The International Physicists’ Tournament (IPT) is a global competition designed to test the problem-solving and presentation skills of undergraduate students interested in physics. Following the same format as the International Young Physicists’ Tournament (IYPT) for secondary schools, the IPT involves teams of up to six undergraduates spending nine months solving up to 17 challenging, open-ended and unsolved problems in physics.
The tournament winner is traditionally crowned at a week-long event that takes place at a different location each year. Previous hosts have included famous institutions such as the Moscow Institute of Physics and Technology (MIPT) in Russia, the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, and Chalmers University of Technology in Sweden. This year, however, which was meant to be the twelfth ever final, things panned out rather differently.
Online challenge
As with many scientific events, conferences, seminars and trade fairs, it was increasingly looking likely that the IPT would have to moved online due to global restrictions designed to combat the spread of COVID-19. And so it was, that after much deliberation on how the pandemic will evolve, the executive team of the IPT decided to replace the physical event with a two-day, online tournament on the weekend of 26–27 September 2020.
The tournament usually consists of a series of “physics fights”
The tournament usually consists of a series of “physics fights”. At the start of each, one team serves as “reporter”, with an other as “opponent”, and a third holds acting as “reviewer”. The reporter is challenged by the opponent to present their work on one of the problems. Once presented, the opponent then has to constructively critique the reporter’s work.
A debate ensues in which the two teams, with guidance from the reviewer, aim to improve upon the approach proposed by the reporter. After the first round, the roles switch and the process repeats until each team has held all roles. A panel of judges grades each role, giving marks out of 10. After a series of fights, the top three teams proceed to a final.
A tense affair
Moving the tournament online was challenging. Time zones were the first major hurdle, with participants stretching from Columbia to China (a huge 13-hour difference). We ended up altering the rules to ensure all teams could participate at reasonable times. We did this by removing the reviewer role for all qualifying fights (apart from the final), which drastically cut the times of each fight.
To allow students from across the world to mingle and mix – one of the unique features of the tournament – we also introduced extra activities and opportunities, including the IPT’s first photo competition. It allowed participants to share their creativity and team camaraderie through submitted photos on social media.
A total of 10 teams took part in the tournament this year, each taking part in three qualifying fights. After the first two, the race looked close with just eight points separating all teams in the top half of the table. It was only after the final fight that the top three teams – MIPT (Russia), Kharkiv Karazin National University (Ukraine) and Rice University (US) – emerged. Rice was one of two teams to appear for the first time in the tournament, the other being from SNS NUST in Islamabad, Pakistan.
The final itself, which you can watch on YouTube, was a tense affair between the teams from Russia and the Ukraine, with only three points out of a total possible 60 separating them after the three rounds. Viewers were treated to a presentation by the YouTube science communicator Bruce Yeany, who gave his thoughts on some of the problems he had presented and investigated himself in the past. In a tense final few moments, the Russian team emerged as the overall winner.
Don’t stop us now
The tournament, however, didn’t end on the Sunday. Recognizing that some teams hadn’t been able to hunt for solutions since March due to COVID-19, the executive committee decided to hold three days of presentations in a traditional conference format. This allowed teams to present solutions that hadn’t been challenged in the tournament, while also giving an opportunity to teams that hadn’t been able to take part at all, such as those from Brazil and Poland, to show the fruits of their labours.
The pandemic is one of the strongest challenges faced so far in many of our lives, with much of our ordinary day-to-day happenings being rattled and our future placed on shaky grounds. However, the online IPT revealed the strengths of our ability to innovate and bring people together in the midst of isolation, adding much welcome streams of positivity for physics students across the world.
I would like to give special thanks on behalf of the executive committee to all the participants who took part and presented high quality solutions, and to our jury who volunteered their weekend to provide valuable feedback to the students. Anyone interested in taking part in future events is welcome to contact the executive committee via this link.
You learn something new every day, goes the old adage – and today was no exception as I gleaned two nuggets of information from the UK-based frozen food retailer Iceland. One is that the chicken nugget was invented in the 1950s by scientists at Cornell University and the other is that Iceland is the biggest seller of chicken nuggets in the UK. To celebrate their market dominance and the 50th anniversary of the chain, Iceland has sent a chicken nugget into space. The morsel was suspended from a balloon and launched from a location in Wales, reaching an altitude of 33.5 km. You can watch its ascent in the above video but being in Wales in October, the view of the Earth is quickly obscured by clouds.
Speaking of sending stuff into space, UK and New Zealand-based Orbital Astronautics has launched two competitions to encourage people to design and build spacecraft payloads. Orbital Start-up is aimed at start-up companies and Orbital Student is aimed at, you guessed it, students. In both cases entries will be judged by industry experts and the top start-up and the two top student entries will be integrated within an Orbital Astronautics satellite and launched into orbit on a SpaceX Falcon 9. The deadline for entries is 15 December.
