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排序方式: 共有691条查询结果,搜索用时 15 毫秒
681.
Kumar R Shard A Bharti R Thopate Y Sinha AK 《Angewandte Chemie (International ed. in English)》2012,51(11):2636-2639
All in one: a tandem strategy has been developed wherein secondary aryl alcohols are directly coupled with aryl halides to provide stilbenoids through a dehydrative Heck sequence in the ionic liquid [hmim]Br, and with water as a by-product under microwave irradiation. Classical methods do not permit this sequence to proceed in one pot, and some methods require multiple steps. hmim=1-n-hexyl-3-methylimidazolium. 相似文献
682.
A mild and efficient synthesis of 1-aryl-1-fluoroethenes from benzothiazolyl (aryl)fluoromethyl sulfones and paraformaldehyde, under DBU- or Cs(2)CO(3)-mediated conditions at room temperature, is described. A comparable diethyl fluoro(naphthalen-2-yl)methylphosphonate reagent does not react with paraformaldehyde under these mild conditions. The utility of the methodology for synthesis of terminal α-fluoroalkenes bearing electron-withdrawing functionalities is also shown. 相似文献
683.
Rao CN Ramakrishna Matte HS Voggu R Govindaraj A 《Dalton transactions (Cambridge, England : 2003)》2012,41(17):5089-5120
Nanoparticles probably constitute the largest class of nanomaterials. Nanoparticles of several inorganic materials have been prepared by employing a variety of synthetic strategies. Besides synthesizing nanoparticles, there has been considerable effort to selectively prepare nanoparticles of different shapes. In view of the great interest in inorganic nanoparticles evinced in the last few years, we have prepared this perspective on the present status of the synthesis of inorganic nanoparticles. This article includes a brief discussion of methods followed by reports on the synthesis of nanoparticles of various classes of inorganic materials such as metals, alloys, oxides chalcogenides and pnictides. A brief section on core-shell nanoparticles is also included. 相似文献
684.
Madharam Sudershan Rao Bhupender S. Chhikara Rakesh Tiwari Amir N. Shirazi Keykavous Parang Anil Kumar 《Monatshefte für Chemie / Chemical Monthly》2012,38(2):263-268
Abstract
Synthesis of 12-aryl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-ones was achieved by one-pot condensation of β-naphthol, substituted benzaldehydes, and 1,3-dicarbonyl compounds catalyzed by Sc(OTf)3 under microwave irradiation in excellent isolated yields. The catalyst was recycled up to four cycles with no appreciable loss in catalytic activity. The compounds were evaluated for Src kinase activity and anticancer activity. 相似文献685.
Nanocomposites of polycarbonate (PC) containing low concentrations of pristine and COOH and OH functionalized single-walled
carbon nanotubes (SWNTs, COOH-SWNTs and OH-SWNTs) were prepared by melt-mixing and analyzed using rheology and scanning electron
microscopy (SEM). The steady state and linear viscoelastic behavior of each nanocomposite material is presented and compared
to that of the neat PC. SEM analysis revealed that samples containing functionalized SWNTs were more dispersible than samples
containing the pristine SWNTs. 相似文献
686.
Subasa C. Sahoo N. Venkataramani Shiva Prasad Murtaza Bohra R. Krishnan 《Applied Physics A: Materials Science & Processing》2012,106(4):931-935
Cobalt ferrite thin films of different thicknesses were pulsed-laser deposited onto a fused quartz substrate held at ambient
temperature (RT) by varying deposition time. The samples were ex-situ annealed at 750°C in air for 2 hours. All the films
were characterized by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The spontaneous magnetization,
4πM
S
, was found to be 6130 G for the 50 nm thick sample, and this is higher than that for the bulk cobalt ferrite of 5300 G, by
16%. The 4πM
S
was found to decrease with the increase in film thickness and an overall decrease of 32% was observed, when the film thickness
increased from 50 nm to 600 nm. In contrast the films of the same thicknesses, when deposited at substrate temperature of
750°C showed an increase of 4πM
S
with the increase in film thickness. The thickness dependence of 4πM
S
in these nanocrystalline thin films has been explained in terms of the cation distribution and the grain size, which are
sensitive to the substrate temperature during deposition. 相似文献
687.
