Response of geostationary communications satellite solid-state power amplifiers to high-energy electron fluence.

The key components in communications satellite payloads are the high-power amplifiers that amplify the received signal so that it can be accurately transmitted to the intended end user. In this study, we examine 26 amplifier anomalies and quantify the high-energy electron environment for periods of time prior to the anomalies. Building on the work of Lohmeyer and Cahoy (2013), we find that anomalies occur at a rate higher than just by chance when the >2 MeV electron fluence accumulated over 14 and 21 days is elevated. To try to understand “why,” we model the amplifier subsystem to assess whether the dielectric material in the radio frequency (RF) coaxial cables, which are the most exposed part of the system, is liable to experience electrical breakdown due to internal charging. We find that the accumulated electric field over the 14 and 21 days leading up to the anomalies is high enough to cause the dielectric material in the coax to breakdown. We also find that the accumulated voltages reached are high enough to compromise components in the amplifier system, for example, the direct current (DC) blocking capacitor. An electron beam test using a representative coaxial cable terminated in a blocking capacitor showed that discharges could occur with peak voltages and energies sufficient to damage active RF semiconductor devices

Interaction and behaviour imaging: a novel method to measure mother–infant interaction using video 3D reconstruction

International audienceStudying early interaction is essential for understanding development and psychopathology. Automatic computational methods offer the possibility to analyse social signals and behaviours of several partners simultaneously and dynamically. Here, 20 dyads of mothers and their 13–36-month-old infants were videotaped during mother–infant interaction including 10 extremely high-risk and 10 low-risk dyads using two-dimensional (2D) and three-dimensional (3D) sensors. From 2D+3D data and 3D space reconstruction, we extracted individual parameters (quantity of movement and motion activity ratio for each partner) and dyadic parameters related to the dynamics of partners heads distance (contribution to heads distance), to the focus of mutual engagement (percentage of time spent face to face or oriented to the task) and to the dynamics of motion activity (synchrony ratio, overlap ratio, pause ratio). Features are compared with blind global rating of the interaction using the coding interactive behavior (CIB). We found that individual and dyadic parameters of 2D+3D motion features perfectly correlates with rated CIB maternal and dyadic composite scores. Support Vector Machine classification using all 2D–3D motion features classified 100% of the dyads in their group meaning that motion behaviours are sufficient to distinguish high-risk from low-risk dyads. The proposed method may present a promising, low-cost methodology that can uniquely use artificial technology to detect meaningful features of human interactions and may have several implications for studying dyadic behaviours in psychiatry. Combining both global rating scales and computerized methods may enable a continuum of time scale from a summary of entire interactions to second-by-second dynamics

Extreme relativistic electron fluxes in the Earth's outer radiation belt: Analysis of INTEGRAL IREM data

Relativistic electrons (E > 500 keV) cause internal charging and are an important space weather hazard. To assess the vulnerability of the satellite fleet to these so-called “killer” electrons, it is essential to estimate reasonable worst cases, and, in particular, to estimate the flux levels that may be reached once in 10 and once in 100 years. In this study we perform an extreme value analysis of the relativistic electron fluxes in the Earth's outer radiation belt as a function of energy and L∗. We use data from the Radiation Environment Monitor (IREM) on board the International Gamma Ray Astrophysical Laboratory (INTEGRAL) spacecraft from 17 October 2002 to 31 December 2016. The 1 in 10 year flux at L∗=4.5, representative of equatorial medium Earth orbit, decreases with increasing energy ranging from 1.36 × 107 cm−2 s−1 sr−1 MeV−1 at E = 0.69 MeV to 5.34 × 105 cm−2 s−1 sr−1 MeV−1 at E = 2.05 MeV. The 1 in 100 year flux at L∗=4.5 is generally a factor of 1.1 to 1.2 larger than the corresponding 1 in 10 year flux. The 1 in 10 year flux at L∗=6.0, representative of geosynchronous orbit, decreases with increasing energy ranging from 4.35 × 106 cm−2 s−1 sr−1 MeV−1 at E = 0.69 MeV to 1.16 × 105 cm−2 s−1 sr−1 MeV−1 at E = 2.05 MeV. The 1 in 100 year flux at L∗=6.0 is generally a factor of 1.1 to 1.4 larger than the corresponding 1 in 10 year flux. The ratio of the 1 in 10 year flux at L∗=4.5 to that at L∗=6.0 increases with increasing energy ranging from 3.1 at E = 0.69 MeV to 4.6 at E = 2.05 MeV

Elevated blood lead levels are associated with reduced risk of malaria in Beninese infants

Introduction Elevated blood lead levels (BLL) and malaria carry an important burden of disease in West Africa. Both diseases might cause anemia and they might entail long-term consequences for the development and the health status of the child. Albeit the significant impact of malaria on lead levels described in Nigeria, no evaluation of the effect of elevated BLL on malaria risk has been investigated so far. Materials and Methods Between 2010 and 2012, blood lead levels of 203 Beninese infants from Allada, a semi-rural area 50km North from Cotonou, were assessed at 12 months of age. To assess lead levels, blood samples were analyzed by mass spectrometry. In parallel, clinical, microbiological and hematological data were collected. More precisely, hemoglobin, serum ferritin, CRP, vitamin B12, folate levels, and Plasmodium falciparum parasitemia were assessed and stool samples were also analyzed. Results At 12 months, the mean BLL of infants was 7.41 μg/dL (CI: 65.2; 83), and 128 infants (63%) had elevated blood lead levels, defined by the CDC as BLL>5 μg/dL. Lead poisoning, defined as BLL>10 μg/dL, was found in 39 infants (19%). Twenty-five infants (12.5%) had a positive blood smear at 12 months and 144 infants were anemic (71%, hemoglobin<110 g/L). Elevated blood lead levels were significantly associated with reduced risk of a positive blood smear (AOR = 0.38, P-value = 0.048) and P. falciparum parasite density (beta-estimate = -1.42, P-value = 0.03) in logistic and negative binomial regression multivariate models, respectively, adjusted on clinical and environmental indicators. Conclusion Our study shows for the first time that BLL are negatively associated with malarial risk considering other risk factors. Malaria is one of the main causes of morbidity and mortality in infants under 5 years worldwide, and lead poisoning is the 6th most important contributor to the global burden of diseases measured in disability adjusted life years (DALYs) according to the Institute of Health Metrics. In conclusion, due to the high prevalence of elevated BLL, health interventions should look forward to minimize the exposure to lead to better protect the population in West Africa