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61.
The magnetic anomaly ΔF due to a long horizontal cylinder yields three points related to its extrema. A nomogram is presented for the determination of some source parameters of the causative body. 相似文献
62.
63.
I. M. Korrat H. M. Hussein I. Marzouk E. M. Ibrahim R. Abdel-Fattah N. Hurukawa 《Acta Geophysica》2006,54(1):33-49
Seismicity in the northernmost part of the Red Sea has been studied using data from Hurghada Seismological Network in addition
to readings from the existing neighbouring networks. Relocated events in addition to data from national centers are used to
obtain a complete and true picture for the seismicity of the area. The spatial distribution of earthquakes defines three earthquake
zones in the Gulf of Aqaba and three zones at the entrance of the Gulf of Suez and southern tip of Sinai Peninsula. The thermal
activity and the triple junction nature control the activity in this area. The activity defines also an active trend extending
from the southern tip of Sinai Peninsula to the median zone of the Red Sea. The seismicity of this trend is probably related
to the active spreading zone associated with the opening of the Red Sea. The b-values are derived for the entrance areas of the two gulfs and for Gulf of Aqaba. Values of b are 1.35 for the triple junction region, 1.13 for the activity before the 22 November 1995 Gulf of Aqaba mainshock and 1.25
for the aftershocks of this event. 相似文献
64.
65.
Amir Shah Ruddin Md Shah Mashhor Mansor Shahrul Anuar Mohd Shah Che Salmah Mohd Rawi Abu Hassan Ahmad Ibrahim Jaafar 《湿地科学》2008,6(1):34-44
A survey was carried out at the largest rice cultivation area in Peninsular Malaysia,the Muda rice agroecosystem.The main objective of this study was to document the overall biodiversity associated with this unique agroecosystem by using a combination of sampling techniques in order to record different groups of fauna and flora.The total number of biota recorded and identified from the rice field ecosystem during the study period consisted of 46 species of zooplankton,81 species of aquatic insects,5 species of rodents,7 species of bats,87 species of birds,11 species of fishes and 58 species of weeds.A long-term study should be carried out as more species are expected to be recorded when more of the Muda rice agroecosystem area has been sampled to obtain sufficient information on the Muda rice agrobiodiversity. 相似文献
66.
This paper reports on the occurrence of layered Pan African dioritetonalite-granodiorite (DTG) rocks. The layering is marked by alternation of melanocratic (M) layers (diorites and tonalites) and leucocratic (L) layers (tonalites and granodiorites). M-samples have cumulus biotite+hornblende+relict pyroxene+plagioclase+K-feldspars+magnetite+apatite, and have transitional calc-alkaline and metaluminous affinities. They were derived from subduction-related magma enriched in Rb, Ba, K and LREE and depleted in Sr and Nb. L-samples have cumulus plagioclase+hornblende. They are enriched in Sr and depleted in Rb, Ba, K, Nb and LREE. They have calc-alkaline and peraluminous affinites.
The formation of the rhythmic layers of DTG composition can be attributed to periodical replenishment of pulses of basic magma into a more evolved acidic magma chamber under open system conditions. Field relations, mineralogy and element concentration among the M- and L-layers indicate that at the subduction zone, the ascending magma was contaminated with lower crustal materials (marginal basin metasediments) which led to LILE-enrichment, Nb-depletion and transition from calc-alkaline to alkaline and from metaluminous to peraluminous affinities as well. 相似文献
The formation of the rhythmic layers of DTG composition can be attributed to periodical replenishment of pulses of basic magma into a more evolved acidic magma chamber under open system conditions. Field relations, mineralogy and element concentration among the M- and L-layers indicate that at the subduction zone, the ascending magma was contaminated with lower crustal materials (marginal basin metasediments) which led to LILE-enrichment, Nb-depletion and transition from calc-alkaline to alkaline and from metaluminous to peraluminous affinities as well. 相似文献
67.
