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11.
Christiana Bondioli 《Mathematische Nachrichten》1994,166(1):273-285
In the previous paper [2], we proposed a definition of a class of function spaces of Nikolskii type on a special class of riemannian manifolds, namely the manifolds M admitting a transitive compact connected Lie group of isometries. In this paper we continue the subject and we complete the proof that the spaces we have introduced coincide with the classical ones, defined through (finitely many) local charts of M. Moreover, our equivalent definition of these spaces allows us to prove here a regularity result for the solution of a Stefan-like problem on M, in which the initial datum is assumed to be of Nikolskii type. 相似文献
12.
Pappa-Louisi A Nikitas P Zisi C Papachristos K 《Journal of separation science》2008,31(16-17):2953-2961
The combined effect of temperature, T, and organic modifier concentration, phi, on the retention under gradient conditions in RPLC is studied by considering, both theoretically and experimentally gradients, of phi at constant T and gradients of T at constant phi. Two approaches are examined: in the first approach the prediction of the elution time of a sample solute is based on the isocratic/isothermal properties of this solute. The second approach is based on a direct fitting procedure of a proper retention model to 2-D isocratic/T-gradient or isothermal/phi-gradient retention data. These approaches were tested using alkylbenzes in eluting systems modified by ACN. We found that both approaches can give excellent predictions under certain prerequisites. However, the first approach exhibits the notable advantage that it can be used effectively to predict retention times under any kind of phi-gradients at constant T or T-gradients at constant phi. The second approach has the advantage that it is relatively simple but its applicability is very restricted since its predictions are satisfactory only if the gradients are of the same kind with those used in the fitting procedure and the conditions lie within those used for fitting. 相似文献
13.
The reactions of Al(III), Ga(III) and In(III) nitrates with 2-quinaldic acid (qaH) afforded [Al2(OH)2(qa)4]·2H2O (1), [Ga(qa)2(H2O)2]NO3 (2) and [In(qa)2(NO3)(H2O)] (3), respectively, in high yields. The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray crystallography. The structure of 1 features a di-hydroxo bridged [Al2(μ-OH)2]4+ dimer in which each Al(III) is further ligated by two bidentate chelate qa? ligands. Complexes 2 and 3 are mononuclear with the M(III) ions in octahedral environments surrounded by two bidentate chelate qa? and two H2O in 2 or one H2O and a terminal NO3? in 3. Characteristic IR as well as thermal analysis and solid-state fluorescence are discussed. 相似文献
14.
Zdenk Klika Ivan Kolomazník Dalibor Matýsek Christiana Klikov 《Crystal Research and Technology》2016,51(4):249-264
The new method for the Chemical Quantitative Mineral Analysis (CQMA) is presented and critically evaluated. The percentages of minerals are calculated of the elemental bulk chemical analysis using identified minerals and their crystallochemical formulas. For this calculation an optimization procedure is used. CQMA enables also the feedback calculation of the bulk chemical analysis from CQMA calculated mineral contents. Subsequent comparison of the feedback calculated bulk chemical analysis and actual bulk chemical analysis of the same sample is used for critical evaluation of the input data. If necessary the input data are completed and/or reanalyzed and used for repeated calculation to achieve better match between the feedback calculated and actual chemical analyses, which consequently leads to more accurate mineral analysis. Moreover the feedback bulk chemical analysis can be also separately calculated from any mineral analyses determined e.g. by XRD, FTIR and/or optical method. Six German rock reference samples representing a very wide range of minerals and chemical composition of materials were selected and their mineral analyses carried out by CQMA and Rietveld X‐ray diffraction methods. The results were compared with reference mineral analyses and critically evaluated. 相似文献
15.
Christiana Kitsiou Jordan J. Hindes Phillip I'Anson Paula Jackson Thomas C. Wilson Eleanor K. Daly Hannah R. Felstead Peter Hearnshaw Dr. William P. Unsworth 《Angewandte Chemie (International ed. in English)》2015,54(52):15794-15798
Structurally diverse macrocycles and medium‐sized rings (9–24 membered scaffolds, 22 examples) can be generated through a telescoped acylation/ring‐expansion sequence, leading to the insertion of linear fragments into cyclic β‐ketoesters without performing a discrete macrocyclization step. The key β‐ketoester motif is regenerated in the ring‐expanded product, meaning that the same sequence of steps can then be repeated (in theory indefinitely) with other linear fragments, allowing macrocycles with precise substitution patterns to be “grown” from smaller rings using the successive ring‐expansion (SuRE) method. 相似文献
16.
