Demonstration of Nautilus Centripetal Capillary Condenser Technology

NASA Technical Reports Server (NTRS)

Wheeler, RIchard; Tang, Linh; Wambolt, Spencer; Golliher, Eric; Agui, Juan

2016-01-01

This paper describes the results of a proof of concept effort for development of a Nautilus Centripetal Capillary Condenser (NCCC or NC3) used for microgravity compatible water recovery from moist air with integral passive phase separation. Removal of liquid condensate from the air stream exiting a condenser is readily performed here on Earth. In order to perform this function in space however, without gravity or mechanical action, other tactics including utilization of inertial, drag and capillary forces are required. Within the NC3, liquid water forms via condensation on cold condenser surfaces as humid air passes along multiple spiral channels, each in its own plane, all together forming a stacked plate assembly. Non-mechanical inertial forces are employed to transfer condensate, as it forms, via centripetal action to the outer perimeter of each channel. A V-shaped groove, constructed on this outer edge of the spiral channel, increases local capillary forces thereby retaining the liquid. Air drag then pulls the liquid along to a collection region near the center of the device. Dry air produced by each parallel spiral channel is combined in a common orthogonal, out-of-plane conduit passing down the axial center of the stacked device. Similarly, the parallel condensate streams are combined and removed from the condenser/separator through yet another out-of-plane axial conduit. NC3 is an integration of conventional finned condenser operation, combined with static phase separation and capillary transport phenomena. A Mars' transit mission would be a logical application for this technology where gravity is absent and the use of vibrating, energy-intensive, motor-driven centrifugal separators is undesired. Here a vapor stream from either the Heat Melt Compactor or the Carbon dioxide Reduction Assembly, for example, would be dried to a dew point of 10 deg using a passive NC3 condenser/separator with the precious water condensate recycled to the water bus.

Capillary test specimen, system, and methods for in-situ visualization of capillary flow and fillet formation

DOEpatents

Hall, Aaron C.; Hosking, F. Michael ,; Reece, Mark

2003-06-24

A capillary test specimen, method, and system for visualizing and quantifying capillary flow of liquids under realistic conditions, including polymer underfilling, injection molding, soldering, brazing, and casting. The capillary test specimen simulates complex joint geometries and has an open cross-section to permit easy visual access from the side. A high-speed, high-magnification camera system records the location and shape of the moving liquid front in real-time, in-situ as it flows out of a source cavity, through an open capillary channel between two surfaces having a controlled capillary gap, and into an open fillet cavity, where it subsequently forms a fillet on free surfaces that have been configured to simulate realistic joint geometries. Electric resistance heating rapidly heats the test specimen, without using a furnace. Image-processing software analyzes the recorded images and calculates the velocity of the moving liquid front, fillet contact angles, and shape of the fillet's meniscus, among other parameters.

A star-shaped poly(2-methyl-2-oxazoline)-based antifouling coating: Application in investigation of the interaction between acetaminophen and bovine serum albumin by frontal analysis capillary electrophoresis.

PubMed

Du, Haiqin; Zhang, Chong; Mao, Ke; Wang, Yanmei

2017-08-01

In this work, an antifouling capillary modified with star-shaped poly(2-methyl-2-oxazoline)-based copolymer was used to study the interaction between acetaminophen (APAP) and bovine serum albumin (BSA) by frontal analysis capillary electrophoresis (FACE). The star-shaped copolymer, poly(ethylene imine)-graft-poly(2-methyl-2-oxazoline) (PEI-g-PMOXA), was immobilized onto the fused-silica capillary inner wall via dopamine-assisted co-deposition strategy, yielding a PEI-g-PMOXA/polydopamine (PDA)-coated antifouling capillary, i.e., an antifouling capillary coated with the PEI-g-PMOXA/PDA co-deposited film. Electroosmotic flow (EOF) mobility of the PEI-g-PMOXA/PDA-coated capillary was almost zero in a wide pH range (3.0-10.0), while the EOF mobility of bare capillary was much larger and increased significantly with pH increasing. When the PEI-g-PMOXA/PDA-coated capillary was exploited to separate a protein mixture including cytochrome c, lysozyme, ribonuclease A and α-chymotrypsinogen A, the theoretical plate numbers were of five orders of magnitude which were about ten-fold higher over those obtained with bare capillary; in addition, the RSD values of migration time were mostly less than 0.7% (30 consecutive runs) which were much smaller than those of bare capillary (c.a. 5.7%). The protein-resistant PEI-g-PMOXA/PDA-coated capillary was then used to investigate the interaction between APAP and BSA by FACE, the binding constant and number of binding sites at 25°C and pH 7.4 (Tris/HCl buffer of 25mM) were 1.39×10 4 M -1 and 1.08, respectively, which were comparable to the results determined by fluorescence spectroscopic measurement (3.18×10 4 M -1 and 1.19, respectively). Copyright © 2017 Elsevier B.V. All rights reserved.

Capillary Structures for Exploration Life Support (Capillary Structures)

NASA Image and Video Library

2017-07-10

iss052e013146 (July 10, 2017) --- Astronaut Jack Fischer is photographed during setup of hardware for the Capillary Structures for Exploration Life Support (Capillary Structures) two sorbent demonstrations. The Capillary Structures for Exploration Life Support (Capillary Structures) investigation studies a new method using structures of specific shapes to manage fluid and gas mixtures. The investigation studies water recycling and carbon dioxide removal, benefiting future efforts to design lightweight, more reliable life support systems for future space missions.

Subtle exchange model of flow depended on the blood cell shape to enhance the micro-circulation in capillary

NASA Astrophysics Data System (ADS)

Chan, Iatneng

2012-02-01

In general the exchange of gases or other material in capillary system is conceptualized by the diffusion effect. But in this model, we investigate a micro-flow pattern by simulation and computation on a micro-exchange model in which the blood cell is a considered factor, especially on its shape. It shows that the cell benefits the circulation while it is moving in the capillary. In the study, the flow detail near the cell surface is mathematically analyzed, such that the Navier-Stokes equations are applied and the viscous factor is also briefly considered. For having a driven force to the motion of micro-circulation, a breathing mode is suggested to approximately compute on the flow rate in the blood capillary during the transfer of cell. The rate is also used to estimate the enhancement to the circulation in additional to the outcome of diffusion. Moreover in the research, the shape change of capillary wall under pressure influence is another element in the beginning calculation for the effect in the assistance to cell motion.

Capillary Structures for Exploration Life Support (Capillary Structures)

NASA Image and Video Library

2017-07-10

iss052e013081 (7/10/2017) --- The Capillary Structures for Exploration Life Support (Capillary Structures) investigation studies a new method using structures of specific shapes to manage fluid and gas mixtures. The investigation studies water recycling and carbon dioxide removal, benefiting future efforts to design lightweight, more reliable life support systems for future space missions.

Investigation of energy dissipation due to contact angle hysteresis in capillary effect

NASA Astrophysics Data System (ADS)

Athukorallage, Bhagya; Iyer, Ram

2016-06-01

Capillary action or Capillarity is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity. Three effects contribute to capillary action, namely, adhesion of the liquid to the walls of the confining solid; meniscus formation; and low Reynolds number fluid flow. We investigate the dissipation of energy during one cycle of capillary action, when the liquid volume inside a capillary tube first increases and subsequently decreases while assuming quasi-static motion. The quasi-static assumption allows us to focus on the wetting phenomenon of the solid wall by the liquid and the formation of the meniscus. It is well known that the motion of a liquid on an non-ideal surface involves the expenditure of energy due to contact angle hysteresis. In this paper, we derive the equations for the menisci and the flow rules for the change of the contact angles for a liquid column in a capillary tube at a constant temperature and volume by minimizing the Helmholtz free energy using calculus of variations. We describe the numerical solution of these equations and present results from computations for the case of a capillary tube with 1 mm diameter.

Numerical simulation of flow for viscoelastic neutrophil models in a rectangular capillary network: effects of capillary shape and cell stiffness on transit time.

PubMed

Shirai, Atsushi; Fujita, Ryo; Hayase, Toshiyuki

2007-01-01

The concentration of neutrophils in the pulmonary microvasculature is higher than in large systemic vessels. It is thought that the high concentration of neutrophils facilitates their effective recruitment to sites of inflammation. Thus, in order to understand the role of neutrophils in the immune system, it is important to clarify their flow characteristics in the pulmonary microvasculature. In a previous study, we developed a model to simulate the flow of neutrophils in a capillary network, in which the cells were modeled as spheres of a Maxwell material with a cortical tension and the capillary segments were modeled as arc-shaped constrictions in straight pipes. In the present paper, the flow of neutrophils in a simplified alveolar capillary network model is investigated for various constriction shapes and cell stiffnesses. Finally, it is shown that both the coefficient of variation of the transit time of the cells, which is the standard deviation divided by the mean transit time, and the mean transit time increase as the capillary segments become steep or tight, or when the cells become hard. The mean value of the transit time exceeds the median for all of the conditions that occur in real lungs, although the difference between them is small.

21 CFR 864.6150 - Capillary blood collection tube.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Capillary blood collection tube. 864.6150 Section... blood collection tube. (a) Identification. A capillary blood collection tube is a plain or heparinized glass tube of very small diameter used to collect blood by capillary action. (b) Classification. Class I...

21 CFR 864.6150 - Capillary blood collection tube.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Capillary blood collection tube. 864.6150 Section... blood collection tube. (a) Identification. A capillary blood collection tube is a plain or heparinized glass tube of very small diameter used to collect blood by capillary action. (b) Classification. Class I...

21 CFR 864.6150 - Capillary blood collection tube.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Capillary blood collection tube. 864.6150 Section... blood collection tube. (a) Identification. A capillary blood collection tube is a plain or heparinized glass tube of very small diameter used to collect blood by capillary action. (b) Classification. Class I...

21 CFR 864.6150 - Capillary blood collection tube.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Capillary blood collection tube. 864.6150 Section... blood collection tube. (a) Identification. A capillary blood collection tube is a plain or heparinized glass tube of very small diameter used to collect blood by capillary action. (b) Classification. Class I...

21 CFR 864.6150 - Capillary blood collection tube.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Capillary blood collection tube. 864.6150 Section... blood collection tube. (a) Identification. A capillary blood collection tube is a plain or heparinized glass tube of very small diameter used to collect blood by capillary action. (b) Classification. Class I...

Synchrotron radiation microtomography of Taylor bubbles in capillary two-phase flow

NASA Astrophysics Data System (ADS)

Boden, Stephan; dos Santos Rolo, Tomy; Baumbach, Tilo; Hampel, Uwe

2014-07-01

We report on a study to measure the three-dimensional shape of Taylor bubbles in capillaries using synchrotron radiation in conjunction with ultrafast radiographic imaging. Moving Taylor bubbles in 2-mm round and square capillaries were radiographically scanned with an ultrahigh frame rate of up to 36,000 fps and 5.6-µm pixel separation. Consecutive images were properly processed to yield 2D transmission radiographs of high contrast-to-noise ratio. Application of 3D tomographic image reconstruction disclosed the 3D bubble shape. The results provide a reference data base for development of sophisticated interface resolving CFD computations.

Computation of three-phase capillary entry pressures and arc menisci configurations in pore geometries from 2D rock images: A combinatorial approach

NASA Astrophysics Data System (ADS)

Zhou, Yingfang; Helland, Johan Olav; Hatzignatiou, Dimitrios G.

2014-07-01

We present a semi-analytical, combinatorial approach to compute three-phase capillary entry pressures for gas invasion into pore throats with constant cross-sections of arbitrary shapes that are occupied by oil and/or water. For a specific set of three-phase capillary pressures, geometrically allowed gas/oil, oil/water and gas/water arc menisci are determined by moving two circles in opposite directions along the pore/solid boundary for each fluid pair such that the contact angle is defined at the front circular arcs. Intersections of the two circles determine the geometrically allowed arc menisci for each fluid pair. The resulting interfaces are combined systematically to allow for all geometrically possible three-phase configuration changes. The three-phase extension of the Mayer and Stowe - Princen method is adopted to calculate capillary entry pressures for all determined configuration candidates, from which the most favorable gas invasion configuration is determined. The model is validated by comparing computed three-phase capillary entry pressures and corresponding fluid configurations with analytical solutions in idealized triangular star-shaped pores. It is demonstrated that the model accounts for all scenarios that have been analyzed previously in these shapes. Finally, three-phase capillary entry pressures and associated fluid configurations are computed in throat cross-sections extracted from segmented SEM images of Bentheim sandstone. The computed gas/oil capillary entry pressures account for the expected dependence of oil/water capillary pressure in spreading and non-spreading fluid systems at the considered wetting conditions. Because these geometries are irregular and include constrictions, we introduce three-phase displacements that have not been identified previously in pore-network models that are based on idealized pore shapes. However, in the limited number of pore geometries considered in this work, we find that the favorable displacements are not generically different from those already encountered in network models previously, except that the size and shape of oil layers that are surrounded by gas and water are described more realistically. The significance of the results for describing oil connectivity in porous media accurately can only be evaluated by including throats with more complex cross-sections in three-phase pore-network models.

Dynamics and Stability of Capillary Surfaces: Liquid Switches at Small Scales

NASA Technical Reports Server (NTRS)

Steen, Paul H.; Bhandar, Anand; Vogel, Michael J.; Hirsa, Amir H.

2004-01-01

The dynamics and stability of systems of interfaces is central to a range of technologies related to the Human Exploration and Development of Space (HEDS). Our premise is that dramatic shape changes can be manipulated to advantage with minimal input, if the system is near instability. The primary objective is to develop the science base to allow novel approaches to liquid management in low-gravity based on this premise. HEDS requires efficient, reliable and lightweight technologies. Our poster will highlight our progress toward this goal using the capillary switch as an example. A capillary surface is a liquid/liquid or liquid/gas interface whose shape is determined by surface tension. For typical liquids (e.g., water) against gas on earth, capillary surfaces occur on the millimeterscale and smaller where shape deformation due to gravity is unimportant. In low gravity, they can occur on the centimeter scale. Capillary surfaces can be combined to make a switch a system with multiple stable states. A capillary switch can generate motion or effect force. To be practical, the energy barriers of such a switch must be tunable, its switching time (kinetics) short and its triggering mechanism reliable. We illustrate these features with a capillary switch that consists of two droplets, coupled by common pressure. As long as contact lines remained pinned, motions are inviscid, even at sub-millimeter scales, with consequent promise of low-power consumption at the device level. Predictions of theory are compared to experiment on i) a soap-film prototype at centimeter scale and ii) a liquid droplet switch at millimeter-scale.

Disposable pen-shaped capillary gel electrophoresis cartridge for fluorescence detection of bio-molecules

NASA Astrophysics Data System (ADS)

Amirkhanian, Varoujan; Tsai, Shou-Kuan

2014-03-01

We introduce a novel and cost-effective capillary gel electrophoresis (CGE) system utilizing disposable pen-shaped gelcartridges for highly efficient, high speed, high throughput fluorescence detection of bio-molecules. The CGE system has been integrated with dual excitation and emission optical-fibers with micro-ball end design for fluorescence detection of bio-molecules separated and detected in a disposable pen-shaped capillary gel electrophoresis cartridge. The high-performance capillary gel electrophoresis (CGE) analyzer has been optimized for glycoprotein analysis type applications. Using commercially available labeling agent such as ANTS (8-aminonapthalene-1,3,6- trisulfonate) as an indicator, the capillary gel electrophoresis-based glycan analyzer provides high detection sensitivity and high resolving power in 2-5 minutes of separations. The system can hold total of 96 samples, which can be automatically analyzed within 4-5 hours. This affordable fiber optic based fluorescence detection system provides fast run times (4 minutes vs. 20 minutes with other CE systems), provides improved peak resolution, good linear dynamic range and reproducible migration times, that can be used in laboratories for high speed glycan (N-glycan) profiling applications. The CGE-based glycan analyzer will significantly increase the pace at which glycoprotein research is performed in the labs, saving hours of preparation time and assuring accurate, consistent and economical results.

Complex patchy colloids shaped from deformable seed particles through capillary interactions.

PubMed

Meester, V; Kraft, D J

2018-02-14

We investigate the mechanisms underlying the reconfiguration of random aggregates of spheres through capillary interactions, the so-called "colloidal recycling" method, to fabricate a wide variety of patchy particles. We explore the influence of capillary forces on clusters of deformable seed particles by systematically varying the crosslink density of the spherical seeds. Spheres with a poorly crosslinked polymer network strongly deform due to capillary forces and merge into large spheres. With increasing crosslink density and therefore rigidity, the shape of the spheres is increasingly preserved during reconfiguration, yielding patchy particles of well-defined shape for up to five spheres. In particular, we find that the aspect ratio between the length and width of dumbbells, L/W, increases with the crosslink density (cd) as L/W = B - A·exp(-cd/C). For clusters consisting of more than five spheres, the particle deformability furthermore determines the patch arrangement of the resulting particles. The reconfiguration pathway of clusters of six densely or poorly crosslinked seeds leads to octahedral and polytetrahedral shaped patchy particles, respectively. For seven particles several geometries were obtained with a preference for pentagonal dipyramids by the rigid spheres, while the soft spheres do rarely arrive in these structures. Even larger clusters of over 15 particles form non-uniform often aspherical shapes. We discuss that the reconfiguration pathway is largely influenced by confinement and geometric constraints. The key factor which dominates during reconfiguration depends on the deformability of the spherical seed particles.

Scaling analysis and SE simulation of the tilted cylinder-interface capillary interaction

NASA Astrophysics Data System (ADS)

Gao, S. Q.; Zhang, X. Y.; Zhou, Y. H.

2018-06-01

The capillary interaction induced by a tilted cylinder and interface is the basic configuration of many complex systems, such as micro-pillar arrays clustering, super-hydrophobicity of hairy surface, water-walking insects, and fiber aggregation. We systematically analyzed the scaling laws of tilt angle, contact angle, and cylinder radius on the contact line shape by SE simulation and experiment. The following in-depth analysis of the characteristic parameters (shift, stretch and distortion) of the deformed contact lines reveals the self-similar shape of contact line. Then a general capillary force scaling law is proposed to incredibly grasp all the simulated and experimental data by a quite straightforward ellipse approximation approach.

The Shape of the Urine Stream — From Biophysics to Diagnostics

PubMed Central

Wheeler, Andrew P. S.; Morad, Samir; Buchholz, Noor; Knight, Martin M.

2012-01-01

We develop a new computational model of capillary-waves in free-jet flows, and apply this to the problem of urological diagnosis in this first ever study of the biophysics behind the characteristic shape of the urine stream as it exits the urethral meatus. The computational fluid dynamics model is used to determine the shape of a liquid jet issuing from a non-axisymmetric orifice as it deforms under the action of surface tension. The computational results are verified with experimental modelling of the urine stream. We find that the shape of the stream can be used as an indicator of both the flow rate and orifice geometry. We performed volunteer trials which showed these fundamental correlations are also observed in vivo for male healthy volunteers and patients undergoing treatment for low flow rate. For healthy volunteers, self estimation of the flow shape provided an accurate estimation of peak flow rate (). However for the patients, the relationship between shape and flow rate suggested poor meatal opening during voiding. The results show that self measurement of the shape of the urine stream can be a useful diagnostic tool for medical practitioners since it provides a non-invasive method of measuring urine flow rate and urethral dilation. PMID:23091609

Microfluidic Investigation Reveals Distinct Roles for Actin Cytoskeleton and Myosin II Activity in Capillary Leukocyte Trafficking

PubMed Central

Gabriele, Sylvain; Benoliel, Anne-Marie; Bongrand, Pierre; Théodoly, Olivier

2009-01-01

Circulating leukocyte sequestration in pulmonary capillaries is arguably the initiating event of lung injury in acute respiratory distress syndrome. We present a microfluidic investigation of the roles of actin organization and myosin II activity during the different stages of leukocyte trafficking through narrow capillaries (entry, transit and shape relaxation) using specific drugs (latrunculin A, jasplakinolide, and blebbistatin). The deformation rate during entry reveals that cell stiffness depends strongly on F-actin organization and hardly on myosin II activity, supporting a microfilament role in leukocyte sequestration. In the transit stage, cell friction is influenced by stiffness, demonstrating that the actin network is not completely broken after a forced entry into a capillary. Conversely, membrane unfolding was independent of leukocyte stiffness. The surface area of sequestered leukocytes increased by up to 160% in the absence of myosin II activity, showing the major role of molecular motors in microvilli wrinkling and zipping. Finally, cell shape relaxation was largely independent of both actin organization and myosin II activity, whereas a deformed state was required for normal trafficking through capillary segments. PMID:19450501

Investigation and visualization of liquid-liquid flow in a vertically mounted Hele-Shaw cell: flow regimes, velocity and shape of droplets

NASA Astrophysics Data System (ADS)

Shad, S.; Gates, I. D.; Maini, B. B.

2009-11-01

The motion and shape of a liquid drop flowing within a continuous, conveying liquid phase in a vertical Hele-Shaw cell were investigated experimentally. The continuous phase was more viscous and wetted the bounding walls of the Hele-Shaw cell. The gap between the Hele-Shaw plates was set equal to 0.0226 cm. Four different flow regimes were observed: (a) small-droplet flow, (b) elongated-droplet flow, (c) churn flow and (d) channel flow. At low capillary number, that is, when capillary forces are larger than viscous forces, the droplet shape was irregular and changed with time and distance, and it moved with lower velocity than that of the conveying phase. At higher capillary number, several different shapes of stabilized elongated and flattened drops were observed. In contrast to gas-liquid systems, the velocities of droplets are higher than that of conveying liquid. New correlations derived from dimensionless analysis and fitted to the experimental data were generated to predict the elongated-drop velocity and aspect ratio.

Dumbbell-Shaped Epidural Capillary Hemangioma Presenting as a Lung Mass: Case Report and Review of the Literature.

PubMed

García-Pallero, María A; Torres, Cristina V; García-Navarrete, Eduardo; Gordillo, Carlos; Delgado, Juan; Penanes, Juan R; García-Campos, María T; Sola, R G

2015-07-15

A case report and literature review. We present the fourth case of a spinal epidural capillary hemangioma with a dumbbell-shaped appearance in the magnetic resonance image reported in the literature and the second presented as a lung mass. Hemangiomas are congenital vascular malformations that pathologists frequently consider to be hamartomatous malformations. Hemangiomas of the spine are usually lesions of the vertebral bodies, but they can sit in other locations such as the intramedullary or epidural space. Purely epidural hemangiomas are rare and most of them are of cavernous type. We present a 67-year-old female with a thoracic dumbbell-shaped capillary hemangioma with both foraminal and intrathoracic extensions, whose presentation was pleural effusion associated with mediastinal mass suggestive of pulmonary neoplasia. Surgical treatment consisted of total removal en bloc of the lesion. Microscopic evaluation showed a fibrofatty tissue with a proliferation of vascular structures that were generally of a small size, with areas of myxoid appearance. To date, there have been 8 epidural capillary hemangiomas of the thoracic and lumbar spine reported in the literature, and only 3 of them were dumbbell-shaped with extraforaminal extension. It is important to consider the diagnosis of hemangiomas in the differential diagnosis of epidural lesions with dumbbell-shaped appearance in the magnetic resonance image, especially at the thoracic level. It is a benign and potentially curable disease and the most appropriate surgical treatment is en bloc resection of the entire lesion. They are usually presented as a progressive myelopathy, so early treatment may prevent permanent neurological deficits. 5.

Design of Capillary Flows with Spatially Graded Porous Films

NASA Astrophysics Data System (ADS)

Joung, Young Soo; Figliuzzi, Bruno Michel; Buie, Cullen

2013-11-01

We have developed a new capillary tube model, consisting of multi-layered capillary tubes oriented in the direction of flow, to predict capillary speeds on spatially graded porous films. Capillary flows through thin porous media have been widely utilized for small size liquid transport systems. However, for most media it is challenging to realize arbitrary shapes and spatially functionalized micro-structures with variable flow properties. Therefore, conventional media can only be used for capillary flows obeying Washburn's equation and the modifications thereof. Given this background, we recently developed a method called breakdown anodization (BDA) to produce highly wetting porous films. The resulting surfaces show nearly zero contact angles and fast water spreading speed. Furthermore, capillary pressure and spreading diffusivity can be expressed as functions of capillary height when customized electric fields are used in BDA. From the capillary tube model, we derived a general capillary flow equation of motion in terms of capillary pressure and spreading diffusivity. The theoretical model shows good agreement with experimental capillary flows. The study will provide novel design methodologies for paper-based microfluidic devices.

Nailfold capillary patterns in healthy subjects: a real issue in capillaroscopy.

PubMed

Ingegnoli, Francesca; Gualtierotti, Roberta; Lubatti, Chiara; Bertolazzi, Chiara; Gutierrez, Marwin; Boracchi, Patrizia; Fornili, Marco; De Angelis, Rossella

2013-11-01

Nailfold capillaroscopy has been extensively applied in a broad spectrum of pathologic conditions, but very few data have been published in healthy individuals. The aim of this study was to describe the nailfold capillary findings on a large series of healthy subjects using the video-capillaroscopy technique. Nailfold capillaries were studied based on their morphology, dimensions and density. Then, to evaluate jointly the association between different capillary findings in groups of subjects which were homogeneous for their characteristics, cluster analysis was performed. The results (median) of capillary measurements were as follows: loop length 207μm, external diameter 39μm, internal diameter 17μm, apical diameter 17μm, and intercapillary distance 143μm. Based on the cluster analysis three major "normal" morphologic capillaroscopic patterns were depicted: 1) the "normal" pattern mainly with 2 to 5 U-shaped loops/mm and ≤2 tortuous loops/mm; 2) the "perfect normal" pattern with ≥5 U-shaped loops/mm and 3) the "unusual normal" with at least 1 meandering or bushy loop, or at least 1 microhemorrhage, or with >4 crossed loops/mm. Regarding the loop measurements, the majority of subjects had a median of 7capillaries/mm with a median length of 198μm. © 2013 Elsevier Inc. All rights reserved.

The Impact of Multiple Freeze-Thaw Cycles on the Microstructure of Aggregates from a Soddy-Podzolic Soil: A Microtomographic Analysis

NASA Astrophysics Data System (ADS)

Skvortsova, E. B.; Shein, E. V.; Abrosimov, K. N.; Romanenko, K. A.; Yudina, A. V.; Klyueva, V. V.; Khaidapova, D. D.; Rogov, V. V.

2018-02-01

With the help of computed X-ray microtomography with a resolution of 2.75 μm, changes in the microstructure and pore space of aggregates of 3 mm in diameter from the virgin soddy-podzolic soil (Glossic Retisol (Loamic)) in the air-dry, capillary-moistened, and frozen states after five freeze-thaw cycles were studied in a laboratory experiment. The freezing of the samples was performed at their capillary moistening. It was shown that capillary moistening of initially air-dry samples from the humus (AY), eluvial (EL), and illuvial (BT1) horizons at room temperature resulted in the development of the platy, fine vesicular, and angular blocky microstructure, respectively. The total volume of tomographically visible pores >10 μm increased by 1.3, 2.2, and 3.4 times, respectively. After freeze-thaw cycles, frozen aggregates partly preserved the structural arrangement formed during the capillary moistening. At the same time, in the frozen aggregate from the AY horizon, the total tomographic porosity decreased to the initial level of the air-dry soil. In the frozen aggregate from the EL horizon, large vesicular pores were formed, owing to which the total pore volume retained its increased values. The resistance of aggregate shape to the action of freeze-thaw cycles differed. The aggregate from the EL horizon completely lost its original configuration by the end of the experiment. The aggregate from the AY horizon displayed definite features of sagging after five freeze-thaw cycles, whereas the aggregate from the BT1 horizon preserved its original configuration.

Method and apparatus for automated processing and aliquoting of whole blood samples for analysis in a centrifugal fast analyzer

DOEpatents

Burtis, Carl A.; Johnson, Wayne F.; Walker, William A.

1988-01-01

A rotor and disc assembly for use in a centrifugal fast analyzer. The assembly is designed to process multiple samples of whole blood followed by aliquoting of the resultant serum into precisely measured samples for subsequent chemical analysis. The assembly requires minimal operator involvement with no mechanical pipetting. The system comprises (1) a whole blood sample disc, (2) a serum sample disc, (3) a sample preparation rotor, and (4) an analytical rotor. The blood sample disc and serum sample disc are designed with a plurality of precision bore capillary tubes arranged in a spoked array. Samples of blood are loaded into the blood sample disc in capillary tubes filled by capillary action and centrifugally discharged into cavities of the sample preparation rotor where separation of serum and solids is accomplished. The serum is loaded into the capillaries of the serum sample disc by capillary action and subsequently centrifugally expelled into cuvettes of the analytical rotor for analysis by conventional methods.

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

PubMed

Mondal, Samir K; Mitra, Anupam; Singh, Nahar; Sarkar, S N; Kapur, Pawan

2009-10-26

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

Novel concept of washing for microfluidic paper-based analytical devices based on capillary force of paper substrates.

PubMed

Mohammadi, Saeed; Busa, Lori Shayne Alamo; Maeki, Masatoshi; Mohamadi, Reza M; Ishida, Akihiko; Tani, Hirofumi; Tokeshi, Manabu

2016-11-01

A novel washing technique for microfluidic paper-based analytical devices (μPADs) that is based on the spontaneous capillary action of paper and eliminates unbound antigen and antibody in a sandwich immunoassay is reported. Liquids can flow through a porous medium (such as paper) in the absence of external pressure as a result of capillary action. Uniform results were achieved when washing a paper substrate in a PDMS holder which was integrated with a cartridge absorber acting as a porous medium. Our study demonstrated that applying this washing technique would allow μPADs to become the least expensive microfluidic device platform with high reproducibility and sensitivity. In a model μPAD assay that utilized this novel washing technique, C-reactive protein (CRP) was detected with a limit of detection (LOD) of 5 μg mL -1 . Graphical Abstract A novel washing technique for microfluidic paper-based analytical devices (μPADs) that is based on the spontaneous capillary action of paper and eliminates unbound antigen and antibody in a sandwich immunoassay is reported.

Insulin regulates its own delivery to skeletal muscle by feed-forward actions on the vasculature

PubMed Central

Wang, Hong; Upchurch, Charles T.; Liu, Zhenqi

2011-01-01

Insulin, at physiological concentrations, regulates the volume of microvasculature perfused within skeletal and cardiac muscle. It can also, by relaxing the larger resistance vessels, increase total muscle blood flow. Both of these effects require endothelial cell nitric oxide generation and smooth muscle cell relaxation, and each could increase delivery of insulin and nutrients to muscle. The capillary microvasculature possesses the greatest endothelial surface area of the body. Yet, whether insulin acts on the capillary endothelial cell is not known. Here, we review insulin's actions at each of three levels of the arterial vasculature as well as recent data suggesting that insulin can regulate a vesicular transport system within the endothelial cell. This latter action, if it occurs at the capillary level, could enhance insulin delivery to muscle interstitium and thereby complement insulin's actions on arteriolar endothelium to increase insulin delivery. We also review work that suggests that this action of insulin on vesicle transport depends on endothelial cell nitric oxide generation and that insulin's ability to regulate this vesicular transport system is impaired by inflammatory cytokines that provoke insulin resistance. PMID:21610226

Development of economic MeV-ion microbeam technology at Chiang Mai University

NASA Astrophysics Data System (ADS)

Singkarat, S.; Puttaraksa, N.; Unai, S.; Yu, L. D.; Singkarat, K.; Pussadee, N.; Whitlow, H. J.; Natyanum, S.; Tippawan, U.

2017-08-01

Developing high technologies but in economic manners is necessary and also feasible for developing countries. At Chiang Mai University, Thailand, we have developed MeV-ion microbeam technology based on a 1.7-MV Tandetron tandem accelerator with our limited resources in a cost-effective manner. Instead of using expensive and technically complex electrostatic or magnetic quadrupole focusing lens systems, we have developed cheap MeV-ion microbeams using programmed L-shaped blade aperture and capillary techniques for MeV ion beam lithography or writing and mapping. The programmed L-shaped blade micro-aperture system consists of a pair of L-shaped movable aperture pieces which are controlled by computer to cut off the ion beam for controlling the beam size down to the micrometer order. The capillary technique utilizes our home-fabricated tapered glass capillaries to realize microbeams. Either system can be installed inside the endstation of the MeV ion beam line of the accelerator. Both systems have been applied to MeV-ion beam lithography or writing of micro-patterns for microfluidics applications to fabricate lab-on-chip devices. The capillary technique is being developed for MeV-ion beam mapping of biological samples. The paper reports details of the techniques and introduces some applications.

The hummingbird tongue is a fluid trap, not a capillary tube

PubMed Central

Rico-Guevara, Alejandro; Rubega, Margaret A.

2011-01-01

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue–fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics). PMID:21536916

The hummingbird tongue is a fluid trap, not a capillary tube.

PubMed

Rico-Guevara, Alejandro; Rubega, Margaret A

2011-06-07

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue-fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).

Scanning Electron Microscopic Structure of the Lingual Papillae of the Common Opossum (Didelphis marsupialis)

NASA Astrophysics Data System (ADS)

Okada, Shigenori; Schraufnagel, Dean E.

2005-08-01

The mammalian tongue has evolved for specialized functions in different species. The structure of its papillae tells about the animal's diet, habit, and taxonomy. The opossum has four kinds of lingual papillae (filiform, conical, fungiform, vallate). Scanning electron microscopy of the external features, connective tissue cores, and corrosion casts of the microvasculature show the filiform papillae have a spearhead-like main process and spiny accessory processes around the apical part of the main process. The shape and number of both processes depend on their position on the tongue. On the apex, the main processes have shovel-like capillary networks and the accessory processes have small conical networks. On the lingual radix, the processes have small capillary loops. In the patch region, conical papillae have capillaries arranged as a full sail curving posteriorly. The fungiform papillae are scattered among the filiform papillae and have capillary baskets beneath each taste bud. Giant fungiform papillae on the tongue tip are three to four times larger than the ones on the lingual body. Capillaries of giant papillae form a fan-shaped network. The opossum has three vallate papillae arranged in a triangle. Their tops have secondary capillary loops but not their lateral surfaces. Mucosal folds on the posterolateral border have irregular, fingerlike projections with cylindrical capillary networks. These findings and the structure of the rest of the masticatory apparatus suggest the lingual papillae of opossum have kept their ancestral carnivorous features but also developed the herbivore characteristics of other marsupials.

Scanning electron microscopic structure of the lingual papillae of the common opossum (Didelphis marsupialis).

PubMed

Okada, Shigenori; Schraufnagel, Dean E

2005-08-01

The mammalian tongue has evolved for specialized functions in different species. The structure of its papillae tells about the animal's diet, habit, and taxonomy. The opossum has four kinds of lingual papillae (filiform, conical, fungiform, vallate). Scanning electron microscopy of the external features, connective tissue cores, and corrosion casts of the microvasculature show the filiform papillae have a spearhead-like main process and spiny accessory processes around the apical part of the main process. The shape and number of both processes depend on their position on the tongue. On the apex, the main processes have shovel-like capillary networks and the accessory processes have small conical networks. On the lingual radix, the processes have small capillary loops. In the patch region, conical papillae have capillaries arranged as a full sail curving posteriorly. The fungiform papillae are scattered among the filiform papillae and have capillary baskets beneath each taste bud. Giant fungiform papillae on the tongue tip are three to four times larger than the ones on the lingual body. Capillaries of giant papillae form a fan-shaped network. The opossum has three vallate papillae arranged in a triangle. Their tops have secondary capillary loops but not their lateral surfaces. Mucosal folds on the posterolateral border have irregular, fingerlike projections with cylindrical capillary networks. These findings and the structure of the rest of the masticatory apparatus suggest the lingual papillae of opossum have kept their ancestral carnivorous features but also developed the herbivore characteristics of other marsupials.

About Mass Transfer in Capillaries of Biological Systems under Influence of Vibrations

NASA Astrophysics Data System (ADS)

Prisniakov, K.

Vibrations accompany the flight of the manned spacecraft both at a stage of a orbital injection to an orbit, and during long flights (as noise), rendering undesirable physiological influence on crew, reducing serviceability and creating constant discomfort. The report represents attempt to predict a state of the cosmonaut in conditions of influence of vibrations for the period of start and stay in Space, being based on researches of mass transfer processes in capillary systems. For this purpose the original researches on heat and mass transfer processes with evaporation of liquids in capillary - porous structures in conditions of vibration actions and changes of a direction of action of gravitation are generalized. Report demonstrates the existence of modes at which increased or lowered mass transfer is achieved on border of separation "liquid - gas". The possible mechanism of influence of vibrations on evaporation of a liquid in capillaries is examined. The magnitudes of frequencies and amplitudes are submitted at which minimax characteristics are observed. The opportunity of application of the developed mathematical model of heat and mass transfer in capillary - porous structures to forecasting influence of vibrations for biological processes in capillaries of alive essences is analyzed. Such approach is justified on the mechanical nature of harmful influence of vibrations on an organism of the person. In addition the range of vibration frequencies which arise during space flights, corresponds to own resonant frequencies of a human body and his separate organs. Comparison of these resonant frequencies of a body of the person (5-80 Hertz) with vibration frequencies of optimum modes of heat and mass transfer in capillary - porous structures (20-40 Hertz) is shown their ranges of coverage. It gives the basis to assume existence of similar effects in capillaries of human body. It is supposed, that the difficulty of breath, change of a rhythm of breath, the subsequent weariness under vibration action are attributable to infringements of normal mass transfer between the inhaled air and blood. The opportunity of use of the received laws is discussed for assessment of influence of gravitational fields on intensity mass transfer in capillaries of biosystems also.

Large scale ZnTe nanostructures on polymer micro patterns via capillary force photolithography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florence, S. Sasi, E-mail: sshanmugaraj@jazanu.edu.sa; Can, N.; Adam, H.

2016-06-10

A novel approach to prepare micro patterns ZnTe nanostructures on Si (100) substrate using thermal evaporation is proposed by capillary Force Lithography (CFL) technique on a self-assembled sacrificial Polystyrene mask. Polystyrene thin films on Si substrates are used to fabricate surface micro-relief patterns. ZnTe nanoparticles have been deposited by thermal evaporation method. The deposited ZnTe nanoparticles properties were assessed by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM). SEM studies indicated that the particles are uniform in size and shape, well dispersed and spherical in shape. This study reports the micro-arrays of ZnTe nanoparticles on a self-assembled sacrificial PS maskmore » using a capillary flow photolithography process which showed excellent, morphological properties which can be used in photovoltaic devices for anti-reflection applications.« less

Mixing in Sessile Drops Merging on a Surface

NASA Astrophysics Data System (ADS)

Anna, Shelley; Zhang, Ying; Oberdick, Samuel; Garoff, Stephen

2011-11-01

We investigate the mixing of two sessile drops that merge on a surface. The drops consist of low viscosity glycerol-water mixtures deposited on a silicone elastomer surface with contact angle near 90°. We observe the shape of the drops and the location of their intersection by placing a fluorescent dye in one drop and using a laser light sheet to image a plane perpendicular to the surface. The initial healing of the meniscus bridge between the merging drops, and the damping of capillary waves appearing on their surfaces occur on timescales comparable to the inertio-capillary relaxation time. However, the interface between the two fluids remains sharp, broadening diffusively over several minutes. The shape of the merged drops and the boundary between them also continues to evolve on a timescale of minutes. This later motion is controlled by gravity, capillary pressure, and viscous stresses. Images of the 3D drop shape indicate that small contact line motions are correlated to the slow relaxation. Although the two drops contain identical liquids except for the presence of the dye, the shape of the interface consistently evolves asymmetrically, assuming a characteristic crescent shape. We note that very tiny surface tension gradients can produce an asymmetric flow like the one observed here. We characterize the long timescale flow as a function of the drop sizes, and we use numerical simulations to aid in elucidating the essential physics.

Laser absorption waves in metallic capillaries

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Kanevskii, M. F.; Kondrashov, V. V.

1987-07-01

The propagation of laser absorption waves in metallic capillaries was studied experimentally and numerically during pulsed exposure to CO2 laser radiation. The dependence of the plasma front propagation rate on the initial air pressure in the capillary is determined. In a broad range of parameters, the formation time of the optically opaque plasma layer is governed by the total laser pulse energy from the beginning of the exposure to the instant screening appears, and is weakly dependent on the pulse shape and gas pressure.

Implementation of digital optical capillaroscopy for quantifying and estimating the microvascular abnormalities in type 2 diabetes mellitus

NASA Astrophysics Data System (ADS)

Gurfinkel, Yu. I.; Suchkova, O. V.; Sasonko, M. L.; Priezzhev, A. V.

2016-04-01

This study is aimed to define the extent of digital capillaroscopy possibilities for the quantification and estimation of microvascular abnormalities in type 2 diabetes mellitus (T2DM). A total of 196 adult persons were enrolled in the study including the group of compensated T2DM (n = 52), decompensated diabetics (n = 68), and healthy volunteers (n = 76) with normal blood glucose and without signs of cardiovascular pathology. All participants of the study were examined with the digital optical capillaroscope ("AET", Russia). This instrument is equipped with an image-processing program allowing for quantifying the diameters of the arterial and venous segments of the capillaries and their ratio (coefficient of remodeling), perivascular zone size, capillary blood velocity, and the degree of arterial loops narrowing and the density of the capillary network. Also we estimated the relative amount of coil-shaped capillaries. The study revealed significant difference in the capillary density and the remodeling coefficient in comparison of T2DM patients with non-diabetic individuals. Significant changes are found in the decompensated T2DM group compared to the compensated group of diabetic patients. Furthermore, the number of coil-shaped capillaries differed greatly in T2DM patients as compared to the healthy subjects. The study did not reveal any statistically significant differences in the capillary density between the patients with compensated and decompensated T2DM. The digital optical capillaroscope equipped with the advanced image-processing algorithm opens up new possibilities for obtaining clinically important information on microvascular abnormalities in patients suffering from diabetes mellitus.

Muscle-Specific Vascular Endothelial Growth Factor Deletion Induces Muscle Capillary Rarefaction Creating Muscle Insulin Resistance

PubMed Central

Bonner, Jeffrey S.; Lantier, Louise; Hasenour, Clinton M.; James, Freyja D.; Bracy, Deanna P.; Wasserman, David H.

2013-01-01

Muscle insulin resistance is associated with a reduction in vascular endothelial growth factor (VEGF) action and muscle capillary density. We tested the hypothesis that muscle capillary rarefaction critically contributes to the etiology of muscle insulin resistance in chow-fed mice with skeletal and cardiac muscle VEGF deletion (mVEGF−/−) and wild-type littermates (mVEGF+/+) on a C57BL/6 background. The mVEGF−/− mice had an ∼60% and ∼50% decrease in capillaries in skeletal and cardiac muscle, respectively. The mVEGF−/− mice had augmented fasting glucose turnover. Insulin-stimulated whole-body glucose disappearance was blunted in mVEGF−/− mice. The reduced peripheral glucose utilization during insulin stimulation was due to diminished in vivo cardiac and skeletal muscle insulin action and signaling. The decreased insulin-stimulated muscle glucose uptake was independent of defects in insulin action at the myocyte, suggesting that the impairment in insulin-stimulated muscle glucose uptake was due to poor muscle perfusion. The deletion of VEGF in cardiac muscle did not affect cardiac output. These studies emphasize the importance for novel therapeutic approaches that target the vasculature in the treatment of insulin-resistant muscle. PMID:23002035

Can flexibility help you float?

NASA Astrophysics Data System (ADS)

Burton, L. J.; Bush, J. W. M.

2012-10-01

We consider the role of flexibility in the weight-bearing characteristics of bodies floating at an interface. Specifically, we develop a theoretical model for a two-dimensional thin floating plate that yields the maximum stable plate load and optimal stiffness for weight support. Plates small relative to the capillary length are primarily supported by surface tension, and their weight-bearing potential does not benefit from flexibility. Above a critical size comparable to the capillary length, flexibility assists interfacial flotation. For plates on the order of and larger than the capillary length, deflection from an initially flat shape increases the force resulting from hydrostatic pressure, allowing the plate to support a greater load. In this large plate limit, the shape that bears the most weight is a semicircle, which displaces the most fluid above the plate for a fixed plate length. Exact results for maximum weight-bearing plate shapes are compared to analytic approximations made in the limits of large and small plate sizes. The value of flexibility for floating to a number of biological organisms is discussed in light of our study.

Microjet formation in a capillary by laser-induced cavitation

NASA Astrophysics Data System (ADS)

Peters, Ivo R.; Tagawa, Yoshiyuki; van der Meer, Devaraj; Prosperetti, Andrea; Sun, Chao; Lohse, Detlef

2010-11-01

A vapor bubble is created by focusing a laser pulse inside a capillary that is partially filled with water. Upon creation of the bubble, a shock wave travels through the capillary. When this shock wave meets the meniscus of the air-water interface, a thin jet is created that travels at very high speeds. A crucial ingredient for the creation of the jet is the shape of the meniscus, which is responsible for focusing the energy provided by the shock wave. We examine the formation of this jet numerically using a boundary integral method, where we prepare an initial interface at rest inside a tube with a diameter ranging from 50 to 500 μm. To simulate the effect of the bubble we then apply a short, strong pressure pulse, after which the jet forms. We investigate the influence of the shape of the meniscus, and pressure amplitude and duration on the jet formation. The jet shape and velocity obtained by the simulation compare well with experimental data, and provides good insight in the origin of the jet.

Visualizing the shape of soft solid and fluid contacts between two surfaces

NASA Astrophysics Data System (ADS)

Pham, Jonathan; Schellenberger, Frank; Kappl, Michael; Vollmer, Doris; Butt, Hans-Jürgen

The soft contact between two surfaces is fundamentally interesting for soft materials and fluid mechanics and relevant for friction and wear. The deformation of soft solid interfaces has received much interest because it interestingly reveals similarities to fluid wetting. We present an experimental route towards visualizing the three-dimensional contact geometry of either liquid-solid (i.e., oil and glass) or solid-solid (i.e., elastomer and glass) interfaces using a home-built combination of confocal microscopy and atomic force microscopy. We monitor the shape of a fluid capillary bridge and the depth of indentation in 3D while simultaneously measuring the force. In agreement with theoretical predictions, the height of the capillary bridge depends on the interfacial tensions. By using a slowly evaporating solvent, we quantify the temporal evolution of the capillary bridge and visualized the influence of pinning points on its shape. The position dependence of the advancing and receding contact angle along the three-phase contact line, particle-liquid-air, is resolved. Extending our system, we explore the contact deformation of soft solids where elasticity, in addition to surface tension, becomes an important factor.

Microvasculature of the cerebral cortex: a vascular corrosion cast and immunocytochemical study.

PubMed

Scala, Gaetano

2014-04-01

In mammals, the cerebral cortex microvasculature (CCM) of the neopallium plays important roles in the physiological and pathological processes of the brain. The aim of the present work is to analyze the CCM by use of the SEM-vascular corrosion cast technique, and to examine the immunocytochemical characteristics of the CCM in adult domestic ruminants (cattle, buffalo, and sheep) by using the SEM-immunogold technique. The CCM originated from the very small, finger-like terminal branches of the macrovasculature of the brain. The superficial cortical arterioles were more numerous than the deep straight arterioles which proceeded toward the white matter. The surface casts of the arterioles and capillaries of the cerebral cortex showed ring-shaped formations in the arterioles and at the origin of the capillaries. All capillaries down-stream from these ring-shaped formations were flaccid. Casts of the capillaries showed wrinkles due to the presence of endothelial folds, which is characteristic of varying blood pressure. Formations having intense anti-GIFAP immunoreactivity were frequently evident along the course of the blood capillaries in the cerebral cortex. These formations were probably astrocytes that might regulate the cerebral microcirculation based on physiological and pathological stimuli, such as neuronal activation. Copyright © 2014 Wiley Periodicals, Inc.

Capillary Pressure of a Liquid Between Uniform Spheres Arranged in a Square-Packed Layer

NASA Technical Reports Server (NTRS)

Alexader, J. Iwan D.; Slobozhanin, Lev A.; Collicott, Steven H.

2004-01-01

The capillary pressure in the pores defined by equidimensional close-packed spheres is analyzed numerically. In the absence of gravity the menisci shapes are constructed using Surface Evolver code. This permits calculation the free surface mean curvature and hence the capillary pressure. The dependences of capillary pressure on the liquid volume constructed here for a set of contact angles allow one to determine the evolution of basic capillary characteristics under quasi-static infiltration and drainage. The maximum pressure difference between liquid and gas required for a meniscus passing through a pore is calculated and compared with that for hexagonal packing and with approximate solution given by Mason and Morrow [l]. The lower and upper critical liquid volumes that determine the stability limits for the equilibrium capillary liquid in contact with square packed array of spheres are tabulated for a set of contact angles.

Hysteresis of the Contact Angle of a Meniscus Inside a Capillary with Smooth, Homogeneous Solid Walls.

PubMed

Kuchin, Igor V; Starov, Victor M

2016-05-31

A theory of contact angle hysteresis of a meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa, and equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero.

Thermal-capillary analysis of small-scale floating zones Steady-state calculations

NASA Technical Reports Server (NTRS)

Duranceau, J. L.; Brown, R. A.

1986-01-01

Galerkin finite element analysis of a thermal-capillary model of the floating zone crystal growth process is used to predict the dependence of molten zone shape on operating conditions for the growth of small silicon boules. The model accounts for conduction-dominated heat transport in the melt, feed rod and growing crystal and for radiation between these phases, the ambient and a heater. Surface tension acting on the shape of the melt/gas meniscus counteracts gravity to set the shape of the molten zone. The maximum diameter of the growing crystal is set by the dewetting of the melt from the feed rod when the crystal radius is large. Calculations with small Bond number show the increased zone lengths possible for growth in a microgravity environment. The sensitivity of the method to the shape and intensity of the applied heating distribution is demonstrated. The calculations are compared with experimental observations.

Microchannel-electrode alignment and separation parameters comparison in microchip capillary electrophoresis by scanning electrochemical microscopy.

PubMed

Wang, Kang; Xia, Xing-Hua

2006-03-31

The end of separation channel in a microchip was electrochemically mapped using the feedback imaging mode of scanning electrochemical microscopy (SECM). This method provides a convenient way for microchannel-electrode alignment in microchip capillary electrophoresis. Influence of electrode-to-channel positions on separation parameters in this capillary electrophoresis-electrochemical detection (CE-ED) was then investigated. For the trapezoid shaped microchannel, detection in the central area resulted in the best apparent separation efficiency and peak shape. In the electrode-to-channel distance ranging from 65 to 15mum, the limiting peak currents of dopamine increased with the decrease of the detection distance due to the limited diffusion and convection of the sample band. Results showed that radial position and axial distance of the detection electrode to microchannel was important for the improvement of separation parameters in CE amperometric detection.

Method and apparatus for automated processing and aliquoting of whole blood samples for analysis in a centrifugal fast analyzer

DOEpatents

Burtis, C.A.; Johnson, W.F.; Walker, W.A.

1985-08-05

A rotor and disc assembly for use in a centrifugal fast analyzer. The assembly is designed to process multiple samples of whole blood followed by aliquoting of the resultant serum into precisely measured samples for subsequent chemical analysis. The assembly requires minimal operator involvement with no mechanical pipetting. The system comprises: (1) a whole blood sample disc; (2) a serum sample disc; (3) a sample preparation rotor; and (4) an analytical rotor. The blood sample disc and serum sample disc are designed with a plurality of precision bore capillary tubes arranged in a spoked array. Samples of blood are loaded into the blood sample disc by capillary action and centrifugally discharged into cavities of the sample preparation rotor where separation of serum and solids is accomplished. The serum is loaded into the capillaries of the serum sample disc by capillary action and subsequently centrifugally expelled into cuvettes of the analyticaly rotor for conventional methods. 5 figs.

Dynamical clustering of red blood cells in capillary vessels.

PubMed

Boryczko, Krzysztof; Dzwinel, Witold; Yuen, David A

2003-02-01

We have modeled the dynamics of a 3-D system consisting of red blood cells (RBCs), plasma and capillary walls using a discrete-particle approach. The blood cells and capillary walls are composed of a mesh of particles interacting with harmonic forces between nearest neighbors. We employ classical mechanics to mimic the elastic properties of RBCs with a biconcave disk composed of a mesh of spring-like particles. The fluid particle method allows for modeling the plasma as a particle ensemble, where each particle represents a collective unit of fluid, which is defined by its mass, moment of inertia, translational and angular momenta. Realistic behavior of blood cells is modeled by considering RBCs and plasma flowing through capillaries of various shapes. Three types of vessels are employed: a pipe with a choking point, a curved vessel and bifurcating capillaries. There is a strong tendency to produce RBC clusters in capillaries. The choking points and other irregularities in geometry influence both the flow and RBC shapes, considerably increasing the clotting effect. We also discuss other clotting factors coming from the physical properties of blood, such as the viscosity of the plasma and the elasticity of the RBCs. Modeling has been carried out with adequate resolution by using 1 to 10 million particles. Discrete particle simulations open a new pathway for modeling the dynamics of complex, viscoelastic fluids at the microscale, where both liquid and solid phases are treated with discrete particles. Figure A snapshot from fluid particle simulation of RBCs flowing along a curved capillary. The red color corresponds to the highest velocity. We can observe aggregation of RBCs at places with the most stagnant plasma flow.

Star-shaped oscillations of Leidenfrost drops

NASA Astrophysics Data System (ADS)

Ma, Xiaolei; Liétor-Santos, Juan-José; Burton, Justin C.

2017-03-01

We experimentally investigate the self-sustained, star-shaped oscillations of Leidenfrost drops. The drops levitate on a cushion of evaporated vapor over a heated, curved surface. We observe modes with n =2 -13 lobes around the drop periphery. We find that the wavelength of the oscillations depends only on the capillary length of the liquid and is independent of the drop radius and substrate temperature. However, the number of observed modes depends sensitively on the liquid viscosity. The dominant frequency of pressure variations in the vapor layer is approximately twice the drop oscillation frequency, consistent with a parametric forcing mechanism. Our results show that the star-shaped oscillations are driven by capillary waves of a characteristic wavelength beneath the drop and that the waves are generated by a large shear stress at the liquid-vapor interface.

Automatic sampling and analysis of organics and biomolecules by capillary action-supported contactless atmospheric pressure ionization mass spectrometry.

PubMed

Hsieh, Cheng-Huan; Meher, Anil Kumar; Chen, Yu-Chie

2013-01-01

Contactless atmospheric pressure ionization (C-API) method has been recently developed for mass spectrometric analysis. A tapered capillary is used as both the sampling tube and spray emitter in C-API. No electric contact is required on the capillary tip during C-API mass spectrometric analysis. The simple design of the ionization method enables the automation of the C-API sampling system. In this study, we propose an automatic C-API sampling system consisting of a capillary (∼1 cm), an aluminium sample holder, and a movable XY stage for the mass spectrometric analysis of organics and biomolecules. The aluminium sample holder is controlled by the movable XY stage. The outlet of the C-API capillary is placed in front of the orifice of a mass spectrometer, whereas the sample well on the sample holder is moved underneath the capillary inlet. The sample droplet on the well can be readily infused into the C-API capillary through capillary action. When the sample solution reaches the capillary outlet, the sample spray is readily formed in the proximity of the mass spectrometer applied with a high electric field. The gas phase ions generated from the spray can be readily monitored by the mass spectrometer. We demonstrate that six samples can be analyzed in sequence within 3.5 min using this automatic C-API MS setup. Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells. Therefore, the C-API capillary could be readily flushed between runs. No carryover problems are observed during the analyses. The sample volume required for the C-API MS analysis is minimal, with less than 1 nL of the sample solution being sufficient for analysis. The feasibility of using this setup for quantitative analysis is also demonstrated.

Evaporation effect on two-dimensional wicking in porous media.

PubMed

Benner, Eric M; Petsev, Dimiter N

2018-03-15

We analyze the effect of evaporation on expanding capillary flow for losses normal to the plane of a two-dimensional porous medium using the potential flow theory formulation of the Lucas-Washburn method. Evaporation induces a finite steady state liquid flux on capillary flows into fan-shaped domains which is significantly greater than the flux into media of constant cross section. We introduce the evaporation-capillary number, a new dimensionless quantity, which governs the frontal motion when multiplied by the scaled time. This governing product divides the wicking behavior into simple regimes of capillary dominated flow and evaporative steady state, as well as the intermediate regime of evaporation influenced capillary driven motion. We also show flow dimensionality and evaporation reduce the propagation rate of the wet front relative to the Lucas-Washburn law. Copyright © 2017 Elsevier Inc. All rights reserved.

The Micromechanics of the Moving Contact Line

NASA Technical Reports Server (NTRS)

Lichter, Seth

1999-01-01

A transient moving contact line is investigated experimentally. The dynamic interface shape between 20 and 800 microns from the contact line is compared with theory. A novel experiment is devised, in which the contact line is set into motion by electrically altering the solid-liquid surface tension gamma(sub SL). The contact line motion simulates that of spontaneous wetting along a vertical plate with a maximum capillary number Ca approx. = 4 x 10(exp -2). The images of the dynamic meniscus are analyzed as a funtion of Ca. For comparison, the steady-state hydrodynamic equation based on the creeping flow model in a wedge geometry and the three-region uniform perturbation expansion of Cox (1986) is adopted. The interface shape is well depicted by the uniform solutions for Ca <= 10(exp -3). However, for Ca > 10(exp -3), the uniform solution over-predicts the viscous bending. This over-prediction can be accounted for by modifying the slip coefficient within the intermediate solution. With this correction, the measured interface shape is seen to match the theoretical prediction for all capillary numbers. The amount of slip needed to fit the measurements does not scale with the capillary number.

Microgravity Investigation of Capillary Driven Imbibition

NASA Astrophysics Data System (ADS)

Dushin, V. R.; Nikitin, V. F.; Smirnov, N. N.; Skryleva, E. I.; Tyurenkova, V. V.

2018-05-01

The goal of the present paper is to investigate the capillary driven filtration in porous media under microgravity conditions. New mathematical model that allows taking into account the blurring of the front due to the instability of the displacement that is developing at the front is proposed. The constants in the mathematical model were selected on the basis of the experimental data on imbibition into unsaturated porous media under microgravity conditions. The flow under the action of a combination of capillary forces and a constant pressure drop or a constant flux is considered. The effect of capillary forces and the type of wettability of the medium on the displacement process is studied. A criterion in which case the capillary effects are insignificant and can be neglected is established.

Combined electrophoresis-electrospray interface and method

DOEpatents

Smith, Richard D.; Udseth, Harold R.; Barinaga, Charles J.

1995-01-01

An improvement to the system and method for analyzing molecular constituents of a composition sample that comprises improvements to an electrospray ionization source for interfacing to mass spectrometers and other detection devices. The improvement consists of establishing a unique electrical circuit pattern and nozzle configuration, a metallic coated and conical shaped capillary outlet, coupled with sizing of the capillary to obtain maximum sensitivity.

[Magnetotherapy in obliterating vascular diseases of the lower extremities].

PubMed

Kirillov, Iu B; Shval'b, P G; Lastushkin, A V; Baranov, V M; Sigaev, A A; Zueva, G V; Karpov, E I

1992-01-01

The investigators have developed a polymagnetic system "Avrora-MK-01" employing running impulse magnetic field to treat diseases of the leg vessels by the action on peripheral capillary bed. At a pregangrene stage a positive effect on peripheral capillaries was achieved in 75-82% of the patients treated.

Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.

PubMed

Iliev, Stanimir; Pesheva, Nina

2016-06-01

We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1-0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012)LANGD50743-746310.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

Chitosan as cationic polyelectrolyte for the modification of electroosmotic flow and its utilization for the separation of inorganic anions by capillary zone electrophoresis.

PubMed

Takayanagi, Toshio; Motomizu, Shoji

2006-09-01

Cationic polyelectrolyte of chitosan was used for the reversal of electroosmotic flow in capillary zone electrophoresis. The chitosan was dissolved in acetic acid solution, and stable electroosmotic flow was obtained at the chitosan concentrations between 50 and 300 microg/mL. Separation of inorganic anions was carried out using the dynamically coated capillary by capillary zone electrophoresis. Nine kinds of anions were separated and detected with the capillary. The electrophoretic mobility of the analyte anions decreased with increasing concentrations of chitosan in the migrating solution through ion-ion interaction, but the migration order of the analyte anions was not changed in the concentration range of the chitosan examined. The signal shape for the analyte anions was developed by using field-enhanced sample stacking with 10 mM sodium sulfate.

Effect of dispersion forces on the capillary-wave fluctuations of liquid surfaces.

PubMed

Chacón, Enrique; Fernández, Eva M; Tarazona, Pedro

2014-04-01

We present molecular dynamics evidence for the nonanalytic effects of the long-range dispersion forces on the capillary waves fluctuations of a Lennard-Jones liquid surface. The results of the intrinsic sampling method, for the analysis of the instantaneous interfacial shape, are obtained in large systems for several cut-off distances of the potential tail, and they show good agreement with the theoretical prediction by Napiórkowski and Dietrich, based on a density functional analysis. The enhancement of the capillary waves is quantified to be within 1% for a simple liquid near its triple point.

Stabilizing detached Bridgman melt crystal growth: Proportional-integral feedback control

NASA Astrophysics Data System (ADS)

Yeckel, Andrew; Daoutidis, Prodromos; Derby, Jeffrey J.

2012-10-01

The dynamics, operability limits, and tuning of a proportional-integral feedback controller to stabilize detached vertical Bridgman crystal growth are analyzed using a capillary model of shape stability. The manipulated variable is the pressure difference between upper and lower vapor spaces, and the controlled variable is the gap width at the triple-phase line. Open and closed loop dynamics of step changes in these state variables are analyzed under both shape stable and shape unstable growth conditions. Effects of step changes in static contact angle and growth angle are also studied. Proportional and proportional-integral control can stabilize unstable growth, but only within tight operability limits imposed by the narrow range of allowed meniscus shapes. These limits are used to establish safe operating ranges of controller gain. Strong nonlinearity of the capillary model restricts the range of perturbations that can be stabilized, and under some circumstances, stabilizes a spurious operating state far from the set point. Stabilizing detachment at low growth angle proves difficult and becomes impossible at zero growth angle.

Wrapping a liquid drop with a thin elastic sheet

NASA Astrophysics Data System (ADS)

Paulsen, Joseph; Démery, Vincent; Davidovitch, Benny; Santangelo, Chris; Russell, Thomas; Menon, Narayanan

2014-11-01

We study the wrapping of a liquid drop by an initially-planar ultrathin (~ 100 nm) circular sheet. These elastic sheets can completely relax compressive stresses by forming wrinkles. In the experiment, we find that when a small fraction of the drop is covered, the overall shape of the sheet (i.e. averaging over the wrinkles) is axisymmetric. As we shrink the drop further, the sheet develops radial folds that break the axisymmetry of the sheet and the drop. Our data are consistent with a model where the sheet selects the shape that minimizes the exposed liquid surface area. We thus identify a ``geometric wrapping'' regime, where the partially-wrapped shape depends only on the relative radii of the sheet and the drop; the global breaking of axisymmetry is independent of the elastic energy of the deformed sheet. This regime requires that bending energy is negligible compared to surface energy, in contrast to the ``capillary origami'' regime where the static shape of the drop comes from a balance of bending and capillary forces.

Combined electrophoresis-electrospray interface and method

DOEpatents

Smith, R.D.; Udseth, H.R.; Barinaga, C.J.

1995-06-13

An improvement to the system and method is disclosed for analyzing molecular constituents of a composition sample that comprises improvements to an electrospray ionization source for interfacing to mass spectrometers and other detection devices. The improvement consists of establishing a unique electrical circuit pattern and nozzle configuration, a metallic coated and conical shaped capillary outlet, coupled with sizing of the capillary to obtain maximum sensitivity. 10 figs.

Self-assembly of triangular particles via capillary interactions

NASA Astrophysics Data System (ADS)

Bedi, Deshpreet; Zhou, Shangnan; Ferrar, Joseph; Solomon, Michael; Mao, Xiaoming

Colloidal particles adsorbed to a fluid interface deform the interface around them, resulting in either attractive or repulsive forces mediated by the interface. In particular, particle shape and surface roughness can produce an undulating contact line, such that the particles will assume energetically-favorable relative orientations and inter-particle distances to minimize the excess interfacial surface area. By expediently selecting specific particle shapes and associated design parameters, capillary interactions can be utilized to promote self-assembly of these particles into extended regular open structures, such as the kagome lattice, which have novel mechanical properties. We present the results of numerical simulations of equilateral triangle microprisms at an interface, including individually and in pairs. We show how particle bowing can yield two distinct binding events and connect it to theory in terms of a capillary multipole expansion and also to experiment, as presented in an accompanying talk. We also discuss and suggest design principles that can be used to create desirable open structures.

Numerical Modeling of Interstitial Fluid Flow Coupled with Blood Flow through a Remodeled Solid Tumor Microvascular Network

PubMed Central

Soltani, M.; Chen, P.

2013-01-01

Modeling of interstitial fluid flow involves processes such as fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. To date, majority of microvascular flow modeling has been done at different levels and scales mostly on simple tumor shapes with their capillaries. However, with our proposed numerical model, more complex and realistic tumor shapes and capillary networks can be studied. Both blood flow through a capillary network, which is induced by a solid tumor, and fluid flow in tumor’s surrounding tissue are formulated. First, governing equations of angiogenesis are implemented to specify the different domains for the network and interstitium. Then, governing equations for flow modeling are introduced for different domains. The conservation laws for mass and momentum (including continuity equation, Darcy’s law for tissue, and simplified Navier–Stokes equation for blood flow through capillaries) are used for simulating interstitial and intravascular flows and Starling’s law is used for closing this system of equations and coupling the intravascular and extravascular flows. This is the first study of flow modeling in solid tumors to naturalistically couple intravascular and extravascular flow through a network. This network is generated by sprouting angiogenesis and consisting of one parent vessel connected to the network while taking into account the non-continuous behavior of blood, adaptability of capillary diameter to hemodynamics and metabolic stimuli, non-Newtonian blood flow, and phase separation of blood flow in capillary bifurcation. The incorporation of the outlined components beyond the previous models provides a more realistic prediction of interstitial fluid flow pattern in solid tumors and surrounding tissues. Results predict higher interstitial pressure, almost two times, for realistic model compared to the simplified model. PMID:23840579

Thin sheets achieve optimal wrapping of liquids

NASA Astrophysics Data System (ADS)

Paulsen, Joseph; Démery, Vincent; Davidovitch, Benny; Santangelo, Christian; Russell, Thomas; Menon, Narayanan

2015-03-01

A liquid drop can wrap itself in a sheet using capillary forces [Py et al., PRL 98, 2007]. However, the efficiency of ``capillary origami'' at covering the surface of a drop is hampered by the mechanical cost of bending the sheet. Thinner sheets deform more readily by forming small-scale wrinkles and stress-focussing patterns, but it is unclear how coverage efficiency competes with mechanical cost as thickness is decreased, and what wrapping shapes will emerge. We place a thin (~ 100 nm) polymer film on a drop whose volume is gradually decreased so that the sheet covers an increasing fraction of its surface. The sheet exhibits a complex sequence of axisymmetric and polygonal partially- and fully- wrapped shapes. Remarkably, the progression appears independent of mechanical properties. The gross shape, which neglects small-scale features, is correctly predicted by a simple geometric approach wherein the exposed area is minimized. Thus, simply using a thin enough sheet results in maximal coverage.

