Home About us Contact
|
Home About us Contact | ||
|
|
||
Important Fraction (important + fraction)
Selected AbstractsAssessing diversity and biogeography of aerobic anoxygenic phototrophic bacteria in surface waters of the Atlantic and Pacific Oceans using the Global Ocean Sampling expedition metagenomesENVIRONMENTAL MICROBIOLOGY, Issue 6 2007Natalya Yutin Summary Aerobic anoxygenic photosynthetic bacteria (AAnP) were recently proposed to be significant contributors to global oceanic carbon and energy cycles. However, AAnP abundance, spatial distribution, diversity and potential ecological importance remain poorly understood. Here we present metagenomic data from the Global Ocean Sampling expedition indicating that AAnP diversity and abundance vary in different oceanic regions. Furthermore, we show for the first time that the composition of AAnP assemblages change between different oceanic regions, with specific bacterial assemblages adapted to open ocean or coastal areas respectively. Our results support the notion that marine AAnP populations are complex and dynamic, and compose an important fraction of bacterioplankton assemblages in certain oceanic areas. [source] Critical evaluation of the chemical standardization procedure for measuring gastric emptying of solidsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2002P. Goethals Abstract The purpose of this study was to evaluate the baking process of yolk spiked with octanoate to measure gastric emptying rate of solids. [1- 11C]octanoate was produced by the reaction of [11C]CO2 with heptyl magnesium bromide in tetrahydrofuran (THF), followed by purification with HPLC. The decay corrected radiochemical yield ranged from 24 to 38% (5.9,9.8 GBq EOS, synthesis time: 25 min; specific radioactivity ,90 GBq ,mol,1). To check the evaporation of [1- 11C]octanoate during the baking process of yolk, [1- 11C]octanoate or potassium [1- 11C]octanoate, respectively, was added. An important fraction of the acid evaporated while for the potassium [1- 11C]octanoate <10% disappeared. Conclusion: potassium (1- 13C)octanoate is a better tracer than (1- 13C) octanoate to study gastroenterological phenomena. Copyright © 2002 John Wiley & Sons, Ltd. [source] Press Advertising and the Political Differentiation of NewspapersJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 3 2002Jean J. Gabszewicz The press industry depends in a crucial way on the possibility of financing an important fraction of its activities by advertising receipts. We show that this may induce the editors of the newspapers to moderate the political message they display to their readers, compared with the political opinions they would have expressed otherwise. [source] Partition of metals in the Vistula River and in effluents from sewage treatment plants in the region of Cracow (Poland)LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2000C. Guéguen Abstract The Vistula River suffers from heavy pollution with multiple origins. In the upper reaches, metallic and chlorine pollution originates from the mining and industrial region of Upper Silesia. Downstream from Upper Silesia, urban and industrial sewage adds more metallic and organic contaminants from the large urban agglomeration of Cracow. Although the river status is monitored routinely, little is known about the partition of metals between particulate and dissolved forms. This study focuses on metal partitioning and on the impact of the two main wastewater treatment plants at Cracow on metal concentrations in the Vistula River. The Cd, Co, Cu, Mn, Pb and Zn content was measured in both dissolved and particulate fractions. High metal concentrations in the Vistula River persist, although current levels seem to be lower than those in the past. Metal concentrations in the Vistula River and effluents from the sewage treatment plants at Cracow are similar, indicating a relatively minor contribution from the treated sewage. However, untreated sewage may be a significant source of contaminants. Despite high anthropogenic metal concentrations, the metal partitioning coefficients (Kd) in the Vistula are similar to these found in unpolluted rivers. Within a narrow pH range, Kd values depend on the metal affinity to particles, but there is no evidence of dependence on particle or chloride concentrations. An important fraction of the toxic metals Pb and Cd is associated with particles, which may decrease their immediate availability to the biota of the river. [source] The effect of a binary source companion on the astrometric microlensing behaviourMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001Cheongho Han If gravitational microlensing occurs in a binary source system, both source components are magnified, and the resulting light curve deviates from the standard one of a single source event. However, in most cases only one source component is highly magnified and the other component (the companion) can be treated as a simple blending source: this is a blending approximation. In this paper we show that, unlike the light curves, the astrometric curves, representing the trajectories of the source image centroid, of an important fraction of binary source events will not be sufficiently well-modelled by the blending effect alone. This is because the centroid shift induced by the source companion endures to considerable distances from the lens. Therefore, in determining the lens parameters from astrometric curves to be measured by future high-precision astrometric instruments, it will be important to take the full effect of the source