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831.
Nikolaos S. Papageorgiou 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(17):6487-6498
We consider a semilinear Neumann problem with an asymptotically linear reaction term. We assume that resonance occurs at infinity. Using variational methods based on the critical point theory, together with the reduction technique and Morse theory, we show that the problem has at least four nontrivial smooth solutions. 相似文献
832.
Samaras VG Thomaidis NS Stasinakis AS Lekkas TD 《Analytical and bioanalytical chemistry》2011,399(7):2549-2561
This article presents an analytical method based on solid-phase extraction (SPE) and gas chromatography coupled with mass
spectrometry for the simultaneous determination of the most frequently used acidic pharmaceutical residues, ibuprofen, diclofenac,
naproxen and ketoprofen (KFN), and phenolic endocrine disruptors, bisphenol (BPA), triclosan (TCS), nonylphenol, nonylphenol
monoethoxylate and nonylphenol diethoxylate, in wastewater and sewage sludge samples. In the first phase of the study, each
compound has been characterized individually and afterwards in mixture as a trimethylsilyl derivative in order to identify
the characteristic ions (m/z ratio) constituting the mass spectrum and to choose the ions for quantification and confirmation. Subsequently, derivatization
was evaluated by testing different variables such as the volume of the derivatization solvent bis(trimethylsilyl)trifluoroacetamide
and the effect of each catalyst, pyridine and 1% trimethyl chlorosilane, in the derivatized solution. For the analysis of
wastewater samples, two commercial SPE cartridges, C18 and Oasis HLB, were compared for their extraction efficiency of the
target compounds. The key parameter of extraction procedure included the effect of pH (2.5, 5.3 and 7) of the loading solution.
For solid samples, parameters such as the extracted biomass, the volume of the extraction organic solvent and the effect of
matrix interferences in chromatographic analysis were evaluated. By using C18 cartridges as purification procedure and ultrasound
sonication, satisfactory mean relative recoveries with BPA-d16 and meclofenamic acid as surrogates were obtained ranging from
91% to 117% for wastewater and 84% to 107% for sewage sludge samples. Nine-point calibration of the standard mixture was performed
by linear regression analysis with a correlation coefficient >0.99 for all the tested compounds. Limits of detection for the
developed methods were established between 0.3 (KFN) and 14.8 (BPA) ng L−1, and 15.0 (TCS) and 32.9 (BPA) ng g−1 for wastewater and sewage sludge, respectively. Application to real samples of the wastewater treatment plant in Athens,
the capital of Greece, demonstrated the presence of all tested compounds in most of the samples. 相似文献
833.
Casitas A Ioannidis N Mitrikas G Costas M Ribas X 《Dalton transactions (Cambridge, England : 2003)》2011,40(35):8796-8799
Well-defined aryl-Cu(III) species undergo rapid reductive elimination upon reaction with phenolates (PhO(-)), to form aryl-OPh cross-coupling products. Kinetic studies show that the reaction follows a different mechanistic pathway compared to the reaction with phenols. The pH active cyclized pincer-like ligand undergoes an initial amine deprotonation that triggers a faster reactivity at room temperature. A mechanistic proposal for the enhanced reactivity and the role of EPR-detected Cu(II) species will be discussed in detail. 相似文献
834.
Tsoureas N Nunn J Bevis T Haddow MF Hamilton A Owen GR 《Dalton transactions (Cambridge, England : 2003)》2011,40(4):951-958
The complexes [Ru(Tai)Cl{=C(H)Ph}(PCy(3))] (4) and [Ru((Ph)Bai)Cl{=C(H)Ph}(PCy(3))] (5) [where Tai = HB(7-azaindolyl)(3) and (Ph)Bai = Ph(H)B(7-azaindolyl)(2)] have been prepared and structurally characterised. The borohydride unit is located in the coordination site trans to the chloride ligand in both complexes. The degree of interaction between the borohydride group and the metal centre was found to be significantly large in both cases. Thermolysis reactions involving complex 4 led to a dehydrogenation reaction forming [Ru(Tai)Cl{PCy(2)(η(2)-C(6)H(9))}] (6) where the benzylidene group acts as a hydrogen acceptor. 相似文献
835.
We give a sufficient condition for the sum of two closed operators to be closed. In particular, we study the sum of two sectorial operators with the sum of their sectoriality angles greater than π . We show that if one of the operators admits bounded H∞-calculus and the resolvent of the other operator satisfies a boundedness condition stronger than the standard sectoriality, but weaker than the bounded imaginary powers property in the case of UMD spaces, then the sum is closed. We apply the result to the abstract parabolic problem and give a sufficient condition for Lp-maximal regularity. 相似文献
836.
