Da Vinci Fluids, catch-up dynamics and dense granular flow

We introduce and study a da Vinci Fluid, a fluid whose dissipation is dominated by solid friction. We analyse the flow rheology of a discrete model and then coarse-grain it to the continuum. We find that the model gives rise to behaviour that is characteristic of dense granular fluids. In particular, it leads to plug flow. We analyse the nucleation mechanism of plugs and their development. We find that plug boundaries generically expand and we calculate the growth rate of plug regions. In systems whose internal effective friction coefficient is relatively uniform we find that the linear size of plug regions grows as (time)$^{1/3}$. The suitability of the model to granular materials is discussed.Comment: 5 pages, 3 figures, edited for clarifications and added reference

Local School Wellness Policies: How Are Schools Implementing the Congressional Mandate?

Summarizes research on school policies to reduce childhood obesity, with a focus on their quality, evaluation, and funding; nutritional standards and nutrition education requirements; and physical education requirements. Identifies remaining challenges

Demonstration of the feasibility of automated silicon solar cell fabrication

A study effort was undertaken to determine the process, steps and design requirements of an automated silicon solar cell production facility. Identification of the key process steps was made and a laboratory model was conceptually designed to demonstrate the feasibility of automating the silicon solar cell fabrication process. A detailed laboratory model was designed to demonstrate those functions most critical to the question of solar cell fabrication process automating feasibility. The study and conceptual design have established the technical feasibility of automating the solar cell manufacturing process to produce low cost solar cells with improved performance. Estimates predict an automated process throughput of 21,973 kilograms of silicon a year on a three shift 49-week basis, producing 4,747,000 hexagonal cells (38mm/side), a total of 3,373 kilowatts at an estimated manufacturing cost of $0.866 per cell or$1.22 per watt

Expression of active human sialyltransferase ST6GalNAcI in Escherichia coli

Georgios Skretas, Sean Carroll, and George Georgiou are with the Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712, USA -- George Georgiou is with the Department of Biomedical Engineering, University of Texas at Austin and the Section of Microbiology and Molecular Genetics, University of Texas at Austin, Austin, TX 78712, USA -- Georgios Skretas and George Georgiou are with the Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA -- Shawn DeFrees, Karl F. Johnson, and Marc F. Schwartz are with Neose Technologies Inc, 102 Rock Road, Horsham, PA, 19044, USABackground: The presence of terminal, surface-exposed sialic acid moieties can greatly enhance the in vivo half-life of glycosylated biopharmaceuticals and improve their therapeutic efficacy. Complete and homogeneous sialylation of glycoproteins can be efficiently performed enzymically in vitro but this process requires large amounts of catalytically active sialyltransferases. Furthermore, standard microbial hosts used for large-scale production of recombinant enzymes can only produce small quantities of glycosyltransferases of animal origin, which lack catalytic activity. Results and conclusion: In this work, we have expressed the human sialyltransferase ST6GalNAc I (ST6), an enzyme that sialylates O-linked glycoproteins, in Escherichia coli cells. We observed that wild-type bacterial cells are able to produce only very small amounts of soluble ST6 enzyme. We have found, however, that engineered bacterial strains which possess certain types of oxidative cytoplasm or which co-express the molecular chaperones/co-chaperones trigger factor, DnaK/DnaJ, GroEL/GroES, and Skp, can produce greatly enhanced amounts of soluble ST6. Furthermore, we have developed a novel high-throughput assay for the detection of sialyltransferase activity and used it to demonstrate that the bacterially expressed ST6 enzyme is active and able to transfer sialic acid onto a desialylated O-glycoprotein, bovine submaxillary mucin. To the best of our knowledge, this is the first example of expression of active human sialyltransferase in bacteria. This system may be used as a starting point for the evolution of sialyltransferases with better expression characteristics or altered donor/acceptor specificities.Chemical EngineeringBiomedical EngineeringInstitute for Cellular and Molecular [email protected]