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surface curvature

Rex T Skodje, Jonathan R Church
A novel double hydrogen atom exchange process, HX+H'O2H'X+HO2 for the halogen series X=F, Cl, Br, and I, is identified using theoretical methods. These concerted reactions are mediated through a stabilized five-member planar ring transition state structure. The transition state barrier for the double exchange process is found to be significantly lower than that for the abstraction reaction of a single hydrogen atom, . Density functional theory employing the M11 exchange functional is used to compute parameters of the potential energy surface and the rate coefficients are obtained using transition state theory with small curvature tunneling...
May 24, 2018: Journal of Physical Chemistry. A
Hongxia Li, Ablimit Aili, Mohamed H Alhosani, Qiaoyu Ge, TieJun Zhang
Condensation widely exists in nature and industry, and its performance heavily relies on the efficiency of condensate removal. Recent advances in micro/nano-scale surface engineering enable condensing droplet removal from solid surfaces without extra energy cost, but it is still challenging to achieve passive transport of micro-droplets over long distance along horizontal surfaces. The mobility of these condensate droplets can be enhanced by lubricant oil infusion on flat surfaces and frequent coalescence, which lead to fast growth but random motion of droplets...
May 24, 2018: ACS Applied Materials & Interfaces
Joakim Arnlind, Christoffer Holm
A noncommutative algebra corresponding to the classical catenoid is introduced together with a differential calculus of derivations. We prove that there exists a unique metric and torsion-free connection that is compatible with the complex structure, and the curvature is explicitly calculated. A noncommutative analogue of the fact that the catenoid is a minimal surface is studied by constructing a Laplace operator from the connection and showing that the embedding coordinates are harmonic. Furthermore, an integral is defined and the total curvature is computed...
2018: Letters in Mathematical Physics
Feng Chen, Suren Chen, Xiaoxiang Ma
INTRODUCTION: Driving environment, including road surface conditions and traffic states, often changes over time and influences crash probability considerably. It becomes stretched for traditional crash frequency models developed in large temporal scales to capture the time-varying characteristics of these factors, which may cause substantial loss of critical driving environmental information on crash prediction. METHOD: Crash prediction models with refined temporal data (hourly records) are developed to characterize the time-varying nature of these contributing factors...
June 2018: Journal of Safety Research
Brian Moths, T A Witten
Conventional micelles, composed of simple amphiphiles, exhibit only a few standard morphologies, each characterized by its mean surface curvature set by the amphiphiles. Here we demonstrate a rational design scheme to construct micelles of more general shape from polymeric amphiphiles. We replace the many amphiphiles of a conventional micelle by a single flexible, linear, block copolymer chain containing two incompatible species arranged in multiple alternating segments. With suitable segment lengths, the chain exhibits a condensed spherical configuration in solution, similar to conventional micelles...
March 2018: Physical Review. E
Jingyuan Chen, Xiangjun Xing, Zhenwei Yao
Understanding the interplay between ordered structures and substrate curvature is an interesting problem with versatile applications, including functionalization of charged supramolecular surfaces and modern microfluidic technologies. In this work, we investigate the two-dimensional packing structures of charged particles confined on a pinched sphere. By continuously pinching the sphere, we observe cleavage of elongated scars into pleats, proliferation of disclinations, and subsequently, emergence of a depletion zone at the negatively curved waist that is completely void of particles...
March 2018: Physical Review. E
N C Costa, T Blommel, W-T Chiu, G Batrouni, R T Scalettar
The Holstein model describes the interaction between fermions and a collection of local (dispersionless) phonon modes. In the dilute limit, the phonon degrees of freedom dress the fermions, giving rise to polaron and bipolaron formation. At higher densities, the phonons mediate collective superconducting (SC) and charge-density wave (CDW) phases. Quantum Monte Carlo (QMC) simulations have considered both these limits but have not yet focused on the physics of more general phonon spectra. Here we report QMC studies of the role of phonon dispersion on SC and CDW order in such models...
May 4, 2018: Physical Review Letters
Joanna Kim, John A Cooper
Junctional integrity of endothelial monolayers is crucial to control movement of molecules and cells across the endothelium. Examining the structure and dynamics of cell junctions in endothelial monolayers, we discovered a role for septins. Contacts between adjacent endothelial cells were dynamic, with protrusions extending above or below neighboring cells. VE-cadherin was present at cell junctions, with a membrane-associated layer of F-actin. Septins localized at cell-junction membranes, in patterns distinct from VE-cadherin and F-actin...
