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51.
Imen Abdelhedi Miladi Bhanu Prakash Mudraboyina Ahmed Oueslati Eric Drockenmuller Hatem Ben Romdhane 《Journal of polymer science. Part A, Polymer chemistry》2014,52(2):223-231
Polyesters and polyethers containing norbornadiene (NBD) and 1,2,3‐triazole units in the main chain are prepared by step growth polymerization of diester or diether NBD‐based dialkynes with different aromatic diazides using copper‐catalyzed azide–alkyne cycloaddition. The solubility and the physical properties of the resulting polytriazoles are investigated by differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and 1H NMR spectroscopy, and are discussed taking into account of the chemical structures of the monomers. All of them are amorphous with glass transition temperatures ranging from 51 to 117 °C, number average molecular weight (Mn) values from 16 to 43 kDa and thermal degradation (Td10) values from 175 to 292 °C. The photochemical valence isomerization (PVI) of the NBD units into quadricyclanes (QC) is investigated using UV–vis spectroscopy of polymer films spin‐coated onto quartz substrates. For the first time the PVI of NBD into QC is demonstrated by 1H NMR spectroscopy. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 223–231 相似文献
52.
In this article, we propose to study, in more generality, the probability-weighted moments method used by Hosking and Wallis (1987) in the case of generalized Pareto distributions which depend on two parameters γ and σ. The objective is to extend the domain of validity: γ<1/2 required in order to obtain the asymptotic properties of their estimators. By simulations, we show the efficiency of our technique. To cite this article: J. Diebolt et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
53.
The 139La NMR spin-echo spectra of La2Fe14BHx are reported. Since lanthanum has no 4f electrons, the observed quadrupole splittings are directly proportional to the lattice part of the electric field gradient, Vzzlat. This quantity decreases as the content of interstitial hydrogen x grows. To describe the fall-off of Vzzlat, a dimensionless function f2(x) is introduced, normalised so that f2(0)=1. Analysis of the new and earlier published data obtained by several experimental techniques demonstrates that the reduction of both the second-order crystal field parameter A20 and the lattice electric field gradient Vzzlat is described by the same function f2(x) in all R2Fe14BHx. The only distinction that needs to be made is between R being a light and a heavy rare earth. 相似文献
54.
We consider a continuous time multivariate financial market with proportional transaction costs and study the problem of finding the minimal initial capital needed to hedge, without risk, European-type contingent claims. The model is similar to the one considered in Bouchard and Touzi [B. Bouchard, N. Touzi, Explicit solution of the multivariate super-replication problem under transaction costs, The Annals of Applied Probability 10 (3) (2000) 685–708] except that some of the assets can be exchanged freely, i.e. without paying transaction costs. In this context, we generalize the result of the above paper and prove that the super-replication price is given by the cost of the cheapest hedging strategy in which the number of non-freely exchangeable assets is kept constant over time. Our proof relies on the introduction of a new auxiliary control problem whose value function can be interpreted as the super-hedging price in a model with unbounded stochastic volatility (in the directions where transaction costs are non-zero). In particular, it confirms the usual intuition that transaction costs play a similar role to stochastic volatility. 相似文献
55.
Hadji I Marzouki MN Ferraro D Fasano E Majdoub H Pani G Limam F 《Applied biochemistry and biotechnology》2007,143(2):129-141
Crude garlic extract contains one Mn-superoxide dismutase designated as SOD1 and two Cu,Zn superoxide dismutases as SOD2 and
SOD3. The major isoform SOD2 was purified to homogeneity by Sephacryl S200-HR gel filtration, DEAE Sepharose ion exchange
chromatography, and chromatofocusing using PBE 94. SOD2 was purified 82-fold with a specific activity of 4,960 U/mg protein.
This enzyme was stable in a broad pH range from 5.0 to 10.0 and at various temperatures from 25 to 60°C. The native molecular
mass of SOD2 estimated by high performance liquid chromatography on TSK gel G2000SW column was 39 kDa. Sodium dodecyl sulfate–polyacrylamide
gel electrophoresis analysis showed a single band near 18 kDa, suggesting that native enzyme was homodimeric. The isoelectric
point as determined by chromatofocusing was 5. Analysis of its N terminal amino acid sequence revealed high sequence homology
with several other cytosolic Cu,Zn-SODs from plants. Exposure of cancer cell lines to garlic Cu,Zn-SOD2 led to a significant
decrease in superoxide content with a concomitant rise in intracellular peroxides, indicating that the enzyme is active in
mammalian cells and could, therefore, be used in pharmacological applications. 相似文献
56.
