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https://www.readbyqxmd.com/read/28813565/selectivity-hyperselectivity-and-the-tuning-of-v1-neurons
#1
Kedarnath P Vilankar, David J Field
In this article, we explore two forms of selectivity in sensory neurons. The first we call classic selectivity, referring to the stimulus that optimally stimulates a neuron. If a neuron is linear, then this stimulus can be determined by measuring the response to an orthonormal basis set (the receptive field). The second type of selectivity we call hyperselectivity; it is either implicitly or explicitly a component of several models including sparse coding, gain control, and some linear-nonlinear models. Hyperselectivity is unrelated to the stimulus that maximizes the response...
August 1, 2017: Journal of Vision
https://www.readbyqxmd.com/read/28810800/confinement-curvature-and-attractive-interaction-effects-on-polymer-surface-adsorption
#2
Wei Chien, Yeng-Long Chen
We investigate the conformation and dynamics of a semi-flexible polymer near an attractive plane or a cylindrical post using Langevin dynamics. We characterize the transition from the desorbed to absorbed state and quantify how absorption depends on the attraction interaction, polymer molecular weight, polymer flexibility, intra-polymer interaction, and micro-confinement. We find that the critical point of adsorption for ideal flexible polymers only weakly depends on confinement. However, the critical point of adsorption increases significantly for self-avoiding flexible polymers and under confinement, deviating from scaling theory predictions...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28805387/polymyxin-binding-to-the-bacterial-outer-membrane-reveals-cation-displacement-and-increasing-membrane-curvature-in-susceptible-but-not-in-resistant-lps-chemotypes
#3
Denys Ewerton da Silva Santos, Laércio Pol-Fachin, Roberto D Lins, Thereza A Soares
Lipid-A is the causative agent of Gram-negative sepsis and responsible for increasingly high mortality rate among hospitalized patients. Compounds that bind Lipid-A can limit this inflammatory process. The cationic antimicrobial peptide polymyxin B (Pmx-B) is one of the simplest molecules capable of selectively bind to Lipid-A, and may serve as a model for further development of Lipid-A binding agents. Gram-negative bacteria resistance to Pmx-B relies on the upregulation of a number of regulatory systems, which promote chemical modifications of the LPS structure, and leads to major changes in the physical-chemical properties of the outer membrane...
August 14, 2017: Journal of Chemical Information and Modeling
https://www.readbyqxmd.com/read/28805223/the-effect-of-defects-on-the-catalytic-activity-of-single-au-atom-supported-carbon-nanotubes-and-reaction-mechanism-for-co-oxidation
#4
Sajjad Ali, Tian Fu Liu, Zan Lian, Bo Li, Dang Sheng Su
The mechanism of CO oxidation by O2 on a single Au atom supported on pristine, mono atom vacancy (m), di atom vacancy (di) and the Stone Wales defect (SW) on single walled carbon nanotube (SWCNT) surface is systematically investigated theoretically using density functional theory. We determine that single Au atoms can be trapped effectively by the defects on SWCNTs. The defects on SWCNTs can enhance both the binding strength and catalytic activity of the supported single Au atom. Fundamental aspects such as adsorption energy and charge transfer are elucidated to analyze the adsorption properties of CO and O2 and co-adsorption of CO and O2 molecules...
August 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28805041/direct-microrolling-processing-on-a-silicon-wafer
#5
Kanna Aoki, Keita Ishiguro, Masaki Denokami, Yuya Tanahashi, Kentaro Furusawa, Norihiko Sekine, Tadafumi Adschiri, Minoru Fujii
Although, varieties of micro- to nanoscale fabrication technologies have been invented and refined for silicon (Si) processing because Si is the basic material of integrated circuits, the layouts are based on layer-by-layer approaches, making it difficult to realize three-dimensional (3D) structures with complicated shapes normal to the planar surface (along the out-of-plane direction) of the wafers used. Here, a novel and direct Si-processing technology that enables to bend thin layers of Si surfaces into various 3D curved structures at the micrometer scale is introduced...
