Josephson current in a superconductor -- ferromagnet -- superconductor junction with in-plane ferromagnetic domains

We study a diffusive superconductor--ferromagnet--superconductor (SFS) junction with in-plane ferromagnetic domains. Close to the superconducting transition temperature, we describe the proximity effect in the junction with the linearized Usadel equations. We find that properties of such a junction depend on the size of the domains relative to the magnetic coherence length. In the case of large domains, the junction exhibits transitions to the $\pi$ state, similarly to a single-domain SFS junction. In the case of small domains, the magnetization effectively averages out, and the junction is always in the zero state, similarly to a superconductor--normal metal--superconductor (SNS) junction. In both those regimes, the influence of domain walls may be approximately described as an effective spin-flip scattering. We also study the inhomogeneous distribution of the local current density in the junction. Close to the 0--$\pi$ transitions, the directions of the critical current may be opposite in the vicinity of the domain wall and in the middle of the domains.Comment: 9 pages, 6 figure

Decoding the role of the lncRNA HOTAIRM1 in human motor neurons

The mammalian genome produces thousands of long non-coding RNAs (lncRNAs), which have been demonstrated to be fundamental in the control of many biological processes. These molecules play a crucial role in the multilayered regulation of physiological and disease-related gene expression programs, having significant implications in shaping central nervous system (CNS) complexity. Neuronal differentiation is a timely and spatially regulated process, relying on precisely orchestrated gene expression control. The coordinated activity of transcription factors and non-coding RNAs (ncRNAs), organized in intricate regulatory networks, drives cell fate specification ensuring correct and specific neuronal functions. We previously described,1 at both the molecular and functional level, the lncRNA nHOTAIRM1 as a neuronal-enriched transcript, which is upregulated during in vitro neuronal differentiation and highly expressed in post-mitotic motor neurons (MNs). We demonstrated that the nuclear nHOTAIRM1, even if much less abundant than its cytoplasmic counterpart, it is involved in the achievement of correct neuronal differentiation timing as an epigenetic regulator of NEUROG2 expression.1 Remarkably, among all human brain tissues, nHOTAIRM1 is specifically expressed in the spinal cord. Consistently, we found that nHOTAIRM1 accumulates in MN-enriched ventral spinal cord lineages differentiated from human induced pluripotent stem cells (iPSCs).1 All this evidence prompted us to further investigate the role of the highly expressed nHOTAIRM1 specifically on MN generation and/or function, to ultimately determine whether its deregulation affects MN differentiation and activity. To experimentally address these questions, here we applied a genome editing-based loss-of-function approach to a model system that efficiently recapitulates spinal MN differentiation, and we identified key nHOTAIRM1 target genes implicated in MN maturation, morphology and activity. Our findings allowed us to conclude that nHOTAIRM1 directs multiple crucial aspects of MN physiology, from their development to the acquisition of appropriate morphological features and motor function

Amical et respectuex hommage à Maurice Toussaint: une lecture de sa thèorie linguistique

A partir de las bases teóricas sobre las que Gustave Guillaume ha asentado la psicomecánica del lenguaje, de la que es creador, Maurice Toussaint ha desarrollado individualmente un enfoque lingüístico que finalmente ha denominado “neurosemántica epistémica”. En su construcción y sus desarrollos sucesivos, desde 1962 hasta 2010, año en que nos ha dejado, ha deseado situarla con respecto al legado guillaumiano en el que no ha cesado de ahondar; pero que ha criticado y desviado con el objetivo de mejorar el rigor de este, su coherencia y rendimiento. En suma, nos ha cedido una lingüística todavía demasiado poco conocida pero francamente original con innegables cualidades heurísticas: conjuntamente neurónica y epistémica, cognitiva y antisubjetivista, naturalista pero también social, continuista y monista. Una lingüística que finalmente se revela ventajosa y engarzada en ciertas investigaciones contemporáneas.From the theoretical framework in which Gustave Guillaume consolidated the psychomechanics of language, of which he was the creator, Maurice Toussaint developed on his own a linguistic approach which he finally called “epistemic neurosemantics”. In its construction and successive developments from 1962 to 2010, he tried to locate it in the Guillaumian legacy. Toussaint continued going into Guillaume’s theory in depth, although he often criticized it and diverted from it in order to improve its rigour, coher¬ence and performance. Toussaint left us some hardly known linguistics, but full of originalith and with undeniable heuristic qualities: it is neuronic and epistemic, cognitive and antisubjectivist, naturalist and social, continuist and monistic. This is a linguistics that finally shows to be advantageous and included in contemporary research.peerReviewe

On finding a minimum vertex cover of a series-parallel graph

AbstractWe present a simple linear time algorithm for finding a minimum vertex cover for series-parallel graphs

The zipper mechanism in phagocytosis: energetic requirements and variability in phagocytic cup shape

Phagocytosis is the fundamental cellular process by which eukaryotic cells bind and engulf particles by their cell membrane. Particle engulfment involves particle recognition by cell-surface receptors, signaling and remodeling of the actin cytoskeleton to guide the membrane around the particle in a zipper-like fashion. Despite the signaling complexity, phagocytosis also depends strongly on biophysical parameters, such as particle shape, and the need for actin-driven force generation remains poorly understood. Here, we propose a novel, three-dimensional and stochastic biophysical model of phagocytosis, and study the engulfment of particles of various sizes and shapes, including spiral and rod-shaped particles reminiscent of bacteria. Highly curved shapes are not taken up, in line with recent experimental results. Furthermore, we surprisingly find that even without actin-driven force generation, engulfment proceeds in a large regime of parameter values, albeit more slowly and with highly variable phagocytic cups. We experimentally confirm these predictions using fibroblasts, transfected with immunoreceptor FcyRIIa for engulfment of immunoglobulin G-opsonized particles. Specifically, we compare the wild-type receptor with a mutant receptor, unable to signal to the actin cytoskeleton. Based on the reconstruction of phagocytic cups from imaging data, we indeed show that cells are able to engulf small particles even without support from biological actin-driven processes. This suggests that biochemical pathways render the evolutionary ancient process of phagocytic highly robust, allowing cells to engulf even very large particles. The particle-shape dependence of phagocytosis makes a systematic investigation of host-pathogen interactions and an efficient design of a vehicle for drug delivery possible.Comment: Accepted for publication in BMC Systems Biology. 17 pages, 6 Figures, + supplementary informatio

Fast Reachability Using DAG Decomposition

We present a fast and practical algorithm to compute the transitive closure (TC) of a directed graph. It is based on computing a reachability indexing scheme of a directed acyclic graph (DAG), G = (V, E). Given any path/chain decomposition of G we show how to compute in parameterized linear time such a reachability scheme that can answer reachability queries in constant time. The experimental results reveal that our method is significantly faster in practice than the theoretical bounds imply, indicating that path/chain decomposition algorithms can be applied to obtain fast and practical solutions to the transitive closure (TC) problem. Furthermore, we show that the number of non-transitive edges of a DAG G is ? width*|V| and that we can find a substantially large subset of the transitive edges of G in linear time using a path/chain decomposition. Our extensive experimental results show the interplay between these concepts in various models of DAGs