39 results match your criteria thickness converges

Bio-Design, Fabrication and Analysis of a Flexible Valve.

Biomimetics (Basel) 2022 Jul 14;7(3). Epub 2022 Jul 14.

Key Laboratory of Bionic Engineering, Ministry of Education, Jilin University, Changchun 130022, China.

Fluid-driven soft robots offer many advantages over robots driven by other means in terms of universal preparation processes and high-power density ratios, but are largely limited by their inherit characteristics of rigid pressure sources, fluid control elements and complex fluid pipelines. In this paper, inspired by the principle of biofluid control and actuation, we combine simulation analysis and experimental validation to conduct a bionic design study of an efficient flexible fluid control valve with different actuation diaphragm structures. Under critical flexural load, the flexible valve undergoes a continuous flexural instability overturning process, generating a wide range of displacements. Read More

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Constrained 3D gravity interface inversion for layer structures: implications for assessment of hydrocarbon sources in the Ziway-Shala Lakes basin, Central Main Ethiopian rift.

Heliyon 2022 Jul 19;8(7):e09980. Epub 2022 Jul 19.

School of Earth Science, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.

Multi layer 3D gravity inversion for layered structures and density interfaces are performed in the Central Main Ethiopian rift bounded between 3800'-3930' E and 700'-830' N. The inversion is carried out in wave number domain using Parker-Oldenburg algorithm and is constrained with initial model information. The previous studies in the region focused on mapping crustal structures and Moho depths and least is known about the shallow earth. Read More

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A New Nonlinear Photothermal Iterative Theory for Port-Wine Stain Detection.

Int J Environ Res Public Health 2022 05 5;19(9). Epub 2022 May 5.

Shaanxi Key Laboratory of Ultrasound, School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China.

The development of appropriate photothermal detection of skin diseases to meet complex clinical demands is an urgent challenge for the prevention and therapy of skin cancer. An extensive body of literature has ignored all high-order harmonics above the second order and their influences on low-order harmonics. In this paper, a new iterative numerical method is developed for solving the nonlinear thermal diffusion equation to improve nonlinear photothermal detection for the noninvasive assessment of the thickness of port-wine stain (PWS). Read More

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Midsagittal corpus callosal thickness and cognitive impairment in Parkinson's disease.

Eur J Neurosci 2022 04 22;55(7):1859-1872. Epub 2022 Mar 22.

Research Centre for the Neurosciences of Ageing, Academic Unit of Psychiatry and Addiction Medicine, School of Clinical Medicine, Medical School, Australian National University, Canberra, ACT, Australia.

People diagnosed with Parkinson's disease (PD) can experience significant neuropsychiatric symptoms, including cognitive impairment and dementia, the neuroanatomical substrates of which are not fully characterised. Symptoms associated with cognitive impairment and dementia in PD may relate to direct structural changes to the corpus callosum via primary white matter pathology or as a secondary outcome due to the degeneration of cortical regions. Using magnetic resonance imaging, the corpus callosum can be investigated at the midsagittal plane, where it converges to a contiguous mass and is not intertwined with other tracts. Read More

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Stochastic Navier-Stokes Equations on a Thin Spherical Domain.

Appl Math Optim 2021 11;84(2):1971-2035. Epub 2020 Jul 11.

School of Mathematics and Statistics, University of New South Wales, Sydney, NSW 2052 Australia.

Incompressible Navier-Stokes equations on a thin spherical domain along with free boundary conditions under a random forcing are considered. The convergence of the martingale solution of these equations to the martingale solution of the stochastic Navier-Stokes equations on a sphere as the thickness converges to zero is established. Read More

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Swimming droplets in 1D geometries: an active Bretherton problem.

Soft Matter 2021 Jul;17(27):6646-6660

UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 75005 Paris, France.

We investigate experimentally the behavior of self-propelled water-in-oil droplets, confined in capillaries of different square and circular cross-sections. The droplet's activity comes from the formation of swollen micelles at its interface. In straight capillaries the velocity of the droplet decreases with increasing confinement. Read More

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A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs. Borophene.

