Hydrophobicity of silver surfaces with microparticle geometry
NASA Astrophysics Data System (ADS)
Macko, Ján; Oriňaková, Renáta; Oriňak, Andrej; Kovaľ, Karol; Kupková, Miriam; Erdélyi, Branislav; Kostecká, Zuzana; Smith, Roger M.
2016-11-01
The effect of the duration of the current deposition cycle and the number of current pulses on the geometry of silver microstructured surfaces and on the free surface energy, polarizability, hydrophobicity and thus adhesion force of the silver surfaces has been investigated. The changes in surface hydrophobicity were entirely dependent on the size and density of the microparticles on the surface. The results showed that formation of the silver microparticles was related to number of current pulses, while the duration of one current pulse played only a minor effect on the final surface microparticle geometry and thus on the surface tension and hydrophobicity. The conventional geometry of the silver particles has been transformed to the fractal dimension D. The surface hydrophobicity depended predominantly on the length of the dendrites not on their width. The highest silver surface hydrophobicity was observed on a surface prepared by 30 current pulses with a pulse duration of 1 s, the lowest one when deposition was performed by 10 current pulses with a duration of 0.1 s. The partial surface tension coefficients γDS and polarizability kS of the silver surfaces were calculated. Both parameters can be applied in future applications in living cells adhesion prediction and spectral method selection. Silver films with microparticle geometry showed a lower variability in final surface hydrophobicity when compared to nanostructured surfaces. The comparisons could be used to modify surfaces and to modulate human cells and bacterial adhesion on body implants, surgery instruments and clean surfaces.
Local geometry of isoscalar surfaces.
Dopazo, César; Martín, Jesús; Hierro, Juan
2007-11-01
An inert dynamically passive scalar in a constant density fluid forced by a statistically homogeneous field of turbulence has been investigated using the results of a 256(3) grid direct numerical simulation. Mixing characteristics are characterized in terms of either principal curvatures or mean and Gauss curvatures. The most probable small-scale scalar geometries are flat and tilelike isosurfaces. Preliminary correlations between flow and scalar small-scale structures associate highly curved saddle points with large-strain regions and elliptic points with vorticity-dominated zones. The concavity of the scalar profiles along the isosurface normal coordinate xn correlates well with negative mean curvatures, Gauss curvatures displaying any sign, which correspond to scalar minima, tiles, or saddle points; on the other hand, convexity along xn is associated with positive mean curvatures, Gauss curvatures ranging from negative to positive signs, featuring maxima, tiles, or saddle points; inflection points along xn correlate well with small values of the mean curvature and zero or negative values of kg, corresponding to plane isosurfaces or saddle points with curvatures of equal and opposite signs. Small values of the scalar gradient are associated with elliptic points, either concave or convex (kg>0) , for both concave and convex scalar profiles along xn. Large values of the scalar gradient (or, equivalently, scalar fluctuation dissipation rates) are generally connected with small values of the Gauss curvature (either flat or moderate-curvature tilelike local geometries), with both concave and convex scalar profiles along xn equally probable. Vortical local flow structures correlate well with small and moderate values of the scalar gradient, while strain-dominated regions are associated with large values. PMID:18233765
Geometry program for aerodynamic lifting surface theory
NASA Technical Reports Server (NTRS)
Medan, R. T.
1973-01-01
A computer program that provides the geometry and boundary conditions appropriate for an analysis of a lifting, thin wing with control surfaces in linearized, subsonic, steady flow is presented. The kernel function method lifting surface theory is applied. The data which is generated by the program is stored on disk files or tapes for later use by programs which calculate an influence matrix, plot the wing planform, and evaluate the loads on the wing. In addition to processing data for subsequent use in a lifting surface analysis, the program is useful for computing area and mean geometric chords of the wing and control surfaces.
Surface grid generation for complex three-dimensional geometries
NASA Technical Reports Server (NTRS)
Luh, Raymond Ching-Chung
1988-01-01
An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code base on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry.
Surface grid generation for complex three-dimensional geometries
NASA Technical Reports Server (NTRS)
Luh, Raymond Ching-Chung
1988-01-01
An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code based on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry.
Ideal spiral bevel gears: A new approach to surface geometry
NASA Technical Reports Server (NTRS)
Huston, R. L.; Coy, J. J.
1980-01-01
The fundamental geometrical characteristics of spiral bevel gear tooth surfaces are discussed. The parametric representation of an ideal spiral bevel tooth is developed based on the elements of involute geometry, differential geometry, and fundamental gearing kinematics. A foundation is provided for the study of nonideal gears and the effects of deviations from ideal geometry on the contact stresses, lubrication, wear, fatigue life, and gearing kinematics.
Ideal spiral bevel gears - A new approach to surface geometry
NASA Technical Reports Server (NTRS)
Huston, R. L.; Coy, J. J.
1980-01-01
This paper discusses the fundamental geometrical characteristics of spiral bevel gear tooth surfaces. The parametric representation of an ideal spiral bevel tooth is developed. The development is based on the elements of involute geometry, differential geometry, and fundamental gearing kinematics. A foundation is provided for the study of nonideal gears and the effects of deviations from ideal geometry on the contact stresses, lubrication, wear, fatigue life, and gearing kinematics.
Triangle Geometry Processing for Surface Modeling and Cartesian Grid Generation
NASA Technical Reports Server (NTRS)
Aftosmis, Michael J. (Inventor); Melton, John E. (Inventor); Berger, Marsha J. (Inventor)
2002-01-01
Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.
Triangle geometry processing for surface modeling and cartesian grid generation
Aftosmis, Michael J [San Mateo, CA; Melton, John E [Hollister, CA; Berger, Marsha J [New York, NY
2002-09-03
Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.
Surface geometry of circular cut spiral bevel gears
NASA Technical Reports Server (NTRS)
Huston, R. L.; Coy, J. J.
1981-01-01
An analysis of the surface geometry of spiral bevel gears formed by a circular cutter is presented. The emphasis is upon determining the tooth surface principal radii of curvature of crown (flat) gears. Specific results are presented for involute, straight, and hyperbolic cutter profiles. It is shown that the geometry of circular cut spiral bevel gears is somewhat simpler than a theoretical logarithmic spiral bevel gear.
Self-dual geometry of generalized Hermitian surfaces
Arsen'eva, O E; Kirichenko, V F
1998-02-28
Several results on the geometry of conformally semiflat Hermitian surfaces of both classical and hyperbolic types (generalized Hermitian surfaces) are obtained. Some of these results are generalizations and clarifications of already known results in this direction due to Koda, Itoh, and other authors. They reveal some unexpected beautiful connections between such classical characteristics of conformally semiflat (generalized) Hermitian surfaces as the Einstein property, the constancy of the holomorphic sectional curvature, and so on. A complete classification of compact self-dual Hermitian RK-surfaces that are at the same time generalized Hopf manifolds is obtained. This provides a complete solution of the Chen problem in this class of Hermitian surfaces.
Investigation of Surface Phenomena in Shocked Tin in Converging Geometry
Rousculp, Christopher L.; Oro, David Michael; Margolin, Len G.; Griego, Jeffrey Randall; Reinovsky, Robert Emil; Turchi, Peter John
2015-08-06
There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the Richtmyer-Meshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface is adjacent to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIX capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release.
Using Dynamic Geometry Software for the Intersection Surfaces
ERIC Educational Resources Information Center
Koparan, Timur; Yilmaz, Gül Kaleli
2015-01-01
The purpose of this study is to define prospective teacher views about using dynamic geometry software for intersection surfaces. The study was conducted as a case study. For this purpose, data collection tool was developed based on the opinion of two experts. The data collection tool consists of 4 open-ended questions related to the intersection…
Surface geometry of circular cut spiral bevel gears
NASA Technical Reports Server (NTRS)
Huston, R. L.; Coy, J. J.
1981-01-01
The tooth surface principal radii of curvature of crown (flat) gears were determined. Specific results are presented for involute, straight, and hyperbolic cutter profiles. It is shown that the geometry of circular cut spiral bevel gears is somewhat simpler than a theoretical logarithmic spiral bevel gear.
Martian Surface Properties: Inferences from Resolved Differences in Crater Geometries
NASA Technical Reports Server (NTRS)
Valiant, G. J.; Stewart, S. T.
2004-01-01
Impact craters are a natural probe of planetary sub-surfaces, both from the excavated material and from crater geometries, which are sensitive to material properties of the target. One of the most intriguing aspects of Martian craters is the morphology of the ejecta blankets. All fresh and many older Martian craters larger than a few km are surrounded by ejecta blankets which appear fluidized, with morphologies believed to form by entrainment of liquid water. In addition to the ejecta morphology, quantitative information about the subsurface composition may be derived from geometrical measurements, e.g., rim uplift height and ejecta blanket volumes. In order to use craters to derive subsurface composition or test rampart morphology formation hypotheses, accurate measurements with quantified error estimates are required. We have developed and tested a toolkit for measurements of crater geometry using the MOLA altimetry data. Here, we present the results from geometry measurements on fresh craters in Lunae Planum and Utopia Planitia.
Viscous damping of microcantilevers with modified surfaces and geometries
NASA Astrophysics Data System (ADS)
Ergincan, O.; Palasantzas, G.; Kooi, B. J.
2012-08-01
Noise measurements were performed to determine the quality factor Q and the resonating frequency shift as a function of gas pressure P for microcantilevers with modified surfaces and geometries. In the molecular and continuum regimes, energy loss is dominated by the surrounding fluid leading to reduction of the Q factor and shift of the resonance frequency by Δf, which becomes significant in the continuum regime showing sensitivity on surface changes. This is shown via three methods: frequency shift Δf vs. P, Q factor vs. P, and direct calculation using surface roughness details acquired via atomic force microscopy.
[Phenotypic and phytochemical differences between Mentha arvensis L. and Mentha canadiensis L].
Shelepova, O V; Voronkova, T V; Kondrat'eva, V V; Semenova, M V; Bidiukova, G F; Olekhnovich, L S
2014-01-01
A taxonomic study of anatomical, morphological, and phytochemical characteristics of Mentha arvensis L. and Mentha canadiensis L. using hierarchical cluster analysis has been conducted and the differences between the species studied have been revealed. The ratio between the lengths of the calyx tube and the calyx lobes, the number of secretory glands on the upper and lower surfaces of the leaf, and the composition of the essen- tial oil were shown to be the most appropriate parameters for classification.
3D stochastic geophysical inversion for contact surface geometry
NASA Astrophysics Data System (ADS)
Lelièvre, Peter; Farquharson, Colin; Bijani, Rodrigo
2015-04-01
Geologists' interpretations about the Earth typically involve distinct rock units with contacts (interfaces) between them. As such, 3D geological Earth models typically comprise wireframe contact surfaces of tessellated triangles or other polygonal planar facets. In contrast, standard minimum-structure geophysical inversions are performed on meshes of space-filling cells (typically prisms or tetrahedra) and recover smoothly varying physical property distributions that are inconsistent with typical geological interpretations. There are several approaches through which mesh-based geophysical inversion can help recover models with some of the desired characteristics. However, a more effective strategy is to consider a fundamentally different type of inversion that works directly with models that comprise surfaces representing contacts between rock units. We are researching such an approach, our goal being to perform geophysical forward and inverse modelling directly with 3D geological models of any complexity. Geological and geophysical models should be specified using the same parameterization such that they are, in essence, the same Earth model. We parameterize the wireframe contact surfaces in a 3D model as the coordinates of the nodes (facet vertices). The physical properties of each rock unit in a model remain fixed while the geophysical inversion controls the position of the contact surfaces via the control nodes, perturbing the surfaces as required to fit the geophysical data responses. This is essentially a "geometry inversion", which can be used to recover the unknown geometry of a target body or to investigate the viability of a proposed Earth model. We apply global optimization strategies to solve the inverse problem, including stochastic sampling to obtain statistical information regarding the likelihood of particular features in the model, helping to assess the viability of a proposed model. Jointly inverting multiple types of geophysical data is simple
Effects of hillslope geometry on surface and subsurface flows
NASA Astrophysics Data System (ADS)
Sabzevari, T.; Noroozpour, S.
2014-07-01
Dividing a catchment to subcatchment or hillslope scales allows for better scrutiny of the changes in spatial distribution of rainfall, soil attributes and plant cover across the catchment. An instantaneous unit hydrograph model is suggested for simulating runoff hydrographs for complex hillslopes. This model is able to estimate surface and subsurface flows of the catchment based on the Dunne-Black mechanism. For this purpose, a saturation model is used to separate the saturated and unsaturated zones in complex hillslopes. The profile curvatures (concave, straight and convex) and plan shapes (convergent, parallel and divergent) of complex hillslopes are considered, in order to compute the travel time of surface and subsurface flows. The model was used for prediction of the direct runoff hydrograph and subsurface flow hydrograph of Walnut Gulch No. 125 catchment in Arizona (USA). Based on results, the geometry of hillslopes can change the peak of the direct runoff hydrograph up to two-fold, either higher or lower. The divergent hillslopes show higher peaks in comparison with the parallel and convergent hillslopes. The highest and lowest peak flows correspond to divergent-concave and convergent-straight hillslopes, respectively.
Hydromechanical Normal Deformation Experiments and Coupling to Fracture Surface Geometry
NASA Astrophysics Data System (ADS)
Thörn, J.; Fransson, A. M.
2015-12-01
Civil engineering structures founded in fractured crystalline rock, such as the Fennoscandian Shield (Norway-Sweden-Finland) requires allowance for both stability and/or deformations of the rock mass and groundwater ingress and groundwater pressure changes. Coupling these issues could be the key to solving the challenges that arise from construction of e.g. hydropower dams, road and railroad tunnels, and most certainly the construction of nuclear waste repositories within fractured crystalline rock, all of which are currently planned in Sweden. Excavation related deformation in fractures may cause groundwater leakage even from the most elaborate pre-excavation grouting works. A better understanding on hydraulically (or grouting) induced deformations in the near-field of tunnels, where the stress field is re-distributed due to the opening may both provide a basis for more accurate numerical modelling and grouting or excavation procedures that minimize the damage on the completed grouting fans. Subjects of this study were experiments conducted as measurement of deformations in boreholes close to tunnels due to stepwise injection tests, and laboratory hydromechanical experiments conducted as flow and normal deformation measurements in a permeameter during cycles of up to 2.5 MPa confining pressure, and subsequent surface scanning of the samples for coupling of HM-results to geometric appearance, aperture and contact geometry. When expressed in terms of hydraulic aperture (b) and fracture normal stiffness (kn) the results of both in situ and lab experiments support a previously suggested relationship based on field data where kn is inversely proportional to roughly b2. The relationship was assumed to be valid for low compressive stress across fractures with limited previous deformation. One important data set used to establish the relationship was transmissivity and storage coefficients from hydraulic interference tests previously performed at Äspö Hard Rock
A basis for the analysis of surface geometry of spiral bevel gears
NASA Technical Reports Server (NTRS)
Huston, R. L.; Coy, J. J.
1983-01-01
Geometrical procedures helpful in the fundamental studies of the surface geometry of spiral bevel gears are summarized. These procedures are based upon: (1) fundamental gear geometry and kinematics as exposited by Buckingham, et al; (2) formulas developed from differential geometry; and (3) geometrical concepts developed in recent papers and reports on spiral bevel gear surface geometry. Procedures which characterize the geometry so that the surface parametric equations, the principal radii of curvature, and the meshing kinematics are systematically determined are emphasized. Initially, the focus in on theoretical, logarithmic spiral bevel gears as defined by Buckingham. The gears, however, are difficult to fabricate and are sometimes considered to be too straight. Circular-cut spiral bevel gears are an alternative to this. Surface characteristics of crown circular cut gears are analyzed.
NASA Astrophysics Data System (ADS)
Kiefer, W. S.
1993-02-01
For a fixed heat flow, the surface flow velocity of a convecting layer is not strongly sensitive to the variation of viscosity as a function of depth. Thus, the inferred absence of a low viscosity asthenosphere on Venus can not account for the limited surface motions there. The surface velocity is dependent on the convective geometry. Cartesian geometry convection can produce large surface velocities if the high viscosity surface layer is broken in places by weak zones. On the other hand, a high viscosity surface layer may inhibit the development of large surface velocities in axisymmetric convection.
Holographic entanglement entropy of anisotropic minimal surfaces in LLM geometries
NASA Astrophysics Data System (ADS)
Kim, Chanju; Kim, Kyung Kiu; Kwon, O.-Kab
2016-08-01
We calculate the holographic entanglement entropy (HEE) of the Zk orbifold of Lin-Lunin-Maldacena (LLM) geometries which are dual to the vacua of the mass-deformed ABJM theory with Chern-Simons level k. By solving the partial differential equations analytically, we obtain the HEEs for all LLM solutions with arbitrary M2 charge and k up to μ02 -order where μ0 is the mass parameter. The renormalized entanglement entropies are all monotonically decreasing near the UV fixed point in accordance with the F-theorem. Except the multiplication factor and to all orders in μ0, they are independent of the overall scaling of Young diagrams which characterize LLM geometries. Therefore we can classify the HEEs of LLM geometries with Zk orbifold in terms of the shape of Young diagrams modulo overall size. HEE of each family is a pure number independent of the 't Hooft coupling constant except the overall multiplication factor. We extend our analysis to obtain HEE analytically to μ04 -order for the symmetric droplet case.
Detecting Translation Errors in CAD Surfaces and Preparing Geometries for Mesh Generation
Petersson, N Anders; Chand, K K
2001-08-27
The authors have developed tools for the efficient preparation of CAD geometries for mesh generation. Geometries are read from IGES files and then maintained in a boundary-representation consisting of a patchwork of trimmed and untrimmed surfaces. Gross errors in the geometry can be identified and removed automatically while a user interface is provided for manipulating the geometry (such as correcting invalid trimming curves or removing unwanted details). Modifying the geometry by adding or deleting surfaces and/or sectioning it by arbitrary planes (e.g. symmetry planes) is also supported. These tools are used for robust and accurate geometry models for initial mesh generation and will be applied to in situ mesh generation requirements of moving and adaptive grid simulations.
Trapped surfaces in the Schwarzschild geometry and cosmic censorship
Wald, R.M.; Iyer, V. )
1991-12-15
We prove that in extended Schwarzschild spacetime there exists a family of Cauchy surfaces which come arbitrarily close to the black-hole singularity at {ital r}=0 but are such that there do not exist any outer trapped surfaces lying within the past of any of these Cauchy surfaces. We argue that, in any spherically symmetric spacetime describing gravitational collapse to a Schwarzschild black hole, it should be possible to choose a spacelike slicing by Cauchy surfaces which terminates when a singularity (outside the matter) is reached, such that the region of the spacetime covered by the slicing contains no outer trapped surfaces. Thus, an important feature of the numerical collapse examples of Shapiro and Teukolsky, cited by them as evidence against cosmic censorship, does not appear to be qualitatively different from features which occur (for an appropriate choice of slicing) in the standard examples of collapse to a black hole.
Mechanics and geometry in the seashell-like (Turritella) surface
NASA Astrophysics Data System (ADS)
Guo, Qiaohang; Chen, Zi; Li, Wei; Ren, Kun; Lin, Junjie; Taber, Larry A.; Chen, Wenzhe
2013-03-01
Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, adds to the variety of this family of aesthetic beauty. Here we report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves an equilibrium. In this study, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessary be locally optimized. This novel approach can be applied to develop materials and systems with desirable geometries by exploiting mechanics of geometric frustration. The authors would like to thank Yushan Huang, Zhen Liu, Si Chen for their assistance in the experimental demonstration. This work has been in part supported by NSFC (Grant No.11102040 and No.11201001044), the Sigma Xi Grants-in-Aid of Research (GIAR) program, American Academy of Mechanics Founder's Award from the Robert M. and Mary Haythornthwaite Foundation, and Society in Science, The Branco Weiss Fellowship, administered by ETH Zurich. Qiaohang Guo and Zi Chen contributed equally to this work.
On the Use of CAD-Native Predicates and Geometry in Surface Meshing
NASA Technical Reports Server (NTRS)
Aftosmis, M. J.
1999-01-01
Several paradigms for accessing computer-aided design (CAD) geometry during surface meshing for computational fluid dynamics are discussed. File translation, inconsistent geometry engines, and nonnative point construction are all identified as sources of nonrobustness. The paper argues in favor of accessing CAD parts and assemblies in their native format, without translation, and for the use of CAD-native predicates and constructors in surface mesh generation. The discussion also emphasizes the importance of examining the computational requirements for exact evaluation of triangulation predicates during surface meshing.
The solid angle (geometry factor) for a spherical surface source and an arbitrary detector aperture
Favorite, Jeffrey A.
2016-01-13
It is proven that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture.
Costa, Filippo; Monorchio, Agostino; Manara, Giuliano
2016-01-01
A methodology to obtain wideband scattering diffusion based on periodic artificial surfaces is presented. The proposed surfaces provide scattering towards multiple propagation directions across an extremely wide frequency band. They comprise unit cells with an optimized geometry and arranged in a periodic lattice characterized by a repetition period larger than one wavelength which induces the excitation of multiple Floquet harmonics. The geometry of the elementary unit cell is optimized in order to minimize the reflection coefficient of the fundamental Floquet harmonic over a wide frequency band. The optimization of FSS geometry is performed through a genetic algorithm in conjunction with periodic Method of Moments. The design method is verified through full-wave simulations and measurements. The proposed solution guarantees very good performance in terms of bandwidth-thickness ratio and removes the need of a high-resolution printing process. PMID:27181841
An interactive approach to surface-fitting complex geometries for flowfield applications
NASA Technical Reports Server (NTRS)
Dejarnette, Fred R.; Hamilton, H. Harris, II; Cheatwood, F. Mcneil
1987-01-01
Numerical flowfield methods require a geometry subprogram which can calculate body coordinates, slopes, and radii of curvature for typical aircraft and spacecraft configurations. The objective of this paper is to develop a new surface-fitting technique which addresses two major problems with existing geometry packages: computer storage requirements and the time required of the user for the initial set-up of the geometry model. In the present method, coordinates of cross sections are fit in a least-squares sense using segments of general conic sections. After fitting each cross section, the next step is to blend the cross-sectional curve-fits in the longitudinal direction using general conics to fit specific meridional half-planes. For the initial setup of the geometry model, an interactive, completely menu-driven computer code has been developed to allow the user to make modifications to the initial fit for a given cross section or meridional cut. Graphic displays are provided to assist the user in the visualization of the effect of each modification. The completed model may be viewed from any angle using the code's three-dimensional graphics package. Geometry results for the modeling of the Space Shuttle and a proposed Aeroassist Flight Experiment (AFE) geometry are presented, in addition to calculated heat-transfer rates based on these models.
Geometry Laboratory (GEOLAB) surface modeling and grid generation technology and services
NASA Technical Reports Server (NTRS)
Kerr, Patricia A.; Smith, Robert E.; Posenau, Mary-Anne K.
1995-01-01
The facilities and services of the GEOmetry LABoratory (GEOLAB) at the NASA Langley Research Center are described. Included in this description are the laboratory functions, the surface modeling and grid generation technologies used in the laboratory, and examples of the tasks performed in the laboratory.
Basevi, Hector R A; Guggenheim, James A; Dehghani, Hamid; Styles, Iain B
2013-03-25
Knowledge of the surface geometry of an imaging subject is important in many applications. This information can be obtained via a number of different techniques, including time of flight imaging, photogrammetry, and fringe projection profilometry. Existing systems may have restrictions on instrument geometry, require expensive optics, or require moving parts in order to image the full surface of the subject. An inexpensive generalised fringe projection profilometry system is proposed that can account for arbitrarily placed components and use mirrors to expand the field of view. It simultaneously acquires multiple views of an imaging subject, producing a cloud of points that lie on its surface, which can then be processed to form a three dimensional model. A prototype of this system was integrated into an existing Diffuse Optical Tomography and Bioluminescence Tomography small animal imaging system and used to image objects including a mouse-shaped plastic phantom, a mouse cadaver, and a coin. A surface mesh generated from surface capture data of the mouse-shaped plastic phantom was compared with ideal surface points provided by the phantom manufacturer, and 50% of points were found to lie within 0.1mm of the surface mesh, 82% of points were found to lie within 0.2mm of the surface mesh, and 96% of points were found to lie within 0.4mm of the surface mesh. PMID:23546107
On the Use of CAD-Native Predicates and Geometry in Surface Meshing
NASA Technical Reports Server (NTRS)
Aftosmis, M. J.
1999-01-01
Several paradigms for accessing CAD geometry during surface meshing for CFD are discussed. File translation, inconsistent geometry engines and non-native point construction are all identified as sources of non-robustness. The paper argues in favor of accessing CAD parts and assemblies in their native format, without translation, and for the use of CAD-native predicates and constructors in surface mesh generation. The discussion also emphasizes the importance of examining the computational requirements for exact evaluation of triangulation predicates during surface meshing. The native approach is demonstrated through an algorithm for the generation of closed manifold surface triangulations from CAD geometry. CAD parts and assemblies are used in their native format, and a part's native geometry engine is accessed through a modeler-independent application programming interface (API). In seeking a robust and fully automated procedure, the algorithm is based on a new physical space manifold triangulation technique specially developed to avoid robustness issues associated with poorly conditioned mappings. In addition, this approach avoids the usual ambiguities associated with floating-point predicate evaluation on constructed coordinate geometry in a mapped space. The technique is incremental, so that each new site improves the triangulation by some well defined quality measure. The algorithm terminates after achieving a prespecified measure of mesh quality and produces a triangulation such that no angle is less than a given angle bound, a or greater than pi - 2alpha. This result also sets bounds on the maximum vertex degree, triangle aspect-ratio and maximum stretching rate for the triangulation. In addition to the output triangulations for a variety of CAD parts, the discussion presents related theoretical results which assert the existence of such an angle bound, and demonstrate that maximum bounds of between 25 deg and 30 deg may be achieved in practice.
Dokukin, M. E.; Guz, N. V.; Woodworth, C.D.; Sokolov, I.
2015-01-01
Despite considerable advances in understanding the molecular nature of cancer, many biophysical aspects of malignant development are still unclear. Here we study physical alterations of the surface of human cervical epithelial cells during stepwise in vitro development of cancer (from normal to immortal (premalignant), to malignant). We use atomic force microscopy to demonstrate that development of cancer is associated with emergence of simple fractal geometry on the cell surface. Contrary to the previously expected correlation between cancer and fractals, we find that fractal geometry occurs only at a limited period of development when immortal cells become cancerous; further cancer progression demonstrates deviation from fractal. Because of the connection between fractal behaviour and chaos (or far from equilibrium behaviour), these results suggest that chaotic behaviour coincides with the cancer transformation of the immortalization stage of cancer development, whereas further cancer progression recovers determinism of processes responsible for cell surface formation. PMID:25844044
NASA Astrophysics Data System (ADS)
Dokukin, M. E.; Guz, N. V.; Woodworth, C. D.; Sokolov, I.
2015-03-01
Despite considerable advances in understanding the molecular nature of cancer, many biophysical aspects of malignant development are still unclear. Here we study physical alterations of the surface of human cervical epithelial cells during stepwise in vitro development of cancer (from normal to immortal (premalignant), to malignant). We use atomic force microscopy to demonstrate that development of cancer is associated with emergence of simple fractal geometry on the cell surface. Contrary to the previously expected correlation between cancer and fractals, we find that fractal geometry occurs only at a limited period of development when immortal cells become cancerous; further cancer progression demonstrates deviation from fractal. Because of the connection between fractal behaviour and chaos (or far from equilibrium behaviour), these results suggest that chaotic behaviour coincides with the cancer transformation of the immortalization stage of cancer development, whereas further cancer progression recovers determinism of processes responsible for cell surface formation.
Arnida; Janát-Amsbury, M.M.; Ray, A.; Peterson, C. M.; Ghandehari, H.
2010-01-01
Spherical and rod-shaped gold nanoparticles with surface poly (ethylene glycol) (PEG) chains were characterized for size, shape, charge, poly dispersity and surface plasmon resonance. The nanoparticles were injected intravenously to 6–8 weeks old female nu/nu mice bearing orthotopic ovarian tumors and their biodistribution in vital organs was compared. Gold nanorods were taken up to a lesser extent by the liver, had longer circulation time in the blood, and higher accumulation in the tumors, compared with their spherical counterparts. The cellular uptake of PEGylated gold nanoparticles by a murine macrophage-like cell line as a function of geometry was examined. Compared to nanospheres, PEGylated gold nanorods were taken up to a lesser extent by macrophages. These studies point to the importance of gold nanoparticle geometry and surface properties on transport across biological barriers. PMID:21093587
An interactive user-friendly approach to surface-fitting three-dimensional geometries
NASA Technical Reports Server (NTRS)
Cheatwood, F. Mcneil; Dejarnette, Fred R.
1988-01-01
A surface-fitting technique has been developed which addresses two problems with existing geometry packages: computer storage requirements and the time required of the user for the initial setup of the geometry model. Coordinates of cross sections are fit using segments of general conic sections. The next step is to blend the cross-sectional curve-fits in the longitudinal direction using general conics to fit specific meridional half-planes. Provisions are made to allow the fitting of fuselages and wings so that entire wing-body combinations may be modeled. This report includes the development of the technique along with a User's Guide for the various menus within the program. Results for the modeling of the Space Shuttle and a proposed Aeroassist Flight Experiment geometry are presented.
NASA Technical Reports Server (NTRS)
Gyekenyesi, J. P.; Mendelson, A.
1977-01-01
The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement field in a finite geometry bar containing a variable depth rectangular surface crack under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Using the obtained displacement field, normal stresses, and the stress-intensity factor variation along the crack periphery are calculated for different crack depth to bar thickness ratios. Crack opening displacements and stress-intensity factors are also obtained for a through-thickness, center-cracked bar with variable thickness. The reported results show a considerable potential for using this method in calculating stress-intensity factors for commonly encountered surface crack geometries in finite solids
NASA Technical Reports Server (NTRS)
Gyekenyesi, J. P.; Mendelson, A.
1975-01-01
The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement field in a finite geometry bar containing a variable depth rectangular surface crack under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Using the obtained displacement field, normal stresses and the stress intensity factor variation along the crack periphery are calculated for different crack depth to bar thickness ratios. Crack opening displacements and stress intensity factors are also obtained for a through-thickness, center cracked bar with variable thickness. The reported results show a considerable potential for using this method in calculating stress intensity factors for commonly encountered surface crack geometries in finite solids.
Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D; Sebastiani, Daniel
2012-11-21
We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials. PMID:23181297
NASA Astrophysics Data System (ADS)
Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D.; Sebastiani, Daniel
2012-11-01
We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials.
NASA Technical Reports Server (NTRS)
Glazman, R. E.
1986-01-01
Statistics of two-dimensional wave groups, of steep wave events, and of a cascade pattern manifested in the surface geometry in a developed sea state are derived. A systematic view is presented of the spectral moment problem, highlighting its physical meaning and showing its relationship with the theory of random fields. A solution of this problem is suggested that is appropriate to the case of wind-generated surface waves. The solution method treats the surface elevation field as specified on a spatial (temporal) running grid, developing an averaging procedure which employs the Taylor microscale as the mesh size. The technique is illustrated by first exposing errors in direct calculations of the effective surface impedance for a coherently reflected L-band radio wave. The technique is then used to study wave groups and steep waves for a Gaussian, two-dimensional, time-varying surface. Finally, the theory is applied to estimate breaking wave statistics,
Instability of a Möbius Strip Minimal Surface and a Link with Systolic Geometry
NASA Astrophysics Data System (ADS)
Pesci, Adriana I.; Goldstein, Raymond E.; Alexander, Gareth P.; Moffatt, H. Keith
2015-03-01
We describe the first analytically tractable example of an instability of a nonorientable minimal surface under parametric variation of its boundary. A one-parameter family of incomplete Meeks Möbius surfaces is defined and shown to exhibit an instability threshold as the bounding curve is opened up from a double-covering of the circle. Numerical and analytical methods are used to determine the instability threshold by solution of the Jacobi equation on the double covering of the surface. The unstable eigenmode shows excellent qualitative agreement with that found experimentally for a closely related surface. A connection is proposed between systolic geometry and the instability by showing that the shortest noncontractable closed geodesic on the surface (the systolic curve) passes near the maximum of the unstable eigenmode.
Instability of a Möbius strip minimal surface and a link with systolic geometry.
Pesci, Adriana I; Goldstein, Raymond E; Alexander, Gareth P; Moffatt, H Keith
2015-03-27
We describe the first analytically tractable example of an instability of a nonorientable minimal surface under parametric variation of its boundary. A one-parameter family of incomplete Meeks Möbius surfaces is defined and shown to exhibit an instability threshold as the bounding curve is opened up from a double-covering of the circle. Numerical and analytical methods are used to determine the instability threshold by solution of the Jacobi equation on the double covering of the surface. The unstable eigenmode shows excellent qualitative agreement with that found experimentally for a closely related surface. A connection is proposed between systolic geometry and the instability by showing that the shortest noncontractable closed geodesic on the surface (the systolic curve) passes near the maximum of the unstable eigenmode. PMID:25860771
Manufacturing lot affects polyethylene tibial insert volume, thickness, and surface geometry.
Teeter, Matthew G; Milner, Jaques S; MacDonald, Steven J; Naudie, Douglas D R
2013-08-01
To perform wear measurements on retrieved joint replacement implants, a reference geometry of the implant's original state is required. Since implants are rarely individually scanned before implantation, a different, new implant of the same kind and size is frequently used. However, due to manufacturing variability, errors may be introduced into these measurements, as the dimensions between the retrieved and reference components may not be exactly the same. The hypothesis of this study was that new polyethylene tibial inserts from different manufacturing lots would demonstrate greater variability than those from the same lot. In total, 12 new tibial inserts of the same model and size were obtained, 5 from the same lot and the remainder from different lots. The geometry of each tibial insert was obtained using microcomputed tomography. Measurements of tibial insert volume, thickness, and three-dimensional surface deviations were obtained and compared between tibial inserts from the same and different manufacturing lots. Greater variability was found for the tibial inserts from different manufacturing lots for all types of measurements, including a fourfold difference in volume variability (p < 0.001) and a maximum of 0.21 mm difference in thickness (p < 0.001). Investigators should be aware of this potential confounding error and take steps to minimize it, such as by averaging together the geometries of multiple new components from different manufacturing lots for use as the reference geometry.
Multi-sensor system for surface inspection and 3D-geometry assessment
NASA Astrophysics Data System (ADS)
Becker, Markus; Weber, Juergen; Schubert, Erhard
1997-09-01
This paper addresses an installed application in quality control where a 100% inspection of geometry (3D) and surface of cuboid (parallelpiped) and ring-shaped magnets is done using a system of 2 CCD matrix cameras, one of which is equipped with on-board processing components and a transmitted-light sensor with microcontroller based data processing for the measurement of the height of the objects. The geometry and surface properties are measured with a diffuse indirect IR-LED flash, mounted in a ring around the object and a telecentric lens to avoid perspective distortions due to different heights of the measured objects. The surface inspection looks for broken pieces, surface faults due to spalling/chipping and for cracks. The second CCD camera uses the same illumination and algorithm to inspect the surface of the other side of the objects after it has been turned around in a return conveyor belt. All components are triggered by separate light barriers and perform their tasks independently. The integration of the results of each measurement is done by an SPC which also controls the actors that handle the three different classes of objects (good, bad, rework). These actors are valves and the objects are separated by pressurized air. The main concern of this paper is the system aspect, how the measurement results are evaluated and combined to achieve a correct classification of the objects which are inspected by three independent sensors and arrive at unpredictable time intervals.
Surface geometry of protoplanetary disks inferred from near-infrared imaging polarimetry
Takami, Michihiro; Hasegawa, Yasuhiro; Gu, Pin-Gao; Karr, Jennifer L.; Chapillon, Edwige; Tang, Ya-Wen; Muto, Takayuki; Dong, Ruobing; Hashimoto, Jun; Kusakabe, Nobuyuki; Akiyama, Eiji; Kwon, Jungmi; Itoh, Youchi; Carson, Joseph; Follette, Katherine B.; Mayama, Satoshi; Sitko, Michael; Janson, Markus; Grady, Carol A.; Kudo, Tomoyuki; and others
2014-11-01
We present a new method of analysis for determining the surface geometry of five protoplanetary disks observed with near-infrared imaging polarimetry using Subaru-HiCIAO. Using as inputs the observed distribution of polarized intensity (PI), disk inclination, assumed properties for dust scattering, and other reasonable approximations, we calculate a differential equation to derive the surface geometry. This equation is numerically integrated along the distance from the star at a given position angle. We show that, using these approximations, the local maxima in the PI distribution of spiral arms (SAO 206462, MWC 758) and rings (2MASS J16042165-2130284, PDS 70) are associated with local concave-up structures on the disk surface. We also show that the observed presence of an inner gap in scattered light still allows the possibility of a disk surface that is parallel to the light path from the star, or a disk that is shadowed by structures in the inner radii. Our analysis for rings does not show the presence of a vertical inner wall as often assumed in studies of disks with an inner gap. Finally, we summarize the implications of spiral and ring structures as potential signatures of ongoing planet formation.
Numerical modelling of the effect of changing surface geometry on mountain glacier mass balance
NASA Astrophysics Data System (ADS)
Williams, C.; Carrivick, J.; Evans, A.; Carver, S.
2012-12-01
Mountain glaciers and ice caps are extremely useful indicators of environmental change. Due to their small size, they have much faster response times to climate changes than the large ice masses of Greenland and Antarctica. Mountain glaciers are important for society as sources of water for energy production and irrigation. The meltwater cycles significantly impact local ecology. Consequently, models assessing the effect of complicated glacier surface geometry on glacier mass balance are becoming increasingly popular. Here we apply such a model to a glacier record spanning 100 years. Our study encompasses the creation of a GIS enabling analysis of changing glacier geometry over the 20th and early 21st Centuries and the development and testing of a novel user-friendly distributed-surface energy balance model that is designed specifically to consider the effect that these changes have on mountain glacier mass balance. Long-term records of mass balance are rare for arctic Mountain glaciers, making model development and evaluation difficult. One exception is Kårsaglaciären in arctic Sweden for which there is a variety of data for the past 100 years, sourced from historical surveys, satellite imagery and recent field work. Firstly, we present the construction of robust three-dimensional glacier surface reconstructions for Kårsaglaciären within a GIS, specifically discussing the methods of interpolation used to create the surfaces. We highlight the methods and importance of inter-model sensitivity analyses as well as Monte Carlo simulations used to assess the effect of the input data utilised in the kriging algorithms. Analyses integral to the modelling stage of the project, such as the geometries of the resultant surfaces as well as the interrelationships between them, will be discussed. Secondly, we present the melt model which has been constructed in order to test the effect of changing geometry on mass balance. Our melt model can carry out systematic testing of
Adsorption process, atomic geometry, electronic structure and stability of Si(001)/Te surface
NASA Astrophysics Data System (ADS)
Miwa, R. H.; Ferraz, A. C.
2000-03-01
The adsorption process, atomic geometry, electronic structure and energetics of a Si(001) surface covered by Te atoms have been studied using first-principles total-energy calculations. Our findings indicate that the Te atoms adsorb in the 'bridge' site on the surface Si dimer bond, in agreement with recent experimental results. We have also verified that the Si dimers (underneath adsorbed Te atoms) do not dissociate. The subsequent atomic exchange between the adsorbed Te atom and the surface Si atom, giving rise to an interdiffusion process of Te atoms towards Si substrate, is not an exothermic process. We have considered a number of possible coverages of Te atoms on Si(001) surface and our results indicate that for a coverage of one monolayer (1 ML), the Si(001)/Te-(1×1) surface represents the energetically more stable configuration. For a coverage of 2/3 ML, we have verified the formation of TeSiTe mixed trimers, in a (3×1) reconstructed surface. At 1/3 ML coverage, we have obtained the formation of Si dimers with a single Te atom at the surface, in a (3×1) reconstruction. Finally, for a coverage of 1/2 ML, we have obtained the formation of SiTe mixed dimers, in a (2×1) reconstructed surface, but the calculated formation energy indicates that this atomic configuration is not energetically favourable.
Numerical modelling of the effect of changing surface geometry on mountain glacier mass balance
NASA Astrophysics Data System (ADS)
Williams, Chris; Carrivick, Jonathan; Evans, Andrew; Carver, Steve
2013-04-01
Mountain glaciers and ice caps are extremely useful indicators of environmental change. Due to their small size, they have much faster response times to climate changes than the large ice masses of Greenland and Antarctica. Mountain glaciers are important for society as sources of water for energy production and irrigation and the meltwater cycles significantly impact local ecology. We have applied a spatially distributed surface energy balance model to a glacier record spanning 100 years. Our study encompasses (i) the creation of a GIS enabling quantitative analysis of changing glacier geometry; absolute length, area, surface lowering and volume change, over the 20th and early 21st Centuries and (ii) the development and testing of a novel user-friendly distributed-surface energy balance model that is designed specifically to consider the effect that these geometrical changes have on mountain glacier mass balance. Our study site is Kårsaglaciären in Arctic Sweden for which there is a variety of data for the past 100 years, sourced from historical surveys, satellite imagery and recent field work. This contrasts with other Arctic mountain glaciers where long-term records are rare, making model development and evaluation very difficult. Kårsaglaciären has been in a state of negative balance throughout the 20th century. Disintegration of the glacier occurred during the 1920s, breaking the glacier into two separate bodies. Between 1926 and 2008, the glacier retreated 1.3 km and reduced in area by 3.41km2. In 2008 the glacier had an estimated surface area of 0.89km2 and a length of approximately 1.0km. Firstly, we present the GIS based construction of robust three-dimensional glacier surface reconstructions for Kårsaglaciären from 1926 to 2010 using a decadal interval. We highlight the kriging interpolation methods used for surface development and the importance of inter-model sensitivity analyses as well as the use of Monte Carlo simulations used to assess the
NASA Technical Reports Server (NTRS)
Li, C. J.; Devries, W. R.; Ludema, K. C.
1983-01-01
Measurements made with a stylus surface tracer which provides a digitized representation of a surface profile are discussed. Parameters are defined to characterize the height (e.g., RMS roughness, skewness, and kurtosis) and length (e.g., autocorrelation) of the surface topography. These are applied to the characterization of crank shaft journals which were manufactured by different grinding and lopping procedures known to give significant differences in crank shaft bearing life. It was found that three parameters (RMS roughness, skewness, and kurtosis) are necessary to adequately distinguish the character of these surfaces. Every surface specimen has a set of values for these three parameters. They can be regarded as a set coordinate in a space constituted by three characteristics axes. The various journal surfaces can be classified along with the determination of a proper wavelength cutoff (0.25 mm) by using a method of separated subspace. The finite radius of the stylus used for profile tracing gives an inherent measurement error as it passes over the fine structure of the surface. A mathematical model is derived to compensate for this error.
High Resolution Surface Geometry and Albedo by Combining Laser Altimetry and Visible Images
NASA Technical Reports Server (NTRS)
Morris, Robin D.; vonToussaint, Udo; Cheeseman, Peter C.; Clancy, Daniel (Technical Monitor)
2001-01-01
The need for accurate geometric and radiometric information over large areas has become increasingly important. Laser altimetry is one of the key technologies for obtaining this geometric information. However, there are important application areas where the observing platform has its orbit constrained by the other instruments it is carrying, and so the spatial resolution that can be recorded by the laser altimeter is limited. In this paper we show how information recorded by one of the other instruments commonly carried, a high-resolution imaging camera, can be combined with the laser altimeter measurements to give a high resolution estimate both of the surface geometry and its reflectance properties. This estimate has an accuracy unavailable from other interpolation methods. We present the results from combining synthetic laser altimeter measurements on a coarse grid with images generated from a surface model to re-create the surface model.
Geometry of GLP on silver surface by surface-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Bao, PeiDi; Bao, Lang; Huang, TianQuan; Liu, XinMing; Wu, GuoFeng
2000-05-01
Leptospirosis is one of the most harmful zoonosis, it is a serious public health issue in some area of Sichuan province. Surface-Enhance Raman Scattering (SERS) Spectroscopy is an effective approach for the study of biomolecular adsorption on metal surface and provides information about the adsorbed species. Two samples of Leptospiral Glycolipoprotein (GLP-1) and GLP-2 which have different toxic effects have been obtained and investigated.
Influence of cross sectional geometry on surface plasmon polariton propagation in gold nanowires.
Nauert, Scott; Paul, Aniruddha; Zhen, Yu-Rong; Solis, David; Vigderman, Leonid; Chang, Wei-Shun; Zubarev, Eugene R; Nordlander, Peter; Link, Stephan
2014-01-28
We investigated the effects of cross sectional geometry on surface plasmon polariton propagation in gold nanowires (NWs) using bleach-imaged plasmon propagation and electromagnetic simulations. Chemically synthesized NWs have pentagonally twinned crystal structures, but recent advances in synthesis have made it possible to amplify this pentagonal shape to yield NWs with a five-pointed-star cross section and sharp end tips. We found experimentally that NWs with a five-pointed-star cross section, referred to as SNWs, had a shorter propagation length for surface plasmon polaritons at 785 nm, but a higher effective incoupling efficiency compared to smooth NWs with a pentagonal cross section, labeled as PNWs. Electromagnetic simulations revealed that the electric fields were localized at the sharp ridges of the SNWs, leading to higher absorptive losses and hence shorter propagation lengths compared to PNWs. On the other hand, scattering losses were found to be relatively uncorrelated with cross sectional geometry, but were strongly dependent on the plasmon mode excited. Our results provide insight into the shape-dependent waveguiding properties of chemically synthesized metal NWs and the mode-dependent loss mechanisms that govern surface plasmon polariton propagation. PMID:24308802
NASA Astrophysics Data System (ADS)
Moghaddam, M.; Akbar, R.; West, R. D.; Colliander, A.; Kim, S.; Dunbar, R. S.
2015-12-01
The NASA Soil Moisture Active-Passive Mission (SMAP), launched in January 2015, provides near-daily global surface soil moisture estimates via combined Active Radar and Passive Radiometer observations at various spatial resolutions. The goal of this mission is to enhance our understanding of global carbon and water cycles. This presentation will focus on a comprehensive assessment of the SMAP high resolution radar backscatter data (formally the L1C_S0_HiRes data product) obtained over a 3 km Woody Savanna region in north-central California during a 2.5 month period starting late May 2015. The effects of spacecraft observation geometry (fore- and aft-looks as well as ascending and descending obits) along with regional topography on soil moisture estimation abilities will be examined. Furthermore surface soil moisture retrievals, obtained through utilization of different combinations of observation geometries, will be compared to an existing network of in situsensors. Current electromagnetic scattering and emission models do not properly account for surface topography, therefore physical forward model predictions and observations have unaccounted mismatch errors which also affect soil moisture estimation accuracies. The goal of this study is to quantify these soil moisture prediction errors and highlight the need for new and complete Electromagnetic modeling efforts.
Evaluation of Missing Pellet Surface Geometry on Cladding Stress Distribution and Magnitude
Capps, Nathan A.; Montgomery, Robert O.; Sunderland, Dion J.; Spencer, Ben; Pytel, Martin; Wirth, Brian D.
2014-10-01
Missing pellet surface (MPS) defects are local geometric defects that periodically occur in nuclear fuel pellets, usually as a result of the mishandling during the manufacturing process. The presences of these defects can lead to clad stress concentrations that are substantial enough to cause a through wall failure for certain conditions of power level, burnup, and power increase. Consequently, the impact of potential MPS defects has limited the rate of power increase or ramp rates in both PWR and BWR systems. Improved 3D MPS models that consider the effect of the MPS geometry can provide better understanding of the margins against PCMI clad failure. The Peregrine fuel performance code has been developed as a part the Consortium of Advanced Simulations of Light Water Reactors (CASL) to consider the inherently multi-physics and multi-dimensional mechanisms that control fuel behavior, including cladding failure by the presence of MPS defects. This paper presents an evaluation of the cladding stress concentrations as a function of MPS defect geometry. The results are the first step in a probabilistic approach to assess cladding failure during power maneuvers. This analysis provides insight into how varying pellet defect geometries affect the distribution of the cladding stress and fuel and cladding temperature and will be used to develop stress concentration factors for 2D and 3D models.
The effect of surface anisotropy and viewing geometry on the estimation of NDVI from AVHRR
Meyer, D.; Verstraete, M.; Pinty, B.
1995-01-01
Since terrestrial surfaces are anisotropic, all spectral reflectance measurements obtained with a small instantaneous field of view instrument are specific to these angular conditions, and the value of the corresponding NDVI, computed from these bidirectional reflectances, is relative to the particular geometry of illumination and viewing at the time of the measurement. This paper documents the importance of these geometric effects through simulations of the AVHRR data acquisition process, and investigates the systematic biases that result from the combination of ecosystem-specific anisotropies with instrument-specific sampling capabilities. Typical errors in the value of NDVI are estimated, and strategies to reduce these effects are explored. -from Authors
Multiple patterns of diblock copolymer confined in irregular geometries with soft surface
NASA Astrophysics Data System (ADS)
Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun
2015-12-01
The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.
Automatic Generation of CFD-Ready Surface Triangulations from CAD Geometry
NASA Technical Reports Server (NTRS)
Aftosmis, M. J.; Delanaye, M.; Haimes, R.; Nixon, David (Technical Monitor)
1998-01-01
This paper presents an approach for the generation of closed manifold surface triangulations from CAD geometry. CAD parts and assemblies are used in their native format, without translation, and a part's native geometry engine is accessed through a modeler-independent application programming interface (API). In seeking a robust and fully automated procedure, the algorithm is based on a new physical space manifold triangulation technique which was developed to avoid robustness issues associated with poorly conditioned mappings. In addition, this approach avoids the usual ambiguities associated with floating-point predicate evaluation on constructed coordinate geometry in a mapped space, The technique is incremental, so that each new site improves the triangulation by some well defined quality measure. Sites are inserted using a variety of priority queues to ensure that new insertions will address the worst triangles first, As a result of this strategy, the algorithm will return its 'best' mesh for a given (prespecified) number of sites. Alternatively, the algorithm may be allowed to terminate naturally after achieving a prespecified measure of mesh quality. The resulting triangulations are 'CFD-ready' in that: (1) Edges match the underlying part model to within a specified tolerance. (2) Triangles on disjoint surfaces in close proximity have matching length-scales. (3) The algorithm produces a triangulation such that no angle is less than a given angle bound, alpha, or greater than Pi - 2alpha This result also sets bounds on the maximum vertex degree, triangle aspect-ratio and maximum stretching rate for the triangulation. In addition to tile output triangulations for a variety of CAD parts, tile discussion presents related theoretical results which assert the existence of such all angle bound, and demonstrate that maximum bounds of between 25 deg and 30 deg may be achieved in practice.
Future lunar mission Active X-ray Spectrometer development: Surface roughness and geometry studies
NASA Astrophysics Data System (ADS)
Naito, M.; Hasebe, N.; Kusano, H.; Nagaoka, H.; Kuwako, M.; Oyama, Y.; Shibamura, E.; Amano, Y.; Ohta, T.; Kim, K. J.; Lopes, J. A. M.
2015-07-01
The Active X-ray Spectrometer (AXS) is considered as one of the scientific payload candidates for a future Japanese mission, SELENE-2. The AXS consists of pyroelectric X-ray generators and a Silicon Drift Detector to conduct X-Ray Fluorescence spectroscopy (XRF) on the Moon to measure major elements: Mg, Al, Si, Ca, Ti, and Fe; minor elements: Na, K, P, S, Cr and Mn; and the trace element Ni depending on their concentration. Some factors such as roughness, grain size and porosity of sample, and the geometry of X-ray incidence, emission and energy will affect the XRF measurements precision. Basic studies on the XRF are required to develop the AXS. In this study, fused samples were used to make homogeneous samples free from the effect of grain size and porosity. Experimental and numerical studies on the XRF were conducted to evaluate the effects from incidence and emission angles and surface roughness. Angle geometry and surface roughness will be optimized for the design of the AXS on future missions from the results of the experiment and the numerical simulation.
The reproductive strategies of the heterocarpic annual Calendula arvensis (Asteraceae)
NASA Astrophysics Data System (ADS)
Ruiz De Clavijo, E.
2005-09-01
Achene polymorphism and various aspects of the reproductive biology of the annual Calendula arvensis L. (Field marigold), were studied to determine the reproductive strategies of the plant. This species normally produces three types of achene: rostrate, cymbiform and annular. Rostrate and cymbiform achenes are larger and heavier than annular achenes, and are adapted to long-range dispersal (by epizoochory and anemochory, respectively). In contrast, annular achenes are smaller in size and weight, and are adapted to short-range dispersal. Achenes germinate over a broad range of temperatures (both in light and in darkness), exhibiting cymbiform achenes the highest germination percentages and annular achenes the lowest under all conditions tested. A fraction of the three types of achenes exhibit dormancy and presumably enter the soil seedbank. Achene types adapted for long-range dispersal (rostrate and cymbiform achenes) produce seedlings that are best able to emerge from deeper burial depths, and that are initially stronger and exhibit earlier flowering than the plants from the annular achenes (which are likely to disperse over shorter distances). These features, together with the fact that fruiting occurs even in the absence of pollinators (automatic geitonogamy), the different mechanisms for achene dispersal (zoochory, anemochory and myrmerochory), and the extended germination, flowering and fruiting periods, facilitate establishment and expansion of this species in unpredictable and disturbed habitats.
Issues Related to Cleaning Complex Geometry Surfaces with ODC-Free Solvents
NASA Technical Reports Server (NTRS)
Bradford, Blake F.; Wurth, Laura A.; Nayate, Pramod D.; McCool, Alex (Technical Monitor)
2001-01-01
Implementing ozone depleting chemicals (ODC)-free solvents into full-scale reusable solid rocket motor cleaning operations has presented problems due to the low vapor pressures of the solvents. Because of slow evaporation, solvent retention is a problem on porous substrates or on surfaces with irregular geometry, such as threaded boltholes, leak check ports, and nozzle backfill joints. The new solvents are being evaluated to replace 1,1,1-trichloroethane, which readily evaporates from these surfaces. Selection of the solvents to be evaluated on full-scale hardware was made based on results of subscale tests performed with flat surface coupons, which did not manifest the problem. Test efforts have been undertaken to address concerns with the slow-evaporating solvents. These concerns include effects on materials due to long-term exposure to solvent, potential migration from bolthole threads to seal surfaces, and effects on bolt loading due to solvent retention in threads. Tests performed to date have verified that retained solvent does not affect materials or hardware performance. Process modifications have also been developed to assist drying, and these can be implemented if additional drying becomes necessary.
Pappas, Janice L
2005-01-01
Diatoms have attracted the interest of those involved in nanotechnology and the development of this discipline for research and practical application. These microorganisms exhibit self-assembly of silica on the micrometer scale, with parts of diatoms measuring on the nanometer scale. They exhibit a wide variety of shapes and patterns. An interest in diatom development and the geometry and topology of diatom shapes and gross patterns formed the focus of this study. Diatoms may be theoretically created on the basis of conic sections and quadratic surfaces expressed in parametric two-dimensional (2D) and three-dimensional (3D) functions (as sheets). Recreated diatom shapes, surfaces, and gross patterns based on 3D parametric equations are presented. Changes from one form to another are discussed as changes in magnitude or functional element within a given set of 3D equations for sequences that are phylogenetically or taxonomically related. Topological evolution and combinations of diatom shapes and surfaces are explored. An example shows how diatom forms depicted as 2-manifolds can be subjected to topological gluing to create a form whose surface is topologically different from the original. Topological surgery and gluing of diatoms as geometric forms may be useful in hypotheses about creating nanosubstrates and nanopatterned nanomaterials or in other applications of nanotechnology.
Barriers to gene flow from oilseed rape (Brassica napus) into populations of Sinapis arvensis.
Moyes, C L; Lilley, J M; Casais, C A; Cole, S G; Haeger, P D; Dale, P J
2002-01-01
One concern over growing herbicide-tolerant crops is that herbicide-tolerance genes may be transferred into the weeds they are designed to control. Brassica napus (oilseed rape) has a number of wild relatives that cause weed problems and the most widespread of these is Sinapis arvensis (charlock). Sinapis arvensis seed was collected from 102 populations across the UK, within and outside B. napus-growing areas. These populations were tested for sexual compatibility with B. napus and it was found that none of them hybridized readily in the glasshouse. In contrast to previous studies, we have found that hybrids can be formed naturally with S. arvensis as the maternal parent. Six diverse B. napus cultivars (Capricorn, Drakkar, Falcon, Galaxy, Hobson and Regent) were tested for their compatibility with S. arvensis but no cultivar hybridized readily in the glasshouse. We were unable to detect gene transfer from B. napus to S. arvensis in the field, confirming the extremely low probability of hybridization predicted from the glasshouse work. PMID:11903908
NASA Astrophysics Data System (ADS)
Ross, C.; Rowe, C. D.; Pollock, S. G.; Swanson, M.; Tarling, M.; Backeberg, N. R.; Coulson, S.; Barshi, N.; Bate, C.; Dascher-Cousineau, K.; Scibek, J.; Harrichhausen, N.; Timofeev, A.; Rakoczy, P.; Nisbet, H.; Castro, A.; Smith, H.
