Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification

Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phase should be sufficiently fast compared to the outflow of the liquid that is forming the droplet. The ratio of the viscosities was therefore varied by using a range of continuous and dispersed phases, both experimentally and computationally. At high viscosity ratio (η _d/η _c), the droplet size is constant; the inflow of the continuous phase is fast compared to the outflow of the dispersed phase. At lower ratios, the droplet diameter increases, until a viscosity ratio is reached at which droplet formation is no longer possible (the minimal ratio). This was confirmed and elucidated through CFD simulations. The limiting value is shown to be a function of the microchannel design, and this should be adapted to the viscosity of the two fluids that need to be emulsified.     

Process engineering parameters and type of n-octenylsuccinate-derivatised starch affect oxidative stability of microencapsulated long chain polyunsaturated fatty acids

Aim of the present study was to investigate the impact of the emulsifying carrier matrix constituent, n-octenylsuccinate-derivatised (OSA)-starch, and process conditions on physical characteristics and oxidative stability of microencapsulated fish oil. Furthermore, the effect of the drying medium, i.e. air or nitrogen, on lipid oxidation during spray-drying and subsequent storage was investigated. Particle characteristics and lipid oxidation of microencapsulated fish oil were both influenced by the type of OSA-starch and the drying conditions. The highest oxidative stability was observed for fish oil microencapsulated in OSA-starch with the lowest average molecular weight and glucose syrup spray-dried at a moderate temperature setting. Particle characteristics of the microcapsules were not attributable for differences in lipid oxidation during storage. In spray-dried carrier matrix particles, the particle size increased with increasing average molecular weight of the OSA-starch and was attributed to an increase in air inclusion. Thus differences in lipid oxidation of the microencapsulated fish oil were attributed to differences in air inclusion as affected by the type of OSA-starch. In terms of spray-drying under inert conditions and in the presence of air, lipid oxidation of microencapsulated fish oil was rather attributed to oxygen availability in the feed emulsion than in the drying gas.     

Spatially resolved positron annihilation spectroscopy on friction stir weld induced defects

A friction stir welded (FSW) Al alloy sample was investigated by Doppler broadening spectroscopy (DBS) of the positron annihilation line. The spatially resolved defect distribution showed that the material in the joint zone becomes completely annealed during the welding process at the shoulder of the FSW tool, whereas at the tip, annealing is prevailed by the deterioration of the material due to the tool movement. This might be responsible for the increased probability of cracking in the heat affected zone of friction stir welds. Examination of a material pairing of steel S235 and the Al alloy Silafont36 by coincident Doppler broadening spectroscopy (CDBS) indicates the formation of annealed steel clusters in the Al alloy component of the sample. The clear visibility of Fe in the CDB spectra is explained by the very efficient trapping at the interface between steel cluster and bulk.     

A Fully Automated Process Using a Magnetic Particle Based Kit for Removal of Dye Terminators from Sequencing Reactions

Prolinx,® Inc. of Bothell, WA has developed the RapXtract™ 384 Dye Terminator Removal Kit for full automation of DNA sequencing reaction purification. The RapXtract product line is based upon proprietary superparamagnetic particle technology that eliminates the need for centrifugation, vacuum filtration, or modified primers to achieve purification of sequencing reactions. The kit described here is pre-dispensed in a 384-well microtiter plate and run on the TECAN GENESIS Workstation 150 (Tecan U.S. Inc., Research Triangle Park, NC). This system enables rapid purification of up to 384 sequencing reactions in a single run.As the completion of the Human Genome Project nears, it is imperative for biotechnology and pharmaceutical companies to increase throughput of DNA sequencing in order to be competitive in the drug discovery and validation process. The “race to market” requires a shift from standard DNA sequencing processes-including DNA sequencing reaction purification-towards complete walk-away automation for all steps.Existing sequencing reaction purification methods (Table 1) require considerable resources including: plastic and other laboratory consumables; specialized equipment, such as high-speed centrifuges or vacuum filtration apparatus; and labor-intensive protocols requiring large amounts of technician time. As a result, walk-away automation of standard purification methods is difficult and expensive.     

