General description of electromagnetic radiation processes based on instantaneous charge acceleration in `endpoints'

We present a new methodology for calculating the electromagnetic radiation from accelerated charged particles. Our formulation --- the `endpoint formulation' --- combines numerous results developed in the literature in relation to radiation arising from particle acceleration using a complete, and completely general, treatment. We do this by describing particle motion via a series of discrete, instantaneous acceleration events, or `endpoints', with each such event being treated as a source of emission. This method implicitly allows for particle creation/destruction, and is suited to direct numerical implementation in either the time- or frequency-domains. In this paper, we demonstrate the complete generality of our method for calculating the radiated field from charged particle acceleration, and show how it reduces to the classical named radiation processes such as synchrotron, Tamm's description of Vavilov-Cherenkov, and transition radiation under appropriate limits. Using this formulation, we are immediately able to answer outstanding questions regarding the phenomenology of radio emission from ultra-high-energy particle interactions in both the Earth's atmosphere and the Moon. In particular, our formulation makes it apparent that the dominant emission component of the Askaryan Effect (coherent radio-wave radiation from high-energy particle cascades in dense media) comes from coherent `bremsstrahlung' from particle acceleration, rather than coherent Vavilov-Cherenkov radiation.Comment: accepted by Phys. Rev. E, new title, some corrections in equations and references, figure styles updated to match journal policie

Chain Governance Systems and Sustainable Capital Use – A Conceptual Approach

Due to pressures such as climate change, globalization, price volatility and scarcity of natural resources, our agri-food chain is urged to make a transition towards more sustainable production. How to organize such a transition, given the various stakeholders involved, and how to monitor progress still remain important challenges. This paper presents a new conceptual framework that follows an integrated chain approach to help address these challenges. First, it tackles the complex ecological and socio-economic challenges along the chain and its members (agriculture and food industries), and second, allows for decision support to chain members and policy.This framework combines two existing theoretical frameworks. The first framework is global chain value analysis (GCVA) of Gereffi (2005) which has its roots in institutional economics. GCVA categorizes five governance types of value chains (markets – modular – relational – captive – hierarchy) based on three variables: (i) the complexity of information and knowledge transfer required to sustain a particular transaction, (ii) the ability to regulate transactions, and (iii) the capabilities of actual and potential suppliers. The second framework, which was first formulated in ecological economics, extends the set of traditional economic resources to various forms of capital in the production system. These are natural (land, water, …), manufactured (buildings, machinery, ...), human (labour, skills,…), and social capital (networks,…). The economic system is fully embedded in the social system which in turn is embedded within the finite ecological system. Throughput of natural, social, human, and manufactured capital allows for the description of agri-food systems in terms of the maximal sustainable use of their stocks and flows.These two frameworks can be combined to perform an integrated system analysis of the agri-food chain, including the governance structures and the boundary conditions for the various types of capital. This paper describes this new conceptual framework illustrated by means of a case study of the agri-food chain in Flanders, Belgium

An impact model to understand and improve work-life balance in early-career researchers in radiation oncology.

Purpose The COVID-19 pandemic had a substantial effect on mental health and work productivity of early-career researchers working in Radiation Oncology (RO). However, the underlying mechanisms of these effects are unclear. The aim of the current qualitative study was therefore to achieve a better understanding of how these effects arose and could be managed in the future. Methods This study was conducted jointly by RO and qualitative health researchers. Data was collected in four online Focus Groups with 6-11 RO researchers (total N = 31) working in Europe. The transcripts were analysed through a qualitative cross-impact analysis. Results Causal relations were identified between seventeen variables that depict the impact of disrupted working conditions. Mental health and work productivity were indeed the most important affected variables, but relations between variables towards these impacts were complex. Relations could either be positive or negative and direct or indirect, leading to a cascade of interrelated events which are highly personal and could change over time. We developed the model 'impact of disrupted working conditions' depicting the identified variables and their relations, to allow more individual assessment and personalised solutions. Conclusion The impacts of disrupted working conditions on RO researchers varied due to the complexity of interrelated variables. Consequently, collective actions are not sufficient, and a more personal approach is needed. Our impact model is recommended to help guide conversations and reflections with the aim of improving work/life balance. The participants showed high levels of personal responsibility towards their own mental health and work productivity. Although being an individual issue, a collective responsibility in developing such approaches is key due to the dependency on organizational variables