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32 result(s) for "Wilcke, Holger"
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Imperceptible Politics: Illegalized Migrants and Their Struggles for Work and Unionization
This article argues that illegalized migrants carry the potential for social change not only through their acts of resistance but also in their everyday practices. This is the case despite illegalized migrants being the most disenfranchised subjects produced by the European border regime. In line with Jacques Rancière (1999) these practices can be understood as ‘politics’. For Rancière, becoming a political subject requires visibility, while other scholars (Papadopoulos & Tsianos, 2007; Rygiel, 2011) stress that this is not necessarily the case. They argue that political subjectivity can also be achieved via invisible means; important in this discussion as invisibility is an essential strategy of illegalized migrants. The aim of this article is to resolve this binary and demonstrate, via empirical examples, that the two concepts of visibility and imperceptibility are often intertwined in the messy realities of everyday life. In the first case study, an intervention at the ver.di trade union conference in 2003, analysis reveals that illegalized migrants transformed society in their fight for union membership, but also that their visible campaigning simultaneously comprised strategies of imperceptibility. The second empirical section, which examines the employment stories of illegalized migrants, demonstrates that the everyday practices of illegal work can be understood as ‘imperceptible politics’. The discussion demonstrates that despite the exclusionary mechanisms of the existing social order, illegalized migrants are often able to find work. Thus, they routinely undermine the very foundations of the order that produces their exclusions. I argue that this disruption can be analyzed as migrants’ ‘imperceptible politics’, which in turn can be recognized as migrants’ transformative power.
Comparison as a method for geography education
Comparison is an everyday process of thinking, which is also frequently used in geography lessons. However, in geography pedagogy, the term 'comparison' remains vague and insufficiently defined. In this paper, we will propose a clear definition of what comparison is and introduce it as a systematic method for secondary school geography education. This definition and method is the result of our theoretical-conceptual approach, according to which we have analyzed the current academic discussion about scientific comparison and converted it into a method for teaching. We argue that applying comparison as a pedagogical tool may improve students' skills to argue, reflect, solve problems, and promote good judgement. (Orig.).
Contested Health Care System in Berlin: Are Illegalized Migrants Becoming Urban Citizens?
This article argues for an urban citizenship perspective which explores the struggle for rights and the everyday practices of illegalized migrants. Analyzing the concept of Anonymized Health Certificates as a result of such a struggle allows for examination of urban citizenship in this context. The implementation of the Anonymized Health Certificates program would facilitate access to medical care for people who live in the city of Berlin but are excluded from this right due to their lack of residency status. However, such a perspective also makes it possible to examine the limitation of the Anonymized Health Certificates, which would allow illegalized migrants in Berlin to circumvent access barriers, while at the same time the exclusion mechanisms of these barriers would remain uncontested at the national level. Whilst Anonymize Health Certificates will greatly improve access to medical care, illegalized migrants have by no means been passive subjects and have been actively rejecting their exclusion from health care: Practices include sharing health insurance cards with friends, visiting doctors who help for free as a form of solidarity, and sharing information about these doctors within their social networks. Even if they do not contest the social order visibly, they refuse to passively accept their social exclusion. Illegalized migrants perform such practices of urban citizenship in their everyday life as they actively take ownership of their rights to participate in urban life, even whilst being formally denied these rights.
Biotic and Abiotic Properties Mediating Plant Diversity Effects on Soil Microbial Communities in an Experimental Grassland
Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities.
The emergence of dyslexia in the developing brain
Developmental dyslexia, a severe deficit in literacy learning, is a neurodevelopmental learning disorder. Yet, it is not clear whether existing neurobiological accounts of dyslexia capture potential predispositions of the deficit or consequences of reduced reading experience. Here, we longitudinally followed 32 children from preliterate to school age using functional and structural magnetic resonance imaging techniques. Based on standardised and age-normed reading and spelling tests administered at school age, children were classified as 16 dyslexic participants and 16 controls. This longitudinal design allowed us to disentangle possible neurobiological predispositions for developing dyslexia from effects of individual differences in literacy experience. In our sample, the disorder can be predicted already before literacy learning from auditory cortex gyrification and aberrant downstream connectivity within the speech processing system. These results provide evidence for the notion that dyslexia may originate from an atypical maturation of the speech network that precedes literacy instruction. •Longitudinal MRI study following preliterate children developing dyslexia.•Auditory cortex folding was more variable in dyslexic children.•Altered speech network connectivity in dyslexia predates literacy instruction.•Combination of neural and behavioural data reliably predicted dyslexia before school.
