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1.
We present a new procedure, the pdf method (pdf=probability density function), for reconstructing Quaternary climate utilizing botanical data. The procedure includes the advantages of the indicator species method by considering the fossil and modern presence and absence of taxa rather than their frequencies, thus avoiding the need for modern analog plant communities. Overcoming the problematic use of absolute limits to describe climate response ranges is the main progress of the pdf method in comparison to the indicator species method. This advantage results from estimating probability density functions (pdfs) for monthly mean January and July temperature conditional on the present day occurrence of single taxa. Gaussian distributions sufficiently approximate pdfs of many, although not all, studied taxa. On the assumption of statistical independence, the procedure calculates a joint pdf as the product of the pdfs of the individual taxa. This algorithm weights each taxon according to the extent of its climate response range expressed by its covariance structure. We interpret the maximum of the resulting pdf as the most likely climate and its confidence interval as the uncertainty range. To avoid an artificial reduction of uncertainty arising from the use of numerous similar pdfs, a preselection method is proposed based on the Mahalanobis distance between pdfs. The pdf method was applied to the Carpinus phase of a profile from Gröbern, Germany, that spans the last interglaciation (Eemian). The reconstructed most probable January and July temperatures of about 0.0°C and 18.4°C barely differ from the modern values of −0.5°C and 18.3°C. 相似文献
2.
Secondary carbonate formations, such as travertine and calcareous tufa deposits, are important archives for quaternary continental climate studies and archaeology. The extremely complex growth mechanisms result in some serious problems for precise mass spectrometric uranium-series dating. Often, detrital and organic particles contaminate the carbonate and large pore volumes yield a great potential for open system behavior. We utilized microscopic, mineralogical and geochemical methods prior to sample selection to determine the abundance of primary calcite, i.e. micrite and spar. Furthermore, the state of alteration was characterized by cathodoluminescence and trace-element analysis. We conclude that travertine and calcareous tufa are appropriate for precise U-series age determination if a) micrite and/or spar are the dominant phases; b) cathodoluminescence of both phases is weak or absent; c) Fe and Al levels are low; and d) Sr concentrations are close to the average of the studied site. We mapped and sampled solely areas of major micrite/spar abundance having minor alteration for accurate U-series dating. When this new method was applied, travertines located in eastern Germany (sites Bad Langensalza, Burgtonna and Weimar-Ehringsdorf) gave single 230Th/238U-ages consistent with the lithological growth sequence and greatly improved compared to previously published chronologies. In addition, we determined 230Th/U isochron ages on bulk samples that confirm our single ages. In contrast to primary calcite, pore cements are homogeneously distributed throughout the travertine fabric and reflect early diagenetic processes and/or weathering. 相似文献
3.
湖泊沉积物中胶黄铁矿的鉴出及其磁学意义 总被引:6,自引:1,他引:6
对青藏高原东部若尔盖盆地钻孔获取的湖泊沉积物进行了详细的岩石磁学调查及矿物学鉴定, 发现大量胶黄铁矿存在, 并认定其为主要的磁载体. 该矿物颗粒细小, 粒度均匀, 可能为生物化学成因. 与大量文献报道的相反, 在长期暴露于空气后, 样品中的胶黄铁矿仍未被氧化. 这可能与钻孔内该矿物被硅质胶结物包裹有关. 研究结果初步揭示了湖泊沉积物磁学研究的复杂性, 同时也为环境磁学机理的研究提供了新的线索. 相似文献
4.
5.
Norbert I. K 《冰川冻土》2004,26(Z1):310-318
The exploration of ice sheets by melting vertical holes into the ground has some tradition in terrestrial glaciology. Such probes have been used since the 1960's to investigate the vertical structure of the ice in Greenland and Antarctica and in alpine glaciers. In this paper we look into the possibility to develop similar devices for use on extraterrestrial icy bodies, like e.g. the polar areas on Mars or the icy satellites of the outer solar system. We report on some basic experiments performed in the cryo-vacuum laboratory of the Space Research Institute of the Austrian Academy of Sciences, Graz. In these experiments the penetration of a simple melting probe into compact and porous water ice (with a snow-like texture) was monitored, both under vacuum conditions and under air pressure. The observed penetration speeds for a given power supply are compared with a simple mathematical model. We conclude that a miniature melting probe with small overall dimensions and a reasonable power demand could well be part of the payload of a future planetary mission, for example to the poles of Mars. Such missions are currently under discussion in several space agencies. Moreover such probes could also e? ectively be used in terrestrial environments. A possible design is presented at the end of the paper. 相似文献
6.
