Tunable remote pinning of domain walls in magnetic nanowires

Domain wall (DW) pinning in ferromagnetic nanowires is in general a complex process. Distortions of the DW shape make quantitative agreement between modeling and experiment difficult. Here we demonstrate pinning using nanometer scale localized stray fields. This type of interaction gives well-characterized, tailorable potential landscapes that do not appreciably distort the DW. Our experimental results are in excellent quantitative agreement with an Arrhenius-Néel model of depinning--a result only possible when the modeled potential profile agrees fully with that experienced by the DW.     

Modified radiation laws of a rectangular Kerr nonlinear blackbody

A Kerr nonlinear blackbody (KNB) is a new kind of blackbody in which bare photons with opposite wave vectors and helicities are bound into pairs and unpaired photons are transformed into nonpolaritons. In the present paper, we focus our investigation on the modified radiation laws, such as Planck and Stefan-Boltzmann radiation laws, of a rectangular KNB. Besides, the case of a KNB with no symmetry axes is also discussed. Finally, we make a numerical calculation of modified radiation laws of a cubic KNB under appropriate conditions, and we consider this work may lay the foundation for the experimental verification of the model of a KNB.     

Remote substituent effects on homolytic Fe?C bond energies of p‐G‐C6H4CH2Fe(CO)2(η5‐C5H5) and p‐G‐C6H4(H)(CN)CFe(CO)2(η5‐C5H5) studied by Hartree–Fock and density functional theory methods

In general, both stoichiometric and catalytic reactions of organometallic complexes involve breaking and forming metal–ligand bonds. Therefore, an evaluation of the thermodynamics of such reactions requires the knowledge of metal–ligand bond energies (BDEs). The homolytic Fe? C bond dissociation energies [i.e., ΔH_homo(Fe? C)s] of 12 para‐substituted benzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐C₆H₄CH₂Fp [1,G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, NMe₂; Fp = (η⁵‐C₅H₅)(CO)₂Fe] and 12 para‐substituted α‐cyanobenzyldicarbonyl (η⁵‐cyclopentadienyl)iron, p‐G‐PANFp [2,PAN = C₆H₄CH(CN)] were studied using Hartree–Fock (HF) and density functional theory (DFT) methods with large basis sets. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_homo(Fe? C)s. The B3LYP method satisfactorily predicts the α and remote substituent effects on ΔH_homo(Fe? C)s [ΔΔH_homo(Fe? C)s]. The fair correlations [r = 0.97 (g, 1), 0.99(g, 2)] of ΔΔH_homo(Fe? C)s of series 1 and 2 with the substituent σ constants imply that the para substituent effects on ΔH_homo(Fe? C)s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. The molecule stabilization effects (MEs) causes that not only the magnitude of ΔΔH_homo(Fe? C)s(1) varies significantly but also the direction changes from S‐pattern to O‐pattern. ΔΔH_homo(Fe? C)s(2) were found to conform to the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp? C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation on FR(LT)–FR(HT) phase transition and pyroelectric properties of pulsed laser deposited Pb(Zr0.93Ti0.07)O3 thin films

The preparation process, crystallinity and electrical properties of pulse laser deposited Pb(Zr_xTi_1−x)O₃ (PZT) thin films were investigated in this paper. PZT (x = 0.93) thin film samples deposited at different substrate temperatures were prepared. Si (1 1 0) was the substrate; Ag and YBCO were the top electrode and the bottom electrode respectively. The bottom electrode YBCO was deposited on the Si substrate by pulsed laser deposition (PLD), and then PZT was epitaxially deposited on YBCO also by PLD. After annealing, the top electrode Ag was prepared on PZT by thermal evaporation, and then the Ag/PZT/YBCO/Si structured thin films were obtained. The XRD and the analysis of their electrical characters showed that, when the substrate temperature was elevated from 600 °C to 800 °C, the crystallinity and electrical properties of PZT thin films became better and better, and the F_R(LT)–F_R(HT) phase transition of PZT (x = 0.93) thin films occurred at 62 °C. The PZT film deposited at 800 °C had the best pyroelectric properties, and when the F_R(LT)–F_R(HT) phase transition of this film occurred, the peak value of pyroelectric coefficient (p) was obtained, with a value of 1.96 × 10⁻⁶ C/(cm² K). The PZT film deposited at 800 °C had the highest remnant polarization (P_r) and the lowest coercive field (E_c), with the values of 34.3 μC/cm² and 41.7 kV/cm respectively.     

