Nanosecond X-Ray Photon Correlation Spectroscopy on Magnetic Skyrmions.

We report an x-ray photon correlation spectroscopy method that exploits the recent development of the two-pulse mode at the Linac Coherent Light Source. By using coherent resonant x-ray magnetic scattering, we studied spontaneous fluctuations on nanosecond time scales in thin films of multilayered Fe/Gd that exhibit ordered stripe and Skyrmion lattice phases. The correlation time of the fluctuations was found to differ between the Skyrmion phase and near the stripe-Skyrmion boundary. This technique will enable a significant new area of research on the study of equilibrium fluctuations in condensed matter.

The fluctuation-dissipation measurement instrument at the Linac Coherent Light Source.

The development of new modes at x-ray free electron lasers has inspired novel methods for studying fluctuations at different energies and timescales. For closely spaced x-ray pulses that can be varied on ultrafast time scales, we have constructed a pair of advanced instruments to conduct studies targeting quantum materials. We first describe a prototype instrument built to test the proof-of-principle of resonant magnetic scattering using ultrafast pulse pairs. This is followed by a description of a new endstation, the so-called fluctuation-dissipation measurement instrument, which was used to carry out studies with a fast area detector. In addition, we describe various types of diagnostics for single-shot contrast measurements, which can be used to normalize data on a pulse-by-pulse basis and calibrate pulse amplitude ratios, both of which are important for the study of fluctuations in materials. Furthermore, we present some new results using the instrument that demonstrates access to higher momentum resolution.

Case report: revision anterior cruciate ligament reconstruction.

A case report is presented in which a professional football player, who was 4 years status post anterior cruciate ligament (ACL) reconstruction with autogenous patellar tendon, ruptured his graft. The contralateral patellar tendon was not available as a graft because of a more recent ACL reconstruction using that autogenous patellar tendon. This case reports the use of a previous donor site for supplying a patellar tendon autograft. Biopsy of the donor graft was consistent with normal tendon. The use of a healed patellar tendon donor site is a viable option for revision anterior cruciate reconstructive surgery. This option prevents the possibility of disease transmission with use of an allograft. We have shown grossly and histologically that the donor site has the potential to regenerate to tissue that has the appearance of normal tendon. This option could be available for revision surgery, but would not be recommended if the initial surgery was < 18 months-2 years in the past.

Localization of the acromioclavicular joint.

Localizing the acromioclavicular joint can be difficult. Using bony landmarks--the clavicle and the spine of the scapula--the acromioclavicular joint can be consistently localized for physical examination, injections, and surgery.