2015-12-01
Earthquake rupture surfaces are typically treated as single rupture planes. However, the observation of four linked, non-parallel to sub-parallel slip surfaces on a mining induced earthquake in 2004 shows that rupture geometries may be more complicated (Heesakkers et al., 2011). Multiple pseudotachylyte-bearing fault surfaces are exposed within a 1.1 km wide mylonite zone of the Paleozoic Norumbega fault system. The pseudotachylytes are present in two juxtaposed mylonite zones: the Ray Corner mylonite and a mylonite derived from Scarboro Formation metavolcanics. The Ray Corner mylonite crosscuts pelitic schists of the Cape Elizabeth Formation, at upper greenschist-facies conditions (quartz + feldspar + chlorite + muscovite ± titanite ± pyrite). The pseudotachylyte veins formed late in the deformational history, during a period of predominantly brittle dextral offset. The pseudotachylytes are cryptocrystalline and have rounded porphyroclasts of quartz and feldspar. Microstructural observations show evidence for static and dynamic recrystallization overprinting the primary quench textures, suggesting that previous generations of rupture surfaces have been recycled into the mylonitic fabric (Price et al., 2012). Many of the pseudotachylyte veins have a sharp boundary on one side and are poorly defined on the other, providing insight to the propagation direction. This confirms that the paleo-earthquake ruptures occurred at conditions where quartz and feldspar were able to deform plastically, near the base of the seismogenic zone. Using differential GPS, we mapped the geometry of pseudotachylyte fault veins, injection veins, and slip surface intersections. At Ray Corner, there are 7 layer-parallel pseudotachylytes in a 4 m wide zone with linking and subsequent oblique pseudotachylytes. Some intersections between pseudotachylytes are dilational, depending on the intersection angle and relative displacement on the two faults. At these sites, pseudotachylyte melt sourced
Connecting the surface of the Sun to the Heliosphere : wind speed and magnetic field geometry
NASA Astrophysics Data System (ADS)
Pinto, Rui
2016-07-01
The large-scale solar wind speed distribution varies in time in response to the cyclic variations of the strength and geometry of the magnetic field of the corona. Based on this idea, semi-empirical predictive laws for the solar wind speed (such as in the widely-used WSA law) use simple parameters describing the geometry of the coronal magnetic field. In practice, such scaling laws require ad-hoc corrections and empirical fits to in-situ spacecraft data, and a predictive law based solely on physical principles is still missing. I will discuss improvements to this kind of laws based on the analysis of very large samples of wind acceleration profiles in open flux-tubes (both from MHD simulations and potential-field extrapolations), and possible strategies for corona and heliosphere model coupling. I will, furthermore present an ongoing modelling effort to determine the magnetic connectivity, paths and propagation delays of any type of disturbance (slow/fast solar wind, waves, energetic particles, ballistic propagation) between the solar surface and any point in the interplanetary space at any time. This is a key point for the exploitation of data from Solar Orbiter and Solar Probe Plus, and more generally for establishing connections between remote and in-situ spacecraft data. This is work is supported by the FP7 project #606692 (HELCATS).
Phukan, Ujjal J; Mishra, Sonal; Timbre, Khilesh; Luqman, Suaib; Shukla, Rakesh Kumar
2014-05-01
Waterlogging is becoming a critical threat to plants growing in areas prone to flooding. Some plants adapt various morphological and biochemical alterations which are regulated transcriptionally to cope with the situation. A comparative study of waterlogging response in two different varieties of Mentha namely Mentha piperita and Mentha arvensis was performed. M. arvensis showed better response towards waterlogging in comparison to M. piperita. M. arvensis maintained a healthy posture by utilizing its carbohydrate content; also, it showed a flourished vegetative growth under waterlogged condition. Soluble protein, chlorophyll content, relative water content, and nitric oxide scavenging activity were comparatively more salient in M. arvensis during this hypoxia treatment. Lipid peroxidation was less in M. arvensis. M. arvensis also showed vigorous outgrowth of adventitious roots to assist waterlogging tolerance. To further investigate the possible gene transcripts involved in this response, we did cDNA subtraction of waterlogging treated M. piperita and M. arvensis seedlings. cDNA subtraction has identified thirty seven novel putative Expressed Sequence Tags which were further classified functionally. Functional classification revealed that maximum percentage of proteins belonged to hypothetical proteins followed by proteins involved in biosynthesis. Some of the identified ESTs were further quantified for their induced expression in M. arvensis in comparison to M. piperita through quantitative real-time PCR.
Anomalous Effect of Surface Diffusion on NMR Signal: Tracing the Fiber Geometry
NASA Astrophysics Data System (ADS)
Apalkov, Vadym; Edirisinghe, Neranjan; Cymbalyuk, Gennady
2008-03-01
We show the strong qualitative effect of the surface diffusion channel on the echo attenuation of the NMR signal from restricted geometry, e.g. fiber system. In some range of parameters of the system the residual echo signal, which is obtained by subtracting the background value, can have anomalous behavior, which means that the echo signal has a maximum value at some finite value of the magnitude of the gradient pulses. This fact can be used to enhance the accuracy of the measurements by studying the echo signal around the maximum value. Effect described here could be also used for tuning the MRI measurements to trace fibers with particular characteristic diameters or for timely detection of changes in the diffusion coefficients and fiber diameters.
Booth, Ivan; Fairhurst, Stephen
2007-04-15
We study the geometry and dynamics of both isolated and dynamical trapping horizons by considering the allowed variations of their foliating two-surfaces. This provides a common framework that may be used to consider both their possible evolutions and their deformations as well as derive the well-known flux laws. Using this framework, we unify much of what is already known about these objects as well as derive some new results. In particular we characterize and study the 'almost isolated' trapping horizons known as slowly evolving horizons. It is for these horizons that a dynamical first law holds and this is analogous and closely related to the Hawking-Hartle formula for event horizons.
NASA Astrophysics Data System (ADS)
Orantin, N.
2007-09-01
The 2-matrix model has been introduced to study Ising model on random surfaces. Since then, the link between matrix models and combinatorics of discrete surfaces has strongly tightened. This manuscript aims to investigate these deep links and extend them beyond the matrix models, following my work's evolution. First, I take care to define properly the hermitian 2 matrix model which gives rise to generating functions of discrete surfaces equipped with a spin structure. Then, I show how to compute all the terms in the topological expansion of any observable by using algebraic geometry tools. They are obtained as differential forms on an algebraic curve associated to the model: the spectral curve. In a second part, I show how to define such differentials on any algebraic curve even if it does not come from a matrix model. I then study their numerous symmetry properties under deformations of the algebraic curve. In particular, I show that these objects coincide with the topological expansion of the observable of a matrix model if the algebraic curve is the spectral curve of this model. Finally, I show that fine tuning the parameters ensure that these objects can be promoted to modular invariants and satisfy the holomorphic anomaly equation of the Kodaira-Spencer theory. This gives a new hint that the Dijkgraaf-Vafa conjecture is correct.
Lithological and Surface Geometry Joint Inversions Using Multi-Objective Global Optimization Methods
NASA Astrophysics Data System (ADS)
Lelièvre, Peter; Bijani, Rodrigo; Farquharson, Colin
2016-04-01
Geologists' interpretations about the Earth typically involve distinct rock units with contacts (interfaces) between them. In contrast, standard minimum-structure geophysical inversions are performed on meshes of space-filling cells (typically prisms or tetrahedra) and recover smoothly varying physical property distributions that are inconsistent with typical geological interpretations. There are several approaches through which mesh-based minimum-structure geophysical inversion can help recover models with some of the desired characteristics. However, a more effective strategy may be to consider two fundamentally different types of inversions: lithological and surface geometry inversions. A major advantage of these two inversion approaches is that joint inversion of multiple types of geophysical data is greatly simplified. In a lithological inversion, the subsurface is discretized into a mesh and each cell contains a particular rock type. A lithological model must be translated to a physical property model before geophysical data simulation. Each lithology may map to discrete property values or there may be some a priori probability density function associated with the mapping. Through this mapping, lithological inverse problems limit the parameter domain and consequently reduce the non-uniqueness from that presented by standard mesh-based inversions that allow physical property values on continuous ranges. Furthermore, joint inversion is greatly simplified because no additional mathematical coupling measure is required in the objective function to link multiple physical property models. In a surface geometry inversion, the model comprises wireframe surfaces representing contacts between rock units. This parameterization is then fully consistent with Earth models built by geologists, which in 3D typically comprise wireframe contact surfaces of tessellated triangles. As for the lithological case, the physical properties of the units lying between the contact
Surface Geometry and Stomatal Conductance Effects on Evaporation From Aquatic Macrophytes
NASA Astrophysics Data System (ADS)
Anderson, Michael G.; Idso, Sherwood B.
1987-06-01
Evaporative water loss rates of several floating and emergent aquatic macrophytes were studied over a 4-year period through comparison of daily evaporative water losses from similar-sized vegetated (E) and open water (E0) surfaces. Two species with planate floating leaves (water fern and water lily) yielded E/E0 values of 0.90 for one and four growing seasons, respectively, and displayed stomatal regulation of potential evaporation. Water hyacinths grown in ponds with different diameters exhibited E/E0 ratios which decreased with increasing pond diameter for both short (0.06-0.36 m) and tall (0.63-0.81 m) plants, producing high linear correlations with amount of peripheral vegetative surface area. The latter relationships suggested an E/E0 value less than unity for a relatively extensive canopy of short water hyacinths and a value of the order of 1.4 for a tall canopy possessing similar two-dimensional surface area characteristics. The latter results were also demonstrated in a separate study utilizing polyurethane foam to insulate the peripheral exposure of tall water hyacinth canopies from advective energy. Finally, simultaneous stomatal conductance and daily E/E0 measurements on cattail and water hyacinth canopies with identical tank diameters indicated that although the mean stomatal conductance of the peripheral exposure of the cattail canopy was 72% less than that of the water hyacinth canopy, its total evaporative water loss was nearly equivalent, due to its greater height. Reducing the surface area of the peripheral cattail exposure by the fractional amount suggested by the stomatal conductance measurements harmonized its surface geometry-evaporation relationship with that of the water hyacinth canopy and once again demonstrated the reality of stomatal control of potential evaporation.
SU-E-J-128: 3D Surface Reconstruction of a Patient Using Epipolar Geometry
Kotoku, J; Nakabayashi, S; Kumagai, S; Ishibashi, T; Kobayashi, T; Haga, A; Saotome, N; Arai, N
2014-06-01
Purpose: To obtain a 3D surface data of a patient in a non-invasive way can substantially reduce the effort for the registration of patient in radiation therapy. To achieve this goal, we introduced the multiple view stereo technique, which is known to be used in a 'photo tourism' on the internet. Methods: 70 Images were taken with a digital single-lens reflex camera from different angles and positions. The camera positions and angles were inferred later in the reconstruction step. A sparse 3D reconstruction model was locating by SIFT features, which is robust for rotation and shift variance, in each image. We then found a set of correspondences between pairs of images by computing the fundamental matrix using the eight-point algorithm with RANSAC. After the pair matching, we optimized the parameter including camera positions to minimize the reprojection error by use of bundle adjustment technique (non-linear optimization). As a final step, we performed dense reconstruction and associate a color with each point using the library of PMVS. Results: Surface data were reconstructed well by visual inspection. The human skin is reconstructed well, althogh the reconstruction was time-consuming for direct use in daily clinical practice. Conclusion: 3D reconstruction using multi view stereo geometry is a promising tool for reducing the effort of patient setup. This work was supported by JSPS KAKENHI(25861128)
Milne, A D; Lee, J M
1999-01-01
The direct current electromagnetic tracking device has seen increasing use in biomechanics studies of joint kinematics and anatomical surface geometry. In these applications, a stylus is attached to a sensor to measure the spatial location of three-dimensional landmarks. Stylus calibration is performed by rotating the stylus about a fixed point in space and using regression analysis to determine the tip offset vector. Measurement errors can be induced via several pathways, including; intrinsic system errors in sensor position or angle and tip offset calibration errors. A detailed study was performed to determine the errors introduced in digitizing small surfaces with different stylus lengths (35, 55, and 65 mm) and approach angles (30 and 45 degrees) using a plastic calibration board and hemispherical models. Two-point discrimination errors increased to an average of 1.93 mm for a 254 mm step size. Rotation about a single point produced mean errors of 0.44 to 1.18 mm. Statistically significant differences in error were observed with increasing approach angles (p < 0.001). Errors of less than 6% were observed in determining the curvature of a 19 mm hemisphere. This study demonstrates that the "Flock of Birds" can be used as a digitizing tool with accuracy better than 0.76% over 254 mm step sizes. PMID:11143353
Li, Yajun
2011-06-01
The theory developed in Part I of this study [Y. Li, "Differential geometry of the ruled surfaces optically generated by mirror-scanning devices. I. Intrinsic and extrinsic properties of the scan field," J. Opt. Soc. Am. A28, 667 (2011)] for the ruled surfaces optically generated by single-mirror scanning devices is extended to multimirror scanning systems for an investigation of optical generation of the well-known ruled surfaces, such as helicoid, Plücker's conoid, and hyperbolic paraboloid.
A new class of actuator surface models incorporating wind turbine blade and nacelle geometry effects
NASA Astrophysics Data System (ADS)
Yang, Xiaolei; Sotiropoulos, Fotis
2015-11-01
It was shown by Kang, Yang and Sotiropoulos that the nacelle has significant effects on the turbine wake even in the far wake region, which the standard actuator line model is not able to predict. We develop a new class of actuator surface models for the blades and nacelle, which is able to resolve the effects of both tip vortices and nacelle vortex. The new nacelle model, which is based on distributing forces from the actual nacelle geometry as in the diffused interface immersed boundary methods, is first tested by carrying out LES of the flow past a sphere and demonstrating good agreement with available in the literature DNS results. The proposed model is subsequently validated by simulating the flow past the hydrokinetic turbine used in the simulations of Kang et al. and good agreement with the measurements is demonstrated. Finally, the proposed model is applied to utility scale wind turbines to elucidate the role of nacelle vortex dynamics on turbine wake meandering. This work was supported by Department of Energy DOE (DE-EE0002980, DE-EE0005482 and DE-AC04-94AL85000), and Sandia National Laboratories. Computational resources were provided by SNL and MSI.
Determination of the genotoxic effects of Convolvulus arvensis extracts on corn (Zea mays L.) seeds.
Sunar, Serap; Yildirim, Nalan; Aksakal, Ozkan; Agar, Guleray
2013-06-01
In this research, the methanolic extracts of Convolvulus arvensis were tested for genotoxic and inhibitor activity on the total soluble protein content and the genomic template stability against corn Zea mays L. seed. The methanol extracts of leaf, stem and root of C. arvensis were diluted to 50, 75 and 100 μl concentrations and applied to corn seed. The total soluble protein and genomic template stability results were compared with the control. The results showed that especially 100 μl extracts of diluted leaf, stem and root had a strong inhibitory activity on the genomic template stability. The changes occurred in random amplification of polymorphic DNA (RAPD) profiles of C. arvensis extract treatment included variation in band intensity, loss of bands and appearance of new bands compared with control. Also, the results obtained from this study revealed that the increase in the concentrations of C. arvensis extract increased the total soluble protein content in maize. The results suggested that RAPD analysis and total protein analysis could be applied as a suitable biomarker assay for the detection of genotoxic effects of plant allelochemicals.
Mathur, R
1991-01-01
50% ethanolic extract of Mentha arvensis Linn. (leaves) has been found to reduce the fructose synthesis in seminal vesicles; as a result of which the viability of spermatozoa seems to be altered. Fertility testing revealed sterile matings till 30 days of last treatment.
NASA Astrophysics Data System (ADS)
Brown, Philip S.; Bhushan, Bharat
2016-02-01
Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.
NASA Astrophysics Data System (ADS)
Brown, Philip S.; Bhushan, Bharat
2016-02-01
Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.
Brown, Philip S.; Bhushan, Bharat
2016-01-01
Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices. PMID:26876479
Evans, Alistair R.; McHenry, Colin R.
2015-01-01
The reliability of finite element analysis (FEA) in biomechanical investigations depends upon understanding the influence of model assumptions. In producing finite element models, surface mesh resolution is influenced by the resolution of input geometry, and influences the resolution of the ensuing solid mesh used for numerical analysis. Despite a large number of studies incorporating sensitivity studies of the effects of solid mesh resolution there has not yet been any investigation into the effect of surface mesh resolution upon results in a comparative context. Here we use a dataset of crocodile crania to examine the effects of surface resolution on FEA results in a comparative context. Seven high-resolution surface meshes were each down-sampled to varying degrees while keeping the resulting number of solid elements constant. These models were then subjected to bite and shake load cases using finite element analysis. The results show that incremental decreases in surface resolution can result in fluctuations in strain magnitudes, but that it is possible to obtain stable results using lower resolution surface in a comparative FEA study. As surface mesh resolution links input geometry with the resulting solid mesh, the implication of these results is that low resolution input geometry and solid meshes may provide valid results in a comparative context. PMID:26056620
McCurry, Matthew R; Evans, Alistair R; McHenry, Colin R
2015-01-01
The reliability of finite element analysis (FEA) in biomechanical investigations depends upon understanding the influence of model assumptions. In producing finite element models, surface mesh resolution is influenced by the resolution of input geometry, and influences the resolution of the ensuing solid mesh used for numerical analysis. Despite a large number of studies incorporating sensitivity studies of the effects of solid mesh resolution there has not yet been any investigation into the effect of surface mesh resolution upon results in a comparative context. Here we use a dataset of crocodile crania to examine the effects of surface resolution on FEA results in a comparative context. Seven high-resolution surface meshes were each down-sampled to varying degrees while keeping the resulting number of solid elements constant. These models were then subjected to bite and shake load cases using finite element analysis. The results show that incremental decreases in surface resolution can result in fluctuations in strain magnitudes, but that it is possible to obtain stable results using lower resolution surface in a comparative FEA study. As surface mesh resolution links input geometry with the resulting solid mesh, the implication of these results is that low resolution input geometry and solid meshes may provide valid results in a comparative context.
NASA Astrophysics Data System (ADS)
Waychunas, G. A.; Rea, B. A.; Fuller, C. C.; Davis, J. A.
1993-05-01
EXAFS spectra were collected on both the As and Fe K-edges from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages. Spectra also were collected for arsenate adsorbed on the surfaces of three FeOOH crystalline polymorphs, α (goethite), β (akaganeite), and γ (lepidocrocite), and as a free ion in aqueous: solution. Analyses of the As EXAFS show clear evidence for inner sphere bidentate (bridging) arsenate complexes on the ferrihydrite surface and on the surfaces of the crystalline FeOOH polymorphs. The bridging arsenate is attached to adjacent apices of edge-sharing Fe oxyhydroxyl octahedra. The arsenic-iron distance at the interface ( 3.28 ±0.01 Å) is close to that expected for this geometry on the FeOOH polymorph surfaces, but is slightly shorter on the ferrihydrite surfaces ( 3.25 ± 0.02 Å). Mono-dentate arsenate linkages ( 3.60 ± 0.03 Å) also occur on the ferrihydrite, but are not generally observed on the crystalline FeOOH polymorphs. The proportion of monodentate bonds appears largest for adsorption samples with the smallest As/Fe molar ratio. In all cases the arsenate tetrahedral complex is relatively undistorted with As-O bonds of 1.66 ± 0.01 Å. Precipitation of arsenate or scorodite-like phases was not observed for any samples, all of which were prepared at a pH value of 8. The Fe EXAFS results confirm that the Fe-Fe correlations in the ferrihydrite are progressively disrupted in the CPT samples as the As/Fe ratio is increased. Coherent crystallite size is probably no more than 10 Å in diameter and no Fe oxyhydroxyl octahedra corner-sharing linkages (as would be present in FeOOH polymorphs) are observed at the largest As/Fe ratios. Comparison of the number and type of Fe-Fe neighbors with the topological constraints imposed by the arsenate saturation limit in the CPT samples (about 0.7 As/Fe) indicates ferrihydrite units consisting mainly of Fe
Waychunas, G.A.; Rea, B.A.; Fuller, C.C.; Davis, J.A.
1993-01-01
EXAFS spectra were collected on both the As and Fe K-edges from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages. Spectra also were collected for arsenate adsorbed on the surfaces of three FeOOH crystalline polymorphs, ?? (goethite), ?? (akaganeite), and ?? (lepidocrocite), and as a free ion in aqueous: solution. Analyses of the As EXAFS show clear evidence for inner sphere bidentate (bridging) arsenate complexes on the ferrihydrite surface and on the surfaces of the crystalline FeOOH polymorphs. The bridging arsenate is attached to adjacent apices of edge-sharing Fe oxyhydroxyl octahedra. The arsenic-iron distance at the interface (3.28 ??0.01 A ??) is close to that expected for this geometry on the FeOOH polymorph surfaces, but is slightly shorter on the ferrihydrite surfaces (3.25 ?? 0.02 A ??). Mono-dentate arsenate linkages (3.60 ?? 0.03 A ??) also occur on the ferrihydrite, but are not generally observed on the crystalline FeOOH polymorphs. The proportion of monodentate bonds appears largest for adsorption samples with the smallest As Fe molar ratio. In all cases the arsenate tetrahedral complex is relatively undistorted with As-O bonds of 1.66 ?? 0.01 A ??. Precipitation of arsenate or scorodite-like phases was not observed for any samples, all of which were prepared at a pH value of 8. The Fe EXAFS results confirm that the Fe-Fe correlations in the ferrihydrite are progressively disrupted in the CPT samples as the As Fe ratio is increased. Coherent crystallite size is probably no more than 10 A?? in diameter and no Fe oxyhydroxyl octahedra corner-sharing linkages (as would be present in FeOOH polymorphs) are observed at the largest As Fe ratios. Comparison of the number and type of Fe-Fe neighbors with the topological constraints imposed by the arsenate saturation limit in the CPT samples (about 0.7 As Fe) indicates ferrihydrite units consisting mainly
Deep RNA-Seq to unlock the gene bank of floral development in Sinapis arvensis.
Liu, Jia; Mei, Desheng; Li, Yunchang; Huang, Shunmou; Hu, Qiong
2014-01-01
Sinapis arvensis is a weed with strong biological activity. Despite being a problematic annual weed that contaminates agricultural crop yield, it is a valuable alien germplasm resource. It can be utilized for broadening the genetic background of Brassica crops with desirable agricultural traits like resistance to blackleg (Leptosphaeria maculans), stem rot (Sclerotinia sclerotium) and pod shatter (caused by FRUITFULL gene). However, few genetic studies of S. arvensis were reported because of the lack of genomic resources. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive dataset for S. arvensis for the first time. We used Illumina paired-end sequencing technology to sequence the S. arvensis flower transcriptome and generated 40,981,443 reads that were assembled into 131,278 transcripts. We de novo assembled 96,562 high quality unigenes with an average length of 832 bp. A total of 33,662 full-length ORF complete sequences were identified, and 41,415 unigenes were mapped onto 128 pathways using the KEGG Pathway database. The annotated unigenes were compared against Brassica rapa, B. oleracea, B. napus and Arabidopsis thaliana. Among these unigenes, 76,324 were identified as putative homologs of annotated sequences in the public protein databases, of which 1194 were associated with plant hormone signal transduction and 113 were related to gibberellin homeostasis/signaling. Unigenes that did not match any of those sequence datasets were considered to be unique to S. arvensis. Furthermore, 21,321 simple sequence repeats were found. Our study will enhance the currently available resources for Brassicaceae and will provide a platform for future genomic studies for genetic improvement of Brassica crops.
Effect of Sulfate on Selenium Uptake And Chemical Speciation in Convolvulus Arvensis L
Cruz-Jimenez, G.; Peralta-Video, J.R.; Rosa, G.de la; Meitzner, G.; Parson, J.G.; Gardea-Torresdey, J.L.
2007-08-08
Hydroponic experiments were performed to study several aspects of Se uptake by C. arvensis plants. Ten day old seedlings were exposed for eight days to different combinations of selenate (SeO{sub 4}{sup 2-}), sulfate (SO{sub 4}{sup 2-}), and selenite (SeO{sub 3}{sup 2-}). The results showed that in C. arvensis, SO{sub 4}{sup 2-} had a negative effect (P < 0.05) on SeO{sub 4}{sup 2-} uptake. However, a positive interaction produced a significant increase in SO{sub 4}{sup 2-} uptake when SeO{sub 4}{sup 2-} was at high concentration in the media. X-ray absorption spectroscopy studies showed that C. arvensis plants converted more than 70% of the supplied SeO{sub 3}{sup 2-} into organoselenium compounds. However, only approximately 50% of the supplied SeO{sub 4}{sup 2-} was converted into organoselenium species while the residual 50% remained in the inorganic form. Analysis using LC-XANES fittings confirmed that the S metabolic pathway was affected by the presence of Se. The main Se compounds that resembled those Se species identified in C. arvensis were Se-cystine, Se-cysteine, SeO{sub 3}{sup 2-}, and SeO{sub 4}{sup 2-}, whereas for S the main compounds were cysteine, cystine, oxidized glutathione, reduced glutathione, and SO{sub 4}{sup 2-}. The results of these studies indicated that C. arvensis could be considered as a possible option for the restoration of soil moderately contaminated with selenium even in the presence of sulfate.
Deep RNA-Seq to Unlock the Gene Bank of Floral Development in Sinapis arvensis
Liu, Jia; Mei, Desheng; Li, Yunchang; Huang, Shunmou; Hu, Qiong
2014-01-01
Sinapis arvensis is a weed with strong biological activity. Despite being a problematic annual weed that contaminates agricultural crop yield, it is a valuable alien germplasm resource. It can be utilized for broadening the genetic background of Brassica crops with desirable agricultural traits like resistance to blackleg (Leptosphaeria maculans), stem rot (Sclerotinia sclerotium) and pod shatter (caused by FRUITFULL gene). However, few genetic studies of S. arvensis were reported because of the lack of genomic resources. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive dataset for S. arvensis for the first time. We used Illumina paired-end sequencing technology to sequence the S. arvensis flower transcriptome and generated 40,981,443 reads that were assembled into 131,278 transcripts. We de novo assembled 96,562 high quality unigenes with an average length of 832 bp. A total of 33,662 full-length ORF complete sequences were identified, and 41,415 unigenes were mapped onto 128 pathways using the KEGG Pathway database. The annotated unigenes were compared against Brassica rapa, B. oleracea, B. napus and Arabidopsis thaliana. Among these unigenes, 76,324 were identified as putative homologs of annotated sequences in the public protein databases, of which 1194 were associated with plant hormone signal transduction and 113 were related to gibberellin homeostasis/signaling. Unigenes that did not match any of those sequence datasets were considered to be unique to S. arvensis. Furthermore, 21,321 simple sequence repeats were found. Our study will enhance the currently available resources for Brassicaceae and will provide a platform for future genomic studies for genetic improvement of Brassica crops. PMID:25192023
Deep RNA-Seq to unlock the gene bank of floral development in Sinapis arvensis.
Liu, Jia; Mei, Desheng; Li, Yunchang; Huang, Shunmou; Hu, Qiong
2014-01-01
Sinapis arvensis is a weed with strong biological activity. Despite being a problematic annual weed that contaminates agricultural crop yield, it is a valuable alien germplasm resource. It can be utilized for broadening the genetic background of Brassica crops with desirable agricultural traits like resistance to blackleg (Leptosphaeria maculans), stem rot (Sclerotinia sclerotium) and pod shatter (caused by FRUITFULL gene). However, few genetic studies of S. arvensis were reported because of the lack of genomic resources. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive dataset for S. arvensis for the first time. We used Illumina paired-end sequencing technology to sequence the S. arvensis flower transcriptome and generated 40,981,443 reads that were assembled into 131,278 transcripts. We de novo assembled 96,562 high quality unigenes with an average length of 832 bp. A total of 33,662 full-length ORF complete sequences were identified, and 41,415 unigenes were mapped onto 128 pathways using the KEGG Pathway database. The annotated unigenes were compared against Brassica rapa, B. oleracea, B. napus and Arabidopsis thaliana. Among these unigenes, 76,324 were identified as putative homologs of annotated sequences in the public protein databases, of which 1194 were associated with plant hormone signal transduction and 113 were related to gibberellin homeostasis/signaling. Unigenes that did not match any of those sequence datasets were considered to be unique to S. arvensis. Furthermore, 21,321 simple sequence repeats were found. Our study will enhance the currently available resources for Brassicaceae and will provide a platform for future genomic studies for genetic improvement of Brassica crops. PMID:25192023
Non-parametric deprojection of surface brightness profiles of galaxies in generalised geometries
NASA Astrophysics Data System (ADS)
Chakrabarty, D.
2010-02-01
Aims: We present a new Bayesian non-parametric deprojection algorithm DOPING (Deprojection of Observed Photometry using an INverse Gambit), that is designed to extract 3-D luminosity density distributions ρ from observed surface brightness maps I, in generalised geometries, while taking into account changes in intrinsic shape with radius, using a penalised likelihood approach and an Markov Chain Monte Carlo optimiser. Methods: We provide the most likely solution to the integral equation that represents deprojection of the measured I to ρ. In order to keep the solution modular, we choose to express ρ as a function of the line-of-sight (LOS) coordinate z. We calculate the extent of the system along the z-axis, for a given point on the image that lies within an identified isophotal annulus. The extent along the LOS is binned and density is held a constant over each such z-bin. The code begins with a seed density and at the beginning of an iterative step, the trial ρ is updated. Comparison of the projection of the current choice of ρ and the observed I defines the likelihood function (which is supplemented by Laplacian regularisation), the maximal region of which is sought by the optimiser (Metropolis Hastings). Results: The algorithm is successfully tested on a set of test galaxies, the morphology of which ranges from an elliptical galaxy with varying eccentricity to an infinitesimally thin disk galaxy marked by an abruptly varying eccentricity profile. Applications are made to faint dwarf elliptical galaxy Ic 3019 and another dwarf elliptical that is characterised by a central spheroidal nuclear component superimposed upon a more extended flattened component. The result of deprojection of the X-ray image of cluster A1413 - assumed triaxial - the axial ratios and inclination of which are taken from the literature, is also presented.
NASA Astrophysics Data System (ADS)
Nedeljković, N. N.; Majkić, M. D.; Božanić, D. K.; Dojčilović, R. J.
2016-06-01
We consider the population dynamics of the intermediate Rydberg states of highly charged ions (core charge Z\\gg 1, principal quantum number {n}{{A}}\\gg 1) interacting with solid surfaces at arbitrary collision geometry. The recently developed resonant two-state vector model for the grazing incidence (2012 J. Phys. B: At. Mol. Opt. Phys. 45 215202) is extended to the quasi-resonant case and arbitrary angle of incidence. According to the model, the population probabilities depend both on the projectile parallel and perpendicular velocity components, in a complementary way. A cascade neutralization process for {{{Xe}}}Z+ ions, for Z=15{--}45, interacting with a conductive-surface is considered by taking into account the population dynamics. For an arbitrary collision geometry and given range of ionic velocities, a micro-staircase model for the simultaneous calculation of the kinetic energy gain and the charge state of the ion in front of the surface is proposed. The relevance of the obtained results for the explanation of the formation of nanostructures on solid surfaces by slow highly charged ions for normal incidence geometry is briefly discussed.
Transport of Ions and Particles Through Single Pores of Controlled Geometry and Surface Chemistry
NASA Astrophysics Data System (ADS)
Pevarnik, Matthew A.
Synthetic nanopores are a powerful tool to control the transport of ions, molecules, and water at the molecular level, mimicking biological systems. In this research, polymer pores are prepared of different geometries, sizes, and surface chemistry to utilize features seen in naturally occurring systems. Specifically, it was one of the goals of this research to prepare and characterize single polymer pores that rectify the current due to a combination of electrostatic and hydrophobic interactions, similar to naturally occurring ion channels. Prior to modification, aqueous electrolytic solutions are able to conduct readily through the single polymer pores, but after the chemisorption of hydrophobic chemical groups, the pore demonstrates open and closed states. This behavior is also observed to be voltage dependent. Increasing voltage increases the probability of the pore to be in the open states. There is also a voltage range where the pore does not conduct at all. The hydrophobic gating was studied as a function of pore diameter and charge of the residual groups and could be used for an on demand drug delivery system. Another technique that was utilized in this research is the resistive-pulse technique, which is a powerful approach to detect single molecules and particles. A single particle passing through a pore can be observed as a transient drop of the transmembrane current. This research focuses on resistive-pulse sensing experiments performed with track-etched polymer pores characterized by an undulating diameter along the pore length. The resistive pulses generated by spherical beads passing through these pores have a repeatable pattern of large variations corresponding to these diameter changes. We show that this pattern of variations enables the unambiguous resolution of multiple particles simultaneously in the pore, the detection of transient sticking of particles within the pore, and confirmation whether any individual particle completely translocates the
Larsson, Magnus
2005-12-01
A critical issue in pollination ecology is the evolution of generalist pollination systems, and under which conditions floral specializations evolve from these. The gynodioecious herb Knautia arvensis (Dipsacaceae) exhibits a generalized pollination system, but is visited by both generalist and specialist flower-visitors. The present study tested pollinator effectiveness and pollinator importance of the pollen specialist solitary bee Andrena hattorfiana (Andrenidae) vs. the generalist flower-visitors to K. arvensis on the island of Oland, SE Sweden. Females of the specialist bee removed more pollen per inflorescence-visit than the major groups of generalist visitors such as bumblebees and flies. They also deposited more pollen per inflorescence-visit than any of the generalist visitor groups. The females have a preference for pollen-presenting vs. stigma-presenting inflorescences, a pattern shared with most of the generalist flower-visitors. Females of the specialist exert such a strong preference that they, despite their great pollinator effectiveness, make modest contribution to pollen transfer in K. arvensis. The females of A. hattorfiana accounted for 14.2% of the overall visits and 5.8% of the total pollination, the rest being performed by generalist visitors and males of A. hattorfiana. This study shows that pollinator effectiveness of a specialist can be superior while generalist flower-visitors select floral characters towards generalization through their greater contribution to overall pollen flow.
Antimicrobial, antitumor and brine shrimp lethality assay of Ranunculus arvensis L. extracts.
Bhatti, Muhammad Zeeshan; Ali, Amjad; Saeed, Asma; Saeed, Ahmad; Malik, Salman Akbar
2015-05-01
To investigate the antitumor activity, brine shrimp lethality assay, antibacterial and antifungal activity of Methanol Extract (ME), Water Extract (WE), Acetone Extract (AE), Chloroform Extract (CE), Methanol-Water Extract (MWE), Methanol-Acetone Extract (MAE), Methanol-Chloroform Extract (MCE) of Ranunculus arvensis (L.). Antitumor activity was evaluated with Agrobacterium tumefaciens (At10) induced potato disc assay. Cytotoxicity was evaluated with brine shrimp lethality assay. Antibacterial activity was evaluated with six bacterial strains including Escherichia coli, Enterobacter aerogenes, Bordetella bronchiseptica, Klebsiella pneumoniae, Micrococcus luteus and Streptococcus anginosus and antifungal screening was done against five fungal strains including Aspergillus niger, A. flavus, A. fumigates, Fusarium solani and Mucor species by using disc diffusion method. Best antitumor activity was obtained with ME and WE, having highest IC50 values 20.27 ± 1.62 and 93.01 ± 1.33μg/disc. Brine shrimp lethality assay showed LC50 values of AE, MAE and ME were obtained as 384.66 ± 9.42μg/ml, 724.11 ± 8.01μg/ml and 978.7 ±8.01 μg/ml respectively. WE of R. arvensis revealed weak antimicrobial result against the tested microorganisms. On the other hand, the antifungal activity of the plant extracts was found to be insignificant. These findings demonstrate that extracts of R. arvensis possesses significant antitumor activity. Further extensive study is necessary to assess the therapeutic potential of the plant. PMID:26004705
NASA Astrophysics Data System (ADS)
Coh, Senia
Tetraphenylporphyrin (TPP)-derived molecules have been studied extensively as efficient photosensitizers when chemisorbed on the metal oxide substrates in dye-sensitized solar cells. Still, many fundamental electronic properties of the dye/oxide interface are not understood and need careful consideration. In this thesis we present a comprehensive study of the electronic structure, energy level alignment and the adsorption geometry of the TPP-derived dye molecules adsorbed on TiO2(110), ZnO(1120) and Ag(100) single crystal surfaces using ultra-high vacuum (UHV) based surface sensitive techniques. The alignment of the molecular energy levels with respect to the TiO 2 and ZnO band edges for all TPP-derived molecules we studied was found to be insensitive to either the nature of the functional groups located on the phenyl rings, presence of zinc as a central metal ion and different binding geometry of the molecules. Binding geometry, molecule-molecule interaction and the aggregation effects in the adsorbed layer, that were observed in the UV-visible spectra of the molecules adsorbed on ZnO substrate were not observed in the ultraviolet photoemission (UPS) and inverse photoemission (IPS) spectra of the occupied and unoccupied molecular states. Using near edge X-ray absorption fine structure (NEXAFS) and scanning tunneling microscopy (STM), binding geometry of the two representative TPP-derivatives was directly determined to be upright, with the porphyrin ring under large angle with respect to the surface for the p-ZnTCPP molecules and with the porphyrin ring parallel to the surface for the m-ZnTCPP molecules. We observe that the energies and the energy level alignment of the ZnTPP molecular levels measured in UPS and IPS depend on the substrate on which the molecules are adsorbed (Ag(100) or TiO2(110) single crystal surfaces). The differences are attributed to different charge screening properties of these two materials. Image charges created in the substrates during
Marocico, C. A.; Knoester, J.
2011-11-15
We use a Green's tensor method to investigate the spontaneous emission rate of a molecule and the energy-transfer rate between molecules placed in two types of layered geometries: a slab geometry and a planar waveguide. We focus especially on the role played by surface-plasmon polaritons in modifying the spontaneous emission and energy-transfer rates as compared to free space. In the presence of more than one interface, the surface-plasmon polariton modes split into several branches, and each branch can contribute significantly to modifying the electromagnetic properties of atoms and molecules. Enhancements of several orders of magnitude both in the spontaneous emission rate of a molecule and the energy-transfer rate between molecules are obtained and, by tuning the parameters of the geometry, one has the ability to control the range and magnitude of these enhancements. For the energy-transfer rate interference effects between contributions of different plasmon-polariton branches are observed as oscillations in the distance dependence of this rate.
NASA Technical Reports Server (NTRS)
Lucero, John M.
2003-01-01
A new optically based measuring capability that characterizes surface topography, geometry, and wear has been employed by NASA Glenn Research Center s Tribology and Surface Science Branch. To characterize complex parts in more detail, we are using a three-dimensional, surface structure analyzer-the NewView5000 manufactured by Zygo Corporation (Middlefield, CT). This system provides graphical images and high-resolution numerical analyses to accurately characterize surfaces. Because of the inherent complexity of the various analyzed assemblies, the machine has been pushed to its limits. For example, special hardware fixtures and measuring techniques were developed to characterize Oil- Free thrust bearings specifically. We performed a more detailed wear analysis using scanning white light interferometry to image and measure the bearing structure and topography, enabling a further understanding of bearing failure causes.
Belchenko, Yu; Sanin, A.; Sotnikov, O.
2014-02-15
Negative ion extraction from continuous-wave (CW) magnetron and semiplanotron discharges was studied and it was compared with that for the source with Penning electrode geometry. The CW negative ion beam up current to 13 mA was extracted from the magnetron source with emission aperture of 3.5 mm in diameter, while the beam with current up to 8 mA was obtained from the semiplanotron source modification. Characteristics of CW magnetron and semiplanotron sources are presented and analyzed.
Geometry of Optimal Paths around Focal Singular Surfaces in Differential Games
Melikyan, Arik Bernhard, Pierre
2005-06-15
We investigate a special type of singularity in non-smooth solutions of first-order partial differential equations, with emphasis on Isaacs' equation. This type, called focal manifold, is characterized by the incoming trajectory fields on the two sides and a discontinuous gradient. We provide a complete set of constructive equations under various hypotheses on the singularity, culminating with the case where no a priori hypothesis on its geometry is known, and where the extremal trajectory fields need not be collinear. We show two examples of differential games exhibiting non-collinear fields of extremal trajectories on the focal manifold, one with a transversal approach and one with a tangential approach.
Hochkirch, Axel; Mertes, Tamara; Rautenberg, Julia
2012-03-01
Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species (Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from nativespecies.
NASA Astrophysics Data System (ADS)
Hochkirch, Axel; Mertes, Tamara; Rautenberg, Julia
2012-03-01
Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species ( Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from native species.
Gillespie, D.R.H.; Wang, Z.; Ireland, P.T.; Kohler, S.T.
1998-01-01
Cast impingement cooling geometries offer the gas turbine designer higher structural integrity and improved convective cooling when compared to traditional impingement cooling systems, which rely on plate inserts. In this paper, it is shown that the surface that forms the jets contributes significantly to the total cooling. Local heat transfer coefficient distributions have been measured in a model of an engine wall cooling geometry using the transient heat transfer technique. The method employs temperature-sensitive liquid crystals to measure the surface temperature of large-scale perspex models during transient experiments. Full distributions of local Nusselt number on both surfaces of the impingement plate, and on the impingement target plate, are presented at engine representative Reynolds numbers. The relative effects of the impingement plate thermal boundary condition and the coolant supply temperature on the target plate heat transfer have been determined by maintaining an isothermal boundary condition at the impingement plate during the transient tests. The results are discussed in terms of the interpreted flow field.
Grey-body surface radiation coupled with conduction and convection for general geometries
NASA Astrophysics Data System (ADS)
Engelman, Michael; Jamnia, Mohammad-Ali
1991-11-01
This paper presents a numerical technique for the simulation of the effects of grey-diffuse surface radiation on the temperature field of fluid flows using FIDAP, a general purpose incompressible, viscous fluid code. The radiating surface relationships assume a non-participating medium, constant surface temperature and heat fluxes at the discretized elemental level. The technique involves the decoupling of energy and radiation exchange equations. A concept of macrosurfaces, each containing a number of radiating boundary surfaces, is introduced. These boundary macroelements then carry the information from the radiating boundary into the fluid regime. A number of simulations illustrating the algorithm are presented.
Entanglement entropy of Wilson surfaces from bubbling geometries in M-theory
NASA Astrophysics Data System (ADS)
Gentle, Simon A.; Gutperle, Michael; Marasinou, Chrysostomos
2015-08-01
We consider solutions of eleven-dimensional supergravity constructed in [1, 2] that are half-BPS, locally asymptotic to AdS 7 × S 4 and are the holographic dual of heavy Wilson surfaces in the six-dimensional (2 , 0) theory. Using these bubbling solutions we calculate the holographic entanglement entropy for a spherical entangling surface in the presence of a planar Wilson surface. In addition, we calculate the holographic stress tensor and, by evaluating the on-shell supergravity action, the expectation value of the Wilson surface operator.
Control of bacterial biofilm growth on surfaces by nanostructural mechanics and geometry
NASA Astrophysics Data System (ADS)
Epstein, A. K.; Hochbaum, A. I.; Kim, Philseok; Aizenberg, J.
2011-12-01
Surface-associated communities of bacteria, called biofilms, pervade natural and anthropogenic environments. Mature biofilms are resistant to a wide range of antimicrobial treatments and therefore pose persistent pathogenic threats. The use of surface chemistry to inhibit biofilm growth has been found to only transiently affect initial attachment. In this work, we investigate the tunable effects of physical surface properties, including high-aspect-ratio (HAR) surface nanostructure arrays recently reported to induce long-range spontaneous spatial patterning of bacteria on the surface. The functional parameters and length scale regimes that control such artificial patterning for the rod-shaped pathogenic species Pseudomonas aeruginosa are elucidated through a combinatorial approach. We further report a crossover regime of biofilm growth on a HAR nanostructured surface versus the nanostructure effective stiffness. When the 'softness' of the hair-like nanoarray is increased beyond a threshold value, biofilm growth is inhibited as compared to a flat control surface. This result is consistent with the mechanoselective adhesion of bacteria to surfaces. Therefore by combining nanoarray-induced bacterial patterning and modulating the effective stiffness of the nanoarray—thus mimicking an extremely compliant flat surface—bacterial mechanoselective adhesion can be exploited to control and inhibit biofilm growth.
In the urbanization of watersheds, impervious surface is the primary agent of hydrologic change. The impact of impervious surface on hydrology and sediment transport is understood only in terms of unverified models not specifically adapted for urban watersheds. Therefore, in this...
OPUS – Outer Planets Unified Search with Enhanced Surface Geometry Parameters – Not Just for Rings
NASA Astrophysics Data System (ADS)
Gordon, Mitchell; Showalter, Mark Robert; Ballard, Lisa; Tiscareno, Matthew S.; Heather, Neil
2016-10-01
In recent years, with the massive influx of data into the PDS from a wide array of missions and instruments, finding the precise data you need has been an ongoing challenge. For remote sensing data obtained from Jupiter to Pluto, that challenge is being addressed by the Outer Planets Unified Search, more commonly known as OPUS.OPUS is a powerful search tool available at the PDS Ring-Moon Systems Node (RMS) – formerly the PDS Rings Node. While OPUS was originally designed with ring data in mind, its capabilities have been extended to include all of the targets within an instrument's field of view. OPUS provides preview images of search results, and produces a zip file for easy download of selected products, including a table of user specified metadata. For Cassini ISS and Voyager ISS we have generated and include calibrated versions of every image.Currently OPUS supports data returned by Cassini ISS, UVIS, VIMS, and CIRS (Saturn data through June 2010), New Horizons Jupiter LORRI, Galileo SSI, Voyager ISS and IRIS, and Hubble (ACS, WFC3 and WFPC2).At the RMS Node, we have developed and incorporated into OPUS detailed geometric metadata, based on the most recent SPICE kernels, for all of the bodies in the Cassini Saturn observations. This extensive set of geometric metadata is unique to the RMS Node and enables search constraints such as latitudes and longitudes (Saturn, Titan, and icy satellites), viewing and illumination geometry (phase, incidence and emission angles), and distances and resolution.Our near term plans include adding the full set of Cassini CIRS Saturn data (with enhanced geometry), New Horizons MVIC Jupiter encounter images, New Horizons LORRI and MVIC Pluto data, HST STIS observations, and Cassini and Voyager ring occultations. We also plan to develop enhanced geometric metadata for the New Horizons LORRI and MVIC instruments for both the Jupiter and the Pluto encounters.OPUS: http://pds-rings.seti.org/search/
Impact of Cubic Pin Finned Surface Structure Geometry upon Spray Cooling Heat Transfer
NASA Technical Reports Server (NTRS)
Silk, Eric A.; Kim, Jungho; Kiger, Ken
2005-01-01
Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of cubic pin fins machined on the top surface of copper heater blocks. The structure height, pitch, and width were parametrically vaned. Each copper block had a projected cross-sectional area of 2.0 sq cm. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2 x 2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data were obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 100.7 kPa) with a bulk fluid temperature of 20.5 C. Results for both the degassed and gassy cases show that structure width and separation distance have a dominant effect upon the heat transfer for the size ranges used. Cubic pin fin height had little impact upon heat flux. The maximum critical heat flux (CHF) attained for any of the surfaces was 121 W/sq cm, giving an enhancement of 51% relative to the flat surface case under nominally degassed conditions. The gassy case had a maximum CHF of 149 W/sq cm, giving an enhancement of 38% relative to the flat surface case.
Flatow, Daniel; Leelananda, Sumudu P; Skliros, Aris; Kloczkowski, Andrzej; Jernigan, Robert L
2014-01-01
Computing volumes and surface areas of molecular structures is generally considered to be a solved problem, however, comparisons presented in this review show that different ways of computing surface areas and volumes can yield dramatically different values. Volumes and surface areas are the most basic geometric properties of structures, and estimating these becomes especially important for large scale simulations when individual components are being assembled in protein complexes or drugs being fitted into proteins. Good approximations of volumes and surfaces are derived from Delaunay tessellations, but these values can differ significantly from those from the rolling ball approach of Lee and Richards (3V webserver). The origin of these differences lies in the extended parts and the less well packed parts of the proteins, which are ignored in some approaches. Even though surface areas and volumes from the two approaches differ significantly, their correlations are high. Atomic models have been compared, and the poorly packed regions of proteins are found to be most different between the two approaches. The Delaunay complexes have been explored for both fully atomic and for coarse-grained representations of proteins based on only C(α) atoms. The scaling relationships between the fully atomic models and the coarse-grained model representations of proteins are reported, and the lines fit yield simple relationships for the surface areas and volumes as a function of the number of protein residues and the number of heavy atoms. Further, the atomic and coarse-grained values are strongly correlated and simple relationships are reported.
Stretch-induced changes in geometry and ultrastructure of transporting surfaces of toad bladder.
Gfeller, E; Walser, M
1971-12-01
Methods were developed for estimation of the area of the microscopic and ultramicroscopic surface of the toad bladder epithelium at various degrees of stretch. Bladder sacs fixed while containing 2.5, 5, 25 or 50 ml of mucosal fluid were studied. For a perfect, hollow elastic sphere, this range of volume corresponds to a sevenfold range of surface area. In the bladder, this increase could be achieved by unfolding of surface irregularities, with no change in surface area, or by stretching the epithelial membrane. The measured microscopic surface area increased threeinstead of sevenfold, but the ultramicroscopic surface remained constant. Thus the bladder stretches (1) by unfolding of the mucosal epithelium, and (2) by flattening of the microvilli. From measurements of the apparent thickness of the mucosal epithelium alone and of the entire bladder, we conclude that the former behaves like a flexible inelastic sheet, whereas the submucosa and serosa stretch elastically. Lateral intercellular spaces do not widen with stretch, but they do become more convoluted because of thinning of the epithelium. Thinning is unlikely to explain the increased sodium transport which follows stretching, because cytoplasmic resistance cannot approach total transepithelial resistance of this preparation. PMID:24174226
NASA Technical Reports Server (NTRS)
Bodonyi, R. J.; Tadjfar, M.; Welch, W. J. C.; Duck, P. W.
1989-01-01
A numerical study of the generation of Tollmien-Schlichting (T-S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite-difference and spectral methods. The nonlinear steady flow is of the viscous-inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier-Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T-S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T-S waves.
SPH-DCDEM model for arbitrary geometries in free surface solid-fluid flows
NASA Astrophysics Data System (ADS)
Canelas, Ricardo B.; Crespo, Alejandro J. C.; Domínguez, Jose M.; Ferreira, Rui M. L.; Gómez-Gesteira, Moncho
2016-05-01
A unified discretization of rigid solids and fluids is introduced, allowing for resolved simulations of fluid-solid phases within a meshless framework. The numerical solution, attained by Smoothed Particle Hydrodynamics (SPH) and a variation of Discrete Element Method (DEM), the Distributed Contact Discrete Element Method (DCDEM) discretization, is achieved by directly considering solid-solid and solid-fluid interactions. The novelty of the work is centred on the generalization of the coupling of the DEM and SPH methodologies for resolved simulations, allowing for state-of-the-art contact mechanics theories to be used in arbitrary geometries, while fluid to solid and vice versa momentum transfers are accurately described. The methods are introduced, analysed and discussed. Initial validations on the DCDEM and the fluid coupling are presented, drawing from test cases in the literature. An experimental campaign serves as a validation point for complex, large scale solid-fluid flows, where a set of blocks in several configurations is subjected to a dam-break wave. Blocks are tracked and positions are then compared between experimental data and the numerical solutions. A Particle Image Velocimetry (PIV) technique allows for the quantification of the flow field and direct comparison with numerical data. The results show that the model is accurate and is capable of treating highly complex interactions, such as transport of debris or hydrodynamic actions on structures, if relevant scales are reproduced.
CALCULATION OF PARTICLE BOUNCE AND TRANSIT TIMES ON GENERAL GEOMETRY FLUX SURFACES
Swanson, D.; Menard, J.
2007-01-01
A viable nuclear fusion reactor must confi ne energetic plasmas long enough so that the fusion energy produced exceeds the energy consumed to heat the plasma and maintain confi nement. It is well-known that magnetohydrodynamic (MHD) or plasma fl uid instabilities limit confi nement. One such important instability is the resistive wall mode (RWM). Plasma rotation faster than a critical frequency has been observed to stabilize the RWM. Some theories predict that the critical frequency will vary inversely with the characteristic times particles take to orbit the plasma. Previous calculations of these orbit times have assumed high aspect ratio and circular plasma cross-section, approximations unsuitable for the National Spherical Torus Experiment (NSTX). Analytic solutions for the orbit times have been derived as functions of particle energy and magnetic moment for low aspect ratio and elliptical cross-sections. Numeric solutions for arbitrary aspect ratio and cross-sectional geometry were also computed using Mathematica and IDL and agree with the analytic forms. In typical parameter regimes for NSTX, the generalized orbit times can differ from the high aspect ratio, circular approximations by as much as 40%. This result might help to assess how accurately theory describes RWM stabilization in NSTX. If theory and experiment are found to agree, generalized orbit times can be used to predict RWM stabilization in low aspect ratio nuclear fusion reactors.
Atomic geometry, electronic states and possible hydrogen passivation of the InP(1 1 1)A surface
NASA Astrophysics Data System (ADS)
Chuasiripattana, K.; Srivastava, G. P.
2006-08-01
We present a first-principles theoretical study of the atomic geometry and electronics states of the InP(1 1 1)A surface under In- and P-rich conditions. The In-rich surface, characterised by an In vacancy per unit ( 2×2) cell, obeys the electron counting rule (ECR) and is semiconducting. Under P-rich conditions we have considered two surface reconstructions: ( 2×2) with 3/4 monolayer (ML) P coverage and ( √{3}×√{3}) with 1 ML coverage. In complete agreement with a recent experimental work by Li et al., it is found that the ( √{3}×√{3}) reconstruction is more stable than the ( 2×2) reconstruction. However, the ( √{3}×√{3}) reconstruction has a metallic band structure and thus does not satisfy the ECR. The stability of this reconstruction is explained to arise from a competition between the ECR and a significant elastic deformation in the surface region. We confirm the suggestion by Li et al. that this surface can be passivated both chemically as well as electronically with 1/4 ML coverage of hydrogen.
NASA Astrophysics Data System (ADS)
Floß, Gereon; Granucci, Giovanni; Saalfrank, Peter
2012-12-01
With ongoing miniaturization of electronic devices, the need for individually addressable, switchable molecules arises. An example are azobenzenes on surfaces which have been shown to be switchable between trans and cis forms. Here, we examine the "direct" (rather than substrate-mediated) channel of the trans → cis photoisomerization after ππ* excitation of tetra-tert-butyl-azobenzene physisorbed on surfaces mimicking Au(111) and Bi(111), respectively. In spirit of the direct channel, the electronic structure of the surface is neglected, the latter merely acting as a rigid platform which weakly interacts with the molecule via Van-der-Waals forces. Starting from thermal ensembles which represent the trans-form, sudden excitations promote the molecules to ππ*-excited states which are non-adiabatically coupled among themselves and to a nπ*-excited and the ground state, respectively. After excitation, relaxation to the ground state by internal conversion takes place, possibly accompanied by isomerization. The process is described here by "on the fly" semiclassical surface hopping dynamics in conjunction with a semiempirical Hamiltonian (AM1) and configuration-interaction type methods. It is found that steric constraints imposed by the substrate lead to reduced but non-vanishing, trans → cis reaction yields and longer internal conversion times than for the isolated molecule. Implications for recent experiments for azobenzenes on surfaces are discussed.
Liquid drops on vertical and inclined surfaces; I. An experimental study of drop geometry.
ElSherbini, A I; Jacobi, A M
2004-05-15
Experiments have been conducted to investigate the geometric parameters necessary to describe the shapes of liquid drops on vertical and inclined plane surfaces. Two liquids and eight surfaces have been used to study contact angles, contact lines, profiles, and volumes of drops of different sizes for a range of surface conditions. The results show the contact-angle variation along the circumference of a drop to be best fit by a third-degree polynomial in the azimuthal angle. This contact-angle function is expressed in terms of the maximum and minimum contact angles of the drop, which are determined for various conditions. The maximum contact angle, thetamax, is approximately equal to the advancing contact angle, thetaA, of the liquid on the surface. As the Bond number, Bo, increases from 0 to a maximum, the minimum contact angle, thetamin, decreases almost linearly from the advancing to the receding angle. A general relation is found between thetamin/thetaA and Bo for different liquid-surface combinations. The drop contour can be described by an ellipse, with the aspect ratio increasing with Bo. These experimental results are valuable in modeling drop shape, as presented in Part II of this work.
Initial geometries, interaction mechanism and high stability of silicene on Ag(111) surface.
Gao, Junfeng; Zhao, Jijun
2012-01-01
Using ab initio methods, we have investigated the structures and stabilities of Si(N) clusters (N ≤ 24) on Ag(111) surface as the initial stage of silicene growth. Unlike the dome-shaped graphene clusters, Si clusters prefer nearly flat structures with low buckling, more stable than directly deposition of the 3D freestanding Si clusters on Ag surface. The p-d hybridization between Ag and Si is revealed as well as sp(2) characteristics in Si(N)@Ag(111). Three types of silicene superstructures on Ag(111) surface have been considered and the simulated STM images are compared with experimental observations. Molecular dynamic simulations show high thermal stability of silicene on Ag(111) surfaces, contrast to that on Rh(111). The present theoretical results constitute a comprehensive picture about the interaction mechanism of silicene on Ag(111) surface and explain the superiority of Ag substrate for silicene growth, which would be helpful for improving the experimentally epitaxial growth of silicene.
