4,701 research outputs found

    Economic principles of state aid control

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    This paper summarizes the economic principles of European state aid control. We start with a discussion of the economic justification for state aid control, including the definition of state aid in European law and exceptions to the general ban of state aid. We then explore the motives for granting state aid, ranging from the correction of market failures over political motives to political economy considerations. We then discuss how state aid control fits into the framework of European competition policy before we comment extensively on the more economic approach to state aid control, as implemented by the European Commission, and the state aid action plan. --

    Dynamic Coalition Formation and the Core

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    This paper presents a dynamic model of endogenous coalition formation in cooperative games with transferable utility. The players are boundedly rational. At each time step, a player decides which of the existing coalitions to join, and demands a payoff. These decisions are determined by a (non- cooperative) best-reply rule, given the coalition structure and allocation in the previous period. We show that absorbing states of the process exist if the game is essential. Further, if the players are allowed to experiment with myopically suboptimal strategies whenever there are potential gains from trade, an isomorphism between the set of absorbing states of the process and the set of core allocations can beestablished, and the process converges to one of these states with probability one whenever the core is non-empty. This result holds independently of the form of the characteristic function.TU Games; Coalition Formation; Bounded Rationality; Core

    Inter-firm R&D networks in the global pharmaceutical biotechnology industry during 1985 - 1998: A conceptual and empirical analysis

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    This paper analyses a large database on inter-firm R&D cooperation formed in the pharmaceutical biotechnology industry during the period 1985 - 1998. The results indicate that network size largely grows, whereas the density of the network declines during the periods. In the network analysis that emphasizes individual structural positions, the empirical results show that small biotechnological companies had a crucial bridging role for the large pharmaceutical firms in the second half of the 1980s. In the 1990s, the bridge role of biotechnology companies became less important and established pharmaceutical companies developed into dominant start players with many collaborators while holding central roles in the research network. The current analysis also shows that degree-based and betweenness-based network centralization are both low implying that the overall positional advantages are relatively equally distributed in the inter-firm R&D network of the pharmaceutical biotechnology industry. --R&D networks,pharmaceutical biotechnology,network analysis,conceptual centrality,network visualization software

    Metal-ion binding and metal-ion induced folding of the adenine-sensing riboswitch aptamer domain

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    Divalent cations are important in the folding and stabilization of complex RNA structures. The adenine-sensing riboswitch controls the expression of mRNAs for proteins involved in purine metabolism by directly sensing intracellular adenine levels. Adenine binds with high affinity and specificity to the ligand binding or aptamer domain of the adenine-sensing riboswitch. The X-ray structure of this domain in complex with adenine revealed an intricate RNA-fold consisting of a three-helix junction stabilized by long-range base-pairing interactions and identified five binding sites for hexahydrated Mg2+-ions. Furthermore, a role for Mg2+-ions in the ligand-induced folding of this RNA was suggested. Here, we describe the interaction of divalent cations with the RNA–adenine complex in solution as studied by high-resolution NMR spectroscopy. Paramagnetic line broadening, chemical shift mapping and intermolecular nuclear Overhauser effects (NOEs) indicate the presence of at least three binding sites for divalent cations. Two of them are similar to those in the X-ray structure. The third site, which is important for the folding of this RNA, has not been observed previously. The ligand-free state of the RNA is conformationally heterogeneous and contains base-pairing patterns detrimental to ligand binding in the absence of Mg2+, but becomes partially pre-organized for ligand binding in the presence of Mg2+. Compared to the highly similar guanine-sensing riboswitch, the folding pathway for the adenine-sensing riboswitch aptamer domain is more complex and the influence of Mg2+ is more pronounced

    From isomorphism to polymorphism: connecting interzeolite transformations to structural and graph similarity

