FHIRing up OpenMRS: Architecture, Implementation and Real-World Use-Cases in Global Health.

HL7 FHIR was created almost a decade ago and is seeing increasingly wide use in high income settings. Although some initial work was carried out in low and middle income (LMIC) settings there has been little impact until recently. The need for reliable and easy to implement interoperability between health information systems in LMICs is growing with large scale deployments of EHRs, national reporting systems and mHealth applications. The OpenMRS open source EHR has been deployed in more than 44 LMIC with increasing needs for interoperability with other HIS. We describe here the development and deployment of a new FHIR module supporting the latest standards and its use in interoperability with laboratory systems, mHealth applications, pharmacy dispensing system and as a tool for supporting advanced user interface designs. We also show how it facilitates date science projects and deployment of machine leaning based CDSS and precision medicine in LMICs.

Going home positive: a qualitative study of the experiences of care for patients with COVID-19 who are not hospitalized.

BACKGROUND: Most Canadians diagnosed with COVID-19 have had mild symptoms not requiring hospitalization. We sought to understand the patient experience of care while being isolated at home after testing positive for SARS-CoV-2 infection. METHODS: We conducted a phenomenologically informed qualitative descriptive study using in-depth semistructured interviews to identify common themes of experience for patients sent home from hospital with a positive COVID-19 diagnosis. Between July and December 2020, we conducted interviews with patients who were followed by the North York General Hospital COVID Follow-Up Clinic. Patients with mild to moderate symptoms were interviewed 4 weeks after their COVID-19 diagnosis. We conducted the interviews and performed a thematic analysis of the data concurrently, in keeping with the iterative process of qualitative methodology. RESULTS: We conducted interviews with 26 patients. From our analysis, 3 themes were developed regarding participants' overall experience: lack of adequate communication, inconsistency of information from various sources, and the social implications of a COVID-19 diagnosis. The implications of a positive test for SARS-CoV-2 infection are substantial, even when symptoms are mild and patients self-isolate as recommended. Participants noted communication challenges and inconsistent information, leading to exacerbated stress. INTERPRETATION: Participants shared their experiences of the stigma of testing positive and the frustration of poor communication structures and inconsistent information. Experiencing care during self-isolation at home is an area of increasing importance, and these findings can inform improved support, ensuring access to equitable and safe COVID-19 care for these patients.

"It saved me from the emergency department": A qualitative study of patient experience of virtual urgent care in Ontario.

INTRODUCTION: In response to the COVID-19 pandemic, the Ontario Ministry of Health introduced a pilot program of 14 virtual urgent care (VUC) initiatives across the province to encourage physical distancing and provision of care by telephone and video-enabled visits. The implementation of the VUC pilot is currently being evaluated by an external academic team. The objective of this study was to understand patient experiences with VUC to determine barriers and facilitators to optimal virtual care as it rapidly expands during the current pandemic and beyond. METHOD: The qualitative component of the evaluation used one-on-one telephone interviews with patients, families, providers, and program administrators as the main method of data collection. Patient and family participants were invited to participate by the triage nurse after their VUC visit. Data analysis, using thematic analysis, occurred in conjunction with data collection to monitor emerging themes and areas for further exploration. RESULTS: Between April and October 2021, we completed 14 patient and/or family interviews from a representative cross-section of 6 pilot sites. Participants had a range of presenting complaints including infection, injury, medication side effects, and abdominal pain. The vast majority of participants were female (90%), and 70% were VUC patients themselves. Our analysis identified three key themes in the data which characterise patient and family member experience with VUC: a) emphasis on access to the ED; b) efficiency and quality of care; c) obtaining reassurance and next steps. CONCLUSION: Virtual care options are valued by patients and families; however, the nature of care needed by those accessing VUC and who can best provide that care needs to be evaluated to position it for sustainability. Understanding how virtual care performs from both a provider and patient perspective during the current crisis has implications for designing alternative care options beyond the COVID-19 pandemic.

Phase behaviour of coarse-grained fluids.

