Frequency multiplication in high-energy electron beams Semiannual progress report, Oct. 1, 1966 - Apr. 1, 1967

Frequency multiplication in high energy electron beam

Cross-Product Extensions of the Gene Ontology

The Gene Ontology is being normalized and extended to include computable logical definitions. These definitions are partitioned into mutually exclusive cross-product sets, many of which reference other OBO Foundry ontologies. The results can be used to reason over the ontology, and to make cross-ontology queries

Limitations of phase-sorting based pencil beam scanned 4D proton dose calculations under irregular motion.

Objective.4D dose calculation (4DDC) for pencil beam scanned (PBS) proton therapy is typically based on phase-sorting of individual pencil beams onto phases of a single breathing cycle 4DCT. Understanding the dosimetric limitations and uncertainties of this approach is essential, especially for the realistic treatment scenario with irregular free breathing motion.Approach.For three liver and three lung cancer patient CTs, the deformable multi-cycle motion from 4DMRIs was used to generate six synthetic 4DCT(MRI)s, providing irregular motion (11/15 cycles for liver/lung; tumor amplitudes ∼4-18 mm). 4DDCs for two-field plans were performed, with the temporal resolution of the pencil beam delivery (4-200 ms) or with 8 phases per breathing cycle (500-1000 ms). For the phase-sorting approach, the tumor center motion was used to determine the phase assignment of each spot. The dose was calculated either using the full free breathing motion or individually repeating each single cycle. Additionally, the use of an irregular surrogate signal prior to 4DDC on a repeated cycle was simulated. The CTV volume with absolute dose differences >5% (Vdosediff>5%) and differences in CTVV95%andD5%-D95%compared to the free breathing scenario were evaluated.Main results.Compared to 4DDC considering the full free breathing motion with finer spot-wise temporal resolution, 4DDC based on a repeated single 4DCT resulted inVdosediff>5%of on average 34%, which resulted in an overestimation ofV95%up to 24%. However, surrogate based phase-sorting prior to 4DDC on a single cycle 4DCT, reduced the averageVdosediff>5%to 16% (overestimationV95%up to 19%). The 4DDC results were greatly influenced by the choice of reference cycle (Vdosediff>5%up to 55%) and differences due to temporal resolution were much smaller (Vdosediff>5%up to 10%).Significance.It is important to properly consider motion irregularity in 4D dosimetric evaluations of PBS proton treatments, as 4DDC based on a single 4DCT can lead to an underestimation of motion effects

Characterizing the Rigidly Rotating Magnetosphere Stars HD 345439 and HD 23478

The SDSS III APOGEE survey recently identified two new $\sigma$ Ori E type candidates, HD 345439 and HD 23478, which are a rare subset of rapidly rotating massive stars whose large (kGauss) magnetic fields confine circumstellar material around these systems. Our analysis of multi-epoch photometric observations of HD 345439 from the KELT, SuperWASP, and ASAS surveys reveals the presence of a $\sim$0.7701 day period in each dataset, suggesting the system is amongst the faster known $\sigma$ Ori E analogs. We also see clear evidence that the strength of H-alpha, H I Brackett series lines, and He I lines also vary on a $\sim$0.7701 day period from our analysis of multi-epoch, multi-wavelength spectroscopic monitoring of the system from the APO 3.5m telescope. We trace the evolution of select emission line profiles in the system, and observe coherent line profile variability in both optical and infrared H I lines, as expected for rigidly rotating magnetosphere stars. We also analyze the evolution of the H I Br-11 line strength and line profile in multi-epoch observations of HD 23478 from the SDSS-III APOGEE instrument. The observed periodic behavior is consistent with that recently reported by Sikora and collaborators in optical spectra.Comment: Accepted in ApJ

The broken 'Ring of Fire'; a new radiological sign as predictor of syndesmosis injury?

Background We noticed that subcircumferential periosteal oedema above the ankle joint was frequently present on MRI with syndesmosis injuries but was not previously reported. Fluid height within the interosseous membrane has also not been shown to be associated with syndesmosis injury severity. Purpose Investigate whether a new sign on MRI and measurement of the length of fluid within the interosseous membrane above the ankle may be used to enable early identification of a syndesmosis injury and allow differentiation from lateral ligament injury. Methods Three groups of patients were identified from a database and the MRI scans retrieved – those with an isolated syndesmosis injury (SI group), isolated lateral ligament injury (LLI group) and or no injury (NI group) who had an ankle MRI for another reason. The scans were anonymized and independently assessed by eight clinicians (surgeons and radiologists) who were blinded to the diagnosis. The maximum length of fluid above the ankle within the intraosseous membrane was measured for each patient. The presence or absence of distal anterior, lateral and posterior tibial periosteal oedema was recorded (‘Ring of Fire’). Results Measurement of the length of fluid above the ankle had excellent intra-observer reliability (ICC=0.97 [0.93-0.99]) but poor interobserver reliability. Fluid extended higher in both the LLI group (p=0.0043) and SI group (p=0.0058) than the NI group but there was no significant difference between the LLI and SI groups (p=0.3735) indicating that this measurement cannot differentiate between the injuries. The presence of the ‘Ring of Fire’ around the distal tibia was significantly more frequent in the SI group when compared to both LLI and NI groups (p<0.00001). The sensitivity of this sign is 49% but when present this sign has a 98% specificity for syndesmosis injury

