Showing papers by "Paris West University Nanterre La Défense published in 2018"

Phase-engineered metalenses to generate converging and non-diffractive vortex beam carrying orbital angular momentum in microwave region

Abstract: In this paper, ultra-thin metalenses are proposed to generate converging and non-diffractive vortex beam carrying orbital angular momentum (OAM) in microwave region. Phase changes are introduced to the transmission cross-polarized wave by tailoring spatial orientation of Pancharatnam-Berry phase unit cell. Based on the superposition of phase profile of spiral phase plate and that of a converging lens or an axicon, vortex beam carrying OAM mode generated by the metalens can also exhibit characteristics of a focusing beam or a Bessel beam. Measured field intensities and phase distributions at microwave frequencies verify the theoretical design procedure. The proposed method provides an efficient approach to control the radius of vortex beam carrying OAM mode in microwave wireless applications for medium-short range distance.

Differential coding of perception in the world's languages

Abstract: Is there a universal hierarchy of the senses, such that some senses (e.g., vision) are more accessible to consciousness and linguistic description than others (e.g., smell)? The long-standing presumption in Western thought has been that vision and audition are more objective than the other senses, serving as the basis of knowledge and understanding, whereas touch, taste, and smell are crude and of little value. This predicts that humans ought to be better at communicating about sight and hearing than the other senses, and decades of work based on English and related languages certainly suggests this is true. However, how well does this reflect the diversity of languages and communities worldwide? To test whether there is a universal hierarchy of the senses, stimuli from the five basic senses were used to elicit descriptions in 20 diverse languages, including 3 unrelated sign languages. We found that languages differ fundamentally in which sensory domains they linguistically code systematically, and how they do so. The tendency for better coding in some domains can be explained in part by cultural preoccupations. Although languages seem free to elaborate specific sensory domains, some general tendencies emerge: for example, with some exceptions, smell is poorly coded. The surprise is that, despite the gradual phylogenetic accumulation of the senses, and the imbalances in the neural tissue dedicated to them, no single hierarchy of the senses imposes itself upon language.

CSR needs CPR: Corporate sustainability and politics

Abstract: Corporate sustainability has gone mainstream, and many companies have taken meaningful steps to improve their own environmental performance. But while corporate political actions such as lobbying can have a greater impact on environmental quality, they are ignored in most current sustainability metrics. It is time for these metrics to be expanded to critically assess firms based on the sustainability impacts of their public policy positions. To enable such assessments, firms must become as transparent about their corporate political responsibility (CPR) as their corporate social responsibility (CSR). For their part, rating systems must demand such information from firms and include evaluations of corporate political activity in their assessments of corporate environmental responsibility.

Reconfigurable meta-mirror for wavefronts control: applications to microwave antennas.

Abstract: A planar metasurface composed of electronically tunable meta-atoms incorporating voltage-controlled varactor diodes is proposed as a reconfigurable meta-mirror for wavefronts control in microwave antenna applications. The dispersion responses of the cells are individually tailored in the reconfigurable metasurface so as to overcome the bandwidth limitations of passive metasurfaces and also to control the phase characteristics. By controlling the bias voltage of the varactor diodes on the planar metasurface, the phase characteristics of reflectors can be engineered. The reconfigurable meta-mirror is utilized to implement three different types of reflectors. As such, a reflectarray, a cylindrical parabolic reflector and a dihedral reflector are numerically verified in microwave regime through finite element method. Moreover, experimental measurements are performed on a fabricated prototype to validate the proposed device. Frequency agility, beam deflection and beam focusing are the main functionalities demonstrated from the proposed reconfigurable meta-mirror.

Controlling Diffraction Patterns with Metagratings

Abstract: Although various wavefront-manipulation capabilities have been demonstrated with metasurfaces, both fundamental and practical difficulties remain. This study elaborates on a synergistic approach that combines metamaterials and gratings to achieve complete control of diffraction patterns. Unlike in a metasurface, in a metagrating the number of scatterers is significantly reduced, relaxing fabrication tolerance. Strong control of diffraction with simple excitation, ultrawide bandwidth, and significantly fewer scatterers is particularly interesting at optical and infrared frequencies, for $e.g.$ efficient, reconfigurable antennas in microwave communication systems.

