39 research outputs found
Interband mixing between two-dimensional states localized in a surface quantum well and heavy hole states of the valence band in narrow gap semiconductor
Theoretical calculations in the framework of Kane model have been carried out
in order to elucidate the role of interband mixing in forming the energy
spectrum of two-dimensional carriers, localized in a surface quantum well in
narrow gap semiconductor. Of interest was the mixing between the 2D states and
heavy hole states in the volume of semiconductor. It has been shown that the
interband mixing results in two effects: the broadening of 2D energy levels and
their shift, which are mostly pronounced for semiconductors with high doping
level. The interband mixing has been found to influence mostly the effective
mass of 2D carriers for large their concentration, whereas it slightly changes
the subband distribution in a wide concentration range.Comment: 12 pages (RevTEX) and 4 PostScript-figure
Anomalous magneto-oscillations in two-dimensional systems
The frequencies of Shubnikov-de Haas oscillations have long been used to
measure the unequal population of spin-split two-dimensional subbands in
inversion asymmetric systems. We report self-consistent numerical calculations
and experimental results which indicate that these oscillations are not simply
related to the zero-magnetic-field spin-subband densities.Comment: 4 pages, 3 figures; changed content (clarifications
Repeat Composition of CenH3-chromatin and H3K9me2-marked heterochromatin in Sugar Beet (Beta vulgaris)
Kowar T, Zakrzewski F, Macas J, et al. Repeat Composition of CenH3-chromatin and H3K9me2-marked heterochromatin in Sugar Beet (Beta vulgaris). BMC Plant Biology. 2016;16(1): 120.Background
Sugar beet (Beta vulgaris) is an important crop of temperate climate zones, which provides nearly 30 % of the world’s annual sugar needs. From the total genome size of 758 Mb, only 567 Mb were incorporated in the recently published genome sequence, due to the fact that regions with high repetitive DNA contents (e.g. satellite DNAs) are only partially included. Therefore, to fill these gaps and to gain information about the repeat composition of centromeres and heterochromatic regions, we performed chromatin immunoprecipitation followed by sequencing (ChIP-Seq) using antibodies against the centromere-specific histone H3 variant of sugar beet (CenH3) and the heterochromatic mark of dimethylated lysine 9 of histone H3 (H3K9me2).
Results
ChIP-Seq analysis revealed that active centromeres containing CenH3 consist of the satellite pBV and the Ty3-gypsy retrotransposon Beetle7, while heterochromatin marked by H3K9me2 exhibits heterogeneity in repeat composition. H3K9me2 was mainly associated with the satellite family pEV, the Ty1-copia retrotransposon family Cotzilla and the DNA transposon superfamily of the En/Spm type. In members of the section Beta within the genus Beta, immunostaining using the CenH3 antibody was successful, indicating that orthologous CenH3 proteins are present in closely related
species within this section.
Conclusions
The identification of repetitive genome portions by ChIP-Seq experiments complemented the sugar beet reference sequence by providing insights into the repeat composition of poorly characterized CenH3-chromatin and H3K9me2-heterochromatin. Therefore, our work provides the basis for future research and application concerning the sugar beet centromere and repeat rich heterochromatic regions characterized by the presence of H3K9me2