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Effect of crop improvement on genetic diversity in oilseed Brassica rapa (turnip-rape) cultivars, detected by SSR markers

100%
Ofori A., Becker C., Kopisch-Obuch F. J.
Journal of Applied Genetics
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2008
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vol. 49
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issue 3
207-212
EN
With the improvement of seed quality, Brassica rapa oilseed germplasm went through 2 major breeding bottlenecks during the introgression of genes for zero erucic acid content and low glucosinolate content, respectively. This study investigates the impact of these bottlenecks on the genetic diversity in European winter B. rapa by comparing 3 open-pollinated cultivars, each representing a different breeding period. Diversity was estimated on 32 plants per cultivar, with 16 simple sequence repeat (SSR) markers covering each of the B. rapa linkage groups. There was no significant loss of genetic diversity over the 3 cultivars as indicated by allele number (ranging from 59 to 55), mean allele number (from 3.68 to 3.50), Shannon information index (from 0.94 to 0.87) and expected heterozygosity (from 0.53 to 0.48). About 83% of the total variation was attributed to within-cultivar variation, and the remaining 17% to between-cultivar variation by analysis of molecular variance (AMOVA). Individual plants were separated into the 3 cultivars by principal coordinate analysis (PCoA). In conclusion, genetic diversity within cultivars was high and quality breeding in B. rapa did not significantly reduce the genetic diversity of B. rapa winter cultivars, so there is no risk of decline in performance due to quality improvement.
2
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Characterization of Bimetallic Systems with UPS and PAX: Gold on Platinum and Palladium Surfaces

88%
Moors M., Kobiela T., Krupski A., Becker C., Wandelt K.
Acta Physica Polonica A
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2008
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vol. 114
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issue S
S-77-S-92
EN
In the present study the thermal behavior of ultrathin Au films deposited on different noble metal single crystal surfaces was studied by means of ultraviolet photoelectron spectroscopy and photoemission of adsorbed xenon. The primary goal of this work was to demonstrate the power of photoemission of adsorbed xenon as an easy to handle and very surface sensitive technique for the characterization of multi-component systems. All investigated systems, Au-Pt(111), Au-Pd(111) and Au-Pd(110) show a particular dependence of their electronic and structural properties on the annealing temperature. Au multilayer films with a thickness of 3 monolayer prepared at 150 K undergo in all cases a smoothening by annealing up to room temperature. While on Pd this effect is mainly detectable on the topmost atomic layer the ordering process on Pt is also affecting the deeper layers. Further annealing of the Au-Pd system to 450 K and the Au-Pt system to 750 K, respectively, results in the onset of the alloying process at the interface between metal film and substrate. After annealing to 650 and 950 K, respectively, the alloying finally extends to the very surface. The complete loss of Au from the surface can be detected at 1050 K on Pd and at 1150 K on Pt. The orientation of the substrate has only a weak influence, showing up e.g. in additional electronic states of the not alloyed Au-Pd(111) and Au-Pd(111) systems. Adsorption of CO as a probe molecule illustrates the formation of different adsorption sites on the bimetallic systems during the Au diffusion process.
3
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Optical Properties and Microstructure of InGaN Grown by Molecular Beam Epitaxy

52%
Böttcher T., Einfeldt S., Figge S., Kirchner V., Hommel D., Selke H., Ryder P., Bertram F., Riemann T., Christen J., Lunz U., Becker C.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
260-264
EN
The luminescence of In_{x}Ga_{1-x}N is studied for thick epitaxial layers and quantum wells. Using spatially resolved cathodoluminescence spectroscopy the commonly observed broad integral photoluminescence spectra were found to result from spectral and lateral inhomogeneous emission across the samples. Moreover, the integral photoluminescence and absorption spectra show different temperature dependences. The effects can be explained assuming fluctuations of the composition associated with a variation of the band gap.
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