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71.
Alexander Čeklovský Juraj Bujdák Adriana Czímerová Nobuo Iyi 《Central European Journal of Physics》2007,5(2):236-243
Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites.
The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite;
KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of
linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting
angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined
angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly
higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or
the change of molecular comformation after the intercalation of the dye.
Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia 相似文献
72.
Daniela M. Fidalgo Adriana A. Kolender Oscar Varela 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):463-470
Novel linear carbohydrate‐derived [m,n]‐polyurethanes are successfully prepared using D ‐mannitol as renewable and low cost starting material. The key comonomer, 1,6‐di‐O‐phenylcarbonyl‐2,3,4,5‐tetra‐O‐methyl‐D ‐mannitol is polymerized with a diamine synthesized from D ‐mannitol or with alkylenediamines. These polymerization reactions afford, respectively, a [6,6]‐polyurethane entirely based on a carbohydrate derivative or [m,n]‐polyurethanes constituted by a poly‐O‐methyl substituted unit alternating with a polymethylene chain. All these polymers are stereoregular, as result of the C2 axis of symmetry of mannitol. The optically active polyurethanes are characterized by standard methods (FTIR, RMN, GPC, TGA, and DSC). Thus, GPC analysis reveals weight‐average molecular weights between 18,000 and 25,000 Da. Thermal studies (DSC) indicate that the polymers obtained are amorphous materials with Tg values dependent on the structure and chain length of the diamine constituent. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
73.
Long range correlation concerning hydrophilicity and flexibility along a number of 80 calcium binding protein sequences is confirmed by using spectral analysis and detrended fluctuations analysis methods, as well as by Hurst exponent calculations. There are no significant differences between the correlation properties concerning these properties for the two structural subfamilies, extended and compact, of the calcium binding proteins and they are also similar with the correlation properties revealed by other investigated proteins. This result sustains the hypothesis that the long range correlation of hydrophilicity and flexibility along the chain is a common feature of proteins. 相似文献
74.
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76.
Gradient bounds for minimizers of free discontinuity problems related to cohesive zone models in fracture mechanics 总被引:2,自引:0,他引:2
Gianni Dal Maso Adriana Garroni 《Calculus of Variations and Partial Differential Equations》2008,31(2):137-145
In this note we consider a free discontinuity problem for a scalar function, whose energy depends also on the size of the
jump. We prove that the gradient of every smooth local minimizer never exceeds a constant, determined only by the data of
the problem. 相似文献
77.
POPMUSIC for the point feature label placement problem 总被引:1,自引:0,他引:1
Point feature label placement is the problem of placing text labels adjacent to point features on a map so as to maximize legibility. The goal is to choose positions for the labels that do not give rise to label overlaps and that minimize obscuration of features. A practical goal is to minimize the number of overlaps while considering cartographic preferences. This article proposes a new heuristic for solving the point feature label placement problem based on the application of the POPMUSIC frame. Computational experiments show that the proposed heuristic outperformed other recent metaheuristics approaches in the literature. Experiments with problem instances involving up to 10 million points show that the computational time of the proposed heuristic increases almost linearly with the problem size. New problem instances based on real data with more than 13,000 labels are proposed. 相似文献
78.
Luisa Célia Melo Djenaine De Souza Pedro de Lima‐Neto Adriana Nunes Correia 《Electroanalysis》2010,22(21):2502-2510
The highly boron‐doped diamond electrode (HBDD) combined with square wave voltammetry (SWV) was used in the development of an analytical procedure for diquat determination in potato and sugar cane samples and lemon, orange, tangerine and pineapple juices. Preliminary experiments realised in a medium of 0.05 mol L?1 Na2B4O7 showed the presence of two voltammetric peaks around ?0.6 V and around ?1.0 V vs. Ag/AgCl/Cl? 3.0 mol L?1, where the first peak could be successfully used for analytical proposes due the facility in the electrode surface renovation. After the experimental and voltammetric optimisation, the calculated detection and quantification limits were 1.6×10?10 mol L?1 and 5.3×10?10 mol L?1 (0.057 µg L?1 and 0.192 µg L?1, respectively), which are lower than the maximum residue limit established for fresh food samples by the Brazilian Sanitary Vigilance Agency. The proposed methodology was used to determine diquat residues in potato and sugar cane samples and lemon, orange, tangerine and pineapple juices and the calculated recovery efficiencies indicated that the proposed procedure presents higher robustness, stability and sensitivity, good reproducibility, and is very adequate for diquat determination in complex samples. 相似文献
79.
Pavlo Solokha Serena De Negri Bernhard Eck Adriana Saccone 《Journal of solid state chemistry》2010,183(12):2995-3001
The crystal structures of two new ternary phases, La4Ag10Mg3 and La4Ag10.3Mg12, were refined from X-ray single crystal diffraction data. La4Ag10Mg3 crystallizes in the Ca4Au10In3 structure type, an ordered variant of the binary Zr7Ni10 compound: orthorhombic, Cmce, oS68, a=14.173(5), b=10.266(3), c=10.354(3) Å, Z=4, wR2=0.0826, 676 F2 values, 50 variables. La4Ag10.3Mg12 represents a new structure type: orthorhombic, Cmmm, oS116-10.32, a=9.6130(3), b=24.9663(8), c=9.6333(2) Å, Z=4, wR2=0.0403, 1185 F2 values, 101 variables. The structural analysis of both compounds, highlighting a significant contraction of the Ag-Mg distances, suggests the existence of three-dimensional [Ag-Mg] networks hosting La atoms. LMTO calculations applied to La4Ag10Mg3 indicate that the strongest bonds occur for Ag-Ag and Ag-Mg interactions, and confirm the presence of a 3D∞[Ag10Mg3]δ− polyanionic framework balanced by positively charged La atoms. 相似文献
80.
Noemí Andrade-López Tracy A. Hanna José G. Alvarado-Rodríguez Adriana Luqueño-Reyes Bernat A. Martínez-Ortega Daniel Mendoza-Espinosa 《Polyhedron》2010
Cis-diaquobis{di-(2-pyridyl)-N-ethylimine}nickel(II) chloride (2) was obtained from the reaction of di-(2-pyridyl)-N-ethylimine (1) and [NiCl2dppe] [dppe = cis-1,2-bis(diphenylphosphino)ethylene] in a 2:1 ratio in hot acetonitrile. Cis-dichloro{di-(2-pyridyl)-N-ethylimine}palladium(II) (3) and cis-dichloro{di-(2-pyridyl)-N-ethylimine}platinum(II) (4) complexes were obtained from the reaction of MCl2 (M = Pd, Pt) and (1) in equimolar ratio in hot acetonitrile. Compounds 1–4 were characterized by IR spectroscopy, elemental analysis, and mass spectrometry; the complexes 3 and 4 were characterized in solution by NMR. In addition, solid state structures of compounds 1–4 were determined using single crystal X-ray diffraction analyses. X-ray diffraction data of the complexes 3 and 4 showed a distorted square planar local geometry at palladium and platinum atoms with the chlorine atoms in a cis-coordination; in 2 a local octahedral geometry at nickel atom was observed. Complexes 3 and 4 are arranged as dimers with a M?M distance of 3.4567(4) Å (M = Pd) and 3.4221(4) Å (M = Pt), respectively; 2 consists of units linked by intermolecular hydrogen bonding. 相似文献