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21.
Roman Borisov Cesar Esparza Nikolai Polovkov Artyom Topolyan Vladimir Zaikin 《Journal of separation science》2019,42(22):3470-3478
On‐spot derivatization has been suggested for the modification of primary amine containing compounds for their analysis by thin‐layer chromatography hyphenated with matrix‐assisted laser desorption ionization mass spectrometry. The proposed approach was based on post‐chromatographic treatment of separated analytes inside the chromatographic zones on the thin‐layer chromatography plates by tris(2,6‐dimethoxyphenyl)methilium reagent. The derivatives, containing permanent positive charge, reveal exceptionally intense peaks of their cationic moieties and high signal/noise ratio in mass spectra recorded directly from the plates. The method was tested on a series of aliphatic, aromatic, and amine‐containing pharmaceuticals. 相似文献
22.
Mechanochemical reaction of cluster coordination polymers 1infinity[M3Q7Br4] (M = Mo, W; Q = S, Se) with solid K2C2O4 leads to cluster core excision with the formation of anionic complexes [M3Q7(C2O4)3]2-. Extraction of the reaction mixture with water followed by crystallization gives crystalline K2[M3Q7(C2O4)3].0.5KBr.nH2O (M = Mo, Q = S, n = 3 (1); M = Mo, Q = Se, n = 4 (2); M = W, Q = S, n = 5 (3)). Cs2[Mo3S7(C2O4)3].0.5CsCl.3.5H2O (4) and (Et4N)1.5H0.5K{[Mo3S7(C2O4)3]Br}.2H2O (5) were also prepared. Close Q...Br contacts result in the formation of ionic triples {[M3Q7(C2O4)3](2)Br}5- in 1-4 and the 1:1 adduct {[Mo3S7(C2O4)3]Br}3- in 5. Treatment of 1 or 2 with PPh(3) leads to chalcogen abstraction with the formation of [Mo3(mu3-Q)(mu2-Q)3(C2O4)3(H2O)3]2-, isolated as (Ph4P)2[Mo3(mu3-S)(mu2-S)3(C2O4)3(H2O)3].11H2O (6) and (Ph4P2[Mo3(mu3-Se)(mu2-Se)3(C2O4)3(H2O)3].8.5H2O.0.5C2H5OH (7). All compounds were characterized by X-ray structure analysis. IR, Raman, electronic, and 77Se NMR spectra are also reported. Thermal decomposition of 1-3 was studied by thermogravimetry. 相似文献
23.
Artyom A. Astafiev Olga V. Repina Boris S. Tupertsev Alexey A. Nazarov Maria R. Gonchar Anna V. Vologzhanina Valentine G. Nenajdenko Andreii S. Kritchenkov Victor N. Khrustalev Victor N. Nadtochenko Alexander G. Tskhovrebov 《Molecules (Basel, Switzerland)》2021,26(6)
Arylazoimidazoles are important dyes which were intensively studied in the past. In contrast, triarylazoimidazoles (derivatives which carry aryl substituents at the imidazole core) received almost no attention in the scientific literature. Here, we report a new family of simple and easily accessible triarylazoimidazole-group 12 metal complexes, which feature highly efficient photo-luminescence emission (Φ up to 0.44). Novel compounds exhibit bright red emission in solution, which could be excited with a visible light. 相似文献
24.
We introduce a generalized criterion for the stability of Markovian queueing systems in terms of stochastic fluid limits.
We consider an example in which this criterion may be applied: a polling system with two stations and two heterogeneous servers.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Vladimir O. Abramov Anna V. Abramova Vadim M. Bayazitov Alexander V. Marnosov Sergey P. Kuleshov Artyom S. Gerasin 《Applied Acoustics》2016
A technique for treatment of perforation zones of horizontal oil wells for water cut reduction based on selective ultrasonic treatment was suggested. The technique involves online geophysical studies of horizontal wells, determination of treatment intervals based on these studies, selective ultrasonic treatment of the chosen interval and subsequent pump-out using a specially designed jet pump. The technology does not involve reduction of the flow in the well. The developed innovative technique of water cut reduction using selective ultrasonic treatment is studied within this article. Theoretical estimations and computer modeling revealed that the position of the downhole ultrasonic tool near the sidewall of the well leads to more homogeneous distribution of the induced acoustical field and wider penetration of the acoustical waves. The developed method was tested on a horizontal well in Western Siberia, which was characterized by high water cut. Based on geophysical studies only zones with low water and high oil production were treated, this lead to a decrease of the water cut by 20% and an increase of oil production by 91% after treatment of the test well. 相似文献
28.
We present a continuous, bilinear formulation for the fixed charge network flow problem. This formulation is used to derive
an exact algorithm for the fixed charge network flow problem converging in a finite number of steps. Some preliminary computational
experiments are reported to show the performance of the algorithm. 相似文献
29.
This paper proposes a system optimal dynamic traffic assignment model that does not require the network to be empty at the
beginning or at the end of the planning horizon. The model assumes that link travel times depend on traffic densities and
uses a discretized planning horizon. The resulting formulation is a nonlinear program with binary variables and a time-expanded
network structure. Under a relatively mild condition, the nonlinear program has a feasible solution. When necessary, constraints
can be added to ensure that the solution satisfies the First-In-First-Out condition. Also included are approximation schemes
based on linear integer programs that can provide solutions arbitrarily close to that of the original nonlinear problem. 相似文献
30.
We approximate the objective function of the fixed charge network flow problem (FCNF) by a piecewise linear one, and construct
a concave piecewise linear network flow problem (CPLNF). A proper choice of parameters in the CPLNF problem guarantees the
equivalence between those two problems. We propose a heuristic algorithm for solving the FCNF problem, which requires solving
a sequence of CPLNF problems. The algorithm employs the dynamic cost updating procedure (DCUP) to find a solution to the CPLNF
problems. Preliminary numerical experiments show the effectiveness of the proposed algorithm. In particular, it provides a
better solution than the dynamic slope scaling procedure in less CPU time.
Research was partially supported by NSF and Air Force grants. 相似文献