Dynamically important magnetic fields near accreting supermassive black holes.

Accreting supermassive black holes at the centres of active galaxies often produce 'jets'--collimated bipolar outflows of relativistic particles. Magnetic fields probably play a critical role in jet formation and in accretion disk physics. A dynamically important magnetic field was recently found near the Galactic Centre black hole. If this is common and if the field continues to near the black hole event horizon, disk structures will be affected, invalidating assumptions made in standard models. Here we report that jet magnetic field and accretion disk luminosity are tightly correlated over seven orders of magnitude for a sample of 76 radio-loud active galaxies. We conclude that the jet-launching regions of these radio-loud galaxies are threaded by dynamically important fields, which will affect the disk properties. These fields obstruct gas infall, compress the accretion disk vertically, slow down the disk rotation by carrying away its angular momentum in an outflow and determine the directionality of jets.

Three-dimensional electrical impedance tomography based on the complete electrode model.

In electrical impedance tomography an approximation for the internal resistivity distribution is computed based on the knowledge of the injected currents and measured voltages on the surface of the body. It is often assumed that the injected currents are confined to the two-dimensional (2-D) electrode plane and the reconstruction is based on 2-D assumptions. However, the currents spread out in three dimensions and, therefore, off-plane structures have significant effect on the reconstructed images. In this paper we propose a finite element-based method for the reconstruction of three-dimensional resistivity distributions. The proposed method is based on the so-called complete electrode model that takes into account the presence of the electrodes and the contact impedances. Both the forward and the inverse problems are discussed and results from static and dynamic (difference) reconstructions with real measurement data are given. It is shown that in phantom experiments with accurate finite element computations it is possible to obtain static images that are comparable with difference images that are reconstructed from the same object with the empty (saline filled) tank as a reference.

Adhesion to laminin and expression of laminin in clonally related transformed and control sublines from an alveolar epithelial cell strain.

Clonally related sublines of the NAL1A cell strain were used to examine the expression of laminin and the importance for the attachment and morphology of these control and spontaneously transformed alveolar epithelial cells. A laminin component was detected by immunoblot analysis in extracts of control cells cultured on plastic as a Mr 410,000 species consisting of disulfide-linked Mr 200,000 components. The laminin content of the malignant cells was reduced at least 40-fold as compared to that of the control cells. Cell attachment to laminin or to a laminin-like neurite promotion factor was compared with attachment to fibronectin and to extracellular matrix from bovine endothelial cells. Both control and transformed cells attached as well to laminin or neurite promotion factor as to fibronectin, in a serum-free adhesion assay. The control cells showed enhanced cell spreading on the surfaces coated with laminin, neurite promotion factor, or fibronectin. The transformed cells had very similar cell shape, as determined by phase contrast and scanning electron microscopy, when cultured on laminin or neurite promotion factor or fibronectin, as on tissue culture plastic.

Expression of fibronectin on clonally related transformed and control sublines from an epithelial cell strain and a tumor line of mouse alveolus.

The cellular expression of fibronectin and the importance of fibronectin for the morphology of cultured cells were studied in a lung epithelial cell system. The cells used were clonally related control NAL1A, spontaneously transformed NAL1AS cells of the NAL1A cell strain, and transformed clonal sublines of the cell line NAL1AM and the tumor cell line NUL1. Fibronectin was detected on the surface of NAL1A cells by surface iodination; fibronectin synthesis, secretion, and pericellular accumulation were detected in each of the control sublines by immunoblot assay, immunoprecipitation of metabolically labeled cell extracts and conditioned medium, and was confirmed by immunofluorescence microscopy. Fibronectin synthesis, secretion, or accumulation could not be detected by these methods in NAL1AS and NAL1AM sublines, or the sublines of NUL1. The control NAL1A cells showed enhanced cell spreading on culture substrata of fibronectin or extracellular matrix from bovine endothelial cells, as compared to plastic. The transformed NAL1AS and NAL1AM cells had the same cell shape when cultured on the three different substrata. For these cultured epithelial cells, cellular fibronectin expression and sensitivity to the presence of adhesive glycoproteins in the culture substrata are seen in the control, anchorage-dependent cells, but the transformed cells appear not to express fibronectin and to have a cell shape that is unaffected by the nature of the culture substratum.

Determination of melamine in air by high-performance liquid chromatography with ultraviolet detection.

An air sampling and liquid chromatographic separation method for melamine is described. Collection efficiency on 13-mm glass fibre filters was determined. No breakthrough was detected under a contamination level of 0.4 mg/m3 for 40-1 air samples. The detection limit for a 60-1 air sample at 215 nm is 450 ng/mg. Retention behaviour of melamine on four different reversed-phase columns is described. Column packings tested are Spherisorb ODS, Supelcosil ODS, Spherisorb CN and PRP-1. Results of electrochemical detection studies are discussed.