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41.
It is unlikely that the intact or commonly preserved varieties of Ordovician-Silurian nautiloid shells were able to drift for any distance at the surface of the sea even if they died there. Their cameral capacity was much larger than the volume of the extracted or decayed body, and it would have contained a partial vacuum and cameral liquid when they were alive. The closely spaced and thin septa of the shallow-water adapted species were liable to buckle in compression and then implode in local tension during reverse hydrostatic loading by water pressure. This reverse loading and internal implosion of the septa was probably initiated by the sudden cameral refilling of an apical chamber caused by the depositional rupture of the apical siphuncle at or near the maximum habitat depth of these species. The instantaneous buckling of the more adorai septa was potentially terminated by variations in the septum thickness and cameral fill-fractions at that time, and they imply that some of the Silurian nautiloids from Bohemia were deposited at a minimum depth of about 65 m. Alternative interpretations involving the breakage of the same septa in tension, or buckling due to the difference in pressure between adjacent flooded chambers, set a maximum depth limit of about 160 m for the same facies. Many of the smaller Silurian nautiloids were unlikely to buckle during refilling, and they were potentially flooded faster than they could sink, below a depth of 100–300 m. 相似文献
42.
Gerd Esser 《Plant Ecology》1995,121(1-2):175-188
The High Resolution Biosphere Model (HRBM), which has been developed by the group of the author, was used to investigate the carbon balance of the vegetation and the soil in the ecosystems of Monsoon Asia in comparison to the rest of the world. The HRBM is a global grid-based (0.5 degree resolution) model with a monthly time step. It includes modules for natural vegetation, land use, vegetation fires, vegetation composition. A historical carbon budget was calculated for the period 1860–1978 and, on a global scale, validated using atmospheric CO2 data. Based on the per-country development of the population and their requirements, different reasonable scenarios were used to investigate the potential impacts of land use and deforestation in the period 1990–2050. The HRBM calculates considerable contributions of Monsoon Asia to the global CO2 emissions due to land use changes in the past. Between 1860 and 1978, about 1/4 of the global releases from land use changes came from South Asian and Southeast Asian biota. The future contributions in the period 1990–2050 depend on the assumed development of the agricultural methods. If the intensity of agriculture and the agricultural productivity will stay the same as in the 1980s, there will be a strong need to increase agricultural areas, and thus deforestation will dominate. If there will be a change over to intensive methods of agricultural production, the presently used areas might be sufficient to provide resources to the growing population. 相似文献
43.
Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressMorphology and Physiology: Orientation
Subject: Navigation and orientation 相似文献44.
Modification of sialic acids by 9-O-acetylation is detected in human leucocytes using the lectin property of influenza C virus 总被引:1,自引:0,他引:1
Zimmer Gert; Suguri Toshiaki; Reuter Gerd; Yu Robert K.; Schauer Roland; Herrler Georg 《Glycobiology》1994,4(3):343-349
Influenza C virus spike glycoprotein HEF specifically recognizesglycoconjugates containing 9-O-acetyl-N-acetylneuraminic acid.The same protein also contains an esterase activity. Takingadvantage of these two properties, influenza C virus was usedas a very sensitive probe for the detection of traces of 9-O-acetyl-N-acetylneuraminicacid in human leucocytes. The binding of influenza C virus toleucocyte glycoproteins and gangliosides separated by sodiumdodecyl sulphatepolyacrylamide gel electrophoresis andthin-layer chromatography, respectively, was assayed using achromogenic esterase substrate. In this way, glycoproteins ofB-lymphocytes and T-lymphocytes were found to contain 9-O-acetylatedsialic acids. Of the various 9-O-acetylated gangliosides detected,one had the characteristics of 9-O-acetylated GD3. The identificationof 9-O-acetylated sialic acids on distinct glycoproteins andglycolipids should be helpful in assigning a physiological roleto this sugar. O-acetylation gangliosides influenza C virus lymphocytes sialic acids 相似文献
45.
Gerd Johansson 《Plant and Soil》1993,151(1):11-20
Distribution of net assimilated C in meadow fescue (Fectuca pratensi L.) was followed before and after cutting of the shoots. Plants were continuously labelled in a growth chamber with 14C-labelled CO2 in the atmosphere from seedling to cutting and with 13C-labelled CO2 in the atmosphere during regrowth after the cutting. Labelled C, both 14C and 13C, was determined at the end of the two growth periods in shoots, crowns, roots, soil and rhizosphere respiration.
Distribution of net assimilated C followed almost the same pattern at the end of the two growth periods, i.e. at the end of
the 14C- and the 13C-labelling periods. Shoots retained 71–73% of net assimilated C while 9% was detected in the roots and 11–14% was released
from the roots, determined as labelled C in soil and as rhizosphere respiration.