Leila Kalai-Grami Sabrine Saidi Sarra Bachkouel Imen Ben Slimene Monia Mnari-Hattab Mohamed Rebah Hajlaoui Ferid Limam 《Applied biochemistry and biotechnology》2014,174(1):365-375
A collection of 200 bacterial isolates recovered from citrus plants (Citrus limon, Citrus sinensis, and Citrus reticulata), Medicago truncatula and Laurus nobilis, was established. In vitro screening indicated that 28 isolates exhibited an inhibitory activity against the vascular pathogens Phoma tracheiphila and Verticillium albo-atrum. Isolates were screened according to their hydrolytic activities, plant growth-promoting bacteria (PGPB) abilities, as well as for the presence of nonribosomal peptide synthetase (NRPS) genes responsible of the lipopeptide biosynthesis. The results were positive for 16 isolates which exhibited at least two PGPB activities and a single NRPS gene. Genetic diversity of the selected isolates was studied using random amplified polymorphic DNA (RAPD) and repetitive element PCR (REP) tools that showed clustering of strains into three major groups (I, II, and III) (i, ii, and iii), respectively. Clustering was further confirmed by the 16S rDNA sequencing that assigned nine isolates to Bacillus velezensis, four isolates to Bacillus methyltrophicus, one isolate to Bacillus amyloliquefaciens, and two isolates to Bacillus mojavensis. Organ-bacterial genotype interaction as well as positive correlation with NRPS genes are discussed. 相似文献
57.
Tabbene O Ben Slimene I Bouabdallah F Mangoni ML Urdaci MC Limam F 《Applied biochemistry and biotechnology》2009,157(3):407-419
B38 bacterial strain, isolated from Tunisian soil showed a strong antimicrobial activity. Based on biochemical characterization
and 16S rDNA sequence analysis, B38 strain was identified as Bacillus subtilis. Cell culture supernatant showed antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus species and several Gram-positive and Gram-negative bacteria. Antifungal activity against phytopathogenic fungi was also
observed. Antibacterial activity production started at early exponential growth phase, and maximum activity was reached at
the stationary phase. This antibacterial activity was neither affected by proteases, lipase, and organic solvents, nor by
surfactants. It was stable over a wide pH range and still active after autoclaving at 121 °C during 20 min. Thin layer chromatography
followed by bioautography assay allowed the detection of four active spots with R
f values of 0.30, 0.47, 0.70, and 0.82. The single spot with R
f 0.30 showed antifungal activity, whereas the spots with R
f values of 0.47, 0.70, and 0.82 exhibited antibacterial activity. 相似文献
58.
In order to assist physically handicapped persons in their movements,
we developed an embedded isolated word speech recognition system (ASR)
applied to voice control of smart wheelchairs. However, in spite of the existence
in the industrial market of several kinds of electric wheelchairs, the problem
remains the need to manually control this device by hand via joystick; which limits
their use especially by people with severe disabilities. Thus, a significant number
of disabled people cannot use a standard electric wheelchair or drive it with
difficulty. The proposed solution is to use the voice to control and drive the wheelchair
instead of classical joysticks. The intelligent chair is equipped with an obstacle
detection system consisting of ultrasonic sensors, a moving navigation
algorithm and a speech acquisition and recognition module for voice control
embedded in a DSP card. The ASR architecture consists of two main modules.
The first one is the speech parameterization module (features extraction) and
the second module is the classifier which identifies the speech and generates
the control word to motors power unit. The training and recognition phases are
based on Hidden Markov Models (HMM), K-means, Baum-Welch and Viterbi
algorithms. The database consists of 39 isolated speaker words (13 words pronounced
3 times under different environments and conditions). The simulations
are tested under Matlab environment and the real-time implementation is performed
by C language with code composer studio embedded in a TMS 320
C6416 DSP kit. The results and experiments obtained gave promising recognition
ratio and accuracy around 99% in clean environment. However, the system accuracy
decreases considerably in noisy environments, especially for SNR values
below 5 dB (in street: 78%, in factory: 52%). 相似文献
59.
60.
Transesterification of β-keto esters with a wide variety of allyl, benzyl, propargyl, and alkyl alcohols using, for the first time, commercially available and inexpensive Et3N as a Brønsted base additive, is efficiently performed in toluene at reflux. The corresponding esters are exclusively obtained in 57–98% yields with no trace amounts of γ,δ-ketones, usually expected from the decarboxylative Carroll rearrangement. 相似文献