Search results for "Tree"
showing 10 items of 1841 documents
Gaussian processes retrieval of leaf parameters from a multi-species reflectance, absorbance and fluorescence dataset.
2013
Abstract: Biochemical and structural leaf properties such as chlorophyll content (Chl), nitrogen content (N), leaf water content (LWC), and specific leaf area (SLA) have the benefit to be estimated through nondestructive spectral measurements. Current practices, however, mainly focus on a limited amount of wavelength bands while more information could be extracted from other wavelengths in the full range (400-2500 nm) spectrum. In this research, leaf characteristics were estimated from a field-based multi-species dataset, covering a wide range in leaf structures and Chl concentrations. The dataset contains leaves with extremely high Chl concentrations (>100 mu g cm(-2)), which are seldom es…
Biosystematic studies on the genus Polygonatum (Convallariaceae) IV. Molecular phylogenetic analysis based on restriction site mapping of the chlorop…
1997
Phylogenetic relationships of 14 species and one variety of the genus Polygonatum as well as three species of the genus Disporopsis and Heteropolygonatum roseolum were analyzed based on mapped restriction site variation in a PCR-amplified chloroplast genome region, trnK. In agreement with earlier taxonomic treatments it was found that Disporopsis and Heteropolygonatum should be distinguished from Polygonatum at generic level, and that P. sect. Polygonatum can be recognized as a monophyletic group. Earlier series concepts in P. sect. Polygonatum based on chromosome number and characteristics of staminal filaments are not supported by the molecular data. The molecular data suggest that satell…
Transition from Protozoa to Metazoa: An Experimental Approach
1998
Until recently, stromatolites were thought to be the oldest fossils on earth that were very abundant 2000 to 3000 Ma (million years) ago (Walter 1994). Recently, the biological origin of these fossils has been questioned (Walter 1996). The universal phylogenetic tree exhibits a tripartite division of the living world into Bacteria (“eubacterial”), Archaea (“archebacterial”), and Eucarya [“eukaryotic” (Woese 1987; Woese et al. 1991)]. Based on comparisons of amino acid (aa) sequence data from enzymes, it has been proposed that the common ancestor of prokaryotes and eukaryotes lived about 2000 Ma ago (Doolittle et al. 1996). Phylogenetic analysis of the 70kDa heat-shock proteins suggested tha…
Phylogenetic relationship of the green alga Nanochlorum eukaryotum deduced from its chloroplast rRNA sequences.
1995
The marine green coccoidal alga Nanochlorum eukaryotum (N.e.) is of small size with an average diameter of 1.5 microns. It is characterized by primitive-appearing biochemical and morphological properties, which are considerably different from those of other green algae. Thus, it has been proposed that N.e. may be an early developed algal form. To prove this hypothesis, DNA of N.e. was isolated by a phenol extraction procedure, and the chloroplast DNA separated by preparative CsCl density-gradient centrifugation. The kinetic complexity of the nuclear and of the chloroplast DNA was evaluated by reassociation kinetics to 3 x 10(7) bp and 9 x 10(4) bp, respectively. Several chloroplast genes, i…
EphrinB2 controls vessel pruning through STAT1-JNK3 signalling
2014
Angiogenesis produces primitive vascular networks that need pruning to yield hierarchically organized and functional vessels. Despite the critical importance of vessel pruning to vessel patterning and function, the mechanisms regulating this process are not clear. Here we show that EphrinB2, a well-known player in angiogenesis, is an essential regulator of endothelial cell death and vessel pruning. This regulation depends upon phosphotyrosine-EphrinB2 signalling repressing c-jun N-terminal kinase 3 activity via STAT1. JNK3 activation causes endothelial cell death. In the absence of JNK3, hyaloid vessel physiological pruning is impaired, associated with abnormal persistence of hyaloid vessel…
Study of polychlorinated biphenyls in street dust by supercritical fluid extraction-gas chromatography/mass spectrometry
1996
Street dust samples have been collected from highways, urban streets, a gasoline station, a pedestrian tunnel, and railway stations in some German cities. Nine polychlorinated biphenyls (PCBs from tri- to heptachlorobiphenyls) were quantitatively extracted by supercritical fluid extraction with CO2 at 200 bar and 40°C and analyzed by gas chromatography/mass spectrometry. The highest PCB loads (sum of the nine studied PCBs) of ca. 1 to 4 μg/g have been found in the samples from motorway A60 near Mainz, while in almost all other samples PCBs could be detected at only ca. 0.1 to 1 μg/g. At three sampling sites, a winter maximum of the PCB concentrations has been found.
Fast authentication of tea tree oil through spectroscopy
2018
Two new procedures, based on infrared spectroscopy in the near infrared (NIR) and mid infrared (MIR), have been developed for the authentication of tea tree oil (TTO) commercial samples. Infrared measurements were made on untreated samples by transmission NIR and attenuated total reflectance (ATR) followed by partial least square discriminant analysis (PLS-DA). These methods offer a fast and low cost alternative to enantiomeric two-dimensional gas chromatography coupled to mass detection usually employed to discriminate between authentic and non-authentic samples. In these studies, a set of 267 samples, including authentic and non-authentic labelled tea tree oil samples, were used to build …
Identification and determination of amphetamine and methamphetamine in street drugs
2000
Abstract A procedure to identify and quantify amphetamine and/or methamphetamine in street drugs is proposed. The procedure is based on the application of the ACC method (Apparent content curves method) to emission and absorption data of samples. Discrimination and quantification of amphetamine and methamphetamine in samples is carried out based on their different behavior in acid and basic medium. Potential interfering drugs are tested and the accuracy of the method is verified in prepared and real samples. Results obtained are in agreement with a HPLC procedure used as reference.
Chromosome painting of the pygmy tree shrew shows that no derived cytogenetic traits link primates and scandentia.
2012
We hybridized human chromosome paints on metaphases of the pygmy tree shrew (<i>Tupaia minor</i>, Scandentia). The lack of the ancestral mammalian 4/8 association in both Primates and Scandentia was long considered a cytogenetic landmark that phylogenetically linked these mammalian orders. However, our results show that the association 4/8 is present in <i>Tupaia </i>along with not previously reported associations for 1/18 and 7/10. Altogether there are 11 syntenic associations of human chromosome segments in the pygmy tree shrew karyotype: 1/18, 2/21, 3/21, 4/8, 7/10, 7/16, 11/20, 12/22 (twice), 14/15 and 16/19. Our data remove any cytogenetic evidence that Scandent…
Eight million years of maintained heterozygosity in chromosome homologs of cercopithecine monkeys
2020
In the Cercopithecini ancestor two chromosomes, homologous to human chromosomes 20 and 21, fused to form the Cercopithecini specific 20/21 association. In some individuals from the genus Cercopithecus, this association was shown to be polymorphic for the position of the centromere, suggesting centromere repositioning events. We set out to test this hypothesis by defining the evolutionary history of the 20/21 association in four Cercopithecini species from three different genera. The marker order of the various 20/21 associations was established using molecular cytogenetic techniques, including an array of more than 100 BACs. We discovered that five different forms of the 20/21 association w…