August 14, 2017: Small
https://www.readbyqxmd.com/read/28804520/fast-simulation-of-lipid-vesicle-deformation-using-spherical-harmonic-approximation
#6
Michael Mikucki, Yongcheng Zhou
Lipid vesicles appear ubiquitously in biological systems. Understanding how the mechanical and intermolecular interactions deform vesicle membranes is a fundamental question in biophysics. In this article we develop a fast algorithm to compute the surface configurations of lipid vesicles by introducing surface harmonic functions to approximate the membrane surface. This parameterization allows an analytical computation of the membrane curvature energy and its gradient for the efficient minimization of the curvature energy using a nonlinear conjugate gradient method...
January 2017: Communications in Computational Physics
https://www.readbyqxmd.com/read/28800096/an-iterative-closest-points-algorithm-for-registration-of-3d-laser-scanner-point-clouds-with-geometric-features
#7
Ying He, Bin Liang, Jun Yang, Shunzhi Li, Jin He
The Iterative Closest Points (ICP) algorithm is the mainstream algorithm used in the process of accurate registration of 3D point cloud data. The algorithm requires a proper initial value and the approximate registration of two point clouds to prevent the algorithm from falling into local extremes, but in the actual point cloud matching process, it is difficult to ensure compliance with this requirement. In this paper, we proposed the ICP algorithm based on point cloud features (GF-ICP). This method uses the geometrical features of the point cloud to be registered, such as curvature, surface normal and point cloud density, to search for the correspondence relationships between two point clouds and introduces the geometric features into the error function to realize the accurate registration of two point clouds...
August 11, 2017: Sensors
https://www.readbyqxmd.com/read/28799367/effect-of-entropy-on-the-nucleation-of-cavitation-bubbles-in-water-under-tension
#8
Georg Menzl, Christoph Dellago
Water can exist in a metastable liquid state under tension for long times before the system relaxes into the vapor via cavitation, i.e., bubble nucleation. Microscopic information on the cavitation process can be extracted from experimental data by the use of the nucleation theorem, which relates measured cavitation rates to the size of the critical bubble. To apply the nucleation theorem to experiments performed along an isochoric path, for instance, in cavitation experiments in mineral inclusions, knowledge of the bubble entropy is required...
December 7, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28794042/palmitoylation-contributes-to-membrane-curvature-in-influenza-a-virus-assembly-and-hemagglutinin-mediated-membrane-fusion
#9
Petr Chlanda, Elena Mekhedov, Hang Waters, Alexander Sodt, Cindi Schwartz, Vinod Nair, Paul S Blank, Joshua Zimmerberg
The highly conserved cytoplasmic tail of influenza virus glycoprotein hemagglutinin (HA) contains three cysteines, post-translationally modified by covalently bound fatty acids. While viral HA acylation is crucial in virus replication, its physico-chemical role is unknown. We used virus-like particles (VLP) to study the effect of acylation on morphology, protein incorporation, lipid composition, and membrane fusion. De-acylation interrupted HA-M1 interactions since de-acylated mutant HA fail to incorporate an M1 layer within spheroidal VLP, and filamentous particles incorporated increased numbers of neuraminidase (NA)...
August 9, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28793193/accuracy-of-axisymmetric-drop-shape-analysis-in-determining-surface-and-interfacial-tensions
#10
Jinlong Yang, Kyle Yu, Yi Y Zuo
Axisymmetric drop shape analysis (ADSA) has been used in a broad range of applications for determining surface tensions of the air-liquid surfaces and interfacial tensions of the liquid-liquid interfaces. However, it is well known that the accuracy of ADSA deteriorates upon the reduction of drop volume. Here, we systematically compared different criteria/parameters in evaluating the accuracy of ADSA upon reducing drop volume. By scrutinizing the dependence of ADSA accuracy on various parameters, including the capillary constant (c), the Bond number (Bo), the Worthington number (Wo), and the shape parameter (Ps), we concluded that the classical Bond number failed to predict the accuracy of drop shape analysis at very small drop volumes...
