Search results for " Geometry."
showing 10 items of 2189 documents
L'analyse fractale, un nouvel outil pour l'analyse spatiale des agglomérations urbaines
1997
The fractal approach. A new tool for the spatial analysis of urban agglomerations. Fractal geometry is a new approach for the study of spatial distributions. The basic model is a law of hierarchical distribution corresponding to Pareto's law which is familiar to urban geographers and demographers. The methods of fractal analysis can be used to study the spatial organization of human activities across scales. The regularities and the discontinuities in the distributions can then be identified. These discontinuities can be spatially situated. Applying this concept to urbanized areas has shown that districts can be defined and classified according to their scaling relations, thereby allowing d…
Estimation géométrique des tangentes à partir de coniques et algèbre géométrique. Exemples sous GAviewer
2018
National audience; Les nombres complexes sont fortement liés à la géométrie plane. Si les rotations, symétries et similitudes planes parmi d'autres s'expriment aisément à l'aide des complexes, le mérite de ce mode de représentation prend tout son sens dans toutes les compositions de ces transformations. Cette algébrisation des problèmes géométriques est le fil directeur de l'article. Elle fournit ainsi des formules de calcul aisément exploitables sur ordinateur. A titre d'exemple, l'article propose un algorithme géométrique de calcul de tangentes à une conique, son adaptation au contexte de l'algèbre géométrique et son implémentation au moyen d'un logiciel dédié. L'algorithme repose sur le …
Effect of dual blockade of renin-angiotensin system on TGF beta 1 and left ventricular structure and function in hypertensive patients
2007
The effects of 24 weeks losartan and ramipril treatment,both alone and in combination, on left ventricular mass (LVM), circulating transforming growth factor b1(TGFb1), procollagen type I (PIP) and III (PIIIP), havebeen evaluated in hypertensive (HT) patients. A total of 57 HT with stage 1 and 2 essential hypertension were included. After 4 weeks run in, a randomized double blind, three arms, double dummy, independent trial was used. All HT patients were randomly allocated to three treatment arms consisting of losartan (50 mg/daily),ramipril (5 mg/ daily) and combined (losartan 50 mg/daily plus ramipril 5 mg/daily) for 24 weeks. TGFb1, PIP and PIIIP, LVM, LVM/h 2.7 and other echocardiograph…
Coupled fixed point results in cone metric spaces for -compatible mappings
2011
In this paper, we introduce the concepts of -compatible mappings, b-coupled coincidence point and b-common coupled fixed point for mappings F, G : X × X → X, where (X, d) is a cone metric space. We establish b-coupled coincidence and b-common coupled fixed point theorems in such spaces. The presented theorems generalize and extend several well-known comparable results in the literature, in particular the recent results of Abbas et al. [Appl. Math. Comput. 217, 195-202 (2010)]. Some examples are given to illustrate our obtained results. An application to the study of existence of solutions for a system of non-linear integral equations is also considered. 2010 Mathematics Subject Classificati…
Do Extremely Bent Allenes Exist?
2009
Bent allenes: Theoretical calculations show that extremely bent allenes, cyclic or acyclic, adopt a ground state that only bears a formal relationship to classical allenes. Consequently, five-membered ring allenes favor a carbene-like electronic structure and formally contain a trivalent carbon(II) center. peerReviewed
Transmission Electron Microscopy of GroEL, GroES, and the Symmetrical GroEL/ES Complex
1994
Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indic…
Über gemischte bindungen in der IV. hauptgruppe
1987
Abstract Reaction of Ph3SnLi with Ph2SiCl2 or Ph2GeCl2 at −78°C in THF yields (Ph3Sn)2SiPh2 (1) and (Ph3Sn)2GePh2 (2). The crystal structure of 1 (R = 0.075) exhibits SnSi distances of 257.2(4) and 257.9(5) pm, an SnSiSn angle of 118.5(2)°, and a central C3SnSiC2SnC3 molecular skeleton with symmetry close to C2. The geminal NMR coupling 2J(119Sn ⋯ 119Sn) in 1, and in a tri-, tetra- and pentastannane series shows a linear correlation to their respective non-bonded d(Sn ⋯ Sn) distances (I(t-Bu2Sn)4I: 20 Hz/496 pm; 1: 724 Hz/443 pm).
Algebraic models of the real affine plane
2017
We introduce a new invariant, the real (logarithmic)-Kodaira dimension, that allows to distinguish smooth real algebraic surfaces up to birational diffeomorphism. As an application, we construct infinite families of smooth rational real algebraic surfaces with trivial homology groups, whose real loci are diffeomorphic to $\mathbb{R}^2$, but which are pairwise not birationally diffeomorphic. There are thus infinitely many non-trivial models of the real affine plane, contrary to the compact case.
The ends of manifolds with bounded geometry and linear growth
2004
We prove that simply connected open manifolds of bounded geometry, linear growth and sublinear filling growth (e.g. finite filling area) are simply connected at infinity.
Alternative method for binary shape alignment of non-symmetrical shapes based on minimal enclosing box
2012
Proposed is a novel method based on the minimal enclosing box (MEB) to determine the canonical orientation associated with a three-dimensional binary shape. It is suggested that, when the shape has no clear distinctive features and two or more of the eigenvalues are similar, this method is more suitable than the commonly used method based on principal component analysis (PCA). An experiment is performed with shapes of human livers by measuring the degree on which a prototypical image (atlas) matches to a new shape after alignment by PCA, minimal area projection (MAP), and MEB showing that in this case MEB outperforms the usual PCA-based alignment method and also the MAP method.