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51.
M. Kamal I. K. Battisha M. A. Salem A. M. S. El Nahrawy 《Journal of Sol-Gel Science and Technology》2011,58(2):507-517
A sol–gel process for producing monolithic silica–phosphate (SiO2–P2O5) system different concentrations of P2O5, starting with tetra-ethoxysilane TEOS, and triethyl-phosphate as sources of SiO2 and P2O5 was performed. The gels were heat-treated at temperatures ranging from 100 up to 900 °C. The structural and chemical analyses
of the samples were determined by using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). It was
found from the XRD that the existence of phosphorus enhances the crystallization of silica gel, while the FTIR indicated the
main functional groups of silica–phosphate. It is important to study the effect of hydroxyl in silica–phosphate glass. The
results obtained are promising to use the prepared samples in a variety of applications, ranging from traditional application
such as lighting products) to the modern application (such as optical fibers. Optical studies were measured by using the spectrophotometer
in wavelength range 0.2–2.5 μm. The refractive index (n) was calculated for the prepared samples, it was found to be strongly affected by structural rearrangement resulting from
the elimination of the solvent and the Si–OH, Si–O–Si and Si–O–OH bonding by phosphate and aluminum and it increases by increasing
phosphate concentrations. The weight losses have investigated for prepared samples. 相似文献
52.
Chu TY Lu J Beaupré S Zhang Y Pouliot JR Wakim S Zhou J Leclerc M Li Z Ding J Tao Y 《Journal of the American Chemical Society》2011,133(12):4250-4253
A new alternating copolymer of dithienosilole and thienopyrrole-4,6-dione (PDTSTPD) possesses both a low optical bandgap (1.73 eV) and a deep highest occupied molecular orbital energy level (5.57 eV). The introduction of branched alkyl chains to the dithienosilole unit was found to be critical for the improvement of the polymer solubility. When blended with PC(71)BM, PDTSTPD exhibited a power conversion efficiency of 7.3% on the photovoltaic devices with an active area of 1 cm(2). 相似文献
53.
Eljazi Salem Najoua Gamara 《Calculus of Variations and Partial Differential Equations》2011,42(1-2):107-136
In this paper we consider the problem of prescribing the Webster scalar curvature on the three CR sphere of ${\mathbb{C}^{2}}$ . We use techniques related to the theory of critical points at infinity, and obtain existence results for curvature satisfying an assumption of Bahri?CCoron type. 相似文献
54.
A new series of 1,3-thiazole and benzo[d]thiazole derivatives 10-15 has been developed, characterized, and evaluated for in vitro antimicrobial activity at concentrations of 25-200 μg/mL against Gram+ve organisms such as methicillin-resistant Staphylococcus aureus (MRSA), Gram-ve organisms such as Escherichia coli (E. coli), and the fungal strain Aspergillus niger (A. niger) by the cup plate method. Ofloxacin and ketoconazole (10 μg/mL) were used as reference standards for antibacterial and antifungal activity, respectively. Compounds 11 and 12 showed notable antibacterial and antifungal activities at higher concentrations (125-200 μg/mL), whereas benzo[d]thiazole derivatives 13 and 14 were found to display significant antibacterial or antifungal activity (50-75 μg/mL) against the Gram+ve, Gram-ve bacteria, or fungal cells used in the present study. In addition, a correlation between calculated and determined partition coefficient (log P) was established which allows future development of compounds within this series to be carried out based on calculated log P values. Moreover, compounds 13 and 14 show that the optimum logarithm of partition coefficient (log P) should be around 4. 相似文献
55.
