Ultrafast sub-nanometer matter-wave temporal Talbot effect

[EN]The coherent manipulation of the electron wavefunction at the atomic spatial and temporal scales is the fundamental breakthrough underlying far-reaching ultrafast phenomena as high-order harmonic radiation and attosecond pulse generation. In this work, we present a next step in the coherent control of matter waves by translating the concept of Talbot interferometry to the subnanomenter–femtosecond realm.We study the high-harmonic emission from a periodic system irradiated by an intense mid-infrared laser beam at grazing incidence. Our calculations show that Bloch electrons, once ionized, follow a sequence of ultrafast (femtosecond) revivals associated with the temporal Talbot effect. We demonstrate that these revivals leave a distinct signature in the high-frequency harmonic spectrum, in the form of structures extending beyond the main spectral cutoff, toward the x-rays. The reinterpretation of the process of high-order harmonic generation as the temporal realization of a Talbot–Lau interferometer suggests high-harmonic spectroscopy as an appropriate scheme to develop subnanometer ultrafast Talbot interferometry.We acknowledge support Ministerio de Ciencia e Innovación (PID2019-106910GB-I00). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 851201). We also acknowledge support from Junta de Castilla y León FEDER funds (Project No. SA287P18). AG-C acknowledges support from Ministerio de Educación, Cultura y Deporte (FPU18/03348). CH-G acknowledges Ministerio de Ciencia, Innovación, y Universidades for a Ramón y Cajal contract (RYC-2017-22745), co-funded by the European. Social Fund

Plan de actividades deportivo-recreativas para favorecer la práctica de las habilidades motrices específicas: saque, pase y recibo, del voleibol en niños de 10-11 años de la circunscripción 197 de la comunidad Las Ovas

El trabajo que se presenta, titulado: Plan de actividades deportivo recreativas para favorecer las habilidades motrices especificas saque, pase y recibo del voleibol en los niños de 10-11 años en la comunidad de Las Ovas, se fundamenta en la inexistencia de actividades deportivas recreativas, que con este fin, tanto el profesor de recreacion, como el técnico deportivo comunitario le pudieran brindar a los niños en sus respectivas áreas de trabajo para desarrollar las habilidades motrices, debido entre otros factores a la falta de una guía o plan de actividades que les posibilite aplicarla según los intereses, gustos, necesidades y preferencias de los niños, por lo que el mismo persigue como objetivo fundamental proponer actividades deportivo- recreativas para desarrollar las habilidades motrices en niños de 10-11 años, en la comunidad. Los elementos presentados permiten en primer lugar recrear y satisfacer a los niños en estas edades y en segundo lugar familiarizarlos con los elementos técnicos del voleibol saque, pase y recibo. Para cumplir el mismo se utilizaron diferentes métodos de investigación, rectorados por el materialista-dialéctico, como son: los teóricos; empíricos y estadísticos; destacándose dentro de los primeros el histórico-lógico, enfoque de sistema y el análisis documental, dentro de los empíricos la encuesta y la observación; además se utilizaron algunas técnicas de intervención comunitaria como: entrevista a informantes claves y el forum comunitario; dentro de los estadísticos, el cálculo porcentual y la media aritmética. La investigación se puso en práctica durante un periodo de 3 meses donde se obtuvieron resultados satisfactorios, con lo cual se espera hacerla extensiv

Non-classical high harmonic generation in graphene driven by linearly-polarized laser pulses

[EN]Recent studies in high-order harmonic generation (HHG) in solid targets reveal new scenarios of extraordinary rich electronic dynamics, in comparison to the atomic and molecular cases. For the later, the main aspects of the process can be described semiclassically in terms of electrons that recombine when the trajectories revisit the parent ion. HHG in solids has been described by an analogous mechanism, in this case involving electron-hole pair recombinations. However, it has been recently reported that a substantial part of the HHG emission corresponds to situations where the electron and hole trajectories do not overlap in space. According to the present knowledge, HHG from this imperfect recollisions reflects the quantum nature of the process, arising in systems with large Berry curvatures or for elliptically polarized driving fields. In this work, we demonstrate that imperfect recollisions are also relevant in the more general case. We show the signature of such recollisions in the HHG spectrum from monolayer graphene —a system with null Berry curvature— irradiated by linearly polarized driving fields. Our calculations also reveal that imperfect multiple-order recollisions contribute to the harmonic emission when electron-hole excursion times exceed one cycle of the driving field. We believe that our work adds a substantial contribution to the full understanding of the sub-femtosecond dynamics of HHG in solid systems.European Research Council (851201); Ministerio de Educación, Cultura y Deporte (FPU18/03348); FEDER funds (SA287P18); Junta de Castilla y León (SA287P18); Ramón y Cajal (RYC-2017-22745); Ministerio de Ciencia, Innovación y Universidades (PID2019-106910GB-100)