Polyhydroxylated pyrrolizidines bearing a methyl group at C-5 have been synthesized by 1,3-dipolar cycloaddition of five membered cyclic nitrones with methyl vinyl ketone followed by a N–O reductive cleavage and in situ intramolecular reductive amination. The stereochemistry of the obtained compounds is examined in relation to the reactions mechanism. 相似文献
837.
Dr. Georgios S. E. Antipas Eleftherios Statharas Philippos Tserotas Dr. Nikolaos Papadopoulos Prof. Dr. E. Hristoforou 《Chemphyschem》2013,14(9):1934-1942
Magnetic iron oxide nanoparticles synthesized by coprecipitation and thermal decomposition yield largely monodisperse size distributions. The diameters of the coprecipitated particles measured by X‐ray diffraction and transmission electron microscopy are between approximately 9 and 15 nm, whereas the diameters of thermally decomposed particles are in the range of 8 to 10 nm. Coprecipitated particles are indexed as magnetite‐rich and thermally decomposed particles as maghemite‐rich; however, both methods produce a mixture of magnetite and maghemite. Fourier transform IR spectra reveal that the nanoparticles are coated with at least two layers of oleic acid (OA) surfactant. The inner layer is postulated to be chemically adsorbed on the nanoparticle surface whereas the rest of the OA is physically adsorbed, as indicated by carboxyl O? H stretching modes above 3400 cm?1. Differential thermal analysis (DTA) results indicate a double‐stepped weight loss process, the lower‐temperature step of which is assigned to condensation due to physically adsorbed or low‐energy bonded OA moieties. Density functional calculations of Fe–O clusters, the inverse spinel cell, and isolated OA, as well as OA in bidentate linkage with ferrous and ferric atoms, suggest that the higher‐temperature DTA stage could be further broken down into two regions: one in which condensation is due ferrous/ferrous– and/or ferrous/ferric–OA and the other due to condensation from ferrous/ferric– and ferric/ferric–OA complexes. The latter appear to form bonds with the OA carbonyl group of energy up to fivefold that of the bond formed by the ferrous/ferrous pairs. Molecular orbital populations indicate that such increased stability of the ferric/ferric pair is due to the contribution of the low‐lying Fe3+ t2g states into four bonding orbitals between ?0.623 and ?0.410 a.u. 相似文献
838.
Nikolaos Papaioannou Vasilios MarathiasZhao-Kui Wan Neelu KailaZahid Ali Eddine Saiah 《Tetrahedron letters》2011,52(48):6317-6320
A convenient synthesis of 2-(2-methyl-1-(4-oxo-3,4-dihydrophthalazin-1-yl)-1H-indol-3-yl)acetic acid derivatives is described using a microwave-promoted multi-step SNAr reaction. The desired products were found to exhibit atropisomerism. 相似文献
839.
Nikolaos Pahimanolis Ulla Hippi Leena-Sisko Johansson Tapio Saarinen Nikolay Houbenov Janne Ruokolainen Jukka Seppälä 《Cellulose (London, England)》2011,18(5):1201-1212
In the present work, amino functionalized nanofibrillated cellulose (NFC) was prepared using click-chemistry in aqueous reaction
conditions. First, reactive azide groups were introduced on the surface of NFC by the etherification of 1-azido-2,3-epoxypropane
in alkaline water/isopropanol-mixture at ambient temperature. Then the azide groups were reacted with propargyl amine utilizing
copper catalyzed azide-alkyne cycloaddition (CuAAC), leading to pH-responsive 1,2,3-triazole-4-methanamine decorated NFC.
The reaction products were characterized using Fourier transform infrared spectroscopy, elemental analysis and X-ray photoelectron
spectroscopy. The presence of the attached azide groups was also confirmed by reacting them with 5-(dimethylamino)-N-(2-propyl)-1-naphthalenesulfonamide
by CuAAC, yielding highly fluorescent NFC. In addition, atom force microscopy and rheology studies confirmed that the original
NFC nanostructure was maintained during the synthesis. 相似文献
840.
Lingling Zhang Yunhong Jiang Yulong Ding Nikolaos Daskalakis Lars Jeuken Malcolm Povey Alex J. O’Neill David W. York 《Journal of nanoparticle research》2010,12(5):1625-1636
Aqueous suspensions containing 4.45 × 10−5 − 1.25 × 10−3 M ZnO particles exhibit a strong antibacterial activity against E. coli under the dark conditions. The dominant mechanisms of such antibacterial behaviour are found to be either or both of chemical
interactions between hydrogen peroxide and membrane proteins, and chemical interactions between other unknown chemical species
generated due to the presence of ZnO particles with the lipid bilayer. The effect of direct physical interactions between
nanoparticles and biological cells are found to play a relatively small role under the conditions of this study. 相似文献