Biomedical subjects

Matthias Scholz

Publications and source records attributed to Matthias Scholz.

4 recordsLinked to original sources

PubMed2007

Visualization and analysis of molecular data.

This chapter provides an overview of visualization and analysis techniques applied to large-scale datasets from genomics, metabolomics, and proteomics. The aim is to reduce the number of variables (genes, metabolites, or proteins) by extracting a small set of new relevant variables, usually termed components. The advantages and disadvantages of the classical principal component analysis (PC A) are discussed and a link is given to the closely related singular value decomposition and multidimensional scaling. Special emphasis is given to the recent trend toward the use of independent component analysis, which aims to extract statistically independent components and, therefore, provides usually more meaningful components than PCA. We also discuss normalization techniques and their influence on the result of different analytical techniques.

Algorithms↗

PubMed2005

Non-linear PCA: a missing data approach.

MOTIVATION: Visualizing and analysing the potential non-linear structure of a dataset is becoming an important task in molecular biology. This is even more challenging when the data have missing values. RESULTS: Here, we propose an inverse model that performs non-linear principal component analysis (NLPCA) from incomplete datasets. Missing values are ignored while optimizing the model, but can be estimated afterwards. Results are shown for both artificial and experimental datasets. In contrast to linear methods, non-linear methods were able to give better missing value estimations for non-linear structured data. APPLICATION: We applied this technique to a time course of metabolite data from a cold stress experiment on the model plant Arabidopsis thaliana, and could approximate the mapping function from any time point to the metabolite responses. Thus, the inverse NLPCA provides greatly improved information for better understanding the complex response to cold stress. CONTACT: scholz@mpimp-golm.mpg.de.

Adaptation, Physiological↗

PubMed2003

Offset compensation by use of amplitude-modulated sidebands in optical frequency standards.

We present a general method for continuously measuring and compensating for offsets (due to residual amplitude modulation, parasitic resonances, or electronic offset voltages, for example) in frequency stabilization systems. The spectral power distribution of the oscillator waveform is modified by amplitude-modulated sidebands, and the error signal is corrected to null the induced periodic lock-point shifts. We demonstrate significant improvements to the frequency stability of standards based on cryogenic optical resonators and molecular iodine.

Journal Article↗

PubMed2002

Diagnostic odyssey of a cutaneous mycobacteriosis rare in central Europe.

Cutaneous infection with Mycobacterium chelonae is an uncommon disease, although this atypical mycobacterium is an acid-fast bacillus ubiquitous in the environment. It is often misdiagnosed and treated as a fungal or common bacterial infection. We report a case of disseminated atypical mycobacterial skin infection of a 72-year-old woman who was treated with different topical and systemic antimycotic and antibiotic drugs over a period of 5 months without remarkable improvement. Eventually, repeated tissue cultures on special medium and performance of PCR led to the diagnosis of M. chelonae infection. The patient was treated successfully with oral clarithromycin within 8 weeks. In case of abscessing cutaneous infection, M. chelonae should be considered in the differential diagnosis of prolonged disease when common antibiotics are not effective after 2-4 weeks of treatment.

Aged↗