Polyalanine expansion in the human HOXD13 gene induces synpolydactyly (SPD), an inherited congenital limb malformation. A mouse model was isolated, which showed a spontaneous alanine expansion due to a 21-bp duplication at the corresponding place in the mouse gene. This mutation (synpolydactyly homolog, spdh), when homozygous, causes malformations in mice similar to those seen in affected human patients. We have studied the genetics of this condition, by using several engineered Hoxd alleles, as well as by looking at the expression of Hox and other marker genes. We show that the mutated SPDH protein induces a gain-of-function phenotype, likely by behaving as a dominant negative over other Hox genes. The mutation, however, seems to act independently from Hoxa13 and doesn't appear to affect Hox gene expression, except for a slight reduction of the HOXD13 protein itself. Developmental studies indicate that the morphological effect is mostly due to a severe retardation in the growth and ossification of the bony elements, in agreement with a general impairment in the function of posterior Hoxd genes.

The purpose of the present study was to examine the possibility of laser-machining of CuInSe 2-based photovoltaic devices. Therefore, ablation thresholds and ablation rates of ZnO, CuInSe 2 and Mo thin films have been measured for irradiation with nanosecond laser pulses of ultraviolet and visible light and subpicosecond laser pulses of a Ti : sapphire laser. The experimental results were compared with the theoretical evaluation of the samples heat regime obtained from numerical calculations. In addition, the photo-electrical properties of the solar cells were measured before and after laser-machining. Scanning electron microscopy and energy dispersive x-ray analyses were employed to characterize the laser-induced ablation channels. As a result, two phenomena were found to limit the laser-machining process: (i) residues of Mo that were projected onto the walls of the ablation channel and (ii) the metallization of the CuInSe 2 semiconductor close to the channel. Both effects lead to a shunt in the device that decreases the photovoltaic efficiency. As a consequence of these limiting effects, micromachining of CuInSe 2-based solar cells was not possible with nanosecond laser pulses. Only subpicosecond laser pulses provided selective or complete ablation of the thin layers without a relevant change in the photoelectrical properties.

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