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71.
Axel Schmidt Christina E. Stringer Ulrike Haferkorn Michael Schubert 《Environmental Geology》2009,56(5):855-863
A case study was carried out with the aim to practically test whether estimates of
groundwater discharge rates into dredging lakes can be made via an uncomplicated and
straightforward technique using radon-222 as naturally-occurring groundwater tracer.
Lake Ammelshainer See, a dredging, seepage lake, approximately 25 km east of Leipzig,
Germany, was chosen as the investigation site. In order to evaluate changes in the
spatial and temporal radon-222 patterns in the lake during different stages of stratification, sampling campaigns were conducted
in April 2007 (well mixed stage) and in
May 2007 (thermal stratification stage). Groundwater flow estimates were made using a radon mass balance approach accounting
for all radon fluxes into and out of the lake
and assuming steady-state conditions with respect to these radon fluxes. Once all positive and negative radon fluxes related
to the lake water volume were determined, groundwater discharge was estimated by using the advective radon input and the radon
activity concentration of the pore water as key parameters. The results showed that in case of a lake with a size and shape
of Lake Ammelshainer See (530,000 m2) reasonable groundwater discharge estimates can be made by collection and analyzing just a few water samples and a few samples
from the sediment layer. 相似文献
72.
Claudia Comito Peter Schilke Ulrike Endesfelder Izaskun Jiménez-Serra Jesus Martín-Pintado 《Astrophysics and Space Science》2008,313(1-3):59-63
The direct detection of accretion onto massive protostars through rotating disks constitutes an important tile in the massive-star-formation-theory
mosaic. This task is however observationally very challenging. A very interesting example is Cepheus A HW2. The properties
of the molecular emission around this YSO seems to suggest the presence of a massive rotating disk (cf. Patel et al. in Nature
437:109, 2005). We have carried out sub-arcsec-resolution PdBI observations of high-density and shock tracers such as SO2, SiO, CH3CN, and CH3OH towards the center of the outflow. A detailed analysis of the spatial distribution and of the velocity field traced by
all observed species leads us to conclude that, on a ∼700 AU scale, the Cep-A “disk” is actually the result of the superposition
of multiple hot-core-type objects, at least one of them ejecting an outflow at a small angle with respect to the line of sight.
Together with the well-known large-scale outflow ejected by HW2, this setup makes for a very complex spatial and kinematic
picture.
Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG
(Germany) and IGN (Spain). 相似文献
73.
Ulrike Sailer-Fliege 《GeoJournal》1999,49(1):7-16
The development of the post-socialist city has already been characterised by substantial restructuring processes. Particular
emphasis should be drawn to the take-off of the tertiary sector and the comprehensive blight phenomena in the previously industrial
areas. The urban housing sector has witnessed increasing housing affordability problems, a marginalisation of communal housing
stock, an increase of segregation and an intensification of the decay in the old housing stock. In all East Central European
states the spatial development processes of industry and services within the cities basically show clear parallels to the
pattern of urban development in continental Europe. In Hungary housing policy, tenure structure and the level of segregation
already show relatively closer similarities to the neoliberal, Anglo–American pattern of development. The other ECE states
show closer similarities to the corporatist welfare states of continental Europe. As far as medium-term urban development
in East Central Europe is concerned, it is to be assumed that – regardless of the specific path of further development – overall
solutions shall not be found for the fundamental problems which are the legacy of the socialist era – the decay of old housing
stock, large scale derelict industrial areas and the extent and deficiencies of high-rise housing estates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
74.
Regional anomalies of the surface climate over Europe are defined by a simultanous EOF-analysis of the normalized monthly mean sea level pressure, temperature and precipitation fields of 100 winters (December–February, 1887–1986) at 40 stations. The monthly amplitudes of the first EOF (about 25% of the total variance) are used as an index for the monthly winter climate anomaly. They characterize a high (low) pressure cell over central Europe associated with a positive (negative) temperature and precipitation anomaly over northern (central-southern) Europe as indicated by a northward (southward) shift of the tail end of the cross-Atlantic cyclone track. These patterns resemble the phenomenological anticyclonic (cyclonic) Grosswetter classification and the European blocking (enhanced zonal flow) regime. The second EOF is of similar magnitude and gives latitudinal corrections to these two basic flow regimes. The joint probability distribution of both amplitudes shows a weak bimodality mainly associated with the first EOF. Further insight into the underlying physical processes of the climate anomaly patterns in Europe is obtained from the extended Eliassen-Palm flux diagnostics of the barotropic transient eddy-mean flow interaction (Hoskins et al. 1983) and the stationary wave propagation (Plumb 1985). The diagnostics confined to the barotropic components and applied to the regression and the composite anomaly fields of the transient and stationary eddy flows of the 500 hPa geopotential (1946–87, north of 20°N) leads to the following results: (1) The bandpass filtered transient eddy variances of the 500 hPa geopotential show a shift of the cross-Atlantic storm track: In high (low) pressure situations over Europe the cross-Atlantic storm track intensity is enhanced (reduced) and its tail end is shifted northward (remains zonal); the North Pacific storm track extends further (less) eastward and thus closer to the west coast of North America. (2) The extreme high pressure system over Europe tends to be supported by an anomalous transient eddy forcing of the mean flow stream-function: it enhances the zonal wind to its north and generates anticyclonic vorticity about 10° upstream from its center. In the low pressure composite the anomalous cyclonic vorticity is generated reducing the zonal flow to its north. (3) The occurrence (lack) of a strong eastward stationary wave activity flux over the Atlantic is associated with the high (low) pressure situations over Europe. Finally, a positive feedback is conjectured between the stationary wavetrain modifying the tail end of the cross-Atlantic storm track and the transient eddies intensifying this anomaly. 相似文献
75.
