Thermoregulation, water balance and plasma constituents in Sudanese desert sheep: responses to diet and solar radiation     

A. M. Abdelatif  M. M. M. Ahmed 《Journal of Arid Environments》1993,25(4)

The responses of desert rams to diet composition (concentrate vs. lucerne hay) in unshaded and shaded environments were investigated. The rectal temperature was higher (p < 0·01) with the concentrate diet but only in the afternoon, whereas the respiration rate was higher (p < 0·01) with the concentrate diet in unshaded and shaded environments during both morning and afternoon. Dry matter intake (DMI) was higher (p < 0·05) with the concentrate diet, while the ratio of water intake to DMI was higher (p < 0·01) with lucerne hay. Water gain through preformed and metabolic avenues and water loss through faeces and evaporative avenues were higher (p < 0·01) with the concentrate diet. With both diets, water turnover rate was higher (p < 0·05) in the unshaded environment. Feeding lucerne hay increased plasma total protein (p < 0·01) and albumin (p < 0·05) in unshaded and shaded environments. Plasma urea was higher (p < 0·01) with the concentrate diet. Plasma glucose level and plasma osmalality were higher (p < 0.01) and level of free fatty acids was lower (p < 0·01) with the concentrate diet in both thermal environments. Plasma cholesterol level was higher (p < 0·05) with the concentrate diet in the shaded environment, but lower (p < 0·05) in the unshaded environment. With lucerne hay, plasma cholesterol level remained the same in both environments.  相似文献   

Future research problems in marine organic chemistry     

Robert B. Gagosian  Saiyed I. Ahmed  John W. Farrington  Richard F. Lee  Richard F. C. Mantoura  Kenneth H. Nealson  Theodore T. Packard  Kenneth L. Reinhart  Jr. 《Marine Chemistry》1978,6(4):375-382

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Nannostructure and significance of fish coprolites in phosphorites     

Michel Lamboy  Venigalla Purnachandra Rao  Ezzat Ahmed  Nasreddine Azzouzi 《Marine Geology》1994,120(3-4):373-383

Phosphatic coprolites (0.5–2 cm long) occurring in Cretaceous-Eocene phosphorites of Tunisia, Morocco, Mauritania, Senegal, and Egypt were investigated for their petrology by using SEM. They exhibit a homogeneous porous apatite structure with a few fish remains. The nannostructures of the coprolites consist of inframicron-sized and botryoid-type apatite microparticles. Spherical cavities and cavity-infill cavity-infilled inframicron-sized apatite globules are typical in the coprolites and are apparently formed by extracellular precipitation of phosphate around microbial organisms. We presume that the coprolites studied here may belong to fishes, whose excrements contain abundant organic matter and phosphate. Phosphatization of excrements appears to be a microbial process controlled by the microenvironment.

The nannostructures observed in the coprolites investigated here differ significantly from the nannostructures of other studied phosphatic grains (pellets and coated grains) in the same samples which are mostly heterogeneous and consist of ovoid-type apatite particles. In the case they are not reworked, the centimetre to decimetre thick coprolite beds in phosphorites indicate a lack of detrital input and strong bottom water currents at the sediment-water interface during deposition and subsequent phosphatization of the excrements.  相似文献   

Generation and expulsion of oils from Permian coals of the Sydney Basin,Australia     

Manzur Ahmed  Herbert Volk  Simon C. George  Mohinudeen Faiz  Linda Stalker 《Organic Geochemistry》2009,40(7):810-831

Organic geochemical and petrological assessment of coals/coaly shales and fine grained sediments, coupled with organic geochemical analyses of oil samples, all from Permo–Triassic sections of the Southern Sydney Basin (Australia), have enabled identification of the source for the widely distributed oil shows and oil seeps in this region. The Permian coals have higher hydrogen indices, higher liptinite contents, and much higher total organic matter extract yields than the fine grained sediments. A variety of source specific parameters obtained from n-alkanes, regular isoprenoids, terpanes, steranes and diasteranes indicate that the oil shows and seeps were generated and expelled predominantly from higher plant derived organic matter deposited in oxic environments. The source and maturity related biomarkers and aromatic hydrocarbon distributions of the oils are similar to those of the coals. The oil-coal relationship also is demonstrated by similarities in the carbon isotopic composition of the total oils, coal extracts, and their individual n-alkanes. Extracts from the Permo–Triassic fine grained sediments, on the other hand, have organic geochemical signatures indicative of mixed terrestrial and prokaryotic organic matter deposited in suboxic environments, which are significantly different from both the oils and coal extracts. The molecular signatures indicating the presence of prokaryotic organic matter in some of the coal extracts and oils may be due to thin sections of possibly calcareous lithologies interbedded within the coal measures. The genetic relationship between the oils and coals provides new evidence for the generation and expulsion of oils from the Permian coals and raises the possibility for commercial oil accumulations in the Permian and Early Triassic sandstones, potentially in the deeper offshore part of the Sydney Basin.  相似文献   

Reply to the comment on “Arsenic release from biotite into a Holocene groundwater aquifer in Bangladesh” by Hossain M. Anawar and Martin Mihaljevič     

Ashraf Ali Seddique  Harue Masuda  Muneki Mitamura  Keiji Shinoda  Takamoto Okudaira  Toshiro Yamanaka  Takaaki Itai  Teruyuki Maruoka  Kenji Uesugi  Kazi Matin Ahmed 《Applied Geochemistry》2009

