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排序方式: 共有140条查询结果,搜索用时 15 毫秒
111.
Akbar Heydari Samad Khaksar Hamid Reza Bijanzadeh 《Journal of fluorine chemistry》2009,130(7):609-5476
Hantzsch 1,4-dihydropyridine, polyhydroquinoline and 1,8-dioxodecahydroacridines derivatives were synthesized in excellent yields in trifluoroethanol (TFE). The solvent (TFE) can be readily separated from reaction products and recovered in excellent purity for direct reuse. 相似文献
112.
Lilia C. Courrol Izilda M. Ranieri Snia L. Baldochi Ricardo E. Samad Anderson Z. de Freitas Larcio Gomes Nilson D. Vieira Jr. 《Optics Communications》2007,270(2):340-346
In this work, we report the influence of the presence of photochromic and color centers in the photobleaching of thulium ions blue emission in YLF (YLiF4) crystals doped with 1 mol% Tm (3+). The samples were irradiated at room temperature both with electron beam and high intensity ultrashort pulses from a Ti:Sapphire CPA laser system. In both irradiations the production of photochromic and color centers was observed via the absorption bands in the UV and visible ranges. Pure LiF and pure and oxygen doped YLF crystals were used to identify the color centers produced and their optical properties. From a phenomenological model it was possible to study the interaction between color centers and thulium ions, and their effect in photobleaching and photodarkening behaviors. Finally, the blue up laser level population was computed using a rate equation analysis. 相似文献
113.
Faiza?Zarif Sajid?Rauf Muhammad?Zahid?Qureshi Noor?Samad?Shah Akhtar?HayatEmail author Nawshad?MuhammadEmail author Abdur?Rahim Mian?Hasnain?Nawaz Muhammad?Nasir 《Mikrochimica acta》2018,185(6):302
Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30–300 μM H2O2 concentration range, and the detection limit is 0.15 μM. 相似文献
114.
Akbar Heydari Samad Khaksar Maryam Esfandyari Mahmoud Tajbakhsh 《Tetrahedron letters》2007,48(7):1135-1138
A simple and convenient procedure for direct reductive amination of aldehydes and ketones with sodium borohydride is described. The reaction has been carried out in methanol in the presence of a catalytic amount of H3PW12O40 (0.5 mol %). α,β-Unsaturated aldehydes and ketones can be easily converted into the corresponding allyl alcohols by reaction with H3PW12O40 (0.5 mol %)/NaBH4. 相似文献
115.
Fifteen new chromophoric chain β‐aryl substituted butadienyl‐benzothiazole asy‐cyanine colorants are synthesized by condensing substituted 3‐isopropylbenzothiazolium iodides and 4‐dimethylaminostyrylphenyl ketones using alkaline ethanolic DMF solution. The colorants show bathochromic shifts in comparison with unsubstituted analogues and styryl analogues but hypsochromic shifts when compared to 3‐methylbenzothiazolium analogues. The highly purified samples are screened in vitro against gram positive and gram negative microbes using Disc diffusion technique and found to be mildly active against some of them. 相似文献
116.
Ali Souldozi Samad Karami 《Phosphorus, sulfur, and silicon and the related elements》2016,191(6):867-870
(N-isocyanimino)triphenylphosphorane, 2-pyridinecarbaldehyde, and aromatic carboxylic acids (benzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-methoxybenzoic acid, 1-naphthoic acid, and 2-naphthoic acid) undergo a 1:1:1 addition reaction under mild conditions in a one-pot reaction to afford novel series of fully substituted 1,3,4-oxadiazole derivatives in good yields. 相似文献
117.
