {H}_{ 2} {O)} present in the salt deposit. Radioactive wastes emit a large amount of heat and hydrogen during the process of disposal, which may result in thermal damage of the surrounding rocks and cause a great change in their permeability and tightness. Therefore, it is necessary to investigate the permeability evolution of the gypsum interlayer under high temperature and high pressure in order to evaluate the tightness and security of the nuclear waste repositories in bedded rock salt. In this study, a self-designed rock triaxial testing system by which high temperature and pressure can be applied is used; the μCT225kVFCB micro-CT system is also employed to investigate the permeability and microstructure of gypsum specimens under a constant hydrostatic pressure of 25 MPa, an increasing temperature (ranging from 20 to 650 °C), and a variable inlet gas pressure (1, 2, 4, 6 MPa). The experimental results show: (a) the maximum permeability measured during the whole experiment is less than 10-17 m2, which indicates that the gypsum interlayer has low permeability under high temperature and pressure that meet the requirements for radioactive waste repository. (b) Under the same temperature, the permeability of the gypsum specimen decreases at the beginning and then increases as the pore pressure elevates. When the inlet gas pressure is between 0 and 2 MPa, the Klinkenberg effect is very pronounced. Then, as the pore pressure increases, the movement behavior of gas molecules gradually changes from free motion to forced directional motion. So the role of free movement of gas molecules gradually

  20. A Systematic Procedure to Describe Shale Gas Permeability Evolution during the Production Process

    Jia, B.; Tsau, J. S.; Barati, R.

    2017-12-01

    Gas flow behavior in shales is complex due to the multi-physics nature of the process. Pore size reduces as the in-situ stress increases during the production process, which will reduce intrinsic permeability of the porous media. Slip flow/pore diffusion enhances gas apparent permeability, especially under low reservoir pressures. Adsorption not only increases original gas in place but also influences gas flow behavior because of the adsorption layer. Surface diffusion between free gas and adsorption phase enhances gas permeability. Pore size reduction and the adsorption layer both have complex impacts on gas apparent permeability and non-Darcy flow might be a major component in nanopores. Previously published literature is generally incomplete in terms of coupling of all these four physics with fluid flow during gas production. This work proposes a methodology to simultaneously take them into account to describe a permeability evolution process. Our results show that to fully describe shale gas permeability evolution during gas production, three sets of experimental data are needed initially: 1) intrinsic permeability under different in-situ stress, 2) adsorption isotherm under reservoir conditions and 3) surface diffusivity measurement by the pulse-decay method. Geomechanical effects, slip flow/pore diffusion, adsorption layer and surface diffusion all play roles affecting gas permeability. Neglecting any of them might lead to misleading results. The increasing in-situ stress during shale gas production is unfavorable to shale gas flow process. Slip flow/pore diffusion is important for gas permeability under low pressures in the tight porous media. They might overwhelm the geomechanical effect and enhance gas permeability at low pressures. Adsorption layer reduces the gas permeability by reducing the effective pore size, but the effect is limited. Surface diffusion increases gas permeability more under lower pressures. The total gas apparent permeability might

  1. Structure and morphology of pentacene thin films - from sub-monolayers to application relevant multilayers

    Resel, R.; Werzer, O.; Nabok, D.; Puschnig, P.; Ambrosch-Draxl, C.; Smilgies, D.; Haase, A.; Stadlober, B.

    2008-01-01

    Full text: The conjugated molecule pentacene is one of the most prominent material for application in organic thin film transistors. Charge carrier mobilities of about 1 cm 2 /Vs are realized in different device geometries which are used in integrated circuits. The device performance depends on the detailed structure and morphology of the pentacene thin films. This work presents an combined atomic force microscopy / x-ray scattering study on the formation of pentacene thin films starting from sub-monolayer coverage to the first closed monolayer to finally multilayer structures as they are used in device structures. Thin films of pentacene are prepared on oxidized silicon wafer with nominal thicknesses between 0.2 nm up to 180 nm. The films are investigated ex-situ by x-ray reflectivity and grazing incidence diffraction. In the sub-monolayer regime the formation of separated islands with up-right standing molecules are observed. The islands show typically dendritic shape with a separation of 2 μm from each other. With increasing coverage the dendritic islands coalescent until the first monolayer closes. Fitting of the x-ray reflectivity reveals that an additional layer between the substrate and the up-right standing pentacene molecules is present. During the formation of the second monolayer crystalline islands are formed. The crystallites grow in lateral and vertical size with increasing film thickness. The crystal structure of pentacene within the films is a surface induced phase. The crystal structure of this metastable phase could be solved by a combined experimental and theoretical approach. At a nominal film thickness of about 40 nm the equilibrium bulk structure of pentacene appears; both phases remain existent up the thickest films investigated in this study. (author)

  2. Surface-subsurface turbulent interaction at the interface of a permeable bed: influence of the wall permeability

    Kim, T.; Blois, G.; Best, J.; Christensen, K. T.

    2017-12-01

    Coarse-gravel river beds possess a high degree of permeability. Flow interactions between surface and subsurface flow across the bed interface is key to a number of natural processes occurring in the hyporheic zone. In fact, it is increasingly recognized that these interactions drive mass, momentum and energy transport across the interface, and consequently control biochemical processes as well as stability of sediments. The current study explores the role of the wall permeability in surface and subsurface flow interaction under controlled experimental conditions on a physical model of a gravel bed. The present wall model was constructed by five layers of cubically arranged spheres (d=25.4mm, where d is a diameter) providing 48% of porosity. Surface topography was removed by cutting half of a diameter on the top layer of spheres to render the flow surface smooth and highlight the impact of the permeability on the overlying flow. An impermeable smooth wall was also considered as a baseline of comparison for the permeable wall flow. To obtain basic flow statistics, low-frame-rate high-resolution PIV measurements were performed first in the streamwise-wall-normal (x-y) plane and refractive-index matching was employed to optically access the flow within the permeable wall. Time-resolved PIV experiments in the same facility were followed to investigate the flow interaction across the wall interface in sptaio-temporal domain. In this paper, a detailed analysis of the first and second order velocity statistics as well as the amplitude modulation for the flow overlying the permeable smooth wall will be presented.

  3. Crustal permeability: Introduction to the special issue

    Ingebritsen, Steven E.; Gleeson, Tom

    2015-01-01

    The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

  4. Polysulfone - CNT composite membrane with enhanced water permeability

    Hirani, Bhakti; Kar, Soumitra; Aswal, V. K.; Bindal, R. C.; Goyal, P. S.

    2018-04-01

    Polymeric membranes are routinely used for water purification. The performance of these conventional membranes can be improved by incorporating nanomaterials, such as metal oxide nanoparticle and carbon nanotubes (CNTs). This manuscript reports the synthesis and characterization of polysulfone (Psf) based nanocomposite membranes where multi wall carbon nanotubes (MWCNTs) and oleic acid coated Fe3O4 nanoparticles have been impregnated onto the polymeric host matrix. The performance of the membranes was evaluated by water permeability and solute rejection measurements. It was observed that the permeability of Psf membrane increases three times at 0.1% loading of MWCNT without compromise in selectivity. It was further observed that the increase in permeability is not affected upon addition of Fe3O4 nanoparticles into the membrane. In order to get a better insight into the membrane microstructure, small angle neutron scattering (SANS) studies were carried out. There is a good correlation between the water permeability and the pore sizes of the membranes as measured using SANS.

  5. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    Lien, Der-Hsien; Amani, Matin; Desai, Sujay B.; Ahn, Geun Ho; Han, Kevin; He, Jr-Hau; Ager, Joel W.; Wu, Ming C.; Javey, Ali

    2018-01-01

    Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

  6. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    Lien, Der-Hsien

    2018-04-04

    Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

  7. A pentacene monolayer trapped between graphene and a substrate.

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-09-21

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures.

