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1.
Ernst van der Maaten Marieke van der Maaten-Theunissen Allan Buras Tobias Scharnweber Sonia Simard Knut Kaiser Sebastian Lorenz Martin Wilmking 《PloS one》2015,10(8)
In this study, we explore the potential to reconstruct lake-level (and groundwater) fluctuations from tree-ring chronologies of black alder (Alnus glutinosa L.) for three study lakes in the Mecklenburg Lake District, northeastern Germany. As gauging records for lakes in this region are generally short, long-term reconstructions of lake-level fluctuations could provide valuable information on past hydrological conditions, which, in turn, are useful to assess dynamics of climate and landscape evolution. We selected black alder as our study species as alder typically thrives as riparian vegetation along lakeshores. For the study lakes, we tested whether a regional signal in lake-level fluctuations and in the growth of alder exists that could be used for long-term regional hydrological reconstructions, but found that local (i.e. site-specific) signals in lake level and tree-ring chronologies prevailed. Hence, we built lake/groundwater-level reconstruction models for the three study lakes individually. Two sets of models were considered based on (1) local tree-ring series of black alder, and (2) site-specific Standardized Precipitation Evapotranspiration Indices (SPEI). Although the SPEI-based models performed statistically well, we critically reflect on the reliability of these reconstructions, as SPEI cannot account for human influence. Tree-ring based reconstruction models, on the other hand, performed poor. Combined, our results suggest that, for our study area, long-term regional reconstructions of lake-level fluctuations that consider both recent and ancient (e.g., archaeological) wood of black alder seem extremely challenging, if not impossible. 相似文献
2.
Maria D Mjaavatten Désirée van der Heijde Till Uhlig Anne J Haugen Halvor Nygaard Göran Sidenvall Knut Helgetveit Tore K Kvien 《Arthritis research & therapy》2010,12(3):R76
Introduction
We wanted to assess the importance of the levels of anti-citrullinated peptide antibody (anti-CCP) and immunoglobulin M (IgM) rheumatoid factor (RF) in predicting development of persistent arthritis from undifferentiated arthritis (UA), and to investigate whether there is an added predictive value for persistent arthritis in testing for both anti-CCP and IgM RF. 相似文献3.
The naïve user of PAUP 3.1.1 (and earlier versions) is warned about a shortcoming in the program's successive weighting facility. With matrices containing multistate terminals, PAUP, under the "polymorphism" interpretation, will assign higher weight to characters with more within-terminal steps, other things being equal, i.e. to characters with the largest amount of homoplasy. The shortcoming has been corrected in PAUP* version 4.0. 相似文献
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Because Pee-Wee (version 2.5.1 and earlier versions) treats all within-terminal steps (internal steps) as homoplasies, if the command "ccode = (space).;" is in effect, it reports incorrect, and consistently too low, fit values for characters having states that occur only within polymorphic terminals (WPTO states). For matrices with WPTO states, this property of Pee-Wee may bias tree search in favour of characters having fewer WPTO states, other things being equal. Contrary to the intended purpose of the Goloboff criterion, Pee-Wee may even, in certain cases involving WPTO states, assign higher weight (fit) to characters with more homoplasy and therefore resolve character conflict in favour of less reliable characters. 相似文献
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Olav Hungnes Knut Jønsrud Enok Tjøtta Bjørn Grinde 《Journal of molecular evolution》1993,37(2):198-203
The large number of sequenced clones of HIV-1 and related viruses made it possible to indicate conserved elements with potential
regulatory or structural functions. Such analysis was combined with directed mutagenesis in order to investigate the importance
of elements that may influence the initiation of plus-strand DNA synthesis. The main site for plus-strand initiation is a
polypurine tract near the 3′ end of the viral RNA (the 3′ PPT). An exact copy of this PPT is located in the middle of the
genome (the internal PPT). Upstream from the internal PPT there is an inverted repeat. Mutants designed to upset the internal
PPT (i.e., purine to pyrimidine changes), as well as mutants designed to abolish the potential stem-loop formation (changes
around the internal PPT or in the upstream inverted repeat) both resulted in viruses with a reduced ability to replicate.
Upsetting the stem-loop formation was, however, less harmful than changing the polypurine nature of the PPT. Changing a conserved
T on the 3′ side of the PPT to a C did not affect the phenotype.
Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992 相似文献
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Knut M. Wittkowski 《Biometrical journal. Biometrische Zeitschrift》1988,30(7):799-808
A rank test is presented for analysis of incomplete unbalanced designs, i.e. for designs that may have been originally planned to be either balanced or unbalanced and where some observations may be missing at random. This test is a modification of the procedure of Benard and van El-teren (1953) based on a generalization of block weights proposed by Prentice (1979). It is compared with the tests of Haux, Schumacher, and Weckesser (1984) and Rai (1987). For incomplete or unbalanced designs with more than two treatments the quadratic forms proposed by these authors are proven to be invalid for small sample sizes, except for special cases. A necessary condition is given for test statistics to be valid also for small samples. 相似文献
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