Dynamics of piecewise contractions of the interval

We study the asymptotical behaviour of iterates of piecewise contractive maps of the interval. It is known that Poincar\'e first return maps induced by some Cherry flows on transverse intervals are, up to topological conjugacy, piecewise contractions. These maps also appear in discretely controlled dynamical systems, describing the time evolution of manufacturing process adopting some decision-making policies. An injective map $f:[0,1)\to [0,1)$ is a {\it piecewise contraction of $n$ intervals}, if there exists a partition of the interval $[0,1)$ into $n$ intervals $I_1$,..., $I_n$ such that for every $i\in{1,...,n}$, the restriction $f|_{I_i}$ is $\kappa$-Lipschitz for some $\kappa\in (0,1)$. We prove that every piecewise contraction $f$ of $n$ intervals has at most $n$ periodic orbits. Moreover, we show that every piecewise contraction is topologically conjugate to a piecewise linear contraction

A gene catalogue of the amphioxus nervous system.

The elaboration of extremely complex nervous systems is a major success of evolution. However, at the dawn of the post-genomic era, few data have helped yet to unravel how a nervous system develops and evolves to complexity. On the evolutionary road to vertebrates, amphioxus occupies a key position to tackle this exciting issue. Its "simple" nervous system basically consists of a dorsal nerve cord and a diffuse net of peripheral neurons, which contrasts greatly with the complexity of vertebrate nervous systems. Notwithstanding, increasing data on gene expression has faced up this simplicity by revealing a mounting level of cryptic complexity, with unexpected levels of neuronal diversity, organisation and regionalisation of the central and peripheral nervous systems. Furthermore, recent gene expression data also point to the high neurogenic potential of the epidermis of amphioxus, suggestive of a skin-brain track for the evolution of the vertebrate nervous system. Here I attempt to catalogue and synthesise current gene expression data in the amphioxus nervous system. From this global point of view, I suggest scenarios for the evolutionary origin of complex features in the vertebrate nervous system, with special emphasis on the evolutionary origin of placodes and neural crest, and postulate a pre-patterned migratory pathway of cells, which, in the epidermis, may represent an intermediate state towards the deployment of one of the most striking innovative features of vertebrates: the neural crest and its derivatives

El petit amfiox: el miratge de l'origen dels vertebrats

L'origen dels vertebrats és un dels centres d'interès de molts científics i de la societat, i el nostre animal favorit, el petit i amigable amfiox, fa més d'un segle que ocupa aquesta posició privilegiada, i reflecteix en un miratge, com a fòssil vivent, el que va ocórrer en aquell transcendental moment de l'evolució. No és només morfològicament el representant viu de l'ancestre de tots els cordats, sinó que a més posseeix un genoma preduplicatiu, un model en versió simple del genoma de tots els vertebrats, incloent-hi l'humà. L'anàlisi del genoma de l'amfiox ha permès clarificar l'origen del nostre genoma propi, alhora que l'ha situat en una posició clau per entendre l'origen i funcionament de famílies i xarxes gèniques importants per al desenvolupament embrionari i la fisiologia. A més, els avenços tècnics en la reproducció i experimentació permeten raonadament somiar a resoldre els secrets dels nostres orígens i del funcionament del genoma.The little amphious: a mirage to the origen of vertebrates. The origin of vertebrates is one of the top interests for many scientists and the society, and our favorite animal has occupied this privileged position for more than a century, reflecting in a mirage, as a living fossil, what occurred in this critical landmark of evolution. It is not only morphologically the closest living relative of Chordates, but also possesses a preduplicative genome, a simple model for the genome of all vertebrates, including humans. The analysis of the amphioxus genome has served to clarify the origin of our own genome, and as showed it is in a key position to understand the origin and functioning of gene families and gene networks critical for embryonic development and physiology. Besides, technical advances in its reproduction and experimentation make plausible to dream in illuminating the secrets of our origins and the functioning of the genome

Trade and credit : revisiting the evidence

Este trabajo investiga los efectos de shocks de crédito sobre las exportaciones de las empresas españolas. Para ello, combinamos la información procedente de los microdatos de transacciones con el exterior de la Balanza de Pagos con datos de crédito procedentes de la Central de Información de Riesgos a lo largo del período 2002-2013. A continuación, identificamos shocks de oferta de crédito específcos para cada banco y año siguiendo la metodología de Amiti y Weinstein (2018) y estimamos su efecto sobre las ventas exteriores de las empresas españolas. Los resultados indican que los shocks de crédito tienen efectos significativos tanto sobre el margen intensivo (cantidad exportada) como sobre el margen extensivo del comercio (probabilidad de empezar a exportar o dejar de hacerlo)This paper explores the effects of bank lending shocks on export behavior of Spanish firms. For that purpose, we combine Balance of Payments data on exports at the firm-product-destination level with a matched bank-firm dataset incorporating information on the universe of corporate loans from 2002 to 2013. Armed with this dataset, we identify bankyear specific credit supply shocks following Amiti and Weinstein (2018) and estimate their impact on firms’ exports at the product-destination level. According to our estimates, credit supply shocks have sizable effects on both the intensive margin (amount exported) and the extensive margin of trade (decision to export

