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21.
Summary A review is made of the existing theoretical expressions, describing the change of the scattered light intensity and the birefringence by application of an electrical field to a colloid solution.Furthermore, the geometrical functions for disc-shaped particles are calculated in this article for the case of electric light scattering and are. presented graphically. In addition, expressions are derived for the average value of the electrical polarizability () for the case of polydisperse solutions.
With 1 figure and 1 table 相似文献
Zusammenfassung Es wird ein überblick über die existierenden theoretischen Beziehungen gegeben, die die Änderung der Intensität des Streulichtes und der Doppelbrechung von Kolloidsuspensionen im elektrischen Feld beschreiben.Weiterhin sind die geometrischen Funktionen für scheibchenförmige Teilchen in dieser Arbeit für den Fall der elektrooptischen Lichtstreuung berechnet und grafisch dargestellt. Außerdem werden Beziehungen für den Mittelwert der elektrischen Polarisierbarkeit () für den Fall polydisperser Suspensionen abgeleitet.
With 1 figure and 1 table 相似文献
22.
Hans R. Kricheldorf Radka Hobzova Gert Schwarz Claus‐Ludolf Schultz 《Journal of polymer science. Part A, Polymer chemistry》2004,42(15):3751-3760
3,5‐Diacetoxybenzoic acid was polycondensed at temperatures in the range of 200–250 °C either in the absence of a catalyst or with addition of MgO or SnCl2. The highest molecular weight was obtained in the absence of a catalyst. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed the formation of cyclic hyperbranched polyesters. The content of polyesters with cyclic core increased with higher conversions, and thus, with higher molecular weights. Furthermore, a loss of acetyl groups was found to be a significant side reaction. The same side reactions were found when trimethylsilyl 3,5‐bisacetoxybenzoate was polycondensed at 280 or 310 °C. Model reactions concerning the deacetylation mechanism were performed and the results are discussed. Size exclusion chromatography measurements in two different solvents proved that the high‐molecular‐weight fraction is not the result of aggregation via hydrogen bonds. Yet, the nature of the solvent, the profile of the columns, and the character of the detector had a significant influence on the shape of the elution curves and on the apparent molecular weights. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3751–3760, 2004 相似文献
23.
Prof. Jana Kasparkova Dr. Hana Kostrhunova Dr. Olga Novakova Dr. Radka Křikavová Dr. Ján Vančo Prof. Zdeněk Trávníček Prof. Viktor Brabec 《Angewandte Chemie (International ed. in English)》2015,54(48):14478-14482
We report toxic effects of a photoactivatable platinum(IV) complex conjugated with suberoyl‐bis‐hydroxamic acid in tumor cells. The conjugate exerts, after photoactivation, two functions: activity as both a platinum(II) anticancer drug and histone deacetylase (HDAC) inhibitor in cancer cells. This approach relies on the use of a PtIV pro‐drug, acting by two independent mechanisms of biological action in a cooperative manner, which can be selectively photoactivated to a cytotoxic species in and around a tumor, thereby increasing selectivity towards cancer cells. These results suggest that this strategy is a valuable route to design new platinum agents with higher efficacy for photodynamic anticancer chemotherapy. 相似文献
24.
The electronegativity equalization method (EEM) was developed by Mortier et al. as a semiempirical method based on the density-functional theory. After parameterization, in which EEM parameters A(i), B(i), and adjusting factor kappa are obtained, this approach can be used for calculation of average electronegativity and charge distribution in a molecule. The aim of this work is to perform the EEM parameterization using the Merz-Kollman-Singh (MK) charge distribution scheme obtained from B3LYP/6-31G* and HF/6-31G* calculations. To achieve this goal, we selected a set of 380 organic molecules from the Cambridge Structural Database (CSD) and used the methodology, which was recently successfully applied to EEM parameterization to calculate the HF/STO-3G Mulliken charges on large sets of molecules. In the case of B3LYP/6-31G* MK charges, we have improved the EEM parameters for already parameterized elements, specifically C, H, N, O, and F. Moreover, EEM parameters for S, Br, Cl, and Zn, which have not as yet been parameterized for this level of theory and basis set, we also developed. In the case of HF/6-31G* MK charges, we have developed the EEM parameters for C, H, N, O, S, Br, Cl, F, and Zn that have not been parameterized for this level of theory and basis set so far. The obtained EEM parameters were verified by a previously developed validation procedure and used for the charge calculation on a different set of 116 organic molecules from the CSD. The calculated EEM charges are in a very good agreement with the quantum mechanically obtained ab initio charges. 相似文献
25.