August 9, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28773024/mechanical-behavior-of-steel-fiber-reinforced-concrete-beams-bonded-with-external-carbon-fiber-sheets
#11
Viktor Gribniak, Vytautas Tamulenas, Pui-Lam Ng, Aleksandr K Arnautov, Eugenijus Gudonis, Ieva Misiunaite
This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection...
June 17, 2017: Materials
https://www.readbyqxmd.com/read/28770254/3d-correction-of-ais-in-braces-designed-using-cad-cam-and-fem-a-randomized-controlled-trial
#12
Nikita Cobetto, Carl-Éric Aubin, Stefan Parent, Soraya Barchi, Isabelle Turgeon, Hubert Labelle
BACKGROUND: Recent studies showed that finite element model (FEM) combined to CAD/CAM improves the design of braces for the conservative treatment of adolescent idiopathic scoliosis (AIS), using 2D measurements from in-brace radiographs. We aim to assess the immediate effectiveness on curve correction in all three planes of braces designed using CAD/CAM and numerical simulation compared to braces designed with CAD/CAM only. METHODS: SRS standardized criteria for bracing were followed to recruit 48 AIS patients who were randomized into two groups...
2017: Scoliosis and Spinal Disorders
https://www.readbyqxmd.com/read/28764948/effects-of-the-incorporation-of-%C3%AE%C2%B5-aminocaproic-acid-chitosan-particles-to-fibrin-on-cementoblast-differentiation-and-cementum-regeneration
#13
Chan Ho Park, Joung-Hwan Oh, Hong-Moon Jung, Yoonnyoung Choi, Saeed Rahman, Sungtae Kim, Tae-Il Kim, Hong-In Shin, Yun-Sil Lee, Frank H Yu, Jeong-Hwa Baek, Hyun-Mo Ryoo, Kyung Mi Woo
Cementum formation on the exposed tooth-root surface is a critical process in periodontal regeneration. Although various therapeutic approaches have been developed, regeneration of integrated and functional periodontal complexes is still wanting. Here, we found that the OCCM30 cementoblasts cultured on fibrin matrix express substantial levels of matrix proteinases, leading to the degradation of fibrin and the apoptosis of OCCM30 cells, which was reversed upon treatment with a proteinase inhibitor, ε-aminocaproic acid (ACA)...
July 29, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28764428/diffuse-ultrasonic-backscatter-using-a-multi-gaussian-beam-model
#14
Xiongbing Li, Yongfeng Song, Andrea P Arguelles, Joseph A Turner
Diffuse ultrasonic backscatter is widely used to evaluate microstructural parameters of heterogeneous materials. Recent singly scattered response (SSR) models utilize a single-Gaussian beam (SGB) assumption which is expected to have limitations. Following a similar formalism, a model is presented using a multi-Gaussian beam (MGB) assumption to characterize the transducer beam for longitudinal-to-longitudinal scattering at normal incidence through an interface with arbitrary curvature. First, the Wigner transform of the transducer field is defined using conjugate double-layer MGB expressions...
July 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28764362/the-mesoscopic-membrane-with-proteins-mesm-p-model
#15
Aram Davtyan, Mijo Simunovic, Gregory A Voth
We present the Mesoscopic Membrane with Proteins (MesM-P) model, an extension of a previously developed elastic membrane model for mesoscale simulations of lipid membranes. MesM-P employs a discrete mesoscopic quasi-particle approach to model protein-facilitated shape and topology changes of the lipid membrane on length and time scales inaccessible to all-atom and quasimolecular coarse-grained molecular dynamics simulations. We investigate the ability of MesM-P to model the behavior of large lipid vesicles as a function of bound protein density...
