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flat fluide

Saeed Rismani Yazi, Reza Nosrati, Corey A Stevens, David Vogel, Carlos Escobedo
Magnetotactic bacteria (MTB) migrate in complex porous sediments where fluid flow is ubiquitous. Here, we demonstrate that magnetotaxis enables MTB to migrate effectively through porous micromodels. Directed MTB can circumvent curved obstacles by traveling along the boundaries and pass flat obstacles by repeatedly switching between forward and backward runs. Magnetotaxis enables directed motion of MTB through heterogeneous porous media, overcoming tortuous flow fields with local velocities as high as 250  μ m s-1 ...
January 2018: Biomicrofluidics
Teresa Veselack, Gregoire Aldebert, Ana-Maria Trunfio-Sfarghiu, Thomas M Schmid, Michel P Laurent, Markus A Wimmer
Introduction: Pre-clinical testing of hemiarthroplasty devices requires that the tribological conditions present in vivo with live cartilage be closely duplicated. A current limitation in the tribological testing of live cartilage involves the use of cell-culture media as lubricant. Study Aim: to develop and test a new hyaluronan-phospholipid based medium (HA-phospholipid medium) that combines the rheological and frictional properties of synovial fluid with the nourishing properties of culture media to keep cells alive...
2018: Lubricants
James K C Liu
BACKGROUND: Intracranial hypotension from cerebrospinal fluid hypovolemia resulting in cerebral herniation is a rare but known complication that can occur following neurosurgical procedures, usually encountered in correlation with perioperative placement of a lumbar subarachnoid drain. Decrease in CSF volume resulting in loss of buoyancy results in downward herniation of the brain without contributing mass effect, causing a phenomenon known as 'brain sag.' Unreported previously is brain sag occurring without concomitant occult CSF leak or lumbar drainage...
March 7, 2018: World Neurosurgery
Edward J Casswell, Sleiman Abou Ltaif, Thomas Carr, Pearse A Keane, David G Charteris, Louisa Wickham
PURPOSE: To describe the widefield spectral-domain optical coherence tomography features of peripheral round retinal holes, with or without associated retinal detachment (RD). METHODS: Retrospective, observational study of 28 eyes with peripheral round retinal holes, with and without RD. Patients underwent imaging with a widefield 50-degree spectral-domain optical coherence tomography (Heidelberg Engineering, Germany) and Optos ultra-widefield imaging systems (Optos, United Kingdom)...
March 2, 2018: Retina
SriniVas R Sadda, Lisa L Tuomi, Beiying Ding, Anne E Fung, J Jill Hopkins
PURPOSE: To evaluate macular atrophy (MA) presence in the 24-month HARBOR study (NCT00891735) for neovascular age-related macular degeneration (AMD). DESIGN: Post hoc analysis of a phase 3 multicenter, prospective, randomized, double-masked, active treatment-controlled clinical trial. PARTICIPANTS: Evaluable subjects (N = 1095) with subfoveal choroidal neovascularization (CNV) secondary to neovascular AMD treated with ranibizumab 0.5 mg or 2...
February 21, 2018: Ophthalmology
Yihua Ren, Wei Cui, Shuiqing Li
We report an electrohydrodynamic instability in a premixed stagnation flame under manipulations of a dc electric field. This instability occurs when the electric field strength is at a certain value below the breakdown threshold, which is 0.75 kV/cm in the experimental setup. Above this value the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field. At the transition moment, the flame spontaneously propagates upstream to the nozzle while the flow velocity at the upstream of the flame front decreases to zero, as revealed by high-speed photographs and PIV measurements...
January 2018: Physical Review. E
James T Waters, Ya Liu, Like Li, Anna C Balazs
Using computational modeling, we show that the dynamic interplay between a flowing fluid and the appropriately designed surface relief pattern can inhibit the fouling of the substrate. We specifically focus on surfaces that are decorated with three-dimensional chevron or sawtooth "micromixer" patterns and model the fouling agents (e.g., cells) as spherical microcapsules. The interaction between the imposed shear flow and the chevrons on the surface generates 3D vortices in the system. We pinpoint a range of shear rates where the forces from these vortices can rupture the bonds between two mobile microcapsules near the surface...
