Cohesive mixed-mode damage model applied to the simulation of the mechanical behaviour of a repaired sandwich beam

The behaviour of a repaired sandwich beam loaded under four point bending is simulated using theABAQUS® software. Both overlap and scarf repair, suitable for sandwich structures, were simulatedconsidering two dimensional nonlinear material and geometrical analysis. Special developed interfacefinite elements including a trapezoidal cohesive mixed-mode damage model appropriate for ductileadhesives were used in order to simulate the adhesive layer. The proposed model is intended to replacethe continuum finite elements traditionally used to simulate the adhesive layer, thus reducing thecomputational effort necessary to obtain results. Double Cantilever Beam (DCB) and End NotchedFlexure (ENF) tests were used to obtain the cohesive laws of the adhesive in pure modes I and II,respectively. The fracture energies (JIc and JIIc) are obtained using a new data reduction scheme based oncrack equivalent concept allowing overcoming crack monitoring difficulties during propagation in thesefracture characterization tests. The remaining cohesive parameters (1,I, 1,II, 2,I, 2,II)are obtained usingan inverse method, which is based on the fitting of the numerical and experimental P- curves by a finetuning process. This procedure allows fixing the referred cohesive parameters to be used in the stressanalyses and strength predictions of repaired sandwiches. The numerical model allowed the simulation ofdamage initiation and growth. Geometric changes, such as patch overlap length and scarf angle wereconsidered in the analysis in order to assess their influence on the repair efficiency. Conclusions weredrawn about design guidelines of sandwich composite material repair

Interlaminar fracture characterization of a carbon-epoxy composite in Pure Mode II

The interlaminar fracture toughness in pure mode II (GIIc) of a Carbon-Fibre ReinforcedPlastic (CFRP) composite is characterized experimentally and numerically in this work, using theEnd-Notched Flexure (ENF) fracture characterization test. The value of GIIc was extracted by a newdata reduction scheme avoiding the crack length measurement, named Compliance-Based BeamMethod (CBBM). This method eliminates the crack measurement errors, which can be nonnegligible,and reflect on the accuracy of the fracture energy calculations. Moreover, it accounts forthe Fracture Process Zone (FPZ) effects. A numerical study using the Finite Element Method (FEM)and a triangular cohesive damage model, implemented within interface finite elements and based onthe indirect use of Fracture Mechanics, was performed to evaluate the suitability of the CBBM toobtain GIIc. This was performed comparing the values of GIIc inputted in the numerical models withthe ones resulting from the application of the CBBM to the numerical load-displacement (P-)curve. In this numerical study, the Compliance Calibration Method (CCM) was also used to extractGIIc, for comparison purposes

Safety of Levetiracetam in paediatrics: a systematic review

Objective To identify adverse events (AEs) associated with Levetiracetam (LEV) in children. Methods Databases EMBASE (1974-February 2015) and Medline (1946-February 2015) were searched for articles in which paediatric patients (≤18 years) received LEV treatment for epilepsy. All studies with reports on safety were included. Studies involving adults, mixed age population (i.e. children and adults) in which the paediatric subpopulation was not sufficiently described, were excluded. A meta-analysis of the RCTs was carried out and association between the commonly reported AEs or treatment discontinuation and the type of regimen (polytherapy or monotherapy) was determined using Chi2 analysis. Results Sixty seven articles involving 3,174 paediatric patients were identified. A total of 1,913 AEs were reported across studies. The most common AEs were behavioural problems and somnolence, which accounted for 10.9% and 8.4% of all AEs in prospective studies. 21 prospective studies involving 1120 children stated the number of children experiencing AEs. 47% of these children experienced AEs. Significantly more children experienced AEs with polytherapy (64%) than monotherapy (22%) (p<0.001). Levetiracetam was discontinued in 4.5% of all children on polytherapy and 0.9% on monotherapy (p<0.001), the majority were due to behavioural problems. Conclusion Behavioural problems and somnolence were the most prevalent adverse events to LEV and the most common causes of treatment discontinuation. Children on polytherapy have a greater risk of adverse events than those receiving monotherapy

Defective removal of ribonucleotides from DNA promotes systemic autoimmunity

Genome integrity is continuously challenged by the DNA damage that arises during normal cell metabolism. Biallelic mutations in the genes encoding the genome surveillance enzyme ribonuclease H2 (RNase H2) cause Aicardi-Goutières syndrome (AGS), a pediatric disorder that shares features with the autoimmune disease systemic lupus erythematosus (SLE). Here we determined that heterozygous parents of AGS patients exhibit an intermediate autoimmune phenotype and demonstrated a genetic association between rare RNASEH2 sequence variants and SLE. Evaluation of patient cells revealed that SLE- and AGS-associated mutations impair RNase H2 function and result in accumulation of ribonucleotides in genomic DNA. The ensuing chronic low level of DNA damage triggered a DNA damage response characterized by constitutive p53 phosphorylation and senescence. Patient fibroblasts exhibited constitutive upregulation of IFN-stimulated genes and an enhanced type I IFN response to the immunostimulatory nucleic acid polyinosinic:polycytidylic acid and UV light irradiation, linking RNase H2 deficiency to potentiation of innate immune signaling. Moreover, UV-induced cyclobutane pyrimidine dimer formation was markedly enhanced in ribonucleotide-containing DNA, providing a mechanism for photosensitivity in RNase H2-associated SLE. Collectively, our findings implicate RNase H2 in the pathogenesis of SLE and suggest a role of DNA damage-associated pathways in the initiation of autoimmunity

Panayiotopoulos-Syndrom – oder doch nicht?

Seltene fokal autonome Krampfanfälle sind ein typisches Merkmal des Panayiotopoulos-Syndroms, einer selbstlimitierenden fokalen Epilepsie des Kindesalters. Doch auch bei vermeintlich typischer Semiologie und EEG-Befund kann eine zerebrale Bildgebung die Verdachtsdiagnose auf den Kopf stellen. = Panayiotopoulos syndrome is a self-limiting focal epilepsy of childhood characterized by rare but prolonged focal autonomic seizures. Despite supposedly typical semiological and electroencephalogram (EEG) features, cerebral imaging can completely change the suspected diagnosis