Weighted model-based clustering for remote sensing image analysis     

Joseph W. Richards  Johanna Hardin  Eric B. Grosfils 《Computational Geosciences》2010,14(1):125-136

We introduce a weighted method of clustering the individual units of a segmented image. Specifically, we analyze geologic maps generated from experts’ analysis of remote sensing images and provide geologists with a powerful method to numerically test the consistency of a mapping with the entire multidimensional dataset of that region. Our weighted model-based clustering method (WMBC) employs a weighted likelihood and assigns fixed weights to each unit corresponding to the number of pixels located within the unit. WMBC characterizes each unit by the means and standard deviations of the pixels within that unit and uses the expectation-maximization algorithm with a weighted likelihood function to cluster the units. With both simulated and real data sets, we show that WMBC is more accurate than standard model-based clustering. Specifically, we analyze Magellan data from a large, geologically complex region of Venus to validate the mapping efforts of planetary geologists.  相似文献   

Long-term Field Observations on Seasonality in Chlorophyll-<Emphasis Type="Italic">a</Emphasis> Concentrations in a Shallow Coastal Marine Ecosystem,the Wadden Sea     

Catharina Johanna Maria Philippart  Jolanda Martine van Iperen  Gerhard Cornelis Cadée  Alain François Zuur 《Estuaries and Coasts》2010,33(2):286-294

Analyses of long-term field observations (1974–2007) on chlorophyll-a concentrations in the western Wadden Sea showed no long-term trends in the timing of the wax and wane of phytoplankton spring blooms. There is weak evidence, however, that the height of the autumn bloom has decreased since the early 1990s. This fading of the autumn bloom may have had consequences for the carbon transfer to higher trophic levels, currently hampering primary consumer species that mostly rely on food supply during late summer. Current and other findings suggest a shortening of the growing season due to the fading of the autumn bloom in the Wadden Sea and a lengthening of the growing season due to an advancement of the spring bloom in the North Sea. These regionally different changes in seasonality may have contributed to the coinciding decrease in bivalve filtering capacity in the western Wadden Sea and the large-scale offshore shift of juvenile plaice from the Wadden Sea to the adjacent North Sea.  相似文献   

Are there social limits to adaptation to climate change?   总被引：1，自引：0，他引：1  

W. Neil Adger  Suraje Dessai  Marisa Goulden  Mike Hulme  Irene Lorenzoni  Donald R. Nelson  Lars Otto Naess  Johanna Wolf  Anita Wreford 《Climatic change》2009,93(3-4):335-354

While there is a recognised need to adapt to changing climatic conditions, there is an emerging discourse of limits to such adaptation. Limits are traditionally analysed as a set of immutable thresholds in biological, economic or technological parameters. This paper contends that limits to adaptation are endogenous to society and hence contingent on ethics, knowledge, attitudes to risk and culture. We review insights from history, sociology and psychology of risk, economics and political science to develop four propositions concerning limits to adaptation. First, any limits to adaptation depend on the ultimate goals of adaptation underpinned by diverse values. Second, adaptation need not be limited by uncertainty around future foresight of risk. Third, social and individual factors limit adaptation action. Fourth, systematic undervaluation of loss of places and culture disguises real, experienced but subjective limits to adaptation. We conclude that these issues of values and ethics, risk, knowledge and culture construct societal limits to adaptation, but that these limits are mutable.  相似文献   

Variability of heat shock proteins and glutathione S-transferase in gill and digestive gland of blue mussel,Mytilus edulis     

Lyons C  Dowling V  Tedengren M  Gardeström J  Hartl MG  O'Brien N  van Pelt FN  O'Halloran J  Sheehan D 《Marine environmental research》2003,56(5):585-597

Glutathione S-transferase (GST) and heat shock proteins (hsps) 40, 60, 70 and 90 were determined by immunoblotting using actin as an internal control in Mytilus edulis from one station outside (site1) and three stations within (sites 2-4) Cork Harbour, Ireland. Comparisons were made between gill and digestive gland and between sites. Gill shows generally higher hsp 60, 70 and 90 while digestive gland has higher hsp 40. Site 1 showed higher gill hsps 40 and 70 than sites 2-4 while gill GST was higher in sites 3 and 4 than 1 and 2. Comparison with sites in the North Sea (site 5: outside Tj?rn? in The Koster archipelago in the Skagerack) and Baltic Sea (site 6: Ask? island) also revealed lower hsps 40 and 70 in site 6 (low salinity) than site 5 (high salinity) although hsps 60, 70 and 90 were detectable in digestive gland unlike sites 1-4. Previously, only hsp 70 had been studied at these sites [Mar. Environ. Res. 39. (1995), 181]. At the mRNA level, gill hsp 70 is 80-fold higher at Tj?rn? than Ask?. These data suggest that, while salinity may slightly decrease hsp 40 and 70, both hsp 70 and GST are selectively up-regulated by approx. 10- and 3-fold, respectively, at Tj?rn? compared to the other sites which we attribute to exposure to more widely fluctuating pollution levels.  相似文献   

Combined climatic and geological forcings on the spatio-temporal variability of piezometric levels in the chalk aquifer of Upper Normandy (France) at pluridecennal scale     

Smail Slimani  Nicolas Massei  Johanna Mesquita  Danièle Valdés  Matthieu Fournier  Benoît Laignel  Jean-Paul Dupont 《Hydrogeology Journal》2009,17(8):1823-1832