  8. Microorganism Removal in Permeable Pavement Parking Lots ...

    Three types of permeable pavements (pervious concrete, permeable interlocking concrete pavers, and porous asphalt) were monitored at the Edison Environmental Center in Edison, New Jersey for indicator organisms such as fecal coliform, enterococci, and E. coli. Results showed that porous asphalt had much lower concentration in monitored infiltrate compared to pervious concrete and permeable interlocking concrete pavers. Concentrations of monitored organisms in infiltrate from porous asphalt were consistently below the bathing water quality standard. Fecal coliform and enterococci exceeded bathing water quality standards more than 72% and 34% of the time for permeable interlocking concrete pavers and pervious concrete, respectively. Purpose is to evaluate the performance of permeable pavement in removing indicator organisms from infiltrating stormwater runoff.

  9. Acute effects of carprofen and meloxicam on canine gastrointestinal permeability and mucosal absorptive capacity.

    Craven, Melanie; Chandler, Marge L; Steiner, Jörg M; Farhadi, Ashkan; Welsh, Elizabeth; Pratschke, Kathryn; Shaw, Darren J; Williams, David A

    2007-01-01

    Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently prescribed to dogs for their analgesic, antipyretic, and anti-inflammatory properties. Their beneficial actions can be offset by gastrointestinal (GI) toxicosis. Endoscopy has traditionally been employed to detect GI lesions, but alterations in GI permeability precede the development of mucosal damage. Carprofen and meloxicam alter GI permeability and mucosal absorptive capacity of dogs. Twenty adult dogs treated with an NSAID for >7 days were evaluated by permeability tests while receiving either carprofen (10 dogs) or meloxicam (10 dogs). Prospective, longitudinal observational study. A 6-sugar permeability test (sucrose, lactulose, rhamnose, 3-O-methyl-D-glucose, D-xylose, and sucralose) was performed on the day before NSAID treatment, and after 3 and 8 days of treatment. There were no significant differences in the urinary recovery ratios of lactulose: rhamnose, D-xylose: 3-O-methyl-D-glucose, or sucralose recovery within either group at any time during the study. Sucrose permeability in the meloxicam group did not alter significantly over time. However, sucrose permeability in the carprofen group decreased significantly by day 3 (P = .049) and increased again by day 8 (P = .049), to a level that was not significantly different to permeability before treatment (P = .695). The absence of increased GI permeability and diminished mucosal absorptive capacity in this group of dogs does not support the development of acute GI toxicosis during treatment with either meloxicam or carprofen.

  10. Corneal and conjunctival drug permeability: Systematic comparison and pharmacokinetic impact in the eye.

    Ramsay, Eva; Del Amo, Eva M; Toropainen, Elisa; Tengvall-Unadike, Unni; Ranta, Veli-Pekka; Urtti, Arto; Ruponen, Marika

    2018-07-01

    On the surface of the eye, both the cornea and conjunctiva are restricting ocular absorption of topically applied drugs, but barrier contributions of these two membranes have not been systemically compared. Herein, we studied permeability of 32 small molecular drug compounds across an isolated porcine cornea and built a quantitative structure-property relationship (QSPR) model for the permeability. Corneal drug permeability (data obtained for 25 drug molecules) showed a 52-fold range in permeability (0.09-4.70 × 10 -6  cm/s) and the most important molecular descriptors in predicting the permeability were hydrogen bond donor, polar surface area and halogen ratio. Corneal permeability values were compared to their conjunctival drug permeability values. Ocular drug bioavailability and systemic absorption via conjunctiva were predicted for this drug set with pharmacokinetic calculations. Drug bioavailability in the aqueous humour was simulated to be drug across the conjunctiva to the blood circulation restricts significantly ocular drug bioavailability and, therefore, ocular absorption does not increase proportionally with the increasing corneal drug permeability. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Colloid transport in dual-permeability media

    Leij, Feike J.; Bradford, Scott A.

    2013-07-01

    It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.

  12. Comparison of the permeability of metoprolol and labetalol in rat, mouse, and Caco-2 cells: use as a reference standard for BCS classification.

    Incecayir, Tuba; Tsume, Yasuhiro; Amidon, Gordon L

    2013-03-04

    The purpose of this study was to investigate labetalol as a potential high permeability reference standard for the application of Biopharmaceutics Classification Systems (BCS). Permeabilities of labetalol and metoprolol were investigated in animal intestinal perfusion models and Caco-2 cell monolayers. After isolating specific intestinal segments, in situ single-pass intestinal perfusions (SPIP) were performed in rats and mice. The effective permeabilities (Peff) of labetalol and metoprolol, an FDA standard for the low/high Peff class boundary, were investigated in two different segments of rat intestine (proximal jejunum and distal ileum) and in the proximal jejunum of mouse. No significant difference was found between Peff of metoprolol and labetalol in the jejunum and ileum of rat (0.33 ± 0.11 × 10(-4) vs 0.38 ± 0.06 × 10(-4) and 0.57 ± 0.17 × 10(-4) vs 0.64 ± 0.30 × 10(-4) cm/s, respectively) and in the jejunum of mouse (0.55 ± 0.05 × 10(-4) vs 0.59 ± 0.13 × 10(-4) cm/s). However, Peff of metoprolol and labetalol were 1.7 and 1.6 times higher in the jejunum of mouse, compared to the jejunum of rat, respectively. Metoprolol and labetalol showed segmental-dependent permeability through the rat intestine, with increased Peff in the distal ileum in comparison to the proximal jejunum. Most significantly, Peff of labetalol was found to be concentration-dependent. Decreasing concentrations of labetalol in the perfusate resulted in decreased Peff compared to Peff of metoprolol. The intestinal epithelial permeability of labetalol was lower than that of metoprolol in Caco-2 cells at both apical pH 6.5 and 7.5 (5.96 ± 1.96 × 10(-6) vs 9.44 ± 3.44 × 10(-6) and 15.9 ± 2.2 × 10(-6) vs 23.2 ± 7.1 × 10(-6) cm/s, respectively). Labetalol exhibited higher permeability in basolateral to apical (BL-AP) compared to AP-BL direction in Caco-2 cells at 0.1 times the highest dose strength (HDS) (46.7 ± 6.5 × 10(-6) vs 14.2 ± 1.5 × 10(-6) cm/s). The P

  13. A study of the inhibiton of copper corrosion by triethyl phosphate and triphenyl phosphate self-assembled monolayers

    HOUYI MA

    2006-02-01

    Full Text Available Two kinds of phosphates, triethyl phosphate (TEP and triphenyl phosphate (TPP, were used to form self-assembled monolayers for the inhibition of the corrosion of copper in 0.2 mol dm–3 NaCl solution. Electrochemical impedance spectroscopy (EIS was applied to investigate the inhibition effects. The results showed that their inhibition ability first increased with increasing immersion time in ethanolic solutions of the corresponding compounds. However, when the immersion time was increased over some critical point, the inhibition effect decreased. For the same immersion time, the inhibition effect of the TPP monolayer was more pronounced than that of the TEP monolayer. Thus, ab initio calculations were used to interpret the relationship between the inhibition effects and the structures of the compounds.

  14. Compact rock material gas permeability properties

    Wang, Huanling, E-mail: whl_hm@163.com [Key Laboratory of Coastal Disaster and Defence, Ministry of Education, Hohai University, Nanjing 210098 (China); LML, University of Lille, Cite Scientifique, 59655 Villeneuve d’Ascq (France); Xu, Weiya; Zuo, Jing [Institutes of Geotechnical Engineering, Hohai University, Nanjing 210098 (China)

    2014-09-15

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO{sub 2,} 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{sup −19} m{sup 2}; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10{sup −17} m{sup 2}; 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.

  15. Suitability of Torrent Permeability Tester to measure air-permeability of covercrete

    Andrade, C.; Gonzales-Gasca, C. [Institute of Construction Sciences ' Eduardo Torroja' , Madrid (Spain); Torrent, R. [Portland Cement Institute, (Argentina)

    2000-07-01

    Suitability of the Torrent Permeability Tester (TPT) to measure the permeability of covercrete to air, both in the laboratory and the field, is investigated, and test results obtained in laboratory studies are discussed. The tests performed included the determination of air permeability (TPT method), oxygen permeability (Cembureau method) and capillary suction, rapid chloride permeability test (ASTM C 1202), as well as a one-year carbonation depth test. Concrete specimens of various compositions and curing regimes were used in the tests; the gas-permeability tests were repeated on the same specimens after 28 days, than again at 6 months and 12 months. Test results confirmed the suitability of the TPT as a useful tool in the characterization of the quality the of concrete cover. It was found to be sensitive to changes in concrete quality; repeatable for sensitive properties such as gas permeability ; also, it was found to correlate well with other durability-related properties. 10 refs., 8 tabs., 8 figs.