Not wanting to be upstaged by Iceland or Orbital Astronautics, NASA and Nokia are joining forces to put a 4G mobile phone network on the Moon. Described as “ultra-compact, low-power and space-hardened,” the Guardian reports that the lunar network will be part of NASA’s plan to establish a long-term human presence on the moon by 2030.
The network will be installed remotely using a “lunar hopper” built by US based Intuitive Machines and will be used for navigation and streaming video. The deal is worth $14.1m to Nokia’s US subsidiary.
A team at Massachusetts General Hospital (MGH) has developed RadCollision – an open-source collision detection tool designed to aid dosimetrists planning photon or proton beam radiotherapy. When embedded in a treatment planning system (TPS), the modular software platform takes just seconds to automatically calculate whether a gantry head will collide with the patient or treatment couch. In addition to greatly reducing the need for replanning if a collision is detected during the dry run, the tool helps planners choose optimum and feasible irradiation angles to potentially increase the quality of treatment plans.
The MGH research initiative began when the radiotherapy department’s medical dosimetrists requested software to eliminate guesswork regarding collision risks. The dosimetrists previously relied on their experience and intuition to determine which incident beam directions and isocentre positions may be infeasible, a time-consuming and less than optimum process.
“The frequency of potential collisions in the clinic has been mitigated by rudimentary physical measurements and conservative planning decisions,” explains co-author Kyla Remillard, a photon dosimetry team leader. “Without these steps, potential collisions would be observed more frequently. However, no two patients’ geometries or setups are identical, and so we say there’s an opportunity for improvement.”
Writing in Biomedical Physics & Engineering Express, Remillard and colleagues explain that equipment movement during photon treatments can be considerable, with the treatment head mounted on a rotating gantry and a patient couch rotating around a vertical axis. Movement during proton therapy is even greater, and therefore more complex to calculate, because the moving snout of the treatment head nozzle supports apertures, compensators and range shifters positioned close to the surface of a patient. Additionally, couches with robotic arms can lead to some extra risk of collision when the beam is incident from below.
Collision avoidance is based on a detailed 3D description of static objects in each treatment room, as well as the patient’s 3D anatomy, the authors explain. Current methods of assessing potential collisions include the use of 3D scanners or cameras, patient geometry data from a CT scan, and/or analytic software. These typically require setup-related costs, especially if a cancer treatment centre uses multiple types of treatment systems and patient couches. Some vendors include 3D visualization tools for real-time interaction with the delivery machine. But these are not usually embedded in the planning software and may also add licensing costs.
The free RadCollision software does not require purchase of additional software or hardware, and is easily adaptable by any institution for any type of treatment equipment configuration. RadCollision relies on an initial 3D modelling of the treatment machine, and optionally incorporates the full patient geometry recorded with any 3D scanner or surface imaging device. It provides a realistic 3D visualization of nozzle, couch and patient, and its modularity enables the user to add or remove room elements from the 3D visualization.
Illustration of a collision between gantry (blue) and couch (green) at a gantry angle of 90° detected in the 3D viewer tab of the RayStation TPS. A collision report warns about a collision of gantry with couch, whereas none is found with the right leg. (Courtesy: Biomed. Phys. Eng. Express 10.1088/2057-1976/aba442)
Other features include the ability to evaluate the independent movement of each treatment room element with real-time feedback, and interactive sliders that help planners choose optimal beam angles. Users also can choose automatic or visual detection modes, with the latter relying on the planner’s ability to assess the collision risk in incomplete patient geometries.
RadCollision can be used as soon as the patient’s contour data are added. The program automatically selects the machine and couch model from the active treatment plan. Dosimetrists may adjust the irradiation settings, after which, the software transforms in real time the regions-of-interest (ROIs) corresponding to the treatment machine, calculating any collision (overlap of ROIs) with the patient or couch. Collision reports can be automatically calculated for each beam defined in the plan.
The tool requires an initial setup performed by a hospital’s information technology department. The RadCollision software needs to be embedded into each TPS database (if more than one TPS is used) and a folder (STL files) with the 3D models of the machines prepared. RadCollision is currently limited to use with the RayStation TPS, but versions for use with other commercial TPS are planned, says first author Fernando Hueso-González.
The researchers quantitatively evaluated their software using the RayStation TPS with four patient treatment plans that were found infeasible during previous collision checks by therapists. The software reported collisions with the couch at similar angles to those reported experimentally. The team also tested the software with a model of a proton treatment room and a robotic patient positioning system.
“In one case, we tested in the RadCollision software a beam where the dosimetrist doubted that there was enough clearance with the toe of a patient’s foot. RadCollision predicted that clearance would be very tight, but the irradiation-optimized TPS was feasible,” comments Remillard. “When we performed a dry run, there was no collision.”
The team note that the reliability of the collision assessment depends upon the accuracy of the input data. Sources of uncertainty include changes in patient anatomy or position, patient motion, CT and/or 3D scan data, and the accuracy of 3D models of the machine and couch.