Nanomaterials (Basel) 2021 May 11;11(5). Epub 2021 May 11.

Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Alessandria Campus, Viale Teresa Michel 5, 15121 Alessandria, Italy.

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed combined atomistic continuum multi-scale modeling to explore the effective thermal conductivity of polymer nanocomposites made of polydimethylsiloxane (PDMS) polymer as the matrix and graphene and borophene as nanofillers. PDMS is a versatile polymer due to its chemical inertia, flexibility and a wide range of properties that can be tuned during synthesis. Read More

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Numerical Analysis of Thermophoresis of a Charged Spheroidal Colloid in Aqueous Media.

Micromachines (Basel) 2021 Feb 23;12(2). Epub 2021 Feb 23.

Key Laboratory of High Performance Ship Technology, Ministry of Education, School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430063, China.

Thermophoresis of charged colloids in aqueous media has wide applications in biology. Most existing studies of thermophoresis focused on spherical particles, but biological compounds are usually non-spherical. The present paper reports a numerical analysis of the thermophoresis of a charged spheroidal colloid in aqueous media. Read More

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February 2021

X-ray mirror figure correction by differential deposition and off-line metrology.

J Synchrotron Radiat 2019 Nov 10;26(Pt 6):1872-1878. Epub 2019 Oct 10.

X-ray Optics Group, ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38043 Grenoble, France.

The surface figure error of a hard X-ray mirror was improved by combining differential deposition and off-line metrology tools. Thin Cr layers were deposited on flat substrates by DC magnetron sputtering. The substrates were moved in front of a beam-defining aperture. Read More

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November 2019

Confinement-Induced Stiffening of Elastomer Thin Films.

J Phys Chem B 2018 Nov 16;122(47):10767-10773. Epub 2018 Nov 16.

While entropy is understood to dictate the elastic mechanics of elastomers, a consensus has not been reached regarding why they stiffen when confined to thin films or even the magnitude of this effect. Here, we present a combined computational and experimental approach to measure the confinement-induced stiffening of thin elastomer films using nanoindentation. First, we use finite element computations to modify the adhesion-free contact model to include the presence of a rigid substrate and verify this correction using indentation experiments on macroscopic polydimethylsiloxane (PDMS) films. Read More

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November 2018

Signaling by FGF Receptor 2, Not FGF Receptor 1, Regulates Myelin Thickness through Activation of ERK1/2-MAPK, Which Promotes mTORC1 Activity in an Akt-Independent Manner.

J Neurosci 2017 03 13;37(11):2931-2946. Epub 2017 Feb 13.

Department of Neuroscience, University of Connecticut Medical School, Farmington, Connecticut 06030

FGF signaling has emerged as a significant "late-stage" regulator of myelin thickness in the CNS, independent of oligodendrocyte differentiation. Therefore, it is critically important to identify the specific FGF receptor type and its downstream signaling molecules in oligodendrocytes to obtain better insights into the regulatory mechanisms of myelin growth. Here, we show that FGF receptor type 2 (FGFR2) is highly enriched at the paranodal loops of myelin. Read More

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Focal temporal pole atrophy and network degeneration in semantic variant primary progressive aphasia.

Brain 2017 02 31;140(2):457-471. Epub 2016 Dec 31.

Department of Neurology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, USA

A wealth of neuroimaging research has associated semantic variant primary progressive aphasia with distributed cortical atrophy that is most prominent in the left anterior temporal cortex; however, there is little consensus regarding which region within the anterior temporal cortex is most prominently damaged, which may indicate the putative origin of neurodegeneration. In this study, we localized the most prominent and consistent region of atrophy in semantic variant primary progressive aphasia using cortical thickness analysis in two independent patient samples (n = 16 and 28, respectively) relative to age-matched controls (n = 30). Across both samples the point of maximal atrophy was located in the same region of the left temporal pole. Read More

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February 2017

Thickness-dependent glass transition temperature and charge mobility in cross-linked polyfluorene thin films.

