排序方式: 共有143条查询结果,搜索用时 15 毫秒
81.
R. G. Andrew R. E. Conrow J. D. Elliott W. S. Johnson S. Ramezani 《Tetrahedron letters》1987,28(52):6535-6538
Several (3S,4S)- and (3S,4R)-statine derivatives have been prepared by attack of nucleophiles on crystalline, epimeric N-BOC-lactams 7a and 7b. The key step in the synthesis of the lactams was the TiCl4-catalyzed coupling reactions of acetals derived from (R)-1,3-butanediol with allyltrimethylsilane.
Several enantiometrically pure (3S,4S- and (3S, 4R)-statine derivatives were made by sodium cyanide-catalyzed reaction of nucleophiles with the lactams 3a and 3b which were synthesized by the scheme 1 → 2 → 3. 相似文献
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83.
Optical properties of TiO2 nanowires, synthesized by two-step thermal evaporation process, have been studied experimentally and theoretically. Based on the theoretical method optical constants of nanowires have been calculated with the use of the effective medium approximation (EMA). As evidenced by X-ray diffraction patterns our synthesized nanowires, whose diameters and lengths were within the ranges of 50-90 nm and 500-1500 nm, respectively, were found to be crystalline rutile TiO2 with the major refraction being along the (1 1 0) direction. The experimental data of the reflectance of TiO2 nanowires has been obtained using spectrometer in wavelength 250-800 nm, and then, compared with the spectrum of reflectance predicted by the EMA theoretical model. Our measured experimental optical data has been found to be in good accord with our predicted results spectrum with the use of the EMA modeling; this agreement indicates that our estimation of the volume fraction from atomic force microscopy (AFM) data was accurate. 相似文献
84.
Parvin Ramezani Kharazi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1399-1403
Abstract Garlic antibiotic action is well known; it is reputed to offer protection against coronary thrombosis and atherosclerosis exhibiting antioxidant and anticancer effects. 1,2 In this work 1 H NMR and gas chromatography in conjunction with mass spectrometry have been used for the identification and determination of these compounds in two varieties of Iranian garlic [Allium sativum var. sativum (I) and Allium sativum var. holmense (II)]. The organosulfur compounds in (I) exhibiting a concentration higher than 1% are diallyl sulfide (1.3%), diallyl disulfide (8%), methyl allyl disulfide (19%), methyl allyl trisulfide (3.2%), diallyl trisulfide (5.5%), diallyl tetrasulfide (2%), 2,3-dimethyl thiophen (1.8%), 5-methyl-1,2,3-thiadiazol (5%), and 1,2-ditiolan-3-carboxilic acid (1.5%). The amount of organosulfur compounds in (II) are diallyl disulfide (2%), methyl allyl trisulfide (6.3%), diallyl tetrasulfide (5%), and cyclopentanthiol (2.5%). 相似文献
85.
Journal of Thermal Analysis and Calorimetry - An innovative modeling and optimizing of fire and water tube heat recovery steam generators (HRSG) for gas engine cogeneration plant are performed... 相似文献
86.
Elham Sameiyan Parirokh Lavaee Mohammad Ramezani Mona Alibolandi Zahra Khoshbin Prof. Khalil Abnous Dr. Seyed Mohammad Taghdisi 《Electroanalysis》2023,35(3):e202200243
In this study, a simple electrochemical sensing platform with the employment of a bivalent binding aptamer-cDNA probe (BBA-cDNA) structure is constructed for the detection of aflatoxin B1 (AFB1) as a mycotoxin. The BBA-cDNA structure is composed of two strands of aptamer (Apts) and their complementary strand (CS). Using a simple but accurate design, the presented measurement approach showed enhanced sensitivity and selectivity for AFB1 detection with a LOD of 0.1 ng/mL. The approach presented in this study can be applied to the development of biosensors for the measurement of various toxins by substituting the proper aptamers and complementary strands. 相似文献
87.
Mohammad Hossein Mashhadizadeh Soleyman Ramezani Abbas Shockravi Mahmood Kamali 《Journal of inclusion phenomena and macrocyclic chemistry》2013,76(3-4):283-291
Two new Ag(I) chemically modified carbon paste electrodes were prepared with comparative potentiometric study of 1,3,6,10,13-pentaaza-2,14-(2,6-pyridyl)-cyclotetradecane-4,12-dione (PPCT) and 1,3,6,9,11,12-pentaaza-2,13-(2,6-pyridyle)-bicycle[2,2,9]pentadecane-4,11-dione (PPBP) as ionophore. These sensors have been modified with sol–gel–Au nanoparticles to obtain a wide concentration range for potentiometric determination of Ag(I) in aqueous solutions. The sensors exhibit significantly enhanced selectivity toward Ag(I) ions over a wide concentration range of 4.0 × 10?9–2.2 × 10?2 and 2.2 × 10?7–2.0 × 10?2 mol L?1 with a lower detection limit of 2.5 × 10?9 and 2.0 × 10?7 mol L?1 for PPCT and PPBP modified electrodes respectively. The electrodes are highly selective to Ag(I) ions over a large number of mono, bi, and tri-valent cations. These electrodes were successfully used as indicator electrode for potentiometric determination of silver in sulphadiazine (burning cream) and radiological film. 相似文献
88.
Sakineh Asghari Fahimeh Molaee Samaneh Ramezani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1896-1904
Deoxybenzoin undergoes a smooth reaction with acetylenic esters in the presence of triphenylphosphine to produce phosphorus ylides. Only the tert-butyl phosphorus ylide undergoes an intramolecular Wittig reaction to produce highly strained cyclobutenes in boiling toluene, which spontaneously undergoes ring-opening reactions to produce highly functionalized 1,3-dienes. The unstable ylides undergo a 1,2-proton transfer and the loss of PPh3 to produce functionalized alkenes. 相似文献
89.
It is proved that the Cartesian product of an odd cycle with the complete graph on 2 vertices, is determined by the spectrum of the adjacency matrix. We also present some computational results on the spectral characterization of cubic graphs on at most 20 vertices. 相似文献
90.
An adsorbent catalyst was proposed to reduce the leaching of active species of the catalyst and enhance the kinetics of the oxidative desulfurization (ODS) reaction of dibenzothiophene (DBT) from model diesel fuel. By loading phosphotungstic acid (HPW) species onto a zirconium-modified hexagonal mesoporous silica (Zr-HMS), a novel catalyst was synthesized and utilized for the ODS process. An ultrafast ODS kinetics was specifically identified using 20%HPW/Zr-HMS as catalyst. Within 30 min, more than 95% of the 350 ppm DBT content of the model fuel was oxidized by H2O2. The synthesized catalyst retained its sulfur removal ability even after five subsequent ODS reactions and the leaching of HPW species was found to be suppressed successfully. Overall, this new reusable catalyst provided an alternative for highly efficient ultra-deep desulfurization process. 相似文献