Distribution and cloning of eukaryotic mRNAs by means of differential display: refinements and optimization.

Differential display has been developed as a tool to detect and characterize altered gene expression in eukaryotic cells. The basic principle is to systematically amplify messenger RNAs and then distribute their 3' termini on a denaturing polyacrylamide gel. Here we provide methodological details and examine in depth the specificity, sensitivity and reproducibility of the method. We show that the number of anchored oligo-dT primers can be reduced from twelve to four that are degenerate at the penultimate base from the 3' end. We also demonstrate that using optimized conditions described here, multiple RNA samples from related cells can be displayed simultaneously. Therefore process-specific rather than cell-specific genes could be more accurately identified. These results enable further streamlining of the technique and make it readily applicable to a broad spectrum of biological systems

Dynamic usability principles in rehabilitation, work and communication

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich. - This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively

Luminescence studies of a Si/SiO₂ superlattice

Photoluminescence and electroluminescence from a Si/SiO2 superlattice have been measured. They show similar characteristics and exhibit an inhomogeneously broadened photoluminescence band peaked at 2.06 eV. The excitation spectrum indicates that excitations occur in the Si layers. The insensitivity of the luminescence spectrum and decay to temperature and excitation wavelength suggests that luminescence originates from transitions between localized defect states. These localized states are most likely defect states residing at the Si/SiO2 interfaces, because there should be a significant concentration of defects at the interface and SiO2 due to the large lattice mismatch and the amorphous state. The close proximity of these states offers a more rapid transition path for the excited electrons. An energy band diagram of the superlattice is constructed based on our results

Classification and control of the origin of photoluminescence from Si nanocrystals.

Silicon dominates the electronics industry, but its poor optical properties mean that III–V compound semiconductors are preferred for photonics applications. Photoluminescence at visible wavelengths was observed from porous Si at room temperature in 1990, but the origin of these photons (do they arise from highly localized defect states or quantum confinement effects?) has been the subject of intense debate ever since. Attention has subsequently shifted from porous Si to Si nanocrystals, but the same fundamental question about the origin of the photoluminescence has remained. Here we show, based on measurements in high magnetic fields, that defects are the dominant source of light from Si nanocrystals. Moreover, we show that it is possible to control the origin of the photoluminescence in a single sample: passivation with hydrogen removes the defects, resulting in photoluminescence from quantum-confined states, but subsequent ultraviolet illumination reintroduces the defects, making them the origin of the light again