Accurate simulations of laser material processing techniques require realistic values of laser absorptivity as a function of angle of incidence and material temperature. The laser absorptivity can be calculated with the Fresnel equations, for which one needs the temperature dependent values of the refractive index n and extinction coefficient k of the material for the laser wavelength in question. However, there are hardly any published values for the n and k of metals at high temperatures, especially in the liquid state. This proof-of-principle paper presents a novel and simple experimental method for measuring the refractive index and extinction coefficient of liquid metals and thus their absorptivity as a function of angle of incidence and temperature for a short wavelength range. The method has been developed to determine n and k through the thermal emission over the curvature of a spheroidal droplet and is therefore not based on reflection measurements, which require a flat surface. The thermal emission was recorded using a linear polarizer, a bandpass filter and a camera. The method is demonstrated for liquid copper at a wavelength of 850 nm, and the results are in good agreement with published absorptivity values at a similar wavelength (1064 nm) and temperature range. It was found that the accuracy of the measurements in future work could be greatly increased by using spatial resolutions >= 1000 pixels/radius.

A combined numerical and experimental analysis of melt-pool dimensions and resulting solidification conditions was carried out on small laser powder bed fusion (L-PBF) struts (0.2 mm to 2 mm diameters), considered as single constitutive parts of the structure lattice. In the beginning, the high-speed imaging monitoring of melt pools was performed on a dedicated instrumented L-PBF set-up for various scan strategies. In the subsequent stage, a numerical thermal model was employed on COMSOL Multiphysics® to determine the alteration of the melt pool by the struts' diameter and scanning strategy for constant (power, scan speed) conditions. A good agreement was obtained between experimental and numerical melt-pool areas. This allowed validation of calculated local cooling rates and thermal gradients near the solidification front. A clear difference was shown between outside-in or inside-out strategies, and contour-hatching in terms of local solidification conditions. Higher cooling rates were obtained for outside-in conditions, especially near the external part of struts whereas inside-out conditions promoted more uniform cooling rates and thermal gradients. Moreover, a reduction of strut diameter induced the formation of a single melt-pool on the full strut’s surface, which promoted lower and more uniform cooling rates and a highly textured built material. A fairly good agreement was found between simulated thermal data and local microstructure development at the scale of solidification cells. Finally, the current work provides a deeper understanding on size and L-PBF strategy versus microstructure formation, and allows adapting build conditions on strut diameters.

OBJECTIVES:Inflammatory mediators such as interleukin 6 (IL-6) are known to activate catabolic responses in chondrocytes during osteoarthritis (OA). This study aimed to investigate the role of a downstream target gene of IL-6, the serine protease inhibitor SerpinA3N, in the development of cartilage damage in OA. METHODS:RNA sequencing was performed in murine primary chondrocytes treated with IL-6, and identified target genes were confirmed in human and murine OA cartilage samples. Male cartilage-specific Serpina3n-deficient mice and control mice underwent meniscectomy (MNX) or sham surgery at 10 weeks of age. Intra-articular injections of SerpinA3N or sivelestat (an inhibitor of leucocyte elastase (LE), a substrate for SerpinA3N) were performed in wild-type mice after MNX. Joint damage was assessed 3-9 weeks after surgery by histology and micro-CT. The effect of sivelestat was assessed in cartilage explants exposed to macrophage-derived conditioned media. RESULTS:RNA sequencing revealed that SerpinA3N is a major target gene of IL-6 in chondrocytes. The expression of SerpinA3N is increased in OA cartilage. Conditional loss of SerpinA3N in chondrocytes aggravated OA in mice, while intra-articular injection of SerpinA3N limited joint damage. Chondrocytes did not produce serine proteases targeted by SerpinA3N. By contrast, macrophages produced LE on IL-6 stimulation. Sivelestat limited the cartilage catabolism induced by conditioned media derived from IL-6-stimulated macrophages. Additionally, an intra-articular injection of sivelestat is protected against OA in the MNX model. CONCLUSIONS:SerpinA3N protects cartilage against catabolic factors produced by macrophages, including LE. SerpinA3N and LE represent new therapeutic targets to dampen cartilage damage in OA.

