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surface curvature

David A Slatter, Charles L Percy, Keith Allen-Redpath, Joshua M Gajsiewicz, Nick J Brooks, Aled Clayton, Victoria J Tyrrell, Marcela Rosas, Sarah N Lauder, Andrew Watson, Maria Dul, Yoel Garcia-Diaz, Maceler Aldrovandi, Meike Heurich, Judith Hall, James H Morrissey, Sebastien Lacroix-Desmazes, Sandrine Delignat, P Vincent Jenkins, Peter W Collins, Valerie B O'Donnell
Hemostatic defects are treated using coagulation factors; however, clot formation also requires a procoagulant phospholipid (PL) surface. Here, we show that innate immune cell-derived enzymatically oxidized phospholipids (eoxPL) termed hydroxyeicosatetraenoic acid-phospholipids (HETE-PLs) restore hemostasis in human and murine conditions of pathological bleeding. HETE-PLs abolished blood loss in murine hemophilia A and enhanced coagulation in factor VIII- (FVIII-), FIX-, and FX-deficient human plasma . HETE-PLs were decreased in platelets from patients after cardiopulmonary bypass (CPB)...
March 22, 2018: JCI Insight
Alexandra Victoria Bayles, Tamás Antal Prileszky, Patrick T Spicer, Eric M Furst
A model of internally-structured emulsion droplets is presented that accounts for the traction forces generated by interfacial tension and the von Mises yield criterion of the internal supporting network. For symmetric droplets, the method calculates the total stress acting on a droplet locally, allowing droplet stability and location of failure to be predicted. It is not regions of high interfacial curvature that prompt droplet reconfiguration, rather regions transitioning from high to low curvature. The model enables the design of emulsion droplet response and reconfigurability to external triggers such as changes in surface tension (surfactant concentration) and temperature...
March 20, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Delia Bucher, Felix Frey, Kem A Sochacki, Susann Kummer, Jan-Philip Bergeest, William J Godinez, Hans-Georg Kräusslich, Karl Rohr, Justin W Taraska, Ulrich S Schwarz, Steeve Boulant
Although essential for many cellular processes, the sequence of structural and molecular events during clathrin-mediated endocytosis remains elusive. While it was long believed that clathrin-coated pits grow with a constant curvature, it was recently suggested that clathrin first assembles to form flat structures that then bend while maintaining a constant surface area. Here, we combine correlative electron and light microscopy and mathematical growth laws to study the ultrastructural rearrangements of the clathrin coat during endocytosis in BSC-1 mammalian cells...
March 16, 2018: Nature Communications
Alvaro Domínguez
A planar colloidal monolayer exhibits anomalous collective diffusion due to the hydrodynamic interactions. We investigate how this behavior is affected by the curvature of the monolayer when it resides on the interface of a spherical droplet. It is found that the characteristic times of the dynamics still exhibit the same anomalous scaling as in the planar case. The spatial distribution, however, shows a difference due to the relevance of the radius of the droplet. Since for the droplet this is both a global magnitude, i...
February 2018: Physical Review. E
Paolo Malgaretti, Markus Bier
We derive a general closed expression for the local pressure exerted onto the corrugated walls of a channel confining a fluid medium. When the fluid medium is at equilibrium, the local pressure is a functional of the shape of the walls. It is shown that, due to the intrinsic nonlocal character of the interactions among the particles forming the fluid, the applicability of approximate schemes such as the concept of a surface of tension or morphometric thermodynamics is limited to wall curvatures that are small compared to the range of particle-particle interactions...
February 2018: Physical Review. E
Matthieu Fumagalli, Julien Berriot, Benoit de Gaudemaris, Anne Veyland, Jean-Luc Putaux, Sonia Molina-Boisseau, Laurent Heux
Rubber materials with well-dispersed fillers and large mechanical reinforcement have been obtained by melt-processing a diene elastomer matrix and tailored nanocellulose powders having both a high specific surface area and a modified interface. Such filler powders with a specific surface area of 180 m2 g-1 and 100 m2 g-1 have been obtained by freeze-drying suspensions of short needle-like cellulose nanocrystals (CNCs) and entangled networks of microfibrillated cellulose (MFC) in tert-butanol/water, respectively...