High-order harmonic spectroscopy of polycrystalline graphene

European Research Council (851201); Ministerio de Educación y Formación Profesional (FPU18/03348); Junta de Castilla y León (SA287P18); Ministerio de Ciencia, Innovación y Universidades (PID2019-106910GB-100, RYC-2017-22745).Present mass production of large-area single-layer graphene relies fundamentally on chemical vapor deposition methods. The generation of grain boundaries, which divides the sample into a set of crystalline domains, is inherent to these fabrication methods. Recent studies have demonstrated a strong anisotropy in the ultrafast non-linear response of single-layer graphene when subjected to non-perturbative, intense laser fields below the damage threshold. We propose to exploit this anisotropy to characterize the size distribution of graphene domains in polycrystals via high-order harmonic polarimetry. Our simulation results demonstrate the sensitivity of the harmonic polarization state to details of the polycrystal grain distribution. In particular, we show that the rotation in the polarization tilt of the highest-order harmonics holds information about the grain distribution in the polycrystal. As a proof-of-concept, we propose a method to determine the standard deviation of the grain size distribution from the values of the most frequent grain size and the standard deviation of the harmonic tilt rotation from a set of hypothetical measurements on different polycrystal realizations. Our work reveals the capability of high-order harmonic polarimetry to characterize polycrystalline two-dimensional materials

The mitochondrial lineage U8a reveals a Paleolithic settlement in the Basque country

BACKGROUND: It is customary, in population genetics studies, to consider Basques as the direct descendants of the Paleolithic Europeans. However, until now there has been no irrefutable genetic proof to support this supposition. Even studies based on mitochondrial DNA (mtDNA), an ideal molecule for constructing datable maternal genealogies, have failed to achieve this. It could be that incoming gene flow has replaced the Basque ancient lineages but it could also be that these lineages have not been detected due to a lack of resolution of the Basque mtDNA genealogies. To assess this possibility we analyzed here the mtDNA of a large sample of autochthonous Basques using mtDNA genomic sequencing for those lineages that could not be unequivocally classified by diagnostic RFLP analysis and control region (HVSI and HVSII) sequencing. RESULTS: We show that Basques have the most ancestral phylogeny in Europe for the rare mitochondrial subhaplogroup U8a. Divergence times situate the Basque origin of this lineage in the Upper Palaeolithic. Most probably, their primitive founders came from West Asia. The lack of U8a lineages in Africa points to an European and not a North African route of entrance. Phylogeographic analysis suggest that U8a had two expansion periods in Europe, the first, from a south-western area including the Iberian peninsula and Mediterranean France before 30,000 years ago, and the second, from Central Europe around 15,000–10,000 years ago. CONCLUSION: It has been demonstrated, for the first time, that Basques show the oldest lineages in Europe for subhaplogroup U8a. Coalescence times for these lineages suggest their presence in the Basque country since the Upper Paleolithic. The European U8 phylogeography is congruent with the supposition that Basques could have participated in demographic re-expansions to repopulate central Europe in the last interglacial periods

Unpacking Entrepreneurial Education: Learning Activities, Students’ Gender, and Attitude Toward Entrepreneurship.

To promote entrepreneurship among students, academic institutions should focus on developing a positive entrepreneurial personal attitude (EPA), since it is a strong antecedent of entrepreneurial intentions, which in turn predict actual entrepreneurship. Previous research finds that EPA is lower for women than men, which is related to the acknowledged gap between women and men in entrepreneurial activity. The present work builds on the elaboration likelihood model (ELM) to examine how nine different entrepreneurship-focused academic activities in school impact on students’ EPA, paying special attention to gender differences. We use a sample of 918 students from a French business school to analyse gender differences in the mechanisms based on ELM central and peripheral routes to promote EPA through academic activities. Post hoc tests are also performed to explore differences by gender at different academic levels. The results have important implications for academic institutions wishing to promote entrepreneurship since we unpack entrepreneurial education into individual academic activities. In particular, results suggest that students’ gender and academic level should be considered when designing activities to promote entrepreneurship

Immigrants’ entrepreneurial motivation in europe: liabilities and assets.

