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https://www.readbyqxmd.com/read/29143028/frame-metric-and-geodesic-evolution-in-shape-changing-nematic-shells
#1
Cyrus Mostajeran, Mark Warner, Carl D Modes
Non-uniform director fields in flat, responsive, glassy nematic sheets lead to the induction of shells with non-trivial topography on the application of light or heat. Contraction along the director causes metric change, with, in general, the induction of Gaussian curvature, that drives the topography change. We describe the metric change, the evolution of the director field, and the transformation of reference state material curves, e.g. spirals into radii, as curvature develops. The non-isometric deformations associated with heat or light change the geodesics of the surface, intriguingly even in regions where no Gaussian curvature results...
November 16, 2017: Soft Matter
https://www.readbyqxmd.com/read/29142242/emergent-patterns-of-collective-cell-migration-under-tubular-confinement
#2
Wang Xi, Surabhi Sonam, Thuan Beng Saw, Benoit Ladoux, Chwee Teck Lim
Collective epithelial behaviors are essential for the development of lumens in organs. However, conventional assays of planar systems fail to replicate cell cohorts of tubular structures that advance in concerted ways on out-of-plane curved and confined surfaces, such as ductal elongation in vivo. Here, we mimic such coordinated tissue migration by forming lumens of epithelial cell sheets inside microtubes of 1-10 cell lengths in diameter. We show that these cell tubes reproduce the physiological apical-basal polarity, and have actin alignment, cell orientation, tissue organization, and migration modes that depend on the extent of tubular confinement and/or curvature...
November 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/29141428/effect-of-surface-curvature-on-diffusion-limited-reactions-on-a-curved-surface
#3
Changsun Eun
To investigate how the curvature of a reactive surface can affect reaction kinetics, we use a simple model in which a diffusion-limited bimolecular reaction occurs on a curved surface that is hollowed inward, flat, or extended outward while keeping the reactive area on the surface constant. By numerically solving the diffusion equation for this model using the finite element method, we find that the rate constant is a non-linear function of the surface curvature and that there is an optimal curvature providing the maximum value of the rate constant, which indicates that a spherical reactant whose entire surface is reactive (a uniformly reactive sphere) is not the most reactive species for a given reactive surface area...
November 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29141112/multiscale-geometric-design-principles-applied-to-3d-printed-schwarzites
#4
Seyed Mohammad Sajadi, Peter Samora Owuor, Steven Schara, Cristiano F Woellner, Varlei Rodrigues, Robert Vajtai, Jun Lou, Douglas S Galvão, Chandra Sekhar Tiwary, Pulickel M Ajayan
Schwartzites are 3D porous solids with periodic minimal surfaces having negative Gaussian curvatures and can possess unusual mechanical and electronic properties. The mechanical behavior of primitive and gyroid schwartzite structures across different length scales is investigated after these geometries are 3D printed at centimeter length scales based on molecular models. Molecular dynamics and finite elements simulations are used to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments...
November 15, 2017: Advanced Materials
https://www.readbyqxmd.com/read/29139530/when-droplets-become-stars-charged-dielectric-droplets-beyond-the-rayleigh-limit
#5
Myong In Oh, Anatoly Malevanets, Maxim Paliy, Daan Frenkel, Styliani Consta
When a nano-drop comprising a single spherical central ion and dielectric solvent is charged above a well-defined threshold, it acquires a stable star morphology. In contrast, conducting droplets, will undergo fission. Here we report combined atomistic molecular dynamics and continuum modelling study of star formation of droplets that contain a highly charged ion. We assume that in the continuum model the dielectric response is linear. In this linear continuum model, which is an extension of Rayleigh model, the energy of the drop is comprised of terms analogous to those in Rayleigh model, which are surface energy and electrostatic energy of dielectric droplet charged by a central point charge...
