Photoconductive hybrid films via directional self-assembly of C 60 on aligned carbon nanotubes

Hybrid nanostructured materials can exhibit different properties than their constituent components, and can enable decoupled engineering of energy conversion and transport functions. Novel means of building hybrid assemblies of crystalline C 60 and carbon nanotubes (CNTs) are presented, wherein aligned CNT films direct the crystallization and orientation of C 60 rods from solution. In these hybrid films, the C 60 rods are oriented parallel to the direction of the CNTs throughout the thickness of the film. High-resolution imaging shows that the crystals incorporate CNTs during growth, yet grazing-incidence X-ray diffraction (GIXD) shows that the crystal structure of the C 60 rods is not perturbed by the CNTs. Growth kinetics of the C 60 rods are enhanced 8-fold on CNTs compared to bare Si, emphasizing the importance of the aligned, porous morphology of the CNT films as well as the selective surface interactions between C 60 and CNTs. Finally, it is shown how hybrid C 60-CNT films can be integrated electrically and employed as UV detectors with a high photoconductive gain and a responsivity of 10 5 A W -1 at low biases (± 0.5 V). The finding that CNTs can induce rapid, directional crystallization of molecules from solution may have broader implications to the science and applications of crystal growth, such as for inorganic nanocrystals, proteins, and synthetic polymers. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of C-C chemokine receptor subfamily in teleost fish

Chemokines and their receptors play important roles in nervous and immune systems. Little information, however, exists concerning this gene family in teleost fish. In the present Study, 17 C-C chemokine receptors genes were identified from Danio rerio, 9 from Gasterosteus aculeatus, 10 from Oryzius latipes, 8 from Takifugu rubripes and 5 from Tetraodon nigroviridis. Phylogenetic analysis showed that the orthologs to mammalian CCR6, 7, 8, 9 and CCRL1 receptors were evident in zebrafish, but the clear orthologs to mammalian CCR1, 2, 3, 4, 5 and 10 were not found in zebrafish. The gene structure of zebrafish CCR (zfCCR) was further analyzed. The open reading frame of zfCCR3-1, zfCCR3-3, zfCCR6-1, zfCCR6-2, zfCCR8-2 contain one exon, and two exons were identified for zfCCR2-1, zfCCR2-2, zfCCR4 and zfCCRLI-1, three exons for zfCCR3-2, zfCCR5 and zfCCR7, four exons for zfCCR8-1 and zfCCR9-1. The expression analyses showed that in zebrafish, most C-C chemokine receptor genes Were expressed in fertilized eggs and oocytes, and all the receptor genes were expressed in larval stages. The zfCCR2-2, zfCCR3-1, zfCCR4 and zfCCR6-2 genes were expressed in all normal organs examined, whereas not for zfCCR2-1, zfCCR3-3, zfCCR6-1, zfCCR8-1, zfCCR9-2 and zfCCRL1-2. The expression of zfCCR3-2, zfCCR5, zfCCR7, zfCCR9-1 and zfCCRLI-1 were detected in the majority organs. and zfCCR8-2 and zfCCR8-3 detected only in brain. The differential expression pattern of different paralogues in organs may indicate their difference in function, which requires further investigation. (C) 2008 Elsevier Ltd. All rights reserved.

The recombinant beta subunit of C-phycocyanin inhibits cell proliferation and induces apoptosis

C-Phycocyanin (C-PC) from blue-green algae has been reported to have various pharmacological characteristics, including antiinflammatory and anti-tumor activities. In this study, we expressed the beta-subunit of C-PC (ref to as C-POP) in Escherichia coli. We found that the recombinant C-PC/beta has anti-cancer properties. Under the treatment of 5 mu M of the recombinant C-PC/beta, four different cancer cell lines accrued high proliferation inhibition and apoptotic induction. Substantially, a lower response occurred in non-cancer cells. We investigated the mechanism by which C-PC/beta inhibits cancer cell proliferation and induces apoptosis. We found that the C-PC/beta interacts with membrane-associated beta-tubulin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Under the treatment of the C-PC/beta, depolymerization of microtubules and actin-filaments were observed. The cells underwent apoptosis with an increase in caspase-3, and caspase-8 activities. The cell cycle was arrested at the G0/G1 phase under the treatment of C-PC/beta. In addition, the nuclear level of GAPDH decreased significantly. Decrease in the nuclear level of GAPDH prevents the cell cycle from entering into the S phase. Inhibition of cancer cell proliferation and induction of apoptosis may potentate the C-POP as a promising cancer prevention or therapy agent. (c) 2006 Elsevier Ireland Ltd. All rights reserved.