Soft condensed matter structures often challenge us with complex many-body phenomena governed by collective modes spanning wide spatial and temporal domains. In order to successfully tackle such problems, mesoscopic coarse-grained (CG) statistical models are being developed, providing a dramatic reduction in computational complexity. CG models provide an intermediate step in the complex statistical framework of linking the thermodynamics of condensed phases with the properties of their constituent atoms and molecules. These allow us to offload part of the problem to the CG model itself and reformulate the remainder in terms of reduced CG phase space. However, such exchange of pawns to chess pieces, or 'Hamiltonian renormalization', is a radical step and the thermodynamics of the primary atomic and CG models could be quite distinct. Here, we present a comprehensive study of the phase diagram including binodal and interfacial properties of a dissipative particle dynamics (DPD) model, extended to include finite-range attraction to support the liquid-gas equilibrium. Despite the similarities with the atomic model potentials, its phase envelope is markedly different featuring several anomalies such as an unusually broad liquid range, change in concavity of the liquid coexistence branch with variation of the model parameters, volume contraction on fusion, temperature of maximum density in the liquid phase and negative thermal expansion in the solid phase. These results provide new insight into the connection between simple potential models and complex emergent condensed matter phenomena.

"I don't know how we would have coped without it." Understanding the Importance of a Virtual Hospital Visiting Program During the COVID-19 Pandemic.

As the COVID-19 pandemic reached Canada in full strength, the concept of allowing visiting to patients became an impossibility in most healthcare organizations. In March 2020, hospitals across Canada made the decision to close to visitors. This was a complicated decision which left admitted patients with very little option for connecting with family and friends other than through the telephone. In response, North York General Hospital launched a virtual family visiting (VFV) program across all inpatient units. Here we report the findings of a qualitative study of the program informed by an interpretive descriptive approach. Interviews were conducted with families who participated in the VFV program at North York General Hospital in Toronto, Canada during the first wave of the COVID pandemic. A total of 24 family members were interviewed. As anticipated, the family members were all extremely pleased with the opportunity to connect virtually and very satisfied with the VFV program. What was less anticipated was the anxiety and distress that families experienced in being separated from their loved ones. Our data analysis revealed 4 key themes which we have labeled (a) the unforeseen consequences of separation trauma, (b) increased vulnerability of patients and family, (c) a lifeline of human connection, and (d) the role of the facilitator as a connector. This work contributes significantly to a system-level understanding of the impact of imposed separation, increased vulnerability, and the importance of providing an alternative way for families to be present with their loved ones in these unprecedented times.

Training the Next Generation of Diabetes Researchers: Evaluation of the Diabetes Action Canada Training and Mentoring Program.

BACKGROUND: The Diabetes Action Canada Training and Mentoring (DAC-TM) Program launched in June 2017, with the goal of building capacity in the next generation of diabetes researchers in Canada in patient-oriented research (POR). METHODS: We conducted a program evaluation of the DAC-TM program using a sequential, mixed-methods research design. RESULTS: Our analysis of 82 surveys and 22 in-depth interviews from a wide range of DAC-TM Program stakeholders revealed consistent patterns in experience with the program. The training sessions were perceived to be well-organized, convenient educational opportunities to gain new knowledge about POR and become integrated into a community of practice of POR researchers who study diabetes and its complications in Canada. The content of the training was perceived to be useful and relevant to participants, although improvements could be made to help address the training needs of the broader DAC community. There is broad support for and appreciation of the mentorship awards, which were perceived to be appropriately targeted to early-career investigators. The mentor-mentee relationships were perceived to be positive, productive and career-advancing overall, but could benefit from a more strategic design and promote better connectivity to foster mentor-mentee relationships. In addition, feedback about opportunities to network and forge new connections was mixed and represents another opportunity for improvement to strengthen capacity building. CONCLUSIONS: Findings from this formative evaluation study show key strengths and opportunities to improve the DAC-TM Program, which can be used to help enhance its function and promote its long-term sustainability.

Virtual Specialist Care During the COVID-19 Pandemic: Multimethod Patient Experience Study.

