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The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of gravitational waves can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.

Introduction. Gastrointestinal stromal tumors of the esophagus are rare. Case Presentation. This is a case of a 50-year-old male patient who was referred to our department complaining of atypical chest pain. A chest computed tomographic scan and endoscopic ultrasound revealed a submucosal esophageal tumor measuring 5 cm in its largest diameter. Suspecting a leiomyoma, we performed enucleation via right thoracotomy. The pathology report yielded a diagnosis of an esophageal gastrointestinal stromal tumor. The patient has shown no evidence of recurrence one year postoperatively. Conclusions. This report illustrates the complexity and dilemmas inherent in diagnosing and treating esophageal GISTs.

LISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the early inspirals of stellar-mass black holes that will ultimately venture into the ground-based detectors’ view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA’s discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This White Paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome.

Donor morbidity rates vary between 0 and 67 per cent depending on the definition and the recognition of them.1 Donor mortality has been estimated between 0.2 and 0.9 per cent.1 Most commonly reported complications are infections, development of incisional hernias, biliary complications (stricture or leakage), respiratory complications (pleural effusions, atelectasis, pneumonia, and pulmonary embolism), vascular complications (bleeding and portal vein thrombosis), and postoperative liver failure.1 Diaphragmatic hernia (DH) affecting the donor is a rare complication with nine cases reported so far. [...]the vast majority of reports about this complication refer to donors that have undergone emergency surgery with a DH diagnosed on admission.1-4 On every report the diagnosis had been established with a thorax-abdomen CT scan with a better depiction on a coronal reformation.1-3 It is the failure to diagnose the hernia earlier, that has led the patients to emergency surgery and around 25 per cent of them had to undergo intestine resection.1, 3 Hypothesized causes for iatrogenic DH have been many such as direct trauma to the diaphragm during the operation, thermal or cryoinjury caused by coagulation or ablation instruments used during surgery and solutions used for cardiac surgery and diaphragmatic injury during laparoscopic liver resection or bariatric surgery.1 In the cases reviewed, there were no indications of congenital weaknesses or defects of the diaphragm during the liver procurement.

LISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the early inspirals of stellar-mass black holes that will ultimately venture into the ground-based detectors’ view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA’s discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This White Paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome.

The objective of this study is to assess long-term prognosis and patterns of failure in patients with retroperitoneal sarcoma who underwent surgery with curative intent at a single institution. We also provide a thorough review of the literature including several series and widely variable data regarding local and distant failure. During a 25-year period (1988–2013), 45 consecutive patients who underwent surgery for retroperitoneal sarcoma at a single referral center were reviewed retrospectively. We recorded and analyzed the presenting symptoms, type of surgical excision, and the 5-year survival rate as well as the local recurrence rate of patients with complete tumor resection. Overall survival is significantly diminished in patients in whom resection margins are not adequate. In our series, 5-year recurrence rate for patients with complete and incomplete resection of the tumor was 30.76 and 68.42 %, respectively. The 5-year survival rate was 51.12 %, and the 5-year survival rate according to type of resection was 76.93 % for complete and 15.79 % for incomplete resections. Local recurrence after first surgery and high-grade malignancy are associated with poor survival. The role of radiation therapy and chemotherapy in the treatment of retroperitoneal sarcoma (RPS) should be investigated further. Complete en bloc resection of the tumor mass and adjacent structures is the single most important factor that improves survival.

Background The Belsey Mark IV operation has been used for the management of hiatal hernia for over 40 years, but with the introduction of laparoscopic techniques its role has become questionable. To determine the current role of this procedure we present a contemporary series of patients. Methods We reviewed fifteen consecutive patients, mean age of 63 years, who underwent a Belsey Mark IV fundoplication for gastroesophageal reflux in the presence of a hiatal hernia in our Department from January 2005 to March 2011. Indications for the thoracic approach included paraesophageal hernias, recurrent hiatal hernias and previous upper abdominal surgery. Results There was no operative mortality. Immediate postoperative morbidity included 1 case of bleeding, 1 case of pneumonia and 1 case of atrial fibrillation. The mean length of stay was 5.9 days. After a mean follow-up time of 49 months, all patients reported total or partial alleviation of their symptoms. No hernia recurrence was detected during barium swallow examination. Conclusions The Belsey approach is a procedure that can be useful as an alternative in selected cases when there are co-morbidities complicating the transabdominal (laparoscopic) approach.

We develop a geometrical treatment of general relativistic magnetohydrodynamics for perfectly conducting fluids in Einstein–Maxwell–Euler spacetimes. The theory is applied to describe a neutron star that is rotating or is orbiting a black hole or another neutron star. Under the hypotheses of stationarity and axisymmetry, we obtain the equations governing magnetohydrodynamic equilibria of rotating neutron stars with poloidal, toroidal or mixed magnetic fields. Under the hypothesis of an approximate helical symmetry, we obtain the first law of thermodynamics governing magnetized equilibria of double neutron star or black hole - neutron star systems in close circular orbits. The first law is written as a relation between the change in the asymptotic Noether charge δQ and the changes in the area and electric charge of black holes, and in the vorticity, baryon rest mass, entropy, charge and magnetic flux of the magnetofluid. In an attempt to provide a better theoretical understanding of the methods used to construct models of isolated rotating stars and corotating or irrotational binaries and their unexplained convergence properties, we analytically examine the behavior of different iterative schemes near a static solution. We find the spectrum of the linearized iteration operator and show for self-consistent field methods that iterative instability corresponds to unstable modes of this operator. On the other hand, we show that the success of iteratively stable methods is due to (quasi-)nilpotency of this operator. Finally, we examine the integrability of motion of test particles in a stationary axisymmetric gravitational field. We use a direct approach to seek nontrivial constants of motion polynomial in the momenta—in addition to energy and angular momentum about the symmetry axis. We establish the existence and uniqueness of quadratic constants and the nonexistence of quartic constants for stationary axisymmetric Newtonian potentials with equatorial symmetry and elucidate their relativistic analogues.

This work outlines a time-domain numerical integration technique for linear hyperbolic partial differential equations sourced by distributions (Dirac \\(\\delta\\)-functions and their derivatives). Such problems arise when studying binary black hole systems in the extreme mass ratio limit. We demonstrate that such source terms may be converted to effective domain-wide sources when discretized, and we introduce a class of time-steppers that directly account for these discontinuities in time integration. Moreover, our time-steppers are constructed to respect time reversal symmetry, a property that has been connected to conservation of physical quantities like energy and momentum in numerical simulations. To illustrate the utility of our method, we numerically study a distributionally-sourced wave equation that shares many features with the equations governing linear perturbations to black holes sourced by a point mass.

We report work towards a relativistic formulation for modeling strongly magnetized neutron stars, rotating or in a close circular orbit around another neutron star or black hole, under the approximations of helical symmetry and ideal MHD. The quasi-stationary evolution is governed by the frst law of thermodynamics for helically symmetric systems, which is generalized to include magnetic felds. The formulation involves an iterative scheme for solving the Einstein-Maxwell and relativistic MHD-Euler equations numerically. The resulting configurations for binary systems could be used as self-consistent initial data for studying their inspiral and merger.