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71.
We present a mechanical method to horizontally section soft bottom sediment cores to minimize the vertical post-sampling redistribution
of motile infaunal macroinvertebrates. A clear acrylic core tube for a standard Kajak-Brinkhurst corer was modified by cutting
a series of horizontal slits into the side of the core tube to allow the insertion of sectioning plates for physically sealing
each section immediately after core retrieval. The modification is simple, inexpensive and easily adapted to any open barrel
gravity corer. 相似文献
72.
73.
74.
Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O: corrections and additional experimental data 总被引:2,自引:0,他引:2
Melting relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been reinvestigated using Schreinemakers analysis and hydrothermal experiments. The reaction sanidine+muscovite+zoisite+quartz+vapor =melt has been bracketed at 10, 15, and 20 kbars and 670–680, 680–690, and 690–700° C, respectively and it marks the lowest solidus temperatures in the system investigated.Below 10 kbars, experimental data on the beginning of melting in zoisite- or muscovite-bearing anorthite+sanidine assemblages have been obtained, which are not showing any differences and therefore point to melt compositions close to the feldspar-quartz join. 相似文献
75.
The spectral irradiance at the center of the solar H I Lyman α (, referred to as Lyα in this paper) line profile is the main excitation source responsible for the atomic hydrogen resonant scattering of cool material in our Solar System. It has therefore to be known with the best possible accuracy in order to model the various Lyα emissions taking place in planetary, cometary, and interplanetary environments. Since the only permanently monitored solar irradiance is the total one (i.e. integrated over the whole Lyα line profile), Vidal-Madjar [1975. Evolution of the solar Lyman alpha flux during four consecutive years. Solar Phys. 40, 69-86] using Orbiting Solar Observatory 5 (OSO-5) satellite Lyα data, established a semi-empirical formula allowing him to deduce the central spectral Lyα irradiance from the total one. This relation has been extensively used for three decades. But, at the low altitude of the OSO-5 orbit, the central part of the solar line profile was deeply absorbed by a large column of exospheric atomic hydrogen. Consequently, the spectral irradiance at the center of the line was obtained by a complex procedure confronting the observations with simulations of both the geocoronal absorption and the self-reversed shape of the solar Lyα profile. The SUMER spectrometer onboard SOHO positioned well outside the hydrogen geocorona, provided full-Sun Lyα profiles, not affected by such an absorption [Lemaire et al., 1998. Solar H I Lyman α full disk profile obtained with the SUMER/SOHO spectrometer. Astron. Astrophys. 334, 1095-1098; 2002. Variation of the full Sun Hydrogen Lyman α and β profiles with the activity cycle. Proc. SOHO 11 Symposium, ESA SP-508, 219-222; 2004. Variation of the full Sun Hydrogen Lyman profiles through solar cycle 23. COSPAR 2004 Meeting], making it—for the first time—possible to measure the spectral and total Lyα solar irradiances directly and simultaneously. A new relation between these two quantities is derived in an expression that is formally similar to the previous one, but with significantly different parameters. After having discussed the potential causes for such differences, it is suggested that the new relation should replace the old one for any future modeling of the numerous Lyα absorptions and emissions observed in the Solar System. 相似文献
76.
Paulo Cesar Abreu César S. B. Costa Carlos Bemvenuti Clarisse Odebrecht Wilhelm Graneli Alexandre M. Anesio 《Estuaries and Coasts》2006,29(2):277-285
Stable isotopes ratios (δ13C and δ15N) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the Patos Lagoon
estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that
receives the Rio Grande city sewage and effluencts of several industries. δ13C values of organisms collected in both subsystems were not different, but δ15N values had significant statistical differences, ca. 3.5‰ higher in the Mangueira bay. It is likely that primary producers
and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The
stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and
due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital
fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms.
The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet
compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus
do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate
their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants. 相似文献
77.
