Observation of Nonlinear Standing Waves Excited by Plasma-Series-Resonance-Enhanced Harmonics in Capacitive Discharges.

We report the first experimental observation of nonlinear standing waves excited by plasma-series-resonance-enhanced harmonics in low pressure, very high frequency, parallel plate, capacitively coupled plasmas. Spatial structures of the harmonics of the magnetic field, measured by a magnetic probe, are in very good agreement with simulations based on a nonlinear electromagnetics model. At relatively low pressure, the nonlinear sheath motion generates high-order harmonics that can be strongly enhanced near the series resonance frequencies. Satisfying certain conditions, such nonlinear harmonics induce radial standing waves, with voltage and current maxima on axis, resulting in center-high plasma density. Excitation of higher harmonics is suppressed at higher pressures.

Dynamic model of streamer coupling for the homogeneity of glowlike dielectric barrier discharges at near-atmospheric pressure.

A streamer coupling theory is developed to describe the formation of homogenous emission and the high propagation speed of emission patterns in near-atmospheric pressure discharges. By considering the effects of both electron diffusion and electronic drift in the streamer head, the minimum required preionization level n(min) for the formation of streamer coupling is found to be dependent on electric field strength, gas pressure, and electron temperature. The final stage of discharge is a microdischarge, when the preionization level n(0) is smaller than n(min). However, when n(0) is larger than n(min), streamers can couple to each other and form a glowlike discharge, and the homogeneity and propagation speed of the emission pattern in the streamer coupling head increases with the preionization level. The streamer coupling model can also be possibly used to explain many phenomenon in near-atmospheric pressure discharges, such as the bulletlike luminous discharge when atmospheric pressure plasma jets eject into ambient air.

Proteomic, microarray, and signature-tagged mutagenesis analyses of anaerobic Pseudomonas aeruginosa at pH 6.5, likely representing chronic, late-stage cystic fibrosis airway conditions.

Patients suffering from cystic fibrosis (CF) commonly harbor the important pathogen Pseudomonas aeruginosa in their airways. During chronic late-stage CF, P. aeruginosa is known to grow under reduced oxygen tension and is even capable of respiring anaerobically within the thickened airway mucus, at a pH of approximately 6.5. Therefore, proteins involved in anaerobic metabolism represent potentially important targets for therapeutic intervention. In this study, the clinically relevant "anaerobiome" or "proteogenome" of P. aeruginosa was assessed. First, two different proteomic approaches were used to identify proteins differentially expressed under anaerobic versus aerobic conditions. Microarray studies were also performed, and in general, the anaerobic transcriptome was in agreement with the proteomic results. However, we found that a major portion of the most upregulated genes in the presence of NO(3)(-) and NO(2)(-) are those encoding Pf1 bacteriophage. With anaerobic NO(2)(-), the most downregulated genes are those involved postglycolytically and include many tricarboxylic acid cycle genes and those involved in the electron transport chain, especially those encoding the NADH dehydrogenase I complex. Finally, a signature-tagged mutagenesis library of P. aeruginosa was constructed to further screen genes required for both NO(3)(-) and NO(2)(-) respiration. In addition to genes anticipated to play important roles in the anaerobiome (anr, dnr, nar, nir, and nuo), the cysG and dksA genes were found to be required for both anaerobic NO(3)(-) and NO(2)(-) respiration. This study represents a major step in unraveling the molecular machinery involved in anaerobic NO(3)(-) and NO(2)(-) respiration and offers clues as to how we might disrupt such pathways in P. aeruginosa to limit the growth of this important CF pathogen when it is either limited or completely restricted in its oxygen supply.

Perturbation of a Cartilage Autocrine/Paracrine Basic Fibroblast Growth Factor Metabolic Regulatory Network by Osteoarthritic Synovial Tissue.

Studies have focused on control of expression and the relative importance of basic fibroblast growth factor (bFGF) in a purported autocrine/paracrine regulatory network functioning in the modulation of cartilage metabolic and structural homeostasis. Preformed and newly synthesized bFGF and concurrent antagonist activity could be identified by bioassay in cell/pericellular matrix extracts of normal bovine articular chondrocytes maintained in suspension culture. Specificity was determined using antibody neutralization. Prostanoids (PGE(1), PGE(2)) enhanced chondrocyte expression of the putative inhibitor. The antagonist, recognized in the presence of suboptimally triggered bFGF receptors, was active against both endogenously produced and recombinant bFGF. Chondrocyte expression of bFGF was significantly altered following exposure to conditioned medium obtained from explant cultures of osteoarthritic synovial tissue. Response pattern, that is, an upregulation or downregulation of growth factor expression, was dependent on medium concentration and the duration of chondrocyte exposure. Synovium-conditioned medium generated in the presence of PGE(1) appeared to attenuate suppressive responses seen with naive conditioned medium. Promotion of expression of bFGF inhibitory activity within the milieu of the diseased joint may negate potential detrimental pathophysiologic effects of this competence factor on cartilage, synovial tissue, and bone metabolism and repair.