  16. Interactions between an anticancer drug - edelfosine - and cholesterol in Langmuir monolayers

    Wiecek, Agata; Dynarowicz-Latka, Patrycja; Minones, J.; Conde, Olga; Casas, Matilde

    2008-01-01

    Edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, abbr. Et-18-OCH 3 ) is a new generation anticancer drug based on a phospholipids-like structure. Since its mechanism of action is believed to be related to the lipids of cellular membrane, we have investigated the interactions between edelfosine and main mammalian sterol: cholesterol, using the Langmuir monolayer technique. The interactions have been analyzed by comparing the experimental curves with theoretical ones, obtained basing on the additivity rule. The observed contraction together with negative deviations from ideality observed on the mean molecular area (A 12 ) vs film composition plots proves the existence of strong attractive forces between edelfosine and cholesterol, which have been quantified with the excess free energy of mixing (ΔG exc ) values, calculated from the surface pressure-area isotherms datapoints. The most negative values of ΔG exc have been found for the mixture of equimolar composition, proving its highest thermodynamic stability and the existence of the strongest interactions between film components. Thus, it has been postulated that at the surface edelfosine and cholesterol form stable complexes of 1:1 stoichiometry. The analysis of the collapse pressure values for the investigated mixed monolayers proves that films of edelfosine mole fraction ≤ 0.5 are miscible within the whole range of surface pressures, while monolayers richer in edelfosine mix in the pressure region below ca. 37.6 mN/m, which corresponds to the collapse of pure edelfosine monolayer. At this very surface pressure, edelfosine is expelled from the mixed monolayer and the remaining film is composed by surface complexes of high stability. The hypothesis of complex formation explains the results performed in vitro on cell cultures, indicating that the increase of cholesterol content significantly reduces the uptake of edelfosine

  17. Vector assembly of colloids on monolayer substrates

    Jiang, Lingxiang; Yang, Shenyu; Tsang, Boyce; Tu, Mei; Granick, Steve

    2017-06-01

    The key to spontaneous and directed assembly is to encode the desired assembly information to building blocks in a programmable and efficient way. In computer graphics, raster graphics encodes images on a single-pixel level, conferring fine details at the expense of large file sizes, whereas vector graphics encrypts shape information into vectors that allow small file sizes and operational transformations. Here, we adapt this raster/vector concept to a 2D colloidal system and realize `vector assembly' by manipulating particles on a colloidal monolayer substrate with optical tweezers. In contrast to raster assembly that assigns optical tweezers to each particle, vector assembly requires a minimal number of optical tweezers that allow operations like chain elongation and shortening. This vector approach enables simple uniform particles to form a vast collection of colloidal arenes and colloidenes, the spontaneous dissociation of which is achieved with precision and stage-by-stage complexity by simply removing the optical tweezers.

  18. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina

    2016-01-01

    Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with a lower tendency to form defect induced deep gap states are termed defect-tolerant. Here we provide a systematic first...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within......-principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...

  19. Beam damage of self-assembled monolayers

    Rieke, P.C.; Baer, D.R.; Fryxell, G.E.; Engelhard, M.H.; Porter, M.S.

    1993-01-01

    X-ray and electron beam damage studies were performed on Br-terminated and methyl-terminated alkylsilane self-assembled monolayers. X-ray beam initiated damage was primarily limited to removal of the labile Br group and did not significantly damage the hydrocarbon chain. Some of the x-ray beam damage could be attributed to low-energy electrons emitted by the non-monochromatic source, but further damage was attributed to secondary electrons produced in the sample by x-ray exposure. Electron beams caused significant damage to the hydrocarbon chains. Maximum damage occurred with a beam energy of 600 eV and a dosage of 6x10 -3 C/cm 2

  20. Enhanced photocurrent in engineered bacteriorhodopsin monolayer.

    Patil, Amol V; Premaruban, Thenhuan; Berthoumieu, Olivia; Watts, Anthony; Davis, Jason J

    2012-01-12

    The integration of the transmembrane protein bacteriorhodopsin (BR) with man-made electrode surfaces has attracted a great deal of interest for some two decades or more and holds significant promise from the perspective of derived photoresponse or energy capture interfaces. Here we demonstrate that a novel and strategically engineered cysteine site (M163C) can be used to intimately and effectively couple delipidated BR to supporting metallic electrode surfaces. By virtue of the combined effects of the greater surface molecular density afforded by delipidation, and the vicinity of the electrostatic changes associated with proton pumping to the transducing metallic continuum, the resulting films generate a considerably greater photocurrent density on wavelength-selective illumination than previously achievable with monolayers of BR. Given the uniquely photoresponsive, wavelength-selective, and photostable characteristics of this protein, the work has implications for utilization in solar energy capture and photodetector devices.

  1. Headgroup effects of template monolayers on the adsorption behavior and conformation of glucose oxidase adsorbed at air/liquid interfaces.

    Wang, Ke-Hsuan; Syu, Mei-Jywan; Chang, Chien-Hsiang; Lee, Yuh-Lang

    2011-06-21

    Stearic acid (SA) and octadecylamine (ODA) monolayers at the air/liquid interface were used as template layers to adsorb glucose oxidase (GOx) from aqueous solution. The effect of the template monolayers on the adsorption behavior of GOx was studied in terms of the variation of surface pressure, the evolution of surface morphology observed by BAM and AFM, and the conformation of adsorbed GOx. The results show that the presence of a template monolayer can enhance the adsorption rate of GOx; furthermore, ODA has a higher ability, compared to SA, to adsorb GOx, which is attributed to the electrostatic attractive interaction between ODA and GOx. For adsorption performed on a bare surface or on an SA monolayer, the surface pressure approaches an equilibrium value (ca. 8 mN/m) after 2 to 3 h of adsorption and remains nearly constant in the following adsorption process. For the adsorption on an ODA monolayer, the surface pressure will increase further 1 to 2 h after approaching the first equilibrium pressure, which is termed the second adsorption stage. The measurement of circular dichroism (CD) spectroscopy indicates that the Langmuir-Blodgett films of adsorbed GOx transferred at the first equilibrium state (π = 8 mN/m) have mainly a β-sheet conformation, which is independent of the type of template monolayers. However, the ODA/GOx LB film transferred at the second adsorption stage has mainly an α-helix conformation. It is concluded that the specific interaction between ODA and GOx not only leads to a higher adsorption rate and adsorbed amount of GOx but also induces a conformation change in adsorbed GOx from β-sheet to α-helix. The present results indicate that is possible to control the conformation of adsorbed protein by selecting the appropriate template monolayer. © 2011 American Chemical Society

  2. Effect of Perfluoroalkyl Endgroups on the Interactions of Tri-Block Copolymers with Monofluorinated F-DPPC Monolayers

    Syed W. H. Shah

    2017-10-01

    Full Text Available We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl-sn-glycero-3-phosphocholine, a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC. The amphiphilic block copolymers contained a hydrophobic poly(propylene oxide block flanked by hydrophilic poly(glycerol monomethacrylate blocks (GP. F-GP was derived from GP by capping both termini with perfluoro-n-nonyl segments. We first studied the adsorption of GP and F-GP to lipid monolayers of F-DPPC. F-GP was inserted into the monolayer up to a surface pressure Π of 42.4 mN m−1, much higher than GP (32.5 mN m−1. We then studied isotherms of lipid-polymer mixtures co-spread at the air-water interface. With increasing polymer content in the mixture a continuous shift of the onset of the liquid-expanded (LE to liquid-condensed (LC transition towards higher molecular and higher area per lipid molecule was observed. F-GP had a larger effect than GP indicating that it needed more space. At a Π-value of 32 mN m−1, GP was excluded from the mixed monolayer, whereas F-GP stayed in F-DPPC monolayers up to 42 mN m−1. F-GP is thus more stably anchored in the monolayer up to higher surface pressures. Images of mixed monolayers were acquired using different fluorescent probes and showed the presence of perfluorinated segments of F-GP at LE-LC domain boundaries.

