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surface curvature

Wolfgang Carl
The present paper studies semidiscrete surfaces in three-dimensional Euclidean space within the framework of integrable systems. In particular, we investigate semidiscrete surfaces with constant mean curvature along with their associated families. The notion of mean curvature introduced in this paper is motivated by a recently developed curvature theory for quadrilateral meshes equipped with unit normal vectors at the vertices, and extends previous work on semidiscrete surfaces. In the situation of vanishing mean curvature, the associated families are defined via a Weierstrass representation...
2017: Monatshefte Für Mathematik
Srinivas Tenneti, Sri Ganesh Subramanian, Monojit Chakraborty, Gaurav Soni, Sunando DasGupta
An extended meniscus of a ferrofluid solution on a silicon surface is subjected to axisymmetric, non-uniform magnetic field resulting in significant forward movement of the thin liquid film. Image analyzing interferometry is used for accurate measurement of the film thickness profile, which in turn, is used to determine the instantaneous slope and the curvature of the moving film. The recorded video, depicting the motion of the film in the Lagrangian frame of reference, is analyzed frame by frame, eliciting accurate information about the velocity and acceleration of the film at any instant of time...
March 17, 2017: Scientific Reports
Benny Wah, Jeffrey Michael Breidigan, Joseph Adams, Piotr Horbal, Sumit Garg, Lionel Porcar, Ursula Perez-Salas
Maintaining compositional lipid gradients across membranes in animal cells is essential to biological function, but what is the energetic cost to maintain these differences? It has long been recognized that studying the passive movement of lipids in membranes can provide insight into this toll. Unfortunately the reported values of inter, and particularly, intra- lipid transport rates of lipids in membranes show significant differences. To overcome this difficulty, biases introduced by experimental approaches have to be identified...
March 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Keisuke Matsuki, Hiroyuki Sugaya, Shota Hoshika, Yusuke Ueda, Norimasa Takahashi, Morihito Tokai, Kazutomo Onishi, Scott A Banks
The implants used in reverse shoulder arthroplasty were originally designed for white patients; thus, they might not be optimal for smaller Asian patients. The selection of reverse shoulder arthroplasty systems is limited in Japan. The purpose of this study was to measure the geometry of the proximal humerus in elderly Japanese patients to inform implant selection according to humerus size. This study included 155 shoulders from 148 patients 50 years or older who underwent computed tomography for shoulder disorders other than arthritis and trauma...
March 14, 2017: Orthopedics
Philip P Cheney, Alan W Weisgerber, Alec M Feuerbach, Michelle K Knowles
The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature...
March 15, 2017: Membranes
Tod A Pascal, Irune Villaluenga, Kevin Hamilton Wujcik, Didier Devaux, Xi Jiang, Dunyang Rita Wang, Nitash P Balsara, David Prendergast
Impregnation of porous carbon matrices with liquid sulfur has been exploited to fabricate composite cathodes for lithium-sulfur batteries, aimed at confining soluble sulfur species near conducting carbon to prevent both loss of active material into the electrolyte and parasitic reactions at the lithium metal anode. Here, through extensive computer simulations, we uncover the strongly favorable interfacial free energy between liquid sulfur and graphitic surfaces that underlies this phenomenon. Previously unexplored curvature dependent enhancements are shown to favors the filling of smaller pores first and effect a quasi-liquid sulfur phase in microporous domains (diameters < 2nm), that persists ~30o below the expected freezing point...
March 14, 2017: Nano Letters
Jyh-Ping Hsu, Hou-Hsueh Wu, Chih-Yuan Lin, Shiojenn Tseng
The ion current rectification behavior of bioinspired nanopores is modeled by adopting a bullet-shaped nanopore having a pH-tunable zwitterionic surface, focusing on discussing the underlying mechanisms. We show that with its specific geometry, such nanopore is capable of exhibiting several interesting behaviors, including ion concentration polarization and ion current rectification. The influences of the nanopore shape, solution pH, and bulk salt concentration on the associated ion current rectification behavior are examined...
