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Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.
Methods and Materials:
Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.
Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.
There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.
This is a copy of the slides presented at the meeting but not formally written up for the volume.
To address the needs of a wide variety of potential application domains, the sophistication and structural complexity of engineered nanoparticle systems has been steadily increasing. Often the unique functionality of these systems depends on the 3-dimensional distribution of multiple phases, ranging from simple coatings to core-shell morphologies to multifunctionalizations for drug delivery. This need for controlled 3-dimensional chemical heterogeneity at the nanoscale presents significant challenges both for the nanomanufacturing of these materials and their metrology and characterization. Even when the nanoparticles have relatively simple structures, the demands of modern process control methodologies and the specifications of end users frequently require increased metrology precision and decreased measurement bias for critical measurands such as coating thicknesses or particle size distributions. Recent advances in electron microscopy and focused ion beam (FIB) technology provide powerful tools for the 3-dimensional structural and elemental characterization of nanomaterials. Dimensional metrology using phase contrast high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) can measure the physical dimensions of nanostructures at the single nanometer level. Elemental mapping using energy-filtered TEM (EFTEM) can be used to map the spatial distribution of different stoichiometries, while electron tomography can reconstruct the 3-dimensional morphology of nanoparticle assemblies. Examples of the above techniques will be presented along with recent NIST efforts to fuse these techniques into a methodology for 3-dimensional chemical imaging of engineered nanostructures.
In late summer, sometime between cal a.d. 340–405, a hoard of tightly packed, stacked copper-alloy vessels was deposited in the Vale of Pewsey, Wiltshire. The corrosion of the vessels allowed for the preservation of delicate plant macrofossils and pollen. Analysis of this material has provided insights into the date, season and context of this act of structured deposition. A second hoard of similar vessels was deposited in the fourth or fifth century only a few miles away at Wilcot. The hoards and their deposition relate to Romano-British lifeways, at a time when the region was on the cusp of a dramatic period of change. The distribution of late Roman coins and belt fittings offers further insights into the social and economic character of Wiltshire at their times of deposition.
Childhood maltreatment (CM) plays an important role in the development of major depressive disorder (MDD). The aim of this study was to examine whether CM severity and type are associated with MDD-related brain alterations, and how they interact with sex and age.
Within the ENIGMA-MDD network, severity and subtypes of CM using the Childhood Trauma Questionnaire were assessed and structural magnetic resonance imaging data from patients with MDD and healthy controls were analyzed in a mega-analysis comprising a total of 3872 participants aged between 13 and 89 years. Cortical thickness and surface area were extracted at each site using FreeSurfer.
CM severity was associated with reduced cortical thickness in the banks of the superior temporal sulcus and supramarginal gyrus as well as with reduced surface area of the middle temporal lobe. Participants reporting both childhood neglect and abuse had a lower cortical thickness in the inferior parietal lobe, middle temporal lobe, and precuneus compared to participants not exposed to CM. In males only, regardless of diagnosis, CM severity was associated with higher cortical thickness of the rostral anterior cingulate cortex. Finally, a significant interaction between CM and age in predicting thickness was seen across several prefrontal, temporal, and temporo-parietal regions.
Severity and type of CM may impact cortical thickness and surface area. Importantly, CM may influence age-dependent brain maturation, particularly in regions related to the default mode network, perception, and theory of mind.
With the discovery of both binary black hole mergers and a binary neutron star merger, the field of gravitational wave astrophysics has really begun. The LIGO and Virgo detectors will soon improve their sensitivity allowing for the detection of thousands new sources. All these measurements will provide new answers to open questions in binary evolution related to mass transfer, out-of-equilibrium stars and the role of metallicity. The data will give new constraints on uncertainties in the evolution of (massive) stars, such as stellar winds, the role of rotation and the final collapse to a neutron star or black hole. In the long run, the thousands of detections by the Einstein Telescope will enable us to probe their population in great detail over the history of the Universe. For neutron stars, the first question is whether the first detection GW170817 is a typical source or not. In any case, it has spectacularly shown the promise of complementary electromagnetic follow-up. For white dwarfs, we have to wait for LISA (around 2034), but new detections by, e.g., Gaia and LSST will prepare for the astrophysical exploitation of the LISA measurements.
