Biomedical subjects

H Rothermel

Publications and source records attributed to H Rothermel.

9 recordsLinked to original sources

PubMed2003

Kinetic measurements of shock wave propagation in a three-dimensional complex (dusty) plasma.

"Complex plasmas" consist of electrons, ions, and charged microparticles. The latter are individually observable, allowing kinetic measurements in plasmas. Using a sudden gas pulse, a traveling perturbation was initiated in such a complex plasma and its propagation, acceleration, and steepening-possibly into a shock was followed. The experiment was performed in the PKE-Nefedov laboratory under microgravity conditions on the international space station, i.e., in a complex plasma cloud with very little stored (potential or free) energy and thus free of, e.g., parametric instabilities. The perturbation front remained remarkably smooth, with a microroughness of the order of the interparticle distance. The observations are presented and interpreted.

Journal Article↗

PubMed2003

Decharging of complex plasmas: first kinetic observations.

The first experiment on the decharging of a complex plasma in microgravity conditions was conducted. After switching off the rf power, in the afterglow plasma, ions and electrons rapidly recombine and leave a cloud of charged microparticles. Because of microgravity, the particles remain suspended in the experimental chamber for a sufficiently long time, allowing precise measurements of the rest particle charge. A simple theoretical model for the decharging is proposed which agrees quite well with the experiment results and predicts the rest charge at lower gas pressures.

Journal Article↗

PubMed2002

Complex-plasma boundaries.

This study deals with the boundary between a normal plasma of ions and electrons, and an adjacent complex plasma of ions, electrons, and microparticles, as found in innumerable examples in nature. Here we show that the matching between the two plasmas involve electrostatic double layers. These double layers explain the sharp boundaries observed in the laboratory and in astrophysics. A modified theory is derived for the double layers that form at the discontinuity between two different complex plasmas and at the point of contact of three complex plasmas. The theory is applied to the first measurements from the Plasma Kristall Experiment (PKE) Nefedov Laboratory in the International Space Station.

Journal Article↗

PubMed2002

Gravity compensation in complex plasmas by application of a temperature gradient.

Micron-sized particles are suspended or lifted up in a gas by thermophoresis. This allows the study of many processes occurring in strongly coupled complex plasmas at the kinetic level in a relatively stress-free environment. First results of this study are presented. The technique is also of interest for technological applications.

Journal Article↗

PubMed2002

Measurements of forces acting on suspended microparticles in the void region of a complex plasma.

A laboratory experiment has been performed in which a temperature gradient is used to generate a large central void in a rf-generated complex plasma. Through the use of laser flashing techniques, two-dimensional velocity vectors have been obtained from particles falling from the top to the bottom of the void. These particles are used to generate a two-dimensional map of the acceleration, and consequently the net forces, that act upon particles in the void.

Journal Article↗

PubMed2001

Recognition of multiple antibody epitopes throughout Borrelia burgdorferi p66, a candidate adhesin, in patients with early or late manifestations of Lyme disease.

Antibody responses to p66, a candidate integrin ligand of Borrelia burgdorferi, were studied in 79 patients with early or late manifestations of Lyme disease. The central portion of p66 was previously shown to contain all of the information required for specific recognition of beta3-chain integrins, but work by others had suggested that the C-terminal portion of the protein contains a single surface-exposed, immunodominant loop. In examining antibody responses to full-length p66 and to three overlapping fragments of the protein, we found that the majority of Lyme disease patients had immunoglobulin M (IgM) and/or IgG responses to p66 and that, particularly early in the disease, epitopes throughout p66 were recognized. Among patients with later manifestations of the illness, antibody responses to the C-terminal portion of the protein were more prominent. These results demonstrate that Lyme disease patient sera recognize epitopes throughout p66.

Antibodies, Bacterial↗

PubMed2001

Optic neuropathy in children with Lyme disease.

Involvement of the optic nerve, either because of inflammation or increased intracranial pressure, is a rare manifestation of Lyme disease. Of the 4 children reported here with optic nerve abnormalities, 2 had decreased vision months after disease onset attributable to optic neuritis, and 1 had headache and diplopia early in the infection because of increased intracranial pressure associated with Lyme meningitis. In these 3 children, optic nerve involvement responded well to intravenous ceftriaxone therapy. The fourth child had headache and visual loss attributable to increased intracranial pressure and perhaps also to optic neuritis. Despite treatment with ceftriaxone and steroids, he had persistent increased intracranial pressure leading to permanent bilateral blindness. Clinicians should be aware that neuro-ophthalmologic involvement of Lyme disease may have significant consequences. If increased intracranial pressure persists despite antibiotic therapy, measures must be taken quickly to reduce the pressure.

Adolescent↗

PubMed2000

Three-dimensional strongly coupled plasma crystal under gravity conditions.

Experiments were carried out to investigate a three-dimensional (3D) plasma crystal. A method of determining the positions of each individual microparticle has been developed. A crystal volume of about 2x10(4) particles in 19 horizontal planes was analyzed. Direct imaging and the 3D pair correlation function show that "domains" of fcc and hcp lattices coexist in the crystal. Other structures, in particular, the theoretically predicted bcc lattice, were not observed.

Journal Article↗

PubMed1988

Production of interleukin-1 and tumor necrosis factor by human peripheral monocytes activated by periodontal bacteria and extracted lipopolysaccharides.

Whole Gram-negative bacteria associated with juvenile and adult periodontitis, and their respective extracted lipopolysaccharides (LPS), were tested for the ability to activate quiescent human peripheral blood monocytes. All pathogenic Gram-negative bacteria and all LPS tested were able to induce the production of significant amounts of IL-1 and TNF, monokines known to induce osteoclastic bone resorption. Haemophilus segnis, which has not been associated with any form of periodontal disease, did not activate monocytes. Purified LPS from Actinobacillus actinomycetemcomitans Y4 was able to elicit IL-1 and TNF release at a threshold concentration of 1-10 ng/mL. To examine the mechanism whereby whole bacteria activated monocytes, we added polymixin B in culture with glutaraldehyde-fixed bacteria to bind LPS. This resulted in the abrogation of IL-1 and TNF production. To compare the effects of Gram-positive oral bacteria on monocytes, we also tested Staphylococcus epidermidis and the Gram-positive amphipathic equivalent of LPS, lipoteichoic acid (LTA) extracted from Staphylococcus aureus bacteria. Whereas whole Gram-positive bacteria had no stimulatory effect on monocytes, LTA induced IL-1 and TNF production at a concentration range equivalent to that of the LPS. These results indicate that monocytes are activated by free LPS or LPS bound to Gram-negative pathogenic periodontal bacteria to produce monokines which may contribute to the destruction of periodontal bone.

Gram-Negative Bacteria↗