Magnetic quantum oscillations for the surface states of topological insulator Bi2Se3

We study quantum oscillations of the magnetization in Bi2Se3 (111) surface system in the presence of a perpendicular magnetic field. The combined spin-chiral Dirac cone and Landau quantization produce profound effects on the magnetization properties that are fundamentally different from those in the conventional semiconductor two-dimensional electron gas. In particular, we show that the oscillating center in the magnetization chooses to pick up positive or negative values depending on whether the zero-mode Landau level is occupied or empty. An intuitive analysis of these features is given and the subsequent effects on the magnetic susceptibility and Hall conductance are also discussed.

Electronic states of InAs/GaAs tyre-shape quantum ring

In the framework of the effective mass theory, this paper calculates the electron energy levels of an InAs/GaAs tyre-shape quantum ring (TSQR) by using the plane wave basis. The results show that the electron energy levels are sensitively dependent on the TSQR's section thickness d, and insensitively dependent on TSQR's section inner radius R-1 and TSQR's inner radius R-2. The model and results provide useful information for the design and fabrication of InAs/GaAs TSQRs.

Growth of c-oriented ZnO films on (001) SMO3 substrates by MOCVD

The growth direction of ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD) is modulated by pretreatment of (001) SMO3 (STO) substrates. ZnO films show a-oriented smooth surface with epitaxial relationship of < 001 > ZnO//< 110 > STO on as-received SfO, and c-axis columnar growth with < 010 > ZnO//< 110 > STO on etched STO, respectively. The orientation alteration of ZnO films is supposed to be caused by the change of STO surface polarity. In addition, the c-ZnO films exhibit an enhanced photoluminescence (PL) intensity due to the improved crystal quality, while the blueshift of PL peak is attributed to the smaller tensile strain. These results show that high quality c-ZnO, which is essential for electronic and optoelectronic device applications, can be grown on (001) SfO by MOCVD. (C) 2008 Elsevier B.V. All rights reserved.

Method for generating maximally entangled states of multiple three-level atoms in cavity QED

We propose a scheme to generate maximally entangled states (MESs) of multiple three-level atoms in microwave cavity QED based on the resonant atom-cavity interaction. In the scheme, multiple three-level atoms initially in their ground states are sequently sent through two suitably prepared cavities. After a process of appropriate atom-cavity interaction, a subsequent measurement on the second cavity field projects the atoms onto the MESs. The practical feasibility of this method is also discussed.

Local transformation of mixed states of two qubits to Bell diagonal states

The optimal entanglement manipulation for a single copy of mixed states of two qubits is to transform it to a Bell diagonal state. In this paper we derive an explicit form of the local operation that can realize such a transformation. The result obtained is universal for arbitrary entangled two-qubit states and it discloses that the corresponding local filter is not unique for density matrices with rank n = 2 and can be exclusively determined for that with n = 3 and 4. As illustrations, a four-parameter family of mixed states are explored, the local filter as well as the transformation probability are given explicitly, which verify the validity of the general result.

Investigation of {111}A and {111} planes of c-GaN epilayers grown on GaAs(001) by MOCVD

A determination of {1 1 1}A and {1 1 1}B in cubic GaN(c-GaN) was investigated by X-ray diffraction technique in detail. The c-GaN films are grown on GaAs(0 0 1) substrates by metalorganic chemical vapor deposition(MOCVD). The difference of integrated intensities measured by omega scan for the different order diffractions from {1 1 1}A and {1 1 1}B planes in the four-circle diffractometer gives convincing evidence as to which is the {1 1 1}A and which is the {1 1 1}B planes. The lesser deviation between the ratios of /F-h k l/(2)//F-(h) over bar (k) over bar (l) over bar/(2) and the calculated values after dispersion correction for atomic scattering factor shows that the content of parasitic hexagonal GaN(h-GaN) grown on c-GaN{1 1 1}A planes is higher than that on {1 1 1}B planes. The reciprocal space mappings provide additional proof that the h-GaN inclusions in c-GaN films appear as lamellar structure. (C) 2001 Published by Elsevier Science B.V.

