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  • 1
    Electronic Resource
    Electronic Resource
    Comparisons of phylogenetic hypotheses among different data sets in dwarf dandelions (Krigia, Asteraceae): Additional information from internal transcribed spacer sequences of nuclear ribosomal DNA (1994)
    Springer
    Plant systematics and evolution 190 (1994), S. 157-185 
    Details
    ISSN: 1615-6110
    Keywords: Asteraceae ; Lactuceae ; Microseridinae ; Krigia ; Internal transcribed spacer (ITS) ; ITS region (ITS 1, 5.8 S rDNA, and ITS 2) ; intergenic spacer (IGS) region ; nuclear ribosomal DNA (nrDNA) ; chloroplast DNA (cpDNA) ; sequence divergence ; polymerase chain reaction (PCR) ; maximum parsimony (MP) tree ; neighbor joining (NJ) tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The internal transcribed spacer (ITS) region of the 18 S–25 S nuclear ribosomal DNA repeat was sequenced from 19 populations of the tribeLactuceae, including all species of dwarf dandelion (Krigia) and five outgroup genera. The incidence of length changes and base substitutions was at least two times higher for ITS 1 than ITS 2. Interspecific sequence divergence withinKrigia averaged 9.62% (1.61%–15.19%) and 4.26% (0%–6.64%) in ITS 1 and ITS 2, respectively. Intergeneric sequence divergence ranged from 15.6% to 44.5% in ITS 1 and from 8.0% to 28.6% in ITS 2. High sequence divergence and homoplasy among genera of tribeLactuceae suggest that the phylogenetic utility of ITS sequence data is limited to interspecific studies or comparisons among closely related genera. Trees generated from ITS sequences are essentially identical to those from restriction site comparisons of the entire nuclear ribosomal (nr) DNA region. The degree of tree resolution differed depending on how gaps were treated in phylogenetic analyses. The ITS trees were congruent with the chloroplast DNA and morphological phylogenies in three major ways: 1) the sister group relationship betweenKrigia andPyrrhopappus; 2) the recognition of two monophyletic sections,Krigia andCymbia, in genusKrigia; and 3) the monophyly of theK. occidentalis-K. cespitosa clade in sect.Cymbia. However, the two nrDNA-based trees are not congruent with morphology/chloroplast DNA-based trees for the interspecific relationships in sect.Krigia. An average of 22.5% incongruence was observed among fourKrigia data sets. The relatively high degree of incongruence among data sets is due primarily to conflict between trees based on nrDNA and morphological/cpDNA data. The incongruence is probably due to the concerted evolution of nrDNA repeating units. The results fromKrigia and theLactuceae suggest that nrDNA data may have limited utility in phylogenetic studies of plants, especially in groups which exhibit high levels of sequence divergence. Our combined phylogenetic analysis as a total evidence shows the least conflict to each of the individual data sets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00986191
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  • 2
    Electronic Resource
    Electronic Resource
    Phylogenetic and evolutionary implications of nuclear ribosomal DNA variation in dwarf dandelions (Krigia, Lactuceae, Asteraceae) (1991)
    Springer
    Plant systematics and evolution 177 (1991), S. 53-69 
    Details
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asteraceae ; Lactuceae ; Krigia ; Nuclear ribosomal DNA (nrDNA) ; inter-cistronic spacer (ITS) ; intergenic spacer (IGS) ; subrepeating unit ; chloroplast DNA (cpDNA) ; allopolyploid ; restriction site mapping ; methylation ; bootstrap resampling analysis ; sequence divergence value ; cladistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Restriction site and length variations of nrDNA were examined for 51 populations of seven species ofKrigia. The nrDNA repeat ranged in size from 8.7 to 9.6 kilobase (kb). The transcribed region, including the two ITSs, was 5.35 kb long in all examinedKrigia populations. In contrast, the size of the nontranscribed IGS varied from 3.35 to 4.25 kb. Eight different types of length-variations were identified among the 51 populations, including distinct nrDNA lengths in the tetraploid and diploid populations of bothK. biflora andK. virginica. However, a few variations were detected among populations of the same species or within a cytotype. All populations ofKrigia sect.Cymbia share a 600 bp insertion in IGS near the 18 S gene, and this feature suggests monophyly of the section. AllKrigia spp. had a conjugated type of subrepeat composed of approximately 75 basepairs (bp) and 125 bp. Base modifications in the gene coding regions were highly conserved among species. Forty-five restriction sites from 15 enzymes were mapped, 24 of which were variable among populations. Only four of the variable sites occurred in the rRNA coding region while 20 variable sites were detected in the noncoding regions. Collectively, 25 enzymes generated about 66 restriction sites in each nrDNA; this amounts to about 4.3% of the nrDNA repeat. A total of 50 restriction sites was variable, 28 of which were phylogenetically informative. Phylogenetic analyses of site mutations indicated that two sections ofKrigia, sect.Cymbia and sect.Krigia, are monophyletic. In addition, relationships among several species were congruent with other sources of data, such as cpDNA restriction site variation and morphology. Both length and restriction site variation supported an allopolyploid origin of the hexaploidK. montana. The average sequence divergence value inKrigia nrDNA was 40 times greater than that of the chloroplast DNA. The rapid evolution of nrDNA sequences was primarily due to changes of the IGS sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00937826
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  • 3
    Electronic Resource
    Electronic Resource
    Drop-size distributions from pneumatic atomizers (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 575-584 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study was made of the atomizing characteristics of convergent-type pneumatic nozzles. Drop-size correlations were obtained for the following ranges: drop size, 6 to 350 μ, mass median diameter; mass flow ratio, 0.06 to 40; relative velocity, 250 ft./sec. to sonic velocity; and viscosity. 1 to 50 cp. The technique employed was to spray cool a molten wax, and melts of wax-polyethylene mixtures. The most important operating variables in pneumatic atomization are the dynamic force of the atomizing gas, and the mass flow ratio of air to liquid. The cumulative volume drop-size distribution of spray from a pneumatic nozzle was fitted by a modified logistic equation. Empirical correlations developed in the study can be used to design nozzles or to predict drop size for sprays produced by the types of nozzles studied. In particular, this study provides new experimental data on the performance of pneumatic atomizers in producing relatively large drops.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170318
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Diffusion in nickel oxide pellets-effects of sintering and reduction (1974)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 20 (1974), S. 670-678 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion rates were measured at 25°C and 1 atm by a steady state method in pellets of nonporous nickel oxide particles in order to determine the effects of sintering and chemical reduction. Sintering led to a striking decrease in diffusion flux; tortuosities above 100 were found for highly sintered (porosity 0.03) pellets. Reduction caused a sharp increase in diffusion rate when the original pellet was highly sintered. For an originally unsintered pellet the diffusion rate decreased with extent of reduction.These phenomena were explained quantitatively by using: (1) the random pore model to predict tortuosity factors for an unsintered, unreduced pellet, and (2) the extent of pore interconnections and the fractional reduction to treat the effects of sintering and reduction. In this way an approximate, predictive equation was derived which contained no arbitrary parameters and which required for application only data on porosity and extent of chemical reduction.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690200407
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    Paper (German National Licenses)
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