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971.
Carbon isotope fractionation in phospholipid fatty acid biomarkers of bacteria and fungi native to an acid mine drainage lake 总被引:3,自引:0,他引:3
Benjamin R. Cowie Gregory F. Slater Luc Bernier Lesley A. Warren 《Organic Geochemistry》2009,40(9):956-962
This study identifies isotope signatures associated with autotrophic and heterotrophic microbial communities that may provide a means to determine carbon cycling relationships in situ for acid mine drainage (AMD) sites. Stable carbon isotope ratios (δ13C) of carbon sources, bulk cells, and membrane phospholipids (PLFA) were measured for autotrophic and heterotrophic microbial enrichment cultures from a mine tailings impoundment in northern Ontario, Canada, and for pure strains of the sulfur oxidizing bacteria Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The autotrophic enrichments had indistinguishable PLFA distributions from the pure cultures, and the PLFA cyc-C19:0 was determined to be a unique biomarker in this system for these sulfur oxidizing bacteria. The PLFA distributions produced by the heterotrophic enrichments were distinct from the autotrophic distributions and the C18:2 PLFA was identified as a biomarker for these heterotrophic enrichments. Genetic analysis (16S, 18S rRNA) of the heterotrophic cultures indicated that these communities were primarily composed of Acremonium fungi.Stable carbon isotope analysis revealed that bulk cellular material in all autotrophic cultures was depleted in δ13C by 5.6–10.9‰ relative to their atmospheric CO2 derived carbon source, suggesting that inorganic carbon fixation in these cultures is carbon limited. Individual PLFA from these autotrophs were further depleted by 8.2–14.6‰ compared to the bulk cell δ13C, which are among the largest biosynthetic isotope fractionation factors between bulk cell and PLFA reported in the literature. In contrast, the heterotrophic bulk cells were not significantly fractionated in δ13C relative to their carbon source and heterotrophic PLFA ranged from 3‰ enriched to 4‰ depleted relative to the isotopic composition of their total biomass. These distinct PLFA biomarkers and isotopic fractionations associated with autotrophic and heterotrophic activity in this laboratory study provide potential biomarkers for delineating autotrophic and heterotrophic carbon cycling in AMD environments. 相似文献
972.
Mark B. Dyurgerov & Mark F. Meier 《Geografiska Annaler: Series A, Physical Geography》1999,81(4):541-554
Seasonal mass balance components bw (winter balance) and bs (summer balance) as well as ct (total accumulation) and at (total ablation), can be used directly to infer climate variables. In contrast, ac (net balance of the accumulation area) and aa (net balance of the ablation area), and ba or bn (annual or net balance) can not. The traditional Alpine system of observations of ac and aa , however, can be converted to true seasonal values bw and bs if both pairs of components are simultaneously observed for some years, because a correlation between the two pairs of components exists. We analyzed bw and bs data and their mean, standard deviations and ratios of these to the corresponding net or annual balances for 50 glaciers with relatively long records representing different regions in the northern hemisphere. We also investigated correlations between seasonal components. A negative correlation between bw and bs exists at many glaciers. About two-thirds of the glaciers show insignificant correlations (?0.3 < r < 0.3), implying independence of summer and winter balances. In a few unusual cases the correlations are positive. These different correlations, or lack thereof, may offer insight into feedback conditions that must exist in this climate-related system. The correspondence of the bw and ct , and bs and at , appears to depend largely on the relative amounts of summer snowfall, a function of their climatic environment expressed as [α = (bw+bs)/2]. The contribution of variability of bs to the net balance increases markedly with decreasing values of α. The variability of bw and bs , and therefore the net balance, has been increasing with time; whether this is due to an increase in climate variability or to other causes is not clear. It appears that bw has been increasing with time at the highest altitudes, but bs has been increasing more rapidly especially at low altitudes; the many-glacier average net balance is becoming more negative. 相似文献
973.
