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Image-based analytical tools in geosciences are indispensable for the characterization of minerals, but most of them are limited to the surface of a polished plane in a sample and lack 3D information. X-ray micro computed tomography (micro CT) provides the missing 3D information of the microstructures inside samples. However, a major drawback of micro CT in the characterization of minerals is the lack of chemical information that makes mineral classification challenging. Spectral X-ray micro computed tomography (Sp-CT) is a new and evolving tool in different applications such as medicine, security, material science, and geology. This non-destructive method uses a multi-pixel photon-counting detector (PCD) such as cadmium telluride (CdTe) in combination with a conventional CT scanner (TESCAN CoreTOM) to image a sample and detect its transmitted polychromatic X-ray spectrum. Based on the spectrum, elements in a sample can be identified by an increase in attenuation at specific K-edge energies. Therefore, chemically different particles can be distinguished inside a sample from a single CT scan. The method is able to distinguish elements with K-edges in the range from 25 to 160 keV, which applies to elements with Z > 48. We present results from various sample materials. Different pure elements and element oxides were measured to compare the position of theoretical and measured K-edge energies. All measured K-edge energies are slightly above the theoretical value, but based on the results a correction algorithm could be developed. Furthermore, different monazite grains were investigated, which can be divided into two groups with respect to the content of different RE elements on the basis of the spectrum: La-Ce-rich and La-Ce-poor. In addition, samples from the Au-U Witwatersrand Supergroup demonstrate the potential applications of Sp-CT for geological samples. We measured different drill core samples from the Kalkoenkrans Reef at the Welkom Gold field. Sp-CT can disting

Image-based analytical tools in geosciences are indispensable for the characterization of minerals, but most of them are limited to the surface of a polished plane in a sample and lack 3D information. X-ray micro computed tomography (micro CT) provides the missing 3D information of the microstructures inside samples. However, a major drawback of micro CT in the characterization of minerals is the lack of chemical information that makes mineral classification challenging. Spectral X-ray micro computed tomography (Sp-CT) is a new and evolving tool in different applications such as medicine, security, material science, and geology. This non-destructive method uses a multi-pixel photon-counting detector (PCD) such as cadmium telluride (CdTe) in combination with a conventional CT scanner (TESCAN CoreTOM) to image a sample and detect its transmitted polychromatic X-ray spectrum. Based on the spectrum, elements in a sample can be identified by an increase in attenuation at specific K-edge energies. Therefore, chemically different particles can be distinguished inside a sample from a single CT scan. The method is able to distinguish elements with K-edges in the range from 25 to 160 keV, which applies to elements with Z > 48. We present results from various sample materials. Different pure elements and element oxides were measured to compare the position of theoretical and measured K-edge energies. All measured K-edge energies are slightly above the theoretical value, but based on the results a correction algorithm could be developed. Furthermore, different monazite grains were investigated, which can be divided into two groups with respect to the content of different RE elements on the basis of the spectrum: La-Ce-rich and La-Ce-poor. In addition, samples from the Au-U Witwatersrand Supergroup demonstrate the potential applications of Sp-CT for geological samples. We measured different drill core samples from the Kalkoenkrans Reef at the Welkom Gold field. Sp-CT can disting

BACKGROUND: The optimum method of defining cognitive impairment in virally suppressed people living with HIV is unknown. We evaluated the relationships between cognitive impairment, including using a novel multivariate method (NMM), patient- reported outcome measures (PROMs), and neuroimaging markers of brain structure across 3 cohorts. METHODS: Differences in the prevalence of cognitive impairment, PROMs, and neuroimaging data from the COBRA, CHARTER, and POPPY cohorts (total n = 908) were determined between HIV-positive participants with and without cognitive impairment defined using the HIV-associated neurocognitive disorders (HAND), global deficit score (GDS), and NMM criteria. RESULTS: The prevalence of cognitive impairment varied by up to 27% between methods used to define impairment (eg, 48% for HAND vs 21% for NMM in the CHARTER study). Associations between objective cognitive impairment and subjective cognitive complaints generally were weak. Physical and mental health summary scores (SF-36) were lowest for NMM-defined impairment ( P < .05).There were no differences in brain volumes or cortical thickness between participants with and without cognitive impairment defined using the HAND and GDS measures. In contrast, those identified with cognitive impairment by the NMM had reduced mean cortical thickness in both hemispheres ( P < .05), as well as smaller brain volumes ( P < .01). The associations with measures of white matter microstructure and brain-predicted age generally were weaker. CONCLUSION: Different methods of defining cognitive impairment identify different people with varying symptomatology and measures of brain injury. Overall, NMM-defined impairment was associated with most neuroimaging abnormalities and poorer self-reported health status. This may be due to the statistical advantage of using a multivariate approach.

