Controlled release of vancomycin from cross-linked gelatine

This paper explores the possibility of using biodegradable cross-linked gelatines as antibiotic devices for a long-term elution (80 days). Capillary electrophoresis (CE) has been utilized to evaluate the mass percentage of vancomycin and gelatine contemporary released from differently cross-linked vancomycin loaded gelatine samples in an elution time ranging from 24 to 1920 h. While the solubilization kinetic of gelatine samples differently cross-linked can be very close described by the simplified Higuchi model, the vancomycin release kinetic is contemporary governed by both the Fickian diffusion process trough the gelatine matrix network and the dissolution process of the matrix due to its degradation. Comparing the antibiotic eluting kinetics from gelatine at diverse cross-linking degree we observed that the degradation of the proteic matrix appears to have a minor influence in the drug release control. Vancomycin released from all the gelatine partially cross-linked samples results active against Staphylococcus aureus and Streptococcus faecalis which represent the most pathogens commonly isolated in orthopaedic infections. Vancomycin overcomes the minimum inhibitory concentration for both the bacteria in the whole range of elution time. Cross-linked gelatine devices appear to represent a useful biodegradable delivery system for local anti-infective therapy in arthoplasty.     

The VSS approach to the model reference control of nonminimum phaselinear plants

A nontrivial application of the discontinuous control system theory, based on Filippov's solution concept, is presented. The problem addressed is the model reference output feedback control of linear plants with non-Hurwitzian numerator in the transfer function. A solution in the case of known systems is presented first. An error state equation, whose state is accessible, is then derived for the case in which the plant parameters are unknown. In the case in which some bounds on the plant characteristics are supposed known, a pair of discontinuous signals acting on both the plant and the model is chosen, causing the error state to vanish asymptotically     

Probabilistic ecological risk assessment of 1,2,4-trichlorobenzene at a former industrial contaminated site

Measured concentrations of 1,2,4-trichlorobenzene (1,2,4-TCB) in soil and groundwater detected in an industrial contaminated site were used to test several probabilistic options for refining site-specific ecological risks assessment, ranging from comparison of single effects and exposure values through comparison of probabilistic distributions for exposure and effects to the use of distribution based quotients (DBQs) obtained through Monte Carlo simulations. The results of the deterministic approach, which suggest that risk exceeds a level of concern for soil organisms, were influenced mainly by the presence of hot spots reaching concentrations able to affect acutely a large proportion of species, while the large majority of the area presents 1,2,4-TCB concentrations below those reported as toxic. Ground-(pore)water concentrations were compared with aquatic ecotoxicity data in orderto obtain an estimation of the potential risk for aquifers and streams in the adjacent area as well as for soil-dwelling organisms exposed via pore water. In this case, the risk is distributed over a large proportion of the site, while the local risk of hot spots was low, showing that risk characterization based exclusively on soil concentrations might be insufficient.