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1.
2.
Dr. Andrei V. Dronov 《Facies》1993,28(1):169-180
Summary Several Waulsortian-type mud mounds nearly 500 m thick and about 5 km long occur in the Middle Paleozoic carbonate section
of the Aktur nappe in the mountains on the right bank of Isfara river. These buildups form a well developed barrier system
that stretches along the South Ferganian carbonate platform margin and divides the carbonate complex into a fore-reef and
a back-reef part. The time of the mounds' most active growth was from the Late Silurian (Ludlow) to the Middle Devonian (Eifel).
Three main facies types can be recognized in the mud mounds: 1. micritic core facies, 2. sparitic flank facies and 3. loferitic
capping facies. The central massive or crudely bedded part of the mounds consists of white or light grey clotted micrite.
Macrofossils are rare. The sparitic flank facies in contrast consists of coarse and densely packed crinoidal wackestone-floatstones
with some brachiopod shell debris. Solitary rugose corals, tabulate corals, stromato-poroids and fragments of mollusks are
also abundant. The tops of the mounds are usually covered with loferitic pelmicrites or oolitic grainstone caps. Stromatactis-like
structures are very rare and poorly developed in the South Ferganian mud mounds. However, almostin all such mounds horizons
of calcitic breccias can be found.
In order to explain all the features found in the Fergana mounds an ‘atoll-like’ model has been proposed which starts the
evolution of the mud mounds with a small nucleus bioherm. The main stage of the evolution corresponds to an atoll-like structure
developing on the surface of shallow water platforms. White clotted micrite of the mound core facies is interpreted as a accumulation
of fine-grained sediment in an inner lagoon flanked by crinoidal bar deposits. The mound flank facies represents the atoll
rim deposits from where the carbonate mud is derived. The capping loferitic facies is considered as tidal flat deposit that
developed on top of the buildups during the last stage of its evolution. The knoll shape of the mounds is explained by the
retreat of the atoll flanking crinoidal bars back into the inner lagoon during the rise in sea level. Stromatactis-like structures
of small cavities filled with sparry calcite owe their existence to burrowing organisms. Calcitic breccias are interpreted
as paleokarst collapse breccias. They indicate that the tops of the mud mound became subaerially exposed. Other evidence for
a subaerial exposure can be seen in the occurrence of Variscian ‘black and white’ limestone gravel on the tops of some mud
mounds. According toWard et al. (1970) these sediments were produced above the sea level at the edge of hypersaline lakes situated on islands. 相似文献
3.
Andrei O. Zalensky John W. Breneman Irina A. Zalenskaya B. R. Brinkley E. Morton Bradbury 《Chromosoma》1993,102(8):509-518
The localization of centromeres in mature human sperm was shown by immunofluorescent labeling and nonisotopic in situ hybridization. In the decondensed nucleus structural elements (dimers, tetramers, linear arrays and V shape structures) formed by individual centromeres of nonhomologous chromosomes were observed. They organize the compact chromocenter, which was shown for nuclei decondensed to a low extent. The chromocenter is buried inside the nucleus; in contrast, telomeric regions of chromosomes were tentatively localized on the periphery. Thus, a gross architecture, which can influence selective unpackaging of the paternal genome upon fertilization, exists in human sperm. 相似文献
4.
Anastassia M. Makarieva Andrei V. Nefiodov Antonio Donato Nobre Mara Baudena Ugo Bardi Douglas Sheil Scott R. Saleska Ruben D. Molina Anja Rammig 《Global Change Biology》2023,29(9):2536-2556
The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well-being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re-greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling due to additional vegetation increases precipitation but decreases local water yield and steady-state runoff. Therefore, in the drier regions/periods and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Recent analyses indicate that the latter regime dominates the global response of the terrestrial water cycle to re-greening. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation as well as for motivating and guiding ecological restoration. 相似文献
5.
Andrei G. Pakhomov Boris V. Dubovick Igor G. Degtyariov Anatoly N. Pronkevich 《Bioelectromagnetics》1995,16(4):250-254
The combined effects of microwave radiation and some drugs were studied in an isolated frog auricle preparation. The experiments established that exposure to pulse-modulated 915 MHz microwaves for up to 40 min had no effect on either the rate or the amplitude of spontaneous auricle twitches, unless the average absorbed power was high enough to produce preparation heating. Treatment of the preparation with saline containing (0.6–3.0) 10?5 M of propranolol or (0.5–1.5) 10?7 M of atropine altered neither its pacemaker nor its contractile functions; these drugs also had no effect when they were combined with nonthermal microwave irradiation. Caffeine (1 mM) strongly increased the average heart power, which was calculated as the product of twitch rate and amplitude. The caffeine effect appeared to be significantly augmented (by about 15%, P<0.02) under exposure to burst-type pulsed microwaves (pulse width, 1.5 msec; pause, 2.5 msec; 8 pulses/burst, 16 bursts/s; average SAR, 8–10 W/kg). By itself, this modulation was not effective; the heating of the preparation and saline during exposure was approximately 0.1°C, which could not account for the detected changes. The experimental results demonstrate that caffeine treatment increases the microwave sensitivity of the frog auricle preparation and reveals primarily subthreshold, nonthermal microwave effect. © 1995 Wiley-Liss, Inc. 相似文献
6.