companion into consideration. [source] Molecular Responses to Stress Induced in Normal Human Caucasian Melanocytes in Culture by Exposure to Simulated Solar UV,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Laurent Marrot ABSTRACT Melanocytes play a central role in the response of skin to sunlight exposure. They are directly involved in UV-induced pigmentation as a defense mechanism. However, their alteration can lead to melanoma, a process where the role of sun overexposure is highly probable. The transformation process whereby UV damage may result in melanoma initiation is poorly understood, especially in terms of UV-induced genotoxicity in pigmented cells, where melanin can act either as a sunscreen or as a photosensitizer. The aim of this study was to analyze the behavior of melanocytes from fair skin under irradiation mimicking environmental sunlight in terms of spectral power distribution. To do this, normal human Caucasian melanocytes in culture were exposed to simulated solar UV (SSUV, 300,400 nm). Even at relatively high doses (until 20 min exposure, corresponding to 12 kJ/m2 UV-B and 110 kJ/m2 UV-A), cell death was limited, as shown by cell viability and low occurrence of apoptosis (caspase-3 activation). Moreover, p53 accumulation was three times lower in melanocytes than in unpigmented cells such as fibroblasts after SSUV exposure. However, an important fraction of melanocyte population was arrested in G2-M phase, and this correlated well with a high induction level of the gene GADD45, 4 h after exposure. Among the genes involved in DNA repair, gene XPC was the most inducible because its expression increased more than two-fold 15 h after a 20 min exposure, whereas expression of P48 was only slightly increased. In addition, an early induction of Heme Oxygenase 1 (HO1) gene, a typical response to oxidative stress, was also observed for the first time in melanocytes. Interestingly, this induction remained significant when melanocytes were exposed to UV-A radiation only (320,400 nm), and stimulation of melanogenesis before irradiation further increased HO1 induction. These results were obtained with normal human cells after exposure to SSUV radiation, which mimicked natural sunlight. They provide new data related to gene expression and suggest that melanin in light skin could contribute to sunlight-induced genotoxicity and maybe to melanocyte transformation. [source] Hypolipidemic activity of Anethum graveolens in ratsPHYTOTHERAPY RESEARCH, Issue 3 2008Valiollah Hajhashemi Abstract The aerial parts of Anethum graveolens (dillweed) are used in Iran as a hypolipidemic agent. The scientific basis for its use has yet to be established. In this study the hypolipidemic activity of dill powder and its essential oil (its most important fraction) were evaluated in male Wistar rats (180 ± 20 g) fed a high cholesterol diet. Anethum graveolens essential oil (AGEO) was prepared by hydrodistillation and analysed using GC/MS. AGEO had a yield of 2% and GC/MS analysis showed that , -phellandrene (32%), limonene (28%) and carvone (28%) were its major components. Daily oral administration of AGEO to rats at doses of 45, 90 and 180 mg/kg for 2 weeks significantly and in a dose-dependent manner reduced total cholesterol, triglyceride and low density lipoprotein cholesterol (LDL-C). AGEO also increased significantly high density lipoprotein cholesterol (HDL-C). Anethum graveolens powder when added to the diet of animals showed similar effects on serum lipids. It is concluded that Anethum graveolens has significant lipid lowering effects and is a promising cardioprotective agent. Copyright © 2007 John Wiley & Sons, Ltd. [source] Does flooding of rice fields after cultivation contribute to wetland plant conservation in southern Brazil?APPLIED VEGETATION SCIENCE, Issue 1 2010Ana S. Rolon Abstract Question: Does flooding of rice fields after cultivation contribute to wetland plant conservation in southern Brazil? Location: Rice fields in the coastal plain of southern Brazil. Methods: Six rice fields with different management practices were randomly selected (three dry rice fields and three flooded rice fields). Six collections were carried out over the rice cultivation cycle. Richness and biomass were measured using the quadrat method. Results: A total of 88 macrophyte species was recorded. There was no statistical interaction between management practices and rice cultivation phases for macrophyte richness and biomass. Macrophyte species richness and biomass changed over time, but were similar between flooded and dry rice fields. The first three axes generated by detrended correspondence analysis explained 29% of the variation in species composition and the multivariate analysis of variance showed that there was a statistical interaction between management practices and agricultural periods. Conclusions: Rice fields may help to conserve an important fraction of the aquatic macrophyte diversity of wetlands of southern Brazil by providing the setting up of a greater number of species within the agricultural landscape. However, rice fields must not be viewed as surrogate systems for natural wetlands. The difference in species composition between flooded and dry rice fields is interesting in terms of biodiversity conservation. If rice producers could keep part of their agricultural land flooded during the fallow phase, this management practice could be an important strategy for the conservation of biodiversity in areas where natural wetlands have been converted to rice fields. [source] | |||||||||||||