Biodiversity–multifunctionality relationships depend on identity and number of measured functions
Biodiversity ensures ecosystem functioning and provisioning of ecosystem services, but it remains unclear how biodiversity–ecosystem multifunctionality relationships depend on the identity and number of functions considered. Here, we demonstrate that ecosystem multifunctionality, based on 82 indicator variables of ecosystem functions in a grassland biodiversity experiment, increases strongly with increasing biodiversity. Analysing subsets of functions showed that the effects of biodiversity on multifunctionality were stronger when more functions were included and that the strength of the biodiversity effects depended on the identity of the functions included. Limits to multifunctionality arose from negative correlations among functions and functions that were not correlated with biodiversity. Our findings underline that the management of ecosystems for the protection of biodiversity cannot be replaced by managing for particular ecosystem functions or services and emphasize the need for specific management to protect biodiversity. More plant species from the experimental pool of 60 species contributed to functioning when more functions were considered. An individual contribution to multifunctionality could be demonstrated for only a fraction of the species. Analysis of 82 indictors of ecosystem functioning at the Jena grassland biodiversity experiment shows that multifunctionality increases strongly with diversity, but depends on the number and identity of the functions considered.
Plant species richness and functional groups have different effects on soil water content in a decade-long grassland experiment
1. The temporal and spatial dynamics of soil water are closely interlinked with terrestrial ecosystems functioning. The interaction between plant community properties such as species composition and richness and soil water mirrors fundamental ecological processes determining above-ground-below-ground feedbacks. Plantwater relations and water stress have attracted considerable attention in biodiversity experiments. Yet, although soil scientific research suggests an influence of ecosystem productivity on soil hydraulic properties, temporal changes of the soil water content and soil hydraulic properties remain largely understudied in biodiversity experiments. Thus, insights on how plant diversity—productivity relationships affect soil water are lacking. 2. Here, we determine which factors related to plant community composition (species and functional group richness, presence of plant functional groups) and soil (organic carbon concentration) affect soil water in a long-term grassland biodiversity experiment (The Jena Experiment). 3. Both plant species richness and the presence of particular functional groups affected soil water content, while functional group richness played no role. The effect of species richness changed from positive to negative and expanded to deeper soil with time. Shortly after establishment, increased topsoil water content was related to higher leaf area index in species-rich plots, which enhanced shading. In later years, higher species richness increased topsoil organic carbon, likely improving soil aggregation. Improved aggregation, in turn, dried topsoils in species-rich plots due to faster drainage of rainwater. Functional groups affected soil water distribution, likely due to plant traits affecting root water uptake depths, shading, or water-use efficiency. For instance, topsoils in plots containing grasses were generally drier, while plots with legumes were moister. 4. Synthesis. Our decade-long experiment reveals that the maturation of grasslands changes the effects of plant richness from influencing soil water content through shading effects to altering soil physical characteristics in addition to modification of water uptake depth. Functional groups affected the soil water distribution by characteristic shifts of root water uptake depth, but did not enhance exploitation of the overall soil water storage. Our results reconcile previous seemingly contradictory results on the relation between grassland species diversity and soil moisture and highlight the role of vegetation composition for soil processes.