The role of recharge and evapotranspiration as hydraulic drivers of ion concentrations in shallow groundwater on Everglades tree islands,Florida (USA)
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Pamela L. Sullivan René M. Price Fernando Miralles‐Wilhelm Mike S. Ross Leonard J. Scinto Thomas W. Dreschel Fred H. Sklar Eric Cline 《水文研究》2014,28(2):293-304
Recently, evapotranspiration has been hypothesized to promote the secondary formation of calcium carbonate year‐round on tree islands in the Everglades by influencing groundwater ions concentrations. However, the role of recharge and evapotranspiration as drivers of shallow groundwater ion accumulation has not been investigated. The goal of this study is to develop a hydrologic model that predicts the chloride concentrations of shallow tree island groundwater and to determine the influence of overlying biomass and underlying geologic material on these concentrations. Groundwater and surface water levels and chloride concentrations were monitored on eight constructed tree islands at the Loxahatchee Impoundment Landscape Assessment (LILA) from 2007 to 2010. The tree islands at LILA were constructed predominately of peat, or of peat and limestone, and were planted with saplings of native tree species in 2006 and 2007. The model predicted low shallow groundwater chloride concentrations when inputs of regional groundwater and evapotranspiration‐to‐recharge rates were elevated, while low evapotranspiration‐to‐recharge rates resulted in a substantial increase of the chloride concentrations of the shallow groundwater. Modeling results indicated that evapotranspiration typically exceeded recharge on the older tree islands and those with a limestone lithology, which resulted in greater inputs of regional groundwater. A sensitivity analysis indicated the shallow groundwater chloride concentrations were most sensitive to alterations in specific yield during the wet season and hydraulic conductivity in the dry season. In conclusion, the inputs of rainfall, underlying hydrologic properties of tree islands sediments and forest structure may explain the variation in ion concentration seen across Everglades tree islands. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
78.
Klaus Wilhelm Ingolf E. Dammasch Donald M. Hassler 《Astrophysics and Space Science》2002,282(1):189-207
The plasma conditions in the solar atmosphere and, in particular, in coronal holes are summarized, before space-borne instrumentation
for observing these regions in vacuum-ultraviolet light is briefly introduced with the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) as example. Spectroscopic measurements of
small plasma jets are then analyzed in detail. Magnetic reconnection is thought to be responsible for heating the corona of
the Sun as well as accelerating the solar wind by converting magnetic energy into thermal and kinetic energies. The continuous
outflow of the fast solar wind from coronal holes on ‘open’ field lines, which reach out into interplanetary space, then requires
many reconnection events of very small scale sizes – most of them probably below the resolution capabilities of present-day
instruments. Our observations of such an event have been obtained with the Solar and Heliospheric Observatory (SOHO) providing
both high-resolution imaging and spectral information for structural and dynamical studies. We find whirling or rotating motions
as well as jets with acceleration along their propagation paths in close spatial and temporal vicinity to the coronal jet.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
A. Glindemann J. Algomedo R. Amestica P. Ballester B. Bauvir E. Bugueño S. Correia F. Delgado F. Delplancke F. Derie Ph. Duhoux E. di Folco A. Gennai B. Gilli P. Giordano Ph. Gitton S. Guisard N. Housen A. Huxley P. Kervella M. Kiekebusch B. Koehler S. Lévêque A. Longinotti S. Ménardi S. Morel F. Paresce T. Phan Duc A. Richichi M. Schöller M. Tarenghi A. Wallander M. Wittkowski R. Wilhelm 《Astrophysics and Space Science》2003,286(1-2):35-44
The Very Large Telescope (VLT) Observatory on Cerro Paranal (2635 m) in Northern Chile is approaching completion. After the
four 8-m Unit Telescopes (UT) individually saw first light in the last years, two of them were combined for the first time
on October 30, 2001 to form a stellar interferometer, the VLT Interferometer. The combination in pairs of all four UTs was
completed in September 2002. In this article, we will describe the subsystems of the VLTI and the planning for the following
years.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
80.