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711.
Pierce JP Torija MA Gai Z Shi J Schulthess TC Farnan GA Wendelken JF Plummer EW Shen J 《Physical review letters》2004,92(23):237201
We report collective ferromagnetic behavior with high Curie temperatures (T(c)) in Fe dot assemblies supported by the Cu(111) surface. Our ability to tune the average size and spacing of the individual dots allows us to conclude that enhanced magnetic anisotropy cannot account for this high-T(c) ferromagnetic order. Because our Monte Carlo simulations have ruled out the dipolar interaction as the dominant factor in this system, we attribute the origin of the ferromagnetic order to indirect exchange coupling via the Cu(111) substrate. 相似文献
712.
A.?Marcinkevi?iusEmail author R.?Tommasini G.D.?Tsakiris K.J.?Witte E.?Gai?auskas U.?Teubner 《Applied physics. B, Lasers and optics》2004,79(5):547-554
We present an experimental and theoretical study of the influence of the spatial beam quality (fluence and phase distributions) on the second-harmonic generation in KDP crystals pumped by 180-fs pulses at 790 nm. Conversion efficiency and beam focusability are investigated experimentally and theoretically by the numerical analysis of the second harmonic, considering effects due to the cubic nonlinearity, beam diffraction, group-velocity walk-off, and dispersion of the pulses. It was found that the uniform intensity and phase distributions of the fundamental beam are essential to obtain a high focal intensity of the second-harmonic beam. PACS 42.65.Ky; 42.65.Re 相似文献
713.
Transparent conducting Zn−Sn−O films were deposited on Polypropylene adipate thin-film substrates at low temperature by r.
f. magnetron sputtering. The structural, electrical and optical properties of the deposited films were investigated. All the
obtained films are of amorphous structure and have a very good adhesion to the substrates. The resistivity, carrier concentration
and Hall mobility of the film are 1.3×10−2 Ω·cm, 4.1×1019 cm−3 and 12.4 cm2· V−1· s−1, respectively. The transmittance of the film reaches 82%. 相似文献
714.
Schümann F Hammache F Typel S Uhlig F Sümmerer K Böttcher I Cortina D Förster A Gai M Geissel H Greife U Iwasa N Koczoń P Kohlmeyer B Kulessa R Kumagai H Kurz N Menzel M Motobayashi T Oeschler H Ozawa A Płoskoń M Prokopowicz W Schwab E Senger P Strieder F Sturm C Sun ZY Surówka G Wagner A Waluś W 《Physical review letters》2003,90(23):232501
An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254A MeV allowed the study of the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S17(0)=18.6+/-1.2+/-1.0 eV b, where the first error is experimental and the second one reflects the theoretical uncertainty in the extrapolation. 相似文献
715.
Structure of the replicative helicase of the oncoprotein SV40 large tumour antigen 总被引:14,自引:0,他引:14
Li D Zhao R Lilyestrom W Gai D Zhang R DeCaprio JA Fanning E Jochimiak A Szakonyi G Chen XS 《Nature》2003,423(6939):512-518
The oncoprotein large tumour antigen (LTag) is encoded by the DNA tumour virus simian virus 40. LTag transforms cells and induces tumours in animals by altering the functions of tumour suppressors (including pRB and p53) and other key cellular proteins. LTag is also a molecular machine that distorts/melts the replication origin of the viral genome and unwinds duplex DNA. LTag therefore seems to be a functional homologue of the eukaryotic minichromosome maintenance (MCM) complex. Here we present the X-ray structure of a hexameric LTag with DNA helicase activity. The structure identifies the p53-binding surface and reveals the structural basis of hexamerization. The hexamer contains a long, positively charged channel with an unusually large central chamber that binds both single-stranded and double-stranded DNA. The hexamer organizes into two tiers that can potentially rotate relative to each other through connecting alpha-helices to expand/constrict the channel, producing an 'iris' effect that could be used for distorting or melting the origin and unwinding DNA at the replication fork. 相似文献
716.
Effects of 3-D disturbances on a separating flow past a rearward facing step have been studied with emphasis on pressure distributions in the separation and reattachment regions. The results show that the 3-D disturbances to a separating shear layer diminish rapidly and the flow downstream of reattachment appears to have a 2-D global shearlayer structure. 相似文献
717.
本文介绍了一种利用自适应信号增强技术检测并跟踪视觉诱发电位的新方法,自适应信号增强器有两个输人端,其主通道输人为带噪声的原始记录;参考输人需经设计使系统产生最佳性能,我们用移动窗口平均法形成动态参考输人,使系统具备较好的跟踪能力实验表明,利用这种方法可以检测到单一记录的视觉诱发电位信号,并能获得信号随时间变化的轨迹。 相似文献
718.
719.
陈概 《华南师范大学学报(自然科学版)》1994,(3):122-127
本文回答P.R.Hugbo提出的一个问题:“是否由7个非berguereanAndre拟域坐标的平面可能全部同构?”给出的结论是:有且只有3个25阶非DesarguesianAndre平面。 相似文献
720.