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Degradation of Monochloronitrobenzenes by Pseudomonas acidovorans CA50 Pseudomonas acidovorans strain CA50 was used for degradation experiments with monochloronitrobenzenes in aerobic batch culture. The monochloronitrobenzenes were reduced to the corresponding monochloroanilines. The reduction only occurred with an additional carbon and nitrogen source. Chlorocatechols were found to be present. 3-Chlorocatechol accumulated in the presence of 2-chloroaniline, whereas 4-chlorocatechol was an intermediate metabolite of 3- and 4-chloroaniline. Contrary to the degradation of monochloronitrobenzenes, Pseudomonas acidovorans strain CA50 used the monochloroanilines as a sole source of carbon, energy, and nitrogen for growth. The oxidation of monochloroanilines was not repressed by the additional substrates. 2-Chloronitrobenzene was degraded with the lowest rate because of the low turnover of the intermediate metabolite 2-chloroaniline. 3-Chloronitrobenzene was completely degraded also in a mixture. A complete degradation of 4-chloronitrobenzene was achieved only when it was the sole chloronitrobenzene. The results suggest that a dechlorination and mineralization of monochlornitrobenzenes is possible, but for a final proof, further investigations will be necessary. 相似文献
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Helen V. McGregor Lydie Dupont Jan-Berend W. Stuut Holger Kuhlmann 《Quaternary Science Reviews》2009,28(15-16):1434-1448
Understanding past human–climate–environment interactions is essential for assessing the vulnerability of landscapes and ecosystems to future climate change. This is particularly important in southern Morocco where the current vegetation is impacted by pastoralism, and the region is highly sensitive to climate variability. Here, we present a 2000-year record of vegetation, sedimentation rate, XRF chemical element intensities, and particle size from two decadal-resolved, marine sediment cores, raised from offshore Cape Ghir, southern Morocco. The results show that between 650 and 850 AD the sedimentation rate increased dramatically from 100 cm/1000 years to 300 cm/1000 years, and the Fe/Ca and pollen flux doubled, together indicating higher inputs of terrestrial sediment. Particle size measurements and end-member modelling suggest increased fluvial transport of the sediment. Beginning at 650 AD pollen levels from Cichorioideae species show a sharp rise from 10% to 20%. Pollen from Atemisia and Plantago, also increase from this time. Deciduous oak pollen percentages show a decline, whereas those of evergreen oak barely change. The abrupt increase in terrestrial/fluvial input from 650 to 850 AD occurs, within the age uncertainty, of the arrival of Islam (Islamisation) in Morocco at around 700 AD. Historical evidence suggests Islamisation led to population increase and development of southern Morocco, including expanded pastoralism, deforestation and agriculture. Livestock pressure may have changed the vegetation structure, accounting for the increase in pollen from Cichorioideae, Plantago, and Artemisia, which include many weedy species. Goats in particular may have played a dominant role as agents of erosion, and intense browsing may have led to the decline in deciduous oak; evergreen oak is more likely to survive as it re-sprouts more vigorously after browsing. From 850 AD to present sedimentation rates, Fe/Ca ratios and fluvial discharge remain stable, whereas pollen results suggest continued degradation. Pollen results from the past 150 years suggest expanded cultivation of olives and the native argan tree, and the introduction of Australian eucalyptus trees. The rapidly increasing population in southern Morocco is causing continued pressure to expand pastoralism and agriculture. The history of land degradation presented here suggests that the vegetation in southern Morocco may have been degraded for a longer period than previously thought and may be particularly sensitive to further land use changes. These results should be included in land management strategies for southern Morocco. 相似文献
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Approximating covariance matrices estimated in multivariate models by estimated auto- and cross-covariances 总被引：1，自引：1，他引：0
Quantities like tropospheric zenith delays or station coordinates are repeatedly measured at permanent VLBI or GPS stations
so that time series for the quantities at each station are obtained. The covariances of these quantities can be estimated
in a multivariate linear model. The covariances are needed for computing uncertainties of results derived from these quantities.