Macroeconomic evidence suggests that asylum seekers are not a ``burden'' for Western European countries

Abstract: This paper aims to evaluate the economic and fiscal effects of inflows of asylum seekers into Western Europe from 1985 to 2015. It relies on an empirical methodology that is widely used to estimate the macroeconomic effects of structural shocks and policies. It shows that inflows of asylum seekers do not deteriorate host countries’ economic performance or fiscal balance because the increase in public spending induced by asylum seekers is more than compensated for by an increase in tax revenues net of transfers. As asylum seekers become permanent residents, their macroeconomic impacts become positive.

Phase-modulation based transmitarray convergence lens for vortex wave carrying orbital angular momentum.

Abstract: Vortex electromagnetic (EM) waves hold promise for their ability to significantly increase the transmission capacity of wireless communication systems via the torsion resistance defined by different topological charges associated with the orbital angular momentum (OAM). However, the application of vortex waves in remote distance transmission is limited by its characteristic of divergence. In this paper, a lens based on a phase-modulation metasurface (MS) is proposed that enables vortex EM waves to converge, thereby improving their propagation performance at microwave frequencies. A phase-shift distribution on the plane of the MS is obtained based on the concept of the optical converging axicon, which can convert a Laguerre-Gaussian (LG) beam to a Bessel beam based on changing the propagation direction. Simulation results verify the ability of the MS lens to achieve OAM beam focusing, which is advantageous for enhancing the propagation directivity and increasing the gain in the main lobes of vortex waves. This is of particular importance in microwave wireless communication applications.

Curvature and transport inequalities for Markov chains in discrete spaces

Abstract: We study various transport-information inequalities under three different notions of Ricci curvature in the discrete setting: the curvature-dimension condition of Bakry and Emery (In Seminaire de Probabilites, XIX, 1983/84 (1985) 177–206 Springer), the exponential curvature-dimension condition of Bauer et al. (Li-Yau Inequality on Graphs (2013)) and the coarse Ricci curvature of Ollivier (J. Funct. Anal. 256 (2009) 810–864). We prove that under a curvature-dimension condition or coarse Ricci curvature condition, an $L_{1}$ transport-information inequality holds; while under an exponential curvature-dimension condition, some weak-transport information inequalities hold. As an application, we establish a Bonnet–Myers theorem under the curvature-dimension condition $\operatorname{CD}(\kappa,\infty)$ of Bakry and Emery (In Seminaire de Probabilites, XIX, 1983/84 (1985) 177–206 Springer).

Active metasurface for reconfigurable reflectors

Abstract: Metasurfaces relying solely on passive unit cells printed on a dielectric substrate present limited characteristics due to their intrinsic dispersions. A metasurface composed of active unit cells incorporating voltage-controlled varactor diodes, where the dispersion responses of the cells can be tailored, is proposed to overcome the limitations of passive metasurfaces. Two functionalities are numerically and experimentally demonstrated from the active metasurface used as an electronically reconfigurable reflector. First, we show that anomalous reflection properties can be produced within a broad frequency range and second, we show that the direction of the reflected beam can be scanned within an angular range.

Understanding delays in acute stroke care: a systematic review of reviews.

Abstract: Background Stroke is the leading cause of adult long-term disability in Western countries. Intravenous thrombolytic therapy with recombinant tissue plasminogen activator is safe and effective within the first 4.5 h after the onset of stroke. Various factors delaying acute stroke care have been identified in the literature. This review aimed to provide an overview of factors delaying acute stroke care and attempted to show how they interact in a synthetic framework. Methods We conducted a systematic review of literature reviews published in Medline and DORIS until 2016 on factors influencing acute stroke pathway timeframe. Results We analyzed 31 reviews that cover all factors of delays from stroke onset to treatment. We identified 27 factors that had a significant impact on acute stroke care and can be categorized into four distinct categories: patient-related factors, training, resources and lack of coordination. We also reported associations between factors observed in both between categories (mainly between patients and organizational/logistical factors) and within categories. Conclusion This review provides a wide overview of factors influencing acute stroke pathway. Since it was observed that the identified factors were interrelated, they needed to be analyzed in a systematic way. We hence created a synthetic framework that combines several categories of factors while assuming that factor weight varies from a study context to another. Better knowledge on underlying mechanisms between factors would provide crucial improvement of the interventions aiming at reducing delays in both pre-hospital and inhospital stages. For future research, we recommend adopting a systemic perspective on factors influencing acute stroke pathway.