BACKGROUND: Transitioning nonemergency, ambulatory medical care to virtual visits in light of the COVID-19 global pandemic has been a massive shift in philosophy and practice that naturally came with a steep learning curve for patients, physicians, and clinic administrators. OBJECTIVE: We undertook a multimethod study to understand the key factors associated with successful and less successful experiences of virtual specialist care, particularly as they relate to the patient experience of care. METHODS: This study was designed as a multimethod patient experience study using survey methods, descriptive qualitative interview methodology, and administrative virtual care data collected by the hospital decision support team. Six specialty departments participated in the study (endoscopy, orthopedics, neurology, hematology, rheumatology, and gastroenterology). All patients who could speak and read English and attended a virtual specialist appointment in a participating clinic at St. Michael's Hospital (Toronto, Ontario, Canada) between October 1, 2020, and January 30, 2021, were eligible to participate. RESULTS: During the study period, 51,702 virtual specialist visits were conducted in the departments that participated in the study. Of those, 96% were conducted by telephone and 4% by video. In both the survey and interview data, there was an overall consensus that virtual care is a satisfying alternative to in-person care, with benefits such as reduced travel, cost, time, and SARS-CoV-2 exposure, and increased convenience. Our analysis further revealed that the specific reason for the visit and the nature and status of the medical condition are important considerations in terms of guidance on where virtual care is most effective. Technology issues were not reported as a major challenge in our data, given that the majority of "virtual" visits reported by our participants were conducted by telephone, which is an important distinction. Despite the positive value of virtual care discussed by the majority of interview participants, 50% of the survey respondents still indicated they would prefer to see their physician in person. CONCLUSIONS: Patient experience data collected in this study indicate a high level of satisfaction with virtual specialty care, but also signal that there are nuances to be considered to ensure it is an appropriate and sustainable part of the standard of care.

Staff perceptions of the implementation of a trauma video review program at a level I trauma center.

OBJECTIVES: Successful implementation of any new technology requires extensive engagement with front-line staff. We explored the perceptions of emergency department and trauma staff about a trauma video review program (TVR) prior to implementation of the first such program in Canada at our level I trauma center. METHODS: We conducted semi-structured individual interviews and in situ small group interviews with 35 multidisciplinary ED and trauma staff members of a teaching and research hospital in Toronto, Canada. We sought maximum variation in the sample of purposively selected participants. Interviews were recorded with audiotapes or detailed field notes, transcribed verbatim, coded, and analyzed using standard thematic analysis techniques. RESULTS: Participants expressed overall support for the concept of TVR, but there is a core sense of unease that influenced overall staff perceptions. Despite several departmental presentations, very few participants actually had a solid understanding of how the TVR worked. Many were apprehensive about their own professional privacy, deeply concerned about vulnerable patients being filmed without consent, and questioned how video data would be used. Despite significant hesitancy, ED and trauma staff identified positive opportunities that TVR could bring, including providing an evidence base for quality improvement. CONCLUSIONS: TVR is an evolving approach to evaluate quality and patient safety in the trauma bay. As such it brings with it natural concerns and apprehension from staff regarding privacy, confidentiality, and how data will be captured and used. There is opportunity for these types of concerns to be addressed with a robust knowledge translation plan and engagement of staff throughout the implementation process.

Moving from physical survival to psychologic recovery: a qualitative study of survivor perspectives on long-term outcome after sudden cardiac arrest.

BACKGROUND: Over 400,000 adults suffer out-of-hospital cardiac arrests (OHCA) each year in North America. Despite a very high mortality rate, even 10% survival means that a minimum of 3500 people return to their lives and their families. However, their experience of living and their health-related quality of life after such a life-changing event are quite variable, much more complex than just having lived or died, and should not be reduced to crude measures of neurological functioning. METHODS: We conducted 32 in-depth qualitative interviews with survivor/family member dyads at various stages of survival. The interviews focused on the recovery journey, long-term issues most important to them and how measuring such concepts could help. Interviews were audio-taped, transcribed verbatim and analyzed using constant comparative thematic analysis techniques. RESULTS: During in-depth interviews with more than 30 survivors and caregivers we have heard that despite being a relatively high functioning group, their lives have been deeply affected by their cardiac arrest experience. They speak about the importance of both psychologic and physical recovery, the impact of return to work or changes in work identity and the necessity of support from family members in the recovery process. Spouses/family members also mentioned differences in perspective on their loved one's recovery and how they manage the fear of recurrence. CONCLUSIONS: This work purposively brings a unique lens to the concept of cardiac arrest outcomes by placing priority on what is important to survivors and their families and what we may be missing in standard outcomes measures. There is a clear need for a more patient-centred outcome set for this population and our work indicates that psychologic assessment, return to work status and family input are key domains to be considered.

Partnering with survivors & families to determine research priorities for adult out-of-hospital cardiac arrest: A James Lind Alliance Priority Setting Partnership.

