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1.
Piotr Bogusaw Mucha Witold Sadowski 《Mathematical Methods in the Applied Sciences》2005,28(15):1867-1880
The paper analyses long time behaviour of solutions of the Navier–Stokes equations in a two‐dimensional pipe‐like domain. The system is studied with perfect slip boundary conditions with arbitrary inflow conditions at infinity. The main results show the existence of global in time solutions and of an attractor for the dynamical system generated by the model. The paper also establishes an upper bound for the Hausdorff dimension of the attractor. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
2.
Witold Kuran Jerzy Borycki 《Journal of polymer science. Part A, Polymer chemistry》1981,19(5):1251-1259
Polymerization of acrylonitrile in the presence of systems that consisted of triphenylphosphine (PPh3) and a Lewis acid RmMXn (ZnCl2, Me3Al, Et3Al, Et2AlCl, EtAlCl2, AlCl3) was studied. The systems that contained Me3Al and Et3Al (i.e., Lewis acid of moderate acidity) were the most efficient catalysts. Conductometric measurements carried out in the polymerization systems showed the presence of ions. The presence of phosphonium cation in the polyacrylonitrile chain formed by the PPh3–RmMXn catalytic systems was determined by IR, 1H-NMR, and 31P-NMR spectroscopy. The average molecular weight measurements and kinetic chain lengths of polyacrylonitrile formed within the reaction time in the presence of PPh3–Et3Al showed that transfer reactions occur. According to the results obtained, the polymerization reaction of acrylonitrile by PPh3–RmMXn involved a zwitterion formed by the attack of PPh3 on acrylonitrile complexed by Lewis acid [Ph3P⊕? CH2? C?H? C?N → MRmXn] and the anion [CH2?C?? C?N] formed by the proton abstraction from the monomer. 相似文献
3.
Substituted benzoic acid anions undergo decarboxylation in the medium-pressure region of an electrospray ion source yielding in most cases the correspondingly substituted phenide anions in high yield. The location of the anionic center is specified by the position of the carboxylic group. The only exceptions are compounds with substituents containing acidic hydrogen atoms, like OH and NH(2) groups. For such compounds, either an intra- or an intermolecular (mediated by the molecules of methanol or water) proton transfer from the more acidic position to the benzene ring is observed. The generated anions can be selected using the first quadrupole for studying their ion-molecule chemistry in the second quadrupole of a triple quadrupole mass spectrometer. Their reactions with CO(2), O(2), CH(3)COCH(3) and CCl(4) may serve as typical examples. The general applicability of this method for the generation of phenide anions has been confirmed on three different mass spectrometers. Experiments performed using carboxylic acids other then benzoic acid and its derivatives show that this method is not limited to phenide anions and can be used for the generation of a much wider range of carbanions in the gas phase. 相似文献
4.
Unimolecular fragmentation patterns of the molecular ions of selected lactams and sultams bearing alkoxymethyl group at the nitrogen atom were studied. The main common fragmentation reaction observed for all compounds studied in this work is the elimination of an aldehyde molecule. This reaction is considered to proceed via two different mechanisms. For lactams, hydrogen rearrangement within an alkoxymethyl group is observed, which leads to the appropriate N-methyl derivatives. For sultams, transfer of the methyl group to the nitrogen and oxygen atoms, proceeding through an ion-neutral complex, dominates. Another important fragmentation channel characteristic exclusively for lactams is the loss of an alkyl radical. This process takes place within the N-alkoxymethyl moiety, yielding the appropriate protonated ion of N-formyllactams. This process is accompanied by relatively high kinetic energy release. 相似文献
5.
I. Nowik Y. Levi I. Felner E. R. Bauminger C. Mermelstein 《Journal of Radioanalytical and Nuclear Chemistry》1995,190(2):413-418
Mössbauer studies of dilute57Fe and151Eu in RMn2Si2-xGex (R=La, Sm, Eu and Gd) at temperatures 4.2 K to 480 K have been performed. The diamagnetic iron and europium reveal the magnetic order of the Mn and rare earth sublattices through transferred hyperfine interactions. The57Fe studies show that in LaMn2Si2, LaMn2Ge2, and SmMn2Ge2 the Mn is magnetically ordered above the known Curie temperatures, and the compounds are antiferromagnets up to TN=470 K, 415 K and 385 K respectively. Studies of151Eu in R1-xEuxMn2Si2, (R=La, Gd) display Eu subspectra corresponding to Eu2+, Eu3+ and intermediate valant Eu. All display large magnetic hyperfine fields. 相似文献
6.
