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101.
Liu P Guan Y van Santen RA Li C Hensen EJ 《Chemical communications (Cambridge, England)》2011,47(41):11540-11542
Chromium (III)-containing hydrotalcites show strong synergy with gold nanoparticles in achieving high activity in the aerobic oxidation of alcohols. 相似文献
102.
Kwee TC Takahara T Niwa T Yamashita T Van Cauteren M Nievelstein RA Luijten PR 《Magnetic resonance imaging》2011,29(6):877-880
Bowel contents and peripheral nerves often show high signal intensity at diffusion-weighted imaging (DWI) of the abdomen and pelvis, obscuring or mimicking pathology. This study introduced and compared short tau inversion recovery (STIR) with single-axis DWI to the usual combination of spectral fat suppression (SFS) with trace DWI in the suppression of bowel contents and peripheral nerves. Five volunteers underwent both STIR with single-axis DWI and SFS with trace DWI of the abdomen and pelvis. Images were evaluated by two observers with respect to the suppression of signal of bowel contents and peripheral nerves using four-point grading scales (4=poor suppression; 3=moderate suppression; 2=good suppression; 1=excellent suppression). Mean scores (±S.D.) regarding the suppression of bowel contents were 1.60±0.55 and 1.40±0.89 for STIR with single-axis DWI and 3.40±0.55 and 3.00±1.00 for SFS with trace DWI for observers 1 and 2, respectively. Mean scores regarding the suppression of peripheral nerves were 1.20±0.45 and 1.20±0.45 for STIR with single-axis DWI and 2.40±0.89 and 2.80±0.84 for SFS with trace DWI for observers 1 and 2, respectively. In conclusion, STIR with single-axis DWI is superior to SFS with trace DWI in the suppression of bowel signal and peripheral nerves. 相似文献
103.
Rutger Kuyper 《Mathematical Logic Quarterly》2014,60(6):444-470
We consider the complexity of satisfiability in ε‐logic, a probability logic. We show that for the relational fragment this problem is ‐complete for rational , answering a question by Terwijn. In contrast, we show that satisfiability in 0‐logic is decidable. The methods we employ to prove this fact also allow us to show that 0‐logic is compact, while it was previously shown that ε‐logic is not compact for . 相似文献
104.
Mignon P Pidko EA Van Santen RA Geerlings P Schoonheydt RA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5168-5177
The disproportionation of N(2)O(4) into NO(3)(-) and NO(+) on Y zeolites has been studied through periodic DFT calculations to unravel 1) the role of metal cations and the framework oxygen atoms and 2) the relationship between the NO(+) stretching frequency and the basicity of zeolites. We have considered three situations: adsorption on site II cations with and without a cation at site III and adsorption on a site III cation. We observed that cations at sites II and III cooperate to stabilize N(2)O(4) and that the presence of a cation at site III is necessary to allow the disproportionation reaction. The strength of the stabilization is due to the number of stabilizing interactions increasing with the size of the cation and to the Lewis acidity of the alkali cations, which increases as the size of the cations decreases. In the product, NO(3)(-) interacts mainly with the cations and NO(+) with the basic oxygen atoms of the tetrahedral aluminium through its nitrogen atom. As the cation size increases, the NO(3)(-)...cation interaction increases. As a result, the negative charge of the framework is less well screened by the larger cations and the interaction between NO(+) and the basic oxygen atoms becomes stronger. NO(+) appears to be a good probe of zeolite basicity, in agreement with experimental observations. 相似文献
105.
Wijdeven MA Wijtmans R van den Berg RJ Noorduin W Schoemaker HE Sonke T van Delft FL Blaauw RH Fitch RW Spande TF Daly JW Rutjes FP 《Organic letters》2008,10(18):4001-4003
A stereoselective synthesis of (+)-epiquinamide is presented in combination with determination of the absolute configuration of the natural product. Key steps in the sequence involved chemoenzymatic formation of an enantiomerically pure cyanohydrin, reductive cyclization to the corresponding cyclic N,N-acetal, and subsequent conversion into a suitable N-acyliminium ion precursor to enable construction of the second ring. 相似文献
106.
AJ Markvoort RA van Santen PA Hilbers EJ Hensen 《Angewandte Chemie (International ed. in English)》2012,51(36):9015-9019
Long carbon chains: Self-assembly of monomeric carbon intermediates into long-chain hydrocarbons on catalytically reactive surface was studied when full reversibility of the chain growth is included in the kinetic model. Using Br?nsted-Evans-Polanyi relations, the maximum chain growth as a function of the surface reactivity is predicted. 相似文献
107.
Kuyper CL Budzinski KL Lorenz RM Chiu DT 《Journal of the American Chemical Society》2006,128(3):730-731
This Communication reports real-time sizing of nanoparticles in microfluidic systems using confocal correlation spectroscopy (CCS). CCS can be used to measure the size of both fluorescent and nonfluorescent particles at low concentrations (相似文献
108.
Botterhuis NE Sun Q Magusin PC van Santen RA Sommerdijk NA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(5):1448-1456
Herein we report the synthesis and characterization of hollow silica spheres with a narrow size distribution, uniform wall thickness, and a worm-like pore structure. The formation of these spheres was monitored by confocal laser scanning microscopy and dynamic light scattering. A model for the molecular build-up of these silica hollow spheres is derived from these data in combination with studies of the as-made particles by transmission electron microscopy, scanning electron microscopy, pore size analysis, thermogravimetric analysis, and solid-state nuclear magnetic resonance. We further demonstrate that these spheres can be used for the encapsulation and subsequent release of different dye molecules. 相似文献