RadCollision has been created with the hope that it will aid in the development of optimally individualized treatment plans. “By providing a real-time assurance that the selected angles do not present a risk of collision, dosimetrists are less likely to shy away from irradiation geometries beneficial from the dose perspective,” write the authors. “RadCollision could be most helpful for clinical cases such as stereotactic treatments, extremities, partial breast irradiation and prone breast treatments, electron beams, and plans with drastically anterior or posterior isocentres.”
“We are aware of hospitals in the UK, France, Italy, the Netherlands, Spain and the United States trying out our script,” Hueso-González tells Physics World. “We can’t use it yet on a clinical basis here at Mass General because we are awaiting an upgrade of TPS software that will be compatible. We anticipate starting to use it clinically in January 2021.”
The toughening mechanisms that make the diabolical ironclad beetle extremely resistant to crushing have been uncovered by researchers in the US and Japan. David Kisailus at the University of California, Riverside and colleagues found that interlocking sutures in the exoskeletons of the insects allowed them to stiffen when under stress. The team then created artificial materials inspired by this design – which could allow engineers to develop better techniques for fastening objects together.
Engineers have a wealth of techniques at their disposal for joining dissimilar materials together: including welding, gluing, and mechanical fastening. However, these joins tend to fail when subjugated to crushing and high-stress impacts. Over many millions of years of evolution, a variety of plant and animal species have found highly sophisticated solutions to this problem. One particularly striking example is the diabolical ironclad beetle, which inhabits the deserts of southern California. The secret to the ironclad’s toughness lies in its exoskeletal forewings, or elytra, which allow it to easily withstand impacts during attacks from predators.
Compression tests
In their study, Kisailus’ team studied the properties of the ironclad’s elytra in detail to understand why they are so resistant to crushing. Firstly, they performed compression tests on exoskeletons of the insects. As stress increased, they observed the structures becoming stiffer – enabling them to withstand a maximum force close to 39,000 times their own weight.
Strong bonds: cross section of the medial suture, where two halves of the diabolical ironclad beetle’s elytra meet, showing the jigsaw puzzle configuration. (Courtesy: Jesus Rivera/UCI)
In the main part of the study, Kisailus and colleagues used high-resolution microscopy – including computerized tomography and scanning electron microscopy – to uncover the multiscale architectures responsible for this stiffening. Whereas the elytra in most beetles are free to move independently, the team’s images revealed unique medial sutures that permanently fused both parts of the ironclad’s elytra together. These sutures used interlocking jigsaw-puzzle arrangements of ellipsoidal blades (see figure: “Strong bonds”).
Next, the researchers created 3D-printed replicas of these sutures and subjected them to high stresses in the lab. These tests revealed that the interlocking blades did not suddenly snap at their thinnest points to release stress; instead, they gave way gradually as the blades split apart into layers, which remained connected by fibre bridges. This meant that mechanical failure could occur gradually.
Finally, Kisailus and colleagues used carbon fibre-reinforced elements to create artificial sutures from interlocking blades. This enabled them to fuse segments of aircraft made from different materials, without the need for rivets or fasteners – which can fail catastrophically when too much stress is applied. By clearly demonstrated the superior qualities of their bio-inspired material, the team hopes that their discoveries will lead to tough, impact- and crush-resistant structures for joining dissimilar materials together.
The ASTRO Annual Meeting is the world’s largest scientific meeting on radiation oncology. And like many conferences and other events around the globe, this year’s meeting has gone entirely virtual. Billed as “a virtual experience unlike any other”, the 2020 ASTRO Annual Meeting includes live and pre-recorded education and scientific presentations, many with live Q&A sessions, as well as breakout rooms for networking, chat and product demonstrations.
The theme of this year’s meeting is “global oncology: radiation therapy in a changing world”. According to ASTRO president Thomas Eichler, the primary focus will be on global cancer issues, with expert analysis, fireside chats and TED style presentations. The meeting will also include information regarding the impact of the coronavirus pandemic on healthcare professionals and patients.
This year’s meeting also incorporates a cutting-edge Virtual Exhibit Hall. This highly interactive online environment allows attendees to visit exhibitors, learn about their products and services, and chat with booth representatives. It also includes industry expert theatres and industry satellite symposia, where attendees can find out about trends and treatment options on the horizon and how these will impact patient care. Here’s a selection of some of the innovations on show at the 2020 ASTRO Annual Meeting.
Innovating and evolving radiotherapy quality assurance
Quality assurance (QA) plays a fundamental role in any radiotherapy procedure. IBA Dosimetry is working to shape QA to advance patient safety in radiation therapy, proton therapy and medical imaging. The company predicts that its latest innovations will bring the accuracy and efficiency of QA to a new level. Future solutions, meanwhile, will significantly reduce QA times and further streamline the medical physics workload.
