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排序方式: 共有80条查询结果,搜索用时 15 毫秒
41.
42.
Saqlain A. Shah M.U. Hashmi A. Shamim 《Journal of magnetism and magnetic materials》2010,322(3):375-5218
Glass ceramics of the composition xZnO·25Fe2O3·(40−x)SiO2·25CaO·7P2O5·3Na2O were prepared by the melt-quench method using oxy-acetylene flame. Glass-powder compacts were sintered at 1100 °C for 3 h and then rapidly cooled at −10 °C. X-ray diffraction (XRD) revealed 3 prominent crystalline phases: ZnFe2O4, CaSiO3 and Ca10(PO4)6(OH)2. Vibrating sample magnetometer (VSM) data at 10 KOe and 500 Oe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. Nano-sized ZnFe2O4 crystallites were of pseudo-single domain structure and thus coercivity increased with the increase in crystallite size. ZnFe2O4 exhibited ferrimagnetism due to the random distribution of Zn2+ and Fe3+ cations at tetrahedral A sites and octahedral B sites. This inversion/random distribution of cations was probably due to the surface effects of nano-ZnFe2O4 and rapid cooling of the material from 1100 °C (thus preserving the high temperature state of the random distribution of cations). Calorimetric measurements were carried out using magnetic induction furnace at 500 Oe magnetic field and 400 KHz frequency. The data showed that maximum specific power loss and temperature increase after 2 min were 26 W/g and 37 °C, respectively for the sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and XRD results confirmed the growth of precipitated hydroxyapatite phase after immersion in SBF, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to the living tissues in physiological environment. 相似文献
43.
Meredith A. Matoian Richard Sweetman Emily C. Hall Shayna Albanese William B. Euler 《Journal of fluorescence》2013,23(5):877-880
Metal Enhanced Fluorescence (MEF) typically produces enhancement factors of 10 to 50. By using a polymer layer as the dielectric spacer enhancements as high as 1,600 can be observed. The effect occurs with a variety of different polymers and substrates, all of which act to trap light in the dielectric layer. This allows the fabrication of sensors with improved sensitivity as demonstrated for detection of trinitrotoluene (TNT). 相似文献
44.
I.R. Siddiqui RahilaShayna Shamim Pragati RaiShireen Malik A. WaseemAfaf A.H. Abumhdi 《Tetrahedron letters》2013
A new and convenient one-pot methodology for the reaction of N-methyl isatin, alkynes and phenacyl bromides to selectively afford spiro dihydrofuran oxindole derivatives catalyzed by indium bromide under ambient temperature conditions has been documented. The method has been applied for the synthesis of a range of compounds with variable functionalities in good to excellent yields (76–92%). The significant advantages of this protocol are highlighted by excellent yields, cleaner reaction profiles and avoidance of expensive catalysts. 相似文献
45.
This study was designed to isolate, characterise and explore in vitro antioxidant potential of compounds from the chloroform extract of Cedrus deodara wood belonging to Pinacae family. We have investigated the in vitro free radical scavenging activity of isolated compounds by measuring total antioxidant capacity (TAC) and reducing power ability. From the chloroform extract five sesquiterpenes namely atlantone, himaphenolone, atlantolone, deodardione and atlantone-2,3-diol were identified. Himaphenolone and deodardione from the chloroform extract of this plant have been isolated for the first time. A marked dose-dependent reducing power and strong TAC were found in favour of himaphenolone and atlantone-2,3-diol, respectively. Moreover, deodardione and atlantolone also exhibit good antioxidant potentials. However, atlantone has showed least antioxidant activity. In conclusion, the chloroform extract of C. deodara exhibited significant antioxidant potential mainly due to the presence of sesquiterpenes which may be responsible for various pharmacological activities of this plant. 相似文献
46.
Liaqat Ali Imtiaz Hussain Tania Shamim Rizvi Abdul Latif Khan Shaukat Shujah Jawahar Mohammed Salim Al‐Sahi Ahmed Al‐Harrasi Javid Hussain 《Helvetica chimica acta》2015,98(10):1462-1465
A new trihydroxy sesquiterpene, rel‐(1R,4aR,5S,6S,7S,8aR)‐decahydro‐6,8a‐dimethyl‐5‐(propan‐2‐yl)naphthalene‐1,6,7‐triol ( 1 ), has been isolated as a result of the phytochemical investigation on the CH2Cl2 extract of Teucrium mascatense. The structure elucidation of the new constituent was carried out by the combined use of 1D‐ (1H‐ and 13C‐NMR) and 2D‐NMR (HMBC and HSQC) spectroscopic analysis, along with mass spectrometric techniques. In addition to the new constituent 1 , the known metabolite 2 , previously isolated from Crataegus pinnatifida, was also identified. 相似文献
47.
Najeeb Ur Rehman Abdul Latif Khan Zahid Hassan Tania Shamim Rizvi Ahmed Al‐Harrasi Zabta Khan Shinwari Javid Hussain 《Helvetica chimica acta》2015,98(9):1240-1244
One new cyclopropyl‐triterpenoid ( 1 ), along with four known constituents including octacosan‐1‐ol ( 2 ), pentacosanoic acid ( 3 ), β‐sitosterol ( 4 ), and β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 5 ) were isolated from the aerial parts of Ochradenus arabicus for the first time. These compounds were isolated by repeated column chromatography followed by further purification through recycling HPLC. The structure of the new secondary metabolite 1 was established on the basis of UV, IR, 1D‐ (1H‐ and 13C‐) and 2D‐NMR (HMBC and HSQC), and MS spectral data. The molecular mass was determined by HR‐MS, and hence the molecular formula was deduced. The configurations of stereogenic centers in the molecule were assigned by NOESY experiments, along with biogenetic considerations. The structures of the known compounds were confirmed by comparison of their physical and spectroscopic data with those reported in literature. 相似文献
48.
Task specific [bmim]BF4 was found to be reusable, alternative, and effective reaction media for multicomponent synthesis of highly functionalized pyrroles. Generality of the procedure was established by synthesizing various pyrroles from wide range of aromatic/aliphatic amine, phenacyl bromide, and electrophilic alkynes by utilizing this protocol without any acid or metal catalyst. Ecocompatibility, short reaction time, excellent yield, recyclability of [bmim]BF4, low cost, easy work‐up, and mild reaction conditions are additional advantages of the procedure in the context of sustainable and green chemistry. 相似文献
49.
AbstractA simple, mild, straightforward, efficient and eco-friendly protocol has been developed for the synthesis of a series of α-aminonitriles via the one-pot three-component Strecker reactions between various aldehydes, amines and trimethylsilyl cyanide using a catalytic amount of mandelic acid as a naturally occurring, low-cost, efficient organo-catalyst under solvent-free conditions at room temperature. Under the same optimized conditions synthesis of α-aminophosphonates were also achieved via the one-pot three-component Kabachnik-Fields reactions of aldehydes, amines and triethyl phosphate. 相似文献
50.
Abdolahi Nafiseh Javan Masoud Bezi Katin Konstantin P. Soltani Alireza Shojaee Shamim Kaveh Sara 《Structural chemistry》2020,31(5):1959-1967
Structural Chemistry - Herein, we evaluated the adsorption of thiazole over the surface of BC2N nanotube using PBE and M06-2X functionals and 6-311G** standard basis set. We considered one and two... 相似文献