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201.
Sawicki M Siaugue JM Jacopin C Moulin C Bailly T Burgada R Meunier S Baret P Pierre JL Taran F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3689-3697
New tripodal gem-(bis-phosphonates) uranophiles were discovered by a screening method that allowed for the selection of ligands with strong uranyl-binding properties in a convenient microtiter-plate format. The method is based on competitive uranium binding by using Sulfochlorophenol S as chromogenic chelate. This dye compound was found to present high uranyl complexation properties and allowed to highlight ligands presenting association constants for UO(2+)(2) up to 10(18) at pH 7.4 and 10(20) at pH 9. A collection of 40 known ligands including polycarboxylate, hydroxamate, catecholate, hydroxypyridonate and hydroxyquinoline derivatives was tested. Also screened was a combinatorial library prepared from seven amine scaffolds and eight acrylates bearing diverse chelating moieties. Among these 96 tested candidates, a tripod derivative bearing gem-bis-phosphonates moieties was found to present the highest complexation properties over a wide range of pH and was further studied. 相似文献
202.
G. R. van der Hoff R. Hoogerbrugge R. A. Baumann U. A. Th. Brinkman P. van Zoonen 《Chromatographia》2000,52(7-8):433-438
Summary Normal-phase LC (NPLC) is a powerful method for the clean-up of fatty samples in the determination of organochlorine pesticides
(OCPs). The injected sample deactivates the stationary phase and the triglyceride matrix therefore serves as a polarity modifier
in the NPLC separation. Thus, the amount of sample injected is the key to both selectivity and sensitivity in matrixmodified
LC coupled to capillary GC.
In coupled LC-GC the NPLC separation becomes particularly critical because only a limited amount of the LC eluent can be transferred
to the GC and the triglyceride matrix must be prevented from entering the GC, because it degrades the performance of the injector
and the column. In previous applications method development was seriously hampered by these boundary conditions and tedious
and lengthy trial-and-error experiments were required to determine suitable experimental conditions. In this study an empirical
model was developed that describes the NPLC separation process in terms of column dimensions and fat loadability. The output
is given as the probability of achieving successful LC-GC analysis of a particular set of analytes, thus furnishing a useful
tool for the development of new applications in the field of exposure assessment and analysis of residues of apolar compounds
in fatty samples. The limitations of current procedures—maximum transfer volumes and minimal separation—are also discussed. 相似文献
203.
Bauer T Köhler M Lunkenheimer P Loidl A Angell CA 《The Journal of chemical physics》2010,133(14):144509
We report a thorough characterization of the dielectric relaxation behavior and the ionic conductivity in the plastic-crystalline mixture of 60% succinonitrile and 40% glutaronitrile. The plastic phase can be easily supercooled and the relaxational behavior is investigated by broadband dielectric spectroscopy in the liquid, plastic crystalline, and glassy crystal phases. The α-relaxation found in the spectra is characterized in detail. A well-pronounced secondary and faint indications for a third relaxation process were found. The latter most likely is of Johari-Goldstein type. From the temperature dependence of the α-relaxation time, a fragility parameter of 62 was determined. Thus, together with Freon112, this material stands out among all other plastic crystals by being a relatively fragile glass former. This finding provides strong support for an energy-landscape related explanation of the fragility of glass formers. In addition, unusually strong conductivity contributions were detected in the spectra exhibiting the typical features of ionic charge transport making this material a good basis for solid-state electrolytes. 相似文献
204.
Two interpretations have been proposed of dark triangles observed in scanning tunneling microscopy (STM) images of the best bound, √37×√37-R25.3°, and √39×√39-R16.1° periodic water monolayers on Pt(111). In one, a "Y"-shaped tetramer of water molecules is removed, leaving a vacancy island behind; the other assumes the Y is replaced by a hexagon of H(2)O molecules, amounting to a di-interstitial. Consistent only with the di-interstitial model are thermal desorption and CO coadsorption data, STM line scans, and total energies obtained from density functional theory calculations. 相似文献
205.
Polte J Erler R Thünemann AF Emmerling F Kraehnert R 《Chemical communications (Cambridge, England)》2010,46(48):9209-9211
A new setup for fast in situ SAXS studies of early stages in the nucleation and growth of colloidal nanoparticles is presented. Evading the disturbing influence of container walls and minimizing the possibility of beam-induced reactions, the benefits of the setup are demonstrated exemplarily for the well-known synthesis of gold nanoparticles via the Turkevich method. Analysis with the new experimental setup reveals the initial rate of particle formation, and enables analysis of particle growth rates. 相似文献
206.
