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Sample records for permeability surface cerebral

  1. EPA Permeable Surface Research

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  2. EPA Permeable Surface Research

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  3. Vascular permeability in cerebral cavernous malformations

    PubMed Central

    Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik BW; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A

    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 observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy. PMID:25966944

  4. Vascular permeability in cerebral cavernous malformations.

    PubMed

    Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik B W; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A

    2015-10-01

    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 observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy.

  5. EPA Permeable Surface Research - Poster

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  6. EPA Permeable Surface Research - Poster

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  7. Application of Blood-Brain Barrier Permeability Imaging in Global Cerebral Edema.

    PubMed

    Ivanidze, J; Kallas, O N; Gupta, A; Weidman, E; Baradaran, H; Mir, D; Giambrone, A; Segal, A Z; Claassen, J; Sanelli, P C

    2016-09-01

    Blood-brain barrier permeability is not routinely evaluated in the clinical setting. Global cerebral edema occurs after SAH and is associated with BBB disruption. Detection of global cerebral edema using current imaging techniques is challenging. Our purpose was to apply blood-brain barrier permeability imaging in patients with global cerebral edema by using extended CT perfusion. Patients with SAH underwent CTP in the early phase after aneurysmal rupture (days 0-3) and were classified as having global cerebral edema or nonglobal cerebral edema using established noncontrast CT criteria. CTP data were postprocessed into blood-brain barrier permeability quantitative maps of PS (permeability surface-area product), K(trans) (volume transfer constant from blood plasma to extravascular extracellular space), Kep (washout rate constant of the contrast agent from extravascular extracellular space to intravascular space), VE (extravascular extracellular space volume per unit of tissue volume), VP (plasmatic volume per unit of tissue volume), and F (plasma flow) by using Olea Sphere software. Mean values were compared using t tests. Twenty-two patients were included in the analysis. Kep (1.32 versus 1.52, P < .0001), K(trans) (0.15 versus 0.19, P < .0001), VP (0.51 versus 0.57, P = .0007), and F (1176 versus 1329, P = .0001) were decreased in global cerebral edema compared with nonglobal cerebral edema while VE (0.81 versus 0.39, P < .0001) was increased. Extended CTP was used to evaluate blood-brain barrier permeability in patients with SAH with and without global cerebral edema. Kep is an important indicator of altered blood-brain barrier permeability in patients with decreased blood flow, as Kep is flow-independent. Further study of blood-brain barrier permeability is needed to improve diagnosis and monitoring of global cerebral edema. © 2016 by American Journal of Neuroradiology.

  8. Permeability of disrupted cerebral microvessels in the frog.

    PubMed

    Fraser, P A; Dallas, A D

    1993-02-01

    1. This study reports the results of varying the hydrostatic pressure on measurements of permeability coefficient to the low molecular weight impermeant dye carboxyfluorescein (MW = 376) in single leaky cerebral microvessels. A mathematical model, that solved the convective diffusion equations used to analyse the measurements, showed that the measurements were consistent with leakiness being due to 22 nm wide parallel-sided slits between endothelial cells. 2. Microvessels on the surface of the frog's brain were cannulated with a micropipette and perfused with an artificial cerebrospinal fluid containing the dye. Vessels were occluded with a glass microneedle and the rate of change in dye concentration in a 12 microns length section was measured using video-intensified microscopy. 3. It was found that the rate of dye loss at all points along the occluded microvessel segment could be accounted for by a model for convection and diffusion, and that changes in dye concentration at a point remote from the segment entrance can give a good measure of diffusive permeability. 4. When series of measurements were carried out on a single vessel, permeability rose over the course of 20 min. Mean permeability for all measurements was 3.01 x 10(-5) cm sec-1, n = 64 (mode, 2.0; range, 0.48-9.6). The hydrostatic pressure applied during the perfusion had no effect on the measured permeability. 5. The dye concentration along the vessel axis was measured at the steady state and was shown to respond to changes in hydrostatic perfusion pressure in a way predicted by the model. This indicates that hydrostatically driven bulk flow can be important, and thus convection may account for effects previously ascribed to vesicular transcytosis. 6. The possible anatomical basis for the porous pathway is discussed in the light of recent observations on the presence of 0.5 microns perijunctional gaps, the possibility of transendothelial channels, and the unzipping of tight junctions to leave a 22 nm

  9. Positron emission tomographic measurement of cerebral blood flow and permeability-surface area product of water using (/sup 15/O)water and (/sup 11/C)butanol

    SciTech Connect

    Herscovitch, P.; Raichle, M.E.; Kilbourn, M.R.; Welch, M.J.

    1987-10-01

    We have previously adapted Kety's tissue autoradiographic method for measuring regional CBF in laboratory animals to the measurement of CBF in humans with positron emission tomography (PET) and H/sub 2/(/sup 15/)O. Because this model assumes diffusion equilibrium between tissue and venous blood, the use of a diffusion-limited tracer, such as H/sub 2/(/sup 15/)O, may lead to an underestimation of CBF. We therefore validated the use of (/sup 11/C)butanol as an alternative freely diffusible tracer for PET. We then used it in humans to determine the underestimation of CBF that occurs with H/sub 2/(/sup 15/)O, and thereby were able to calculate the extraction Ew and permeability-surface area product PSw of H/sub 2/(/sup 15/)O. Measurements of the permeability of rhesus monkey brain to (/sup 11/C)butanol, obtained by means of an intracarotid injection, external detection technique, demonstrated that this tracer is freely diffusible up to a CBF of at least 170 ml/min-100 g. CBF measured in baboons with the PET autoradiographic method and (/sup 11/C)butanol was then compared with CBF measured in the same animals with a standard residue detection method. An excellent correspondence was obtained between both of these measurements. Finally, paired PET measurements of CBF were made with both H/sub 2/(/sup 15/)O and (/sup 11/C)butanol in 17 normal human subjects. Average global CBF was significantly greater when measured with (/sup 11/C)butanol (53.1 ml/min-100 g) than with H/sub 2/(/sup 15/)O (44.4 ml/min-100 g). Average global Ew was 0.84 and global PSw was 104 ml/min-100 g. Regional measurements showed a linear relationship between local PSw and CBF, while Ew was relatively uniform throughout the brain. Simulations were used to determine the potential error associated with the use of an incorrect value for the brain-blood partition coefficient for (/sup 11/C)butanol and to calculate the effect of tissue heterogeneity and errors in flow measurement on the calculation of PSw.

  10. Semaphorin3A elevates vascular permeability and contributes to cerebral ischemia-induced brain damage

    PubMed Central

    Hou, Sheng Tao; Nilchi, Ladan; Li, Xuesheng; Gangaraju, Sandhya; Jiang, Susan X.; Aylsworth, Amy; Monette, Robert; Slinn, Jacqueline

    2015-01-01

    Semaphorin 3A (Sema3A) increased significantly in mouse brain following cerebral ischemia. However, the role of Sema3A in stroke brain remains unknown. Our aim was to determine wether Sema3A functions as a vascular permeability factor and contributes to ischemic brain damage. Recombinant Sema3A injected intradermally to mouse skin, or stereotactically into the cerebral cortex, caused dose- and time-dependent increases in vascular permeability, with a degree comparable to that caused by injection of a known vascular permeability factor vascular endothelial growth factor receptors (VEGF). Application of Sema3A to cultured endothelial cells caused disorganization of F-actin stress fibre bundles and increased endothelial monolayer permeability, confirming Sema3A as a permeability factor. Sema3A-mediated F-actin changes in endothelial cells were through binding to the neuropilin2/VEGFR1 receptor complex, which in turn directly activates Mical2, a F-actin modulator. Down-regulation of Mical2, using specific siRNA, alleviated Sema3A-induced F-actin disorganization, cellular morphology changes and endothelial permeability. Importantly, ablation of Sema3A expression, cerebrovascular permeability and brain damage were significantly reduced in response to transient middle cerebral artery occlusion (tMCAO) and in a mouse model of cerebral ischemia/haemorrhagic transformation. Together, these studies demonstrated that Sema3A is a key mediator of cerebrovascular permeability and contributes to brain damage caused by cerebral ischemia. PMID:25601765

  11. Semaphorin3A elevates vascular permeability and contributes to cerebral ischemia-induced brain damage.

    PubMed

    Hou, Sheng Tao; Nilchi, Ladan; Li, Xuesheng; Gangaraju, Sandhya; Jiang, Susan X; Aylsworth, Amy; Monette, Robert; Slinn, Jacqueline

    2015-01-20

    Semaphorin 3A (Sema3A) increased significantly in mouse brain following cerebral ischemia. However, the role of Sema3A in stroke brain remains unknown. Our aim was to determine wether Sema3A functions as a vascular permeability factor and contributes to ischemic brain damage. Recombinant Sema3A injected intradermally to mouse skin, or stereotactically into the cerebral cortex, caused dose- and time-dependent increases in vascular permeability, with a degree comparable to that caused by injection of a known vascular permeability factor vascular endothelial growth factor receptors (VEGF). Application of Sema3A to cultured endothelial cells caused disorganization of F-actin stress fibre bundles and increased endothelial monolayer permeability, confirming Sema3A as a permeability factor. Sema3A-mediated F-actin changes in endothelial cells were through binding to the neuropilin2/VEGFR1 receptor complex, which in turn directly activates Mical2, a F-actin modulator. Down-regulation of Mical2, using specific siRNA, alleviated Sema3A-induced F-actin disorganization, cellular morphology changes and endothelial permeability. Importantly, ablation of Sema3A expression, cerebrovascular permeability and brain damage were significantly reduced in response to transient middle cerebral artery occlusion (tMCAO) and in a mouse model of cerebral ischemia/haemorrhagic transformation. Together, these studies demonstrated that Sema3A is a key mediator of cerebrovascular permeability and contributes to brain damage caused by cerebral ischemia.

  12. Dispersion controlled by permeable surfaces: surface properties and scaling

    SciTech Connect

    Ling, Bowen; Tartakovsky, Alexandre M.; Battiato, Ilenia

    2016-07-19

    Permeable and porous surfaces are common in natural and engineered systems. Flow and transport above such surfaces are significantly affected by the surface properties, e.g. matrix porosity and permeability. However, the relationship between such properties and macroscopic solute transport is largely unknown. In this work, we focus on mass transport in a two-dimensional channel with permeable porous walls under fully developed laminar flow conditions. By means of perturbation theory and asymptotic analysis, we derive the set of upscaled equations describing mass transport in the coupled channel–porous-matrix system and an analytical expression relating the dispersion coefficient with the properties of the surface, namely porosity and permeability. Our analysis shows that their impact on the dispersion coefficient strongly depends on the magnitude of the Péclet number, i.e. on the interplay between diffusive and advective mass transport. Additionally, we demonstrate different scaling behaviours of the dispersion coefficient for thin or thick porous matrices. Our analysis shows the possibility of controlling the dispersion coefficient, i.e. transverse mixing, by either active (i.e. changing the operating conditions) or passive mechanisms (i.e. controlling matrix effective properties) for a given Péclet number. By elucidating the impact of matrix porosity and permeability on solute transport, our upscaled model lays the foundation for the improved understanding, control and design of microporous coatings with targeted macroscopic transport features.

  13. Increased blood-brain barrier permeability on perfusion CT might predict malignant middle cerebral artery infarction.

    PubMed

    Bektas, Hesna; Wu, Tzu-Ching; Kasam, Mallikarjunarao; Harun, Nusrat; Sitton, Clark W; Grotta, James C; Savitz, Sean I

    2010-11-01

    Perfusion CT has been used to assess the extent of blood-brain barrier breakdown. The purpose of this study was to determine the predictive value of blood-brain barrier permeability measured using perfusion CT for development of malignant middle cerebral artery infarction requiring hemicraniectomy (HC). We retrospectively identified patients from our stroke registry who had middle cerebral artery infarction and were evaluated with admission perfusion CT. Blood-brain barrier permeability and cerebral blood volume maps were generated and infarct volumes calculated. Clinical and radiographic characteristics were compared between those who underwent HC versus those who did not undergo HC. One hundred twenty-two patients (12 HC, 110 no HC) were identified. Twelve patients who underwent HC had developed edema, midline shift, or infarct expansion. Infarct permeability area, infarct cerebral blood volume area, and infarct volumes were significantly different (P < 0.018, P < 0.0211, P < 0.0001, P < 0.0014) between HC and no HC groups. Age (P = 0.03) and admission National Institutes of Health Stroke Scale (P = 0.0029) were found to be independent predictors for HC. Using logistic regression modeling, there was an association between increased infarct permeability area and HC. The OR for HC based on a 5-, 10-, 15-, or 20-cm² increase in infarct permeability area were 1.179, 1.390, 1.638, or 1.932, respectively (95% CI, 1.035 to 1.343, 1.071 to 1.804, 1.108 to 2.423, 1.146 to 3.255, respectively). Increased infarct permeability area is associated with an increased likelihood for undergoing HC. Because early HC for malignant middle cerebral artery infarction has been associated with better outcomes, the infarct permeability area on admission perfusion CT might be a useful tool to predict malignant middle cerebral artery infarction and need for HC.

  14. Vascular permeability and iron deposition biomarkers in longitudinal follow-up of cerebral cavernous malformations.

    PubMed

    Girard, Romuald; Fam, Maged D; Zeineddine, Hussein A; Tan, Huan; Mikati, Abdul Ghani; Shi, Changbin; Jesselson, Michael; Shenkar, Robert; Wu, Meijing; Cao, Ying; Hobson, Nicholas; Larsson, Henrik B W; Christoforidis, Gregory A; Awad, Issam A

    2016-08-05

    OBJECTIVE Vascular permeability and iron leakage are central features of cerebral cavernous malformation (CCM) pathogenesis. The authors aimed to correlate prospective clinical behavior of CCM lesions with longitudinal changes in biomarkers of dynamic contrast-enhanced quantitative permeability (DCEQP) and quantitative susceptibility mapping (QSM) assessed by MRI. METHODS Forty-six patients with CCMs underwent 2 or more permeability and/or susceptibility studies in conjunction with baseline and follow-up imaging and clinical surveillance during a mean 12.05 months of follow-up (range 2.4-31.27 months). Based on clinical and imaging features, cases/lesions were classified as stable, unstable, or recovering. Associated and predictive changes in quantitative permeability and susceptibility were investigated. RESULTS Lesional mean permeability and QSM values were not significantly different in stable versus unstable lesions at baseline. Mean lesional permeability in unstable CCMs with lesional bleeding or growth increased significantly (+85.9% change; p = 0.005), while mean permeability in stable and recovering lesions did not significantly change. Mean lesional QSM values significantly increased in unstable lesions (+44.1% change; p = 0.01), decreased slightly with statistical significance in stable lesions (-3.2% change; p = 0.003), and did not significantly change in recovering lesions. Familial cases developing new lesions during the follow-up period showed a higher background brain permeability at baseline (p = 0.001), as well as higher regional permeability (p = 0.003) in the area that would later develop a new lesion as compared with the homologous contralateral brain region. CONCLUSIONS In vivo assessment of vascular permeability and iron deposition on MRI can serve as objective and quantifiable biomarkers of disease activity in CCMs. This may be applied in natural history studies and may help calibrate clinical trials. The 2 techniques are likely applicable in

  15. Mapping permeability over the surface of the Earth

    USGS Publications Warehouse

    Gleeson, T.; Smith, L.; Moosdorf, N.; Hartmann, J.; Durr, H.H.; Manning, A.H.; Van Beek, L. P. H.; Jellinek, A. Mark

    2011-01-01

    Permeability, the ease of fluid flow through porous rocks and soils, is a fundamental but often poorly quantified component in the analysis of regional-scale water fluxes. Permeability is difficult to quantify because it varies over more than 13 orders of magnitude and is heterogeneous and dependent on flow direction. Indeed, at the regional scale, maps of permeability only exist for soil to depths of 1-2 m. Here we use an extensive compilation of results from hydrogeologic models to show that regional-scale (>5 km) permeability of consolidated and unconsolidated geologic units below soil horizons (hydrolithologies) can be characterized in a statistically meaningful way. The representative permeabilities of these hydrolithologies are used to map the distribution of near-surface (on the order of 100 m depth) permeability globally and over North America. The distribution of each hydrolithology is generally scale independent. The near-surface mean permeability is of the order of ???5 ?? 10-14 m2. The results provide the first global picture of near-surface permeability and will be of particular value for evaluating global water resources and modeling the influence of climate-surface-subsurface interactions on global climate change. Copyright ?? 2011 by the American Geophysical Union.

  16. Mapping permeability over the surface of the Earth

    USGS Publications Warehouse

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

    2011-01-01

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

  17. Application of Blood-Brain Barrier Permeability Imaging in Global Cerebral Edema

    PubMed Central

    Ivanidze, Jana; Kallas, Omar N.; Gupta, Ajay; Weidman, Elizabeth; Baradaran, Hediyeh; Mir, Danial; Giambrone, Ashley; Segal, Alan Z.; Claassen, Jan; Sanelli, Pina C.

    2016-01-01

    Background and Purpose Blood brain barrier permeability (BBBP) is not presently routinely evaluated in the clinical setting. Global cerebral edema (GCE) occurs after SAH and is associated with BBB disruption. Detection of GCE is challenging using current imaging techniques. Our purpose was to apply BBBP imaging in patients with GCE using extended pass CT Perfusion (CTP). Methods SAH patients underwent CTP in the early phase after aneurysmal rupture (days 0-3) and were classified as GCE or non-GCE using established non-contrast CT criteria. CTP were post-processed into BBBP quantitative maps of PS (permeability surface area product), K-trans (volume transfer constant from blood plasma to extravascular extracellular space, EES), Kep (washout rate constant of the contrast agent from EES to intravascular space), VE (EES volume per unit of tissue volume), VP (plasmatic volume per unit of tissue volume) and F (plasma flow) using Olea Sphere software. Mean values were compared using t-tests. Results 22 patients were included in the analysis. Kep (1.32 versus 1.52, p < 0.0001), K-trans (0.15 versus 0.19, p < 0.0001), VP (0.51 versus 0.57, p = 0.0007) and F (1176 versus 1329, p = 0.0001) were decreased in GCE compared to non-GCE while VE (0.81 versus 0.39, p < 0.0001) was increased. Conclusion Extended CTP was utilized to evaluate BBBP in SAH patients with and without GCE. Kep is an important indicator of altered BBBP in patients with decreased blood flow, as Kep is flow-independent. Further study of BBBP is needed to improve diagnosis and monitoring of GCE. PMID:27127002

  18. Assessing the potential for restoration of surface permeability for permeable pavements through maintenance.

    PubMed

    Drake, Jennifer; Bradford, Andrea

    2013-01-01

    Permeable pavements (PPs) have been in use as stormwater management systems in Canada and the United States for over 20 years. After years of exposure to sediment and debris build-up, surface clogging reduces the infiltration of stormwater and inhibits the hydraulic and environmental functions of the pavement. Removal of surface material has been shown to restore infiltration but the majority of studies have been limited to small-scale testing. This paper presents the results of small- and full-sized equipment testing aimed at restoring surface permeability, including the first testing of regenerative-air and vacuum-sweeping streetsweepers in Ontario. Maintenance achieved partial restoration of PP surface permeability. Post-treatment surface infiltration rates displayed large spatial variability, highlighting that localized conditions throughout the pavement have a confounding influence on the overall effectiveness of maintenance. The impact of maintenance may be improved by establishing regular cleaning intervals and developing instructional guidelines for pavement owners and equipment operators.

  19. The effect of ASK1 on vascular permeability and edema formation in cerebral ischemia.

    PubMed

    Song, Juhyun; Cheon, So Yeong; Lee, Won Taek; Park, Kyung Ah; Lee, Jong Eun

    2015-01-21

    Apoptosis signal-regulating kinase-1 (ASK1) is the mitogen-activated protein kinase kinase kinase (MAPKKK) and participates in the various central nervous system (CNS) signaling pathways. In cerebral ischemia, vascular permeability in the brain is an important issue because regulation failure of it results in edema formation and blood-brain barrier (BBB) disruption. To determine the role of ASK1 on vascular permeability and edema formation following cerebral ischemia, we first investigated ASK1-related gene expression using microarray analyses of ischemic brain tissue. We then measured protein levels of ASK1 and vascular endothelial growth factor (VEGF) in brain endothelial cells after hypoxia injury. We also examined protein expression of ASK1 and VEGF, edema formation, and morphological alteration through cresyl violet staining in ischemic brain tissue using ASK1-small interference RNA (ASK1-siRNA). Finally, immunohistochemistry was performed to examine VEGF and aquaporin-1 (AQP-1) expression in ischemic brain injury. Based on our findings, we propose that ASK1 is a regulating factor of vascular permeability and edema formation in cerebral ischemia.

  20. Host defenses to Rickettsia rickettsii infection contribute to increased microvascular permeability in human cerebral endothelial cells.

    PubMed

    Woods, Michael E; Olano, Juan P

    2008-03-01

    Rickettsiae are arthropod-borne intracellular bacterial pathogens that primarily infect the microvascular endothelium leading to systemic spread of the organisms and the major pathophysiological effect, increased microvascular permeability, and edema in vital organs such as the lung and brain. Much work has been done on mechanisms of immunity to rickettsiae, as well as the responses of endothelial cells to rickettsial invasion. However, to date, no one has described the mechanisms of increased microvascular permeability during acute rickettsiosis. We sought to establish an in vitro model of human endothelial-target rickettsial infection using the etiological agent of Rocky Mountain spotted fever, Rickettsia rickettsii, and human cerebral microvascular endothelial cells. Endothelial cells infected with R. rickettsii exhibited a dose-dependent decrease in trans-endothelial electrical resistance, which translates into increased monolayer permeability. Additionally, we showed that the addition of pro-inflammatory stimuli essential to rickettsial immunity dramatically enhanced this effect. This increase in permeability correlates with dissociation of adherens junctions between endothelial cells and is not dependent on the presence of nitric oxide. Taken together, these results demonstrate for the first time that increased microvascular permeability associated with rickettsial infection is partly attributable to intracellular rickettsiae and partly attributable to the immune defenses that have evolved to protect the host from rickettsial spread.

  1. MEAUSREMENT OF THE SURFACE PERMEABILITY OF BASEMENT CONCRETES

    EPA Science Inventory

    The report discusses the development, testing, and use of a portable surface permeameter suitable for field use in measuring the surface permeability of concrete in new houses. he permeameter measures the airflow induced by a pressure difference across a temporary test seal appli...

  2. MEAUSREMENT OF THE SURFACE PERMEABILITY OF BASEMENT CONCRETES

    EPA Science Inventory

    The report discusses the development, testing, and use of a portable surface permeameter suitable for field use in measuring the surface permeability of concrete in new houses. he permeameter measures the airflow induced by a pressure difference across a temporary test seal appli...

  3. Effect of surface preparation on gas permeability of wood

    Treesearch

    E.T. Choong; C.W. McMillin; F.O. Tesoro

    1975-01-01

    Surface preparation has a profound effect on the rate of flow of fluid through wood, particularly in the longitudinal direction of flow. For best results, the surface must be devoid of any debris and/or obstruction. The use of a sharp, thin knife appears to be an effective way of preparing samples for natural permeability measurements.

  4. Evaluating blood-brain barrier permeability in delayed cerebral infarction after aneurysmal subarachnoid hemorrhage.

    PubMed

    Ivanidze, J; Kesavabhotla, K; Kallas, O N; Mir, D; Baradaran, H; Gupta, A; Segal, A Z; Claassen, J; Sanelli, P C

    2015-05-01

    Patients with SAH are at increased risk of delayed infarction. Early detection and treatment of delayed infarction remain challenging. We assessed blood-brain barrier permeability, measured as permeability surface area product, by using CTP in patients with SAH with delayed infarction. We performed a retrospective study of patients with SAH with delayed infarction on follow-up NCCT. CTP was performed before the development of delayed infarction. CTP data were postprocessed into permeability surface area product, CBF, and MTT maps. Coregistration was performed to align the infarcted region on the follow-up NCCT with the corresponding location on the CTP maps obtained before infarction. Permeability surface area product, CBF, and MTT values were then obtained in the location of the subsequent infarction. The contralateral noninfarcted region was compared with the affected side in each patient. Wilcoxon signed rank tests were performed to determine statistical significance. Clinical data were collected at the time of CTP and at the time of follow-up NCCT. Twenty-one patients with SAH were included in the study. There was a statistically significant increase in permeability surface area product in the regions of subsequent infarction compared with the contralateral control regions (P < .0001). However, CBF and MTT values were not significantly different in these 2 regions. Subsequent follow-up NCCT demonstrated new delayed infarction in all 21 patients, at which time 38% of patients had new focal neurologic deficits. Our study reveals a statistically significant increase in permeability surface area product preceding delayed infarction in patients with SAH. Further investigation of early permeability changes in SAH may provide new insights into the prediction of delayed infarction. © 2015 by American Journal of Neuroradiology.

  5. Real-time estimation of paracellular permeability of cerebral endothelial cells by capacitance sensor array

    PubMed Central

    Hyun Jo, Dong; Lee, Rimi; Hyoung Kim, Jin; Oh Jun, Hyoung; Geol Lee, Tae; Hun Kim, Jeong

    2015-01-01

    Vascular integrity is important in maintaining homeostasis of brain microenvironments. In various brain diseases including Alzheimer’s disease, stroke, and multiple sclerosis, increased paracellular permeability due to breakdown of blood-brain barrier is linked with initiation and progression of pathological conditions. We developed a capacitance sensor array to monitor dielectric responses of cerebral endothelial cell monolayer, which could be utilized to evaluate the integrity of brain microvasculature. Our system measured real-time capacitance values which demonstrated frequency- and time-dependent variations. With the measurement of capacitance at the frequency of 100 Hz, we could differentiate the effects of vascular endothelial growth factor (VEGF), a representative permeability-inducing factor, on endothelial cells and quantitatively analyse the normalized values. Interestingly, we showed differential capacitance values according to the status of endothelial cell monolayer, confluent or sparse, evidencing that the integrity of monolayer was associated with capacitance values. Another notable feature was that we could evaluate the expression of molecules in samples in our system with the reference of real-time capacitance values. We suggest that this dielectric spectroscopy system could be successfully implanted as a novel in vitro assay in the investigation of the roles of paracellular permeability in various brain diseases. PMID:26047027

  6. Real-time estimation of paracellular permeability of cerebral endothelial cells by capacitance sensor array

    NASA Astrophysics Data System (ADS)

    Hyun Jo, Dong; Lee, Rimi; Hyoung Kim, Jin; Oh Jun, Hyoung; Geol Lee, Tae; Hun Kim, Jeong

    2015-06-01

    Vascular integrity is important in maintaining homeostasis of brain microenvironments. In various brain diseases including Alzheimer’s disease, stroke, and multiple sclerosis, increased paracellular permeability due to breakdown of blood-brain barrier is linked with initiation and progression of pathological conditions. We developed a capacitance sensor array to monitor dielectric responses of cerebral endothelial cell monolayer, which could be utilized to evaluate the integrity of brain microvasculature. Our system measured real-time capacitance values which demonstrated frequency- and time-dependent variations. With the measurement of capacitance at the frequency of 100 Hz, we could differentiate the effects of vascular endothelial growth factor (VEGF), a representative permeability-inducing factor, on endothelial cells and quantitatively analyse the normalized values. Interestingly, we showed differential capacitance values according to the status of endothelial cell monolayer, confluent or sparse, evidencing that the integrity of monolayer was associated with capacitance values. Another notable feature was that we could evaluate the expression of molecules in samples in our system with the reference of real-time capacitance values. We suggest that this dielectric spectroscopy system could be successfully implanted as a novel in vitro assay in the investigation of the roles of paracellular permeability in various brain diseases.

  7. Liquid Spills on Permeable Soil Surfaces: Experimental Confirmations

    SciTech Connect

    Simmons, Carver S.; Keller, Jason M.

    2005-09-29

    Predictive tools for assessing the quantity of a spill on a soil from the observed spreading area could contribute to improving remediation when it is necessary. On a permeable soil, the visible spill area only hints about the amount of liquid that might reside below the surface. An understanding of the physical phenomena involved with spill propagation on a soil surface is key to assessing the liquid amount possibly present beneath the surface. The objective of this study is an improved prediction capability for spill behavior.

  8. TNFα alters occludin and cerebral endothelial permeability: Role of p38MAPK

    PubMed Central

    Ni, Yawen; Teng, Tao; Li, Runting; Simonyi, Agnes; Sun, Grace Y.; Lee, James C.

    2017-01-01

    Occludin is a key tight junction (TJ) protein in cerebral endothelial cells (CECs) playing an important role in modulating blood-brain barrier (BBB) functions. This protein (65kDa) has been shown to engage in many signaling pathways and phosphorylation by both tyrosine and threonine kinases. Despite yet unknown mechanisms, pro-inflammatory cytokines and endotoxin (lipopolysaccharides, LPS) may alter TJ proteins in CECs and BBB functions. Here we demonstrate the responses of occludin in an immortalized human cerebral endothelial cell line (hCMEC/D3) to stimulation by TNFα (10 ng/mL), IL-1β (10 ng/mL) and LPS (100 ng/mL). Exposing cells to TNFα resulted in a rapid and transient upward band-shift of occludin, suggesting of an increase in phosphorylation. Exposure to IL-1β produced significantly smaller effects and LPS produced almost no effects on occludin band-shift. TNFα also caused transient stimulation of p38MAPK and ERK1/2 in hCMEC/D3 cells, and the occludin band-shift induced by TNFα was suppressed by SB202190, an inhibitor for p38MAPK, and partly by U0126, the MEK1/2-ERK1/2 inhibitor. Cells treated with TNFα and IL-1β but not LPS for 24 h resulted in a significant (p < 0.001) decrease in the expression of occludin, and the decrease could be partially blocked by SB202190, the inhibitor for p38MAPK. Treatment with TNFα also altered cell morphology and enhanced permeability of the CEC layer as measured by the FITC-dextran assay and the trans-endothelial electrical resistances (TEER). However, treatment with SB202190 alone could not effectively reverse the TNFα -induced morphology changes or the enhanced permeability changes. These results suggest that despite effects of TNFα on p38MAPK-mediated occludin phosphorylation and expression, these changes are not sufficient to avert the TNFα-induced alterations on cell morphology and permeability. PMID:28170408

  9. Multiscale modeling of bone tissue with surface and permeability control.

    PubMed

    Gonçalves Coelho, Pedro; Rui Fernandes, Paulo; Carriço Rodrigues, Helder

    2011-01-11

    Natural biological materials usually present a hierarchical arrangement with various structural levels. The biomechanical behavior of the complex hierarchical structure of bone is investigated with models that address the various levels corresponding to different scales. Models that simulate the bone remodeling process concurrently at different scales are in development. We present a multiscale model for bone tissue adaptation that considers the two top levels, whole bone and trabecular architecture. The bone density distribution is calculated at the macroscale (whole bone) level, and the trabecular structure at the microscale level takes into account its mechanical properties as well as surface density and permeability. The bone remodeling process is thus formulated as a material distribution problem at both scales. At the local level, the biologically driven information of surface density and permeability characterizes the trabecular structure. The model is tested by a three-dimensional simulation of bone tissue adaptation for the human femur. The density distribution of the model shows good agreement with the actual bone density distribution. Permeability at the microstructural level assures interconnectivity of pores, which mimics the interconnectivity of trabecular bone essential for vascularization and transport of nutrients. The importance of this multiscale model relays on the flexibility to control the morphometric parameters that characterize the trabecular structure. Therefore, the presented model can be a valuable tool to define bone quality, to assist with diagnosis of osteoporosis, and to support the development of bone substitutes.

  10. Permeability of Luminal Surface of Intestinal Mucosal Cells

    PubMed Central

    Lindemann, B.; Solomon, A. K.

    1962-01-01

    A method has been devised to measure the permeability characteristics of the intestinal mucosal cells in the rat. The method makes use of an electrical recording balance to register changes in weight when the mucosal face of a small strip of intestine is exposed to anisotonic solutions. The permeability coefficient of the luminal surface of intestinal mucosal cells to water is measured as 0.15 cm4/OSM, sec. and reasons are adduced to suggest that the true value might be higher than this. The equivalent pore radius of the luminal face of the tissue, measured in experiments in which lipid-insoluble non-electrolytes have been used according to the method of Goldstein and Solomon, appears to be 4.0 Å. PMID:14465429

  11. Placental ischemia in pregnant rats impairs cerebral blood flow autoregulation and increases blood–brain barrier permeability

    PubMed Central

    Warrington, Junie P.; Fan, Fan; Murphy, Sydney R.; Roman, Richard J.; Drummond, Heather A.; Granger, Joey P.; Ryan, Michael J.

    2014-01-01

    Abstract Cerebrovascular events contribute to ~40% of preeclampsia/eclampsia‐related deaths, and neurological symptoms are common among preeclamptic patients. We previously reported that placental ischemia, induced by reducing utero‐placental perfusion pressure, leads to impaired myogenic reactivity and cerebral edema in the pregnant rat. Whether the impaired myogenic reactivity is associated with altered cerebral blood flow (CBF) autoregulation and the edema is due to altered blood–brain barrier (BBB) permeability remains unclear. Therefore, we tested the hypothesis that placental ischemia leads to impaired CBF autoregulation and a disruption of the BBB. CBF autoregulation, measured in vivo by laser Doppler flowmetry, was significantly impaired in placental ischemic rats. Brain water content was increased in the anterior cerebrum of placental ischemic rats and BBB permeability, assayed using the Evans blue extravasation method, was increased in the anterior cerebrum. The expression of the tight junction proteins: claudin‐1 was increased in the posterior cerebrum, while zonula occludens‐1, and occludin, were not significantly altered in either the anterior or posterior cerebrum. These results are consistent with the hypothesis that placental ischemia mediates anterior cerebral edema through impaired CBF autoregulation and associated increased transmission of pressure to small vessels that increases BBB permeability leading to cerebral edema. PMID:25168877

  12. Perfusion computed tomography of intracranial meningiomas: In vivo correlation of cerebral blood volume and vascular permeability.

    PubMed

    Granata, Francesca; Morabito, Rosa; Alafaci, Concetta; Barresi, Valeria; Tomasello, Francesco; Vinci, Sergio; Mormina, Enricomaria; Calamuneri, Alessandro; Grasso, Giovanni; Salpietro, Francesco Maria; Longo, Marcello

    2015-06-01

    A noninvasive method to predict the grade of a meningioma would be desirable since it would anticipate information about tumour nature, recurrence and improve tumour management and outcomes. The aim of the present study was to assess the ability of perfusion computed tomography (PCT) technique in predicting the meningioma grade before surgery. Data from PCT, such as cerebral blood volume (CBV) and permeability surface (PS), were correlated with immunohistolopathological information. Twenty-three patients with a diagnosis of intracranial meningioma underwent PCT for pre-surgical evaluation of CBV and PS. During surgery, samples from the centre and periphery of the tumour were obtained. Two correspondent regions of interest (ROIs) were drawn on CBV and PS maps. Central and peripheral CBV and PS mean values were calculated. PCT parameters were correlated to CD-34 and endoglin. There was a positive correlation between PS and CD-34. No correlation was found between PS values and endoglin, CBV values and CD-34 and endoglin values. Our findings suggest that PCT may support conventional morphological imaging in predicting meningioma grading before surgery. © The Author(s) 2015.

  13. Permeable Surface Corrections for Ffowcs Williams and Hawkings Integrals

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Casper, Jay H.

    2005-01-01

    The acoustic prediction methodology discussed herein applies an acoustic analogy to calculate the sound generated by sources in an aerodynamic simulation. Sound is propagated from the computed flow field by integrating the Ffowcs Williams and Hawkings equation on a suitable control surface. Previous research suggests that, for some applications, the integration surface must be placed away from the solid surface to incorporate source contributions from within the flow volume. As such, the fluid mechanisms in the input flow field that contribute to the far-field noise are accounted for by their mathematical projection as a distribution of source terms on a permeable surface. The passage of nonacoustic disturbances through such an integration surface can result in significant error in an acoustic calculation. A correction for the error is derived in the frequency domain using a frozen gust assumption. The correction is found to work reasonably well in several test cases where the error is a small fraction of the actual radiated noise. However, satisfactory agreement has not been obtained between noise predictions using the solution from a three-dimensional, detached-eddy simulation of flow over a cylinder.

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

    PubMed

    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.

  15. ANKS1B Interacts with the Cerebral Cavernous Malformation Protein-1 and Controls Endothelial Permeability but Not Sprouting Angiogenesis

    PubMed Central

    Moll, Iris; Yang, Wan-Jen; Wüstehube-Lausch, Joycelyn; Fischer, Andreas

    2015-01-01

    Cerebral cavernous malformations are fragile blood vessel conglomerates in the central nervous system that are caused by mutations in the CCM1/KRIT1, CCM2 or CCM3 genes. The gene products form a protein complex at adherens junctions and loss of either CCM protein disrupts endothelial cell quiescence leading to increased permeability and excessive angiogenesis. We performed a yeast 2-hybrid screen to identify novel proteins directly interacting with KRIT1. The ankyrin repeat and sterile alpha motif domain-containing protein 1B (ANKS1B) was identified as a novel binding partner of KRIT1. Silencing of ANKS1B or the related gene ANKS1A in primary human endothelial cells had no significant effects on cellular proliferation, migration and sprouting angiogenesis. However, silencing of ANKS1B expression disturbed endothelial cell barrier functions leading to increased permeability. Forced ANKS1B expression reduced permeability. This was independent of Rho kinase activity and the presence of KRIT1. Taken together, ANKS1B was identified as a novel KRIT1-interacting protein that selectively controls endothelial permeability but not angiogenesis. PMID:26698571

  16. Anatomical characteristics of the cerebral surface in bulimia nervosa.

    PubMed

    Marsh, Rachel; Stefan, Mihaela; Bansal, Ravi; Hao, Xuejun; Walsh, B Timothy; Peterson, Bradley S

    2015-04-01

    The aim of this study was to examine morphometric features of the cerebral surface in adolescent and adult female subjects with bulimia nervosa (BN). Anatomical magnetic resonance images were acquired from 34 adolescent and adult female subjects with BN and 34 healthy age-matched control subjects. We compared the groups in the morphological characteristics of their cerebral surfaces while controlling for age and illness duration. Significant reductions of local volumes on the brain surface were detected in frontal and temporoparietal areas in the BN compared with control participants. Reductions in inferior frontal regions correlated inversely with symptom severity, age, and Stroop interference scores in the BN group. These findings suggest that local volumes of inferior frontal regions are smaller in individuals with BN compared with healthy individuals. These reductions along the cerebral surface might contribute to functional deficits in self-regulation and to the persistence of these deficits over development in BN. © 2014 Society of Biological Psychiatry.

  17. Evaluation of permeable pavement responses to urban surface runoff.

    PubMed

    Kamali, Meysam; Delkash, Madjid; Tajrishy, Massoud

    2017-02-01

    The construction of permeable pavement (PP) in sidewalks of urban areas is an alternative low impact development (LID) to control stormwater runoff volume and consequently decrease the discharge of pollutants in receiving water bodies. In this paper, some laboratory experiments were performed to evaluate the efficiency of a PP subjected to sediment loadings during its life span. Simple infiltration models were validated by the laboratory experiments to evaluate the trend and extend of PP infiltration capacity throughout the life of the pavement operation. In addition, performances of the PP in removing total suspended solids (TSS) and selective nutrient pollutants such as NO3(-),NH4(+) and PO4(-3) from the surface runoff have been investigated. Experimental data showed that the PP was completely clogged after seven hydrological years. The model revealed that the ratio of horizontal to vertical hydraulic conductivity is 3.5 for this PP. Moreover, it was found that 20% reduction in hydraulic conductivity occurred after three hydrological years. The PP showed 100%, 23% and 59% efficiencies in sediment retention (TSS removal), (PO4(-3)), and N-NH4(+) removal during the entire study, respectively. However, the removal efficiency of (N-NO3(-)) was -12% and we suspect the increase in effluent (N-NO3(-)) is due to the nitrification process in subsurface layers. This study demonstrated that when PPs are annually cleaned, it is expected that PPs can function hydraulically and be able to remove particulate pollutants during their life span by a proper maintenance. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Fractal dimension of cerebral surfaces using magnetic resonance images

    SciTech Connect

    Majumdar, S.; Prasad, R.R.

    1988-11-01

    The calculation of the fractal dimension of the surface bounded by the grey matter in the normal human brain using axial, sagittal, and coronal cross-sectional magnetic resonance (MR) images is presented. The fractal dimension in this case is a measure of the convolutedness of this cerebral surface. It is proposed that the fractal dimension, a feature that may be extracted from MR images, may potentially be used for image analysis, quantitative tissue characterization, and as a feature to monitor and identify cerebral abnormalities and developmental changes.

  19. Dynamical instability in surface permeability characteristics of building sandstones in response to salt accumulation over time

    NASA Astrophysics Data System (ADS)

    McCabe, S.; McKinley, J. M.; Gomez-Heras, M.; Smith, B. J.

    2011-07-01

    This paper explores how the surface permeability of sandstone blocks changes over time in response to repeated salt weathering cycles. Surface permeability controls the amount of moisture and dissolved salt that can penetrate in and facilitate decay. Connected pores permit the movement of moisture (and hence soluble salts) into the stone interior, and where areas are more or less permeable soluble salts may migrate along preferred pathways at differential rates. Previous research has shown that salts can accumulate in the near-surface zone and lead to partial pore blocking which influences subsequent moisture ingress and causes rapid salt accumulation in the near-surface zone. Two parallel salt weathering simulations were carried out on blocks of Peakmoor Sandstone of different volumes. Blocks were removed from simulations after 2, 5, 10, 20 and 60 cycles. Permeability measurements were taken for these blocks at a resolution of 20 mm, providing a grid of 100 permeability values for each surface. The geostatistical technique of ordinary kriging was applied to the data to produce a smoothed interpolation of permeability for these surfaces, and hence improve understanding of the evolution of permeability over time in response to repeated salt weathering cycles. Results illustrate the different responses of the sandstone blocks of different volumes to repeated salt weathering cycles. In both cases, after an initial subtle decline in the permeability (reflecting pore blocking), the permeability starts to increase — reflected in a rise in mean, maximum and minimum values. However, between 10 and 20 cycles, there is a jump in the mean and range permeability of the group A block surfaces coinciding with the onset of meaningful debris release. After 60 cycles, the range of permeability in the group A block surface had increased markedly, suggesting the development of a secondary permeability. The concept of dynamic instability and divergent behaviour is applied at the

  20. A connection between the mitochondrial permeability transition pore, autophagy, and cerebral amyloidogenesis.

    PubMed

    Soskić, Vukić; Klemm, Martina; Proikas-Cezanne, Tassula; Schwall, Gerhard P; Poznanović, Slobodan; Stegmann, Werner; Groebe, Karlfried; Zengerling, Helmut; Schoepf, Rainer; Burnet, Michael; Schrattenholz, André

    2008-06-01

    In a drug reprofiling attempt, we explored novel neuroprotective properties of 4-azasteroids by synthesizing chemical affinity tags capturing adenine nucleotide translocator-1, as a potential target. Dutasteride inhibits the mitochondrial transition pore and induces an increase of autophagosomal structures in human cell lines. In vivo, a surprising reduction of the beta-amyloid plaque load in a model for cerebral amyloidosis appears to connect release of neurotoxic peptides, mitochondrial apoptosis and autophagy.

  1. Surface potential and permeability of rock cores under asphaltenic oil flow conditions

    SciTech Connect

    Alkafeef, S.F.; Gochin, R.J.; Smith, A.L.

    1995-12-31

    The surface properties, wetting behaviour and permeability of rock samples are central to understanding recovery behaviour in oil reservoirs. This paper will present a method new to petroleum engineering to show how area/length ratios for porous systems can be obtained by combining streaming potential and streaming current measurements on rock cores. This has allows streaming current measurements (independent of surface conductivity errors) to be made on rock samples using hydrocarbon solvents with increasing concentrations of asphaltene. Negative surface potentials for the rock became steadily more positive as asphaltene coated the pore surfaces, with permeability reduction agreeing well with petrographic analysis.

  2. Effects of skin surface temperature on epidermal permeability barrier homeostasis.

    PubMed

    Denda, Mitsuhiro; Sokabe, Takaaki; Fukumi-Tominaga, Tomoko; Tominaga, Makoto

    2007-03-01

    Members of the transient receptor potential (TRP) family are temperature sensors, and TRPV1, V3, and V4 are expressed in epidermal keratinocytes. To evaluate the influence of these receptors on epidermal permeability barrier homeostasis, we kept both hairless mouse skin and human skin at various temperatures immediately after tape stripping. At temperatures from 36 to 40 degrees C, barrier recovery was accelerated in both cases compared with the area at 34 degrees C. At 34 or 42 degrees C, barrier recovery was delayed compared with the un-occluded area. 4Alpha-phorbol 12,13-didecanone, an activator of TRPV4, accelerated barrier recovery, whereas ruthenium red, a blocker of TRPV4, delayed barrier recovery. Capsaicin, an activator of TRPV1, delayed barrier recovery, whereas capsazepin, an antagonist of TRPV1, blocked this delay. 2-Aminoethoxydiphenyl borate and camphor, TRPV3 activators, did not affect the barrier recovery rate. As TRPV4 is activated at about 35 degrees C and above, whereas TRPV1 is activated at about 42 degrees C and above, these results suggest that both TRPV1 and TRPV4 play important roles in skin permeability barrier homeostasis. Previous reports suggest the existence of a water flux sensor in the epidermis, and as TRPV4 is known to be activated by osmotic pressure, our results indicate that it might be this sensor.

  3. Influence of multi-wavelength laser irradiation of enamel and dentin surfaces on surface morphology and permeability

    NASA Astrophysics Data System (ADS)

    Chang, Nai-Yuan N.; Jew, Jamison; Simon, Jacob C.; Chan, Kenneth H.; Lee, Robert C.; Fried, William A.; Cho, Jinny; Darling, Cynthia L.; Fried, Daniel

    2017-02-01

    UV and IR lasers can be used to specifically target protein, water, and the mineral phase of dental hard tissues to produce varying changes in surface morphology. In this study, we irradiated enamel and dentin surfaces with various combinations of lasers operating at 0.355, 2.94, and 9.4 μm, exposed those surfaces to topical fluoride, and subsequently evaluated the influence of these changes on surface morphology and permeability. Digital microscopy and surface dehydration rate measurements were used to monitor changes in the samples overtime. The surface morphology and permeability (dehydration rate) varied markedly with the different laser treatments on enamel. On dentin, fluoride was most effective in reducing the permeability.

  4. Cerebral cavernous malformations as a disease of vascular permeability: from bench to bedside with caution.

    PubMed

    Yadla, Sanjay; Jabbour, Pascal M; Shenkar, Robert; Shi, Changbin; Campbell, Peter G; Awad, Issam A

    2010-09-01

    Tremendous insight into the molecular and genetic pathogenesis of cerebral cavernous malformations (CCMs) has been gained over the past 2 decades. This includes the identification of 3 distinct genes involved in familial CCMs. Still, a number of unanswered questions regarding the process from gene mutation to vascular malformation remain. It is becoming more evident that the disruption of interendothelial junctions and ensuing vascular hyperpermeability play a principal role. The purpose of this review is to summarize the current understanding of CCM genes, associated proteins, and functional pathways. Promising molecular and genetic therapies targeted at identified molecular aberrations are discussed as well.

  5. On the hydrodynamic interaction between a particle and a permeable surface

    NASA Astrophysics Data System (ADS)

    Ramon, Guy Z.; Huppert, Herbert E.; Lister, John R.; Stone, Howard A.

    2013-07-01

    The motion and deposition of a particle translating perpendicular to a rigid, permeable surface is considered. The lubrication approximation is used to derive an equation for the pressure in the gap between the particle and the permeable surface, with a symmetric shape prescribed for the particle. The hydrodynamic force on a particle is, in general, a function of the particle size and shape, the distance from the surface and the surface permeability, and its sign depends on the relative motion of the particle and the background fluid permeating through the surface. As the particle becomes flatter, this force generally increases and is more sensitive to the surface permeability. In the case of a spherical particle, closed-form, approximate solutions are obtained using perturbation methods, in the limits of small permeability and close approach to contact. It is also shown that a sedimenting particle attains a finite velocity on close approach, which scales as k1/2 and k for a sphere and a disc, respectively, where k is the permeability per unit thickness of the surface. In the case of a particle advected toward the surface, as is common in membrane filtration, a balance of electrostatic repulsion and viscous drag is used to calculate a possible equilibrium position of the particle, at some finite distance from the surface. The dependence of the equilibrium and its stability is shown in terms of the ratio of electrostatic and lubrication forces at contact, as well as the ratio of characteristic lengths over which the two forces decay away from the boundary. The latter is found to be a significant factor in determining the conditions under which a stable equilibrium exists. These results are useful for estimating deposition propensity in membrane filtration processes, as affected by operational conditions.

  6. Permeability Parameters Measured with Dynamic Contrast-Enhanced MRI: Correlation with the Extravasation of Evans Blue in a Rat Model of Transient Cerebral Ischemia.

    PubMed

    Choi, Hyun Seok; Ahn, Sung Soo; Shin, Na-Young; Kim, Jinna; Kim, Jae Hyung; Lee, Jong Eun; Lee, Hye Yeon; Heo, Ji Hoe; Lee, Seung-Koo

    2015-01-01

    The purpose of this study was to correlate permeability parameters measured with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a clinical 3-tesla scanner with extravasation of Evans blue in a rat model with transient cerebral ischemia. Sprague-Dawley rats (n = 13) with transient middle cerebral artery occlusion were imaged using a 3-tesla MRI with an 8-channel wrist coil. DCE-MRI was performed 12 hours, 18 hours, and 36 hours after reperfusion. Permeability parameters (K(trans), ve, and vp) from DCE-MRI were calculated. Evans blue was injected after DCE-MRI and extravasation of Evans blue was correlated as a reference with the integrity of the blood-brain barrier. Correlation analysis was performed between permeability parameters and the extravasation of Evans blue. All permeability parameters (K(trans), ve, and vp) showed a linear correlation with extravasation of Evans blue. Among them, K(trans) showed highest values of both the correlation coefficient and the coefficient of determination (0.687 and 0.473 respectively, p < 0.001). Permeability parameters obtained by DCE-MRI at 3-T are well-correlated with Evans blue extravasation, and K(trans) shows the strongest correlation among the tested parameters.

  7. Laser surfacing of high density polyethylene for reduction in fuel permeability

    SciTech Connect

    Duley, W.W. ); Ogmen, M.; Steel, T. ); Mihailov, S. )

    1992-01-01

    This paper reports that the increasing use of plastics by the automobile industry has resulted in new manufacturing technology. For example, high density polyethylene (HDPE) fuel tanks can now be blow-molded to fit available vehicle space. Such HDPE tanks offer several advantages over conventional metal tanks. Some of these advantages are: lower production cost; ease of fabrication and fitting to vehicle; reduced explosion hazard; 40 - 50 % reduction in weight; impact resistance; and lack of corrosion. The effect of UV and CO[sub 2] laser radiation on the surface of HDPE gas tank material in relation to the permeability of the surface to unleaded gasoline has been investigated. It is found that while excimer (UV) laser radiation has no effect on permeability, CO[sub 2] laser radiation at low intensity modifies the surface so as to reduce permeability over timescales of 1 - 2 days. A possible origin for this modification is suggested.

  8. Liquid film condensation along a vertical surface in a thin porous medium with large anisotropic permeability.

    PubMed

    Sanya, Arthur S O; Akowanou, Christian; Sanya, Emile A; Degan, Gerard

    2014-01-01

    The problems of steady film condensation on a vertical surface embedded in a thin porous medium with anisotropic permeability filled with pure saturated vapour are studied analytically by using the Brinkman-Darcy flow model. The principal axes of anisotropic permeability are oriented in a direction that non-coincident with the gravity force. On the basis of the flow permeability tensor due to the anisotropic properties and the Brinkman-Darcy flow model adopted by considering negligible macroscopic and microscopic inertial terms, boundary-layer approximations in the porous liquid film momentum equation is solved analytically. Scale analysis is applied to predict the order-of-magnitudes involved in the boundary layer regime. The first novel contribution in the mathematics consists in the use of the anisotropic permeability tensor inside the expression of the mathematical formulation of the film condensation problem along a vertical surface embedded in a porous medium. The present analytical study reveals that the anisotropic permeability properties have a strong influence on the liquid film thickness, condensate mass flow rate and surface heat transfer rate. The comparison between thin and thick porous media is also presented.

  9. Surface tension driven processes densify and retain permeability in magma and lava

    NASA Astrophysics Data System (ADS)

    Kennedy, Ben M.; Wadsworth, Fabian B.; Vasseur, Jérémie; Ian Schipper, C.; Mark Jellinek, A.; von Aulock, Felix W.; Hess, Kai-Uwe; Kelly Russell, J.; Lavallée, Yan; Nichols, Alexander R. L.; Dingwell, Donald B.

    2016-01-01

    We offer new insights into how an explosive eruption can transition into an effusive eruption. Magma containing >0.2 wt% dissolved water has the potential to vesiculate to a porosity in excess of 80 vol.% at atmospheric pressure. Thus all magmas contain volatiles at depth sufficient to form foams and explosively fragment. Yet gas is often lost passively and effusive eruptions ensue. Magmatic foams are permeable and understanding permeability in magma is crucial for models that predict eruptive style. Permeability also governs magma compaction models. Those models generally imply that a reduction in magma porosity and permeability generates an increased propensity for explosivity. Here, our experimental results show that surface tension stresses drive densification without creating an impermeable 'plug', offering an additional explanation of why dense magmas can avoid explosive eruption. In both an open furnace and a closed autoclave, we subject pumice samples with initial porosity of ∼70 vol.% to a range of isostatic pressures (0.1-11 MPa) and temperatures (350-950 °C) relevant to shallow volcanic environments. Our experimental data and models constrain the viscosity, permeability, timescales, and length scales over which densification by pore-scale surface tension stresses competes with density-driven compaction. Where surface tension dominates the dynamics, densification halts at a plateau connected porosity of ∼25 vol.% for our samples. SEM, pycnometry and micro-tomography show that in this process (1) microporous networks are destroyed, (2) the relative pore network surface area decreases, and (3) a remaining crystal framework enhances the longevity of macro-pore connectivity and permeability critical for sustained outgassing. We propose that these observations are a consequence of a surface tension-driven retraction of viscous pore walls at areas of high bubble curvature (micro-vesicular network terminations), and that this process drives bulk

  10. Evaluation of Surface Infiltration Testing Procedures in Permeable Pavement Systems

    EPA Science Inventory

    The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete provides limited guidance on how to select testing locations, so research is needed to evaluate how testing sites should be selected and how results should be interpreted to assess surface ...

  11. Evaluation of Surface Infiltration Testing Procedures in Permeable Pavement Systems

    EPA Science Inventory

    The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete provides limited guidance on how to select testing locations, so research is needed to evaluate how testing sites should be selected and how results should be interpreted to assess surface ...

  12. Permeability- and Surface-Energy-Tunable Polyurethane Acrylate Molds for Capillary Force Lithography.

    PubMed

    Suh, Dongchul; Tak, Hyowon; Choi, Se-jin; Kim, Tae-il

    2015-11-04

    A permeability- and surface-energy-controllable polyurethane acrylate (PUA) mold, a "capillary-force material (CFM)" mold, is introduced for capillary-force lithography (CFL). In CFL, the surface energy and gas permeability of the mold are crucial. However, the modulation of these two main factors at a time is difficult. Here, we introduce new CFM molds in which the surface energy and permeability can be modified by controlling the degree of cross-linking of the CFM. As the degree of cross-linking of the CFM mold increases, the surface energy and air permeability decrease. The high average functionality of the mold material makes it possible to produce patterns relatively finely and rapidly due to the high rate of capillary rise and stiffness, and the low functionality allows for patterns to form on a curved surface with conformal contact. CFMs with different functionality and controllable-interfacial properties will extend the capabilities of capillary force lithography to overcome the geometric limitations of patterning on a scale below 100 nm and micro- and nanopatterning on the curved region.

  13. Evaluation of Surface and Subsurface Processes in Permeable Pavement Infiltration Trenches

    EPA Science Inventory

    The hydrologic performance of permeable pavement systems can be affected by clogging of the pavement surface and/or clogging at the interface where the subsurface storage layer meets the underlying soil. As infiltration and exfiltration are the primary functional mechanisms for ...

  14. Evaluation of Surface and Subsurface Processes in Permeable Pavement Infiltration Trenches

    EPA Science Inventory

    The hydrologic performance of permeable pavement systems can be affected by clogging of the pavement surface and/or clogging at the interface where the subsurface storage layer meets the underlying soil. As infiltration and exfiltration are the primary functional mechanisms for ...

  15. Methods to Use Surface Infiltration Tests in Permeable Pavement Systems to Determine Maintenance Frequency

    EPA Science Inventory

    Currently, there is limited guidance on selecting test sites to measure surface infiltration rates in permeable pavement systems to determine maintenance frequency. The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete suggest to either (1) p...

  16. Methods to Use Surface Infiltration Tests in Permeable Pavement Systems to Determine Maintenance Frequency

    EPA Science Inventory

    Currently, there is limited guidance on selecting test sites to measure surface infiltration rates in permeable pavement systems to determine maintenance frequency. The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete suggest to either (1) p...

  17. Liquid-gas relative permeabilities in fractures: Effects of flow structures, phase transformation and surface roughness

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Ying

    2005-11-01

    Two-phase flow through fractured media is important in petroleum, geothermal, and environmental applications. However, the actual physics and phenomena that occur inside fractures are poorly understood, and oversimplified relative permeability curves are commonly used in fractured reservoir simulations. In this work, an experimental apparatus equipped with a high-speed data acquisition system, real-time visualization, and automated image processing technology was constructed to study three transparent analog fractures with distinct surface roughnesses: smooth, homogeneously rough, and randomly rough. Air-water relative permeability measurements obtained in this study were compared with models suggested by earlier studies and analyzed by examining the flow structures. A method to evaluate the tortuosities induced by the blocking phase, namely the channel tortuosity, was proposed from observations of the flow structure images. The relationship between the coefficients of channel tortuosity and the relative permeabilities was studied with the aid of laboratory experiments and visualizations. Experimental data from these fractures were used to develop a broad approach for modeling two-phase flow behavior based on the flow structures. Finally, a general model deduced from these data was proposed to describe two-phase relative permeabilities in both smooth and rough fractures. For the theoretical analysis of liquid-vapor relative permeabilities, accounting for phase transformations, the inviscid bubble train models coupled with relative permeability concepts were developed. The phase transformation effects were evaluated by accounting for the molecular transport through liquid-vapor interfaces. For the steam-water relative permeabilities, we conducted steam-water flow experiments in the same fractures as used for air-water experiments. We compared the flow behavior and relative permeability differences between two-phase flow with and without phase transformation effects

  18. Melatonin decreases neurovascular oxidative/nitrosative damage and protects against early increases in the blood-brain barrier permeability after transient focal cerebral ischemia in mice.

    PubMed

    Chen, Hung-Yi; Chen, Tsung-Ying; Lee, Ming-Yang; Chen, Shur-Tzu; Hsu, Yun-Shang; Kuo, Yen-Liang; Chang, Guan-Liang; Wu, Tian-Shung; Lee, E-Jian

    2006-09-01

    We have recently shown that melatonin decreases the late (24 hr) increase in blood-brain barrier (BBB) permeability and the risk of tissue plasminogen activator-induced hemorrhagic transformation following ischemic stroke in mice. In the study, we further explored whether melatonin would reduce postischemic neurovascular oxidative/nitrosative damage and, therefore, improve preservation of the early increase in the BBB permeability at 4 hr after transient focal cerebral ischemia for 60 min in mice. Melatonin (5 mg/kg) or vehicle was given intraperitoneally at the beginning of reperfusion. Hydroethidine (HEt) in situ detection and immunohistochemistry for nitrotyrosine were used to evaluate postischemic accumulation in reactive oxygen and nitrogen species, respectively, in the ischemic neurovascular unit. BBB permeability was evaluated by spectrophotometric and microscopic quantitation of Evans Blue leakage. Relative to controls, melatonin-treated animals not only had a significantly reduced superoxide accumulation in neurovascular units in boundary zones of infarction, by reducing 35% and 54% cytosolic oxidized HEt in intensity and cell-expressing percentage, respectively (P < 0.001), but also exhibited a reduction in nitrotyrosine by 52% (P < 0.01). Additionally, melatonin-treated animals had significantly reduced early postischemic disruption in the BBB permeability by 53% (P < 0.001). Thus, melatonin reduced postischemic oxidative/nitrosative damage to the ischemic neurovascular units and improved the preservation of BBB permeability at an early phase following transient focal cerebral ischemia in mice. The findings further highlight the ability of melatonin in anatomical and functional preservation for the ischemic neurovascular units and its relevant potential in the treatment of ischemic stroke.

  19. Influence of thickness and permeability of endothelial surface layer on transmission of shear stress in capillaries

    NASA Astrophysics Data System (ADS)

    Zhang, SongPeng; Zhang, XiangJun; Tian, Yu; Meng, YongGang; Lipowsky, Herbert

    2015-07-01

    The molecular coating on the surface of microvascular endothelium has been identified as a barrier to transvascular exchange of solutes. With a thickness of hundreds of nanometers, this endothelial surface layer (ESL) has been treated as a porous domain within which fluid shear stresses are dissipated and transmitted to the solid matrix to initiate mechanotransduction events. The present study aims to examine the effects of the ESL thickness and permeability on the transmission of shear stress throughout the ESL. Our results indicate that fluid shear stresses rapidly decrease to insignificant levels within a thin transition layer near the outer boundary of the ESL with a thickness on the order of ten nanometers. The thickness of the transition zone between free fluid and the porous layer was found to be proportional to the square root of the Darcy permeability. As the permeability is reduced ten-fold, the interfacial fluid and solid matrix shear stress gradients increase exponentially two-fold. While the interfacial fluid shear stress is positively related to the ESL thickness, the transmitted matrix stress is reduced by about 50% as the ESL thickness is decreased from 500 to 100 nm, which may occur under pathological conditions. Thus, thickness and permeability of the ESL are two main factors that determine flow features and the apportionment of shear stresses between the fluid and solid phases of the ESL. These results may shed light on the mechanisms of force transmission through the ESL and the pathological events caused by alterations in thickness and permeability of the ESL.

