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Delta
Kinds of Delta Terms modified by Delta Selected AbstractsA RE-APPRAISAL OF THE APPLICATION OF ROCK-EVAL PYROLYSIS TO SOURCE ROCK STUDIES IN THE NIGER DELTAJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2005A. Akinlua Thirty four shale samples from the Tertiary Agbada Formation were analysed for TOC and Rock-Eval pyrolysis parameters in order to evaluate the effect of oil-based mud contamination on source-rock characterization. The samples were obtained from five wells in the offshore Niger Delta over a depth range of 5,460ft to 11,580ft. The results indicated that the raw (unextracted) samples were dominated by Type III kerogen. However, after extraction, both Types II/III and III kerogen were identified, consistent with previous studies. These results demonstrate that it is essential that shale samples should be extracted prior to TOC and Rock-Eval pyrolysis for accurate source-rock evaluation. [source] SOURCE ROCK EVALUATION AND GEOCHEMISTRY OF CONDENSATES AND NATURAL GASES, OFFSHORE NILE DELTA, EGYPTJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2003L. M. Sharaf Geochemical analyses of mudstones from wells in the NE offshore Nile Delta suggest that the Early Miocene Qantara Formation has "good" potential to generate hydrocarbons at the studied locations. Its generating capability and oil-proneness increase northwards, towards areas where better organic-matter preservation and a greater contribution from marine source material can be expected. By contrast, the Middle Miocene Sidi Salem Formation has "poor to fair" potential to generate mixed gas and oil, while the overlying Wakar and Kafr El Sheikh Formations have "poor" capability to generate gas with minor oil. Based on pyrolysis Tmax and thermal alteration index assessments, the Wakar and Kafr El Sheikh Formations are immature in the study area. The Sidi Salem and Qantara Formations are immature in the southern part of the study area, but are within the oil window in the north, around well Temsah-4. Biomarker distributions based on GC-MS analyses of two condensate samples from the Wakar and Sidi Salem Formations indicate that hydrocarbons are derived from siliciclastic source rocks containing significant terrestrial material and limited marine organic matter. The condensates were generated during early maturation of Type III kerogen from deeper and more mature source rocks than those encountered in the drilled wells. Geochemical and isotopic data from natural gas produced from the Kafr El Sheikh Formation suggest mixed biogenic and thermogenic sources. [source] The small-angle and wide-angle X-ray scattering set-up at beamline BL9 of DELTA.JOURNAL OF SYNCHROTRON RADIATION, Issue 4 2007Erratum A correction is made to the equation in Krywka et al.(2007), J. Synchrotron Rad.14, 244251. [source] The small-angle and wide-angle X-ray scattering set-up at beamline BL9 of DELTAJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2007Christina Krywka The multi-purpose experimental endstation of beamline BL9 at the Dortmund Electron Accelerator (DELTA) is dedicated to diffraction experiments in grazing-incidence geometry, reflectivity and powder diffraction measurements. Moreover, fluorescence analysis and inelastic X-ray scattering experiments can be performed. Recently, a new set-up for small-angle and wide-angle X-ray scattering utilizing detection by means of an image-plate scanner was installed and is described in detail here. First small-angle X-ray scattering experiments on aqueous solutions of lysozyme with different cosolvents and of staphylococcal nuclease are discussed. The application of the set-up for texture analysis is emphasized and a study of the crystallographic texture of natural bio-nanocomposites, using lobster and crab cuticles as model materials, is presented. [source] The new diffractometer for surface X-ray diffraction at beamline BL9 of DELTAJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2006Christof Krywka The experimental endstation of the hard X-ray beamline BL9 of the Dortmund Electron Accelerator is equipped with a Huber six-circle diffractometer. It is dedicated to grazing-incidence X-ray diffraction and X-ray reflectivity experiments on solid surfaces and thin films as well as to powder diffraction measurements. A new set-up for grazing-incidence X-ray scattering of liquids has been built up using a silicon mirror to reflect the incident X-ray to the liquid surface at angles of incidence around the critical angle of total reflection of the sample. X-ray reflectivity measurements of a polymer film and grazing-incidence X-ray diffraction measurements of an epitaxically grown Gd40Y60 film, an oxidized surface of Fe-15at.