Projection of time-mean geopotential heights onto normal,hough modes     

Dr. J. J. Tribbia  Dr. R. A. Madden 《Meteorology and Atmospheric Physics》1988,38(1-2):9-21

Summary Bernhard Haurwitz discussed theoretically the roles of forced stationary and traveling free waves in the atmosphere. At least some of the prediction errors of the large-scale weather are thought to result from the improper partitioning of energy between the forced stationary fields and free traveling or normal modes of the forecast models. Here we project observed average fields for a given time of the year onto normal modes of a forecast model. It is important to have estimates of how the stationary, forced fields project onto these modes since the model must partition energy correctly between the stationary, forced fields and real, traveling modes in order to more accurately predict the evolution of the large scales.With 6 Figures  相似文献   

Salinity and Chlorophyll a as Performance Measures to Rehabilitate a Mangrove-Dominated Deltaic Coastal Region: the Ci��naga Grande de Santa Marta�CPajarales Lagoon Complex, Colombia     

Victor H. Rivera-Monroy  Robert R. Twilley  J. Ernesto Mancera-Pineda  Christopher J. Madden  Ariel Alcantara-Eguren  E. Barry Moser  Bror F. Jonsson  Edward Casta?eda-Moya  Oscar Casas-Monroy  Paola Reyes-Forero  Jorge Restrepo 《Estuaries and Coasts》2011,34(1):1-19

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Bioreduction of hematite nanoparticles by the dissimilatory iron reducing bacterium Shewanella oneidensis MR-1     

Saumyaditya Bose  Michael F. Hochella Jr.  David W. Kennedy  Andrew S. Madden 《Geochimica et cosmochimica acta》2009,73(4):962-976

We examined the reduction of different size hematite (α-Fe₂O₃) nanoparticles (average diameter of 11, 12, 30, 43, and 99 nm) by the dissimilatory iron reducing bacteria (DIRB), Shewanella oneidensis MR-1, to determine how S. oneidensis MR-1 may utilize these environmentally relevant solid-phase electron acceptors. The surface-area-normalized-bacterial Fe(III) reduction rate for the larger nanoparticles (99 nm) was one order of magnitude higher than the rate observed for the smallest nanoparticles (11 nm). The Fe(III) reduction rates for the 12, 30, and 43 nm nanoparticles fell between these two extremes. Whole-cell TEM images showed that the mode of Fe₂O₃ nanoparticle attachment to bacterial cells was different for the aggregated, pseudo-hexagonal/irregular and platey 11, 12, and 99 nm nanoparticles compared to the non-aggregated 30 and 43 nm rhombohedral nanoparticles. Due to differences in aggregation, the 11, 12, and 99 nm nanoparticles exhibited less cell contact and less cell coverage than did the 30 and 43 nm nanoparticles. We hypothesize that S. oneidensis MR-1 employs both indirect and direct mechanisms of electron transfer to Fe(III)-oxide nanoparticles and that the bioreduction mechanisms employed and Fe(III) reduction rates depend on the nanoparticles’ aggregation state, size, shape and exposed crystal faces.  相似文献   

Long-Period Magnetotelluric Measurements Near the Central California Coast: A Land-Locked View of the Conductivity Structure Under the Pacific Ocean   总被引：2，自引：0，他引：2  

R. L. Mackie  B. R. Bennett  T. R. Madden 《Geophysical Journal International》1988,95(1):181-194

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Observations of OCS and a search for OC3S in the interstellar medium     

Matthews HE  MacLeod JM  Broten NW  Madden SC  Friberg P 《The Astrophysical journal》1987,315(2):646-653

Observations of OCS and a search for OC3S are reported, with particular reference to cold dust clouds. OCS has been detected for the first time in dark clouds with a mean fractional abundance relative to hydrogen of approximately 3 x 10(-9); this is approximately 4 times greater than that observed for giant molecular clouds. This results is discussed in the context of molecule formation mechanisms. Observations of the J = 1 --> 0 transition of OCS indicate that this transition is amplifying the background continuum radiation in the direction of Sgr B2.  相似文献   

