Electron density and temperature measurements in a magnetized expanding hydrogen plasma

We report measurements of electron densities, n_{e}, and temperatures, T_{e}, in a magnetized expanding hydrogen plasma performed using Thomson scattering. The effects of applying an axial magnetic field and changing the background pressure in the plasma vessel on n_{e} and T_{e} along the expansion axis are reported. Magnetic field strengths (B field) up to 170 mT were applied, which are one order of magnitude larger than previously reported. The main effect of the applied B field is the plasma confinement, which leads to higher n_{e}. At B fields larger than 88 mT the electron density along the expansion axis does not depend strongly on the magnetic field strength. However, T_{e} is susceptible to the B field and reaches at 170 mT a maximum of 2.5 eV at a distance of 1.5 cm from the exit of the cascaded arc. To determine also the effect of the arc current through the arc, measurements were performed with arc currents of 45, 60, and 75 A at background pressures of 9.7 and 88.3 Pa. At constant magnetic field n_{e} decreases from the exit of the arc along the expansion axis when the arc current is decreased. At 88.3 Pa n_{e} shows a higher value close to the exit of the arc, but a faster decay along the expansion axis with respect to the 9.7 Pa case. T_{e} is overall higher at lower pressure reaching a maximum of 3.2 eV at the lower arc current of 45 A. The results of this study complement our understanding and the characterization of expanding hydrogen plasmas.

Balmer-beta line asymmetry characteristics in a high pressure, microwave-produced argon plasma

This paper presents a study on the asymmetry of the Balmer H(beta) profile in plasmas produced by microwaves at high pressure with the help of some functions of asymmetry for the whole profile, as well as by means of some specific parameters characterizing only its central dip. The study shows how this asymmetry--very low in our case--depends on the electron density and flux of gases and how the existence of inhomogeneities in the plasma can affect the shape and symmetry of this line. Also, limitations on the determination of the asymmetry are pointed out and the use of this profile for plasma diagnosis is discussed.

[Evidence for glutamatergic neurotransmission in the geniculo-cortical pathway in the rat]

PURPOSE

To investigate the possible participation of glutamate in the neurotransmission of the rat geniculo-cortical pathway.

METHODS

In a first set of experiments, we studied the effects of microiontophoresis of kynurenate, a broad spectrum antagonist of glutamate receptors, on the excitation evoked in visual cortex cells by electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract. Cell activity was determined by extracellular unit recordings. In a second set of experiments, we studied the effects of electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract on the release of glutamate and aspartate in the visual cortex in vivo. Push pull perfusions were made in the visual cortex and the amino acids contents of the perfusates were analysed by high performance liquid chromatography.

RESULTS

Microiontophoresis of kynureate in area 17 cells selectively supressed the excitatory response to dorsal geniculate nucleus and optic tract stimulation. On the other hand, stimulation of these structures significantly increased glutamate, but not aspartate, release in area 17.

CONCLUSIONS

These results demonstrate that glutamate is the neurotransmitter of the geniculo-cortical pathway in the rat.

Atypical Thyroiditis in Huelva, Spain

OBJECTIVE

To report an epidemic of atypical thyroiditis that occurred in southwestern Europe during 1995.

METHODS

We present the clinical, laboratory, morphologic, and histologic features of 672 cases of thyroiditis and describe the results of treatment.

RESULTS

During 1995, atypical thyroiditis was diagnosed in 672 of 725 patients with thyroid disorders encountered at our medical center in Huelva, Spain. Of these patients, 98% were women with normal ovarian function. The clinical findings were acute or subacute manifestation of diffuse nodular enlargement of the thyroid and spontaneous, severe pain on deglutition and palpation of the gland. Initial hematology and serum biochemistry studies, free triiodothyronine, free thyroxine, thyrotropin, and thyroid-stimulating immunoglobulins were in the normal range, but after the second week, the thyrotropin level began to increase. Thyroid antibodies (thyroglobulin and thyroid peroxidase) increased up to 300 times the high-normal level. Ultrasonography exhibited diffuse nodular enlargement of the thyroid gland, with irregular hypoechoic, normal, and hyperechoic zones. Fine-needle aspiration biopsy showed abundant lymphocytic infiltration. The best treatment results were obtained with the combination of levothyroxine and deflazacort. Because the epidemic appeared after a severe drought of 5-year duration (1991 to 1995) and affected women with normal ovarian function, our etiopathogenetic hypothesis was that an estrogen-like chemical substance polluted the area swamps. The high concentration of the pollutant was attributable to diminished water levels (8% of their capacity at the end of the drought period), and this situation may have affected the population through tap water used for human consumption.

CONCLUSION

We describe an atypical autoimmune thyroiditis that affected primarily women of reproductive age, after a severe drought. The main features were a very painful, diffuse nodular enlargement of the thyroid gland, substantially increased thyroid antibodies, good response to levothyroxine and deflazacort combination treatment, and a benign evolution to chronic thyroiditis. Pollutants from various sources should be considered when atypical thyroiditis occurs in any community.

Electrophysiological and neurochemical study of the rat geniculo-cortical pathway. Evidence for glutamatergic neurotransmission

The projection from the dorsal lateral geniculate nucleus to the primary visual cortex of the rat was studied electrophysiologically. Electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract produced three types of responses on neurons of area 17: excitation followed by inhibition, excitation and inhibition. These results extend and confirm, in adult rats, previous studies done in rat geniculate-visual cortex cocultures preparations in vitro. The role of glutamate in the neurotransmission of the rat geniculo-cortical pathway was also investigated. In a first set of experiments, the effects of kynurenate, an antagonist of glutamate receptors, on visual cortex neurons with a monosynaptic excitatory response to dorsal lateral geniculate nucleus stimulation were studied. Microiontophoresis of kynurenate in area 17 neurons selectively suppressed the excitatory response to dorsal lateral geniculate nucleus and optic tract stimulation. In a second set of experiments, the effects of electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract on the release of amino acids in the rat visual cortex in vivo were studied. Using the push-pull method, we perfused a discrete region of the visual cortex with artificial cerebrospinal fluid (CSF), and the amino acid content of the perfusates was analysed by high performance liquid chromatography (HPLC). Stimulation of either the dorsal lateral geniculate nucleus or the optic tract significantly increased glutamate release in area 17. The rest of the amino acids studied did not show significant changes. The results provide evidence for the participation of glutamate in the neurotransmission of the geniculo-cortical pathway in the rat.