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排序方式: 共有263条查询结果,搜索用时 15 毫秒
241.
Goswamee R.L. Bosc F. Cot D. Mansouri A. El Lopez M. Morato F. Ayral A. 《Journal of Sol-Gel Science and Technology》2004,29(2):97-105
Two types of nanocomposites and nanoporous powders and related coatings were prepared by the sol-gel route. These silica-based materials contain dispersed reactive oxides, ZnO and ZnCr2O4, respectively. Experiments evidenced their ability of reversible chemisorption of H2S as ZnS. Their attractive porous characteristics (small pore size 2–2.5 nm, high specific surface area 900–1100 m2· g–1, high porosity 50–60%) are not significantly modified during the successive treatments of H2S chemisorption and oxide regeneration. These preliminary results encourage to pursue this study which aims at the preparation of nanofilters for the desulfurization of gas mixtures. 相似文献
242.
J. Alizon J.P. Battut J. Dupuis H. Robert I. Mansouri D. Avignant 《Solid State Communications》1983,47(12):969-972
Spin-lattice relaxation times in the laboratory Tl and rotating frames Tl? for both 19F and 205Tl nuclei were measured as a function of temperature. Comparison of the temperature dependence of longitudinal NMR relaxation rates of both 19F and 205Tl suggests that Tl+ ions are more mobile than F? ones at high temperatures. Furthermore Fourier transform experiments show that two kinds of Tl+ ion can be distinguished at high temperatures, one of them being more mobile than the other one and probably responsible for the ionic conductivity of this material. 相似文献
243.
Ahmed E Malik A Afza N Riaz N Anis I Sharif A Farheen S Lodhi MA Choudhary MI 《Natural product research》2007,21(1):69-75
Haloxylase, the triglyceride (1), unsaturated fatty acid (2), and saturated fatty acid methyl ester (3) have been isolated from the chloroform-soluble fraction of Haloxylon recurvum. Their structures have been elucidated through spectroscopic studies and chemical transformation. All these compounds showed significant inhibitory activity against the enzyme chymotrypsin in a concentration dependent fashion. 相似文献
244.
Present study evaluates the effects of photodynamic therapy (PDT) with aminolevulinic acid (5-ALA) as photo sensitizer using Human embryonic kidney (HEK293T) cell line as an experimental model. Porphyrins derivatives are used as active cytotoxic antitumor agents in PDT. Above mentioned cell line were irradiated with red light (a diode laser, λ = 635 nm) at different doses (0–160 J/cm2) of light. The influence/effectiveness of incubation time, various concentrations of aminolevulinic acid (5-ALA) and light doses on the cellular viability was studied. HEK293T cells were deliberated by exposing the ALA-PpIX (0–1000 μg/ml) of concentrations. The optimal uptakes of photosensitizer (PS) in cell lines were investigated by means of spectro photo metric measurements. Cells viability was determined by means of neutral red assay (NRA). It was observed that alone, neither photosensitizer nor light dose have significant effect on cells viability, but optimal concentration of PS along with suitable dose of light exhibit effective impact on the viability of cell. Our results showed that light doses of 40 J/cm2 demonstrates effective PDT outcome for HEK293T cell line when incubated with 400 μg/ml, with wrapping up view that HEK293T cell line is very sensitive to ALA-mediated PDT as compared to cell line published in our data. At the end results has been verified by using reactive oxygen species (ROS) measure test. 相似文献
245.
Multicomponent spectrometric analysis of riboflavin and photoproducts and their kinetic applications
Muhammad A. Sheraz Sadia H. Kazi Sofia Ahmed Kiran Qadeer Marium F. Khan Iqbal Ahmad 《Central European Journal of Chemistry》2014,12(6):635-642
Riboflavin (RF) is a light sensitive compound and is known to form a number of photoproducts. These photoproducts possess the same nucleus and may interfere in the analysis of RF by UV and visible spectrometry. Therefore, it is necessary to apply the methods of multicomponent spectrometric analysis to quantify the vitamin and its photoproducts accurately. Such methods are useful in the study of the kinetics of photodegradation reactions of RF to obtain accurate and reliable results. Any interference in these methods due to linear or nonlinear irrelevant absorption of the minor unknown products can be accounted for by the application of appropriate correction procedures prior to kinetic treatment. Various factors affecting the accuracy, precision and selectivity of these analytical procedures are also discussed. This review highlights the principles and applications of multicomponent spectrometric methods and their application to the simultaneous determination of RF and its major photoproducts in degraded solutions to evaluate the kinetics of degradation. 相似文献
246.