Adsorption geometry of anthracene and 4-bromobiphenyl on TiO{sub 2}(110) surfaces
Potapenko, Denis; Choi, Nicholas; Osgood, Richard
2010-01-01
Adsorption of anthracene and 4-bromobiphenyl on a TiO{sub 2} rutile(110) surface has been studied under ultrahigh vacuum conditions with scanning tunneling microscopy (STM) and thermal programmed desorption (TPD). Multilayer and single-layer desorption peaks were observed at 270 and 360 K for anthracene and at 260 and 360 K for bromobiphenyl, respectively. STM images taken at room temperature show that both molecules form periodic patterns on the TiO{sub 2} surface with individual molecules aligned along the 5-coordinated Ti atom row of the substrate. Individual molecules of the organic adsorbates are mobile on the surface in the [001] direction parallel to the atomic rows. The observed lateral alignment of the molecules suggests attractive interactions in the case of anthracene and repulsive in the case of bromobiphenyl.
Waychunas, G.A.; Fuller, C.C.; Davis, J.A.; Rehr, J.J.
2003-01-01
X-ray absorption near-edge spectroscopy (XANES) analysis of sorption complexes has the advantages of high sensitivity (10- to 20-fold greater than extended X-ray absorption fine structure [EXAFS] analysis) and relative ease and speed of data collection (because of the short k-space range). It is thus a potentially powerful tool for characterization of environmentally significant surface complexes and precipitates at very low surface coverages. However, quantitative analysis has been limited largely to "fingerprint" comparison with model spectra because of the difficulty of obtaining accurate multiple-scattering amplitudes for small clusters with high confidence. In the present work, calculations of the XANES for 50- to 200-atom clusters of structure from Zn model compounds using the full multiple-scattering code Feff 8.0 accurately replicate experimental spectra and display features characteristic of specific first-neighbor anion coordination geometry and second-neighbor cation geometry and number. Analogous calculations of the XANES for small molecular clusters indicative of precipitation and sorption geometries for aqueous Zn on ferrihydrite, and suggested by EXAFS analysis, are in good agreement with observed spectral trends with sample composition, with Zn-oxygen coordination and with changes in second-neighbor cation coordination as a function of sorption coverage. Empirical analysis of experimental XANES features further verifies the validity of the calculations. The findings agree well with a complete EXAFS analysis previously reported for the same sample set, namely, that octahedrally coordinated aqueous Zn2+ species sorb as a tetrahedral complex on ferrihydrite with varying local geometry depending on sorption density. At significantly higher densities but below those at which Zn hydroxide is expected to precipitate, a mainly octahedral coordinated Zn2+ precipitate is observed. An analysis of the multiple scattering paths contributing to the XANES
Root growth responses of Anagallis arvensis L., primulaceae to air pollution.
Khan, F A; Ghouse, A K
1988-01-01
The root growth response to air pollution in populations of Anagallis arvensis growing about 0.5, 2, 6, 12 and 20 km leeward from a power plant complex varied with the level of pollution, age of the stand and meteorological conditions. The roots were more affected by the pollutants at a young stage and the loss in net primary productivity was proportional to the pollution level. The populations up to 2 km from the source of pollution completed their life cycle quickly. The coal consumption rate at the power plant, relative humidity, wind direction and other environmental factors were found to influence the degree of growth response to air pollution.
Characterization of internal geometry / covered surface defects with a visible light sensing system
NASA Astrophysics Data System (ADS)
Straub, Jeremy
2016-05-01
Previous work has used visible light scanning to detect and characterize defects in 3D printed objects. This paper focuses on assessing the internal structures and external surfaces (that will be later hidden) of complex objects. These features make in-process defect detection far more important than it would be with an object that can be fully assessed with a post-completion scan, as it is required both for in-process correction and end-product quality assurance. This paper presents work on the use of a multi-camera visible light 3D scanning system to identify defects with printed objects' interior and covered / obscured exterior surfaces.
Characterization and extraction of the synaptic apposition surface for synaptic geometry analysis
Morales, Juan; Rodríguez, Angel; Rodríguez, José-Rodrigo; DeFelipe, Javier; Merchán-Pérez, Angel
2013-01-01
Geometrical features of chemical synapses are relevant to their function. Two critical components of the synaptic junction are the active zone (AZ) and the postsynaptic density (PSD), as they are related to the probability of synaptic release and the number of postsynaptic receptors, respectively. Morphological studies of these structures are greatly facilitated by the use of recent electron microscopy techniques, such as combined focused ion beam milling and scanning electron microscopy (FIB/SEM), and software tools that permit reconstruction of large numbers of synapses in three dimensions. Since the AZ and the PSD are in close apposition and have a similar surface area, they can be represented by a single surface—the synaptic apposition surface (SAS). We have developed an efficient computational technique to automatically extract this surface from synaptic junctions that have previously been three-dimensionally reconstructed from actual tissue samples imaged by automated FIB/SEM. Given its relationship with the release probability and the number of postsynaptic receptors, the surface area of the SAS is a functionally relevant measure of the size of a synapse that can complement other geometrical features like the volume of the reconstructed synaptic junction, the equivalent ellipsoid size and the Feret's diameter. PMID:23847474
ERIC Educational Resources Information Center
Kelly, Debbie M.; Bischof, Walter F.
2008-01-01
We investigated how human adults orient in enclosed virtual environments, when discrete landmark information is not available and participants have to rely on geometric and featural information on the environmental surfaces. In contrast to earlier studies, where, for women, the featural information from discrete landmarks overshadowed the encoding…
Influence of tailored MLI for complex surface geometries on heat transfer
NASA Astrophysics Data System (ADS)
Neumann, H.; Mayrhofer, R.; Richter, T.
2015-12-01
Complex, non-developable surfaces require a tailored multi-layer insulation (MLI) for lowest heat load. The most experiments showing the heat transfer through MLI are performed under quasi-ideal conditions determining the principle insulation quality. But the surface to be insulated in real cryostats implies feed-throughs and other non-developable surface parts. The thermal performance of MLI is degraded significantly at cutting points. To investigate this degrading effect a LN2-filled cylinder with a diameter of 219 mm and a length of 1820 mm was insulated with MLI and the heat load was measured by means of calorimetry. In addition the heat load to an insulated cylinder with eighteen branches was measured. Both cylinders have the same surface of 1.37 m2 for a comparison of the results. This article describes the experiments with different ways of tailoring the MLI for the cylinder with branches and discusses their results. It was shown that the cutting points at the branches have a significant degrading influence on the thermal performance of MLI.
Catchings, R.D.; Gandhok, G.; Goldman, M.R.; Okaya, D.; Rymer, M.J.; Bawden, G.W.
2008-01-01
High-resolution seismic-reflection and seismic-refraction imaging, combined with existing borehole, earthquake, and paleoseismic trenching data, suggest that the Santa Monica fault zone in Los Angeles consists of multiple strands from several kilometers depth to the near surface. We interpret our seismic data as showing two shallow-depth low-angle fault strands and multiple near-vertical (???85??) faults in the upper 100 m. One of the low-angle faults dips northward at about 28?? and approaches the surface at the base of a topographic scarp on the grounds of the Wadsworth VA Hospital (WVAH). The other principal low-angle fault dips northward at about 20?? and projects toward the surface about 200 m south of the topographic scarp, near the northernmost areas of the Los Angeles Basin that experienced strong shaking during the 1994 Northridge earthquake. The 20?? north-dipping low-angle fault is also apparent on a previously published seismic-reflection image by Pratt et al. (1998) and appears to extend northward to at least Wilshire Boulevard, where the fault may be about 450 m below the surface. Slip rates determined at the WVAH site could be significantly underestimated if it is assumed that slip occurs only on a single strand of the Santa Monica fault or if it is assumed that the near-surface faults dip at angles greater than 20-28??. At the WVAH, tomographic velocity modeling shows a significant decrease in velocity across near-surface strands of the Santa Monica fault. P-wave velocities range from about 500 m/sec at the surface to about 4500 m/sec within the upper 50 m on the north side of the fault zone at WVAH, but maximum measured velocities on the south side of the low-angle fault zone at WVAH are about 3500 m/sec. These refraction velocities compare favorably with velocities measured in nearby boreholes by Gibbs et al. (2000). This study illustrates the utility of com- bined seismic-reflection and seismic-refraction methods, which allow more accurate
Sapra, Vipul; Taneja, Sonali; Kumar, Mohit
2013-01-01
Aim: This in vitro study assessed the surface quality of three nanoparticle composites with four commercially available polishing systems. Materials and Methods: A total of 180 specimens (10 × 2 mm) were prepared in metal molds using three nanocomposites, Filtek Z-350 XT, Ceram-X Mono, and Tetric N-Ceram. Sixty specimens of each material were then randomly assigned to five study groups. Control specimens were left untreated and the remaining specimens were subjected to polishing with SpinBrite, CompoMaster, AstroPol, and SofLex polishing systems. Average roughness (Ra) and average ten-point roughness (Rz) were calculated using Perthometer, and the data were analyzed by two-way analysis of variance (ANOVA) and post-hoc Tukey's tests. Results: For all the materials, the roughest surfaces were observed for control specimens, with no statistically significant differences between the material groups. For Filtek Z-350 XT, the decrease in surface roughness after two-step polishing was insignificant. For Ceram-X, SpinBrite specimens showed similar degree of roughness as control specimens. For Tetric N-Ceram, no significant decrease in roughness was observed after one-step polishing. Two-way ANOVA (interaction of subgroups and groups) did not show a significant association with the outcome. Conclusions: For nanofilled composites (Filtek Z-350 XT), the surface roughness decreased with the increase in number of polishing steps, whereas one-step and multi-step polishing procedures produced similar quality of smoothness for nanohybrid composites (Ceram-X, Tetric N-Ceram). Ra and Rz values of surface roughness are a function of type of finishing/polishing only. PMID:24347894
NASA Astrophysics Data System (ADS)
Schermer, Elizabeth; Redfield, Tim
2013-04-01
The distribution and geometry of relict surfaces adjacent to the northern Norwegian passive margin can help constrain the post-rift evolution of the onshore region. A swath map of relict surfaces, covering the coast of Senja Island and extending SE to the drainage divide, was constructed from DEMs, aerial photos and an NGU digital map database of Quaternary features. The map and histograms of elevation distribution depict three distinctly stepped, coast-parallel belts of preserved relict surfaces. The belts increase in mean elevation from coast to the southeast and, to a certain degree, correlate with the bedrock geology. Overall, the relict surfaces dip to the NW. Locally SE dipping surfaces in the coastal and central belts may be controlled by post-surface reactivation of normal faults. The coastal belt coincides with a fault-bounded horst of Precambrian rock. Although deeply incised by Alpine glaciers and fjords, relict surfaces are preserved on ridge tops and local broad peaks at 700-800 m. A central belt of much lower relief and with surfaces averaging 900-1100 m high coincides with Caledonian nappe rocks and exhibits few preserved surfaces. An inner belt of extensive and well preserved surfaces averaging 1300-1400m high coincides with peaks and the gently rolling upland of the Scandinavian mountain crest. Here, NW-trending paleoridges and paleovalleys are evident in contours of the highest surfaces. NW-SE topographic profiles (perpendicular to the COB) show distinct steps in the maximum height of the relict surfaces, interpreted to coincide with mapped normal faults whose vertical offsets (throw) may be up to 600-700 m. The geometry of relict surfaces is consistent with multiple rock column uplift events. Published apatite fission track (AFT) apparent ages are ~200 Ma (range ~170-220 Ma), indicating the onshore bedrock was within ~2-3 km of the surface since Early Jurassic time. No distinct AFT age offsets can be resolved within the data, limiting net throw
Gu, Haiwei; Yang, Shuiping; Li, Jianqiang; Hu, Bin; Chen, Huanwen; Zhang, Lili; Fei, Qiang
2010-04-01
A novel geometry-independent neutral desorption (GIND) device was successfully developed, which made neutral desorption (ND) sampling easier and more robust on virtually all types of surfaces. The GIND device features a small air-tight enclosure with fixed space between the ND gas emitter, the sample surface, and the sample collector. Besides easy fabrication and convenient use, this configuration facilitates efficient neutral sample transfer and results in high sensitivity by preventing material loss during the ND process. The effects of various operating parameters of the GIND device such as desorption gas composition, surface wetness, gas flow rate, distance between the surface and the gas emitter, internal diameter of the sample outlet, and GIND device material were experimentally investigated. By using the GIND device, trace amounts of typical explosives such as TNT, RDX, HMX, TATP, etc., were successfully sampled from many different kinds of surfaces, including human skin, glove, glass, envelope, plastic, leather, glass, and clothes. GIND-sampled explosives were detected by multiple-stage extractive electrospray ionization mass spectrometry (EESI-MS). Ion/molecule reactions of explosives such as RDX and TATP were implemented in the EESI source for the rapid detection with enhanced sensitivity and specificity. The typical time for a single sample analysis was a few seconds. Successful transportation of the neutral analytes over a distance longer than 10 m was demonstrated, without either significant signal loss or serious delay of signal response. The limit of detection for these explosives in the study was in the range of ca. 59-842 fg (S/N = 3, n = 8) on various surfaces. Acceptable relative standard deviation (RSD) values (ca. 4.6-10.2%, n = 8) were obtained for all the surfaces tested, showing the successful sampling of trace non-volatile explosive compounds (sub-picogram) by the GIND device for the EESI mass spectrometric analysis. PMID:20349542
Effect of surface interactions and geometry on the motion of micro bio robots
NASA Astrophysics Data System (ADS)
Wong, Denise; Beattie, Elizabeth E.; Steager, Edward B.; Kumar, Vijay
2013-10-01
Micro Bio Robots (MBRs) are synthetic microstructures with a monolayer of flagellated bacteria adhered to the surface. The flagella of the bacteria propel the microstructure causing it to rotate and translate in a fluidic environment on a planar surface in the absence of external forces. This paper investigates the force contributions of bacteria adhered to the edge versus the center of the micro-structure by selectively altering their behavior using near-UV light. In particular, we investigate the forces that cause predominant clockwise MBR rotation when viewed from above. Additionally, asymmetric shapes, particularly gears, are used to compare the effect of the adherent bacteria with that of collisions among free-swimming bacteria and the microstructure. We find that bacteria adhered near the edge of the MBR interact with the glass substrate under the MBR, accounting for statistically biased clockwise rotation of MBRs.
Joint effects of illumination geometry and object shape in the perception of surface reflectance
Olkkonen, Maria; Brainard, David H
2011-01-01
Surface properties provide useful information for identifying objects and interacting with them. Effective utilization of this information, however, requires that the perception of object surface properties be relatively constant across changes in illumination and changes in object shape. Such constancy has been studied separately for changes in these factors. Here we ask whether the separate study of the illumination and shape effects is sufficient, by testing whether joint effects of illumination and shape changes can be predicted from the individual effects in a straightforward manner. We found large interactions between illumination and object shape in their effects on perceived glossiness. In addition, analysis of luminance histogram statistics could not account for the interactions. PMID:23145259
Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect
NASA Astrophysics Data System (ADS)
Ozgoren, M.; Dogan, S.; Okbaz, A.; Aksoy, M. H.; Sahin, B.; Akıllı, H.
2013-04-01
Comparison of the experimental results of turbulent flow structures between a smooth sphere and a sphere with a vent hole, roughened, and o-ring is presented in the presence of a free-surface. Dye visualization and particle image velocimetry (PIV) techniques were performed to examine effects of passive control methods on the sphere wake for Reynolds number Re = 5000 based on the sphere diameter with a 42.5mm in an open water channel. Instantaneous and time-averaged flow patterns in the wake region of the sphere were examined from point of flow physics for the different sphere locations in the range of 0≤h/D≤2.0 where h was the space between the top point of the sphere and the free surface. The ratio of ventilation hole to sphere diameter was 0.15, o-ring was located at 55° with a 2 mm from front stagnation point of the sphere and roughened surface was formed by means of totally 410 circular holes with a 3 mm diameter and around 2 mm depth in an equilateral triangle arrangement. The flow characteristics of instantaneous velocity vectors, vorticity contours, time-averaged streamline patterns, Reynolds stress correlations and streamwise and cross-stream velocity fluctuations for both the smooth and passively controlled sphere were interpreted.
Boesi, R.; Polidori, C.; Andrietti, F.; Gayubo, S.F.; Tormos, J.; Asis, J.D.
2007-03-15
Recently re-named as a sub-species of Mellinus arvensis, Mellinus arvensis obscurus Handlirsch 1888 was investigated ecologically and morphologically in Nepal, in order to underline the most important differences with the well known M. arvensis arvensis. Mellinus arvensis obscurus females nested in clumped aggregations on inclined plains at high altitudes, both on sunny bare soil and on a shaded grassy one. Beginning of monsoon season probably interfered with wasp activity, and females performed few provisioning flights during the day. Prey consisted of a broad range of Diptera, except for one case of a spider. Many females were observed not provisioning a nest but floating on the nesting site, and many intraspecific interactions suggested a high degree of usurpation attempts. At least one species of flies and two of ants probably acted as natural enemies of the wasp. Morphological observations on females showed that the Nepal population shares more similarities (shape of tergite I, body punctation) with the European populations than with the closer Japanese population; melanization is strong, according to west-east and altitudinal cline. The mature larva of M. arvensis obscurus Handlirsch is described, illustrated, and compared with the other mature larva of the genus. The differences between both larvae mainly lie in the presence/absence, and number or differentiation of integumental structures. We conclude that morphological traits are more important than ecological and behavioral ones in distinguishing M. arvensis obscurus from M. arvensis arvensis. (author) [Spanish] En el presente articulo se aportan los resultados y conclusiones de un estudio, llevado a cabo en Nepal, en el que se abordaron aspectos ecologicos, comportamentales y morfologicos (tanto del ultimo estado de la fase larvaria como del adulto) de Mellinus arvensis obscurus Handlirsch 1888. El principal objetivo del estudio radicaba en mostrar las principales diferencias que separan a esta
Garza-García, Lucía D; García-López, Erika; Camacho-León, Sergio; Del Refugio Rocha-Pizaña, María; López-Pacheco, Felipe; López-Meza, Julián; Araiz-Hernández, Diana; Tapia-Mejía, Eduardo J; Trujillo-de Santiago, Grissel; Rodríguez-González, Ciro A; Alvarez, Mario Moisés
2014-04-01
We used continuous flow micro-devices as bioreactors for the production of a glycosylated pharmaceutical product (a monoclonal antibody). We cultured CHO cells on the surface of PMMA/PDMS micro-channels that had been textured by micromachining and coated with fibronectin. Three different micro-channel geometries (a wavy channel, a zigzag channel, and a series of donut-shape reservoirs) were tested in a continuous flow regime in the range of 3 to 6 μL min(-1). Both the geometry of the micro-device and the flow rate had a significant effect on cell adhesion, cell proliferation, and monoclonal antibody production. The most efficient configuration was a series of donut-shaped reservoirs, which yielded mAb concentrations of 7.2 mg L(-1) at residence times lower than one minute and steady-state productivities above 9 mg mL(-1) min(-1). These rates are at about 3 orders of magnitude higher than those observed in suspended-cell stirred tank fed-batch bioreactors.
Appelo, D; Petersson, N A
2007-12-17
The isotropic elastic wave equation governs the propagation of seismic waves caused by earthquakes and other seismic events. It also governs the propagation of waves in solid material structures and devices, such as gas pipes, wave guides, railroad rails and disc brakes. In the vast majority of wave propagation problems arising in seismology and solid mechanics there are free surfaces. These free surfaces have, in general, complicated shapes and are rarely flat. Another feature, characterizing problems arising in these areas, is the strong heterogeneity of the media, in which the problems are posed. For example, on the characteristic length scales of seismological problems, the geological structures of the earth can be considered piecewise constant, leading to models where the values of the elastic properties are also piecewise constant. Large spatial contrasts are also found in solid mechanics devices composed of different materials welded together. The presence of curved free surfaces, together with the typical strong material heterogeneity, makes the design of stable, efficient and accurate numerical methods for the elastic wave equation challenging. Today, many different classes of numerical methods are used for the simulation of elastic waves. Early on, most of the methods were based on finite difference approximations of space and time derivatives of the equations in second order differential form (displacement formulation), see for example [1, 2]. The main problem with these early discretizations were their inability to approximate free surface boundary conditions in a stable and fully explicit manner, see e.g. [10, 11, 18, 20]. The instabilities of these early methods were especially bad for problems with materials with high ratios between the P-wave (C{sub p}) and S-wave (C{sub s}) velocities. For rectangular domains, a stable and explicit discretization of the free surface boundary conditions is presented in the paper [17] by Nilsson et al. In summary
NASA Technical Reports Server (NTRS)
Podwysocki, M. H.; Gold, D. P.
1974-01-01
Hypothetical models are considered for detecting subsurface structure from the fracture or joint pattern, which may be influenced by the structure and propagated to the surface. Various patterns of an initially orthogonal fracture grid are modeled according to active and passive deformation mechanisms. In the active periclinal structure with a vertical axis, fracture frequency increased both over the dome and basin, and remained constant with decreasing depth to the structure. For passive periclinal features such as a reef or sand body, fracture frequency is determined by the arc of curvature and showed a reduction over the reefmound and increased over the basin.
Salin, Olli; Törmäkangas, Liisa; Leinonen, Maija; Saario, Elise; Hagström, Marja; Ketola, Raimo A; Saikku, Pekka; Vuorela, Heikki; Vuorela, Pia M
2011-12-28
Corn mint ( Mentha arvensis ) provides a good source of natural phenols such as flavone glycosides and caffeic acid derivatives, which may have prophylactic properties against inflammations. This study investigated whether corn mint extract would be beneficial against a universal respiratory tract pathogen, Chlamydia pneumoniae , infection. The extract inhibited the growth of C. pneumoniae CWL-029 in vitro in a dose-dependent manner. The inhibition was confirmed against a clinical isolate K7. The phenolic composition of the extract was analyzed by UPLC-ESI/Q-TOF/MS, the main components being linarin and rosmarinic acid. These compounds were active in vitro against C. pneumoniae. Linarin completely inhibited the growth at 100 μM. Inbred C57BL/6J mice were inoculated with C. pneumoniae K7. M. arvensis extract was given intraperitoneally once daily for 3 days prior to inoculation and continued for 10 days postinfection. The extract was able to diminish the inflammatory parameters related to C. pneumoniae infection and significantly (p = 0.019) lowered the number of C. pneumoniae genome equivalents detected by PCR at biologically relevant amounts.
NASA Technical Reports Server (NTRS)
Hefner, J. N.
1973-01-01
Studies have shown that vortices can produce relatively severe heating on the leeward surfaces of conceptual hypersonic vehicles and that surface geometry can strongly influence this vortex-induced heating. Results which show the effects of systematic geometry variations on the vortex-induced lee-surface heating on simple flat-bottom three-dimensional bodies at angles of attack of 20 deg and 40 deg are presented. The tests were conducted at a free-stream Mach number of 6 and at a Reynolds number of 1.71 x 10 to the 7th power per meter.
Free Energy Calculations for DNA Near Surfaces Using an Ellipsoidal Geometry
Ambia-Garrido, J.; Pettitt, B. Montgomery
2009-01-01
The change in some thermodynamic quantities such as Gibbs' free energy, entropy and enthalpy of the binding of two DNA strands (forming a double helix), while one is tethered to a surface and are analytically calculated. These particles are submerged in an electrolytic solution; the ionic strength of the media allows the linearized version of the Poisson-Boltzmann equation (from the theory of the double layer interaction) to properly describe the interactions [13]. There is experimental and computational evidence that an ion penetrable ellipsoid is an adequate model for the single strand and the double helix [22–25]. The analytic solution provides simple calculations useful for DNA chip design. The predicted electrostatic effects suggest the feasibility of electronic control and detection of DNA hybridization in the fast growing area of DNA recognition. PMID:20011625
Sensing (un)binding events via surface plasmons: effects of resonator geometry
NASA Astrophysics Data System (ADS)
Antosiewicz, Tomasz J.; Claudio, Virginia; Käll, Mikael
2016-04-01
The resonance conditions of localized surface plasmon resonances (LSPRs) can be perturbed in any number ways making plasmon nanoresonators viable tools in detection of e.g. phase changes, pH, gasses, and single molecules. Precise measurement via LSPR of molecular concentrations hinge on the ability to confidently count the number of molecules attached to a metal resonator and ideally to track binding and unbinding events in real-time. These two requirements make it necessary to rigorously quantify relations between the number of bound molecules and response of plasmonic sensors. This endeavor is hindered on the one hand by a spatially varying response of a given plasmonic nanosensor. On the other hand movement of molecules is determined by stochastic effects (Brownian motion) as well as deterministic flow, if present, in microfluidic channels. The combination of molecular dynamics and the electromagnetic response of the LSPR yield an uncertainty which is little understood and whose effect is often disregarded in quantitative sensing experiments. Using a combination of electromagnetic finite-difference time-domain (FDTD) calculations of the plasmon resonance peak shift of various metal nanosensors (disk, cone, rod, dimer) and stochastic diffusion-reaction simulations of biomolecular interactions on a sensor surface we clarify the interplay between position dependent binding probability and inhomogeneous sensitivity distribution. We show, how the statistical characteristics of the total signal upon molecular binding are determined. The proposed methodology is, in general, applicable to any sensor and any transduction mechanism, although the specifics of implementation will vary depending on circumstances. In this work we focus on elucidating how the interplay between electromagnetic and stochastic effects impacts the feasibility of employing particular shapes of plasmonic sensors for real-time monitoring of individual binding reactions or sensing low concentrations
Jugulam, M.; Ziauddin, Asma; So, Kenny K. Y.; Chen, Shu; Hall, J. Christopher
2015-01-01
Auxinic herbicides (e.g. dicamba) are extensively used in agriculture to selectively control broadleaf weeds. Although cultivated species of Brassicaceae (e.g. Canola) are susceptible to auxinic herbicides, some biotypes of Sinapis arvensis (wild mustard) were found dicamba resistant in Canada. In this research, dicamba tolerance from wild mustard was introgressed into canola through embryo rescue followed by conventional breeding. Intergeneric hybrids between S. arvensis (2n = 18) and B. napus (2n = 38) were produced through embryo rescue. Embryo formation and hybrid plant regeneration was achieved. Transfer of dicamba tolerance from S. arvensis into the hybrid plants was determined by molecular analysis and at the whole plant level. Dicamba tolerance was introgressed into B. napus by backcrossing for seven generations. Homozygous dicamba-tolerant B. napus lines were identified. The ploidy of the hybrid progeny was assessed by flow cytometry. Finally, introgression of the piece of DNA possibly containing the dicamba tolerance gene into B. napus was confirmed using florescence in situ hybridization (FISH). This research demonstrates for the first time stable introgression of dicamba tolerance from S. arvensis into B. napus via in vitro embryo rescue followed by repeated backcross breeding. Creation of dicamba-tolerant B. napus varieties by this approach may have potential to provide options to growers to choose a desirable herbicide-tolerant technology. Furthermore, adoption of such technology facilitates effective weed control, less tillage, and possibly minimize evolution of herbicide resistant weeds. PMID:26536372
Jugulam, M; Ziauddin, Asma; So, Kenny K Y; Chen, Shu; Hall, J Christopher
2015-01-01
Auxinic herbicides (e.g. dicamba) are extensively used in agriculture to selectively control broadleaf weeds. Although cultivated species of Brassicaceae (e.g. Canola) are susceptible to auxinic herbicides, some biotypes of Sinapis arvensis (wild mustard) were found dicamba resistant in Canada. In this research, dicamba tolerance from wild mustard was introgressed into canola through embryo rescue followed by conventional breeding. Intergeneric hybrids between S. arvensis (2n = 18) and B. napus (2n = 38) were produced through embryo rescue. Embryo formation and hybrid plant regeneration was achieved. Transfer of dicamba tolerance from S. arvensis into the hybrid plants was determined by molecular analysis and at the whole plant level. Dicamba tolerance was introgressed into B. napus by backcrossing for seven generations. Homozygous dicamba-tolerant B. napus lines were identified. The ploidy of the hybrid progeny was assessed by flow cytometry. Finally, introgression of the piece of DNA possibly containing the dicamba tolerance gene into B. napus was confirmed using florescence in situ hybridization (FISH). This research demonstrates for the first time stable introgression of dicamba tolerance from S. arvensis into B. napus via in vitro embryo rescue followed by repeated backcross breeding. Creation of dicamba-tolerant B. napus varieties by this approach may have potential to provide options to growers to choose a desirable herbicide-tolerant technology. Furthermore, adoption of such technology facilitates effective weed control, less tillage, and possibly minimize evolution of herbicide resistant weeds.
Jugulam, M; Ziauddin, Asma; So, Kenny K Y; Chen, Shu; Hall, J Christopher
2015-01-01
Auxinic herbicides (e.g. dicamba) are extensively used in agriculture to selectively control broadleaf weeds. Although cultivated species of Brassicaceae (e.g. Canola) are susceptible to auxinic herbicides, some biotypes of Sinapis arvensis (wild mustard) were found dicamba resistant in Canada. In this research, dicamba tolerance from wild mustard was introgressed into canola through embryo rescue followed by conventional breeding. Intergeneric hybrids between S. arvensis (2n = 18) and B. napus (2n = 38) were produced through embryo rescue. Embryo formation and hybrid plant regeneration was achieved. Transfer of dicamba tolerance from S. arvensis into the hybrid plants was determined by molecular analysis and at the whole plant level. Dicamba tolerance was introgressed into B. napus by backcrossing for seven generations. Homozygous dicamba-tolerant B. napus lines were identified. The ploidy of the hybrid progeny was assessed by flow cytometry. Finally, introgression of the piece of DNA possibly containing the dicamba tolerance gene into B. napus was confirmed using florescence in situ hybridization (FISH). This research demonstrates for the first time stable introgression of dicamba tolerance from S. arvensis into B. napus via in vitro embryo rescue followed by repeated backcross breeding. Creation of dicamba-tolerant B. napus varieties by this approach may have potential to provide options to growers to choose a desirable herbicide-tolerant technology. Furthermore, adoption of such technology facilitates effective weed control, less tillage, and possibly minimize evolution of herbicide resistant weeds. PMID:26536372
Technology Transfer Automated Retrieval System (TEKTRAN)
Biotypes of the broad-leaved wild mustard (Sinapis arvensis L.) found in wheat fields of the Aegean and Marmara regions of Turkey, were characterized and shown to have developed resistance to sulfonylurea (chlorsulfuron), an inhibitor of acetolactate synthase (ALS). DNA sequence analysis of the ALS...
Nonradiative Plasmon Decay and Hot Carrier Dynamics: Effects of Phonons, Surfaces, and Geometry.
Brown, Ana M; Sundararaman, Ravishankar; Narang, Prineha; Goddard, William A; Atwater, Harry A
2016-01-26
The behavior of metals across a broad frequency range from microwave to ultraviolet frequencies is of interest in plasmonics, nanophotonics, and metamaterials. Depending on the frequency, losses of collective excitations in metals can be predominantly classical resistive effects or Landau damping. In this context, we present first-principles calculations that capture all of the significant microscopic mechanisms underlying surface plasmon decay and predict the initial excited carrier distributions so generated. Specifically, we include ab initio predictions of phonon-assisted optical excitations in metals, which are critical to bridging the frequency range between resistive losses at low frequencies and direct interband transitions at high frequencies. In the commonly used plasmonic materials, gold, silver, copper, and aluminum, we find that resistive losses compete with phonon-assisted carrier generation below the interband threshold, but hot carrier generation via direct transitions dominates above threshold. Finally, we predict energy-dependent lifetimes and mean free paths of hot carriers, accounting for electron-electron and electron-phonon scattering, to provide insight toward transport of plasmonically generated carriers at the nanoscale. PMID:26654729
Surface transport in the Ria de Vigo - Transport barriers in a tidal estuary with a complex geometry
NASA Astrophysics Data System (ADS)
Huhn, F.; von Kameke, A.; Montero, P.; Allen-Perkins, S.; Venancio, A.; Pérez-Muñuzuri, V.
2012-04-01
We study the submesoscale surface transport in the Ria de Vigo, NW Spain, an estuary with tidal and wind-driven circulation, analyzing the output of the coastal model MOHID with state-of-the-art Lagrangian methods, and comparing the results to drifter experiments. We extract Lagrangian Coherent Structures (LCS) as ridges in fields of the Finite-Time Lyapunov Exponent (FTLE) that can be identified with transport barriers. The LCS reveal the fundamental structure of the modelled circulation in the estaury that is a superposition of the tidal inflow and outflow, the wind-driven currents and the long-term drift on the shelf. In the Ria de Vigo, LCS are attached to prominent coastal boundaries, as islands or capes, indicating that the geometry of the flow patterns is dominated by bathymetry. Although the vertical flow which is not represented in the horizontal surface flow can be important at the coast, the found transport patterns can be seen as the surface footprint of the 3D circulation in the estaury. Comparing the trajectories of real surface drifters from four deployments to the computed transport barriers in different typical meteorological sitiations, we find that the drifter trajectories are in agreement with the different coherent water masses predicted by the model. The knowledge of the global transport patterns of water masses in this highly populated coastal region is indispensable for the assessment of the fate of contaminations, like possible oil spills or released waste water, but also for biological studies that deal with the drift of eggs and larvae of fish and other marine species, or investigate plankton blooms.
Laine, Elodie; Carbone, Alessandra
2015-12-01
Protein-protein interactions (PPIs) are essential to all biological processes and they represent increasingly important therapeutic targets. Here, we present a new method for accurately predicting protein-protein interfaces, understanding their properties, origins and binding to multiple partners. Contrary to machine learning approaches, our method combines in a rational and very straightforward way three sequence- and structure-based descriptors of protein residues: evolutionary conservation, physico-chemical properties and local geometry. The implemented strategy yields very precise predictions for a wide range of protein-protein interfaces and discriminates them from small-molecule binding sites. Beyond its predictive power, the approach permits to dissect interaction surfaces and unravel their complexity. We show how the analysis of the predicted patches can foster new strategies for PPIs modulation and interaction surface redesign. The approach is implemented in JET2, an automated tool based on the Joint Evolutionary Trees (JET) method for sequence-based protein interface prediction. JET2 is freely available at www.lcqb.upmc.fr/JET2.
Laine, Elodie; Carbone, Alessandra
2015-01-01
Protein-protein interactions (PPIs) are essential to all biological processes and they represent increasingly important therapeutic targets. Here, we present a new method for accurately predicting protein-protein interfaces, understanding their properties, origins and binding to multiple partners. Contrary to machine learning approaches, our method combines in a rational and very straightforward way three sequence- and structure-based descriptors of protein residues: evolutionary conservation, physico-chemical properties and local geometry. The implemented strategy yields very precise predictions for a wide range of protein-protein interfaces and discriminates them from small-molecule binding sites. Beyond its predictive power, the approach permits to dissect interaction surfaces and unravel their complexity. We show how the analysis of the predicted patches can foster new strategies for PPIs modulation and interaction surface redesign. The approach is implemented in JET2, an automated tool based on the Joint Evolutionary Trees (JET) method for sequence-based protein interface prediction. JET2 is freely available at www.lcqb.upmc.fr/JET2. PMID:26690684
NASA Technical Reports Server (NTRS)
Vidal, A.; Mueller, K.; Golombek, M. P.
2003-01-01
We undertook axial surface mapping of selected wrinkle ridges on Solis Planum, Mars in order to assess the subsurface geometry of blind thrusts proposed to exist beneath them. This work builds on previous work that defined structural families of wrinkle ridges based on their surface morphology in this region. Although a growing consensus exists for models of wrinkle ridge kinematics and mechanics, a number of current problems remain. These include the origin of topographic offset across the edges of wrinkle ridges, the relationship between broad arches and superposed ridges, the origin of smaller wrinkles, and perhaps most importantly, the trajectory of blind thrusts that underlie wrinkle ridges and accommodate shortening at deeper crustal levels. We are particularly interested in defining the depths at which blind thrusts flatten under wrinkle ridges in order to provide constraints on the brittle-ductile transition during Early Hesperian time. We also seek to test whether wrinkle ridges on Solis Planum develop above reactivated faults or newly formed ones.
Landesmann, Jennifer B; Gundel, Pedro E; Martínez-Ghersa, M Alejandra; Ghersa, Claudio M
2013-01-01
Tropospheric ozone is one of the major drivers of global change. This stress factor alters plant growth and development. Ozone could act as a selection pressure on species communities composition, but also on population genetic background, thus affecting life history traits. Our objective was to evaluate the consequences of prolonged ozone exposure of a weed community on phenotypic traits of Spergulaarvensis linked to persistence. Specifically, we predicted that the selection pressure exerted by high ozone concentrations as well as the concomitant changes in the weed community would drive population adaptive changes which will be reflected on seed germination, dormancy and longevity. In order to test seed viability and dormancy level, we conducted germination experiments for which we used seeds produced by S. arvensis plants grown within a weed community exposed to three ozone treatments during four years (0, 90 and 120 ppb). We also performed a soil seed bank experiment to test seed longevity with seeds coming from both the four-year ozone exposure experiment and from a short-term treatment conducted at ambient and added ozone concentrations. We found that prolonged ozone exposure produced changes in seed germination, dormancy and longevity, resulting in three S. arvensis populations. Seeds from the 90 ppb ozone selection treatment had the highest level of germination when stored at 75% RH and 25 °C and then scarified. These seeds showed the lowest dormancy level when being subjected to 5 ºC/5% RH and 25 ºC/75% followed by 5% RH storage conditions. Furthermore, ozone exposure increased seed persistence in the soil through a maternal effect. Given that tropospheric ozone is an important pollutant in rural areas, changes in seed traits due to ozone exposure could increase weed persistence in fields, thus affecting weed-crop interactions, which could ultimately reduce crop production.
Landesmann, Jennifer B.; Gundel, Pedro E.; Martínez-Ghersa, M. Alejandra; Ghersa, Claudio M.
2013-01-01
Tropospheric ozone is one of the major drivers of global change. This stress factor alters plant growth and development. Ozone could act as a selection pressure on species communities composition, but also on population genetic background, thus affecting life history traits. Our objective was to evaluate the consequences of prolonged ozone exposure of a weed community on phenotypic traits of Spergulaarvensis linked to persistence. Specifically, we predicted that the selection pressure exerted by high ozone concentrations as well as the concomitant changes in the weed community would drive population adaptive changes which will be reflected on seed germination, dormancy and longevity. In order to test seed viability and dormancy level, we conducted germination experiments for which we used seeds produced by S. arvensis plants grown within a weed community exposed to three ozone treatments during four years (0, 90 and 120 ppb). We also performed a soil seed bank experiment to test seed longevity with seeds coming from both the four-year ozone exposure experiment and from a short-term treatment conducted at ambient and added ozone concentrations. We found that prolonged ozone exposure produced changes in seed germination, dormancy and longevity, resulting in three S. arvensis populations. Seeds from the 90 ppb ozone selection treatment had the highest level of germination when stored at 75% RH and 25 °C and then scarified. These seeds showed the lowest dormancy level when being subjected to 5 ºC/5% RH and 25 ºC/75% followed by 5% RH storage conditions. Furthermore, ozone exposure increased seed persistence in the soil through a maternal effect. Given that tropospheric ozone is an important pollutant in rural areas, changes in seed traits due to ozone exposure could increase weed persistence in fields, thus affecting weed-crop interactions, which could ultimately reduce crop production. PMID:24086640
Del Santo, Francesco; Gelli, Francesca; Ginanneschi, Federica; Popa, Traian; Rossi, Alessandro
2007-08-13
Evidence exists that shoulder joint geometry influences recruitment efficiency and force-generating capacity of hand muscles [Ginanneschi, F., Del Santo, F., Dominici, F., Gelli, F., Mazzocchio, R., Rossi, A., 2005. Changes in corticomotor excitability of hand muscles in relation to static shoulder positions. Exp. Brain Res. 161 (3), 374-382; Dominici, F., Popa, T., Ginanneschi, F., Mazzocchio, R., Rossi, A., 2005. Cortico-motoneural output to intrinsic hand muscles is differentially influenced by static changes in shoulder positions. Exp. Brain Res. 164 (4), 500-504]. The present study was designed to examine the impact of changing shoulder joint position on the relation between surface EMG amplitude and isometric force production of the abductor digiti minimi muscle (ADM). EMG-force relation of ADM was examined in two shoulder positions: 30 degrees adduction (ANT) and 30 degrees abduction (POST) on the horizontal plane, i.e. under higher and lower force-generating capacity, respectively. The relation was studied over the full range isometric force (10-100% of maximum force in 10% increments, 3 s duration) by analysing root mean square (RMS), median frequency (Mf) of the power spectrum and non-linear recurrence quantification analysis (percentage of determinism: %DET) of the surface EMG signals. We found that in POST, the slope of the RMS-force relation was significantly higher than in ANT, while its general shape (strictly linear) was preserved. Averaged Mf of the EMG power spectrum was significantly higher in POST that in ANT, while no difference in %DET was observed between the two shoulder positions. The higher slope of the EMG-force relation in POST than in ANT is interpreted in terms of increased gain of the excitatory drive-firing rate relation. It is concluded that discharge from sensory receptors signalling shoulder position may act to regulate the gain of the excitatory drive-firing rate relation of motoneurones in order to compensate for reduced
Cheah, May J; Kevrekidis, Ioannis G; Benziger, Jay B
2013-08-01
Water emerging from ∼100 μm pores into millimeter-size gas flow channels forms drops that grow and become slugs which span the flow channel. Flowing gas causes the slugs to detach and move down the channel. The effect of channel geometry, surface wettability, and gravity on the formation and motion of water slugs has been analyzed using high-speed video images of the drops and differential pressure-time traces. Drops grow and appear, assuming a sequence of shapes that minimize the total interfacial energy of the gas-liquid and liquid-solid interfaces. The drops are initially spherical caps centered on the pore (the liquid contacts one wall). Above a certain size, the drops move to the corner, forming "corner drops" (the liquid contacts two walls). Corner drops grow across the channel, evolving into partial liquid bridges (drops confined by three walls), and finally the drops span the channel cross-section forming slugs (contacting all four walls). Smaller slugs are formed in channels with hydrophobic walls than in channels with hydrophilic walls. Smaller slugs are formed in channels with curved walls than in square or rectangular channels. Slugs move when the differential gas pressure overcomes the force to move the advancing and receding gas-liquid-solid contact lines of the slugs. Residual water left behind in corners by moving slugs reduces the barriers for drops to form slugs, causing the steady-state slug volumes to be smaller than those seen at start-up in dry channels.
Tumova, Lenka; Tuma, Jiri; Dolezal, Martin
2011-11-01
The effect of new synthetic pyrazinecarboxamide derivatives as potential elicitors of flavonolignan and flavonoid production in Silybum marianum and Ononis arvensis cultures in vitro was investigated. Both tested elicitors increased the production of flavonolignans in S. marianum callus and suspension cultures and flavonoids in O. arvensis callus and suspension cultures. Compound I, 5-(2-hydroxybenzoyl)-pyrazine-2-carboxamide, has shown to be an effective elicitor of flavonolignans and taxifoline production in Silybum marianum culture in vitro. The maximum content of silydianin (0.11%) in S. marianum suspension culture was induced by 24 h elicitor application in concentration of 1.159 × 10⁻³ mol/L. The maximum content of silymarin complex (0.08%) in callus culture of S. marianum was induced by 168 h elicitor application of a concentration 1.159 × 10⁻⁴ mol/L, which represents contents of silydianin (0.03%), silychristin (0.01%) and isosilybin A (0.04%) compared with control. All three tested concentrations of compound II, N-(2-bromo-3-methylphenyl)-5-tert-butylpyrazin-2-carboxamide increased the flavonoid production in callus culture of O. arvensis in a statistically significant way. The best elicitation effect of all elicitor concentrations had the weakest c₃ concentration (8.36 × 10⁻⁶ mol/L) after 168 h time of duration. The maximum content of flavonoids (about 5,900%) in suspension culture of O. arvensis was induced by 48 h application of c₃ concentration (8.36 × 10⁻⁶ mol/L).
NASA Astrophysics Data System (ADS)
Hsieh, Shang Yu; Neubauer, Franz
2015-04-01
The internal structure of major strike-slip faults is still poorly understood, particularly how to extrapolate subsurface structures by surface expressions. Series of brittle analogue experiments by Leever et al., 2011 resulted the convergence angle is the most influential factor for surface structures. Further analogue models with different ductile settings allow a better understanding in extrapolating surface structures to the subsurface geometry of strike-slip faults. Fifteen analogue experiments were constructed to represent strike-slip faults in nature in different geological settings. As key parameters investigated in this study include: (a) the angle of convergence, (b) the thickness of brittle layer, (c) the influence of a rheological weak layer within the crust, and (d) influence of a thick and rheologically weak layer at the base of the crust. The experiments are aimed to explain first order structures along major transcurrent strike-slip faults such as the Altyn, Kunlun, San Andrea and Greendale (Darfield earthquake 2010) faults. The preliminary results show that convergence angle significantly influences the overall geometry of the transpressional system with greater convergence angles resulting in wider fault zones and higher elevation. Different positions, densities and viscosities of weak rheological layers have not only different surface expressions but also affect the fault geometry in the subsurface. For instance, rheological weak material in the bottom layer results in stretching when experiment reaches a certain displacement and a buildup of a less segmented, wide positive flower structure. At the surface, a wide fault valley in the middle of the fault zone is the reflection of stretching along the velocity discontinuity at depth. In models with a thin and rheologically weaker layer in the middle of the brittle layer, deformation is distributed over more faults and the geometry of the fault zone below and above the weak zone shows significant
NASA Astrophysics Data System (ADS)
Almansa, Julio; Salvat-Pujol, Francesc; Díaz-Londoño, Gloria; Carnicer, Artur; Lallena, Antonio M.; Salvat, Francesc
2016-02-01
The Fortran subroutine package PENGEOM provides a complete set of tools to handle quadric geometries in Monte Carlo simulations of radiation transport. The material structure where radiation propagates is assumed to consist of homogeneous bodies limited by quadric surfaces. The PENGEOM subroutines (a subset of the PENELOPE code) track particles through the material structure, independently of the details of the physics models adopted to describe the interactions. Although these subroutines are designed for detailed simulations of photon and electron transport, where all individual interactions are simulated sequentially, they can also be used in mixed (class II) schemes for simulating the transport of high-energy charged particles, where the effect of soft interactions is described by the random-hinge method. The definition of the geometry and the details of the tracking algorithm are tailored to optimize simulation speed. The use of fuzzy quadric surfaces minimizes the impact of round-off errors. The provided software includes a Java graphical user interface for editing and debugging the geometry definition file and for visualizing the material structure. Images of the structure are generated by using the tracking subroutines and, hence, they describe the geometry actually passed to the simulation code.
Ribeiro Filho, Mateus Rosas; Siqueira, José Oswaldo; Vangronsveld, Jaco; Soares, Cláudio Roberto Fonsêca Sousa; Curi, Nilton
2011-01-01
The ameliorating effects of different inorganic materials were investigated on a soil originating from a zinc smelter dumping site contaminated by toxic metals. Wild mustard (Sinapis arvensis L.) was used as a test plant. The soil was amended with different doses of mining sludge, Perferric Red Latosol (LVj), steel shots, cyclonic ash, silifertil, and superphosphate. The most effective amendments improved plant growth with 45% and reduced metal uptake by over 70% in comparison to untreated soil. Reductions in availability as estimated by BaCl2-extractable metals reached up to 90% for Zn and 65% for Cd as compared to unamended soil. These reductions were associated with lower shoot and root metal contents. Shoot Zn content was reduced from 1,369 microg g(-1) in plants grown on untreated soil to 377 microg g(-1) when grown on cyclonic ash amended soil while Cd decreased from 267 to 44 microg g(-1) in steel shots amended soil. Superphosphate addition had no ameliorating effect. On the contrary, it increased BaCl2-extractable amounts of Zn. Considering all parameters we determined, steel shots, cyclonic ash and silifertil are the most promising for remediating metal contaminated soil in the tropics. Further studies evaluating impacts, cost-effectiveness and durability of effects will be conducted. PMID:21598779
The Effect of Convolvulus arvensis Dried Extract as a Potential Antioxidant in Food Models
Mohd Azman, Nurul Aini; Gallego, Maria Gabriela; Juliá, Luis; Fajari, Lluis; Almajano, MaríaPilar
2015-01-01
In this study, the antioxidant activity of the Convolvulus arvensis Linn (CA) ethanol extract has been evaluated by different ways. The antioxidant activity of the extract assessed by 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) was 1.62 mmol Trolox equivalents (TE)/g DW, 1.71 mmol TE/g DW and 2.11 mmol TE/g DW, respectively. CA ethanol extract exhibited scavenging activity against the methoxy radical initiated by the Fenton reaction and measured by Electron Paramagnetic Resonance (EPR). The antioxidant effects of lyophilised CA measured in beef patties containing 0.1% and 0.3% (w/w) CA stored in modified atmosphere packaging (MAP) (80% O2 and 20% CO2) was determined. A preliminary study of gelatine based film containing CA showed a strong antioxidant effect in preventing the degradation of lipid in muscle food. Thus, the present results indicate that CA extract can be used as a natural food antioxidant. PMID:26785344
Participation of Photosynthesis in Floral Induction of the Long Day Plant Anagallis arvensis L. 1
Quedado, Rosario M.; Friend, Douglas J.
1978-01-01
The saturating photon flux density (400 to 700 nanometers) for induction of flowering of the long day plant Anagallis arvensis L. was 1,900 micromoles per square meter per second (6,000 foot-candles) when an 8-hour daylength was extended to 24 hours by a single period of supplementary irradiation. The saturating photon flux density for photosynthetic CO2 uptake during the same single supplementary light period was lower, at about 1,000 to 650 micromoles per square meter per second (3,000 to 2,000 foot-candles). The per cent flowering and mean number of floral buds per plant were significantly reduced when the light extension treatment was given in CO2-free air, and glucose (10 kilograms per cubic meter in water) relieved this effect. Glucose solution also significantly increased flowering of plants given supplementary light treatment in atmospheric air under a photon flux density of 80 micromoles per square meter per second. Increasing the CO2 concentration to 1.27 grams per cubic meter of CO2 in air during the supplementary light period did not increase flowering. It is concluded that high photon flux densities promote flowering of Anagallis through both increased photosynthesis and the photomorphogenic action of high irradiance. PMID:16660610
Air pollution induced alterations in assimilate partitioning in Anagallis arvensis L
Khan, F.A.; Iqbal, M.; Ahmad, Z.; Saquib, M.; Ghouse, A.K.M. )
1989-04-01
The Thermal Power Plant Complex of Kasimpur (Aligarh, UP, India) emits enormous amounts of oxides of sulfur, nitrogen, and carbon as well as particulate matters on consuming 3192 MT of coal/day. These effluents induce significant alterations in carbon allocation in Anagallis arvensis populations. Monthly samples of 10 plants each were collected on random basis at seedling to mature stage from 0.5, 2, 6, 12 and 20 km leeward from the power plant. In oven dried samples, assimilate partitioning was noted to be more severely altered by the air pollutants in the seedling stage. In 2 and 3 months old populations, photosynthate allocation to root and shoot was not altered noticeably. Considerable changes in carbon allocation were noted in 4 mo old mature stage. The carbon allocation to fruit was 3 fold and to seed was about 4 fold greater in the population thriving 20 km away from the source than in those growing in the vicinity of the source. Assimilate partitioning was linearly related to the distance from power plant and the productivity of the populations.
ERIC Educational Resources Information Center
National Aeronautics and Space Administration, Hampton, VA. Langley Research Center.
This teaching unit is designed to help students in grades 4-8 explore the concepts of geometry in the context of space navigation. The units in this series have been developed to enhance and enrich mathematics, science, and technology education and to accommodate different teaching and learning styles. Each unit consists of a storyline presenting…
Li, Yajun
2011-04-01
Rectilinear propagation of light rays in homogeneous isotropic media makes it possible for optical generation of ruled surfaces as the ray is deflected by a rotatable mirror. Scan patterns on a plane or curved surface are merely curves on the ruled surface. Based on this understanding, structures of the scan fields produced by mirror-scanning devices of different configurations are investigated in terms of differential geometry. Expressions of the first and second fundamental coefficients and the first and second Gauss differential forms are given for an investigation of the intrinsic properties of the optically generated ruled surfaces. The Plücker ruled conoid is then generalized for mathematical modeling of the scan fields produced by single-mirror scanning devices of different configurations. Part II will be devoted to a study of multi-mirror scanning systems for optical generation of well-known ruled surfaces such as helicoids and hyperbolic paraboloids.
Wei, Wenhui; Li, Yunchang; Wang, Lijun; Liu, Shengyi; Yan, Xiaohong; Mei, Desheng; Li, Yinde; Xu, Yusong; Peng, Pengfei; Hu, Qiong
2010-04-01
An allo-cytoplasmic male sterile line, which was developed through somatic hybridization between Brassica napus and Sinapis arvensis (thus designated as Nsa CMS line), possesses high potential for hybrid production of rapeseed. In order to select for restorer lines, fertile plants derived from the same somatic hybridization combination were self-pollinated and testcrossed with the parental Nsa CMS line for six generations. A novel disomic alien addition line, B. napus-S. arvensis, has been successfully developed. GISH analysis showed that it contains one pair of chromosomes from S. arvensis and 19 pairs from B. napus, and retains stable and regular mitotic and meiotic processes. The addition line displays very strong restoration ability to Nsa CMS line, high resistance to Sclerotinia sclerotiorum and a low incidence of pod shattering. Because the addition line shares these very important agricultural characters, it is a valuable restorer to Nsa CMS line, and is named NR1 here (Nsa restorer no. 1).
Topuz, Muhamet; Nemli, Yildiz; Fatima, Tahira; Mattoo, Autar K
2015-01-01
Biotypes of the broad-leaved wild mustard (Sinapis arvensis L.) found in wheat fields of Aegean and Marmara region of Turkey were characterized and shown to have developed resistance to sulfonylurea (chlorsulfuron), an inhibitor of acetolactate synthase (ALS). DNA sequence analysis of the ALS genes from two such resistant ("R") biotypes, KNF-R1 and KNF-R2, revealed point mutations, CCT (Pro 197) to TCT (Ser 197) in KNF-R1 and CCT (Pro 197) to ACT (Thr 197) in KNF-R2; these substitutions are consistent with the presence of chlorsulfuron-insensitive ALS enzyme activity in the "R" S. arvensis biotypes. An additional phenotype of chlorsulfuron resistance in the Turkish S. arvensis "R" biotypes was revealed in the form of an altered seed dormancy behavior over 4-48 months of dry storage (after-ripening) compared to the susceptible ("S") biotypes. Seeds of the "S" biotypes dry stored for 4 months had a higher initial germination, which sharply decreased with storage time, while the seeds of the "R" biotypes had lower germination after 4-months storage, rising sharply and peaking thereafter by 24 months' of dry storage. The "R" biotype seeds continued to maintain a higher germination percentage even after 48 months of after-ripening. The seed weight of "R" and "S" biotypes after-ripened for 4 months was similar but those after-ripened for 48 months differed, "R" seeds were significantly heavier than those of the "S" seeds. Differential seed germinability between "S" and "R" biotypes was found not a case of differential viability, temperature regimen or non-response to pro-germination hormone GA3. These studies are of relevance to ecological fitness of herbicide-resistant biotypes in terms of seed viability and germination. PMID:26258120
NASA Astrophysics Data System (ADS)
Topuz, Muhamet; Nemli, Yildiz; Fatima, Tahira; Mattoo, Autar
2015-07-01
Biotypes of the broad-leaved wild mustard (Sinapis arvensis L.) found in wheat fields of Aegean and Marmara region of Turkey were characterized and shown to have developed resistance to sulfonylurea (chlorsulfuron), an inhibitor of acetolactate synthase (ALS). DNA sequence analysis of the ALS genes from two such resistant (‘R’) biotypes, KNF-R1 and KNF-R2, revealed point mutations, CCT (Pro 197) to TCT (Ser 197) in KNF-R1 and CCT (Pro 197) to ACT (Thr 197) in KNF-R2; these substitutions are consistent with the presence of chlorsulfuron-insensitive ALS enzyme activity in the ‘R’ S. arvensis biotypes. An additional phenotype of chlorsulfuron resistance in the Turkish S. arvensis ‘R’ biotypes was revealed in the form of an altered seed dormancy behavior over 4 to 48 months of dry storage (after-ripening) compared to the susceptible (‘S’) biotypes. Seeds of the ‘S’ biotypes dry stored for 4 months had a higher initial germination, which sharply decreased with storage time, while the seeds of the ‘R’ biotypes had lower germination after 4-months storage, rising sharply and peaking thereafter by 24 months’ of dry storage. The ‘R’ biotype seeds continued to maintain a higher germination percentage even after 48 months of after-ripening. The seed weight of ‘R’ and ‘S’ biotypes after-ripened for 4 months was similar but those after-ripened for 48 months differed, ‘R’ seeds were significantly heavier than those of the ‘S’ seeds. Differential seed germinability between ‘S’ and ‘R’ biotypes was found not a case of differential viability, temperature regimen or non-response to pro-germination hormone GA3. These studies are of relevance to ecological fitness of herbicide-resistant biotypes in terms of seed viability and germination.
