Adsorption capacity and mineralogical and physico-chemical characteristics of Shuwaymiyah palygorskite (Oman)     

Ahmed Al-Futaisi  Ahmad Jamrah  Amer Al-Rawas  Saif Al-Hanai 《Environmental Geology》2007,51(8):1317-1327

In this paper, Shuwaymiyah palygorskite in the Sultanate of Oman has been characterized mineralogically by X-ray diffraction (XRD) and electron microscopy, chemically by oxide compositions, structural formulae, and cation exchange capacity (CEC), and physically by specific surface area and adsorption isotherms. Batch adsorption studies were performed to evaluate the adsorption performance of methylene blue (MB) basic dye on the local clay mineral. The quantitative XRD analysis indicates that the purity of some selected samples of palygorskite clay is very high (about 70% of the clay minerals are palygorskite and 30% kaolinite). The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly support this conclusion. The adsorption equilibrium revealed that Shuwaymiyah palygorskite clay can uptake up to 51 mg of MB per 1 g mass of clay. MB adsorption is best fitted by Langmuir isotherm, and a pseudo-second-order kinetic model can be efficiently used to predict the kinetic of adsorption of MB by the palygorskite. The results obtained from these laboratory-scale adsorption tests indicate the promising adsorption capability of the Omani palygorskite.  相似文献   

One-dimensional steady state seawater intrusion in leaky aquifers     

Mohamed A. Hashish  Mohamed E. Rasmy  Abdelwahab M. Amer 《Advances in water resources》1981,4(1):34-42

An iterative technique is presented to compute the location and shape of the interior interface for the one-dimensional steady state seawater intrusion problem in a coastal leaky aquifer. Upper and lower bounds on the location of the top tip point of the interface are deduced based upon the aquifer geometry. Moreover, the dependency of the locations of the top tip point as well as the toe of the interface on the inland boundary condition are obtained through variational analysis of the governing equations. A considerable reduction in the computational effort is shown to be possible provided there is available information about whether the water hinge point lies on or outside the interface. Numerical results are furnished to indicate the efficiency of the proposed algorithm.  相似文献   

Variation of the solar atmospheric rotation over the 11 year cycle     

Mohamed El-Raey  R. Amer 《Solar physics》1975,45(2):533-542

The synodic rotation period and power spectra of solar microwave sources are investigated using accurate data in the interval 1956 to 1970. The variation of the approximate 27 day period is obtained over a complete solar cycle and is thought to be a result of the latitude change over the solar cycle of the origins of the radio emissions. High resolution power spectra have also been obtained and revealed the existence of a double peaked line near 160 day period. This line is attributed to changes in either the Eartn's heliographic latitudes or the Earth's inclination to the Earth-Sun line.  相似文献   

Egypt and the Nile Basin   总被引：1，自引：0，他引：1  

Magdy Hefny  Salah El-Din Amer 《Aquatic Sciences - Research Across Boundaries》2005,67(1):42-50

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Climate volatility and poverty vulnerability in Tanzania     

Syud Amer Ahmed  Noah S. Diffenbaugh  Thomas W. Hertel  David B. Lobell  Navin Ramankutty  Ana R. Rios  Pedram Rowhani 《Global Environmental Change》2011,21(1):46-55

Climate volatility could change in the future, with important implications for agricultural productivity. For Tanzania, where food production and prices are sensitive to climate, changes in climate volatility could have severe implications for poverty. This study uses climate model projections, statistical crop models, and general equilibrium economic simulations to determine how the vulnerability of Tanzania's population to impoverishment by climate variability could change between the late 20th Century and the early 21st Century. Under current climate volatility, there is potential for a range of possible poverty outcomes, although in the most extreme of circumstances, poverty could increase by as many as 650,000 people due to an extreme interannual decline in grain yield. However, scenarios of future climate from multiple climate models indicate no consensus on future changes in temperature or rainfall volatility, so that either an increase or decrease is plausible. Scenarios with the largest increases in climate volatility are projected to render Tanzanians increasingly vulnerable to poverty through impacts on staple grains production in agriculture, with as many as 90,000 additional people entering poverty on average. Under the scenario where precipitation volatility decreases, poverty vulnerability decreases, highlighting the possibility of climate changes that oppose the ensemble mean, leading to poverty impacts of opposite sign. The results suggest that evaluating potential changes in volatility and not just the mean climate state may be important for analyzing the poverty implications of climate change.  相似文献   

Structuring and evolution of Neogene transcurrent basins in the Tellian foreland domain, north-eastern Tunisia     

Fetheddine Melki  Taher Zouaghi  Salah Harrab  Antonio Casas Sainz  Mourad Bdir  Fouad Zargouni 《Journal of Geodynamics》2011,52(1):57-69

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Attempt to identify seismic sources in the eastern Mitidja basin using gravity data and aftershock sequence of the Boumerdes (May 21, 2003; Algeria) earthquake     

Merzouk Ouyed  Mouloud Idres  Amar Bourmatte  Mohamed Salah Boughacha  Sadek Samai  Abdelkrim Yelles  Abderrahmene Haned  Chafik Aidi 《Journal of Seismology》2011,15(2):173-189

