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1.
Olev Vinn Ahmed M. El-Sabbagh Magdy M. El-Hedeny Mohamed A. Rashwan Saleh A. Al Farraj 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(6):790-796
The ichnogenus Arachnostega Bertling, 1992 is recorded for the first time from a bioeroded, coral-rich, Middle Miocene limestone bed in the middle Siwa Escarpment Member (Marmarica Formation) at Siwa Oasis, northern Western Desert of Egypt. These burrowing traces are preserved on the surface of a few internal moulds of bivalves and gastropods. Until now, the ichnogenus Arachnostega included a single ichnospecies, A. gastrochaenae Bertling, 1992. In the material studied herein, two ichnospecies are identified, described, illustrated and compared with other, similar traces. One of these is a new ichnospecies of Arachnostega; this is here named A. siwaensis ichnosp. nov. It is distinguished from A. gastrochaenae in the possession of tunnels that usually branch in a V-pattern; intervals of ramification are longest in the main branch and decrease in second- and third-order branches. Arachnostega traces were produced in a warm, low-energy, shallow-marine (<10?m water depth) environment. Polychaetes are the most likely producers of marine Arachnostega, which are commonly occurred in the same studied bed. This new occurrence is significant in extending the known stratigraphical and geographical ranges of Arachnostega into the Middle Miocene of Egypt. 相似文献
2.
A numerical study on 2-D compressive wave propagation in rock masses with a set of joints along the radial direction normal to the joints 总被引：1，自引：0，他引：1
An explosion in a borehole or an accidental explosion in a tunnel will generate a two-dimensional (2-D) compressive wave that travels through the surrounding rock mass. For the problem of 2-D compressive wave propagation in a rock mass with parallel joints in the radial direction normal to the joints, parametric studies on the transmission ratio and the maximum rebound ratio are performed in universal distinct element code. The variation of the transmission ratio with the ratio of joint spacing to wavelength is generalized into a characteristic curve, which can be used as a prediction model for estimating the transmission ratio. The relationship between the maximum rebound ratio and the influence factors is obtained in charts. The charts can be used as a prediction model for estimating the maximum rebound ratio. The proposed prediction models for estimating the transmission ratio and the maximum rebound ratio are applied to a field explosion test, Mandai test in Singapore. The minimum possible values of peak particle velocity (PPV) at the monitoring points are estimated by using the proposed prediction model for estimating the transmission ratio along the radial direction normal to the joints. On the other hand, the maximum possible values of PPV are estimated by using the proposed prediction model for estimating the maximum rebound ratio along the same radial direction. The comparison shows a good agreement between the field-recorded PPVs and the estimated range of PPVs given by the minimum possible PPVs and the maximum possible PPVs at the monitoring points in Mandai test. The good agreement between the estimated and field-recorded values validates the proposed prediction models for estimating peak particle velocity in a rock mass with a set of joints due to application of a compressive wave at the boundary of a tunnel or a borehole. 相似文献
3.
In a previous paper Mayer and Hanna (1991) discussed the process of binary orbit circularization for detached eclipsing binaries. An agreement of observational data with Tassoul's circularization time formula for binaries with masses greater than 2.5 M was found. In the present paper we also examine orbital circularization in evolved spectroscopic binaries. 相似文献
4.
Magdy T. Khalil 《International Journal of Salt Lake Research》1996,5(3):241-251
Growth rates of the main mullet species (Liza ramada andMugil cephalus) in Lake Manzala are low compared to those in other Egyptian lakes. But average growth rates during the period 1989–1993 were relatively faster than in the 1960's. Spawning and migration seasons have been determined for every species, and their distribution in the lake, in terms of certain ecological parameters (salinity, turbidity and dissolved oxygen) have been investigated. Changes in the mullet fishery in the lake during the past 70 years have been studied. Due to an increase in nutrient loading and a decrease in salinity, mullet declined from 65 per cent of the total catch during the 1920's to only 2.2 per cent during the early 1980's. As a result of fisheries management and development programmes from 1989 to 1993, mullet production increased to 9.2 per cent of the total catch. 相似文献
5.
The accuracy of the new equations for long frame-type structures, derived by Kerr and Zarembski, and extended recently by Kerr and Accorsi also to dynamic analyses, is investigated. At first, the natural frequencies of a tall frame-type structure, with twenty floors, are determined using the new equations, and then they are compared with the corresponding results calculated using the finite element method and the common shear-building analysis. The found agreement with the finite element analysis is close. To check further the accuracy of the new equations, small scale models are tested on a shake table. The natural frequencies recorded in the tests are then compared with those determined from the new equations, for a wide range of geometrical parameters. The agreement with the test data is good. The presented study indicates that the new equations are well suited for analyzing the dynamic response of tall frame-type structures. 相似文献
6.
Egypt and the Nile Basin 总被引：1，自引：0，他引：1
7.
