Tunneling resistance model for piezoresistive carbon nanotube polymer composites.

Carbon nanotube (CNT) polymer composites exhibit outstanding electrical conductivity that enables a myriad of sensing and actuation applications. Highly sensitive strain sensors can be realized through piezoresistivity in which a resistance change is induced by mechanical strains. Tunneling conduction between CNTs in close proximity is a major mechanism contributing to the overall piezoresistivity of the CNT network, and is sensitive to the separation distance, lattice registry and the orbital overlap of the interacting CNTs. In this paper, we propose a tunneling resistance model that relate these effects to the CNT chirality, geometry, and orientation. We construct the model based on the distance-dependent Landauer equation, and introduce two additional geometric variables, namely the lattice alignment angle and the axis alignment angle. The tunneling resistance model is incorporated into a CNT network representative volume element to determine the piezoresistivity of the CNT polymer composite. The model reproduces the periodic variation of tunneling resistance consistent with experimental observations and quantum simulations in the literature, and provides improved predictive accuracy of piezoresistivity in CNT polymer composites.

Three-year prospective clinical performance of a one-step self-etch adhesive and a nanofiller hybrid resin composite in Class V lesions.

PURPOSE: This 3-year prospective clinical study evaluated the clinical performance of a one-step self-etching adhesive (Futurabond NR) in combination with a nanohybrid composite (Grandio) for the treatment of different Class V cavities. METHODS: 122 restorations were placed in 42 patients (mean age of 54 +/- 13.2 years) evaluated according to modified Ryge-criteria at baseline, 6 months, 1, 2 and 3 years. The lesions comprised 91 Class V non-caries cervical lesions (NCCL) and 31 Class V cavities due to caries or restoration replacement. While carious lesions as well as restoration replacement required preparation of dentin, it was not roughened in case of NCCL. Macro-mechanical retention with undercuts was not used. The statistical analysis was carried out based on Bonferroni adjusted McNemar test (global alpha = 0.05) including the criteria marginal adaptation, color match, surface texture, anatomical form, retention and clinical acceptance and pain. The occurrence of secondary caries, preoperative and postoperative sensitivity was also examined. RESULTS: After 3 years of clinical service the restorations showed a significant deterioration of all studied parameters. After 3 years, 65% of the restorations were rated as excellent or acceptable in terms of clinical acceptance, 9% appeared tolerable and 26% were rated as not acceptable which mainly resulted from restoration losses. Within the observed timeframe the retention rate decreased to 75%, which means that 30 out of the 122 restorations were partially or completely lost. There was a difference in the 3-year retention rate of NCCL (71%) and the caries/restoration replacement group (87%) but it was not statistically significant.

Identification and characterization of CaApe2--a neutral arginine/alanine/leucine-specific metallo-aminopeptidase from Candida albicans.

The proteolytic potential of the pathogenic fungus Candida albicans was evaluated by the identification and functional characterization of a peptidolytic enzyme isolated from the cell wall of the microorganism. Determination of basic structural and kinetic data identified a neutral arginine/alanine/leucine-specific metallo-aminopeptidase of unknown function termed CaApe2, which is encoded by ORF CaO19.5197 (GenBank RefSeq XM_705313). Mass spectrometric tryptic peptide analysis and N-terminal protein sequencing revealed serine-88 to represent the N-terminus of CaApe2. Taking into account the results of DNA and protein sequence analysis including inspection of the genomic region upstream of ORF CaO19.5197, the gene CaAPE2 is likely to consist of two exons linked by a phase-2 intron with exons 1 and 2 encoding a signal peptide and the amino acids 88-954 of ORF CaO19.5197, respectively. The isolated CaApe2 protein shares an equally high similarity with the gene products ScAap1 and ScApe2, suggesting duplication of a phylogenetically ancient precursor gene in Saccharomyces cerevisiae. The observed failure to cleave human type-I and type-IV collagen in vitro challenges a direct role that secreted CaApe2 might play in the degradation of extracellular matrix components during host colonization, but does not exclude per se a contribution of the aminopeptidase to the pathogenicity of C. albicans.