Hierarchical modelling and X-ray analysis of human dentine and enamel

Human teeth consist of enamel, dentine and cementum, hierarchical mineralised tissues with a two-level composite structure. The understanding of the mechanical behaviour of dentine and enamel in terms of their micro- and nano-scale structure has been somewhat limited. Here we present an overview of our recent work aimed at improving the understanding of the internal lattice strain response of the mineral crystallites of different orientations under external in situ loading. A range of experimental techniques was employed for the purpose of this analysis. Small- and Wide- Angle X-ray Scattering (SAXS/WAXS) were used to determine the internal lattice strain and orientational distribution of HAp crystals, while quantitative stress distribution evaluation in the birefringent mounting epoxy surrounding the sample was carried out in parallel using photoelasticity. Finite element analysis and advanced multi-scale Eshelby inclusion modelling were used to interpret the data. The satisfactory agreement achieved between the model and the experimental data, in terms of the values of multi-directional strain components under the action of differently orientated loads, demonstrates that our multi-scale approach captures successfully the structure-property relationships between the hierarchical architecture of human dental tissues and their response to the applied forces. Our systematic approach can be used to improve the insight into the mechanical properties of dentine and enamel, and of textured hierarchical biomaterials (such as bones) in general.</p

<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data

Développement de la population nicheuse de Héron cendré

Le Héron cendré nouvellement installé en Camargue niche surtout dans les marais. La première nidification a été observée en 1964, mais ce n’est qu’à partir de 1968 que l’on peut parler d’une population nicheuse. Les recensements annuels montrent la crois sance constante de cette population (tab. I). Une nidification tardive d’une partie de la population a été observée en 1972 (fig. 1), et l’architecture des nids a été étudiée. Le sud de la France représente une étape migratoire et un lieu d’hivernage très importants pour les populations de Hérons cen drés d’Europe centrale et du Nord. 65,5 % des reprises provenant de la Suisse et de l’Allemagne laissent à penser que la population camarguaise trouverait son origine dans ces deux pays.The Camargue is the breeding ground of eight European breeding species of Ardeidae, Cattle Egret and Grey Heron being the most recent additions to the list. Grey Herons were first discovered breeding in 1964, but only established themselves as a breeding population in 1968. During the intermediate years 1965 - 1967 there was no evidence of further nesting. Annual censuses have shown a steady expansion of the population in the Camargue since 1968 (Table I). Delayed breeding recorded in 1972 was probably caused by exceptional climatic conditions in April and May (Figure 1). The composition of 110 nests has been examined, and six types of nest construction have so far been determined (Table II). No detailed study has yet been made of the prey taken by Grey Herons in the Camargue, but it would appear that fish is the predominant food. The south of France is situated on a direct south-westerly migration route for populations in central and northern Europe, and is an important wintering ground as well as a port of call for passage migrants. Ringing recoveries show that 65.5 % of birds recovered in the south of France between 1921 and 1970 came from Switzerland or Germany. This fact, together with the fact that there have been recoveries from one or other of these two countries in every month of the year, may suggest that the new breeding population in the Camargue is of Swiss or German origin, unless there is some change in the trend of movement of Grey Herons in Europe

The development of a breeding population of grey herons (Ardea Cinerea) in the Camargue

The Camargue is the breeding ground of eight European breeding species of Ardeidae, Cattle Egret and Grey Heron being the most recent additions to the list. Grey Herons were first discovered breeding in 1964, but only established themselves as a breeding population in 1968. During the intermediate years 1965 -1967 there was no evidence of further nesting. Annual censuses have shown a steady expansion of the population in the Camargue since 1968 (Table I). Delayed breeding recorded in 1972 was probably caused by exceptional climatic conditions in April and May (Figure 1). The composition of 110 nests has been examined, and six types of nest construction have so far been determined (Table II). No detailed study has yet been made of the prey taken by Grey Herons in the Camargue, but it would appear that fish is the predominant food. The south of France is situated on a direct south-westerly migration route for populations in central and northern Europe, and is an important wintering ground as well as a port of call for passage migrants. Ringing recoveries show that 65.5 % of birds recovered in the south of France between 1921 and 1970 came from Switzerland or Germany. This fact, together with the fact that there have been recoveries from one or other of these two countries in every month of the year, may suggest that the new breeding population in the Camargue is of Swiss or German origin, unless there is some change in the trend of movement of Grey Herons in Europe.Le Héron cendré nouvellement installé en Camargue niche surtout dans les marais. La première nidification a été observée en 1964, mais ce n’est qu’à partir de 1968 que l’on peut parler d’une population nicheuse. Les recensements annuels montrent la croissance constante de cette population (tab. I). Une nidification tardive d’une partie de la population a été observée en 1972 (fig. 1), et l’architecture des nids a été étudiée. Le sud de la France représente une étape migratoire et un lieu d’hivernage très importants pour les populations de Hérons cendrés d’Europe centrale et du Nord. 65,5 % des reprises provenant de la Suisse et de l’Allemagne laissent à penser que la population camarguaise trouverait son origine dans ces deux pays.Walmsley J.G. The development of a breeding population of grey herons (Ardea Cinerea) in the Camargue. In: La Terre et La Vie, Revue d'Histoire naturelle, tome 29, n°1, 1975. pp. 89-99

The Graduating European Dentist: Contemporaneous Methods of Teaching, Learning and Assessment in Dental Undergraduate Education

It is often the case that good teachers just “intuitively” know how to teach. Whilst that may be true, there is now a greater need to understand the various processes that underpin both the ways in which a curriculum is delivered, and the way in which the students engage with learning; curricula need to be designed to meet the changing needs of our new graduates, providing new, and robust learning opportunities, and be communicated effectively to both staff and students. The aim of this document is to draw together robust and contemporaneous methods of teaching, learning and assessment that help to overcome some of the more traditional barriers within dental undergraduate programmes. The methods have been chosen to map specifically to The Graduating European Dentist, and should be considered in parallel with the benchmarking process that educators and institutions employ locally. © 2017 John Wiley &amp; Sons A/S. Published by John Wiley &amp; Sons Lt