May 17, 2018: Molecular Biology of the Cell
Maryam Jalali, Andrew R White, James Marti, Jian Sheng
Texturing a large surface with oily micro-drops with controlled size, shape and volume provides an unprecedented capability in investigating complex interactions of bacteria, cells and interfaces. It has particular implications in understanding key microbial processes involved in remediation of environmental disasters, such as Deepwater Horizon oil spill. This work presents a development of scalable micro-transfer molding to functionalize a substrate with oily drop array to generate a microcosm mimicking bacteria encountering a rising droplet cloud...
May 15, 2018: Scientific Reports
Shane Breheny, Angela Christine Chang, April De Silva, Paul Allcock
PURPOSE: Volar distal radius plates are pre-contoured to aid restoration of anatomy during open reduction internal fixation of distal radius fractures. Incorrectly contoured plates can result in malreduction, leading to malunion, pain, and loss of function. The purpose of this study was to investigate whether adolescent distal radius anatomy on the palmar cortical surface differs from that in adults, in order to determine whether adult plates are suitable for use in adolescents. METHODS: Lateral wrist radiographs were used to measure the distal radius palmar cortical angle (PCA) in adolescent age groups (12-13, 14-15, and 16-17 years old) and compared to a skeletally mature control group (30-50 years old)...
May 2018: Journal of Orthopaedic Surgery
Subramani Ponnusamy, Sandhiya Lakshmanan, Kittusamy Senthilkumar
In the present work the reaction mechanism of two segregated hydrofluoroethers (HFEs), CH3OCF3 (HFE-143a) and CH3OCHF2 (HFE-152a) and a non-segregated HFEs, CHF2OCH2CF3 (HFE-245fa2) with OH radical is studied using electronic structure calculations. The initial reaction between HFE and OH radical is studied by considering two (three for CHF2OCH2CF3) pathways, H-atom abstraction and C-O bond breaking, OH addition reaction and C-C bond breaking, OH addition reaction, which leads to the formation of alkyl radical intermediate...
May 15, 2018: Journal of Physical Chemistry. A
Silke Henkes, M Cristina Marchetti, Rastko Sknepnek
Using simulations of self-propelled agents with short-range repulsion and nematic alignment, we explore the dynamical phases of a dense active nematic confined to the surface of a sphere. We map the nonequilibrium phase diagram as a function of curvature, alignment strength, and activity. Our model reproduces several phases seen in recent experiments on active microtubule bundles confined the surfaces of vesicles. At low driving, we recover the equilibrium nematic ground state with four +1/2 defects. As the driving is increased, geodesic forces drive the transition to a polar band wrapping around an equator, with large empty spherical caps corresponding to two +1 defects at the poles...
April 2018: Physical Review. E
Tobias Peikert, Fenghai Duan, Srinivasan Rajagopalan, Ronald A Karwoski, Ryan Clay, Richard A Robb, Ziling Qin, JoRean Sicks, Brian J Bartholmai, Fabien Maldonado
PURPOSE: Optimization of the clinical management of screen-detected lung nodules is needed to avoid unnecessary diagnostic interventions. Herein we demonstrate the potential value of a novel radiomics-based approach for the classification of screen-detected indeterminate nodules. MATERIAL AND METHODS: Independent quantitative variables assessing various radiologic nodule features such as sphericity, flatness, elongation, spiculation, lobulation and curvature were developed from the NLST dataset using 726 indeterminate nodules (all ≥ 7 mm, benign, n = 318 and malignant, n = 408)...
2018: PloS One
Haris Sideroudi, Apostolos Lazaridis, Anke Messerschmidt-Roth, Georgios Labiris, Vassilios Kozobolis, Walter Sekundo
PURPOSE: To evaluate the long-term changes in anterior and posterior corneal irregular astigmatism and curvatures after small incision lenticule extraction (SMILE). METHODS: Fifty eyes of 28 patients underwent SMILE for myopic astigmatism. All procedures were performed using the VisuMax® femtosecond laser. A Scheimpflug camera was used for preoperative and 3-year postoperative tomography. Anterior and posterior corneal Fourier parameters (spherical component, regular astigmatism, asymmetry, and irregularity) and curvature data were evaluated and compared within 2 subgroups according to the magnitude of the refractive correction (low myopia group: spherical equivalent (SEQ) ≥ -6 D; high myopia group: (SEQ) < -6 D)...
