Statistical Inference for Power-Law Process With Competing Risks

The focus of this article is on failure history of a repairable system for which the relevant data comprise successive event times for a recurrent phenomenon along with an event-count indicator. We undertake an investigation for analyzing failures from repairable systems that are subject to multiple failure modes. Failure data representing a cluster of recurrent events from a single system are studied under the parametric framework of a power-law process, a model that has found considerable attention in industrial applications. Some interesting and nonstandard asymptotic results ensue in this context that are discussed in detail. Extensive simulation has been carried out that supplements the theoretical findings. An extension to the case where the specific cause of failure may be missing is investigated in detail. The methodology has been implemented on recurrent failure data obtained from a warranty claim database for a fleet of automobiles. Supplementary material for this article is available online.     

Preparation of chitosan nanoparticles for encapsulation and release of protein

Chitosan nanoparticles were prepared by ionic cross-linking with tripolyphosphate (TPP). The major effect on encapsulation and release of protein in chitosan-TPP nanoparticles was investigated in order to control the loading and release efficiency. A set of the same molecular weight (MW) proteins with different pI and a set of the same pI proteins with different MW were studied. The influence of protein concentration, pH of solution, and the activity of released protein were examined. It was found that the encapsulation efficiency (EE) of a set of the different MW protein decreased with increasing of MW of protein and protein concentration. The protein with having pI higher than pH of solution was attracted to the positively charged chitosan, resulting in increasing of EE. The release of protein from the nanoparticles showed that the protein release decreased with increasing of chitosan concentration, high MW protein, low pH, and less swelling of the particle. The released protein in chitosan-TPP matrix was still active in the buffer solution.