Vector constants of motion for time-dependent Kepler and isotropic harmonic oscillator potentials

A method of obtaining vector constants of motion for time-independent as well as time-dependent central fields is discussed. Some well-established results are rederived in this alternative way and new ones obtained.Comment: 18 pages, no figures, regular Latex article forma

Decoherence-protected memory for a single-photon qubit

The long-lived, efficient storage and retrieval of a qubit encoded on a photon is an important ingredient for future quantum networks. Although systems with intrinsically long coherence times have been demonstrated, the combination with an efficient light-matter interface remains an outstanding challenge. In fact, the coherence times of memories for photonic qubits are currently limited to a few milliseconds. Here we report on a qubit memory based on a single atom coupled to a high-finesse optical resonator. By mapping and remapping the qubit between a basis used for light-matter interfacing and a basis which is less susceptible to decoherence, a coherence time exceeding 100 ms has been measured with a time-independant storage-and-retrieval efficiency of 22%. This demonstrates the first photonic qubit memory with a coherence time that exceeds the lower bound needed for teleporting qubits in a global quantum internet.Comment: 3 pages, 4 figure

Growing Faults in the Lab: Insights into the Scale Dependence of the Fault Zone Evolution Process

Analog sandbox experiments are a widely used method to investigate tectonic processes that cannot be resolved from natural data alone, such as strain localization and the formation of fault zones. Despite this, it is still unclear, to which extent the dynamics of strain localization and fault zone formation seen in sandbox experiments can be extrapolated to a natural prototype. Of paramount importance for dynamic similarity is the proper scaling of the work required to create the fault system, Wprop. Using analog sandbox experiments of strike-slip deformation, we show Wprop to scale approximately with the square of the fault system length, l, which is consistent with the theory of fault growth in nature. Through quantitative measurements of both Wprop and strain distribution we are able to show that Wprop is mainly spent on diffuse deformation prior to localization, which we therefore regard as analogous to distributed deformation on small-scale faults below seismic resolution in natural fault networks. Finally, we compare our data to estimates of the work consumed by natural fault zones to verify that analog sandbox experiments scale properly with respect to energy, i. e. that they scale truly dynamically

The use of invasive techniques, angiography and indicator dilution, for quantification of valvular regurgitations

Angiographic techniques have been used for the quantification of mitral or aortic and rarely tricuspid regurgitation. Mitral or aortic regurgitant volume per beat and the regurgitation fraction (fao and fm, respectively) are obtained from the angiographic determination of total left ventricular stroke volume (TSV) and forward stroke volume (FSV) estimated by a different technique. Although this procedure is generally accepted as the gold standard for quantification of left heart regurgitations, there are several limitations: In the presence of mitral and aortic regurgitation no separate quantification of fao and fm is feasible; heart rate at the time of determination of FSV (from Fick or dye dilution cardiac output) and of TSV (angio) may be different; there is a tendency to consistently overestimate stroke volume by angio techniques; repeated estimations of TSV by angio are influenced by the circulatory effects of the contrast dye. In contrast indicator dilution techniques, where upstream and downstream sampling allow the simultaneous estimation of forward and regurgitant flow, the accuracy of the determination of FSV is well established and repeated estimations of fao and fm are possible because the indicators do not have cardiovascular effects. These methods are, however, crucially dependent on thorough mixing of the regurgitant volume with the blood in the upstream chamber. In 23 patients with isolated aortic regurgitation there was a positive correlation between fao evaluated by thermodilution and fao determined by the biplane angio-Fick method (r = 0.59). fao by thermodilution averaged 0.40 and fao by angio-Fick 0.46 (NS). In 23 patients with isolated mitral regurgitation there was also a positive correlation between fm determined by thermodilution and fm determined by angio-Fick (r = 0.71). However, fm by thermodilution was consistently smaller than fm by angio-Fick (average values 0.45 and 0.55, respectively, P < 0.005

Graphene on Si(111)7x7

We demonstrate that it is possible to mechanically exfoliate graphene under ultra high vacuum conditions on the atomically well defined surface of single crystalline silicon. The flakes are several hundred nanometers in lateral size and their optical contrast is very faint in agreement with calculated data. Single layer graphene is investigated by Raman mapping. The G and 2D peaks are shifted and narrowed compared to undoped graphene. With spatially resolved Kelvin probe measurements we show that this is due to p-type doping with hole densities of n_h \simeq 6x10^{12} cm^{-2}. The in vacuo preparation technique presented here should open up new possibilities to influence the properties of graphene by introducing adsorbates in a controlled way.Comment: 8 pages, 7 figure

Geant4 Simulation of a filtered X-ray Source for Radiation Damage Studies

Geant4 low energy extensions have been used to simulate the X-ray spectra of industrial X-ray tubes with filters for removing the uncertain low energy part of the spectrum in a controlled way. The results are compared with precisely measured X-ray spectra using a silicon drift detector. Furthermore, this paper shows how the different dose rates in silicon and silicon dioxide layers of an electronic device can be deduced from the simulations

A non-apoptotic role for caspase-9 in muscle differentiation

Caspases, a family of cysteine proteases most often investigated for their roles in apoptosis, have also been demonstrated to have functions that are vital for the efficient execution of cell differentiation. One such role that has been described is the requirement of caspase-3 for the differentiation of skeletal myoblasts into myotubes but, as yet, the mechanism leading to caspase-3 activation in this case remains elusive. Here, we demonstrate that caspase-9, an initiator caspase in the mitochondrial death pathway, is responsible for the activation of caspase-3 in differentiating C2C12 cells. Reduction of caspase-9 levels, using an shRNA construct, prevented caspase-3 activation and inhibited myoblast fusion. Myosin-heavy-chain expression, which accompanies myoblastic differentiation, was not caspase-dependent. Overexpression of Bcl-xL, a protein that inhibits caspase-9 activation, had the same effect on muscle differentiation as knockdown of caspase-9. These data suggest that the mitochondrial pathway is required for differentiation; however, the release of cytochrome c or Smac (Diablo) could not be detected, raising the possibility of a novel mechanism of caspase-9 activation during muscle differentiation.</jats:p