Time-Reversal of Nonlinear Waves - Applicability and Limitations

Time-reversal (TR) refocusing of waves is one of fundamental principles in wave physics. Using the TR approach, "Time-reversal mirrors" can physically create a time-reversed wave that exactly refocus back, in space and time, to its original source regardless of the complexity of the medium as if time were going backwards. Lately, laboratory experiments proved that this approach can be applied not only in acoustics and electromagnetism but also in the field of linear and nonlinear water waves. Studying the range of validity and limitations of the TR approach may determine and quantify its range of applicability in hydrodynamics. In this context, we report a numerical study of hydrodynamic TR using a uni-directional numerical wave tank, implemented by the nonlinear high-order spectral method, known to accurately model the physical processes at play, beyond physical laboratory restrictions. The applicability of the TR approach is assessed over a variety of hydrodynamic localized and pulsating structures' configurations, pointing out the importance of high-order dispersive and particularly nonlinear effects in the refocusing of hydrodynamic stationary envelope solitons and breathers. We expect that the results may motivate similar experiments in other nonlinear dispersive media and encourage several applications with particular emphasis on the field of ocean engineering.Comment: 14 pages, 17 figures ; accepted for publication in Phys. Rev. Fluid

Framework for the implementation of urban big screens in the public space

In the last decade, big urban screens have appeared in town squares and on building facades across the UK. The use of these screens brings new potentials and challenges for city regulators, artists, architects, urban designers, producers, broadcasters and advertisers. Dynamic moving images form new architectural material, affecting our perception and the experience of the space around us. A new form of urban space is emerging that is fundamentally different from what we have known, and it seems that we are ill-equipped to deal with and analyse it. We are just beginning to understand the opportunities for public information, art and community engagement. Most of screens at present serve mainly commercial purposes, they do not broadcast information aimed at sharing community content nor do they support public social interactions. We need to see more negotiation between commercial, public and cultural interests. The SCREAM project addresses these new challenges by looking at the physical urban spaces and the potential spaces created by the new technologies

An Econometric Analysis of Investment in Hungary

Input-output analysis has found widespread empirical application, in studies of how certain industrial sectors react to changes in national and international economic conditions and in static and dynamic investigations of the interrelationships between industries. Since 1979 IIASA has been consistently active in this field, primarily through extensive collaboration with the Inter-Industry Forecasting Program (INFORUM) coordinated at the University of Maryland by Clopper Almon and Douglas Nyhus. IIASA's aims have been to further the development of econometric input-output models, to assist in the linkage of national models, and to participate in and extend the international network of collaborating scientists. To date, eighteen national models have been installed at IIASA, the software package SLIMFORP has been distributed widely, and linked runs of some of the national models have been carried out. Furthermore, annual task force meetings on input-output modeling have served to bring together present and prospective members of the INFORUM-IIASA "family" to review progress and to exchange ideas for further work. Gerhard Fink (Vienna Institute for Comparative Economic Studies) and Andras Simon (Institute for Economic and Market Research, Budapest) are collaborating in the development of an INFORUM-type input-output model for Hungary. In this paper they describe a study of Hungarian investment policy over recent decades, dealing with both the sectoral allocation of total investment and the cyclical investment patterns observed. The results are being used in the construction of an econometric submodel of investment for the Hungarian INFORUM model

Early life adversity, biological adaptation, and human capital: evidence from an interrupted malaria control program in Zambia

Growing evidence from evolutionary biology demonstrates how early life shocks trigger physiological changes designed to be adaptive in challenging environments. We examine the implications of one type of physiological adaptation - immunity formation - for human capital accumulation. Using variation in early life malaria risk generated by an interrupted disease control program in Zambia, we show that exposure to infectious diseases during the first two years of life can reduce the harmful effects of malaria exposure on cognitive development during the preschool years. These findings suggest a non-linear and trajectory-dependent relationship between early life adversity and human capital formation

Multi-Modal Human-Machine Communication for Instructing Robot Grasping Tasks

A major challenge for the realization of intelligent robots is to supply them with cognitive abilities in order to allow ordinary users to program them easily and intuitively. One way of such programming is teaching work tasks by interactive demonstration. To make this effective and convenient for the user, the machine must be capable to establish a common focus of attention and be able to use and integrate spoken instructions, visual perceptions, and non-verbal clues like gestural commands. We report progress in building a hybrid architecture that combines statistical methods, neural networks, and finite state machines into an integrated system for instructing grasping tasks by man-machine interaction. The system combines the GRAVIS-robot for visual attention and gestural instruction with an intelligent interface for speech recognition and linguistic interpretation, and an modality fusion module to allow multi-modal task-oriented man-machine communication with respect to dextrous robot manipulation of objects.Comment: 7 pages, 8 figure

Mobile nudges and financial incentives to improve coverage of timely neonatal vaccination in rural areas (GEVaP trial): a 3-armed cluster randomized controlled trial in Northern Ghana

