The Experts below are selected from a list of 13149 Experts worldwide ranked by ideXlab platform
Mae Sexauer Gustin - One of the best experts on this subject based on the ideXlab platform.
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gas particle partitioning of atmospheric hg ii and its effect on global mercury deposition
Atmospheric Chemistry and Physics, 2011Co-Authors: H M Amos, Daniel J Jacob, Christopher D Holmes, Jenny A Fisher, Qiaoqiao Wang, Robert M Yantosca, Elizabeth Sturges Corbitt, Elisabeth Galarneau, Andrew P Rutter, Mae Sexauer GustinAbstract:Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous Component of Hg(II)), particle-bound mercury (PBM, the Particulate Component of Hg(II)), fine Particulate matter (PM 2.5), and temperature (T ) at five sites in North America to derive an empirical gas-particle partitioning relationship log 10(K 1 ) = (10±1)- (2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in µg m 3 , and T in K. This relationship is within the range of previ- ous work but is based on far more extensive data from mul- tiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) be- tween the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with lit- tle aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more effi- cient scavenging of Particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North Ameri- can surface sites suggests that subsidence from the free tro- posphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associ- ated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduc- tion of Hg(II) emitted from coal combustion and by assum- ing that anthropogenic Particulate Hg(p) behaves as semi- volatile Hg(II) rather than as a refractory Particulate compo- nent. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout al- gorithm. The observed wintertime minimum in wet depo- sition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).
Eliezer Masliah - One of the best experts on this subject based on the ideXlab platform.
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expression pattern of synucleins non aβ Component of alzheimer s disease amyloid precursor protein α synuclein during murine brain development
Journal of Neurochemistry, 2002Co-Authors: Margaret Mallory, Isaac Veinbergs, Makoto Hashimoto, Makoto Yoshimoto, Leon J Thal, Tsunao Saitoh, Eliezer MasliahAbstract:Abstract: The non-Aβ Component of Alzheimer's disease amyloid precursor protein (NACP) is predominantly a neuron-specific presynaptic protein that may play a central role in neurodegeneration because NACP fragments are found in Alzheimer's disease amyloid and a mutation in the NACP gene is associated with familial Parkinson's disease. In addition, NACP may play an important role during synaptogenesis and CNS development. To understand better the patterns of NACP expression during development, we analyzed the levels of this protein as well as the levels of another synaptic protein (synaptophysin) by ribonuclease protection assay, western blotting, and immunocytochemistry in fetal, juvenile, and adult mouse brain. From embryonic day 12 to 15, there was a slight increase, which was then followed by a more dramatic increase at later time points. Immunocytochemical staining for NACP increases throughout these stages as well. Although NACP appeared early in CNS development, synaptophysin levels started to rise at a later stage. These findings support the contention that NACP might be important for CNS development. Furthermore, the cytosolic Component of NACP precedes the Particulate Component in development, indicating that a redistribution of the protein to the membrane fraction may be important for events later in neuronal development and in synaptogenesis.