Electronic states of a two-dimensional electron system in a lateral superlattice and a perpendicular magnetic field

The electronic state of a two-dimensional electron system (2DES) in the presence of a perpendicular uniform magnetic field and a lateral superlattice (LS) is investigated theoretically. A comparative study is made between a LS induced by a spatial electrostatic potential modulation (referred to as a PMLS) and that induced by a spatial magnetic-field modulation (referred ro asa MMLS). By utilizing a finite-temperature self-consistent Hartree-Fock approximation scheme; the dependence of the electronic state on different system parameters (e.g., the modulation period, the modulation strength, the effective electron-electron interaction strength, the averaged electron density, and the system temperature) is studied in detail. The inclusion of exchange effect is found to bring qualitative changes to the electronic state of a PMLS, leading generally to a nonuniform spin splitting, and consequently the behavior of the electronic state becomes similar to that of a MMLS. The Landau-level coupling is taken into account, and is found to introduce some interesting features not observed before. It is also found that, even in the regime of intermediate modulation strength, the density dependence of the spin splitting of energy levels, either for a PMLS or a MMLS, can be qualitatively understood within the picture of a 2DES in a perpendicular magnetic field with the modulation viewed as a perturbation. [S0163-1829(97)02248-0].

Electronic states of InAs verfically-assembled quantum disks in magnetic fields and two-electron quantum-disk qubit

We have studied the single-electron and two-electron vertically-assembled quantum disks in an axial magnetic field using the effective mass approximation. The electron interaction is treated accurately by the direct diagonalization of the Hamiltonian matrix. We calculate the six criergy levels of single-electron quantum disks and the two lowest energy levels of two-electron quantum disks in an axial magnetic field. The change of the magnetic field as an effective potential strongly modifies the electronic structures. leading to splittings and crossings between levels The results demonstrate the switching between the around states with the total spins S = 0 and S = 1. The switching results in a qubit allowed to fabricate by current growth techniques.

ELECTRON-STATES OF A STACKING-FAULT RIBBON IN SILICON

The electronic structure of a bounded intrinsic stacking fault in silicon is calculated. The method used is an LCAO-scheme (Linear Combinations of Atomic Orbitals) taking ten atomic orbitals of s-, p-, and d-type into account. The levels in the band gap are extracted using Lanczos' algorithm and a continued fraction representation of the local density of states. We find occupied states located up to 0.3 eV above the valence band maximum (E(v)). This significantly differs from the result obtained for the ideal infinite fault for which the interface state is located at E(v)+ 0.1 eV.

INVESTIGATION OF C-60 SINGLE-CRYSTAL BY X-RAY-METHODS

C-60 Single crystals grown by a single-temperature-gradient technique were characterized by synchrotron radiation white beam x-ray topography and x-ray double crystal diffraction with Cu K-alpha 1 radiation on conventional x-ray source. The results show that the crystal is rather well crystallized, The x-ray topographies give an evidence of dendritic growth mechanism of C-60 Single crystal, and x-ray double crystal diffraction rocking curve shows that there are mosaic structural defects in the sample. A phase transition st 249+/-1.5% K from a simple cubic to a face centered cubic structure is confirmed by in situ observation of synchrotron radiation white beam x-ray topography with the temperature varing from 230 to 295 K.

ELECTRON-STATES OF A VACANCY IN THE CORE OF THE 90-DEGREES PARTIAL DISLOCATION IN SILICON

An LCAO scheme (linear combination of atomic orbitals) taking into account ten atomic orbitals (s-, p-, and d-type) is used to calculate the electronic structure of a vacancy present in the core of the reconstructed 90 degrees partial dislocation in silicon. The levels in the band gap are extracted using Lanczos' algorithm and a continued fraction representation of the local density of states. The three-fold degenerate stale of the ideal vacancy is split into three levels with energies 0.26, 1.1, and 1.9 eV measured from the valence band edge.

Energy level analyses of even-parity J=1 and 2 Rydberg states of Sn I by multichannel quantum defect theory

This paper analyzes the energy levels along the even-parity J=1 and 2 Rydberg series of Sn I by multichannel quantum defect theory. A good agreement between theoretical and experimental energy levels was achieved. Below 59198 cm~(-1), a total of 85 and 23 new energy levels, respectively, in the J=1 and J=2 series, which cannot be measured previously by experiments, are predicted in this work. Based on the calculated admixture coefficients of each channel, interchannel interactions were discussed in detail. The results are helpful to understand the characteristics of configuration interaction among even-parity levels in Sn I.