Phys Rev E 2016 Nov 4;94(5-1):052503. Epub 2016 Nov 4.

School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China.

We report thickness-dependent glass transition temperature (T_{g}) and charge mobility in cross-linked thin films made of conjugated polymer poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB). Monotonic T_{g} depressions with reducing film thickness in thermally and UV cross-linked TFB thin films supported on Si-SiOx substrates are observed through ellipsometry measurements, suggesting that a surface mobile layer with enhanced chain dynamics still exists in cross-linked TFB thin films, even with a high cross-linking percentage. Data fitting using a three-layer model shows that the T_{g} in the interface, bulk and surface layer both increases with increasing cross-linking, while the thickness of the interface and surface layer increases and reduces, respectively. Read More

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November 2016

Theoretical Study on the Dynamic Behavior of a Plate-Like Micro-Cantilever with Multiple Particles Attached.

PLoS One 2016 29;11(3):e0151821. Epub 2016 Mar 29.

School of Mechanical and Electronic Engineering, Harbin Institute of Technology, Harbin 150001, China.

In this study, the dynamic characteristics of a plate-like micro-cantilever beam attached with multiple concentrated masses are studied. The vibration modes of the cantilever plate are represented by combinations of beam functions. Using classical mechanics (the effect of size is not considered) and the corrected Cosserat's theorem (the effect of size is considered), we employ the Lagrange equations to establish a dynamic model of the plate-like micro-cantilever beam attached with multiple concentrated masses. Read More

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A comparison of no-slip, stress-free and inviscid models of rapidly rotating fluid in a spherical shell.

Sci Rep 2016 Mar 16;6:22812. Epub 2016 Mar 16.

School of Mathematics, University of Leeds, Leeds, LS2 9JT, UK.

We investigate how the choice of either no-slip or stress-free boundary conditions affects numerical models of rapidly rotating flow in Earth's core by computing solutions of the weakly-viscous magnetostrophic equations within a spherical shell, driven by a prescribed body force. For non-axisymmetric solutions, we show that models with either choice of boundary condition have thin boundary layers of depth E(1/2), where E is the Ekman number, and a free-stream flow that converges to the formally inviscid solution. At Earth-like values of viscosity, the boundary layer thickness is approximately 1 m, for either choice of condition. Read More

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Colloidal interactions in a homeotropic nematic cell with different elastic constants.

Phys Rev E Stat Nonlin Soft Matter Phys 2015 Oct 26;92(4):042505. Epub 2015 Oct 26.

Bogolyubov Institute for Theoretical Physics, NAS of Ukraine, Metrologichna 14-b, Kyiv 03680,Ukraine.

We propose a theoretical description of the interaction mediated by a nematic-liquid-crystal host with different Frank elastic constants. A general expression for the energy of such an interaction between colloidal particles of arbitrary size and shape suspended in a homeotropic cell is obtained. In the cells of large thickness, the presented potential converges to that found previously for small particles in the nematic bulk. Read More

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October 2015

Retinal Nerve Fiber Layer Converges More Convexly on Normal Smaller Optic Nerve Head.

J Glaucoma 2015 Aug;24(6):448-54

Department of Ophthalmology and Visual Science, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.

Purpose: To investigate retinal nerve fiber layer (RNFL) configuration in the optic nerve head (ONH) and peripapillary area according to disc size and to determine whether it explains cup discrepancy among eyes with different disc sizes.

Methods: Horizontal and vertical RNFL curvature and mean thickness were measured using confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph) in 63 normal subjects grouped by disc size. Average and quadrant RNFL thickness, disc size, average cup-to-disc ratio (CDR), and convergence angle at the optic disc were also measured using Cirrus HD-optical coherence tomography. Read More

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Thickness-shear modes of an elliptical, contoured AT-cut quartz resonator.

