Please be advised that this information was generated on 2018-05-08 and may be subject to change.Facioscapulohumeral muscular dystrophy (FSHD) has recently been shown to be associated with deletions that are detectable using probe p13E-11 (D4F104S1). Although these deletions reside within large, highly polymorphic restriction fragments (20-300 kb), the " mutant" fragment is usually shorter than 28 kb and can routinely be detected using conventional agarose gel electrophoresis. Yet, the complete vi sualization of the alleles requires pulsed-field gel electrophoresis (PFGE). Family studies showed that p13E-11 detects two nonallelic loci in this size range, only one of which originates from chromosome 4q35. We have assigned the other p13E-11 locus to chromosome lOqter by linkage analysis in CEPH pedigrees. Knowing the location of both loci improves the diagnostic reliability, as the exact origin of "small" EcoRI fragments can be determined by haplotyping. Since FSHD shows ge netic heterogeneity, this 10qter locus became an interesting candidate to be the second FSHD locus. However, analysis of a large chromosome 4-unlinked FSHD family did not provide evidence for linkage on chro mosome 10qter>

We report the direct imaging of electrically active Si dopants near the GaAs(110) surface with a scanning tunneling microscope at a temperature of 4.2 K. In the filled state images, we observe patterns of rings which are centered around the individual doping atoms. We believe these ring patterns are induced by the individual impurities, which, due to their charge, disturb the local potential and cause oscillations in the charge density, also called Friedel oscillations. In the empty state images no Friedel oscillations can be observed.

We used a low-temperature scanning tunneling microscope to study Zn-and Cd-doping atoms near the ͑110͒-cleavage surfaces of GaAs and InP at 4.2 K. The filled-state images showed centro-symmetric elevations while the empty-state images showed circular depressions. We attribute these features to the influence of the Coulomb potential of the ionized doping atoms on the number of states available for tunneling. In a few empty-state images of the GaAs͑110͒ surface, the depressions were surrounded by maxima, which are probably direct observations of Friedel oscillations. For the InP͑110͒ surface, all depressions were surrounded by noncentrosymmetric maxima. Upon moving the tip Fermi level to the bottom of the conduction band, we observed that the depressions turned into elevations with a triangular shape for both the GaAs͑110͒ and the InP͑110͒ surface. This shape was independent of the depth of the dopants, and the chemical nature of the dopants ͑Zn or Cd͒ did not influence the triangular shape either. The orientation of these triangular features was the same for all observed doping atoms and was geometrically determined with respect to the host lattice. Furthermore, we determined the location of a triangular feature with respect to a doping atom. The features were only visible when tunneling to the impurity band suggesting that the features are a direct image of the acceptor state although the origin of the triangular shape is not clear at present.

Semiconductor tips are used as local photodetectors in a scanning tunneling microscope. We demonstrate that this configuration is sensitive to small light intensity variations, as supported by a simple model. The principle is applied to the detection of Faraday ellipticity of a Pt/Co multilayer sample. The outlook of this new technique in magnet-optical imaging is briefly discussed.

No abstract