March 10, 2017: Analytical Chemistry
Tao Liu, Larry N Thibos
PURPOSE: Oblique astigmatism is a prominent optical aberration of peripheral vision caused by oblique incidence of rays striking the refracting surfaces of the cornea and crystalline lens. We inquired whether oblique astigmatism from these two sources should be expected, theoretically, to have the same or opposite signs across the visual field at various states of accommodation. METHODS: Oblique astigmatism was computed across the central visual field for a rotationally-symmetric schematic-eye using optical design software...
March 9, 2017: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
Lipika Parida, Udita Uday Ghosh, Venkat Padmanabhan
The physical environment surrounding an animal has a significant impact on its behavior. The nematode Caenorhabditis elegans (C. elegans) has proved to be an excellent choice for understanding the adaptability of organisms crawling on soft surfaces. In this work, we investigate the modulation of C. elegans' behavioral kinematics in response to changes in the stiffness of the substrate and study the effect of grooves incised by the worms on their locomotion speed and efficiency. We measure the height of the grooves created by the animals on surfaces with different rigidity using confocal microscopy...
February 23, 2017: Journal of Biomechanics
Jean Kany, Belliappa Codanda
INTRODUCTION: Glenoid bone defect remains a surgical challenge in managing anterior shoulder instability. The technique first described by Latarjet has become the gold-standard, but may fail to restore fully normal anatomy in case of severe "inverted pear" glenoid bone defect. Likewise, the naturally "banana-shaped" coracoid process fails to match this flat shoulder. The congruent-arc modified Latarjet technique, which consists in pivoting the coracoid process through 90°, optimizes the contact surface, adapting to the glenoid curvature radius and increasing the articular surface of the graft...
March 5, 2017: Orthopaedics & Traumatology, Surgery & Research: OTSR
Xiangbiao Liao, Junfeng Xiao, Yong Ni, Chaorong Li, Xi Chen
Through strain-induced morphological instability, protruding patterns of roughly commensurate nanostructures are self-assembled on the surface of spherical core/shell systems. A three-dimensional (3D) phase field model is established for a closed substrate. We investigate both numerically and analytically the kinetics of the morphological evolution, from grooves to separated islands, which are sensitive to substrate curvature, misfit strain, and modulus ratio between the core and shell. The faster growth rate of surface undulation is associated with the core/shell system of a harder substrate, larger radius, or misfit strain...
March 13, 2017: ACS Nano
Long Ma, Jing Peng, Changzheng Wu, Linghui He, Yong Ni
Nanotube formation in low-temperature solution has attracted intense interest since the 1990s. How to disclose the in-depth physicochemical nature of nanotubes and pursue new available chemical strategies is still highly desirable but remains a challenge. Here, we report that sphere-to-tube transition triggered by inverse Plateau-Rayleigh instability can be a chemical route for scalable production of nanotubes. As a proof of concept, formation of a phosphorus nitride (PN) nanotube and various hierarchical nanotube architectures by coalescence of the PN hollow spheres is achieved under systematic solvothermal reaction...
March 13, 2017: ACS Nano
Joost Robert Wolters, Joanne E Verweij, Guido Avvisati, Marjolein Dijkstra, Willem K Kegel
In this paper, we demonstrate the stabilization of polystyrene microspheres by encapsulating them with dumbbell-shaped colloids with a sticky and a non-sticky lobe. Upon adding a depletant, an effective short ranged attraction is induced between the microspheres and the smaller, smooth lobes of the dumbbells, making those specifically sticky, whereas the interaction with the larger lobes of the dumbbells is considerably less attractive due to their rough surface, which reduces the overlap volume and leaves them non-sticky...