March 16, 2018: Soft Matter
Pavithra Madhavi Naullage, Yuqing Qiu, Valeria Molinero
Cold-adapted organisms produce antifreeze proteins and glycoproteins to control the growth, melting and recrystallization of ice. It has been proposed that these molecules pin the crystal surface, creating a surface curvature that arrests its growth and melting. Here we use thermodynamic modeling and molecular simulations to elucidate how does the curvature of the metastable ice front depend on the temperature and distance between pinned molecules, and what determines the thermal hysteresis on melting and freezing, i...
March 15, 2018: Journal of Physical Chemistry Letters
Tamako Nishimura, Nobuhiro Morone, Shiro Suetsugu
Lipid membranes are structural components of cell surfaces and intracellular organelles. Alterations in lipid membrane shape are accompanied by numerous cellular functions, including endocytosis, intracellular transport, and cell migration. Proteins containing Bin-Amphiphysin-Rvs (BAR) domains (BAR proteins) are unique, because their structures correspond to the membrane curvature, that is, the shape of the lipid membrane. BAR proteins present at high concentration determine the shape of the membrane, because BAR domain oligomers function as scaffolds that mould the membrane...
March 14, 2018: Biochemical Society Transactions
Paul Dillon, L Alison Phillips, Paul Gallagher, Susan M Smith, Derek Stewart, Gráinne Cousins
Background: The Necessity-Concerns Framework (NCF) is a multidimensional theory describing the relationship between patients' positive and negative evaluations of their medication which interplay to influence adherence. Most studies evaluating the NCF have failed to account for the multidimensional nature of the theory, placing the separate dimensions of medication "necessity beliefs" and "concerns" onto a single dimension (e.g., the Beliefs about Medicines Questionnaire-difference score model)...
February 5, 2018: Annals of Behavioral Medicine: a Publication of the Society of Behavioral Medicine
Antonio R Porras, Beatriz Paniagua, Andinet Enquobahrie, Scott Ensel, Hina Shah, Robert Keating, Gary F Rogers, Marius George Linguraru
The outcome of cranial vault reconstruction for the surgical treatment of craniosynostosis heavily depends on the surgeon's expertise because of the lack of an objective target shape. We introduce a surface-based diffeomorphic registration framework to create the optimal post-surgical cranial shape during craniosynostosis treatment. Our framework estimates and labels where each bone piece needs to be cut using a reference template. Then, it calculates how much each bone piece needs to be translated and in which direction, using the closest normal shape from a multi-atlas as a reference...
September 2017: Medical Image Computing and Computer-assisted Intervention: MICCAI ..
Xiaokang Yu, Na Lei, Yalin Wang, Xianfeng Gu
3D dynamic surface tracking is an important research problem and plays a vital role in many computer vision and medical imaging applications. However, it is still challenging to efficiently register surface sequences which has large deformations and strong noise. In this paper, we propose a novel automatic method for non-rigid 3D dynamic surface tracking with surface Ricci flow and Teichmüller map methods. According to quasi-conformal Teichmüller theory, the Techmüller map minimizes the maximal dilation so that our method is able to automatically register surfaces with large deformations...
October 2017: Proceedings
Guillaume Duclos, Maxime Deforet, Hannah G Yevick, Olivier Cochet-Escartin, Flora Ascione, Sarah Moitrier, Trinish Sarkar, Victor Yashunsky, Isabelle Bonnet, Axel Buguin, Pascal Silberzan
Confinement and substrate topology strongly affect the behavior of cell populations and, in particular, their collective migration. In vitro experiments dealing with these aspects require strategies of surface patterning that remain effective over long times (typically several days) and ways to control the surface topology in three dimensions. Here, we describe protocols addressing these two aspects. High-resolution patterning of a robust cell-repellent coating is achieved by etching the coating through a photoresist mask patterned directly on the coated surface...
2018: Methods in Molecular Biology
Zhen Li, Yonghui Zhang, Chun Chan, Chunyi Zhi, Xiaolin Cheng, Jun Fan
Two-dimensional (2D) materials can mechanically insert into cell membranes and extract lipids out, thus leading to the destruction of cell integrity. On the one hand, the cytotoxicity of 2D materials can be harnessed in surface engineering to resist biofouling; on the other hand, it causes great concern on in vivo biomedical applications ranging from drug delivery to nano-imaging. To understand the nature of this cytotoxic behavior and find strategies to control it, we performed molecular dynamics (MD) simulations on the lipid extraction of hexagonal boron nitride (BN) nanosheets from lipid membranes...
