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31.
Yiwu Zhu Kurt S. Tande Meng Zhou 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1922
Northern Norwegian shelf regions are highly productive, supporting fisheries rich in commercially important species such as cod, herring and capelin. It has been long recognized that the mesoscale jets, meanders and eddies associated with interactions between the North Atlantic Current, Norwegian Coastal Current and regional bottom topographic features such as troughs, banks and shelfbreaks play important roles in transporting and retaining zooplankton. To investigate zooplankton distributions and their correspondence with the physical fields, three large-scale surveys with mesoscale resolutions on physical and biological fields were conducted in northern Norwegian shelf regions between latitudes 68°15′N and 70°15′N in springs of 2000–2002. Survey results provide insights into the relationships between zooplankton distributions and the physical features such as fronts, the Norwegian Coastal Current and eddies related to topographic features. The physical and biological data are integrated and analyzed focusing on water types, estimation of geostrophic currents from direct current measurements, along-shelf transport of zooplankton, and retention of zooplankton by the mesoscale meander–eddy over a typical bank area on the shelf. The estimated mean transport in the upper 100 m on the shelf in the survey region is approximately 6.4×103 tonnes wet weight day−1 northward. High zooplankton abundances were found over both Malangsgrunnen and Sveinsgrunnen banks. The specific accumulation rate from northward–southward transport in the upper 100 m over Malangsgrunnen was approximately 0.08 day−1, while variable currents with an offshore gradient of zooplankton abundance over Sveinsgrunnen implies an offshore dispersion of coastal-originated zooplankton cohort. 相似文献
32.
33.
Kurt Liffman 《Astrophysics and Space Science》2007,311(1-3):69-74
We discuss the star-disk electric circuit for a young stellar object (YSO) and calculate the expected torques on the star
and the disk. We obtain the same disk magnetic field and star-disk torques as given by standard magnetohydrodynamic (MHD)
analysis. We show how a short circuit in the star-disk electric circuit may produce a magnetically-driven jet flow from the
inner edge of a disk surrounding a young star.
An unsteady bipolar jet flow is produced that flows perpendicular to the disk plane. Jet speeds of order hundreds of kilometers
per second are possible, while the outflow mass loss rate is proportional to the mass accretion rate and is a function of
the disk inner radius relative to the disk co-rotation radius. 相似文献
34.
A database combining information about solar proton enhancements (SPEs) near the Earth and soft X-ray flares (GOES measurements)
has been used for the study of different correlations through the period from 1975 to May 2006. The emphasis of this work
is on the treatment of peak-size distributions of SXR flares and SPEs. The frequency of SXR flares and solar proton events
(>10 and >100 MeV, respectively) for the past three solar cycles has been found to follow mainly a power-law distribution
over three to five orders of magnitude of fluxes, which is physically correct beyond the “sensitivity” problem with the smallest
peak values. The absence of significant spectral steepening in the domain of the highest peak values demonstrates that during
the period considered, lasting 30 years, the limit of the highest flare’s energy release has not yet been achieved. The power-law
exponents were found to be −2.19±0.04, −1.34±0.02, and −1.46±0.04, for the total SXR flare distribution and the total SPE
distributions (for both E
P>10 MeV and E
P>100 MeV), respectively. For SPEs associated with flares located to the West of 20° W, the exponents are −1.22±0.05 (E
P>10 MeV) and −1.26±0.03 (E
P>100 MeV). The size distribution for corresponding flares follows a power law with a slope of −1.29±0.12. Thus, X-ray and
proton fluxes produced in the same solar events have very similar distribution shapes. Moreover, the derived slopes are not
incompatible with a linear dependence between X-ray flare power and proton fluxes near the Earth. A similar statistical relation
is obtained independently from the direct comparison of the X-ray and proton fluxes. These all argue for a statistically significant
relationship between X-ray and proton emissions. 相似文献
35.