Independent QA is essential to ensure reliable, trustworthy and accurate QA, and has been assumed as a given in the radiotherapy community. But as radiotherapy systems increasingly offer built-in “self-check” QA, the need for independent QA becomes imperative. To raise awareness of this topic, IBA Dosimetry has teamed with radiotherapy QA equipment vendors worldwide to launch an “Independent Quality Assurance” initiative.
Convergence of machine QA and patient QA will unlock the potential of real risk-based radiotherapy QA. (Courtesy: IBA Dosimetry)
IBA Dosimetry also highlights the need for convergence of machine and patient QA. Today, QA applications for validating the treatment machine and those for verifying the patient-specific plan generally have little or no connectivity. Combining data from patient QA and machine QA will provide more precise outcomes and faster results.
These QA innovations are based on four strategic pillars – implementation of measurements, integration, smart automation and prediction of QA results – that help save valuable time of the medical physicist and provide higher accuracy and increased confidence. IBA Dosimetry notes that while measurements will remain important for future QA, further integration, Monte Carlo-based predictive QA and automation will enable users to measure only where it really matters, leading to fewer measurements with better quality results.
IBA Dosimetry’s QA innovation strategy is based on four pillars: measure, integrate, automate and predict. (Courtesy: IBA Dosimetry)
Motion phantoms provide end-to-end radiotherapy QA
With the advancement of radiotherapy techniques designed to escalate delivered tumour doses, there is an increasing need for quality assurance tools (QA) in radiation treatment planning. Medical physicists are looking to improve treatment delivery by optimizing current 4D image-guided radiotherapy (IGRT) protocols and exploring rapidly advancing adaptive techniques.
Modus QA specializes in high-quality radiotherapy QA phantoms, including end-to-end QA solutions for 4D IGRT. Designed by medical physicists and built based on clinical needs, the company’s product range includes targeting QA phantoms, motion QA phantoms, as well as geometric distortion devices for MR-guided radiotherapy and 3D dosimetry systems.
Modus QA offers a range of motion QA phantoms for MR-guided radiotherapy and respiratory motion simulation. (Courtesy: Modus QA)
In this on-demand presentation, End-to-end motion QA in radiation therapy treatment planning, Rocco Flores provides an overview of the company’s CT and MR-safe motion phantoms, with an emphasis on how the phantoms can meet current and future QA needs. Flores, a product manager at Modus QA, discusses 4D IGRT, explaining the need to reduce treatment volumes and the methods used to mitigate patient motion. He goes on to describe how the company’s motion QA phantoms can be used to provide end-to-end QA of CT-based and MRI-based treatment systems.
SunCHECK Platform optimizes remote QA
For too long, radiation therapy quality assurance (QA) has required multiple databases and manual processes to get the job done. Fragmentation with no automation makes working at home harder than it needs to be. Sun Nuclear’s SunCHECK Platform solves this.
On-site or at home, SunCHECK users can perform QA in the same way. (Courtesy: Sun Nuclear)
SunCHECK aggregates disparate databases, automates inefficient tasks and centralizes critical patient and machine data to provide easier access by staff. The platform delivers a worklist-oriented dashboard, remote development of tests, as well as real-time results via direct device connectivity, automated data transfer and analysis.
Over 800 centres worldwide have adopted SunCHECK. Many users report that the platform has proved essential to their operational continuity through the COVID-19 pandemic. SunCHECK’s remote access helps minimize time in the clinic, for example, while automation reduces reliance on physical tools.
Patient QA and machine QA information are presented in a single interface. (Courtesy: Sun Nuclear)
Sun Nuclear is hosting a session entitled “Performing QA remotely in the age of COVID” at the 2020 ASTRO Annual Meeting, in the Innovation Hub. Presented by Jason Tracy, a medical physicist at Sun Nuclear, the session will take place on 26 October at 11.45 EST.
SBRT for localized prostate cancer: Biology Meets Technology
When hypofractionated radiotherapy is delivered via stereotactic body radiation therapy (SBRT), a strict adherence to dose–volume constraints to the surrounding at-risk organs is paramount. Specifically, the steep dose gradients associated with SBRT plans require a high level of reliability during the entire treatment delivery process.
The RayPilot HypoCath offers real-time prostate tracking, without surgical intervention. (Courtesy: Micropos Medical)
The RayPilot HypoCath from Micropos Medical is designed to enhance the precision of prostate cancer SBRT. The system is a removable electromagnetic tracking device that enables real-time localization of the prostate during both conventional and hypofractionated radiotherapy. With the transmitter integrated in a standard Foley catheter, RayPilot HypoCath may offer better localization of the prostate and its motion (for accurate treatment) and helps outline the urethra. It can be used with conventional linacs and requires no surgical intervention.
The white paper, SBRT for localized prostate cancer: Biology Meets Technology, describes the first clinical experience using the RayPilot HypoCath at Ospedale San Gererdo in Monza, Italy. The hospital started SBRT treatment of prostate cancer patients using RayPilot HypoCath in June. In the white paper, head of the clinic Stefano Arcangeli describes how the tracking device fits into precision radiation treatment of prostate cancer.
