LetF be a finite set of cardinality ¦F¦ =q 2,n 1 an integer and :Fn×Fn0 theHamming metric. Acode isomorphism C D between two block codesC,D
Fn is defined as an isometry which can be extended to an isometry of the whole space Fn. Any permutation Sn of the positions canonically induces a so-calledequivalence map
Aut Fn; any system (1,2,...,n) ofn permutations of the character setF induces a so-calledconfiguration Aat Fn. The group Aut Fn of all isometries of Fn turns out to be semidirect product of the configuration group with the symmetric group of degreen. The codeword estimating failure probability of a maximum likelihood codeword estimator for aq-nary symmetric channel does not depend on the transmitted codeword, if the automorphism group of the code acts transitively on the set of codewords. When using a systematic (n, k)-encoder, the symbol decoding failure probability does not depend on the transmitted symbol or on the time of transmission if the configuration group and the automorphism group act transitively on the set of codewords resp. on the set of thek information positions.In memoriam Giuseppe Tallini 相似文献
New polyazines have been synthesized by the polycondensation of 9,10-phenanthrenequinone, 9,10-anthraquinone, 1- and 2-chloroanthraquinone with hydrazine hydrate and disulphinylhydrazine. A reaction mechanism has been proposed for the polycondensation of phenanthrenequinone with hydrazine hydrate in DMF in the presence of zinc chloride. The electrical conductivity (10?10–10?6 ohm?1 cm?1) and the paramagnetic particle concentration (1018–1021 spin/g indicate the semiconducting properties of these polyazines. 相似文献
In this work a sample of SBA-15 mesoporous silica was synthesized and characterized by TEM, XRD, and N2 adsorption. The sample had a high value of specific surface area (1007 m2 g(-1)) and total pore volume (2.1 cm3 g(-1)). The pore diameter was 67 angstroms, so it was large enough to accommodate protein molecules inside the channels. Immobilization by physical adsorption of a commercial lipase preparation from Mucor javanicus was performed at different pH values (pH 5-8). pH 6 gave the highest lipase loading and hydrolytic activity of the corresponding biocatalyst. Chemical modification of the SBA-15 via glutardialdehyde allowed also the enzyme immobilization through chemical adsorption. This preparation was active toward tributyrin hydrolysis. On the contrary, very low activity toward triolein hydrolysis was observed. The reduction of the size of the channels due the immobilization process has been suggested as a possible explanation. 相似文献
Matrix assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been used to determine peptide distributions directly from rat, mouse and human pituitary tissue sections. Since these organs are small (102–103 μm) the spatial resolution of IMS is a key issue in molecular imaging of pituitary tissue sections. Here we show that high-resolution IMS allows localization of neuropeptide distributions within different cell clusters of a single organ of a pituitary tissue section. The sample preparation protocol does not result in analyte redistribution and is therefore applicable to IMS experiments at cellular length scales. The stigmatic imaging mass spectrometer used in this study produces selected-ion-count images with pixel sizes of 500 nm and a resolving power of 4 μm, yielding superior spatial detail compared to images obtained in microprobe imaging experiments. Furthermore, we show that with imaging mass spectrometry a distinction can be made between different mammalian tissue sections based on differences in the amino acid sequence of neuropeptides with the same function. This example demonstrates the power of IMS for label-free molecular imaging at relevant biological length scales. 相似文献
A series of novel 3′-difluoromethyl-taxoids and 3′-trifluoromethyl-taxoids with modifications at the C2 and C10 positions were synthesized and evaluated for their in vitro cytotoxicities against human breast carcinoma (MCF7-S, MCF7-R, LCC6-WT, LCC6-MDR), non-small cell lung carcinoma (H460) and colon adenocarcinoma (HT-29) cell lines. These second-generation fluoro-taxoids exhibited several times to more than 20 times better potency than paclitaxel against drug-sensitive cancer cell lines, MCF7-S, LCC6-WT, H460, and HT-29. These fluoro-taxoids also possess two orders of magnitude higher potency than paclitaxel against drug-resistant cancer cell lines, MCF7-R and LCC6-MDR. Structure-activity relationship study shows the importance of the C10 modification for increasing the activity against multidrug-resistant cancer cell lines. Effects of the C2-benzoate modifications on the potency in the 3′-difluoromethyl-taxoid series are very clear (i.e., F < MeO < Cl < N3), while those in the 3′-trifluoromethyl-taxoid series are less obvious. Also, different trends in the sensitivity to the C2-substitution are observed between drug-sensitive cell lines and drug-resistant cancer cell lines that overexpress efflux pumps. 相似文献
A new HPLC method based on a mixed mode stationary phase Hypersil Duet C18/SAX was developed and applied for the simultaneous determination of acetaminophen, acetylsalicylic acid and codeine. Parameters, such as the composition of the mobile phase, the nature of the organic modifier, the buffer type and the flow rate were investigated to optimize the separation. The results obtained show that the new HPLC method is rapid, highly efficient and selective. The studied compounds are separated in 10 min, by means of a mobile phase containing phosphate buffer (pH 7.50) and methanol (65:35 v v−1). The retention mechanisms of each analyte were investigated using both the linear solvent strength theory and stoichiometric displacement model. The method was fully validated and showed good linearity for each compound for a concentration ranging between 2.0 and 40 μg mL−1. The limits of detection and quantification were determined and they are lower than 0.1 μg mL−1. The precision (RSD) of the method does not exceed 2 % for all studied compounds. The method was successfully applied for the assay of acetaminophen, acetylsalicylic acid and codeine in pharmaceutical formulations.
