Tubular chemical reactors: the "lumping approximation" and bifurcation of oscillatory states

We study axial heat and mass transfer in a highly diffusive tubular chemical reactor in which a simple reaction is occurring. Singular perturbation techniques are used to derive approximate equations governing the situation. Attention is then focused on the bifurcation of oscillatory states from steady operating characteristics. By means of numerical calculations and phase plane illustrations we follow the bifurcated periodic solution branches along their complete lengths

Rad51 knockout does not increase the frequency of DNA repair via mmBIR

Common fragile sites are large chromosomal regions that are especially prone to double-strand breaks and are associated with cancer progression. We are studying how breaks at Fragile Site 2 (FS2), on Saccharomyces cerevisiae chromosome III, are repaired. Rad51p is a DNA-binding protein involved in DNA repair pathways. We hypothesize that the rad51Δ mutation, which results in complete loss of Rad51p, will promote the use of the error-prone mmBIR repair pathway. Because Rad51p is involved in higher fidelity repair pathways, we expect other repair pathways to be used when it is absent. Breaks were induced at FS2 in rad51Δ mutant diploids and repair events were characterized in cultures that underwent DNA repair. We categorized repair events by testing three single nucleotide polymorphisms (SNPs). We determined the chromosome size by performing CHEF gel electrophoresis and Southern blotting on isolated chromosomal DNA. We determined the sequence of the entire genome and further analyzed each repair event using next-generation paired-end sequencing. Contrary to our hypothesis, the results of this study suggest that the loss of Rad1p does not significantly increase the frequency of repair events by mmBIR. The findings of this study suggest that Rad51p does not play a significant role in cellular choice of repair pathways. Moreover, because no mmBIR was observed in rad51 mutants, this is consistent with the possibility that Rad51p may be needed in the mmBIR pathway

Distribution and Efficiency of Hydrocarbon-Oxidizing Bacteria in a Freshwater Reservoir

Hydrocarbon-oxidizing bacteria were identified from three stations on DeGray Reservoir, Arkansas. The organisms were primarily gram-negative rods representing 9 taxa and 37 biotypes Pseudomonas spp. were the most common isolates. The largest populations were found in areas most frequently used by boaters, although seasonal fluctuations were apparent during the spring and fall. The degradation of outboard motor oil by the five most rapidly growing isolates was studied. Each species had a different decomposition profile, and substrate oxidation rates were variable Acinetobacter calcoaceticus var. anitratus was the most efficient decomposer

Multiplier-continuation algorthms for constrained optimization

Several path following algorithms based on the combination of three smooth penalty functions, the quadratic penalty for equality constraints and the quadratic loss and log barrier for inequality constraints, their modern counterparts, augmented Lagrangian or multiplier methods, sequential quadratic programming, and predictor-corrector continuation are described. In the first phase of this methodology, one minimizes the unconstrained or linearly constrained penalty function or augmented Lagrangian. A homotopy path generated from the functions is then followed to optimality using efficient predictor-corrector continuation methods. The continuation steps are asymptotic to those taken by sequential quadratic programming which can be used in the final steps. Numerical test results show the method to be efficient, robust, and a competitive alternative to sequential quadratic programming

Remote sensing in the coastal and marine environment. Proceedings of the US North Atlantic Regional Workshop

Presentations were grouped in the following categories: (1) a technical orientation of Earth resources remote sensing including data sources and processing; (2) a review of the present status of remote sensing technology applicable to the coastal and marine environment; (3) a description of data and information needs of selected coastal and marine activities; and (4) an outline of plans for marine monitoring systems for the east coast and a concept for an east coast remote sensing facility. Also discussed were user needs and remote sensing potentials in the areas of coastal processes and management, commercial and recreational fisheries, and marine physical processes