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The design and features of a beamline control software system for macromolecular crystallography (MX) experiments developed at the European Synchrotron Radiation Facility (ESRF) are described. This system, MxCuBE, allows users to easily and simply interact with beamline hardware components and provides automated routines for common tasks in the operation of a synchrotron beamline dedicated to experiments in MX. Additional functionality is provided through intuitive interfaces that enable the assessment of the diffraction characteristics of samples, experiment planning, automatic data collection and the on-line collection and analysis of X-ray emission spectra. The software can be run in a tandem client-server mode that allows for remote control and relevant experimental parameters and results are automatically logged in a relational database, ISPyB. MxCuBE is modular, flexible and extensible and is currently deployed on eight macromolecular crystallography beamlines at the ESRF. Additionally, the software is installed at MAX-lab beamline I911-3 and at BESSY beamline BL14.1.

Several acquisitions of X-ray microtomography have been performed on a beads packing while it compacts under vertical vibrations. An image analysis allows to study the evolution of the packing structure during its progressive densification. In particular, the volume distribution of the pores reveals a large tail, compatible to an exponential law, which slowly reduces as the system gets more compact. This is quite consistent, for large pores, with the free volume theory. These results are also in very good agreement with those obtained by a previous numerical model of granular compaction.

Résumé -Évolution des paramètres hydrauliques et de la microgéométrie d'un calcaire pendant sa dissolution par une eau acide -Nous reportons dans cet article les résultats d'une expérience de percolation réactive menée, à température ambiante, dans un calcaire poreux par une eau saturée en CO 2 à la pression partielle de 0,1 MPa, afin d'évaluer les relations entre la chimie de l'eau et les modifications hydrodynamiques et structurales de l'échantillon. Une méthode d'analyse, basée sur l'utilisation répétée de l'imagerie microtomographique à rayons X, a été développée pour suivre en détail l'évolution de la structure et de l'interface fluide-solide de l'échantillon, tandis que sa porosité et sa perméabilité augmentaient au cours de sa dissolution. Plusieurs mécanismes à l'origine de l'augmentation rapide de la perméa-bilité ont été identifiés. Au début de l'expérience, cette augmentation a été reliée à la dissolution et à la migration concomitantes de particules carbonatées. Ensuite, la perméabilité a continué d'augmenter par suite de la dissolution des aspérités à l'interface fluide-solide, et de l'accroissement de la connectivité du réseau poral. Abstract -Hydraulic Properties and Microgeometry Evolution Accompanying Limestone Dissolution By Acidic Water -A reactive flow-through experiment by carbon dioxide-saturated water at the partial pressure of 0.1 MPa and room temperature was conducted on a porous limestone in order to identify the relationships between fluid chemistry, hydrodynamics and structural properties. Periodic imaging by nondestructive X-ray microtomography allowed following the evolution of the core micro-geometry and fluid-rock interface in detail while its porosity and permeability increased due to dissolution. Several mechanisms were successively involved in the rapid permeability increase. Early in the experiment, the permeability increase was related to concomitant particle dissolution and displacement. Later on, permeability continued to rise due to solid-fluid interface smoothing and to pore connectivity increase.

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