In this study the runoff of
137Cs, mainly originated from the Chernobyl fallout, from highly contaminated alpine regions in Salzburg (Austria) is discussed.
Twenty-five water-samples and 25 ...sediment-samples were taken from creeks of different size to determine the runoff of dissolved
137Cs and Cs-binding characteristics to different particle size classes in the sediments. The hypothesis, that specific activity of the sediments depended on particle size and the surface of the particle, was proved with some modifications. Caesium activity concentration in water showed a negative correlation with electrical conductivity, while no significant correlations were detectable with other variables (pH, temperature, and altitude). Enormous differences and the variations found in the
137Cs-concentrations in water can be explained by the electrical conductivity without any dependency on the inventory of the catchment.
The sediment samples analysed showed a negative correlation between specific activity Bq/kg and particle-diameter, mainly explained by
137Cs-uptake proportional to the particle surface per mass.
Platinum-group element (Os, Ir, Ru, Pt and Pd) abundances and Re–Os isotopic composition of fifteen peridotites (eleven spinel lherzolites and four spinel harzburgites) from the Mamonia complex, ...Cyprus, were determined as well as major and trace element compositions of bulk-rocks and minerals. Spinel lherzolites show excellent correlation between parameters indicating the degree of melting — e.g. Fo content in olivine, Cr# (Cr/(Cr
+
Al)) of Cr-spinel, Al and Yb concentrations in clinopyroxene. The degree of partial melting, calculated using Cr-spinel compositions, range from 1% to 9%. The PGE contents in spinel lherzolites show correlation with each other and with the spinel compositions, and thus can be related to the partial melting of the mantle source. The PGE abundances of the mantle source are estimated using the least depleted spinel lherzolite samples: Os 3.6
±
0.5, Ir 3.4
±
0.5, Ru 6.5
±
0.9, Pt 6.1
±
0.2, Pd 3.9
±
0.2 (in ppb).
Spinel harzburgites, despite a good correlation between the whole rock major element abundances and mineral compositions (e.g., Yb in clinopyroxene and Cr# of spinel), indicate no relationship between the Fo content of olivine and the Cr# of spinel. Hence, the harzburgites cannot be the residuum of simple partial melting, but have a more complex origin (e.g. melt percolation). Pt/Ir ratios increase in the harzburgites as Pt increases. Similar behavior of Pt and Pd is observed in abyssal and SCLM harzburgites, and explained by sulfide precipitation during melt percolation.
Rhenium concentrations in most Mamonia peridotites are significantly higher than in the primitive mantle and does not show correlations with PGE. Indeed Re concentrations tend to increase with the Cr# of spinel. Thus its distribution is not governed by partial melting and we suggest that Re addition to the peridotites of Mamonia occurred during serpentinization.
The Re–Os model ages of peridotites form three age clusters at 250 Ma, 600–800 Ma and >
1000 Ma. The youngest age is consistent with the age of magmatic rocks in the Mamonia Complex, whereas the “oldest” peridotites may belong to remnants of the subcontinental mantle.
•We model the flow of a rheological, more viscous, heterogeneity in a mantle plume.•Stretching of the heterogeneity depends on the viscosity ratio and on the plume flow.•A blob-like-shape is more ...easily preserved in a plume with a low buoyancy flux.•Intra-conduit mixing induced by a rheological heterogeneity is minor.•We discuss the implications for Hawaii and for French Polynesian hotspots.
The geochemical record of Hawaiian basalts has been interpreted to reflect vertically stretched, partly filament-like heterogeneities in the Hawaiian plume, but one alternative interpretation has been that this record reflects intra-conduit mixing, caused by rheological contrasts across the conduit. Here we present numerical simulations of a mantle plume carrying rheological heterogeneities λ times more viscous than the surrounding fluid. Our first objective is to quantify how the heterogeneity deforms during upwelling. We find a full spectrum of shapes, from stretched filaments to nearly undeformed blobs, and we map the respective stability domain as a function of the viscosity ratio λ and of the flow characteristics, including the plume buoyancy flux. Our second objective is to test the hypothesis that a rheological heterogeneity can cause intra-conduit mixing. Although horizontal velocities do appear across the plume conduit, we have not found any toroidal “doughnut-shaped swirl” mode. Instead we show that perturbations of the flow trajectories are a local phenomenon, unable to cause permanent mixing. Our third objective is to determine over which time-scales a rheological heterogeneity crosses the magma capture zone (MCZ) beneath a hotspot volcano. For a blob-like heterogeneity of radius 30–40 km and viscosity ratio 15–20, the crossing time-scale is less than 1 Myr. Contrary to a stretched filament, a blob can entirely fill the MCZ, thereby representing the unique source rock of partial melts feeding a volcano. If the heterogeneity has a distinct isotopic fingerprint (or a distinct fertility), surface lavas will then record an isotopic fluctuation (or a fluctuation in melt productivity) lasting 0.5–0.8 Myr. Our simulations predict that such fluctuations should occur preferentially in low buoyancy flux hotspots, where blob-like rheological heterogeneities are more easily preserved than in the vigorous Hawaiian plume.
