scholarly journals Submersed micropatterned structures control active nematic flow, topology, and concentration

2021 ◽  
Vol 118 (38) ◽  
pp. e2106038118
Author(s):  
Kristian Thijssen ◽  
Dimitrius A. Khaladj ◽  
S. Ali Aghvami ◽  
Mohamed Amine Gharbi ◽  
Seth Fraden ◽  
...  
Keyword(s):  
Internal Structure ◽  
Viscous Dissipation ◽  
Material Properties ◽  
Microfluidic Systems ◽  
Flow Topology ◽  
Equilibrium Dynamics ◽  
Continuous Energy ◽  
Accessible Method

Coupling between flows and material properties imbues rheological matter with its wide-ranging applicability, hence the excitement for harnessing the rheology of active fluids for which internal structure and continuous energy injection lead to spontaneous flows and complex, out-of-equilibrium dynamics. We propose and demonstrate a convenient, highly tunable method for controlling flow, topology, and composition within active films. Our approach establishes rheological coupling via the indirect presence of fully submersed micropatterned structures within a thin, underlying oil layer. Simulations reveal that micropatterned structures produce effective virtual boundaries within the superjacent active nematic film due to differences in viscous dissipation as a function of depth. This accessible method of applying position-dependent, effective dissipation to the active films presents a nonintrusive pathway for engineering active microfluidic systems.

Modeling and Simulation of Polymer Solar Cells

2015 ◽  
pp. 439-472 ◽  
Author(s):  
Gavin Buxton
Keyword(s):  
Solar Cells ◽  
Excited State ◽  
Solar Cell ◽  
Modeling And Simulation ◽  
Internal Structure ◽  
Material Properties ◽  
Polymer Solar Cell ◽  
Polymer Solar Cells ◽  
Free Charge ◽  
Widespread Application

Polymer solar cells are attracting attention as inexpensive versatile devices for generating electricity from sunlight. However, relatively low efficiencies are currently hindering their widespread application. The typically low efficiencies arise because of the complex physics within these devices. In particular, photons must first be absorbed to create a mobile excited state, or exciton. Then this exciton must dissociate into free charge at the interface between an acceptor and a donor polymer, and finally, the free charge must traverse the polymer solar cell to the correct electrodes. Mathematical and computer models play an important role in understanding the physics of these devices and ultimately allow us to tailor the internal structure and material properties to optimize device performance. A brief review of polymer solar cells is presented, with particular emphasis on their nanoscale architecture, before the chapter turns its attention to the simulations and models that can predict their behavior.

Form and internal structure of active-layer detachment slides, Fosheim Peninsula, Ellesmere Island, Northwest Territories, Canada

1993 ◽  
Vol 30 (8) ◽  
pp. 1708-1714 ◽  
Author(s):  
Charles Harris ◽  
Antoni G. Lewkowicz
Keyword(s):  
Northwest Territories ◽  
Internal Structure ◽  
Shear Zone ◽  
Active Layer ◽  
Material Properties ◽  
Slope Failure ◽  
Shallow Landslides ◽  
Ellesmere Island ◽  
Basal Shear ◽  
Hydrological Regimes

Three recent shallow landslides over permafrost are described. Slides occur in low- to medium-plasticity clays containing some bands of silts and fine sands. Slope failure results from rapid thaw at the base of the active layer of soil that is ice-rich due to antecedent two-sided freezing. Displaced slide blocks retain their integrity because of hardening of the active layer by cryodesiccation and summer evaporation. Blocks move over a soft basal shear zone a few millimetres to several centimetres thick. Compression in the toe zone of slides is low at sites where runout is possible, but in other locations causes emergent shears and complex folding. Failure histories are varied and range from simple unitary slides to complex sequential failures in which active-layer segments are mobilized progressively higher up the slope. This study demonstrates the importance of active-layer thermal and hydrological regimes, in addition to material properties, in determining the mode of slope failure.

The Effect of Material Properties on the Efficiency of Valve-Less Rectification Micropumps

2010 ◽  
Author(s):  
Ahmed Fadl ◽  
Stefanie Demming ◽  
Zongqin Zhang ◽  
Bjo¨rn Hoxhold ◽  
Stephanus Bu¨ttgenbach ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Material Properties ◽  
High Efficiency ◽  
Experimental Results ◽  
Apparent Effect ◽  
Microfluidic Systems ◽  
Flow Rates

High efficiency valve-less rectification micropumps are essential in developing effective microfluidic systems. Many parameters have been reported in the literature to have an effect on the efficiency of valve-less rectification micropumps. These parameters are related to the dynamics of fluid flow (such as Reynolds number), rectifying geometries, or actuators (such as actuator frequency). In this work, we studied the effect of the material properties on the efficiency of valve-less rectification micropumps. Two valve-less rectification micropumps based on the same rectifying geometry, bifurcation, are fabricated using two different materials, Polydimethylsiloxane (PDMS) and SU-8 photoresist. The pumps are tested and results are compared. Experimental results suggest that the material properties have an apparent effect on the pumping performance of valve less rectification micropumps. The results are presented in terms of flow rates and maximum back pressures.

scholarly journals Development and Validation of Subject-Specific 3D Human Head Models Based on a Nonlinear Visco-Hyperelastic Constitutive Framework

2021 ◽  
Author(s):  
Kshitiz Upadhyay ◽  
Ahmed Alshareef ◽  
Andrew K. Knutsen ◽  
Curtis L. Johnson ◽  
Aaron Carass ◽  
...  
Keyword(s):  
Brain Tissue ◽  
Viscous Dissipation ◽  
Material Properties ◽  
Constitutive Models ◽  
Human Head ◽  
Strain Response ◽  
Modeling Framework ◽  
Strain Evolution ◽  
Subject Specific

