Detection of elemental sulphur on galena oxidized in acidic solution

Galena (PbS) oxidation on potentiostatically treated specimens in acetate buffer was investigated by atomic force microscopy (AFM) and by X-ray photoelectron spectroscopy (XPS), Elemental sulphur was detected as an oxidation product by XPS. To minimize the evaporation of elemental sulphur during the XPS experiments in ultra high vacuum, sample cooling was required before the evacuation was started. Decreasing the pressure to 1 torr for 5 min, before the sample was cooled, removed the elemental sulphur almost completely from the surface, In addition, when an electrochemically oxidized sample was exposed to air at ambient pressure for about 3 h, the relative intensity of the S2p component of elemental sulphur was observed to decrease to about half of the value achieved by instant cooling and measuring, AFM images showed elemental sulphur to be present on galena surface as local accumulations rather than as a uniform layer, The sulphur formation is highly localized, but does not seem to occur preferentially at steps, (C) 1997 Elsevier Science B.V

Who is expected to make contact? Interpretative repertoires related to an intergroup encounter between Finnish majority mothers and immigrant mothers

Although the benefits of contact for positive intergroup relations are widely acknowledged, less is known about how group members construct the agency and responsibility of contact participants in intergroup encounters. Using critical discursive psychology, we analysed the interpretative repertoires that Finnish majority mothers (N=13) and mothers with an immigrant background (N=10) used when talking about a hypothetical intergroup encounter among Finnish and immigrant mothers in a ‘family café’ (a group for mothers and children). Our analysis identified five interpretative repertoires that differed in terms of the levels of categorisation used (individual, group, motherhood) and how agency and responsibility for initiating contact were discursively attributed to the parties in the intergroup encounter. Overall, constructing someone as agentic did not automatically result in their being portrayed as more responsible for making contact. Respondents described contact to occur with only two repertoires, in which both agency and responsibility for initiating contact were discursively attributed to the same party. This highlights the need to consider both agency and sense of responsibility as possible factors preceding intergroup contact

X-ray induced surface modification of aluminovanadate oxide

Aluminovanadate oxide, ‘‘V–Al–O’’, has been studied by X-ray photoelectron spectroscopy (XPS) with the emphasis to reveal chemical modifications as a function of the X-irradiation time. Considerable damage was found for V–Al–O and less so for vanadium pentoxide, V2O5, and sapphire, a-Al2O3, both serving as reference samples. Modifications in V–Al–O were seen even at low radiation doses. Absolute and relative shifts in binding energies along with changes of peak intensities and widths demonstrate that an appreciable amount of V5+ is reduced to lower oxidation states. X-ray induced chemical modifications extend at least to the depth sampled by the V3p electrons. It is suggested that the damage is caused by electron-hole pair generation and Auger decay. Al–O–H in V–Al–O is also affected by X-rays. This causes O2 and water desorption as followed by mass spectrometry of the residual gas.info:eu-repo/semantics/publishe