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排序方式: 共有340条查询结果,搜索用时 31 毫秒
81.
82.
M. Abdelhamid S. Grassini E. Angelini G.M. Ingo M.A. Harith 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
Laser-induced breakdown spectroscopy (LIBS) is a relatively novel technique that is being applied to the characterization of interfaces in layered materials as an alternative to other classic surface analytical techniques. 相似文献
83.
Tarek M. Trad Kyle B. Donley David C. Look Kurt G. Eyink David H. Tomich Curtis R. Taylor 《Journal of Crystal Growth》2010,312(24):3675-3679
ZnO nanoparticles as small as 80 nm were successfully synthesized using a modified vapor phase transport (VPT) process at substrate temperatures as low as 222 °C. Particle size distribution and morphology were characterized by scanning electron microscopy and atomic force microscopy. Energy dispersive X-ray spectroscopy and X-ray diffraction indicate the synthesis of high quality crystalline ZnO structures. Low temperature (4.2 K) photoluminescence (PL) spectroscopy was used to characterize the optical quality of the nanoparticles. Ultraviolet emission and a nanostructure specific feature at 3.366 eV are strong in the PL spectra. The 3.366 eV feature is observed to predominate the spectrum with decrease in particle size. This size effect corroborates the luminescence as a nanostructure-specific surface related exciton feature as previously speculated in the literature. In addition, self-assembled ZnO mesoparticles (>100 nm) were realized by increasing the growth time. Low growth temperatures of the particles allow for their potential utilization in flexible organic hybrid optoelectronics. However, this work focuses mainly on the modified synthesis and optical characterization of nanoparticles. 相似文献
84.
Teresa López‐León Dr. Delfina Bastos‐González Dr. Juan Luis Ortega‐Vinuesa Dr. Abdelhamid Elaïssari Prof. 《Chemphyschem》2010,11(1):188-194
Poly(N‐isopropylacrylamide) (PNIPAM) is well known to exhibit reentrant behavior or cononsolvency in response to the composition of a mixed solvent consisting of water and a low‐chain alcohol. Since the solvent structure plays an important role in this phenomenon, the presence of structure‐breaking/structure‐making ions in solution is expected to have a dramatic effect on the cononsolvency of PNIPAM. The present work examines the way that the presence of different salts can modify the reentrant‐phase diagram displayed by a cationic PNIPAM microgel in the mixed ethanol/water solvent. The effects of four Hofmeister anions—SO42?, Cl?, NO3? and SCN?—with different abilities to modify the solvent structure are analyzed. The species with kosmotropic or structure‐making character show a clear competition with ethanol for the water molecules, intensifying the nonsolvency of the PNIPAM with the EtOH volume fraction (?e). However, striking results are found with the most chaotropic or structure‐breaking anion, SCN?. In contrast to what happens in water‐rich solutions, the presence of SCN? in alcohol‐rich solvents enhances the solubility of the polymer, which macroscopically results in the microgel swelling. Moreover, this ion displays great stabilizing properties when ?e> is 0.2. These results have been explained by considering how chaotropic or structure‐breaking ions interact with water and ethanol molecules. 相似文献
85.
Abdou O. Abdelhamid Ahmed H. Elghandour Sayed A. Ahmed Yasser H. Zaki 《Journal of heterocyclic chemistry》2006,43(2):249-254
86.
We present a sensitive measurement of the dissipation and the effective viscosity of a simple confined liquid (octamethylcyclotetrasiloxane) using an atomic force microscope. The experimental data show that the damping and the effective viscosity increase and present oscillations as the gap between the cantilever tip and the surface is diminished. To our knowledge, the damping and the viscosity modulation are reported here with such good accuracy for the first time. Such an experimental result is different from what has been reported earlier where only a continuous increase of the damping and the viscosity are observed. 相似文献
87.
Mediterranean Journal of Mathematics - We consider degenerate parabolic equations with nonsmooth right hand parts of a special form. We derive unique solvability of the Cauchy problem and an... 相似文献
88.
Marzouki H Khaldi A Falconieri D Piras A Marongiu B Molicotti P Zanetti S 《Natural product communications》2010,5(12):1955-1958
The essential oils and supercritical CO2 extracts of wild Daucus carota L. subsp. carota from two different sites in Tunisia were investigated. The main components of the essential oil of the flowering and mature umbels with seeds from Sejnane were eudesm-7(11)-en-4-ol (8.2 - 8.5%), carotol (3.5 - 5.2%), sabinene (12.0 -14.5%), a-selinene (7.4 - 8.6) and 11-alpha-(H)-himachal-4-en-1-beta-ol (12.7 - 17.4%), whereas the oils from Tunis were predominantly composed of elemicin (31.5 - 35.3%) and carotol (48.0 - 55.7%). The antimicrobial activity of the essential oils were assayed by using the broth dilution method on Escherichia coli ATCC 35218 and Staphylococcus aureus ATCC 43300, and clinical strains of Candida albicans and C. tropicalis 1011 RM. The MIC values obtained were all > 2.5% (v/v). 相似文献
89.
Abdelhamid Meziani 《Journal of Geometric Analysis》1999,9(2):301-315
This paper deals with the integrability problem for structures on the sphere S2 which are elliptic on the upper and lower hemispheres, and which are given by a simple fold on the equator. Criteria for
standardness are given. Existence and factorization of first integrals are studied. 相似文献
90.
Nabil M. Hassan Abdelgawad A. Fahmi Fouad F. Abd-El-Mageid Abdou O. Abdelhamid 《中国化学会会志》1996,43(6):493-496
Several new pyrazolo[5,I-c]triazine, selenadiazoline, thiadiazoline, selenadiazolo[3,2-a]quitiazolone, and arylazothiazole derivatives were synthesised by the reaction of hydrazonoyl halides with different reagents. The structure of new heterocycles were assigned on the basis of their elemental analysis, spectral data, and alternate synthesis whenever possible. 相似文献