Polarity effects on ZnO films grown along the nonpolar [1120] direction

The surface electrical properties of ZnO thin films grown along the nonpolar [1120] direction have been investigated by Kelvin probe microscopy on a nanometer scale. Two different charge domains, with a 75 meV work function difference, coexist within the ZnO surface, which is covered by rhombohedral pyramids whose sidewalls are shown to be {1011}-type planes. The presence and relative orientation of the two kinds of charge domains are explained in terms of the atomic arrangement at the {1011} polar surfaces.     

The Hamiltonian constraint in the teleparallel equivalent of general relativity

In the teleparallel equivalent of general relativity the integral form of the Hamiltonian constraint contains explicitly theadm energy in the case of asymptotically flat space-times. We show that such expression of the constraint leads to a natural and straightforward construction of a Schrödinger equation for time-dependent physical states. The quantized Hamiltonian constraint is thus written as an energy eigenvalue equation. We further analyse the constraint equations in the case of a space-time endowed with a spherically symmetric geometry. We find the general functional form of the time-dependent solutions of the quantized Hamiltonian and vector constraints.     

Nonlocal forces of inertia in cosmology

This paper reviews the origin of inertia according to Mach's principle and Weber's law of gravitation. The resulting theory is based on simultaneous nonlocal gravitational interactions between particles in the solar system and others in the remote universe beyond the Milky Way galaxy. It explains the precession of the perihelion of Mercury. A most important implication of the Mach-Weber theory of the force of inertia is the necessity for a large amount of uniformly distributed matter in the galactic universe. This matter could be the source of the cosmic background radiation. Nonlocal inertia forces are compatible with a static universe and also with an expanding universe but the latter would demand slow changes in the mass of particles and the gravitational constant.     

Laser location and manipulation of a single quantum tunneling channel in an InAs quantum dot

We use a femtowatt focused laser beam to locate and manipulate a single quantum tunneling channel associated with an individual InAs quantum dot within an ensemble of dots. The intensity of the directed laser beam tunes the tunneling current through the targeted dot with an effective optical gain of 10(7) and modifies the curvature of the dot's confining potential and the spatial extent of its ground state electron eigenfunction. These observations are explained by the effect of photocreated hole charges which become bound close to the targeted dot, thus acting as an optically induced gate electrode.     

Nanocrystalline CoSn2-carbon composite electrode prepared by using sonochemistry

A sonochemical method has been used to prepare negative electrode materials containing intermetallic nanoparticles and polyacrylonitrile (PAN). The ultrasound irradiation is applied to achieve small particle size. After annealing at 490 °C under Ar-flow, the polymer PAN is partially carbonized and the metallic nanoparticles are surrounded by a carbonaceous matrix. The main metallic phase is CoSn₂. The carbonaceous coating and the surface oxides have been explored by using XPS. The resulting CoSn₂-carbonaceous phase electrode (CoSn₂@C) shows improved electrochemical behavior (ca. 450 mAh/g after 50 cycles) in comparison with previous reports on pure crystalline CoSn₂. The reaction between CoSn₂@C and Li has been studied by using XRD and ¹¹⁹Sn Mössbauer spectroscopy. The formation of large grains of crystalline Li_xSn phases after the first discharge is discarded. The small particle size which is achieved by using ultrasonication and the carbonaceous matrix contribute to maintain the Co-Sn interactions during the electrochemical cycling. The aggregation of the nanosized metallic particles upon electrochemical cycling can be suppressed by the carbonaceous matrix (pyrolytic PAN).     

Differentiation of aminomethyl corrole isomers by mass spectrometry

Two new isomeric aminomethyl corrole derivatives of [5,10,15-tris(pentafluorophenyl)corrolato]gallium(III) were synthesized with pyridine (py) molecules as axial ligands. When investigated by electrospray ionization mass spectrometry, in the positive and the negative ion modes, these compounds showed an unusual gas-phase behavior that could be used for their differentiation. In the positive ion mode, the differentiation was achieved through the formation of diagnostic fragment ions formed from [M-py?+?H](+) precursors, by (CH(3) )(2) NH and HF losses. An unusual addition of water to the main fragment ions provides an alternative route for isomer identification. Semi-empirical calculations were performed to elucidate the structures and stabilities of the main ionic species formed in the positive ion mode. In the negative ion mode isomer discrimination is accomplished via the fragmentation of the methoxide adduct ions [M-py?+?CH(3) O](-) through (CH(3) )(2) N(.) and HF losses.