Biomedical subjects

U Oertel

Publications and source records attributed to U Oertel.

6 recordsLinked to original sources

PubMed2006

Photolabile carboxylic acid protected terpolymers for surface patterning. Part 2: Photocleavage and film patterning.

The surface properties of films made of p-methoxyphenacyl derivative terpolymers, associated with photocleavage by UV irradiation, and their optical patterning are investigated. The deprotection reaction has been monitored by UV and FTIR spectroscopy, contact angle measurements, and X-ray photoelectron spectroscopy, revealing the photoremoval of the protecting p-methoxyphenacyl group in high yields under mild conditions. Parallel and serial patterning of the films has been performed by selective irradiation through optical masks and by laser irradiation via fiber tips of a scanning near-field optical microscope, respectively. By irradiation of photolabile protected functional groups, free carboxylic groups become exposed to the surface with which fluorescent dyes and proteins can be associated specifically.

Carboxylic Acids↗

PubMed2000

Noise affects auditory and linguistic processing differently: an MEG study.

We investigated the influence of noise on brain responses to spoken sentences in MEG. Sixteen subjects had to listen to acoustically presented sentences and judge their syntactic correctness. Sentences were either presented on a silent background or with noise. Noise had differential effects on early auditory and syntactic processes. While noise affected early auditory processes only in the right hemisphere, noise had a general effect on syntactical processes. The evoked responses to syntactic violations compared with correct sentences, namely an early left anterior negativity, were significantly suppressed when noise was present The noise suppression effect, however, was not lateralized.

Acoustic Stimulation↗

PubMed2000

Localization of early syntactic processes in frontal and temporal cortical areas: a magnetoencephalographic study.

Previous electrophysiological studies had found an early anterior negativity often with a maximum over the left hemisphere to correlate with the early detection of an error in the syntactic structure of a sentence. In this paper, the cortical structures involved in such early syntactic parsing processes were localized using MEG. Subjects were presented with acoustic sentences and asked to judge their syntactic correctness. The subjects' brain responses to syntactic violations were recorded with a 148-channel whole-head magnetometer. Dipole source localization was performed using a realistically shaped standard volume conductor model with fMRI constraints. The results show that the early syntactic parsing processes are supported by temporal regions, possibly the planum polare, as well as by fronto-lateral regions. As indicated by the resultant dipole strengths, these regions are activated bilaterally with a dominance in the left hemisphere for four out of the five subjects. The contribution of the left temporal regions to the early syntactic processes seems to be larger than that of the left fronto-lateral regions.

Adolescent↗

PubMed2000

Estimating scalp MEG from whole-head MEG measurements.

Studies based on whole-head MEG recordings are providing more and more impressive results. In such recordings, the MEG sensors are several centimeters away from the scalp and the positions of the MEG sensors with respect to the head differ from subject to subject, and from session to session for the same subject. In this paper, a method is presented and tested to estimate the scalp MEG distributions from whole-head MEG measurements. The goal is to remove the discrepancy of MEG measurements caused by the various sensor positions with respect to the head, as well as to reduce the smearing effect caused by the distance of the MEG sensors from the scalp. The MEG measurement was first projected to a hypothetical dipole layer within the head volume conductor model using the inverse solution. The scalp MEG estimation was then obtained from the resultant dipole layer by the forward solution. The results from simulation studies, phantom experiments, and the auditory evoked field analysis demonstrated that, with reasonable signal to noise ratios, this method is a feasible way to achieve our goals.

Auditory Cortex↗

PubMed1997

Sequence comparison of the 3'-terminal parts of the RNA of four German isolates of sugarcane mosaic potyvirus (SCMV).

The 3'-termini of the genome of four German isolates of sugarcane mosaic potyvirus (SCMV) were cloned and sequenced. The sequence data covered the 3' non-coding region (3'NCR), coat protein and part of the nuclear inclusion b (NIb) genes of the isolates. Comparisons of the sequences revealed that the investigated isolates are very closely related. An alignment of the predicted coat protein amino acid sequences of the German isolates with sequence data for other members of the SCMV subgroup, in particular the two SCMV strains, SCMV-SC and SCMV-MDB, showed a limited degree of homology indicating that the German isolates may represent a distinct virus. However, this is mainly due to the previously reported unexpected sequence diversity in the surface exposed N-terminal region of coat protein of SCMV isolates. Comparisons of the amino acid sequences of the core region of the coat proteins and the nucleotide sequences of the 3' NCR clearly show that the German isolates are strains of SCMV.

Amino Acid Sequence↗

PubMed1994

[Acne].

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Acne Vulgaris↗