Gregoria Gregoriou Christiana M. Neophytou Alexandru Vasincu Yiota Gregoriou Haria Hadjipakkou Eftychia Pinakoulaki Marios C. Christodoulou Georgia D. Ioannou Ioannis J. Stavrou Atalanti Christou Constantina P. Kapnissi-Christodoulou Siegfried Aigner Hermann Stuppner Antonis Kakas Andreas I. Constantinou 《Molecules (Basel, Switzerland)》2021,26(16)
Extracts derived from the Ceratonia siliqua L. (carob) tree have been widely studied for their ability to prevent many diseases mainly due to the presence of polyphenolic compounds. In this study, we explored, for the first time, the anti-cancer properties of Cypriot carobs. We produced extracts from ripe and unripe whole carobs, pulp and seeds using solvents with different polarities. We measured the ability of the extracts to inhibit proliferation and induce apoptosis in cancer and normal immortalized breast cells, using the MTT assay, cell cycle analysis and Western Blotting. The extracts’ total polyphenol content and anti-oxidant action was evaluated using the Folin–Ciocalteu method and the DPPH assay. Finally, we used LC-MS analysis to identify and quantify polyphenols in the most effective extracts. Our results demonstrate that the anti-proliferative capacity of carob extracts varied with the stage of carob maturity and the extraction solvent. The Diethyl-ether and Ethyl acetate extracts derived from the ripe whole fruit had high Myricetin content and also displayed specific activity against cancer cells. Their mechanism of action involved caspase-dependent and independent apoptosis. Our results indicate that extracts from Cypriot carobs may have potential uses in the development of nutritional supplements and pharmaceuticals. 相似文献
17.
Liang HC Zhang CX Henson MJ Sommer RD Hatwell KR Kaderli S Zuberbühler AD Rheingold AL Solomon EI Karlin KD 《Journal of the American Chemical Society》2002,124(16):4170-4171
Copper(I)-dioxygen interactions are of great interest due to their role in biological O2-processing as well as their importance in industrial oxidation processes. We describe here the study of systems which lead to new insights concerning the factors which govern Cu(II)-mu-eta2:eta2 (side-on) peroxo versus Cu(III)-bis-mu-oxo species formation. Drastic differences in O2-reactivity of Cu(I) complexes which differ only by a single -CH3 versus -H substituent on the central amine of the tridentate ligands employed are observed. [Cu(MeAN)]B(C6F5)4 (1) (MeAN = N,N,N',N',N'-pentamethyl-dipropylenetriamine) reacts with O2 at -80 degrees C to form almost exclusively the side-on peroxo complex [{CuII(MeAN)}2(O2)]2+ (3) in CH2Cl2, tetrahydrofuran, acetone, and diethyl ether solvents, as characterized by UV-vis and resonance Raman spectroscopies. In sharp contrast, [Cu(AN)]B(C6F5)4 (2) (AN = 3, 3'-iminobis(N,N-dimethyl-propylamine) can support either Cu2O2 structures in a strongly solvent-dependent manner. Extreme behavior is observed in CH2Cl2 solvent, where 1 reacts with O2 giving 3, while 2 forms exclusively the bis-mu-oxo species [{CuIII(AN)}2(O)2]2+ (4Oxo). Stopped-flow kinetics measurements also reveal significant variations in the oxygenation reactions of 1 versus 2, including the observations that 4Oxo forms much faster than does 3; the former decomposes quickly, while the latter is quite stable at 193 K. The solvent-dependence of the bis-mu-oxo versus side-on peroxo preference observed for 2 is opposite to that reported for other known copper(I) complexes; the factors which may be responsible for the unusual behavior of 1/O2 versus 2/O2 (possibly N-H hydrogen bonding in the AN chemistry) are suggested. The factors which affect bis-mu-oxo versus side-on peroxo formation continue to be of interest. 相似文献
18.
