A review on emulsification via microfluidic processes

Emulsion is a disperse system with two immiscible liquids, which demonstrates wide applications in diverse industries. Emulsification technology has advanced well with the development of microfluidic process. Compared to conventional methods, the microfluidics-based process can produce controllable droplet size and distribution. The droplet formation or breakup is the result of combined effects resulting from interfacial tension, viscous, and inertial forces as well as the forces generated due to hydrodynamic pressure and external stimuli. In the current study, typical microfluidic systems, including microchannel array, T-shape, flow-focusing, co-flowing, and membrane systems, are reviewed and the corresponding mechanisms, flow regimes, and main parameters are compared and summarized.     

16th International Drying Symposium (IDS2008)

This study introduces sensor psychrometrics, as opposed to the physically constrained static gravimetric experimentation, for the characterisation of cobed maize drying. Simultaneous spreadsheet integration and Solver analytics were used to interpret the digital drying curve from sensor-sampled psychrometric data. The results were validated gravimetrically at dryer settings of 37, 43, and 53°C. The ear drying curves were reproduced with a goodness-of-fit consistency of 0.997–0.999 across the different calibration settings. The new methodology, presented along with its uncertainty, exploits advances in computing and instrumentation to digitize empirical drying, moving experimentation beyond the rigid confines of the lab to the desktop.     

Oligodendrocyte-type 2 astrocyte progenitors use a metalloendoprotease to spread and migrate on CNS myelin

Oligodendrocyte-type 2 astrocyte (O-2A) progenitors are highly motile cells which migrate in the developing and adult central nervous system (CNS). Adult CNS myelin, however, contains inhibitory proteins, the neurite growth inhibitors NI 35/250, which block neurite outgrowth and spreading of many different cell types, such as astrocytes and fibroblasts. In the present study we investigated the spreading of dissociated cells and migration out of aggregates ('spheres') of primary O-2A cultures and of a glial precursor cell line (CG-4) on purified CNS myelin and on CNS tissue. Primary O-2A progenitors and CG-4 cells quickly attached to and spread on CNS myelin-coated culture dishes, showing no inhibition by the neurite growth inhibitors. CG-4 cells migrated with a velocity of 30 microns/h on a CNS myelin protein extract and at 5.7 microns/h on adult spinal cord tissue. Both cell spreading and migration on a CNS substrate could be specifically blocked by metalloprotease blockers like o-phenanthroline and the tetrapeptide carbobenzoxy-phe-ala-phe-tyr-amide, whereas blockers of the serine, aspartyl and cysteine proteases had no effect. On differentiation to astrocytes, the O-2A progenitors lost their ability to spread on CNS myelin. These results suggest the crucial involvement of a metalloprotease in the mechanism of migration on a CNS substrate. In vivo, migration of oligodendrocyte progenitors may be an important aspect of myelin repair following local traumatic, inflammatory or toxin-induced myelin loss.     

Design of a Microstructured System for Homogenization of Dairy Products with High Fat Content

High pressure homogenization of dairy products is today state of the art but limited by the fat content (max 17 vol.‐%). This article describes the development of a novel simultaneous homogenization and mixing (SHM) valve which allows homogenization of dairy products with a fat content of up to 42 vol.‐%. The challenging task of homogenizing dairy products with high fat content is to stabilize disrupted fat droplets especially against extensive aggregation. Aggregation and coalescence rates could be significantly reduced by a new microstructured valve allowing the emulsifier‐containing phase to be injected directly into the zone of droplet disruption.     

Cloning, sequencing, and expression of the gene encoding cyclic 2, 3-diphosphoglycerate synthetase, the key enzyme of cyclic 2, 3-diphosphoglycerate metabolism in Methanothermus fervidus

Cyclic 2,3-diphosphoglycerate synthetase (cDPGS) catalyzes the synthesis of cyclic 2,3-diphosphoglycerate (cDPG) by formation of an intramolecular phosphoanhydride bond in 2,3-diphosphoglycerate. cDPG is known to be accumulated to high intracellular concentrations (>300 mM) as a putative thermoadapter in some hyperthermophilic methanogens. For the first time, we have purified active cDPGS from a methanogen, the hyperthermophilic archaeon Methanothermus fervidus, sequenced the coding gene, and expressed it in Escherichia coli. cDPGS purification resulted in enzyme preparations containing two isoforms differing in their electrophoretic mobility under denaturing conditions. Since both polypeptides showed the same N-terminal amino acid sequence and Southern analyses indicate the presence of only one gene coding for cDPGS in M. fervidus, the two polypeptides originate from the same gene but differ by a not yet identified modification. The native cDPGS represents a dimer with an apparent molecular mass of 112 kDa and catalyzes the reversible formation of the intramolecular phosphoanhydride bond at the expense of ATP. The enzyme shows a clear preference for the synthetic reaction: the substrate affinity and the Vmax of the synthetic reaction are a factor of 8 to 10 higher than the corresponding values for the reverse reaction. Comparison with the kinetic properties of the electrophoretically homogeneous, apparently unmodified recombinant enzyme from E. coli revealed a twofold-higher Vmax of the enzyme from M. fervidus in the synthesizing direction.     

Using domain decomposition to solve symmetric,positive-definite systems on the hypercube computer

A distributed method of solving sparse, positive-definite systems of equations, like those arising from many finite-element problems, on a hypercube computer is studied. A domain-decomposition method is introduced wherein the domain of the problem to be solved is physically split into several subdomains. Each of these subdomains is then distributed to a separate processor on the hypercube where the fill, factorization and solution of the system of equations proceeds. This physical split is based on a nodal ordering known as one-way dissection.⁴ The method is applied to two-dimensional electrostatic problems which are governed by Laplace's equation. Since the finite-element method is used to discretize the problem, the algorithm is developed to take full advantage of the inherent sparsity in the system of equations by using an envelope storage scheme. The method is applied to several geometries, and results as well as performance data for the algorithm will be given.     

A metalloprotease activity from C6 glioma cells inactivates the myelin-associated neurite growth inhibitors and can be neutralized by antibodies

Glioblastoma cells infiltrate brain tissue and migrate preferentially along white matter fibre tracts, an environment that is highly inhibitory to the migration of astrocytes and the growth of neurites because of the presence of specific inhibitory proteins. In vitro, spreading and migration of rat C6 glioma cells on a CNS (central nervous system) myelin substrate is correlated with and dependent on the presence of a metalloprotease. This membrane-bound metalloendoprotease exhibits a blocker profile different from known proteases. Pretreatment of CNS myelin or of a highly purified CNS myelin component, the inhibitory protein bNI-220, with C6 metalloproteolytic activity converts these non-permissive substrates into permissive environments for astrocytes and fibroblasts, indicating that this C6 cell-derived metalloprotease may inactivate myelin-associated inhibitory proteins. Antibodies were raised in chicken against fractions enriched in metalloproteolytic activity; these antibodies were able to inhibit specifically spreading and migration of C6 glioma cells on a CNS myelin substrate, as well as the invasion of C6 cells into adult rat optic nerve explants in vitro. These results suggest a crucial involvement of a membrane-bound metalloprotease in the mechanisms of C6 glioma migration and infiltration of brain tissue by proteolytic inactivation of the neurite growth inhibitory proteins present in CNS myelin.