K. Sioud - One of the best experts on this subject based on the ideXlab platform.
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Partitioning of trace metals between the dissolved and Particulate phases and Particulate surface reactivity in the Lena River estuary and the Laptev Sea (Russia)
Marine Chemistry, 1996Co-Authors: J.-m. Garnier, J.-m. Martin, Jean-marie Mouchel, K. SioudAbstract:Trace metal distribution between suspended matter and dissolved phase has been determined in an organic rich aquatic system: the Lena River estuary and the adjacent Laptev Sea. The partitioning between dissolved and Particulate phases of Cs Cd, Co, Cs, Mn and Zn is determined through the so- called fast distribution coefficient (FDC). Application of a surface complexation model has been attempted so as to describe the FDC's variations in the estuarine system. The relative effects of inorganic dissolved species and colloidal and Particulate reactivity on FDC are discussed. The Particulate reactivity is related either to the composition of the Particulate Component (mineral and organic) or to the bulk Particulate surface properties such as the ammonium saturation index or the heat of immersion in water. For Cd, the low FDC variation with the salinity can be explained by the variation of the chloro and sulphato dissolved species, by the complexation of some colloidal organic species and by a high Particulate surface reactivity. The complexation constant of the Particulate phase (log K(s(Cd))) has been calculated equal to 5.2. Zn exhibits a similar range of FDC variations but the scattered relationship with salinity does not allow an identification of the determining parameters. Co and Mn exhibit similar behaviours. The high changes in their FDC (compared to Cd) have been simulated by a surface complexation model in which the effect of the major cations (Ca2+ and Mg2+) is taken into account. The complexation constant of the Particulate phase (log K(s(Mn))) and log K(s(Co)) calculated from the model is 7.2. For Cs, the competitive sorption with K+ chiefly controls the change in FDC. Using the number of sites given by the ammonium saturation index, a mean value of the Particulate complexation constant (log K(s(Cs))) has been estimated to be 5.1. Implications of the low temperature of the water in the studied area on the trace metal sorption on the Particulate phase are discussed.
H M Amos - One of the best experts on this subject based on the ideXlab platform.
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gas particle partitioning of atmospheric hg ii and its effect on global mercury deposition
Atmospheric Chemistry and Physics, 2011Co-Authors: H M Amos, Daniel J Jacob, Christopher D Holmes, Jenny A Fisher, Qiaoqiao Wang, Robert M Yantosca, Elizabeth Sturges Corbitt, Elisabeth Galarneau, Andrew P Rutter, Mae Sexauer GustinAbstract:Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous Component of Hg(II)), particle-bound mercury (PBM, the Particulate Component of Hg(II)), fine Particulate matter (PM 2.5), and temperature (T ) at five sites in North America to derive an empirical gas-particle partitioning relationship log 10(K 1 ) = (10±1)- (2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in µg m 3 , and T in K. This relationship is within the range of previ- ous work but is based on far more extensive data from mul- tiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) be- tween the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with lit- tle aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more effi- cient scavenging of Particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North Ameri- can surface sites suggests that subsidence from the free tro- posphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associ- ated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduc- tion of Hg(II) emitted from coal combustion and by assum- ing that anthropogenic Particulate Hg(p) behaves as semi- volatile Hg(II) rather than as a refractory Particulate compo- nent. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout al- gorithm. The observed wintertime minimum in wet depo- sition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).
M. A. Russell - One of the best experts on this subject based on the ideXlab platform.
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Sediment-associated nutrient transport in UK rivers
1997Co-Authors: Desmond E. Walling, B. W. Webb, M. A. RussellAbstract:Monitoring programmes established to document river nutrient loads have commonly focused on quantifying total loads, without distinguishing between the dissolved and Particulate Components. There is now a growing recognition of the need to distinguish these two Components which may exhibit contrasting behaviour and reflect different sources and controls. Few reliable data are currently available with which to assess the role of sediment-asso ciated transport in nutrient transport by British rivers and this contribution reports the results of a study aimed at assessing this role for four contrasting river basins in Britain. The study rivers were selected to embrace a range of basin characteristics and include the River Severn, the Warwickshire Avon, the River Exe and its tributary the River Dart. Detailed monitoring of the N and P loads transported by these four rivers was undertaken during the period January to December 1995, and the dissolved and sediment-associated Components of the total N and P flux were determined with a view to assessing the significance of the latter Component. Significant differences existed between the four rivers in terms of both specific N and P yields and the relative contribution of the Particulate Component. These contrasts reflected variations in the magnitude of the specific suspended sediment yields and in the relative importance of point and non-point sources as well as other basin characteristics. In the case of phosphorus, sediment-associated transport accounted for between 26.3% and 75.4% of the annual total P load of the study rivers, whereas for N the sediment-associated contribution was much less and ranged between 3.3% and 8.0%. The magnitude of the sediment-associated contribution varied through the year in response to a number of controls, including the seasonal pattern of suspended sediment transport.