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“Determination of chemical composition of individual airborne particles by SEM/EDX and micro-Raman spectrometry : a review”. Stefaniak EA, Buczyńska A, Novakovic V, Kuduk R, Van Grieken R, Journal of physics : conference series 162, 012019 (2009). http://doi.org/10.1088/1742-6596/162/1/012019
Abstract: The strategies for sampling and analysis by SEM/EDX and micro-Raman spectrometry for individual airborne particles analysis as applied at the University of Antwerp (Belgium) by the MITAC group have been reviewed. Microbeam techniques provide detailed information concerning the origin, formation, transport, reactivity, transformation reactions and environmental impact of particulate matter. Moreover, some particles of certain chemical properties have been recognized as a threat for human health and cultural heritage objects. However, the small sizes of particles result in specific problems with respect to single particle analysis. Development of equipment and software for improvement of analysis and quantification are reported.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1088/1742-6596/162/1/012019
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“Inferring episodic atmospheric iron fluxes in the Western South Atlantic”. Evangelista H, Maldonado J, dos Santos EA, Godoi RHM, Garcia CAE, Garcia VMT, Johnson E, da Cunha KD, Leite CB, Van Grieken R, van Meel K, Makarovska Y, Gaiero DM, Atmospheric environment : an international journal 44, 703 (2010). http://doi.org/10.1016/J.ATMOSENV.2009.11.018
Abstract: Iron (Fe) and other trace elements such as Zn, Mn, Ni and Cu are known as key-factors in marine biogeochemical cycles. It is believed that ocean primary productivity blooms in iron deficient regions can be triggered by iron in aeolian dust. Up to now, scarce aerosol elemental composition, based on measurements over sea at the Western South Atlantic (WSA), exist. An association between the Patagonian semi-desert dust/Fe and chlorophyll-a variability at the Argentinean continental shelf is essentially inferred from models. We present here experimental data of Fe enriched aerosols over the WSA between latitudes 22°S62°S, during 4 oceanographic campaigns between 2002 and 2005. These data allowed inferring the atmospheric Fe flux onto different latitudinal bands which varied from 30.4 to 1688 nmolFe m−2 day−1 (October 29thNovember 15th, 2003); 5.831586 nmolFe m−2 day−1 (February 15thMarch 6th, 2004) and 4.73586 nmolFe m−2 day−1(October 21stNovember 5th, 2005).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.ATMOSENV.2009.11.018
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“Microchemical investigation of bone derived from mice treated with strontium in different chemical forms using scanning electron microscopy and micro-Raman spectroscopy”. Jabłoński MB, Stefaniak EA, Darchuk L, Turzańska K, Gorzelak M, Kuduk R, Dorriné, W, Van Grieken R, Microchemical journal 108, 168 (2013). http://doi.org/10.1016/J.MICROC.2012.10.015
Abstract: We used SEM/EDX and micro-Raman spectroscopy to investigate the chemical changes (both on the level of elementary and molecular composition) of mice bones when strontium is incorporated in their microstructure after being administered in the form of two salts: chloride and ranelate. Strontium accumulated mainly in vicinity of bone edges, both cortical and close to bone marrow. The distribution of other elements comprising bone samples (Ca, P, Mg, K etc.) was also determined by energy-dispersive X-ray analysis (EDX). The area adjacent to a cortical bone edge with accumulated strontium has presented modified Raman spectral profiles. Besides most of the Raman bands typical for both mineral (hydroxyapatite with carbonate substitution type B) and organic phases of a bone, we observed a Raman band at 811 cm− 1. It was detected regularly in the sample with high strontium concentration.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.MICROC.2012.10.015
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“New insight into UO2F2 particulate structure by micro-Raman spectroscopy”. Stefaniak EA, Darchuk L, Sapundjiev D, Kips R, Aregbe Y, Van Grieken R, Journal of molecular structure 1040, 206 (2013). http://doi.org/10.1016/J.MOLSTRUC.2013.02.012
