Direct Laser Sintering of Ceramics

For more than one decade layer manufacturing technologies assist the development of new products. Due to a layer-wise build-up of a three-dimensional geometry, nearly every complex design is producible in a short period of time. Selective Laser Sintering is a powderbased technique to produce plastic prototypes (Rapid Prototyping) or metal mould inserts (Rapid Tooling). The laser sintering of ceramic powder is not yet commercialized but applications could be both Rapid Prototyping and Rapid Tooling. The former involves the laser sintering of investment casting shells and cores to cast metal prototypes and the latter the laser sintering of ceramic master patterns for metal spray forming of steel mould inserts. The advantage compared to actual processes are a faster availability of the final product. To facilitate these applications, special ceramic powders as well as new process parameter combinations were investigated. This paper will present achieved results within the abovedescribed applications.Mechanical Engineerin

Large-Area RPE Removal by Microsecond Laser followed by hiPS-RPE transplantation

Cell therapeutics for AMD were often implanted regardless of RPE status in the target zone. This may result in RPE multilayering. Here we study a novel laser to remove RPE without collateral damage prior to RPE implantation to encourage better subretinal integration. Pigment rabbits (n=24) were immunosuppressed with Sirolimus, Doxycyclin and Minocyclin. Using a SLO/ OCT (Heidelberg Engineering) extended with a prototype laser (Meridian Medical; wavelength: 532 nm; pulse duration, 8 µs), a large area of RPE was selectively removed in 19 rabbits. Animals without laser lesions served as controls (n=5). A 25 gauge vitrectomy (Geuder) with removal of posterior hyaloid membrane was performed thereafter. Human iPS-RPE (1000 cells/ µl) were manually injected using a 100 µl syringe (Hamilton) connected to a 38G cannula (MedOne) into the RPE laser lesion, or over healthy RPE in controls, monitored by intraoperative OCT imaging (RESCAN 700, Zeiss). In vivo follow up/ retinal imaging was up to 12 weeks including fluorescein and indocyanine angiography, as well as SD-OCT (Spectralis ®, Heidelberg Engineering). Representative RPE laser wounds exhibited mild late phase FA& ICGA leakage, without abnormal outer retinal or choroidal hyperreflectivity on OCT. By contrast, lesions with earlier leakage on FA/ ICGA showed beam-sized outer retinal hyperreflectivity on OCT, suggesting coagulation. The size of the RPE wounds was typically 10-12mm2.iOCT demonstrated in an immediate and directed spread of the bleb retinal detachment (bRD) within the lasered zone. By contrast, bRDs performed over non-lasered RPE raised slower with a circular spread. Subretinal injection ranged from 5-70µl, with lesser volumes/ larger bRDs areas over lasered regions.At 6 and 12 weeks, none of implanted regions showed FA/ICGA leakage, some lesions had blockage due to hyperpigmentation; on OCT, representative areas showed preserved ellipsoid bands, with some RPE undulations. Lasered/implanted areas with a peripheral hyperpigmentation showed central outer retinal atrophy along with irregular RPE. Control implantation sites showed retinal atrophy and a variably thickened RPE band. Large-area RPE removal with laser disruption is feasible in healthy rabbits and appears to facilitate superior integration of RPE suspension grafts, compared to subretinal injection alone. Future work aims to correlate histology with in vivo imaging. This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually

Microbial life and biogeochemical cycling on land 3,220 million years ago

The colonization of emergent continental landmass by microbial life was an evolutionary step of paramount importance in Earth history. Here we report direct fossil evidence for life on land 3,220 million years ago (Ma) in the form of terrestrial microbial mats draping fluvial conglomerates and gravelly sandstones of the Moodies Group, South Africa. Combined field, petrographic, carbon isotope and Raman spectroscopic analyses confirm the synsedimentary origin and biogenicity of these unique fossil mats as well as their fluvial habitat. The carbon isotope compositions of organic matter (delta C-13(org)) from these mats define a narrow range centred on -21 parts per thousand, in contrast to fossil mats of marine origin from nearby tidal deposits that show delta C-13(org) values as low as -34 parts per thousand. Bulk nitrogen isotope compositions (2 < delta N-15 < 5 parts per thousand) are also significantly different from their marine counterparts (0 < delta N-15 < 3 parts per thousand), which we interpret as reflecting denitrification in the terrestrial habitat, possibly of an atmospheric source of nitrate. Our results support the antiquity of a thriving terrestrial biosphere during the Palaeoarchaean and suggest that a complex and microbially driven redox landscape existed during the deposition of the Moodies Group, with distinct biogeochemical cycling occurring on land by 3,220 Ma

Author Correction: Microbial life and biogeochemical cycling on land 3,220 million years ago

International audienceIn the version of this Article originally published, author Magali Ader was wrongly linked to affiliation 3; it should have been affiliation 2. This error has now been corrected in the online versions