4,573 research outputs found
New obstructions to symplectic embeddings
In this paper we establish new restrictions on symplectic embeddings of
certain convex domains into symplectic vector spaces. These restrictions are
stronger than those implied by the Ekeland-Hofer capacities. By refining an
embedding technique due to Guth, we also show that they are sharp.Comment: 80 pages, 3 figures, v2: improved exposition and minor corrections,
v3: Final version, expanded and improved exposition and minor corrections.
The final publication is available at link.springer.co
Leaf-wise intersections and Rabinowitz Floer homology
In this article we explain how critical points of a particular perturbation
of the Rabinowitz action functional give rise to leaf-wise intersection points
in hypersurfaces of restricted contact type. This is used to derive existence
and multiplicity results for leaf-wise intersection points in hypersurfaces of
restricted contact type in general exact symplectic manifolds. The notion of
leaf-wise intersection points was introduced by Moser.Comment: 18 pages, 1 figure; v3: completely rewritten, improved result
Causation, Measurement Relevance and No-conspiracy in EPR
In this paper I assess the adequacy of no-conspiracy conditions employed in
the usual derivations of the Bell inequality in the context of EPR
correlations. First, I look at the EPR correlations from a purely
phenomenological point of view and claim that common cause explanations of
these cannot be ruled out. I argue that an appropriate common cause explanation
requires that no-conspiracy conditions are re-interpreted as mere common
cause-measurement independence conditions. In the right circumstances then,
violations of measurement independence need not entail any kind of conspiracy
(nor backwards in time causation). To the contrary, if measurement operations
in the EPR context are taken to be causally relevant in a specific way to the
experiment outcomes, their explicit causal role provides the grounds for a
common cause explanation of the corresponding correlations.Comment: 20 pages, 1 figur
High-resolution remote thermography using luminescent low-dimensional tin-halide perovskites
While metal-halide perovskites have recently revolutionized research in
optoelectronics through a unique combination of performance and synthetic
simplicity, their low-dimensional counterparts can further expand the field
with hitherto unknown and practically useful optical functionalities. In this
context, we present the strong temperature dependence of the photoluminescence
(PL) lifetime of low-dimensional, perovskite-like tin-halides, and apply this
property to thermal imaging with a high precision of 0.05 {\deg}C. The PL
lifetimes are governed by the heat-assisted de-trapping of self-trapped
excitons, and their values can be varied over several orders of magnitude by
adjusting the temperature (up to 20 ns {\deg}C-1). Typically, this sensitive
range spans up to one hundred centigrade, and it is both compound-specific and
shown to be compositionally and structurally tunable from -100 to 110 {\deg} C
going from [C(NH2)3]2SnBr4 to Cs4SnBr6 and (C4N2H14I)4SnI6. Finally, through
the innovative implementation of cost-effective hardware for fluorescence
lifetime imaging (FLI), based on time-of-flight (ToF) technology, these novel
thermoluminophores have been used to record thermographic videos with high
spatial and thermal resolution.Comment: 25 pages, 4 figure
Identification of antischistosomal leads by evaluating peroxides of beta-dicarbonyl compounds and their heteroanalogs : bridged 1,2,4,5-tetraoxanes and alphaperoxides, and beta,delta-triketones: tricyclic monoperoxides
Although antischistosomal properties of peroxides were studied in recent years, systematic structure-activity relationships have not been conducted. We evaluated the antischistosomal potential of 64 peroxides belonging to bridged 1,2,4,5-tetraoxanes, alphaperoxides and beta,delta-triketones. Thirty-nine compounds presented IC50 values > 15 microM on newly transformed schistosomula. Active drugs featured phenyl-, adamantane- or alkyl residues at the methylene bridge. Lower susceptibility was documented on adult schistosomes, with most hit compounds being tricyclic monoperoxides (IC50: 7.7-13.4 microM). A bridged 1,2,4,5-tetraoxane characterized by an adamantane residue showed the highest activity (IC50: 0.3 microM) on adult Schistosoma mansoni. Studies with hemin and heme supplemented medium indicated that antischistosomal activation of peroxides is not necessarily triggered by iron porphyrins. Two compounds (tricyclic monoperoxide; bridged 1,2,4,5-tetraoxane) revealed high worm burden reductions in the chronic (WBR: 75.4-82.8 %) but only moderate activity in the juvenile (WBR:18.9-43.1%) S. mansoni mouse model. Our results might serve as starting point for the preparation and evaluation of related derivative
