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排序方式: 共有104条查询结果,搜索用时 15 毫秒
71.
72.
Jeffrey F. Godsell Keith P. Donegan Joseph M. Tobin Mark P. Copley Fernando M.F. Rhen David J. Otway Michael A. Morris Terence O’Donnell Justin D. Holmes Saibal Roy 《Journal of magnetism and magnetic materials》2010,322(9-12):1269-1274
Ni nanoparticles (~32 nm particle diameter) have been synthesized on the walls of microporous (~1 nm pore diameter) silica spheres (~2.6 μm sphere diameter) and characterised magnetically to potentially produce a new class of core (silica micro-spheres)-shell (nanometallic)-type nanocomposite material. These magnetic nanocomposite materials display a characteristic increase in coercivity with reducing temperature. The average particle size has been used to calculate the anisotropy constant for the system, K. The discussion postulates the potential mechanisms contributing to the difference between the calculated K value and the magnetocrystalline anisotropy constant of bulk Ni. Various factors such as surface anisotropy and interparticle interactions are discussed as possible contributing factors to the anisotropy values calculated in the paper. 相似文献
73.
Elizabeth Blackburn John Goodkind Sunil K. Sinha Collin Broholm John Copley Ross Erwin 《Pramana》2008,71(4):673-678
There has been a resurgence of interest in the properties of solid helium due to the recent discovery of non-classical rotational
inertia (NCRI) in solid 4He by Chan and coworkers below 200 mK which they have interpreted as a transition to a ‘supersolid’ phase. We have carried
out a series of elastic and inelastic neutron scattering measurements on single crystals of hcp 4He at temperatures down to 60 mK. While we have found no direct evidence of any change in the excitation spectrum at low temperatures,
we have found that the excitation spectrum of solid 4He shows several interesting features, including extra branches in addition to the phonon branches. We interpret these extra
branches as single particle excitations due to propagating vacancy waves, which map on to the famous ‘roton minimum’ long
known in the excitation spectrum of superfluid liquid 4He. The results show that in fact solid 4He shares several features in common with the superfluid.
相似文献
74.
Phelan D Louca D Rosenkranz S Lee SH Qiu Y Chupas PJ Osborn R Zheng H Mitchell JF Copley JR Sarrao JL Moritomo Y 《Physical review letters》2006,96(2):027201
Inelastic cold-neutron scattering on LaCoO3 provided evidence for a distinct low energy excitation at 0.6 meV coincident with the thermally induced magnetic transition. Coexisting strong ferromagnetic (FM) and weaker antiferromagnetic correlations that are dynamic follow the activation to the excited state, identified as the intermediate S = 1 spin triplet. This is indicative of dynamical orbital ordering favoring the observed magnetic interactions. With hole doping as in La(1-x)Sr(x)CoO3 , the FM correlations between Co spins become static and isotropically distributed due to the formation of FM droplets. The correlation length and condensation temperature of these droplets increase rapidly with metallicity due to the double exchange mechanism. 相似文献
75.
Chumachenko N Novikov Y Shoemaker RK Copley SD 《The Journal of organic chemistry》2011,76(22):9409-9416
Photolabile 3',5'-dimethoxybenzoin-based linkers are advantageous for a variety of solid-phase synthetic procedures and manipulations of biomolecules because UV irradiation in aqueous media provides fast and essentially quantitative release of tethered molecules, while generating unreactive side products. Practical applications of previously reported linkers are compromised to some extent by the 1,3-dithiane protection of the benzoin carbonyl group and the lengthy synthesis. We have extended the group of photocleavable 3',5'-dimethoxybenzoin-based linkers by designing and synthesizing a linker in which the carbonyl group is protected as a dimethyl ketal. This protection is compatible with commonly used esterification and amide bond formation techniques, including the Fmoc/tBu strategy for solid phase peptide synthesis, is stable under mild acidic conditions, and can be quantitatively removed in <5 min by 3% TFA in dichloromethane. Irradiation of beads carrying peptides attached to the linker at 350 nm in aqueous or partially aqueous media affords >90% release after 30 min. The linker was synthesized from commercially available starting materials in five steps with an overall yield of 40% and without any column chromatography purification. Additionally, we developed a route to a dithiane-protected linker that requires only two steps and proceeds in 65% yield, a significant improvement over previous synthetic routes. 相似文献
76.
First‐Generation Subporphyrinatoboron(III) Sensitizers Surpass the 10 % Power Conversion Efficiency Threshold 下载免费PDF全文
Dr. Graeme Copley Daesub Hwang Prof. Dr. Dongho Kim Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2016,55(35):10287-10291
Subporphyrinatoboron(III) (SubB) sensitizers were synthesized for use in dye‐sensitized solar cells (DSSCs). The prototype, which comprises a sterically demanding 3,5‐di‐tert‐butylphenyl scaffold, a meso‐ethynylphenyl spacer, and a cyanoacrylic acid anchoring group, achieved an open‐circuit voltage VOC of 836 mV, short‐circuit current density JSC of 15.3 mA cm?2, fill factor of 0.786, and a photon‐to‐current conversion efficiency of 10.1 %. Such astonishing figures suggest that a bright future lies ahead for SubB in the realm of DSSCs. 相似文献
77.
78.
G.H. Copley 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(5):377-384
Foreign gas broadening and shift coefficients for Ne and Ar emission lines produced in a high pressure (0·5-2·0 atm) He discharge have been measured. The shift coefficients vary significantly for different transitions. This variation results from the differing excited state potentials for the He-Ne1 and He-Ar1 collision pairs, which must be included in any reasonable quantum-mechanical calculation of line shifts. Even the small differences in broadening coefficients demonstrate the inadequacy of calculation of broadening from equations based on the Lindholm(1)-Foley(2) theory of collision broadening. 相似文献
79.
80.