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info:eu-repo/semantics/published

A NNW-oriented thrust is exposed in the western part of the Dikulushi mine, marked by ductile deformed shale that was transported upward and is in faulted contact with an overlying dolomite-sandstone sequence. The brecciated layers in the west and non-brecciated sandstone layers in the central part of the mine are crosscut by several E-W and NE-oriented faults. The complex set of faults produced a damage zone that was a favorable site for the migration of mineralising fluids. The faults and brecciated layers contain Cu-Pb-Zn-Fe mineralisation consisting of chalcopyrite, bornite and chalcocite, with minor pyrite, arsenopyrite, sphalerite, and galena, with dolomite, calcite, and quartz as gangue minerals. The fault zones were sites of remobilisation and enrichment of the previously deposited Cu-Pb-Zn-Fe mineralisation. The remobilised sulphides consist of Ag-rich chalcocite, with barite, calcite and quartz as gangue minerals. The deposit is structurally controlled by a crosscutting set of E-W and NE-oriented faults. Similar structural settings in the mine and in the Dikulushi region represent important future exploration targets., A NNW-oriented thrust is exposed in the western part of the Dikulushi mine, marked by ductile deformed shale that was transported upward and is in faulted contact with an overlying dolomite-sandstone sequence. The brecciated layers in the west and non-brecciated sandstone layers in the central part of the mine are crosscut by several E-W and NE-oriented faults. The complex set of faults produced a damage zone that was a favorable site for the migration of mineralising fluids. The faults and brecciated layers contain Cu-Pb-Zn-Fe mineralisation consisting of chalcopyrite, bornite and chalcocite, with minor pyrite, arsenopyrite, sphalerite, and galena, with dolomite, calcite, and quartz as gangue minerals. The fault zones were sites of remobilisation and enrichment of the previously deposited Cu-Pb-Zn-Fe mineralisation. The remobilised sulphides consist of Ag-rich chalcocite, with barite, calcite and quartz as gangue minerals. The deposit is structurally controlled by a crosscutting set of E-W and NE-oriented faults. Similar structural settings in the mine and in the Dikulushi region represent important future exploration targets.

Following the UN initiative to fingerprint the origin of conflict materials, the German Federal Ministry for Economic Cooperation and Development has decided to fund a pilot study on coltan ores. Since 2006, a working group has been investigating columbitetantalite (coltan) mineralisation, also within the wider framework of establishing certified trade chains. More than 300 samples were obtained from the world's major coltan-producing areas. Special attention is directed to samples and concentrates from Ta-Nb-Sn provinces in: Democratic Republic of the Congo, Rwanda, Mozambique, Ethiopia and Namibia. State of the art analytical tools were employed, including fully automated electron microscopy (mineral liberation analysis), electron microprobe analysis (major and minor elements), laser ablation plasma-source mass spectrometry (trace elements and U-Pb dating), X-ray fluorescence spectroscopy (bulk major and trace elements), X-ray diffraction analysis (mineralogy and structure) and thermal-ionisation mass-spectrometry (U-Pb dating). Major and trace element concentration patterns, mineral assemblages in the ore concentrates, age populations (Archaean to early Palaeozoic), and zoning characteristics in the different pegmatites from Africa differ distinctly from each other. Preliminary analytical results indicate that a certification scheme including fingerprinting of sources of coltan ores is feasible., Following the UN initiative to fingerprint the origin of conflict materials, the German Federal Ministry for Economic Cooperation and Development has decided to fund a pilot study on coltan ores. Since 2006, a working group has been investigating columbitetantalite (coltan) mineralisation, also within the wider framework of establishing certified trade chains. More than 300 samples were obtained from the world's major coltan-producing areas. Special attention is directed to samples and concentrates from Ta-Nb-Sn provinces in: Democratic Republic of the Congo, Rwanda, Mozambique, Ethiopia and Namibia. State of the art analytical tools were employed, including fully automated electron microscopy (mineral liberation analysis), electron microprobe analysis (major and minor elements), laser ablation plasma-source mass spectrometry (trace elements and U-Pb dating), X-ray fluorescence spectroscopy (bulk major and trace elements), X-ray diffraction analysis (mineralogy and structure) and thermal-ionisation mass-spectrometry (U-Pb dating). Major and trace element concentration patterns, mineral assemblages in the ore concentrates, age populations (Archaean to early Palaeozoic), and zoning characteristics in the different pegmatites from Africa differ distinctly from each other. Preliminary analytical results indicate that a certification scheme including fingerprinting of sources of coltan ores is feasible.

