9,219 research outputs found
Spatially resolved photo ionization of ultracold atoms on an atom chip
We report on photo ionization of ultracold magnetically trapped Rb atoms on
an atom chip. The atoms are trapped at 5 K in a strongly anisotropic
trap. Through a hole in the chip with a diameter of 150 m two laser beams
are focussed onto a fraction of the atomic cloud. A first laser beam with a
wavelength of 778 nm excites the atoms via a two photon transition to the 5D
level. With a fiber laser at 1080 nm the excited atoms are photo ionized.
Ionization leads to depletion of the atomic density distribution observed by
absorption imaging. The resonant ionization spectrum is reported. The setup
used in this experiment is not only suitable to investigate BEC ion mixtures
but also single atom detection on an atom chip
Quantum-degenerate mixture of fermionic lithium and bosonic rubidium gases
We report on the observation of sympathetic cooling of a cloud of fermionic
6-Li atoms which are thermally coupled to evaporatively cooled bosonic 87-Rb.
Using this technique we obtain a mixture of quantum-degenerate gases, where the
Rb cloud is colder than the critical temperature for Bose-Einstein condensation
and the Li cloud colder than the Fermi temperature. From measurements of the
thermalization velocity we estimate the interspecies s-wave triplet scattering
length |a_s|=20_{-6}^{+9} a_B. We found that the presence of residual rubidium
atoms in the |2,1> and the |1,-1> Zeeman substates gives rise to important
losses due to inelastic collisions.Comment: 4 pages, 3 figure
The evolution of the jet from Herbig Ae star HD 163296 from 1999 to 2011
Young A and B stars, the so-called Herbig Ae/Be stars (HAeBe), are surrounded
by an active accretion disk and drive outflows. We study the jet HH 409, which
is launched from the HAeBe star HD 163296, using new and archival observations
from Chandra and HST/STIS. In X-rays we can show that the central source is not
significantly extended. The approaching jet, but not the counter-jet, is
detected in Ly alpha. In addition, there is red-shifted Ly alpha emission
extended in the same direction as the jet, that is also absent in the
counter-jet. We can rule out an accretion or disk-wind origin for this feature.
In the optical we find the knots B and B2 in the counter-jet. Knot B has been
observed previously, so we can derive its proper motion of 0.37+-0.01
arcsec/yr. Its electron density is 3000/cm^3, thus the cooling time scale is a
few months only, so the knot needs to be reheated continuously. The shock speed
derived from models of H alpha and forbidden emission lines (FELs) decreased
from 50 km/s in 1999 to 30 km/s in 2011 because the shock front loses energy as
it travels along the jet. Knot B2 is observed at a similar position in 2011 as
knot B was in 1999, but shows a lower ionization fraction and higher mass loss
rate, proving variations in the jet launching conditions.Comment: 14 pages, 8 figures, accepted by A&
Constancy of Expression of the Protein Kinase A Regulatory Subunit Rla in Hepatoma Cell Lines of Different Phenotypes
Combined rock slope stability and shallow landslide susceptibility assessment of the Jasmund cliff area (Rügen Island, Germany)
In this contribution we evaluated both the structurally-controlled failure susceptibility of the fractured Cretaceous chalk rocks and the topographically-controlled shallow landslide susceptibility of the overlying glacial sediments for the Jasmund cliff area on Rügen Island, Germany. We employed a combined methodology involving spatially distributed kinematical rock slope failure testing with tectonic fabric data, and both physically- and inventory-based shallow landslide susceptibility analysis. The rock slope failure susceptibility model identifies areas of recent cliff collapses, confirming its value in predicting the locations of future failures. The model reveals that toppling is the most important failure type in the Cretaceous chalk rocks of the area. The shallow landslide susceptibility analysis involves a physically-based slope stability evaluation which utilizes material strength and hydraulic conductivity data, and a bivariate landslide susceptibility analysis exploiting landslide inventory data and thematic information on ground conditioning factors. Both models show reasonable success rates when evaluated with the available inventory data, and an attempt was made to combine the individual models to prepare a map displaying both terrain instability and landslide susceptibility. This combination highlights unstable cliff portions lacking discrete landslide areas as well as cliff sections highly affected by past landslide events. Through a spatial integration of the rock slope failure susceptibility model with the combined shallow landslide assessment we produced a comprehensive landslide susceptibility map for the Jasmund cliff area
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