IEEE Trans Ultrason Ferroelectr Freq Control 2013 Jun;60(6):1192-8

We study free vibrations of an elliptical crystal resonator of AT-cut quartz with an optimal ratio between the semi-major and semi-minor axes as defined by Mindlin. The resonator is contoured with a quadratic thickness variation. The scalar equation for thickness-shear modes in an AT-cut quartz plate by Tiersten and Smythe is used. Read More

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Mobility improvement and temperature dependence in MoSe2 field-effect transistors on parylene-C substrate.

ACS Nano 2014 May 16;8(5):5079-88. Epub 2014 Apr 16.

Department of Physics and Astronomy, Wayne State University , Detroit, Michigan 48201, United States.

We report low-temperature scanning tunneling microscopy characterization of MoSe2 crystals and the fabrication and electrical characterization of MoSe2 field-effect transistors on both SiO2 and parylene-C substrates. We find that the multilayer MoSe2 devices on parylene-C show a room-temperature mobility close to the mobility of bulk MoSe2 (100-160 cm(2) V(-1) s(-1)), which is significantly higher than that on SiO2 substrates (≈50 cm(2) V(-1) s(-1)). The room-temperature mobility on both types of substrates are nearly thickness-independent. Read More

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Theory of elastic interaction between arbitrary colloidal particles in confined nematic liquid crystals.

Phys Rev E Stat Nonlin Soft Matter Phys 2012 Dec 26;86(6 Pt 1):061703. Epub 2012 Dec 26.

Bogolyubov Institute for Theoretical Physics, NAS Ukraine, Metrologichna 14-b, Kyiv 03680, Ukraine.

We develop the method proposed by Chernyshuk and Lev [Phys. Rev. E 81, 041701 (2010)] for theoretical investigation of elastic interactions between colloidal particles of arbitrary shape and chirality (polar as well as azimuthal anchoring) in the confined nematic liquid crystal (NLC). Read More

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December 2012

Competition between substrate-mediated π-π stacking and surface-mediated T(g) depression in ultrathin conjugated polymer films.

Eur Phys J E Soft Matter 2012 Dec 14;35(12):9807. Epub 2012 Dec 14.

Department of Physics and Astronomy, University of Sheffield, UK.

We report surface and interface effects in dynamics and chain conformation in the thin film of conjugated polymer PCDTBT. To probe dynamic anomalies, we measure the glass transition temperature (T(g)) of PCDTBT films as a function of thickness, and find that there is a significant depression in T(g) for films less than 100 nm thick; a result qualitatively similar to that observed in many other polymer film systems. However, for films less than 40 nm, the T(g) converges to a constant value of 20 K below its bulk value. Read More

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December 2012

Time-reversed ultrasonically encoded optical focusing into tissue-mimicking media with thickness up to 70 mean free paths.

J Biomed Opt 2011 Aug;16(8):086009

Washington University in St. Louis, Department of Biomedical Engineering, Optical Imaging Laboratory, St. Louis, Missouri 63130, USA.

In turbid media such as biological tissue, multiple scattering hinders direct light focusing at depths beyond one transport mean free path. As a solution to this problem, time-reversed ultrasonically encoded (TRUE) optical focusing is proposed based on ultrasonic encoding of diffused laser light and optical time reversal. In TRUE focusing, a laser beam of long coherence length illuminates a turbid medium, where the incident light undergoes multiple scattering and part of it gets ultrasonically encoded within the ultrasonic focal zone. Read More

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Monte Carlo simulation of atom diffusion via vacancies in nanofilms with a model simple cubic lattice system.

J Nanosci Nanotechnol 2011 Mar;11(3):2376-83

Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan.

Monte Carlo simulation was employed to investigate correlation factors of atoms (f(A)) diffusing via vacancies in nanofilms possessing a simple cubic lattice that was selected as a model system. The correlation factors change significantly with varying the film thickness, as well as jump frequency ratios. When the film thickness is sufficiently large, f(A) approaches 0. Read More

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Molecular modeling of intermolecular and intramolecular excluded volume interactions for polymers at interfaces.

J Chem Phys 2009 Dec;131(24):244115

Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, Wageningen 6703HB, The Netherlands.