November 15, 2017: Soft Matter
https://www.readbyqxmd.com/read/29124253/exploring-gyral-patterns-of-infant-cortical-folding-based-on-multi-view-curvature-information
#6
Dingna Duan, Shunren Xia, Yu Meng, Li Wang, Weili Lin, John H Gilmore, Dinggang Shen, Gang Li
The human cortical folding is intriguingly complex in its variability and regularity across individuals. Exploring the principal patterns of cortical folding is of great importance for neuroimaging research. The term-born neonates with minimum exposure to the complicated environments are the ideal candidates to mine the postnatal origins of principal cortical folding patterns. In this work, we propose a novel framework to study the gyral patterns of neonatal cortical folding. Specifically, first, we leverage multi-view curvature-derived features to comprehensively characterize the complex and multi-scale nature of cortical folding...
September 2017: Medical Image Computing and Computer-assisted Intervention: MICCAI ..
https://www.readbyqxmd.com/read/29123120/membrane-curvature-induced-by-proximity-of-anionic-phospholipids-can-initiate-endocytosis
#7
Takashi Hirama, Stella M Lu, Jason G Kay, Masashi Maekawa, Michael M Kozlov, Sergio Grinstein, Gregory D Fairn
The plasma membrane is uniquely enriched in phosphatidylserine (PtdSer). This anionic phospholipid is restricted almost exclusively to the inner leaflet of the plasmalemma. Because of their high density, the headgroups of anionic lipids experience electrostatic repulsion that, being exerted asymmetrically, is predicted to favor membrane curvature. We demonstrate that cholesterol limits this repulsion and tendency to curve. Removal of cholesterol or insertion of excess PtdSer increases the charge density of the inner leaflet, generating foci of enhanced charge and curvature where endophilin and synaptojanin are recruited...
November 9, 2017: Nature Communications
https://www.readbyqxmd.com/read/29123094/human-sperm-steer-with-second-harmonics-of-the-flagellar-beat
#8
Guglielmo Saggiorato, Luis Alvarez, Jan F Jikeli, U Benjamin Kaupp, Gerhard Gompper, Jens Elgeti
Sperm are propelled by bending waves traveling along their flagellum. For steering in gradients of sensory cues, sperm adjust the flagellar waveform. Symmetric and asymmetric waveforms result in straight and curved swimming paths, respectively. Two mechanisms causing spatially asymmetric waveforms have been proposed: an average flagellar curvature and buckling. We image flagella of human sperm tethered with the head to a surface. The waveform is characterized by a fundamental beat frequency and its second harmonic...
November 10, 2017: Nature Communications
https://www.readbyqxmd.com/read/29121981/intrinsic-dna-curvature-in-trypanosomes
#9
Pablo Smircich, Najib M El-Sayed, Beatriz Garat
BACKGROUND: Trypanosoma cruzi and Trypanosoma brucei are protozoan parasites causing Chagas disease and African sleeping sickness, displaying unique features of cellular and molecular biology. Remarkably, no canonical signals for RNA polymerase II promoters, which drive protein coding genes transcription, have been identified so far. The secondary structure of DNA has long been recognized as a signal in biological processes and more recently, its involvement in transcription initiation in Leishmania was proposed...
November 9, 2017: BMC Research Notes
https://www.readbyqxmd.com/read/29121077/a-functional-pipeline-framework-for-landmark-identification-on-3d-surface-extracted-from-volumetric-data
#10
Pan Zheng, Bahari Belaton, Iman Yi Liao, Zainul Ahmad Rajion
Landmarks, also known as feature points, are one of the important geometry primitives that describe the predominant characteristics of a surface. In this study we proposed a self-contained framework to generate landmarks on surfaces extracted from volumetric data. The framework is designed to be a three-fold pipeline structure. The pipeline comprises three phases which are surface construction, crest line extraction and landmark identification. With input as a volumetric data and output as landmarks, the pipeline takes in 3D raw data and produces a 0D geometry feature...
