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141.
Quéléver G Kachidian P Melon C Garino C Laras Y Pietrancosta N Sheha M Louis Kraus J 《Organic & biomolecular chemistry》2005,3(13):2450-2457
Inhibition of gamma-secretase, one of the enzymes responsible for the cleavage of the amyloid precursor protein (APP) to produce pathogenic Abeta peptides, is an attractive approach for the treatment of Alzheimer's disease. We designed a gamma-secretase inhibitor bearing an ascorbic acid moiety which allows a specific delivery of the drug to the brain. Through, on the one hand, Abeta peptide production measurements by specific in vitro assays (gamma-secretase cell free assay and cell based assay on HEK 293 APP transfected cells) and on the other hand through pharmacokinetic studies on animal models, the new inhibitor shows a good pharmacokinetic profile as well as a potent gamma-secretase inhibitory activity in vitro. From the obtained results, it is expected that drug will be mainly delivered to the CNS with a low diffusion in the peripheral tissues. Consequently the side effects of this gamma-secretase inhibitor on the immune cells could be reduced. 相似文献
142.
Clinoptilolite-supported TiO2 (TiO2/CPMOCVD) has been synthesized by metal organic chemical vapor deposition method (MOCVD). Titanium precursor was evaporated at 110 °C under nitrogen flow rate to promote the surface interaction between titanium species and clinoptilolite. The effect of titanium precursor on the crystalline structure and the surface area of clinoptilolite were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and Brunauer–Emmett–Teller measurement. XRD and SEM results indicate that TiO2 precursor interacted with the support, decreasing the crystallinity of the clinoptilolite. The analysis by FT-IR spectroscopy further confirms that the titanium species were bound to clinoptilolite through Ti–O–Si bonds. The TiO2/CPMOCVD catalyst showed a mesoporous structure with the distribution of pores in several dimensions 3.7–7.1 nm, with high specific surface area (~ 471 m2/g). MOCVD improved the adsorption capacity of the catalyst surface towards the pollutants. TiO2/CPMOCVD particles turn yellow after adsorption of salicylic acid. The development of the yellow color is a clear indication of the formation of charge transfer titanium (IV) salicylate surface complex. Photocatalytic decomposition of SA in aqueous solution was carried out using TiO2/CPMOCVD. Experimental results revealed that TiO2/CPMOCVD required shorter irradiation time (120 min) for complete decomposition of SA than commercial P25 Degussa and TiO2/CPimp (clinoptilolite-supported TiO2 using impregnation method). The TiO2/CPMOCVD can be recycled at least four times without loss in activity, indicating their magnificent stability. 相似文献
143.
Several pyrazolo[3,4-b]pyridine (3,4) and pyrazolo-[3,4-d]pyrimidine (5-13) derivatives were prepared using 5-amino-l-(5-ethyl-5H-1,2,4-triazino[5,6-b]-indol-3-yl)-lH-pyrazole-4-carbonitrile (2) . The pyridine derivatives 3 and 4 were obtained by reaction of 2 with malononitrile and ethyl cyanoacetate, respectively, while pyrimidine analogs 5-13 were synthesized cither by a one-step or multi-step sequence. 相似文献
144.
Younes Ben Taarit 《Chemical physics letters》1979,62(2):211-215
13C NMR spectroscopy was used to investigate the nature of carbon monoxide adsorbed on transition metal ions hosted in a synthetic faujasite type zeolite. The adsorbed CO species was characterised by a highly shielded carbon nucleus. Using the Pople approximation for the paramagnetic shielding term, the observed chemical shift was rationalised assuming the formation of a cationic carbonyl species with an appreciable electronic transfer from the carbon lone pair to the transition metal ion and negligible π back-bonding if at all. 相似文献
145.
Mehdi Bahrami Younes Hanifehpour Nadia Fattahi Saeid Taghavi Fardood Pegah Azimzadeh Asiabi 《Phosphorus, sulfur, and silicon and the related elements》2016,191(10):1368-1374
Protonation of the highly reactive 1:1 intermediate produced in the reaction between triphenylphosphine and an acetylenic ester by a N-H acid (4-phenylphthalazin-1(2 H)-one, 5,5-diphenylimidazolidine-2,4-dione) leads to the formation of a vinyltriphenylphosphonium salt. The cation of the salt undergoes an addition reaction with the counter anion in CH2Cl2 at room temperature to yield the corresponding stabilized phosphorus ylide. Elimination of triphenylphosphine from the stabilized phosphorus ylides leads to the formation of corresponding electron-poor N-vinylated heterocycles in moderate to high yields (67–95%). The reaction is completely regio- and stereoselective. 相似文献
146.