Topuz, Muhamet; Nemli, Yildiz; Fatima, Tahira; Mattoo, Autar K.
2015-01-01
Biotypes of the broad-leaved wild mustard (Sinapis arvensis L.) found in wheat fields of Aegean and Marmara region of Turkey were characterized and shown to have developed resistance to sulfonylurea (chlorsulfuron), an inhibitor of acetolactate synthase (ALS). DNA sequence analysis of the ALS genes from two such resistant (“R”) biotypes, KNF-R1 and KNF-R2, revealed point mutations, CCT (Pro 197) to TCT (Ser 197) in KNF-R1 and CCT (Pro 197) to ACT (Thr 197) in KNF-R2; these substitutions are consistent with the presence of chlorsulfuron-insensitive ALS enzyme activity in the “R” S. arvensis biotypes. An additional phenotype of chlorsulfuron resistance in the Turkish S. arvensis “R” biotypes was revealed in the form of an altered seed dormancy behavior over 4–48 months of dry storage (after-ripening) compared to the susceptible (“S”) biotypes. Seeds of the “S” biotypes dry stored for 4 months had a higher initial germination, which sharply decreased with storage time, while the seeds of the “R” biotypes had lower germination after 4-months storage, rising sharply and peaking thereafter by 24 months' of dry storage. The “R” biotype seeds continued to maintain a higher germination percentage even after 48 months of after-ripening. The seed weight of “R” and “S” biotypes after-ripened for 4 months was similar but those after-ripened for 48 months differed, “R” seeds were significantly heavier than those of the “S” seeds. Differential seed germinability between “S” and “R” biotypes was found not a case of differential viability, temperature regimen or non-response to pro-germination hormone GA3. These studies are of relevance to ecological fitness of herbicide-resistant biotypes in terms of seed viability and germination. PMID:26258120
Kolář, Filip; Fér, Tomáš; Štech, Milan; Trávníček, Pavel; Dušková, Eva; Schönswetter, Peter; Suda, Jan
2012-01-01
Polyploidization is one of the leading forces in the evolution of land plants, providing opportunities for instant speciation and rapid gain of evolutionary novelties. Highly selective conditions of serpentine environments act as an important evolutionary trigger that can be involved in various speciation processes. Whereas the significance of both edaphic speciation on serpentine and polyploidy is widely acknowledged in plant evolution, the links between polyploid evolution and serpentine differentiation have not yet been examined. To fill this gap, we investigated the evolutionary history of the perennial herb Knautia arvensis (Dipsacaceae), a diploid-tetraploid complex that exhibits an intriguing pattern of eco-geographic differentiation. Using plastid DNA sequencing and AFLP genotyping of 336 previously cytotyped individuals from 40 populations from central Europe, we unravelled the patterns of genetic variation among the cytotypes and the edaphic types. Diploids showed the highest levels of genetic differentiation, likely as a result of long term persistence of several lineages in ecologically distinct refugia and/or independent immigration. Recurrent polyploidization, recorded in one serpentine island, seems to have opened new possibilities for the local serpentine genotype. Unlike diploids, the serpentine tetraploids were able to escape from the serpentine refugium and spread further; this was also attributable to hybridization with the neighbouring non-serpentine tetraploid lineages. The spatiotemporal history of K. arvensis allows tracing the interplay of polyploid evolution and ecological divergence on serpentine, resulting in a complex evolutionary pattern. Isolated serpentine outcrops can act as evolutionary capacitors, preserving distinct karyological and genetic diversity. The serpentine lineages, however, may not represent evolutionary 'dead-ends' but rather dynamic systems with a potential to further influence the surrounding populations, e.g., via
Kolář, Filip; Fér, Tomáš; Štech, Milan; Trávníček, Pavel; Dušková, Eva; Schönswetter, Peter; Suda, Jan
2012-01-01
Polyploidization is one of the leading forces in the evolution of land plants, providing opportunities for instant speciation and rapid gain of evolutionary novelties. Highly selective conditions of serpentine environments act as an important evolutionary trigger that can be involved in various speciation processes. Whereas the significance of both edaphic speciation on serpentine and polyploidy is widely acknowledged in plant evolution, the links between polyploid evolution and serpentine differentiation have not yet been examined. To fill this gap, we investigated the evolutionary history of the perennial herb Knautia arvensis (Dipsacaceae), a diploid-tetraploid complex that exhibits an intriguing pattern of eco-geographic differentiation. Using plastid DNA sequencing and AFLP genotyping of 336 previously cytotyped individuals from 40 populations from central Europe, we unravelled the patterns of genetic variation among the cytotypes and the edaphic types. Diploids showed the highest levels of genetic differentiation, likely as a result of long term persistence of several lineages in ecologically distinct refugia and/or independent immigration. Recurrent polyploidization, recorded in one serpentine island, seems to have opened new possibilities for the local serpentine genotype. Unlike diploids, the serpentine tetraploids were able to escape from the serpentine refugium and spread further; this was also attributable to hybridization with the neighbouring non-serpentine tetraploid lineages. The spatiotemporal history of K. arvensis allows tracing the interplay of polyploid evolution and ecological divergence on serpentine, resulting in a complex evolutionary pattern. Isolated serpentine outcrops can act as evolutionary capacitors, preserving distinct karyological and genetic diversity. The serpentine lineages, however, may not represent evolutionary ‘dead-ends’ but rather dynamic systems with a potential to further influence the surrounding populations, e
Kolář, Filip; Fér, Tomáš; Štech, Milan; Trávníček, Pavel; Dušková, Eva; Schönswetter, Peter; Suda, Jan
2012-01-01
Polyploidization is one of the leading forces in the evolution of land plants, providing opportunities for instant speciation and rapid gain of evolutionary novelties. Highly selective conditions of serpentine environments act as an important evolutionary trigger that can be involved in various speciation processes. Whereas the significance of both edaphic speciation on serpentine and polyploidy is widely acknowledged in plant evolution, the links between polyploid evolution and serpentine differentiation have not yet been examined. To fill this gap, we investigated the evolutionary history of the perennial herb Knautia arvensis (Dipsacaceae), a diploid-tetraploid complex that exhibits an intriguing pattern of eco-geographic differentiation. Using plastid DNA sequencing and AFLP genotyping of 336 previously cytotyped individuals from 40 populations from central Europe, we unravelled the patterns of genetic variation among the cytotypes and the edaphic types. Diploids showed the highest levels of genetic differentiation, likely as a result of long term persistence of several lineages in ecologically distinct refugia and/or independent immigration. Recurrent polyploidization, recorded in one serpentine island, seems to have opened new possibilities for the local serpentine genotype. Unlike diploids, the serpentine tetraploids were able to escape from the serpentine refugium and spread further; this was also attributable to hybridization with the neighbouring non-serpentine tetraploid lineages. The spatiotemporal history of K. arvensis allows tracing the interplay of polyploid evolution and ecological divergence on serpentine, resulting in a complex evolutionary pattern. Isolated serpentine outcrops can act as evolutionary capacitors, preserving distinct karyological and genetic diversity. The serpentine lineages, however, may not represent evolutionary 'dead-ends' but rather dynamic systems with a potential to further influence the surrounding populations, e.g., via
Winter, Klaus; Usuda, Hideaki; Tsuzuki, Mikio; Schmitt, Mark; Edwards, Gerald E.; Thomas, Richard J.; Evert, Ray F.
1982-01-01
The leaf anatomy and certain photosynthetic properties of nitrate- and ammonia-grown plants of Moricandia arvensis (L.) DC., a species previously reported to be a C3-C4 intermediate, were investigated. Nitrate-grown plants had a high level of malate in the leaves while ammonia-grown plants had low levels of malate. In young leaves of nitrate-grown plants, there was a diurnal fluctuation of malate content, increasing during the day and decreasing during the night. Titratable acidity remained low in leaves of both nitrate- and ammonia-grown plants. In nitrate-grown plants, the activity of phosphoenolpyruvate (PEP) carboxylase was about 2-fold higher than in ammonia-grown plants, the latter having activity typical of C3 species. Also, in nitrate-grown plants, the ratio of activities of ribulose 1,5-bisphosphate (RuBP) carboxylase/PEP carboxylase was lower than in ammonia-grown plants. Nitrate reductase activities were higher in nitrate- than in ammonia-grown plants and the greatest activity was found in younger leaves. With nitrate-grown plants, during a pulse-chase experiment the label in malate, as a percentage of the total labeled products, increased from about 7% after a 10-second pulse with 14CO2 up to 17% during a 5-minute chase with 12CO2. The pattern of 14C labeling in various metabolites suggests the primary carboxylation is through RuBP carboxylase with a secondary carboxylation through PEP carboxylase. In similar experiments, with ammonia-grown plants, the percentage label in malate was only 0% to 4% with no increase in malate labeling during the chase period. The CO2 compensation point was lower in nitrate-grown than ammonia-grown plants. There was no evidence of Kranz-like anatomy in either the nitrate or ammonia-grown plants. Mitochondria of bundle-sheath cells were strikingly positioned along the inner tangential wall. This might allow the chloroplasts of these cells to fix the mitochondrial photorespired CO2 more effectively and contribute to the low
Cheung, Kyle W; Razeq, Fakhria M; Sauder, Connie A; James, Tracey; Martin, Sara L
2015-05-01
With transgenic crop development it is important to evaluate the potential for transgenes to escape into populations of wild, weedy relatives. Ethiopian mustard (Brassica carinata, BBCC) is easily transformed and is being investigated for uses from biodiesel fuels to biopharmaceuticals. However, little work has been done evaluating its ability to cross with relatives such as wild mustard (Sinapsis arvensis, SrSr), an abundant, cosmopolitan weedy relative. Here we conducted bidirectional crosses with Ethiopian mustard as a maternal parent in 997 crosses and paternal parent in 1,109 crosses. Hybrids were confirmed using flow cytometry and species-specific ITS molecular markers and indicate a high hybridization rate of 6.43 % between Ethiopian mustard (♀) and wild mustard (♂) and a lower, but not insignificant, hybridization rate of 0.01 % in the reverse direction. The majority of the hybrids were homoploid (BCSr) with less than 1 % of pollen production of their parents and low seed production (0.26 seeds/pollination) in crosses and backcrosses indicating a potential for advanced generation hybrids. The accession used had a significant effect on hybrid seed production with different accessions of Ethopian mustard varying in their production of hybrid offspring from 2.69 to 16.34 % and one accession of wild mustard siring almost twice as many hybrid offspring per flower as the other. One pentaploid (BBCCSr) and one hexaploid (BBCCSrSr) hybrid were produced and had higher pollen viability, though no and low seed production, respectively. As wild mustard is self-incompatible and the outcrossing rate of Ethiopian mustard has been estimated as 30 % potential for hybrid production in the wild appears to be high, though the hybridization rate found here represents a worst case scenario as it does not incorporate pre-pollination barriers. Hybridization in the wild needs to be directly evaluated as does the propensity of Ethiopian mustard to volunteer. PMID:25698113
Do the effects of crops on skylark (Alauda arvensis) differ between the field and landscape scales?
Barbottin, Aude; Jiguet, Frédéric; Martin, Philippe
2015-01-01
The promotion of biodiversity in agricultural areas involves actions at the landscape scale, and the management of cropping patterns is considered an important means of achieving this goal. However, most of the available knowledge about the impact of crops on biodiversity has been obtained at the field scale, and is generally grouped together under the umbrella term “crop suitability.” Can field-scale knowledge be used to predict the impact on populations across landscapes? We studied the impact of maize and rapeseed on the abundance of skylark (Alauda arvensis). Field-scale studies in Western Europe have reported diverse impacts on habitat selection and demography. We assessed the consistency between field-scale knowledge and landscape-scale observations, using high-resolution databases describing crops and other habitats for the 4 km2 grid scales analyzed in the French Breeding Bird Survey. We used generalized linear models to estimate the impact of each studied crop at the landscape scale. We stratified the squares according to the local and geographical contexts, to ensure that the conclusions drawn were valid in a wide range of contexts. Our results were not consistent with field knowledge for rapeseed, and were consistent for maize only in grassland contexts. However, the effect sizes were much smaller than those of structural landscape features. These results suggest that upscaling from the field scale to the landscape scale leads to an integration of new agronomic and ecological processes, making the objects studied more complex than simple “crop ∗ species” pairs. We conclude that the carrying capacity of agricultural landscapes cannot be deduced from the suitability of their components. PMID:26213656
NASA Astrophysics Data System (ADS)
Lee, Wei Li; Low, Hong Yee
2016-03-01
Micro- and nanoscale surface textures, when optimally designed, present a unique approach to improve surface functionalities. Coupling surface texture with shape memory polymers may generate reversibly tuneable surface properties. A shape memory polyetherurethane is used to prepare various surface textures including 2 μm- and 200 nm-gratings, 250 nm-pillars and 200 nm-holes. The mechanical deformation via stretching and recovery of the surface texture are investigated as a function of length scales and shapes. Results show the 200 nm-grating exhibiting more deformation than 2 μm-grating. Grating imparts anisotropic and surface area-to-volume effects, causing different degree of deformation between gratings and pillars under the same applied macroscopic strain. Full distribution of stress within the film causes the holes to deform more substantially than the pillars. In the recovery study, unlike a nearly complete recovery for the gratings after 10 transformation cycles, the high contribution of surface energy impedes the recovery of holes and pillars. The surface textures are shown to perform a switchable wetting function. This study provides insights into how geometric features of shape memory surface patterns can be designed to modulate the shape programming and recovery, and how the control of reversibly deformable surface textures can be applied to transfer microdroplets.
Lee, Wei Li; Low, Hong Yee
2016-01-01
Micro- and nanoscale surface textures, when optimally designed, present a unique approach to improve surface functionalities. Coupling surface texture with shape memory polymers may generate reversibly tuneable surface properties. A shape memory polyetherurethane is used to prepare various surface textures including 2 μm- and 200 nm-gratings, 250 nm-pillars and 200 nm-holes. The mechanical deformation via stretching and recovery of the surface texture are investigated as a function of length scales and shapes. Results show the 200 nm-grating exhibiting more deformation than 2 μm-grating. Grating imparts anisotropic and surface area-to-volume effects, causing different degree of deformation between gratings and pillars under the same applied macroscopic strain. Full distribution of stress within the film causes the holes to deform more substantially than the pillars. In the recovery study, unlike a nearly complete recovery for the gratings after 10 transformation cycles, the high contribution of surface energy impedes the recovery of holes and pillars. The surface textures are shown to perform a switchable wetting function. This study provides insights into how geometric features of shape memory surface patterns can be designed to modulate the shape programming and recovery, and how the control of reversibly deformable surface textures can be applied to transfer microdroplets. PMID:27026290
Ovchinnikova, Olga S; Kertesz, Vilmos; Van Berkel, Gary J
2011-01-01
This paper describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection into a continuous flow surface sampling probe/electrospray emitter for mass spectrometry based chemical imaging. The flow probe/emitter device was placed in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collected was immediately aspirated into the probe and on to the electrospray emitter, ionized and detected with the mass spectrometer. Freehand drawn ink lines and letters and an inked fingerprint on microscope slides were analyzed. The circular laser ablation area was about 210 m in diameter and under the conditions used in these experiments the spatial resolution, as determined by the size of the surface features distinguished in the chemical images, was about 100 m.
Solomon-Sathish, Emmanuel; Venkatalakshmi-Aparna, Potluri; Balagopal, Sunderasan
2016-01-01
Background The purpose of this study was to relate the fracture resistance of endodontically treated teeth in relation to post geometry. Material and Methods Forty single rooted mandibular premolars were instrumented by step - back technique and obturated by lateral condensation. Forty teeth were randomly divided into four groups: Reforpost glass fiber X-ray®, RelyX®, Exacto conical® and Parapost Fiber Lux®. The post spaces were prepared using respective drills and luted. The core build up was done and metal crowns were luted. Fracture resistance was determined in universal testing machine. The statistical analysis was done using one way ANOVA and post hoc Tukey Kramer test. Results The teeth restored with Reforpost showed highest fracture resistance followed by Parapost and Exacto conical. The teeth restored with RelyX showed least fracture resistance. The teeth restored with Parapost had less unfavourable fracture followed by exacto conical. Conclusions Parallel design had less number of catastrophic failure and had better fracture resistance. Key words:Fracture resistance, glass fiber post, post geometry, stress. PMID:26855705
Lee, Robert J.; Smithson, Hannah E.
2016-01-01
We tested whether surface specularity alone supports operational color constancy – the ability to discriminate changes in illumination or reflectance. Observers viewed short animations of illuminant or reflectance changes in rendered scenes containing a single spherical surface, and were asked to classify the change. Performance improved with increasing specularity, as predicted from regularities in chromatic statistics. Peak performance was impaired by spatial rearrangements of image pixels that disrupted the perception of illuminated surfaces, but was maintained with increased surface complexity. The characteristic chromatic transformations that are available with non-zero specularity are useful for operational color constancy, particularly if accompanied by appropriate perceptual organisation. PMID:26974938
Savoy, Elizabeth S; Escobedo, Fernando A
2012-11-20
When in contact with a rough solid surface, fluids with low surface tension, such as oils and alkanes, have their lowest free energy in the fully wetted state. For applications where nonwetting by these phillic fluids is desired, some barrier must be introduced to maintain the nonwetted composite state. One way to create this free-energy barrier is to fabricate roughness with reentrant geometry, but the question remains as to whether the free-energy barrier is sufficiently high to prevent wetting. Our goal is to quantify the free-energy landscape for the wetting transition of an oily fluid on a surface of nails and identify significant surface features and conditions that maximize the wetting free-energy barrier (ΔGfwd*). This is a departure from most work on wetting, which focuses on the equilibrium composite and wetted states. We use boxed molecular dynamics (BXD) (Glowacki, D. R.; Paci, E.; Shalashilin, D. V. J. Phys. Chem. B2009, 113, 16603-16611) with a modified control scheme to evaluate both the thermodynamics and kinetics of the transition over a range of surface affinities (chemistry). We find that the reentrant geometry of the nails does create a free-energy barrier to transition for phillic chemistry whereas a corresponding system on straight posts wets spontaneously and, that doubling the nail height more than doubles ΔGfwd*. For neutral to phillic chemistry, the dewetting free-energy barrier is at least an order of magnitude higher than that for wetting, indicating an essentially irreversible wetting transition. Transition rates from BXD simulations and the associated trends agree well with those in our previous study that used forward flux sampling to compute transition rates for similar systems.
NASA Astrophysics Data System (ADS)
Bircher, Chad; Shao, Yiping
2012-11-01
Depth of Interaction (DOI) information can improve quality of reconstructed images acquired from Positron Emission Tomography (PET), especially in high resolution and compact scanners dedicated for breast, brain, or small animal imaging applications. Additionally, clinical scanners with time of flight capability can also benefit from DOI information. One of the most promising methods of determining DOI in a crystal involves reading the signal from two ends of a scintillation crystal, and calculating the signal ratio between the two detectors. This method is known to deliver a better DOI resolution with rough crystals compared to highly polished crystals. However, what is still not well studied is how much of a tradeoff is involved between spatial, energy, temporal, and DOI resolutions as a function of the crystal surface treatment and geometry with the use of Silicon Photomultipliers (SiPM) as the photo detectors. This study investigates the effects of different crystal surface finishes and geometries on energy, timing and DOI resolutions at different crystal depths. The results show that for LYSO scintillators of 1.5×1.5×20 mm3 and 2×2×20 mm3 with their surfaces finished from 0.5 to 30 μm roughness, almost the same energy and coincidence timing resolutions were maintained, around 15% and 2.4 ns, respectively across different crystal depths, while the DOI resolutions were steadily improved from worse than 5 mm to better than 2 mm. They demonstrate that crystal roughness, with proper surface preparing, does not have a significant effect on the energy and coincidence timing resolutions in the crystals examined, and there does not appear to be a tradeoff between improving DOI resolution and degrading other detector performances. These results will be valuable to guide the selection of crystal surface conditions for developing a DOI measurable PET detector with a full array of LYSO scintillators coupled to SiPM arrays.
Manikandan, R.; Sahi, S. V.; Venkatachalam, P.
2015-01-01
The present study was focused on examining the effect of Hg oxidative stress induced physiochemical and genetic changes in M. arvensis seedlings. The growth rate of Hg treated seedlings was decreased to 56.1% and 41.5% in roots and shoots, respectively, compared to the control. Accumulation of Hg level in both roots and shoots was increased with increasing the concentration of Hg. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were found to be increased with increasing the Hg concentration up to 20 mg/L; however, it was decreased at 25 mg/L Hg concentration. The POX enzyme activity was positively correlated with Hg dose. The changes occurring in the random amplification of ploymorphic DNA (RAPD) profiles generated from Hg treated seedlings included variations in band intensity, disappearance of bands, and appearance of new bands compared with the control seedlings. It was concluded that DNA polymorphisms observed with RAPD profile could be used as molecular marker for the evaluation of heavy metal induced genotoxic effects in plant species. The present results strongly suggested that Mentha arvensis could be used as a potential phytoremediator plant in mercury polluted environment. PMID:25654134
Manikandan, R; Sahi, S V; Venkatachalam, P
2015-01-01
The present study was focused on examining the effect of Hg oxidative stress induced physiochemical and genetic changes in M. arvensis seedlings. The growth rate of Hg treated seedlings was decreased to 56.1% and 41.5% in roots and shoots, respectively, compared to the control. Accumulation of Hg level in both roots and shoots was increased with increasing the concentration of Hg. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were found to be increased with increasing the Hg concentration up to 20 mg/L; however, it was decreased at 25 mg/L Hg concentration. The POX enzyme activity was positively correlated with Hg dose. The changes occurring in the random amplification of ploymorphic DNA (RAPD) profiles generated from Hg treated seedlings included variations in band intensity, disappearance of bands, and appearance of new bands compared with the control seedlings. It was concluded that DNA polymorphisms observed with RAPD profile could be used as molecular marker for the evaluation of heavy metal induced genotoxic effects in plant species. The present results strongly suggested that Mentha arvensis could be used as a potential phytoremediator plant in mercury polluted environment.
Sichinava, M B; Mchelidze, K Z; Churadze, M V; Alaniia, M D; Aneli, Dzh N
2014-06-01
The paper presents the results of the study of anatomy and chemical composition of Field Restharrow (Ononis arvensis L.). The existence of triterpene alcohol α-onocerin and isoflavons in the overground organs of the plant is established by chemical analysis. Oxycumarines - scopoletin and scopolin are isolated and identified. Morphological characterization of the whole plant is given. Anatomy of the vegetative organs of the species is examined. Among the main microstructural characteristics multilayer integumentary tissues, active periderm and sclerenchyma cells were specified in roots; and complex radial rays and structural units of wood, located radially, were observed in the central cylinder. Shoots are characterized with intensive pubescence. Mechanical tissues of different structures exist in the parenchime of crust and central cylinder of shoots. Vessels with spiral and spiro-annular thickened walls are located in the libriforms of wood. Leaves of Ononis arvensis are bifacial, mesophile is of dorsiventral structure; central conductive bunch is complex-collateral. Basal cells of upper and lower epidermis belong to of bent-walled type, where paracytal and anisocytal cells of stomatal apparatus are scattered chaotically. PMID:25020180
Manikandan, R; Sahi, S V; Venkatachalam, P
2015-01-01
The present study was focused on examining the effect of Hg oxidative stress induced physiochemical and genetic changes in M. arvensis seedlings. The growth rate of Hg treated seedlings was decreased to 56.1% and 41.5% in roots and shoots, respectively, compared to the control. Accumulation of Hg level in both roots and shoots was increased with increasing the concentration of Hg. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were found to be increased with increasing the Hg concentration up to 20 mg/L; however, it was decreased at 25 mg/L Hg concentration. The POX enzyme activity was positively correlated with Hg dose. The changes occurring in the random amplification of ploymorphic DNA (RAPD) profiles generated from Hg treated seedlings included variations in band intensity, disappearance of bands, and appearance of new bands compared with the control seedlings. It was concluded that DNA polymorphisms observed with RAPD profile could be used as molecular marker for the evaluation of heavy metal induced genotoxic effects in plant species. The present results strongly suggested that Mentha arvensis could be used as a potential phytoremediator plant in mercury polluted environment. PMID:25654134
Perveen, K.; Haseeb, A.; Shukla, P.K.
2010-01-01
Experiment was carried out to determine the effect of Sclerotinia sclerotiorum on the disease development, growth, oil yield and biochemical changes in the plants of Mentha arvensis. With the increase in initial inoculum levels of S. sclerotiorum a corresponding decrease in plant fresh and dry weights were recorded. The maximum reduction in the shoot-roots/suckers fresh weight and shoot-roots/suckers dry weights (39.8%, 43.6%, 40.3% and 42.9%), respectively, was observed at the highest initial inoculum level of 12 g fungal mycelium/5 kg soil as compared to uninoculated control. The infection of roots and suckers due to S. sclerotiorum increased with increasing initial inoculum levels. At the lowest initial inoculum (1.0 g mycelium/5 kg soil), infection was observed 18.0% and at the highest (12 g mycelium/5 kg soil), it was 80.2%. Significant (P ⩽ 0.01) reduction in oil yield, total chlorophyll, total phenol and total sugar content of M. arvensis plants was observed at the lowest inoculum level as compared to uninoculated control. PMID:23961091
NASA Astrophysics Data System (ADS)
Chattopadhyay, A.; Jain, M.; Bhattacharjee, D.
2014-12-01
Sinuous traces of emerging thrust tips, comprising multiple salients and recesses, are commonly observed in orogenic belts (e.g. Lesser Himalayas of India, Nepal and Bhutan) and in accretionary prisms (e.g. Nankai Trough off the coast of Japan). Lateral (along the strike of the deformation zone) variation in the depths of foreland basins (i.e. variable sediment thickness) or in the strength of the basal detachment, or presence of a curved indenter has been traditionally cited to explain the formation of salients in fold-and-thrust belts, although they are not applicable in all cases. In the present work, we have carried out four series of scaled analog model experiments using dry quartz sand, changing the dip of the basal decollément (β = 0° or 5°) and the basal friction (μb = 0.5 or 0.3) to investigate the 3D shape of thrust surfaces under varying overall boundary conditions, but without any lateral variation of these parameters, within the models. The experimental results show that under all boundary conditions, thrust surfaces are curved both in their dip and strike directions (i.e. spoon-shaped in 3D). Multiple concave-upward and convex-upward segments constitute a thrust surface, which produces a sinuous trace when the tip line intersects the Earth's surface. It is also shown that thrust surface curvatures occur at different scales, and the overall thrust surface roughness (corrugations) has a self-affine fractal geometry.
NASA Astrophysics Data System (ADS)
Pommerol, A.; Schmitt, B.
Near-IR reflectance spectroscopy is widely used to detect mineral hydration on Solar System surfaces by the observation of absorption bands at 1.9 and 3 µm. Recent studies established empirical relationships between the strength of the 3 µm band and the water content of the studied minerals (Milliken et al., 2005). These results have especially been applied to the OMEGA dataset to derive global maps of the Martian regolith water content (Jouglet et al., 2006 and Milliken et al., 2006). However, parameters such as surface texture and measurement geometry are known to have a strong effect on reflectance spectra but their influence on the hydration bands is poorly documented. The aim of this work is the determination of the quantitative effects of particle size, mixing between materials with different albedo and measurement geometry on the absorption bands at 1.9 and 3 µm. We used both an experimental and a modeling approach to study these effects. Bidirectional reflectance spectra were measured for series of well characterized samples (smectite, volcanic tuff and coals, pure and mixed) and modeled with optical constants of a smectite (Roush, 2005). Criteria commonly used to estimate the strength of the bands were then calculated on these spectra. We show that particle size has a strong effect on the 1.9 and 3 µm bands strength, especially for the finest particles (less than 200 µm). Mixing between a fine smectite powder and anthracite powders with various particle sizes (modeled by a synthetic neutral material) highlights the strong effect of the materials albedo on the hydration band estimation criteria. Measurement geometry has a significant effect on the bands strength for high phase angles. Furthermore, the relative variations of band strength with measurement geometry appear very dependent on the surface texture. We will present in details the relationships between these physical parameters and various criteria chosen to estimate the hydration bands
Larue, D.K.; Martinez, P.A.
1989-01-01
Based on a combination of Walther's Law of Facies and bed-form climb theory, the authors propose a model that explains how erosion surfaces and vertical sequences of clastic strata are preserved where deposition occurs in channelized or locally erosional environments including fluvial and submarine-channel deposits, barred beaches, and transgressive coastlines. the model considers both lateral and vertical migration of a scour surface and its associated depositional products. As in studies of bed-form climb, they recognize subcritical, critical, and supercritical climb of scour surfaces relative to adjacent depositional forms. 12 figures.
2013-01-01
The effect of B doping on the surface (111) reactivity has, in the present study, been investigated for various surface terminations, H, OH, Oon-top, and F. This type of surface modification has experimentally been proven to be extremely important for, for example, applications based on surface electrochemistry. Density functional theory (DFT) has here been used to study both the local and more global effects of substitutionally positioned B atoms in the upper part of the diamond (111) surface. For this purpose, adsorption energies for the various terminating species have been calculated, and the observed results have been carefully analyzed in order to gain a deeper knowledge about the atomic-level cause of the observed effects. As a result, the B dopant shows a clear, but local, effect for all terminating species investigated. In addition, it is only the radical O-terminating species that show a special and high reactivity on the diamond surface. The other terminating species show a much lower reactivity, which in addition are very similar. PMID:24501614
Ripka, Géza
2014-12-22
A new species of eriophyoid mite, Aculus castriferrei n. sp., associated with Agrimonia eupatoria (Rosaceae) is described and illustrated from Hungary. Morphological differences distinguishing this vagrant species from other rosaceous inhabiting congeners are discussed. Aceria malherbae Nuzzaci is a new record for the eriophyoid fauna of Hungary after it was found causing severe damage symptoms to Convolvulus arvensis L. (Convolvulaceae).
ERIC Educational Resources Information Center
Desseyn, H. O.; And Others
1985-01-01
Compares linear-nonlinear and planar-nonplanar geometry through the valence-shell electron pairs repulsion (V.S.E.P.R.), Mulliken-Walsh, and electrostatic force theories. Indicates that although the V.S.E.P.R. theory has more advantages for elementary courses, an explanation of the best features of the different theories offers students a better…
NASA Astrophysics Data System (ADS)
Korayem, A. H.; Kianfar, A.; Korayem, M. H.
2016-10-01
Atomic force microscopy (AFM) is widely used as a tool in studying surfaces and mechanical properties of materials at nanoscale. This paper deals with mechanical and vibration analysis of AFM vibration in the non-contact and tapping modes for V-shaped piezoelectric micro-cantilever (MC) with geometric discontinuities and cross section variation in the air ambient. In the vibration analysis, Euler-Bernoulli beam theory based on modified couple stress (MCS) theory has been used. The governing equation of motion has been derived by using Hamilton's principle. By adopting finite element method (FEM), the MC differential equation has been solved. Damping matrix was considered in the modal space. Frequency response was obtained by using Laplace transform, and it has been compared with experimental results. Newmark algorithm has been used based on constant average acceleration to analyze time response of MC, and then time response results in the vibration mode, far from the sample surface have been compared with experimental data. In vicinity of sample surface, MC is influenced by various nonlinear forces between the probe tip and sample surface, including van der Waals, contact, and capillary forces. Time response was examined at different distances between MC base and sample surface, and the best distance was selected for topography. Topography results of different types of roughness showed that piezoelectric MC has been improved in the air ambient. Topography showed more accurate forms of roughness, when MC passes through sample surface at higher frequencies. The surface topography investigation for tapping and non-contact modes showed that using of these two modes are suitable for topography.
Floß, Gereon; Granucci, Giovanni; Saalfrank, Peter
2012-12-21
With ongoing miniaturization of electronic devices, the need for individually addressable, switchable molecules arises. An example are azobenzenes on surfaces which have been shown to be switchable between trans and cis forms. Here, we examine the "direct" (rather than substrate-mediated) channel of the trans → cis photoisomerization after ππ∗ excitation of tetra-tert-butyl-azobenzene physisorbed on surfaces mimicking Au(111) and Bi(111), respectively. In spirit of the direct channel, the electronic structure of the surface is neglected, the latter merely acting as a rigid platform which weakly interacts with the molecule via Van-der-Waals forces. Starting from thermal ensembles which represent the trans-form, sudden excitations promote the molecules to ππ∗-excited states which are non-adiabatically coupled among themselves and to a nπ∗-excited and the ground state, respectively. After excitation, relaxation to the ground state by internal conversion takes place, possibly accompanied by isomerization. The process is described here by "on the fly" semiclassical surface hopping dynamics in conjunction with a semiempirical Hamiltonian (AM1) and configuration-interaction type methods. It is found that steric constraints imposed by the substrate lead to reduced but non-vanishing, trans → cis reaction yields and longer internal conversion times than for the isolated molecule. Implications for recent experiments for azobenzenes on surfaces are discussed.
Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E.
2014-06-15
An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label.
NASA Astrophysics Data System (ADS)
Oswald, Patrick; Poy, Guilhem
2015-12-01
Shape measurements after the coalescence of isotropic droplets embedded in a thin sample of a homeotropic nematic phase provides a tool to measure the nematic-isotropic surface tension. In addition, this experiment allows us to check the scaling laws recently given by Brun et al. [P.-T. Brun, M. Nagel, and F. Gallaire, Phys. Rev. E 88, 043009 (2013), 10.1103/PhysRevE.88.043009] to explain the relaxation of ellipsoidal droplets in a Hele-Shaw cell.
Boularas, A. Baudoin, F.; Villeneuve-Faure, C.; Clain, S.; Teyssedre, G.
2014-08-28
Electric Force-Distance Curves (EFDC) is one of the ways whereby electrical charges trapped at the surface of dielectric materials can be probed. To reach a quantitative analysis of stored charge quantities, measurements using an Atomic Force Microscope (AFM) must go with an appropriate simulation of electrostatic forces at play in the method. This is the objective of this work, where simulation results for the electrostatic force between an AFM sensor and the dielectric surface are presented for different bias voltages on the tip. The aim is to analyse force-distance curves modification induced by electrostatic charges. The sensor is composed by a cantilever supporting a pyramidal tip terminated by a spherical apex. The contribution to force from cantilever is neglected here. A model of force curve has been developed using the Finite Volume Method. The scheme is based on the Polynomial Reconstruction Operator—PRO-scheme. First results of the computation of electrostatic force for different tip–sample distances (from 0 to 600 nm) and for different DC voltages applied to the tip (6 to 20 V) are shown and compared with experimental data in order to validate our approach.
Iqbal, M.; Khan, F.A.; Saquib, M.; Ahmad, Z.; Ghouse, A.K.M. )
1989-04-01
Oxides of sulfur, nitrogen and carbon and particulates are the major air pollutants emitted in huge amounts by the Thermal Power Plant Complex of Kasimpur (Aligarh, UP, India) running on 3192 MT of coal/day. These effluents significantly affect reproductive phase of Anagallis arvensis L. Samples of 10 plants each were randomly collected at monthly intervals at seedling to mature stage from 0.5, 2, 6, 12 and 20 km leeward from the power plant complex. Bud formation and flowering were delayed in the population thriving at 0.5 km from the pollution source. As a 2 month old stage, 60% of the population showed a decline in bud formation in the vicinity of the source compared to a heavy bud emergence in the whole population thriving 20 km away from it. Bud formation, flowering fruit set and seed set showed a correlation with multiple growth factors viz productivity, shoot length and distance from the source.
Bittkau, C; Comes, H P
2005-11-01
Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of past fragmentation, dispersal, and genetic drift on taxon diversification. We used phylogeographical (nested clade) and population genetic analyses to elucidate the relative roles of these processes in the evolutionary history of the Aegean Nigella arvensis alliance (= 'coenospecies'). We surveyed chloroplast DNA (cpDNA) variation in 455 individuals from 47 populations (nine taxa) of the alliance throughout its core range in the Aegean Archipelago and surrounding mainland areas of Greece and Turkey. The study revealed the presence of three major lineages, with largely nonoverlapping distributions in the Western, Central, and Eastern Aegean. There is evidence supporting the idea that these major lineages evolved in situ from a widespread (pan-Aegean) ancestral stock as a result of multiple fragmentation events, possibly due to the influence of post-Messinian sea flooding, Pleistocene eustatic changes and corresponding climate fluctuations. Over-sea dispersal and founder events appear to have played a rather insignificant role in the group's history. Rather, all analytical approaches identified the alliance as an organism group with poor seed dispersal capabilities and a susceptibility to genetic drift. In particular, we inferred that the observed level of cpDNA differentiation between Kikladian island populations of Nigella degenii largely reflects population history, (viz. Holocene island fragmentation) and genetic drift in the near absence of seed flow since their time of common ancestry. Overall, our cpDNA data for the N. arvensis alliance in general, and N. degenii in particular, indicate that historical events were important in determining the phylogeographical patterns seen, and that genetic drift has historically been relatively more influential on population structure than has cytoplasmic gene flow.
NASA Astrophysics Data System (ADS)
Vange, Vibekke; Heuch, Ivar; Vandvik, Vigdis
2004-05-01
Germination and seedling establishment are vulnerable stages in the plant life cycle. We investigated how seed mass and family (progeny origin) affect germination and juvenile performance in the grassland herb Knautia arvensis. Seeds were produced by cross-pollination by hand. The fate of 15 individually weighed seeds from each of 15 plants was followed during a 3-month growth chamber experiment. Progeny origin affected germination, both through seed mass and as an independent factor. Two groups of progenies could be distinguished by having rapid or delayed germination. The two groups had similar mean seed masses, but a positive relationship between seed mass and germination rate could be established only among the rapidly germinating progenies. These biologically relevant patterns were revealed because timing of germination was taken into account in the analyses, not only frequencies. Time-to-event data were analysed with failure-time methods, which gave more stable estimates for the relation between germination and seed mass than the commonly applied logistic regression. Progeny origin and seed mass exerted less impact on later characters like juvenile survival, juvenile biomass, and rosette number. These characters were not affected by the timing of germination under the competition-free study conditions. The decrease in the effect of progeny origin from the seed and germination to the juvenile stages suggests that parental effects other than those contributing to the offspring genotype strongly influenced the offspring phenotype at the earliest life stages. Further, the division of progeny germination patterns into two fairly distinct groups indicates that there was a genetic basis for the variation in stratification requirements among parental plants. Field studies are needed to elucidate effects of different timing of germination in the seasonal grasslands that K. arvensis inhabits.
NASA Astrophysics Data System (ADS)
Landis, Emily K.; Karnick, Pushpak
2006-02-01
This study uses new three-dimensional imaging techniques to compare the articular curvature of the proximal tibial articular surface of hominoids. It has been hypothesized that the curvature of the anteroposterior contour of the lateral condyle in particular can be used to differentiate humans and apes and reflect locomotor function. This study draws from a large comparative sample of extant hominoids to obtain quantitative curvature data. Three-dimensional models of the proximal tibiae of 26 human, 15 chimpanzee, 15 gorilla, 17 orangutan, 16 gibbon and four Australopithecus fossil casts (AL 129-1b, AL 288-1aq, AL 333x-26, KNM-KP 29285A) were acquired with a Cyberware Model 15 laser digitizer. Curvature analysis was accomplished using a software program developed at Arizona State University's Partnership for Research In Stereo Modeling (PRISM) lab, which enables the user to extract curvature profiles and compute the difference between analogous curves from different specimens. Results indicate that the curvature of chimpanzee, gorilla and orangutan tibiae is significantly different from the curvature of human tibiae, thus supporting the hypothesized dichotomy between humans and great apes. The non-significant difference between gibbons and all other taxa indicates that gibbons have an intermediate pattern of articular curvature. All four Australopithecus tibia were aligned with the great apes.
NASA Technical Reports Server (NTRS)
Chaussee, Denny S.
1993-01-01
The steady 3D viscous flow past the ONERA M6 wing and a slender delta wing-body with trailing edge control surfaces has been computed. A cell-centered finite-volume Navier-Stokes patched zonal method has been used for the numerical simulation. Both diagonalized and LUSGS schemes have been implemented. Besides the standard nonplanar zonal interfacing techniques, a new virtual zone capability has been employed. For code validation, the transonic flow past the ONERA M5 wing is calculated for angles-of-attack of 3.06 deg and 5.06 deg and compared with the available experiments. The wing-body computational results are compared with experimental data for both trailing-edge flaps deflected. The experimental flow conditions are M subinfinity = 0.4, a turbulent Reynolds number of 5.41 million based on a mean aerodynamic chord of 25.959 inches, adiabatic wall, and angles-of-attack varying from 0 deg to 23.85 deg. The computational results are presented for the 23.85 deg angle-of-attack case. The effects of the base flow due to a model sting, the varying second and fourth order numerical dissipation, and the turbulence model are all considered.
NASA Astrophysics Data System (ADS)
Wang, Wenshan; Zender, Charles S.; van As, Dirk; Smeets, Paul C. J. P.; van den Broeke, Michiel R.
2016-03-01
cycles and inter-annual variabilities of albedo agree better with previous studies. This tilt-corrected shortwave radiation data set derived using the Retrospective, Iterative, Geometry-Based (RIGB) method provide more accurate observations and validations for surface energy budgets studies on the Greenland Ice Sheet, including albedo variations, surface melt simulations and cloud radiative forcing estimates.
Tsutsui, Kota; Jeong, Bum Hee; Ito, Yukiko; Bang, Sang Woo; Kaneko, Yukio
2011-12-01
Intergeneric hybridization was performed between Moricandia arvensis and four inbred lines of Brassica rapa following embryo rescue. Three F(1) hybrid plants were developed from three cross combinations of M. arvensis × B. rapa, and amphidiploids were synthesized by colchicine treatment. Six BC(1) plants were generated from a single cross combination of amphidipolid × B. rapa 'Ko1-303' through embryo rescue. One BC(2) and three BC(3) plants were obtained from successive backcrossing with B. rapa 'Ko1-303' employing embryo rescue. Alloplasmic and monosomic addition lines of B. rapa (Allo-MALs, 2n = 21) were obtained from backcrossed progeny of three BC(3) plants (2n = 21, 22 and 23) without embryo rescue. An alloplasmic line of B. rapa (2n = 20) degenerated before floliation on 1/2 MS medium due to severe chlorosis. Allo-MALs of B. rapa (2n = 21) showed stable male sterility without any abnormal traits in vegetative growth and female fertility. Molecular analyses revealed that the same chromosome and cytoplasm of M. arvensis had been added to each Allo-MAL of B. rapa. This Allo-MAL of B. rapa may be useful material for producing cytoplasmic male sterile lines of B. rapa.
Mao, Shufang; Han, Yonghua; Wu, Xiaoming; An, Tingting; Tang, Jiali; Shen, Junjun; Li, Zongyun
2012-06-01
To further understand the relationships between the SS genome of Sinapis arvensis and the AA, BB genomes in Brassica, genomic DNA of Sinapis arvensis was hybridized to the metaphase chromosomes of Brassica nigra (BB genome), and the metaphase chromosomes and interphase nucleus of Brassica rapa (AA genome) by comparative genomic in situ hybridization (cGISH). As a result, every chromosome of B. nigra had signals along the whole chromosomal length. However, only half of the condensed heterochromatic areas in the interphase nucleus and the chromosomes showed rich signals in Brassica rapa. Interphase nucleus and the metaphase chromosomes of S. arvensis were simultaneously hybridized with digoxigenin-labeled genomic DNA of B. nigra and biotin-labeled genomic DNA of B. rapa. Signals of genomic DNA of B. nigra hybridized throughout the length of all chromosomes and all the condensed heterochromatic areas in the interphase nucleus, except chromosome 4, of which signals were weak in centromeric regions. Signals of the genomic DNA of B. rapa patterned the most areas of ten chromosomes and ten condensed heterochromatic areas, others had less signals. The results showed that the SS genome had homology with AA and BB genomes, but the homology between SS genome and AA genome was clearly lower than that between the SS genome and BB genome.
Mao, Shufang; Han, Yonghua; Wu, Xiaoming; An, Tingting; Tang, Jiali; Shen, Junjun; Li, Zongyun
2012-06-01
To further understand the relationships between the SS genome of Sinapis arvensis and the AA, BB genomes in Brassica, genomic DNA of Sinapis arvensis was hybridized to the metaphase chromosomes of Brassica nigra (BB genome), and the metaphase chromosomes and interphase nucleus of Brassica rapa (AA genome) by comparative genomic in situ hybridization (cGISH). As a result, every chromosome of B. nigra had signals along the whole chromosomal length. However, only half of the condensed heterochromatic areas in the interphase nucleus and the chromosomes showed rich signals in Brassica rapa. Interphase nucleus and the metaphase chromosomes of S. arvensis were simultaneously hybridized with digoxigenin-labeled genomic DNA of B. nigra and biotin-labeled genomic DNA of B. rapa. Signals of genomic DNA of B. nigra hybridized throughout the length of all chromosomes and all the condensed heterochromatic areas in the interphase nucleus, except chromosome 4, of which signals were weak in centromeric regions. Signals of the genomic DNA of B. rapa patterned the most areas of ten chromosomes and ten condensed heterochromatic areas, others had less signals. The results showed that the SS genome had homology with AA and BB genomes, but the homology between SS genome and AA genome was clearly lower than that between the SS genome and BB genome. PMID:22804340
Zargarzadeh, Leila; Elliott, Janet A W
2013-10-22
The behavior of pure fluid confined in a cone is investigated using thermodynamic stability analysis. Four situations are explained on the basis of the initial confined phase (liquid/vapor) and its pressure (above/below the saturation pressure). Thermodynamic stability analysis (a plot of the free energy of the system versus the size of the new potential phase) reveals whether the phase transition is possible and, if so, the number and type (unstable/metastable/stable) of equilibrium states in each of these situations. Moreover we investigated the effect of the equilibrium contact angle and the cone angle (equivalent to the confinement's surface separation distance) on the free energy (potential equilibrium states). The results are then compared to our previous study of pure fluid confined in the gap between a sphere and a flat plate and the gap between two flat plates.1 Confined fluid behavior of the four possible situations (for these three geometries) can be explained in a unified framework under two categories based on only the meniscus shape (concave/convex). For systems with bulk-phase pressure imposed by a reservoir, the stable coexistence of pure liquid and vapor is possible only when the meniscus is concave. PMID:24041429
Shum, D.K.; Bryson, J.W.; Merkle, J.G.
1993-09-01
This study presents preliminary estimates on whether an shallow, axially oriented, inner-surface finite-length flaw in a PWR-RPV would tend to elongate in the axial direction and/or deepen into the wall of the vessel during a postulated PTS transient. Analysis results obtained based on the assumptions of (1) linear-elastic material response, and (2) cladding with same toughness as the base metal, indicate that a nearly semicircular flaw would likely propagate in the axial direction followed by propagation into the wall of the vessel. Note that these results correspond to initiation within the lower-shelf fracture toughness temperature range, and that their general validity within the lower-transition temperature range remains to be determined. The sensitivity of the numerical results aid conclusions to the following analysis assumptions are evaluated: (1) reference flaw geometry along the entire crack front and especially within the cladding region; (2) linear-elastic vs elastic-plastic description of material response; and (3) base-material-only vs bimaterial cladding-base vessel-model assumption. The sensitivity evaluation indicates that the analysis results are very sensitive to the above assumptions.
Waychunas, G.A.; Fuller, C.C.; Davis, J.A.
2002-01-01
"Two-line" ferrihydrite samples precipitated and then exposed to a range of aqueous Zn solutions (10-5 to 10-3 M), and also coprecipitated in similar Zn solutions (pH 6.5), have been examined by Zn and Fe K-edge X-ray absorption spectroscopy. Typical Zn complexes on the surface have Zn-O distances of 1.97(0.2) A?? and coordination numbers of about 4.0(0.5), consistent with tetrahedral oxygen coordination. This contrasts with Zn-O distances of 2.11(.02) A?? and coordination numbers of 6 to 7 in the aqueous Zn solutions used in sample preparation. X-ray absorption extended fine structure spectroscopy (EXAFS) fits to the second shell of cation neighbors indicate as many as 4 Zn-Fe neighbors at 3.44(.04) A?? in coprecipitated samples, and about two Zn-Fe neighbors at the same distance in adsorption samples. In both sets of samples, the fitted coordination number of second shell cations decreases as sorption density increases, indicating changes in the number and type of available complexing sites or the onset of competitive precipitation processes. Comparison of our results with the possible geometries for surface complexes and precipitates suggests that the Zn sorption complexes are inner sphere and at lowest adsorption densities are bidentate, sharing apical oxygens with adjacent edge-sharing Fe(O,OH)6 octahedra. Coprecipitation samples have complexes with similar geometry, but these are polydentate, sharing apices with more than two adjacent edge-sharing Fe(O,OH)6 polyhedra. The results are inconsistent with Zn entering the ferrihydrite structure (i.e., solid solution formation) or formation of other Zn-Fe precipitates. The fitted Zn-Fe coordination numbers drop with increasing Zn density with a minimum of about 0.8(.2) at Zn/(Zn + Fe) of 0.08 or more. This change appears to be attributable to the onset of precipitation of zinc hydroxide polymers with mainly tetrahedral Zn coordination. At the highest loadings studied, the nature of the complexes changes further
Langridge, R.M.; Stenner, H.D.; Fumal, T.E.; Christofferson, S.A.; Rockwell, T.K.; Hartleb, R.D.; Bachhuber, J.; Barka, A.A.
2002-01-01
The Mw 7.4 17 August 1999 İzmit earthquake ruptured five major fault segments of the dextral North Anatolian Fault Zone. The 26-km-long, N86°W-trending Sakarya fault segment (SFS) extends from the Sapanca releasing step-over in the west to near the town of Akyazi in the east. The SFS emerges from Lake Sapanca as two distinct fault traces that rejoin to traverse the Adapazari Plain to Akyazi. Offsets were measured across 88 cultural and natural features that cross the fault, such as roads, cornfield rows, rows of trees, walls, rails, field margins, ditches, vehicle ruts, a dike, and ground cracks. The maximum displacement observed for the İzmit earthquake (∼5.1 m) was encountered on this segment. Dextral displacement for the SFS rises from less than 1 m at Lake Sapanca to greater than 5 m near Arifiye, only 3 km away. Average slip decreases uniformly to the east from Arifiye until the fault steps left from Sagir to Kazanci to the N75°W, 6-km-long Akyazi strand, where slip drops to less than 1 m. The Akyazi strand passes eastward into the Akyazi Bend, which consists of a high-angle bend (18°-29°) between the Sakarya and Karadere fault segments, a 6-km gap in surface rupture, and high aftershock energy release. Complex structural geometries exist between the İzmit, Düzce, and 1967 Mudurnu fault segments that have arrested surface ruptures on timescales ranging from 30 sec to 88 days to 32 yr. The largest of these step-overs may have acted as a rupture segmentation boundary in previous earthquake cycles.
NASA Astrophysics Data System (ADS)
McLin, Kristie S.
Alta Stock does not define a regular isogradic surface, unlike isograds in the inner aureole. Examination of mineral and fluid stabilities in the H2O-CO 2-NaCl system shows that several fluid evolution scenarios, including fluid immiscibility, may produce the observed talc heterogeneity.
Cylindrical geometry hall thruster
Raitses, Yevgeny; Fisch, Nathaniel J.
2002-01-01
An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.
NASA Astrophysics Data System (ADS)
Duke, C. B.; Paton, A.; Lazarides, A.; Kahn, A.
1996-11-01
The atomic geometries of the nonpolar (110) surfaces of CuCl and CuBr are determined by dynamical analysis of the intensities of 13 diffracted beams for CuCl and 16 beams for CuBr associated with normally incident electrons at T=125 and 100 K, respectively. The structural model is specified by six independent variables consisting of the tilt angles (ωi) of the top two layers, the three independent bond lengths (ci-aj) associated with atoms in the top two layers, and the inner potential. The focus of our analysis is the accuracy and precision with which these six structural parameters can be extracted from the measured intensities. A six-dimensional statistical error analysis was performed for two electron-solid scattering models: one model in which all nonstructural parameters assumed the values used in a family of previous structural analyses for the (110) surface of CuCl and other binary zinc-blende structure materials, and one in which these parameters were treated as adjustable parameters to fit the measured intensities. The structural parameters emanating from these two analyses differ by Δω<=4° and Δ(ci-aj)<=0.3 Å. Statistical analysis of uncertainties in the structural parameters resulting only from uncertainties in the measured intensities yields Δω<=1.3°, Δ(ci-aj)<=0.02 Å. Thus, the uncertainties in the structural parameters associated with the selection of the nonstructural parameters, especially the model of the electron exchange interaction, dominate those associated with the uncertainties in the experimental intensity data. Within these uncertainties we find the top-layer bond lengths are contracted by 0.3 Å for CuCl(110) and 0.1 Å or less for CuBr(110). Changes in the backbonds from the anion and cation cannot be established for CuCl using the existing intensity data in our analysis. For CuBr(110) the backbond from the top-layer cation is contracted by 0.35+/-0.2 Å. The tilt angles are ω1=(53+/-2)° for CuCl and (35+/-2)° for CuBr with
Muenchausen, R.E.; Nguyen, D.C.; Keller, R.A.; Nogar, N.S.
1986-01-01
Doubly resonantly enhanced sum frequency generation from rhodamine 6G monolayers adsorbed on glass substates is compared with resonantly enhanced second harmonic generation using a collinear excitation geometry. Second harmonic and sum frequency generation with a non-collinear excitation geometry is also reported where spatial filtering of the non-collinear output is shown to increase the scattered light rejection by more than 4 orders of magnitude.
Doubková, Pavla; Kohout, Petr; Sudová, Radka
2013-10-01
Arbuscular mycorrhizal (AM) symbiosis is among the factors contributing to plant survival in serpentine soils characterised by unfavourable physicochemical properties. However, AM fungi show a considerable functional diversity, which is further modified by host plant identity and edaphic conditions. To determine the variability among serpentine AM fungal isolates in their effects on plant growth and nutrition, a greenhouse experiment was conducted involving two serpentine and two non-serpentine populations of Knautia arvensis plants grown in their native substrates. The plants were inoculated with one of the four serpentine AM fungal isolates or with a complex AM fungal community native to the respective plant population. At harvest after 6-month cultivation, intraradical fungal development was assessed, AM fungal taxa established from native fungal communities were determined and plant growth and element uptake evaluated. AM symbiosis significantly improved the performance of all the K. arvensis populations. The extent of mycorrhizal growth promotion was mainly governed by nutritional status of the substrate, while the effect of AM fungal identity was negligible. Inoculation with the native AM fungal communities was not more efficient than inoculation with single AM fungal isolates in any plant population. Contrary to the growth effects, a certain variation among AM fungal isolates was revealed in terms of their effects on plant nutrient uptake, especially P, Mg and Ca, with none of the AM fungi being generally superior in this respect. Regardless of AM symbiosis, K. arvensis populations significantly differed in their relative nutrient accumulation ratios, clearly showing the plant's ability to adapt to nutrient deficiency/excess.
Instability of supersymmetric microstate geometries
NASA Astrophysics Data System (ADS)
Eperon, Felicity C.; Reall, Harvey S.; Santos, Jorge E.
2016-10-01
We investigate the classical stability of supersymmetric, asymptotically flat, microstate geometries with five non-compact dimensions. Such geometries admit an "evanescent ergosurface": a timelike hypersurface of infinite redshift. On such a surface, there are null geodesics with zero energy relative to infinity. These geodesics are stably trapped in the potential well near the ergosurface. We present a heuristic argument indicating that this feature is likely to lead to a nonlinear instability of these solutions. We argue that the precursor of such an instability can be seen in the behaviour of linear perturbations: nonlinear stability would require that all linear perturbations decay sufficiently rapidly but the stable trapping implies that some linear perturbation decay very slowly. We study this in detail for the most symmetric microstate geometries. By constructing quasinormal modes of these geometries we show that generic linear perturbations decay slower than any inverse power of time.
Cunningham, S.D.; Kapulnik, Y.; Phillips, D.A.