  20. Influence of surface-active food additives on the integrity and permeability of rat intestinal mucosa.

    PubMed

    Tagesson, C; Edling, C

    1984-11-01

    The influence of two surface-active food additives on the integrity and permeability of rat ileal mucosa has been studied. We determined the activity of N-acetyl-beta-glucosaminidase, a lysosomal enzyme, in the rat intestinal lumen after deposition of polyoxyethylene (20) sorbitan monostearate (polysorbate 60; Tween 60) or polyoxyethylene (20) sorbitan monooleate (polysorbate 80; Tween 80) in a section of ligated, cannulated gut. We also determined the activities of N-acetyl-beta-glucosaminidase, alkaline phosphatase, 5'-nucleotidase and phospholipase A2 in mixtures of isolated mucosal cells and polysorbate 60 or polysorbate 80. The activity of N-acetyl-beta-glucosaminidase was increased in the luminal contents of the cannulated gut 15 min after deposition of either polysorbate 60 or polysorbate 80 (10 mg/ml fluid instilled into gut). It was also increased in mixtures of mucosal cells and polysorbate 60 or polysorbate 80 (0.1-10 mg/ml). In contrast, the activities of alkaline phosphatase and 5'-nucleotidase were unaffected and that of phospholipase A2 was decreased by the presence of either polysorbate. These findings indicated that polysorbate 60 and polysorbate 80 released lysosomal enzymes from the intestinal mucosal cells and that these agents might damage the intestinal mucosa and increase its permeability. We therefore determined the intestinal permeability to sodium fluorescein in the absence and presence of polysorbate 60 or 80 and found that the permeability was slightly increased in the presence of either of the compounds at concentrations of 10 mg/ml fluid instilled into gut. It is possible therefore that surface-active food additives might impair the function of the mucosal barrier and increase the permeability of the gut to potentially toxic and pathogenic molecules.

  1. Effect of perfusate hematocrit on urea permeability-surface area in isolated dog lung

    SciTech Connect

    Parker, R.E.; Roselli, R.J.; Haselton, F.R.; Harris, T.R.

    1986-10-01

    Seven dog lower left lung lobes were statically inflated and perfused at a constant rate for each lobe with a perfusate in which the hematocrit was altered over a wide range. The permeability-surface area of urea was calculated from multiple indicator dilution curves using two separate injectates for each hematocrit level. One injectate contained only /sup 125/I-albumin as the vascular reference tracer and the other contained both /sup 51/Cr-erythrocytes and /sup 125/I-albumin as the vascular reference tracers; both contained (/sup 14/C)urea as the permeating tracer. The results strongly indicate that the phenomenon of erythrocyte trapping of urea does not affect the calculation of urea permeability-surface area product provided the appropriate albumin-erythrocyte composite reference tracer is utilized in its calculation.

  2. Delayed astrocytic contact with cerebral blood vessels in FGF-2 deficient mice does not compromise permeability properties at the developing blood-brain barrier.

    PubMed

    Saunders, Norman R; Dziegielewska, Katarzyna M; Unsicker, Klaus; Ek, C Joakim

    2016-11-01

    The brain functions within a specialized environment tightly controlled by brain barrier mechanisms. Understanding the regulation of barrier formation is important for understanding brain development and may also lead to finding new ways to deliver pharmacotherapies to the brain; access of many potentially promising drugs is severely hindered by these barrier mechanisms. The cellular composition of the neurovascular unit of the blood-brain barrier proper and their effects on regulation of its function are beginning to be understood. One hallmark of the neurovascular unit in the adult is the astroglial foot processes that tightly surround cerebral blood vessels. However their role in barrier formation is still unclear. In this study we examined barrier function in newborn, juvenile and adult mice lacking fibroblast growth factor-2 (FGF-2), which has been shown to result in altered astroglial differentiation during development. We show that during development of FGF-2 deficient mice the astroglial contacts with cerebral blood vessels are delayed compared with wild-type animals. However, this delay did not result in changes to the permeability properties of the blood brain barrier as assessed by exclusion of either small or larger sized molecules at this interface. In addition cerebral vessels were positive for tight-junction proteins and we observed no difference in the ultrastructure of the tight-junctions. The results indicate that the direct contact of astroglia processes to cerebral blood vessels is not necessary for either the formation of the tight-junctions or for basic permeability properties and function of the blood-brain barrier. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1201-1212, 2016. © 2016 Wiley Periodicals, Inc.

  3. Multiscale Characterization of Porosity, Permeability and reactive Surface Changes During Dissolution.

    NASA Astrophysics Data System (ADS)

    Gouze, P.; Sadhukhan, S.; Dentz, M.; Luquot, L.; Dweik, J.

    2011-12-01

    Meshed models in which equations are solved assuming that constant macroscopic properties can be defined in each cells are essential tools for predicting reservoir properties changes triggered by dissolution and precipitation. However, the parameterization of the dissolution-precipitation problem and their feedback effects on the flow field are still challenging. The problem arises from the mismatch between the scales at which averaged parameters and parameters relationships (such as the porosity-permeability heuristic relation) are defined and the scale at which chemical reactions occur according to the pore scale fluid concentration and flow heterogeneities and modify the pore network geometry. Here, we investigate the links between the dissolution mechanisms that control the porosity changes and the related changes of the reactive surface area and of the permeability. We used X-ray microtomography data obtained before and after a set of dissolution experiments of pure calcite rocks using distinctly different brine- CO2 mixtures. The objective is to characterize pore scale changes and constrain the macroscale relationships between permeability, porosity and reactive surface area by introducing parameters that can be computed from the X-ray microtomography images, e.g. pore size distribution, pore network and surface tortuosity and multifractal properties. For instance it is shown that depending on the initial heterogeneity and the dissolution capacity of the inlet fluid (here CO2 concentration) permeability increase is due to distinctly combinations of tortuosity decrease and hydraulic radius increase. Such changes can be investigated using pore scale modeling for simple pore network geometries and chemical systems for which reactions can be linked to pore scale and sample scale mixing mechanisms.

  4. Surface Infiltration Rates of Permeable Surfaces: Six Month Update (November 2009 through April 2010)

    EPA Science Inventory

    At the end of October 2009, EPA opened a parking lot on the Edison Environmental Center that included three parking rows of permeable pavement. The construction was a cooperative effort among EPA’s Office of Administration and Resources Management, National Risk Management Resea...

  5. Surface Infiltration Rates of Permeable Surfaces: Six Month Update (November 2009 through April 2010)

    EPA Science Inventory

    At the end of October 2009, EPA opened a parking lot on the Edison Environmental Center that included three parking rows of permeable pavement. The construction was a cooperative effort among EPA’s Office of Administration and Resources Management, National Risk Management Resea...

  6. Rigid gas permeable contact lenses surface roughness examined by interferential shifting phase and scanning electron microscopies.

    PubMed

    Merindano, M D; Canals, M; Saona, C; Costa, J

    1998-01-01

    The anterior surface roughness of seven factory new rigid gas permeable (RGP) contact lenses has been studied by interferential shifting phase microscopy (ISPM) and scanning electron microscopy (SEM). Five lenses were fluorsilicone acrylate and two lenses were silicone acrylate. Their material Dk ranged from 14 to 210. ISPM is shown to be a reliable and non-destructive method to observe and measure the relief of the contact lens surface. Moreover, profile and contour data are easily stored for further quantitative studies. ISPM contour patterns of the studied lenses are qualitatively compared with those obtained by SEM for the same lenses. Results point out that ISPM gives similar accuracy but it is non-destructive and cheaper than SEM. Moreover, the quantitative study of surface roughness suggests that there is a relationship between surface roughness and Dk of the lens material: surface roughness increases with Dk and allows to distinguish between lenses with low, medium and high Dk.

  7. High microvascular endothelial water permeability in mouse lung measured by a pleural surface fluorescence method.

    PubMed Central

    Carter, E P; Olveczky, B P; Matthay, M A; Verkman, A S

    1998-01-01

    Transport of water between the capillary and airspace compartments in lung encounters serial barriers: the alveolar epithelium, interstitium, and capillary endothelium. We previously reported a pleural surface fluorescence method to measure net capillary-to-airspace water transport. To measure the osmotic water permeability across the microvascular endothelial barrier in intact lung, the airspace was filled with a water-immiscible fluorocarbon. The capillaries were perfused via the pulmonary artery with solutions of specified osmolalites containing a high-molecular-weight fluorescent dextran. An increase in perfusate osmolality produced a prompt decrease in surface fluorescence due to dye dilution in the capillaries, followed by a slower return to initial fluorescence as capillary and lung interstitial osmolality equilibrate. A mathematical model was developed to determine the osmotic water permeability coefficient (Pf) of lung microvessels from the time course of pleural surface fluorescence. As predicted, the magnitude of the prompt change in surface fluorescence increased with decreased pulmonary artery perfusion rate and increased osmotic gradient size. With raffinose used to induce the osmotic gradient, Pf was 0.03 cm/s at 23 degrees C and was reduced 54% by 0.5 mM HgCl2. Temperature dependence measurements gave an Arrhenius activation energy (Ea) of 5.4 kcal/mol (12-37 degrees C). The apparent Pf induced by the smaller osmolytes mannitol and glycine was 0.021 and 0.011 cm/s (23 degrees C). Immunoblot analysis showed approximately 1.4 x 10(12) aquaporin-1 water channels/cm2 of capillary surface, which accounted quantitatively for the high Pf. These results establish a novel method for measuring osmotically driven water permeability across microvessels in intact lung. The high Pf, low Ea, and mercurial inhibition indicate the involvement of molecular water channels in water transport across the lung endothelium. PMID:9545071

  8. The effect of different surface materials on runoff quality in permeable pavement systems.

    PubMed

    Li, Haiyan; Li, Zhifei; Zhang, Xiaoran; Li, Zhuorong; Liu, Dongqing; Li, Tanghu; Zhang, Ziyang

    2017-07-20

    To investigate the effect of different permeable pavement surface materials on the removal of pollutants from urban storm-runoff, six commonly surface materials (porous asphalt, porous concrete, cement brick, ceramic brick, sand base brick, and shale brick) were selected in this study and the research was carried out by column experiments. Except the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), total nitrogen (TN), and total phosphorus (TP) in the influent and effluent that were measured, the removal mechanism of pollutants was discussed further. The results indicate that the surface materials influence the removal efficiency of pollutants greatly and have different effects on certain pollutant. Furthermore, the physical interception and adsorption would be the main mechanism for the removal of pollutants from runoff. For example, for all surface materials, the average removal efficiency of TSS is nearly about 90.0% because of physical interception. Due to the amount of iron oxide, the removal efficiency of COD, NO3-N, and TN of shale brick was 88.2, 35.1, and 17.5%, respectively. NH4-N and TN can be easily removed by porous asphalt due to the high content of organic matter. By lacking of useful adsorption sites, all the surface materials had little effect on the removal of TP from runoff. This research could offer useful guidelines for the better design of permeable pavement system and promote the insight into the removal mechanism of pollutants in permeable pavement system. Graphical abstract Different types of materials for the different types of pollutants in the runoff purification capacity were significantly different, overall, shale brick and porous asphalt Shale bricks and porous asphalt have a better purification effect according to the six kinds of materials.

  9. Surface Properties and Permeability of Poly(Vinylidene Fluoride)-Clays (PVDF/Clays) Composite Membranes

    NASA Astrophysics Data System (ADS)

    Pramono, E.; Ahdiat, M.; Simamora, A.; Pratiwi, W.; Radiman, C. L.; Wahyuningrum, D.

    2017-07-01

    Surface properties are important factors that determine the performance of ultrafiltration membranes. This study aimed to investigate the effects of clay addition on the surface properties and membrane permeability of PVDF (poly-vinylidene fluoride) membranes. Three types of clay with different particle size were used in this study, namely montmorillonite-MMT, bentonite-BNT and cloisite 15A-CLS. The PVDF-clay composite membranes were prepared by phase inversion method using PEG as additive. The hydrophobicity of membrane surface was characterized by contact angle. The membrane permeability was determined by dead- end ultrafiltration with a trans-membrane pressure of 2 bars. In contact angle measurement, water contact angle of composite membranes is higher than PVDF membrane. The addition of clays decreased water flux but increased of Dextran rejection. The PVDF-BNT composite membranes reach highest Dextran rejection value of about 93%. The type and particle size of clay affected the hydrophobicity of membrane surface and determined the resulting membrane structure as well as the membrane performance.

  10. Identification of Spurious Signals from Permeable Ffowcs Williams and Hawkings Surfaces

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard V.; Boyd, David D., Jr.; Nark, Douglas M.; Wiedemann, Karl E.

    2017-01-01

    Integral forms of the permeable surface formulation of the Ffowcs Williams and Hawkings (FW-H) equation often require an input in the form of a near field Computational Fluid Dynamics (CFD) solution to predict noise in the near or far field from various types of geometries. The FW-H equation involves three source terms; two surface terms (monopole and dipole) and a volume term (quadrupole). Many solutions to the FW-H equation, such as several of Farassat's formulations, neglect the quadrupole term. Neglecting the quadrupole term in permeable surface formulations leads to inaccuracies called spurious signals. This paper explores the concept of spurious signals, explains how they are generated by specifying the acoustic and hydrodynamic surface properties individually, and provides methods to determine their presence, regardless of whether a correction algorithm is employed. A potential approach based on the equivalent sources method (ESM) and the sensitivity of Formulation 1A (Formulation S1A) is also discussed for the removal of spurious signals.

  11. A Review of the Mechanisms of Blood-Brain Barrier Permeability by Tissue-Type Plasminogen Activator Treatment for Cerebral Ischemia

    PubMed Central

    Suzuki, Yasuhiro; Nagai, Nobuo; Umemura, Kazuo

    2016-01-01

    Cerebrovascular homeostasis is maintained by the blood-brain barrier (BBB), which forms a mechanical and functional barrier between systemic circulation and the central nervous system (CNS). In patients with ischemic stroke, the recombinant tissue-type plasminogen activator (rt-PA) is used to accelerate recanalization of the occluded vessels. However, rt-PA is associated with a risk of increasing intracranial bleeding (ICB). This effect is thought to be caused by the increase in cerebrovascular permeability though various factors such as ischemic reperfusion injury and the activation of matrix metalloproteinases (MMPs), but the detailed mechanisms are unknown. It was recently found that rt-PA treatment enhances BBB permeability not by disrupting the BBB, but by activating the vascular endothelial growth factor (VEGF) system. The VEGF regulates both the dissociation of endothelial cell (EC) junctions and endothelial endocytosis, and causes a subsequent increase in vessel permeability through the VEGF receptor-2 (VEGFR-2) activation in ECs. Here, we review the possibility that rt-PA increases the penetration of toxic molecules derived from the bloodstream including rt-PA itself, without disrupting the BBB, and contributes to these detrimental processes in the cerebral parenchyma. PMID:26834557

  12. Impact of caprock permeability on vertical ground surface displacements in geological underground utilisation

    NASA Astrophysics Data System (ADS)

    Kempka, Thomas; Tillner, Elena

    2015-04-01

    Geological underground utilisation inducing pore pressure changes in underground reservoirs is generally accompanied by hydro-mechanical processes. Thereby, pore pressure increase due to fluid injection may trigger ground surface uplift, while a decrease in pore pressure due to reservoir fluid production is known to induce ground subsidence. Different coupled hydro-mechanical simulation studies (e.g. Klimkowski et al., 2015, Kempka et al., 2014, Tillner et al., 2014) indicate that ground surface displacements can achieve a magnitude of several decimetres, if storage or production operations are being carried out at an industrial scale. Consequently, detailed knowledge on the parameters impacting ground surface uplift or subsidence is of major interest for the success of any geological underground utilisation in order to avoid surface infrastructure damage by spatially varying deformations. Furthermore, ground subsidence may result increased groundwater levels as experienced in different underground coal mining districts. In the present study, we carried out coupled hydro-mechanical simulations to account for the impact of caprock permeability on ground surface displacements resulting from geological underground utilisation. Thereto, different simulation scenarios were investigated using a synthetic 3D coupled numerical simulation model with varying caprock permeability and vertical location of the open well section in the target reservoir. Material property ranges were derived from available literature, while a normal faulting stress state was applied in all simulation scenarios. Our simulation results demonstrate that caprock permeability has a significant impact on the pressure development, and thus on vertical displacements at the ground surface as well as at the reservoir top. An increase in caprock permeability from 1 x 10-20 m2 by two orders of magnitude doubles vertical displacements at the ground surface, whereas vertical displacements at the reservoir top

  13. Continuum percolation on nonorientable surfaces: the problem of permeable disks on a Klein bottle

    NASA Astrophysics Data System (ADS)

    Borman, V. D.; Grekhov, A. M.; Tronin, V. N.; Tronin, I. V.

    2015-11-01

    The percolation threshold and wrapping probability (R ∞) for the two-dimensional problem of continuum percolation on the surface of a Klein bottle have been calculated by the Monte Carlo method with the Newman-Ziff algorithm for completely permeable disks. It has been shown that the percolation threshold of disks on the Klein bottle coincides with the percolation threshold of disks on the surface of a torus, indicating that this threshold is topologically invariant. The scaling exponents determining corrections to the wrapping probability and critical concentration owing to the finite-size effects are also topologically invariant. At the same time, the quantities R ∞ are different for percolation on the torus and Klein bottle and are apparently determined by the topology of the surface. Furthermore, the difference between the R ∞ values for the torus and Klein bottle means that at least one of the percolation clusters is degenerate.

  14. The neuroprotective effect of olive leaf extract is related to improved blood-brain barrier permeability and brain edema in rat with experimental focal cerebral ischemia.

    PubMed

    Mohagheghi, Fatemeh; Bigdeli, Mohammad Reza; Rasoulian, Bahram; Hashemi, Payman; Pour, Marzyeh Rashidi

    2011-01-15

    Recent studies suggest that olive extracts suppress inflammation and reduce stress oxidative injury. We sought to extend these observations in an in vivo study of rat cerebral ischemia-reperfusion injury. Four groups, each of 18 Wister rats, were studied. One (control) group received distilled water, while three treatment groups received oral olive leaf extract (50, 75 and 100mg/kg/day respectively). After 30 days, blood lipid profiles were determined, before a 60 min period of middle cerebral artery occlusion (MCAO). After 24h reperfusion, neurological deficit scores, infarct volume, brain edema, and blood-brain barrier permeability were each assessed in subgroups of six animals drawn from each main group. Olive leaf extract reduced the LDL/HDL ratio in doses 50, 75, and 100mg/kg/day in comparison to the control group (P<0.001), and offered cerebroprotection from ischemia-reperfusion. For controls vs. doses of 50mg/kg/day vs. 75 mg/kg/day vs. 100mg/kg/day, attenuated corrected infarct volumes were 209.79 ± 33.05 mm(3) vs. 164.36 ± 13.44 mm(3) vs. 123.06 ± 28.83 mm(3) vs. 94.71 ± 33.03 mm(3); brain water content of the infarcted hemisphere 82.33 ± 0.33% vs. 81.33 ± 0.66% vs. 80.75 ± 0.6% vs. 80.16 ± 0.47%, and blood-brain barrier permeability of the infarcted hemisphere 11.22 ± 2.19 μg/g vs. 9.56 ± 1.74 μg/g vs. 6.99 ± 1.48 μg/g vs. 5.94 ± 1.73 μg/g tissue (P<0.05 and P<0.01 for measures in doses 75 and 100mg/kg/day vs. controls respectively). Oral administration of olive leaf extract reduces infarct volume, brain edema, blood-brain barrier permeability, and improves neurologic deficit scores after transient middle cerebral artery occlusion in rats.

  15. Assessment of Blood-Brain Barrier Permeability by Dynamic Contrast-Enhanced MRI in Transient Middle Cerebral Artery Occlusion Model after Localized Brain Cooling in Rats

    PubMed Central

    Kim, Eun Soo; Kwon, Mi Jung; Lee, Phil Hye; Ju, Young-Su; Yoon, Dae Young; Kim, Hye Jeong; Lee, Kwan Seop

    2016-01-01

    Objective The purpose of this study was to evaluate the effects of localized brain cooling on blood-brain barrier (BBB) permeability following transient middle cerebral artery occlusion (tMCAO) in rats, by using dynamic contrast-enhanced (DCE)-MRI. Materials and Methods Thirty rats were divided into 3 groups of 10 rats each: control group, localized cold-saline (20℃) infusion group, and localized warm-saline (37℃) infusion group. The left middle cerebral artery (MCA) was occluded for 1 hour in anesthetized rats, followed by 3 hours of reperfusion. In the localized saline infusion group, 6 mL of cold or warm saline was infused through the hollow filament for 10 minutes after MCA occlusion. DCE-MRI investigations were performed after 3 hours and 24 hours of reperfusion. Pharmacokinetic parameters of the extended Tofts-Kety model were calculated for each DCE-MRI. In addition, rotarod testing was performed before tMCAO, and on days 1-9 after tMCAO. Myeloperoxidase (MPO) immunohisto-chemistry was performed to identify infiltrating neutrophils associated with the inflammatory response in the rat brain. Results Permeability parameters showed no statistical significance between cold and warm saline infusion groups after 3-hour reperfusion 0.09 ± 0.01 min-1 vs. 0.07 ± 0.02 min-1, p = 0.661 for Ktrans; 0.30 ± 0.05 min-1 vs. 0.37 ± 0.11 min-1, p = 0.394 for kep, respectively. Behavioral testing revealed no significant difference among the three groups. However, the percentage of MPO-positive cells in the cold-saline group was significantly lower than those in the control and warm-saline groups (p < 0.05). Conclusion Localized brain cooling (20℃) does not confer a benefit to inhibit the increase in BBB permeability that follows transient cerebral ischemia and reperfusion in an animal model, as compared with localized warm-saline (37℃) infusion group. PMID:27587960

  16. Assessment of Blood-Brain Barrier Permeability by Dynamic Contrast-Enhanced MRI in Transient Middle Cerebral Artery Occlusion Model after Localized Brain Cooling in Rats.

    PubMed

    Kim, Eun Soo; Lee, Seung-Koo; Kwon, Mi Jung; Lee, Phil Hye; Ju, Young-Su; Yoon, Dae Young; Kim, Hye Jeong; Lee, Kwan Seop

    2016-01-01

    The purpose of this study was to evaluate the effects of localized brain cooling on blood-brain barrier (BBB) permeability following transient middle cerebral artery occlusion (tMCAO) in rats, by using dynamic contrast-enhanced (DCE)-MRI. Thirty rats were divided into 3 groups of 10 rats each: control group, localized cold-saline (20℃) infusion group, and localized warm-saline (37℃) infusion group. The left middle cerebral artery (MCA) was occluded for 1 hour in anesthetized rats, followed by 3 hours of reperfusion. In the localized saline infusion group, 6 mL of cold or warm saline was infused through the hollow filament for 10 minutes after MCA occlusion. DCE-MRI investigations were performed after 3 hours and 24 hours of reperfusion. Pharmacokinetic parameters of the extended Tofts-Kety model were calculated for each DCE-MRI. In addition, rotarod testing was performed before tMCAO, and on days 1-9 after tMCAO. Myeloperoxidase (MPO) immunohisto-chemistry was performed to identify infiltrating neutrophils associated with the inflammatory response in the rat brain. Permeability parameters showed no statistical significance between cold and warm saline infusion groups after 3-hour reperfusion 0.09 ± 0.01 min(-1) vs. 0.07 ± 0.02 min(-1), p = 0.661 for K(trans); 0.30 ± 0.05 min(-1) vs. 0.37 ± 0.11 min(-1), p = 0.394 for kep, respectively. Behavioral testing revealed no significant difference among the three groups. However, the percentage of MPO-positive cells in the cold-saline group was significantly lower than those in the control and warm-saline groups (p < 0.05). Localized brain cooling (20℃) does not confer a benefit to inhibit the increase in BBB permeability that follows transient cerebral ischemia and reperfusion in an animal model, as compared with localized warm-saline (37℃) infusion group.

  17. Atomic diffusion on vicinal surfaces: step roughening impact on step permeability

    NASA Astrophysics Data System (ADS)

    Ranguelov, B.; Michailov, M.

    2014-12-01

    The problem of mass transport in material science for systems with reduced dimensionality holds special academic and technological attention since the fine diffusion control of adatoms could initiate exotic nanoscale patterning at epitaxial interfaces. The present study brings out important details of the atomic diffusion mechanisms on vicinal surfaces, accounting for the subtle competition between an external field imposed on the migrating adatoms and the roughening of the steps bordering the atomic terraces. The computational model reveals a temperature gap for breakdown of step permeability in the vicinity of the step roughening transition and sheds light on recently observed experimental results for atomic step dynamics on Si surfaces. The present study also demonstrates the extended capability of atomistic models in computer simulations to unravel simultaneous effects, to distinguish between them, and finally to assess their specific contribution to experimentally observed complex physical phenomena.

  18. Boundary layer flow near a stagnation point on a permeable vertical surface immersed in a nanofluid

    NASA Astrophysics Data System (ADS)

    Othman, Noor Adila; Yacob, Nor Azizah; Bachok, Norfifah; Ramli, Nazirah; Ishak, Anuar

    2015-10-01

    A steady mixed convection boundary layer flow near a stagnation point on a permeable vertical surface immersed in a nanofluid is investigated. The velocity of the external flow is assumed to vary linearly with the distance from the stagnation-point. The governing partial differential equations are first transformed into ordinary differential equations, before being solved numerically using the Keller box method with the help of MATLAB software. The effects of physical parameters such as the suction/injection parameter, Brownian motion parameter, thermophoresis parameter and Lewis number on the heat and mass transfer rate at the surface as well as the temperature and concentration profiles are analyzed and discussed. Both assisting and opposing flows are considered. It is found that, increasing the thermophoresis parameter, Brownian motion parameter and Lewis number are to decrease the heat transfer rate at the surface, but on the other hand increase the mass transfer rate at the surface for both assisting and opposing flows. In addition, increasing suction parameter tends to increase the heat transfer rate at the surface. However, the opposite behavior occurs for the effect of mass transfer rate at the surface.

  19. Stormwater infiltration and surface runoff pollution reduction performance of permeable pavement layers.

    PubMed

    Niu, Zhi-Guang; Lv, Zhi-Wei; Zhang, Ying; Cui, Zhen-Zhen

    2016-02-01

    In this paper, the laboratory-scale permeable pavement layers, including a surface permeable brick layer, coarse sand bedding layers (thicknesses = 2, 3.5, and 5 cm), and single-graded gravel sub-base layers (thicknesses = 15, 20, 25, and 30 cm), were built to evaluate stormwater infiltration and surface runoff pollution reduction performance. And, the infiltration rate (I) and concentrations of suspended solids (SS), total phosphorus (TP), chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen (TN) were measured under the simulated rainfall intensity of 72.4 mm/h over duration of 60 min. The results indicate that the thickness factor primarily influences the infiltration rate and pollutant removal rate. The highest steady infiltration rate was for surface brick layer 51.0 mm/h, for 5-cm sand bedding layer 32.3 mm/h, and for 30-cm gravel sub-base layer 42.3 mm/h, respectively. The SS average removal rate was relative higher (79.8 ∼ 98.6 %) for all layers due to the interception and filtration. The average removal rates of TP and COD were for surface layer 71.2 and 24.1 %, for 5-cm bedding layer 54.8 and 9.0 %, and for 20-cm sub-base layer 72.2 and 26.1 %. Ammonia nitrogen and TN cannot steadily be removed by layers according to the experiment results. The optimal thickness of bedding sands was 5 cm, and that of sub-base gravels was 20 ∼ 30 cm.

  20. Lactobacillus fermentum AGR1487 cell surface structures and supernatant increase paracellular permeability through different pathways

    PubMed Central

    Sengupta, Ranjita; Anderson, Rachel C; Altermann, Eric; McNabb, Warren C; Ganesh, Siva; Armstrong, Kelly M; Moughan, Paul J; Roy, Nicole C

    2015-01-01

    Lactobacillus fermentum is commonly found in food products, and some strains are known to have beneficial effects on human health. However, our previous research indicated that L. fermentum AGR1487 decreases in vitro intestinal barrier integrity. The hypothesis was that cell surface structures of AGR1487 are responsible for the observed in vitro effect. AGR1487 was compared to another human oral L. fermentum strain, AGR1485, which does not cause the same effect. The examination of phenotypic traits associated with the composition of cell surface structures showed that compared to AGR1485, AGR1487 had a smaller genome, utilized different sugars, and had greater tolerance to acid and bile. The effect of the two strains on intestinal barrier integrity was determined using two independent measures of paracellular permeability of the intestinal epithelial Caco-2 cell line. The transepithelial electrical resistance (TEER) assay specifically measures ion permeability, whereas the mannitol flux assay measures the passage of uncharged molecules. Both live and UV-inactivated AGR1487 decreased TEER across Caco-2 cells implicating the cell surfaces structures in the effect. However, only live AGR1487, and not UV-inactivated AGR1487, increased the rate of passage of mannitol, implying that a secreted component(s) is responsible for this effect. These differences in barrier integrity results are likely due to the TEER and mannitol flux assays measuring different characteristics of the epithelial barrier, and therefore imply that there are multiple mechanisms involved in the effect of AGR1487 on barrier integrity. PMID:25943073

  1. Effects of Streptococcus sanguinis Bacteriocin on Cell Surface Hydrophobicity, Membrane Permeability, and Ultrastructure of Candida Thallus.

    PubMed

    Ma, Shengli; Zhao, Yingnan; Xia, Xue; Dong, Xue; Ge, Wenyu; Li, Hui

    2015-01-01

    Candida albicans (C.a) and Candida tropicalis (C.t) were treated with Streptococcus sanguinis bacteriocin (S.s bacteriocin), respectively; the bacteriostatic dynamics of S.s bacteriocin, their effects on cell surface hydrophobicity, leakage of inorganic phosphorus and macromolecular substance, cytosolic calcium concentration, and ultrastructure changes of Candida thallus were detected and analyzed. The results showed that inhibitory effect of S.s bacteriocin on C.a and C.t reached peak level at 24 h, the cell-surface hydrophobicity decreased significantly (P < 0.05) after S.s bacteriocin treatment, and there was leakage of cytoplasmic inorganic phosphorus and macromolecular substance from C.a and C.t; cytosolic calcium concentration decreased greatly. After 24 h treatment by S.s bacteriocin, depressive deformity and defect could be found in the cell surface of C.a and C.t; the thallus displayed irregular forms: C.a was shrunken, there was unclear margins abutting upon cell wall and cell membrane, nucleus disappeared, and cytoplasm was inhomogeneous; likewise, C.t was first plasmolysis, and then the cytoplasm was shrunk, the ultrastructure of cell wall and cell membrane was continuously damaged, and the nucleus was karyolysis. It was illustrated that S.s bacteriocin had similar antifungal effect on C.a and C.t; their cell surface hydrophobicity, membrane permeability, and ultrastructure were changed significantly on exposure to S.s bacteriocin.

  2. Effects of Streptococcus sanguinis Bacteriocin on Cell Surface Hydrophobicity, Membrane Permeability, and Ultrastructure of Candida Thallus

    PubMed Central

    Ma, Shengli; Zhao, Yingnan; Xia, Xue; Dong, Xue; Ge, Wenyu; Li, Hui

    2015-01-01

    Candida albicans (C.a) and Candida tropicalis (C.t) were treated with Streptococcus sanguinis bacteriocin (S.s bacteriocin), respectively; the bacteriostatic dynamics of S.s bacteriocin, their effects on cell surface hydrophobicity, leakage of inorganic phosphorus and macromolecular substance, cytosolic calcium concentration, and ultrastructure changes of Candida thallus were detected and analyzed. The results showed that inhibitory effect of S.s bacteriocin on C.a and C.t reached peak level at 24 h, the cell-surface hydrophobicity decreased significantly (P < 0.05) after S.s bacteriocin treatment, and there was leakage of cytoplasmic inorganic phosphorus and macromolecular substance from C.a and C.t; cytosolic calcium concentration decreased greatly. After 24 h treatment by S.s bacteriocin, depressive deformity and defect could be found in the cell surface of C.a and C.t; the thallus displayed irregular forms: C.a was shrunken, there was unclear margins abutting upon cell wall and cell membrane, nucleus disappeared, and cytoplasm was inhomogeneous; likewise, C.t was first plasmolysis, and then the cytoplasm was shrunk, the ultrastructure of cell wall and cell membrane was continuously damaged, and the nucleus was karyolysis. It was illustrated that S.s bacteriocin had similar antifungal effect on C.a and C.t; their cell surface hydrophobicity, membrane permeability, and ultrastructure were changed significantly on exposure to S.s bacteriocin. PMID:26064919

  3. Method for the preparation of high surface area high permeability carbons

    DOEpatents

    Lagasse, R.R.; Schroeder, J.L.

    1999-05-11

    A method for preparing carbon materials having high surface area and high macropore volume to provide high permeability. These carbon materials are prepared by dissolving a carbonizable polymer precursor, in a solvent. The solution is cooled to form a gel. The solvent is extracted from the gel by employing a non-solvent for the polymer. The non-solvent is removed by critical point drying in CO{sub 2} at an elevated pressure and temperature or evaporation in a vacuum oven. The dried product is heated in an inert atmosphere in a first heating step to a first temperature and maintained there for a time sufficient to substantially cross-link the polymer material. The cross-linked polymer material is then carbonized in an inert atmosphere. 3 figs.

  4. Method for the preparation of high surface area high permeability carbons

    DOEpatents

    Lagasse, Robert R.; Schroeder, John L.

    1999-05-11

    A method for preparing carbon materials having high surface area and high macropore volume to provide high permeability. These carbon materials are prepared by dissolving a carbonizable polymer precursor, in a solvent. The solution is cooled to form a gel. The solvent is extracted from the gel by employing a non-solvent for the polymer. The non-solvent is removed by critical point drying in CO.sub.2 at an elevated pressure and temperature or evaporation in a vacuum oven. The dried product is heated in an inert atmosphere in a first heating step to a first temperature and maintained there for a time sufficient to substantially cross-link the polymer material. The cross-linked polymer material is then carbonized in an inert atmosphere.

  5. Stability analysis of MHD viscous flow and heat transfer over a permeable shrinking surface

    NASA Astrophysics Data System (ADS)

    Hafidzuddin, Mohd Ezad Hafidz; Nazar, Roslinda

    2015-10-01

    In this study, a problem of steady laminar magnetohydrodynamic (MHD) viscous boundary layer flow and heat transfer over a permeable shrinking surface is considered. The governing nonlinear partial differential equations are transformed into a system of nonlinear ordinary differential equations using a similarity transformation. The transformed ordinary differential equations are then solved numerically using the bvp4c function in MATLAB software. Dual solutions are found for a certain range of the suction parameter. A stability analysis has been performed to determine which solution is stable and physically realizable. The effects of the suction parameter, the Hartmann number and the Prandtl number on the skin friction and heat transfer coefficients as well as the velocity and temperature profiles are presented and discussed in detail.

  6. [The permeability of the hemato-encephalic barrier for superoxide dismutase following the unilateral intracarotid hyperperfusion of the cerebral vessels].

    PubMed

    Aleksandrova, L A; Sorokoumova, V A; Shabunevich, L V; Pugacheva, E L

    1993-06-01

    On the model of acute blood-brain barrier injury in rats after a short-term hyperperfusion of one brain hemisphere with blood, the injection of exogenic superoxide dismutase (SOD) was accompanied by pronounced increase in the activity of SOD in the damaged brain tissue. This fact and other data of the authors on this model confirm the penetration of SOD over the microvessel endothelium into the extracellular space of the same damaged brain areas that are permeable for plasma albumin.

  7. Clinical findings correlated with contact angles on rigid gas permeable contact lens surfaces in vivo.

    PubMed

    Bourassa, S; Benjamin, W J

    1989-08-01

    Functional wettability of daily wear rigid gas permeable (RGP) contact lenses worn by 16 human subjects was monitored over a 4-month period during which wettability was also assessed with an equilibrium sessile-drop contact angle method in vivo. In all, 2,128 lens surface break-up time (LBUT) and in vivo contact angle data points were accumulated. Six hundred thirty-one associated graded evaluations of lens surface deposition and patient discomfort were also recorded. The four factors (LBUT, contact angle, deposition, and discomfort) were found to be correlated to each other, their paired values having statistically significant correlation coefficients. Contact angles were of predictive value for extremes of functional wettability, based on criterion of 20 degrees equivalent to an LBUT of 5 seconds. We confirm that surface deposition and subject discomfort are related to RGP lens wettability on the eye. In addition, the in vivo contact angle is perhaps the first contact angle measurement to be correlated with functional RGP wettability.

  8. A highly permeable and enhanced surface area carbon-cloth electrode for vanadium redox flow batteries

    NASA Astrophysics Data System (ADS)

    Zhou, X. L.; Zhao, T. S.; Zeng, Y. K.; An, L.; Wei, L.

    2016-10-01

    In this work, a high-performance porous electrode, made of KOH-activated carbon-cloth, is developed for vanadium redox flow batteries (VRFBs). The macro-scale porous structure in the carbon cloth formed by weaving the carbon fibers in an ordered manner offers a low tortuosity (∼1.1) and a broad pore distribution from 5 μm to 100 μm, rendering the electrode a high hydraulic permeability and high effective ionic conductivity, which are beneficial for the electrolyte flow and ion transport through the porous electrode. The use of KOH activation method to create nano-scale pores on the carbon-fiber surfaces leads to a significant increase in the surface area for redox reactions from 2.39 m2 g-1 to 15.4 m2 g-1. The battery assembled with the present electrode delivers an energy efficiency of 80.1% and an electrolyte utilization of 74.6% at a current density of 400 mA cm-2, as opposed to an electrolyte utilization of 61.1% achieved by using a conventional carbon-paper electrode. Such a high performance is mainly attributed to the combination of the excellent mass/ion transport properties and the high surface area rendered by the present electrode. It is suggested that the KOH-activated carbon-cloth electrode is a promising candidate in redox flow batteries.

  9. Consequences of Anisotropic Permeability and Surface Tension for Magmatic Segregation in Deforming Mantle Rock

    NASA Astrophysics Data System (ADS)

    Taylor-West, J.; Katz, R. F.

    2014-12-01

    The mechanics of partially molten regions of the mantle are not well understood--in part due to the inaccessibility of these regions to observation. However it is widely agreed that experiments performed on synthetic mantle rocks [e.g KZK10] act as a reasonable test of theoretical models of magma dynamics. One robust feature of experiments on partially molten mantle rocks deformed under strain is the emergence of high-porosity bands at an angle of between 15° and 20° to the shear plane. A number of theoretical approaches have been made to reproduce the formation of these low angle bands in models. The most recent approaches, for example by Takei and Katz [TK13], have involved the inclusion of anisotropic viscosity in diffusion creep arising from the grain-scale redistribution of melt as formulated in a theoretical model by Takei and Holtzman [TH09]. It is reasonable to assume that this melt-preferred orientation (MPO) that leads to anisotropy in viscosity may also lead to anisotropy in permeability. However, the effect of anisotropic permeability remains unexplored. We investigate its impact on the dynamics of partially molten rock, and specifically on its role in low-angle band formation in deformation under simple shear. We work with the continuum model of two-phase-flow as formulated by McKenzie [M84] with the addition of anisotropic permeability. There are some apparent inconsistencies in this model. Firstly, the model predicts continued segregation of melt into bands of 100% porosity, while experiments report maximum porosities in the region of 30%. Secondly, linear stability analyses find maximal growth-rates for porosity perturbations that vary on arbitrarily small length-scales. We study how the inclusion of surface forces into the model could regulate these effects. REFERENCES: KZK10 = King, Zimmerman, & Kohlstedt (2010), J Pet, 10.1093/petrology/egp062. TK13 = Takei & Katz (2013), JFM, 10.1017/jfm.2013.482. TH09 = Takei & Holtzman (2009a), JGR, 10

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

    SciTech Connect

    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 /sup 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.

  11. An automated pipeline for cortical surface generation and registration of the cerebral cortex

    NASA Astrophysics Data System (ADS)

    Li, Wen; Ibanez, Luis; Gelas, Arnaud; Yeo, B. T. Thomas; Niethammer, Marc; Andreasen, Nancy C.; Magnotta, Vincent A.

    2011-03-01

    The human cerebral cortex is one of the most complicated structures in the body. It has a highly convoluted structure with much of the cortical sheet buried in sulci. Based on cytoarchitectural and functional imaging studies, it is possible to segment the cerebral cortex into several subregions. While it is only possible to differentiate the true anatomical subregions based on cytoarchitecture, the surface morphometry aligns closely with the underlying cytoarchitecture and provides features that allow the surface of the cortex to be parcellated based on the sulcal and gyral patterns that are readily visible on the MR images. We have developed a fully automated pipeline for the generation and registration of cortical surfaces in the spherical domain. The pipeline initiates with the BRAINS AutoWorkup pipeline. Subsequently, topology correction and surface generation is performed to generate a genus zero surface and mapped to a sphere. Several surface features are then calculated to drive the registration between the atlas surface and other datasets. A spherical diffeomorphic demons algorithm is used to co-register an atlas surface onto a subject surface. A lobar based atlas of the cerebral cortex was created from a manual parcellation of the cortex. The atlas surface was then co-registered to five additional subjects using a spherical diffeomorphic demons algorithm. The labels from the atlas surface were warped on the subject surface and compared to the manual raters. The average Dice overlap index was 0.89 across all regions.

  12. Surface altered zeolites as permeable barriers for in situ treatment of contaminated groundwater

    SciTech Connect

    1996-11-01

    The authors characterized surfactant-modified zeolite (SMZ) for its ability to sorb organic and inorganic contaminants from water. The ultimate objective is to use SMZ as a permeable barrier to prevent migration of contaminants in groundwater. This report summarizes results under Phase 1 of a three-phase project leading to a full-scale field demonstration of SMZ permeable- barrier technology.

  13. SURFACE-ALTERED ZEOLITES AS PERMEABLE BARRIERS FOR IN SITU TREATMENT OF CONTAMINATED GROUNDWATER

    SciTech Connect

    Robert S. Bowman; Zhaohui Li; Stephen J. Roy; Todd Burt; Timothy L. Johnson; Richard L. Johnson

    1999-08-30

    The overall objective of this effort is to develop and test a zeolite-based permeable barrier system for containing and remediating contaminated groundwater. The projected product is an engineered and tested permeable barrier system that can be adopted by the commercial sector.

  14. Changes in the permeability and morphology of dentine surfaces after brushing with a Thai herbal toothpaste: A preliminary study

    PubMed Central

    Vajrabhaya, La-ongthong; Korsuwannawong, Suwanna; Harnirattisai, Choltacha; Teinchai, Chayada

    2016-01-01

    Objectives: The aim of this study was to evaluate dentine permeability after brushing with Twin Lotus®, Thai herbal toothpaste by comparing with Sensodyne Rapid Relief®, a commercial desensitizing toothpaste, and also after artificial saliva (AS) immersion or citric acid challenge. Materials and Methods: Dentine discs from human mandibular third molars were divided into three groups (n = 20) and brushed with either experimental toothpaste or water (control) for 2 min with an automated toothbrush. Then, 10 discs were immersed in AS, and the other 10 discs were immersed in 6% citric acid to simulate the conditions of the oral environment. The dentine permeability of each specimen was measured before brushing and after each treatment using a fluid filtration system. Morphological changes in the dentine were observed using scanning electron microscopy (SEM). Results: Both toothpastes significantly reduced dentine permeability, and a crystalline precipitate was observed on the dentine surface under SEM observation. No significant difference was found between the two toothpaste groups with regard to dentine permeability after brushing and AS or acid immersion. Conclusions: The dentine permeability reduction caused by the two toothpastes did not differ after brushing or after AS or citric acid immersion. PMID:27095904

  15. Effect of dDAVP on basolateral cell surface water permeability in the outer medullary collecting duct.

    PubMed

    Solenov, E I; Nesterov, V V; Baturina, G S; Khodus, G R; Ivanova, L N

    2003-11-01

    We report a novel approach for assessing the volume of living cells which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The aim of this study was to evaluate the short-term effect of vasopressin on basolateral cell surface water permeability in the outer medullary collecting duct (OMCD). The permeability of the basolateral cell membrane was determined in the tubules where the apical membrane was blocked with oil injected into the lumen. The apparent coefficient of water permeability (Pf) was evaluated by measuring the cell swelling after the step from hypertonic to isotonic medium (600 mosm to 300 mosm). Desmopressin (dDAVP) induced an increase of the basolateral Pf from 113.7+/-8.5 microm/s in control cells to 186.6+/-11.4 mum/s in micro-dissected fragments of the OMCD incubated in vitro (10(-7) M dDAVP, 30 min at 37 degrees C) (P<0.05). Mercury caused pronounced inhibition of basolateral water permeability (26.0+/-6.9 microm/s; P<0.05). The effect of mercury (1.0 mM HgCl2) was reversible: after washing the fragments with PBS for 20 min, Pf values were restored to the control levels (125.0+/-9.5 microm/s). The results of the study indicate the existence of a mechanism controlling the osmotic water permeability of the basolateral cell membrane in the OMCD epithelium.

  16. Optimized water vapor permeability of sodium alginate films using response surface methodology

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Xu, Jiachao; Gao, Xin; Fu, Xiaoting

    2013-11-01

    The water vapor permeability (WVP) of films is important when developing pharmaceutical applications. Films are frequently used as coatings, and as such directly influence the quality of the medicine. The optimization of processing conditions for sodium alginate films was investigated using response surface methodology. Single-factor tests and Box-Behnken experimental design were employed. WVP was selected as the response variable, and the operating parameters for the single-factor tests were sodium alginate concentration, carboxymethyl cellulose (CMC) concentration and CaCl2 solution immersion time. The coefficient of determination ( R 2) was 0.97, indicating statistical significance. A minimal WVP of 0.389 8 g·mm/(m2·h·kPa) was achieved under the optimum conditions. These were found to be a sodium alginate concentration, CMC concentration and CaCl2 solution immersion time at 8.04%, 0.13%, and 12 min, respectively. This provides a reference for potential applications in manufacturing film-coated hard capsule shells.

  17. Water Permeability Adjusts Resorption in Lung Epithelia to Increased Apical Surface Liquid Volumes.

    PubMed

    Schmidt, Hanna; Michel, Christiane; Braubach, Peter; Fauler, Michael; Neubauer, Daniel; Thompson, Kristin E; Frick, Manfred; Mizaikoff, Boris; Dietl, Paul; Wittekindt, Oliver H

    2016-11-04

    The apical surface liquid layer (ASL) covers the airways and forms a first line of defense against pathogens. Maintenance of ASL volume by airway epithelia is essential for maintaining lung function. The proteolytic activation of epithelial Na(+) channels (ENaC) is believed to be the dominating mechanism to cope with increases in ASL volumes. Alternative mechanisms, in particular increases in epithelial water permeability (Posm), have so far been regarded as rather less important. However, most studies mainly addressed immediate effects upon apical volume expansion (AVE) and increases in ASL. This study addresses the response of lung epithelia to long term AVE. NCI-H441 cells and primary human tracheal epithelial cells (hTEpC), both cultivated at air liquid interface conditions, were used as models for the lung epithelium. AVE was established by adding isotonic solution onto the apical surface of differentiated lung epithelia and time course of ASL volume restoration was assessed by the D2O dilution method. Concomitant ion transport was investigated in Ussing chambers. We identified a low resorptive state (lowRS) immediately after AVE, which coincided with proteolytic ion transport activation within 10 to 15 min after AVE. The main clearance of excess ASL occurred during a delayed (hours after AVE) high resorptive state (highRS), which did not correlate with ion transport activation. Instead, highRS onset coincided with an increase in Posm, which depended on aquapoprin upregulation. In summary, our data demonstrates that, besides to ion transport activation, modulation of Posm is a major mechanism to compensate long-term AVE in lung epithelia.

  18. An integrated software suite for surface-based analyses of cerebral cortex

    NASA Technical Reports Server (NTRS)

    Van Essen, D. C.; Drury, H. A.; Dickson, J.; Harwell, J.; Hanlon, D.; Anderson, C. H.

    2001-01-01

    The authors describe and illustrate an integrated trio of software programs for carrying out surface-based analyses of cerebral cortex. The first component of this trio, SureFit (Surface Reconstruction by Filtering and Intensity Transformations), is used primarily for cortical segmentation, volume visualization, surface generation, and the mapping of functional neuroimaging data onto surfaces. The second component, Caret (Computerized Anatomical Reconstruction and Editing Tool Kit), provides a wide range of surface visualization and analysis options as well as capabilities for surface flattening, surface-based deformation, and other surface manipulations. The third component, SuMS (Surface Management System), is a database and associated user interface for surface-related data. It provides for efficient insertion, searching, and extraction of surface and volume data from the database.

  19. An integrated software suite for surface-based analyses of cerebral cortex

    NASA Technical Reports Server (NTRS)

    Van Essen, D. C.; Drury, H. A.; Dickson, J.; Harwell, J.; Hanlon, D.; Anderson, C. H.

    2001-01-01

    The authors describe and illustrate an integrated trio of software programs for carrying out surface-based analyses of cerebral cortex. The first component of this trio, SureFit (Surface Reconstruction by Filtering and Intensity Transformations), is used primarily for cortical segmentation, volume visualization, surface generation, and the mapping of functional neuroimaging data onto surfaces. The second component, Caret (Computerized Anatomical Reconstruction and Editing Tool Kit), provides a wide range of surface visualization and analysis options as well as capabilities for surface flattening, surface-based deformation, and other surface manipulations. The third component, SuMS (Surface Management System), is a database and associated user interface for surface-related data. It provides for efficient insertion, searching, and extraction of surface and volume data from the database.

  20. Transalveolar osmotic and diffusional water permeability in intact mouse lung measured by a novel surface fluorescence method.

    PubMed

    Carter, E P; Matthay, M A; Farinas, J; Verkman, A S

    1996-09-01

    A surface fluorescence method was developed to measure transalveolar transport of water, protons, and solutes in intact perfused lungs. Lungs from c57 mice were removed and perfused via the pulmonary artery (approximately 2 ml/min). The airspace was filled via the trachea with physiological saline containing a membrane-impermeant fluorescent indicator (FITC-dextran or aminonapthalene trisulfonic acid, ANTS). Because fluorescence is detected only near the lung surface due to light absorption by lung tissue, the surface fluorescence signal is directly proportional to indicator concentration. Confocal microscopy confirmed that the fluorescence signal arises from fluorophores in alveoli just beneath the pleural surface. Osmotic water permeability (Pf) was measured from the time course of intraalveolar FITC-dextran fluorescence in response to changes in perfusate osmolality. Transalveolar Pf was 0.017 +/- 0.001 cm/s at 23 degrees C, independent of the solute used to induce osmosis (sucrose, NaCl, urea), independent of osmotic gradient size and direction, weakly temperature dependent (Arrhenius activation energy 5.3 kcal/mol) and inhibited by HgCl2. Pf was not affected by cAMP activation but was decreased by 43% in lung exposed to hyperoxia for 5 d. Diffusional water permeability (Pd) and Pf were measured in the same lung from intraalveolar ANTS fluorescence, which increased by 1.8-fold upon addition of 50% D2O to the perfusate, Pd was 1.3 x 10(-5) cm/s at 23 degrees C. Transalveolar proton transport was measured from FITC-dextran fluorescence upon switching perfusate pH between 7.4 and 5.6; alveolar pH half-equilibrated in 1.9 and 1.0 min without and with HCO3-, respectively. These results indicate high transalveolar water permeability in mouse lung, implicating the involvement of molecular water channels, and establish a quantitative surface fluorescence method to measure water and solute permeabilities in intact lung.

  1. The Influence of Selected Liquid and Soil Properties on the Propagation of Spills over Flat Permeable Surfaces

    SciTech Connect

    Keller, Jason M.; Simmons, Carver S.

    2005-02-15

    In an effort to determine spill characteristics, information about a spill's spatial distribution with time is being studied. For permeable surfaces, spill phenomenology is controlled by liquid and soil properties, the most relevant of which are presented in this report. The pertinent liquid and soil properties were tabulated for ten liquids and four soils. The liquids represented an array of organic compounds, some of which are or are soon to be documented in the liquid spectra library by the Environmental Molecular Science Laboratory at Pacific Northwest National Laboratory. The soils were chosen based on ongoing surface spectra work and to represent a range of relevant soil properties. The effect of the liquid and soil properties on spill phenomenology were explored using a spill model that couples overland flow described by gravity currents with the Green-Ampt infiltration model. From the simulations, liquid viscosity was found to be a controlling liquid property in determining the amount of time a spill remains on the surface, with the surface vanish time decreasing as viscosity decreased. This was attributed to decreasing viscosity increasing both the hydraulic conductivity of the soil and allowing for the spill to more quickly spread out onto an unsaturated soil surface. Soil permeability also controlled vanish times with the vanish times increasing as permeability decreased, corresponding to finer textured materials. Maximum spill area was found to be largely controlled by liquid viscosity on coarse, highly permeable soils. On the less permeable soils maximum spill area began to be controlled by the steady-area spill height due to the restricting of infiltration to the extent that the spill is then able to reach its steady-area spill height. Simulations performed with and without the inclusion of capillarity in the Green-Ampt infiltration model displayed the importance of capillarity in describing infiltration rate in fine textured soils. In coarse textured

  2. Focal cerebral ischemic tolerance and change in blood-brain barrier permeability after repetitive pure oxygen exposure preconditioning in a rodent model.

    PubMed

    Wang, Xi; Kang, Kai; Wang, Shiquan; Yao, Jianhua; Zhang, Xijing

    2016-10-01

    A significant increase in PaO2 was seen after O2PC. The neurological score was significantly increased in the O2PC groups (10.6 ± 0.6 in the 3-day O2PC group, p < 0.05; 12 ± 0.84 in the 7-day O2PC group, p < 0.05) compared with the control group (7 ± 0.55). The ratio of cerebral infarct volume to contralateral cerebral hemisphere volume was significantly lower in the O2PC group than in the control group (0.204 ± 0.03 vs 0.48 ± 0.05, p < 0.05). The amount of leaked EB in the ischemic cerebral hemisphere was also lower in the O2-treated rats than in controls (7.53 ± 1.4 vs 11.79 ± 3.3 μg EB/g brain weight, p < 0.05). However, fluorescence microscopy showed significantly greater BBB permeability in the nonischemic areas in the O2PC group than in controls (p < 0.05). More red fluorescence could be observed in the nonischemic areas in both the ipsilateral and contralateral sides of the ischemic brain in the O2PC animals than in the nonischemic areas in the corresponding sides of the controls. Further investigation of the effect of the O2PC itself on the BBB of rats that were not subjected to MCAO showed that there was no EB leakage in the brain parenchyma in the rats exposed to room air, but some red fluorescence patches were noticed in the normal brain from the rats in the O2PC group. Astrocytes, including those from areas around the BBB, were activated in the O2PC group. Levels of both aquaporin 4 (AQP4) and vascular endothelial growth factor (VEGF) were significantly increased in cultured astrocytes after O2PC. CONCLUSIONS These findings suggest that O2PC is able to induce IT, which makes it a strong candidate for clinical use. Moreover, O2PC can also promote BBB opening, which may contribute to the induction of IT as well as representing a possible strategy for promoting drug transportation into the CNS. Activated astrocytes are likely to be involved in these processes through astrocyte-derived factors, such as AQP4 and VEGF.

  3. Apical membrane potassium and chloride permeabilities in surface cells of rabbit descending colon epithelium.

    PubMed Central

    Wills, N K

    1985-01-01

    The apical membranes of surface cells in the rabbit descending colon possess a significant ionic conductance in parallel to amiloride-blockable Na+ channels. The identity of the ion(s) responsible for the amiloride-insensitive conductance is unknown. The purpose of the present paper was to assess the permeability and net driving forces for K+ and Cl- across this membrane using conventional and ion-sensitive micro-electrode techniques. Intracellular Cl- activity (aiCl) averaged 23 +/- 2 mM with an equilibrium potential (ECl) of -38 +/- 2 mV. This value is less than previous estimates of the electromotive force (e.m.f.) of the amiloride-insensitive pathway (ca. -50 mV). Consequently, Cl- alone cannot account for the amiloride-insensitive conductance. Replacement of Cl- by gluconate in the serosal solution decreased aiCl to 17 +/- 2.8 mM. aiCl was lowered to approximately 1 mM by replacement in the mucosal bath or by replacement in both solutions. The results indicate a low Cl- conductance in the basolateral membrane, in agreement with previous electrophysiological studies of this epithelium. In contrast to Cl-, the chemical driving force for K+ was large enough to support the e.m.f. of the amiloride-insensitive pathway (K+ equilibrium potential, EK = -66 mV). The basolateral membrane potential (Vbl), EK and the intracellular K+ activity (aiK) were decreased in parallel following inhibition of the basolateral Na-K pump, providing evidence that Vbl is largely due to a K+ diffusion potential. In the presence of serosal 10(-4) M-ouabain, aiK appeared to remain above equilibrium and more than doubled after addition of Ba2+ to the serosal bath. Replacement of the mucosal bathing solution with KCl or gluconate Ringer solution largely restored Vbl and the transepithelial potential (VT) in tissues which had been previously treated with ouabain. The restoration of VT was decreased and the transepithelial resistance (RT) was increased by addition of tetraethylammonium to the

  4. Surface Vulnerability of Cerebral Cortex to Major Depressive Disorder

    PubMed Central

    Li, Gang; Fralick, Drew; Shen, Ting; Qiu, Meihui; Liu, Jun; Jiang, Kaida; Shen, Dinggang; Fang, Yiru

    2015-01-01

    Major depressive disorder (MDD) is accompanied by atypical brain structure. This study first presents the alterations in the cortical surface of patients with MDD using multidimensional structural patterns that reflect different neurodevelopment. Sixteen first-episode, untreated patients with MDD and 16 matched healthy controls underwent a magnetic resonance imaging (MRI) scan. The cortical maps of thickness, surface area, and gyrification were examined using the surface-based morphometry (SBM) approach. Increase of cortical thickness was observed in the right posterior cingulate region and the parietal cortex involving the bilateral inferior, left superior parietal and right paracentral regions, while decreased thickness was noted in the parietal cortex including bilateral pars opercularis and left precentral region, as well as the left rostral-middle frontal regions in patients with MDD. Likewise, increased or decreased surface area was found in five sub-regions of the cingulate gyrus, parietal and frontal cortices (e.g., bilateral inferior parietal and superior frontal regions). In addition, MDD patients exhibited a significant hypergyrification in the right precentral and supramarginal region. This integrated structural assessment of cortical surface suggests that MDD patients have cortical alterations of the frontal, parietal and cingulate regions, indicating a vulnerability to MDD during earlier neurodevelopmental process. PMID:25793287

  5. Functional and structural mapping of human cerebral cortex: solutions are in the surfaces

    NASA Technical Reports Server (NTRS)

    Van Essen, D. C.; Drury, H. A.; Joshi, S.; Miller, M. I.

    1998-01-01

    The human cerebral cortex is notorious for the depth and irregularity of its convolutions and for its variability from one individual to the next. These complexities of cortical geography have been a chronic impediment to studies of functional specialization in the cortex. In this report, we discuss ways to compensate for the convolutions by using a combination of strategies whose common denominator involves explicit reconstructions of the cortical surface. Surface-based visualization involves reconstructing cortical surfaces and displaying them, along with associated experimental data, in various complementary formats (including three-dimensional native configurations, two-dimensional slices, extensively smoothed surfaces, ellipsoidal representations, and cortical flat maps). Generating these representations for the cortex of the Visible Man leads to a surface-based atlas that has important advantages over conventional stereotaxic atlases as a substrate for displaying and analyzing large amounts of experimental data. We illustrate this by showing the relationship between functionally specialized regions and topographically organized areas in human visual cortex. Surface-based warping allows data to be mapped from individual hemispheres to a surface-based atlas while respecting surface topology, improving registration of identifiable landmarks, and minimizing unwanted distortions. Surface-based warping also can aid in comparisons between species, which we illustrate by warping a macaque flat map to match the shape of a human flat map. Collectively, these approaches will allow more refined analyses of commonalities as well as individual differences in the functional organization of primate cerebral cortex.

  6. Water Quality Performance of Three Side-by-Side Permeable Pavement Surface Materials: Three Year Update

    EPA Science Inventory

    Communities are increasingly installing structural low impact development (LID) practices to mange stormwater and reduce pollutant loads associated with stormwater runoff. Permeable pavement is a LID practice that has limited research on working-scale, side-by-side performance o...

  7. Light-controlled gas permeability of mesoporous silica glass bearing photochromic spironaphthoxazine on its surface.

    PubMed

    Yagi, Shigeyuki; Minami, Naemi; Fujita, Junpei; Hyodo, Yutaka; Nakazumi, Hiroyuki; Yazawa, Tetsuo; Kami, Tetsuro; Ali, Aliyar Hyder

    2002-10-21

    N2 and CO2 gas permeability of mesoporous silica glass bearing photochromic indolinospironaphth[2,1-b][1,4]oxazine through a covalent linkage was controlled by photo-irradiation: the photo-isomerization of the spironaphthoxazine to the photomerocyanine form suppressed the gas permeation of the glass.

  8. Water Quality Performance of Three Side-by-Side Permeable Pavement Surface Materials: Three Year Update

    EPA Science Inventory

    Communities are increasingly installing structural low impact development (LID) practices to mange stormwater and reduce pollutant loads associated with stormwater runoff. Permeable pavement is a LID practice that has limited research on working-scale, side-by-side performance o...

  9. Influence of a Magnetically Permeable Surface Layer on Transient Fields for a Thin Circular Loop Antenna

    NASA Astrophysics Data System (ADS)

    Sami, Ghada M.

    2004-04-01

    The transient fields, in the time-domain, of a thin circular loop antenna, on a two-layered earth’s model are reexamined when the usually neglected magnetic permeability contrast is considered. It is shown that for a two-layered earth model, where the upper layer is permeable, the transient fields are modified over the nonpermeable case. The fields in the time domain are obtained as the inverse Laplace transforms of derived full wave time-harmonic solution. These time-domain solutions are obtained as a summation of waveguide modes plus contributions from branch cuts in the complex plane of the longitudinal wave number. The results should be useful for interpreting airborne electromagnetic systems and in cases where super-paramagnetic mineral constant is present.

  10. SURFACE-ALTERED ZEOLITES AS PERMEABLE BARRIERS FOR IN SITU TREATMENT OF CONTAMINATED GROUNDWATER

    SciTech Connect

    Robert S. Bowman; Pengfei Zhang; Xian Tao

    2002-03-01

    This report summarizes experiments to develop and test surfactant-modified zeolite/zero-valent iron (SMZ/ZVI) pellets for permeable reactive barriers to treat groundwater contamination. Coating a glass foam core with a mixture of hexadecyltrimethylammonium surfactant, zeolite, and ZVI produced a high hydraulic conductivity, mechanically stable pellet. Laboratory experiments showed that the pellets completely removed soluble chromate from aqueous solution, and reduced perchloroethylene (PCE) concentrations more than pellets that lacked surfactant. Based upon the laboratory results, they predicted a 1-m-wide SMZ/ZVI barrier that would reduce PCE concentrations by four orders of magnitude. Thirteen cubic meters (470 cubic feet) of SMZ/ZVI pellets were manufactured and emplaced in a permeable barrier test facility. A controlled plume of chromate and PCE was allowed to contact the barrier for four weeks. The entire plume was captured by the barrier. No chromate was detected downgradient of the barrier. The PCE broke through the barrier after four weeks, and downgradient concentrations ultimately exceeded 10% of the influent PCE. The less-than-expected PCE reduction was attributed to insufficient surfactant content, the large size, and pH-altering characteristics of the bulk-produced pellets. The pellets developed here can be improved to yield a performance- and cost-competitive permeable barrier material.

  11. Entrance surface dose in cerebral interventional radiology procedures

    NASA Astrophysics Data System (ADS)

    Barrera-Rico, M.; López-Rendón, X.; Rivera-Ordóñez, C. E.; Gamboa-deBuen, I.

