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  • 1
    Electronic Resource
    Electronic Resource
    An Expectation Maximization Approach to Estimate Malaria Haplotype Frequencies in Multiply Infected Children (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Statistical applications in genetics and molecular biology 6.2007, 1, art33 
    Details
    ISSN: 1544-6115
    Source: Berkeley Electronic Press Academic Journals
    Topics: Biology
    Notes: Characterizing genetic variability in the human pathogenic Plasmodium species, the group of parasites that cause Malaria, may have broad global health implications. Specifically, discerning the combinations of mutations that lead to viable parasites and the population level frequencies of these clonal sequences will allow for targeted vaccine development and individualized treatment choices. This presents an analytical challenge, however, since haplotypic phase (i.e. the alignment of bases on a single DNA strand) is generally unobservable in multiply infected individuals. This manuscript describes an expectation maximization (EM) approach to maximum likelihood estimation of haplotype frequencies in this missing data setting. The approach is applied to a cohort of N=341 malaria infected children in Uganda, Cameroon and Sudan to characterize regional differences. A simulation study is also presented to characterize method performance and assess sensitivity to distributional assumptions.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/sagmb/vol6/iss1/art33
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic clonal diversity predicts progression to esophageal adenocarcinoma (2006)
    [s.l.] : Nature Publishing Group
    Nature genetics 38 (2006), S. 468-473 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Neoplasms are thought to progress to cancer through genetic instability generating cellular diversity and clonal expansions driven by selection for mutations in cancer genes. Despite advances in the study of molecular biology of cancer genes, relatively little is known about evolutionary mechanisms ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/ng1768
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  • 3
    Electronic Resource
    Electronic Resource
    Oxidative coupling of methane by water as the oxidant on perovskite oxide catalysts (1996)
    Springer
    Catalysis letters 36 (1996), S. 21-24 
    Details
    ISSN: 1572-879X
    Keywords: oxidative coupling of methane ; oxide ion defect ; perovskite oxide ; steam as oxidant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We found that methane was selectively oxidized by water to give C2 hydrocarbons and hydrogen on ATi1−xBxO3−δ (A=Sr, Ba, B=Mg, Ca). The coupling activity and selectivity on SrTi0.4Mg0.6O3−δ in the presence of steam was ∼95%, which was much higher than that on pure SrTiO3. This suggests that the selective oxidative coupling of methane by water was catalyzed by the oxide ion defects on ATi1−xBxO3−δ (A=Sr, Ba, B=Mg, Ca).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807200
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  • 4
    Electronic Resource
    Electronic Resource
    Optimal sampling and spatial distribution of Ixodes pacificus, Dermacentor occidentalis and Dermacentor variabilis ticks (Acari: Ixodidae) (1998)
    Springer
    Experimental and applied acarology 22 (1998), S. 233-248 
    Details
    ISSN: 1572-9702
    Keywords: tick density ; distribution pattern ; sampling ; Ixodes ; Dermacentor ; California.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A common method for sampling tick populations is flagging, which is a method of dragging a white cloth over a plant substrate for a fixed distance along a transect. Flagging over rough physical surfaces or using long subtransect lengths could lead to the underestimation of tick densities. Using estimates of the drop-off rates of adult Ixodes pacificus in flag sampling, optimal sampling schemes (the length and number of subtransects) were examined using the relationships between the tick drop-off rates (c), the tick density and distribution patterns and the roughness of the sampled plant substrate. It was found that the optimal number of subtransects and Lmax, the longest subtransect length which did not significantly underestimate the tick density from c, were affected by the tick density, substrate roughness and tick distribution pattern. This study also showed that the density and distribution of I. pacificus and Dermacentor occidentalis varied greatly over time in the populations sampled, while the Dermacentor variabilis densities were low and showed no significant changes over time. Both I. pacificus and D. occidentalis had clumped distributions along trails and these clumps were aggregated. However, the clump sizes (or individual clump areas) changed significantly over time because of density fluctuation or the movement of ticks. Finally, a positive association between the number of I. pacificus and D. occidentalis adults was observed from 2 m subtransect flag collections in March 1995; no relationship was found in 1994. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006018432064
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  • 5
    Electronic Resource
    Electronic Resource
    Application of Sol-Gel Method to Preparation of Ultra-Uniform Co-Based Catalysts for Fischer-Tropsch Reaction (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 519-523 
    Details
    ISSN: 1573-4846
    Keywords: additive ; Co/SiO2 catalyst ; Fischer-Tropsch synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Uniformly dispersed Co/SiO2 catalysts (10–60 wt% on metal basis) were prepared by the sol-gel method, and used for the Fischer-Tropsch (F-T) synthesis in slurry phase at 503 K and 1 MPa in a flow of synthesis gas (H2/CO = 2/1, W/F = 10 g-catal·h/mol). The catalysts were characterized by temperature-programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and chemisorption. Although CO conversion over the unpromoted catalysts prepared by the sol-gel method was lower than the conventional catalysts prepared by impregnation, the catalytic activity of the former catalysts was more stable than the latter catalysts. The conversion was improved drastically, when 0.01–1 wt% of Ir or Ru (on metal basis) was added to the catalysts prepared by the sol-gel method. The TPR and XPS spectra and the H2 chemisorption revealed that the noble metal addition was responsible for the reduction of Co particles in the catalysts. It is supposed that the durability of the promoted catalysts prepared by the sol-gel method was ascribed to the high dispersion of Co particles stabilized on the catalyst surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008780404363
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of magnetic polymer microspheres and application for immobilization of proteinase of balillus sublitis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1991-1997 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Core-shell composite magnetic polymer microspheres, containing a magnetic core and a polymer shell, were synthesized by dispersion copolymerization of styrene (St) and 2-hydroxyethyl methacrylate (HEMA) in the presence of magnetic oxide (Fe3O4) powder. The Fe3O4 powder was ultrasonically disperesed in poly(ethylene glycol) (PEG) and the affinity between the obtained superfine powder and the monomer and initator was improved. It shows that the dispersion medium and stabilizer system have a great effect on the diameter and dispersion parameter of microspheres. In the condition of controlling polymerization, the magnetic polymer microspheres containing surface —OH groups, having 50-500 μm diameter and with better magnetic induction, were synthesized. The proteinase of Balillus sublitis was immobilized on magnetic polymer microspheres with an average diameter of 50-60 μm by covalent coupling. The magnetic immobilized proteinase shows an enzyme activity of 1000 U/g, the enzyme yields are usually 20-30 mg/g of carriers, and the activity retention is about 40%. The stability of the immobilized enzyme was obviously improved. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070581109
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