Search results for " Geometry"
showing 10 items of 2294 documents
Extremal polynomials in stratified groups
2018
We introduce a family of extremal polynomials associated with the prolongation of a stratified nilpotent Lie algebra. These polynomials are related to a new algebraic characterization of abnormal subriemannian geodesics in stratified nilpotent Lie groups. They satisfy a set of remarkable structure relations that are used to integrate the adjoint equations.
Deducing self-interaction in eye movement data using sequential spatial point processes
2016
Eye movement data are outputs of an analyser tracking the gaze when a person is inspecting a scene. These kind of data are of increasing importance in scientific research as well as in applications, e.g. in marketing and man-machine interface planning. Thus the new areas of application call for advanced analysis tools. Our research objective is to suggest statistical modelling of eye movement sequences using sequential spatial point processes, which decomposes the variation in data into structural components having interpretation. We consider three elements of an eye movement sequence: heterogeneity of the target space, contextuality between subsequent movements, and time-dependent behaviou…
Malliavin calculus of Bismut type without probability
2007
We translate in semigroup theory Bismut's way of the Malliavin calculus.
3-D shape reconstruction in an active stereo vision system using genetic algorithms
2003
Abstract The recovery of 3-D shape information (depth) using stereo vision analysis is one of the major areas in computer vision and has given rise to a great deal of literature in the recent past. The widely known stereo vision methods are the passive stereo vision approaches that use two cameras. Obtaining 3-D information involves the identification of the corresponding 2-D points between left and right images. Most existing methods tackle this matching task from singular points, i.e. finding points in both image planes with more or less the same neighborhood characteristics. One key problem we have to solve is that we are on the first instance unable to know a priori whether a point in t…
A linear open-chain piperazine-pyridine ligand and its meso-helical Co complex
1998
Abstract An oligomeric ligand (HPPy) 2 P, N , N ′-bis[2-(6-( N -( N ′-(2-hydroxyethyl)piperazinyl)methyl)]piperazine, was designed to resemble structurally open-chain aza-crowns. Owing to the all- trans configuration of piperazine and pyridine free electron pairs, it should adopt a near linear overall structure in solvent. Theoretical calculations at ab initio level confirm the overall linear structure of free ligand. The crystal structure of the complex [(HPPy) 2 P][Co(NO 3 ) 2 ] 2 shows a contraction from ∼3 to 2 nm structure. Each coordination site creates either a Δ or Δ configuration around the metal ion, thus causing a ligand with an even number of coordination centres to be meso -hel…
Unusual interaction extended between the pyranose ring oxygen and Zn(II) center in the complexes derived from 4,6-O-butylidene/ethylidene-N-(α-hydrox…
2003
The Zn(II) complexes of 4,6-O-butylidene/ethylidene-N-(α-hydroxynaphthylidene/o-hydroxybenzylidene)-β-Image -glucopyranosylamine have been synthesized and characterized using spectral and analytical methods and structure for one of the products was established. The geometry of the complexes vary from unusual distorted trigonal bipyramidal to pseudo-bicapped tetrahedron depending upon the extent of binding of pyranose ring oxygens to the Zn(II) ion, as evidenced from crystal structures. Such interaction is also reflected on the optical rotation and CD spectral properties of these complexes in solution.
Über polygermane
1984
Abstract The optimum conditions for selectively cleaving off two phenyl groups in Ge2Ph6 by trichloroacetic acid have been determined. Neither trihaloacetic acids nor HCl/AlCl3 nor reactive tetrahalides MCl4 are suitable reagents for cleaving one phenyl group alone. The 13C NMR chemical shifts of functional phenyl-mono- and -digermanes are given. The crystal structure of 1,2-bis(trichloroacetate)tetraphenyldigermane has been determined and refined to R = 0.048. The digermane bond is bridged by both acetates (distances GeGe 239.3(2), GeO 207.3(3) and 231.4(3) pm). The Ge atoms have trigonal bipyramidal coordination.
Synthesis, structural characterization and electrochemical activity of oxidovanadium(IV/V) complexes of a diprotic ONS chelating ligand
2010
Abstract The present work reports the chemistry of a few oxidovanadium(IV) and (V) complexes of the ONS chelating ligand S-benzyl-β-N-(2-hydroxyphenylethylidine) dithiocarbazate (H2L). Major objective of this work is to arrive at some general conclusions about the influence of binding environment generated by the replacement of an O-donor center by a S-donor point in a ligand (of a similar arrangement of the other O- and N-donor points) on the redox behavior and on the structural features of comparable [VO(OEt)(ONS)] and [VO(OEt)(ONO)] complexes. Synthesis, characterization by various physicochemical techniques (UV–Vis, IR, EPR and elemental analysis), exploration of electrochemical activit…
Strukturen von [Me4Sb]2[MeSbI4]MeSbI2, und [Me4Sb]I. Darstellung von Me3Sb · MeSbI2 und farbwechsel bei Me4Sb2 · Me2SbBr
1992
Abstract The crystal structures of the complex [Me 4 Sb] 2 [MeSbI 4 ] ( 1 ) and its precursors MeSbI 2 ( 2 ) and [Me 4 Sb]I ( 3 ) are reported. In 1 there are tetrahedral cations and square pyramidal anions with Sb-I distances of 290–320 pm. The structure of 2 contains MeSbI 2 molecules. They associate via iodine bridges to form linear chains with alternating short and long Sb-I distances. The coordination around antimony is distorted tetragonal pyramidal. The tetrahedral coordination of the ions in 3 results in the formation of a wurtzite type structure with antimony-iodine distances of 406 and 435 pm. The novel adducts Me 3 Sb·Me 2 SbI 2 ( 4 ) and Me 2 SbSbMe 2 ·Me 2 SbBr ( 5 ) are formed…
Synthesis, structural and magnetic characterizations of new complexes of di-2,6-(2-pyridylcarbonyl)pyridine (pyCOpyCOpy) ligand
2013
International audience; Using the di-2,6-(2-pyridylcarbonyl)pyridine ligand (L1) as starting framework, five new mononuclear complexes were obtained: [Cu(L1)(MeCN)(ClO4)2] (1) [Co(L1)(MeCN)(Br)2]*MeCN (2), [Fe(L1)2](BF4)2*MeOH*H2O (3), [Cr(L2a)Cl2]*2MeOH (where HL2a is (6-(hydroxyl(methoxy)(pyridin-2-yl)methyl)pyridin-2-yl)(pyridin-2-yl)methanone) (4) and one trinuclear [NiII3] complex, [Ni3(L2b)2(Bz)2(EtOH)2](ClO4)2*2EtOH (where HL2b is (6-(hydroxyl(ethoxy)(pyridin-2-yl)methyl)pyridin-2-yl)(pyridin-2-yl)methanone; Bz = benzoato) (5). Their structural and magnetic characterizations are herein reported. All the metal ions show octahedral coordination geometry, which is slightly unusual for t…