    2012-10-01

    At the Instituto Nacional de Neurología y Neurocirugía (INNN) diagnostic as well as therapeutic procedures of interventional radiology are carried out. Since the procedures can last from some minutes to several hours, the absorbed dose for the patient could increase dangerously. An investigation had begun in order to determine the entrance surface dose (ESD) using 25 thermoluminiscent dosimeters TLD-100 and 8 strips of 15 ×1 cm2 of Gafchromic XR-QA2 film bound in a holder of 15×15 cm2 in the posteroanterior (PA) and lateral (LAT) positions during all the procedure. The results show that maximum ESD could be from 0.9 to 2.9 Gy for the PA position and between 1.6 and 2.5 Gy for the lateral position. The average ESD was between 0.7 and 1.3 Gy for the PA position, and from 0.44 to 1.1 Gy for the lateral position in a therapeutic procedure.

  12. Entrance surface dose in cerebral interventional radiology procedures

    SciTech Connect

    Barrera-Rico, M.; Lopez-Rendon, X.; Rivera-Ordonez, C. E.; Gamboa-deBuen, I.

    2012-10-23

    At the Instituto Nacional de Neurologia y Neurocirugia (INNN) diagnostic as well as therapeutic procedures of interventional radiology are carried out. Since the procedures can last from some minutes to several hours, the absorbed dose for the patient could increase dangerously. An investigation had begun in order to determine the entrance surface dose (ESD) using 25 thermoluminiscent dosimeters TLD-100 and 8 strips of 15 Multiplication-Sign 1 cm{sup 2} of Gafchromic XR-QA2 film bound in a holder of 15 Multiplication-Sign 15 cm{sup 2} in the posteroanterior (PA) and lateral (LAT) positions during all the procedure. The results show that maximum ESD could be from 0.9 to 2.9 Gy for the PA position and between 1.6 and 2.5 Gy for the lateral position. The average ESD was between 0.7 and 1.3 Gy for the PA position, and from 0.44 to 1.1 Gy for the lateral position in a therapeutic procedure.

  13. Decreased muscle capillary permeability surface area in type 2 diabetic subjects.

    PubMed

    Gudbjörnsdóttir, Soffia; Sjöstrand, Mikaela; Strindberg, Lena; Lönnroth, Peter

    2005-02-01

    Capillary recruitment in muscles, induced by insulin, has been proposed to be impaired in insulin-resistant states. To elucidate the mechanisms regulating capillary transport of insulin and glucose in type 2 diabetes, we directly calculated the permeability-surface area product (PS) for glucose and insulin in muscle. Intramuscular microdialysis in combination with the forearm model and blood flow measurements was performed in type 2 diabetic male subjects and age- and weight-matched controls during a euglycemic-hyperinsulinemic clamp. During steady-state hyperinsulinemia, arterial plasma glucose was 5.8 +/- 0.1 and 5.9 +/- 0.1 mmol/liter [not significant (NS)] in the obese and type 2 diabetic subjects, respectively. Venous glucose was significantly lower in the obese group compared with the type 2 diabetic subjects, 4.3 +/- 02 vs. 4.9 +/- 0.2 mmol/liter (P < 0.05). Arterial insulin was 1494 +/- 90 and 1458 +/- 132 pmol/liter (NS) in the obese and type 2 diabetic subjects, respectively. The glucose infusion rate during steady-state hyperinsulinemia was 10.8 +/- 0.8 and 7.2 +/- 0.4 mg/kg.min in the obese and diabetic subjects, respectively (P < 0.01). Interstitial-arterial lactate difference was significantly higher in the obese subjects. During steady-state hyperinsulinemia, PS for glucose was significantly higher in the obese subjects (1.1 +/- 0.2 vs. 0.5 +/- 0.1 ml/min.100 g, P < 0.05). Glucose uptake was also significantly higher in the obese subjects (3.0 +/- 0.4 vs. 1.8 +/- 0.3 mumol/min.100 g, P < 0.05). During steady-state hyperinsulinemia, PS for insulin was 0.4 +/- 0.1 and 0.3 +/- 0.1 ml/min.100 g in the obese and diabetic subjects, respectively (NS), and insulin uptake was 258 +/- 54 vs. 168 +/- 24, respectively (NS). When both subject groups were pooled together, a significant correlation was found between PS for glucose and glucose uptake during steady-state hyperinsulinemia. Skeletal muscle blood flow during steady-state hyperinsulinemia was 1.9 +/- 0

  14. Surface-subsurface turbulent interaction at the interface of a permeable bed: physical modeling of coarse-gravel river bed

    NASA Astrophysics Data System (ADS)

    Kim, T.; Blois, G.; Best, J.; Christensen, K. T.

    2016-12-01

    Coarse-gravel river beds posses 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 biogeochemical processes as well as stability of sediments. Yet, the flow physics in the vicinity of a permeable interface are still poorly understood. This is in part due to a lack of quantitative direct observations near and within the wall. The latter are particularly challenging to conduct in field survey. For this reason, in this work we conduct controlled experiments on a physical model of a gravel bed. We consider an idealized permeable bed and use Refractive index matching (RIM) technique coupled with particle image velocimetry (PIV) to minimize the optical aberration and light reflection at the solid-liquid interface and thus to accurately quantify such flow interactions. A number of idealized acrylic wall models, based on spheres, were considered herein. Two different porous structures, were used to vary the permeability: simple cubic and body centered tetragonal arrangements. Additionally, two different topographies (smooth vs cubically arranged hemispheres) were considered for each wall structure. Measurements in the streamwise and wall-normal (x-y) plane were performed at two spanwise locations, one of which is along the top of the roughness elements and the other is along the valley side between neighboring spheres. These flow measurements, covering one wavelength of the roughness element, enable us to utilize double-averaging method to extract statistically-significant velocity profiles. In this paper, a detailed analysis of the first and second order velocity statistics associated with the different wall models will be presented.

  15. Permeability, porosity, and mineral surface area changes in basalt cores induced by reactive transport of CO2-rich brine

    NASA Astrophysics Data System (ADS)

    Luhmann, Andrew J.; Tutolo, Benjamin M.; Bagley, Brian C.; Mildner, David F. R.; Seyfried, William E.; Saar, Martin O.

    2017-03-01

    Four reactive flow-through laboratory experiments (two each at 0.1 mL/min and 0.01 mL/min flow rates) at 150°C and 150 bar (15 MPa) are conducted on intact basalt cores to assess changes in porosity, permeability, and surface area caused by CO2-rich fluid-rock interaction. Permeability decreases slightly during the lower flow rate experiments and increases during the higher flow rate experiments. At the higher flow rate, core permeability increases by more than one order of magnitude in one experiment and less than a factor of two in the other due to differences in preexisting flow path structure. X-ray computed tomography (XRCT) scans of pre- and post-experiment cores identify both mineral dissolution and secondary mineralization, with a net decrease in XRCT porosity of ˜0.7%-0.8% for the larger pores in all four cores. (Ultra) small-angle neutron scattering ((U)SANS) data sets indicate an increase in both (U)SANS porosity and specific surface area (SSA) over the ˜1 nm to 10 µm scale range in post-experiment basalt samples, with differences due to flow rate and reaction time. Net porosity increases from summing porosity changes from XRCT and (U)SANS analyses are consistent with core mass decreases. (U)SANS data suggest an overall preservation of the pore structure with no change in mineral surface roughness from reaction, and the pore structure is unique in comparison to previously published basalt analyses. Together, these data sets illustrate changes in physical parameters that arise due to fluid-basalt interaction in relatively low pH environments with elevated CO2 concentration, with significant implications for flow, transport, and reaction through geologic formations.

  16. Permeability and porosity images based on P-wave surface seismic data: Application to a south Florida aquifer

    NASA Astrophysics Data System (ADS)

    Parra, Jorge O.; Hackert, Chris L.; Bennett, Michael W.

    2006-02-01

    P-wave surface seismic reflection data, acquired from a carbonate aquifer in southeastern Florida, are used to delineate flow units in a proposed aquifer storage and recovery (ASR) horizon. The impedance image determined by inversion from P-wave reflection data captures most of the boundaries between hydraulic facies. The hydraulic facies properties are based on integration of the well logs and the lithology, which consists of vuggy carbonate units and sandstones. Within the proposed ASR horizon, located in the upper Floridan aquifer, low-permeability zones consist of sandstones and highly permeable zones are carbonates with interconnected vuggy porosity. High-resolution porosity, permeability, and impedance images based on cross-well reflection and well logs help us evaluate the P-wave seismic reflection results. We use well logs and cross-well seismic data to support whether two-dimensional seismic reflection measurements detect important flow units delineated by cross-well high-resolution seismic data. The data analysis demonstrates that major flow units are resolved and imaged with two-dimensional seismic reflection techniques, although not as clearly as in the high-resolution cross-well data. The results suggest that the surface seismic reflection method, integrated with well logs and geology, provides the tools to assess water resources in this south Florida carbonate aquifer. However, we recommend conducting a cross-well survey in areas where an understanding of the petrophysics is imperative to relating the seismic attributes to rock and fluid properties. This can be a critical step for planning purposes when considering a large surface-oriented seismic survey.

  17. [Reducing centers on the surface of Escherichia coli bacteria and their role in copper-induced plasma membrane permeability].

    PubMed

    Lebedev, V S; Veselovskiĭ, A V; Deĭnega, E Iu; Fedorov, Iu I

    2000-01-01

    The reducing properties of Escherichia coli and their role in the induction of nonselective cationic permeability of plasma membrane by the action of Cu2+ ions were studied. The ability of cells to reduce exogenous dithiopyridine was shown to be maximal in freshly collected culture and to decrease upon starvation or exhaustion of bacteria by dinitrophenol, in the presence of other oxidants of cell thiols in the medium, and after the disturbance of the barrier properties of membrane by tetrachloracetic acid or butanol. The alkylation of cell thiols accessible for N-ethyl maleimide completely disrupted the reducing activity of bacteria. These data are consistent with the conception that the reduction of dithiopyridine and Cu2+ ions by bacteria occurs on the thiol-containing centers of the cell surface, which are continuously reduced by the transfer of cell reducing equivalents from the inner to the outer surface of plasma membrane. The analysis of data on the effect of external oxidizing and reducing agents on the copper-induced plasmolysis of bacteria showed that the induction of membrane permeability by the action of copper can occur upon interaction with critical targets on the surface of Cu+ ions formed in the periplasmic space in the reaction of Cu2+ ions with reducing centers.

  18. A micro-aerodynamic decelerator based on permeable surfaces of nanofiber mats

    NASA Astrophysics Data System (ADS)

    Zussman, E.; Yarin, A. L.; Weihs, D.

    2002-05-01

    This work deals with nonwoven permeable light mats made of submicron-diameter nanofibers. The nanofibers were obtained through electrospinning of polymer solutions. The mats were positioned on light pyramid-shaped frames. These platforms fell freely through the air, apex down, at a constant velocity. The drag of such passive airborne platforms is of significant interest in a number of modern aerodynamics applications including, for example, dispersion of "smart dust" carrying various chemical and thermal sensors, dispersion of seeds, as well as movement of small organisms with bristle appendages. In the present work, drag is measured using the free fall method supplemented by extensive flow visualization. The effects of platform weight, average nanofiber diameter, and porosity of the nonwoven mats on the drag force are studied. The results are compared to data for the corresponding impermeable structures that are covered with plastic wrap. The data are presented in the form of standard dependencies of drag coefficient on the Reynolds number of the structure. It was found that permeable platforms with holes on the order of several microns (which is about ten times the diameter of the nanofibers) are essentially impermeable for airflow.

  19. Functional specializations in human cerebral cortex analyzed using the Visible Man surface-based atlas

    NASA Technical Reports Server (NTRS)

    Drury, H. A.; Van Essen, D. C.

    1997-01-01

    We used surface-based representations to analyze functional specializations in the human cerebral cortex. A computerized reconstruction of the cortical surface of the Visible Man digital atlas was generated and transformed to the Talairach coordinate system. This surface was also flattened and used to establish a surface-based coordinate system that respects the topology of the cortical sheet. The linkage between two-dimensional and three-dimensional representations allows the locations of published neuroimaging activation foci to be stereotaxically projected onto the Visible Man cortical flat map. An analysis of two activation studies related to the hearing and reading of music and of words illustrates how this approach permits the systematic estimation of the degree of functional segregation and of potential functional overlap for different aspects of sensory processing.

  20. Permeability and kinetic coefficients for mesoscale BCF surface step dynamics: Discrete two-dimensional deposition-diffusion equation analysis

    SciTech Connect

    Zhao, Renjie; Evans, James W.; Oliveira, Tiago J.

    2016-04-08

    Here, a discrete version of deposition-diffusion equations appropriate for description of step flow on a vicinal surface is analyzed for a two-dimensional grid of adsorption sites representing the stepped surface and explicitly incorporating kinks along the step edges. Model energetics and kinetics appropriately account for binding of adatoms at steps and kinks, distinct terrace and edge diffusion rates, and possible additional barriers for attachment to steps. Analysis of adatom attachment fluxes as well as limiting values of adatom densities at step edges for nonuniform deposition scenarios allows determination of both permeability and kinetic coefficients. Behavior of these quantities is assessed as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.

  1. Permeability and kinetic coefficients for mesoscale BCF surface step dynamics: Discrete two-dimensional deposition-diffusion equation analysis

    DOE PAGES

    Zhao, Renjie; Evans, James W.; Oliveira, Tiago J.

    2016-04-08

    Here, a discrete version of deposition-diffusion equations appropriate for description of step flow on a vicinal surface is analyzed for a two-dimensional grid of adsorption sites representing the stepped surface and explicitly incorporating kinks along the step edges. Model energetics and kinetics appropriately account for binding of adatoms at steps and kinks, distinct terrace and edge diffusion rates, and possible additional barriers for attachment to steps. Analysis of adatom attachment fluxes as well as limiting values of adatom densities at step edges for nonuniform deposition scenarios allows determination of both permeability and kinetic coefficients. Behavior of these quantities is assessedmore » as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.« less

  2. Unsteady boundary layer flow of Carreau fluid over a permeable stretching surface

    NASA Astrophysics Data System (ADS)

    Khan, Masood; Azam, Muhammad

    The main objective of the present work is to present numerical solutions of the unsteady two-dimensional boundary layer flow and heat transfer of an incompressible Carreau fluid over a permeable time dependent stretching sheet. Using suitable transformations, the time dependent partial differential equations are converted to non-linear ordinary differential equations. The numerical results of these non-linear ordinary differential equations with associated boundary conditions are determined by using the bvp4c function in MATLAB. The numerical results are investigated for the emerging parameters namely, the unsteadiness parameter A, mass transfer parameter S, Prandtl number Pr, power law index n and Weissenberg number We. It is important to state that both the momentum and thermal boundary layer thicknesses diminish with increasing values of the unsteadiness and mass transfer parameters. A comparison with the available literature in limiting cases is performed and found to be in good agreement.

  3. Influence of the surface permeability on the GRACE water mass variations. Case of the Lake Chad basin.

    NASA Astrophysics Data System (ADS)

    Lopez, Teodolina; Ramillien, Guillaume; Antoine, Raphaël; Rabinowicz, Michel

    2017-04-01

    Since its launch in 2002, the Gravity Recovery And Climate Experiment (GRACE) has been measured the tiny variations of the gravity field due to redistributions of water mass in the surface envelops of Earth. At a spatial resolution of 400 km, these satellite data offer a unique perspective to understand the evolution of continental water storage at regional and global scales, and therefore they enable the monitoring of the hydrological systems such as river basins. It is well known that seasonal cycle, droughts, vegetation and human extractions are the main contributors of the hydrology signals sensed by GRACE. However, the coupling between land surface and the atmosphere is important in semi-arid and arid regions, in particular in West Africa. We propose to quantify the surface water fluxes in the Lake Chad region by using the daily (and 10-day) water mass solutions of the GRACE mission in the context of the regular West African monsoon. Alternation of the evaporation/condensation cycles during the recent period are interpreted in terms of surface vertical permeability changes that control the thermal evolution in this region [2]. GRACE solutions reveal an interannual increase of surface water mass during dry seasons, especially in 2005 and 2007. We propose that this gain of surface water mass is caused by a seasonal cycle of clay fracturing. [1] Koster et al. (2004). Science, 305, 1138-1140. [2] Lopez et al. (2016). Surv. Geophys., 37 (2), 471-502.

  4. Structural and functional analyses of human cerebral cortex using a surface-based atlas

    NASA Technical Reports Server (NTRS)

    Van Essen, D. C.; Drury, H. A.

    1997-01-01

    We have analyzed the geometry, geography, and functional organization of human cerebral cortex using surface reconstructions and cortical flat maps of the left and right hemispheres generated from a digital atlas (the Visible Man). The total surface area of the reconstructed Visible Man neocortex is 1570 cm2 (both hemispheres), approximately 70% of which is buried in sulci. By linking the Visible Man cerebrum to the Talairach stereotaxic coordinate space, the locations of activation foci reported in neuroimaging studies can be readily visualized in relation to the cortical surface. The associated spatial uncertainty was empirically shown to have a radius in three dimensions of approximately 10 mm. Application of this approach to studies of visual cortex reveals the overall patterns of activation associated with different aspects of visual function and the relationship of these patterns to topographically organized visual areas. Our analysis supports a distinction between an anterior region in ventral occipito-temporal cortex that is selectively involved in form processing and a more posterior region (in or near areas VP and V4v) involved in both form and color processing. Foci associated with motion processing are mainly concentrated in a region along the occipito-temporal junction, the ventral portion of which overlaps with foci also implicated in form processing. Comparisons between flat maps of human and macaque monkey cerebral cortex indicate significant differences as well as many similarities in the relative sizes and positions of cortical regions known or suspected to be homologous in the two species.

  5. Structural and functional analyses of human cerebral cortex using a surface-based atlas

    NASA Technical Reports Server (NTRS)

    Van Essen, D. C.; Drury, H. A.

    1997-01-01

    We have analyzed the geometry, geography, and functional organization of human cerebral cortex using surface reconstructions and cortical flat maps of the left and right hemispheres generated from a digital atlas (the Visible Man). The total surface area of the reconstructed Visible Man neocortex is 1570 cm2 (both hemispheres), approximately 70% of which is buried in sulci. By linking the Visible Man cerebrum to the Talairach stereotaxic coordinate space, the locations of activation foci reported in neuroimaging studies can be readily visualized in relation to the cortical surface. The associated spatial uncertainty was empirically shown to have a radius in three dimensions of approximately 10 mm. Application of this approach to studies of visual cortex reveals the overall patterns of activation associated with different aspects of visual function and the relationship of these patterns to topographically organized visual areas. Our analysis supports a distinction between an anterior region in ventral occipito-temporal cortex that is selectively involved in form processing and a more posterior region (in or near areas VP and V4v) involved in both form and color processing. Foci associated with motion processing are mainly concentrated in a region along the occipito-temporal junction, the ventral portion of which overlaps with foci also implicated in form processing. Comparisons between flat maps of human and macaque monkey cerebral cortex indicate significant differences as well as many similarities in the relative sizes and positions of cortical regions known or suspected to be homologous in the two species.

  6. Chronic global analysis of vascular permeability and cerebral blood flow after bone marrow stromal cell treatment of traumatic brain injury in the rat: A long-term MRI study.

    PubMed

    Li, Lian; Chopp, Michael; Ding, Guangliang; Li, Qingjiang; Mahmood, Asim; Jiang, Quan

    2017-11-15

    Vascular permeability and hemodynamic alteration in response to the transplantation of human bone marrow stromal cells (hMSCs) after traumatic brain injury (TBI) were longitudinally investigated in non directly injured and normal-appearing cerebral tissue using magnetic resonance imaging (MRI). Male Wistar rats (300-350g, n=30) subjected to controlled cortical impact TBI were intravenously injected with 1ml of saline (at 6-h or 1-week post-injury, n=5/group) or with hMSCs in suspension (∼3×10(6) hMSCs, at 6-h or 1-week post-injury, n=10/group). MRI measurements of T2-weighted imaging, cerebral blood flow (CBF) and blood-to-brain transfer constant (Ki) of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA), and neurological behavioral estimates were performed on all animals at multiple time points up to 3-months post-injury. Our long-term imaging data show that blood-brain barrier (BBB) breakdown and hemodynamic disruption after TBI, as revealed by Ki and CBF, respectively, affect both hemispheres of the brain in a diffuse manner. Our data reveal a sensitive vascular permeability and hemodynamic reaction in response to the time-dependent transplantation of hMSCs. A more rapid reduction of Ki following cell treatment is associated with a higher level of CBF in the injured brain, and acute (6h) cell administration leads to enhanced therapeutic effects on both the recovery of vascular integrity and stabilization of cerebral perfusion compared to delayed (1w) cell engraftment. Our results indicate that cell-enhanced BBB reconstitution plays an important role in underlying the restoration of CBF in the injured brain, which in turn, contributes to the improvement of functional outcome. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Hydrogen permeability through beryllium films and the impact of surface oxides

    NASA Astrophysics Data System (ADS)

    Zajec, Bojan; Nemanič, Vincenc; Žumer, Marko; Porosnicu, Corneliu; Lungu, Cristian P.

    2013-11-01

    Beryllium will constitute the major part of the first wall of ITER, however, several aspects of the tritium retention and recycling in fusion reactors are still open. Studying details of the hydrogen isotope interactions on Be films is in principle easier and more accurate than on the bulk Be metal since a thin (and therefore more permeable) layer of Be film could be deposited on a desired substrate by applying well controlled methods. Results of the hydrogen permeation through 8 micrometer thick Be films deposited by the thermionic vacuum arc method on Eurofer steel membranes with exposed area of 8.4 cm2 are presented. The permeation reduction factor (PRF) at 400 °C varied on six samples from 14 to 135 with respect to the bare Eurofer membrane. The highest PRF value enables expression of the Be film permeability coefficient P by means of a simple model which gives PBe ˜ 2 × 10-15 mol H2/m s Pa0.5. Lower PRF values could be explained by microscopic imperfections which represent parallel hydrogen paths through the Be film and enhance the permeation rate. Some of them were revealed by the SEM while their presence could be confirmed also by observing permeation flux transients recorded after the hydrogen exposure. The two-step process of achieving the steady flux agrees with our numerical simulation. It was found that for unintentionally oxidized samples the extracted regular (eliminated contribution of the pinholes in Be film) permeation rate is almost identical from sample to sample and accounts to j ≈ 1.2 × 10-7 H2/m2 s at 1 bar hydrogen driving pressure due to BeO formation. For a non-oxidized sample this value is several times higher, j ≈ 6.5 × 10-7 mol H2/m2 s. From the latter follows that PBe ≈ 1.9 × 10-14 mol H2/m s Pa0.5, while PBeO ˜ 1 × 10-17 mol H2/m s Pa0.5 can be estimated by assuming a 35 nm thick BeO layer.

  8. Regional Cerebral Blood Flow (rCBF) in Developmental Dyslexia: Activation during Reading in a Surface and Deep Dyslexic.

    ERIC Educational Resources Information Center

    Hynd, George W.; And Others

    1987-01-01

    The exploratory study examined patterns of regional cerebral blood flow in a surface and a deep dyslexic during reading. Significant differences in gray matter blood flow were found between subjects and normal controls. Also differences existed between the surface and deep dyslexic in the distribution of cortical perfusion. (Author/DB)

  9. Regional Cerebral Blood Flow (rCBF) in Developmental Dyslexia: Activation during Reading in a Surface and Deep Dyslexic.

    ERIC Educational Resources Information Center

    Hynd, George W.; And Others

    1987-01-01

    The exploratory study examined patterns of regional cerebral blood flow in a surface and a deep dyslexic during reading. Significant differences in gray matter blood flow were found between subjects and normal controls. Also differences existed between the surface and deep dyslexic in the distribution of cortical perfusion. (Author/DB)

  10. A novel control algorithm for interaction between surface waves and a permeable floating structure

    NASA Astrophysics Data System (ADS)

    Tsai, Pei-Wei; Alsaedi, A.; Hayat, T.; Chen, Cheng-Wu

    2016-04-01

    An analytical solution is undertaken to describe the wave-induced flow field and the surge motion of a permeable platform structure with fuzzy controllers in an oceanic environment. In the design procedure of the controller, a parallel distributed compensation (PDC) scheme is utilized to construct a global fuzzy logic controller by blending all local state feedback controllers. A stability analysis is carried out for a real structure system by using Lyapunov method. The corresponding boundary value problems are then incorporated into scattering and radiation problems. They are analytically solved, based on separation of variables, to obtain series solutions in terms of the harmonic incident wave motion and surge motion. The dependence of the wave-induced flow field and its resonant frequency on wave characteristics and structure properties including platform width, thickness and mass has been thus drawn with a parametric approach. From which mathematical models are applied for the wave-induced displacement of the surge motion. A nonlinearly inverted pendulum system is employed to demonstrate that the controller tuned by swarm intelligence method can not only stabilize the nonlinear system, but has the robustness against external disturbance.

  11. Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance.

    PubMed

    Chang, Nai-Yuan N; Jew, Jamison M; Simon, Jacob C; Chen, Kenneth H; Lee, Robert C; Fried, William A; Cho, Jinny; Darling, Cynthia L; Fried, Daniel

    2017-07-12

    Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. Cell-Based in Vitro Blood–Brain Barrier Model Can Rapidly Evaluate Nanoparticles’ Brain Permeability in Association with Particle Size and Surface Modification

    PubMed Central

    Hanada, Sanshiro; Fujioka, Kouki; Inoue, Yuriko; Kanaya, Fumihide; Manome, Yoshinobu; Yamamoto, Kenji

    2014-01-01

    The possibility of nanoparticle (NP) uptake to the human central nervous system is a major concern. Recent reports showed that in animal models, nanoparticles (NPs) passed through the blood–brain barrier (BBB). For the safe use of NPs, it is imperative to evaluate the permeability of NPs through the BBB. Here we used a commercially available in vitro BBB model to evaluate the permeability of NPs for a rapid, easy and reproducible assay. The model is reconstructed by culturing both primary rat brain endothelial cells and pericytes to support the tight junctions of endothelial cells. We used the permeability coefficient (Papp) to determine the permeability of NPs. The size dependency results, using fluorescent silica NPs (30, 100, and 400 nm), revealed that the Papp for the 30 nm NPs was higher than those of the larger silica. The surface charge dependency results using Qdots® (amino-, carboxyl-, and PEGylated-Qdots), showed that more amino-Qdots passed through the model than the other Qdots. Usage of serum-containing buffer in the model resulted in an overall reduction of permeability. In conclusion, although additional developments are desired to elucidate the NPs transportation, we showed that the BBB model could be useful as a tool to test the permeability of nanoparticles. PMID:24469316

  13. Cell-based in vitro blood-brain barrier model can rapidly evaluate nanoparticles' brain permeability in association with particle size and surface modification.

    PubMed

    Hanada, Sanshiro; Fujioka, Kouki; Inoue, Yuriko; Kanaya, Fumihide; Manome, Yoshinobu; Yamamoto, Kenji

    2014-01-24

    The possibility of nanoparticle (NP) uptake to the human central nervous system is a major concern. Recent reports showed that in animal models, nanoparticles (NPs) passed through the blood-brain barrier (BBB). For the safe use of NPs, it is imperative to evaluate the permeability of NPs through the BBB. Here we used a commercially available in vitro BBB model to evaluate the permeability of NPs for a rapid, easy and reproducible assay. The model is reconstructed by culturing both primary rat brain endothelial cells and pericytes to support the tight junctions of endothelial cells. We used the permeability coefficient (P(app)) to determine the permeability of NPs. The size dependency results, using fluorescent silica NPs (30, 100, and 400 nm), revealed that the Papp for the 30 nm NPs was higher than those of the larger silica. The surface charge dependency results using Qdots® (amino-, carboxyl-, and PEGylated-Qdots), showed that more amino-Qdots passed through the model than the other Qdots. Usage of serum-containing buffer in the model resulted in an overall reduction of permeability. In conclusion, although additional developments are desired to elucidate the NPs transportation, we showed that the BBB model could be useful as a tool to test the permeability of nanoparticles.

  14. A new presentation and exploration of human cerebral vasculature correlated with surface and sectional neuroanatomy.

    PubMed

    Nowinski, Wieslaw L; Thirunavuukarasuu, Arumugam; Volkau, Ihar; Marchenko, Yevgen; Aminah, Bivi; Gelas, Arnaud; Huang, Su; Lee, Looi Chow; Liu, Jimin; Ng, Ting Ting; Nowinska, Natalia G; Qian, Guoyu Yu; Puspitasari, Fiftarina; Runge, Val M

    2009-01-01

    The increasing complexity of human body models enabled by advances in diagnostic imaging, computing, and growing knowledge calls for the development of a new generation of systems for intelligent exploration of these models. Here, we introduce a novel paradigm for the exploration of digital body models illustrating cerebral vasculature. It enables dynamic scene compositing, real-time interaction combined with animation, correlation of 3D models with sectional images, quantification as well as 3D manipulation-independent labeling and knowledge-related meta labeling (with name, diameter, description, variants, and references). This novel exploration is incorporated into a 3D atlas of cerebral vasculature with arteries and veins along with the surrounding surface and sectional neuroanatomy derived from 3.0 Tesla scans. This exploration paradigm is useful in medical education, training, research, and clinical applications. It enables development of new generation systems for rapid and intelligent exploration of complicated digital body models in real time with dynamic scene compositing from highly parcellated 3D models, continuous navigation, and manipulation-independent labeling with multiple features.

  15. Permeability of anti-fouling PEGylated surfaces probed by fluorescence correlation spectroscopy.

    PubMed

    Daniels, Charlisa R; Reznik, Carmen; Kilmer, Rachel; Felipe, Mary Jane; Tria, Maria Celeste R; Kourentzi, Katerina; Chen, Wen-Hsiang; Advincula, Rigoberto C; Willson, Richard C; Landes, Christy F

    2011-11-01

    The present work reports on in situ observations of the interaction of organic dye probe molecules and dye-labeled protein with different poly(ethylene glycol) (PEG) architectures (linear, dendron, and bottle brush). Fluorescence correlation spectroscopy (FCS) and single molecule event analysis were used to examine the nature and extent of probe-PEG interactions. The data support a sieve-like model in which size-exclusion principles determine the extent of probe-PEG interactions. Small probes are trapped by more dense PEG architectures and large probes interact more with less dense PEG surfaces. These results, and the tunable pore structure of the PEG dendrons employed in this work, suggest the viability of electrochemically-active materials for tunable surfaces.

  16. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells.

    PubMed

    Gao, Yunyi; Haso, Fadi; Szymanowski, Jennifer E S; Zhou, Jing; Hu, Lang; Burns, Peter C; Liu, Tianbo

    2015-12-14

    The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li48+m K12(OH)m [UO2(O2)(OH)]60-(H2O)n (m ≈ 20 and n ≈ 310) (U60) shows selective permeability to different alkali ions. The subnanometer pores on the water-ligand-rich surface of U60 are able to block Rb(+) and Cs(+) ions from passing through, while allowing Na(+) and K(+) ions, which possess larger hydrated sizes, to enter the interior space of U60. An interestingly high entropy gain during the binding process between U60 and alkali ions suggests that the hydration shells of Na(+)/K(+) and U60 are damaged during the interaction. The ion selectivity of U60 is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells

    SciTech Connect

    Gao, Yunyi; Haso, Fadi; Szymanowski, Jennifer E. S.; Zhou, Jing; Hu, Lang; Burns, Peter C.; Liu, Tianbo

    2015-11-16

    The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li48+mK12(OH)m[UO2(O2)(OH)]60-(H2O)n (m≈20 and n≈310) (U60) shows selective permeability to different alkali ions. The subnanometer pores on the water–ligand-rich surface of U60 are able to block Rb+ and Cs+ ions from passing through, while allowing Na+ and K+ ions, which possess larger hydrated sizes, to enter the interior space of U60. An interestingly high entropy gain during the binding process between U60 and alkali ions suggests that the hydration shells of Na+/K+ and U60 are damaged during the interaction. The ion selectivity of U60 is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells.

  18. Effect of Size and Surface Charge of Gold Nanoparticles on their Skin Permeability: A Molecular Dynamics Study.

    PubMed

    Gupta, Rakesh; Rai, Beena

    2017-03-28

    Molecular level understanding of permeation of nanoparticles through human skin establishes the basis for development of novel transdermal drug delivery systems and design and formulation of cosmetics. Recent experiments suggest that surface coated nano-sized gold nanoparticles (AuNPs) can penetrate the rat and human skin. However, the mechanisms by which these AuNPs penetrate are not well understood. In this study, we have carried out coarse grained molecular dynamics simulations to explore the permeation of dodecanethiol coated neutral hydrophobic AuNPs of different sizes (2-5 nm) and surface charges (cationic and anionic) through the model skin lipid membrane. The results indicate that the neutral hydrophobic AuNPs disrupted the bilayer and entered in it with in ~200 ns, while charged AuNPs were adsorbed on the bilayer headgroup. The permeation free energy calculation revealed that at the head group of the bilayer, a very small barrier existed for neutral hydrophobic AuNP while a free energy minimum was observed for charged AuNPs. The permeability was maximum for neutral 2 nm gold nanoparticle (AuNP) and minimum for 3 nm cationic AuNP. The obtained results are aligned with recent experimental findings. This study would be helpful in designing customized nanoparticles for cosmetic and transdermal drug delivery application.

  19. Effect of Size and Surface Charge of Gold Nanoparticles on their Skin Permeability: A Molecular Dynamics Study

    PubMed Central

    Gupta, Rakesh; Rai, Beena

    2017-01-01

    Molecular level understanding of permeation of nanoparticles through human skin establishes the basis for development of novel transdermal drug delivery systems and design and formulation of cosmetics. Recent experiments suggest that surface coated nano-sized gold nanoparticles (AuNPs) can penetrate the rat and human skin. However, the mechanisms by which these AuNPs penetrate are not well understood. In this study, we have carried out coarse grained molecular dynamics simulations to explore the permeation of dodecanethiol coated neutral hydrophobic AuNPs of different sizes (2–5 nm) and surface charges (cationic and anionic) through the model skin lipid membrane. The results indicate that the neutral hydrophobic AuNPs disrupted the bilayer and entered in it with in ~200 ns, while charged AuNPs were adsorbed on the bilayer headgroup. The permeation free energy calculation revealed that at the head group of the bilayer, a very small barrier existed for neutral hydrophobic AuNP while a free energy minimum was observed for charged AuNPs. The permeability was maximum for neutral 2 nm gold nanoparticle (AuNP) and minimum for 3 nm cationic AuNP. The obtained results are aligned with recent experimental findings. This study would be helpful in designing customized nanoparticles for cosmetic and transdermal drug delivery application. PMID:28349970

  20. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells

    NASA Astrophysics Data System (ADS)

    Gao, Yunyi; Szymanowski, Jennifer; Burns, Peter; Liu, Tianbo

    The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of ion transport mechanism through nanosized channels and offer new views for designing nanodevices. Here we reveal that a 2.5-nm-size, fullerene-shaped molecular cluster Li48+mK12(OH)m[UO2(O2) (OH)]60-(H2O)n (m ~20 and n ~310) (U60) shows selective permeability to different alkali ions. The sub-nanometer pores on the water-ligand-rich surface of U60 are able to block Rb+ and Cs+ ions from passing through, while allow Na+ and K+ ions, which possess larger hydrated sizes, to enter the interior space of U60. An interestingly high entropy gain during the binding process between U60 and alkali ions suggest that the hydration shells of Na+i/K+ and U60 are damaged during the interaction. The ion selectivity of U60 is greatly influenced by both the morphologies of surface nanopores and the dynamics of the hydration shells. This material is based upon work supported as part of the Materials Science of Actinides Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001089.

  1. Effect of Seat Surface Inclination on Postural Stability and forward Reaching Efficiency in Children with Spastic Cerebral Palsy

    ERIC Educational Resources Information Center

    Cherng, Rong-Ju; Lin, Hui-Chen; Ju, Yun-Huei; Ho, Chin-Shan

    2009-01-01

    The purpose of this study was to examine the effect of seat surface inclination on postural stability and forward reaching efficiency in 10 children with spastic cerebral palsy (CP) and 16 typically developing (TD) children. The children performed a static sitting and a forward reaching task while sitting on a height- and inclination-adjustable…

  2. Effect of Seat Surface Inclination on Postural Stability and forward Reaching Efficiency in Children with Spastic Cerebral Palsy

    ERIC Educational Resources Information Center

    Cherng, Rong-Ju; Lin, Hui-Chen; Ju, Yun-Huei; Ho, Chin-Shan

    2009-01-01

    The purpose of this study was to examine the effect of seat surface inclination on postural stability and forward reaching efficiency in 10 children with spastic cerebral palsy (CP) and 16 typically developing (TD) children. The children performed a static sitting and a forward reaching task while sitting on a height- and inclination-adjustable…

  3. Regional and Local Control of Arsenic Concentrations in Shallow Aquifers by the Permeability of Surface Soils

    NASA Astrophysics Data System (ADS)

    van Geen, A.; Aziz, Z.; Goodbred, S. L.; Zheng, Y.; Horneman, A.; Dhar, R.; Weinman, B.; Cheng, Z.; Stute, M.; Hoque, M. A.; Seddique, A. A.; Ahmed, K. M.

    2004-12-01

    One of the bewildering aspects of the current arsenic crisis in Bangladesh and other South Asian countries is the extreme degree of spatial variability of groundwater As concentrations. This presentation focuses on the origin of this variability in the top 20 meters of shallow aquifers by combining surface geophysical measurements (EM31) with groundwater and sediment properties obtained by modifying a local hand-drilling method in three contrasting areas of Bangladesh: (1) Birganj, in northwestern Bangladesh, where groundwater As concentrations rarely exceed 50 ug/L, (2) Araihazar, a central portion of the country where shallow groundwater As concentrations are highly variable, and (3) Lakshmipur, where essentially all shallow wells are elevated in As. Comparison with a series of auger cores collected in Araihazar indicates that the EM31 signal combines contributions related to the ionic strength of soil water as well as the proportion of fine-grained sediment. The combined set of observations shows a rather consistent relation between the conductivity of surface soils measured by induction and shallow groundwater As. In Birganj, EM31 conductivities rarely exceed 10 mS/m and can be below the detection limit of the instrument (~0.1 mS/m) over distances of 100s of meters. In Araihazar, areas with EM31 conductivities ranging form 10-15 mS/m are intermixed with regions with EM31 readings of 20-30 mS/m. The lower and higher EM31 conductivity ranges are generally associated with low and elevated As concentrations, respectively. In contrast, EM31 readings in the portion of Lakshmipur that was surveyed are consistently high and range from 30-50 mS/m. Overall, therefore, it appears that high groundwater As concentrations are typically associated with aquifers capped by fine-grained sediment whereas low groundwater As concentrations prevail in aquifers overlain by sandy deposits. This association, combined with gradual downstream fining of surface deposits of the Ganges

  4. Permeability of displaced fractures

    NASA Astrophysics Data System (ADS)

    Kluge, Christian; Milsch, Harald; Blöcher, Guido

    2017-04-01

    Flow along fractures or in fissured systems becomes increasingly important in the context of Enhanced Geothermal Systems (EGS), shale gas recovery or nuclear waste deposit. Commonly, the permeability of fractures is approximated using the Hagen-Poiseuille solution of Navier Stokes equation. Furthermore, the flow in fractures is assumed to be laminar flow between two parallel plates and the cubic law for calculating the velocity field is applied. It is a well-known fact, that fracture flow is strongly influenced by the fracture surface roughness and the shear displacement along the fracture plane. Therefore, a numerical approach was developed which calculates the flow pattern within a fracture-matrix system. The flow in the fracture is described by a free fluid flow and the flow in the matrix is assumed to be laminar and therefore validates Darcy's law. The presented approach can be applied for artificially generated fractures or real fractures measured by surface scanning. Artificial fracture surfaces are generated using the power spectral density of the surface height random process with a spectral exponent to define roughness. For calculating the permeability of such fracture-matrix systems the mean fracture aperture, the shear displacement and the surface roughness are considered by use of a 3D numerical simulator. By use of this approach correlation between shear displacement and mean aperture, shear displacement and permeability, as well as surface roughness and permeability can be obtained. Furthermore, the intrinsic measured permeability presents a combination of matrix and fracture permeability. The presented approach allows the separation and quantification of the absolute magnitudes of the matrix and the fracture permeability and the permeability of displaced fractures can be calculated. The numerical approach which is a 3D numerical simulation of the fracture-matrix system can be applied for artificial as well as real systems.

  5. Crustal permeability

    USGS Publications Warehouse

    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. 

  6. Influence of Crassostrea gigas on the permeability and microstructure of the surface layer of concrete exposed to the tidal zone of the Yellow Sea.

    PubMed

    Lv, JianFu; Mao, JiZe; Ba, HengJing

    2015-01-01

    Concrete exposed to the tidal zone of the Yellow Sea and bearing Crassostrea gigas (CG) with differing areal coverages was investigated for evidence of biologically induced corrosion prevention. The experimental results indicated that both the chloride ion profile and the neutralization depth of the concrete decreased with increasing CG coverage. Moreover, the water absorption rate and the chloride ion permeability of concrete with the original surface intact also declined with increasing degrees of CG coverage. However, the water absorption rates of three concrete samples with 2 mm of the surface layer removed were similar, as was their chloride ion permeability. Mercury intrusion porosimetry tests indicated that CG significantly reduced the pore structure of the concrete surface layer. SEM observation revealed that the CG cementation membrane and left valve were tightly glued to the concrete surface and had a dense structure. Concrete durability indices showed that high CG coverage greatly improved concrete durability.

  7. Permeable reactive barrier of surface hydrophobic granular activated carbon coupled with elemental iron for the removal of 2,4-dichlorophenol in water.

    PubMed

    Yang, Ji; Cao, Limei; Guo, Rui; Jia, Jinping

    2010-12-15

    Granular activated carbon was modified with dimethyl dichlorosilane to improve its surface hydrophobicity, and therefore to improve the performance of permeable reactive barrier constructed with the modified granular activated carbon and elemental iron. X-ray photoelectron spectroscopy shows that the surface silicon concentration of the modified granular activated carbon is higher than that of the original one, leading to the increased surface hydrophobicity. Although the specific surface area decreased from 895 to 835 m(2)g(-1), the modified granular activated carbon could adsorb 20% more 2,4-dichlorophenol than the original one did in water. It is also proven that the permeable reactive barrier with the modified granular activated carbon is more efficient at 2,4-dichlorophenol dechlorination, in which process 2,4-dichlorophenol is transformed to 2-chlorophenol or 4-chlorophenol then to phenol, or to phenol directly. Copyright © 2010 Elsevier B.V. All rights reserved.

  8. A polymeric micelle magnetic resonance imaging (MRI) contrast agent reveals blood-brain barrier (BBB) permeability for macromolecules in cerebral ischemia-reperfusion injury.

    PubMed

    Shiraishi, Kouichi; Wang, Zuojun; Kokuryo, Daisuke; Aoki, Ichio; Yokoyama, Masayuki

    2017-05-10

    Blood-brain barrier (BBB) opening is a key phenomenon for understanding ischemia-reperfusion injuries that are directly linked to hemorrhagic transformation. The recombinant human tissue-type plasminogen activator (rtPA) increases the risk of symptomatic intracranial hemorrhages. Recent imaging technologies have advanced our understanding of pathological BBB disorders; however, an ongoing challenge in the pre-"rtPA treatment" stage is the task of developing a rigorous method for hemorrhage-risk assessments. Therefore, we examined a novel method for assessment of rtPA-extravasation through a hyper-permeable BBB. To examine the image diagnosis of rtPA-extravasation for a rat transient occlusion-reperfusion model, in this study we used a polymeric micelle MRI contrast-agent (Gd-micelles). Specifically, we used two MRI contrast agents at 1h after reperfusion. Gd-micelles provided very clear contrast images in 15.5±10.3% of the ischemic hemisphere at 30min after i.v. injection, whereas a classic gadolinium chelate MRI contrast agent provided no satisfactorily clear images. The obtained images indicate both the hyper-permeable BBB area for macromolecules and the distribution area of macromolecules in the ischemic hemisphere. Owing to their large molecular weight, Gd-micelles remained in the ischemic hemisphere through the hyper-permeable BBB. Our results indicate the feasibility of a novel clinical diagnosis for evaluating rtPA-related hemorrhage risks. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy.

    PubMed

    Tsai, Yung-Shen; Yu, Yi-Chen; Huang, Po-Chang; Cheng, Hsin-Yi Kathy

    2014-12-01

    The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 15° anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty.

  10. Longitudinal Effect of Surface Treatments Modified by NaOCl-Induced Deproteinization and Nd:YAG Laser on Dentin Permeability.

    PubMed

    Esteves, Stella Renata Machado Silva; Huhtala, Maria Filomena Rocha Lima; Gomes, Ana Paula Martins; Ye, Qiang; Spencer, Paulette; De Paiva Gonçalves, Sérgio Eduardo

    2016-02-01

    The purpose of this study was to evaluate dentin permeability after dentin hypersensitivity treatments: fluoride, adhesive system, and collagen deproteinization with and without Nd:YAG laser exposure, and after erosive and abrasive challenges. Dentin permeability was assessed by measuring dentinal fluid flow using a permeability device. Eighty bovine dentin specimens (6 mm diameter/1 mm thickness) had permeability measured in the presence of the smear layer and after removal of the smear layer by ethylenediaminetetraacetic acid (EDTA). They were then divided into eight groups according to treatment (n = 10): Group C, control; Group L, Nd:YAG laser; Group F, fluoride; Group FL, fluoride plus Nd:YAG laser; Group A, adhesive; Group AL, adhesive plus Nd:YAG laser; Group D, 10% NaOCl plus adhesive; and group DL, NaOCl plus adhesive plus Nd:YAG laser. Nd:YAG laser was irradiated at 60 mJ/pulse/10 Hz/47.7 J/cm2/1 W and applied freehanded without contact for 60 sec. Permeability was measured 24 h after the treatments. The specimens were exposed to erosive and abrasive challenges for 5 days. Erosive challenge was done by immersion in Coca-Cola, four times a day/90 sec each. After the first and last erosive challenge of the day, the abrasive challenge was conducted by brushing the specimens (24,000 cycles/3.8 cm range/200 g weight), and permeability was measured again. Results were analyzed statistically using two factor ANOVA and Tukey tests (α = 0.05). With the exception of groups FL and A, all treatments reduced permeability. A significant reduction in permeability was seen when the treatments were combined with laser exposure. The association of adhesive and Nd:YAG laser led to the lowest rate of permeability after 24 h. NaOCl-induced deproteinization associated with Nd:YAG laser showed the lowest permeability rate after erosive/abrasive challenges. Dentin hypersensitivity treatments reduced dentin permeability when associated with Nd

  11. Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses1

    PubMed Central

    Yu, Qing; Wu, Jiang-Xiu; Zhang, He-Ning; Ye, Sheng; Dong, Shi-Qi; Zhang, Chen-Hao

    2013-01-01

    AIM To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. METHODS The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. RESULTS Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows: root mean square (RMS) (pre)=(1.438±0.328)µm, RMS (30 minutes)=(1.076±0.355)µm, RMS (1 day)=(1.362±0.402)µm, RMS (3 days)=(1.373±0.398)µm, RMS (7 days)=(1.387±0.415)µm, and RMS (14 days)=(1.430±0.423)µm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2nd- and 3rd-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4th-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. CONCLUSION The use RGP contact lenses greatly reduced total aberration of

  12. Maintenance measures for preservation and recovery of permeable pavement surface infiltration rate--The effects of street sweeping, vacuum cleaning, high pressure washing, and milling.

    PubMed

    Winston, Ryan J; Al-Rubaei, Ahmed M; Blecken, Godecke T; Viklander, Maria; Hunt, William F

    2016-03-15

    The surface infiltration rates (SIR) of permeable pavements decline with time as sediment and debris clog pore spaces. Effective maintenance techniques are needed to ensure the hydraulic functionality and water quality benefits of this stormwater control. Eight different small-scale and full-scale maintenance techniques aimed at recovering pavement permeability were evaluated at ten different permeable pavement sites in the USA and Sweden. Maintenance techniques included manual removal of the upper 2 cm of fill material, mechanical street sweeping, regenerative-air street sweeping, vacuum street sweeping, hand-held vacuuming, high pressure washing, and milling of porous asphalt. The removal of the upper 2 cm of clogging material did not significantly improve the SIR of concrete grid paves (CGP) and permeable interlocking concrete pavers (PICP) due to the inclusion of fines in the joint and bedding stone during construction, suggesting routine maintenance cannot overcome improper construction. For porous asphalt maintenance, industrial hand-held vacuum cleaning, pressure washing, and milling were increasingly successful at recovering the SIR. Milling to a depth of 2.5 cm nearly restored the SIR for a 21-year old porous asphalt pavement to like-new conditions. For PICP, street sweepers employing suction were shown to be preferable to mechanical sweepers; additionally, maintenance efforts may become more intensive over time to maintain a threshold SIR, as maintenance was not 100% effective at removing clogging material.

  13. Permeability of R6G across Cx43 hemichannels through a novel combination of patch clamp and surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Madhavan Nair, C.; Sabna, C.; Murty, K. V. G. K.; Ramanan, S. V.

    2005-10-01

    We have measured the permeability of rhodamine-6G across Cx43 hemichannels reconstituted on a pipette tip. Cx43 hemichannels were overexpressed in Sf9 cells, and affinity-purified. The hemichannels were reconstituted in a lipid bilayer on a pipette tip by the tip-dip method. R6G in the pipette permeated across the channels into the bath. The permeability of R6G was quantified by measuring R6G concentration in the bath after several hours by surface enhanced Raman spectroscopy (SERS) with 100 nm silver colloid particles. The ratio of the permeability of dye to salt, as extracted by this combined electrical-SERS technique, is compatible with similar ratios for other dyes across whole gap junction channels. The results for the permeability ratio were further compared to fluorescence measurements. The novel combination of patch and SERS techniques can be extended to quantifying the transport of biologically significant non-fluorescent molecules, such as cAMP and IP3, across 1 nm sized pores, such as the gap junction channel.

  14. Application of histogram analysis for the evaluation of vascular permeability in glioma by the K2 parameter obtained with the dynamic susceptibility contrast method: Comparisons with Ktrans obtained with the dynamic contrast enhance method and cerebral blood volume.

    PubMed

    Taoka, Toshiaki; Kawai, Hisashi; Nakane, Toshiki; Hori, Saeka; Ochi, Tomoko; Miyasaka, Toshiteru; Sakamoto, Masahiko; Kichikawa, Kimihiko; Naganawa, Shinji

    2016-09-01

    The "K2" value is a factor that represents the vascular permeability of tumors and can be calculated from datasets obtained with the dynamic susceptibility contrast (DSC) method. The purpose of the current study was to correlate K2 with Ktrans, which is a well-established permeability parameter obtained with the dynamic contrast enhance (DCE) method, and determine the usefulness of K2 for glioma grading with histogram analysis. The subjects were 22 glioma patients (Grade II: 5, III: 6, IV: 11) who underwent DSC studies, including eight patients in which both DSC and DCE studies were performed on separate days within 10days. We performed histogram analysis of regions of interest of the tumors and acquired 20th percentile values for leakage-corrected cerebral blood volume (rCBV20%ile), K2 (K220%ile), and for patients who underwent a DCE study, Ktrans (Ktrans20%ile). We evaluated the correlation between K220%ile and Ktrans20%ile and the statistical difference between rCBV20%ile and K220%ile. We found a statistically significant correlation between K220%ile and Ktrans20%ile (r=0.717, p<0.05). rCBV20%ile showed a significant difference between Grades II and III and between Grades II and IV, whereas K220%ile showed a statistically significant (p<0.05) difference between Grades II and IV and between Grades III and IV. The K2 value calculated from the DSC dataset, which can be obtained with a short acquisition time, showed a correlation with Ktrans obtained with the DCE method and may be useful for glioma grading when analyzed with histogram analysis. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Permeability of stylolite-bearing chalk

    SciTech Connect

    Lind, I.; Nykjaer, O.; Priisholm, S. ); Springer, N.

    1994-11-01

    Permeabilities were measured on core plugs from stylolite-bearing chalk of the Gorm field in the Danish North Sea. Air and liquid permeabilities were measured in directions parallel to and perpendicular to the stylolite surface. Permeability was measured with sleeve pressure equal to in-situ reservoir stress. Permeabilities of plugs with stylolites but without stylolite-associated fractures were equal in the two directions. The permeability is equal to the matrix permeability of non-stylolite-bearing chalk. In contrast, when fractures were associated with the stylolites, permeability was enhanced. The enhancement was most significant in the horizontal direction parallel to the stylolites.

  16. Antibody responses to the merozoite surface protein-1 complex in cerebral malaria patients in India

    PubMed Central

    Lucchi, Naomi W; Tongren, Jon Eric; Jain, Vidhan; Nagpal, Avinash C; Kauth, Christian W; Woehlbier, Ute; Bujard, Hermann; Dash, Aditya P; Singh, Neeru; Stiles, Jonathan K; Udhayakumar, Venkatachalam

    2008-01-01

    Background Plasmodium falciparum infection causes cerebral malaria (CM) in a subset of patients with anti-malarial treatment protecting only about 70% to 80% of patients. Why a subset of malaria patients develops CM complications, including neurological sequelae or death, is still not well understood. It is believed that host immune factors may modulate CM outcomes and there is substantial evidence that cellular immune factors, such as cytokines, play an important role in this process. In this study, the potential relationship between the antibody responses to the merozoite surface protein (MSP)-1 complex (which consists of four fragments namely: MSP-183, MSP-130, MSP-138 and MSP-142), MSP-636 and MSP-722 and CM was investigated. Methods Peripheral blood antibody responses to recombinant antigens of the two major allelic forms of MSP-1 complex, MSP-636 and MSP-722 were compared between healthy subjects, mild malaria patients (MM) and CM patients residing in a malaria endemic region of central India. Total IgG and IgG subclass antibody responses were determined using ELISA method. Results The prevalence and levels of IgG and its subclasses in the plasma varied for each antigen. In general, the prevalence of total IgG, IgG1 and IgG3 was higher in the MM patients and lower in CM patients compared to healthy controls. Significantly lower levels of total IgG antibodies to the MSP-1f38, IgG1 levels to MSP-1d83, MSP-119 and MSP-636 and IgG3 levels to MSP-1f42 and MSP-722 were observed in CM patients as compared to MM patients. Conclusion These results suggest that there may be some dysregulation in the generation of antibody responses to some MSP antigens in CM patients and it is worth investigating further whether perturbations of antibody responses in CM patients contribute to pathogenesis. PMID:18601721

  17. Folding, But Not Surface Area Expansion, Is Associated with Cellular Morphological Maturation in the Fetal Cerebral Cortex.

    PubMed

    Wang, Xiaojie; Studholme, Colin; Grigsby, Peta L; Frias, Antonio E; Cuzon Carlson, Verginia C; Kroenke, Christopher D

    2017-02-22

    Altered macroscopic anatomical characteristics of the cerebral cortex have been identified in individuals affected by various neurodevelopmental disorders. However, the cellular developmental mechanisms that give rise to these abnormalities are not understood. Previously, advances in image reconstruction of diffusion magnetic resonance imaging (MRI) have made possible high-resolution in utero measurements of water diffusion anisotropy in the fetal brain. Here, diffusion anisotropy within the developing fetal cerebral cortex is longitudinally characterized in the rhesus macaque, focusing on gestation day (G85) through G135 of the 165 d term. Additionally, for subsets of animals characterized at G90 and G135, immunohistochemical staining was performed, and 3D structure tensor analyses were used to identify the cellular processes that most closely parallel changes in water diffusion anisotropy with cerebral cortical maturation. Strong correlations were found between maturation of dendritic arbors on the cellular level and the loss of diffusion anisotropy with cortical development. In turn, diffusion anisotropy changes were strongly associated both regionally and temporally with cortical folding. Notably, the regional and temporal dependence of diffusion anisotropy and folding were distinct from the patterns observed for cerebral cortical surface area expansion. These findings strengthen the link proposed in previous studies between cellular-level changes in dendrite morphology and noninvasive diffusion MRI measurements of the developing cerebral cortex and support the possibility that, in gyroencephalic species, structural differentiation within the cortex is coupled to the formation of gyri and sulci.SIGNIFICANCE STATEMENT Abnormal brain morphology has been found in populations with neurodevelopmental disorders. However, the mechanisms linking cellular level and macroscopic maturation are poorly understood, even in normal brains. This study contributes new

  18. Permeable Pavement Research - Edison, New Jersey

    EPA Science Inventory

    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. ...

  19. Permeable Pavement Research - Edison, New Jersey

    EPA Science Inventory

    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. ...

  20. Comparative study of dentine permeability after apicectomy and surface treatment with 9.6 microm TEA CO2 and Er:YAG laser irradiation.

    PubMed

    Gouw-Soares, S; Stabholz, A; Lage-Marques, J L; Zezell, D M; Groth, E B; Eduardo, C P

    2004-04-01

    Failure of apicectomies is generally attributed to dentine surface permeability as well as to the lack of an adequate marginal sealing of the retrofilling material, which allows the percolation of microorganisms and their products from the root canal system to the periodontal region, thus compromising periapical healing. The purpose of this study was to evaluate dentine and the marginal permeability after apicectomy and surface treatment with 9.6 micro m TEA CO(2) or Er:YAG 2.94 micro m laser irradiation. Sixty-five single rooted human endodontically treated teeth were divided into five experimental groups: group I (control), apicectomy with high speed bur; group II, similar procedure to that of group I, followed by dentinal surface treatment with 9.6 micro m CO(2) laser; group III, similar procedure to group I followed by dentinal surface treatment with Er:YAG laser 2.94 micro m; group IV, apicectomy and surface treatment with CO(2) 9.6 micro m laser; and group V, apicectomy and surface treatment with Er:YAG laser 2.94 micro m. The analysis of methylene blue dye infiltration through the dentinal surface and the retrofilling material demonstrated that the samples from the groups that were irradiated with the lasers showed significantly lower infiltration indexes than the ones from the control group. These results were compatible with the structural morphological changes evidenced through SEM analysis. Samples from groups II and IV (9.6 micro m CO(2)) showed clean smooth surfaces, fusion, and recrystallized dentine distributed homogeneously throughout the irradiated area sealing the dentinal tubules. Samples from groups III and V (Er:YAG 2.94 micro m) also presented clean surfaces, without smear layer, but roughly compatible to the ablationed dentine and without evidence of dentinal tubules. Through the conditions of this study, the Er:YAG 2.94 micro m and the 9.6 micro m CO(2) laser used for root canal resection and dentine surface treatment showed a reduction of

  1. A New Presentation and Exploration of Human Cerebral Vasculature Correlated with Surface and Sectional Neuroanatomy

    ERIC Educational Resources Information Center

    Nowinski, Wieslaw L.; Thirunavuukarasuu, Arumugam; Volkau, Ihar; Marchenko, Yevgen; Aminah, Bivi; Gelas, Arnaud; Huang, Su; Lee, Looi Chow; Liu, Jimin; Ng, Ting Ting; Nowinska, Natalia G.; Qian, Guoyu Yu; Puspitasari, Fiftarina; Runge, Val M.

    2009-01-01

    The increasing complexity of human body models enabled by advances in diagnostic imaging, computing, and growing knowledge calls for the development of a new generation of systems for intelligent exploration of these models. Here, we introduce a novel paradigm for the exploration of digital body models illustrating cerebral vasculature. It enables…

  2. A New Presentation and Exploration of Human Cerebral Vasculature Correlated with Surface and Sectional Neuroanatomy

    ERIC Educational Resources Information Center

    Nowinski, Wieslaw L.; Thirunavuukarasuu, Arumugam; Volkau, Ihar; Marchenko, Yevgen; Aminah, Bivi; Gelas, Arnaud; Huang, Su; Lee, Looi Chow; Liu, Jimin; Ng, Ting Ting; Nowinska, Natalia G.; Qian, Guoyu Yu; Puspitasari, Fiftarina; Runge, Val M.

    2009-01-01

    The increasing complexity of human body models enabled by advances in diagnostic imaging, computing, and growing knowledge calls for the development of a new generation of systems for intelligent exploration of these models. Here, we introduce a novel paradigm for the exploration of digital body models illustrating cerebral vasculature. It enables…

  3. Antidepressants Alter Cerebrovascular Permeability and Metabolic Rate in Primates

    NASA Astrophysics Data System (ADS)

    Preskorn, Sheldon H.; Raichle, Marcus E.; Hartman, Boyd K.

    1982-07-01

    External detection of the annihilation radiation produced by water labeled with oxygen-15 was used to measure cerebrovascular permeability and cerebral blood flow in six rhesus monkeys. Use of oxygen-15 also permitted assessment of cerebral metabolic rate in two of the monkeys. Amitriptyline produced a dose-dependent, reversible increase in permeability at plasma drug concentrations which are therapeutic for depressed patients. At the same concentrations the drug also produced a 20 to 30 percent reduction in cerebral metabolic rate. At higher doses normal autoregulation of cerebral blood flow was suspended, but responsivity to arterial carbon dioxide was normal.

  4. The sperm surface localization of the TRP-3/SPE-41 Ca2+-permeable channel depends on SPE-38 function in Caenorhabditis elegans

    PubMed Central

    Singaravelu, Gunasekaran; Chatterjee, Indrani; Rahimi, Sina; Druzhinina, Marina K.; Kang, Lijun; Xu, X. Z. Shawn; Singson, Andrew

    2012-01-01

    Despite undergoing normal development and acquiring normal morphology and motility, mutations in spe-38 or trp-3/spe-41 cause identical phenotypes in Caenorhabditis elegans – mutant sperm fail to fertilize oocytes despite direct contact. SPE-38 is a novel, four-pass transmembrane protein and TRP-3/SPE-41 is a Ca2+-permeable channel. Localization of both of these proteins is confined to the membranous organelles (MOs) in undifferentiated spermatids. In mature spermatozoa, SPE-38 is localized to the pseudopod and TRP-3/SPE-41 is localized to the whole plasma membrane. Here we show that the dynamic redistribution of TRP-3/SPE-41 from MOs to the plasma membrane is dependent on SPE-38. In spe-38 mutant spermatozoa, TRP-3/SPE-41 is trapped within the MOs and fails to reach the cell surface despite MO fusion with the plasma membrane. Split-ubiquitin yeast-two-hybrid analyses revealed that the cell surface localization of TRP-3/SPE-41 is likely regulated by SPE-38 through a direct protein-protein interaction mechanism. We have identified sequences that influence the physical interaction between SPE-38 and TRP-3/SPE-41, and show that these sequences in SPE-38 are required for fertility in transgenic animals. Despite the mislocalization of TRP-3/SPE-41 in spe-38 mutant spermatozoa, ionomycin or thapsigargin induced influx of Ca2+ remains unperturbed. This work reveals a new paradigm for the regulated surface localization of a Ca2+-permeable channel. PMID:22425620

  5. Computerized mappings of the cerebral cortex: a multiresolution flattening method and a surface-based coordinate system

    NASA Technical Reports Server (NTRS)

    Drury, H. A.; Van Essen, D. C.; Anderson, C. H.; Lee, C. W.; Coogan, T. A.; Lewis, J. W.