STEEV phantom enables end-to-end testing of SRS systems
Stereotactic Radiosurgery (SRS) necessitates a high degree of accuracy in target localization and dose delivery. With this in mind, CIRS offers the Stereotactic End-to-End Verification (STEEV) phantom, which provides a means to check all necessary steps of a treatment planning system – from diagnostic imaging with CT, MR and PET, through to plan verification.
The STEEV phantom (left) and a CT image of the phantom with the 038-13 insert. (Courtesy: CIRS)
STEEV’s anthropomorphic exterior enables the use of clinical positioning and fixation. The phantom’s internal details – such as cortical and trabecular bone, brain, spinal cord, teeth, sinuses and trachea – provide a realistic clinical simulation, enabling end-to-end testing of SRS systems in the most challenging anatomical regions. Geometric and organic target inserts enable comprehensive image quality assurance (QA), geometric machine QA and treatment planning system QA.
STEEV accommodates five interchangeable multi-modality inserts, which come with a variety of internal targets and are filled with MRI- or PET-compatible liquids. Five external MRI/CT fiducials enable additional alignment and distortion evaluation. The phantom can also accommodate a variety of tissue-equivalent inserts suitable for small-field dosimetry.
Persona CT streamlines radiology and oncology treatment planning
CT is an invaluable tool when treating cancer with radiation therapy. Studies have shown that CT is increasingly used in tumour volume estimation, with image quality critical to the accuracy and ease of treatment planning.
The Persona CT system offers advanced imaging with high precision, accuracy and reliability. (Courtesy: Fujifilm)
Fujifilm and Analogic have joined forces to offer healthcare providers an innovative CT system that enables new workflows in oncology imaging and treatment, while seamlessly executing diagnostic radiology requirements for all body types. With a unique 85 cm bore and 64-/128-slice performance, the Persona CT is a revolutionary CT system that helps to simplify oncology treatment planning.
The Persona CT’s large bore adds comfort for patients of any size. Fast acquisition further enhances the patient experience, while easy operation improves workflow, speed and accuracy. The scanner offers advanced automated dose optimization and synchronized dose-lowering acquisition technologies. Meanwhile, its low-noise acquisition system and refined image processing with artificial intelligence deliver exceptional image quality.
Finally, the Persona CT offers advanced applications powered by Fujifilm’s Synapse 3D software, as well as specialized 3D tools for coronary, brain, respiratory, orthopaedics and whole-body applications.
ExacTrac Dynamic patient positioning system merges surface and X-ray tracking
ExacTrac Dynamic is the next-generation patient positioning and monitoring system from Brainlab. The new system offers never-before-seen, high-speed thermal surface tracking technology combined with an update of ExacTrac X-ray monitoring.
ExacTrac Dynamic combines cutting-edge tracking technologies to achieve radiotherapy positioning and monitoring with submillimetre accuracy. (Courtesy: Brainlab)
For thermal tracking, the 4D thermal camera creates a highly accurate and reliable hybrid thermal surface by correlating the patient’s heat signature to their reconstructed 3D surface structure. To achieve this, 300,000 3D surface points are acquired and matched to the heat signal generated by the thermal camera, creating another dimension to track their position.
The X-ray monitoring system includes larger (compared with ExacTrac 6.5 or 6.2) panels that show more anatomy for easier orientation and interpretation of X-ray images, while improved soft-tissue contrast and enhanced read-out speed prevent motion blurring effects. The higher heat capacity of the X-ray tubes supports more automated, high-frequency imaging. New clinical workflows allow for treatment of a wide array of indications. Together, these advancements make ExacTrac Dynamic the all-in-one radiotherapy tracking solution.
The MRgRT Motion Management QA phantom from CIRS is designed to address the quality assurance (QA) needs of MR-guided radiotherapy. The phantom is MR-safe due to the use of piezoelectric motors and non-ferromagnetic materials. The two piezoelectric motors move a cylindrical insert, which contains a tracking target, through a gel/liquid-fillable body by rotating it independently from the motion in the inferior–superior direction.
The MRgRT Motion Management QA phantom (left) and an MR image of the phantom. (Courtesy: CIRS)
The moving insert contains a “tumour” target filled with gel, surrounded by the same background gel used to fill the “body”. This body includes simulated lungs, liver, kidney and spine, providing a heterogeneous background. The simulated organs are filled with gels that provide CT and MR contrast versus the background gel. All organs (except for the lungs) also offer ion chamber dosimetry cavities, enabling completion of the entire QA process: from imaging to planning to verification of the delivered dose.
The phantom is driven by CIRS Motion Control software, which offers multiple built-in motion profiles for commissioning and routine QA, as well as allowing import of complex patient-specific respiratory waveforms. It can also set up independently controllable waveforms for the insert’s linear and rotational motion. To enable verification of beam latency, the inferior–superior motion of the insert/moving target can be gated based on amplitude.
