Feedback model of secondary electron emission in DC gas discharge plasmas

Feedback is said to exist in any amplifier when the fraction of output power in fed back as an input.Similarly,in gaseous discharge ions that incident on the cathode act as a natural feedback element to stabilize and self sustain the discharge.The present investigation is intended to emphasize the feedback nature of ions that emits secondary electrons（SEs）from the cathode surface in DC gas discharges.The average number of SEs emitted per incident ion and non ionic species（energetic neutrals,metastables and photons）which results from ion is defined as effective secondary electronemission coefficient（ESEEC,Eg）.In this study,we derive an analytic expression that corroborates the relation betweenEg and power influx by ion to the cathode based on the feedback theory of an amplifier.In addition,experimentally,we confirmed the typical positive feedback nature of SEEfrom the cathode in argon DC glow discharges.The experiment is done for three different cathode material of same dimension（tungsten（W）,copper（Cu）and brass）under identical discharge conditions（pressure：0.45 mbar,cathode bias：-600 V,discharge gab：15 cm and operating gas：argon）.Further,we found that theEg value of these cathode material controls the amount of feedback power given by ions.The difference in feedback leads different final output i.e the power carried by ion at cathode（Pi C￠∣）.The experimentally obtained value of Pi C￠∣is 4.28 W,6.87 W and9.26 W respectively for W,Cu and brass.In addition,the present investigation reveals that the amount of feedback power in a DC gas discharges not only affect the fraction of power fed back to the cathode but also the entire characteristics of the discharge.

Activation of hypothalamic gono-like neurons in female rats during estrus

In mammals, gonadal function is controlled by the activity of hypothalamic gonadotropin-releasing hormone neurons, which control the secretion of adenohypophyseal and gonadal hormones. However, there are a number of unanswered questions in relation to gonadal function. It is currently unknown how erotogenic stimulation of the genitals influences the subpopulation of hypothalamic medial preoptic area neurons, antidromically identified as projecting to the median eminence at different periods of the estrous cycle. Additionally, the distinctiveness of hypothalamic medial preoptic area neurons, with respect to methods of feedback control by exogenous hormones, is also unknown. In this study, spontaneous discharges from individual neurons encountered within the medial preoptic area, gono-like neurons, were recorded extracellularly using glass microelectrodes. To confirm the cellular and histochemical properties of the recording units, antidromic stimulation was performed using a side-by-side bipolar stimulating electrode placed into the median eminence, alongside microiontophoretic injections of the conventional tracer, horseradish peroxidase. In addition, further immunohistochemical analyses were performed. Results showed that elevated gono-neuron activity was accompanied by increased background activity and greater responses to erotogenic stimuli during estrus. Application of clitoral traction stimulation resulted in increased activation of the gono-like neurons. This neuronal activity was noticeably inhibited by β-estradiol administration. Immunohistochemical analyses revealed the presence of gonadotropin-releasing hormone-reactive protein in hypothalamic cells in which electrophysiological recordings were taken. Thus, medial preoptic area neurons represent the subset of hypothalamic gonadotropin-releasing hormone neurons described from brain slices in vitro, and might serve as a useful physiological model to form the basis of future in vivo studies.