Abstract: Uranyl fluoride particles produced via hydrolysis of uranium hexafluoride have been deposited on different substrates: polished graphite disks, silver foil, stainless steel and gold-coated silicon wafer, and measured with micro-Raman spectroscopy (MRS). All three metallic substrates enhanced the Raman signal delivered by UO2F2 in comparison to graphite. The fundamental stretching of the UO band appeared at 867 cm−1 in case of the graphite substrate, while in case of the others it was shifted to lower frequencies (down to 839 cm−1). All applied metallic substrates showed the expected effect of Raman signal enhancement; however the gold layer appeared to be most effective. Application of new substrates provides more information on the molecular structure of uranyl fluoride precipitation, which is interesting for nuclear safeguards and nuclear environmental analysis.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.MOLSTRUC.2013.02.012
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“Determination of fluorine in uranium oxyfluoride particles as an indicator of particle age”. Kips R, Pidduck AJ, Houlton MR, Leenaers A, Mace JD, Marie O, Pointurier F, Stefaniak EA, Taylor PDP, van den Berghe S, van Espen P, Van Grieken R, Wellum R, Spectrochimica acta: part B : atomic spectroscopy 64, 199 (2009). http://doi.org/10.1016/J.SAB.2008.12.001
Abstract: As swipe samples from enrichment activities typically contain uranium particles with a detectable amount of fluorine, the question was raised whether the analysis of fluorine in particles could complement the information on the uranium isotope ratios. For this, uranium oxyfluoride particles were prepared from the controlled hydrolysis of uranium hexafluoride (UF6). The relative amount of fluorine was characterized by scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDX), as well as ion-microprobe secondary ion mass spectrometry (IM-SIMS). Of particular interest was the assessment of the reduction of the amount of fluorine over time, and after exposure to UV-light and high temperatures. Micro-Raman spectrometry (MRS) was applied to look for differences in molecular structure between these various sample types. Both SEM-EDX and IM-SIMS showed a general reduction of the fluorine-to-uranium ratio after 12 years of storage. The exposure to UV-light and high temperatures was found to have accelerated the loss of fluorine. A distinct peak at 865 cm− 1 Raman shift was detected for the majority of particles analyzed by MRS. For the particles that were heat-treated, the Raman spectra were similar to the spectrum of U3O8. Although often large variations were observed between particles from the same sample, the three particle measurement techniques (IM-SIMS, SEM-EDX and MRS) showed some consistent trends. They therefore appear promising in terms of the ability to place bounds on particle age, as well as shedding light on the complex processes involved in UO2F2 particle ageing.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
DOI: 10.1016/J.SAB.2008.12.001
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“Argentinean prehistoric pigments' study by combined SEM/EDX and molecular spectroscopy”. Darchuk L, Tsybrii Z, Worobiec A, Vázquez C, Palacios OM, Stefaniak EA, Gatto Rotondo G, Sizov F, Van Grieken R, Spectrochimica acta: part A: molecular and biomolecular spectroscopy 75, 1398 (2010). http://doi.org/10.1016/J.SAA.2010.01.006
Abstract: Composition of the prehistoric pigments (from Carriqueo rock shelter, Rio Negro province, Argentina) has been analysed by means of molecular spectroscopy (Fourier transform infrared (FTIR) and micro-Raman) and scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDS). Red and yellow pigments were recognized as red and yellow ochre. The matrix of the pigments is composed of one or more substances. According to the matrix composition yellow and red pigments were also divided into two groupsi.e. those containing kaolinite or sulphates. Green pigment was detected as green earth, made up of celadonite as a chromophore.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1016/J.SAA.2010.01.006
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“Characterisation of Amazon Basin aerosols at the individual particle level by X-ray microanalytical techniques”. Worobiec A, Szalóki I, Osán J, Maenhaut W, Stefaniak EA, Van Grieken R, Atmospheric environment : an international journal 41, 9217 (2007). http://doi.org/10.1016/J.ATMOSENV.2007.07.056
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1016/J.ATMOSENV.2007.07.056
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“Characterisation of individual atmospheric particles within the Royal Museum of the Wawel Castle in Cracow, Poland”. Worobiec A, Stefaniak EA, Kontozova V, Samek L, Karaszkiewicz P, van Meel K, Van Grieken R, e-Preservation Science 3, 63 (2006)
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
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“Composition of pigments on human bones found in excavations in Argentina studied with micro-Raman spectrometry and scanning electron microscopy”. Darchuk L, Stefaniak EA, Vázquez C, Palacios OM, Worobiec A, Van Grieken R, e-Preservation Science 6, 112 (2009)
