排序方式: 共有52条查询结果,搜索用时 25 毫秒
41.
Molecular mechanics calculations were performed with the JUMNA program on d(GCGTGOGTGCG) · d(CGCACTCACGC) where “O” is a
modified abasic site: 3-hydroxy-2-(hydroxymethyl)tetrahydrofuran. From energy minimizations, for intrahelical or extrahelical
positions of the unpaired thymine, various structures with different curvatures were obtained. Dynamical properties of this
abasic sequence were also investigated through the controlled studies of DNA bending. Poisson-Boltzmann calculations were
used to mimic the electrostatic effect of solvent on this sequence. The lowest energy structures show an acceptable agreement
with experimental data.
Received: 1 June 1998 / Accepted: 17 September 1998 / Published online: 10 December 1998 相似文献
42.
Abstract— White light irradiation of a microsomal fraction from etiolated plants affects their ATP-dependent Ca2+ accumulation by inhibiting active uptake and enhancing passive efflux. The succinate-dependent mitochondrial Ca2 + accumulation as well is decreased by light. The wavelength dependence of these light effects as well as their low quantum yield suggest non-phototransformable protochloro-phyll(ide) [PChl(ide)] to be the photoreceptor. PChlide has been isolated from corn leaves pretreated with 5-amino levulinic acid. Addition of Pchlide causes photosensitization of an otherwise light insensitive microsomal Ca2+ accumulation. The observed light effect may be due to contamination of the mitochondrial as well as the microsomal fractions with PChl(ide)‡ containing particles. Irradiation of the intact tissue leads to the almost complete disappearance of the light effect on the in vitro Ca2 + accumulation. 相似文献
43.
This paper revisits a few aspects of laser-dynamics with a strong-harmonic expansion analysis from which new analytical information, within the intrinsic pulsing regime that characterizes the non-linearly coupled differential Lorenz–Haken equations, is extracted. The analysis is expected to provide clearer insights to the physics involved in the laser-dynamics issue. Carried out to third-order in electric field amplitude, the procedure allows for the derivation of a closed form expression which describes the permanent-oscillation frequency of the unstable periodic state. Comparison between the frequency values evaluated from the literal formula and those obtained through direct numerical simulations shows a realistic fit inside the control parameters space that displays symmetric period-one pulsing solutions. 相似文献
44.
S. Ayadi M. Abderrabba 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(7):1080-1085
In this work, we theoretically study Diels-Alder reactions between cyclohexadiene and a series of 2-aryl-4,6-dinitrobenzotriazole
1-oxides (5a-d). Based on various calculation methods such as SCF/6–31G* and DFT/B3LYP with the 6–31G* standard basis set, we discuss the
thermodynamic possibility of these reactions. The reactions between a series of 6-nitrobenzotriazole 1-oxides(5aa
1
-ab
1
) and cyclohexadiene are also studied.
The text was submitted by the authors in English. 相似文献
45.
Numerical solutions of the Benjamin‐Bona‐Mahony‐Burgers equation in one space dimension are considered using Crank‐Nicolson‐type finite difference method. Existence of solutions is shown by using the Brower's fixed point theorem. The stability and uniqueness of the corresponding methods are proved by the means of the discrete energy method. The convergence in L∞‐norm of the difference solution is obtained. A conservative difference scheme is presented for the Benjamin‐Bona‐Mahony equation. Some numerical experiments have been conducted in order to validate the theoretical results.© 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
46.
The objective of this paper is to characterize the hydrodynamic and thermal behaviors of yield stress fluids within a cylindrical agitated vessel equipped with simple helical ribbon stirrers (SHR) (one and two-stages) by means of the numerical simulation approach. For this purpose, a computational fluid dynamic simulation using the 3D finite volume technique has been carried out to solve the continuity, momentum and thermal energy equations. In this study, we have analyzed the Oldroyd and Reynolds numbers effects on the hydrodynamic and thermal behaviors for the two mentioned stirrers types. In addition, the influence of the impeller width and its clearance from the vessel wall on the velocity and thermal fields has been investigated. Velocity and thermal fields’ visualization has been presented in different (r–z) and (r–θ) planes. Moreover, the power constant and Nusselt number are correlated by a relationship relating the physical properties and the geometric ratios defining the SHR. 相似文献
47.