March 8, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Rosita Shishegar, Mary Tolcos, David W Walker, Leigh A Johnston
The complexity of the human cortex is demonstrated in the intricate pattern of gyri and sulci that arise from the cortical folding process during development. Quantitative assessment of cortical folding is important in the definition of normal brain development and provides insight into neurodevelopmental disorders. In this work, a method for sulcal curve extraction is proposed that combines the advantages of previously proposed depth based and curvature based methods. The technique, derived from Laplace Beltrami eigenfunction level sets, maps mean curvature on the level sets, and incorporates depth information using extracted sulci and gyri, a characteristic previously attributed only to depth based methods...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Kristina E Shillieto, Prasanth Ganesan, Anthony J Salmin, Elizabeth M Cherry, Arkady M Pertsov, Behnaz Ghoraani
Simulations are excellent tools for assessing new therapeutic strategies and are often conducted before implementing new therapy options in a clinical practice. For patients suffering from a heart arrhythmia, the main source of information comes from an intracardiac catheter. One of the common catheters is a Lasso multi-pole diagnostic catheter, which is a catheter that has 20 electrodes in a circular pattern. In this paper, we developed algorithm and simulation software that allows the users to place a multi-pole catheter on the atrial endocardial surface and record electrograms...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Joshua D Roth, Stephen M Howell, Maury L Hull
Previous reports of tibial force sensors have neither characterized nor corrected errors in the computed contact location between the femoral and tibial components in total knee arthroplasty (TKA) that are theoretically caused by the curved articular surface of the tibial component. The objectives were to experimentally characterize there errors and to develop and validate an error correction algorithm. The errors were characterized by calculating the difference between the errors in the computed contact location when forces were applied normal to the tibial articular surface and those when forces were applied normal to the tibial baseplate...
March 7, 2017: Journal of Biomechanical Engineering
Shuai Wei, Logan S Ahlstrom, Charles L Brooks
Understanding the fundamental biophysics behind protein-nanoparticle (NP) interactions is essential for the design and engineering bio-NP systems. The authors describe the development of a coarse-grained protein-NP model that utilizes a structure centric protein model. A key feature of the protein-NP model is the quantitative inclusion of the hydrophobic character of residues in the protein and their interactions with the NP surface. In addition, the curvature of the NP is taken into account, capturing the protein behavior on NPs of different size...
March 7, 2017: Small
Jinglu Ying, Jianqiu Cai, Leru Zhu, Yi Zha
To evaluate the change in the anterior corneal asphericity (ΔQ) comprehensively calculated using the tangential radius (rt ) after LASIK. Forty-two right eyes were evaluated using the Orbscan II corneal topographer. The pre- and postoperative Q-values of the flat principal semimeridians calculated by the sagittal radius were compared to those by the tangential radius. The Q-value of each semimeridian in the horizontal region was calculated by rt . Fourier fitting was used to model the 360-semimeridional variation of Q-values and to fit the Q-values in the vertical region before and after surgery...
2017: Journal of Ophthalmology
H Nassar, A Lebée, L Monasse
Origami tessellations are particular textured morphing shell structures. Their unique folding and unfolding mechanisms on a local scale aggregate and bring on large changes in shape, curvature and elongation on a global scale. The existence of these global deformation modes allows for origami tessellations to fit non-trivial surfaces thus inspiring applications across a wide range of domains including structural engineering, architectural design and aerospace engineering. The present paper suggests a homogenization-type two-scale asymptotic method which, combined with standard tools from differential geometry of surfaces, yields a macroscopic continuous characterization of the global deformation modes of origami tessellations and other similar periodic pin-jointed trusses...
January 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Lushen Li, Shaneen S Baxter, Ning Gu, Min Ji, Xi Zhan
Surface expression of chemokine receptor CXCR4 is downregulated by MIM, a member of the inverse BAR (I-BAR) domain protein family that recognizes and generates membranes with negative curvatures. Yet, the mechanism for the regulation is unknown. Here, we showed that MIM formed a complex with CXCR4 via binding to E3 ubiquitin ligase AIP4 in response to SDF-1. Overexpression of MIM promoted CXCR4 ubiquitination, inhibited cellular response to SDF-1, caused accumulation and aggregation of MVBs in the cytoplasm, and promoted CXCR4 sorting into MVBs in a manner depending on binding to AIP4...
March 6, 2017: Journal of Cell Science
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