Abstract: Results on analysis of prehistoric pigments from excavations and pigments on coloured child bones from North Patagonia, Argentina, are reported. To analyze their composition we used two micro-analytical techniques: micro- Raman spectrometry (MRS) and scanning electron microscopy coupled with X-ray micro-analysis (SEM/EDX). Most investigated excavated pigments show red or yellow ochres consistent with reddish or yellow minerals, such as á- and ã-goethite, haematite, erdite, haapalaite and jarosite. Raman spectra show also evidence of calcium oxalate monohydrate and calcite indicating lichen activity. Pigments covering human bones were identified as hematite and magnetite. This study allows us to infer that pigments found in excavation were employed for burial ceremonies, even though distances between excavated pigment archaeological site and buried remains are quite far, more than 50 km in a straight line.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
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“Historical changes in air pollution in the tri-border region of Poland, Czech Republic and Germany”. Worobiec A, Zwozdziak A, Sówka I, Zwozdziak J, Stefaniak EA, Buczyńska A, Krata A, van Meel K, Van Grieken R, Górka M, Jedrysek M-O, Environment protection engineering 34, 81 (2008)
Abstract: In this study, we show the trends in the concentration Of SO2 and particulate matter (PM) in two health resorts, located in the tri-border region of Poland, Germany and Czech Republic. We analyze the annual time series and the seasonal variability of PM concentration for the months of July and February over the period of 1996-2007. Additionally, in July 2006, we measured the mean 24-hour concentration of PM and the content of heavy metals (by EDXRF analysis). We prove that nowadays air pollution in this region has diminished to a large extent as compared to the 90s of the last century. In Cieplice, the local influence is still evident; while Czerniawa is exposed to a periodical advection of polluted air from regional sources.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
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“Infrared investigation of hard human teeth tissues exposed to various doses of ionizing radiation from the 1986 Chernobyl accident”. Darchuk LA, Zaverbna LV, Bebeshko VG, Worobiec A, Stefaniak EA, Van Grieken R, Spectroscopy 22, 105 (2008). http://doi.org/10.1155/2008/843612
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1155/2008/843612
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“Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy”. Swaenen M, Stefaniak EA, Frost R, Worobiec A, Van Grieken R, Analytical and bioanalytical chemistry 397, 2659 (2010). http://doi.org/10.1007/S00216-009-3351-2
Abstract: Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1007/S00216-009-3351-2
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“A seasonal study of atmospheric conditions influenced by the intensive tourist flow in the Royal Museum of Wawel Castle in Cracow, Poland”. Worobiec A, Samek L, Karaszkiewicz P, Kontozova-Deutsch V, Stefaniak EA, van Meel K, Krata A, Bencs L, Van Grieken R, Microchemical journal 90, 99 (2008). http://doi.org/10.1016/J.MICROC.2008.04.005
Abstract: Increasingmass tourismcan generate importantmicroclimatic perturbations and also elevate indoor pollution by the transport of fine particulatematter. The purpose of this researchwas to study the indoor air conditions in the RoyalMuseum ofWawel Castle in Cracow, Poland, displaying amongst other valuable works of art also a unique collection of Flemish tapestries. The investigation involved in the determination of transport and deposition of particulate matter brought in by visitors. The microclimate inside the exhibition rooms was also monitored. Samples of suspended particulateswere collected inside and outside themuseuminwinterand summer2006.On days with intensive tourist visits the concentration of total suspended particulates was significantly higher (i.e., 130 µg/m3 inwinter and 49 µg/m3 in summer) than on those days without tourists (i.e., 73 µg/m3 and 22 µg/m3 in winter and summer, respectively). The concentrations of all investigated elementswere also considerably higher during the tourist flow. This was especially valid for soil dust associated elements (Si, K, Ca, Al, and Ti), with considerably higher levels in summer than winter. This could be linked with much more frequent tourist activity in the summer period. Also, the concentration of Clwasmuch higher inwinter than summer, due to the use of deicing salts on the roads and pavements.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1016/J.MICROC.2008.04.005
