Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1  fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15}  g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3)  fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5  mHz we observe a low-frequency tail that stays below 12  fm s^{-2}/sqrt[Hz] down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Treatment and outcome of coronary artery perforations using a dual guiding catheter technique

OBJECTIVES

To evaluate the success rate and outcome of coronary artery perforation treatment using a dual guiding catheter technique.

BACKGROUND

Coronary artery perforation is a rare but severe complication during percutaneous coronary intervention (PCI) with high mortality. The use of a second guiding catheter is a helpful technique to minimize hemorrhage through the perforation during interventional repair.

METHODS

We screened all patients between March 2004 and December 2014 who underwent PCI in our department for the occurrence of peri-interventional coronary perforation that was treated using a dual catheter technique. Patient and lesion characteristics as well as outcome were determined.

RESULTS

We identified 8 patients who experienced coronary artery perforations (Ellis grade III) during coronary intervention and were treated using a dual guiding catheter approach. The procedure was technically successful (placement of covered stent and sealing of perforation) in 6 patients. Pericardiocentesis was required in 3 patients (38%). Total mortality was 12% (n=1). No coronary or peripheral vascular access complication occurred due to the use of a second guiding catheter.

CONCLUSIONS

We suggest that the dual guiding catheter technique is a useful and alternative approach to treat severe Ellis grade III coronary artery perforations that occur in the context of percutaneous coronary interventions.

Differential phase-noise properties of a ytterbium-doped fiber amplifier for the Laser Interferometer Space Antenna

The interferometric gravitational-wave detector Laser Interferometer Space Antenna (LISA) needs to transfer clock information among its three spacecraft in the form of phase-modulation sidebands. For this reason phase noise introduced by the optical chain between the carrier and a sideband must be low. We have measured this differential phase noise for a ytterbium-doped fiber amplifier emitting up to 2 W. For 1 W of output power as required for LISA, the measured differential phase noise was within its requirement. For 2 W output power the amplifier exhibited stimulated Brillouin scattering and showed a differential phase-noise factor of up to 15 higher. Dependencies on operating parameters and optical length noise of the amplifier were also measured.

Modulation-free sub-Doppler laser frequency stabilization to molecular iodine with a common-path, two-color interferometer

Recently, a simple common-path, two-color interferometer has been used for Doppler-free saturated dispersion spectroscopy of iodine. We have used such a set-up to stabilize a Nd:YAG laser for the first time, to our knowledge. This method requires only a small number of low-cost optical components compared to frequency modulation techniques.We have measured a root Allan variance of 5 . 10(-12) for 0.2 s, and below 5 . 10 (-11) for integration times up to 300 s.