BACKGROUND: Research priority setting in health care has historically been done by expert health care providers and researchers and has not involved patients, family or the public. Survivors & family members have been particularly absent from this process in the field of resuscitation research and specifically adult out of hospital cardiac arrest (OHCA). As such, we sought to conduct a priority setting exercise in partnership with survivors, lay responders and their families in order to ensure that their priorities were visible. We partnered with the James Lind Alliance (UK) and used their commonly used consensus methodology for Public Priority Setting Partnerships (PSPs) to identify research priorities that reflected the perspectives of all stakeholders. METHODS: We used two rounds of public and health care professional surveys to create the initial priority lists. The initial survey collected open-ended questions while the second round consolidated the list of initial questions into a refined list for prioritization. This was done by reviewing existing evidence and thematic categorization by the multi-disciplinary steering committee. An in-person consensus workshop was conducted to come to consensus on the top ten priorities from all perspectives. The McMaster PPEET tool was used to measure engagement. RESULTS: The initial survey yielded more than 425 responses and 1450 "questions" from survivors and family members (18%), lay responders, health care providers and others. The second survey asked participants to rank a short list of 125 questions. The final top 25 questions were brought to the in-person meeting, and a top ten were selected through the JLA consensus process. The final list of top ten questions included how to improve the rate of lay responder CPR, what interventions used at the scene of an arrest can improve resuscitation and survival, how survival can be improved in rural areas of Canada, what resuscitation medications are most effective, what care patient's family members need, what post-discharge support is needed for survivors, how communication should work for everyone involved with a cardiac arrest, what factors best predict neurologically intact survival, whether biomarkers/genetic tests are effective in predicting OHCA and more research on the short and long-term psycho-social impacts of OHCA on survivors. The PPEET showed overwhelmingly positive results for the patient and family engagement experience during the final workshop. CONCLUSIONS: This inclusive research priority setting provides essential information for those doing resuscitation research internationally. The results provide a guide for priority areas of research and should drive our community to focus on questions that matter to survivors and their families in our work. In particular the Canadian Resuscitation Outcomes Consortium will be incorporating the top ten list into its strategic plan for the future.

Qualitative evaluation of a mandatory provincial programme auditing emergency department return visits.

OBJECTIVE: The objective of this qualitative study was to evaluate the perceived impact and value of the Return Visit Quality Programme (RVQP), a mandatory province-wide emergency department audit programme. DESIGN: We employed an interpretive descriptive qualitative approach with maximum variation sampling to ensure diverse representation across several geographical and institutional factors. RVQP programme leads were invited to participate in semistructured interviews and snowball sampling was used to reach non-lead physicians to capture the perspectives of those working within the programme. SETTING: In Ontario's RVQP, participating emergency departments must audit their return visits resulting in admission to identify issues that can be addressed through quality improvement initiatives. PARTICIPANTS: Between June and August 2018, we interviewed 32 participants (local programme leads and non-lead physicians) from 23 out of the 86 participating centres. RESULTS: Participants' perceived impact and value of the programme was associated with the existence (or absence) and nature of the local quality improvement culture, the implementation approach of the programme within their emergency departments, and key aspects of the programme pertaining to medicolegal concerns and resource availability. CONCLUSIONS: This study of an innovative, large-scale programme aimed at promoting continuous quality improvement in emergency departments showed that while its perceived impact has been meaningful, there are key structural and operational elements that support and hinder this aim. Healthcare leaders should consider these findings when looking to implement large-scale audit or quality improvement programmes.

Reframing How Early Pregnancy Loss Is Viewed in the Emergency Department.

Women experiencing early pregnancy loss frequently seek care in emergency departments or early pregnancy clinics. The existing qualitative literature on the experience of miscarriage has yet to address how to connect how these women perceive their care experience and the prevailing structures which may be at the root of why their experience continues to be challenging. This study aimed to look deeper into the sources of negative experiences of early pregnancy loss for insight into how to rethink where to make impactful changes to care. Phenomenologically informed interviews with 59 women revealed several points of tension in the framing of early pregnancy loss, including the view of miscarriage as common, of it as a medical versus emotional experience, and the assumptions around care needs. Our work suggests that these tensions need to be dismantled through more patient-centered approaches to patient-provider relationships, policies, models of care, and medical discourse.

PROM-ED: Development and Testing of a Patient-Reported Outcome Measure for Emergency Department Patients Who Are Discharged Home.