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“Transport and deposition of airborne pollutants in exhibition areas located in historical buildings: study in Wawel Castle Museum in Cracow, Poland”. Worobiec A, Samek J, Krata A, van Meel K, Krupińska B, Stefaniak EA, Karaszkiewicz P, Van Grieken R, Journal of cultural heritage 11, 354 (2010). http://doi.org/10.1016/J.CULHER.2009.11.009
Abstract: Historical buildings and castles that have been turned nowadays into museums, as an exhibition area for precious cultural heritage (CH) items, need more attention since they are CH objects by themselves. Moreover, the preservation techniques require often, significant interventions; however such changes are not always possible or are very limited. The aim of the present study was to investigate the influence of outdoor air pollution on the composition of particulate matter and gases inside the museum of Wawel Castle in Cracow, Poland. During this study a combination of micro and trace analysis techniques were applied, including energy dispersive X-ray fluorescence (EDXRF) and electron probe microanalysis (EPMA). An intensive transport of air pollutants coupled with accumulation of the particles inside the museum was noticed (considerably higher in winter than summer). A high content of carbon and organic matter agglomerated with inorganic particles was determined. Those particles are of special concern because of their adhesive properties and reactivity. It was also noted that the conditions inside the museum favour the reaction of the particles with gaseous pollutants. It was especially the case for nitrate particles.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1016/J.CULHER.2009.11.009
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“Binding energies of positive and negative trions: From quantum wells to quantum dots”. Bracker AS, Stinaff EA, Gammon D, Ware ME, Tischler JG, Park D, Gershoni D, Filinov AV, Bonitz M, Peeters F, Riva C, Physical review : B : condensed matter and materials physics 72, 035332 (2005). http://doi.org/10.1103/PhysRevB.72.035332
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 77
DOI: 10.1103/PhysRevB.72.035332
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“Equivalence of 3D bipolarons in a strong magnetic field to 1D bipolarons”. Smondyrev MA, Kochetov EA, Verbist G, Peeters FM, Devreese JT, Europhysics letters 19, 519 (1992). http://doi.org/10.1209/0295-5075/19/6/013
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 2.095
Times cited: 17
DOI: 10.1209/0295-5075/19/6/013
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“Direct and indirect effect of irrigation water availability on crop revenue in northwest Ethiopia : a structural equation model”. Chekol Zewdie M, Van Passel S, Cools J, Tenessa DB, Ayele ZA, Tsegaye EA, Minale AS, Nyssen J, Agricultural Water Management 220, 27 (2019). http://doi.org/10.1016/J.AGWAT.2019.04.013
Abstract: Development of a clear understanding of the relationship between the availability of dam-driven irrigation water and crop revenue is important in poverty reduction and food security process. As a result, large research efforts are devoted to understanding the relationship between the availability of irrigation water and crop revenue. However, earlier studies do have several limitations. For example, without considering its indirect effect, prior studies focused solely on the direct effect of availability of irrigation water on crop revue. In this study, using a structural equation model analysis, the direct and indirect effect of availability of dam-driven irrigation water on crop revenue is decomposed and quantified specifically for the Koga irrigation scheme, located in the Mecha district of Amhara region in Ethiopia. A primary data set was collected from a randomly selected sample of 450 households in the Koga irrigation scheme. More than half of the households (254) are supported by the Koga Dam irrigation water during the dry season, and the other 196 households depended only on rainfall. The results of the study showed that, in addition to its direct effect, the availability of irrigation water indirectly affected crop revenue through receptivity of the farmers to use modern farm inputs. Around 27 percent of the total effect of dam-driven irrigation water on crop revenue was mediated by farmers’ receptivity to use yield-enhancing modern farm inputs. The results of this study suggested that the availability of irrigation water is essential to improve both crop revenue and receptivity of the farmers to use modern farm inputs. This finding also drives a strategic framework that the receptivity of the farmers to use modern farm inputs is crucial for utilizing the positive effects of irrigation water availability on crop revenue.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