    1996-01-01

    We present a new method for generating two-dimensional maps of the cerebral cortex. Our computerized, two-stage flattening method takes as its input any well-defined representation of a surface within the three-dimensional cortex. The first stage rapidly converts this surface to a topologically correct two-dimensional map, without regard for the amount of distortion introduced. The second stage reduces distortions using a multiresolution strategy that makes gross shape changes on a coarsely sampled map and further shape refinements on progressively finer resolution maps. We demonstrate the utility of this approach by creating flat maps of the entire cerebral cortex in the macaque monkey and by displaying various types of experimental data on such maps. We also introduce a surface-based coordinate system that has advantages over conventional stereotaxic coordinates and is relevant to studies of cortical organization in humans as well as non-human primates. Together, these methods provide an improved basis for quantitative studies of individual variability in cortical organization.

  6. The optical measurement of 1,2-propanediol for the determination of lung capillary permeability surface area

    SciTech Connect

    Galloway, R.L. Jr.; Staton, D.J.; Harris, T.R. )

    1989-06-01

    A technique has been developed which allows for the optical measurement of the concentration-time relationship for a diffusion-limited material in indicator dilution studies. The material, 1-2 propanediol, is used as a probe of the permeability of capillaries in the lung. Comparisons between standard radioisotope measurements and the optical measurements are provided and show excellent agreement. The optical method represents an improvement over the standard radioisotope method in that it provides the same data at lower cost, lower risk, and without the delay required by the radiographic methods.

  7. Turbulent drag reduction by permeable coatings

    NASA Astrophysics Data System (ADS)

    Garcia-Mayoral, Ricardo; Abderrahaman-Elena, Nabil

    2015-11-01

    We present an assessment of permeable coatings as a form of passive drag reduction, proposing a simplified model to quantify the effect of the coating thickness and permeability. To reduce skin friction, the porous layer must be preferentially permeable in the streamwise direction, so that a slip effect is produced. For small permeability, the controlling parameter is the difference between streamwise and spanwise permeability lengths, scaled in viscous units, √{Kx+}-√{Kz+}. In this regime, the reduction in drag is proportional to that difference. However, the proportional performance eventually breaks down for larger permeabilities. A degradation mechanism is investigated, common to other obstructed surfaces in general and permeable substrates in particular, which depends critically on the geometric mean of the streamwise and wall-normal permeabilities, √{Kx+ Ky+}. For a streamwise-to-cross-plane permeability ratio of order Kx+/Ky+ = Kx+/Kz+ 10 -100, the model predicts a maximum drag reduction of order 15-25%.

  8. Steady laminar mixed convection stagnation-point flow of a nanofluid over a vertical permeable surface in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Tamim, H.; Dinarvand, S.; Hosseini, R.; Rahimi, H.; Pop, I.

    2016-11-01

    A similarity solution for a steady laminar mixed convection boundary layer flow of a nanofluid near the stagnation point on a vertical permeable plate with a magnetic field and a buoyancy force is obtained by solving a system of nonlinear ordinary differential equations. These equations are solved analytically by using a new kind of a powerful analytic technique for nonlinear problems, namely, the homotopy analysis method (HAM). Three different types of nanoparticles, namely, copper (Cu), alumina (Al2O3), and titanium oxide (TiO2), with water as the base fluid are considered. The influence of the volume fraction of nanoparticles, permeability parameter, magnetic parameter, and mixed convection parameter on the surface shear stress and surface heat transfer, as well as on the velocity and temperature profiles, is considered. It is observed that the skin friction coefficient and the local Nusselt number increase with the nanoparticle volume fraction for all types of nanoparticles considered in this study. The greatest values of the skin friction coefficient and the local Nusselt number are obtained for Cu nanoparticles.

  9. Boundary layer flow and heat transfer over a permeable surface moving with exponentially decreasing velocities in a parallel free stream

    NASA Astrophysics Data System (ADS)

    Ramli, Norshafira; Ahmad, Syakila; Pop, Ioan

    2014-07-01

    In this paper, we investigate the problem of steady boundary layer flow and heat transfer of a viscous and incompressible fluid over a permeable semi-infinite flat plate moving with exponentially decreasing velocities in a parallel free stream. The velocities of the moving flat plate and the free stream as well as the temperature of the moving plate are assumed to have a specific exponential decreasing function forms. The governing equations are first transformed to the similarity equations using an appropriate similarity transformation. Then, the resulting equations are solved by using shooting technique which is done with the aid of shootlib function in Maple software. The effects of the mass flux for suction and lateral injection, and the parameter that controls the exponential increment of the temperature on the flow characteristics are analysed and discussed. It is observed that there exist dual solutions for this present study.

  10. Amyloid-β Peptide on Sialyl-LewisX-Selectin-Mediated Membrane Tether Mechanics at the Cerebral Endothelial Cell Surface

    PubMed Central

    Askarova, Sholpan; Sun, Zhe; Sun, Grace Y.; Meininger, Gerald A.; Lee, James C-M.

    2013-01-01

    Increased deposition of amyloid-β peptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewisx (sLex) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLex and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf), and produced a bimodal population of Fmtf, suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf. In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB. PMID:23593361

  11. Amyloid-β peptide on sialyl-Lewis(X)-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface.

    PubMed

    Askarova, Sholpan; Sun, Zhe; Sun, Grace Y; Meininger, Gerald A; Lee, James C-M

    2013-01-01

    Increased deposition of amyloid-β peptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewis(x) (sLe(x)) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLe(x) and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf ), and produced a bimodal population of Fmtf , suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf . In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB.

  12. Liquid-permeable electrode

    DOEpatents

    Folser, George R.

    1980-01-01

    Electrodes for use in an electrolytic cell, which are liquid-permeable and have low electrical resistance and high internal surface area are provided of a rigid, porous, carbonaceous matrix having activated carbon uniformly embedded throughout. The activated carbon may be catalyzed with platinum for improved electron transfer between electrode and electrolyte. Activated carbon is mixed with a powdered thermosetting phenolic resin and compacted to the desired shape in a heated mold to melt the resin and form the green electrode. The compact is then heated to a pyrolyzing temperature to carbonize and volatilize the resin, forming a rigid, porous structure. The permeable structure and high internal surface area are useful in electrolytic cells where it is necessary to continuously remove the products of the electrochemical reaction.

  13. Morphometry, asymmetry and variations of cerebral sulci on superolateral surface of cerebrum in autopsy cases.

    PubMed

    Gonul, Yucel; Songur, Ahmet; Uzun, Ibrahim; Uygur, Ramazan; Alkoc, Ozan Alper; Caglar, Veli; Kucuker, Hudaverdi

    2014-09-01

    The cerebral sulci are known as main microanatomical borders that serve as a gateway and surgical passage to reach the ventricles or to the deeper lesions. It is a matter of curiosity that whether there is a convergence between the morphological asymmetry and the functional asymmetry, and also its significance in surgery. The aim of this study is make morphometric measurements and evaluate asymmetry of several sulci on the lateral aspects of the cerebrum in regard to main sulci and related reference key points. A total of 100 cerebral hemispheres from 50 autopsy cadavers were examined. The lengths of several sulci on the superolateral aspect of the hemispheres and the distances between the sulci and nearby sulci and the reference key points were measured. Encountered variations were examined and photographed. Evaluation of the variations: superior frontal sulcus (SFS), inferior frontal sulcus, superior temporal sulcus (STS), precentral sulcus and postcentral sulcus were found to be discontinuous in 60, 46, 41, 84 and 70 % of the hemispheres, respectively. Evaluation of the asymmetry: the distances between SFS posterior end and longitudinal fissure, STS posterior end and lateral sulcus posterior end, as well as lengths of external occipital fissure (EOF), and discontinuous course of STS were significantly different between left and right hemispheres. There is usually a morphological partial asymmetry between the right and left hemispheres for any individual. Also, some of our measurements were found to be compatible with the ones in the literature, while others were incompatible.

  14. Mathematical Analysis of Hall Effect on Transient Hartman Flow about a Rotating Horizontal Permeable Surface in a Porous Medium under Inclined Magnetic Field.

    PubMed

    Suresh, M; Manglik, A

    2014-01-01

    This paper proposes the exact solution for unsteady flow of a viscous incompressible electrically conducting fluid past a impulsively started infinite horizontal surface which is rotating with an angular velocity embedded in a saturated porous medium under the influence of strong magnetic field with hall effect. Our study focuses on the change of direction of the external magnetic field on the flow system which leads to change in the flow behavior and skin frictional forces at the boundary. Systems of flow equations are solved using Laplace transform technique. The impacts of control parameters Hartman number, rotation of the system, hall effect, inclination of the magnetic field, and Darcy number on primary and secondary velocities are shown graphically, skin friction at horizontal boundary in tabular form. For validating our results, in the absence of permeability of the porous medium and inclination of the magnetic field the results are in good agreement with the published results.

  15. Mathematical Analysis of Hall Effect on Transient Hartman Flow about a Rotating Horizontal Permeable Surface in a Porous Medium under Inclined Magnetic Field

    PubMed Central

    Suresh, M.; Manglik, A.

    2014-01-01

    This paper proposes the exact solution for unsteady flow of a viscous incompressible electrically conducting fluid past a impulsively started infinite horizontal surface which is rotating with an angular velocity embedded in a saturated porous medium under the influence of strong magnetic field with hall effect. Our study focuses on the change of direction of the external magnetic field on the flow system which leads to change in the flow behavior and skin frictional forces at the boundary. Systems of flow equations are solved using Laplace transform technique. The impacts of control parameters Hartman number, rotation of the system, hall effect, inclination of the magnetic field, and Darcy number on primary and secondary velocities are shown graphically, skin friction at horizontal boundary in tabular form. For validating our results, in the absence of permeability of the porous medium and inclination of the magnetic field the results are in good agreement with the published results. PMID:27433540

  16. Unsteady mixed convection flow through a permeable stretching flat surface with partial slip effects through MHD nanofluid using spectral relaxation method

    NASA Astrophysics Data System (ADS)

    Ahamed, Sami M.; Mondal, Sabyasachi; Sibanda, Precious

    2017-05-01

    An unsteady, laminar, mixed convective stagnation point nanofluid flow through a permeable stretching flat surface using internal heat source or sink and partial slip is investigated. The effects of thermophoresis and Brownian motion parameters are revised on the traditional model of nanofluid for which nanofluid particle volume fraction is passively controlled on the boundary. Spectral relaxation method is applied here to solve the non-dimensional conservation equations. The results show the illustration of the impact of skin friction coefficient, different physical parameters, and the heat transfer rate. The nanofluid motion is enhanced with increase in the value of the internal heat sink or source. On the other hand, the rate of heat transfer on the stretching sheet and the skin friction coefficient are reduced by an increase in internal heat generation. This study further shows that the velocity slip increases with decrease in the rate of heat transfer. The outcome results are benchmarked with previously published results.

  17. Human arachnoid granulations Part I: a technique for quantifying area and distribution on the superior surface of the cerebral cortex

    PubMed Central

    Grzybowski, Deborah M; Herderick, Edward E; Kapoor, Kapil G; Holman, David W; Katz, Steven E

    2007-01-01

    Background The arachnoid granulations (AGs) are herniations of the arachnoid membrane into the dural venous sinuses on the surface of the brain. Previous morphological studies of AGs have been limited in scope and only one has mentioned surface area measurements. The purpose of this study was to investigate the topographic distribution of AGs on the superior surface of the cerebral cortex. Methods En face images were taken of the superior surface of 35 formalin-fixed human brains. AGs were manually identified using Adobe Photoshop, with a pixel location containing an AG defined as 'positive'. A set of 25 standard fiducial points was marked on each hemisphere for a total of 50 points on each image. The points were connected on each hemisphere to create a segmented image. A standard template was created for each hemisphere by calculating the average position of the 25 fiducial points from all brains. Each segmented image was mapped to the standard template using a linear transformation. A topographic distribution map was produced by calculating the proportion of AG positive images at each pixel in the standard template. The AG surface area was calculated for each hemisphere and for the total brain superior surface. To adjust for different brain sizes, the proportional involvement of AGs was calculated by dividing the AG area by the total area. Results The total brain average surface area of AGs was 78.53 ± 13.13 mm2 (n = 35) and average AG proportional involvement was 57.71 × 10-4 ± 7.65 × 10-4. Regression analysis confirmed the reproducibility of AG identification between independent researchers with r2 = 0.97. The surface AGs were localized in the parasagittal planes that coincide with the region of the lateral lacunae. Conclusion The data obtained on the spatial distribution and en face surface area of AGs will be used in an in vitro model of CSF outflow. With an increase in the number of samples, this analysis technique can be used to study the relationship

  18. The effect of surface and internal electrodes on the gait of children with cerebral palsy, spastic diplegic type.

    PubMed

    Young, C C; Rose, S E; Biden, E N; Wyatt, M P; Sutherland, D H

    1989-01-01

    The purpose of this study was to determine whether surface and internal fine-wire electromyography electrodes had an effect on gait. The subjects for the experiments were 38 children with the spastic diplegic type of cerebral palsy. The children were filmed using the high-speed cinematographic technique while they walked (a) with no electrodes (unencumbered), (b) with only surface electrodes, and (c) with internal electrodes. Single stance time, step length, cadence, and walking velocity were compared with analysis of variance and Bonferroni t tests. The results included a significant decrease in cadence (-6.3% of unencumbered walking; p less than 0.05) when comparing walking with surface electrodes with walking without any electrodes. The internal electrodes caused significant decreases from normal walking in the following parameters: step length for both the measured leg (-18.6%; p less than 0.005) and the nonmeasured leg (-18.0%; p less than 0.005), cadence (-7.9%; p less than 0.02), and walking velocity (-23.5%; p less than 0.005). Internal electrodes caused significant decreases as compared with surface electrodes in the step length for both the measured leg (15.7%; p less than 0.01) and the nonmeasured leg (15.6%; p less than 0.005) and walking velocity (19.7%; p less than 0.005). Single stance phase did not change significantly in any of the comparisons. It appears that the addition of the surface electrode apparatus does change the normal gait of a subject, causing a large decrease in cadence. The measurement of gait with internal electrodes causes further change in gait, resulting in large decreases in step length and walking velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Interpretation of surface EMGs in children with cerebral palsy: An initial study using a fuzzy expert system.

    PubMed

    Schmidt-Rohlfing, Bernhard; Bergamo, Ferdinand; Williams, Sybele; Erli, Hans J; Rau, Günther; Niethard, Fritz U; Disselhorst-Klug, Catherine

    2006-03-01

    Surface EMG detected simultaneously at different muscles has become an important tool for analysing the gait of children with cerebral palsy (CP), as it offers essential information about muscular coordination. However, the interpretation of surface EMG is a difficult task that assumes extensive knowledge and experience. As such, this noninvasive procedure is not frequently used in the general clinical routine. An Artificial Intelligence (AI) system for interpreting surface EMG signals and the resulting muscular coordination patterns could overcome these limitations. To support such interpretation, an expert system based on fuzzy inference methodology was developed. The knowledge-base of the system implemented 15 rules, from which the fuzzy inference methodology performs a prediction of the effectiveness of the muscular coordination during gait. Our aim was to assess the feasibility and value of such an expert system in clinical applications. Surface EMG signals were recorded from the tibialis anterior, soleus muscle, and gastrocnemius muscles of children with CP to assess muscular coordination patterns of ankle movement during gait. Nineteen children underwent 114 surface EMG measurements. Simultaneously, the gait cycles of each patient were determined using foot switches and videotapes. From the EMG signals, the effectiveness of the ankle movement was predicted by the expert system, and predictions were classified using a three-point ordinal scale. In 91 cases (80%), the clinical findings matched the predictions of the expert system. In 23 cases (20%) the predictions of the expert system differed from the clinical findings with 12 cases revealing worse and 11 cases revealing better results in comparison to the clinical findings. As this study is a first attempt to verify the feasibility and correctness of this expert system, the results are promising. Further study is required to assess the correlation with the kinematic data and to include the whole leg

  20. [Structural modifications of the surface of Escherichia coli bacteria and copper-induced permeability of plasma membrane].

    PubMed

    Lebedev, V S; Volodina, L A; Deĭnega, E Iu; Fedorov, Iu I

    2005-01-01

    The effect of Cu2+ on the structural organization of the cell surface of Escherichia coli bacteria during the induction of conductivity of a plasma membrane was studied. A fluorescent study did not reveal any substantial changes in the microviscosity of lipids by the action of copper ions. At the same time, a substantial reorganization of membrane proteins during plasmolysis was observed. A model of the copper-induced structural reorganization of membrane lipids was constructed, according to which the reorganization leads to the opening in the membrane of channels of nonspecific conductivity for cations. The opening of conductivity channels results from the break of disulfide bonds in critical membrane proteins during the interaction with Cu+, which form either due to the reduction of Cu2+ on specific sites of cell surface or by means of external reducing agents.

  1. Relative Permeability of Fractured Rock

    SciTech Connect

    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.

  2. Effects of cancer cell permeability control on the efficiency of cell damage through surface plasmon resonance of gold nanoparticle (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hsiao, Jen-Hung; Yu, Jian-He; He, Yulu; Tu, Yi-Chou; Hua, Wei-Hsiang; Low, Meng Chun; Hsieh, Cheng-Che; Kiang, Yean-Woei; Yang, Chih-Chung

    2017-02-01

    Cancer cell killing efficiencies based on the photothermal effect caused by the surface plasmon resonance of metal nanoparticles (NPs) and the photodynamic effect caused by the singlet oxygen generation of a photosensitizer rely on the cell uptake efficiency of metal NP and photosensitizer. Perforation and heating can increase cell membrane permeability and hence can increase the cell uptake efficiency of NPs and drugs. In this paper, we demonstrate the variations of the cell damage efficiency under the illuminations of different lasers, which can produce mainly photothermal effect, mainly photodynamic effect, and mixed effect, when a pre-perforation and a pre-heating processes are applied. Au nanorings (NRIs) with their localized surface plasmon resonance wavelength around 1064 nm are used. The perforation process is undertaken by illuminating the cell samples by a femtosecond laser at 1064 nm with the power density lower than the cell damage threshold intensity. The heating process is implemented by illuminating cells with a low power continuous laser at 1064 nm. It is found that with the pre-perforation and pre-heating processes, the photodynamic effect is enhanced because the internalized Au NRI number and hence the internalized photosensitizer (AlPcS) molecule number are increased. However, the photothermal effect can be reduced because the adsorbed Au NRIs on cell membrane are effectively internalized during the pre-perforation and pre-heating processes. The photothermal effect is more effective when Au NRIs are adsorbed on cell membrane.

  3. In-situ monitoring of flow-permeable surface area of high explosive powder using small sample masses

    SciTech Connect

    Maiti, Amitesh; Han, Yong; Zaka, Fowzia; Gee, Richard H.

    2015-02-17

    To ensure good performance of high explosive devices over long periods of time, initiating powders need to maintain their specific surface area within allowed margins during the entire duration of deployment. A common diagnostic used in this context is the Fisher sub-sieve surface area (FSSA). Furthermore, commercial permeametry instruments measuring the FSSA requires the utilization of a sample mass equal to the crystal density of the sample material, an amount that is often one or two orders of magnitude larger than the typical masses found in standard detonator applications. Here we develop a customization of the standard device that can utilize just tens of milligram samples, and with simple calibration yield FSSA values at ac curacy levels comparable to the standard apparatus. This necessitated a newly designed sample holder, made from a material of low coefficient of thermal expansion, which is conveniently transferred between an aging chamber and a re-designed permeametry tube. This improves the fidelity of accelerated aging studies by allowing measurement on the same physical sample at various time - instants during the aging process, and by obviating the need for a potentially FSSA-altering powder re-compaction step. We used the customized apparatus to monitor the FSSA evolution of a number of undoped and homolog-doped PETN powder samples that were subjected to artificial aging for several months at elevated temperatures. These results, in conjunction with an Arrhenius-based aging model were used to assess powder-coarsening - rates under long-term storage.

  4. Sensitivity Analysis and Parameter Identifiability of the Land Surface Model JULES at the point scale in permeable catchments

    NASA Astrophysics Data System (ADS)

    Bakopoulou, C.; Bulygina, N.; Butler, A. P.; McIntyre, N. R.

    2012-04-01

    Land surface models (LSMs) are recognised as important components of Global Circulation Models (GCMs). Simulating exchanges of the moisture, carbon and energy between land surface and atmosphere in a consistent manner requires physics-based LSMs of high complexity, fine vertical resolution and a large number of parameters that need to be estimated. The "physics" that is incorporated in such models is generally based on our knowledge of point (or very small) scale hydrological processes. Therefore, while larger GCM grid-scale performance may be the ultimate goal, the ability of the model to simulate the point-scale processes is, intuitively, a pre-requisite for its reliable use at larger scales. Critical evaluation of model performance and parameter uncertainty at point scales is therefore a rational starting point for critical evaluation of LSMs; and identification of optimal parameter sets at the point scale is a significant stage of the model evaluation at larger scales. The Joint UK Land Environment Simulator (JULES) is a complex LSM, which is used to represent surface exchanges in the UK Met Office's forecast and climate change models. This complexity necessitates a large number of model parameters (in total 108) some of which are incapable of being measured directly at large (i.e. kilometer) scales. For this reason, a parameter sensitivity analysis is a vital confidence building process within the framework of every LSM, and as a part of the calibration strategy. The problem of JULES parameter estimation and uncertainty at the point scale with a view to assessing the accuracy and the uncertainty in the default parameter values is addressed. The sensitivity of the JULES output of soil moisture is examined using parameter response surface analysis. The implemented technique is based on the Regional Sensitivity Analysis method (RSA), which evaluates the model response surface over a region of parameter space using Monte Carlo sampling. The modified version of RSA

  5. Parcellations and Hemispheric Asymmetries of Human Cerebral Cortex Analyzed on Surface-Based Atlases

    PubMed Central

    Glasser, Matthew F.; Dierker, Donna L.; Harwell, John; Coalson, Timothy

    2012-01-01

    We report on surface-based analyses that enhance our understanding of human cortical organization, including its convolutions and its parcellation into many distinct areas. The surface area of human neocortex averages 973 cm2 per hemisphere, based on cortical midthickness surfaces of 2 cohorts of subjects. We implemented a method to register individual subjects to a hybrid version of the FreeSurfer “fsaverage” atlas whose left and right hemispheres are in precise geographic correspondence. Cortical folding patterns in the resultant population-average “fs_LR” midthickness surfaces are remarkably similar in the left and right hemispheres, even in regions showing significant asymmetry in 3D position. Both hemispheres are equal in average surface area, but hotspots of surface area asymmetry are present in the Sylvian Fissure and elsewhere, together with a broad pattern of asymmetries that are significant though small in magnitude. Multiple cortical parcellation schemes registered to the human atlas provide valuable reference data sets for comparisons with other studies. Identified cortical areas vary in size by more than 2 orders of magnitude. The total number of human neocortical areas is estimated to be ∼150 to 200 areas per hemisphere, which is modestly larger than a recent estimate for the macaque. PMID:22047963

  6. [Cerebral ischemia and histamine].

    PubMed

    Adachi, Naoto

    2002-10-01

    Cerebral ischemia induces excess release of glutamate and an increase in the intracellular Ca2+ concentration, which provoke catastrophic enzymatic processes leading to irreversible neuronal injury. Histamine plays the role of neurotransmitter in the central nervous system, and histaminergic fibers are widely distributed in the brain. In cerebral ischemia, release of histamine from nerve endings has been shown to be enhanced by facilitation of its activity. An inhibition of the histaminergic activity in ischemia aggravates the histologic outcome. In contrast, intracerebroventricular administration of histamine improves the aggravation, whereas blockade of histamine H2 receptors aggravates ischemic injury. Furthermore, H2 blockade enhances ischemic release of glutamate and dopamine. These findings suggest that central histamine provides beneficial effects against ischemic neuronal damage by suppressing release of excitatory neurotransmitters. However, histaminergic H2 action facilitates the permeability of the blood-brain barrier and shows deleterious effects on cerebral edema.

  7. In-situ monitoring of flow-permeable surface area of high explosive powder using small sample masses

    DOE PAGES

    Maiti, Amitesh; Han, Yong; Zaka, Fowzia; ...

    2015-02-17

    To ensure good performance of high explosive devices over long periods of time, initiating powders need to maintain their specific surface area within allowed margins during the entire duration of deployment. A common diagnostic used in this context is the Fisher sub-sieve surface area (FSSA). Furthermore, commercial permeametry instruments measuring the FSSA requires the utilization of a sample mass equal to the crystal density of the sample material, an amount that is often one or two orders of magnitude larger than the typical masses found in standard detonator applications. Here we develop a customization of the standard device that canmore » utilize just tens of milligram samples, and with simple calibration yield FSSA values at ac curacy levels comparable to the standard apparatus. This necessitated a newly designed sample holder, made from a material of low coefficient of thermal expansion, which is conveniently transferred between an aging chamber and a re-designed permeametry tube. This improves the fidelity of accelerated aging studies by allowing measurement on the same physical sample at various time - instants during the aging process, and by obviating the need for a potentially FSSA-altering powder re-compaction step. We used the customized apparatus to monitor the FSSA evolution of a number of undoped and homolog-doped PETN powder samples that were subjected to artificial aging for several months at elevated temperatures. These results, in conjunction with an Arrhenius-based aging model were used to assess powder-coarsening - rates under long-term storage.« less

  8. Numerical investigation of velocity slip and temperature jump effects on unsteady flow over a stretching permeable surface

    NASA Astrophysics Data System (ADS)

    Hosseini, E.; Loghmani, G. B.; Heydari, M.; Rashidi, M. M.

    2017-02-01

    In this paper, the boundary layer flow and heat transfer of unsteady flow over a porous accelerating stretching surface in the presence of the velocity slip and temperature jump effects are investigated numerically. A new effective collocation method based on rational Bernstein functions is applied to solve the governing system of nonlinear ordinary differential equations. This method solves the problem on the semi-infinite domain without truncating or transforming it to a finite domain. In addition, the presented method reduces the solution of the problem to the solution of a system of algebraic equations. Graphical and tabular results are presented to investigate the influence of the unsteadiness parameter A , Prandtl number Pr, suction parameter fw, velocity slip parameter γ and thermal slip parameter φ on the velocity and temperature profiles of the fluid. The numerical experiments are reported to show the accuracy and efficiency of the novel proposed computational procedure. Comparisons of present results are made with those obtained by previous works and show excellent agreement.

  9. Kinetic modeling in the context of cerebral blood flow quantification by H2(15)O positron emission tomography: the meaning of the permeability coefficient in Renkin-Crone׳s model revisited at capillary scale.

    PubMed

    Lorthois, Sylvie; Duru, Paul; Billanou, Ian; Quintard, Michel; Celsis, Pierre

    2014-07-21

    One the one hand, capillary permeability to water is a well-defined concept in microvascular physiology, and linearly relates the net convective or diffusive mass fluxes (by unit area) to the differences in pressure or concentration, respectively, that drive them through the vessel wall. On the other hand, the permeability coefficient is a central parameter introduced when modeling diffusible tracers transfer from blood vessels to tissue in the framework of compartmental models, in such a way that it is implicitly considered as being identical to the capillary permeability. Despite their simplifying assumptions, such models are at the basis of blood flow quantification by H2(15)O Positron Emission Tomgraphy. In the present paper, we use fluid dynamic modeling to compute the transfers of H2(15)O between the blood and brain parenchyma at capillary scale. The analysis of the so-obtained kinetic data by the Renkin-Crone model, the archetypal compartmental model, demonstrates that, in this framework, the permeability coefficient is highly dependent on both flow rate and capillary radius, contrarily to the central hypothesis of the model which states that it is a physiological constant. Thus, the permeability coefficient in Renkin-Crone׳s model is not conceptually identical to the physiologic permeability as implicitly stated in the model. If a permeability coefficient is nevertheless arbitrarily chosen in the computed range, the flow rate determined by the Renkin-Crone model can take highly inaccurate quantitative values. The reasons for this failure of compartmental approaches in the framework of brain blood flow quantification are discussed, highlighting the need for a novel approach enabling to fully exploit the wealth of information available from PET data.

  10. Effects of specific surface area and porosity on cube counting fractal dimension, lacunarity, configurational entropy, and permeability of model porous networks: Random packing simulations and NMR micro-imaging study

    NASA Astrophysics Data System (ADS)

    Lee, Bum Han; Lee, Sung Keun

    2013-07-01

    Despite the importance of understanding and quantifying the microstructure of porous networks in diverse geologic settings, the effects of the specific surface area and porosity on the key structural parameters of the networks have not been fully understood. We performed cube-counting fractal dimension (Dcc) and lacunarity analyses of 3D porous networks of model sands and configurational entropy analysis of 2D cross sections of model sands using random packing simulations and nuclear magnetic resonance (NMR) micro-imaging. We established relationships among porosity, specific surface area, structural parameters (Dcc and lacunarity), and the corresponding macroscopic properties (configurational entropy and permeability). The Dcc of the 3D porous networks increases with increasing specific surface area at a constant porosity and with increasing porosity at a constant specific surface area. Predictive relationships correlating Dcc, specific surface area, and porosity were also obtained. The lacunarity at the minimum box size decreases with increasing porosity, and that at the intermediate box size (∼0.469 mm in the current model sands) was reproduced well with specific surface area. The maximum configurational entropy increases with increasing porosity, and the entropy length of the pores decreases with increasing specific surface area and was used to calculate the average connectivity among the pores. The correlation among porosity, specific surface area, and permeability is consistent with the prediction from the Kozeny-Carman equation. From the relationship between the permeability and the Dcc of pores, the permeability can be expressed as a function of the Dcc of pores and porosity. The current methods and these newly identified correlations among structural parameters and properties provide improved insights into the nature of porous media and have useful geophysical and hydrological implications for elasticity and shear viscosity of complex composites of rock

  11. A framework to analyze cerebral mean diffusivity using surface guided diffusion mapping in diffusion tensor imaging

    PubMed Central

    Kwon, Oh-Hun; Park, Hyunjin; Seo, Sang-Won; Na, Duk L.; Lee, Jong-Min

    2015-01-01

    The mean diffusivity (MD) value has been used to describe microstructural properties in Diffusion Tensor Imaging (DTI) in cortical gray matter (GM). Recently, researchers have applied a cortical surface generated from the T1-weighted volume. When the DTI data are analyzed using the cortical surface, it is important to assign an accurate MD value from the volume space to the vertex of the cortical surface, considering the anatomical correspondence between the DTI and the T1-weighted image. Previous studies usually sampled the MD value using the nearest-neighbor (NN) method or Linear method, even though there are geometric distortions in diffusion-weighted volumes. Here we introduce a Surface Guided Diffusion Mapping (SGDM) method to compensate for such geometric distortions. We compared our SGDM method with results using NN and Linear methods by investigating differences in the sampled MD value. We also projected the tissue classification results of non-diffusion-weighted volumes to the cortical midsurface. The CSF probability values provided by the SGDM method were lower than those produced by the NN and Linear methods. The MD values provided by the NN and Linear methods were significantly greater than those of the SGDM method in regions suffering from geometric distortion. These results indicate that the NN and Linear methods assigned the MD value in the CSF region to the cortical midsurface (GM region). Our results suggest that the SGDM method is an effective way to correct such mapping errors. PMID:26236180

  12. Aquifer and Shallow San Andreas Fault Permeabilities Inferred from Poroelastic Modeling of InSAR Measurements of Land Surface Deformation in Coachella Valley, California. Ravi Appana and Martin O. Saar

    NASA Astrophysics Data System (ADS)

    Appana, R.; Saar, M. O.

    2009-12-01

    Coachella Valley, in southern California, is located in a region where the southern San Andreas Fault system, comprising three main faults, cuts through the valley aquifer dividing it into many sub-basins. Satellite interferometry (InSAR) has revealed differential uplift of the land surface across the Banning Strand - San Andreas Fault (BSF) and the Garnet Hill Fault (GHF) in the upper Coachella Valley. This uplift is suggested to be caused by the elastic response of the aquifer to artificial groundwater recharge and the tectonic stresses acting in this region. However, the differential uplift appears to be mainly caused by the semi-permeable faults which partially restrict pore-fluid pressure diffusion and related groundwater flow. Hence, by employing numerical models of coupled groundwater flow and poroelastic deformation of the aquifer sediments, the land surface uplift can be utilized to constrain a large-scale hydrologic model of the region that includes hydraulic representations of the faults and the sub-basins. Such a regional model can aide in developing better groundwater management strategies that aim at uniform restorations of ground surface elevations and groundwater table levels and would better constrain fault permeabilities with implications for research related to earthquake dynamics and estimates of potential slip along segments of the southern San Andreas Fault system. Studies have suggested that these segments have reached the end of the inter-seismic strain accumulation period posing the biggest risk to seismic hazards in California. InSAR data showing regional land surface uplift and well data of water table elevations, collected in this region, are used to constrain the model yielding hydraulic parameters. Specifically, our results suggest that the horizontal permeability, kxWWB, of the White Water sub-basin (WWB) and its permeability anisotropy, aWWB = (kz/kx)WWB, are on the order of 0.20x10-11 m2 ≤ kxWWB ≤ 1.2x10-11 m2 and 0.04 ≤ a

  13. Permeability enhancement by shock cooling

    NASA Astrophysics Data System (ADS)

    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

  14. Incorporating surface indicators of reservoir permeability into reservoir volume calculations: Application to the Colli Albani caldera and the Central Italy Geothermal Province

    NASA Astrophysics Data System (ADS)

    Giordano, Guido; De Benedetti, Arnaldo Angelo; Bonamico, Andrea; Ramazzotti, Paolo; Mattei, Massimo

    2014-01-01

    The Quaternary Roman Volcanic Province extends for over 200 km along the Tyrrhenian margin of the Italian peninsula and is composed of several caldera complexes with significant associated geothermal potential. In spite of the massive programs of explorations conducted by the then state-owned ENEL and AGIP companies between the 1970s and 1990s, and the identification of several high enthalpy fields, this resource remains so far unexploited, although it occurs right below the densely populated metropolitan area of Roma capital city. The main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks, the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain. As a consequence, almost half of the many exploration deep bore-holes drilled in the area reached a dry target. This work reviews available data and re-assesses the geothermal potential of caldera-related systems in Central Italy, by analysing in detail the case of the Colli Albani caldera system, the closest to Roma capital city. A GIS based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential. The approach is based on a three dimensional matrix of georeferenced spatial data; the A axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data; the B axis accounts for the thermal modelling of the crust (i.e. T with depth) based on measured thermal gradients. Both A and B data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs. We discuss the implementation of a C axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation. We consider datasets on: i

  15. Three-dimensional reconstruction of the topographical cerebral surface anatomy for presurgical planning with free OsiriX Software.

    PubMed

    Harput, Mehmet V; Gonzalez-Lopez, Pablo; Türe, Uğur

    2014-09-01

    During surgery for intrinsic brain lesions, it is important to distinguish the pathological gyrus from the surrounding normal sulci and gyri. This task is usually tedious because of the pia-arachnoid membranes with their arterial and venous complexes that obscure the underlying anatomy. Moreover, most tumors grow in the white matter without initially distorting the cortical anatomy, making their direct visualization more difficult. To create and evaluate a simple and free surgical planning tool to simulate the anatomy of the surgical field with and without vessels. We used free computer software (OsiriX Medical Imaging Software) that allowed us to create 3-dimensional reconstructions of the cerebral surface with and without cortical vessels. These reconstructions made use of magnetic resonance images from 51 patients with neocortical supratentorial lesions operated on over a period of 21 months (June 2011 to February 2013). The 3-dimensional (3-D) anatomic images were compared with the true surgical view to evaluate their accuracy. In all patients, the landmarks determined by 3-D reconstruction were cross-checked during surgery with high-resolution ultrasonography; in select cases, they were also checked with indocyanine green videoangiography. The reconstructed neurovascular structures were confirmed intraoperatively in all patients. We found this technique to be extremely useful in achieving pure lesionectomy, as it defines tumor's borders precisely. A 3-D reconstruction of the cortical surface can be easily created with free OsiriX software. This technique helps the surgeon perfect the mentally created 3-D picture of the tumor location to carry out cleaner, safer surgeries.

  16. Anisotropic hydraulic permeability in compressed articular cartilage.

    PubMed

    Reynaud, Boris; Quinn, Thomas M

    2006-01-01

    The extent to which articular cartilage hydraulic permeability is anisotropic is largely unknown, despite its importance for understanding mechanisms of joint lubrication, load bearing, transport phenomena, and mechanotransduction. We developed and applied new techniques for the direct measurement of hydraulic permeability within statically compressed adult bovine cartilage explant disks, dissected such that disk axes were perpendicular to the articular surface. Applied pressure gradients were kept small to minimize flow-induced matrix compaction, and fluid outflows were measured by observation of a meniscus in a glass capillary under a microscope. Explant disk geometry under radially unconfined axial compression was measured by direct microscopic observation. Pressure, flow, and geometry data were input to a finite element model where hydraulic permeabilities in the disk axial and radial directions were determined. At less than 10% static compression, near free-swelling conditions, hydraulic permeability was nearly isotropic, with values corresponding to those of previous studies. With increasing static compression, hydraulic permeability decreased, but the radially directed permeability decreased more dramatically than the axially directed permeability such that strong anisotropy (a 10-fold difference between axial and radial directions) in the hydraulic permeability tensor was evident for static compression of 20-40%. Results correspond well with predictions of a previous microstructurally-based model for effects of tissue mechanical deformations on glycosaminoglycan architecture and cartilage hydraulic permeability. Findings inform understanding of structure-function relationships in cartilage matrix, and suggest several biomechanical roles for compression-induced anisotropic hydraulic permeability in articular cartilage.

  17. Cerebrovascular permeability and cognition in the aging rat.

    PubMed

    Goldman, H; Berman, R F; Gershon, S; Murphy, S; Morehead, M; Altman, H J

    1992-01-01

    Regional cerebrovascular permeability-capillary surface area products (rPS) and brain vascular space (BVS) were measured in aging, conscious, unrestrained Sprague-Dawley rats. Three groups of animals were examined: young-mature (6 months), middle-aged (12-14 months), and old (24-26 months) rats. Complex maze learning had been previously characterized in these same animals. Maze learning declined with age. Brain vascular space did not differ significantly with age in any brain region. However, small, but significant age-dependent decreases in rPS (25-33%) were observed. These decreases occurred mainly in the old animals in the basal ganglia and parietal cortex, and in the middle-aged and old rats in the olfactory bulbs. Significant and unexpected positive average correlations between brain permeability-capillary surface area products (PS) and learning errors occurred primarily in young rats and were attributable mainly to changes in 5 of 14 brain regions; hypothalamus, hippocampus, parietal cortex, septal area and superior colliculus. The higher correlations between maze learning errors and PS in young animals may indicate dynamic regulation of this cerebrovascular parameter which is lessened with aging. Average correlations between PS and cerebral blood flow also were determined and found to be generally small and not significant for most brain regions and age groups.

  18. Studying the Variation in Gas Permeability of Porous Building Substrates

    NASA Astrophysics Data System (ADS)

    Townsend, L.; Savidge, C. R.; Hu, L.; Rizzo, D. M.; Hayden, N. J.; Dewoolkar, M.

    2009-12-01

    Understanding permeability of building materials is important for problems involving studies of contaminant transport. Examples include contamination from fire, acid rain, and chemical and biological weapons. Our research investigates the gas permeability of porous building substrates such as concretes, limestones, sandstones, and bricks. Each sample was cored to produce 70 mm (2.75”) diameter cores approximately 75-130 mm (3-5”) tall. The surface gas permeability was measured on the top surface of these specimens using the AutoScan II device manufactured by New England Research, Inc. The measurements were taken along a 3 mm grid producing a map of surface gas permeability. An example map is shown in Figure 1. The macroscopic measurements were performed along the entire cored specimen. A second set of measurements were made on a 5 mm thick slice cut from the top of each specimen to examine whether these measurements compare better with the surface measurements. The macroscopic gas permeability was measured for all specimens using ASTM D 4525. The results are summarized in Table 1. In general, the surface and macroscopic gas permeability measurements (Table 1) compare reasonably well (within one order of magnitude). The permeability of the 5 mm slices is not significantly different from the entire core for the specimens tested. Figure 1. Results of surface permeability mappingof Ohio Sandstone using the AutoScan II device. a) Map of gas permeability b) Range of gas permeability c) Density function of permeability. Table 1. Gas permeability values (mD)

  19. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

    This paper presents an investigation on the effect of clay addition on water permeability and air permeability of concretes. Clay concrete mixes consisted of 0 to 40% clay content incorporated as cement replacement. Flow methods using triaxial cells and air permeameters were used for measuring the injected water and air flows under pressure. It was found that the higher the clay content in the mixture, the greater the permeability. At higher water-cement ratios (w/c), the paste matrix is less dense and easily allows water to ingress into concrete. But at high clay contents of 30 to 40% clay, the variation in permeability was significantly diminished among different concrete mixtures. It was confirmed that air permeability results were higher than the corresponding water permeability values when all permeability coefficients were converted to intrinsic permeability values.

  20. Endomorphins exit the brain by a saturable efflux system at the basolateral surface of cerebral endothelial cells.

    PubMed

    Somogyvari-Vigh, Aniko; Kastin, Abba J; Liao, Jie; Zadina, James E; Pan, Weihong

    2004-05-01

    Endomorphin-1 (EM-1) and endomorphin-2 (EM-2) are two highly selective mu-opiate receptor agonists. We recently demonstrated that EM-1 and EM-2 have a saturable transport system from brain-to-blood in vivo. Since the endothelial cells are the main component of the non-fenestrated microvessels of the blood-brain barrier (BBB), we examined whether these endogenous tetrapeptides have a saturable transport system in cultured cerebral endothelial cells. EM-1 and EM-2 binding and transport were studied in a transwell system in which primary mouse endothelial cells were co-cultured with rat glioma cells. We found that binding of both endomorphins was greater on the basolateral than the apical cell surface. Flux of EM-1 and EM-2 occurred predominantly in the basolateral to apical direction, each showing self-inhibition with an excess of the respective endomorphin. Transport was not influenced by the addition of the P-glycoprotein inhibitor, cyclosporin A. Neither the mu-opiate receptor agonist DAMGO nor the delta-opiate receptor agonist DPDPE had any effect on the transport. Thus, the results show that a saturable transport system for EM-1 and EM-2 occurs at the level of endothelial cells of the BBB, and unlike beta-endorphin and morphine, P-glycoprotein is not needed for the brain-to-blood transport. Cross-inhibition of the transport of each endomorphin by the other suggests a shared transport system that is different from mu- or delta-opiate receptors. As endormorphins are mainly produced in the CNS, the presence of the efflux system at the BBB could play an important role in pain modulation and neuroendocrine control.

  1. Cerebral Aneurysms

    MedlinePlus

    ... cerebral aneurysm may be required to restore deteriorating respiration and reduce abnormally high pressure within the brain. ... cerebral aneurysm may be required to restore deteriorating respiration and reduce abnormally high pressure within the brain. ...

  2. Cerebral Palsy

    MedlinePlus

    ... ol (Spanish) Recommend on Facebook Tweet Share Compartir Cerebral palsy (CP) is a group of disorders that affect ... resource—it highlights the ADDM Network’s data on cerebral palsy in a way that is useful for stakeholders ...

  3. Cerebral Palsy

    MedlinePlus

    Cerebral palsy is a group of disorders that affect a person's ability to move and to maintain balance ... do not get worse over time. People with cerebral palsy may have difficulty walking. They may also have ...

  4. Film Permeability Determination Using Static Permeability Cells

    EPA Pesticide Factsheets

    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).

  5. Scanning electron microscopy and dentinal permeability analysis of smear layer.

    PubMed

    Prati, C; Mongiorgi, R; Pashley, D H; Riva di Sanseverino, L

    1991-05-01

    The aim of the present study was to evaluate the surface morphology and the permeability of dentine after different acid treatments: polyacrylic acid, maleic acid, phosphoric acid and saline solution as control. Dentine permeability was expressed as hydraulic conductance. All the acid treatments removed the smear layer and increased the dentine permeability.

  6. Long-term Metal Performance of Three Permeable Pavements

    EPA Science Inventory

    EPA constructed a 4,000-m2 parking lot surfaced with three permeable pavements (permeable interlocking concrete pavers, pervious concrete, and porous asphalt) on the Edison Environmental Center in Edison, NJ in 2009. Samples from each permeable pavement infiltrate were collected...

  7. Stress does not increase blood–brain barrier permeability in mice

    PubMed Central

    Roszkowski, Martin

    2016-01-01

    Several studies have reported that exposure to acute psychophysiological stressors can lead to an increase in blood–brain barrier permeability, but these findings remain controversial and disputed. We thoroughly examined this issue by assessing the effect of several well-established paradigms of acute stress and chronic stress on blood–brain barrier permeability in several brain areas of adult mice. Using cerebral extraction ratio for the small molecule tracer sodium fluorescein (NaF, 376 Da) as a sensitive measure of blood–brain barrier permeability, we find that neither acute swim nor restraint stress lead to increased cerebral extraction ratio. Daily 6-h restraint stress for 21 days, a model for the severe detrimental impact of chronic stress on brain function, also does not alter cerebral extraction ratio. In contrast, we find that cold forced swim and cold restraint stress both lead to a transient, pronounced decrease of cerebral extraction ratio in hippocampus and cortex, suggesting that body temperature can be an important confounding factor in studies of blood–brain barrier permeability. To additionally assess if stress could change blood–brain barrier permeability for macromolecules, we measured cerebral extraction ratio for fluorescein isothiocyanate-dextran (70 kDa). We find that neither acute restraint nor cold swim stress affected blood–brain barrier permeability for macromolecules, thus corroborating our findings that various stressors do not increase blood–brain barrier permeability. PMID:27146513

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

    PubMed

    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. Experimental Volcanology: Fragmentation and Permeability

    NASA Astrophysics Data System (ADS)

    Spieler, O.

    2005-12-01

    An increasing number of scientists design new experiments to analyse processes that control the dynamics of explosive eruptions. There research is mostly coupled to numerical models and aims toward its controlling parameters. The fragmentation process, its threshold and the speed of the fragmentation wave as well as the energy consumed by the fragmentation are some hot spots of the experimental volcanology. Analysing the fragmentation behaviour of volcaniclastics as close to the natural system as possible, we found a number of physical constrains. Identifying the porosity as determining factor of the threshold, we realised that neither threshold nor the speed of the fragmentation process are solely controlled by the rock density. The later results of the shock tube type apparatus lead to the analysis of the specific surface area and permeability as direct links to textural features. Permeability analysis performed in a modified shock tube type apparatus, show two clear, distinct trends for dome rock and pyroclastic samples. The specific surface determined by Argon sorbtion (BET) as well as textural features of pumices from Campi Flegrei, Montserrat and Krakatoa (1883) give in contrary evidence of a more complex story. Large spherical, or ellipsoidal bubbles around fractured crystals prove that the high permeability of the pumice has partially developed after the fixing of the bubble size distribution. This puts up the question, if permeability measurements on pyroclastic samples reveal relevant numbers! The surface tension controlled 'self sealing' behaviour of surfaces from foaming obsidian hinders in situ measurements. Close textural investigations will have to clarify how the 'post process' samples deviate from the syneruptive conduit filling.

  10. Permeable membrane experiment

    NASA Technical Reports Server (NTRS)

    Slavin, Thomas J.; Cao, Tuan Q.; Kliss, Mark H.

    1993-01-01

    The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.

  11. Cytokines and Chemokines in Cerebral Malaria Pathogenesis.

    PubMed

    Dunst, Josefine; Kamena, Faustin; Matuschewski, Kai

    2017-01-01

    Cerebral malaria is among the major causes of malaria-associated mortality and effective adjunctive therapeutic strategies are currently lacking. Central pathophysiological processes involved in the development of cerebral malaria include an imbalance of pro- and anti-inflammatory responses to Plasmodium infection, endothelial cell activation, and loss of blood-brain barrier integrity. However, the sequence of events, which initiates these pathophysiological processes as well as the contribution of their complex interplay to the development of cerebral malaria remain incompletely understood. Several cytokines and chemokines have repeatedly been associated with cerebral malaria severity. Increased levels of these inflammatory mediators could account for the sequestration of leukocytes in the cerebral microvasculature present during cerebral malaria, thereby contributing to an amplification of local inflammation and promoting cerebral malaria pathogenesis. Herein, we highlight the current knowledge on the contribution of cytokines and chemokines to the pathogenesis of cerebral malaria with particular emphasis on their roles in endothelial activation and leukocyte recruitment, as well as their implication in the progression to blood-brain barrier permeability and neuroinflammation, in both human cerebral malaria and in the murine experimental cerebral malaria model. A better molecular understanding of these processes could provide the basis for evidence-based development of adjunct therapies and the definition of diagnostic markers of disease progression.

  12. Cytokines and Chemokines in Cerebral Malaria Pathogenesis

    PubMed Central

    Dunst, Josefine; Kamena, Faustin; Matuschewski, Kai

    2017-01-01

    Cerebral malaria is among the major causes of malaria-associated mortality and effective adjunctive therapeutic strategies are currently lacking. Central pathophysiological processes involved in the development of cerebral malaria include an imbalance of pro- and anti-inflammatory responses to Plasmodium infection, endothelial cell activation, and loss of blood-brain barrier integrity. However, the sequence of events, which initiates these pathophysiological processes as well as the contribution of their complex interplay to the development of cerebral malaria remain incompletely understood. Several cytokines and chemokines have repeatedly been associated with cerebral malaria severity. Increased levels of these inflammatory mediators could account for the sequestration of leukocytes in the cerebral microvasculature present during cerebral malaria, thereby contributing to an amplification of local inflammation and promoting cerebral malaria pathogenesis. Herein, we highlight the current knowledge on the contribution of cytokines and chemokines to the pathogenesis of cerebral malaria with particular emphasis on their roles in endothelial activation and leukocyte recruitment, as well as their implication in the progression to blood-brain barrier permeability and neuroinflammation, in both human cerebral malaria and in the murine experimental cerebral malaria model. A better molecular understanding of these processes could provide the basis for evidence-based development of adjunct therapies and the definition of diagnostic markers of disease progression. PMID:28775960

  13. Fluoxetine ameliorates cognitive impairments induced by chronic cerebral hypoperfusion via down-regulation of HCN2 surface expression in the hippocampal CA1 area in rats.

    PubMed

    Luo, Pan; Zhang, Xiaoxue; Lu, Yun; Chen, Cheng; Li, Changjun; Zhou, Mei; Lu, Qing; Xu, Xulin; Shen, Guanxin; Guo, Lianjun

    2016-01-01

    Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). Two weeks later, rats were treated with 30 mg/kg fluoxetine (intragastric injection, i.g.) for 6 weeks. Cognitive function was evaluated by Morris water maze (MWM) and novel objects recognition (NOR) test. Long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Western blotting was used to quantify the protein levels. Our results showed that fluoxetine treatment significantly improved the cognitive impairments caused by 2VO, accompanied with a reversion of 2VO-induced inhibitory of LTP. Furthermore, 2VO caused an up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) surface expressions in the hippocampal CA1 area and fluoxetine also effectively recovered the disorder of HCN2 surface expressions, which may be a possible mechanism that fluoxetine treatment ameliorates cognitive impairments in rats with CCH.

  14. Permeability of Dentine

    PubMed Central

    Ghazali, Farid Bin Che

    2003-01-01

    This is an update on the present integrated knowledge regarding dentine permeability that assumed a role in dentine sensitivity and contribute clinically to the effective bonding properties of restorative dental materials. This paper will attempt to refer to in vivo and in vitro studies of dentine permeability and the various interrelated factors governing it. PMID:23365497

  15. Permeability of dentine.

    PubMed

    Ghazali, Farid Bin Che

    2003-01-01

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

  16. Nexal membrane permeability to anions

    PubMed Central

    1978-01-01

    The permeability of the septa of the earthworm in the median axon has been calculated for the anions fluorescein and its halogen derivatives. The values ranged from 5.4 X 10(-5) to 4 X 10(-6) cm/s. Previously, the septa had been shown to contain nexuses. By using freeze-fracture material, the surface area of nexus on the septal membranes was determined to be 4.5%, very similar to the percentage of nexus in the intercalated disk of mammalian myocardium. Plasma membrane permeability to these dyes was also calculated and shown to be much less than that of the septal membranes. In addition, an estimate of cytoplasmic binding for each dye was made, and most dyes showed little or no binding with the exception of aminofluorescein. PMID:702107

  17. Effect of surface permeability on the structure of a separated turbulent flow and heat transfer behind a backward-facing step

    NASA Astrophysics Data System (ADS)

    Terekhov, V. V.; Terekhov, V. I.

    2017-03-01

    The structure and heat transfer in a turbulent separated flow in a suddenly expanding channel with injection (suction) through a porous wall are numerically simulated with the use of two-dimensional averaged Navier-Stokes equations, energy equations, and v 2- f turbulence model. It is shown that enhancement of the intensity of the transverse mass flux on the wall reduces the separation region length in the case of suction and increases the separation region length in the case of injection up to complete boundary layer displacement. The maximum heat transfer coefficient as a function of permeability is accurately described by the asymptotic theory of a turbulent boundary layer.

  18. Cerebral malaria

    PubMed Central

    Rénia, Laurent; Wu Howland, Shanshan; Claser, Carla; Charlotte Gruner, Anne; Suwanarusk, Rossarin; Hui Teo, Teck; Russell, Bruce; Ng, Lisa

    2012-01-01

    Cerebral malaria is the most severe pathology caused by the malaria parasite, Plasmodium falciparum. The pathogenic mechanisms leading to cerebral malaria are still poorly defined as studies have been hampered by limited accessibility to human tissues. Nevertheless, histopathology of post-mortem human tissues and mouse models of cerebral malaria have indicated involvement of the blood-brain barrier in cerebral malaria. In contrast to viruses and bacteria, malaria parasites do not infiltrate and infect the brain parenchyma. Instead, rupture of the blood-brain barrier occurs and may lead to hemorrhages resulting in neurological alterations. Here, we review the most recent findings from human studies and mouse models on the interactions of malaria parasites and the blood-brain barrier, shedding light on the pathogenesis of cerebral malaria, which may provide directions for possible interventions. PMID:22460644

  19. Systematization, description, and territory of the caudal cerebral artery in surface of the brain of the ostrich (Struthio camelus).

    PubMed

    Nazer, Manoel; Campos, Rui

    2014-08-01

    Brain specimens from 30 ostriches were injected with red-dyed latex via the internal carotid arteries, and the caudal cerebral arteries and their branches were systematically described. On the right side, the caudal cerebral artery was double-, triple-, quadruple-, and single-branched in 73.5%, 23.3%, 3.3%, and 3.3% of cases, respectively; on the left side, it was double-, triple-, quadruple-, and single-branched in 76.7%, 20%, 3.3%, and 3.3% of cases, respectively. The dorsal tectal mesencephalic artery appeared as a single vessel in 96.7% of cases, emerging as a collateral branch of the caudal cerebral artery. The dorsal mesencephalic tectal artery originated from the right dorsal cerebellar artery in 40% of cases and from the left side in 63.3% of cases. On the right side, there were four and three medial occipital hemispheric branches in 46.7% and 20% of cases, respectively; on the left side, there were four and three branches in 30% and 26.7% of cases. On the right side, the pineal artery was double-, single-, triple-, and quadruple-branched in 50%, 23.3%, 20%, and 6.7% of cases, respectively; on the left side, this artery was double-, single-, triple-, and quadruple-branched in 50%, 23.3%, 16.7%, and 10% of cases, respectively. The diencephalic artery was on the right side in 43.3% of cases and on the left side in 56.7% of cases. The interhemispheric artery was on the right side in 56.7% of cases and on the left side in 43.3% of cases; four, three, two, five, and one dorsal hemispheric trunks branched off of the interhemispheric artery in 40%, 40%, 10%, 6.7%, and 26.7% of cases, respectively. The caudal cerebral artery was classified as Type I in 56.7% of cases (subtype IA in 33.3% of cases and IB in 23.3% of cases), Type II in 40% of cases (subtype IIA in 20% of cases and IIB in 20% of cases), and Type III in 3.3% of cases.

  20. Dentin permeability after toothbrushing with different toothpastes.

    PubMed

    Prati, C; Chersoni, S; Lucchese, A; Pashley, D H; Mongiorgi, R

    1999-08-01

    To evaluate the interaction of smear layer produced during brushing and dentifrice particles. Dentin disks were obtained from extracted human third molars. Dentin permeability was evaluated using a hydraulic pressure apparatus working at 1 psi of pressure. After preparation, each sample was connected to the hydraulic pressure apparatus to evaluate the permeability of dentin with the smear layer produced during specimen preparation. After 5 min of measurements dentin was etched with 37% phosphoric acid gel for 2 min, washed and gently dried with cotton to measure the permeability after smear layer removal. This was done to measure the maximum permeability of each specimen (expressed as 100%). Then a second smear layer was produced using a #400 carbide paper under water for 1 min. Dentin permeability of the smear layer covered dentin was then measured, and expressed as a percent of the maximum permeability of that specimen, permitting each specimen to serve as its own control. The three toothpastes used (Merfluan powder, Merfluan paste and Fluorigard) were applied on dentin surfaces using a small sponge to completely cover the dentin surface. After 5 s, each sample was connected to a mechanical device and brushed under water for 3 min with constant pressure of 250 gr using a Colgate medium toothbrush. After this treatment, each sample was gently washed with tap water, gently air dried for 3-5 s and connected with the pressure apparatus to remeasure the permeability after brushing. For SEM examination of dentin before and after treatment with toothpaste and brushing, each dentin and enamel sample was fixed in 2% buffered glutaraldehyde. Dentin permeability proved unaffected by dentifrice treatments. SEM observations demonstrated the presence of dentifrice particles on dentin surface and inside dentin tubules. Smear plugs produced during dentin brushing were not removed by dentifrices.

  1. Fluid permeability of deformable fracture networks

    SciTech Connect

    Brown, S.R.; Bruhn, R.L.

    1997-04-01

    The authors consider the problem of defining the fracture permeability tensor for each grid lock in a rock mass from maps of natural fractures. For this purpose they implement a statistical model of cracked rock due to M. Oda [1985], where the permeability tensor is related to the crack geometry via a volume average of the contribution from each crack in the population. In this model tectonic stress is implicitly coupled to fluid flow through an assumed relationship between crack aperture and normal stress across the crack. The authors have included the following enhancements to the basic model: (1) a realistic model of crack closure under stress has been added along with the provision to apply tectonic stresses to the fracture system in any orientation, the application of stress results in fracture closure and consequently a reduction in permeability; (2) the fracture permeability can be superimposed onto an arbitrary anisotropic matrix permeability; (3) the fracture surfaces are allowed to slide under the application of shear stress, causing fractures to dilate and result in a permeability increase. Through an example, the authors demonstrate that significant changes in permeability magnitudes and orientations are possible when tectonic stress is applied to a fracture system.

  2. Permeability of porour rhyolite

    NASA Astrophysics Data System (ADS)

    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

  3. Permeability of edible coatings.

    PubMed

    Mishra, B; Khatkar, B S; Garg, M K; Wilson, L A

    2010-01-01

    The permeabilities of water vapour, O2 and CO2 were determined for 18 coating formulations. Water vapour transmission rate ranged from 98.8 g/m(2).day (6% beeswax) to 758.0 g/m(2).day (1.5% carboxymethyl cellulose with glycerol). O2 permeability at 14 ± 1°C and 55 ± 5% RH ranged from 1.50 to 7.95 cm(3)cm cm(-2)s(-1)Pa(-1), with CO2 permeability 2 to 6 times as high. Permeability to noncondensable gases (O2 and CO2) was higher for hydrophobic (peanut oil followed by beeswax) coatings as compared to hydrophilic (whey protein concentrate and carboxymethyl cellulose).

  4. Axisymmetric rotational stagnation point flow impinging radially a permeable stretching/shrinking surface in a nanofluid using Tiwari and Das model.

    PubMed

    Roşca, Natalia C; Pop, Ioan

    2017-01-12

    In this paper, the problem of normal impingement rotational stagnation-point flow on a radially permeable stretching sheet in a viscous fluid, recently studied in a very interesting paper, is extended to a water-based nanofluid. A similarity transformation is used to reduce the system of governing nonlinear partial differential equations to a system of ordinary differential equations, which is then solved numerically using the function bvp4c from Matlab. It is found that dual (upper and lower branch) solutions exist for some values of the governing parameters. From the stability analysis, it is found that the upper branch solution is stable, while the lower branch solution is unstable. Sample velocity and temperature profiles along both solution branches are graphically presented.

  5. Axisymmetric rotational stagnation point flow impinging radially a permeable stretching/shrinking surface in a nanofluid using Tiwari and Das model

    NASA Astrophysics Data System (ADS)

    Roşca, Natalia C.; Pop, Ioan

    2017-01-01

    In this paper, the problem of normal impingement rotational stagnation-point flow on a radially permeable stretching sheet in a viscous fluid, recently studied in a very interesting paper, is extended to a water-based nanofluid. A similarity transformation is used to reduce the system of governing nonlinear partial differential equations to a system of ordinary differential equations, which is then solved numerically using the function bvp4c from Matlab. It is found that dual (upper and lower branch) solutions exist for some values of the governing parameters. From the stability analysis, it is found that the upper branch solution is stable, while the lower branch solution is unstable. Sample velocity and temperature profiles along both solution branches are graphically presented.

  6. Axisymmetric rotational stagnation point flow impinging radially a permeable stretching/shrinking surface in a nanofluid using Tiwari and Das model

    PubMed Central

    Roşca, Natalia C.; Pop, Ioan

    2017-01-01

    In this paper, the problem of normal impingement rotational stagnation-point flow on a radially permeable stretching sheet in a viscous fluid, recently studied in a very interesting paper, is extended to a water-based nanofluid. A similarity transformation is used to reduce the system of governing nonlinear partial differential equations to a system of ordinary differential equations, which is then solved numerically using the function bvp4c from Matlab. It is found that dual (upper and lower branch) solutions exist for some values of the governing parameters. From the stability analysis, it is found that the upper branch solution is stable, while the lower branch solution is unstable. Sample velocity and temperature profiles along both solution branches are graphically presented. PMID:28079124

  7. Seismic waves increase permeability.

    PubMed

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

    2006-06-29

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

  8. Cerebral Paragonimiasis.

    PubMed

    Miyazaki, I

    1975-01-01

    The first case of cerebral paragonimiasis was reported by Otani in Japan in 1887. This was nine years after Kerbert's discovery of the fluke in the lungs of Bengal tigers and seven years after a human pulmonary infection by the fluke was demonstrated by Baelz and Manson. The first case was a 26-year-old man who had been suffering from cough and hemosputum for one year. The patient developed convulsive seizures with subsequent coma and died. The postmortem examination showed cystic lesions in the right frontal and occipital lobes. An adult fluke was found in the occipital lesion and another was seen in a gross specimen of normal brain tissue around the affected occipital lobe. Two years after Otani's discovery, at autopsy a 29-year-old man with a history of Jacksonian seizure was reported as having cerebral paragonimiasis. Some time later, however, it was confirmed that the case was actually cerebral schistosomiasis japonica. Subsequently, cases of cerebral paragonimiasis were reported. However, the majority of these cases were not confirmed histologically. It was pointed out that some of these early cases were probably not Paragonimus infection. After World War II, reviews as well as case reports were published. Recently, investigations have been reported from Korea, with a clinicla study on 62 cases of cerebral paragonimiasis seen at the Neurology Department of the National Medical Center, Seoul, between 1958 and 1964. In 1971 Higashi described a statistical study on 105 cases of cerebral paragonimiasis that had been treated surgically in Japan.

