人工聚沙堤防治铁路沙害的初期试验研究

本文介绍了在高寒干旱的青藏铁路线伏沙梁地段,采用人工聚沙堤阻截外来风沙流的试验。通过初期试验观测,对人工聚沙堤的聚沙形式结构和防沙效果进行了阐述,提出人工聚沙堤是整治该段铁路沙害的一种主要措施。     

Depositional Environment and Lithofacies Analyses of Eocene Lacustrine Shale in the Bohai Bay Basin: Insights from Mineralogy and Elemental Geochemistry

The effect of various depositional parameters including paleoclimate, paleosalinity and provenance, on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment. The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity. The lower 3^rd member of the Eocene Shahejie Formation(Es₃^x shale) was sel...     

Rain induced attenuation studies for V-band satellite communication in tropical region

Satellite communications operating at 10 GHz and above in the tropics suffer severe signal degradation due to rain. Attenuation due to rain at 38 GHz had been measured for a period of 20 months in Malaysia. Analyses carried out include seasonal variations, diurnal effects and the annual cumulative distributions. Obtained results were compared with several established prediction models including the ITU-R. The rain fade characteristics were also investigated in determining the levels of signal loss and fading. In addition, the studies highlight several potential fade mitigation techniques that can be embarked. These fundamental aprehensions are very critical for future earth space communication link design and can be exploited as preliminary groundwork plan for the researchers as well as engineers.     

Antibiotic resistant bacteria as bio-indicator of polluted effluent in the green turtles, Chelonia mydas in Oman

Antibiotic resistant bacteria were studied as bio-indicators of marine polluted effluents during egg-laying in green turtles. A non-invasive procedure for sampling oviductal fluid was used to test for exposure of turtles to pollution in Ras Al-Hadd, Oman, which is one of the most important nesting beaches in the world. Each sample was obtained by inserting a 15 cm sterile swab gently into the cloacal vent as the sphincter muscle is relaxed and the cloacal lining is unfolded to the outside. Forty turtles were sampled. A hundred and thirty-two species of bacteria from 7 genera were isolated. The dominant isolate was Citrobacter. Among the isolates 60.6% were multiple resistant to 15 tested antibiotics. The dominant resistance to antibiotics was ampicillin followed by streptomycin and sulphamethoxazole. Sampling oviductal fluid for resistant bacteria to antibiotics is valuable way to assess exposure to polluted effluents during feeding and migratory in turtles. Polluted effluents using bacteria as bio-indicator may influence reproductive potential in this endangered species.     

Optimal filtration and a pulsar time scale

An algorithm is proposed for constructing a group (ensemble) pulsar time based on the application of optimal Wiener filters. This algorithm makes it possible to separate the contributions of variations of the atomic time scale and of the pulsar rotation to barycentric residual deviations of the pulse arrival times. The method is applied to observations of the pulsars PSR B1855+09 and PSR B1937+21, and is used to obtain corrections to UTC relative to the group pulsar time PT_ens. Direct comparison of the terrestial time TT(BIPM06) and the group pulsar time PT_ens shows that they disagree by no more than 0.4 ± 0.17 μs. Based on the fractional instability of the time difference TT(BIPM06)-PT_ens, σ _z = (0.5 ± 2) × 10⁻¹⁵, a new limit for the energy density of the gravitational-wave background is established at the level Ω _g h ² ∼ 10⁻⁹.     

Qualitative and Quantitative Characterization of Mangrove Vegetation Structure and Dynamics in a Peri-urban Setting of Douala (Cameroon): An Approach Using Air-Borne Imagery