The development of next-generation sequencing has led to a breakthrough in the analysis of ancient genomes, and the subsequent genomic analyses of ancient human skeletal remains have revolutionized our understanding of human evolution. This research led to the discovery of a new hominin lineage, and demonstrated multiple admixture events with more distantly related archaic human populations such as Neandertals and Denisovans over the last 100,000 years. Moreover, it has also yielded novel insights into the evolution of ancient pathogens. The analysis of ancient microbial genomes enables the study of their recent evolution, presently covering the last several millennia. These spectacular results have been obtained despite the degradation of DNA that takes place after the death of the host and increases with time. This cumulative degradation results in very short ancient DNA molecules, low in quantity, and highly prone to contamination by modern DNA molecules, especially from human and animal DNA present in reagents used in downstream biomolecular analyses. Finally, the minute amounts of ancient molecules are further diluted in environmental DNA from the soil microorganisms that colonize bones and teeth. Thus, ancient skeletal remains can share DNA profiles with environmental samples, and the identification of ancient microbial genomes among the more recent, presently poorly characterized, environmental microbiome is particularly challenging. Here, we describe the methods developed and/or in use in our laboratory to produce reliable and reproducible paleogenomic results from ancient skeletal remains that can be used to identify the presence of ancient microbiota.

Laser welding of pure copper and its alloys is a challenging process with a growing industrial interest due to the latest development in the field of electric mobility. The difficulties are mainly related to the material's high thermal conductivity and a poor absorptivity of few percent at the classical IR laser (YAG). It is also well known that such a configuration can lead to the formation of undesirable defects, such as pores or spatters as a consequence of melt pool instabilities. It has been observed experimentally that the usage of a laser at both high speed and high power tends to limit those instabilities. Although this positive influence has already been observed for equivalent materials, a physical explanation is not yet available. In this perspective, a multiphysical simulation of the process at the melt pool scale is currently being developed by using comsol Multiphysics® software. The latter includes an Eulerian interface tracking method for the liquid-gas interface (phase field) and a ray-tracing description of the laser beam to take into account the well-known beam trapping effect under a keyhole regime. For the sake of time computation, the numerical model is first developed in an axisymmetric coordinate system (r,z) to be representative of a laser spot welding process and to validate the numerical coupling methodology. The model will then be extended to a 3D welding case and used as a predictive tool to make appropriate choices on welding parameters to obtain good quality welds (stable melt pool, low porosity rate, etc.).

The cat has long been important to human societies as a pest-control agent, object of symbolic value and companion animal, but little is known about its domestication process and early anthropogenic dispersal. Here we show, using ancient DNA analysis of geographically and temporally widespread archaeological cat remains, that both the Near Eastern and Egyptian populations of Felis silvestris lybica contributed to the gene pool of the domestic cat at different historical times. While the cat’s worldwide conquest began during the Neolithic period in the Near East, its dispersal gained momentum during the Classical period, when the Egyptian cat successfully spread throughout the Old World. The expansion patterns and ranges suggest dispersal along human maritime and terrestrial routes of trade and connectivity. A coat-colour variant was found at high frequency only after the Middle Ages, suggesting that directed breeding of cats occurred later than with most other domesticated animals.

The development of next-generation sequencing has led to a breakthrough in the analysis of ancient genomes, and the subsequent genomic analyses of the skeletal remains of ancient humans have revolutionized the knowledge of the evolution of our species, including the discovery of a new hominin, and demonstrated admixtures with more distantly related archaic populations such as Neandertals and Denisovans. Moreover, it has also yielded novel insights into the evolution of ancient pathogens. The analysis of ancient microbial genomes allows the study of their recent evolution, presently over the last several millennia. These spectacular results have been attained despite the degradation of DNA after the death of the host, which results in very short DNA molecules that become increasingly damaged, only low quantities of which remain. The low quantity of ancient DNA molecules renders their analysis difficult and prone to contamination with modern DNA molecules, in particular via contamination from the reagents used in DNA purification and downstream analysis steps. Finally, the rare ancient molecules are diluted in environmental DNA originating from the soil microorganisms that colonize bones and teeth. Thus, ancient skeletal remains can share DNA profiles with environmental samples and identifying ancient microbial genomes among the more recent, presently poorly characterized, environmental microbiome is particularly challenging. Here, we describe the methods developed and/or in use in our laboratory to produce reliable and reproducible paleogenomic results from ancient skeletal remains that can be used to identify the presence of ancient microbiota.

