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The refined theory of the electroviscous lift forces is presented for the case when the separation distance between the particle and the wall is larger than the double-layer thickness. The theory is based on the lubrication approximation for motion of a long cylinder near a solid wall in creeping flow. The approximate analytical formula for the lift force valid for Pe=1 is derived and compared with the results of numerical calculations performed for an arbitrary Peclet number. The resulting electrokinetic lift force exceeds by several orders of magnitude one predicted by the previously developed theories of the lift force. The results for the electroviscous drag force indicate that when the double layer is thin compared with the particle size, the electroviscous drag is only a small correction (at most 10%) to the hydrodynamic drag force acting on a neutral particle moving near the wall. Copyright 2000 Academic Press. 相似文献
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Stefka Kaloyanova Valeriya M. Trusova Galyna P. Gorbenko Todor Deligeorgiev 《Journal of photochemistry and photobiology. A, Chemistry》2011,217(1):147-156
Sixteen new asymmetric monomethine cyanine dyes have been synthesized and their spectral characteristics and interaction with double stranded DNA have been investigated. The dyes absorb in the region 453–519 nm and have molar absorptivities in the range 37.900–93.100 l M?1 cm?1. The dyes do not have intrinsic fluorescence, but in the presence of dsDNA they exhibited a significant enhancement in fluorescence. The most pronounced increase was found for D9, D10, D12 and D16 allowing the recommendation of these dyes as the most sensitive DNA markers. Thermodynamic analysis of cyanine–DNA complexation was carried out using the McGhee & von Hippel non-cooperative excluded site model, and binding parameters have been derived. A hypothesis describing the DNA–dye binding mode has been proposed. 相似文献
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Fürstenberg A Deligeorgiev TG Gadjev NI Vasilev AA Vauthey E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(30):8600-8609
The fluorescence enhancement mechanisms of a series of DNA stains of the oxazole yellow (YO) family have been investigated in detail using steady-state and ultrafast time-resolved fluorescence spectroscopy. The strong increase in the fluorescence quantum yield of these dyes upon DNA binding is shown to originate from the inhibition of two distinct processes: 1) isomerisation through large-amplitude motion that non-radiatively deactivates the excited state within a few picoseconds and 2) formation of weakly emitting H-dimers. As the H-dimers are not totally non-fluorescent, their formation is less efficient than isomerisation as a fluorescent contrast mechanism. The propensity of the dyes to form H-dimers and thus to reduce their fluorescence contrast upon DNA binding is shown to depend on several of their structural parameters, such as their monomeric (YO) or homodimeric (YOYO) nature, their substitution and their electric charge. Moreover, these parameters also have a substantial influence on the affinity of the dyes for DNA and on the ensuing sensitivity for DNA detection. The results give new insight into the development and optimisation of fluorescent DNA probes with the highest contrast. 相似文献
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Elena Kostadinova Pavlina Dolashka Stefka Kaloyanova Ludmyla Velkova Todor Deligeorgiev Wolfgang Voelter Ivan Petkov 《Journal of fluorescence》2012,22(6):1609-1615
In this study, an improved, rapid, high yield synthesis of N,N’-4,4’-bis(benzyl-2-boronic acid)-bipyridinium dibromide (o-BBV) is described. The obtained o-BVV is applied in a two-component saccharide sensing system (complex) where it serves as a fluorescence quencher and a saccharide receptor. This system was applied to different natural oligosaccharides isolated from molluscan Rapana venosa (RvH1-a) and arthropodan Carcinus aestuarii (CaeH) hemocyanins (Hcs) and cyclodextrins (CDs). The carbohydrate contents of both Hcs were calculated in our previous work to be 1,6 % and 7 % for CaeH and RvH1-a, respectively. We propose that the difference in fluorescence increase of the native CaeH and RvH1-a when titrating them with the complex is due to the fact that the carbohydrate content of CaeH is lower and the carbohydrate chains are buried in between the structural subunits of the native molecule, while the glycans of the functional unit RvH1-a are exposed on the surface of the molecule leading to a 4-fold fluorescence’s intensity change. 相似文献
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I. Petkov F. Charra J -M. Nunzi T. Deligeorgiev 《Central European Journal of Chemistry》2004,2(2):290-301
The influence of UV light and temperature on poly(methylmethacrylate) (PMMA) and poly(vinylchloride) (PVC) films, doped with
2[(1,3,3-trimethylindoline-2(1H)-yliden)propen-1-yl]-3,3-dimethylindolino[1,2-b]-oxazolidine has been investigated. The radiation-induced
colour was analyzed spectrophotometrically at the maximum of the absorption peak at 560 nm. The effect of the temperature
on unirradiated and irradiated films was studied. The results demonstrate a strong photochromic and a weak thermochromic behaviour
of the PMMA and PVC films. The relationship of photocolouration-thermal decolouration is discussed based on the spectral results
reported here. 相似文献
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Todor G. Deligeorgiev Stefka Kaloyanova Aleksey Vasilev Juan J. Vaquero 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2292-2302
An improved green procedure for the synthesis of 2-aryl- and 2-hetarylbenzothiazoles by condensation of equivalent amounts of 2,2′-diaminodiphenyldisulfides or 2-aminothiophenols and various aromatic aldehydes in PEG 200/400 under microwave irradiation has been developed. This method allows the synthesis of 2-arylbenzothiazoles in high yields and with high purity regardless of the state of the starting compounds (liquid or solid) or the nature of the substituents in the aromatic ring. 相似文献
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Todor Deligeorgiev Stefka Kaloyanova Nedyalko Lesev Juan J. Vaquero 《Ultrasonics sonochemistry》2010,17(5):783-788
A series of 2-alkylthio derivatives of hetaryl thiols were synthesized by selective S-alkylation with alkyl halides (bromides and iodides) with ultrasonic irradiation at room temperature. The reaction was found to be generally applicable to hetaryl thiol derivatives with different substituents in the aromatic nucleus and various alkyl halides. The reaction gives high to excellent yields of products with high purity. 相似文献
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Novel poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes have been synthesized by an improved procedure
using the Atherton–Todd reaction conditions. N-ethyldiisopropylamine has been used as a mild base and propylene oxide as an
acid scavenger in order to obtain poly(oxyethylene phosphate) in yield and purity higher than those achieved by conventional
methods. The compounds have been characterized by 1H, 13C, and 31P NMR and FTIR techniques. Their absorption, fluorescent excitation and emission spectra of chloroform and abs. ethanol solutions
have been recorded and studied. The luminescent quantum yields and decay times have been determined and a dependence on the
length of the oxyethylene spacer between phosphate groups has been established. The new polymer complexes are water soluble
and have increased luminescence decay time in comparison with corresponding ternary complexes. 相似文献