Time-domain induced polarization as a tool to image clogging in treatment wetlands.

During the last decade, treatment (artificial) wetlands have flourished all over Europe for the treatment of sewages from small communities thanks to their low cost of operation. The clogging of the filter of these wetlands is an issue affecting their efficiency and considered as their main operational problem. The present work shows the results of the application of a geophysical method called time-domain induced polarization. It is used to non-intrusively image, in 3D, the clogging of the gravel filters in a quick and efficient way. Induced polarization characterizes the ability of a porous material to reversibly store electrical charges when submitted to an electrical field. The material property characterizing this ability is called normalized chargeability. A set of laboratory experiments allows to determine an empirical relationship between the normalized chargeability and the weight amount of clogging. Induced polarization measurements have been performed in the field over a treatment wetland to get a 3D reconstructed image (tomography) of the normalized chargeability. From this tomography and the previously defined relationship, we are able to image in 3D the distribution of clogging and where it is concentrated in the filter. We can therefore identify the areas requiring preventive measures to minimize this clogging issue.

Color Doppler sonography in monitoring after free jejunum transplantation.

The authors assessed the usefulness of color Doppler imaging in the monitoring of vascular circulation after free jejunum transplantation. Seven male patients were examined daily with color Doppler sonography for the first postoperative week between 1999 and 2000. All sonographic examinations were performed with an SSD5500 ultrasound scanner. Arterial and venous signals were documented reliably in all patients. The flashing red spots around the serosal wall revealed the patency of the anastomosed artery and vein. No failures of the graft occurred. The presence of the color Doppler signals was considered sufficient to define vascular patency. The real-time monographic (B-mode) examination revealed the thickness and the plicae circulares of the jejunum wall. These monographic (B-mode) images supported the viability of the transplanted jejuna. The authors found color Doppler sonography to be a reliable and effective form of monitoring after free jejunum transplantation.