Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational-Wave Event S190521g.

We report the first plausible optical electromagnetic counterpart to a (candidate) binary black hole merger. Detected by the Zwicky Transient Facility, the electromagnetic flare is consistent with expectations for a kicked binary black hole merger in the accretion disk of an active galactic nucleus [B. McKernan, K. E. S. Ford, I. Bartos et al., Astrophys. J. Lett. 884, L50 (2019)AJLEEY2041-821310.3847/2041-8213/ab4886] and is unlikely [

Hierarchical Black Hole Mergers in Active Galactic Nuclei.

The origins of the stellar-mass black hole mergers discovered by LIGO/Virgo are still unknown. Here we show that if migration traps develop in the accretion disks of active galactic nuclei (AGNs) and promote the mergers of their captive black holes, the majority of black holes within disks will undergo hierarchical mergers-with one of the black holes being the remnant of a previous merger. 40% of AGN-assisted mergers detected by LIGO/Virgo will include a black hole with mass ≳50M_{⊙}, the mass limit from stellar core collapse. Hierarchical mergers at traps in AGNs will exhibit black hole spins (anti)aligned with the binary's orbital axis, a distinct property from other hierarchical channels. Our results suggest, although not definitively (with odds ratio of ∼1), that LIGO's heaviest merger so far, GW170729, could have originated from this channel.

A simple and inexpensive method to routinely produce customized neck supports for patient immobilization during radiotherapy.

Accurate and reproducible patient positioning is fundamental to the success of fractionated radiotherapy. Poor patient positioning could result in geographic misses. We have recently reported on an improved method of customized face mask production using laser surface scanning. In this report, we sought to identify and develop a method to routinely make customized neck supports for patients prescribed radiotherapy to the brain or head and neck regions. We identified a potentially suitable product--sealed packs containing two liquids that produce expanding polyurethane foam when mixed--and developed a method for their use. The neck supports are inexpensive and simple to produce (taking less than 5 min of radiation therapist labour). We assessed the customized neck supports in several ways. The effect on setup accuracy was assessed by comparing two consecutive cohorts of patients. Statistically significant differences favouring the customized neck supports included a reduced total displacement error (mean 3.4 vs. 2.1 mm) and a reduced left-right setup error (mean 1.8 vs. 1.1 mm). This is consistent with the greater support provided by the customized neck supports. This method could easily be undertaken by other departments.

Surface laser scanning to routinely produce casts for patient immobilization during radiotherapy.

Immobilization casts are used to reduce patient movement during the radiotherapy of head and neck and brain malignancies. Polyethylene-based casts are produced by first taking a Plaster of Paris 'negative' impression of the patient. A 'positive' mould is then made, which is used to vacuum form an immobilization cast. Taking the 'negative' cast can be messy, stressful for patients and labour intensive. Recently, lightweight hand-held laser surface scanners have become available. These allow an accurate 3-D representation of objects to be generated non-invasively. This technology has now been applied to the production of casts for radiotherapy. Each patient's face and head is digitized using the Polhemus FastSCAN (Polhemus, Colchester, VT, USA) scanner. The electronic data are transferred to a computer numerical controlled mill, where a positive impression is machined. The feasibility of the process was examined, the labour required and radiation therapists' satisfaction with aspects of the produced masks assessed. The scanner-based method of mask production was found to be simple, accurate and non-invasive. There was a reduction in radiation therapist labour required. Masks produced with the scanner-based method were reported to result in improved mask fitting, daily reproducibility, patient immobilization and patient comfort.

Causes of recurrence after laparoscopic hernioplasty. A multicenter study.

BACKGROUND: To determine if there are common factors beyond the learning curve that lead to recurrence after laparoscopic hernioplasty, we analyzed failures seen in seven centers specializing in laparoscopic hernia repair. METHOD: We performed a retrospective review of patients who had a laparoscopic hernioplasty (Tapp or Tep) between 1990 and 1996 at centers specializing in laparoscopic repairs (>500 repairs at each center). RESULTS: In all, 7661 patients had 10,053 hernias repaired by the transabdominal preperitoneal or the totally extraperitoneal approach; they were followed for 1 month to 6 years. In patients followed for >/=6 months with a median follow-up of 36 months, 35 repairs failed (0.4%), and all but one of these patients underwent a remedial operation. Twenty-nine had a laparoscopic repair, four had a combined laparoscopic and anterior repair, and one had an anterior repair alone. The cause of failure was determined in all 34 patients. The mechanism of recurrence was inadequate lateral fixation of the mesh in 11 cases, inadequate lateral fixation compounded by too small a mesh in three cases, missed lipoma of the cord in four cases, inadequate fixation of the mesh medially to Cooper's ligament in eight cases (seven of which were associated with too small a mesh), a missed hernia in four cases, and a hernia through a keyhole in the mesh in five cases. As surgeons gained experience, the incidence of recurrence due to missed hernias or too small a mesh decreased. CONCLUSIONS: This large multicenter study demonstrated that the incidence of recurrence after laparoscopic hernioplasty performed by experienced surgeons was extremely low and that some causes could be corrected by experience, whereas others will require changes in technique or equipment.

Incidence of complications following laparoscopic hernioplasty.

Smaller individual series on the outcome of laparoscopic hernioplasty techniques have been reported. This study reports on the complications of 3,229 laparoscopic hernia repairs performed by the authors in 2,559 patients. The TAPP (transabdominal preperitoneal) technique was the most frequently performed: 1,944 (60%). The totally preperitoneal technique was performed 578 (18%) times. The IPOM (intraperitoneal onlay mesh) repair was performed 345 (11%) times. The plug-and-patch technique was used 286 (9%) times and simple closure of the hernia defect without mesh was used in 76 (2%) repairs. Overall, there were 336 (10%) complications: 17 (0.5%) major and 265 (8%) minor. There were 54 (1.6%) recurrences, with a mean follow-up of 22 months. The TAPP technique had 19 (1%) recurrences and 141 (7%) complications. There were four bowel obstructions in this subgroup from herniation of small bowel through the peritoneal closure and trocar sites. The totally preperitoneal technique had no recurrence and 60 (10%) complications. The IPOM group had 7 (2%) recurrences and 47 (14%) complications. The plug-and-patch technique had 26 (9%) recurrences and 24 (8%) complications. The simple closure of the internal ring had 2 (3%) recurrences and 10 (13%) complications. Laparoscopic hernioplasty is not without complications. Laparoscopic hernioplasty is not without complications. Training, experience, and attention to technique will prevent some of these complications.