De sectorstudie benadert de branche van de tuincentra vanuit vijf invalshoeken. In het eerste deel wordt de sector duidelijk getypeerd. Daarna worden de structuurkenmerken besproken. Vervolgens gaan de auteurs dieper in op de bedrijfsvoering van de tuincentra. Naast het aanbod van tuincentra wordt in het vierde deel de vraagzijde en meer specifiek het consumentengedrag behandeld. Tenslotte worden de toekomstperspectieven alsook de kansen en bedreigingen van de tuincentrabranche besproken

The mechanisms for the 3PbO-PbSO4-H2O (denoted 3BS) → PbO2 and 4PbO-PbSO4 (denoted 4BS) → PbO2 transformations were studied from well-defined, pure samples formed in a laboratory cycling test cell. The oxidation reactions were observed using X-ray diffraction and scanning electron microscopy (SEM). No structural memory effect was found between 3BS and PbO2 since the 3BS → PbO2 reaction occurred through a dissolution recrystallization process. In contrast, textural relationships between needle-shaped 4BS and PbO2 were evidenced by SEM analyses. Indeed. 4BS was found to transform into PbSO4, which in turn transformed into PbO2 while retaining the needle shape as long the reaction proceeded. The thickness of the PbO2 needle crust surrounding the 4BS needle core was found to depend on both the temperature and soaking duration. A model predicting a decrease in the capacity with the increase in the needle thickness, as a consequence of the inactive 4BS presence inside the needles, is proposed. The ability to prepare samples of controlled morphology revealed a decrease in capacity with the increase in the needle thickness, thereby confirming the model prediction. But more importantly, we showed that a 20-25% increase in the positive electrode efficiency could be achieved by reducing the thickness of the usual 4BS cured industrial samples from 10-15 to 3-4 μm.

Soaking and formation (first charge) stages of the Faure process were studied as separate stages from various 4PbO·PbSO4 (4BS) precursors (pure tetrabasic lead sulfate or industrial tetrabasic positive active material). The evolution during soaking and formation of the various well-defined 4BS precursors was followed by means of scanning electron microscopy, X-ray diffraction and wet chemical analysis. The following results arise from this approach. The sulfation stage results in the formation of PbSO4 crystals with two completely different morphologies. The first type of PbSO4 crystals nucleate at the 4BS needle surface and this leads rapidly to large polyhedral particles of 2 μm in diameter. The second type of PbSO4 crystals consist of very small interconnected grains (0.2 μm) that result from the slow transformation of the 4BS needle into PbSO4 via a metasomatic process. Since the 2 μm PbSO4 polyhedral particles resulting from the first sulfation process are more difficult to convert into PbO2, the PbO2 crystal growth mainly takes place on the second type of PbSO4 small 0.2 μm interconnected crystals. It can be concluded that the 4BS formation route mainly proceeds via the double metasomatic process 4BS → PbSO4 → PbO2 leading to the textural relationship between PbO2 and its precursor 4BS. The double metasomatic process gives rise to the same type of macrotexture at 20 and 55°C with a rigid skeleton and a high porosity. On the other hand, the thickness of the individual PbO2 grains (i.e. the microtexture) depends on temperature. Very thin interconnected PbO2 crystals are obtained at 20°C while thicker grains are observed at 55°C. These textural observations are confirmed by C/20 discharge capacity measurements on tetrabasic-based plates and batteries. The influence of soaking duration is outlined.