Política de acceso abierto tomada de: International Journal of Entrepreneurial Behavior & Research © Emerald Publishing LimitedPurpose: This paper examines how the institutional distance between immigrants’ country of residence and country of origin, as well as the regulative and normative aspects of institutions in immigrants’ country of residence, social context variables and individual psycho-behavioural factors, condition immigrants’ entrepreneurial motivation (i.e., mainly by necessity, by a combination of necessity and opportunity, or mainly by opportunity), which is in contrast to the previous literature on immigrant entrepreneurship that mainly focuses on micro-level factors. Design/methodology/approach: By using hierarchical linear regression models to test our hypotheses, we analyse 468 first-generation immigrant entrepreneurs settled in 31 European countries using data from the European Working Conditions Survey (6th EWCS; Eurofound, 2015 database) combined with other datasets to derive the macro-level variables (i.e., the Doing Business Project; Hofstede, Hofstede and Minkov, 2010). Findings: We find that distance in the normative aspects of institutions harms entrepreneurial opportunity motivation. At the same time, however, opportunity motivation is likely to benefit from both the normative aspects of institutions that reduce locals’ opportunity motivation and the distance in the regulative aspects of institutions. Originality/value: This article analyses immigrant entrepreneurship in Europe, which has been underexamined in the extant literature, and takes into account the micro-, meso- and macro-level factors affecting the entrepreneurial motivation of immigrants in Europe. This analysis responds to the need already highlighted by previous research to include not only micro-level factors but also meso- and macro-level factors in the analysis of immigrant entrepreneurship (Aliaga-Isla and Rialp, 2013)

Comparing risk of failure models in water supply networks using ROC curves

[EN] The problem of predicting the failure of water mains has been considered from different perspectives and using several methodologies in engineering literature. Nowadays, it is important to be able to accurately calculate the failure probabilities of pipes over time, since water company profits and service quality for citizens depend on pipe survival; forecasting pipe failures could have important economic and social implications. Quantitative tools (such as managerial or statistical indicators and reliable databases) are required in order to assess the current and future state of networks. Companies managing these networks are trying to establish models for evaluating the risk Of failure in order to develop a proactive approach to the renewal process, instead of using traditional reactive pipe substitution schemes. The main objective of this paper is to compare models for evaluating the risk of failure in water supply networks. Using real data from a water Supply company, this study has identified which network characteristics affect the risk of failure and which models better fit data to predict service breakdown. The comparison using the receiver operating characteristics (ROC) graph leads us to the conclusion that the best model is a generalized linear model. Also, we propose a procedure that can be applied to a pipe failure database, allowing the most appropriate decision rule to be chosen. (C) 2009 Elsevier Ltd. All rights reserved.The authors are indebted to the anonymous referees whose suggestions improved the original manuscript. This study was partially supported by a grant from MEyC (Ministerio de Educacion y Ciencia, Spain, Project CGL2004-05507). The research of Ana Debon was partially supported by a grant from Generalitat Valenciana (Grant no. GVPRE/2008/103).Debón Aucejo, AM.; Carrión García, A.; Cabrera Marcet, E.; Solano, H. (2010). Comparing risk of failure models in water supply networks using ROC curves. Reliability Engineering & System Safety. 95(1):43-48. doi:10.1016/j.ress.2009.07.004S434895

Micromobility Users' Behaviour and Perceived Risk During Meeting Manoeuvres

[EN] Mobility patterns and lifestyles have changed in recent years in cities worldwide, thanks to the strong rise in modes of travel commonly referred to as micromobility. In this context, e-scooters have experienced a great rise globally which has led to an increase of crashes involving this type of micromobility vehicle in urban areas. Thus, there is a need to study e-scooter users¿ behaviour and their interaction with cyclists. This research aimed at characterizing the meeting manoeuvre between micromobility users along diverse typologies of two-way bicycle track by using an in-strumented e-scooter. As a result, bicycle tracks having concrete or vegetated curb presented lower clearance distance (¿0.8 m) than those without edge elements (>1 m), with no statistically signif-icant differences found between the interaction with bicycles and e-scooters. Additionally, an online questionnaire was proposed to assess users¿ perceived risk during the meeting manoeuvre, concluding that micromobility users feel safer and more comfortable riding on pavements away from parked or moving motorized traffic, and on protected bicycle tracks.FundingThis research is part of the research project PID2019-111744RB-I00, funded by MCIN/AEI/10.13039/501100011033.Fonseca-Cabrera, AS.; Llopis-Castelló, D.; Pérez Zuriaga, AM.; Alonso-Troyano, C.; García García, A. (2021). Micromobility Users' Behaviour and Perceived Risk During Meeting Manoeuvres. International Journal of Environmental research and Public Health (Online). 18(23):1-15. https://doi.org/10.3390/ijerph182312465S115182