Loss of UBE3A expression, a gene regulated by genomic imprinting, causes Angelman Syndrome (AS), a rare neurodevelopmental disorder. The UBE3A gene encodes an E3 ubiquitin ligase with three known protein isoforms in humans. Studies in mouse suggest that the human isoforms may have differences in localization and neuronal function. A recent case study reported mild AS phenotypes in individuals lacking one specific isoform. Here we have used CRISPR/Cas9 to generate isogenic human embryonic stem cells (hESCs) that lack the individual protein isoforms. We demonstrate that isoform 1 accounts for the majority of UBE3A protein in hESCs and neurons. We also show that UBE3A predominantly localizes to the cytoplasm in both wild type and isoform-null cells. Finally, we show that neurons lacking isoform 1 display a less severe electrophysiological AS phenotype.

A concept for the fabrication of monolithically integrated silicon solar cells is presented. The concept is based on standard Si wafer technology and does not use thin-film approaches. A key feature is isolation trenches dividing the wafer into several unit solar cells. Due to the imperfect isolation between unit cells defined on the same conductive wafer, some device aspects deviating from an ordinary series connection of solar cells arise. For the theoretical description, a model proposed by Valco et al. [G. J. Valco, V. J. Kapoor, J. C. Evans, Jr., and A. T. Chin, in Proceedings of the 15th IEEE Photovoltaic Specialists Conference, Orlando, FL (1981), p. 187] has been generalized by using a two-diode concept for the unit cells and by weakening the assumption of identical unit cells. The model was used to simulate the cell performance in dependence on light intensity, isolation resistance, cell area, and number of unit cells. As a result, general design rules for these truly monolithically integrated solar cells are given. The theoretical predictions could be partially confirmed by experimental prototypes. The best cell with a total area of 21 cm2 and six unit cells exhibits an open-circuit voltage of 3.43 V and a conversion efficiency of 10.9% under 100 mW/cm2 AM1.5G illumination and standard reporting conditions.

Key parameters for the quantification of minority carrier recombination in solar cells are the effective bulk diffusion length, the bulk diffusion length and the back surface recombination velocity. As wafer thickness decreases and bulk quality increases the simultaneous determinat-ion of these parameters gains importance for cell process optimization in PV industry. Methods for obtaining these parameters have been described in literature, such as the linear approximation on the inverse IQE vs. light penetration depth. We will formulate the limitations of this approach using numerically and experimentally determined IQE-data. The ambiguity of the older approach is solved by an improved equation, making it possible to obtain these parameters from a fit on the IQE within 820 -940 nm. In addition an equation incl. the loss in the emitter is presented. Both methods are ideally suited for fast LBIC scan evaluations.

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