76.
Klaus Peter Jochum Ulrike Weis Brigitte Stoll Dmitry Kuzmin Qichao Yang Ingrid Raczek Dorrit E. Jacob Andreas Stracke Karin Birbaum Daniel A. Frick Detlef Günther Jacinta Enzweiler 《Geostandards and Geoanalytical Research》2011,35(4):397-429
We present new reference values for the NIST SRM 610–617 glasses following ISO guidelines and the International Association of Geoanalysts’ protocol. Uncertainties at the 95% confidence level (CL) have been determined for bulk‐ and micro‐analytical purposes. In contrast to former compilation procedures, this approach delivers data that consider present‐day requirements of data quality. New analytical data and the nearly complete data set of the GeoReM database were used for this study. Data quality was checked by the application of the Horwitz function and by a careful investigation of analytical procedures. We have determined quantitatively possible element inhomogeneities using different test portion masses of 1, 0.1 and 0.02 μg. Although avoiding the rim region of the glass wafers, we found moderate inhomogeneities of several chalcophile/siderophile elements and gross inhomogeneities of Ni, Se, Pd and Pt at small test portion masses. The extent of inhomogeneity was included in the determination of uncertainties. While the new reference values agree with the NIST certified values with the one exception of Mn in SRM 610, they typically differ by as much as 10% from the Pearce et al. (1997) values in current use. In a few cases (P, S, Cl, Ta, Re) the discrepancies are even higher. 相似文献
77.
78.
Holocene environmental and climatic changes inferred from Wulungu Lake in northern Xinjiang, China 总被引:7,自引:0,他引:7
Xingqi Liu Ulrike Herzschuh Ji Shen Qingfen Jiang Xiayun Xiao 《Quaternary Research》2008,70(3):412-425
Sedimentological, geochemical and palynological data from Wulungu Lake in northern Xinjiang, China, are used to reconstruct environmental and climate changes since 9550 cal yr BP. High abundance of Sparganium and Poaceae, low Md (median diameter) and δ13Corganic values indicate aridity between 9550 and 6730 cal yr BP. High Md and δ13Corganic values, and the prevalence of desert-steppe and steppe vegetation between 4200 and 560 cal yr BP, indicate that effective moisture increased after 6730 cal yr BP, peaking at 4200 and 560 cal yr BP. Low Md values, a negative excursion of δ13Corg, and the transition from steppe to desert vegetation since 560 cal yr BP reflect a decrease in effective moisture during the latest Holocene. Late Holocene human activities were indicated by sharp increase in the abundance of Pediastrum then. Variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr BP, low between 7740 and 6730 cal yr BP, intermediate between 6730 and 560 cal yr BP, and low during the last 560 yr. Regional comparison indicates that the Asian monsoon did not extend to Wulungu Lake and westerlies were the main factor in determining the moisture availability during the Holocene. 相似文献
79.
Astronomical-topographic levelling using high-precision astrogeodetic vertical deflections and digital terrain model data 总被引:2,自引:1,他引:1
At the beginning of the twenty-first century, a technological change took place in geodetic astronomy by the development of
Digital Zenith Camera Systems (DZCS). Such instruments provide vertical deflection data at an angular accuracy level of 0.̋1
and better. Recently, DZCS have been employed for the collection of dense sets of astrogeodetic vertical deflection data in
several test areas in Germany with high-resolution digital terrain model (DTM) data (10–50 m resolution) available. These
considerable advancements motivate a new analysis of the method of astronomical-topographic levelling, which uses DTM data
for the interpolation between the astrogeodetic stations. We present and analyse a least-squares collocation technique that
uses DTM data for the accurate interpolation of vertical deflection data. The combination of both data sets allows a precise
determination of the gravity field along profiles, even in regions with a rugged topography. The accuracy of the method is
studied with particular attention on the density of astrogeodetic stations. The error propagation rule of astronomical levelling
is empirically derived. It accounts for the signal omission that increases with the station spacing. In a test area located
in the German Alps, the method was successfully applied to the determination of a quasigeoid profile of 23 km length. For
a station spacing from a few 100 m to about 2 km, the accuracy of the quasigeoid was found to be about 1–2 mm, which corresponds
to a relative accuracy of about 0.05−0.1 ppm. Application examples are given, such as the local and regional validation of
gravity field models computed from gravimetric data and the economic gravity field determination in geodetically less covered
regions. 相似文献
80.
Accuracy analysis of vertical deflection data observed with the Hannover Digital Zenith Camera System TZK2-D 总被引:4,自引:1,他引:3
This paper analyses the accuracy of vertical deflection measurements carried out with the Digital Zenith Camera System TZK2-D,
an astrogeodetic state-of-the-art instrumentation developed at the University of Hannover. During 107 nights over a period
of 3.5 years, the system was used for repeated vertical deflection observations at a selected station in Hannover. The acquired
data set consists of about 27,300 single measurements and covers 276 h of observation time, respectively. For the data collected
at an earlier stage of development (2003 to 2004), the accuracy of the nightly mean values has been found to be about 0′′.10−0′′.12.
Due to applying a refined observation strategy since 2005, the accuracy of the vertical deflection measurements was enhanced
into the unprecedented range of 0′′.05 − 0′′.08. Accessing the accuracy level of 0′′.05 requires usually 1 h of observational
data, while the 0′′.08 accuracy level is attained after 20 min measurement time. In comparison to the analogue era of geodetic
astronomy, the accuracy of vertical deflection observations is significantly improved by about one order of magnitude. 相似文献