Constructing bispectral dual Hahn polynomials

Using the concept of $\mathcal{D}$-operator and the classical discrete family of dual Hahn, we construct orthogonal polynomials $(q_n)_n$ which are also eigenfunctions of higher order difference operators

Matrix differential equations and scalar polynomials satisfying higher order recursions

We show that any scalar differential operator with a family of polyno- mials as its common eigenfunctions leads canonically to a matrix differen- tial operator with the same property. The construction of the correspond- ing family of matrix valued polynomials has been studied in [D1, D2, DV] but the existence of a differential operator having them as common eigen- functions had not been considered This correspondence goes only one way and most matrix valued situations do not arise in this fashion. We illustrate this general construction with a few examples. In the case of some families of scalar valued polynomials introduced in [GH] we take a first look at the algebra of all matrix differential operators that share these common eigenfunctions and uncover a number of phenomena that are new to the matrix valued case

Morphological changes, beach inundation and overwash caused by an extreme storm on a low-lying embayed beach bounded by a dune system (NW Mediterranean)

The geomorphological evolution of a low-lying, micro-tidal sandy beach in the western Mediterranean, Pals beach, was characterized using airborne Light Detection and Ranging (LiDAR) data. Data were collected in prior to and six months after the impact of an extreme storm with a return period of approx. 50 years, with the aim of characterizing the beach's response to the storm. The use of repeated high-resolution topographic data to quantify beach geomorphic changes has allowed assessment of the accuracy of different proxies for estimating beach volume changes. Results revealed that changes in the shoreline position cannot accurately reproduce beach volume changes on low-lying beaches where overwash processes are significant. Observations also suggested that volume estimations from beach profiles do not accurately represent subaerial volume changes at large profile distances on beaches with significant alongshore geomorphological variability. Accordingly, the segmentation of the beach into regularly spaced bins is proposed to assess alongshore variations in the beach volume with the accuracy of the topographic data. The morphological evolution of Pals beach during the study period showed a net shoreline retreat (- 4 m) and a significant sediment gain on the subaerial beach (+ 7.5 m3/m). The net gain of sediment is mostly due to the impact of the extreme storm, driving significant overwash processes that transport sediment landwards, increasing volume on the backshore and dunes. The increase of volume on the foreshore and the presence of cuspate morphologies along the shoreline also evidence post-storm beach recovery. Observed morphological changes exhibit a high variability along the beach related to variations in beach morphology. Changes in the morphology and migration of megacusps result in a high variability in the shoreline position and foreshore volume changes. On the other hand, larger morphological changes on the backshore and larger inundation distances occur when the beach and the dunes are lower, favouring the dominance of overwash. The observed storm-induced morphological changes differ from predicted beach storm impacts because of spatial and temporal variations in the beach morphology, suggesting that detailed morphological parameters and indicators used for predicting beach vulnerability to storms should be regularly updated in order to represent the pre-storm beach conditions. Finally, observed morphological changes in Pals Bay evidenced a different behaviour between natural and urban areas, with better post-storm beach recovery on natural areas where the beach is not artificially narrowed.Peer ReviewedPostprint (author's final draft

Población, progreso técnico y economía

Economists are learning the truth as old as the Bible that population growth is good for progress. This article discusses how the growth of population stimulates technical progress while stagnation limits the numbers born of creative persons who are the real motors of growth. The Universe still has many secrets to reveal so it is a big mistake to penalize fiscally and culturally large families. The Welfare State gives misleading answers as to what should be done in the face of the ageing of society

‘Here and There, Then and Now’: Envisioning a Palimpsest Methodology

Black feminisms challenge Western conceptions of linearity as an optic for understanding the experiences of Black folx in the United States social imaginary. As such, this article centers the understanding that for Black and minoritized folx, historical legacies carry the lingering effects of what may seem over and done with. These tensions converge on what M. Jacqui Alexander (2005) called the palimpsest, or “a parchment that has been inscribed two or three times, the previous text having been imperfectly erased” (Alexander, 2005, p. 190). A framing of time and realities as palimpsestic, or imperfect erasure, suggests that the past is visible and acting upon the present. The potential of a palimpsest methodology rests on the ethical entanglements of the body, memory, and space-time and afterlives with respect to existing tendencies and reliable possibilities. Methodologically, we propose that the palimpsest necessarily reads data and researcher positionalities as woven together, written over, and grappling with one another. In turn, this article intends to pursue embodied research by envisioning the notion of the palimpsest as a methodological tool. To accomplish this, we begin with a brief review of the literature and disciplinary grounds that root the notion of the palimpsest. From there, we discuss the guiding principles for this approach before offering methodological considerations. Against the violence of complicity, temporality, and objectivity, for researchers, a palimpsest approach argues for an assumed responsibility to the work they engage in, the lives they work with, and sites that ground their work

Motivations for Queer Women of Color to Join Culturally Based Sororities

This critical narrative inquiry explored the motivations for Queer Women of Color to join culturally based sororities. Using Muñoz’s concept of disidentifications, we found that participants made strategic decisions when navigating the sorority membership process as well as in deciding what organization to join. Findings showed the importance of race/ethnicity, sexuality and gender, and other important connections to individual identities in participants’ motivations. Implications for research and practice are discussed