Ayesha Murtaza Zia Ulhaq Bahareh Shirinfar Sadia Rani Samina Aslam Guilherme M. Martins Nisar Ahmed 《Chemical record (New York, N.Y.)》2023,23(10):e202300119
C−H bond functionalization generates molecular complexity in single-step transformation. However, the activation of C−H bonds requires expensive metals or stoichiometric amounts of oxidizing/reducing species. In many cases, they often require pre-functionalization of starting molecules. Such pre-activating measures cause waste generation and their separation from the final product is also troublesome. In such a scenario, reactions activating elements generating from renewable energy resources such as electricity and light would be more efficient, green, and cost-effective. Further, incorporation of growing flow technology in chemical transformation processes will accelerate the safer accesses of valuable products. Arenes & heteroarenes are ubiquitous in pharmaceuticals, natural products, medicinal compounds, and other biologically important molecules. Herein, we discussed enabling tools and technologies used for the recent C−H bonds functionalization of arenes and heteroarenes. 相似文献
247.
Ounissa Kebiche-Senhadji Lynda Mansouri Sophie Tingry Patrick Seta Mohamed Benamor 《Journal of membrane science》2008,310(1-2):438-445
PIMs have been involved as affinity membranes for recovery of metals (Cd, Pb, Zn) by facilitated transport from aqueous solutions under different speciation forms, either anionic or cationic. The motivation of this work is to compare the efficiency of the recovery process in the case of Cd(II) using extractants such as D2EHPA and Aliquat 336 that can form complexes with the cation Cd2+ or the anions CdCl3− and CdCl42−, respectively. The maximal Cd(II) recovery factors obtained in 8 h are 97.5% and 91.8% with D2EHPA and Aliquat 336, respectively. Although the transport fluxes with both carriers are not strongly different (ca. 2 μmol m−2 s−1), the recovery process in case of mixture of metals is better achieved with Aliquat 336. PIMs have shown a very good stability and a constancy of the transmembrane transport flux over 12 replicate measurements, each one lasting for 8 h repeated every 24 h. 相似文献
248.
We consider the problem of computing heat kernel small-time asymptotics for hypoelliptic Laplacians associated to left-invariant sub-Riemannian structures on unimodular Lie groups of type I. We use the non-commutative Fourier transform of the Lie group together with perturbation theory for semigroups of operators in deriving these asymptotics. We illustrate our approach on the example of the Heisenberg group, and, as an application, we compute the short-time behaviour of the hypoelliptic heat kernel on the step 3 nilpotent Cartan and Engel groups, for which no closed-form expression for the hypoelliptic heat kernel is yet known. 相似文献
249.
We are interested in a class of linear bilevel programs where the upper level is a linear scalar optimization problem and the lower level is a linear multi-objective optimization problem. We approach this problem via an exact penalty method. Then, we propose an algorithm illustrated by numerical examples. 相似文献
250.
A ZnO thin film transistor (TFT) was fabricated on a SiO2/Si substrate by sol-gel method. Electrical characteristics of the zinc oxide transistor under various illuminations were analyzed. We have developed a method to extract the TFT parameters under dark and under UV illuminations. This component requires an ohmic source and drain contacts for ideal operation. The performance of electronic-device is often limited by injection. In many real situations, the injection of charge carriers from metals into semiconductors is non-linear. This paper deals with the effects of non-ohmic contacts on the modeling of ZnO thin film transistor and gives specific rules on how to extract the real transistor parameters using only electrical measurements under dark and illumination.We have extracted the TFT parameters using developed method from output characteristics under dark and UV illumination. The drain current of the ZnO thin film transistor under UV illumination is improved. We have demonstrated that the UV illumination reduce the total resistance and improve the performance of the transistor. 相似文献