The origin and dispersal of the domestic cat remain elusive despite its importance to human societies around the world. Archaeological evidence for domestication centers in the Near East and in Egypt is contested, and genetic data on modern cats show that Felis silvestris lybica , the subspecies of wild cat inhabiting at present the Near East and Northern Africa, is the only ancestor of the domestic cat. Here we provide the first broad geographic and chronological dataset of ancient cat mtDNA sequences, drawing on archaeological specimens from across western Eurasia and northern and eastern Africa, dating from throughout the Holocene and spanning ~9,000 years. We characterized the ancient phylogeography of F. s. lybica, showing that it expanded up to southeastern Europe prior to the Neolithic, and reconstructed the subsequent movements that profoundly transformed its distribution and shaped its early cultural history. We found that maternal lineages from both the Near East and Egypt contributed to the gene pool of the domestic cat at different historical times, with the Near Eastern population providing the first major contribution during the Neolithic and the Egyptian cat spreading efficiently across the Old World during the Classical period. This expansion pattern and range suggest dispersal along maritime and terrestrial routes of trade and connectivity. Late trait selection is suggested by the first occurrence in our dataset of the major allele for blotched-tabby body marking not earlier than during the Late Middle Ages. Significance The cat has long been important to human societies as a pest-control agent, object of symbolic value, and companion animal, but little is known about its domestication process and early anthropogenic dispersal. Our DNA analyses of geographically and temporally widespread archaeological cat remains show that while the cat’s world-wide conquest began in prehistoric times, when tamed cats accompanied humans on their journeys over land and sea, it gained momentum during the Classical period, when the Egyptian cat successfully spread throughout the ancient world. The appearance of a new coat pattern at the end of the Middle Ages suggests late breeding control that might explain the semi-domestic status of the cat. This distinguishes the domestication process of cats from that of most other domesticates.

Human gastrointestinal parasites are good indicators for hygienic conditions and health status of past and present individuals and communities. While microscopic analysis of eggs in sediments of archeological sites often allows their taxonomic identification, this method is rarely effective at the species level, and requires both the survival of intact eggs and their proper identification. Genotyping via PCR-based approaches has the potential to achieve a precise species-level taxonomic determination. However, so far it has mostly been applied to individual eggs isolated from archeological samples. To increase the throughput and taxonomic accuracy, as well as reduce costs of genotyping methods, we adapted a PCR-based approach coupled with next-generation sequencing to perform precise taxonomic identification of parasitic helminths directly from archeological sediments. Our study of twenty-five 100 to 7,200 year-old archeological samples proved this to be a powerful, reliable and efficient approach for species determination even in the absence of preserved eggs, either as a stand-alone method or as a complement to microscopic studies.

A novel method of library construction that takes advantage of a single-stranded DNA ligase has been recently described and used to generate high-resolution genomes from ancient DNA samples. While this method is effective and appears to recover a greater fraction of endogenous ancient material, there has been no direct comparison of results from different library construction methods on a diversity of ancient DNA samples. In addition, the single-stranded method is limited by high cost and lengthy preparation time and is restricted to the Illumina sequencing platform. Here we present in-depth comparisons of the different available library construction methods for DNA purified from 16 ancient and modern faunal and human remains, covering a range of different taphonomic and climatic conditions. We further present a DNA purification method for ancient samples that permits the concentration of a large volume of dissolved extract with minimal manipulation and methodological improvements to the single-stranded method to render it more economical and versatile, in particular to expand its use to both the Illumina and the Ion Torrent sequencing platforms. We show that the single-stranded library construction method improves the relative recovery of endogenous to exogenous DNA for most, but not all, of our ancient extracts.