1986-11-01
H/sub 2/ evolved by alfalfa root nodules during the process of N/sub 2/ fixation may be an important factor influencing the distribution of soil bacteria. To test this hypothesis under field conditions, over 700 bacterial isolates were obtained from fallow soil or from the 3-mm layer of soil surrounding alfalfa (Medicago sativa L.) root nodules, alfalfa roots, or bindweed (Convolvulus arvensis L.) roots. Bacteria were isolated under either aerobic or microaerophilic conditions and were tested for their capacity to metabolize H/sub 2/. Isolates showing net H/sub 2/ uptake and /sup 3/H/sub 2/ incorporation activity under laboratory conditions were assigned a Hup/sup +/ phenotype, whereas organisms with significant H/sub 2/ output capacity were designated as a Hout/sup +/ phenotype. Under aerobic isolation conditions two Hup/sup +/ isolates were obtained, whereas under microaerophilic conditions five Hup/sup +/ and two Hout/sup +/ isolates were found. The nine isolates differed on the basis of 24 standard bacteriological characteristics or fatty acid composition. Five of the nine organisms were isolated from soil around root nodules, whereas the other four were found distributed among the other three soil environments. On the basis of the microaerophilic isolations, 4.8% of the total procaryotic isolates from soil around root nodules were capable of oxidizing H/sub 2/, and 1.2% could produce H/sub 2/. Two of the Hup/sup +/ isolates were identified as Rhizobium meliloti by root nodulation tests, but the fact that none of the isolates reduced C/sub 2/H/sub 2/ under the assay conditions suggested that the H/sub 2/ metabolism traits were associated with various hydrogenase systems rather than with nitrogenase activity.
ERIC Educational Resources Information Center
Cukier, Mimi; Asdourian, Tony; Thakker, Anand
2012-01-01
Geometry provides a natural window into what it is like to do mathematics. In the world of geometry, playful experimentation is often more fruitful than following a procedure, and logic plus a few axioms can open new worlds. Nonetheless, teaching a geometry course in a way that combines both rigor and play can be difficult. Many geometry courses…
Nađpal, Jelena D; Lesjak, Marija M; Šibul, Filip S; Anačkov, Goran T; Četojević-Simin, Dragana D; Mimica-Dukić, Neda M; Beara, Ivana N
2016-02-01
The aim of this study was to compare phenolic profile, vitamin C content, antioxidant, anti-inflammatory and cytotoxic activity of rose hips and the preserves (purée and jam) of two Rosa species: renowned Rosa canina L. and unexplored Rosa arvensis Huds. The liquid chromatography-tandem mass spectrometry analysis of 45 phenolics resulted in quantification of 14 compounds, with quercitrin, gallic and protocatechuic acids as the most dominant. High antioxidant potential of R. canina and a moderate activity of R. arvensis extracts were determined through several assays. Purée of both species and methanol extract of air-dried R. canina hips showed some anti-inflammatory (cyclooxygenase-1 and 12-lipooxygense inhibition potency) activity. Purée of R. canina exerted cytotoxic activity only against the HeLa cell line among several others (HeLa, MCF7, HT-29 and MRC-5). The presented results support traditional use of rose hips and their fruit preserves as food with health and nutritional benefits.
Geometry Dependence of Stellarator Turbulence
H.E. Mynick, P. Xanthopoulos and A.H. Boozer
2009-08-10
Using the nonlinear gyrokinetic code package GENE/GIST, we study the turbulent transport in a broad family of stellarator designs, to understand the geometry-dependence of the microturbulence. By using a set of flux tubes on a given flux surface, we construct a picture of the 2D structure of the microturbulence over that surface, and relate this to relevant geometric quantities, such as the curvature, local shear, and effective potential in the Schrodinger-like equation governing linear drift modes.
Combinatorial Geometry Printer Plotting.
1987-01-05
Picture generates plots of two-dimensional slices through the three-dimensional geometry described by the combinatorial geometry (CG) package used in such codes as MORSE and QAD-CG. These plots are printed on a standard line printer.
ERIC Educational Resources Information Center
McDonald, Nathaniel J.
2001-01-01
Chronicles a teacher's first year teaching geometry at the Hershey Montessori Farm School in Huntsburg, Ohio. Instructional methods relied on Euclid primary readings and combined pure abstract logic with practical applications of geometry on the land. The course included geometry background imparted by Montessori elementary materials as well as…
NASA Technical Reports Server (NTRS)
Walker, R. E.; Gokham, B.; Bryant, N. A.; Zobrist, A. L.
1985-01-01
The geometry of two TIPS processed Landsat-5 Thematic Mapper scenes was analyzed and compared with that of SCROUNGE processed Landsat-4 data. Swath-to-swath and band-to-band registration of Washington, DC, and northeastern Iowa scenes was found to be similar to or better than that of Landsat-4 data. Results indicate a high degree of geometric conformity between the images produced by the different systems. The geometric conformity of the TIPS processed images to the Space Oblique Mercator projection, however, proved to be less accurate than the targeted processing error of 15 meters.
Frustrated Order on Extrinsic Geometries
Mbanga, Badel L.; Grason, Gregory M.; Santangelo, Christian D.
2012-01-03
We study, numerically and theoretically, defects in an anisotropic liquid that couple to the extrinsic geometry of a surface. Though the intrinsic geometry tends to confine topological defects to regions of large Gaussian curvature, extrinsic couplings tend to orient the order along the local direction of maximum or minimum bending. This additional frustration is generically unavoidable, and leads to complex ground-state thermodynamics. Using the catenoid as a prototype, we show, in contradistinction to the well-known effects of intrinsic geometry, that extrinsic curvature expels disclinations from the region of maximum curvature above a critical coupling threshold. On catenoids lacking an “inside-outside” symmetry, defects are expelled altogether above a critical neck size.
The Geometry of the Universe: Part 2
ERIC Educational Resources Information Center
Francis, Stephanie
2009-01-01
Hyperbolic geometry occurs on hyperbolic planes--the most commonly cited one being a saddle shape. In this article, the author explores negative hyperbolic curvature, and provides a detailed description of how she constructed two hyperbolic paraboloids. Hyperbolic geometry occurs on surfaces that have negative curvature. (Contains 11 figures and 4…
Warwick, S I; Simard, M-J; Légère, A; Beckie, H J; Braun, L; Zhu, B; Mason, P; Séguin-Swartz, G; Stewart, C N
2003-08-01
The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F(1) hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n=29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum x B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an unreduced gamete of R. raphanistrum and a reduced gamete of B. napus (RrRrAC, 2n=37), both B. napus- and R. raphanistrum-specific AFLP markers, and had <1% pollen viability. No hybrids were detected in the greenhouse experiments (1,534 seedlings), the GFP field experiment (4,059 seedlings) or in commercial fields in Québec and Alberta (22,114 seedlings). No S. arvensis or E. gallicum x B. napus hybrids were detected (42,828 and 21,841 seedlings, respectively) from commercial fields in
Warwick, S I; Simard, M-J; Légère, A; Beckie, H J; Braun, L; Zhu, B; Mason, P; Séguin-Swartz, G; Stewart, C N
2003-08-01
The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F(1) hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n=29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum x B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an unreduced gamete of R. raphanistrum and a reduced gamete of B. napus (RrRrAC, 2n=37), both B. napus- and R. raphanistrum-specific AFLP markers, and had <1% pollen viability. No hybrids were detected in the greenhouse experiments (1,534 seedlings), the GFP field experiment (4,059 seedlings) or in commercial fields in Québec and Alberta (22,114 seedlings). No S. arvensis or E. gallicum x B. napus hybrids were detected (42,828 and 21,841 seedlings, respectively) from commercial fields in
Panda, Pragyanshree; Aiko, Visenuo; Mehta, Alka
2015-06-01
Due to growing concern of consumers about chemical residues in food products, the demand for safe and natural food is increasing greatly. The use of natural additives such as spices and herbal oil as seasoning agents for their antimicrobial activity has been extensively investigated. This paper discusses the efficacy of the aqueous extract of mint (Mentha arvensis) and betel (Piper betle) on the mycelial growth and citrinin production of Penicillium citrinum. The present investigation revealed that mint extract inhibited citrinin production up to 73 % without inhibiting the mycelium growth. The citrinin production decreased with increase in the concentration of mint extract as observed from the data obtained from High pressure liquid chromatography. The samples also showed reduced cytotoxicity on HeLa cells. On the other hand betel extract resulted in stimulatory effect on citrinin production and mycelial growth. The study showed that mint extract has the potential to be used safely for restraining citrinin contamination.
Kolář, Filip; Štech, Milan; Trávníček, Pavel; Rauchová, Jana; Urfus, Tomáš; Vít, Petr; Kubešová, Magdalena; Suda, Jan
2009-01-01
Background and Aims Detailed knowledge of variations in ploidy levels and their geographic distributions is one of the key tasks faced in polyploid research in natural systems. Flow cytometry has greatly facilitated the field of cytogeography by allowing characterization of ploidy levels at both the regional and population scale, and at multiple stages of the life cycle. In the present study, flow cytometry was employed to investigate the patterns and dynamics of ploidy variation in the taxonomically challenging complex Knautia arvensis (Dipsacaceae) and some of its allies (K. dipsacifolia, K. slovaca) in Central Europe. Methods DNA ploidy levels were estimated by DAPI flow cytometry in 5205 adult plants, 228 seedlings and 400 seeds collected from 292 Knautia populations in seven European countries. The flow cytometric data were supplemented with conventional chromosome counts. A subset of 79 accessions was subjected to estimation of the absolute genome size using propidium iodide flow cytometry. Key Results and Conclusions Five different ploidy levels (from 2x to 6x) were found, with triploids of K. arvensis being recorded for the first time. The species also exhibited variation in the monoploid genome size, corresponding to the types of habitats occupied (grassland diploid populations had larger genome sizes than relict and subalpine diploid populations). Disregarding relict populations, the distribution of 2x and 4x cytotypes was largely parapatric, with a diffuse secondary contact zone running along the north-west margin of the Pannonian basin. Spatial segregation of the cytotypes was also observed on regional and microgeographic scales. The newly detected sympatric growth of diploids and tetraploids in isolated relict habitats most likely represents the primary zone of cytotype contact. Ploidy level was found to be a major determinant of the strength of inter-cytotype reproductive barriers. While mixed 2x + 4x populations virtually lacked the intermediate
Planetary Image Geometry Library
NASA Technical Reports Server (NTRS)
Deen, Robert C.; Pariser, Oleg
2010-01-01
The Planetary Image Geometry (PIG) library is a multi-mission library used for projecting images (EDRs, or Experiment Data Records) and managing their geometry for in-situ missions. A collection of models describes cameras and their articulation, allowing application programs such as mosaickers, terrain generators, and pointing correction tools to be written in a multi-mission manner, without any knowledge of parameters specific to the supported missions. Camera model objects allow transformation of image coordinates to and from view vectors in XYZ space. Pointing models, specific to each mission, describe how to orient the camera models based on telemetry or other information. Surface models describe the surface in general terms. Coordinate system objects manage the various coordinate systems involved in most missions. File objects manage access to metadata (labels, including telemetry information) in the input EDRs and RDRs (Reduced Data Records). Label models manage metadata information in output files. Site objects keep track of different locations where the spacecraft might be at a given time. Radiometry models allow correction of radiometry for an image. Mission objects contain basic mission parameters. Pointing adjustment ("nav") files allow pointing to be corrected. The object-oriented structure (C++) makes it easy to subclass just the pieces of the library that are truly mission-specific. Typically, this involves just the pointing model and coordinate systems, and parts of the file model. Once the library was developed (initially for Mars Polar Lander, MPL), adding new missions ranged from two days to a few months, resulting in significant cost savings as compared to rewriting all the application programs for each mission. Currently supported missions include Mars Pathfinder (MPF), MPL, Mars Exploration Rover (MER), Phoenix, and Mars Science Lab (MSL). Applications based on this library create the majority of operational image RDRs for those missions. A
Manukyan, Liana; Milinkovitch, Michel C.
2015-01-01
While recent imaging techniques provide insights into biological processes from the molecular to the cellular scale, phenotypes at larger scales remain poorly amenable to quantitative analyses. For example, investigations of the biophysical mechanisms generating skin morphological complexity and diversity would greatly benefit from 3D geometry and colour-texture reconstructions. Here, we report on R2OBBIE-3D, an integrated system that combines a robotic arm, a high-resolution digital colour camera, an illumination basket of high-intensity light-emitting diodes and state-of-the-art 3D-reconstruction approaches. We demonstrate that R2OBBIE generates accurate 3D models of biological objects between 1 and 100 cm, makes multiview photometric stereo scanning possible in practical processing times, and enables the capture of colour-texture and geometric resolutions better than 15 μm without the use of magnifying lenses. R2OBBIE has the potential to greatly improve quantitative analyses of phenotypes in addition to providing multiple new applications in, e.g., biomedical science. PMID:26039509
NASA Astrophysics Data System (ADS)
Aminfar, H.; Mohammadpourfard, M.; Khajeh, K.
2016-01-01
Effect of geometry on the atherosclerosis is a significant issue, so the 3D s-shape and 2D axisymmetric stenosis tube as a blood vessel have been analyzed in this work. This paper has focused on the most important parameters in the LSC uptake, inlet Re number and infiltration velocity in the presence of non-uniform magnetic field. The magnetic field is arising from the thin wire with electric current placed vertically to the arterial blood vessel. According to the results of this study, applying magnetic field can be a treatment for atherosclerosis by reducing LSC along the vessel wall. It is observed that, application of magnetic field leads to production of a vortex in the flow, high strain rate, increment of WSS, and also reduction in LSC. For solving the mass transport equation, Lumen-wall model has been used. Blood flow has been considered laminar and incompressible containing Ferro fluid (blood and 4 vol% Fe3O4) under steady state conditions. Numerical solution of governing equations was obtained by using the single-phase model and control volume technique for flow field.
Martins, António F; Bessant, Michel; Manukyan, Liana; Milinkovitch, Michel C
2015-01-01
While recent imaging techniques provide insights into biological processes from the molecular to the cellular scale, phenotypes at larger scales remain poorly amenable to quantitative analyses. For example, investigations of the biophysical mechanisms generating skin morphological complexity and diversity would greatly benefit from 3D geometry and colour-texture reconstructions. Here, we report on R(2)OBBIE-3D, an integrated system that combines a robotic arm, a high-resolution digital colour camera, an illumination basket of high-intensity light-emitting diodes and state-of-the-art 3D-reconstruction approaches. We demonstrate that R(2)OBBIE generates accurate 3D models of biological objects between 1 and 100 cm, makes multiview photometric stereo scanning possible in practical processing times, and enables the capture of colour-texture and geometric resolutions better than 15 μm without the use of magnifying lenses. R(2)OBBIE has the potential to greatly improve quantitative analyses of phenotypes in addition to providing multiple new applications in, e.g., biomedical science. PMID:26039509
NASA Astrophysics Data System (ADS)
Boutron, Olivier; Margoum, Christelle; Chovelon, Jean-Marc; Guillemain, CéLine; Gouy, VéRonique
2011-08-01
Pesticides, which have been extensively used in agriculture, have become a major environmental issue, especially regarding surface and groundwater contamination. Of particular importance are vegetated farm drainage ditches, which can play an important role in the mitigation of pesticide contamination by adsorption onto ditch bed substrates. This role is, however, poorly understood, especially regarding the influence of hydrodynamic parameters, which make it difficult to promote best management practice of these systems. We have assessed the influence of three of these parameters (speed of the surface water flow, submergence, and geometrical characteristics of the bed forms) on the transfer and adsorption of selected pesticides (isoproturon, diuron, tebuconazole, and azoxystrobin) into the bed substrate by performing experiments with a tilted experimental flume, using hemp fibers as a standard of natural organic substrates that are found at the bottom of agricultural ditches. Results show the transfer of pesticides from surface water flow into bed substrate is favored, both regarding the amounts transferred into the bed substrate and the kinetics of the transfer, when the surface water speed and the submergence increase and when the bed forms are made of rectangular shapes. Extrapolation of flume data over a distance of several hundred meters suggests that an interesting possibility for improving the mitigation of pesticides in ditches would be to increase the submergence and to favor bed forms that tend to enhance perturbations and subsequent infiltration of the surface water flow.
NASA Astrophysics Data System (ADS)
Zhou, Hu; Zhou, Wang; Zhang, Meixiao; Zhou, Lihua; Ma, Yulong; Wang, Guangyi; Wu, Yong; Li, Bowen; Chen, Ximeng
2016-06-01
We propose a simple theoretical approach to consider negative-ion conversion of neutral atoms grazing on alkali-metal-halide crystal surfaces over the complete velocity range. The conversion process is viewed as a series of successive binary collisions between the projectile and the negatively charged sites on the surface along their trajectories due to localization of valence-band electrons at the anionic sites of the crystal. Conversion from F0 to F- via grazing scattering in LiF(100) and KI(100) is demonstrated with this model, which incorporates the key factors of image interaction and Mott-Littleton polarization interaction for electron capture. It also incorporates the decrease in the electron affinity due to Coulomb barrier tunneling of large-velocity negative ions to the vacuum level near surface anion sites. The pronounced differences in the efficiency of F- formation at LiF(100) and KI(100) surfaces are well explained by the proposed model. The relative efficiency and related saturation of the negative-ion formation for LiF and KI crystals compare well with experimental results.
ERIC Educational Resources Information Center
Lyublinskaya, Irina; Funsch, Dan
2012-01-01
Several interactive geometry software packages are available today to secondary school teachers. An example is The Geometer's Sketchpad[R] (GSP), also known as Dynamic Geometry[R] software, developed by Key Curriculum Press. This numeric based technology has been widely adopted in the last twenty years, and a vast amount of creativity has been…
Euclidean Geometry via Programming.
ERIC Educational Resources Information Center
Filimonov, Rossen; Kreith, Kurt
1992-01-01
Describes the Plane Geometry System computer software developed at the Educational Computer Systems laboratory in Sofia, Bulgaria. The system enables students to use the concept of "algorithm" to correspond to the process of "deductive proof" in the development of plane geometry. Provides an example of the software's capability and compares it to…
NASA Astrophysics Data System (ADS)
Lazarides, A. A.; Duke, C. B.; Paton, A.; Kahn, A.
1995-11-01
Contrary to expectations based on results for other cubic binary semiconductors, an analysis of surface Pb core-level shifts from rocksalt structure PbS(100) suggests large top-layer contractions for group-IV A element chalcogenides. To examine this possibility, we performed a surface-structure analysis for PbTe(100) using eight beams of low-energy electrons diffracted from PbTe(100) at 50 K. A dynamical analysis of the intensities of these beams, based on relativistic potentials shown to be accurate for fifth-row elements, leads to the conclusion that the Pb sublattice in the outer layer is relaxed into the bulk by 0.22 Å (7%) relative to the outer-layer Te sublattice. The average spacing between the first and second layers is 4% smaller than the bulk interlayer spacing, while the average second-to-third-layer spacing is expanded 2% relative to the bulk spacing. Our results are analogous to those found for the (100) surfaces of other cubic materials. A covariance analysis of parameter estimation error indicates that the relaxation detected by the normal-incidence low-energy electron-diffraction experiment is statistically significant, i.e., the deviations of the three surface-structure parameters from the corresponding bulk-structure values are many times larger than the parameter estimation error levels associated with errors in the measured intensities. Moreover, deviations from the bulk structure of the top two layers alone suffice to describe the measurements. Surface-structure optimization that allowed two additional structural parameters (second-layer rumple and third-to-fourth interlayer spacing) to vary yielded a structure insignificantly different from that produced by the three-variable-parameter optimization.
Frolov, Vadim A; Escalada, Artur; Akimov, Sergey A; Shnyrova, Anna V
2015-01-01
Cellular membranes define the functional geometry of intracellular space. Formation of new membrane compartments and maintenance of complex organelles require division and disconnection of cellular membranes, a process termed membrane fission. Peripheral membrane proteins generally control membrane remodeling during fission. Local membrane stresses, reflecting molecular geometry of membrane-interacting parts of these proteins, sum up to produce the key membrane geometries of fission: the saddle-shaped neck and hour-glass hemifission intermediate. Here, we review the fundamental principles behind the translation of molecular geometry into membrane shape and topology during fission. We emphasize the central role the membrane insertion of specialized protein domains plays in orchestrating fission in vitro and in cells. We further compare individual to synergistic action of the membrane insertion during fission mediated by individual protein species, proteins complexes or membrane domains. Finally, we describe how local geometry of fission intermediates defines the functional design of the protein complexes catalyzing fission of cellular membranes. PMID:25062896
NASA Astrophysics Data System (ADS)
Kulikov, G. M.; Mamontov, A. A.; Plotnikova, S. V.; Mamontov, S. A.
2015-11-01
A hybrid-mixed ANS four-node shell element by using the sampling surfaces (SaS) technique is developed. The SaS formulation is based on choosing inside the nth layer In not equally spaced SaS parallel to the middle surface of the shell in order to introduce the displacements of these surfaces as basic shell variables. Such choice of unknowns with the consequent use of Lagrange polynomials of degree In - 1 in the thickness direction for each layer permits the presentation of the layered shell formulation in a very compact form. The SaS are located inside each layer at Chebyshev polynomial nodes that allows one to minimize uniformly the error due to the Lagrange interpolation. To implement the efficient analytical integration throughout the element, the enhanced ANS method is employed. The proposed hybrid-mixed four-node shell element is based on the Hu-Washizu variational equation and exhibits a superior performance in the case of coarse meshes. It could be useful for the 3D stress analysis of thick and thin doubly-curved shells since the SaS formulation gives the possibility to obtain numerical solutions with a prescribed accuracy, which asymptotically approach the exact solutions of elasticity as the number of SaS tends to infinity.
Geometry creation for MCNP by Sabrina and XSM
Van Riper, K.A.
1994-02-01
The Monte Carlo N-Particle transport code MCNP is based on a surface description of 3-dimensional geometry. Cells are defined in terms of boolean operations on signed quadratic surfaces. MCNP geometry is entered as a card image file containing coefficients of the surface equations and a list of surfaces and operators describing cells. Several programs are available to assist in creation of the geometry specification, among them Sabrina and the new ``Smart Editor`` code XSM. We briefly describe geometry creation in Sabrina and then discuss XSM in detail. XSM is under development; our discussion is based on the state of XSM as of January 1, 1994.
Watanabe, Kenichi; Kyomoto, Masayuki; Saiga, Kenichi; Taketomi, Shuji; Inui, Hiroshi; Kadono, Yuho; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Moro, Toru
2015-01-01
The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.
Watanabe, Kenichi; Kyomoto, Masayuki; Saiga, Kenichi; Taketomi, Shuji; Inui, Hiroshi; Kadono, Yuho; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Moro, Toru
2015-01-01
The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances. PMID:26583106
Gu, Weixing; Stalzer, Madelyn Marie; Nicholas, Christopher P; Bhattacharyya, Alak; Motta, Alessandro; Gallagher, James R; Zhang, Guanghui; Miller, Jeffrey T; Kobayashi, Takeshi; Pruski, Marek; Delferro, Massimiliano; Marks, Tobin J
2015-06-01
Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.
Applications of Differential Geometry to Cartography
ERIC Educational Resources Information Center
Benitez, Julio; Thome, Nestor
2004-01-01
This work introduces an application of differential geometry to cartography. The mathematical aspects of some geographical projections of Earth surface are revealed together with some of its more important properties. An important problem since the discovery of the 'spherical' form of the Earth is how to compose a reliable map of the surface of…
Noncommutative Geometry and Physics
Connes, Alain
2006-11-03
In this very short essay we shall describe a 'spectral' point of view on geometry which allows to start taking into account the lessons from both renormalization and of general relativity. We shall first do that for renormalization and explain in rough outline the content of our recent collaborations with Dirk Kreimer and Matilde Marcolli leading to the universal Galois symmetry of renormalizable quantum field theories provided by the renormalization group in its cosmic Galois group incarnation. As far as general relativity is concerned, since the functional integral cannot be treated in the traditional perturbative manner, it relies heavily as a 'sum over geometries' on the chosen paradigm of geometric space. This will give us the occasion to discuss, in the light of noncommutative geometry, the issue of 'observables' in gravity and our joint work with Ali Chamseddine on the spectral action, with a first attempt to write down a functional integral on the space of noncommutative geometries.
ERIC Educational Resources Information Center
Chern, Shiing-Shen
1990-01-01
Discussed are the major historical developments of geometry. Euclid, Descartes, Klein's Erlanger Program, Gaus and Riemann, globalization, topology, Elie Cartan, and an application to molecular biology are included as topics. (KR)
Proof in Transformation Geometry
ERIC Educational Resources Information Center
Bell, A. W.
1971-01-01
The first of three articles showing how inductively-obtained results in transformation geometry may be organized into a deductive system. This article discusses two approaches to enlargement (dilatation), one using coordinates and the other using synthetic methods. (MM)
ERIC Educational Resources Information Center
Emenaker, Charles E.
1999-01-01
Describes a sixth-grade interdisciplinary geometry unit based on Charles Dickens's "A Christmas Carol". Focuses on finding area, volume, and perimeter, and working with estimation, decimals, and fractions in the context of making gingerbread houses. (ASK)
Induced geometry from disformal transformation
NASA Astrophysics Data System (ADS)
Yuan, Fang-Fang; Huang, Peng
2015-05-01
In this note, we use the disformal transformation to induce a geometry from the manifold which is originally Riemannian. The new geometry obtained here can be considered as a generalization of Weyl integrable geometry. Based on these results, we further propose a geometry which is naturally a generalization of Weyl geometry.
Software Geometry in Simulations
NASA Astrophysics Data System (ADS)
Alion, Tyler; Viren, Brett; Junk, Tom
2015-04-01
The Long Baseline Neutrino Experiment (LBNE) involves many detectors. The experiment's near detector (ND) facility, may ultimately involve several detectors. The far detector (FD) will be significantly larger than any other Liquid Argon (LAr) detector yet constructed; many prototype detectors are being constructed and studied to motivate a plethora of proposed FD designs. Whether it be a constructed prototype or a proposed ND/FD design, every design must be simulated and analyzed. This presents a considerable challenge to LBNE software experts; each detector geometry must be described to the simulation software in an efficient way which allows for multiple authors to easily collaborate. Furthermore, different geometry versions must be tracked throughout their use. We present a framework called General Geometry Description (GGD), written and developed by LBNE software collaborators for managing software to generate geometries. Though GGD is flexible enough to be used by any experiment working with detectors, we present it's first use in generating Geometry Description Markup Language (GDML) files to interface with LArSoft, a framework of detector simulations, event reconstruction, and data analyses written for all LAr technology users at Fermilab. Brett is the other of the framework discussed here, the General Geometry Description (GGD).
2005-01-01
The Common Geometry Module (CGM) is a code library which provides geometry functionality used for mesh generation and other applications. This functionality includes that commonly found in solid modeling engines, like geometry creation, query and modification; CGM also includes capabilities not commonly found in solid modeling engines, like geometry decomposition tools and support for shared material interfaces. CGM is built upon the ACIS solid modeling engine, but also includes geometry capability developed beside and onmore » top of ACIS. CGM can be used as-is to provide geometry functionality for codes needing this capability. However, CGM can also be extended using derived classes in C++, allowing the geometric model to serve as the basis for other applications, for example mesh generation. CGM is supported on Sun Solaris, SGI, HP, IBM, DEC, Linux and Windows NT platforms. CGM also indudes support for loading ACIS models on parallel computers, using MPI-based communication. Future plans for CGM are to port it to different solid modeling engines, including Pro/Engineer or SolidWorks. CGM is being released into the public domain under an LGPL license; the ACIS-based engine is available to ACIS licensees on request.« less
On the geometry of a smooth model of a fibre product of families of K3 surfaces
Nikol'skaya, O V
2014-02-28
The Hodge conjecture on algebraic cycles is proved for a smooth projective model X of a fibre product X{sub 1}×{sub C}X{sub 2} of nonisotrivial 1-parameter families of K3 surfaces (possibly with degeneracies) X{sub k}→C (k=1,2) over a smooth projective curve C under the assumption that, for generic geometric fibres X{sub 1s} and X{sub 2s}, the ring End{sub Hg(X{sub 1{sub s)}}}NS{sub Q}(X{sub 1s}){sup ⊥} is an imaginary quadratic field, rankNS(X{sub 1s})≠18, and End{sub Hg(X{sub 2{sub s)}}}NS{sub Q}(X{sub 2s}){sup ⊥} is a totally real field or else rankNS(X{sub 1s})
NASA Technical Reports Server (NTRS)
Whitehead, V. S.; Johnson, W. R.; Mathews, M. L.; Horvath, N. C.
1983-01-01
Data from the Advanced Very High Resolution Radiometer aboard the NOAA polar orbiting satellite are being operationally applied to provide estimates of vegetation cover and/or condition over a large part of the earth by the USDA. The wide scan angle (+ or - 54 deg) of this system permits daily views of the earth when used to its limits. Five-day repetitive coverage is acquired, assuming cloud-free conditions, in current operations which limit the use of the scan to the center + or - 14 deg of swath. While use of the full scan width would provide clear acquisitions frequent enough to monitor crop development and condition even with normal cloudiness, these off-nadir data are made difficult to interpret due to the non-Lambertian nature of the surface, enhanced effect of the atmosphere, inclusion of subpixel and thin invisible clouds in the scene, and differences in illumination across the scene; all of which contribute to variations in observed reflected radiation. Some approaches to provide corrections for these effects are discussed here.
Interactive rendering of dynamic geometry.
Ponchio, Federico; Hormann, Kai
2008-01-01
Fluid simulations typically produce complex three-dimensional (3D) isosurfaces whose geometry and topology change over time. The standard way of representing such "dynamic geometry" is by a set of isosurfaces that are extracted individually at certain time steps. An alternative strategy is to represent the whole sequence as a four-dimensional (4D) tetrahedral mesh. The iso-surface at a specific time step can then be computed by intersecting the tetrahedral mesh with a 3D hyperplane. This not only allows the animation of the surface continuously over time without having to worry about the topological changes, but also enables simplification algorithms to exploit temporal coherence. We show how to interactively render such 4D tetrahedral meshes by improving previous GPU-accelerated techniques and building an out-of-core multi-resolution structure based on quadric error simplification. As a second application, we apply our framework to time-varying surfaces that result from morphing one triangle mesh into another. PMID:18467764
Nesa, Mst. Luthfun; Jahan, Ismet Ara
2015-01-01
Cnicus arvensis is used by many ethnic groups for inflammation, pain, and other ailments. In this study, reducing sugar, carbohydrate, alkaloid, steroid, tannin, flavonoid, and saponin groups were identified using standard chromogenic method. In high-performance liquid chromatography, vanillic acid and epicatechin were identified in the extract. Antinociceptive test by acetic acid induced writhing inhibition resulted 43.17 and 95.08% inhibition for 100 and 200 mg/kg body weight, comparing with standard diclofenac Na with 74.86% inhibition for 25 mg/kg body weight. In formalin induced paw licking test for antinociceptive activity, the extract inhibited 69.87 and 75.55% licking for 150 and 300 mg/kg body weight comparing with the inhibition (68.56%) of diclofenac Na for 10 mg/kg body weight at first phase. At late phase, the extract showed 73.12 and 87.46% licking comparing with licking inhibition (71.69%) by diclofenac Na at the same dose. In open field test for CNS depressant activity, the extract showed depression of locomotor activity for 150 and 300 mg/kg body weight comparing with diazepam for 10 mg/kg body weight. All results were statistically significant (P < 0.01). The identified polyphenols are reputed for antinociceptive and CNS depressant activity. The present findings support the use of this plant in pain. PMID:25648520
Viji, Pankyamma; Binsi, Puthanpurakkal Kizhakkathil; Visnuvinayagam, Sivam; Bindu, Jaganath; Ravishankar, Chandragiri Nagarajarao; Srinivasa Gopal, Teralandur Krishnaswamy
2015-10-01
Efficacy of mint (Mentha arvensis) leaf and citrus (Citrus aurantium) peel extracts in retarding the quality changes in Indian mackerel during chilled storage was investigated. Mint leaf extract showed higher quantity of phenolics and superior in-vitro antioxidant activities than citrus peel extract. Gutted mackerel were given a dip treatment in mint extract (0.5 %, w/v) and citrus extract (1 % w/v), packed in LDPE pouches and stored at 0-2 °C. The biochemical quality indices viz. total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), free fattyacids (FFA) were significantly (p < 0.05) lower in mint extract (ME) treated fishes compared to citrus extract (CE) treated and control fishes (C) without any treatment. Plant extract treatment significantly inhibited lipid oxidation in mackerel as indicated by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Aerobic plate count (APC) was markedly higher in C group followed by CE group throughout the storage period. As per sensory evaluation, shelf life of Indian mackerel was determined to be 11-13 days for C group, 13-15 days for CE group and 16-17 days for ME group, during storage at 0-2 °C. PMID:26396373
Viji, Pankyamma; Binsi, Puthanpurakkal Kizhakkathil; Visnuvinayagam, Sivam; Bindu, Jaganath; Ravishankar, Chandragiri Nagarajarao; Srinivasa Gopal, Teralandur Krishnaswamy
2015-10-01
Efficacy of mint (Mentha arvensis) leaf and citrus (Citrus aurantium) peel extracts in retarding the quality changes in Indian mackerel during chilled storage was investigated. Mint leaf extract showed higher quantity of phenolics and superior in-vitro antioxidant activities than citrus peel extract. Gutted mackerel were given a dip treatment in mint extract (0.5 %, w/v) and citrus extract (1 % w/v), packed in LDPE pouches and stored at 0-2 °C. The biochemical quality indices viz. total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), free fattyacids (FFA) were significantly (p < 0.05) lower in mint extract (ME) treated fishes compared to citrus extract (CE) treated and control fishes (C) without any treatment. Plant extract treatment significantly inhibited lipid oxidation in mackerel as indicated by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Aerobic plate count (APC) was markedly higher in C group followed by CE group throughout the storage period. As per sensory evaluation, shelf life of Indian mackerel was determined to be 11-13 days for C group, 13-15 days for CE group and 16-17 days for ME group, during storage at 0-2 °C.
Vimolmangkang, Sornkanok; Sitthithaworn, Worapan; Vannavanich, Danai; Keattikunpairoj, Sunisa; Chittasupho, Chuda
2010-01-01
The purpose of this study was to determine the differences between spearmint (Mentha spicata L.) and Japanese mint (M. arvensis L. var. piperascens Malinv.) cultivated in either soil or nutrient solution using the deep flow technique (DFT). The differences were measured in terms of harvest period (full bloom period) and quantity and chemical components of volatile oils. The spearmint and Japanese mint were cultivated in four different nutrient formulas: plant standard nutrient, plant standard nutrient with an amino acid mixture, plant standard nutrient with a sulphur compound, and a combination of plant standard nutrient with an amino acid mixture and a sulphur compound. We observed that cultivation of spearmint and Japanese mint in nutrient solution using DFT is an effective method to provide high production of volatile oil, since it results in an earlier harvest period and higher quantity of volatile oil. We determined that for spearmint an amino acid mixture is an appropriate nutrient supplement to enhance production of volatile oil with optimum carvone content. Finally, we observed high menthol content in Japanese mint grown in all four nutrient formulas; however, supplementation with a combination of sulphur fertilisation and amino acid mixture yields the highest quantity of volatile oil.
Kiran, Usha; Patra, D D
2003-02-01
Pot experiments were conducted to evaluate the relative performance of medicinal and aromatic plant materials and dicyandiamide (DCD) as nitrification inhibitors to regulate transformation of N from urea. Their effect on the efficiencies of use of N by Japanese mint (Mentha arvensis cv. Hy 77) was tested. Urea was coated with these materials viz., Mentha spicata, Artemisia annua or DCD at the rate of 5% (w/w) of fertilizer urea using an appropriate coating technique. Nimin (tetranortriterpenoids, an ethanol extract of neem (Azadirachta indica Juss) coating was done at the rate of 1% w/w of urea. Fertilizer nitrogen was applied at 100 and 200 mg kg(-1) soil. These natural coating materials significantly increased the herb and essential oil yields of the crop at both rates of fertilizer nitrogen compared to urea alone and were found to be as effective as DCD in retarding NO3- formation in soil. Herb yield increased by 6-81% when compared to uncoated urea. The increase in essential oil yield ranged between 3% and 68% due to coating. The effectiveness of the nitrification-inhibitor--coated urea, however, varied with the soils used and the rate of fertilizer nitrogen applied. The results suggest that the natural products could be potential nitrification inhibitors for increasing fertilizer N use efficiency.
NASA Astrophysics Data System (ADS)
Ochiai, T.; Nacher, J. C.
2011-09-01
Recently, the application of geometry and conformal mappings to artificial materials (metamaterials) has attracted the attention in various research communities. These materials, characterized by a unique man-made structure, have unusual optical properties, which materials found in nature do not exhibit. By applying the geometry and conformal mappings theory to metamaterial science, it may be possible to realize so-called "Harry Potter cloaking device". Although such a device is still in the science fiction realm, several works have shown that by using such metamaterials it may be possible to control the direction of the electromagnetic field at will. We could then make an object hidden inside of a cloaking device. Here, we will explain how to design invisibility device using differential geometry and conformal mappings.
2011-01-01
Cells are highly complex and orderly machines, with defined shapes and a startling variety of internal organizations. Complex geometry is a feature of both free-living unicellular organisms and cells inside multicellular animals. Where does the geometry of a cell come from? Many of the same questions that arise in developmental biology can also be asked of cells, but in most cases we do not know the answers. How much of cellular organization is dictated by global cell polarity cues as opposed to local interactions between cellular components? Does cellular structure persist across cell generations? What is the relationship between cell geometry and tissue organization? What ensures that intracellular structures are scaled to the overall size of the cell? Cell biology is only now beginning to come to grips with these questions. PMID:21880160
Students Discovering Spherical Geometry Using Dynamic Geometry Software
ERIC Educational Resources Information Center
Guven, Bulent; Karatas, Ilhan
2009-01-01
Dynamic geometry software (DGS) such as Cabri and Geometers' Sketchpad has been regularly used worldwide for teaching and learning Euclidean geometry for a long time. The DGS with its inductive nature allows students to learn Euclidean geometry via explorations. However, with respect to non-Euclidean geometries, do we need to introduce them to…
Computational fluid dynamics using CATIA created geometry
NASA Astrophysics Data System (ADS)
Gengler, Jeanne E.
1989-07-01
A method has been developed to link the geometry definition residing on a CAD/CAM system with a computational fluid dynamics (CFD) tool needed to evaluate aerodynamic designs and requiring the memory capacity of a supercomputer. Requirements for surfaces suitable for CFD analysis are discussed. Techniques for developing surfaces and verifying their smoothness are compared, showing the capability of the CAD/CAM system. The utilization of a CAD/CAM system to create a computational mesh is explained, and the mesh interaction with the geometry and input file preparation for the CFD analysis is discussed.
Computational synthetic geometry
Sturmfels, B. )
1988-01-01
This book deals with methods for realizing abstract geometric objects in concrete vector spaces. It considers a large class of problems from convexity and discrete geometry including constructing convex polytopes from simplicial complexes, vector geometries from incidence structures and hyperplane arrangements from oriented matroids. It appears that algorithms for these constructions exist if and only if arbitrary polynomial equations are decidable with respect to the underlying field. Besides such complexity theorems, a variety of symbolic algorithms are discussed, and the methods are applied to obtain mathematical results on convex polytopes, projective configurations and the combinatories of Grassmann varieties.
Advanced geometries and regimes
Bulanov, S. S.; Bulanov, S. V.; Turchetti, G.; Limpouch, J.; Klimo, O.; Psikal, J.; Margarone, D.; Korn, G.
2013-07-26
We review and discuss different schemes of laser ion acceleration as well as advanced target geometries in connection with the development of the laser-driven proton source for hadron therapy of oncological diseases, which is a part of the ELIMED project.
Spacetime and Euclidean geometry
NASA Astrophysics Data System (ADS)
Brill, Dieter; Jacobson, Ted
2006-04-01
Using only the principle of relativity and Euclidean geometry we show in this pedagogical article that the square of proper time or length in a two-dimensional spacetime diagram is proportional to the Euclidean area of the corresponding causal domain. We use this relation to derive the Minkowski line element by two geometric proofs of the spacetime Pythagoras theorem.
ERIC Educational Resources Information Center
Cooper, Brett D.; Barger, Rita
2009-01-01
The many connections between music and mathematics are well known. The length of a plucked string determines its tone, the time signature of a piece of music is a ratio, and note durations are measured in fractions. One connection commonly overlooked is that between music and geometry--specifically, geometric transformations, including…
ERIC Educational Resources Information Center
Hartz, Viggo
1981-01-01
Allowing students to use a polystyrene cutter to fashion their own three-dimensional models is suggested as a means of allowing individuals to experience problems and develop ideas related to solid geometry. A list of ideas that can lead to mathematical discovery is provided. (MP)
Teaching Geometry with Tangrams.
ERIC Educational Resources Information Center
Russell, Dorothy S.; Bologna, Elaine M.
1982-01-01
Geometry is viewed as the most neglected area of the elementary school mathematics curriculum. Tangram activities provide numerous worthwhile mathematical experiences for children. A method of constructing tangrams through paper folding is followed by suggested spatial visualization, measurement, and additional activities. (MP)
Sliding vane geometry turbines
Sun, Harold Huimin; Zhang, Jizhong; Hu, Liangjun; Hanna, Dave R
2014-12-30
Various systems and methods are described for a variable geometry turbine. In one example, a turbine nozzle comprises a central axis and a nozzle vane. The nozzle vane includes a stationary vane and a sliding vane. The sliding vane is positioned to slide in a direction substantially tangent to an inner circumference of the turbine nozzle and in contact with the stationary vane.
ERIC Educational Resources Information Center
MacKeown, P. K.
1984-01-01
Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)
ERIC Educational Resources Information Center
Martin, John
2010-01-01
The cycloid has been called the Helen of Geometry, not only because of its beautiful properties but also because of the quarrels it provoked between famous mathematicians of the 17th century. This article surveys the history of the cycloid and its importance in the development of the calculus.
Atiyah, Michael; Dijkgraaf, Robbert; Hitchin, Nigel
2010-01-01
We review the remarkably fruitful interactions between mathematics and quantum physics in the past decades, pointing out some general trends and highlighting several examples, such as the counting of curves in algebraic geometry, invariants of knots and four-dimensional topology. PMID:20123740
ERIC Educational Resources Information Center
Case, Christine L.
1991-01-01
Presented is an activity in which students make models of viruses, which allows them to visualize the shape of these microorganisms. Included are some background on viruses, the biology and geometry of viruses, directions for building viruses, a comparison of cells and viruses, and questions for students. (KR)
ERIC Educational Resources Information Center
KLIER, KATHERINE M.
PRESENTED IS A FUSED COURSE IN PLANE, SOLID, AND COORDINATE GEOMETRY. ELEMENTARY SET THEORY, LOGIC, AND THE PRINCIPLE OF SEPARATION PROVIDE UNIFYING THREADS THROUGHOUT THE TEXT. THE TWO CURRICULUM GUIDES HAVE BEEN PREPARED FOR USE WITH TWO DIFFERENT TEXTS. EITHER CURRICULUM GUIDE MAY BE USED DEPENDING UPON THE CHOICE OF THE TEACHER AND THE NEEDS…
NASA Astrophysics Data System (ADS)
Prástaro, Agostino
2008-02-01
Following our previous results on this subject [R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(I): Webs on PDE's and integral bordism groups. The general theory, Adv. Math. Sci. Appl. 17 (2007) 239-266; R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(II): Webs on PDE's and integral bordism groups. Applications to Riemannian geometry PDE's, Adv. Math. Sci. Appl. 17 (2007) 267-285; A. Prástaro, Geometry of PDE's and Mechanics, World Scientific, Singapore, 1996; A. Prástaro, Quantum and integral (co)bordism in partial differential equations, Acta Appl. Math. (5) (3) (1998) 243-302; A. Prástaro, (Co)bordism groups in PDE's, Acta Appl. Math. 59 (2) (1999) 111-201; A. Prástaro, Quantized Partial Differential Equations, World Scientific Publishing Co, Singapore, 2004, 500 pp.; A. Prástaro, Geometry of PDE's. I: Integral bordism groups in PDE's, J. Math. Anal. Appl. 319 (2006) 547-566; A. Prástaro, Geometry of PDE's. II: Variational PDE's and integral bordism groups, J. Math. Anal. Appl. 321 (2006) 930-948; A. Prástaro, Th.M. Rassias, Ulam stability in geometry of PDE's, Nonlinear Funct. Anal. Appl. 8 (2) (2003) 259-278; I. Stakgold, Boundary Value Problems of Mathematical Physics, I, The MacMillan Company, New York, 1967; I. Stakgold, Boundary Value Problems of Mathematical Physics, II, Collier-MacMillan, Canada, Ltd, Toronto, Ontario, 1968], integral bordism groups of the Navier-Stokes equation are calculated for smooth, singular and weak solutions, respectively. Then a characterization of global solutions is made on this ground. Enough conditions to assure existence of global smooth solutions are given and related to nullity of integral characteristic numbers of the boundaries. Stability of global solutions are related to some characteristic numbers of the space-like Cauchy dataE Global solutions of variational problems constrained by (NS) are classified by means of suitable integral bordism groups too.
An introduction to Minkowski geometries
NASA Astrophysics Data System (ADS)
Farnsworth, David L.
2016-07-01
The fundamental ideas of Minkowski geometries are presented. Learning about Minkowski geometries can sharpen our students' understanding of concepts such as distance measurement. Many of its ideas are important and accessible to undergraduate students. Following a brief overview, distance and orthogonality in Minkowski geometries are thoroughly discussed and many illustrative examples and applications are supplied. Suggestions for further study of these geometries are given. Indeed, Minkowski geometries are an excellent source of topics for undergraduate research and independent study.
ERIC Educational Resources Information Center
Actuarial Foundation, 2013
2013-01-01
"Setting the Stage with Geometry" is a new math program aligned with the National Council of Teachers of Mathematics (NCTM) standards that is designed to help students in grades 6-8 build and reinforce basic geometry skills for measuring 2D and 3D shapes. Developed by The Actuarial Foundation, this program seeks to provide skill-building math…
Geometry and the Design of Product Packaging
ERIC Educational Resources Information Center
Cherico, Cindy M.
2011-01-01
The most common question the author's students ask is, "When will I ever use this in real life?" To address this question in her geometry classes, the author sought to create a project that would incorporate a real-world business situation with their lesson series on the surface area and volume of three-dimensional objects--specifically, prisms,…
Transport Code for Regular Triangular Geometry
1993-06-09
DIAMANT2 solves the two-dimensional static multigroup neutron transport equation in planar regular triangular geometry. Both regular and adjoint, inhomogeneous and homogeneous problems subject to vacuum, reflective or input specified boundary flux conditions are solved. Anisotropy is allowed for the scattering source. Volume and surface sources are allowed for inhomogeneous problems.
Convex geometry analysis method of hyperspectral data
NASA Astrophysics Data System (ADS)
Gong, Yanjun; Wang, XiChang; Qi, Hongxing; Yu, BingXi
2003-06-01
We present matrix expression of convex geometry analysis method of hyperspectral data by linear mixing model and establish a mathematic model of endmembers. A 30-band remote sensing image is applied to testify the model. The results of analysis reveal that the method can analyze mixed pixel questions. The targets that are smaller than earth surface pixel can be identified by applying the method.
Nebeck, H.E.
1986-08-01
The MAZE mesh generator represents an arbitrary two dimensional region of space as an ordered collection of quadrilateral elements. Each element is defined by its four corner points (nodes) and an integer material number. Models are created by subdividing the region(s) of interest into one or more PARTS and specifying the element distribution in each part. Then, parts can be merged together to form the meshed representation of the entire region. Applying boundary conditions and describing material properties completes the model construction process. This activity takes place in three distinct phases: phase I-define geometry, subdivide regions into elements; phase II-refine geometry, establish interface and boundary conditions; phase III-describe material properties. This work presents explanations and examples of the phase I commands, along with an overview of the MAZE mesh generation process.
Inflation from quantum geometry.
Bojowald, Martin
2002-12-23
Quantum geometry predicts that a universe evolves through an inflationary phase at small volume before exiting gracefully into a standard Friedmann phase. This does not require the introduction of additional matter fields with ad hoc potentials; rather, it occurs because of a quantum gravity modification of the kinetic part of ordinary matter Hamiltonians. An application of the same mechanism can explain why the present day cosmological acceleration is so tiny.
NASA Astrophysics Data System (ADS)
Bengtsson, Ingemar; Zyczkowski, Karol
2007-12-01
Preface; 1. Convexity, colours and statistics; 2. Geometry of probability distributions; 3. Much ado about spheres; 4. Complex projective spaces; 5. Outline of quantum mechanics; 6. Coherent states and group actions; 7. The stellar representation; 8. The space of density matrices; 9. Purification of mixed quantum states; 10. Quantum operations; 11. Duality: maps versus states; 12. Density matrices and entropies; 13. Distinguishability measures; 14. Monotone metrics and measures; 15. Quantum entanglement; Epilogue; Appendices; References; Index.
Freezing in confined geometries
NASA Technical Reports Server (NTRS)
Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.
1992-01-01
Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.
Integral geometry and holography
Czech, Bartlomiej; Lamprou, Lampros; McCandlish, Samuel; Sully, James
2015-10-27
We present a mathematical framework which underlies the connection between information theory and the bulk spacetime in the AdS_{3}/CFT_{2} correspondence. A key concept is kinematic space: an auxiliary Lorentzian geometry whose metric is defined in terms of conditional mutual informations and which organizes the entanglement pattern of a CFT state. When the field theory has a holographic dual obeying the Ryu-Takayanagi proposal, kinematic space has a direct geometric meaning: it is the space of bulk geodesics studied in integral geometry. Lengths of bulk curves are computed by kinematic volumes, giving a precise entropic interpretation of the length of any bulk curve. We explain how basic geometric concepts -- points, distances and angles -- are reflected in kinematic space, allowing one to reconstruct a large class of spatial bulk geometries from boundary entanglement entropies. In this way, kinematic space translates between information theoretic and geometric descriptions of a CFT state. As an example, we discuss in detail the static slice of AdS_{3} whose kinematic space is two-dimensional de Sitter space.
Integral geometry and holography
Czech, Bartlomiej; Lamprou, Lampros; McCandlish, Samuel; Sully, James
2015-10-27
We present a mathematical framework which underlies the connection between information theory and the bulk spacetime in the AdS3/CFT2 correspondence. A key concept is kinematic space: an auxiliary Lorentzian geometry whose metric is defined in terms of conditional mutual informations and which organizes the entanglement pattern of a CFT state. When the field theory has a holographic dual obeying the Ryu-Takayanagi proposal, kinematic space has a direct geometric meaning: it is the space of bulk geodesics studied in integral geometry. Lengths of bulk curves are computed by kinematic volumes, giving a precise entropic interpretation of the length of any bulkmore » curve. We explain how basic geometric concepts -- points, distances and angles -- are reflected in kinematic space, allowing one to reconstruct a large class of spatial bulk geometries from boundary entanglement entropies. In this way, kinematic space translates between information theoretic and geometric descriptions of a CFT state. As an example, we discuss in detail the static slice of AdS3 whose kinematic space is two-dimensional de Sitter space.« less
Emergent Complex Network Geometry
NASA Astrophysics Data System (ADS)
Wu, Zhihao; Menichetti, Giulia; Rahmede, Christoph; Bianconi, Ginestra
2015-05-01
Networks are mathematical structures that are universally used to describe a large variety of complex systems such as the brain or the Internet. Characterizing the geometrical properties of these networks has become increasingly relevant for routing problems, inference and data mining. In real growing networks, topological, structural and geometrical properties emerge spontaneously from their dynamical rules. Nevertheless we still miss a model in which networks develop an emergent complex geometry. Here we show that a single two parameter network model, the growing geometrical network, can generate complex network geometries with non-trivial distribution of curvatures, combining exponential growth and small-world properties with finite spectral dimensionality. In one limit, the non-equilibrium dynamical rules of these networks can generate scale-free networks with clustering and communities, in another limit planar random geometries with non-trivial modularity. Finally we find that these properties of the geometrical growing networks are present in a large set of real networks describing biological, social and technological systems.
Topping, Christopher J.; Odderskær, Peter; Kahlert, Johnny
2013-01-01
Agent-based simulation models provide a viable approach for developing applied models of species and systems for predictive management. However, there has been some reluctance to use these models for policy applications due to complexity and the need for improved testing and communication of the models. We present the development and testing of a comprehensive model for Skylark (Alauda arvensis) in Danish agricultural landscapes. The model is part of the ALMaSS system, which considers not only individual skylarks, but also the detailed dynamic environment from which they obtain the information necessary to simulate their behaviour. Population responses emerge from individuals interacting with each other and the environment. Model development and testing was carried out using pattern-oriented modelling. The testing procedure was based on the model's ability to represent detailed real world patterns of distribution and density, reproductive performance and seasonal changes in territory numbers. Data to support this was collected over a 13-year period and comprised detailed field observations of breeding birds and intensive surveys. The model was able to recreate the real world data patterns accurately; it was also able to simultaneously fit a number of other secondary system properties which were not formally a part of the testing procedure. The correspondence of model output to real world data and sensitivity analysis are presented and discussed, and the model's description is provided in ODdox format (a formal description inter-linked to the program code). Detailed and stringent tests for model performance were carried out, and standardised model description and open access to the source code were provided to open development of the skylark model to others. Over and above documenting the utility of the model, this open process is essential to engender the user trust and ensure continued development of these comprehensive systems for applied purposes. PMID:23762430
Bose, Subir K; Yadav, Ritesh Kumar; Mishra, Smrati; Sangwan, Rajender S; Singh, A K; Mishra, B; Srivastava, A K; Sangwan, Neelam S
2013-05-01
Extensive research is going on throughout the world to find out new molecules from natural sources to be used as plant growth promoter. Mentha arvensis L. is the main source of menthol rich essential oil used commercially in various food, pharmaceutical and other preparations. Experiments were conducted on field grown plants for understanding the effect of calliterpenone (CA), a stereo-isomer of abbeokutone, in comparison to gibberellic acid (GA3) on growth attributes, trichomes, essential oil biosynthesis and expression of some oil biosynthetic pathway genes. The exogenous application of CA (1 μM, 10 μM and 100 μM) was found to be better in improving plant biomass and stolon yield, leaf area, branching and leaf stem ratio than with counterpart GA3 at the same concentrations. CA treated plants showed higher glandular trichome number, density and diameter and also correlated with enhanced oil biogenetic capacity as revealed by feeding labeled (14)C-sucrose for 72 h to excised shoots. Semi-quantitative PCR analysis of key pathway genes revealed differential up regulation under CA treatments. Transcript level of menthol dehydrogenase/menthone reductase was found highly up regulated in CA treated plants with increased content of menthone and menthol in oil. These findings demonstrate that CA positively regulated the yields by enhanced branching and higher density of trichomes resulting into higher accumulation of essential oil. The results suggest CA as a novel plant derived diterpenoid with growth promoting action and opens up new possibilities for improving the crop yields and essential oil biosynthesis in qualitative and quantitative manner. PMID:23514759
Bose, Subir K; Yadav, Ritesh Kumar; Mishra, Smrati; Sangwan, Rajender S; Singh, A K; Mishra, B; Srivastava, A K; Sangwan, Neelam S
2013-05-01
Extensive research is going on throughout the world to find out new molecules from natural sources to be used as plant growth promoter. Mentha arvensis L. is the main source of menthol rich essential oil used commercially in various food, pharmaceutical and other preparations. Experiments were conducted on field grown plants for understanding the effect of calliterpenone (CA), a stereo-isomer of abbeokutone, in comparison to gibberellic acid (GA3) on growth attributes, trichomes, essential oil biosynthesis and expression of some oil biosynthetic pathway genes. The exogenous application of CA (1 μM, 10 μM and 100 μM) was found to be better in improving plant biomass and stolon yield, leaf area, branching and leaf stem ratio than with counterpart GA3 at the same concentrations. CA treated plants showed higher glandular trichome number, density and diameter and also correlated with enhanced oil biogenetic capacity as revealed by feeding labeled (14)C-sucrose for 72 h to excised shoots. Semi-quantitative PCR analysis of key pathway genes revealed differential up regulation under CA treatments. Transcript level of menthol dehydrogenase/menthone reductase was found highly up regulated in CA treated plants with increased content of menthone and menthol in oil. These findings demonstrate that CA positively regulated the yields by enhanced branching and higher density of trichomes resulting into higher accumulation of essential oil. The results suggest CA as a novel plant derived diterpenoid with growth promoting action and opens up new possibilities for improving the crop yields and essential oil biosynthesis in qualitative and quantitative manner.
Automatic Conversion of Conceptual Geometry to CFD Geometry for Aircraft Design
NASA Technical Reports Server (NTRS)
Li, Wu
2007-01-01
Conceptual aircraft design is usually based on simple analysis codes. Its objective is to provide an overall system performance of the developed concept, while preliminary aircraft design uses high-fidelity analysis tools such as computational fluid dynamics (CFD) analysis codes or finite element structural analysis codes. In some applications, such as low-boom supersonic concept development, it is important to be able to explore a variety of drastically different configurations while using CFD analysis to check whether a given configuration can be tailored to have a low-boom ground signature. It poses an extremely challenging problem of integrating CFD analysis in conceptual design. This presentation will discuss a computer code, called iPatch, for automatic conversion of conceptual geometry to CFD geometry. In general, conceptual aircraft geometry is not as well-defined as a CAD geometry model. In particular, a conceptual aircraft geometry model usually does not define the intersection curves for the connecting surfaces. The computer code iPatch eliminates the gap between conceptual geometry and CFD geometry by accomplishing the following three tasks automatically: (1) use bicubic B-splines to extrapolate (if necessary) each surface in a conceptual geometry so that all the independently defined geometry components (such as wing and fuselage) can be intersected to form a watertight CFD geometry, (2) compute the intersection curves of surface patches at any resolution (up to 10-7 accuracy) specified by users, and (3) write the B-spline surface patches and the corresponding boundary points for the watertight CFD geometry in the format that can be directly exported to the meshing tool VGRID in the CFD software TetrUSS. As a result, conceptual designers can get quick feedback on the aerodynamic characteristics of their concepts, which will allow them to understand some subtlety in their concepts and to be able to assess their concepts with a higher degree of
Thermal geometry from CFT at finite temperature
NASA Astrophysics Data System (ADS)
Gan, Wen-Cong; Shu, Fu-Wen; Wu, Meng-He
2016-09-01
We present how the thermal geometry emerges from CFT at finite temperature by using the truncated entanglement renormalization network, the cMERA. For the case of 2d CFT, the reduced geometry is the BTZ black hole or the thermal AdS as expectation. In order to determine which spacetimes prefer to form, we propose a cMERA description of the Hawking-Page phase transition. Our proposal is in agreement with the picture of the recent proposed surface/state correspondence.
