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491.
Response of clupeid fish to ultrasound: a review 总被引:2,自引:0,他引:2
Popper Arthur N.; Plachta Dennis T.T.; Mann David A.; Higgs Dennis 《ICES Journal of Marine Science》2004,61(7):1057-1061
492.
Dennis M. Lavoie Dawn L. Lavoie H. Alan Pittenger Richard H. Bennett 《Geo-Marine Letters》1996,16(3):226-231
Sediments from Eckernförde Bay, Germany, are characterized by an aggregate and channel microstructure, with channel dimensions about two orders of magnitude larger than interparticle distances within aggregates. Porosity within aggregates as determined by image analysis of transmission electron micrographs was about 12% less than bulk porosity. Illite and smectite formed the bulk of most aggregates, while numerous biogenic particles generally occurred outside or on the periphery of aggregates. Microfabric analysis provides insights into permeability and consolidometer behavior of this sediment, reveals characteristics not apparent from bulk analyses, and may have implications for geochemistry and physical behavior of the sediment. 相似文献
493.
Seasonal and spatial distribution of particulate organic matter (POM) in the Chukchi and Beaufort Seas 总被引:1,自引:0,他引:1
Nicholas R. Bates Dennis A. Hansell S. Bradley Moran Louis A. Codispoti 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3324
As part of the Western Arctic Shelf–Basin Interactions (SBI) project, the production and fate of organic carbon and nitrogen from the Chukchi and Beaufort Sea shelves were investigated during spring (5 May–15 June) and summer (15 July–25 August) cruises in 2002. Seasonal observations of suspended particulate organic carbon (POC) and nitrogen (PON) and large-particle (>53 μm) size class suggest that there was a large accumulation of carbon (C) and nitrogen (N) between spring and summer in the surface mixed layer due to high phytoplankton productivity. Considerable organic matter appeared to be transported from the shelf into the Arctic Ocean basin in an elevated POC and PON layer at the top of the upper halocline. Seasonal changes in the molar carbon:nitrogen (C:N) ratio of the suspended particulate organic matter (POM) pool reflect a change in the quality of the organic material that was present and presumably being exported to the sediment and to Arctic Ocean waters adjacent to the Chukchi and Beaufort Sea shelves. In spring, low particulate C:N ratios (<6; i.e., N rich) were observed in nitrate-replete surface waters. By the summer, localized high particulate C:N ratios (>9; i.e., N-poor) were observed in nitrate-depleted surface waters. Low POC and inorganic nutrient concentrations observed in the surface layer suggest that rates of primary, new and export production are low in the Canada Basin region of the Arctic Ocean. 相似文献
494.
Hiroshi Murakami Kosei Sasaoka Kohtaro Hosoda Hajime Fukushima Mitsuhiro Toratani Robert Frouin B. Greg Mitchell Mati Kahru Pierre-Yves Deschamps Dennis Clark Stephanie Flora Motoaki Kishino Sei-Ichi Saitoh Ichio Asanuma Akihiko Tanaka Hiroaki Sasaki Katsumi Yokouchi Yoko Kiyomoto Hiroaki Saito Cécile Dupouy Absornsuda Siripong Satsuki Matsumura Joji Ishizaka 《Journal of Oceanography》2006,62(3):373-393
The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April
2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between
GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for
aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI
ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences
(MedPD) between GLI and in-situ data were 14.1–35.7% for nLws at 380–565 nm, 52.5–74.8% nLws at 625–680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6%
for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products
are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated
in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that
we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection
for further applications, including coastal monitoring and the combined use of products from multiple sensors. 相似文献
495.
The three-dimensional array of current velocity and temperature sensors for the Internal Wave Experiment (IWEX) was supported on a tripod mooring rising from the sea floor to a height of 5 km in water
km deep. The mooring was so designed that its current-induced motions would be small, as required by the experiment. Sensitivity of the mooring excursions to cable buoyancy, leg inclination, apex buoyancy and cable size was examined by computer simulation to optimize the design.When deployed the mooring carried nine precision pressure recorders to monitor its configuration and stability. After removal of the tidal pressure variations, the pressure records confirmed vertical excursions small enough to contribute only insignificant noise to the velocity measurements. Comparison of the measured excursions with those predicted by computer simulation using actual current measurements showed good agreement. 相似文献
496.
Observations of gamma-ray lines from solar flares by SMM demonstrated that energetic protons and heavy ions are accelerated during the impulsive phase. In order to understand the acceleration mechanism for gamma-ray producing protons and heavy ions, we have studied the characteristics of the flares from which gamma-ray lines were observed by SMM In order to identify the characteristics unique to the gamma-ray line flares, we have also studied intense hard X-ray flares with no gamma-ray line emissions. We have found the following characteristics: 1) Most of the gamma-ray line flares produced intense radio bursts of types II and IV. 2) For most of the gamma-ray line flares, the time profiles of high-energy (? 300 keV) hard X-rays are delayed by order of several seconds with respect to those of low-energy hard X-rays. The delay times seem to be correlated with the spatial sizes of the flares. 3) In Hα importance, the gamma-ray line flares range from sub-flares to importance-3 flares. 4) The hard X-ray spectra of the gamma-ray line flares are generally flatter (harder) than those of flares with no gamma-ray line emission. From these characteristics, we conclude that the first-order Fermi acceleration operating in a flare loop is likely to be the acceleration mechanism for energetic protons and heavy ions as well as relativistic electrons. 相似文献
497.
Alan L. Kiplinger B. R. Dennis A. Gordon Emslie K. J. Frost L. E. Orwig 《Solar physics》1983,86(1-2):239-240
We present the results of a search for fast spikes in 5483 hard X-ray solar flares as observed with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission (SMM). Hundreds of fast spikes with durations of less than 1 second have been detected at time resolutions of 128 ms and 10 ms. Fast spikes have been detected with rise and decay times as short as 20 ms and with widths as short at 45 ms that represent the fastest hard X-ray variations yet seen from the Sun. The observations of such fast variations place new constraints on the physical nature of the source. 相似文献
498.
499.
500.
We report observations at 0.56 and 2.2 μm of the Apollo asteroid 1976 AA made during its discovery apparition. We derive a 2.2-μm relative spectral reflectance (scaled to unity at 0.56 μm) of R(2.2 μm) = 1.5 ± 0.3. This 2.2-μm reflectance is not compatible with a carbonaceous surface composition. However, it is compatible with a wide variety of meteoritic types including ordinary chondrites, stony irons, and mesosiderites. Thus, 1976 AA may have a silicate surface similar to other Apollo-Amor objects. 相似文献