The effects of irregularities of internal structure in determining the ultraviolet properties of interstellar grains     

Hoyle  F.  Wickramasinghe  N. C.  Al-Mufti  S.  Karim  L. M. 《Astrophysics and Space Science》1985,114(2):303-309

Whereas data for the extinction of starlight in the visible show the interstellar grains must be partially hollow, data in the ultraviolet show the vesicular interiors must be irregular. In particular, the absorbing materials responsible for excess extinction over a band centred at 2175 Å are required to be concentrated in irregularly distributed chromophores with dimensions of the order of or less than one-tenth of the whole grain.The laboratory measurements of absorptions produced by microorganisms agree very closely with astronomical observations for a large number of early-type stars. Since the interior structures of microorganisms are indeed highly irregular, the laboratory measurements made with microorganisms suspended in a fluid, can reasonably be transferred to microorganismsin vacuo.The characteristic dimension for the scattering of visible light by rod-like grains has in the past been taken to be rod diameters. An alternate interpretation with the characteristic dimension taken instead to be rod-oengths may turn out to have advantages in respect of data in the ultraviolet, as well as agreeing in scale with bacteria-like objects found in meteorites, and possibly also, in particles entering the Earth's atmosphere from the zodiacal cloud.  相似文献   

Karez irrigation in Pakistan     

Muhammad Fazle Karim Khan  Muhammad Nawaz 《GeoJournal》1995,37(1):91-100

Karez is an indigenous method of irrigation in which groundwater is tapped by a tunnel. After running for some distance the tunnel comes out in the open and the water is conducted to the command area. Karez irrigation is practised in 22 countries from China to Chile including Pakistan. In Pakistan it is confined to the province of Balochistan which has a tribal society.Karez is an old and stable irrigation system of Pakistan. It is a community enterprise managed by tribal tradition and run by social control. Spacing of the karez, their types, life, length, discharge, land development and allocation, water distribution and management are important aspects of karez irrigation which have been discussed in this paper. Differences in karez maintenance and management produced by differences in tradition and customs of various tribes inhabiting Balochistan are brought out. Furthermore recent changes in Karez irrigation caused by changes in the socio-economic conditions are also analysed.  相似文献   

Species and size selectivity in a Portuguese multispecies artisanal long-line fishery   总被引：1，自引：0，他引：1  

Erzini  Karim; Goncalves  Jorge M. S.; Bentes  Luis; Lino  Pedro G.; Cruz  Joao 《ICES Journal of Marine Science》1996,53(5):811-819

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Sea surface temperature trends in Kuwait Bay,Arabian Gulf   总被引：1，自引：0，他引：1  

Thamer B. Al-Rashidi  Hamdy I. El-Gamily  Carl L. Amos  Karim A. Rakha 《Natural Hazards》2009,50(1):73-82

The magnitude 8.1 earthquake and subsequent tsunami killed 52 people when it hit the Solomon Islands on 2 April 2007. That number would have likely been considerably higher were it not for the appropriate reaction of the indigenous coastal populations and a helpful physical geography. Buffering coral reefs reflected some wave energy back to sea, reducing the power of the wave. Hills a short distance behind the coastal villages provided accessible havens. Despite this beneficial physiography, immigrant populations died at disproportionately high rates in comparably damaged areas because they did not recognize the signs of the impeding tsunami. The indigenous population of Tapurai, which lacks a steep barrier reef to reflect the incoming energy, experienced a much more powerful wave, and the population suffered heavy losses. Indigenous knowledge as an integral tool in basin wide tsunami warning systems has the potential to mitigate disasters in the near field. Community-based disaster management plans must be cognizant of educating diverse populations that have different understandings of their environment.  相似文献   

Ground motion selection for scenario ruptures using the generalised conditional intensity measure (GCIM) method   总被引：1，自引：0，他引：1       下载免费PDF全文

Karim Tarbali  Brendon A. Bradley 《地震工程与结构动力学》2015,44(10):1601-1621

In this paper, the generalised conditional intensity measure (GCIM) method is extended to ground motion selection for scenario earthquake ruptures. The selection algorithm is based on generating random realisations of the considered intensity measure (IM) distributions for a specific rupture scenario and then finding the prospective ground motions that best fit the realisations using an optimal amplitude scale factor. Using different rupture scenarios and site conditions, two important aspects of the GCIM methodology are scrutinised: (i) different weight vectors for the various IMs considered and (ii) quantifying the importance of replicate selections for ensembles with different numbers of desired ground motions. It is demonstrated that considering only spectral acceleration (SA) ordinates in the selection process, as is common in many conventional selection procedures, may result in selected motions with a biased representation for duration and cumulative ground motion effects. In contrast, considering IMs other than SA ordinates (in particular, significant duration, cumulative absolute velocity, and Arias intensity) results in ensembles with an appropriate representation of these IMs, without a practically significant effect on SA ordinates. The benefit of conducting replicate selections to obtain a suite of motions with an improved representation for the distribution of the considered IMs is demonstrated, and a minimum number of replicates are suggested for different ground motion ensemble sizes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Simulating spatiotemporal variability of blue and green water resources availability with uncertainty analysis   总被引：3，自引：0，他引：3       下载免费PDF全文

Depeng Zuo  Zongxue Xu  Dingzhi Peng  Jinxi Song  Lei Cheng  Shouke Wei  Karim C. Abbaspour  Hong Yang 《水文研究》2015,29(8):1942-1955

