Fast Fourier Transform computations and build-up of plastic deformation in 2D, elastic-perfectly plastic, pixelwise disordered porous media

Stress and strain fields in a two-dimensional pixelwise disordered system are computed by a Fast Fourier Transform method. The system, a model for a ductile damaged medium, consists of an elastic-perfectly matrix containing void pixels. Its behavior is investigated under equibiaxial or shear loading. We monitor the evolution with loading of plastically deformed zones, and we exhibit a nucleation / growth / coalescence scenario of the latter. Identification of plastic ``clusters'' is eased by using a discrete Green function implementing equilibrium and continuity at the level of one pixel. Observed morphological regimes are put into correspondence with some features of the macroscopic stress / strain curves.Comment: 6 pages, 5 figures. Presented at the "11th International Symposium On Continuum Models and Discrete Systems (CMDS 11)" (Ecole des Mines, Paris, July 30- August 3 2007

Localization of elastic deformation in strongly anisotropic, porous, linear materials with periodic microstructures: exact solutions and dilute expansions

Exact solutions are derived for the problem of a two-dimensional, infinitely anisotropic, linear-elastic medium containing a periodic lattice of voids. The matrix material possesses either one infinitely soft, or one infinitely hard loading direction, which induces localized (singular) field configurations. The effective elastic moduli are computed as functions of the porosity in each case. Their dilute expansions feature half-integer powers of the porosity, which can be correlated to the localized field patterns. Statistical characterizations of the fields, such as their first moments and their histograms are provided, with particular emphasis on the singularities of the latter. The behavior of the system near the void close packing fraction is also investigated. The results of this work shed light on corresponding results for strongly nonlinear porous media, which have been obtained recently by means of the ``second-order'' homogenization method, and where the dilute estimates also exhibit fractional powers of the porosity.Comment: 22 pages, 10 figure

Vaccination coverage of children with inflammatory bowel disease after an awareness campaign on the risk of infection

International audienceBACKGROUND: Children with inflammatory bowel disease are at risk of vaccine-preventable diseases mostly due to immunosuppressive drugs. AIM: To evaluate coverage after an awareness campaign informing patients, their parents and general practitioner about the vaccination schedule. METHODS: Vaccination coverage was firstly evaluated and followed by an awareness campaign on the risk of infection via postal mail. The trial is a case-control study on the same patients before and after the awareness campaign. Overall, 92 children were included. A questionnaire was then completed during a routine appointment to collect data including age at diagnosis, age at data collection, treatment history, and vaccination status. RESULTS: Vaccination rates significantly increased for vaccines against diphtheria-tetanus-poliomyelitis (92% vs. 100%), Haemophilus influenzae (88% vs. 98%), hepatitis B (52% vs. 71%), pneumococcus (36% vs. 57%), and meningococcus C (17% vs. 41%) (p\textless0.05). Children who were older at diagnosis were 1.26 times more likely to be up-to-date with a minimum vaccination schedule (diphtheria-tetanus-poliomyelitis, pertussis, H. influenzae, measles-mumps-rubella, tuberculosis) (p=0.002). CONCLUSION: Informing inflammatory bowel disease patients, their parents and general practitioner about the vaccination schedule via postal mail is easy, inexpensive, reproducible, and increases vaccination coverage. This method reinforces information on the risk of infection during routine visit

The economic integration of Germany - an update

SIGLEIAB-90-0DE0-101100 AT 265 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman