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Asa means to stimulate wound healing, a hollow fiber membranesystem might be placed within a wound bed to provide local and externallyregulated controlled delivery of regenerative factors. After sufficienthealing, it would be desirable to triggerably degrade these fibersas opposed to pulling them out. Accordingly, a series of enzymaticallydegradable thermoplastic elastomers was developed as potential hollowfiber base material. Polyurethane ureas (PUUs) were synthesized basedon 1, 4-diisocyanatobutane, polycaprolactone (PCL) diol and polyethyleneglycol (PEG) at different molar fractions as soft segments, and collagenase-sensitivepeptide GGGLGPAGGK-NH2as a chain extender (definedas PUU-CLxEGy-peptide, where xand yare therespective molar percents). In these polymers, PEG in the polymerbackbone decreased tensile strengths and initial moduli of solvent-castfilms in the wet state, while increasing water absorption. Collagenasedegradation was observed at 75% relative PEG content in the soft segment.Control PUUs with putrescine or nonsense peptide chain extenders didnot degrade acutely in collagenase. Conduits electrospun from PUU-CL25EG75-peptide and PUU-CL50EG50-peptide exhibited appropriate mechanical strength and sustainedrelease of a model protein from the tube lumen for 7 days. Collapseof PUU-CL25EG75-peptide tubes occurred aftercollagenase degradation for 3 days. In conclusion, through moleculardesign, synthesis and characterization, a collagenase-labile PUU-CL25EG75-peptide polymer was identified that exhibitedthe desired traits of triggerable lability, processability, and thecapacity to act as a membrane to facilitate controlled protein release. [ABSTRACT FROM AUTHOR]

This paper presents a transient simulation method for simulating an air-conditioning (AC) system in a commercial building. Using the simulation program, a typical air-water cooling system in a commercial building was simulated with real data from Hong Kong. The impacts of several different control strategies (start/stop, continuous, start/stop with night ventilation, economiser) on energy saving were computed and the energy consumptions were compared. The effects on energy saving of the control mode before the occupied period and the chilled water outlet temperature from the chillers were also simulated. The computational results show that the control strategy has a significant effect on the energy consumption of an air-conditioning system and that there is an optimal range of chilled water outlet temperature within which the system energy consumption is a minimum. [ABSTRACT FROM PUBLISHER]

Novel cholic acid functionalized branched oligo/poly(epsilon-caprolactone)s were synthesized through the ring-opening polymerization of epsilon-caprolactone initiated by cholic acid with hydroxyl groups. The molecular weight of the branched polymers can be adjusted by controlling the feed ratio of the initiator cholic acid to the monomer epsilon-caprolactone. Comparing with linear homopolymer poly(epsilon-caprolactone) (PCL), these branched oligo/poly(epsilon-caprolactone)s show much faster hydrolytic degradation rates, implies that our approach provides a convenient and effective strategy to accelerate degradation of the biodegradable polymers with slow degradation rates such as PCL. The cell culture experiment indicates the incorporation of cholic acid moiety to the polymer chain can improve both cell adherence and proliferation obviously., ((c) 2006 Wiley Periodicals, Inc.)