Modeling projected changes of mangrove biomass in different climatic scenarios in the Sunda Banda Seascapes     

Mingshu Wang  Marguerite Madden  Ian Hendy  Estradivari  Gabby N. Ahmadia 《International Journal of Digital Earth》2017,10(4):457-468

ABSTRACT

Mangroves are critical in the ecological, economic and social development of coastal rural and urban communities. However, they are under threat by climate change and anthropogenic activities. The Sunda Banda Seascape (SBS), Indonesia, is among the world’s richest regions of mangrove biomass and biodiversity. To inform current and future management strategies, it is critical to provide estimates of how mangroves will respond to climate change in this region. Therefore, this paper utilized spatial analysis with model-based climatic indicators (temperature and precipitation) and mangrove distribution maps to estimate a benchmark for the mangrove biomass of the SBS in six scenarios, namely the Last Inter-glacial Period, the current scenario (1950–2000) and all four projected Representative Concentration Pathways in 2070 due to climate change. Despite mangroves gaining more biomass with climate change (the increase in CO₂ concentration), this paper highlighted the great proportion of below-ground biomass in mangrove forests. It also showed that the changes in spatial distribution of mangrove biomass became more variable in the context of climate change. As mangroves have been proposed as an essential component of climate change strategies, this study can serve as a baseline for future studies and resource management strategies.  相似文献   

Artificial muscle technology: physical principles and naval prospects   总被引：1，自引：0，他引：1  

Madden  J.D.W. Vandesteeg  N.A. Anquetil  P.A. Madden  P.G.A. Takshi  A. Pytel  R.Z. Lafontaine  S.R. Wieringa  P.A. Hunter  I.W. 《Oceanic Engineering, IEEE Journal of》2004,29(3):706-728

The increasing understanding of the advantages offered by fish and insect-like locomotion is creating a demand for muscle-like materials capable of mimicking nature's mechanisms. Actuator materials that employ voltage, field, light, or temperature driven dimensional changes to produce forces and displacements are suggesting new approaches to propulsion and maneuverability. Fundamental properties of these new materials are presented, and examples of potential undersea applications are examined in order to assist those involved in device design and in actuator research to evaluate the current status and the developing potential of these artificial muscle technologies. Technologies described are based on newly explored materials developed over the past decade, and also on older materials whose properties are not widely known. The materials are dielectric elastomers, ferroelectric polymers, liquid crystal elastomers, thermal and ferroelectric shape memory alloys, ionic polymer/metal composites, conducting polymers, and carbon nanotubes. Relative merits and challenges associated with the artificial muscle technologies are elucidated in two case studies. A summary table provides a quick guide to all technologies that are discussed.  相似文献   

Near‐infrared spectroscopy of a hydroecological indicator: new tool for determining sustainable yield for Floridan aquifer system     

Sydney T. Bacchus  Douglas D. Archibald  George A. Brook  Kerry O. Britton  Bruce L. Haines  Stephen L. Rathbun  Marguerite Madden 《水文研究》2003,17(9):1785-1809