%Al alloy and aqueous salt solutions are presented and discussed. [source] WATER QUALITY IMPACTS OF CONSERVATION AGRICULTURAL PRACTICES IN THE MISSISSIPPI DELTA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2002Walaiporn Intarapapong ABSTRACT: Nonpoint pollution in the form of runoff generated by conventional agricultural practices is one of the major sources of environmental degradation of surface water bodies. Agricultural conservation practices including no-tillage operations have been introduced as alternatives to cope with such challenges. This study attempts to examine the economic and environmental impacts of no-tillage as compared to conventional agricultural practices for cotton, soybeans and corn cultivated in the Mississippi Delta. Impacts in the form of sediment, nutrient and pesticide runoff at farm level are investigated, using the Erosion Productivity Impact Calculator (EPIC). [source] THE ORIGIN OF BLACK-FIGURE GREEK CERAMICS FOUND IN NAUCRATIS (NILE DELTA)*ARCHAEOMETRY, Issue 3 2005G. HARBOTTLE At the site of the Greek trading port of Naucratis, located on the Canopic mouth of the Nile inland from Alexandria, Flinders Petrie and later archaeologists encountered sherds of Classical Greek black-figure pottery. We have characterized the pastes of 14 of these specimens, drawn from the collections of the British Museum and the Ashmolean Museum at Oxford, by neutron activation analysis and numerical taxonomy. The ceramics agree in composition with a reference group centred on Athens. We also investigated a small number of additional black-figure sherds from other sites. One specimen, from Ruvo di Puglia (Italy), actually originated in or near Marseilles. There was no evidence for local manufacture of black-figure pottery at Naucratis. [source] Corporate,community relations in Nigeria's oil industry: challenges and imperativesCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 4 2006Uwafiokun Idemudia Abstract The adoption of corporate social responsibility (CSR) policies and corporate,community relation (CCR) strategies by oil companies has failed to reduce the incidence of violent conflict between the host communities and oil companies in the Niger Delta, Nigeria. This paper argues that the failure to seek, understand and integrate community perceptions into CSR policies and practices, the over-emphasis of affirmative duties to the detriment of negative injunction duties and the absence of an enabling environment due to government failure are responsible for the observed problem. The paper concludes that unless these gaps are addressed, CSR by the Nigerian oil industry is likely to continue to fail to achieve its full potential. However, CCR in the Nigerian oil industry will be significantly improved if, and when, the needs and aspirations of the major stakeholders are addressed through a tri-sector partnership approach to development and conflict resolution. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment. [source] The Shaping of San Livelihood Strategies: Government Policy and Popular ValuesDEVELOPMENT AND CHANGE, Issue 3 2002Michael Taylor The importance of understanding the livelihood strategies of poor people has received a fresh impetus over the last few years with the emphasis by many Western donors on poverty reduction. This article examines the livelihood strategies of San people in three villages on the northern peripheries of the Okavango Delta in Botswana. Their economic marginalization is compounded by their ethnic background; a stigma that also marginalizes them politically and socially. The analysis presented here not only challenges stereotypes commonly associated with San by demonstrating the interconnectedness of different means of ,looking for life', but it also brings to the fore the importance of considering institutional factors that regulate livelihood strategies. The article focuses on some of the unexpected consequences of the wider policy environment, and on how the values associated with different ways of life affect material subsistence strategies. These are particularly pronounced for people with a heritage of hunting and gathering living in a society that regards such practices as ,backward'. [source] Differing strategies for forming the arthropod body plan: Lessons from Dpp, Sog and Delta in the fly Drosophila and spider AchaearaneaDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2008Hiroki Oda In the insect Drosophila embryo, establishment of maternal transcription factor gradients, rather than cell,cell interactions, is fundamental to patterning the embryonic axes. In contrast, in the chelicerate spider embryo, cell,cell interactions are thought to play a crucial role in the development of the embryonic axes. A grafting experiment by Holm using spider eggs resulted in duplication of the embryonic axes, similar to the Spemann's organizer experiment using amphibian eggs. Recent work using the house spider Achaearanea tepidariorum has demonstrated that the homologs of decapentaplegic (dpp), short gastrulation (sog) and Delta, which encode a bone morphogenetic protein (BMP)-type ligand, its antagonist and a Notch ligand, respectively, are required in distinct aspects of axis formation. Achaearanea Dpp appears to function as a symmetry-breaking signal, which could account for Holm's results to some extent. Experimental findings concerning Achaearanea sog and Delta have highlighted differences in the mechanisms underlying ventral and posterior development between Drosophila and Achaearanea. Achaearanea ventral patterning essentially depends on sog function, in contrast to the Drosophila patterning mechanism, which is based on the nuclear gradient of Dorsal. Achaearanea posterior (or opisthosomal) patterning relies on the function of the caudal lobe, which develops from cells surrounding the blastopore through progressive activation of Delta-Notch signaling. In this