When the beachhopper looks at the moon: The moon compass hypothesis

The function of moon position for shoreline orientation by talitrids is investigated. Three major results were found: (1) Observed cases of compensation for changes in the direction of the moon are based on physiological rhythm with a period of about 25 hours which can persist for at least several days under constant conditions. (2) The zeitgeber for physiological rhythm may be either moonlight or some other factor associated with the tides. (3) If talitrids are long removed from environmental entrainment, either artifically or naturally, the internal rhythm no longer exerts an appreciable influence on the angle of lunar orientation; in such cases the system deteriorates into constant angle orientation, with an angle which is determined by the beach orgin, but may be modified by lighting conditions

Paradoxical monocular stereopsis and perspective vergence

The question of how to most effectively convey depth in a picture is a multifaceted problem, both because of potential limitations of the chosen medium (stereopsis, image motion), and because effectiveness can be defined in various ways. Practical applications usually focus on information transfer, i.e., effective techniques for evoking recognition of implied depth relationships, but this issue depends on subjective judgements which are difficult to scale when stimuli are above threshold. Two new approaches to this question are proposed here which are based on alternative criteria for effectiveness. Paradoxical monocular stereopsis is a remarkably compelling impression of depth which is evoked during one-eyed viewing of only certain illustrations; it can be unequivocally recognized because the feeling of depth collapses when one shifts to binocular viewing. An exploration of the stimulus properties which are effective for this phenomenon may contribute useful answers for the more general perceptual problem. Positive vergence is an eye-movement response associated with changes of fixation point within a picture which implies depth; it also arises only during monocular viewing. The response is directionally appropriate (i.e., apparently nearer objects evoke convergence, and vice versa), but the magnitude of the response can be altered consistently by making relatively minor changes in the illustration. The cross-subject agreement in changes of response magnitude would permit systematic exploration to determine which stimulus configurations are most effective in evoking perspective vergence, with quantitative answers based upon this involuntary reflex. It may well be that most effective pictures in this context will embody features which would increase effectiveness of pictures in a more general sense

Maps of random walks on complex networks reveal community structure

To comprehend the multipartite organization of large-scale biological and social systems, we introduce a new information theoretic approach that reveals community structure in weighted and directed networks. The method decomposes a network into modules by optimally compressing a description of information flows on the network. The result is a map that both simplifies and highlights the regularities in the structure and their relationships. We illustrate the method by making a map of scientific communication as captured in the citation patterns of more than 6000 journals. We discover a multicentric organization with fields that vary dramatically in size and degree of integration into the network of science. Along the backbone of the network -- including physics, chemistry, molecular biology, and medicine -- information flows bidirectionally, but the map reveals a directional pattern of citation from the applied fields to the basic sciences.Comment: 7 pages and 4 figures plus supporting material. For associated source code, see http://www.tp.umu.se/~rosvall

Restrictions of generalized Verma modules to symmetric pairs

We initiate a new line of investigation on branching problems for generalized Verma modules with respect to complex reductive symmetric pairs (g,k). Here we note that Verma modules of g may not contain any simple module when restricted to a reductive subalgebra k in general. In this article, using the geometry of K_C orbits on the generalized flag variety G_C/P_C, we give a necessary and sufficient condition on the triple (g,k, p) such that the restriction X|_k always contains simple k-modules for any g-module $X$ lying in the parabolic BGG category O^p attached to a parabolic subalgebra p of g. Formulas are derived for the Gelfand-Kirillov dimension of any simple k-module occurring in a simple generalized Verma module of g. We then prove that the restriction X|_k is multiplicity-free for any generic g-module X \in O if and only if (g,k) is isomorphic to a direct sum of (A_n,A_{n-1}), (B_n,D_n), or (D_{n+1},B_n). We also see that the restriction X|_k is multiplicity-free for any symmetric pair (g, k) and any parabolic subalgebra p with abelian nilradical and for any generic g-module X \in O^p. Explicit branching laws are also presented.Comment: 31 pages, To appear in Transformation Group

Perspectives of autistic adolescent girls and women on the determinants of their mental health and social and emotional well-being: A systematic review and thematic synthesis of lived experience