Impact Factor: 2.848
Times cited: 1
DOI: 10.1016/J.AGWAT.2019.04.013
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“Eliciting farmers' preferences and willingness to pay for land use attributes in Northwest Ethiopia : a discrete choice experiment study”. Admasu WF, Van Passel S, Nyssen J, Minale AS, Tsegaye EA, Land Use Policy 109 (2021). http://doi.org/10.1016/J.LANDUSEPOL.2021.105634
Abstract: This study investigates farmers' preferences and willingness to pay for cropland attributes in Bahir Dar, north-west Ethiopia. A choice experiment is used to elicit farmers' preferences between different land use attributes, including a monetary attribute. The study was conducted in the croplands that are threatened by land expro-priation for urban expansion. A survey was undertaken with 144 farmers in four rural kebeles surrounding the city (Addis Alem, Weramit, Wereb and Zenzelima). In the survey, respondents were provided with hypothetical land purchasing decisions, with three alternatives (i.e., two hypothetical parcels and an opt-out option). A choice experiment was undertaken to measure farmers' interest in different types of croplands, which varies with respect to irrigability, number of trees per ha, soil erosion resistance and water holding capacity of the cropland. Estimation of two mixed logit models was carried out. The estimation results show that, although the farmers did not show strong preferences for each attribute of the cropland, many farmers in the area showed interest in the proposed alternative croplands. Farmers show more interest for the land that is irrigable, gentle slope and with medium water holding capacity. The results also indicate that farmers assign highest marginal willingness to pay (MWTP) (79.01 ETB per square meter) for irrigated land, followed by medium water holding capacity with MWTP of 52.13 ETB per square meter. We believe that the results of this study would help land use policy and decision makers in the study area to consider the various attributes of cropland in land use planning, including land expropriation programs, which assures the sustainability of ecosystem services.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
Impact Factor: 3.089
DOI: 10.1016/J.LANDUSEPOL.2021.105634
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“Pathways how irrigation water affects crop revenue of smallholder farmers in northwest Ethiopia: A mixed approach”. Zewdie MC, Van Passel S, Moretti M, Annys S, Tenessa DB, Ayele ZA, Tsegaye EA, Cools J, Minale AS, Nyssen J, Agricultural Water Management 233, 106101 (2020). http://doi.org/10.1016/j.agwat.2020.106101
Abstract: The relationship between irrigation water availability and crop revenue is multifaceted. However, most of the previous studies focused only on the direct effect of irrigation water on crop revenue or considered that the indirect effect passes only through the farmers’ improved farm inputs usage. Nevertheless, unlike previous studies, this study argues that a one-sided argument that irrigation water directly causes high crop revenue or indirectly affects crop revenue only via the farmers’ improved farm inputs usage is incomplete, as irrigation water not only directly contributes to crop revenue but also indirectly conduces to crop revenue via both the type of crops produced and the farmers’ improved farm inputs usage. Considering the previous studies’ limitations, this study investigates pathways how small-scale irrigation water affects crop revenue and identifies challenges of small-scale irrigation farming in Fogera district, Ethiopia. Results endorsed that irrigation water has both direct and indirect effects on crop revenue. The indirect effect is 67 percent of the total effect and it is mediated by both the type of crops produced and farmers’ improved farm inputs usage. The result also indicated that irrigation user farmers have a higher income, more livestock assets and resources and better food, housing, and cloths than the non-users. Moreover, challenges related to agricultural output and input market were identified as the most severe problem followed by crop disease. The findings of our study suggest that to utilize the benefits of irrigation water properly, it is crucial to encourage farmers to use more improved farm inputs and to shift from staple to cash crop production. Moreover, farmers are frequently exposed to cheating by illegal brokers in the output market, therefore it is also important to increase farmers’ accessibility to output and input markets, the quality of improved farm inputs, and the bargaining power of farmers with market information.
