Search

Crossed-Field Vacuum Electron Devices are ubiquitous in the High-Power Microwave field in either an oscillator/source or amplifier variant. A typical configuration consists of a magnetically insulated laminar electron flow in an anode–cathode gap with crossed electric (∝ V , voltage) and magnetic (B-) fields and a series of open resonant cavities/vanes located on the anode block that serve as a slow-wave structure (SWS). The SWS slows the phase velocity of the electromagnetic signal down so that the wave becomes synchronous with a layer of the electron flow but is often neglected when calculating the Hull magnetic field necessary to insulate the electrons. In particular, the guiding design equation for the critical cutoff B-field assumes a smooth anode wall. In this paper, we show that such an assumption severely narrows the operating regime in B–V space and that upon inclusion of a revised Hull Cutoff condition taking into account the SWS, operation at lower B and higher V is possible. This revised Hull Cutoff criterion for magnetic insulation in crossed-field devices is corroborated by Particle-in-Cell simulations using CST Particle Studio. [ABSTRACT FROM AUTHOR]

We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d/h < 2: The calculations are spot checked against COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields. [ABSTRACT FROM AUTHOR]

A study was conducted to analyze the anti-inflammatory function of nitric oxide in a framework of hepatic ischemia-reperfusion in rats. A Sigma diagnostic kit was utilized to determine alanine aminotransferase activity while the Nitric Oxide Analyser was used to measure nitrite. Results indicated that endogenous nitric oxide minimized the systemic vascular resistance index and supported increases in the cardiac index and stroke volume index.

Observation of the proteolytic cleavage of poly(ADP-ribose) polymerase and monitoring of the caspace-3 proenzyme proteolysis were undertaken during peroxynitrite-induced apoptosis in HL60 cells to elucidate the mechanism of apoptosis secondary to the biological product of nitric oxide and superoxide combination. Enzyme inhibition studies reveal that proteases belonging to the caspace-3 family are activated during peroxynitrite-induced apoptosis.

The effects of rodent myocardial ischemia induced by occlusion of the left main coronary artery in rats on NO nd superoxide synthesis was analyzed during myocardial ischemia-reperfusion (MI/R). MI/R in rats induced regional inflammatory response characterized by polymorphonuclear leucocyte infiltration and generation of inflammatory mediators such as superoxide and NO. Furthermore, MI/R also induced systemic inflammatory response such as increased superoxide and peroxynitrite levels.

The role of nitric oxide (NO) in the development of endotoxin-induced circulatory dysfunction was analyzed in rats after the administration of aminoguanidine (AG). Administration of Salmonella typhimurium lipopolysaccharide (LPS) in rats reduced mean arterial blood pressure, systemic vascular resistance index and cardiac index. However, AG reduced elevated plasma nitrate/nitrite levels without affecting cardiac depression. Furthermore, inhibition of cytoplasmic NO synthase increased mean arterial blood pressure without affecting plasma volume.