Biomedical subjects

J De Clercq

Publications and source records attributed to J De Clercq.

6 recordsLinked to original sources

PubMed2003

A new one-dimensional clarifier model--verification using full-scale experimental data.

A new one-dimensional clarifier model was developed, including components of existing models, and extended with a height-dependent cross-sectional area and two flowrate-dependent dispersion coefficients. This model is evaluated using data from a detailed one-month measuring campaign on a full-scale wastewater treatment plant. The data included hourly sludge concentration profile, sludge heights at 10 minute intervals, sludge concentrations in inlet, effluent and recycle flows and regular settling properties characterised by batch setting tests. Due to the poor quality concentration measurements at the surface of the clarifier, the model was not calibrated to perform well in concentration predictions at this surface. However, excellent descriptive capabilities were obtained for sludge profiles and blanket level. The Cho et al. setting velocity function was found to be significantly better in terms of description capability than the more traditional Vesilind function.

Calibration↗

PubMed2000

EEG dipole source localization using artificial neural networks.

Localization of focal electrical activity in the brain using dipole source analysis of the electroencephalogram (EEG), is usually performed by iteratively determining the location and orientation of the dipole source, until optimal correspondence is reached between the dipole source and the measured potential distribution on the head. In this paper, we investigate the use of feed-forward layered artificial neural networks (ANNs) to replace the iterative localization procedure, in order to decrease the calculation time. The localization accuracy of the ANN approach is studied within spherical and realistic head models. Additionally, we investigate the robustness of both the iterative and the ANN approach by observing the influence on the localization error of both noise in the scalp potentials and scalp electrode mislocalizations. Finally, after choosing the ANN structure and size that provides a good trade off between low localization errors and short computation times, we compare the calculation times involved with both the iterative and ANN methods. An average localization error of about 3.5 mm is obtained for both spherical and realistic head models. Moreover, the ANN localization approach appears to be robust to noise and electrode mislocations. In comparison with the iterative localization, the ANN provides a major speed-up of dipole source localization. We conclude that an artificial neural network is a very suitable alternative for iterative dipole source localization in applications where large numbers of dipole localizations have to be performed, provided that an increase of the localization errors by a few millimetres is acceptable.

Brain↗

PubMed2000

The combined IOP and CCT measurement in glaucoma screening.

In a prospective study we measure the intra-ocular pressure (IOP) by means of a pneumotonometer and the central corneal thickness (CCT) in 245 healthy emmetropic or ametropic eyes consulting in a private practice. There is a linear relation between IOP measurement and CCT. The same measurements are done in 30 glaucomatous eyes and in 16 eyes with ocular hypertension. The mean CCT is similar in normal and glaucomatous eyes (554 mu). In eyes with ocular hypertension there is a manifest elevated CCT.

Glaucoma↗

PubMed2000

The correlation between IOP measurement, central corneal thickness and corneal curvature.

In a prospective study we measured the intraocular pressure (IOP), the central corneal thickness (CCT) and the central corneal curvature in 172 myopic eyes before and after LASIK treatment. We find a significant decrease in intraocular pressure. Statistical evaluation reveals a linear correlation between the IOP decrease and the amount of stromal ablation. The IOP and corneal curvature are measured in 21 hyperopic eyes before and after LASIK treatment. We do not find a change in the IOP. In a retrospective study of 47 myopic eyes before and after RADIAL KERATOTOMY we find no change in IOP. We conclude that CCT is important in evaluating the IOP and that corneal curvature has little effect on IOP measurement.

Cornea↗

PubMed2000

Analysis of bruchid resistance in the wild common bean accession G02771: no evidence for insecticidal activity of arcelin 5.

Arcelins are abundant seed storage proteins thought to be implicated in the resistance of wild Phaseolus vulgaris (L.) genotypes against Zabrotes subfasciatus (Boheman), an important storage insect pest of common bean. Here, the insecticidal activity of the arcelin-5 variant that is present in the highly resistant P. vulgaris accession G02771 was investigated. No correlation could be established between the presence of arcelin 5 and the insecticidal effects observed in G02771 seeds. Insect feeding assays with artificial seeds into which purified arcelin-5 protein was incorporated and with transgenic P. acutifolius (A. Gray) seeds in which the arcelin-5 genes were expressed, showed that the presence of arcelin-5 proteins, even at elevated levels, was not sufficient to achieve adequate resistance against Z. subfasciatus. The same might apply to other arcelin variants. Nevertheless, as resistance is clearly closely linked to the presence of the arcelin-1 or arcelin-5 locus, arcelins remain useful markers in breeding programmes aimed at introgressing high levels of resistance to Z. subfasciatus in P. vulgaris cultivars.

Animals↗

PubMed1999

The arcelin-5 gene of Phaseolus vulgaris directs high seed-specific expression in transgenic Phaseolus acutifolius and Arabidopsis plants.

The regulatory sequences of many genes encoding seed storage proteins have been used to drive seed-specific expression of a variety of proteins in transgenic plants. Because the levels at which these transgene-derived proteins accumulate are generally quite low, we investigated the utility of the arcelin-5 regulatory sequences in obtaining high seed-specific expression in transgenic plants. Arcelin-5 is an abundant seed protein found in some wild common bean (Phaseolus vulgaris L.) genotypes. Seeds of Arabidopsis and Tepary bean (Phaseolus acutifolius A. Gray) plants transformed with arcelin-5 gene constructs synthesized arcelin-5 to levels of 15% and 25% of the total protein content, respectively. To our knowledge, such high expression levels directed by a transgene have not been reported before. The transgenic plants also showed low plant-to-plant variation in arcelin expression. Complex transgene integration patterns, which often result in gene silencing effects, were not associated with reduced arcelin-5 expression. High transgene expression was the result of high mRNA steady-state levels and was restricted to seeds. This indicates that all requirements for high seed-specific expression are cis elements present in the cloned genomic arcelin-5 sequence and trans-acting factors that are available in Arabidopsis and Phaseolus spp., and thus probably in most dicotyledonous plants.

Arabidopsis↗