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Spatial model of convective solute transport in brain extracellular space does not support a "glymphatic" mechanism.
A "glymphatic system," which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier-Stokes and convection-diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces. Major model parameters include para-arterial and paravenous pressures, ECS volume fraction, solute diffusion coefficient, and astrocyte foot-process water permeability. The model predicts solute accumulation and clearance from the ECS after a step change in solute concentration in para-arterial fluid. The principal and robust conclusions of the model are as follows: (a) significant convective transport requires a sustained pressure difference of several mmHg between the para-arterial and paravenous fluid and is not affected by pulsatile pressure fluctuations; (b) astrocyte endfoot water permeability does not substantially alter the rate of convective transport in ECS as the resistance to flow across endfeet is far greater than in the gaps surrounding them; and (c) diffusion (without convection) in the ECS is adequate to account for experimental transport studies in brain parenchyma. Therefore, our modeling results do not support a physiologically important role for local parenchymal convective flow in solute transport through brain ECS
A simple method for enhanced vibration-based structural health monitoring
This study suggests a novel method for structural vibration-based health monitoring for beams which only utilises the first natural frequency of the beam in order to detect and localise a defect. The method is based on the application of a static force in different positions along the beam. It is shown that the application of a static force on a damaged beam induces stresses at the defect which in turn cause changes in the structural natural frequencies. A very simple procedure for damage detection is suggested which uses a static force applied in just one point, in the middle of the beam. Localisation is made using two additional application points of the static force. Damage is modelled as a small notch through the whole width of the beam. The method is demonstrated and validated numerically, using a finite element model of the beam, and experimentally for a simply supported beam. Our results show that the frequency variation with the change of the force application point can be used to detect and in the same time localize very precisely even a very small defect. The method can be extended for health monitoring of other more complicated structures
A simple method for enhanced vibration-based structural health monitoring
This study suggests a novel method for structural vibration-based health monitoring for beams which only utilises the first natural frequency of the beam in order to detect and localise a defect. The method is based on the application of a static force in different positions along the beam. It is shown that the application of a static force on a damaged beam induces stresses at the defect which in turn cause changes in the structural natural frequencies. A very simple procedure for damage detection is suggested which uses a static force applied in just one point, in the middle of the beam. Localisation is made using two additional application points of the static force. Damage is modelled as a small notch through the whole width of the beam. The method is demonstrated and validated numerically, using a finite element model of the beam, and experimentally for a simply supported beam. Our results show that the frequency variation with the change of the force application point can be used to detect and in the same time localize very precisely even a very small defect. The method can be extended for health monitoring of other more complicated structures
The role of the resonance in the reaction
We investigate the photo-production in the reaction within the effective Lagrangian method near
threshold. In addition to the "background" contributions from the contact,
channel exchange, and channel nucleon pole terms, which were
already considered in previous works, the contribution from the nucleon
resonance (spin-parity ) is also considered. We show
that the inclusion of the nucleon resonance leads to a fairly good
description of the new LEPS differential cross section data, and that these
measurements can be used to determine some of the properties of this latter
resonance. However, serious discrepancies appear when the predictions of the
model are compared to the photon-beam asymmetry also measured by the LEPS
Collaboration.Comment: 9 pages,6 figures, 1 tabl
The Impacts of Climate Change on Chinese Agriculture - Phase II National Level Study final report
Properties of a highly birefringent photonic crystal fiber
Author name used in this publication: J. JuAuthor name used in this publication: W. JinAuthor name used in this publication: M. S. Demokan2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 µm
Author name used in this publication: M. Suleyman Demokan2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Two-mode operation in highly birefringent photonic crystal fiber
Author name used in this publication: J. JuAuthor name used in this publication: W. JinAuthor name used in this publication: M. S. Demokan2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Inhibition of Inducible Nitric Oxide Synthase, Cycleooxygenase-2 and Lipid Peroxidation by Methanol Extract of Pericarpium Zanthoxyli
Purpose: To explore the antioxidant properties of the methanol extract of Pericarpium Zanthoxyli and its effect on inducible nitric oxide synthase (iNOS), cycleooxygenase-2 (COX-2) and lipopolysaccharides (LPS)-induced cell damage in macrophage cells.Methods: Anti-oxidant activities were tested by measuring free radical scavenging activity (DPPH, NO) and lipid peroxidation levels. The mechanism of anti-oxidant action of Pericarpium Zanthoxyli extractwas determined by Western blot analysis for iNOS and COX-2 expression in LPS-stimulated RAW 264.7 cells.Results: Pericarpium Zanthoxyli extract contained anti-oxidant components including phenolics (2.456 mg/g), flavonoids (0.127 mg/g) and anthocyanins (20.34 mg/g). The extract exerted significant radicalscavenging activity in a dose-dependent manner. It also inhibited lipid peroxidation and exerted dramatic reducing power (28.9-fold compared with control at a concentration of 1 mg/ml). Production of iNOS induced by LPS was significantly (p < 0.05) inhibited by the extract, suggesting that the extract inhibits nitric oxide (NO) production by suppressing iNOS expression. Strikingly, COX-2 induced by LPS was also significantly (p < 0.05) inhibited by the extract.Conclusion: These results suggest that the methanol extract of Pericarpium Zanthoxyli exerts significant anti-oxidant activity via inhibiting free radicals, iNOS and lipid peroxidation as well as by inhibition of COX-2 enzyme.Keywords: Pericarpium Zanthoxyli, Nitric oxide, iNOS, COX-2, Lipid peroxidation, Antioxidan
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