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Utilization of geoinformation tools for the development of forest fire hazard mapping system: example of Pekan fire, Malaysia     

Ahmad Rodzi Mahmud  Iwan Setiawan  Shattri Mansor  Abdul Rashid Mohamed Shariff  Biswajeet Pradhan  Ahmed Nuruddin 《Central European Journal of Geosciences》2009,1(4):456-462

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Structural elements and incremental strain history of the basement rocks of Um Had area, central Eastern Desert, Egypt     

Ahmed Akawy 《Arabian Journal of Geosciences》2009,2(4):285-300

The Um Had area, central Eastern Desert, Egypt shows a regional stretching in the NW–SE and a contraction in the NE–SW direction. Major NW–SE folds, small recumbent folds, and local thrusts and reverse faults were recognized. Complicated relation between folds and boudinage was identified. This stretching amount ranges from 1.282 to 1.309. Earlier coaxial and later non-coaxial strains were inferred. The change from axial to non-coaxial stress regime was gradual and the latter was associated with minor clockwise and anticlockwise rotation of structural elements. During the non-coaxial strain, strain fringes were formed as a consequence of the high circulation of fluids in low temperature and high pressure conditions. Superimposed strain fringes indicating right- and left-lateral senses of movement were recognized. At least three generations of fringes were recognized, implying three stages of non-coaxial stretching. Each generation has about 15 increments which show irregular strain gradient and intensity over the different increments. Eastwards, the strain increments became mature and westwards, the finite strain increases. The strongest finite strain was found in a narrow belt delimiting the basement rocks on the west and underlying the Phanerozoic sediments. Chocolate-tablet structure was recorded and indicates later multidirectional tension. Not all Nubia Sandstone exposures are overlying the basement rocks and some are separated by NW–SE normal faults. Major NW–SE normal faults are cutting basement rocks of different ages.  相似文献   

Suffusion evaluation of coarse-graded soils from Rhine dikes     

Benamar  Ahmed  Correia dos Santos  Ricardo N.  Bennabi  Abdelkrim  Karoui  Tarek 《Acta Geotechnica》2019,14(3):815-823

Acta Geotechnica - An experimental study on internal erosion of coarse-grained soils collected from the Rhine River is presented. The tests performed on laboratory column aim to assess the...  相似文献   

Element partitioning between magnesium silicate perovskite and ferropericlase: New insights into bulk lower-mantle geochemistry     

Anne-Line Auzende  James Badro  Frederick J. Ryerson  Peter K. Weber  Stewart J. Fallon  Ahmed Addad  Julien Siebert  Guillaume Fiquet   《Earth and Planetary Science Letters》2008,269(1-2):164-174

In this study, we investigated iron–magnesium exchange and transition-metal trace-element partitioning between magnesium silicate perovskite (Mg,Fe)SiO₃ and ferropericlase (Mg,Fe)O synthetised under lower-mantle conditions (up to 115 GPa and 2200 K) in a laser-heated diamond anvil cell. Recovered samples were thinned to electron transparency by focused ion beam and characterized by analytical transmission electron microscopy (ATEM) and nanometer-scale secondary ion mass spectroscopy (nanoSIMS). Iron concentrations in both phases were obtained from X-ray energy dispersive spectroscopy measurements and nanoSIMS. Our results are the first to show that recently reported spin-state and phase transitions in the lower mantle directly affect the evolution of Fe–Mg exchange between both phases. Mg-perovskite becomes increasingly iron-depleted above 70–80 GPa possibly due to the high spin–low spin transition of iron in ferropericlase. Conversely, the perovskite to post-perovskite transition is accompanied by a strong iron enrichment of the silicate phase, ferropericlase remaining in the Fe-rich phase though. Nanoparticles of metallic iron were observed in the perovskite-bearing runs, suggesting the disproportionation of ferrous iron oxide, but were not observed when the post-perovskite phase was present. Implications on the oxidation state of the Earth and core segregation will be discussed. Transition trace-element (Ni, Mn) concentrations (determined with the nanoSIMS) show similar trends and could thus be used to trace the origin of diamonds generated at depth. This study provides new results likely to improve the geochemical and geophysical models of the Earth's deep interiors.  相似文献   

Mineral and chemical composition of Karak mudstone, Kohat Plateau, Pakistan: implications for smectite-illitization and provenance   总被引：1，自引：0，他引：1  

Akhtar Ali Saleemi  Zulfiqar Ahmed   《Sedimentary Geology》2000,130(3-4):229-247

The Karak mudstone interbedded in an Eocene evaporite sequence, is dominated by R-1 ordered illite-smectite with a 20 to 30% expandable component. Minor phases include kaolinite, chlorite, illite/muscovite, plagioclase, potash feldspar, quartz, dolomite and pyrite. The present illite-smectite was probably originally smectite or highly expandable illite-smectite which underwent conversion to illite-smectite with a low expandable component in a comparatively low-temperature (ca. 100°C) closed-system sedimentary basinal diagenetic environment at a depth of ca. 5 km. Al³⁺ and K⁺ necessary for the conversion reaction were provided through the breakdown of potash feldspar. Burial under a 5 km thick pile of sediments produced some of the observed structures. Whole-rock chemistry presented here suggests that the mudstone formed by severe weathering of acidic source rocks. The influx of freshwater probably flushed out Ba, Rb, Ca and Mn from the restricted basin.  相似文献