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1.
SM Dippenaar 《African Journal of Marine Science》2016,38(1):1-5
Current knowledge of the biodiversity of the symbiotic marine siphonostomatoids from South African waters (136 species) is sparse compared to that globally (1 388 species). The difference is especially apparent when taking into account the diversity of fish (more than 2 000 species) and invertebrates (approximately 12 914 species) found in South African waters, all of which are all potential hosts of symbiotic siphonostomatoids. Most reports of symbiotic siphonostomatoids from South African waters are from Chondrichthyes and represent 80% of the currently known families and about 66% of the known genera. Taxonomic studies on the siphonostomatoids also provide information about their morphology, biology, habitat preference and host association, as well as the distribution of species and their associated host taxa. Molecular analysis, especially sequencing, provides additional information on the existence of cryptic species and population structure, but has high financial costs and a very low success rate in DNA isolation and PCR amplification. Reported declines in abundance of piscivorous fish species, for example, as a result of fishing pressure, with possible synergistic effects of environmental changes, and also the reported potential effects of anthropogenic and climate change on the broader coastal biota, may result in the loss of siphonostomatoid species before they can be described. Furthermore, in South Africa, there is a lack of professional taxonomists to study poorly known groups and this situation will not improve while research emphasis remains on commercially important groups and while taxonomic studies are not recognised for their value in research programmes. 相似文献
2.
NLTE calculations of carbon abundance in Peg atmosphere revealed a slight deficiency of this element ([C/H] =–0.25). A short discussion of this result is given. The list of CII that could be used for LTE calculation of carbon abundance in hot stars is presented. 相似文献
3.
SM Salem 《Arabian Journal of Geosciences》2017,10(7):166
The ironstone succession at El Gedida-Ghorabi-Naser area of El Bahariya depression is subdivided into lagoonal manganiferous mud and fossiliferous ironstone consisting mainly of hematite and goethite-hydrogoethite. The application of the ASD field spectroradiometer measurements (spectral range) in the ASTER data led to the interpretation of the presence of ferruginous units as quartzitic sandstone, gluconitic sandy clay, and pink marly limestone. The existing iron ore minerals in the iron ore localities were also classified into high Mn hematite, low Mn hematite, goethite, hydrogoethite as well as low- and high-grade Hematite and Barite. Quartz, feldspars, rutile, and clay minerals (e.g., kaolinite and illite) are mainly associated with the iron ore. Accessory minerals of manganese, e.g., psilomelane and pyrolusite, were also present. The Barite mineral is recorded as a common mineral association with the iron ore deposits at El Gedida and Ghorabi localities. The stratigraphical units investigated in the study area include the oldest gravely clayey sandstones of the Bahariya Formation overlain by the fossiliferous and oolitic limestones of the El-Hamra, Qazzun, and Naqb Formations. Quartztic sandstones and clayey sandstones of the Radwan Formation and youngest Quaternary sediments of sandy-clayey materials were often found as intermittent cover and overburden in unconformity surfaces over the iron ore bands. 相似文献
4.
E. A. Panko S. M. Andrievsky S. I. Yemelianov A. M. Stepaniuk 《Astronomy Reports》2018,62(12):911-916
We present the results of study the 2D distribution of galaxies in 254 rich open galaxy clusters. The clusters have no concentration to the center, so all kinds of substructures are clearly seen. Regular linear substructures in galaxy clusters were described in Rood & Sastry scheme of morphological types according to positions of 10 brightest galaxies. Another types of regular substructures were missed. Our study fills the lacuna. We have found about 25% of clusters in our data set having four kinds of regular substructures, beyond founded before linear ones. New kinds of regular substructures are: crossing and divaricating filaments or X and Y-type peculiarities, as well as curved strips and short dense chains. We suppose the distribution of dark matter in founded galaxy clusters with substructures have corresponded regular peculiarities. Hot gas distribution in these clusters must be observed distorted X-ray halo. We suppose also the clusters will evolve in the different ways. 相似文献
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A. V. Yushchenko V. F. Gopka A. V. Shavrina V. A. Yushchenko S. V. Vasileva S. M. Andrievsky A. A. Raikov S. Kim P. Rittipruk Y. Jeong Y.-W. Kang 《Kinematics and Physics of Celestial Bodies》2017,33(5):199-216
The chemical composition of the PMMR23 red supergiant located in the Small Magellanic Cloud (SMC) is analyzed. The abundance of 35 chemical elements and the upper limits of abundance for Tl and U are found. The relative abundance of heavy elements is higher by 0.6–1.0 dex with respect to iron peak elements. The spectra of several SMC red supergiants PMMR27, PMMR28, and PMMR144—located in the region where the velocities of stars and interstellar gas are quite high— show the emission components in the wings of the hydrogen line. This emission is not detected for PMMR23. A possibility of interstellar gas accretion on the atmospheres of PMMR23 and other supergiants in Magellanic Clouds is discussed. The analysis is carried out using spectra measured at ESO 3.6 m telescope with the spectral resolving power R = 30000. 相似文献
7.
