355 research outputs found
Effective slip over superhydrophobic surfaces in thin channels
Superhydrophobic surfaces reduce drag by combining hydrophobicity and
roughness to trap gas bubbles in a micro- and nanoscopic texture. Recent work
has focused on specific cases, such as striped grooves or arrays of pillars,
with limited theoretical guidance. Here, we consider the experimentally
relevant limit of thin channels and obtain rigorous bounds on the effective
slip length for any two-component (e.g. low-slip and high-slip) texture with
given area fractions. Among all anisotropic textures, parallel stripes attain
the largest (or smallest) possible slip in a straight, thin channel for
parallel (or perpendicular) orientation with respect to the mean flow. For
isotropic (e.g. chessboard or random) textures, the Hashin-Strikman conditions
further constrain the effective slip. These results provide a framework for the
rational design of superhydrophobic surfaces.Comment: 4+ page
Lattice Boltzmann simulations in microfluidics: probing the no-slip boundary condition in hydrophobic, rough, and surface nanobubble laden microchannels
In this contribution we review recent efforts on investigations of the effect
of (apparent) boundary slip by utilizing lattice Boltzmann simulations. We
demonstrate the applicability of the method to treat fundamental questions in
microfluidics by investigating fluid flow in hydrophobic and rough
microchannels as well as over surfaces covered by nano- or microscale gas
bubbles.Comment: 11 pages, 6 figure
Crosstalk between Mitochondrial and Sarcoplasmic Reticulum Ca2+ Cycling Modulates Cardiac Pacemaker Cell Automaticity
Mitochondria dynamically buffer cytosolic Ca(2+) in cardiac ventricular cells and this affects the Ca(2+) load of the sarcoplasmic reticulum (SR). In sinoatrial-node cells (SANC) the SR generates periodic local, subsarcolemmal Ca(2+) releases (LCRs) that depend upon the SR load and are involved in SANC automaticity: LCRs activate an inward Na(+)-Ca(2+) exchange current to accelerate the diastolic depolarization, prompting the ensemble of surface membrane ion channels to generate the next action potential (AP).To determine if mitochondrial Ca(2+) (Ca(2+) (m)), cytosolic Ca(2+) (Ca(2+) (c))-SR-Ca(2+) crosstalk occurs in single rabbit SANC, and how this may relate to SANC normal automaticity.Inhibition of mitochondrial Ca(2+) influx into (Ru360) or Ca(2+) efflux from (CGP-37157) decreased [Ca(2+)](m) to 80 ± 8% control or increased [Ca(2+)](m) to 119 ± 7% control, respectively. Concurrent with inhibition of mitochondrial Ca(2+) influx or efflux, the SR Ca(2+) load, and LCR size, duration, amplitude and period (imaged via confocal linescan) significantly increased or decreased, respectively. Changes in total ensemble LCR Ca(2+) signal were highly correlated with the change in the SR Ca(2+) load (r(2) = 0.97). Changes in the spontaneous AP cycle length (Ru360, 111 ± 1% control; CGP-37157, 89 ± 2% control) in response to changes in [Ca(2+)](m) were predicted by concurrent changes in LCR period (r(2) = 0.84).A change in SANC Ca(2+) (m) flux translates into a change in the AP firing rate by effecting changes in Ca(2+) (c) and SR Ca(2+) loading, which affects the characteristics of spontaneous SR Ca(2+) release
Anisotropic colloids through non-trivial buckling
We present a study on buckling of colloidal particles, including
experimental, theoretical and numerical developments. Oil-filled thin shells
prepared by emulsion templating show buckling in mixtures of water and ethanol,
due to dissolution of the core in the external medium. This leads to
conformations with a single depression, either axisymmetric or polygonal
depending on the geometrical features of the shells. These conformations could
be theoretically and/or numerically reproduced in a model of homogeneous
spherical thin shells with bending and stretching elasticity, submitted to an
isotropic external pressure.Comment: submitted to EPJ
A Dissipative-Particle-Dynamics Model for Simulating Dynamics of Charged Colloid
A mesoscopic colloid model is developed in which a spherical colloid is
represented by many interacting sites on its surface. The hydrodynamic
interactions with thermal fluctuations are taken accounts in full using
Dissipative Particle Dynamics, and the electrostatic interactions are simulated
using Particle-Particle-Particle Mesh method. This new model is applied to