In order to try to identify the seismogenic sources in the epicentral area, we interpreted data collected from gravity and aftershocks in the eastern part of the Mitidja basin after the occurrence of the 21 May 2003 Boumerdes earthquake (Mw = 6.8). The residual gravity anomaly and the horizontal gradient maps revealed the basement shape and density discontinuities. A seismotectonic model obtained from the aftershocks distribution and gravity data is proposed. This model highlights three active faults: one offshore and two onshore. The offshore reverse fault striking NE-SW, parallel to the coast, is consistent with the USGS focal mechanism of the main event, which is assumed to have the most moment release. The two onshore dipping blind active faults are postulated at crossing angles near the SW tip of the main fault. The interpretation is based mainly on the re-location and distribution of aftershocks, and their focal solutions. It is also supported by the basin structures obtained from the inversion and interpretation of residual gravity anomalies, as well as by additional compiled information such as the pattern of coastal co-seismic uplift. This configuration puts forward the failure mode complexity during the main shock. The topography of the basement obtained from 3D gravity inversion shows that all the onshore located aftershocks occurred in the basement, and the area between the two onshore faults rose as a consequence of their sliding.  相似文献   

Middle paleolithic to neolithic cultural history of North Iraq     

Thamer Khazal Al-Ameri  Sahar Y. Jasim  Amer J. S. Al-Khafaji 《Arabian Journal of Geosciences》2011,4(5-6):945-972

Six sections of 1–2.7-m depth contain ten sediment samples, each collected from the caves of Shanidar, Hawdian, and Hazar Merd with the nearby river valley sites of Zawi-Chemi, Gawra River, and Barda Balka, respectively, in North Iraq. They have been analyzed palynologically for their climatic significance and vegetational cover during late Quaternary in northeastern Iraq. The main information gathered from these palynological analyses as well as stone tools is ancient open site settlements in Barda Balka of Paleolithic interglacial Acheuleon culture. During the last Ice Age (120,000–10,000 years before present (B.P.)) people refuged to cave settlements. Baradost Mountain as well as the Aqra and Piera Maqroon mountains cavemen of the Middle Paleolithic Period are related to steppe vegetation with cold climate and glacial storms. Those cavemen manufactured stone artifacts of Mousterian to Gravetian culture and have their own religious belief and funeral ceremony especially recorded in the Shanidar cave. They lived by hunting and food collecting from a nearby valley to each cave. During earliest Holocene time (10,000 years B.P.), changing climate to moderately warm climate with Quercus forests and poacean vegetation was recorded, and the cavemen evolved to Neolithic culture and hence moved to settle in plain areas and built the oldest villages of the world, viz., Zawi-Chemi and Jarmo with continuing temporarily living in the caves as well. Their habit changed from food collectors to farmers who cultivated the land with wheat, barley, fruits, olive, legumes, and flowers of brilliant colors, nice odor, and nectariferous as well as domesticated animals for their food resources. Clay tablets of the Sumerians, Babylonians, and Assyrians have documented (Arapha) Kirkuk as one of their cities since 5,500 years B.P. The stone writing records of Assyrian king Sennacherib (705–681 years B.C.) state of making irrigation canals flowing to the temple of Ishtar in Erbil. On the other hand, the similarity of Jarmo village in the present Kurdstan region of Iraq to ancient Tell Hassuna village, south of the present Mosul city (within ancient Nineva city), and the pottery of Jarmo villages to Nineva pottery could give evidence for Jarmo people as followers to the Babylonian–Assyrian cultures within their empire and to prove that people of North Iraq and South Iraq are interrelated cultures through the history within Mesopotamian cultures.  相似文献   

Fractal measures of drainage network to investigate surface deformation from remote sensing data: A paradigm from Hindukush (NE-Afghanistan)   总被引：1，自引：0，他引：1  

Syed Amer MAHMOOD  Richard GLOAGUEN 《山地科学学报》2011,8(5):641-654

This approach represents the relative susceptibility of the topography of the earth to active deformation by means of geometrical distinctiveness of the river networks. This investigation employs the fractal analysis of drainage system extracted from ASTER Global Digital Elevation Model (GDEM-30m resolution). The objective is to mark active structures and to pinpoint the areas robustly influenced by neotectonics. This approach was examined in the Hindukush, NE-Afghanistan. This region is frequently affected by deadly earthquakes and the modern fault activities and deformation are driven by the collision between the northward-moving Indian subcontinent and Eurasia. This attempt is based on the fact that drainage system is strained to linearize due to neotectonic deformation. Hence, the low fractal dimensions of the Kabul, Panjsher, Laghman, Andarab, Alingar and Kocha Rivers are credited to active tectonics. A comprehensive textural examination is conducted to probe the linearization, heterogeneity and connectivity of the drainage patterns. The aspects for these natural textures are computed by using the fractal dimension (FD), lacunarity (LA) and succolarity (SA) approach. All these methods are naturally interrelated, i.e. objects with similar FD can be further differentiated with LA and/or SA analysis. The maps of FD, LA and SA values are generated by using a sliding window of 50 arc seconds by 50 arc seconds (50" × 50"). Afterwards, the maps are interpreted in terms of regional susceptibility to neotectonics. This method is useful to pinpoint numerous zones where the drainage system is highly controlled by Hindukush active structures. In the North-Northeast of the Kabul block, we recognized active tectonic blocks. The region comprising, Kabul, Panjsher, Andrab, Alingar and Badakhshan is more susceptible to damaging events. This investigation concludes that the fractal analysis of the river networks is a bonus tool to localize areas vulnerable to deadly incidents influencing the Earth’s topography and consequently intimidate human lives.  相似文献   

The Condition of Hydrostatic Equilibrium of Stellar Models Using Optimal Control     

Salah Haggag  John L. Safko 《Astrophysics and Space Science》2003,283(3):369-373

The condition of hydrostatic equilibrium of relativistic stellar models is formulated as an optimal control problem. Application of Pontryagin's maximum principle leads directly to the Tolman-Oppenheimer-Volkoff equation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献