Formaldehyde in aqueous solution is hydrolysed and forms methanediol. Using X-ray absorption spectroscopy we show that the hydrolysation product can be identified by a distinct electronic signature in the spectra. This is manifested by the disappearance of the oxygen 1s → π* absorption line. The X-ray absorption spectrum of aqueous formaldehyde is compared with those of the structurally similar formamide and urea, which are in contrast not hydrolysed in aqueous solution. We thereby demonstrate the exceptional sensitivity and simplicity of the technique to monitor this fundamental process in the aqueous phase. 相似文献
Synthesis of some novel fluorescence nanomaterials loaded with photoactive polyphenols originated from plants with a high
spectrum of biological activity, by replacing synthetic chemicals, may open new opportunities for optical and bio-medical
applications. This paper presents the synthesis, characterization and fluorescence properties of a new class of materials
based on host hybrid matrices obtained through templated sol–gel route, by hydrolysis and co-condensation of tetraorthoethylsilicate
with octaisobutyltetracyclo [7.3.3.15,11] octasiloxane-endo-3,7-diol. The aim of paper is focused on the evaluation of the behavior of the fluorescence properties
of ornamental bush extract at immobilization in a templated silica matrix and in a silica-silsesquioxane network, using as
templates a neutral, non-toxic and biodegradable surfactant from poly(ethyleneglycol) class and a high biocompatible non-surfactant
from glucidic class. The proofs of ornamental bush extract entrapment by physical interactions in silica based networks were
provided by FT-IR and UV–VIS spectroscopy. The changes of polymer network due to the hydrogen bond interactions between residual
Si–OH groups and functional groups of organic molecules from extract were evidenced by shifts of specific vibrations. In UV–VIS-NIR
domain, the chromophore groups from ornamental bush extract were also evidenced by similar small shifts. As a result of ornamental
bush extract entrapment, in all the immobilized samples the fluorescence intensity was more than 10 times amplified in samples
templated with poly(ethylenglycol) surfactant) and of about 5 times in samples with glucidic template due to the physical
adsorption of polyphenolic molecules from extract, excellent synergistic optical properties of SiO2 and silsesquioxane compound and also due to a favorable conformational arrangement. The size of synthesized polymeric materials,
estimated by dynamic light scattering technique showed main diameters less then 1.4 μm, namely 1,060 and 211 nm—for samples
with d-glucose template and 1,330 and 531 nm—for samples with poly(ethyleneglycol) template, respectively, with a narrow size distribution
and a polidispersity varying between 0.022 and 0.426. These results are in good accordance with TEM images that evidenced
the presence of some polymeric aggregates which contain the vegetal extract immobilized inside hybrid SiO2-Sq polymeric network of about hundred nanometers size. This study bring new contributions to the development of the sol–gel
procedure by entrapment of a complex vegetable mixture in polymeric matrices as integral component of silica and hybrid silica-silsesquioxane
networks which leads to a significant enhancement of the functional properties of the final material, thus diversifying the
potential applications of organic doped sol–gel glasses. 相似文献
The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion. 相似文献
Starting from the racemic ethyl 3-hydroxy-3-(10-alkyl-10H-phenothiazin-3-yl)propanoates as substrates, a multienzymatic procedure was developed for the efficient synthesis of the corresponding highly enantiomerically enriched (R)- and (S)-3-heteroaryl-3-hydroxypropanoic acids. 相似文献