Effect of signal contamination in matched-filter detection of the signal on a cluttered background

To derive a matched filter for detecting a weak target signal in a hyperspectral image, an estimate of the band-to-band covariance of the target-free background scene is required. We investigate the effects of including some of the target signal in the background scene. Although the covariance is contaminated by the presence of a target signal (there is increased variance in the direction of the target signature), we find that the matched filter is not necessarily affected. In fact, if the variation in plume strength is strictly uncorrelated with the variation in background spectra, the matched filter and its signal-to-clutter ratio (SCR) performance will not be impaired. While there is little a priori reason to expect significant correlation between the plume and the background, there usually is some residual correlation, and this correlation leads to a suppressing effect that limits the SCR obtainable even for strong plumes. These effects are described and quantified analytically, and the crucial role of this correlation is illustrated with some numerical examples using simulated plumes superimposed on real hyperspectral imagery. In one example, we observe an order-of-magnitude loss in SCR for a matched filter based on the contaminated covariance.     

Inverse model method for estimating assimilation by aquatic invertebrates

Physiological data indicate that a 3-compartment model appropriately represents ingestion, assimilation, and accumulation of somatic and reproductive tissue by an aquatic invertebrate predator. A secondary production model calibrated to growth and respiration data is used to constrain the model equations. Inverse solution methods are used to estimate rate constants for digestion and for net accrual of tissue by growing animals at different temperatures. Predicted time to 50% maximum digestion matches well with the empirical rate of digestion of prey enzymes in the predator gut. Model-derived digestion rates are consistent with the assimilation rate constant obtained by independent radiotracer methods, and with experimental detection time for prey enzymes. The model approach permits parameter estimation within a complex system of equations so that results can be compared with experimental data.     

Bromine cycle in subduction zones through in situ Br monitoring in diamond anvil cells

The geochemical partitioning of bromine between hydrous haplogranitic melts, initially enriched with respect to Br and aqueous fluids, has been continuously monitored in situ during decompression. Experiments were carried out in diamond anvil cells from 890 °C to room temperature and from 1.7 GPa to room pressure, typically from high P, T conditions corresponding to total miscibility (presence of a supercritical fluid). Br contents were measured in aqueous fluids, hydrous melts and supercritical fluids. Partition coefficients of bromine were characterized at pressure and temperature between fluids, hydrous melts and/or glasses, as appropriate: D^Br_fluid/melt = (Br)_fluid/(Br)_melt, ranges from 2.18 to 9.2 ± 0.5 for conditions within the ranges 0.66-1.7 GPa, 590-890 °C; and D^Br_fluid/glass = (Br)_fluid/(Br)_glass ranges from 60 to 375 at room conditions. The results suggest that because high pressure melts and fluids are capable of accepting high concentrations of bromine, this element may be efficiently removed from the slab to the mantle source of arc magmas. We show that Br may be highly concentrated in subduction zone magmas and strongly enriched in subduction-related volcanic gases, because its mobility is strongly correlated with that of water during magma degassing. Furthermore, our experimental results suggest that a non negligible part of Br present in the subducted slab may remain in the down-going slab, being transported toward the transition zone. This indicates that the Br cycle in subduction zones is in fact divided in two related but independent parts: (1) a shallower one where recycled Br may leave the slab with a water and silica-bearing “fluid” leading to enriched arc magmas that return Br to the atmosphere. (2) A deeper cycle where Br may be recycled back to the mantle maybe to the transition zone, where it may be present in high pressure water-rich metasomatic fluids.     

Influence of transboundary air pollution on air quality in southwestern China

Air pollution is a grand challenge of our time due to its multitude of adverse impacts on environment and society,with the scale of impacts more severe in developing countries,including China.Thus,China has initiated and implemented strict air pollution control measures over last several years to reduce impacts of air pollution.Monitoring data from Jan 2015 to Dec 2019 on six criteria air pollutants(SO2,NO2,CO,O3,PM2.5,and PM1o)at eight sites in southwestern China were investigated to understand the situation and analyze the impacts of transboundary air pollutants in this region.In terms of seasonal variation,the maximum concentrations of air pollutants at these sites were observed in winter or spring season depending on individual site.For diurnal variation,surface ozone peaked in the afternoon while the other pollutants had a bimodal pattern with peaks in the morning and late afternoon.There was limited trans-port of domestic emissions of air pollutants in China to these sites.Local emissions enhanced the concen-trations of air pollutants during some pollution events.Mostly,the transboundary transport of air pollution from South Asia and Southeast Asia was associated with high concentrations of most air pollu-tants observed in southwestern China.Since air pollutants can be transported to southwestern China over long distances from the source regions,it is necessary to conduct more research to properly attribute and quantify transboundary transport of air pollutants,which will provide more solid scientific guidance for air pollution management in southwestern China.     

