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Drawing on the role of teachers for peer ecologies, we investigated whether students favored ethnically homogenous over ethnically diverse relationships, depending on classroom diversity and perceived teacher care. We specifically studied students’ intra- and interethnic relationships in classrooms with different ethnic compositions, accounting for homogeneous subgroups forming on the basis of ethnicity and gender diversity (i.e., ethnic-demographic faultlines). Based on multilevel social network analyses of dyadic networks between 1299 early adolescents in 70 German fourth grade classrooms, the results indicated strong ethnic homophily, particularly driven by German students who favored ethnically homogenous dyads over mixed dyads. As anticipated, the results showed that there was more in-group bias if perceived teacher care was low rather than high. Moreover, stronger faultlines were associated with stronger in-group bias; however, this relation was moderated by teacher care: If students perceived high teacher care, they showed a higher preference for mixed-ethnic dyads, even in classrooms with strong faultlines. These findings highlight the central role of teachers as agents of positive diversity management and the need to consider contextual classroom factors other than ethnic diversity when investigating intergroup relations in schools.
Current theories of schizophrenia suggest that the pathophysiology of the disorder may be the result of a deficit in the coordination of neural activity within and between areas of the brain, which may lead to impairments in basic cognitive functions such as contextual disambiguation and dynamic grouping (Phillips and Silverstein, 2003). This notion has been supported by recent studies showing that patients with schizophrenia are characterized by reduced synchronous, oscillatory activity in the gamma-frequency band during sensory processing (Spencer et al. 2003, Green et al. 2003, Wynn et al. 2005). However, it is currently unclear to what extent high-frequency gamma-band oscillations (> 60 Hz) contribute to impaired neural synchronization as research has so far focussed on gamma-band oscillations between 30 and 60 Hz. In addition, it is not known whether deficits in high-frequency oscillations are already present at the onset of the disorder and to what extent reductions may be related to the confounding influence of antipsychotic medication. Finally, the neural generators underlying impairments in synchronous oscillatory activity in schizophrenia have not been investigated yet. To address these questions, we recorded MEG activity during a visual closure task (Mooney faces task) in medicated chronic schizophrenia patients, drug-naive first-episode schizophrenia patients and healthy controls. MEG data were analysed for spectral power between 25 and 150 Hz, and beamforming techniques were used to localize the sources of oscillatory gamma-band activity. In healthy controls, we observed that the processing of Mooney faces was associated with sustained high-frequency gamma-band activity (> 60 Hz). A time-resolved analysis of the neural generators underlying perceptual closure revealed a network of distributed sources in occipito-temporal, parietal and frontal regions, which were differentially activated during specific time intervals. In chronic schizophrenia patients, we found a pronounced reduction of high-frequency gamma-band oscillatory activity that was accompanied by an impairment in perceptual organization and involved reduced source power in various brain regions associated with perceptual closure. First-episode patients were also characterized by a deficit in high-frequency gamma-band activity and reductions of source power in multiple areas; these impairments, however, were less pronounced than in chronic patients. Regarding behavioral performance, first-episode patients were not impaired in their ability to detect Mooney faces, but exhibited a loss in specificity of face detection. In conclusion, our results suggest that schizophrenia is associated with a widespread reduction in high-frequency oscillations that indicate local network abnormalities. These dysfunctions are independent of medication status and already present at illness onset, suggesting a possible progressive deficit during the course of the disorder.
Current theories of the pathophysiology of schizophrenia have focused on abnormal temporal coordination of neural activity. Oscillations in the gamma-band range (>25 Hz) are of particular interest as they establish synchronization with great precision in local cortical networks. However, the contribution of high gamma (>60 Hz) oscillations toward the pathophysiology is less established. To address this issue, we recorded magnetoencephalographic (MEG) data from 16 medicated patients with chronic schizophrenia and 16 controls during the perception of Mooney faces. MEG data were analysed in the 25–150 Hz frequency range. Patients showed elevated reaction times and reduced detection rates during the perception of upright Mooney faces while responses to inverted stimuli were intact. Impaired processing of Mooney faces in schizophrenia patients was accompanied by a pronounced reduction in spectral power between 60–120 Hz (effect size: d = 1.26) which was correlated with disorganized symptoms (r = −0.72). Our findings demonstrate that deficits in high gamma-band oscillations as measured by MEG are a sensitive marker for aberrant cortical functioning in schizophrenia, suggesting an important aspect of the pathophysiology of the disorder.
