The present disclosure provides workpiece feed systems, methods and assemblies comprising one or more tapered feed rolls positioned at an angle to incoming workpieces. In particular, the invention includes isolated adipose tissue derived stromal cells that have been induced to express at least one phenotypic characteristic of a neuronal, astroglial, hematopoietic progenitor, or hepatic cell. At the heterointerface between the layer of n-type single-crystal SiGe and the layer of p-type single-crystal SiGeC, the bandgap of the p-type single-crystal SiGeC is larger than that of the layer of n-type single-crystal SiGe.