Protein carbonyls and antioxidant defenses in corkwing wrasse (Symphodus melops) from a heavy metal polluted and a PAH polluted site     

Almroth BC  Sturve J  Stephensen E  Holth TF  Förlin L 《Marine environmental research》2008,66(2):271-277

The use of fish in environmental monitoring has become increasingly important in recent years as anthropogenic substances, many of which function as prooxidants, are accumulating in aquatic environments. We have measured a battery of antioxidant defenses as a measure of oxidative status, as well as protein carbonylation as a measure of oxidative damage, in corkwing wrasse (Symphodus melops) captured near a disused copper mine, where water and sediment are contaminated with heavy metals, and an aluminum smelter, a site contaminated with PAHs. Results were compared to two different reference sites. Fish at the heavy metal site had lower glucose-6-phosphate dehydrogenase activity and elevated protein carbonyls (1.8 times) compared to fish from the reference site. At the PAH site, EROD was increased 2-fold, while total glutathione and methemoglobin reductase concentration, were decreased. No differences were seen in protein carbonyl levels at the PAH site. Measures of both antioxidant defenses and oxidative damage should be used when assessing effects of xenobiotics on oxidative stress in fish species.  相似文献   

Angular momentum transport and disc morphology in smoothed particle hydrodynamics simulations of galaxy formation     

Tobias Kaufmann  Lucio Mayer  James Wadsley  Joachim Stadel  Ben Moore 《Monthly notices of the Royal Astronomical Society》2007,375(1):53-67

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δ13C signature of early graphite and subsequently formed microdiamond from the Saxonian Erzgebirge,Germany     

Hans‐Joachim Massonne  Wenmao Tu 《地学学报》2007,19(6):476-480

Microdiamond and graphite occur in quartzofeldspathic rocks (saidenbachites) of the central Erzgebirge in Saxony. Zircon from such rocks contains not only relatively high but also variable amounts of early formed graphite and later crystallized diamond, however no carbonate. Six purified zircon concentrates were analysed by mass spectrometry for δ₁₃C(PDB) values which were between −24 and −33‰. The carbon inclusions resulted in C contents of the concentrates as high as 0.5 wt%. It is hypothesized that the observed δ₁₃C signature results from organic material in the sedimentary protoliths of the saidenbachites probably deposited not earlier than Mid‐Devonian. This material was transformed to graphite during early metamorphism and subsequently to diamond after an anatectic event at great depths (>150 km). During these processes, the δ₁₃C signature of the carbon did not (significantly) change.  相似文献   

Decorrelated GRACE time-variable gravity solutions by GFZ,and their validation using a hydrological model   总被引：14，自引：6，他引：8  

J. Kusche  R. Schmidt  S. Petrovic  R. Rietbroek 《Journal of Geodesy》2009,83(10):903-913

We have analyzed recent gravity recovery and climate experiment (GRACE) RL04 monthly gravity solutions, using a new decorrelating post-processing approach. We find very good agreement with mass anomalies derived from a global hydrological model. The post-processed GRACE solutions exhibit only little amplitude damping and an almost negligible phase shift and period distortion for relevant hydrological basins. Furthermore, these post-processed GRACE solutions have been inspected in terms of data fit with respect to the original inter-satellite ranging and to SLR and GPS observations. This kind of comparison is new. We find variations of the data fit due to solution post-processing only within very narrow limits. This confirms our suspicion that GRACE data do not firmly ‘pinpoint’ the standard unconstrained solutions. Regarding the original Kusche (J Geod 81:733–749, 2007) decorrelation and smoothing method, a simplified (order-convolution) approach has been developed. This simplified approach allows to realize a higher resolution—as necessary, e.g., for generating computed GRACE observations—and needs far less coefficients to be stored.  相似文献   

Early Mars volcanic sulfur storage in the upper cryosphere and formation of transient SO2‐rich atmospheres during the Hesperian          下载免费PDF全文

F. Schmidt  E. Chassefière  F. Tian  E. Dartois  J.‐M. Herri  O. Mousis 《Meteoritics & planetary science》2016,51(11):2226-2233

In a previous paper (Chassefière et al. 2013 ), we have shown that most volcanic sulfur released to the early Mars atmosphere could have been trapped in the upper cryosphere under the form of CO₂‐SO₂ clathrates. Huge amounts of sulfur, up to the equivalent of an ~1 bar atmosphere of SO₂, would have been stored in the Noachian upper cryosphere, then massively released to the atmosphere during the Hesperian due to rapidly decreasing CO₂ pressure. It could have resulted in the formation of the large sulfate deposits observed mainly in Hesperian terrains, whereas no or little sulfates are found at the Noachian. In the present paper, we first clarify some aspects of our previous work. We discuss the possibility of a smaller cooling effect of sulfur particles, or even of a net warming effect. We point out the fact that CO₂‐SO₂ clathrates formed through a progressive enrichment of a pre‐existing reservoir of CO₂ clathrates and discuss processes potentially involved in the slow formation of a SO₂‐rich upper cryosphere. We show that episodes of sudden destabilization at the Hesperian may generate 1000 ppmv of SO₂ in the atmosphere and contribute to maintaining the surface temperature above the water freezing point.  相似文献   

Editors' note: Astron. Nachr. 6/2010     

Wolfgang Schmidt  Rolf Schlichenmaier  Oskar von der Lühe 《Astronomische Nachrichten》2010,331(6):557-557

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From planetesimals to terrestrial planets: N-body simulations including the effects of nebular gas and giant planets     

