Forensic Microscope

The optimization, through a Design of Experiments (DoE) approach, of a microencapsulation procedure for isolated neonatal porcine islets (NPI) is described. The applied method is based on the generation of monodisperse droplets by a vibrational nozzle. An alginate/polyornithine encapsulation procedure, developed and validated in our laboratory for almost a decade, was used to embody pancreatic islets. We analyzed different experimental parameters including frequency of vibration, amplitude of vibration, polymer pumping rate, and distance between the nozzle and the gelling bath. We produced calcium—alginate gel microbeads with excellent morphological characteristics as well as a very narrow size distribution. The automatically produced microcapsules did not alter morphology, viability and functional properties of the enveloped NPI. The optimization of this automatic procedure may provide a novel approach to obtain a large number of batches possibly suitable for large scale production of immunoisolated NPI for in vivo cell transplantation procedures in humans.

In building and environmental aerodynamics, wind tunnel studies of natural vegetative structures like bushes or trees have to be modelled. From a fluid mechanical point of view, these structures differ essentially from man-made constructions because of their structural flexibility and permeability. Whereas the small-scale modelling of technical structures is widely known, a lack of knowledge exists in an adequate modelling of vegetative structures. In this article, aerodynamic characteristics of inflexible model trees with crowns of varying porosity are presented. Drag force and flow field measurements were performed in a uniform or boundary layer flow, respectively. The force measurements delivered drag coefficients in the range of 0.8–1.2. This is in good accordance with natural trees for low wind velocities (<10 m s^–1). Flow field measurements show typical wake characteristics of permeable structures with recirculation zones being extended or even detached when compared with impermeable bodies. By means of spectral analysis, an energy shift from lower to higher frequencies, i.e. a breakdown of larger eddy structures into smaller eddies, in the crown wake region was found.