Search results for " Geometry"
showing 10 items of 2294 documents
Playing with different metalloligands [NiL] and Hg to [NiL] ratios to tune the nuclearity of Ni(II)–Hg(II) complexes: Formation of di-, tri-, hexa- a…
2015
Abstract Five new hetero-metallic nickel(II)–mercury(II) complexes, [(NiL1)HgCl2] (1), [(NiL1)2HgCl2] (3), [(NiL1)2Hg(N3)2] (4), [{(NiL2)2Hg(N3)(μ1,1-N3)}2] (5) and [{(NiL2)2Hg(N3)(μ1,1-N3)HgCl2}2{Hg(N3)(μ1,1-N3)}] (6) have been synthesized by reacting metalloligands [NiL1] or [NiL2] (where H2L1 is N,N′-bis(salicylidene)-1,2-ethylenediamine and H2L2 is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX2 (X− = Cl− or N3−) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1, the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL1] moiety and two terminal chloride ions to …
Oxalate, squarate and croconate complexes with bis(2-pyrimidylcarbonyl)amidatecopper(II): synthesis, crystal structures and magnetic properties
2005
Abstract The preparation and magnetic properties of three copper(II) compounds of formulae [Cu2(bpcam)2(H2O)2(C2O4)] (1), [Cu2(bpcam)2(H2O)4(C4O4)] · 10 H2O (2) and Cu2(bpcam)2(C5O5)(H2O)3 (3) [bpcam = bis(2-pyrimidyl)amidate, C 2 O 4 2 - = dianion of oxalic acid , C 4 O 4 2 - = dianion of 3 , 4 - dihydroxycyclobut - 3 - ene - 1 , 2 - dione and C 5 O 5 2 - = dianion of 4 , 5 - dihydroxycyclopent - 4 - ene - 1 , 2 , 3 - trione ] are reported. The structures of two of them (1 and 2) have been solved by single crystal X-ray diffraction and consists of centrosymmetric discrete copper(II) dinuclear units bridged by bis-bidentate oxalate (1) and bis-monodentate squarate (2), with the bpcam group …
Structure and magnetic properties of a linear oximato-bridged tetranuclear copper(II) complex
1998
Abstract The tetranuclear copper(II) complex of formula [Cu2(dmg)(Hdmg)(terpy)]2(ClO4)2 (1) (H2dmg = dimethylglyoxime and terpy = 2,2′:6′,2″-terpyridine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the triclinic system, space group P(−1), with a = 14.382(3), b = 13.728(3), c = 8.979(2) A, α = 96.99(2), β = 111.85(2), γ = 111.22(3)°, V = 1465.0(9) A3, Z = 1, Dc = 1.607 g cm−3, Mr = 1418.0, F(000) = 719, λ(Mo Kα) = 0.71073 A, μ(Mo Kα) = 16.61 cm−1 and T = 298 K. A total of 4891 reflections were measured over the range 2 ≤ θ ≤ 25° and 4393 of them were unique (I > 2.5σ(I) and used in the structural analysis. The structure of 1 may …
Magneto-structural correlations and DFT calculations in two rare tetranuclear copper(II)-clusters with doubly phenoxo and end-on azido bridges: Synth…
2010
International audience; By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)Cdouble bond; length as m-dashN(CH2)3Ndouble bond; length as m-dashC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment o…
Base-assisted synthesis of 4-pyridinate gold(I) metallaligands: a study of their use in self-assembly reactions
2021
Made available in DSpace on 2021-06-25T12:16:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-06 Ministerio de Economia y Competitividad (MINECO/FEDER) of Spain Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The synthesis of di- and tritopic gold(I) metallaligands of the type [(Au4-py)(2)(mu(2)-diphosphane)] (diphosphane = bis(diphenylphosphanyl)isopropane or dppip (1), 1,2-bis(diphenylphosphanyl)ethane or dppe (2), 1,3-bis(diphenylphosphanyl)propane or dppp (3) and 1,4-bis(diphenylphosphanyl)butane or dppb (4)) and [(Au4-py)(3)(mu(3)-triphosphane)] (triphosphane = 1,1,1-tris(diphenylphosph…
Pauls rectifiable and purely Pauls unrectifiable smooth hypersurfaces
2020
This paper is related to the problem of finding a good notion of rectifiability in sub-Riemannian geometry. In particular, we study which kind of results can be expected for smooth hypersurfaces in Carnot groups. Our main contribution will be a consequence of the following result: there exists a -hypersurface without characteristic points that has uncountably many pairwise non-isomorphic tangent groups on every positive-measure subset. The example is found in a Carnot group of topological dimension 8, it has Hausdorff dimension 12 and so we use on it the Hausdorff measure . As a consequence, we show that any Lipschitz map defined on a subset of a Carnot group of Hausdorff dimension 12, with…
Computing temporal sequences associated with dynamic patterns on the C. elegans connectome
2021
AbstractUnderstanding how the structural connectivity of a network constrains the dynamics it is able to support is a very active and open area of research. We simulated the plausible dynamics resulting from the known C. elegans connectome using a recent model and theoretical analysis that computes the dynamics of neurobiological networks by focusing on how local interactions among connected neurons give rise to the global dynamics in an emergent way, independent of the biophysical or molecular details of the cells themselves. We studied the dynamics which resulted from stimulating a chemosensory neuron (ASEL) in a known feeding circuit, both in isolation and embedded in the full connectome…
An Optimized Architecture for CGA Operations and Its Application to a Simulated Robotic Arm
2022
Conformal geometric algebra (CGA) is a new geometric computation tool that is attracting growing attention in many research fields, such as computer graphics, robotics, and computer vision. Regarding the robotic applications, new approaches based on CGA have been proposed to efficiently solve problems as the inverse kinematics and grasping of a robotic arm. The hardware acceleration of CGA operations is required to meet real-time performance requirements in embedded robotic platforms. In this paper, we present a novel embedded coprocessor for accelerating CGA operations in robotic tasks. Two robotic algorithms, namely, inverse kinematics and grasping of a human-arm-like kinematics chain, ar…
Implementation and evaluation of medical imaging techniques based on conformal geometric algebra
2020
Medical imaging tasks, such as segmentation, 3D modeling, and registration of medical images, involve complex geometric problems, usually solved by standard linear algebra and matrix calculations. In the last few decades, conformal geometric algebra (CGA) has emerged as a new approach to geometric computing that offers a simple and efficient representation of geometric objects and transformations. However, the practical use of CGA-based methods for big data image processing in medical imaging requires fast and efficient implementations of CGA operations to meet both real-time processing constraints and accuracy requirements. The purpose of this study is to present a novel implementation of …
Points massiques, courbes de Bézier quadratiques et coniques : un état de l'art
2014
It is well known quadratic Bézier curves define conics. The use of massic points permits to define a semi-conic in the Euclidean plane. Moreover, from a given quadratic Bézier curve, we can determine the properties of the underlying conic. Moreover, the choice of an adequat non-degenerate indefinite quadratic form permits to see the non-degenerate central conic as an unitary circle.