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961.
Ph. Komninou Th. Kehagias A. Delimitis G.P. Dimitrakopulos J. Kioseoglou E. Dimakis A. Georgakilas Th. Karakostas 《Superlattices and Microstructures》2004,36(4-6):509
The structural properties of InN thin films, grown by rf plasma-assisted molecular beam epitaxy on Ga-face GaN/Al2O3(0001) substrates, were investigated by means of conventional and high resolution electron microscopy. Our observations showed that a uniform InN film of total thickness up to 1 μm could be readily grown on GaN without any indication of columnar growth. A clear epitaxial orientation relationship of , was determined. The quality of the InN film was rather good, having threading dislocations as the dominant structural defect with a density in the range of 109–1010 cm−2. The crystal lattice parameters of wurtzite InN were estimated by electron diffraction analysis to be a=0.354 nm and c=0.569 nm, using Al2O3 as the reference crystal. Heteroepitaxial growth of InN on GaN was accomplished by the introduction of a network of three regularly spaced misfit dislocation arrays at the atomically flat interface plane. The experimentally measured distance of misfit dislocations was 2.72 nm. This is in good agreement with the theoretical value derived from the in-plane lattice mismatch of InN and GaN, which indicated that nearly full relaxation of the interfacial strain between the two crystal lattices was achieved. 相似文献
962.
C. von Borczyskowski F. Cichos J. Martin J. Schuster A. Issac J. Brabandt 《The European physical journal. Special topics》2007,144(1):13-25
Optical spectroscopy in combination with wide field or confocal optical
microscopy enables the investigation of single quantum objects such as
organic molecules, II/VI semiconductor quantum dots and silicon nanocrystals.
They all have fluctuations of luminescence intensities on time scales longer
than μs in common. A comparison reveals that despite the large differences
of the nature of the respective quantum objects, the intensity fluctuations
are related to a slow ionisation process followed
by a trapping of the photoejected charge in the non-conducing environment.
Detailed aspects of the dynamics are controlled by the dielectric properties
of the matrix. 相似文献
963.
Explosion-produced plasma jets formed in free spece are experimentally investigated. The feasibility of emitting pulsed electromagnetic signals by plasma jets is shown, and the emitting conditions are studied. Comparison is made between the results of experiments with short and long plasma jets. When the jet passes through the field of a helix, a short-term increase in the emitted signal is detected. A linear parametric model of interaction between the plasma jet and an exciting electromagnetic signal is proposed. The operating performance of instrumentation developed for the investigation is presented. 相似文献
964.
A. M. Hashimov Sh. M. Hasanli R. N. Mehdizadeh Sh. M. Azizova Kh. B. Bayramov 《Technical Physics》2007,52(8):1086-1088
The resistivity of composite nonlinear resistors (varistors) consisting of zinc oxide ceramic and high-density polyethylene, as well as IR spectra and X-ray diffraction patterns taken of the samples, are studied. The component composition of the resistor is shown to influence its resistivity and IR and X-ray spectra. 相似文献
965.
Alpeshkumar K. Malde Santosh A. Khedkar Evans C. Coutinho 《Journal of Physical Organic Chemistry》2007,20(2):151-160
Modification of peptides to produce peptidomimetics is of great interest, with the aim of designing potent, selective, and metabolically stable analogs having certain conformational properties. Organoboranes have been reported in the literature with a wide range of therapeutic applications. One of the therapeutically important class of molecules is amine‐carboxyboranes derived from amino acids by replacement of the Cα atom of an amino acid/peptide by boron. The conformational preferences of these peptides, with respect to backbone ω, ?, and ψ torsion angles, have been investigated by theoretical calculations. The amide bond in these molecules has the same geometry in the ground and transition states as the natural peptides. However, the boron isosteres of glycine and alanine peptides are less structured than their natural derivatives, but are distinguished by structures with a positive value for the ? angle, which is normally disfavored for natural peptides. This property could be used to build peptides with a geometry not usually seen in natural peptides. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
966.
P.V.V. Jayaweera P.K.D.D.P. Pitigala M.K.I. Seneviratne A.G.U. Perera K. Tennakone 《Infrared Physics & Technology》2007,50(2-3):270-273
All electronic devices are plagued with 1/f noise originating from many causes. The most important factors contributing to 1/f noise in a semiconductor is believed to be recombination of carriers and their trapping at defects and impurity sites. Adsorption of moisture and electron acceptor molecules enhances the intensity of 1/f noise. Amazingly, some molecular species that strongly chelate to the semiconductor surface, suppress 1/f noise owing to passivation of the recombination sites. Thus in addition to sensitization, the dye adsorbed on the nanocrystallites plays a key role in mitigation of recombinations. For this reason dye-sensitized heterojunctions could also find application as low noise NIR photon detectors. Experiments conducted with oxide semiconductors (TiO2, ZnO, SnO2) indicate that the mode of binding of dyes at specific sites determines the extent to which the recombination and 1/f noise are suppressed. The transport of electrons in a nanocrystalline matrix is diffusive with a diffusion coefficient D depending on the trapping and detrapping processes. Thus passivation of trapping sites by the adsorbed dye is expected to increase the response time which can be expressed as τ L2/D, where L = thickness of the nanocrystalline film. Measurement techniques and construction of a dye-sensitized NIR photon detector will be discussed. 相似文献
967.
We investigate the Scheme programming language opportunities to analytically calculate the Clebsch-Gordan coefficients, Wigner
6j and 9j symbols, and general recoupling coefficients that are used in the quantum theory of angular momentum. The considered coefficients
are calculated by a direct evaluation of the sum formulas. The calculation results for large values of quantum angular momenta
were compared with analogous calculations with FORTRAN and Java programming languages.
The text was submitted by the authors in English. 相似文献
968.
So-Yon Lim Matt Meyer Richard A Kjonaas Swapan K Ghosh 《Journal of immune based therapies and vaccines》2007,5(1):3-1
This is a correction article. 相似文献
969.
E. de A. Gonçalves V. M. de Oliveira A. Rosas P. R.A. Campos 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):127-132
Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective
advantage
to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a
long history
in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces
affecting the strength of natural selection in the populations.
In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations
(demes)
can exchange migrants
among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We
have observed that the migration rate
drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on
the
migration rate, accordingly to
Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when
clonal interference
becomes effective. 相似文献
970.
In experiment PAX, proposed for the new accelerator complex at GSI, investigations in the field of high-energy spin physics
with the use of a polarized antiproton beam are planned. In this paper the possibilities for triggering are considered taking
into account the PAX detector properties and a probable configuration of the trigger system is discussed for the first time.
The text was submitted by the authors in English. 相似文献