It’s the year 3000 and your great, great, great granddaughter is swimming in Kraken Mare, a gigantic lake of liquid methane and ethane, on Saturn’s moon Titan. The low gravity allows her to leap up and out of the water like a dolphin breaching. As she does so, her enormous eyes (inherited from her father, whose family evolved them on dimly lit Mars) peer through the lenses of her thermal suit at the surrounding deep-hulled sailboats zipping along. In the hazy distance, giant server farms pump out their excess heat into the usefully chilly –180 °C surroundings. Inside, trillions of uploaded human consciousnesses do, well, whatever the digital equivalents of brains-in-jars do, I suppose.
This vivid vision of future recreation is just one possibility teased out in the course of science journalist Christopher Wanjek’s enchanting new book, Spacefarers: How Humans Will Settle the Moon, Mars, and Beyond. The work is rich in detail, accessible, refreshingly frank and compellingly written – in fact, I would go as far as to declare it, hands-down, the most enjoyable piece of non-fiction I have read in years. Starting with a captivating review of humanity’s current progress on the path to settling other bodies in the solar system – from geopolitical drivers to financial constraints – Wanjek explores the challenges and motivations of recreating the Earth-like conditions necessary for our survival, out in space and on neighbouring worlds.
Of note is a running (and particularly candid) assessment of NASA’s activities and administrative challenges, which offered much food for thought. Launching from this foundation, the second half of the book sets out to envisage what our future in space might be like. They range from the current interest in returning to the Moon and the challenges of having sex in space – all the way to extracting helium-3 and nitrogen from Uranus to power future fusion reactors and populating the atmospheres of majestically spinning, orbiting cities assembled across the solar system.
It should be said that, for me, Wanjek’s work is stronger when engaging with present-day and historical material. The latter half of Spacefarers is (while no less riveting) obviously speculative, with all the incertitude that such an undertaking makes inherent. There is not a small amount of irony in that Wanjek kicks off the book by criticizing the depictions of space travel in film and, later, the fantasies of some futurists. While I suspect that I shall greet much science fiction now with a more sceptical eye, some of his suggestions (as alluded to above) hardly seem less fantastical.
There were a few aspects of Spacefarers that I did find frustrating. At various points, Wanjek envisages off-world settlements as being appropriate for a certain type of retirement community. Until the final third of the work, however, the reasons to create such a “space Miami” did not seem well articulated – the ultimate rationale seems to be to find a demographic of settler unconcerned by the long-term risks of heightened radiation exposure, the weaker gravity, and potential complications around gestating children.
In the opening chapter, meanwhile, a colourful anecdote about Russia’s first experiment to simulate the psychological and physical impacts of long-term confinement during an interplanetary mission – the usefulness of which was compromised by an episode of drunken fisticuffs and sexual harassment – would have benefitted from a more explicit condemnation of the latter behaviour. That is especially so in the light of the many challenges women face working in STEM fields, not to mention their general side-lining in space programmes to date. Instead, Wanjek immediately notes that a similar experiment conducted almost a decade later, the Mars500 mission, “went more smoothly, as Russia decided to exclude females” – a statement that manages to couple implications of victim-blaming with phrasing many consider to be derogatory as well as grammatically awkward. (Where’s the noun? Are we even talking about humans?)
Similarly, a later joke about the “obscurity” of the Italian Space Agency also read poorly. When added to the awkward implication in the same chapter that “grown men” are only justified in hugging and kissing with “good reason” (that is, celebrating successfully landing tech on Mars), it served to further the unfortunate overall impression that the author’s values might not be quite as progressive as his vision for humanity’s next steps off-world. This may be an accidental misrepresentation in poorly chosen words – and certainly these are minor points in an extensive work – but they sadly detracted from my ability to recommend this book with a total lack of reservation.
This time we are featuring white papers, case studies and a webinar from RaySearch Laboratories.
The machine learning planning module in RayStation* can generate one or multiple deliverable treatment plans in just minutes. The automated treatment planning method learns from historical patient and plan data, and infers a 3D spatial dose on a new patient geometry. This new approach to planning can improve efficiency, reduce treatment plan variability and facilitate knowledge sharing. The white paper, Machine learning automated treatment planning, introduces RayStation’s machine learning planning module and describes a clinical study on head-and-neck cancer cases conducted at University Medical Center Groningen.
Provision CARES Proton Therapy in Nashville, USA, is the first clinic to connect the oncology information system RayCare* directly to the treatment delivery system, using it to record and verify the treatment sessions. In 2018, Provision also became the first clinic worldwide to use RaySearch software exclusively. In the case study, Optimizing the patient journey with RayCare, the Provision team describe their experience of using RayCare and how the system meets the clinic’s specific needs.