Early cortical surface plasticity relates to basic mathematical learning
Children lay the foundation for later academic achievement by acquiring core mathematical abilities in the first school years. Neural reorganization processes associated with individual differences in early mathematical learning, however, are still poorly understood. To fill this research gap, we followed a sample of 5-6-year-old children longitudinally to the end of second grade in school (age 7–8 years) combining magnetic resonance imaging (MRI) with comprehensive behavioral assessments. We report significant links between the rate of neuroplastic change of cortical surface anatomy, and children's early mathematical skills. In particular, most of the behavioral variance (about 73%) of children's visuospatial abilities was explained by the change in cortical thickness in the right superior parietal cortex. Moreover, half of the behavioral variance (about 55%) of children's arithmetic abilities was explained by the change in cortical folding in the right intraparietal sulcus. Additional associations for arithmetic abilities were found for cortical thickness change of the right temporal lobe, and the left middle occipital gyrus. Visuospatial abilities were related to right precentral and supramarginal thickness, as well as right medial frontal gyrus folding plasticity. These effects were independent of other individual differences in IQ, literacy and maternal education. Our findings highlight the critical role of cortical plasticity during the acquisition of fundamental mathematical abilities. •MRI study of cortical plasticity during first years of formal math instruction.•Right superior parietal thickness change was related to visuospatial processing.•Right intraparietal sulcus folding plasticity was related to early arithmetic.•Left occipital, and right fronto-temporal regions showed further associations.•Results link cortical plasticity to basic math learning.
Predicting early signs of dyslexia at a preliterate age by combining behavioral assessment with structural MRI
Recent studies suggest that neurobiological anomalies are already detectable in pre-school children with a family history of developmental dyslexia (DD). However, there is a lack of longitudinal studies showing a direct link between those differences at a preliterate age and the subsequent literacy difficulties seen in school. It is also not clear whether the prediction of DD in pre-school children can be significantly improved when considering neurobiological predictors, compared to models based on behavioral literacy precursors only. We recruited 53 pre-reading children either with (N=25) or without a family risk of DD (N=28). Quantitative T1 MNI data and literacy precursor abilities were assessed at kindergarten age. A subsample of 35 children was tested for literacy skills either one or two years later, that is, either in first or second grade. The group comparison of quantitative T1 measures revealed significantly higher T1 intensities in the left anterior arcuate fascicle (AF), suggesting reduced myelin concentration in preliterate children at risk of DD. A logistic regression showed that DD can be predicted significantly better (p=.024) when neuroanatomical differences between groups are used as predictors (80%) compared to a model based on behavioral predictors only (63%). The Wald statistic confirmed that the T1 intensity of the left AF is a statistically significant predictor of DD (p<.05). Our longitudinal results provide evidence for the hypothesis that neuroanatomical anomalies in children with a family risk of DD are related to subsequent problems in acquiring literacy. Particularly, solid white matter organization in the left anterior arcuate fascicle seems to play a pivotal role.
Genetic dyslexia risk variant is related to neural connectivity patterns underlying phonological awareness in children
Phonological awareness is the best-validated predictor of reading and spelling skill and therefore highly relevant for developmental dyslexia. Prior imaging genetics studies link several dyslexia risk genes to either brain-functional or brain-structural factors of phonological deficits. However, coherent evidence for genetic associations with both functional and structural neural phenotypes underlying variation in phonological awareness has not yet been provided. Here we demonstrate that rs11100040, a reported modifier of SLC2A3, is related to the functional connectivity of left fronto-temporal phonological processing areas at resting state in a sample of 9- to 12-year-old children. Furthermore, we provide evidence that rs11100040 is related to the fractional anisotropy of the arcuate fasciculus, which forms the structural connection between these areas. This structural connectivity phenotype is associated with phonological awareness, which is in turn associated with the individual retrospective risk scores in an early dyslexia screening as well as to spelling. These results suggest a link between a dyslexia risk genotype and a functional as well as a structural neural phenotype, which is associated with a phonological awareness phenotype. The present study goes beyond previous work by integrating genetic, brain-functional and brain-structural aspects of phonological awareness within a single approach. These combined findings might be another step towards a multimodal biomarker for developmental dyslexia. •rs11100040 is related to fronto-temporal functional connectivity at resting state.•rs11100040 is related to the fractional anisotropy of the arcuate fasciculus.•FA of the arcuate fasciculus is related to phonological awareness.