We present a new experimental dataset on the impact of the heavy halogens chlorine, bromine and iodine on the Raman water bands concerning pressure and their concentration at room temperature. These experiments were conducted at ambient temperature, with variations in halogen concentration and pressure ranging from 0 to 1.4 GPa.
The strength of the Raman water band shift change increases with the ionic size from chlorine, over bromine, to iodine. Our experiments further demonstrate that increased pressure diminishes the impact of the halogen shift change to a varying extent for each of the three halogens. This finding can have significant implications for the salinity calculation of fluid inclusions in minerals such as quartz or olivine. Particularly in the low salinity range, the concentration can be markedly underestimated if the pressure effect is neglected. For experiments in diamond anvil cells involving halogens dissolved in water, the change in Raman water band shifts can serve either as a new tool to monitor pressure, or to monitor the salinity.
Highlights
• We find DBrfluid/melt = 1.19 to 3.92 for experimental Br degassing from basalt magma into aqueous fluids.
• D <1 under almost dry conditions propose only little Br degassing for dry intra-plate volcanism relative to volcanic arcs.
• An annual global Br flux of 23.5–72.9 × 109 g/y into the atmosphere was calculated.
Abstract
We present the first in-situ partitioning data for bromine between a natural basaltic melt and a coexisting fluid. For this study hydrothermal diamond anvil cell experiments at pressures up to 1.7 GPa were conducted. We combined laser heating to melt the basalt glass with external heating to lower the temperature gradient in the cell and to initiate circulation for the aqueous fluid. Bromine concentrations were measured in-situ with X-ray fluorescence in the basaltic melts, glasses, and in the fluid. From the results we calculated partition coefficients of DBrfluid/melt = 1.19 to 3.92 in the range of 0.4 to 1 GPa for aqueous fluids. Experiments with neon as the surrounding fluid (DBrfluid/melt = 0.38 ± 0.01 at 1.1 GPa) suggest that Br-release from a basalt into volatiles that have no bonding affinity with Br is weak. This should be the case for dry intra-plate volcanic eruptions. From the experimentally gained partition coefficients and from global Br concentration values in melt inclusions of arc magmas, we calculated an annual global Br flux of 23.5–72.9 × 109 g/y.
Contemporary closed circuits – subversive dialogues : artistic strategies against surveillance
(2010)
In the past years surveillance, especially visual surveillance systems, have entered our cities and streets on a large scale. In my hometown Frankfurt/Main, the city centre and traffic-hubs have become zones under intensive surveillance. Over 120 cameras are installed at the central station, over 2,000 at the airport. In such highly surveilled places it is impossible to remain unobserved. The extent of surveillance in the United Kingdom and the USA offers a glance into the future. In these countries visual surveillance systems have spread into the farthest corners of cities and villages and into the privacy of their inhabitants.
This development calls for artistic endeavours which examine the phenomenon and raise people’s awareness of CCTV. Subversive strategies have to be developed which counter the inherent power relations of surveillance systems and foster self-confident, active behaviour towards the instruments of control.
The ongoing artistic project, Contemporary Closed Circuits – Subversive Dialogues, examines practices of contemporary visual surveillance. The works explore possibilities of interaction with and subversion of systems of observation. Most of the works were produced during the past three years as an artistic final thesis at Goethe University Frankfurt, Germany.
Innovative automated execution strategies like Algorithmic Trading gain significant market share on electronic market venues worldwide, although their impact on market outcome has not been investigated in depth yet. In order to assess the impact of such concepts, e.g. effects on the price formation or the volatility of prices, a simulation environment is presented that provides stylized implementations of algorithmic trading behavior and allows for modeling latency. As simulations allow for reproducing exactly the same basic situation, an assessment of the impact of algorithmic trading models can be conducted by comparing different simulation runs including and excluding a trader constituting an algorithmic trading model in its trading behavior. By this means the impact of Algorithmic Trading on different characteristics of market outcome can be assessed. The results indicate that large volumes to execute by the algorithmic trader have an increasing impact on market prices. On the other hand, lower latency appears to lower market volatility.
