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Halma M.,CNRS Molecular Chemistry Department | Lachenal D.,French National Center for Scientific Research | Marlin N.,French National Center for Scientific Research | Deronzier A.,CNRS Molecular Chemistry Department | And 2 more authors.
Industrial Crops and Products | Year: 2015

This work aims at elucidating some of the key steps of the oxidation pathways of lignin model compounds by hydrogen peroxide under alkaline conditions (0.05. M NaOH) in the presence of copper(II)-phenanthroline complex. Phenolic and non-phenolic β-O-4 dimeric phenyl propane structures were selected as lignin models since they represent the most abundant structures in lignin: 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy) propane-1-ol and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy) propane-1-one, and their methylated counterparts. After 3 h at 80°C the main products in the reaction medium were analyzed by HPLC. The results suggested that the first step was the oxidation of the benzylic OH group to a ketone group. This step would be catalyzed by the copper (II)-phenanthroline complex and favored by the presence of dissolved oxygen. The second step would be the cleavage of the β-O-4 linkage by a series of nucleophilic attacks initiated by the reaction of the perhydroxyl anion on the carbonyl group which would not be influenced by the presence of the copper complex. This mechanism is in accordance with the formation of acetaldehyde, veratric or vanillic acid, and guaiacol which were identified as the main reaction products of the models oxidation. © 2015 Elsevier B.V. Source


Halma M.,CNRS Molecular Chemistry Department | Lachenal D.,Grenoble Institute of Technology | Deronzier A.,CNRS Molecular Chemistry Department | Marlin N.,Grenoble Institute of Technology | Zarubin M.,St Petersburg State Forest Technical Academy
16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC | Year: 2011

This work aims at elucidating some of the key steps of the oxidation pathways of lignin model compounds using Cu(II)-phenantroline as catalyst and hydrogen peroxide as oxidant. Phenolic and non-phenolic beta-O-4 dimeric phenyl propane structures were selected as lignin models since they represent the most abundant structures in lignin. The compounds used in this work are not commercially available; therefore all of them were synthesized. Oxidation reactions were carried out under alkaline conditions, at 80 °C for 3 h. The lignin model dimer (LMD) disappearance and some of the oxidation products were identified by HPLC analyses. Products as acetaldehyde, veratric or vanillic acid, and guaiacol were identified as resultant products of LMD oxidations. A tentative mechanism which involves the oxidation of the benzylic alcohol group followed by the cleavage of the beta-ether linkages is proposed. Source


Perelman A.Y.,St Petersburg State Forest Technical Academy | Shifrin K.S.,Oregon State University | Bulavinscky I.V.,St Petersburg State Forest Technical Academy
Telecommunications and Radio Engineering (English translation of Elektrosvyaz and Radiotekhnika) | Year: 2010

The method to simplify general inversion formula have been developed. The obtained modifications are constructed in correspondence with the structure of the integral coefficient (IC). The most important Qs -model of the IC in described in detail. The typical examples confirm the advantage of the modified inversion formula. © 2010 by Begell House, Inc. Source


Kazakova L.P.,RAS Ioffe Physical - Technical Institute | Tsendin K.D.,RAS Ioffe Physical - Technical Institute | Lebedev E.A.,RAS Ioffe Physical - Technical Institute | Arsova D.,Bulgarian Academy of Science | Obukhova I.A.,St Petersburg State Forest Technical Academy
Semiconductors | Year: 2010

Charge-carrier transport in Ge20As20S60 films has been studied using the transit time method under low-injection conditions at room temperature. It was found that drift mobilities of electrons and holes in Ge20As20S60 films are close to each other, i.e., μe ≈ μh ≈ 2 × 10-3 cm2 V-1 s-1 at T = 295 K and F = 5 × 104 V/cm. It was shown that the time dependence of the photocurrent during carrier drift and the voltage dependence of the drift mobility allowed the use of the concept of anomalous dispersive transport. Experimental data were explained using the model of transport controlled by carrier trapping by localized states with energy distribution near conduction and valence band edges described by the exponential law with a characteristic energy of ~0.05 eV. © 2010 Pleiades Publishing, Ltd. Source


Utkin L.V.,St Petersburg State Forest Technical Academy | Zhuk Y.A.,St Petersburg State Forest Technical Academy
International Journal of Data Analysis Techniques and Strategies | Year: 2012

When it is difficult to get learning data during the training time, we have to classify objects by having extremely small information about their feature. It is assumed in the paper that only some average or mean value of every feature and the lower and upper bounds of a set of its values are known. The main idea for constructing new classification models taking into account this information is to form a set of probability distributions bounded by some lower and upper probability distribution functions (a p-box). A discriminant function is derived in order to maximise the risk measure over the set of distributions and to minimise it over a set of classification parameters. The algorithm for classification is reduced to a parametric linear programming problem. Copyright © 2012 Inderscience Enterprises Ltd. Source

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