February 9, 2018: ACS Applied Materials & Interfaces
Andreas Maximilian Frölich, Marie Teresa Nawka, Marielle Ernst, Isabell Frischmuth, Jens Fiehler, Jan-Hendrik Buhk
BACKGROUND AND PURPOSE: Flow disruption achieved by braided intrasaccular implants is a novel treatment strategy for cerebrovascular aneurysms. We hypothesized that the degree of intra-aneurysmal flow disruption can be quantified in vitro and is influenced by device position across the aneurysm neck. We tested this hypothesis using the Medina® Embolization Device (MED). METHODS: Ten different patient-specific elastic vascular models were manufactured. Models were connected to a pulsatile flow circuit, filled with a blood-mimicking fluid and treated by two operators using a single MED...
2018: PloS One
Jun-Jie Huang, Jie Wu, Haibo Huang
We propose an alternative method to implement the contact angle boundary condition on a solid wall and apply it in hybrid lattice-Boltzmann finite-difference simulations of two-phase flows with immersed surfaces in which the flow equations are solved by the lattice-Boltzmann method and the interface equations are solved by the finite-difference method. Using the hyperbolic tangent profile of the order parameter across an interface in phase-field theory, we were able to obtain its unknown value at a ghost point from the information at only one point in the fluid domain...
February 7, 2018: European Physical Journal. E, Soft Matter
Chang-Min Yoon, Jaehoon Ryu, Juyoung Yun, Yun Ki Kim, Jyongsik Jang
Wrinkled silica nanoparticle (WSN)-based hollow SiO2/TiO2 nanoparticles (W-HNPs) with hierarchically-arrayed internal surfaces were prepared via the combination of sol-gel, TiO2 coating, and etching of core template techniques. The hierarchical internal surface of the W-HNPs was attained by using WSNs as a core template. Compared with SiO2 sphere-templated hollow SiO2/TiO2 nanoparticles (S-HNPs) with flat inner surfaces, the W-HNPs displayed distinctive surface areas, TiO2 loading amounts, and dielectric properties arising from the hierarchical internal surface...
February 1, 2018: ACS Applied Materials & Interfaces
Koh M Nakagawa, Hiroshi Noguchi
Shape transformations of flat bilayer membranes and vesicles induced by hydrolysis and condensation reactions of amphiphilic molecules are studied using coarse-grained molecular dynamics simulations. The hydrolysis and condensation reactions result in the formation and dissociation of amphiphilic molecules, respectively. Asymmetric reactions between the inner and outer leaflets of a vesicle can transport amphiphilic molecules between the leaflets. It is found that the resulting area difference between the two leaflets induces bilayer sheet protrusion (BP) and budding at low reduced volumes of the vesicles, whereas BP only occurs at high reduced volumes...
January 31, 2018: Soft Matter
Pablo E Guevara-Pantoja, Rocío J Jiménez-Valdés, Jose L García-Cordero, Gabriel A Caballero-Robledo
In this article, we describe a microfluidic device with embedded valves and pumps made exclusively of layers of acrylic glass. Flat acrylic sheets are carved out with a micromilling machine and bonded together by solvent bonding. The working principle of the valves is based on a thin flexible membrane (≈100 μm) machined on one acrylic sheet and actuated with pneumatic pressure. A completely closed valve resists a pressure difference of ≈17 kPa (≈2.5 psi), and when open, it can sustain flow rates of up to 100 μL s-1...