July 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28763630/growth-of-hollow-cell-spheroids-in-microbead-templated-chambers
#16
Eddie Wang, Dong Wang, Andrew Geng, Richard Seo, Xiaohua Gong
Cells form hollow, spheroidal structures during the development of many tissues, including the ocular lens, inner ear, and many glands. Therefore, techniques for in vitro formation of hollow spheroids are valued for studying developmental and disease processes. Current in vitro methods require cells to self-organize into hollow morphologies; we explored an alternative strategy based on cell growth in predefined, spherical scaffolds. Our method uses sacrificial, gelatin microbeads to simultaneously template spherical chambers within a hydrogel and deliver cells into the chambers...
July 26, 2017: Biomaterials
https://www.readbyqxmd.com/read/28762721/supramolecular-corrals-on-surfaces-resulting-from-aromatic-interactions-of-nonplanar-triazoles
#17
Siddharth J Jethwa, Esben L Kolsbjerg, Sundar R Vadapoo, Jacob L Cramer, Lutz Lammich, Kurt V Gothelf, Bjørk Hammer, Trolle R Linderoth
Interaction forces between aromatic moieties, often referred to as π-π interactions, are an important element in stabilizing complex supramolecular structures. For supramolecular self-assembly occurring on surfaces, where aromatic moieties are typically forced to adsorb coplanar with the surface, the possible role of intermolecular aromatic interactions is much less explored. Here, we report on unusual, ring-shaped supramolecular corral surface structures resulting from adsorption of a molecule with nonplanar structure, allowing for intermolecular aromatic interactions...
August 1, 2017: ACS Nano
https://www.readbyqxmd.com/read/28761941/effects-of-different-concentrations-and-excipients-of-titanium-tetrafluoride-on-dentin-erosion-prevention
#18
Taís Mantilla, Thayanne Ramos-Oliveira, Camila Silva, Maria Cersosimo, Cecilia Turssi, Patricia Freitas
PURPOSE: To evaluate the preventive effect of titanium fluoride (TiF4) gel and solution, in different concentrations, on dentin erosion. MATERIALS AND METHODS: Of 140 root dentin slabs (3 x 3 x 1 mm) cut from 70 freshly extracted human third molars, 70 with intermediate Knoop microhardness and lowest surface curvature were selected and randomly divided into 7 groups (n = 10): G1: negative control (no treatment); G2: positive control (AmF/NaF/SnCl2 solution); G3: placebo gel (no fluoride); G4: 1% TiF4 solution; G5: 1% TiF4 gel; G6: 4% TiF4 solution; G7: 4% TiF4 gel...
July 31, 2017: Oral Health & Preventive Dentistry
https://www.readbyqxmd.com/read/28754380/magnetocapillary-self-assemblies-locomotion-and-micromanipulation-along-a-liquid-interface
#19
REVIEW
G Grosjean, M Hubert, N Vandewalle
This paper presents an overview and discussion of magnetocapillary self-assemblies. New results are presented, in particular concerning the possible development of future applications. These self-organizing structures possess the notable ability to move along an interface when powered by an oscillatory, uniform magnetic field. The system is constructed as follows. Soft magnetic particles are placed on a liquid interface, and submitted to a magnetic induction field. An attractive force due to the curvature of the interface around the particles competes with an interaction between magnetic dipoles...
July 20, 2017: Advances in Colloid and Interface Science
https://www.readbyqxmd.com/read/28742972/stimuli-responsive-directional-vesicular-assembly-with-tunable-surface-functionality-and-impact-on-enzyme-inhibition
#20
Amrita Sikder, Debes Ray, Vinod K Aswal, Suhrit Ghosh
The article describes the self-assembly of a series of unsymmetrical bola-shaped π-amphiphiles (NDI-1, NDI-1a, NDI-2, NDI-3, and NDI-4) consisting of a hydrophobic naphthalene-diimide (NDI) chromophore attached to a nonionic hydrophilic wedge and an anionic headgroup in the two opposite arms of the central NDI. By design, only a single hydrazide group is linked either on the ionic or nonionic arm of the NDI. NDI-1 and NDI-1a are regioisomers differing only in the location of the hydrazide group, placed in the nonionic or ionic arm, respectively...
August 8, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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