The detection of interstellar methylcyanoacetylene     

Broten NW  MacLeod JM  Avery LW  Irvine WM  Hoglund B  Friberg P  Hjalmarson A 《The Astrophysical journal》1984,(1):L25-L29

A new interstellar molecule, methylcyanoacetylene (CH3C3N), has been detected in the molecular cloud TMC-1. The J = 8 --> 7, J = 7 --> 6, J = 6 --> 5, and J = 5 --> 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 --> 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity VLSR = 5.8 km s-1 for TMC-1, typical of other molecules in the cloud. All observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al., so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 --> 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined for these observations is quite low, with 2.7 K < or = Trot < or = 4 K. the total column density is approximately 5 x 10(12) cm-2.  相似文献   

Inferring marine distribution of Canadian and Irish Atlantic salmon (Salmo salar L.) in the North Atlantic from tissue concentrations of bio-accumulated caesium 137     

Spares  Aaron D.; Reader  Jeffery M.; Stokesbury  Michael J. W.; McDermott  Tom; Zikovsky  Lubomir; Avery  Trevor S.; Dadswell  Michael J. 《ICES Journal of Marine Science》2007,64(2):394-404

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The distribution and abundance of pelagic gammarid amphipods on Georges Bank and Nantucket Shoals     

David E. Avery  Jack Green  Edward G. Durbin 《Deep Sea Research Part II: Topical Studies in Oceanography》1996,43(7-8)

In this study, long-term, broad-scale zooplankton survey data were used to estimate the temporal and spatial distribution and abundance of gammarid amphipods present in the water column on Georges Bank. Delta-mean abundances computed from 10 years of data showed that gammarid amphipod abundances peaked in summer and again in fall. The amphipods were also most numerous in water less than 50 m deep. The statistical tests employed revealed no conclusive evidence for diurnal vertical migration. Interannual delta-mean abundances fluctuated approximately 5-fold between 1977 and 1986, ranging from 217 to 1181 amphipods 100 m⁻³. Peak amphipod biomass occurred in July and was estimated to be 2.8 kcal m⁻². Using production-to-biomass ratios from the literature, mean annual production of amphipods in these samples was estimated to be between 1.6 and 9.8 kcal m⁻². Production in shallow areas was especially high, 22 kcal m⁻² year⁻¹.  相似文献   

Observations of the 2001 Leonid meteor shower using VHF meteor radar     

Santiago de la Peña  Susan K. Avery 《Icarus》2008,196(1):164-170

Every year the Earth crosses or passes near one of the dust trails left by Comet 55P/Tempel-Tuttle in its pass through the Solar System every 33.2 years. This produces a meteor shower Commonly called the Leonid. The 2001 Leonid meteor shower is one of the strongest in recent years. We present observations made by the 50 MHz all-sky meteor radar located at the Platteville Atmospheric Observatory in Colorado (40° N, 105° W). The spatial and temporal distributions of the meteor activity detected by the radar during the 2001 Leonid shower differs from the observed sporadic activity detected by VHF radars. Estimation of the radiant flux of the meteor shower of the shower by a well-known methodology is presented, and the intensity of the phenomena is discussed.  相似文献   

Magnetic helicity and the relaxation of fossil fields     

Avery E. Broderick  Ramesh Narayan 《Monthly notices of the Royal Astronomical Society》2008,383(3):943-956

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Inferring lake depth using diatom assemblages in the shallow,seasonally variable lakes of the Nebraska Sand Hills (USA): calibration,validation, and application of a 69-lake training set     

Avery L. C. Shinneman  Danuta M. Bennett  Sherilyn C. Fritz  Jens Schmieder  Daniel R. Engstrom  Aris Efting  John Holz 《Journal of Paleolimnology》2010,44(2):443-464

The Nebraska Sand Hills are a distinctive eco-region in the semi-arid Great Plains of the western United States. The water table underlying the Sand Hills is part of the High Plains/Ogallala aquifer, an important water resource for the central Great Plains. Lake levels are affected directly by fluctuations in the water table, which is recharged primarily by local precipitation and responds quickly to climatically induced changes in regional water balance. Instrumental records are available for only 50–100 years, and paleolimnological data provide important insights into the extremes and variability in moisture balance over longer time scales. A set of 69 lakes from across Nebraska was used to establish a statistical relationship between diatom community composition and water depth. This relationship was then used to develop a diatom-based inference model for water depth using weighted averaging regression and calibration techniques. Development of the inference model was complicated by strong intra-seasonal variability in water depth and the linkages between depth and other limnologic characteristics, including alkalinity, water clarity and nutrient concentrations. Analysis of historical diatom communities from eight lakes allowed for the reconstruction of lake-level fluctuations over the past several thousand years. Comparisons of the more recent portion of these reconstructions with the instrumental Palmer Drought Severity Index (PDSI) showed that sediment records may not faithfully reflect short-term fluctuations in water level, except where sedimentation rates are very high. However, large and persistent changes in moisture availability were discernible even in longer, low-resolution records. Thus, diatoms are a useful addition to the tools available for understanding past drought in the central Great Plains, especially when trajectories of change are constrained by data from multiple sites or other proxies.  相似文献   

The formation of the Ca ii K line in a spinning spicule     

Lorne W. Avery 《Solar physics》1970,13(2):301-311

The emission of the Ca ii K line from a spinning cylindrical spicule model is considered. In order to reproduce the observed spicule K line profiles, the model must have both radial and axial gradients in N _e and T _e. The rotating spicule model is optically thin at all heights and is hotter and more dense than a stationary model computed in a previous paper. It is proposed that the so-called Type I and Type II spicules may be structurally the same features, with different rotational velocities.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Hydrogen Peroxide at the Bermuda Atlantic Time Series Station. Part 1: Temporal Variability of Atmospheric Hydrogen Peroxide and Its Influence on Seawater Concentrations     

Robert J. Kieber  William J. Cooper  Joan D. Willey  G. Brooks Avery Jr. 《Journal of Atmospheric Chemistry》2001,39(1):1-13

Diurnal and seasonal variations in atmospheric hydrogen peroxideconcentrations wereinvestigated during a summer and winter cruise aboard the R.V. `Endeavor' atthe BermudaAtlantic Time Series Station. Rainwater peroxide concentrations in Augustdisplayed dielvariability while no temporal H₂O₂ pattern was evidentin March rain. Averageconcentrations in March were also significantly lower than August whichindicates photochemicalprocesses are involved in controlling hydrogen peroxide concentrations inmarine rainwaterfalling over the open ocean. The range of gas phase hydrogen peroxideconcentrations wasbetween 1 and 6 ppbv and also exhibited a strong diurnal pattern during bothAugust and Marchwith concentration maxima in the early evening. The influence of atmosphericdeposition onsurface seawater hydrogen peroxide levels was also evaluated. Hydrogenperoxide depth profileswere measured on four separate occasions before and after rain events duringthe Augustsampling period. The input of rainfall hydrogen peroxide was observedthroughout the 25 metermixed layer with surface concentrations two fold larger in the morning aftera rain event. Theintegrated increase in hydrogen peroxide after the rain from 0 to 90 meterswas 1,720 molalmost all of which could be accounted for by the peroxide added from rain.The data presentedin this study represent the first detailed, simultaneous measurements ofhydrogen peroxide inmarine air, rain and surface seawater.  相似文献