A radiation belt of energetic protons located between Saturn and its rings.

Saturn has a sufficiently strong dipole magnetic field to trap high-energy charged particles and form radiation belts, which have been observed outside its rings. Whether stable radiation belts exist near the planet and inward of the rings was previously unknown. The Cassini spacecraft's Magnetosphere Imaging Instrument obtained measurements of a radiation belt that lies just above Saturn's dense atmosphere and is decoupled from the rest of the magnetosphere by the planet's A- to C-rings. The belt extends across the D-ring and comprises protons produced through cosmic ray albedo neutron decay and multiple charge-exchange reactions. These protons are lost to atmospheric neutrals and D-ring dust. Strong proton depletions that map onto features on the D-ring indicate a highly structured and diverse dust environment near Saturn.

Use of new synthetic talc as reinforcing nanofillers for polypropylene and polyamide 6 systems: thermal and mechanical properties.

New layered synthetic nanotalc prepared at a lab-scale by a conventional hydrothermal process and commercial natural fine talc were used in order to establish a comparative study in terms of their contributions on the improvement of the final properties of two different polymers: a nonpolar polyolefin matrix and a polyamide. All samples were prepared by melt extrusion in a co-rotating microcompounder. The surface properties of talc - surface energy and isoelectric point - were probed. The particles' crystalline structure and the distribution/dispersion within the polymer matrix were performed using transmission electron microscopy and X-ray diffraction. The effect of talc particles on the crystallinity, the thermal and mechanical properties was highlighted as a function of the surface properties of talc. In the case of talc-filled PP systems, it seems that the incorporation of both natural and synthetic talc greatly improves the thermal stability of polypropylene matrix. The highest elastic modulus was obtained in presence of highly nucleating natural talc. Oppositely, the best ductility was observed for the synthetic talc-filled PP systems. For PA6/talc nanocomposites, a remarkable improvement in the dispersion of talc layers was shown and a significant increase in Young's modulus was determined due to the closer affinity between the hydrophilic nanotalc lamellae and the polar PA6 matrix.

Methylamine-dependent release of nitric oxide and dopamine in the CNS modulates food intake in fasting rats.

BACKGROUND AND PURPOSE: Methylamine is an endogenous aliphatic amine exhibiting anorexigenic properties in mice. The aim of this work was to show whether methylamine also modifies feeding behaviour in rats and, if so, to identify the mediator(s) responsible for such effects. EXPERIMENTAL APPROACH: Microdialysis experiments with the probe inserted in the periventricular hypothalamic nucleus were carried out in 12 h starved, freely moving rats. Collected perfusate samples following methylamine injection (i.c.v.) were analysed for nitric oxide by chemiluminescence and for dopamine and 5-hydroxytryptamine content by HPLC. Kv1.6 potassium channel expression was reduced by antisense strategy and this decrease quantified by semi-quantitative RT-PCR analysis. KEY RESULTS: Methylamine showed biphasic dose-related effects on rat feeding. At doses of 15-30 microg per rat, it was hyperphagic whereas higher doses (60-80 microg) were hypophagic. Methylamine stimulated central nitric oxide (+115% vs. basal) following hyperphagic and dopamine release (60% over basal values) at hypophagic doses, respectively. Treatment with L-N(G)-nitro-L-arginine-methyl ester (i.c.v. 2 microg 10 microl(-1)) or with alpha-methyl-p-tyrosine (i.p. 100 mg kg(-1)) before methylamine injection, reduced nitric oxide output and hyperphagia, or dopamine release and hypophagia respectively. Moreover, hypophagia and hyperphagia, as well as nitric oxide and dopamine release were significantly reduced by down-regulating brain Kv1.6 potassium channel expression. CONCLUSIONS AND IMPLICATIONS: The effects of methylamine on feeding depend on the hypothalamic release of nitric oxide and dopamine as a result of interaction at the Kv1.6 channels. The study of methylamine levels in the CNS may provide new perspectives on the physiopathology of alimentary behaviour.