Permutonestohedra

There are several real spherical models associated with a root arrangement, depending on the choice of a building set. The connected components of these models are manifolds with corners which can be glued together to obtain the corresponding real De Concini–Procesi models. In this paper, starting from any root system with finite Coxeter group W and any W -invariant building set, we describe an explicit realization of the real spherical model as a union of polytopes (nestohedra) that lie inside the chambers of the arrangement. The main point of this realization is that the convex hull of these nestohedra is a larger polytope, a permutonestohedron, equipped with an action of W or also, depending on the building set, of Aut ( ). The permutonestohedra are natural generalizations of Kapranov’s permutoassociahedra

A Grassmann algebra for matroids

We introduce an idempotent analogue of the exterior algebra for which the theory of tropical linear spaces (and valuated matroids) can be seen in close analogy with the classical Grassmann algebra formalism for linear spaces. The top wedge power of a tropical linear space is its Plucker vector, which we view as a tensor, and a tropical linear space is recovered from its Plucker vector as the kernel of the corresponding wedge multiplication map. We prove that an arbitrary d-tensor satisfies the tropical Plucker relations (valuated exchange axiom) if and only if the d-th wedge power of the kernel of wedge-multiplication is free of rank one. This provides a new cryptomorphism for valuated matroids, including ordinary matroids as a special case

Small-Group Learning in an Upper-Level University Biology Class Enhances Academic Performance and Student Attitudes Toward Group Work

To improve science learning, science educators' teaching tools need to address two major criteria: teaching practice should mirror our current understanding of the learning process; and science teaching should reflect scientific practice. We designed a small-group learning (SGL) model for a fourth year university neurobiology course using these criteria and studied student achievement and attitude in five course sections encompassing the transition from individual work-based to SGL course design. All students completed daily quizzes/assignments involving analysis of scientific data and the development of scientific models. Students in individual work-based (Individualistic) sections usually worked independently on these assignments, whereas SGL students completed assignments in permanent groups of six. SGL students had significantly higher final exam grades than Individualistic students. The transition to the SGL model was marked by a notable increase in 10th percentile exam grade (Individualistic: 47.5%; Initial SGL: 60%; Refined SGL: 65%), suggesting SGL enhanced achievement among the least prepared students. We also studied student achievement on paired quizzes: quizzes were first completed individually and submitted, and then completed as a group and submitted. The group quiz grade was higher than the individual quiz grade of the highest achiever in each group over the term. All students – even term high achievers –could benefit from the SGL environment. Additionally, entrance and exit surveys demonstrated student attitudes toward SGL were more positive at the end of the Refined SGL course. We assert that SGL is uniquely-positioned to promote effective learning in the science classroom

Legitimacy in the Multilevel European Polity

In order to be simultaneously effective and liberal, governments must normally be able to count on voluntary compliance – which, in turn, depends on the support of socially shared legitimacy beliefs. In Western constitutional democracies, such beliefs are derived from the distinct but coexistent traditions of “republican” and “liberal” political philosophy. When judged by these criteria, the European Union – if considered by itself – appears as a thoroughly liberal polity which, however, lacks all republican credentials. But this view (which seems to structure the debates about the “European democratic deficit”) ignores the multilevel nature of the European polity, where the compliance of citizens is requested, and needs to be legitimated by member states – whereas the Union appears as a “government of governments” which is entirely dependent on the voluntary compliance of its member states. What matters primarily, therefore, is the compliance-legitimacy relationship between the Union and its member states – which, however, is normatively constrained by the basic compliance-legitimacy relationship between member governments and their constituents. Given the high consensus requirements of European legislation, member governments could and should be able to assume political responsibility for European policies in which they had a voice, and to justify them in “communicative discourses” in the national public space. This is not necessarily true of “non-political” policy choices imposed by the European Court of Justice. By enforcing its “liberal” program of liberalization and deregulation, the ECJ may presently be undermining the “republican” bases of member-state legitimacy. Where this is the case, open non-compliance is a present danger, and political controls of judicial legislation may be called for.Um gleichzeitig effektiv und liberal sein zu können, ist staatliche Herrschaft auf freiwillige Folgebereitschaft angewiesen – die ihrerseits der Unterstützung durch sozial geteilte Legitimitätsüberzeugungen bedarf. In den demokratischen Verfassungsstaaten des Westens werden solche Überzeugungen aus den unterschiedlichen, aber komplementär zusammenwirkenden Traditionen der „republikanischen“ und der „liberalen“ politischen Philosophie hergeleitet. An diesen Kriterien gemessen erscheint die Europäische Union – wenn man sie für sich betrachtet – als eine „liberale“ politische Ordnung, der jedoch alle „republikanischen“ Legitimitätsmerkmale fehlen. Aber eine solche Sichtweise, die auch die derzeitige Diskussion über ein „europäisches Demokratiedefizit“ bestimmt, verkennt den Mehrebenencharakter des europäischen Gemeinwesens. In ihm sind es die Mitgliedstaaten, die Entscheidungen der Union gegenüber den eigenen Bürgern durchsetzen und auch legitimieren müssen, während es für die Union ihrerseits auf die freiwillige Folgebereitschaft ihrer Mitgliedstaaten ankommt. Dabei werden diese jedoch durch die normativen Grundlagen ihrer eigenen Legitimität begrenzt. Politische Entscheidungen auf europäischer Ebene setzen breiten Konsens voraus, und die Regierungen sollten sie deshalb auch gegenüber den eigenen Bürgern in „kommunikativen Diskursen“ vertreten und dafür die politische Verantwortung übernehmen können. Dies gilt jedoch nicht notwendigerweise auch für Entscheidungen der europäischen Politik, die im nichtpolitischen Modus ohne Beteiligung des Rates und des Parlaments vom Europäischen Gerichtshof bestimmt werden. Mit der gegenwärtigen Radikalisierung seines „liberalen“ Programms der Liberalisierung und Deregulierung des nationalen Rechts könnte der Gerichtshof in der Tat die „republikanischen“ Grundlagen der mitgliedstaatlichen Legitimität unterminieren. In diesem Falle könnte die Union sich nicht länger auf die Folgebereitschaft ihrer Mitgliedstaaten verlassen. Um diese Gefahr für die europäische Integration zu vermeiden, sollte eine stärkere politische Kontrolle der richterlichen Rechtsetzung erwogen werden.1 Legitimacy Republican and liberal legitimating discourses Constitutional democracies – and the EU? 2 Legitimacy in multilevel polities 3 Legitimating member state compliance Political modes of policy making Non-political policy making 4 The need for justification 5 The Court is pushing against the limits of justifiability 6 The liberal undermining of republican legitimacy 7 Needed: A political balance of community and autonomy Reference