Ryuji Morishima  Joachim Stadel 《Icarus》2010,207(2):517-535

We present results from a suite of N-body simulations that follow the formation and accretion history of the terrestrial planets using a new parallel treecode that we have developed. We initially place 2000 equal size planetesimals between 0.5 and 4.0 AU and the collisional growth is followed until the completion of planetary accretion (>100 Myr). A total of 64 simulations were carried out to explore sensitivity to the key parameters and initial conditions. All the important effect of gas in laminar disks are taken into account: the aerodynamic gas drag, the disk-planet interaction including Type I migration, and the global disk potential which causes inward migration of secular resonances as the gas dissipates. We vary the initial total mass and spatial distribution of the planetesimals, the time scale of dissipation of nebular gas (which dissipates uniformly in space and exponentially in time), and orbits of Jupiter and Saturn. We end up with 1-5 planets in the terrestrial region. In order to maintain sufficient mass in this region in the presence of Type I migration, the time scale of gas dissipation needs to be 1-2 Myr. The final configurations and collisional histories strongly depend on the orbital eccentricity of Jupiter. If today’s eccentricity of Jupiter is used, then most of bodies in the asteroidal region are swept up within the terrestrial region owing to the inward migration of the secular resonance, and giant impacts between protoplanets occur most commonly around 10 Myr. If the orbital eccentricity of Jupiter is close to zero, as suggested in the Nice model, the effect of the secular resonance is negligible and a large amount of mass stays for a long period of time in the asteroidal region. With a circular orbit for Jupiter, giant impacts usually occur around 100 Myr, consistent with the accretion time scale indicated from isotope records. However, we inevitably have an Earth size planet at around 2 AU in this case. It is very difficult to obtain spatially concentrated terrestrial planets together with very late giant impacts, as long as we include all the above effects of gas and assume initial disks similar to the minimum mass solar nebular.  相似文献   

Oxidation of CO on surface hematite in high CO₂ atmospheres     

John Lee Grenfell  Joachim W. Stock  Stefanie Gebauer 《Planetary and Space Science》2010,58(10):1252-1257

We propose a mechanism for the oxidation of gaseous CO into CO₂ occurring on the surface mineral hematite (Fe₂O₃(s)) in hot, CO₂-rich planetary atmospheres, such as Venus. This mechanism is likely to constitute an important source of tropospheric CO₂ on Venus and could at least partly address the CO₂ stability problem in Venus’ stratosphere, since our results suggest that atmospheric CO₂ is produced from CO oxidation via surface hematite at a rate of 0.4 petagrammes (Pg) CO₂ per (Earth) year on Venus which is about 45% of the mass loss of CO₂ via photolysis in the Venusian stratosphere. We also investigated CO oxidation via the hematite mechanism for a range of planetary scenarios and found that modern Earth and Mars are probably too cold for the mechanism to be important because the rate-limiting step, involving CO(g) reacting onto the hematite surface, proceeds much slower at lower temperatures. The mechanism may feature on extrasolar planets such as Gliese 581c or CoRoT-7b assuming they can maintain solid surface hematite which, e.g. starts to melt above about 1200 K. The mechanism may also be important for hot Hadean-type environments and for the emerging class of hot Super-Earths with planetary surface temperatures between about 600 and 900 K.  相似文献   

A parallel global-implicit 2-D solver for reactive transport problems in porous media based on a reduction scheme and its application to the MoMaS benchmark problem     

Joachim Hoffmann  Serge Kr?utle  Peter Knabner 《Computational Geosciences》2010,14(3):421-433

In this article, an approach for the efficient numerical solution of multi-species reactive transport problems in porous media is described. The objective of this approach is to reformulate the given system of partial and ordinary differential equations (PDEs, ODEs) and algebraic equations (AEs), describing local equilibrium, in such a way that the couplings and nonlinearities are concentrated in a rather small number of equations, leading to the decoupling of some linear partial differential equations from the nonlinear system. Thus, the system is handled in the spirit of a global implicit approach (one step method) avoiding operator splitting techniques, solved by Newton’s method as the basic algorithmic ingredient. The reduction of the problem size helps to limit the large computational costs of numerical simulations of such problems. If the model contains equilibrium precipitation-dissolution reactions of minerals, then these are considered as complementarity conditions and rewritten as semismooth equations, and the whole nonlinear system is solved by the semismooth Newton method.  相似文献   

Using DORIS measurements for modeling the vertical total electron content of the Earth’s ionosphere     

Denise Dettmering  Marco Limberger  Michael Schmidt 《Journal of Geodesy》2014,88(12):1131-1143

The Doppler orbitography and radiopositioning integrated by satellite (DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth’s ionosphere. It measures with two frequencies in L-band with a relative frequency ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global vertical total electron content (VTEC) modeling can be expected. This paper investigates the capability of DORIS dual-frequency phase observations for deriving VTEC and the contribution of these data to global VTEC modeling. The DORIS preprocessing is performed similar to commonly used global navigation satellite systems (GNSS) preprocessing. However, the absolute DORIS VTEC level is taken from global ionospheric maps (GIM) provided by the International GNSS Service (IGS) as the DORIS data contain no absolute information. DORIS-derived VTEC values show good consistency with IGS GIMs with a RMS between 2 and 3 total electron content units (TECU) depending on solar activity which can be reduced to less than 2 TECU when using only observations with elevation angles higher than \(50^\circ \) . The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12  % can be achieved. The accuracy directly beneath the DORIS satellites’ ground-tracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes.  相似文献