Modification of narrow ablating capillaries under the influence of multiple femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gubin, K. V.; Lotov, K. V.; Trunov, V. I.; Pestryakov, E. V.

2016-09-01

Powerful femtosecond laser pulses that propagate through narrow ablating capillaries cause modification of capillary walls, which is studied experimentally and theoretically. At low intensities, the laser-induced periodic surface structures and porous coating composed of sub-micron particles appear on the walls. At higher intensities, the surface is covered by deposited droplets of the size up to 10 μm. In both cases, the ablated material forms a solid plug that completely blocks the capillary after several hundreds or thousands of pulses. The suggested theoretical model indicates that the plug formation is a universal effect. It must take place in any narrow tube subject to ablation under the action of short laser pulses.

On the unsteady gravity-capillary wave pattern found behind a slow moving localized pressure distribution

NASA Astrophysics Data System (ADS)

Masnadi, N.; Duncan, J. H.

2013-11-01

The non-linear response of a water surface to a slow-moving pressure distribution is studied experimentally using a vertically oriented carriage-mounted air-jet tube that is set to translate over the water surface in a long tank. The free surface deformation pattern is measured with a full-field refraction-based method that utilizes a vertically oriented digital movie camera (under the tank) and a random dot pattern (above the water surface). At towing speeds just below the minimum phase speed of gravity-capillary waves (cmin ~ 23 cm/s), an unsteady V-shaped pattern is formed behind the pressure source. Localized depressions are generated near the source and propagate in pairs along the two arms of the V-shaped pattern. These depressions are eventually shed from the tips of the pattern at a frequency of about 1 Hz. It is found that the shape and phase speeds of the first depressions shed in each run are quantitatively similar to the freely-propagating gravity-capillary lumps from potential flow calculations. In the experiments, the amplitudes of the depressions decrease by approximately 60 percent while travelling 12 wavelengths. The depressions shed later in each run behave in a less consistent manner, probably due to their interaction with neighboring depressions.

A novel model for simulating the racing effect in capillary-driven underfill process in flip chip

NASA Astrophysics Data System (ADS)

Zhu, Wenhui; Wang, Kanglun; Wang, Yan

2018-04-01

Underfill is typically applied in flip chips to increase the reliability of the electronic packagings. In this paper, the evolution of the melt-front shape of the capillary-driven underfill flow is studied through 3D numerical analysis. Two different models, the prevailing surface force model and the capillary model based on the wetted wall boundary condition, are introduced to test their applicability, where level set method is used to track the interface of the two phase flow. The comparison between the simulation results and experimental data indicates that, the surface force model produces better prediction on the melt-front shape, especially in the central area of the flip chip. Nevertheless, the two above models cannot simulate properly the racing effect phenomenon that appears during underfill encapsulation. A novel ‘dynamic pressure boundary condition’ method is proposed based on the validated surface force model. Utilizing this approach, the racing effect phenomenon is simulated with high precision. In addition, a linear relationship is derived from this model between the flow front location at the edge of the flip chip and the filling time. Using the proposed approach, the impact of the underfill-dispensing length on the melt-front shape is also studied.

Carbon Nanotube Bonding Strength Enhancement Using Metal "Wicking" Process

NASA Technical Reports Server (NTRS)

Lamb, James L.; Dickie, Matthew R.; Kowalczyk, Robert S.; Liao, Anna; Bronikowski, Michael J.

2012-01-01

Carbon nanotubes grown from a surface typically have poor bonding strength at the interface. A process has been developed for adding a metal coat to the surface of carbon nano tubes (CNTs) through a wicking process, which could lead to an enhanced bonding strength at the interface. This process involves merging CNTs with indium as a bump-bonding enhancement. Classical capillary theory would not normally allow materials that do not wet carbon or graphite to be drawn into the spacings by capillary action because the contact angle is greater than 90 degrees. However, capillary action can be induced through JPL's ability to fabricate oriented CNT bundles to desired spacings, and through the use of deposition techniques and temperature to control the size and mobility of the liquid metal streams and associated reservoirs. A reflow and plasma cleaning process has also been developed and demonstrated to remove indium oxide, and to obtain smooth coatings on the CNT bundles.

Dumbbell-shaped intrathoracic-extradural haemangioma of the thoracic spine.

PubMed

Doyle, P M; Abou-Zeid, A; Du Plessis, D; Herwadkar, A; Gnanalingham, K K

2008-04-01

Spinal haemangiomas are benign vasoproliferative lesions that are typically intra-osseous and generally asymptomatic, although localized pain can be a symptom. Capillary and cavernous variants have been described. We describe a rare case of a dumbbell-shaped haemangioma of the thoracic spine with both an intraspinal-extradural and intrathoracic component.

Symmetric and asymmetric capillary bridges between a rough surface and a parallel surface.

PubMed

Wang, Yongxin; Michielsen, Stephen; Lee, Hoon Joo

2013-09-03

Although the formation of a capillary bridge between two parallel surfaces has been extensively studied, the majority of research has described only symmetric capillary bridges between two smooth surfaces. In this work, an instrument was built to form a capillary bridge by squeezing a liquid drop on one surface with another surface. An analytical solution that describes the shape of symmetric capillary bridges joining two smooth surfaces has been extended to bridges that are asymmetric about the midplane and to rough surfaces. The solution, given by elliptical integrals of the first and second kind, is consistent with a constant Laplace pressure over the entire surface and has been verified for water, Kaydol, and dodecane drops forming symmetric and asymmetric bridges between parallel smooth surfaces. This solution has been applied to asymmetric capillary bridges between a smooth surface and a rough fabric surface as well as symmetric bridges between two rough surfaces. These solutions have been experimentally verified, and good agreement has been found between predicted and experimental profiles for small drops where the effect of gravity is negligible. Finally, a protocol for determining the profile from the volume and height of the capillary bridge has been developed and experimentally verified.

Wettability control on fluid-fluid displacements in patterned microfluidics and porous media

NASA Astrophysics Data System (ADS)

Juanes, Ruben; Trojer, Mathias; Zhao, Benzhong

2014-11-01

While it is well known that the wetting properties are critical in two-phase flows in porous media, the effect of wettability on fluid displacement continues to challenge our microscopic and macroscopic descriptions. Here we study this problem experimentally, starting with the classic experiment of two-phase flow in a capillary tube. We image the shape of the meniscus and measure the associated capillary pressure for a wide range of capillary numbers. We synthesize new observations on the dependence of the dynamic capillary pressure on wetting properties (contact angle) and flow conditions (viscosity contrast and capillary number). We then conduct experiments on a planar microfluidic device patterned with vertical posts. We track the evolution of the fluid-fluid interface and elucidate the impact of wetting on the cooperative nature of fluid displacement during pore invasion events. We use the insights gained from the capillary tube and patterned microfluidics experiments to elucidate the effect of wetting properties on viscous fingering and capillary fingering in a Hele-Shaw cell filled with glass beads, where we observe a contact-angle-dependent stabilizing behavior for the emerging flow instabilities, as the system transitions from drainage to imbibition.

Interfacial Bubble Deformations

NASA Astrophysics Data System (ADS)

Seymour, Brian; Shabane, Parvis; Cypull, Olivia; Cheng, Shengfeng; Feitosa, Klebert

Soap bubbles floating at an air-water experience deformations as a result of surface tension and hydrostatic forces. In this experiment, we investigate the nature of such deformations by taking cross-sectional images of bubbles of different volumes. The results show that as their volume increases, bubbles transition from spherical to hemispherical shape. The deformation of the interface also changes with bubble volume with the capillary rise converging to the capillary length as volume increases. The profile of the top and bottom of the bubble and the capillary rise are completely determined by the volume and pressure differences. James Madison University Department of Physics and Astronomy, 4VA Consortium, Research Corporation for Advancement of Science.

Mathematical and computational studies of equilibrium capillary free surfaces

NASA Technical Reports Server (NTRS)

Albright, N.; Chen, N. F.; Concus, P.; Finn, R.

1977-01-01

The results of several independent studies are presented. The general question is considered of whether a wetting liquid always rises higher in a small capillary tube than in a larger one, when both are dipped vertically into an infinite reservoir. An analytical investigation is initiated to determine the qualitative behavior of the family of solutions of the equilibrium capillary free-surface equation that correspond to rotationally symmetric pendent liquid drops and the relationship of these solutions to the singular solution, which corresponds to an infinite spike of liquid extending downward to infinity. The block successive overrelaxation-Newton method and the generalized conjugate gradient method are investigated for solving the capillary equation on a uniform square mesh in a square domain, including the case for which the solution is unbounded at the corners. Capillary surfaces are calculated on the ellipse, on a circle with reentrant notches, and on other irregularly shaped domains using JASON, a general purpose program for solving nonlinear elliptic equations on a nonuniform quadrilaterial mesh. Analytical estimates for the nonexistence of solutions of the equilibrium capillary free-surface equation on the ellipse in zero gravity are evaluated.

Interfacing 3D micro/nanochannels with a branch-shaped reservoir enhances fluid and mass transport

NASA Astrophysics Data System (ADS)

Kumar, Prasoon; Gandhi, Prasanna S.; Majumder, Mainak

2017-01-01

Three-dimensional (3D) micro/nanofluidic devices can accelerate progress in numerous fields such as tissue engineering, drug delivery, self-healing and cooling devices. However, efficient connections between networks of micro/nanochannels and external fluidic ports are key to successful applications of 3D micro/nanofluidic devices. Therefore, in this work, the extent of the role of reservoir geometry in interfacing with vascular (micro/nanochannel) networks, and in the enabling of connections with external fluidic ports while maintaining the compactness of devices, has been experimentally and theoretically investigated. A statistical modelling suggested that a branch-shaped reservoir demonstrates enhanced interfacing with vascular networks when compared to other regular geometries of reservoirs. Time-lapse dye flow experiments by capillary action through fabricated 3D micro/nanofluidic devices confirmed the connectivity of branch-shaped reservoirs with micro/nanochannel networks in fluidic devices. This demonstrated a ~2.2-fold enhancement of the volumetric flow rate in micro/nanofluidic networks when interfaced to branch-shaped reservoirs over rectangular reservoirs. The enhancement is due to a ~2.8-fold increase in the perimeter of the reservoirs. In addition, the mass transfer experiments exhibited a ~1.7-fold enhancement in solute flux across 3D micro/nanofluidic devices that interfaced with branch-shaped reservoirs when compared to rectangular reservoirs. The fabrication of 3D micro/nanofluidic devices and their efficient interfacing through branch-shaped reservoirs to an external fluidic port can potentially enable their use in complex applications, in which enhanced surface-to-volume interactions are desirable.

Determination of Surface Tension of Surfactant Solutions through Capillary Rise Measurements: An Image-Processing Undergraduate Laboratory Experiment

ERIC Educational Resources Information Center

Huck-Iriart, Cristia´n; De-Candia, Ariel; Rodriguez, Javier; Rinaldi, Carlos

2016-01-01

In this work, we described an image processing procedure for the measurement of surface tension of the air-liquid interface using isothermal capillary action. The experiment, designed for an undergraduate course, is based on the analysis of a series of solutions with diverse surfactant concentrations at different ionic strengths. The objective of…

Microfluidic devices connected to fused-silica capillaries with minimal dead volume.

PubMed

Bings, N H; Wang, C; Skinner, C D; Colyer, C L; Thibault, P; Harrison, D J

1999-08-01

Fused-silica capillaries have been connected to microfluidic devices for capillary electrophoresis by drilling into the edge of the device using 200-μm tungsten carbide drills. The standard pointed drill bits create a hole with a conical-shaped bottom that leads to a geometric dead volume of 0.7 nL at the junction, and significant band broadening when used with 0.2-nL sample plugs. The plate numbers obtained on the fused-silica capillary connected to the chip were about 16-25% of the predicted numbers. The conical area was removed with a flat-tipped drill bit and the band broadening was substantially eliminated (on average 98% of the predicted plate numbers were observed). All measurements were made while the device was operating with an electrospray from the end of the capillary. The effective dead volume of the flat-bottom connection is minimal and allows microfluidic devices to be connected to a wide variety of external detectors.

Student Design Challenges in Capillary Flow

NASA Technical Reports Server (NTRS)

Stocker, Dennis P.; Wollman, Andrew; Hall, Nancy R.; Weislogel, Mark; DeLombard, Richard

2016-01-01

For some grade 8-12 students, capillary flow has bridged the gap between the classroom and research facility, from normal gravity to microgravity. In the past four years, NASA and the Portland State University (PSU) have jointly challenged students to design test cells, using Computer-Aided Design (CAD), to study capillary action in microgravity as PSU has done on the International Space Station (ISS). Using the student-submitted CAD drawings, the test cells were manufactured by PSU and tested in their 2.1-second drop tower. The microgravity results were made available online for student analysis and reporting. Over 100 such experiments have been conducted, where there has been participation from 15 states plus a German school for the children of U.S. military personnel. In 2016, a related NASA challenge was held in partnership with the ASGSR, again, based on the research conducted by PSU. In this challenge, grade 9-12 students designed and built devices using capillary action to launch droplets as far as possible in NASAs 2.2 Second Drop Tower. Example results will be presented by students at this conference. The challenges engage students in ISS science and technology and can inspire them to pursue technical careers.

Technology Solutions Case Study: Capillary Break Beneath a Slab: Polyethylene Sheeting over Aggregate, Southwestern Pennsylvania

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2014-07-01

In this project, Building America team IBACOS worked with a builder of single- and multifamily homes in southwestern Pennsylvania (climate zone 5) to understand its methods of successfully using polyethylene sheeting over aggregate as a capillary break beneath the slab in new construction. This builder’s homes vary in terms of whether they have crawlspaces or basements. However, in both cases, the strategy protects the home from water intrusion via capillary action (e.g., water wicking into cracks and spaces in the slab), thereby helping to preserve the durability of the home.

Advancement of atmospheric-vacuum interfaces for mass spectrometers with a focus on increasing gas throughput for improving sensitivity.

PubMed

Prasad, Satendra; Wouters, Eloy R; Dunyach, Jean-Jacques

2015-08-18

Ion sampling from an electrospray ionization (ESI) source was improved by increasing gas conductance of the MS inlet by 4.3-fold. Converting the gas throughput (Q) into sensitivity improvement was dependent on ion desolvation and handling of the gas load. Desolvation was addressed by using a novel slot shaped inlet that exhibited desolvation properties identical to the 0.58 mm i.d capillary. An assay tailored for "small molecules" at high chromatographic flow rate (500 μL/min) yielded a compound dependent 6.5 to 14-fold signal gain while analysis at nano chromatographic flow rate (300 nL/min) showed 2 to 3.5-fold improvement for doubly charged peptides. Improvement exceeding the Q (4.3-fold) at high chromatographic flow rate was explained by superior sampling of the spatially dispersed ion spray when using the slot shaped capillary. Sensitivity improvement across a wide range of chromatographic flow rate confirmed no compromise in ion desolvation with the increase in Q. Another improvement included less overflow of gas into the mass analyzer from the foreline region owing to the slot shape of the capillary. By doubling the roughing pump capacity and operating the electrodynamic ion funnel (EDIF) at ∼4 Torr, a single pumping stage was sufficient to handle the gas load. The transport of solvent clusters from the LC effluent into the mass analyzer was prevented by a "wavy shaped" transfer quadrupole and was compared with a benchmark approach that delivered ions orthogonally into a differentially pumped dual EDIF at comparable gas Q.

Continuous-Flow Electrophoresis of DNA and Proteins in a Two-Dimensional Capillary-Well Sieve.

PubMed

Duan, Lian; Cao, Zhen; Yobas, Levent

2017-09-19

Continuous-flow electrophoresis of macromolecules is demonstrated using an integrated capillary-well sieve arranged into a two-dimensional anisotropic array on silicon. The periodic array features thousands of entropic barriers, each resulting from an abrupt interface between a 2 μm deep well (channel) and a 70 nm capillary. These entropic barriers owing to two-dimensional confinement within the capillaries are vastly steep in relation to those arising from slits featuring one-dimensional confinement. Thus, the sieving mechanisms can sustain relatively large electric field strengths over a relatively small array area. The sieve rapidly sorts anionic macromolecules, including DNA chains and proteins in native or denatured states, into distinct trajectories according to size or charge under electric field vectors orthogonally applied. The baseline separation is achieved in less than 1 min within a horizontal migration length of ∼1.5 mm. The capillaries are self-enclosed conduits in cylindrical profile featuring a uniform diameter and realized through an approach that avoids advanced patterning techniques. The approach exploits a thermal reflow of a layer of doped glass for shape transformation into cylindrical capillaries and for controllably shrinking the capillary diameter. Lastly, atomic layer deposition of alumina is introduced for the first time to fine-tune the capillary diameter as well as to neutralize the surface charge, thereby suppressing undesired electroosmotic flows.

Apparent dynamic contact angle of an advancing gas--liquid meniscus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalliadasis, S.; Chang, H.

1994-01-01

The steady motion of an advancing meniscus in a gas-filled capillary tube involves a delicate balance of capillary, viscous, and intermolecular forces. The limit of small capillary numbers Ca (dimensionless speeds) is analyzed here with a matched asymptotic analysis that links the outer capillary region to the precursor film in front of the meniscus through a lubricating film. The meniscus shape in the outer region is constructed and the apparent dynamic contact angle [Theta] that the meniscus forms with the solid surface is derived as a function of the capillary number, the capillary radius, and the Hamaker's constant for intermolecularmore » forces, under conditions of weak gas--solid interaction, which lead to fast spreading of the precursor film and weak intermolecular forces relative to viscous forces within the lubricating film. The dependence on intermolecular forces is very weak and the contact angle expression has a tight upper bound tan [Theta]=7.48 Ca[sup 1/3] for thick films, which is independent of the Hamaker constant. This upper bound is in very good agreement with existing experimental data for wetting fluids in any capillary and for partially wetting fluids in a prewetted capillary. Significant correction to the Ca[sup 1/3] dependence occurs only at very low Ca, where the intermolecular forces become more important and tan [Theta] diverges slightly from the above asymptotic behavior toward lower values.« less

Reconstruction of thin fluorophore-filled capillaries in thick scattering medium using fluorescence diffuse optical tomography within the diffusion approximation

NASA Astrophysics Data System (ADS)

Desrochers, Johanne; Vermette, Patrick; Fontaine, Réjean; Bérubé-Lauzière, Yves

2009-02-01

Current efforts in tissue engineering target the growth of 3D volumes of tissue cultures in bioreactor conditions. Fluorescence optical tomography has the potential to monitor cells viability and tissue growth non-destructively directly within the bioreactor via bio-molecular fluorescent labelling strategies. We currently work on developing the imaging instrumentation for tissue cultures in bioreactor conditions. Previously, we localized in 3D thin fluorescent-labelled capillaries in a cylindrically shaped bioreactor phantom containing a diffusive medium with our time-of-flight localization technique. Here, we present our first reconstruction results of the spatial distribution of fluorophore concentrations for labelled capillaries embedded in a bioreactor phantom.

Tapered monocapillary-optics for point source applications

DOEpatents

Hirsch, Gregory

2000-01-01

A glass or metal wire is precisely etched to form the paraboloidal or ellipsoidal shape of the final desired capillary optic. This shape is created by carefully controlling the withdrawal speed of the wire from an etchant bath. In the case of a complete ellipsoidal capillary, the etching operation is performed twice in opposite directions on adjacent wire segments. The etched wire undergoes a subsequent operation to create an extremely smooth surface. This surface is coated with a layer of material which is selected to maximize the reflectivity of the radiation. This reflective surface may be a single layer for wideband reflectivity, or a multilayer coating for optimizing the reflectivity in a narrower wavelength interval. The coated wire is built up with a reinforcing layer, typically by a plating operation. The initial wire is removed by either an etching procedure or mechanical force. Prior to removing the wire, the capillary is typically bonded to a support substrate. One option for attaching the wire to the substrate produces a monolithic structure by essentially burying it under a layer of plating which covers both the wire and the substrate. The capillary optic is used for efficiently collecting and redirecting the divergent radiation from a source which could be the anode of an x-ray tube, a plasma source, the fluorescent radiation from an electron microprobe, or some other source of radiation.

Supersonic plasma jets in experiments for radiophysical testing of bodies flow

NASA Astrophysics Data System (ADS)

Balakirev, B. A.; Bityurin, V. A.; Bocharov, A. N.; Brovkin, V. G.; Vedenin, P. V.; Lashkov, V. A.; Mashek, I. Ch; Pashchina, A. S.; Petrovskiy, V. P.; Khoronzhuk, R. S.; Dobrovolskaya, A. S.

2018-01-01

The action of differently oriented magnetic fields on the parameters of bow shock created in the vicinity of aerodynamic bodies placed into the supersonic gas-plasma flows is studied. For these experiments two types of the high speed plasma jet sources are used—magneto-plasma compressor (MPC) and powerful pulse capillary type discharge. MPC allows to create the plasma jets with gas flow velocity of 10 ± 2 km/s, lifetime 30-50 μs, temperature Te ≈ 3 ± 0.5 eV, electron density about ne ˜ 1016cm-3 and temperature Te ≈ 3 ± 0.5 eV. The jet source based on powerful capillary discharge creates the flows with lifetime 1-20 ms, Mach numbers 3-8, plasma flow velocity 3-10 km/s, vibration and rotation temperatures 9000-14000 and 3800-6000 K respectively. The results of our first experiments show the possibility of using gas-plasma sources based on MPC and powerful capillary discharge for aerodynamic and radiophysical experiments. Comparatively small magnetic field B = 0.23-0.5 T, applied to the obtained bow shocks, essentially modify them. This can lead to a change in shape and an increase in the distance between the detached shock wave and the streamlined body surface if B is parallel to the jet velocity or to decrease this parameter if B is orthogonal to the oncoming flow. Probably, the first case can be useful for reducing the thermal load and aerodynamic drug of streamlined body and the second case can be used to control the radio-transparency of the plasma layer and solving the blackout problem.

Effect of wave action on near-well zone cleaning

NASA Astrophysics Data System (ADS)

Pen'kovskii, V. I.; Korsakova, N. K.

2017-10-01

Drilling filtrate invasion into the producing formation and native water accumulating of the near-well zone in well operation reduce the well productivity. As a result of that, depending on characteristic capillary pressure scale and differential pressure drawdown, oil production rate may become lower than expected one. In this paper, it is considered the hysteresis effects of capillary pressure after reversion of displacement. As applied to laboratory experiment conditions, the solution of problem of oil flow in formation model with a pressure drop on the model sides harmonically varied with time is presented. It was estimated a range of fluid vibration effective action on the near-well zone cleaning from capillary locking water. The plant simulating extraction of oil from formation using widely practised sucker-rod pump has been created. Formation model is presented as a slot filled with broken glass between two plates. In the process, natural oil and sodium chloride solution were used as working fluids. The experiments qualitatively confirm a positive effect of jack pumps on the near-well zone cleaning.

Motion of deformable drops through granular media and other confined geometries.

PubMed

Davis, Robert H; Zinchenko, Alexander Z

2009-06-15

This article features recent simulation studies of the flow of emulsions containing deformable drops through pores, constrictions, and granular media. The flow is assumed to be at low Reynolds number, so that viscous forces dominate, and boundary-integral methods are used to determine interfacial velocities and, hence, track the drop motion and shapes. A single drop in a flat channel migrates to the channel centerplane due to deformation-induced drift, which increases its steady-state velocity along the channel. A drop moving towards a smaller interparticle constriction squeezes through the constriction if the capillary number (ratio of viscous deforming forces and interfacial tension forces) is large enough, but it becomes trapped when the capillary number is below a critical value. These concepts then influence the flow of an emulsion through a granular medium, for which the drop phase moves faster than the suspending liquid at large capillary numbers but slower than the suspending liquid at smaller capillary numbers. The permeabilities of the granular medium to both phases increase with increasing capillary number, due to the reduced resistance to squeezing of easily deformed drops, though drop breakup must also be considered at large capillary numbers.

Capillary flow enhancement in rectangular polymer microchannels with a deformable wall.

PubMed

Anoop, R; Sen, A K

2015-07-01

We report the capillary flow enhancement in rectangular polymer microchannels, when one of the channel walls is a deformable polymer membrane. We provide detailed insight into the physics of elastocapillary interaction between the capillary flow and elastic membrane, which leads to significant improvements in capillary flow performance. As liquid flows by capillary action in such channels, the deformable wall deflects inwards due to the Young-Laplace pressure drop across the liquid meniscus. This, in turn, decreases the radius of curvature of the meniscus and increases the driving capillary pressure. A theoretical model is proposed to predict the resultant increase in filling speed and rise height, respectively, in deformable horizontal and vertical microchannels having large aspect ratios. A non-dimensional parameter J, which represents the ratio of the capillary force to the mechanical restoring force, is identified to quantify the elastocapillary effects in terms of the improvement in filling speed (for J>0.238) and the condition for channel collapse (J>1). The theoretical predictions show good agreement with experimental data obtained using deformable rectangular poly(dimethylsiloxane) microchannels. Both model predictions and experimental data show that over 15% improvement in the Washburn coefficient in horizontal channels, and over 30% improvement in capillary rise height in vertical channels, are possible prior to channel collapse. The proposed technique of using deformable membranes as channel walls is a viable method for capillary flow enhancement in microfluidic devices.

Exotic containers for capillary surfaces

NASA Technical Reports Server (NTRS)

Concus, Paul; Finn, Robert

1991-01-01

This paper discusses 'exotic' rotationally symmetric containers that admit an entire continuum of distinct equilibrium capillary free surfaces. The paper extends earlier work to a larger class of parameters and clarifies and simplifies the governing differential equations, while expressing them in a parametric form appropriate for numerical integration. A unified presentation suitable for both zero and nonzero gravity is given. Solutions for the container shapes are depicted graphically along with members of the free-surface continuum, and comments are given concerning possible physical experiments.

Infiltration of MHD liquid into a deformable porous material

NASA Astrophysics Data System (ADS)

Naseem, Anum; Mahmood, Asif; Siddique, J. I.; Zhao, Lifeng

2018-03-01

We analyze the capillary rise dynamics for magnetohydrodynamics (MHD) fluid flow through deformable porous material in the presence of gravity effects. The modeling is performed using mixture theory approach and mathematical manipulation yields a nonlinear free boundary problem. Due to the capillary rise action, the pressure gradient in the liquid generates a stress gradient that results in the deformation of porous substrate. The capillary rise process for MHD fluid slows down as compared to Newtonian fluid case. Numerical solutions are obtained using a method of lines approach. The graphical results are presented for important physical parameters, and comparison is presented with Newtonian fluid case.

Self-Sealed Bionic Long Microchannels with Thin Walls and Designable Nanoholes Prepared by Line-Contact Capillary-Force Assembly.

PubMed

Lao, Zhao-Xin; Hu, Yan-Lei; Pan, Deng; Wang, Ren-Yan; Zhang, Chen-Chu; Ni, Jin-Cheng; Xu, Bing; Li, Jia-Wen; Wu, Dong; Chu, Jia-Ru

2017-06-01

Long microchannels with thin walls, small width, and nanoholes or irregular shaped microgaps, which are similar to capillaries or cancerous vessels, are urgently needed to simulate the physiological activities in human body. However, the fabrication of such channels remains challenging. Here, microchannels with designable holes are manufactured by combining laser printing with line-contact capillary-force assembly. Two microwalls are first printed by femtosecond laser direct-writing, and subsequently driven to collapse into a channel by the capillary force that arises in the evaporation of developer. The channel can remain stable in solvent due to the enhanced Van der Waals' force caused by the line-contact of microwalls. Microchannels with controllable nanoholes and almost arbitrary patterns can be fabricated without any bonding or multistep processes. As-prepared microchannels, with wall thicknesses less than 1 µm, widths less than 3 µm, lengths more than 1 mm, are comparable with human capillaries. In addition, the prepared channels also exhibit the ability to steer the flow of liquid without any external pump. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical investigations of two-phase flow with dynamic capillary pressure in porous media via a moving mesh method

NASA Astrophysics Data System (ADS)

Zhang, Hong; Zegeling, Paul Andries

2017-09-01

Motivated by observations of saturation overshoot, this paper investigates numerical modeling of two-phase flow in porous media incorporating dynamic capillary pressure. The effects of the dynamic capillary coefficient, the infiltrating flux rate and the initial and boundary values are systematically studied using a traveling wave ansatz and efficient numerical methods. The traveling wave solutions may exhibit monotonic, non-monotonic or plateau-shaped behavior. Special attention is paid to the non-monotonic profiles. The traveling wave results are confirmed by numerically solving the partial differential equation using an accurate adaptive moving mesh solver. Comparisons between the computed solutions using the Brooks-Corey model and the laboratory measurements of saturation overshoot verify the effectiveness of our approach.

Single particles accelerate final stages of capillary break-up

NASA Astrophysics Data System (ADS)

Lindner, Anke; Fiscina, Jorge Eduardo; Wagner, Christian

2015-06-01

Droplet formation of suspensions is present in many industrial and technological processes such as coating and food engineering. Whilst the finite-time singularity of the minimum neck diameter in capillary break-up of simple liquids can be described by well-known self-similarity solutions, the pinching of non-Brownian suspension depends in a complex way on the particle dynamics in the thinning thread. Here we focus on the very dilute regime where the filament contains only isolated beads to identify the physical mechanisms leading to the pronounced acceleration of the filament thinning observed. This accelerated regime is characterized by an asymmetric shape of the filament with an enhanced curvature that depends on the size and the spatial distribution of the particles within the capillary thread.

Bubble deformations and segmented flows in corrugated microchannels at large capillary numbers

NASA Astrophysics Data System (ADS)

Sauzade, Martin; Cubaud, Thomas

2018-03-01

We experimentally investigate the interaction between individual bubble deformations and collective distortions of segmented flows in nonlinear microfluidic geometries. Using highly viscous carrier fluids, we study the evolution of monodisperse trains of gas bubbles from a square to a smoothly corrugated microchannel characterized with a series of extensions and constrictions along the flow path. The hysteresis in the bubble shape between accelerating and decelerating flow fields is shown to increase with the capillary number. Measurements of instantaneous bubble velocities reveal the presence of a capillary pull that produces a nonmonotonic behavior for the front velocity in accelerating flow regions. Functional relationships are developed for predicting the morphology and dynamics of viscous multiphase flow patterns at the pore scale.

Capillary Origami Inspired Fabrication of Complex 3D Hydrogel Constructs.

PubMed

Li, Moxiao; Yang, Qingzhen; Liu, Hao; Qiu, Mushu; Lu, Tian Jian; Xu, Feng

2016-09-01

Hydrogels have found broad applications in various engineering and biomedical fields, where the shape and size of hydrogels can profoundly influence their functions. Although numerous methods have been developed to tailor 3D hydrogel structures, it is still challenging to fabricate complex 3D hydrogel constructs. Inspired by the capillary origami phenomenon where surface tension of a droplet on an elastic membrane can induce spontaneous folding of the membrane into 3D structures along with droplet evaporation, a facile strategy is established for the fabrication of complex 3D hydrogel constructs with programmable shapes and sizes by crosslinking hydrogels during the folding process. A mathematical model is further proposed to predict the temporal structure evolution of the folded 3D hydrogel constructs. Using this model, precise control is achieved over the 3D shapes (e.g., pyramid, pentahedron, and cube) and sizes (ranging from hundreds of micrometers to millimeters) through tuning membrane shape, dimensionless parameter of the process (elastocapillary number Ce ), and evaporation time. This work would be favorable to multiple areas, such as flexible electronics, tissue regeneration, and drug delivery. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new approach to stability and oscillations of constrained drops and capillary bridges

NASA Astrophysics Data System (ADS)

Fabre, David; Chireux, Veronique; Risso, Frederic; Tordjeman, Philippe

2014-11-01

Static equilibria of liquid inclusions under the effect of gravity and capillarity is a large class of situations which encompasses drops hanging from a ceiling or from a capillary, sessile drops, liquid bridges, etc... In such equilibria the surface shape is governed by the Yong-Laplace equation, which is usually solved in a local way using a ``shooting'' method. We introduce a new method which solves the Laplace-Young in a global way, using an iterative deformation of the shape towards the equilibrium shape. The method is easy to implement and versatile, and allows to prescribe constraints such as the volume of liquid, the angle of attachment, etc... We subsequently consider the issue of stability and oscillations of such configurations. Using finite elements and considering small-amplitude displacements of the surface with respect to the static configuration previously computed, we introduce a global stability approach which allows to predict the stability limits, the oscillation frequencies and the eigenmode shapes for quite general geometries. The approach will be illustrated and compared with experiments in two situations, namely a drop attached to a capilary and a liquid bridge resulting from the coalescence of two facing millimetric drops.

The Effect of Faraday Waves on Gas Transport

NASA Astrophysics Data System (ADS)

Saylor, J. R.; Handler, R. A.

1996-11-01

The increase in the rate of gas transport at the onset of capillary wave formation is a frequently observed phenomenon. However, a causal relationship between the presence of capillary waves and enhanced gas transport has not been experimentally demonstrated. Here we present experimental results of CO2 transport rates across Faraday waves. The piston velocity versus wave slope data explicitly demonstrates an enhancement in gas transport due to these waves. The functional relationship between gas flux and wave slope is also obtained. The Faraday wave system permits investigation of capillary waves in the absence of the obfuscating effects of air turbulence, water turbulence, droplets and bubbles, all of which are present in wind/wave tank studies. Hence, our results are solely due to the effects of capillary wave action. Data for wave frequencies varying from 20Hz to 200Hz are presented.

Modeling the Capillary Pressure for the Migration of the Liquid Phase in Granular Solid-Liquid-Vapor Systems: Application to the Control of the Composition Profile in W-Cu FGM Materials

NASA Astrophysics Data System (ADS)

Missiaen, Jean-Michel; Raharijaona, Jean-Joël; Delannay, Francis

2016-11-01

A model is developed to compute the capillary pressure for the migration of the liquid phase out or into a uniform solid-liquid-vapor system. The capillary pressure is defined as the reduction of the overall interface energy per volume increment of the transferred fluid phase. The model takes into account the particle size of the solid particle aggregate, the packing configuration (coordination number, porosity), the volume fractions of the different phases, and the values of the interface energies in the system. The model is used for analyzing the stability of the composition profile during processing of W-Cu functionally graded materials combining a composition gradient with a particle size gradient. The migration pressure is computed with the model in two stages: (1) just after the melting of copper, i.e., when sintering and shape accommodation of the W particle aggregate can still be neglected and (2) at high temperature, when the system is close to full density with equilibrium particle shape. The model predicts well the different stages of liquid-phase migration observed experimentally.

Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop

NASA Astrophysics Data System (ADS)

Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

2016-04-01

The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996), 10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects—surface charge convection and shape deformation—towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

Fabric-based alkaline direct formate microfluidic fuel cells.

PubMed

Domalaon, Kryls; Tang, Catherine; Mendez, Alex; Bernal, Franky; Purohit, Krutarth; Pham, Linda; Haan, John; Gomez, Frank A

2017-04-01

Fabric-based microfluidic fuel cells (MFCs) serve as a novel, cost-efficient alternative to traditional FCs and batteries, since fluids naturally travel across fabric via capillary action, eliminating the need for an external pump and lowering production and operation costs. Building on previous research with Y-shaped paper-based MFCs, fabric-based MFCs mitigate fragility and durability issues caused by long periods of fuel immersion. In this study, we describe a microfluidic fabric-based direct formate fuel cell, with 5 M potassium formate and 30% hydrogen peroxide as the anode fuel and cathode oxidant, respectively. Using a two-strip, stacked design, the optimized parameters include the type of encasement, the barrier, and the fabric type. Surface contact of the fabric and laminate sheet expedited flow and respective chemical reactions. The maximum current (22.83 mA/cm 2 ) and power (4.40 mW/cm 2 ) densities achieved with a 65% cotton/35% polyester blend material are a respective 8.7% and 32% higher than previous studies with Y-shaped paper-based MFCs. In series configuration, the MFCs generate sufficient energy to power a handheld calculator, a thermometer, and a spectrum of light-emitting diodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Capillary transport of water through textile-reinforced concrete applied in repairing and/or strengthening cracked RC structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lieboldt, M.; Mechtcherine, V., E-mail: mechtcherine@tu-dresden.de

2013-10-15

The use of textile-reinforced concrete (TRC) has great potential for innovative solutions in repairing, protecting, and strengthening concrete and RC structures. The article at hand reports on an investigation on composite concrete specimens made of cracked ordinary concrete as substrate and textile-reinforced concrete (TRC) as a cover layer for its strengthening and repair. The TRC cover layer was assessed with regard to its effectiveness as a protective layer against the ingress of water through capillary action. Since in real applications such TRC layers may be cracked or presumed to be so, thereby activating the load-carrying function of the textile reinforcement,more » the TRC layer was cracked for purposes of this study. The water transport in the cracked ordinary concrete specimens without the TRC layer was used as a reference. Gravimetric measurements and neutron radiography served as the testing techniques. In ordinary concrete quick and deep ingress of water through relatively wide macro-cracks of approximately 100 μm width, followed by transport through the capillary pore system, caused saturation of large areas in a rather short time. TRC applied to the RC surface reduced the ingress of water to a large extent. Its small crack widths of 15 to 20 μm changed suction behaviour fundamentally. In the cracked substrate of ordinary concrete, capillary suction was prevented, and transport through the pore system of the matrix became the prevailing transport mechanism of capillary action. Not only was the mechanism altered, but the transport of water deep into inner regions was markedly retarded as well.« less

Nanostructured Tip-Shaped Biosensors: Application of Six Sigma Approach for Enhanced Manufacturing.

PubMed

Kahng, Seong-Joong; Kim, Jong-Hoon; Chung, Jae-Hyun

2016-12-23

Nanostructured tip-shaped biosensors have drawn attention for biomolecule detection as they are promising for highly sensitive and specific detection of a target analyte. Using a nanostructured tip, the sensitivity is increased to identify individual molecules because of the high aspect ratio structure. Various detection methods, such as electrochemistry, fluorescence microcopy, and Raman spectroscopy, have been attempted to enhance the sensitivity and the specificity. Due to the confined path of electrons, electrochemical measurement using a nanotip enables the detection of single molecules. When an electric field is combined with capillary action and fluid flow, target molecules can be effectively concentrated onto a nanotip surface for detection. To enhance the concentration efficacy, a dendritic nanotip rather than a single tip could be used to detect target analytes, such as nanoparticles, cells, and DNA. However, reproducible fabrication with relation to specific detection remains a challenge due to the instability of a manufacturing method, resulting in inconsistent shape. In this paper, nanostructured biosensors are reviewed with our experimental results using dendritic nanotips for sequence specific detection of DNA. By the aid of the Six Sigma approach, the fabrication yield of dendritic nanotips increases from 20.0% to 86.6%. Using the nanotips, DNA is concentrated and detected in a sequence specific way with the detection limit equivalent to 1000 CFU/mL. The pros and cons of a nanotip biosensor are evaluated in conjunction with future prospects.

Treatment of septic tank effluents by a full-scale capillary seepage soil biofiltration system.

PubMed

Fan, Chihhao; Chang, Fang-Chih; Ko, Chun-Han; Teng, Chia-Ji; Chang, Tzi-Chin; Sheu, Yiong-Shing

2009-03-01

The purpose of this study is to evaluate the efficiency of septic tank effluent treatment by an underground capillary seepage soil biofiltration system in a suburban area of Taipei, Taiwan. In contrast to traditional subsurface wastewater infiltration systems, capillary seepage soil biofiltration systems initially draw incoming influent upwards from the distribution pipe by capillary and siphonage actions, then spread influent throughout the soil biofiltration bed. The underground capillary seepage soil biofiltration system consists of a train of underground treatment units, including one wastewater distribution tank, two capillary seepage soil biofiltration units in series, and a discharge tank. Each capillary seepage soil biofiltration unit contains one facultative digestion tank and one set of biofiltration beds. At the flow rate of 50 m3/day, average influent concentrations of biochemical oxygen demand (BOD), suspended solid (SS), ammonia nitrogen (NH3-N), and total phosphates (TP), were 36.15 mg/L, 29.14 mg/L, 16.05 mg/L, and 1.75 mg/L, respectively. After 1.5 years of system operation, the measured influent and effluent results show that the treatment efficiencies of the soil biofiltration system for BOD, SS, NH3-N, TP, and total coliforms are 82.96%, 60.95%, 67.17%, 74.86%, and 99.99%, respectively.

State diagram for adhesion dynamics of deformable capsules under shear flow.

PubMed

Luo, Zheng Yuan; Bai, Bo Feng

2016-08-17

Due to the significance of understanding the underlying mechanisms of cell adhesion in biological processes and cell capture in biomedical applications, we numerically investigate the adhesion dynamics of deformable capsules under shear flow by using a three-dimensional computational fluid dynamic model. This model is based on the coupling of the front tracking-finite element method for elastic mechanics of the capsule membrane and the adhesion kinetics simulation for adhesive interactions between capsules and functionalized surfaces. Using this model, three distinct adhesion dynamic states are predicted, such as detachment, rolling and firm-adhesion. Specifically, the effects of capsule deformability quantified by the capillary number on the transitions of these three dynamic states are investigated by developing an adhesion dynamic state diagram for the first time. At low capillary numbers (e.g. Ca < 0.0075), whole-capsule deformation confers the capsule a flattened bottom in contact with the functionalized surface, which hence promotes the rolling-to-firm-adhesion transition. It is consistent with the observations from previous studies that cell deformation promotes the adhesion of cells lying in the rolling regime. However, it is surprising to find that, at relatively high capillary numbers (e.g. 0.0075 < Ca < 0.0175), the effect of capsule deformability on its adhesion dynamics is far more complex than just promoting adhesion. High deformability of capsules makes their bottom take a concave shape with no adhesion bond formation in the middle. The appearance of this specific capsule shape inhibits the transitions of both rolling-to-firm-adhesion and detachment-to-rolling, and it means that capsule deformation no longer promotes the capsule adhesion. Besides, it is interesting to note that, when the capillary number exceeds a critical value (e.g. Ca = 0.0175), the rolling state no longer appears, since capsules exhibit large deviation from the spherical shape.

Low cost silicon solar arrays

NASA Technical Reports Server (NTRS)

Ravi, K. V.; Serreze, H. B.; Bates, H. E.; Morrison, A. D.; Jewett, D. N.; Ho, J. C. T.; Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

1975-01-01

Continuous growth methodology for silicon solar cell ribbons deals with capillary effects, die effects, thermal effects and crystal shape effects. Emphasis centers on the shape of the meniscus at the ribbon edge as a factor contributing to ribbon quality with respect to defect densities. Structural and electrical characteristics of edge defined, film-fed grown silicon ribbons are elaborated. Ribbon crystal solar cells produce AMO efficiencies of 6 to 10%.

Condensation in Nanoporous Packed Beds.

PubMed

Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

2016-05-10

In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization.

Capillary forces exerted by liquid drops caught between crossed cylinders. A 3-D meniscus problem with free contact line

NASA Technical Reports Server (NTRS)

Patzek, T. W.; Scriven, L. E.

1982-01-01

The Young-Laplace equation is solved for three-dimensional menisci between crossed cylinders, with either the contact line fixed or the contact angle prescribed, by means of the Galerkin/finite element method. Shapes are computed, and with them the practically important quantities: drop volume, wetted area, capillary pressure force, surface tension force, and the total force exerted by the drop on each cylinder. The results show that total capillary force between cylinders increases with decreasing contact angle, i.e. with better wetting. Capillary force is also increases with decreasing drop volume, approaching an asymptotic limit. However, the wetted area on each cylinder decreases with decreasing drop volume, which raises the question of the optimum drop volume to strive for, when permanent bonding is sought from solidified liquid. For then the strength of the bond is likely to depend upon the area of contact, which is the wetted area when the bonding agent was introduced in liquid form.

Pore-scale imaging of capillary trapped supercritical CO2 as controlled by water-wet vs. CO2-wet media and grain shapes

NASA Astrophysics Data System (ADS)

Chaudhary, K.; Cardenas, M.; Wolfe, W. W.; Maisano, J. A.; Ketcham, R. A.; Bennett, P.

2013-12-01

The capillary trapping of supercritical CO2 (s-CO2) is postulated to comprise up to 90% of permanently trapped CO2 injected during geologic sequestration. Successive s-CO2/brine flooding experiments under reservoir conditions showed that water-wet rounded beads trapped 15% of injected s-CO2 both as clusters and as individual ganglia, whereas CO2¬-wet beads trapped only 2% of the injected s-CO2 as minute pockets in pore constrictions. Angular water-wet grains trapped 20% of the CO2 but flow was affected by preferential flow. Thus, capillary trapping is a viable mechanism for the permanent CO2 storage, but its success is constrained by the media wettability.

Capillary assisted deposition of carbon nanotube film for strain sensing

NASA Astrophysics Data System (ADS)

Li, Zida; Xue, Xufeng; Lin, Feng; Wang, Yize; Ward, Kevin; Fu, Jianping

2017-10-01

Advances in stretchable electronics offer the possibility of developing skin-like motion sensors. Carbon nanotubes (CNTs), owing to their superior electrical properties, have great potential for applications in such sensors. In this paper, we report a method for deposition and patterning of CNTs on soft, elastic polydimethylsiloxane (PDMS) substrates using capillary action. Micropillar arrays were generated on PDMS surfaces before treatment with plasma to render them hydrophilic. Capillary force enabled by the micropillar array spreads CNT solution evenly on PDMS surfaces. Solvent evaporation leaves a uniform deposition and patterning of CNTs on PDMS surfaces. We studied the effect of the CNT concentration and micropillar gap size on CNT coating uniformity, film conductivity, and piezoresistivity. Leveraging the piezoresistivity of deposited CNT films, we further designed and characterized a device for the contraction force measurement. Our capillary assisted deposition method of CNT films showed great application potential in fabrication of flexible CNT thin films for strain sensing.

Bottom-up fabrication of paper-based microchips by blade coating of cellulose microfibers on a patterned surface.

PubMed

Gao, Bingbing; Liu, Hong; Gu, Zhongze

2014-12-23

We report a method for the bottom-up fabrication of paper-based capillary microchips by the blade coating of cellulose microfibers on a patterned surface. The fabrication process is similar to the paper-making process in which an aqueous suspension of cellulose microfibers is used as the starting material and is blade-coated onto a polypropylene substrate patterned using an inkjet printer. After water evaporation, the cellulose microfibers form a porous, hydrophilic, paperlike pattern that wicks aqueous solution by capillary action. This method enables simple, fast, inexpensive fabrication of paper-based capillary channels with both width and height down to about 10 μm. When this method is used, the capillary microfluidic chip for the colorimetric detection of glucose and total protein is fabricated, and the assay requires only 0.30 μL of sample, which is 240 times smaller than for paper devices fabricated using photolithography.

Effects of intermediate wettability on entry capillary pressure in angular pores.

PubMed

Rabbani, Harris Sajjad; Joekar-Niasar, Vahid; Shokri, Nima

2016-07-01

Entry capillary pressure is one of the most important factors controlling drainage and remobilization of the capillary-trapped phases as it is the limiting factor against the two-phase displacement. It is known that the entry capillary pressure is rate dependent such that the inertia forces would enhance entry of the non-wetting phase into the pores. More importantly the entry capillary pressure is wettability dependent. However, while the movement of a meniscus into a strongly water-wet pore is well-defined, the invasion of a meniscus into a weak or intermediate water-wet pore especially in the case of angular pores is ambiguous. In this study using OpenFOAM software, high-resolution direct two-phase flow simulations of movement of a meniscus in a single capillary channel are performed. Interface dynamics in angular pores under drainage conditions have been simulated under constant flow rate boundary condition at different wettability conditions. Our results shows that the relation between the half corner angle of pores and contact angle controls the temporal evolution of capillary pressure during the invasion of a pore. By deviating from pure water-wet conditions, a dip in the temporal evolution of capillary pressure can be observed which will be pronounced in irregular angular cross sections. That enhances the pore invasion with a smaller differential pressure. The interplay between the contact angle and pore geometry can have significant implications for enhanced remobilization of ganglia in intermediate contact angles in real porous media morphologies, where pores are very heterogeneous with small shape factors. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Observation of the thermal influenced quantum behaviour of water near a solid interface.

PubMed

Yoon, Hongkee; Yoon, Byoung Jip

2018-05-03

Water is essential for life. However, the structure and properties of water are still not well understood. It has been introduced that anomalies are in vicinal water near solid interfaces. We performed capillary flow experiments on water with a silica colloid sample using a high-performance liquid chromatography (HPLC) system by accurately varying the temperature and analysed the peak shape rigorously. We obtained a novel anomalous temperature spectrum from the peak-shape analysis. Here we report the observed distinct specific anomalous temperature (SAT) behaviour in vicinal water at silica interface. The anomaly appeared in the viscous force that was derived from a relationship between the shape of the HPLC peak and the velocity profile for the capillary flow. The observations were highly reproducible, and we conclude that the SAT is related to the quantum mechanical behaviour of water, in agreement of the characteristic acceptance of thermal displacement according to the Franck-Condon principle. We performed the same experiments using heavy water and water mixed with a small amount of methanol, and the results support the quantum phenomenological origin.

Method and apparatus for the in situ decontamination of underground water with the aid of solar energy

DOEpatents

Bench, Thomas R.; McCann, Larry D.

1989-01-01

A method for the in situ decontamination of underground water containing -volatile contaminants comprising continuously contacting in situ underground water containing non-volatile contaminants with a liquid-absorbent material possessing high capillary activity, allowing the non-volatile contaminants to deposit in the material while the water moves upwardly through the material by capillary action, allowing substantially decontaminated water to be volatilized by impinging solar radiation, and then allowing the volatilized water to escape from the material into the atmosphere. An apparatus for the in situ decontamination of underground water containing non-volatile contaminants comprising at least one water-impermeable elongated conduit having an upper portion and first and second open ends and containing a homogeneous liquid-absorbent material possessing high capillary activity, means for supporting said conduit, and means for accelerating the escape of the volatilized decontamined water from the material, said means being detachably connected to the second end of the elongated conduit; wherein when underground water contaminated with non-volatile contaminants is continuously contacted in situ with the material contained in the first end of the conduit and the second end of the conduit is placed in contact with atmospheric air, non-volatile contaminants deposit in said material as the water moves upwardly through the material by capillary action, is then volatilized by impinging solar energy and escapes to the atmosphere.

Capillary Flow in Containers of Polygonal Section: Theory and Experiment

NASA Technical Reports Server (NTRS)

Weislogel, Mark M.; Rame, Enrique (Technical Monitor)

2001-01-01

An improved understanding of the large-length-scale capillary flows arising in a low-gravity environment is critical to that engineering community concerned with the design and analysis of spacecraft fluids management systems. Because a significant portion of liquid behavior in spacecraft is capillary dominated it is natural to consider designs that best exploit the spontaneous character of such flows. In the present work, a recently verified asymptotic analysis is extended to approximate spontaneous capillary flows in a large class of cylindrical containers of irregular polygonal section experiencing a step reduction in gravitational acceleration. Drop tower tests are conducted using partially-filled irregular triangular containers for comparison with the theoretical predictions. The degree to which the experimental data agree with the theory is a testament to the robustness of the basic analytical assumption of predominantly parallel flow. As a result, the closed form analytical expressions presented serve as simple, accurate tools for predicting bulk flow characteristics essential to practical low-g system design and analysis. Equations for predicting corner wetting rates, total container flow rates, and transient surfaces shapes are provided that are relevant also to terrestrial applications such as capillary flow in porous media.

Three-Dimensional Simulation of Liquid Drop Dynamics Within Unsaturated Vertical Hele-Shaw Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hai Huang; Paul Meakin

A three-dimensional, multiphase fluid flow model with volume of fluid-interface tracking was developed and applied to study the multiphase dynamics of moving liquid drops of different sizes within vertical Hele-Shaw cells. The simulated moving velocities are significantly different from those obtained from a first-order analytical approximation, based on simple force-balance concepts. The simulation results also indicate that the moving drops can exhibit a variety of shapes and that the transition among these different shapes is largely determined by the moving velocities. More important, there is a transition from a linear moving regime at small capillary numbers, in which the capillarymore » number scales linearly with the Bond number, to a nonlinear moving regime at large capillary numbers, in which the moving drop releases a train of droplets from its trailing edge. The train of droplets forms a variety of patterns at different moving velocities.« less

Rational design of capillary-driven flows for paper-based microfluidics.

PubMed

Elizalde, Emanuel; Urteaga, Raúl; Berli, Claudio L A

2015-05-21

The design of paper-based assays that integrate passive pumping requires a precise programming of the fluid transport, which has to be encoded in the geometrical shape of the substrate. This requirement becomes critical in multiple-step processes, where fluid handling must be accurate and reproducible for each operation. The present work theoretically investigates the capillary imbibition in paper-like substrates to better understand fluid transport in terms of the macroscopic geometry of the flow domain. A fluid dynamic model was derived for homogeneous porous substrates with arbitrary cross-sectional shapes, which allows one to determine the cross-sectional profile required for a prescribed fluid velocity or mass transport rate. An extension of the model to slit microchannels is also demonstrated. Calculations were validated by experiments with prototypes fabricated in our lab. The proposed method constitutes a valuable tool for the rational design of paper-based assays.

Determination of optimum fin profile for a zero-G capillary drained condenser

NASA Technical Reports Server (NTRS)

Mccormick, John A.; Valenzuela, Javier A.; Choudhury, Dipanker

1990-01-01

This paper presents the analytical formulation and numerical results for heat transfer in a high heat flux condenser that relies on capillary flow along shaped fins (Gregorig surfaces) and a drainage network embedded in the condenser walls. Results are shown for a variety of fin profile shapes in order to show the geometric trade-offs involved in seeking a maximum effective heat transfer coefficient for the fin. Predictions of the model show excellent agreement with previously reported measurements for steam. Based on this work, a profile has been selected for a 2 kW ammonia condenser currently under development for use in space. In that design the fin half width is 0.5 mm and the model predicts a heat transfer coefficient referred to the base of the fin of 9 W/sq cm deg C for a heat flux of 10/W sq cm at the base.

Diffusive oxygen shunting between vessels in the preglomerular renal vasculature: anatomic observations and computational modeling.

PubMed

Gardiner, Bruce S; Thompson, Sarah L; Ngo, Jennifer P; Smith, David W; Abdelkader, Amany; Broughton, Brad R S; Bertram, John F; Evans, Roger G

2012-09-01

To understand how geometric factors affect arterial-to-venous (AV) oxygen shunting, a mathematical model of diffusive oxygen transport in the renal cortex was developed. Preglomerular vascular geometry was investigated using light microscopy (providing vein shape, AV separation, and capillary density near arteries) and published micro-computed tomography (CT) data (providing vessel size and AV separation; Nordsletten DA, Blackett S, Bentley MD, Ritman EL, Smith NP. IUPS Physiome Project. http://www.physiome.org.nz/publications/nordsletten_blackett_ritman_bentley_smith_2005/folder_contents). A "U-shaped" relationship was observed between the arterial radius and the distance between the arterial and venous lumens. Veins were found to partially wrap around the artery more consistently for larger rather than smaller arteries. Intrarenal arteries were surrounded by an area of fibrous tissue, lacking capillaries, the thickness of which increased from ∼5 μm for the smallest arteries (<16-μm diameter) to ∼20 μm for the largest arteries (>200-μm diameter). Capillary density was greater near smaller arteries than larger arteries. No capillaries were observed between wrapped AV vessel pairs. The computational model comprised a single AV pair in cross section. Geometric parameters critical in renal oxygen transport were altered according to variations observed by CT and light microscopy. Lumen separation and wrapping of the vein around the artery were found to be the critical geometric factors determining the amount of oxygen shunted between AV pairs. AV oxygen shunting increases both as lumen separation decreases and as the degree of wrapping increases. The model also predicts that capillaries not only deliver oxygen, but can also remove oxygen from the cortical parenchyma close to an AV pair. Thus the presence of oxygen sinks (capillaries or tubules) near arteries would reduce the effectiveness of AV oxygen shunting. Collectively, these data suggest that AV oxygen shunting would be favored in larger vessels common to the cortical and medullary circulations (i.e., arcuate and proximal interlobular arteries) rather than the smaller vessels specific to the cortical circulation (distal interlobular arteries and afferent arterioles).

Agglomeration of Non-metallic Inclusions at Steel/Ar Interface: In- Situ Observation Experiments and Model Validation

NASA Astrophysics Data System (ADS)

Mu, Wangzhong; Dogan, Neslihan; Coley, Kenneth S.

2017-10-01

Better understanding of agglomeration behavior of nonmetallic inclusions in the steelmaking process is important to control the cleanliness of the steel. In this work, a revision on the Paunov simplified model has been made according to the original Kralchevsky-Paunov model. Thus, this model has been applied to quantitatively calculate the attractive capillary force on inclusions agglomerating at the liquid steel/gas interface. Moreover, the agglomeration behavior of Al2O3 inclusions at a low carbon steel/Ar interface has been observed in situ by high-temperature confocal laser scanning microscopy (CLSM). The velocity and acceleration of inclusions and attractive forces between Al2O3 inclusions of various sizes were calculated based on the CLSM video. The results calculated using the revised model offered a reasonable fit with the present experimental data for different inclusion sizes. Moreover, a quantitative comparison was made between calculations using the equivalent radius of a circle and those using the effective radius. It was found that the calculated capillary force using equivalent radius offered a better fit with the present experimental data because of the inclusion characteristics. Comparing these results with other studies in the literature allowed the authors to conclude that when applied in capillary force calculations, the equivalent radius is more suitable for inclusions with large size and irregular shape, and the effective radius is more appropriate for inclusions with small size or a large shape factor. Using this model, the effect of inclusion size on attractive capillary force has been investigated, demonstrating that larger inclusions are more strongly attracted.

SU-E-QI-06: Design and Initial Validation of a Precise Capillary Phantom to Test Perfusion Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, R; Iacobucci, G; Khobragade, P

2014-06-15

Purpose: To design a precise perfusion phantom mimicking capillaries of the brain vasculature which could be used to test various perfusion protocols and algorithms which generate perfusion maps. Methods: A perfusion phantom was designed in Solidworks and built using additive manufacturing. The phantom was an overall cylindrical shape of diameter and height 20mm and containing capillaries of 200μm or 300μm which were parallel and in contact making up the inside volume where flow was allowed. We created a flow loop using a peristaltic pump and contrast agent was injected manually. Digital Subtraction Angiographic images and low contrast images with conemore » beam CT were acquired after the contrast was injected. These images were analyzed by our own code in LabVIEW software and Time-Density Curve, MTT and TTP was calculated. Results: Perfused area was visible in the cone beam CT images; however, individual capillaries were not distinguishable. The Time-Density Curve acquired was accurate, sensitive and repeatable. The parameters MTT, and TTP offered by the phantom were very sensitive to slight changes in the TDC shape. Conclusion: We have created a robust calibrating model for evaluation of existing perfusion data analysis systems. This approach is extremely sensitive to changes in the flow due to the high temporal resolution and could be used as a golden standard to assist developers in calibrating and testing of imaging perfusion systems and software algorithms. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

Use of microcirculatory parameters to evaluate clinical treatments of chronic venous disorder (CVD).

PubMed

Lascasas-Porto, Carmen Lucia; Milhomens, Ana Letícia M; Virgini-Magalhães, Carlos Eduardo; Fernandes, Fabiano F A; Sicuro, Fernando L; Bouskela, Eliete

2008-05-01

To evaluate changes on cutaneous microangiopathy in chronic venous disorder (CVD) after use of Cirkan [venotonic drug containing Ruscus aculeatus (plant extract), hesperidine methylchalcone (flavonoid) and vitamin C], elastic compression stockings (ECS) or no treatment for four weeks. Fifty-five female patients (85 legs), 25 to 57 years, with at least one limb classified as C2,s or C2,3,s (CEAP classification), were allocated consecutively, according to entrance order, in these three groups. Ten healthy women age-matched were also investigated. Using orthogonal polarization spectral technique (noninvasive method), measurements of functional capillary density (FCD, number of capillaries with flowing red blood cells/mm(2)), capillary morphology (CM, % of abnormal capillaries/mm(2)) and diameters (mum) of dermal papilla (DDP), capillary bulk (DCB) and capillary limb (CD) were obtained on the medial perimalleolar region and later analyzed using CapImage software. CVD patients showed significant changes on CD and CM compared to healthy subjects in agreement with our previous findings (J Vasc Surg 43:1037-1044, 2006). On Cirkan-treated patients, after 4 weeks, CD decreased on both limbs and CM improved on the left one, suggesting an amelioration of the chronic venous hypertension. No significant changes could be detected on other patient groups. These results confirm the existence of microcirculatory dysfunction in early stages of CVD, probably due to post-capillary hypertension, and further support the venotonic action of Cirkan.

Influence of Inertial, Visous and Capillary Effects on the Apical Behavior of Taylor Cone Formation in Liquid Metals

NASA Astrophysics Data System (ADS)

Albertson, Theodore; Troian, Sandra

Above a critical applied field strength, the surface of a liquid metal can deform into a conical shape whose apex can emit ions. The precursor shape and dynamics to that event have been debated for decades. In a landmark paper, Zubarev (2001) invoked potential flow theory to predict the existence of self-similar apical sharpening for the case of an ideal perfectly conducting liquid. He found that the Maxwell and capillary pressures at the cone tip scale in time as -2/3 upon approach to the singularity. In this talk, we examine the behavior of thin electrified microscale films placed in close proximity to a grounded planar counter electrode to probe how inertial and viscous forces, diminished or neglected in the original analysis, modify the power law exponents governing the apical self-similar regime. We employ finite element, moving mesh simulations to investigate these effects for low, intermediate and high electric Reynolds and capillary numbers. We confirm the robustness of the self-similar regime characterized by power law exponents despite the lack of potential flow - however, the power law exponents, no longer -2/3, assume values which depend on the choice of dimensionless numbers. TGA gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Velocity measurements of heterogeneous RBC flow in capillary vessels using dynamic laser speckle signal.

PubMed

Li, Chenxi; Wang, Ruikang

2017-04-01

We propose an approach to measure heterogeneous velocities of red blood cells (RBCs) in capillary vessels using full-field time-varying dynamic speckle signals. The approach utilizes a low coherent laser speckle imaging system to record the instantaneous speckle pattern, followed by an eigen-decomposition-based filtering algorithm to extract dynamic speckle signal due to the moving RBCs. The velocity of heterogeneous RBC flows is determined by cross-correlating the temporal dynamic speckle signals obtained at adjacent locations. We verify the approach by imaging mouse pinna in vivo, demonstrating its capability for full-field RBC flow mapping and quantifying flow pattern with high resolution. It is expected to investigate the dynamic action of RBCs flow in capillaries under physiological changes.

A Preliminary Study of the Spreading of AKD in the Presence of Capillary Structures.

PubMed

Shen, Wei; Parker, Ian H.

2001-08-01

There may be several mechanisms at work in the process of migration or redistribution of alkyl ketene dimers (AKD) on cellulose fiber surfaces during paper sizing and curing. This work is the second part of a continuing investigation of the spreading behavior of AKD on the surfaces of hydrophilic substrates. Paper sheets, single cotton, and cotton lint fibers and smooth cellulose film were used as substrates. These represent samples that have pores, V-shaped grooves, and no capillary structure at all. A very simple and effective testing method for studying the AKD migration behavior through these substrates was designed. AFM was used to study the surface capillary structures of cotton and cotton lint fibers. The results of this study provide hard evidence supporting our finding that capillary structures in the form of either interfiber pores in a paper sheet or V-shaped grooves on the surface of single fibers are essential in order for the spreading of molten AKD on a cellulose substrate to occur. Some preliminary results on the existence and the surface diffusion of an autophobic precursor of AKD are also presented. The results support the conclusion we reached in the first part of this investigation; i.e., the molten AKD wets but does not spread on smooth, capillary-free hydrophilic surfaces such as glass and cellulose. The driving force from interfacial energy alone does not cause spontaneous "flow-like" spreading of molten AKD on these surfaces. This is possibly associated with the formation of an autophobic precursor in front of an AKD droplet. The results in this study do not support the perception that molten AKD forms a single molecular layer on the surface of cellulose fibers by spreading during heat treatment, although the autophobic precursor in front of an AKD droplet could theoretically be of a monolayer thickness and the surface diffusion of this precursor may contribute to the sizing development after heat treatment. Copyright 2001 Academic Press.

Numerical Simulation of Passage of a Neutrophil through a Rectangular Channel with a Moderate Constriction

PubMed Central

Shirai, Atsushi; Masuda, Sunao

2013-01-01

The authors have previously presented a mathematical model to predict transit time of a neutrophil through an alveolar capillary segment which was modeled as an axisymmetric arc-shaped constriction settled in a cylindrical straight pipe to investigate the influence of entrance curvature of a capillary on passage of the cell. The axially asymmetric cross section of a capillary also influences the transit time because it requires three-dimensional deformation of a cell when it passes through the capillary and could lead to plasma leakage between the cell surface and the capillary wall. In this study, a rectangular channel was introduced, the side walls of which were moderately constricted, as a representative of axially asymmetric capillaries. Dependence of transit time of a neutrophil passing through the constriction on the constriction geometry, i.e., channel height, throat width and curvature radius of the constriction, was numerically investigated, the transit time being compared with that through the axisymmetric model. It was found that the transit time is dominated by the throat hydraulic diameter and curvature radius of the constriction and that the throat aspect ratio little affects the transit time with a certain limitation, indicating that if an appropriate curvature radius is chosen, such a rectangular channel model can be substituted for an axisymmetric capillary model having the same throat hydraulic diameter in terms of the transit time by choosing an appropriate curvature radius. Thus, microchannels fabricated by the photolithography technique, whose cross section is generally rectangular, are expected to be applicable to in vitro model experiments of neutrophil retention and passage in the alveolar capillaries. PMID:23527190

Liquid film drag out in the presence of molecular forces

NASA Astrophysics Data System (ADS)

Schmidhalter, I.; Cerro, R. L.; Giavedoni, M. D.; Saita, F. A.