This study represents a preliminary investigation of the late Messinian subsurface Marsa Zouaghah Formation in the Western Libyan Offshore, Central Mediterranean Sea. The formation was deposited in three major environmental settings: (a) Marginal Sabkha; (b) Open Lagoon; and (c) Hypersaline Lagoon. The marginal sabkha and open lagoonal settings are locally interrupted by intertidal oolitic shoal deposits. The marginal sabkha facies is replaced in central parts of the Libyan offshore by a narrow zone of aeolian-fluvial facies, the distribution and thickness of which is entirely controlled by a local uplift, the Tripoli Nose'. The marginal sabkha facies broadly defines the late Messinian palaeoshoreline lying parallel to, and north of, the E-W Jifarah fault system which dominated the southern part of the Libyan offshore. This fades is, thus, interpreted as being structurally controlled by fault systems. The hypersaline lagoonal facies is developed in areas of relatively higher rates of subsidence than that of adjacent facies belts. It is therefore, related to restriction formed by continuous subsidence and evaporation. The Marsa Zouaghah Formation constitutes saltern evaporates deposited over a wide platform in sabkha and lagoonal settings, forming part of the 'basin-wide-evaporites' of the Mediterranean Basin deposited during the Messinian salinity crisis. The evaporites formed during a major relative sea-level fall within a subsiding basin situated on the northern continental margin of the African plate. Local, vertical and lateral variations in lithofacies and thickness within the Messinian deposits of the north-west Libyan offshore were controlled by contemporaneous strike-slip movements in addition to sea-level change. 相似文献
68.
Relatively little in the literature on rural change in Southeast Asia engages with Malaysia, where the population is becoming urban‐based more rapidly than in many countries in the region. The literature on change in rural Malaysia during the past 40 years, supplemented by our own research, is used to identify key features of such change, which are considered in the context of existing interpretations to arrive at deeper understandings of rural change. Existing conceptualizations of rural change, it is suggested, must account for the diversity of roles taken by individuals daily, seasonally and at different life stages, as well as in multiple locations. Further attention needs to be paid to gender, generation and class among those experiencing change. Processes of rural (and urban) changes will continue and their complexity will reflect cultural and technological evolutions that affect individuals, households and communities throughout the world. 相似文献
69.
Alaa I. Ibrahim Hisham Anwer Mohamed H. Soliman Nicholas Mackie-Jones Kalvir S. Dhuga William C. Parke Jean H. Swank Tilan Ukwatta M. T. Hussein T. El-Sherbini 《Astrophysics and Space Science》2007,308(1-4):535-539
A 6.4 keV emission line was discovered in an unusual burst from the soft gamma repeater SGR 1900+14 with the Rossi X-ray Timing
Explorer (RXTE). The line was detected in part of a complex multipeak precursor that preceded the unusual burst of 1998 August
29, i.e. two days after the giant flare of August 27 from the source. The origin of the line was not firmly identified and
two possible interpretations were equally plausible including (a) Kα fluorescence from a small iron rich material that was ejected to the magnetosphere during the August 27 flare, and (b) proton
or α-particle cyclotron resonance. If the iron scenario was correct, we expect to find evidence for the line during the intervening
interval between the flare and the August 29 burst, i.e. on August 28. Here we present the results of the August 28 burst
observation, taken with RXTE. We detect a total of seven bursts whose individual and joint spectra do not show evidence for
spectral lines. We also investigated a sample of nine bursts before and after the August 29 burst (from 1998 June to December)
that do not reveal evidence for a spectral line near 6.4 keV or elsewhere. These results disfavor the iron scenario and make
the proton/α-particle cyclotron resonance interpretation more plausible. The appearance of the emission line in part of a complex burst
and its absence from the studied sample indicate that the line is likely due to a transient phenomenon that may depend on
the burst morphology, energetics and the properties of the emission region.
相似文献
70.
Esat Hamzaoğlu 《Astrophysics and Space Science》1981,80(2):517-520
The findings about this unusual eclipsing variable which possesses a white-dwarf component are reported. It was found that the H and K absorption lines of Caii are strongly pressure-broadened, and exhibit two double-reversal emission components. The radial velocities derived from the central strong emission components of Caii (H and K) are in agreement with the mean radial velocity curve obtained from the metallic absorption lines of the existing elements, whereas H (4340.47 Å) does not conform with the mean radial velocity curve. In certain orbital phases the H (6562.82 Å) line occurs in emission. 相似文献