2,959 research outputs found

    Active Brownian particles moving in a random Lorentz gas

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    Biological microswimmers often inhabit a porous or crowded environment such as soil. In order to understand how such a complex environment influences their spreading, we numerically study non-interacting active Brownian particles (ABPs) in a two-dimensional random Lorentz gas. Close to the percolation transition in the Lorentz gas, they perform the same subdiffusive motion as ballistic and diffusive particles. However, due to their persistent motion they reach their long-time dynamics faster than passive particles and also show superdiffusive motion at intermediate times. While above the critical obstacle density ηcthe ABPs are trapped, their long-time diffusion belowηcis strongly influenced by the propulsion speed v0. With increasing v0, ABPs are stuck at the obstacles for longer times. Thus, for large propulsion speed, the long-time diffusion constant decreases more strongly in a denser obstacle environment than for passive particles. This agrees with the behavior of an effective swimming velocity and persistence time, which we extract from the velocity autocorrelation function

    How Novices and Experts Understand Hierarchies in Business Process Modeling

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    Conceptual models are essential for successful IT implementation, as they concisely represent the system\u27s component structures, behavior, and relationships. However, for conceptual models to fully realize their potential, they must be understood. To this end, hierarchy has been employed in business process modeling to enhance understanding of complex models. Prior research has proposed a two-component framework to explain the effects of hierarchy on understanding. Drawing on empirical data, this work extends this framework by investigating the influence of expertise on the understanding of hierarchical business process models. Our findings indicate that experts and novices benefit from hiding task-irrelevant information in subprocesses, with experts benefiting significantly more than novices. Additionally, experts profit more from recognizing familiar patterns in subprocesses than novices. Based on our results, we propose two principles for designing hierarchy and suggest future research avenues. Keywords: Business Process Modeling, Hierarchy, Expertise, Information Hiding

    Historical Reindeer Corrals as Portraits of Human-Nature Relationships in Northern Finland

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    Reindeer herding has been practised in northern boreal and subarctic regions of Fennoscandia for several centuries. The gathering and separation of reindeer for slaughter and calf marking are significant and cyclical activities of reindeer herding that are commonly carried out in reindeer corrals composed of circular-shaped fences of wood or stone construction leading into the corral. Using archaeological databases, we mapped historical reindeer corrals in northern Finland dating from the late 1800s to the 1960s for the entire reindeer herding area and characterized the legacies of their past use on present-day vegetation in Peräpohjola. In total, 94 corrals were located. Reindeer separations created a niche for novel plant communities with increasing graminoids in relation to dwarf shrubs and formation of a dense birch grove. Corrals have also preserved old rare trees left standing inside the corral to provide shelter for reindeer. The positioning of the corrals in the landscape was usually planned in a way that utilized man-made constructions and natural barriers, such as peatlands, and the typical behaviour of the reindeer in combination with both. When the wooden constructions had collapsed and decomposed, only the different vegetation indicates their past existence. L’élevage des rennes est pratiqué dans les régions boréales et subarctiques nordiques de la Fennoscandie depuis des siècles. Le rassemblement et la séparation des rennes à des fins d’abattage et de marquage des veaux sont d’importantes activités cycliques de l’élevage des rennes. Elles s’effectuent généralement dans des enclos à rennes composés de clôtures circulaires en bois ou de constructions en pierre menant aux enclos. À l’aide de bases de données archéologiques, nous avons dressé la carte historique des enclos à rennes du nord de la Finlande de la fin des années 1800 jusqu’aux années 1960 pour l’ensemble de la zone d’élevage des rennes, puis nous avons caractérisé l’héritage de leur utilisation antérieure sur la végétation actuelle de Peräpohjola. Nous avons localisé 94 enclos en tout. Les séparations employées pour les rennes ont donné lieu à la création d’un créneau favorable à l’établissement de nouvelles associations végétales contenant plus de graminiformes par rapport aux arbustes nains et à la formation de boulaies denses. Les enclos ont également permis de préserver d’anciens arbres rares qui sont restés à l’intérieur des enclos en guise d’abri pour les rennes. En général, l’emplacement des enclos était planifié de sorte à tirer parti des constructions artificielles et des obstacles naturels, comme les tourbières, et du comportement typique des rennes à l’égard de ces deux caractéristiques. Une fois les constructions en bois effondrées et décomposées, seule la végétation différente témoigne de leur existence.

    How to strengthen communities in times of crisis

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    Derepression of a Neuronal Inhibitor due to miRNA Dysregulation in a Schizophrenia-Related Microdeletion

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    Summary22q11.2 microdeletions result in specific cognitive deficits and schizophrenia. Analysis of Df(16)A+/− mice, which model this microdeletion, revealed abnormalities in the formation of neuronal dendrites and spines, as well as altered brain microRNAs. Here, we show a drastic reduction of miR-185, which resides within the 22q11.2 locus, to levels more than expected by a hemizygous deletion, and we demonstrate that this reduction alters dendritic and spine development. miR-185 represses, through an evolutionarily conserved target site, a previously unknown inhibitor of these processes that resides in the Golgi apparatus and shows higher prenatal brain expression. Sustained derepression of this inhibitor after birth represents the most robust transcriptional disturbance in the brains of Df(16)A+/− mice and results in structural alterations in the hippocampus. Reduction of miR-185 also has milder age- and region-specific effects on the expression of some Golgi-related genes. Our findings illuminate the contribution of microRNAs in psychiatric disorders and cognitive dysfunction

