Schwarzschild Black Hole from Perturbation Theory to All Orders.

Applying the quantum field theoretic perturbiner approach to Einstein gravity, we compute the metric of a Schwarzschild black hole order by order in perturbation theory. Using recursion, this calculation can be carried out in de Donder gauge to all orders in Newton's constant. The result is a geometric series which is convergent outside a disk of finite radius, and it agrees within its region of convergence with the known de Donder gauge metric of a Schwarzschild black hole.

The Danish sports chiropractic landscape: an exploration of practice characteristics and salient developmental issues.

Background: As is the case around the globe, the Danish chiropractic community appears to be an active service provider for the athletic sub-population. However, a paucity of evidence elucidating the experiences, perceptions, and practices of individuals who identify as 'sports chiropractors' complicates strategic development efforts.

Methods: A sequential mixed-methods study was conceptualized in which interview responses from seven purposefully selected stakeholders provided context and informed a national descriptive survey exploring practice characteristics and opinions regarding sports chiropractic among Danish chiropractors.

Shotgun sequencing of clinical biofilm following scanning electron microscopy identifies bacterial community composition.

Bacterial biofilm infections often involve aggregates of bacteria heterogeneously distributed throughout a tissue or on a surface (such as an implanted medical device). Identification of a biofilm infection requires direct visualization via microscopy, followed by characterization of the microbial community by culturing or sequencing-based approaches. A sample, therefore, must be divided prior to analysis, often leading to inconsistent results.

General Relativity from Scattering Amplitudes.

Weoutline the program to apply modern quantum field theory methods to calculate observables in classical general relativity through a truncation to classical terms of the multigraviton, two-body, on-shell scattering amplitudes between massive fields. Since only long-distance interactions corresponding to nonanalytic pieces need to be included, unitarity cuts provide substantial simplifications for both post-Newtonian and post-Minkowskian expansions. We illustrate this quantum field theoretic approach to classical general relativity by computing the interaction potentials to second order in the post-Newtonian expansion, as well as the scattering functions for two massive objects to second order in the post-Minkowskian expansion.

Ancient human parvovirus B19 in Eurasia reveals its long-term association with humans.

Human parvovirus B19 (B19V) is a ubiquitous human pathogen associated with a number of conditions, such as fifth disease in children and arthritis and arthralgias in adults. B19V is thought to evolve exceptionally rapidly among DNA viruses, with substitution rates previously estimated to be closer to those typical of RNA viruses. On the basis of genetic sequences up to ∼70 years of age, the most recent common ancestor of all B19V has been dated to the early 1800s, and it has been suggested that genotype 1, the most common B19V genotype, only started circulating in the 1960s.