  9. Development of a Digital Aquifer Permeability Map for the ...

    EPA Pesticide Factsheets

    Researchers at the U.S. Environmental Protection Agency’s Western Ecology Division have been developing hydrologic landscape maps for selected U.S. states in an effort to create a method to identify the intrinsic watershed attributes of landscapes in regions with little data. Each hydrologic landscape unit is assigned a categorical value from five key indices of macro-scale hydrologic behavior, including annual climate, climate seasonality, aquifer permeability, terrain, and soil permeability. The aquifer permeability index requires creation of a from-scratch dataset for each state. The permeability index for the Pacific Southwest (California, Nevada, and Arizona) expands and modifies the permeability index for the Pacific Northwest (Oregon, Washington, and Idaho), which preceded it. The permeability index was created by assigning geologic map units to one of 18 categories with presumed similar values of permeability to create a hydrolithologic map. The hydrolithologies were then further categorized into permeability index classifications of high, low, unknown and surface water. Unconsolidated, carbonate, volcanic, and undifferentiated units are classified more conservatively to better address uncertainty in source data. High vs. low permeability classifications are assigned qualitatively but follow a threshold guideline of 8.5x10-2 m/day hydraulic conductivity. Estimates of permeability from surface lithology is the current best practice for broad-sca

  10. Development of a Digital Aquifer Permeability Map for the ...

    EPA Pesticide Factsheets

    Researchers at the U.S. Environmental Protection Agency’s Western Ecology Division have been developing hydrologic landscape maps for selected U.S. states in an effort to create a method to identify the intrinsic watershed attributes of landscapes in regions with little data. Each hydrologic landscape unit is assigned a categorical value from five key indices of macro-scale hydrologic behavior, including annual climate, climate seasonality, aquifer permeability, terrain, and soil permeability. The aquifer permeability index requires creation of a from-scratch dataset for each state. The permeability index for the Pacific Southwest (California, Nevada, and Arizona) expands and modifies the permeability index for the Pacific Northwest (Oregon, Washington, and Idaho), which preceded it. The permeability index was created by assigning geologic map units to one of 18 categories with presumed similar values of permeability to create a hydrolithologic map. The hydrolithologies were then further categorized into permeability index classifications of high, low, unknown and surface water. Unconsolidated, carbonate, volcanic, and undifferentiated units are classified more conservatively to better address uncertainty in source data. High vs. low permeability classifications are assigned qualitatively but follow a threshold guideline of 8.5x10-2 m/day hydraulic conductivity. Estimates of permeability from surface lithology is the current best practice for broad-sca

  11. Studies on water transport through the sweet cherry fruit surface. 11. FeCl3 decreases water permeability of polar pathways.

    PubMed

    Weichert, Holger; Knoche, Moritz

    2006-08-23

    The effect of FeCl3 (10 mM) on osmotic water uptake into detached sweet cherry fruit (Prunus avium L.) and on the (3)H2O permeability (P(d)) of excised exocarp segments (ES) or enzymatically isolated cuticular membranes (CM) was investigated. ES or CM were mounted in an infinite dose diffusion system, where diffusion is monitored from a dilute donor solution through an interfacing ES or CM into a receiver solution under quasi steady-state conditions. In the absence of FeCl3, (3)H2O diffusion through stomatous ES was linear over time, indicating that P(d) was constant. Adding FeCl3 to the donor decreased P(d) by about 60%. P(d) remained at a decreased level when replacing the FeCl3 donor again by deionized water. The decrease in P(d) was positively and linearly related to the stomatal density of the ES. There was no effect of FeCl3 on the P(d) of astomatous sweet cherry fruit ES or CM regardless of the presence of wax (epicuticular or cuticular). FeCl3 decreased P(d) when added to the donor (-63%) or receiver (-16%), but there was no effect when it was added to donor and receiver solutions simultaneously. The decrease in P(d) depended on the pH of the receiver and the presence of citrate buffer. There was no effect of FeCl3 with citrate buffer as a receiver regardless of pH (range 2.0-6.0). When using nonbuffered receiver solutions with pH adjusted to pH 2.0, 3.0, 4.5, or 6.0, FeCl3 markedly decreased (3)H2O diffusion at pH > or = 3 but had no effect at pH 2.0. FeCl3 increased the energy of activation (E(a)) for (3)H2O diffusion (range 15-45 degrees C) through stomatous ES but had no significant effect in astomatous CM. The increase in E(a) by FeCl3 was positively related to stomatal density. FeCl3 decreased the P(d) for 2-(1-naphthyl)[1-(14)C]acetic acid (NAA) and 2,4-dichloro[U-(14)C]phenoxyacetic acid (2,4-D) in stomatous ES. The magnitude of the effect depended on the degree of dissociation and was larger for the dissociated acids (pH 6.2) than for the

  12. Effects of surface modification with Co3O4 nanoparticles on the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ membranes

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Cheng, Jigui; Huang, Min; Liu, Meng; Li, Mingming; Xu, Chenxi

    2017-09-01

    To promote the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) membranes, Co3O4 nanoparticle catalysts were loaded onto the surfaces of BSCF membranes by a dip-coating process. X-ray diffraction (XRD) results reveal that Co3O4 nanoparticles crystalize in spinel phase. Scanning electron microscope (SEM) observation indicates that the mean particle size of the Co3O4 nanoparticles is about 100 nm in diameter and 20 μm in thickness after annealing at 500 °C for 5 h. Energy dispersive spectrometer (EDS) results testify that the percentage of the elements in the modified layer are in accordance with the stoichiometric ratio of Co3O4. Oxygen permeation tests were made in a laboratory self-made device, and the results show that loading Co3O4 nanoparticle catalysts onto the surfaces of BSCF membranes can significantly increase the oxygen permeability of the BSCF membranes. The unmodified BSCF membranes have an oxygen permeation flux of 0.1080 ml cm-2 min-1 at 600 °C. This increases to 0.4302 ml cm-2 min-1, for the modified membranes, which is four times higher than that of the unmodified BSCF membranes. The oxygen permeation activation energy decreases from 91.42 to 50.71 kJ mol-1 at 600-800 °C by loading Co3O4 nanoparticle catalysts on the surface of BSCF membranes.

  13. Permeable pavement study (Edison)

    EPA Pesticide Factsheets

    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 parking lot in Edison, New Jersey, that incorporated permeable interlocking concrete pavement (PICP), pervious concrete (PC), and porous asphalt (PA). Each permeable pavement type has four, 54.9-m2, lined sections that direct all infiltrate into 5.7-m3 tanks enabling complete volume collection and sampling. This paper highlights the results from a 12-month period when samples were collected from 13 rainfall/runoff events and analyzed for nitrogen species, orthophosphate, and organic carbon. Differences in infiltrate concentrations among the three permeable pavement types were assessed and compared with concentrations in rainwater samples and impervious asphalt runoff samples, which were collected as controls. Contrary to expectations based on the literature, the PA infiltrate had significantly larger total nitrogen (TN) concentrations than runoff and infiltrate from the other two permeable pavement types, indicating that nitrogen leached from materials in the PA strata. There was no significant difference in TN concentration between runoff and infiltrate from either PICP or PC, but TN in runoff was significantly larger than in the rainwater, suggesting meaningful inter-event dry de

  14. 2D Si island nucleation on the Si(111) surface at initial and late growth stages: On the role of step permeability in pyramidlike growth

    NASA Astrophysics Data System (ADS)

    Rogilo, D. I.; Fedina, L. I.; Kosolobov, S. S.; Ranguelov, B. S.; Latyshev, A. V.

    2017-01-01

    Initial and late stages of 2D Si island nucleation and growth (2DNG) on extra-large ( 100 μm) and medium size (1-10 μm) atomically flat Si(111)-(7×7) terraces bordered by step bunches have been studied by in situ REM at T =600-750 °С. At first, the layer-by-layer 2DNG takes place on whole terraces and 2D island concentration dependence on deposition rate R corresponds to critical nucleus size i =1. Continuous 2DNG triggers morphological instabilities: elongated pyramidlike waves and separate pyramids emerge on all terraces at T ≤720 °С and T =750 °С, respectively. Both instabilities arise due to the imbalance of uphill/downhill adatom currents related with large Ehrlich-Schwöbel (ES) barriers and permeability of straight [ 11 bar 2 ] -type step edges. However, the first one is initiated by dominant downhill adatom current to distant sinks: bunches, wave's step edges, and "vacancy" islands emerging on terraces due to 2D island coalescence. As a result, top layer size decreases to the critical terrace width λ where 2DNG takes place. From the analysis of λ ∝ R - χ / 2 scaling at T =650 °C, we have found that i increases from i =2 on a three-layer wave to i =6-8 on a six-layer wave. This authenticates the significance of downhill adatom sink to distant steps related to the step permeability. The second instability type at T >720 °C is related to the raising of uphill adatom current due to slightly larger ES barrier for step-up attachment comparing to the step-down one (EES- 0.9 eV [Phys. Rev. Lett. 111 (2013) 036105]). This leads to "second layer" 2D nucleation on top layers, which triggers the growth of separate pyramids. Because of small difference between ES barriers, net uphill/downhill adatom currents are nearly equivalent, and therefore layer coverage distributions of both instabilities display similar linear slopes.

  15. Cerebral Palsy (For Parents)

    MedlinePlus

    ... Old Feeding Your 1- to 2-Year-Old Cerebral Palsy KidsHealth > For Parents > Cerebral Palsy A A A ... kids who are living with the condition. About Cerebral Palsy Cerebral palsy is one of the most common ...

  16. Cerebral palsy - resources

    MedlinePlus

    Resources - cerebral palsy ... The following organizations are good resources for information on cerebral palsy : National Institute of Neurological Disorders and Stroke -- www.ninds.nih.gov/disorders/cerebral_palsy/cerebral_palsy. ...

  17. Cerebral Palsy (For Teens)

    MedlinePlus

    ... Right Sport for You Healthy School Lunch Planner Cerebral Palsy KidsHealth > For Teens > Cerebral Palsy Print A A ... do just what everyone else does. What Is Cerebral Palsy? Cerebral palsy (CP) is a disorder of the ...

  18. The Effects of Buoyancy and Transpiration on the Flow and Heat Transfer over a Moving Permeable Surface in a Parallel Stream in the Presence of Radiation

    NASA Astrophysics Data System (ADS)

    Olanrewaju, P. O.; Hayat, T.

    2014-07-01

    This paper is concerned with steady boundary layer flow over a moving permeable sheet in a viscous and incompressible fluid. In addition to mass transfer from the plate (suction or injection), the buoyancy term is included in the momentum equation and the viscous dissipation and radiation terms are also included in the energy equation. The sheet is assumed to move in the same or opposite direction to the free stream. Using a similarity variable, the steady-state governing nonlinear partial differential equations have been transformed into a set of coupled nonlinear ordinary differential equations, which are solved numerically by applying shooting iteration technique together with sixth-order Runge-Kutta integration scheme. In order to have a true similarity solution, the parameter Grx must be constant and not depend on x. This condition can be met if the thermal expansion coefficient β is proportional to x-1. The effects of Prandtl number, Eckert number, the local Grashof number, and the radiation parameter on the velocity and temperature profiles are illustrated and interpreted in physical terms. A comparison with previously published results on the special case of the problem shows excellent agreement.

  19. Cerebral palsy.

    PubMed

    Colver, Allan; Fairhurst, Charles; Pharoah, Peter O D

    2014-04-05

    The syndrome of cerebral palsy encompasses a large group of childhood movement and posture disorders. Severity, patterns of motor involvement, and associated impairments such as those of communication, intellectual ability, and epilepsy vary widely. Overall prevalence has remained stable in the past 40 years at 2-3·5 cases per 1000 livebirths, despite changes in antenatal and perinatal care. The few studies available from developing countries suggest prevalence of comparable magnitude. Cerebral palsy is a lifelong disorder; approaches to intervention, whether at an individual or environmental level, should recognise that quality of life and social participation throughout life are what individuals with cerebral palsy seek, not improved physical function for its own sake. In the past few years, the cerebral palsy community has learned that the evidence of benefit for the numerous drugs, surgery, and therapies used over previous decades is weak. Improved understanding of the role of multiple gestation in pathogenesis, of gene environment interaction, and how to influence brain plasticity could yield significant advances in treatment of the disorder. Reduction in the prevalence of post-neonatal cerebral palsy, especially in developing countries, should be possible through improved nutrition, infection control, and accident prevention. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. On the effectiveness of viscous dissipation and Joule heating on steady Magnetohydrodynamic heat and mass transfer flow over an inclined radiate isothermal permeable surface in the presence of thermophoresis

    NASA Astrophysics Data System (ADS)

    Alam, M. S.; Rahman, M. M.; Sattar, M. A.

    2009-05-01

    The combined effect of viscous dissipation and joule heating on steady Magnetohydrodynamic heat and mass transfer flow of viscous incompressible fluid over an inclined radiate isothermal permeable surface in the presence of thermophoresis is studied. Numerical results for the dimensionless velocity, temperature and concentration profiles as well as the local skin-friction coefficient, the local Nusselt number and the local Stanton number are displayed graphically for various physical parameters. Comparisons with previously published work are performed and the results are found to be in very good agreement. Results show that rate of heat transfer is sensitive for increasing angle of inclination parameter for the case of fluid injection and it decreases with the increase of magnetic field parameter and Eckert number.

  1. Contrasting pediatric and adult cerebral malaria

    PubMed Central

    Hawkes, Michael; Elphinstone, Robyn E; Conroy, Andrea L; Kain, Kevin C

    2013-01-01

    Malaria affects millions of people around the world and a small subset of those infected develop cerebral malaria. The clinical presentation of cerebral malaria differs between children and adults, and it has been suggested that age-related changes in the endothelial response may account for some of these differences. During cerebral malaria, parasites sequester within the brain microvasculature but do not penetrate into the brain parenchyma and yet, the infection causes severe neurological symptoms. Endothelial dysfunction is thought to play an important role in mediating these adverse clinical outcomes. During infection, the endothelium becomes activated and more permeable, which leads to increased inflammation, hemorrhages, and edema in the surrounding tissue. We hypothesize that post-natal developmental changes, occurring in both endothelial response and the neurovascular unit, account for the differences observed in the clinical presentations of cerebral malaria in children compared with adults. PMID:23924893

  2. Blood-brain barrier tight junction permeability and ischemic stroke.

    PubMed

    Sandoval, Karin E; Witt, Ken A

    2008-11-01

    The blood-brain barrier (BBB) is formed by the endothelial cells of cerebral microvessels, providing a dynamic interface between the peripheral circulation and the central nervous system. The tight junctions (TJs) between the endothelial cells serve to restrict blood-borne substances from entering the brain. Under ischemic stroke conditions decreased BBB TJ integrity results in increased paracellular permeability, directly contributing to cerebral vasogenic edema, hemorrhagic transformation, and increased mortality. This loss of TJ integrity occurs in a phasic manner, which is contingent on several interdependent mechanisms (ionic dysregulation, inflammation, oxidative and nitrosative stress, enzymatic activity, and angiogenesis). Understanding the inter-relation of these mechanisms is critical for the development of new therapies. This review focuses on those aspects of ischemic stroke impacting BBB TJ integrity and the principle regulatory pathways, respective to the phases of paracellular permeability.

  3. Mechanism of dexamethasone suppression of brain tumor-associated vascular permeability in rats. Involvement of the glucocorticoid receptor and vascular permeability factor.

    PubMed Central

    Heiss, J D; Papavassiliou, E; Merrill, M J; Nieman, L; Knightly, J J; Walbridge, S; Edwards, N A; Oldfield, E H

    1996-01-01

    Brain tumor-associated cerebral edema arises because tumor capillaries lack normal blood-brain barrier function; vascular permeability factor (VPF, also known as vascular endothelial growth factor, VEGF) is a likely mediator of this phenomenon. Clinically, dexamethasone reduces brain tumor-associated vascular permeability through poorly understood mechanisms. Our goals were to determine if suppression of permeability by dexamethasone might involve inhibition of VPF action or expression, and if dexamethasone effects in this setting are mediated by the glucocorticoid receptor (GR). In two rat models of permeability (peripheral vascular permeability induced by intradermal injection of 9L glioma cell-conditioned medium or purified VPF, and intracerebral vascular permeability induced by implanted 9L glioma), dexamethasone suppressed permeability in a dose-dependent manner. Since 80% of the permeability-inducing activity in 9L-conditioned medium was removed by anti-VPF antibodies, we examined dexamethasone effects of VPF expression in 9L cells. Dexamethasone inhibited FCS- and PDGF-dependent induction of VPF expression. At all levels (intradermal, intracranial, and cell culture), dexamethasone effects were reversed by the GR antagonist mifepristone (RU486). Dexamethasone may decrease brain tumor-associated vascular permeability by two GR-dependent mechanisms: reduction of the response of the vasculature to tumor-derived permeability factors (including VPF), and reduction of VPF expression by tumor cells. PMID:8823305

  4. Update to Permeable Pavement Research at the Edison ...

    EPA Pesticide Factsheets

    The EPA’s Urban Watershed Management Branch (UWMB) has been monitoring the permeable pavement demonstration site at the Edison Environmental Center, NJ since 2010. This site has three different types of permeable pavements including interlocking concrete permeable pavers, pervious concrete, and porous asphalt. The permeable pavements are limited to parking spaces while adjacent driving lanes are impermeable and drain to the permeable surfaces. The parking lot is instrumented for continuous monitoring with thermistors and water content reflectometers that measure moisture as infiltrate passes through the storage gallery beneath the permeable pavements into the underlying native soil. Each permeable surface of the parking lot has four lined sections that capture infiltrate in tanks for water quality analyses; these tanks are capable of holding volumes up to 4.1 m3, which represents up to 38 mm (1.5 in.) for direct rainfall on the porous pavement and runoff from adjacent driving lanes that drain into the permeable surface.Previous technical releases concerning the demonstration site focused on monitoring techniques, observed chloride and nutrient concentrations, surface hydrology, and infiltration and evaporation rates. This presentation summarizes these past findings and addresses current water quality efforts including pH, solids analysis, total organic carbon, and chemical oxygen demand. Stormwater runoff continues to be a major cause of water pollution in

  5. Structural determinants of glomerular permeability.

    PubMed

    Deen, W M; Lazzara, M J; Myers, B D

    2001-10-01

    Recent progress in relating the functional properties of the glomerular capillary wall to its unique structure is reviewed. The fenestrated endothelium, glomerular basement membrane (GBM), and epithelial filtration slits form a series arrangement in which the flow diverges as it enters the GBM from the fenestrae and converges again at the filtration slits. A hydrodynamic model that combines morphometric findings with water flow data in isolated GBM has predicted overall hydraulic permeabilities that are consistent with measurements in vivo. The resistance of the GBM to water flow, which accounts for roughly half that of the capillary wall, is strongly dependent on the extent to which the GBM surfaces are blocked by cells. The spatial frequency of filtration slits is predicted to be a very important determinant of the overall hydraulic permeability, in keeping with observations in several glomerular diseases in humans. Whereas the hydraulic resistances of the cell layers and GBM are additive, the overall sieving coefficient for a macromolecule (its concentration in Bowman's space divided by that in plasma) is the product of the sieving coefficients for the individual layers. Models for macromolecule filtration reveal that the individual sieving coefficients are influenced by one another and by the filtrate velocity, requiring great care in extrapolating in vitro observations to the living animal. The size selectivity of the glomerular capillary has been shown to be determined largely by the cellular layers, rather than the GBM. Controversial findings concerning glomerular charge selectivity are reviewed, and it is concluded that there is good evidence for a role of charge in restricting the transmural movement of albumin. Also discussed is an effect of albumin that has received little attention, namely, its tendency to increase the sieving coefficients of test macromolecules via steric interactions. Among the unresolved issues are the specific contributions of the

  6. Permeability reduction in granite under hydrothermal conditions

    USGS Publications Warehouse

    Morrow, C.A.; Moore, Diane E.; Lockner, D.A.

    2001-01-01

    The formation of impermeable fault seals between earthquake events is a feature of many models of earthquake generation, suggesting that earthquake recurrence may depend in part on the rate of permeability reduction of fault zone materials under hydrothermal conditions. In this study, permeability measurements were conducted on intact, fractured, and gouge-bearing Westerly granite at an effective pressure of 50 MPa and at temperatures from 150?? to 500??C, simulating conditions in the earthquake-generating portions of fault zones. Pore fluids were cycled back and forth under a 2 MPa pressure differential for periods of up to 40 days. Permeability of the granite decreased with time t, following the exponential relation k = c(10-rt). For intact samples run between 250?? and 500??C the time constant for permeability decrease r was proportional to temperature and ranged between 0.001 and 0.1 days-1 (i.e., between 0.4 and 40 decades year-1 loss of permeability). Values of r for the lower-temperature experiments differed little from the 250??C runs. In contrast, prefractured samples showed higher rates of permeability decrease at a given temperature. The surfaces of the fractured samples showed evidence of dissolution and mineral growth that increased in abundance with both temperature and time. The experimentally grown mineral assemblages varied with temperature and were consistent with a rock-dominated hydrothermal system. As such mineral deposits progressively seal the fractured samples, their rates of permeability decrease approach the rates for intact rocks at the same temperature. These results place constraints on models of precipitation sealing and suggest that fault rocks may seal at a rate consistent with earthquake recurrence intervals of typical fault zones.

  7. Surface-Based fMRI-Driven Diffusion Tractography in the Presence of Significant Brain Pathology: A Study Linking Structure and Function in Cerebral Palsy

    PubMed Central

    Cunnington, Ross; Boyd, Roslyn N.; Rose, Stephen E.

    2016-01-01

    Diffusion MRI (dMRI) tractography analyses are difficult to perform in the presence of brain pathology. Automated methods that rely on cortical parcellation for structural connectivity studies often fail, while manually defining regions is extremely time consuming and can introduce human error. Both methods also make assumptions about structure-function relationships that may not hold after cortical reorganisation. Seeding tractography with functional-MRI (fMRI) activation is an emerging method that reduces these confounds, but inherent smoothing of fMRI signal may result in the inclusion of irrelevant pathways. This paper describes a novel fMRI-seeded dMRI-analysis pipeline based on surface-meshes that reduces these issues and utilises machine-learning to generate task specific white matter pathways, minimising the requirement for manually-drawn ROIs. We directly compared this new strategy to a standard voxelwise fMRI-dMRI approach, by investigating correlations between clinical scores and dMRI metrics of thalamocortical and corticomotor tracts in 31 children with unilateral cerebral palsy. The surface-based approach successfully processed more participants (87%) than the voxel-based approach (65%), and provided significantly more-coherent tractography. Significant correlations between dMRI metrics and five clinical scores of function were found for the more superior regions of these tracts. These significant correlations were stronger and more frequently found with the surface-based method (15/20 investigated were significant; R2 = 0.43–0.73) than the voxelwise analysis (2 sig. correlations; 0.38 & 0.49). More restricted fMRI signal, better-constrained tractography, and the novel track-classification method all appeared to contribute toward these differences. PMID:27487011

  8. [The effect of carbachol on pulmonary vascular permeability and lung water content during oral fluid resuscitation of burn shock induced by a 50% total body surface area full-thickness flame injury in dogs].

    PubMed

    Hu, Sen; Chen, Jin-wei; Bao, Cheng-mei; Sheng, Zhi-yong

    2009-05-01

    To investigate the effects of carbachol (CAR) on pulmonary vascular permeability and pulmonary water content during oral fluid resuscitation of burn shock. Twelve male Beagle dogs with intubation of carotid artery and jugular vein for 24 hours were subjected to a 50% total body surface area (TBSA) full-thickness burn, then they were equally divided into oral resuscitation (OR) and OR plus CAR groups (OR+CAR). Dogs were given either a glucose-electrolyte solution (GES) in OR group or GES containing CAR (20 microg/kg) in OR+CAR group by gavage within 24 hours after burn. Dogs in each group were given intravenous fluid resuscitation after 24 post burn hour (PBH). The delivery rate and volume of GES was in accordance with that of Parkland formula. Respiratory rate (RR), arterial partial pressure of oxygen (PaO(2)), extravascular lung water index (ELWI) and pulmonary vascular permeability index (PVPI) were determined before burn (0 hour), and at 2, 4, 8, 24, 48 and 72 PBH. At 72 PBH or before death, dogs were sacrificed to collect lung tissue for evaluation of myeloperoxidase (MPO), malondialdehyde (MDA), and assessment of the tissue water content by dry to wet weight. Compared with those before burn, RR, ELWI and PVPI were greatly increased, and PaO(2) obviously decreased in two groups after burn (all P<0.01). At 72 PBH, PaO(2) returned to pre-burn level, while RR, ELWI and PVPI were still higher than pre-burn levels. RR, ELWI and PVPI at 4, 8 and 24 PBH, and PaO(2) at 8, 24, 48 PBH in OR+CAR group were respectively lower or higher than those in OR group (P<0.05 or P<0.01), but those measurements showed no statistical differences between two groups at 72 PBH (all P>0.05). MPO, MDA and lung water contents in OR+CAR group were significantly lower than those in OR group at 72 PBH [(2.64+/-0.38) U/mg vs.(4.12+/-0.46) U/mg, P<0.01; (3.60+/-0.54) micromol/mg vs.(5.14+/-0.62) micromol/mg, P<0.01; (77.40+/-0.56)% vs. (78.30+/-0.54)%, P<0.01]. The results indicate that CAR

  9. Cerebral Malaria.

    PubMed

    Marsden, P D; Bruce-Chwatt, L J

    1975-01-01

    Cerebral malaria is an acute diffuse encephalopathy associated only with Plasmodium falciparum. It is probably a consequence of the rapid proliferation of the parasites in the body of man in relation to red cell invasion, and results in stagnation of blood flow in cerebralcapillaries with thromobotic occlusion of large numbers of cerebral capillaries. The subsequent cerebral pathology is cerebral infarction with haemorrhage and cerebral oedema. The wide prevalence of P. falciparum in highly endemic areas results in daily challenges to patients from several infected mosquitoes. It is thus important to understand the characteristics of P. falciparum, since this is one of the most important protozoan parasites of man and severe infection from it constitutes one of the few real clinical emergencies in tropical medicine. One of the more important aspects of the practice of medicine in the tropics is to establish a good understanding of the pattern of medical practice in that area. This applies to malaria as well as to other diseases. The neophyte might be somewhat surprised to learn, for example that an experienced colleague who lives in a holoendemic malarious area such as West Africa, sees no cerebral malaria. But the explanation is simple when the doctor concerned has a practice which involves treating adults only. Cerebral malaria is rare in adults, because in highly endemic areas, by the age of 1 year most of the infants in a group under study have already experienced their first falciparum infection. By the time they reach adult life, they have a solid immunity against severe falciparum infections. In fact, "clinical malaria" could occur in such a group under only two circumstances: 1) in pregnancy, a patent infection with P. falciparum might develop, probably due to an IgG drain across the placenta to the foetus;2) in an individual who has constantly taken antimalarials and who may have an immunity at such a low level that when antimalarial therapy is interrupted

  10. Post Mortem Validation of MRI-Identified Veins on the Surface of the Cerebral Cortex as Potential Landmarks for Neurosurgery

    PubMed Central

    Grabner, Günther; Haider, Thomas; Glassner, Mark; Rauscher, Alexander; Traxler, Hannes; Trattnig, Siegfried; Robinson, Simon D.

    2017-01-01

    Background and Objective: Image-guided neurosurgery uses information from a wide spectrum of methods to inform the neurosurgeon's judgement about which tissue to resect and which to spare. Imaging data are registered to the patient's skull so that they correspond to the intraoperative macro- and microscopic view. The correspondence between imaging and optical systems breaks down during surgery, however, as a result of cerebro-spinal fluid drain age, tissue resection, and gravity-based brain shift. In this work we investigate whether a map of surface veins, automatically segmented from MRI, could serve as additional reference system. Methods: Gradient-echo based T2*-weighted imaging was performed on two human cadavers heads using a 7 Tesla MRI scanner. Automatic vessel segmentation was performed using the Frangi vesselness filter, and surface renderings of vessels compared with photographs of the surface of the brain following craniotomy. Results: A high level of correspondence was established between vessel maps and the post autopsy photographs. Corresponding veins, including the prominent superior anastomotic veins, could be identified in all brain lobes. Conclusion: Automatic surface vessel segmentation is feasible and the high correspondence to post autopsy photographs indicates that they could be used as an additional reference system for image-guided neurosurgery in order to maintain the correspondence between imaging and optical systems.This has the advantage over a skull-based reference system that veins are clearly visible to the surgeon and move and deform with the underlying tissue, potentially making this surface net of landmarks robust to brain shift. PMID:28680389

  11. Quantifying Evaporation in a Permeable Pavement System ...

    EPA Pesticide Factsheets

    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. The U.S. Environmental Protection Agency (USEPA) constructed a 0.4-ha parking lot in Edison, NJ, that incorporated three different permeable pavement types in the parking lanes – permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). An impermeable liner installed 0.4 m below the driving surface in four 11.6-m by 4.74-m sections per each pavement type captures all infiltrating water and routes it to collection tanks that can contain events up to 38 mm. Each section has a design impervious area to permeable pavement area ratio of 0.66:1. Pressure transducers installed in the underdrain collection tanks measured water level for 24 months. Level was converted to volume using depth-to-volume ratios for individual collection tanks. Using a water balance approach, the measured infiltrate volume was compared to rainfall volume on an event-basis to determine the rainfall retained in the pavement strata and underlying aggregate. Evaporation since the previous event created additional storage in the pavement and aggregate layers. Events were divided into three groups based on antecedent dry period (ADP) and three, four-month categories of potential e

  12. Magnesium sulphate treatment decreases blood-brain barrier permeability during acute hypertension in pregnant rats.

    PubMed

    Euser, Anna G; Bullinger, Lisa; Cipolla, Marilyn J

    2008-02-01

    Eclampsia is associated with increased blood-brain barrier (BBB) permeability and formation of cerebral oedema. Magnesium sulphate is used to treat eclampsia despite an unclear mechanism of action. This study was to determine the effect of magnesium sulphate on in vivo BBB permeability and formation of cerebral oedema during acute hypertension and on brain aquaporin-4 (AQP4) protein expression. An in vivo model of hypertensive encephalopathy was used in late-pregnant (LP) rats following magnesium sulphate treatment, 270 mg kg(-1) i.p. injection every 4 h for 24 h. Permeability of the BBB was determined by in situ brain perfusion of Evan's Blue (EB) and sodium fluorescein (NaFl), and dye clearance determined by fluorescence spectrophotometry. Cerebral oedema was determined following acute hypertension by measuring brain water content. The effect of magnesium treatment on AQP4 expression was determined by Western blot analysis. Acute hypertension with autoregulatory breakthrough increased BBB permeability to EB in both brain regions studied (P < 0.05). Magnesium attenuated BBB permeability to EB during acute hypertension by 41% in the posterior cerebrum (P < 0.05) but had no effect in the anterior cerebrum (P > 0.05). Treatment with magnesium did not change NaFl permeability, cerebral oedema formation or AQP4 expression. In summary, BBB permeability to Evan's Blue was increased by acute hypertension in LP rats, and this was attenuated by treatment with magnesium sulphate. The greatest effect on BBB permeability to EB was in the posterior cerebrum, an area particularly susceptible to oedema formation during eclampsia.

  13. Stainless Steel Permeability

    SciTech Connect

    Buchenauer, Dean A.; Karnesky, Richard A.

    2015-09-01

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

  14. New method of measuring permeability of adhesive resin films

    PubMed Central

    Sword, Rhoda J.; Sword, Jeremy J.; Brackett, William W.; Tay, Franklin R.; Pashley, David H.

    2013-01-01

    Summary Objectives To develop a simple gravimetric method for measuring the permeability of adhesive resin films. Methods Using commercially available permeability cups designed for industrial permeability testing, the loss of mass of water vapour or liquid water from a stainless steel cup sealed with a resin film was measured over 1–2 days. The permeabilities of Parafilm (control), Clearfil SE Bond adhesive, Xeno IV and One-Up Bond F were compared. Results The lowest resin film permeability was obtained with Clearfil SE Bond films. The permeabilities of Xeno IV and One-Up Bond F to liquid water were 2.76 and 3.27-fold higher (p<0.001) than that of Clearfil SE Bond. Liquid water permeability was always 2.8 – 3.8-fold higher (p<0.05) than water vapour transmission rate. Conclusions Quantitative comparisons of the permeability properties of resin films can be made gravimetrically. The large permeability cups that are available commercially may be reduced in size in the future for measuring dentine adhesive films with smaller surface areas that are less liable to contain imperfections. PMID:21469402

  15. Objective 3D surface evaluation of intracranial electrophysiologic correlates of cerebral glucose metabolic abnormalities in children with focal epilepsy.

    PubMed

    Jeong, Jeong-Won; Asano, Eishi; Kumar Pilli, Vinod; Nakai, Yasuo; Chugani, Harry T; Juhász, Csaba

    2017-03-21

    To determine the spatial relationship between 2-deoxy-2[(18) F]fluoro-D-glucose (FDG) metabolic and intracranial electrophysiological abnormalities in children undergoing two-stage epilepsy surgery, statistical parametric mapping (SPM) was used to correlate hypo- and hypermetabolic cortical regions with ictal and interictal electrocorticography (ECoG) changes mapped onto the brain surface. Preoperative FDG-PET scans of 37 children with intractable epilepsy (31 with non-localizing MRI) were compared with age-matched pseudo-normal pediatric control PET data. Hypo-/hypermetabolic maps were transformed to 3D-MRI brain surface to compare the locations of metabolic changes with electrode coordinates of the ECoG-defined seizure onset zone (SOZ) and interictal spiking. While hypometabolic clusters showed a good agreement with the SOZ on the lobar level (sensitivity/specificity = 0.74/0.64), detailed surface-distance analysis demonstrated that large portions of ECoG-defined SOZ and interictal spiking area were located at least 3 cm beyond hypometabolic regions with the same statistical threshold (sensitivity/specificity = 0.18-0.25/0.94-0.90 for overlap 3-cm distance); for a lower threshold, sensitivity for SOZ at 3 cm increased to 0.39 with a modest compromise of specificity. Performance of FDG-PET SPM was slightly better in children with smaller as compared with widespread SOZ. The results demonstrate that SPM utilizing age-matched pseudocontrols can reliably detect the lobe of seizure onset. However, the spatial mismatch between metabolic and EEG epileptiform abnormalities indicates that a more complete SOZ detection could be achieved by extending intracranial electrode coverage at least 3 cm beyond the metabolic abnormality. Considering that the extent of feasible electrode coverage is limited, localization information from other modalities is particularly important to optimize grid coverage in cases of large hypometabolic cortex. Hum Brain Mapp, 2017. © 2017

  16. Cerebral malaria

    PubMed Central

    Newton, C.; Hien, T. T.; White, N.

    2000-01-01

    Cerebral malaria may be the most common non-traumatic encephalopathy in the world. The pathogenesis is heterogenous and the neurological complications are often part of a multisystem dysfunction. The clinical presentation and pathophysiology differs between adults and children. Recent studies have elucidated the molecular mechanisms of pathogenesis and raised possible interventions. Antimalarial drugs, however, remain the only intervention that unequivocally affects outcome, although increasing resistance to the established antimalarial drugs is of grave concern. Artemisinin derivatives have made an impact on treatment, but other drugs may be required. With appropriate antimalarial drugs, the prognosis of cerebral malaria often depends on the management of other complications—for example, renal failure and acidosis. Neurological sequelae are increasingly recognised, but further research on the pathogenesis of coma and neurological damage is required to develop other ancillary treatments.

 PMID:10990500

  17. Role of Slip Velocity in a Magneto-Micropolar Fluid Flow from a Radiative Surface with Variable Permeability: A Numerical Study

    NASA Astrophysics Data System (ADS)

    Sharma, B. K.; Tailor, V.; Goyal, M.

    2017-08-01

    An analysis is presented to describe the hydromagnetic mixed convection flow of an electrically conducting micropolar fluid past a vertical plate through a porous medium with radiation and slip flow regime. A uniform magnetic field has been considered in the study which absorbs the micropolar fluid with a varying suction velocity and acts perpendicular to the porous surface of the above plate. The governing non-linear partial differential equations have been transformed into linear partial differential equations, which are solved numerically by applying the explicit finite difference method. The numerical results are presented graphically in the form of velocity, micro-rotation, concentration and temperature profiles, the skin-friction coefficient, the couple stress coefficient, the rate of heat and mass transfers at the wall for different material parameters.

  18. Cerebral Palsy (For Parents)

    MedlinePlus

    ... 10 Tips for Parents Healthy Habits for TV, Video Games, and the Internet Cerebral ... cerebral Cerebral palsy (CP) is a disorder that affects muscle tone, movement, and motor skills (the ability to move in a coordinated and ...

  19. Polycyclic aromatic hydrocarbons in soil and surface marine sediment near Jubany Station (Antarctica). Role of permafrost as a low-permeability barrier.

    PubMed

    Curtosi, Antonio; Pelletier, Emilien; Vodopivez, Cristian L; Mac Cormack, Walter P

    2007-09-20

    Although Antarctica is still considered as one of the most pristine areas of the world, the growing tourist and fisheries activities as well as scientific operations and their related logistic support are responsible for an increasing level of pollutants in this fragile environment. Soils and coastal sediments are significantly affected near scientific stations particularly by polycyclic aromatic hydrocarbons (PAHs). In this work sediment and soil were sampled in two consecutive summer Antarctic expeditions at Potter Cove and peninsula, in the vicinity of Jubany Station (South Shetland Islands). Two- and 3-ring PAHs (methylnaphthalene, fluorene, phenanthrene and anthracene) were the main compounds found in most sites, although total PAH concentrations showed relatively low levels compared with other human-impacted areas in Antarctica. Pattern distribution of PAHs observed in samples suggested that low-temperature combustion processes such as diesel motor combustion and open-field garbage burning are the main sources of these compounds. An increase in PAH concentrations was observed from surface to depth into the active soil layer except for a unique sampling site where a fuel spill had been recently reported and where an inverted PAH concentration gradient was observed. The highest level was detected in the upper layer of permafrost followed by a sharp decrease in depth, showing this layer is acting as a barrier for downward PAH migration. When PAH levels in soil from both sampling programs were compared a significant decrease (p<0.01) was observed in summer 2005 (range at 75-cm depth: 12+/-1-153+/-22 ng/g) compared to summer 2004 (range at 75-cm depth: 162+/-15-1182+/-113 ng/g) whereas concentrations in surface sediment collected nearby the station PAHs increased drastically in 2005 (range: 36+/-3-1908+/-114 ng/g) compared to 2004 (range: 28+/-3-312+/-24 ng/g). Precipitation regime and water run off suggest that an important wash out of soil-PAHs occurred during

  20. Relative permeability through fractures

    SciTech Connect

    Diomampo, Gracel, P.

    2001-08-01

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

  1. Application of the FlexiForce contact surface force sensor to continuous extraocular compression monitoring during craniotomy for cerebral aneurysms.

    PubMed

    Mutoh, Tatsushi; Ishikawa, Tatsuya; Nishimura, Hiromi; Yasui, Nobuyuki

    2010-01-01

    The aims of this study were to introduce our newly developed device equipped with a contact surface force sensor (FlexiForce) for monitoring extraocular compression continuously, and to illustrate its potential clinical application using this device in patients undergoing uncomplicated frontotemporal or bifrontal craniotomy for surgical clipping of unruptured anterior circulation aneurysms. In a pilot study with volunteers, we determined the critical force of 100 gf to cause painful ocular sensation. Then we performed the bilateral extraocular force measurements in 15 patients undergoing uncomplicated frontotemporal or bifrontal craniotomy for surgical clipping of unruptured anterior circulation aneurysms. Extraocular force increased immediately after retraction of the flap, increased to 144+/-26 gf (mean+/-SD) during lower craniotomy close to the orbit, was maintained at 91+/-18 gf during microsurgery, and returned close to baseline at 24+/-14 gf after restoration of skin flap retraction. Such changes were observed only on the surgical side in frontotemporal craniotomy. Abnormal increase in extraocular force was effectively reduced by placing a real-time digital panel meter to warn surgeons to avoid excessive skin flap retraction during the surgical procedure. In conclusion, this new tool may allow us to monitor the external forces that can be applied intraoperatively to the ocular globe in the supine position.

  2. Permeability-porosity relationships in sedimentary rocks

    USGS Publications Warehouse

    Nelson, Philip H.

    1994-01-01

    In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (??). The slope, intercept, and degree of scatter of these log(k)-?? trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing ??. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as ?? decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings from a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-?? plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-?? data trends cut the curves of constant pore size from the pore-dimension models

  3. Effects of CO2 laser energy on dentin permeability.

    PubMed

    Pashley, E L; Horner, J A; Liu, M; Kim, S; Pashley, D H

    1992-06-01

    The effect of a CO2 laser on the structure and permeability of smear layer-covered human dentin was evaluated in vitro. Three different energy levels were used (11, 113, and 566 J/cm2). The lowest exposure to the laser energy increased dentin permeability, measured as a hydraulic conductance, due to partial measured as a hydraulic conductance, due to partial loss of the superficial smear layer and smear plugs. The intermediate energy level also increased dentin permeability by crater formation, making the dentin thinner. The lack of uniform glazing of the surface of the crater, leaving its surface porous and in communication with the underlying dentinal tubules also contributed to the increase in dentin permeability seen with the intermediate laser energy. The highest laser energy produced complete glazing of the crater surfaces and sealed the dentinal tubules beneath the crater. However, it also completely removed the smear layer in a halo zone about 100-microns wide around each crater which increased the permeability of the pericrater dentin at the same time it decreased the permeability of the dentin within the crater. The combined use of scanning electron microscopy and permeability measurements provides important complementary information that is essential in evaluating the effects of lasers on dentin.

  4. Update to permeable pavement research at the Edison ...

    EPA Pesticide Factsheets

    Abstract: The EPA’s Urban Watershed Management Branch (UWMB) has been monitoring the permeable pavement demonstration site at the Edison Environmental Center, NJ since 2010. This site has three different types of permeable pavement including: interlocking concrete permeable pavers; porous concrete; and permeable asphalt. The parking lot is instrumented with water content reflectometers and thermistors for continuous monitoring and has four lined sections for each surface to capture permeable pavement infiltrate for water quality analyses.Previous technical releases concerning the demonstration site focused on monitoring techniques, observed chloride and nutrient concentrations, and infiltration and evaporation rates. Thispresentation summarizes past findings and addresses current water quality efforts. This presentation summarizes past findings and addresses current water quality efforts.

  5. Patterns of effective permeability of leaf cuticles to acids

    SciTech Connect

    Hauser, H.D.; Walters, K.D.; Berg, V.S. )

    1993-01-01

    Plants in the field are frequently exposed to anthropogenic acid precipitation with pH values of 4 and below. For the acid to directly affect leaf tissues, it must pass through the leaf cuticle, but little is known about the permeability of cuticles to protons, of about the effect of different anions on this permeability. We investigated the movement of protons through isolated astomatous leaf cuticles of grapefruit (Citrus x paradisi Macfady.), rough lemon (Citrus limon [L.] Burm. fils cv Ponderosa), and pear (Pyrus communis L.) using hydrochloric, sulfuric, and nitric acids. Cuticles were enzymically isolated from leaves and placed in a diffusion apparatus with pH 4 acid on the morphological outer surface of the cuticle and degassed distilled water on the inner surface. Changes in pH of the solution on the inner surface were used to determine rates of effective permeability of the cuticles to the protons of these acids. Most cuticles exhibited an initial low permeability, lasting hours to days, then after a short transition displayed a significant higher permeability, which persisted until equilibrium was approached. The change in effective permeability appears to be reversible. Effective permeabilities were higher for sulfuric acid than for the others. A model of the movement of protons through the cuticle is presented, proposing that dissociated acid groups in channels within the cutin are first protonated by the acid, accounting for the low initial effective permeability; then protons pass freely through the channels, resulting in a higher effective permeability. 26 refs., 6 figs., 2 tabs.

  6. Rocks of low permeability

    NASA Astrophysics Data System (ADS)

    The 17th International Congress of the IAH (International Association of Hydrogeologists) will meet in Tucson, Ariz., January 7-10, 1985. The deadline for abstracts is March 1, 1984, and final papers are due October 15, 1984.The topic of the congress will be “Hydrogeology of Rocks of Low Permeability,” and speakers will include W. Back, J. F. Bredehoeft, G. de Marsily, J. E. Gale, P. Fritz, L. W. Gelhar, G. E. Grisak, C. W. Kreitler, M. R. Llamas, T. N. Narasimhan, I. Neretnieks, and E. P. Weeks. The congress will conclude with a panel discussion moderated by S. P. Neuman. Panelists include S. N. Davis, G. de Marsily, R. A. Freeze, P. A. Witherspoon, and I. Neretnieks.

  7. Placental Permeability of Lead

    PubMed Central

    Carpenter, Stanley J.

    1974-01-01

    The detection of lead in fetal tissues by chemical analysis has long been accepted as prima facie evidence for the permeability of the placenta to this nonessential trace metal. However, only a few investigations, all on lower mammalian species, have contributed any direct experimental data bearing on this physiological process. Recent radioactive tracer and radioautographic studies on rodents have shown that lead crosses the placental membranes rapidly and in significant amounts even at relatively low maternal blood levels. While it is not possible to extrapolate directly the results of these experiments to humans because of differences in placental structure and other factors, the results do serve as a warning of the possible hazard to the human embryo and fetus of even low levels of lead in the maternal system. PMID:4857497

  8. Long-term Metal Performance of Three Permeable Pavements ...

    EPA Pesticide Factsheets

    EPA constructed a 4,000-m2 parking lot surfaced with three permeable pavements (permeable interlocking concrete pavers, pervious concrete, and porous asphalt) on the Edison Environmental Center in Edison, NJ in 2009. Samples from each permeable pavement infiltrate were collected for six years beginning in January 2010 and analyzed for twenty-two metals. Although the infiltrate metals concentrations varied by surface, metal concentrations in more than 99% of the permeable pavement infiltrate samples met both the groundwater effluent limitations and maximum contaminant levels in national primary drinking water regulations for barium, chromium, copper, manganese, nickel and zinc. Arsenic, cadmium, lead and antimony met those standards in 60% to 98% of the samples with no measurable difference found among pavements. Aluminum and iron in pervious concrete and porous asphalt infiltrates met standards at more than 90%, however permeable interlocking concrete paver infiltrates have 50% and 93% samples exceeds standards, respectively. Concentrations of arsenic, iron, potassium, lithium, magnesium, antimony, tin, manganese, and zinc in all permeable pavement infiltrates decreased with time, whereas, aluminum, barium, calcium, chromium and strontium in porous asphalt infiltrates increased. Most metal concentrations in permeable pavement infiltrates either exhibited no significant difference between snow/no-snow seasons or showed statistically larger concentrations

  9. Gyroid nanoporous membranes with tunable permeability.

    PubMed

    Li, Li; Schulte, Lars; Clausen, Lydia D; Hansen, Kristian M; Jonsson, Gunnar E; Ndoni, Sokol

    2011-10-25

    Understanding the relevant permeability properties of ultrafiltration membranes is facilitated by using materials and procedures that allow a high degree of control on morphology and chemical composition. Here we present the first study on diffusion permeability through gyroid nanoporous cross-linked 1,2-polybutadiene (1,2-PB) membranes with uniform pores that, if needed, can be rendered hydrophilic. The gyroid porosity has the advantage of isotropic percolation with no need for structure prealignment. Closed (skin) or opened (nonskin) outer surface can be simply realized by altering the interface energy in the process of membrane fabrication. The morphology of the membranes' outer surface was investigated by scanning electron microscopy, contact angle, and X-ray photoelectron spectroscopy. The effective diffusion coefficient of glucose decreases from nonskin, to one-sided skin to two-sided skin membranes, much faster than expected by a naive resistance-in-series model; the flux through the two-sided skin membranes even increases with the membrane thickness. We propose a model that captures the physics behind the observed phenomena, as confirmed by flow visualization experiments. The chemistry of 1,2-PB nanoporous membranes can be controlled, for example, by hydrophilic patterning of the originally hydrophobic membranes, which allows for different active porosity toward aqueous solutions and, therefore, different permeability. The membrane selectivity is evaluated by comparing the effective diffusion coefficients of a series of antibiotics, proteins, and other biomolecules; solute permeation is discussed in terms of hindered diffusion. The combination of uniform bulk morphology, isotropically percolating porosity, controlled surface chemistry, and tunable permeability is distinctive for the presented gyroid nanoporous membranes.

  10. Permeable Boundaries in Organizational Learning

    NASA Astrophysics Data System (ADS)

    Hazy, James K.; Tivnan, Brian F.; Schwandt, David R.

    The nature of the organizational boundary is investigated in the context of organizational learning. Boundary permeability is defined and hypotheses relating it to performance are tested computationally using data from 5,500 artificial organizations. We find that matching boundary permeability to the environment predicts both agent and organization survival.

  11. Regional variability in the permeability of human dentine.

    PubMed

    Pashley, D H; Andringa, H J; Derkson, G D; Derkson, M E; Kalathoor, S R

    1987-01-01

    This was measured qualitatively by using dyes and quantitatively by hydraulic conductance in dentine discs and crown segments in vitro. Both types of preparation demonstrated large regional differences in permeability, with the highest values at the periphery and the lowest in the centre of the disc or crown. As dentine permeability may vary 3-10-fold across a few millimetres, investigators should use as large a surface area as possible to compensate for these regional differences.

  12. Permeability of the Body Wall of Romanomermis culicivorax to Lanthanum

    PubMed Central

    Platzer, Ann; Platzer, Edward G.

    1985-01-01

    Ultrastructural study of the body wall of preparasitic, parasitic, and postparasitic stages of Romanomermis culicivorax showed that the cuticle of all three stages was permeable to lanthanum. The cuticle of the parasitic stage was the thinnest and showed the greatest permeability. Lanthanum accumulated on the apical surfaces of the hypodermal cells but was not found intracellularly. The negative staining characteristics of lanthanum enhanced the detection of numerous smooth septate junctions in the hypodermis of the parasitic stage. PMID:19294092

  13. Rapid transport within cerebral perivascular spaces underlies widespread tracer distribution in the brain after intranasal administration.

    PubMed

    Lochhead, Jeffrey J; Wolak, Daniel J; Pizzo, Michelle E; Thorne, Robert G

    2015-03-01

    The intranasal administration route is increasingly being used as a noninvasive method to bypass the blood-brain barrier because evidence suggests small fractions of nasally applied macromolecules may reach the brain directly via olfactory and trigeminal nerve components present in the nasal mucosa. Upon reaching the olfactory bulb (olfactory pathway) or brainstem (trigeminal pathway), intranasally delivered macromolecules appear to rapidly distribute within the brains of rodents and primates. The mechanisms responsible for this distribution have yet to be fully characterized. Here, we have used ex vivo fluorescence imaging to show that bulk flow within the perivascular space (PVS) of cerebral blood vessels contributes to the rapid central distribution of fluorescently labeled 3 and 10 kDa dextran tracers after intranasal administration in anesthetized adult rats. Comparison of tracer plasma levels and fluorescent signal distribution associated with the PVS of surface arteries and internal cerebral vessels showed that the intranasal route results in unique central access to the PVS not observed after matched intravascular dosing in separate animals. Intranasal targeting to the PVS was tracer size dependent and could be regulated by modifying nasal epithelial permeability. These results suggest cerebral perivascular convection likely has a key role in intranasal drug delivery to the brain.

  14. [Cerebral palsy].

    PubMed

    Malagón Valdez, Jorge

    2007-01-01

    The term cerebral palsy (CP), is used for a great number of clinical neurological syndromes. The syndromes are characterized by having a common cause, motor defects. It is important, because they can cause a brain damage by presenting motor defects and some associated deficiencies, such as mental deficiency, epilepsy, language and visual defects and pseudobulbar paralysis, with the non-evolving fact. Some authors prefer using terms such as "non-evolving encephalopathies". In the treatment the utility of prevention programs of early stimulation and special rehabilitation methods, and treatment of associated deficiencies such as epilepsy, mental deficiency, language, audition and visual problems, and the attention deficit improve the prognosis in an important way. The prognosis depends on the severity of the disease and the associated manifestations.

  15. Effect of water on hydrogen permeability

    NASA Technical Reports Server (NTRS)

    Hulligan, David; Tomazic, William A.

    1987-01-01

    Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the protective oxide could be chemically reduced by the hydrogen in the engine. Some oxygen is required in the hydrogen to prevent reduction. Eventually, all the oxygen in the hydrogen gas - whatever its source - shows up as water. This is the result of hydrogen reducing the CO, CO2, or the protective inner surface oxides. This water can condense in the engine system under the right conditions. If the concentration of water vapor is reduced to a low enough level, the hydrogen can chemically reduce the oxide coating, resulting in an increase in permeability. This work was done to define the minimum water content required to avoid this reduction in the oxide coating. The results of this testing show that a minimum of approximately 750 ppm water is required to prevent an increase in permeability of CG-27, a high temperature metal alloy selected for Stirling engine heater tubes.

  16. Detection of semi-volatile organic compounds in permeable ...

    EPA Pesticide Factsheets

    Abstract The Edison Environmental Center (EEC) has a research and demonstration permeable parking lot comprised of three different permeable systems: permeable asphalt, porous concrete and interlocking concrete permeable pavers. Water quality and quantity analysis has been ongoing since January, 2010. This paper describes a subset of the water quality analysis, analysis of semivolatile organic compounds (SVOCs) to determine if hydrocarbons were in water infiltrated through the permeable surfaces. SVOCs were analyzed in samples collected from 11 dates over a 3 year period, from 2/8/2010 to 4/1/2013.Results are broadly divided into three categories: 42 chemicals were never detected; 12 chemicals (11 chemical test) were detected at a rate of less than 10% or less; and 22 chemicals were detected at a frequency of 10% or greater (ranging from 10% to 66.5% detections). Fundamental and exploratory statistical analyses were performed on these latter analyses results by grouping results by surface type. The statistical analyses were limited due to low frequency of detections and dilutions of samples which impacted detection limits. The infiltrate data through three permeable surfaces were analyzed as non-parametric data by the Kaplan-Meier estimation method for fundamental statistics; there were some statistically observable difference in concentration between pavement types when using Tarone-Ware Comparison Hypothesis Test. Additionally Spearman Rank order non-parame

  17. Hybrid green permeable pave with hexagonal modular pavement systems

    NASA Astrophysics Data System (ADS)

    Rashid, M. A.; Abustan, I.; Hamzah, M. O.

    2013-06-01

    Modular permeable pavements are alternatives to the traditional impervious asphalt and concrete pavements. Pervious pore spaces in the surface allow for water to infiltrate into the pavement during rainfall events. As of their ability to allow water to quickly infiltrate through the surface, modular permeable pavements allow for reductions in runoff quantity and peak runoff rates. Even in areas where the underlying soil is not ideal for modular permeable pavements, the installation of under drains has still been shown to reflect these reductions. Modular permeable pavements have been regarded as an effective tool in helping with stormwater control. It also affects the water quality of stormwater runoff. Places using modular permeable pavement has been shown to cause a significant decrease in several heavy metal concentrations as well as suspended solids. Removal rates are dependent upon the material used for the pavers and sub-base material, as well as the surface void space. Most heavy metals are captured in the top layers of the void space fill media. Permeable pavements are now considered an effective BMP for reducing stormwater runoff volume and peak flow. This study examines the extent to which such combined pavement systems are capable of handling load from the vehicles. Experimental investigation were undertaken to quantify the compressive characteristics of the modular. Results shows impressive results of achieving high safety factor for daily life vehicles.

  18. Permeability of protective coatings to tritium

    SciTech Connect

    Braun, J.M.; Williamson, A.S.

    1985-09-01

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

  19. Blood-brain barrier permeability imaging using perfusion computed tomography

    PubMed Central

    Avsenik, Jernej; Bisdas, Sotirios; Popovic, Katarina Surlan

    2015-01-01

    Background. The blood-brain barrier represents the selective diffusion barrier at the level of the cerebral microvascular endothelium. Other functions of blood-brain barrier include transport, signaling and osmoregulation. Endothelial cells interact with surrounding astrocytes, pericytes and neurons. These interactions are crucial to the development, structural integrity and function of the cerebral microvascular endothelium. Dysfunctional blood-brain barrier has been associated with pathologies such as acute stroke, tumors, inflammatory and neurodegenerative diseases. Conclusions. Blood-brain barrier permeability can be evaluated in vivo by perfusion computed tomography - an efficient diagnostic method that involves the sequential acquisition of tomographic images during the intravenous administration of iodinated contrast material. The major clinical applications of perfusion computed tomography are in acute stroke and in brain tumor imaging. PMID:26029020

  20. Permeability testing of biomaterial membranes.

    PubMed

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

    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.

  1. Gas permeability and flow characterization of simulated lunar regolith

    NASA Astrophysics Data System (ADS)

    Toutanji, Houssam; Goff, Christopher M.; Ethridge, Edwin; Stokes, Eric

    2012-04-01

    Recent discoveries of water ice trapped within lunar topsoil (regolith) have placed a new emphasis on the recovery and utilization of water for future space exploration. Upon heating the lunar ice to sublimation, the resulting water vapor could theoretically transmit through the lunar regolith, to be captured on the surface. As the permeability of lunar regolith is essential to this process, this paper seeks to experimentally determine the permeability and flow characteristics of various gas species through simulated lunar regolith (SLR). Two different types of SLR were compacted and placed into the permeability setup to measure the flow-rate of transmitted gas through the sample. Darcy's permeability constant was calculated for each sample and gas combination, and flow characteristics were determined from the results. The results show that Darcy's permeability constant varies with SLR compaction density, and identified no major difference in permeable flow between the several tested gas species. Between the two tested SLR types, JSC-1A was shown to be more permeable than NU-LHT under similar conditions. In addition, a transition zone was identified in the flow when the gas pressure differential across the sample was less than ˜40 kPa.

  2. In silico model of drug permeability across sublingual mucosa.

    PubMed

    Goswami, Tarun; Kokate, Amit; Jasti, Bhaskara R; Li, Xiaoling

    2013-05-01

    The objective of this work was to develop an in silico model to predict the sublingual permeability of a drug based on physicochemical descriptors of a molecule. Fourteen model drugs with diverse physicochemical properties were selected for this study. Molecular volume, molecular weight, logP, logD (pH 6.8), pKa, total polar surface area, hydrogen bond acceptors and donors (HBD), number of rotatable bonds, solubility (pH 6.8), and melting point were used as molecular descriptors. Apparent permeability coefficients (Pe) of drugs across porcine sublingual mucosa were determined experimentally. Multiple linear regression (MLR) was used to develop the model with permeability as the response variable and various descriptors as the predictive variables. Q(2), the cross-validated correlation coefficient, was used to assess the prediction ability of the model. MLR analysis showed that HBD and logD were the significant descriptors (P<0.05, Q(2)=0.88) in the sublingual permeability model. The resulting model is expressed as the following equation:An excellent fit with R(2) of 0.93 was obtained between experimental and predicted permeabilities. The analysis of contributions of molecular descriptors to sublingual permeability revealed the molecular structure basis of permeation across sublingual mucosa. In conclusion, an in silico model was developed to predict sublingual permeability of drugs using known descriptors for evaluating the feasibility of sublingual drug delivery. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Mitigating methane emissions and air intrusion in heterogeneous landfills with a high permeability layer.

    PubMed

    Jung, Yoojin; Imhoff, Paul T; Augenstein, Don; Yazdani, Ramin

    2011-05-01

    Spatially variable refuse gas permeability and landfill gas (LFG) generation rate, cracking of the soil cover, and reduced refuse gas permeability because of liquid addition can all affect CH(4) collection efficiency when intermediate landfill covers are installed. A new gas collection system that includes a near-surface high permeability layer beneath the landfill cover was evaluated for enhancing capture of LFG and mitigating CH(4) emissions. Simulations of gas transport in two-dimensional domains demonstrated that the permeable layer reduces CH(4) emissions up to a factor of 2 for particular spatially variable gas permeability fields. When individual macrocracks formed in the cover soil and the permeable layer was absent, CH(4) emissions increased to as much as 24% of the total CH(4) generated, double the emissions when the permeable layer was installed. CH(4) oxidation in the cover soil was also much more uniform when the permeable layer was present: local percentages of CH(4) oxidized varied between 94% and 100% across the soil cover with the permeable layer, but ranged from 10% to 100% without this layer for some test cases. However, the permeable layer had a minor effect on CH(4) emissions and CH(4) oxidation in the cover soil when the ratio of the gas permeability of the cover soil to the mean refuse gas permeability ≤ 0.05. The modeling approach employed in this study may be used to assess the utility of other LFG collection systems and management practices.

  4. Monitoring Strategies in Permeable Pavement Systems to Optimize Maintenance Scheduling

    EPA Science Inventory

    As the surface in a permeable pavement system clogs and performance decreases, maintenance is required to preserve the design function. Currently, guidance is limited for scheduling maintenance on an as needed basis. Previous research has shown that surface clogging in a permea...

  5. Monitoring Strategies in Permeable Pavement Systems to Optimize Maintenance Scheduling

    EPA Science Inventory

    As the surface in a permeable pavement system clogs and performance decreases, maintenance is required to preserve the design function. Currently, guidance is limited for scheduling maintenance on an as needed basis. Previous research has shown that surface clogging in a permea...

  6. Measuring Clogging with Pressure Transducers in Permeable Pavement Strips

    EPA Science Inventory

    Two issues that have a negative affect on the long term hydrologic performance of permeable pavement systems are surface clogging and clogging at the interface with the underlying soil. Surface clogging limits infiltration capacity and results in bypass if runoff rate exceeds in...

  7. Measuring Clogging with Pressure Transducers in Permeable Pavement Strips

    EPA Science Inventory

    Two issues that have a negative affect on the long term hydrologic performance of permeable pavement systems are surface clogging and clogging at the interface with the underlying soil. Surface clogging limits infiltration capacity and results in bypass if runoff rate exceeds in...

  8. Permeability studies on 3D Ni foam/graphene composites

    NASA Astrophysics Data System (ADS)

    Yang, Zhuxian; Chen, Hongmei; Wang, Nannan; Xia, Yongde; Zhu, Yanqiu

    2017-09-01

    This study investigates the permeability of new 3D Ni foam/graphene composites (Ni foam covered with graphene) using compressed air, Ar and N2 as the probe gases. The results show that the introduction of graphene on the surface of Ni foam via in situ chemical vapour deposition is not detrimental to the permeability of the composites; on the contrary, in some cases it improves permeability. A modified Ergun-type correlation has been proposed, which represents very well the permeability of the Ni foam/graphene composites, especially at flow rates higher than 0.3 m s-1. Further studies show that graphene also helps to improve the thermal conductivity of the composite. These results suggest that the graphene involvement will make the Ni foam/graphene composite a good candidate for potential applications such as filters or heat exchangers suitable for working under harsh conditions such as at high temperatures, in corrosive environments, etc.