Melatonin ingestion after exhaustive late-evening exercise improves sleep quality and quantity, and short-term performances in teenage athletes.

Abstract: The present study aimed to explore the effects of a single 10-mg dose of melatonin (MEL) administration after exhaustive late-evening exercise on sleep quality and quantity, and short-term physical...

Orbital angular momentum generation method based on transformation electromagnetics.

Abstract: Orbital angular momentum (OAM) vortex waves generated by conventional spiral phase plates and metasurfaces have been widely discussed. In this work, we propose an innovative OAM generation method based on transformation optics (TO). By solving Laplace’s equation with specific boundary conditions, an oblate cylindrical shaped physical domain is designed to imitate a gradient shaped virtual domain which is able to generate a vortex beam upon reflection. As a proof-of-concept demonstration, a broadband all-dielectric microwave lens for vortex beam generation is presented with a topological charge of + 1. The corresponding far-field patterns as well as near-field helical phase and doughnut-shaped amplitude distributions of the lens, obtained from numerical simulations, are reported along with a wide operational bandwidth spanning from 8 to 16 GHz. As a transformation method, the proposed TO technique provides an effective way to realize a conversion from plane waves to vortex waves, which can greatly facilitate the potential implementation of OAM waves in microwave wireless communication systems.

Diurnal napping after partial sleep deprivation affected hematological and biochemical responses during repeated sprint

Abstract: The present study aimed to investigate the effects of 20-min (N20) and 90-min (N90) nap opportunities after partial-sleep-deprivation (PSD) on the hematological and biochemical responses to repeate...

Controlling diffraction patterns with metagratings.

Abstract: In this study we elaborate on the recent concept of metagratings proposed in Ra'di et al. [Phys. Rev. Lett. 119, 067404 (2017)] for efficient manipulation of reflected waves. Basically, a metagrating is a set of 1D arrays of polarization line currents which are engineered to cancel scattering in undesirable diffraction orders. We consider a general case of metagratings composed of N polarization electric line currents per supercell. This generalization is a necessary step to totally control diffraction patterns. We show that a metagrating having N equal to the number of plane waves scattered in the far-field can be used for controlling the diffraction pattern. To validate the developed theoretical approach, anomalous and multichannel reflections are demonstrated with 3D full-wave simulations in the microwave regime at 10 GHz. The results can be interesting for the metamaterials community as allow one to significantly decrease the number of used elements and simplify the design of wavefront manipulation devices, what is very convenient for optical and infra-red frequency ranges. Our findings also may serve as a way for development of efficient tunable antennas in the microwave domain.

Attention-deficit hyperactivity disorder and addictions (substance and behavioral): Prevalence and characteristics in a multicenter study in France.

Abstract: AimThe aim of this study is to determine the possible links between attention-deficit hyperactivity disorder (ADHD) and the presence of concomitant addictions with or without substance use in a Fre...

Can we learn to manage stress? A randomized controlled trial carried out on university students