March 8, 2018: ACS Nano
Alexander E Moskalensky, Maxim A Yurkin, Artem R Muliukov, Alena L Litvinenko, Vyacheslav M Nekrasov, Andrei V Chernyshev, Valeri P Maltsev
We present a simple physically based quantitative model of blood platelet shape and its evolution during agonist-induced activation. The model is based on the consideration of two major cytoskeletal elements: the marginal band of microtubules and the submembrane cortex. Mathematically, we consider the problem of minimization of surface area constrained to confine the marginal band and a certain cellular volume. For resting platelets, the marginal band appears as a peripheral ring, allowing for the analytical solution of the minimization problem...
March 8, 2018: PLoS Computational Biology
Morgan Chabanon, Padmini Rangamani
Formation of membrane necks is crucial for fission and fusion in lipid bilayers. In this work, we seek to answer the following fundamental question: what is the relationship between protein-induced spontaneous mean curvature and the Gaussian curvature at a membrane neck? Using an augmented Helfrich model for lipid bilayers to include membrane-protein interaction, we solve the shape equation on catenoids to find the field of spontaneous curvature that satisfies mechanical equilibrium of membrane necks. In this case, the shape equation reduces to a variable coefficient Helmholtz equation for spontaneous curvature, where the source term is proportional to the Gaussian curvature...
March 7, 2018: Soft Matter
Fei Liu, David Z Zhang, Peng Zhang, Miao Zhao, Salman Jafar
Developments in selective laser melting (SLM) have enabled the fabrication of periodic cellular lattice structures characterized by suitable properties matching the bone tissue well and by fluid permeability from interconnected structures. These multifunctional performances are significantly affected by cell topology and constitutive properties of applied materials. In this respect, a diamond unit cell was designed in particular volume fractions corresponding to the host bone tissue and optimized with a smooth surface at nodes leading to fewer stress concentrations...
March 3, 2018: Materials
Mark Warner, Cyrus Mostajeran
We solve the forward and inverse problems associated with the transformation of flat sheets with circularly symmetric director fields to surfaces of revolution with non-trivial topography, including Gaussian curvature, without a stretch elastic cost. We deal with systems slender enough to have a small bend energy cost. Shape change is induced by light or heat causing contraction along a non-uniform director field in the plane of an initially flat nematic sheet. The forward problem is, given a director distribution, what shape is induced? Along the way, we determine the Gaussian curvature and the evolution with induced mechanical deformation of the director field and of material curves in the surface (proto-radii) that will become radii in the final surface...
February 2018: Proceedings. Mathematical, Physical, and Engineering Sciences
Rikkert J Nap, Sung Hyun Park, Igal Szleifer
We have developed a molecular model to describe the structural changes and potential collapse of weak polyelectrolyte layers end-tethered to planar surfaces and spherical nanoparticles as a function of pH and divalent ion concentration. In particular, we describe the structural changes of polymer-coated nanoparticles end-tethered to copolymers of poly(acrylic acid) (pAA) and poly arcrylamido-2-methylpropane sulfonate (pAMPS) in the presence of Ca2+ ions. We find that end-grafted poly(acrylic acid) layers will collapse in aqueous solutions containing sufficient amounts of Ca2+ ions, while polymers and copolymers with sufficient AMPS monomers will not collapse...
March 5, 2018: Soft Matter
Mohammed Ziaei, Jay Meyer, Akilesh Gokul, Hans Vellara, Charles N J McGhee
PURPOSE: To compare the tomography of the corneal epithelium and Bowman layer in eyes with moderate to severe keratoconus before and after epithelial debridement. SETTING: University hospital tertiary referral center. DESIGN: Prospective case series. METHODS: Dual-channel Scheimpflug combined with Placido-disk tomography was used to measure the corneal variables in eyes with keratoconus having corneal crosslinking immediately before and after epithelial debridement...
January 2018: Journal of Cataract and Refractive Surgery
Torbjörn Lundh, Ga-Young Suh, Phillip DiGiacomo, Christopher Cheng
Vascular morphology characterization is useful for disease diagnosis, risk stratification, treatment planning, and prediction of treatment durability. To quantify the dynamic surface geometry of tubular-shaped anatomic structures, we propose a simple, rigorous Lagrangian cylindrical coordinate system to monitor well-defined surface points. Specifically, the proposed system enables quantification of surface curvature and cross-sectional eccentricity. Using idealized software phantom examples, we validate the method's ability to accurately quantify longitudinal and circumferential surface curvature, as well as eccentricity and orientation of eccentricity...
March 3, 2018: Medical & Biological Engineering & Computing
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