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排序方式: 共有1823条查询结果,搜索用时 156 毫秒
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Ewa A. Czy Carla Guilln Escrib Hendrik Wulf Andrew Tedder Meredith C. Schuman Fabian D. Schneider Michael E. Schaepman 《Ecology and evolution》2020,10(14):7419-7430
- The growing pace of environmental change has increased the need for large‐scale monitoring of biodiversity. Declining intraspecific genetic variation is likely a critical factor in biodiversity loss, but is especially difficult to monitor: assessments of genetic variation are commonly based on measuring allele pools, which requires sampling of individuals and extensive sample processing, limiting spatial coverage. Alternatively, imaging spectroscopy data from remote platforms may hold the potential to reveal genetic structure of populations. In this study, we investigated how differences detected in an airborne imaging spectroscopy time series correspond to genetic variation within a population of Fagus sylvatica under natural conditions.
- We used multi‐annual APEX (Airborne Prism Experiment) imaging spectrometer data from a temperate forest located in the Swiss midlands (Laegern, 47°28'N, 8°21'E), along with microsatellite data from F. sylvatica individuals collected at the site. We identified variation in foliar reflectance independent of annual and seasonal changes which we hypothesize is more likely to correspond to stable genetic differences. We established a direct connection between the spectroscopy and genetics data by using partial least squares (PLS) regression to predict the probability of belonging to a genetic cluster from spectral data.
- We achieved the best genetic structure prediction by using derivatives of reflectance and a subset of wavebands rather than full‐analyzed spectra. Our model indicates that spectral regions related to leaf water content, phenols, pigments, and wax composition contribute most to the ability of this approach to predict genetic structure of F. sylvatica population in natural conditions.
- This study advances the use of airborne imaging spectroscopy to assess tree genetic diversity at canopy level under natural conditions, which could overcome current spatiotemporal limitations on monitoring, understanding, and preventing genetic biodiversity loss imposed by requirements for extensive in situ sampling.
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Antonius Rohlmann Thomas Zander Friedmar Graichen Hendrik Schmidt Georg Bergmann 《PloS one》2014,9(4)
Cycling on an ergometer is an effective exercise for improving fitness. However, people with back problems or previous spinal surgery are often not aware of whether cycling could be harmful for them. To date, little information exists about spinal loads during cycling. A telemeterized vertebral body replacement allows in vivo measurement of implant loads during the activities of daily living. Five patients with a severe compression fracture of a lumbar vertebral body received these implants. During one measurement session, four of the participants exercised on a bicycle ergometer at various power levels. As the power level increased, the maximum resultant force and the difference between the maximum and minimum force (force range) during each pedal revolution increased. The average maximum-force increases between the two power levels 25 and 85 W were 73, 84, 225 and 75 N for the four patients. The corresponding increases in the force range during a pedal revolution were 84, 98, 166 and 101 N. There were large variations in the measured forces between the patients and also within the same patient, especially for high power levels. In two patients, the maximum forces during high-power cycling were higher than the forces during walking measured on the same day. Therefore, the authors conclude that patients with back problems should not cycle at high power levels shortly after surgery as a precaution. 相似文献
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Rudy Van Cauwenbergh Harry Robberecht Veerle Van Vlaslaer Hendrik Deelstra 《Journal of trace elements in medicine and biology》2004,18(1):99-112
Graphite furnace atomic absorption spectrometry, after improved matrix modification and using Zeeman background correction, was used to measure the serum selenium content of healthy adults living in the Antwerp region (Belgium). The mean serum concentration of 13 men and 13 women, sampled once a month during 1 year, was 84.3 +/- 9.4ng/ml with a broad range of 51.4-121.7 ng/ml. The intra-individual variation was remarkably high. Recent literature on selenium concentrations is reviewed and values are tabulated, with limitation to healthy adults and European countries. The mean serum selenium concentration measured corresponded well to older literature data for Belgium. The obtained values were found to be in the medium range compared with the literature data for other European countries. 相似文献
7.
Schubert Hendrik; Schiewer Ulrich; Tschirner Erhard 《Journal of plankton research》1989,11(2):353-359
The fluorescence characteristics of the cyanobacteria Synechocystisaquatilis Sauv., Microcystis firma (Breb. et Lenorm.) Schmidleand Synechococcus leopoliensis (Racib.) Kom. and the green algaScenedesmus quadricauda (Turp.) Breb. were examined. In thethree cyanobacteria, phycocyanin is the main accessory pigment.Phycoerythrin is not present in our investigated strains ofcyanobacteria. The highest excitation of the chlorophyll a (Chla) fluorescence of cyanobacteria resulted from light with wavelengthsof 620630 nm. A definite Kautsky effectis also evident at this wavelength. However, excitation withblue light (420520 nm) produced only very slight fluorescence.The Kautsky effect is not evident at these wavelengths, evenat high photon flux densities. For Scenedesmus, fluorescencecharacteristics typical of green algae were found. The fluorescenceexcitation of cyanobacteria at 620 nm corresponds to a photosynthesispeak in the action spectrum measured in terms of O2 production.The results underline the necessity of fluorescence measurementsat several wavelengths whenever mixed populations are involved.Such measurements also present possibilities for more accurateestimation of biomass and potential photosynthetic productionin mixed populations. 相似文献
8.
