Ralph Versteegen

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The complete amino acid sequence of the group-specific antigen gene-encoded RNA binding phosphoprotein p12 has been determined for both Rauscher and Moloney leukemia viruses. Large fragments generated by acid, and cyanogen bromide and hydroxylamine cleavage, and Staphylococcus aureus V8 protease digestion were subjected to automated sequencing. Both(More)
We introduce a new simple framework for texture modelling with Markov--Gibbs random fields (MGRF). The framework learns texture-specific high order pixel interactions described by feature functions of signal patterns. Currently, modelling of high order interactions is almost exclusively achieved by linear filtering. Instead we investigate `binary pattern'(More)
Currently, Markov–Gibbs random field (MGRF) image models which include high-order interactions are almost always built by modelling responses of a stack of local linear filters. Actual interaction structure is specified implicitly by the filter coefficients. In contrast, we learn an explicit high-order MGRF structure by considering the learning process in(More)
The effects of protein modification on the antigenic determinants of p30 and gp70 of type C retroviruses were investigated by using solid-phase competition radioimmunoassays. Proteins were modified by reduction with 2-mercaptoethanol and subsequent carboxymethylation of SH groups with iodoacetamide or by amidination of alpha and epsilon amino groups with(More)
Descriptive abilities of translation-invariant Markov-Gibbs random fields (MGRF), common in texture modelling, are expected to increase if higher-order interactions, i.e. conditional dependencies between larger numbers of pixels, are taken into account. But the complexity of modelling grows as well, so that most of the recent high-order MGRFs are built to a(More)
Markov random field models of textures describe images by statistics of local image features and identify conditional dependencies between pixels. To account for higher-order inter-dependencies between multiple pixels, most common high-order modelling follows the well-known FRAME or Fields of Experts (FoE) frameworks in using marginals of the responses of(More)
A compact flat-field soft x-ray grazing-incidence grating spectrometer equipped with a cryogenically cooled back-illuminated charge-coupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1 to 37 nm using two different gratings. In slitless operation mode, it directly images a(More)
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