2017: PloS One
https://www.readbyqxmd.com/read/29120647/underwater-oil-droplet-splitting-on-a-patterned-template
#11
Xiaolong Yang, Xin Liu, Dennis W Hess, Victor Breedveld
Underwater oil droplets stretched and pinned by dual-dot oleophilic patterns on a superoleophobic substrate have been split into two nearly equal-volume daughter droplets using an underwater superoleophobic blade at substantially lower cutting speeds than reported in previous studies. A 'liquid exchange model' based on Laplace pressure-driven liquid transport has been proposed to explain the mechanism of the underwater droplet split process. The dependence of droplet geometrical shape (curvature) and liquid properties (surface tension, viscosity) on the critical cutting speed that allows equal-volume split was investigated...
November 9, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29119796/supported-lipid-bilayers-with-phosphatidylethanolamine-as-the-major-component
#12
Anne M Sendecki, Matthew F Poyton, Alexis J Baxter, Tinglu Yang, Paul S Cremer
Phosphatidylethanolamine (PE) is notoriously difficult to incorporate into model membrane systems, such as fluid supported lipid bilayers (SLBs), at high concentrations because of its intrinsic negative curvature. Using fluorescence-based techniques, we demonstrate that having fewer sites of unsaturation in the lipid tails leads to high-quality SLBs because these lipids help to minimize the curvature. Moreover, shorter saturated chains can help maintain the membranes in the fluid phase. Using these two guidelines, we find that up to 70 mol % PE can be incorporated into SLBs at room temperature and up to 90 mol % PE can be incorporated at 37 °C...
November 9, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29118666/the-motion-of-a-vortex-on-a-closed-surface-of-constant-negative-curvature
#13
C Grotta Ragazzo
The purpose of this work is to present an algorithm to determine the motion of a single hydrodynamic vortex on a closed surface of constant curvature and of genus greater than one. The algorithm is based on a relation between the Laplace-Beltrami Green function and the heat kernel. The algorithm is used to compute the motion of a vortex on the Bolza surface. This is the first determination of the orbits of a vortex on a closed surface of genus greater than one. The numerical results show that all the 46 vortex equilibria can be explicitly computed using the symmetries of the Bolza surface...
October 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29116952/a-model-of-the-effect-of-lens-development-on-refraction-in-schoolchildren
#14
Ji C He
SIGNIFICANCE: The study provides a new theory on the mechanism underlying myopia development, and it could be useful in clinical practice to control myopia development in schoolchildren. PURPOSE: To model the effect of the crystalline lens on refractive development in schoolchildren. METHODS: The Zemax 13 was used to calculate Zernike aberrations and refractions across 50° horizontal visual fields. Optical effects of the anterior chamber depth, lens thickness, and radii of curvature of the lens surfaces on refractions were modeled...
November 8, 2017: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/29105602/a-new-low-profile-visualized-intraluminal-support-lvis-device-lvis-blue-laboratory-comparison-between-old-and-new-lvis
#15
Joonho Chung, Yoshikazu Matsuda, Jessica Nelson, Kiffon Keigher, Demetrius K Lopes
Objectives The Low-profile Visualized Intraluminal Support (LVIS) device is a flexible intracranial stent. The first generation of this system had significant challenges in consistently providing good wall apposition and aneurysm neck coverage. A new modified LVIS, LVIS Blue (Blue), has been developed to address these issues. The purpose of this study is to report a laboratory comparison of wall apposition and aneurysm neck coverage between the original LVIS and Blue. Methods In bench-top experiments, we noted the visual appearance of the devices and evaluated changes in stent cell angles, neck coverage surface area (%), and stent cell crossing profile for microcatheters using a fusiform aneurysm model...