A hybrid modeling approach is proposed for inhomogeneous polymer solutions. The method is illustrated for the depletion problem with polymer chains up to N=10(3) segments in semidilute solutions and good solvent conditions. In a three-dimensional volume, a set of freely jointed chains is considered for which the translational degrees of freedom are sampled using a coarse grained Monte Carlo simulation and the conformational degrees of freedom of the chains are computed using a modified self-consistent field theory. Read More

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December 2009

Mathematical modelling of atherosclerosis as an inflammatory disease.

Philos Trans A Math Phys Eng Sci 2009 Dec;367(1908):4877-86

Institut Camille Jordan, CNRS, UMR 5208, Université Claude Bernard Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.

Atherosclerosis is an inflammatory disease. The atherosclerosis process starts when low-density lipoproteins (LDLs) enter the intima of the blood vessel, where they are oxidized (ox-LDLs). The anti-inflammatory response triggers the recruitment of monocytes. Read More

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December 2009

Enhancement of image quality with a fast iterative scatter and beam hardening correction method for kV CBCT.

Z Med Phys 2009 ;19(3):158-72

DKFZ Heidelberg, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.

The problem of the enormous amount of scattered radiation in kV CBCT (kilo voltage cone beam computer tomography) is addressed. Scatter causes undesirable streak- and cup-artifacts and results in a quantitative inaccuracy of reconstructed CT numbers, so that an accurate dose calculation might be impossible. Image contrast is also significantly reduced. Read More

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January 2010

Molecular dynamics simulations of concentrated polymer solutions in thin film geometry. II. Solvent evaporation near the glass transition.

J Chem Phys 2009 Jul;131(1):014903

Institut Charles Sadron, 23 Rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France.

We perform molecular dynamics simulations of a coarse-grained model of a polymer-solvent mixture to study solvent evaporation from supported and freestanding polymer films near the bulk glass transition temperature T(g). We find that the evaporation process is characterized by three time (t) regimes: An early regime where the initially large surplus of solvent at the film-vapor interface evaporates and the film thickness h varies little with t, an intermediate regime where h decreases strongly, and a final regime where h slowly converges toward the asymptotic value of the dry film. In the intermediate regime the decrease of h goes along with an increase of the monomer density at the retracting interface. Read More

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Theory and computer simulation for the cubatic phase of cut spheres.

Phys Rev E Stat Nonlin Soft Matter Phys 2009 Mar 4;79(3 Pt 1):031702. Epub 2009 Mar 4.

Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom.

The phase behavior of a system of hard-cut spheres has been studied using a high-order virial theory and by Monte Carlo simulation. The cut-sphere particles are disks of thickness L formed by symmetrically truncating the end caps of a sphere of diameter D . The virial theory predicts a stable nematic phase for aspect ratio LD=0. Read More

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Vibroacoustic behavior of clamp mounted double-panel partition with enclosure air cavity.

J Acoust Soc Am 2008 Dec;124(6):3604-12

MOE Key Laboratory for Strength and Vibration, School of Aerospace, Xi'an Jiaotong University, Xi'an, People's Republic of China.

A theoretical study on the vibroacoustic performance of a rectangular double-panel partition clamp mounted in an infinite acoustic rigid baffle is presented. With the clamped boundary condition taken into account by the method of modal function, a double Fourier series solution to the dynamic response of the structure is obtained by employing the weighted residual method (i.e. Read More

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December 2008

Robust representation of dry cells in single-layer MODFLOW models.

Ground Water 2008 Nov-Dec;46(6):873-81. Epub 2008 Aug 18.

Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166, USA.

Dewatered or "dry" grid cells in the USGS ground water modeling software MODFLOW may cause nonphysical artifacts, trigger convergence failures, or interfere with parameter estimation. These difficulties can be avoided in two dimensions by modifying the spatial differencing scheme and the iterative procedure used to resolve nonlinearities. Specifically, the spatial differencing scheme is modified to use the water level on the upstream side of a pair of adjacent cells to calculate the saturated thickness and hence intercell conductance for the pair. Read More

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