At the end of the 2nd growth period, after cutting and regrowth, 21% of the residual plant 14C at cutting (14C in crowns and roots) was found in the new shoot biomass. A minor part of the residual plant 14C, 12%, was lost from the plants. The decreases in 14C in crowns and roots during the regrowth period suggest that 14C in both crowns and roots was translocated to new shoot tissue.
Approximately half of the total root C at the end of the regrowth period after cutting was 13C-labelled C and thus represents new root growth. Root death after cutting could not be determined in this experiment, since
the decline in root 14C during the regrowth period may also be assigned to root respiration, root exudation and translocation to the shoots. ei]{gnH}{fnLambers}
ei]{gnA C}{fnBorstlap} 相似文献
46.
Jörg Schmid Peter Möller Gerd Moldenhauer Bernd Dörken Heiner Bihl Siegfried Matzku 《Cancer immunology, immunotherapy : CII》1993,36(4):274-280
Accumulation of radiolabelled monoclonal antibodies (mAb) in human B-lymphoma xenografts was found to result in two distinct patterns. The basic elements leading to these patterns were elucidated by autoradiographic and immunohistological analysis applied to the nude mouse xenografts BJAB and OCI.LY1. With BJAB, accumulation occurred exclusively in peripheral cell layers of the lymphoma nodule, while central areas were not accessible irrespective of mAb dose. This feature was the consequence of an inefficient transport across intratumoral vessels together with peripheral mAb supply through a subcapsular pseudosinus. With OCI.LY1, intratumoral vessels showed generalized leakiness. Furthermore, interstitial transport was operative to a fair extent, such that in early images multiple sites of mAb extravasation were obvious, which coalesced during the course of prolonged uptake. The pattern of peripheral mAb uptake resulted in a low overall tumour uptake, while multifocal uptake yielded substantial accumulation values. 相似文献
47.
Isabela Tagomori Vassilis Daioglou Pedro Rochedo Gerd Angelkorte Roberto Schaeffer Detlef van Vuuren Alexandre Szklo 《Global Change Biology Bioenergy》2023,15(2):116-127
Bioenergy could play a major role in decarbonizing energy systems in the context of the Paris Agreement. Large-scale bioenergy deployment could be related to sustainability issues and requires major infrastructure investments. It, therefore, needs to be studied carefully. The Bioenergy and Land Optimization Spatially Explicit Model (BLOEM) presented here allows for assessing different bioenergy pathways while encompassing various dimensions that influence their optimal deployment. In this study, BLOEM was applied to the Brazilian context by coupling it with the Brazilian Land Use and Energy Systems (BLUES) model. This allowed investigating the most cost-effective ways of attending future bioenergy supply projections and studying the role of recovered degraded pasture lands in improving land availability in a sustainable and competitive manner. The results show optimizing for limiting deforestation and minimizing logistics costs results in different outcomes. It also indicates that recovering degraded pasture lands is attractive from both logistics and climate perspectives. The systemic approach of BLOEM provides spatial results, highlighting the trade-offs between crop allocation, land use and the logistics dynamics between production, conversion, and demand, providing valuable insights for regional and national climate policy design. This makes it a useful tool for mapping sustainable bioenergy value chain pathways. 相似文献
48.
49.
Genomic sequencing by ligation-mediated PCR 总被引:8,自引:0,他引:8
Genomic sequencing permits studies of in vivo DNA methylation and protein-DNA interactions, but its use has been limited due
to the complexity of the mammalian genome. Ligation-mediated PCR (LMPCR) is a sensitive genomic sequencing procedure that
generates high quality, reproducible sequence ladders starting with only 1 μg of uncloned mammalian DNA per reaction. This
genomic sequencing procedure can be adapted for various methylation, in vivo footprinting and DNA adduct mapping procedures.
We provide a detailed protocol for genomic sequencing by LMPCR and discuss the principles and applications of the method. 相似文献
50.
This paper shows the effect of re-aeration following hypoxic pretreatment on the glutathione system in plants with different flooding tolerance. Re-aeration of hypoxically pretreated roots led to an increase of TBA-rm content indicating an accelerated lipid peroxidation (post-anoxic injury). Re-admission of oxygen resulted in a clear increase in the content of total glutathione in both flooding-intolerant speciesMyosotis arvensis andSenecio jacobaea. Simultaneously, the high ratio between reduced (GSH) and oxidized (GSSG) glutathione decreased in these species upon the onset of re-aeration, while the tolerantMyosotis palustris andSenecio aquaticus showed only little changes in contents of GSH and GSSG. An imbalance in GSH/GSSG ratio reflects oxidative stress. The glutathione reductase (GR) reacted very differently in the investigated genera. The metabolic response to varying oxygen pressure is much stronger in the flooding-intolerant species compared to species naturally growing in wetlands. The present results suggest that glutathione system is an important component in overcoming oxidative stress. 相似文献