Non-Hermitian Phase Transition from a Polariton Bose-Einstein Condensate to a Photon Laser.

We propose a novel mechanism for a nonequilibrium phase transition in a U(1)-broken phase of an electron-hole-photon system, from a Bose-Einstein condensate of polaritons to a photon laser, induced by the non-Hermitian nature of the condensate. We show that a (uniform) steady state of the condensate can always be classified into two types, namely, arising either from lower or upper-branch polaritons. We prove (for a general model) and demonstrate (for a particular model of polaritons) that an exceptional point where the two types coalesce marks the end point of a first-order-like phase boundary between the two types, similar to a critical point in a liquid-gas phase transition. Since the phase transition found in this paper is not in general triggered by population inversion, our result implies that the second threshold observed in experiments is not necessarily a strong-to-weak-coupling transition, contrary to the widely believed understanding. Although our calculation mainly aims to clarify polariton physics, our discussion is applicable to general driven-dissipative condensates composed of two complex fields.

Partial lateral patellar facetectomy as an alternative to lateral release in Total Knee Arthroplasty (TKA).

This study presents the selective use of partial patellar lateral facetectomy for maltracking during primary TKA, as an alternative to lateral release. Twenty three partial facetectomies were performed out of 191 TKAs (12%). Balanced tracking was achieved in 22 knees. At follow-up 2 patients had persistent anterior knee pain. Mean Knee Society score (KSS) was 94 and mean functional KSS was 86. Mean patellar score was 28. Patellar tilt angles were within 2 degrees in all but one knee. Patellar translation was within 2 mm in all cases. No complications were recorded. A control group of 46 matched patients had similar functional and radiographic results. If tracking is not satisfactory at the conclusion of TKA, our method of choice would be partial lateral facetectomy.

Monte Carlo renormalization-group analysis of percolation.

We describe a Monte Carlo renormalization group approach to the calculation of critical behavior for percolation models. This approach can be utilized to determine the renormalized bond probabilities and the values of the critical exponents. We illustrate the method for two-dimensional bond percolation, but the method is also applicable to other percolation models and other dimensions.

Pseudallescheria boydii infection of a prosthetic hip joint--an uncommon infection in a rare location.

Pseudallescheria boydii infection of the hip joint was diagnosed 2.5 years after implantation of a prosthetic joint in a woman with rheumatoid arthritis. Cure was achieved with a 10-month course of voriconazole coupled with removal of the prosthesis and repeat surgical debridement. Pseudallescheria boydii is an environmental mold that can cause osteoarticular infection, most often not only after local trauma but also after local injections and surgical procedures. Hip involvement was rarely reported, and this is the first description of a prosthetic joint infection with Scedosporium sp.