Qualitative and quantitative characterization of mangrove vegetation structure and dynamics is required for assessment of coastal habitat vulnerability. Changes in mangrove forests around Douala, Cameroon, have been documented using aerial photography between 1974 and 2009. The distribution pattern of tree species was also assessed in 2009 following the point-centered quarter method (PCQM+) protocol. Pristine mangroves observed in 1974 had been disturbed markedly in 2003 and 2009. Some of the pre-existing mangroves were entirely replaced by settlements, road, and crops (maize, bean, banana, oil palm, green vegetables, and sugar cane plantations). From 1974 to 2003, 39.86 % of mangrove forests have disappeared; the net loss of 22.10 % occurred between 2003 and 2009 alone. Mangrove forest area had decreased 53.16 % around Douala over a 35-year period from 1974 to 2009 concurrent with a substantial increase of settlements (60 %), roads (233.33 %), agriculture areas (16 %), non-mangrove areas (193.33 %), and open water (152.94 %). Field survey showed that almost one third of the quadrants in the remaining mangrove forest were empty. The disrupted mangrove forest has an overall mean height, absolute density, and basal area of 19.80 m, 158 trees ha^?1, and 110.44 m² ha^?1, respectively. In comparison with scientific literature on mangrove degradation, this puts the mangroves around Douala at the top of the “peri-urban mangrove degradation” list. In addition, beyond listing of mangrove plants on the Red List of Threatened Species which will seldom lead to widely distributed species being listed, we call for the creation of a Red List of Locally Threatened Ecosystems, which in contrast is likely to list mangroves as an ecosystem under critical risk of (local) extinction in many countries around the globe, in particular, peri-urban sites.     

Rare earth elements in modern coral sands: an environmental proxy

The concentration rare earth elements and Yttrium (REE + Y) were determined in coral sands from Kavaratti Island, Arabian Sea, India. Chondrite-normalized REE + Y patterns show: (1) high REE concentration particularly light REE (LREE) enrichment; (2) consistent negative Ce anomaly; (3) nearly chondritic Y/Ho ratios. All these features are consistent with the geochemistry of well oxygenated seawater with significant terrestrial contribution. The seawater composition of Nd/Yb ratio inferred from the coral record point to the dominance of LREE more than the heavy REE (HREE). The high terrestrial input rich in LREE and property of adsorption/scavenging processes of LREE than that of HREE may be the cause. Terrigenous contributions were detected on the basis of co-occurring trace element concentrations (Sc, Hf and Th) and Y/Ho ratio. Except for La, the REE distribution coefficients, KD(REE)s, are between 100 and 300. KDs are high comparing to the other elements in biogenic calcite which is attributed to detrital contamination during elemental incorporation. This study may not reflect original seawater chemistry but it can be a good proxy to indicate proximity of corals to terrigenous input sources.     

Groundwater quality of Yemen volcanic terrain and their geological and geochemical controls

One hundred thirty boreholes of volcanic aquifers in rural Yemen Highland Groundwaters (YHGs) were chemically investigated to assess the suitability of water for drinking. Focus is to identify inorganic constituents of significant risk to health that occur in groundwaters of this area. Results showed that a number of boreholes contain, apart from fluoride, levels of nitrate, some heavy metals, total dissolved solids, and sulfates that could pose a health risk for consumers. The lateral variations of major ions with depth varied within the same aquifer based on the dynamic equilibrium of groundwater and hydrogeological conditions. The main inorganic groundwater contaminant in volcanic YHG is fluoride which is attributed to groundwater lithology and water type. Fluoride appears high in Ca-poor groundwater and where cation exchanges of Ca for Na are dominant. High F concentration in YHG is an extension of East African fluoride-rich groundwater. Majority of tube wells show that Fe concentration exceeds WHO guideline many folds. Much of the iron and manganese in groundwaters are naturally occurring, since the source rocks are enriched in ferromagnesian minerals. NO ₃ ^? and Cl^? concentrations that have been detected in some wells may indicate sewage and/or agricultural runoff. Elevated concentration of chemical constituents in groundwater is a sign of groundwater degradation.     

Geomorphology and landscape evolution of bharatpur district, rajasthan

The morphometric analysis of the surface drainage has been carried out for the four micro-watersheds of Bharatpur district, Rajasthan to quantify the drainage morphometry of the district. The morphochronology of landseape evolution has been described. Banaganga represents anomalous drainage, which causes large scale inundation during rainy season. The strain of post-collision Himalayan tectonics resulted in slope mulation in Bharatpur district which changed slope from westerly to easterly. The landform characteristics of Bharatpur district have been arehieved at the National Informatics Center, District Data Base, Bharatpur is alpha numeric mode.