2013-03-01

From a practical as well as a conceptual point of view, one of the most interesting problems of physicochemical hydrodynamics is the drag out of a liquid film by a moving solid out of a pool of liquid. The basic problem, sometimes denoted the Landau-Levich problem [L. Landau and B. Levich, "Dragging of a liquid by a moving plate," Acta Physicochim. USSR 17, 42-54 (1942)], involves an interesting blend of capillary and viscous forces plus a matching of the static solution for capillary rise with a numerical solution of the film evolution equation, neglecting gravity, on the downstream region of the flow field. The original solution describes experimental data for a wide range of Capillary numbers but fails to match results for large and very small Capillary numbers. Molecular level forces are introduced to create an augmented version of the film evolution equation to show the effect of van der Waals forces at the lower range of Capillary numbers. A closed form solution for static capillary rise, including molecular forces, was matched with a numerical solution of the augmented film evolution equation in the dynamic meniscus region. Molecular forces do not sensibly modify the static capillary rise region, since film thicknesses are larger than the range of influence of van der Waals forces, but are determinant in shaping the downstream dynamic meniscus of the very thin liquid films. As expected, a quantitatively different level of disjoining pressure for different values of molecular constants remains in the very thin liquid film far downstream. Computational results for a wide range of Capillary numbers and Hamaker constants show a clear transition towards a region where the film thickness becomes independent of the coating speed.

Measurement of surface tension and viscosity by open capillary techniques

DOEpatents

Rye,Robert R. , Yost,Frederick G.

1998-01-01

An open-channel capillary is provided, having preferably a v-shaped groove in a flat wettable surface. The groove has timing marks and a source marker in which the specimen to be tested is deposited. The time of passage between the timing marks is recorded, and the ratio of surface tension .gamma. to viscosity .mu. is determined from the equation given below: ##EQU1## where h.sub.0 is the groove depth, .alpha. is the groove angle, .theta. is the liquid/solid contact angle, and t is the flow time. It has been shown by the

Transient Droplet Behavior and Droplet Breakup during Bulk and Confined Shear Flow in Blends with One Viscoelastic Component: Experiments, Modelling and Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardinaels, Ruth; Verhulst, Kristof; Moldenaers, Paula

2008-07-07

The transient droplet deformation and droplet orientation after inception of shear, the shape relaxation after cessation of shear and droplet breakup during shear, are microscopically studied, both under bulk and confined conditions. The studied blends contain one viscoelastic Boger fluid phase. A counter rotating setup, based on a Paar Physica MCR300, is used for the droplet visualisation. For bulk shear flow, it is shown that the droplet deformation during startup of shear flow and the shape relaxation after cessation of shear flow are hardly influenced by droplet viscoelasticity, even at moderate to high capillary and Deborah numbers. The effects ofmore » droplet viscoelasticity only become visible close to the critical conditions and a novel break-up mechanism is observed. Matrix viscoelasticity has a more pronounced effect, causing overshoots in the deformation and significantly inhibiting relaxation. However, different applied capillary numbers prior to cessation of shear flow, with the Deborah number fixed, still result in a single master curve for shape retraction, as in fully Newtonian systems. The long tail in the droplet relaxation can be qualitatively described with a phenomenological model for droplet deformation, when using a 5-mode Giesekus model for the fluid rheology. It is found that the shear flow history significantly affects the droplet shape evolution and the breakup process in blends with one viscoelastic component. Confining a droplet between two plates accelerates the droplet deformation kinetics, similar to fully Newtonian systems. However, the increased droplet deformation, due to wall effects, causes the steady state to be reached at a later instant in time. Droplet relaxation is less sensitive to confinement, leading to slower relaxation kinetics only for highly confined droplets. For the blend with a viscoelastic droplet, a non-monotonous trend is found for the critical capillary number as a function of the confinement ratio. Finally, experimental data are compared with 3D simulations, performed with a volume-of-fluid algorithm.« less

Visual variability affects early verb learning.

PubMed

Twomey, Katherine E; Lush, Lauren; Pearce, Ruth; Horst, Jessica S

2014-09-01

Research demonstrates that within-category visual variability facilitates noun learning; however, the effect of visual variability on verb learning is unknown. We habituated 24-month-old children to a novel verb paired with an animated star-shaped actor. Across multiple trials, children saw either a single action from an action category (identical actions condition, for example, travelling while repeatedly changing into a circle shape) or multiple actions from that action category (variable actions condition, for example, travelling while changing into a circle shape, then a square shape, then a triangle shape). Four test trials followed habituation. One paired the habituated verb with a new action from the habituated category (e.g., 'dacking' + pentagon shape) and one with a completely novel action (e.g., 'dacking' + leg movement). The others paired a new verb with a new same-category action (e.g., 'keefing' + pentagon shape), or a completely novel category action (e.g., 'keefing' + leg movement). Although all children discriminated novel verb/action pairs, children in the identical actions condition discriminated trials that included the completely novel verb, while children in the variable actions condition discriminated the out-of-category action. These data suggest that - as in noun learning - visual variability affects verb learning and children's ability to form action categories. © 2014 The British Psychological Society.

Fabrication of bimetallic microfluidic surface-enhanced Raman scattering sensors on paper by screen printing.

PubMed

Qu, Lu-Lu; Song, Qi-Xia; Li, Yuan-Ting; Peng, Mao-Pan; Li, Da-Wei; Chen, Li-Xia; Fossey, John S; Long, Yi-Tao

2013-08-20

Au-Ag bimetallic microfluidic, dumbbell-shaped, surface enhanced Raman scattering (SERS) sensors were fabricated on cellulose paper by screen printing. These printed sensors rely on a sample droplet injection zone, and a SERS detection zone at either end of the dumbbell motif, fabricated by printing silver nanoparticles (Ag NPs) and gold nanoparticles (Au NPs) successively with microscale precision. The microfluidic channel was patterned using an insulating ink to connect these two zones and form a hydrophobic circuit. Owing to capillary action of paper in the millimeter-sized channels, the sensor could enable self-filtering of fluids to remove suspended particles within wastewater without pumping. This sensor also allows sensitive SERS detection, due to advantageous combination of the strong surface enhancement of Ag NPs and excellent chemical stability of Au NPs. The SERS performance of the sensors was investigated by employing the probe rhodamine 6G, a limit of detection (LOD) of 1.1×10(-13)M and an enhancement factor of 8.6×10(6) could be achieved. Moreover, the dumbbell-shaped bimetallic sensors exhibited good stability with SERS performance being maintained over 14 weeks in air, and high reproducibility with less than 15% variation in spot-to-spot SERS intensity. Using these dumbbell-shaped bimetallic sensors, substituted aromatic pollutants in wastewater samples could be quantitatively analyzed, which demonstrated their excellent capability for rapid trace pollutant detection in wastewater samples in the field without pre-separation. Copyright © 2013 Elsevier B.V. All rights reserved.

Nanostructured Tip-Shaped Biosensors: Application of Six Sigma Approach for Enhanced Manufacturing

PubMed Central

Kahng, Seong-Joong; Kim, Jong-Hoon; Chung, Jae-Hyun

2016-01-01

Nanostructured tip-shaped biosensors have drawn attention for biomolecule detection as they are promising for highly sensitive and specific detection of a target analyte. Using a nanostructured tip, the sensitivity is increased to identify individual molecules because of the high aspect ratio structure. Various detection methods, such as electrochemistry, fluorescence microcopy, and Raman spectroscopy, have been attempted to enhance the sensitivity and the specificity. Due to the confined path of electrons, electrochemical measurement using a nanotip enables the detection of single molecules. When an electric field is combined with capillary action and fluid flow, target molecules can be effectively concentrated onto a nanotip surface for detection. To enhance the concentration efficacy, a dendritic nanotip rather than a single tip could be used to detect target analytes, such as nanoparticles, cells, and DNA. However, reproducible fabrication with relation to specific detection remains a challenge due to the instability of a manufacturing method, resulting in inconsistent shape. In this paper, nanostructured biosensors are reviewed with our experimental results using dendritic nanotips for sequence specific detection of DNA. By the aid of the Six Sigma approach, the fabrication yield of dendritic nanotips increases from 20.0% to 86.6%. Using the nanotips, DNA is concentrated and detected in a sequence specific way with the detection limit equivalent to 1000 CFU/mL. The pros and cons of a nanotip biosensor are evaluated in conjunction with future prospects. PMID:28025540

Detection system of capillary array electrophoresis microchip based on optical fiber

NASA Astrophysics Data System (ADS)

Yang, Xiaobo; Bai, Haiming; Yan, Weiping

2009-11-01

To meet the demands of the post-genomic era study and the large parallel detections of epidemic diseases and drug screening, the high throughput micro-fluidic detection system is needed urgently. A scanning laser induced fluorescence detection system based on optical fiber has been established by using a green laser diode double-pumped solid-state laser as excitation source. It includes laser induced fluorescence detection subsystem, capillary array electrophoresis micro-chip, channel identification unit and fluorescent signal processing subsystem. V-shaped detecting probe composed with two optical fibers for transmitting the excitation light and detecting induced fluorescence were constructed. Parallel four-channel signal analysis of capillary electrophoresis was performed on this system by using Rhodamine B as the sample. The distinction of different samples and separation of samples were achieved with the constructed detection system. The lowest detected concentration is 1×10-5 mol/L for Rhodamine B. The results show that the detection system possesses some advantages, such as compact structure, better stability and higher sensitivity, which are beneficial to the development of microminiaturization and integration of capillary array electrophoresis chip.

IB-LBM simulation of the haemocyte dynamics in a stenotic capillary.

PubMed

Yuan-Qing, Xu; Xiao-Ying, Tang; Fang-Bao, Tian; Yu-Hua, Peng; Yong, Xu; Yan-Jun, Zeng

2014-01-01

To study the behaviour of a haemocyte when crossing a stenotic capillary, the immersed boundary-lattice Boltzmann method was used to establish a quantitative analysis model. The haemocyte was assumed to be spherical and to have an elastic cell membrane, which can be driven by blood flow to adopt a highly deformable character. In the stenotic capillary, the spherical blood cell was stressed both by the flow and the wall dimension, and the cell shape was forced to be stretched to cross the stenosis. Our simulation investigated the haemocyte crossing process in detail. The velocity and pressure were anatomised to obtain information on how blood flows through a capillary and to estimate the degree of cell damage caused by excessive pressure. Quantitative velocity analysis results demonstrated that a large haemocyte crossing a small stenosis would have a noticeable effect on blood flow, while quantitative pressure distribution analysis results indicated that the crossing process would produce a special pressure distribution in the cell interior and to some extent a sudden change between the cell interior and the surrounding plasma.

Fully packed capillary electrochromatographic microchip with self-assembly colloidal silica beads.

PubMed

Park, Jongman; Lee, Dami; Kim, Won; Horiike, Shigeyoshi; Nishimoto, Takahiro; Lee, Se Hwan; Ahn, Chong H

2007-04-15

A fully packed capillary electrochromatographic (CEC) microchip showing improved solution and chip handling was developed. Microchannels for the CEC microchip were patterned on a cyclic olefin copolymer substrate by injection molding and packed fully with 0.8-microm monodisperse colloidal silica beads utilizing a self-assembly packing technique. The silica packed chip substrate was covered and thermally press-bonded. After fabrication, the chip was filled with buffer solution by self-priming capillary action. The self-assembly packing at each channel served as a built-in nanofilter allowing quick loading of samples and running buffer solution without filtration. Because of a large surface area-to-volume ratio of the silica packing, reproducible control of electroosmotic flow was possible without leveling of the solutions in the reservoirs resulting 1.3% rsd in migration rate. The capillary electrophoretic separation characteristics of the chip were studied using fluorescein isothiocyanate (FITC)-derivatized amino acids as probe molecules. A mixture of FITC and four FITC-derivatized amino acids was successfully separated with 2-mm separation channel length.

Miniaturised electrically actuated high pressure injection valve for portable capillary liquid chromatography.

PubMed

Li, Yan; Pace, Kirsten; Nesterenko, Pavel N; Paull, Brett; Stanley, Roger; Macka, Mirek

2018-04-01

A miniaturised high pressure 6-port injection valve has been designed and evaluated for its performance in order to facilitate the development of portable capillary high performance liquid chromatography (HPLC). The electrically actuated valve features a very small size (65 × 19 × 19mm) and light weight (33g), and therefore can be easily integrated in a miniaturised modular capillary LC system suited for portable field analysis. The internal volume of the injection valve was determined as 98 nL. The novel conical shape of the stator and rotor and the spring-loaded rotor performed well up to 32MPa (4641psi), the maximum operating pressure investigated. Suitability for application was demonstrated using a miniaturised capillary LC system applied to the chromatographic separation of a mixture of biogenic amines and common cations. The RSD (relative standard deviation) values of retention times and peak areas of 6 successive runs were 0.5-0.7% and 1.8-2.8% for the separation of biogenic amines, respectively, and 0.1-0.2% and 2.1-3.0% for the separation of cations, respectively. This performance was comparable with bench-top HPLC systems thus demonstrating the applicability of the valve for use in portable and miniaturised capillary HPLC systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-separation of blood plasma from whole blood during the capillary flow in microchannel

NASA Astrophysics Data System (ADS)

Nunna, Bharath Babu; Zhuang, Shiqiang; Lee, Eon Soo

2017-11-01

Self-separation of blood plasma from whole blood in microchannels is of great importance due to the enormous range of applications in healthcare and diagnostics. Blood is a multiphase complex fluid, composed of cells suspended in blood plasma. RBCs are the suspended particles whose shape changes during the flow of blood. The primary constituents of blood are erythrocytes or red blood cells (RBCs), leukocytes or white blood cells (WBCs), thrombocytes or platelets and blood plasma. The existence of RBCs in blood makes the blood a non-Newtonian fluid. The current study of separation of blood plasma from whole blood during self-driven flows in a single microchannel without bifurcation, by enhancing the capillary effects. The change in the capillary effect results in a change in contact angle which directly influences the capillary flow. The flow velocity directly influences the net force acting on the RBCs and influence the separation process. The experiments are performed on the PDMS microchannels with different contact angles by altering the surface characteristics using plasma treatment. The change in the separation length is studied during the capillary flow of blood in microchannel. Bharath Babu Nunna is a researcher in mechanical engineering and implementing the novel and innovative technologies in the biomedical devices to enhance the sensitivity of the disease diagnosis.

Velocity measurements of heterogeneous RBC flow in capillary vessels using dynamic laser speckle signal

PubMed Central

Li, Chenxi; Wang, Ruikang

2017-01-01

Abstract. We propose an approach to measure heterogeneous velocities of red blood cells (RBCs) in capillary vessels using full-field time-varying dynamic speckle signals. The approach utilizes a low coherent laser speckle imaging system to record the instantaneous speckle pattern, followed by an eigen-decomposition-based filtering algorithm to extract dynamic speckle signal due to the moving RBCs. The velocity of heterogeneous RBC flows is determined by cross-correlating the temporal dynamic speckle signals obtained at adjacent locations. We verify the approach by imaging mouse pinna in vivo, demonstrating its capability for full-field RBC flow mapping and quantifying flow pattern with high resolution. It is expected to investigate the dynamic action of RBCs flow in capillaries under physiological changes. PMID:28384709

The Fast and Non-capillary Fluid Filling Mechanism in the Hummingbird's Tongue

NASA Astrophysics Data System (ADS)

Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret

2014-03-01

Hummingbirds gather nectar by inserting their beaks inside flowers and cycling their tongues at a frequency of up to 20 Hz. It is unclear how they achieve efficiency at this high licking rate. Ever since proposed in 1833, it has been believed that hummingbird tongues are a pair of tiny straws filled with nectar by capillary rise. Our discoveries are very different from this general consensus. The tongue does not draw up floral nectar via capillary action under experimental conditions that resemble natural ones. Theoretical models based on capillary rise were mistaken and unsuitable for estimating the fluid intake rate and to support foraging theories. We filmed (up to 1265 frames/s) the fluid uptake in 20 species of hummingbirds that belong to 7 out of the 9 main hummingbird clades. We found that the fluid filling within the portions of the tongue that remain outside the nectar is about five times faster than capillary filling. We present strong evidence to rule out the capillarity model. We introduce a new fluid-structure interaction and hydrodynamic model and compare the results with field experimental data to explain how hummingbirds actually extract fluid from flowers at the lick level.

Method and apparatus for de-watering biomass materials in a compression drying process

DOEpatents

Haygreen, John G.

1986-01-01

A method and apparatus for more effectively squeezing moisture from wood chips and/or other "green" biomass materials. A press comprising a generally closed chamber having a laterally movable base at the lower end thereof, and a piston or ram conforming in shape to the cross-section of the chamber is adapted to periodically receive a charge of biomass material to be dehydrated. The ram is forced against the biomass material with suffcient force to compress the biomass and to crush the matrix in which moisture is contained within the material with the face of the ram being configured to cause a preferential flow of moisture from the center of the mass outwardly to the grooved walls of the chamber. Thus, the moisture is effectively squeezed from the biomass and flows through the grooves formed in the walls of the chamber to a collecting receptacle and is not drawn back into the mass by capillary action when the force is removed from the ram.

Large-deformation electrohydrodynamics of an elastic capsule in a DC electric field

NASA Astrophysics Data System (ADS)

Das, Sudip; Thaokar, Rochish M.

2018-04-01

The dynamics of a spherical elastic capsule, containing a Newtonian fluid bounded by an elastic membrane and immersed in another Newtonian fluid, in a uniform DC electric field is investigated. Discontinuity of electrical properties such as conductivities of the internal and external fluid media as well as capacitance and conductance of the membrane lead to a net interfacial Maxwell stress which can cause the deformation of such an elastic capsule. We investigate this problem considering well established membrane laws for a thin elastic membrane, with fully resolved hydrodynamics in the Stokes flow limit and describe the electrostatics using the capacitor model. In the limit of small deformation, the analytical theory predicts the dynamics fairly satisfactorily. Large deformations at high capillary number though necessitate a numerical approach (Boundary element method in the present case) to solve this highly non-linear problem. Akin to vesicles, at intermediate times, highly nonlinear biconcave shapes along with squaring and hexagon like shapes are observed when the outer medium is more conducting. The study identifies the essentiality of parameters such as high membrane capacitance, low membrane conductance, low hydrodynamic time scales and high capillary number for observation of these shape transitions. The transition is due to large compressive Maxwell stress at the poles at intermediate times. Thus such shape transition can be seen in spherical globules admitting electrical capacitance, possibly, irrespective of the nature of the interfacial restoring force.

Conformal dip-coating of patterned surfaces for capillary die-to-substrate self-assembly

NASA Astrophysics Data System (ADS)

Mastrangeli, M.; Ruythooren, W.; Van Hoof, C.; Celis, J.-P.

2009-04-01

Capillarity-driven self-assembly of small chips onto planar target substrates is a promising alternative to robotic pick-and-place assembly. It critically relies on the selective deposition of thin fluid films on patterned binding sites, which is anyway normally non-conformal. We found that the addition of a thin wetting sidewall, surrounding the entire site perimeter, enables the conformal fluid coverage of arbitrarily shaped sites through dip-coating, significantly improves the reproducibility of the coating process and strongly reduces its sensitivity to surface defects. In this paper we support the feasibility and potential of this method by demonstrating the conformal dip-coating of square and triangular sites conditioned with combinations of different hydrophobic and hydrophilic surface chemistries. We present both experimental and simulative evidence of the advantages brought by the introduction of the wetting boundary on film coverage accuracy. Application of our surface preparation method to capillary self-assembly could result in higher precision in die-to-substrate registration and larger freedom in site shape design.

Insulin-induced microvascular recruitment in skin and muscle are related and both are associated with whole-body glucose uptake.

PubMed

Meijer, Rick I; De Boer, Michiel P; Groen, Martine R; Eringa, Etto C; Rattigan, Stephen; Barrett, Eugene J; Smulders, Yvo M; Serne, Erik H

2012-08-01

Insulin-induced capillary recruitment is considered a determinant of insulin-mediated glucose uptake. Insulin action on the microvasculature has been assessed in skin; however, there is concern as to whether the vascular responses observed in skin reflect those in the muscle. We hypothesized that insulin-induced capillary recruitment in skin would correlate with microvascular recruitment in muscle in a group of subjects displaying a wide variation in insulin sensitivity. Capillary recruitment in skin was assessed using capillary videomicroscopy, and skeletal muscle microvascular recruitment (i.e., increase in MBV) was studied using CEU in healthy volunteers (n = 18, mean age: 30.6 ± 11.1 years). Both microvascular measurements were performed during saline infusion, and during a hyperinsulinemic euglycemic clamp. During hyperinsulinemia, capillary recruitment in skin was augmented from 58.1 ± 18.2% to 81.0 ± 23.9% (p < 0.0001). Hyperinsulinemia increased MBV in muscle from 7.00 (2.66-17.67) to 10.06 (2.70-41.81) units (p = 0.003). Insulin's vascular effect in skin and muscle was correlated (r = 0.57). Insulin's microvascular effects in skin and muscle showed comparable strong correlations with insulin-mediated glucose uptake (r = 0.73 and 0.68, respectively). Insulin-augmented capillary recruitment in skin parallels insulin-mediated microvascular recruitment in muscle and both are related to insulin-mediated glucose uptake. © 2012 John Wiley & Sons Ltd.

Field-Scale Modeling of Local Capillary Trapping During CO2 Injection into a Saline Aquifer

NASA Astrophysics Data System (ADS)

Ren, B.; Lake, L. W.; Bryant, S. L.

2015-12-01

Local capillary trapping is the small-scale (10-2 to 10+1 m) CO2 trapping that is caused by the capillary pressure heterogeneity. The benefit of LCT, applied specially to CO2 sequestration, is that saturation of stored CO2 is larger than the residual gas, yet these CO2 are not susceptible to leakage through failed seals. Thus quantifying the extent of local capillary trapping is valuable in design and risk assessment of geologic storage projects. Modeling local capillary trapping is computationally expensive and may even be intractable using a conventional reservoir simulator. In this paper, we propose a novel method to model local capillary trapping by combining geologic criteria and connectivity analysis. The connectivity analysis originally developed for characterizing well-to-reservoir connectivity is adapted to this problem by means of a newly defined edge weight property between neighboring grid blocks, which accounts for the multiphase flow properties, injection rate, and gravity effect. Then the connectivity is estimated from shortest path algorithm to predict the CO2 migration behavior and plume shape during injection. A geologic criteria algorithm is developed to estimate the potential local capillary traps based only on the entry capillary pressure field. The latter is correlated to a geostatistical realization of permeability field. The extended connectivity analysis shows a good match of CO2 plume computed by the full-physics simulation. We then incorporate it into the geologic algorithm to quantify the amount of LCT structures identified within the entry capillary pressure field that can be filled during CO2 injection. Several simulations are conducted in the reservoirs with different level of heterogeneity (measured by the Dykstra-Parsons coefficient) under various injection scenarios. We find that there exists a threshold Dykstra-Parsons coefficient, below which low injection rate gives rise to more LCT; whereas higher injection rate increases LCT in heterogeneous reservoirs. Both the geologic algorithm and connectivity analysis are very fast; therefore, the integrated methodology can be used as a quick tool to estimate local capillary trapping. It can also be used as a potential complement to the full-physics simulation to evaluate safe storage capacity.

Disentangling representations of shape and action components in the tool network.

PubMed

Wang, Xiaoying; Zhuang, Tonghe; Shen, Jiasi; Bi, Yanchao

2018-05-30

Shape and how they should be used are two key components of our knowledge about tools. Viewing tools preferentially activated a frontoparietal and occipitotemporal network, with dorsal regions implicated in computation of tool-related actions and ventral areas in shape representation. As shape and manners of manipulation are highly correlated for daily tools, whether they are independently represented in different regions remains inconclusive. In the current study, we collected fMRI data when participants viewed blocks of pictures of four daily tools (i.e., paintbrush, corkscrew, screwdriver, razor) where shape and action (manner of manipulation for functional use) were orthogonally manipulated, to tease apart these two dimensions. Behavioral similarity judgments tapping on object shape and finer aspects of actions (i.e., manners of motion, magnitude of arm movement, configuration of hand) were also collected to further disentangle the representation of object shape and different action components. Information analysis and representational similarity analysis were conducted on regional neural activation patterns of the tool-preferring network. In both analyses, the bilateral lateral occipitotemporal cortex showed robust shape representations but could not effectively distinguish between tool-use actions. The frontal and precentral regions represented kinematic action components, whereas the left parietal region (in information analyses) exhibited coding of both shape and tool-use action. By teasing apart shape and action components, we found both dissociation and association of them within the tool network. Taken together, our study disentangles representations for object shape from finer tool-use action components in the tool network, revealing the potential dissociable roles different tool-preferring regions play in tool processing. Copyright © 2018 Elsevier Ltd. All rights reserved.

The respiratory system under weightlessness

NASA Technical Reports Server (NTRS)

Paiva, M.; Engel, L. A.; Hughes, J. M. B.; Guy, H. J.; Prisk, G. K.; West, J. B.

1987-01-01

Studies of pulmonary functions at rest to be studied on Spacelab mission D-2 are introduced. Gravity dependence of the distribution of ventilation (single breath washout, multibreath washout-washin); chest wall shape and motion; and the vascular compartment (lung blood flow, capillary volume, liquid content, diffusive capacity) are discussed.

Development of a Contingency Capillary Wastewater Management Device

NASA Technical Reports Server (NTRS)

Thomas, Evan A.

2010-01-01

The Personal Body .Attached Liquid Liquidator (PBALL) is conceived as a passive, capillary driven contingency wastewater disposal device. In this contingency scenario, the airflow system on the NASA Crew Exploration Vehicle (CEV) is assumed to have failed, leaving only passive hardware and vacuum vent to dispose of the wastewater. To meet these needs, the PBALL was conceived to rely on capillary action and urine wetting design considerations. The PBALL is designed to accommodate a range of wetting conditions, from 0deg < (theta)adv approx. 90deg, be adaptable for both male and female use, collect and retain up to a liter of urine, minimize splash-back, and allow continuous drain of the wastewater to vacuum while minimizing cabin air loss. A sub-scale PBALL test article was demonstrated on NASA's reduced gravity aircraft in April, 2010.

Arterio-Venous Anastomoses and Thermoregulation (Arterio-Veneuze Anastomosen en Thermoregulatie)

DTIC Science & Technology

1991-08-22

in the skin of the nose, ears and lips. Furthermore, they are found in the nail bed, corpus cavernosum of the penis of the man, ovarium of the woman...diameter of the vessels was a criterion for the existence of an AVA. Enlarged capillaries or preferential channels are thus wrongly seen as AVA. 10 3.3...considerably enlarged . It makes an S-shaped curve and then narrows down to become continuous with a short funnel-shaped vein which opens at right angles, into

Free drainage of aqueous foams: Container shape effects on capillarity and vertical gradients

NASA Astrophysics Data System (ADS)

Saint-Jalmes, A.; Vera, M. U.; Durian, D. J.

2000-06-01

The standard drainage equation applies only to foam columns of constant cross-sectional area. Here, we generalize to include the effects of arbitrary container shape and develop an exact solution for an exponential, "Eiffel Tower", sample. This geometry largely eliminates vertical wetness gradients, and hence capillary effects, and should permit a clean test of dissipation mechanisms. Agreement with experiment is not achieved at late times, however, highlighting the importance of both boundary conditions and coarsening.

Multifunctional Poro-Vascular Composites for UAV Performance Enhancement

DTIC Science & Technology

2012-07-31

structural “skin” materials with surface pores and internal vascular channels filled with an ionic- liquid whose height and shape at the pore exits is...2 V t e e q q          Intrinsic contact angle (zero voltage) Applied potential Interfacial tension (IFT) of ionic liquid Lippmann...Characterization flat plates  single (capillary) pore  PV pore arrays FTA 1000 Drop-Shape Characterization • Microscope lens : 0.5 to 12x magnification • Side

Antibacterial activity and mode of action of the Artemisia capillaris essential oil and its constituents against respiratory tract infection-causing pathogens.

PubMed

Yang, Chang; Hu, Dong-Hui; Feng, Yan

2015-04-01

Inhalation therapy using essential oils has been used to treat acute and chronic sinusitis and bronchitis. The aim of the present study was to determine the chemical composition of the essential oil of Artemisia capillaris, and evaluate the antibacterial effects of the essential oil and its main components, against common clinically relevant respiratory bacterial pathogens. Gas chromatography and gas chromatography‑mass spectrometry revealed the presence of 25 chemical constituents, the main constituents being: α‑pinene, β‑pinene, limonene, 1,8‑cineole, piperitone, β‑caryophyllene and capillin. The antibacterial activities of the essential oil, and its major constituents, were evaluated against Streptococcus pyogenes, methicillin‑resistant Staphylococcus aureus (MRSA), MRSA (clinical strain), methicillin‑gentamicin resistant Staphylococcus aureus (MGRSA), Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae and Escherichia coli. The essential oil and its constituents exhibited a broad spectrum and variable degree of antibacterial activity against the various strains. The essential oil was observed to be much more potent, as compared with any of its major chemical constituents, exhibiting low minimum inhibitory and bacteriocidal concentration values against all of the bacterial strains. The essential oil was most active against S. pyogenes, MRSA (clinical strain), S. pneumoniae, K. pneumoniae, H. influenzae and E. coli. Piperitone and capillin were the most potent growth inhibitors, among the major chemical constituents. Furthermore, the essential oil of A. capillaris induced significant and dose‑dependent morphological changes in the S. aureus bacterial strain, killing >90% of the bacteria when administered at a higher dose; as determined by scanning electron microscopy. In addition, the essential oil induced a significant leakage of potassium and phosphate ions from the S. aureus bacterial cultures. These results indicate that the antibacterial action of A. capillaris essential oil may be mediated through the leakage of these two important ions. In conclusion, A. capillaris essential oil exhibits potent antibacterial activity by inducing morphological changes and leakage of ions in S. aureus bacterial cultures.

SPH-DEM approach to numerically simulate the deformation of three-dimensional RBCs in non-uniform capillaries.

PubMed

Polwaththe-Gallage, Hasitha-Nayanajith; Saha, Suvash C; Sauret, Emilie; Flower, Robert; Senadeera, Wijitha; Gu, YuanTong

2016-12-28

Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries. An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary; (i) the motion of five identical RBCs in a uniform capillary, (ii) the motion of five identical RBCs with different bending stiffness (K b ) values in a stenosed capillary, (iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary. Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained; (i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them. (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (K b ) of the RBCs is changed. (iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted. A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.

Effect of ultrasonic capillary dynamics on the mechanics of thermosonic ball bonding.

PubMed

Huang, Yan; Shah, Aashish; Mayer, Michael; Zhou, Norman Y; Persic, John

2010-01-01

Microelectronic wire bonding is an essential step in today's microchip production. It is used to weld (bond) microwires to metallized pads of integrated circuits using ultrasound with hundreds of thousands of vibration cycles. Thermosonic ball bonding is the most popular variant of the wire bonding process and frequently investigated using finite element (FE) models that simplify the ultrasonic dynamics of the process with static or quasistatic boundary conditions. In this study, the ultrasonic dynamics of the bonding tool (capillary), made from Al(2)O(3), is included in a FE model. For more accuracy of the FE model, the main material parameters are measured. The density of the capillary was measured to be rho(cap) = 3552 +/- 100 kg/m(3). The elastic modulus of the capillary, E(cap) = 389 +/- 11 GPa, is found by comparing an auxiliary FE model of the free vibrating capillary with measured values. A capillary "nodding effect" is identified and found to be essential when describing the ultrasonic vibration shape. A main FE model builds on these results and adds bonded ball, pad, chip, and die attach components. There is excellent agreement between the main model and the ultrasonic force measured at the interface on a test chip with stress microsensors. Bonded ball and underpad stress results are reported. When adjusted to the same ultrasonic force, a simplified model without ultrasonic dynamics and with an infinitely stiff capillary tip is substantially off target by -40% for the maximum underpad stress. The compliance of the capillary causes a substantial inclination effect at the bonding interface between wire and pad. This oscillating inclination effect massively influences the stress fields under the pad and is studied in more detail. For more accurate results, it is therefore recommended to include ultrasonic dynamics of the bonding tool in mechanical FE models of wire bonding.

Wettability Control on Fluid-Fluid Displacements in Patterned Microfluidics

NASA Astrophysics Data System (ADS)

Zhao, B.; Trojer, M.; Cueto-Felgueroso, L.; Juanes, R.

2014-12-01

Two-phase flow in porous media is important in many natural and industrial processes like geologic CO2 sequestration, enhanced oil recovery, and water infiltration in soil. While it is well known that the wetting properties of porous media can vary drastically depending on the type of media and the pore fluids, the effect of wettability on fluid displacement continues to challenge our microscopic and macroscopic descriptions. Here we study this problem experimentally, starting with the classic experiment of two-phase flow in a capillary tube. We image the shape of the meniscus and measure the associated capillary pressure for a wide range of capillary numbers. We confirm that wettability exerts a fundamental control on meniscus deformation, and synthesize new observations on the dependence of the dynamic capillary pressure on wetting properties (contact angle) and flow conditions (viscosity contrast and capillary number). We compare our experiments to a macroscopic phase-field model of two-phase flow. We use the insights gained from the capillary tube experiments to explore the viscous fingering instability in the Hele-Shaw geometry in the partial-wetting regime. A key difference between a Hele-Shaw cell and a porous medium is the existence of micro-structures (i.e. pores and pore throats). To investigate how these micro-structrues impact fluid-fluid displacement, we conduct experiments on a planar microfluidic device patterned with vertical posts. We track the evolution of the fluid-fluid interface and elucidate the impact of wetting on the cooperative nature of fluid displacement during pore invasion events. We use the insights gained from the capillary tube and patterned microfluidics experiments to elucidate the effect of wetting properties on viscous fingering and capillary fingering in a Hele-Shaw cell filled with glass beads, where we observe a contact-angle-dependent stabilizing behavior for the emerging flow instabilities, as the system transitions from drainage to imbibition.

Effect of interfacial slip on the thin film drainage time for two equal-sized, surfactant-free drops undergoing a head-on collision: A scaling analysis

NASA Astrophysics Data System (ADS)

Ramachandran, A.; Leal, L. G.

2016-10-01

Using a scaling analysis, we assess the impact of interfacial slip on the time required for the thin liquid film between two drops undergoing a head-on collision to drain to the critical thickness for rupture by van der Waals forces. Interfacial slip is included in our continuum development using a Navier slip boundary condition, with the slip coefficient modeled using previous theories [Helfand and Tagami, J. Chem. Phys. 57, 1812 (1972), 10.1063/1.1678491; Goveas and Fredrickson, Eur. Phys. J. B 2, 79 (1998), 10.1007/s100510050228]. Slip decreases hydrodynamic resistance and speeds up film drainage. It renders the dependence of the drainage time on capillary number stronger in the spherical-film regime, but, interestingly, this dependence is altered only weakly in the dimpled-film regime. A subtle effect of slip is that it increases the range of capillary numbers in which the film remains predominantly spherical in shape during drainage (as opposed to being dimpled), leading to significantly faster drainage for these capillary numbers. Slip also leads to an increase in the critical capillary number beyond which coalescence is not possible in a head-collision.

The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids.

PubMed

Hu, Bin; Kieweg, Sarah L

2012-07-15

Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability.

Automated processing of whole blood samples into microliter aliquots of plasma.

PubMed

Burtis, C A; Johnson, W W; Walker, W A

1988-01-01

A rotor that accepts and automatically processes a bulk aliquot of a single blood sample into multiple aliquots of plasma has been designed and built. The rotor consists of a central processing unit, which includes a disk containing eight precision-bore capillaries. By varying the internal diameters of the capillaries, aliquot volumes ranging 1 to 10 mul can be prepared. In practice, an unmeasured volume of blood is placed in a centre well, and, as the rotor begins to spin, is moved radially into a central annular ring where it is distributed into a series of processing chambers. The rotor is then spun at 3000 rpm for 10 min. When the centrifugal field is removed by slowly decreasing the rotor speed, an aliquot of plasma is withdrawn by capillary action into each of the capillary tubes. The disk containing the eight measured aliquots of plasma is subsequently removed and placed in a modifed rotor for conventional centrifugal analysis. Initial evaluation of the new rotor indicates that it is capable of producing discrete, microliter volumes of plasma with a degree of accuracy and precision approaching that of mechanical pipettes.

Liquid Droplets Act as "Compass Needles" for the Stresses in a Deformable Membrane.

PubMed

Schulman, Rafael D; Ledesma-Alonso, René; Salez, Thomas; Raphaël, Elie; Dalnoki-Veress, Kari

2017-05-12

We examine the shape of droplets atop deformable thin elastomeric films prepared with an anisotropic tension. As the droplets generate a deformation in the taut film through capillary forces, they assume a shape that is elongated along the high tension direction. By measuring the contact line profile, the tension in the membrane can be completely determined. Minimal theoretical arguments lead to predictions for the droplet shape and membrane deformation that are in excellent agreement with the data. On the whole, the results demonstrate that droplets can be used as probes to map out the stress field in a membrane.

Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications

PubMed Central

Ward, Jonathan M.; Yang, Yong; Nic Chormaic, Síle

2016-01-01

We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated. PMID:27121151

Capillary Assembly of Colloids: Interactions on Planar and Curved Interfaces

NASA Astrophysics Data System (ADS)

Liu, Iris B.; Sharifi-Mood, Nima; Stebe, Kathleen J.

2018-03-01

In directed assembly, small building blocks are assembled into an organized structure under the influence of guiding fields. Capillary interactions provide a versatile route for structure formation. Colloids adsorbed on fluid interfaces distort the interface, which creates an associated energy field. When neighboring distortions overlap, colloids interact to minimize interfacial area. Contact line pinning, particle shape, and surface chemistry play important roles in structure formation. Interface curvature acts like an external field; particles migrate and assemble in patterns dictated by curvature gradients. We review basic analysis and recent findings in this rapidly evolving literature. Understanding the roles of assembly is essential for tuning the mechanical, physical, and optical properties of the structure.

Elastocapillarity: When Surface Tension Deforms Elastic Solids

NASA Astrophysics Data System (ADS)

Bico, José; Reyssat, Étienne; Roman, Benoît

2018-01-01

Although negligible at large scales, capillary forces may become dominant for submillimetric objects. Surface tension is usually associated with the spherical shape of small droplets and bubbles, wetting phenomena, imbibition, or the motion of insects at the surface of water. However, beyond liquid interfaces, capillary forces can also deform solid bodies in their bulk, as observed in recent experiments with very soft gels. Capillary interactions, which are responsible for the cohesion of sandcastles, can also bend slender structures and induce the bundling of arrays of fibers. Thin sheets can spontaneously wrap liquid droplets within the limit of the constraints dictated by differential geometry. This review aims to describe the different scaling parameters and characteristic lengths involved in elastocapillarity. We focus on three main configurations, each characterized by a specific dimension: three-dimensional (3D), deformations induced in bulk solids; 1D, bending and bundling of rod-like structures; and 2D, bending and stretching of thin sheets. Although each configuration deserves a detailed review, we hope our broad description provides a general view of elastocapillarity.

Miniaturized high throughput detection system for capillary array electrophoresis on chip with integrated light emitting diode array as addressed ring-shaped light source.

PubMed

Ren, Kangning; Liang, Qionglin; Mu, Xuan; Luo, Guoan; Wang, Yiming

2009-03-07

A novel miniaturized, portable fluorescence detection system for capillary array electrophoresis (CAE) on a microfluidic chip was developed, consisting of a scanning light-emitting diode (LED) light source and a single point photoelectric sensor. Without charge coupled detector (CCD), lens, fibers and moving parts, the system was extremely simplified. Pulsed driving of the LED significantly increased the sensitivity, and greatly reduced the power consumption and photobleaching effect. The highly integrated system was robust and easy to use. All the advantages realized the concept of a portable micro-total analysis system (micro-TAS), which could work on a single universal serial bus (USB) port. Compared with traditional CAE detecting systems, the current system could scan the radial capillary array with high scanning rate. An 8-channel CAE of fluorescein isothiocyanate (FITC) labeled arginine (Arg) on chip was demonstrated with this system, resulting in a limit of detection (LOD) of 640 amol.

[Blood vessels of the epiphysis in comparative-anatomical aspect].

PubMed

Selin, Iu M

1977-05-01

The structure of the epiphysis and its inner blood vessels were studied in the representatives of nine orders of placental mammals and in man by means of injection of stained masses into the arteries and veins and subsequent preparation of histological sections. Not only form and topography of the organ differ in the representatives of different orders, but histological picture of the epiphysis is specific for each of them. In insectivores and chiroptera the loops of the inner three-dimensional capillary network are stretched along the longitudinal axis of the organ. In the epiphysis of carnivores, ungulata and monkey, the intraorganic vessels are situated in stromal trabeculae and the loops of the capillary network have polygonal shape. The intraepiphyseal vessels in man are arranged in peculiar baskets which envelope parenchymal lobules. The intraorganic veins beginning from the loops of the capillary network do not follow the arteries penetrating into the organ, but independently go to different surface parts of the organ where they flow into extraorganic veins.

Paper-based enzymatic microfluidic fuel cell: From a two-stream flow device to a single-stream lateral flow strip

NASA Astrophysics Data System (ADS)

González-Guerrero, Maria José; del Campo, F. Javier; Esquivel, Juan Pablo; Giroud, Fabien; Minteer, Shelley D.; Sabaté, Neus

2016-09-01

This work presents a first approach towards the development of a cost-effective enzymatic paper-based glucose/O2 microfluidic fuel cell in which fluid transport is based on capillary action. A first fuel cell configuration consists of a Y-shaped paper device with the fuel and the oxidant flowing in parallel over carbon paper electrodes modified with bioelectrocatalytic enzymes. The anode consists of a ferrocenium-based polyethyleneimine polymer linked to glucose oxidase (GOx/Fc-C6-LPEI), while the cathode contains a mixture of laccase, anthracene-modified multiwall carbon nanotubes, and tetrabutylammonium bromide-modified Nafion (MWCNTs/laccase/TBAB-Nafion). Subsequently, the Y-shaped configuration is improved to use a single solution containing both, the anolyte and the catholyte. Thus, the electrolytes pHs of the fuel and the oxidant solutions are adapted to an intermediate pH of 5.5. Finally, the fuel cell is run with this single solution obtaining a maximum open circuit of 0.55 ± 0.04 V and a maximum current and power density of 225 ± 17 μA cm-2 and 24 ± 5 μW cm-2, respectively. Hence, a power source closer to a commercial application (similar to conventional lateral flow test strips) is developed and successfully operated. This system can be used to supply the energy required to power microelectronics demanding low power consumption.

Direct numerical simulation of gas-solid-liquid flows with capillary effects: An application to liquid bridge forces between spherical particles.

PubMed

Sun, Xiaosong; Sakai, Mikio

2016-12-01

In this study, a numerical method is developed to perform the direct numerical simulation (DNS) of gas-solid-liquid flows involving capillary effects. The volume-of-fluid method employed to track the free surface and the immersed boundary method is adopted for the fluid-particle coupling in three-phase flows. This numerical method is able to fully resolve the hydrodynamic force and capillary force as well as the particle motions arising from complicated gas-solid-liquid interactions. We present its application to liquid bridges among spherical particles in this paper. By using the DNS method, we obtain the static bridge force as a function of the liquid volume, contact angle, and separation distance. The results from the DNS are compared with theoretical equations and other solutions to examine its validity and suitability for modeling capillary bridges. Particularly, the nontrivial liquid bridges formed in triangular and tetrahedral particle clusters are calculated and some preliminary results are reported. We also perform dynamic simulations of liquid bridge ruptures subject to axial stretching and particle motions driven by liquid bridge action, for which accurate predictions are obtained with respect to the critical rupture distance and the equilibrium particle position, respectively. As shown through the simulations, the strength of the present method is the ability to predict the liquid bridge problem under general conditions, from which models of liquid bridge actions may be constructed without limitations. Therefore, it is believed that this DNS method can be a useful tool to improve the understanding and modeling of liquid bridges formed in complex gas-solid-liquid flows.

Human action classification using procrustes shape theory

NASA Astrophysics Data System (ADS)

Cho, Wanhyun; Kim, Sangkyoon; Park, Soonyoung; Lee, Myungeun

2015-02-01

In this paper, we propose new method that can classify a human action using Procrustes shape theory. First, we extract a pre-shape configuration vector of landmarks from each frame of an image sequence representing an arbitrary human action, and then we have derived the Procrustes fit vector for pre-shape configuration vector. Second, we extract a set of pre-shape vectors from tanning sample stored at database, and we compute a Procrustes mean shape vector for these preshape vectors. Third, we extract a sequence of the pre-shape vectors from input video, and we project this sequence of pre-shape vectors on the tangent space with respect to the pole taking as a sequence of mean shape vectors corresponding with a target video. And we calculate the Procrustes distance between two sequences of the projection pre-shape vectors on the tangent space and the mean shape vectors. Finally, we classify the input video into the human action class with minimum Procrustes distance. We assess a performance of the proposed method using one public dataset, namely Weizmann human action dataset. Experimental results reveal that the proposed method performs very good on this dataset.

Prediction of Hydraulic Conductivity as Related to Pore Size Distribution in Unsaturated Soils

USDA-ARS?s Scientific Manuscript database

Soil pore volume as well as pore size, shape, type (i.e. biopore versus crack), continuity, and distribution in soil affect soil water and gas exchange. Vertical and lateral drainage of water by gravitational forces occurs through large, non-capillary soil pores, but redistribution and upward moveme...

[Vascular dental anaesthesias and their mechanism].

PubMed

Petrikas, A Zh; Iakupova, L A; Medvedev, A V; Borodina, O E; Egorova, V A; Diuba

2010-01-01

By their mechanism of action local anaesthesia methods were divided into diffused and vascular. Intraosseous, intraseptal and intraligamental anesthaesias are vascular ones at capillary-venous system level. Circulatory mechanism besides effectiveness increased more than 2-fold and also promotes enhancement of cardiovascular system responses.

Characteristics and dispersity of a two gap capillary discharge applied for long spark gap ignition in air

NASA Astrophysics Data System (ADS)

Huang, Dong; Yang, Lanjun; Guo, Haishan; Zhang, Zhiyuan; Jiang, Hongqiu; Xu, Haipeng

2017-07-01

In this paper, the characteristics and dispersity of a two gap capillary (TGC) discharge applied for long spark gap ignition are studied. Under the same discharge condition, 30 repetitive discharges are done to get a certain number of data samples. Accordingly, the change trend of the characteristics and the dispersity with the charging voltage of C1 are analyzed statistically. The delay of soft capillary discharge is determined by the saturation rate of the magnetic core of the pulse transformer and decreases with the increase in the charging voltage. The main discharge delay decreases from 1.0 kV to 2.0 kV and stops the decreasing trend when the charging voltage increases to 2.5 kV. In contrast, the current amplitude of soft capillary discharge and main discharge increases with charging voltage. Long tail extinction is witnessed at the charging voltage of 1.0 kV and the major cause is the insufficient pressure in the post discharge. The waveform of the capillary arc resistivity is U-like shape and the minimum resistivity decreases with the increase in the charging voltage. Meanwhile, the arc resistivity in the ascending stage is much higher than that in the descending stage with the same value of the discharge current. The energy consumption of the TGC discharge can be mainly divided into four parts and more than 70% of the energy is consumed in main discharge.

Electrode configuration for extreme-UV electrical discharge source

DOEpatents

Spence, Paul Andrew; Fornaciari, Neal Robert; Chang, Jim Jihchyun

2002-01-01

It has been demonstrated that debris generation within an electric capillary discharge source, for generating extreme ultraviolet and soft x-ray, is dependent on the magnitude and profile of the electric field that is established along the surfaces of the electrodes. An electrode shape that results in uniform electric field strength along its surface has been developed to minimize sputtering and debris generation. The electric discharge plasma source includes: (a) a body that defines a circular capillary bore that has a proximal end and a distal end; (b) a back electrode positioned around and adjacent to the distal end of the capillary bore wherein the back electrode has a channel that is in communication with the distal end and that is defined by a non-uniform inner surface which exhibits a first region which is convex, a second region which is concave, and a third region which is convex wherein the regions are viewed outwardly from the inner surface of the channel that is adjacent the distal end of the capillary bore so that the first region is closest to the distal end; (c) a front electrode positioned around and adjacent to the proximal end of the capillary bore wherein the front electrode has an opening that is communication with the proximal end and that is defined by a non-uniform inner surface which exhibits a first region which is convex, a second region which is substantially linear, and third region which is convex wherein the regions are viewed outwardly from the inner surface of the opening that is adjacent the proximal end of the capillary bore so that the first region is closest to the proximal end; and (d) a source of electric potential that is connected across the front and back electrodes.

Fingering and Intermittent Flow in Unsaturated Fractured Porous Media

NASA Astrophysics Data System (ADS)

Or, D.; Ghezzehei, T. A.

2003-12-01

Because of the dominance of gravitational forces over capillary and viscous forces in relatively large fracture apertures, flow processes in unsaturated fractures are considerably different from flow in rock matrix or in unsaturated soils. Additionally, variations in fracture geometry and properties perturb the delicate balance between gravitational, capillary, and viscous forces, leading to liquid fragmentation, fingering and intermittent flows. We developed a quantitative framework for modeling fluid fragmentation and the subsequent flow behavior of discrete fluid elements (slugs). The transition from a slowly growing but stationary liquid cluster to a finger-forming mobile slug in a non horizontal fracture is estimated from the force balance between retarding capillary forces dominated by contact angle hysteresis, and the weight and shape of the cluster. For a steady flux we developed a model for liquid fragmentation within the fracture plane that gives rise to intermittent discharge, as has been observed experimentally. Intermittency is shown to be a result of interplay between capillary, viscous, and gravitational forces, much like internal dripping. Liquid slug size, detachment interval, and travel velocity are dependent primarily on the local fracture-aperture geometry shaping the seed cluster, rock-surface roughness and wetness, and liquid flux feeding the bridge (either by film flow or from the rock matrix). We show that the presence of even a few irregularities in a vertical fracture surface could affect liquid cluster formation and growth, resulting in complicated flux patterns at the fracture bottom. Such chaotic-like behavior has been observed in previous studies involving gravity-driven unsaturated flow. Inferences based on statistical description of fracture-aperture variations and simplified representation of the fragmentation processes yield insights regarding magnitude and frequency of liquid avalanches. The study illustrates that attempts at describing intermittent and preferential flow behavior by adjustment of macroscopic continuum approaches are destined to failure at most local scales. In accordance with recent observations, flow behavior in partially saturated fractures tends to produce highly localize pathways that focus otherwise diffusive fluxes (film flow or matrix seepage).

Coplanar electrowetting-induced stirring as a tool to manipulate biological samples in lubricated digital microfluidics. Impact of ambient phase on drop internal flow patterna)

PubMed Central

Davoust, Laurent; Fouillet, Yves; Malk, Rachid; Theisen, Johannes

2013-01-01

Oscillating electrowetting on dielectrics (EWOD) with coplanar electrodes is investigated in this paper as a way to provide efficient stirring within a drop with biological content. A supporting model inspired from Ko et al. [Appl. Phys. Lett. 94, 194102 (2009)] is proposed allowing to interpret oscillating EWOD-induced drop internal flow as the result of a current streaming along the drop surface deformed by capillary waves. Current streaming behaves essentially as a surface flow generator and the momentum it sustains within the (viscous) drop is even more significant as the surface to volume ratio is small. With the circular electrode pair considered in this paper, oscillating EWOD sustains toroidal vortical flows when the experiments are conducted with aqueous drops in air as ambient phase. But when oil is used as ambient phase, it is demonstrated that the presence of an electrode gap is responsible for a change in drop shape: a pinch-off at the electrode gap yields a peanut-shaped drop and a symmetry break-up of the EWOD-induced flow pattern. Viscosity of oil is also responsible for promoting an efficient damping of the capillary waves which populate the surface of the actuated drop. As a result, the capillary network switches from one standing wave to two superimposed traveling waves of different mechanical energy, provided that actuation frequency is large enough, for instance, as large as the one commonly used in electrowetting applications (f ∼ 500 Hz and beyond). Special emphasis is put on stirring of biological samples. As a typical application, it is demonstrated how beads or cell clusters can be focused under flow either at mid-height of the drop or near the wetting plane, depending on how the nature of the capillary waves is (standing or traveling), and therefore, depending on the actuation frequency (150 Hz–1 KHz). PMID:24404038

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes.

PubMed

Stevar, M S P; Vorobev, A

2012-10-01

We report optical observations of the dissolution behaviour of glycerol/water, soybean oil/hexane, and isobutyric acid (IBA)/water binary mixtures within horizontal capillary tubes. Tubes with diameters as small as 0.2mm were initially filled with one component of the binary mixture (solute) and then immersed into a solvent-filled thermostatic bath. Both ends of the tubes were open, and no pressure difference was applied between the ends. In the case of glycerol/water and soybean oil/hexane mixtures, we managed to isolate the dissolution (the interfacial mass transfer) from the hydrodynamic motion. Two phase boundaries moving from the ends into the middle section of the tube with the speeds v∼D(1/3)t(-2/3)d(2) (D,t and d are the coefficient of diffusion, time and the diameter of the tube, respectively) were observed. The boundaries slowly smeared but their smearing occurred considerably slower than their motion. The motion of the phase boundaries cannot be explained by the dependency of the diffusion coefficient on concentration, and should be explained by the effect of barodiffusion. The shapes of the solute/solvent boundaries are defined by the balance between gravity and surface tension effects. The contact line moved together with the bulk interface: no visible solute remained on the walls after the interface passage. Changes in temperature and in the ratio between gravity and capillary forces altered the apparent contact angles. The IBA/water system had different behaviour. Below the critical (consolute) point, no dissolution was observed: IBA and water behaved like two immiscible liquids, with the IBA phase being displaced from the tube by capillary pressure (the spontaneous imbibition process). Above the critical point, two IBA/water interfaces could be identified, however the interfaces did not penetrate much into the tube. Copyright © 2012 Elsevier Inc. All rights reserved.

A proposal to demonstrate production of salad crops in the space station mockup facility with particular attention to space, energy, and labor constraints

NASA Technical Reports Server (NTRS)

Brooks, Carolyn A.; Sharma, Govind C.; Beyl, Caula A.

1990-01-01

A desire for fresh vegetables for consumption during long term space missions has been foreseen. To meet this need in a microgravity environment within the limited space and energy available on Space Station requires highly productive vegetable cultivars of short stature to optimize vegetable production per volume available. Special water and nutrient delivery systems must also be utilized. As a first step towards fresh vegetable production in the microgravity of Space Station, several soil-less capillary action media were evaluated for the ability to support growth of two root crops (radish and carrot) which are under consideration for inclusion in a semi-automated system for production of salad vegetables in a microgravity environment (Salad Machine). In addition, productivity of different cultivars of radish was evaluated as well as the effect of planting density and cultivar on carrot production and size. Red Prince radish was more productive than Cherry Belle and grew best on Jiffy Mix Plus. During greenhouse studies, vermiculite and rock wool supported radish growth to a lesser degree than Jiffy Mix Plus but more than Cellular Rooting Sponge. Comparison of three carrot cultivars (Planet, Short n Sweet, and Goldinhart) and three planting densities revealed that Short n Sweet planted at 25.6 sq cm/plant had the greatest root fresh weight per pot, the shortest mean top length, and intermediate values of root length and top fresh weight per pot. Red Prince radish and Short n Sweet carrot showed potential as productive cultivars for use in a Salad Machine. Results of experiments with solid capillary action media were disappointing. Further research must be done to identify a solid style capillary action media which can productively support growth of root crops such as carrot and radish.

Shape evolution of a melting nonspherical particle

NASA Astrophysics Data System (ADS)

Kintea, Daniel M.; Hauk, Tobias; Roisman, Ilia V.; Tropea, Cameron

2015-09-01

In this study melting of irregular ice crystals was observed in an acoustic levitator. The evolution of the particle shape is captured using a high-speed video system. Several typical phenomena have been discovered: change of the particle shape, appearance of a capillary flow of the melted liquid on the particle surface leading to liquid collection at the particle midsection (where the interface curvature is smallest), and appearance of sharp cusps at the particle tips. No such phenomena can be observed during melting of spherical particles. An approximate theoretical model is developed which accounts for the main physical phenomena associated with melting of an irregular particle. The agreement between the theoretical predictions for the melting time, for the evolution of the particle shape, and the corresponding experimental data is rather good.

Microwave capillary torch as a means for modifying the electrophysical characteristics of metal surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Artem’ev, K. V.; Davydov, A. M.; Ivanov, V. A.

2016-07-15

An experiment layout based on a pulsed capillary microwave torch and making it possible to excite an explosive emission microplasma on a metal surface in open air is implemented for the first time. It is shown that a microrelief in the form of micron-size microcraters forms on the initially smooth surface under the action of microsparks. As a result, the maximum secondary electron emission yield σ{sub max} decreases from ∼2 for the untreated surface to ∼0.4 for the rough treated surface and remains low for a long time when exposed to atmospheric air.

Breakup Behavior of a Capillary Bridge on a Hydrophobic Stripe Separating Two Hydrophilic Stripes

NASA Astrophysics Data System (ADS)

Hartmann, Maximilian; Hardt, Steffen

2017-11-01

The breakup dynamics of a capillary bridge on a hydrophobic area between two liquid filaments occupying two parallel hydrophilic stripes is studied experimentally. In addition calculations with the finite-element software Surface Evolver are performed to obtain the corresponding stable minimal surfaces. Droplets of de-ionized water are placed on substrates with alternating hydrophilic and hydrophobic stripes of different width. Their volume decreases by evaporation. This results in a droplet shaped as the letter ``H'' covering two hydrophilic stripes separated by one hydrophobic stripe. The width of the capillary bridge d(t) on the hydrophobic stripe during the breakup process is observed using a high-speed camera mounted on a bright-field microscope. The results of the experiments and the numerical studies show that the critical width dcrit, indicating the point where the capillary bridge becomes unstable, mainly depends on the width ratio of the hydrophilic and hydrophobic stripes. It is found that the time derivative of d(t) first decreases after dcrit has been reached. The final breakup dynamics then follows a t 2 / 3 scaling. We kindly acknowledge the financial support by the German Research Foundation (DFG) within the Collaborative Research Centre 1194 ``Interaction of Transport and Wetting Processes'', Project A02a.

Electrified Flow in Slender V-Groove Microchannels: Generalized Stability of Steady State Configurations

NASA Astrophysics Data System (ADS)

Markeviciute, Vilda; White, Nicholas; Troian, Sandra

2017-11-01

Although spontaneous capillary flow can be an especially rapid process in slender open microchannels resembling V-grooves, enhanced flow control is possible through implementation of electric field distributions which generate opposing electrohydrodynamic pressures along the air/liquid interface to modulate the capillary pressures. Important fundamental work by Romero and Yost (1996) and Weislogel(1996) has elucidated the behavior of Newtonian films in slender V-grooves driven to flow solely by the streamwise change in capillary pressure due to the change in radius of curvature of the circular arc describing the interface of wetting or non-wetting fluids. Here we augment the Romero and Yost model with inclusion of Maxwell stresses for perfectly conducting wetting films and examine which electric field distributions allow formation of steady state film shapes for various inlet and outlet boundary conditions. We investigate the stability of these steady solutions to small perturbations in film thickness using a generalized stability analysis. These results reveal how the ratio of Maxwell to capillary stresses influences the degree of linearized transient growth or decay for thin films confined to flow within an open V-groove. Funding from the 2017 Caltech Summer Undergraduate Research Fellowship Program (Markeviciute) as well as a 2017 NASA Space Technology Research Fellowship (White) is gratefully acknowledged.

Excimer lasers

NASA Technical Reports Server (NTRS)

Palmer, A. J.; Hess, L. D.; Stephens, R. R.; Pepper, D. M.

1977-01-01

The results of a two-year investigation into the possibility of developing continuous wave excimer lasers are reported. The program included the evaluation and selection of candidate molecular systems and discharge pumping techniques. The K Ar/K2 excimer dimer molecules and the xenon fluoride excimer molecule were selected for study; each used a transverse and capillary discharges pumping technique. Experimental and theoretical studies of each of the two discharge techniques applied to each of the two molecular systems are reported. Discharge stability and fluorine consumption were found to be the principle impediments to extending the XeF excimer laser into the continuous wave regime. Potassium vapor handling problems were the principal difficulty in achieving laser action on the K Ar/K2 system. Of the four molecular systems and pumping techniques explored, the capillary discharge pumped K Ar/K2 system appears to be the most likely candidate for demonstrating continuous wave excimer laser action primarily because of its predicted lower pumping threshold and a demonstrated discharge stability advantage.

The effects of capillary forces on the axisymmetric propagation of two-phase, constant-flux gravity currents in porous media

NASA Astrophysics Data System (ADS)

Golding, Madeleine J.; Huppert, Herbert E.; Neufeld, Jerome A.

2013-03-01

The effects of capillary forces on the propagation of two-phase, constant-flux gravity currents in a porous medium are studied analytically and numerically in an axisymmetric geometry. The fluid within a two-phase current generally only partially saturates the pore space it invades. For long, thin currents, the saturation distribution is set by the vertical balance between gravitational and capillary forces. The capillary pressure and relative permeability of the fluid in the current depend on this saturation. The action of capillary forces reduces the average saturation, thereby decreasing the relative permeability throughout the current. This results in a thicker current, which provides a steeper gradient to drive flow, and a more blunt-nose profile. The relative strength of gravity and capillary forces remains constant within a two-phase gravity current fed by a constant flux and spreading radially, due to mass conservation. For this reason, we use an axisymmetric representation of the framework developed by Golding et al. ["Two-phase gravity currents in porous media," J. Fluid Mech. 678, 248-270 (2011)], 10.1017/jfm.2011.110, to investigate the effect on propagation of varying the magnitude of capillary forces and the pore-size distribution. Scaling analysis indicates that axisymmetric two-phase gravity currents fed by a constant flux propagate like t1/2, similar to their single-phase counterparts [S. Lyle, H. E. Huppert, M. Hallworth, M. Bickle, and A. Chadwick, "Axisymmetric gravity currents in a porous medium," J. Fluid Mech. 543, 293-302 (2005)], 10.1017/S0022112005006713, with the effects of capillary forces encapsulated in the constant of proportionality. As a practical application of our new concepts and quantitative evaluations, we discuss the implications of our results for the process of carbon dioxide (CO2) sequestration, during which gravity currents consisting of supercritical CO2 propagate in rock saturated with aqueous brine. We apply our two-phase model including capillary forces to quantitatively assess seismic images of CO2 spreading at Sleipner underneath the North Sea.

The distribution of 99mTc-EHDP in the tissues of the dog and its application in the assessment of fracture healing.

PubMed

Hughes, S

1977-07-01

Technetium-labelled ethane hydroxydiphosphonate (99mTc-EHDP) is a commonly used bone-scanning agent. After injection it leaves the circulation to enter bone and to be cleared by the kidney. The transcapillary exchange of 99mTc-EHDP in bone was examined and found to be low. The capillary movement was compared with that of sucrose, a freely diffusible substance, and it was found that the permeability ratio of 99mTc-EHDP to 14C-sucrose was similar to the diffusion coefficient ratio, suggesting that 99mTc-EHDP passes through the capillaries by the process of passive diffusion. The renal clearance of 99mTc-EHDP was 24 ml/min and was unaffected by the action of parathyroid hormone. After a fracture the bone blood flow increases, although the transcapillary extraction of 99mTc-EHDP does not change. This is because there is an increase, from recruitment and dilatation of capillaries, in the surface area available for exchange. Therefore the increased isotopic activity seen on a bone scan after a fracture is primarily related to an increase in bone blood supply from capillary enhancement within the cortex.

Hemangiopericytoma in a male breast. Report of a case with cytologic, histologic and immunochemical studies.

PubMed

Jiménez-Ayala, M; Díez-Nau, M D; Larrad, A; Ferrer-Vergara, L; Rodriguez-Costa, J; Lacruz, C; Escalona-Zapata, J

1991-01-01

A hemangiopericytoma in a male breast was studied by fine needle aspiration (FNA) biopsy. The FNA smears contained tissue clumps showing knob-like formations of atypical cells, spindle-shaped cells and fragments of capillaries lined by normal endothelial cells. Immunocytochemical study showed a positive reaction for vimentin, but a negative reaction for desmin and keratin. Staining for Factor VIII was positive only in the capillaries and endothelial cells. The cytodiagnosis was "mesenchymal tumor." Histopathologic study of the mastectomy specimen made the final diagnosis of hemangiopericytoma. While FNA cytology and immunocytochemistry cannot make a definitive diagnosis of this rare vascular tumor, they can be decisive in planning the surgical treatment, as in the present case.

Experimental Investigation on the Resonance of a Liquid Column in a Capillary Tube.

PubMed

Hilpert; Miller

1999-11-01

Using a visualization technique, we observed the resonance of a water column trapped in a vertically oriented capillary tube due to acoustic excitation. The analysis of the quasi-static response suggests that the upper nonvisible meniscus followed the imposed flow by means of a sliding contact line without changing its shape. We compared the experiments with a previously developed theoretical model that addresses dissipation by assuming an axially symmetric and incompressible flow field that is spatially constant along the tube axis. Whereas the model agrees well with the measured quasi-static response, the deviations in the dynamic response reveal shortcomings of the model due to the simplified treatment of the viscous dissipation. Copyright 1999 Academic Press.

CFE-2 Experiment Run

NASA Image and Video Library

2013-11-11

View of Flight Engineer (FE) Mike Hopkins initiating a CFE-2 (Capillary Flow Experiment - 2) Interior Corner Flow - 5 (ICF-5) test run. Liquids behave differently in space than they do on Earth, so containers that can process, hold or transport them must be designed carefully to work in microgravity. The Capillary Flow Experiment-2 furthers research on wetting, which is a liquid's ability to spread across a surface, and its impact over large length scales in strange container shapes in microgravity environments. This work will improve our capabilities to quickly and accurately predict how related processes occur, and allow us to design better systems to process liquids aboard spacecraft (i.e., liquid fuel tanks, thermals fluids, and water processing for life support). Image was released by astronaut on Twitter.

On the shape of giant soap bubbles.

PubMed

Cohen, Caroline; Darbois Texier, Baptiste; Reyssat, Etienne; Snoeijer, Jacco H; Quéré, David; Clanet, Christophe

2017-03-07

We study the effect of gravity on giant soap bubbles and show that it becomes dominant above the critical size [Formula: see text], where [Formula: see text] is the mean thickness of the soap film and [Formula: see text] is the capillary length ([Formula: see text] stands for vapor-liquid surface tension, and [Formula: see text] stands for the liquid density). We first show experimentally that large soap bubbles do not retain a spherical shape but flatten when increasing their size. A theoretical model is then developed to account for this effect, predicting the shape based on mechanical equilibrium. In stark contrast to liquid drops, we show that there is no mechanical limit of the height of giant bubble shapes. In practice, the physicochemical constraints imposed by surfactant molecules limit the access to this large asymptotic domain. However, by an exact analogy, it is shown how the giant bubble shapes can be realized by large inflatable structures.