Layer-by-layer deposition of sodium carboxymethylcellulose (NaCMC) and chitosan (CHI) was used to create polyelectrolyte multilayers on ellipsoidal beta-FeOOH particles at low ionic strength. Using electro-optics, we investigated the formation of films in dependence on the polyelectrolyte charge density by controlling pH of the dipping solutions. We found out a linear growth of the CMC/CHI films when they are constructed from highly charged CHI (at pH 4.0) and weakly charged NaCMC (at pH 4.0 and 5.5). The hydrodynamic thickness of the film constructed at pH 4.0/4.0 is unusually large for a linearly growing film (ca. 220 nm after deposition of 8 bilayers), but it strongly decreases (ca. 4 times) with increasing ionization of NaCMC (at pH 5.5). In both cases, the multilayer buildup proceeded through a series of adsorption-desorption steps. This was explained by a partial loss of CHI from the film surface on exposure to the solution of longer NaCMC molecules. The irregular film growth correlated quite well with the variations in the electrical polarizability of the polymer-coated particles. This correlation enabled us to conclude that the adsorption of both polymers occurs only on the film surface, with no diffusion in and out of the film bulk during deposition of each CMC/CHI bilayer. 相似文献
26.
Klejdus B Lojková L Lapcík O Koblovská R Moravcová J Kubán V 《Journal of separation science》2005,28(12):1334-1346
An efficient method of modifier addition for supercritical fluid extraction (SFE) of polar isoflavones was developed and yielded extraordinarily high recoveries. To find the optimal extraction conditions, a temperature and pressure optimization and modifier impact study was performed in naturally contaminated and spiked samples. Ultra-fast high-performance liquid chromatography/mass spectrometry (HPLC/MS) was used for the determination of isoflavones on an Atlantis dC18 high-speed reversed phase chromatographic column (20 x 2.1 mm, 3 microm particle size). A newly elaborated supercritical fluid extraction (SFE) procedure allowed more accurate (< 5%) and precise (< 4-7%) determination of isoflavones in biological materials. The HPLC/MS method significantly reduced analysis time with simultaneous improvement of sensitivity and detection limits. The on-column limits of detection LOD (S/N = 3) for isoflavone glycosides (daidzin, genistin, glycitin, ononin, and sissotrin) were 1.3-3.6 fmol and 0.2-1.0 fmol for aglycones (daidzein, glycitein, genistein, formononetin, and biochanin A), respectively. 相似文献
27.
Radka Křikavová Ján Vančo Tomáš Šilha Jaromír Marek 《Journal of Coordination Chemistry》2016,69(16):2422-2436
Platinum(II) complexes, [Pt(Lx)X2] (1–6), where X = Br or I and Lx = 2,2′-bipyridine or 1,10-phenanthroline derivatives (5,5′-dimethyl-2,2′-bipyridine (5-Mebpy), 4,4′-dimethyl-2,2′-bipyridine (4-Mebpy), and 5-amino-1,10-phenanthroline (5-NH2phen)) were prepared. The complexes were characterized by the elemental analysis, mass spectrometry, infrared, and multinuclear (1H, 13C and 195Pt) 1-D and 2-D NMR spectroscopies, and by single-crystal X-ray analysis of [Pt(4-Mebpy)I2] (4). All the platinum(II) complexes (1–6) were evaluated for in vitro cytotoxicity against human cancer cell lines A2780 and A2780R, and against non-malignant MRC5 cell line. All the complexes were nontoxic up to the 50 μM concentration, although they were found to readily bind to calf-thymus DNA (CT-DNA), as determined by spectrophotometric titration (Kb ≈ 107 M?1) and ethidium bromide displacement assay. 相似文献
28.