Norbert Schwarzenbeck Ron Erley Belinda S. Mc Swain Peter A. Wilderer Robert L. Irvine 《洁净——土壤、空气、水》2004,32(1):16-24
Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter. At an organic loading rate of 3.2 kg/(m3 d) CODtotal and an influent particle concentration of 0.95 g/L MLSS an average removal of 50% in CODtotal and 80% in CODdissolved could be achieved. A comparison of granular and flocculent sludge grown under the same operating conditions showed no significant difference in removal efficiency although granules exhibited a higher metabolic activity in terms of specific oxygen uptake rate (rO2, X). Two distinct mechanisms of particle removal were observed for granular sludge: during initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge. 相似文献
7.
8.
Olivier Planchon Norbert Silvera Raphael Gimenez David Favis‐Mortlock John Wainwright Yves Le Bissonnais Gerard Govers 《地球表面变化过程与地形》2005,30(7):833-844
This article introduces the SVG (salt‐velocity gauge), a novel automated technique for measuring flow velocity by means of salt tracing. SVG allows a high measuring rate (up to one every 2 seconds), short control section length (down to 10 cm), high accuracy (+[sol ]?1·5 cm s?1), and unbiased calculation of the mean velocity in experimental conditions with turbulent, supercritical flow. A few cubic centimetres of saturated salt solution (NaCl) are injected into the flow at regular time intervals using a programmable solenoid valve. The tracer successively passes two conductivity probes placed a short distance downstream. The transformation of the signal between the two probes is modelled as a one‐dimensional diffusion wave equation. Model calibration gives an estimation of the mean velocity and the diffusion for each salt plume. Two implementations of the SVG technique are described. The first was an outdoors simulated rainfall experiment in Senegal (conductivity probes at 40 cm apart, 8 Hz measurement rate, salt injections at 10 second intervals). Mean velocity was estimated to range between 0·1 and 0·3 m s?1. The second was a laboratory‐based flume experiment (conductivity probes at 10 cm apart, 32 Hz, salt injections at 2 second intervals). Another SVG with probes at 34 cm apart was used for comparison. An acoustic Doppler velocimeter (ADV) was also used to give an independent assessment of velocity. Using the 10 cm salt gauge, estimated mean velocity ranged from 0·6 to 0·9 m s?1 with a standard deviation of 1·5 cm s?1. Comparisons between ADV, 10 cm SVG and 34 cm SVG were consistent and demonstrated that the salt‐tracing results were unbiased and independent of distance between probes. Most peaks were modelled with r2 > 90 per cent. The SVG technology offers an alternative to the dye‐tracing technique, which has been severely criticized in the literature because of the wide interval of recommended values for the correction factor α to be applied to the timings. This article demonstrates that a fixed value of α is inappropriate, since the correction factor varies with velocity, diffusion and the length of the control section. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
10.
Norbert I. Kömle Hui Bing Wen Jie Feng Roman Wawrzaszek Erika S. Hütter Ping He Wojciech Marczewski Borys Dabrowski Kathrin Schröer Tilman Spohn 《Acta Geotechnica》2007,2(2):127-138
A series of thermal conductivity measurements for various materials was performed in a large climate chamber. The size of
the chamber allowed the preparation of relatively large samples in a controlled thermal environment. Three types of thermal
sensors were used: (1) two needle probes; (2) a grid of temperature sensors, evenly distributed inside the sample; (3) two
additional thermal probes, which were simplified versions of an instrument originally developed for measuring thermal properties
of the ice/dust mixture expected to exist at the surface of a comet nucleus. They consist of a series of individual temperature
sensors integrated into a glass fibre rod. Each of these sensors can be operated in an active (heated) or passive (only temperature
sensing) mode. The following sample materials were used: fine-grained reddish sand, coarse-grained moist sand, gravels with
various grain size distributions from < 1 cm up to about 6 cm, and for comparison and calibration pure water (with convection
suppressed by adding agar-agar), compact ice, and compact granite. Of particular interest are the measurements with composite
samples, like stones embedded in an agar-agar matrix. We describe the evaluation methods and present the results of the thermal
conductivity measurements. 相似文献