January 25, 2018: Lab on a Chip
Iain D C Hill, Benzheng Dong, W Jon P Barnes, Aihong Ji, Thomas Endlein
The adhesive mechanisms of climbing animals have become an important research topic because of their biomimetic implications. We examined the climbing abilities of hylid tree frogs on vertical cylinders of differing diameter and surface roughness to investigate the relative roles of adduction forces (gripping) and adhesion. Tree frogs adhere using their toe pads and subarticular tubercles, the adhesive joint being fluid-filled. Our hypothesis was that, on an effectively flat surface (adduction forces on the largest 120 mm diameter cylinder were insufficient to allow climbing), adhesion would effectively be the only means by which tree frogs could climb, but on the two smaller diameter cylinders (44 mm and 13 mm), frogs could additionally utilise adduction forces by gripping the cylinder either with their limbs outstretched or by grasping around the cylinder with their digits, respectively...
January 19, 2018: Journal of Experimental Biology
T W Beck, C E Seaman, M R Shahan, S E Mischler
Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams...
January 2018: Mining Engineering
David R A Ruelas Paredes, Desiderio A Vasquez
We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients...
September 2017: Physical Review. E
Elena Shigorina, Jannes Kordilla, Alexandre M Tartakovsky
We employ a pairwise force smoothed particle hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows modeling of free-surface flows without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on different types of rough surfaces...
September 2017: Physical Review. E
Nathan Legband, Arielle Black, Craig Kreikemeier-Bower, Benjamin S Terry
Purpose/Aim: In developing a novel peritoneal oxygenation therapy, catheters implanted into the peritoneal cavity became obstructed with omental tissue and prevented the infusion and removal of fluid from the peritoneal cavity. The obstruction of peritoneal catheters is a significant failure in researching various peritoneal treatments as further fluid administration is no longer possible. The purpose of this preliminary study was to determine the most effective catheter design for infusion and removal of fluid into the peritoneal cavity of rats...
January 18, 2018: Journal of Investigative Surgery: the Official Journal of the Academy of Surgical Research
Etzer Augustin, Michael Karsy, Jim Bryan, Jian Guan, Richard H Schmidt
Tension pneumocephalus is a rare but dangerous complication of craniotomy, sinus surgery, and traumatic cranial injury. Compared with simple pneumocephalus, which often resolves spontaneously over the course of a few days, tension pneumocephalus tends to increase with ongoing cerebrospinal fluid leak and requires immediate neurosurgical treatment to prevent cerebral herniation. Air transport of patients with tension pneumocephalus for neurosurgical care entails a risk of neurologic worsening because of changes in ambient air pressure with altitude and cabin pressurization...
January 2018: Air Medical Journal
L López-Rosales, A Sánchez-Mirón, F García-Camacho, A R Place, Yusuf Chisti, E Molina-Grima
A pilot-scale bioprocess was developed for the production of karlotoxin-enriched extracts of the marine algal dinoflagellate Karlodinium veneficum. A bubble column and a flat-panel photobioreactors (80-281 L) were used for comparative assessment of growth. Flow hydrodynamics and energy dissipation rates (EDR) in the bioreactors were characterized through robust computational fluid dynamic simulations. All cultures were conducted monoseptically outdoors. Bubble column (maximum cell productivity in semicontinuous operation of 58 × 103 cell mL-1 day-1) proved to be a better culture system for this alga...
December 30, 2017: Bioresource Technology
Sandra Herrera, Maggie J Kuhlmann-Capek, Sarah C Rogan, Antonio F Saad, George R Saade, Gary D V Hankins, Luis D Pacheco
OBJECTIVE:  It is unknown whether the heart operates in the ascending or flat portion of the Starling curve during normal pregnancy. Pregnant women do not respond to the passive leg-raising maneuver secondary to mechanical obstruction of the inferior vena cava by the gravid uterus. Our objective was to evaluate if administration of a fluid bolus increases baseline stroke volume (SV) among healthy pregnant patients during the third trimester. STUDY DESIGN:  Healthy pregnant women who underwent elective term cesarean sections were included...
December 26, 2017: American Journal of Perinatology
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