  3. Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

    Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

    2016-04-21

    We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

  4. Surface-segregated monolayers: a new type of ordered monolayer for surface modification of organic semiconductors.

    Wei, Qingshuo; Tajima, Keisuke; Tong, Yujin; Ye, Shen; Hashimoto, Kazuhito

    2009-12-09

    We report a new type of ordered monolayer for the surface modification of organic semiconductors. Fullerene derivatives with fluorocarbon chains ([6,6]-phenyl-C(61)-buryric acid 1H,1H-perfluoro-1-alkyl ester or FC(n)) spontaneously segregated as a monolayer on the surface of a [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) film during a spin-coating process from the mixture solutions, as confirmed by X-ray photoelectron spectroscopy (XPS). Ultraviolet photoelectron spectroscopy (UPS) showed the shift of ionization potentials (IPs) depending on the fluorocarbon chain length, indicating the formation of surface dipole moments. Surface-sensitive vibrational spectroscopy, sum frequency generation (SFG) revealed the ordered molecular orientations of the C(60) moiety in the surface FC(n) layers. The intensity of the SFG signals from FC(n) on the surface showed a clear odd-even effect when the length of the fluorocarbon chain was changed. This new concept of the surface-segregated monolayer provides a facile and versatile approach to modifying the surface of organic semiconductors and is applicable to various organic optoelectronic devices.

  5. Trench infiltration for managed aquifer recharge to permeable bedrock

    Heilweil, V.M.; Watt, D.E.

    2011-01-01

    Managed aquifer recharge to permeable bedrock is increasingly being utilized to enhance resources and maintain sustainable groundwater development practices. One such target is the Navajo Sandstone, an extensive regional aquifer located throughout the Colorado Plateau of the western United States. Spreading-basin and bank-filtration projects along the sandstone outcrop's western edge in southwestern Utah have recently been implemented to meet growth-related water demands. This paper reports on a new cost-effective surface-infiltration technique utilizing trenches for enhancing managed aquifer recharge to permeable bedrock. A 48-day infiltration trench experiment on outcropping Navajo Sandstone was conducted to evaluate this alternative surface-spreading artificial recharge method. Final infiltration rates through the bottom of the trench were about 0.5 m/day. These infiltration rates were an order of magnitude higher than rates from a previous surface-spreading experiment at the same site. The higher rates were likely caused by a combination of factors including the removal of lower permeability soil and surficial caliche deposits, access to open vertical sandstone fractures, a reduction in physical clogging associated with silt and biofilm layers, minimizing viscosity effects by maintaining isothermal conditions, minimizing chemical clogging caused by carbonate mineral precipitation associated with algal photosynthesis, and diminished gas clogging associated with trapped air and biogenic gases. This pilot study illustrates the viability of trench infiltration for enhancing surface spreading of managed aquifer recharge to permeable bedrock. ?? 2010.

  6. Wetting phase permeability in a partially saturated horizontal fracture

    Nicholl, M.J.; Glass, R.J.

    1994-01-01

    Fractures within geologic media can dominate the hydraulic properties of the system. Therefore, conceptual models used to assess the potential for radio-nuclide migration in unsaturated fractured rock such as that composing Yucca Mountain, Nevada, must be consistent with flow processes in individual fractures. A major obstacle to the understanding and simulation of unsaturated fracture flow is the paucity of physical data on both fracture aperture structure and relative permeability. An experimental procedure is developed for collecting detailed data on aperture and phase structure from a transparent analog fracture. To facilitate understanding of basic processes and provide a basis for development of effective property models, the simplest possible rough-walled fracture is used. Stable phase structures of varying complexity are created within the horizontal analog fracture. Wetting phase permeability is measured under steady-state conditions. A process based model for wetting phase relative permeability is then explored. Contributions of the following processes to reduced wetting phase permeability under unsaturated conditions are considered: reduction in cross-sectional flow area, increased path length, localized flow restriction, and preferential occupation of large apertures by the non-wetting phase

  7. Relationship between changed alveolar-capillary permeability and angiotensin converting enzyme activity in serum in sarcoidosis.

    Eklund, A; Blaschke, E

    1986-01-01

    The effect of altered alveolar-capillary permeability on angiotensin converting enzyme (ACE) activity in serum (SACE) was studied in 45 patients with sarcoidosis and 21 healthy controls. In sarcoidosis increased albumin concentrations in the bronchoalveolar lavage fluid (L albumin) and increased ratios of L albumin to albumin in serum (S albumin) indicated an increased permeability of the alveolar-capillary membrane. ACE activity in the lavage fluid (LACE) was correlated with the number of al...

  8. Thermomechanical effects on permeability for a 3-D model of YM rock

    Berge, P A; Blair, S C; Wang, H F

    1999-01-01

    The authors estimate how thermomechanical processes affect the spatial variability of fracture permeability for a 3-D model representing Topopah Spring tuff at the nuclear-waste repository horizon in Yucca Mountain, Nevada. Using a finite-difference code, they compute thermal stress changes. They evaluate possible permeability enhancement resulting from shear slip along various mapped fracture sets after 50 years of heating, for rock in the near-field environment of the proposed repository. The results indicate permeability enhancement of a factor of 2 for regions about 10 to 30 m above drifts, for north-south striking vertical fractures. Shear slip and permeability increases of a factor of 4 can occur in regions just above drifts, for east-west striking vertical fractures. Information on how permeability may change over the lifetime of a geologic repository is important to the prediction and evaluation of repository performance

  9. Intestinal Permeability and Cellular Antioxidant Activity of Phenolic Compounds from Mango (Mangifera indica cv. Ataulfo Peels

    Ramón Pacheco-Ordaz

    2018-02-01

    Full Text Available Mango (Mangifera indica cv. Ataulfo peel contains bound phenolics that may be released by alkaline or acid hydrolysis and may be converted into less complex molecules. Free phenolics from mango cv. Ataulfo peel were obtained using a methanolic extraction, and their cellular antioxidant activity (CAA and permeability were compared to those obtained for bound phenolics released by alkaline or acid hydrolysis. Gallic acid was found as a simple phenolic acid after alkaline hydrolysis along with mangiferin isomers and quercetin as aglycone and glycosides. Only gallic acid, ethyl gallate, mangiferin, and quercetin were identified in the acid fraction. The acid and alkaline fractions showed the highest CAA (60.5% and 51.5% when tested at 125 µg/mL. The value of the apparent permeability coefficient (Papp across the Caco-2/HT-29 monolayer of gallic acid from the alkaline fraction was higher (2.61 × 10−6 cm/s than in the other fractions and similar to that obtained when tested pure (2.48 × 10−6 cm/s. In conclusion, mango peels contain bound phenolic compounds that, after their release, have permeability similar to pure compounds and exert an important CAA. This finding can be applied in the development of nutraceuticals using this important by-product from the mango processing industry.

  10. Intestinal Permeability and Cellular Antioxidant Activity of Phenolic Compounds from Mango (Mangifera indica cv. Ataulfo) Peels

    Pacheco-Ordaz, Ramón; González-Aguilar, Gustavo A.