review, we describe the differing strategies for forming the arthropod body plan in the fly and spider, and provide a perspective towards understanding the relationship between the arthropod and vertebrate body plans. [source] Genome-wide expression profiling in the Drosophila eye reveals unexpected repression of notch signaling by the JAK/STAT pathwayDEVELOPMENTAL DYNAMICS, Issue 9 2009Maria Sol Flaherty Abstract Although the JAK/STAT pathway regulates numerous processes in vertebrates and invertebrates through modulating transcription, its functionally relevant transcriptional targets remain largely unknown. With one jak and one stat (stat92E), Drosophila provides a powerful system for finding new JAK/STAT target genes. Genome-wide expression profiling on eye discs in which Stat92E is hyperactivated, revealed 584 differentially regulated genes, including known targets domeless, socs36E, and wingless. Other differentially regulated genes (chinmo, lama, Mo25, Imp-L2, Serrate, Delta) were validated and may represent new Stat92E targets. Genetic experiments revealed that Stat92E cell-autonomously represses Serrate, which encodes a Notch ligand. Loss of Stat92E led to de-repression of Serrate in the dorsal eye, resulting in ectopic Notch signaling and aberrant eye growth there. Thus, our micro-array documents a new Stat92E target gene and a previously unidentified inhibitory action of Stat92E on Notch signaling. These data suggest that this study will be a useful resource for the identification of additional Stat92E targets. Developmental Dynamics 238:2235,2253, 2009. © 2009 Wiley-Liss, Inc. [source] Role for notch signaling in salivary acinar cell growth and differentiationDEVELOPMENTAL DYNAMICS, Issue 3 2009Howard Dang Abstract The Notch pathway is crucial for stem/progenitor cell maintenance, growth and differentiation in a variety of tissues. The Notch signaling is essential for Drosophila salivary gland development but its role in mammalian salivary gland remains unclear. The human salivary epithelial cell line, HSG, was studied to determine the role of Notch signaling in salivary epithelial cell differentiation. HSG expressed Notch 1 to 4, and the Notch ligands Jagged 1 and 2 and Delta 1. Treatment of HSG cells with inhibitors of ,-secretase, which is required for Notch cleavage and activation, blocked vimentin and cystatin S expression, an indicator of HSG differentiation. HSG differentiation was also associated with Notch downstream signal Hes-1 expression, and Hes-1 expression was inhibited by ,-secretase inhibitors. siRNA corresponding to Notch 1 to 4 was used to show that silencing of all four Notch receptors was required to inhibit HSG differentiation. Normal human submandibular gland expressed Notch 1 to 4, Jagged 1 and 2, and Delta 1, with nuclear localization indicating Notch signaling in vivo. Hes-1 was also expressed in the human tissue, with staining predominantly in the ductal cells. In salivary tissue from rats undergoing and recovering from ductal obstruction, we found that Notch receptors and ligands were expressed in the nucleus of the regenerating epithelial cells. Taken together, these data suggest that Notch signaling is critical for normal salivary gland cell growth and differentiation. Developmental Dynamics 238:724,731, 2009. © 2009 Wiley-Liss, Inc. [source] Airborne dust deposition in the Okavango Delta, Botswana, and its impact on landformsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2004M. Krah Abstract This study investigated the local-scale generation and movement of dust in the seasonal swamps of the Okavango Delta, Botswana, with a view to examining possible transfer of material between ,ood plains and islands. It was found that most of the dust load was carried in the lowest 3 m of the air column, and consisted mainly of amorphous silica, indicating that dust was generated largely on the ,ood plains. Dust loads were found to be highest above the ,ood plains and lowest over the interiors of islands, probably due to the baf,ing effect of the island trees on wind velocity. The contrast in dust loads between islands and ,ood plains suggests that there is a net transfer of dust from ,ood plains to islands, but it was not possible to quantify this transfer. It is evident, however, that ,ood plains experience net erosion and islands net aggradation. A strong seasonality in dust loads was observed, with the maximum dust loads coinciding with maximum wind velocity in October. This also coincides with peak seasonal ,ooding in the delta, and only non-inundated ,ood plains are capable of generating dust. Years of low ,ood therefore appear to be more dusty. There may also be transfer of material from higher-lying to lower-lying ,ood plains, which may reduce the topographic contrast on the ,ood plains. Copyright © 2004 John Wiley & Sons, Ltd. [source] Channels, wetlands and islands in the Okavango Delta, Botswana, and their relation to hydrological and sedimentological processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2004T. Gumbricht Abstract The Okavango wetland in northern Botswana is one of the world's largest inland deltas. The delta is a dynamic environment with shifting channel routes, causing growth and decay of ,anking wetlands, and giving birth to islands. Primary island nuclei are formed by ,uvial processes and bioengineering, and subsequently grow into secondary larger islands of irregular shape by clastic and chemical sedimentation, and later by coalescence. This article presents classi,cations and quantitative estimations of channels, wetlands and islands of the Okavango Delta. Islands were classi,ed dependent on composition, pattern of composition, shape and juxtaposition. 