Vascular Function, Insulin Action and Exercise: An Intricate Interplay

PubMed Central

Zheng, Chao; Liu, Zhenqi

2015-01-01

Insulin enhances the compliance of conduit arteries, relaxes resistance arterioles to increase tissue blood flow and dilates precapillary arterioles to expand muscle microvascular blood volume. These actions are impaired in the insulin resistant states. Exercise ameliorates endothelial dysfunction and improves insulin responses in insulin resistant patients, but the precise underlying mechanisms remain unclear. The microvasculature critically regulates insulin action in muscle by modulating insulin delivery to the capillaries nurturing the myocytes and trans-endothelial insulin transport. Recent data suggest that exercise may exert its insulin-sensitizing effect via recruiting muscle microvasculature to increase insulin delivery to and action in muscle. The current review focuses on how the interplay among exercise, insulin action and the vasculature contributes to exercise-mediated insulin sensitization in muscle. PMID:25735473

Shaped platinum nanoparticles directly synthesized inside mesoporous silica supports

NASA Astrophysics Data System (ADS)

Kim, Jiwhan; Bae, Youn-Sang; Lee, Hyunjoo

2014-10-01

It is difficult to deposit shape-controlled nanoparticles into a mesoporous framework while preserving the shape. For shaped platinum nanoparticles, which are typically 5-10 nm in size, capillary inclusion by sonication or the formation of a mesoporous framework around the shaped platinum nanoparticles has been attempted, but the nanoparticles aggregated or their shapes were degraded easily. In this work, we directly nucleated platinum on the surface inside a mesoporous silica support and controlled the overgrowth step, producing cubic shaped nanoparticles. Mercaptopropyltrimethoxysilane was used as an anchoring agent causing nucleation at the silica surface, and it also helped to shape the nanoparticles. Platinum nanocubes, which were synthesized with polymeric capping agents separately, were deposited inside the mesoporous silica by sonication, but most of the nanoparticles were clogged at the entrance to the pores, and the surface of the platinum had very few sites that were catalytically active, as evidenced by the small H2 uptake. Unshaped platinum nanoparticles, which were prepared by conventional wet impregnation, showed a similar amount of H2 uptake as the in situ shaped platinum cubes, but the selectivity for pyrrole hydrogenation was poorer towards the production of pyrrolidine. The mesoporosity and the residual thiol groups on the surface of the in situ shaped Pt nanocubes might cause a high selectivity for pyrrolidine.It is difficult to deposit shape-controlled nanoparticles into a mesoporous framework while preserving the shape. For shaped platinum nanoparticles, which are typically 5-10 nm in size, capillary inclusion by sonication or the formation of a mesoporous framework around the shaped platinum nanoparticles has been attempted, but the nanoparticles aggregated or their shapes were degraded easily. In this work, we directly nucleated platinum on the surface inside a mesoporous silica support and controlled the overgrowth step, producing cubic shaped nanoparticles. Mercaptopropyltrimethoxysilane was used as an anchoring agent causing nucleation at the silica surface, and it also helped to shape the nanoparticles. Platinum nanocubes, which were synthesized with polymeric capping agents separately, were deposited inside the mesoporous silica by sonication, but most of the nanoparticles were clogged at the entrance to the pores, and the surface of the platinum had very few sites that were catalytically active, as evidenced by the small H2 uptake. Unshaped platinum nanoparticles, which were prepared by conventional wet impregnation, showed a similar amount of H2 uptake as the in situ shaped platinum cubes, but the selectivity for pyrrole hydrogenation was poorer towards the production of pyrrolidine. The mesoporosity and the residual thiol groups on the surface of the in situ shaped Pt nanocubes might cause a high selectivity for pyrrolidine. Electronic supplementary information (ESI) available: Fig. S1-S9. See DOI: 10.1039/c4nr03951c

Using Molecular Dynamics Simulation to Reinforce Student Understanding of Intermolecular Forces

ERIC Educational Resources Information Center

Burkholder, Phillip R.; Purser, Gordon H.; Cole, Renee S.

2008-01-01

Intermolecular forces play an important role in many aspects of chemistry ranging from inorganic to biological chemistry. These forces dictate molecular conformation, species aggregation (including self-assembly), trends in solubility and boiling points, adsorption characteristics, viscosity, phase changes, surface tension, capillary action, vapor…

Endothelial cells in the oral mucosa of Bufo marinus.

PubMed Central

Loo, S K; Yeo, B C; Kovac, H

1980-01-01

The oral mucosa of the cane toad (Bufo marinus) is lined by a pseudostratified columnar ciliated epithelium containing an intraepithelial network of capillaries, which penetrates it to the bases of the distal layer of cells. The capillaries are lined by fenestrated endothelium lying on a complete basal lamina. A connective tissue sheath, approximately 1 micrometer thick, surrounds the capillaries and separates them from the surrounding epithelial cells. Endothelial cells resemble those in lymphatic capillaries in that they show microvillus-like processes or folds projecting into the lumen and also have extremely attenuated and fenestrated cytoplasm except in the nuclear region. Numerous pinocytotic vesicles, bundles of filaments and many electrondense granules occur in the cytoplasm. These granules are oval or round in shape and approximately 250-400 micrometer in diameter. Histochemical tests on the endothelial cells show that the granules do not contain pigment, as both the Schmorl and argentaffin reactions are negative. Both the Sudan black B and Luxol fast blue reactions are also negative showing the lack of stainable lipids. The formaldehyde-induced fluorescence, the argentaffin reactions and lead haematoxylin reactions are negative, indicating that they do not have the characteristics of endocrine cells. The acid phosphatase reaction gives a positive result, localized to the site of the granules by electron microscopy and suggesting that these granules in amphibian capillaries may have a lysosomal function. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 PMID:6773911

Foam shell cryogenic ICF target

DOEpatents

Darling, Dale H.

1987-01-01

A uniform cryogenic layer of DT fuel is maintained in a fusion target having a low density, small pore size, low Z rigid foam shell saturated with liquid DT fuel. Capillary action prevents gravitational slumping of the fuel layer. The saturated shell may be cooled to produce a solid fuel layer.

Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs.

PubMed

Furrow, E; Lees, G E; Brown, C A; Cianciolo, R E

2017-05-01

Miniature Schnauzer dogs are predisposed to idiopathic hypertriglyerceridemia, which increases risk for diseases such as pancreatitis and gallbladder mucocele. Recently, elevated triglyceride concentrations have been associated with proteinuria in this breed, although it is difficult to determine which abnormality is primary. Retrospective review of renal tissue from 27 proteinuric Miniature Schnauzers revealed that 20 dogs had ultrastructural evidence of osmophilic globules consistent with lipid in glomerular tufts. Seven of these dogs had lipid thromboemboli in glomerular capillary loops that distorted their shape and compressed circulating erythrocytes. Triglyceride concentrations were reported in 6 of these 7 dogs, and all were hypertriglyceridemic. In addition, glomerular lipidosis (defined as accumulation of foam cells within peripheral capillary loops) was identified in a single dog. The remaining 12 dogs had smaller amounts of lipid that could only be identified ultrastructurally. Neither signalment data nor clinicopathologic parameters (serum albumin, serum creatinine, urine protein-to-creatinine ratio, and blood pressure) differed among the various types of lipid lesions. During the time course of this study, all dogs diagnosed with glomerular lipid thromboemboli were Miniature Schnauzers, underscoring the importance of recognizing these clear spaces within capillary loops as lipid.

Water imbibition by mica pores: what happens when capillary flow is suppressed?

NASA Astrophysics Data System (ADS)

Fang, Chao; Qiao, Rui

2017-11-01

The imbibition of liquids into porous media plays a critical role in numerous applications. Most prior studies focused on imbibition driven by capillary flows. In this work, we study the imbibition of water into slit-shaped mica pores filled with pressurized methane using molecular simulations. Despite that capillary flow is suppressed by the high gas pressure, water is imbibed into the pore as monolayer liquid films. Since the classical hydrodynamic flow is not readily applicable for the monolayer water film propagating on the mica wall and the imbibition is driven by the strong affinity of water molecules to the mica walls, the observed imbibition is best taken as surface hydration. We show that the dynamics of water's imbibition front follows a simple diffusive scaling law. The effective diffusion coefficient of the imbibition front, however, is more than ten times larger than the diffusion coefficient of the water molecules in the water film adsorbed on the mica walls. Using a molecular theory originally developed for the spreading of monolayer films on solid substrates, we clarify the mechanism underlying the rapid water imbibition observed here.

π-Extended triptycene-based material for capillary gas chromatographic separations.

PubMed

Yang, Yinhui; Wang, Qinsi; Qi, Meiling; Huang, Xuebin

2017-10-02

Triptycene-based materials feature favorable physicochemical properties and unique molecular recognition ability that offer good potential as stationary phases for capillary gas chromatography (GC). Herein, we report the investigation of utilizing a π-extended triptycene material (denoted as TQPP) for GC separations. As a result, the TQPP capillary column exhibited high column efficiency of 4030 plates m -1 and high-resolution performance for a wide range of analytes, especially structural and positional isomers. Interestingly, the TQPP stationary phase showed unique shape selectivity for alkanes isomers and preferential retention for analytes with halogen atoms and H-bonding nature mainly through their halogen-bonding and H-bonding interactions. In addition, the TQPP column had good repeatability and reproducibility with the RSD values of 0.02-0.34% for run-to-run, 0.09-0.80% for day-to-day and 1.4-5.2% for column-to-column, respectively, and favorable thermal stability up to 280 °C. This work demonstrates the promising future of triptycene-based materials as a new class of stationary phases for GC separations. Copyright © 2017 Elsevier B.V. All rights reserved.

Meniscus on a shaped fibre: singularities and hodograph formulation.

PubMed

Alimov, Mars M; Kornev, Konstantin G

2014-08-08

Using the method of matched asymptotic expansions, the problem of the capillary rise of a meniscus on the complex-shaped fibres was reduced to a nonlinear problem of determination of a minimal surface. This surface has to satisfy a special boundary condition at infinity. The proposed formulation allows one to interpret the meniscus problem as a problem of flow of a fictitious non-Newtonian fluid through a porous medium. As an example, the shape of a meniscus on a fibre of an oval cross section was analysed employing Chaplygin's hodograph transformation. It was discovered that the contact line may form singularities even if the fibre has a smooth profile: this statement was illustrated with an oval fibre profile having infinite curvature at two endpoints.

Meniscus on a shaped fibre: singularities and hodograph formulation

PubMed Central

Alimov, Mars M.; Kornev, Konstantin G.

2014-01-01

Using the method of matched asymptotic expansions, the problem of the capillary rise of a meniscus on the complex-shaped fibres was reduced to a nonlinear problem of determination of a minimal surface. This surface has to satisfy a special boundary condition at infinity. The proposed formulation allows one to interpret the meniscus problem as a problem of flow of a fictitious non-Newtonian fluid through a porous medium. As an example, the shape of a meniscus on a fibre of an oval cross section was analysed employing Chaplygin's hodograph transformation. It was discovered that the contact line may form singularities even if the fibre has a smooth profile: this statement was illustrated with an oval fibre profile having infinite curvature at two endpoints. PMID:25104910

Thromboxane plays a role in postprandial jejunal oxygen uptake and capillary exchange.

PubMed

Alemayehu, A; Chou, C C

1990-09-01

The effects of a thromboxane A2 (TxA2)-endoperoxide receptor antagonist, SQ 29548, on jejunal blood flow, oxygen uptake, and capillary filtration coefficient (Kfc) were determined in anesthetized dogs under resting conditions and during the presence of predigested food in the jejunal lumen in three series of experiments. In series 1, 2.0 micrograms intra-arterial administration of SQ 29548 was found to abolish completely the vasoconstrictor action of graded doses (0.05-2.0 micrograms) of intra-arterial injection of a TxA2-endoperoxide analogue, U44069. SQ 29548 (2.0 micrograms ia) per se did not significantly alter resting jejunal blood flow, oxygen uptake, capillary pressure, or Kfc. Before SQ 29548, placement of food plus bile into the jejunal lumen increased blood flow +42 +/- 9%, oxygen uptake +28 +/- 7%, and Kfc +24 +/- 6%. After SQ 29548, the food placement increased blood flow +37 +/- 8%, oxygen uptake +52 +/- 11%, and Kfc +63 +/- 20%. The food-induced increases in oxygen uptake and Kfc after SQ 29548 were significantly greater than those induced before the blocking of TxA2-endoperoxide receptors by SQ 29548. Our study indicates that endogenous thromboxane does not play a role in regulating jejunal blood flow, capillary filtration, and oxygen uptake under resting conditions. However, it plays a role in limiting the food-induced increases in jejunal oxygen uptake and capillary exchange capacity without influencing the food-induced hyperemia.

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

PubMed Central

Copic, Davor; Park, Sei Jin; Tawfick, Sameh; De Volder, Michael; Hart, A. John

2012-01-01

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3. PMID:22806089

Fabrication, densification, and replica molding of 3D carbon nanotube microstructures.

PubMed

Copic, Davor; Park, Sei Jin; Tawfick, Sameh; De Volder, Michael; Hart, A John

2012-07-02

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques (1, 2), and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization (3).

Bump Bonding Using Metal-Coated Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Lamb, James L.; Dickie, Matthew R.; Kowalczyk, Robert S.; Liao, Anna; Bronikowski, Michael J.

2012-01-01

Bump bonding hybridization techniques use arrays of indium bumps to electrically and mechanically join two chips together. Surface-tension issues limit bump sizes to roughly as wide as they are high. Pitches are limited to 50 microns with bumps only 8-14 microns high on each wafer. A new process uses oriented carbon nanotubes (CNTs) with a metal (indium) in a wicking process using capillary actions to increase the aspect ratio and pitch density of the connections for bump bonding hybridizations. It merges the properties of the CNTs and the metal bumps, providing enhanced material performance parameters. By merging the bumps with narrow and long CNTs oriented in the vertical direction, higher aspect ratios can be obtained if the metal can be made to wick. Possible aspect ratios increase from 1:1 to 20:1 for most applications, and to 100:1 for some applications. Possible pitch density increases of a factor of 10 are possible. Standard capillary theory would not normally allow indium or most other metals to be drawn into the oriented CNTs, because they are non-wetting. However, capillary action can be induced through the ability to fabricate oriented CNT bundles to desired spacings, and the use of deposition techniques and temperature to control the size and mobility of the liquid metal streams and associated reservoirs. This hybridization of two technologies (indium bumps and CNTs) may also provide for some additional benefits such as improved thermal management and possible current density increases.

Unusual Contact-Line Dynamics of Thick Films and Drops

NASA Technical Reports Server (NTRS)

Veretennikov, Igor; Agarwal, Abhishek; Indeikina, Alexandra; Chang, Hsueh-Chia

1999-01-01

We report several novel phenomena In contact-line and fingering dynamics of macroscopic spinning drops and gravity-driven films with dimensions larger than the capillary length. It is shown through experimental and theoretical analysis that such macroscopic films can exhibit various interfacial shapes, including multi valued ones, near the contact line due to a balance between the external body forces with capillarity. This rich variety of front shapes couples with the usual capillary, viscous, and intermolecular forces at the contact line to produce a rich and unexpected spectrum of contact-line dynamics. A single finger develops when part of the front becomes multivalued on a partially wetting macroscopic spinning drop in contrast to a different mechanism for microscopic drops of completely wetting fluids. Contrary to general expectation, we observe that, at high viscosity and low frequencies of rotation, the speed of a glycerine finger increases with increasing viscosity. Completely wetting Dow Corning 200 Fluid spreads faster over a dry inclined plane than a prewetted one. The presence of a thin prewetted film suppresses fingering both for gravity-driven flow and for spin coating. We analyze some of these unique phenomena in detail and offer qualitative physical explanations for the others.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry

NASA Astrophysics Data System (ADS)

Ghomeishi, Mostafa; Mahdiraji, G. Amouzad; Adikan, F. R. Mahamd; Ung, N. M.; Bradley, D. A.

2015-08-01

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2nd order kinetics.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry.

PubMed

Ghomeishi, Mostafa; Mahdiraji, G Amouzad; Adikan, F R Mahamd; Ung, N M; Bradley, D A

2015-08-28

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2(nd) order kinetics.

Stabilization of a capillary bridge far beyond the Rayleigh--Plateau limit using active feedback and acoustic radiation pressure.

NASA Astrophysics Data System (ADS)

Marr-Lyon, Mark J.; Thiessen, David B.; Marston, Philip L.

1997-11-01

A liquid bridge between two solid surfaces is known as a capillary bridge. For a cylindrical bridge in low gravity of radius R and length L, the slenderness S=L/2R has a natural (Rayleigh--Plateau) limit of π beyond which the bridge breaks. Using the radiation pressure of an ultrasonic standing wave to control the shape of the bridge and an optical sensor to detect the shape of the bridge, an active feedback system was constructed that stabilized bridges significantly beyond the Rayleigh limit in simulated low gravity(Marr--Lyon, M. J., phet al., J. Fluid Mech.), accepted for publication.. The Plateau tank which contained the bridge was a dual frequency ultrasonic resonator and the spatial distribution of the radiation pressure was controlled by adjusting the ultrasonic frequency. Bridges have been extended with S as large as 4.3. To be useful in low gravity, modifications for liquid bridges in air are needed. Acoustic resonators in air having the required property that the sound amplitude can be spatially redistributed rapidly are being investigated using gas-filled soap-film bridges. Work supported by NASA.

Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry

PubMed Central

Ghomeishi, Mostafa; Mahdiraji, G. Amouzad; Adikan, F. R. Mahamd; Ung, N. M.; Bradley, D. A.

2015-01-01

With interest in the potential of optical fibres as the basis of next-generation thermoluminescence dosimeters (TLDs), the development of suitable forms of material and their fabrication has become a fast-growing endeavour. Present study focuses on three types of Ge-doped optical fibres with different structural arrangements and/or shapes, namely conventional cylindrical fibre, capillary fibre, and flat fibre, all fabricated using the same optical fibre preform. For doses from 0.5 to 8 Gy, obtained at electron and photon energies, standard thermoluminescence (TL) characteristics of the optical fibres have been the subject of detailed investigation. The results show that in collapsing the capillary fibre into a flat shape, the TL yield is increased by a factor of 5.5, the yield being also some 3.2 times greater than that of the conventional cylindrical fibre fabricated from the same perform. This suggests a means of production of suitably sensitive TLD for in-vivo dosimeter applications. Addressing the associated defects generating luminescence from each of the optical fibres, the study encompasses analysis of the TL glow curves, with computerized glow curve deconvolution (CGCD) and 2nd order kinetics. PMID:26314683

Fluid surface behavior in low gravity. Center discretionary fund no. 83-21

NASA Technical Reports Server (NTRS)

Leslie, F.; Gans, R. F.; Schafer, C.

1985-01-01

Measurements of rotating equilibrium bubble shapes in the low-gravity environment of a free-falling aircraft are presented. Emphasis is placed on bubbles which intersect the container boundaries. These data are compared with theoretical profiles derived from Laplace's formula and are in good agreement with the measurements. Two types of instability are explored. The first occurs when the baffle spacing is too large for the bubble to intersect both the top and bottom boundaries. The second occurs when the hydrostatic pressure beneath a displaced free surface does not compensate for pressure change due to capillary forces. The interface shape depends on the contact angle, the radius of intersection with container, and the parameter F which is a measure of the relative importance of centrifugal force to surface tension. For isolated bubbles, F has a maximum value of 1/2. A further increase in F causes the bubble to break contact with the axis of rotation. For large values of F, the bubble becomes more cylindrical and the capillary rise occurs over a thinner layer so that the small radius of curvature can generate enough pressure drop to balance the increased hydrostatic contribution.

Spectacularly robust! Tensegrity principle explains the mechanical strength of the avian lung.

PubMed

Maina, J N

2007-01-15

Among the air-breathing vertebrates, the respiratory system of birds, the lung-air sac system, is remarkably complex and singularly efficient. The most perplexing structural property of the avian lung pertains to its exceptional mechanical strength, especially that of the minuscule terminal respiratory units, the air- and the blood capillaries. In different species of birds, the air capillaries range in diameter from 3 to 20 micro m: the blood capillaries are in all cases relatively smaller. Over and above their capacity to withstand enormous surface tension forces at the air-tissue interface, the air capillaries resist mechanical compression (parabronchial distending pressure) as high as 20 cm H(2)O (2 kPa). The blood capillaries tolerate a pulmonary arterial vascular pressure of 24.1 mmHg (3.2 kPa) and vascular resistance of 22.5 mmHg (3 kPa) without distending. The design of the avian respiratory system fundamentally stems from the rigidity (strength) of the lung. The gas exchanger (the lung) is uncoupled from the ventilator (the air sacs), allowing the lung (the paleopulmonic parabronchi) to be ventilated continuously and unidirectionally by synchronized bellows like action of the air sacs. Since during the ventilation of the lung the air capillaries do not have to be distended (dilated), i.e., surface tension force does not have to be overcome (as would be the case if the lung was compliant), extremely intense subdivision of the exchange tissue was possible. Minuscule terminal respiratory units developed, producing a vast respiratory surface area in a limited lung volume. I make a case that a firm (rigid) rib cage, a lung tightly held by the ribs and the horizontal septum, a lung directly attached to the trunk, specially formed and compactly arranged parabronchi, intertwined atrial muscles, and tightly set air capillaries and blood capillaries form an integrated hierarchy of discrete network system of tension and compression, a tensegrity (tensional integrity) array, which absorbs, transmits, and dissipates stress, stabilizing (strengthening) the lung and its various structural components.

Evaluation of hollow fiberoptic tips for the conduction of Er:YAG laser.

PubMed

Alves, Paulo Roberto Vieira; Aranha, Norberto; Alfredo, Edson; Marchesan, Melissa Andréia; Brugnera Junior, Aldo; Sousa-Neto, Manoel D

2005-08-01

The use of Er:YAG laser operating in the 3 microm range with adjustable power and pulses has become popular for dental and medical practice due to its high photoablative capacity, surgical precision and antimicrobial action. The existing fiberoptic tips irradiate lasers parallel to the long axes of the tooth limiting its efficiency in the root canal. We evaluated hollow fiberoptic tips obtained from silicate glass as a means of Er:YAG laser conduction in dental procedures. The fiber tips were molded from capillary tubes with different profiles so that their ends would have cylindric, conical or spherical shapes. The performance of the three fibers as a means of propagation of Er:YAG (lambda = 2.94 microm) laser radiation was compared to that of a solid sapphire fiber at 10 Hz and 200 mJ and of 20 Hz and 500 mJ. The profiles of frontal and lateral burning were visualized on thermal paper. Analysis of these profiles demonstrated that the sapphire tip and the hollow fiber of cylindric section did not differ significantly in the profiles of frontal burning, and no lateral burning was detected. The fibers of the conical and spherical sections, although presenting attenuation in the frontal output power, showed a larger burning area in the frontal profile, in addition to producing lateral burning. The results indicate that commercial hollow fiberoptics have advantages such as easy manufacture of the different tip shapes, great adaptability, low cost, and a low loss of transmission.

An integrated passive micromixer-magnetic separation-capillary electrophoresis microdevice for rapid and multiplex pathogen detection at the single-cell level.

PubMed

Jung, Jae Hwan; Kim, Gha-Young; Seo, Tae Seok

2011-10-21

Here we report an integrated microdevice consisting of an efficient passive mixer, a magnetic separation chamber, and a capillary electrophoretic microchannel in which DNA barcode assay, target pathogen separation, and barcode DNA capillary electrophoretic analysis were performed sequentially within 30 min for multiplex pathogen detection at the single-cell level. The intestine-shaped serpentine 3D micromixer provides a high mixing rate to generate magnetic particle-pathogenic bacteria-DNA barcode labelled AuNP complexes quantitatively. After magnetic separation and purification of those complexes, the barcode DNA strands were released and analyzed by the microfluidic capillary electrophoresis within 5 min. The size of the barcode DNA strand was controlled depending on the target bacteria (Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella typhimurium), and the different elution time of the barcode DNA peak in the electropherogram allows us to recognize the target pathogen with ease in the monoplex as well as in the multiplex analysis. In addition, the quantity of the DNA barcode strand (∼10(4)) per AuNP is enough to be observed in the laser-induced confocal fluorescence detector, thereby making single-cell analysis possible. This novel integrated microdevice enables us to perform rapid, sensitive, and multiplex pathogen detection with sample-in-answer-out capability to be applied for biosafety testing, environmental screening, and clinical trials.

An apparatus with a horizontal capillary tube intended for measurement of the surface tension of supercooled liquids

NASA Astrophysics Data System (ADS)

Vinš, Václav; Hošek, Jan; Hykl, Jiří; Hrubý, Jan

2015-05-01

New experimental apparatus for measurement of the surface tension of liquids under the metastable supercooled state has been designed and assembled in the study. The measuring technique is similar to the method employed by P.T. Hacker [NACA TN 2510] in 1951. A short liquid thread of the liquid sample was sucked inside a horizontal capillary tube partly placed in a temperature-controlled glass chamber. One end of the capillary tube was connected to a setup with inert gas which allowed for precise tuning of the gas overpressure in order of hundreds of Pa. The open end of the capillary tube was precisely grinded and polished before the measurement in order to assure planarity and perpendicularity of the outer surface. The liquid meniscus at the open end was illuminated by a laser beam and observed by a digital camera. Application of an increasing overpressure of the inert gas at the inner meniscus of the liquid thread caused variation of the outer meniscus such that it gradually changed from concave to flat and subsequently convex shape. The surface tension at the temperature of the inner meniscus could be evaluated from the overpressure corresponding to exactly planar outer meniscus. Detailed description of the new setup together with results of the preliminary tests is provided in the study.

Rapidly moving contact lines and damping contributions

NASA Astrophysics Data System (ADS)

Xia, Yi; Daniel, Susan; Steen, Paul

2017-11-01

Contact angle varies dynamically with contact line (CL) speed when a liquid moves across a solid support, as when a liquid spreads rapidly. For sufficiently rapid spreading, inertia competes with capillarity to influence the interface shape near the support. We use resonant-mode plane-normal support oscillations of droplets to drive lateral contact-line motion. Reynolds numbers based on CL speeds are high and capillary numbers are low. These are inertial-capillary motions. By scanning the driving frequency, we locate the frequency at peak amplification (resonance), obtain the scaled peak height (amplification factor) and a measure of band-width (damping ratio). We report how a parameter for CL mobility depends on these scanning metrics, with the goal of distinguishing contributions from the bulk- and CL-dissipation to overall damping.

CFE-2 Experiment Run

NASA Image and Video Library

2013-11-21

View of Flight Engineer (FE) Koichi Wakata posing for a photo during a CFE-2 (Capillary Flow Experiment - 2) Interior Corner Flow - 8 (ICF-8) test run. Liquids behave differently in space than they do on Earth, so containers that can process, hold or transport them must be designed carefully to work in microgravity. The Capillary Flow Experiment-2 furthers research on wetting, which is a liquid's ability to spread across a surface, and its impact over large length scales in strange container shapes in microgravity environments. This work will improve capabilities to quickly and accurately predict how related processes occur, and allow us to design better systems to process liquids aboard spacecraft (i.e., liquid fuel tanks, thermals fluids, and water processing for life support). Image was released by astronaut on Twitter.

Forces and dynamics in epithelial domes of controlled size and shape

NASA Astrophysics Data System (ADS)

Latorre-Ibars, Ernest; Casares, Laura; Gomez-Gonzalez, Manuel; Uroz, Marina; Arroyo, Marino; Trepat, Xavier

Mechanobiology of epithelia plays a central role in morphogenesis, wound healing, and tumor progression. Its current understanding relies on mechanical measurements on flat epithelial layers. However, most epithelia in vivo exhibit a curved 3D shape enclosing a pressurized lumen. Using soft micropatterned substrates we produce massive parallel arrays of epithelial domes with controlled size and basal shape. We measure epithelial traction, tension, and luminal pressure in epithelial domes. The local stress tensor on the freestanding epithelial membrane is then mapped by combining measured luminal pressure and local curvature. We show that tension and cell shape are highly anisotropic and vary along the meridional position of the domes. Finally, we establish constitutive relations between shape, tension, and pressure during perturbations of the contractile machinery, osmotic shocks, and spontaneous fluctuations of dome volume. Our findings contradict a description of the epithelium as a fluid capillary surface. Cells in the dome are unable to relax into a uniform and isotropic tensional state through sub- and supra-cellular rearrangements. Mapping epithelial shape, tension, and pressure will enable quantitative studies of mechanobiology in 3D epithelia of controlled size and shape.

Soil water retention and maximum capillary drive from saturation to oven dryness

USGS Publications Warehouse

Morel-Seytoux, Hubert J.; Nimmo, John R.

1999-01-01

This paper provides an alternative method to describe the water retention curve over a range of water contents from saturation to oven dryness. It makes two modifications to the standard Brooks and Corey [1964] (B-C) description, one at each end of the suction range. One expression proposed by Rossi and Nimmo [1994] is used in the high-suction range to a zero residual water content. (This Rossi-Nimmo modification to the Brooks-Corey model provides a more realistic description of the retention curve at low water contents.) Near zero suction the second modification eliminates the region where there is a change in suction with no change in water content. Tests on seven soil data sets, using three distinct analytical expressions for the high-, medium-, and low-suction ranges, show that the experimental water retention curves are well fitted by this composite procedure. The high-suction range of saturation contributes little to the maximum capillary drive, defined with a good approximation for a soil water and air system as HcM = ∫0∞ Krwdhc , where krw is relative permeability (or conductivity) to water and hc is capillary suction, a positive quantity in unsaturated soils. As a result, the modification suggested to describe the high-suction range does not significantly affect the equivalence between Brooks-Corey (B-C) and van Genuchten [1980] parameters presented earlier. However, the shape of the retention curve near “natural saturation” has a significant impact on the value of the capillary drive. The estimate using the Brooks-Corey power law, extended to zero suction, will exceed that obtained with the new procedure by 25 to 30%. It is not possible to tell which procedure is appropriate. Tests on another data set, for which relative conductivity data are available, support the view of the authors that measurements of a retention curve coupled with a speculative curve of relative permeability as from a capillary model are not sufficient to accurately determine the (maximum) capillary drive. The capillary drive is a dynamic scalar, whereas the retention curve is of a static character. Only measurements of infiltration rates with time can determine the capillary drive with precision for a given soil.

A Capillary-Based Static Phase Separator for Highly Variable Wetting Conditions

NASA Technical Reports Server (NTRS)

Thomas, Evan A.; Graf, John C.; Weislogel, Mark M.

2010-01-01

The invention, a static phase separator (SPS), uses airflow and capillary wetting characteristics to passively separate a two-phase (liquid and air) flow. The device accommodates highly variable liquid wetting characteristics. The resultant design allows for a range of wetting properties from about 0 to over 90 advancing contact angle, with frequent complete separation of liquid from gas observed when using appropriately scaled test conditions. Additionally, the design accommodates a range of air-to-liquid flow-rate ratios from only liquid flow to over 200:1 air-to-liquid flow rate. The SPS uses a helix input section with an ice-cream-cone-shaped constant area cross section (see figure). The wedge portion of the cross section is on the outer edge of the helix, and collects the liquid via centripetal acceleration. The helix then passes into an increasing cross-sectional area vane region. The liquid in the helix wedge is directed into the top of capillary wedges in the liquid containment section. The transition from diffuser to containment section includes a 90 change in capillary pumping direction, while maintaining inertial direction. This serves to impinge the liquid into the two off-center symmetrical vanes by the airflow. Rather than the airflow serving to shear liquid away from the capillary vanes, the design allows for further penetration of the liquid into the vanes by the air shear. This is also assisted by locating the air exit ports downstream of the liquid drain port. Additionally, any droplets not contained in the capillary vanes are re-entrained downstream by a third opposing capillary vane, which directs liquid back toward the liquid drain port. Finally, the dual air exit ports serve to slow the airflow down, and to reduce the likelihood of shear. The ports are stove-piped into the cavity to form an unfriendly capillary surface for a wetting fluid to carryover. The liquid drain port is located at the start of the containment region, allowing for draining the bulk fluid in a continuous circuit. The functional operation of the SPS involves introducing liquid flow (from a human body, a syringe, or other source) to the two-phase inlet while an air fan pulls on the air exit lines. The fan is operated until the liquid is fully introduced. The system is drained by negative pressure on the liquid drain lines when the SPS containment system is full.

Physics on Tap

ERIC Educational Resources Information Center

Wheeler, Andrew P. S.

2012-01-01

This article aims to describe how to visualize surface tension effects in liquid jets. A simple experiment is proposed using the liquid jet flow from a mains water tap/faucet. Using a modern digital camera with a high shutter speed, it is possible to visualize the instabilities (capillary waves) that form within the jet due to the action of…

Numerical analysis of flows of rarefied gases in long channels with octagonal cross section shapes

NASA Astrophysics Data System (ADS)

Szalmas, L.

2014-12-01

Isothermal, pressure driven rarefied gas flows through long channels with octagonal cross section shapes are analyzed computationally. The capillary is between inlet and outlet reservoirs. The cross section is constant along the axial direction. The boundary condition at the solid-gas interface is assumed to be diffuse reflection. Since the channel is long, the gaseous velocity is small compared to the average molecular speed. Consequently, a linearized description can be used. The flow is described by the linearized Bhatnagar-Gross-Krook kinetic model. The solution of the problem is divided into two stages. First, the local flow field is determined by assuming the local pressure gradient. Secondly, the global flow behavior is deduced by the consideration of the conservation of the mass along the axis of the capillary. The kinetic equation is solved by the discrete velocity method on the cross section. Both spatial and velocity spaces are discretized. A body fitted rectangular grid is used for the spatial space. Near the boundary, first-order, while in the interior part of the flow domain, second-order finite-differences are applied to approximate the spatial derivatives. This combination results into an efficient and straightforward numerical treatment. The velocity space is represented by a Gauss-Legendre quadrature. The kinetic equation is solved in an iterative manner. The local dimensionless flow rate is calculated and tabulated for a wide range of the gaseous rarefaction for octagonal cross sections with various geometrical parameters. It exhibits the Knudsen minimum phenomenon. The flow rates in the octagonal channel are compared to those through capillaries with circular and square cross sections. Typical velocity profiles are also shown. The mass flow rate and the distribution of the pressure are determined and presented for global pressure driven flows.

Thermal and capillary effects on the caprock mechanical stability at In Salah, Algeria

DOE PAGES

Vilarrasa, Víctor; Rutqvist, Jonny; Rinaldi, Antonio Pio

2015-04-20

Thermo-mechanical effects are important in geologic carbon storage because CO 2 will generally reach the storage formation colder than the rock, inducing thermal stresses. Capillary functions, i.e., retention and relative permeability curves, control the CO 2 plume shape, which may affect overpressure and thus, caprock stability. To analyze these thermal and capillary effects, we numerically solve non-isothermal injection of CO 2 in deformable porous media considering the In Salah, Algeria, CO 2 storage site. Here, we find that changes in the capillary functions have a negligible effect on overpressure and thus, caprock stability is not affected by capillary effects. But,more » we show that for the strike slip stress regime prevalent at In Salah, stability decreases in the lowest parts of the caprock during injection due to cooling-induced thermal stresses. Simulations show that shear slip along pre-existing fractures may take place in the cooled region, whereas tensile failure is less likely to occur. Indeed, only the injection zone and the lowest tens of meters of the 900-m-thick caprock at In Salah might be affected by cooling effects, which would thus not jeopardize the overall sealing capacity of the caprock. Furthermore, faults are likely to remain stable far away from the injection well because outside the cooled region the injection-induced stress changes are not sufficient to exceed the anticipated shear strength of minor faults. Nonetheless, we recommend that thermal effects should be considered in the site characterization and injection design of future CO 2 injection sites to assess caprock stability and guarantee a permanent CO 2 storage.« less

Stabilizing detached Bridgman melt crystal growth: Model-based nonlinear feedback control

NASA Astrophysics Data System (ADS)

Yeckel, Andrew; Daoutidis, Prodromos; Derby, Jeffrey J.

2012-12-01

The dynamics and operability limits of a nonlinear-proportional-integral controller designed to stabilize detached vertical Bridgman crystal growth are studied. The manipulated variable is the pressure difference between upper and lower vapor spaces, and the controlled variable is the gap width at the triple-phase line. The controller consists of a model-based nonlinear component coupled with a standard proportional-integral controller. The nonlinear component is based on a capillary model of shape stability. Perturbations to gap width, pressure difference, wetting angle, and growth angle are studied under both shape stable and shape unstable conditions. The nonlinear-PI controller allows a wider operating range of gain than a standard PI controller used alone, is easier to tune, and eliminates solution multiplicity from closed-loop operation.

Liquid behavior of cross-linked actin bundles.

PubMed

Weirich, Kimberly L; Banerjee, Shiladitya; Dasbiswas, Kinjal; Witten, Thomas A; Vaikuntanathan, Suriyanarayanan; Gardel, Margaret L

2017-02-28

The actin cytoskeleton is a critical regulator of cytoplasmic architecture and mechanics, essential in a myriad of physiological processes. Here we demonstrate a liquid phase of actin filaments in the presence of the physiological cross-linker, filamin. Filamin condenses short actin filaments into spindle-shaped droplets, or tactoids, with shape dynamics consistent with a continuum model of anisotropic liquids. We find that cross-linker density controls the droplet shape and deformation timescales, consistent with a variable interfacial tension and viscosity. Near the liquid-solid transition, cross-linked actin bundles show behaviors reminiscent of fluid threads, including capillary instabilities and contraction. These data reveal a liquid droplet phase of actin, demixed from the surrounding solution and dominated by interfacial tension. These results suggest a mechanism to control organization, morphology, and dynamics of the actin cytoskeleton.

Method of filling a microchannel separation column

DOEpatents

Arnold, Don W.

2002-01-01

A method for packing a stationary phase into a small diameter fluid passageway or flow channel. Capillary action is employed to distribute a stationary phase uniformly along both the length and diameter of the flow channel. The method disclosed here: 1) eliminates the need for high pressure pumps and fittings and the safety hazards associated therewith; 2) allows the use of readily available commercial microparticles, either coated or uncoated, as the stationary phase; 3) provides for different types of particles, different particle sizes, and different particle size distributions to be packed in sequence, or simultaneously; 4) eliminates the need for plugging the flow channel prior to adding the stationary phase to retain the packing particles; and 5) many capillaries can be filled simultaneously.

Modeling of Transient Nectar Flow in Hummingbird Tongues

NASA Astrophysics Data System (ADS)

Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret

2015-11-01

We demonstrate that hummingbirds do not pick up floral nectar via capillary action. The long believed capillary rise models were mistaken and unable to predict the dynamic nectar intake process. Instead, hummingbird's tongue acts as an elastic micropump. Nectar is drawn into the tongue grooves during elastic expansion after the grooves are squeezed flat by the beak. The new model is compared with experimental data from high-speed videos of 18 species and tens of individuals of wild hummingbirds. Self-similarity and transitions of short-to-long time behaviours have been resolved for the nectar flow driven by expansive filling. The transient dynamics is characterized by the relative contributions of negative excess pressure and the apparent area modulus of the tongue grooves.

Carbon monoxide transport and actions in blood and tissues.

PubMed

Thom, Stephen R

2011-01-01

This chapter will discuss the transport of carbon monoxide (CO) from the environment to the tissues of the body and physiological effects on blood-borne cells and perivascular tissues. It will review the physiology of CO exchange between alveolar gas and pulmonary capillary blood, dynamics of hemoglobin transport, the effects of CO on blood elements, and the effects of CO on extravascular tissues at the capillary bed. Effects of CO from exogenous and endogenous sources on the activities of different proteins will be reviewed. Because CO binds competitively to heme-containing proteins its effects depend on CO concentration relative to alternative ligands. Therefore, some discussion is devoted to how nitric oxide and hydrogen sulfide influence CO effects. © 2011 American Physiological Society.

Proceedings of the Second International Colloquium on Drops and Bubbles

NASA Technical Reports Server (NTRS)

Lecroissette, D. H. (Editor)

1982-01-01

Applications of bubble and drop technologies are discussed and include: low gravity manufacturing, containerless melts, microballoon fabrication, ink printers, laser fusion targets, generation of organic glass and metal shells, and space processing. The fluid dynamics of bubbles and drops were examined. Thermomigration, capillary flow, and interfacial tension are discussed. Techniques for drop control are presented and include drop size control and drop shape control.

Universality in the nonlinear leveling of capillary films

NASA Astrophysics Data System (ADS)

Zheng, Zhong; Fontelos, Marco A.; Shin, Sangwoo; Stone, Howard A.

2018-03-01

Many material science, coating, and manufacturing problems involve liquid films where defects that span the film thickness must be removed. Here, we study the surface-tension-driven leveling dynamics of a thin viscous film following closure of an initial hole. The dynamics of the film shape is described by a nonlinear evolution equation, for which we obtain a self-similar solution. The analytical results are verified using time-dependent numerical and experimental results for the profile shapes and the minimum film thickness at the center. The universal behavior we identify can be useful for characterizing the time evolution of the leveling process and estimating material properties from experiments.

Pleural pressure theory revisited: a role for capillary equilibrium.

PubMed

Casha, Aaron R; Caruana-Gauci, Roberto; Manche, Alexander; Gauci, Marilyn; Chetcuti, Stanley; Bertolaccini, Luca; Scarci, Marco

2017-04-01

Theories elucidating pleural pressures should explain all observations including the equal and opposite recoil of the chest wall and lungs, the less than expected pleural hydrostatic gradient and its variation at lobar margins, why pleural pressures are negative and how pleural fluid circulation functions. A theoretical model describing equilibrium between buoyancy, hydrostatic forces, and capillary forces is proposed. The capillary equilibrium model described depends on control of pleural fluid volume and protein content, powered by an active pleural pump. The interaction between buoyancy forces, hydrostatic pressure and capillary pressure was calculated, and values for pleural thickness and pressure were determined using values for surface tension, contact angle, pleural fluid and lung densities found in the literature. Modelling can explain the issue of the differing hydrostatic vertical pleural pressure gradient at the lobar margins for buoyancy forces between the pleural fluid and the lung floating in the pleural fluid according to Archimedes' hydrostatic paradox. The capillary equilibrium model satisfies all salient requirements for a pleural pressure model, with negative pressures maximal at the apex, equal and opposite forces in the lung and chest wall, and circulatory pump action. This model predicts that pleural effusions cannot occur in emphysema unless concomitant heart failure increases lung density. This model also explains how the non-confluence of the lung with the chest wall (e.g., lobar margins) makes the pleural pressure more negative, and why pleural pressures would be higher after an upper lobectomy compared to a lower lobectomy. Pathological changes in pleural fluid composition and lung density alter the equilibrium between capillarity and buoyancy hydrostatic pressure to promote pleural effusion formation.

FMRI evidence of 'mirror' responses to geometric shapes.

PubMed

Press, Clare; Catmur, Caroline; Cook, Richard; Widmann, Hannah; Heyes, Cecilia; Bird, Geoffrey

2012-01-01

Mirror neurons may be a genetic adaptation for social interaction. Alternatively, the associative hypothesis proposes that the development of mirror neurons is driven by sensorimotor learning, and that, given suitable experience, mirror neurons will respond to any stimulus. This hypothesis was tested using fMRI adaptation to index populations of cells with mirror properties. After sensorimotor training, where geometric shapes were paired with hand actions, BOLD response was measured while human participants experienced runs of events in which shape observation alternated with action execution or observation. Adaptation from shapes to action execution, and critically, observation, occurred in ventral premotor cortex (PMv) and inferior parietal lobule (IPL). Adaptation from shapes to execution indicates that neuronal populations responding to the shapes had motor properties, while adaptation to observation demonstrates that these populations had mirror properties. These results indicate that sensorimotor training induced populations of cells with mirror properties in PMv and IPL to respond to the observation of arbitrary shapes. They suggest that the mirror system has not been shaped by evolution to respond in a mirror fashion to biological actions; instead, its development is mediated by stimulus-general processes of learning within a system adapted for visuomotor control.

fMRI Evidence of ‘Mirror’ Responses to Geometric Shapes

PubMed Central

Press, Clare; Catmur, Caroline; Cook, Richard; Widmann, Hannah; Heyes, Cecilia; Bird, Geoffrey

2012-01-01

Mirror neurons may be a genetic adaptation for social interaction [1]. Alternatively, the associative hypothesis [2], [3] proposes that the development of mirror neurons is driven by sensorimotor learning, and that, given suitable experience, mirror neurons will respond to any stimulus. This hypothesis was tested using fMRI adaptation to index populations of cells with mirror properties. After sensorimotor training, where geometric shapes were paired with hand actions, BOLD response was measured while human participants experienced runs of events in which shape observation alternated with action execution or observation. Adaptation from shapes to action execution, and critically, observation, occurred in ventral premotor cortex (PMv) and inferior parietal lobule (IPL). Adaptation from shapes to execution indicates that neuronal populations responding to the shapes had motor properties, while adaptation to observation demonstrates that these populations had mirror properties. These results indicate that sensorimotor training induced populations of cells with mirror properties in PMv and IPL to respond to the observation of arbitrary shapes. They suggest that the mirror system has not been shaped by evolution to respond in a mirror fashion to biological actions; instead, its development is mediated by stimulus-general processes of learning within a system adapted for visuomotor control. PMID:23251653

Evidence for the role of self-priming in epistemic action: expertise and the effective use of memory.

PubMed

Maglio, Paul P; Wenger, Michael J; Copeland, Angelina M

2008-01-01

Epistemic actions are physical actions people take to simplify internal problem solving rather than to move closer to an external goal. When playing the video game Tetris, for instance, experts routinely rotate falling shapes more than is strictly needed to place the shapes. Maglio and Kirsh [Kirsh, D., & Maglio, P. (1994). On distinguishing epistemic from pragmatic action. Cognitive Science, 18, 513-549; Maglio, P. P. (1995). The computational basis of interactive skill. PhD thesis, University of California, San Diego] proposed that such actions might serve the purpose of priming memory by external means, reducing the need for internal computation (e.g., mental rotation), and resulting in performance improvements that exceed the cost of taking additional actions. The present study tests this priming hypothesis in a set of four experiments. The first three explored precisely the conditions under which priming produces benefits. Results showed that presentation of multiple orientations of a shape led to faster responses than did presentation of a single orientation, and that this effect depended on the interval between preview and test. The fourth explored whether the benefit of seeing shapes in multiple orientations outweighs the cost of taking the extra actions to rotate shapes physically. Benefits were measured using a novel statistical method for mapping reaction-time data onto an estimate of the increase in processing capacity afforded by seeing multiple orientations. Cost was measured using an empirical estimate of time needed to take action in Tetris. Results showed that indeed the increase in internal processing capacity obtained from seeing shapes in multiple orientations outweighed the time to take extra actions.

Random-access optical-resolution photoacoustic microscopy using a digital micromirror device

PubMed Central

Liang, Jinyang; Zhou, Yong; Winkler, Amy W.; Wang, Lidai; Maslov, Konstantin I.; Li, Chiye; Wang, Lihong V.

2013-01-01

We developed random-access optical-resolution photoacoustic microscopy using a digital micromirror device. This system can rapidly scan arbitrarily shaped regions of interest within a 40×40 μm2 imaging area with a lateral resolution of 3.6 μm. To identify a region of interest, a global structural image is first acquired, then the selected region is scanned. The random-access ability was demonstrated by imaging two static samples, a carbon fiber cross and a monolayer of red blood cells, with an acquisition rate up to 4 kilohertz. The system was then used to monitor blood flow in vivo in real time within user-selected capillaries in a mouse ear. By imaging only the capillary of interest, the frame rate was increased by up to 9.2 times. PMID:23903111

Random-access optical-resolution photoacoustic microscopy using a digital micromirror device.

PubMed

Liang, Jinyang; Zhou, Yong; Winkler, Amy W; Wang, Lidai; Maslov, Konstantin I; Li, Chiye; Wang, Lihong V

2013-08-01

We developed random-access optical-resolution photoacoustic microscopy using a digital micromirror device. This system can rapidly scan arbitrarily shaped regions of interest within a 40 μm×40 μm imaging area with a lateral resolution of 3.6 μm. To identify a region of interest, a global structural image is first acquired, then the selected region is scanned. The random-access ability was demonstrated by imaging two static samples, a carbon fiber cross and a monolayer of red blood cells, with an acquisition rate up to 4 kHz. The system was then used to monitor blood flow in vivo in real time within user-selected capillaries in a mouse ear. By imaging only the capillary of interest, the frame rate was increased by up to 9.2 times.

Numerical-experimental observation of shape bistability of red blood cells flowing in a microchannel

NASA Astrophysics Data System (ADS)

Guckenberger, Achim; Kihm, Alexander; John, Thomas; Wagner, Christian; Gekle, Stephan

Red blood cells flowing through capillaries assume a wide variety of different shapes owing to their high deformability. Predicting the realized shapes is a complex field as they are determined by the intricate interplay between the flow conditions and the membrane mechanics. In this work we construct the shape phase diagram of a single red blood cell with a physiological viscosity ratio flowing in a microchannel. We use both experimental in-vitro measurements as well as 3D numerical simulations to complement the respective other one. Numerically, we have easy control over the initial starting configuration and natural access to the full 3D shape. With this information we obtain the phase diagram as a function of initial position, starting shape and cell velocity. Experimentally, we measure the occurrence frequency of the different shapes as a function of the cell velocity to construct the experimental diagram which is in good agreement with the numerical observations. Two different major shapes are found, namely croissants and slippers. Notably, both shapes show coexistence at low (<1 mm/s) and high velocities (>3 mm/s) while in-between only croissants are stable. This pronounced bistability indicates that RBC shapes are not only determined by system parameters such as flow velocity or channel size, but also strongly depend on the initial conditions.

Bulk- and surface-modified combinable PDMS capillary sensor array as an easy-to-use sensing device with enhanced sensitivity to elevated concentrations of multiple serum sample components.

PubMed

Fujii, Yuji; Henares, Terence G; Kawamura, Kunio; Endo, Tatsuro; Hisamoto, Hideaki

2012-04-21

To enhance sensitivity and facilitate easy sample introduction into a combinable poly(dimethylsiloxane) (PDMS) capillary (CPC) sensor array, PDMS was modified in bulk and on its surface to prepare "black" PDMS coated with a silver layer and self-assembled monolayer (SAM). India ink, a traditional Japanese black ink, was added to the PDMS pre-polymer for bulk modification. The surface was modified by a silver mirror reaction followed by SAM formation using cysteine. These modifications enhanced the fluorescence signals by reflecting them from the surface and reducing background interference. A decrease in the water contact angle led to enhanced sensitivity and easy sample introduction. Furthermore, a CPC sensor array for multiplex detection of serum sample components was prepared that could quantify the analytes glucose, potassium, and alkaline phosphatase (ALP). When serum samples were introduced by capillary action, the CPC sensor array showed fluorescence responses for each analyte and successfully identified the components with elevated concentrations in the serum samples.

Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs

PubMed Central

Furrow, E.; Lees, G. E.; Brown, C. A.; Cianciolo, R. E.

2017-01-01

Miniature Schnauzer dogs are predisposed to idiopathic hypertriglyerceridemia, which increases risk for diseases such as pancreatitis and gallbladder mucocele. Recently, elevated triglyceride concentrations have been associated with proteinuria in this breed, although it is difficult to determine which abnormality is primary. Retrospective review of renal tissue from 27 proteinuric Miniature Schnauzers revealed that 20 dogs had ultrastructural evidence of osmophilic globules consistent with lipid in glomerular tufts. Seven of these dogs had lipid thromboemboli in glomerular capillary loops that distorted their shape and compressed circulating erythrocytes. Triglyceride concentrations were reported in 6 of these 7 dogs, and all were hypertriglyceridemic. In addition, glomerular lipidosis (defined as accumulation of foam cells within peripheral capillary loops) was identified in a single dog. The remaining 12 dogs had smaller amounts of lipid that could only be identified ultrastructurally. Neither signalment data nor clinicopathologic parameters (serum albumin, serum creatinine, urine protein-to-creatinine ratio, and blood pressure) differed among the various types of lipid lesions. During the time course of this study, all dogs diagnosed with glomerular lipid thromboemboli were Miniature Schnauzers, underscoring the importance of recognizing these clear spaces within capillary loops as lipid. PMID:28005494

Actuation of flexoelectric membranes in viscoelastic fluids with applications to outer hair cells

PubMed Central

Herrera-Valencia, E. E.; Rey, Alejandro D.

2014-01-01

Liquid crystal flexoelectric actuation uses an imposed electric field to create membrane bending, and it is used by the outer hair cells (OHCs) located in the inner ear, whose role is to amplify sound through generation of mechanical power. Oscillations in the OHC membranes create periodic viscoelastic flows in the contacting fluid media. A key objective of this work on flexoelectric actuation relevant to OHCs is to find the relations and impact of the electromechanical properties of the membrane, the rheological properties of the viscoelastic media, and the frequency response of the generated mechanical power output. The model developed and used in this work is based on the integration of: (i) the flexoelectric membrane shape equation applied to a circular membrane attached to the inner surface of a circular capillary and (ii) the coupled capillary flow of contacting viscoelastic phases, such that the membrane flexoelectric oscillations drive periodic viscoelastic capillary flows, as in OHCs. By applying the Fourier transform formalism to the governing equation, analytical expressions for the transfer function associated with the curvature and electrical field and for the power dissipation of elastic storage energy were found. PMID:25332388

Maximal liquid bridges between horizontal cylinders

NASA Astrophysics Data System (ADS)

Cooray, Himantha; Huppert, Herbert E.; Neufeld, Jerome A.

2016-08-01

We investigate two-dimensional liquid bridges trapped between pairs of identical horizontal cylinders. The cylinders support forces owing to surface tension and hydrostatic pressure that balance the weight of the liquid. The shape of the liquid bridge is determined by analytically solving the nonlinear Laplace-Young equation. Parameters that maximize the trapping capacity (defined as the cross-sectional area of the liquid bridge) are then determined. The results show that these parameters can be approximated with simple relationships when the radius of the cylinders is small compared with the capillary length. For such small cylinders, liquid bridges with the largest cross-sectional area occur when the centre-to-centre distance between the cylinders is approximately twice the capillary length. The maximum trapping capacity for a pair of cylinders at a given separation is linearly related to the separation when it is small compared with the capillary length. The meniscus slope angle of the largest liquid bridge produced in this regime is also a linear function of the separation. We additionally derive approximate solutions for the profile of a liquid bridge, using the linearized Laplace-Young equation. These solutions analytically verify the above-mentioned relationships obtained for the maximization of the trapping capacity.

Direct Laser Writing of Single-Material Sheets with Programmable Self-Rolling Capability

NASA Astrophysics Data System (ADS)

Bauhofer, Anton; KröDel, Sebastian; Bilal, Osama; Daraio, Chiara; Constantinescu, Andrei

Direct laser writing, a sub-class of two-photon polymerization, facilitates 3D-printing of single-material microstructures with inherent residual stresses. Here we show that controlled distribution of these stresses allows for fast and cost-effective fabrication of structures with programmable self-rolling capability. We investigate 2D sheets that evolve into versatile 3D structures. Precise control over the shape morphing potential is acquired through variations in geometry and writing parameters. Effects of capillary action and gravity were shown to be relevant for very thin sheets (thickness <1.5um) and have been analytically and experimentally quantified. In contrast to that, the deformations of sheets with larger thickness (>1.5um) are dominated by residual stresses and adhesion forces. The presented structures create local tensions up to 180MPa, causing rolling curvatures of 25E3m-1. A comprehensive analytical model that captures the relevant influence factors was developed based on laminate plate theory. The predicted curvature and directionality correspond well with the experimentally obtained data. Potential applications are found in drug encapsulation and particle traps for emulsions with differing surface energies. This work was supported by the Swiss National Science Foundation.

A facile and efficient approach for pore-opening detection of anodic aluminum oxide membranes

NASA Astrophysics Data System (ADS)

Cui, Jiewu; Wu, Yucheng; Wang, Yan; Zheng, Hongmei; Xu, Guangqing; Zhang, Xinyi

2012-05-01

The well aligned porous anodic aluminum oxide (AAO) membrane is fabricated by a two-step anodization method. The oxide barrier layer of AAO membrane must be removed to get through-hole membrane for synthesizing nanowires and nanotubes of metals, semiconductors and conducting polymers. Removal of the barrier layer of oxide and pore-extending is of significant importance for the preparation of AAO membrane with through-hole pore morphology and desired pore diameter. The conventional method for pore opening is that AAO membrane after removing of aluminum substrate is immersed in chemical etching solution, which is completely empirical and results in catastrophic damage for AAO membrane frequently. A very simple and efficient approach based on capillary action for detecting pore opening of AAO membrane is introduced in this paper, this method can achieve the detection for pore opening visually and control the pore diameter precisely to get desired morphology and the pore diameter of AAO membrane. Two kinds of AAO membranes with different pore shape were obtained by different pore opening methods. In addition, one-dimensional gradient gold nanowires are also fabricated by electrodeposition based on AAO membranes.

Paper pump for passive and programmable transport

PubMed Central

Wang, Xiao; Hagen, Joshua A.; Papautsky, Ian

2013-01-01

In microfluidic systems, a pump for fluid-driving is often necessary. To keep the size of microfluidic systems small, a pump that is small in size, light-weight and needs no external power source is advantageous. In this work, we present a passive, simple, ultra-low-cost, and easily controlled pumping method based on capillary action of paper that pumps fluid through conventional polymer-based microfluidic channels with steady flow rate. By using inexpensive cutting tools, paper can be shaped and placed at the outlet port of a conventional microfluidic channel, providing a wide range of pumping rates. A theoretical model was developed to describe the pumping mechanism and aid in the design of paper pumps. As we show, paper pumps can provide steady flow rates from 0.3 μl/s to 1.7 μl/s and can be cascaded to achieve programmable flow-rate tuning during the pumping process. We also successfully demonstrate transport of the most common biofluids (urine, serum, and blood). With these capabilities, the paper pump has the potential to become a powerful fluid-driving approach that will benefit the fielding of microfluidic systems for point-of-care applications. PMID:24403999

Jet dynamics post drop impact on a deep pool

NASA Astrophysics Data System (ADS)

Michon, Guy-Jean; Josserand, Christophe; Séon, Thomas

2017-02-01

We investigate experimentally the jet formed by the collapse of a cavity created by the impact of a drop on a pool of the same aqueous liquid. We show that jets can emerge with very different shapes and velocities, depending on the impact parameters, thus generating droplets with various initial sizes and velocities. After presenting the jet velocity and top drop radius variation as a function of the impact parameters, we discuss the influence of the liquid parameters on the jet velocity. This allows us to define two different regimes: the singular jet and the cavity jet regimes, where the mechanisms leading to the cavity retraction and subsequent jet dynamics are drastically different. In particular, we demonstrate that in the first regime, a singular capillary wave collapse sparks the whole jet dynamics, making the jet's fast, thin, liquid parameters dependent and barely reproducible. On the contrary, in the cavity jet regime, defined for higher impact Froude numbers, the jets are fat and slow. We show that jet velocity is simply proportional to the capillary velocity √{γ /ρlDd }, where γ is the liquid surface tension, ρl the liquid density, and Dd the impacting drop diameter, and it is in particular independent of viscosity, impact velocity, and gravity, even though the cavity is larger than the capillary length. Finally, we demonstrate that capillary wave collapse and cavity retraction are correlated in the singular regime and decorrelated in the cavity jet regime.

Three-dimensional spatial localization of thin fluorophore-filled capillaries in thick scattering media

NASA Astrophysics Data System (ADS)

Desrochers, Johanne; Vermette, Patrick; Fontaine, Réjean; Bérubé-Lauzière, Yves

2008-06-01

Fluorescence optical diffuse tomography (fDOT) is of much interest in molecular imaging to retrieve information from fluorescence signals emitted from specifically targeted bioprocesses deep within living tissues. An exciting application of fDOT is in the growing field of tissue engineering, where 3D non-invasive imaging techniques are required to ultimately grow 3D engineered tissues. Via appropriate labelling strategies and fluorescent probes, fDOT has the potential to monitor culture environment and cells viability non-destructively directly within the bioreactor environment where tissues are to be grown. Our ultimate objective is to image the formation of blood vessels in bioreactor conditions. Herein, we use a non-contact setup for small animal fDOT imaging designed for 3D light collection around the sample. We previously presented a time of flight approach using a numerical constant fraction discrimination technique to assign an early photons arrival time to every fluorescence time point-spread function collected around the sample. Towards bioreactor in-situ imaging, we have shown the capability of our approach to localize a fluorophore-filled 500 μm capillary immersed coaxially in a cylindrically shaped bioreactor phantom containing an absorbing/scattering medium representative of experiments on real tissue cultures. Here, we go one step further, and present results for the 3D localization of thinner indocyanine green labelled capillaries (250 μm and 360 μm inner diameter) immersed in the same phantom conditions and geometry but with different spatial configurations (10° and 30° capillary inclination).

Capillary flow-driven microfluidic device with wettability gradient and sedimentation effects for blood plasma separation.

PubMed

Maria, M Sneha; Rakesh, P E; Chandra, T S; Sen, A K

2017-03-03

We report a capillary flow-driven microfluidic device for blood-plasma separation that comprises a cylindrical well between a pair of bottom and top channels. Exposure of the well to oxygen-plasma creates wettability gradient on its inner surface with its ends hydrophilic and middle portion hydrophobic. Due to capillary action, sample blood self-infuses into bottom channel and rises up the well. Separation of plasma occurs at the hydrophobic patch due to formation of a 'self-built-in filter' and sedimentation. Capillary velocity is predicted using a model and validated using experimental data. Sedimentation of RBCs is explained using modified Steinour's model and correlation between settling velocity and liquid concentration is found. Variation of contact angle on inner surface of the well is characterized and effects of well diameter and height and dilution ratio on plasma separation rate are investigated. With a well of 1.0 mm diameter and 4.0 mm height, 2.0 μl of plasma was obtained (from <10 μl whole blood) in 15 min with a purification efficiency of 99.9%. Detection of glucose was demonstrated with the plasma obtained. Wetting property of channels was maintained by storing in DI water under vacuum and performance of the device was found to be unaffected over three weeks.

Capillary flow-driven microfluidic device with wettability gradient and sedimentation effects for blood plasma separation

PubMed Central

Maria, M. Sneha; Rakesh, P. E.; Chandra, T. S.; Sen, A. K.

2017-01-01

We report a capillary flow-driven microfluidic device for blood-plasma separation that comprises a cylindrical well between a pair of bottom and top channels. Exposure of the well to oxygen-plasma creates wettability gradient on its inner surface with its ends hydrophilic and middle portion hydrophobic. Due to capillary action, sample blood self-infuses into bottom channel and rises up the well. Separation of plasma occurs at the hydrophobic patch due to formation of a ‘self-built-in filter’ and sedimentation. Capillary velocity is predicted using a model and validated using experimental data. Sedimentation of RBCs is explained using modified Steinour’s model and correlation between settling velocity and liquid concentration is found. Variation of contact angle on inner surface of the well is characterized and effects of well diameter and height and dilution ratio on plasma separation rate are investigated. With a well of 1.0 mm diameter and 4.0 mm height, 2.0 μl of plasma was obtained (from <10 μl whole blood) in 15 min with a purification efficiency of 99.9%. Detection of glucose was demonstrated with the plasma obtained. Wetting property of channels was maintained by storing in DI water under vacuum and performance of the device was found to be unaffected over three weeks. PMID:28256564

A variational approach to the study of capillary phenomena

NASA Technical Reports Server (NTRS)

Emmer, M.; Gonzalez, E.; Tamanini, I.

1982-01-01

The problem of determining the free surface of a liquid in a capillary tube, and of a liquid drop, sitting first on a horizontal plane and then on more general surfaces is considered. With some modifications, the method applies to the study of pendent drops and of rotating drops as well. The standard capillary problem, i.e. the determination of the free surface of a liquid in a thin tube of general cross section, which resuls from the simultaneous action of surface tension, boundary adhesion and gravity is discussed. It turns out that in this case the existence of the solution surface depends heavily on the validity of a simple geometric condition about the mean curvature of the boundary curve of the cross section of the capillary tube. Some particular examples of physical interest are also be discussed. Liquid drops sitting on or hanging from a fixed horizontal plane are discussed. The symmetry of the solutions (which can actually be proved, as consequence of a general symmetrization argument) now plays the chief role in deriving both the existence and the regularity of energy-minimizing configurations. When symmetry fails (this is the case, for example, when the contact angle between the drop and the plate is not constant, or when the supporting surface is not itself symmetric), then more sophisticated methods must be used. Extensions in this direction are outlined.

Polymer microfluidic device replacing fluids using only capillary force

NASA Astrophysics Data System (ADS)

Chung, Kwang Hyo; Lee, Dae Sik; Yang, Haesik; Kim, Sung Jin; Pyo, Hyun Bong

2005-02-01

A novel polymer microfluidic device for self-wash using only capillary force is presented. A liquid filled in a reaction chamber is replaced by another liquid with no external actuation. All the fluidic actuations in the device is pre-programmed about time and sequence, and accomplished by capillary force naturally. Careful design is necessary for exact actions. The fluidic conduits were designed by the newly derived theoretical equations about the capillary stop pressure and flow time. Simulations using CFD-ACE+ were conducted to check the validity of theory and the performance of the chip. These analytic results were consistent with experimental ones. The chip was made of polymers for the purpose of single use and low price. It was fabricated by sealing the hot-embossed PMMA substrate with a PET film. For simpler fabrication, the chip was of a single height. The embossing master was produced from a nickel-electroplating on a SU8-patterned Ni-plate followed by CMP. The contact angles of liquids on substrates were manipulated through the mixing of surfactants, and the temporal variations were monitored for a more exact design. The real actuation steps in experiment revealed the stable performance of selfwash, and coincided well with the designed ones. The presented microfluidic method can be applicable to other LOCs of special purposes through simple modification. For example, array or serial types would be possible for multiple selfwashes.

Sound Waves Levitate Substrates

NASA Technical Reports Server (NTRS)

Lee, M. C.; Wang, T. G.

1982-01-01

System recently tested uses acoustic waves to levitate liquid drops, millimeter-sized glass microballoons, and other objects for coating by vapor deposition or capillary attraction. Cylindrical contactless coating/handling facility employs a cylindrical acoustic focusing radiator and a tapered reflector to generate a specially-shaped standing wave pattern. Article to be processed is captured by the acoustic force field under the reflector and moves as reflector is moved to different work stations.