    Ionisation and discharge in cloud-forming atmospheres of brown dwarfs and extrasolar planets

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    The authors highlight financial support of the European Community under the FP7 by the ERC starting grant 257431.Brown dwarfs and giant gas extrasolar planets have cold atmospheres with a rich chemical compositions from which mineral cloud particles form. Their properties, like particle sizes and material composition, vary with height, and the mineral cloud particles are charged due to triboelectric processes in such dynamic atmospheres. The dynamics of the atmospheric gas is driven by the irradiating host star and/or by the rotation of the objects that changes during its lifetime. Thermal gas ionisation in these ultra-cool but dense atmospheres allows electrostatic interactions and magnetic coupling of a substantial atmosphere volume. Combined with a strong magnetic field ≫ BEarth, a chromosphere and aurorae might form as suggested by radio and X-ray observations of brown dwarfs. Non-equilibrium processes like cosmic ray ionisation and discharge processes in clouds will increase the local pool of free electrons in the gas. Cosmic rays and lighting discharges also alter the composition of the local atmospheric gas such that tracer molecules might be identified. Cosmic rays affect the atmosphere through air showers which was modelled with a 3D Monte Carlo radiative transfer code to be able to visualise their spacial extent. Given a certain degree of thermal ionisation of the atmospheric gas, we suggest that electron attachment to charge mineral cloud particles is too inefficient to cause an electrostatic disruption of the cloud particles. Cloud particles will therefore not be destroyed by Coulomb explosion for the local temperature in the collisional dominated brown dwarf and giant gas planet atmospheres. However, the cloud particles are destroyed electrostatically in regions with strong gas ionisation. The potential size of such cloud holes would, however, be too small and might occur too far inside the cloud to mimic the effect of, e.g., magnetic field induced star spots.PostprintPeer reviewe

    Receptor tyrosine kinase profiling of ischemic heart identifies ROR1 as a potential therapeutic target

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    BackgroundReceptor tyrosine kinases (RTK) are potential targets for the treatment of ischemic heart disease. The human RTK family consists of 55 members, most of which have not yet been characterized for expression or activity in the ischemic heart.MethodsRTK gene expression was analyzed from human heart samples representing healthy tissue, acute myocardial infarction or ischemic cardiomyopathy. As an experimental model, pig heart with ischemia-reperfusion injury, caused by cardiopulmonary bypass,was used, from which phosphorylation status of RTKs was assessed with a phospho-RTK array. Expression and function of one RTK, ROR1, was further validated in pig tissue samples, and in HL-1 cardiomyocytes and H9c2 cardiomyoblasts, exposed to hypoxia and reoxygenation. ROR1 protein level was analyzed by Western blotting. Cell viability after ROR1 siRNA knockdown or activation with Wnt-5a ligand was assessed by MTT assays.ResultsIn addition to previously characterized RTKs, a group of novel active and regulated RTKs was detected in the ischemic heart. ROR1 was the most significantly upregulated RTK in human ischemic cardiomyopathy. However, ROR1 phosphorylation was suppressed in the pig model of ischemia-reperfusion and ROR1 phosphorylation and expression were down-regulated in HL-1 cardiomyocytes subjected to short-term hypoxia in vitro. ROR1 expression in the pig heart was confirmed on protein and mRNA level. Functionally, ROR1 activity was associated with reduced viability of HL-1 cardiomyocytes in both normoxia and during hypoxia-reoxygenation.ConclusionsSeveral novel RTKs were found to be regulated in expression or activity in ischemic heart. ROR1 was one of the most significantly regulated RTKs. The in vitro findings suggest a role for ROR1 as a potential target for the treatment of ischemic heart injury.Peer reviewe

    Caesarean Section in the World: a new ecological approach

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    Introduction. This study aimed to estimate the most recent caesarean section rates in the world and examine the association between these rates and old and new indicators of health care. Methods. Authors analyzed the Caesarean Section (CS) rates, also in geo-economic and economic groups, and correlated them to maternal and neonatal mortality, to births attended by skilled health personnel and to births among adolescents. Analysis of covariance and piecewise regressions were used for the statistical analysis. Results. In 47.2% of the countries, the CS rate exceeded 15%. Countries of Latin America and the Caribbean along with Europe, North America and Oceania had the highest values. The analysis showed an inverse association between CS rates and Maternal Mortality (MMR) and Neonatal Mortality (NMR) for all geographical areas except for Europe. The greatest association was observed in lower-middle-income countries. In developing countries only 50% of cases, occur in medical facilities and only half of these are seen by medical, nursing and obstetrical staff. Age of the mother appears to influence the outcome and choice of delivery type. Countries where an high ABR rate is present have low CS use. Conclusions. To best evaluate the consequences of the increasing rate of CS, it would be useful to identify the most sensitive outcome indicators
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