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    Zeolites are nanoporous crystalline materials with abundant industrial applications. Despite sustained research, only 235 different zeolite frameworks have been realized out of millions of hypothetical ones predicted by computational enumeration. Structure-property relationships in zeolite synthesis are very complex and only marginally understood. Here, we apply structure and graph-based unsupervised machine learning to gain insight on zeolite frameworks and how they relate to experimentally observed polymorphism and phase transformations. We begin by describing zeolite structures using the Smooth Overlap of Atomic Positions method, which clusters crystals with similar cages and density in a way consistent with traditional hand-selected composite building units. To also account for topological differences, zeolite crystals are represented as multigraphs and compared by isomorphism tests. We find that fourteen different pairs and one trio of known frameworks are graph isomorphic. Based on experimental interzeolite conversions and occurrence of competing phases, we propose that the availability of kinetic-controlled transformations between metastable zeolite frameworks is related to their similarity in the graph space. When this description is applied to enumerated structures, over 3,400 hypothetical structures are found to be isomorphic to known frameworks, and thus might be realized from their experimental counterparts. Using a continuous similarity metric, the space of known zeolites shows additional overlaps with experimentally observed phase transformations. Hence, graph-based similarity approaches suggest a venue for realizing novel zeolites from existing ones by providing a relationship between pairwise structure similarity and experimental transformations.Comment: 11 pages, 6 figure

    Verification of Size Invariance in DNN Activations using Concept Embeddings

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    The benefits of deep neural networks (DNNs) have become of interest for safety critical applications like medical ones or automated driving. Here, however, quantitative insights into the DNN inner representations are mandatory. One approach to this is concept analysis, which aims to establish a mapping between the internal representation of a DNN and intuitive semantic concepts. Such can be sub-objects like human body parts that are valuable for validation of pedestrian detection. To our knowledge, concept analysis has not yet been applied to large object detectors, specifically not for sub-parts. Therefore, this work first suggests a substantially improved version of the Net2Vec approach (arXiv:1801.03454) for post-hoc segmentation of sub-objects. Its practical applicability is then demonstrated on a new concept dataset by two exemplary assessments of three standard networks, including the larger Mask R-CNN model (arXiv:1703.06870): (1) the consistency of body part similarity, and (2) the invariance of internal representations of body parts with respect to the size in pixels of the depicted person. The findings show that the representation of body parts is mostly size invariant, which may suggest an early intelligent fusion of information in different size categories.Comment: 12 pages, 7 figures; Camera-ready version for AIAI202

    Modulation of the stability of the Salmonella fourU-type RNA thermometer

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    RNA thermometers are translational control elements that regulate the expression of bacterial heat shock and virulence genes. They fold into complex secondary structures that block translation at low temperatures. A temperature increase releases the ribosome binding site and thus permits translation initiation. In fourU-type RNA thermometers, the AGGA sequence of the SD region is paired with four consecutive uridines. We investigated the melting points of the wild-type and mutant sequences. It was decreased by 5°C when a stabilizing GC basepair was exchanged by an AU pair or increased by 11°C when an internal AG mismatch was converted to a GC pair, respectively. Stabilized or destabilized RNA structures are directly correlated with decreased or increased in vivo gene expression, respectively. Mg2+ also affected the melting point of the fourU thermometer. Variations of the Mg2+ concentration in the physiological range between 1 and 2 mM translated into a 2.8°C shift of the melting point. Thus, Mg2+ binding to the hairpin RNA is regulatory relevant. Applying three different NMR techniques, two Mg2+ binding sites were found in the hairpin structure. One of these binding sites could be identified as outer sphere binding site that is located within the fourU motif. Binding of the two Mg2+ ions exhibits a positive cooperativity with a Hill coefficient of 1.47. Free energy values delta G for Mg2+ binding determined by NMR are in agreement with data determined from CD measurements. Physiological Mg2+ concentrations reduce enthalpy and entropy values of uncorrelated base pair opening processes for almost all nucleobases

    Lipid membrane instability and poration driven by capacitive charging

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    A new model for the interaction of an electric pulse with a lipid membrane is proposed. Using this model we show that when a DC electric pulse is applied to an insulating lipid membrane separating fluids with different conductivities, the capacitive charging current through the membrane drives electrohydrodynamic flow that destabilizes the membrane. The instability is transient and decays as the membrane charges. The bulk conductivity mismatch plays an essential role in this instability because it results in a different rate of charge accumulation on the membrane's physical surfaces. Shearing stresses created by the electric field acting on its own induced free charge are non-zero as long as the charge imbalance exists. Accordingly, the most unstable mode is related to the ratio of membrane charging time and the electrohydrodynamic time.Comment: 4 pages, 4 figure

    Henri Temianka Correspondence; (schwalbe)

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    https://digitalcommons.chapman.edu/temianka_correspondence/2796/thumbnail.jp
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