Sulfide oxidizing bacterial mats are common in regions of the continental shelves characterized by high primary production and the resultant oxygen minimum zone. These mats are made up of several species of Beggiatoa and/or Thioploca, which oxidize sulfide that is generated in the sediment. Thioploca spp. inhabit a large polysaccharide sheath that encompasses bundles of 1–20 filaments (trichomes), each ranging from 3 to 60 μm in diameter. This sheath has been shown to be a critical component of the autecology of Thioploca. Analysis of Thioploca from cold seeps in Monterey Bay using light and transmission electron microscopy identified new and diverse microbial assemblages associated with interstitial spaces between trichomes, inside the sheath. Small diameter, non‐vacuolate, filamentous prokaryotes were numerous. Amoebae, euglenozoa, ciliates and other protists of unknown affiliation were observed in sheaths. Most of the protists possessed food vacuoles and some protists showed ultrastructural evidence of endosymbionts. These observations suggest that Thioploca sheaths may serve as oases on the sea floor, providing nutritional and detoxification services to previously unrecognized microbial partners. 相似文献
36.
Sobhi Samhan Kurt Friese Wolf von Tümpling Herbert Pöllmann Heinz Hoetzl Marwan Ghanem 《Environmental Earth Sciences》2014,71(4):1533-1539
Al-Qilt catchment, located east of both the Ramallah and Jerusalem districts is strongly influenced by waste waters discharged from Israeli settlements and Palestinian urban centers. In this research, our aim was to verify the chemical status of the surface sediments from the Al-Qilt catchment during 2008/2009. For this purpose, 36 surface sediment samples were collected and analyzed with ICP/MS within the fraction of below 63 μm. The extent of contamination of trace metals from Al-Qilt sediments sites were measured by evaluating the contamination factors (CF) from digestion by aqua regia and additionally by sequential extraction steps using the BCR-method. On the basis of the calculated CF, sediments appear particularly contaminated with Zn, Cu, Ag, Sn, Cd, Hg, Bi, and B. Three regions, Wadi Sweanit, Ras Al-Qilt, and Qalandiah have been identified as critical points of contamination. Trace metal inputs to the Al-Qilt catchment need to be kept under strict control in the future since Ras Al-Qilt is considered as one of the important springs in the area and is used for domestic purposes. Moreover, it will be susceptible to pollution if no action is taken to decrease the pollution at the upstream of Al-Qilt. 相似文献
37.
S. Alan Stern Jason C. Cook Jean -Yves Chaufray Paul D. Feldman G. Randall Gladstone Kurt D. Retherford 《Icarus》2013
We report on the detection of H2 as seen in our analysis of twilight observations of the lunar atmosphere observed by the LAMP instrument aboard NASA’s Lunar Reconnaissance Orbiter. Using a large amount of data collected on the lunar atmosphere between September 2009 and March 2013, we have detected and identified, the presence of H2 in the native lunar atmosphere, for the first time. We derive a surface density for H2 of 1.2 ± 0.4 × 103 cm−3 at 120 K. This is about 10 times smaller than originally predicted, and several times smaller than previous upper limits from the Apollo era data. 相似文献
38.
Kuznetsov S. N. Bogomolov A. V. Denisov Yu. I. Kordylewski Z. Kudela K. Kurt V. G. Lisin D. V. Myagkova I. N. Podorol'skii A. N. Podosenova T. B. Svertilov S. I. Sylwester J. Stepanov A. I. Yushkov B. Yu. 《Solar System Research》2003,37(2):121-127
Based on X-ray, gamma-ray, and charged-particle measurements with several instruments onboard the Coronas-F satellite and on ACE and GOES experimental data presented on the Internet, we investigate the parameters of the solar flare of November 4, 2001, and the energetic-particle fluxes produced by it in circumterrestrial space. The increase in relativistic-electron fluxes for about 1.5 days points to a moving source (shock front). The structure of the energetic-particles fluxes in the second half of November 5, 2001, can be explained by the passage of the coronal mass ejection that was ejected on November 1, 2001, and that interacted with the shock wave from the flare of November 4, 2001. 相似文献
39.
40.
We show that smoothed time series of 7 indices of solar activity exhibit significant solar cycle dependent differences in
their relative variations during the past 20 years. In some cases these observed hysteresis patterns start to repeat over
more than one solar cycle, giving evidence that this is a normal feature of solar variability. Among the indices we study,
we find that the hysteresis effects are approximately simple phase shifts, and we quantify these phase shifts in terms of
lag times behind the leading index, the International Sunspot Number. Our measured lag times range from less than one month
to greater than four months and can be much larger than lag times estimated from short-term variations of these same activity
indices during the emergence and decay of major active regions. We argue that hysteresis represents a real delay in the onset
and decline of solar activity and is an important clue in the search for physical processes responsible for changing solar
emission at various wavelengths.
The High Altitude Observatory is sponsored by the National Science Foundation. 相似文献