As brain ventricles lose their ability to regulate the cerebrospinal fluid (CSF) pressure, serious brain conditions collectively named hydrocephalus can appear. By modelling ventricular dynamics with the laws of physics, dynamical instabilities are evidenced, caused by either CSF transport dysregulations or abnormal properties of the elasticity of the ependyma. We show that these instabilities would lead, in most cases, to dilation of the ventricles, establishing a close connection to hydrocephalus, or in some other cases to a ventricular contraction as observed in the slit ventricle syndrome. Signs seem to indicate the possibility of phase transitions occurring as a result of these instabilities, which might have important clinical consequences, such as the inability to recover a healthy state. Even so, our dynamical approach could allow the development of a unified view of these complex intracranial conditions along with a classification that might be clinically relevant.

Study of olive oil packaging in plastic materials.Plastic bottles are economic and light but are not often used at packaging olive oil, even not used in Tunisia. This is due to migration phenomena that can occur from these materials. Thus, the major goals of this work are the verification, in a first time, of the safety of high density polyethylene (HDPE) and polyethylene terephtalate (PET) bottles and, in a second time, the non modification of tensile, luminous transmittance and heat properties of these materials, and finally the stability of olive oil packed in these bottles in comparison with glass bottles. The overall migration found for HDPE and PET materials are fewer then the French norm, they are respectively equals to 17.9 mg/kg and 13.9 mg/kg. None luminous transmittance or heat properties variation are found, but a very important loss of materials rigidity is registered after 30 days contact at 40°C with refined olive oil. Moreover, the results showed that the ranking of stability of virgin olive oil packed on these plastic materials and in glass bottles is Glass > HDPE > PET.

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We present an extensive study of the electric, magnetic and elastic responses of tetragonal ferroelectrics under illumination, using a new theory intertwining material and wave symmetries. Optical rectification, photomagnetic, photovoltaic and phototoroidal vector responses are worked out as functions of the wave vector and wave polarization directions. Second-order response tensors associated with photoelastic, photomagnetoelectric, photorefractive effects and photoconductivity are described. We discuss in detail the photo-Hall and a new non-linear optical effect in tungsten bronzes. Finally, we compare the properties of tetragonal materials with those of hexagonal, orthorhombic and trigonal ferroelectrics previously reported in the literature.