Compensation of Beer-Lambert attenuation using non-diffracting Bessel beams

We report on a versatile method to compensate the linear attenuation in a medium, independently of its microscopic origin. The method exploits diffraction-limited Bessel beams and tailored on-axis intensity profiles which are generated using a phase-only spatial light modulator. This technique for compensating one of the most fundamental limiting processes in linear optics is shown to be efficient for a wide range of experimental conditions (modifying the refractive index and the attenuation coefficient). Finally, we explain how this method can be advantageously exploited in applications ranging from bio-imaging light sheet microscopy to quantum memories for future quantum communication networks

Computational convergence of the path integral for real dendritic morphologies

Neurons are characterised by a morphological structure unique amongst biological cells, the core of which is the dendritic tree. The vast number of dendritic geometries, combined with heterogeneous properties of the cell membrane, continue to challenge scientists in predicting neuronal input-output relationships, even in the case of sub-threshold dendritic currents. The Green’s function obtained for a given dendritic geometry provides this functional relationship for passive or quasi-active dendrites and can be constructed by a sum-over-trips approach based on a path integral formalism. In this paper, we introduce a number of efficient algorithms for realisation of the sum-over-trips framework and investigate the convergence of these algorithms on different dendritic geometries. We demonstrate that the convergence of the trip sampling methods strongly depends on dendritic morphology as well as the biophysical properties of the cell membrane. For real morphologies, the number of trips to guarantee a small convergence error might become very large and strongly affect computational efficiency. As an alternative, we introduce a highly-efficient matrix method which can be applied to arbitrary branching structures

Indexing philosophy – in a fair and inclusive key

Existing indexing systems used to arrange philosophical works have been shown to misrepresent the discipline in ways that reflect and perpetuate exclusionary attitudes within it. In recent years, there has been a great deal of effort to challenge those attitudes and to revise them. But as the discipline moves toward greater equality and inclusivity, the way it has indexed its work has unfortunately not. To course correct, we identify in this article some of the specific changes that are needed within current indexing systems and propose a new model that could embody them. We use the Diversity Reading List in Philosophy as a case study and PhilPapers as a basis for comparison. The model we propose not only represents the discipline in a more inclusive and fair way, but it is also efficient, easy to use or implement, and adaptable for a variety of contexts.Publisher PDFPeer reviewe

Why do religious cultures evolve slowly? The cultural evolution of cooperative calling and the historical study of religions

Collective representations are the result of an immense cooperation, which stretches out not only into space but into time as well; to make them, a multitude of minds have associated, united and combined their ideas and sentiments: for them, long generations have accumulated their experience and their knowledge. A special intellectual activity is therefore concentrated in them, which is infinitely richer and complexer than that of the individual. (Émile Durkheim, Elementary Forms of the Religious Life, [1912] 1965: 29)The languages and folkways of ancient peoples hold little relevance for us, except in one respect: the religions of the ancient world remain our religions. Though religions change, core features of the scriptures and rituals of the world's most popular religious traditions appear to have been conserved with remarkably high fidelity. We explain slow religious change from how religion facilitates cooperation at large social scales. At the end, we clarify how historians of religion, in collaboration with psychologists and computational biologists, might test and improve explanations such as ours.This research was supported by the John F. Templeton Foundation (Testing the Functional Roles of Religion in Human Society, no. 28745), the Royal Society of New Zealand ("e Cultural Evolution of Religion, no. 11-UOA-23

Augment to Interpret: Unsupervised and Inherently Interpretable Graph Embeddings

Unsupervised learning allows us to leverage unlabelled data, which has become abundantly available, and to create embeddings that are usable on a variety of downstream tasks. However, the typical lack of interpretability of unsupervised representation learning has become a limiting factor with regard to recent transparent-AI regulations. In this paper, we study graph representation learning and we show that data augmentation that preserves semantics can be learned and used to produce interpretations. Our framework, which we named INGENIOUS, creates inherently interpretable embeddings and eliminates the need for costly additional post-hoc analysis. We also introduce additional metrics addressing the lack of formalism and metrics in the understudied area of unsupervised-representation learning interpretability. Our results are supported by an experimental study applied to both graph-level and node-level tasks and show that interpretable embeddings provide state-of-the-art performance on subsequent downstream tasks

Population structure and cultural geography of a folktale in Europe.

Despite a burgeoning science of cultural evolution, relatively little work has focused on the population structure of human cultural variation. By contrast, studies in human population genetics use a suite of tools to quantify and analyse spatial and temporal patterns of genetic variation within and between populations. Human genetic diversity can be explained largely as a result of migration and drift giving rise to gradual genetic clines, together with some discontinuities arising from geographical and cultural barriers to gene flow. Here, we adapt theory and methods from population genetics to quantify the influence of geography and ethnolinguistic boundaries on the distribution of 700 variants of a folktale in 31 European ethnolinguistic populations. We find that geographical distance and ethnolinguistic affiliation exert significant independent effects on folktale diversity and that variation between populations supports a clustering concordant with European geography. This pattern of geographical clines and clusters parallels the pattern of human genetic diversity in Europe, although the effects of geographical distance and ethnolinguistic boundaries are stronger for folktales than genes. Our findings highlight the importance of geography and population boundaries in models of human cultural variation and point to key similarities and differences between evolutionary processes operating on human genes and culture

Impact of deposit recoat cycle length on hot corrosion of CMSX-4

Hot corrosion causes significant problems for both aerospace and power generation industries, where the combination of high temperature, corrosive gases, and contaminants severely limits component operating lifetimes in gas turbine hot gas streams. Multiple laboratory testing methodologies exist to study this hot corrosion, and these can be affected by a range of variables. This paper investigated the impact of varying deposit recoat cycle length when using the ‘deposit recoat’ testing method. CMSX-4 samples were exposed to simulated type II (pitting) hot corrosion conditions, with the same overall deposit load (averaged across the total exposure run), but different deposit recoat cycles. Post-exposure, samples underwent dimensional metrology analysis to compare metal loss resulting from different deposit recoat cycle lengths. Results for CMSX-4 suggest very small differences in corrosion losses, indicating CMSX-4 hot corrosion datasets obtained from deposit recoat experiments with different deposit recoat cycle lengths can be compared with confidence

A diffusion model in velocity space to describe the electron dynamics in an ECR plasma thruster with magnetic nozzle

International audienceA quasi-linear heating model for an electron cyclotron resonance acceleration (ECR) thruster is presented. It consists of a Fokker-Planck equation in perpendicular velocity, with a loss term accounting for the deconfinement of electrons from the magnetic field. It is a global model in space that calculates an electron perpendicular velocity distribution function resulting from several passes through the electron cyclotron resonance region. The results are interpreted to provide an estimate of the plasma flow in the jet as well as the accelerating potential. A simple parametric study is presented as well as a preliminary comparison with experimental data