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101.
102.
Blanca Biel Isabel Benito Csar Gnzalez Jos Manuel Blanco Jos Ortega Rubn Prez Fernando Flores 《Applied Surface Science》2002,190(1-4):475-479
Using a molecular dynamics DFT-LDA code, we have analyzed the Schottky-barrier formation of a Se-passivated GaAs(1 0 0)-2×1 reconstruction. In our approach we consider, first, the energetically most favorable interfaces formed by the deposition of either one or two Ga atoms per surface unit cell; then, we analyze the electron density of states and calculate the interface Fermi level and the Schottky-barrier height. We show that the height depends essentially on the very same interface geometry. In particular, the effect of exchanging Ga and Se atoms at the interface (an intermixing process) yields a normal Schottky-barrier height, while the normal passivated surface yields an ohmic contact. 相似文献
103.
Daranas AH Fernández JJ Norte M Gavín JA Suárez-Gómez B Souto ML 《Chemical record (New York, N.Y.)》2004,4(1):1-9
Marine toxins have drawn wide interest because their economical impact and disastrous effect upon the shellfish industry and public health in many parts of the world. One of the most interesting group of substances of marine toxins, from structural and pharmacological points of view are polyether compounds, which generally present a great diversity in size and potent biological activities. The subject of this work was about to biosynthesis of okadaic acid skeleton as leader as DSP toxins. Its biosynthesis attracts considerable attention since the carbon skeleton has been shown to be synthesised via an unusual route. In this paper we report on stable isotope incorporation experiments on DSP toxin in artificial cultures of dinoflagellate. The comparison of the degrees of incorporation in these samples measured by different methods led to contradictory results. This implies that further experimental data is needed in order to propose a logical biogenetic scheme. 相似文献
104.
Pintre IC Serrano JL Ros MB Ortega J Alonso I Martínez-Perdiguero J Folcia CL Etxebarria J Goc F Amabilino DB Puigmartí-Luis J Gomar-Nadal E 《Chemical communications (Cambridge, England)》2008,(22):2523-2525
The synthesis and characterization of bent-core liquid crystals which incorporate TTF groups is reported; different bent-core mesophases are induced depending on the molecular structure and properties derived from their compact packing have been studied. 相似文献
105.
Sandoval Guerrero K Revilla Vázquez A Segura-Pacheco B Dueñas-Gonzalez A 《Electrophoresis》2005,26(6):1057-1062
The determination of the relative methylation in DNA tumor samples, in order to evaluate the activity of some anti-cancer drugs, has become a very important issue in the clinical field. Capillary electrophoresis (CE) applications in this area have been done previously but no good separation for model samples or tumor samples has been reported. In this work, the CE conditions have been optimized in order to obtain baseline separation and efficient peaks for cytosine and 5-methylcytosine in both, standard mixtures and actual tumor samples; other bases (adenine, uracil, guanine, and thymine) have also been integrated in the optimization studies. More efficient peaks and shorter analysis time compared with the already reported conditions have been obtained employing a fused-silica capillary (75 microm inner diameter) of 44.5 cm effective length, 20 mM carbonate buffer (pH 9.6) plus 80 mM sodium dodecyl sulfate, a separation voltage of 20 kV, and detection at 223 nm. 相似文献
106.
The role of irradiation induced defects and temperature in the conducting properties of single-walled (10, 10) carbon nanotubes has been analyzed by means of a first-principles approach. We find that divacancies modify strongly the energy dependence of the differential conductance, reducing also the number of contributing channels from two (ideal) to one. A small number of divacancies (5-9) brings up strong Anderson localization effects and a seemly universal curve for the resistance as a function of the number of defects. It is also shown that low temperatures, about 15-65 K, are enough to smooth out the fluctuations of the conductance without destroying the exponential dependence of the resistivity as a function of the tube length. 相似文献
107.
This communication compares the accuracy of a micro open parallel plate system (microOPPS) with a conventional packed column for predicting isotherm data by using the H-root method (HRM). HRM is restricted to compounds obeying the Langmuir isotherm model. The performance of the two chromatographic systems was simulated by using comprehensive mathematical models. Operating conditions were varied and their effects on the accuracy of predictions was evaluated. Better accuracy in the isotherm predictions was obtained with the packed column due to its higher efficiency. However, good predictions can be obtained with the microOPPS with the advantage of significantly lower sample consumption. 相似文献
108.
M. Carmen Carrin Alberto Díaz Ana Guerrero Flix A. Jaln Blanca R. Manzano Ana Rodríguez Rowena L. Paul John C. Jeffery 《Journal of organometallic chemistry》2002,650(1-2):210-222
New cationic 2-Me-allylpalladium complexes were prepared with the N,N-donor chelate ligands bis(pyrazol-1-yl)(R)methane (R=anisol-2-yl, bpzmArOMe; 2-hydroxyphenyl, bpzmArOH) and bis(3,5-dimethylpyrazol-1-yl)(R)methane (R=anisol-2-yl, bpz*mArOMe; cyclohexyl, bpz*mCy and ferrocenyl, bpz*mFc). The bpz′mR ligands adopt a rigid boat conformation after coordination to the Pd center and the R group is in the axial position of the metallacycle. The new complexes exhibit two isomeric forms in solution that differ in the relative orientation of the 2-Me-allyl group with respect to the bpz′mRPd fragment. The fluxional behavior of the new complexes, mainly in the context of the isomerization process, has been analyzed. Conclusions concerning the influence on this isomerization of the R group and the pyrazole substituents in positions 3 and 5 are discussed. The isomerization process was found to be affected by the presence of coordinating anions (Cl−) or by a change in the complex concentration. The molecular structures of the complexes [Pd(η3-2-Me-C3H4)(bpzmArOMe)]TfO and [Pd(η3-2-Me-C3H4)(bpz*mCy)]TfO have been determined by X-ray diffraction studies. 相似文献
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110.