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111.
Dr. sc. Heinz W. Kozur Univ.-Doz. Dr. Karl Krainer Univ.-Prof. Dr. Helfried Mostler 《Facies》1996,34(1):123-150
Summary Diverse and abundant trace fossils of the deep-waterNereites ichnofacies have been found in well-dated Early Permian deep-water turbidites (Lercara Formation) of western Sicily (Italy).
Conodonts indicate a latest Artinskian to Cathedralian (late Early Permian) age. Microfossils (pelagic conodonts, albaillellid
Radiolaria, paleopsychrospheric ostracods, foraminiferal associations dominated byBathysiphon), trace fossils (deep-bathyal to abyssalNereites ichnofacies) and sedimentologic data collectively indicate a deep-water environment for the Early Permian turbidites of the
Lercara Formation. The dominance ofAgrichnium and of thePaleodictyon subichnogeneraSquamodictyon andMegadictyon suggests that this icnofauna is closely related in ichnotaxonomic composition to other late Paleozoic deep-water ichnofaunas.
The occurrence ofAcanthorhaphe. Dendrotichnium andHelicoraphe, to date only reported from Cretaceous or Tertiary flysch deposits, suggests that the entire ichnofauna corresponds well
to previously documented Silurian-Tertiary flysch ichnofaunas. Eight new ichnospecies and a new ichnosubgenus,Megadictyon, are described. 相似文献
112.
High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, (H2/2), was about 109 Oe2 · cm–1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.Abbreviations HGMF
high-gradient magnetic field
- emu
electromagnetic units
- Oe
Oersted
We thank Dr. John Kiss, Miami University, Ohio for providing the Arabidopsis seeds. This work was supported by NASA grant NAGW-3656 相似文献
113.
Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
114.
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
115.
116.
Evaluation of mass spectrometric techniques for charaterization of engineered proteins 总被引:7,自引:0,他引:7
Roepstorff Peter Schram Karl H. Andersen Jens S. Rafn Kate Baldursson Trausti Krøll Jenny Poulsen Kjeld Knudsen Jens Kristiansen Karsten 《Molecular biotechnology》1995,3(1):1-7
A simple and versatile method of in vitro site-specific mutagenesis based on polymerase chain reaction (PCR) is described.
The complete method required the use of three oligonucleotide primers and two PCRs. The product of the first PCR was used
as one of the primers (megaprimer) in the second PCR. Essentially 100% of the final product incorporated the desired mutation.
The various aspects of the procedure and its application is described in detail. 相似文献
117.
Dr. Karl Kleemann 《Facies》1994,30(1):151-153
Summary The mytilid genusLithophaga is confirmed for the Upper Triassic. The Rhaetian specimen, boring the dead part of coral, is compared with the SenonianL. alpina, which is associated with live coral. 相似文献
118.
Flux density and spectral measurements were carried out on magnetic fields generated by several types of motor-driven personal appliances used near the body. Among the units tested were several for which the average flux densities, as determined at the surfaces of the appliance, exceeded 0.4 mT. Time-rates-of-change (dB/dt) for several units exceeded 1000 T/s, and several units exhibited high-frequency components in the low-MHz range. Use of such appliances, although normally of short duration, can represent exposure to magnetic fields of relatively high flux density, which may also have high-frequency components. Compared to other household and commercial sources of magnetic fields, those generated by certain motor-driven personal appliances may represent a significant contribution to time-weighted average exposure and may represent an important source of local induced currents in the body. Furthermore, high-frequency transients that represent only a minor contribution to time-weighted average exposure may generate significant instantaneous induced currents. © 1994 Wiley-Liss, Inc. 1 This article is a US Government work and, as such, is in the public domain in the United States of America. 相似文献
119.
Inheritance of Strain Instability (Sectoring) in the Commercial Button Mushroom, Agaricus bisporus 总被引:1,自引:1,他引:0
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Aimin Li Marc Begin Karl Kokurewicz Christine Bowden Paul A. Horgen 《Applied microbiology》1994,60(7):2384-2388
The button mushroom, Agaricus bisporus, is a commercially important cultivated filamentous fungus. During the last decade, the button mushroom industry has depended mainly on two strains (or derivatives of these two strains). Using one of these highly successful strains (strain U1) we examined the phenomenon of strain instability, specifically, the production of irreversible sectors. Three “stromatal” and three “fluffy” sectors were compared with a healthy type U1 strain and with a wild-collected isolate. Compost colonization and fruit body morphology were examined. The main objective of this study, however, was to examine the meiotic stability of the sectored phenotype. Single basidiospores were isolated and subjected to a grain bioassay in which the ability to produce sectors was measured. Our results were as follows: (i) basidiospore cultures obtained from a wild-collected isolate showed no tendency to produce sectors; (ii) approximately 5% of the basidiospore cultures obtained from healthy type U1 strains produced irreversible sectors in the grain bioassay; (iii) the five primary sectors examined produced basidiospore cultures, half of which produced normal-looking growth in the grain bioassay and half of which produced some degree of sectoring; and (iv) the one sectored isolate that represented the F2 generation gave ratios similar to the 1:1 ratio observed for the F1 cultures. 相似文献
120.
In situ bag experiments were performed during summer and autumn in a small acidic lake, Tibbs Run Lake, West Virginia, USA. The objective was to evaluate phytoplankton responses to pH manipulation and nutrient addition. Increasing the pH from below 4.5 to over 6.3 resulted in great declines in phytoplankton biovolume. There was also a succession from dinoflagellates (Peridinium inconspicuum to small chlorophytes. The trend was more rapid where phosphorus (P) additions were made along with pH enhancement. During summer, P limitation was indicated, while nitrogen (N) appeared to limit production in autumn. In both seasons, nutrient additions greatly altered the phytoplankton composition in high pH treatments, but had no discernable effects at (the natural) low pH. A low pH, P addition treatment in autumn was the single exception. When N was subsequently added, phytoplankton composition changed dramatically, probably because the proceeding P additions caused severe secondary N-limitation. In general, however, the results supported the view that phytoplankton compositional responses to nutrient additions are suppressed in low pH, relative to high pH lake water. 相似文献