229 research outputs found
Statistical diagnostic and correction of a chemistry-transport model for the prediction of total column ozone
International audienceIn this paper, we introduce a statistical method for examining and adjusting chemical-transport models. We illustrate the findings with total column ozone predictions, based on the University of Illinois at Urbana-Champaign 2-D (UIUC 2-D) chemical-transport model of the global atmosphere. We propose a general diagnostic procedure for the model outputs in total ozone over the latitudes ranging from 60° South to 60° North to see if the model captures some typical patterns in the data. The method proceeds in two steps to avoid possible collinearity issues. First, we regress the measurements given by a cohesive data set from the SBUV(/2) satellite system on the model outputs with an autoregressive noise component. Second, we regress the residuals of this first regression on the solar flux, the annual cycle, the Antarctic or Arctic Oscillation, and the Quasi Biennial Oscillation. If the coefficients from this second regression are statistically significant, then they mean that the model did not simulate properly the pattern associated with these factors. Systematic anomalies of the model are identified using data from 1979 to 1995, and statistically corrected afterwards. The 1996?2003 validation sample confirms that the combined approach yields better predictions than the direct UIUC 2-D outputs
Levels of α7 integrin and laminin-α2 are increased following prednisone treatment in the mdx mouse and GRMD dog models of Duchenne muscular dystrophy
SUMMARY
Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disease for which there is no cure and limited treatment options. Prednisone is currently the first line treatment option for DMD and studies have demonstrated that it improves muscle strength. Although prednisone has been used for the treatment of DMD for decades, the mechanism of action of this drug remains unclear. Recent studies have shown that the α7β1 integrin is a major modifier of disease progression in mouse models of DMD and is therefore a target for drug-based therapies. In this study we examined whether prednisone increased α7β1 integrin levels in mdx mouse and GRMD dog models and myogenic cells from humans with DMD. Our results show that prednisone promotes an increase in α7 integrin protein in cultured myogenic cells and in the muscle of mdx and GRMD animal models of DMD. The prednisone-mediated increase in α7 integrin was associated with increased laminin-α2 in prednisone-treated dystrophin-deficient muscle. Together, our results suggest that prednisone acts in part through increased merosin in the muscle basal lamina and through sarcolemmal stabilization of α7β1 integrin in dystrophin-deficient muscle. These results indicate that therapies that target an increase in muscle α7β1 integrin, its signaling pathways and/or laminin could be therapeutic in DMD
U.S. GLOBAL CHANGE RESEARCH PROGRAM CLIMATE SCIENCE SPECIAL REPORT (CSSR)
Fifth-Order Draft
Table of Contents
Front Matter
About This Report........................................................................................ 1
Guide to the Report......................................................................................4
Executive Summary ................................................................................... 12
Chapters
1. Our Globally Changing Climate .......................................................... 38
2. Physical Drivers of Climate Change ................................................... 98
3. Detection and Attribution of Climate Change .................................... 160
4. Climate Models, Scenarios, and Projections .................................... 186
5. Large-Scale Circulation and Climate Variability ................................ 228
6. Temperature Changes in the United States ...................................... 267
7. Precipitation Change in the United States ......................................... 301
8. Droughts, Floods, and Hydrology ......................................................... 336
9. Extreme Storms ....................................................................................... 375
10. Changes in Land Cover and Terrestrial Biogeochemistry ............ 405
11. Arctic Changes and their Effects on Alaska and the Rest of the United States..... 443
12. Sea Level Rise ....................................................................................... 493
13. Ocean Acidification and Other Ocean Changes .............................. 540
14. Perspectives on Climate Change Mitigation .................................... 584
15. Potential Surprises: Compound Extremes and Tipping Elements .......... 608
Appendices
A. Observational Datasets Used in Climate Studies ............................. 636
B. Weighting Strategy for the Fourth National Climate Assessment ................ 642
C. Detection and Attribution Methodologies Overview ............................ 652
D. Acronyms and Units ................................................................................. 664
E. Glossary ...................................................................................................... 66
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Significance of long-range transport from continental locations in determining oxidant mixing ratios and budgets over the tropical Pacific Ocean.
