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排序方式: 共有190条查询结果,搜索用时 15 毫秒
101.
Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV Quinn B Radeztsky S Rafatian A 《Physical review letters》1996,77(12):2384-2387
102.
103.
The thermal stability of linear low density polyethylene (LLDPE)/ethylene methyl acrylate (EMA) blends was studied using thermogravimetry.
The blend ratio as well as the presence of compatibilizer has significant effect on thermal stability of the blends. The compatibilization
of the blends using LLDPE-g-MA has increased the degradation temperature. Phase morphology was found to be one of the most
decisive factors that affected the thermal stability of both uncompatibilized and compatibilized blends. Dynamic mechanical
behavior of the blend was studied by dynamic mechanical analysis. The storage modulus of the blends decreased with increase
in EMA content. When compatibilized with LLDPE-g-MA the storage modulus of the blend increases. LLDPE-g-MA is an effective
compatibilizer as it increases the thermal stability and modulus of the blend. 相似文献
104.
In this paper, we study a holographic dark energy model with time varying gravitational constant G as well as holographic parameter c 2 in flat FRW space-time geometry. We obtain the evolution of equation of state parameter and the exact differential equation, which determine the evolution of the dark energy density based on varying G and c 2 parameter. Also, we determine the deceleration parameter to explain the expansion of the universe. Further, we study the validity of the generalized second law of thermodynamics in this scenario. Finally, we find out a cosmological implication of our work by evaluating the holographic dark energy equation of state for low red-shifts containing both varying G and c 2 parameter corrections. 相似文献
105.
106.
Limi Goswami Pranjal Gogoi Junali Gogoi Ashwini Borah Manash R. Das Romesh C. Boruah 《Tetrahedron letters》2014
A mild and selective protocol has been developed for the palladium-catalyzed phosphine-free Suzuki cross-coupling reaction of aryl bromides with arylboronic acids in aqueous tea extract at room temperature. It is noteworthy that the aqueous tea extract plays an important role in the reaction, and various functional groups are tolerated under the optimized conditions. The reactions proceeded with very good chemoselectivity in favor of the bromo instead of the chloro group even at higher temperatures. Furthermore, this protocol could be applied to the cross-coupling of 4-bromoindole without protecting the base sensitive amine group with arylboronic acids in moderate to excellent yields. 相似文献
107.
A simple and inexpensive method for the reductive cleavage of N–O bond of benzofuroxans with bakers' yeast under nonfermenting condition in aqueous media was achieved. The procedure gives excellent yields of aryl-1,2-diamines. 相似文献
108.
109.
Asymmetric aminohydroxylation of various olefins was carried out using bromamine-T as nitrogen source in the presence of (DHQ)2PHAL ligand. The new nitrogen source has been found to be effective in terms of yield and reaction time. The optical purities of the products could be obtained with up to 99% ee. 相似文献
110.
Manjit Borah Dambarudhar Mohanta 《Applied Physics A: Materials Science & Processing》2014,115(3):1057-1067
We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd3+) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd3+ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ~10–15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition (n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0–7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tanδ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ~ω s approaches ideal Debye behavior (s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd3+) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers. 相似文献