Quantitative and sensitive detection of rare mutations using droplet-based microfluidics 总被引:2,自引:0,他引:2
Pekin D Skhiri Y Baret JC Le Corre D Mazutis L Salem CB Millot F El Harrak A Hutchison JB Larson JW Link DR Laurent-Puig P Griffiths AD Taly V 《Lab on a chip》2011,11(13):2156-2166
Somatic mutations within tumoral DNA can be used as highly specific biomarkers to distinguish cancer cells from their normal counterparts. These DNA biomarkers are potentially useful for the diagnosis, prognosis, treatment and follow-up of patients. In order to have the required sensitivity and specificity to detect rare tumoral DNA in stool, blood, lymph and other patient samples, a simple, sensitive and quantitative procedure to measure the ratio of mutant to wild-type genes is required. However, techniques such as dual probe TaqMan(?) assays and pyrosequencing, while quantitative, cannot detect less than ~1% mutant genes in a background of non-mutated DNA from normal cells. Here we describe a procedure allowing the highly sensitive detection of mutated DNA in a quantitative manner within complex mixtures of DNA. The method is based on using a droplet-based microfluidic system to perform digital PCR in millions of picolitre droplets. Genomic DNA (gDNA) is compartmentalized in droplets at a concentration of less than one genome equivalent per droplet together with two TaqMan(?) probes, one specific for the mutant and the other for the wild-type DNA, which generate green and red fluorescent signals, respectively. After thermocycling, the ratio of mutant to wild-type genes is determined by counting the ratio of green to red droplets. We demonstrate the accurate and sensitive quantification of mutated KRAS oncogene in gDNA. The technique enabled the determination of mutant allelic specific imbalance (MASI) in several cancer cell-lines and the precise quantification of a mutated KRAS gene in the presence of a 200,000-fold excess of unmutated KRAS genes. The sensitivity is only limited by the number of droplets analyzed. Furthermore, by one-to-one fusion of drops containing gDNA with any one of seven different types of droplets, each containing a TaqMan(?) probe specific for a different KRAS mutation, or wild-type KRAS, and an optical code, it was possible to screen the six common mutations in KRAS codon 12 in parallel in a single experiment. 相似文献
56.
The kinetics of H2O2 decomposition have been investigated using ZrO2 supported with transition metal ions including CuII, AgI, HgII, CoII, MnII, NiII and FeIII. At pH = 6.8, the reaction rate exhibits a first order dependence on the initial H2O2 concentration at low concentrations. The order of activity of the different catalysts is strongly dependent on the [H2O2]0 used. The reaction proceed via the formation of the peroxo-intermediate which has an inhibiting effect on the reaction rate. The rate increases with increasing pH, and attains a limiting rate at higher pH's. A reaction mechanism is proposed involving liberation of HO2 radicals from the peroxo-intermediate as the rate-determining step. 相似文献
57.
Jamel Salem Jacques Walrand Ghislain Blanquet 《Journal of Molecular Spectroscopy》2005,232(2):247-254
Pressure broadening of phosphine lines by helium and argon at room temperature has been experimentally investigated by high-resolution diode-laser spectroscopy. The broadening coefficients are measured for 38 transitions of PH3 in the QR branch of the ν2 band and in the PP and RP branches of the ν4 band. The recorded lines with J values ranging from 3 to 14 and K from 0 to 10 are located between 1062 and 1094 cm−1. The retrieval of the collisional widths is carried out by fitting each spectral line with a Voigt profile, a Rautian profile and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. They are also calculated on the basis of a semiclassical model involving the atom-atom Lennard-Jones potential. The theoretical results are in reasonable agreement with the experimental data and reproduce the J and K dependencies of the broadenings. 相似文献
58.
Summary Exact results on the single-spin-flip Glauber dynamics of six-coupled random field Ising spins with the coordination number
of four are presented. Two distributions of random fields (RF), binary (BD) and Gaussian (GD) ones, are investigated. The
effects of the static magnetic field are discussed. In the zero-magnetic-field case, the number of diverging relaxation times
is equal to the number of energy minima minus one. This rule breaks in the presence of a magnetic field. The longest relaxation
times in the absence of the field verify the Arrhenius law with the energy barrier determined by the energy needed to invert
the ground-state spin configuration. At low temperature, according to the Arrhenius law, the spectrum of relaxation times
shows a two-peaked distribution on a logarithmic scale. In the GD case of RF, the energy barrier distribution is continuous,
while it is quasi-discrete in the BD case. 相似文献
59.
S. A. Salem 《Czechoslovak Journal of Physics》2006,56(6):601-617
In this paper, we determined a numerical solution of the Navier-Stokes equations for the flow of incompressible fluid inside
the contraction geometry. The governing equations are written in the vorticity-stream function formulations. The numerical
solution is based on a technique of automatic numerical generation of a curvilinear coordinate system by transforming the
governing equation into the computational plane. The transformed equations are approximated using central differences and
solved simultaneously by the alternating direction implicit method and successive over relaxation iteration method. 相似文献
60.
Stereoscopic imaging and reconstruction technique is introduced to reconstruct the flame structures that are subject to acoustic excitation. The laminar diffusion flame under investigation was created in a cylindrical tube and excited by a loudspeaker. Stereo images were taken at a shutter speed of 1/10000th second using a ‘stereo camera’ and the depth cue of the flame structures along the camera viewing direction were then computed using machine vision methodology. By visualizing the computed three-dimensional flame models, as well as judging the corresponding attribute such as surface gradient, the understanding of the flame and acoustic wave interaction could be improved. 相似文献