The suppression of protective chromia scale formation in water vapor containing service environments limits in many cases the upper application temperature of high-Cr martensitic and ferritic steels. ...The present paper discusses the mechanisms which are responsible for this technologically important effect, using results of oxidation tests with two types of FeCr model alloys in Ar-O
2
, Ar-O
2
-H
2
O, and Ar(-H
2
)-H
2
O mixtures. The data shows that in atmospheres with a high ratio of water vapor to oxygen, Cr exhibits a higher tendency to become internally oxidized than in dry Ar-O
2
, or e.g. air. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the scale and/or to enhance formation of volatile Cr species, the present results thus reveal that the presence of water vapor also affects the transport processes in the alloy, likely by incorporation of hydrogen.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Binary Fe–Cr alloys were studied with respect to isothermal oxidation behavior at 900
°C in Ar–O
2, Ar–H
2O and Ar–H
2–H
2O gas mixtures. Chromium in solution exhibits a higher tendency to become ...internally oxidized in the gases containing water vapor than in the Ar–O
2 gas because of hydrogen dissolution in the alloy. This mechanism explains why Fe–Cr alloys with intermediate Cr contents (e.g., 10–20
wt.%) exhibit protective chromia-rich scale formation in dry gases but tend to form breakaway-type Fe-rich oxides in wet gases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Several approaches have been described to fluorescently label and image DNA and chromatin in situ on the single-molecule level. These superresolution microscopy techniques are based on detecting ...optically isolated, fluorescently tagged anti-histone antibodies, fluorescently labeled DNA precursor analogs, or fluorescent dyes bound to DNA. Presently they suffer from various drawbacks such as low labeling efficiency or interference with DNA structure. In this report, we demonstrate that DNA minor groove binding dyes, such as Hoechst 33258, Hoechst 33342, and DAPI, can be effectively employed in single molecule localization microscopy (SMLM) with high optical and structural resolution. Upon illumination with low intensity 405 nm light, a small subpopulation of these molecules stochastically undergoes photoconversion from the original blue-emitting form to a green-emitting form. Using a 491 nm laser excitation, fluorescence of these green-emitting, optically isolated molecules was registered until "bleached". This procedure facilitated substantially the optical isolation and localization of large numbers of individual dye molecules bound to DNA in situ, in nuclei of fixed mammalian cells, or in mitotic chromosomes, and enabled the reconstruction of high-quality DNA density maps. We anticipate that this approach will provide new insights into DNA replication, DNA repair, gene transcription, and other nuclear processes.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Six countries within the Baltic Sea Basin: Denmark, Sweden, Finland, Lithuania, Poland and Germany
During transport from the field to the sea nitrogen undergoes natural reduction, but with large ...spatial variations. Mapping this variation would allow more optimal regulation strategies, by imposing most restrictions in areas with low natural reduction. In the present study, a map for spatially variable nitrate reduction in groundwater is developed covering six countries in the Baltic Sea Basin. In contrary to previous studies within the Baltic Sea Basin, the present study provides an independent estimate of the nitrogen reduction in groundwater, based on review of national data and studies. Depending on availability, different approaches were used for the countries ranging from national modelling to expert judgement. Through a joint workshop the assessments were, to the extent possible, harmonised.
The review revealed large variations in the hydro-geochemical conditions important for transport and degradation of nitrogen in groundwater. This includes the hydrogeology, the reducing conditions of the subsurface, and the fraction of water transported by drainage systems bypassing the reducing subsurface environments. Significant variations in groundwater reduction between the countries and within most of the countries were thus found, indicating that strategies for nitrogen regulation and mitigation measures may be optimised, if variation in the natural reduction of nitrate is considered.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this paper is to analyse the situation of aviation and air traffic in European Union and to present the relation between the number of passengers of counties on the Old Continent, which ...will make it possible to observe the relationship and identify the causes of changes. The average growth rate is also presented in this contribution. Such an analysis may be helpful in preparing airports for increasing traffic in the future. A statistical analysis of selected aspects may enable to reveal the situation related to air transport in Europe and the predictions might visualise expectations in the following years. In this paper, the methods of statistical analysis and interpretations of studies presented in a graphical way, were used. The aim of the research was to understand the dependences between countries, trends of annual growth as well as relations between number of passengers with the gross domestic product. It was observed that the number of travelled people is growing as a function of time and it is dependent with the gross domestic product. The analyzed lands have been divided into five group according the average number of passengers. Similar tendencies have been observed in most of the cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present work, the high-temperature decarburization of the austenitic stainless steel S304HCu in Ar–4%H
2
–xH
2
O at temperatures between 1000 and 1150 °C was investigated. The focus was on ...determining parameters that influence the decarburization rate during heat treatment. Thermogravimetric experiments were performed with simultaneous measurements of CO release from the sample using a mass spectrometer. The variation of the experimental parameters included the composition of the atmosphere during pre-oxidation and decarburization, the temperature and the sample thickness. The results indicate that the loss of carbon from the specimen occurs faster through reaction of Cr