High-quality contours of anatomical structures are a vital aspect of radiation therapy, but the process of manually delineating regions-of-interest is time-consuming and suffers from inter- and intra-practitioner variability. With the automatic tools in RayStation, this process can be greatly simplified. The latest technique is deep-learning segmentation, which is able to learn from an unlimited number of patients and still automatically generate contours of all relevant regions-of-interests in under a minute. This approach, described in the white paper Deep-learning segmentation, provides a highly powerful tool for patient modelling in RayStation.
University Medical Center Groningen (UMCG) has teamed up with RaySearch to evaluate the first fully automated machine learning framework for generating robust treatment plans. The case study, Automated robust planning for IMPT in HN cancer using machine learning, describes the use of machine learning to create robust intensity modulated proton (IMPT) plans for oropharyngeal cancer patients. The robust machine learning planning framework* will be clinically available in the RayStation 10B release in December 2020.
Treatment planning for radiation therapy inevitably involves compromises between dose to the tumour volume and sparing of healthy structures. These trade-offs are conventionally handled using trial and error, where parameters such as objective function weights are adjusted and the treatment plan is reoptimized multiple times. Manual parameter tuning is inefficient, and the quality of the result dependent upon the experience and skill of the treatment planner. The white paper Multi-criteria optimization in RayStation introduces the use of multi-criteria optimization (MCO) in treatment planning to provides a more streamlined and intuitive workflow. With MCO, the clinical plan is selected by continuous navigation over the set of possible plans, enabling clinicians to make informed and structured treatment decisions.
Information systems at hospitals support the collection and communication of everything from patient tracking to billing information and treatment history. Commonly, there are multiple information systems, which should seamlessly communicate with each other to support efficient and safe care by avoiding manual transfer of data between hospital systems. The RayCare oncology information system is designed for integration with external healthcare information systems, such as EPIC. The white paper, RayCare connectivity, explores the integration of RayCare between hospital information systems to support a complete view of the patient’s data for clinicians.
Finally, RaySearch presents the webinar Machine learning in radiation oncology. In this virtual product unveiling for ESTRO 2020, Fredrik Löfman and the machine learning team at RaySearch discuss machine learning, including the deep learning segmentation application, machine learning planning and a brief introduction to RaySearch’s latest innovation, RayIntelligence.
Magnetism in two-dimensional materials is difficult to characterize because the materials’ extreme thinness renders conventional techniques ineffective. Researchers in Australia, Russia and China have now used a new method called wide-field nitrogen-vacancy (NV) microscopy to measure the magnetic strength of vanadium triiodide (VI3), a 2D material that is known to be strongly ferromagnetic in its bulk, 3D form. The technique could also be used to study other 2D magnetic materials – including some possible building blocks for future energy-efficient electronic devices.
An NV microscope is a recently-developed instrument that uses defects in diamond as sensitive probes of weak magnetic fields. It is particularly well-suited for analysing samples of van der Waals materials (that is, materials composed of atomically thin layers that interact with each other via weak van der Waals forces) because it enables researchers to image magnetic domains (microscopic regions in which all magnetic moments point in the same direction) in individual flakes of the material with sub-micron resolution.
NV centres as detectors of weak magnetic fields
In the present study, researchers led by Lloyd Hollenberg of the University of Melbourne used an NV microscope made from a diamond substrate with a surface layer of defects. These defects are known as NV centres, and they occur when adjacent carbon atoms in the diamond lattice are replaced with a nitrogen atom and an empty lattice site. The nitrogen has an extra electron that remains unpaired, and therefore behaves as an isolated spin that can be up, down or a superposition of the two. The state of this spin can be probed by illuminating the diamond with laser light and recording the intensity and “spin-active” frequencies of the fluorescence emitted.
Because NV centres are naturally isolated from their surroundings, the spin state of their electrons is not immediately affected by surrounding thermal fluctuations. They can therefore be used to detect the very weak magnetic fields stemming from nearby electronic or nuclear spins – making them highly sensitive probes of magnetic resonance, capable of monitoring local spin changes in a material over distances of a few tens of nanometres.
Measuring magnetic field behaviour
In their experiments, Hollenberg and colleagues placed their sample of VI3 on top of the NV microscope’s defect layer, excited the NV centres with a laser and used a camera to image the resulting fluorescence. By sweeping the frequency of an applied microwave field across the sample (which they placed in a cryostat so that they could repeat the measurements at temperatures ranging from 4 to 300 K), they obtained what is known as an optically-detected magnetic resonance spectrum for their sample.
When the researchers applied a magnetic field of 0.5 to 1 Tesla perpendicular to their samples (the +z direction) at a temperature of 5 K, they observed complete and abrupt switching of the magnetic field direction in most flakes, with no intermediate partially-reversed state. This ferromagnetism persists down to two atomic layers, while the switching remains abrupt up to 50 K, which is VI3’s Curie temperature (that is, the temperature at which the bulk material loses its permanent magnetism).