Social insects dominate arthropod communities worldwide due to cooperation and division of labor in their societies. This, however, makes them vulnerable to exploitation by social parasites, such as slave‐making ants. Slave‐making ant workers pillage brood from neighboring nests of related host ant species. After emergence, host workers take over all nonreproductive colony tasks, whereas slavemakers have lost the ability to care for themselves and their offspring. Here, we compared transcriptomes of different developmental stages (larvae, pupae, and adults), castes (queens and workers), and sexes of two related ant species, the slavemaker Temnothorax americanus and its host Temnothorax longispinosus. Our aim was to investigate commonalities and differences in group‐specific transcriptomes, whereupon across‐species differences possibly can be explained by their divergent lifestyles. Larvae and pupae showed the highest similarity between the two species and upregulated genes with enriched functions of translation and chitin metabolism, respectively. Workers commonly upregulated oxidation‐reduction genes, possibly indicative of their active lifestyle. Host workers, but not workers of the slavemaker, upregulated a “social behavior” gene. In slavemaker queens and workers, genes associated with the regulation of transposable elements were upregulated. Queens of both species showed transcriptomic signals of anti‐aging mechanisms, with hosts upregulating various DNA repair pathways and slavemaker queens investing in trehalose metabolism. The transcriptomes of males showed enriched functions for quite general terms realized in different genes and pathways in each species. In summary, the strong interspecific commonalities in larvae, pupae, and workers were reflected in the same enriched Gene Ontology (GO) terms. Less commonalities occurred in the transcriptomes of queens and males, which apparently utilize different pathways to achieve a long life and sperm production, respectively. We found that all analyzed groups in this study show characteristic GO terms, with similar patterns in both species.
The ability of endothelial cells to properly adapt to changes in a dynamic blood perfused environment is essential to maintain the physiological function of the vascular system and of the organs. Epigenetic control of gene expression is believed to be the mechanism controlling cell-fate determination and cell-phenotype maintenance. In the thesis, two JmjC demethylases were screened for their function in endothelial biology. Both of them were proved to play a central role in angiogenesis.
The histone 3 lysine 4 demethylase JARID1B was identified as the most highly expressed demethylase in endothelial cell. Knockdown of JARID1B in human umbilical vein endothelial cells (HUVEC) attenuated cell migration, angiogenic sprouting and tube formation. Jarid1b null mice exhibited attenuated retinal angiogenesis and reduced endothelial sprout outgrowth from aortic segments. Microarray data identified that the antiangiogenic transcription factor HOXA5 was suppressed by JARID1B. Consistently, chromatin immunoprecipitation experiment revealed that JARID1B occupies and reduces the histone 3 lysine 4 methylation levels at the HOXA5 promoter, demonstrating a direct function of JARID1B in endothelial HOXA5 gene regulation. Hence, as a highly expressed JmjC protein in endothelial cells, JARID1B fundamentally maintains endothelial angiogenic phenotypes perhaps through suppression of HOXA5.
As second enzyme it was identified that the histone plant homeodomain finger protein 8 (PHF8) plays a role in endothelial angiogenic sprouting as well as tube formation and cell migration. Overexpression of PHF8 catalyzed the removal of methyl-groups from histone 3 lysine 9 (H3K9) and H4K20, whereas knockdown of the enzyme increased H3K9 methylation. Knockdown of PHF8 by RNAi also attenuated endothelial proliferation and survival. To characterize the underlying mechanism, E2F transcription factors were screened, which led to the identification of the gene repressor E2F4 to be controlled by PHF8. Importantly, PHF8 maintains E2F4, but not E2F1, expression in endothelial cells. Likewise, chromatin immunoprecipitation revealed that PHF8 reduces the H3K9me2 level at the E2F4 transcriptional start site, demonstrating a direct function of PHF8 in endothelial E2F4 gene regulation. Thus, it is proposed that PHF8 maintains endothelial function by controlling E2F4 expression. On the other hand, microarray and subsequent qPCR validation revealed that the expressions of small nuclear RNAs (snRNAs) were regulated by PHF8. Co-immunoprecipitation experiment demonstrated that PHF8 interacts with spliceosome related proteins SNRP70 and SRPK1 as well as snRNA. Indeed, PHF8 contributed to splicing: GLS and VEGF-A displayed alternative splicing in PHF8 depleted cells. In addition, c-FOS introns were showed to be retained after knockdown of PHF8 in endothelial cells. These results demonstrated that, by controlling angiogenic mRNA splicing, PHF8 could affect endothelial properties.
Collectively, the results uncover the important roles of JARID1B and PHF8 in endothelial cells in the control of angiogenesis. Changing histone modifiers appears as an attractive concept for pro- and antiangiogenic therapy. The present work adds JARID1B and PHF8 as novel potential targets to this emerging field.