A thermo-responsive comb-like polymer with chitosan as the backbone and pendant poly(N-isopropylacrylamide) (PNIPAM) groups has been synthesized by grafting PNIPAM-COOH with a single carboxy end group onto chitosan through amide bond linkages. The copolymer exhibits reversible temperature-responsive soluble-insoluble characteristics with the lower critical solution temperature (LCST) being at around 30 degrees C. Results from SEM observations confirm a porous 3D hydrogel structure with interconnected pores ranging from 10 to 40 microm at physiological temperature. A preliminary in vitro cell culture study has demonstrated the usefulness of this hydrogel as an injectable cell-carrier material for entrapping chondrocytes and meniscus cells. The hydrogel not only preserves the viability and phenotypic morphology of the entrapped cells but also stimulates the initial cell-cell interactions.
Abstract. Ion exchange (IEX) chromatography is commonly used in separation and purification systems. However, micropore blockage within its resin structure can easily lead to a reduction in the effectiveness of purification. To tackle this problem, we adopted the concept of membrane separation by combining electrospinning techniques with rapid alkaline hydrolysis to prepare a weak acid IEX nanofibrous membrane (AEA-COOH), consisting of polyethyleneterephthalate (PET) meltblown fabric as a supporting layer, with upper and lower IEX layers consisting of polyacrylonitrile (PAN) nanofibrous membranes. To determine the characteristics of the AEA-COOH membrane, we used the commercial product Sartobind® C IEX membrane as the standard of comparison. Results showed that the base weight and thickness of AEA-COOH were 33 and 64%, relative to Sartobind ® C membrane. The thermo-degradable temperature of AEA-COOH membrane (320°C) was far higher than that of Sartobind ® C (115°C), indicating high thermal stability. Finally, comparisons between the lysozyme adsorption rates and capacity of various IEX membranes confirmed that AEA-COOH was lighter, thinner, faster, possessing higher protein adsorption efficiency than Sartobind ® C membrane.
In this paper, a multi-mode electromagnetic shunt damper employing the current-flowing
method is newly developed for the semi-active vibration control of flexible structures. The
electromagnetic shunt damper, which is used for the electromagneto-mechanical coupling
transduction between vibrating structures and the electrical shunt circuit, consists of a coil
and a permanent magnet. The conducting coil is attached to the cantilever beams and the
two ends of the coil are connected to the current-flowing shunt circuit for the reduction
of vibration. For the analytical and experimental validation of the multi-mode
electromagnetic shunt damper, the first two modes of the cantilever beam are semi-actively
controlled. In light of the frequency responses, the vibration and damping characteristics of
the flexible beams with the electromagnetic shunt damper are investigated with
reference to changes in the circuit parameters. Also, the time responses of the
integrated systems with an initial condition are experimentally examined for
validation of the proposed damper. The effect of the magnetic intensity on the shunt
damping is studied by varying the gap between the aluminum beam and the
permanent magnet. The theoretical prediction of the frequency response of the
electromagneto-mechanically coupled beams shows good agreement with the experimental
results. The present results show that the current-flowing electromagnetic shunt damper
can be successfully applied to reduce the multi-mode vibration of flexible structures.
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