Electrotransformation of intact and osmotically sensitive cells of Corynebacterium glutamicum 总被引:1,自引:0,他引:1
Hendrik Wolf Alfred Pühler Eberhard Neumann 《Applied microbiology and biotechnology》1989,30(3):283-289
Summary Intact and osmotically sensitive cells of Corynebacterium glutamicum can be efficiently transformed by electroporation. This was shown by using the plasmid vector pUL-330 (5.2 kb), containing the kanamycin resistance gene of transposon Tn5. The following electric parameters yielded efficient transformation. For intact cells: one exponentially decaying field pulse
with time constants
and with initial field intensities of E
0=35–40 kV cm-1; prepulse temperature 20°C. Cell regeneration (survival) was 100%–80%. Transformation efficiency can be increased by an additional freeze and thaw cycle of the cells, prior to electroporation. Lysozyme treated cells (osmotically sensitive) were transformed with three successive pulses of E
0=25–30 kV cm-1. Cell regeneration under these conditions was found to be 20–30%. The optimum yield of transformants/g plasmid-DNA was 3×103 for intact cells, 2×104 for intact cells which were frozen and thawed twice and 7×104 for osmotically sensitive cells if the cell suspension was pulsed at a cell density of 1–3×108/ml and at a DNA concentration of 0.2 g/ml up to 2 g/ml. The data obtained for osmotically sensitive cells suggest that the temperature increase accompanying the electric field pulse enhances colony formation and transformation efficiency if the initial prepulse temperature is 20°C, although regeneration of electroporated C. glutamicum cells starts to decrease at temperatures20°C. 相似文献
9.
Jozef Anné Patrick Verheyen Guido Volckaert Hendrik Eyssen 《Molecular & general genetics : MGG》1985,200(3):506-507
Summary A physical map of the actinophage VWB has been constructed using the restriction endonucleases BglII, ClaI, EcoRI, EcoRV, HindIII, KpnI and SphI. Phage VWB, genome size 47.3 kb, propagates on Streptomyces venezuelae, and it can also lysogenise this species. The three BglII-generated fragments of VWB DNA were cloned in pBR322, and subsequently mapped. In this manner the restriction map of the VWB phage genome was constructed.Abbreviations
dam
DNA adenine methylase activity
- kb
kilobase pairs
- ::
novel joint 相似文献
10.
Mechanisms of glycogenolysis have been investigated in a comparative study with Wistar rats and gsd rats, which maintain a high glycogen concentration in the liver as a result of a genetic deficiency of phosphorylase kinase. In Wistar hepatocytes the rate of glycogenolysis, as modulated by glucagon and by glucose, was proportional to the concentration of phosphorylase a. In suspensions of gsd hepatocytes the rate of glycogenolysis was far too high as compared with the low level of phosphorylase a; in addition, only a minor fraction of the glycogen lost was recovered as glucose and lactate, owing to the accumulation of oligosaccharides. When the gsd hepatocytes were incubated in the presence of an inhibitor of alpha-amylase (BAY e 4609) glycogenolysis and the formation of oligosaccharides virtually ceased; the production of glucose plus lactate, already modest in the absence of BAY e 4609, was further decreased by 40%, owing to the suppression of a pathway for glucose production by the successive actions of alpha-amylase and alpha-glucosidase. Evidence was obtained that gsd hepatocytes are more fragile, and that amylolysis of glycogen occurred in damaged cells and/or in the extracellular medium. This may even occur in vivo, since quick-frozen liver samples from anesthetized gsd rats contained severalfold higher concentrations of oligosaccharides than did similar samples from Wistar rats. However, administration of a hepatotoxic agent (CCl4) caused hepatic glycogen depletion in Wistar rats, but not in gsd rats. The administration of phloridzin and of vinblastine, which have been proposed to induce glycogenolysis in the lysosomal system, did not decrease the hepatic glycogen level in gsd rats. Taken together, the data indicate that only the phosphorolytic degradation of glycogen is metabolically important, and that alpha-amylolysis is an indication of an increased fragility of gsd hepatocytes, which becomes prominent when these cells are incubated in vitro. 相似文献