Production and characterization of a new dextrin based hydrogel

Dextrin is a polymer composed of α-(1→4) d-glucose units produced by partial hydrolysis of starch. In this work, the transesterification of the soluble polysaccharide with vinyl acrylate (VA) was carried out in anhydrous dimethylsulfoxide (DMSO). The effect of the water activity and of the enzyme Proleather, on the reaction rates, was analysed. Different degrees of substitution (DS) ranging from ca. 10% to 70% were obtained by controlling the molar ratio of VA to dextrin. Gels were obtained by free radical polymerization of dextrin-VA, with different degrees of substitution and monomer concentration, in water. A comprehensive solid state-NMR analysis of the hydrogels was performed. These hydrogels are being developed as scaffold materials for bioactive molecule and cell delivery, tissue engineering and a variety of other biomedical applications.     

Collision between scalar and vector spatial solitons in Kerr media

Experimental observation and numerical results concerning collisions between scalar and vector spatial solitons in a Kerr planar waveguide are presented. It is shown that this configuration allows for the full control of spatial and polarization dynamics of the interacting vector solitons. On the one hand, the ability to achieve polarization control of a single-hump vector soliton is demonstrated. On the other hand, the effect of collision on the spatial symmetry-breaking dynamics of multimode vector solitons is investigated.     

Enantioselective sensing of dicarboxylates. Influence of the stoichiometry of the complexes on the sensing mechanism

Two new cyclohexane-based thiourea chiral ligands have been synthesized in their enantiomerically pure forms. Both the ability of these ligands in the complexation of chiral dicarboxylates and their sensing properties have been studied. The influence of the stoichiometry of the formed complexes on the fluorescent properties of the systems has been established. The effect of additional substitution in the cyclohexyl moiety was considered by comparing the properties of the newly prepared ligands with those of similar compounds previously described.     

Design Reuse and Buffers in High-Tech Infrastructure Development: A Stakeholder Perspective

This study investigates the implementation of design reuse and buffers in developing the infrastructure of high-tech production facilities Design reuse entails using the same systems architecture from one project to the next. Design buffers involve building slack into a proven systems architecture to absorb foreseeable change requests. Choosing the appropriate amounts of reuse and slack is dependent on the uncertainty in the manufacturing technology over the infrastructure life cycle. While proven infrastructure designs can economically accommodate incremental changes in technology, adaptation costs escalate when sufficient buffers are not built-in and changes are radical. We uncover opposing stakeholder interests in determining the extent to which reuse or buffers are used. Design reuse is attractive to the client to reduce the risk that a facility fails to perform, but limits the designer's job to tedious customization work. Design buffers are attractive to the designer to do original problem-solving and limit the risks of being unresponsive to uncertainty, but not to the client who is not guaranteed that the investments will pay off. We find that inequalities between the two stakeholders in the governing power on design decision-making compound the difficulties in assessing and implementing the reuse versus buffers tradeoff.     

Design strategies to increase the brightness of gain guided tapered lasers

The basic operating principles of gain guided tapered lasers are studied in detail by means of numerical simulations. The carrier induced lensing effect caused by spatial hole burning is described as the main mechanism limiting the device performance. The influence of the following design parameters in the maximum output power and beam brightness is analyzed: refractive index step of the ridge waveguide section, angle and length of the tapered section, and the use of beam spoilers. The results provide design guidelines for improving the device performance.     

Instabilities during the evaporation of a film: Non-glassy polymer + volatile solvent

: We consider solutions where the surface tension of the solvent s is smaller than the surface tension of the polymer p. In an evaporating film, a “plume”, of solvent-rich fluid, then induces a local depression in surface tension, and the surface forces tend to strengthen the plume. We give an estimate (at the level of scaling laws) for the minimum thickness e ^* required to obtain this instability. We predict that a) e ^* is a decreasing function of the solvent vapor pressure pv(e ^* ~ pv^-1/2); b) e ^* should be very small (< 1 micron) provided that the initial solution is rather dilute; c) the overall evaporation time for the film should be much longer than the growth time of the instability. The instability should lead to distortions of the free surface and may be optically observable. It should dominate over the classical Benard-Marangoni instability induced by cooling.