Laser cooling and magnetic trapping at several tesla

Laser cooling and magnetic trapping of (85)Rb atoms have been performed in extremely strong and tunable magnetic fields, extending these techniques to a new regime and setting the stage for a variety of cold atom and plasma experiments. Using a superconducting Ioffe-Pritchard trap and an optical molasses, 2.4 x 10(7) atoms were laser cooled to the Doppler limit and magnetically trapped at bias fields up to 2.9 T. At magnetic fields up to 6 T, 3 x 10(6) cold atoms were laser cooled in a pulsed loading scheme. These bias fields are well beyond an order of magnitude larger than those in previous experiments. Loading rates, molasses lifetimes, magnetic-trapping times, and temperatures were measured using photoionization and electron detection.     

Morphing of curved corrugated shells

Thin sheet materials of low bending stiffness but high membrane stiffness are often corrugated in order to achieve improvements of several orders of magnitude in bending stiffness with only minimal increases in weight and cost. If these corrugated sheets are initially curved along the corrugations, much of this stiffness gain is lost. In return, the sheets are then capable of significant elastic changes in shape overall, including large changes in overall Gaussian curvature. These shape changes are described here by non-linear and coupled kinematical relationships, which are verified against experiment and finite-element simulations. It is found that gross simplifications can be made about the large displacement behaviour of such shells without a loss of accuracy.     

Preface

The International Conference on Group Theory and Related Topics, sponsored by Xuzhou Normal University, was held from April 19 to 25, 2008. The conference was cosponsored by Science in China Press and supported by National Natural Science Foundation of China, a Key Subject Foundation of Province Jiangsu of China and Xuzhou Normal University.     

MECHANISMS OF THE ICOSAHEDRAL COMPOUND OF TEN TETRAHEDRA

Ten regular tetrahedra can be arranged in such a way that their vertices are coincident with the vertices of a regular dodecahedron and that two tetrahedra meet at each vertex of the dodecahedron. If the resultant structure is considered as a bar-and-joint structure, there will be 60 bars, lying along the edges of the tetrahedra, and 20 joints at the vertices of the dodecahedra; six bars meet at each joint. Although the structure more than satisfies Maxwell's rule, it is known to admit finite mechanisms. Recently, a new method for detecting symmetric finite mechanisms in symmetric bar-and-node structures has been developed. The method only requires a count of the number of bars, and the number of nodes, that are left unmoved by each of the symmetry operations allowable for the structure. This paper will describe the application of this method to the structure described above. The structure has icosahedral symmetry, I _h , and the analysis confirms the existence of the mechanisms with C _3v and C _5v symmetry that have previously been detected using ad-hoc methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Gasuntersuchungen

Ohne Zusammenfassung