Patterns of Nd and Sr isotopic ratios produced by magmatic and post-magmatic processes in the Shiant Isles Main Sill, Scotland 总被引:3,自引:0,他引:3
K. A. Foland F. G. F. Gibb C. M. B. Henderson 《Contributions to Mineralogy and Petrology》2000,139(6):655-671
The Shiant Isles Main Sill of the British Tertiary Igneous Province is a classic example of a differentiated, alkaline basic
sill. Four separate intrusions, each emplaced internally in rapid succession, form a 165-m-thick sill hosted by Lower Jurassic
sedimentary rocks. Extensive Nd and Sr isotopic studies were conducted on samples from a vertical section through the sill
where the relationships of samples to one another are well defined. The results illuminate patterns of modification of isotopic
ratios and clarify the petrogenesis (magma sources, crustal contamination), magmatic processes (bulk mixing, interstitial
liquid mixing), and post-magmatic alteration (hydrothermal effects on Sr and Nd). Overall, the whole-rock initial 87Sr/86Sr ratios range from ∼0.7037 to 0.7061 while initial 143Nd/144Nd ratios vary from ∼0.51243 to 0.51286 (ɛNd∼−0.7 to +5.7) – values that contrast markedly with those of the country rock. Acid leaching (HCl) of the whole-rock samples
that removes analcime indicates that most of the scatter in the 87Sr/86Sr is caused by the ubiquitous sub-solidus, aqueous alteration during which more-radiogenic Sr was introduced into the sill,
especially along the margins, and also reveals magmatic isotopic ratios. In contrast, Nd was immobile during fluid interaction
so that the sill 143Nd/144Nd ratios were not affected, even <1 m from the country-rock contact. Using leached rock values, 87Sr/86Sr and 143Nd/144Nd ratios are inversely correlated from magmatic processes. Magmas with two distinct isotopic compositions were involved:
a more primitive one with 143Nd/144Nd ∼0.51285 and 87Sr/86Sr ∼0.7035 that produced the first two intrusions and a more evolved one (with 0.51252 and 0.7048) that produced the third
intrusion. Mixing of the two magmas was very limited, restricted to near contacts between units, and apparently occurred by
interstitial melt migration. The more evolved crinanitic magma was probably produced from a batch of the more primitive picritic
melt by a small degree of crustal contamination and crystal fractionation during a short crustal residence prior to ascent
and emplacement.
Received: 20 December 1999 / Accepted: 5 May 2000 相似文献
974.
Sh. B. Akhmedov G. B. Gelfreikh F. Fürstenberg J. Hildebrandt A. Krüger 《Solar physics》1983,88(1-2):103-108
Model calculations of the S-component are compared with observations of the RATAN-600 telescope at five discrete microwave frequencies referring to active region McMath No. 15974 on May 1, 1979. The spectral variations of source diameter, flux density, and degree of polarization are used to derive the height scale of the magnetic field in accordance with a magnetic dipole distribution under the assumption of advanced temperature and electron density distributions according to most recent EUV observations. 相似文献
975.
976.
We present the thermal infrared (5-35 μm) spectrum of 956 Elisa as measured by the Spitzer Infrared Spectrograph (“IRS”; Houck, J.R. et al. [2004]. Astrophys. J. Suppl. 154, 18-24) together with new groundbased lightcurve data and near-IR spectra. From the visible lightcurve photometry, we determine a rotation period of 16.494 ± 0.001 h, identify the rotational phase of the Spitzer observations, and estimate the visible absolute magnitude (HV) at that rotational phase to be 12.58 ± 0.04. From radiometric analysis of the thermal flux spectrum, we find that at the time of observation 956 Elisa had a projected radius of 5.3 ± 0.4 km with a visible albedo pV = 0.142 ± 0.022, significantly lower than that of the prototype V-type asteroid, 4 Vesta. (This corresponds to a radius of 5.2 ± 0.4 km at lightcurve mean.) Analysis with the standard thermal model (STM) results in a sub-solar temperature of 292.3 ± 2.8 K and beaming parameter η = 1.16 ± 0.05. Thermophysical modeling places a lower limit of on the thermal inertia of the asteroid’s surface layer (if the surface is very smooth) but more likely values fall between 30 and depending on the sense of rotation.The emissivity spectrum, calculated by dividing the measured thermal flux spectrum by the modeled thermal continuum, exhibits mineralogically interpretable spectral features within the 9-12 μm reststrahlen band, the 15-16.5 μm Si-O-Si stretching region, and the 16-25 μm reststrahlen region that are consistent with pyroxene of diogenitic composition: extant diogenitic pyroxenes fall within the narrow compositional range Wo2±1En74±2Fs24±1. Spectral deconvolution of the 9-12 μm reststrahlen features indicates that up to ≈20% olivine may also be present, suggesting an olivine-diogenite-like mineralogy. The mid-IR spectrum is inconsistent with non-cumulate eucrite as the major component on the surface of 956 Elisa, although cumulate eucrite material may be present at abundances lower than that of the diogenite component.Analysis of new near-IR spectra of 956 Elisa with the Modified Gaussian Model (MGM; Sunshine, J.M., Pieters, C.M., Pratt, S.F. [1990]. J. Geophys. Res. 95 (May), 6955-6966) results in two pyroxene compositions: 75% magnesian low-Ca pyroxene and 25% high-Ca pyroxene. High-Ca pyroxene is not evident in the mid-IR data, but may belong to a component that is underrepresented in the mid-IR spectrum either because of its spatial distribution on the asteroid or because of its particle size. High-Ca pyroxenes that occur as exsolution lamellae may also be more evident spectrally in the NIR than in the mid-IR. In any case, we find that the mid-IR spectrum of 956 Elisa is dominated by emission from material of diogenite-like composition, which has very rarely been observed among asteroids. 相似文献
977.
Zaznobin I. A. Burenin R. A. Lyapin A. R. Khorunzhev G. A. Afanasiev V. L. Grokhovskaya A. A. Dodonov S. N. Eselevich M. V. Uklein R. I. Bikmaev I. F. Khamitov I. M. Gilfanov M. R. Lyskova N. S. Medvedev P. S. Sunyaev R. A. 《Astronomy Letters》2021,47(3):141-149
Astronomy Letters - We present the first results of our program of optical observations for galaxy clusters from the Lockman Hole X-ray survey with the eROSITA telescope onboard the SRG space... 相似文献
978.
Bikmaev I. F. Irtuganov E. N. Nikolaeva E. A. Sakhibullin N. A. Gumerov R. I. Sklyanov A. S. Glushkov M. V. Khamitov I. M. Borisov V. D. Burenin R. A. Zaznobin I. A. Krivonos R. A. Lyapin A. R. Medvedev P. S. Meshcheryakov A. V. Sazonov S. Yu. Sunyaev R. A. Khorunzhev G. A. Gilfanov M. R. 《Astronomy Letters》2021,47(5):277-290
Astronomy Letters - Results of the spectroscopic observations at the 1.5-m Russian–Turkish telescope for another group of 12 X-ray sources discovered by the eROSITA telescope onboard the SRG... 相似文献
979.
The propagation time for solar protons observed during the events of January 24, February 25 and March 17, 1969 are compared with those estimated from numerical solutions of the Fokker-Planck transport equation, using values of the diffusion coefficient of the form K
r
= K
0
r
b
where r is radial distance from the Sun, K
0 is obtained from the plasma-field parameters near the Earth and b varies from - 3 to + 1. K
0 is derived either by assuming that all the magnetic fluctuation power is in small amplitude transverse waves or alternatively in discontinuous changes in ¦B¦ along the flux tube of propagation. In the first case it is found that the K
0 values calculated require either b -3, implying a very rapid wave growth with r, or the Fokker-Planck equation reduces to the situation of purely convective transport which is at variance with the experimental observations. More reasonable results are found in the second case although even here K
0 is probably underestimated. Alternative ways of deducing K
0 empirically from particle anisotropy measurements are put forward and these seem to favour the discontinuity model. 相似文献
980.
Solar radio bursts were observed with a 4-channel radiometer and polarization analyser at wavelenghts around 12 m. The time and frequency resolutions were 10 ms and 100 kHz respectively. Observations on the duration, time profile and frequency splitting are described. 相似文献