Micha Kosno Tomasz Laskowski Joanna E. Frackowiak Agnieszka Potga Agnieszka Kurdyn Witold Andraoj Julia Borzyszkowska-Bukowska Katarzyna Szwarc-Karabyka Zofia Mazerska 《Molecules (Basel, Switzerland)》2022,27(13)
Unsymmetrical bisacridines (UAs) represent a novel class of anticancer agents previously synthesized by our group. Our recent studies have demonstrated their high antitumor potential against multiple cancer cell lines and human tumor xenografts in nude mice. At the cellular level, these compounds affected 3D cancer spheroid growth and their cellular uptake was selectively modulated by quantum dots. UAs were shown to undergo metabolic transformations in vitro and in tumor cells. However, the physicochemical properties of UAs, which could possibly affect their interactions with molecular targets, remain unknown. Therefore, we selected four highly active UAs for the assessment of physicochemical parameters under various pH conditions. We determined the compounds’ pKa dissociation constants as well as their potential to self-associate. Both parameters were determined by detailed and complex chemometric analysis of UV-Vis spectra supported by nuclear magnetic resonance (NMR) spectroscopy. The obtained results indicate that general molecular properties of UAs in aqueous media, including their protonation state, self-association ratio, and solubility, are strongly pH-dependent, particularly in the physiological pH range of 6 to 8. In conclusion, we describe the detailed physicochemical characteristics of UAs, which might contribute to their selectivity towards tumour cells as opposed to their effect on normal cells. 相似文献
7.
Dorota Nowak-Wo?ny Tomasz Janiczek Witold Mielcarek Juliusz B. Gajewski 《Journal of Electrostatics》2009,67(1):18-21
Modified bismuth oxide (Bi2O3) is of great importance to fuel cells and oxide varistors. The electrical parameters of Bi2O3 vary with its modifying components as well as with its aging temperature. This paper presents an analysis of impedance test results carried out to find an equivalent electric model and the relationship between the model's elements to various additives used to modify Bi2O3 and to changes in aging temperature. The proposed model was tested via computer simulation and the model parameters correlated to individual modifiers. 相似文献
8.
Kamil Wojciechowski Anna Brzozowska Sebastien Cap Witold Rzodkiewicz Thomas Gutberlet 《Applied Surface Science》2009,256(1):274-279
Adsorption of two alkylated N,N′-diaza-18-crown-6 ethers (decyl- and hexadecyl-derivatives, ACE-10 and ACE-16, respectively) on solid surfaces was studied by using contact angle and neutron reflectivity measurements. The solid substrates used were (a) Si covered with a native oxide layer (Si/SiO2) and (b) Si with sputtered Pt layer (Si/Pt). The sensitivity of neutron reflectivity was drastically improved by applying the intermediate Pt layer of 150 Å, which gave rise to several Kiessig fringes in the experimentally accessible q-range. The position of the fringes is very sensitive to slight changes of the interfacial composition induced by adsorption of a thin monolayer, otherwise very difficult to detect. Unfortunately, in the studied case this sensitivity is immediately lost due to undesired adsorption of a protonated material on the Pt surface exposed to the lab air. A decrease of surface energy (increase of contact angle) of both Si/SiO2 and Si/Pt upon exposure to toluene solutions of ACEs suggests that the latter are attached to the surface via the hydrophilic azacrown ether head with alkyl chains standing upright towards the liquid phase. 相似文献
9.
Stochastic and deterministic simulations of dispersion in cylindrical channels on the Poiseuille flow have been presented. The random walk (stochastic) and the uniform dispersion (deterministic) models have been used for computations of flow injection analysis responses. These methods coupled with the genetic algorithm and the Levenberg–Marquardt optimization methods, respectively, have been applied for determination of diffusion coefficients. The diffusion coefficients of fluorescein sodium, potassium hexacyanoferrate and potassium dichromate have been determined by means of the presented methods and FIA responses that are available in literature. The best-fit results agree with each other and with experimental data thus validating both presented approaches. 相似文献
10.
Prof. Dr. Sjoerd Harder Dominik Naglav Dr. Christian Ruspic Prof. Dr. Claudia Wickleder Dr. Matthias Adlung Dr. Wilfried Hermes Dr. Matthias Eul Prof. Dr. Rainer Pöttgen Dr. Daniel B. Rego Prof. Dr. Frederic Poineau Prof. Dr. Kenneth R. Czerwinski Prof. Dr. Rolfe H. Herber Prof. Dr. Israel Nowik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(37):12173-12173