Search results for "Geometry"

Influence of Structural Isomerism on the Electronic Properties of Extended Phthalocyanines

1993

Abstract The electronic structure of isomeric naphthalocyanines (H2Nc) is investigated using the nonempirical valence effective Hamiltonian (VEH) technique. The way the outer benzene rings are annelated (linearly as in 2,3-H2Nc or angularly as in 1,2-H2Nc) is shown to determine very important changes in the electronic properties. While similar properties to those of phthalocyanine are calculated for 1,2-H2Nc, lower oxidation potentials and red-shifted optical absorptions are predicted for 2,3-H2Nc in agreement with experimental data. The isomerism resulting from the different relative positions of the angularly annelated benzene rings in 1,2-H2Nc is shown to have almost no effect on the ele…

Anthropogenic disturbance and diversity of species: polypores and polypore-associated beetles in forest, forest edge and clear-cut

2005

In boreal coniferous forests, artificial edges often modify the habitat, increasing the likelihood that the diversity and composition of species changes. This study examined the assemblage of polypores and polypore-associated beetles at the edge of mature managed spruce-dominated forests and clear-cuts. The highest number of polypore occurrences and the greatest diversity of polypore species occurred at the clear-cut. In south-facing edges polypores occurred closer to the edge both in clear-cut and in forest than in the north-facing edges. The number of polypore-associated beetle individuals was greatest in the clear-cut, but there was no effect of edge on species richness of beetles. Orien…

Boundary angles, cusps and conformal mappings

1986

Let f be a conformal mapping of a bounded Jordan domain D in the complex plane onto the unit disk . This paper examines the consequences for the local geometry of D near a boundary point z 0 of the mapping f-or, to be more precise, of the homeomorphic extension of this mapping to the closure of D—satisfying a Holder condition at z 0 or, alternatively, of its inverse satisfying a Holder condition at the point f(z 0). In particular, the compatibility of Holder conditions with the presence of cusps in the boundary of D is investigated.

Bounded Geometry, Growth and Topology

2011

Target point calculation in the computerized tomography. Comparison of different stereotactic methods

1995

The adaptation of computerized tomography for stereotactic operations requires the transformation of the coordinates of the target point from the CT image space into the stereotactic frame space. Two basic solutions for this transformation are realized in the most of the contemporary stereotactical systems. The indirect geometric method adjusts the frame coordinate system mechanically and identifies its origin in the CT image. There are 6 degrees of freedom: 3 of rotation and 3 of translation which have to be taken into consideration. The second method is a based on direct algebraic coordinate transformation and is independent of the explicite knowledge of the relationship between the image…

A method to reduce the FP/imm number through CC and MLO views comparison in mammographic images

2008

In this paper we propose a method to reduce the FP/imm number through CC and MLO mammographic views comparison of the same patient. The proposed solution uses the symmetry properties of the breast to compute a geometric transformation that permits to represent the two images in comparable coordinates systems. Through this method, potential pathological ROIs of one of the projections are correlated with the ROIs in the second view. To show the effectiveness of the result we apply the method on a dataset composed of 112 couples of pathological images. Experiments shows that method enables a reduction by up to 700/0 of the FP/imm number detected after the classification step

The transition from single layer to foliation boudinage: A dynamic modelling approach

2012

Abstract Foliation boudinage is a deflection of foliation in the vicinity of a central discontinuity in foliated rocks, mostly filled with vein material. It shows evidence for brittle deformation and void-opening during ductile flow. We used a two-dimensional visco-elastic spring model based on a discrete element approach to study the dynamic development of foliation boudinage and the behaviour of anisotropic visco-elastic material deformed under pure shear conditions. The anisotropies are set by defining rheological heterogeneities in the models with (1) a single layer in a weaker matrix; (2) multi-layers with different elastic properties and (3) random-distributed “micas”, rows of horizon…

Fracture and Fatigue of Travelling Plates

2013

In this chapter, problems of fracture and stability of a moving plate, travelling in a system of rollers at a constant velocity, are studied. It is known that in the manufacturing process, there may occur many kinds of defects in the paper web, such as edge cracks and blister and fiber cuts. Our aim is to tackle this problem and analyse theoretically how the defects change the behaviour. We will use the model of a thin elastic plate made of brittle material. A plate with initial cracks is studied, subjected to constant tension and cyclic tension. As a result, we will show how to find safe parameter ranges of transport velocities and in-plane tensions when fracture, stability and constraints…

Über zinn-haltige heterocyclen

1981

Abstract A complete series of diphenyl and mixed methyl/chlorine/bromine/iodinephenyl substituted oxadithia- and trithiastannocanes has been prepared by reactions between the respective disodium dithiolates and tin dihalides. The 13C NMR chemical shifts of these compounds and the coupling constants J(119Sn13C) are dependent upon the magnetic anisotropy of the substituents and the bond angles at the tin atom. The crystal structure of 2,2-diphenyl-1,3,6-trithia-2-stannocane has been determined and refined to R = 0.039. The environment of Sn is a monocapped tetrahedron (transannular distance Sn⋯S 324.6(1) pm). This type of coordination, intermediate between a tetrahedron and a trigonal bipyra…

Foliar influences on the vegetative development of grapevine

1997

<p style="text-align: justify;">Various defoliation treatments were applied to grapevine shoots during the whole duration of the growth period: full defoliation of every shoot of vine, defoliations retaining a various number of adult leaves to the base of every shoot and defoliations retaining a various number of young leaves to the top. The effects of these treatments allow to identify the major foliar influences on the vegetative development. Total defoliation induced a lesser intemodal elongation. This result is probably due, in part, to a carbohydrates deficiency consecutive to this drastic treatment. The defoliations with variation of the number of young leaves showed that the le…