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61.
Christiane Reutel Edwin Weber Ulrich Henseler Martin Jansen 《Journal of chemical crystallography》1993,23(1):55-60
Crystal structure determination reveals that the unknown cycloaddition product between maleic anhydride, cyclopentadiene, and 1,2-bis(dibromomethyl)benzene has a nona-cyclic centrosymmetric structure. The compound was studied as DMF solvate (12). There is no significant intermolecular interaction between the title molecule and the DMF. Packing is in layers for both molecular species. A possible mechanism of formation of the title compound is discussed. 相似文献
62.
We report herein on changes in the Fe3+/ΣFe ratios induced by the electromigration of alkali ions (Alk+s) in natural alkali silicate glasses by measuring the shift of the Fe Lα emission peak at the electron microprobe. The Fe3+ reduction to Fe2+ classically occurs by electron transfer (Fe3+ + e? → Fe2+). The inward diffusion (to the bulk) of Alk+s is correlated with the outward diffusion (to the surface) of electrons transferred from a Fe2+ site to a neighboring Fe3+ site. This reduction process is somewhat different when iron is found at low amounts in glasses. In the latter case, Fe3+ is an efficient electron trap and its reduction to Fe2+ occurs by direct capture of a free electron. The Fe2+ oxidation is induced by the formation and the outward diffusion of O2? interstitial ions produced at the sites of paired nonbridging oxygens after the departure of the charge compensating Alk+s. The accumulation of free oxygens beneath the surface makes Fe3+-rich oxide phases to precipitate as separate nanometer sized particles. Outgassing of atomic oxygens as bubbles is also observed. 相似文献
63.
[reaction: see text] The combination of diethyl phosphite and DMAP as ligands for nickel in an 8:1 THF-N-ethylpyrrolidinone (NEP) mixture allows a very efficient cross-coupling reaction to be performed between various functionalized arylzinc halides and aryl bromides, triflates and activated chlorides. The reaction proceeds at 25 degrees C within 1-48 h and requires only 0.05 mol % of the nickel catalyst. 相似文献
64.
Leibold C Alvarez RM Cutin EH Della Vedova CO Oberhammer H 《Inorganic chemistry》2003,42(13):4071-4075
The IR (gas) and Raman (liquid) spectra of FC(O)NSCl(2) demonstrate the presence of a conformational mixture in both phases. According to a gas electron diffraction study, the main conformer (94(8)%) possesses a syn-syn structure (C(O)F group synperiplanar with respect to the SCl(2) bisector and the C=O bond synperiplanar to the N=S bond). Quantum chemical calculations (HF, B3LYP and MP2 with 6-31G basis set, and MP2/6-311(2df)) predict a syn-anti structure for the second conformer. Analysis of the IR (gas) spectrum results in a contribution of 5(1)% of the minor form, corresponding to a Gibbs free energy difference DeltaG degrees = G degrees (syn-anti) - G degrees (syn-syn) = 1.75(15) kcal/mol. This value is reproduced very well by quantum chemical calculations, which include electron correlation effects (DeltaG degrees = 1.28-1.56 kcal/mol). The HF approximation overestimates this energy difference (DeltaG degrees = 3.24 kcal/mol). 相似文献
65.
Harald Hagendorfer Christiane Lorenz Ralf Kaegi Brian Sinnet Robert Gehrig Natalie V. Goetz Martin Scheringer Christian Ludwig Andrea Ulrich 《Journal of nanoparticle research》2010,12(7):2481-2494
This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles
(ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized
environment. Time dependence of the particle size distribution in a size range of 10–500 nm and ENP release rates were studied
using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic
TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing
software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles
from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing
unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant
spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable
nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be
assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and
after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of
ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first
study presenting results concerning the release of ENP from spray products. 相似文献
66.
67.
A one-pot procedure to difunctionalized fused tricyclic bispyrroloquinone derivatives involving the condensation of N-tosylindoledione and α-ketoamines is described. 相似文献
68.
Christiane Fernandes James L. Wardell Janet M. S. Skakle 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):o499-o502
The molecule of 2-(hydroxymethyl)-1,3-propanediol, C4H10O3, lies across a mirror plane in space group P21/m, with disorder of both terminal hydroxyl H atoms. The molecules are linked by three O—H⋯O hydrogen bonds which combine to form sheets; in each O—H⋯O bond, the H atom resonates between the two O atoms. In the crystal structure of N,N′-bis[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]malonamide, C11H22N2O8, the molecule lies about a twofold axis and has four strong hydrogen bonds which form a mixture of chains and dimers; these combine to give a three-dimensional supramolecular framework. 相似文献
69.
Dendritic Glycopolymer as Drug Delivery System for Proteasome Inhibitor Bortezomib in a Calcium Phosphate Bone Cement: First Steps Toward a Local Therapy of Osteolytic Bone Lesions 下载免费PDF全文
70.
Marius Durea Radu Strugariu Christiane Tammer 《Journal of Optimization Theory and Applications》2017,175(3):738-763
The aim of this paper is to address new approaches, in separate ways, to necessary and, respectively, sufficient optimality conditions in constrained vector optimization. In this respect, for the necessary optimality conditions that we derive, we use a kind of vectorial penalization technique, while for the sufficient optimality conditions we make use of an appropriate scalarization method. In both cases, the approaches couple a basic technique (of penalization or scalarization, respectively) with several results in variational analysis and optimization obtained by the authors in the last years. These combinations allow us to arrive to optimality conditions which are, in terms of assumptions made, new. 相似文献