The elemental abundances, temperatures, gravities and microturbulence velocities were derived for 14 non-variable supergiants from the Cepheids' instability strip and two hotter supergiants. For 8 stars the abundances were determined for the first time. The comparable analysis of the program stars' chemical composition and that of the small-amplitude Cepheids has shown that there is no essential differences in the elemental abundances for two stellar groups. Some discussion of the phenomenon of non-variable supergiants in the instability strip is given. 相似文献
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Squalus acutipinnis (previously included in S. megalops) individuals caught off the east, south and west coasts of South Africa were examined for siphonostomatoid copepod infection. Collected siphonostomatoids were fixed and preserved in 70% ethanol and studied under microscopes using both transmitted and incidental light. The copepods were identified and the host-parasite associations estimated by calculating their prevalence, mean intensity and mean abundance. The siphonostomatoids represented four families and six species, and included new host records for Nemesis sp., Lernaeopoda sp. and Eudactylina acanthii, and a new geographical record for E. acanthii. Squalus acutipinnis individuals were infected by relatively low loads of siphonostomatoids. The most commonly found species was Achtheinus pinguis, the only species found off all three coasts. There was no difference in the prevalence of A. pinguis in sharks sampled off the three coasts but the highest mean intensity was found on the East Coast followed by the West Coast. The overall prevalence of A. pinguis was 33.6%, and was an order of magnitude higher than that of the other siphonostomatoids recorded. At such low levels of infection it will thus be necessary to examine a large number of hosts to determine the biodiversity of siphonostomatoids and geographical differences in prevalence in South African waters. 相似文献
10.
Geomatics Based Analysis of Predicted Sea Level Rise and its Impacts in Parts of Tamil Nadu Coast,India 总被引：1，自引：0，他引：1
SM. Ramasamy C. J. Kumanan J. Saravanavel A. S. Rajawat V. Tamilarasan Ajay 《Journal of the Indian Society of Remote Sensing》2010,38(4):640-653
The coastal zones around the world are very densely populated and hence heavily packed with related infrastructures. So, the
territorial nations have obvious apprehensions against the IPCC SRES (Intergovernmental Panel on Climate Change, Special Report
on Emission Scenario) predicted sea level rise, as it would cause flooding of the low lying coasts and also other related
chains of environmental endangers. This has driven these nations to initiate research studies in multiple directions for scientifically
evaluating the phenomenon and impacts of sea level rise using all possible technologies including the Geomatics which possesses
unique credentials in geosystem mapping. But certain advanced virtues available with Geomatics technology are yet to be capitalized
deservingly in this. In addition, almost all the earlier studies have focused only on the impacts of sea level rise (SLR)
and not on the predicted shift of high tide line (HTL) and the related inter tidal activities, which would cause a series
of environmental disaster. Hence, the present research study was undertaken in a test site of 750 km2 in central Tamil Nadu coast to visualize the areas prone to submergence due to predicted SLR and areas prone to environmental
disasters/degradation viz. erosion, deposition, salination of agricultural lands, pollution of aquifers, etc. due to predicted
shift of HTL, using digital elevation models derived from SRTM data (Shuttle Radar Topographic Mission), geomorphology and
land use/cover maps interpreted using IRS P6 LISS IV satellite data. The paper narrates the certain newer concepts and methodologies
adopted in the study and the results. 相似文献