Keywords: A1 Journal article; Economics; Engineering sciences. Technology; Engineering Management (ENM); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 6.7
DOI: 10.1016/j.agwat.2020.106101
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“Boron-rich inclusions and boron distribution in HPHT polycrystalline superconducting diamond”. Lu Y-G, Turner S, Ekimov EA, Verbeeck J, Van Tendeloo G, Carbon 86, 156 (2015). http://doi.org/10.1016/j.carbon.2015.01.034
Abstract: Polycrystalline boron-doped superconducting diamond, synthesized at high pressure and high temperature (HPHT) via a reaction of a single piece of crystalline boron with monolithic graphite, has been investigated by analytical transmission electron microscopy. The local boron distribution and boron environment have been studied by a combination of (scanning) transmission electron microscopy ((S)TEM) and spatially resolved electron energy-loss spectroscopy (EELS). High resolution TEM imaging and EELS elemental mapping have established, for the first time, the presence of largely crystalline diamond-diamond grain boundaries within the material and have evidenced the presence of substitutional boron dopants within individual diamond grains. Confirmation of the presence of substitutional B dopants has been obtained through comparison of acquired boron K-edge EELS fine structures with known references. This confirmation is important to understand the origin of superconductivity in polycrystalline B-doped diamond. In addition to the substitutional boron doping, boron-rich inclusions and triple-points, both amorphous and crystalline, with chemical compositions close to boron carbide B4C, are evidenced. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.337
Times cited: 20
DOI: 10.1016/j.carbon.2015.01.034
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“Catalytic and molecular separation properties of Zeogrids and Zeotiles”. Martens JA, Thybaut JW, Denayer JFM, Sree SP, Aerts A, Reyniers M-F, van Speybroeck V, Waroquier M, Buekenhoudt A, Vankelecom I, Buijs W, Persoons J, Baron GV, Bals S, Van Tendeloo G, Marin GB, Jacobs PA, Kirschhock CEA, Catalysis today 168, 17 (2011). http://doi.org/10.1016/j.cattod.2011.01.036
Abstract: Zeogrids and Zeotiles are hierarchical materials built from assembled MFI zeolite precursor units. Permanent secondary porosity in these materials is obtained through self assembly of nanoparticles encountered in MFI zeolite synthesis in the presence of supramolecular templates. Hereon, the aggregated species are termed nanoslabs. Zeogrids are layered materials with lateral spacings between nanoslabs creating galleries qualifying as supermicropores. Zeotiles present a diversity of tridimensional nanoslab assemblies with mesopores. Zeotile-1, -4 and -6 are hexagonal mesostructures. Zeotile-1 has triangular and hexagonal channels; Zeotile-4 has hexagonal channels interconnected via slits. Zeotile-2 has a cubic structure with gyroid type mesoporosity. The behavior of Zeogrids and Zeotiles in adsorption, membrane and chromatographic separation and catalysis has been characterized and compared with zeolites and mesoporous materials derived from unstructured silica sources. Shape selectivity was detected via adsorption of n- and iso-alkanes. The mesoporosity of Zeotiles can be exploited in chromatographic separation of biomolecules. Zeotiles present attractive separation properties relevant to CO2 sequestration. Because of its facile synthesis procedure without hydrothermal steps Zeogrid is convenient for membrane synthesis. The performance of Zeogrid membrane in gas separation, nanofiltration and pervaporation is reported. In the Beckmann rearrangement of cyclohexanone oxime Zeogrids and Zeotiles display a catalytic activity characteristic of silicalite-1 zeolites. Introduction of acidity and redox catalytic activity can be achieved via incorporation of Al and Ti atoms in the nanoslabs during synthesis. Zeogrids are active in hydrocracking, catalytic cracking, alkylation and epoxidation reactions. Zeogrids and Zeotiles often behave differently from ordered mesoporous materials as well as from zeolites and present a valuable extension of the family of hierarchical silicate based materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.636
Times cited: 13
DOI: 10.1016/j.cattod.2011.01.036
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“Catalytic carbon oxidation over ruthenium-based catalysts”. Villani K, Kirschhock CEA, Liang D, Van Tendeloo G, Martens JA, Angewandte Chemie: international edition in English 45, 3106 (2006). http://doi.org/10.1002/anie.200503799
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 36
DOI: 10.1002/anie.200503799
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“Chabazite : stable cation-exchanger in hyper alkaline concrete pore water”. Van Tendeloo L, Wangermez W, Kurttepeli M, de Blochouse B, Bals S, Van Tendeloo G, Martens JA, Maes A, Kirschhock CEA, Breynaert E, Environmental science and technology 49, 2358 (2015). http://doi.org/10.1021/es505346j