Abstract: In our research, we examined the efficacy of an Internet-based stress management program Our interest in evaluating this type of intervention is based on the increasing accessibility of the Internet today, the growth of Internet-based interventions for various psychopathological problems, and the observation that despite the prevalence of stress among university students, only a fraction of students ever seek professional help Methodology: “I’m managing my stress” (“Je gere mon stresse”), an Internet-based self-help program composed of four sessions, was examined in this study The aforementioned program is based on cognitive-behavioral therapy and was inspired by the “Funambule” program in Quebec Four questionnaires (Perceived Stress Scale, Rosenberg Self-Esteem Scale, Scale of Satisfaction in Studies, and General Health Questionnaire) uploaded online were answered thrice: during “preintervention”, “postintervention”, and “follow-up” stages, the latter of which occurred three months after the intervention The sample comprised 128 university students, with the majority being women (8125%) The subjects were divided randomly into two groups (an experimental group and a control group that did not follow the program) Results: The self-esteem scores of the control group were significantly higher than those of the experimental group at the preintervention stage, but this difference disappeared at the postintervention and follow-up stages There were also significantly lower scores on the General Health Questionnaire subfactors of somatic symptoms and anxiety/insomnia in the experimental group than in the control group during the postintervention stage, though no differences were observed before the intervention These differences no longer remained after three months ANOVA revealed significant effects of the intervention over time in the experimental group Effects were observed at both the postintervention and follow-up stages for self-esteem, perceived stress, satisfaction in studies, and in the somatic symptoms, anxiety and insomnia and severe depression aspects of the General Health Questionnaire (Cohen’s d = 038 to 458) In contrast, no effects were observed in the control group Conclusion: This type of Internet-based program has the ability to reach a large number of students due to its rather short format and accessibility It has already shown improvements in terms of the levels of perceived stress, psychological distress and satisfaction with studies The option of online interventions could appeal specifically to students who do not seek professional help However, even though these results are promising at the postintervention stage, they are limited, as indicated by the lack of significant differences between the two groups after the initial three months of follow-up We still, specifically, need to improve this intervention program and, generally, need more research to address the methodological problems raised by this type of intervention Trial registration: ISRCTN registry, ISRCTN13709272

Cultural Values Moderate the Impact of Relative Deprivation

Abstract: Relative deprivation (RD) is the judgment that one or one's ingroup is worse off compared with some relevant standard coupled with feelings of dissatisfaction, anger, and resentment. RD predicts a wide range of outcomes, but it is unclear whether this relationship is moderated by national cultural differences. Therefore, in the first study, we used national assessments of individual-collectivism and power distance to code 303 effect sizes from 31 different countries with 200,578 participants. RD predicted outcomes ranging from life satisfaction to collective action more strongly within individualistic nations. A second survey of 6,112 undergraduate university students from 28 different countries confirmed the predictive value of RD. Again, the relationship between individual RD and different outcomes was stronger for students who lived in more individualistic countries. Group-based RD also predicted political trust more strongly for students who lived in countries marked by lower power distance. RD effects, although consistent predictors, are culturally bounded. In particular, RD is more likely to motivate reactions within individualistic countries that emphasize individual agency and achievement as a source of self-worth.

Analysis of Gambling in the Media Related to Screens: Immersion as a Predictor of Excessive Use?

Abstract: This study investigates the intricacies between the player interface proposed by the screens, (in particular on smartphone applications or in video games) and gambling. Recent research indicates connections between "immersion" and excessive screen practice. We want to understand the causal-effects between online gambling and the "immersion" variable and understand their relationship and its contingencies. This article empirically investigates whether and how it is possible to observe immersion with its sub-dimensions in gambling on different screens. The objective of this study was to analyze: (1) the costs and benefits associated with gambling practice on screens (2) the link between gambling practice and screen practice (video game, Internet, mobile screen); (3) to observe the propensity to immersion for individuals practicing gambling on screens; and (4) to examine the comorbidities and cognitive factors associated with the practice of gambling on screen. A total of 432 adults (212 men, 220 women), recruited from Ile-de-France (France), responded to a battery of questionnaires. Our study suggests that immersion variables make it possible to understand the cognitive participation of individuals towards screens in general, the practice of gambling on screens and the excessive practice of screens.

All-dielectric transformation medium mimicking a broadband converging lens

Abstract: Radio waves carrying orbital angular momentum (OAM) may potentially increase spectrum efficiency and channel capacity based on their extra rotational degree of freedom. However, due to their divergence characteristics, vortex waves are not suitable to transmit over a long distance in the radio frequency (RF) and microwave domains. In this paper, a transformation optics (TO) based all-dielectric converging lens is proposed. The beam divergence angle of the vortex wave passing through the lens can be decreased from 25° to 9°. The transformed material parameters of the converging lens are determined by solving Laplace's equation subject to specific boundary conditions. Far-field antenna radiation patterns as well as near-field helical phase and electric field amplitude distributions obtained from numerical simulations are reported, demonstrating the broadband characteristics of the proposed microwave lens. Moreover, the all-dielectric compact lens design comprised by a graded permittivity profile can be fabricated by additive manufacturing technology, which greatly facilitates the potential development and application of vortex wave based wireless communications.

