Degradation of a-Si:H Solar Cells: New Evidence for a Bulk Effect

Well defined sequences of non-uniform and uniform degradation steps are applied on several high quality bifacial p-i-n solar cells with different thicknesses of the intrinsic layer. This procedure allows one to separate interface and bulk effects in the degradation of a-Si:H solar cells, or more precisely to separate the influence of the modification of the internal electric field profile (due mainly to effect near the interface) from that of an increase in the deep defect density in the bulk; according to present data the latter is clearly responsible for the major part of a-Si:H cell degradation

Stable transduction with lentiviral vectors and amplification of immature hematopoietic progenitors from cord blood of preterm human fetuses

Umbilical cord blood (CB) from the early gestational human fetus is recognized as a rich source of hematopoietic stem cells. To examine the value of fetal CB for gene therapy of inborn immunohematopoietic disorders, we tested the feasibility of genetic modification of CD34(+) cells from CB at weeks 24 to 34 of pregnancy, using lentiviral vector-mediated transfer of the green fluorescent protein (GFP) gene. The transduction rate of CD34(+) cells was 42 +/- 9%, resulting in GFP expression in 23 +/- 4% of colonies derived from colony-forming units (CFUs) and 11 +/- 1% from primitive long-term culture-initiating cells (LTC-ICs). Cell cycle analysis demonstrated transduction and GFP expression in cells in the G(0) phase, which contains immature hematopoietic progenitors. Transduced fetal CD34(+) cells could be expanded 1000-fold in long-term cultures supplemented with megakaryocyte growth and development factor along with Flt-3 ligand. At week 10, expression of GFP was observed in 40.5 +/- 11.7% of CFU-derived colonies. While prestimulation of CD34(+) cells with cytokines prior to transduction increased the efficiency of GFP transfer 2- to 3-fold, long-term maintenance of GFP-expressing CFUs occurred only in the absence of prestimulation. The GFP gene was found integrated into the genomic DNA of 35% of LTC-IC-derived colonies initiated at week 10, but GFP expression was not detectable, suggesting downregulation of transgene activity during the extended culture period. These results indicate that human fetal CB progenitors are amenable to genetic modification by lentiviral vectors and may serve as a target for gene therapy of hematopoietic disorders by prenatal autologous transplantation

An amorphous silicon photodiode array for glass-based optical MEMS application

A highly sensitive photo-detector array deposited on a glass substrate with an optional integrated optical filter have been presented. The active element is a vertically integrated hydrogenated amorphous silicon photodiode featuring a dark current of less than 1e-10 A/cm2 for -3V polarization and a maximal quantum efficiency of 80% near 580 nm. The prototype was encapsulated and successfully tested optically. It has a fill factor of only 44% which, however, can be easily increased to 90% using flip-chip bonding to an integrated electronic circuit for signal conditioning. The sensor is biocompatible and can be integrated with other glass-based and glass compatible micro-fabricated devices such as optical, microfluidic, lab-on-a-chip, chemical and biological devices in which photo-detection is a desired feature. ©2009 IEEE