Yeast cell wall particles: a promising class of nature-inspired microcarriers for multimodal imaging

This communication demonstrates that yeast cell wall particles (YCWPs) are a promising class of nature-inspired biocompatible microcarriers for the delivery of amphipathic/lipophilic imaging reporters. When a paramagnetic MRI agent is loaded, the longitudinal relaxivity per particle at 0.5 T is the highest ever reported for Gd-based systems.     

Dynamics on certain sets of stochastic matrices

We study iteration of polynomials on symmetric stochastic matrices. In particular, we focus on a certain one-parameter family of quadratic maps which exhibits chaotic behavior for a wide range of the parameters. The well-known dynamical behavior of the quadratic family on the interval, and its dependence on the parameter, is reproduced on the spectrum of the stochastic matrices. For certain subclasses of stochastic matrices the referred dynamical behavior is also obtained in the matrix entries. Since a stochastic matrix characterizes a Markov chain, we obtain a discrete dynamical system on the space of reversible Markov chains. Therefore, depending on the parameter, there are initial conditions for which the corresponding reversible Markov chains will lead under iteration to a fixed point, to a periodic point, or to an aperiodic point. Moreover, there are sensitivity to initial conditions and the coexistence of infinite repulsive periodic orbits, both features of chaos.     

Copolyimides containing alicyclic and fluorinated groups: Characterization of the film microstructure

The microstructures of a series of copolyimide films were characterized with different experimental methods such as density measurements, X‐ray diffraction, ultraviolet‐visible spectrophotometry, positron annihilation spectroscopy, and dynamic mechanical analysis. The experimental data were linked to the chemical structures of the polymers and especially the alicyclic and fluorinated monomers. Some analysis responses were directly dependent on the fluorine atoms and, therefore, did not provide clear information about the microstructures. The chain organization in the amorphous films appeared to be significantly dependent on the effect of the casting solvent. The influence of the alicyclic group content was quite significant for a nonsubstituted diamine but was strongly attenuated with a fluorinated diamine. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2998–3010, 2003     

Specific features of absorption spectra of fractal-structured silver sols

Effects exerted on plasmon absorption spectra by different characteristics of aggregating silver sols with a fractal distribution of particles whose sizes are in the range 5–30 nm are studied by mathematical simulation with the aid of a modification of the method of coupled dipoles. Distinctive features of plasmon absorption contours of silver sols having different particle-size distribution functions and different properties of the adsorption layers of the particles are explained.     

The relationship between formation kinetics and microdroplet size of epoxy-based polymer-dispersed liquid crystals

Polymer films containing dispersions of liquid crystal microdroplets have considerable potential for use in displays and other light control devices. These polymer-dispersed liquid crystal (PDLC) films operate by electric field control of light scattering, rather than by polarization control as in the case of twisted nematic systems. The scattering characteristics of the PDLC films are determined by the refractive indices of the polymer and liquid crystal and by the size of the microdroplets. We have found that it is possible to regulate the microdroplet size by controlling the droplet formation rate (i.e. the cure kinetics of the film). Using calorimetry and scanning electron microscopy, we determined the influence of cure kinetics on microdroplet size for epoxy-based PDLCs. We found that droplet size increased with increasing cure time constant. However, the relationship changed as cure temperature was varied, perhaps as a result of competing cure processes. We also determined the phase behaviour of the epoxy-based PDLCs. The liquid crystal acted as a plasticizer, depressing the glass transition temperature of the PDLC samples slightly below that of the pure epoxy. The temperature and enthalpy of the nematic to isotropic transition of the liquid crystal material in the microdroplets were both functions of cure temperature. From the transition enthalpy it was possible to estimate a, the fraction of liquid crystal contained in the droplets; we found that a decreased with increasing cure temperature, presumably as a result of greater liquid crystal solubility in the epoxy matrix at higher temperatures.     

Über die relativistische Elektronenoptik elektrostatischer Beschleuniger

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