Thermostatistical properties of a q-deformed bosonic exciton gas

We present the calculations of the electronic structure and transport properties on the filled-skutterudites LaFe₄Sb₁₂ and CeFe₄Sb₁₂ using the full-potential linearized augmented plane-wave method and the semi-classical Boltzmann theory. Our calculation indicates that LaFe₄Sb₁₂ and CeFe₄Sb₁₂ have the large density of states near the Fermi level. The obtained Seebeck coefficient and the magnetic susceptibilities are in good agreement with experimental results. It is found that n-type doping in the CeFe₄Sb₁₂ compound may be more favorable than p-type doping below 900 K and p-type doping in the CeFe₄Sb₁₂ compound may be more favorable than n-type doping above 900 K. It is also seen that n-type doping in the LaFe₄Sb₁₂ compound may be more favorable than p-type doping below 700 K and p-type doping in the LaFe₄Sb₁₂ compound may be more favorable than n-type doping above 700 K. Ultimately, we found that LaFe₄Sb₁₂ is more suitable for thermoelectric applications than CeFe₄Sb₁₂.     

On the rank-dependence of coal tar secondary reactions

The secondary reactions of volatile compounds, including coal tar and light gases, accounts for a great portion of soot formation and the subsequent heat release and pollutant emissions in the combustion zone. While coal primary pyrolysis has been extensively studied over the last few decades and several network pyrolysis models has been developed to describe this process, coal secondary pyrolysis is still not well understood. The Babcock and Wilcox Company has been investigating coal secondary pyrolysis in order to develop a comprehensive mechanism for inclusion in predictive computational fluid dynamics and coal combustion models. Supportive experiments were carried out in an entrained-flow reactor. Tar was extracted from the pyrolysis byproducts of seven coals of widely-distributed rank at temperatures ranging from 923 to 1473 K, and analyzed by ¹³C NMR. Tars formed from higher rank coals generally demonstrated higher sooting propensities. This rank-dependent sooting propensity is associated with tar’s chemical structure properties. With increased heat treatment severity, tar molecules lose a substantial amount of aliphatic attachments, and the average size of substitution per cluster decreases. Compared to tars formed from high-rank bituminous coals, those formed from low-rank sub-bituminous coals have a larger attachment portion, higher averaged substitution, and higher oxygen-containing functional groups. These differences contribute to the higher cracking propensity observed for low-rank coal tars.     

Evidence for a biogenic, microorganismal origin of rock varnish from the Gangdese Belt of Tibet

In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish matrix, that surrounds the varnish bodies]. The bacillus-like forms are embedded in a network of filaments that have diameters between 35 and 45 nm. These bacilli with the surrounding filaments are assumed to have been involved in biofilm formation (synthesis of extracellular polymeric substances) prior to their live burial. We concluded that the formation of the varnish layers was for the most part biogenically driven by microorganisms.     

新型罗丹明B席夫碱荧光探针的光谱性质研究

合成了一种席夫碱结构的罗丹明B衍生物.研究表明,该衍生物能与Fe3+形成稳定配合物,同时伴随显著的荧光增敏和吸收增强.衍生物不仅对Fe3+呈现良好的荧光及比色探针性能,其与金属离子形成的配合物也是一种研究牛血清白蛋白的高灵敏荧光探钊.     

考虑意外事件对交通流影响的元胞自动机交通流模型

在NaSh模型的基础上,考虑交通事故和养护路段等意外事件对高速公路交通流的影响,建立了有意外事件影响的在车道管制下的高速公路交通流元胞自动机模型,并进行数值模拟. 研究发现:意外事件对高速公路交通流有明显影响,并且意外事件对交通流的影响在某一密度值范围内尤其明显,且意外事件堵塞点在第一车道比在第二车道对交通流的影响小;同时,在该密度值范围内,意外事件堵塞时间和堵塞路段长度越长,对交通流的影响就越大. 关键词： 元胞自动机 交通流 意外事件     

钶铁矿型MnNb2O6的熔盐法合成、钒掺杂与磁性研究

采用了熔盐法新工艺制备了纯相与掺钒的MnNb₂O₆粉晶,利用X射线衍射仪(XRD),扫描电子显微镜(SEM),能谱分析(EDX),透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)和电子衍射(SAED)分析了其物相、形貌及微结构.结果表明合成产物为正交晶系钶铁矿型MnNb₂O₆;在不同的熔盐中合成出了棒状、片状与长方体形貌的纯相产物.讨论了温度与掺杂对结构与形貌的影响,HRTEM与SAED分析表明了产物的各向异性生 关键词： 熔盐法 结构与形貌 掺杂 反铁磁性