Landing of Mars or Ceres on Earth (new model of our solar system)     

Osman M. Kamel 《Earth, Moon, and Planets》1992,58(1):97-103

Motivated by the recent proposals of A. Abian, we investigate in this paper the second order perturbations up to the second degree in eccentricity-inclination of a new model of our solar system after the landing of Mars or Ceres on the Earth. The theory is established through the HoriLie technique and in terms of Jacobi coordinates and Poincare canonical variables.  相似文献   

Expansion of the planetary Hamiltonian function     

Osman M. Kamel  Adel S. Soliman 《Earth, Moon, and Planets》1993,62(1):3-45

We expand the planetary Hamiltonian function with its two parts, the principal and the indirect, up to the seventh order in the planetary masses. We adopt the Jacobi-Radau system of origins. The expansiion is valid for any number of planets.  相似文献   

The construction of a fifth-order Jupiter-Saturn motion: Analytical theory     

Osman M. Kamel  Adel S. Soliman 《Earth, Moon, and Planets》1991,52(3):253-289

We construct a fifth-order with respect to masses Jupiter-Saturn secular theory by Hori-Lie canonical technique. The J-S Hamiltonian includes both parts of the perturbing function. The influence of the 2:5 critical terms is taken into consideration. The Jacobi-Radau system of origins is adopted and the theory is expressed in terms of the Poincaré canonical variables.  相似文献   

Structures controlling U and Th mineralisation in the Gebel Felat area of the south Eastern Desert of Egypt     

Ahmed Farouk Kamel 《Journal of African Earth Sciences》1997,24(4):649-652

In the Eastern Desert of Egypt, younger granites host U and Th mineralisations which are concentrated along faults and joints. In particular, the Gebel Felat Pluton is characterised by a high level of radioactivity as shown by an aeroradiometric survey. The U content is 82 ppm and the Th content is 15 ppm in areas of high radioactivity. The rocks are cross-cut by two main sets of fractures trending east-west and northwest-southeast. The contour maps of these two trends can be correlated with the aeroradiometric map of the same area.  相似文献   

Cotton production under risk: a simultaneous adoption of risk coping tools     

Farhad Zulfiqar  Raza Ullah  Muhammad Abid  Abid Hussain 《Natural Hazards》2016,84(2):959-974

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Ecohydrological responses to surface flow across borders: Two decades of changes in vegetation greenness and water use in the riparian corridor of the Colorado River delta     

Pamela L. Nagler  Armando Barreto-Muñoz  Sattar Chavoshi Borujeni  Christopher J. Jarchow  Martha M. Gómez-Sapiens  Hamideh Nouri  Stefanie M. Herrmann  Kamel Didan 《水文研究》2020,34(25):4851-4883

Hydrological and bioclimatic processes that lead to drought may stress plants and wildlife, restructure plant community type and architecture, increase monotypic stands and bare soils, facilitate the invasion of non-native plant species and accelerate soil erosion. Our study focuses on the impact of a paucity of Colorado River surface flows from the United States (U.S.) to Mexico. We measured change in riparian plant greenness and water use over the past two decades using remotely sensed measurements of vegetation index (VI), evapotranspiration (ET) and a new annualized phenology assessment metric (PAM) for ET. We measure these long-term (2000–2019) metrics and their short-term (2014–2019) response to an environmental pulse flow in 2014, as prescribed under Minute 319 of the 1944 Water Treaty between the two nations. In subsequent years, small-directed flows were provided to restoration areas under Minute 323. We use 250 m MODIS and 30 m Landsat imagery to evaluate three vegetation indices (NDVI, EVI, EVI2). We select EVI2 to parameterize an optical-based ET algorithm and test the relationship between ET from Landsat and MODIS by regression approaches. Our analyses show significant decreases in VIs and ET for both the 20-year and post-pulse 5-year periods. Over the last 20 years, EVI _Landsat declined 34% (30% by EVI_MODIS) and ET_Landsat-EVI declined 38% (27% by ET_MODIS-EVI), overall ca. 1.61 mm/day or 476 mm/year drop in ET; using PAM ET_Landsat-EVI the drop was from 1130 to 654 mm/year. Over the 5 years since the 2014 pulse flow, EVI_Landsat declined 20% (13% by EVI_MODIS) and ET_Landsat-EVI declined 23% (4% by ET_MODIS-EVI) with a 0.77 mm/day or a 209 mm/year 5-year drop in ET; using PAM ET_Landsat-EVI the drop was from 863 to 654 mm/year. Data and change maps show the pulse flow contributed enough water to slow the rate of loss, but only for the very short-term (1–2 years). These findings are critically important as they suggest further deterioration of biodiversity, wildlife habitat and key ecosystem services due to anthropogenic diversions of water in the U.S. and Mexico and from land clearing, fires and plant-related drought which affect hydrological processes.  相似文献   

