Active SU(1,1) atom interferometry

Active interferometers use amplifying elements for beam splitting and recombination. We experimentally implement such a device by using spin exchange in a Bose-Einstein condensate. The two interferometry modes are initially empty spin states that get spontaneously populated in the process of parametric amplification. This nonlinear mechanism scatters atoms into both modes in a pairwise fashion and generates a nonclassical state. Finally, a matched second period of spin exchange is performed that nonlinearly amplifies the output signal and maps the phase onto readily detectable first moments. Depending on the accumulated phase this nonlinear readout can reverse the initial dynamics and deamplify the entangled state back to empty spin states. This sequence is described in the framework of SU(1,1) mode transformations and compared to the SU(2) angular momentum description of passive interferometers.Comment: 10 pages, 6 figures; invited article for Quantum Science and Technolog

Influence of Different Strain Rates on the Flow Curve and the Formability of Thin Aluminium and Tinplate Sheets

Due to this high number of produced units and the very thin sheet metals used for beverage cans, precise production processes with high production volumes are necessary. To save expenses, while optimising these processes, numerical simulation methods are exploited. Considering this, it is indispensable to identify the material behaviour as exactly as possible. In practise, often results of quasi static tensile tests are used, although these are insufficient for the precise modelling of the material behaviour during can production, since strain rates of up to 10³ s-1 can occur, here. Therefore, quasi static and high speed tensile test have been done on specimens featuring the typical materials and thicknesses of semi-finished parts used for beverage can production. The results were compared with similar materials at higher sheet metal thicknesses and authenticated by numerical simulation. It was shown that there is an influence of the strain rate on the material behaviour and it is necessary to determine material characteristics at strain rates, which are close to the process speed. Furthermore, the results were classified in their signification for beverage can production and forming technologies in general

Lifetime determination of excited states in Cd-106

Two separate experiments using the Differential Decay Curve Method have been performed to extract mean lifetimes of excited states in 106 Cd. The inedium-spin states of interest were populated by the Mo-98(C-12, 4n) Cd-106 reaction performed at the Wright Nuclear Structure Lab., Yale University. From this experiment, two isomeric state mean lifetimes have been deduced. The low-lying states were populated by the Mo-96(C-13, 3n)Cd-106 reaction performed at the Institut fur Kernphysik, Universitat zu Koln. The mean lifetime of the I-pi = 2(1)(+) state was deduced, tentatively, as 16.4(9) ps. This value differs from the previously accepted literature value from Coulomb excitation of 10.43(9) ps

Повседневность первобытного человека

Seven samples of Siluro-Devonian sedimentary rocks from the Cantabrian and Central Iberian zones of the Iberian Variscan belt have been investigated for provenance and contain four main age populations in variable relative proportion: Ediacaran–Cryogenian (c. 0.55–0.8Ga), Tonian–Stenian (0.85–1.2Ga), Palaeoproterozoic (c. 1.8–2.2Ga) and Archaean (c. 2.5–3.3Ga). Five samples contain very minor Palaeozoic (Cambrian) zircons and six samples contain minor but significant zircons of Middle and Early Mesoproterozoic (Ectasian–Calymmian, 1.6–1.8) age. These data highlight the transition from an arc environment to a stable platform following the opening of the Rheic Ocean. Variations in detrital zircon populations in Middle–Late Devonian times reflect the onset of Variscan convergence between Laurussia and Gondwana. The presence of a high proportion of zircons of Tonian–Stenian age in Devonian sedimentary rocks may be interpreted as (1) the existence of a large Tonian–Stenian arc terrane exposed in the NE African realm (in or around the Arabian–Nubian Shield), (2) the participation, from the Ordovician time, of a more easterly alongshore provenance of Tonian–Stenian zircons, and (3) an increase in the relative proportion of Tonian–Stenian zircons with respect to the Ediacaran–Cryogenian population owing to the drift of the Avalonian–Cadomian ribbon continent, or the progressive burial of Ediacaran–Cryogenian rocks coeval with the denudation of older source rocks from the craton interior