investigate the electrophoretic mobility of a charged colloid under an external
electric field, and the influence of salt concentration and colloid charge are
systematically studied. The simulation results show good agreement with
predictions from the electrokinetic theory.Comment: 17 pages, 8 figures, submitted to the proceedings of High Performance
Computing in Science & Engineering '1
Equitable and Effective Climate Policy: Integrating Less Developed Countries into a Global Climate Agreement
ISSN:1612-4804ISSN:1612-481
Results of Modeling Experiments in Designing Immuno-Enzyme Test-System for the Detection of Antibodies to <I>Yersinia pestis</I> F1 (ELISA-Ab-F1 <I>Yersinia pestis</I>)
Designed is immuno-enzyme test-system for the detection of antibodies to Yersinia pestis capsular antigen F1 – “ELISA-Ab-F1
Yersinia pestis”. On the model of laboratory mice it is demonstrated that this test-system is highly specific, its diagnostic titer being 1/320.Diagnostic value of the test-system is 83.3–88.9 % as revealed through investigations of sera and blood suspension samples, swabs of thoracic organs of animals, inoculated with live plague vaccine, strains of plague microbe, containing and deprived of pFra, as well as with heterologous bacteria
Exposure to bisphosphonates and risk of common non-gastrointestinal cancers: series of nested case–control studies using two primary-care databases
Background: Bisphosphonates are the most commonly prescribed osteoporosis drugs but long-term effects are unclear, although antitumour properties are known from preclinical studies.
Methods: Nested case–control studies were conducted to investigate bisphosphonate use and risks of common nongastrointestinal cancers (breast, prostate, lung, bladder, melanoma, ovarian, pancreas, uterus and cervical). Patients 50 years and older, diagnosed with primary cancers between 1997 and 2011, were matched to five controls using the UK practice-based QResearch and Clinical Practice Research Datalink (CPRD) databases. The databases were analysed separately and the results combined.
Results: A total of 91 556 and 88 845 cases were identified from QResearch and CPRD, respectively. Bisphosphonate use was associated with reduced risks of breast (odds ratio (OR): 0.92, 95% confidence interval (CI): 0.87–0.97), prostate (OR: 0.87, 95% CI: 0.79–0.96) and pancreatic (OR: 0.79, 95% CI: 0.68–0.93) cancers in the combined analyses, but no significant trends with duration. For alendronate, reduced risk associations were found for prostate cancer in the QResearch (OR: 0.81, 95% CI: 0.70–0.93) and combined (OR: 0.84, 95% CI: 0.75–0.93) analyses (trend with duration P-values 0.009 and 0.001). There were no significant associations from any of the other analyses.
Conclusion: In this series of large population-based case–control studies, bisphosphonate use was not associated with increased risks for any common non-gastrointestinal cancers
Integrin β3 Crosstalk with VEGFR Accommodating Tyrosine Phosphorylation as a Regulatory Switch
Integrins mediate cell adhesion, migration, and survival by connecting intracellular machinery with the surrounding extracellular matrix. Previous studies demonstrated the importance of the interaction between β3 integrin and VEGF type 2 receptor (VEGFR2) in VEGF-induced angiogenesis. Here we present in vitro evidence of the direct association between the cytoplasmic tails (CTs) of β3 and VEGFR2. Specifically, the membrane-proximal motif around 801YLSI in VEGFR2 mediates its binding to non-phosphorylated β3CT, accommodating an α-helical turn in integrin bound conformation. We also show that Y747 phosphorylation of β3 enhances the above interaction. To demonstrate the importance of β3 phosphorylation in endothelial cell functions, we synthesized β3CT-mimicking Y747 phosphorylated and unphosphorylated membrane permeable peptides. We show that a peptide containing phospho-Y747 but not F747 significantly inhibits VEGF-induced signaling and angiogenesis. Moreover, phospho-Y747 peptide exhibits inhibitory effect only in WT but not in β3 integrin knock-out or β3 integrin knock-in cells expressing β3 with two tyrosines substituted for phenylalanines, demonstrating its specificity. Importantly, these peptides have no effect on fibroblast growth factor receptor signaling. Collectively these data provide novel mechanistic insights into phosphorylation dependent cross-talk between integrin and VEGFR2
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