Differential Geometry Based Multiscale Models
Wei, Guo-Wei
2010-01-01
Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atom-istic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier–Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson–Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson–Nernst–Planck equations that
Differential geometry based multiscale models.
Wei, Guo-Wei
2010-08-01
Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atomistic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier-Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson-Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson-Nernst-Planck equations that are
Differential geometry based multiscale models.
Wei, Guo-Wei
2010-08-01
Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atomistic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier-Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson-Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson-Nernst-Planck equations that are
Geometry for the Secondary School
ERIC Educational Resources Information Center
Moalem, D.
1977-01-01
A sequential but non-axiomatic high school geometry course which includes Euclidean, transformation, and analytic geometry and vectors and matrices, and emphasizes the invariance property of transformations, is outlined. Sample problems, solutions, and comments are included. (MN)
Computer-Aided Geometry Modeling
NASA Technical Reports Server (NTRS)
Shoosmith, J. N. (Compiler); Fulton, R. E. (Compiler)
1984-01-01
Techniques in computer-aided geometry modeling and their application are addressed. Mathematical modeling, solid geometry models, management of geometric data, development of geometry standards, and interactive and graphic procedures are discussed. The applications include aeronautical and aerospace structures design, fluid flow modeling, and gas turbine design.
Teaching of Geometry in Bulgaria
ERIC Educational Resources Information Center
Bankov, Kiril
2013-01-01
Geometry plays an important role in the school mathematics curriculum all around the world. Teaching of geometry varies a lot (Hoyls, Foxman, & Kuchemann, 2001). Many countries revise the objectives, the content, and the approaches to the geometry in school. Studies of the processes show that there are not common trends of these changes…
GEMPAK: An arbitrary aircraft geometry generator
NASA Technical Reports Server (NTRS)
Stack, S. H.; Edwards, C. L. W.; Small, W. J.
1977-01-01
A computer program, GEMPAK, has been developed to aid in the generation of detailed configuration geometry. The program was written to allow the user as much flexibility as possible in his choices of configurations and the detail of description desired and at the same time keep input requirements and program turnaround and cost to a minimum. The program consists of routines that generate fuselage and planar-surface (winglike) geometry and a routine that will determine the true intersection of all components with the fuselage. This paper describes the methods by which the various geometries are generated and provides input description with sample input and output. Also included are descriptions of the primary program variables and functions performed by the various routines. The FORTRAN program GEMPAK has been used extensively in conjunction with interfaces to several aerodynamic and plotting computer programs and has proven to be an effective aid in the preliminary design phase of aircraft configurations.
First-order Dyson coordinates and geometry.
Hermes, Matthew R; Hirata, So
2013-08-15
The mathematical constructs of the Dyson coordinates and geometry are introduced. The former are a unitary transformation of the normal coordinates and the anharmonic vibrational counterpart of the Dyson orbitals in electronic structure theory. The first-order Dyson coordinates bring the sums of the harmonic force constants and their first-order diagrammatic perturbation corrections (the first-order Dyson self-energy) to a diagonal form. The first-order Dyson geometry has no counterpart in electronic structure theory. It is the point on the potential energy surface at which the sums of the energy gradients and their first-order diagrammatic perturbation corrections vanish. It agrees with the vibrationally averaged geometry of vibrational self-consistent field (VSCF) theory in the bulk limit. These constructs provide a unified view of the relationship of VSCF and its diagrammatically size-consistent modifications as well as the self-consistent phonon method widely used in solid-state physics.
NASA Astrophysics Data System (ADS)
Bengtsson, Ingemar; Zyczkowski, Karol
2006-05-01
Quantum information theory is at the frontiers of physics, mathematics and information science, offering a variety of solutions that are impossible using classical theory. This book provides an introduction to the key concepts used in processing quantum information and reveals that quantum mechanics is a generalisation of classical probability theory. After a gentle introduction to the necessary mathematics the authors describe the geometry of quantum state spaces. Focusing on finite dimensional Hilbert spaces, they discuss the statistical distance measures and entropies used in quantum theory. The final part of the book is devoted to quantum entanglement - a non-intuitive phenomenon discovered by Schrödinger, which has become a key resource for quantum computation. This richly-illustrated book is useful to a broad audience of graduates and researchers interested in quantum information theory. Exercises follow each chapter, with hints and answers supplied. The first book to focus on the geometry of quantum states Stresses the similarities and differences between classical and quantum theory Uses a non-technical style and numerous figures to make the book accessible to non-specialists
Geometry of Fractional Quantum Hall Fluids
NASA Astrophysics Data System (ADS)
Cho, Gil Young
2015-03-01
Fractional quantum Hall (FQH) fluids of two-dimensional electron gases (2DEG) in large magnetic fields are fascinating topological states of matter. As such they are characterized by universal properties such as their fractional quantum Hall conductivity, fractionally charged anyonic excitations and a degeneracy of topological origin on surfaces with the topology of a torus. Quite surprisingly these topological fluids also couple to the geometry on which the 2DEG resides and have universal responses to adiabatic changes in the geometry. These responses are given by a Wen-Zee term (which describes the coupling of the currents to the spin connection of the geometry) and a gravitational Chern-Simons term which reflects the universal energy and momentum transport along the edges of the FQH state. We use a field theory of the FQH states to derive these universal responses. To account for the coupling to the background geometry, we show that the concept of flux attachment needs to be modified and use it to derive the geometric responses from Chern-Simons theories. We show that the resulting composite particles minimally couple to the spin connection of the geometry. Taking account of the framing anomaly of the quantum Chern-Simons theories, we derive a consistent theory of geometric responses from the Chern-Simons effective field theories and from parton constructions, and apply it to both abelian and non-abelian states. This work was supported in part by the NSF Grant DMR-1408713.
Correa, Diego H.; Silva, Guillermo A.
2008-07-28
We discuss how geometrical and topological aspects of certain (1/2)-BPS type IIB geometries are captured by their dual operators in N = 4 Super Yang-Mills theory. The type IIB solutions are characterized by arbitrary droplet pictures in a plane and we consider, in particular, axially symmetric droplets. The 1-loop anomalous dimension of the dual gauge theory operators probed with single traces is described by some bosonic lattice Hamiltonians. These Hamiltonians are shown to encode the topology of the droplets. In appropriate BMN limits, the Hamiltonians spectrum reproduces the spectrum of near-BPS string excitations propagating along each of the individual edges of the droplet. We also study semiclassical regimes for the Hamiltonians. For droplets having disconnected constituents, the Hamiltonian admits different complimentary semiclassical descriptions, each one replicating the semiclassical description for closed strings extending in each of the constituents.
Critique of information geometry
Skilling, John
2014-12-05
As applied to probability, information geometry fails because probability distributions do not form a metric space. Probability theory rests on a compelling foundation of elementary symmetries, which also support information (aka minus entropy, Kullback-Leibler) H(p;q) as the unique measure of divergence from source probability distribution q to destination p. Because the only compatible connective H is from≠to asymmetric, H(p;q)≠H(q;p), there can be no compatible geometrical distance (which would necessarily be from=to symmetric). Hence there is no distance relationship compatible with the structure of probability theory. Metrics g and densities sqrt(det(g)) interpreted as prior probabilities follow from the definition of distance, and must fail likewise. Various metrics and corresponding priors have been proposed, Fisher's being the most popular, but all must behave unacceptably. This is illustrated with simple counter-examples.
Optically defined mechanical geometry
NASA Astrophysics Data System (ADS)
Barasheed, Abeer Z.; Müller, Tina; Sankey, Jack C.
2016-05-01
In the field of optomechanics, radiation forces have provided a particularly high level of control over the frequency and dissipation of mechanical elements. Here we propose a class of optomechanical systems in which light exerts a similarly profound influence over two other fundamental parameters: geometry and mass. By applying an optical trap to one lattice site of an extended phononic crystal, we show it is possible to create a tunable, localized mechanical mode. Owing to light's simultaneous and constructive coupling with the structure's continuum of modes, we estimate that a trap power at the level of a single intracavity photon should be capable of producing a significant effect within a realistic, chip-scale device.
Magnetism in curved geometries
NASA Astrophysics Data System (ADS)
Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys
2016-09-01
Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.
Magnetism in curved geometries
NASA Astrophysics Data System (ADS)
Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys
2016-09-01
Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii-Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.
The geometry of the 37-tile microwave antenna support structure
NASA Technical Reports Server (NTRS)
Finley, L. A.
1980-01-01
The geometry of the support structure for a proposed parabolic shaped microwave antenna is examined. The surface of the antenna is comprised of 37 hexagonal shaped tiles, each connected to a truss module. The units are joined together to form a rigidized, faceted, concave parabolic surface. The geometry specifications are described through an explanation of the structural components which make up the antenna, a description of the coordinate system devised to identify the structure, and a presentation of the nondimensional results.
Extraction electrode geometry for a calutron
Veach, A.M.; Bell, W.A. Jr.
1975-09-23
This patent relates to an improved geometry for the extraction electrode and the ground electrode utilized in the operation of a calutron. The improved electrodes are constructed in a partial-picture-frame fashion with the slits of both electrodes formed by two tungsten elongated rods. Additional parallel spaced-apart rods in each electrode are used to establish equipotential surfaces over the rest of the front of the ion source. (auth)
Investigating Fractal Geometry Using LOGO.
ERIC Educational Resources Information Center
Thomas, David A.
1989-01-01
Discusses dimensionality in Euclidean geometry. Presents methods to produce fractals using LOGO. Uses the idea of self-similarity. Included are program listings and suggested extension activities. (MVL)
ERIC Educational Resources Information Center
Scanlon, Regina M.
2003-01-01
Describes an engaging project in which students have to design and construct a three-dimensional candy box that would appeal to children. Requires students to make the box out of prisms, pyramids, or cylinders, determine the surface area and volume of the solids, and write a persuasive business letter. (YDS)
GPS: Geometry, Probability, and Statistics
ERIC Educational Resources Information Center
Field, Mike
2012-01-01
It might be said that for most occupations there is now less of a need for mathematics than there was say fifty years ago. But, the author argues, geometry, probability, and statistics constitute essential knowledge for everyone. Maybe not the geometry of Euclid, but certainly geometrical ways of thinking that might enable us to describe the world…
Linguistic geometry for autonomous navigation
Stilman, B.
1995-09-01
To discover the inner properties of human expert heuristics, which were successful in a certain class of complex control systems, we develop a formal theory, the Linguistic Geometry. This paper reports two examples of application of Linguistic Geometry to autonomous navigation of aerospace vehicles that demonstrate dramatic search reduction.
Lobachevsky's Geometry and Research of Geometry of the Universe
NASA Astrophysics Data System (ADS)
Brylevskaya, L. I.
2008-10-01
For the first time N. I. Lobachevsky gave a talk on the new geometry in 1826; three years after he had published a work "On the fundamentals of geometry", containing all fundamental theorems and methods of non-Euclidean geometry. A small part of the article was devoted to the study of geometry of the Universe. The interpretation of geometrical concepts in pure empirical way was typical for mathematicians at the beginning of the XIX century; in this connection it was important for scientists to find application of his geometry. Having the purpose to determine experimentally the properties of real physical Space, Lobachevsky decided to calculate the sum of angles in a huge triangle with two vertexes in opposite points of the terrestrial orbit and the third -- on the remote star. Investigating the possibilities of solution of the set task, Lobachevsky faced the difficulties of theoretical, technical and methodological character. More detailed research of different aspects of the problem led Lobachevsky to the comprehension of impossibility to obtain the values required for the goal achievement, and he called his geometry an imaginary geometry.
An elementary discussion of propellant flame geometry
Buckmaster, J.; Jackson, T.L.; Yao, J.
1999-05-01
The authors examine the geometry of diffusion flames generated by the burning of a heterogeneous solid propellant, using a simple model designed to provide qualitative insights. In the fast chemistry limit a strategy is used which has its roots in Burke and Schumann`s 1928 study of diffusion flames, albeit with different boundary conditions. This shows that the stoichiometric level surface (SLS) intersects the propellant surface at a point displaced from the fuel/oxidizer interface, and the variations of this displacement with Peclet number are discussed. The authors show that for model sandwich propellants, or their axisymmetric counterpart, the geometry of the SLS when the core is oxidizer is quite different from the geometry of the SLS when the core is fuel. Also, it is much easier to quench the flame on an oxidizer core, by reducing the Peclet number, than it is to quench the flame on a fuel core. When finite chemistry effects are accounted for, the flame only occupies a portion of the SLS, and there is a leading edge structure in which premixing plays a role. Enhancement of the burning rate due to premixing is identified, but a well-defined tribrachial structure is not observed. The authors show how a sharp reduction in pressure can lead to a detachment of the flame from the SLS, with subsequent quenching as it is swept downstream.
Generating Composite Overlapping Grids on CAD Geometries
Henshaw, W.D.
2002-02-07
We describe some algorithms and tools that have been developed to generate composite overlapping grids on geometries that have been defined with computer aided design (CAD) programs. This process consists of five main steps. Starting from a description of the surfaces defining the computational domain we (1) correct errors in the CAD representation, (2) determine topology of the patched-surface, (3) build a global triangulation of the surface, (4) construct structured surface and volume grids using hyperbolic grid generation, and (5) generate the overlapping grid by determining the holes and the interpolation points. The overlapping grid generator which is used for the final step also supports the rapid generation of grids for block-structured adaptive mesh refinement and for moving grids. These algorithms have been implemented as part of the Overture object-oriented framework.
Tube-based geometries for organic photovoltaics
NASA Astrophysics Data System (ADS)
Li, Yuan; Peterson, Eric D.; Huang, Huihui; Wang, Mingjun; Xue, Dan; Nie, Wanyi; Zhou, Wei; Carroll, David L.
2010-06-01
We demonstrate a waveguiding tube-based optical geometry that provides a general approach to improving organic photovoltaic performance. By fabricating bulk-heterojunction photovoltaics onto thin tubular light pipes, the optical energy can be effectively captured within the absorbing layer without associated reflective losses at the front and rear surfaces of the devices as is typical in planar structures. We have used a common absorber system: poly-3-hexyl-thiophene:phenyl-C61-butyric-acid-methyl-ester to demonstrate these tubular optical geometries result in very little overall radiative loss. Surprisingly, this also leads to an overall broadening of the absorption window for the device as indicated by the external quantum efficiency.
Guiding chemical pulses through geometry: Y junctions.
Qiao, L; Kevrekidis, I G; Punckt, C; Rotermund, H H
2006-03-01
We study computationally and experimentally the propagation of chemical pulses in complex geometries. The reaction of interest, CO oxidation, takes place on single crystal Pt(110) surfaces that are microlithographically patterned; they are also addressable through a focused laser beam, manipulated through galvanometer mirrors, capable of locally altering the crystal temperature and thus affecting pulse propagation. We focus on sudden changes in the domain shape (corners in a Y-junction geometry) that can affect the pulse dynamics; we also show how brief, localized temperature perturbations can be used to control reactive pulse propagation. The computational results are corroborated through experimental studies in which the pulses are visualized using reflection anisotropy microscopy. PMID:16605643
Quantum Consequences of Parameterizing Geometry
NASA Astrophysics Data System (ADS)
Wanas, M. I.
2002-12-01
The marriage between geometrization and quantization is not successful, so far. It is well known that quantization of gravity , using known quantization schemes, is not satisfactory. It may be of interest to look for another approach to this problem. Recently, it is shown that geometries with torsion admit quantum paths. Such geometries should be parameterizied in order to preserve the quantum properties appeared in the paths. The present work explores the consequences of parameterizing such geometry. It is shown that quantum properties, appeared in the path equations, are transferred to other geometric entities.
NASA Astrophysics Data System (ADS)
Belogurov, S.; Berchun, Yu; Chernogorov, A.; Malzacher, P.; Ovcharenko, E.; Semennikov, A.
2011-12-01
Due to conceptual difference between geometry descriptions in Computer-Aided Design (CAD) systems and particle transport Monte Carlo (MC) codes direct conversion of detector geometry in either direction is not feasible. An original set of tools has been developed for building a GEANT4/ROOT compatible geometry in the CATIA CAD system and exchanging it with mentioned MC packages using GDML file format. A Special structure of a CATIA product tree, a wide range of primitives, different types of multiple volume instantiation, and supporting macros have been implemented.
Influence of geometry on natural convection in buildings
White, M.D.; Winn, C.B.; Jones, G.F.; Balcomb, J.D.
1985-01-01
Strong free convection airflows occur within passive solar buildings resulting from elevated temperatures of surfaces irradiated by solar energy compared with the cooler surfaces not receiving radiation. The geometry of a building has a large influence on the directions and magnitudes of natural airflows, and thus heat transfer between zones. This investigation has utilized a variety of reduced-scale building configurations to study the effects of geometry on natural convection heat transfer. Similarity between the reduced-scale model and a full-scale passive solar building is achieved by having similar geometries and by replacing air with Freon-12 gas as the model's working fluid. Filling the model with Freon-12 gas results in similarity in Prandtl numbers and Rayleigh numbers based on temperature differences in the range from 10/sup 9/ to 10/sup 11/. Results from four geometries are described with an emphasis placed on the effects of heat loss on zone temperature stratification shifts.
Flexible intuitions of Euclidean geometry in an Amazonian indigene group.
Izard, Véronique; Pica, Pierre; Spelke, Elizabeth S; Dehaene, Stanislas
2011-06-14
Kant argued that Euclidean geometry is synthesized on the basis of an a priori intuition of space. This proposal inspired much behavioral research probing whether spatial navigation in humans and animals conforms to the predictions of Euclidean geometry. However, Euclidean geometry also includes concepts that transcend the perceptible, such as objects that are infinitely small or infinitely large, or statements of necessity and impossibility. We tested the hypothesis that certain aspects of nonperceptible Euclidian geometry map onto intuitions of space that are present in all humans, even in the absence of formal mathematical education. Our tests probed intuitions of points, lines, and surfaces in participants from an indigene group in the Amazon, the Mundurucu, as well as adults and age-matched children controls from the United States and France and younger US children without education in geometry. The responses of Mundurucu adults and children converged with that of mathematically educated adults and children and revealed an intuitive understanding of essential properties of Euclidean geometry. For instance, on a surface described to them as perfectly planar, the Mundurucu's estimations of the internal angles of triangles added up to ~180 degrees, and when asked explicitly, they stated that there exists one single parallel line to any given line through a given point. These intuitions were also partially in place in the group of younger US participants. We conclude that, during childhood, humans develop geometrical intuitions that spontaneously accord with the principles of Euclidean geometry, even in the absence of training in mathematics.
Unstructured Cartesian/prismatic grid generation for complex geometries
NASA Technical Reports Server (NTRS)
Karman, Steve L., Jr.
1995-01-01
The generation of a hybrid grid system for discretizing complex three dimensional (3D) geometries is described. The primary grid system is an unstructured Cartesian grid automatically generated using recursive cell subdivision. This grid system is sufficient for computing Euler solutions about extremely complex 3D geometries. A secondary grid system, using triangular-prismatic elements, may be added for resolving the boundary layer region of viscous flows near surfaces of solid bodies. This paper describes the grid generation processes used to generate each grid type. Several example grids are shown, demonstrating the ability of the method to discretize complex geometries, with very little pre-processing required by the user.
View Factor Calculation for Three-Dimensional Geometries.
1989-06-20
Version 00 MCVIEW calculates the radiation geometric view factor between surfaces for three dimensional geometries with and without interposed third surface obstructions. It was developed to calculate view factors for input data to heat transfer analysis programs such as SCA-03/TRUMP, SCA-01/HEATING-5 and PSR-199/HEATING-6.
High resolution channel geometry from repeat aerial imagery
NASA Astrophysics Data System (ADS)
King, T.; Neilson, B. T.; Jensen, A.; Torres-Rua, A. F.; Winkelaar, M.; Rasmussen, M. T.
2015-12-01
River channel cross sectional geometry is a key attribute for controlling the river energy balances where surface heat fluxes dominate and discharge varies significantly over short time periods throughout the open water season. These dynamics are seen in higher gradient portions of Arctic rivers where surface heat fluxes can dominates river energy balances and low hillslope storage produce rapidly varying hydrographs. Additionally, arctic river geometry can be highly dynamic in the face of thermal erosion of permafrost landscape. While direct in-situ measurements of channel cross sectional geometry are accurate, they are limited in spatial resolution and coverage, and can be access limited in remote areas. Remote sensing can help gather data at high spatial resolutions and large areas, however techniques for extracting channel geometry is often limited to the banks and flood plains adjacent to river, as the water column inhibits sensing of the river bed itself. Green light LiDAR can be used to map bathymetry, however this is expensive, difficult to obtain at large spatial scales, and dependent on water quality. Alternatively, 3D photogrammetry from aerial imagery can be used to analyze the non-wetted portion of the river channel, but extracting full cross sections requires extrapolation into the wetted portion of the river. To bridge these gaps, an approach for using repeat aerial imagery surveys with visual (RGB) and near infrared (NIR) to extract high resolution channel geometry for the Kuparuk River in the Alaskan Arctic was developed. Aerial imagery surveys were conducted under multiple flow conditions and water surface geometry (elevation and width) were extracted through photogrammetry. Channel geometry was extracted by combining water surface widths and elevations from multiple flights. The accuracy of these results were compared against field surveyed cross sections at many locations throughout the study reach and a digital elevation model created under
NASA Astrophysics Data System (ADS)
Dunn, Stanley M.; Liang, Tajen
1989-03-01
Our overall goal is to develop an image understanding system for automatically interpreting dental radiographs. This paper describes the module that integrates the intrinsic image data to form the region adjacency graph that represents the image. The specific problem is to develop a robust method for segmenting the image into small regions that do not overlap anatomical boundaries. Classical algorithms for finding homogeneous regions (i.e., 2 class segmentation or connected components) will not always yield correct results since blurred edges can cause adjacent anatomical regions to be labeled as one region. This defect is a problem in this and other applications where an object count is necessary. Our solution to the problem is to guide the segmentation by intrinsic properties of the constituent objects. The module takes a set of intrinsic images as arguments. A connected components-like algorithm is performed, but the connectivity relation is not 4- or 8-neighbor connectivity in binary images; the connectivity is defined in terms of the intrinsic image data. We shall describe both the classical method and the modified segmentation procedures, and present experiments using both algorithms. Our experiments show that for the dental radiographs a segmentation using gray level data in conjunction with edges of the surfaces of teeth give a robust and reliable segmentation.
Core systems of geometry in animal minds
Spelke, Elizabeth S.; Lee, Sang Ah
2012-01-01
Research on humans from birth to maturity converges with research on diverse animals to reveal foundational cognitive systems in human and animal minds. The present article focuses on two such systems of geometry. One system represents places in the navigable environment by recording the distance and direction of the navigator from surrounding, extended surfaces. The other system represents objects by detecting the shapes of small-scale forms. These two systems show common signatures across animals, suggesting that they evolved in distant ancestral species. As children master symbolic systems such as maps and language, they come productively to combine representations from the two core systems of geometry in uniquely human ways; these combinations may give rise to abstract geometric intuitions. Studies of the ontogenetic and phylogenetic sources of abstract geometry therefore are illuminating of both human and animal cognition. Research on animals brings simpler model systems and richer empirical methods to bear on the analysis of abstract concepts in human minds. In return, research on humans, relating core cognitive capacities to symbolic abilities, sheds light on the content of representations in animal minds. PMID:22927577
Core systems of geometry in animal minds.
Spelke, Elizabeth S; Lee, Sang Ah
2012-10-01
Research on humans from birth to maturity converges with research on diverse animals to reveal foundational cognitive systems in human and animal minds. The present article focuses on two such systems of geometry. One system represents places in the navigable environment by recording the distance and direction of the navigator from surrounding, extended surfaces. The other system represents objects by detecting the shapes of small-scale forms. These two systems show common signatures across animals, suggesting that they evolved in distant ancestral species. As children master symbolic systems such as maps and language, they come productively to combine representations from the two core systems of geometry in uniquely human ways; these combinations may give rise to abstract geometric intuitions. Studies of the ontogenetic and phylogenetic sources of abstract geometry therefore are illuminating of both human and animal cognition. Research on animals brings simpler model systems and richer empirical methods to bear on the analysis of abstract concepts in human minds. In return, research on humans, relating core cognitive capacities to symbolic abilities, sheds light on the content of representations in animal minds. PMID:22927577
SAR imagery in non-Cartesian geometries
NASA Astrophysics Data System (ADS)
Dendal, Didier
1995-11-01
The subject of the reported work is the improvement of geometrical models for a SAR scanning in pushbroom, spotlight, scansar or bistatic imaging modes. This research has been motivated by the planetary cornerstone mission of ESA's long term program for European Space Science ('rendezvous' with a comet, and fly-bys of asteroids). In this specific context, the synthetic aperture radar is destined for an important role, but the rules and standard backgrounds of the Cartesian geometry are no longer justified. Several new techniques are proposed to handle with an optimal precision the data relative to celestial bodies with a complex geometry (coherent and non-coherent imagery). On the basis of a mathematical rigor (singleness of solutions, convergence of processes, biunivocity of transformations and generalizations), a lot of scenarios are discussed with key relations established (plane and spherical models, bodies with a symmetry of revolution and general bodies, specific sensor(s) trajectories as fly-bys or flight into orbit with the possibility of an approaching probe). The four methods developed are the tomographic analogy of radar principles (only known, previously, in the usual case of a straight line flight at constant altitude over a plane surface) and Hilbertian techniques for a direct adaptation to the scanned surface geometry, an automated autofocusing which enhances the contrast resulting from a Cartesian reconstruction and the coordinates transformation where the real space is converted into a fictitious space where Cartesian algorithms are fully rigorous. Beyond the fact that an interpolation step is often unavoidable, the major conclusion of the research is that all the prospected techniques are complementary and that the choice between the methods has to be made according to geometry, objectives and time requirements (reconstruction on board or not). In particular, coordinates transformation techniques are worthy of commendation in the case of plane
Danielson, Thomas; Hin, Celine; Savara, Aditya
2016-08-10
Lattice based kinetic Monte Carlo (KMC) simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and for estimating the coverage at a certain pressure. The generalized form has been calculatedmore » by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. Finally, the equations have been shown to be general for any value of the adsorption equilibrium constant.« less
NASA Astrophysics Data System (ADS)
Danielson, Thomas; Hin, Celine; Savara, Aditya
2016-08-01
Lattice based kinetic Monte Carlo simulations have been used to determine a functional form for the second order adsorption isotherms on two commonly investigated crystal surfaces: the (111) fluorite surface and the (100) perovskite surface which has the same geometric symmetry as the NaCl (100) surface. The functional form is generalized to be applicable to all values of the equilibrium constant by a shift along the pressure axis. Functions have been determined for estimating the pressure at which a desired coverage would be achieved and, conversely, for estimating the coverage at a certain pressure. The generalized form has been calculated by investigating the surface adsorbate coverage across a range of thermodynamic equilibrium constants that span the range 10-26 to 1013. The equations have been shown to be general for any value of the adsorption equilibrium constant.
Intelligent Patching of Conceptual Geometry for CFD Analysis
NASA Technical Reports Server (NTRS)
Li, Wu
2010-01-01
The iPatch computer code for intelligently patching surface grids was developed to convert conceptual geometry to computational fluid dynamics (CFD) geometry (see figure). It automatically uses bicubic B-splines to extrapolate (if necessary) each surface in a conceptual geometry so that all the independently defined geometric components (such as wing and fuselage) can be intersected to form a watertight CFD geometry. The software also computes the intersection curves of surface patches at any resolution (up to 10.4 accuracy) specified by the user, and it writes the B-spline surface patches, and the corresponding boundary points, for the watertight CFD geometry in the format that can be directly used by the grid generation tool VGRID. iPatch requires that input geometry be in PLOT3D format where each component surface is defined by a rectangular grid {(x(i,j), y(i,j), z(i,j)):1less than or equal to i less than or equal to m, 1 less than or equal to j less than or equal to n} that represents a smooth B-spline surface. All surfaces in the PLOT3D file conceptually represent a watertight geometry of components of an aircraft on the half-space y greater than or equal to 0. Overlapping surfaces are not allowed, but could be fixed by a utility code "fixp3d". The fixp3d utility code first finds the two grid lines on the two surface grids that are closest to each other in Hausdorff distance (a metric to measure the discrepancies of two sets); then uses one of the grid lines as the transition line, extending grid lines on one grid to the other grid to form a merged grid. Any two connecting surfaces shall have a "visually" common boundary curve, or can be described by an intersection relationship defined in a geometry specification file. The intersection of two surfaces can be at a conceptual level. However, the intersection is directional (along either i or j index direction), and each intersecting grid line (or its spine extrapolation) on the first surface should intersect
Earthquake cycles in complex geometries
NASA Astrophysics Data System (ADS)
Romanet, Pierre; Bhat, Harsha; Madariaga, Raul
2016-04-01
Our understanding of earthquake cycles, from a modelling perspective, comes mainly from theoretical, and numerical, work on a single straight fault. However, natural fault systems are geometrically complex. Modelling complex fault geometry (bends, kinks and multiple faults) is in itself a challenge as it is computationally intensive. To overcome this difficulty, we appeal to the Fast Multipole Method which was developed in the context of modelling N-body problems. This method is then used to model the quasi-dynamic response of multiple faults, with complex geometries, that are governed by rate and state friction laws. Our preliminary findings tell us that when stress interaction between faults, due to complex geometry, is accounted then even strongly rate-weakening faults (a-b)<0 show a complex spectrum of slow slip and dynamic ruptures.
Conventionalism and integrable Weyl geometry
NASA Astrophysics Data System (ADS)
Pucheu, M. L.
2015-03-01
Since the appearance of Einstein's general relativity, gravitation has been associated to the space-time curvature. This theory introduced a geometrodynamic language which became a convenient tool to predict matter behaviour. However, the properties of space-time itself cannot be measurable by experiments. Taking Poincaré idea that the geometry of space-time is merely a convention, we show that the general theory of relativity can be completely reformulated in a more general setting, a generalization of Riemannian geometry, namely, the Weyl integrable geometry. The choice of this new mathematical language implies, among other things, that the path of particles and light rays should now correspond to Weylian geodesies. Such modification in the dynamic of bodies brings a new perception of physical phenomena that we will explore.
Quantum geometry and gravitational entropy
Simon, Joan; Balasubramanian, Vijay; Czech, Bart Iomiej; Larjo, Klaus; Marolf, Donald; Simon, Joan
2007-05-29
Most quantum states have wavefunctions that are widely spread over the accessible Hilbert space and hence do not have a good description in terms of a single classical geometry. In order to understand when geometric descriptions are possible, we exploit the AdS/CFT correspondence in the half-BPS sector of asymptotically AdS_5 x S5 universes. In this sector we devise a"coarse-grained metric operator" whose eigenstates are well described by a single spacetime topology and geometry. We show that such half-BPS universes have a non-vanishing entropy if and only if the metric is singular, and that the entropy arises from coarse-graining the geometry. Finally, we use our entropy formula to find the most entropic spacetimes with fixed asymptotic moments beyond the global charges.
Ionization coefficient approach to modeling breakdown in nonuniform geometries.
Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Nicolaysen, Scott D.
2003-11-01
This report summarizes the work on breakdown modeling in nonuniform geometries by the ionization coefficient approach. Included are: (1) fits to primary and secondary ionization coefficients used in the modeling; (2) analytical test cases for sphere-to-sphere, wire-to-wire, corner, coaxial, and rod-to-plane geometries; a compilation of experimental data with source references; comparisons between code results, test case results, and experimental data. A simple criterion is proposed to differentiate between corona and spark. The effect of a dielectric surface on avalanche growth is examined by means of Monte Carlo simulations. The presence of a clean dry surface does not appear to enhance growth.
RSRM Propellant Grain Geometry Modification
NASA Technical Reports Server (NTRS)
Schorr, Andrew A.; Endicott, Joni B.; McCool, Alex (Technical Monitor)
2000-01-01
This document is composed of viewgraphs about the RSRM propellant grain geometry modification project, which hopes to improve personnel and system safety by modifying propellant grain geometry to improve structural factors of safety. Using techniques such as Finite Element Analysis to determine blend radii required to reduce localized stresses, and ballistic predictions to ensure that the ballistics, ignition transient and Block Model have not been adversely affected, the project hopes to build and test FSM-10 with a new design, and determine flight effectivity pending successful test evaluation.
Geometry, topology, and string theory
Varadarajan, Uday
2003-07-10
A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.
Geometry of generalized depolarizing channels
Burrell, Christian K.
2009-10-15
A generalized depolarizing channel acts on an N-dimensional quantum system to compress the 'Bloch ball' in N{sup 2}-1 directions; it has a corresponding compression vector. We investigate the geometry of these compression vectors and prove a conjecture of Dixit and Sudarshan [Phys. Rev. A 78, 032308 (2008)], namely, that when N=2{sup d} (i.e., the system consists of d qubits), and we work in the Pauli basis then the set of all compression vectors forms a simplex. We extend this result by investigating the geometry in other bases; in particular we find precisely when the set of all compression vectors forms a simplex.
NASA Astrophysics Data System (ADS)
Nerlov, Jesper; Christensen, Søren V.; Weichel, Steen; Pedersen, Eddie H.; Møller, Preben J.
1997-02-01
The coadsorption of CO 2 and Na on TiO 2(110)-(1 × 1) and -(1 × 2) surfaces have been investigated by synchrotron-radiation based core-level and valence band photoemission. We find that the initially adsorbed Na exhibits a core-level shift of 1.15 eV when the two surfaces are compared. From a simple adsorption model this binding energy shift is understood in terms of a difference in initial Na adsorption site on these surfaces. While the (1 × 1) surface seems to favor Na adsorption in a hollow site "between" bridging surface oxygen atoms, it is found that the (1 × 2) surface facilitates a chemically more advantageous Na adsorption "adjacent to" the bridging oxygen atoms. Valence band measurements support this model since Na adsorption on the (1 × 2) surface leads to emission characteristic of alkali-oxygen-like compounds while this is not the case for the {Na}/{TiO2(110) }-(1 × 1) system. Finally, the relatively high resolution of the core-level emission allows in a direct way the various features contributing to the Na 2p core-level emission to be determined. With respect to adsorption of CO 2 we find for the (1 × 2) surface that CO 2 uptake saturates around 0.5 ML Na coverage compared to 1 ML for the (1 × 1) surface, indicating that the Na coverage required for saturation of CO 2 uptake is proportional to the density of protruded oxygen rows present at the surface. The CO 2 uptake, however, increases as the density of the oxygen rows decreases. Valence band photoemission data obtained from both interfaces show that a surface carbonate species is formed. At lower coverages/exposures there are, however, indications of the presence of a CO -2 species rather than carbonate, thereby suggesting that the carbonate species is formed through the surface reaction: 2CO -2→CO 2-3 + CO.
TES Limb-Geometry Observations of Aerosols
NASA Technical Reports Server (NTRS)
Smith, Michael D.
2003-01-01
The Thermal Emission Spectrometer (TES) on-board Mars Global Surveyor (MGS) has a pointing mirror that allows observations in the plane of the orbit anywhere from directly nadir to far above either the forward or aft limbs for details about the TES instrument). Nadir-geometry observations are defined as those where the field-of-view contains the surface of Mars (even if the actual observation is at a high emission angle far from true nadir). Limb-geometry observations are defined as those where the line-of-sight of the observations does not intersect the surface. At a number of points along the MGS orbit (typically every 10 deg. or 20 deg. of latitude) a limb sequence is taken, which includes a stack of overlapping TES spectra from just below the limb to more than 120 km above the limb. A typical limb sequence has approx. 20 individual spectra, and the projected size of a TES pixel at the limb is 13 km.
Parametric design and gridding through relational geometry
NASA Technical Reports Server (NTRS)
Letcher, John S., Jr.; Shook, D. Michael
1995-01-01
Relational Geometric Synthesis (RGS) is a new logical framework for building up precise definitions of complex geometric models from points, curves, surfaces and solids. RGS achieves unprecedented design flexibility by supporting a rich variety of useful curve and surface entities. During the design process, many qualitative and quantitative relationships between elementary objects may be captured and retained in a data structure equivalent to a directed graph, such that they can be utilized for automatically updating the complete model geometry following changes in the shape or location of an underlying object. Capture of relationships enables many new possibilities for parametric variations and optimization. Examples are given of panelization applications for submarines, sailing yachts, offshore structures, and propellers.
Geometry of aortic heart valves. [prosthetic design
NASA Technical Reports Server (NTRS)
Karara, H. M.
1975-01-01
Photogrammetric measurements of the surface topography of the aortic valves obtained from silicon rubber molds of freshly excised human aortic valves are presented. The data are part of an investigation into the design of a new prosthetic valve which will be a central-flow device, like the real valve and unlike previous central-occluding prostheses. Since the maximum stress on the heart valve is induced when the valve is closed and subject to diastolic back-pressure, it was decided to determine the valve geometry during diastole. That is, the molds were formed by pouring the rubber down the excised aortas, causing the valves to close. The molds were made under different pressures (20-120 torr); photogrammetry served as a vehicle for the assessment of the mold topography through the following outputs: digital models, surface profiles, and contour maps.
GEMPAK- AN ARBITRARY AIRCRAFT GEOMETRY GENERATOR
NASA Technical Reports Server (NTRS)
Stack, S. H.
1994-01-01
GEMPAK was developed to aid designers in the generation of detailed configuration geometry. This program was written to allow the user as much flexibility as possible in his choice of configurations and detail of description desired while at the same time, keeping input requirements, program turnaround time, and cost to a minimum. The program consists of routines that generate fuselage and planar surface (wing-like) geometry and a routine that determines the true intersection of all components with the fuselage. GEMPAK consists of three major parts: the fuselage generator, the generator for planar surfaces, and the module for integrating the configuration components with the fuselage. Each component is input and generated independently. The program then scales the resulting individual geometries for compatibility and merges the components into an integrated configuration. This technique permits the user to easily make isolated changes to the configuration. There are three modes of modeling the fuselage. The first is complete lofting where the fuselage is defined analytically by three to eleven lofting curves that may be continuous or discontinuous. The user needs to input only the minimum number of points that can be fitted with conic sections for a good reproduction of his configuration. The second mode of fuselage modeling is cross-section lofting. This mode is structured around lofting data input for discrete prescribed cross-section locations. The model is not analytic in the longitudinal direction in mode two. The third mode is a point by point mode and requires that all surface points be input at discrete longitudinal locations. The model resulting from this mode is completely nonanalytic. No interpolation routines are provided in either longitudinal or cross-sectional directions. The amount of required input is least for mode one and greatest for mode three. The wing, canard, horizontal tail, fin, and elevon are all generated with a single type of
Teaching Activity-Based Taxicab Geometry
ERIC Educational Resources Information Center
Ada, Tuba
2013-01-01
This study aimed on the process of teaching taxicab geometry, a non-Euclidean geometry that is easy to understand and similar to Euclidean geometry with its axiomatic structure. In this regard, several teaching activities were designed such as measuring taxicab distance, defining a taxicab circle, finding a geometric locus in taxicab geometry, and…
LOGO Based Instruction in Geometry.
ERIC Educational Resources Information Center
Yusuf, Mian Muhammad
The objective of this pretest-posttest Quasi-Experimental Design study was to determine the effects of LOGO Based Instruction (LBI) compared to instruction by teacher lecture and pencil-and-paper activities on: (1) students' understanding of the concepts of point, ray, line, and line segment; (2) students' attitudes toward learning geometry,…
Exploring Bundling Theory with Geometry
ERIC Educational Resources Information Center
Eckalbar, John C.
2006-01-01
The author shows how instructors might successfully introduce students in principles and intermediate microeconomic theory classes to the topic of bundling (i.e., the selling of two or more goods as a package, rather than separately). It is surprising how much students can learn using only the tools of high school geometry. To be specific, one can…
General Relativity: Geometry Meets Physics
ERIC Educational Resources Information Center
Thomsen, Dietrick E.
1975-01-01
Observing the relationship of general relativity and the geometry of space-time, the author questions whether the rest of physics has geometrical explanations. As a partial answer he discusses current research on subatomic particles employing geometric transformations, and cites the existence of geometrical definitions of physical quantities such…
Teaching Geometry According to Euclid.
ERIC Educational Resources Information Center
Hartshorne, Robin
2000-01-01
This essay contains some reflections and questions arising from encounters with the text of Euclid's Elements. The reflections arise out of the teaching of a course in Euclidean and non-Euclidean geometry to undergraduates. It is concluded that teachers of such courses should read Euclid and ask questions, then teach a course on Euclid and later…
Analogical Reasoning in Geometry Education
ERIC Educational Resources Information Center
Magdas, Ioana
2015-01-01
The analogical reasoning isn't used only in mathematics but also in everyday life. In this article we approach the analogical reasoning in Geometry Education. The novelty of this article is a classification of geometrical analogies by reasoning type and their exemplification. Our classification includes: analogies for understanding and setting a…
Foucault pendulum through basic geometry
NASA Astrophysics Data System (ADS)
von Bergmann, Jens; von Bergmann, HsingChi
2007-10-01
We provide a thorough explanation of the Foucault pendulum that utilizes its underlying geometry on a level suitable for science students not necessarily familiar with calculus. We also explain how the geometrically understood Foucault pendulum can serve as a prototype for more advanced phenomena in physics known as Berry's phase or geometric phases.
Spectral geometry of symplectic spinors
NASA Astrophysics Data System (ADS)
Vassilevich, Dmitri
2015-10-01
Symplectic spinors form an infinite-rank vector bundle. Dirac operators on this bundle were constructed recently by Habermann, K. ["The Dirac operator on symplectic spinors," Ann. Global Anal. Geom. 13, 155-168 (1995)]. Here we study the spectral geometry aspects of these operators. In particular, we define the associated distance function and compute the heat trace asymptotics.
Exploring Fractal Geometry with Children.
ERIC Educational Resources Information Center
Vacc, Nancy Nesbitt
1999-01-01
Heightens the awareness of elementary school teachers, teacher educators, and teacher-education researchers of possible applications of fractal geometry with children and, subsequently, initiates discussion about the appropriateness of including this new mathematics in the elementary curriculum. Presents activities for exploring children's…
Differential geometry meets the cell.
Marshall, Wallace F
2013-07-18
A new study by Terasaki et al. highlights the role of physical forces in biological form by showing that connections between stacked endoplasmic reticulum cisternae have a shape well known in classical differential geometry, the helicoid, and that this shape is a predictable consequence of membrane physics.
Instructional Identities of Geometry Students
ERIC Educational Resources Information Center
Aaron, Wendy Rose; Herbst, Patricio
2012-01-01
We inspect the hypothesis that geometry students may be oriented toward how they expect that the teacher will evaluate them as students or otherwise oriented to how they expect that their work will give them opportunities to do mathematics. The results reported here are based on a mixed-methods analysis of twenty-two interviews with high school…
Physiological optics and physical geometry.
Hyder, D J
2001-09-01
Hermann von Helmholtz's distinction between "pure intuitive" and "physical" geometry must be counted as the most influential of his many contributions to the philosophy of science. In a series of papers from the 1860s and 70s, Helmholtz argued against Kant's claim that our knowledge of Euclidean geometry was an a priori condition for empirical knowledge. He claimed that geometrical propositions could be meaningful only if they were taken to concern the behaviors of physical bodies used in measurement, from which it followed that it was posterior to our acquaintance with this behavior. This paper argues that Helmholtz's understanding of geometry was fundamentally shaped by his work in sense-physiology, above all on the continuum of colors. For in the course of that research, Helmholtz was forced to realize that the color-space had no inherent metrical structure. The latter was a product of axiomatic definitions of color-addition and the empirical results of such additions. Helmholtz's development of these views is explained with detailed reference to the competing work of the mathematician Hermann Grassmann and that of the young James Clerk Maxwell. It is this separation between 1) essential properties of a continuum, 2) supplementary axioms concerning distance-measurement, and 3) the behaviors of the physical apparatus used to realize the axioms, which is definitive of Helmholtz's arguments concerning geometry.
Noncommutative geometry inspired entropic inflation
NASA Astrophysics Data System (ADS)
Nozari, Kourosh; Akhshabi, Siamak
2011-06-01
Recently Verlinde proposed that gravity can be described as an emergent phenomena arising from changes in the information associated with the positions of material bodies. By using noncommutative geometry as a way to describe the microscopic microstructure of quantum spacetime, we derive modified Friedmann equation in this setup and study the entropic force modifications to the inflationary dynamics of early universe.
Math Sense: Algebra and Geometry.
ERIC Educational Resources Information Center
Howett, Jerry
This book is designed to help students gain the range of math skills they need to succeed in life, work, and on standardized tests; overcome math anxiety; discover math as interesting and purposeful; and develop good number sense. Topics covered in this book include algebra and geometry. Lessons are organized around four strands: (1) skill lessons…
Signature geometry and quantum engineering
NASA Astrophysics Data System (ADS)
Samociuk, Stefan
2013-09-01
As the operating frequency of electromagnetic based devices increase, physical design geometry is playing an ever more important role. Evidence is considered in support of a relationship between the dimensionality of primitive geometric forms, such as transistors, and corresponding electromagnetic coupling efficiency. The industry of electronics is defined as the construction of devices by the patterning of primitive forms to physical materials. Examples are given to show the evolution of these primitives, down to nano scales, are requiring exacting geometry and three dimensional content. Consideration of microwave monolithic integrated circuits,(MMIC), photonics and metamaterials,(MM), support this trend and also add new requirements of strict geometric periodicity and multiplicity. Signature geometries,(SG), are characterized by distinctive attributes and examples are given. The transcendent form transcode algorithm, (TTA) is introduced as a multi dimensional SG and its use in designing photonic integrated circuits and metamaterials is discussed . A creative commons licensed research database, TRANSFORM, containing TTA geometries in OASIS file formats is described. An experimental methodology for using the database is given. Multidimensional SG and extraction of three dimensional cross sections as primitive forms is discussed as a foundation for quantum engineering and the exploitation of phenomena other than the electromagnetic.
Electromagnetic properties of material coated surfaces
NASA Technical Reports Server (NTRS)
Beard, L.; Berrie, J.; Burkholder, R.; Dominek, A.; Walton, E.; Wang, N.
1989-01-01
The electromagnetic properties of material coated conducting surfaces were investigated. The coating geometries consist of uniform layers over a planar surface, irregularly shaped formations near edges and randomly positioned, electrically small, irregularly shaped formations over a surface. Techniques to measure the scattered field and constitutive parameters from these geometries were studied. The significance of the scattered field from these geometries warrants further study.
SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry
Chi, Y; Tian, Z; Jiang, S; Jia, X
2015-06-15
Purpose: Monte Carlo simulation on GPU has experienced rapid advancements over the past a few years and tremendous accelerations have been achieved. Yet existing packages were developed only in voxelized geometry. In some applications, e.g. radioactive seed modeling, simulations in more complicated geometry are needed. This abstract reports our initial efforts towards developing a quadric geometry module aiming at expanding the application scope of GPU-based MC simulations. Methods: We defined the simulation geometry consisting of a number of homogeneous bodies, each specified by its material composition and limiting surfaces characterized by quadric functions. A tree data structure was utilized to define geometric relationship between different bodies. We modified our GPU-based photon MC transport package to incorporate this geometry. Specifically, geometry parameters were loaded into GPU’s shared memory for fast access. Geometry functions were rewritten to enable the identification of the body that contains the current particle location via a fast searching algorithm based on the tree data structure. Results: We tested our package in an example problem of HDR-brachytherapy dose calculation for shielded cylinder. The dose under the quadric geometry and that under the voxelized geometry agreed in 94.2% of total voxels within 20% isodose line based on a statistical t-test (95% confidence level), where the reference dose was defined to be the one at 0.5cm away from the cylinder surface. It took 243sec to transport 100million source photons under this quadric geometry on an NVidia Titan GPU card. Compared with simulation time of 99.6sec in the voxelized geometry, including quadric geometry reduced efficiency due to the complicated geometry-related computations. Conclusion: Our GPU-based MC package has been extended to support photon transport simulation in quadric geometry. Satisfactory accuracy was observed with a reduced efficiency. Developments for charged
Non-Euclidean geometry of twisted filament bundle packing
Bruss, Isaac R.; Grason, Gregory M.
2012-01-01
Densely packed and twisted assemblies of filaments are crucial structural motifs in macroscopic materials (cables, ropes, and textiles) as well as synthetic and biological nanomaterials (fibrous proteins). We study the unique and nontrivial packing geometry of this universal material design from two perspectives. First, we show that the problem of twisted bundle packing can be mapped exactly onto the problem of disc packing on a curved surface, the geometry of which has a positive, spherical curvature close to the center of rotation and approaches the intrinsically flat geometry of a cylinder far from the bundle center. From this mapping, we find the packing of any twisted bundle is geometrically frustrated, as it makes the sixfold geometry of filament close packing impossible at the core of the fiber. This geometrical equivalence leads to a spectrum of close-packed fiber geometries, whose low symmetry (five-, four-, three-, and twofold) reflect non-Euclidean packing constraints at the bundle core. Second, we explore the ground-state structure of twisted filament assemblies formed under the influence of adhesive interactions by a computational model. Here, we find that the underlying non-Euclidean geometry of twisted fiber packing disrupts the regular lattice packing of filaments above a critical radius, proportional to the helical pitch. Above this critical radius, the ground-state packing includes the presence of between one and six excess fivefold disclinations in the cross-sectional order. PMID:22711799
Gupta, M L; Prasad, Arun; Ram, Muni; Kumar, Sushil
2002-01-01
The effects of inoculation with vesicular-arbuscular mycorrhizal (VAM) fungus Glomusfasciculatum on the root colonization, growth, essential oil yield and nutrient acquisition of three cultivars of menthol mint (Mentha arvensis); Kalka, Shivalik and Gomti, were studied under field conditions. The VAM inoculation significantly increased the root colonization, plant height, fresh herbage and dry matter yield. oil content and oil yield as compared to non-inoculated cultivars. The effect of VAM inoculation on the root colonization, growth and yield of mint was more pronounced with the cv Shivalik than the cvs Kalka and Gomati, indicating Shivalik as a highly mycorrhizal dependent genotype. VAM inoculation significantly increased the uptake of N, P and K by shoot tissues of mint, but most markedly increased the uptake of P. The VAM-inoculated mint plants depleted the available N, P and K in the rhizosphere soil as compared to non-inoculated control plants, however the extent of nutrient depletion was greater for P than N and K. We conclude that the VAM inoculation could significantly increase the root colonization, growth, essential oil yield and nutrient acquisition of mint for obtaining economic production under field conditions.
Roles of starting geometries in quantum mechanics studies of cellobiose
Technology Transfer Automated Retrieval System (TEKTRAN)
A relaxed HF/6 31G(d) energy surface was constructed for the fraction of phi,psi space that contains most geometries from crystals of molecules similar to cellobiose. Two regions around other minima were examined with unconstrained B3LYP/6 31+G(d) minimizations, as were two sub regions covered by th...
Pore geometry information via pulsed field gradient NMR.
Lucas, A J; Gibbs, S J; Peyron, M; Pierens, G K; Hall, L D; Stewart, R C; Phelps, D W
1994-01-01
Studies of echo attenuation at long diffusion times in pulsed field gradient NMR experiments on a variety of rock core samples are interpreted in the light of recent theoretical analysis of the effect of pore geometry and surface relaxation. This study is motivated by the need to test the applicability of that theory to real rock systems.
Using Origami Boxes to Explore Concepts of Geometry and Calculus
ERIC Educational Resources Information Center
Wares, Arsalan
2011-01-01
The purpose of this classroom note is to provide an example of how a simple origami box can be used to explore important concepts of geometry and calculus. This article describes how an origami box can be folded, then it goes on to describe how its volume and surface area can be calculated. Finally, it describes how the box could be folded to…
Stringy differential geometry, beyond Riemann
NASA Astrophysics Data System (ADS)
Jeon, Imtak; Lee, Kanghoon; Park, Jeong-Hyuck
2011-08-01
While the fundamental object in Riemannian geometry is a metric, closed string theories call for us to put a two-form gauge field and a scalar dilaton on an equal footing with the metric. Here we propose a novel differential geometry that treats the three objects in a unified manner, manifests not only diffeomorphism and one-form gauge symmetry but also O(D,D) T-duality, and enables us to rewrite the known low energy effective action of them as a single term. Further, we develop a corresponding vielbein formalism and gauge the internal symmetry that is given by a direct product of two local Lorentz groups, SO(1,D-1)×SŌ(1,D-1). We comment that the notion of cosmological constant naturally changes.
Geometry-invariant resonant cavities
Liberal, I.; Mahmoud, A. M.; Engheta, N.
2016-01-01
Resonant cavities are one of the basic building blocks in various disciplines of science and technology, with numerous applications ranging from abstract theoretical modelling to everyday life devices. The eigenfrequencies of conventional cavities are a function of their geometry, and, thus, the size and shape of a resonant cavity is selected to operate at a specific frequency. Here we demonstrate theoretically the existence of geometry-invariant resonant cavities, that is, resonators whose eigenfrequencies are invariant with respect to geometrical deformations of their external boundaries. This effect is obtained by exploiting the unusual properties of zero-index metamaterials, such as epsilon-near-zero media, which enable decoupling of the temporal and spatial field variations in the lossless limit. This new class of resonators may inspire alternative design concepts, and it might lead to the first generation of deformable resonant devices. PMID:27010103
Geometry of area without length
NASA Astrophysics Data System (ADS)
Ho, Pei-Ming; Inami, Takeo
2016-01-01
To define a free string by the Nambu-Goto action, all we need is the notion of area, and mathematically the area can be defined directly in the absence of a metric. Motivated by the possibility that string theory admits backgrounds where the notion of length is not well defined but a definition of area is given, we study space-time geometries based on the generalization of a metric to an area metric. In analogy with Riemannian geometry, we define the analogues of connections, curvatures, and Einstein tensor. We propose a formulation generalizing Einstein's theory that will be useful if at a certain stage or a certain scale the metric is ill defined and the space-time is better characterized by the notion of area. Static spherical solutions are found for the generalized Einstein equation in vacuum, including the Schwarzschild solution as a special case.
Hyperbolic geometry for colour metrics.
Farup, Ivar
2014-05-19
It is well established from both colour difference and colour order perpectives that the colour space cannot be Euclidean. In spite of this, most colour spaces still in use today are Euclidean, and the best Euclidean colour metrics are performing comparably to state-of-the-art non-Euclidean metrics. In this paper, it is shown that a transformation from Euclidean to hyperbolic geometry (i.e., constant negative curvature) for the chromatic plane can significantly improve the performance of Euclidean colour metrics to the point where they are statistically significantly better than state-of-the-art non-Euclidean metrics on standard data sets. The resulting hyperbolic geometry nicely models both qualitatively and quantitatively the hue super-importance phenomenon observed in colour order systems.
Parametric Deformation of Discrete Geometry for Aerodynamic Shape Design
NASA Technical Reports Server (NTRS)
Anderson, George R.; Aftosmis, Michael J.; Nemec, Marian
2012-01-01
We present a versatile discrete geometry manipulation platform for aerospace vehicle shape optimization. The platform is based on the geometry kernel of an open-source modeling tool called Blender and offers access to four parametric deformation techniques: lattice, cage-based, skeletal, and direct manipulation. Custom deformation methods are implemented as plugins, and the kernel is controlled through a scripting interface. Surface sensitivities are provided to support gradient-based optimization. The platform architecture allows the use of geometry pipelines, where multiple modelers are used in sequence, enabling manipulation difficult or impossible to achieve with a constructive modeler or deformer alone. We implement an intuitive custom deformation method in which a set of surface points serve as the design variables and user-specified constraints are intrinsically satisfied. We test our geometry platform on several design examples using an aerodynamic design framework based on Cartesian grids. We examine inverse airfoil design and shape matching and perform lift-constrained drag minimization on an airfoil with thickness constraints. A transport wing-fuselage integration problem demonstrates the approach in 3D. In a final example, our platform is pipelined with a constructive modeler to parabolically sweep a wingtip while applying a 1-G loading deformation across the wingspan. This work is an important first step towards the larger goal of leveraging the investment of the graphics industry to improve the state-of-the-art in aerospace geometry tools.
