ABSTRACT
The paper examines the effect of exposure time of Langmuir probes in an atmospheric premixed methane-air flame. The effects of probe size and material composition on current measurements were investigated, with molybdenum and tungsten probe tips ranging in diameter from 0.0508 to 0.1651 mm. Repeated prolonged exposures to the flame, with five runs of 60 s, resulted in gradual probe degradations (-6% to -62% area loss) which affected the measurements. Due to long flame exposures, two ion saturation currents were observed, resulting in significantly different ion densities ranging from 1.16 × 1016 to 2.71 × 1019 m-3. The difference between the saturation currents is caused by thermionic emissions from the probe tip. As thermionic emission is temperature dependent, the flame temperature could thus be estimated from the change in current. The flame temperatures calculated from the difference in saturation currents (1734-1887 K) were compared to those from a conventional thermocouple (1580-1908 K). Temperature measurements obtained from tungsten probes placed in rich flames yielded the highest percent error (9.66%-18.70%) due to smaller emission current densities at lower temperatures. The molybdenum probe yielded an accurate temperature value with only 1.29% error. Molybdenum also demonstrated very low probe degradation in comparison to the tungsten probe tips (area reductions of 6% vs. 58%, respectively). The results also show that very little exposure time (<5 s) is needed to obtain a valid ion density measurement and that prolonged flame exposures can yield the flame temperature but also risks damage to the Langmuir probe tip.
ABSTRACT
This paper presents the use of thermocouples and line broadening of argon 2p-1s emission lines for the measurement of gas temperature of an atmospheric argon microplasma jet. The measured temperatures are compared with rotational spectra fitting of OH (A-X) and N2 (C-B) emission. An rf microplasma jet with two electrical configurations and different temperature ranges was used. The calculated gas temperatures with thermocouples, argon lines, and OH ranged from 290 to 423 K and 393-510 K for the two configurations, depending on the rf power. The temperature from fitting the N2 spectra overestimated the gas temperatures in both configurations (593-680 and 664-853 K). The non-nitrogen temperature measurements agree well with each other within the measurement uncertainty. The results show that not all optical emission temperature methods are appropriate and the accuracy of argon line broadening is dependent on the device configuration. The results also show that conventional thermocouples are surprisingly accurate and viable for these plasmas.
ABSTRACT
OBJECTIVE: To examine the effects of acute hypobaric by hypoxia on the distribution of Somatostatin (SS) contains in lower gastrointestinal tract of rats. METHOD: 36 Wistar [correction of Wister] male rats were divided into 6 groups. Three were control groups, three were ulcerous groups. Each group contains ground, 5000 m above sea level and 10000 m above sea level. SS contents were determined with radioimmunoassay [correction of radioimmunoassy] methods. RESULT: Statistically significant difference was exhibited among each group. There was no significant difference of SS contents in each altitude between model and control. SS contents were significantly increased in intestine of control in 5000 m groups, in caecum in 5000 m groups, compared with that in ground (P<0.05). It was also significantly increased in intestine of model in 5000 m groups, in caecum in 5000 m groups, compared with that in ground (P<0.01). SS contents was significantly increased in caecum of model in 10000 m groups compared with that in ground (P<0.05). Except this, There was no significant difference of ss contents in lower gastrointestinal tract among each group. CONCLUSION: SS contents in lower gastrointestinal tract were significantly increased in acute hypobaric hypoxia rats. This result suggested that ss contents in lower gastrointestinal tract may play an important protective role in acute hypobaric hypoxia rats.