The covariance matrix for many permanent stations becomes large, the need for simplifying it may therefore arise under the
condition that the uncertainties of derived results still agree. This is accomplished by assuming that the different time
series of a quantity like the station height for each permanent station can be combined to obtain one time series. The covariance
matrix then follows from the estimates of the auto- and cross-covariance functions of the combined time series. A further
approximation is found, if compactly supported covariance functions are fitted to an estimated autocovariance function in
order to obtain a covariance matrix which is representative of different kinds of measurements. The simplification of a covariance
matrix estimated in a multivariate model is investigated here for the coordinates of points of a grid measured repeatedly
by a laserscanner. The approximations are checked by determining the uncertainty of the sum of distances to the points of
the grid. To obtain a realistic value for this uncertainty, the covariances of the measured coordinates have to be considered.
Three different setups of measurements are analyzed and a covariance matrix is found which is representative for all three
setups. Covariance matrices for the measurements of laserscanners can therefore be determined in advance without estimating
them for each application. 相似文献
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M. Focardi E. Pace M. Farina A. M. Di Giorgio J. Colomé Ferrer I. Ribas C. Sierra Roig L. Gesa Bote J. C. Morales J. Amiaux C. Cara J. L. Augurés E. Pascale G. Morgante V. Da Deppo M. Pancrazzi V. Noce S. Pezzuto M. Frericks F. Zwart G. Bishop K. Middleton P. Eccleston G. Micela G. Tinetti 《Experimental Astronomy》2018,45(1):1-20
In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern. 相似文献
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Katja K. Hirsch Magdalena Scheck-Wenderoth Jan-Diederik van Wees Gesa Kuhlmann Douglas A. Paton 《Marine and Petroleum Geology》2010
The Orange Basin offshore southwest Africa appears to represent a classical example of continental rifting and break up associated with large-scale, transient volcanism. The presence of lower crustal bodies of high seismic velocities indicates that large volumes of igneous crust formed as a consequence of lithospheric extension. 相似文献
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Seismic velocities from the Yaquina forearc basin off Peru: evidence for free gas within the gas hydrate stability zone 总被引：3，自引：0，他引：3
Gesa L. Netzeband Christian P. Hübscher Dirk Gajewski Jan W. G. Grobys Jörg Bialas 《International Journal of Earth Sciences》2005,94(3):420-432
Multichannel seismic (MCS) data from the Yaquina forearc basin off Peru reveal a complex distribution of gas and gas hydrate related reflections. Lateral variations of the reflection pattern at the assumed base of the gas hydrate stability zone in terms of continuity, amplitude, and signal attenuation underneath are observed, as well as the possible occurrence of paleo-bottom simulating reflectors (BSRs). Phase reversed reflections above the bottom simulating reflector point to free gas within the gas hydrate stability zone (GHSZ). To constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the MCS line from high-resolution ocean bottom hydrophone recordings with two independent methods. Heat flux values estimated on the basis of the velocity-depth functions increase with decreasing amplitude of the BSR and peak near chemoherms. These results suggest a model of the Yaquina Basin where free gas is trapped under parts of the BSR, and within the GHSZ, particularly under the seafloor and under an erosional unconformity. The hypothesis of a paleo-BSR that reflects the uplift of the base of the hydrate stability zone caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values. 相似文献
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O. Esper K. A. F. Zonneveld C. Höll B. Karwath H. Kuhlmann R. R. Schneider A. Vink I. Weise-Ihlo H. Willems 《International Journal of Earth Sciences》2000,88(4):680-693
Despite the increasing interest in the South Atlantic Ocean as a key area of the heat exchange between the southern and the
northern hemisphere, information about its palaeoceanographic conditions during transitions from glacial to interglacial stages,
the so-called Terminations, are not well understood. Herein we attempt to increase this information by studying the calcareous
dinoflagellate cysts and the shells of Thoracosphaera heimii (calcareous cysts) of five Late Quaternary South Atlantic Ocean cores. Extremely high accumulation rates of calcareous cysts
at the Terminations might be due to a combined effect of increased cyst production and better preservation as result of calm,
oligotrophic conditions in the upper water layers. Low relative abundance of Sphaerodinella albatrosiana compared with Sphaerodinella tuberosa in the Cape Basin may be the result of the relatively colder environmental conditions in this region compared with the equatorial
Atlantic Ocean with high relative abundance of S. albatrosiana. Furthermore, the predominance of S. tuberosa during glacials and interglacials at the observed site of the western Atlantic Ocean reflects decreased salinity in the upper
water layer.
Received: 9 November 1998 / Accepted: 26 October 1999 相似文献