The statistical distributions of main-sequence multiple-star properties reveal invaluable insights into the processes of binary star formation, and they provide initial conditions for population synthesis studies of binary star evolution. Binary stars are discovered and characterised through a variety of techniques. Correcting for their respective selection effects and combining the bias-corrected results is not a trivial process. This is partially because the intrinsic distributions of companion frequency, primary mass M1, orbital period P, mass ratio q and eccentricity e are all interrelated , i.e., f(M1,P,q,e)/= f(M1)f(P)f(q)f(e). In particular, the binary fraction increases with primary mass, especially across short orbital periods, and binaries become weighted towards larger eccentricities and more extreme mass ratios with increasing separation, especially for more massive primaries. Moreover, binary star statistics vary with age, environment and metallicity. This chapter summarises the strengths and limitations of the various observational techniques, and reviews the statistical correlations in the intrinsic (bias-corrected) multiple-star properties.
Any white dwarf or neutron star that accretes enough material from a red giant companion, such that this interaction can be detected at some wavelength, is currently termed a symbiotic star (orbital period ∼2–3 years). In the majority of ∼400 known systems, the white dwarf burns nuclearly at its surface the accreted material, and the resulting high temperature and luminosity allow ionisation of a large fraction of the cool giant’s wind. X-ray observations are revealing the existence of a parallel (and large ?) population of optically quiet, accreting-only symbiotic stars. Accretion flows and disks, ionisation fronts and shock, complex 3D geometries and new evolution channels are gaining relevance and are reshaping our understanding of symbiotic stars. The chapter reviews the different types of symbiotic stars currently in the family and their variegated outburst behaviours.
Binary stars are of course more than two stars, but they are also at least two stars. This chapter will review some aspects of the physics governing the evolution of single massive stars. It will also review the uncertainties of key physical ingredients: mass loss, rotation and convection.
Many aspects of the evolution of stars, and in particular the evolution of binary stars, are beyond our ability to model them in detail. Instead, we rely on observations to guide our often phenomenological models and pin down uncertain model parameters. To do this statistically requires population synthesis. Populations of stars modelled on computers are compared to populations of stars observed with our best telescopes. The closest match between observations and models provides insight into unknown model parameters and hence the underlying astrophysics. This chapter reviews the impact that modern big-data surveys will have on population synthesis, the large parameter space problem that is rife for the application of modern data science algorithms and some examples of how population synthesis is relevant to modern astrophysics.
Short-duration gamma-ray bursts (short-GRBs) are thought to be produced during the merger of compact binary stars involving at least one neutron star. The recent detection of a gravitational wave signal coincident with a short-GRB (170817), albeit one with unusually low intrinsic luminosity, has cemented this link and opened a new era of multimessenger astrophysics. Long-duration gamma-ray bursts are produced by the core collapse of envelope-stripped massive stars, which may also be the end product of binary evolution. Establishing the nature of the long-GRB progenitor more definitely is important not only for our understanding of GRBs, but also for their use as probes of the distant Universe, many of which depend on how representative GRBs are of the general population of massive stars.
We still do not have an end-to-end theory of binary star formation that both satisfies observational constraints and also includes all necessary physical ingredients. Large-scale star formation simulations do an excellent job of replicating binary statistics under severely simplified physical conditions (neglect of thermal feedback and magnetic fields). Simulations that include these processes, however, tend to suppress binary formation, and their extra computational expense makes it hard to generate statistical samples of binaries for observational comparison. In addition to reviewing the literature on binary formation simulations, this chapter also examines the insights into the process that are provided by observations of the youngest protomultiple systems.