Gupta RK Trivedi R Awasthi R Paliwal VK Prasad KN Rathore RK 《Magnetic resonance imaging》2012,30(1):104-111
Diffusion tensor imaging (DTI) was performed on 25 patients with neurocysticercosis (NCC). The aim of this study was to investigate the changes in DTI measures during the evolutionary course of NCC lesions from vesicular to calcified stage in the brain. DTI measures were quantified from the NCC lesions of all patients. On the basis of conventional imaging findings, NCC lesions were classified into vesicular, vesicular colloidal, granular nodular and calcified stages. Significant inverse correlation was observed between the evolutionary stage of NCC lesion and mean diffusivity (MD; r=−0.748, P<0.001) and spherical anisotropy (CS; r=−0.585, P<.001) values. Significant direct correlations were observed between evolutionary stages of NCC lesion and mean fractional anisotropy (FA; r=0.575, P<0.001), linear anisotropy (CL; r=0.478, p<0.001) and planar anisotropy (CP; r=0.561, p<0.001) values. Successive decrease in MD values calculated from NCC lesions was observed, moving from vesicular to granular nodular stage. On FA, CL and CP maps, a significant increase in signal intensity value was observed in calcified as compared to other stages. We conclude that DTI measures may indicate the evolutionary changes in NCC from vesicular to calcified stage. 相似文献
688.
A simple interferometric polarimeter with an integrated calibration scheme is proposed for accurate and fast mapping of the state of polarization (SOP). Conventional single-shot polarimeters that detect the amplitude and phase of orthogonally polarized field components by interferometry using Fourier fringe analysis suffers from errors caused by the imperfect reference beam and ambiguity in the spatial carrier frequency in the fringe pattern. In the proposed system, the integrated calibration scheme eliminates those error sources and enables accurate measurement of SOP without prior knowledge of the reference beam and the spatial carrier frequency. 相似文献
689.
S. Mathew Amit kumar Prasad Thomas Benoy P. P. Rakesh Misha Hari T. M Libish P. Radhakrishnan V. P. N. Nampoori C. P. G. Vallabhan 《Journal of fluorescence》2012,22(6):1563-1569
TiO2 colloidal nanoparticles and nanocrystals are prepared by hydrolysis of titanium isopropoxide employing a surfactant-free synthetic hydrothermal method. The synthesized samples are characterized by X-ray diffraction (XRD), HRTEM and FTIR. The XRD study confirms that the size of the colloidal nanoparticle is around 4?nm which the HRTEM analysis indicates the sizes of the colloidal nanoparticles are in the range of 2.5?nm. The fluorescence property of the TiO2 colloidal nanoparticles studied by the emission spectrum confirms the presence of defect levels caused by the oxygen vacancies. We have observed new emission bands at 387?nm,421?nm, 485?nm, 530?nm and 574?nm wavelengths, first one (387?nm) being emission due to annihilation of excitons while remaining four could be arising from surface states. The emission spectrum of annealed nanocrystallites is also having these four band emissions. It is observed that the surface state emission basically consists of two categories of emission. 相似文献
690.
Arvind Sharma Kanika Arora Harapriya Mohapatra Rakesh K. Sindhu Madalin Bulzan Simona Cavalu Gulsheen Paneshar Hosam O. Elansary Ahmed M. El-Sabrout Eman A. Mahmoud Abdullah Alaklabi 《Molecules (Basel, Switzerland)》2022,27(9)
At present, the majority of APIs synthesized today remain challenging tasks for formulation development. Many technologies are being utilized or explored for enhancing solubility, such as chemical modification, novel drug delivery systems (microemulsions, nanoparticles, liposomes, etc.), salt formation, and many more. One promising avenue attaining attention presently is supersaturated drug delivery systems. When exposed to gastrointestinal fluids, drug concentration exceeds equilibrium solubility and a supersaturation state is maintained long enough to be absorbed, enhancing bioavailability. In this review, the latest developments in supersaturated drug delivery systems are addressed in depth. 相似文献