Abstract: To avoid impact on the environment, facilities for permanent disposal of hazardous waste adopt multibarrier design schemes. As the primary barrier very often consists of cement-based materials, two distinct aspects are essential for the selection of suitable complementary barriers: (1) selective sorption of the contaminants in the repository and (2) long-term chemical stability in hyperalkaline concrete-derived media. A multidisciplinary approach combining experimental strategies from environmental chemistry and materials science is therefore essential to provide a reliable assessment of potential candidate materials. Chabazite is typically synthesized in 1 M KOH solutions but also crystallizes in simulated young cement pore water, a pH 13 aqueous solution mainly containing K+ and Na+ cations. Its formation and stability in this medium was evaluated as a function of temperature (60 and 85 °C) over a timeframe of more than 2 years and was also asessed from a mechanistic point of view. Chabazite demonstrates excellent cation-exchange properties in simulated young cement pore water. Comparison of its Cs+ cation exchange properties at pH 8 and pH 13 unexpectedly demonstrated an increase of the KD with increasing pH. The combined results identify chabazite as a valid candidate for inclusion in engineered barriers for concrete-based waste disposal.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.198
Times cited: 13
DOI: 10.1021/es505346j
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“Conceptual frame rationalizing the self-stabilization of H-USY zeolites in hot liquid water”. Ennaert T, Geboers J, Gobechiya E, Courtin CM, Kurttepeli M, Houthoofd K, Kirschhock CEA, Magusin PCMM, Bals S, Jacobs PA, Sels BF, ACS catalysis 5, 754 (2015). http://doi.org/10.1021/cs501559s
Abstract: The wide range of liquid-phase reactions required for the catalytic conversion of biomass compounds into new bioplatform molecules defines a new set of challenges for the development of active, selective, and stable catalysts. The potential of bifunctional Ru/H-USY catalysts for conversions in hot liquid water (HLW) is assessed in terms of physicochemical stability and long-term catalytic performance of acid sites and noble metal functionality, as probed by hydrolytic hydrogenation of cellulose. It is shown that zeolite desilication is the main zeolite degradation mechanism in HLW. USY zeolite stability depends on two main parameters, viz., framework and extra-framework aluminum content. The former protects the zeolite lattice by counteracting hydrolysis of framework bonds, and the latter, when located at the external crystal surface, prevents solubilization of the zeolite framework which is the result of its low water-solubility. Hence, the hot liquid water stability of commercial H-USY zeolites, in contrast to their steam stability, increased with decreasing Si/AI ratio. As a result, mildly steamed USY zeolites containing a high amount of both Al species exhibit the highest resistance to HLW. During an initial period of transformations, Al-rich zeolites form additional protective extra-framework Al species at the outer surface, self-stabilizing the framework. A critical bulk Si/AI ratio of 3 was determined whereby USY zeolites with a lower Si/AI ratio will self-stabilize over time. Besides, due to the initial transformation period, the accessibility of the catalytic active sites is extensively enhanced resulting in a material that is more stable and drastically more accessible to large substrates than the original zeolite. When these findings are applied in the hydrolytic hydrogenation of cellulose, unprecedented nearly quantitative hexitol yields were obtained with a stable catalytic system.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 10.614
Times cited: 65
DOI: 10.1021/cs501559s
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“Copper benzene tricarboxylate metal-organic framework with wide permanent mesopores stabilized by keggin polyoxometallate ions”. Wee LH, Wiktor C, Turner S, Vanderlinden W, Janssens N, Bajpe SR, Houthoofd K, Van Tendeloo G, De Feyter S, Kirschhock CEA, Martens JA;, Journal of the American Chemical Society 134, 10911 (2012). http://doi.org/10.1021/ja302089w
Abstract: Porous solids with organized multiple porosity are of scientific and technological importance for broadening the application range from traditional areas of catalysis and adsorption/separation to drug release and biomedical imaging. Synthesis of crystalline porous materials offering a network of uniform micro- and mesopores remains a major scientific challenge. One strategy is based on variation of synthesis parameters of microporous networks, such as, for example, zeolites or metal organic frameworks (MOFs). Here, we show the rational development of an hierarchical variant of the microporous cubic Cu-3(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate) HKUST-1 MOF having strictly repetitive S inn wide mesopores separated by uniform microporous walls in a single crystal structure. This new material coined COK-15 (COK = Centrum voor Oppervlaktechemie en Katalyse) was synthesized via a dual-templating approach. Stability was enhanced by Keggin type phosphotungstate (HPW) systematically occluded in the cavities constituting the walls between the mesopores.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 83
