8,581 research outputs found
Radiation resistance and comparative performance of ITO/InP and n/p InP homojunction solar cells
The radiation resistance of ITO/InP cells processed by DC magnetron sputtering is compared to that of standard n/p InP and GaAs homojunction cells. After 20 MeV proton irradiations, it is found that the radiation resistance of the present ITO/InP cell is comparable to that of the n/p homojunction InP cell and that both InP cell types have radiation resistance significantly greater than GaAs. The relatively lower radiation resistance, observed at higher fluence, for the InP cell with the deepest junction depth, is attributed to losses in the cells emitter region. Diode parameters obtained from I sub sc - V sub oc plots, data from surface Raman spectroscopy, and determinations of surface conductivity types are used to investigate the configuration of the ITO/InP cells. It is concluded that thesee latter cells are n/p homojunctions, the n-region consisting of a disordered layer at the oxide semiconductor
Endophytic Agrobacterium in crown gall-resistant and -susceptible Vitis genotypes
Several methods were used to study endophytic colonization of Vitis genotypes by Agrobacterium vitis (AV). AV was seldom detected except at inoculated sites, indicating little systemic movement of the bacterium under the conditions of these experiments. AV populations at inoculated sites were evaluated for 10 months following inoculation of crown gall-resistant and -susceptible genotypes. Two months after inoculation, V. amurensis selections had significantly smaller populations than V. vinifera (Cabernet Sauvignon) or V. riparia x V. rupestris (C3309). All crown gall-resistant genotypes had significantly lower populations than Cabernet Sauvignon 10 months after inoculation. Examination of vines one year after inoculation indicated that AV populations were much higher at inoculated sites when crown galls developed. However, even when no galls were apparent, Cabernet Sauvignon had significantly higher AV populations than V. amurensis 689 (6-fold higher) and C3309 (70-fold higher). Crown gall-resistant genotypes appear to support lower populations of AV than the crow gall-susceptible Cabernet Sauvignon. Freezing followed by a two-day incubation significantly increased recovery of Agrobacterium using vascular fluid displacement in naturally-infected and artifically-inoculated vines and therefore increased the sensitivity of indexing for AV in grapevines
Transformation of crown gall resistant and susceptible Vitis genotypes by Agrobacterium vitis
Transformation of crown gall-susceptible and -resistant Vitis genotypes by Agrobacterium vitis strain CG49 was studied using uidA (GUS) in the p35SGUSINT construct. When greenhouse-grown material propagated through tissue culture was inoculated with CG49(p35SGUSINT) in vitro, the highly crown gall-susceptible V. vinifera Cabernet Sauvignon displayed GUS activity on 53 % of inoculated explants vs. 5 % for the resistant V. amurensis and 0 % for the resistant Couderc 3309. Response of Cabernet Sauvignon suggested a strong effect of shoot polarity on transformation. Inoculation of basal vs. apical explant surface in Cabernet Sauvignon indicated transformation in 88 % of basal inoculated explants with no transformation from apical inoculation. Basal inoculations indicated no transformation of V. amurensis and transformation in 10 % of Couderc 3309 explants. Inoculation of intact plants with CG49(p35SGUSINT) produced GUS-positive sites at 56 % of inoculated sites in Cabernet Sauvignon, 10 % of V. amurensis inoculated sites and 9 % of Couderc 3309 inoculated sites. Resistance to crown gall in these genotypes appears to be due to reduced susceptibility to transformation by A. vitis rather than post-transformation phenomena. These studies were complicated by production of GUS-positive spots from in vitro inoculations using wild-type CG49. Resident microorganisms producing b-glucuronidase may proliferate after tissue degradation by A. vitis-induced cell disruption. Use of in vitro internodal explants from tissue culture-propagated vines greatly reduced GUS expression from control CG49 inoculations and these were readily distinguished (by appearance and location) from GUS-positive spots resulting from transformation with uidA
Lattice-dynamics of a Disordered solid-solid Interface
Generic properties of elastic phonon transport at a disordered interface are
studied. The results show that phonon transmittance is a strong function of
frequency and the disorder correlation length. At frequencies lower than the
van Hove singularity the transmittance at a given frequency increases as the
correlation length decreases. At low frequencies, this is reflected by
different power-laws for phonon conductance across correlated and uncorrelated
disordered interfaces which are in approximate agreement with perturbation
theory of an elastic continuum. These results can be understood in terms of
