Gravitational Wave Detection by Interferometry (Ground and Space)

Significant progress has been made in recent years on the development of gravitational wave detectors. Sources such as coalescing compact binary systems, neutron stars in low-mass X-ray binaries, stellar collapses and pulsars are all possible candidates for detection. The most promising design of gravitational wave detector uses test masses a long distance apart and freely suspended as pendulums on Earth or in drag-free craft in space. The main theme of this review is a discussion of the mechanical and optical principles used in the various long baseline systems in operation around the world - LIGO (USA), Virgo (Italy/France), TAMA300 and LCGT (Japan), and GEO600 (Germany/U.K.) - and in LISA, a proposed space-borne interferometer. A review of recent science runs from the current generation of ground-based detectors will be discussed, in addition to highlighting the astrophysical results gained thus far. Looking to the future, the major upgrades to LIGO (Advanced LIGO), Virgo (Advanced Virgo), LCGT and GEO600 (GEO-HF) will be completed over the coming years, which will create a network of detectors with significantly improved sensitivity required to detect gravitational waves. Beyond this, the concept and design of possible future "third generation" gravitational wave detectors, such as the Einstein Telescope (ET), will be discussed.Comment: Published in Living Reviews in Relativit

Long-term morphology of a healing bone–tendon interface: a histological observation in the sheep model

The purpose of this study was to examine and describe the sequence of events involved in long-term biological reconstruction of a tendon–bone interface following surgical reattachment. Patellar tendon re-attachment in the adult sheep was used to investigate and describe the biological components involved in healing and repair of a tendon enthesis. Light microscopy was used to describe the healing morphology at time intervals of 8, 12, 26, 52 and 104 weeks. By 8 weeks a collagen continuum was observed between the tendon and bone. Over time this fibrous bridge became anchored into the original tissues (tendon and bone), with the resultant enthesis resembling more a fibrous rather than the original fibrocartilagenous enthesis. The associated collagen fibrils between the two tissues gradually changed in morphology over time to reflect the fibres seen in the original tendon tissue. The fibrous tissue of the forming enthesis remained hypercellular when compared with the controls. The resultant long-term morphology may be a reflection of functional adaptation rather than anatomical replication

Recombined bone xenografts enhance tendon graft osteointegration of anterior cruciate ligament reconstruction

The objective of the study was to discover whether recombined bone xenograft (RBX), a porous solid material, could augment healing of the tendon-to-bone interface after anterior cruciate ligament (ACL) reconstruction. ACL reconstruction was performed bilaterally in 25 skeletally mature rabbits using long digital extensor tendon grafts. RBX was implanted into the treated knee, with the contralateral knee serving as control. Three rabbits were killed at postoperative weeks two, six and 12 for routine histology. The remaining 16 rabbits were killed at weeks six and 12, and their femur-graft-tibia complexes were harvested for mechanical testing. The treatment and control groups produced different histological findings at the interface between the tendon and bone. In the treatment group, large areas of chondrocyte-like cells were noted around the tendon-bone interface two weeks after the operation. At six weeks, more abundant bone formation was observed around the tendon. At 12 weeks, an immature neoenthesis structure was seen. In biomechanical evaluation six and 12 weeks after the operation, the ultimate strength of tendon in the bone tunnel was significantly higher in the treatment group than in the control group. RBX can augment the osteointegration of tendon to bone after ACL reconstruction