Maria Karayianni Radka Radeva Neli Koseva Stergios Pispas 《Journal of Polymer Science.Polymer Physics》2016,54(15):1515-1529
The electrostatic complexation between the polyelectrolyte block of the novel double hydrophilic copolymer quaternized poly(3,5‐bis(dimethylaminomethylene) hydroxystyrene)‐b‐poly(ethylene oxide) (QNPHOS‐PEO) and proteins of different molecular shape, that is globular bovine serum albumin (BSA) or rod‐like bovine fibrinogen (FBG), is investigated by means of dynamic, static, and electrophoretic light scattering, as well as analytical ultracentrifugation measurements. The solution behavior, structure, and properties of the formed complexes at pH 7 and 0.01 M ionic strength, as a function of the protein concentration in the solution (or equivalently the charge ratio of the two components), depend on the protein concentration and molecular characteristics. Moreover, the structure of the complexes is greatly influenced by the intrinsic structure of the block polyelectrolyte, which forms rather loose multichain aggregates, due to hydrophobic interactions. A direct correlation between the stability of the preformed complexes against the increase of the solution ionic strength and their structure is established. Finally, the spectroscopic structural investigation of both complexed proteins reveals no signs of protein denaturation upon complexation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1515–1529 相似文献
29.
Automatic alignment of individual peaks in large high-resolution spectral data sets 总被引:10,自引:0,他引:10
Stoyanova R Nicholls AW Nicholson JK Lindon JC Brown TR 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):622-335
Pattern recognition techniques are effective tools for reducing the information contained in large spectral data sets to a much smaller number of significant features which can then be used to make interpretations about the chemical or biochemical system under study. Often the effectiveness of such approaches is impeded by experimental and instrument induced variations in the position, phase, and line width of the spectral peaks. Although characterizing the cause and magnitude of these fluctuations could be important in its own right (pH-induced NMR chemical shift changes, for example) in general they obscure the process of pattern discovery. One major area of application is the use of large databases of (1)H NMR spectra of biofluids such as urine for investigating perturbations in metabolic profiles caused by drugs or disease, a process now termed metabonomics. Frequency shifts of individual peaks are the dominant source of such unwanted variations in this type of data. In this paper, an automatic procedure for aligning the individual peaks in the data set is described and evaluated. The proposed method will be vital for the efficient and automatic analysis of large metabonomic data sets and should also be applicable to other types of data. 相似文献
30.
Two combinations of sodium poly(4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) of different chain length and charge density are employed to construct multilayer films. The polyelectrolytes are assembled layer-by-layer on colloidal particles in the absence of salt. We have investigated the formation and electrical characteristics of the films by using electric light scattering technique. The results show that the film thickness is independent of the chain length when fully charged PAH (at pH 4.6) is combined with fully charged PSS. When the films are prepared with less charged PAH (at pH 6.7) and fully charged PSS, lower thickness is found for the film with shorter polymer chains. In all cases, the thickness increment realized on addition of the polymer with lower molar concentration is partially lost on exposure to the solution with higher concentration of the oppositely charged partner. When the film growth is regular (at equal molar concentrations of the fully charged polyelectrolytes), the ratio of PSS to PAH charge, estimated from the electro-optical effect values, exceeds 1. The electro-optical effect is also higher for the films ending with PSS when fully charged PSS is combined with less charged PAH (at pH 6.7). This reveals the key role of the charge in the last-adsorbed layer for the electro-optical behavior of the whole film. 相似文献