Design and Performance Tests of a Low Power DC Arcjet Thruster

This paper describes a quasi-one-dimensional flow model which can be used for the design of an arcjet thruster. Owing to the simplicity of the model, the performance characteristics of the thruster can be calculated easily for finding an optimum configuration suitable for various missions. In order to verify adequacy of the model, a thruster was fabricated and its performance characteristics were measured. The experimental results were compared with the calculation predicted with the model. Both are in satisfactory agreement, and it is concluded that this flow model is a useful tool for the design of the arcjet thruster

Fibroblasts as Local Immune Modulators in Ocular Allergic Disease

ABSTRACTVernal keratoconjunctivitis (VKC), a severe form of ocular allergic disease, is characterized by the formation of giant papillae at the upper tarsal conjunctiva and corneal lesions that threaten vision. Recent evidence indicates that resident fibroblasts function as immune modulators in the pathogenesis of the chronic allergic inflammation associated with VKC. The T helper 2 (Th2) cell-derived cytokines interleukin (IL)-4 and IL-13 stimulate the migration and proliferation of conjunctival fibroblasts as well as protecting these cells from apoptotic cell death, effects that likely underlie the hyperplasia of fibroblasts that contributes to the formation of giant papillae. Conjunctival fibroblasts also synthesize extracellular matrix proteins and tissue inhibitors of metalloproteinases as well as down-regulate the expression of matrix metalloproteinases in response to these cytokines, effects that likely contribute to the excessive deposition of extracellular matrix that is characteristic of giant papillae. Stimulation of fibroblasts in the corneal stroma with the combination of a proinflammatory cytokine and either IL-4 or IL-13 results in up-regulation of the expression of the chemokine eotaxin and thymus- and activation-regulated chemokine as well as of vascular cell adhesion molecule-1, which together mediate the infiltration and activation of eosinophils and Th2 cells. Fibroblasts therefore appear to play a central role in the induction and amplification of ocular allergic inflammation and the consequent development of giant papillae and corneal disorders in individuals with VKC. Fibroblasts and fibroblast-derived factors thus represent new and potentially important therapeutic targets for treatment of the giant papillae and corneal disorders associated with VKC

Domain distributions in tetragonal Pb(Zr,Ti)O3 thin films probed by polarized Raman spectroscopy

We have investigated polarized Raman spectra of (001)/(100)-oriented tetragonal epitaxial Pb(ZrxTi1–x)O3 (PZT) thin films (x=~0.35) in which the volume fraction of the polar c domain is systematically varied from 4% to 96%. From polarization analyses using high epitaxial quality films, we have successfully isolated the A1 and B1 phonons from the E phonons, thus offering a distinctive evaluation of the c domains. As increasing c-domain volume, the A1(TO) modes linearly increase in their intensity. A remarkable correlation is found between the A1(1TO)-mode intensity and the c-domain volume for PZT films. We suggest that this correlation as well as the A1(1TO)-mode intensity provide a simple and useful probe for characterization of c-domain volume and ferroelectric properties in PZT-based devices

Time and Composition Dependent Electrical Conductivity of Vanadate Glasses Showing Both Cationic Conduction and Electronic Conduction

Silver vanadate glasses show electrical conductivity higher than 10–2 S cm–1, caused by the electron hopping from VIV to VV together with an ionic conduction due to Ag+. Lithium vanadate glasses show electrical conductivity of the order of 10–6 S cm–1 which is primarily due to an electron hopping from VIV to VV. Fraction of the Ag+ or Li+ conduction and that of electron hopping from VIV to VV can be estimated by measuring both AC- and DC-conductivities. The latter becomes saturated after 50 min or more due to polarization of the mobile Ag+ or Li+ ions at around the cathode

Characteristics of aerodynamic sound sources generated by coiled wires in a uniform air-flow

This study deals experimentally with aerodynamic sounds generated by coiled wires in a uniform air-flow. The coiled wire is a model of the hair dryer\u27s heater. In the experiment, the effects of the coil diameter D, wire diameter d and coil spacing s of the coiled wire on the aerodynamic sound have been clarified. The results of frequency analyses of the aerodynamic sounds show that an Aeolian sound is generated by the coiled wire, when s/d is larger than I. Also the peak frequencies of Aeolian sounds generated by the coiled wires are higher than the ones generated by a straight cylinder having the same diameter d. To clarify the characteristics of the aerodynamic sound sources, the directivity of the aerodynamic sound generated by the coiled wire has been examined, and the coherent function between the velocity fluctuation around the coiled wire and the aerodynamic sound has been calculated. Moreover, the band overall value of coherent output power between the sound and the velocity fluctuations has been calculated. This method has clarified the sound source region of the Aeolian sound generated by the coiled wire. These results show that the Aeolian sound is generated by the arc part of the coiled wire, which is located in the upstream side of the air-flow