2
O
3
with C from the steel compared to the reaction of C at the steel surface with H
2
O, provided that in the former case CO can easily evaporate. The overall decarburization process is governed by competing reactions; the destruction of chromium oxide by C and the formation of oxide scale by water vapour. The relative rates of these two reactions determines whether decarburization will occur or whether formation of a protective oxide stops the release of CO, the latter being promoted at lower temperatures and high water vapour contents. A dense, sufficiently thick chromia scale retards the onset of decarburization but does eventually not stop the carbon loss. Indications were found that the destruction of a pre-formed chromia scale by carbon involves a two-step process whereby presence of hydrogen is important.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Binary Fe–Cr alloys containing 10 and 20 mass% Cr were studied with respect to isothermal oxidation behavior at 900 and 1,050 °C in Ar–20%O
2
, Ar–7%H
2
O and Ar–4%H
2
−7%H
2
O. Thermogravimetric ...analyses in combination with analytical studies using SEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is the source of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar–O
2
gas. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the scale, the present results thus reveal that the presence of water vapor also affects the transport processes in the alloy. This mechanism is an “easy” explanation of the frequently observed effect that Fe–Cr alloys with intermediate Cr contents (e.g. 10–20%, depending on temperature) exhibit protective chromia-rich scale formation in dry gases but breakaway type Fe-rich oxides in wet gases, provided the oxygen partial pressure is sufficiently high for Fe to become oxidized.
The oxidation behavior of a number of selected ferritic steels in a simulated steam environment at temperatures between 550 and 650 °C was studied. In the prevailing test gas, some of the studied ...9–12% Cr steels tended to exhibit an anomalous temperature dependence of the oxidation behavior. This means, that the oxidation rates do not steadily increase with increasing temperature. At higher temperatures, some of the studied steels tend to form a very thin and protective oxide scale whereas at lower temperature rapidly growing, less-protective oxides are being developed. The anomalous temperature dependence is related to differences in chromium distribution in the inner part of the oxide scale. The effect is observed for steels with intermediate-Cr contents (∼10–12%) whereas steels with either lower or higher Cr contents exhibit an increasing oxidation rate with increasing temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Water Framework Directive and Groundwater Directive aim at preserving and improving the groundwater status. Groundwater bodies are classified as being or not being at risk of failing to meet ...these objectives. Those at risk are subject to more precise risk assessment where the concept of vulnerability is considered in the pathway part of the source–pathway–receptor scheme. However, no further details on implementation strategies are provided. In order to support groundwater managers and decision-makers in implementation of programs protecting groundwater, a systematic operational approach based on a decision tree is proposed, which leads the user through the stages of vulnerability assessment. First, a problem has to be formulated related to a threatening of the quantitative and/or qualitative status of a groundwater body. Next, the stated problem needs to be related to the intrinsic or specific vulnerability. Methods used for the intrinsic vulnerability assessment belong to two categories: subjective rating and objective methods. Method selection depends primarily on: data availability, knowledge and available resources. A key issue is the lag time associated with transport between a source/event of contamination and the water body. This lag time is primarily controlled by the temporal scale of water flow. It provides information about flow processes and at the same time also about timescales required for the implementation of strategies. Effects of any measures taken cannot be observed immediately but at the earliest after these estimated lag times emphasizing the need to also proactively safeguard groundwater resources and preserve their good status.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Microstructural features, mechanical and steam oxidation properties of ferritic 18–23 wt% chromium model steels, strengthened by the precipitation of intermetallic phases, were investigated. The ...behavior of the commercially available ferritic steel Crofer® 22 H 1–4, originally developed for the application in automotive solid oxide fuel cell (SOFC) powered auxiliary power units (APUs) 5–7, was compared with that of optimized model alloys with systematic variations in Cr, Nb, W and Ti content. The main aim of the studies was the estimation of the potential suitability of these steels as construction materials in power plants with live steam temperatures around 600°C.
Some of the optimized trial alloys demonstrated remarkable characteristics at 600°C. Results of constant load creep experiments and steam oxidation tests indicate the potential of these alloys as candidate materials for application in highly efficient steam power plants with steam temperatures above 620°C. At high stress levels some of the presented alloys, especially those containing enhanced levels of W and Nb, even exhibit higher creep strength than standard ferritic–martensitic steel P92. The amount of strengthening (Fe,Si,Cr)2(W,Nb) – Laves phase particles is found to correlate well with the level of W- and Nb-alloying and in contrast to ferritic–martensitic steels, the formed Laves phase particles are highly stable at elevated temperature. Owing to the high contents of chromium, the model alloys have excellent steam oxidation resistance. A way to preserve favorable steam oxidation properties and diminish undesirable (Fe,Cr)-σ-phase formation is outlined.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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