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    Towards multiscale X-ray tomographic imaging in membrane science : A perspective

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    Tomographic X-ray imaging techniques offer novel opportunities for studying membranes and membrane processes in 3D on a spatial resolution not seen before. Traditional 2D imaging techniques used to characterise membranes have limitations that can be overcome by tomographic X-ray imaging. Tomographic X-ray imaging can provide information in 2D/3D or 4D (3D plus time) on membranes, membrane modules, and membrane processes on a scale ranging from micro- to nanometre. They offer the possibility to uncover many fundamental issues related to membrane science, including the detection and monitoring of macroscopic biofilm formation, scaling, and cake build-up. High-resolution nanotomographic X-ray imaging enables even microscopic characterisations such as pore size distribution or pore network analysis. This Perspective paper introduces the tomographic X-ray imaging techniques with the most potential for membrane science: microtomography, nanotomography, holotomography, and ptychotomography, and presents their applications in the literature regarding the field of membrane science. Based on these findings and our experiences opportunities, challenges, and limitations of tomographic X-ray imaging techniques are discussed. It is concluded that in the near future tomographic X-ray imaging techniques will become increasingly common analytical techniques for membrane manufacturers, scientists, and users

    The successful use of a search strategy improves with visuospatial working memory in 2- to 4.5-year-olds

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    Using spatial cues such as shape, orientation, and pattern aids visuospatial working memory because it allows strategies that reduce the load on this cognitive resource. One such strategy, namely taking advantage of patterned spatial distributions, remains understudied to date. This strategy demands keeping track of already-searched locations and excluding them from further search and so correlates with visuospatial working memory. The use of such strategies should, in principle, develop in early childhood, but because most studies focus on chunking, the development of other strategies reducing the load on working memory is understudied in young children. Therefore, in this study we tested whether children aged 2 to 4.5 years (N = 97) could take advantage of spatial cues in their search and whether this ability correlated with their age, verbal ability, and visuospatial working memory. The results showed that the ability to use a patterned spatial distribution (searching a row of locations from one side to the other instead of a random search) significantly improved with visuospatial working memory but not with age or verbal ability. These results suggest that visuospatial abilities may rapidly develop from 2 to 4.5 years of age, and given their impact on later mathematic achievement, demand increased attention in cognitive developmental research and early childhood education

    Part III. Key Concepts in Climate Policy: Stranded Assets

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    Spectral representation of EEG data using learned graphs with application to motor imagery decoding

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    Electroencephalography (EEG) data entail a complex spatiotemporal structure that reflects ongoing organization of brain activity. Characterization of the spatial patterns is an indispensable step in numerous EEG processing pipelines. We present a novel method for transforming EEG data into a spectral representation. First, we learn subject-specific graphs from each subject's EEG data. Second, by eigendecomposition of the normalized Laplacian matrix of each subject's graph, an orthonormal basis is obtained using which any given EEG map of the subject can be decomposed, providing a spectral representation of the data. We show that energy of EEG maps is strongly associated with low frequency components of the learned basis, reflecting the smooth topography of EEG maps. As a proof-of-concept for this alternative view of EEG data, we consider the task of decoding two-class motor imagery (MI) data. To this aim, the spectral representations are first mapped into a discriminative subspace for differentiating two-class data using a projection matrix obtained by the Fukunaga–Koontz transform (FKT). An SVM classifier is then trained and tested on the resulting features to differentiate MI classes. The method is benchmarked against features extracted from a subject-specific functional connectivity matrix as well as four alternative MI-decoding methods on Dataset IVa of BCI Competition III. Experimental results show the superiority of the proposed method over alternative approaches in differentiating MI classes, reflecting the added benefit of (i) decomposing EEG data using data-driven, subject-specific harmonic bases, and (ii) accounting for class-specific temporal variations in spectral profiles

    Marine sediments are identified as an environmental reservoir for Escherichia coli : Comparing signature-based and novel amplicon sequencing approaches for microbial source tracking

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    Viable Escherichia coli were detected in sediments near a point of wastewater discharge in a marine coastal environment in Sweden. Since high concentrations were found in the sediments nearest the pipe, this suggested that treated wastewater effluent was the source of the microbes. In order to examine this hypothesis, different bioinformatics approaches were applied using 16S rRNA gene V3-V4 amplicon sequences from the sediments. Both signature-based source tracking using sequence libraries describing known sources of fecal water pollution (SourceTracker); and, a curated source tracking method, indicated that sediments were contaminated with wastewater. The results from the curated approach were independently confirmed using differential abundance analysis (DESeq2). A number of taxa originating from wastewater were identified which can be used to describe contamination of the sediments, and examine the spread of these specific taxa, even at low relative abundance, along the urban coast. Sequences of phylum Bacteroidetes (such as Bacteroides and Prevotella) and Firmicutes (such as Romboutsia) increased in sediments with higher concentrations of E. coli. In addition, sequences from Trichococcus are proposed as an indicator for treated wastewater. All three source tracking approaches, and the detection of viable E. coli, suggest that urban sediments can be a reservoir for indicator bacteria