Taher Alizadeh Mahrokh Shokri Younes Hanifehpour Sang Woo Joo 《International journal of environmental analytical chemistry》2016,96(8):763-775
Graphene quantum dots (GQDs), synthesised via controlled carbonisation of citric acid, were reduced by hydrazine hydrate and then used as hydrogen cyanide (HCN) gas sensors. Checking of the reduction step by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques revealed that most of the oxygen-containing functional groups were removed from the GQDs. It was observed the reduction process is necessary for sensitising of GQDs for HCN gas. The electrical resistance of the reduced GQDs was increased as a result of their exposure to HCN gas. Accepting a p-type semiconducting characteristic for GQD material, the above-mentioned behaviour suggested electron donation from HCN to GQD. The sensor response to HCN gas was reversible, suggesting a reversible adsorption/desorption phenomenon of HCN to the GQDs. The response as well as the recovery time of the sensor was different depending on the HCN concentration tested. The developed sensor showed linear HCN response from 1 to 100 ppm. The detection limit of the sensor was estimated to be 0.6 ppm (S/N). Relative standard deviation f HCN determination by the developed sensor was calculated to be 5.7% (n = 4, [HCN] = 50 ppm). The sensor response was did not vary significantly within 6 months. 相似文献
147.
Shaaban K. Mohamed Sabry H. H. Younes Eman M. M. Abdel‐Raheem Peter N. Horton Mehmet Akkurt Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(1):57-62
Pyrazolidine‐3,5‐diones and their derivatives exhibit a wide range of biological activities. Seeking to explore the effect of combining a hydrocarbyl ring substituent, as present in sulfinpyrazone (used to treat gout), with a chlorinated aryl ring, as present in muzolimine (a diuretic), we explored the reaction between 1‐phenylpyrazolidine‐3,5‐dione and 4‐chlorobenzaldehyde under mildly basic conditions in the expectation of producing the simple condensation product 4‐(4‐chlorobenzylidene)‐1‐phenylpyrazolidine‐3,5‐dione. However, the reaction product proved to be meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene), C26H20Cl2N4, and a tentative mechanism is proposed. Crystallization from ethanol produces two concomitant polymorphs, i.e. a triclinic form, (I), in the space group P, and a monoclinic form, (II), in the space group C2/c. In both polymorphs, the molecules lie across centres of inversion, but in (II), the molecules are subject to whole‐molecule disorder equivalent to configurational disorder with occupancies of 0.6021 (19) and 0.3979 (19). There are no hydrogen bonds in the crystal structure of polymorph (I), but the molecules of polymorph (II) are linked by C—H...π(arene) hydrogen bonds into complex chains, which are further linked into sheets by C—H...N interactions. 相似文献
148.
Davood Azarifar Younes Abbasi Omolbanin Badalkhani 《Journal of the Iranian Chemical Society》2016,13(11):2029-2038
Sulfonic acid-functionalized titanomagnetite (Fe3?x Ti x O4@SO3H) nanoparticles were prepared by grafting sulfonic acid groups on Fe3?x Ti x O4 nanoparticles. This new heterogeneous acid nanocatalyst demonstrated an efficient catalytic performance in the one-pot synthesis of dihydropyrimidin-2(1H)-one/thione derivatives under solvent-free conditions with high yields. The nanocatalyst could easily be separated from the reaction mixture simply by using an external magnet, recycled and reused for several times with no significant loss of catalytic activity. These nanoparticles were characterized by different physicochemical techniques, such as Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric and vibrating sample magnetometer (VSM) analyses. 相似文献
149.
Sakhri Nasreddine Menni Younes Chamkha Ali J. Lorenzini Giulio Ameur Houari Kaid Noureddine Bensafi Mohammed 《Journal of Thermal Analysis and Calorimetry》2021,145(6):3349-3358
Journal of Thermal Analysis and Calorimetry - Arid regions around the world are characterized by hard summer and winter seasons, which leads to thermal discomfort. The southwest of Algeria is... 相似文献
150.
Fernando A. Sigoli Younes Messaddeq Sidney J. L. Ribeiro 《Journal of Sol-Gel Science and Technology》2008,45(2):179-185
The sol–gel method combined with a spin-coating technique has been successfully applied for the preparation of rare-earth
doped silica:germania films used for the fabrication of erbium-doped waveguide amplifiers (EDWA), presenting several advantages
over other methods for the preparation of thin films. As with other methods, the sol–gel route also shows some drawbacks,
such as cracks related to the thickness of silica films and high hydrolysis rate of certain precursors such as germanium alkoxides.
This article describes the preparation and optical characterization of erbium and ytterbium co-doped SiO2:GeO2 crack-free thick films prepared by the sol–gel route combined with a spin-coating technique using a chemically stable non-aqueous
germanium oxide solution as an alternative precursor. The non-crystalline films obtained are planar waveguides exhibiting
a single mode at 1,550 nm with an average thickness of 3.9 μm presenting low percentages of porosity evaluated by the Lorentz–Lorenz
Effective Medium Approximation, and low stress, according to the refractive index values measured in both transversal electric
and magnetic polarizations. Weakly confining core layers (0.3% < Δn < 0.75%) were obtained according to the refractive index difference between the core and buffer layers, suggesting that low-loss
coupling EDWA may be obtained. The life time of the erbium 4I13/2 metastable state was measured as a function of erbium concentration in different systems and based on these values it is
possible to infer that the hydroxyl group was reduced and the formation of rare-earth clusters was avoided. 相似文献