Poly(methyl methacrylate) as Healing Agent for Carbon Fibre Reinforced Epoxy Composites

Self-healing materials offer a potential solution to the problem of damage to fibre-reinforced plastics (FRPs) by allowing for the in-service repair of composite materials at a lower cost, in less time, and with improved mechanical properties compared to traditional repair methods. This study investigates for the first time the use of poly(methyl methacrylate) (PMMA) as a self-healing agent in FRPs and evaluates its effectiveness both when blended with the matrix and when applied as a coating to carbon fibres. The self-healing properties of the material are evaluated using double cantilever beam (DCB) tests for up to three healing cycles. The blending strategy does not impart a healing capacity to the FRP due to its discrete and confined morphology; meanwhile, coating the fibres with the PMMA results in healing efficiencies of up to 53% in terms of fracture toughness recovery. This efficiency remains constant, with a slight decrease over three subsequent healing cycles. It has been demonstrated that spray coating is a simple and scalable method of incorporating a thermoplastic agent into an FRP. This study also compares the healing efficiency of specimens with and without a transesterification catalyst and finds that the catalyst does not increase the healing efficiency, but it does improve the interlaminar properties of the material.

Electrodiagnostic and nerve ultrasonographic features in upper limb spasticity: an observational study

To better understand the effects of spasticity on peripheral nerves, we evaluated the electrodiagnostic and nerve ultrasonographic features of the median and ulnar nerves in adults with upper limb spasticity. Twenty chronic stroke patients with spastic hemiparesis underwent nerve conduction study and nerve ultrasonography of the median and ulnar nerves at both upper limbs. Affected versus unaffected upper limb comparisons showed significant differences in the median and ulnar nerve distal motor latencies, compound muscle action potentials and F-wave minimal latencies. Furthermore, we observed a significantly greater median nerve crosssectional area at the elbow of the affected upper limb compared with the unaffected one. Our findings confirmed electrodiagnostic asymmetries and nerve ultrasonographic abnormalities in the affected versus the unaffected upper limb after stroke. Slight changes in lower motor neuron activity and spasticity might contribute to these alterations.

DNA flow cytometry of left and right testes in normospermic patients affected by left varicocele

To assess whether changes in spermatogenesis are present in men suffering from varicocele who are still normospermic, a comparative flow cytometric analysis of the left and right testicular DNA content was performed on 26 young normospermic males (sperm density > 20 x 10(6)/ml), with varying degrees of asthenospermia. Cell samples were obtained by fine needle aspiration biopsy. Flow cytometric analysis revealed four peaks in the nuclear DNA content: (i) two peaks for haploid cells (1-A), the first composed of highly condensed nuclear cells (1Ac), essentially spermatozoa, and the second of less condensed cells, essentially spermatids (1-Anc): (ii) a third peak of diploid cells (2-D): somatic cells, G1-stage spermatogonia, primary and secondary spermatocytes and (iii) a fourth peak of tetraploid cells, essentially postleptotene primary spermatocytes and G2-M-stage spermatogonia (4-T). Flow cytometry showed the left testis to have a lower percentage of haploid cells than the right (mean 48.4 +/- 17.9 versus 57 +/- 15.4%, P < 0.05). Significantly fewer condensed cells were found on the left side than on the right (respectively 19.7 +/- 11.2 versus 31.5 +/- 13.5%, P < 0.004). The diploid cell percentage was significantly higher in the left testis than in the right (37.0 +/- 18.5 versus 25.5 +/- 9.6, P < 0.003). No statistically significant differences were found in respect of percentages of either non-condensed and tetraploid cells (respectively 26.6 +/- 14.8 and 11.3 +/- 5.6 on the left and 25.9 +/- 10.3 and 12.4 +/- 6.2 on the right). Flow cytometric analysis of cadaver biopsy tissue showed no statistically significant difference between left and right testicles in respect of the percentages of haploid, diploid and tetraploid cells. The reduced percentage of haploid cells and the increase in diploid cells observed in the left testis of our subjects indicate that the testicular function is impaired to a greater extent in the testis ipsilateral to varicocele than in the contralateral testicle.