Electrophysical characteristics and stability of solid apatite-like electrolytes La x Si6O12 + 1.5x and La x Ge6O12 + 1.5x

Oxygen-ion conduction in apatite-like compounds based on silicates and germanates of lanthanum La _x A₆O_{12 + 1.5x} (A = Si, Ge; x = 9.11–10.22) is studied. The compounds are shown to be purely ionic conductors at 600–900°C and partial oxygen pressures 10^?16 to 10⁵ Pa. The electroconductivity of the best conducting specimens of La _x A₆O_{12 + 1.5x} (A = Si, Ge; x = 9.77–10) exceeds that of electrolyte YSZ at moderate temperatures. The electroconductivity of lanthanum germanate is substantially greater than that of lanthanum silicate, specifically, 7.85 × 10^?2 and 2.35 × 10^?2 S cm^?1, respectively, at 800°C. An inflection is discovered at ～750°C in the temperature dependences of electroconductivity of La _x Ge₆O_{12 + 1.5x} (x = 9.77–10.22). A dilatometric examination points to a second-kind phase transition that may be due to the oxygen sublattice disordering. The behavior of apatite-like electrolytes La _x A₆O_{12 + 1.5x} (A = Si, Ge) during long exploitation periods in the interval of working temperatures of electrochemical devices is studied for the first time ever. The electrolytes’ aging at 800°C in air for 1000 h was investigated by the electroconductivity method. The electroconductivity of lanthanum germanates decayed with time by 5% and that of lanthanum silicates, by 9.5%. The steady-state values of electroconductivity of all compounds studied is reached after 600–700 h. The compounds studied form a class of materials that hold some promise as solid electrolytes for medium-temperature fuel cells and other electrochemical devices.     

Conjugates of Iron-Transporting N-Hydroxylactams with Ciprofloxacin

Screening of a library of novel N-hydroxylactams amenable by the Castagnoli-Cushman reaction identified four lead compounds that facilitated ⁵⁵Fe transport into P. aeruginosa cells (one of these synthetic siderophores was found to be as efficient at promoting iron uptake as the natural siderophores pyoverdine, pyochelin or enterobactin). Conjugates of the four lead siderophores with ciprofloxacin were tested for antibacterial activity against P. aeruginosa POA1 (wild type) and the ∆pvdF∆pchA mutant strain. The antibacterial activity was found to be pronounced against the ∆pvdF∆pchA mutant strain grown in CAA medium but not for the POA1 strain. This may be indicative of these compounds being ‘Trojan horse’ antibiotics. Further scrutiny of the mechanism of the antibacterial action of the newly developed conjugates is warranted.     

气相生长氮化铝单晶的新方法

通过在钨坩埚盖开小孔的方法改变氮化铝结晶衬底上的温度场分布,在开孔处形成局部低温区;由于孔的几何尺寸的限制和氮化铝晶体生长的各向异性,开孔处的氮化铝晶体单晶化;随后,开孔处的单晶起籽晶的作用,逐渐长成较大尺寸、较高质量的氮化铝单晶.目前用该方法已经制备出直径大于2mm的氮化铝单晶体.     

Comparative study on transport properties of N-, P-, and As-doped SiC nanowires: Calculated based on first principles

According to the one-dimensional quantum state distribution, carrier scattering, and fixed range hopping model, the structural stability and electron transport properties of N-, P-, and As-doped SiC nanowires(N-SiCNWs, P-SiCNWs, and As-SiCNWs) are simulated by using the first principles calculations. The results show that the lattice structure of NSiCNWs is the most stable in the lattice structures of the above three kinds of doped SiCNWs. At room temperature,for unpassivated SiCNWs, the doping effect of P and As are better than that of N. After passivation, the conductivities of all doped SiCNWs increase by approximately two orders of magnitude. The N-SiCNW has the lowest conductivity. In addition, the N-, P-, As-doped SiCNWs before and after passivation have the same conductivity–temperature characteristics,that is, above room temperature, the conductivity values of the doped SiCNWs all increase with temperature increasing.These results contribute to the electronic application of nanodevices.     

石墨烯纳米带电极区N掺杂电子输运性质研究

运用密度泛函理论和非平衡格林函数结合的方法,研究电极区N掺杂对扶手椅型石墨烯纳米带电子输运特性的影响.结果表明,与本征扶手椅型石墨烯纳米带电流-电压曲线相比,宽度为7的石墨烯纳米带电流-电压曲线表现出明显的不对称性,其中心N掺杂表现强烈的整流特性,整流系数达到102数量级,且将N原子从电极区中心位置移动到边缘,整流特性减弱.研究结果表明宽度为7的扶手椅型石墨烯纳米带出现强整流现象的原因主要是负向偏压下能量窗内没有透射峰引起的,该研究结果对将来石墨烯整流器件的设计具有重要的意义.     

二维多群辐射输运程序LARED-R-1的并行化

利用有向图描述数据依赖关系,应用已有的并行流水线通量扫描算法,实现基于非协调网格的二维辐射输运程序LARED-R-1的并行化.同时,采用消息缓冲技术提高并行程序的性能.经测试,对于典型的问题规模(100群、3800个网格单元、40个方向),在某并行机的64个和128个处理器上,并行程序分别获得80%和53%的并行效率.     

一维线性非共轭石墨烯基(CH2)n分子链的电子输运

一维非共轭烷烃链虽不具富电子或少电子特征,但常存在于单分子器件或多肽、蛋白质等生物分子中,对电子传输产生重要影响.为理解这类物质的电子输运特征,本研究设计了一维线性非共轭(CH2)n分子结模型,并利用密度泛函理论结合非平衡态格林函数的方法,对(CH2)n(n=1—12)线性分子链与两个石墨烯电极耦合而成的分子结进行了第...     

Spin Transport in a Rashba Ring-Quantum Dot System Pumped by Microwave Fields

We report a theoretical study on producing electrically spin-polarized current in the Rashba ring with parallel double dots embedded, which are subject to two time-dependent microwave fields. By means of the Keldysh Green's function method, we present an analytic result of the pumped current at adiabatic limit and demonstrate that the interplay between the quantum pumping effectand spin-dependent quantum interference can lead to an arbitrarily controllable spin-polarized current in the device. The magnitude and direction of the charge and spin current can be effectively modulated by system parameters such as the pumping phase difference, Rashba precession phase, and the dynamic phase difference of electron traveling in two arms of ring; moreover, thespin-polarization degree of the charge current can also be tuned in the range [-∞, +∞]. Our findings may shed light on the all-electric way to produce the controllable spin-polarized charge current in the field of spintronics.     

An introduction to molecular spintronics

We review the progress and future possibilities in the emerging area of molecular spintronics. We first provide an overview of the different transport regimes in which electronic nanodevices can operate, then briefly overview the important characteristics of molecular magnetic materials that can be useful for application in spintronics and we eventually present several schemes to include such systems into spintronic nanodevices. We hightlight the importance of a chemical approach to the area, and in the last section we showcase some approaches to the creation of hybrids made of carbon nanostructures and molecular magnets, which are gaining increasing attention.     

Brownian diode: Molecular motor based on a semi-permeable Brownian particle with internal potential drop

A model of an autonomous isothermal Brownian motor with an internal propulsion mechanism is considered. The motor is a Brownian particle which is semi-transparent for molecules of surrounding ideal gas. Molecular passage through the particle is controlled by a potential similar to that in the transition rate theory, i.e. characterized by two stationary states with a finite energy difference separated by a potential barrier. The internal potential drop maintains the diode-like asymmetry of molecular fluxes through the particle, which results in the particle?s stationary drift.