Comparative evaluation of the impact of WRF/NMM and WRF/ARW meteorology on CMAQ simulations for PM_2.5 and its related precursors during the 2006 TexAQS/GoMACCS study

This study presents a comparative evaluation of the impact of WRF-NMM and WRF-ARW meteorology on CMAQ simulations of PM_2.5, its composition and related precursors over the eastern United States with the intensive observations obtained by aircraft (NOAA WP-3), ship and surface monitoring networks (AIRNow, IMPROVE, CASTNet and STN) during the 2006 TexAQS/GoMACCS study. The results at the AIRNow surface sites show that both ARW-CMAQ and NMM-CMAQ reproduced day-to-day variations of observed PM_2.5 and captured the majority of observed PM_2.5 within a factor of 2 with a NMB value of −0.4% for ARW-CMAQ and −18% for NMM-CMAQ. Both models performed much better at the urban sites than at the rural sites, with greater underpredictions at the rural sites. Both models consistently underestimated the observed PM_2.5 at the rural IMPROVE sites by −1% for the ARW-CMAQ and −19% for the NMM-CMAQ. The greater underestimations of SO₄²⁻, OC and EC by the NMM-CMAQ contributed to increased underestimation of PM_2.5 at the IMPROVE sites. The NMB values for PM_2.5 at the STN urban sites are 15% and −16% for the ARW-CMAQ and NMM-CMAQ, respectively. The underestimation of PM_2.5 at the STN sites by the NMM-CMAQ mainly results from the underestimations of the SO₄²⁻, NH₄⁺ and TCM components, whereas the overestimation of PM_2.5 at the STN sites by the ARW-CMAQ results from the overestimations of SO₄²⁻, NO₃⁻, and NH₄⁺. The Comparison with WP-3 aircraft measurements reveals that both ARW-CMAQ and NMM-CMAQ have very similar model performance for vertical profiles for PM_2.5 chemical components (SO₄²⁻, NH₄⁺) and related gaseous species (HNO₃, SO₂, NH₃, isoprene, toluene, terpenes) as both models used the same chemical mechanisms and emissions. The results of ship along the coast of southeastern Texas over the Gulf of Mexico show that both models captured the temporal variations and broad synoptic change seen in the observed HCHO and acetaldehyde with the means NMB <30% most of the time but they consistently underestimated terpenes, isoprene, toluene and SO₂

Key stages in mammary gland development - Involution: apoptosis and tissue remodelling that convert the mammary gland from milk factory to a quiescent organ

Involution of the mammary gland is an essential process that removes the milk-producing epithelial cells when they become redundant at weaning. It is a two-step process that involves the death of the secretory epithelium and its replacement by adipo-cytes. During the first phase, remodelling is inhibited and apoptotic cells can be seen in the lumena of the alveoli. In the second phase, apoptosis is accompanied by remodelling of the surrounding stroma and re-differentiation of the adipocytes. Considerable effort has been directed towards understanding the molecular mechanisms of the involution process and this has resulted in the identification of the principal signalling pathways involved

Impact of a new condensed toluene mechanism on air quality model predictions in the US

A new condensed toluene mechanism is incorporated into the Community Multiscale Air Quality Modeling system. Model simulations are performed using the CB05 chemical mechanism containing the existing (base) and the new toluene mechanism for the western and eastern US for a summer month. With current estimates of tropospheric emission burden, the new toluene mechanism increases monthly mean daily maximum 8-h ozone by 1.0-3.0 ppbv in Los Angeles, Portland, Seattle, Chicago, Cleveland, northeastern US, and Detroit compared to that with the base toluene chemistry. It reduces model mean bias for ozone at elevated observed ozone concentrations. While the new mechanism increases predicted ozone, it does not enhance ozone production efficiency. A sensitivity study suggests that it can further enhance ozone if elevated toluene emissions are present. While it increases in-cloud secondary organic aerosol substantially, its impact on total fine particle mass concentration is small

In situ diagnostic of two-phase flow phenomena in polymer electrolyte fuel cells by neutron imaging: Part B. Material variations

The formation of liquid water in operating polymer electrolyte fuel cells (PEFC) of industrial and laboratory size has been investigated by in situ neutron imaging. The influence of the materials chosen for the structural components of the cell on droplet formation and transport in flow fields and on liquid formation in gas diffusion layers has been studied. The changing of the cathodic gas diffusion layer material allowed the relationship between materials, liquid accumulation, and electrochemical performance to be examined. It has been shown that material choice has considerable bearing on the presence of liquid inside the porous structures and the electrochemical characteristics. A simplified quasi one-dimensional cell with an active area of 25 cm(2) was used for materials comparison, and the results were related to technically relevant operating conditions - where inhomogeneities have to be considered - by subsequent examination of cells with an active area of 100 cm(2)

PMCA2 regulates apoptosis during mammary gland involution and predicts outcome in breast cancer

After lactation, weaning causes mammary epithelial cell (MEC) apoptosis. MECs express the plasma membrane calcium-ATPase 2 (PMCA2), which transports calcium across the apical surface of the cells into milk. Here we show that PMCA2 is down-regulated early in mammary involution associated with changes in MEC shape. We demonstrate that loss of PMCA2 expression raises intracellular calcium levels and sensitizes MECs to apoptosis. In contrast, overexpression of PMCA2 in T47D breast cancer cells lowers intracellular calcium and protects them from apoptosis. Finally, we show that high PMCA2 expression in breast cancers is associated with poor outcome. We conclude that loss of PMCA2 expression at weaning triggers apoptosis by causing cellular calcium crisis. PMCA2 overexpression, on the other hand, may play a role in breast cancer progression by conferring resistance to apoptosis