BACKGROUND: Despite progress in vaccination coverage, timeliness of childhood vaccination remains a challenge in many settings. We aimed to assess if mobile phone-based reminders and incentives to health workers and caregivers could increase timely neonatal vaccination in a rural, low-resource setting. METHODS: We conducted an open-label cluster randomized controlled 1:1:1 trial with three arms in 15 communities in Northern Ghana. Communities were randomized to 1) a voice call reminder intervention; 2) a community health volunteer (CHV) intervention with incentivized rewards; 3) control. In the voice call reminder arm, a study staff member made voice calls to mothers shortly after birth to encourage vaccination and provide personalized information about available vaccination services. In the incentive arm, CHVs promoted infant vaccination and informed women with recent births about available vaccination opportunities. Both CHVs and women were provided small monetary incentives for on-time early infant vaccination in this arm, delivered using mobile phone-based banking applications. No study activities were conducted in control communities. A population-based survey compared vaccination coverage across arms in the pre-intervention and intervention periods. The primary endpoint was completion of at least one dose of Polio vaccine within 14 days of life and BCG vaccination within 28 days of life. RESULTS: Six-hundred ninety births were identified; 106, 88, and 88 from pre-intervention and 150, 135, and 123 in the intervention period, in the control, voice call reminder and CHV incentive arms, respectively. In adjusted intent-to-treat analysis, voice call reminders were associated with 10.5 percentage point (95% CI: 4.0, 17.1) higher coverage of on-time vaccination, while mobile phone-based incentives were associated with 49.5 percentage point (95% CI: 26.4, 72.5) higher coverage. CONCLUSION: Community-based interventions using mobile phone technologies can improve timely early vaccination coverage. A CHV approach with incentives to community workers and caregivers was a more effective strategy than voice call reminders. The impact of vaccination "nudges" via voice calls may be constrained in settings where network coverage and phone ownership are limited. TRIAL REGISTRATION: This trial was registered at ClinicalTrials.gov; NCT03797950

Impact of COVID-19 on maternal health and child care behavior: evidence from a quasi-experimental study of vulnerable communities in Boa Vista, Brazil

BACKGROUND: COVID-19 related distress has been shown to have negative associations with family well-being. OBJECTIVES: To determine the immediate impact of acute COVID-19 infection on maternal well-being and parenting practices among Brazilian families. PARTICIPANTS AND SETTING: We studied 2'579 mothers (29'913 observations) of young children from vulnerable neighborhoods in Boa Vista, Brazil over 12 months. METHODS: We monitored family health and caregiving behavior including the incidence of COVID-19 infections in the surveyed households through bi-weekly phone interviews over 50 weeks, from June 2020 to May 2021. Primary outcomes were home-based child stimulation, positive parenting behavior, and parenting stress. We used fixed effects panel regressions to estimate the impact of household COVID-19 infections on parenting outcomes. RESULTS: Over the study period, 441 participants (17.1%; 831 (3.0%) observations) reported at least 1 positive COVID-19 infection in their household. Household COVID-19 infections significantly reduced home-based stimulation by 0.10 SDs (95%CI: -0.18, -0.01), positive parenting behaviors by 0.14 SDs (-0.21, -0.01), and increased parenting stress by 0.07 SDs (0.02, 0.12). The impact on home-based stimulation was most pronounced when the mother herself had a COVID-19 infection (-0.16; -0.29, -0.04). Parenting stress responded most strongly to mother or child COVID-19 infections. Effects were relatively short-lived, only children's infections' on parental stress was still detectable 2 weeks after initial infection. CONCLUSION: Our findings suggest that COVID-19 infections cause substantial disruptions in children's home environments - additional short-term support for families with acute infections could attenuate the negative impact on children's home environment during the pandemic

In utero exposure to threat of evictions and preterm birth: evidence from the United States

OBJECTIVE: To estimate county-level associations between in utero exposure to threatened evictions and preterm birth in the United States. DATA SOURCES: Complete birth records were obtained from the National Center for Health Statistics (2009-2016). Threatened evictions were measured at the county level using eviction case filing data obtained from The Eviction Lab (2008-2016). Additional economic and demographic data were obtained from the United States Census Bureau and Bureau of Labor Statistics. STUDY DESIGN: We conducted a retrospective cohort analysis using 7.3 million births from 1,633 counties. We defined threatened eviction exposures as the z-score of average case filings over the pregnancy and by trimester. Our primary outcome was an indicator for preterm birth (born < 37 completed weeks of gestation). Secondary outcomes included a continuous measure for gestational length, a continuous measure for birth weight, and an indicator for low birth weight (born < 2500 g). We estimated within-county associations controlling for individual- and time-varying county-level characteristics, state-of-residence-year-and-month-of-conception fixed effects, and a county-specific time trend. DATA COLLECTION/EXTRACTION: We merged birth records with threatened eviction data at the county-month-year level using mother's county of residence at delivery and month-year of conception. We supplemented these data with information on county-level annual 18-and-over population, annual poverty rate, and monthly unemployment rate. PRINCIPAL FINDINGS: Increased levels of eviction case filings over a pregnancy were associated with an increased risk of prematurity and low birth weight. These associations appeared to be sensitive to exposure in the second and third trimesters. Associations with secondary outcomes and within various population subgroups were, in general, imprecisely estimated. CONCLUSIONS: Higher exposure to eviction case filings within counties, particularly in the latter stages of a pregnancy, was associated with an increased risk of adverse birth outcomes. Future research should identify the causal effect of threatened evictions on maternal and child health outcomes