We report a case of lymphocytic colitis in a 74-year-old woman presenting with watery diarrhea since 1 year and in whom previous extensive investigations were normal. The diagnosis could be made on the basis of typical pathological pattern in colonic biopsies. The outcome was favourable with salazopyrine therapy. The clinical, histological and pathophysiological aspects of lymphocytic colitis are discussed.

Electron microprobe analysis results showed that the occurrence of pyrite is related to different episodes in the evolution of the fold belt. Pyrite occurs as a pre- or as a syn-deformation phase in the metamorphosed sedimentary and igneous rocks. Pre-cleavage pyrite in greenschist-metamorphosed sedimentary rocks has a relatively high Ni content which could be due to the release of Ni from organic matter during diagenesis. Pre-cleavage pyrite in the igneous rocks has higher Cu, Pb, Cd and Zn contents, which could have been caused by the incorporation of these elements in the sulphide phase during the final stage of crystallisation of the magma. Syn-deformation pyrite along cleavage planes and in quartz/carbonate veins is characterised by higher As, Sb, Se and Au contents, typical for hydrothermal mineralisation in a greenschist-facies fold belt., Electron microprobe analysis results showed that the occurrence of pyrite is related to different episodes in the evolution of the fold belt. Pyrite occurs as a pre- or as a syn-deformation phase in the metamorphosed sedimentary and igneous rocks. Pre-cleavage pyrite in greenschist-metamorphosed sedimentary rocks has a relatively high Ni content which could be due to the release of Ni from organic matter during diagenesis. Pre-cleavage pyrite in the igneous rocks has higher Cu, Pb, Cd and Zn contents, which could have been caused by the incorporation of these elements in the sulphide phase during the final stage of crystallisation of the magma. Syn-deformation pyrite along cleavage planes and in quartz/carbonate veins is characterised by higher As, Sb, Se and Au contents, typical for hydrothermal mineralisation in a greenschist-facies fold belt.

Turbidite-hosted mesothermal gold formed during the accretion of the Laurentia, Baltica and Gondwana terranes in the Caledonian orogeny has been identified in Wales, Scotland, Ireland, the Meguma Province in Nova Scotia and the Baie Verte Peninsula of Newfoundland. Absolute timing is crucial to understanding the ore-forming events but application of Ar-Ar dating techniques is not always straightforward. Recent borehole data has identified polysulphide mineralisation in an intensely altered shear zone through Ordovician turbidites in the Marcq area. Ar-Ar dating of sericite from different depths shows a homogeneous time interval between 417 and 414 Ma with the exception of one 426 Ma sample. Circulation of fluids could have taken place episodically over 12 m.y., a period consistent with a model of prolonged deformation and comparable with that for mesothermal gold emplacement in Wales, Scotland and Ireland. Geochemical and microthermometric data also show similar characteristics to those of the Caledonian orogenic belt in Europe and fold belts throughout the world. Minimal gold enrichment probably reflects lack of sufficient heat to mobilise gold in the lower crust., Turbidite-hosted mesothermal gold formed during the accretion of the Laurentia, Baltica and Gondwana terranes in the Caledonian orogeny has been identified in Wales, Scotland, Ireland, the Meguma Province in Nova Scotia and the Baie Verte Peninsula of Newfoundland. Absolute timing is crucial to understanding the ore-forming events but application of Ar-Ar dating techniques is not always straightforward. Recent borehole data has identified polysulphide mineralisation in an intensely altered shear zone through Ordovician turbidites in the Marcq area. Ar-Ar dating of sericite from different depths shows a homogeneous time interval between 417 and 414 Ma with the exception of one 426 Ma sample. Circulation of fluids could have taken place episodically over 12 m.y., a period consistent with a model of prolonged deformation and comparable with that for mesothermal gold emplacement in Wales, Scotland and Ireland. Geochemical and microthermometric data also show similar characteristics to those of the Caledonian orogenic belt in Europe and fold belts throughout the world. Minimal gold enrichment probably reflects lack of sufficient heat to mobilise gold in the lower crust.