Henson MJ Vance MA Zhang CX Liang HC Karlin KD Solomon EI 《Journal of the American Chemical Society》2003,125(17):5186-5192
The effect of endogenous donor strength on Cu(2)O(2) bonds was studied by electronically perturbing [[(R-TMPA)Cu(II)]](2)(O(2))](2+) and [[(R-MePY2)Cu](2)(O(2))](2+) (R = H, MeO, Me(2)N), which form the end-on mu-1,2 bound peroxide and an equilibrium mixture of side-on peroxo-dicopper(II) and bis-mu-oxo-dicopper(III) isomers, respectively. For [[(R-TMPA)Cu(II)](2)(O(2))](2+), nu(O-O) shifts from 827 to 822 to 812 cm(-1) and nu(Cu)(-)(O(sym)) shifts from 561 to 557 to 551 cm(-1), respectively, as R- varies from H to MeO to Me(2)N. Thus, increasing the N-donor strength to the copper decreases peroxide pi(sigma) donation to the copper, weakening the Cu-O and O-O bonds. A decrease in nu(Cu-O) of the bis-mu-oxo-dicopper(III) complex was also observed with increasing N-donor strength for the R-MePY2 ligand system. However, no change was observed for nu(O-O) of the side-on peroxo. This is attributed to a reduced charge donation from the peroxide pi(sigma) orbital with increased N-donor strength, which increases the negative charge on the peroxide and adversely affects the back-bonding from the Cu to the peroxide sigma orbital. However, an increase in the bis-mu-oxo-dicopper(III) isomer relative to side-on peroxo-dicopper(II) species is observed for R-MePY2 with R = H < MeO < Me(2)N. This effect is attributed to the thermodynamic stabilization of the bis-mu-oxo-dicopper(III) isomer relative to the side-on peroxo-dicopper(II) isomer by strong donor ligands. Thus, the side-on peroxo-dicopper(II)/bis-mu-oxo-dicopper(III) equilibrium can be controlled by electronic as well as steric effects. 相似文献
19.
Liang HC Henson MJ Hatcher LQ Vance MA Zhang CX Lahti D Kaderli S Sommer RD Rheingold AL Zuberbühler AD Solomon EI Karlin KD 《Inorganic chemistry》2004,43(14):4115-4117
A new tridentate ligand, PYAN, is employed to investigate solvent influences for dioxygen reactivity with [Cu(PYAN)(MeCN)]B(C(6)F(5))(4) (1). Stopped-flow kinetic studies confirm that the adducts [[u(II)(PYAN)]2)(O(2))][B(C(6)F(5))(4)](2) (2(Peroxo)) and [[u(III)(PYAN)]2)(O)(2)][B(C(6)F(5))(4)](2) (2(Oxo)) are in rapid equilibrium. Thermodynamic parameters for the equilibrium between 2(Peroxo) and 2(Oxo) re as follows: THF, deltaH degrees approximately -15.7 kJ/mol, deltaS degrees approximately -83 J/K.mol; acetone, deltaH degrees approximately -15.8 kJ/mol, deltaS degrees approximately -76 J/K.mol. UV-visible absorption and resonance Raman spectroscopic signatures demonstrate that the equilibrium is highly solvent dependent; the mixture is mostly 2(Peroxo) in CH(2)Cl(2), but there are significantly increasing quantities of 2(Oxo) along the series methylene chloride --> diethyl ether --> acetone --> tetrahydrofuran (THF). Copper(II)-N(eq) stretches (239, 243, 244, and 246 cm(-)(1) in CH(2)Cl(2), Et(2)O, acetone, and THF, respectively) are identified for 2(Peroxo), but they are not seen in 2(Oxo), revealing for the first time direct evidence for solvent coordination in the more open 2(Peroxo) structure. 相似文献
20.
Asimina Bourboula Olga G. Mountanea George Krasakis Dr. Christiana Mantzourani Prof. Dr. Maroula G. Kokotou Prof. Dr. Christoforos G. Kokotos Prof. Dr. George Kokotos 《European journal of organic chemistry》2023,26(24):e202300008
In recent years, the development of light-mediated methods for synthetic applications has attracted high interest, because such methods constitute alternative approaches for the production of valuable chemical products. We study herein a photochemical protocol for the synthesis of Weinreb amides and morpholine amides from carboxylic acids. Various carboxylic acids were directly coupled to N,O-dimethylhydroxylamine, upon irradiation with either LED 370 nm or sunlight in the presence of 4-dimethylaminopyridine and bromotrichloromethane, providing Weinreb amides in moderate to high yields. Similarly, morpholine amides were obtained in satisfactory to high yields under sunlight or LED 370 nm irradiation. Thus, the versatile building blocks Weinreb amides and morpholine amides may be efficiently synthesized directly from carboxylic acids by light-mediated approaches, without the need of coupling reagents or pre-activation of carboxylic acids. 相似文献