STUDY OBJECTIVE: Common outcomes of care valued by emergency department (ED) patients who are not hospitalized have been characterized, but no measurement instrument has been developed to date. We developed and validated a patient-reported outcome measure for use with adult ED patients who are discharged home (PROM-ED). METHODS: In previous research, 4 main outcomes of importance to ED patients were defined: symptom relief, understanding, reassurance, and having a plan. We developed a bank of potential questions (phase 1) that were first tested for suitability through cognitive debriefing with patients (phase 2). Revised questions were then tested quantitatively with a large panel of participants who had recently received ED care (phase 3). Informed by these results, a panel of experts used a modified Delphi process to make decisions on item reduction. The resulting instrument (PROM-ED 1.0) was then evaluated for its measurement properties (structural validity, hypothesis testing, and reliability). RESULTS: Sixty-seven questions divided among 4 scales (1 for each outcome domain) were assembled. In accordance with cognitive debriefing with 8 patients (phase 2), 15 questions were modified and 13 removed. Testing of these questions with 444 participants (phase 3) identified problematic floor or ceiling effects (n=10), excessive correlations between items (n=11), and low item-total correlations (n=7). The expert panel (22 participants, phase 4) made decisions using this information on the exclusion of items, resulting in 22 questions across 4 scales that together constitute the PROM-ED 1.0. Testing provided good evidence of validity and test-retest reliability (n=200). CONCLUSION: The PROM-ED enables the measurement of patient-centered outcomes of importance to patients receiving care in the ED who are not hospitalized. These data could have important applications in research and care improvement.

"Drones are a great idea! What is an AED?" novel insights from a qualitative study on public perception of using drones to deliver automatic external defibrillators.

BACKGROUND: The quickest way to ensure survival in an out-of-hospital cardiac arrest (OHCA) is for a bystander to provide immediate cardiopulmonary resuscitation (CPR) and apply an automated external defibrillator (AED). The urgency of OHCA treatment has led to the proposal of alternative avenues for better access to AEDs, particularly in rural settings. More recently, using unmanned aerial vehicles (or drones) to deliver AEDs to rural OHCA sites has proven promising in improving survival rates. OBJECTIVE: A pilot drone AED delivery program is currently being piloted in the community of Caledon, Ontario. The purpose of this study was to develop an understanding of public perception and acceptance of the use of drones for this purpose and to identify tailored community engagement strategies to ensure successful uptake. METHODS: In-depth qualitative descriptive study using interviews and focus group data collection and inductive thematic analysis. Purposive sampling was used to recruit 67 community members (40 interviews; 2 focus groups of 15) at existing community events in the project area. Interview guides were used to ensure consistency across data collection events. Detailed field notes were recorded when audio-recording was not possible. RESULTS: The central message seen throughout the data was quickly identified as the potential impact of low levels of CPR and AED literacy in the community over anything else including concerns about the drone. The impact of the community's existing relationship with the EMS; the need for bystander CPR & AED promotion prior to the program launch; and the value the community places on transparency and accountability related to the research and the drones were also key findings. In general, the drone concept was found to be acceptable but concerns about providing CPR and using the AED was what created anxieties in the lay public that we underestimated. CONCLUSION: Drone-delivered AEDs may be feasible and effective but successful uptake in smaller communities will require a deep understanding of a community's cardiac arrest literacy levels, information needs and readiness for innovation. This work will inform a robust community engagement plan that will be scalable to other locations considering a drone AED program.

"I Want to Help, but What Do You Do in a Situation Like That?" Health Care Providers' Qualitative Perspectives on Working with Disabled Women in Breast Cancer Screening.

BACKGROUND: Disabled women find that social and physical discomforts during encounters with health providers pose barriers to breast cancer screening. We studied providers' perspectives and learning needs related to this problem in order to develop a disability education initiative. DESIGN: This was a descriptive qualitative study with focus group methods. Participants were recruited from staff of a joint Department of Medical Imaging at three academic teaching hospitals in Toronto, Canada. Seven focus groups were held with 43 clerical staff, mammography technologists, and radiologists. RESULTS: Participants reported that they aimed to provide positive breast screening experiences for disabled women but expressed uncertainty about respectful and appropriate communication with disabled women. Novel situations with disabled women were challenging and, without formal disability education, most relied on experiential learning. CONCLUSIONS: Our study elicited important information about the concerns and learning needs of health professionals who provide breast screening services to disabled women. This information supported development of a disability education curriculum for these providers.

Home Visit-Based Community Paramedicine and Its Potential Role in Improving Patient-Centered Primary Care: A Grounded Theory Study and Framework.