The patterning toolbox FIB-o-mat: Exploiting the full potential of focused helium ions for nanofabrication

Focused beams of helium ions are a powerful tool for high-fidelity machining with spatial precision below 5 nm. Achieving such a high patterning precision over large areas and for different materials in a reproducible manner, however, is not trivial. Here, we introduce the Python toolbox FIB-o-mat for automated pattern creation and optimization, providing full flexibility to accomplish demanding patterning tasks. FIB-o-mat offers high-level pattern creation, enabling high-fidelity large-area patterning and systematic variations in geometry and raster settings. It also offers low-level beam path creation, providing full control over the beam movement and including sophisticated optimization tools. Three applications showcasing the potential of He ion beam nanofabrication for two-dimensional material systems and devices using FIB-o-mat are presented

Lesion-induced accumulation of platelets promotes survival of adult neural stem / progenitor cells.

The presence of neural stem/progenitor cells (NSPCs) in specific areas of the central nervous system (CNS) supports tissue maintenance as well as regeneration. The subependymal zone (SEZ), located at the lateral ventricle’s wall, represents a niche for NSPCs and in response to stroke or demyelination becomes activated with progenitors migrating towards the lesion and differentiating into neurons and glia. The mechanisms that underlie this phenomenon remain largely unknown. The vascular niche and in particular blood-derived elements such as platelets, has been shown to contribute to CNS regeneration in different pathological conditions. Indeed, intracerebroventricularly administrated platelet lysate (PL) stimulates angiogenesis, neurogenesis and neuroprotection in the damaged CNS. Here, we explored the presence of platelets in the activated SEZ after a focal demyelinating lesion in the corpus callosum of mice and we studied the effects of PL on proliferating SEZ-derived NSPCs in vitro. We showed that the lesion-induced increase in the size of the SEZ and in the number of proliferating SEZ-resident NSPCs correlates with the accumulation of platelets specifically along the activated SEZ vasculature. Expanding on this finding, we demonstrated that exposure of NSPCs to PL in vitro led to increased numbers of cells by enhanced cell survival and reduced apoptosis without differences in proliferation and in the differentiation potential of NSPCs. Finally, we demonstrate that the accumulation of platelets within the SEZ is spatially correlated with reduced numbers of apoptotic cells when compared to other periventricular areas. In conclusion, our results show that platelet-derived compounds specifically promote SEZ-derived NSPC survival and suggest that platelets might contribute to the enlargement of the pool of SEZ NSPCs that are available for CNS repair in response to injury

The patterning toolbox FIB o mat Exploiting the full potential of focused helium ions for nanofabrication

Focused beams of helium ions are a powerful tool for high fidelity machining with spatial precision below 5 nm. Achieving such a high patterning precision over large areas and for different materials in a reproducible manner, however, is not trivial. Here, we introduce the Python toolbox FIB o mat for automated pattern creation and optimization, providing full flexibility to accomplish demanding patterning tasks. FIB o mat offers high level pattern creation, enabling high fidelity large area patterning and systematic variations in geometry and raster settings. It also offers low level beam path creation, providing full control over the beam movement and including sophisticated optimization tools. Three applications showcasing the potential of He ion beam nanofabrication for two dimensional material systems and devices using FIB o mat are presente

Self Catalyzed Growth of Vertically Aligned InN Nanorods by Metal Organic Vapor Phase Epitaxy

Vertically aligned hexagonal InN nanorods were grown mask free by conventional metal amp; 8722;organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self catalytic vapor amp; 8722;liquid amp; 8722;solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usuallyinapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy dispersive X ray spectroscopy, X ray diffraction, X ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high efficiency hot carrier solar cell