PARTICLE TRAJECTORIES AND THE PERCEPTION OF CLASSICAL MOTION IN THE FREE PROPAGATION OF WAVE PACKETS.

The free propagation in time of a normalisable wave packet is the oldest problem of continuum quantum mechanics. Its motion from microscopic to macroscopic distance is the way in which most quantum systems are detected experimentally. Although much studied and analysed since 1927 and presented in many text books, here the problem is re-appraised from the standpoint of semi-classical mechanics. Particular aspects are the emergence of deterministic trajectories of particles emanating from a region of atomic dimensions and the interpretation of the wave function as describing a single particle or an ensemble of identical particles. Of possible wave packets, that of gaussian form is most studied due to the simple exact form of the time-dependent solution in real and in momentum space. Furthermore, this form is important in laser optics. Here the equivalence of the time-dependent Schroedinger equation to the paraxial equation for the propagation of light is demonstrated explicitly. This parallel helps to understand the relevance of trajectory concepts and the conditions necessary for the perception of motion as classical.

Three-Dimensional Assessment of Bronchiectasis in a Mouse Model of Mucociliary Clearance Disorder

Bronchiectasis is a chronic pulmonary disease affecting the conducting air ways of the lung, which may result from congenital disorders that affect ciliary motility. The disease is being recognised with increasing frequency around the world. Patients with bronchiectasis show permanent enlargement of peripheral bronchi accompanied by repeated respiratory infections, disabling productive cough and shortness of breath, resulting in loss of lung function. Mouse models of reduced mucociliary clearance have failed to display signs of bronchiectasis in multiple studies, hindering the development of targeted therapies. In this brief report we present the detection and quantification of bronchiectasis in TAp73 knockout mice using synchrotron radiation-based free-propagation phase contrast CT imaging, allowing the study of bronchiectasis in a pre-clinical and translational setting for the assessment of novel treatment strategies.Clinical Relevance: Murine models of reduced mucociliary clearance have been established to investigate their pathobiology and develop novel treatment approaches but failed to develop visible airway enlargements. Synchrotron free-propagation phase contrast CT imaging is an innovative, sensitive, non-destructive in-situ technique, that allows for three-dimensional ultra-high-resolution detection of bronchiectasis in murine models of impaired mucociliary clearance.