OBJECTIVE: Community paramedicine (CP) is a model of community-based health care being used around the world. Our objective was to study the patient perspective and valuation of this type of program to understand its potential value for primary care innovation in the future. STUDY SETTING: The EPIC community paramedicine program is a partnership between primary care physicians and specially trained community paramedics, designed to provide in-home support for complex chronic disease patients in Ontario, Canada. STUDY DESIGN: As part of an ongoing clinical trial we designed an embedded qualitative evaluation using constructionist grounded theory methodology. DATA COLLECTION METHODS: Data collection included in-depth interviews with 30 patients and/or family members and 60 hours of observation. PRINCIPAL FINDINGS: The health care needs of this complex population are largely attributes that impact a patient's quality of life-including recognition of their vulnerability, providing a safety-net in times of exacerbation and health education and accountability. This seems to be facilitated by a relationship with a dedicated provider that increases continuity of care. CONCLUSIONS: Home-based community paramedicine programs like EPIC appear to be able to create a patient-centered, safe, responsive therapeutic relationship that is often not possible within the standard primary health care system.

Patients' Perspectives on Outcomes of Care After Discharge From the Emergency Department: A Qualitative Study.

STUDY OBJECTIVE: Much effort has been expended to understand what care experiences patients value in the emergency department (ED), yet little is known about which outcomes patients value after ED care. Our goal is to define outcomes of ED care that are valued by patients discharged from the ED, with the goal of informing the development of a patient-reported outcome measure for ED care. METHODS: We conducted qualitative semistructured interviews with patients recruited during their care at 1 of 2 EDs and interviewed in either English or French 1 to 9 days after their visit. Patients who were hospitalized were excluded. Interviews focused on perceived outcomes of care since the ED visit and expectations of care before the ED visit. We identified themes with standard descriptive content analysis techniques and a modified version of the constant comparative method, drawing on grounded theory methods. RESULTS: We interviewed 46 patients in English (n=38) or French (n=8). Participants with diverse reasons for seeking care appeared to value common outcomes from ED care that centered around 4 themes: understanding the cause and expected trajectory of their symptoms; reassurance; symptom relief; and having a plan to manage their symptoms, resolve their issue, or pursue further medical care. These themes were also reflected in the expectations participants recalled having when they decided to seek care in the ED. CONCLUSION: The 4 outcomes defined constitute areas for improvement and will inform the development of an ED patient-reported outcome questionnaire. Consideration should be given to measuring patient-reported outcomes separately from patient experience.

Electronic effects in high-energy radiation damage in tungsten.

Although the effects of the electronic excitations during high-energy radiation damage processes are not currently understood, it is shown that their role in the interaction of radiation with matter is important. We perform molecular dynamics simulations of high-energy collision cascades in bcc-tungsten using the coupled two-temperature molecular dynamics (2T-MD) model that incorporates both the effects of electronic stopping and electron-phonon interaction. We compare the combination of these effects on the induced damage with only the effect of electronic stopping, and conclude in several novel insights. In the 2T-MD model, the electron-phonon coupling results in less damage production in the molten region and in faster relaxation of the damage at short times. These two effects lead to a significantly smaller amount of the final damage at longer times.

Electronic effects in high-energy radiation damage in iron.

Electronic effects have been shown to be important in high-energy radiation damage processes where a high electronic temperature is expected, yet their effects are not currently understood. Here, we perform molecular dynamics simulations of high-energy collision cascades in α-iron using a coupled two-temperature molecular dynamics (2T-MD) model that incorporates both the effects of electronic stopping and electron-phonon interaction. We subsequently compare it with the model employing electronic stopping only, and find several interesting novel insights. The 2T-MD results in both decreased damage production in the thermal spike and faster relaxation of the damage at short times. Notably, the 2T-MD model gives a similar amount of final damage at longer times, which we interpret to be the result of two competing effects: a smaller amount of short-time damage and a shorter time available for damage recovery.

The nature of high-energy radiation damage in iron.

Understanding and predicting a material's performance in response to high-energy radiation damage, as well as designing future materials to be used in intense radiation environments, requires knowledge of the structure, morphology and amount of radiation-induced structural changes. We report the results of molecular dynamics simulations of high-energy radiation damage in iron in the range 0.2-0.5 MeV. We analyze and quantify the nature of collision cascades both at the global and the local scale. We observe three distinct types of damage production and relaxation, including reversible deformation around the cascade due to elastic expansion, irreversible structural damage due to ballistic displacements and smaller reversible deformation due to the shock wave. We find that the structure of high-energy collision cascades becomes increasingly continuous as opposed to showing sub-cascade branching as reported previously. At the local length scale, we find large defect clusters and novel small vacancy and interstitial clusters. These features form the basis for physical models aimed at understanding the effects of high-energy radiation damage in structural materials.