  9. Geothermal Permeability Enhancement - Final Report

    SciTech Connect

    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.

  10. Permeability of soils in Mississippi

    USGS Publications Warehouse

    O'Hara, Charles G.

    1994-01-01

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

  11. Crucial Role of Rapgef2 and Rapgef6, a Family of Guanine Nucleotide Exchange Factors for Rap1 Small GTPase, in Formation of Apical Surface Adherens Junctions and Neural Progenitor Development in the Mouse Cerebral Cortex123

    PubMed Central

    Maeta, Kazuhiro; Edamatsu, Hironori; Nishihara, Kaori; Ikutomo, Junji; Bilasy, Shymaa E.

    2016-01-01

    Abstract Cerebral neocortex development in mammals requires highly orchestrated events involving proliferation, differentiation, and migration of neural progenitors and neurons. Rapgef2 and Rapgef6 constitute a unique family of guanine nucleotide exchange factors for Rap1 small GTPase, which is known to play crucial roles in migration of postmitotic neurons. We previously reported that conditional knockout of Rapgef2 in dorsal telencephalon (Rapgef2-cKO) resulted in the formation of an ectopic cortical mass (ECM) resembling that of subcortical band heterotopia. Here we show that double knockout of Rapgef6 in Rapgef2-cKO mice (Rapgef2/6-dKO) results in marked enlargement of the ECM. While Rapgef2-cKO affects late-born neurons only, Rapgef2/6-dKO affects both early-born and late-born neurons. The Rapgef2-cKO cortex at embryonic day (E) 15.5, and the Rapgef2/6-dKO cortex at E13.5 and E15.5 show disruption of the adherens junctions (AJs) on the apical surface, detachment of radial glial cells (RGCs) from the apical surface and disorganization of the radial glial fiber system, which are accompanied by aberrant distribution of RGCs and intermediate progenitors, normally located in the ventricular zone and the subventricular zone, respectively, over the entire cerebral cortex. Moreover, intrauterine transduction of Cre recombinase into the Rapgef2flox/flox brains also results in the apical surface AJ disruption and the RGC detachment from the apical surface, both of which are effectively suppressed by cotransduction of the constitutively active Rap1 mutant Rap1G12V. These results demonstrate a cell-autonomous role of the Rapgef2/6-Rap1 pathway in maintaining the apical surface AJ structures, which is necessary for the proper development of neural progenitor cells. PMID:27390776

  12. Permeability of cork to gases.

    PubMed

    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.

  13. Permeability theory and Palace Athena.

    PubMed

    Stamps, Arthur E

    2013-06-01

    Permeability theory suggests that safety in environments depends on how far and how easily one can perceive or move through environments. Parts of environments that limit perception or retard locomotion elicit impressions of being enclosed, so properties of environments that influence perceived enclosure are important in permeability theory. One prediction of permeability theory is that the more permeable the boundary, the less enclosed the region within that boundary will seem to be. Another prediction is that boundary depth will have little influence on perceived enclosure. These predictions were tested in the venue of Greek temples. 30 participants were tested (14 men, 16 women; M age = 40 yr.), who rated perceived enclosure for 18 stimuli. The stimuli were constructed using a virtual scene from the Tholos in Delphi with the positions of the columns forming the boundaries. The boundaries were designed to have different levels of permeability and depth. Data were analyzed in terms of effect sizes and focused comparisons. Results indicated that perceived enclosure was most strongly influenced by the visual permeability of the boundary, while depth of boundary had a much smaller effect on perceived enclosure.

  14. United Cerebral Palsy

    MedlinePlus

    ... stay up to date with everything UCP! Affiliate Network UCP affiliates provide services and support on a ... with Cerebral Palsy and other disabilities and their networks. Individuals with cerebral palsy and other disabilities deserve ...

  15. Cerebral Palsy (For Kids)

    MedlinePlus

    ... Emergency Room? What Happens in the Operating Room? Cerebral Palsy KidsHealth > For Kids > Cerebral Palsy A A A ... the things that kids do every day. What's CP? Some kids with CP use wheelchairs and others ...

  16. The geometric mean concept for interpreting the permeability of heterogeneous geomaterials

    NASA Astrophysics Data System (ADS)

    Selvadurai, Patrick; Selvadurai, Paul

    2015-04-01

    Naturally occurring geomaterials are heterogeneous and the estimation of the effective permeability characteristics of such geomaterials presents a challenge not only in terms of the experimental procedures that should be used to ensure flow through the porous medium but also in the correct use of the theoretical concepts needed to accurately interpret the data. The general consensus is that the flow path in a test needs to be drastically reduced if steady state tests are considered as a suitable experimental technique. The disadvantage of flow path reduction is that the tested volume may not be altogether representative of the rock, particularly if it displays heterogeneity in the scale of the sample being tested. Also, if the sample is not correctly restrained, the differential pressures needed to initiate steady flow can introduce damage in the sample leading to erroneous estimates of permeability. The alternative approach is to use large enough samples that can capture the spatial heterogeneity but develop testing procedures that can test examine the steady state flow process as a problem in three-dimensional fluid flow that can capture the spatial distribution of permeability. The paper discusses theoretical and computational approaches that have been developed for the estimation of the spatial distribution of permeability in a cuboidal Indiana Limestone sample measuring 450 mm. The "Patch Permeability Test" developed in connection with the research allows the measurements of the surface permeability of the block and through kriging techniques estimate the permeability within the block sample. The research promotes the use of the "Geometric Mean" concept for the description of the effective permeability of the heterogeneous porous medium where the spatial distribution conforms to a lognormal pattern. The effectiveness of the approach is that the techniques can be applied to examine the effective permeability of heterogeneous low permeability materials such as

  17. Techniques to Determine Maintenace Frequency of Permeable Pavement Systems with Time Domain Reflectometers (TDRs

    EPA Science Inventory

    As the surface clogs in permeable pavement systems, they lose effectiveness and require maintenance. There is limited direct guidance for determining when maintenance is needed to prevent surface runoff bypass. Research is being conducted using multiple time domain reflectomete...

  18. Use of Time Domain Reflectometers (TDRs) in Permeable Pavement Systems to Predict Maintenance Needs and Effectiveness

    EPA Science Inventory

    As the surface in permeable pavement systems clogs, infiltration capacity decreases, so maintenance is required to maintain hydrologic performance. There is limited direct guidance for determining when maintenance is needed to prevent surface runoff bypass. Research is being co...

  19. Use of Time Domain Reflectometers (TDRs) in Permeable Pavement Systems to Predict Maintenance Needs and Effectiveness

    EPA Science Inventory

    As the surface in permeable pavement systems clogs, infiltration capacity decreases, so maintenance is required to maintain hydrologic performance. There is limited direct guidance for determining when maintenance is needed to prevent surface runoff bypass. Research is being co...

  20. Techniques to Determine Maintenace Frequency of Permeable Pavement Systems with Time Domain Reflectometers (TDRs

    EPA Science Inventory

    As the surface clogs in permeable pavement systems, they lose effectiveness and require maintenance. There is limited direct guidance for determining when maintenance is needed to prevent surface runoff bypass. Research is being conducted using multiple time domain reflectomete...

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    likely persistently re-fracture and keep the conduit margin permeable. The modelling therefore supports the notion that repeated fracture-healing cycles are responsible for the successive low-magnitude earthquakes associated with silicic dome extrusion. Taken together, our results indicate that the transition from effusive to explosive behaviour may rest on the competition between permeability reduction within the conduit and outgassing through fractures at the conduit margin. If the conditions for explosive behaviour are satisfied, the magma densification clock will be reset and the process will start again. The timescales of permeability reduction and strength recovery presented in this study may aid our understanding of the permeability evolution of conduit margin fractures, magma fracture-healing cycles, surface outgassing cycles, and the timescales required for pore pressure augmentation and the initiation of explosive eruptions.

  2. Cerebral Palsy (For Kids)

    MedlinePlus

    ... CPR: A Real Lifesaver Kids Talk About: Coaches Cerebral Palsy KidsHealth > For Kids > Cerebral Palsy Print A A A What's in this article? ... the first word you spoke? For kids with cerebral palsy, called CP for short, taking a first step ...

  3. Aging and Cerebral Palsy.

    ERIC Educational Resources Information Center

    Networker, 1993

    1993-01-01

    This special edition of "The Networker" contains several articles focusing on aging and cerebral palsy (CP). "Aging and Cerebral Palsy: Pathways to Successful Aging" (Jenny C. Overeynder) reports on the National Invitational Colloquium on Aging and Cerebral Palsy held in April 1993. "Observations from an Observer" (Kathleen K. Barrett) describes…

  4. Simulating gas-water relative permeabilities for nanoscale porous media with interfacial effects

    NASA Astrophysics Data System (ADS)

    Wang, Jiulong; Song, Hongqing; Li, Tianxin; Wang, Yuhe; Gao, Xuhua

    2017-08-01

    This paper presents a theoretical method to simulate gas-water relative permeability for nanoscale porous media utilizing fractal theory. The comparison between the calculation results and experimental data was performed to validate the present model. The result shows that the gas-water relative permeability would be underestimated significantly without interfacial effects. The thinner the liquid film thickness, the greater the liquid-phase relative permeability. In addition, both liquid surface diffusion and gas diffusion coefficient can promote gas-liquid two-phase flow. Increase of liquid surface diffusion prefer to increase liquid-phase permeability obviously as similar as increase of gas diffusion coefficient to increase gas-phase permeability. Moreover, the pore structure will become complicated with the increase of fractal dimension, which would reduce the gas-water relative permeability. This study has provided new insights for development of gas reservoirs with nanoscale pores such as shale.

  5. Activation of GABAB receptors ameliorates cognitive impairment via restoring the balance of HCN1/HCN2 surface expression in the hippocampal CA1 area in rats with chronic cerebral hypoperfusion.

    PubMed

    Li, Chang-jun; Lu, Yun; Zhou, Mei; Zong, Xian-gang; Li, Cai; Xu, Xu-lin; Guo, Lian-jun; Lu, Qing

    2014-10-01

    Hyperpolarization-activated cyclic-nucleotide-gated cation nonselective (HCN) channels are involved in the pathology of nervous system diseases. HCN channels and γ-aminobutyric acid (GABA) receptors can mutually co-regulate the function of neurons in many brain areas. However, little is known about the co-regulation of HCN channels and GABA receptors in the chronic ischemic rats with possible features of vascular dementia. Protein kinase A (PKA) and TPR containing Rab8b interacting protein (TRIP8b) can modulate GABAB receptors cell surface stability and HCN channel trafficking, respectively, and adaptor-associated kinase 1 (AAK1) inhibits the function of the major TRIP8b-interacting protein adaptor protein 2 (AP2) via phosphorylating the AP2 μ2 subunit. Until now, the role of these regulatory factors in chronic cerebral hypoperfusion is unclear. In the present study, we evaluated whether and how HCN channels and GABAB receptors were pathologically altered and investigated neuroprotective effects of GABAB receptors activation and cross-talk networks between GABAB receptors and HCN channels in the hippocampal CA1 area in chronic cerebral hypoperfusion rat model. We found that cerebral hypoperfusion for 5 weeks by permanent occlusion of bilateral common carotid arteries (two-vessel occlusion, 2VO) induced marked spatial and nonspatial learning and memory deficits, significant neuronal loss and decrease in dendritic spine density, impairment of long-term potentiation (LTP) at the Schaffer collateral-CA1 synapses, and reduction of surface expression of GABAB R1, GABAB R2, and HCN1, but increase in HCN2 surface expression. Meanwhile, the protein expression of TRIP8b (1a-4), TRIP8b (1b-2), and AAK1 was significantly decreased. Baclofen, a GABAB receptor agonist, markedly improved the memory impairment and alleviated neuronal damage. Besides, baclofen attenuated the decrease of surface expression of GABAB R1, GABAB R2, and HCN1, but downregulated HCN2 surface expression

  6. Permeability parameter as a function of population density in classical infiltration equation

    NASA Astrophysics Data System (ADS)

    Abidin, Nor Hafizah; Ahmad, Rohanin; Nordin, Syarifah Zyurina

    2014-12-01

    Rapid development of urban areas has caused many problems especially related to water issues. The increase in urban development also means the increase in impervious surfaces due to expansion of buildings, roads, parking lots to name a few. Impervious surfaces have low water permeability compared to pervious surfaces. Also, infiltration capacity is dependent on the permeability of the area and subsequently permeability is dependent on the surface conditions. In this paper, we study the infiltration capacity with the assumption that permeability parameter can be described in the term of the population density of the area. The modified model is based on the original form of Green-Ampt equation. The new model with population density is able to describe permeability, hence the infiltration capacity of an area.

  7. Modulation of blood-brain barrier permeability in mice using synthetic E-cadherin peptide.

    PubMed

    On, Ngoc H; Kiptoo, Paul; Siahaan, Teruna J; Miller, Donald W

    2014-03-03

    The present work characterizes the effects of synthetic E-cadherin peptide (HAV) on blood-brain barrier (BBB) integrity using various techniques including magnetic resonance imaging (MRI) and near-infrared fluorescent imaging (NIRF). The permeability of small molecular weight permeability marker gadolinium diethylenetriaminepentaacetate (Gd-DTPA) contrast agent, the large molecular weight permeability marker, IRDye 800CW PEG, and the P-glycoprotein (P-gp) efflux transporter contrast agent, rhodamine 800 (R800), were examined in the presence and absence of HAV peptide. The results consistently demonstrated that systemic iv administration of HAV peptide resulted in a reversible disruption of BBB integrity and enhanced the accumulation of all the dyes examined. The magnitude of increase ranged from 2-fold to 5-fold depending on the size and the properties of the permeability markers. The time frame for BBB disruption with HAV peptide was rapid, occurring within 3-6 min following injection of the peptide. Furthermore, modulation of BBB permeability was reversible with the barrier integrity being restored within 60 min of the injection. The increased BBB permeability observed following HAV peptide administration was not attributable to changes in cerebral blood flow. These studies support the potential use of cadherin peptides to rapidly and reversibly modulate BBB permeability of a variety of therapeutic agents.

  8. Prediction of hemorrhagic transformation after recanalization therapy using T2*-permeability magnetic resonance imaging.

    PubMed

    Bang, Oh Young; Buck, Brian H; Saver, Jeffrey L; Alger, Jeffry R; Yoon, Sa Rah; Starkman, Sidney; Ovbiagele, Bruce; Kim, Doojin; Ali, Latisha K; Sanossian, Nerses; Jahan, Reza; Duckwiler, Gary R; Viñuela, Fernando; Salamon, Noriko; Villablanca, J Pablo; Liebeskind, David S

    2007-08-01

    Predicting hemorrhagic transformation (HT) is critical in the setting of recanalization therapy for acute stroke. Dedicated magnetic resonance imaging (MRI) sequences for detection of increased blood-brain barrier (BBB) permeability recently have been developed. We evaluated the ability of a novel MRI permeability technique to detect baseline derangements predictive of various forms of HT after recanalization therapy. We retrospectively analyzed the clinical and pretreatment MRI data on patients undergoing recanalization therapy for acute cerebral ischemia at a university medical center from January 2004 to November 2006. Pretreatment MRI permeability images derived from perfusion source data were compared with posttreatment imaging to evaluate whether baseline BBB permeability derangements may predict HT after recanalization therapy. The use of a novel permeability technique to illustrate BBB derangements was based on the detection of decreased signal intensity at later time points in perfusion MRI acquisition, signifying continued local accumulation of contrast caused by leakage. Among 32 patients, some degree of HT occurred in 12. Permeability image abnormalities at baseline were present in 7 of 12 patients with HT and none of the 20 patients without HT on follow-up images. The sensitivity of permeability abnormality for parenchymal hematoma was 83%. False-negative findings were noted in five cases, most commonly asymptomatic or minor HT after mechanical clot retrieval. Permeability images derived from pretreatment perfusion MRI source data may identify patients at risk for HT with high specificity. Our preliminary demonstration of permeability imaging based on standard perfusion data for prediction of hemorrhage merits further study with dedicated MRI BBB permeability acquisitions and multicenter validation.

  9. Influence of the surface electrostimulation controlled by muscle contraction on the bioelectric muscle activity and restoration of the hand function in cerebral stroke patients.

    PubMed

    Krukowska, Jolanta; Swiątek, Ewa; Sienkiewicz, Monika; Czernicki, Jan

    2014-01-01

    Impaired limb mobility is the most troublesome condition in patients after cerebral stroke. The application of the electrode-glove might reduce dysfunctions in patients treated due to stroke. The electrode-glove use in rehabilitation is investigated. The study was conducted on 54 patients aged 28 - 72 (the mean age 54.3 ± 10.3) with hemiparesis who had suffered from cerebral stroke. The patients from Group 1 were applied bipolar stimulation of forearm muscles (flexors and extensors of the wrist joint and hand) with the use of two flat electrodes of the same size. With regards to Group 2, in the study used an electrode-glove. The excitation threshold was determined once a week with the use of the EMG. The evaluation of the electromyographic bioelectric activity of flexor and extensor muscles in the forearm, of the functional mobility of the hand according to the Brunnström test and of the functional mobility of the hand according to the seven-graded task Frenchay scale. The authors of the study observed a much greater improvement in the function of the hand in Group 2, where the mean value increased by 2.1 points. With regards to Group 1, the mean value increased by 1 point and the differences of the results in the studied groups after the therapy were statistically significant (p = 2.830). The electrical stimulation method controlled/triggered by muscle contractions is an effective method of normalization of muscle tension in the forearm and hand as well as restoration of the hand function in patients with cerebral stroke.

  10. Study on infrared differential thermal non-destructive testing technology of the permeability of hot mix asphalt pavements

    NASA Astrophysics Data System (ADS)

    Wang, Duanyi; Shi, Jicun

    2017-06-01

    In order to non-destructive test (NDT) the permeability coefficient of hot mix asphalt (HMA) pavements fast, A methodology for assessing the permeability coefficient was proposed by infrared differential thermal testing of pavement after rain. The relationship between permeability coefficient and air voids of HMA specimen deter-mined. Finite element method (FEM) models were built to calculate the surface temperature difference with different exposure time after precipitation. Simulated solar radiation source and fully saturated plate specimens were set in laboratory, tests verify that the different exposure time the specimen surface temperature difference. Infrared differential thermal detection permeable pavement hardware and corresponding software developed. Based on many test results, the evaluation index and criteria of permeability coefficient of HMA pavements tested by infrared differential thermal were developed. The results showed that: There is correlation between air voids and permeability coefficient of HMA specimen. Permeability coefficient of HMA pavements can be determined by different surface temperature at different exposure time. 9:00 am - 14:00 pm is the best time to detect permeability coefficient by infrared differential thermal NDT. Permeable asphalt pavement permeability can be achieved by infrared detector quickly and continuously, a lane testing; Per the permeable assessment criteria, in-place pavements permeability coefficients can be accurately evaluated.

  11. Pyrotechnic deflagration velocity and permeability

    SciTech Connect

    Begeal, D R; Stanton, P L

    1982-01-01

    Particle size, porosity, and permeability of the reactive material have long been considered to be important factors in propellant burning rates and the deflagration-to-detonation transition in explosives. It is reasonable to assume that these same parameters will also affect the deflagration velocity of pyrotechnics. This report describes an experimental program that addresses the permeability of porous solids (particulate beds), in terms of particle size and porosity, and the relationship between permeability and the behavior of pyrotechnics and explosives. The experimental techniques used to acquire permeability data and to characterize the pyrotechnic burning are discussed. Preliminary data have been obtained on the burning characteristics of titanium hydride/potassium perchlorate (THKP) and boron/calcium chromate (BCCR). With THKP, the velocity of a pressure wave (from hot product gases) in the unburned region shows unsteady behavior which is related to the initial porosity or permeability. Simultaneous measurements with pressure gauges and ion gauges reveal that the pressure wave precedes the burn front. Steady burning of BCCR was observed with pressure gauge diagnostics and with a microwave interferometry technique.

  12. Platelets can enhance vascular permeability.

    PubMed

    Cloutier, Nathalie; Paré, Alexandre; Farndale, Richard W; Schumacher, H Ralph; Nigrovic, Peter A; Lacroix, Steve; Boilard, Eric

    2012-08-09

    Platelets survey blood vessels, searching for endothelial damage and preventing loss of vascular integrity. However, there are circumstances where vascular permeability increases, suggesting that platelets sometimes fail to fulfill their expected function. Human inflammatory arthritis is associated with tissue edema attributed to enhanced permeability of the synovial microvasculature. Murine studies have suggested that such vascular leak facilitates entry of autoantibodies and may thereby promote joint inflammation. Whereas platelets typically help to promote microvascular integrity, we examined the role of platelets in synovial vascular permeability in murine experimental arthritis. Using an in vivo model of autoimmune arthritis, we confirmed the presence of endothelial gaps in inflamed synovium. Surprisingly, permeability in the inflamed joints was abrogated if the platelets were absent. This effect was mediated by platelet serotonin accumulated via the serotonin transporter and could be antagonized using serotonin-specific reuptake inhibitor antidepressants. As opposed to the conventional role of platelets to microvascular leakage, this demonstration that platelets are capable of amplifying and maintaining permeability adds to the rapidly growing list of unexpected functions for platelets.

  13. Effective pressure law for permeability of E-bei sandstones

    NASA Astrophysics Data System (ADS)

    Li, M.; Bernabé, Y.; Xiao, W.-I.; Chen, Z.-Y.; Liu, Z.-Q.

    2009-07-01

    Laboratory experiments were conducted to determine the effective pressure law for permeability of tight sandstone rocks from the E-bei gas reservoir, China. The permeability k of five core samples was measured while cycling the confining pressure pc and fluid pressure pf. The permeability data were analyzed using the response-surface method, a statistical model-building approach yielding a representation of k in (pc, pf) space that can be used to determine the effective pressure law, i.e., peff = pc - κpf. The results show that the coefficient κ of the effective pressure law for permeability varies with confining pressure and fluid pressure as well as with the loading or unloading cycles (i.e., hysteresis effect). Moreover, κ took very small values in some of the samples, even possibly lower than the value of porosity, in contradiction with a well-accepted theoretical model. We also reanalyzed a previously published permeability data set on fissured crystalline rocks and found again that the κ varies with pc but did not observe κ values lower than 0.4, a value much larger than porosity. Analysis of the dependence of permeability on effective pressure suggests that the occurrence of low κ values may be linked to the high-pressure sensitivity of E-bei sandstones.

  14. Permeability diagnosis model in drug discovery: a diagnostic tool to identify the most influencing properties for gastrointestinal permeability.

    PubMed

    Wang, Jianling; Skolnik, Suzanne

    2013-01-01

    Permeability is important in governing the ability of drug substances to transport across gastrointestinal membrane and also crucial for proper drug distribution to pharmacological target organs and cells, and is therefore frequently utilized in drug discovery and development. In this report, we have performed a systematic analysis, using principal component analysis on the historically measured permeability data from in-house Caco-2 and parallel artificial membrane permeability assays on discovery new chemical entities from multiple projects. This work allows for establishment of a permeability diagnosis model by purposefully identifying most influencing physicochemical properties of the permeability issues, including polarity-lipophilicity line contributed primarily by polar surface area and LogP, number of rotation bond, fractional ionization at neutral pH and efflux ratio. A number of cases were also shown to demonstrate the applicability of the current model. The analysis of the model over internal drug discovery compounds exhibited promising diagnostic and predictive power of the model. The advantages and limitation of the model as well as the integral strategy to apply it in drug discovery to guide projects for permeability-related optimization were also presented.

  15. Periosteum, bone's "smart" bounding membrane, exhibits direction-dependent permeability.

    PubMed

    Evans, Sarah F; Parent, Jonathan B; Lasko, Colin E; Zhen, Xiaowen; Knothe, Ulf R; Lemaire, Thibault; Knothe Tate, Melissa L

    2013-03-01

    The periosteum serves as bone's bounding membrane, exhibits hallmarks of semipermeable epithelial barrier membranes, and contains mechanically sensitive progenitor cells capable of generating bone. The current paucity of data regarding the periosteum's permeability and bidirectional transport properties provided the impetus for the current study. In ovine femur and tibia samples, the periosteum's hydraulic permeability coefficient, k, was calculated using Darcy's Law and a custom-designed permeability tester to apply controlled, volumetric flow of phosphate-buffered saline through periosteum samples. Based on these data, ovine periosteum demonstrates mechanically responsive and directionally dependent (anisotropic) permeability properties. At baseline flow rates comparable to interstitial fluid flow (0.5 µL/s), permeability is low and does not exhibit anisotropy. In contrast, at high flow rates comparable to those prevailing during traumatic injury, femoral periosteum exhibits an order of magnitude higher permeability compared to baseline flow rates. In addition, at high flow rates permeability exhibits significant directional dependence, with permeability higher in the bone to muscle direction than vice versa. Furthermore, compared to periosteum in which the intrinsic tension (pre-stress) is maintained, free relaxation of the tibial periosteum after resection significantly increases its permeability in both flow directions. Hence, the structure and mechanical stress state of periosteum influences its role as bone's bounding membrane. During periods of homeostasis, periosteum may serve as a barrier membrane on the outer surface of bone, allowing for equal albeit low quiescent molecular communication between tissue compartments including bone and muscle. In contrast, increases in pressure and baseline flow rates within the periosteum resulting from injury, trauma, and/or disease may result in a significant increase in periosteum permeability and consequently in

  16. Permeability study of cancellous bone and its idealised structures.

    PubMed

    Syahrom, Ardiyansyah; Abdul Kadir, Mohammed Rafiq; Harun, Muhamad Nor; Öchsner, Andreas

    2015-01-01

    Artificial bone is a suitable alternative to autografts and allografts, however their use is still limited. Though there were numerous reports on their structural properties, permeability studies of artificial bones were comparably scarce. This study focused on the development of idealised, structured models of artificial cancellous bone and compared their permeability values with bone surface area and porosity. Cancellous bones from fresh bovine femur were extracted and cleaned following an established protocol. The samples were scanned using micro-computed tomography (μCT) and three-dimensional models of the cancellous bones were reconstructed for morphology study. Seven idealised and structured cancellous bone models were then developed and fabricated via rapid prototyping technique. A test-rig was developed and permeability tests were performed on the artificial and real cancellous bones. The results showed a linear correlation between the permeability and the porosity as well as the bone surface area. The plate-like idealised structure showed a similar value of permeability to the real cancellous bones.

  17. Aneurysm permeability following coil embolization: packing density and coil distribution

    PubMed Central

    Chueh, Ju-Yu; Vedantham, Srinivasan; Wakhloo, Ajay K; Carniato, Sarena L; Puri, Ajit S; Bzura, Conrad; Coffin, Spencer; Bogdanov, Alexei A; Gounis, Matthew J

    2015-01-01

    Background Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Methods Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. Results All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r2=0.73) than with packing density alone (r2=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. Conclusions A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability. PMID:25031179

  18. Effect of endodontic procedures on root dentin permeability.

    PubMed

    Tao, L; Anderson, R W; Pashley, D H

    1991-12-01

    The purpose of this study was to quantitate the sequential effects of endodontic procedures on the permeability of human root dentin in vitro. Forty single-rooted teeth were used. Both the crown and the apical 2 mm of the root were removed. The hydraulic conductance of the root before and after various endodontic procedures was measured using a fluid filtration method. Measurements were also made of dentin thickness, intracanal diameter changes, and changes in intracanal surface area. The results showed that instrumentation by K files alone or in combination with Gates Glidden drills did not alter radicular dentin permeability when the cementum remained intact. After removing the cementum, the creation of a smear layer and smear plugs on the canal surface tended to offset the expected increase in dentin permeability created by increasing the intracanal surface area and decreasing root dentin thickness. EDTA treatment inside the instrumented canal to remove the smear layer did not increase permeability significantly. The use of K files followed by Gates Glidden drills tended to remove more cervical dentin, increased the intracanal surface area, and increased the hydraulic conductance of root dentin more than the use of K files alone.

  19. Trench infiltration for managed aquifer recharge to permeable bedrock

    USGS Publications Warehouse

    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.

  20. Permeability dependence of streaming potential in rocks for various fluid conductivities

    NASA Astrophysics Data System (ADS)

    Jouniaux, Laurence; Pozzi, Jean-Pierre

    1995-02-01

    Streaming potentials have been measured on sandstone and limestone samples in a large range of permeabilities. The electrokinetic coupling coefficient increases with permeability and we explain this effect by the related variation of surface conductivity. A model is proposed to study this effect for various fluid conductivities and it is shown that the dependence of the electrokinetic coupling coefficient on permeability is stronger for high fluid resistivity and is weaker for lower fluid resistivity. When fluid resistivity is below 1 Ohm-meter permeability and streaming potential are no more related.

  1. Rigid gas permeable extended wear.

    PubMed

    Maehara, J R; Kastl, P R

    1994-04-01

    We have reviewed the pertinent literature on rigid gas permeable (RGP) extended wear contact lenses, and we discuss the benefits and adverse reactions of this contact lens modality, drawing conclusions from reviewed studies. We suggest parameters for success with these lenses and guidelines for the prevention of adverse reactions.

  2. Permeability Evolution of Propped Artificial Fractures in Green River Shale

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Feng, Zijun; Han, Gang; Elsworth, Derek; Marone, Chris; Saffer, Demian; Cheon, Dae-Sung

    2017-06-01

    This paper compares the evolution of permeability with effective stress in propped fractures in shale for native CH4 compared with that for sorbing CO2, slightly sorbing N2 and non-sorbing He. We examine the response for laboratory experiments on artificial propped fractures in Green River Shale to explore mechanisms of proppant embedment and fracture diagenesis. Split cylindrical specimens sandwich a proppant bead-pack at a constant confining stress of 20 MPa and with varied pore pressure. Permeability and sorption characteristics are measured with the pulse transient method. To explore the effect of swelling and embedment on fracture surface geometry, we measure the evolution of conductivity characteristics for different proppant geometries (single layer vs. multilayer), gas saturation and specimen variation in order to simulate both production and enhanced gas recovery. The resulting morphology of embedment is measured by white light interferometry and characterized via surface roughness parameter of mean, maximum and root-mean-square amplitudes. For both strongly (CO2, CH4) and slightly adsorptive gases (N2), the permeability first decreases with an increase in gas pressure due to swelling before effective stress effects dominate above the Langmuir pressure threshold. CO2 with its highest adsorption affinity produces the lowest permeability among these three gas permeants. Monolayer propped specimens show maximum swelling and lowered k/k 0 ratio and increased embedment recorded in the surface roughness relative to the multilayered specimens. Permeabilities measured for both injection and depletion cycles generally overlap and are repeatable with little hysteresis. This suggests the dominant role of reversible swelling over irreversible embedment. Gas permeant composition and related swelling have an important effect on the permeability evolution of shales.

  3. Enhanced contractility of intraparenchymal arterioles after global cerebral ischaemia in rat - new insights into the development of delayed cerebral hypoperfusion.

    PubMed

    Spray, S; Johansson, S E; Radziwon-Balicka, A; Haanes, K A; Warfvinge, K; Povlsen, G K; Kelly, P A T; Edvinsson, L

    2017-08-01

    Delayed cerebral hypoperfusion is a secondary complication found in the days after transient global cerebral ischaemia that worsens the ischaemic damage inflicted by the initial transient episode of global cerebral ischaemia. A recent study demonstrated increased cerebral vasoconstriction in the large arteries on the brain surface (pial arteries) after global cerebral ischaemia. However, smaller arterioles inside the brain (parenchymal arterioles) are equally important in the regulation of cerebral blood flow and yet their pathophysiology after global cerebral ischaemia is largely unknown. Therefore, we investigated whether increased contractility occurs in the intraparenchymal arterioles. Global cerebral ischaemia was induced in male Wistar rats by bilateral common carotid occlusion for 15 min combined with hypovolaemia. Regional cerebral blood flow was determined by quantitative autoradiography. Intraparenchymal arterioles were isolated and pressurized, and concentration-response curves to endothelin-1 with and without the endothelin B receptor-selective antagonist BQ788 was generated. Endothelin B receptor expression was investigated by quantitative flow cytometry and immunohistochemistry. We observed increased endothelin-1-mediated contractility of parenchymal arterioles correlating with reduced cerebral blood flow of the cortex, hippocampus and caudate nucleus 48 h after global cerebral ischaemia. The increased endothelin-1-mediated contractility was abolished by BQ788, and the vascular smooth muscle cell-specific expression of endothelin B receptors was significantly increased after global cerebral ischaemia. Increased endothelin-1-mediated contractility and expression of endothelin B receptors in the intraparenchymal vasculature contributes to the development of delayed cerebral hypoperfusion after global cerebral ischaemia in combination with vascular changes of the pial vasculature. © 2016 Scandinavian Physiological Society. Published by John Wiley

  4. Scale Dependence of Soil Permeability to Air: Measurement Method and Field Investigation

    SciTech Connect

    Garbesi, K.; Sextro, R.G.; Robinson, Arthur L.; Wooley, J.D.; Owens, J.A.; Nazaroff, W.W.

    1995-11-01

    This work investigates the dependence soil air-permeability on sampling scale in near-surface unsaturated soils. A new dual-probe dynamic pressure technique was developed to measure permeability in situ over different length scales and different spatial orientations in the soil. Soils at three sites were studied using the new technique. Each soil was found to have higher horizontal than vertical permeability. Significant scale dependence of permeability was also observed at each site. Permeability increased by a factor of 20 as sampling scale increased from 0.1 to 2 m in a sand soil vegetated with dry grass, and by a factor of 15 as sampling scale increased from 0.1 to 3.5 m in a sandy loam with mature Coast Live Oak trees (Quercus agrifolia). The results indicate that standard methods of permeability assessment can grossly underestimate advective transport of gas-phase contaminants through soils.

  5. High membrane permeability for melatonin

    PubMed Central

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

    2016-01-01

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

  6. [Reversible cerebral vasoconstriction syndrome].

    PubMed

    Laakso, Elina; Pekkola, Johanna; Soinne, Lauri; Putaala, Jukka

    2014-01-01

    Reversible cerebral vasoconstriction syndrome (RCVS) is increasingly recognized. The condition is characterized by multifocal vasoconstriction lesions in cerebral arteries. Headache is the central symptom, with an acute onset and paroxysmal occurrence. Some of the patients develop intracranial hemorrhage, ischemic disturbance of the cerebral circulation, hypertensive encephalopathy (PRES) or epileptic seizures as complications. The disease is most common in middle-aged women. Most patients have an underlying predisposing factor, most commonly vasoactive medications, drugs or puerperium. There is no evidence-based practice.

  7. A Large Block Experiment for Measurement of the Effective Permeability of Indiana Limestone

    NASA Astrophysics Data System (ADS)

    Selvadurai, P. A.; Selvadurai, A. P.

    2009-12-01

    The measurement of permeability of large specimens of a rock specimen is bound to provide a clearer picture of the distribution of permeability of predominantly sedimentary rocks. Such distributions can be the basis for evaluating the effective permeability of the rock specimen in the presence of permeability inhomogeneity. This paper discusses the development of a patch permeability test that can be used to measure the near surface permeability characteristics of a large cuboidal block of Indiana Limestone measuring 508 mm. The test is used to generate the near surface permeability of six faces of the cuboid and these estimates are used to generate, via a kriging procedure, the interior permeability distributions of permeability. These permeability distributions are used to examine the validity of theoretical estimates that have been developed in the literature to determine the effective permeability of the material. The classical Wiener (1912) bounds, the estimates provided by Matheron (1967) and Journel et al. (1993) are developed using the experimentally derived data. The procedure is also validated by conducting computational experiments involving one-dimensional flow along three orthogonal directions. References: Wiener, O. (1912) Die Theorie des Mischkörpers für das Feld des stationaären Strömung. Erste Abhandlung die Mittelswertesätsze für Kraft, Polarisation und Energie. Abh. Math.-Physischen Klasse Königl. Säcsh Gesell. Wissen, 32: 509-604. Matheron, G. (1967) Eléments pour une Théorie des Milieux Poroeux, Masson, Paris. Journel, A.G, Deutsch, C.V. and Desbrats, A.J. (1986) Power averaging for block effective permeability, SPE 15128, Society of Petroleum Engineers.

  8. Statins and cerebral hemodynamics

    PubMed Central

    Giannopoulos, Sotirios; Katsanos, Aristeidis H; Tsivgoulis, Georgios; Marshall, Randolph S

    2012-01-01

    HMG-CoA reductase inhibitors (statins) are associated with improved stroke outcome. This observation has been attributed in part to the palliative effect of statins on cerebral hemodynamics and cerebral autoregulation (CA), which are mediated mainly through the upregulation of endothelium nitric oxide synthase (eNOS). Several animal studies indicate that statin pretreatment enhances cerebral blood flow after ischemic stroke, although this finding is not further supported in clinical settings. Cerebral vasomotor reactivity, however, is significantly improved after long-term statin administration in most patients with severe small vessel disease, aneurysmal subarachnoid hemorrhage, or impaired baseline CA. PMID:22929438

  9. Quantifying Evaporation in a Permeable Pavement System

    EPA Science Inventory

    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...

  10. Quantifying Evaporation in a Permeable Pavement System

    EPA Science Inventory

    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...

  11. Drug permeability prediction using PMF method.

    PubMed

    Meng, Fancui; Xu, Weiren

    2013-03-01

    Drug permeability determines the oral availability of drugs via cellular membranes. Poor permeability makes a drug unsuitable for further development. The permeability may be estimated as the free energy change that the drug should overcome through crossing membrane. In this paper the drug permeability was simulated using molecular dynamics method and the potential energy profile was calculated with potential of mean force (PMF) method. The membrane was simulated using DPPC bilayer and three drugs with different permeability were tested. PMF studies on these three drugs show that doxorubicin (low permeability) should pass higher free energy barrier from water to DPPC bilayer center while ibuprofen (high permeability) has a lower energy barrier. Our calculation indicates that the simulation model we built is suitable to predict drug permeability.

  12. THE PERMEABILITY OF RAT TRANSITIONAL EPITHELIUM

    PubMed Central

    Hicks, R. M.

    1966-01-01

    Permeability barriers must exist in transitional epithelium to prevent the free flow of water from underlying blood capillaries through the epithelium into the hypertonic urine, and such a barrier has now been demonstrated in isolated bladders. This barrier is passive in function and can be destroyed by damaging the luminal surface of the transitional epithelium with sodium hydroxide and 8 M urea solutions, by digesting it with trypsin, lecithinase C, and lecithinase D, or by treating it with lipid solvents such as Triton x 100 and saponin. From this it is concluded that the barrier depends on the integrity of lipoprotein cell membranes. The barrier function is also destroyed by sodium thioglycollate solutions, and electron microscope investigations show that sodium thioglycollate damages the thick asymmetric membrane which limits the luminal face of the superficial squamous cell. Cytochemical staining shows the epithelium to contain disulfide and thiol groups and to have a concentration of these groups at the luminal margin of the superficial cells. It thus appears that the permeability barrier also depends on the presence of disulfide bridges in the epithelium, and it is presumed that these links are located in keratin. Because of the effect of thioglycollates, both on the barrier function and on the morphology of the membrane, it is suggested that keratin may be incorporated in the thick barrier membrane. It is proposed that the cells lining the urinary bladder and ureters should be regarded as a keratinizing epitheluim. PMID:5901498

  13. Why do malaria parasites increase host erythrocyte permeability?

    PubMed Central

    Desai, Sanjay A.

    2014-01-01

    Malaria parasites increase erythrocyte permeability to diverse solutes including anions, some cations, and organic solutes, as characterized with several independent methods. Over the last decade, patch-clamp studies have determined that the permeability results from one or more ion channels on the infected erythrocyte host membrane. However, the biological role(s) served by these channels, if any, remain controversial. Recent studies implicate the plasmodial surface anion channel (PSAC) and a role in parasite nutrient acquisition. A debated alternative role in remodeling host ion composition for the benefit of the parasite appears to be nonessential. Because both channel activity and the associated clag3 genes are strictly conserved in malaria parasites, channel-mediated permeability is an attractive target for development of new therapies. PMID:24507014

  14. The Structure of the Mitochondrial Membrane: Inferences from Permeability Properties

    PubMed Central

    Tedeschi, Henry

    1959-01-01

    Mitochondria possess a semipermeable membrane with properties similar to the cell membrane. Despite the presence of a limiting membrane, mitochondria swell approximately 4 to 5 times their original volume without lysis or loss of internal solute. For this reason, it has been argued that the membrane might be convoluted. The present kinetic study of the permeability of isolated mitochondria was undertaken to clarify this question. A photometric method described previously was used. In the case of highly lipid soluble penetrants, the results suggest that neither the permeability nor the surface area available for penetration varies significantly during considerable swelling. These results may be interpreted to mean that the mitochondrial membrane is convoluted. For highly polar compounds, the permeability of the membrane also remains unchanged during swelling, but the surface area available to penetration increases. These results may be interpreted to mean that in this latter case, the surface of the convolutions becomes available only after they are unfolded by swelling. The simplest model that can explain the permeability properties of this membrane consists of a bimolecular lipid layer where the inner monomolecular layer is convoluted. PMID:13837259

  15. Turbulent Hyporheic Exchange in Permeable Sediments

    NASA Astrophysics Data System (ADS)

    Roche, K. R.; Aubeneau, A. F.; Li, A.; Packman, A. I.

    2015-12-01

    Solute delivery from the water column into a streambed strongly influences metabolism in rivers. Current hydrological models simplify surface-subsurface (hyporheic) exchange by treating each domain separately, constraining turbulent flows to the water column. Studies have shown, however, that turbulence penetrates into permeable sediments. Evidence is lacking for how this highly coupled flow regime influences hyporheic exchange. We characterized the dynamics of turbulent exchange between surface and porewaters in a 2.5 m recirculating flume. The channel was packed with 3.8 cm PVC spheres to form a coarse gravel bed, with a total depth of 21 cm. We implanted microsensors onto an array of spheres to measure in situsalt concentrations within the streambed. Water was recirculated in the channel, and concentrated salt solution was continuously injected upstream of the sensor array. We observed solute exchange increased with free-stream Reynolds number and decreased with depth in the sediment bed. Mass of injected solute remaining in the bed decreased rapidly in all cases, with only 10-30% of mass recovered 50 cm downstream of the injection point at Re = 25,000. We observed high-frequency (1-10 Hz) concentration fluctuations at bed depths of at least 4.75 cm, and sporadic low-frequency fluctuations at depths of 12.5 cm. Spectral analysis revealed increased filtering of high frequencies with depth. We used particle-tracking simulations to fit depth-dependent turbulent diffusion profiles to experimental results. These results demonstrate that free-stream turbulence impacts hyporheic mixing deep into permeable streambeds, and mixing is strongly influenced by the coupled surface-subsurface flow field.

  16. The impacts of effective stress and CO2 sorption on the matrix permeability of shale reservoir rocks [The impacts of CO2 sorption and effective stress on the matrix permeability of shale reservoir rocks

    DOE PAGES

    Wu, Wei; Zoback, Mark D.; Kohli, Arjun H.

    2017-05-02

    We assess the impacts of effective stress and CO2 sorption on the bedding-parallel matrix permeability of the Utica shale through pressure pulse-decay experiments. We first measure permeability using argon at relatively high (14.6 MPa) and low (2.8 MPa) effective stresses to assess both pressure dependence and recoverability. We subsequently measure permeability using supercritical CO2 and again using argon to assess changes due to CO2 sorption. We find that injection of both argon and supercritical CO2 reduces matrix permeability in distinct fashion. Samples with permeability higher than 10–20 m2 experience a large permeability reduction after treatment with argon, but a minormore » change after treatment with supercritical CO2. However, samples with permeability lower than this threshold undergo a slight change after treatment with argon, but a dramatic reduction after treatment with supercritical CO2. These results indicate that effective stress plays an important role in the evolution of relatively permeable facies, while CO2 sorption dominates the change of ultra-low permeability facies. The permeability reduction due to CO2 sorption varies inversely with initial permeability, which suggests that increased surface area from hydraulic stimulation with CO2 may be counteracted by sorption effects in ultra-low permeability facies. As a result, we develop a conceptual model to explain how CO2 sorption induces porosity reduction and volumetric expansion to constrict fluid flow pathways in shale reservoir rocks.« less

  17. Regulation of intestinal permeability: The role of proteases

    PubMed Central

    Van Spaendonk, Hanne; Ceuleers, Hannah; Witters, Leonie; Patteet, Eveline; Joossens, Jurgen; Augustyns, Koen; Lambeir, Anne-Marie; De Meester, Ingrid; De Man, Joris G; De Winter, Benedicte Y

    2017-01-01

    The gastrointestinal barrier is - with approximately 400 m2 - the human body’s largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extra-intestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases. PMID:28405139

  18. Relating tortuosity and permeability in the Niobrara Formation

    NASA Astrophysics Data System (ADS)

    Tokan-Lawal, A.; Landry, C.; Prodanovic, M.; Eichhubl, P.

    2013-12-01

    Natural fractures are typically partially lined and/or filled with mineral cements, which can constrict fluid flow and create very rough fracture wall surfaces. In this study, we investigate fluid flow in the carbonate-rich, low-matrix permeability Niobrara formation. We focus on correlating fluid flow parameters (such as permeability) with the geometric tortuosity of the fracture (pore space) and the individual fluid phases for a fractured carbonate. We use x-ray microtomography imaging to provide information on fracture geometry. Image analysis is performed (via 3DMA Rock software), to characterize the connectivity and geometric tortuosity of the pore space and individual fluid phases at different saturations. We also use a combination of the level-set-method-based progressive-quasistatic algorithm (LSMPQS software), and lattice Boltzmann simulation (Palabos software) to characterize the capillary dominated displacement properties and the relative permeability of the naturally cemented fractures within. Finally, we numerically investigate the effect of (uniform) cementation on the fracture permeability as well as the tortuosity of the pore space and the capillary pressure-water saturation (Pc-Sw) relationship using two different methods. Permeability estimates in the Niobrara sample were consistent regardless of the method used. Pore space tortuosity and capillary pressure as a function of water saturation relationships both increase with cementation, and while the behavior is similar to that of cementation effects in sandstones, it is much more abrupt in fractures. This is likely because the fluid pathways are restricted to nearly planar spaces.

  19. Determination of hydrogen permeability in commercial and modified superalloys

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.; Peterman, W.

    1983-01-01

    The results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-ranged ordered alloys over the range of 705 to 870 C (1300 to 1600 F) are summarized. The test alloys included wrought alloys N-155, IN 800, A-286, 19-9DL, and 19-9DL modifications with aluminum, niobium, and misch metal. In addition, XF-818, CRM-6D, SA-F11, and HS-31 were evaluated. Two wrought long-range ordered alloys, Ni3Al and (Fe,Ni)3(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO2-doped H2 for test periods as long as 133 h. Detailed analyses were conducted to determine the relative permeability rankings of these alloys and the effect of doping, exit surface oxidation, specimen design variations, and test duration on permeability coefficient, and permeation activation energies were determined. The two long-range ordered alloys had the lowest permeability coefficients in pure H2 when compared with the eight commercial alloys and their modifications. With CO2 doping, significant decrease in permeability was observed in commercial alloys--no doped tests were conducted with the long-range ordered alloys.

  20. Simulating bioclogging effects on dynamic riverbed permeability and infiltration

    NASA Astrophysics Data System (ADS)

    Newcomer, Michelle E.; Hubbard, Susan S.; Fleckenstein, Jan H.; Maier, Ulrich; Schmidt, Christian; Thullner, Martin; Ulrich, Craig; Flipo, Nicolas; Rubin, Yoram

    2016-04-01

    Bioclogging in rivers can detrimentally impact aquifer recharge. This is particularly so in dry regions, where losing rivers are common, and where disconnection between surface water and groundwater (leading to the development of an unsaturated zone) can occur. Reduction in riverbed permeability due to biomass growth is a time-variable parameter that is often neglected, yet permeability reduction from bioclogging can introduce order of magnitude changes in seepage fluxes from rivers over short (i.e., monthly) timescales. To address the combined effects of bioclogging and disconnection on infiltration, we developed numerical representations of bioclogging processes within a one-dimensional, variably saturated flow model representing losing-connected and losing-disconnected rivers. We tested these formulations using a synthetic case study informed with biological data obtained from the Russian River, California, USA. Our findings show that modeled biomass growth reduced seepage for losing-connected and losing-disconnected rivers. However, for rivers undergoing disconnection, infiltration declines occurred only after the system was fully disconnected. Before full disconnection, biologically induced permeability declines were not significant enough to offset the infiltration gains introduced by disconnection. The two effects combine to lead to a characteristic infiltration curve where peak infiltration magnitude and timing is controlled by permeability declines relative to hydraulic gradient gains. Biomass growth was found to hasten the onset of full disconnection; a condition we term `effective disconnection'. Our results show that river infiltration can respond dynamically to bioclogging and subsequent permeability declines that are highly dependent on river connection status.

  1. Permeability changes in layered sediments: impact of particle release.

    PubMed

    Blume, Theresa; Weisbrod, Noam; Selker, John S

    2002-01-01

    One of the mechanisms of sudden particle release from grain surfaces in natural porous media is a decrease in salt concentration of the permeating fluid to below the critical salt concentration. Particle release can cause a change in hydraulic conductivity of the matrix, either by washing out the fines and thus increasing the pore sizes or by the plugging of pore constrictions. The phenomenon of permeability changes as a result of particle detachment was investigated in a series of column experiments. Coarse and fine sediments from the Hanford Formation in southeast Washington were tested. Columns were subject to a pulse of highly saline solution (NaNO3) followed by a fresh water shock causing particle release. Outflow rates and changes in hydraulic head as well as electric conductivity and pH were monitored over time. No permeability decrease occurred within the coarse matrix alone. However, when a thin layer of fine sediment was embedded within the coarse material (mimicking field conditions at the Hanford site), permeability irreversibly decreased to 10% to 20% of the initial value. Evidence suggests that most of this permeability decrease was a result of particles detached within the fine layer and its subsequent clogging. An additional observation was a sudden increase in pH in the outflow solution, generated in situ during the fresh water shock. Because layered systems are common in natural settings, our results suggest that alteration between sodium solution and fresh water can lead to particle release and subsequently reduce the overall permeability of the matrix.

  2. Cerebral Asymmetries and Reading Acquisition

    ERIC Educational Resources Information Center

    Pirozzolo, Francis J.

    1978-01-01

    Reviewed are historical developments regarding the concepts of cerebral localization, and analyzed are implications of current research on the role of the cerebral hemispheres in reading disorders. (CL)

  3. Review of Hydrogen Isotope Permeability Through Materials

    SciTech Connect

    Steward, S. A.

    1983-08-15

    This report is the first part of a comprehensive summary of the literature on hydrogen isotope permeability through materials that do not readily form hydrides. While we mainly focus on pure metals with low permeabilities because of their importance to tritium containment, we also give data on higher-permeability materials such as iron, nickel, steels, and glasses.

  4. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Frederking, T. H. K.

    1981-01-01

    Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

  5. Structure/Permeability Relationships Of Polyimide Membranes

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; Yamamoto, H.; Mi, Y.; Stern, S. A.

    1995-01-01

    Report describes experimental study of permeabilities, by each of five gases, of membranes made of four different polyimides. Conducted to gain understanding of effects of molecular structures of membranes on permeabilities and to assess potential for exploitation of selective permeability in gas-separation processes. Gases used: H2, O2, N2, CO2, and CH4.

  6. Structure/Permeability Relationships Of Polyimide Membranes

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; Yamamoto, H.; Mi, Y.; Stern, S. A.

    1995-01-01

    Report describes experimental study of permeabilities, by each of five gases, of membranes made of four different polyimides. Conducted to gain understanding of effects of molecular structures of membranes on permeabilities and to assess potential for exploitation of selective permeability in gas-separation processes. Gases used: H2, O2, N2, CO2, and CH4.

  7. Novel additives to retard permeable flow

    SciTech Connect

    Golombok, Michael; Crane, Carel; Ineke, Erik; Welling, Marco; Harris, Jon

    2008-09-15

    Low concentrations of surfactant and cosolute in water, can selectively retard permeable flow in high permeability rocks compared to low permeability ones. This represents a way forward for more efficient areal sweep efficiency when water flooding a reservoir during improved oil recovery. (author)

  8. Permeability effects on the seismic response of gas reservoirs

    NASA Astrophysics Data System (ADS)

    Rubino, J. Germán.; Velis, Danilo R.; Holliger, Klaus

    2012-04-01

    In this work, we analyse the role of permeability on the seismic response of sandstone reservoirs characterized by patchy gas-water saturation. We do this in the framework of Johnson's model, which is a generalization of White's seminal model allowing for patches of arbitrary geometry. We first assess the seismic attenuation and velocity dispersion characteristics in response to wave-induced fluid flow. To this end, we perform an exhaustive analysis of the sensitivity of attenuation and velocity dispersion of compressional body waves to permeability and explore the roles played by the Johnson parameters T and S/V, which characterize the shape and size of the gas-water patches. Our results indicate that, within the typical frequency range of exploration seismic data, this sensitivity may indeed be particularly strong for a variety of realistic and relevant scenarios. Next, we extend our analysis to the corresponding effects on surface-based reflection seismic data for two pertinent models of typical sandstone reservoirs. In the case of softer and more porous formations and in the presence of relatively low levels of gas saturation we observe that the effects of permeability on seismic reflection data are indeed significant. These prominent permeability effects prevail for normal-incidence and non-normal-incidence seismic data and for a very wide range of sizes and shapes of the gas-water patches. For harder and less porous reservoirs, the normal-incidence seismic responses exhibit little or no sensitivity to permeability, but the corresponding non-normal-incidence responses show a clear dependence on this parameter, again especially so for low gas saturations. The results of this study therefore suggest that, for a range of fairly common and realistic conditions, surface-based seismic reflection data are indeed remarkably sensitive to the permeability of gas reservoirs and thus have the potential of providing corresponding first-order constraints.

  9. Pore-structure models of hydraulic conductivity for permeable pavement

    NASA Astrophysics Data System (ADS)

    Kuang, X.; Sansalone, J.; Ying, G.; Ranieri, V.

    2011-03-01

    SummaryPermeable pavement functions as a porous infrastructure interface allowing the infiltration and evaporation of rainfall-runoff while functioning as a relatively smooth load-bearing surface for vehicular transport. Hydraulic conductivity ( k) of permeable pavement is an important hydraulic property and is a function of the pore structure. This study examines k for a cementitious permeable pavement (CPP) through a series of pore-structure models. Measurements utilized include hydraulic head as well as total porosity, ( ϕ t), effective porosity ( ϕ e), tortuosity ( L e/ L) and pore size distribution (PSD) indices generated through X-ray tomography (XRT). XRT results indicate that the permeable pavement pore matrix is hetero-disperse, with high tortuosity and ϕ t ≠ ϕ e. Power law models of k- ϕ t and k- ϕ e relationships are developed for a CPP mix design. Results indicate that the Krüger, Fair-Hatch, Hazen, Slichter, Beyer and Terzaghi models based on simple pore-structure indices do not reproduce measured k values. The conventional Kozeny-Carman model (KCM), a more parameterized pore-structure model, did not reproduce measured k values. This study proposes a modified KCM utilizing ϕ e, specific surface area (SSA) pe and weighted tortuosity ( L e/ L) w. Results demonstrate that such permeable pavement pore-structure parameters with the modified KCM can predict k. The k results are combined with continuous simulation modeling using historical rainfall to provide nomographs examining permeable pavement as a low impact development (LID) infrastructure component.

  10. Long-term stormwater quantity and quality performance of permeable pavement systems.

    PubMed

    Brattebo, Benjamin O; Booth, Derek B

    2003-11-01

    This study examined the long-term effectiveness of permeable pavement as an alternative to traditional impervious asphalt pavement in a parking area. Four commercially available permeable pavement systems were evaluated after 6 years of daily parking usage for structural durability, ability to infiltrate precipitation, and impacts on infiltrate water quality. All four permeable pavement systems showed no major signs of wear. Virtually all rainwater infiltrated through the permeable pavements, with almost no surface runoff. The infiltrated water had significantly lower levels of copper and zinc than the direct surface runoff from the asphalt area. Motor oil was detected in 89% of samples from the asphalt runoff but not in any water sample infiltrated through the permeable pavement. Neither lead nor diesel fuel were detected in any sample. Infiltrate measured 5 years earlier displayed significantly higher concentrations of zinc and significantly lower concentrations of copper and lead.

  11. Permeability enhancement using explosive techniques

    SciTech Connect

    Adams, T.F.; Schmidt, S.C.; Carter, W.J.

    1980-01-01

    In situ recovery methods for many of our hydrocarbon and mineral resources depend on the ability to create or enhance permeability in the resource bed to allow uniform and predictable flow. To meet this need, a new branch of geomechanics devoted to computer prediction of explosive rock breakage and permeability enhancement has developed. The computer is used to solve the nonlinear equations of compressible flow, with the explosive behavior and constitutive properties of the medium providing the initial/boundary conditions and material response. Once the resulting computational tool has been verified and calibrated with appropriate large-scale field tests, it can be used to develop and optimize commercially useful explosive techniques for in situ resource recovery.

  12. THE GRADIENT OF VASCULAR PERMEABILITY

    PubMed Central

    Smith, Frederick; Rous, Peyton

    1931-01-01

    A mounting gradient of permeability exists along the capillaries of frog muscle. In chicken muscle on the other hand none has been demonstrated; but the close-knit vascularization is arranged in duplicate in such manner that the blood runs in opposite directions through the capillaries of nearly adjacent fibres. In a flight muscle of the pigeon there exists in addition to this artifice what appears to be a special collecting system of venous capillaries. In the mammalian diaphragm indications of such a system are also to be found, and a gradient of capillary permeability like that in the other skeletal muscles is probably present. These vascular conditions are briefly considered in terms of function. PMID:19869836

  13. STUDIES IN CEREBRAL METABOLISM

    PubMed Central

    Gordan, Gilbert S.; Adams, John E.; Bentinck, Richard C.; Eisenberg, Eugene; Harper, Harold; Hobson, Quentin J. G.

    1953-01-01

    In numerous clinical observations, it has been noted that steroid hormones have effects upon the central nervous system. Earlier interpretations of this relationship were largely speculative until newer methods permitted quantitation of actions of hormones and hormonal deficiencies on cerebral metabolism. The present studies indicate that certain steroids which affect behavior also influence cerebral metabolism. PMID:13019600

  14. Reversible cerebral vasoconstriction syndrome.

    PubMed

    Lee, R; Ramadan, H; Bamford, J

    2013-01-01

    Reversible cerebral vasoconstriction syndrome (RCVS) is an underdiagnosed condition which usually presents as severe headache with or without neurological deficit. We report the case of a 55-year-old woman who presented with headache and multifocal intracerebral haemorrhage. We review the literature regarding the presentation, pathophysiology and management of RCVS and discuss how to differentiate it from cerebral vasculitis.

  15. Cerebral Palsy (CP) Quiz

    MedlinePlus

    ... SSI file Error processing SSI file Pop Quiz: Cerebral Palsy Language: English Español (Spanish) Recommend on Facebook Tweet ... Sandy is the parent of a child with cerebral palsy and the Board President of Gio’s Garden , a ...

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

    EPA Science Inventory

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

  17. Generating enhanced site topography data to improve permeable pavement performance assessment methods - presentation

    EPA Science Inventory

    Permeable pavement surfaces are infiltration based stormwater control measures (SCM) commonly applied in parking lots to decrease impervious area and reduce runoff volume. Many are not optimally designed however, as little attention is given to draining a large enough contributin...

  18. Generating enhanced site topography data to improve permeable pavement performance assessment methods - presentation

    EPA Science Inventory

    Permeable pavement surfaces are infiltration based stormwater control measures (SCM) commonly applied in parking lots to decrease impervious area and reduce runoff volume. Many are not optimally designed however, as little attention is given to draining a large enough contributin...

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

    EPA Science Inventory

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

  20. Osmotic flow through fully permeable nanochannels.

    PubMed

    Lee, C; Cottin-Bizonne, C; Biance, A-L; Joseph, P; Bocquet, L; Ybert, C

    2014-06-20

    Osmosis across membranes is intrinsically associated with the concept of semipermeability. Here, however, we demonstrate that osmotic flow can be generated by solute gradients across nonselective, fully permeable nanochannels. Using a fluorescence imaging technique, we are able to measure the water flow rate inside single nanochannels to an unprecedented sensitivity of femtoliters per minute flow rates. Our results indicate the onset of a convective liquid motion under salinity gradients, from the higher to lower electrolyte concentration, which is attributed to diffusio-osmotic transport. To our knowledge, this is the first experimental evidence and quantitative investigation of this subtle interfacially driven transport, which need to be accounted for in nanoscale dynamics. Finally, diffusio-osmotic transport under a neutral polymer gradient is also demonstrated. The experiments highlight the entropic depletion of polymers that occurs at the nanochannel surface, resulting in convective flow in the opposite direction to that seen for electrolytes.

  1. Osmotic Flow through Fully Permeable Nanochannels

    NASA Astrophysics Data System (ADS)

    Lee, C.; Cottin-Bizonne, C.; Biance, A.-L.; Joseph, P.; Bocquet, L.; Ybert, C.

    2014-06-01

    Osmosis across membranes is intrinsically associated with the concept of semipermeability. Here, however, we demonstrate that osmotic flow can be generated by solute gradients across nonselective, fully permeable nanochannels. Using a fluorescence imaging technique, we are able to measure the water flow rate inside single nanochannels to an unprecedented sensitivity of femtoliters per minute flow rates. Our results indicate the onset of a convective liquid motion under salinity gradients, from the higher to lower electrolyte concentration, which is attributed to diffusio-osmotic transport. To our knowledge, this is the first experimental evidence and quantitative investigation of this subtle interfacially driven transport, which need to be accounted for in nanoscale dynamics. Finally, diffusio-osmotic transport under a neutral polymer gradient is also demonstrated. The experiments highlight the entropic depletion of polymers that occurs at the nanochannel surface, resulting in convective flow in the opposite direction to that seen for electrolytes.

  2. Composite binders for concrete with reduced permeability

    NASA Astrophysics Data System (ADS)

    Fediuk, R.; Yushin, A.

    2016-02-01

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

  3. Permeability of dentin to adhesive agents.

    PubMed

    Pashley, D H; Ciucchi, B; Sano, H; Horner, J A

    1993-09-01

    The permeability of dentin to adhesive agents is of crucial importance in obtaining good dentinal bonding. In those systems that remove the smear layer, the opportunity exists for resin to infiltrate both tubules and intertubular dentin. Resin penetration into tubules can effectively seal the tubules and can contribute to bond strength if the resin bonds to the tubule wall. Resin infiltration into intertubular dentin can only occur if the mineral phase of dentin is removed by acidic conditioners or chelators. This is more easily accomplished in fractured dentin than in smear layer-covered dentin because of the residual collagen debris that remains on the surface following acid etching of smear layers. The channels for resin infiltration are the perifibrillar spaces created around the collagen fibers of dentin following removal of apatite mineral by acids. The diffusion of adhesive resins through these narrow, tortuous, long channels in 1 to 2 minutes offers a number of challenges that require further research.