A combined remote sensing, petrographic and fluid inclusion microthermometric analysis is presented of the Kinkumbi sediment-hosted stratiform copper prospect at Lufukwe in the Lufilian foreland. The mineralisation is hosted in the lower part of the Munwezi Sandstone of the Nguba Group, spatially related to strike-slip faults with a NE-SW to ENE-WSW orientation, which postdate the Lufilian folding and the deposition of the Katanga Supergroup. Copper mineralisation is mainly concentrated in feldspar dissolution cavities and is both hypogene (chalcopyrite, bornite and chalcocite) and supergene (digenite, covellite and minor native copper). The data support a post-orogenic fluid mixing model. Microthermometry of fluid inclusions indicates that authigenic quartz precipitated from high-salinity fluids at moderate temperatures and that the mineralising fluid was of low- to intermediate salinity and high temperature. The mineralisation was controlled by faulting, fracturing, folding and diagenesis and by the lithology of the Monwezi Sandstone. Areas with (E)NE to (W)NW lineaments, especially where these cut previously-deformed Katanga sediments, are considered favourable sites for further exploration, particularly coarse-grained sandstones with feldspar dissolution cavities., A combined remote sensing, petrographic and fluid inclusion microthermometric analysis is presented of the Kinkumbi sediment-hosted stratiform copper prospect at Lufukwe in the Lufilian foreland. The mineralisation is hosted in the lower part of the Munwezi Sandstone of the Nguba Group, spatially related to strike-slip faults with a NE-SW to ENE-WSW orientation, which postdate the Lufilian folding and the deposition of the Katanga Supergroup. Copper mineralisation is mainly concentrated in feldspar dissolution cavities and is both hypogene (chalcopyrite, bornite and chalcocite) and supergene (digenite, covellite and minor native copper). The data support a post-orogenic fluid mixing model. Microthermometry of fluid inclusions indicates that authigenic quartz precipitated from high-salinity fluids at moderate temperatures and that the mineralising fluid was of low- to intermediate salinity and high temperature. The mineralisation was controlled by faulting, fracturing, folding and diagenesis and by the lithology of the Monwezi Sandstone. Areas with (E)NE to (W)NW lineaments, especially where these cut previously-deformed Katanga sediments, are considered favourable sites for further exploration, particularly coarse-grained sandstones with feldspar dissolution cavities.

The Kundelungu foreland contains various vein-type and stratiform Cu mineralisations. The vein-type Cu-Ag ore deposit is the most significant in the region. Mineralisation comprises two major styles, a polysulphide assemblage (Zn-Pb-Fe-Cu-As) within brecciated rocks along an anticlinal closure and a vein-hosted Cu-Ag assemblage. Petrographic and fluid inclusion studies indicate that the early Zn-Pb-Fe-Cu-As assemblage formed from a high-salinity Ca-Na-Cl fluid at a temperature of 135-172 degrees C. The more economically significant vein-related Cu-Ag mineralisation formed from intermediate salinity, lower temperature (46-82 degrees C) Na-Cl fluids. Weathering of the sulphide minerals resulted in supergene enrichment with the formation of secondary Cu-minerals., The Kundelungu foreland contains various vein-type and stratiform Cu mineralisations. The vein-type Cu-Ag ore deposit is the most significant in the region. Mineralisation comprises two major styles, a polysulphide assemblage (Zn-Pb-Fe-Cu-As) within brecciated rocks along an anticlinal closure and a vein-hosted Cu-Ag assemblage. Petrographic and fluid inclusion studies indicate that the early Zn-Pb-Fe-Cu-As assemblage formed from a high-salinity Ca-Na-Cl fluid at a temperature of 135-172 degrees C. The more economically significant vein-related Cu-Ag mineralisation formed from intermediate salinity, lower temperature (46-82 degrees C) Na-Cl fluids. Weathering of the sulphide minerals resulted in supergene enrichment with the formation of secondary Cu-minerals.