November 5, 2017: Neurological Research
https://www.readbyqxmd.com/read/29104940/semi-interpenetrating-polymer-networks-for-enhanced-supercapacitor-electrodes
#16
Kara D Fong, Tiesheng Wang, Hyun-Kyung Kim, R Vasant Kumar, Stoyan K Smoukov
Conducting polymers show great promise as supercapacitor materials due to their high theoretical specific capacitance, low cost, toughness, and flexibility. Poor ion mobility, however, can render active material more than a few tens of nanometers from the surface inaccessible for charge storage, limiting performance. Here, we use semi-interpenetrating networks (sIPNs) of a pseudocapacitive polymer in an ionically conductive polymer matrix to decrease ion diffusion length scales and make virtually all of the active material accessible for charge storage...
September 8, 2017: ACS Energy Letters
https://www.readbyqxmd.com/read/29104792/three-anatomical-levels-possibilities-to-decrease-invasiveness-of-reconstructive-surgery-for-congenital-penile-curvature
#17
Wojciech Perdzyński, Marek Adamek
Introduction: The aim of the study was to report methods - based on penile anatomy - leading to the minimization in the invasiveness of reconstructive surgery for congenital penile curvature (CPC). Material and methods: From 2006 to 2016 authors operated on 186 adult men with CPC.To avoid degloving, the authors used the longitudinal skin and tunica dartos incision. For decreasing invasiveness to the dorsal neurovascular bundle (NVB), the authors separated it only locally in the shape of a triangle or a trapezium, elevating it only over the place of the tunical reconstruction...
2017: Central European Journal of Urology
https://www.readbyqxmd.com/read/29100537/extra-uterine-abdominal-full-term-foetus-in-a-15-day-pregnant-rabbit
#18
Francisco Marco-Jiménez, Ximo García-Domínguez, Jesús Valdes-Hernández, José Salvador Vicente
BACKGROUND: While ectopic pregnancies account for 1-2% of all pregnancies, abdominal pregnancy is extremely rare, accounting for approximately 1% of ectopic pregnancies. Extrauterine abdominal pregnancy is defined as the implantation and development of an embryo in the peritoneal cavity. The present report is the first of an incidental case of abdominal pregnancy within four full-term foetus simultaneously with 2 weeks of physiological gestation in a healthy doe rabbit. CASE PRESENTATION: The doe was born on November 3, 2014 and the first partum took place on May 18, 2015...
November 3, 2017: BMC Veterinary Research
https://www.readbyqxmd.com/read/29094783/surface-based-electrode-localization-and-standardized-regions-of-interest-for-intracranial-eeg
#19
Michael S Trotta, John Cocjin, Emily Whitehead, Srikanth Damera, John H Wittig, Ziad S Saad, Sara K Inati, Kareem A Zaghloul
Intracranial recordings captured from subdural electrodes in patients with drug resistant epilepsy offer clinicians and researchers a powerful tool for examining neural activity in the human brain with high spatial and temporal precision. There are two major challenges, however, to interpreting these signals both within and across individuals. Anatomical distortions following implantation make accurately identifying the electrode locations difficult. In addition, because each implant involves a unique configuration, comparing neural activity across individuals in a standardized manner has been limited to broad anatomical regions such as cortical lobes or gyri...
November 2, 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/29094166/the-relationship-between-high-order-aberration-and-anterior-ocular-biometry-during-accommodation-in-young-healthy-adults
#20
Bilian Ke, Xinjie Mao, Hong Jiang, Jichang He, Che Liu, Min Li, Ying Yuan, Jianhua Wang
Purpose: This study investigated the anterior ocular anatomic origin of high-order aberration (HOA) components using optical coherence tomography and a Shack-Hartmann wavefront sensor. Methods: A customized system was built to simultaneously capture images of ocular wavefront aberrations and anterior ocular biometry. Relaxed, 2-diopter (D) and 4-D accommodative states were repeatedly measured in 30 young subjects. Custom software was used to correct optical distortions and measure biometric parameters from the images...
November 1, 2017: Investigative Ophthalmology & Visual Science
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