The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the ...‘first stars’, which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the γ-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of γ-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources—in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to γ-rays than previously thought.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A quantification of proteins of different molecular size has been shown to be useful in characterizing the mechanism and medical causes of proteinuria. By analyzing urine albumin, α1-microglobulin, ...immunoglobulin G and α2-macroglobulin together with total protein, prerenal, glomerular, tubular and postrenal causes of proteinuria can be detected and differentiated by their specific urine protein patterns. Using automated turbidimetric procedures, prerenal proteinurias are characterized by an albumin/total protein ratio below 0.4. Tubulo-interstitial diseases which are negative in the protein test strip procedure are detected and clearly differentiated from other causes of proteinuria by their high α1-microglobulin/albumin ratios. In postrenal proteinuria, α2-macroglobulin proved to be a useful marker, when albumin excretion exceeds 100 mg/l urine. This protein exhibits plasma-like ratios to albumin in postrenal causes, whereas it is much lower in renal proteinurias. The new strategy, which has been evaluated in more than 500 clinically and partly histologically proven cases of renal diseases, more sensitively detects glomerular and tubulo-interstitial diseases when applied in urine screening and allows us to distinguish all clinically important causes from analysis of a morning spot urine sample.
The relationship between localized fluid dynamics and localized particle deposition patterns within bronchial airway bifurcations upon inspiration and expiration was analyzed for different ...bifurcation geometries, flow conditions, and particle sizes. For the simulation of three-dimensional airflow patterns in airway bifurcation models, the Navier-Stokes and continuity equations were solved numerically by the finite volume Computational Fluid Dynamics (CFD) program package FIRE. Spatial particle deposition patterns were determined by the intersection of randomly selected particle trajectories with the surrounding wall surfaces. While three-dimensional flow patterns were characterized by their corresponding two-dimensional secondary flow fields, three-dimensional deposition patterns were represented by their related two-dimensional deposition density plots. Two particle sizes were selected to explore the relationship between secondary flows and localized particle deposition patterns: 0.01 w m, to illustrate the effects of Brownian motion, and 10 w m, to display the effects of impaction and sedimentation. Changes in bifurcation geometry (shape of bifurcation zone, branching angle) and flow conditions (flow rate, inlet flow profile, direction of flow) lead to variations in resulting secondary flow patterns, which were reflected by corresponding differences in related particle deposition patterns. In conclusion, a distinct relationship could be observed between secondary flow patterns and deposition density plots, demonstrating that particle deposition patterns in airway bifurcations are not only determined by physical forces acting upon individual particles, but also by convective transport processes of the carrier fluid.
Aerosol deposition studies with tracheobronchial casts and models have demonstrated that inhaled particles are preferentially deposited within transitional bifurcation zones, exhibiting hot spots in ...the vicinity of carinal ridges. The goal of the present study is to quantify the inhomogeneity of theoretically predicted deposition patterns by local deposition enhancement factors. First, inspiratory particle deposition patterns of unattached (1 nm), ultrafine (10 nm and 20 nm), and attached (100 nm and 200 nm) radon progeny within three-dimensional models of segmental bronchial airway bifurcations were simulated by a numerical fluid dynamics and particle trajectory model. Second, local deposition enhancement factors were computed by scanning along the surface of the bifurcation models with prespecified surface area elements. Maximum values and frequency distributions of local deposition enhancement factors of inhaled radon progeny were derived for different sizes of the scanning element in a "narrow" and a "physiologically realistic" bifurcation model and for two different flow rates (10 L min(-1) and 60 L min(-1) in the trachea). Computed enhancement factors indicate that cells located at carinal ridges may receive localized doses which are 20-40 times (1 nm) and 50-115 times higher (10 nm-200 nm), respectively, than the corresponding average doses. This may have important implications for the microdosimetry of inhaled radon progeny and the resulting lung cancer risk.
A significant reduction of catalase activity, a peroxisomal marker enzyme, occurs in human hepatic neoplasias, but no information is available on other peroxisomal proteins. We have studied by means ...of immunohistochemistry four specific proteins of peroxisomes (catalase and three enzymes of lipid beta-oxidation) in human hepatocellular tumors of various differentiation grades from adenoma to anaplastic carcinoma. In all tumors, except the adenomas, the tumor cells contained fewer peroxisomes than extrafocal hepatocytes and the reduction of antigenic sites in the tumor types generally correlated with the degree of tumor dedifferentiation as assessed by classical histopathological criteria. Two poorly differentiated tumors had no detectable peroxisomes at all. There were no major differences in the intensities of the immunocytochemical staining for all four studied peroxisomal antigens in different tumors, suggesting that the neoplastic transformation affects the biogenesis of the entire organelle and not merely the individual peroxisomal enzyme proteins. Some tumors exhibited a distinct peripheral distribution of peroxisomes. In cases with associated liver cirrhosis, the hepatocytes in the adjacent liver showed marked peroxisome proliferation, forming large perinuclear aggregates, occupying occasionally the entire cytoplasm. Taken together, our observations indicate that peroxisomes are significantly altered in both hepatocellular tumors and liver cirrhosis and, thus, could be responsible for some of the metabolic derangements observed in those disease processes.
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