Laser Guide Star for 3.6- and 8-m telescopes: Performance and astrophysical implications

We have constructed an analytical model to simulate the behaviour of an adaptive optics system coupled with a sodium laser guide star. The code is applied to 3.6- and 8-m class telescopes. The results are given in terms of Strehl ratio and full width at half-maximum of the point spread function. Two atmospheric models are used, one representing good atmospheric conditions (20 per cent of the time), the other median conditions.   Sky coverage is computed for natural guide star and laser guide star systems, with two different methods. The first one is a statistical approach, using stellar densities to compute the probability of finding a nearby reference. The second is a cross-correlation of a science-object catalogue and the USNO catalogue. Results are given in terms of percentage of the sky that can be accessed with given performances, and in terms of the number of science objects that can be observed, with Strehls greater than 0.2 and 0.1 in the K and J bands.     

Detailed analysis of cool stars

We present the detailed analysis of fourteen cool stars, nine of which have been associated by Eggen with four moving groups from the kinematics and the photometric properties; the five remaining stars are characterized by a large-spatial velocity. From the scatter of the chemical composition among the program stars belonging to a same group, we discuss that the moving groups Her, Wolf 630, and Kapteyn could really exist, and that Groombridge 1830 do not. No peculiar abundance relative to iron is found except a possible relative overabundance of Ni for the most metal-poor stars in this sample. The results of the detailed analyses are discussed in terms of the chemical abundances of our Galaxy.Based on observations collected at European Southern Observatory, La Silla, Chile and Observatoire de Haute-Provence, France.     

Impacts of Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau

Air pollutants can be transported to the pristine regions such as the Tibetan Plateau,by monsoon and stratospheric intrusion.The Tibetan Plateau region has limited local anthropogenic emissions,while this region is influenced strongly by transport of heavy emissions mainly from South Asia.We conducted a comprehensive study on various air pollutants(PM2.5,total gaseous mercury,and surface ozone)at Nam Co Station in the inland Tibetan Plateau.Monthly mean PM2.5 concentration at Nam Co peaked in April before monsoon season,and decreased during the whole monsoon season(June-September).Monthly mean total gaseous mercury concentrations at Nam Co peaked in July and were in high levels during monsoon season.The Indian summer monsoon acted as a facilitator for transporting gaseous pol-lutants(total gaseous mercury)but a suppressor for particulate pollutants(PM2.5)during the monsoon season.Different from both PM2.5 and total gaseous mercury variabilities,surface ozone concentrations at Nam Co are primarily attributed to stratospheric intrusion of ozone and peaked in May.The effects of the Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau are complex and require further studies.     

A Review and Evaluation of Uncertainty Classification and the Error‐Band Geometry Model

Advances in computer technologies have improved the quality of maps, making map comparison and analysis easier, but uncertainty and error still exist in GIS when overlaying geographic data with multiple or unknown confidence levels. The goals of this research are to review current geospatial uncertainty literature, present the Error‐Band Geometry Model (EBGM) for classifying the size and shape of spatial confidence intervals for vector GIS data, and to analyze the interpretability of the model by looking at how people use metadata to classify the uncertainty of geographic objects. The results from this research are positive and provide important insight into how people interpret maps and geographic data. They suggest that uncertainty is more easily interpreted for well defined point data and GPS data. When data is poorly defined, people are unable to determine an approach to model uncertainty and generate error‐bands. There is potential for using the EBGM to aid in the development of a GIS tool that can help individuals parameterize and model spatial confidence intervals, but more research is needed to refine the process by which people use the decision tree. A series of guiding questions or an “uncertainty wizard” tool that helps one select an uncertainty modeling approach might improve the way people apply this model to real‐world applications.     

Imaging with Amber/VLTI: the case of microjets

The engine that powers pre-main-sequence micro-jets is still unknown and remains a fundamental open question in star formation. The engine can be located solely on the inner disk or in the interaction of the inner disk with the star. In order to ease interpretation problems, imaging the jet engine is the ideal probe to disentangle between the old models and shed evidence for new ones. In this paper, we analyse the feasability of imaging bright southern targets, and show that even at low SNR, accurate image reconstructionis still possible with high contrast. However, the small number of ATs requires a fast reconfigurable array. This revised version was published online in July 2006 with corrections to the Cover Date.     

The fiberless multislit spectrograph SFM

We describe the multislit spectrograph SFM. It is designed to obtain simultaneously spectrograms of faint objects over a field of 10 arcminutes for an entrance aperture ratio f/10, or of 15 arcmin for f/8. The SFM makes the dispersed image of the entrance slits directly, without any fiber optics. The number of entrance slits can be as large as a few hundreds, depending on the distribution of the sources on the sky and on the wavelength range. The present reciprocal dispersion is 79Åmm^–1 in the wavelength range 3600 – 6400Å. The SFM is expected to reachm _v22 with a signal to noise ratio of 10 for a spectral resolution of 3.3Å and an integration time of 5 hours, when used with the photon counting detector CP40.Radial velocities can be measured either by using calibration spectrograms or by the objective prism technique.The mask of entrance slits is made photochemically from a plate previously recorded of the field to be observed, taken during the same observing run. The auxiliary equipment Mascograph, specially designed for this purpose, is described.First spectrograms in the field of M15 obtained with the SFM using the Calar-Alto 3.50m telescope are presented.Based on observations collected at the Calar-Alto 3.5m telescope, operated by the German MPIfA (Heidelberg), and at the 3.60m CFHT, operated jointly by the Canadian SRC, the French CNRS and the University of Hawaii