Search results for "Geometry"
showing 10 items of 4487 documents
Visual Acuity and Contrast Sensitivity Depending from Keratoconus Apex Position
2017
Abstract Various studies have demonstrated that patients with keratoconus have significant loss of contrast sensitivity while its value varies in different studies. None of these studies has analysed reduced contrast sensitivity depending on the position of apex of corneal conus. Visual acuity and contrast sensitivity were evaluated for patients with keratoconus using the FrACT software. Contrast sensitivity was assessed at the following frequencies: 1, 3, 5, 7, 9, 11, 13, and 15 cycles per degree (cpd). Twenty-four eyes with keratoconus were analysed. Contrast sensitivity was significantly lower for patients with the apex at the centre compared with apex on the periphery both with (p = 0.0…
Search for Cosmic Neutrino Point Sources with Four Year Data of the ANTARES Telescope
2012
In this paper, a time-integrated search for point sources of cosmic neutrinos is presented using the data collected from 2007 to 2010 by the ANTARES neutrino telescope. No statistically significant signal has been found and upper limits on the neutrino flux have been obtained. Assuming an E ¿2 n; spectrum, these flux limits are at 1-10 ¿10¿8 GeV cm¿2 s¿1 for declinations ranging from ¿90° to 40°. Limits for specific models of RX J1713.7¿3946 and Vela X, which include information on the source morphology and spectrum, are also given.
Points massiques, espace des sphères et « hyperbole »
2015
The use of massic points permits to define a branch of a hyperbola in the Euclidean plane using a Rational Quadratic Bézier Curve. In the space of spheres, a circular cone, a circular cylinder, a torus, a pencil of spheres or a Dupin cyclide is represented by a conic. If the kind of the pencil is Poncelet or if the canal surface is a circular cone, a spindle torus, a spindle or a horned Dupin cyclide, the curve is a circle which is seen as a hyperbole. The limit points of the pencil or the singular points of the Dupin cyclide can be determined using the asymptotes of this circle. In this article, we show that the use of massic points simplifies the modelization of these pencils or these Dup…
Crystal structure of tricarbonyl(N-diphenylphosphanyl-N,N′-diisopropyl-P-phenylphosphonous diamide-κ2 P,P′)cobalt(I) tetracarbonylcobaltate(−…
2014
The title compound {Co(CO)3[Ph2PN(i-Pr)P(Ph)N(H)i-Pr]}[Co(CO)4] is an ionic species consisting of a Co(CO)3[Ph2PN(i-Pr)P(Ph)N(H)i-Pr] cation and a [Co(CO)4] anion.
Crystal structure of bis{μ2-3-(pyridin-2-yl)-5-[(1,2,4-triazol-1-yl)methyl]-1,2,4-triazolato}bis[aquanitratocopper(II)] dihydrate
2016
The title complex is a centrosymmetric dimer with a copper–copper distance of 4.0408 (3) Å. The Cu ions in the dimer are bridged by two triazole rings and oxygen donor ligands from water molecules and nitrate anions in a distorted octahedral coordination geometry.
Crystal structures of organoplatinum complexes containing alkyleugenoxyacetate and p-chloroaniline
2016
In the title trans-dichloridoplatinum(II) complexes, the central PtII atom is further coordinated by the p-chloroaniline N atom and ethylenic double bond of alkyleugenoxyacetate.
Bis{3,5-di-tert-butyl-N-[(4-dimethylamino)phenyl]salicylaldiminato}cobalt(II)
2017
In the title complex [systematic name: bis(2,4-di-tert-butyl-6-{N-[4-(dimethylamino)phenyl]carboximidoyl}phenolato)cobalt(II)], [Co(C23H31N2O)2], the cobalt(II) atom is coordinated by pairs of O and N atoms in a distorted tetrahedral coordination geometry. The dihedral angles formed by the aromatic rings of the same ligand are 51.99 (11) and 36.58 (9)°. The molecular conformation features weak intramolecular C—H...O hydrogen bonds. In the crystal, inversion-related pairs of complex molecules are linked into dimers by weak C—H...π interactions. The methyl C atoms oftert-butyl groups have rotational disorder, with site occupancies of 0.647 (7) and 0.617 (6) for the major components and 0.353 …
Bis(4,6-di-tert-butyl-2-{N-[4-(diethylamino)phenyl]carboximidoyl}phenolato)cobalt(II)
2017
In the title complex, [Co(C25H35N2O)2], the cobalt(II) atom has a distorted tetrahedral geometry provided by pairs of O and N atoms. The dihedral angles between the benzene rings of the same ligand are 52.39 (9) and 34.96 (9)°. The molecular structure is stabilized by weak intramolecular C—H...O hydrogen bonds. The crystal packing is stabilized mainly by van der Waals forces. The structure contains a solvent-accessible void of 276 Å3which was treated using the SQUEEZE routine fromPLATON[Spek (2015).Acta Cryst.C71, 9–18]. The methyl C atoms of thetert-butyl groups are rotationally disordered, with site occupancies of 0.802 (3) and 0.548 (9) for the major components and 0.198 (3) and 0.452 (9…
{Bis[2-(diisopropylphosphanyl)ethyl]amine}carbonyl(tetrahydroborato)cobalt(I)
2018
In the structure of title borohydride pincer complex, [Co(BH4)(C16H37NP2)(CO)], the cobalt(I) metal exhibits a distorted square-pyramidal coordination geometry with the basal positions occupied by the P and N atoms of the tridentate ligand and by the C atom of the carbon monoxide ligand. In the crystal, molecules interact only by van der Waals forces.
Crystal structure of chlorido(2-{1-[2-(4-chlorophenyl)hydrazin-1-ylidene-κN]ethyl}pyridine-κN)(η5-pentamethylcyclopentadienyl)rhodium(III) chloride
2015
The title compound, [Rh(η5-C5Me5)Cl(C13H12ClN3)]Cl, is chiral at the metal and crystallizes as a racemate. Upon coordination, the hydrazinylidenepyridine ligand is non-planar, an angle of 54.42 (7)° being observed between the pyridine ring and the aromatic ring of the [2-(4-chlorophenyl)hydrazin-1-ylidene]ethyl group.