Surface magnetism in O2 dissociation-from basics to application

First-principles calculations were performed to investigate magnetic phenomena in surface reactions involving O(2). We present two magnetized surface cases: (1) oxidation of paramagnetic Ag, and magnetic properties of the high coverage oxide phase, which correspond to a magnetic impurity superlattice on paramagnetic surfaces and (2) oxidation of ferromagnetic Pt, represented by the Pt layer on M (M = Fe and Co) relevant to the oxidation reduction reaction (ORR) on Pt, in relation to both fundamental and application interests. In the first case, we found that the dissociative adsorption of O(2), resulting in oxide phases in Ag(111), reveals interesting magnetic interactions. We note that the magnetic states are induced by the ferromagnetic superexchange interactions and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Specifically, the superlattice structures with short O-O distances have an effective ferromagnetic superexchange and RKKY interaction. In the second case, we found that a magnetic moment is induced on the Pt layer by the M substrate. The spin polarization of Pt-d states is due to hybridization with M-d states. The d-band center (ε(d)) of Pt (on M), is shifted downwards with respect to pure Pt. However, because of the spin polarization, the otherwise filled spin-down d(zz) orbital in paramagnetic pure Pt is shifted towards the Fermi level. This promotes π(z↑)-d(zz↓) interactions, which influences the O(2)-Pt interaction at O(2) far from the surface. Details and mechanisms of these two magnetic phenomena are discussed.     

Codimension Two PL Embeddings of Spheres with Nonstandard Regular Neighborhoods

For a given polyhedron K(?)M,the notation RM(K)denotes a regular neigh- borhood of K in M.The authors study the following problem:find all pairs(m,k) such that if K is a compact k-polyhedron and M a PL m-manifold,then R_M(f(K))≌R_M(g(K))for each two homotopic PL embeddings f,g:K→M.It is proved that R_S~(k 2)(S~k)(?)S~k×D~2 for each k(?)2 and some PL sphere S~k(?)S~(k 2)(even for any PL sphere S~k(?)S~(K 2)having an isolated non-locally flat point with the singularity S~(k-1)(?) S~(k 1)such thatπ_1(S~(k 1)-S~(k-1))(?)Z).     

Sharp Inequalities for BMO Functions

The purpose of the paper is to study sharp weak-type bounds for functions of bounded mean oscillation. Let 0 p ∞ be a fixed number and let I be an interval contained in R. The author shows that for any φ : I → R and any subset E I of positive measure,For each p, the constant on the right-hand side is the best possible. The proof rests on the explicit evaluation of the associated Bellman function. The result is a complement of the earlier works of Slavin, Vasyunin and Volberg concerning weak-type, L ~p and exponential bounds for the BMO class.     

Third Generation Horseradish Peroxidase Biosensor Based on Self-assembling Carbon Nanotubes to Gold Electrode Surface

Carbon nanotube (CNT) is a novel carbon material discovered by Iijima1. It had beenfound to have the ability to promote electron transfer reactions when it was used tofabricate electrodes for the oxidation of biomolecules2-4. Just recently, the interest indemonstrating CNT for biosensing applications is now emerging5-10. However, most ofthese biosensors were based on CNT paste electrode or CNT modified glassy carbonelectrode by casting technology. Here, we reported another assembly…     

Microstructural evaluation and nanohardness of an AlCoCuCrFeNiTi high-entropy alloy

An AlCoCuCrFeNiTi high-entropy alloy(HEA) was prepared by mechanical alloying and sintering to study the effect of Ti addition to the widely studied AlCoCuCrFeNi system. The structural and microstructural characteristics were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). The formation of four micrometric phases was detected: a Cu-rich phase with a face-centered cubic(fcc) structure, a body-centered cubic(bcc) solid solution with Cu-rich plate-like precipitates(fcc), an ordered bcc phase, and a tetragonal structure. The XRD patterns corroborate the presence of a mixture of bcc-, fcc-, and tetragonal-structured phases. The Vickers hardness of the alloy under study was more than twice that of the AlCoCuCrFeNi alloy. Nanoindentation tests were performed to evaluate the mechanical response of the individual phases to elucidate the relationship between chemical composition, crystal structure, and mechanical performance of the multiphase microstructure of the AlCoCuCrFeNiTi HEA.     