Marika Di Berto Mancini Marianna Bernardini Beniamin Emanuel Birzu Arianna De Santis Prof. Dr. Stefano Di Stefano Federico Frateloreto Daria Khaksar Prof. Dr. Andrea Lapi Dr. Giorgio Olivo Prof. Dr. Osvaldo Lanzalunga 《European journal of organic chemistry》2023,26(30):e202300360
The chemoselectivity between S-oxidation and hydrogen atom transfer (HAT) from C−H bonds has been investigated in the oxidations of a series of aryl sulfides, alkyl aromatic compounds and benzylic alcohols promoted by the iron(IV)-oxo complex [(N4Py)FeIV(O)]2+ (N4Py: N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)-methylamine) either alone or in the presence of the N-hydroxyphthalimide (NHPI) mediator via kinetic and product studies. Kinetic analyses indicate a generally higher reactivity of [(N4Py)FeIV(O)]2+ for S-oxidation process while HAT is favored in the reactions promoted by phthalimide-N-oxyl radical (PINO) deriving from NHPI oxidation. Product analysis in intermolecular competitive oxidations confirms the kinetic results with sulfoxides obtained as major products in the oxidation promoted by [(N4Py)FeIV(O)]2+. Conversely, when NHPI is employed as a mediator, significant differences in terms of chemoselectivity are observed, and HAT-derived products are obtained in higher yields which translate into an inversion of selectivity in the case of the substrates containing activated C−H bonds like diphenylmethane, triphenylmethane and benzylic alcohols. A similar change of chemoselectivity is also observed in the oxidation of aromatic substrates containing both a sulfur atom and α to OH benzylic C−H bonds, with the sulfoxide product more abundant in the absence of NHPI and carbonyl products prevailing with the [(N4Py)FeIV(O)]2+/NHPI system. 相似文献
118.
Faezeh Fathi Samad N. Ebrahimi Ana I. G. Valado Nelson Andrade Anabela S. G. Costa Cludia Silva Alireza Fathi Peyman Salehi Ftima Martel Rita C. Alves Maria Beatriz P. P. Oliveira 《Molecules (Basel, Switzerland)》2021,26(19)
Gunnera tinctoria, an underexplored invasive plant found in Azores, Portugal, was studied regarding its nutritional, antioxidant, and antitumoral properties. Higher antioxidant activity was found in baby leaves, followed by adult leaves and inflorescences. A phenolic fraction of the plant was enriched using adsorbent resin column chromatography (DiaionTM HP20LX, and Relite EXA90). Antitumoral effects were observed with the enriched fractions in breast (MCF-7) and pancreatic (AsPC-1) cancer cell lines, being more pronounced in the latter. To improve protection and membrane absorption rates of phenolic compounds, nano-phytosomes and cholesterol-conjugated phytosomes coated with natural polymers were loaded with the enriched fraction. The particles were characterized, and their physiochemical properties were evaluated and compared. All samples presented anionic charge and nanometer size in relation to the inner layer and micrometer size regarding the external layers. In addition, the molecular arrangement of phenolics within both types of phytosomes were studied for the first time by molecular docking. Polarity and molecular size were key factors on the molecular arrangement of the lipid bilayer. In conclusion, G. tinctoria showed to be an interesting source of nutrients and phenolic compounds with anti-tumoral potential. Moreover, phytosome loading with these compounds can increase their stability and bioavailability having in view future applications. 相似文献
119.
120.
Mechanical joints such as bolted or pinned connections are commonly used to fasten mechanical or structural members together. Inadequate knowledge of the stresses at the edge of the loaded holes can render it difficult to stress analyze such mechanical fasteners theoretically or numerically. Thermoelastic stress analysis (TSA) is utilized here to analyze a plane-stressed pin-loaded plate. The approach combines the recorded temperature information with an Airy stress function, plus imposes the traction-free conditions on the non-contacting edge of the hole and on the external boundaries of the plate. Individual components of stress are determined full-field as well as on the pin-plate interface. In addition to agreeing with the frequently assumed interface contact stresses in mechanical connections having zero clearance, the TSA results satisfy force equilibrium, are compatible with residual markings on the contacted surfaces of the pin and the hole, and correlate with FEM predictions. Significant advantages of TSA here include neither needing to know the elastic modulus nor to differentiate the recorded information. 相似文献