A drop does not fall in a straight line: a rationale for the width of stalagmites.

Drops loaded in calcium ions detach from stalactites and impact the underlying stalagmites, thereby allowing these latter to grow through calcite precipitation. Nevertheless, little is known about the influence of the drop free fall and splash dynamics on stalagmite shape and width. Through high-speed imaging of impacting drops on stalagmites from several caves, we observed that the impact point position of the drops is scattered, sometimes over several centimetres. We show that this dispersal has no external cause and must, therefore, be self-induced. Using a Langevin-like equation, we then propose a prediction of the impact point dispersal as a function of the falling height travelled by the drops. We finally show that measured stalagmite widths are correlated to the dispersal in the impact point position of the drop.

Conservation of prehistoric caves and stability of their inner climate: lessons from Chauvet and other French caves.

In the last 150 years, some prehistoric painted caves suffered irreversible degradations due to misperception of conservation issues and subsequent mismanagement. These sites presented naturally an exceptional stability of their internal climate allowing conservation in situ of outstanding fragile remains, some for nearly 40,000 years. This is for a large part due to exchanges of air, CO2, heat and water with the karstic system in which these caves are included. We introduce the concept of underground confinement, based on the stability of the inner cave climate parameters, especially its temperature. Confined caves present the best conservative properties. It is emphasized that this confined state implies slow exchanges with the surrounding karst and that a stable cave cannot be viewed as a closed system. This is illustrated on four case studies of French caves of various confinement states evidenced by long term continuous monitoring and on strategies to improve their conservation properties. The Chauvet cave presents optimal conservation properties. It is wholly confined as shown by the stability of its internal parameters since its discovery in 1994. In Marsoulas cave, archeological works removed the entrance scree and let a strong opening situation of the decorated zone. Remediation is expected by adding a buffer structure at the entrance. In Pech Merle tourist cave, recurrent painting fading was related to natural seasonal drying of walls. Improvement of the cave closure system restored a confined state insuring optimal visibility of the paintings. In Gargas tourist cave, optimization of closures, lighting system and number of visitors, allowed it to gradually reach a semi-confined state that improved the conservation properties. Conclusions are drawn on the characterization of confinement state of caves and on the ways to improve their conservation properties by restoring their initial regulation mechanisms and to avoid threats to their stability.

Effects of electron beam irradiation on the migration of antioxidants and their degradation products from commercial polypropylene into food simulating liquids.

The influence of electron beam irradiation on migrational behaviour of additives present in food packaging material was studied. The migration experiments were carried out on irradiated and non-irradiated polypropylene pouches containing aqueous food simulating liquids (FSL) for 10 days at 40 degrees C. The controls were irradiated and non-irradiated pouches without FSL contact. After the contact period, the polypropylene and the FSL were analysed. A comparison between the results obtained by the two analyses showed the migration of three products of antioxidant degradation from the polypropylene into the FSL, and a partial decomposition of these migrants in the FSL.

Expression of a subclass of human blood group A antigenicity in A+ rabbit jejunum: specific glycosylation of the glycocalyx and a 140 K brush border glycoprotein.

A monoclonal antibody (14 A4) raised against human A erythrocytes has been produced. It specifically reacts with a subclass of human blood group A determinants. Whereas all the major secreted and membrane-bound glycoproteins of A+ rabbit jejunum epithelium bear human blood group A-like determinants recognized by anti-A polyclonal serum or a monoclonal antibody with broad specificity (Cl 3.3), expression of the A-subclass recognized by 14 A4 is very restricted. The contents of secretory granules of Paneth cells but not the mucins of goblet cells were labeled by 14 A4. In the enterocytes, glycans recognized by 14 A4 were present in the glycocalyx, on an early expressed 140 K glycoprotein of brush border membranes and also on a glycoconjugate of the basolateral membrane of immature crypt cells. In the jejunal brush border membrane of blood group A secretor humans, only one glycoprotein of molecular weight 140 K bears the A-subclass recognized by 14 A4.