U.S. GLOBAL CHANGE RESEARCH PROGRAM CLIMATE SCIENCE SPECIAL REPORT (CSSR)
Fifth-Order Draft
Table of Contents
Front Matter
About This Report........................................................................................ 1
Guide to the Report......................................................................................4
Executive Summary ................................................................................... 12
Chapters
1. Our Globally Changing Climate .......................................................... 38
2. Physical Drivers of Climate Change ................................................... 98
3. Detection and Attribution of Climate Change .................................... 160
4. Climate Models, Scenarios, and Projections .................................... 186
5. Large-Scale Circulation and Climate Variability ................................ 228
6. Temperature Changes in the United States ...................................... 267
7. Precipitation Change in the United States ......................................... 301
8. Droughts, Floods, and Hydrology ......................................................... 336
9. Extreme Storms ....................................................................................... 375
10. Changes in Land Cover and Terrestrial Biogeochemistry ............ 405
11. Arctic Changes and their Effects on Alaska and the Rest of the United States..... 443
12. Sea Level Rise ....................................................................................... 493
13. Ocean Acidification and Other Ocean Changes .............................. 540
14. Perspectives on Climate Change Mitigation .................................... 584
15. Potential Surprises: Compound Extremes and Tipping Elements .......... 608
Appendices
A. Observational Datasets Used in Climate Studies ............................. 636
B. Weighting Strategy for the Fourth National Climate Assessment ................ 642
C. Detection and Attribution Methodologies Overview ............................ 652
D. Acronyms and Units ................................................................................. 664
E. Glossary ...................................................................................................... 66
Effects of stratospheric aerosol surface processes on the LLNL two-dimensional zonally averaged model
We have investigated the effects of incorporating representations of heterogeneous chemical processes associated with stratospheric sulfuric acid aerosol into the LLNL two-dimensional, zonally averaged, model of the troposphere and stratosphere. Using distributions of aerosol surface area and volume density derived from SAGE II satellite observations, we were primarily interested in changes in partitioning within the Cl- and N- families in the lower stratosphere, compared to a model including only gas phase photochemical reactions. We have considered the heterogeneous hydrolysis reactions N2O5 + H2O(aerosol) yields 2 HNO3 and ClONO2 + H2O(aerosol) yields HOCl + HNO3 alone and in combination with the proposed formation of nitrosyl sulfuric acid (NSA) in the aerosol and its reaction with HCl. Inclusion of these processes produces significant changes in partitioning in the NO(y) and ClO(y) families in the middle stratosphere
Aircraft Emissions: Current Inventories and Future Scenarios
Three-dimensional (latitude, longitude, altitude) global inventories of civil and military aircraft fuel burned and emissions have been developed for the United States National Aeronautics and Space Administration (NASA) for the years 1976, 1984, and 1992, and by the European Abatement of Nuisances Caused by Air Transport (ANCAT)/European Commission (EC) Working Group and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) for 1991/92. For 1992, the results of the inventory calculations are in good agreement, with total fuel used by aviation calculated to be 129.3 Tg (DLR), 131.2 Tg (ANCAT), and 139.4 Tg (NASA). Total emissions of NOx (as N02) in 1992 were calculated to range from 1.7 Tg (NASA) to 1.8 Tg (ANCAT and DLR).
Forecasts of air travel demand and technology developed by NASA and ANCAT for 2015 have been used to create three-dimensional (3-D) data sets of fuel burn and NOx emissions for purposes of modeling the near-term effects of aircraft. The NASA 2015 forecast results in a global fuel burn of 309 Tg, with a NOx emission of 4.1 Tg (as N02); the global emission index, EI(NOx) (g NOx/kg fuel), is 13.4. In contrast, the ANCAT 2015 forecast results in lower values-a global fuel burn of 287 Tg, an emission of 3.5 Tg of NOx and a global emission index of 12.3. The differences arise from the distribution of air travel demand and technology assumptions
Modelling future changes to the stratospheric source gas injection of biogenic bromocarbons
Simulations with a chemistry-climate model (CCM) show a future increase in the stratospheric source gas injection (SGI) of biogenic very short-lived substances (VSLS). For 2000, the modelled SGI of bromine from VSLS is similar to 1.7 parts per trillion (pptv) and largest over the tropical West Pacific. For 2100, this increases to similar to 2.0 and similar to 2.7 pptv when the model is forced with Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways (RCPs) 4.5 and 8.5. The increase is largely due to stronger tropical deep convection transporting more CHBr3 to the lower stratosphere. For CH2Br2, CHBr2Cl, CH2BrCl and CHBrCl2, changes to primary oxidant OH determines their SGI contribution. Under RCP 4.5 (moderate warming), OH increases in a warmer, more humid troposphere. Under RCP 8.5 (extreme warming) OH decreases significantly due to a large methane increase, allowing greater SGI of bromine from these VSLS. Potentially enhanced VSLS emissions in the future would further increase these estimates. Citation: Hossaini, R., et al. (2012), Modelling future changes to the stratospheric source gas injection of biogenic bromocarbons, Geophys. Res. Lett., 39, L20813, doi:10.1029/2012GL053401
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