Individuals Among the Pots: How Do Traditional Ceramic Shapes Vary Between Potters?

Abstract: At the crossroad of archeology and experimental psychology, we addressed the issue of interindividual variability in traditional ceramic shapes. The goal was to explore whether such variability cou...

High-Q Fano resonances via direct excitation of an antisymmetric dark mode.

Abstract: The engineering of metal-insulator-metal metasurfaces (MSs) displaying sharp spectral features based on Fano-type interference between a symmetric bright mode and an antisymmetric dark mode is reported. The proposed mechanism for direct excitation of antisymmetric mode avoids the necessity of mode hybridization through near-field coupling. Modeling and experimental results bring evidence that such MSs operating in the microwave or terahertz domains provide greater flexibility for Fano resonance engineering and provide strong enhancement of the spectral selectivity factor. It is shown that the occurring Fano resonance interference is related to the broken eigenmode orthogonality in open systems and is independent of hybridization mechanism.

Information Circulation in times of Ebola: Twitter and the Sexual Transmission of Ebola by Survivors

Abstract: INTRODUCTION The 2013-2015 outbreak of Ebola was by far the largest to date, affecting Guinea, Liberia, Sierra Leone, and secondarily, Nigeria, Senegal and the United States. Such an event raises questions about the circulation of health information across social networks. This article presents an analysis of tweets concerning a specific theme: the sexual transmission of the virus by survivors, at a time when there was a great uncertainty about the duration and even the possibility of such transmission. METHODS This article combines quantitative and qualitative analysis. From a sample of 50,000 tweets containing the words "Ebola" in French and English, posted between March 15 and November 8, 2014, we created a graphic representation of the number of tweets over time, and identified two peaks: the first between July 27 and August 16, 2014 (633 tweets) and the second between September 28 and November 8, 2014 (2,577 tweets). This sample was divided into two parts, and every accessible publication was analyzed and coded according to the authors' objectives, feelings expressed and/or publication type. RESULTS While the results confirm the significant role played by mainstream media in disseminating information, media did not create the debate around the sexual transmission of Ebola and Twitter does not fully reflect mainstream media contents. Social media rather work like a "filter": in the case of Ebola, Twitter preceded and amplified the debate with focusing more than the mainstream media on the sexual transmission, as expressed in jokes, questions and criticism. DISCUSSION Online debates can of course feed on journalistic or official information, but they also show great autonomy, tinged with emotions or criticisms. Although numerous studies have shown how this can lead to rumors and disinformation, our research suggests that this relative autonomy makes it possible for Twitter users to bring into the public sphere some types of information that have not been widely addressed. Our results encourage further research to understand how this "filter" works during health crises, with the potential to help public health authorities to adjust official communications accordingly. Without a doubt, the health authorities would be well advised to put in place a special watch on the comments circulating on social media (in addition to that used by the health monitoring agencies).

Cluster Concept: Lessons for the Sport Sector? Toward a Two-Step Model of Sport Cluster Development Based on Socioeconomic Proximity

Abstract: Sport clusters are geographical concentrations of private, public, and nonprofit organizations in a denominated area with a shared interest in one or similar sports This paper addresses the question: How does socioeconomic proximity—linkages between organizations or individuals, which go beyond spatial proximity—influence the development and properties of sport clusters? This qualitative study investigates four sport clusters in surfing and sailing The findings indicate two types of sport clusters based on different forms of socioeconomic proximity The surfing clusters are characterized by cognitive proximity based on convergent perceptions and managerial practices The sailing clusters are characterized by organizational proximity based on complementarity This article (a) discusses the resilience properties of these two types of clusters and (b) proposes a two-step model of cluster development Cluster policy makers can draw on this research to consider how to engage early with emerging clusters and