Towards predicting the laser damage threshold of large-area optics

As the size of optics increases, such as in the optical coatings being developed for the National Ignition Facility in US and the Laser MegaJoules in France, the difficulty also increases in measuring and defining their laser damage threshold. Measuring the threshold on small witness samples ({le}cm) rather than full aperture optic (=m) is advantageous, and in this article, the threshold of large-area components is addressed in two ways. First, a model based on the R-on-l threshold distribution is shown to predict the threshold of a large optic with a high degree of confidence. The average R-on-l threshold provides a reliable, accurate value to evaluate coatings. An automated damage test bench has been developed at CEA. Secondly, the damage threshold has to be defined according to final use of the component. LLNL has defined a functional damage threshold to set limits on maximum damage size. An empirical power law dependence of average damage size on peak fluence was found; this can be used to predict the damage behavior of large-aperture optics exhibiting the same damage morphology

The ARGO-YBJ Experiment Progresses and Future Extension

Gamma ray source detection above 30TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1km2 is proposed to boost the sensitivity. Hybrid detection with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual specie. Fluorescence light detector array will extend the spectrum measurement above 100PeV where the second knee is located. An energy scale determined by balloon experiments at 10TeV will be propagated to ultra high energy cosmic ray experiments

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Influence of growth stage and variety on the pigment levels in Ipomoea batatas (sweet potato) leaves

The study of pigments and nutritional composition in Ipomoea batatas has been intensive, yet little studies have been conducted on their leaves. I. batatas (sweet potato) leaves which are discarded after the harvesting period can be used as a potential source of natural dye extraction due to their high level of carotenoids (particularly lutein). Selection of leaves material is dependable on factors such as leaves varieties and stages of growth developments. Variations in chlorophyll a, chlorophyll b, total carotenoids and lutein level were determined spectrophotometrically at different stages of leaves development in 6 different varieties of I. batatas leaves. Result showed that chlorophyll a, b, total carotenoids and lutein pigments increased rapidly when measured from day 1 to 7 and remained stagnant or decreased at older stages (day 15 to 18). Both the I. batatas var Oren and Biru Putih contained the highest amount of carotenoids and lutein from day 7 onwards compared to the other varieties and thus can be used as a suitable source of natural yellow dye. © 2011 Academic Journals

Status of the caviar detector at LISE-GANIL

Spectromètre LISEInternational audienceIPhysics that motivated the building of the LISE magnetic spectrometer, main ideas exposed in the scientific council of GANIL June 4th 1981 by M. Brian and M. Fleury, were: atomic physics studies with stripped ions and the study of new isotopes produced by the fragmentation of beams. The LISE line is a doubly-achromatic spectrometer (angle and position), with a resolution better than 10-3. Since the first experiment performed in 1984, several improvements of the spectrometer were made: use of an achromatic degrader (1987, used for the first time in the world), building of the achromatic deviation and the Wien Filter (1990), building of a new selection dipole and associated vertical platform (1994), building of the new LISE2000 line (2001), use of the Caviar detector (2002), building of the CLIM target (2007). Despite an extreme international competition, the LISE spectrometer remains a world-leader equipment using more than 50 % and up to 90 % of the beam time available at GANIL. This paper presents the status of CAVIAR detector which consist of a MPWC dedicated to in flight particle position at the first dispersive plane of LISE. Since two years, intensive efforts were done with the objective to propose a 'plug and play' detector for nuclear physic experiments. We will describe the motivations and the system from MPWC up to the acquisition system. As example few experimental results will be presented

Combined Juno observations and modeling of the Jovian auroral electron interaction with the Jovian upper atmosphere

The Juno mission provides a unique opportunity during each perijove pass to sample the downward electron flux at spacecraft altitude while observing far ultraviolet H2 and infrared H3+ emissions at Juno’s magnetic footprint. In addition, the ratio of the H2 spectral band absorbed by hydrocarbons to the unabsorbed portion of the spectrum (FUV color ratio) is often used as a proxy for the depth of the penetration of energetic electrons (relative to the hydrocarbon homopause). The relationship between the color ratio and the electron penetration has been simulated with a Monte Carlo model solving the Boltzmann transport equation. Analysis of concurrent FUV and IR images obtained during the first perijove (PJ1) suggests that the ratio of H3+ radiance to H2 unabsorbed emission is maximal in regions with low FUV color ratio. This result suggests that part of the H3+ column is lost in reactions with methane which converts H3+ into heavier ions. We also examine the observed relationship between the detailed morphology of the ultraviolet structures and of the associated UV color ratio, the total downward electron energy flux and its spectral characteristics

Transient Luminous Events observed in Jupiter's upper atmosphere

The Ultraviolet Spectrograph (UVS) is a long-slit imaging spectrograph on the Juno mission, which has been in orbit around Jupiter since July 2016. UVS covers the 68-210 nm wavelength range with a spectral resolution of 1.3-3.0 nm, and makes use of the spacecraft’s rotation to build up an ultraviolet image as the instrument slit sweeps across the planet. The primary purpose of UVS is to map Jupiter’s far-UV auroral emissions, but the instrument has also detected seven transient bright flashes, which we suggest may be Transient Luminous Events in Jupiter’s upper atmosphere. These bright flashes are only observed in a single spin of the spacecraft and their brightness decays exponentially with time, with a duration of ~1.6 ms. Their spectra are dominated by H2 Lyman band emission and based on the level of atmospheric absorption, we estimate a source altitude of 250 km above the 1-bar level. As seen by UVS, the emission regions are point sources, with maximum widths of 600-1800 km. These properties are consistent with the predicted properties of Sprites or Elves in Jupiter’s atmosphere (Yair et al., 2009, doi: 10.1029/2008JE003311, Luque et al., 2014, doi: 10.1002/2014JA020457). While tropospheric lightning has been frequently observed in Jupiter’s atmosphere, including by several other instruments on the Juno mission, Transient Luminous Events have not previously been observed in a planet other than Earth

Jupiter's average ultraviolet aurora

Using the best UVS data from each of Junos completed perijoves, we have created average (and variance) maps for the northern and southern auroras of Jupiter. The individual maps for each perijove contain a variety of auroral forms and represent many different levels of activity at a variety of local times. In contrast, the average maps allow features that are nearly always present, but at a lower brightness level, to stand out. The variance maps, on the other hand, tend to highlight auroral structures which occur only rarely. In this presentation we examine what can be learned from these ensemble maps which provide a new look at Jupiter's always surprising auroras