    2018-01-01

    Mango (Mangifera indica cv. Ataulfo) peel contains bound phenolics that may be released by alkaline or acid hydrolysis and may be converted into less complex molecules. Free phenolics from mango cv. Ataulfo peel were obtained using a methanolic extraction, and their cellular antioxidant activity (CAA) and permeability were compared to those obtained for bound phenolics released by alkaline or acid hydrolysis. Gallic acid was found as a simple phenolic acid after alkaline hydrolysis along with mangiferin isomers and quercetin as aglycone and glycosides. Only gallic acid, ethyl gallate, mangiferin, and quercetin were identified in the acid fraction. The acid and alkaline fractions showed the highest CAA (60.5% and 51.5%) when tested at 125 µg/mL. The value of the apparent permeability coefficient (Papp) across the Caco-2/HT-29 monolayer of gallic acid from the alkaline fraction was higher (2.61 × 10−6 cm/s) than in the other fractions and similar to that obtained when tested pure (2.48 × 10−6 cm/s). In conclusion, mango peels contain bound phenolic compounds that, after their release, have permeability similar to pure compounds and exert an important CAA. This finding can be applied in the development of nutraceuticals using this important by-product from the mango processing industry. PMID:29419800

  11. Caco-2 Permeability Studies and In Vitro hERG Liability Assessment of Tryptanthrin and Indolinone.

    Jähne, Evelyn A; Eigenmann, Daniela E; Moradi-Afrapoli, Fahimeh; Verjee, Sheela; Butterweck, Veronika; Hebeisen, Simon; Hettich, Timm; Schlotterbeck, Götz; Smieško, Martin; Hamburger, Matthias; Oufir, Mouhssin

    2016-08-01

    Tryptanthrin and (E,Z)-3-(4-hydroxy-3,5-dimethoxybenzylidene)indolinone (indolinone) were recently isolated from Isatis tinctoria as potent anti-inflammatory and antiallergic alkaloids, and shown to inhibit COX-2, 5-LOX catalyzed leukotriene synthesis, and mast cell degranulation at low µM to nM concentrations. To assess their suitability for oral administration, we screened the compounds in an in vitro intestinal permeability assay using human colonic adenocarcinoma cells. For exact quantification of the compounds, validated UPLC-MS/MS methods were used. Tryptanthrin displayed high permeability (apparent permeability coefficient > 32.0 × 10(-6) cm/s) across the cell monolayer. The efflux ratio below 2 ( 10 µM) and indolinone (IC50 of 24.96 µM). The analysis of compounds using various in silico methods confirmed favorable pharmacokinetic properties, as well as a slight inhibition of the human ether-a-go-go-related gene potassium channel at micromolar concentrations. Georg Thieme Verlag KG Stuttgart · New York.

  12. Intestinal Permeability and Cellular Antioxidant Activity of Phenolic Compounds from Mango (Mangifera indica cv. Ataulfo) Peels.

    Pacheco-Ordaz, Ramón; Antunes-Ricardo, Marilena; Gutiérrez-Uribe, Janet A; González-Aguilar, Gustavo A

    2018-02-08

    Mango ( Mangifera indica cv. Ataulfo) peel contains bound phenolics that may be released by alkaline or acid hydrolysis and may be converted into less complex molecules. Free phenolics from mango cv. Ataulfo peel were obtained using a methanolic extraction, and their cellular antioxidant activity (CAA) and permeability were compared to those obtained for bound phenolics released by alkaline or acid hydrolysis. Gallic acid was found as a simple phenolic acid after alkaline hydrolysis along with mangiferin isomers and quercetin as aglycone and glycosides. Only gallic acid, ethyl gallate, mangiferin, and quercetin were identified in the acid fraction. The acid and alkaline fractions showed the highest CAA (60.5% and 51.5%) when tested at 125 µg/mL. The value of the apparent permeability coefficient (Papp) across the Caco-2/HT-29 monolayer of gallic acid from the alkaline fraction was higher (2.61 × 10 -6 cm/s) than in the other fractions and similar to that obtained when tested pure (2.48 × 10 -6 cm/s). In conclusion, mango peels contain bound phenolic compounds that, after their release, have permeability similar to pure compounds and exert an important CAA. This finding can be applied in the development of nutraceuticals using this important by-product from the mango processing industry.

  13. A new structure of permeable pavement for mitigating urban heat island.

    Liu, Yong; Li, Tian; Peng, Hangyu

    2018-09-01

    The urban heat island (UHI) effect has been a great threat to human habitation, and how to mitigate this problem has been a global concern over decades. This paper addresses the cooling effect of a novel permeable pavement called evaporation-enhancing permeable pavement, which has capillary columns in aggregate and a liner at the bottom. To explore the efficiency of mitigating the UHI, bench-scale permeable pavement units with capillary columns were developed and compared with conventional permeable pavement. Criteria of capillary capacities of the column, evaporation rates, and surface temperature of the pavements were monitored under simulated rainfall and Shanghai local weather conditions. Results show the capillary column was important in increasing evaporation by lifting water from the bottom to the surface, and the evaporation-enhancing permeable pavement was cooler than a conventional permeable pavement by as much as 9.4°C during the experimental period. Moreover, the cooling effect of the former pavement could persist more than seven days under the condition of no further rainfall. Statistical analysis result reveals that evaporation-enhancing permeable pavement can mitigate the UHI effect significantly more than a conventional permeable pavement. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. In vitro bioacessibility and transport across Caco-2 monolayers of haloacetic acids in drinking water.

    Melo, A; Faria, M A; Pinto, E; Mansilha, C; Ferreira, I M P L V O

    2016-10-01

    Water disinfection plays a crucial role in water safety but it is also a matter of concern as the use of disinfectants promotes the formation of disinfection by-products (DBPs). Haloacetic acids (HAAs) are one of the major classes of DBPs since they are frequently found in treated water, are ubiquitous, pervasive and have high water solubility, so a great concern emerged about their formation, occurrence and toxicity. Exposure to HAAs is influenced by consumption patterns and diet of individuals thus their bioavailability is an important parameter to the overall toxicity. In the current study the bioacessibility of the most representative HAAs (chloroacetic acid - MCAA, bromoacetic acid - MBAA, dichloroacetic acid - DCAA, dibromoacetic acid - DBAA, and trichloroacetic acid - TCAA) after simulated in vitro digestion (SIVD) in tap water and transport across Caco-2 monolayers was evaluated. Compounds were monitored in 8 points throughout the digestion phases by an optimized LC-MS/MS methodology. MCAA and MBAA were not bioaccessible after SIVD whereas DCAA, DBAA and TCAA are highly bioaccessible (85 ± 4%, 97 ± 4% and 106 ± 7% respectively). Concerning transport assays, DCAA and DBAA were highly permeable throughout the Caco-2 monolayer (apparent permeability and calculated fraction absorbed of 13.62 × 10(-6) cm/s and 90% for DCAA; and 8.82 × 10(-6) cm/s and 84% for DBAA), whereas TCAA showed no relevant permeability. The present results may contribute to efficient risk analysis studies concerning HAAs oral exposure from tap water taking into account the different biological behaviour of these chemically similar substances. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccaride Sensing-Interface

    Kwangnak Koh

    2007-08-01

    Full Text Available We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing through the formation ofself-assembled monolayer (SAM. In this study, self-assembled phenylboronic acidderivative monolayers were formed on Au surface and carefully characterized by atomicforce microscopy (AFM, Fourier transform infrared reflection absorption spectroscopy(FTIR-RAS, surface enhanced Raman spectroscopy (SERS, and surface electrochemicalmeasurements. The saccharide sensing application was investigated using surface plasmonresonance (SPR spectroscopy. The phenylboronic acid monolayers showed goodsensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10-12 M.The SPR angle shift derived from interaction between phenylboronic acid andmonosaccharide was increased with increasing the alkyl spacer length of synthesizedphenylboronic acid derivatives.

  16. Oleic acid and docosahexaenoic acid cause an increase in the paracellular absorption of hydrophilic compounds in an experimental model of human absorptive enterocytes

    Aspenstroem-Fagerlund, Bitte; Ring, Linda; Aspenstroem, Pontus; Tallkvist, Jonas; Ilbaeck, Nils-Gunnar; Glynn, Anders W.

