Constraining Cosmological Phase Transitions with the Parkes Pulsar Timing Array.

A cosmological first-order phase transition is expected to produce a stochastic gravitational wave background. If the phase transition temperature is on the MeV scale, the power spectrum of the induced stochastic gravitational waves peaks around nanohertz frequencies, and can thus be probed with high-precision pulsar timing observations. We search for such a stochastic gravitational wave background with the latest data set of the Parkes Pulsar Timing Array. We find no evidence for a Hellings-Downs spatial correlation as expected for a stochastic gravitational wave background. Therefore, we present constraints on first-order phase transition model parameters. Our analysis shows that pulsar timing is particularly sensitive to the low-temperature (T∼1-100 MeV) phase transition with a duration (ß/H_{*})^{-1}∼10^{-2}-10^{-1} and therefore can be used to constrain the dark and QCD phase transitions.

Clinical evidence shows no difference between single- and double-row repair for rotator cuff tears.

Tears of the rotator cuff may be repaired by single- or double-row techniques. Single-row methods do not restore the rotator cuff footprint but do provide a good functional outcome. We surveyed the literature to ascertain the origin of the current trend of using double-row methods of repair. The footprint repair is a benefit of double-row fixation with strong evidence of its biomechanical success. However, the functional outcome of double-row fixation is equivalent to single-row fixation. Given the lack of scientific evidence and despite the enthusiasm of surgeons for this new technique, single-row fixation remains an acceptable method for managing these injuries, and it is our opinion that it is the preferable method.