Wong WW Vak D Singh TB Ren S Yan C Jones DJ Liaw II Lamb RN Holmes AB 《Organic letters》2010,12(21):5000-5003
A new class of self-assembling hexa-peri-hexbenzocoronene (HBC)-fullerene hybrid materials has been synthesized and characterized. Photoluminescence experiments indicate that energy transfer processes can be tuned in these donor-acceptor systems by varying the length and nature of the linker group. In preliminary device testing, ambipolar charge transport behavior is observed in organic field effect transistors, while single active component organic photovoltaic devices consisting of these materials achieved a maximum external quantum efficiency of 30%. 相似文献
207.
Brownian dynamics algorithms integrate Langevin equations numerically and allow to probe long time scales in simulations. A common requirement for such algorithms is that interactions in the system should vary little during an integration time step; therefore, computational efficiency worsens as the interactions become steeper. In the extreme case of hard-body interactions, standard numerical integrators become ill defined. Several approximate schemes have been invented to handle such cases, but little emphasis has been placed on testing the correctness of the integration scheme. Starting from the two-body Smoluchowski equation, the authors discuss a general method for the overdamped Brownian dynamics of hard spheres, recently developed by one of the authors. They test the accuracy of the algorithm and demonstrate its convergence for a number of analytically tractable test cases. 相似文献
208.
Dynamic Nuclear Polarization Provides New Insights into Chromophore Structure in Phytochrome Photoreceptors 下载免费PDF全文
Daniel Stöppler Dr. Chen Song Dr. Barth‐Jan van Rossum Michel‐Andreas Geiger Christina Lang Prof. Dr. Maria‐Andrea Mroginski Dr. Anil Pandurang Jagtap Prof. Dr. Snorri Th. Sigurdsson Prof. Dr. Jörg Matysik Prof. Dr. Jon Hughes Prof. Dr. Hartmut Oschkinat 《Angewandte Chemie (International ed. in English)》2016,55(52):16017-16020
209.
Gotchev G Kolarov T Levecke B Tadros T Khristov K Exerowa D 《Langmuir : the ACS journal of surfaces and colloids》2007,23(11):6091-6094
The interaction forces in emulsion films stabilized using hydrophobically modified inulin (INUTEC SP1) were investigated as a function of concentrations of electrolytes of different types (NaCl, Na2SO4, and MgSO4). At a constant disjoining pressure of 36 kPa, a constant temperature of 22 degrees C, and a film radius of 100 microm, the film thickness, hw, decreased with an increase in electrolyte concentration until a critical value, Cel,cr, was reached above which hw remained constant. Cel,cr decreased with an increase in electrolyte valency (Cel,cr = 5 x 10(-2) mol.dm(-3) for NaCl and 1 x 10(-2) mol.dm(-3) for Na2SO4 and MgSO4). The reduction in film thickness below Cel,cr could be accounted for by the compression of the electrical double layer. The Pi-hw isotherms below Cel,cr could be fitted using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (constant charge and constant potential cases were considered). At a certain pressure, the film jumped to a Newton black film. The pressure at the jump decreased with an increase in electrolyte valency as a result of the reduction of the electrostatic barrier. At electrolyte (NaCl, Na2SO4, or MgSO4) concentrations higher than Cel,cr, the jump occurred at a low pressure that was independent of the electrolyte type. The thickness of the Newton black film was independent of both the concentration and nature of the electrolytes studied. The results show clearly that the polyfructose loops and tails remain strongly hydrated both in water and in high concentrations of electrolytes of different types, and these results explain the high INUTEC SP1 emulsion stability against coalescence of emulsions prepared under such conditions. 相似文献
210.
A. A. Isaeva A. I. Baranov Th. Doert M. Ruck V. A. Kulbachinskii R. A. Lunin B. A. Popovkin 《Russian Chemical Bulletin》2007,56(9):1694-1700
New metal-rich mixed nickel-silicon and nickel-germanium chalcogenides, Ni5.68SiSe2, Ni5.46GeSe2, and Ni5.42GeTe2, were synthesized by high-temperature ceramic techniques. The X-ray diffraction study of single crystals grown from a molten
flux revealed that the compounds are isostructural and crystallize in the tetragonal system (space group I4/mmm, Z = 2). These compounds are the first members of the family of M7−δEX2-type (M = Ni or Pd; E = Sn or Sb; X is chalcogen) intergrowth structures containing “light” p elements E. Resistivity measurements on pressed textured pellets showed that both selenides are anisotropic metallic conductors
in the directions parallel and perpendicular to the heterometallic bond systems. The geometric criteria of stability of the
intergrowth structure type under consideration are discussed.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1632–1638, September, 2007. 相似文献