    2007-01-01

    Surface active compounds present in food possibly have the ability to enhance the absorption of water soluble toxic agents. Therefore, we investigated whether fatty acids such as oleic acid and docosahexaenoic acid (DHA), both commonly present in food, negatively affect the integrity of tight junctions (TJ) in the intestinal epithelium and thereby increase the absorption of poorly absorbed hydrophilic substances. Caco-2 cells, which are derived from human absorptive enterocytes, were grown on permeable filters for 20-25 days. Differentiated cell monolayers were apically exposed for 90 min to mannitol in emulsions of oleic acid (5, 15 or 30 mM) or DHA (5, 15 or 30 mM) in an experimental medium with or without Ca 2+ and Mg 2+ . Absorption of 14 C-mannitol increased and trans-epithelial electrical resistance (TEER) decreased in cell monolayers exposed to oleic acid and DHA, compared to controls. Cytotoxicity, measured as leakage of LDH, was higher in groups exposed to 30 mM oleic acid and all concentrations of DHA. Morphology of the cell monolayers was studied by using fluorescence microscopy. Exposure of cell monolayers to 5 mM DHA for 90 min resulted in a profound alteration of the cell-cell contacts as detected by staining the cells for β-catenin. Oleic acid (30 mM) treatment also induced dissolution of the cell-cell contacts but the effect was not as pronounced as with DHA. Cell monolayers were also exposed for 180 min to 250 nM cadmium (Cd) in emulsions of oleic acid (5 or 30 mM) or DHA (1 or 5 mM), in an experimental medium with Ca 2+ and Mg 2+ . Retention of Cd in Caco-2 cells was higher after exposure to 5 mM oleic acid but lower after exposure to 30 mM oleic acid and DHA. Absorption of Cd through the monolayers increased after DHA exposure but not after exposure to oleic acid. Our results indicate that fatty acids may compromise the integrity of the intestinal epithelium and that certain lipids in food may enhance the paracellular absorption of poorly

  17. Permeability Barrier Generation in the Martian Lithosphere

    Schools, Joe; Montési, Laurent

    2015-11-01

    Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

  18. The solubility-permeability interplay and its implications in formulation design and development for poorly soluble drugs.

    Dahan, Arik; Miller, Jonathan M

    2012-06-01

    While each of the two key parameters of oral drug absorption, the solubility and the permeability, has been comprehensively studied separately, the relationship and interplay between the two have been largely ignored. For instance, when formulating a low-solubility drug using various solubilization techniques: what are we doing to the apparent permeability when we increase the solubility? Permeability is equal to the drug's diffusion coefficient through the membrane times the membrane/aqueous partition coefficient divided by the membrane thickness. The direct correlation between the intestinal permeability and the membrane/aqueous partitioning, which in turn is dependent on the drug's apparent solubility in the GI milieu, suggests that the solubility and the permeability are closely associated, exhibiting a certain interplay between them, and the current view of treating the one irrespectively of the other may not be sufficient. In this paper, we describe the research that has been done thus far, and present new data, to shed light on this solubility-permeability interplay. It has been shown that decreased apparent permeability accompanies the solubility increase when using different solubilization methods. Overall, the weight of the evidence indicates that the solubility-permeability interplay cannot be ignored when using solubility-enabling formulations; looking solely at the solubility enhancement that the formulation enables may be misleading with regards to predicting the resulting absorption, and hence, the solubility-permeability interplay must be taken into account to strike the optimal solubility-permeability balance, in order to maximize the overall absorption.

  19. Strain engineering the work function in monolayer metal dichalcogenides

    Lanzillo, Nicholas A; Simbeck, Adam J; Nayak, Saroj K

    2015-01-01

    We use first-principles density functional theory to investigate the effect of both tensile and compressive strain on the work functions of various metal dichalcogenide monolayers. We find that for all six species considered, including MoS 2 , WS 2 , SnS 2 , VS 2 , MoSe 2 and MoTe 2 , that compressive strain of up to 10% decreases the work function continuously by as much as 1.0 eV. Large enough tensile strain is also found to decrease the work function, although in some cases we observe an increase in the work function for intermediate values of tensile strain. This work function modulation is attributed to a weakening of the chalcogenide-metal bonds and an increase in total energy of each system as a function of strain. Values of strain which bring the metal atoms closer together lead to an increase in electrostatic potential energy, which in turn results in an increase in the vacuum potential level. The net effect on the work function can be explained in terms of the balance between the increases in the vacuum potential levels and Fermi energy. (paper)

  20. Permeability Tests on Silkeborg Sand No. 0000

    Lund, Willy; Jakobsen, Kim Parsberg

    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......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...

  1. Permeability Tests on Eastern Scheldt Sand

    Jakobsen, Kim Parsberg

    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......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...

  2. Defect Structure of Localized Excitons in a WSe2 Monolayer

    Zhang, Shuai

    2017-07-26

    The atomic and electronic structure of intrinsic defects in a WSe2 monolayer grown on graphite was revealed by low temperature scanning tunneling microscopy and spectroscopy. Instead of chalcogen vacancies that prevail in other transition metal dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work provided the first atomic-scale understanding of defect excitons and paved the way toward deciphering the defect structure of single quantum emitters previously discovered in the WSe2 monolayer.

  3. Aldehydes react with scribed silicon to form alkyl monolayers Characterization by ToF-SIMS suggests an even-odd effect

    Lua, Y.-Y.; Fillmore, W. Jonathan J.; Linford, Matthew R.

    2004-01-01

    Alkyl monolayers are formed when silicon is chemomechanically scribed in the presence of aldehydes (from butanal to nonanal). X-ray photoelectron spectroscopy (XPS), wetting, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) suggest increasingly thick and hydrophobic monolayers with increasing aldehyde chain length. Superimposed on the general trend of stronger ToF-SIMS signals for hydrocarbon fragments from longer aldehyde precursors is an even-odd effect. This effect is most pronounced for smaller (one- and two-carbon) hydrocarbon fragments and for monolayers prepared with shorter aldehyde precursors. This is the first time than an even-odd effect has been demonstrated for monolayers on scribed silicon

  4. Aldehydes react with scribed silicon to form alkyl monolayers Characterization by ToF-SIMS suggests an even-odd effect

    Lua, Y.-Y.; Fillmore, W. Jonathan J.; Linford, Matthew R

    2004-06-15

    Alkyl monolayers are formed when silicon is chemomechanically scribed in the presence of aldehydes (from butanal to nonanal). X-ray photoelectron spectroscopy (XPS), wetting, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) suggest increasingly thick and hydrophobic monolayers with increasing aldehyde chain length. Superimposed on the general trend of stronger ToF-SIMS signals for hydrocarbon fragments from longer aldehyde precursors is an even-odd effect. This effect is most pronounced for smaller (one- and two-carbon) hydrocarbon fragments and for monolayers prepared with shorter aldehyde precursors. This is the first time than an even-odd effect has been demonstrated for monolayers on scribed silicon.

  5. Adaptive Methods for Permeability Estimation and Smart Well Management

    Lien, Martha Oekland

    2005-04-01

    The main focus of this thesis is on adaptive regularization methods. We consider two different applications, the inverse problem of absolute permeability estimation and the optimal control problem of estimating smart well management. Reliable estimates of absolute permeability are crucial in order to develop a mathematical description of an oil reservoir. Due to the nature of most oil reservoirs, mainly indirect measurements are available. In this work, dynamic production data from wells are considered. More specifically, we have investigated into the resolution power of pressure data for permeability estimation. The inversion of production data into permeability estimates constitutes a severely ill-posed problem. Hence, regularization techniques are required. In this work, deterministic regularization based on adaptive zonation is considered, i.e. a solution approach with adaptive multiscale estimation in conjunction with level set estimation is developed for coarse scale permeability estimation. A good mathematical reservoir model is a valuable tool for future production planning. Recent developments within well technology have given us smart wells, which yield increased flexibility in the reservoir management. In this work, we investigate into the problem of finding the optimal smart well management by means of hierarchical regularization techniques based on multiscale parameterization and refinement indicators. The thesis is divided into two main parts, where Part I gives a theoretical background for a collection of research papers that has been written by the candidate in collaboration with others. These constitutes the most important part of the thesis, and are presented in Part II. A brief outline of the thesis follows below. Numerical aspects concerning calculations of derivatives will also be discussed. Based on the introduction to regularization given in Chapter 2, methods for multiscale zonation, i.e. adaptive multiscale estimation and refinement

  6. Frost Resistance and Permeability of Cement Stabilized Gravel used as Filling Material for Pearl-Chain Bridges

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard; Hertz, Kristian Dahl

    2014-01-01

    several requirements on its moisture properties. In this paper the frost resistance, the liquid water permeability and the water vapour permeability of cement stabilized gravel are examined for two different cement contents. It is found that a small increase in cement content from 4% to 5% increases...... the 28-days compressive strength from 6.2 MPa to 12.3 MPa. The frost resistance of cement stabilized gravel with 5% cement content is better than for cement stabilized gravel with 4% cement content. The liquid water permeability coefficient and the water vapour permeability coefficient are significantly...