simple mosaic and two-colour models of the interface.Comment: 17 pages, 5 figures, submitted to PR
Pure O-sequences and matroid h-vectors
We study Stanley's long-standing conjecture that the h-vectors of matroid
simplicial complexes are pure O-sequences. Our method consists of a new and
more abstract approach, which shifts the focus from working on constructing
suitable artinian level monomial ideals, as often done in the past, to the
study of properties of pure O-sequences. We propose a conjecture on pure
O-sequences and settle it in small socle degrees. This allows us to prove
Stanley's conjecture for all matroids of rank 3. At the end of the paper, using
our method, we discuss a first possible approach to Stanley's conjecture in
full generality. Our technical work on pure O-sequences also uses very recent
results of the third author and collaborators.Comment: Contains several changes/updates with respect to the previous
version. In particular, a discussion of a possible approach to the general
case is included at the end. 13 pages. To appear in the Annals of
Combinatoric
X-ray photoemission spectroscopy determination of the InN/yttria stabilized cubic-zirconia valence band offset
The valence band offset of wurtzite InN(0001)/yttria stabilized cubic-zirconia (YSZ)(111) heterojunctions is determined by x-ray photoemission spectroscopy to be 1.19±0.17 eV giving a conduction band offset of 3.06±0.20 eV. Consequently, a type-I heterojunction forms between InN and YSZ in the straddling arrangement. The low lattice mismatch and high band offsets suggest potential for use of YSZ as a gate dielectric in high-frequency InN-based electronic devices
Realistic constraints on the doubly charged bilepton couplings from Bhabha scattering with LEP data
Upper limits on doubly charged bilepton couplings and masses are extracted
from LEP data for Bhabha scattering at energy range GeV
using standard model program ZFITTER which calculates radiative corrections. We
find that at 95% C.L. for scalar and
vector bileptons.Comment: 5 pages, 1 EPS figur
Calculation of thermal parameters of SiGe microbolometers
The thermal parameters of a SiGe microbolometer were calculated using
numerical modeling. The calculated thermal conduction and thermal response time
are in good agreement with the values found experimentally and range between
2x10 and 7x10 W/K and 1.5 and 4.5 ms, respectively. High sensitivity
of microbolometer is achieved due to optimization of the thermal response time
and thermal conduction by fitting the geometry of supporting heat-removing legs
or by selection of a suitable material providing boundary thermal resistance
higher than 8x10 cmK/W at the SiGe interface.Comment: 11 pages, 6 figure
Dielectric nonlinearity of relaxor ferroelectric ceramics at low ac drives
Dielectric nonlinear response of
(PbMgNbO)(PbTiO) (0.9PMN-0.1PT) relaxor
ceramics was investigated under different ac drive voltages. It was observed
that: (i) the dielectric permittivity is independent on ac field amplitude at
high temperatures; (ii) with increasing ac drive, the permittivity maximum
increases, and the temperature of the maximum shifts to lower temperature;
(iii) the nonlinear effect is weakened when the measurement frequency
increases. The influences of increasing ac drive were found to be similar to
that of decreasing frequency. It is believed that the dielectric nonlinearities
of relaxors at low drives can be explained by the phase transition theory of
ergodic space shrinking in succession. A Monte Carlo simulation was performed
on the flips of micro polarizations at low ac drives to verify the theory.Comment: Submitted to J. Phys.: Cond. Matte
Comparison of high-latitude line-of-sight ozone column density with derived ozone fields and the effects of horizontal inhomogeneity
International audienceExtensive ozone measurements were made during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II). We compare high-latitude line-of-sight (LOS) slant column ozone measurements from the NASA DC-8 to ozone simulated by forward integration of measurement-derived ozone fields constructed both with and without the assumption of horizontal homogeneity. The average bias and rms error of the simulations assuming homogeneity are relatively small (?6 and 10%, respectively) in comparison to the LOS measurements. The comparison improves significantly (?2% bias; 8% rms error) using forward integrations of three-dimensional proxy ozone fields reconstructed from potential vorticity-O3 correlations. The comparisons provide additional verification of the proxy fields and quantify the influence of large-scale ozone inhomogeneity. The spatial inhomogeneity of the atmosphere is a source of error in the retrieval of trace gas vertical profiles and column abundance from LOS measurements, as well as a complicating factor in intercomparisons that include LOS measurements at large solar zenith angles
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