  4. Evaluation of macroscopic porosity-permeability relationships in heterogeneous mineral dissolution and precipitation scenarios

    NASA Astrophysics Data System (ADS)

    Beckingham, L. E.

    2016-12-01

    Mineral dissolution and precipitation reactions, such as those resulting from CO2 injection in saline aquifers, can impact flow and transport in porous media and alter porosity and permeability. While porosity, in general, increases with mineral dissolution and decreases with precipitation, permeability alterations are complex and predicative capabilities remain limited. The locations of geochemical reactions in individual pores and throats and in the greater pore network control permeability evolution. Experimental studies have observed geochemical reactions to occur uniformly or non-uniformly, controlled, for example, by pore size, PeDa, or mineral distribution. For a given change in porosity, this may result in a wide range of permeability alterations. Macroscopic relationships that predict permeability evolutions resulting from these pore-scale reactions are needed for reactive transport simulations at the core-to-field scale. Currently, empirical relationships such as the Kozney-Carman equation are widely used to predict permeability evolution. These relationships, however, are unable to predict permeability alterations resulting from non-uniform pore network structure modifications. This work will use pore network models to investigate variations in sandstone permeability resulting from a range of uniform and heterogeneous dissolution and precipitation patterns and extents and evaluate the validity of existing porosity-permeability relationships under these scenarios. This will include mineral dissolution and precipitation occurring uniformly in pores and throats in addition to pore and pore-throat size, mineral surface, and preferential flow path dependent reactions.

  5. A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

    NASA Astrophysics Data System (ADS)

    Achtziger-Zupančič, P.; Loew, S.; Mariéthoz, G.

    2017-05-01

    A comprehensive worldwide permeability data set has been compiled consisting of 29,000 in situ permeabilities from 221 publications and reports and delineating the permeability distribution in crystalline rocks into depths of 2000 meters below ground surface (mbgs). We analyze the influence of technical factors (measurement method, scale effects, preferential sampling, and hydraulic anisotropy) and geological factors (lithology, current stress regime, current seismotectonic activity, and long-term tectonogeological history) on the permeability distribution with depth, by using regression analysis and k-means clustering. The influence of preferential sampling and hydraulic anisotropy are negligible. A scale dependency is observed based on calculated rock test volumes equaling 0.6 orders of magnitude of permeability change per order of magnitude of rock volume tested. Based on the entire data set, permeability decreases as log(k) = -1.5 × log(z) - 16.3 with permeability k (m2) and positively increasing depth z (km), and depth is the main factor driving the permeability distribution. The permeability variance is about 2 orders of magnitude at all depths, presumably representing permeability variations around brittle fault zones. Permeability and specific yield/storage exhibit similar depth trends. While in the upper 200 mbgs fracture flow varies between confined and unconfined, we observe confined fracture and matrix flow below about 600 mbgs depth. The most important geological factors are current seismotectonic activity (determined by peak ground acceleration) and long-term tectonogeological history (determined by geological province). The impact of lithology is less important. Based on the regression coefficients derived for all the geological key factors, permeability ranges of crystalline rocks at site scale can be predicted. First tests with independent data sets are promising.

  6. Permeability Evolution With Shearing of Simulated Faults in Unconventional Shale Reservoirs

    NASA Astrophysics Data System (ADS)

    Wu, W.; Gensterblum, Y.; Reece, J. S.; Zoback, M. D.

    2016-12-01

    Horizontal drilling and multi-stage hydraulic fracturing can lead to fault reactivation, a process thought to influence production from extremely low-permeability unconventional reservoir. A fundamental understanding of permeability changes with shear could be helpful for optimizing reservoir stimulation strategies. We examined the effects of confining pressure and frictional sliding on fault permeability in Eagle Ford shale samples. We performed shear-flow experiments in a triaxial apparatus on four shale samples: (1) clay-rich sample with sawcut fault, (2) calcite-rich sample with sawcut fault, (3) clay-rich sample with natural fault, and (4) calcite-rich sample with natural fault. We used pressure pulse-decay and steady-state flow techniques to measure fault permeability. Initial pore and confining pressures are set to 2.5 MPa and 5.0 MPa, respectively. To investigate the influence of confining pressure on fault permeability, we incrementally raised and lowered the confining pressure and measure permeability at different effective stresses. To examine the effect of frictional sliding on fault permeability, we slide the samples four times at a constant shear displacement rate of 0.043 mm/min for 10 minutes each and measure fault permeability before and after frictional sliding. We used a 3D Laser Scanner to image fault surface topography before and after the experiment. Our results show that frictional sliding can enhance fault permeability at low confining pressures (e.g., ≥5.0 MPa) and reduce fault permeability at high confining pressures (e.g., ≥7.5 MPa). The permeability of sawcut faults almost fully recovers when confining pressure returns to the initial value, and increases with sliding due to asperity damage and subsequent dilation at low confining pressures. In contrast, the permeability of natural faults does not fully recover. It initially increases with sliding, but then decreases with further sliding most likely due to fault gouge blocking fluid

  7. Urban evaporation rates for water-permeable pavements.

    PubMed

    Starke, P; Göbel, P; Coldewey, W G

    2010-01-01

    In urban areas the natural water balance is disturbed. Infiltration and evaporation are reduced, resulting in a high surface runoff and a typical city climate, which can lead to floods and damages. Water-permeable pavements have a high infiltration rate that reduces surface runoff by increasing the groundwater recharge. The high water retention capacity of the street body of up to 51 l/m(2) and its connection via pores to the surface lead to higher evaporation rates than impermeable surfaces. A comparison of these two kinds of pavements shows a 16% increase in evaporation levels of water-permeable pavements. Furthermore, the evaporation from impermeable pavements is linked directly to rain events due to fast-drying surfaces. Water-permeable pavements show a more evenly distributed evaporation after a rain event. Cooling effects by evaporative heat loss can improve the city climate even several days after rain events. On a large scale use, uncomfortable weather like sultriness or dry heat can be prevented and the urban water balance can be attenuated towards the natural.

  8. Soil permeability profiling using multiple geophysical data

    NASA Astrophysics Data System (ADS)

    Takahashi, Toru

    2014-05-01

    We propose a new method to estimate permeability of soils with multiple geophysical data based on rock physics. The method uses the unconsolidated sand model in rock physics to identify the soil type with seismic velocity and resistivity. The grain size representing each soil type thus derived and porosity estimated from resistivity by the modified Archie's law are input to the Kozeny-Carman equation for estimating permeability of the soil. The proposed method is applied to S-wave velocity and resistivity profiles obtained in well logging in saturated diluvial soils and acquired on an earthen levee to estimate soil permeability profiles. Comparison of estimated permeability with actual measurements by the in-situ permeability tests and laboratory tests shows that permeability can be estimated in accuracy less than one order of magnitude. This result indicates that the proposed method is promising for permeability profiling of soils using geophysical data.

  9. Enhancement and inhibition effects on the corneal permeability of timolol maleate: Polymers, cyclodextrins and chelating agents.

    PubMed

    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.

  10. Measurements of turbulent flow overlying impermeable and permeable walls

    NASA Astrophysics Data System (ADS)

    Kim, Taehoon; Blois, Gianluca; Best, James; Christensen, Kenneth

    2016-11-01

    There exist an array of natural and industrial flow systems wherein the flow is bounded by a surface that is both permeable and rough (e.g. river beds, bed reactors). In such scenarios, the wall boundary condition is complex as it involves both slip and penetration which together significantly modify the statistical and structural modifications the overlying flow owing to momentum exchange across the wall. The current investigation explores the individual roles of topography and permeability in such flows by systematically decoupling one from the other with a number of wall models having the same porous structure (i.e. cubically arranged spheres; two and five layers, respectively, to highlight the effect of turbulence penetration depth) but with different surface topography (smooth versus cubically arranged hemispheres). High resolution particle-image velocimetry measurements were conducted in the streamwise-wall-normal (x - y) plane and refractive-index matching was employed to optically access the flow within the permeable wall. First- and second-order velocity statistics are used to assess the flow modifications associated with the different wall models and thus ascertain the individual impacts of permeability and topography. NSF.

  11. Droplet spreading and absorption on rough, permeable substrates

    NASA Astrophysics Data System (ADS)

    Espin, Leonardo; Kumar, Satish

    2015-11-01

    Wetting of permeable substrates by liquids is an important phenomenon in many natural and industrial processes. Substrate heterogeneities may significantly alter liquid spreading and interface shapes, which in turn may alter liquid imbibition. A new lubrication-theory-based model for droplet spreading on permeable substrates that incorporates surface roughness is developed in this work. The substrate is assumed to be saturated with liquid, and the contact-line region is described by including a precursor film and disjoining pressure. A novel boundary condition for liquid imbibition is applied that eliminates the need for a droplet-thickness-dependent substrate permeability that has been employed in previous models. A nonlinear evolution equation describing droplet height as a function of time and the radial coordinate is derived and then numerically solved to characterize the influence of substrate permeability and roughness on axisymmetric droplet spreading. Because it incorporates surface roughness, the new model is able to describe the contact-line pinning that has been observed in experiments but not captured by previous models.

  12. Permeability prediction of high Spor samples from spectral induced polarization (SIP): limitations of existing models

    NASA Astrophysics Data System (ADS)

    Robinson, J.; Slater, L. D.; Keating, K.; Parker, B. L.; Day-Lewis, F. D.; Robinson, T.

    2016-12-01

    Over the past two decades, mechanistic and empirical models have been proposed to predict permeability from spectral induced polarization (SIP) data. Given the sensitivity to mineral surfaces and pore spaces, SIP models that use length scales related to the pore volume normalized surface area (Spor) or pore diameter have been proposed. We performed extensive petrophysical measurements on two sandstone formations with contrasting lithology to investigate the sensitivity of SIP measurements to (1) Spor, and (2) the diameter at which pores are considered interconnected (Λ) as defined by mercury injection porosimetry. We then compared these hydraulic length scales to SIP measures of length scales associated with interfacial polarization. Imaginary conductivity, mean relaxation time () and normalized chargeability from a Debye decomposition were correlated with Spor and Λ. Application of these SIP proxies of hydraulic length scale in recently proposed SIP permeability models revealed that permeability of high Spor samples over-predict measured values by an order of magnitude. The high Spor samples were also outliers when permeability was predicted based on a recent model formulated in terms of the SIP relaxation time, electrical formation factor and a single, fixed diffusion coefficient. Improved permeability prediction from this model was explored by determining apparent diffusion coefficients based on formation type, Spor and imaginary conductivity. A Spor -specific diffusion coefficient improved the permeability predictions, although a similar improvement was not obtained using imaginary conductivity. Our findings suggest that existing SIP models for permeability prediction underperform in the case of low permeability, high Spor materials.

  13. Permeability evolution of shale during spontaneous imbibition

    DOE PAGES

    Chakraborty, N.; Karpyn, Z. T.; Liu, S.; ...

    2017-01-05

    Shales have small pore and throat sizes ranging from nano to micron scales, low porosity and limited permeability. The poor permeability and complex pore connectivity of shales pose technical challenges to (a) understanding flow and transport mechanisms in such systems and, (b) in predicting permeability changes under dynamic saturation conditions. This paper presents quantitative experimental evidence of the migration of water through a generic shale core plug using micro CT imaging. In addition, in-situ measurements of gas permeability were performed during counter-current spontaneous imbibition of water in nano-darcy permeability Marcellus and Haynesville core plugs. It was seen that water blocksmore » severely reduced the effective permeability of the core plugs, leading to losses of up to 99.5% of the initial permeability in experiments lasting 30 days. There was also evidence of clay swelling which further hindered gas flow. When results from this study were compared with similar counter-current gas permeability experiments reported in the literature, the initial (base) permeability of the rock was found to be a key factor in determining the time evolution of effective gas permeability during spontaneous imbibition. With time, a recovery of effective permeability was seen in the higher permeability rocks, while becoming progressively detrimental and irreversible in tighter rocks. Finally, these results suggest that matrix permeability of ultra-tight rocks is susceptible to water damage following hydraulic fracturing stimulation and, while shut-in/soaking time helps clearing-up fractures from resident fluid, its effect on the adjacent matrix permeability could be detrimental.« less

  14. Quantification of transient increase of the blood-brain barrier permeability to macromolecules by optimized focused ultrasound combined with microbubbles.

    PubMed

    Shi, Lingyan; Palacio-Mancheno, Paolo; Badami, Joseph; Shin, Da Wi; Zeng, Min; Cardoso, Luis; Tu, Raymond; Fu, Bingmei M

    2014-01-01

    Radioimmunotherapy using a radiolabeled monoclonal antibody that targets tumor cells has been shown to be efficient for the treatment of many malignant cancers, with reduced side effects. However, the blood-brain barrier (BBB) inhibits the transport of intravenous antibodies to tumors in the brain. Recent studies have demonstrated that focused ultrasound (FUS) combined with microbubbles (MBs) is a promising method to transiently disrupt the BBB for the drug delivery to the central nervous system. To find the optimal FUS and MBs that can induce reversible increase in the BBB permeability, we employed minimally invasive multiphoton microscopy to quantify the BBB permeability to dextran-155 kDa with similar molecular weight to an antibody by applying different doses of FUS in the presence of MBs with an optimal size and concentration. The cerebral microcirculation was observed through a section of frontoparietal bone thinned with a micro-grinder. About 5 minutes after applying the FUS on the thinned skull in the presence of MBs for 1 minute, TRITC (tetramethylrhodamine isothiocyanate)-dextran-155 kDa in 1% bovine serum albumin in mammalian Ringer's solution was injected into the cerebral circulation via the ipsilateral carotid artery by a syringe pump. Simultaneously, the temporal images were collected from the brain parenchyma ~100-200 μm below the pia mater. Permeability was determined from the rate of tissue solute accumulation around individual microvessels. After several trials, we found the optimal dose of FUS. At the optimal dose, permeability increased by ~14-fold after 5 minutes post-FUS, and permeability returned to the control level after 25 minutes. FUS without MBs or MBs injected without FUS did not change the permeability. Our method provides an accurate in vivo assessment for the transient BBB permeability change under the treatment of FUS. The optimal FUS dose found for the reversible BBB permeability increase without BBB disruption is reliable and

  15. Permeability and stress-jump effects on magnetic drug targeting in a permeable microvessel using Darcy model

    NASA Astrophysics Data System (ADS)

    Shaw, S.; Sutradhar, A.; Murthy, PVSN

    2017-05-01

    In the present paper, we investigated the influence of permeability of the carrier particle and stress jump condition on the porous spherical surface in magnetic drug targeting through a permeable microvessel. The nature of blood is defined by non-Newtonian Casson fluid in the core region of the microvessel and Newtonian fluid in the peripheral region which is located near the surface of the wall of the microvessel. The magnetic particles are considered as spherical and in nanosize, embedded in the carrier particle along with drug particles. A magnet is placed near the tumor position to generate a magnetic field. The relative motion of the carrier particle is the resultant of the fluidic force, magnetic force and Saffman drag force which are calculated for the spherical carrier particle. Trajectories of the carrier particle along the radial and axial direction are calculated. Effect of different parameters such as stress-jump constant, permeability of the carrier particle, pressure gradient, yield stress, Saffman force, volume fraction of the embedded magnetic nanoparticles, permeability of the microvessel wall, and the radius of the carrier particle on the trajectory of the carrier particle are discussed and displayed graphically.

  16. Metalloendopeptidases EC 3.4.24.15/16 regulate bradykinin activity in the cerebral microvasculature.

    PubMed

    Norman, M Ursula; Lew, Rebecca A; Smith, A Ian; Hickey, Michael J

    2003-06-01

    Bradykinin is a vasoactive peptide that has been shown to increase the permeability of the cerebral microvasculature to blood-borne macromolecules. The two zinc metalloendopeptidases EC (EP 24.15) and EC (EP 24.16) degrade bradykinin in vitro and are highly expressed in the brain. However, the role that these enzymes play in bradykinin metabolism in vivo remains unclear. In the present study, we investigated the role of EP 24.15 and EP 24.16 in the regulation of bradykinin-induced alterations in microvascular permeability. Permeability of the cerebral microvasculature was assessed in anesthetized Sprague-Dawley rats by measuring the clearance of 70-kDa FITC dextran from the brain. Inhibition of EP 24.15 and EP 24.16 by the specific inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA-2) resulted in the potentiation of bradykinin-induced increases in cerebral microvessel permeability. The level of potentiation was comparable to that achieved by the inhibition of angiotensin-converting enzyme. These findings provide the first evidence of an in vivo role for EP 24.15/EP 24.16 in brain function, specifically in regulating alterations in microvessel permeability induced by exogenous bradykinin.

  17. The Membrane Permeability Outcome study.

    PubMed

    Locatelli, Francesco; Cavalli, Andrea; Manzoni, Celestina; Pontoriero, Giuseppe

    2011-01-01

    Many observational studies have consistently shown that high-flux hemodialysis has positive effects on the survival and morbidity of uremic patients when compared with low-flux hemodialysis. However, the HEMO study, a randomized trial designed to evaluate the effect of membrane permeability on patient survival, showed only an 8% non-statistically significant reduction of mortality, albeit a secondary analysis suggested an advantage for high-flux membranes in certain patient subgroups. The prospective, randomized Membrane Permeability Outcome (MPO) study investigated the impact of membrane permeability on survival in incident hemodialysis patients who had low albumin (≤4 g/dl) and normal albumin ( >4 g/dl) as separate randomization groups. Patients with serum albumin ≤4 g/dl had significantly better survival rates in the high-flux group compared with the low-flux group (p = 0.032). Moreover, a post-hoc secondary analysis showed that high-flux membranes may significantly improve survival in diabetic patients. No difference was found in patients with normal albumin levels. Considering the increasing number of dialysis patients with low serum albumin levels and with diabetes, the relevance of the MPO study led to the publication of a position statement by the European Renal Best Practice Advisory Board. This board strongly recommended that high-flux hemodialysis should be used for high-risk patients and, with a lower degree of evidence, even also for low-risk subjects due to the substantial reduction in β(2)-microglobulin levels observed in the high-flux group.

  18. Permeability of normal versus carious dentin.

    PubMed

    Pashley, E L; Talman, R; Horner, J A; Pashley, D H

    1991-10-01

    Although a number of reports have been published demonstrating that carious dentin is less permeable than normal dentin, these reports have been qualitative rather than quantitative. The purpose of this in vitro study was to apply a quantitative technique to the study of the permeability of carious human teeth before and after excavation, before and after removal of the smear layer and before and after preparation of a control cavity of similar size and depth in normal dentin subjected to the same measurements, for comparative purposes. Dentin permeability was measured as a hydraulic conductance. The permeability values measured at each step in the protocol were expressed as a percent of the maximum permeability of both cavities, permitting each tooth the serve as its own control. Carious lesions exhibited a slight degree of permeability (2.3 +/- 0.6% of controls) which remained unchanged after excavation of the lesions. Removal of the smear layer in the excavated carious lesions increased the permeability significantly to 6.9 +/- 3.2%. Preparation of a control cavity of the same area and depth increased the permeability slightly. Removal of its smear layer increased the permeability of the dentin 91%. These results confirm previous qualitative studies that carious dentin, even after excavation and removal of the smear layer has a very low permeability.

  19. Comparison of three techniques to measure unsaturated-zone air permeability at Picatinny Arsenal, NJ

    NASA Astrophysics Data System (ADS)

    Olson, Mira Stone; Tillman, Fred D.; Choi, Jee-Won; Smith, James A.

    2001-12-01

    The purpose of this study is to compare three techniques to measure the air permeability of the unsaturated zone at Picatinny Arsenal, NJ and to examine the effects of moisture content and soil heterogeneity on air permeability. Air permeability was measured in three ways: laboratory experiments on intact soil cores, field-scale air pump tests and calibration of air permeability to air pressures measured in the field under natural air pressure conditions using a numerical airflow model. The results obtained from these three methods were compared and found to be similar. Laboratory experiments performed on intact cores measured air permeability values on the order of 10 -14 to 10 -9 m 2. Low-permeability cores were found between land surface and a depth of 0.6 m. The soil core data were divided into two layers with composite vertical permeability values of 1.3×10 -13 m 2 from land surface to a 0.6-m depth and 3.8×10 -10 m 2 for the lower layer. Analyses of the field-scale pump tests were performed for two scenarios: one in which the entire unsaturated zone was open to the atmosphere and one assuming a cap of low permeability extending 0.6 m below land surface. The vertical air permeability values obtained for the open scenario ranged from 1.2×10 -9 to 1.5×10 -9 m 2, and ranged from 3.6×10 -9 to 6.8×10 -9 m 2 in the lower layer, assuming an upper cap permeability of 6.0×10 -14 m 2. The results from the open scenario are much higher than expected and the possible reasons for this ambiguity are discussed. The results from the capped scenario matched closely with those from the other methods and indicated that it is important to have background information on the study site to correctly analyze the pump test data. The optimized fit of the natural subsurface air pressure was achieved with an intrinsic permeability value of 3.3×10 -14 m 2. When the data were refitted to the model assuming two distinct layers of the unsaturated zone, the optimized fit was achieved

  20. Heterogeneity, permeability patterns, and permeability upscaling: Physical characterization of a block of Massillon sandstone exhibiting nested scales of heterogeneity

    SciTech Connect

    TIDWELL,VINCENT C.; WILSON,JOHN L.

    2000-04-20

    Over 75,000 permeability measurements were collected from a meter-scale block of Massillon sandstone, characterized by conspicuous cross bedding that forms two distinct nested-scales of heterogeneity. With the aid of a gas minipermeameter, spatially exhaustive fields of permeability data were acquired at each of five different sample supports (i.e. sample volumes) from each block face. These data provide a unique opportunity to physically investigate the relationship between the multi-scale cross-stratified attributes of the sandstone and the corresponding statistical characteristics of the permeability. These data also provide quantitative physical information concerning the permeability upscaling of a complex heterogeneous medium. Here, a portion of the data taken from a single block face cut normal to stratification is analyzed. Results indicate a strong relationship between the calculated summary statistics and the cross-stratified structural features visible evident in the sandstone sample. Specifically, the permeability fields and semivariograms are characterized by two nested scales of heterogeneity, including a large-scale structure defined by the cross-stratified sets (delineated by distinct bounding surfaces) and a small-scale structure defined by the low-angle cross-stratification within each set. The permeability data also provide clear evidence of upscaling. That is, each calculated summary statistic exhibits distinct and consistent trends with increasing sample support. Among these trends are an increasing mean, decreasing variance, and an increasing semivariogram range. Results also clearly indicate that the different scales of heterogeneity upscale differently, with the small-scale structure being preferentially filtered from the data while the large-scale structure is preserved. Finally, the statistical and upscaling characteristics of individual cross-stratified sets were found to be very similar owing to their shared depositional environment

  1. Plasma from patients with HELLP syndrome increases blood-brain barrier permeability.

    PubMed

    Wallace, Kedra; Tremble, Sarah M; Owens, Michelle Y; Morris, Rachael; Cipolla, Marilyn J

    2015-03-01

    Circulating inflammatory factors and endothelial dysfunction have been proposed to contribute to the pathophysiology of hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. To date, the occurrence of neurological complications in these women has been reported, but few studies have examined whether impairment in blood-brain barrier (BBB) permeability or cerebrovascular reactivity is present in women having HELLP syndrome. We hypothesized that plasma from women with HELLP syndrome causes increased BBB permeability and cerebrovascular dysfunction. Posterior cerebral arteries from female nonpregnant rats were perfused with 20% serum from women with normal pregnancies (n = 5) or women with HELLP syndrome (n = 5), and BBB permeability and vascular reactivity were compared. Plasma from women with HELLP syndrome increased BBB permeability while not changing myogenic tone and reactivity to pressure. Addition of the nitric oxide (NO) synthase inhibitor N(ω)-nitro-L-arginine methyl ester caused constriction of arteries that was not different with the different plasmas nor was dilation to the NO donor sodium nitroprusside different between the 2 groups. However, dilation to the small- and intermediate-conductance, calcium-activated potassium channel activator NS309 was decreased in vessels exposed to HELLP plasma. Thus, increased BBB permeability in response to HELLP plasma was associated with selective endothelial dysfunction.

  2. Stability and permeability of amphiphile bilayers.

    PubMed

    Exerowa, D; Kashchiev, D; Platikanov, D

    1992-05-30

    In this review the rupture and permeability of bilayers are considered on the basis of a mechanism of the formation of microscopic holes as fluctuations in the bilayers. The hole formation is treated as a nucleation process of a new phase in a two-dimensional system with short-range intermolecular forces. Free rupture and deliberate rupture (by alpha-particles) of foam bilayers (Newtonian black films) are discussed. A comparison is made between the rupture of foam and emulsion bilayers. Experimental methods for obtaining foam and emulsion bilayers from thin liquid films are considered. Methods for investigating the stability and permeability of foam bilayers, which are based on a microscopic model allowing the use of amphiphile solutions with very low concentrations, are described. Experimental dependences of the lifetime of bilayers, the probability of observing the foam bilayer in a foam film, the gas permeability of bilayers, etc. on the concentration of amphiphile molecules in the solution are reported. The influence of temperature and external impact (e.g. alpha-particle irradiation) have also been experimentally studied. A good agreement between theory and experiment is established, allowing determination of several characteristics of foam and emulsion bilayers obtained from ionics or non-ionics: the specific edge energy of bilayer holes, equilibrium surfactant concentration below which the bilayer is thermodynamically metastable, work for the formation of a nucleus hole, number of vacancies in the nucleus hole, coefficient of gas diffusion through the bilayer, etc. On the basis of the effect of temperature on the rupture of foam bilayers the binding energy of a surfactant molecule in the bilayer is determined. The adsorption isotherm of surfactant vacancies in the foam bilayer is obtained which shows a first-order phase transition. Some applications to scientific, technological and medical problems are considered. The foam bilayer is used as a model for

  3. Intravesical oxybutynin affects bladder permeability.

    PubMed

    Ersay, A; Demirtas, O C

    2001-01-01

    To investigate the effects of intravesical application of oxybutynin chloride on bladder permeability we designed an animal model. Female Guinea pigs were given 3 different test solutions: phosphate buffered saline (PBS), 50% acetone and 1.27 x 10(-2) M oxybutynin chloride solution. Then 99mTc-DTPA 45 microCi in 2 ml normal saline was instilled into the bladder lumen in each animals and allowed to dwell for 30 minutes. At the end of exposure time, the net count data in each 1 ml serum sample were corrected for radioactive decay and converted to the total percentage of administered dose. 99mTc-DTPA absorption percentages of both acetone and oxybutynin groups were significantly higher than that of PBS group (mean 3.2 +/- 2.9% p < 0.001). Intravesical oxybutynin application increases bladder permeability 5 times compared with PBS administration. This observation can also explain how rapid absorption of oxybutynin through the bladder into the systemic circulation occurs.

  4. Steam-water relative permeability

    SciTech Connect

    Ambusso, W.; Satik, C.; Home, R.N.

    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.

  5. Brain permeability of inhaled corticosteroids.

    PubMed

    Arya, Vikram; Issar, Manish; Wang, Yaning; Talton, James D; Hochhaus, Guenther

    2005-09-01

    The aim of this study was to evaluate if the permeability of inhaled corticosteroids entering the brain is reduced and if P-glycoprotein (P-gp) transporters are involved. Currently employed inhaled corticosteroids were given intravenously and intratracheally to rats at a dose of 100 microg kg-1. An ex-vivo receptor binding assay was used to monitor over 12 h the glucocorticoid receptor occupancy in the brain and a systemic reference organ (kidney). The involvement of P-gp in the brain permeability of triamcinolone acetonide was assessed in wild-type mice and mdr1a(-/-) knockout mice (mice lacking the gene for expressing P-gp). After both forms of administration, the average brain receptor occupancies were 20-56% of those of the reference organ, with the more lipophilic drugs showing a more pronounced receptor occupation. While the receptor occupancies in the liver of wild-type and mdr1a(-/-) mice were similar after administration of triamcinolone acetonide, brain receptor occupancies in mdr1a(-/-) mice were significantly greater (mdr1a(-/-): 47.6%, 40.2-55.0%, n=14; 2; wild-type: 11.5+/-33.0%, n=14; 3). Penetration into the brain for inhaled corticosteroids (especially those of lower lipophilicity) is reduced. Experiments in mdr1a(-/-) mice confirmed the involvement of P-gp transporters. Further studies are needed to assess whether potential drug interactions at the transporter level are of pharmacological significance.

  6. Structure of fault zones in sandstone and its effect on permeability

    SciTech Connect

    Seeburger, D.A.; Warner, J.L.; White, R.E. ); Aydin, A. )

    1991-03-01

    Faults in clean porous sandstone occur as thin, 3-D deformed zones containing crushed grains. Field observations and laboratory measurements show that fault zones have a profound effect on fluid flow. Field observations indicate that most fault zones across which there have been more than a few cm of displacement develop a slip surface that is bounded on one side by the deformed zone in which porosity, grain sizes, and the degree of sorting of the sand grains are reduced, and on the other side by nearly undeformed rock. Permeability along this slip surface could be large, as for a fracture, allowing fluid migration in all directions parallel to the slip surface. Laboratory measurements confirm that permeability in the deformed, low porosity zone is low. Fault zone permeability could thus be extremely anisotropic with low permeability on one side due to the deformed zone, and high permeability parallel to the fault on the other side related to the through-going slip surface. The slip surface may occur more often on the hanging wall side of the deformed zone providing asymmetry in permeability distribution and, thus, asymmetry in trapping and migration potential. This asymmetry could explain many oil-water-fault relations such as those reported from the Niger Delta.

  7. Tubular hydrogen permeable metal foil membrane and method of fabrication

    DOEpatents

    Paglieri, Stephen N.; Birdsell, Stephen A.; Barbero, Robert S.; Snow, Ronny C.; Smith, Frank M.

    2006-04-04

    A tubular hydrogen permeable metal membrane and fabrication process comprises obtaining a metal alloy foil having two surfaces, coating the surfaces with a metal or metal alloy catalytic layer to produce a hydrogen permeable metal membrane, sizing the membrane into a sheet with two long edges, wrapping the membrane around an elongated expandable rod with the two long edges aligned and overlapping to facilitate welding of the two together, placing the foil wrapped rod into a surrounding fixture housing with the two aligned and overlapping foil edges accessible through an elongated aperture in the surrounding fixture housing, expanding the elongated expandable rod within the surrounding fixture housing to tighten the foil about the expanded rod, welding the two long overlapping foil edges to one another generating a tubular membrane, and removing the tubular membrane from within the surrounding fixture housing and the expandable rod from with the tubular membrane.

  8. Permeability reductions induced by sorption of surfactant

    NASA Astrophysics Data System (ADS)

    Renshaw, Carl E.; Zynda, Gregory D.; Fountain, John C.

    Surfactant enhanced aquifer remediation (SEAR) is an attractive alternative to traditional pump and treat methods for remediating aquifers contaminated with nonaqueous phase liquids. However, initial studies indicate that the application of surfactant can reduce aquifer permeability by more than an order of magnitude, limiting the efficiency of SEAR. A series of column experiments using mixtures of medium sand and montmorillonite clay demonstrate that existing permeability reduction models for biofouling and deep-bed filtration poorly predict surfactant induced permeability reductions. An alternative permeability reduction model is proposed which is based on the assumption that the sorbed surfactant effectively increases the volume fraction of the clay. The model is shown to reasonably predict observed permeability reductions, particularly for clay fractions less than 20%. A numerical simulation of surfactant transport that incorporates the effective clay fraction model demonstrates that induced permeability reductions significantly influence the transport of surfactant through an aquifer.

  9. Vortex rings impinging on permeable boundaries

    NASA Astrophysics Data System (ADS)

    Mujal-Colilles, Anna; Dalziel, Stuart B.; Bateman, Allen

    2015-01-01

    Experiments with vortex rings impinging permeable and solid boundaries are presented in order to investigate the influence of permeability. Utilizing Particle Image Velocimetry, we compared the behaviour of a vortex ring impinging four different reticulated foams (with permeability k ˜ 26 - 85 × 10-8 m2) and a solid boundary. Results show how permeability affects the stretching phenomena of the vortex ring and the formation and evolution of the secondary vortex ring with opposite sign. Moreover, permeability also affects the macroscopic no-slip boundary condition found on the solid boundary, turning it into an apparent slip boundary condition for the most permeable boundary. The apparent slip-boundary condition and the flux exchange between the ambient fluid and the foam are jointly responsible for both the modified formation of the secondary vortex and changes on the vortex ring diameter increase.

  10. Clogging in permeable concrete: A review.

    PubMed

    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.

  11. Model-based Permeability Estimation of Shaly Sands Using Seismic Velocity and Resistivity Data

    NASA Astrophysics Data System (ADS)

    Takahashi, T.

    2016-12-01

    Permeability is an indispensable parameter for hydraulic characterization of soils and rocks in many applications. Permeability of soils and rocks is usually obtained with the in-situ permeability test in a borehole and/or laboratory permeability test of soil/rock core samples obtained in the borehole. Many boreholes are necessary for building a hydraulic model of a large soil/rock mass. It is, however, often difficult to drill many boreholes due to time and cost constraints. For such a case, geophysical methods can be effectively utilized for profiling permeability of a large soil/rock mass if geophysical properties such as seismic velocity and resistivity can be used for estimating permeability. We, therefore, propose an effective method for estimating permeability of shaly sands by applying a rock physics model to seismic velocity and resistivity data. Because consolidated shaly sand is a key rock for aquifers and oil/gas reservoirs, and unconsolidated shaly sand is very common soils whose hydraulic properties are often important for safety evaluation of river embankments and designing countermeasure of its liquefaction. The method first estimates the grain size distribution of the shaly sand by applying a shaly sand model to seismic velocity and resistivity data obtained with seismic and resistivity measurements. The grain size of the soil/rock thus obtained and porosity estimated from resistivity data by applying the Glover's equation are then input to the Kozeny-Carman equation for estimating permeability of the shaly sand. The proposed method is applied to P- and S-wave velocities and resistivity data measured in the laboratory, well logging and surface seismic and electric surveys for shaly sands. Comparison of estimated permeability with actual measurements reveals that permeability can be estimated in accuracy less than one order of magnitude and the method can be used for profiling permeability of a large shaly sand using geophysical data measured on it.

  12. Cerebral Cavernous Malformations (CCM)

    MedlinePlus

    ... Contact Registry Interest Form Contact Us | Login Disorder Definitions Learn More > Disorder Definitions Cerebral Cavernous Malformations (CCM) ... until it is too late to salvage vision. Routine screening is very important, even if there are ...

  13. Cerebral Aneurysms Fact Sheet

    MedlinePlus

    ... Caregiver Education » Fact Sheets Cerebral Aneurysms Fact Sheet Table of Contents (click to jump to sections) What ... Information Page NINDS Epilepsy Information Page NINDS Familial Periodic Paralyses Information Page NINDS Farber's Disease Information Page ...

  14. Acquired Cerebral Trauma: Epilogue.

    ERIC Educational Resources Information Center

    Bigler, Erin D., Ed.

    1988-01-01

    The article summarizes a series of articles concerning acquired cerebral trauma. Reviewed are technological advances, treatment, assessment, potential innovative therapies, long-term outcome, family impact of chronic brain injury, and prevention. (DB)

  15. Cerebral amyloid angiopathy

    MedlinePlus

    ... 911) if you have sudden loss of movement , sensation, vision, or speech. Alternative Names Amyloidosis - cerebral; CAA; Congophilic angiopathy Images Amyloidosis on the fingers Arteries of the brain References Kase CS, Shoamanesh A. Intracerebral hemorrhage. In: Daroff ...

  16. The hydrogen permeability of Pd{sub 4}S

    SciTech Connect

    O'Brien, Casey; Miller, James; Gellman, Andrew; Morreale, Bryan

    2011-04-01

    Hydrogen permeates rapidly through pure Pd membranes, but H{sub 2}S, a common minor component in hydrogen-containing streams, produces a Pd{sub 4}S film on the Pd surface that severely retards hydrogen permeation. Hydrogen still permeates through the bi-layered Pd{sub 4}S/Pd structure, indicating that the Pd{sub 4}S surface is active for H{sub 2} dissociation; the low hydrogen permeability of the Pd4S film is responsible for the decreased rate of hydrogen transport. In this work, the hydrogen permeability of Pd{sub 4}S was determined experimentally in the 623-773 K temperature range. Bi-layered Pd{sub 4}S/Pd foils were produced by exposing pure Pd foils to H{sub 2}S. H{sub 2} fluxes through the bi-layered Pd{sub 4}S/Pd foils were measured during exposure to both pure H{sub 2} and a 1000 ppm H{sub 2}S in H{sub 2} gas mixture. Our results show that H{sub 2}S slows hydrogen permeation through Pd mainly by producing a Pd{sub 4}S film on the Pd surface that is roughly an order-of-magnitude less permeable to hydrogen (k{sub Pd{sub 4}S} = 10{sup −7.5} exp(−0.22 eV/k{sub B}T) molH{sub 2}/m/s/Pa{sup 1/2}) than pure Pd. The presence of H{sub 2}S in the gas stream results in greater inhibition of hydrogen transport than can be explained by the very low permeability of Pd{sub 4}S. H{sub 2}S may block H2 dissociation sites at the Pd{sub 4}S surface.

  17. Percolation threshold of the permeable disks on the projective plane

    NASA Astrophysics Data System (ADS)

    Borman, V. D.; Grekhov, A. M.; Tronin, I. V.; Tronin, V. N.

    2016-09-01

    The percolation threshold and wrapping probability for the two-dimensional problem of continuum percolation on the projecive plane have been calculated by the Monte Carlo method with the Newman-Ziff algorithm for completely permeable disks. It has been shown that the percolation threshold of disks on the projective plane coincides with the percolation threshold of disks on the surfaces of a torus and Klein bottle, indicating that this threshold is topologically invariant.

  18. Iron abundance and magnetic permeability of the moon

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.; Daily, W. D.; Dyal, P.

    1974-01-01

    A set of simultaneous data from the Apollo 12 lunar surface magnetometer and the Explorer 35 Ames magnetometer are used to construct a whole-moon hysteresis curve, from which a new value of global lunar permeability is determined to be mu = 1.012 + or - 0.006. The corresponding global induced dipole moment is 2.1 x 10 to the 18th power gauss-cucm for typical inducing fields of .1000 gauss in the lunar environment. From the permeability measurement, lunar free iron abundance is determined to be 2.5 + or - 2.0 wt. %. Total iron abundance is calculated for two assumed compositional models of the lunar interior: a free iron/orthopyroxene lunar composition and a free iron/olivine composition. The overall lunar total iron abundance is determined to be 9.0 + or - 4.7 wt. %. Other lunar models with a small iron core and with a shallow iron-rich layer are discussed in light of the measured global permeability. Effects on permeability and iron content calculations due to a possible lunar ionosphere are also considered.

  19. Nanomedicine in cerebral palsy

    PubMed Central

    Balakrishnan, Bindu; Nance, Elizabeth; Johnston, Michael V; Kannan, Rangaramanujam; Kannan, Sujatha

    2013-01-01

    Cerebral palsy is a chronic childhood disorder that can have diverse etiologies. Injury to the developing brain that occurs either in utero or soon after birth can result in the motor, sensory, and cognitive deficits seen in cerebral palsy. Although the etiologies for cerebral palsy are variable, neuroinflammation plays a key role in the pathophysiology of the brain injury irrespective of the etiology. Currently, there is no effective cure for cerebral palsy. Nanomedicine offers a new frontier in the development of therapies for prevention and treatment of brain injury resulting in cerebral palsy. Nanomaterials such as dendrimers provide opportunities for the targeted delivery of multiple drugs that can mitigate several pathways involved in injury and can be delivered specifically to the cells that are responsible for neuroinflammation and injury. These materials also offer the opportunity to deliver agents that would promote repair and regeneration in the brain, resulting not only in attenuation of injury, but also enabling normal growth. In this review, the current advances in nanotechnology for treatment of brain injury are discussed with specific relevance to cerebral palsy. Future directions that would facilitate clinical translation in neonates and children are also addressed. PMID:24204146

  20. Nanomedicine in cerebral palsy.

    PubMed

    Balakrishnan, Bindu; Nance, Elizabeth; Johnston, Michael V; Kannan, Rangaramanujam; Kannan, Sujatha

    2013-01-01

    Cerebral palsy is a chronic childhood disorder that can have diverse etiologies. Injury to the developing brain that occurs either in utero or soon after birth can result in the motor, sensory, and cognitive deficits seen in cerebral palsy. Although the etiologies for cerebral palsy are variable, neuroinflammation plays a key role in the pathophysiology of the brain injury irrespective of the etiology. Currently, there is no effective cure for cerebral palsy. Nanomedicine offers a new frontier in the development of therapies for prevention and treatment of brain injury resulting in cerebral palsy. Nanomaterials such as dendrimers provide opportunities for the targeted delivery of multiple drugs that can mitigate several pathways involved in injury and can be delivered specifically to the cells that are responsible for neuroinflammation and injury. These materials also offer the opportunity to deliver agents that would promote repair and regeneration in the brain, resulting not only in attenuation of injury, but also enabling normal growth. In this review, the current advances in nanotechnology for treatment of brain injury are discussed with specific relevance to cerebral palsy. Future directions that would facilitate clinical translation in neonates and children are also addressed.

  1. Effect of oxide films on hydrogen permeability of candidate Stirling heater head tube alloys

    SciTech Connect

    Schuon, S R; Misencik, J A

    1981-01-01

    High pressure hydrogen has been selected as the working fluid for the developmental automotive Stirling engine. Containment of the working fluid during operation of the engine at high temperatures and at high hydrogen gas pressures is essential for the acceptance of the Stirling engine as an alternative to the internal combustion engine. Most commercial alloys are extremely permeable to pure hydrogen at high temperatures. A program was undertaken at NASA Lewis Research Center (LeRC) to reduce hydrogen permeability in the Stirling engine heater head tubes by doping the hydrogen working fluid with CO or CO/sub 2/. Small additions of these gases were shown to form an oxide on the inside tube wall and thus reduce hydrogen permeability. A study of the effects of dopant concentration, alloy composition, and effects of surface oxides on hydrogen permeability in candidate heater head tube alloys is summarized. Results showed that hydrogen permeability was similar for iron-base alloys (N-155, A286, IN800, 19-9DL, and Nitronic 40), cobalt-base alloys (HS-188) and nickel-base alloys (IN718). In general, the permeability of the alloys decreased with increasing concentration of CO or CO/sub 2/ dopant, with increasing oxide thickness, and decreasing oxide porosity. At high levels of dopants, highly permeable liquid oxides formed on those alloys with greater than 50% Fe content. Furthermore, highly reactive minor alloying elements (Ti, Al, Nb, and La) had a strong influence on reducing hydrogen permeability.

  2. Improved permeability of acyclovir: optimization of mucoadhesive liposomes using the phospholipid vesicle-based permeation assay.

    PubMed

    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.

  3. Schisandrin B enhances cerebral mitochondrial antioxidant status and structural integrity, and protects against cerebral ischemia/reperfusion injury in rats.

    PubMed

    Chen, Na; Chiu, Po Yee; Ko, Kam Ming

    2008-07-01

    Schisandrin B (Sch B), a dibenzocyclooctadiene derivative isolated from the fruit of Schisandra chinensis, has been shown to enhance mitochondrial antioxidant status in liver, heart and brain tissues in rodents. Whether or not long-term Sch B treatment can protect against oxidative stress-induced cerebral damage remains unclear. In the present study, the effect of long-term Sch B treatment (1-30 mg/kg/dx15) on cerebral ischemia/reperfusion (I/R) injury was examined in rats. Sch B treatment protected against I/R-induced cerebral damage, as evidenced by the significant increase in the percentage of 2,3,5-triphenyl tetrazolium chloride (TTC)-stained tissues in representative brain slices, when compared with the Sch B-untreated and I/R control. The cerebroprotection was associated with an enhancement in cerebral mitochondrial antioxidant status, as assessed by the level/activity of reduced glutathione, alpha-tocopherol and Mn-superoxide dismutase, as well as the improvement/preservation of mitochondrial structural integrity, as assessed by the extents of malondialdehyde production, Ca(2+) loading and cytochrome c release, as well as the sensitivity to Ca(2+)-induced permeability transition, in control and I/R-challenged rats. In conclusion, long-term Sch B treatment could enhance cerebral mitochondrial antioxidant status as well as improve mitochondrial structural integrity, thereby protecting against I/R injury.

  4. Drainage hydraulics of permeable friction courses

    NASA Astrophysics Data System (ADS)

    Charbeneau, Randall J.; Barrett, Michael E.

    2008-04-01

    This paper describes solutions to the hydraulic equations that govern flow in permeable friction courses (PFC). PFC is a layer of porous asphalt approximately 50 mm thick that is placed as an overlay on top of an existing conventional concrete or asphalt road surface to help control splash and hydroplaning, reduce noise, and enhance quality of storm water runoff. The primary objective of this manuscript is to present an analytical system of equations that can be used in design and analysis of PFC systems. The primary assumptions used in this analysis are that the flow can be modeled as one-dimensional, steady state Darcy-type flow and that slopes are sufficiently small so that the Dupuit-Forchheimer assumptions apply. Solutions are derived for cases where storm water drainage is confined to the PFC bed and for conditions where the PFC drainage capacity is exceeded and ponded sheet flow occurs across the pavement surface. The mathematical solutions provide the drainage characteristics (depth and residence time) as a function of rainfall intensity, PFC hydraulic conductivity, pavement slope, and maximum drainage path length.

  5. [Nontraumatic arterial dissection of the anterior cerebral artery with simultaneous cerebral infarction and subarachnoid hemorrhage: a case report].

    PubMed

    Kimura, Shigeyoshi; Igarashi, Takahiro; Kotani, Akio; Katayama, Yoichi

    2010-03-01

    We encountered a case of nontraumatic arterial dissection of the anterior cerebral artery (ACA) which exhibited cerebral infarction and subarachnoid hemorrhage (SAH) simultaneously, and whose symptoms were improved by conservative treatment. A 55-year-old female presenting with headache and weakness in her left leg was admitted to our hospital. CT scans on admission revealed SAH in the interhemispheric fissure and surface of the right frontal lobe, but CT scans at 3 days after onset demonstrated cerebral infarction in the medial part of the right frontal lobe. Cerebral angiography on day 6 disclosed an aneurysmal dilatation and narrowing at the right A2-A3 segment. We continued conservative therapy including blood pressure control, since there was no symptomatic deterioration. The aneurysmal dilatation disappeared and the weakness of the left leg also improved. This case indicates that conservative treatment could be an option for the management of nontraumatic arterial dissection of the ACA with simultaneous cerebral infarction and SAH.

  6. Borosilicate films as permeability barriers

    NASA Astrophysics Data System (ADS)

    Applegate, J. R.; Steinmetz, C. E.; Hettinger, J. D.; Carroll, J. F.; Krchnavek, R.

    2009-03-01

    Borosilicate films have been deposited using rf-sputtering techniques from a composite target at room temperature onto polypropylene (PP), high density polyethylene(HDPE), low density polyethylene(LDPE), and polyethylene terephthalate (PETG) substrates. Films were found to be smooth, flexible, with excellent adhesion to the substrates. Repeated rolling the coated substrates on a radius of 0.5mm resulted in no discernable damage for films less than 200nm in thickness. Creasing the substrates did result in local damage. However excellent adhesion did not allow the fractured glass to come off the substrate. Heat generated during deposition only influenced the films grown on LDPE where the thermal expansion mismatch between the film and substrate induced strains caused fractures in thick films. Modifications to processing parameters allowed thick films to be grown without fractures. Permeability measurements of nitrogen resulted in significant improvements in comparison to uncoated substrates.

  7. Cerebral Oedema, Blood-Brain Barrier Breakdown and the Decrease in Na(+),K(+)-ATPase Activity in the Cerebral Cortex and Hippocampus are Prevented by Dexamethasone in an Animal Model of Maple Syrup Urine Disease.

    PubMed

    Rosa, Luciana; Galant, Leticia S; Dall'Igna, Dhébora M; Kolling, Janaina; Siebert, Cassiana; Schuck, Patrícia F; Ferreira, Gustavo C; Wyse, Angela T S; Dal-Pizzol, Felipe; Scaini, Giselli; Streck, Emilio L

    2016-08-01

    Maple syrup urine disease (MSUD) is a rare metabolic disorder associated with acute and chronic brain dysfunction. This condition has been shown to lead to macroscopic cerebral alterations that are visible on imaging studies. Cerebral oedema is widely considered to be detrimental for MSUD patients; however, the mechanisms involved are still poorly understood. Therefore, we investigated whether acute administration of branched-chain amino acids (BCAA) causes cerebral oedema, modifies the Na(+),K(+)-ATPase activity, affects the permeability of the blood-brain barrier (BBB) and alters the levels of cytokines in the hippocampus and cerebral cortex of 10-day-old rats. Additionally, we investigated the influence of concomitant administration of dexamethasone on the alterations caused by BCAA. Our results showed that the animals submitted to the model of MSUD exhibited an increase in the brain water content, both in the cerebral cortex and in the hippocampus. By investigating the mechanism of cerebral oedema, we discovered an association between H-BCAA and the Na(+),K(+)-ATPase activity and the permeability of the BBB to small molecules. Moreover, the H-BCAA administration increases Il-1β, IL-6 and TNF-α levels in the hippocampus and cerebral cortex, whereas IL-10 levels were decreased in the hippocampus. Interestingly, we showed that the administration of dexamethasone successfully reduced cerebral oedema, preventing the inhibition of Na(+),K(+)-ATPase activity, BBB breakdown and the increase in the cytokines levels. In conclusion, these findings suggest that dexamethasone can improve the acute cerebral oedema and brain injury associated with high levels of BCAA, either through a direct effect on brain capillary Na(+),K(+)-ATPase or through a generalized effect on the permeability of the BBB to all compounds.

  8. Cerebrovascular dysfunction and blood-brain barrier permeability induced by oxidized LDL are prevented by apocynin and magnesium sulfate in female rats

    PubMed Central

    Schreurs, Malou P.H.; Cipolla, Marilyn J.

    2013-01-01

    Oxidized low-density lipoprotein (oxLDL) is elevated during several neurologic conditions that involve cerebral edema formation, including severe preeclampsia and eclampsia; however, our understanding of its effect on the cerebral vasculature is limited. We hypothesized that oxLDL induced blood-brain barrier (BBB) disruption and changes in cerebrovascular reactivity occurs through NADPH oxidase-derived superoxide. We also investigated the effect of MgSO4 on oxLDL-induced changes in the cerebral vasculature as this is commonly used in preventing cerebral edema formation. Posterior cerebral arteries (PCA) from female rats were perfused with 5μg/mL oxLDL in rat serum with or without 50μM apocynin or 16mM MgSO4 and BBB permeability and vascular reactivity were compared. oxLDL increased BBB permeability and decreased myogenic tone that were prevented by apocynin. oxLDL increased constriction to the nitric oxide synthase inhibitor L-NNA that was unaffected by apocynin. oxLDL enhanced dilation to the NO donor sodium nitroprusside that was prevented by apocynin. MgSO4 prevented oxLDL-induced BBB permeability without affecting oxLDL-induced changes in myogenic tone. Thus, oxLDL appears to cause BBB disruption and vascular tone dysregulation through NADPH oxidase-derived superoxide. These results highlight oxLDL and NADPH oxidase as potentially important therapeutic targets in neurologic conditions that involve elevated oxLDL. PMID:24084218

  9. Extreme Rainfall Impacts in Fractured Permeable Catchments

    NASA Astrophysics Data System (ADS)

    Ireson, A. M.; Butler, A. P.

    2009-12-01

    Serious groundwater flooding events have occurred on Chalk catchments in both the UK and north west Europe in the last decade, causing substantial amounts of disruption and economic damage. These fractured, permeable catchments are characterized by low surface runoff, high baseflow indices and strongly attenuated streamflow hydrographs. They have a general resilience to drought and pluvial/fluvial flooding. The small pore size of the Chalk matrix (~ 1 µm) exerts a high suction, such that dynamic storage is primarily due to the fractures, and amounts to ~ 1% of the total volume. As a result, under sustained rainfall the water table can rise up to exceptional levels leading to surface water emergence from springs and valleys. Floodwater may slowly drain with the topography, or, in localized depressions, it may simply pond until the groundwater levels decline. In winter 2000/1, a sequence of individually unexceptional rainfall events over several months led to large scale flooding in the Pang catchment, Berkshire, UK. By contrast, an extreme rainfall event on 20th July 2007 in the same catchment caused a very rapid response at the water table, but due to the antecedent conditions did not lead to flooding. The objective of this study is to quantify how the water table in a fractured permeable catchment responds to different types of rainfall, and the implications of this for groundwater flooding. We make use of measurements from the Pang catchment, including: rainfall (tipping bucket gauges); actual evaporation (eddy flux correlation); soil water content (profile probes and neutron probes); near surface matric potential (tensiometers and equitensiometers); deep (>10m) matric potential (deep jacking tensiometers); and water table elevation (piezometers). Conventional treatment of recharge in Chalk aquifers considers a fixed bypass component of rainfall, normally 15%, to account for the role of the fractures. However, interpretation of the field data suggest three modes

  10. Development of a direct contact astrocyte-human cerebral microvessel endothelial cells blood-brain barrier coculture model.

    PubMed

    Kulczar, Chris; Lubin, Kelsey E; Lefebvre, Sylvia; Miller, Donald W; Knipp, Gregory T

    2017-09-05

    In conventional in-vitro blood-brain barrier (BBB) models, primary and immortalized brain microvessel endothelial cell (BMEC) lines are often cultured in a monolayer or indirect coculture or triculture configurations with astrocytes or pericytes, for screening permeation of therapeutic or potentially neurotoxic compounds. In each of these cases, the physiological relevancy associated with the direct contact between the BMECs, pericytes and astrocytes that form the BBB and resulting synergistic interactions are lost. We look to overcome this limitation with a direct contact coculture model. We established and optimized a direct interaction coculture system where primary human astrocytes are cultured on the apical surface of a Transwell® filter support and then human cerebral microvessel endothelial cells (hCMEC/D3) seeded directly on the astrocyte lawn. The studies suggest the direct coculture model may provide a more restrictive and physiologically relevant model through a significant reduction in paracellular transport of model compounds in comparison with monoculture and indirect coculture. In comparison with existing methods, the indirect coculture and monoculture models utilized may limit cell-cell signaling between human astrocytes and BMECs that are possible with direct configurations. Paracellular permeability reductions with the direct coculture system may enhance therapeutic agent and potential neurotoxicant screening for BBB permeability better than the currently available monoculture and indirect coculture in-vitro models. © 2017 Royal Pharmaceutical Society.

  11. Structural asymmetry of the human cerebral cortex: Regional and between-subject variability of surface area, cortical thickness, and local gyrification.

    PubMed

    Chiarello, Christine; Vazquez, David; Felton, Adam; McDowell, Alessandra

    2016-12-01

    Structural asymmetry varies across individuals, brain regions, and metrics of cortical organization. The current study investigated regional differences in asymmetry of cortical surface area, thickness, and local gyrification, and the extent of between-subject variability in these metrics, in a sample of healthy young adults (N=200). Between-subject variability in cortical structure may provide a means to assess the extent of biological flexibility or constraint of brain regions, and we explored the potential influence of this variability on the phenotypic expression of structural asymmetry. The findings demonstrate that structural asymmetries are nearly ubiquitous across the cortex, with differing regional organization for the three cortical metrics. This implies that there are multiple, only partially overlapping, maps of structural asymmetry. The results further indicate that the degree of asymmetry of a brain region can be predicted by the extent of the region's between-subject variability. These findings provide evidence that reduced biological constraint promotes the expression of strong structural asymmetry.

  12. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals associated with Deicing Chemicals from Edison Parking Lot, NJ - abstract

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  13. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals Associated with Deicing Chemicals from Edison Parking Lot, NJ

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  14. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals Associated with Deicing Chemicals from Edison Parking Lot, NJ

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  15. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals associated with Deicing Chemicals from Edison Parking Lot, NJ - abstract

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  16. Tritium Permeability of Incoloy 800H and Inconel 617

    SciTech Connect

    Philip Winston; Pattrick Calderoni; Paul Humrickhouse

    2012-07-01

    Design of the Next Generation Nuclear Plant (NGNP) reactor and its high-temperature components requires information regarding the permeation of fission generated tritium and hydrogen product through candidate heat exchanger alloys. Release of fission-generated tritium to the environment and the potential contamination of the helium coolant by permeation of product hydrogen into the coolant system represent safety basis and product contamination issues. Of the three potential candidates for high-temperature components of the NGNP reactor design, only permeability for Incoloy 800H has been well documented. Hydrogen permeability data have been published for Inconel 617, but only in two literature reports and for partial pressures of hydrogen greater than one atmosphere, far higher than anticipated in the NGNP reactor. To support engineering design of the NGNP reactor components, the tritium permeability of Inconel 617 and Incoloy 800H was determined using a measurement system designed and fabricated at Idaho National Laboratory. The tritium permeability of Incoloy 800H and Inconel 617, was measured in the temperature range 650 to 950°C and at primary concentrations of 1.5 to 6 parts per million volume tritium in helium. (partial pressures of 10-6 atm)—three orders of magnitude lower partial pressures than used in the hydrogen permeation testing. The measured tritium permeability of Incoloy 800H and Inconel 617 deviated substantially from the values measured for hydrogen. This may be due to instrument offset, system absorption, presence of competing quantities of hydrogen, surface oxides, or other phenomena. Due to the challenge of determining the chemical composition of a mixture with such a low hydrogen isotope concentration, no categorical explanation of this offset has been developed.

  17. Tritium Permeability of Incoloy 800H and Inconel 617

    SciTech Connect

    Philip Winston; Pattrick Calderoni; Paul Humrickhouse

    2011-09-01

    Design of the Next Generation Nuclear Plant (NGNP) reactor and its high-temperature components requires information regarding the permeation of fission generated tritium and hydrogen product through candidate heat exchanger alloys. Release of fission-generated tritium to the environment and the potential contamination of the helium coolant by permeation of product hydrogen into the coolant system represent safety basis and product contamination issues. Of the three potential candidates for high-temperature components of the NGNP reactor design, only permeability for Incoloy 800H has been well documented. Hydrogen permeability data have been published for Inconel 617, but only in two literature reports and for partial pressures of hydrogen greater than one atmosphere, far higher than anticipated in the NGNP reactor. To support engineering design of the NGNP reactor components, the tritium permeability of Inconel 617 and Incoloy 800H was determined using a measurement system designed and fabricated at Idaho National Laboratory. The tritium permeability of Incoloy 800H and Inconel 617, was measured in the temperature range 650 to 950 C and at primary concentrations of 1.5 to 6 parts per million volume tritium in helium. (partial pressures of 10-6 atm) - three orders of magnitude lower partial pressures than used in the hydrogen permeation testing. The measured tritium permeability of Incoloy 800H and Inconel 617 deviated substantially from the values measured for hydrogen. This may be due to instrument offset, system absorption, presence of competing quantities of hydrogen, surface oxides, or other phenomena. Due to the challenge of determining the chemical composition of a mixture with such a low hydrogen isotope concentration, no categorical explanation of this offset has been developed.

  18. Permeability of human amniotic membrane to ofloxacin in vitro.

    PubMed

    Resch, Miklós D; Resch, Béla E; Csizmazia, Eszter; Imre, László; Németh, János; Révész, Piroska; Csányi, Erzsébet

    2010-02-01

    The aim of this study was to develop a model to investigate the permeability of the amniotic membrane (AM) to ofloxacin eye drops, a widely used topical antibiotic in ocular surface disease after AM transplantation. AM pieces on cellulose acetate filter membranes were mounted in a vertical Franz-diffusion cell system equipped with an autosampler. In vitro release of 300 mg of 3% commercially available ofloxacin ophthalmic solution was determined by quantitative absorbance measurement carried out with a UV spectrophotometer (wavelength, 287 nm). Freshly prepared and cryopreserved AMs were compared. Filter membranes without AM served as positive controls. Ofloxacin was detectable in the acceptor phase 1 minute after instillation, and a gradual increase of concentration could be detected in a period of 90 minutes in all groups. At 30 minutes 3.35% +/- 2.23% of ofloxacin penetrated the freshly prepared AM, 4.35% +/- 1.8% through cryopreserved AM compared with 17.52% +/- 3.91% filter membrane alone. At 90 minutes, penetration rates of ofloxacin were 5.04% +/- 1.11%, 5.26% +/- 3.21%, and 27.91% +/- 3.05%, respectively. Difference (P > 0.05; t-test) was not significant between freshly prepared and cryopreserved AMs. Compared with control, both membranes showed significant differences (P < 0.05; t-test) at all time points. The in vitro model of the Franz-diffusion cell system was found to be applicable for drug permeability studies of human amniotic membranes to water-based solutions. The filter membrane and AM were permeable to a water-based solution of ofloxacin. Significant barrier function of the AM could be measured in ofloxacin permeability. Cryopreservation did not influence the permeability of the AM.

  19. A method of determination of permeability

    SciTech Connect

    Kuznetsov, S.V.; Trofimov, V.A.

    2007-11-15

    A method is proposed for determining permeability of coals under conditions of steady-state deformation and stationary filtration mode by employing a reference core made of gas-non-sorbing material with a known permeability. The approach has been developed to assess the time of transition to the stable filtration.

  20. Influence of fiber packing structure on permeability

    NASA Technical Reports Server (NTRS)

    Cai, Zhong; Berdichevsky, Alexander L.

    1993-01-01

    The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

  1. Crustal permeability: Introduction to the special issue

    USGS Publications Warehouse

    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.

  2. Pressure sensitivity of low permeability sandstones

    USGS Publications Warehouse

    Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.

    1987-01-01

    Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.

  3. Effect of Dead Algae on Soil Permeability

    SciTech Connect

    Harvey, R.S.

    2003-02-21

    Since existing basins support heavy growths of unicellular green algae which may be killed by temperature variation or by inadvertent pH changes in waste and then deposited on the basin floor, information on the effects of dead algae on soil permeability was needed. This study was designed to show the effects of successive algal kills on the permeability of laboratory soil columns.