DOI: 10.1021/ja302089w
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“Crystal structure and magnetic properties of complex oxides Mg4-xNixO9, 0\leq x\leq4”. Tarakina NV, Nikulina EA, Hadermann J, Kellerman DG, Tyutunnik AP, Berger IF, Zubkov VG, Van Tendeloo G, Journal of solid state chemistry 180, 3180 (2007). http://doi.org/10.1016/j.jssc.2007.09.007
Abstract: In the Mg4−xNixNb2O9 (0x4) system two ranges of solid solution have been found. One of the solid solutions has a corundum-related structure type (space group ); the second one adopts the II-Ni4Nb2O9 structure type (space group Pbcn). The unit cell constants and atomic positions have been determined and refined using neutron powder diffraction data. Electron diffraction and high-resolution transmission electron microscopy (HRTEM) from MgNi3Nb2O9 crystals identify the presence of planar defects and the intergrowth of several (structurally related) phases. The magnetic susceptibility of Mg3NiNb2O9, measured in the temperature range T=2300 K, shows no indications of magnetic ordering at low temperatures, while for MgNi3Nb2O9 there is a magnetic ordering at temperatures below 45.5 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 3
DOI: 10.1016/j.jssc.2007.09.007
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“Design and synthesis of hierarchical materials from ordered zeolitic building units”. Kirschhock CEA, Kremer SPB, Vermant J, Van Tendeloo G, Jacobs PA, Martens JA, Chemistry: a European journal 11, 4306 (2005). http://doi.org/10.1002/chem.200401329
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 93
DOI: 10.1002/chem.200401329
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“Design of zeolite by inverse sigma transformation”. Verheyen E, Joos L, Van Havenbergh K, Breynaert E, Kasian N, Gobechiya E, Houthoofd K, Martineau C, Hinterstein M, Taulelle F, Van Speybroeck V, Waroquier M, Bals S, Van Tendeloo G, Kirschhock CEA, Martens JA;, Nature materials 11, 1059 (2012). http://doi.org/10.1038/NMAT3455
Abstract: Although the search for new zeolites has traditionally been based on trial and error, more rational methods are now available. The theoretical concept of inverse transformation of a zeolite framework to generate a new structure by removal of a layer of framework atoms and contraction has for the first time been achieved experimentally. The reactivity of framework germanium atoms in strong mineral acid was exploited to selectively remove germanium-containing four-ring units from an UTL type germanosilicate zeolite. Annealing of the leached framework through calcination led to the new all-silica COK-14 zeolite with intersecting 12- and 10-membered ring channel systems. An intermediate stage of this inverse transformation with dislodged germanate four-rings still residing in the pores could be demonstrated. Inverse transformation involving elimination of germanium-containing structural units opens perspectives for the synthesis of many more zeolites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 39.737
Times cited: 140
DOI: 10.1038/NMAT3455
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“Self-Assembly of Pluronic F127—Silica Spherical Core–Shell Nanoparticles in Cubic Close-Packed Structures”. Kerkhofs S, Willhammar T, Van Den Noortgate H, Kirschhock CEA, Breynaert E, Van Tendeloo G, Bals S, Martens JA, Chemistry of materials 27, 5161 (2015). http://doi.org/10.1021/acs.chemmater.5b01772
Abstract: A new ordered mesoporous silica material (COK-19) with cubic symmetry is synthesized by silicate polycondensation in a citric acid/citrate buffered micellar solution of Pluronic F127 triblock copolymer near neutral pH. SAXS, nitrogen adsorption, TEM, and electron tomography reveal the final material has a cubic close packed symmetry (Fm3̅m) with isolated spherical mesopores interconnected through micropores. Heating of the synthesis medium from room temperature to 70 °C results in a mesopore size increase from 7.0 to 11.2 nm. Stepwise addition of the silicate source allows isolation of a sequence of intermediates that upon characterization with small-angle X-ray scattering uncovers the formation process via formation and aggregation of individual silica-covered Pluronic micelles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 39
DOI: 10.1021/acs.chemmater.5b01772
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“Formation of ZSM-22 zeolite catalytic particles by fusion of elementary nanorods”. Hayasaka K, Liang D, Huybrechts W, De Waele BR, Houthoofd KJ, Eloy P, Gaigneaux EM, Van Tendeloo G, Thybaut JW, Marin GB, Denayer JFM, Baron GV, Jacobs PA, Kirschhock CEA, Martens JA;, Chemistry: a European journal 13, 10070 (2007). http://doi.org/10.1002/chem.200700967
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 52
DOI: 10.1002/chem.200700967
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