VI3 is a nucleation-type hard ferromagnet
In hard magnetic materials like VI3, the direction-switching process depends on one of two mechanisms: nucleation or pinning of domain walls. In bulk materials, these mechanisms can normally be distinguished by their initial magnetization curves. These curves are produced by placing a sample of a magnetic material in a magnetic field and measuring how its magnetization increases.
In a nucleation-type magnet, the domain walls move freely. In a pinning-type magnet, as the name suggests, they are constantly being trapped. To determine which type of mechanism was at play in ultrathin VI3, Hollenberg and colleagues applied short magnetic pulses (around 10 nanoseconds long) in the -z direction to samples that had initially been magnetized in the +z direction and imaged the magnetization in a low magnet field after each pulse.
The results obtained suggest that ultrathin VI3 is a nucleation-type hard ferromagnet. However, the researchers also found that the magnetic strength of 2D VI3 is roughly half that of its 3D counterpart. “This was a bit of a surprise, and we are currently trying to understand why the magnetisation is weaker in 2D, which will be important for applications,” says team member Jean-Philippe Tetienne.
According to Artem Oganov of the Skolkovo Institute of Science and Technology in Moscow, the group’s work could lead to new technologies. “Just a few years ago, scientists doubted that two-dimensional-magnets are possible at all,” says Oganov, who was also part of the research team. “With the discovery of two-dimensional ferromagnetic VI3, a new exciting class of materials emerged. New classes of material always mean that new technologies will appear, both for studying such materials and harnessing their properties.”
Members of the team, who include researchers from the University of Basel, RMIT University, Nanjing University of Posts and Telecommunications, Moscow Institute of Physics and Technology, Northwestern Polytechnical University, and Renmin University of China, say they now plan to use their NV microscope to study other 2D magnetic materials. They report their work in Advanced Materials.
In this podcast, Ranga Dias talks about research that is described in a paper in Nature. This paper has since been retracted by the journal.
Finding a material that is a superconductor at room temperature has been the Holy Grail of condensed matter physics for over a century. In this episode we meet Ranga Dias of the University of Rochester whose team has created a material that is a superconductor at 15 °C. The only catch is that it has to be squeezed at a pressure of two million atmospheres, and Dias explains how this pressure could be reduced.
The direct detection of dark matter is also worthy of Holy Grail status, which is why particle physicists where thrilled in June 2020 when the XENON1T collaboration reported a mysterious signal in their dark-matter detector. After the announcement, theorists around the world scrambled to make sense of the signal – resulting in five tantalizing explanations being published in the journal Physical Review Letters. One of those papers was from an international team that includes Jayden Newstead of the University of Melbourne, who joins us to talk about what the XENON1T signal could mean.
A leading theory as to why regions of the Moon’s crust are magnetized has been debunked by researchers in the US, Germany, and Australia. Through a combination of simulation techniques, a team led by Rona Oran at the Massachusetts Institute of Technology concluded that the lunar surface could not have become magnetized following high-velocity meteorite impacts in the distant past.
When the Moon’s surface was first studied in detail 50 years ago during the Apollo missions, researchers discovered regions of magnetization in the lunar crust that spanned hundreds of kilometres. In the decades since, scientists have not been able to provide a conclusive explanation for how these mysterious features formed – which would require the presence of a magnetic field of a strength that does not currently exist on the Moon.
According to the “core dynamo” theory, the rotation and convection of molten metal in the core of the ancient Moon created the required magnetic field a very long time long ago. However, many scientists have remained sceptical of this idea. Another leading theory suggests that sections of the lunar crust were vapourized by the impacts of high-velocity meteorites, releasing dense clouds of plasma. These expanding clouds would then compress and enhance the interplanetary magnetic field and amplify the induced field inside the Moon.
Several simulations
In the new study, Oran’s team put the impact theory to the test using a combination of high-resolution magnetohydrodynamic simulations – which model the coupled interactions between plasmas and magnetic fields – and simulations of the vapour clouds created by the impacts responsible for large craters on the Moon’s surface. By calculating the mass and thermal energy of the vapour emitted in these events, the group determined the extent to which compression of the interplanetary magnetic field could have induced magnetization in the crust.
Oran and colleagues identified several factors – not previously considered – that reduce the overall enhancement of the magnetic field. These include electrically resistive outer layers in the Moon’s upper mantle, which would have removed magnetic energy; a diffusive effect that would have caused the Moon’s internal field to slip around its core; and the pushing away of the compressed interplanetary magnetic field. As a result, they conclude that the fields produced following high-velocity impacts would have been some three orders of magnitude too weak to produce the magnetized regions that we observe today.
The researchers say that their study leaves the core dynamo theory as the only plausible explanation for the magnetized crust. They also suggest that equivalent dynamo mechanisms could be responsible for magnetized crusts on Mercury, as well as many of the solar system’s meteor-forming asteroids.
