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排序方式: 共有80条查询结果,搜索用时 31 毫秒
1.
Dan Donescu Sever Serban Kristiana Gosa Cristian Petcu 《Central European Journal of Chemistry》2005,3(1):10-27
The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl
acrylate) (PEtA) with TiO2 was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved
simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl
acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane
derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl
acetate (VAc). The PVAc-TiO2 hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane
derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly
affected by TiO2 presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of
TiO2 inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network. 相似文献
2.
Gas chromatography-mass spectrometry of carbonyl compounds in cigarette mainstream smoke after derivatization with 2,4-dinitrophenylhydrazine 总被引:3,自引:0,他引:3
An improved gas chromatography-mass spectrometry (GC-MS) method was described for the analysis of carbonyl compounds in cigarette mainstream smoke (CMS) after 2,4-dinitrophenylhydrazine (DNPH) derivatization. Besides formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, methyl ethyl ketone, butyraldehyde, and crotonaldehyde that are routinely analyzed in cigarette smoke, this technique separates and allows the analysis of several C4, C5 and C6 isomeric carbonyl compounds. Differentiation could be made between the linear and branched carbon chain components. In cigarette smoke, the branched chain carbonyls are found at higher level than the linear chain carbonyls. Also, several trace carbonyl compounds such as methoxyacetaldehyde were found for the first time in cigarette smoke. For the analysis, cigarette smoke was collected using DNPH-treated pads, which is a simpler procedure compared to conventional impinger collection. Thermal decomposition of DNPH-carbonyl compounds was minimized by the optimization of the GC conditions. The linear range of the method was significantly improved by using a standard mixture of DNPH-carbonyl compounds instead of individual compounds for calibration. The minimum detectable quantity for the carbonyls ranged from 1.4 to 5.6 microg/cigarette. 相似文献
3.
Dan Donescu Liana Fusulan Stela Lungoci Sever Serban Cristian Peteu 《Journal of Dispersion Science and Technology》2013,34(5):647-653
ABSTRACT The modification of decomposition rate of the potassium persulfate initiator during the synthesis of “two-stage latexes” polystyrene-ethyl acrylate (EtA) of butyl acrylale (BuA) and of 2-ethylhexyl acrylate (EHA) is studied. This rate is minimum for BuA and maximum for EHA, in good agreement with the value of solubility parameters. The appearance of poryacrvlaf.es determines the existence of water bonded to the polar polymer. The amount of water bonded increases in the sequence PEtA?PBuA?PEHA, function of the modification of the diameters of the particles resulted from the latexes obtained. 相似文献
4.
A significant amount of work has been previously dedicated to the understanding of methylene selectivity parameter. The conventional theory applied for this understanding was mostly based on the assumption that the difference in the Gibbs free energy of transfer from the mobile phase to the stationary phase is a constant for any two compounds in a homologous series that differ by a CH2 group. In the present study, it is shown based on solvophobic theory that this assumption is indeed correct, but it provides a theoretical justification for it. Exemplification of the results of theory was obtained using the values for methylene selectivity (α(CH2)) measured experimentally for seven different C18 chromatographic columns including two core–shell columns and using water and either methanol or acetonitrile as an organic component. Four different homologous series of compounds were used for evaluation. The study proved the theoretical prediction that the values for α(CH2) obtained using different homologous series of compounds are only slightly different from those obtained using the toluene–butylbenzene series. Even using different homologous series, the same type of information regarding the columns comparison, and the changes in log α(CH2) with the solvent composition was obtained. 相似文献
5.
A simple and quick ultra performance liquid chromatography method (UPLC) has been developed for determination of methyl paraben (MP) and its major metabolites p‐hydroxybenzoic acid (pHBA) and phenol (Phe), following its biotransformations in Eisenia foetida. After different exposure time to paper contact test, the presence of methyl paraben and his biotransformation products in adult earthworms was monitored. Determination of its metabolites was achieved with a BEH (bridged ethane‐silicon hybrid) C18 column (2.1×50 mm i.d., 1.7 µm particle size), using methanol/water/phosphoric acid as mobile phase, under a gradient elution program, and a PDA (photo‐diode array) detection (quantification with MaxPlot in the range 210–400 nm). The absorption of MP did not exceed 30% and in the first 4–6 h after exposure only minute amounts of pHBA and Phe were detected in the worm homogenates. After 48 h of exposures, almost 70% of absorbed MP was already metabolized to Phe and around 20% could be found as pHBA. 相似文献
6.
LetH be a Hopf algebra andM a representation or a corepresentation ofH. In this paper we study semiinvariants ofM. This notion generalizes the known concept of weight spaces in the context of representations of Lie algebras. Our best results are attained for pointed Hopf algebras, and semiinvariants which are related to the coradical filtration ofH. 相似文献
7.
8.
Electronic Olfactory Sensor Based on A. mellifera Odorant‐Binding Protein 14 on a Reduced Graphene Oxide Field‐Effect Transistor 下载免费PDF全文
Dr. Melanie Larisika Caroline Kotlowski Christoph Steininger Rosa Mastrogiacomo Prof. Paolo Pelosi Prof. Stefan Schütz Serban F. Peteu Prof. Christoph Kleber Ciril Reiner‐Rozman Dr. Christoph Nowak Prof. Wolfgang Knoll 《Angewandte Chemie (International ed. in English)》2015,54(45):13245-13248
An olfactory biosensor based on a reduced graphene oxide (rGO) field‐effect transistor (FET), functionalized by the odorant‐binding protein 14 (OBP14) from the honey bee (Apis mellifera) has been designed for the in situ and real‐time monitoring of a broad spectrum of odorants in aqueous solutions known to be attractants for bees. The electrical measurements of the binding of all tested odorants are shown to follow the Langmuir model for ligand–receptor interactions. The results demonstrate that OBP14 is able to bind odorants even after immobilization on rGO and can discriminate between ligands binding within a range of dissociation constants from Kd=4 μM to Kd=3.3 mM . The strongest ligands, such as homovanillic acid, eugenol, and methyl vanillate all contain a hydroxy group which is apparently important for the strong interaction with the protein. 相似文献
9.
M. Petrascu A. Constantinescu I. Cruceru M. Giurgiu A. Isbasescu H. Petrascu C. Bordeanu S. Serban V. Stoica I. Tanihata W. G. Lynch V. L. Lyuboshits V. V. Lyuboshits 《Physics of Atomic Nuclei》2006,69(7):1261-1266
The preemission of neutrons from 11Li halo nuclei is considered. The present problems of investigation of 11Li halo nucleus structure by means of the C
nn correlation function are briefly presented. The influence of the target screening on the halo neutron preemission is described.
It is shown that, owing to the diminishing of the screening effect, the yield of preemission neutron pairs is expected to
be much larger in the case of 12C than in the case of Si target. It is shown that a new experiment on a 12C target will allow one to solve the standing problems of C
nn and to test experimentally a recent new theory of C
nn.
The text was submitted by the authors in English. 相似文献
10.
The Ramanujan Journal - Inspired by the work of Lang–Trotter on the densities of primes with fixed Frobenius traces for elliptic curves defined over $${\mathbb {Q}}$$ and by the subsequent... 相似文献