90 per cent of all islands in the entire wetland were identi,ed, with a classi,cation accuracy of 60 to 85 per cent. Smaller islands of the nucleus types dominate the upper parts of the delta, whereas larger secondary islands are more common in the distal part, a re,ection of the age of the islands. Islands in the entry valley of the delta, the Panhandle, are larger in the top end , the primary region of recent clastic sedimentation. The overall size distribution of islands in the delta, however, shows no clumps, indicating that island growth is a uniform process over time and space. The total area ,ooded at least every decade is approximately 14 000 km2, of which 9000 km2 is classi,ed as actual wetland. Channel meandering decreases from the Panhandle to the distal part of the delta, with the abandoned Thaoge channel as an exception. Occurrence of ,uvially formed islands in the distal delta indicates that the water ,ow and area of inundation must once have been much larger. Copyright © 2004 John Wiley & Sons, Ltd. [source] Tales from Two Deltas: Catfish Fillets, High-Value Foods, and GlobalizationECONOMIC GEOGRAPHY, Issue 2 2005Dominique M. Duval-Diop Abstract: This article examines two places of catfish production, the Mekong River Delta of Vietnam and the Mississippi River Delta of the United States, and uses the concept of globalization to illustrate how these distant places have been brought into competition and how this competition is mediated. Bringing these deltas together is a similar commitment to an economic development strategy that is based on catfish production, a desire to gain access to wealthy consumers who are willing to purchase this high-value food item, and processing and transportation technologies that allow this perishable product to be made more "durable" and to be shipped great distances. Mediating this relationship are consumers' preferences, product labeling, and the U.S. state. This case study illustrates the heterogeneous outcomes of globalization as these deltas are brought into a relationship that, in some ways, is closer than their absolute distance may indicate. The "backlash" forces, such as nontariff trade barriers, nationalism, and a still-powerful state (as both a regulator and consumer), characterize these globalizations. [source] Agricultural productivity and rural incomes in England and the Yangtze Delta, c.1620,c.18201ECONOMIC HISTORY REVIEW, Issue 3 2009ROBERT C. ALLEN The productivity of agriculture in England and the Yangtze Delta are compared c.1620 and c.1820 in order to gauge the performance of the most advanced part of China vis-ŕ-vis its counterpart in Europe. The value of real output is compared using purchasing power parity exchange rates. Output per hectare was nine times greater in the Yangtze Delta than in England. More surprisingly, output per day worked was about 90 per cent of the English performance. This put Yangtze farmers slightly behind English and Dutch farmers c.1820, but ahead of most other farmers in Europe,an impressive achievement. There was little change in Yangtze agricultural productivity between 1620 and 1820. In 1820, the real income of a Yangtze peasant family was also about the same as that of an English agricultural labourer. All was not rosy in the Yangtze, however, for incomes there were on a downward trajectory. Agriculture income per family declined between 1620 and 1820, even though income per day worked changed little since population growth led to smaller farms and fewer days worked per year. The real earnings of women in textile production also declined, since the relative price of cotton cloth dropped,possibly also because a larger population led to greater production. The implication is that the Yangtze family, unlike the English family, had a considerably higher real income c.1620, and that period was the Delta's golden age. [source] The responses of photosynthesis and oxygen consumption to short-term changes in temperature and irradiance in a cyanobacterial mat (Ebro Delta, Spain)ENVIRONMENTAL MICROBIOLOGY, Issue 4 2000Eric Epping We have evaluated the effects of short-term changes in incident irradiance and temperature on oxygenic photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat from the Ebro Delta, Spain, in which Microcoleus chthonoplastes was the dominant phototrophic organism. The mat was incubated in the laboratory at 15, 20, 25 and 30°C at incident irradiances ranging from 0 to 1000 µmol photons m,2 s,1. Oxygen microsensors were used to measure steady-state oxygen profiles and the rates of gross photosynthesis, which allowed the calculation of areal gross photosynthesis, areal net oxygen production, and oxygen consumption in the aphotic layer of the mat. The lowest surface irradiance that resulted in detectable rates of gross photosynthesis increased with increasing temperature from 50 µmol photons m,2 s,1 at 15°C to 500 µmol photons m,2 s,1 at 30°C. These threshold