Passive mobile data for studying seasonal tourism mobilities: an application in a Mediterranean Coastal destination

The article uses passive mobile data to analyse the complex mobilities that occur in a coastal region characterised by seasonal patterns of tourism activity. A large volume of data generated by mobile phone users has been selected and processed to subsequently display the information in the form of visualisations that are useful for transport and tourism research, policy, and practice. More specifically, the analysis consisted of four steps: (1) a dataset containing records for four days—two on summer days and two in winter—was selected, (2) these were aggregated spatially, temporally, and differentiating trips by local residents, national tourists, and international tourists, (3) origindestination matrices were built, and (4) graph-based visualisations were created to provide evidence on the nature of the mobilities affecting the study area. The results of our work provide new evidence of how the analysis of passive mobile data can be useful to study the effects of tourism seasonality in local mobility patterns

Population dynamics during the COVID-19 pandemic

El año 2020 se caracterizó por unas dinámicas de migración neta en España que desembocaron en un aumento de la población rural en detrimento de la población urbana, rompiendo la tendencia secular hacia una mayor urbanización vigente desde mediados del siglo pasado. De acuerdo con los resultados de este documento, el dinamismo poblacional de las áreas rurales obedeció tanto a un aumento de las llegadas de población procedentes del resto del país como —en mayor medida— a un freno de las salidas desde dichas áreas. Asimismo, un análisis de regresión muestra que las dinámicas demográficas durante el éxodo rural (1950-1990), el porcentaje de viviendas secundarias y la accesibilidad a servicios (tanto físicos como digitales) se revelan como factores explicativos a la hora de caracterizar los cambios poblacionales a nivel municipal durante la pandemia. Cabe señalar que el año 2020 constituye un período excepcional, caracterizado por importantes restricciones a la movilidad y a la actividad, así como por profundas medidas de distanciamiento social. Este contexto, así como los niveles modestos de implantación del teletrabajo, arroja notables dudas e incertidumbre a la hora de anticipar hasta qué punto el freno a la urbanización observado en dicho año tiene visos de permanecer en un horizonte temporal más amplio.The year 2020 was marked by net migration dynamics in Spain that resulted in an increase in the rural population at the expense of the urban population, interrupting the secular trend towards greater urbanisation prevailing since the middle of the last century. According to the findings of this paper, the demographic momentum of rural areas was attributable both to higher population inflows from elsewhere in the country and, in particular, to a slowdown in outflows from rural areas. In addition, a regression analysis shows that the demographic dynamics during the rural exodus (1950-1990), the percentage of second homes and accessibility to services, both physical and digital, are explanatory factors when characterising municipal-level population changes during the pandemic. 2020 represents a unique period, marked by strict restrictions on movement and on activity, along with stringent social distancing measures. This setting, along with the modest levels of remote working, raise significant doubts and uncertainty as to the extent to which the slowdown in urbanisation observed in that year will continue over a longer time horizon

Financialization, new bussiness perimeter and union action challenges

El fenómeno de la financiarización es escudriñado desde el análisis de su origen en las políticas económicas, tanto internacionales, públicas como microeconómicas y empresariales. El artículo aborda la cuestión del proceso de endeudamiento y apalancamiento financiero, y se identifican las figuras y vehículos de la financiarización y su aplicación concreta por los actores financieros y empresariales. El propósito del artículo persigue no sólo diagnosticar el origen, o identificar actores responsables, sino también aportar una serie de propuestas para reconducir los efectos negativos de la financiarización y contribuir con una línea de medidas contra la crisis capitalista.The phenomenon of financialization is analyzed since their origin in economic policies, both international, public and in a microeconomic dimension. This paper addresses the question of the process of debt and financial leverage, and identify financial and business actors which have developed it. The purpose is not only to diagnose, but also provide a series of proposals to redirect the negative effects of financialization and contribute to a line of action against the capitalist crisis

