A dynamically young and perturbed Milky Way disk.

The evolution of the Milky Way disk, which contains most of the stars in the Galaxy, is affected by several phenomena. For example, the bar and the spiral arms of the Milky Way induce radial migration of stars1 and can trap or scatter stars close to orbital resonances2. External perturbations from satellite galaxies can also have a role, causing dynamical heating of the Galaxy3, ring-like structures in the disk4 and correlations between different components of the stellar velocity5. These perturbations can also cause 'phase wrapping' signatures in the disk6-9, such as arched velocity structures in the motions of stars in the Galactic plane. Some manifestations of these dynamical processes have already been detected, including kinematic substructure in samples of nearby stars10-12, density asymmetries and velocities across the Galactic disk that differ from the axisymmetric and equilibrium expectations13, especially in the vertical direction11,14-16, and signatures of incomplete phase mixing in the disk7,12,17,18. Here we report an analysis of the motions of six million stars in the Milky Way disk. We show that the phase-space distribution contains different substructures with various morphologies, such as snail shells and ridges, when spatial and velocity coordinates are combined. We infer that the disk must have been perturbed between 300 million and 900 million years ago, consistent with estimates of the previous pericentric passage of the Sagittarius dwarf galaxy. Our findings show that the Galactic disk is dynamically young and that modelling it as time-independent and axisymmetric is incorrect.

MRI of acute disseminated encephalomyelitis after coxsackie B infection.

Acute disseminated encephalomyelitis (ADEM) is a rare demyelinating condition of the central nervous system, usually developing after a viral infection or vaccination. We report a case of ADEM predominantly affecting the spinal cord in an 8-year old boy evaluated by MRI. The radiographic picture consisted of multiple focal lesions of the spinal cord, a left posterior thalamic lesion and a subcortical right posterior parietal lesion. These lesions regressed several weeks after corticosteroid treatment. The clinical presentation, the laboratory results and the radiological findings suggest the diagnosis of ADEM secondary to viral infection by Coxsackie B.

[The control of foodstuffs at the beginning of 1993]. / Le contrôle des denrées alimentaires à l'aube de 1993.

The 1st January 1993 the frontiers between the Member States of the European Community and the customs controls will disappear. The abolition of this type of control won't affect the food security. The french administration has strong legal rules to ensure the protection of consumer's health. The regulations prepared by European Community in order to allow the free circulation of goods also ensure a high level of consumer's protection. In case of harmonization, each Member state keeps some rights when there are risks for consumer's health. In absence of community regulations the principal of mutual acknowledgement aiming to avoid the barriers to trade can then not be applied for health and security necessities. The authorities controls are now resolutely inserted in an european context: priority to controls during production, harmonized methods of intervention to promote the required acknowledgement of controls enforced in each Member state, involvement in an european alert system, and development of the cooperation between the national administrative authorities of inspection. Regarding the matter of food security the authorities need the assistance of the scientific community and of its national and international representative organisations. They take an essential part in diagnosing, emergency and advice during the elaboration of regulations. Their power should be even greater with the implementation of the european scientific cooperation.