Search results for " Geometry"
showing 10 items of 2294 documents
Structural basis and effect of copper(II) complexes with 4-oxo-thiazolidine ligands on DNA binding and nuclease activity
2020
Abstract Seven novel Copper(II) complexes, namely [Cu(Am4DHotaz)(H2O)2](ClO4) (1), [Cu(Am4DHotaz)(NO3)(MeOH)]·H2O (2), [Cu(Am4Motaz)2(H2O)](ClO4)2·0.83H2O (3), [Cu(Am4Motaz)2(NO3)]NO3·MeOH (4), [Cu(Am4Eotaz)2(NO3)]3(NO3)3·2H2O (5), [Cu(Am4Eotaz)2(ClO4)](ClO4) (6) and [Cu(Am4Eotaz)(ClO4)(H2O)](ClO4) (6a) (HAm4DHotaz = N′-(4-oxothiazolidin-2-ylidene)pyridine-2-carbohydrazonamide, Am4Motaz = N′-(3-methyl-4-oxothiazolidin-2-ylidene)pyridine-2-carbohydrazonamide and Am4Eotaz = N′-(3-ethyl-4-oxothiazolidin-2-ylidene)pyridine-2-carbohydrazonamide), have been successfully synthesized and characterized by several physicochemical techniques and, for 1–6 complexes, single crystal X-ray diffraction. Ha…
Study of the mutual influence of ligands in cobalt(II) complexes containing thiocyanate and imidazole derivatives
1997
Abstract The cobalt(II) complexes of formula [Co(NCS)2L2] and [Co(NCS)2L′4] (L = imidazole (iz) derivatives, I-Meiz (1), Z-Meiz (2), 2-Etiz (3), 2-Isopropiz (4), 2-Pheniz (5), 1,2-Me2iz (6), Biz (7), 2-Mebiz (8), 2-Etbiz (9); L′ = iz (10), 1-Meiz (11)) have been synthesized and characterized by spectroscopic methods and magnetic measurements. The crystal and molecular structures of complexes 6 and 11 have been determined by X-ray diffraction methods. Complex 6 crystallizes inthe orthorhombic space group Pnma with cell constants a=9.209 (3), b = 12.462 (5), c = 14.851(3) A ; V = 1704.3(9) A 3 , D ( calc ., Z = 4) = 1.43 g cm −3 , M r =367.35, F(000)=640 , λ( Mo K α)=0.71079 A , μ=11.2 cm−1 a…
Ferromagnetic Coupling Through the End-to-End Thiocyanate Bridge in Cobalt(II) and Nickel(II) Chains
2015
The preparation, spectroscopic characterization, and X-ray crystal structure of two novel one-dimensional compounds of formula [MII(tppz)(NCS)(μ-1,3-NCS)]n [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and M = Co(1) and Ni (2)] are reported. 1 and 2 are isomorphous compounds, and they crystallize in the P21/n space group. Their structures are made up of zigzag chains of cobalt(II) (1) and nickel(II) ions (2) bridged by single end-to-end thiocyanate groups with a tridentate tppz molecule and a terminally bound thiocyanate-N ligand achieving distorted MN5S octahedral surroundings around each metal center. The main source of the distortion of the ideal octahedron is due to the geometrical constr…
Syntheses, crystal structures and magnetic properties of copper(II) polynuclear and dinuclear compounds with 2,3-bis(2-pyridyl)pyrazine (dpp) and pse…
2001
Abstract The preparation, crystal structures and magnetic properties of four heteroleptic copper(II) complexes with 2,3-bis(2-pyridyl)pyrazine (dpp) and azide, cyanate or thiocyanate as ligands are reported, [Cu(dpp)(N3)2]n (1), [Cu(dpp)(NCO)2]n (2), [Cu(dpp)(NCS)2]2 (3) and [Cu(H2O)(dpp)(NCS)2]2·2H2O (4). Compounds 1 and 2 are isomorphous, triclinic, space group P1, and consist of mononuclear building blocks featuring copper atoms with close to square planar coordination geometries. The mononuclear units are, however, associated into chains through weak axial Cu–N bonds formed by end-on asymmetrically bridging azido/cyanato groups and by pyridyl nitrogen atoms. Taking these contacts into a…
Epistemic and didactic values of the demonstrative process in different cultures: a case study in Geometry with Chinese and Italian students
2011
Three-Dimensional Surface Display in Blood Pool Gated SPECT
1994
In 14 patients (4 in good health and 10 with coronary heart disease) a blood pool gated single photon emission computed tomography (SPECT) was executed. The transaxial slices of the cardiac blood pool were reconstructed. A three-dimensional surface display was employed for the analysis of the tomographic data. A fixed distance, a fixed threshold (50%), and some different planes of view were employed. The test permitted visualiza tion of the ventricular and the atrial movements in all patients. The right ventricle was clearly seen in the right anterior oblique plane of view. The aortic beating was seen. In normal patients the left ventricle, clearly seen in left anterior oblique plane, shra…
Volume-convergent sequences of Haken 3-manifolds
2003
Abstract Let M be a closed orientable 3-manifold and let Vol(M) denote its Gromov simplicial volume. This paper is devoted to the study of sequences of non-zero degree maps f i :M→N i to Haken manifolds. We prove that any sequence of Haken manifolds (Ni,fi), satisfying limi→∞deg(fi)×Vol(Ni)=Vol(M) is finite up to homeomorphism. As an application, we deduce from this fact that any closed orientable 3-manifold with zero Gromov simplicial volume and in particular any graph manifold dominates at most finitely many Haken 3-manifolds. To cite this article: P. Derbez, C. R. Acad. Sci. Paris, Ser. I 336 (2003).
Smooth surjections and surjective restrictions
2017
Given a surjective mapping $f : E \to F$ between Banach spaces, we investigate the existence of a subspace $G$ of $E$, with the same density character as $F$, such that the restriction of $f$ to $G$ remains surjective. We obtain a positive answer whenever $f$ is continuous and uniformly open. In the smooth case, we deduce a positive answer when $f$ is a $C^1$-smooth surjection whose set of critical values is countable. Finally we show that, when $f$ takes values in the Euclidean space $\mathbb R^n$, in order to obtain this result it is not sufficient to assume that the set of critical values of $f$ has zero-measure.
Trace and density results on regular trees
2019
We give characterizations for the existence of traces for first order Sobolev spaces defined on regular trees.