Biochemical adaptation of phytoplankton to salinity and nutrient gradients in a coastal solar saltern,Tunisia     

Olfa Abid  Alya Sellami-Kammoun  Habib Ayadi  Zaher Drira  Abderrahmen Bouain  Lotfi Aleya 《Estuarine, Coastal and Shelf Science》2008

The distribution of protein and carbohydrate concentrations of the particulate matter (size fraction: 0.45–160 μm) was studied, from 22 January 2003 to 02 December 2003, in three ponds of increasing salinity in the Sfax solar saltern (Tunisia). The coupling of N/P: DIN (DIN = NO₂⁻ + NO₃⁻ + NH₄⁺) to DIP (DIP = PO₄³⁻) with P/C: protein/carbohydrates ratios along salinity gradient allowed the discrimination of three types of ecosystems. Pond A1 (mean salinity: 45.0 ± 5.4) having marine characteristics showed enhanced P/C ratios during a diatom bloom. N/P and P/C ratios were closely coupled throughout the sampling period, suggesting that the nutritional status is important in determining the seasonal change in the phytoplankton community in pond A1. In pond A16 (mean salinity: 78.7 ± 8.8), despite the high nitrate load, P/C ratios were overall lower than in pond A1. This may be explained by the fact that dinoflagellates, which were the most abundant phytoplankton in pond A16 might be strict heterotrophs and/or mixotrophs, and so they may have not contributed strongly to anabolic processes. Also, N/P and P/C ratios were uncoupled, suggesting that cells in pond A16 were stressed due to the increased salinity caused by water evaporation, and so cells synthesized reserve products such as carbohydrates. In pond M2 (mean salinity: 189.0 ± 13.8), P/C levels were higher than those recorded in either pond A1 or A16. N/P and P/C were more coupled than in pond A16. Species in the hypersaline pond seemed paradoxally less stressed than in pond A16, suggesting that salt-tolerant extremophile species overcome hypersaline constraints and react metabolically by synthesizing carbohydrates and proteins.  相似文献   

Development Of The Hamiltonian Function Using The Jacobi System Of Reference     

Kamel  Osman M. 《Earth, Moon, and Planets》1998,81(3):179-185

In this paper we describe two different methods to expand the second term of the planetary Hamiltonian function. The Jacobi system of coordinates is adopted leading to a unique evaluation of the Hamiltonian. Previous analytical or semi-analytical planetary theories suffer from the drawback of computing the perturbation function for each planet, which is quite cumbersome. The inclinations of planets are referred to a common fixed plane and the longitudes to a common origin. This is necessary when we deal with n > 2 planets. The treatment is straightforward, and no complexities appear throughout the analysis. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Geologic hazards assessment of Cairo and vicinity     

A. F. Kamel  A. A. El Sokkary 《Natural Hazards》1996,13(3):253-274

The greater area from Cairo to west of Suez and a smaller area directly around Cairo are subjected to general and detailed analysis of hazard due to geological fractures. Fracture density contour maps and rose diagrams of the fracture trends are provided. Possible natural geologic hazards which might affect the area are discussed. These include landslides, block failure, earthquakes, maars, fumarolic activity, hot springs, caves and possible rejuvenation of old fault systems.  相似文献   

The elimination of the critical terms of a first order Uranus-Neptune theory by Hori's method     

Osman M. Kamel 《Earth, Moon, and Planets》1983,28(3):221-245

In this part we determine the value ofS ₁, and in terms of the canonical variables of H. Poincaré. A complete solution of the auxiliary system of equations generated by the Hamiltonian is presented.  相似文献