  7. Directing reaction pathways by catalyst active-site selection using self-assembled monolayers.

    Pang, Simon H; Schoenbaum, Carolyn A; Schwartz, Daniel K; Medlin, J Will

    2013-01-01

    One key route for controlling reaction selectivity in heterogeneous catalysis is to prepare catalysts that exhibit only specific types of sites required for desired product formation. Here we show that alkanethiolate self-assembled monolayers with varying surface densities can be used to tune selectivity to desired hydrogenation and hydrodeoxygenation products during the reaction of furfural on supported palladium catalysts. Vibrational spectroscopic studies demonstrate that the selectivity improvement is achieved by controlling the availability of specific sites for the hydrogenation of furfural on supported palladium catalysts through the selection of an appropriate alkanethiolate. Increasing self-assembled monolayer density by controlling the steric bulk of the organic tail ligand restricts adsorption on terrace sites and dramatically increases selectivity to desired products furfuryl alcohol and methylfuran. This technique of active-site selection simultaneously serves both to enhance selectivity and provide insight into the reaction mechanism.

  8. Strictly monolayer large continuous MoS{sub 2} films on diverse substrates and their luminescence properties

    Mohapatra, P. K.; Deb, S.; Singh, B. P.; Vasa, P.; Dhar, S., E-mail: dhar@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2016-01-25

    Despite a tremendous interest on molybdenum disulfide as a thinnest direct band gap semiconductor, single step synthesis of a large area purely monolayer MoS{sub 2} film has not yet been reported. Here, we report a CVD route to synthesize a continuous film of strictly monolayer MoS{sub 2} covering an area as large as a few cm{sup 2} on a variety of different substrates without using any seeding material or any elaborate pretreatment of the substrate. This is achieved by allowing the growth to take place in the naturally formed gap between a piece of SiO{sub 2} coated Si wafer and the substrate, when the latter is placed on top of the former inside a CVD reactor. We propose a qualitative model to explain why the MoS{sub 2} films are always strictly monolayer in this method. The photoluminescence study of these monolayers shows the characteristic excitonic and trionic features associated with monolayer MoS{sub 2}. In addition, a broad defect related luminescence band appears at ∼1.7 eV. As temperature decreases, the intensity of this broad feature increases, while the band edge luminescence reduces.

  9. Tuning the Electronic, Optical, and Magnetic Properties of Monolayer GaSe with a Vertical Electric Field

    Ke, Congming; Wu, Yaping; Guo, Guang-Yu; Lin, Wei; Wu, Zhiming; Zhou, Changjie; Kang, Junyong

    2018-04-01

    Inspired by two-dimensional material with their unique physical properties and innovative device applications, here we report a design framework on monolayer GaSe, an important member of the two-dimensional material family, in an effort to tune the electronic, optical, and magnetic properties through a vertical electric field. A transition from indirect to direct band gap in monolayer GaSe is found with an electric field of 0.09 V /Å . The giant Stark effect results in a reduction of the band gap with a Stark coefficient of 3.54 Å. Optical and dielectric properties of monolayer GaSe are dependent on the vertical electric field. A large regulation range for polarization E ∥c ^ is found for the static dielectric constant. The optical anisotropy with the dipole transition from E ∥c ^ to E ⊥c ^ is achieved. Induced by the spin-orbit coupling, spin-splitting energy at the valence band maximum increases linearly with the electric field. The effective mass of holes is highly susceptible to the vertical electric field. Switchable spin-polarization features in spin texture of monolayer GaSe are predicted. The tunable electronic, optical, and magnetic properties of monolayer GaSe hold great promise for applications in both the optoelectronic and spintronic devices.

  10. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    Hakamada, Masataka, E-mail: hakamada.masataka.3x@kyoto-u.ac.jp; Kato, Naoki, E-mail: katou.naoki.75w@st.kyoto-u.ac.jp; Mabuchi, Mamoru, E-mail: mabuchi@energy.kyoto-u.ac.jp

    2016-11-30

    Highlights: • Nanoporous gold is modified with thiol-containing self-assembled monolayers. • The electrical resistivity of the thiol-modified nanoporous gold increases. • The electrical resistivity increases with increasing thiol concentration. • Monolayer tail groups enhance the atmosphere dependence of electrical resistivity. - Abstract: The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  11. PLVAP in diabetic retinopathy: A gatekeeper of angiogenesis and vascular permeability

    Wiśniewska-Kruk, J.

    2014-01-01

    Nowadays, approximately 4 million people worldwide experience blindness or severe vision loss caused by diabetic retinopathy. Diabetic retinopathy is a multifactorial disease that can progress from minor changes in vascular permeability, into a proliferative retinal disorder. The increasing

  12. Enhancing the intestinal membrane permeability of zanamivir: a carrier mediated prodrug approach.

    Gupta, Sheeba Varghese; Gupta, Deepak; Sun, Jing; Dahan, Arik; Tsume, Yasuhiro; Hilfinger, John; Lee, Kyung-Dall; Amidon, Gordon L

    2011-12-05

    The purpose of this study was to improve the membrane permeability and oral absorption of the poorly permeable anti-influenza agent, zanamivir. The poor oral bioavailability is attributed to the high polarity (cLogP ∼ -5) resulting from the polar and zwitterionic nature of zanamivir. In order to improve the permeability of zanamivir, prodrugs with amino acids were developed to target the intestinal membrane transporter, hPepT1. Several acyloxy ester prodrugs of zanamivir conjugated with amino acids were synthesized and characterized. The prodrugs were evaluated for their chemical stability in buffers at various pHs and for their transport and tissue activation by enzymes. The acyloxy ester prodrugs of zanamivir were shown to competitively inhibit [(3)H]Gly-Sar uptake in Caco-2 cells (IC(50): 1.19 ± 0.33 mM for L-valyl prodrug of zanamivir). The L-valyl prodrug of zanamivir exhibited ∼3-fold higher uptake in transfected HeLa/hPepT1 cells compared to wild type HeLa cells, suggesting, at least in part, carrier mediated transport by the hPepT1 transporter. Further, enhanced transcellular permeability of prodrugs across Caco-2 monolayer compared to the parent drug (P(app) = 2.24 × 10(-6) ± 1.33 × 10(-7) cm/s for L-valyl prodrug of zanamivir), with only parent zanamivir appearing in the receiver compartment, indicates that the prodrugs exhibited both enhanced transport and activation in intestinal mucosal cells. Most significantly, several of these prodrugs exhibited high intestinal jejunal membrane permeability, similar to metoprolol, in the in situ rat intestinal perfusion system, a system highly correlated with human jejunal permeability. In summary, this mechanistic targeted prodrug strategy, to enhance oral absorption via intestinal membrane carriers such as hPepT1, followed by activation to parent drug (active pharmaceutical ingredient or API) in the mucosal cell, significantly improves the intestinal epithelial cell permeability of zanamivir and has the

  13. Hydrotropic Solubilization of Lipophilic Drugs for Oral Delivery: The Effects of Urea and Nicotinamide on Carbamazepine Solubility–Permeability Interplay