Social labs as good practice for transdisciplinary engagement processes in research and innovation
This article discusses a ‘Social Lab process’ applied in the field of research and innovation as good practice for transdisciplinary processes, and elaborates upon the structure and dynamics of these processes. It sheds light on how engagement processes could be set up for a more inclusive and participant-friendly atmosphere, allowing for meaningful and sustainable outcomes. Supported by data from a qualitative analysis of 19 Social Lab experiences according to the thematic programmes of the European Commission Horizon 2020 research framework programme, this article outlines requirements that need to be taken into account when implementing a transdisciplinary process in a Social Lab. Based on the concept of transdisciplinary research and the experience of this one-and-a-half-year process, the elements of participatory approaches required for successful implementation of a Social Lab, starting with inviting participants to develop small implementation projects (pilot activities) are described. The qualitative analysis of the process documentations highlights the importance of a clear definition of the framework and purpose of the process. Concrete assignments of the lab teams and roles, and the implementation of pilot activities, further proved crucial for successful and sustainable results. On this basis, recommendations for a fruitful participatory process are formulated
Chemical ordering and composition fluctuations at the (001) surface of the Fe-Ni Invar alloy
We report on a study of (001) oriented fcc Fe-Ni alloy surfaces which
combines first-principles calculations and low-temperature STM experiments.
Density functional theory calculations show that Fe-Ni alloy surfaces are
buckled with the Fe atoms slightly shifted outwards and the Ni atoms inwards.
This is consistent with the observation that the atoms in the surface layer can
be chemically distinguished in the STM image: brighter spots (corrugation
maxima with increased apparent height) indicate iron atoms, darker ones nickel
atoms. This chemical contrast reveals a c2x2 chemical order (50% Fe) with
frequent Fe-rich defects on Invar alloy surface. The calculations also indicate
that subsurface composition fluctuations may additionally modulate the apparent
height of the surface atoms. The STM images show that this effect is pronounced
compared to the surfaces of other disordered alloys, which suggests that some
chemical order and corresponding concentration fluctuations exist also in the
subsurface layers of Invar alloy. In addition, detailed electronic structure
calculations allow us to identify the nature of a distinct peak below the Fermi
level observed in the tunneling spectra. This peak corresponds to a surface
resonance band which is particularly pronounced in iron-rich surface regions
and provides a second type of chemical contrast with less spatial resolution
but one that is essentially independent of the subsurface composition.Comment: 7 pages, 5 figure
Visual intracortical and transthalamic pathways carry distinct information to cortical areas.
Sensory processing involves information flow between neocortical areas, assumed to rely on direct intracortical projections. However, cortical areas may also communicate indirectly via higher-order nuclei in the thalamus, such as the pulvinar or lateral posterior nucleus (LP) in the visual system of rodents. The fine-scale organization and function of these cortico-thalamo-cortical pathways remains unclear. We find that responses of mouse LP neurons projecting to higher visual areas likely derive from feedforward input from primary visual cortex (V1) combined with information from many cortical and subcortical areas, including superior colliculus. Signals from LP projections to different higher visual areas are tuned to specific features of visual stimuli and their locomotor context, distinct from the signals carried by direct intracortical projections from V1. Thus, visual transthalamic pathways are functionally specific to their cortical target, different from feedforward cortical pathways, and combine information from multiple brain regions, linking sensory signals with behavioral context
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