Pond‐cypress (Taxodium ascendens Brong.) is a dominant canopy species in depressional wetlands of the south‐eastern Coastal Plain. Unsustainable withdrawals from the karst Floridan aquifer system have caused premature decline and death of pond‐cypress trees, presumably owing to altered hydroperiods (which alter the flow of water and nutrients in trees). There has been no scientifically based means to determine sustainable yield from this regional aquifer system or to detect early stages of physical/ecological damage associated with groundwater mining and aquifer storage and recovery (ASR, which also can alter natural hydroperiods). In this study, the relationship between visual symptoms (indicators) of stress or premature decline, and spectral reflectance was evaluated using dried, milled branch tips collected from natural stands of mature pond‐cypress. Depressional systems evaluated represented four of the six aquifer system subregions where subsurface perturbations from groundwater mining: (i) were presumed not to be occurring (reference wetlands); (ii) may be occurring but are not documented; and (iii) have been confirmed. Sampled trees were assigned to one of three stress classes (1, no/minimal; 2, moderate; 3, severe) based on the visual indicators. Partial least squares–linear discriminant analysis of second derivative spectral transformations in the visible/shortwave near‐infrared (NIR) region (400–1100 nm) and the NIR region (1100–2500 nm) was used to evaluate the samples in assigned classes. Class 1 samples were discriminated from combined class 2 and 3 samples in the NIR region with 100% and 97% accuracy for consecutive winter sample periods (before bud‐break). The percentage of correctly classified samples in this spectral region was lower (85%) for summer samples (full leaf‐out). Second‐derivative models for the NIR region developed from the winter data sets predicted assigned classes for alternate winter's samples with an accuracy of 97% and 100%. High correlation between spectral reflectance of dried, milled branch tips collected from mature pond‐cypress in winter and visual indicators of premature decline suggests in situ pond‐cypress are hydroecological indicators of anthropogenic subsurface hydroperiod perturbations. This approach provides objective means for early detection of unsustainable aquifer yield and adverse impacts from ASR activities in the south‐eastern Coastal Plain. Used in conjunction with hydrological monitoring and modelling, the hydroecological indicators should provide the means with which sustainable yield in the south‐eastern Coastal Plain can be achieved and maintained. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Hierarchical Bayesian modeling of spatio-temporal patterns of lung cancer incidence risk in Georgia,USA: 2000–2007     

Ping Yin  Lan Mu  Marguerite Madden  John E. Vena 《Journal of Geographical Systems》2014,16(4):387-407

Lung cancer is the second most commonly diagnosed cancer in both men and women in Georgia, USA. However, the spatio-temporal patterns of lung cancer risk in Georgia have not been fully studied. Hierarchical Bayesian models are used here to explore the spatio-temporal patterns of lung cancer incidence risk by race and gender in Georgia for the period of 2000–2007. With the census tract level as the spatial scale and the 2-year period aggregation as the temporal scale, we compare a total of seven Bayesian spatio-temporal models including two under a separate modeling framework and five under a joint modeling framework. One joint model outperforms others based on the deviance information criterion. Results show that the northwest region of Georgia has consistently high lung cancer incidence risk for all population groups during the study period. In addition, there are inverse relationships between the socioeconomic status and the lung cancer incidence risk among all Georgian population groups, and the relationships in males are stronger than those in females. By mapping more reliable variations in lung cancer incidence risk at a relatively fine spatio-temporal scale for different Georgian population groups, our study aims to better support healthcare performance assessment, etiological hypothesis generation, and health policy making.  相似文献   

Potential effects of obliquity change on gas hydrate stability zones on Mars     

Margaret J. Root  Megan E. Elwood Madden 《Icarus》2012,218(1):534-544

Methane hydrate dissociation due to obliquity-driven temperature change has been suggested as a potential source of atmospheric methane plumes recently observed on Mars. This work uses both equilibrium and time-dependent models to determine how geothermal gradients change on Mars as a result of obliquity and predict how these changes affect gas hydrate stability zones (HSZs). The models predict that the depth to the HSZ decreases with increasing latitude for both CO₂ and CH₄ hydrate, with CO₂ hydrate occurring at shallower depths than CH₄ hydrate over all latitudes. The depth of the HSZ increases as surface temperatures warm and decreases as surface temperatures cool with changing obliquity, with the largest change in HSZ volume predicted near the equator and the poles. Therefore, changes in the depth to the HSZ may cause hydrate dissociation near the equator and poles as the geothermal gradient moves in and out of the hydrate stability field over hundreds of thousands of years. Sublimation of overlying ice containing diffused methane could account for recent observations of seasonal methane plumes on Mars. In addition, near-surface gas hydrate reservoirs may be preserved at mid-latitudes due to minimal changes in surface temperature with obliquity over geologic time scales. Comparisons of the predicted changes in the HSZ with hydrate dissociation and diffusion rates reveal that metastable hydrate may also remain in the near subsurface, especially at high latitudes, for millions to billions of years. The presence of methane hydrate in the near subsurface at midlatitudes could be an important analytical target for future Mars missions, as well as serving as a source of fuel for future spacecraft.  相似文献