April 27, 2018: Cornea
Aleksandr S Oreshonkov, Evgenii Roginskii, Alexander S Krylov, Alexandr A Ershov, Vladimir Nikolaevich Voronov
Crystal structure of LaF3 single crystal is refined in tysonite-type trigonal unit cell P-3c1 using density functional theory calculations and Raman spectroscopy. It is shown that trigonal structure with P-3c1 space group is more energy-efficient than hexagonal structure with space group P63cm. Simulated Raman spectra obtained using LDA approximation is in much better agreement with experimental data than obtained with PBE and PBEsol functionals of GGA. The calculated frequency value of silent mode B2 in case of hexagonal structure P63cm was found to be imaginary (unstable mode), thus the energy surface obtains negative curvature with respect to the corresponding normal coordinates of the mode which leads to instability of the hexagonal structure in harmonic approximation...
May 14, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Oscar Mickelin, Jonasz Słomka, Keaton J Burns, Daniel Lecoanet, Geoffrey M Vasil, Luiz M Faria, Jörn Dunkel
Recent experiments demonstrate the importance of substrate curvature for actively forced fluid dynamics. Yet, the covariant formulation and analysis of continuum models for nonequilibrium flows on curved surfaces still poses theoretical challenges. Here, we introduce and study a generalized covariant Navier-Stokes model for fluid flows driven by active stresses in nonplanar geometries. The analytical tractability of the theory is demonstrated through exact stationary solutions for the case of a spherical bubble geometry...
April 20, 2018: Physical Review Letters
Afreen Haider, Yu-Chen Wei, Koini Lim, Antonio D Barbosa, Che-Hsiung Liu, Ursula Weber, Marek Mlodzik, Kadri Oras, Simon Collier, M Mahmood Hussain, Liang Dong, Satish Patel, Anna Alvarez-Guaita, Vladimir Saudek, Benjamin J Jenkins, Albert Koulman, Marcus K Dymond, Roger C Hardie, Symeon Siniossoglou, David B Savage
Cell and organelle membranes consist of a complex mixture of phospholipids (PLs) that determine their size, shape, and function. Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic membranes, yet how cells sense and regulate its levels in vivo remains unclear. Here we show that PCYT1A, the rate-limiting enzyme of PC synthesis, is intranuclear and re-locates to the nuclear membrane in response to the need for membrane PL synthesis in yeast, fly, and mammalian cells. By aligning imaging with lipidomic analysis and data-driven modeling, we demonstrate that yeast PCYT1A membrane association correlates with membrane stored curvature elastic stress estimates...
May 7, 2018: Developmental Cell
K Lee, M Kim, K Kim
BACKGROUND: Skin surface evaluation has been studied using various imaging techniques. However, all these studies had limited impact because they were performed using visual exam only. To improve on this scenario with haptic feedback, we propose 3D reconstruction of the skin surface using a single image. Unlike extant 3D skin surface reconstruction algorithms, we utilize the local texture and global curvature regions, combining the results for reconstruction. MATERIALS AND METHODS: The first entails the reconstruction of global curvature, achieved by bilateral filtering that removes noise on the surface while maintaining the edge (ie, furrow) to obtain the overall curvature...
May 11, 2018: Skin Research and Technology
Wenjie Fei, Michelle M Driscoll, Paul M Chaikin, Kyle J M Bishop
A homogeneous magnetic field can exert no net force on a colloidal particle. However, by coupling the particle's orientation to its position on a curved interface, even static homogeneous fields can be used to drive rapid particle motions. Here, we demonstrate this effect using magnetic Janus particles with amphiphilic surface chemistry adsorbed at the spherical interface of a water drop in decane. Application of a static homogeneous field drives particle motion to the drop equator where the particle's magnetic moment can align parallel to the field...
May 11, 2018: Soft Matter
Wenjing Xi, Hoa T Phan, Amanda J Haes
Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles are dispersed in various solvents and matrices. While extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory has been successfully applied to predict nanoparticle stability in solution, this model fails to accurately predict the physical stability of anisotropic nanostructures; thus limiting its applicability in practice. Herein, DLVO theory was used to accurately predict gold nanostar stability in solution by investigating how the choice of the nanostar dimension considered in calculations influences the calculated attractive and repulsive interactions between nanostructures...
May 11, 2018: Analytical and Bioanalytical Chemistry
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