irradiances were also apparent from the areal rates of net oxygen production and point to the shift of M. chthonoplastes from anoxygenic to oxygenic photosynthesis and stimulation of sulphide production and oxidation rates at elevated temperatures. The rate of net oxygen production per unit area of mat at maximum irradiance, J0, did not change with temperature, whereas, JZphot, the flux of oxygen across the lower boundary of the euphotic zone increased linearly with temperature. The rate of oxygen consumption per volume of aphotic mat increased with temperature. This increase occurred in darkness, but was strongly enhanced at high irradiances, probably as a consequence of increased rates of photosynthate exudation, stimulating respiratory processes in the mat. The compensation irradiance (Ec) marking the change of the mat from a heterotrophic to an autotrophic community, increased exponentially in this range of temperatures. [source] Modeling polycyclic aromatic hydrocarbon composition profiles of sources and receptors in the Pearl River Delta, China,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Chang Lang Abstract Changes in concentration profiles of polycyclic aromatic hydrocarbons (PAHs) from emission sources to various environmental media in the Pearl River Delta, China were investigated using fugacity modeling under steady state assumption. Both assumed evenly and observed unevenly distributed PAH moles emission profiles were applied. Applicability of the fugacity model was validated against the observed media PAH concentrations and profiles. At equal emission rates, the differences of media concentrations among various PAHS were as high as three (air) to seven (soil and sediment) orders of magnitude. Dramatic changes of PAH profiles from emission sources to various bulk environmental media also were demonstrated by using the actual emission rates. In general, the fractions of higher molecular weight PAHs in air and water were much lower than those at the emission sources, although the PAH profiles in soil and sediment were characterized by a significant reduction of lower molecular weight PAHs. It is likely that the field-measured median concentration profiles cannot be adopted directly for source apportionment without rectification. The most influential parameters affecting PAH profiles in the study area were emission rates, degradation rates, adsorption coefficient, Henry's law constant, PAH concentrations in upstream surface water, fugacity ratio, vapor pressure, and diffusion coefficient in air. [source] Vegetated agricultural drainage ditches for the mitigation of pyrethroid-associated runoffENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2005Erin R. Bennett Abstract Drainage ditches are indispensable components of the agricultural production landscape. A benefit of these ditches is contaminant mitigation of agricultural storm runoff. This study determined bifenthrin and lambda-cyhalothrin (two pyrethroid insecticides) partitioning and retention in ditch water, sediment, and plant material as well as estimated necessary ditch length required for effective mitigation. A controlled-release runoff simulation was conducted on a 650-m vegetated drainage ditch in the Mississippi Delta, USA. Bifenthrin and lambda-cyhalothrin were released into the ditch in a water-sediment slurry. Samples of water, sediment, and plants were collected and analyzed for pyrethroid concentrations. Three hours following runoff initiation, inlet bifenthrin and lambda-cyhalothrin water concentrations ranged from 666 and 374 ,g/L, respectively, to 7.24 and 5.23 ,g/L at 200 m downstream. No chemical residues were detected at the 400-m sampling site. A similar trend was observed throughout the first 7 d of the study where water concentrations were elevated at the front end of the ditch (0,25 m) and greatly reduced by the 400-m sampling site. Regression formulas predicted that bifenthrin and lambda-cyhalothrin concentrations in ditch water were reduced to 0.1% of the initial value within 280 m. Mass balance calculations determined that ditch plants were the major sink and/or sorption site responsible for the rapid aqueous pyrethroid dissipation. By incorporating vegetated drainage ditches into a watershed management program, agriculture can continue to decrease potential non-point source threats to downstream aquatic receiving systems. Overall results of this study illustrate that aquatic macrophytes play an important role in the retention and distribution of pyrethroids in vegetated agricultural drainage ditches. [source] Dichlorodiphenyltrichloroethane in the aquatic ecosystem of the Okavango Delta, Botswana, South AfricaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003Bontle Mbongwe Abstract Concentrations of DDT and its metabolites were measured in water, plants, invertebrates, and fish from lagoons in the Okavango Delta, Botswana (Africa), where DDT has been used for approximately 50 years. The sampling area was sectioned to distinguish spraying for malaria and for African sleeping sickness. Average concentrations of total DDT (sum of DDT and its metabolites) in the Okavango ranged from 0.009 ng/L in water to 18.76 ng/g wet weight in fish. These levels are approximately 1% of those found in piscivorous fish from temperate North America. The dichlorodiphenyl