Computational models of the human head are promising tools for the study and prediction of traumatic brain injuries (TBIs). Most available head models are developed using inputs (i.e., head geometry, material properties, and boundary conditions) derived from ex-vivo experiments on cadavers or animals and employ linear viscoelasticity (LVE)-based constitutive models, which leads to high uncertainty and poor accuracy in capturing the nonlinear response of brain tissue under impulsive loading conditions. To resolve these issues, a framework for the development of fully subject-specific 3D human head models is proposed, in which model inputs are derived from the same living human subject using a comprehensive in-vivo brain imaging protocol, and the viscous dissipation-based visco-hyperelastic constitutive modeling framework is employed. Specifically, brain tissue material properties are derived from in-vivo magnetic resonance elastography (MRE), and full-field strain-response of brain under rapid rotational acceleration is obtained from tagged MRI, which is used for model validation. The constitutive model comprises the Ogden hyperelastic strain energy density and the Upadhyay-Subhash-Spearot viscous dissipation potential. The simulated strain-response is compared with experimental data and with predictions from subject-specific models employing two commonly used LVE-based constitutive models, using a rigorous validation procedure that evaluates agreement in spatial strain distribution, temporal strain evolution, and differences in maximum values of peak and average strain. Results show that the head model developed in this work reasonably captures 3D brain dynamics, and when compared to LVE-based models, provides improvements in the prediction of peak strains and temporal strain evolution.

X-ray microtomography

1988 ◽  
Vol 46 ◽  
pp. 998-999
Author(s):  
H.W. Deckman ◽  
B.F. Flannery ◽  
J.H. Dunsmuir ◽  
K.D' Amico
Keyword(s):  
Computed Tomography ◽  
Internal Structure ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Tissue Structure ◽  
Individual Element ◽  
X Ray ◽  
Non Invasive ◽  
Panoramic Imaging ◽  
Three Dimensional Images

We have developed a new X-ray microscope which produces complete three dimensional images of samples. The microscope operates by performing X-ray tomography with unprecedented resolution. Tomography is a non-invasive imaging technique that creates maps of the internal structure of samples from measurement of the attenuation of penetrating radiation. As conventionally practiced in medical Computed Tomography (CT), radiologists produce maps of bone and tissue structure in several planar sections that reveal features with 1mm resolution and 1% contrast. Microtomography extends the capability of CT in several ways. First, the resolution which approaches one micron, is one thousand times higher than that of the medical CT. Second, our approach acquires and analyses the data in a panoramic imaging format that directly produces three-dimensional maps in a series of contiguous stacked planes. Typical maps available today consist of three hundred planar sections each containing 512x512 pixels. Finally, and perhaps of most import scientifically, microtomography using a synchrotron X-ray source, allows us to generate maps of individual element.

The internal structure of medullated wool

1984 ◽  
Vol 42 ◽  
pp. 388-389
Author(s):  
Leo Barish
Keyword(s):  
Light Microscopy ◽  
Internal Structure ◽  
Wool Fiber ◽  
Guard Hair ◽  
Bright Field ◽  
Wool Fibers ◽  
Thin Skin ◽  
Air Pockets

Although most of the wool used today consists of fine, unmedullated down-type fibers, a great deal of coarse wool is used for carpets, tweeds, industrial fabrics, etc. Besides the obvious diameter difference, coarse wool fibers are often medullated.Medullation may be easily observed using bright field light microscopy. Fig. 1A shows a typical fine diameter nonmedullated wool fiber, Fig. IB illustrates a coarse fiber with a large medulla. The opacity of the medulla is due to the inability of the mounting media to penetrate to the center of the fiber leaving air pockets. Fig. 1C shows an even thicker fiber with a very large medulla and with very thin skin. This type of wool is called “Kemp”, is shed annually or more often, and corresponds to guard hair in fur-bearing animals.

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

Relationships Between Grain Boundary Structure and Material Properties

1980 ◽  
Vol 38 ◽  
pp. 366-369
Author(s):  
Brian Ralph ◽  
Barlow Claire ◽  
Nicola Ecob
Keyword(s):  
Grain Boundary ◽  
Material Properties ◽  
Main Property ◽  
Grain Structure ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Property Changes

This brief review seeks to summarize some of the main property changes which may be induced by altering the grain structure of materials. Where appropriate an interpretation is given of these changes in terms of current theories of grain boundary structure, and some examples from current studies are presented at the end of this paper.

The German Post-Critical Belief Scale: Internal and External Validity

2003 ◽  
Vol 34 (4) ◽  
pp. 219-226 ◽  
Author(s):  
Bart Duriez ◽  
Claudia Appel ◽  
Dirk Hutsebaut
Keyword(s):  
Internal Structure ◽  
Present Article ◽  
External Validity ◽  
German Version ◽  
Dutch Version ◽  
German Sample ◽  
Belief Scale ◽  
Internal And External Validity

Abstract: Recently, Duriez, Fontaine and Hutsebaut (2000) and Fontaine, Duriez, Luyten and Hutsebaut (2003) constructed the Post-Critical Belief Scale in order to measure the two religiosity dimensions along which Wulff (1991 , 1997 ) summarized the various possible approaches to religion: Exclusion vs. Inclusion of Transcendence and Literal vs. Symbolic. In the present article, the German version of this scale is presented. Results obtained in a heterogeneous German sample (N = 216) suggest that the internal structure of the German version fits the internal structure of the original Dutch version. Moreover, the observed relation between the Literal vs. Symbolic dimension and racism, which was in line with previous studies ( Duriez, in press ), supports the external validity of the German version.

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