Orbit propagation in Minkowskian geometry
NASA Astrophysics Data System (ADS)
Roa, Javier; Peláez, Jesús
2015-09-01
The geometry of hyperbolic orbits suggests that Minkowskian geometry, and not Euclidean, may provide the most adequate description of the motion. This idea is explored in order to derive a new regularized formulation for propagating arbitrarily perturbed hyperbolic orbits. The mathematical foundations underlying Minkowski space-time are exploited to describe hyperbolic orbits. Hypercomplex numbers are introduced to define the rotations, vectors, and metrics in the problem: the evolution of the eccentricity vector is described on the Minkowski plane in terms of hyperbolic numbers, and the orbital plane is described on the inertial reference using quaternions. A set of eight orbital elements is introduced, namely a time-element, the components of the eccentricity vector in , the semimajor axis, and the components of the quaternion defining the orbital plane. The resulting formulation provides a deep insight into the geometry of hyperbolic orbits. The performance of the formulation in long-term propagations is studied. The orbits of four hyperbolic comets are integrated and the accuracy of the solution is compared to other regularized formulations. The resulting formulation improves the stability of the integration process and it is not affected by the perihelion passage. It provides a level of accuracy that may not be reached by the compared formulations, at the cost of increasing the computational time.
New geometries for black hole horizons
NASA Astrophysics Data System (ADS)
Armas, Jay; Blau, Matthias
2015-07-01
We construct several classes of worldvolume effective actions for black holes by integrating out spatial sections of the worldvolume geometry of asymptotically flat black branes. This provides a generalisation of the blackfold approach for higher-dimensional black holes and yields a map between different effective theories, which we exploit by obtaining new hydrodynamic and elastic transport coefficients via simple integrations. Using Euclidean minimal surfaces in order to decouple the fluid dynamics on different sections of the worldvolume, we obtain local effective theories for ultraspinning Myers-Perry branes and helicoidal black branes, described in terms of a stress-energy tensor, particle currents and non-trivial boost vectors. We then study in detail and present novel compact and non-compact geometries for black hole horizons in higher-dimensional asymptotically flat space-time. These include doubly-spinning black rings, black helicoids and helicoidal p-branes as well as helicoidal black rings and helicoidal black tori in D ≥ 6.
Hageneder, Simone; Bauch, Martin; Dostalek, Jakub
2016-08-15
This paper investigates plasmonic amplification in two commonly used optical configurations for fluorescence readout of bioassays - epifluorescence (EPF) and total internal reflection fluorescence (TIRF). The plasmonic amplification in the EPF configuration was implemented by using crossed gold diffraction grating and Kretschmann geometry of attenuated total reflection method (ATR) was employed in the TIRF configuration. Identical assay, surface architecture for analyte capture, and optics for the excitation, collection and detection of emitted fluorescence light intensity were used in both TIRF and EPF configurations. Simulations predict that the crossed gold diffraction grating (EPF) can amplify the fluorescence signal by a factor of 10(2) by the combination of surface plasmon-enhanced excitation and directional surface plasmon-coupled emission in the red part of spectrum. This factor is about order of magnitude higher than that predicted for the Kretschmann geometry (TIRF) which only took advantage of the surface plasmon-enhanced excitation. When applied for the readout of sandwich interleukin 6 (IL-6) immunoassay, the plasmonically amplified EPF geometry designed for Alexa Fluor 647 labels offered 4-times higher fluorescence signal intensity compared to TIRF. Interestingly, both geometries allowed reaching the same detection limit of 0.4pM despite of the difference in the fluorescence signal enhancement. This is attributed to inherently lower background of fluorescence signal for TIRF geometry compared to that for EPF which compensates for the weaker fluorescence signal enhancement. The analysis of the inflammation biomarker IL-6 in serum at medically relevant concentrations and the utilization of plasmonic amplification for the fluorescence measurement of kinetics of surface affinity reactions are demonstrated for both EPF and TIRF readout. PMID:27260457
Hageneder, Simone; Bauch, Martin; Dostalek, Jakub
2016-08-15
This paper investigates plasmonic amplification in two commonly used optical configurations for fluorescence readout of bioassays - epifluorescence (EPF) and total internal reflection fluorescence (TIRF). The plasmonic amplification in the EPF configuration was implemented by using crossed gold diffraction grating and Kretschmann geometry of attenuated total reflection method (ATR) was employed in the TIRF configuration. Identical assay, surface architecture for analyte capture, and optics for the excitation, collection and detection of emitted fluorescence light intensity were used in both TIRF and EPF configurations. Simulations predict that the crossed gold diffraction grating (EPF) can amplify the fluorescence signal by a factor of 10(2) by the combination of surface plasmon-enhanced excitation and directional surface plasmon-coupled emission in the red part of spectrum. This factor is about order of magnitude higher than that predicted for the Kretschmann geometry (TIRF) which only took advantage of the surface plasmon-enhanced excitation. When applied for the readout of sandwich interleukin 6 (IL-6) immunoassay, the plasmonically amplified EPF geometry designed for Alexa Fluor 647 labels offered 4-times higher fluorescence signal intensity compared to TIRF. Interestingly, both geometries allowed reaching the same detection limit of 0.4pM despite of the difference in the fluorescence signal enhancement. This is attributed to inherently lower background of fluorescence signal for TIRF geometry compared to that for EPF which compensates for the weaker fluorescence signal enhancement. The analysis of the inflammation biomarker IL-6 in serum at medically relevant concentrations and the utilization of plasmonic amplification for the fluorescence measurement of kinetics of surface affinity reactions are demonstrated for both EPF and TIRF readout.
Network geometry with flavor: From complexity to quantum geometry
NASA Astrophysics Data System (ADS)
Bianconi, Ginestra; Rahmede, Christoph
2016-03-01
Network geometry is attracting increasing attention because it has a wide range of applications, ranging from data mining to routing protocols in the Internet. At the same time advances in the understanding of the geometrical properties of networks are essential for further progress in quantum gravity. In network geometry, simplicial complexes describing the interaction between two or more nodes play a special role. In fact these structures can be used to discretize a geometrical d -dimensional space, and for this reason they have already been widely used in quantum gravity. Here we introduce the network geometry with flavor s =-1 ,0 ,1 (NGF) describing simplicial complexes defined in arbitrary dimension d and evolving by a nonequilibrium dynamics. The NGF can generate discrete geometries of different natures, ranging from chains and higher-dimensional manifolds to scale-free networks with small-world properties, scale-free degree distribution, and nontrivial community structure. The NGF admits as limiting cases both the Bianconi-Barabási models for complex networks, the stochastic Apollonian network, and the recently introduced model for complex quantum network manifolds. The thermodynamic properties of NGF reveal that NGF obeys a generalized area law opening a new scenario for formulating its coarse-grained limit. The structure of NGF is strongly dependent on the dimensionality d . In d =1 NGFs grow complex networks for which the preferential attachment mechanism is necessary in order to obtain a scale-free degree distribution. Instead, for NGF with dimension d >1 it is not necessary to have an explicit preferential attachment rule to generate scale-free topologies. We also show that NGF admits a quantum mechanical description in terms of associated quantum network states. Quantum network states evolve by a Markovian dynamics and a quantum network state at time t encodes all possible NGF evolutions up to time t . Interestingly the NGF remains fully classical but
Network geometry with flavor: From complexity to quantum geometry.
Bianconi, Ginestra; Rahmede, Christoph
2016-03-01
Network geometry is attracting increasing attention because it has a wide range of applications, ranging from data mining to routing protocols in the Internet. At the same time advances in the understanding of the geometrical properties of networks are essential for further progress in quantum gravity. In network geometry, simplicial complexes describing the interaction between two or more nodes play a special role. In fact these structures can be used to discretize a geometrical d-dimensional space, and for this reason they have already been widely used in quantum gravity. Here we introduce the network geometry with flavor s=-1,0,1 (NGF) describing simplicial complexes defined in arbitrary dimension d and evolving by a nonequilibrium dynamics. The NGF can generate discrete geometries of different natures, ranging from chains and higher-dimensional manifolds to scale-free networks with small-world properties, scale-free degree distribution, and nontrivial community structure. The NGF admits as limiting cases both the Bianconi-Barabási models for complex networks, the stochastic Apollonian network, and the recently introduced model for complex quantum network manifolds. The thermodynamic properties of NGF reveal that NGF obeys a generalized area law opening a new scenario for formulating its coarse-grained limit. The structure of NGF is strongly dependent on the dimensionality d. In d=1 NGFs grow complex networks for which the preferential attachment mechanism is necessary in order to obtain a scale-free degree distribution. Instead, for NGF with dimension d>1 it is not necessary to have an explicit preferential attachment rule to generate scale-free topologies. We also show that NGF admits a quantum mechanical description in terms of associated quantum network states. Quantum network states evolve by a Markovian dynamics and a quantum network state at time t encodes all possible NGF evolutions up to time t. Interestingly the NGF remains fully classical but its
Network geometry with flavor: From complexity to quantum geometry.
Bianconi, Ginestra; Rahmede, Christoph
2016-03-01
Network geometry is attracting increasing attention because it has a wide range of applications, ranging from data mining to routing protocols in the Internet. At the same time advances in the understanding of the geometrical properties of networks are essential for further progress in quantum gravity. In network geometry, simplicial complexes describing the interaction between two or more nodes play a special role. In fact these structures can be used to discretize a geometrical d-dimensional space, and for this reason they have already been widely used in quantum gravity. Here we introduce the network geometry with flavor s=-1,0,1 (NGF) describing simplicial complexes defined in arbitrary dimension d and evolving by a nonequilibrium dynamics. The NGF can generate discrete geometries of different natures, ranging from chains and higher-dimensional manifolds to scale-free networks with small-world properties, scale-free degree distribution, and nontrivial community structure. The NGF admits as limiting cases both the Bianconi-Barabási models for complex networks, the stochastic Apollonian network, and the recently introduced model for complex quantum network manifolds. The thermodynamic properties of NGF reveal that NGF obeys a generalized area law opening a new scenario for formulating its coarse-grained limit. The structure of NGF is strongly dependent on the dimensionality d. In d=1 NGFs grow complex networks for which the preferential attachment mechanism is necessary in order to obtain a scale-free degree distribution. Instead, for NGF with dimension d>1 it is not necessary to have an explicit preferential attachment rule to generate scale-free topologies. We also show that NGF admits a quantum mechanical description in terms of associated quantum network states. Quantum network states evolve by a Markovian dynamics and a quantum network state at time t encodes all possible NGF evolutions up to time t. Interestingly the NGF remains fully classical but its
Geometry and wetting of capillary folding.
Péraud, Jean-Philippe; Lauga, Eric
2014-04-01
Capillary forces are involved in a variety of natural phenomena, ranging from droplet breakup to the physics of clouds. The forces from surface tension can also be exploited in industrial applications provided the length scales involved are small enough. Recent experimental investigations showed how to take advantage of capillarity to fold planar structures into three-dimensional configurations by selectively melting polymeric hinges joining otherwise rigid shapes. In this paper we use theoretical calculations to quantify the role of geometry and fluid wetting on the final folded state. Considering folding in two and three dimensions, studying both hydrophilic and hydrophobic situations with possible contact-angle hysteresis, and addressing the shapes to be folded to be successively infinite, finite, curved, kinked, and elastic, we are able to derive an overview of the geometrical parameter space available for capillary folding.
Geometry in the mechanics of origami
NASA Astrophysics Data System (ADS)
Dias, Marcelo A.; Santangelo, Christian D.
2012-02-01
We present a mechanical model for curved fold origami in which the bending energies of developable regions are balanced with a phenomenological energy for the crease. The latter energy comes into play as a source of geometric frustration, allowing us to study shape formation by prescribing crease patterns. For a single fold annular configuration, we show how geometry forces a symmetry breaking of the ground state by increasing the width of the ribbon. We extend our model to study multiple fold structures, where we derive geometrical constraints that can be written as recursive relations to build the surface from valley to mountain, and so on. We also suggest a mechanical model for single vertex folds, mapping this problem to an elastica on the sphere.
Geometry and mechanics of thin growing bilayers.
Pezzulla, Matteo; Smith, Gabriel P; Nardinocchi, Paola; Holmes, Douglas P
2016-05-11
We investigate how thin sheets of arbitrary shapes morph under the isotropic in-plane expansion of their top surface, which may represent several stimuli such as nonuniform heating, local swelling and differential growth. Inspired by geometry, an analytical model is presented that rationalizes how the shape of the disk influences morphing, from the initial spherical bending to the final isometric limit. We introduce a new measure of slenderness that describes a sheet in terms of both thickness and plate shape. We find that the mean curvature of the isometric state is three fourths the natural curvature, which we verify by numerics and experiments. We finally investigate the emergence of a preferred direction of bending in the isometric state, guided by numerical analyses. The scalability of our model suggests that it is suitable to describe the morphing of sheets spanning several orders of magnitude.
Jet-contaminant interactions in confined geometries
NASA Astrophysics Data System (ADS)
1985-02-01
A numerical simulation is presented for investigation of the early phase of the flow interaction between a water jet and a chemical contaminant residing in cavities of a wall and in corners of two perpendicular walls. Such an interaction often occurs in surface decontamination processes. The flow model for this analysis is a two-dimensional, two-fluid flow governed by the unsteady Navier-Stokes equations. The equations were solved via finite difference schemes using the SOLA-VOF code. Computer plots of the flow development are presented. The results show that an inclined jet is more effective than a normal jet for decontaminating these confined geometries. In all flow cases studied, the impact pressure on the impingement wall far exceeds the corresponding steady-state dynamic pressure of the jet.
Geometry and mechanics of thin growing bilayers.
Pezzulla, Matteo; Smith, Gabriel P; Nardinocchi, Paola; Holmes, Douglas P
2016-05-11
We investigate how thin sheets of arbitrary shapes morph under the isotropic in-plane expansion of their top surface, which may represent several stimuli such as nonuniform heating, local swelling and differential growth. Inspired by geometry, an analytical model is presented that rationalizes how the shape of the disk influences morphing, from the initial spherical bending to the final isometric limit. We introduce a new measure of slenderness that describes a sheet in terms of both thickness and plate shape. We find that the mean curvature of the isometric state is three fourths the natural curvature, which we verify by numerics and experiments. We finally investigate the emergence of a preferred direction of bending in the isometric state, guided by numerical analyses. The scalability of our model suggests that it is suitable to describe the morphing of sheets spanning several orders of magnitude. PMID:27098344
ERIC Educational Resources Information Center
Kutluca, Tamer
2013-01-01
The aim of this study is to investigate the effect of dynamic geometry software GeoGebra on Van Hiele geometry understanding level of students at 11th grade geometry course. The study was conducted with pre and posttest control group quasi-experimental method. The sample of the study was 42 eleventh grade students studying in the spring term of…
A Whirlwind Tour of Computational Geometry.
ERIC Educational Resources Information Center
Graham, Ron; Yao, Frances
1990-01-01
Described is computational geometry which used concepts and results from classical geometry, topology, combinatorics, as well as standard algorithmic techniques such as sorting and searching, graph manipulations, and linear programing. Also included are special techniques and paradigms. (KR)
Optimizing solar-cell grid geometry
NASA Technical Reports Server (NTRS)
Crossley, A. P.
1969-01-01
Trade-off analysis and mathematical expressions calculate optimum grid geometry in terms of various cell parameters. Determination of the grid geometry provides proper balance between grid resistance and cell output to optimize the energy conversion process.
The Geometry of Quasar Outflows
NASA Astrophysics Data System (ADS)
Ganguly, Rajib
2012-10-01
Quasar outflows are important for understanding the accretion and growth processes of the central black hole, but also potentially play a role in feedback to the galaxy, halting star formation and infall of gas. A big uncertainty lies in the geometry and density of these outflows, especially as a function of ionization and velocity. We aim to tackle this using the archival COS M grating spectra of 266 quasars. We separate the geometry of outflows into two parts: the solid angle subtended around the black hole, and the distance of the outflow from the central engine. Large numbers of quasars with high resolution spectra are required for each aspect of this statistical investigation. First, we will determine which/how many absorption-line systems are intrinsic through both partial covering methods and statistical assessments. Second, we will consider the incidence of intrinsic absorbers as a function of quasar property {e.g., radio-loudness, SED shape, black hole mass, bolometric luminosity}. This will reveal what determines the solid angle. This can only be done at moderate redshifts where quasars with a larger range of properties are observable, and hence requires HST/COS. Third, we will use the wide range of diagnostic lines to constrain the physical conditions of the absorbers. We will target the CIII*1175 complex and apply photoionization models to constrain the densities and ionization parameters. This will provide the largest set yet of intrinsic absorbers with systematic distance constraints. In tandem with the solid angles, this work will inform models regarding the geometry of quasar outflows.
McMechan, G.A.; Soegaard, K.
1998-05-25
An integrated sedimentologic and GPR investigation has been carried out on a fluvial channel sandstone in the mid-Cretaceous Ferron Sandstone at Coyote Basin along the southwestern flank of the San Rafael Uplift in east-central Utah. This near-surface study, which covers a area of 40 {times} 16.5 meters to a depth of 15 meters, integrates detailed stratigraphic data from outcrop sections and facies maps with multi-frequency 3-D GPR surveys. The objectives of this investigation are two-fold: (1) to develop new ground-penetrating radar (GPR) technology for imaging shallow subsurface sandstone bodies, and (2) to construct an empirical three-dimensional sandstone reservoir model suitable for hydrocarbon flow-simulation by imaging near-surface sandstone reservoir analogs with the use of GPR. The sedimentological data base consists of a geologic map of the survey area and a detailed facies map of the cliff face immediately adjacent to the survey area. Five vertical sections were measured along the cliff face adjacent to the survey area. In addition, four wells were cored within the survey area from which logs were recorded. In the sections and well logs primary sedimentary structures were documented along with textural information and permeability data. Gamma-ray profiles were also obtained for all sections and core logs. The sedimentologic and stratigraphic information serves as the basis from which much of the processing and interpretation of the GPR data was made. Three 3-D GPR data sets were collected over the survey area at frequencies of 50 MHZ, 100 MHZ, and 200 MHZ.
The geometry of musical chords.
Tymoczko, Dmitri
2006-07-01
A musical chord can be represented as a point in a geometrical space called an orbifold. Line segments represent mappings from the notes of one chord to those of another. Composers in a wide range of styles have exploited the non-Euclidean geometry of these spaces, typically by using short line segments between structurally similar chords. Such line segments exist only when chords are nearly symmetrical under translation, reflection, or permutation. Paradigmatically consonant and dissonant chords possess different near-symmetries and suggest different musical uses.
Worldsheet geometries of ambitwistor string
NASA Astrophysics Data System (ADS)
Ohmori, Kantaro
2015-06-01
Mason and Skinner proposed the ambitwistor string theory which directly reproduces the formulas for the amplitudes of massless particles proposed by Cachazo, He and Yuan. In this paper we discuss geometries of the moduli space of worldsheets associated to the bosonic or the RNS ambitwistor string. Further, we investigate the factorization properties of the amplitudes when an internal momentum is near on-shell in the abstract CFT language. Along the way, we propose the existence of the ambitwistor strings with three or four fermionic worldsheet currents.
Ooguri, Hirosi; Yamazaki, Masahito
2009-04-24
We show how the smooth geometry of Calabi-Yau manifolds emerges from the thermodynamic limit of the statistical mechanical model of crystal melting defined in our previous paper. In particular, the thermodynamic partition function of molten crystals is shown to be equal to the classical limit of the partition function of the topological string theory by relating the Ronkin function of the characteristic polynomial of the crystal melting model to the holomorphic 3-form on the corresponding Calabi-Yau manifold. PMID:19518695
Exceptional geometry and Borcherds superalgebras
NASA Astrophysics Data System (ADS)
Palmkvist, Jakob
2015-11-01
We study generalized diffeomorphisms in exceptional geometry with U-duality group E n( n) from an algebraic point of view. By extending the Lie algebra {e}_n to an infinite-dimensional Borcherds superalgebra, involving also the extension to {e}_{n+1} , the generalized Lie derivatives can be expressed in a simple way, and the expressions take the same form for any n ≤ 7. The closure of the transformations then follows from the Jacobi identity and the grading of {e}_{n+1} with respect to {e}_n.
Teaching Geometry: An Experiential and Artistic Approach.
ERIC Educational Resources Information Center
Ogletree, Earl J.
The view that geometry should be taught at every grade level is promoted. Primary and elementary school children are thought to rarely have any direct experience with geometry, except on an incidental basis. Children are supposed to be able to learn geometry rather easily, so long as the method and content are adapted to their development and…
Preservice Primary School Teachers' Elementary Geometry Knowledge
ERIC Educational Resources Information Center
Marchis, Iuliana
2012-01-01
Geometrical notions and properties occur in real-world problems, thus Geometry has an important place in school Mathematics curricula. Primary school curricula lays the foundation of Geometry knowledge, pupils learn Geometry notions and properties by exploring their environment. Thus it is very important that primary school teachers have a good…
Geometry in the Early Years: A Commentary
ERIC Educational Resources Information Center
Dindyal, Jaguthsing
2015-01-01
The primary goal of this paper is to provide a commentary on the teaching and learning of geometry in the early years of schooling with the set of papers in this issue as a guiding factor. It is structured around issues about geometry education of young learners, such as: what should we teach in geometry and why; representation of geometrical…
Engaging All Students with "Impossible Geometry"
ERIC Educational Resources Information Center
Wiest, Lynda R.; Ayebo, Abraham; Dornoo, Michael D.
2010-01-01
Geometry is an area in which Australian students performed particularly poorly on the 2007 Trends in International Mathematics and Science Study (TIMSS). One innovative area of recreational geometry that has rich potential to engage and challenge a wide variety of students is "impossible geometry." An impossible geometric object is a…
Geometry: Career Related Units. Teacher's Edition.
ERIC Educational Resources Information Center
Pierro, Mike; And Others
Using six geometry units as resource units, the document explores 22 math-related careers. The authors intend the document to provide senior high school students with career orientation and exploration experiences while they learn geometry skills. The units are to be considered as a part of a geometry course, not a course by themselves. The six…
Use of Geometry for Spatial Reorientation in Children Applies Only to Symmetric Spaces
ERIC Educational Resources Information Center
Lew, Adina R.; Gibbons, Bryony; Murphy, Caroline; Bremner, J. Gavin
2010-01-01
Proponents of the geometric module hypothesis argue that following disorientation, many species reorient by use of macro-environment geometry. It is suggested that attention to the surface layout geometry of natural terrain features may have been selected for over evolutionary time due to the enduring and unambiguous location information it…
Reconstruction of Human Monte Carlo Geometry from Segmented Images
NASA Astrophysics Data System (ADS)
Zhao, Kai; Cheng, Mengyun; Fan, Yanchang; Wang, Wen; Long, Pengcheng; Wu, Yican
2014-06-01
Human computational phantoms have been used extensively for scientific experimental analysis and experimental simulation. This article presented a method for human geometry reconstruction from a series of segmented images of a Chinese visible human dataset. The phantom geometry could actually describe detailed structure of an organ and could be converted into the input file of the Monte Carlo codes for dose calculation. A whole-body computational phantom of Chinese adult female has been established by FDS Team which is named Rad-HUMAN with about 28.8 billion voxel number. For being processed conveniently, different organs on images were segmented with different RGB colors and the voxels were assigned with positions of the dataset. For refinement, the positions were first sampled. Secondly, the large sums of voxels inside the organ were three-dimensional adjacent, however, there were not thoroughly mergence methods to reduce the cell amounts for the description of the organ. In this study, the voxels on the organ surface were taken into consideration of the mergence which could produce fewer cells for the organs. At the same time, an indexed based sorting algorithm was put forward for enhancing the mergence speed. Finally, the Rad-HUMAN which included a total of 46 organs and tissues was described by the cuboids into the Monte Carlo Monte Carlo Geometry for the simulation. The Monte Carlo geometry was constructed directly from the segmented images and the voxels was merged exhaustively. Each organ geometry model was constructed without ambiguity and self-crossing, its geometry information could represent the accuracy appearance and precise interior structure of the organs. The constructed geometry largely retaining the original shape of organs could easily be described into different Monte Carlo codes input file such as MCNP. Its universal property was testified and high-performance was experimentally verified
Geometry of modified Newtonian dynamics
NASA Astrophysics Data System (ADS)
Skordis, Constantinos; Zlosnik, Tom
2012-02-01
Modified Newtonian dynamics is an empirical modification to Poisson’s equation which has had success in accounting for the “gravitational field” Φ in a variety of astrophysical systems. The field Φ may be interpreted in terms of the weak-field limit of a variety of spacetime geometries. Here we consider three of these geometries in a more comprehensive manner and look at the effect on timelike and null geodesics. In particular we consider the aquadratic Lagrangian (AQUAL) theory, tensor-vector-scalar (TeVeS) theory and generalized Einstein-aether theory. We uncover a number of novel features, some of which are specific to the theory considered while others are generic. In the case of AQUAL and TeVeS theories, the spacetime exhibits an excess (AQUAL) or deficit TeVeS solid angle akin to the case of a Barriola-Vilenkin global monopole. In the case of generalized Einstein-aether, a disformal symmetry of the action emerges in the limit of ∇→Φ→0. Finally, in all theories studied, massive particles can never reach spatial infinity while photons can do so only after experiencing infinite redshift.
Quanta of geometry: noncommutative aspects.
Chamseddine, Ali H; Connes, Alain; Mukhanov, Viatcheslav
2015-03-01
In the construction of spectral manifolds in noncommutative geometry, a higher degree Heisenberg commutation relation involving the Dirac operator and the Feynman slash of real scalar fields naturally appears and implies, by equality with the index formula, the quantization of the volume. We first show that this condition implies that the manifold decomposes into disconnected spheres, which will represent quanta of geometry. We then refine the condition by involving the real structure and two types of geometric quanta, and show that connected spin manifolds with large quantized volume are then obtained as solutions. The two algebras M_{2}(H) and M_{4}(C) are obtained, which are the exact constituents of the standard model. Using the two maps from M_{4} to S^{4} the four-manifold is built out of a very large number of the two kinds of spheres of Planckian volume. We give several physical applications of this scheme such as quantization of the cosmological constant, mimetic dark matter, and area quantization of black holes. PMID:25793795
Turbine engine variable geometry device
NASA Technical Reports Server (NTRS)
Rogo, Casimir (Inventor); Lenz, Herman N. (Inventor)
1985-01-01
A variable geometry device for use with the turbine nozzle of a turbine engine of the type having a support housing and a combustion chamber contained within the support housing. A pair of spaced walls in the support housing define an annular and radially extending nozzle passageway. The outer end of the nozzle passageway is open to the combustion chamber while the inner end of the nozzle passageway is open to one or more turbine stages. A plurality of circumferentially spaced nozzle vanes are mounted to one of the spaced walls and protrude across the nozzle passageway. An annular opening is formed around the opposite spaced wall and an annular ring is axially slidably mounted within the opening. A motor is operatively connected to this ring and, upon actuation, axially displaces the ring within the nozzle passageway. In addition, the ring includes a plurality of circumferentially spaced slots which register with the nozzle vanes so that the vane geometry remains the same despite axial displacement of the ring.
Geometry and the quantum: basics
NASA Astrophysics Data System (ADS)
Chamseddine, Ali H.; Connes, Alain; Mukhanov, Viatcheslav
2014-12-01
Motivated by the construction of spectral manifolds in noncommutative geometry, we introduce a higher degree Heisenberg commutation relation involving the Dirac operator and the Feynman slash of scalar fields. This commutation relation appears in two versions, one sided and two sided. It implies the quantization of the volume. In the one-sided case it implies that the manifold decomposes into a disconnected sum of spheres which will represent quanta of geometry. The two sided version in dimension 4 predicts the two algebras M 2(ℍ) and M 4(ℂ) which are the algebraic constituents of the Standard Model of particle physics. This taken together with the non-commutative algebra of functions allows one to reconstruct, using the spectral action, the Lagrangian of gravity coupled with the Standard Model. We show that any connected Riemannian Spin 4-manifold with quantized volume > 4 (in suitable units) appears as an irreducible representation of the two-sided commutation relations in dimension 4 and that these representations give a seductive model of the "particle picture" for a theory of quantum gravity in which both the Einstein geometric standpoint and the Standard Model emerge from Quantum Mechanics. Physical applications of this quantization scheme will follow in a separate publication.
Neuronal activity controls transsynaptic geometry
Glebov, Oleg O.; Cox, Susan; Humphreys, Lawrence; Burrone, Juan
2016-01-01
The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792
Alternative cosmology from cusp geometries
NASA Astrophysics Data System (ADS)
Rosa, Reinaldo; Herbin Stalder Díaz, Diego
We study an alternative geometrical approach on the problem of classical cosmological singularity. It is based on a generalized function f(x,y)=x(2+y^2=(1-z)z^n) which consists of a cusped projected coupled isosurface. Such a projected geometry is computed and analized into the context of Friedmann singularity-free cosmology where a pre-big bang scenario is considered. Assuming that the mechanism of cusp formation is described by non-linear oscillations of a pre- big bang extended very high energy density field (>3x10^{94} kg/m^3$), we show that the action under the gravitational field follows a tautochrone of revolution, understood here as the primary projected geometry that alternatively replaces the Friedmann singularity in the standard big bang theory. As shown here this new approach allows us to interpret the nature of both matter and dark energy from first geometric principles [1]. [1] Rosa et al. DOI: 10.1063/1.4756991
Fuzzy Logic for Incidence Geometry
2016-01-01
The paper presents a mathematical framework for approximate geometric reasoning with extended objects in the context of Geography, in which all entities and their relationships are described by human language. These entities could be labelled by commonly used names of landmarks, water areas, and so forth. Unlike single points that are given in Cartesian coordinates, these geographic entities are extended in space and often loosely defined, but people easily perform spatial reasoning with extended geographic objects “as if they were points.” Unfortunately, up to date, geographic information systems (GIS) miss the capability of geometric reasoning with extended objects. The aim of the paper is to present a mathematical apparatus for approximate geometric reasoning with extended objects that is usable in GIS. In the paper we discuss the fuzzy logic (Aliev and Tserkovny, 2011) as a reasoning system for geometry of extended objects, as well as a basis for fuzzification of the axioms of incidence geometry. The same fuzzy logic was used for fuzzification of Euclid's first postulate. Fuzzy equivalence relation “extended lines sameness” is introduced. For its approximation we also utilize a fuzzy conditional inference, which is based on proposed fuzzy “degree of indiscernibility” and “discernibility measure” of extended points. PMID:27689133
Weyl gravity and Cartan geometry
NASA Astrophysics Data System (ADS)
Attard, J.; François, J.; Lazzarini, S.
2016-04-01
We point out that the Cartan geometry known as the second-order conformal structure provides a natural differential geometric framework underlying gauge theories of conformal gravity. We are concerned with two theories: the first one is the associated Yang-Mills-like Lagrangian, while the second, inspired by [1], is a slightly more general one that relaxes the conformal Cartan geometry. The corresponding gauge symmetry is treated within the Becchi-Rouet-Stora-Tyutin language. We show that the Weyl gauge potential is a spurious degree of freedom, analogous to a Stueckelberg field, that can be eliminated through the dressing field method. We derive sets of field equations for both the studied Lagrangians. For the second one, they constrain the gauge field to be the "normal conformal Cartan connection.''Finally, we provide in a Lagrangian framework a justification of the identification, in dimension 4, of the Bach tensor with the Yang-Mills current of the normal conformal Cartan connection, as proved in [2].
Target Detection Using Fractal Geometry
NASA Technical Reports Server (NTRS)
Fuller, J. Joseph
1991-01-01
The concepts and theory of fractal geometry were applied to the problem of segmenting a 256 x 256 pixel image so that manmade objects could be extracted from natural backgrounds. The two most important measurements necessary to extract these manmade objects were fractal dimension and lacunarity. Provision was made to pass the manmade portion to a lookup table for subsequent identification. A computer program was written to construct cloud backgrounds of fractal dimensions which were allowed to vary between 2.2 and 2.8. Images of three model space targets were combined with these backgrounds to provide a data set for testing the validity of the approach. Once the data set was constructed, computer programs were written to extract estimates of the fractal dimension and lacunarity on 4 x 4 pixel subsets of the image. It was shown that for clouds of fractal dimension 2.7 or less, appropriate thresholding on fractal dimension and lacunarity yielded a 64 x 64 edge-detected image with all or most of the cloud background removed. These images were enhanced by an erosion and dilation to provide the final image passed to the lookup table. While the ultimate goal was to pass the final image to a neural network for identification, this work shows the applicability of fractal geometry to the problems of image segmentation, edge detection and separating a target of interest from a natural background.
NASA Astrophysics Data System (ADS)
Cieslinski, Jan L.; Ferapontov, Eugene V.; Kitaev, Alexander V.; Nimmo, Jonathan J. C.
2009-10-01
Geometric ideas are present in many areas of modern theoretical physics and they are usually associated with the presence of nonlinear phenomena. Integrable nonlinear systems play a prime role both in geometry itself and in nonlinear physics. One can mention general relativity, exact solutions of the Einstein equations, string theory, Yang-Mills theory, instantons, solitons in nonlinear optics and hydrodynamics, vortex dynamics, solvable models of statistical physics, deformation quantization, and many others. Soliton theory now forms a beautiful part of mathematics with very strong physical motivations and numerous applications. Interactions between mathematics and physics associated with integrability issues are very fruitful and stimulating. For instance, spectral theories of linear quantum mechanics turned out to be crucial for studying nonlinear integrable systems. The modern theory of integrable nonlinear partial differential and difference equations, or the `theory of solitons', is deeply rooted in the achievements of outstanding geometers of the end of the 19th and the beginning of the 20th century, such as Luigi Bianchi (1856-1928) and Jean Gaston Darboux (1842-1917). Transformations of surfaces and explicit constructions developed by `old' geometers were often rediscovered or reinterpreted in a modern framework. The great progress of recent years in so-called discrete geometry is certainly due to strong integrable motivations. A very remarkable feature of the results of the classical integrable geometry is the quite natural (although nontrivial) possibility of their discretization. This special issue is dedicated to Jean Gaston Darboux and his pioneering role in the development of the geometric ideas of modern soliton theory. The most famous aspects of his work are probably Darboux transformations and triply orthogonal systems of surfaces, whose role in modern mathematical physics cannot be overestimated. Indeed, Darboux transformations play a central
Geometry optimization for micro-pressure sensor considering dynamic interference.
Yu, Zhongliang; Zhao, Yulong; Li, Lili; Tian, Bian; Li, Cun
2014-09-01
Presented is the geometry optimization for piezoresistive absolute micro-pressure sensor. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency, and acceleration interference. Three geometries are proposed through introducing islands and sensitive beams into typical flat diaphragm. The stress distributions of sensitive elements are analyzed by finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations about surface stress, deflection, and resonant frequency. Optimization by MATLAB is carried out to determine the dimensions of the geometries. Convex corner undercutting is evaluated. Each PF of the three geometries with the determined dimensions is calculated and compared. Silicon bulk micromachining is utilized to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results demonstrate the rationality of the defined performance factor and reveal that the geometry with quad islands presents the highest PF of 210.947 Hz(1/4). The favorable overall performances enable the sensor more suitable for altimetry.
Geometry optimization for micro-pressure sensor considering dynamic interference
Yu, Zhongliang; Zhao, Yulong Li, Lili; Tian, Bian; Li, Cun
2014-09-15
Presented is the geometry optimization for piezoresistive absolute micro-pressure sensor. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency, and acceleration interference. Three geometries are proposed through introducing islands and sensitive beams into typical flat diaphragm. The stress distributions of sensitive elements are analyzed by finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations about surface stress, deflection, and resonant frequency. Optimization by MATLAB is carried out to determine the dimensions of the geometries. Convex corner undercutting is evaluated. Each PF of the three geometries with the determined dimensions is calculated and compared. Silicon bulk micromachining is utilized to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results demonstrate the rationality of the defined performance factor and reveal that the geometry with quad islands presents the highest PF of 210.947 Hz{sup 1/4}. The favorable overall performances enable the sensor more suitable for altimetry.
Tuning spin transport properties and molecular magnetoresistance through contact geometry
Ulman, Kanchan; Narasimhan, Shobhana; Delin, Anna
2014-01-28
Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its “closed” and “open” conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%.
Descriptive Geometry and Geometric Modeling.
ERIC Educational Resources Information Center
Adams, J. Alan
1988-01-01
Describes experiences for engineering students to develop spatial awareness and reasoning capability. Describes geometric modeling, basic geometric concepts, operations, surface modeling, and conclusions. (YP)
Lefort, Natalie; LeBlanc, Rémi; Giroux, Marie-Andrée; Surette, Marc E
2016-01-01
Enrichment of tissues with ≥20-carbon n-3 PUFA like EPA is associated with positive cardiovascular outcomes. Stearidonic acid (SDA; 18 : 4n-3) and α-linolenic acid (ALA; 18 : 3n-3) are plant-derived dietary n-3 PUFA; however, direct comparisons of their impact on tissue n-3 PUFA content are lacking. Ahiflower(®) oil extracted from Buglossoides arvensis seeds is the richest known non-genetically modified source of dietary SDA. To investigate the safety and efficacy of dietary Ahiflower oil, a parallel-group, randomised, double-blind, comparator-controlled phase I clinical trial was performed. Diets of healthy subjects (n 40) were supplemented for 28 d with 9·1 g/d of Ahiflower (46 % ALA, 20 % SDA) or flax seed oil (59 % ALA). Blood and urine chemistries, blood lipid profiles, hepatic and renal function tests and haematology were measured as safety parameters. The fatty acid composition of fasting plasma, erythrocytes, polymorphonuclear cells and mononuclear cells were measured at baseline and after 14 and 28 d of supplementation. No clinically significant changes in safety parameters were measured in either group. Tissue ALA and EPA content increased in both groups compared with baseline, but EPA accrual in plasma and in all cell types was greater in the Ahiflower group (time × treatment interactions, P ≤ 0·01). Plasma and mononuclear cell eicosatetraenoic acid (20 : 4n-3) and docosapentaenoic acid (22 : 5n-3) content also increased significantly in the Ahiflower group compared with the flax group. In conclusion, the consumption of Ahiflower oil is safe and is more effective for the enrichment of tissues with 20- and 22-carbon n-3 PUFA than flax seed oil. PMID:26793308
Gully geometry: what are we measuring?
NASA Astrophysics Data System (ADS)
Casalí, Javier; Giménez, Rafael; Ángel Campo, Miguel
2014-05-01
Gully erosion has attracted the attention of many scientists during the last decades, and gullies are an important source of sediment within catchments. For succeeding in gully erosion research, gullies must be properly characterized. Characterization includes the determination of gully morphology and volume, being the definition of gully width (W) and depth (D) -and consequently related variables such as the well-known W/D ratio- key issues toward to this goal. However, and surprisingly, universally accepted criteria (rules or guidance) to define gully morphology are lacking. This because the protocol every researcher follows to measure the eroded channel geometry is generally taken for granted and most of the time even no explanation is given about it. For example, when analyzing a gully cross section we usually just identify gully depth with gully maximum depth. But, is this the right protocol? What does this length really represent? What is its meaning? All this uncertainties can lead to non-comparable results and then important inconsistencies. So, to define universal rules of procedure would allow gully scientists "speak the same language" and then deliver truly comparable gully geometry and volume. On the other hand, there are other misunderstandings. For example, very frequently we characterize or depict a whole gully only through some of its cross sections. Again, is this correct? The problem is even more complex when considering that gully geometry may (largely) change along the channel. The main aim of this presentation is to highlight some (unnoticed) common flaws when measuring and describing gully geometry, hoping ultimately to open a debate on that subject. For this last purpose, a conceptual approach to define gully cross section width and other derived variables is firstly proposed. It is based on the subtraction of a highly detailed digital elevation model of a landscape surface containing the studied gully (DEM1) from a detailed spatial
Powell, Rocky O.; Miller, Sarah J.; Westergard, Britt E.; Mulvihill, Christiane I.; Baldigo, Barry P.; Gallagher, Anne S.; Starr, Richard R.
2004-01-01
Many disturbed streams within New York State are being restored in an effort to provide bank and bed stability and thereby decrease sedimentation and erosion. Efforts to identify and provide accurate indicators for stable-channel characteristics for ungaged streams have been hampered by the lack of regional equations or relations that relate drainage area to bankfull discharge and to channel depth, width, and cross-sectional area (bankfull hydraulic-geometry relations). Regional equations are needed to confirm bankfull hydraulic-geometry, assess stream stability, evaluate restoration needs, and verify restoration design for ungaged streams that lack stage-to-discharge ratings or historic peak-flow records. This report presents guidelines for surveying bankfull channel geometry at USGS stream gages and developing regional hydraulic-geometry relations (equations) for wadeable streams in New York. It summarizes methods to (1) compile and assess existing hydrologic, geometric, photographic, and topographic data, (2) conduct stream-reconnaissance inspections, (3) identify channel-bankfull characteristics, (4) conduct longitudinal and cross-section surveys, (5) measure stream discharge, (6) develop and refine bankfull hydraulic-geometry equations, and (7) analyze and assure data completeness and quality. The techniques primarily address wadeable streams with either active or discontinued surface-water and crest-stage gages. The relations can be applied to ungaged or actively gaged streams that are wadeable, and may be extended to non-wadeable streams (with some limitations) if they have drainage areas comparable to those used to develop the relations.
Quadric solids and computational geometry
Emery, J.D.
1980-07-25
As part of the CAD-CAM development project, this report discusses the mathematics underlying the program QUADRIC, which does computations on objects modeled as Boolean combinations of quadric half-spaces. Topics considered include projective space, quadric surfaces, polars, affine transformations, the construction of solids, shaded image, the inertia tensor, moments, volume, surface integrals, Monte Carlo integration, and stratified sampling. 1 figure.
Interactive graphics for geometry modeling
NASA Technical Reports Server (NTRS)
Wozny, M. J.
1984-01-01
An interactive vector capability to create geometry and a raster color shaded rendering capability to sample and verify interim geometric design steps through color snapshots is described. The development is outlined of the underlying methodology which facilitates computer aided engineering and design. At present, raster systems cannot match the interactivity and line-drawing capability of refresh vector systems. Consequently, an intermediate step in mechanical design is used to create objects interactively on the vector display and then scan convert the wireframe model to render it as a color shaded object on a raster display. Several algorithms are presented for rendering such objects. Superquadric solid primitive extend the class of primitives normally used in solid modelers.
Quantum gauge theories from geometry
NASA Astrophysics Data System (ADS)
Galehouse, Daniel C.
2006-03-01
Geometrical theories have been developed to describe quantum interacting particles with full mathematical covariance. They possess a sophisticated gauge structure that derives from the fundamental properties of the geometry. These theories are all implicitly quantized and come in three known types: Weyl, non-compactified Kaluza-Klein, and, as presented here, Dirac. The spin one-half particle is a conformal wave in an eight dimensional Riemannian space. The coordinates transform locally as spinors and project into space time to give the known gravitational and electromagnetic forces. The gauge structure of the weak interactions appears as well, as in this space the electron transforms into a neutrino under hyper-rotations. The possibility of including the strong interactions and the corresponding gauge system is discussed.
Noncommutative Geometry and Basic Physics
NASA Astrophysics Data System (ADS)
Kastler, Daniel
Alain Connes' noncommutative geometry, started in 1982 [0], widely developed in 1994 as expounded in his book at this date [0] (it has grown meanwhile) is a systematic quantization of mathematics parallel to the quantization of physics effected in the twenties.This theory widens the scope of mathematics in a manner congenial to physics, reorganizes the existing ("classical") mathematics of which it produces an hitherto unsuspected unification, and provides basic physics (the synthesis of elementary particles and gravitation) with a programme of renewal which has thus far achieved a clarification of the classical (tree-level) aspects of a new synthesis of the (Euclidean) standard model with gravitation [32],[33]: this is the subject of the present lectures - with the inherent tentative prediction of the Higgs mass.
Eddy Current Inspection of Components with Complex Geometries
NASA Astrophysics Data System (ADS)
Plotnikov, Yuri; Wang, Changting; McKnight, William; Suh, Ui
2008-02-01
Eddy current (EC) technique is a common inspection method for the detection of open surface cracks and subsurface anomalies. While manual EC inspection is quite reliable on parts with flat (or large curvature) surfaces and parts with consistent subsurface geometry, EC inspection of parts having more complicated surface and subsurface profiles has to rely on automated scan/data collection and post-processing. Examples of the structures with complex geometries are aircraft engine rotating parts and multi-layer aircraft structures (lap joints). Data collection for such structures, in most cases, can be performed by using multiple scans of a single sensor EC probe with multi-frequency excitation. To improve productivity of the inspection, arrays of EC sensors are applied during inspection for surface flaws. In this work, the flexible ECAP (EC array probe) with sensitivity to the cracks of variable orientations is presented. To resolve the complex subsurface geometry of the aircraft skin, pulsed excitation is employed. This makes for a faster data collection and full post-processing capabilities. Conversion to multi-frequency (multi-layer) image analysis is done after data collection is completed. The subsurface flaws present in a particular layer of a riveted lap joint become evident from several EC images, which cannot be accomplished by manual inspection.
Geometry of discrete quantum computing
NASA Astrophysics Data System (ADS)
Hanson, Andrew J.; Ortiz, Gerardo; Sabry, Amr; Tai, Yu-Tsung
2013-05-01
Conventional quantum computing entails a geometry based on the description of an n-qubit state using 2n infinite precision complex numbers denoting a vector in a Hilbert space. Such numbers are in general uncomputable using any real-world resources, and, if we have the idea of physical law as some kind of computational algorithm of the universe, we would be compelled to alter our descriptions of physics to be consistent with computable numbers. Our purpose here is to examine the geometric implications of using finite fields Fp and finite complexified fields \\mathbf {F}_{p^2} (based on primes p congruent to 3 (mod4)) as the basis for computations in a theory of discrete quantum computing, which would therefore become a computable theory. Because the states of a discrete n-qubit system are in principle enumerable, we are able to determine the proportions of entangled and unentangled states. In particular, we extend the Hopf fibration that defines the irreducible state space of conventional continuous n-qubit theories (which is the complex projective space \\mathbf {CP}^{2^{n}-1}) to an analogous discrete geometry in which the Hopf circle for any n is found to be a discrete set of p + 1 points. The tally of unit-length n-qubit states is given, and reduced via the generalized Hopf fibration to \\mathbf {DCP}^{2^{n}-1}, the discrete analogue of the complex projective space, which has p^{2^{n}-1} (p-1)\\,\\prod _{k=1}^{n-1} ( p^{2^{k}}+1) irreducible states. Using a measure of entanglement, the purity, we explore the entanglement features of discrete quantum states and find that the n-qubit states based on the complexified field \\mathbf {F}_{p^2} have pn(p - 1)n unentangled states (the product of the tally for a single qubit) with purity 1, and they have pn + 1(p - 1)(p + 1)n - 1 maximally entangled states with purity zero.
Changing the Structure Boundary Geometry
Karasev, Viktor; Dzlieva, Elena; Ivanov, Artyom
2008-09-07
Analysis of previously obtained results shows that hexagonal crystal lattice is the dominant type of ordering, in particular, in striated glow discharges. We explore the possibility for changing the dust distribution in horizontal cross sections of relatively highly ordered structures in a glow-discharge. Presuming that boundary geometry can affect dust distribution, we used cylindrical coolers held at 0 deg. C and placed against a striation containing a structure, to change the geometry of its outer boundary. By varying the number of coolers, their positions, and their separations from the tube wall, azimuthally asymmetric thermophoretic forces can be used to form polygonal boundaries and vary the angles between their segments (in a horizontal cross section). The corner in the structure's boundary of 60 deg. stimulates formation of hexagonal cells. The structure between the supported parallel boundaries is also characterized by stable hexagonal ordering. We found that a single linear boundary segment does not give rise to any sizable domain, but generates a lattice extending from the boundary (without edge defects). A square lattice can be formed by setting the angle equal to 90 deg. . However, angles of 45 deg. and 135 deg. turned out easier to form. Square lattice was created by forming a near-135 deg. corner with four coolers. It was noted that no grain ordering is observed in the region adjacent to corners of angles smaller than 30 deg. , which do not promote ordering into cells of any shape. Thus, manipulation of a structure boundary can be used to change dust distribution, create structures free of the ubiquitous edge defects that destroy orientation order, and probably change the crystal lattice type.
Digital breast tomosynthesis geometry calibration
NASA Astrophysics Data System (ADS)
Wang, Xinying; Mainprize, James G.; Kempston, Michael P.; Mawdsley, Gordon E.; Yaffe, Martin J.
2007-03-01
Digital Breast Tomosynthesis (DBT) is a 3D x-ray technique for imaging the breast. The x-ray tube, mounted on a gantry, moves in an arc over a limited angular range around the breast while 7-15 images are acquired over a period of a few seconds. A reconstruction algorithm is used to create a 3D volume dataset from the projection images. This procedure reduces the effects of tissue superposition, often responsible for degrading the quality of projection mammograms. This may help improve sensitivity of cancer detection, while reducing the number of false positive results. For DBT, images are acquired at a set of gantry rotation angles. The image reconstruction process requires several geometrical factors associated with image acquisition to be known accurately, however, vibration, encoder inaccuracy, the effects of gravity on the gantry arm and manufacturing tolerances can produce deviations from the desired acquisition geometry. Unlike cone-beam CT, in which a complete dataset is acquired (500+ projections over 180°), tomosynthesis reconstruction is challenging in that the angular range is narrow (typically from 20°-45°) and there are fewer projection images (~7-15). With such a limited dataset, reconstruction is very sensitive to geometric alignment. Uncertainties in factors such as detector tilt, gantry angle, focal spot location, source-detector distance and source-pivot distance can produce several artifacts in the reconstructed volume. To accurately and efficiently calculate the location and angles of orientation of critical components of the system in DBT geometry, a suitable phantom is required. We have designed a calibration phantom for tomosynthesis and developed software for accurate measurement of the geometric parameters of a DBT system. These have been tested both by simulation and experiment. We will present estimates of the precision available with this technique for a prototype DBT system.
Convection in Slab and Spheroidal Geometries
NASA Technical Reports Server (NTRS)
Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.
2000-01-01
Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.
Fuel Injector Design Optimization for an Annular Scramjet Geometry
NASA Astrophysics Data System (ADS)
Steffen, Christopher J., Jr.
2003-01-01
A four-parameter, three-level, central composite experiment design has been used to optimize the configuration of an annular scramjet injector geometry using computational fluid dynamics. The computational fluid dynamic solutions played the role of computer experiments, and response surface methodology was used to capture the simulation results for mixing efficiency and total pressure recovery within the scramjet flowpath. An optimization procedure, based upon the response surface results of mixing efficiency, was used to compare the optimal design configuration against the target efficiency value of 92.5%. The results of three different optimization procedures are presented and all point to the need to look outside the current design space for different injector geometries that can meet or exceed the stated mixing efficiency target.
Acoustic Radiation from Smart Foam for Various Foam Geometries
NASA Astrophysics Data System (ADS)
Shivakumar, Nishkala
2011-10-01
Smart foam is an emerging active-passive noise control technology with many applications. Smart foam consists of passive foam with an embedded curved piezoelectric (PZT) film. We experimented with three geometries of varying film curvatures and a constant cross-sectional area of 58 cm^2, constructed using melamine foam covered with 28 μm thick polyvinylidene fluoride (piezoelectric) films with Cu-Ni surface electrodes. An AC voltage provided by a signal generator and amplifier drives the smart foam. An omnidirectional microphone mounted at a distance 100mm from the foam surface measured the sound level (dB) and harmonic distortion generated by the smart foam. Experiments were repeated for voltages, 40V-140V, and frequencies, 300Hz-2000Hz. The result show that the sound level generated by the smart foams has a characteristic frequency response common to all geometries and a peak sound level between 900 to 1,100 Hz.
Interactive Isogeometric Volume Visualization with Pixel-Accurate Geometry.
Fuchs, Franz G; Hjelmervik, Jon M
2016-02-01
A recent development, called isogeometric analysis, provides a unified approach for design, analysis and optimization of functional products in industry. Traditional volume rendering methods for inspecting the results from the numerical simulations cannot be applied directly to isogeometric models. We present a novel approach for interactive visualization of isogeometric analysis results, ensuring correct, i.e., pixel-accurate geometry of the volume including its bounding surfaces. The entire OpenGL pipeline is used in a multi-stage algorithm leveraging techniques from surface rendering, order-independent transparency, as well as theory and numerical methods for ordinary differential equations. We showcase the efficiency of our approach on different models relevant to industry, ranging from quality inspection of the parametrization of the geometry, to stress analysis in linear elasticity, to visualization of computational fluid dynamics results. PMID:26731454
Interactive Isogeometric Volume Visualization with Pixel-Accurate Geometry.
Fuchs, Franz G; Hjelmervik, Jon M
2016-02-01
A recent development, called isogeometric analysis, provides a unified approach for design, analysis and optimization of functional products in industry. Traditional volume rendering methods for inspecting the results from the numerical simulations cannot be applied directly to isogeometric models. We present a novel approach for interactive visualization of isogeometric analysis results, ensuring correct, i.e., pixel-accurate geometry of the volume including its bounding surfaces. The entire OpenGL pipeline is used in a multi-stage algorithm leveraging techniques from surface rendering, order-independent transparency, as well as theory and numerical methods for ordinary differential equations. We showcase the efficiency of our approach on different models relevant to industry, ranging from quality inspection of the parametrization of the geometry, to stress analysis in linear elasticity, to visualization of computational fluid dynamics results.
Riemannian geometry of fluctuation theory: An introduction
NASA Astrophysics Data System (ADS)
Velazquez, Luisberis
2016-05-01
Fluctuation geometry was recently proposed as a counterpart approach of Riemannian geometry of inference theory (information geometry), which describes the geometric features of the statistical manifold M of random events that are described by a family of continuous distributions dpξ(x|θ). This theory states a connection among geometry notions and statistical properties: separation distance as a measure of relative probabilities, curvature as a measure about the existence of irreducible statistical correlations, among others. In statistical mechanics, fluctuation geometry arises as the mathematical apparatus of a Riemannian extension of Einstein fluctuation theory, which is also closely related to Ruppeiner geometry of thermodynamics. Moreover, the curvature tensor allows to express some asymptotic formulae that account for the system fluctuating behavior beyond the gaussian approximation, while curvature scalar appears as a second-order correction of Legendre transformation between thermodynamic potentials.
Geometry of solar coronal rays
NASA Astrophysics Data System (ADS)
Filippov, B. P.; Martsenyuk, O. V.; Platov, Yu. V.; Den, O. E.
2016-02-01
Coronal helmet streamers are the most prominent large-scale elements of the solar corona observed in white light during total solar eclipses. The base of the streamer is an arcade of loops located above a global polarity inversion line. At an altitude of 1-2 solar radii above the limb, the apices of the arches sharpen, forming cusp structures, above which narrow coronal rays are observed. Lyot coronagraphs, especially those on-board spacecrafts flying beyond the Earth's atmosphere, enable us to observe the corona continuously and at large distances. At distances of several solar radii, the streamers take the form of fairly narrow spokes that diverge radially from the Sun. This radial direction displays a continuous expansion of the corona into the surrounding space, and the formation of the solar wind. However, the solar magnetic field and solar rotation complicate the situation. The rotation curves radial streams into spiral ones, similar to water streams flowing from rotating tubes. The influence of the magnetic field is more complex and multifarious. A thorough study of coronal ray geometries shows that rays are frequently not radial and not straight. Coronal streamers frequently display a curvature whose direction in the meridional plane depends on the phase of the solar cycle. It is evident that this curvature is related to the geometry of the global solar magnetic field, which depends on the cycle phase. Equatorward deviations of coronal streamers at solar minima and poleward deviations at solar maxima can be interpreted as the effects of changes in the general topology of the global solar magnetic field. There are sporadic temporal changes in the coronal rays shape caused by remote coronal mass ejections (CMEs) propagating through the corona. This is also a manifestation of the influence of the magnetic field on plasma flows. The motion of a large-scale flux rope associated with a CME away from the Sun creates changes in the structure of surrounding field
Effect of torso geometry on the magnetocardiogram.
Tripp, J H
1977-01-01
Calculations of the effect of torso geometry on the extracorporeal magnetic field produced by a simple cardiac source have been carried out. Contrary to the results at present in the literature, it is found that the field solution is stable under perturbations of geometry in the sense that small relative changes in geometry produce comparably small changes in the magnetic field. Thus, simplified torso models may have a wider range of validity and usefulness than was previously thought. PMID:890026
Disformal transformation in Newton-Cartan geometry
NASA Astrophysics Data System (ADS)
Huang, Peng; Yuan, Fang-Fang
2016-08-01
Newton-Cartan geometry has played a central role in recent discussions of the non-relativistic holography and condensed matter systems. Although the conformal transformation in non-relativistic holography can easily be rephrased in terms of Newton-Cartan geometry, we show that it requires a nontrivial procedure to arrive at the consistent form of anisotropic disformal transformation in this geometry. Furthermore, as an application of the newly obtained transformation, we use it to induce a geometric structure which may be seen as a particular non-relativistic version of the Weyl integrable geometry.