ethylene (DDE) metabolite was the most abundant fraction of total DDT. Although total DDT concentrations were higher in areas treated for malaria than areas treated for sleeping sickness, these concentrations were likely driven by factors other than the historic application of the pesticide. Equilibration with air concentrations is the most likely explanation for these levels. Since the mean annual temperature exceeds the temperature of vaporization of DDT, this research points to the need for reliable transport models. Our results showed that total DDT concentration in fish was best explained by lipid content of the fish and trophic position inferred by ,15N, regardless of DDT application history in those areas. The reservoir above Gaborone Dam, an area downstream of the Okavango but where DDT had not been used, was sampled to compare total DDT levels to the treated areas. The two species (a herbivorous threespot talapia and the omnivorous sharptooth catfish) from Gaborone had levels higher than those found in the Okavango Delta, but these differences can again be explained using trophic position inferred by ,15N rather than by fish size or location. [source] Distribution of polycyclic aromatic hydrocarbons in particle-size separates and density fractions of typical agricultural soils in the Yangtze River Delta, east ChinaEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2008J. Z. Ni Summary Soil organic matter can be divided into different organic carbon (C) pools with different turnover rates. The organic pollutants in soils associated with these organic C pools may have different bioavailability and environmental risks during the decomposition of soil organic matter. We studied the distribution patterns of 15 USEPA priority polycyclic aromatic hydrocarbons (PAHs) in different particle-size separates (clay, fine silt, coarse silt, fine sand and coarse sand) and density fractions (light and heavy fractions) of nine agricultural topsoils (0,20 cm depth) from a contaminated area in the Yangtze River Delta region of east China. There was a decreasing trend in PAH concentration in particle-size separates with decreasing particle size. However, the different particle-size separates had similar PAH composition. The concentration of PAHs in the light fraction ranged from 13 037 to 107 299 ,g kg,1, far higher than in the heavy fraction, which ranged from 222 to 298 ,g kg,1. Although the light fraction accounted for only 0.4,2.3% of the soils, it was associated with 31.5,69.5% of soil PAHs. The organic matter in coarse silt had the strongest capacity for enrichment with PAHs. Combining the distributions of PAHs and the turnover rates of organic matter in different soil fractions, the environmental risks of PAH-polluted soils may be due mainly to the PAHs associated with sand and the light fraction. [source] Allelopathic effect of the aquatic macrophyte, Stratiotes aloides, on natural phytoplanktonFRESHWATER BIOLOGY, Issue 3 2006GABI MULDERIJ Summary 1. A survey of different Dutch Stratiotes stands showed that the density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between the rosettes of S. aloides. Analyses of water samples revealed that nutrient limitation was unlikely to have caused the lower phytoplankton biomass in the vicinity of S. aloides. 2. An in situ incubation experiment in the Danube Delta, Romania, indicated allelopathic activity against phytoplankton in S. aloides stands. The growth rate of natural phytoplankton populations exposed to water from S. aloides stands was significantly lower than that of populations that had not been in contact with S. aloides exudates. 3. A laboratory microcosm experiment showed a significantly lower phytoplankton biomass in treatments with S. aloides exudates. Nutrient concentrations and the light intensity were high enough that the lower phytoplankton biomass could not be explained by nutrient or light limitation. [source] Late Bronze Age paleogeography along the ancient Ways of Horus in Northwest Sinai, EgyptGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2008Stephen O. Moshier The northwest Sinai contained the eastern frontier of New Kingdom Egypt during the Late Bronze Age. The ancient Pelusaic branch of the Nile Delta influenced the environmental setting of this region at that time. Fortresses were built along the coastal byway through the study area known as the Ways of Horus to protect Egyptian-held territory from immigrants and intruders from Canaan and the Mediterranean Sea. Building on previous geomorphic studies in the region, this paper presents the results of field investigations of Holocene sedimentary deposits, aided by satellite photography, used to create a paleogeographic map that places archaeological sites in their proper environmental context. CORONA satellite photographs from the late 1960s reveal surface features that have been obscured by more recent agricultural development in the region. Canals dug for an agricultural project provided easy access to the shallow subsurface for mapping the extent of Holocene sediments representing barrier coast, lagoon, estuarine, fluvial, and marsh depositional environments. © 2008 Wiley Periodicals, Inc. [source] A 3.5 ka record of paleoenvironments and human occupation at Angkor Borei, Mekong Delta, southern CambodiaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2003Paul Bishop Microfossil and sedimentological data from a 3.1 m core extracted from a reservoir (baray) at the ancient Cambodian settlement of Angkor Borei in the Mekong Delta have provided a continuous record of sedimentation and paleoenvironments dating from about 2000 cal yr B.C. Palynological data indicate that for much of the cal. 1st and 2nd millennia B.C. mangroves dominated the regional vegetation, while extensively and regularly burnt grasslands dominated the local vegetation. Turbid, nutrient-rich standing water characterized the core locality, perhaps suggesting a connection with rivers in the area. An abrupt change during the cal. 5th to 6th centuries A.D. involved a dramatic reduction in grasslands and the expansion of secondary forest or re-growth taxa. These changes are synchronous with an abrupt decline in the concentration of microscopic charcoal particles in the sediments, and the colonization of the core locality by swamp forest plants. These changes are taken to indicate a shift in land-use strategies or, possibly, a period of land abandonment. The age for the construction of the baray is interpreted to be in the 17th,19th centuries, but this dating remains speculative. Construction of the Angkor Borei baray exploited a preexisting body of standing water, so its construction was fundamentally different from the methods used at the Angkorian capital in northern Cambodia. © 2003 Wiley Periodicals, Inc. [source] THE STORM OF NOVEMBER 1826 IN THE CANARY ISLANDS: POSSIBLY A TROPICAL CYCLONE?GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2010JOSÉ BETHENCOURT-GONZÁLEZ ABSTRACT. This work analyses a storm that occurred in the Canary Islands early in November 1826. Through a study based on historical climate data, some of the adverse effects of the storm are described and some of the possible causes are discussed. The main goal of this work is to establish an approximate reconstruction of this historical event which will allow us to compare it to a recent meteorological event that had a great impact on the archipelago: "Tropical Storm Delta", in November 2005. Studying and reviewing the origin of the 1826 storm verifies the hypothesis that extremely violent perturbations have not only occurred in the Canaries on other occasions, but that these past events were also more intense and had more serious consequences than Delta. Therefore, the idea that other tropical perturbations have occurred in the region of the Canary Islands before Delta is presented. [source] Hurricanes Create a Crossroads for Hydrological Management of the Mississippi River DeltaGROUND WATER, Issue 2 2006Richard F. Keim No abstract is available for this article. [source] Evidence for prolonged clinical benefit from initial combination antiretroviral therapy: Delta extended follow-upHIV MEDICINE, Issue 3 2001Delta Coordinating Committee Background The findings from therapeutic trials in HIV infection with surrogate endpoints based on laboratory markers are only partially relevant for clinical decisions on treatment. Although the collection of clinical follow-up data from such a trial would be relatively straightforward, this rarely occurs. An important reason for this may be the perception that such data have little value because the number of participants remaining on their original allocated therapy has usually fallen substantially. Methods Delta was an international, multicentre trial in which 3207 HIV infected individuals were randomly allocated to treatment with zidovudine (ZDV) alone, ZDV combined with didanosine (ddI) or ZDV combined with zalcitabine (ddC). Although the trial closed in September 1995, information on vital status, AIDS events, treatment changes and CD4 counts was still collected every 12 months until at least March 1997. This has allowed analyses of the longer term clinical effect of treatment. Results The median follow-up to date of death or last known vital status was 43 months (10th percentile 18 months; 90th percentile 55 months). The proportion of participants remaining on their allocated treatment fell steadily over time; by 4 years after trial entry, 3% remained on ZDV, 20% on ZDV + ddI and 21% on ZDV + ddC. Changes mainly involved the stopping, addition or switching of a nucleoside reverse transcriptase inhibitor (NRTIs). There was little use of protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) before the third year of the trial. Between the third and fourth years, regimens included a drug from one of these classes for approximately 17% of person-time in all treatment groups. Relative to ZDV monotherapy, the beneficial effects of combination therapy on mortality and disease progression rates increased significantly with time since randomization. The maximum effects on mortality were observed between 2 and 3 years, with a 48% reduction for ZDV + ddI and a 26% reduction for ZDV + ddC. These rates were observed when the original allocated treatment was received 42% and 47% of the time in the ZDV + ddI and ZDV + ddC groups, respectively. The mean CD4 count remained significantly higher (approximately 50 cells/,L) in the combination therapy groups 4 years after randomization, suggesting a projection of a clinical benefit beyond this time point. Conclusions The sustained clinical effect