Geometric and dynamic perspectives on phase-coherent and noncoherent chaos

Statistically distinguishing between phase-coherent and noncoherent chaotic dynamics from time series is a contemporary problem in nonlinear sciences. In this work, we propose different measures based on recurrence properties of recorded trajectories, which characterize the underlying systems from both geometric and dynamic viewpoints. The potentials of the individual measures for discriminating phase-coherent and noncoherent chaotic oscillations are discussed. A detailed numerical analysis is performed for the chaotic R\"ossler system, which displays both types of chaos as one control parameter is varied, and the Mackey-Glass system as an example of a time-delay system with noncoherent chaos. Our results demonstrate that especially geometric measures from recurrence network analysis are well suited for tracing transitions between spiral- and screw-type chaos, a common route from phase-coherent to noncoherent chaos also found in other nonlinear oscillators. A detailed explanation of the observed behavior in terms of attractor geometry is given.Comment: 12 pages, 13 figure

A losing battle? Women's sport pre- and post-COVID-19

Research question: In 2019, women's sport was reported as being on the rise. Increased participation rates, media coverage, investment and support were evident. Following the spread of COVID-19 across the globe, which halted most forms of competitive sport, there were repeated concerns about the future of women’s sport. This research aims to document elite sportswomen’s perceptions of the state of women's sport pre-COVID-19 and the possible impact moving forwards. Research methods: Ninety five responses from an online, anonymous, qualitative questionnaire completed by elite sportswomen mainly based, in the UK, on the impact of COVID-19 on women's sport were collected. Data were subject to a thematic analysis, to determine key concerns, and the frequency data of responses were quantitatively recorded. Results and findings: Most sportswomen felt that women’s sport was on an upward trajectory, but many juxtaposed that against inequality compared to men's sport in terms of media coverage and finance. There were concerns that the subordinate position women's sport, with less resources and support, will have severe implications post-COVID-19. However, there were considerations that a pause in sport would allow for personal development, increased participation upon sports return and space for a reconfiguration of sport. Implications: Those involved in sport are encouraged to think more critically about progress narratives in women's sport. We caution that these hide perpetual, structural and symbolic inequalities and propose that they are positioned more coherently within wider gender equity agenda. This is a process that will require widespread cultural change

Microwave device investigations

Several tasks were active during this report period: (1) noise modulation in avalanche-diode devices; (2) schottky-barrier microwave devices; (3) intermodulation products in IMPATT diode amplifiers; (4) harmonic generation using Read-diode varactors; and (5) fabrication of GaAs Schottky-barrier IMPATT diodes

A treatment planning intercomparison of proton and intensity modulated photon radiotherapy.

peer reviewedAbstract Purpose: A comparative treatment planning study has been undertaken between standard photon delivery techniques,b intensity modulated photon methods and spot scanned protons in order to investigate the merits and limitations of each of these treatment approaches. Methods: Plans for each modality were performed using CT scans and planning information for nine patients with varying indications and lesion sites and the results have been analysed using a variety of dose and volume based parameters. Results: Over all cases, it is predicted that the use of protons could lead to a reduction of the total integral dose by a factor three compared to standard photon techniques and a factor two compared to IM photon plans. In addition, in all but one Organ at Risk (OAR) for one case, protons are predicted to reduce both mean OAR dose and the irradiated volume at the 50% mean target dose level compared to both photon methods. However, when considering the volume of an OAR irradiated to 70% or more of the target dose, little difference could be shown between proton and intensity modulated photon plans. On comparing the magnitude of dose hot spots in OARs resulting from the proton and IM photon plans, more variation was observed, and the ranking of the plans was then found to be case and OAR dependent. Conclusions: The use of protons has been found to reduce the medium to low dose load (below about 70% of the target dose) to OARs and all non-target tissues compared to both standard and inversely planned photons, but that the use of intensity modulated photons can result in similar levels of high dose conformation to that afforded by protons. However, the introduction of inverse planning methods for protons is necessary before general conclusions on the relative efficacy of photons and protons can be drawn

The gendered effects of COVID-19 on elite women's sport

The coronavirus (Covid-19) pandemic in early 2020 prompted widespread global lockdowns as the world looked to contain and reduce the impact of the virus, including a pause on most sporting competitions (Parnell et al., 2020). Covid-19 has greatly affected the world, exposing stark inequalities, especially across gendered lines, in areas of society such as the labour market, domestic responsibility, and economic hardship (Alon et al., 2020). Sport is a crucial, interwoven aspect of society and like wider societal trends, elite women’s sport has been adversely affected by the pandemic, facing an existential threat (Bowes et al., 2020; Clarkson et al., 2020a; Rowe, 2020). The aim of this chapter is to provide an overview of how the pandemic is negatively impacting a wide variety of elite women’s sports. Specifically, we cover sports where women have traditionally existed on the margins of the sport and could be considered as male-dominated labour industries. Centring primarily on the United Kingdom (UK), we present a brief chronology of the impact of the crisis on elite women’s sport, across football, rugby, cricket and golf - in many ways different to the men’s versions - spanning the eight months since the start of the pandemic in March 2020 until the time of writing in November 2020. Throughout, the chapter utilises qualitative data from elite sportswomen encouraged to share their experiences during the pandemic (see Bowes et al., 2020). Subsequently, this chapter concludes with a summary of the challenges for women operating in (semi-)professional sports environments