  4. Effects of ozone on airway epithelial permeability and ion transport.

    PubMed

    Bromberg, P A; Ranga, V; Stutts, M J

    1991-12-01

    Ozone is a highly reactive form of oxygen produced in the atmosphere by photochemical reactions involving substrates emitted from automobile engines. Outdoor air concentrations as high as 0.4 parts per million (ppm) occur. The respiratory tract extracts about 90% of inhaled ozone. From the chemical reactivity of ozone, it is expected to attack organic molecules located on or near the respiratory surfaces. The airways are covered with a cohesive layer of epithelial cells that forms the boundary between the external environment and the respiratory tissues. One important role of this epithelial layer is its barrier function. Airborne particles that deposit (and dissolve) in the airway surface liquid are not readily absorbed, and soluble tissue components are excluded from the surface liquid. The epithelium also controls the volume and composition of the surface liquid. One important process in this regard is the absorption and secretion of ions and water. We have studied the effects of inhalation of ozone on the barrier function (permeability to dissolved molecules) and the ion transport activity of epithelium using both in vivo and in vitro techniques. All our experiments were performed with male Hartley strain guinea pigs. Conscious, unrestrained animals were exposed to a concentration of ozone of 1 ppm for three hours in controlled environmental chambers in the Health Effects Research Laboratory, U.S. Environmental Protection Agency (EPA), Research Triangle Park, NC. Such exposures caused a marked increase in the rate of appearance in blood of various water-soluble compounds instilled onto the surface of the trachea, indicating increased permeability of the airway epithelium. This interpretation was supported by electron microscopy, which showed that the tracer molecule horseradish peroxidase was present in the intercellular spaces of tracheal epithelium from ozone-exposed, but not air-exposed (control), animals. However, when the tracheas were excised after ozone

  5. Fracture network topology and characterization of structural permeability

    NASA Astrophysics Data System (ADS)

    Hansberry, Rowan; King, Rosalind; Holford, Simon

    2017-04-01

    There are two fundamental requirements for successful geothermal development: elevated temperatures at accessible depths, and a reservoir from which fluids can be extracted. The Australian geothermal sector has successfully targeted shallow heat, however, due in part to the inherent complexity of targeting permeability, obtaining adequate flow rates for commercial production has been problematic. Deep sedimentary aquifers are unlikely to be viable geothermal resources due to the effects of diagenetic mineral growth on rock permeability. Therefore, it is likely structural permeability targets, exploiting natural or induced fracture networks will provide the primary means for fluid flow in geothermal, as well as unconventional gas, reservoirs. Recent research has focused on the pattern and generation of crustal stresses across Australia, while less is known about the resultant networks of faults, joints, and veins that can constitute interconnected sub-surface permeability pathways. The ability of a fracture to transmit fluid is controlled by the orientation and magnitude of the in-situ stress field that acts on the fracture walls, rock strength, and pore pressure, as well as fracture properties such as aperture, orientation, and roughness. Understanding the distribution, orientation and character of fractures is key to predicting structural permeability. This project focuses on extensive mapping of fractures over various scales in four key Australian basins (Cooper, Otway, Surat and Perth) with the potential to host geothermal resources. Seismic attribute analysis is used in concert with image logs from petroleum wells, and field mapping to identify fracture networks that are usually not resolved in traditional seismic interpretation. We use fracture network topology to provide scale-invariant characterisation of fracture networks from multiple data sources to assess similarity between data sources, and fracture network connectivity. These results are compared with

  6. Microorganism Removal in Permeable Pavement Parking Lots ...

    EPA Pesticide Factsheets

    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.

  7. Permeability measurement and control for epoxy composites

    NASA Astrophysics Data System (ADS)

    Chang, Tsun-Hsu; Tsai, Cheng-Hung; Wong, Wei-Syuan; Chen, Yen-Ren; Chao, Hsien-Wen

    2017-08-01

    The coupling of the electric and magnetic fields leads to a strong interplay in materials' permittivity and permeability. Here, we proposed a specially designed cavity, called the mu cavity. The mu cavity, consisting of a mushroom structure inside a cylindrical resonator, is exclusively sensitive to permeability, but not to permittivity. It decouples materials' electromagnetic properties and allows an accurate measurement of the permeability. With the help of an epsilon cavity, these two cavities jointly determine the complex permeability and permittivity of the materials at microwave frequencies. Homemade epoxy-based composite materials were prepared and tested. Measurement and manipulation of the permeability and permittivity of the epoxy composites will be shown. The results will be compared with the effective medium theories.

  8. Modeling Corneal Oxygen with Scleral Gas Permeable Lens Wear.

    PubMed

    Compañ, Vicente; Aguilella-Arzo, Marcel; Edrington, Timothy B; Weissman, Barry A

    2016-11-01

    The main goal of this current work is to use an updated calculation paradigm, and updated boundary conditions, to provide theoretical guidelines to assist the clinician whose goal is to improve his or her scleral gas permeable (GP) contact lens wearing patients' anterior corneal oxygen supply. Our model uses a variable value of corneal oxygen consumption developed through Monod equations that disallows negative oxygen tensions within the stroma to predict oxygen tension at the anterior corneal surface of scleral GP contact lens wearing eyes, and to describe oxygen tension and flux profiles, for various boundary conditions, through the lens, tears, and cornea. We use several updated tissue and boundary parameters in our model. Tear exchange with GP scleral lenses is considered nonexistent in this model. The majority of current scleral GP contact lenses should produce some levels of corneal hypoxia under open eye conditions. Only lenses producing the thinnest of tear vaults should result in anterior corneal surface oxygen tensions greater than a presumed critical oxygen tension of 100 mmHg. We also find that corneal oxygen tension and flux are each more sensitive to modification in tear vault than to changes in lens oxygen permeability, within the ranges of current clinical manipulation. Our study suggests that clinicians would be prudent to prescribe scleral GP lenses manufactured from higher oxygen permeability materials and especially to fit without excessive corneal clearance.

  9. Modeling the Hydrologic Processes of a Permeable Pavement ...

    EPA Pesticide Factsheets

    A permeable pavement system can capture stormwater to reduce runoff volume and flow rate, improve onsite groundwater recharge, and enhance pollutant controls within the site. A new unit process model for evaluating the hydrologic performance of a permeable pavement system has been developed in this study. The developed model can continuously simulate infiltration through the permeable pavement surface, exfiltration from the storage to the surrounding in situ soils, and clogging impacts on infiltration/exfiltration capacity at the pavement surface and the bottom of the subsurface storage unit. The exfiltration modeling component simulates vertical and horizontal exfiltration independently based on Darcy’s formula with the Green-Ampt approximation. The developed model can be arranged with physically-based modeling parameters, such as hydraulic conductivity, Manning’s friction flow parameters, saturated and field capacity volumetric water contents, porosity, density, etc. The developed model was calibrated using high-frequency observed data. The modeled water depths are well matched with the observed values (R2 = 0.90). The modeling results show that horizontal exfiltration through the side walls of the subsurface storage unit is a prevailing factor in determining the hydrologic performance of the system, especially where the storage unit is developed in a long, narrow shape; or with a high risk of bottom compaction and clogging. This paper presents unit

  10. Structural basis of the Escherichi coli outer-membrane permeability

    NASA Astrophysics Data System (ADS)

    Amro, Nabil A.; Kotra, Lakshmi P.; Wadu-Mesthrige, Kapila; Bulychev, Alexy; Mobashery, Shahriar; Liu, Gang-yu

    1999-06-01

    We have studied, using AFM, the structural basis of the outer membrane permeability for the bacterium E. col. The surface of the bacteria is visualized with an unprecedented details. Our AFM images clearly reveal that the outer membrane exhibits protrusions, which correspond to patches of LPS containing hundreds to thousands of LPS molecules. The packing of the nearest neighbor patches is tight, and as such the LPS layer provides an effective permeability barrier for the Gram-negative bacteria. We have also studied the mechanism of their permeability increase upon metal depletion. Our AFM images reveal that LPS molecules are released from the boundaries of some patches during the initial EDTA treatment. Further metal depletion produces a very distinct structure at the outer membrane: appearance of irregularly shaped pits. The pits are likely formed as a result of liberation of LPS patches and lipoproteins, exposing areas of peptidoglacan surface. Our study has proven AFM to be a very useful technique in providing structural basis for the functions of organisms.

  11. Contrasting pediatric and adult cerebral malaria: the role of the endothelial barrier.

    PubMed

    Hawkes, Michael; Elphinstone, Robyn E; Conroy, Andrea L; Kain, Kevin C

    2013-08-15

    Malaria affects millions of people around the world and a small subset of those infected develop cerebral malaria. The clinical presentation of cerebral malaria differs between children and adults, and it has been suggested that age-related changes in the endothelial response may account for some of these differences. During cerebral malaria, parasites sequester within the brain microvasculature but do not penetrate into the brain parenchyma and yet, the infection causes severe neurological symptoms. Endothelial dysfunction is thought to play an important role in mediating these adverse clinical outcomes. During infection, the endothelium becomes activated and more permeable, which leads to increased inflammation, hemorrhages, and edema in the surrounding tissue. We hypothesize that post-natal developmental changes, occurring in both endothelial response and the neurovascular unit, account for the differences observed in the clinical presentations of cerebral malaria in children compared with adults.

  12. On the Examination of Darcy Permeability a Thin Fibrous Porous Layer

    NASA Astrophysics Data System (ADS)

    Zhu, Zenghao; Wang, Qiuyun; Wu, Qianhong; Vucbmss Team

    2016-11-01

    In this paper, we report a novel experimental approach to investigate the Darcy permeability of a soft and thin fibrous porous layer. The project is inspired by recent studies involved compression of very thin porous films and the resultant pore fluid flow inside the confined porous structure. The Darcy permeability plays a critical role during the process, which however, is tricky to measure due to the very thin nature of the porous media. In the current study, a special micro-fluidic device is developed that consists of a rectangular flow channel with adjustable gap height ranging from 20 mm to 0.5 mm. Air is forced through the thin gap filled with testing fibrous materials. By measuring the flow rate and the pressure drop, we have successfully obtained the Darcy permeability of different thin porous sheets at different compression ratios. Furthermore, the surface area of the fibers are evaluated using a Micromeritics® ASAP 2020 (Accelerated Surface Area and Porosimetry) system. We found that, although the functions relating the permeability and porosities are different for different fibrous materials, these functions collapse to a single relationship if one express the permeability as a function of the solid phase surface area per unit volume. This finding provides a useful approach to evaluate the permeability of very thin fibrous porous sheet, which otherwise is difficult to measure directly. This research was supported by the National Science Foundation under Award #1511096.

  13. Cerebral blood volume changes during brain activation

    PubMed Central

    Krieger, Steffen Norbert; Streicher, Markus Nikolar; Trampel, Robert; Turner, Robert

    2012-01-01

    Cerebral blood volume (CBV) changes significantly with brain activation, whether measured using positron emission tomography, functional magnetic resonance imaging (fMRI), or optical microscopy. If cerebral vessels are considered to be impermeable, the contents of the skull incompressible, and the skull itself inextensible, task- and hypercapnia-related changes of CBV could produce intolerable changes of intracranial pressure. Because it is becoming clear that CBV may be useful as a well-localized marker of neural activity changes, a resolution of this apparent paradox is needed. We have explored the idea that much of the change in CBV is facilitated by exchange of water between capillaries and surrounding tissue. To this end, we developed a novel hemodynamic boundary-value model and found approximate solutions using a numerical algorithm. We also constructed a macroscopic experimental model of a single capillary to provide biophysical insight. Both experiment and theory model capillary membranes as elastic and permeable. For a realistic change of input pressure, a relative pipe volume change of 21±5% was observed when using the experimental setup, compared with the value of approximately 17±1% when this quantity was calculated from the mathematical model. Volume, axial flow, and pressure changes are in the expected range. PMID:22569192

  14. The basic nonuniformity of the cerebral cortex

    PubMed Central

    Herculano-Houzel, Suzana; Collins, Christine E.; Wong, Peiyan; Kaas, Jon H.; Lent, Roberto

    2008-01-01

    Evolutionary changes in the size of the cerebral cortex, a columnar structure, often occur through the addition or subtraction of columnar modules with the same number of neurons underneath a unit area of cortical surface. This view is based on the work of Rockel et al. [Rockel AJ, Hiorns RW, Powell TP (1980) The basic uniformity in structure of the neocortex. Brain 103:221–244], who found a steady number of approximately 110 neurons underneath a surface area of 750 μm2 (147,000 underneath 1 mm2) of the cerebral cortex of five species from different mammalian orders. These results have since been either corroborated or disputed by different groups. Here, we show that the number of neurons underneath 1 mm2 of the cerebral cortical surface of nine primate species and the closely related Tupaia sp. is not constant and varies by three times across species. We found that cortical thickness is not inversely proportional to neuronal density across species and that total cortical surface area increases more slowly than, rather than linearly with, the number of neurons underneath it. The number of neurons beneath a unit area of cortical surface varies linearly with neuronal density, a parameter that is neither related to cortical size nor total number of neurons. Our finding of a variable number of neurons underneath a unit area of the cerebral cortex across primate species indicates that models of cortical organization cannot assume that cortical columns in different primates consist of invariant numbers of neurons. PMID:18689685

  15. Hypernatraemia in cerebral disorders

    PubMed Central

    Taylor, W. H.

    1962-01-01

    Six patients are described in whom cerebral damage was associated with raised plasma sodium and chloride concentrations and with extremely low urinary outputs of sodium and chloride. The patients were not clinically dehydrated and direct determinations showed that the blood and plasma volumes, the endogenous creatinine clearance, and the urinary output of antidiuretic hormone were normal. For these and other reasons it is concluded that the metabolic picture results not from diminished circulatory volume, water deficiency, sodium deficiency, undetected diabetes insipidus or osmotic diuresis, but from the cerebral damage itself. In these and other cited cases, the cerebral damage was localized chiefly in the frontal lobes, hypothalamus or lower brain-stem, thus suggesting a descending pathway, the relationship of which to the pineal area controlling aldosterone secretion requires clarification. Images PMID:13920001

  16. Duplicated middle cerebral artery.

    PubMed

    Perez, Jesus; Machado, Calixto; Scherle, Claudio; Hierro, Daniel

    2009-01-01

    Duplicated middle cerebral artery (DMCA) is an anomalous vessel arising from the internal carotid artery. The incidence DMCA is relatively law, and an association between this anomaly and cerebral aneurysms has been documented. There is a controversy whether DMCA may have perforating arteries. This is an important fact to consider in aneurysm surgery. We report the case of a 34-year-old black woman who suffered a subarachnoid hemorrhage and the angiography a left DMCA, and an aneurysm in an inferior branch of the main MCA. The DMCA and the MCA had perforating arteries. The aneurysm was clipped without complications. The observation of perforating arteries in our patient confirms that the DMCA may have perforating arteries. This is very important to be considered in cerebral aneurysms surgery. Moreover, the DMCA may potentially serve as a collateral blood supply to the MCA territory in cases of MCA occlusion.

  17. Permeability modification of porous media by surfactant solutions

    SciTech Connect

    Kalpakci, B.; Klaus, E.E.; Duda, J.L.; Nagarajan, R.

    1981-01-01

    Results are presented of a study on the flow properties of surfactant solutions in porous media, using the Penn State Porous Media Viscometer. The effects of permeability, shear rate, and surface characteristics of the porous media on the flow of oil-external, and water-external type microemulsions as well as surfactant solutions with lamellar structures have been examined. Flow studies have been carried out in untreated Bradford and Berea sandstones, oil-wet and water-wet treated sandstones, and filter papers. This study shows that the flow of surfactant solutions causes a decrease in permeability which reaches a stable value after the flow of several hundred pore volumes of the surfactant solution. This work is pertinent to flooding with surfactants. 33 refs.

  18. Gravity Current in Horizontal Porous Media with A Permeability Gradient

    NASA Astrophysics Data System (ADS)

    Zheng, Zhong; Tsai, Peichun; Al-Housseiny, Talal; Stone, Howard; Complex Fluid Group Team

    2011-11-01

    We study the influence of a power-law porosity and permeability gradient on the front propagation of a gravity current in an unconfined porous media. We neglect mass transfer and surface tension on the interface. A similarity solution is found for the propagating front, which is different from the homogeneous case. Experiments have been performed using liquid pushing air in a Hele-Shaw cell with a constant gradient in gap thickness in the vertical direction. We measure the speed of the front and the shape of the interface. We observe a third layer of trapped air in the region where the permeability is low, while it appears that the propagating front still satisfies the similarity solution with a modified coefficient. This work is supported by a funding from Carbon Mitigation Initiative at Princeton University

  19. Permittivity and permeability of semi-infinite metamaterial

    NASA Astrophysics Data System (ADS)

    Porvatkina, O. V.; Tishchenko, A. A.; Strikhanov, M. N.

    2016-08-01

    In our work we investigate dielectric and magnetic properties of semi-infinite metamaterial consisting of particles of different possible nature: atoms, molecules, nanoparticles, etc. It is important that these particles would have magnetic properties. Polarization of a near-surface layer is known to differ from its bulk value for non-magnetic materials; for magnetic materials, including metamaterials, the situation should be similar, which is the subject of our research. We obtain analogues of the Clausius-Mossotti relation both for permittivity and permeability taking into account the local field effects in the longwave approximation for semi-infinite metamaterial. These relations describe the connection between macroscopic characteristics of the semi-infinite metamaterial (permittivity and permeability) and characteristics of constituent particles (dielectric polarizability and magnetic polarizability), which is a bright example of multi-scale approach - method very popular today in physical and computer simulating.

  20. Negative correlation of CD34+ cells with blood-brain barrier permeability following traumatic brain injury in a rat model.

    PubMed

    Jin, Xuelong; Wang, Feifei; Liu, Xingju; Liang, Bin; Chen, Zequn; He, Junfeng; Zhang, Hong; Zhang, Jianning

    2014-11-01

    TBI causes localized cerebral ischemia that, in turn, is accompanied by both changes in BBB permeability and recruitment of CD34(+) cells to the injured tissue. However, it remains unknown whether CD34(+) cell recruitment is linked to BBB permeability. This study is a preliminary investigation into possible correlations between CD34(+) cell recruitment and BBB permeability following TBI in a rat model. Male SD rats were subjected to mild fluid percussion injury. BBB permeability was assessed by measuring extrinsic EB dye extravasation and endogenous EBA expression at days 1, 3, 5, 7, and 12 post injury. The number of CD34(+) cells in the damaged tissue was analyzed by immunohistochemistry at each time point. EB dye extravasation reached a peak at day 3 following TBI, while EBA expression displayed the reverse profile. Accumulation of CD34(+) cells in injured brain tissue was evident at five days post injury. It revealed a negative linear correlation between CD34(+) cell and BBB permeability. The negative linear correlation between CD34(+) cell recruitment and BBB permeability following TBI provides a support for further study of CD34(+) cell transplantation for BBB repair after TBI. © 2014 John Wiley & Sons Ltd.

  1. Numerical simulation of the permeable base transistor

    NASA Astrophysics Data System (ADS)

    Navon, D. H.; Tang, T. W.

    1982-08-01

    Predictions of improved high frequency performance of the gallium arsenide permeable base transistor (PBT) have been made by the exact diffusion-drift, two-dimensional numerical analysis of several PBT designs. In this study, both the device geometry and/or the impurity doping profile were varied and the corresponding unity-current-gain frequency, (f sub T), calculated. More than a 35% improvement in (f sub T) was predicted when the ration of the metal (Schottky) gate width to the space between gate fingers was varied. More than a doubling of (f sub T) could be obtained when the source and drain doping was increased to produce and n(+) n n(+) configuration. Each device design was analyzed to determine the change in mobile charge density with gate bias in the major areas of the structure in order to compute its contribution to the device input capacitance. In this way information was obtained on design details for reduced capacitance and transconductance change for improved (f sub T). A new UPBT structure was investigated where the semiconductor material above the gate electrode was removed in order to reduce this region's contribution to the capacitance. A 100% improvement in high frequency performance was predicted for this structure, operating at low gate voltages. Less gain was obtained at higher voltages. Control of the surface states on the exposed walls of this device must be provided to obtain this advantage.

  2. Permeability and Retentivity Curves In Mountain Soils

    NASA Astrophysics Data System (ADS)

    Barontini, S.; Ranzi, R.

    The saturated conductivity, Ks, and the retentivity curves, for mountain non-mature soils have been determined after laboratory- and field-experiments carried out over about 146 soil samples in the Toce river basin (Val d'Ossola, Northern Italian Alps). Eightythree samples only have been used to measure the retentivity curves using 15 bar and 5 bar Richard's extractors. Coherently with other researches, traditional meth- ods used to derive Ks on the basis of in situ infiltration test with a single ring infiltrom- eter provided values grater than those calculated using a variable head permeameter in laboratory. So other simplified methods have been used to estimate Ks after field analysis: the traditional method based on the Darcy's law, modified in respect of soil saturation; a method based on an application of Green and Ampt infiltration model; and a method based on the Wooding's works. All these methods, in particular the Wooding (1968) solution, gave estimates of Ks closer to the laboratory ones and to the results of a finite elements numerical solution of the Richard's equation in a 3D domain with axial simmetry. As a result an updated legend for the existing surface soil saturated conductivity map for the of the Toce basin is proposed. Inhomogeneities in the vertical permeability profiles have been identified also.

  3. Plasmodium falciparum histidine-rich protein II causes vascular leakage and exacerbates experimental cerebral malaria in mice.

    PubMed

    Pal, Priya; Balaban, Amanda E; Diamond, Michael S; Sinnis, Photini; Klein, Robyn S; Goldberg, Daniel E

    2017-01-01

    A devastating complication of Plasmodium falciparum infection is cerebral malaria, in which vascular leakage and cerebral swelling lead to coma and often death. P. falciparum produces a protein called histidine-rich protein II (HRPII) that accumulates to high levels in the bloodstream of patients and serves as a diagnostic and prognostic marker for falciparum malaria. Using a human cerebral microvascular endothelial barrier model, we previously found that HRPII activates the endothelial cell inflammasome, resulting in decreased integrity of tight junctions and increased endothelial barrier permeability. Here, we report that intravenous administration of HRPII induced blood-brain barrier leakage in uninfected mice. Furthermore, HRPII infusion in P. berghei-infected mice increased early mortality from experimental cerebral malaria. These data support the hypothesis that HRPII is a virulence factor that contributes to cerebral malaria by compromising the integrity of the blood-brain barrier.

  4. Cerebral venous sinus thrombosis with cerebral hemorrhage during early pregnancy

    PubMed Central

    Nie, Quanmin; Guo, Pin; Ge, Jianwei; Qiu, Yongming

    2015-01-01

    Cerebral venous sinus thrombosis (CVST) rarely induces cerebral hemorrhage, and CVST with cerebral hemorrhage during early pregnancy is extremely rare. Upon literature review, we are able to find only one case of CVST with cerebral hemorrhage in early pregnancy. In this paper, we report another case of a 27-year-old patient who developed CVST with cerebral hemorrhage in her fifth week of pregnancy. Although the optimal treatment for this infrequent condition remains controversial, we adopted anticoagulation as the first choice of treatment and obtained favorable results. PMID:25630781

  5. Plant actin controls membrane permeability.

    PubMed

    Hohenberger, Petra; Eing, Christian; Straessner, Ralf; Durst, Steffen; Frey, Wolfgang; Nick, Peter

    2011-09-01

    The biological effects of electric pulses with low rise time, high field strength, and durations in the nanosecond range (nsPEFs) have attracted considerable biotechnological and medical interest. However, the cellular mechanisms causing membrane permeabilization by nanosecond pulsed electric fields are still far from being understood. We investigated the role of actin filaments for membrane permeability in plant cells using cell lines where different degrees of actin bundling had been introduced by genetic engineering. We demonstrate that stabilization of actin increases the stability of the plasma membrane against electric permeabilization recorded by penetration of Trypan Blue into the cytoplasm. By use of a cell line expressing the actin bundling WLIM domain under control of an inducible promotor we can activate membrane stabilization by the glucocorticoid analog dexamethasone. By total internal reflection fluorescence microscopy we can visualize a subset of the cytoskeleton that is directly adjacent to the plasma membrane. We conclude that this submembrane cytoskeleton stabilizes the plasma membrane against permeabilization through electric pulses. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Protozoon infections and intestinal permeability.

    PubMed

    Dagci, Hande; Ustun, Sebnem; Taner, Memduh S; Ersoz, Galip; Karacasu, Ferit; Budak, Seza

    2002-01-01

    Intestinal permeability (IP) studies using some macromolecules have been assumed to demonstrate the intactness of intestinal mucosa. The aim of the present study is to determine the changes in IP among patients with protozoan infections. Thirty nine patients with protozoan infections and ten healthy controls were enrolled in the study. Protozoa were diagnosed by Native-lugol, Richie and Trichrome staining of faeces. IP was evaluated by diethyl triamine penta acetic acid labeled with 99m Technetium (99mTc labeled DTPA) assay. The IP was found to have increased in patients with protozoan infections compared with control patients (7.20+/-5.52 vs. 4.47+/-0.65%, P=0.0017). The IP values were 9.91+/-10.05% in Giardia intestinalis group, 6.81+/-2.25% in Blastocystis hominis group, 5.78+/-2.84% in Entamoeba coli group. In comparison with the control group, the IP was significantly higher in G. intestinalis and B. hominis patients (P=0.0025, P=0.00037, respectively), but not in E. coli patients. In conclusion, the IP increases in patients with G. intestinalis and B. hominis but not with E. coli infection. This finding supports the view that IP increases during the course of protozoan infections which cause damage to the intestinal wall while non-pathogenic protozoan infections have no effect on IP. The increase in IP in patients with B. hominis brings forth the idea that B. hominis can be a pathogenic protozoan.

  7. Relative ion permeability of normal and cystic fibrosis nasal epithelium.

    PubMed Central

    Knowles, M; Gatzy, J; Boucher, R

    1983-01-01

    The raised transepithelial electric potential difference (PD) across respiratory epithelia in cystic fibrosis (CF) has suggested an abnormality in ion permeation. We characterized this abnormality further by measuring in the nasal epithelia of CF and normal subjects the concentration-PD relationship for amiloride, an inhibitor of cell Na+ permeability, and PD responses to superfusion with solutions of different composition. Amiloride was more efficacious in the CF subjects but the ED50 was not different from that of normals (approximately 2 X 10(-6) M). Na+ replacement by choline induced effects similar to those of amiloride, i.e. a greater depolarization in CF subjects. A 10-fold increase in the K+ concentration of the perfusate induced a small (less than 10 mV) depolarization in both subject populations. When Cl- in the perfusate was replaced by gluconate or SO2-(4) the nasal PD of normal subjects hyperpolarized (lumen became more negative) by approximately 35 mV. A significantly smaller response (less than 17 mV) was induced in CF homozygotes but not in heterozygotes (38 mV). The smaller response of CF subjects appears to reflect an absolute decrease in luminal surface Cl- permeability because pretreatment with amiloride did not increase the response to Cl- free solution (7 mV). Accordingly, three abnormalities (decreased Cl- permeability, raised PD, greater amiloride efficacy) have been identified in CF respiratory epithelia. Whereas "excessive" active Na+ transport can account for these abnormalities and the dessication of airway surface liquid, it is possible that a lower lumenal cell membrane Cl- permeability and inhibition of a potential path of Cl- secretion can also explain the observations. PMID:6853720

  8. Permeability of enamel following light-activated power bleaching.

    PubMed

    Turssi, Cecilia P; Schiavoni, Renato J; Serra, Monica C; Froner, Izabel C

    2006-01-01

    This study sought to ascertain whether in-office photocured bleaching techniques would increase permeability to enamel. A 7.1 mm2 circular area located in the middle third of the coronal portion of 90 human canines was isolated by applying an acid-resistant varnish to the remaining surfaces of the tooth. According to a randomized complete block design (n = 15), specimens were treated using a 35% hydrogen peroxide bleaching product activated by an integrated LED/diode laser (LED/laser) source or a quartz tungsten halogen (QTH) light. Bleaching was accomplished by applying the 35% hydrogen peroxide agent to the enamel surface in three 10-minute sessions, conducted at one-week intervals over a period of three weeks. For the photocured bleached groups, a bleaching agent was applied to the specimen and irradiated with the LED/laser device or the QTH light for 30 seconds. Negative control groups were exposed to artificial saliva or irradiated by the LED/laser device or the QTH light. Specimens were subjected to a histochemical coloring method that employed copper sulfate and dithio-oxamide solutions. Three 300-microm thick sections taken from the exposed area were imaged in an optical microscope. Permeability was measured in the digitized images as the percentage of copper ions penetration over the total enamel thickness. Friedman's test (alpha = 0.05) showed significant difference among groups. Least significant difference test revealed that in comparison with the group treated with 35% hydrogen peroxide only, there was no significant increase in enamel permeability when bleaching was activated by either the LED/laser or QTH light devices but all bleached groups showed higher permeability than the unbleached/nonirradiated group.

  9. Permeable Gas Flow Influences Magma Fragmentation Speed.

    NASA Astrophysics Data System (ADS)

    Richard, D.; Scheu, B.; Spieler, O.; Dingwell, D.

    2008-12-01

    Highly viscous magmas undergo fragmentation in order to produce the pyroclastic deposits that we observe, but the mechanisms involved remain unclear. The overpressure required to initiate fragmentation depends on a number of physical parameters, such as the magma's vesicularity, permeability, tensile strength and textural properties. It is clear that these same parameters control also the speed at which a fragmentation front travels through magma when fragmentation occurs. Recent mathematical models of fragmentation processes consider most of these factors, but permeable gas flow has not yet been included in these models. However, it has been shown that permeable gas flow through a porous rock during a sudden decompression event increases the fragmentation threshold. Fragmentation experiments on natural samples from Bezymianny (Russia), Colima (Mexico), Krakatau (Indonesia) and Augustine (USA) volcanoes confirm these results and suggest in addition that high permeable flow rates may increase the speed of fragmentation. Permeability from the investigated samples ranges from as low as 5 x 10-14 to higher than 9 x 10- 12 m2 and open porosity ranges from 16 % to 48 %. Experiments were performed for each sample series at applied pressures up to 35 MPa. Our results indicate that the rate of increase of fragmentation speed is higher when the permeability is above 10-12 m2. We confirm that it is necessary to include the influence of permeable flow on fragmentation dynamics.

  10. Intestinal permeability, leaky gut, and intestinal disorders.

    PubMed

    Hollander, D

    1999-10-01

    A major task of the intestine is to form a defensive barrier to prevent absorption of damaging substances from the external environment. This protective function of the intestinal mucosa is called permeability. Clinicians can use inert, nonmetabolized sugars such as mannitol, rhamnose, or lactulose to measure the permeability barrier or the degree of leakiness of the intestinal mucosa. Ample evidence indicates that permeability is increased in most patients with Crohn's disease and in 10% to 20% of their clinically healthy relatives. The abnormal leakiness of the mucosa in Crohn's patients and their relatives can be greatly amplified by aspirin preadministration. Permeability measurements in Crohn's patients reflect the activity, extent, and distribution of the disease and may allow us to predict the likelihood of recurrence after surgery or medically induced remission. Permeability is also increased in celiac disease and by trauma, burns, and nonsteroidal anti-inflammatory drugs. The major determinant of the rate of intestinal permeability is the opening or closure of the tight junctions between enterocytes in the paracellular space. As we broaden our understanding of the mechanisms and agents that control the degree of leakiness of the tight junctions, we will be increasingly able to use permeability measurements to study the etiology and pathogenesis of various disorders and to design or monitor therapies for their management.

  11. Development of Cassette PAMPA for Permeability Screening.

    PubMed

    Oh, Mun Hwan; Lee, Hye Jin; Jo, Sang Hyun; Park, Bernie Byunghoon; Park, Sae-Bom; Kim, Eun-Yeong; Zhou, Yuanyuan; Jeon, Young Ho; Lee, Kiho

    2017-01-01

    The parallel artificial membrane permeability assay (PAMPA) is widely used in early-stage drug discovery to discriminate compounds by intestinal permeability. The purpose of the current study was to establish a cassette (n-in-1) PAMPA to enable permeability screening of lipophilic compounds. A double-sink PAMPA consisting of a pH gradient (i.e., pH 6.5 and 7.4 for the donor and receiver compartments, respectively) and a lipophilic sink (i.e., a surfactant in the receiver solution) was utilized with cassette incubation of 10 reference compounds. Sample analysis was conducted using selected reaction monitoring (SRM) with a triple quadrupole LC-MS/MS system. Correlation between PAMPA permeability and human intestinal absorption (HIA) of the reference compounds yielded two false negatives, namely propranolol (PPN) and verapamil (VER); these two compounds showed a substantially lower recovery (ca. 10%) than other reference compounds (>69%). This cassette PAMPA was repeated subsequently with polysorbate 80 added to the donor compartments, which resulted in a significant increase in both the recovery and the permeability of the false negatives. Accordingly, the permeability class of all reference compounds could be unambiguously differentiated using this cassette PAMPA. Also, a strong linear correlation (r=0.9845) was observed between the cassette and discrete permeability of all reference compounds.

  12. Anisotropy of permeability in faulted porous sandstones

    NASA Astrophysics Data System (ADS)

    Farrell, N. J. C.; Healy, D.; Taylor, C. W.

    2014-06-01

    Studies of fault rock permeabilities advance the understanding of fluid migration patterns around faults and contribute to predictions of fault stability. In this study a new model is proposed combining brittle deformation structures formed during faulting, with fluid flow through pores. It assesses the impact of faulting on the permeability anisotropy of porous sandstone, hypothesising that the formation of fault related micro-scale deformation structures will alter the host rock porosity organisation and create new permeability pathways. Core plugs and thin sections were sampled around a normal fault and oriented with respect to the fault plane. Anisotropy of permeability was determined in three orientations to the fault plane at ambient and confining pressures. Results show that permeabilities measured parallel to fault dip were up to 10 times higher than along fault strike permeability. Analysis of corresponding thin sections shows elongate pores oriented at a low angle to the maximum principal palaeo-stress (σ1) and parallel to fault dip, indicating that permeability anisotropy is produced by grain scale deformation mechanisms associated with faulting. Using a soil mechanics 'void cell model' this study shows how elongate pores could be produced in faulted porous sandstone by compaction and reorganisation of grains through shearing and cataclasis.

  13. Ultramorphology and dentine permeability changes induced by prophylactic procedures on exposed dentinal tubules in middle dentine.

    PubMed

    Sauro, S; Watson, T-F; Thompson, I

    2011-11-01

    The purpose of this study was to evaluate the changes in dentinal permeability (i.e. hydraulic conductance) after prophylactic treatment performed using prophy-powders with air-polishing system or prophy-pastes applied on exposed middle dentine. The changes in dentine morphology were evaluate by SEM. Several prophylactic pastes or air-polishing powders were tested in this study. Dentine discs from human third molars were used to study the quantitative reduction of the dentine permeability under simulated pulpal pressure (20 cm H₂O). Further specimens were gold-coated and observed with the use of a SEM. The results of this study showed different reductions of dentin permeability effects based on the type of product employed (i.e. prophylactic paste or air-polishing powders). The use of Sylc bioactive glass and sodium bicarbonate were the most effective in reducing dentine permeability of the specimens etched with the phosphoric. The air-polishing procedures performed with Sylc bioactive glass created a dentine surface devoid of exposed dentinal tubules due to the presence of a compact multilayered smear layer. Colgate Sensitive Pro-Relief and Nupro NU-Solution reduced the dentine permeability up to 69.8% and 66.9% respectively. Although all the tested products are able to statistically reduce dentine permeability, Sylc bioactive glass is an innovative and effective product suitable for the reducing of the dentine permeability during prophylactic procedures of air-polishing.

  14. Decision trees to characterise the roles of permeability and solubility on the prediction of oral absorption.

    PubMed

    Newby, Danielle; Freitas, Alex A; Ghafourian, Taravat

    2015-01-27

    Oral absorption of compounds depends on many physiological, physiochemical and formulation factors. Two important properties that govern oral absorption are in vitro permeability and solubility, which are commonly used as indicators of human intestinal absorption. Despite this, the nature and exact characteristics of the relationship between these parameters are not well understood. In this study a large dataset of human intestinal absorption was collated along with in vitro permeability, aqueous solubility, melting point, and maximum dose for the same compounds. The dataset allowed a permeability threshold to be established objectively to predict high or low intestinal absorption. Using this permeability threshold, classification decision trees incorporating a solubility-related parameter such as experimental or predicted solubility, or the melting point based absorption potential (MPbAP), along with structural molecular descriptors were developed and validated to predict oral absorption class. The decision trees were able to determine the individual roles of permeability and solubility in oral absorption process. Poorly permeable compounds with high solubility show low intestinal absorption, whereas poorly water soluble compounds with high or low permeability may have high intestinal absorption provided that they have certain molecular characteristics such as a small polar surface or specific topology. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  15. Cocrystals of Hydrochlorothiazide: Solubility and Diffusion/Permeability Enhancements through Drug-Coformer Interactions.

    PubMed

    Sanphui, Palash; Devi, V Kusum; Clara, Deepa; Malviya, Nidhi; Ganguly, Somnath; Desiraju, Gautam R

    2015-05-04

    Hydrochlorothiazide (HCT) is a diuretic and a BCS class IV drug with low solubility and low permeability, exhibiting poor oral absorption. The present study attempts to improve the physicochemical properties of the drug using a crystal engineering approach with cocrystals. Such multicomponent crystals of HCT with nicotinic acid (NIC), nicotinamide (NCT), 4-aminobenzoic acid (PABA), succinamide (SAM), and resorcinol (RES) were prepared using liquid-assisted grinding, and their solubilities in pH 7.4 buffer were evaluated. Diffusion and membrane permeability were studied using a Franz diffusion cell. Except for the SAM and NIC cocrystals, all other binary systems exhibited improved solubility. All of the cocrystals showed improved diffusion/membrane permeability compared to that of HCT with the exception of the SAM cocrystal. When the solubility was high, as in the case of PABA, NCT, and RES cocrystals, the flux/permeability dropped slightly. This is in agreement with the expected interplay between solubility and permeability. Improved solubility/permeability is attributed to new drug-coformer interactions. Cocrystals of SAM, however, showed poor solubility and flux. This cocrystal contains a primary sulfonamide dimer synthon similar to that of HCT polymorphs, which may be a reason for its unusual behavior. Hirshfeld surface analysis was carried out in all cases to determine whether a correlation exists between cocrystal permeability and drug-coformer interactions.

  16. Permeability Barrier Generation in the Martian Lithosphere

    NASA Astrophysics Data System (ADS)

    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

  17. Escin attenuates cerebral edema induced by acute omethoate poisoning.

    PubMed

    Wang, Tian; Jiang, Na; Han, Bing; Liu, Wenbo; Liu, Tongshen; Fu, Fenghua; Zhao, Delu

    2011-06-01

    Organophosphorus exposure affects different organs such as skeletal muscles, the gastrointestinal tract, liver, lung, and brain. The present experiment aimed to evaluate the effect of escin on cerebral edema induced by acute omethoate poisoning. Sprague-Dawley rats were administered subcutaneously with omethoate at a single dose of 60 mg/kg followed by escin treatment. The results showed that escin reduced the brain water content and the amount of Evans blue in omethoate-poisoned animals. Treatment with escin decreased the levels of tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase-9 (MMP-9), cyclooxygenase-2 (COX-2), and prostaglandin E₂ (PGE₂) in the brain. Escin also alleviated the histopathological change induced by acute omethoate poisoning. The findings demonstrated that escin can attenuate cerebral edema induced by acute omethoate poisoning, and the underlying mechanism was associated with ameliorating the permeability of the blood-brain barrier.

  18. Seinpin knockout exacerbates cerebral ischemia/reperfusion damage in mice.

    PubMed

    Chen, Yong; Wei, Lili; Tian, Jing; Wang, Yu-Hui; Liu, George; Wang, Chun

    2016-05-27

    Seipin, which regulates adipocyte differentiation and lipolysis, inducing severe lipodystrophy and metabolic syndromes, is also highly expressed in the nervous system and affects some neurological diseases. However, the impacts of seipin in stroke remain unclear. In this study, we subjected seipin knockout mice to cerebral ischemia/reperfusion injury and found that seipin knockout mice exhibited exacerbated neurological disorder and enlarged infarct size, companied by blood-brain barrier (BBB) damages. Furthermore, we showed that seipin knockout aggravated endoplasmic reticulum (ER) stress and significantly increased glucose levels, decreased leptin and adiponectin levels in mouse plasma. Our findings reveal that seipin knockout exacerbates cerebral I/R-induced damages by increasing BBB permeability, amplifying ER stress and increasing glucose levels, as well as decreasing leptin and adiponectin levels, indicating that seipin may be a potential therapeutic target for stroke. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Gas Permeable Chemochromic Compositions for Hydrogen Sensing

    NASA Technical Reports Server (NTRS)

    Bokerman, Gary (Inventor); Mohajeri, Nahid (Inventor); Muradov, Nazim (Inventor); Tabatabaie-Raissi, Ali (Inventor)

    2013-01-01

    A (H2) sensor composition includes a gas permeable matrix material intermixed and encapsulating at least one chemochromic pigment. The chemochromic pigment produces a detectable change in color of the overall sensor composition in the presence of H2 gas. The matrix material provides high H2 permeability, which permits fast permeation of H2 gas. In one embodiment, the chemochromic pigment comprises PdO/TiO2. The sensor can be embodied as a two layer structure with the gas permeable matrix material intermixed with the chemochromic pigment in one layer and a second layer which provides a support or overcoat layer.

  20. Monitoring Strategies in Permeable Pavement Systems to Optimize Maintenance Scheduling - abstract

    EPA Science Inventory

    As the surface in a permeable pavement system clogs and performance decreases, maintenance is required to preserve the design function. Currently, guidance is limited for scheduling maintenance on an as needed basis. Previous research has shown that surface clogging in a permea...

  1. Monitoring Strategies in Permeable Pavement Systems to Optimize Maintenance Scheduling - abstract

    EPA Science Inventory

    As the surface in a permeable pavement system clogs and performance decreases, maintenance is required to preserve the design function. Currently, guidance is limited for scheduling maintenance on an as needed basis. Previous research has shown that surface clogging in a permea...

  2. Inferring Firn Permeability from Pneumatic Testing: A Case Study on the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Sommers, Aleah N.; Rajaram, Harihar; Weber, Eliezer P.; MacFerrin, Michael J.; Colgan, William T.; Stevens, C. Max

    2017-03-01

    Across the accumulation zone of the Greenland ice sheet, summer temperatures can be sufficiently warm to cause widespread melting, as was the case in July 2012 when the entire ice sheet experienced a brief episode of enhanced surface ablation. The resulting meltwater percolates into the firn and refreezes, to create ice lenses and layers within the firn column. This is an important process to consider when estimating the surface mass balance of the ice sheet. The rate of meltwater percolation depends on the permeability of the firn, a property that is not well constrained in the presence of refrozen ice layers and lenses. We present a novel, inexpensive method for measuring in-situ firn permeability using pneumatic testing, a well-established technique used in environmental engineering and hydrology. To illustrate the capabilities of this method, we estimate both horizontal and vertical permeability from pilot tests at six sites on the Greenland ice sheet: KAN-U, DYE-2, EKT, NASA-SE, Saddle, and EastGRIP. These sites cover a range of conditions from mostly dry firn (EastGRIP), to firn with several ice layers and lenses from refrozen meltwater (Saddle, NASA-SE, EKT), to firn with extensive ice layers (DYE-2 and KAN-U). The estimated permeability in firn without refrozen ice layers at EastGRIP agrees well with the range previously reported using an air permeameter to measure permeability through firn core samples at Summit, Greenland. At sites with ice lenses or layers, we find high degrees of anisotropy, with vertical permeability much lower than horizontal permeability. Pneumatic testing is a promising and low-cost technique for measuring firn permeability, particularly as meltwater production increases in the accumulation zone and ice layers and lenses from refrozen melt layers become more prevalent. In these initial proof-of-concept tests, the estimated permeabilities represent effective permeability at the meter scale. With appropriately higher vacuum pressures

  3. [Variation in the flow and branching of the anterior and middle cerebral arteries].

    PubMed

    Kulenović, Amela; Dilberović, Faruk; Ovcina, Fehim

    2003-01-01

    We used injection and corrosion method to study path, caliber and branching of anterior and middle cerebral artery, which supplies anterior two thirds of medial and external surface of cerebral hemispheres and associated subcortical structures. When we studied our specimens, we observed that internal carotid artery always bifurcates and gives anterior and middle cerebral artery. Precommunicant segment of anterior cerebral artery has variable appearance. In 65 percent this path of anterior cerebral artery is arch shaped with convexity laterally and forward, but in 44 percent it is straight and oblique in direction. We observer that in 1 percent of cases precommunicant segment of anterior cerebral artery has wavey path. In one percent of the cases anterior third of pericallosal artery is branching from anterior communicating artery. This third pericallosal artery is smaller than the other pair of pericallosal arteries branching from anterior cerebral artery. Initial segment of middle cerebral artery(pars sphenoidalis) is 2.5 cm long. In 70 percent of cases terminal part of sphenidal segment of middle cerebral artery bifurcates, in 30 percent of cases we studied this segment trifucates. Insular segment of the middle cerebral artery branches into several segments which are narrower. When we studied our specimens we found one rare variation branching from middle cerebral artery where it bifurcated into anterior smaller and posterior larger branch, than they divide into multiple smaller branches in periinsular segment.

  4. Cerebral Folate Deficiency

    ERIC Educational Resources Information Center

    Gordon, Neil

    2009-01-01

    Cerebral folate deficiency (CFD) is associated with low levels of 5-methyltetrahydrofolate in the cerebrospinal fluid (CSF) with normal folate levels in the plasma and red blood cells. The onset of symptoms caused by the deficiency of folates in the brain is at around 4 to 6 months of age. This is followed by delayed development, with deceleration…

  5. [Multiple cerebral tuberculomas].

    PubMed

    Noriega, L; Villarreal, F

    The tuberculosis is a disease that continues being important cause of morbidity and mortality at worldwide level. Its presentation as tuberculomas cerebral manifold at level of the central nervous system is little frequent in immunocompetent patients and can be confused with other etiology. An indigenous young man, immunocompetent consulted for history of headache, nausea, vomits, convulsions, double vision and hemiparesia left side, which in the cerebral tomography of revenue was showing injuries compatible with cerebral abscesses; for which he received treatment with antibiotics without improvement for what there takes biopsy of the injuries that reported tuberculomas, specific treatment being initiated later and the primary area being investigated without the same one be detecting. After the first procedural step with evident clinical and radiographic improvement. The tuberculosis in anyone of their forms of presentation must be included within the diagnosis differential of the patients in our endemic countries for this disease. The clinical and radiological diagnosis of cerebral injuries is difficult and single usually it obtains to the diagnosis during a pathology study that shows tuberculomas with caseosa necrosis, epiteliodes cell and the acid alcohol bacilli resistant.

  6. Cerebral Folate Deficiency

    ERIC Educational Resources Information Center

    Gordon, Neil

    2009-01-01

    Cerebral folate deficiency (CFD) is associated with low levels of 5-methyltetrahydrofolate in the cerebrospinal fluid (CSF) with normal folate levels in the plasma and red blood cells. The onset of symptoms caused by the deficiency of folates in the brain is at around 4 to 6 months of age. This is followed by delayed development, with deceleration…

  7. Cerebral Palsy (For Teens)

    MedlinePlus

    ... brain is affected and which parts of the body that section of the brain controls. If CP affects both arms and both legs, ... the case of spastic CP) or to help control seizures. And some might have special surgeries to keep their arms or legs straighter and more ... Coping With Cerebral Palsy Puberty can ...

  8. Reversible cerebral vasoconstriction syndrome.

    PubMed

    Ducros, Anne

    2012-10-01

    Recurrent thunderclap headaches, seizures, strokes, and non-aneurysmal subarachnoid haemorrhage can all reveal reversible cerebral vasoconstriction syndrome. This increasingly recognised syndrome is characterised by severe headaches, with or without other symptoms, and segmental constriction of cerebral arteries that resolves within 3 months. Reversible cerebral vasoconstriction syndrome is supposedly due to a transient disturbance in the control of cerebrovascular tone. More than half the cases occur post partum or after exposure to adrenergic or serotonergic drugs. Manifestations have a uniphasic course, and vary from pure cephalalgic forms to rare catastrophic forms associated with several haemorrhagic and ischaemic strokes, brain oedema, and death. Diagnosis can be hampered by the dynamic nature of clinicoradiological features. Stroke can occur a few days after initial normal imaging, and cerebral vasoconstriction is at a maximum on angiograms 2-3 weeks after clinical onset. The calcium channel blocker nimodipine seems to reduce thunderclap headaches within 48 h of administration, but has no proven effect on haemorrhagic and ischaemic complications. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Reversible cerebral vasoconstriction syndrome.

    PubMed

    Ducros, Anne

    2014-01-01

    Reversible cerebral vasoconstriction syndrome is characterized by severe headaches with or without focal neurologic deficits and/or seizures, and segmental constriction of cerebral arteries that resolves within 3 months. This increasingly recognized syndrome is supposedly due to a transient disturbance in the control of cerebral vascular tone with sympathetic overactivity. It can cause stroke in the young. It affects mainly middle-aged women. More than half the cases occur after exposure to vasoactive substances or during postpartum. The manifestations have a monophasic course, without new clinical symptom after 4 weeks, and range from pure cephalalgic forms with recurrent thunderclap headaches over 1-2 weeks to rare catastrophic forms with multiple hemorrhagic and ischemic strokes, brain edema and death. Diagnosis may be hampered by the dynamic nature of clinicoradiological features. Convexity subarachnoid hemorrhage or stroke may occur a few days after initial normal imaging, and cerebral vasoconstriction is maximal on angiography 2-3 weeks after clinical onset. Symptomatic treatment includes rest and removal of vasoactive substances. Nimodipine has been proposed to reduce thunderclap headaches within 48 hours, but has no proven effect on the hemorrhagic and ischemic complications. © 2014 Elsevier B.V. All rights reserved.

  10. Cerebral Palsy Litigation

    PubMed Central

    Sartwelle, Thomas P.

    2015-01-01

    The cardinal driver of cerebral palsy litigation is electronic fetal monitoring, which has continued unabated for 40 years. Electronic fetal monitoring, however, is based on 19th-century childbirth myths, a virtually nonexistent scientific foundation, and has a false positive rate exceeding 99%. It has not affected the incidence of cerebral palsy. Electronic fetal monitoring has, however, increased the cesarian section rate, with the expected increase in mortality and morbidity risks to mothers and babies alike. This article explains why electronic fetal monitoring remains endorsed as efficacious in the worlds’ labor rooms and courtrooms despite being such a feeble medical modality. It also reviews the reasons professional organizations have failed to condemn the use of electronic fetal monitoring in courtrooms. The failures of tort reform, special cerebral palsy courts, and damage limits to stem the escalating litigation are discussed. Finally, the authors propose using a currently available evidence rule—the Daubert doctrine that excludes “junk science” from the courtroom—as the beginning of the end to cerebral palsy litigation and electronic fetal monitoring’s 40-year masquerade as science. PMID:25183322

  11. [Prothrombotic states and cerebral ischemia].

    PubMed

    Barinagarrementeria, F; González-Duarte, A; Cantú-Brito, C

    1998-01-01

    Hematological disorders per se represent unusual causes of cerebral ischemia, explaining in young people 4% of strokes. Hematological disorders that induce a thrombotic tendency contribute to overall ischemic stroke risk and may directly cause cerebral ischemia in patients without other risk factors. The frequency of cerebral infarctions caused by prothrombotic states is not known. This review will focus on disorders such as prothrombotic coagulopaties, including resistance to activated protein C and antiphospholipid syndrome as cause of cerebral infarction. Cerebral venous thrombosis and cerebral infarction from arterial origin are the most common form of neurological involvement. Pathophysiological mechanism of stroke in these patients are multiple and can include as in antiphospholipid syndrome embolism from valves abnormalities related to hematological disturbance, as well as thrombosis of extracranial or intracranial vessels. Is clear, however, that prothrombotic states could explains a high percentage of cases of those so called cryptogenic cerebral infarction in young people.

  12. The use of reflective and permeable pavements as a potential practice for heat island mitigation and stormwater management

    NASA Astrophysics Data System (ADS)

    Li, H.; Harvey, J. T.; Holland, T. J.; Kayhanian, M.

    2013-03-01

    To help address the built environmental issues of both heat island and stormwater runoff, strategies that make pavements cooler and permeable have been investigated through measurements and modeling of a set of pavement test sections. The investigation included the hydraulic and thermal performance of the pavements. The permeability results showed that permeable interlocking concrete pavers have the highest permeability (or infiltration rate, ˜0.5 cm s-1). The two permeable asphalt pavements showed the lowest permeability, but still had an infiltration rate of ˜0.1 cm s-1, which is adequate to drain rainwater without generating surface runoff during most typical rain events in central California. An increase in albedo can significantly reduce the daytime high surface temperature in summer. Permeable pavements under wet conditions could give lower surface temperatures than impermeable pavements. The cooling effect highly depends on the availability of moisture near the surface layer and the evaporation rate. The peak cooling effect of watering for the test sections was approximately 15-35 °C on the pavement surface temperature in the early afternoon during summer in central California. The evaporative cooling effect on the pavement surface temperature at 4:00 pm on the third day (25 h after watering) was still 2-7 °C lower compared to that on the second day, without considering the higher air temperature on the third day. A separate and related simulation study performed by UCPRC showed that full depth permeable pavements, if designed properly, can carry both light-duty traffic and certain heavy-duty vehicles while retaining the runoff volume captured from an average California storm event. These preliminarily results indicated the technical feasibility of combined reflective and permeable pavements for addressing the built environment issues related to both heat island mitigation and stormwater runoff management.

  13. Heavy Cigarette Smokers in a Chinese Population Display a Compromised Permeability Barrier

    PubMed Central

    Xin, Shujun; Ye, Li; Lv, Chengzhi; Elias, Peter M.

    2016-01-01

    Cigarette smoking is associated with various cutaneous disorders with defective permeability. Yet, whether cigarette smoking influences epidermal permeability barrier function is largely unknown. Here, we measured skin biophysical properties, including permeability barrier homeostasis, stratum corneum (SC) integrity, SC hydration, skin surface pH, and skin melanin/erythema index, in cigarette smokers. A total of 99 male volunteers were enrolled in this study. Smokers were categorized as light-to-moderate (<20 cigarettes/day) or heavy smokers (≥20 cigarettes/day). An MPA5 was used to measure SC hydration and skin melanin/erythema index on the dorsal hand, forehead, and cheek. Basal transepidermal water loss (TEWL) and barrier recovery rates were assessed on the forearm. A Skin-pH-Meter pH900 was used to measure skin surface pH. Our results showed that heavy cigarette smokers exhibited delayed barrier recovery after acute abrogation (1.02% ± 13.06 versus 16.48% ± 6.07), and barrier recovery rates correlated negatively with the number of daily cigarettes consumption (p = 0.0087). Changes in biophysical parameters in cigarette smokers varied with body sites. In conclusion, heavy cigarette smokers display compromised permeability barrier homeostasis, which could contribute, in part, to the increased prevalence of certain cutaneous disorders characterized by defective permeability. Thus, improving epidermal permeability barrier should be considered for heavy cigarette smokers. PMID:27437403

  14. Influence of fly ash fineness and shape on the porosity and permeability of blended cement pastes

    NASA Astrophysics Data System (ADS)

    Sinsiri, Theerawat; Chindaprasirt, Prinya; Jaturapitakkul, Chai

    2010-12-01

    The effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes were investigated. Pulverized coal combustion (PCC) fly ash and fluidized bed coal combustion (FBC) fly ash classified into three different finenesses were used. River sand with particle size distribution similar to that of fly ash was also used for comparison. Portland cement was replaced with fly ash and ground sand at the dosages of 0, 20wt%, and 40wt%. A water-to-binder ratio (w/b) of 0.35 was used throughout the experiment. The results show that the porosity and air permeability of the pastes are influenced by the shape, fineness, and replacement level of fly ash. The porosity and air permeability of FBC fly ash pastes are higher than those of PCC fly ash pastes. This is due to the higher irregular shape and surface of FBC fly ash compared to the spherical shape and relatively smooth surface of PCC fly ash. The porosity increases with the increase in fly ash replacement level and decreases with the increase in its fineness. The permeability of PCC fly ash pastes decreases with the increase in replacement level and fineness, while for FBC fly ash, the permeability increases with the increase in replacement level. Decreases in porosity and permeability are due to a combined effect of the packing of fine particles and the reaction of fly ash.

  15. Cerebral Venous Thrombosis.

    PubMed

    Sassi, Samia Ben; Touati, Nahla; Baccouche, Hela; Drissi, Cyrine; Romdhane, Neila Ben; Hentati, Fayçal

    2016-01-01

    Data regarding cerebral venous thrombosis in North Africa are scarce. This study aims to identify the clinical features, risk factors, outcome, and prognosis of cerebral venous thrombosis in Tunisia. Data of 160 patients with radiologically confirmed cerebral venous thrombosis, hospitalized in Mongi Ben Hmida National Institute of Neurology (Tunis, Tunisia), were retrospectively collected and analyzed. The mean age was 37.3 years with a female predominance (83.1%). The mode of onset was subacute in most cases (56.2%). Headache was the most common symptom (71.3%), and focal neurologic symptoms were the main clinical presentation (41.8%). The most common sites of thrombosis were the superior sagittal sinus (65%) and the lateral sinus (60.6%). More than 1 sinus was involved in 114 (71.2%) patients. Parenchymal lesions observed in 85 (53.1%) patients did not correlate with cerebral venous thrombosis extent. Major risk factors were obstetric causes (pregnancy and puerperium) found in 46 (38.6% of women aged <50 years) patients, followed by anemia (28.1%) and congenital or acquired thrombophilia (16.2%). Mortality rate was of 6.6%. Good outcome at 6 months (modified Rankin Scale ≤2) was observed in 105 (87.5%)of 120 patients available for follow-up. Predictors of poor outcome were altered consciousness and elevated plasma C-reactive protein levels. Clinical and radiologic presentation of cerebral venous thrombosis in Tunisia was quite similar to other parts of the world with, however, a particularly high frequency of obstetric causes. Plasma C-reactive protein level should be considered as a prognostic factor in CVT.

  16. Cerebral White Matter

    PubMed Central

    Schmahmann, Jeremy D.; Smith, Eric E.; Eichler, Florian S.; Filley, Christopher M.

    2013-01-01

    Lesions of the cerebral white matter (WM) result in focal neurobehavioral syndromes, neuropsychiatric phenomena, and dementia. The cerebral WM contains fiber pathways that convey axons linking cerebral cortical areas with each other and with subcortical structures, facilitating the distributed neural circuits that subserve sensorimotor function, intellect, and emotion. Recent neuroanatomical investigations reveal that these neural circuits are topographically linked by five groupings of fiber tracts emanating from every neocortical area: (1) cortico-cortical association fibers; (2) corticostriatal fibers; (3) commissural fibers; and cortico-subcortical pathways to (4) thalamus and (5) pontocerebellar system, brain stem, and/or spinal cord. Lesions of association fibers prevent communication between cortical areas engaged in different domains of behavior. Lesions of subcortical structures or projection/striatal fibers disrupt the contribution of subcortical nodes to behavior. Disconnection syndromes thus result from lesions of the cerebral cortex, subcortical structures, and WM tracts that link the nodes that make up the distributed circuits. The nature and the severity of the clinical manifestations of WM lesions are determined, in large part, by the location of the pathology: discrete neurological and neuropsychiatric symptoms result from focal WM lesions, whereas cognitive impairment across multiple domains—WM dementia—occurs in the setting of diffuse WM disease. We present a detailed review of the conditions affecting WM that produce these neurobehavioral syndromes, and consider the pathophysiology, clinical effects, and broad significance of the effects of aging and vascular compromise on cerebral WM, in an attempt to help further the understanding, diagnosis, and treatment of these disorders. PMID:18990132

  17. Stereochemistry Balances Cell Permeability and Solubility in the Naturally Derived Phepropeptin Cyclic Peptides.

    PubMed

    Schwochert, Joshua; Lao, Yongtong; Pye, Cameron R; Naylor, Matthew R; Desai, Prashant V; Gonzalez Valcarcel, Isabel C; Barrett, Jaclyn A; Sawada, Geri; Blanco, Maria-Jesus; Lokey, R Scott

    2016-08-11

    Cyclic peptide (CP) natural products provide useful model systems for mapping "beyond-Rule-of-5" (bRo5) space. We identified the phepropeptins as natural product CPs with potential cell permeability. Synthesis of the phepropeptins and epimeric analogues revealed much more rapid cellular permeability for the natural stereochemical pattern. Despite being more cell permeable, the natural compounds exhibited similar aqueous solubility as the corresponding epimers, a phenomenon explained by solvent-dependent conformational flexibility among the natural compounds. When analyzing the polarity of the solution structures we found that neither the number of hydrogen bonds nor the total polar surface area accurately represents the solvation energies of the high and low dielectric conformations. This work adds to a growing number of natural CPs whose solvent-dependent conformational behavior allows for a balance between aqueous solubility and cell permeability, highlighting structural flexibility as an important consideration in the design of molecules in bRo5 chemical space.

  18. Ion permeability of polydopamine films revealed using a Prussian blue-based electrochemical method.

    PubMed

    Gao, Bowen; Su, Lei; Tong, Ying; Guan, Miao; Zhang, Xueji

    2014-11-06

    Polydopamine (PDA) is fast becoming a popular surface modification technique. Detailed understanding of the ion permeability properties of PDA films will improve their applications. Herein, we report for the first time the thickness-independent ion permeability of PDA films using a Prussian blue (PB)-based electrochemical method. In this method, PDA films are deposited via ammonium persulfate-induced dopamine polymerization onto a PB electrode. The ion permeability of the PDA films can thus be detected by observing the changes in electrochemical behaviors of the PB coated by PDA films. On the basis of this method, it was unexpectedly found that the PDA films with thickness greater than 45 nm (e.g., ~60 and ~113 nm) can exhibit pH-switchable but thickness-insensitive permeability to monovalent cations such as potassium and sodium ions. These observations clearly indicate the presence of a continuous network of interconnected intermolecular voids within PDA films, regardless of film thickness.

  19. Prediction of permeability of regular scaffolds for skeletal tissue engineering: a combined computational and experimental study.

    PubMed

    Truscello, S; Kerckhofs, G; Van Bael, S; Pyka, G; Schrooten, J; Van Oosterwyck, H

    2012-04-01

    Scaffold permeability is a key parameter combining geometrical features such as pore shape, size and interconnectivity, porosity and specific surface area. It can influence the success of bone tissue engineering scaffolds, by affecting oxygen and nutrient transport, cell seeding efficiency, in vitro three-dimensional (3D) cell culture and, ultimately, the amount of bone formation. An accurate and efficient prediction of scaffold permeability would be highly useful as part of a scaffold design process. The aim of this study was (i) to determine the accuracy of computational fluid dynamics (CFD) models for prediction of the permeability coefficient of three different regular Ti6Al4V scaffolds (each having a different porosity) by comparison with experimentally measured values and (ii) to verify the validity of the semi-empirical Kozeny equation to calculate the permeability analytically. To do so, five CFD geometrical models per scaffold porosity were built, based on different geometrical inputs: either based on the scaffold's computer-aided design (CAD) or derived from 3D microfocus X-ray computed tomography (micro-CT) data of the additive manufactured (AM) scaffolds. For the latter the influence of the spatial image resolution and the image analysis algorithm used to determine the scaffold's architectural features on the predicted permeability was analysed. CFD models based on high-resolution micro-CT images could predict the permeability coefficients of the studied scaffolds: depending on scaffold porosity and image analysis algorithm, relative differences between measured and predicted permeability values were between 2% and 27%. Finally, the analytical Kozeny equation was found to be valid. A linear correlation between the ratio Φ(3)/S(s)(2) and the permeability coefficient k was found for the predicted (by means of CFD) as well as measured values (relative difference of 16.4% between respective Kozeny coefficients), thus resulting in accurate and efficient

  20. Permeable Reactive Zones for Groundwater Remediation

    EPA Science Inventory

    The presentation will cover aspects of the application of permeable reactive zones to treat contaminated ground water. Specific field studies will be discussed covering both granular iron-based and organic carbon-based reactive barriers. Specific contaminants addressed include:...