Research of Radon Detection Based on Air Mesh and Pulse Ionization Chamber at Normal

The research of radon detection based on air mesh and pulse chamber at normal is presented in details. The Instrument consists of air mesh, pulse chamber, signal amplification and discriminator and MCU. Radon of ambient air can directly make a free diffusion to the high-pressure chamber, because The Instrument uses a new type of atmospheric air-gridded pulse ionization chamber, ventilated with ambient air. A voltage pulse in the Resistance connected to Collecting electrode is produced when the charged particles moving through the gas in high-pressure chamber, can make the air ionize to create the charged ion-pairs (negatively charged ion and positively charged ion), which drift to the cathode and anode respectively with the effect of the directional electric field. The voltage pulse height represents the ionizability of an incident particle. And the relative counting can be made for the incident particles, reflecting the changes of the radon concentrations in air, and the total measurement too. But the pulse signal, from Front-end detector, is very weak, so they need to be amplified and shaped by amplification and discriminator circuit and RC-CR band-pass filter, compared with a given threshold voltage through the Pulse discriminator to produce the digital signals which micro-controller system can handle and for which SCM can make the counting, storage and display. Then, this Instrument is a design of appropriate devices for short-term measurements, and some criteria used in the design of this instrument are field measurements applicability, portability, convenience and reliability.

Acute facilitory action of progesterone on gonadotropin secretion of perifused rat pituitary cells

The purpose of this study was to investigate the kinetics and estrogen dependence of the facilitory progesterone action on LH and FSH secretion from pituitary cells under dynamic culture conditions. Anterior pituitary cells obtained from ovariectomized or intact adult Wistar rats were cultivated on Cytodex 1 microcarrier beads. The perifusion experiments were performed with four separate perifusion chambers. The cells of chambers I+II had been pretreated with medium containing vehicle (0.1% ethanol), those of chambers III + IV with medium containing 1 nmol/l estradiol for 48 h. After perifusion was started, each of the chambers was challenged with an initial 2-min GnRH (1 nmol/l) pulse. Chamber I was further perifused with medium containing vehicle, chamber II with medium containing vehicle + 100 nmol/l progesterone, chamber III with medium containing 1 nmol/l estradiol, and chamber IV with medium containing 1 nmol/l estradiol + 100 nmol/l progesterone. Three further GnRH pulses were administered at 50-min intervals to each of the chambers. In estradiolprimed cells from intact rats, progesterone induced a positive effect on LH and FSH secretion after 50 min of exposure to progesterone. After 100 min of progesterone treatment, LH and FSH release were enhanced to 420 and 500 per cent, respectively. When such cells were not primed with estradiol, a slight though insignificant positive action of progesterone on LH release was present after 50 and 100 min of treatment, whereas FSH secretion was not influenced. The facilitory effect of progesterone occurred only after 100 min when estradiol-primed cells from ovariectomized rats were used. LH and FSH secretion were only enhanced by up to 210 and 233 per cent, respectively. When these cells were not primed with estradiol the positive progesterone effect was absent. In conclusion, progesterone induces an acute facilitory effect on GnRH-induced LH and FSH secretion which is estrogen-dependent.