Life Cycle Analysis of Sugarcane Bagasse and Switchgrass under Dilute Phosphoric Acid Pretreatment and Simultaneous Saccharification and CoFermentation

Under provisions of the Energy Independence and Security Act and the Renewable Fuel Standard, production of cellulosic ethanol is mandated to increase. Corn dominates the first generation ethanol industry in the United States. Already a high-demand crop, when subject to agricultural intensification, the carbon-neutrality potential associated with biofuels, and other environmental implications, fall into question. Sugarcane bagasse, a lignocellulosic byproduct of sugarcane manufacturing with limited economic value, and switchgrass (Panicum virgatum), a native, perennial, high-yield crop, are alternative resources that might used to produce ethanol. Life cycle assessment of second generation feedstocks has focused exhaustively on global warming potential with minimal consideration to broader impact categories. In this study, traditional dry-milled corn ethanol is compared to sugarcane bagasse and switchgrass that is derived using dilute phosphoric steam acid pretreatment and simultaneous saccharifcation and cofermentation. Modeled over ten-year scales, using E85 and E15 fuel blends scenarios, switchgrass and sugarcane bagasse fuel blends had greater global warming potential (kg CO2-eq) compared to corn at equal blend ratios. As the ethanol ratio increased, the hotspot would transition from fossil fuel production and emissions to fermentation driven by increases in enzymes, chemicals, and electricity. Water consumption, stratospheric ozone depletion, and marine eutrophication were reduced for switchgrass compared to corn due to lesser agricultural demands predominantly associated with upstream processes. Further research should include reduction of enzymes while maintaining ethanol yield and characterization of stillage

Oscillations in a maturation model of blood cell production.

We present a mathematical model of blood cell production which describes both the development of cells through the cell cycle, and the maturation of these cells as they differentiate to form the various mature blood cell types. The model differs from earlier similar ones by considering primitive stem cells as a separate population from the differentiating cells, and this formulation removes an apparent inconsistency in these earlier models. Three different controls are included in the model: proliferative control of stem cells, proliferative control of differentiating cells, and peripheral control of stem cell committal rate. It is shown that an increase in sensitivity of these controls can cause oscillations to occur through their interaction with time delays associated with proliferation and differentiation, respectively. We show that the characters of these oscillations are quite distinct and suggest that the model may explain an apparent superposition of fast and slow oscillations which can occur in cyclical neutropenia. © 2006 Society for Industrial and Applied Mathematics

Huygens Titan Probe Trajectory Reconstruction Using Traditional Methods and the Program to Optimize Simulated Trajectories II

On January 14, 2005, ESA's Huygens probe separated from NASA's Cassini spacecraft, entered the Titan atmosphere and landed on its surface. As part of NASA Engineering Safety Center Independent Technical Assessment of the Huygens entry, descent, and landing, and an agreement with ESA, NASA provided results of all EDL analyses and associated findings to the Huygens project team prior to probe entry. In return, NASA was provided the flight data from the probe so that trajectory reconstruction could be done and simulation models assessed. Trajectory reconstruction of the Huygens entry probe at Titan was accomplished using two independent approaches: a traditional method and a POST2-based method. Results from both approaches are discussed in this paper

Force-plate quantification of progressive behavioral deficits in the R6/2 mouse model of Huntington’s disease

The R6/2 mouse is a popular model of Huntington’s disease (HD) because of its rapid progression and measurable behavioral phenotype. Yet current behavioral phenotyping methods are usually univariate (e.g., latency to fall from a rotarod) and labor intensive. We used a force-plate actometer and specialized computer algorithms to partition the data into topographically specific behavioral categories that were sensitive to HD-like abnormalities. Seven R6/2 male mice and 7 wild type (WT) controls were placed in a 42 cm X 42 cm force-plate actometer for 20-min recording sessions at 6–7, 8–9, 10–11 and 12–13 weeks of age. Distance traveled, number of wall rears, and number of straight runs (traveling 175 mm or more in 1.5 s) were reduced in R6/2 relative to WT mice at all ages tested. Low mobility bouts (each defined as remaining continuously in a virtual circle of 15 mm radius for 5 s) were increased in R6/2 mice at 6–7 wk and beyond. Independent of body weight, force off-load during wall rears was reduced in R6/2 mice except at 6–7 wk. Power spectra of force variation during straight runs indicated an age-related progressive loss of rhythmicity in R6/2 compared to WT, suggesting gait dysrhythmia and dysmetria. Collectively, these data, which extend results obtained with other widely different behavioral phenotyping methods, document a multifaceted syndrome of motor abnormalities in R6/2 mice. We suggest, moreover, that the force-plate actometer offers a high-throughput tool for screening drugs that may affect symptom expression in R6/2 or other HD model mice