Yuan-Pu Di Elizabeth Repasky Andrei Laszlo Stuart Calderwood John Subjeck 《Journal of cellular physiology》1995,165(2):228-238
The percentage of T and B lymphocytes expressing a distinct cytoplasmic aggregate enriched in spectrin, ankyrin, and in several other proteins including protein kinase C greatly increases following various activation protocols. Members of the 70 kDa family of heat shock proteins (hsp70) temporarily bind to and stabilize unfolded segments of other proteins, a function apparently required for proper protein folding and assembly. Considering the multiprotein and dynamic nature of the lymphocyte aggregate, the possibility that hsp70 also might be associated with componets of this structure is considered here. Double immunofluorescence analysis indicates that hsp70 is a component of the lymphocyte aggregate and is coincident with spectrin in a subpopulation of freshly isolated, untreated lymphocytes from various murine tissues and in a T-lymphocyte hybridoma. When cell lysates of lymph node T cells are immunoprecipitated using an antibody against hsp70 or spectrin and then analyzed by Western blot utilizing the alternate antibody, it was found that hsp70 and spectrin coprecipitated with one another. Moreover, this coprecipitation could be abolished by addition of ATP. This latter observation was extended to lymphoid cells using a transient permeabilization procedure, and it was shown that addition of exogenous ATP results in the dissipation of the aggregate structure itself. Finally, conditions that result in T-cell activation and aggregate formation, i.e., treatment with the phorbol ester PMA or T-cell receptor cross-linking, also lead to the repositioning of hsp70 into the aggregate from a membrane/cytosolic locale in congruence with spectrin. These data suggest that hsp70 is an active component of the aggregate and that it may function in the interactions believed to occur in this unique activation-associated organelle. © 1995 Wiley-Liss, Inc. 相似文献
7.
Abraham J. Koster Jochen Walz Andrei Lupas Wolfgang Baumeister 《Molecular biology reports》1995,21(1):11-20
The 26S proteasome is the central protease of the ubiquitin-dependent pathway of protein degradation. The molecule has a molecular mass of approximately 2000 kD and has a highly conserved structure in eukaryotes. The 26S proteasome is formed by a barrel-shaped 20S core complex and two polar 19S complexes. The 20S complex has C2 symmetry and is formed by four seven-membered rings of which the outer rings (-type subunits) are rotated by 25.7° relative to the inner rings while the inner rings (-type subunits) are in register. From a comparison of the activity and regulation of the 26S and 20S particles it can be deduced that the 20S particle contains the protease activity while the 19S complex contains isopeptidase, ATPase and protein unfolding activities. In this article we describe the structures of various proteasome complexes as determined by electron microscopy and discuss structural implications of their subunit sequences. 相似文献
8.
Hummel Herman Bogaards Roelof Bek Tatiana Polishchuk Lennard Amiard-Triquet Claude Bachelet Guy Desprez Michel Strelkov Peter Sukhotin Alex Naumov Andrei Dahle Salve Denisenko Stanislav Gantsevich Michael Sokolov Kirill Wolf Lein de 《Hydrobiologia》1997,355(1-3):127-138
The stress sensitivity, determined in copper exposureexperiments and in survival in air tests, and thegenetic structure, measured by means of isoenzymeelectrophoresis, were assessed in populations of theBaltic clam Macoma balthica (L.) from itssouthern to its northern distribution limit, in orderto test the hypotheses that near the distributionlimit the clams would be more stress sensitive andwould have a lower genetic variability. Thepopulations in west and north Europe show a stronggenetic resemblance. The populations in the sub-ArcticWhite Sea are genetically slightly different, and showa low stress sensitivity. The populations in theArctic Pechora Sea are genetically very distant fromthe other populations, and show the lowest stresssensitivity. Near the southern distribution limit, inagreement with the hypotheses, genetic variability islow and stress sensitivity high. On the other hand, incontrast to expectation, near the northerndistribution limit, in the populations of the PechoraSea, the genetic variability was higher, thus notreduced, and the stress sensitivity was low comparedto all other populations. Yet, it remains a questionif such is due to gradual physiologicalacclimatization (and ongoing differential selection)or to genetic adaptation. 相似文献
9.
10.
Andrei A. Raibekas 《Luminescence》1991,6(3):169-176
A green flavoprotein (GFP) was isolated and purified to homogeneity from Photobacterium leiognathi, strain 208. GFP is a homodimer of molecular weight 54000 and contains two molecules of an unusual flavin per molecule of protein. Various biochemical characteristics including isoelectric point, trypsin and chymotrypsin degradation, SDS and temperature influence on subunit dissociation and the dissociation of the flavin chromophore, were investigated. The sequence of 23 N-terminal amino acids was determined and found to be concurrent with the N-terminal amino acids was determined and found to be concurrent with the N-terminal amino acid sequence encoded by the lux G (N) gene of P. leiognathi. This fact suggests that GFP is a structural component of the Photobacterium luminescence system. 相似文献