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排序方式: 共有75条查询结果,搜索用时 15 毫秒
51.
Tobias Kaper Dr. Malte Fischer Michael Warsitz René Zimmering Prof. Dr. Ruediger Beckhaus Prof. Dr. Sven Doye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14300-14304
Intermolecular hydroaminoalkylation reactions of propadiene with selected secondary amines take place in the presence of a 2,6-bis(phenylamino)pyridinato titanium catalyst. The corresponding products, synthetically useful allylamines, are formed in convincing yields and with high selectivities. In addition, propadiene easily inserts into the titanium-carbon bond of a titanaaziridine. 相似文献
52.
D.Ø. Eriksen R. Sidhu E. Strålberg K. I. Iden K. Hylland A. Ruus O. Røyset M. H. G. Berntssen H. Rye 《Czechoslovak Journal of Physics》2006,56(1):D43-D48
Substantial amounts of produced water, containing elevated levels of radionuclides (mainly 226Ra and 228Ra) are discharged to the sea as a result of oil and gas production on the Norwegian Continental Shelf. So far no study has
assessed the potential radiological effects on marine biota in connection with radionuclide discharges to the North Sea. The
main objective of the project is to establish radiological safe discharge limits for radium, lead and polonium associated
with other components in produced water from oil and gas installations on the Norwegian continental shelf.
This study reports results indicating that the presence of added chemicals such as scale inhibitors in produced water has
a marked influence on the formation of radium and barium sulphates when produced water is mixed with sea water. Thus, the
mobility and bioavailability of radium (and barium) will be larger than anticipated. Also, the bioavailability of food-borne
radium is shown to increase due to presence of such chemicals. 相似文献
53.
In terms of regular n-gons a left distributive quasigroup operation is defined on the complex plane. This operation can be expressed by means of a semidirect product G of the translation group (which is sharply transitive on the points of the plane and hence may be identified with the plane) by a finite cyclic group of rotations of order n. That observation makes possible a wide generalization of this geometric quasigroup construction. The connection in general between algebraic properties of the quasigroup and various properties of the group G is discussed, in particular it is studied what the consequences for the quasigroup Q are if G is interpreted as a topological group or an algebraic group. 相似文献
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A new method is described based on mixed-mode high-performance liquid chromatography with electrospray mass spectrometry detection for comprehensive quantitative analysis of nonylphenol (NP) and nonylphenol ethoxylates (NPEOs) in wastewater and sediment. Efficient separation, reduced band broadening, and high sensitivity were achieved by employing a methanol-water gradient on a mixed-solvent gel filtration column designed for MS interfacing. Quantitative accuracy and precision of the method were improved by the use of custom-synthesized [13C6]NPEO analogs as isotope-dilution surrogate standards. Method detection limits for NP and individual NPEOs ranged from I to 55 pg injected on column. 相似文献
57.
H.-D. Martin R. Iden D. Scheutzow L. M. Jackman 《Magnetic resonance in chemistry : MRC》1980,14(3):192-197
The proton spectra of exo- and endo-3-thiatricyclo[4.2.1.02,5]non-7-ene 3,3-dioxide have been analysed and completely assigned. Considerations of coupling constants indicate that the thietane ring is nonplanar and that the norbornene residue is significantly distorted from the geometry of norbornene itself. The sulfone group induces significant changes in the shielding of the proximate olefinic proton in the endo isomer and the bridge protons in the exo isomer. These shifts appear to be the result of the electrostatic effects and effects associated with the diagmagnetic anisotropy of the sulfone group. 相似文献
58.
Kamphausen S Höltge N Wirsching F Morys-Wortmann C Riester D Goetz R Thürk M Schwienhorst A 《Journal of computer-aided molecular design》2002,16(8-9):551-567
The design of molecules with desired properties is still a challenge because of the largely unpredictable end results. Computational methods can be used to assist and speed up this process. In particular, genetic algorithms have proved to be powerful tools with a wide range of applications, e.g. in the field of drug development. Here, we propose a new genetic algorithm that has been tailored to meet the demands of de novo drug design, i.e. efficient optimization based on small training sets that are analyzed in only a small number of design cycles. The efficiency of the design algorithm was demonstrated in the context of several different applications. First, RNA molecules were optimized with respect to folding energy. Second, a spinglass was optimized as a model system for the optimization of multiletter alphabet biopolymers such as peptides. Finally, the feasibility of the computer-assisted molecular design approach was demonstrated for the de novo construction of peptidic thrombin inhibitors using an iterative process of 4 design cycles of computer-guided optimization. Synthesis and experimental fitness determination of only 600 different compounds from a virtual library of more than 1017 molecules was necessary to achieve this goal.These authors contributed equally to the results presentedThese authors contributed equally to the results presentedThese authors contributed equally to the results presentedThese authors contributed equally to the results presented 相似文献
59.
ZHANG Heng-Li 张怀金 LI Dai-Jun 王继扬 SHI Peng Haas Ruediger李红霞 蒋民华DU Keming 《中国物理快报》2005,22(9):2276-2277
We report a diode stack end-pumped Nd:GdV04 slab laser with a near-diffraction-limited beam. The output power of 45.8 W at 1064nm is obtained under the pumping power of 147 W, with the optical-optical conversion efficiency of 31.2%, and the slope efficiency is 39.6%. 相似文献
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