Steady boiling of vapor bubbles in rectangular channels

NASA Astrophysics Data System (ADS)

Ajaev, Vladimir S.; Homsy, George M.

2000-11-01

We consider vapor bubbles in microchannels in which the vapor is produced by a heater element and condenses in cooler parts of the interface. The free boundary problem is formulated for a long steady-state bubble in a rectangular channel with a heated bottom. The shape of the liquid-vapor interface is described using lubrication-type equations in the regime in which the vapor phase fills most of the cross-section. Contact lines may be present, marking the transitions between molecularly thin films and macroscopic ones. The main parameters are the differences between heater, saturation, and top wall temperatures. The equations are solved numerically over a range of parameter values with an integral condition requiring the evaporation near the heater to balance condensation in colder areas of the interface. Depending on the temperature, the side walls can be either dry or covered with a liquid film; we identify criteria for these two different regimes. The asymptotic method breaks down in the limit when capillary condensation becomes important near the bubble top and a different approach is used to determine the shape of the bubble in this limit. Solutions here involve localized regions of large mass fluxes, which are asymptotically matched to capillary-statics regions where the heat transfer is negligible.

Reconfigurable Photonic Crystals Enabled by Multistimuli-Responsive Shape Memory Polymers Possessing Room Temperature Shape Processability.

PubMed

Fang, Yin; Leo, Sin-Yen; Ni, Yongliang; Wang, Junyu; Wang, Bingchen; Yu, Long; Dong, Zhe; Dai, Yuqiong; Basile, Vito; Taylor, Curtis; Jiang, Peng

2017-02-15

Traditional shape memory polymers (SMPs) are mostly thermoresponsive, and their applications in nano-optics are hindered by heat-demanding programming and recovery processes. By integrating a polyurethane-based shape memory copolymer with templating nanofabrication, reconfigurable/rewritable macroporous photonic crystals have been demonstrated. This SMP coupled with the unique macroporous structure enables unusual all-room-temperature shape memory cycles. "Cold" programming involving microscopic order-disorder transitions of the templated macropores is achieved by mechanically deforming the macroporous SMP membranes. The rapid recovery of the permanent, highly ordered photonic crystal structure from the temporary, disordered configuration can be triggered by multiple stimuli including a large variety of vapors and solvents, heat, and microwave radiation. Importantly, the striking chromogenic effects associated with these athermal and thermal processes render a sensitive and noninvasive optical methodology for quantitatively characterizing the intriguing nanoscopic shape memory effects. Some critical parameters/mechanisms that could significantly affect the final performance of SMP-based reconfigurable photonic crystals including strain recovery ratio, dynamics and reversibility of shape recovery, as well as capillary condensation of vapors in macropores, which play a crucial role in vapor-triggered recovery, can be evaluated using this new optical technology.

Parallel capillary-tube-based extension of thermoacoustic theory for random porous media.

PubMed

Roh, Heui-Seol; Raspet, Richard; Bass, Henry E

2007-03-01

Thermoacoustic theory is extended to stacks made of random bulk media. Characteristics of the porous stack such as the tortuosity and dynamic shape factors are introduced into the thermoacoustic wave equation in the low reduced frequency approximation. Basic thermoacoustic equations for a bulk porous medium are formulated analogously to the equations for a single pore. Use of different dynamic shape factors for the viscous and thermal effects is adopted and scaling using the dynamic shape factors and tortuosity is demonstrated. Comparisons of the calculated and experimentally derived thermoacoustic properties of reticulated vitreous carbon and aluminum foam show good agreement. A consistent mathematical model of sound propagation in a random porous medium with an imposed temperature is developed. This treatment leads to an expression for the coefficient of the temperature gradient in terms of scaled cylindrical thermoviscous functions.

A pore-level scenario for the development of mixed-wettability in oil reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovscek, A.R.; Wong, H.; Radke, C.J.

Understanding the role of thin films in porous media is vital if wettability is to be elucidated at the pore level. The type and thickness of films coating pore walls determines reservoir wettability and whether or not reservoir rock can be altered from its initial state of wettability. Pore shape, especially pore wall curvature, is an important factor in determining wetting-film thicknesses. Yet, pore shape and the physics of thin wetting films are generally neglected in models of flow in porous rocks. This paper incorporates thin-film forces into a collection of star-shaped capillary tubes model to describe the geological developmentmore » of mixed-wettability in reservoir rock. Here, mixed-wettability refers to continuous and distinct oil and water-wetting surfaces coexisting in the porous medium. The proposed model emphasizes the remarkable role of thin films. New pore-level fluid configurations arise that are quite unexpected. For example, efficient water displacement of oil (i.e, low residual oil saturation) characteristic of mixed-wettability porous media is ascribed to interconnected oil lenses or rivulets which bridge the walls adjacent to a pore corner. Predicted residual oil saturations are approximately 35 % less in mixed-wet rock compared to completely water-wet rock. Calculated capillary pressure curves mimic those of mixed-wet porous media in the primary drainage of water, imbibition of water, and secondary drainage modes. Amott-Harvey indices range from {minus}0.18 to 0.36 also in good agreement with experimental values. (Morrow et al, 1986; Judhunandan and Morrow, 1991).« less

Porous micropillar structures for retaining low surface tension liquids.

PubMed

Agonafer, Damena D; Lee, Hyoungsoon; Vasquez, Pablo A; Won, Yoonjin; Jung, Ki Wook; Lingamneni, Srilakshmi; Ma, Binjian; Shan, Li; Shuai, Shuai; Du, Zichen; Maitra, Tanmoy; Palko, James W; Goodson, Kenneth E

2018-03-15

The ability to manipulate fluid interfaces, e.g., to retain liquid behind or within porous structures, can be beneficial in multiple applications, including microfluidics, biochemical analysis, and the thermal management of electronic systems. While there are a variety of strategies for controlling the disposition of liquid water via capillarity, such as the use of chemically modified porous adhesive structures and capillary stop valves or surface geometric features, methods that work well for low surface tension liquids are far more difficult to implement. This study demonstrates the microfabrication of a silicon membrane that can retain exceptionally low surface tension fluorinated liquids against a significant pressure difference across the membrane via an array of porous micropillar structures. The membrane uses capillary forces along the triple phase contact line to maintain stable liquid menisci that yield positive working Laplace pressures. The micropillars have inner diameters and thicknesses of 1.5-3 μm and ∼1 μm, respectively, sustaining Laplace pressures up to 39 kPa for water and 9 kPa for Fluorinert™ (FC-40). A theoretical model for predicting the change in pressure as the liquid advances along the porous micropillar structure is derived based on a free energy analysis of the liquid meniscus with capped spherical geometry. The theoretical prediction was found to overestimate the burst pressure compared with the experimental measurements. To elucidate this deviation, transient numerical simulations based on the Volume of Fluid (VOF) were performed to explore the liquid pressure and evolution of meniscus shape under different flow rates (i.e., Capillary numbers). The results from VOF simulations reveal strong dynamic effects where the anisotropic expansion of liquid along the outer micropillar edge leads to an irregular meniscus shape before the liquid spills along the micropillar edge. These findings suggest that the analytical prediction of burst Laplace pressure obtained under quasi-static condition (i.e., equilibrium thermodynamic analysis under low capillary number) is not applicable to highly dynamic flow conditions, where the liquid meniscus shape deformation by flow perturbation cannot be restored by surface tension force instantaneously. Therefore, the critical burst pressure is dependent on the liquid velocity and viscosity under dynamic flow conditions. A numerical simulation using Surface Evolver also predicts that surface defects along the outer micropillar edge can yield up to 50% lower Laplace pressures than those predicted with ideal feature geometries. The liquid retention strategy developed here can facilitate the routing and phase management of dielectric working fluids for application in heat exchangers. Further improvements in the retention performance can be realized by optimizing the fabrication process to reduce surface defects. Copyright © 2017 Elsevier Inc. All rights reserved.

Pleural pressure theory revisited: a role for capillary equilibrium

PubMed Central

Caruana-Gauci, Roberto; Manche, Alexander; Gauci, Marilyn; Chetcuti, Stanley; Bertolaccini, Luca

2017-01-01

Background Theories elucidating pleural pressures should explain all observations including the equal and opposite recoil of the chest wall and lungs, the less than expected pleural hydrostatic gradient and its variation at lobar margins, why pleural pressures are negative and how pleural fluid circulation functions. Methods A theoretical model describing equilibrium between buoyancy, hydrostatic forces, and capillary forces is proposed. The capillary equilibrium model described depends on control of pleural fluid volume and protein content, powered by an active pleural pump. Results The interaction between buoyancy forces, hydrostatic pressure and capillary pressure was calculated, and values for pleural thickness and pressure were determined using values for surface tension, contact angle, pleural fluid and lung densities found in the literature. Modelling can explain the issue of the differing hydrostatic vertical pleural pressure gradient at the lobar margins for buoyancy forces between the pleural fluid and the lung floating in the pleural fluid according to Archimedes’ hydrostatic paradox. The capillary equilibrium model satisfies all salient requirements for a pleural pressure model, with negative pressures maximal at the apex, equal and opposite forces in the lung and chest wall, and circulatory pump action. Conclusions This model predicts that pleural effusions cannot occur in emphysema unless concomitant heart failure increases lung density. This model also explains how the non-confluence of the lung with the chest wall (e.g., lobar margins) makes the pleural pressure more negative, and why pleural pressures would be higher after an upper lobectomy compared to a lower lobectomy. Pathological changes in pleural fluid composition and lung density alter the equilibrium between capillarity and buoyancy hydrostatic pressure to promote pleural effusion formation. PMID:28523153

Penile Erection Induced by Scoparone from Artemisia capillaris through the Nitric Oxide-Cyclic Guanosine Monophosphate Signaling Pathway.

PubMed

Choi, Bo Ram; Kim, Hye Kyung; Park, Jong Kwan

2017-12-01

The objective of this study was to evaluate the relaxant effect of scoparone from Artemisia capillaris on rabbit penile corpus cavernosum smooth muscle (PCCSM) and to elucidate the mechanism of action of scoparone for the treatment of erectile dysfunction (ED). PCCSM that had been precontracted with phenylephrine was treated with 3 Artemisia herbs (A. princeps, A. capillaris, and A. iwayomogi) and 3 fractions (n-hexane, ethyl acetate, and n-butanol) with different concentrations (0.1, 0.5, 1.0, and 2.0 mg/mL). Four components (esculetin, scopoletin, capillarisin, and scoparone) isolated from A. capillaris were also evaluated. The PCCSM was preincubated with Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) and 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (ODQ). Cyclic nucleotides in the perfusate were measured by a radioimmunoassay. The interactions of scoparone with udenafil and rolipram were also evaluated. A. capillaris extract relaxed PCCSM in a concentration-dependent manner. Scoparone had the highest relaxant effect on PCCSM among the 4 components (esculetin, scopoletin, capillarisin, and scoparone) isolated from the ethyl acetate fraction. The application of scoparone on PCCSM pretreated with L-NAME and ODQ led to significantly less relaxation. Scoparone also increased the cyclic guanosine monophosphate (cGMP) levels in the perfusate in a concentration-dependent manner. Furthermore, scoparone enhanced udenafil- and rolipram-induced relaxation of the PCCSM. Scoparone relaxed the PCCSM mainly by activating the nitric oxide-cGMP signaling pathway, and it may be a new promising treatment for ED patients who do not completely respond to udenafil. Copyright © 2017 Korean Society for Sexual Medicine and Andrology

Penile Erection Induced by Scoparone from Artemisia capillaris through the Nitric Oxide-Cyclic Guanosine Monophosphate Signaling Pathway

PubMed Central

2017-01-01

Purpose The objective of this study was to evaluate the relaxant effect of scoparone from Artemisia capillaris on rabbit penile corpus cavernosum smooth muscle (PCCSM) and to elucidate the mechanism of action of scoparone for the treatment of erectile dysfunction (ED). Materials and Methods PCCSM that had been precontracted with phenylephrine was treated with 3 Artemisia herbs (A. princeps, A. capillaris, and A. iwayomogi) and 3 fractions (n-hexane, ethyl acetate, and n-butanol) with different concentrations (0.1, 0.5, 1.0, and 2.0 mg/mL). Four components (esculetin, scopoletin, capillarisin, and scoparone) isolated from A. capillaris were also evaluated. The PCCSM was preincubated with Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) and 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (ODQ). Cyclic nucleotides in the perfusate were measured by a radioimmunoassay. The interactions of scoparone with udenafil and rolipram were also evaluated. Results A. capillaris extract relaxed PCCSM in a concentration-dependent manner. Scoparone had the highest relaxant effect on PCCSM among the 4 components (esculetin, scopoletin, capillarisin, and scoparone) isolated from the ethyl acetate fraction. The application of scoparone on PCCSM pretreated with L-NAME and ODQ led to significantly less relaxation. Scoparone also increased the cyclic guanosine monophosphate (cGMP) levels in the perfusate in a concentration-dependent manner. Furthermore, scoparone enhanced udenafil- and rolipram-induced relaxation of the PCCSM. Conclusions Scoparone relaxed the PCCSM mainly by activating the nitric oxide-cGMP signaling pathway, and it may be a new promising treatment for ED patients who do not completely respond to udenafil. PMID:29164835

Radiation source with shaped emission

DOEpatents

Kubiak, Glenn D.; Sweatt, William C.

2003-05-13

Employing a source of radiation, such as an electric discharge source, that is equipped with a capillary region configured into some predetermined shape, such as an arc or slit, can significantly improve the amount of flux delivered to the lithographic wafers while maintaining high efficiency. The source is particularly suited for photolithography systems that employs a ringfield camera. The invention permits the condenser which delivers critical illumination to the reticle to be simplified from five or more reflective elements to a total of three or four reflective elements thereby increasing condenser efficiency. It maximizes the flux delivered and maintains a high coupling efficiency. This architecture couples EUV radiation from the discharge source into a ring field lithography camera.

Additive Routes to Action Learning: Layering Experience Shapes Engagement of the Action Observation Network.

PubMed

Kirsch, Louise P; Cross, Emily S

2015-12-01

The way in which we perceive others in action is biased by one's prior experience with an observed action. For example, we can have auditory, visual, or motor experience with actions we observe others perform. How action experience via 1, 2, or all 3 of these modalities shapes action perception remains unclear. Here, we combine pre- and post-training functional magnetic resonance imaging measures with a dance training manipulation to address how building experience (from auditory to audiovisual to audiovisual plus motor) with a complex action shapes subsequent action perception. Results indicate that layering experience across these 3 modalities activates a number of sensorimotor cortical regions associated with the action observation network (AON) in such a way that the more modalities through which one experiences an action, the greater the response is within these AON regions during action perception. Moreover, a correlation between left premotor activity and participants' scores for reproducing an action suggests that the better an observer can perform an observed action, the stronger the neural response is. The findings suggest that the number of modalities through which an observer experiences an action impacts AON activity additively, and that premotor cortical activity might serve as an index of embodiment during action observation. © The Author 2015. Published by Oxford University Press.

Phenomenological model of sintering of oxide nuclear fuel with doping admixtures

NASA Astrophysics Data System (ADS)

Baranov, V. G.; Devyatko, Yu. N.; Tenishev, A. V.; Khomyakov, O. V.

2015-12-01

It is shown that a change in the linear dimension of compacted UO2 in the sintering process is associated with its plastic yielding under the action of the forces of residual stress and capillary forces. From the curves of sintering of a fuel with doping admixtures in various gaseous media, its rate of creep is reduced.

Subirrigation for production of native plants in nurseries - concepts, current knowledge, and implementation

Treesearch

Justin L. Schmal; Kas Dumroese; Anthony S. Davis; Jeremy Pinto; Douglass F. Jacobs

2011-01-01

Subirrigation, a method whereby water is allowed to move upward into the growing medium by capillary action, has been the focus of recent research in forest and conservation nurseries growing a wide variety of native plants. Subirrigation reduces the amount of water needed for producing high-quality plants, discharged wastewater, and leaching of nutrients compared with...

Displacement of plasma protein and conduction velocity in rats under action of acceleration forces and hypokinesia

NASA Technical Reports Server (NTRS)

Baranski, S.; Edelwejn, Z.; Wojtkowiak, M.

1980-01-01

The permeability of capillary vessels was investigated in order to determine if acceleration alone or following prolonged hypokinesia would induce changes in the vascular wall leading to the penetration by l-albumins and/or proteins with larger molecules. In rats undergoing action of +5 Gz accelerations, no increase in vascular permeability, as tested with the use of (Cr-5k)-globulin, was demostrated. In rats immobilized for 4 weeks before centrifugation, rather weak migration of (Cr-51)-globulin from the vessels was observed. Immobilization resulted also in lowering of conduction velocity in the sciatic nerve.

The Shape We're In: Community Action Guide.

ERIC Educational Resources Information Center

2003

"The Shape We're In" is a national public education initiative that places a media spotlight on physical activity and obesity to promote public awareness and spark dialogue and action across the country. The centerpiece is a five-part newspaper series delivered to newspapers nationwide. This community action guide begins by describing…

The Performance and Observation of Action Shape Future Behaviour

ERIC Educational Resources Information Center

Welsh, Timothy N.; McDougall, Laura M.; Weeks, Daniel J.

2009-01-01

The observation of other people's actions plays an important role in shaping the perceptual, cognitive, and motor processes of the observer. It has been suggested that these social influences occur because the observation of action evokes a representation of that response in the observer and that these codes are subsequently accessed by other…

Formation of printable granular and colloidal chains through capillary effects and dielectrophoresis

PubMed Central

Rozynek, Zbigniew; Han, Ming; Dutka, Filip; Garstecki, Piotr; Józefczak, Arkadiusz; Luijten, Erik

2017-01-01

One-dimensional conductive particle assembly holds promise for a variety of practical applications, in particular for a new generation of electronic devices. However, synthesis of such chains with programmable shapes outside a liquid environment has proven difficult. Here we report a route to simply ‘pull' flexible granular and colloidal chains out of a dispersion by combining field-directed assembly and capillary effects. These chains are automatically stabilized by liquid bridges formed between adjacent particles, without the need for continuous energy input or special particle functionalization. They can further be deposited onto any surface and form desired conductive patterns, potentially applicable to the manufacturing of simple electronic circuits. Various aspects of our route, including the role of particle size and the voltages needed, are studied in detail. Looking towards practical applications, we also present the possibility of two-dimensional writing, rapid solidification of chains and methods to scale up chain production. PMID:28497791

Formation of printable granular and colloidal chains through capillary effects and dielectrophoresis

NASA Astrophysics Data System (ADS)

Rozynek, Zbigniew; Han, Ming; Dutka, Filip; Garstecki, Piotr; Józefczak, Arkadiusz; Luijten, Erik

2017-05-01

One-dimensional conductive particle assembly holds promise for a variety of practical applications, in particular for a new generation of electronic devices. However, synthesis of such chains with programmable shapes outside a liquid environment has proven difficult. Here we report a route to simply `pull' flexible granular and colloidal chains out of a dispersion by combining field-directed assembly and capillary effects. These chains are automatically stabilized by liquid bridges formed between adjacent particles, without the need for continuous energy input or special particle functionalization. They can further be deposited onto any surface and form desired conductive patterns, potentially applicable to the manufacturing of simple electronic circuits. Various aspects of our route, including the role of particle size and the voltages needed, are studied in detail. Looking towards practical applications, we also present the possibility of two-dimensional writing, rapid solidification of chains and methods to scale up chain production.

Flows of Newtonian and Power-Law Fluids in Symmetrically Corrugated Cappilary Fissures and Tubes

NASA Astrophysics Data System (ADS)

Walicka, A.

2018-02-01

In this paper, an analytical method for deriving the relationships between the pressure drop and the volumetric flow rate in laminar flow regimes of Newtonian and power-law fluids through symmetrically corrugated capillary fissures and tubes is presented. This method, which is general with regard to fluid and capillary shape, can also be used as a foundation for different fluids, fissures and tubes. It can also be a good base for numerical integration when analytical expressions are hard to obtain due to mathematical complexities. Five converging-diverging or diverging-converging geometrics, viz. wedge and cone, parabolic, hyperbolic, hyperbolic cosine and cosine curve, are used as examples to illustrate the application of this method. For the wedge and cone geometry the present results for the power-law fluid were compared with the results obtained by another method; this comparison indicates a good compatibility between both the results.

Acute macular neuroretinopathy associated with systemic lupus erythematosus.

PubMed

Lee, D H; Lee, S C; Kim, M

2016-04-01

Acute macular neuroretinopathy (AMN) is a rare disorder that presents with abrupt visual change with wedge-shaped or flower-like lesions pointing towards the fovea. Ischemic insults to the retinal capillary plexus may be important for development of this disease. While many case reports have been published on AMN, none have described AMN in association with systemic lupus erythematosus (SLE). Here, we report a case of AMN associated with newly-diagnosed SLE. We speculate that in patients with lupus flares, immune complex-mediated vascular injury and microvascular thrombosis may disrupt the deep retinal capillary network, causing ischemic damages to the outer retina and leading to the development of AMN. AMN can develop in patients with lupus flares, and must be considered as an SLE-associated ophthalmologic complication. To the best of our knowledge, this is the first case report of AMN associated with SLE. © The Author(s) 2015.

Adhesion of bubbles and drops to solid surfaces, and anisotropic surface tensions studied by capillary meniscus dynamometry.

PubMed

Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Marinova, Krastanka G; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Cox, Andrew R; Pelan, Eddie G

2016-07-01

Here, we review the principle and applications of two recently developed methods: the capillary meniscus dynamometry (CMD) for measuring the surface tension of bubbles/drops, and the capillary bridge dynamometry (CBD) for quantifying the bubble/drop adhesion to solid surfaces. Both methods are based on a new data analysis protocol, which allows one to decouple the two components of non-isotropic surface tension. For an axisymmetric non-fluid interface (e.g. bubble or drop covered by a protein adsorption layer with shear elasticity), the CMD determines the two different components of the anisotropic surface tension, σs and σφ, which are acting along the "meridians" and "parallels", and vary throughout the interface. The method uses data for the instantaneous bubble (drop) profile and capillary pressure, but the procedure for data processing is essentially different from that of the conventional drop shape analysis (DSA) method. In the case of bubble or drop pressed against a substrate, which forms a capillary bridge, the CBD method allows one to determine also the capillary-bridge force for both isotropic (fluid) and anisotropic (solidified) adsorption layers. The experiments on bubble (drop) detachment from the substrate show the existence of a maximal pulling force, Fmax, that can be resisted by an adherent fluid particle. Fmax can be used to quantify the strength of adhesion of bubbles and drops to solid surfaces. Its value is determined by a competition of attractive transversal tension and repulsive disjoining pressure forces. The greatest Fmax values have been measured for bubbles adherent to glass substrates in pea-protein solutions. The bubble/wall adhesion is lower in solutions containing the protein HFBII hydrophobin, which could be explained with the effect of sandwiched protein aggregates. The applicability of the CBD method to emulsion systems is illustrated by experiments with soybean-oil drops adherent to hydrophilic and hydrophobic substrates in egg yolk solutions. The results reveal how the interfacial rigidity, as well as the bubble/wall and drop/wall adhesion forces, can be quantified and controlled in relation to optimizing the properties of foams and emulsions. Copyright © 2015 Elsevier B.V. All rights reserved.

A glass capillary based microfluidic electromembrane extraction of basic degradation products of nitrogen mustard and VX from water.

PubMed

Tak, Vijay; Kabra, Ankur; Pardasani, Deepak; Goud, D Raghavender; Jain, Rajeev; Dubey, D K

2015-12-24

In this work, a glass capillary based microfluidic electromembrane extraction (μ-EME) was demonstrated for the first time. The device was made by connecting an auxillary borosilicate glass tubing (O.D. 3mm, I.D. 2mm) perpendicular to main borosilicate glass capillary just below one end of the capillary (O.D. 8mm, I.D. 1.2mm). It generated the distorted T-shaped device with inlet '1' and inlet '2' for the introduction of sample and acceptor solutions, respectively. At one end of this device (inlet '2'), a microsyringe containing acceptor solution along with hollow fiber (O.D. 1000μm) was introduced. This configuration creates the micro-channel between inner wall of glass capillary and outer surface of hollow fiber. Sample solution was pumped into the system through another end of glass capillary (inlet '1'), with a micro-syringe pump. The sample was in direct contact with the supported liquid membrane (SLM), consisted of 20% (w/w) di-(2-ethylhexyl)phosphate in 2-nitrophenyl octyl ether immobilized in the pores of the hollow fiber. In the lumen of the hollow fiber, the acceptor phase was present. The driving force for extraction was direct current (DC) electrical potential sustained over the SLM. Highly polar (logP=-2.5 to 1.4) basic degradation products of nitrogen mustard and VX were selected as model analytes. The influence of chemical composition of SLM, extraction time, voltage and pH of donor and acceptor phase were investigated. The model analytes were extracted from 10μL of pure water with recoveries ranging from 15.7 to 99.7% just after 3min of operation time. Under optimized conditions, good limits of detection (2-50ngmL(-1)), linearity (from 5-1000 to 100-1000ngmL(-1)), and repeatability (RSDs below 11.9%, n=3) were achieved. Applicability of the proposed μ-EME was proved by recovering triethanolamine (31.3%) from 10μL of five times diluted original water sample provided by the Organization for the Prohibition of Chemical Weapons during 28th official proficiency test. Copyright © 2015 Elsevier B.V. All rights reserved.

Droplets coalescence at microchannel intersection chambers with different shapes

NASA Astrophysics Data System (ADS)

Liu, Zhaomiao; Wang, Xiang; Cao, Rentuo; Pang, Yan

2016-11-01

The influence of microchannel intersection chamber shape on droplets coalescence process is investigated in this study. Three kinds of chamber shapes (half-round, triangle and camber) are designed to realize head-on droplets coalescence. The coalescence processes are visualized with high-speed camera system and the internal flow patterns are resolved with micro-PIV system. Experimental analyses on droplets coalescence position, coalescence time and the critical conditions are discussed. Both direct coalescence and late coalescence can be observed in the camber junction while only the late coalescence is present for the half-round and the triangle junction. The critical capillary number Ca* varies for different working systems or intersection shapes. Ca* in the camber junction is larger than that in the other two junctions for each working system and it decreases with the increase of the viscosity ratios for each intersection shape. Moreover, the characteristics of the velocity fields for different coalescence cases are analyzed for in-depth understanding of the process. The authors do appreciate the financial support of No.11572013 of National Nature Scicence Funding of China.

Time to make the doughnuts: Building and shaping seamless tubes.

PubMed

Sundaram, Meera V; Cohen, Jennifer D

2017-07-01

A seamless tube is a very narrow-bore tube that is composed of a single cell with an intracellular lumen and no adherens or tight junctions along its length. Many capillaries in the vertebrate vascular system are seamless tubes. Seamless tubes also are found in invertebrate organs, including the Drosophila trachea and the Caenorhabditis elegans excretory system. Seamless tube cells can be less than a micron in diameter, and they can adopt very simple "doughnut-like" shapes or very complex, branched shapes comparable to those of neurons. The unusual topology and varied shapes of seamless tubes raise many basic cell biological questions about how cells form and maintain such structures. The prevalence of seamless tubes in the vascular system means that answering such questions has significant relevance to human health. In this review, we describe selected examples of seamless tubes in animals and discuss current models for how seamless tubes develop and are shaped, focusing particularly on insights that have come from recent studies in Drosophila and C. elegans. Copyright © 2016 Elsevier Ltd. All rights reserved.

Encapsulation of Fluidic Tubing and Microelectrodes in Microfluidic Devices: Integrating Off-Chip Process and Coupling Conventional Capillary Electrophoresis with Electrochemical Detection

PubMed Central

Becirovic, Vedada; Doonan, Steven R.; Martin, R. Scott

2013-01-01

In this paper, an approach to fabricate epoxy or polystyrene microdevices with encapsulated tubing and electrodes is described. Key features of this approach include a fixed alignment between the fluidic tubing and electrodes, the ability to polish the device when desired, and the low dead volume nature of the fluidic interconnects. It is shown that a variety of tubing can be encapsulated with this approach, including fused silica capillary, polyetheretherketone (PEEK), and perfluoroalkoxy (PFA), with the resulting tubing/microchip interface not leading to significant band broadening or plug dilution. The applicability of the devices with embedded tubing is demonstrated by integrating several off-chip analytical methods to the microchip. This includes droplet transfer, droplet desegmentation, and microchip-based flow injection analysis. Off-chip generated droplets can be transferred to the microchip with minimal coalescence, while flow injection studies showed improved peak shape and sensitivity when compared to the use of fluidic interconnects with an appreciable dead volume. Importantly, it is shown that this low dead volume approach can be extended to also enable the integration of conventional capillary electrophoresis (CE) with electrochemical detection. This is accomplished by embedding fused silica capillary along with palladium (for grounding the electrophoresis voltage) and platinum (for detection) electrodes. With this approach, up to 128,000 theoretical plates for dopamine was possible. In all cases, the tubing and electrodes are housed in a rigid base; this results in extremely robust devices that will be of interest to researchers wanting to develop microchips for use by non-experts. PMID:24159363

Encapsulation of Fluidic Tubing and Microelectrodes in Microfluidic Devices: Integrating Off-Chip Process and Coupling Conventional Capillary Electrophoresis with Electrochemical Detection.

PubMed

Becirovic, Vedada; Doonan, Steven R; Martin, R Scott

2013-08-21

In this paper, an approach to fabricate epoxy or polystyrene microdevices with encapsulated tubing and electrodes is described. Key features of this approach include a fixed alignment between the fluidic tubing and electrodes, the ability to polish the device when desired, and the low dead volume nature of the fluidic interconnects. It is shown that a variety of tubing can be encapsulated with this approach, including fused silica capillary, polyetheretherketone (PEEK), and perfluoroalkoxy (PFA), with the resulting tubing/microchip interface not leading to significant band broadening or plug dilution. The applicability of the devices with embedded tubing is demonstrated by integrating several off-chip analytical methods to the microchip. This includes droplet transfer, droplet desegmentation, and microchip-based flow injection analysis. Off-chip generated droplets can be transferred to the microchip with minimal coalescence, while flow injection studies showed improved peak shape and sensitivity when compared to the use of fluidic interconnects with an appreciable dead volume. Importantly, it is shown that this low dead volume approach can be extended to also enable the integration of conventional capillary electrophoresis (CE) with electrochemical detection. This is accomplished by embedding fused silica capillary along with palladium (for grounding the electrophoresis voltage) and platinum (for detection) electrodes. With this approach, up to 128,000 theoretical plates for dopamine was possible. In all cases, the tubing and electrodes are housed in a rigid base; this results in extremely robust devices that will be of interest to researchers wanting to develop microchips for use by non-experts.

In-capillary derivatization with o-phthalaldehyde in the presence of 3-mercaptopropionic acid for the simultaneous determination of monosodium glutamate, benzoic acid, and sorbic acid in food samples via capillary electrophoresis with ultraviolet detection.

PubMed

Aung, Hnin-Pwint; Pyell, Ute

2016-06-03

For the rapid simultaneous determination of monosodium glutamate (MSG), benzoic acid (BA), and sorbic acid (SA) in canned food and other processed food samples, we developed a method that combines in-capillary derivatization with separation by capillary electrophoresis. This method employs the rapid derivatization of MSG with o-phthalaldehyde (OPA) in the presence of 3-mercaptopropionic acid (3-MPA) and enables the detection of the resulting OPA-MSG derivative and of non-derivatized BA and SA at 230nm. The composition of the background electrolyte and the parameters of derivatization and separation are as follows: 25mM borax containing 5mM OPA and 6mM 3-MPA, separation voltage 25mV, injection at 30mbar for 20s, and column temperature 25°C. Because of the high reaction rate and suitably adapted effective electrophoretic mobilities, band broadening due to the derivatization reaction at the start of the separation process is kept to a minimum. The optimized method is validated with respect to LOD, LOQ, linearity, recovery, and precision. This method can be applied to real samples such as soy, fish, oyster and sweet and sour chili sauces after application of appropriate clean-up steps. Mechanisms of zone broadening and zone focusing are discussed showing the validity of the employed theoretical approach regarding the dependence of the peak shape for OPA-MSG on the concentration of MSG in the sample. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of thermodynamic values of acidic dissociation constants and complexation constants of profens and their utilization for optimization of separation conditions by Simul 5 Complex.

PubMed

Riesová, Martina; Svobodová, Jana; Ušelová, Kateřina; Tošner, Zdeněk; Zusková, Iva; Gaš, Bohuslav

2014-10-17

In this paper we determine acid dissociation constants, limiting ionic mobilities, complexation constants with β-cyclodextrin or heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and mobilities of resulting complexes of profens, using capillary zone electrophoresis and affinity capillary electrophoresis. Complexation parameters are determined for both neutral and fully charged forms of profens and further corrected for actual ionic strength and variable viscosity in order to obtain thermodynamic values of complexation constants. The accuracy of obtained complexation parameters is verified by multidimensional nonlinear regression of affinity capillary electrophoretic data, which provides the acid dissociation and complexation parameters within one set of measurements, and by NMR technique. A good agreement among all discussed methods was obtained. Determined complexation parameters were used as input parameters for simulations of electrophoretic separation of profens by Simul 5 Complex. An excellent agreement of experimental and simulated results was achieved in terms of positions, shapes, and amplitudes of analyte peaks, confirming the applicability of Simul 5 Complex to complex systems, and accuracy of obtained physical-chemical constants. Simultaneously, we were able to demonstrate the influence of electromigration dispersion on the separation efficiency, which is not possible using the common theoretical approaches, and predict the electromigration order reversals of profen peaks. We have shown that determined acid dissociation and complexation parameters in combination with tool Simul 5 Complex software can be used for optimization of separation conditions in capillary electrophoresis. Copyright © 2014 Elsevier B.V. All rights reserved.

The Effect of Electrokinetic Controlled Wettability on Externally Measured Pressures for a Micro-Fluidic Channel

NASA Astrophysics Data System (ADS)

Zhou, X.; Nolte, D. D.; Pyrak-Nolte, L. J.

2017-12-01

The hysteretic relationship between capillary pressure (Pc) on saturation (S) has been shown to be a projection of a higher-dimensional surface that depends on interfacial area per volume (IAV) as the additional state variable. Most studies that validate the capillary-pressure-saturation-IAV relationship are performed on 2D micro-models or cores where scanning is performed in pressure and not in saturation. We have developed an EWOD technique (electro-wetting on dielectric) to internally manipulate fluid saturation to determine the effect on externally measured pressures. Applying electric fields to electrolytic fluids changes the contact angle among the fluids and the solid. For a parallel-plate electro-wetting set-up, the pressure difference is given by gsl (cosq'EW - cosqEW )/d', where d' is the aperture, qEQ and q'EW are the contact angles before and after the application of voltage, V, and gsl is the interfacial tension between the solid and liquid phases. This pressure difference enables direct control over internal fluid distributions. The contact angle reverts to the original value when V = 0. A sealed micro-model with Electro-Wetting on Dielectric (EWOD) electrodes was fabricated using a PDMS wedge-shaped channel with an entrance width of 1 mm and an exit width of 2 mm. The channel length was 2 mm, and had a depth of 0.9 mm. The PDMS channel was attached to an aluminum plate that served as the ground electrode. An ITO slide coated with PDMS formed the high voltage electrode and was used to seal the micro-model. X-ray Micro-CT scans showed that the contact angle between electrodes changes from from 110˚ (non-wetting) to 70˚ (wetting) for an applied voltage of 318 V AC. By applying voltage to the wedge-shaped micromodel, with the inlet and the outlet opened to the atmosphere, the externally measured capillary pressure remained constant even though the fluid-air interface moved and the saturation increased. For a closed system, the externally measured change in capillary pressure was 30 Pa and the saturation in the channel increased. EWOD provides method to assess the contributions of wettability to the fundamental physics of immiscible fluids in analog porous media. Acknowledgment: This research was supported by the National Science Foundation (1314663-EAR).

Dynamical behavior of surface tension on rotating fluids in low and microgravity environments

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.

1989-01-01

Consideration is given to the time-dependent evolutions of the free surface profile (bubble shapes) of a cylindrical container, partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry in low and microgravity environments. The dynamics of the bubble shapes are calculated for four cases: linear time-dependent functions of spin-up and spin-down in low and microgravity, linear time-dependent functions of increasing and decreasing gravity at high and low rotating cylinder speeds, time-dependent step functions of spin-up and spin-down in low gravity, and sinusoidal function oscillation of the gravity environment in high and low rotating cylinder speeds. It is shown that the computer algorithms developed by Hung et al. (1988) may be used to simulate the profile of time-dependent bubble shapes under variations of centrifugal, capillary, and gravity forces.

Generalized elastica patterns in a curved rotating Hele-Shaw cell

NASA Astrophysics Data System (ADS)

Brandão, Rodolfo; Miranda, José A.

2017-08-01

We study a family of generalized elasticalike equilibrium shapes that arise at the interface separating two fluids in a curved rotating Hele-Shaw cell. This family of stationary interface solutions consists of shapes that balance the competing capillary and centrifugal forces in such a curved flow environment. We investigate how the emerging interfacial patterns are impacted by changes in the geometric properties of the curved Hele-Shaw cell. A vortex-sheet formalism is used to calculate the two-fluid interface curvature, and a gallery of possible shapes is provided to highlight a number of peculiar morphological features. A linear perturbation theory is employed to show that the most prominent aspects of these complex stationary patterns can be fairly well reproduced by the interplay of just two interfacial modes. The connection of these dominant modes to the geometry of the curved cell, as well as to the fluid dynamic properties of the flow, is discussed.

Direct measurement of erythrocyte deformability in diabetes mellitus with a transparent microchannel capillary model and high-speed video camera system.

PubMed

Tsukada, K; Sekizuka, E; Oshio, C; Minamitani, H

2001-05-01

To measure erythrocyte deformability in vitro, we made transparent microchannels on a crystal substrate as a capillary model. We observed axisymmetrically deformed erythrocytes and defined a deformation index directly from individual flowing erythrocytes. By appropriate choice of channel width and erythrocyte velocity, we could observe erythrocytes deforming to a parachute-like shape similar to that occurring in capillaries. The flowing erythrocytes magnified 200-fold through microscopy were recorded with an image-intensified high-speed video camera system. The sensitivity of deformability measurement was confirmed by comparing the deformation index in healthy controls with erythrocytes whose membranes were hardened by glutaraldehyde. We confirmed that the crystal microchannel system is a valuable tool for erythrocyte deformability measurement. Microangiopathy is a characteristic complication of diabetes mellitus. A decrease in erythrocyte deformability may be part of the cause of this complication. In order to identify the difference in erythrocyte deformability between control and diabetic erythrocytes, we measured erythrocyte deformability using transparent crystal microchannels and a high-speed video camera system. The deformability of diabetic erythrocytes was indeed measurably lower than that of erythrocytes in healthy controls. This result suggests that impaired deformability in diabetic erythrocytes can cause altered viscosity and increase the shear stress on the microvessel wall. Copyright 2001 Academic Press.

Capillary gas chromatographic separation of organic bases using a pH-adjusted basic water stationary phase.

PubMed

Darko, Ernest; Thurbide, Kevin B

2016-09-23

The use of a pH-adjusted water stationary phase for analyzing organic bases in capillary gas chromatography (GC) is demonstrated. Through modifying the phase to typical values near pH 11.5, it is found that various organic bases are readily eluted and separated. Conversely, at the normal pH 7 operating level, they are not. Sodium hydroxide is found to be a much more stable base than ammonium hydroxide for altering the pH due to the higher volatility and evaporation of the latter. In the basic condition, such analytes are not ionized and are observed to produce good peak shapes even for injected masses down to about 20ng. By comparison, analyses on a conventional non-polar capillary GC column yield more peak tailing and only analyte masses of 1μg or higher are normally observed. Through carefully altering the pH, it is also found that the selectivity between analytes can be potentially further enhanced if their respective pKa values differ sufficiently. The analysis of different pharmaceutical and petroleum samples containing organic bases is demonstrated. Results indicate that this approach can potentially offer unique and beneficial selectivity in such analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

NASA Technical Reports Server (NTRS)

Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

1995-01-01

Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed when cytoskeletal stiffness was measured directly in living cells using magnetic twisting cytometry. These results emphasize the importance of matrix-dependent changes in cell and nuclear shape as well as higher order structural interactions between different cytoskeletal filament systems for control of capillary cell growth during angiogenesis.

Numerical modeling of heat and mass transport processes in an evaporative thermal protection system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobrov, I.N.; Kuryachii, A.P.

1992-08-01

We propose a mathematical model of heat and mass transport processes in a moist, porous material subject to capillary action. The material is in contact with a heated surface, and the processes take place while the liquid is evaporating in a cavity with a drainage hole. A sample calculation based on the model is presented. 45 refs., 4 figs.

Optimized Structures for Low-Profile Phase Change Thermal Spreaders

NASA Astrophysics Data System (ADS)

Sharratt, Stephen Andrew

Thin, low-profile phase change thermal spreaders can provide cooling solutions for some of today's most pressing heat flux dissipation issues. These thermal issues are only expected to increase as future electronic circuitry requirements lead to denser and potentially 3D chip packaging. Phase change based heat spreaders, such as heat pipes or vapor chambers, can provide a practical solution for effectively dissipating large heat fluxes. This thesis reports a comprehensive study of state-of-the-art capillary pumped wick structures using computational modeling, micro wick fabrication, and experimental analysis. Modeling efforts focus on predicting the shape of the liquid meniscus inside a complicated 3D wick structure. It is shown that this liquid shape can drastically affect the wick's thermal resistance. In addition, knowledge of the liquid meniscus shape allows for the computation of key parameters such as permeability and capillary pressure which are necessary for predicting the maximum heat flux. After the model is validated by comparison to experimental results, the wick structure is optimized so as to decrease overall wick thermal resistance and increase the maximum capillary limited heat flux before dryout. The optimized structures are then fabricated out of both silicon and copper using both traditional and novel micro-fabrication techniques. The wicks are made super-hydrophilic using chemical and thermal oxidation schemes. A sintered monolayer of Cu particles is fabricated and analyzed as well. The fabricated wick structures are experimentally tested for their heat transfer performance inside a well controlled copper vacuum chamber. Heat fluxes as high as 170 W/cm2 are realized for Cu wicks with structure heights of 100 μm. The structures optimized for both minimized thermal resistance and high liquid supply ability perform much better than their non-optimized counterparts. The super-hydrophilic oxidation scheme is found to drastically increase the maximum heat flux and decrease thermal resistance. This research provides key insights as to how to optimize heat pipe structures to minimize thermal resistance and increase maximum heat flux. These thin wick structures can also be combined with a thicker liquid supply layer so that thin, low-resistance evaporator layers can be constructed and higher heat fluxes realized. The work presented in this thesis can be used to aid in the development of high-performance phase change thermal spreaders, allowing for temperature control of a variety of powerful electronic components.

Capillary rise between planar surfaces

NASA Astrophysics Data System (ADS)

Bullard, Jeffrey W.; Garboczi, Edward J.

2009-01-01

Minimization of free energy is used to calculate the equilibrium vertical rise and meniscus shape of a liquid column between two closely spaced, parallel planar surfaces that are inert and immobile. States of minimum free energy are found using standard variational principles, which lead not only to an Euler-Lagrange differential equation for the meniscus shape and elevation, but also to the boundary conditions at the three-phase junction where the liquid meniscus intersects the solid walls. The analysis shows that the classical Young-Dupré equation for the thermodynamic contact angle is valid at the three-phase junction, as already shown for sessile drops with or without the influence of a gravitational field. Integration of the Euler-Lagrange equation shows that a generalized Laplace-Young (LY) equation first proposed by O’Brien, Craig, and Peyton [J. Colloid Interface Sci. 26, 500 (1968)] gives an exact prediction of the mean elevation of the meniscus at any wall separation, whereas the classical LY equation for the elevation of the midpoint of the meniscus is accurate only when the separation approaches zero or infinity. When both walls are identical, the meniscus is symmetric about the midpoint, and the midpoint elevation is a more traditional and convenient measure of capillary rise than the mean elevation. Therefore, for this symmetric system a different equation is fitted to numerical predictions of the midpoint elevation and is shown to give excellent agreement for contact angles between 15° and 160° and wall separations up to 30mm . When the walls have dissimilar surface properties, the meniscus generally assumes an asymmetric shape, and significant elevation of the liquid column can occur even when one of the walls has a contact angle significantly greater than 90°. The height of the capillary rise depends on the spacing between the walls and also on the difference in contact angles at the two surfaces. When the contact angle at one wall is greater than 90° but the contact angle at the other wall is less than 90°, the meniscus can have an inflection point separating a region of positive curvature from a region of negative curvature, the inflection point being pinned at zero height. However, this condition arises only when the spacing between the walls exceeds a threshold value that depends on the difference in contact angles.

Hysteresis of Contact Angle of Sessile Droplets on Smooth Homogeneous Solid Substrates via Disjoining/Conjoining Pressure.

PubMed

Kuchin, I; Starov, V

2015-05-19

A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr < θ < θa, which are different from the unique equilibrium contact angle θ ≠ θe, correspond to the state of slow "microscopic" advancing or receding motion of the liquid if θe < θ < θa or θr < θ < θe, respectively. This "microscopic" motion almost abruptly becomes fast "macroscopic" advancing or receding motion after the contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid-solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.

Separation performance of cucurbit[7]uril in ionic liquid-based sol-gel coating as stationary phase for capillary gas chromatography.

PubMed

Wang, Xiaogang; Qi, Meiling; Fu, Ruonong

2014-12-05

Here we report the separation performance of a new stationary phase of cucurbit[7]uril (CB7) incorporated into an ionic liquid-based sol-gel coating (CB7-SG) for capillary gas chromatography (GC). The CB7-SG stationary phase showed an average polarity of 455, suggesting its polar nature. Abraham system constants revealed that its major interactions with analytes include H-bond basicity (a), dipole-dipole (s) and dispersive (l) interactions. The CB7-SG stationary phase achieved baseline separation for a wide range of analytes with symmetrical peak shapes and showed advantages over the conventional polar stationary phase that failed to resolve some critical analytes. Also, it exhibited different retention behaviors from the conventional stationary phase in terms of retention times and elution order. Most interestingly, in contrast to the conventional polar phase, the CB7-SG stationary phase exhibited longer retentions for analytes of lower polarity but relatively comparable retentions for polar analytes such as alcohols and phenols. The high resolving ability and unique retention behaviors of the CB7-SG stationary phase may stem from the comprehensive interactions of the aforementioned interactions and shape selectivity. Moreover, the CB7-SG column showed good peak shapes for analytes prone to peak tailing, good thermal stability up to 280°C and separation repeatability with RSD values in the range of 0.01-0.11% for intra-day, 0.04-0.41% for inter-day and 2.5-6.0% for column-to-column, respectively. As demonstrated, the proposed coating method can simultaneously address the solubility problem with CBs for the intended purpose and achieve outstanding GC separation performance. Copyright © 2014 Elsevier B.V. All rights reserved.

1D and 2D diffusion pore imaging on a preclinical MR system using adaptive rephasing: Feasibility and pulse sequence comparison

NASA Astrophysics Data System (ADS)

Bertleff, Marco; Domsch, Sebastian; Laun, Frederik B.; Kuder, Tristan A.; Schad, Lothar R.

2017-05-01

Diffusion pore imaging (DPI) has recently been proposed as a means to acquire images of the average pore shape in an image voxel or region of interest. The highly asymmetric gradient scheme of its sequence makes it substantially demanding in terms of the hardware of the NMR system. The aim of this work is to show the feasibility of DPI on a preclinical 9.4 T animal scanner. Using water-filled capillaries with an inner radius of 10 μm, four different variants of the DPI sequence were compared in 1D and 2D measurements. The pulse sequences applied cover the basic implementation using one long and one temporally narrow gradient pulse, a CPMG-like variant with multiple refocusing RF pulses as well as two variants splitting up the long gradient and distributing it on either side of the refocusing pulse. Substantial differences between the methods were found in terms of signal-to-noise ratio, contrast, blurring, deviations from the expected results and sensitivity to gradient imperfections. Each of the tested sequences was found to produce characteristic gradient mismatches dependent on the absolute value, direction and sign of the applied q-value. Read gradients were applied to compensate these mismatches translating them into time shifts, which enabled 1D DPI yielding capillary radius estimations within the tolerances specified by the manufacturer. For a successful DPI application in 2D, a novel gradient amplitude adaption scheme was implemented to correct for the occurring time shifts. Using this adaption, higher conformity to the expected pore shape, reduced blurring and enhanced contrast were achieved. Images of the phantom's pore shape could be acquired with a nominal resolution of 2.2 μm.

Capillary-Driven Heat Transfer Experiment: Keeping It Cool in Space

NASA Technical Reports Server (NTRS)

Lekan, Jack F.; Allen, Jeffrey S.

1998-01-01

Capillary-pumped loops (CPL's) are devices that are used to transport heat from one location to another--specifically to transfer heat away from something. In low-gravity applications, such as satellites (and possibly the International Space Station), CPL's are used to transfer heat from electrical devices to space radiators. This is accomplished by evaporating one liquid surface on the hot side of the CPL and condensing the vapor produced onto another liquid surface on the cold side. Capillary action, the phenomenon that causes paper towels to absorb spilled liquids, is used to "pump" the liquid back to the evaporating liquid surface (hot side) to complete the "loop." CPL's require no power to operate and can transfer heat over distances as large as 30 ft or more. Their reliance upon evaporation and condensation to transfer heat makes them much more economical in terms of weight than conventional heat transfer systems. Unfortunately, they have proven to be unreliable in space operations, and the explanation for this unreliability has been elusive. The Capillary-Driven Heat Transfer (CHT) experiment is investigating the fundamental fluid physics phenomena thought to be responsible for the failure of CPL's in low-gravity operations. If the failure mechanism can be identified, then appropriate design modifications can be developed to make capillary phase-change heat-transport devices a more viable option in space applications. CHT was conducted onboard the Space Shuttle Columbia during the first Microgravity Science Laboratory (MSL-1) mission, STS-94, which flew from July 1 to 17, 1997. The CHT glovebox investigation, which was conceived by Dr. Kevin Hallinan and Jeffrey Allen of the University of Dayton, focused on studying the dynamics associated with the heating and cooling at the evaporating meniscus within a capillary phase-change device in a low-gravity environment. The CHT experimental hardware was designed by a small team of engineers from Aerospace Design & Fabrication (ADF), the NASA Lewis Research Center, and the University of Dayton. The hardware consisted of two experiment modules that each contained an instrumented test loop (idealized capillary-pumped loop), a base unit for power conversion and backlighting, a display unit with 15 LED's (light-emitting diodes) to display temperatures, pressure, heater power, and time, a control unit to select heaters and heater settings, a cooling fan, and associated cables.

Partitioning of a Falling Droplet's Energy After Surface Impact

NASA Astrophysics Data System (ADS)

Kern, Vanessa; Steen, Paul

2017-11-01

Understanding energy partitioning post-impact is a first step to understanding immersive flow-forming processes. Here we investigate the partitioning of kinetic energy into surface energies for capillary water droplets falling onto homogeneous prepared hydrophilic, hydrophobic and super-hydrophobic surfaces. We analyze high-speed images of the impact event. Pre-impact Weber numbers range from 0-15. After impact and initial spreading, the droplet's contact line pins. After pinning, there is a slow decay to the rest state. During this underdamped decay, the droplet's remaining kinetic energy partitions into a linear combination of mode shape energies. These mode shapes and their frequencies correspond to those of pinned sessile droplets from theory. The influence of impact energy on modes excited will be discussed.

Ferrofluid patterns in Hele-Shaw cells: Exact, stable, stationary shape solutions.

PubMed

Lira, Sérgio A; Miranda, José A

2016-01-01

We investigate a quasi-two-dimensional system composed of an initially circular ferrofluid droplet surrounded by a nonmagnetic fluid of higher density. These immiscible fluids flow in a rotating Hele-Shaw cell, under the influence of an in-plane radial magnetic field. We focus on the situation in which destabilizing bulk magnetic field effects are balanced by stabilizing centrifugal forces. In this framing, we consider the interplay of capillary and magnetic normal traction effects in determining the fluid-fluid interface morphology. By employing a vortex-sheet formalism, we have been able to find a family of exact stationary N-fold polygonal shape solutions for the interface. A weakly nonlinear theory is then used to verify that such exact interfacial solutions are in fact stable.

Quercetin, Inflammation and Immunity

PubMed Central

Li, Yao; Yao, Jiaying; Han, Chunyan; Yang, Jiaxin; Chaudhry, Maria Tabassum; Wang, Shengnan; Liu, Hongnan; Yin, Yulong

2016-01-01

In vitro and some animal models have shown that quercetin, a polyphenol derived from plants, has a wide range of biological actions including anti-carcinogenic, anti-inflammatory and antiviral activities; as well as attenuating lipid peroxidation, platelet aggregation and capillary permeability. This review focuses on the physicochemical properties, dietary sources, absorption, bioavailability and metabolism of quercetin, especially main effects of quercetin on inflammation and immune function. According to the results obtained both in vitro and in vivo, good perspectives have been opened for quercetin. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of quercetin on inflammation and immunity. PMID:26999194

Treatment modalities for caries management, including a new resin infiltration system.

PubMed

Kugel, Gerard; Arsenault, Peter; Papas, Athena

2009-10-01

Seemingly against all odds, dental caries still affects most people in the US. While fluoridated products, school-based screening and cleaning programs, better patient education, and professional and chemotherapeutic interventions have all impacted certain populations, caries is still the most prevalent chronic childhood disease and continues to affect a high percentage of adolescents, young and middle-aged adults, and seniors. Much research has proven that dental caries is not just an occasional cycle of cavitation but a complex and infectious disease process. Historically, addressing the caries challenge has relied on prevention and restoration, with no intermediary means to stop lesion progression. Recently, a technique called caries infiltration was introduced that fills the noncavitated pores of an incipient lesion with a low-viscosity resin by capillary action, creating a barrier that blocks further bacterial diffusion and lesion development. This microinvasive method for stabilizing early lesions requires no drilling or anesthesia and does not alter the tooth's anatomic shape. In cases of white spot lesions in the esthetic zone, it also eliminates opaqueness and blends with surrounding natural teeth. This article presents an overview of caries prevention initiatives and a case demonstrating the new caries infiltration technique. Combined with shifting the focus to caries risk assessment, this promising technology may prove to be a significant addition to the profession's caries treatment armamentarium.

Intense laser pulse propagation in ionizing gases

NASA Astrophysics Data System (ADS)

Bian, Zhigang

2003-10-01

There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The intensity on the inner wall of the capillary is monitored to assure realistic simulations, consistent with optical breakdown of the waveguide material. Generally speaking the intensity on the wall increases with gas pressure due to the scattering of the lowest order capillary mode. Finally, the high order harmonic generation (HHG) in a capillary is investigated. The phase matching condition is studied to increase the conversion efficiency for high order harmonics generation. The phase matching occurs as a balance of the dispersion of the neutral gas, plasma and the waveguide.

Modeling of FMISO [F18] nanoparticle PET tracer in normal-cancerous tissue based on real clinical image.

PubMed

Asgari, Hanie; Soltani, M; Sefidgar, Mostafa

2018-07-01

Hypoxia as one of the principal properties of tumor cells is a reaction to the deprivation of oxygen. The location of tumor cells could be identified by assessment of oxygen and nutrient level in human body. Positron emission tomography (PET) is a well-known non-invasive method that is able to measure hypoxia based on the FMISO (Fluoromisonidazole) tracer dynamic. This paper aims to study the PET tracer concentration through convection-diffusion-reaction equations in a real human capillary-like network. A non-uniform oxygen pressure along the capillary path and convection mechanism for FMISO transport are taken into account to accurately model the characteristics of the tracer. To this end, a multi-scale model consists of laminar blood flow through the capillary network, interstitial pressure, oxygen pressure, FMISO diffusion and FMISO convection transport in the extravascular region is developed. The present model considers both normal and tumor tissue regions in computational domain. The accuracy of numerical model is verified with the experimental results available in the literature. The convection and diffusion types of transport mechanism are employed in order to calculate the concentration of FMISO in the normal and tumor sub-domain. The influences of intravascular oxygen pressure, FMISO transport mechanisms, capillary density and different types of tissue on the FMISO concentration have been investigated. According to result (Table 4) the convection mechanism of FMISO molecules transportation is negligible, but it causes more accuracy of the proposed model. The approach of present study can be employed in order to investigate the effects of various parameters, such as tumor shape, on the dynamic behavior of different PET tracers, such as FDG, can be extended to different case study problems, such as drug delivery. Copyright © 2018 Elsevier Inc. All rights reserved.

Experimental Simulations of Methane Gas Migration through Water-Saturated Sediment Cores

NASA Astrophysics Data System (ADS)

Choi, J.; Seol, Y.; Rosenbaum, E. J.

2010-12-01

Previous numerical simulations (Jaines and Juanes, 2009) showed that modes of gas migration would mainly be determined by grain size; capillary invasion preferably occurring in coarse-grained sediments vs. fracturing dominantly in fine-grained sediments. This study was intended to experimentally simulate preferential modes of gas migration in various water-saturated sediment cores. The cores compacted in the laboratory include a silica sand core (mean size of 180 μm), a silica silt core (1.7 μm), and a kaolin clay core (1.0 μm). Methane gas was injected into the core placed within an x-ray-transparent pressure vessel, which was under continuous x-ray computed tomography (CT) scanning with controlled radial (σr), axial (σa), and pore pressures (P). The CT image analysis reveals that, under the radial effective stress (σr') of 0.69 MPa and the axial effective stress (σa') of 1.31 MPa, fracturings by methane gas injection occur in both silt and clay cores. Fracturing initiates at the capillary pressure (Pc) of ~ 0.41 MPa and ~ 2.41 MPa for silt and clay cores, respectively. Fracturing appears as irregular fracture-networks consisting of nearly invisibly-fine multiple fractures, longitudinally-oriented round tube-shape conduits, or fine fractures branching off from the large conduits. However, for the sand core, only capillary invasion was observed at or above 0.034 MPa of capillary pressure under the confining pressure condition of σr' = 1.38 MPa and σa' = 2.62 MPa. Compared to the numerical predictions under similar confining pressure conditions, fracturing occurs with relatively larger grain sizes, which may result from lower grain-contact compression and friction caused by loose compaction and flexible lateral boundary employed in the experiment.

Automated structure and flow measurement - a promising tool in nailfold capillaroscopy.

PubMed

Berks, Michael; Dinsdale, Graham; Murray, Andrea; Moore, Tonia; Manning, Joanne; Taylor, Chris; Herrick, Ariane L

2018-07-01

Despite increasing interest in nailfold capillaroscopy, objective measures of capillary structure and blood flow have been little studied. We aimed to test the hypothesis that structural measurements, capillary flow, and a combined measure have the predictive power to separate patients with systemic sclerosis (SSc) from those with primary Raynaud's phenomenon (PRP) and healthy controls (HC). 50 patients with SSc, 12 with PRP, and 50 HC were imaged using a novel capillaroscopy system that generates high-quality nailfold images and provides fully-automated measurements of capillary structure and blood flow (capillary density, mean width, maximum width, shape score, derangement and mean flow velocity). Population statistics summarise the differences between the three groups. Areas under ROC curves (A Z ) were used to measure classification accuracy when assigning individuals to SSc and HC/PRP groups. Statistically significant differences in group means were found between patients with SSc and both HC and patients with PRP, for all measurements, e.g. mean width (μm) ± SE: 15.0 ± 0.71, 12.7 ± 0.74 and 11.8 ± 0.23 for SSc, PRP and HC respectively. Combining the five structural measurements gave better classification (A Z  = 0.919 ± 0.026) than the best single measurement (mean width, A Z  = 0.874 ± 0.043), whilst adding flow further improved classification (A Z  = 0.930 ± 0.024). Structural and blood flow measurements are both able to distinguish patients with SSc from those with PRP/HC. Importantly, these hold promise as clinical trial outcome measures for treatments aimed at improving finger blood flow or microvascular remodelling. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Pore-Lining Composition and Capillary Breakthrough Pressure of Mudstone Caprocks: Sealing Efficiency of Geologic CO2 Storage Sites

NASA Astrophysics Data System (ADS)

Heath, J. E.; Dewers, T. A.; McPherson, B. J.; Kotula, P. G.

2010-12-01

Subsurface containment of CO2 is predicated on effective caprock sealing. Many previous studies have relied on macroscopic measurements of capillary breakthrough pressure and other petrophysical properties without direct examination of solid phases that line pore networks and directly contact fluids. However, pore-lining phases strongly contribute to sealing behavior through interfacial interactions among CO2, brine, and the mineral or non-mineral phases. Our high resolution (i.e., sub-micron) examination of the composition of pore-lining phases of several continental and marine mudstones indicates that sealing efficiency (i.e., breakthrough pressure) is governed by pore shapes and pore-lining phases that are not identifiable except through direct characterization of pores. Bulk X-ray diffraction data does not indicate which phases line the pores and may be especially lacking for mudstones with organic material. Organics can line pores and may represent once-mobile phases that modify the wettability of an originally clay-lined pore network. For shallow formations (i.e., < ~800 m depth), interfacial tension and contact angles result in breakthrough pressures that may be as high as those needed to fracture the rock—thus, in the absence of fractures, capillary sealing efficiency is indicated. Deeper seals have poorer capillary sealing if mica-like wetting dominates the wettability. We thank the U.S. Department of Energy’s National Energy Technology Laboratory and the Office of Basic Energy Sciences, and the Southeast and Southwest Carbon Sequestration Partnerships for supporting this work. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Recognizing human actions by learning and matching shape-motion prototype trees.

PubMed

Jiang, Zhuolin; Lin, Zhe; Davis, Larry S

2012-03-01

A shape-motion prototype-based approach is introduced for action recognition. The approach represents an action as a sequence of prototypes for efficient and flexible action matching in long video sequences. During training, an action prototype tree is learned in a joint shape and motion space via hierarchical K-means clustering and each training sequence is represented as a labeled prototype sequence; then a look-up table of prototype-to-prototype distances is generated. During testing, based on a joint probability model of the actor location and action prototype, the actor is tracked while a frame-to-prototype correspondence is established by maximizing the joint probability, which is efficiently performed by searching the learned prototype tree; then actions are recognized using dynamic prototype sequence matching. Distance measures used for sequence matching are rapidly obtained by look-up table indexing, which is an order of magnitude faster than brute-force computation of frame-to-frame distances. Our approach enables robust action matching in challenging situations (such as moving cameras, dynamic backgrounds) and allows automatic alignment of action sequences. Experimental results demonstrate that our approach achieves recognition rates of 92.86 percent on a large gesture data set (with dynamic backgrounds), 100 percent on the Weizmann action data set, 95.77 percent on the KTH action data set, 88 percent on the UCF sports data set, and 87.27 percent on the CMU action data set.

Surface tension-driven self-alignment.

PubMed

Mastrangeli, Massimo; Zhou, Quan; Sariola, Veikko; Lambert, Pierre

2017-01-04

Surface tension-driven self-alignment is a passive and highly-accurate positioning mechanism that can significantly simplify and enhance the construction of advanced microsystems. After years of research, demonstrations and developments, the surface engineering and manufacturing technology enabling capillary self-alignment has achieved a degree of maturity conducive to a successful transfer to industrial practice. In view of this transition, a broad and accessible review of the physics, material science and applications of capillary self-alignment is presented. Statics and dynamics of the self-aligning action of deformed liquid bridges are explained through simple models and experiments, and all fundamental aspects of surface patterning and conditioning, of choice, deposition and confinement of liquids, and of component feeding and interconnection to substrates are illustrated through relevant applications in micro- and nanotechnology. A final outline addresses remaining challenges and additional extensions envisioned to further spread the use and fully exploit the potential of the technique.

Acoustic Streaming in Microgravity: Flow Stability and Heat Transfer Enhancement

NASA Technical Reports Server (NTRS)

Trinh, E. H.

1999-01-01

Experimental results are presented for drops and bubbles levitated in a liquid host, with particular attention given to the effect of shape oscillations and capillary waves on the local flow fields. Some preliminary results are also presented on the use of streaming flows for the control of evaporation rate and rotation of electrostatically levitated droplets in 1 g. The results demonstrate the potential for the technological application of acoustic methods to active control of forced convection in microgravity.

Barbell-shaped stir bar sorptive extraction using dummy template molecularly imprinted polymer coatings for analysis of bisphenol A in water.

PubMed

Liu, Ruimei; Feng, Feng; Chen, Guolin; Liu, Zhimin; Xu, Zhigang

2016-07-01

This study reports the development of a novel dummy template molecularly imprinted polymer (MIP)-coated barbell-shaped stir bar. The MIP stir bar coatings were prepared by using 2,2-bis(4-hydroxyphenyl)butane (BPB), 4,4'-dihydroxydiphenylmethane (BPF), 4-tert-butylphenol (PTBP), and tetrabromobisphenol A (TBBA) as dummy templates using a capillary in situ polymerization method. Uniform coatings can be prepared controllably. The method is simple, easy, and reproducible. The barbell-shaped stir bar was developed by using medical silicone tubes as wheels. The wheels could be removed and reinstalled when necessary; therefore, the barbell-shaped stir bar was easy to disassemble and reassemble. The novel MIP-coated stir bar showed good selectivity for the target analyte, bisphenol A (BPA). The established method is selective and sensitive with a lower detection limit for BPA of 0.003 μg/L. The dummy template MIP-coated stir bar is suitable for trace BPA analysis in real environmental water samples without template leakage. The novel stir bar can be used at least 100 times.

Centrifugal fingering in a curved Hele-Shaw cell: A generalized Euler's elastica shape for the two-fluid interface

NASA Astrophysics Data System (ADS)

Miranda, Jose; Brandao, Rodolfo

2017-11-01

We study a family of generalized elastica-like equilibrium shapes that arise at the interface separating two fluids in a curved rotating Hele-Shaw cell. This family of stationary interface solutions consists of shapes that balance the competing capillary and centrifugal forces in such a curved flow environment. We investigate how the emerging interfacial patterns are impacted by changes in the geometric properties of the curved Hele-Shaw cell. A vortex-sheet formalism is used to calculate the two-fluid interface curvature, and a gallery of possible shapes is provided to highlight a number of peculiar morphological features. A linear perturbation theory is employed to show that the most prominent aspects of these complex stationary patterns can be fairly well reproduced by the interplay of just two interfacial modes. The connection of these dominant modes to the geometry of the curved cell, as well as to the fluid dynamic properties of the flow, is discussed. We thank CNPq (Brazilian Research Council) for financial support under Grant No. 304821/2015-2.

Brain activation related to the perception of minimal agency cues: the role of the mirror system.