    The Black Swan problem : The role of capital, liquidity and operating flexibility

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    How firms cope with tail risk is an under-researched problem in the literature on corporate risk management. This paper presents stylized facts on the nature of revenue shocks based on 65 years worth of Compustat data. We define a Black Swan as an unexpected year-on-year drop in revenue between 30%–90%. The rate of Black Swans has increased markedly since the 1970's and there are more pronounced cyclical peaks in the three most recent decades. We also examine the role of three general determinants of firms’ ability to absorb Black Swans: equity capital, liquidity, and operating flexibility. The conclusion to emerge from this analysis is that the deciding factor in mediating the effects of revenue shocks on employment is liquidity. Cash reserves and cash margins make firms less fragile, but neither equity capital nor operating flexibility robustly buffer against Black Swans. The results continue to hold when we restrict the analysis to transient and cyclical revenue shocks, as well as when we use only a strictly exogenous revenue shock based on the airline industry

    Theatres of Powerlessness : Acts of Knowledge and the Performance of the Many

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    Theatres of Powerlessness departs from Edit Kaldor’s Inventory of Powerlessness (2013-16), a multi-year theatre project in which hundreds of participants articulated their emergent knowledge about contemporary forms of powerlessness. It is aimed, among others, at student readers in an increasingly diversified educational context, who are learning to develop models of transformative, creative practice with which to put their own experiences of the world to work. Combining process and performance documentation of Inventory, with critical analysis of a global range of contemporary performance practices, Theatres of Powerlessness offers practical considerations for an extended 21st century theatre aesthetic, through which undervalued ‘acts of knowledge’ and their generative potential can be brought to light

    Performance and Militant Curating: Rehearsing democratic imaginaries through critical spaces and publics : Rehearsing democratic imaginaries through critical spaces and publics

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    During the last couple of decades in Europe we have witnessed a proliferation of artistic practices -what we might call the “political turn” - that sought to experiment with models of democracy and participation, as well as forms of intervention in socio-political realities. At the same time, in Southern Europe and beyond a series of social collective practices emerged in the face of an ongoing economic crisis seeking to offer alternative modes of solidarity and social organisation taking the form of medical clinics, social kitchens, food exchange networks, platforms against evictions, refugee support and cultural venues amongst others. Democratic imaginaries were practiced and contested through both artistic experimentations as well as such collective grassroots practices of commoning and solidarity. Critically reflecting on such practices might we be able to identify appropriate models of social/political pedagogy today? What practices might contribute in reforming democratic imaginaries and social modus operandi of co-existence? Can artistic venues and practices weighted upon calls for participation, inclusion and impact offer such models? How might practices and experiences of assembling and togetherness help us redefine what counts as‘democratic” or “non-democratic” today? Questioning the ongoing recuperation of “participation” and the potential of the “political turn” in the arts in conditions of precarity this article traces specific experiences of assembling in order toexamine models and practices that renew our habits of togetherness and bear the potential to form new political pedagogies

    A TDLAS-based photofragmentation method for spatially resolved measurement of KOH and KCl as well as its application in biomass combustion processes

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    The release of gas-phase potassium species, mainly KOH, KCl, and K atoms, from burning biomass fuels can introduce severe problems to boilers, such as fouling, slagging, and corrosion. In the present work, an optical technique combining laser-induced photofragmentation and tunable diode laser absorption spectroscopy is developed for simultaneously measuring the concentration of KOH, KCl and K atoms with a high temporal and spatial resolution. Two laser sheets with a thickness of about 1 mm at wavelengths of 266 and 355 nm, respectively, were adopted to photodissociate KOH and KCl molecules into K atoms. A continuous wave laser at 766 nm generated by a tunable diode laser passed perpendicularly through the laser sheet to detect the K atom. The measured fragmentation-induced K-atom absorbance was correlated to KOH and KCl concertation through a calibration process in a homogenous combustion environment where the concentrations of KOH and KCl were monitored by UV absorption spectroscopy. The calibration curves were verified to be independent of temperature. A typical spatial resolution of 1 mm3 was realized where the value depended on the overlap volume of the UV laser sheet and the 766 nm laser beam. Finally, this technique was applied to measure the release behavior of KOH, KCl and K atoms from burning wood and straw pellets


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    Lund University Publications is based in Sweden
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