一种基于CloudSim的分级云存储仿真模型

随着云存储技术的发展,云存储平台解决了大数据存储与管理的难题。然而当数据量与用户量进一步扩大,系统性能要求逐步提升,需要对目前云存储环境中的数据存储管理技术进行深入的研究与改进。由于应用实际的云存储集群进行优化研究极易受到平台环境的限制,因此基于CloudSim实现了一个分级云存储的仿真模型TCSS,给出了一种三层次的设备分级组织结构,构建了完善的数据I/O业务处理与数据存储管理等功能结构。已经将所有拓展功能模块集成到了CloudSim仿真工具的CloudSim层中,用户可以依据TCSS模型,突破平台限制,完成云存储优化策略的建模与测试工作。     

阵列式压电振子超声复合喷丸强化*

为了进一步改善超声喷丸强化质量,提升工件表面残余应力和显微硬度的均匀性,对压电振子阵列型超声喷丸强化加工系统进行了改进,提出了在强化加工过程中辅助工件往复运动的方法。对改进后的压电振子阵列型超声喷丸强化加工原理进行了阐述,分析了激振片的振动特性并进行了结构尺寸优化,应用Abaqus对工件往复运动下超声喷丸强化过程进行了仿真研究,分析了在不同的工件往复运动频率下,工件表面残余应力分布情况。实验测试了在不同喷丸强化时间及工件往复运动频率下超声喷丸强化加工质量,探究了喷丸时间和工件往复运动频率对工件表面显微硬度的影响。结果表明：在压电振子阵列型超声喷丸强化过程中辅助工件往返运动,可以有效提高工件表面残余应力和显微硬度分布的均匀性,工件表面强化质量得到提升。     

消息与动态

<正> 台式扭摆转动惯量测试仪台式扭摆转动惯量测试仪由空心转轴台式扭摆和电子测试仪两部分组成.空心转轴台式扭摆作为物理量变换器与电子测试仪连接.空心转轴台式扭摆主要包括空心转轴、可拆卸平台,平面螺旋弹簧、通孔光照式电传感器、定位机构及可调节 V 型架等.可调节 V 型架固定在可拆平台上,可拆卸平台可以放     

线性特性与卡氏定理

<正> 力学中的卡氏(Castigliano)定理是说,变形能“对任一外力 P.的偏导数,等于 P.作用点沿 P.方向上的位移δ,用公式表示这一公式在教科书中是从变形能出发得到的,并且在推导过程中假定所求的位移点及方向上有力作用.但在实际应用中,往往在所要求的点及位移方向上没有力作用.这时教科书告诉我们是用附加力的办     

Application of colloidal palladium nanoparticles for labeling in electron microscopy

The application of palladium nanoparticles as electron-dense markers for labeling in both transmission and scanning electron microscopy requires their conjugation to a specific protein. The conjugation protocol described here includes the dihydrolipoic acid (DHLA) capping of Pd nanoparticles (8 nm equivalent diameter) and their subsequent covalent attachment to functional protein molecules such as streptavidin, protein A, or avidin. The single-step reaction was mediated using the cross-linking agent ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). The final Pd conjugates were fully functional, as demonstrated by labeling of ultrathin resin sections of either bovine serum albumin or secretory granules of the salivary gland isolated from the partially fed female Ixodes ricinus tick. The results of bovine serum labeling were quantified, statistically evaluated, and compared with results obtained using commercially available gold particle conjugates (10 nm diameter). The highest values of labeling density were achieved using both streptavidin-Pd (106 ± 7 particles/μm2) and protein A-Au conjugates (130 ± 18 particles/μm2) compared to a commercial streptavidin-Au (66 ± 16 particles/μm2) and protein A-Pd conjugates (70 ± 11 particles/μm2). The concentrations of both DHLA and EDC, pH during conjugation, and finally thorough washing away of unbound proteins crucially influenced conjugation.