Airborne sampling of aerosol particles: Comparison between surface sampling at Christmas Island and P-3 sampling during PEM-Tropics B

Bulk aerosol sampling of soluble ionic compounds from the NASA Wallops Island P-3 aircraft and a tower on Christmas Island during PEM-Tropics B provides an opportunity to assess the magnitude of particle losses in the University of New Hampshire airborne bulk aerosol sampling system. We find that most aerosol-associated ions decrease strongly with height above the sea surface, making direct comparisons between mixing ratios at 30 m on the tower and the lowest flight level of the P-3 (150 m) open to interpretation. Theoretical considerations suggest that vertical gradients of sea-salt aerosol particles should show exponential decreases with height. Observed gradients of Na+ and Mg2+, combining the tower observations with P-3 samples collected below 1 km, are well described by exponential decreases (r values of 0.88 and 0.87, respectively), though the curve fit underestimates average mixing ratios at the surface by 25%. Cascade impactor samples collected on the tower show that \u3e99% of the Na+ and Mg2+mass is on supermicron particles, 65% is in the 1–6 micron range, and just 20% resides on particles with diameters larger than 9 microns. These results indicate that our airborne aerosol sampling probes must be passing particles up to at least 6 microns with high efficiency. We also observed that nss SO42− and NH4+, which are dominantly on accumulation mode particles, tended to decrease between 150 and 1000 m, but they were often considerably higher at the lowest P-3 sampling altitudes than at the tower. This finding is presently not well understood

Expression of LIM kinase 1 is associated with reversible G1/S phase arrest, chromosomal instability and prostate cancer

<p>Abstract</p> <p>Background</p> <p>LIM kinase 1 (LIMK1), a LIM domain containing serine/threonine kinase, modulates actin dynamics through inactivation of the actin depolymerizing protein cofilin. Recent studies have indicated an important role of LIMK1 in growth and invasion of prostate and breast cancer cells; however, the molecular mechanism whereby LIMK1 induces tumor progression is unknown. In this study, we investigated the effects of ectopic expression of LIMK1 on cellular morphology, cell cycle progression and expression profile of LIMK1 in prostate tumors.</p> <p>Results</p> <p>Ectopic expression of LIMK1 in benign prostatic hyperplasia cells (BPH), which naturally express low levels of LIMK1, resulted in appearance of abnormal mitotic spindles, multiple centrosomes and smaller chromosomal masses. Furthermore, a transient G1/S phase arrest and delayed G2/M progression was observed in BPH cells expressing LIMK1. When treated with chemotherapeutic agent Taxol, no metaphase arrest was noted in these cells. We have also noted increased nuclear staining of LIMK1 in tumors with higher Gleason Scores and incidence of metastasis.</p> <p>Conclusion</p> <p>Our results show that increased expression of LIMK1 results in chromosomal abnormalities, aberrant cell cycle progression and alteration of normal cellular response to microtubule stabilizing agent Taxol; and that LIMK1 expression may be associated with cancerous phenotype of the prostate.</p

Radiative forcing in the 21st century due to ozone changes in the troposphere and the lower stratosphere

Radiative forcing due to changes in ozone is expected for the 21st century. An assessment on changes in the tropospheric oxidative state through a model intercomparison ("OxComp'') was conducted for the IPCC Third Assessment Report (IPCC-TAR). OxComp estimated tropospheric changes in ozone and other oxidants during the 21st century based on the "SRES'' A2p emission scenario. In this study we analyze the results of 11 chemical transport models (CTMs) that participated in OxComp and use them as input for detailed radiative forcing calculations. We also address future ozone recovery in the lower stratosphere and its impact on radiative forcing by applying two models that calculate both tropospheric and stratospheric changes. The results of OxComp suggest an increase in global-mean tropospheric ozone between 11.4 and 20.5 DU for the 21st century, representing the model uncertainty range for the A2p scenario. As the A2p scenario constitutes the worst case proposed in IPCC-TAR we consider these results as an upper estimate. The radiative transfer model yields a positive radiative forcing ranging from 0.40 to 0.78 W m(-2) on a global and annual average. The lower stratosphere contributes an additional 7.5-9.3 DU to the calculated increase in the ozone column, increasing radiative forcing by 0.15-0.17 W m(-2). The modeled radiative forcing depends on the height distribution and geographical pattern of predicted ozone changes and shows a distinct seasonal variation. Despite the large variations between the 11 participating models, the calculated range for normalized radiative forcing is within 25%, indicating the ability to scale radiative forcing to global-mean ozone column change

Wet deposition in a global size-dependent aerosol transport model 1. Comparison of a I year løpb simulation with ground measurements

International audienceWe present and discuss results from a 1 year (1991) global simulation of the transport and deposition of •øPb with a new size-resolved aerosol transport model. The model accounts for aerosol size distribution and its evolution during transport. Our wet deposition scheme is size-dependent and distinguishes between scavenging by deep and shallow convective rains. It treats separately below-and in-cloud scavenging by synoptic rains. Although the model is formulated to treat all aerosol sizes, the vahdation was done for the •øPb submicronic aerosol for which the main sink is wet deposition. We assess the model transport and deposition of submicron aerosols by a comparison of model results with available surface measurements. Annual mean surface concentrations are compared at 117 stations throughout the globe; seasonal variations are examined for 35 of these sites. The mean bias between simulated and measured yearly averaged surface concentrations is-2.7%, and the correlation coefficient is 0.80. The observed seasonal cycle and the annual mean concentrations are particularly well reproduced, although the model's poor vertical resolution does not capture the strong winter peak at some continental stations, nor the transport to Indian Ocean stations. Using the observed precipitation at or near the sites studied, we were able to explain a large part of the bias in model annual deposition. Deposition at coastal sites deserves also a special treatment since influenced by the land-ocean partition inherent to the model. When we represent correctly these coastal stations, we reduce the mean bias between observed and predicted annual deposition fluxes from 7.7% to 1.2% at 147 stations, and the correlation coefficient improves from 0.70 to 0.77

Global simulation of the mineral aerosol distribution and its effect on the radiation balance

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Model Components Necessary to Capture a Dust Plume Pattern Over the Mediterranean Sea

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Remote sensing of airborne desert dust mass over oceans using Meteosat and CZCS imagery

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