PubMed

Stosic, Marina; Brass, Marcel; Van Hoeck, Nicole; Ma, Ning; Van Overwalle, Frank

2014-02-01

Recent fMRI studies indicate that the posterior superior temporal sulcus (pSTS) and the mirror system are involved in analyzing goal-directed actions performed by non-human objects. However, these studies have some limitations: the animations showed moving shapes that resemble humans and human movement, or showed the interaction of two moving shapes rather than one alone. This may have prompted participants to assume a human agent instead of an object. To avoid this potential confound, in this study, animations showed a small circular shape (agent) jumping toward a bigger circular shape (goal) with an obstacle separating them. We manipulated agency of the small circular shape by showing its movements as self-propelled (Agent condition) or as launched by a lever mechanism (Non-agent condition). The small shape succeeded in avoiding an obstacle and reaching the goal object or failed to do so. Our results showed that goal-directed actions performed by an agentic shape recruited the mirror system (the inferior parietal lobe and the premotor cortex) in comparison with shapes that were launched. Success or failure to avoid the obstacle had no effect on these areas. These results complement and further extend previous findings indicating that the mirror system does not appear to be selective for biological actions and their goals, nor does it require the presence of a human, human body parts or human-made objects. Instead, it seems to play a general role in representing goal-directed actions of agents regardless of their form. © 2013.

Writing Bragg Gratings in Multicore Fibers.

PubMed

Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

2016-04-20

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

Writing Bragg Gratings in Multicore Fibers

PubMed Central

Lindley, Emma Y.; Min, Seong-sik; Leon-Saval, Sergio G.; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C.; Bland-Hawthorn, Joss

2016-01-01

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

Assembly of Nanorods into Designer Superstructures: The Role of Templating, Capillary Forces, Adhesion, and Polymer Hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciszek, Jacob W.; Huang, Ling; Tsonchev, Stefan

The assembly mechanism by which hundreds of thousands of two-segment gold-polypyrrole nanorods are assembled into kinetically controlled shape-directed superstructures is examined to predict the range of nanoparticle sizes and materials that can be utilized in their formation. Four processes are responsible for assembly: templating, capillary force assembly, adhesion, and polymer hydration. It is shown that templating, where rods are prepositioned for assembly, is scale invariant and that the energy-minimized state after this step is highly disordered. In addition, we predict that superstructures can be made independently from patterns of rods separated by a distance as small as six times themore » inter-rod spacing. Both modeling and experiment show that adhesion and polymer dehydration, which induces curvature in the superstructures, are applicable to other materials. However, the high surface energy and low elastic modulus of polypyrrole are advantageous toward generating three-dimensional structures, inducing curvature at gold/polypyrrole length ratios as large as 7:1.« less

[Evaluation of chromatographic performance of polymerized ionic liquid stationary phase for capillary gas chromatography].

PubMed

Chen, Xiaoyan; Lu, Kai; Qi, Meiling; Fu, Ruonong

2009-11-01

The selectivity and thermal stability of ionic liquids as the stationary phases for capillary gas chromatography (CGC) have attracted much attention of researchers in recent years. In this study, 1-vinyl-3-benzyl imidazolium-bis(trifluoromethane-sulphonyl)imidate (VBIm-NTf2) was synthesized and polymerized (PVBIm-NTf2) in a CGC column. In comparison with VBIm-NTf2, PVBIm-NTf2 exhibits much better thermal stability and chromatographic selectivity, and achieves satisfactory resolution for Grob test mixture, alcohols mixture, esters mixture and aromatics mixture with narrow and symmetric peak shapes. The satisfactory resolution and selectivity of the polymerized column still remain after conditioned at 250 degrees C for 6 h. Additionally, the Abraham solvation parameters of PVBIm-NTf2 were determined and the interactions between the stationary phase and solutes were elucidated. The present work demonstrates that the polymerization is an effective way to improve the selectivity and thermal stability of common ionic liquids as CGC stationary phases.

Dopamine-imprinted monolithic column for capillary electrochromatography.

PubMed

Aşır, Süleyman; Sarı, Duygu; Derazshamshir, Ali; Yılmaz, Fatma; Şarkaya, Koray; Denizli, Adil

2017-11-01

A dopamine-imprinted monolithic column was prepared and used in capillary electrochromatography as stationary phase for the first time. Dopamine was selectively separated from aqueous solution containing the competitor molecule norepinephrine, which is similar in size and shape to the template molecule. Morphology of the dopamine-imprinted column was observed by scanning electron microscopy. The influence of the organic solvent content of mobile phase, applied pressure and pH of the mobile phase on the recognition of dopamine by the imprinted monolithic column has been evaluated, and the imprinting effect in the dopamine-imprinted monolithic polymer was verified. Developed dopamine-imprinted monolithic column resulted in excellent separation of dopamine from structurally related competitor molecule, norepinephrine. Separation was achieved in a short period of 10 min, with the electrophoretic mobility of 5.81 × 10 -5  m 2 V -1 s -1 at pH 5.0 and 500 mbar pressure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas permeability of ice-templated, unidirectional porous ceramics

NASA Astrophysics Data System (ADS)

Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

2016-01-01

We investigate the gas flow behavior of unidirectional porous ceramics processed by ice-templating. The pore volume ranged between 54% and 72% and pore size between 2.9 ?m and 19.1 ?m. The maximum permeability (?? m?) was measured in samples with the highest total pore volume (72%) and pore size (19.1 ?m). However, we demonstrate that it is possible to achieve a similar permeability (?? m?) at 54% pore volume by modification of the pore shape. These results were compared with those reported and measured for isotropic porous materials processed by conventional techniques. In unidirectional porous materials tortuosity (?) is mainly controlled by pore size, unlike in isotropic porous structures where ? is linked to pore volume. Furthermore, we assessed the applicability of Ergun and capillary model in the prediction of permeability and we found that the capillary model accurately describes the gas flow behavior of unidirectional porous materials. Finally, we combined the permeability data obtained here with strength data for these materials to establish links between strength and permeability of ice-templated materials.

Self-Similar Taylor Cone Formation in Conducting Viscous Films: Computational Study of the Influence of Reynolds Number

NASA Astrophysics Data System (ADS)

Albertson, Theodore; Troian, Sandra

2017-11-01

Previous studies by Zubarev (2001) and Suvorov and Zubarev (2004) have shown that above a critical field strength, an ideal (inviscid) conducting fluid film will deform into a singular profile characterized by a conic cusp. The governing equations for the electrohydrodynamic response beneath the cusp admit self-similar solutions leading to so-called blow-up behavior in the Maxwell pressure, capillary pressure and kinetic energy density. The runaway behavior in these variables reflects divergence in time characterized by an exponent of -2/3. Here we extend the physical system to include viscous effects and conduct a computational study of the cusp region as a function of increasing electrical Reynolds number ReE . We employ a finite element, moving mesh algorithm to examine the behavior of the film shape, Maxwell pressure and capillary pressure upon approach to the blow-up event. Our study indicates that self-similarity establishes at relatively low ReE despite the presence of vorticity, which is localized to the cusp surface region. With increasing ReE , the period of self-similiarity extends further in time as the exponent changes from about -4/5 to the ideal value of -2/3, with slightly different values distinguishing the Maxwell and capillary stresses. T. Albertson gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Adhesion mechanisms on solar glass: Effects of relative humidity, surface roughness, and particle shape and size

DOE PAGES

Moutinho, Helio R.; Jiang, Cun -Sheng; To, Bobby; ...

2017-07-27

To better understand and quantify soiling rates on solar panels, we are investigating the adhesion mechanisms between dust particles and solar glass. In this work, we report on two of the fundamental adhesion mechanisms: van der Waals and capillary adhesion forces. The adhesion was determined using force versus distance (F-z) measurements performed with an atomic force microscope (AFM). To emulate dust interacting with the front surface of a solar panel, we measured how oxidized AFM tips, SiO 2 glass spheres, and real dust particles adhered to actual solar glass. The van der Waals forces were evaluated by measurements performed withmore » zero relative humidity in a glove box, and the capillary forces were measured in a stable environment created inside the AFM enclosure with relative humidity values ranging from 18% to 80%. To simulate topographic features of the solar panels caused by factors such as cleaning and abrasion, we induced different degrees of surface roughness in the solar glass. As a result, we were able to 1) identify and quantify both the van der Waals and capillary forces, 2) establish the effects of surface roughness, relative humidity, and particle size on the adhesion mechanisms, and 3) compare adhesion forces between well-controlled particles (AFM tips and glass spheres) and real dust particles.« less

Micro-engineered remote palpation device for assessing tissue compliance.

PubMed

Hien, M; Yang, T H J; Leung, S K W; Reuben, R L; Habib, F K; McNeill, S A; Schneider, A; McBride, G; Stevens, R; Else, R W

2008-01-01

This paper concerns the operation of the actuator for a prototype micro-engineered mechanical palpation device for deployment via a cystoscope to measure the dynamic mechanical properties of the prostate gland in vivo. The subassembly consists of a 400x200 microm silicon (Si) piston manufactured using deep reactive ion etching (DRIE) housed within an anodically bonded glass-Si-glass sandwiched housing. The micro-channel on the Si layer was formed by powder blasting and contains the micro-piston with one end pointing to the side of the housing and the other facing a via hole leading to a capillary tube. The opening on the side of the housing was sealed by a 5 microm thick silicone membrane which acts to retain the micro-piston and act as a return spring. A 320 microm diameter capillary forms the connection between the micro-channel and a micro-syringe which is operated by a programmable syringe pump to produce a reciprocating action. A pressure sensor is connected along the capillary tube to measure the dynamic pressure within the system. The micro-piston has already been used, separately actuated to measure the dynamic mechanical properties of known viscoelastic materials and prostate tissue. The purpose of the present work is to assess the functionality of the actuator assembly.

Capillary thermoconcentration instability and processes of heat and mass transfer in laser technology

NASA Astrophysics Data System (ADS)

Maiorov, Vladimir S.

2002-04-01

The paper gives a description of the phenomenon that has a considerable, and often a decisive, influence on the course of physical processes under laser radiation interaction with a substance having at least one liquid phase. The explanation of the essence of this phenomenon lies at the intersection of two branches of science: mechanics of liquids and gases, and physical chemistry (thermodynamics of heterogeneous systems). Capillary thermo-concentration instability (CTCI) is present at any non-isotropic input of energy to a heterogeneous thermodynamical system having several phases. This instability manifests itself at the phase boundary and causes processes of mass transfer, redistribution of components, emergence of new phases, relaxation vibrations. This phenomenon is most pronounced in local processes at interaction of laser radiation with matter. The theory and practice of this phenomenon unite and describe a new class of effects widely spread in nature, which play a decisive role in many physical and chemical processes and find even more various spheres of practical application. A number of examples of capillary thermo- concentration instability application are given: separation of liquid mixtures to components under thermal action of laser beam; a new method of thermal silver-free photography; control of liquid metal convection in laser alloying.

Micro-Masonry: Construction of 3D Structures by Mesoscale Self-Assembly

PubMed Central

Fernandez, Javier G.; Khademhosseini, Ali

2010-01-01

A general method for construction of three dimensional structures by directed assembly of microscale polymeric sub-units is presented. Shape-controlled microgels are directed to assemble into different shapes by limiting their movement onto a molded substrate. The capillary forces, resulting from the presence of a liquid polymer, assemble the microgels in close contact with the rest of the units and with the free surface, the latter imposing the final geometry of the resulting construct. The result is a freestanding structure composed of one or multiple layers of sub-units assembled in a tightly packed conformation. The applicability of the technique for the construction of scaffolds with cell-laden sub-units is demonstrated. In addition, scaffolds formed by the sequential aggregation of sub-units are produced. PMID:20440697

Structural characteristics of a gas-liquid flow in a microchannel with a T-shaped mixer

NASA Astrophysics Data System (ADS)

Kuznetsov, V. V.; Kozulin, I. A.

2017-11-01

The results of experimental studies of the structural characteristics of a nitrogen-water mixture flow in a horizontal microchannel provided with a T-shaped mixer are presented. The experiments are performed in a channel with a rectangular cross section of 250 × 315 μm under the conditions of a dominating influence of capillary forces. Structural characteristics of the flow are determined using the two-beam laser scanning and high-speed video capture at a distance of 500 calibers from the inlet in a wide range of reduced gas- and liquid-flow rates. A new method for the identification of flow regimes is proposed based on the statistical treatment of the laser-scanning data, and a map of flow patterns is constructed.

The early days of blotting.

PubMed

Southern, Edwin

2015-01-01

The history of the development of DNA blotting is described in this chapter. DNA blotting, involving the transfer of electrophoretically separated DNA fragments to a membrane support through capillary action, is also known as Southern blotting. This procedure enables the detection of a specific DNA sequence by hybridization with probes. The term Southern blotting led to a "geographic" naming tradition, with RNA blotting bearing the name Northern blotting and protein transfer to membranes becoming known as Western blotting.

Shaping drops with textured surfaces

NASA Astrophysics Data System (ADS)

Ehlinger, Quentin; Biance, Anne-Laure; Ybert, Christophe

2017-11-01

When a drop impacts a substrate, it can behave differently depending on the nature of the surface and of the liquid (spreading, bouncing, resting, splashing ...). Understanding these behaviors is crucial to predict the drop morphology during and after impact. Whereas surface wettability has extensively been studied, the effect of surface roughness remains hardly explored. In this work, we consider the impact of a drop in a pure non-wetting situation by using superheated substrates i.e. in the Leidenfrost regime. The surface texture consists of a well-controlled microscopic defect shaped with photolithography on a smooth silicon wafer. Different regimes are observed, depending on the distance between the defect and the impact point and the defect size. Comparing the lamella thickness versus the defect height proves relevant as the transition criteria between regimes. Others characteristics of the drop behavior (direction of satellite droplet ejection, lamella rupture) are also well captured by inertial/capillary models. Drop impacts on multiple defects are also investigated and drop shape well predicted considering the interactions between the local flow and the defects.

Assembly of silver nanowire ring induced by liquid droplet

NASA Astrophysics Data System (ADS)

Seong, Baekhoon; Park, Hyun Sung; Chae, Ilkyeong; Lee, Hyungdong; Wang, Xiaofeng; Jang, Hyung-Seok; Jung, Jaehyuck; Lee, Changgu; Lin, Liwei; Byun, Doyoung

2017-11-01

Several forces in the liquid droplet drive the nanomaterials to naturally form an assembled structure. During evaporation of a liquid droplet, nanomaterials can move to the rim of the droplet by convective flow and capillary flow, due to the difference in temperature between the top and contact line of the droplet. Here, we demonstrate a new, simple and scalable technology for the fabrication of ring-shaped Ag NWs by a spraying method. We experimentally identify the compressive force of the droplet driven by surface tension as the key mechanism for the self-assembly of ring structures. We investigated the progress of ring shape formation of Ag NWs according to the droplet size with theoretically calculated optimal conditions. As such, this self-assembly technique of making ring-shaped structures from Ag NWs could be applied to other nanomaterials. This work was supported by the New & Renewable Energy R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) Grant funded by the Korea government Ministry of Trade, Industry and Energy. (No. 20163010071630).

Drop deformation and breakup in a partially filled horizontal rotating cylinder

NASA Astrophysics Data System (ADS)

White, Andrew; Pereira, Caroline; Hyacinthe, Hyaquino; Ward, Thomas

2014-11-01

Drop deformation and breakup due to shear flow has been studied extensively in Couette devices as well as in gravity-driven flows. In these cases shear is generated either by the moving wall or the drop's motion. For such flows the drop shape remains unperturbed at low capillary number (Ca), deforms at moderate Ca , and can experience breakup as Ca --> 1 and larger. Here single drops of NaOH(aq) will be placed in a horizontal cylindrical rotating tank partially filled with vegetable oil resulting in 10-2 < Ca <101 . It will be shown that the reactive vegetable oil-NaOH(aq) system, where surfactants are produced in situ by saponification, can yield lower minimum surface tensions and faster adsorption than non-reactive surfactant systems. Oil films between the wall and drop as well as drop shape will be observed as rotation rates and NaOH(aq) concentration are varied. Results will be presented in the context of previous work on bubble and drop shapes and breakup. NSF CBET #1262718.

Spreading law of non-Newtonian power-law liquids on a spherical substrate by an energy-balance approach.

PubMed

Iwamatsu, Masao

2017-07-01

The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids, both shear-thickening and shear-thinning liquids, that completely wet a spherical substrate is theoretically investigated in the capillary-controlled spreading regime. The crater-shaped droplet model with the wedge-shaped meniscus near the three-phase contact line is used to calculate the viscous dissipation near the contact line. Then the energy balance approach is adopted to derive the equation that governs the evolution of the contact line. The time evolution of the dynamic contact angle θ of a droplet obeys a power law θ∼t^{-α} with the spreading exponent α, which is different from Tanner's law for Newtonian liquids and those for non-Newtonian liquids on a flat substrate. Furthermore, the line-tension dominated spreading, which could be realized on a spherical substrate for late-stage of spreading when the contact angle becomes low and the curvature of the contact line becomes large, is also investigated.

Fabrication of PDMS through-holes using the MIMIC method and the surface treatment by atmospheric-pressure CH4/He RF plasma

NASA Astrophysics Data System (ADS)

Choi, Jongchan; Lee, Kyeong-Hwan; Yang, Sung

2011-09-01

This note presents a simple fabrication process for patterning micro through-holes in a PDMS layer by a combination of the micromolding in capillaries (MIMIC) method and the surface treatment by atmospheric-pressure CH4/He RF plasma. The fabrication process is confirmed by forming micro through-holes with various shapes including circle, C-shape, open microfluidic channel and hemisphere. All micro through-holes of various shapes in a wide range of diameters and heights are well fabricated by the proposed method. Also, a 3D micromixer containing a PDMS micro through-hole layer formed by the proposed method is built and its performance is tested as another practical demonstration of the proposed fabrication method. Therefore, we believe that the proposed fabrication process will build a PDMS micro through-hole layer in a simple and easy way and will contribute to developing highly efficient multi-layered microfluidic systems, which may require PDMS micro through-hole layers.

Analytical description of the breakup of liquid jets in air

NASA Technical Reports Server (NTRS)

Papageorgiou, Demetrios T.

1993-01-01

A viscous or inviscid cylindrical jet with surface tension in a vacuum tends to pinch due to the mechanism of capillary instability. Similarity solutions are constructed which describe this phenomenon as a critical time is encountered, for two physically distinct cases: inviscid jets governed by the Euler equations and highly viscous jets governed by the Stokes equations. In both cases the only assumption imposed is that at the time of pinching the jet shape has a radial length scale which is smaller than the axial length scale. For the inviscid case, we show that our solution corresponds exactly to one member of the one-parameter family of solutions obtained from slender jet theories and the shape of the jet is locally concave at breakup. For highly viscous jets our theory predicts local shapes which are monotonic increasing or decreasing indicating the formation of a mother drop connected to the jet by a thin fluid tube. This qualitative behavior is in complete agreement with both direct numerical simulations and experimental observations.

Bundled monocapillary optics

DOEpatents

Hirsch, Gregory

2002-01-01

A plurality of glass or metal wires are precisely etched to form the desired shape of the individual channels of the final polycapillary optic. This shape is created by carefully controlling the withdrawal speed of a group of wires from an etchant bath. The etched wires undergo a subsequent operation to create an extremely smooth surface. This surface is coated with a layer of material which is selected to maximize the reflectivity of the radiation being used. This reflective surface may be a single layer of material, or a multilayer coating for optimizing the reflectivity in a narrower wavelength interval. The collection of individual wires is assembled into a close-packed multi-wire bundle, and the wires are bonded together in a manner which preserves the close-pack configuration, irrespective of the local wire diameter. The initial wires are then removed by either a chemical etching procedure or mechanical force. In the case of chemical etching, the bundle is generally segmented by cutting a series of etching slots. Prior to removing the wire, the capillary array is typically bonded to a support substrate. The result of the process is a bundle of precisely oriented radiation-reflecting hollow channels. The capillary optic is used for efficiently collecting and redirecting the radiation from a source of radiation which could be the anode of an x-ray tube, a plasma source, the fluorescent radiation from an electron microprobe, a synchrotron radiation source, a reactor or spallation source of neutrons, or some other source.

Interplay between shape and roughness in early-stage microcapillary imbibition.

PubMed

Girardo, Salvatore; Palpacelli, Silvia; De Maio, Alessandro; Cingolani, Roberto; Succi, Sauro; Pisignano, Dario

2012-02-07

Flows in microcapillaries and associated imbibition phenomena play a major role across a wide spectrum of practical applications, from oil recovery to inkjet printing and from absorption in porous materials and water transport in trees to biofluidic phenomena in biomedical devices. Early investigations of spontaneous imbibition in capillaries led to the observation of a universal scaling behavior, known as the Lucas-Washburn (LW) law. The LW allows abstraction of many real-life effects, such as the inertia of the fluid, irregularities in the wall geometry, and the finite density of the vacuum phase (gas or vapor) within the channel. Such simplifying assumptions set a constraint on the design of modern microfluidic devices, operating at ever-decreasing space and time scales, where the aforementioned simplifications go under serious question. Here, through a combined use of leading-edge experimental and simulation techniques, we unravel a novel interplay between global shape and nanoscopic roughness. This interplay significantly affects the early-stage energy budget, controlling front propagation in corrugated microchannels. We find that such a budget is governed by a two-scale phenomenon: The global geometry sets the conditions for small-scale structures to develop and propagate ahead of the main front. These small-scale structures probe the fine-scale details of the wall geometry (nanocorrugations), and the additional friction they experience slows the entire front. We speculate that such a two-scale mechanism may provide a fairly general scenario to account for extra dissipative phenomena occurring in capillary flows with nanocorrugated walls.

A two scale modeling and computational framework for vibration-induced Raynaud syndrome.

PubMed

Hua, Yue; Lemerle, Pierre; Ganghoffer, Jean-François

2017-07-01

Hand-Arm Vibration syndrome (HAVS), usually caused by long-term use of hand-held power tools, can in certain manifestations alter the peripheral blood circulation in the hand-arm region. HAVS typically occurs after exposure to cold, causing an abnormally strong vasoconstriction of blood vessels. A pathoanatomical mechanism suggests that a reduction of the lumen of the blood vessels in VWF (Vibration White Finger) subjects, due to either hypertrophy or thickening of the vessel wall, may be at the origin of the disease. However, the direct and indirect effects of the load of the hand-held tools on the structure of blood vessels remain controversial:.one hypothesis is the mechanical action of vibration on the local acral dysregulation and/or on the vessel histomorphological modifications. Another hypothesis is the participation of the sympathetic nervous system to this dysregulation. In this paper, we assume the modifications as mechanobiological growth and the load-effect relationship may be interpreted as directly or indirectly induced. This work is the first attempt to model the effect of vibration through soft tissues onto the distal capillaries, addressing the double paradigm of multi space-time scales, i.e. low period vibration versus high time constant of the growth phenomenon as well as vibrations propagating in the macroscopic tissue including the microscopic capillary structures subjected to a pathological microstructural evolution. The objective is to lay down the theoretical basis of growth modeling for the small distal artery, with the ability to predict the geometrical and structural changes of the arterial walls caused by vibration exposure. We adopt the key idea of splitting the problem into one global vibration problem at the macroscopic scale and one local growth problem at the micro level. The macroscopic hyperelastic viscous dynamic model of the fingertip cross-section is validated by fitting experimental data. It is then used in steady-state vibration conditions to predict the mechanical fields in the close vicinity of capillaries. The space scale transfer from macroscopic to microscopic levels is ensured by considering a representative volume element (RVE) embedding a single capillary in its center. The vibrations emitted by the hand held power tool are next linked to the capillary growth through the adopted biomechanical growth model at the capillary level. The obtained results show that vibrations induce an increase of the thickness of the capillary's wall, thereby confirming the scenario of vibrations induced reduction of the lumen of blood vessels. Copyright © 2017 Elsevier Ltd. All rights reserved.

Clients, Colleagues or Experts? Defining Identities in an Action Research Project

ERIC Educational Resources Information Center

Coco, Angela; Varnier, Catherine; Deftereos, Chris

2007-01-01

This article examines how discourses shaped and were shaped by participants' identities in a participatory action research (PAR) project in a tertiary education environment. The primary researcher and the director of the university's desktop publishing team explored the idea of working together to help the newly formed team to develop strategies…

Hierarchical human action recognition around sleeping using obscured posture information

NASA Astrophysics Data System (ADS)

Kudo, Yuta; Sashida, Takehiko; Aoki, Yoshimitsu

2015-04-01

This paper presents a new approach for human action recognition around sleeping with the human body parts locations and the positional relationship between human and sleeping environment. Body parts are estimated from the depth image obtained by a time-of-flight (TOF) sensor using oriented 3D normal vector. Issues in action recognition of sleeping situation are the demand of availability in darkness, and hiding of the human body by duvets. Therefore, the extraction of image features is difficult since color and edge features are obscured by covers. Thus, first in our method, positions of four parts of the body (head, torso, thigh, and lower leg) are estimated by using the shape model of bodily surface constructed by oriented 3D normal vector. This shape model can represent the surface shape of rough body, and is effective in robust posture estimation of the body hidden with duvets. Then, action descriptor is extracted from the position of each body part. The descriptor includes temporal variation of each part of the body and spatial vector of position of the parts and the bed. Furthermore, this paper proposes hierarchical action classes and classifiers to improve the indistinct action classification. Classifiers are composed of two layers, and recognize human action by using the action descriptor. First layer focuses on spatial descriptor and classifies action roughly. Second layer focuses on temporal descriptor and classifies action finely. This approach achieves a robust recognition of obscured human by using the posture information and the hierarchical action recognition.

Robots show us how to teach them: feedback from robots shapes tutoring behavior during action learning.

PubMed

Vollmer, Anna-Lisa; Mühlig, Manuel; Steil, Jochen J; Pitsch, Karola; Fritsch, Jannik; Rohlfing, Katharina J; Wrede, Britta

2014-01-01

Robot learning by imitation requires the detection of a tutor's action demonstration and its relevant parts. Current approaches implicitly assume a unidirectional transfer of knowledge from tutor to learner. The presented work challenges this predominant assumption based on an extensive user study with an autonomously interacting robot. We show that by providing feedback, a robot learner influences the human tutor's movement demonstrations in the process of action learning. We argue that the robot's feedback strongly shapes how tutors signal what is relevant to an action and thus advocate a paradigm shift in robot action learning research toward truly interactive systems learning in and benefiting from interaction.

Robots Show Us How to Teach Them: Feedback from Robots Shapes Tutoring Behavior during Action Learning

PubMed Central

Vollmer, Anna-Lisa; Mühlig, Manuel; Steil, Jochen J.; Pitsch, Karola; Fritsch, Jannik; Rohlfing, Katharina J.; Wrede, Britta

2014-01-01

Robot learning by imitation requires the detection of a tutor's action demonstration and its relevant parts. Current approaches implicitly assume a unidirectional transfer of knowledge from tutor to learner. The presented work challenges this predominant assumption based on an extensive user study with an autonomously interacting robot. We show that by providing feedback, a robot learner influences the human tutor's movement demonstrations in the process of action learning. We argue that the robot's feedback strongly shapes how tutors signal what is relevant to an action and thus advocate a paradigm shift in robot action learning research toward truly interactive systems learning in and benefiting from interaction. PMID:24646510

Single-step CE for miniaturized and easy-to-use system.

PubMed

Ono, Koichi; Kaneda, Shohei; Fujii, Teruo

2013-03-01

We developed a novel single-step capillary electrophoresis (SSCE) scheme for miniaturized and easy to use system by using a microchannel chip, which was made from the hydrophilic material polymethyl methacrylate (PMMA), equipped with a capillary stop valve. Taking the surface tension property of liquids into consideration, the capillary effect was used to introduce liquids and control capillary stop valves in a partial barrier structure in the wall of the microchannel. Through the combined action of stop valves and air vents, both sample plug formation for electrophoresis and sample injection into a separation channel were successfully performed in a single step. To optimize SSCE, different stop valve structures were evaluated using actual microchannel chips and the finite element method with the level set method. A partial barrier structure at the bottom of the channel functioned efficiently as a stop valve. The stability of stop valve was confirmed by a shock test, which was performed by dropping the microchannel chip to a floor. Sample plug deformation could be reduced by minimizing the size of the side partial barrier. By dissolving hydroxyl ethyl cellulose and using it as the sample solution, the EOF and adsorption of the sample into the PMMA microchannel were successfully reduced. Using this method, a 100-bp DNA ladder was concentrated; good separation was observed within 1 min. At a separation length of 5 mm, the signal was approximately 20-fold higher than a signal of original sample solution by field-amplified sample stacking effect. All operations, including liquid introduction and sample separation, can be completed within 2 min by using the SSCE scheme. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Using Sound To Study the Effect of Frothers on the Breakaway of Air Bubbles at an Underwater Capillary.

PubMed

Chu, Pengbo; Pax, Randolph; Li, Ronghao; Langlois, Ray; Finch, James A

2017-04-04

Frothers, a class of surfactants, are widely employed in froth flotation to aid the generation of small bubbles. Their action is commonly explained by their ability to hinder coalescence. There are occasional references suggesting that the frother may also play a role in the initial breakup of the injected air mass. This work investigates the possible effect of the frother on breakup by monitoring air bubbles produced quasi-statically at an underwater capillary. Under this condition, breakup is isolated from coalescence and an impact of frothers on the detached bubble can be ascribed to an impact on breakup. The breakaway process was monitored by an acoustic technique along with high-speed cinematography. The results showed that the presence of frothers did influence the breakaway process and that the acoustic technique was able to detect the impact. It was demonstrated that the acoustic frequency and acoustic damping ratio depend upon the frother type and concentration and that they are associated with a liquid jet, which initially excites the bubble and then decays to form a surface wave. The addition of the frother did not influence the formation of the jet but did increase its decay rate, hence, dampening the surface wave. It is postulated that the action of the frother is related to an effect on the magnitude of surface tension gradients.

Dialectical theory and the study of HIV/AIDS and other epidemics

PubMed Central

Rossi, Diana

2011-01-01

Epidemics have been important in human history. This article discusses epidemics as part of a metabolic dialectics of humanity within nature. The creative thoughts and actions of those people most threatened by HIV/AIDS, and the thoughts and actions of science, have shaped both each other and the virus. The virus has reacted through mutation in ways that mimic strategic intelligence. The dialectics of capital and states has shaped these interactions and, in some cases, been shaped by them. Practical action to minimize the harms epidemics do can be strengthened by understanding of these epidemics, and Marxist theory and practices can be strengthened by understanding the dialectics of public health and the struggles around it more fully. PMID:23894218

Dynamics of Liquids in Edges and Corners (DYLCO): IML-2 Experiment for the BDPU

NASA Technical Reports Server (NTRS)

Langbein, D.; Weislogel, M.

1998-01-01

Knowledge of the behavior of fluids possessing free surfaces is important to many fluid systems, particularly in space, where the normally subtle effects of surface wettability play a more dramatic and often surprising role. DYLCO for the IML-2 mission was proposed as a simple experiment to probe the particular behavior of capillary surfaces in containers of irregular cross section. Temperature control was utilized to vary the fluid-solid contact angle, a questionable thermodynamic parameter of the system, small changes in which can dramatically influence the configuration, stability, and flow of a capillary surface. Container shapes, test fluid, and temperature ranges were selected for observing both local changes in interface curvature as well as a global change in fluid orientation due to a critical wetting phenomenon. The experiment hardware performed beyond what was expected and fluid interfaces could be readily digitized post flight to show the dependence of the interface curvature on temperature. For each of the containers tested surfaces were observed which did not satisfy the classic equations for the prediction of interface shape with constant contact angle boundary condition. This is explained by the presence of contact angle hysteresis arising from expansion and contraction of the liquid during the heating and cooling steps of the test procedure. More importantly, surfaces exceeding the critical surface curvature required for critical wetting were measured, yet no wetting was observed. These findings are indeed curious and pose key questions concerning the role of hysteresis for this critical wetting phenomena. The stability of such surfaces was determined numerically and it is shown that stability is enhance (reduced) when a surface is in its 'advancing' ('receding') state, The analysis shows complete instability as the critical wetting condition is reached. The case of ideal dynamic wetting is addressed analytically in detail with results of significant flow characteristics presented in closed form. The solutions indicate a square root of T dependence of the capillary 'rise' rate which is corroborated by drop tower tests. The analysis clearly shows that infinite time is necessary for surfaces to reorient at the critical wetting transition.

Neurotrophins promote revascularization by local recruitment of TrkB+ endothelial cells and systemic mobilization of hematopoietic progenitors

PubMed Central

Kermani, Pouneh; Rafii, Dahlia; Jin, David K.; Whitlock, Paul; Schaffer, Wendy; Chiang, Anne; Vincent, Loic; Friedrich, Matthias; Shido, Koji; Hackett, Neil R.; Crystal, Ronald G.; Rafii, Shahin; Hempstead, Barbara L.

2005-01-01

The neurotrophin brain-derived neurotrophic factor (BDNF) is required for the maintenance of cardiac vessel wall stability during embryonic development through direct angiogenic actions on endothelial cells expressing the tropomysin receptor kinase B (TrkB). However, the role of BDNF and a related neurotrophin ligand, neurotrophin-4 (NT-4), in the regulation of revascularization of the adult tissues is unknown. To study the potential angiogenic capacity of BDNF in mediating the neovascularization of ischemic and non-ischemic adult mouse tissues, we utilized a hindlimb ischemia and a subcutaneous Matrigel model. Recruitment of endothelial cells and promotion of channel formation within the Matrigel plug by BDNF and NT-4 was comparable to that induced by VEGF-A. The introduction of BDNF into non-ischemic ears or ischemic limbs induced neoangiogenesis, with a 2-fold increase in the capillary density. Remarkably, treatment with BDNF progressively increased blood flow in the ischemic limb over 21 days, similar to treatment with VEGF-A. The mechanism by which BDNF enhances capillary formation is mediated in part through local activation of the TrkB receptor and also by recruitment of Sca-1+CD11b+ pro-angiogenic hematopoietic cells. BDNF induces a potent direct chemokinetic action on subsets of marrow-derived Sca-1+ hematopoietic cells co-expressing TrkB. These studies suggest that local regional delivery of BDNF may provide a novel mechanism for inducing neoangiogenesis through both direct actions on local TrkB-expressing endothelial cells in skeletal muscle and recruitment of specific subsets of TrkB+ bone marrow–derived hematopoietic cells to provide peri-endothelial support for the newly formed vessels. PMID:15765148

Morphometric analysis of polygonal cracking patterns in desiccated starch slurries

NASA Astrophysics Data System (ADS)

Akiba, Yuri; Magome, Jun; Kobayashi, Hiroshi; Shima, Hiroyuki

2017-08-01

We investigate the geometry of two-dimensional polygonal cracking that forms on the air-exposed surface of dried starch slurries. Two different kinds of starches, made from potato and corn, exhibited distinguished crack evolution, and there were contrasting effects of slurry thickness on the probability distribution of the polygonal cell area. The experimental findings are believed to result from the difference in the shape and size of starch grains, which strongly influence the capillary transport of water and tensile stress field that drives the polygonal cracking.

Deformation of the free surface of a conducting fluid in the magnetic field of current-carrying linear conductors

NASA Astrophysics Data System (ADS)

Zubarev, N. M.; Zubareva, O. V.

2017-06-01

The magnetic shaping problem is studied for the situation where a cylindrical column of a perfectly conducting fluid is deformed by the magnetic field of a system of linear current-carrying conductors. Equilibrium is achieved due to the balance of capillary and magnetic pressures. Two two-parametric families of exact solutions of the problem are obtained with the help of conformal mapping technique. In accordance with them, the column essentially deforms in the cross section up to its disintegration.

The possible equilibrium shapes of static pendant drops

NASA Astrophysics Data System (ADS)

Sumesh, P. T.; Govindarajan, Rama

2010-10-01

Analytical and numerical studies are carried out on the shapes of two-dimensional and axisymmetric pendant drops hanging under gravity from a solid surface. Drop shapes with both pinned and equilibrium contact angles are obtained naturally from a single boundary condition in the analytical energy optimization procedure. The numerical procedure also yields optimum energy shapes, satisfying Young's equation without the explicit imposition of a boundary condition at the plate. It is shown analytically that a static pendant two-dimensional drop can never be longer than 3.42 times the capillary length. A related finding is that a range of existing solutions for long two-dimensional drops correspond to unphysical drop shapes. Therefore, two-dimensional drops of small volume display only one static solution. In contrast, it is known that axisymmetric drops can display multiple solutions for a given volume. We demonstrate numerically that there is no limit to the height of multiple-lobed Kelvin drops, but the total volume is finite, with the volume of successive lobes forming a convergent series. The stability of such drops is in question, though. Drops of small volume can attain large heights. A bifurcation is found within the one-parameter space of Laplacian shapes, with a range of longer drops displaying a minimum in energy in the investigated space. Axisymmetric Kelvin drops exhibit an infinite number of bifurcations.

Dynamics of tongue shaped cavity generated during the impact of high-speed microdrops

NASA Astrophysics Data System (ADS)

Deka, Hiranya; Ray, Bahni; Biswas, Gautam; Dalal, Amaresh

2018-04-01

Tongue shaped cavities are seen during the hydrophobic sphere impact, jet impact, and impact of a train of microdrops on a deep liquid pool. For the multiple microdrops' impact, the mechanisms, which lead to deep cavity formation and later bubble entrapment inside the liquid pool, are presented here. The investigations are performed in an air-water system at large values of Froude numbers, thus having a negligible effect of gravity. Depending on the train length, the capillary wave generating from each drop impact affects the necking. The temporal variation of the neck radius shows power law behavior. We delineate the distinctive feature of pinch-off of the cavity in terms of the critical length of the train. Pinch-off is observed when the penetration depth of the cavity is more than three times the diameter of the cavity.

Wrapping with a splash: High-speed encapsulation with ultrathin sheets

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Paulsen, Joseph D.; Russell, Thomas P.; Menon, Narayanan

2018-02-01

Many complex fluids rely on surfactants to contain, protect, or isolate liquid drops in an immiscible continuous phase. Thin elastic sheets can wrap liquid drops in a spontaneous process driven by capillary forces. For encapsulation by sheets to be practically viable, a rapid, continuous, and scalable process is essential. We exploit the fast dynamics of droplet impact to achieve wrapping of oil droplets by ultrathin polymer films in a water phase. Despite the violence of splashing events, the process robustly yields wrappings that are optimally shaped to maximize the enclosed fluid volume and have near-perfect seams. We achieve wrappings of targeted three-dimensional (3D) shapes by tailoring the 2D boundary of the films and show the generality of the technique by producing both oil-in-water and water-in-oil wrappings.

Nonuniform Changes in the Distribution of Visual Attention from Visual Complexity and Action: A Driving Simulation Study.

PubMed

Park, George D; Reed, Catherine L

2015-02-01

Researchers acknowledge the interplay between action and attention, but typically consider action as a response to successful attentional selection or the correlation of performance on separate action and attention tasks. We investigated how concurrent action with spatial monitoring affects the distribution of attention across the visual field. We embedded a functional field of view (FFOV) paradigm with concurrent central object recognition and peripheral target localization tasks in a simulated driving environment. Peripheral targets varied across 20-60 deg eccentricity at 11 radial spokes. Three conditions assessed the effects of visual complexity and concurrent action on the size and shape of the FFOV: (1) with no background, (2) with driving background, and (3) with driving background and vehicle steering. The addition of visual complexity slowed task performance and reduced the FFOV size but did not change the baseline shape. In contrast, the addition of steering produced not only shrinkage of the FFOV, but also changes in the FFOV shape. Nonuniform performance decrements occurred in proximal regions used for the central task and for steering, independent of interference from context elements. Multifocal attention models should consider the role of action and account for nonhomogeneities in the distribution of attention. © 2015 SAGE Publications.

Expansion of a compressible gas bubble in Stokes flow

NASA Astrophysics Data System (ADS)

Pozrikidis, C.

2001-09-01

The flow-induced deformation of an inviscid bubble occupied by a compressible gas and suspended in an ambient viscous liquid is considered at low Reynolds numbers with particular reference to the pressure developing inside the bubble. Ambient fluid motion alters the bubble pressure with respect to that established in the quiescent state, and requires the bubble to expand or contract according to an assumed equation of state. When changes in the bubble volume are prohibited by a global constraint on the total volume of the flow, the ambient pressure is modified while the bubble pressure remains constant during the deformation. A numerical method is developed for evaluating the pressure inside a two-dimensional bubble in an ambient Stokes flow on the basis of the normal component of the interfacial force balance involving the capillary pressure, the normal viscous stress, and the pressure at the free surface on the side of the liquid; the last is computed by evaluating a strongly singular integral. Dynamical simulations of bubble deformation are performed using the boundary integral method properly implemented to remove the multiplicity of solutions due to the a priori unknown rate of expansion, and three particular problems are discussed in detail: the shrinkage of a bubble at a specified rate, the deformation of a bubble subject to simple shear flow, and the deformation of a bubble subject to a purely elongational flow. In the case of shrinkage, it is found that the surface tension plays a critical role in determining the behaviour of the bubble pressure near the critical time when the bubble disappears. In the case of shear or elongational flow, it is found that the bubble contracts during an initial period of deformation from the circular shape, and then it expands to obtain a stationary shape whose area is higher than that assumed in the quiescent state. Expansion may destabilize the bubble by raising the capillary number above the critical threshold under which stationary shapes can be found.

A performance comparison of ultrasonically aided electric propulsion extractor configurations

NASA Astrophysics Data System (ADS)

Dong, L.; Song, W.; Kang, X. M.; Zhao, W. S.

2012-08-01

As a novel propulsion technology, ultrasonically aided electric propulsion (UAEP) offers a high specific impulse and a high thrust density. In this paper, the effects of extractor grid configuration on performance of a UAEP thruster have been investigated by both experimental studies and numerical simulation. Relationships between spray current and operation parameters, including applied voltage, propellant flow rate, and vibration power and frequency, are explored for different extractor mesh sizes and shapes. Numerical simulation is also carried out for a better understanding of the formation of capillary standing waves as well as the electric field distribution in the acceleration zone. Experimental results show that compared with a circular shaped extractor, a reticular shaped extractor is able to produce a higher spray current. The current density increases with a denser mesh, which agrees well with the numerical simulation results. This phenomenon indicates that optimizing extractors with appropriate shapes and sizes can be an effective way to improve the performance of a UAEP system. A performance evaluation based on hydrodynamic and electrostatic calculations indicates that the present UAEP system can produce a thrust competitive to that of the colloid thruster with an emitter array.

An Optical Fiber Viscometer Based on Long-Period Fiber Grating Technology and Capillary Tube Mechanism

PubMed Central

Wang, Jian-Neng; Tang, Jaw-Luen

2010-01-01

This work addresses the development and assessment of a fiber optical viscometer using a simple and low-cost long-period fiber grating (LPFG) level sensor and a capillary tube mechanism. Previous studies of optical viscosity sensors were conducted by using different optical sensing methods. The proposed optical viscometer consists of an LPFG sensor, a temperature-controlled chamber, and a cone-shaped reservoir where gravitational force could cause fluid to flow through the capillary tube. We focused on the use of LPFGs as level sensors and the wavelength shifts were not used to quantify the viscosity values of asphalt binders. When the LPFG sensor was immersed in the constant volume (100 mL) AC-20 asphalt binder, a wavelength shift was observed and acquired using LabVIEW software and GPIB controller. The time spent between empty and 100 mL was calculated to determine the discharge time. We simultaneously measured the LPFG-induced discharge time and the transmission spectra both in hot air and AC-20 asphalt binder at five different temperatures, 60, 80, 100, 135, and 170 Celsius. An electromechanical rotational viscometer was also used to measure the viscosities, 0.15–213.80 Pa·s, of the same asphalt binder at the above five temperatures. A non-linear regression analysis was performed to convert LPFG-induced discharge time into viscosities. Comparative analysis shows that the LPFG-induced discharge time agreed well with the viscosities obtained from the rotational viscometer. PMID:22163519

Hydraulic conductivity of variably saturated porous media: Film and corner flow in angular pore space

NASA Astrophysics Data System (ADS)

Tuller, Markus; Or, Dani

2001-05-01

Many models for hydraulic conductivity of partially saturated porous media rely on oversimplified representation of the pore space as a bundle of cylindrical capillaries and disregard flow in liquid films. Recent progress in modeling liquid behavior in angular pores of partially saturated porous media offers an alternative framework. We assume that equilibrium liquid-vapor interfaces provide well-defined and stable boundaries for slow laminar film and corner flow regimes in pore space comprised of angular pores connected to slit-shaped spaces. Knowledge of liquid configuration in the assumed geometry facilitates calculation of average liquid velocities in films and corners and enables derivation of pore-scale hydraulic conductivity as a function of matric potential. The pore-scale model is statistically upscaled to represent hydraulic conductivity for a sample of porous medium. Model parameters for the analytical sample-scale expressions are estimated from measured liquid retention data and other measurable medium properties. Model calculations illustrate the important role of film flow, whose contribution dominates capillary flow (in full pores and corners) at relatively high matric potentials (approximately -100 to -300 J kg-1, or -1 to 3 bars). The crossover region between film and capillary flow is marked by a significant change in the slope of the hydraulic conductivity function as often observed in measurements. Model predictions are compared with the widely applied van Genuchten-Mualem model and yield reasonable agreement with measured retention and hydraulic conductivity data over a wide range of soil textural classes.

Microstructure and network organization of the microvasculature in the human macula.

PubMed

Yu, Paula K; Balaratnasingam, Chandrakumar; Cringle, Stephen J; McAllister, Ian L; Provis, Jan; Yu, Dao-Yi

2010-12-01

To characterize the topography and cellular structure of the macular microvasculature using a recently developed technique of arterial cannulation, perfusion, fixation, and staining of human donor eyes. Sixteen human donor eyes were used. The central retinal artery was cannulated and perfused with Ringer's, then fixative, membrane permeabilizing, and selected labeling solutions. The eyes were immersion fixed, and the retina was flat mounted for confocal microscopy. The macular area, including the foveola, fovea, and parafovea, was sampled. The intracellular cytoskeleton of vascular endothelial and smooth muscle cells was studied in different orders of arterioles and venules and in the capillaries. To evaluate the degree of asymmetry within vascular networks, the distribution of generation numbers and the Horton-Strahler approach to vessel naming were compared. The distribution of the microvascular network in the macular region was complex but followed a general theme. The parafoveal region was supplied by dense vasculature with approximately nine closely arranged pairs of arterioles and venules. Each arteriole had abundant branches and a high degree of asymmetry (∼10 generations and 3.5 orders within 1.2-mm length). Only a few arterioles (average ∼2.9) supplied the terminal capillary ring. Very long spindle endothelial cells were seen in the superficial and deep capillaries. Significant heterogeneity of distribution and shape of the endothelial and smooth muscle cells was evident in different orders of the macular vasculature. The authors have demonstrated for the first time the cellular structure and topographic features of the macular microvasculature in human donor eyes.

Aggregation behavior of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow field-flow fractionation study.

PubMed

Astefanei, Alina; Núñez, Oscar; Galceran, Maria Teresa; Kok, Wim Th; Schoenmakers, Peter J

2015-10-01

In this work, the electrophoretic behavior of hydrophobic fullerenes [buckminsterfullerene (C60), C70, and N-methyl-fulleropyrrolidine (C60-pyrr)] and water-soluble fullerenes [fullerol (C60(OH)24); polyhydroxy small gap fullerene, hydrated (C120(OH)30); C60 pyrrolidine tris acid (C60-pyrr tris acid); and (1,2-methanofullerene C60)-61-carboxylic acid (C60CHCOOH)] in micellar electrokinetic capillary chromatography (MECC) was evaluated. The aggregation behavior of the water-soluble compounds in MECC at different buffer and sodium dodecyl sulfate (SDS) concentrations and pH values of the background electrolyte (BGE) was studied by monitoring the changes observed in the electrophoretic pattern of the peaks. Broad and distorted peaks that can be attributed to fullerene aggregation were obtained in MECC which became narrower and more symmetric by working at low buffer and SDS concentrations (below the critical micelle concentration, capillary zone electrophoresis (CZE) conditions). For the characterization of the suspected aggregates formed (size and shape), asymmetrical flow field-flow fractionation (AF4) and transmission electron microscopy (TEM) were used. The results showed that the increase in the buffer concentration promoted the aggregation of the particles, while the presence of SDS micelles revealed multiple peaks corresponding to particles of different aggregation degrees. Furthermore, MECC has been applied for the first time for the analysis of C60 in two different cosmetic products (i.e., anti-aging serum and facial mask).

Tapered capillary optics

DOEpatents

Hirsch, Gregory

1998-01-01

A metal or glass wire is etched with great precision into a very narrowly tapering cone which has the shape of the desired final capillary-optics bore. By controlling the rate of removal of the wire from an etchant bath, a carefully controlled taper is produced. A sensor measures the diameter of the wire as it leaves the surface of the etchant. This signal is used for feedback control of the withdrawal speed. The etched wire undergoes a treatment to produce an extremely low surface-roughness. The etched and smoothed wire is coated with the material of choice for optimizing the reflectivity of the radiation being focused. This could be a vacuum evaporation, sputtering, CVD or aqueous chemical process. The coated wire is either electroplated, built up with electroless plating, or encapsulated in a polymer cylinder such as epoxy to increase the diameter of the wire for easier handling and greater robustness. During this process, the wire is vertically oriented and tensioned to assure that the wire is absolutely straight. The coated and electroformed wire is bonded to a flat, rigid substrate and is then periodically segmented by cutting or etching a series of narrow slits or grooves into the wire. The wire is vertically oriented and tensioned during the bonding process to assure that it is straight. The original wire material is then chemically etched away through the slits or otherwise withdrawn to leave the hollow internal bore of the final tapered-capillary optical element.

Comparison of oxidative stress in four Tillandsia species exposed to cadmium.

PubMed

Kováčik, Jozef; Babula, Petr; Klejdus, Bořivoj; Hedbavny, Josef

2014-07-01

This is first study comparing four morphologically variable species of the genus Tillandsia and therefore various responses to the cadmium (Cd) action were expected. In accordance, Cd accumulation increased in order Tillandsia fasciculata < Tillandsia brachycaulos < Tillandsia pruinosa < Tillandsia capillaris, reaching 29.6 and 197.4 μg g(-1) DW in first and last species after watering with 2 μM Cd(2+) solution over 30 days. Fluorescence visualization of oxidative stress confirmed increase in ROS and especially elevation in hydroperoxides though no visible symptoms appeared on the plants. At the same time, nitric oxide generation and nitroso-glutathione depletion by Cd treatment were typically observed. Fluorescence staining of Cd using two dyes (PhenGreen and Leadmium) showed that Leadmium fits better with AAS quantification. Macro- and micro-nutrients were not considerably affected except for zinc. Reduced glutathione content was the highest in control T. fasciculata while oxidized glutathione in T. capillaris. Ascorbic acid amount revealed extreme quantitative differences among species and decreased in T. fasciculata only. Free amino acids accumulation was similar among species except for T. capillaris and Cd caused both depletion and increase but without high quantitative differences. Data are explanatively discussed in the context of limited literature related to oxidative stress in epiphytic plants and with general responses of plants to cadmium/heavy metals. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Selection of root-zone media for higher plant cultivation in space.

PubMed

Guo, Shuang-sheng; Ai, Wei-dang; Zhao, Cheng-jian; Han, Li-jun; Wang, Jian-xiao

2004-04-01

To investigate the cultivating effects of several mineral matters used as root-zone media for higher plant growth in space. Four kinds of artificial and natural mineral matters were used as plant root-zone media based on lots of investigation and analysis. Nutrient liquid was delivered into the media by a long capillary material, and roots of plants obtained nutrition and water from the media. The related parameters such as plant height and photosynthetic efficiency were measured and analyzed. The growing effect in a mixture of coarse and fine ceramic particles with equal quantity proportion was the best, that in fine ceramic particles was the second best, that in clinoptilolite particles was the third and that in diorite particles was the last. The mixture of coarse and fine ceramic particles with equal quantity possesses not only fine capillary action, but also good aerating ability, and therefore is capable of being utilized as an effective root-zone media for higher plants intended to be grown in space.

Fluid dynamics of two-dimensional pollination in Ruppia maritima

NASA Astrophysics Data System (ADS)

Musunuri, Naga; Bunker, Daniel; Pell, Susan; Pell, Fischer; Singh, Pushpendra

2016-11-01

The aim of this work is to understand the physics underlying the mechanisms of two-dimensional aquatic pollen dispersal, known as hydrophily. We observed two mechanisms by which the pollen released from male inflorescences of Ruppia maritima is adsorbed on a water surface: (i) inflorescences rise above the surface and after they mature their pollen mass falls onto the surface as clumps and disperses on the surface; (ii) inflorescences remain below the surface and produce air bubbles which carry their pollen mass to the surface where it disperses. In both cases dispersed pollen masses combined under the action of capillary forces to form pollen rafts. This increases the probability of pollination since the capillary force on a pollen raft towards a stigma is much larger than on a single pollen grain. The presence of a trace amount of surfactant can disrupt the pollination process so that the pollen is not transported or captured on the water surface. National Science Foundation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, Andrew M.; Kurecka, Patrick; Yim, Tsz Kwan

An X-ray fluorescence flow cytometer that can determine the total metal content of single cells has been developed. Capillary action or pressure was used to load cells into hydrophilic or hydrophobic capillaries, respectively. Once loaded, the cells were transported at a fixed vertical velocity past a focused X-ray beam. X-ray fluorescence was then used to determine the mass of metal in each cell. By making single-cell measurements, the population heterogeneity for metals in the µ M to m M concentration range on fL sample volumes can be directly measured, a measurement that is difficult using most analytical methods. This approachmore » has been used to determine the metal composition of 936 individual bovine red blood cells (bRBC), 31 individual 3T3 mouse fibroblasts (NIH3T3) and 18 Saccharomyces cerevisiae (yeast) cells with an average measurement frequency of ~4 cells min –1. These data show evidence for surprisingly broad metal distributions. Lastly, details of the device design, data analysis and opportunities for further sensitivity improvement are described.« less

Capillary electrophoretic analysis of flavonoids in single-styled hawthorn (Crataegus monogyna Jacq.) ethanolic extracts.

PubMed

Urbonaviciūte, A; Jakstas, V; Kornysova, O; Janulis, V; Maruska, A

2006-04-21

Flavonoids are an important group of natural compounds, which can prevent coronary heart disease and have antioxidant properties. Hawthorn is a well known and widely used medicinal plant due to its cardiotonic activity. Previous studies refer mostly to the HPLC analysis of the flavonoids: vitexin, quercetin, hyperoside, oligomeric procyanidins, which appear to be primarily responsible for the cardiac action of the plant. Aqueous ethanolic extracts of single-styled hawthorn (Crataegus monogyna Jacq., f.: Rosaceae Juss.) leaves and sprouts were analyzed by means of capillary zone electrophoresis (CZE). Influence of vegetation period on the extract qualitative composition and flavonoids quantities was evaluated. Sample preparation by extraction using different concentration of aqueous ethanol (40-96%, v/v) and the influence of extractant composition on the recovery of flavonoids are discussed in detail. The results obtained using CZE are compared to the results of spectrophotometric and HPLC analysis of the extracts. The effect of storage conditions of extracts (solar irradiation, temperature and duration) on degradation of flavonoids was investigated.

A novel method for the fabrication of microfluidic devices by photopolymerization of polymethylmethacrylate

NASA Astrophysics Data System (ADS)

Forstater, Jacob; Augustine, Brian; Hughes, Chris

2006-11-01

We have developed a new technique for the rapid fabrication of structures useful for microfluidic devices called micromolding by photopolymerization in capillaries (μ-PIC). The technique involves the replication of features from a silicon master in which features on the order of tens to hundreds of microns have been formed by crystallographic etching. The negative of the features is then transferred to a sheet of polymethylmethacrylate (PMMA) by placing the PMMA sheet over the silicon master and injecting a solution of methylmethacrylate monomer with a benzoin methyl ether photoinitiator. This solution is drawn between the PMMA and the silicon by capillary action forming a liquid layer that is no more than a few hundred microns thick. This liquid is then polymerized by exposure to ultraviolet light for less than a half hour. The features transferred in this manner have nearly identical surface structure and roughness. Analysis of these surfaces and structures by atomic force microscopy and scanning electron microscopy will be presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkov, N. B.; Zubarev, N. M., E-mail: nick@iep.uran.ru; Zubareva, O. V.

Exact solutions are obtained for the problem of an equilibrium configuration of an uncharged cylindrical jet of a conducting liquid in a transverse electric field. The transverse cross section of the jet moving between two planar electrodes is deformed under the action of electrostatic forces (capillary forces play a stabilizing role). According to the solutions obtained, the initially circular cross section of the jet may be significantly (formally, unboundedly) stretched along the lines of forces of the field, and the boundaries of the jet asymptotically approach the electrodes.

Wick for metal vapor laser

DOEpatents

Duncan, David B.

1992-01-01

An improved wick for a metal vapor laser is made of a refractory metal cylinder, preferably molybdenum or tungsten for a copper laser, which provides the wicking surface. Alternately, the inside surface of the ceramic laser tube can be metalized to form the wicking surface. Capillary action is enhanced by using wire screen, porous foam metal, or grooved surfaces. Graphite or carbon, in the form of chunks, strips, fibers or particles, is placed on the inside surface of the wick to reduce water, reduce metal oxides and form metal carbides.

Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

PubMed

Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

2011-12-23

Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum Dots Microstructured Optical Fiber for X-Ray Detection

NASA Technical Reports Server (NTRS)

DeHaven, Stan; Williams, Phillip; Burke, Eric

2015-01-01

Microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide are presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dot application technique are discussed.

Modelling the Transport of Nanoparticles under Blood Flow using an Agent-based Approach.

PubMed

Fullstone, Gavin; Wood, Jonathan; Holcombe, Mike; Battaglia, Giuseppe

2015-06-10

Blood-mediated nanoparticle delivery is a new and growing field in the development of therapeutics and diagnostics. Nanoparticle properties such as size, shape and surface chemistry can be controlled to improve their performance in biological systems. This enables modulation of immune system interactions, blood clearance profile and interaction with target cells, thereby aiding effective delivery of cargo within cells or tissues. Their ability to target and enter tissues from the blood is highly dependent on their behaviour under blood flow. Here we have produced an agent-based model of nanoparticle behaviour under blood flow in capillaries. We demonstrate that red blood cells are highly important for effective nanoparticle distribution within capillaries. Furthermore, we use this model to demonstrate how nanoparticle size can selectively target tumour tissue over normal tissue. We demonstrate that the polydispersity of nanoparticle populations is an important consideration in achieving optimal specificity and to avoid off-target effects. In future this model could be used for informing new nanoparticle design and to predict general and specific uptake properties under blood flow.

Ultrastructural study of spermatogenesis in Phoronopsis harmeri (Lophophorata, Phoronida)

NASA Astrophysics Data System (ADS)

Reunov, Arkadiy; Klepal, Waltraud

2004-02-01

The process of sperm development in Phoronopsis harmeri was studied by electron microscopy. Developing spermatogenical cells are aggregated around the capillaries of the haemal plexus. The spermatogonia, which are situated around the capillary walls of the caeca, are remarkable for the presence of germ-line vesicles and contain their centrioles near the cell membrane. The spermatocytes and spermatids are flagellated cells arranged in clusters. During spermiogenesis the basal body/flagellum complex migrates to the apical pole of the spermatid. The acrosome-like structure arises from material produced by the Golgi complex. It lacks a surrounding membrane and has a fibrillar content. The nucleus elongates and the condensation of chromatin is caused by an activation of 'initiation centres'. The late spermatid and the spermatozoon appear as two-armed 'V'-shaped cells in which one arm contains the nucleus and posteriorly located mitochondria, and the other one is the axoneme. Spermatogenesis of P. harmeri is an interesting example of gamete differentiation where advanced sperm structure is combined with a plesiomorphic pattern of sperm development characterized as 'flagellate spermatogenesis'.

Ultrastructural study of spermatogenesis in Phoronopsis harmeri (Lophophorata, Phoronida)

NASA Astrophysics Data System (ADS)

Reunov, Arkadiy; Klepal, Waltraud

The process of sperm development in Phoronopsis harmeri was studied by electron microscopy. Developing spermatogenical cells are aggregated around the capillaries of the haemal plexus. The spermatogonia, which are situated around the capillary walls of the caeca, are remarkable for the presence of germ-line vesicles and contain their centrioles near the cell membrane. The spermatocytes and spermatids are flagellated cells arranged in clusters. During spermiogenesis the basal body/flagellum complex migrates to the apical pole of the spermatid. The acrosome-like structure arises from material produced by the Golgi complex. It lacks a surrounding membrane and has a fibrillar content. The nucleus elongates and the condensation of chromatin is caused by an activation of 'initiation centres'. The late spermatid and the spermatozoon appear as two-armed 'V'-shaped cells in which one arm contains the nucleus and posteriorly located mitochondria, and the other one is the axoneme. Spermatogenesis of P. harmeri is an interesting example of gamete differentiation where advanced sperm structure is combined with a plesiomorphic pattern of sperm development characterized as 'flagellate spermatogenesis'.

Reproducible preparation of nanospray tips for capillary electrophoresis coupled to mass spectrometry using 3D printed grinding device.

PubMed

Tycova, Anna; Prikryl, Jan; Foret, Frantisek

2016-04-01

The use of high quality fused silica capillary nanospray tips is critical for obtaining reliable and reproducible electrospray/MS data; however, reproducible laboratory preparation of such tips is a challenging task. In this work, we report on the design and construction of low-cost grinding device assembled from 3D printed and commercially easily available components. Detailed description and characterization of the grinding device is complemented by freely accessible files in stl and skp format allowing easy laboratory replication of the device. The process of sharpening is aimed at achieving maximal symmetricity, surface smoothness and repeatability of the conus shape. Moreover, the presented grinding device brings possibility to fabricate the nanospray tips of desired dimensions regardless of the commercial availability. On several samples of biological nature (reserpine, rabbit plasma, and the mixture of three aminoacids), performance of fabricated tips is shown on CE coupled to MS analysis. The special interest is paid to the effect of tip sharpness. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Natural Length Scales Shape Liquid Phase Continuity in Unsaturated Flows

NASA Astrophysics Data System (ADS)

Assouline, S.; Lehmann, P. G.; Or, D.

2015-12-01

Unsaturated flows supporting soil evaporation and internal drainage play an important role in various hydrologic and climatic processes manifested at a wide range of scales. We study inherent natural length scales that govern these flow processes and constrain the spatial range of their representation by continuum models. These inherent length scales reflect interactions between intrinsic porous medium properties that affect liquid phase continuity, and the interplay among forces that drive and resist unsaturated flow. We have defined an intrinsic length scale for hydraulic continuity based on pore size distribution that controls soil evaporation dynamics (i.e., stage 1 to stage 2 transition). This simple metric may be used to delineate upper bounds for regional evaporative losses or the depth of soil-atmosphere interactions (in the absence of plants). A similar length scale governs the dynamics of internal redistribution towards attainment of field capacity, again through its effect on hydraulic continuity in the draining porous medium. The study provides a framework for guiding numerical and mathematical models for capillary flows across different scales considering the necessary conditions for coexistence of stationarity (REV), hydraulic continuity and intrinsic capillary gradients.

Acidic methanolysis v. alkaline saponification in gas chromatographic characterization of mycobacteria: differentiation between Mycobacterium avium-intracellulare and Mycobacterium gastri.

PubMed

Larsson, L

1983-08-01

Mycobacterium avium-intracellulare and M.gastri were analyzed with capillary gas chromatography after each strain had been subjected to acidic methanolysis or to alkaline saponification followed by methylation. Prominent peaks of myristic, palmitoleic, palmitic, oleic, stearic and tuberculostearic acids were found in the chromatograms of both species, whereas 2-octadecanol and 2-eicosanol were detected only in M. avium-intracellulare. In initial runs, both of the derivatization principles yielded virtually identical chromatograms for a given strain. After repeated injections of extracts from alkaline saponification, however, the alcohol peaks showed pronounced tailing and finally almost disappeared from the chromatograms. This disadvantage, which was not observed when only acid methanolysis was used, could be overcome with trifluoroacetylation. Restored peak shape of the underivatized alcohols could be achieved by washing the cross-linked stationary phase in the capillary tubing with organic solvents. The study demonstrated the importance of conditions which enable separation of 2-octadecanol and 2-eicosanol when gas chromatography is used for species identification of mycobacteria.

Curvature-driven capillary migration and assembly of rod-like particles

PubMed Central

Cavallaro, Marcello; Botto, Lorenzo; Lewandowski, Eric P.; Wang, Marisa; Stebe, Kathleen J.

2011-01-01

Capillarity can be used to direct anisotropic colloidal particles to precise locations and to orient them by using interface curvature as an applied field. We show this in experiments in which the shape of the interface is molded by pinning to vertical pillars of different cross-sections. These interfaces present well-defined curvature fields that orient and steer particles along complex trajectories. Trajectories and orientations are predicted by a theoretical model in which capillary forces and torques are related to Gaussian curvature gradients and angular deviations from principal directions of curvature. Interface curvature diverges near sharp boundaries, similar to an electric field near a pointed conductor. We exploit this feature to induce migration and assembly at preferred locations, and to create complex structures. We also report a repulsive interaction, in which microparticles move away from planar bounding walls along curvature gradient contours. These phenomena should be widely useful in the directed assembly of micro- and nanoparticles with potential application in the fabrication of materials with tunable mechanical or electronic properties, in emulsion production, and in encapsulation. PMID:22184218

Vascular development in the vertebrate pancreas

PubMed Central

Azizoglu, D. Berfin; Chong, Diana C.; Villasenor, Alethia; Magenheim, Judith; Barry, David M.; Lee, Simon; Marty-Santos, Leilani; Fu, Stephen; Dor, Yuval; Cleaver, Ondine

2016-01-01

The vertebrate pancreas is comprised of a highly branched tubular epithelium, which is intimately associated with an extensive and specialized vasculature. While we know a great deal about basic vascular anatomy of the adult pancreas, as well as islet capillaries, surprisingly little is known about the ontogeny of its blood vessels. Here, we analyze development of the pancreatic vasculature in the mouse embryo. We show that pancreatic epithelial branches intercalate with the fine capillary plexus of the surrounding pancreatic mesenchyme. Endothelial cells (ECs) within this mesenchyme are heterogeneous from the onset of organogenesis. Pancreatic arteries take shape before veins, in a manner analogous to early embryonic vessels. The main central artery forms during mid-gestation, as a result of vessel coalescence and remodeling of a vascular plexus. In addition, we show that vessels in the forming pancreas display a predictable architecture that is dependent on VEGF signaling. Over-expression of VEGF disrupts vascular patterning and arteriovenous differentiation within the developing pancreas. This study constitutes a first-time cellular and molecular characterization of pancreatic blood vessels, as they coordinately grow along with the pancreatic epithelium. PMID:27789228

Simplified transient isotachophoresis/capillary gel electrophoresis method for highly sensitive analysis of polymerase chain reaction samples on a microchip with laser-induced fluorescence detection.