of the initial allocation to combination therapy, particularly ZDV + ddI, was remarkable in light of the convergence of drug regimens actually received across the three treatment groups. Interpretation of this finding is not straightforward. One of the possible explanations is that the effectiveness of ddI and ddC is diminished if first used later in infection or with greater prior exposure to ZDV, although the data do not clearly support either hypothesis. This analysis highlights the value of long-term clinical follow-up of therapeutic trials in HIV infection, which should be considered in the planning of all new studies. [source] Spatial assessment of hydrologic alteration across the Pearl River Delta, China, and possible underlying causesHYDROLOGICAL PROCESSES, Issue 11 2009Qiang Zhang Abstract The alterations of the water level across the Pearl River Delta (PRD) were investigated using a ,range of variability approach' (RVA) based on monthly water level datasets extracted from 17 gauging stations. A mapping method was used to illustrate the spatial patterns in the degrees of alteration of water levels. The results indicated that more stations showing moderate and high alterations in monthly mean maximum and minimum water levels when compared with monthly maximum and minimum water levels. River channels characterized by higher alterations of water levels were observed mainly in the regions north of 22° 30,N. Alterations of water levels across the PRD were a consequence of various influencing factors. However, changed hypsography due to extensive and intensive human activities, particularly the large-scale dredging and excavation of the river sand, may be taken as one of the major causes for the substantial hydrologic alteration. This study indicated that the river channels characterized by altered water levels are mostly those characterized by highly and moderately intensive sand dredging. The changed ratio of the streamflow between Makou and Sanshui stations, the major upstream flow control stations, also influenced the water level alterations of the Pearl River delta. The results of this study will be of great significance in water resources management and better human mitigation of the natural hazards due to the altered water level under the changing environment. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydro-climatic impacts on the ice cover of the lower Peace RiverHYDROLOGICAL PROCESSES, Issue 17 2008Spyros Beltaos Abstract Since the late 1960s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace,Athabasca Delta (PAD) region. Though major ice jams occur at breakup, antecedent conditions play a significant role in their frequency and severity. These conditions are partly defined by the mode of freezeup and the maximum thickness that is attained during the winter, shortly before the onset of spring and development of positive net heat fluxes to the ice cover. Data from hydrometric gauge records and from field surveys are utilized herein to study these conditions. It is shown that freezeup flows are considerably larger at the present time than before regulation, and may be responsible for more frequent formation of porous accumulation covers. Despite a concomitant rise in winter temperatures, solid-ice thickness has increased since the 1960s. Using a simple ice growth model, specifically developed for the study area, it is shown that porous accumulation covers enhance winter ice growth via accelerated freezing into the porous accumulation. Coupled with a reduction in winter snowfall, this effect can not only negate, but reverse, the effect of warmer winters on ice thickness, thus explaining present conditions. The present model is also shown to be a useful prediction tool, especially for extrapolating incomplete data to the end of the winter. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Evapotranspiration rates and crop coefficients for a restored marsh in the Sacramento,San Joaquin Delta, California, USA,HYDROLOGICAL PROCESSES, Issue 6 2008Judy Z. Drexler Abstract The surface renewal method was used to estimate evapotranspiration (ET) for a restored marsh on Twitchell Island in the Sacramento,San Joaquin Delta, California, USA. ET estimates for the marsh, together with reference ET measurements from a nearby climate station, were used to determine crop coefficients over a 3-year period during the growing season. The mean ET rate for the study period was 6 mm day,1, which is high compared with other marshes with similar vegetation. High ET rates at the marsh may be due to the windy, semi-arid Mediterranean climate of the region, and the permanently flooded nature of the marsh, which results in very low surface resistance of the vegetation. Crop coefficient (Kc) values for the marsh ranged from 0·73 to 1·18. The mean Kc value over the entire study period was 0·95. The daily Kc values for any given month varied from year to year, and the standard deviation of daily Kc values varied between months. Although several climate variables were undoubtedly responsible for this variation, our analysis revealed that wind direction and the temperature of standing water in the wetland were of particular importance in determining ET rates and Kc values. Published in 2007 by John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||||||||