El Hedeny Magdy Rashwan Mohamed Richiano Sebastián Al Farraj Saleh Al Basher Ghada 《中国海洋湖沼学报》2021,39(1):198-207
The exposed calcareous rocky area of the Abu Qir Headland,east of Alexandria,Egypt which range from coarse grains,through pebbles,cobbles,and boulders to rocky platforms,was significantly colonized by sclerobionts(epibionts and endobionts).The epibiont species diversity was comparatively higher than that of endobionts.Epibiont communities included bryozoans(the anascan-grade cheilostome Bifiustra savartii),serpulid(Hydroides elegans,Spirobranchus cf.tetraceros,Vermiliopsis striaticeps and Protula or Apomatus) and spirorbid(Spirorbis) wormtubes,and balanoid barnacles(Amphibalanus amphitrite,Balanus trigonus,and Perforatus perforatus).The cheilostome bryozoan colonies,which developed extensive sheets,proliferated on the study rocky shore either encrusting the bioeroded basement directly,or encrusting other epilithic taxa,particularly balanoid barnacles and serpulid worms.Encrusters displayed a remarkable marginal competitive interaction(overgrowth and stand-off) for space on the study rocky shore.On the other hand,endobionts were not well represented on the studied rocky shore exposure.It was possible to identify three ichnotaxa:Gastrochaenolites,Maeandropolydora,and Finichnus.The findings documented represent a significant contribution to our knowledge of sclerobionts composition,sequence of their colonization and/or bioero sion,and their mutual relationships on the intertidal rocky shore of the Abu Qir Headland. 相似文献
8.
Gamal B. Ali Eman A. Shaban Magdy Y. Amin M. A. Rassem 《Astrophysics and Space Science》2014,352(2):789-800
We present a detailed photometric study of the cD galaxies NGC 4839 and NGC 4874 based on the technique of surface photometry by fitting ellipses to the isophotes of the galaxies in the u, g, r, i, and z bands using Data Release 7 (DR7) of the Sloan Digital Sky Survey (SDSS). The motivation of this paper is to study the properties (e.g. break radius and surface brightness, color gradient, etc.) of the extended envelope of the two cD galaxies. The surface brightness profile in each band is obtained and fitted to the de Vaucouleurs r 1/4 model. A deviation of the observed profile brighter than the fitted r 1/4 model is noticed especially in the outer part of each galaxy. The profiles of ellipticity, position angle, B4 and shifts with respect to the center of each isophote are also obtained. The color index profiles, u-g, g-r, r-i, and i-z are also obtained and no significant color gradients are noticed except in the outer parts of the two galaxies. The integrated magnitude in each band and color indices are obtained and found to be in good agreement with the published ones. 相似文献
9.
Abdelhamid Elshater Abdelaziz Elhaddad Attef Elattaar Magdy Abugharbia Waffa Soliman 《Arabian Journal of Geosciences》2018,11(14):385
This paper aims to prepare purified Na-bentonite with improved properties for its use in the pharmaceutical industry. Calcium bentonite from the Sohag region of Egypt was activated with various proportions of sodium carbonate (2, 3, 5 and 8 wt.%). Additionally, bentonite was purified by sedimentation to eliminate impurities, especially quartz. The results of X-ray diffraction (XRD) and swelling volume data confirmed that raw bentonite was converted to sodium bentonite using 5% Na2CO3. The sodium bentonite (M5) obtained by activation met the chemical and microbiological requirements set by the pharmacopoeias regarding toxic trace elemental contents (As, Pb and Cd), the absence of E. coli, the total contents of aerobic microbes and physicochemical properties such as swelling volume, pH and sedimentation volume. Therefore, (M5) bentonite can be designated as being potentially appropriate for pharmaceutical applications. The cation exchange capacity (CEC), surface area, porosity, pH, gel formation and swelling volume data indicated that M5 bentonite could be used to formulate oral suspensions and in topical application. 相似文献
10.
Abdulwahab S. Alaug Magdy S. Mahmoud Amr S. Deaf Thamer K. AL-Ameri 《Arabian Journal of Geosciences》2014,7(6):2515-2530
The current work investigates the hydrocarbon potentiality of the upper Jurassic–lower Cretaceous rocks in the Marib-Shabwah Basin, Central Yemen, through the Sabatayn-1 well. Therefore, palynological and organic geochemical analyses were carried out on 37 ditch cutting and 12 core samples from the well. Palynofacies analysis of the Madbi (late Oxfordian–early Tithonian) and Nayfa (Berriasian–Valanginian) Formations sediments indicates deposition of their organic-rich shale, calcareous shale and marl in middle to outer shelf environments under dysoxic–anoxic conditions, containing mainly kerogen of types II to III. However, the shales of the lower Sabatayn (Tithonian) Formation were deposited in an inner shelf environment of prevailing dysoxic–suboxic conditions, and show kerogen types III to II. Regional warm and relatively dry palaeoclimate but with local humid conditions developed near the site of the well is thought to have prevailed during deposition of the studied well sediments. The geochemical analyses of the Madbi Formation show higher total organic carbon content (TOC) than the overlying Sabatayn and Nayfa formations: it is varies between 1.2 and 7, and with average 4 wt% TOC, and the obtained S2 values (～3–10, average 7 mg HC/g rock) indicates that the Madbi Formation is mainly good source rock. It shows a good petroleum potential of 4–11 mg HC/g dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen types II to III (oil to gas prone) of hydrogen index values (132–258, and only one sample from Lam Member is of 360 and average 215 mg HC/g TOC). The thermal maturation parameters as T max (425–440 °C), production index (average 0.13 mg HC/g rock) and thermal alteration index (2 to 2+) reflected that this formation is present at margin of maturation to early mature stage oil window. So, the Lam Member (upper part) of the Madbi Formation is considered the main hydrocarbon (oil and gas) source rock in the Marib-Shabwah Basin. Accordingly, we predict that the Meem Member is an active source for gas and oil accumulations in the overlying sandstone reservoir of the Sabatayn Formation in the Sabatayn-1 well. 相似文献