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Interest in tissue adhesives as alternatives for conventional wound closing applications, such as sutures and staples, has increased in the last few decades due to numerous possible advantages, including less discomfort and lower cost. Novel tissue adhesives based on gelatin, with alginate as a polymeric additive and crosslinked by carbodiimide were developed and loaded with two types of drugs for pain relief, bupivacaine and ibuprofen, in order to improve the therapeutic effect. The release of the drugs from the adhesive matrix was found to be controlled mainly by the adhesive's characteristics, i.e. swelling and hydrophilic group concentration. The drug characteristics, i.e. hydrophilicity and electrical interactions between the drug and the polymeric components, were also found to have some effect. Incorporation of bupivacaine was found to improve the bonding strength of the adhesive due to its inert nature and the reinforcing effect of its fibrous crystals, whereas incorporation of ibuprofen was found to have an adverse effect on the bonding strength, probably due to its reaction with the other adhesive components which increased the crosslinking density. Overall, the novel drug-eluting gelatin-based bioadhesives investigated in this research, especially those loaded with bupivacaine, demonstrated a promising potential for use in wound closing applications.

Increasing complexity of Industrial automated systems requires high level discrete event control implementation in programmable logic controllers (PLCs). To date most PLC applications for industrial discrete event control systems (DECS) are basically heuristic, mostly supported by partial system analysis and limited performance evaluation. Consequently the application of formal methods in PLC programming became extremely essential for industrial automation. During the past few decades Petri Nets (PN) have evolved to a very promising formal tool to establish an integrated solution for modeling, analysis, simulation and control of industrial automated systems. This paper presents a methodology for implementation of high level DECS PN models in PLCs using IEC 1131-3 standard programming languages. The produced PLC code is completely dual to its original PN model capturing completely its dynamic properties and can be fully restored directly from its PLC code. The flexibility of the PN models is reflected in the DECS's PLC code being simply and accurately updated following the changes conducted in the DECS's model. Index Terms-Petri Net (PN), Discrete Event Control System (DECS), Programmable Logic Controller (PLC).

Interest in soft and hard tissue adhesives as alternatives for conventional wound closing and bone fixation applications has increased in recent decades as a result of numerous possible advantages such as better comfort and lower cost. A novel bioadhesive based on the natural polymers GA has recently been developed and studied in our laboratory. Hydroxyapatite and tricalcium phosphate are two bioactive ceramics known for their ability to enhance bone regeneration. In the current study, these two bioactive fillers were incorporated into the bioadhesive at concentrations of 0.125, 0.25 and 0.5% w/v, and their effects on the resulting adherence properties to soft and hard tissues were studied. Porcine skin and cortical portions of bovine femurs were used as soft and hard tissue specimens, respectively. The bonding strength was evaluated using an Instron universal testing machine in tensile mode, and the microstructure analysis was based on environmental scanning electron microscope observations. Both bioactive fillers were found to have a reinforcing effect on the adhesives, significantly improving their adhesion to soft tissues in certain concentrations. The best bonding strength results were obtained for 0.25% hydroxyapatite and 0.5% w/v tricalcium phosphate-18.1 ± 4.0 and 15.2 ± 2.6 kPa, respectively, compared with 8.4 ± 2.3 kPa for adhesive with no fillers. The improved adherence is probably related to the stiffness of the insoluble hydroxyapatite and tricalcium phosphate particles which reinforce the adhesive. These particles can clearly be observed in the environmental scanning electron microscope analysis. The potential of these fillers to increase the bonding strength of the adhesive to hard tissues was also demonstrated. Hydroxyapatite and tricalcium phosphate thus improve our new gelatin-alginate bioadhesives, which can be used for both soft and hard tissue adhesive applications.

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