Manejo multidisciplinar y tratamiento del cáncer de colon y recto

El Fast Track o ERAS es el conjunto de medidas perioperatorias y técnicas quirúrgico-anestésicas basadas en la evidencia que tienen como objetivo acelerar la recuperación de los pacientes intervenidos por cáncer colorrectal, sin incrementar la morbilidad de los cuidados perioperatorios tradicionales y minimizando los costes sanitarios. Sus pilares fundamentales son: evitar el ayuno preoperatorio, no realizar preparación intestinal, restringir la fluidoterapia, realizar un abordaje laparoscópico, retirar la sonda nasogástrica al final de la cirugía, no emplear drenajes, promover una movilización y deambulación precoz, así como una pronta tolerancia oral. Se han evaluado tanto los resultados clínicos como oncológicos obtenidos en una Unidad de Cirugía Colorrectal; concluyéndose que existe una clara mejoría tanto en la cirugía como en el postoperatorio, respecto a los protocolos tradicionales. Del mismo modo, la dedicación exclusiva de una patóloga a patología de cáncer colorrectal, ha supuesto una mejoría en la estadificación, y por tanto en el tratamiento de estos pacientes.Grado en Medicin

Restricted proliferation during neurogenesis contributes to regionalization of the amphioxus nervous system

The central nervous system of the cephalochordate amphioxus consists of a dorsal neural tube with an anterior brain. Two decades of gene expression analyses in developing amphioxus embryos have shown that, despite apparent morphological simplicity, the amphioxus neural tube is highly regionalised at the molecular level. However, little is known about the morphogenetic mechanisms regulating the spatiotemporal emergence of cell types at distinct sites of the neural axis and how their arrangements contribute to the overall neural architecture. In vertebrates, proliferation is key to provide appropriate cell numbers of specific types to particular areas of the nervous system as development proceeds, but in amphioxus proliferation has never been studied at this level of detail, nor in the specific context of neurogenesis. Here, we describe the dynamics of cell division during the formation of the central nervous system in amphioxus embryos, and identify specific regions of the nervous system that depend on proliferation of neuronal precursors at precise time-points for their maturation. By labelling proliferating cells in vivo at specific time points in development, and inhibiting cell division during neurulation, we demonstrate that localised proliferation in the anterior cerebral vesicle is required to establish the full cell type repertoire of the frontal eye complex and the putative hypothalamic region of the amphioxus brain, while posterior proliferating progenitors, which were found here to derive from the dorsal lip of the blastopore, contribute to elongation of the caudal floor plate. Between these proliferative domains, we find that trunk nervous system differentiation is independent from cell division, in which proliferation decreases during neurulation and resumes at the early larval stage. Taken together, our results highlight the importance of proliferation as a tightly controlled mechanism for shaping and regionalising the amphioxus neural axis during development, by addition of new cells fated to particular types, or by influencing tissue geometry.Whitten Trus

AMPK activation does not enhance autophagy in neurons in contrast to MTORC1 inhibition: different impact on β-amyloid clearance.

The physiological AKT-MTORC1 and AMPK signaling pathways are considered key nodes in the regulation of anabolism-catabolism, and particularly of macroautophagy/autophagy. Indeed, it is reported that these are altered processes in neurodegenerative proteinopathies such as Alzheimer disease (AD), mainly characterized by deposits of β-amyloid (Aβ) and hyperphosphorylated MAPT. These accumulations disrupt the optimal neuronal proteostasis, and hence, the recovery/enhancement of autophagy has been proposed as a therapeutic approach against these proteinopathies. The purpose of the present study was to characterize the modulation of autophagy by MTORC1 and AMPK signaling pathways in the highly specialized neurons, as well as their repercussions on Aβ production. Using a double transgenic mice model of AD, we demonstrated that MTORC1 inhibition, either in vivo or ex vivo (primary neuronal cultures), was able to reduce amyloid secretion through moderate autophagy induction in neurons. The pharmacological prevention of autophagy in neurons augmented the Aβ secretion and reversed the effect of rapamycin, confirming the anti-amyloidogenic effects of autophagy in neurons. Inhibition of AMPK with compound C generated the expected decrease in autophagy induction, though surprisingly did not increase the Aβ secretion. In contrast, increased activity of AMPK with metformin, AICAR, 2DG, or by gene overexpression did not enhance autophagy but had different effects on Aβ secretion: whereas metformin and 2DG diminished the secreted Aβ levels, AICAR and PRKAA1/AMPK gene overexpression increased them. We conclude that AMPK has a significantly different role in primary neurons than in other reported cells, lacking a direct effect on autophagy-dependent amyloidosis.pre-print832 K