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Tourism is a growing concern for the conservation of heritage sites. In the Dordogne, the Cap Blanc shelter attracts many visitors and their presence may affect its parietal frieze by altering the thermal environment. To assess this impact, a study is carried out using numerical simulation, a non-intrusive conservation tool that can model the thermal behaviour of the cavity during tourist visits. We validate the numerical model with the temperature measurements taken inside the shelter during three tourist visits. We show that the heat emitted by the tourists is mostly absorbed by the walls, resulting in a small increase in air temperature (between 1°C and 2°C) and a large temperature gradient near the walls during the visits, which favours condensation and possible conservation problems. [ABSTRACT FROM AUTHOR]

The goal of data classification is to organize them into relevant groups using algorithms. In this study, two clustering algorithms are applied to classify a set of geophysical measurements performed around the Lascaux Cave (Dordogne, France). Based on a non-destructive geophysical method, electrical resistivity tomography (ERT), the data (resistivity values) are supposed to characterize the rock mass around the cave. The rock mass must be divided into an optimal number of homogeneous domains with specific thermal properties to integrate them in the future thermo-aeraulic simulations of the cave. Since the data are georeferenced, a given resistivity cluster corresponds to a specific spatial domain of the rock mass. This study aims to compare two different clustering methods, the Hierarchical Agglomerative Clustering (HAC) and the K-means methods, on the resistivity data set. Thus, the objective of this study is to determine which of the two methods leads to a partition of the massif with an optimal number of classes, allowing us to find the geological structures partially known thanks to previous studies. The results of these methods are analyzed in light of two different indices, the Silhouette Index (SI) and the Coefficient of Variation (CV). Based on these indices alone, K-means might seem to be the best algorithm, but a fine analysis of each cluster shows that the HAC method gives better results. Indeed, only the HAC method highlights areas already known to be either waterlogged or clayey. Our partial geological knowledge, which is of paramount importance in such a study, also supports the choice of the HAC method. [ABSTRACT FROM AUTHOR]

The fundamental physical constants are at the root of physics theories, but no theoretical framework provides their experimental values. In addition, they are assumed to be independent of each other. Here, we present two valuable dimensionless numbers based on vacuum properties and fundamental constants. The value of these dimensionless numbers provokes questioning, since they are of order 101. In particular, they mean that it is possible to build a velocity and a parameter homogeneous to the Planck constant of the same order as the speed of light and the Planck constant respectively, only based on five well-known physical parameters. These formulas are very unlikely to be two coincidences and suggest that the parameters involved depend on each other. They also seem to indicate that light is a material wave and quantum mechanics is a deterministic theory. A link between these numbers and the fine-structure constant is also established. [ABSTRACT FROM AUTHOR]

Water migration within the rock mass during a fire has not yet been studied. Here, an innovative high-resolution micro-ERT method is developed at a centimetric scale to measure this phenomenon. The method is two-step based: first, a correction of the electrode effect, and second, the correction of resistivity for rapid variations in temperature with high values. Water migration is successfully described within the wall of an underground limestone quarry with three phases: from fire ignition to 36 min, the surface dries to a 3-cm depth and a higher saturated layer forms deeper than 0.10 m; from 36 min to 46 min (fire supply stops), the rock dries out and water migrates from deeper parts of the rock wall, deeper than 20 cm, towards the surface; finally, after fire extinction, the water migrates through a readjustment phase until it returns to its initial state. [ABSTRACT FROM AUTHOR]

Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of painted caves, with respect to parameters such as its geological stage, the presence of water and carbon dioxide, the geological state of its walls, and the size of the cave. These wall states are studied to better understand the conditions of conservation of rock art caves without damaging them. The choice of an equivalent medium, i.e., a non-painted cave, was made to be able to conduct experiments or take measurements that would not have been possible in a rock art cave. The climatic conditions (temperature, hygrometry, etc.) monitored since 2011 are central to our understanding of the genesis and evolution of wall states. Leye Cave is sub-horizontal then descendant, forming a cold air trap. The phenomenon of condensation is thought to be important in the genesis of these wall states. Our article presents a model which describes the competition that exists between the conduction of the rock heating the air and the convection cooling the rock, in the area named the "Throne Chamber", located in the deepest parts of the cave. [ABSTRACT FROM AUTHOR]