Autistic girls and women experience more mental health difficulties and poorer well-being than their non-autistic peers. Little emphasis has been placed on the perspectives of the girls and women within the literature. This review aims to provide an overview of the factors that impact autistic females’ emotional and social well-being and mental health, as described in self-report qualitative studies. The protocol for the present review was pre-registered on PROSPERO (CRD42020184983), and this article follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PsycInfo, Academic Search Complete and MEDLINE were systematically searched using a pre-defined search string. This yielded 877 unique records, which were systematically screened by two reviewers, resulting in 52 eligible studies. Structured data extraction and quality appraisal were completed. The present review presents the perspectives of 973 autistic females aged 13–70+. Thematic synthesis identified three themes and nine subthemes. Our findings suggest that autistic girls’ and women’s experiences can be conceptualised within a social model, where biological and psychological factors (‘The Autistic Neurotype’) are experienced through the lens of social factors (‘The Neurotypical World’ and ‘Stigma’), together shaping well-being and mental health outcomes. Lay abstract Difficulties with mental health and low levels of well-being are more common among autistic girls and women than non-autistic people, but we do not fully understand why. Research does not focus enough on what autistic girls and women could tell us about this. This review aims to summarise the studies where autistic girls and women explain things that affect their mental health and well-being to help us understand how to prevent these difficulties from developing. Three research databases were searched to find possibly relevant studies. There were 877 studies found, which two researchers screened according to particular criteria. They found 52 studies that could be included in this review. One researcher evaluated the quality of these studies and extracted the key information from them. This review summarises the views of 973 autistic girls and women aged between 13 and 70+. The findings from the 52 studies were analysed, and we found many factors that affect the mental health and well-being of autistic girls and women. These factors fall into two categories: (1) difficulties living in a world not designed for autistic people and (2) the impact of stigma due to being autistic

Lattice Kinetics of Diffusion-Limited Coalescence and Annihilation with Sources

We study the 1D kinetics of diffusion-limited coalescence and annihilation with back reactions and different kinds of particle input. By considering the changes in occupation and parity of a given interval, we derive sets of hierarchical equations from which exact expressions for the lattice coverage and the particle concentration can be obtained. We compare the mean-field approximation and the continuum approximation to the exact solutions and we discuss their regime of validity.Comment: 24 pages and 3 eps figures, Revtex, accepted for publication in J. Phys.

The influence of correlation on the extreme traffic loading of bridges

Accurate traffic loading models based on measured data are essential for the accurate assessment of existing bridges. There are well-established methods for the Monte Carlo simulation of single lanes of traffic, and this can easily be extended to model the loading on bridges with two independent streams of traffic in opposing directions. However, a typical highway bridge will have multiple lanes in the same direction, and various types of correlation are evident in measured traffic. This paper analyses traffic patterns using multi-lane WIM data collected at two European sites. It describes an approach to the Monte Carlo simulation of this traffic which applies variable bandwidth kernel density estimators to empirical traffic patterns of vehicle weights, gaps and speeds. This method provides a good match with measured data for multi-truck bridge loading events, and it is shown that correlation has a small but significant effect on lifetime maximum load effects

Rendering a Redeveloped France

International audienc

Migration potential as a new predictor of long-distance dispersal rate for plants

How biotic and abiotic factors interact to shape the overall pattern of dispersal of propagules is critical in understanding the evolution of dispersal mechanisms as well as predicting dispersal rates between patchily-distributed habitats. But which plant traits, demographic and/or habitat factors best predict the capacity for dispersal? We introduce the concept of migration potential (v), a readily interpretable parameter that combines recruitment efficiency (recruits per adult / seeds per adult per dispersal cycle) with level of habitat occupancy for predicting effective long-distance dispersal (LDD) of seeds. Using our empirical (genotype assignment) estimates of LDD and statistics on life-history traits and demographic features for contrasting co-occurring shrub species as a test case, and comparing alternative plant traits, we demonstrate that rate of LDD is best described as a simple function of v. As the direct consequence of life-history and demographic traits in a specific environmental context, v has the potential to predict LDD rates in both stable and changing ecosystems

Phenotypic variation and differentiated gene expression of Australian plants in response to declining rainfall

Declining rainfall is projected to have negative impacts on the demographic performance of plant species. Little is known about the adaptive capacity of species to respond to drying climates, and whether adaptation can keep pace with climate change. In fire-prone ecosystems, episodic recruitment of perennial plant species in the first year postfire imposes a specific selection environment, offering a unique opportunity to quantify the scope for adaptive response to climate change. We examined the growth of seedlings of four fire-killed species under control and drought conditions for seeds from populations established in years following fire receiving average-to-above-average winter rainfall, or well-below-average winter rainfall. We show that offspring of plants that had established under drought had more efficient water uptake, and/or stored more water per unit biomass, or developed denser leaves, and all maintained higher survival in simulated drought than did offspring of plants established in average annual rainfall years. Adaptive phenotypic responses were not consistent across all traits and species, while plants that had established under severe drought or established in years with average-to-above-average rainfall had an overall different physiological response when growing either with or without water constraints. Seedlings descended from plants established under severe drought also had elevated gene expression in key pathways relating to stress response. Our results demonstrate the capacity for rapid adaptation to climate change through phenotypic variation and regulation of gene expression. However, effective and rapid adaptation to climate change may vary among species depending on their capacity to maintain robust populations under multiple stresses