Leaching requirement and salinity threshold for the yield and agronomic characteristics of halophytes under salt stress

An experiment was carried out at Nahshala Farm, north west of Al-Ain City, U.A.E. during the 1998–2000 growing seasons, using six halophytes (Batis maritima, Distichlis spicata, Juncus roemerianus, Paspalum vaginatum, Salicornia bigelovii and Spartina alterniflora) and two levels of leaching fraction (0·25 and 0·50) under three irrigation salinity levels (10, 20, and 40 gL⁻¹) in a randomized complete block design arranged in split plots. The purpose of the research was to apply the theory of crop salt tolerance on aboveground yields and agronomic characteristics of halophytes to determine their thresholds for salinity and to determine leaching requirements. The results indicated that the halophyte species tested can grow with minimum reduction in the growth potential at <20 gL⁻¹of mean salinity of soil solution. Leaching fraction (LF) of 0·25 at the highest salinity of irrigation water (40 gL⁻¹) was inadequate to attain the steady-state salt balance during the growth period, although the drainage salinity reached more than 90 g L⁻¹. Furthermore, if the same level of LF is used for longer period, soil salinity under this high salt treatment will continue to rise, and plant growth may deteriorate. Leaching fraction of 0·50 is preferable if salinity of irrigation water was more than 20 gL⁻¹and dry matter production is considered, although the amount of water use will be excessive     

Health care pattern and planning in Saudi Arabia

Amazonia I is a large multi-disciplinary project, now in its fourth year, concerned with the effects of changing land use on the ecology and climate of the Brazilian Amazon. It is primarily concerned with investigating the water, carbon and nutrient cycles, and brings together about 80 scientists from a number of Brasilian institutes, but especially from INPA in Manaus, CENA/USP in Piracicaba and EMBRAPA/CPATU in Belem.Major activities include the better identification of water vapour producing precipitation, to establish better water vapour circulation models (via ¹⁸O, deuterium and ³H analysis, plus radiosonding); the study of water relations of isolated forest areas; the study of various phases of the carbon cycle especially soil organic matter; primary production; and nitrogen and soil fertility studies.A first phase Regional Amazon Model (RAM) for hydrology is being developed, and it should shortly be possible to make a first research-based attempt at modelling the carbon cycle of the Amazon region.This coordinated project represents in most ways the type of research required for the International Geosphere-Biosphere Programme (IGBP) and is a major Brasilian initiative.     

埃及东部沙漠Gasco天然气公司工程场地大地构造参数和地震灾害评估

根据埃及Gasco天然气公司工程场地的现场调查资料、地震活动性和地震灾害评估结果,对该场地进行了评估.通过浅源地震波折射勘探,对8个地震剖面上的土壤和岩石的弹性动态常数进行了分析.场地地面模型包括两层,分析表明它们具有从中值到高值的弹性动态常数,说明场地有良好的土壤条件和基岩岩性.同时,我们搜集和分析了研究区周围150 km半径范围内的历史和仪器记录地震,从构造环境、地震活动性、地质构造和主要地震的断层面解等方面进行了研究,认为场地受4个震源区的影响:苏伊士中部海湾、开罗-苏伊士地区、开罗西南和Beni-Suef地区.我们采用地震活动性统计方法并结合专家判定,确定了这些震源区内最大地震的矩震级(MW).另外,依据场地峰值加速度(PGA)和反应谱,用随机方法对场地进行了地震灾害评估.4个震源区中,Beni-Suef地区距离工程场地最近,其PGA最大值为9.34cm/s2,但这个值很小,表明地震不会对工程场地产生破坏性影响.最后,我们还模拟了阻尼为1%、3%和5%时的伪加速度场地反应谱.     

Mean runoff coefficient estimation for ungauged streams in the Kingdom of Saudi Arabia

Runoff coefficient estimation in ungauged watersheds has a priority for rain water harvesting and management of runoff water, for domestic and agriculture activities, in semi-arid and arid regions. To estimate mean runoff coefficient (C _Re) for ungauged streams, Pearson's coefficient of linear correlation (r) was measured. The method of linear regression (y?=?mx?+?c) was applied for 16 gauged catchments representing several regions in the Kingdom of Saudi Arabia, such as Al Qassim, Al Madinah, Riyadh, Asir, Makkah, and Jazan. The studied catchments were equally divided into two groups based on their main streams slopes; group A includes eight gauged streams having main stream slope less than 0.01, where group B includes eight gauged streams having main stream slope equal to or greater than 0.01. The result yields the constant of the linear regression for each group and the mean runoff coefficient of basin by an independent value (basin slope) for group A and an independent value (stream slope) for group B. The results indicate that the measured runoff coefficient (C _Rm) and the estimated runoff coefficient (C _Re) are almost equal to each other.     

Effect of animal borings on geotechnical properties of coralline limestone in NW Jeddah City, Red Sea Coast, Saudi Arabia

The coralline limestone covers large areas in the western and northern parts of Jeddah City. This coralline limestone is composed mainly of shelly limestone with pencil-sized animal borings. These borings increase the primary porosity and make the rock weak enough to have low-bearing capacity. The dry density (γ _dry) values of the study coralline limestone ranges from 1.54 to 2.09 g/cm³. The total porosity varies from 12.34 to 28.42 %. The absorption percentage fluctuates between 6.49 and 17.75 %. More than 95 % of the tested rock core samples have compressive strength less than 15 MPa. The compressive strength commonly decreased with the increase of animal borings. The obtained results cause the study coralline limestone weak enough to support heavy structures.     

Oblateneess and drag effects on the motion of satellites in the set of Eulerian redundant parameters

In this paper, the perturbed motion of the artificial satellites under the effects of the earth's oblateness and atmospheric drag will be established. These equations will be expressed in terms of the Eulerian redundant parameters. Applications of the method for the perturbed motion are illustrated by numerical examples for some test cases of the orbits.     

Analytical solution to the perturbedJ 2 motion of Artificial Satellite in terms of Euler parameters

In this paper an analytical solution for the differential equations governing the motion of Artificial Satellite under the oblateness of the earth will be developed. We start with the differential equations in terms of Euler parameters. To compact algebra, we introduce the Cayley-Klein type complex variables. Comparison between numerical and analytical final states withJ ₂ will be given for a test case.     

Efficient algorithms for the earth's gravitational potential and its partial derivatives for satellite prediction

In this paper, economical recursion formulae for the Earth's gravitational potential and its partial derivatives with respect to the Cartesian coordinates, and time will be established for any number and any type of the harmonic coefficients. General computational algorithms for their implementations on digital computers are also given.Now at the Department of Astronomy, King Abdul-Aziz Univ., Jeddah, Saudi Arabia.Now at the Department of Mathematics, Girls College of Education, Jeddah, Saudi Arabia.     

Magnetic interpretation of long horizontal cylinders using correlation factors between successive least-squares residual anomaly profiles

Procedures are formulated using the correlation factors between successive least-squares residual magnetic anomaly profiles due to long horizontal cylinders for interpreting the three principal anomalies (vertical, horizontal, and total). It is demonstrated that correlation values can be used to determine the depth to the center of the buried structure and the index parameter. Procedures are also formulated to estimate the amplitude coefficient. Two worked examples using theoretical data show the effectiveness of the present method.