PubMed

Liu, Dayu; Ou, Ziyou; Xu, Mingfei; Wang, Lihui

2008-12-19

We present a sensitive, simple and robust on-chip transient isotachophoresis/capillary gel electrophoresis (tITP/CGE) method for the analysis of polymerase chain reaction (PCR) samples. Using chloride ions in the PCR buffer and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) in the background electrolyte, respectively, as the leading and terminating electrolytes, the tITP preconcentration was coupled with CGE separation with double-T shaped channel network. The tITP/CGE separation was carried out with a single running buffer. The separation process involved only two steps that were performed continuously with the sequential switching of four voltage outputs. The tITP/CGE method showed an analysis time and a separation efficiency comparable to those of standard CGE, while the signal intensity was enhanced by factors of over 20. The limit of detection of the chip-based tITP/CGE method was estimated to be 1.1 ng/mL of DNA in 1x PCR buffer using confocal fluorescence detection following 473 nm laser excitation.

Tortuous Microvessels Contribute to Wound Healing via Sprouting Angiogenesis.

PubMed

Chong, Diana C; Yu, Zhixian; Brighton, Hailey E; Bear, James E; Bautch, Victoria L

2017-10-01

Wound healing is accompanied by neoangiogenesis, and new vessels are thought to originate primarily from the microcirculation; however, how these vessels form and resolve during wound healing is poorly understood. Here, we investigated properties of the smallest capillaries during wound healing to determine their spatial organization and the kinetics of formation and resolution. We used intravital imaging and high-resolution microscopy to identify a new type of vessel in wounds, called tortuous microvessels. Longitudinal studies showed that tortuous microvessels increased in frequency after injury, normalized as the wound healed, and were closely associated with the wound site. Tortuous microvessels had aberrant cell shapes, increased permeability, and distinct interactions with circulating microspheres, suggesting altered flow dynamics. Moreover, tortuous microvessels disproportionately contributed to wound angiogenesis by sprouting exuberantly and significantly more frequently than nearby normal capillaries. A new type of transient wound vessel, tortuous microvessels, sprout dynamically and disproportionately contribute to wound-healing neoangiogenesis, likely as a result of altered properties downstream of flow disturbances. These new findings suggest entry points for therapeutic intervention. © 2017 The Authors.

Influence of Air Discontinuity and Wall Effects on the Measurements of Hydraulic Parameters Under Dynamic Conditions

NASA Astrophysics Data System (ADS)

Looms, M. C.; Jensen, K. H.; Wildenschild, D.; Christensen, B. S.; Gudbjerg, J.

2003-12-01

Both dynamic (one-step) and semi-static (syringe pump) outflow experiments were carried out in the lab to test whether the resulting retention characteristics differed according to experiment type. Three sands of varying uniformity and coarseness were packed in a cylindrical sample holder. Compressed air was used to control the air phase pressure, while water was allowed to drain at atmospheric pressure from the outlet at the bottom of the sample. During the outflow experiments the capillary pressure was measured within the sample holder using a tensiometer connected to a pressure transducer. A medical CT-scanner was used to visualize and quantify the outflow patterns within the sand matrix during selected outflow experiments. Positive vertical shifts in capillary pressure during dynamic experiments were found in all three sand types at saturations close to porosity. The size and shape of the shifts corresponded with the dynamic effects found in previous work on the topic. Furthermore, the shifts were slightly greater in the coarsest and most uniform sand type. Numerical simulations of the one-step experiments using HYDRUS1D and T2VOC showed, however, that one of the basic assumptions when calculating the capillary pressure was most likely violated. The air phase could not be considered to be continuous at all times, and assuming this to be the case would result in positive shifts of the retention curves when running T2VOC. The results of using the CT-scanner showed the importance of achieving a homogeneous packing, since the investigated sand packing turned out to have an area at the edge of the sample holder with a higher porosity. This caused the edge to control the initial drainage. Therefore, the data collected at high saturations could not be expected to adequately describe the hydraulic properties of the inner sand. We also found that the time at which the inner sand commenced drainage coincided with a jump in capillary pressure for the resulting measured retention curve.

Expression of receptor-type protein tyrosine phosphatase in developing and adult renal vasculature

PubMed Central

Takahashi, Keiko; Kim, Rachel; Lauhan, Colette; Park, Yuna; Nguyen, Nghiep G.; Vestweber, Dietmar; Dominguez, Melissa G.; Valenzuela, David M.; Murphy, Andrew J.; Yancopoulos, George D.; Gale, Nicholas W.; Takahashi, Takamune

2017-01-01

Renal vascular development is a coordinated process that requires ordered endothelial cell proliferation, migration, intercellular adhesion, and morphogenesis. In recent decades, studies have defined the pivotal role of endothelial receptor tyrosine kinases (RPTKs) in the development and maintenance of renal vasculature. However, the expression and the role of receptor tyrosine phosphatases (RPTPs) in renal endothelium are poorly understood, though coupled and counterbalancing roles of RPTKs and RPTPs are well defined in other systems. In this study, we evaluated the promoter activity and immunolocalization of two endothelial RPTPs, VE-PTP and PTPμ, in developing and adult renal vasculature using the heterozygous LacZ knock-in mice and specific antibodies. In adult kidneys, both VE-PTP and PTPμ were expressed in the endothelium of arterial, glomerular, and medullary vessels, while their expression was highly limited in peritubular capillaries and venous endothelium. VE-PTP and PTPμ promoter activity was also observed in medullary tubular segments in adult kidneys. In embryonic (E12.5, E13.5, E15.5, E17.5) and postnatal (P0, P3, P7) kidneys, these RPTPs were expressed in ingrowing renal arteries, developing glomerular microvasculature (as early as the S-shaped stage), and medullary vessels. Their expression became more evident as the vasculatures matured. Peritubular capillary expression of VE-PTP was also noted in embryonic and postnatal kidneys. Compared to VE-PTP, PTPμ immunoreactivity was relatively limited in embryonic and neonatal renal vasculature and evident immunoreactivity was observed from the P3 stage. These findings indicate 1) VE-PTP and PTPμ are expressed in endothelium of arterial, glomerular, and medullary renal vasculature, 2) their expression increases as renal vascular development proceeds, suggesting that these RPTPs play a role in maturation and maintenance of these vasculatures, and 3) peritubular capillary VE-PTP expression is down-regulated in adult kidneys, suggesting a role of VE-PTP in the development of peritubular capillaries. PMID:28542220

Uniform Laser Excitation And Detection In Capillary Array Electrophoresis System And Method.

DOEpatents

Li, Qingbo; Zhou, Songsan; Liu, Changsheng

2003-10-07

A capillary electrophoresis system comprises capillaries positioned in parallel to each other forming a plane. The capillaries are configured to allow samples to migrate. A light source is configured to illuminate the capillaries and the samples therein. This causes the samples to emit light. A lens is configured to receive the light emitted by the samples and positioned directly over a first group of the capillaries and obliquely over a second group of the capillaries. The light source is further configured to illuminate the second group of capillaries more than the first group of the capillaries such that amount of light received by the lens from the first group of capillaries is substantially identical to amount of light received from the second group of capillaries when an identical amount of the samples is migrating through the first and second group capillaries.

Capillary electrophoresis electrospray ionization mass spectrometry interface

DOEpatents

Smith, Richard D.; Severs, Joanne C.

1999-01-01

The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

Human action recognition based on point context tensor shape descriptor

NASA Astrophysics Data System (ADS)

Li, Jianjun; Mao, Xia; Chen, Lijiang; Wang, Lan

2017-07-01

Motion trajectory recognition is one of the most important means to determine the identity of a moving object. A compact and discriminative feature representation method can improve the trajectory recognition accuracy. This paper presents an efficient framework for action recognition using a three-dimensional skeleton kinematic joint model. First, we put forward a rotation-scale-translation-invariant shape descriptor based on point context (PC) and the normal vector of hypersurface to jointly characterize local motion and shape information. Meanwhile, an algorithm for extracting the key trajectory based on the confidence coefficient is proposed to reduce the randomness and computational complexity. Second, to decrease the eigenvalue decomposition time complexity, a tensor shape descriptor (TSD) based on PC that can globally capture the spatial layout and temporal order to preserve the spatial information of each frame is proposed. Then, a multilinear projection process is achieved by tensor dynamic time warping to map the TSD to a low-dimensional tensor subspace of the same size. Experimental results show that the proposed shape descriptor is effective and feasible, and the proposed approach obtains considerable performance improvement over the state-of-the-art approaches with respect to accuracy on a public action dataset.

Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides

NASA Astrophysics Data System (ADS)

Fiedler, Kevin; Troian, Sandra

The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Evolution of the Shape of Detached GeSi Crystals in Microgravity

NASA Technical Reports Server (NTRS)

Volz, M. P.; Mazuruk, K.

2013-01-01

A series of GeSi crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. An objective of these experiments is to understand the mechanisms of detached Bridgman growth, a process in which a gap exists between the growing semiconductor crystal and the crucible wall. Crystals grown without wall contact have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. Numerical calculations are used to determine the conditions in which a gap can exist. According to crystal shape stability theory, only some of these gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. Depending on the initial conditions and growth parameters, the crystal shape will evolve towards the crucible wall, towards a stable gap width, or towards the center of the crucible, collapsing the meniscus.

Nonlinear deformations of microcapsules in elongation flow

NASA Astrophysics Data System (ADS)

Deschamps, Julien; de Loubens, Clément; Boedec, Gwenn; Georgelin, Marc; Leonetti, Marc; Soft Matter; Biophysics Group Team

2014-11-01

Soft microcapsules are drops bounded by a thin elastic shell made of cross-linked proteins. They have numerous applications for drug delivery in bioengineering, pharmaceutics and medicine, where their mechanical stability and their dynamics under flow are crucial. They can also be used as red blood cells models. Here, we investigate the mechanical behaviour of microcapsules made of albumine in strong elongational flow, up to a stretching of 180% just before breaking. The set-up allows us to visualize the deformed shape in the two perpendicular main fields of view, to manage high capillary number and to manipulate soft microcapsules. The steady-state shape of a capsule in the planar elongational flow is non-axisymmetric. In each cross section, the shape is an ellipse but with different small axis which vary in opposite sense with the stretching. Whatever the degree of cross-linking and the size of the capsules, the deformations followed the same master-curve. Comparisons between numerical predictions and experimental results permit to conclude unambiguously that the more properly strain-energy model of membrane is the generalized Hooke model.

Solution of the Inverse Problem for Thin Film Patterning by Electrohydrodynamic Forces

NASA Astrophysics Data System (ADS)

Zhou, Chengzhe; Troian, Sandra

2017-11-01

Micro- and nanopatterning techniques for applications ranging from optoelectronics to biofluidics have multiplied in number over the past decade to include adaptations of mature technologies as well as novel lithographic techniques based on periodic spatial modulation of surface stresses. We focus here on one such technique which relies on shape changes in nanofilms responding to a patterned counter-electrode. The interaction of a patterned electric field with the polarization charges at the liquid interface causes a patterned electrostatic pressure counterbalanced by capillary pressure which leads to 3D protrusions whose shape and evolution can be terminated as needed. All studies to date, however, have investigated the evolution of the liquid film in response to a preset counter-electrode pattern. In this talk, we present solution of the inverse problem for the thin film equation governing the electrohydrodynamic response by treating the system as a transient control problem. Optimality conditions are derived and an efficient corresponding solution algorithm is presented. We demonstrate such implementation of film control to achieve periodic, free surface shapes ranging from simple circular cap arrays to more complex square and sawtooth patterns.

Space for action: How practitioners influence environmental assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kågström, Mari, E-mail: mari.kagstrom@slu.se; Richardson, Tim, E-mail: tim.richardson@nmbu.no

2015-09-15

Highlights: • The concept of ‘space for action’ offers an important new lens on EA practice. • Focuses on the relation between practitioner's understanding and their actions • Environmental assessment practice is decisively shaped by practitioners. • Practitioners may underestimate their potential to make a difference. • Contributes to understanding change in the environmental assessment field. This article contributes to understanding of how change occurs in the field of environmental assessment (EA). It argues that the integration of new issues in EA, such as human health, is significantly influenced by how practitioners' understandings shape their actions, and by what happensmore » when those, possibly different, interpretations of appropriate action are acted out. The concept of space for action is developed as a means of investigating this relation between understanding and action. Frame theory is also used, to develop a sharper focus on how ‘potential spaces for action’ are created, what these imply for (individuals') preferred choices and actions in certain situations, and what happens in practice when these are acted out and ‘actual spaces for action’ are created. This novel approach is then applied in a Swedish case study of transport planning. The analysis reveals the important work done by practitioners, revealing just how EA practice is decisively shaped by practitioners. Analysis of practice using the lens of spaces for action offers an important new perspective in understanding how the field adapts to new challenges.« less

Diameter-dependent wetting of tungsten disulfide nanotubes

PubMed Central

Goldbart, Ohad; Cohen, Sidney R.; Kaplan-Ashiri, Ifat; Glazyrina, Polina; Wagner, H. Daniel; Enyashin, Andrey; Tenne, Reshef

2016-01-01

The simple process of a liquid wetting a solid surface is controlled by a plethora of factors—surface texture, liquid droplet size and shape, energetics of both liquid and solid surfaces, as well as their interface. Studying these events at the nanoscale provides insights into the molecular basis of wetting. Nanotube wetting studies are particularly challenging due to their unique shape and small size. Nonetheless, the success of nanotubes, particularly inorganic ones, as fillers in composite materials makes it essential to understand how common liquids wet them. Here, we present a comprehensive wetting study of individual tungsten disulfide nanotubes by water. We reveal the nature of interaction at the inert outer wall and show that remarkably high wetting forces are attained on small, open-ended nanotubes due to capillary aspiration into the hollow core. This study provides a theoretical and experimental paradigm for this intricate problem. PMID:27856759

Spontaneous Spreading of a Droplet: The Role of Solid Continuity and Advancing Contact Angle.

PubMed

Jiang, Youhua; Sun, Yujin; Drelich, Jaroslaw W; Choi, Chang-Hwan

2018-05-01

Spontaneous spreading of a droplet on a solid surface is poorly understood from a macroscopic level down to a molecular level. Here, we investigate the effect of surface topography and wettability on spontaneous spreading of a water droplet. Spreading force is measured for a suspended droplet that minimizes interference of kinetic energy in the spontaneous spreading during its contact with solid surfaces of discontinuous (pillar) and continuous (pore) patterns with various shapes and dimensions. Results show that a droplet cannot spread spontaneously on pillared surfaces regardless of their shapes or dimensions because of the solid discontinuity. On the contrary, a droplet on pored surfaces can undergo spontaneous spreading whose force increases with a decrease in the advancing contact angle. Theoretical models based on both the system free energy and capillary force along the contact line validate the direct and universal dependency of the spontaneous spreading force on the advancing contact angle.

Jet atomization and cavitation induced by interactions between focused ultrasound and a water surfacea)

NASA Astrophysics Data System (ADS)

Tomita, Y.

2014-09-01

Atomization of a jet produced by the interaction of 1 MHz focused ultrasound with a water surface was investigated using high-speed photography. Viewing various aspects of jet behavior, threshold conditions were obtained necessary for water surface elevation and jet breakup, including drop separation and spray formation. In addition, the position of drop atomization, where a single drop separates from the tip of a jet without spraying, showed good correlation with the jet Weber number. For a set of specified conditions, multiple beaded water masses were formed, moving upwards to produce a vigorous jet. Cavitation phenomena occurred near the center of the primary drop-shaped water mass produced at the leading part of the jet; this was accompanied by fine droplets at the neck between the primary and secondary drop-shaped water masses, due to the collapse of capillary waves.

Electrosprayed synthesis of red-blood-cell-like particles with dual modality for magnetic resonance and fluorescence imaging.

PubMed

Hayashi, Koichiro; Ono, Kenji; Suzuki, Hiromi; Sawada, Makoto; Moriya, Makoto; Sakamoto, Wataru; Yogo, Toshinobu

2010-11-05

Red blood cells (RBCs) are able to avoid filtration in the spleen to prolong their half-time in the body because of their flexibility and unique shape, or a concave disk with diameter of some 10 μm. In addition, they can flow through capillary blood vessels, which are smaller than the diameter of RBCs, by morphing into a parachute-like shape. In this study, flexible RBC-like polymer particles are synthesized by electrospraying based on electrospinning. Furthermore, magnetite nanoparticles and fluorescent dye are encapsulated in the particles via in situ hydrolysis of an iron-organic compound in the presence of celluloses. The superparamagnetic behavior of the particles is confirmed by low-temperature magnetic measurements. The particles exhibited not only a dark contrast in magnetic resonance imaging (MRI), but also effective fluorescence. The RBC-like particles with flexibility are demonstrated to have a dual-modality for MRI and fluorescence imaging.

Spatial Working Memory Is Necessary for Actions to Guide Thought

ERIC Educational Resources Information Center

Thomas, Laura E.

2013-01-01

Directed actions can play a causal role in cognition, shaping thought processes. What drives this cross-talk between action and thought? I investigated the hypothesis that representations in spatial working memory mediate interactions between directed actions and problem solving. Participants attempted to solve an insight problem while…

There may be Fermi Energy levels in the hollow interiors of Nanotubes that would allow for a type of Quantum

NASA Astrophysics Data System (ADS)

Kriske, Richard

2011-04-01

There may be Fermi Energy levels that would allow for easy travel by Atoms, Molecules and Particles, in the hollow interior of Nanotubes. This may result in a Quantum Mechanical explaination of Capillary Action, and it may result in devices could take advantage of the idea that it takes no energy to rise in a Capillary tube, only in leaving it. This no-energy conjecture of Capillarity sounds very much like the idea that Electrons in obitals lose no Energy staying in orbit, only in changing orbits.It is this conjecture that may reveal that a Fermi Energy state is essentially in a weak orbital. This weak orbital could be exploited to store Anti-matter for instance. More profoundly it clearly shows how the Quantum Mechanical states meld smoothly into Classical Physics. It also reveals how extremely efficient Classical Machines could be constructed to take advantage of this spontaneous action. Say a tube could be designed to nudge electrons out of a weak obital in one place, sent down the tube (which is another weak orbital) and deposited in a weak orbital of another very distant Atom, apparently with little or perhaps no work being done, as long as the orbitals are the same energy. This may already exist in some Biological systems. Although more experimentation is needed, this would be the breakthrough that is needed to unify Classical and Quantum Mechanics.

The Stanford Nutrition Action Program: a dietary fat intervention for low-literacy adults.

PubMed Central

Howard-Pitney, B; Winkleby, M A; Albright, C L; Bruce, B; Fortmann, S P

1997-01-01

OBJECTIVES: This study was undertaken to test the effectiveness of the Stanford Nutrition Action Program, an experimental trial to reduce dietary fat intake among low-literacy, low-income adults. METHODS: Twenty-four paired adult education classes (351 participants, 85% women, mean age = 31 years) were randomly assigned to receive a newly developed dietary fat curriculum (the Stanford Nutrition Action Program) or an existing general nutrition curriculum. Food frequency and nutrition-related data, body mass index, and capillary blood cholesterol were collected at baseline and at two postintervention follow-ups. RESULTS: The Stanford Nutrition Action Program classes showed significantly greater net improvements in nutrition knowledge (+7.7), attitudes (/0.2), and self-efficacy (-0.2) than the general nutrition classes; they also showed significantly greater reductions in the percentage of calories from total (-2.3%) and saturated (-0.9%) fat. There were no significant differences in body mass index or blood cholesterol. All positive intervention effects were maintained for 3 months postintervention. CONCLUSIONS: The Stanford Nutrition Action Program curriculum, tailored to the cultural, economic, and learning needs of low-literacy, low-income adults, was significantly more effective in achieving fat-related nutritional changes than the general nutrition curriculum. PMID:9431286

Myocardial Drug Distribution Generated from Local Epicardial Application: Potential Impact of Cardiac Capillary Perfusion in a Swine Model Using Epinephrine

PubMed Central

Maslov, Mikhail Y.; Edelman, Elazer R.; Pezone, Matthew J.; Wei, Abraham E.; Wakim, Matthew G.; Murray, Michael R.; Tsukada, Hisashi; Gerogiannis, Iraklis S.; Groothuis, Adam; Lovich, Mark A.

2014-01-01

Prior studies in small mammals have shown that local epicardial application of inotropic compounds drives myocardial contractility without systemic side effects. Myocardial capillary blood flow, however, may be more significant in larger species than in small animals. We hypothesized that bulk perfusion in capillary beds of the large mammalian heart enhances drug distribution after local release, but also clears more drug from the tissue target than in small animals. Epicardial (EC) drug releasing systems were used to apply epinephrine to the anterior surface of the left heart of swine in either point-sourced or distributed configurations. Following local application or intravenous (IV) infusion at the same dose rates, hemodynamic responses, epinephrine levels in the coronary sinus and systemic circulation, and drug deposition across the ventricular wall, around the circumference and down the axis, were measured. EC delivery via point-source release generated transmural epinephrine gradients directly beneath the site of application extending into the middle third of the myocardial thickness. Gradients in drug deposition were also observed down the length of the heart and around the circumference toward the lateral wall, but not the interventricular septum. These gradients extended further than might be predicted from simple diffusion. The circumferential distribution following local epinephrine delivery from a distributed source to the entire anterior wall drove drug toward the inferior wall, further than with point-source release, but again, not to the septum. This augmented drug distribution away from the release source, down the axis of the left ventricle, and selectively towards the left heart follows the direction of capillary perfusion away from the anterior descending and circumflex arteries, suggesting a role for the coronary circulation in determining local drug deposition and clearance. The dominant role of the coronary vasculature is further suggested by the elevated drug levels in the coronary sinus effluent. Indeed, plasma levels, hemodynamic responses, and myocardial deposition remote from the point of release were similar following local EC or IV delivery. Therefore, the coronary vasculature shapes the pharmacokinetics of local myocardial delivery of small catecholamine drugs in large animal models. Optimal design of epicardial drug delivery systems must consider the underlying bulk capillary perfusion currents within the tissue to deliver drug to tissue targets and may favor therapeutic molecules with better potential retention in myocardial tissue. PMID:25234821

Micro-X-ray fluorescence spectrometer with x-ray single bounce metallic capillary optics for light element analysis (Conference Presentation)

NASA Astrophysics Data System (ADS)

Mroczka, Robert; Żukociński, Grzegorz; Łopucki, Rafał

2017-05-01

In the last 20 years, , due to the rapid development of X-ray optics, micro X-ray fluorescence spectrometry (micro-XRF) has become a powerful tool to determine the spatial distribution of major, minor, and trace elements within a sample. Micro-X-ray fluorescence (micro-XRF) spectrometers for light element analysis (6 <= Z <= 14) using glass polycapillary optics are usually designed and applied to confocal geometry. Two such X-ray optics systems are used in this setup. The first one focuses the primary beam on the sample; the second restricts the field of view of the detector. In order to be able to analyze a wider range of elements especialy with (6 <= Z <= 14), both sample and detector are under vacuum. Depth resolution varies between 100 μm at 1 keV fluorescence energy (Na-Kα) and 30 μm for 17.5 keV (Mo-Kα) [1,2]. In order to improve resolution at energies below 9 keV, our group designed similar spectrometer (in cooperation with PREVAC) but instead of primary polycapillary optics we applied single bounce metallic capillaries optics , designed and manufactured in our Laboratory. The vacuum chumber is currently under construction and is expected to be fully operational in September this year. Single bounce gold capillaries with elliptic internal shape have recently been redesigned and developed in our Laboratory. Surface roughness was reduced up to 0.5 nm and slope error to 0.3 mrad. For these capillaries an expected depth resolution varies from 3 μm (1 keV) and 10 µm for 9 keV (Cu-Kα). The spectrometer equipped with gold capillaries offers the possibility of elemental analysis with better depth resolution than is offerred by glass polycapillaries at energies below 9 keV. Furthermore, we will compare the capabilities and limitations of this spectrometer with others, that use laboratory and/or synchrotron sources. Acknowledgments: This work was supported and co-funded by the European Union as part of the Operational Programme Development of Eastern Poland for 2007-2013, Priority I Innovative Economy, Measure I.3. Support for Innovations and The National Centre for Research and Development, Project no. TANGO1,267102/NCBR/2015

Laser illumination of multiple capillaries that form a waveguide

DOEpatents

Dhadwal, Harbans S.; Quesada, Mark A.; Studier, F. William

1998-08-04

A system and method are disclosed for efficient laser illumination of the interiors of multiple capillaries simultaneously, and collection of light emitted from them. Capillaries in a parallel array can form an optical waveguide wherein refraction at the cylindrical surfaces confines side-on illuminating light to the core of each successive capillary in the array. Methods are provided for determining conditions where capillaries will form a waveguide and for assessing and minimizing losses due to reflection. Light can be delivered to the arrayed capillaries through an integrated fiber optic transmitter or through a pair of such transmitters aligned coaxially at opposite sides of the array. Light emitted from materials within the capillaries can be carried to a detection system through optical fibers, each of which collects light from a single capillary, with little cross talk between the capillaries. The collection ends of the optical fibers can be in a parallel array with the same spacing as the capillary array, so that the collection fibers can all be aligned to the capillaries simultaneously. Applicability includes improving the efficiency of many analytical methods that use capillaries, including particularly high-throughput DNA sequencing and diagnostic methods based on capillary electrophoresis.

Laser illumination of multiple capillaries that form a waveguide

DOEpatents

Dhadwal, H.S.; Quesada, M.A.; Studier, F.W.

1998-08-04

A system and method are disclosed for efficient laser illumination of the interiors of multiple capillaries simultaneously, and collection of light emitted from them. Capillaries in a parallel array can form an optical waveguide wherein refraction at the cylindrical surfaces confines side-on illuminating light to the core of each successive capillary in the array. Methods are provided for determining conditions where capillaries will form a waveguide and for assessing and minimizing losses due to reflection. Light can be delivered to the arrayed capillaries through an integrated fiber optic transmitter or through a pair of such transmitters aligned coaxially at opposite sides of the array. Light emitted from materials within the capillaries can be carried to a detection system through optical fibers, each of which collects light from a single capillary, with little cross talk between the capillaries. The collection ends of the optical fibers can be in a parallel array with the same spacing as the capillary array, so that the collection fibers can all be aligned to the capillaries simultaneously. Applicability includes improving the efficiency of many analytical methods that use capillaries, including particularly high-throughput DNA sequencing and diagnostic methods based on capillary electrophoresis. 35 figs.

TRH regulates action potential shape in cerebral cortex pyramidal neurons.

PubMed

Rodríguez-Molina, Víctor; Patiño, Javier; Vargas, Yamili; Sánchez-Jaramillo, Edith; Joseph-Bravo, Patricia; Charli, Jean-Louis

2014-07-07

Thyrotropin releasing hormone (TRH) is a neuropeptide with a wide neural distribution and a variety of functions. It modulates neuronal electrophysiological properties, including resting membrane potential, as well as excitatory postsynaptic potential and spike frequencies. We explored, with whole-cell patch clamp, TRH effect on action potential shape in pyramidal neurons of the sensorimotor cortex. TRH reduced spike and after hyperpolarization amplitudes, and increased spike half-width. The effect varied with dose, time and cortical layer. In layer V, 0.5µM of TRH induced a small increase in spike half-width, while 1 and 5µM induced a strong but transient change in spike half-width, and amplitude; after hyperpolarization amplitude was modified at 5µM of TRH. Cortical layers III and VI neurons responded intensely to 0.5µM TRH; layer II neurons response was small. The effect of 1µM TRH on action potential shape in layer V neurons was blocked by G-protein inhibition. Inhibition of the activity of the TRH-degrading enzyme pyroglutamyl peptidase II (PPII) reproduced the effect of TRH, with enhanced spike half-width. Many cortical PPII mRNA+ cells were VGLUT1 mRNA+, and some GAD mRNA+. These data show that TRH regulates action potential shape in pyramidal cortical neurons, and are consistent with the hypothesis that PPII controls its action in this region. Copyright © 2014 Elsevier B.V. All rights reserved.

Upscaling gas permeability in tight-gas sandstones

NASA Astrophysics Data System (ADS)

Ghanbarian, B.; Torres-Verdin, C.; Lake, L. W.; Marder, M. P.

2017-12-01

Klinkenberg-corrected gas permeability (k) estimation in tight-gas sandstones is essential for gas exploration and production in low-permeability porous rocks. Most models for estimating k are a function of porosity (ϕ), tortuosity (τ), pore shape factor (s) and a characteristic length scale (lc). Estimation of the latter, however, has been the subject of debate in the literature. Here we invoke two different upscaling approaches from statistical physics: (1) the EMA and (2) critical path analysis (CPA) to estimate lc from pore throat-size distribution derived from mercury intrusion capillary pressure (MICP) curve. τ is approximated from: (1) concepts of percolation theory and (2) formation resistivity factor measurements (F = τ/ϕ). We then estimate k of eighteen tight-gas sandstones from lc, τ, and ϕ by assuming two different pore shapes: cylindrical and slit-shaped. Comparison with Klinkenberg-corrected k measurements showed that τ was estimated more accurately from F measurements than from percolation theory. Generally speaking, our results implied that the EMA estimated k within a factor of two of the measurements and more precisely than CPA. We further found that the assumption of cylindrical pores yielded more accurate k estimates when τ was estimated from concepts of percolation theory than the assumption of slit-shaped pores. However, the EMA with slit-shaped pores estimated k more precisely than that with cylindrical pores when τ was estimated from F measurements.

Device to improve detection in electro-chromatography

DOEpatents

Garguilo, Michael G.; Paul, Phillip H.; Rakestraw, David J.

2000-01-01

Apparatus and method for improving the resolution of non-pressure driven capillary chromatographic systems, and particularly for capillary electrochromatography (CEC) systems. By reducing the cross-sectional area of a packed capillary column by means of a second open capillary contiguous with the outlet end of a packed capillary column, where the packed capillary column has a cross sectional area of between about 2 and 5 times that of the open capillary column, the phenomenon of band broadening in the transition region between the open capillary and the packed capillary column, where the individual components of the mixture are analyzed, can be eliminated, thereby providing for a significant improvement in resolution and more accurate detection and analysis.

Device to improve detection in electro-chromatography

DOEpatents

Garguilo, Michael G.; Paul, Phillip H.; Rakestraw, David J.

2002-01-01

Apparatus and method for improving the resolution of non-pressure driven capillary chromatographic systems, and particularly for capillary electrochromatography (CEC) systems. By reducing the cross-sectional area of a packed capillary column by means of a second open capillary contiguous with the outlet end of a packed capillary column, where the packed capillary column has a cross sectional area of between about 2 and 5 times that of the open capillary column, the phenomenon of band broadening in the transition region between the open capillary and the packed capillary column, where the individual components of the mixture are analyzed, can be eliminated, thereby providing for a significant improvement in resolution and more accurate detection and analysis.

Parallel-plate heat pipe apparatus having a shaped wick structure

DOEpatents

Rightley, Michael J.; Adkins, Douglas R.; Mulhall, James J.; Robino, Charles V.; Reece, Mark; Smith, Paul M.; Tigges, Chris P.

2004-12-07

A parallel-plate heat pipe is disclosed that utilizes a plurality of evaporator regions at locations where heat sources (e.g. semiconductor chips) are to be provided. A plurality of curvilinear capillary grooves are formed on one or both major inner surfaces of the heat pipe to provide an independent flow of a liquid working fluid to the evaporator regions to optimize heat removal from different-size heat sources and to mitigate the possibility of heat-source shadowing. The parallel-plate heat pipe has applications for heat removal from high-density microelectronics and laptop computers.

Hemangiopericytoma in a young dog: Evaluation of histopathological and immunohistochemical features.

PubMed

Namazi, Fatemeh; Abbaszadeh Hasiri, Mohammad; Oryan, Ahmad; Moshiri, Ali

2014-01-01

In the present study, we describe a subcutaneous mass between the left flank and hip in a 2-year-old male Great Dane dog. Histopathologically, cells appeared to be spindle shaped around a central capillary together with a fingerprint pattern. Immunohistochemical analysis presented that the neoplastic cells expressed vimentin, but did not stain for S-100 protein. On the basis of histopathology and immunohistochemical findings, the present tumor was diagnosed as canine hemangiopericytoma. Hemangiopericytoma could be considered in differential diagnosis list of any mass in the skin (even in young dogs) and must be identified histopathologically.

Hemangiopericytoma in a young dog: Evaluation of histopathological and immunohistochemical features

PubMed Central

Namazi, Fatemeh; Abbaszadeh Hasiri, Mohammad; Oryan, Ahmad; Moshiri, Ali

2014-01-01

In the present study, we describe a subcutaneous mass between the left flank and hip in a 2-year-old male Great Dane dog. Histopathologically, cells appeared to be spindle shaped around a central capillary together with a fingerprint pattern. Immunohistochemical analysis presented that the neoplastic cells expressed vimentin, but did not stain for S-100 protein. On the basis of histopathology and immunohistochemical findings, the present tumor was diagnosed as canine hemangiopericytoma. Hemangiopericytoma could be considered in differential diagnosis list of any mass in the skin (even in young dogs) and must be identified histopathologically. PMID:25568712

Capillary origami: spontaneous wrapping of a droplet with an elastic sheet.

PubMed

Py, Charlotte; Reverdy, Paul; Doppler, Lionel; Bico, José; Roman, Benoît; Baroud, Charles N

2007-04-13

The interaction between elasticity and capillarity is used to produce three-dimensional structures through the wrapping of a liquid droplet by a planar sheet. The final encapsulated 3D shape is controlled by tailoring the initial geometry of the flat membrane. Balancing interfacial energy with elastic bending energy provides a critical length scale below which encapsulation cannot occur, which is verified experimentally. This length is found to depend on the thickness as h3/2, a scaling favorable to miniaturization which suggests a new way of mass production of 3D micro- or nanoscale objects.

Sheathless interface for coupling capillary electrophoresis with mass spectrometry

DOEpatents

Wang, Chenchen; Tang, Keqi; Smith, Richard D.

2014-06-17

A sheathless interface for coupling capillary electrophoresis (CE) with mass spectrometry is disclosed. The sheathless interface includes a separation capillary for performing CE separation and an emitter capillary for electrospray ionization. A portion of the emitter capillary is porous or, alternatively, is coated to form an electrically conductive surface. A section of the emitter capillary is disposed within the separation capillary, forming a joint. A metal tube, containing a conductive liquid, encloses the joint.

Patterns through elastic instabilities, from thin sheets to twisted ribbons

NASA Astrophysics Data System (ADS)

Damman, Pascal

Sheets embedded in a given shape by external forces store the exerted work in elastic deformations. For pure tensile forces, the work is stored as stretching energy. When the forces are compressive, several ways to store the exerted work, combining stretching and bending deformations can be explored. For large deflections, the ratio of bending, Eh3ζ2 /L4 and stretching, Ehζ4 /L4 energies, suggests that strain-free solutions should be favored for thin sheets, provided ζ2 >>h2 (where E , ζ , Land h are the elastic modulus, the deflection, a characteristic sheet size and its thickness). For uniaxially constrained sheets deriving from the Elastica, strain-free solutions are obvious, i.e., buckles, folds or wrinkles grow to absorb the stress of compression. In contrast, crumpled sheets exhibit ``origami-like'' solutions usually described as an assembly of flat polygonal facets delimitated by ridges focusing strains are observed. This type of solutions is particularly interesting since a faceted morphology is isometric to the undeformed sheet, except at those narrow ridges. In some cases however, the geometric constraints imposed by the external forces do not allow solutions with negligible strain in the deformed state. For instance, considering a circular sheet on a small drop, so thin that bending becomes negligible, i.e., Eh3 / γL2 << 1 . The capillary tension, γ at the edge forces the sheet to follow the spherical shape of the drop. Depending on the magnitude of the capillary tension with respect to the stretching modulus, such a sheet on a sphere can be in full tension or subjected to azimuthal compression. These spherical solutions could generate a hoop stress of compression within a small strip at the sheet's edge. The mechanical response of the sheet will generate tiny wrinkles decorating the edge to relax the compression stress while keeping its spherical shape. Finally, twisting a paper ribbon under high tension spontaneously produces helicoidal shapes that also reflect stretching and bending deformations. When the tension is progressively relieved, longitudinal and transverse compressive stresses build. To relax the longitudinal stress while keeping the helicoid shape, the ribbons produce wrinkles that ultimately becomes sharp folds similar to the ridge singularities observed in crumpled paper. The relaxation of the transverse compression stress produces cylindrical solutions. All these examples illustrates the natural tendency of an elastic sheet to stay as close as possible to the imposed shape, i.e. flat, spherical, helicoid. The mechanical response of the elastic sheet aims to relieve the compressive stress by growing a given micro-structure, i.e. wrinkles, singularities. In this talk, we will explore the general mechanisms at work, based on geometry and a competition between various energy terms, involving stretching and bending modes.

A Galinstan-Filled Capillary Probe for Thermal Conductivity Measurements and Its Application to Molten Eutectic {KNO}_3-{NaNO}_3-{NO}_2 (HTS) up to 700 K

NASA Astrophysics Data System (ADS)

Le Brun, Niccolò; Markides, Christos N.

2015-11-01

The successful measurement of the thermal conductivity of molten salts is a challenging undertaking due to the electrically conducting and possibly also aggressive nature of the materials, as well as the elevated temperatures at which these data are required. For accurate and reproducible measurements, it is important to develop a suitable experimental apparatus and methodology. In this study, we explore a modified version of the transient hot-wire method, which employs a molten-metal-filled capillary in order to circumvent some of the issues encountered in previous studies. Specifically, by using a novel flexible U-shaped quartz-capillary, filled with a eutectic mixture of gallium, indium and tin, commercially known as Galinstan, we proceed to measure the thermal conductivity of molten eutectic {KNO}_3-{NaNO}_3-{NaNO}_2. The new probe is demonstrated as being able to measure the thermal conductivity of this molten salt, which is found to range from 0.48 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} at 500 K to 0.47 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} at close to 700 K, with an overall expanded uncertainty (95 % confidence) of 3.1 %. The quartz is found to retain its electrically insulating properties and no current leakage is detected in the sample over the investigated temperature range. The thermal conductivity data reported in the present study are also used to elucidate a partial disagreement found in the literature for this material.

Development of the areola in the early placenta of the one-humped camel (Camelus dromedarius): a light, scanning and transmission electron microscopical study.

PubMed

Abd-Elnaeim, M M M; Saber, A; Hassan, A; Abou-Elmagd, A; Klisch, K; Jones, C J P; Leiser, R

2003-12-01

This study aimed to elucidate development of the areola in the early dromedary placenta in comparison with that of the pig and mare. Placental tissues from 25 pregnant camels were obtained from Cairo abattoir and prepared for light, scanning and transmission electron microscopy by routine methods. Vascular casts were made by injection of 4 : 1 liquid plastic mixture of mercox and methylmethacrylate. Areolar formation was first observed at 4.5 cm curved-crown-rump CVR length, while by 5-9 cm CVR length, the endometrial surface was uneven and studded with numerous uterine gland openings, where corresponding foetal areolae were barely detectable and the foetal areolar cells were of variable appearance and covered with long microvilli. At 10-13 cm CVR length the uterine gland openings developed irregular folds and the maternal areolar cells showed numerous apical blebs. At 14-29 cm CVR length the foetal areolae showed a great increase in height at the expense of their width. At 30-34 cm (CVR) length the maternal areolae appeared discoid and sharply demarcated from the surrounding inter-areolar tissues and the foetal areolae were rounded to irregular in shape with well-developed areolar rims. The vascular casts showed a widely meshed capillary network on the maternal areola, connecting with the pre- and post-capillary vessels, whereas the foetal side showed a relatively dense capillary meshwork. These studies indicate that the areola in the placenta of the one-humped camel is of the regular type like in the pig, and is poorly vascularized.

In Vivo Microscopy Reveals Extensive Embedding of Capillaries within the Sarcolemma of Skeletal Muscle Fibers

PubMed Central

Glancy, Brian; Hsu, Li-Yueh; Dao, Lam; Bakalar, Matthew; French, Stephanie; Chess, David J.; Taylor, Joni L.; Picard, Martin; Aponte, Angel; Daniels, Mathew P.; Esfahani, Shervin; Cushman, Samuel; Balaban, Robert S.

2013-01-01

Objective To provide insight into mitochondrial function in vivo, we evaluated the 3D spatial relationship between capillaries, mitochondria, and muscle fibers in live mice. Methods 3D volumes of in vivo murine Tibialis anterior muscles were imaged by multi-photon microscopy (MPM). Muscle fiber type, mitochondrial distribution, number of capillaries, and capillary-to-fiber contact were assessed. The role of myoglobin-facilitated diffusion was examined in myoglobin knockout mice. Distribution of GLUT4 was also evaluated in the context of the capillary and mitochondrial network. Results MPM revealed that 43.6 ± 3.3% of oxidative fiber capillaries had ≥ 50% of their circumference embedded in a groove in the sarcolemma, in vivo. Embedded capillaries were tightly associated with dense mitochondrial populations lateral to capillary grooves and nearly absent below the groove. Mitochondrial distribution, number of embedded capillaries, and capillary-to-fiber contact were proportional to fiber oxidative capacity and unaffected by myoglobin knockout. GLUT4 did not preferentially localize to embedded capillaries. Conclusions Embedding capillaries in the sarcolemma may provide a regulatory mechanism to optimize delivery of oxygen to heterogeneous groups of muscle fibers. We hypothesize that mitochondria locate to paravascular regions due to myofibril voids created by embedded capillaries, not to enhance the delivery of oxygen to the mitochondria. PMID:25279425

Transforming "apathy into movement": the role of prosocial emotions in motivating action for social change.

PubMed

Thomas, Emma F; McGarty, Craig; Mavor, Kenneth I

2009-11-01

This article explores the synergies between recent developments in the social identity of helping, and advantaged groups' prosocial emotion. The authors review the literature on the potential of guilt, sympathy, and outrage to transform advantaged groups' apathy into positive action. They place this research into a novel framework by exploring the ways these emotions shape group processes to produce action strategies that emphasize either social cohesion or social change. These prosocial emotions have a critical but underrecognized role in creating contexts of in-group inclusion or exclusion, shaping normative content and meaning, and informing group interests. Furthermore, these distinctions provide a useful way of differentiating commonly discussed emotions. The authors conclude that the most "effective" emotion will depend on the context of the inequality but that outrage seems particularly likely to productively shape group processes and social change outcomes.

Integrating Public Health Policy, Practice, Evaluation, Surveillance, and Research: The School Health Action Planning and Evaluation System

PubMed Central

Cameron, Roy; Manske, Stephen; Brown, K. Stephen; Jolin, Mari Alice; Murnaghan, Donna; Lovato, Chris

2007-01-01

The Canadian Cancer Society and the National Cancer Institute of Canada have charged their Centre for Behavioral Research and Program Evaluation with contributing to the development of the country’s systemic capacity to link research, policy, and practice related to population-level interventions. Local data collection and feedback systems are integral to this capacity. Canada’s School Health Action Planning and Evaluation System (SHAPES) allows data to be collected from all of a school’s students, and these data are used to produce computer-generated school “health profiles.” SHAPES is being used for intervention planning, evaluation, surveillance, and research across Canada. Strong demand and multipartner investment suggest that SHAPES is adding value in all of these domains. Such systems can contribute substantially to evidence-informed public health practice, public engagement, participatory action research, and relevant, timely population intervention research. PMID:17329662

Biochar particle size, shape, and porosity act together to influence soil water properties

PubMed Central

Dugan, Brandon; Masiello, Caroline A.; Gonnermann, Helge M.

2017-01-01

Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar’s effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar’s intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles’ elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils. PMID:28598988

The effects of particle size, shape, density and flow characteristics on particle margination to vascular walls in cardiovascular diseases.

PubMed

Ta, Hang T; Truong, Nghia P; Whittaker, Andrew K; Davis, Thomas P; Peter, Karlheinz

2018-01-01

Vascular-targeted drug delivery is a promising approach for the treatment of atherosclerosis, due to the vast involvement of endothelium in the initiation and growth of plaque, a characteristic of atherosclerosis. One of the major challenges in carrier design for targeting cardiovascular diseases (CVD) is that carriers must be able to navigate the circulation system and efficiently marginate to the endothelium in order to interact with the target receptors. Areas covered: This review draws on studies that have focused on the role of particle size, shape, and density (along with flow hemodynamics and hemorheology) on the localization of the particles to activated endothelial cell surfaces and vascular walls under different flow conditions, especially those relevant to atherosclerosis. Expert opinion: Generally, the size, shape, and density of a particle affect its adhesion to vascular walls synergistically, and these three factors should be considered simultaneously when designing an optimal carrier for targeting CVD. Available preliminary data should encourage more studies to be conducted to investigate the use of nano-constructs, characterized by a sub-micrometer size, a non-spherical shape, and a high material density to maximize vascular wall margination and minimize capillary entrapment, as carriers for targeting CVD.

Biochar particle size, shape, and porosity act together to influence soil water properties.

PubMed

Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A; Gonnermann, Helge M

2017-01-01

Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar's effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar's intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles' elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils.

CSE-MECC two-dimensional capillary electrophoresis analysis of proteins in the mouse tumor cell (AtT-20) homogenate

PubMed Central

Chen, Xingguo; Fazal, Md. Abul; Dovichi, Norman J.

2007-01-01

Two-dimensional capillary electrophoresis was used for the separation of proteins and biogenic amines from the mouse AtT-20 cell line. The first-dimension capillary contained a TRIS-CHES-SDS-dextran buffer to perform capillary sieving electrophoresis, which is based on molecular weight of proteins. The second-dimension capillary contained a TRIS-CHES-SDS buffer for micel1ar electrokinetic capillary chromatography. After a 61 seconds preliminary separation, fractions from the first-dimension capillary were successively transferred to the second-dimension capillary, where they further separated by MECC. The two-dimensional separation required 60 minutes. PMID:17637850

Method for removing semiconductor layers from salt substrates

DOEpatents

Shuskus, Alexander J.; Cowher, Melvyn E.

1985-08-27

A method is described for removing a CVD semiconductor layer from an alkali halide salt substrate following the deposition of the semiconductor layer. The semiconductor-substrate combination is supported on a material such as tungsten which is readily wet by the molten alkali halide. The temperature of the semiconductor-substrate combination is raised to a temperature greater than the melting temperature of the substrate but less than the temperature of the semiconductor and the substrate is melted and removed from the semiconductor by capillary action of the wettable support.

Increased technetium uptake is not equivalent to muscle necrosis: scintigraphic, morphological and intramuscular pressure analyses of sore muscles after exercise

NASA Technical Reports Server (NTRS)

Crenshaw, A. G.; Friden, J.; Hargens, A. R.; Lang, G. H.; Thornell, L. E.

1993-01-01

A scintigraphic technique employing technetium pyrophosphate uptake was used to identify the area of skeletal muscle damage in the lower leg of four runners 24 h after an ultramarathon footrace (160 km). Most of the race had been run downhill which incorporated an extensive amount of eccentric work. Soreness was diffuse throughout the posterior region of the lower leg. In order to interpret what increased technetium uptake reflects and to express extreme endurance related damages, a biopsy was taken from the 3-D position of abnormal uptake. In addition, intramuscular pressures were determined in the deep posterior compartment. Scintigraphs revealed increased technetium pyrophosphate uptake in the medial portion of the gastrocnemius muscle. For 3698 fibres analysed, 33 fibres (1%) were necrotic, while a few other fibres were either atrophic or irregular shaped. A cluster of necrotic fibres occurred at the fascicular periphery for one subject and fibre type grouping occurred for another. Ultrastructural analysis revealed Z-line streaming near many capillaries and variously altered subsarcolemmal mitochondria including some with paracrystalline inclusions. The majority of the capillaries included thickened and irregular shaped endothelial cells. Intramuscular pressures of the deep posterior compartment were slightly elevated (12-15 mmHg) for three of the four subjects. Increased technetium uptake following extreme endurance running does not just reflect muscle necrosis but also subtle fibre abnormalities. Collectively, these pathological findings are attributed to relative ischaemia occurring during the race and during pre-race training, whereas, intramuscular pressure elevations associated with muscle soreness are attributed to mechanical stress caused by extensive eccentric work during the race.

Differential Mouse Pulmonary Dose and Time Course Responses to Titanium Dioxide Nanospheres and Nanobelts

PubMed Central

Porter, Dale W.

2013-01-01

Three anatase titanium dioxide (TiO2) nanoparticles (NPs) were prepared; nanospheres (NSs), short nanobelts (NB1), and long nanobelts (NB2). These NPs were used to investigate the effect of NP shape and length on lung toxicity. Mice were exposed (0–30 µg per mouse) by pharyngeal aspiration and pulmonary toxicity was assessed over a 112-day time course. Whole lung lavage data indicated that NB1- and NB2-exposed mice, but not NS-exposed mice, had significant dose- and time-dependent pulmonary inflammation and damage. Histopathological analyses at 112 days postexposure determined no interstitial fibrosis in any NS-exposed mice, an increased incidence in 30 µg NB1-exposed mice, and significant interstitial fibrosis in 30 µg NB2-exposed mice. At 112 days postexposure, lung burden of NS was decreased by 96.4% and NB2 by 80.5% from initial deposition levels. At 112 days postexposure, enhanced dark field microscopy determined that alveolar macro- phages were the dominant deposition site, but a fraction of NB1 and NB2 was observed in the alveolar interstitial spaces. For the 30 µg exposure groups at 112 days postexposure, confocal micro- scopy and immunofluorescent staining demonstrated that retained NB2 but not NS were present in the interstitium subjacent to the terminal bronchiole near the normal location of the smallest lymphatic capillaries in the lung. These lymphatic capillaries play a critical role in particle clearance, and the accumulation of NB2, but not NS, suggests possible impaired lymphatic clearance by the high aspect ratio particles. In summary, our data indicate that TiO2 NP shape alters pulmonary responses, with severity of responses being ranked as NS < NB1 < NB2. PMID:22956629

Capillary electrophoresis investigation on equilibrium between polymer-related and surfactant-related species in aqueous polymer-surfactant solutions.

PubMed

Wu, Yefan; Chen, Miaomiao; Fang, Yun; Zhu, Meng

2017-03-17

It was inferred from aqueous solution behavior of nonionic polymers and anionic surfactants that the formation of charged polymer-bound surfactant micelle above critical aggregation concentration (cac) and the formation of free surfactant micelle beyond polymer saturation point (psp), but there was still a lack of direct experimental evidence for the considered equilibrium chemical species. Three modes of capillary electrophoresis are applied in this paper to study the complexation between nonionic polymers, polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate (SDBS) by successfully distinguishing the imaginary charged polymer-bound SDBS micelle from nonionic polymer and SDBS molecule. Perhaps even more important, it is the action of SDBS as both a main surfactant and a UV probe that makes the free surfactant micelle emerged in electropherogram beyond psp, and thus makes it possible for the first time to provide the equilibrium relationship of the polymer-related and the surfactant-related species in the concentration regions divided into by cac and psp. Copyright © 2017 Elsevier B.V. All rights reserved.

An evaluation of the HemoCue for measuring haemoglobin in field studies in Jamaica.

PubMed Central

Hudson-Thomas, M.; Bingham, K. C.; Simmons, W. K.

1994-01-01

The HemoCue system utilizes the principle of oxidation of haemoglobin to hemiglobin by sodium nitrite and the subsequent conversion of hemiglobin to hemiglobinazide by sodium azide. The reagents for these reactions are contained within a small disposable microcuvette of approximately 10 microliters in volume. A venous or capillary sample is introduced into the microcuvette by capillary action and, after reaction with the reagents, the absorbance is read in the HemoCue photometer at 565 and 880 nm. The haemoglobin concentration is then displayed as a digital reading, in either g/dl or mmol/l in 15-45 seconds. We compared haemoglobin values obtained by the HemoCue system with those from the Coulter Counter S-Plus IV in 366 pregnant women in urban Jamaica, and found a highly significant correlation (r = 0.78, P < 0.01). However, because of the convenience and ease of use of this instrument and considering the relatively high cost, we recommend it for use only as a research tool in field studies where accurate and rapid haemoglobin determinations are required. PMID:8062400

Development of a single-cell X-ray fluorescence flow cytometer

DOE PAGES

Crawford, Andrew M.; Kurecka, Patrick; Yim, Tsz Kwan; ...

2016-06-17

An X-ray fluorescence flow cytometer that can determine the total metal content of single cells has been developed. Capillary action or pressure was used to load cells into hydrophilic or hydrophobic capillaries, respectively. Once loaded, the cells were transported at a fixed vertical velocity past a focused X-ray beam. X-ray fluorescence was then used to determine the mass of metal in each cell. By making single-cell measurements, the population heterogeneity for metals in the µ M to m M concentration range on fL sample volumes can be directly measured, a measurement that is difficult using most analytical methods. This approachmore » has been used to determine the metal composition of 936 individual bovine red blood cells (bRBC), 31 individual 3T3 mouse fibroblasts (NIH3T3) and 18 Saccharomyces cerevisiae (yeast) cells with an average measurement frequency of ~4 cells min –1. These data show evidence for surprisingly broad metal distributions. Lastly, details of the device design, data analysis and opportunities for further sensitivity improvement are described.« less

Sympathetic nerves: How do they affect angiogenesis, particularly during wound healing of soft tissues?

PubMed

Pan, Liangli; Tang, Jianbing; Liu, Hongwei; Cheng, Biao

2016-01-01

Angiogenesis is essential for wound healing, and angiogenesis impairment can result in chronic ulcers. Studies have shown that the sympathetic nervous system has an important role in angiogenesis. In recent years, researchers have focused on the roles of sympathetic nerves in tumor angiogenesis. In fact, sympathetic nerves can affect angiogenesis in the wound healing of soft tissues, and may have a similar mechanism of action as that seen in tumorigenesis. Sympathetic nerves act primarily through interactions between the neurotransmitters released from nerve endings and receptors present in target organs. Among this, activation or inhibition of adrenergic receptors (mainly β-adrenergic receptors) influence formation of new blood vessels considerably. As sympathetic nerves locate near pericytes in microvessel, go along the capillaries and there are adrenergic receptors present in endothelial cells and pericytes, sympathetic nerves may participate in angiogenesis by influencing the endothelial cells and pericytes of new capillaries. Studying the roles of sympathetic nerves on the angiogenesis of wound healing can contribute to understanding the mechanisms of tissue repair, tissue regeneration, and tumorigenesis, thereby providing new therapeutic perspectives.

Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

DOEpatents

Yeung, Edward S.; Kuhr, Werner G.

1996-02-20

A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

DOEpatents

Yeung, Edwards; Kuhr, Werner G.

1991-04-09

A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

Enhancing separation in short-capillary electrophoresis via pressure-driven backflow.

PubMed

Tian, Miaomiao; Wang, Yujia; Mohamed, Amara Camara; Guo, Liping; Yang, Li

2015-07-01

We present a novel easy-to-operate and efficient method to improve the separation efficiency in short-capillary electrophoresis by introducing steady backflow to counterbalance electro-osmotic flow without the use of any external pressure. The backflow was easily generated by tapering the capillary end, which was achieved by heating a straight capillary and stretching it with a constant force. We investigated the net fluidic transport rate under different tip lengths and separation voltages. Good run-to-run repeatability and capillary-to-capillary reproducibility of the present method were obtained with RSD less than 1.5%, indicating the stability of the fluid transport rate in the tapered capillary, which ensures the quantification and repeatability of capillary zone electrophoresis (CZE) analysis. Enhanced separation of the tapered short capillary electrophoresis was demonstrated by CZE analyzing amino acids and positional isomers. Baseline separations were achieved in less than 60 s using a tapered capillary with the effective length of 5 cm, while no separation was achieved using a normal capillary without a tapered tip. The present study provides a promising method to use pressure-driven backflow to enhance separation efficiency in short-capillary electrophoresis, which would be of potential value in a wide application for fast analysis of complex samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating category- and shape-selective neural processing in ventral and dorsal visual stream under interocular suppression.

PubMed

Ludwig, Karin; Kathmann, Norbert; Sterzer, Philipp; Hesselmann, Guido

2015-01-01

Recent behavioral and neuroimaging studies using continuous flash suppression (CFS) have suggested that action-related processing in the dorsal visual stream might be independent of perceptual awareness, in line with the "vision-for-perception" versus "vision-for-action" distinction of the influential dual-stream theory. It remains controversial if evidence suggesting exclusive dorsal stream processing of tool stimuli under CFS can be explained by their elongated shape alone or by action-relevant category representations in dorsal visual cortex. To approach this question, we investigated category- and shape-selective functional magnetic resonance imaging-blood-oxygen level-dependent responses in both visual streams using images of faces and tools. Multivariate pattern analysis showed enhanced decoding of elongated relative to non-elongated tools, both in the ventral and dorsal visual stream. The second aim of our study was to investigate whether the depth of interocular suppression might differentially affect processing in dorsal and ventral areas. However, parametric modulation of suppression depth by varying the CFS mask contrast did not yield any evidence for differential modulation of category-selective activity. Together, our data provide evidence for shape-selective processing under CFS in both dorsal and ventral stream areas and, therefore, do not support the notion that dorsal "vision-for-action" processing is exclusively preserved under interocular suppression. © 2014 Wiley Periodicals, Inc.

Quantitative fine structure of capillaries in subregions of the rat subfornical organ.

PubMed

Shaver, S W; Sposito, N M; Gross, P M

1990-04-01

The differentiated cytology across subregions of the rat subfornical organ (SFO) prompted our hypothesis that ultrastructural features of capillary endothelial cells would vary topographically and quantitatively within this small nucleus. We used electron microscopic and computer-based morphometric methods to assess fine structural dimensions of the capillary endothelium in four distinct subregions of the SFO from Long-Evans and homozygous Brattleboro rats. Three types of capillary were present. Type III capillaries (resembling those of endocrine glands) had an average wall thickness of 0.17 microns, 54% thinner than those of Type I and II capillaries. Pericapillary spaces around Type III capillaries measured 56 microns2, 100% larger than for Type I vessels (resembling those of skeletal muscle). Only Type III capillaries contained fenestrations (9 per microns2 of endothelial cell) and were the predominant type of capillary in central and caudal subregions of the SFO. Type I capillaries, prevalent in the transitional subregion between the central and rostral parts of the SFO, had 10 cytoplasmic vesicles per micron2 of endothelial cell area, a number not different from that of Type III capillaries but 3x the frequency found in Type II vessels. Type II capillaries (those typical of "blood-brain barrier" endothelium) had low vesicular density (3 per microns2), no fenestrations, and no pericapillary spaces. Luminal diameters and the densities of mitochondria and intercellular junctions were not different among capillary types or subregions in the SFO. Furthermore, there were no morphometric differences for any capillary dimensions between Long-Evans and Brattleboro rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of Capillary Radius and Contact Angle within Porous Media.

PubMed

Ravi, Saitej; Dharmarajan, Ramanathan; Moghaddam, Saeed

2015-12-01

The pore radius (i.e., capillary radius) and contact angle determine the capillary pressure generated in a porous medium. The most common method to determine these two parameters is through measurement of the capillary pressure generated by a reference liquid (i.e., a liquid with near-zero contact angle) and a test liquid. The rate of rise technique, commonly used to determine the capillary pressure, results in significant uncertainties. In this study, we utilize a recently developed technique for independently measuring the capillary pressure and permeability to determine the equivalent minimum capillary radii and contact angle of water within micropillar wick structures. In this method, the experimentally measured dryout threshold of a wick structure at different wicking lengths is fit to Darcy's law to extract the maximum capillary pressure generated by the test liquid. The equivalent minimum capillary radii of different wick geometries are determined by measuring the maximum capillary pressures generated using n-hexane as the working fluid. It is found that the equivalent minimum capillary radius is dependent on the diameter of pillars and the spacing between pillars. The equivalent capillary radii of micropillar wicks determined using the new method are found to be up to 7 times greater than the current geometry-based first-order estimates. The contact angle subtended by water at the walls of the micropillars is determined by measuring the capillary pressure generated by water within the arrays and the measured capillary radii for the different geometries. This mean contact angle of water is determined to be 54.7°.

Single-phase and two-phase flow properties of mesaverde tight sandstone formation; random-network modeling approach

NASA Astrophysics Data System (ADS)

Bashtani, Farzad; Maini, Brij; Kantzas, Apostolos

2016-08-01

3D random networks are constructed in order to represent the tight Mesaverde formation which is located in north Wyoming, USA. The porous-space is represented by pore bodies of different shapes and sizes which are connected to each other by pore throats of varying length and diameter. Pore bodies are randomly distributed in space and their connectivity varies based on the connectivity number distribution which is used in order to generate the network. Network representations are then validated using publicly available mercury porosimetry experiments. The network modeling software solves the fundamental equations of two-phase immiscible flow incorporating wettability and contact angle variability. Quasi-static displacement is assumed. Single phase macroscopic properties (porosity, permeability) are calculated and whenever possible are compared to experimental data. Using this information drainage and imbibition capillary pressure, and relative permeability curves are predicted and (whenever possible) compared to experimental data. The calculated information is grouped and compared to available literature information on typical behavior of tight formations. Capillary pressure curve for primary drainage process is predicted and compared to experimental mercury porosimetry in order to validate the virtual porous media by history matching. Relative permeability curves are also calculated and presented.

Thin film drainage between pre-inflated capsules or vesicles

NASA Astrophysics Data System (ADS)

Keh, Martin; Walter, Johann; Leal, Gary

2013-11-01

Capsules and vesicles are often used as vehicles to carry active ingredients or fragrance in drug delivery and consumer products and oftentimes in these applications the particles may be pre-inflated due to the existence of a small osmotic pressure difference between the interior and exterior fluid. We study the dynamics of thin film drainage between capsules and vesicles in flow as it is crucial to fusion and deposition of the particles and, therefore, the stability and effectiveness of the products. Simulations are conducted using a numerical model coupling the boundary integral method for the motion of the fluids and a finite element method for the membrane mechanics. For low capillary numbers, the drainage behavior of vesicles and capsules are approximately the same, and also similar to that of drops as the flow-independent and uniform tension due to pre-inflation dominates. The tension due to deformation caused by flow will become more important as the strength of the external flow (i.e. the capillary number) increases. In this case, the shapes of the thin film region are fundamentally different for capsules and vesicles, and the drainage behavior in both cases differs from a drop. Funded by P&G.

Numerical simulations of elastic capsules with nucleus in shear flow

NASA Astrophysics Data System (ADS)

Alizad Banaei, Arash; Loiseau, Jean-Christophe; Lashgari, Iman; Brandt, Luca

2017-03-01

The shear-induced deformation of a capsule with a stiff nucleus, a model of eukaryotic cells, is studied numerically. The membrane of the cell and of its nucleus are modelled as a thin elastic material obeying a Neo-Hookean constitutive law. The fluid-structure coupling is obtained using an immersed boundary method. The variations induced by the presence of the nucleus on the cell deformation are investigated when varying the viscosity ratio between the inner and outer fluids, the membrane elasticity and its bending stiffness. The deformation of the eukaryotic cell is smaller than that of the prokaryotic one. The reduction in deformation increases for larger values of the capillary number. The eukaryotic cell remains thicker in its middle part compared to the prokaryotic one, thus making it less flexible to pass through narrow capillaries. For a viscosity ratio of 5, the deformation of the cell is smaller than in the case of uniform viscosity. In addition, for non-zero bending stiffness of the membrane, the deformation decreases and the shape is closer to an ellipsoid. Finally, we compare the results obtained modelling the nucleus as an inner stiffer membrane with those obtained using a rigid particle.

Vascular development in the vertebrate pancreas.

PubMed

Azizoglu, D Berfin; Chong, Diana C; Villasenor, Alethia; Magenheim, Judith; Barry, David M; Lee, Simon; Marty-Santos, Leilani; Fu, Stephen; Dor, Yuval; Cleaver, Ondine

2016-12-01

The vertebrate pancreas is comprised of a highly branched tubular epithelium, which is intimately associated with an extensive and specialized vasculature. While we know a great deal about basic vascular anatomy of the adult pancreas, as well as islet capillaries, surprisingly little is known about the ontogeny of its blood vessels. Here, we analyze development of the pancreatic vasculature in the mouse embryo. We show that pancreatic epithelial branches intercalate with the fine capillary plexus of the surrounding pancreatic mesenchyme. Endothelial cells (ECs) within this mesenchyme are heterogeneous from the onset of organogenesis. Pancreatic arteries take shape before veins, in a manner analogous to early embryonic vessels. The main central artery forms during mid-gestation, as a result of vessel coalescence and remodeling of a vascular plexus. In addition, we show that vessels in the forming pancreas display a predictable architecture that is dependent on VEGF signaling. Over-expression of VEGF disrupts vascular patterning and arteriovenous differentiation within the developing pancreas. This study constitutes a first-time in-depth cellular and molecular characterization of pancreatic blood vessels, as they coordinately grow along with the pancreatic epithelium. Copyright © 2016 Elsevier Inc. All rights reserved.

Enantiomeric separation of fluoxetine and norfluoxetine in plasma and serum samples with high detection sensitivity capillary electrophoresis.

PubMed

Desiderio, C; Rudaz, S; Raggi, M A; Fanali, S

1999-11-01

A capillary electrophoresis method was optimized for the stereoselective analysis of the antidepressant drug fluoxetine and its main demethylated metabolite norfluoxetine using a cyclodextrin-modified sodium phosphate buffer at pH 2.5. The combination of a neutral and a negatively charged cyclodextrin, dimethylated-beta- and phosphated-gamma-respectively, provided the baseline enantiomeric separation of the two compounds. The very low concentrations of chiral selectors employed together with the use of a high sensitivity detection cell of special design (zeta-shaped) in a diode array UV detector allowed us to reach a limit of detection of 0.005 and 0.01 microg/mL for fluoxetine and norfluoxetine, respectively. Analysis of fluoxetine and norfluoxetine standard mixtures showed a reproducibility of migration times and peak area and linearity in the concentration range of 0.1-2.0 microg/mL. The optimized method was applied to the analysis of clinical serum and plasma samples of patients under depression therapy. In all the analyzed samples the enantiomeric forms of fluoxetine and norfluoxetine were easily identified. The fluoxetine and metabolite enantiomeric ratio confirmed the stereoselectivity of the metabolic process of the fluoxetine drug in accordance with the literature data.

