排序方式: 共有56条查询结果,搜索用时 31 毫秒
41.
Stanciu CD Tsukamoto A Kimel AV Hansteen F Kirilyuk A Itoh A Rasing T 《Physical review letters》2007,99(21):217204
Subpicosecond magnetization reversal is experimentally demonstrated by ultrafast heating of a ferrimagnet across its compensation points, under an applied magnetic field. While the reversal is initiated by crossing the magnetization compensation temperature, the short reversal time is related to the angular momentum compensation, where the dynamics of the system is highly accelerated owing to the divergence of the gyromagnetic ratio. These results demonstrate the feasibility of subpicosecond magnetization reversal previously believed impossible. 相似文献
42.
Mircea Teodorescu Bogdan Cursaru Paul Stanescu Constantin Draghici Nicoleta Doriana Stanciu Dumitru Mircea Vuluga 《先进技术聚合物》2009,20(12):907-915
New hydrogels were prepared from diepoxy‐terminated poly(ethylene glycol)s of approximate molecular weights 600, 1000, 2000, and 4000 Da and aliphatic primary diamines with different numbers of carbon atoms (ethylenediamine, 1,4‐diaminobutane, hexamethylenediamine, 1,8‐octanediamine, 1,10‐decanediamine, 1,12‐dodecanediamine), in water or ethanol–water mixture, depending on the amine solubility. The swelling behavior of these gels was tested in distilled water/aqueous solution at constant temperature and the equilibrium swelling degree (ESD) was determined for structurally different hydrogels and under various environmental conditions. It was shown that ESD was influenced by the molecular weight of PEG oligomers, amine/epoxy groups mole ratio, amine chain length, temperature, pH, and concentration of salts present in the swelling medium. Higher ESDs were obtained for either longer‐chain PEGs, non‐stoichiometric amine/epoxy groups ratio, shorter amines, acidic pH, lower temperatures, or in the absence of salts. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
43.
Segmented poly(ester-siloxane)urethanes containing hard and soft segments were prepared by melt polyaddition using a multistep procedure. The soft segments based on poly(ethylene glycol adipate)diol as ester sequences and α,ω-poly(dimethylsiloxane)diol as silicone sequences were synthesized. The hard segments were based on aromatic or aliphatic diisocyanates and butanediol was used as chain extender. These polyurethane materials were analysed by differential scanning calorimetry and dynamic-mechanical analysis measurements. The shapes of thermal plots are significantly influenced by the soft and hard segment structures and also the compositional parameters. 相似文献
44.
The detection of the lactate level in blood plays a key role in diagnosis of some pathological conditions including cardiogenic or endotoxic shocks, respiratory failure, liver disease, systemic disorders, renal failure, and tissue hypoxia. Here, we described for the first time the use of a novel mixed metal oxide solution system to address the oxygen dependence challenge of first generation amperometric lactate biosensors. The biosensors were constructed using ceria-copper oxide (CeO2–CuO) mixed metal oxide nanoparticles for lactate oxidase immobilization and as electrode material. The oxygen storage capacity (OSC, 492 μmol-O2/g) of these metal oxides has the potential to reduce the oxygen dependency, and thus eliminate false results originated from the fluctuations in the oxygen concentration. In an effort to compare the performance of our novel sensor design, ceria nanoparticle decorated lactate sensors were also constructed. The enzymatic activity of the sensors were tested in oxygen-rich and oxygen-lean solutions. Our results showed that the OSC of the electrode material has a big influence on the activity of the biosensors in oxygen-lean environments. While the CeO2 containing biosensor showed an almost 21% decrease in the sensitivity in a O2-depleted solution, the CeO2–CuO containing electrode, with a higher OSC value, experienced no drop in sensitivity when moving from oxygen-rich to oxygen-lean conditions. The CeO2–CuO decorated sensor showed a high sensitivity (89.3 ± 4 μA mM−1 cm−2), a wide linear range up to 0.6 mM, and a low limit of detection of 3.3 μM. The analytical response of the CeO2–CuO decorated sensors was studied by detecting lactate in human serum with good selectivity and reliability. The results revealed that CeO2–CuO containing sensors are promising candidates for continuous lactate detection. 相似文献
45.
Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1?xCrx and Fe1?xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 °C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mössbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mössbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1?xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 °C. Annealing at 1250 °C in He enhances drastically the Cr clustering around Fe nuclei. 相似文献
46.
47.
Victoria Stanciu 《Annali dell'Universita di Ferrara》2003,49(1):37-42
We prove sufficient criteria in order for a family ofBMO-quasiconformal mappings between two Riemann surfaces to be normal and closed.
We prove sufficient criteria in order for a family ofBMO-quasiconformal mappings between two Riemann surfaces to be normal and closed.
Sunto Si ottengono condizioni sufficiente per la normalità e chiusura di una famiglia di applicazioniBMO-quasiconforme fra due superficie di Riemann.相似文献
48.
A. M. Blixt G. Andersson V. Stanciu B. Skubic E. Holmstrm P. Nordblad B. Hjrvarsson 《Journal of magnetism and magnetic materials》2004,280(2-3):346-357
Fe0.82Ni0.18/V(0 0 1) superlattices grown by DC magnetron sputtering on MgO(0 0 1) substrates have been investigated using longitudinal MOKE, SQUID magnetometry and magnetoresistance measurements. The varying sign and strength of the interlayer exchange coupling (IEC) were identified in the thin layer region (0.4–2.4 nm) and a magnetic IEC phase diagram was deduced and analyzed in terms of density functional calculations. The maximum giant magnetoresistance effect was determined to be 2.5% at 21 K. The balance between the magnetic anisotropy and IEC was found to be significantly different from that of previously studied Fe/V superlattices, also causing a different dependence of both IEC strength and observed anisotropy on the magnetic layer thickness. 相似文献
49.
A. Jitianu M. Raileanu M. Crisan D. Predoi M. Jitianu L. Stanciu M. Zaharescu 《Journal of Sol-Gel Science and Technology》2006,40(2-3):317-323
The magnetic nanocomposite materials represent an important class of nanomaterials extensively studied nowadays due to their varied applications from medical diagnostic to storage information. The iron oxides in silica matrix systems are highly investigated. The sol-gel method is a suitable way of preparation of Fe3O4-SiO2 nanocomposite materials, since this method allowed the preparation of nanocomposite materials with narrow size distribution of magnetite in silica matrix. In the present work, nanocomposite materials in the Fe3O4-SiO2 system were prepared by sol-gel method via alkoxide and aqueous route. As SiO2 sources, tetraethoxysilan (TEOS) for the alkoxide route, as well as silica sol Ludox (30%) for the aqueous route, were used. This study shows the influence of the type of silica matrix on the structure, size, and distribution of the Fe3O4 nanoparticles in the Fe3O4-SiO2 systems. The gels were annealed at 550°C in order to consolidate the matrices. The structural characterization of the obtained materials via the two preparation routes was performed by DTA/TGA analysis, X-ray diffraction, IR and Mössbauer spectroscopy, Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). 相似文献
50.
Adell M Kanski J Ilver L Sadowski J Stanciu V Svedlindh P 《Physical review letters》2005,94(13):139701; author reply 139702