Characterization of silica-based monoliths with bimodal pore size distribution

Band dispersion was studied and the retention thermodynamics addressed for insulin and angiotensin II on C18 silica monoliths with a bimodal pore size distribution, covering linear mobile-phase velocities up to 1 cm/s and different temperatures. These data suggest that the influence of average column pressure on retention (between 0 and 10 MPa) is not negligible. Plate height curves were interpreted with the van Deemter equation by assuming an independent contribution from mechanical and non-mechanical dispersion mechanisms. This analysis revealed diffusion-limited mass transfer in the mesoporous silica skeleton which, in turn, allowed us to calculate an equivalent dispersion particle diameter (d(disp) = 3 microm) using the C-term parameter of the van Deemter equation. The resulting superposition of reduced plate height curves for monolithic and particulate beds confirmed that this view presents an adequate analogy. The macroporous interskeleton network responsible for the hydraulic permeability of a monolith was translated to the interparticle pore space of particulate beds, and an equivalent permeability particle diameter (d(perm) = 15 microm) was obtained by scaling based on the Kozeny-Carman equation.     

Prediction of chromatographic retention and protein identification in liquid chromatography/mass spectrometry

Liquid chromatography coupled on- or off-line with mass spectrometry is rapidly advancing as a tool in proteomics capable of dealing with the inherent complexity in biology and complementing conventional approaches based on two-dimensional gel electrophoresis. Proteins can be identified by proteolytic digestion and peptide mass fingerprinting or by searching databases using short-sequence tags generated by tandem mass spectrometry. This paper shows that information on the chromatographic behavior of peptides can assist protein identification by peptide mass fingerprinting in liquid chromatography/mass spectrometry. This additional information is significant and already available at no extra experimental cost.     

The SARS Crisis: Was Anybody Responsible?

As scholars in fields such as media studies, crisis studies and public policy studies have argued, there exists a fundamental link between crises and the media. Once an event has been interpreted as a crisis, questions of accountability inevitably appear on the media agenda, and the struggle to attribute blame and responsibility to a specific entity or entities—the blame game—thus becomes an inexorable part of the crisis process. Focusing on three liberal Western newspapers with an international, primarily Western elite readership and a reputation for in‐depth analysis of global events, The Economist, the Financial Times and the International Herald Tribune, this article employs Iyengar's and Valkenburg's notions of responsibility frames to examine whether initial coverage of the 2003 SARS crisis in these accounts held any particular entity accountable for the crisis, looks at three key themes used to communicate to the reader a particular way of thinking about responsibility for SARS and examines some of the consequences of the kind of responsibility frame constructed around the SARS crisis in these accounts. As our findings show, there is an entity that the early news accounts studied consistently held responsible for the 2003 SARS crisis, the Chinese system, and the corresponding responsibility frame at operation in these accounts is thematic rather than episodic in nature, since it consistently places the SARS crisis within a broader context (a product of “China” itself and/or of societal‐governmental forces in China) rather than in relation to a specific episode or as the result of the particular actions of individuals. The SARS crisis narrative therefore presented in these accounts tells the story of an anachronistic Chinese system faced with a contemporary health threat that, by its very nature, it is incapable of assessing accurately or managing responsibly. By way of conclusion, we argue that, while the use of such a thematic frame to explain China's role in the 2003 SARS crisis may be accurate in certain respects, this frame falls short in other respects and proves particularly inadequate to the challenge of capturing the economic complexities of China's role during the crisis.     

DEVAN: a tool for detailed video analysis of user test data

A tool was developed for structured and detailed analysis of video data from user tests of interactive systems. It makes use of a table format for representing an interaction at multiple levels of abstraction. Interactions are segmented based on threshold times for pauses between actions. Usability problems are found using a list of observable indications for the occurrence of problems. The tool was evaluated by having two analysts apply it to three data sets from user tests on two different products. The segmentation technique proved to yield meaningful segments that helped in understanding the interaction. The interaction table was explicit enough to discuss in detail what had caused the differences in the analysts' lists of usability problems. The results suggested that the majority of differences were caused by unavoidable differences in interpretations of subjects' behaviour and that only minor improvements should be expected by refining the tool.