The temporal variability of water-level fluctuations in the chalk aquifer of Upper Normandy, France is constrained by natural climate fluctuations and is closely linked to the regional geological patterns. The chalk plateaus are covered with 5–50 m thick semi-permeable surficial formations; the thickness of the underlying chalk aquifer varies from 50 to 300 m. The relationship among climate oscillations, piezometric levels, and geologic structure were investigated by correlation, Fourier spectral, and continuous wavelet analyses of selected piezometric time-series data. Analysis focused on two piezometers located on the uplifted side of a major fault and two piezometers on the downthrown side. After generalization to other piezometers in the region, it was deduced that, in the downthrown compartments, a substantial aquifer and surficial formations thickness would imply a strong attenuation of annual variability, while multi-year variability is clearly expressed. Conversely, in the uplifted compartments, a thin layer of surficial formations and small thickness of the chalk authorizes strong variations on the annual mode with respect to the contribution of long-term climatic oscillations (multi-year variability). The results then demonstrated—and proposed a spatial determination of—the differential influence of geological patterns on the filtering of climate-induced oscillations in piezometric variability.  相似文献   

Development of a generic concept to analyze the accessibility of emergency facilities in critical road infrastructure for disaster scenarios: exemplary application for the 2017 wildfires in Chile and Portugal     

Guth  Johanna  Wursthorn  Sven  Braun  Andreas Ch.  Keller  Sina 《Natural Hazards》2019,97(3):979-999

Natural Hazards - Natural hazards such as earthquakes, floods, or wildfires pose a serious threat to road infrastructure. Especially in emergency situations, the society depends on the road...  相似文献   

Latest Cretaceous storm-generated sea grass accumulations in the Maastrichtian type area,the Netherlands – preliminary observations     

John W.M. Jagt  Mart Deckers  Stephen K. Donovan  René Fraaije  Stijn Goolaerts  Raymond van der Ham  Malcolm B. Hart  Elena A. Jagt-Yazykova  Johanna van Konijnenburg-van Cittert  Sjir Renkens 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(5):590-598

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Impact of different energies of precipitating particles on NOx generation in the middle and upper atmosphere during geomagnetic storms     

Esa Turunen  Pekka T. Verronen  Annika Seppälä  Craig J. Rodger  Mark A. Clilverd  Johanna Tamminen  Carl-Fredrik Enell  Thomas Ulich 《Journal of Atmospheric and Solar》2009,71(10-11):1176-1189

Energetic particle precipitation couples the solar wind to the Earth's atmosphere and indirectly to Earth's climate. Ionisation and dissociation increases, due to particle precipitation, create odd nitrogen (NO_x) and odd hydrogen (HO_X) in the upper atmosphere, which can affect ozone chemistry. The long-lived NO_x can be transported downwards into the stratosphere, particularly during the polar winter. Thus, the impact of NO_x is determined by both the initial ionisation production, which is a function of the particle flux and energy spectrum, as well as transport rates. In this paper, we use the Sodankylä Ion and Neurtal Chemistry (SIC) model to simulate the production of NO_x from examples of the most representative particle flux and energy spectra available today of solar proton events (SPE), auroral energy electrons, and relativistic electron precipitation (REP). Large SPEs are found to produce higher initial NO_x concentrations than long-lived REP events, which themselves produce higher initial NO_x levels than auroral electron precipitation. Only REP microburst events were found to be insignificant in terms of generating NO_x. We show that the Global Ozone Monitoring by Occultation of Stars (GOMOS) observations from the Arctic winter 2003–2004 are consistent with NO_x generation by a combination of SPE, auroral altitude precipitation, and long-lived REP events.  相似文献   

The Dakhleh Glass: Product of an impact airburst or cratering event in the Western Desert of Egypt?     

Gordon R. OSINSKI  Johanna KIENIEWICZ  Jennifer R. SMITH  Mark B. E. BOSLOUGH  Mark ECCLESTON  Henry P. SCHWARCZ  Maxine R. KLEINDIENST  Albert F. C. HALDEMANN  Charles S. CHURCHER 《Meteoritics & planetary science》2008,43(12):2089-2107

Abstract— Impact cratering is a ubiquitous geological process on the terrestrial planets. Meteorite impact craters are the most visible product of impact events, but there is a growing recognition that large aerial bursts or airbursts should occur relatively frequently throughout geological time. In this contribution, we report on an unusual impact glass‐the Dakhleh Glass (DG)–which is distributed over an area of ?400 km ²of the Dakhleh Oasis, Egypt. This region preserves a rich history of habitation stretching back to over 400,000 years before the emergence of Homo sapiens. We report on observations made during recent fieldwork and subsequent analytical analyses that strengthen previous suggestions that the DG formed during an impact event. The wide distribution and large size of DG specimens (up to ?50 cm across), the chemistry (e.g., CaO and Al₂O₃ contents up to ?25 and ?18 wt, respectively), the presence of lechatelierite and burnt sediments, and the inclusion of clasts and spherules in the DG is inconsistent with known terrestrial processes of glass formation. The age and other textural characteristics rule out a human origin. Instead, we draw upon recent numerical modeling of airbursts to suggest that the properties of DG, coupled with the absence of a confirmed crater, can best be explained by melting of surficial sediments as a result of a large airburst event. We suggest that glass produced by such events should, therefore, be more common in the rock record than impact craters, assuming that the glass formed in a suitable preserving environment.  相似文献   

Period analysis for the peculiar variable FG sagittae     

Johanna Jurcsik  László Szabados 《Astrophysics and Space Science》1989,153(1):45-54

The analysis of the available photoelectric observations covering the interval 1970–1987 was performed. The rapid secular variation of the physical parameters of the star makes the analysis of the whole data set impossible. From the yearly observations (2–3 cycles long) only one period can be determined, the variation of these periods shows a 4–5 year periodicity. The analysis of 2–5 years of observations shows two close frequency components with a nearly constant frequency ratio but with varying amplitudes. The two frequency fits, however, do not describe all the characteristics of the light curve. New photoelectric observations carried out between 1980 and 1987 are also published.  相似文献