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31.
S. Knox W. J. Langston M. Whitfield D. R. Turner M. I. Liddicoat 《Estuarine, Coastal and Shelf Science》1984,18(6):623-638
By combining field observations with a statistical approach and a simple but effective estuarine analogue, the main features of the cycling of arsenic in the Tamar estuary have been elucidated. As(III) and As(V) enrichment in the water column is due to a combination of localized inputs and effective recycling of sediment interstitial waters. The profiles of As(V) are similar to those of NH4+ and are dominated by an estuarine maximum resulting from an input from the sediments. As(III) profiles are correlated with those of dissolved manganese and exhibit both fresh water and estuarine maxima. As(III) appears to be effectively removed at the freshwater/brackish water interface by a combination of heterogenous oxidation, catalysed by hydrous manganese dioxide, and adsorption on to iron oxyhydroxide. The estuarine distribution of As(III) within the water column is consistent with the published rates of oxidation of As(III) to As(V) by both inorganic and microbiological processes. The reduction of As(V) to As(III) in the sediments is incomplete. On the basis of our observations a tentative estuarine arsenic cycle is presented. 相似文献
32.
James B. S. G. Greensky Wojciech Walter Czech David A. Yuen Michael Richard Knox Megan Rose Damon Shi Steve Chen M. Charley Kameyama 《Visual Geosciences》2008,13(1):105-115
We have developed a new strategy and espouse a novel paradigm for large-scale computing and real-time interactive visualization.
This philosophy calls for intense interactive sessions for a couple of hours at a time at the expense of storing data on many
disk drives during regular or heroic runs on massively parallel systems. We have already carried out successfully real-time
volume-rendering visualization by employing hundreds of processors for a grid with over 25 million unknowns. Both Cartesian
and spherical 3D mantle convection are visualized. The volume-rendered images are viewed on a large display device, with many
panels holding around 13 million pixels. We will employ a software strategy involving an hierarchical rendering service, which
will have as software an Ajax interface for interactive visualization of large data sets on many different platforms from
desktop PC’s to hand-held devices, such as the OQO and the Nokia N-800. An option for stereo viewing is also implemented.
We have installed a user interface as web application, using Java and Ajax framework in order to achieve over the Internet
reasonable accessibility to our ongoing runs. Our goal is to expand the array of interactive devices, which will make it feasible
to carry out ubiquitous visualization and monitoring of large-scale simulations or onsite events and to allow for collaborations
across oceans. 相似文献
33.
The chirality of high-latitude coronal arcades in the declining phase of cycle 22 has been studied. It is found that the observed skew of the high-latitude arcades is opposite to the dominant arcade skew at lower latitudes. This new result which applies only to the declining phase of the solar cycle is consistent with differential rotation and the simulations of Mackay and van Ballegooijen (2001). Limitations of the present study are discussed along with its consequences for the global pattern of filaments in each hemisphere. The results suggest that, for the declining phase, the previously observed global pattern may be more complex with latitudinal variations. Future observing programs required to clarify the issue are discussed. 相似文献
34.
Philip C. Farese Giorgio DallOglio Josh Gundersen Brian Keating Slade Klawikowski Lloyd Knox Alan Levy Chris ODell Alan Peel Lucio Piccirillo John Ruhl Peter Timbie 《New Astronomy Reviews》2003,47(11-12):1033
COMPASS is an on-axis 2.6-m telescope coupled to a correlation polarimeter. The entire instrument was built specifically for CMB polarization studies. Careful attention was given to receiver and optics design, stability of the pointing platform, avoidance of systematic offsets, and development of data analysis techniques. Here we describe the experiment, its strengths and weaknesses, and the various things we have learned that may benefit future efforts to measure the polarization of the CMB. 相似文献
35.
Boris T. Gäansicke Domitilla De Martino Thomas R. Marsh Carole A. Haswell Christian Knigge Knox S. Long Steven N. Shore 《Astrophysics and Space Science》2006,303(1-4):53-68
Interacting Binaries consist of a variety of stellar objects in different stages of evolution and those containing accreting compact objects still represent a major challenge to our understanding of not only close binary evolution but also of the chemical evolution of the Galaxy. These end-points of binary star evolution are ideal laboratories for the study of accretion and outflow processes, and provide insight on matter under extreme physical conditions. One of the key-questions of fundamental relevance is the nature of SN Ia progenitors. The study of accreting compact binary systems relies on observations over the entire electromagnetic spectrum and we outline here those unresolved questions for which access to the ultraviolet range is vital, as they cannot be addressed by observations in any other spectral region.An erratum to this article can be found at 相似文献
36.
Lloyd Knox 《New Astronomy Reviews》2003,47(11-12):883
I comment on the challenges and opportunities presented by an extended period of reionization. 相似文献
37.
38.
Parameters of community structure (species composition and relative abundance, number of taxa, diversity, evenness, and cell density) were measured for a mudflat diatom community in the Avon‐Heathcote estuary, New Zealand. Fifty three diatom species were identified: 25 taxa (species and varieties) are new New Zealand records. The Shannon‐Wiener information index (H') was 3.46, indicating high diversity. Evenness (J') ranged from 0.57–0.67. The association between the biomass of the pulmonate gastropod, Amphibola crenata, and benthic diatom community structure was studied using large open enclosures (4.0 m2) to manipulate snail biomass. Community structure was compared at 0, 5 (natural biomass), and 10 g A. crenata dry weight per m. A similarity index (SIMI=0.88–0.95), as well as H’ and J’ indicated close similarity between the diatom assemblages within all enclosures, but number of taxa increased from 33 to 49 with increasing snail biomass. Cell densities were significantly lower at high snail biomass (6088 valves per mm2) compared to enclosures with no snails (10 110 valves per mm ). A. crenata had a higher ratio of diatom fragments to whole diatom valves in its faeces (2.42) than in its crop (0.55), indicating that it is capable of fragmenting diatoms. 相似文献
39.
B. E. Woodgate E. A. Tandberg-Hanssen E. C. Bruner J. M. Beckers J. C. Brandt W. Henze C. L. Hyder M. W. Kalet P. J. Kenny E. D. Knox A. G. Michalitsianos R. Rehse R. A. Shine H. D. Tinsley 《Solar physics》1980,65(1):73-90
The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design, performance, and modes of operation. The instrument operates in the wavelength range 1150–3600 Å with better than 2 arc sec spatial resolution, raster range 256 × 256 arc sec2, and 20 mÅ spectral resolution in second order. Observations can be made with specific sets of 4 lines simultaneously, or with both sides of 2 lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere.Currently at MMTO, University of Arizona, Tucson, Ariz. 85721, U.S.A. 相似文献
40.
The morphology of paleosols and radiocarbon-dated charcoal from buried surface horizons of soils provide evidence to suggest that between periods of northward forest encroachment tundra climate has dominated areas at least 50 km south of the present forest/tundra border in southwest Keewatin. The present forest/tundra border climate is nearly as severe as any climate that has prevailed in the area since deglaciation. 相似文献