1,721,119 research outputs found
A comparative study of rotational temperatures using diatomic OH, O-2 and N-2(+) molecular spectra emitted from atmospheric plasmas
No full textFrom the application point of view, gas temperature is one of the most important parameters for atmospheric plasmas. Based on the fact that the gas temperature is closely related with the rotational temperature of an atmospheric plasma, a spectroscopic method of measuring the rotational temperature is described in this work by analyzing OH, O-2 and N-2(+) molecular spectra emitted from the atmospheric plasma in ambient air. The OH and N-2(+) molecular spectra are emitted because of the oxygen, hydrogen and nitrogen atoms existing in the ambient air. The O-2 diatomic molecular spectrum is emitted from the oxygen plasma that is frequently produced for atmospheric plasma applications. In order to utilize a spectrometer with modest spectral resolution, a synthetic diatomic molecular spectrum was compared with the experimentally obtained spectrum. The rotational temperatures determined by the above three different molecular spectra are in good agreement within 2.4% error. In the case of a plasma with low gas temperature, the temperature measured by a thermocouple was compared to verify the accuracy of the spectroscopic method; and the results show excellent agreement. From the study, it was found that an appropriate diatomic molecular species can be chosen to be used as a thermometer depending on experimental circumstances. (C) 2002 Elsevier Science B.V All rights reserved.This work was supported by Grant No. R01-
2000-00254 from the Korea Science and Engineering
Foundation, and the BK21 Project
Study of the electrical characteristics of a large-area argon assisted glow discharge produced in the ambient air
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Prediction of maximum yields of metabolites and optimal pathways for their production by metabolic flux analysis
No full textThe intracellular metabolic fluxes can be calculated by metabolic flux analysis, which uses a stoichiometric model for the intracellular reactions along with mass balances around the intracellular metabolites. In this study, metabolic flux analyses were carried out to estimate flux distributions for the maximum in silico yields of various metabolites in Escherichia coli. The maximum in silico yields of acetic acid and lactic acid were identical to their theoretical yields. On the other hand, the in silico yields of succinic acid and ethanol were only 83% and 6.5% of their theoretical yields, respectively. The lower in silico yield of succinic acid was found to be due to the insufficient reducing power, but this lower yield could be increased to its theoretical yield by supplying more reducing power. The maximum theoretical yield of ethanol could be achieved, when a reaction catalyzed by pyruvate decarboxylase was added in the metabolic network. Furthermore, optimal metabolic pathways for the production of various metabolites could be proposed, based on the results of metabolic flux analyses. In the case of succinic acid production, it was found that the pyruvate carboxylation pathway should be used for its optimal production in E. coli rather than the phosphoenolpyruvate carboxylation pathway
Feasibility study of material surface treatment using an atmospheric large-area glow plasma
No full textApplication of atmospheric large-area plasma of a volume of 200 x 50 x 4 mm(3) to various material surfaces was attempted for modification of surface properties. Based on the electrical and optical diagnostics, the plasma used for the treatment exhibited normal glow discharge characteristics with relatively low gas temperature, which might enable surface modification without thermal effect. Contact angle measurement showed that the plasma treatment, in general, changed surface characteristics such as wettability of paper, glass, and a silicon (Si) wafer from being hydrophobic to hydrophilic. In addition, ashing of the photoresist coated on a Si demonstrated that the measured ashing rate was found to vary depending on the plasma exposure time and the oxygen amount added to the argon supply gas. Based on the results, it is expected that the atmospheric plasma can be effectively utilized to some processes to which conventional low-pressure plasmas are employed. (c) 2005 Elsevier B.V. All rights reserved.This work was supported by KAIST and PLASMART
Inc
Parametric study of atmospheric pressure microwave-induced Ar∕O2 plasmas and the ambient air effect on the plasma
No full textA torch type microwave-induced afterglow plasma was produced at atmospheric pressure using an open-ended fused silica concentric double tube assisted by Ar and O-2 supply gases. The plasma emerged from the end of the discharge tube and was exposed to ambient air. A parametric study of the plasma characteristics was performed by measuring the temperature, density, and plasma volume as the operational parameters such as microwave power, gas flow rate, and its composition were varied. The excitation temperature (T-exc) obtained from the Ar I emission spectrum ranged from 3010 to 4350 K and the rotational temperature (T-rot) measured from the OH and O-2 diatomic molecular spectra ranged from 2250 to 3550 K. The electron density (n(e)) from the H-beta Stark broadening width at the plasma core was in the range of 6.6 to 7.6x10(14) cm(-3). The two-dimensional distribution of T-exc and T-rot was also obtained. Experiments while varying the Ar and O-2 gas flow rate and the O-2/Ar ratio showed that n(e) was reduced but T-exc was increased as the O-2 flow rate was increased. Using an additional dielectric tube for shielding the plasma from the ambient air demonstrated a significantly enlarged plasma length and lower T-rot due to the nitrogen entrainment, as compared to the unshielded case. (c) 2006 American Institute of Physics.Agency for Defence Developmen
DORYPHORIBIUS-KOREANUS, A NEW SPECIES OF TARDIGRADA FROM KOREA
No full textDoryphoribius koreanus, a new tradigrade species collected from terrestrial mosses and freshwater habitats in Korea, is described. The present new species mainly differs from the other species of the genus Doryhoribius in the following characteristics: smooth cuticle, two macroplacoids, presence of lunules only in the internal or anterior claws of legs, and very reduced buccal armature
Incidental Detection of Meningioma on 18F-Flutemetamol PET
No full textMeningioma is typically a benign tumor that may incidentally be found on imaging. This case demonstrates the utility of 18 F-flutemetamol (FMM) PET/CT in an 80-year-old woman evaluated for memory decline. Although the scan was performed for dementia assessment, it revealed an incidental mass in the frontal region. Early-phase PET showed relatively low uptake, while delayed-phase imaging displayed intense uptake of 18 F-FMM. Magnetic resonance imaging and surgical pathology confirmed the lesion as a meningioma. This report may aid in interpreting incidental mass lesions on 18 F-FMM PET, providing a reference for physicians who may encounter similar findings
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