    Beig, Avital; Lindley, David; Miller, Jonathan M.; Agbaria, Riad; Dahan, Arik

    2016-01-01

    Hydrotropy refers to increasing the water solubility of otherwise poorly soluble compound by the presence of small organic molecules. While it can certainly increase the apparent solubility of a lipophilic drug, the effect of hydrotropy on the drugs’ permeation through the intestinal membrane has not been studied. The purpose of this work was to investigate the solubility–permeability interplay when using hydrotropic drug solubilization. The concentration-dependent effects of the commonly used hydrotropes urea and nicotinamide, on the solubility and the permeability of the lipophilic antiepileptic drug carbamazepine were studied. Then, the solubility–permeability interplay was mathematically modeled, and was compared to the experimental data. Both hydrotropes allowed significant concentration-dependent carbamazepine solubility increase (up to ∼30-fold). A concomitant permeability decrease was evident both in vitro and in vivo (∼17-fold for nicotinamide and ∼9-fold for urea), revealing a solubility–permeability tradeoff when using hydrotropic drug solubilization. A relatively simplified simulation approach based on proportional opposite correlation between the solubility increase and the permeability decrease at a given hydrotrope concentration allowed excellent prediction of the overall solubility–permeability tradeoff. In conclusion, when using hydrotropic drug solubilization it is prudent to not focus solely on solubility, but to account for the permeability as well; achieving optimal solubility–permeability balance may promote the overall goal of the formulation to maximize oral drug exposure. PMID:27826241

  14. Hydrotropic solubilization of lipophilic drugs for oral delivery: The effects of urea and nicotinamide on carbamazepine solubility-permeability interplay

    Avital Beig

    2016-10-01

    Full Text Available Hydrotropy refers to increasing the water solubility of otherwise poorly soluble compound by the presence of small organic molecules. While it can certainly increase the apparent solubility of a lipophilic drug, the effect of hydrotropy on the drugs' permeation through the intestinal membrane has not been studied. The purpose of this work was to investigate the solubility-permeability interplay when using hydrotropic drug solubilization. The concentration-dependent effects of the commonly used hydrotropes urea and nicotinamide, on the solubility and the permeability of the lipophilic antiepileptic drug carbamazepine were studied. Then, the solubility-permeability interplay was mathematically modeled, and was compared to the experimental data. Both hydrotropes allowed significant concentration-dependent carbamazepine solubility increase (up to ~30-fold. A concomitant permeability decrease was evident both in-vitro and in-vivo (~17-fold for nicotinamide and ~9-fold for urea, revealing a solubility-permeability tradeoff when using hydrotropic drug solubilization. A relatively simplified simulation approach based on proportional opposite correlation between the solubility increase and the permeability decrease at a given hydrotrope concentration allowed excellent prediction of the overall solubility-permeability tradeoff. In conclusion, when using hydrotropic drug solubilization it is prudent to not focus solely on solubility, but to account for the permeability as well; achieving optimal solubility-permeability balance may promote the overall goal of the formulation to maximize oral drug exposure.

  15. Octopus microvasculature: permeability to ferritin and carbon.

    Browning, J

    1979-01-01

    The permeability of Octopus microvasculature was investigated by intravascular injection of carbon and ferritin. Vessels were tight to carbon while ferritin penetrated the pericyte junction, and was found extravascularly 1-2 min after its introduction. Vesicles occurred rarely in pericytes; fenestrae were absent. The discontinuous endothelial layer did not consitute a permeability barrier. The basement membrane, although retarding the movement of ferritin, was permeable to it; carbon did not penetrate the basement membrane. Evidence indicated that ferritin, and thus similarly sized and smaller water soluble materials, traverse the pericyte junction as a result of bulk fluid flow. Comparisons are made with the convective (or junctional) and slower, diffusive (or vesicular) passage of materials known to occur across the endothelium of continuous capillaries in mammals. Previous macrophysiological determinations concerning the permeability of Octopus vessels are questioned in view of these findings. Possible reasons for some major structural differences in the microcirculatory systems of cephalopods and vertebrates are briefly discussed.

  16. Dentin Permeability of Carious Primary Teeth

    primary dental pulp make it difficult to determine which modality offers the best ... The most common pathology of the dentine is dental caries. ... to evaluate dentine permeability is to calculate its hydraulic conductance (Lp) using fluid filtration ...

  17. Permeability response of oil-contaminated compacted clays

    Silvestri, V.; Mikhail, N.; Soulie, M.

    1997-01-01

    This paper presents the results of a laboratory investigation on the behavior of motor oil-contaminated, partially saturated compacted clays. For the study, both a natural clay and an artificially purified kaolinite, contaminated with 0 to 8% of motor oil, were firstly compacted following the ASTM standard procedure. Secondly, permeability tests were carried out in a triaxial cell on 10 cm-diameter compacted clay specimens. The results of the investigation indicate that increasing percentages of motor oil decrease both the optimum water content and the optimum dry density of the two clays. However, whereas the optimum water content on the average decreases by about 6% when the percentage contamination increases from 0 to 8%, the corresponding decrease in the optimum dry density is less than 3%. Even though the optimum dry density decreases as the percentage of oil increases from 0 to 8%, there is, however, a range in oil content varying between 2 and 4% for which the optimum dry density is slightly greater than that of the untreated soils. As far as the permeability tests are concerned, the results indicate that as the percentage of oil increases, the coefficient of permeability decreases substantially, especially for clay specimens which were initially compacted on the dry side of optimum

  18. Permeability coefficient of proton irradiated polyethylene terephatalate thin films

    Bassani, L.C.; Santos, W.M.S.; Marechal, B.

    1983-01-01

    The principle of operation of an apparatus developed to study gas permation through thin films is described and the measurement method is discussed. Use is made of diffusion theory to obtain a expression for the permeability coefficient as a function of the rate of increase of the pressure in the receiving volume. The Gibbs function for permeation of Helium through Polyethylene Terephtalate (P.E.T.) is determined. The permeability coefficient of Helium is found to increase significantly with the range of the implanted protons although the incident charge has been kept constant. The hypothesis of structural modifications of the proton implanted P.E.T. seems to be confirmed by small angles X-rays scattering experiments on the irradiated samples. (Author) [pt

  19. MRP2 mediated drug-drug interaction: indomethacin increases sulfasalazine absorption in the small intestine, potentially decreasing its colonic targeting.

    Dahan, Arik; Amidon, Gordon L

    2010-02-15

    We have recently shown that efflux transport, mediated by multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP), is responsible for sulfasalazine low-permeability in the small intestine, thereby enabling its colonic targeting and therapeutic action. The purpose of the present study was to evaluate the potential pharmacokinetic interaction between indomethacin and sulfasalazine, in the mechanism of efflux transporter competition. The concentration-dependent effects of indomethacin on sulfasalazine intestinal epithelial transport were investigated across Caco-2 cell monolayers, in both apical to basolateral (AP-BL) and BL-AP directions. The interaction was then investigated in the in situ single-pass rat jejunal perfusion model. Sulfasalazine displayed 30-fold higher BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. Indomethacin significantly increased AP-BL and decreased BL-AP sulfasalazine Caco-2 transport, in a concentration-dependent manner, with IC(50) values of 75 and 196 microM respectively. In the rat model, higher sulfasalazine concentrations resulted in higher intestinal permeability, consistent with saturation of efflux transporter. Without indomethacin, sulfasalazine demonstrated low rat jejunal permeability (vs. metoprolol). Indomethacin significantly increased sulfasalazine P(eff), effectively shifting it from BCS (biopharmaceutics classification system) Class IV to II. In conclusion, the data indicate that concomitant intake of indomethacin and sulfasalazine may lead to increased absorption of sulfasalazine in the small intestine, thereby reducing its colonic concentration and potentially altering its therapeutic effect. Copyright 2009 Elsevier B.V. All rights reserved.

  20. Surface sedimentation at permeable pavement systems

    Støvring, Jan; Dam, Torben; Jensen, Marina Bergen

    2018-01-01

    Newly installed permeable pavement (PP) systems provide high surface infiltration capacity, but the accumulation of sediments causes a decrease in capacity over time, eventually leading to surface clogging. With the aim of investigating local sedimentation processes and the importance of restorat......Newly installed permeable pavement (PP) systems provide high surface infiltration capacity, but the accumulation of sediments causes a decrease in capacity over time, eventually leading to surface clogging. With the aim of investigating local sedimentation processes and the importance...