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排序方式: 共有194条查询结果,搜索用时 15 毫秒
81.
Herzog B Katzenstein A Quass K Stehlin A Luther H 《Journal of colloid and interface science》2004,271(1):136-144
In this study microparticles consisting of a benzotriazole derivative, which are used as absorbers for UV radiation in cosmetic sunscreens, were investigated. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. The particle sizes obtained after different stages of the micronization process were measured using fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry. All methods showed satisfactory agreement over the whole range of sizes. With the FOQELS technique the particle size distribution could be resolved to sizes well below 0.1 microm. 相似文献
82.
T. Win W. Luther J. Jacob H. A. M. G. Vaessen A. Boenke 《Fresenius' Journal of Analytical Chemistry》1998,360(6):640-644
This certification exercise was the final stage of a stepwise interlaboratory study approach, organized within the SMT-program
of the EC, for the development of certified reference materials (CRMs) for the determination of PAHs in foodstuffs. The certification
exercise was carried out by thirteen European laboratories using a variety of extraction and clean-up procedures and different
analytical procedures. Two different coconut oil materials were certified for their mass fractions of six selected PAHs.
Received: 25 May 1997 / Revised: 5 September 1997 / Accepted: 28 September 1997 相似文献
83.
In this paper, we determine the necessary and sufficient conditions for the existence of an equitably ?‐colorable balanced incomplete block design for any positive integer . In particular, we present a method for constructing nontrivial equitably ?‐colorable BIBDs and prove that these examples are the only nontrivial examples that exist. We also observe that every equitable ?‐coloring of a BIBD yields both an equalized ?‐coloring and a proper 2‐coloring of the same BIBD. 相似文献
84.
Fernandes RX Luther K Troe J Ushakov VG 《Physical chemistry chemical physics : PCCP》2008,10(29):4313-4321
The recombination reaction H + O(2) (+M) --> HO(2) (+M) was studied by laser flash photolysis in a high pressure flow cell, over the temperature range 300-900 K, the pressure range 1.5-950 bar and in the bath gases M = He and N(2). Earlier experiments by Hahn et al. (Phys. Chem. Chem. Phys. 2004, 6, 1997) in the bath gas M = Ar were also extended. The data were analyzed in terms of unimolecular rate theory employing new calculations of relevant molecular parameters. Improved energy transfer parameters for the bath gases M = He, Ar, N(2), and H(2)O could thus be obtained and complete falloff curves were constructed. In the case of water, the high pressure rates well connect with pulse radiolysis results obtained in supercritical water by Janik et al. (J. Phys. Chem. A 2007, 111, 79). 相似文献
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87.
Acoustically induced cavitation at 20 kHz is observed by means of high speed CCD recording at a frame-rate of 2250 per second. Using digital image processing the bubbles' trajectories are reconstructed. The experimental data reveal that collision and coalescence of bubbles is a predominant phenomenon that limits their individual lifetime. Measurements of bubble sizes and velocities are in agreement with previous results. 相似文献
88.
Nanophase Fe3O4 and Fe2O3 were synthesized through a precipitation method and were utilized for the removal of either arsenic (III) or (V) from aqueous solution as a possible method for drinking water treatment. The synthesized nanoparticles were characterized using X-ray diffraction, which showed that the Fe3O4 and the Fe2O3 nanoparticles had crystal structures of magnetite and hematite, respectively. In addition, Secherrer's equation was used to determine that the grain size nanoparticles were 12 ± 1.0 nm and 17 ± 0.5 nm for the Fe2O3 and Fe3O4, respectively. Under a 1 h contact time, batch pH experiments were performed to determine the optimum pH for binding using 300 ppb of either As(III) or (V) and 10 mg of either Fe3O4 or Fe2O3. The binding was observed to be pH independent from pH 6 through pH 9 and a significant drop in the binding was observed at pH 10. Furthermore, batch isotherm studies were performed using the Fe2O3 and Fe3O4 to determine the binding capacity of As(III) and As(V) to the iron oxide nanomaterials. The binding was found to follow the Langmuir isotherm and the capacities (mg/kg) of 1250 (Fe2O3) and 8196 (Fe3O4) for As(III) as well as 20,000 (Fe2O3) and 5680 (Fe3O4) for As(III), at 1 and 24 h of contact time, respectively. The As(V) capacities were determined to be 4600 (Fe2O3), 6711(Fe3O4), 4904 (Fe2O3), and 4780 (Fe3O4) mg/kg for nanomaterials at contact times of 1 and 24 h respectively. 相似文献
89.
Nitrosation of acrylophenone oxime or of methacrylophenone oxime with n-butyl nitrite in the presence of pyridine and copper(II) sulfate gives the copper complexes of the title compounds. The free 1-hydroxypyrazole 2 -oxides are isolated by treating the copper complexes with dilute sodium hydroxide, filtration, and acidification of the basic filtrates. The title compounds are the first examples of 1-hydroxypyrazole 2 -oxides in which the C3(5) ring position is unsubstituted. 相似文献
90.
A broadband,quasi‐continuous,mid‐infrared supercontinuum generated in a chalcogenide glass waveguide
Yi Yu Xin Gai Pan Ma Duk‐Yong Choi Zhiyong Yang Rongping Wang Sukanta Debbarma Stephen J. Madden Barry Luther‐Davies 《Laser \u0026amp; Photonics Reviews》2014,8(5):792-798
The production of a broadband supercontinuum spanning from 1.8 μm to >7.5 μm is reported which was created by pumping a chalcogenide glass waveguide with ≈320 fs pulses at 4 μm. The total power was ≈20 mW and the source brightness was 100 that of current synchrotrons. This source promises to be an excellent laboratory tool for infrared microspectroscopy. 相似文献