排序方式: 共有27条查询结果,搜索用时 31 毫秒
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H. Jordan D. Hebert K. Fröhlich R.-P. Scholz R. Gellermann 《Isotopes in environmental and health studies》2013,49(3):79-82
The migration of radionuclides and other tracers in porous layers is determined by substance transport. The physical and hydraulic basis of retardation is investigated. A definition of a factor of retardation is given, describing the ratio between the pore velocity of the water and the velocity of tracer migration. Consequences to the groundwater protection are discussed. 相似文献
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Uwe Klingebiel Stefan Schmatz Eike Gellermann Christian Drost Mathias Noltemeyer 《Monatshefte für Chemie / Chemical Monthly》2001,40(5):1105-1124
This review describes the synthesis and isomerization reactions of cyclic silylhydrazines. Topics of discussion are the ring
expansion of the three-membered Si(SiN2) to the four-membered (SiN)2 ring by lithiation of the (SiN2) ring and by thermal silyl group insertion into the N*N bond, the ring expansion of a three-membered (SiN2) to a five-membered (CSi2N2) ring by SiCH2 insertion into the Si*N bond, the formation of isomeric four- and six-membered (SiN2)2 rings, the synthesis of five- and six-membered silylhydrazine rings, and the expansion of a five-membered (N2Si2N)N ring to the isomeric six-membered (SiNN)2 ring. The mechanisms of the isomerizations are explained by quantum chemical calculations, and the results are verified by
crystal structure determinations. 相似文献
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Dembski S Milde M Dyrba M Schweizer S Gellermann C Klockenbring T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14025-14032
A novel method for the synthesis of luminescent SiO(2)/calcium phosphate (CaP):Eu(3+) core-shell nanoparticles (NPs) was developed via a sol-gel route followed by annealing at a temperature of 800 °C. The object of this study was the investigation of the effect of pH on the formation of a CaP shell around the silica core. The resulting annealed NPs exhibited an amorphous SiO(2) core and a crystalline luminescent shell. The formation of a CaP layer was possible at pH below 4.5 and above 6.5 during the coating step. The crystal structure of the shell was studied by X-ray diffraction analysis. Hydroxyapatite (HAp) and α-tricalcium phosphate were detected as crystal phases of the surrounding layer. However, NPs produced under basic conditions exhibited a higher crystallinity of the CaP layer than did samples coated at pH below 4.5. In the pH interval between 4.5 and 6.5, no shell growth but the formation of secondary NPs containing CaO and Ca(OH)(2) was observed. Furthermore, SiO(2)/CP:Eu(3+) core-shell NPs were investigated by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. The resulting HAp-coated NPs were successfully tested by a cell-culture-based viability assay with respect to a later application as a luminescent marker for biomedical applications. 相似文献
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B. Bräutigam B. Vogel R. Gellermann 《Isotopes in environmental and health studies》2013,49(3):287-292
Abstract Since the 1960s intensive isotope hydrogeological studies have been carried out in the Finne mountain range between Herrengosserstedt in Thuringia and the River Unstrut near Karsdorf in Saxony-Anhalt. The new railway line Erfurt-Leipzig/Halle, a part of the traffic projects German Union - Railway-No. 8-, will cross this area with two tunnels, each of which is 6 km long. The tunnelling of the Middle Bunter rocks on the west side involves the crossing of an area with deep wells used for drinking water supply. To clarify the hydrodynamic situation in this area, the planning company for railway construction German Union (PB DE) contracted Trischler und Partner to carry out an extensive exploration programme. This programme included not only investigations using the isotopes 2H, 18O, 3H, 13C and 14C, but also single measurements of chlorofluorocarbons (CFC) and a multitude of hydrochemical analyses. Because of stratum related ground water sampling, an aquifer related evaluation of the investigation results was possible. Based on these results a fundamentally new structural-geological model for the investigation area was developed. In addition to its great importance for the tunnel planning, with the new model it will be possible to solve urgent questions concerning the drinking water supply in this region. 相似文献
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K. Fröhlich T. Franke R. Gellermann D. Hebert H. Jordan 《Isotopes in environmental and health studies》2013,49(9):355-360
This paper presents results of a study carried out in order to assess the applicability of 32Si for groundwater dating. Measurements of 32Si in soil samples of the unsaturated zone, of drainage waters and plant material give a basis for estimating the 32Si initial concentration in groundwater. Different aquifers with groundwater of young and moderate ages have been selected for groundwater studies. For obtaining independent age information tritium was found to be a suitable reference isotope. A quantitative interpretation of the 32Si data is generally complicated by geochemical processes, preferably in the unsaturated zone. Favourable conditions concerning the use of 32Si in hydrogeology seem to exist in phreatic sandy aquifers, in limestone aquifers, and, depending on the thickness and composition of the unsaturated zone, in sandstone aquifers. Further improvements of the 32Si method needs a better understanding of the geochemical processes affecting this isotope. 相似文献
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I. V. Ermakov T. T. Basiev K. K. Pukhov W. Gellermann 《Physics of the Solid State》2000,42(3):473-476
The paper reports on a measurement and calculation of the dependence of LiF: F 2 luminescence polarization and intensity on the polarization of high-power laser radiation (λex=1064 nm) producing two-photon excitation of F 2 centers. It is shown that the two-photon transition results in the excitation of a previously unknown electronic level of F 2 centers of the A 1g symmetry. 相似文献
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Michael Schneider André Tschöpe Doris Hanselmann Thomas Ballweg Carsten Gellermann Matthias Franzreb Karl Mandel 《Particle & Particle Systems Characterization》2020,37(2):1900487
Micron-sized supraparticles, consisting of a plurality of discrete nano- and microscale functional units, are assembled and fused by means of a droplet extrusion process. By combining nano magnetite, activated carbon, and conductive carbon with a polymeric binder matrix, particles are obtained which unite good magnetic properties, electrical conductivity, and adsorber activity through the high accessible surface area of the incorporated activated carbon of about 570 m2 g−1, thereby enabling a new approach toward sustainable water treatment processes. Due to the interplay of the components, it is possible to adsorb target substances, dissolved in the water which is demonstrated by the adsorption of the model dye methylene blue. A very fast adsorption kinetic and an adsorption capacity of about 400 mg g−1 is determined. By using the developed composite particles, it is also possible to electrochemically alter substances flowing through a magnetically-stabilized fluidized-bed reactor by electrochemically charging/discharging, significantly supported by the magnetic field enabling alternatingly optimum mobility/adsorption phases with contact/charging intervals. The electrochemical conversion can be increased up to 151% depending on the applied flow-rate and electrical voltage. By applying an external magnetic field, a further increase of electrochemical conversion of up to 70% can be observed. 相似文献
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