Elasto-Capillary Folding Using Stop-Programmable Hinges Fabricated by 3D Micro-Machining

PubMed Central

Legrain, Antoine; Berenschot, Erwin J. W.; Tas, Niels R.; Abelmann, Leon

2015-01-01

We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of (70.6 ± 0.1)° and demonstrate the feasibility of such accurate micro-assembly with a final folding angle of 90°. The folding angle is defined by stop-programmable hinges that are fabricated starting from silicon molds employing accurate three-dimensional corner lithography. This nano-patterning method exploits the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as an inversion mask in subsequent steps. Hinges designed to stop the folding at 70.6° were fabricated batchwise by machining the V-grooves obtained by KOH etching in (110) silicon wafers; 90° stop-programmable hinges were obtained starting from silicon molds obtained by dry etching on (100) wafers. The presented technique has potential to achieve any folding angle and opens a new route towards creating structures with increased complexity, which will ultimately lead to a novel method for device fabrication. PMID:25992886

Quantitation in chiral capillary electrophoresis: theoretical and practical considerations.

PubMed

D'Hulst, A; Verbeke, N

1994-06-01

Capillary electrophoresis (CE) represents a decisive step forward in stereoselective analysis. The present paper deals with the theoretical aspects of the quantitation of peak separation in chiral CE. Because peak shape is very different in CE with respect to high performance liquid chromatography (HPLC), the resolution factor Rs, commonly used to describe the extent of separation between enantiomers as well as unrelated compounds, is demonstrated to be of limited value for the assessment of chiral separations in CE. Instead, the conjunct use of a relative chiral separation factor (RCS) and the percent chiral separation (% CS) is advocated. An array of examples is given to illustrate this. The practical aspects of method development using maltodextrins--which have been proposed previously as a major innovation in chiral selectors applicable in CE--are documented with the stereoselective analysis of coumarinic anticoagulant drugs. The possibilities of quantitation using CE were explored under two extreme conditions. Using ibuprofen, it has been demonstrated that enantiomeric excess determinations are possible down to a 1% level of optical contamination and stereoselective determinations are still possible with a good precision near the detection limit, increasing sample load by very long injection times. The theoretical aspects of this possibility are addressed in the discussion.

Type 3 Neovascularization Associated with Retinitis Pigmentosa.

PubMed

Sayadi, Jihene; Miere, Alexandra; Souied, Eric H; Cohen, Salomon Y

2017-01-01

To report a case of type 3 neovascular lesion in a patient with retinitis pigmentosa (RP) complicated by macular edema. A 78-year-old man with a long follow-up for RP was referred for painless visual acuity decrease in the right eye. Best-corrected visual acuity was 20/125 in the right eye and 20/40 in the left. Fundus examination showed typical RP and macular edema in both eyes. In the right eye, spectral domain optical coherence tomography revealed a marked cystic macular edema associated with disruption of the Bruch membrane/retinal pigment epithelium complex overlying a pigmentary epithelium detachment, with a vascular structure which appeared to originate from the deep capillary plexus and to be connected with the subretinal pigment epithelium space. Optical coherence tomography angiography showed a high-flow vessel infiltrating the outer retinal layers in the deep capillary plexus segmentation, and a tuft-shaped, bright, high-flow network that seemed to be connected with the subretinal pigment epithelium space in the outer retinal layer segmentation. This presentation was consistent with an early type 3 neovascular lesion in the right eye. Type 3 neovascularization may be considered a possible complication of RP.

Gas permeability of ice-templated, unidirectional porous ceramics.

PubMed

Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J

2016-01-01

We investigate the gas flow behavior of unidirectional porous ceramics processed by ice-templating. The pore volume ranged between 54% and 72% and pore size between 2.9 [Formula: see text]m and 19.1 [Formula: see text]m. The maximum permeability ([Formula: see text] [Formula: see text] m[Formula: see text]) was measured in samples with the highest total pore volume (72%) and pore size (19.1 [Formula: see text]m). However, we demonstrate that it is possible to achieve a similar permeability ([Formula: see text] [Formula: see text] m[Formula: see text]) at 54% pore volume by modification of the pore shape. These results were compared with those reported and measured for isotropic porous materials processed by conventional techniques. In unidirectional porous materials tortuosity ([Formula: see text]) is mainly controlled by pore size, unlike in isotropic porous structures where [Formula: see text] is linked to pore volume. Furthermore, we assessed the applicability of Ergun and capillary model in the prediction of permeability and we found that the capillary model accurately describes the gas flow behavior of unidirectional porous materials. Finally, we combined the permeability data obtained here with strength data for these materials to establish links between strength and permeability of ice-templated materials.

Microvascular Remodeling and Wound Healing: A Role for Pericytes

PubMed Central

Dulmovits, Brian M.; Herman, Ira M.

2012-01-01

Physiologic wound healing is highly dependent on the coordinated functions of vascular and non-vascular cells. Resolution of tissue injury involves coagulation, inflammation, formation of granulation tissue, remodeling and scarring. Angiogenesis, the growth of microvessels the size of capillaries, is crucial for these processes, delivering blood-borne cells, nutrients and oxygen to actively remodeling areas. Central to angiogenic induction and regulation is microvascular remodeling, which is dependent upon capillary endothelial cell and pericyte interactions. Despite our growing knowledge of pericyte-endothelial cell crosstalk, it is unclear how the interplay among pericytes, inflammatory cells, glia and connective tissue elements shape microvascular injury response. Here, we consider the relationships that pericytes form with the cellular effectors of healing in normal and diabetic environments, including repair following injury and vascular complications of diabetes, such as diabetic macular edema and proliferative diabetic retinopathy. In addition, pericytes and stem cells possessing “pericyte-like” characteristics are gaining considerable attention in experimental and clinical efforts aimed at promoting healing or eradicating ocular vascular proliferative disorders. As the origin, identification and characterization of microvascular pericyte progenitor populations remains somewhat ambiguous, the molecular markers, structural and functional characteristics of pericytes will be briefly reviewed. PMID:22750474

High-speed video capillaroscopy method for imaging and evaluation of moving red blood cells

NASA Astrophysics Data System (ADS)

Gurov, Igor; Volkov, Mikhail; Margaryants, Nikita; Pimenov, Aleksei; Potemkin, Andrey

2018-05-01

The video capillaroscopy system with high image recording rate to resolve moving red blood cells with velocity up to 5 mm/s into a capillary is considered. Proposed procedures of the recorded video sequence processing allow evaluating spatial capillary area, capillary diameter and central line with high accuracy and reliability independently on properties of individual capillary. Two-dimensional inter frame procedure is applied to find lateral shift of neighbor images in the blood flow area with moving red blood cells and to measure directly the blood flow velocity along a capillary central line. The developed method opens new opportunities for biomedical diagnostics, particularly, due to long-time continuous monitoring of red blood cells velocity into capillary. Spatio-temporal representation of capillary blood flow is considered. Experimental results of direct measurement of blood flow velocity into separate capillary as well as capillary net are presented and discussed.

Automated Parallel Capillary Electrophoretic System

DOEpatents

Li, Qingbo; Kane, Thomas E.; Liu, Changsheng; Sonnenschein, Bernard; Sharer, Michael V.; Kernan, John R.

2000-02-22

An automated electrophoretic system is disclosed. The system employs a capillary cartridge having a plurality of capillary tubes. The cartridge has a first array of capillary ends projecting from one side of a plate. The first array of capillary ends are spaced apart in substantially the same manner as the wells of a microtitre tray of standard size. This allows one to simultaneously perform capillary electrophoresis on samples present in each of the wells of the tray. The system includes a stacked, dual carousel arrangement to eliminate cross-contamination resulting from reuse of the same buffer tray on consecutive executions from electrophoresis. The system also has a gel delivery module containing a gel syringe/a stepper motor or a high pressure chamber with a pump to quickly and uniformly deliver gel through the capillary tubes. The system further includes a multi-wavelength beam generator to generate a laser beam which produces a beam with a wide range of wavelengths. An off-line capillary reconditioner thoroughly cleans a capillary cartridge to enable simultaneous execution of electrophoresis with another capillary cartridge. The streamlined nature of the off-line capillary reconditioner offers the advantage of increased system throughput with a minimal increase in system cost.

Fluid Delivery System For Capillary Electrophoretic Applications.

DOEpatents

Li, Qingbo; Liu, Changsheng; Kane, Thomas E.; Kernan, John R.; Sonnenschein, Bernard; Sharer, Michael V.

2002-04-23

An automated electrophoretic system is disclosed. The system employs a capillary cartridge having a plurality of capillary tubes. The cartridge has a first array of capillary ends projecting from one side of a plate. The first array of capillary ends are spaced apart in substantially the same manner as the wells of a microtitre tray of standard size. This allows one to simultaneously perform capillary electrophoresis on samples present in each of the wells of the tray. The system includes a stacked, dual carrousel arrangement to eliminate cross-contamination resulting from reuse of the same buffer tray on consecutive executions from electrophoresis. The system also has a gel delivery module containing a gel syringe/a stepper motor or a high pressure chamber with a pump to quickly and uniformly deliver gel through the capillary tubes. The system further includes a multi-wavelength beam generator to generate a laser beam which produces a beam with a wide range of wavelengths. An off-line capillary reconditioner thoroughly cleans a capillary cartridge to enable simultaneous execution of electrophoresis with another capillary cartridge. The streamlined nature of the off-line capillary reconditioner offers the advantage of increased system throughput with a minimal increase in system cost.

Determination of glutathione in apoptotic SMMC-7221 cells induced by xylitol selenite using capillary electrophoresis.

PubMed

Wu, Xue; Cao, Yu; Zhang, Jian; Lei, Ming; Deng, Xiaojie; Zahid, Kashif Rafiq; Liu, Yanli; Liu, Ke; Yang, Jihong; Xiong, Guomei; Yao, Hanchao; Qi, Chao

2016-05-01

To determine the glutathione (GSH) content in a human hepatoma cell line (SMMC-7221) treated with xylitol/selenite, providing a part of an investigation of its anti-cancer mechanisms. The nuclei of SMMC-7221 cells were stained with Hoechst 33258 in an apoptosis assay, and their morphology subsequently changed from circular to crescent shape. The calibration curve (r(2) = 0.992) was established, and GSH content markedly decreased after treated with 0.5 and 1 mg xylitol/selenite l(-1) for 12, 36 and 60 h (12 h: from 95.57 ± 19.57 to 29.09 ± 7.74 and 24.27 ± 11.15; 36 h: from 70.73 ± 11.35 to 19.54 ± 6.39 and 9.35 ± 6.69; 60 h: from 72.63 ± 16.94 to 7.432 ± 3.84 and 0). The depletion rate of GSH was more related to the concentration of xylitol/selenite than the treatment time (from 69.95 ± 1.87 to 100 % vs. 0.22 ± 0.2 to 100 %). Xylitol/selenite is a promising anti-cancer drug to induce apoptosis in SMMC-7221 cells. It may regulate the apoptosis through the co-action of multiple mechanisms related to GSH depletion.

Shaping Social Justice Leadership: Insights of Women Educators Worldwide

ERIC Educational Resources Information Center

Lyman, Linda L.; Strachan, Jane; Lazaridou, Angeliki

2012-01-01

"Shaping Social Justice Leadership: Insights of Women Educators Worldwide" contains evocative portraits of twenty-three women educators and leaders from around the world whose actions are shaping social justice leadership. Woven from words of their own narratives, the women's voices lift off the page into readers' hearts and minds to inspire and…

Early changes in fiber profile and capillary density in long-term stimulated muscles.

PubMed

Hudlická, O; Dodd, L; Renkin, E M; Gray, S D

1982-10-01

Predominantly fast skeletal muscles of rabbits [tibialis anterior (TA), extensor digitorum longus (EDL)] were stimulated at a frequency naturally occurring in nerves to slow muscles (10 Hz continuously) for 8 h/day for 2--4 days. Such stimulation is known to convert all glycolytic fibers to oxidative and to increase capillary density. Our aim was to study early stages of conversion to investigate the factors responsible for the changes. Staining of quick-frozen sections for myosin ATPase, succinic dehydrogenase, and alkaline phosphatase was used to study the distribution of different fiber types and to measure fiber cross-sectional areas, capillaries per square millimeter, and capillary-to-fiber ratios in each fiber category. TA but not EDL showed conversion of fast glycolytic to fast oxidative fibers after 2 days, more after 4 days of stimulation. In both muscles, the largest fast glycolytic fibers were diminished in number after stimulation. There was significant increase in total capillaries per square millimeter after 4 days and some increase after 2 days of stimulation. The increase in capillaries per square millimeter exceeded the increase in the number of fibers per square millimeter, and since there was no change in mean fiber area, the increase is attributed to capillary growth. In EDL, there was an increase in the number of capillaries supplying both fast glycolytic and fast oxidative fibers, suggesting that capillary growth precedes fiber type conversion. In TA, the number of capillaries supplying fast oxidative fibers was increased but that to fast glycolytic fibers, was not. This is consistent with capillary growth simultaneous with or following fiber conversion. In both TA and EDL the number of capillaries perfused after contraction was higher in stimulated muscles, suggesting that increased capillary flow contributed to capillary growth.

Quantitative analysis of nailfold capillary morphology in patients with fibromyalgia

PubMed Central

Choi, Dug-Hyun

2015-01-01

Background/Aims Nailfold capillaroscopy (NFC) has been used to examine morphological and functional microcirculation changes in connective tissue diseases. It has been demonstrated that NFC patterns reflect abnormal microvascular dynamics, which may play a role in fibromyalgia (FM) syndrome. The aim of this study was to determine NFC patterns in FM, and their association with clinical features of FM. Methods A total of 67 patients with FM, and 30 age- and sex-matched healthy controls, were included. Nailfold capillary patterns were quantitatively analyzed using computerized NFC. The parameters of interest were as follows: number of capillaries within the central 3 mm, deletion score, apical limb width, capillary width, and capillary dimension. Capillary dimension was determined by calculating the number of capillaries using the Adobe Photoshop version 7.0. Results FM patients had a lower number of capillaries and higher deletion scores on NFC compared to healthy controls (17.3 ± 1.7 vs. 21.8 ± 2.9, p < 0.05; 2.2 ± 0.9 vs. 0.7 ± 0.6, p < 0.05, respectively). Both apical limb width (µm) and capillary width (µm) were significantly decreased in FM patients (1.1 ± 0.2 vs. 3.7 ± 0.6; 5.4 ± 0.5 vs. 7.5 ± 1.4, respectively), indicating that FM patients have abnormally decreased digital capillary diameter and density. Interestingly, there was no difference in capillary dimension between the two groups, suggesting that the length or tortuosity of capillaries in FM patients is increased to compensate for diminished microcirculation. Conclusions FM patients had altered capillary density and diameter in the digits. Diminished microcirculation on NFC may alter capillary density and increase tortuosity. PMID:26161020

How many taxa can be recognized within the complex Tillandsia capillaris (Bromeliaceae, Tillandsioideae)? Analysis of the available classifications using a multivariate approach.

PubMed

Castello, Lucía V; Galetto, Leonardo

2013-01-01

Tillandsia capillaris Ruiz & Pav., which belongs to the subgenus Diaphoranthema is distributed in Ecuador, Peru, Bolivia, northern and central Argentina, and Chile, and includes forms that are difficult to circumscribe, thus considered to form a complex. The entities of this complex are predominantly small-sized epiphytes, adapted to xeric environments. The most widely used classification defines 5 forms for this complex based on few morphological reproductive traits: Tillandsia capillaris Ruiz & Pav. f. capillaris, Tillandsia capillaris f. incana (Mez) L.B. Sm., Tillandsia capillaris f. cordobensis (Hieron.) L.B. Sm., Tillandsia capillaris f. hieronymi (Mez) L.B. Sm. and Tillandsia capillaris f. virescens (Ruiz & Pav.) L.B. Sm. In this study, 35 floral and vegetative characters were analyzed with a multivariate approach in order to assess and discuss different proposals for classification of the Tillandsia capillaris complex, which presents morphotypes that co-occur in central and northern Argentina. To accomplish this, data of quantitative and categorical morphological characters of flowers and leaves were collected from herbarium specimens and field collections and were analyzed with statistical multivariate techniques. The results suggest that the last classification for the complex seems more comprehensive and three taxa were delimited: Tillandsia capillaris (=Tillandsia capillaris f. incana-hieronymi), Tillandsia virescens s. str. (=Tillandsia capillaris f. cordobensis) and Tillandsia virescens s. l. (=Tillandsia capillaris f. virescens). While Tillandsia capillaris and Tillandsia virescens s. str. co-occur, Tillandsia virescens s. l. is restricted to altitudes above 2000 m in Argentina. Characters previously used for taxa delimitation showed continuous variation and therefore were not useful. New diagnostic characters are proposed and a key is provided for delimiting these three taxa within the complex.

How many taxa can be recognized within the complex Tillandsia capillaris (Bromeliaceae, Tillandsioideae)? Analysis of the available classifications using a multivariate approach

PubMed Central

Castello, Lucía V.; Galetto, Leonardo

2013-01-01

Abstract Tillandsia capillaris Ruiz & Pav., which belongs to the subgenus Diaphoranthema is distributed in Ecuador, Peru, Bolivia, northern and central Argentina, and Chile, and includes forms that are difficult to circumscribe, thus considered to form a complex. The entities of this complex are predominantly small-sized epiphytes, adapted to xeric environments. The most widely used classification defines 5 forms for this complex based on few morphological reproductive traits: Tillandsia capillaris Ruiz & Pav. f. capillaris, Tillandsia capillaris f. incana (Mez) L.B. Sm., Tillandsia capillaris f. cordobensis (Hieron.) L.B. Sm., Tillandsia capillaris f. hieronymi (Mez) L.B. Sm. and Tillandsia capillaris f. virescens (Ruiz & Pav.) L.B. Sm. In this study, 35 floral and vegetative characters were analyzed with a multivariate approach in order to assess and discuss different proposals for classification of the Tillandsia capillaris complex, which presents morphotypes that co-occur in central and northern Argentina. To accomplish this, data of quantitative and categorical morphological characters of flowers and leaves were collected from herbarium specimens and field collections and were analyzed with statistical multivariate techniques. The results suggest that the last classification for the complex seems more comprehensive and three taxa were delimited: Tillandsia capillaris (=Tillandsia capillaris f. incana-hieronymi), Tillandsia virescens s. str. (=Tillandsia capillaris f. cordobensis) and Tillandsia virescens s. l. (=Tillandsia capillaris f. virescens). While Tillandsia capillaris and Tillandsia virescens s. str. co-occur, Tillandsia virescens s. l. is restricted to altitudes above 2000 m in Argentina. Characters previously used for taxa delimitation showed continuous variation and therefore were not useful. New diagnostic characters are proposed and a key is provided for delimiting these three taxa within the complex. PMID:23805053

Probing the micro-rheological properties of aerosol particles using optical tweezers

NASA Astrophysics Data System (ADS)

Power, Rory M.; Reid, Jonathan P.

2014-07-01

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability.

New type of capillary for use as ion beam collimator and air-vacuum interface

NASA Astrophysics Data System (ADS)

Stoytschew, V.; Schulte-Borchers, M.; Božičević Mihalića, Iva; Perez, R. D.

2016-08-01

Glass capillaries offer a unique way to combine small diameter ion beam collimation with an air-vacuum interface for ambient pressure ion beam applications. Usually they have an opening diameter of a few microns, limiting the air inflow sufficiently to maintain stable conditions on the vacuum side. As the glass capillaries generally are quite thin and fragile, handling of the capillary in the experiment becomes difficult. They also introduce an X-ray background produced by the capillary wall material, which has to be shielded or subtracted from the data for Particle Induced X-ray Emission (PIXE) applications. To overcome both drawbacks, a new type of conical glass capillary has been developed. It has a higher wall thickness eliminating the low energy X-ray background produced by common capillaries and leading to a more robust lens. The results obtained in first tests show, that this new capillary is suitable for ion beam collimation and encourage further work on the capillary production process to provide thick wall capillaries with an outlet diameter in the single digit micro- or even nanometre range.

Pore-scale modeling of Capillary Penetration of Wetting Liquid into 3D Fibrous Media: A Critical Examination of Equivalent Capillary Concept

NASA Astrophysics Data System (ADS)

Palakurthi, Nikhil Kumar; Ghia, Urmila; Comer, Ken

2013-11-01

Capillary penetration of liquid through fibrous porous media is important in many applications such as printing, drug delivery patches, sanitary wipes, and performance fabrics. Historically, capillary transport (with a distinct liquid propagating front) in porous media is modeled using capillary-bundle theory. However, it is not clear if the capillary model (Washburn equation) describes the fluid transport in porous media accurately, as it assumes uniformity of pore sizes in the porous medium. The present work investigates the limitations of the applicability of the capillary model by studying liquid penetration through virtual fibrous media with uniform and non-uniform pore-sizes. For the non-uniform-pore fibrous medium, the effective capillary radius of the fibrous medium was estimated from the pore-size distribution curve. Liquid penetration into the 3D virtual fibrous medium at micro-scale was simulated using OpenFOAM, and the numerical results were compared with the Washburn-equation capillary-model predictions. Preliminary results show that the Washburn equation over-predicts the height rise in the early stages (purely inertial and visco-inertial stages) of capillary transport.

Two-dimensional capillary electrophoresis: capillary isoelectric focusing and capillary zone electrophoresis with laser-induced fluorescence detection

PubMed Central

Dickerson, Jane A.; Ramsay, Lauren M.; Dada, Oluwatosin O.; Cermak, Nathan

2011-01-01

Capillary isoelectric focusing and capillary zone electrophoresis are coupled with laser-induced fluorescence detection to create an ultrasensitive two-dimensional separation method for proteins. In this method, two capillaries are joined through a buffer filled interface. Separate power supplies control the potential at the injection end of the first capillary and at the interface; the detector is held at ground potential. Proteins are labeled with the fluorogenic reagent Chromeo P503, which preserves the isoelectric point of the labeled protein. The labeled proteins were mixed with ampholytes and injected into the first dimension capillary. A focusing step was performed with the injection end of the capillary at high pH and the interface at low pH. To mobilize components, the interface was filled with a high pH buffer, which was compatible with the second dimension separation. A fraction was transferred to the second dimension capillary for separation. The process of fraction transfer and second dimension separation was repeated two dozen times. The separation produced a spot capacity of 125. PMID:20603830

Capillarics: pre-programmed, self-powered microfluidic circuits built from capillary elements.

PubMed

Safavieh, Roozbeh; Juncker, David

2013-11-07

Microfluidic capillary systems employ surface tension effects to manipulate liquids, and are thus self-powered and self-regulated as liquid handling is structurally and chemically encoded in microscale conduits. However, capillary systems have been limited to perform simple fluidic operations. Here, we introduce complex capillary flow circuits that encode sequential flow of multiple liquids with distinct flow rates and flow reversal. We first introduce two novel microfluidic capillary elements including (i) retention burst valves and (ii) robust low aspect ratio trigger valves. These elements are combined with flow resistors, capillary retention valves, capillary pumps, and open and closed reservoirs to build a capillary circuit that, following sample addition, autonomously delivers a defined sequence of multiple chemicals according to a preprogrammed and predetermined flow rate and time. Such a circuit was used to measure the concentration of C-reactive protein. This work illustrates that as in electronics, complex capillary circuits may be built by combining simple capillary elements. We define such circuits as "capillarics", and introduce symbolic representations. We believe that more complex circuits will become possible by expanding the library of building elements and formulating abstract design rules.

Particle sizer and DNA sequencer

DOEpatents

Olivares, Jose A.; Stark, Peter C.

2005-09-13

An electrophoretic device separates and detects particles such as DNA fragments, proteins, and the like. The device has a capillary which is coated with a coating with a low refractive index such as Teflon.RTM. AF. A sample of particles is fluorescently labeled and injected into the capillary. The capillary is filled with an electrolyte buffer solution. An electrical field is applied across the capillary causing the particles to migrate from a first end of the capillary to a second end of the capillary. A detector light beam is then scanned along the length of the capillary to detect the location of the separated particles. The device is amenable to a high throughput system by providing additional capillaries. The device can also be used to determine the actual size of the particles and for DNA sequencing.

Critical Action Learning: Extending Its Reach

ERIC Educational Resources Information Center

Ram, Monder

2012-01-01

The trend to imbue action learning with an explicit conception of criticality appears to be gathering momentum. The idea of critical action learning (CAL) foregrounds the connection between power, emotion and organizing. How this triumvirate of forces relate to each other fundamentally shapes the scope for learning. Theoretical and empirical…

Drop dynamics in space and interference with acoustic field (M-15)

NASA Technical Reports Server (NTRS)

Yamanaka, Tatsuo

1993-01-01

The objective of the experiment is to study contactless positioning of liquid drops, excitation of capillary waves on the surface of acoustically levitated liquid drops, and deformation of liquid drops by means of acoustic radiation pressure. Contactless positioning technologies are very important in space materials processing because the melt is processed without contacting the wall of a crucible which can easily contaminate the melt specifically for high melting temperatures and chemically reactive materials. Among the contactless positioning technologies, an acoustic technology is especially important for materials unsusceptible to electromagnetic fields such as glasses and ceramics. The shape of a levitated liquid drop in the weightless condition is determined by its surface tension and the internal and external pressure distribution. If the surface temperature is constant and there exist neither internal nor external pressure perturbations, the levitated liquid drop forms a shape of perfect sphere. If temperature gradients on the surface and internal or external pressure perturbations exist, the liquid drop forms various modes of shapes with proper vibrations. A rotating liquid drop was specifically studied not only as a classical problem of theoretical mechanics to describe the shapes of the planets of the solar system, as well as their arrangement, but it is also more a contemporary problem of modern non-linear mechanics. In the experiment, we are expecting to observe various shapes of a liquid drop such as cocoon, tri-lobed, tetropod, multi-lobed, and doughnut.

Selection of Two-Phase Flow Patterns at a Simple Junction in Microfluidic Devices

NASA Astrophysics Data System (ADS)

Engl, W.; Ohata, K.; Guillot, P.; Colin, A.; Panizza, P.

2006-04-01

We study the behavior of a confined stream made of two immiscible fluids when it reaches a T junction. Two flow patterns are witnessed: the stream is either directed in only one sidearm, yielding a preferential flow pathway for the dispersed phase, or splits between both. We show that the selection of these patterns is not triggered by the shape of the junction nor by capillary effects, but results from confinement. It can be anticipated in terms of the hydrodynamic properties of the flow. A simple model yielding universal behavior in terms of the relevant adimensional parameters of the problem is presented and discussed.

Experimental Investigation of Relative Permeability Upscaling from the Micro-Scale to the Macro-Scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyrak-Nolte, Laura J.; Cheng, JiangTao; Yu, Ping

2003-01-29

During this reporting period, shown experimentally that the optical coherence imaging system can acquire information on grain interfaces and void shape for a maximum depth of half a millimeter into sandstone. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures has shown the existence of a unique relationship among these hydraulic parameters for different pore geometry. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, has shown the homogeneity of IAV with depth in a sample when the fluids are in equilibrium.

Capillarity-induced disassembly of virions in carbon nanotubes

NASA Astrophysics Data System (ADS)

Fan, Xiaobin; Barclay, J. Elaine; Peng, Wenchao; Li, Yang; Li, Xianyu; Zhang, Guoliang; Evans, David J.; Zhang, Fengbao

2008-04-01

Studying the transport and fate of viruses through nanochannels is of great importance. By using the nanochannel of a carbon nanotube (CNT) as an ideal model, we evaluated the possibility of capillarity-induced viral transport through a closely fitting nanochannel and explored the mechanisms involved. It is shown both experimentally and theoretically that Cowpea mosaic virus can enter CNTs by capillarity. However, when introduced into a nanotube the protein capsid may disassemble. During the initial capillary filling stage, anomalous needle-shaped high pressure exists in the centre of the nanotube's entrance. This high pressure, combining with the significant negative pressure within the nanotube, may account for the disassembly of the virions.

Analysis of the boundary conditions for a Hele--Shaw bubble

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgess, D.; Foster, M.R.

1990-07-01

Effective boundary conditions are derived to be used with the classical Hele--Shaw equations in calculating the shape and motion of a Hele--Shaw bubble. The main assumptions of this analysis are that the displaced fluid wets the plates, and that the capillary number Ca and the ratio of gap width to characteristic bubble length {epsilon} are both small. In a small region at the sides of the bubble, it is found that the thin-film thickness scales with {epsilon}{sup 2/5} Ca{sup 4/5}, rather than the Ca{sup 2/3} scaling that is valid over most of the thin film above and below the bubble.

[A novel method based on Y-shaped cotton-polyester thread microfluidic channel].

PubMed

Wang, Lu; Shi, Yan-ru; Yan, Hong-tao

2014-08-01

A novel method based on Y-shaped microfluidic channel was firstly proposed in this study. The microfluidic channel was made of two cotton-polyester threads based on the capillary effect of cotton-polyester threads for the determination solutions. A special device was developed to fix the Y-shaped microfluidic channel by ourselves, through which the length and the tilt angle of the channel can be adjusted as requested. The spectrophotometry was compared with Scan-Adobe Photoshop software processing method. The former had a lower detection limit while the latter showed advantages in both convenience and fast operations and lower amount of samples. The proposed method was applied to the determination of nitrite. The linear ranges and detection limits are 1.0-70 micromol x L(-1), 0.66 micromol x L(-1) (spectrophotometry) and 50-450 micromol x L(-1), 45.10 micromol x L(-1) (Scan-Adobe Photoshop software processing method) respectively. This method has been successfully used to the determination of nitrite in soil samples and moat water with recoveries between 96.7% and 104%. It was proved that the proposed method was a low-cost, rapid and convenient analytical method with extensive application prospect.

Predictive models for moving contact line flows

NASA Technical Reports Server (NTRS)

Rame, Enrique; Garoff, Stephen

2003-01-01

Modeling flows with moving contact lines poses the formidable challenge that the usual assumptions of Newtonian fluid and no-slip condition give rise to a well-known singularity. This singularity prevents one from satisfying the contact angle condition to compute the shape of the fluid-fluid interface, a crucial calculation without which design parameters such as the pressure drop needed to move an immiscible 2-fluid system through a solid matrix cannot be evaluated. Some progress has been made for low Capillary number spreading flows. Combining experimental measurements of fluid-fluid interfaces very near the moving contact line with an analytical expression for the interface shape, we can determine a parameter that forms a boundary condition for the macroscopic interface shape when Ca much les than l. This parameter, which plays the role of an "apparent" or macroscopic dynamic contact angle, is shown by the theory to depend on the system geometry through the macroscopic length scale. This theoretically established dependence on geometry allows this parameter to be "transferable" from the geometry of the measurement to any other geometry involving the same material system. Unfortunately this prediction of the theory cannot be tested on Earth.

Multiple capillary biochemical analyzer

DOEpatents

Dovichi, N.J.; Zhang, J.Z.

1995-08-08

A multiple capillary analyzer allows detection of light from multiple capillaries with a reduced number of interfaces through which light must pass in detecting light emitted from a sample being analyzed, using a modified sheath flow cuvette. A linear or rectangular array of capillaries is introduced into a rectangular flow chamber. Sheath fluid draws individual sample streams through the cuvette. The capillaries are closely and evenly spaced and held by a transparent retainer in a fixed position in relation to an optical detection system. Collimated sample excitation radiation is applied simultaneously across the ends of the capillaries in the retainer. Light emitted from the excited sample is detected by the optical detection system. The retainer is provided by a transparent chamber having inward slanting end walls. The capillaries are wedged into the chamber. One sideways dimension of the chamber is equal to the diameter of the capillaries and one end to end dimension varies from, at the top of the chamber, slightly greater than the sum of the diameters of the capillaries to, at the bottom of the chamber, slightly smaller than the sum of the diameters of the capillaries. The optical system utilizes optic fibers to deliver light to individual photodetectors, one for each capillary tube. A filter or wavelength division demultiplexer may be used for isolating fluorescence at particular bands. 21 figs.

Progression of Diabetic Capillary Occlusion: A Model

PubMed Central

Gens, John Scott; Glazier, James A.; Burns, Stephen A.; Gast, Thomas J.

2016-01-01

An explanatory computational model is developed of the contiguous areas of retinal capillary loss which play a large role in diabetic maculapathy and diabetic retinal neovascularization. Strictly random leukocyte mediated capillary occlusion cannot explain the occurrence of large contiguous areas of retinal ischemia. Therefore occlusion of an individual capillary must increase the probability of occlusion of surrounding capillaries. A retinal perifoveal vascular sector as well as a peripheral retinal capillary network and a deleted hexagonal capillary network are modelled using Compucell3D. The perifoveal modelling produces a pattern of spreading capillary loss with associated macular edema. In the peripheral network, spreading ischemia results from the progressive loss of the ladder capillaries which connect peripheral arterioles and venules. System blood flow was elevated in the macular model before a later reduction in flow in cases with progression of capillary occlusions. Simulations differing only in initial vascular network structures but with identical dynamics for oxygen, growth factors and vascular occlusions, replicate key clinical observations of ischemia and macular edema in the posterior pole and ischemia in the retinal periphery. The simulation results also seem consistent with quantitative data on macular blood flow and qualitative data on venous oxygenation. One computational model applied to distinct capillary networks in different retinal regions yielded results comparable to clinical observations in those regions. PMID:27300722

Multiple capillary biochemical analyzer

DOEpatents

Dovichi, Norman J.; Zhang, Jian Z.

1995-01-01

A multiple capillary analyzer allows detection of light from multiple capillaries with a reduced number of interfaces through which light must pass in detecting light emitted from a sample being analyzed, using a modified sheath flow cuvette. A linear or rectangular array of capillaries is introduced into a rectangular flow chamber. Sheath fluid draws individual sample streams through the cuvette. The capillaries are closely and evenly spaced and held by a transparent retainer in a fixed position in relation to an optical detection system. Collimated sample excitation radiation is applied simultaneously across the ends of the capillaries in the retainer. Light emitted from the excited sample is detected by the optical detection system. The retainer is provided by a transparent chamber having inward slanting end walls. The capillaries are wedged into the chamber. One sideways dimension of the chamber is equal to the diameter of the capillaries and one end to end dimension varies from, at the top of the chamber, slightly greater than the sum of the diameters of the capillaries to, at the bottom of the chamber, slightly smaller than the sum of the diameters of the capillaries. The optical system utilizes optic fibres to deliver light to individual photodetectors, one for each capillary tube. A filter or wavelength division demultiplexer may be used for isolating fluorescence at particular bands.

Stability analysis for capillary channel flow: 1d and 3d computations

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The subject of the presentation are numerical studies on capillary channel flow, based on results of the sounding rocket TEXUS experiments. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behavior, a dimensionless one-dimensional model and a corresponding three-dimensional model were developed. The one-dimensional model is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The experimental and evaluated contour data show good agreement for a sequence of transient flow rate perturbations. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies lead to a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate.

The effects of wettability and trapping on relationships between interfacial area, capillary pressure and saturation in porous media: A pore-scale network modeling approach

NASA Astrophysics Data System (ADS)

Raeesi, Behrooz; Piri, Mohammad

2009-10-01

SummaryWe use a three-dimensional mixed-wet random pore-scale network model to investigate the impact of wettability and trapping on the relationship between interfacial area, capillary pressure and saturation in two-phase drainage and imbibition processes. The model is a three-dimensional network of interconnected pores and throats of various geometrical shapes. It allows multiple phases to be present in each capillary element in wetting and spreading layers, as well as occupying the center of the pore space. Two different random networks that represent the pore space in Berea and a Saudi Arabia reservoir sandstone are used in this study. We allow the wettability of the rock surfaces contacted by oil to alter after primary drainage. The model takes into account both contact angle and trapping hystereses. We model primary oil drainage and water flooding for mixed-wet conditions, and secondary oil injection for a water-wet system. The total interfacial area for pores and throats are calculated when the system is at capillary equilibrium. They include contributions from the arc menisci (AMs) between the bulk and corner fluids, and from the main terminal menisci (MTMs) between different bulk fluids. We investigate hysteresis in these relationships by performing water injection into systems of varying wettability and initial water saturation. We show that trapping and contact angle hystereses significantly affect the interfacial area. In a strongly water-wet system, a sharp increase is observed at the beginning of water flood, which shifts the area to a higher level than primary drainage. As we change the wettability of the system from strongly water-wet to strongly oil-wet, the trapped oil saturation decreases significantly. Starting water flood from intermediate water saturations, greater than the irreducible water saturation, can also affect the non-wetting phase entrapment, resulting in different interfacial area behaviors. This can increase the interfacial area significantly in oil-wet systems. A qualitative comparison of our results with the experimental data available in literature for glass beads shows, with some expected differences, an encouraging agreement. Also, our results agree well with those generated by the previously developed models.

CO2 storage capacity estimates from fluid dynamics (Invited)

NASA Astrophysics Data System (ADS)

Juanes, R.; MacMinn, C. W.; Szulczewski, M.

2009-12-01

We study a sharp-interface mathematical model for the post-injection migration of a plume of CO2 in a deep saline aquifer under the influence of natural groundwater flow, aquifer slope, gravity override, and capillary trapping. The model leads to a nonlinear advection-diffusion equation, where the diffusive term describes the upward spreading of the CO2 against the caprock. We find that the advective terms dominate the flow dynamics even for moderate gravity override. We solve the model analytically in the hyperbolic limit, accounting rigorously for the injection period—using the true end-of-injection plume shape as an initial condition. We extend the model by incorporating the effect of CO2 dissolution into the brine, which—we find—is dominated by convective mixing. This mechanism enters the model as a nonlinear sink term. From a linear stability analysis, we propose a simple estimate of the convective dissolution flux. We then obtain semi-analytic estimates of the maximum plume migration distance and migration time for complete trapping. Our analytical model can be used to estimate the storage capacity (from capillary and dissolution trapping) at the geologic basin scale, and we apply the model to various target formations in the United States. Schematic of the migration of a CO2 plume at the geologic basin scale. During injection, the CO2 forms a plume that is subject to gravity override. At the end of the injection, all the CO2 is mobile. During the post-injection period, the CO2 migrates updip and also driven by regional groundwater flow. At the back end of the plume, where water displaces CO2, the plume leaves a wake or residual CO2 due to capillary trapping. At the bottom of the moving plume, CO2 dissolves into the brine—a process dominated by convective mixing. These two mechanisms—capillary trapping and convective dissolution—reduce the size of the mobile plume as it migrates. In this communication, we present an analytical model that predicts the migration distance and time for complete trapping. This is used to estimate storage capacity of geologic formations at the basin scale.

Nailfold capillaroscopy in systemic lupus erythematosus: A systematic review and critical appraisal.

PubMed

Cutolo, Maurizio; Melsens, Karin; Wijnant, Sara; Ingegnoli, Francesca; Thevissen, Kristof; De Keyser, Filip; Decuman, Saskia; Müller-Ladner, Ulf; Piette, Yves; Riccieri, Valeria; Ughi, Nicola; Vandecasteele, Els; Vanhaecke, Amber; Smith, Vanessa

2018-04-01

Nailfold capillaroscopy is an easy, non-invasive technique to assess microvascular involvement in rheumatic diseases. Multiple studies describe capillaroscopic changes in systemic lupus erythematosus (SLE), including a wide range of non-specific findings. On behalf of the European League Against Rheumatism (EULAR) study group on microcirculation in rheumatic diseases, a systematic review was done to obtain all original research studies (in English) in which SLE patients had capillaroscopy. Forty such studies are identified. This article firstly provides a résumé of the results of these studies according to capillaroscopic parameters (density, dimensions, morphology, haemorrhages), semi-quantitative assessment and qualitative assessment of capillaroscopy in SLE patients. Secondly, the correlations between capillaroscopic parameters in SLE patients and clinical and laboratory parameters (including auto-immune parameters) are outlined. The following capillaroscopic parameters are found to be significantly more prevalent in SLE patients compared to healthy controls: tortuous capillaries, abnormal morphology and haemorrhages. Hairpin-shaped capillaries are significantly less prevalent than in healthy persons. The semi-quantitatively determined nailfold capillaroscopic score (NFC score) in SLE patients is also higher than in healthy controls. Several correlations between clinical and laboratory parameters and capillaroscopic parameters are identified in the review. Disease activity is correlated with NFC score in seven studies, with abnormal morphology (i.e. "meandering") in one study and with haemorrhages in one study. Frequent attacks of Raynaud's phenomenon (RP) and gangrene are significantly correlated with dilated capillaries. In two studies a possible correlation between anti-SSA antibodies and lower density of capillaries is withheld. About other immune parameters conflicting results are found. In one study a significant negative correlation is found between 24-hour proteinuria and abnormal morphology (i.e. "meandering"). For the first time, an overview of the nailfold capillaroscopic changes that have been described in SLE and their correlations with clinical and laboratory findings is given. Further large-scale research on the identification of capillaroscopic changes in SLE and their correlations with standardised clinical and laboratory parameters, is ongoing at the EULAR study group on microcirculation in rheumatic diseases. Copyright © 2018 Elsevier B.V. All rights reserved.

Sealed Gravitational Capillary Viscometry of Dimethyl Ether and Two Next-Generation Alternative Refrigerants

PubMed Central

Cousins, Dylan S.; Laesecke, Arno

2012-01-01

The viscosities of dimethyl ether (DME, C2H6O) and of the fluorinated propene isomers 2,3,3,3-tetrafluoroprop-1-ene (R1234yf, C3H2F4) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) were measured in a combined temperature range from 242 K to 350 K at saturated liquid conditions. The instrument was a sealed gravitational capillary viscometer developed at NIST for volatile liquids. Calibration and adjustment of the instrument constant were conducted with n-pentane. The repeatability of the measurements was found to be approximately 1.5 %, leading to a temperature-dependent estimated combined standard uncertainty of the experimental data between 5.7 % at 242 K for dimethyl ether and 2.6 % at 340 K for R1234yf. The measurements were supplemented by ab initio calculations of the molecular size, shape, and charge distributions of the measured compounds. The viscosity results for dimethyl ether were compared with literature data. One other data set measured with a sealed capillary viscometer and exceeding the present results by up to 7 % could be reconciled by applying the vapor buoyancy correction. Then, all data agreed within the estimated uncertainty of the present results. Viscosities for the fluorinated propene isomers deviate up to 4 % from values predicted with the NIST extended corresponding-states model. The viscosities of the two isomers do not scale with their dipole moments. While the measured viscosity of R1234ze(E) with the lower dipole moment is close to that of R134a, the refrigerant to be replaced, that of R1234yf with the higher dipole moment is up to 25 % lower. The viscosity of dimethyl ether is compared with those of water and methanol. PMID:26900526

Comparison of generated parallel capillary arrays to three-dimensional reconstructed capillary networks in modeling oxygen transport in discrete microvascular volumes.

PubMed

Fraser, Graham M; Goldman, Daniel; Ellis, Christopher G

2013-11-01

We compare RMN to PCA under several simulated physiological conditions to determine how the use of different vascular geometry affects oxygen transport solutions. Three discrete networks were reconstructed from intravital video microscopy of rat skeletal muscle (84 × 168 × 342 μm, 70 × 157 × 268 μm, and 65 × 240 × 571 μm), and hemodynamic measurements were made in individual capillaries. PCAs were created based on statistical measurements from RMNs. Blood flow and O₂ transport models were applied, and the resulting solutions for RMN and PCA models were compared under four conditions (rest, exercise, ischemia, and hypoxia). Predicted tissue PO₂ was consistently lower in all RMN simulations compared to the paired PCA. PO₂ for 3D reconstructions at rest were 28.2 ± 4.8, 28.1 ± 3.5, and 33.0 ± 4.5 mmHg for networks I, II, and III compared to the PCA mean values of 31.2 ± 4.5, 30.6 ± 3.4, and 33.8 ± 4.6 mmHg. Simulated exercise yielded mean tissue PO₂ in the RMN of 10.1 ± 5.4, 12.6 ± 5.7, and 19.7 ± 5.7 mmHg compared to 15.3 ± 7.3, 18.8 ± 5.3, and 21.7 ± 6.0 in PCA. These findings suggest that volume matched PCA yield different results compared to reconstructed microvascular geometries when applied to O₂ transport modeling; the predominant characteristic of this difference being an over estimate of mean tissue PO₂. Despite this limitation, PCA models remain important for theoretical studies as they produce PO₂ distributions with similar shape and parameter dependence as RMN. © 2013 John Wiley & Sons Ltd.

Laser-induced spalling of thin metal film from silica substrate followed by inflation of microbump

NASA Astrophysics Data System (ADS)

Inogamov, N. A.; Zhakhovsky, V. V.; Migdal, K. P.

2016-04-01

Dynamics of a thin gold film on a silica substrate triggered by fast heating with the use of a subpicosecond laser pulse is studied. The pressure waves generated by such heating may result in spalling (delamination) of the film and its flying away from the substrate after an acoustic time defined by the film thickness and speed of sound in metal. Intensity of the heating laser beam has the spatial Gaussian distribution in a cross section. Therefore, the heating of film surface is non-uniform along cylindrical radius measured from the beam axis. As a result of such heating, the velocity distribution in material flying away from the substrate has a maximum at the beam axis. Thus, the separated film has dome-like shape which inflates with time. Volume of an empty cavity between the separated film and the substrate increases during inflation. Typical flight velocities are in the range of 30-200 m/s. The inflation stage can last from few to several tens of nanoseconds if the diffraction-limited micron-sized laser focal spots are used. Capillary forces acting along the warped flying film decelerate the inflation of dome. Capillary deceleration of a bulging dome focuses mass flow along the dome shell in the direction of its axis. This results in formation of an axial jet and droplet in a tip of the dome. Our new simulation results and comparisons with experiments are presented. The results explain appearance of debris in a form of frozen droplets on a surface of an irradiated spot. This is the consequence of the capillary return of a droplet.

Evidence for a neural law of effect.

PubMed

Athalye, Vivek R; Santos, Fernando J; Carmena, Jose M; Costa, Rui M

2018-03-02

Thorndike's law of effect states that actions that lead to reinforcements tend to be repeated more often. Accordingly, neural activity patterns leading to reinforcement are also reentered more frequently. Reinforcement relies on dopaminergic activity in the ventral tegmental area (VTA), and animals shape their behavior to receive dopaminergic stimulation. Seeking evidence for a neural law of effect, we found that mice learn to reenter more frequently motor cortical activity patterns that trigger optogenetic VTA self-stimulation. Learning was accompanied by gradual shaping of these patterns, with participating neurons progressively increasing and aligning their covariance to that of the target pattern. Motor cortex patterns that lead to phasic dopaminergic VTA activity are progressively reinforced and shaped, suggesting a mechanism by which animals select and shape actions to reliably achieve reinforcement. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Design and fabrication of thin microvascularised polymer matrices inspired from secondary lamellae of fish gills

NASA Astrophysics Data System (ADS)

Kumar, Prasoon; Gandhi, Prasanna S.; Majumder, Mainak

2016-04-01

Gills are one of the most primitive gas, solute exchange organs available in fishes. They facilitate exchange of gases, solutes and ions with a surrounding water medium through their functional unit called secondary lamella. These lamellae through their extraordinary morphometric features and peculiar arrangement in gills, achieve remarkable mass transport properties. Therefore, in the current study, modeling and simulation of convection-diffusion transport through a two dimensional model of secondary lamella and theoretical analysis of morphometric features of fish gills were carried out. Such study suggested an evolutionary conservation of parametric ratios across fishes of different weights. Further, we have also fabricated a thin microvascularised PDMS matrices mimicking secondary lamella by use of micro-technologies like electrospinning. In addition, we have also demonstrated the fluid flow by capillary action through these thin microvascularised PDMS matrices. Eventually, we also illustrated the application of these thin microvascularied PDMS matrices in solute exchange process under capillary flow conditions. Thus, our study suggested that fish gills have optimized parameteric ratios, at multiple length scale, throughout an evolution to achieve an organ with enhanced mass transport capabilities. Thus, these defined parametric ratios could be exploited to design and develop efficient, scaled-up gas/solute exchange microdevices. We also proposed an inexpensive and scalable method of fabrication of thin microvascularised polymer matrices and demonstrated its solute exchange capabilities under capillary flow conditions. Thus, mimicking the microstructures of secondary lamella will enable fabrication of microvascularised thin polymer systems through micro manufacturing technologies for potential applications in filtration, self-healing/cooling materials and bioengineering.

Capillary reference half-cell

DOEpatents

Hall, Stephen H.

1996-01-01

The present invention is a reference half-cell electrode wherein intermingling of test fluid with reference fluid does not affect the performance of the reference half-cell over a long time. This intermingling reference half-cell may be used as a single or double junction submersible or surface reference electrode. The intermingling reference half-cell relies on a capillary tube having a first end open to reference fluid and a second end open to test fluid wherein the small diameter of the capillary tube limits free motion of fluid within the capillary to diffusion. The electrode is placed near the first end of the capillary in contact with the reference fluid. The method of operation of the present invention begins with filling the capillary tube with a reference solution. After closing the first end of the capillary, the capillary tube may be fully submerged or partially submerged with the second open end inserted into test fluid. Since the electrode is placed near the first end of the capillary, and since the test fluid may intermingle with the reference fluid through the second open end only by diffusion, this intermingling capillary reference half-cell provides a stable voltage potential for long time periods.

Capillary reference half-cell

DOEpatents

Hall, S.H.

1996-02-13

The present invention is a reference half-cell electrode wherein intermingling of test fluid with reference fluid does not affect the performance of the reference half-cell over a long time. This intermingling reference half-cell may be used as a single or double junction submersible or surface reference electrode. The intermingling reference half-cell relies on a capillary tube having a first end open to reference fluid and a second end open to test fluid wherein the small diameter of the capillary tube limits free motion of fluid within the capillary to diffusion. The electrode is placed near the first end of the capillary in contact with the reference fluid. The method of operation of the present invention begins with filling the capillary tube with a reference solution. After closing the first end of the capillary, the capillary tube may be fully submerged or partially submerged with the second open end inserted into test fluid. Since the electrode is placed near the first end of the capillary, and since the test fluid may intermingle with the reference fluid through the second open end only by diffusion, this intermingling capillary reference half-cell provides a stable voltage potential for long time periods. 11 figs.

Electrphoretic Sample Excitation Light Assembly.

DOEpatents

Li, Qingbo; Liu, Changsheng

2002-04-02

An automated electrophoretic system is disclosed. The system employs a capillary cartridge having a plurality of capillary tubes. The cartridge has a first array of capillary ends projecting from one side of a plate. The first array of capillary ends are spaced apart in substantially the same manner as the wells of a microtitre tray of standard size. This allows one to simultaneously perform capillary electrophoresis on samples present in each of the wells of the tray. The system includes a stacked, dual carrousel arrangement to eliminate cross-contamination resulting from reuse of the same buffer tray on consecutive executions from electrophoresis. The system also has a gel delivery module containing a gel syringe/a stepper motor or a high pressure chamber with a pump to quickly and uniformly deliver gel through the capillary tubes. The system further includes a multi-wavelength beam generator to generate a laser beam which produces a beam with a wide range of wavelengths. An off-line capillary reconditioner thoroughly cleans a capillary cartridge to enable simultaneous execution of electrophoresis with another capillary cartridge. The streamlined nature of the off-line capillary reconditioner offers the advantage of increased system throughput with a minimal increase in system cost.

Motorized Positioning Apparatus Having Coaxial Carrousels.

DOEpatents

Li, Qingbo; Kane, Thomas E.; Liu, Changsheng; Sonnenschein, Bernard; Sharer, Michael V.; Kernan, John R.

2002-04-02

An automated electrophoretic system is disclosed. The system employs a capillary cartridge having a plurality of capillary tubes. The cartridge has a first array of capillary ends projecting from one side of a plate. The first array of capillary ends are spaced apart in substantially the same manner as the wells of a microtitre tray of standard size. This allows one to simultaneously perform capillary electrophoresis on samples present in each of the wells of the tray. The system includes a stacked, dual carrousel arrangement to eliminate cross-contamination resulting from reuse of the same buffer tray on consecutive executions from electrophoresis. The system also has a gel delivery module containing a gel syringe/a stepper motor or a high pressure chamber with a pump to quickly and uniformly deliver gel through the capillary tubes. The system further includes a multi-wavelength beam generator to generate a laser beam which produces a beam with a wide range of wavelengths. An off-line capillary reconditioner thoroughly cleans a capillary cartridge to enable simultaneous execution of electrophoresis with another capillary cartridge. The streamlined nature of the off-line capillary reconditioner offers the advantage of increased system throughput with a minimal increase in system cost.

Measurement of the refractive index of microquantity liquid filled in a capillary and a capillary wall without destruction.

PubMed

Li, Qiang; Pu, Xiaoyun

2013-07-20

A method for measuring the refractive index (RI) of a small volume of liquid and a capillary wall is presented in this paper. A transparent capillary filled with liquid is used as a cylindrical positive lens; subsequently, the focal length of the lens is derived through the base of paraxial approximation, which is recorded as a function of the RIs of the liquid and capillary wall. With the RI of a capillary wall known, the RI of the liquid can be obtained by measuring the focal length of the lens, which is characterized by a microquantity liquid, spatial resolution, and easy operation. The RI of the capillary wall can be calculated without ruining the capillary if the capillary is filled with a standard liquid (RI is known), the deviation of which is less than 0.003 RIU. The factors affecting accuracy of the measurement, for instance, the depth of a field (DOF) in a reading microscope system and the outer and inner diameters of a capillary are analyzed, while illustrating that the effective DOF plays an essential role in accurate measurement.

Physiologic upper limits of pore size of different blood capillary types and another perspective on the dual pore theory of microvascular permeability.

PubMed

Sarin, Hemant

2010-08-11

Much of our current understanding of microvascular permeability is based on the findings of classic experimental studies of blood capillary permeability to various-sized lipid-insoluble endogenous and non-endogenous macromolecules. According to the classic small pore theory of microvascular permeability, which was formulated on the basis of the findings of studies on the transcapillary flow rates of various-sized systemically or regionally perfused endogenous macromolecules, transcapillary exchange across the capillary wall takes place through a single population of small pores that are approximately 6 nm in diameter; whereas, according to the dual pore theory of microvascular permeability, which was formulated on the basis of the findings of studies on the accumulation of various-sized systemically or regionally perfused non-endogenous macromolecules in the locoregional tissue lymphatic drainages, transcapillary exchange across the capillary wall also takes place through a separate population of large pores, or capillary leaks, that are between 24 and 60 nm in diameter. The classification of blood capillary types on the basis of differences in the physiologic upper limits of pore size to transvascular flow highlights the differences in the transcapillary exchange routes for the transvascular transport of endogenous and non-endogenous macromolecules across the capillary walls of different blood capillary types. The findings and published data of studies on capillary wall ultrastructure and capillary microvascular permeability to lipid-insoluble endogenous and non-endogenous molecules from the 1950s to date were reviewed. In this study, the blood capillary types in different tissues and organs were classified on the basis of the physiologic upper limits of pore size to the transvascular flow of lipid-insoluble molecules. Blood capillaries were classified as non-sinusoidal or sinusoidal on the basis of capillary wall basement membrane layer continuity or lack thereof. Non-sinusoidal blood capillaries were further sub-classified as non-fenestrated or fenestrated based on the absence or presence of endothelial cells with fenestrations. The sinusoidal blood capillaries of the liver, myeloid (red) bone marrow, and spleen were sub-classified as reticuloendothelial or non-reticuloendothelial based on the phago-endocytic capacity of the endothelial cells. The physiologic upper limit of pore size for transvascular flow across capillary walls of non-sinusoidal non-fenestrated blood capillaries is less than 1 nm for those with interendothelial cell clefts lined with zona occludens junctions (i.e. brain and spinal cord), and approximately 5 nm for those with clefts lined with macula occludens junctions (i.e. skeletal muscle). The physiologic upper limit of pore size for transvascular flow across the capillary walls of non-sinusoidal fenestrated blood capillaries with diaphragmed fenestrae ranges between 6 and 12 nm (i.e. exocrine and endocrine glands); whereas, the physiologic upper limit of pore size for transvascular flow across the capillary walls of non-sinusoidal fenestrated capillaries with open 'non-diaphragmed' fenestrae is approximately 15 nm (kidney glomerulus). In the case of the sinusoidal reticuloendothelial blood capillaries of myeloid bone marrow, the transvascular transport of non-endogenous macromolecules larger than 5 nm into the bone marrow interstitial space takes place via reticuloendothelial cell-mediated phago-endocytosis and transvascular release, which is the case for systemic bone marrow imaging agents as large as 60 nm in diameter. The physiologic upper limit of pore size in the capillary walls of most non-sinusoidal blood capillaries to the transcapillary passage of lipid-insoluble endogenous and non-endogenous macromolecules ranges between 5 and 12 nm. Therefore, macromolecules larger than the physiologic upper limits of pore size in the non-sinusoidal blood capillary types generally do not accumulate within the respective tissue interstitial spaces and their lymphatic drainages. In the case of reticuloendothelial sinusoidal blood capillaries of myeloid bone marrow, however, non-endogenous macromolecules as large as 60 nm in diameter can distribute into the bone marrow interstitial space via the phago-endocytic route, and then subsequently accumulate in the locoregional lymphatic drainages of tissues following absorption into the lymphatic drainage of periosteal fibrous tissues, which is the lymphatic drainage of myeloid bone marrow. When the ultrastructural basis for transcapillary exchange across the capillary walls of different capillary types is viewed in this light, it becomes evident that the physiologic evidence for the existence of aqueous large pores ranging between 24 and 60 nm in diameter in the capillary walls of blood capillaries, is circumstantial, at best.

Critical capillary channel flow

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The main subject are numerical studies on capillary channel flow, based on results of the sounding rocket experiments TEXUS 41/42. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behaviour, a dimensionless transient model was developed. It is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The pressure is related to the curvature of the free liquid surface by the dimensionless Gauss-Laplace equation with two principal radii. The experimental and evaluated contour data shows good agreement for a sequence of transient flow rate perturbations. The surface oscillation frequencies and amplitudes can be predicted with quite high accuracy. The dynamic of the pump is defined by the increase of the flow rate in a time period. To study the unsteady system behavior in the "worst case", we use a perturbations related to the natural frequency of the oscillating liquid. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value Sca = 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index D considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies result in a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate. It may serve as a road map for open capillary channel flow control.

Method of making tapered capillary tips with constant inner diameters

DOEpatents

Kelly, Ryan T [West Richland, WA; Page, Jason S [Kennewick, WA; Tang, Keqi [Richland, WA; Smith, Richard D [Richland, WA

2009-02-17

Methods of forming electrospray ionization emitter tips are disclosed herein. In one embodiment, an end portion of a capillary tube can be immersed into an etchant, wherein the etchant forms a concave meniscus on the outer surface of the capillary. Variable etching rates in the meniscus can cause an external taper to form. While etching the outer surface of the capillary wall, a fluid can be flowed through the interior of the capillary tube. Etching continues until the immersed portion of the capillary tube is completely etched away.

Chemical microreactor and method thereof

DOEpatents

Morse, Jeffrey D [Martinez, CA; Jankowski, Alan [Livermore, CA

2011-08-09

A method for forming a chemical microreactor includes forming at least one capillary microchannel in a substrate having at least one inlet and at least one outlet, integrating at least one heater into the chemical microreactor, interfacing the capillary microchannel with a liquid chemical reservoir at the inlet of the capillary microchannel, and interfacing the capillary microchannel with a porous membrane near the outlet of the capillary microchannel, the porous membrane being positioned beyond the outlet of the capillary microchannel, wherein the porous membrane has at least one catalyst material imbedded therein.

Electromyography (image)

MedlinePlus

... inserted through the skin into the muscle. Each muscle fiber that contracts will produce an action potential. The presence, size, and shape of the wave form of the action potential ... the ability of the muscle to respond to nervous stimulation.

"..., But I Cannot Do Research": Action-Research and Early Childhood Teachers. A Case Study from Greece

ERIC Educational Resources Information Center

Magos, Kostas

2012-01-01

Although action-research is a well-known research methodology in the field of education, in the case of Greece there are few actions-researches carried out by early childhood teachers. The absence of action-research in early childhood education settings is related to the way many early childhood teachers shape their professional role as well as…

Laws of physics help explain capillary non-perfusion in diabetic retinopathy.

PubMed

Stefánsson, E; Chan, Y K; Bek, T; Hardarson, S H; Wong, D; Wilson, D I

2018-02-01

The purpose is to use laws of physics to elucidate the mechanisms behind capillary non-perfusion in diabetic retinopathy. In diabetic retinopathy, loss of pericytes weakens capillary walls and the vessel dilates. A dilated capillary has reduced resistance to flow, therefore increased flow in that vessel and decreased in adjoining capillaries. A preferential shunt vessel is thus formed from the dilated capillary and the adjacent capillaries become non-perfused. We apply the laws of Laplace and Hagen-Poiseuille to better understand the phenomena that lead to capillary non-perfusion. These laws of physics can give a foundation for physical or mathematical models to further elucidate this field of study. The law of Laplace predicts that a weaker vessel wall will dilate, assuming constant transmural pressure. The Hagen-Poiseuille equation for flow and the Ostwald-de Waele relationship for viscosity predict that a dilated vessel will receive a higher portion of the fluid flow than the adjoining capillaries. Viscosity will decrease in the dilated vessel, furthering the imbalance and resulting in a patch of non-perfused capillaries next to the dilated 'preferential' shunt vessel. Physical principles support or inspire novel hypotheses to explain poorly understood phenomena in ophthalmology. This thesis of pericyte death and capillary remodelling, which was first proposed by Cogan and Kuwabara, already agrees with histological and angiographical observations in diabetic retinopathy. We have shown that it is also supported by classical laws of physics.

Deformable cells in confined geometries: From hemolysis to hydrodynamic interactions

NASA Astrophysics Data System (ADS)

Abkarian, Manouk; Faivre, Magalie; Stone, Howard A.

2004-11-01

Recent developments in microfluidics allow a wide range of possibilities for studying cellular-scale hydrodynamics. Here we use microfluidic technology to address several open questions in the blood flow literature where cell deformation and hydrodynamic interactions are significant. In particular, we investigate the pressure-driven flow of a dilute suspension in a channel and characterize the transition from steady axisymmetric cell shapes (for which numerical calculations exist) to asymmetric, highly extended shapes, which are precursors to hemolysis (i.e. destruction of the cell). In addition, we examine the influence of geometry on hydrodynamic interactions of deformable cells by contrasting one-dimensional motion of a train of particles in a channel with two-dimensional motions in a Hele-Shaw cell. This study can help to understand flow of cells in microcirculation from the unidirectional flow in capillaries to the two-dimensional flow in the lung alveoli and provides the basic steps to understand certain aspects of microcirculatory deseases like sickle cell anemia for example.

Self-Similar Apical Sharpening of an Ideal Perfecting Conducting Fluid Subject to Maxwell Stresses

NASA Astrophysics Data System (ADS)

Zhou, Chengzhe; Troian, Sandra M.

2016-11-01

We examine the apical behavior of an ideal, perfectly conducting incompressible fluid surrounded by vacuum in circumstances where the capillary, Maxwell and inertial forces contribute to formation of a liquid cone. A previous model based on potential flow describes a family of self-similar solutions with conic cusps whose interior angles approach the Taylor cone angle. These solutions were obtained by matching powers of the leading order terms in the velocity and electric field potential to the asymptotic form dictated by a stationary cone shape. In re-examining this earlier work, we have found a more important, neglected leading order term in the velocity and field potentials, which satisfies the governing, interfacial and far-field conditions as well. This term allows for the development of additional self-similar, sharpening apical shapes, including time reversed solutions for conic tip recoil after fluid ejection. We outline the boundary-element technique for solving the exact similarity solutions, which have parametric dependence on the far-field conditions, and discuss consequences of our findings.

Wrapping with a splash: High-speed encapsulation with ultrathin sheets.

PubMed

Kumar, Deepak; Paulsen, Joseph D; Russell, Thomas P; Menon, Narayanan

2018-02-16

Many complex fluids rely on surfactants to contain, protect, or isolate liquid drops in an immiscible continuous phase. Thin elastic sheets can wrap liquid drops in a spontaneous process driven by capillary forces. For encapsulation by sheets to be practically viable, a rapid, continuous, and scalable process is essential. We exploit the fast dynamics of droplet impact to achieve wrapping of oil droplets by ultrathin polymer films in a water phase. Despite the violence of splashing events, the process robustly yields wrappings that are optimally shaped to maximize the enclosed fluid volume and have near-perfect seams. We achieve wrappings of targeted three-dimensional (3D) shapes by tailoring the 2D boundary of the films and show the generality of the technique by producing both oil-in-water and water-in-oil wrappings. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Deformable micro torque swimmer

NASA Astrophysics Data System (ADS)

Ishikawa, Takuji; Tanaka, Tomoyuki; Omori, Toshihiro; Imai, Yohsuke

2015-11-01

We investigated the deformation of a ciliate swimming freely in a fluid otherwise at rest. The cell body was modeled as a capsule with a hyper elastic membrane enclosing Newtonian fluid. Thrust forces due to the ciliary beat were modeled as torques distributed above the cell body. Effects of the membrane elasticity, the aspect ratio of cell's reference shape and the density difference between the cell and the surrounding fluid were investigated. The results showed that the cell deformed like heart shape when Capillary number (Ca) was sufficiently large, and the swimming velocity decreased as Ca was increased. The gravity effect on the membrane tension suggested that the upwards and downwards swimming velocities of Paramecium might be reglated by the calcium ion channels distributed locally around the anterior end. Moreover, the gravity induced deformation made a cell directed vertically downwards, which resulted in a positive geotaxis like behavior with physical origin. These results are important to understand physiology of ciliate's biological responses to mechanical stimuli.

Lock and Key Colloids through Polymerization-Induced Buckling of Monodispersed Silicon Oil Droplets

NASA Astrophysics Data System (ADS)

Sacanna, Stefano; Irvine, William T. M.; Chaikin, Paul M.; Pine, David J.

2010-03-01

Colloidal particles can spontaneously associate into larger structured aggregates when driven by selective and directional interactions. Colloidal organization can be programmed by engineering shapes and interactions of basic building blocks in a manner similar to molecular self-assembly. Examples of successful strategies that allow non-trivial assembly of particles include template-directed patterning, capillary forces and, most commonly, the functionalization of the particle surfaces with ``sticky patches'' of biological or synthetic molecules. The level of complexity of the realizable assemblies, increases when particles with well defined shape anisotropies are used. In particular depletion forces and specific surface treatments in combination with non spherical particles have proven to be powerful tools to self-assembly complex microstructures. We describe a simple, high yield, synthetic pathway to fabricate monodisperse hybrid silica spheres with well defined cavities. Because the particle morphologies are reproducible and tunable with precision, the resulting particles can be used as basic building blocks in the assembly of larger monodisperse clusters. This is demonstrated using depletion to drive the self-assembly.