Burel-Deschamps L Mével M Loizeau D Ayadi F Yaouanc JJ Clément JC Jaffrès PA Giamarchi P 《Journal of fluorescence》2008,18(5):835-841
We report here a study on the physicochemical properties of cationic phospholipids liposomes used for lipoplex formulation
and DNA transfer. The original cationic phospholipids synthesized in our laboratory are first presented with the liposome
formulation process. The second part deals with the liposomes fusogenic properties studied by fluorescence resonant energy
transfer (FRET). The nature of the cationic polar head and the formulation with or without a neutral colipid have a great
influence on the FRET signal. The third part reports the study of the viscosity of the liposome by fluorescence anisotropy
measurements. It has been observed that the vectors having a saturated lipid chain exhibit a more pronounced anisotropy than
those having unsaturated lipid chains. Finally, liposomes formed by a mixture of phospholipids and DC-Chol (a rigid lipid)
leads to increase the anisotropy denoting a more rigid liposome. 相似文献
48.
M. Zemzemi S. Alaya Z. Ben Ayadi 《Journal of Experimental and Theoretical Physics》2014,118(6):945-950
Solar cells based on transparent conductive oxides such as ZnO/Cu2O constitute a very advanced way to build high-performance cells. In this work, we are interested in the characterization of the interface through nanoscale modeling based on ab initio approaches (density functional theory, local density approximation, and pseudopotential). This work aims to build a supercell containing a heterojunction ZnO/Cu2O and study the structural properties and the discontinuity of the valence band (band offset) from a semiconducting to another phase. We build a zinc oxide in the wurtzite structure along [0001] on which we place the copper oxide in the hexagonal (CdI2-type) structure. We choose the method of Van de Walle and Martin to calculate the energy offset. This approach fits well the density functional theory. Our calculation of the band offset gives a value that corresponds to other experimental and theoretical values. 相似文献
49.
Inhibition of Fungi and Gram-Negative Bacteria by Bacteriocin BacTN635 Produced by Lactobacillus plantarum sp. TN635 总被引:1,自引:0,他引:1
Slim Smaoui Lobna Elleuch Wacim Bejar Ines Karray-Rebai Imen Ayadi Bassem Jaouadi Florence Mathieu Hichem Chouayekh Samir Bejar Lotfi Mellouli 《Applied biochemistry and biotechnology》2010,162(4):1132-1146
The aim of this study was to evaluate 54 lactic acid bacteria (LAB) strains isolated from meat, fermented vegetables and dairy products for their capacity to produce antimicrobial activities against several bacteria and fungi. The strain designed TN635 has been selected for advanced studies. The supernatant culture of this strain inhibits the growth of all tested pathogenic including the four Gram-negative bacteria (Salmonella enterica ATCC43972, Pseudomonas aeruginosa ATCC 49189, Hafnia sp. and Serratia sp.) and the pathogenic fungus Candida tropicalis R2 CIP203. Based on the nucleotide sequence of the 16S rRNA gene of the strain TN635 (1,540 pb accession no FN252881) and the phylogenetic analysis, we propose the assignment of our new isolate bacterium as Lactobacillus plantarum sp. TN635 strain. Its antimicrobial compound was determined as a proteinaceous substance, stable to heat and to treatment with surfactants and organic solvents. Highest antimicrobial activity was found between pH 3 and 11 with an optimum at pH?=?7. The BacTN635 was purified to homogeneity by a four-step protocol involving ammonium sulfate precipitation, centrifugal microconcentrators with a 10-kDa membrane cutoff, gel filtration Sephadex G-25, and C18 reverse-phase HPLC. SDS-PAGE analysis of the purified BacTN635, revealed a single band with an estimated molecular mass of approximately 4 kDa. The maximum bacteriocin production (5,000 AU/ml) was recorded after a 16-h incubation in Man, Rogosa, and Sharpe (MRS) medium at 30?°C. The mode of action of the partial purified BacTN635 was identified as bactericidal against Listeria ivanovii BUG 496 and as fungistatic against C. tropicalis R2 CIP203. 相似文献
50.
We prove real Paley-Wiener type theorems for the Dunkl transform ℱ
D
on the space
of tempered distributions. Let T∈S′(ℝ
d
) and Δ
κ
the Dunkl Laplacian operator. First, we establish that the support of ℱ
D
(T) is included in the Euclidean ball
, M>0, if and only if for all R>M we have lim
n→+∞
R
−2n
Δ
κ
n
T=0 in S′(ℝ
d
). Second, we prove that the support of ℱ
D
(T) is included in ℝ
d
∖B(0,M), M>0, if and only if for all R<M, we have lim
n→+∞
R
2n
ℱ
D
−1(‖y‖−2n
ℱ
D
(T))=0 in S′(ℝ
d
). Finally, we study real Paley-Wiener theorems associated with
-slowly increasing function.
相似文献