排序方式: 共有22条查询结果,搜索用时 15 毫秒
1.
Jerald S. Bradshaw Reed M. Izatt James J. Christensen Krzystof E. Krakowiak Bryon J. Tarbet Ronald L. Bruening S. Lifson 《Journal of inclusion phenomena and macrocyclic chemistry》1989,7(2):127-136
Silica gel-bound crown ethers and aza macrocycles have been synthesized with the attaching arm connected to the carbon framework of the macrocycles. The interactions of these bound macrocycles with cations are almost identical to those involving the analogous free macrocycles. This has allowed for predictable cation separation, concentration, and removal processes to be performed on a small scale. Quantum mechanical calculations and NMR measurements indicate that similarly bound chiral macrocycles will be capable of use in separating chiral organic amines.Dedicated to the memory of Professor James J. Christensen who died on 5 September 1987. 相似文献
2.
Dr. Xuecheng Chen Dr. Krzysztof Kierzek Karolina Wenelska Krzystof Cendrowski Jiang Gong Dr. Xin Wen Prof. Tao Tang Prof. Paul K. Chu Prof. Ewa Mijowska 《化学:亚洲杂志》2013,8(11):2627-2633
Core–shell‐structured mesoporous silica spheres were prepared by using n‐octadecyltrimethoxysilane (C18TMS) as the surfactant. Hollow mesoporous carbon spheres with controllable diameters were fabricated from core–shell‐structured mesoporous silica sphere templates by chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres (HCSs) with different diameters can be obtained. The use of ethylene as the carbon precursor in the CVD process produces the materials in a single step without the need to remove the surfactant. The mechanism of formation and the role played by the surfactant, C18TMS, are investigated. The materials have large potential in double‐layer supercapacitors, and their electrochemical properties were determined. HCSs with thicker mesoporous shells possess a larger surface area, which in turn increases their electrochemical capacitance. The samples prepared at a lower temperature also exhibit increased capacitance as a result of the Brunauer–Emmett–Teller (BET) area and larger pore size. 相似文献
3.
Małgorzata Borówko Krzystof Stępniak Stefan Sokołowski Roman Zagórski 《Czechoslovak Journal of Physics》1999,49(7):1067-1075
The structure of liquid-gas interface of associating Lennard-Jones particles is studied using the density-functional theory
and the Monte Carlo simulation. The model with one bonding site per particle is considered. It is shown that the considered
version of the density functional is quite successful in predicting the gas-liquid density profile. 相似文献
4.
K. Cendrowski X. Chen B. Zielinska R. J. Kalenczuk M. H. Rümmeli B. Büchner R. Klingeler E. Borowiak-Palen 《Journal of nanoparticle research》2011,13(11):5899-5908
The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such
as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica
nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and
hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected. 相似文献
5.
We present a rigorous analysis of the Schrödinger picture quantization for theSU(2) Chern-Simons theory on 3-manifold torusxline, with insertions of Wilson lines. The quantum states, defined as gauge covariant holomorphic functionals ofsu(2)-connections on the torus, are expressed by degree 2k theta-functions satisfying additional conditions. The conditions are obtained by splitting the space of semistablesu(2)-connections into nine submanifolds and by analyzing the behavior of states at four codimension 1 strata. We construct the Knizhnik-Zamolodchikov-Bernard connection allowing to compare the states for different complex structures of the torus and different positions of the Wilson lines. By letting two Wilson lines come together, we prove a recursion relation for the dimensions of the spaces of states which, together with the (unproven) absence of states for spins>1/2 level implies the Verlinde dimension formula. 相似文献
6.
We study the relations between different determinants of the Dirac operator over a manifold with boundary considered as sections of a holomorphic line bundle over the Grassmannian of boundary conditions of Atiyah–Patodi–Singer type. 相似文献
7.
8.
Cavazzini A Bardin G Kaczmarski K Szabelski P Al-Bokari M Guiochon G 《Journal of chromatography. A》2002,957(2):111-126
The adsorption isotherms of butyl- and amylbenzene on silica monolithic columns were measured by frontal analysis. The external, internal and total porosities of these columns were determined by inverse size-exclusion chromatography. The adsorption isotherms are concave upward in the entire concentration range investigated. They were fitted to the anti-Langmuir model, an unusual model in liquid-solid and liquid-liquid phase equilibria. Band profiles under overloaded conditions were recorded. They were in good agreement with the profiles calculated using th,e lumped pore diffusion model of chromatography and these adsorption isotherms. 相似文献
9.
Gadzała-Kopciuch R Cendrowski K Cesarz A Kiełbasa P Buszewski B 《Analytical and bioanalytical chemistry》2011,401(7):2069-2078
This study presents a selective method of isolation of zearalenone (ZON) and its metabolite, α-zearalenol (α-ZOL), in neoplastically
changed human tissue by accelerated solvent and ultrasonic extractions using a mixture of acetonitrile/water (84/16% v/v) as the extraction solvent. Extraction effectiveness was determined through the selection of parameters (composition of the
solvent mixture, temperature, pressure, number of cycles) with tissue contamination at the level of nanograms per gram. The
produced acetonitrile/water extracts were purified, and analytes were enriched in columns packed with homemade molecularly
imprinted polymers. Purified extracts were determined by liquid chromatography (LC) coupled with different detection systems
(diode array detection - DAD and mass spectrometry - MS) involving the Ascentis RP-Amide as a stationary phase and gradient
elution. The combination of UE-MISPE-LC (ultrasonic extraction - molecularly imprinted solid-phase extraction - liquid chromatography)
produced high (R ≈ 95–98%) and repeatable (RSD < 3%) recovery values for ZON and α-ZOL. 相似文献
10.
Krzystof Szalewicz Bogumil Jeziorski Hendrik J. Monkhorst John G. Zabolitzky 《Chemical physics letters》1982,91(3):169-172
Second-order correlation energies for atoms and molecules are calculated with a novel variational functional that is closely related to the one used before but neglects the most time-consuming terms. Consequently much larger basis sets could be used. Results for He, Be, H2 and LiH obtained with an explicitly correlated gaussian geminal basis are better than the best published results by 0.32, 0.06, 3.3, and 6.2% and are estimated to be accurate to within a fraction of 1%. 相似文献