9,769 research outputs found
Difference of optical conductivity between one- and two-dimensional doped nickelates
We study the optical conductivity in doped nickelates, and find the dramatic
difference of the spectrum in the gap (\alt4 eV) between one- (1D)
and two-dimensional (2D) nickelates. The difference is shown to be caused by
the dependence of hopping integral on dimensionality. The theoretical results
explain consistently the experimental data in 1D and
2D nickelates, YCaBaNiO and LaSrNiO,
respectively. The relation between the spectrum in the X-ray aborption
experiments and the optical conductivity in LaSrNiO is
discussed.Comment: RevTeX, 4 pages, 4 figure
Formation of diluted III–V nitride thin films by N ion implantation
iluted III–Nₓ–V₁ˍₓ alloys were successfully synthesized by nitrogen implantation into GaAs,InP, and AlyGa1−yAs. In all three cases the fundamental band-gap energy for the ion beam synthesized III–Nₓ–V₁ˍₓ alloys was found to decrease with increasing N implantation dose in a manner similar to that observed in epitaxially grownGaNₓAs1−x and InNₓP₁ˍₓalloys. In GaNₓAs₁ˍₓ the highest value of x (fraction of “active” substitutional N on As sublattice) achieved was 0.006. It was observed that NAs is thermally unstable at temperatures higher than 850 °C. The highest value of x achieved in InNₓP₁ˍₓ was higher, 0.012, and the NP was found to be stable to at least 850 °C. In addition, the N activation efficiency in implantedInNₓP₁ˍₓ was at least a factor of 2 higher than that in GaNₓAs₁ˍₓ under similar processing conditions. AlyGa1−yNₓAs₁ˍₓ had not been made previously by epitaxial techniques. N implantation was successful in producing AlyGa1−yNₓAs₁ˍₓalloys. Notably, the band gap of these alloys remains direct, even above the value of y (y>0.44) where the band gap of the host material is indirect.This work was supported by the ‘‘Photovoltaic Materials
Focus Area’’ in the DOE Center of Excellence for the Synthesis
and Processing of Advanced Materials, Office of Science,
Office of Basic Energy Sciences, Division of Materials
Sciences under U.S. Department of Energy Contract No. DE-ACO3-76SF00098. The work at UCSD was partially supported
by Midwest Research Institute under subcontractor
No. AAD-9-18668-7 from NREL
The superheated Melting of Grain Boundary
Based on a model of the melting of Grain Boundary (GB), we discuss the
possibility of the existence of superheated GB state. A Molecular Dynamics
simulation presented here shows that the superheated GB state can realized in
the high symmetric tilt GB. Whether the sizes of liquid nuclei exceed a
critical size determined the superheating grain boundary melting or not. Our
results also indicate that the increase of melting point due to pressure is
smaller than the superheating due to nucleation mechanism.Comment: Accepted by PRB, 7 pages and 5 figure
Quantum master equation scheme of time-dependent density functional theory to time-dependent transport in nano-electronic devices
In this work a practical scheme is developed for the first-principles study
of time-dependent quantum transport. The basic idea is to combine the transport
master-equation with the well-known time-dependent density functional theory.
The key ingredients of this paper include: (i) the partitioning-free initial
condition and the consideration of the time-dependent bias voltages which base
our treatment on the Runge-Gross existence theorem; (ii) the non-Markovian
master equation for the reduced (many-body) central system (i.e. the device);
and (iii) the construction of Kohn-Sham master equation for the reduced
single-particle density matrix, where a number of auxiliary functions are
introduced and their equations of motion (EOM) are established based on the
technique of spectral decomposition. As a result, starting with a well-defined
initial state, the time-dependent transport current can be calculated
simultaneously along the propagation of the Kohn-Sham master equation and the
EOM of the auxiliary functions.Comment: 9 pages, no figure
Trade-off between multiple-copy transformation and entanglement catalysis
We demonstrate that multiple copies of a bipartite entangled pure state may
serve as a catalyst for certain entanglement transformations while a single
copy cannot. Such a state is termed a "multiple-copy catalyst" for the
transformations. A trade-off between the number of copies of source state and
that of the catalyst is also observed. These results can be generalized to
probabilistic entanglement transformations directly.Comment: Essentially the journal version. 7 pages, no figures. Minor
correction
Supervised Learning in Multilayer Spiking Neural Networks
The current article introduces a supervised learning algorithm for multilayer
spiking neural networks. The algorithm presented here overcomes some
limitations of existing learning algorithms as it can be applied to neurons
firing multiple spikes and it can in principle be applied to any linearisable
neuron model. The algorithm is applied successfully to various benchmarks, such
as the XOR problem and the Iris data set, as well as complex classifications
problems. The simulations also show the flexibility of this supervised learning
algorithm which permits different encodings of the spike timing patterns,
including precise spike trains encoding.Comment: 38 pages, 4 figure
Multiple-copy entanglement transformation and entanglement catalysis
We prove that any multiple-copy entanglement transformation [S.
Bandyopadhyay, V. Roychowdhury, and U. Sen, Phys. Rev. A \textbf{65}, 052315
(2002)] can be implemented by a suitable entanglement-assisted local
transformation [D. Jonathan and M. B. Plenio, Phys. Rev. Lett. \textbf{83},
3566 (1999)]. Furthermore, we show that the combination of multiple-copy
entanglement transformation and the entanglement-assisted one is still
equivalent to the pure entanglement-assisted one. The mathematical structure of
multiple-copy entanglement transformations then is carefully investigated. Many
interesting properties of multiple-copy entanglement transformations are
presented, which exactly coincide with those satisfied by the
entanglement-assisted ones. Most interestingly, we show that an arbitrarily
large number of copies of state should be considered in multiple-copy
entanglement transformations.Comment: 11 pages, RevTex 4. Main results unchanged. Journal versio
Studying arsenic trioxide-induced apoptosis of Colo-16 cells with two-photon and confocal laser scanning microscopy
With two-photon and confocal laser scanning microscopy in combination with fluorescent probes Hoechst 33342, 2′,7′-dichlorofluorescin diacetate (DCFH-DA) and Fluo 3-AM, we simultaneously observed arsenic trioxide (As2O3)-induced changes in nuclear morphology, reactive oxygen species (ROS) and intracellular calcium concentration (Ca2+)i within human skin squamous carcinoma cells (Colo-16 cells). Our results indicated that As2O3 induced (Ca2+)i elevation and ROS production within Colo-16 cells, and both (Ca2+)i elevation and ROS production were involved in the apoptosis of Colo-16 cells. These results suggested that two-photon and confocal laser scanning microscopy might provide a real-time, sensitive and noninvasive method for simultaneously multi-parameter observation of As2O3- induced apoptosis at the single cell level.Key words: Two-photon laser scanning microscopy, confocal laser scanning microscopy, human skin squamous carcinoma cells (Colo-16 cells), arsenic trioxide, apoptosi
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