Due to rapid socioeconomic development, continuous population growth and urbanization, the world is facing a severe shortage of fresh water, particularly in arid and semi‐arid regions. A lack of water will put pressure on agricultural production, water pollution, as well as eco‐environmental degradation. Traditional water resources assessment mainly focused on blue water, ignoring green water. Therefore, analysis of spatiotemporal distribution of blue and green water resources in arid and semi‐arid regions is of great significance for water resources planning and management, especially for harmonizing agricultural water use and eco‐environmental water requirements. This study applied the Soil and Water Assessment Tool (SWAT) model and the Sequential Uncertainty Fitting algorithm (SUFI‐2) to calibrate and validate the SWAT model based on river discharges in the Wei River, the largest tributary of the Yellow River in China. Uncertainty analysis was also performed to quantify the blue and green water resources availability at different spatial scales. The results showed that most parts of the Wei River basin (WRB) experienced a decrease in blue water resources during the recent 50 years with a minimum value in the 1990s. The decrease is particularly significant in the most southern part of the WRB (the Guanzhong Plain), one of the most important grain production bases in China. Variations of green water flow and green water storage were relatively small both on spatial and temporal dimensions. This study provides strategic information for optimal utilization of water resources in arid and semi‐arid river basin. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Pushover analysis of asymmetric-plan buildings based on distribution of the combined modal story shear and torsional moment     

Kazem Shakeri  Karim Tarbali  Mohtasham Mohebbi 《地震工程与工程振动(英文版)》2014,(4)

A pushover procedure with a load pattern based on the height-wise distribution of the combined modal story shear and torsional moment is proposed to estimate the seismic response of 3D asymmetric-plan building frames. Contribution of the higher modes and torsional response of asymmetric-plan buildings are incorporated into the proposed load pattern. The proposed pushover method is a single-run procedure, which enables tracing the nonlinear response of the structure during the analysis and averts the elusiveness of conducting multiple pushover analyses. The proposed method has been used to estimate the response of two moment-resisting building frames with 9 and 20 stories. The obtained results indicate the appropriate accuracy and efficiency of the proposed procedure in estimating the trend of the drift profiles of the structures resulted from nonlinear time history analyses.  相似文献   

L'upwelling de la côte atlantique du Maroc entre 1994 et 1998     

Ahmed Makaoui  Abdelattif Orbi  Karim Hilmi  Soukaina Zizah  Jamila Larissi  Mohammed Talbi 《Comptes Rendus Geoscience》2005,337(16):1518

The pelagic ecosystem of the Moroccan Atlantic coast is influenced by the spatiotemporal variability of upwelling. The changes in the physicochemical and biological parameters as well as their interrelationship and regrouping by the principal components analysis allowed us to subdivide the Atlantic coast in four active areas: two areas located at the north of Cape Juby (28°N), characterised by a summery activity and two areas located at the south, active permanently, with a variable intensity. To cite this article: A. Makaoui et al., C. R. Geoscience 337 (2005).  相似文献   

Spectroscopic characterization of geological materials from the United Arab Emirates     

Karim N. Jallad  Cyntia Espada-Jallad 《Arabian Journal of Geosciences》2008,1(2):119-127

Throughout the United Arab Emirates, the sand differs in color and composition, depending on its source. This study reports the collection of 70 sediment samples from coastal district areas of seven emirates in the United Arab Emirates, namely, Abu Dhabi, Dubai, Sharjah, Ajman, Umm Al Quwain, Ras Al-Khaimah, and Fujairah for the purposes of spectroscopic characterization and color justification. The compositions of these naturally occurring sand samples obtained were tested using different spectroscopic techniques. The techniques included both destructive instrumentation as scanning electron microscopy with energy dispersive X-ray analysis and X-ray powder diffraction and nondestructive instrumentation as confocal Raman microscopy. It was concluded that the sand can acquire various colors ranging from white to black due to the presence of certain chemical compounds.  相似文献   

Organic contamination identification in sediments from a Mediterranean coastal ecosystem: The case of the Nador lagoon (Eastern Morocco)     

Mohamed Karim Bloundi  Pierre Faure  Joëlle Duplay 《Comptes Rendus Geoscience》2008,340(12):840-849

The Nador lagoon ecosystem (North-East of Morocco) displays a major socioeconomic interest. In fact, it is essential to evaluate consequences of anthropogenic activities in the lagoon especially by organic matter studies (nature and distribution) in the sedimentary compartment. Surface sediments show variable rates in total organic carbon and in sulfur, high in some cases (7.5 and 1.8% respectively). These high contents are recorded in the center of the lagoon. Their distributions are controlled by the hydrodynamism and the anthropogenic degree. The molecular biomarkers analyses and especially n-alkanes distribution reveal: a zone of marine influence; and a zone of continental influence. The occurrence of pentacyclic triterpanes with a typical distribution of a thermally mature organic matter reveals a contamination due to petroleum products in the entire lagoon except for the center. Coprostanol occurrence near cities indicates wastewater effluents inputs and reducing conditions underlined by high values of stanols/sterol ratios. Thus, the organic contamination (petroleum by-products and wastewater effluents) occurs in the vicinity of the cities whereas the littoral edge and center remain weakly affected by these contaminations.  相似文献