410 research outputs found

    Synthesis of TCNE and TCNQ Derivatives and the Preparation of Conducting Polymers

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    Tetracyanoethylene and tetracyanoquinodimethane were reacted with various N,N-dimethyl-a, w-alkyldiamines to produce TCNE and TCNQ diamino and monoamino derivatives. NMR and ir spectra of the monoamino derivatives, 1-(N,N-dimethyl-a,w-alkyldiamino)-1,2,2-tricyanoethylenes and 7-(N,N-dimethyl-a,w-alkyldiamino)-7,8,8-tricyanoquinodimethans, indicated that these compounds exhibited strong nitrogen-hydrogen-nitrogen intramolecular hydrogen bonding. This phenomenon was corroborated by molecular weight and preliminary x-ray analyses. The 1,1-bis(N,N-dimethyl-a,w-alkyldiamino)-2,2-dicyanoethylene and 7,7-bis(N,N-dimethyl-a,m-alkyldiamino)-8,8-dicyanoquinodimethan derivatives were polymerized with a,m-alkyldibromides containing two to six methylene groups to produce the corresponding ionene polymers. Viscosity measurements of the polymers indicated that the TCNE copolymers were generally of higher molecular weight than the corresponding TCNQ copolymers. The two polymer series were treated with lithium tetracyanoquinodi-methanide to produce semiconducting polymers. Electrical measurements indicated that these materials had conductivities on the order of 10-7 ohm-1 cm-1. Treatment of the polymers with neutral TCNQ resulted in increased conductivities ranging from two to five orders of magnitude

    River Run Off Measurement With SAR Along Track Interferometry

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    The paper summarizes the need for global space borne river run-off measurements. It reports about an airborne SAR experiment aimed to measure the surface velocity of the river Isar in Bavaria / Germany. The results from two different SAR techniques, including Along Track Interferometry (ATI) show good correspondence. Finally suggestions for further studies are given

    Reducing spectral reflections through image inpainting

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    Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 45-46).The goal of this thesis is to produce an image processing tool that could, with limited user interaction, significantly reduce spectral reflections. The resulting process can then be used by biological researchers in the process of cataloging and recognizing individual organisms via collected images. The process involves the generation of a mask, refinements to that mask such as background segmentation and morphological dilation, and finally the inpainting of the specular regions. This method improves on existing single pixel methods by incorporating both color and texture infilling of the specular reflections. It also works on images with no special setup or preparation.by Joshua Runge.M.Eng

    An Interferometric SAR Satellite Mission

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    The paper provides a critical review of the achievements in SAR interferometry from the ERS mission as well as from the Shuttle Radar Topography Mission SRTM. It describes the development from the original idea of the Interferometric Cartwheel to the concept of a formation flight of identical and active SAR satellites. From the experience gained from ERS and SRTM interferometric data processing as well as from the analysis of the Cartwheel concept a list of mission requirements has been set up. The most demanding one is the autonomous configuration flight of a tight x-band constellation, where the satellites fly as close as up to 30 m with a dead-band of +/- 10 m. The guidance, navigation and control considerations come to the conclusion that such a mission is feasible

    Typology and function of Late Bronze Age and Early Iron Age cremation graves: a micro-regional case study

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    In Denmark, there has been little focus on characteristic differences between grave types from the transition period between the Late Bronze Age and the Early Iron Age with limited elaboration on the nature of the differences and on chronological variation. In nearby Scania, Sweden, a grave type classic for Southern Scandinavia, the ‘cremation pit’, has been interpreted as in situ remains of the actual cremation pyre, that is, a form of bustum. Here, we further explore this interpretation through both osteological and archaeological analyses of recently excavated graves from the Fraugde region on northern Funen ,Denmark. In the Fraugde region, pyre debris in cremation graves clearly gain significance during the transition period from the Bronze Age towards the Pre-Roman Iron Age. The exclusive presence of cremation pits on the Pre-Roman Iron Age grave sites in contrast to the varied grave types present on the Bronze Age sites implies a change in cremation practice and technology during the transition period. Although clearly commemorated and left undisturbed for centuries, the cremation pits on the pre-Roman Iron Age sites must be interpreted as intentional, secondary deposits of the debris from the cremation pyre, but not as in situ pyre sites

    Assessing Allowable Take of Migratory Birds

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    Legal removal of migratory birds from the wild occurs for several reasons, including subsistence, sport harvest, damage control, and the pet trade. We argue that harvest theory provides the basis for assessing the impact of authorized take, advance a simplified rendering of harvest theory known as potential biological removal as a useful starting point for assessing take, and demonstrate this approach with a case study of depredation control of black vultures (Coragyps atratus) in Virginia, USA. Based on data from the North American Breeding Bird Survey and other sources, we estimated that the black vulture population in Virginia was 91,190 (95% credible interval = 44,520–212,100) in 2006. Using a simple population model and available estimates of life-history parameters, we estimated the intrinsic rate of growth (rmax) to be in the range 7–14%, with 10.6% a plausible point estimate. For a take program to seek an equilibrium population size on the conservative side of the yield curve, the rate of take needs to be less than that which achieves a maximum sustained yield (0.5 x rmax). Based on the point estimate for rmax and using the lower 60% credible interval for population size to account for uncertainty, these conditions would be met if the take of black vultures in Virginia in 2006 was rmax. Further, the ratio of desired harvest rate to 0.5 x rmax may be a useful metric for ascertaining the applicability of specific requirements of the National Environmental Protection Act

    Site factors determining epiphytic lichen distribution in a dieback-affected spruce-fir forest on Whiteface Mountain, New York: stemflow chemistry

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    Epiphytic lichen diversity in a dieback-affected forest of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) on Whiteface Mountain, New York, U.S.A., was higher on dead compared with living trees and on fir compared with spruce. Diversity differed more between living and dead spruce than between living and dead fir. Cover of all lichen species that occurred on more than 50% of the sample trees, except for two species, decreased with increasing mean concentration of NO3– in stemflow. Concentrations of NO3– were higher on living spruce compared with dead spruce and with living and dead fir. The negative correlations between lichen cover and NO3– concentration may reflect either a decrease of lichen abundance caused by toxic effects of higher NO3– concentrations or a removal of NO3– from stemflow by epiphytic lichens. Experimental exposure of Hypogymnia physodes to NaNO3 reduced chlorophyll concentrations. This result, together with estimations of lichen and needle biomass, indicates that a dependence of lichen cover on NO3– concentrations in stemflow may be the cause for the negative correlations. The sulphur concentration in stemflow did not affect lichen abundance on Whiteface Mountain. The manganese concentration in stemflow may have an effect on single species
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