Cusp geometry in MHD simulations
NASA Astrophysics Data System (ADS)
Siscoe, George; Crooker, Nancy; Siebert, Keith; Maynard, Nelson; Weimer, Daniel; White, Willard
2005-01-01
The MHD simulations described here show that the latitude of the high-altitude cusp decreases as the IMF swings from North to South, that there is a pronounced dawn dusk asymmetry at high-altitude associated with a dawn dusk component of the IMF, and that at the same time there is also a pronounced dawn dusk asymmetry at low-altitude. The simulations generate a feature that represents what has been called the cleft. It appears as a tail (when the IMF has a By component) attached to the cusp, extending either toward the dawn flank or the dusk flank depending on the dawn dusk orientation of the IMF. This one-sided cleft connects the cusp to the magnetospheric sash. We compare cusp geometry predicted by MHD simulations against published observations based on Hawkeye and DMSP data. Regarding the high-altitude predictions, the comparisons are not definitive, mainly because the observations are incomplete or mutually inconsistent. Regarding the low-altitude prediction of a strong dawn dusk asymmetry, the observations are unambiguous and are in good qualitative agreement with the prediction.
NASA Astrophysics Data System (ADS)
Anderson, Lara B.; Heckman, Jonathan J.; Katz, Sheldon
2014-05-01
T-branes are a non-abelian generalization of intersecting branes in which the matrix of normal deformations is nilpotent along some subspace. In this paper we study the geometric remnant of this open string data for six-dimensional F-theory vacua. We show that in the dual M-theory / IIA compactification on a smooth Calabi-Yau threefold X smth, the geometric remnant of T-brane data translates to periods of the three-form potential valued in the intermediate Jacobian of X smth. Starting from a smoothing of a singular Calabi-Yau, we show how to track this data in singular limits using the theory of limiting mixed Hodge structures, which in turn directly points to an emergent Hitchin-like system coupled to defects. We argue that the physical data of an F-theory compactification on a singular threefold involves specifying both a geometry as well as the remnant of three-form potential moduli and flux which is localized on the discriminant. We give examples of T-branes in compact F-theory models with heterotic duals, and comment on the extension of our results to four-dimensional vacua.
Eye movements and information geometry.
Lenz, Reiner
2016-08-01
The human visual system uses eye movements to gather visual information. They act as visual scanning processes and can roughly be divided into two different types: small movements around fixation points and larger movements between fixation points. The processes are often modeled as random walks, and recent models based on heavy tail distributions, also known as Levý flights, have been used in these investigations. In contrast to these approaches we do not model the stochastic processes, but we will show that the step lengths of the movements between fixation points follow generalized Pareto distributions (GPDs). We will use general arguments from the theory of extreme value statistics to motivate the usage of the GPD and show empirically that the GPDs provide good fits for measured eye tracking data. In the framework of information geometry the GPDs with a common threshold form a two-dimensional Riemann manifold with the Fisher information matrix as a metric. We compute the Fisher information matrix for the GPDs and introduce a feature vector describing a GPD by its parameters and different geometrical properties of its Fisher information matrix. In our statistical analysis we use eye tracker measurements in a database with 15 observers viewing 1003 images under free-viewing conditions. We use Matlab functions with their standard parameter settings and show that a naive Bayes classifier using the eigenvalues of the Fisher information matrix provides a high classification rate identifying the 15 observers in the database. PMID:27505658
Combinatorics, geometry, and mathematical physics
Chen, W.Y.C.; Louck, J.D.
1998-11-01
This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Combinatorics and geometry have been among the most active areas of mathematics over the past few years because of newly discovered inter-relations between them and their potential for applications. In this project, the authors set out to identify problems in physics, chemistry, and biology where these methods could impact significantly. In particular, the experience suggested that the areas of unitary symmetry and discrete dynamical systems could be brought more strongly under the purview of combinatorial methods. Unitary symmetry deals with the detailed description of the quantum mechanics of many-particle systems, and discrete dynamical systems with chaotic systems. The depth and complexity of the mathematics in these physical areas of research suggested that not only could significant advances be made in these areas, but also that here would be a fertile feedback of concept and structure to enrich combinatorics itself by setting new directions. During the three years of this project, the goals have been realized beyond expectation, and in this report the authors set forth these advancements and justify their optimism.
The effects of solidification on sill propagation dynamics and geometry
NASA Astrophysics Data System (ADS)
Lola, Chanceaux; Thierry, Menand
2015-04-01
The effects of solidification on sill propagation dynamics and geometry are studied by means of analogue laboratory experiments. Hot fluid vegetable oil (a magma analogue), that solidifies during its propagation, is injected as a sill in a colder layered gelatine solid (an elastic host rock analogue). The injection flux and temperature are maintained constant during an experiment. In order to vary the importance of solidification and quantify its effect on sill propagation, the injection flux and temperature are systematically varied between each experiment. Depending on the importance of solidification effects, two extreme behaviours for sill propagation dynamics and geometry are observed. When solidification effects are small (high injection temperatures and fluxes), the propagation is continuous and the sill has a regular and smooth surface. Inversely, when solidification effects are important (low injection temperatures and fluxes), sill propagation is discontinuous and occurs by steps. After each propagation step, the sill stalls, thickens progressively by storing hot fluid vegetable oil beneath the partially solidified intrusion, without growing neither in length nor in breadth, and after a pause, the propagation initiates again, soon followed by a new episode of momentary arrest. The geometry of these sills displays folds, ropy structures on their surface, and lobes with imprints of the leading fronts that correspond to each step of surface creation. These experiments show that for a given, constant injected volume, as solidification effects increase, the surface of the sills decreases, their thickness increases, and the number of propagation steps increases. In the same way lower solidification effects promote larger sill surfaces, lower thicknesses, and a lower number of propagation steps. These results have various geological and geophysical implications. Regarding the geometry of sills, 3D seismic studies in sedimentary basins reveal sills with lobate
Geometry attained by pressurized membranes
NASA Astrophysics Data System (ADS)
Palisoc, Arthur; Veal, Gordon; Cassapakis, Constantine; Greschik, Gyula; Mikulas, Martin
1998-08-01
An intensive investigation has been carried out to study the surface profiles obtained as a result of the large deformations of pressurized membranes. The study shows that the inflated membrane shapes may have the requisite surface accuracy for use in future large space apertures. Both analytical and experimental work have been carried out. On the analytical side, the classical work of Hencky on flat circular membranes was extended to eliminate the limitations it imposed; namely a lateral non-follower pressure with no pre-stress. The result is a computer program for the solution of the pressurized circular membrane problem. The reliability of the computer program is demonstrated via verification against FAIM, a nonlinear finite element solver developed primarily for the analysis of inflated membrane shapes. The experimental work includes observations made by Veal on the (W-shaped) deviations between the membrane deflected shape and the predicted profile. More recent measurements have been made of the deformations of pressurized flat circular and parabolic membranes using photogrammetric techniques. The surface error quantification analyses include the effect of material properties, geometric properties, loading uncertainties, and boundary conditions. These effects are very easily handled by the special FEM code FAIM which had recently been enhanced to predict the on-orbit dynamics, RF, and solar concentration characteristics of inflatable parabolic antennas/reflectors such as the IAE that flew off the space shuttle Endeavour in May 1996. The results of measurements have been compared with analyses and their ramifications on precision-shape, large-aperture parabolic space reflectors are discussed. Results show that very large space apertures with surface slope error accuracies on the order to space reflectors are discussed. Results show that very large space apertures with surface slope error accuracies on the order of 1 milliradian or less are feasible. Surface
Finite-geometry models of electric field noise from patch potentials in ion traps
Low, Guang Hao; Herskind, Peter F.; Chuang, Isaac L.
2011-11-15
We model electric field noise from fluctuating patch potentials on conducting surfaces by taking into account the finite geometry of the ion trap electrodes to gain insight into the origin of anomalous heating in ion traps. The scaling of anomalous heating rates with surface distance d is obtained for several generic geometries of relevance to current ion trap designs, ranging from planar to spheroidal electrodes. The influence of patch size is studied both by solving Laplace's equation in terms of the appropriate Green's function as well as through an eigenfunction expansion. Scaling with surface distance is found to be highly dependent on the choice of geometry and the relative scale between the spatial extent of the electrode, the ion-electrode distance, and the patch size. Our model generally supports the d{sup -4} dependence currently found by most experiments and models, but also predicts geometry-driven deviations from this trend.
NASA Astrophysics Data System (ADS)
Maheshwarla, S. V.; Venkatasubramanian, R.; Boehm, Robert F.
1995-08-01
We propose three nontraditional dielectric geometries and present an experimental and theoretical analysis and comparison of time domain reflectometry (TDR) performances for them. The traditional geometry (the probes inserted in material of essentially infinite extent) is compared to three nontraditional geometries where the probes are affixed outside of a core sample, inside of a bore, or flat on the surface of a semi-infinite solid. Our derivation relates the velocity of electromagnetic wave propagation to the complex permittivities and permeabilities of the media and the geometry for the three nontraditional configurations. Experimental results for air, styrofoam, dry sand, wet sand of varying water content, nylon, dry wood, and ferromagnetic steel are obtained for the three proposed configurations and are in fair agreement with the literature within the experimental uncertainties. Through experiments and theoretical analysis, the TDR performance is found to be the same within the experimental uncertainties for the three nontraditional geometries. The proposed geometries yield slightly lower sensitivities compared to the traditional geometry. Advantages and disadvantages of the geometries compared to the traditional geometry are also discussed.
Geometry definition and grid generation for a complete fighter aircraft
NASA Technical Reports Server (NTRS)
Edwards, T. A.
1986-01-01
Recent advances in computing power and numerical solution procedures have enabled computational fluid dynamicists to attempt increasingly difficult problems. In particular, efforts are focusing on computations of complex three-dimensional flow fields about realistic aerodynamic bodies. To perform such computations, a very accurate and detailed description of the surface geometry must be provided, and a three-dimensional grid must be generated in the space around the body. The geometry must be supplied in a format compatible with the grid generation requirements, and must be verified to be free of inconsistencies. This paper presents a procedure for performing the geometry definition of a fighter aircraft that makes use of a commercial computer-aided design/computer-aided manufacturing system. Furthermore, visual representations of the geometry are generated using a computer graphics system for verification of the body definition. Finally, the three-dimensional grids for fighter-like aircraft are generated by means of an efficient new parabolic grid generation method. This method exhibits good control of grid quality.
Bivoltametric titrations using electrodes with innovative geometry.
Surmann, P; Peter, B; Stark, C
1996-09-01
Electrodes with different surface areas were investigated for the determination of reversible, quasireversible, irreversible or electroinactive substrates. Two kinds of electrodes were constructed, a helical electrode with a given asymmetry and a platinum array electrode with a variable area. These electrodes were applied for the cerimetry of ammonium iron(II) sulfate and for the bromatometry of various organic substances. The theoretically derived effects on the shape of the voltametric titration curve are verified experimentally. It is possible to sharpen one side of the peak and to broaden the other side, depending on the system and the side of the peak one is interested in. It is possible to improve the bivoltametric determination of hydroquinone, benzocaine and sulfaguanidine by bromatometry by the directed employment of electrodes of different areas. For the bromatometric determination of electrochemically irreversible substrates the use of the electrode geometries proposed is a way to obtain a sharp bend and a steep decrease of titration curves with low values of the constant current which is a basic requirement for the accuracy.
Contrasting origins of breached relay zone geometries
NASA Astrophysics Data System (ADS)
Conneally, J.; Childs, C.; Walsh, J. J.
2014-01-01
Relay zones accommodate transfer of displacement between pairs of adjacent segments of a fault array that become linked to form a through-going fault as displacement increases. 3D geometric and kinematic analysis of two vertically aligned relay zones, that form a complex boundary between two fault segments, generally support this model of relay zone growth but they also highlight some departures from this scheme. The two seismically mapped relay zones, although separated vertically by 100 m, were synchronously active over most of their development history. A causal relationship between them is proposed with the geometric complexity arising from the formation of the lower relay zone triggering the formation of the upper. The lower relay zone is now breached but originally formed a hole within the fault surface up to throws of ca. 50 m. The upper relay zone displays both breached and intact relay zone geometries at different structural levels demonstrating that relay zone breaching is a protracted rather than geologically instantaneous process. Geometrically the lower part of this structure resembles a breached relay zone, but it formed by propagation of a splay fault from a pre-existing bend to enclose an intervening and steepening ramp, a growth scheme which is the opposite of conventional relay zone models.
Accretion shock geometries in the magnetic variables
NASA Technical Reports Server (NTRS)
Stockman, H. S.
1988-01-01
The first self consistent shock models for the AM Herculis-type systems successfully identified the dominant physical processes and their signatures. These homogenous shock models predict unpolarized, Rayleigh-Jeans optical spectra with sharp cutoffs and rising polarizations as the shocks become optically thin in the ultraviolet. However, the observed energy distributions are generally flat with intermediate polarizations over a broad optical band. These and other observational evidence support a non-homogenous accretion profile which may extend over a considerable fraction of the stellar surface. Both the fundamental assumptions underlying the canonical 1-D shock model and the extension of this model to inhomogenous accretion shocks were identified, for both radial and linear structures. The observational evidence was also examined for tall shocks and little evidence was found for relative shock heights in excess of h/R(1) greater than or equal to 0.1. For several systems, upper limits to the shock height can be obtained from either x ray or optical data. These lie in the region h/R(1) is approximately 0.01 and are in general agreement with the current physical picture for these systems. The quasi-periodic optical variations observed in several magnetic variables may eventually prove to be a major aid in further understanding their accretion shock geometries.
Topological string theory and enumerative geometry
NASA Astrophysics Data System (ADS)
Song, Yun S.
2001-10-01
In this thesis we investigate several problems which have their roots in both topological string theory and enumerative geometry. In the former case, underlying theories are topological field theories, whereas the latter case is concerned with intersection theories on moduli spaces. A permeating theme in this thesis is to examine the close interplay between these two complementary fields of study. The main problems addressed are as follows: In considering the Hurwitz enumeration problem of branched covers of compact connected Riemann surfaces, we completely solve the problem in the case of simple Hurwitz numbers. In addition, utilizing the connection between Hurwitz numbers and Hodge integrals, we derive a generating function for the latter on the moduli space overline Mg,2 of 2- pointed, genus- g Deligne-Mumford stable curves. We also investigate Givental's recent conjecture regarding semisimple Frobenius structures and Gromov- Witten invariants, both of which are closely related to topological field theories; we consider the case of a complex projective line P1 as a specific example and verify his conjecture at low genera. In the last chapter, we demonstrate that certain topological open string amplitudes can be computed via relative stable morphisms in the algebraic category.
Computer aided design and analysis of gear tooth geometry
NASA Technical Reports Server (NTRS)
Chang, S. H.; Huston, R. L.
1987-01-01
A simulation method for gear hobbing and shaping of straight and spiral bevel gears is presented. The method is based upon an enveloping theory for gear tooth profile generation. The procedure is applicable in the computer aided design of standard and nonstandard tooth forms. An inverse procedure for finding a conjugate gear tooth profile is presented for arbitrary cutter geometry. The kinematic relations for the tooth surfaces of straight and spiral bevel gears are proposed. The tooth surface equations for these gears are formulated in a manner suitable for their automated numerical development and solution.
Detonation diffraction through different geometries
NASA Astrophysics Data System (ADS)
Sorin, Rémy; Zitoun, Ratiba; Khasainov, Boris; Desbordes, Daniel
2009-04-01
We performed the study of the diffraction of a self-sustained detonation from a cylindrical tube (of inner diameter d) through different geometric configurations in order to characterise the transmission processes and to quantify the transmission criteria to the reception chamber. For the diffraction from a tube to the open space the transmission criteria is expressed by d c = k c · λ (with λ the detonation cell size and k c depending on the mixture and on the operture configuration, classically 13 for alkane mixtures with oxygen). The studied geometries are: (a) a sharp increase of diameter ( D/ d > 1) with and without a central obstacle in the diffracting section, (b) a conical divergent with a central obstacle in the diffracting section and (c) an inversed intermediate one end closed tube insuring a double reflection before a final diffraction between the initiator tube and the reception chamber. The results for case A show that the reinitiation process depends on the ratio d/ λ. For ratios below k c the re-ignition takes place at the receptor tube wall and at a fixed distance from the step, i.e. closely after the diffracted shock reflection shows a Mach stem configuration. For ratios below a limit ratio k lim (which depends on D/ d) the re-ignition distance increases with the decrease of d/λ. For both case A and B the introduction of a central obstacle (of blockage ratio BR = 0.5) at the exit of the initiator tube decreases the critical transmission ratio k c by 50%. The results in configuration C show that the re-ignition process depends both on d/ λ and the geometric conditions. Optimal configuration is found that provides the transmission through the two successive reflections (from d = 26 mm to D ch = 200 mm) at as small d/ λ as 2.2 whatever the intermediate diameter D is. This configuration provides a significant improvement in the detonation transmission conditions.
Quantum groups: Geometry and applications
Chu, C.S.
1996-05-13
The main theme of this thesis is a study of the geometry of quantum groups and quantum spaces, with the hope that they will be useful for the construction of quantum field theory with quantum group symmetry. The main tool used is the Faddeev-Reshetikhin-Takhtajan description of quantum groups. A few content-rich examples of quantum complex spaces with quantum group symmetry are treated in details. In chapter 1, the author reviews some of the basic concepts and notions for Hopf algebras and other background materials. In chapter 2, he studies the vector fields of quantum groups. A compact realization of these vector fields as pseudodifferential operators acting on the linear quantum spaces is given. In chapter 3, he describes the quantum sphere as a complex quantum manifold by means of a quantum stereographic projection. A covariant calculus is introduced. An interesting property of this calculus is the existence of a one-form realization of the exterior differential operator. The concept of a braided comodule is introduced and a braided algebra of quantum spheres is constructed. In chapter 4, the author considers the more general higher dimensional quantum complex projective spaces and the quantum Grassman manifolds. Differential calculus, integration and braiding can be introduced as in the one dimensional case. Finally, in chapter 5, he studies the framework of quantum principal bundle and construct the q-deformed Dirac monopole as a quantum principal bundle with a quantum sphere as the base and a U(1) with non-commutative calculus as the fiber. The first Chern class can be introduced and integrated to give the monopole charge.
A computer program for analyzing channel geometry
Regan, R.S.; Schaffranek, R.W.
1985-01-01
The Channel Geometry Analysis Program (CGAP) provides the capability to process, analyze, and format cross-sectional data for input to flow/transport simulation models or other computational programs. CGAP allows for a variety of cross-sectional data input formats through use of variable format specification. The program accepts data from various computer media and provides for modification of machine-stored parameter values. CGAP has been devised to provide a rapid and efficient means of computing and analyzing the physical properties of an open-channel reach defined by a sequence of cross sections. CGAP 's 16 options provide a wide range of methods by which to analyze and depict a channel reach and its individual cross-sectional properties. The primary function of the program is to compute the area, width, wetted perimeter, and hydraulic radius of cross sections at successive increments of water surface elevation (stage) from data that consist of coordinate pairs of cross-channel distances and land surface or channel bottom elevations. Longitudinal rates-of-change of cross-sectional properties are also computed, as are the mean properties of a channel reach. Output products include tabular lists of cross-sectional area, channel width, wetted perimeter, hydraulic radius, average depth, and cross-sectional symmetry computed as functions of stage; plots of cross sections; plots of cross-sectional area and (or) channel width as functions of stage; tabular lists of cross-sectional area and channel width computed as functions of stage for subdivisions of a cross section; plots of cross sections in isometric projection; and plots of cross-sectional area at a fixed stage as a function of longitudinal distance along an open-channel reach. A Command Procedure Language program and Job Control Language procedure exist to facilitate program execution on the U.S. Geological Survey Prime and Amdahl computer systems respectively. (Lantz-PTT)
Computing Bisectors in a Dynamic Geometry Environment
ERIC Educational Resources Information Center
Botana, Francisco
2013-01-01
In this note, an approach combining dynamic geometry and automated deduction techniques is used to study the bisectors between points and curves. Usual teacher constructions for bisectors are discussed, showing that inherent limitations in dynamic geometry software impede their thorough study. We show that the interactive sketching of bisectors…
Geometry and Education in the Internet Age.
ERIC Educational Resources Information Center
Kortenkamp, Ulrich H.; Richter-Gebert, Jurgen
This paper discusses the requirements of Interactive Geometry Systems (IGSs) and how they can be fulfilled, explains how a geometry tool can benefit from the Internet, and presents Cinderella's Cafe. Cinderella's Cafe is a new IGS with a high mathematical background that uses the most general mathematical models whenever possible, is highly…
Improving African American Achievement in Geometry Honors
ERIC Educational Resources Information Center
Mims, Adrian B.
2010-01-01
This case study evaluated the significance of implementing an enrichment mathematics course during the summer to rising African American ninth graders entitled, "Geometry Honors Preview." In the past, 60 to 70 percent of African American students in this school district had withdrawn from Geometry Honors by the second academic quarter. This study…
Historical Digressions in Greek Geometry Lessons.
ERIC Educational Resources Information Center
Thomaidis, Yannis
1991-01-01
Presents an attempt to combine the history of mathematics of ancient Greece with the course on theoretical geometry taught in Greek secondary schools. Three sections present the history of ancient Greek geometry, geometrical constructions using straightedges and compasses, and an application of Ptolemy's theorem in solving ancient astronomy…
Different lattice geometries with a synthetic dimension
NASA Astrophysics Data System (ADS)
Suszalski, Dominik; Zakrzewski, Jakub
2016-09-01
The possibility of creating different geometries with the help of an extra synthetic dimension in optical lattices is studied. The additional linear potential together with Raman-assisted tunnelings are used to engineer well-controlled tunnelings between available states. The great flexibility of the system allows us to obtain different geometries of synthetic lattices with the possibility for adding synthetic gauge fields.
The slab geometry laser. I - Theory
NASA Technical Reports Server (NTRS)
Eggleston, J. M.; Kane, T. J.; Kuhn, K.; Byer, R. L.; Unternahrer, J.
1984-01-01
Slab geometry solid-state lasers offer significant performance improvements over conventional rod-geometry lasers. A detailed theoretical description of the thermal, stress, and beam-propagation characteristics of a slab laser is presented. The analysis includes consideration of the effects of the zig-zag optical path, which eliminates thermal and stress focusing and reduces residual birefringence.
Cell division intersects with cell geometry.
Moseley, James B; Nurse, Paul
2010-07-23
Single-celled organisms monitor cell geometry and use this information to control cell division. Such geometry-sensing mechanisms control both the decision to enter into cell division and the physical orientation of the chromosome segregation machinery, suggesting that signals controlling cell division may be linked to the mechanisms that ensure proper chromosome segregation.
Geometry, Student's Text, Part II, Unit 14.
ERIC Educational Resources Information Center
Allen, Frank B.; And Others
Unit 14 in the SMSG secondary school mathematics series is a student text covering the following topics in geometry: areas of polygonal regions, similarity, circles and spheres, characterization of sets, constructions, areas of circles and sectors, volumes of solids, and plane coordinate geometry. Appendices cover Eratosthenes' measurement of the…
Reasoning by Contradiction in Dynamic Geometry
ERIC Educational Resources Information Center
Baccaglini-Frank, Anna; Antonini, Samuele; Leung, Allen; Mariotti, Maria Alessandra
2013-01-01
This paper addresses contributions that dynamic geometry systems (DGSs) may give in reasoning by contradiction in geometry. We present analyses of three excerpts of students' work and use the notion of pseudo object, elaborated from previous research, to show some specificities of DGS in constructing proof by contradiction. In particular, we…
Teaching Geometry to Visually Impaired Students
ERIC Educational Resources Information Center
Pritchard, Christine K.; Lamb, John H.
2012-01-01
NCTM (2000) described geometry as "a means of describing, analyzing, and understanding the world and seeing beauty in its structures" (p. 309). Dossey et al. (2002) captured the essence of this aspect of visualization by stating that geometry fosters in students an ability to "visualize and mentally manipulate geometric objects." (p. 200).…
Making Euclidean Geometry Compulsory: Are We Prepared?
ERIC Educational Resources Information Center
Van Putten, Sonja; Howie, Sarah; Stols, Gerrit
2010-01-01
This study investigated the attitude towards, as well as the level of understanding of Euclidean geometry in pre-service mathematics education (PME) students. In order to do so, a case study was undertaken within which a one group pre-post-test procedure was conducted around a geometry module, and a representative group of students was interviewed…
Stop Teaching and Let Students Learn Geometry
ERIC Educational Resources Information Center
Bosse, Michael J.; Adu-Gyamfi, Kwaku
2011-01-01
For many high school students as well as preservice teachers, geometry can be difficult to learn without experiences that allow them to build their own understanding. The authors' approach to geometry instruction--with its integration of content, multiple representations, real-world examples, reading and writing, communication and collaboration as…
An approach for management of geometry data
NASA Technical Reports Server (NTRS)
Dube, R. P.; Herron, G. J.; Schweitzer, J. E.; Warkentine, E. R.
1980-01-01
The strategies for managing Integrated Programs for Aerospace Design (IPAD) computer-based geometry are described. The computer model of geometry is the basis for communication, manipulation, and analysis of shape information. IPAD's data base system makes this information available to all authorized departments in a company. A discussion of the data structures and algorithms required to support geometry in IPIP (IPAD's data base management system) is presented. Through the use of IPIP's data definition language, the structure of the geometry components is defined. The data manipulation language is the vehicle by which a user defines an instance of the geometry. The manipulation language also allows a user to edit, query, and manage the geometry. The selection of canonical forms is a very important part of the IPAD geometry. IPAD has a canonical form for each entity and provides transformations to alternate forms; in particular, IPAD will provide a transformation to the ANSI standard. The DBMS schemas required to support IPAD geometry are explained.
Teaching Geometry through Problem-Based Learning
ERIC Educational Resources Information Center
Schettino, Carmel
2011-01-01
About seven years ago, the mathematics teachers at the author's secondary school came to the conclusion that they were not satisfied with their rather traditional geometry textbook. The author had already begun using a problem-based approach to teaching geometry in her classes, a transition for her and her students that inspired her to write about…
A Multivariate Model of Achievement in Geometry
ERIC Educational Resources Information Center
Bailey, MarLynn; Taasoobshirazi, Gita; Carr, Martha
2014-01-01
Previous studies have shown that several key variables influence student achievement in geometry, but no research has been conducted to determine how these variables interact. A model of achievement in geometry was tested on a sample of 102 high school students. Structural equation modeling was used to test hypothesized relationships among…
Readings in Geometry from the Arithmetic Teacher.
ERIC Educational Resources Information Center
Brydegaard, Marguerite; Inskeep, James E., Jr.
This is a book of readings from the "Arithmetic Teacher" on selected topics in geometry. The articles chosen are samples of material published in the journal from its beginning in February 1954 through February 1970. The articles are of three major types. The first is classified "involvement." These articles describe geometry units in which the…
Mohamad, Rapidah; Awang, Normah; Jotani, Mukesh M; Tiekink, Edward R T
2016-08-01
The crystal and mol-ecular structures of two di-phenyl-tin bis-(di-thio-carbamate)s, [Sn(C6H5)2(C5H10NOS2)2], (I), and [Sn(C6H5)2(C7H14NO2S2)2], (II), are described. In (I), in which the metal atom lies on a twofold rotation axis, the di-thio-carbamate ligand coordinates with approximately equal Sn-S bond lengths and the ipso-C atoms of the Sn-bound phenyl groups occupy cis-positions in the resulting octa-hedral C2S4 donor set. A quite distinct coordination geometry is noted in (II), arising as a result of quite disparate Sn-S bond lengths. Here, the four S-donors define a trapezoidal plane with the ipso-C atoms lying over the weaker of the Sn-S bonds so that the C2S4 donor set defines a skewed trapezoidal bipyramid. The packing of (I) features supra-molecular layers in the ab plane sustained by methyl-ene-C-H⋯π(Sn-ar-yl) inter-actions; these stack along the c-axis direction with no specific inter-actions between them. In (II), supra-molecular chains along the b-axis direction are formed by methyl-ene-C-O(ether) inter-actions; these pack with no directional inter-actions between them. A Hirshfeld surface analysis was conducted on both (I) and (II) and revealed the dominance of H⋯H inter-actions contributing to the respective surfaces, i.e. >60% in each case, and other features consistent with the description of the mol-ecular packing above. PMID:27536397
NASA Astrophysics Data System (ADS)
Zwinkels, Joanne; Neil, William; Noël, Mario
2016-10-01
For highest accuracy fluorescence colorimetry, standardizing organizations recommend the use of a two-monochromator method with a bidirectional illumination and viewing geometry (45:0 or 0:45). For this reason, reference fluorescence instruments developed by National Measurement Institutes (NMIs) have largely conformed to this bidirectional geometry. However, for many practical applications in colorimetry where the samples exhibit texture, surface roughness or other spatial non-uniformities, the relevant standard test methods specify a sphere geometry with diffuse illumination or viewing (e.g. d:8 or 8:d) which gives improved measurement precision. This difference in the measurement geometry between the primary instrument used to realize the fluorescence scale and the secondary testing instruments used for practical measurements, compromises the traceability of these fluorescence calibrations. To address this metrology issue, a two-monochromator goniospectrofluorimeter instrument has been developed at the National Research Council of Canada (NRC). This instrument can be configured for different illumination and viewing geometries to conform with international standards for different colorimetric applications. To improve the traceability chain for measurements using different geometries, the instrument has been thoroughly characterized and validated by means of comparison measurements with NRC’s other spectrophotometric and fluorescence reference instruments. This uncertainty analysis has been carried out in a step-wise manner; first, for a bidirectional geometry (45:0) and then for a sphere geometry (8:d) to provide an uninterrupted traceability to primary radiometric scales. The first paper in this two paper series reviews the background to this work and provides details of the basic design of the new instrument and its characterization for measurements using a bidirectional geometry (45:0), including a representative uncertainty budget. In part 2, the major
FINAL REPORT: GEOMETRY AND ELEMENTARY PARTICLE PHYSICS
Singer, Isadore M.
2008-03-04
The effect on mathematics of collaborations between high-energy theoretical physics and modern mathematics has been remarkable. Mirror symmetry has revolutionized enumerative geometry, and Seiberg-Witten invariants have greatly simplified the study of four manifolds. And because of their application to string theory, physicists now need to know cohomology theory, characteristic classes, index theory, K-theory, algebraic geometry, differential geometry, and non-commutative geometry. Much more is coming. We are experiencing a deeper contact between the two sciences, which will stimulate new mathematics essential to the physicists’ quest for the unification of quantum mechanics and relativity. Our grant, supported by the Department of Energy for twelve years, has been instrumental in promoting an effective interaction between geometry and string theory, by supporting the Mathematical Physics seminar, postdoc research, collaborations, graduate students and several research papers.
Drawing Dynamic Geometry Figures Online with Natural Language for Junior High School Geometry
ERIC Educational Resources Information Center
Wong, Wing-Kwong; Yin, Sheng-Kai; Yang, Chang-Zhe
2012-01-01
This paper presents a tool for drawing dynamic geometric figures by understanding the texts of geometry problems. With the tool, teachers and students can construct dynamic geometric figures on a web page by inputting a geometry problem in natural language. First we need to build the knowledge base for understanding geometry problems. With the…
Visuospatial Working Memory in Intuitive Geometry, and in Academic Achievement in Geometry
ERIC Educational Resources Information Center
Giofre, David; Mammarella, Irene C.; Ronconi, Lucia; Cornoldi, Cesare
2013-01-01
A study was conducted on the involvement of visuospatial working memory (VSWM) in intuitive geometry and in school performance in geometry at secondary school. A total of 166 pupils were administered: (1) six VSWM tasks, comprising simple storage and complex span tasks; and (2) the intuitive geometry task devised by Dehaene, Izard, Pica, and…
Analogy and Dynamic Geometry System Used to Introduce Three-Dimensional Geometry
ERIC Educational Resources Information Center
Mammana, M. F.; Micale, B.; Pennisi, M.
2012-01-01
We present a sequence of classroom activities on Euclidean geometry, both plane and space geometry, used to make three dimensional geometry more catchy and simple. The activity consists of a guided research activity that leads the students to discover unexpected properties of two apparently distant geometrical entities, quadrilaterals and…
Macroscopic resonances in planar geometry
NASA Astrophysics Data System (ADS)
Strutinsky, V.; Vydrug-Vlasenko, S.; Magner, A.
1987-09-01
Resonating response is a characteristic feature of free-particle system contained between two vibrating planar surfaces. Resonance frequencies and widths are determined by a mean period of motion of particles reflected from the walls. Resonances due to quasiperiodic macroscopic motion appear when the interaction among quasi-particles by means of perturbations of the common self-consistent field is included. They have finite widths corresponding to collisionless Landau dissipation. Possible relationship of this phenomenon to nuclear giant resonances is discussed.
Digital Topology and Geometry in Medical Imaging: A Survey.
Saha, Punam K; Strand, Robin; Borgefors, Gunilla
2015-09-01
Digital topology and geometry refers to the use of topologic and geometric properties and features for images defined in digital grids. Such methods have been widely used in many medical imaging applications, including image segmentation, visualization, manipulation, interpolation, registration, surface-tracking, object representation, correction, quantitative morphometry etc. Digital topology and geometry play important roles in medical imaging research by enriching the scope of target outcomes and by adding strong theoretical foundations with enhanced stability, fidelity, and efficiency. This paper presents a comprehensive yet compact survey on results, principles, and insights of methods related to digital topology and geometry with strong emphasis on understanding their roles in various medical imaging applications. Specifically, this paper reviews methods related to distance analysis and path propagation, connectivity, surface-tracking, image segmentation, boundary and centerline detection, topology preservation and local topological properties, skeletonization, and object representation, correction, and quantitative morphometry. A common thread among the topics reviewed in this paper is that their theory and algorithms use the principle of digital path connectivity, path propagation, and neighborhood analysis.
NASA CONNECT: Geometry of Exploration: Water Below Mars?
NASA Technical Reports Server (NTRS)
1999-01-01
'Geometry of Exploration: Water Below the Surface of Mars?' is the third of seven programs in the 1999-2000 NASA CONNECT series. Produced by NASA Langley Research Center's Office of Education, NASA CONNECT is an award-winning series of instructional programs designed to enhance the teaching of math, science and technology concepts in grades 5-8. NASA CONNECT establishes the 'connection' between the mathematics, science, and technology concepts taught in the classroom and NASA research. Each program in the series supports the national mathematics, science, and technology standards; includes a resource-rich teacher guide; and uses a classroom experiment and web-based activity to complement and enhance the math, science, and technology concepts presented in the program. NASA CONNECT is FREE and the programs in the series are in the public domain. Visit our web site and register. http://connect.larc.nasa.gov In 'Geometry of Exploration: Water Below the Surface of Mars?' students will learn how engineers and scientists are using geometry and the solar system to navigate spacecraft to Mars.
Geometry optimization made simple with translation and rotation coordinates.
Wang, Lee-Ping; Song, Chenchen
2016-06-01
The effective description of molecular geometry is important for theoretical studies of intermolecular interactions. Here we introduce a new translation-rotation-internal coordinate (TRIC) system which explicitly includes the collective translations and rotations of molecules, or parts of molecules such as monomers or ligands, as degrees of freedom. The translations are described as the centroid position and the orientations are represented with the exponential map parameterization of quaternions. When TRIC is incorporated into geometry optimization calculations, the performance is consistently superior to existing coordinate systems for a diverse set of systems including water clusters, organic semiconductor donor-acceptor complexes, and small proteins, all of which are characterized by nontrivial intermolecular interactions. The method also introduces a new way to scan the molecular orientations while allowing orthogonal degrees of freedom to relax. Our findings indicate that an explicit description of molecular translation and rotation is a natural way to traverse the many-dimensional potential energy surface. PMID:27276946
Stationary metrics and optical Zermelo-Randers-Finsler geometry
Gibbons, G. W.; Warnick, C. M.; Herdeiro, C. A. R.; Werner, M. C.
2009-02-15
We consider a triality between the Zermelo navigation problem, the geodesic flow on a Finslerian geometry of Randers type, and spacetimes in one dimension higher admitting a timelike conformal Killing vector field. From the latter viewpoint, the data of the Zermelo problem are encoded in a (conformally) Painleve-Gullstrand form of the spacetime metric, whereas the data of the Randers problem are encoded in a stationary generalization of the usual optical metric. We discuss how the spacetime viewpoint gives a simple and physical perspective on various issues, including how Finsler geometries with constant flag curvature always map to conformally flat spacetimes and that the Finsler condition maps to either a causality condition or it breaks down at an ergo surface in the spacetime picture. The gauge equivalence in this network of relations is considered as well as the connection to analogue models and the viewpoint of magnetic flows. We provide a variety of examples.
Integrated geometry and grid generation system for complex configurations
NASA Technical Reports Server (NTRS)
Akdag, Vedat; Wulf, Armin
1992-01-01
A grid generation system was developed that enables grid generation for complex configurations. The system called ICEM/CFD is described and its role in computational fluid dynamics (CFD) applications is presented. The capabilities of the system include full computer aided design (CAD), grid generation on the actual CAD geometry definition using robust surface projection algorithms, interfacing easily with known CAD packages through common file formats for geometry transfer, grid quality evaluation of the volume grid, coupling boundary condition set-up for block faces with grid topology generation, multi-block grid generation with or without point continuity and block to block interface requirement, and generating grid files directly compatible with known flow solvers. The interactive and integrated approach to the problem of computational grid generation not only substantially reduces manpower time but also increases the flexibility of later grid modifications and enhancements which is required in an environment where CFD is integrated into a product design cycle.
Geometry optimization made simple with translation and rotation coordinates
NASA Astrophysics Data System (ADS)
Wang, Lee-Ping; Song, Chenchen
2016-06-01
The effective description of molecular geometry is important for theoretical studies of intermolecular interactions. Here we introduce a new translation-rotation-internal coordinate (TRIC) system which explicitly includes the collective translations and rotations of molecules, or parts of molecules such as monomers or ligands, as degrees of freedom. The translations are described as the centroid position and the orientations are represented with the exponential map parameterization of quaternions. When TRIC is incorporated into geometry optimization calculations, the performance is consistently superior to existing coordinate systems for a diverse set of systems including water clusters, organic semiconductor donor-acceptor complexes, and small proteins, all of which are characterized by nontrivial intermolecular interactions. The method also introduces a new way to scan the molecular orientations while allowing orthogonal degrees of freedom to relax. Our findings indicate that an explicit description of molecular translation and rotation is a natural way to traverse the many-dimensional potential energy surface.
Ambient Occlusion Effects for Combined Volumes and Tubular Geometry
Schott, Mathias; Martin, Tobias; Grosset, A.V. Pascal; Smith, Sean T.; Hansen, Charles D.
2013-01-01
This paper details a method for interactive direct volume rendering that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube-shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The algorithm extends the recently presented the directional occlusion shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. Stream tube geometries are computed using an effective spline-based interpolation and approximation scheme that avoids self-intersection and maintains coherent orientation of the stream tube segments to avoid surface deforming twists. Furthermore, strategies to reduce the geometric and specular aliasing of the stream tubes are discussed. PMID:23559506
Measurement and reconstruction of the leaflet geometry for a pericardial artificial heart valve.
Jiang, Hongjun; Campbell, Gord; Xi, Fengfeng
2005-03-01
This paper describes the measurement and reconstruction of the leaflet geometry for a pericardial heart valve. Tasks involved include mapping the leaflet geometries by laser digitizing and reconstructing the 3D freeform leaflet surface based on a laser scanned profile. The challenge is to design a prosthetic valve that maximizes the benefits offered to the recipient as compared to the normally operating naturally-occurring valve. This research was prompted by the fact that artificial heart valve bioprostheses do not provide long life durability comparable to the natural heart valve, together with the anticipated benefits associated with defining the valve geometries, especially the leaflet geometries for the bioprosthetic and human valves, in order to create a replicate valve fabricated from synthetic materials. Our method applies the concept of reverse engineering in order to reconstruct the freeform surface geometry. A Brown & Shape coordinate measuring machine (CMM) equipped with a HyMARC laser-digitizing system was used to measure the leaflet profiles of a Baxter Carpentier-Edwards pericardial heart valve. The computer software, Polyworks was used to pre-process the raw data obtained from the scanning, which included merging images, eliminating duplicate points, and adding interpolated points. Three methods, creating a mesh model from cloud points, creating a freeform surface from cloud points, and generating a freeform surface by B-splines are presented in this paper to reconstruct the freeform leaflet surface. The mesh model created using Polyworks can be used for rapid prototyping and visualization. To fit a freeform surface to cloud points is straightforward but the rendering of a smooth surface is usually unpredictable. A surface fitted by a group of B-splines fitted to cloud points was found to be much smoother. This method offers the possibility of manually adjusting the surface curvature, locally. However, the process is complex and requires additional
Numerical Simulations of High-Speed Flows Over Complex Geometries
NASA Astrophysics Data System (ADS)
Greene, Patrick Timothy
The effects of surface roughness on the stability of hypersonic flow are of great importance to hypersonic vehicles. Surface roughness can greatly alter boundary-layer flow and cause transition to turbulence to occur much earlier compared to a smooth wall, which will result in a significant increase of wall heating and skin friction drag. The work presented in this dissertation was motivated by a desire to study the effects of isolated roughness elements on the stability of hypersonic boundary layers. A new code was developed which can perform high-order direct numerical simulations of high-speed flows over arbitrary geometries. A fifth-order hybrid weighted essentially non-oscillatory scheme was implemented to capture any steep gradients in the flow created by the geometries. The simulations are carried out on Cartesian grids with the geometries imposed by a third-order cut-cell method. A multi-zone refinement method is also implemented to provide extra resolution at locations with expected complex physics. The combination results in a globally fourth-order scheme. Results for two-dimensional and three-dimensional test cases show good agreement with previous results and will be presented. Results confirming the code's high order of convergence will also be shown. Two-dimensional simulations of flow over complex geometries will be presented to demonstrate the code's capabilities. Results for Mach 6 flow over a three-dimensional cylindrical roughness element will also be presented. The results will show that the code is a promising tool for the study of hypersonic roughness-induced transition.
NASA Technical Reports Server (NTRS)
Sharobeam, Monir H.
1994-01-01
Load separation is the representation of the load in the test records of geometries containing cracks as a multiplication of two separate functions: a crack geometry function and a material deformation function. Load separation is demonstrated in the test records of several two-dimensional geometries such as compact tension geometry, single edge notched bend geometry, and center cracked tension geometry and three-dimensional geometries such as semi-elliptical surface crack. The role of load separation in the evaluation of the fracture parameter J-integral and the associated factor eta for two-dimensional geometries is discussed. The paper also discusses the theoretical basis and the procedure for using load separation as a simplified yet accurate approach for plastic J evaluation in semi-elliptical surface crack which is a three-dimensional geometry. The experimental evaluation of J, and particularly J(sub pl), for three-dimensional geometries is very challenging. A few approaches have been developed in this regard and they are either complex or very approximate. The paper also presents the load separation as a mean to identify the blunting and crack growth regions in the experimental test records of precracked specimens. Finally, load separation as a methodology in elastic-plastic fracture mechanics is presented.
Effects of branched defect geometry on the propagation of Rayleigh waves
NASA Astrophysics Data System (ADS)
Hernandez-Valle, F.; Clough, A. R.; Dutton, B.; Edwards, R. S.
2014-02-01
Rayleigh waves can be used for characterisation of surface-breaking defects, giving a measure of the depth and the angle of propagation of a defect with simple (i.e. single crack) geometry. However, surface breaking defects will often grow with a more complicated geometry. We present here results of experimental measurements using laser generated and detected Rayleigh waves on aluminium samples containing machined slots with varied branched geometries. The signal enhancement found in the near-field, and the reflection and transmission of different wavemodes can be used to position the defect and gain an idea of its geometry. This research can be applied to monitor components prone to developing stress corrosion cracking (branched-like defects). Results are shown of the near-field interactions of Rayleigh waves with this type of cracking in stainless steel pipe samples, in order to resolve the spatial extent and geometric alignment of those defects.
Chandra, Santanu; Gnanaruban, Vimalatharmaiyah; Riveros, Fabian; Rodriguez, Jose F; Finol, Ender A
2016-10-01
In this work, we present a novel method for the derivation of the unloaded geometry of an abdominal aortic aneurysm (AAA) from a pressurized geometry in turn obtained by 3D reconstruction of computed tomography (CT) images. The approach was experimentally validated with an aneurysm phantom loaded with gauge pressures of 80, 120, and 140 mm Hg. The unloaded phantom geometries estimated from these pressurized states were compared to the actual unloaded phantom geometry, resulting in mean nodal surface distances of up to 3.9% of the maximum aneurysm diameter. An in-silico verification was also performed using a patient-specific AAA mesh, resulting in maximum nodal surface distances of 8 μm after running the algorithm for eight iterations. The methodology was then applied to 12 patient-specific AAA for which their corresponding unloaded geometries were generated in 5-8 iterations. The wall mechanics resulting from finite element analysis of the pressurized (CT image-based) and unloaded geometries were compared to quantify the relative importance of using an unloaded geometry for AAA biomechanics. The pressurized AAA models underestimate peak wall stress (quantified by the first principal stress component) on average by 15% compared to the unloaded AAA models. The validation and application of the method, readily compatible with any finite element solver, underscores the importance of generating the unloaded AAA volume mesh prior to using wall stress as a biomechanical marker for rupture risk assessment. PMID:27538124
Chandra, Santanu; Gnanaruban, Vimalatharmaiyah; Riveros, Fabian; Rodriguez, Jose F; Finol, Ender A
2016-10-01
In this work, we present a novel method for the derivation of the unloaded geometry of an abdominal aortic aneurysm (AAA) from a pressurized geometry in turn obtained by 3D reconstruction of computed tomography (CT) images. The approach was experimentally validated with an aneurysm phantom loaded with gauge pressures of 80, 120, and 140 mm Hg. The unloaded phantom geometries estimated from these pressurized states were compared to the actual unloaded phantom geometry, resulting in mean nodal surface distances of up to 3.9% of the maximum aneurysm diameter. An in-silico verification was also performed using a patient-specific AAA mesh, resulting in maximum nodal surface distances of 8 μm after running the algorithm for eight iterations. The methodology was then applied to 12 patient-specific AAA for which their corresponding unloaded geometries were generated in 5-8 iterations. The wall mechanics resulting from finite element analysis of the pressurized (CT image-based) and unloaded geometries were compared to quantify the relative importance of using an unloaded geometry for AAA biomechanics. The pressurized AAA models underestimate peak wall stress (quantified by the first principal stress component) on average by 15% compared to the unloaded AAA models. The validation and application of the method, readily compatible with any finite element solver, underscores the importance of generating the unloaded AAA volume mesh prior to using wall stress as a biomechanical marker for rupture risk assessment.
Geometry of thin liquid sheet flows
NASA Technical Reports Server (NTRS)
Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.
1994-01-01
Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.
Interferometers as probes of Planckian quantum geometry
NASA Astrophysics Data System (ADS)
Hogan, Craig J.
2012-03-01
A theory of position of massive bodies is proposed that results in an observable quantum behavior of geometry at the Planck scale, tP. Departures from classical world lines in flat spacetime are described by Planckian noncommuting operators for position in different directions, as defined by interactions with null waves. The resulting evolution of position wave functions in two dimensions displays a new kind of directionally coherent quantum noise of transverse position. The amplitude of the effect in physical units is predicted with no parameters, by equating the number of degrees of freedom of position wave functions on a 2D space-like surface with the entropy density of a black hole event horizon of the same area. In a region of size L, the effect resembles spatially and directionally coherent random transverse shear deformations on time scale ≈L/c with typical amplitude ≈ctPL. This quantum-geometrical “holographic noise” in position is not describable as fluctuations of a quantized metric, or as any kind of fluctuation, dispersion or propagation effect in quantum fields. In a Michelson interferometer the effect appears as noise that resembles a random Planckian walk of the beam splitter for durations up to the light-crossing time. Signal spectra and correlation functions in interferometers are derived, and predicted to be comparable with the sensitivities of current and planned experiments. It is proposed that nearly colocated Michelson interferometers of laboratory scale, cross-correlated at high frequency, can test the Planckian noise prediction with current technology.
NASA Astrophysics Data System (ADS)
Cieslinski, Jan L.; Ferapontov, Eugene V.; Kitaev, Alexander V.; Nimmo, Jonathan J. C.
2009-10-01
Geometric ideas are present in many areas of modern theoretical physics and they are usually associated with the presence of nonlinear phenomena. Integrable nonlinear systems play a prime role both in geometry itself and in nonlinear physics. One can mention general relativity, exact solutions of the Einstein equations, string theory, Yang-Mills theory, instantons, solitons in nonlinear optics and hydrodynamics, vortex dynamics, solvable models of statistical physics, deformation quantization, and many others. Soliton theory now forms a beautiful part of mathematics with very strong physical motivations and numerous applications. Interactions between mathematics and physics associated with integrability issues are very fruitful and stimulating. For instance, spectral theories of linear quantum mechanics turned out to be crucial for studying nonlinear integrable systems. The modern theory of integrable nonlinear partial differential and difference equations, or the `theory of solitons', is deeply rooted in the achievements of outstanding geometers of the end of the 19th and the beginning of the 20th century, such as Luigi Bianchi (1856-1928) and Jean Gaston Darboux (1842-1917). Transformations of surfaces and explicit constructions developed by `old' geometers were often rediscovered or reinterpreted in a modern framework. The great progress of recent years in so-called discrete geometry is certainly due to strong integrable motivations. A very remarkable feature of the results of the classical integrable geometry is the quite natural (although nontrivial) possibility of their discretization. This special issue is dedicated to Jean Gaston Darboux and his pioneering role in the development of the geometric ideas of modern soliton theory. The most famous aspects of his work are probably Darboux transformations and triply orthogonal systems of surfaces, whose role in modern mathematical physics cannot be overestimated. Indeed, Darboux transformations play a central
Fractal Geometry in the High School Classroom.
ERIC Educational Resources Information Center
Camp, Dane R.
1995-01-01
Discusses classroom activities that involve applications of fractal geometry. Includes an activity sheet that explores Pascal's triangle, Sierpinsky's gasket, and modular arithmetic in two and three dimensions. (Author/MKR)
The Soap-Bubble-Geometry Contest.
ERIC Educational Resources Information Center
Morgan, Frank; Melnick, Edward R.; Nicholson, Ramona
1997-01-01
Presents an activity on soap-bubble geometry using a guessing contest, explanations, and demonstrations that allow students to mesh observation and mathematical reasoning to discover that mathematics is much more than just number crunching. (ASK)
Emergence of wave equations from quantum geometry
Majid, Shahn
2012-09-24
We argue that classical geometry should be viewed as a special limit of noncommutative geometry in which aspects which are inter-constrained decouple and appear arbitrary in the classical limit. In particular, the wave equation is really a partial derivative in a unified extra-dimensional noncommutative geometry and arises out of the greater rigidity of the noncommutative world not visible in the classical limit. We provide an introduction to this 'wave operator' approach to noncommutative geometry as recently used[27] to quantize any static spacetime metric admitting a spatial conformal Killing vector field, and in particular to construct the quantum Schwarzschild black hole. We also give an introduction to our related result that every classical Riemannian manifold is a shadow of a slightly noncommutative one wherein the meaning of the classical Ricci tensor becomes very natural as the square of a generalised braiding.
The Oak Leaf: Connecting Geometry and Biology.
ERIC Educational Resources Information Center
Snyder, Judy
1999-01-01
Presents an activity that integrates biology and mathematics. Involves students in actual biological research and uses geometry, statistics, and computers to interpret data about the leaves of a tree. (ASK)
Minimal five dimensional supergravities and complex geometries
Herdeiro, Carlos A. R.
2010-07-28
We discuss the relation between solutions admitting Killing spinors of minimal super-gravities in five dimensions, both timelike and null, and complex geometries. For the timelike solutions the results may be summarised as follows. In the ungauged case (vanishing cosmological constant {Lambda} 0) the solutions are determined in terms of a hyper-Kaehler base space; in the gauged case ({Lambda}<0) the complex geometry is Kaehler; in the de Sitter case ({Lambda}>0) the complex geometry is hyper-Kaehler with torsion (HKT). For the null solutions we shall focus on the de Sitter case, for which the solutions are determined by a constrained Einstein-Weyl 3-geometry called Gauduchon-Tod space. The method for constructing explicit solutions is discussed in each case.
Computer aided surface representation
Barnhill, R.E.
1990-02-19
The central research problem of this project is the effective representation, computation, and display of surfaces interpolating to information in three or more dimensions. If the given information is located on another surface, then the problem is to construct a surface defined on a surface''. Sometimes properties of an already defined surface are desired, which is geometry processing''. Visualization of multivariate surfaces is possible by means of contouring higher dimensional surfaces. These problems and more are discussed below. The broad sweep from constructive mathematics through computational algorithms to computer graphics illustrations is utilized in this research. The breadth and depth of this research activity makes this research project unique.
Phase distribution in complex geometry conduits
Lahey, R.T. Jr.; Lopez de Bertodano, M.; Jones, O.C. Jr.
1992-12-31
Some of the most important and challenging problems in two-phase flow today have to do with the understanding and prediction of multidimensional phenomena, in particular, lateral phase distribution in both simple and complex geometry conduits. A prior review paper summarized the state-of-the-art in the understanding of phase distribution phenomena, and the ability to perform mechanistic multidimensional predictions. The purpose of this paper is to update that review, with particular emphasis on complex geometry conduit predictive capabilities.
Validation of efficiency transfer for Marinelli geometries.
Ferreux, Laurent; Pierre, Sylvie; Thanh, Tran Thien; Lépy, Marie-Christine
2013-11-01
In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe).
NASA Astrophysics Data System (ADS)
Papanikolaou, Ioannis; Roberts, Gerald; Foumelis, Michael; Parcharidis, Issaac; Lekkas, Efthimios; Fountoulis, Ioannis
2010-05-01
the maximum subsidence is not recorded near the ruptured fault trace, but closer to the hangingwall centre. The deformation pattern is asymmetrical expanding significantly towards the southeast. A part of this asymmetry can be attributed to contribution of the 7th of April event in the deformation field. Fault geometry influenced significantly the damage pattern. Villages located on the hangingwall experienced higher intensity values, compared to villages located on the footwall. This is also verified by the DInSAR which shows that the hangingwall area was subjected to higher deformation values. On average, subsidence values were two and a half times up to three times larger than the uplift values, leading to more violent shaking. The large number and extensive spatial distribution of secondary surface ruptures that occurred not only within the recent sediments of the Aterno basin, but also on pre-existing fault planes was another characteristic of this earthquake. These ruptures are usually disregarded in seismic hazard assessment planning and design studies, but can produce significant damage. Finally, basin effects and the bedrock geology played once more a decisive role to the damage pattern, even at short distances. It is interesting to note that villages that were only 1.5km apart, but founded on different bedrock geology recorded up to three intensity values difference.
Modeling and optimization of shark-inspired riblet geometries for low drag applications.
Martin, Samuel; Bhushan, Bharat
2016-07-15
Fast-swimming sharks have scales with microgrooves called riblets aligned in the direction of fluid flow. Riblets result in water moving efficiently over the surface. In previous experimental and modeling studies, it has been shown that riblets provide drag reduction by lifting vortices formed in turbulent flow decreasing overall shear stresses. Riblets have shown drag reductions on the order of 10% when compared to a flat surface. Modeling data of blade riblets exist showing the role of drag and vortex structures. However, various other geometries have not been modeled. To optimize riblet geometries for low drag, three different geometries were modeled and their drag properties and vortex structures were compared. In addition, a shark-inspired geometry with riblets arranged in a scale pattern was modeled to compare shark scales to these riblet geometries. Through this work, optimal riblet geometries and dimensions were determined. A better understanding of riblet design for drag allows for the fabrication of drag-reducing surfaces in transportation, medical, and industrial applications. Riblet features in the designs can range from the micro- to nanoscale dependent upon the scale of the components.
Modeling and optimization of shark-inspired riblet geometries for low drag applications.
Martin, Samuel; Bhushan, Bharat
2016-07-15
Fast-swimming sharks have scales with microgrooves called riblets aligned in the direction of fluid flow. Riblets result in water moving efficiently over the surface. In previous experimental and modeling studies, it has been shown that riblets provide drag reduction by lifting vortices formed in turbulent flow decreasing overall shear stresses. Riblets have shown drag reductions on the order of 10% when compared to a flat surface. Modeling data of blade riblets exist showing the role of drag and vortex structures. However, various other geometries have not been modeled. To optimize riblet geometries for low drag, three different geometries were modeled and their drag properties and vortex structures were compared. In addition, a shark-inspired geometry with riblets arranged in a scale pattern was modeled to compare shark scales to these riblet geometries. Through this work, optimal riblet geometries and dimensions were determined. A better understanding of riblet design for drag allows for the fabrication of drag-reducing surfaces in transportation, medical, and industrial applications. Riblet features in the designs can range from the micro- to nanoscale dependent upon the scale of the components. PMID:27131153
Low torque hydrodynamic lip geometry for rotary seals
Dietle, Lannie L.; Schroeder, John E.
2015-07-21
A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.