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As urban food systems erode the ecological foundations of society, researchers advocate multi‐level and adaptive governance to promote transitions toward sustainability. Agroecological discourse proposes transition to resilient, localized, and democratic city–region food systems, but neoliberal interpretations subvert radical aspirations. In the South African metropoles of Johannesburg and Cape Town, the governance terrain entails a concentrated industrial food system providing large, impoverished populations with unhealthy food derived from monocultures and transported along global value chains. Governing these urban food systems toward agroecological transition requires engagement with state governance mechanisms and rationalities. Considering state capabilities to promote agroecological transitions, the paper shows that fragmented institutional structures, policy patchworks, intersecting logics of control, and divergent ideologies constitute an ambiguous governance terrain posing major hurdles to transition. For metropolitan states to muster the will and assemble means for deep transformation of food systems and dominant state rationalities, a compelling alternative narrative must emerge. This requires persistent strategic engagement between officials and agroecological movements. To cultivate fertile political ground for seeds of deep, just transitions to take root, agroecology movements must grasp the nettle of metropolitan state capabilities. Core Ideas Metropoles in the Global South are sites of struggle for agroecological transition. South African cities entail large, impoverished, food insecure populations. Hybrid metropolitan food systems are dominated by a corporate–industrial core. Deep, just transitions depend on state will and means to govern food systems Agroecology must engage the incoherent metropolitan will and means for transition.

Recent oncological studies identified beneficial properties of radiation applied at ultrahigh dose rates, several orders of magnitude higher than the clinical standard of the order of Gy min –1 . Sources capable of providing these ultrahigh dose rates are under investigation. Here we show that a stable, compact laser-driven proton source with energies greater than 60 MeV enables radiobiological in vivo studies. We performed a pilot irradiation study on human tumours in a mouse model, showing the concerted preparation of mice and laser accelerator, dose-controlled, tumour-conform irradiation using a laser-driven as well as a clinical reference proton source, and the radiobiological evaluation of irradiated and unirradiated mice for radiation-induced tumour growth delay. The prescribed homogeneous dose of 4 Gy was precisely delivered at the laser-driven source. The results demonstrate a complete laser-driven proton research platform for diverse user-specific small animal models, able to deliver tunable single-shot doses up to around 20 Gy to millimetre-scale volumes on nanosecond timescales, equivalent to around 10 9  Gy s –1 , spatially homogenized and tailored to the sample. The platform provides a unique infrastructure for translational research with protons at ultrahigh dose rates. A laser–plasma accelerator provides proton beams for the precise irradiation of human tumours in a mouse model. This work advances translational research with ultrahigh proton dose rates at laser-driven sources.

Intense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. Here we experimentally show the successful implementation of a highly efficient (50% transmission) and tuneable dual pulsed solenoid setup to generate a homogeneous (laterally and in depth) volumetric dose distribution (cylindrical volume of 5 mm diameter and depth) at a single pulse dose of 0.7 Gy via multi-energy slice selection from the broad input spectrum. The experiments were conducted at the Petawatt beam of the Dresden Laser Acceleration Source Draco and were aided by a predictive simulation model verified by proton transport studies. With the characterised beamline we investigated manipulation and matching of lateral and depth dose profiles to various desired applications and targets. Using an adapted dose profile, we performed a first proof-of-technical-concept laser-driven proton irradiation of volumetric in-vitro tumour tissue (SAS spheroids) to demonstrate concurrent operation of laser accelerator, beam shaping, dosimetry and irradiation procedure of volumetric biological samples.

To examine underlying political economy factors that enable or impede the integration of nutrition considerations into food system governance. Comparative political economy analysis of data collected through (1) value chain analyses of selected healthy and unhealthy commodities and (2) food system policy analyses, using a theoretical framework focused on power, politics, interests and ideas. Ghana and South Africa. Value chain actors relevant to healthy and unhealthy foods (Ghana 121; South Africa 72) and policy stakeholders from government (Health, Agriculture, Trade and Industry, Finance), academia, civil society, development partners, Civil Society Organization (CSO) and private sector (Ghana 28; South Africa 48). Nutrition was a stated policy priority in both countries; however, policy responsibility was located within the health sector, with limited integration of nutrition into food system sectors (including Agriculture, Trade and Industry). Contributing factors included a conceptions of policy responsibilities for nutrition and food systems, dominant ideas and narratives regarding the economic role of the food industry and the purpose of food system policy, the influence of large food industry actors, and limited institutional structures for cross-sectoral engagement and coordination. Integrating nutrition into multi-sectoral food policy to achieve multiple food system policy goals will require strategic action across jurisdictions and regional levels. Opportunities included increasing investment in healthy traditional foods, strengthening urban/rural linkages and informal food systems, and strengthening institutional structures for policy coherence and coordination related to nutrition.

This study aimed to determine differences in food consumption by the NOVA food categories in South Africa and Ghana and how they relate to poverty and food supply systems. This study used a cross-sectional design to assess household food acquisition and lived poverty index. The study was conducted in Khayelitsha and Mount Frere, urban and rural communities in South Africa, respectively, and Ahodwo and Ejuratia, urban and rural communities in Ghana, respectively. An adult in charge of or knowledgeable about household food acquisition and consumption was selected to participate in the study. A total of 1299 households participated in the study. Supermarkets were a prominent source of ultra-processed foods for households in South Africa, while informal outlets were an important source of ultra-processed foods in Ghana. Consumption of unprocessed foods was higher among South African households (58·2 %) than Ghanaian households (41·8 %). In South Africa, deprivation was associated with increased odds of infrequent consumption of both unprocessed foods (OR 3·431 < 0·001) and ultra-processed foods (OR 2·656 < 0·001) compared with non-deprivation. In Ghana, no significant differences were observed between deprived households and non-deprived households in relation to the consumption of the NOVA food classes. Different food supply systems and poverty are associated with household acquisition of the different NOVA food classes. Policies should be geared towards formal shops in South Africa and informal shops in Ghana to reduce the consumption of key obesogenic foods.

The pulsed nature of laser-driven ion sources and their relative large emission angles result in the production of secondary, undesired, pulsed neutron (and photon) radiation. Conventional neutron monitors struggle to accurately measure in such environments, yet characterizing these fields is crucial for applications like hadron therapy. Parasitic neutron dose measurements were performed at the Petawatt beam of the Dresden Laser Acceleration Source (DRACO) employing laser energies from 4.5 to 18 J. An active extended-range neutron REM counter specifically developed for pulsed neutron fields, the LUPIN-II, was employed, as well as a passive extended-range neutron REM counter, the Passive LINUS. Neutron doses were recorded on a single-bunch level with values up to about 260 nSv per proton bunch characterized by a proton cutoff energy of about 60 MeV at about 2 m from the DRACO vacuum chamber, confirming the expected pulsed nature of the neutron field. Results of passive measurements were compared to the LUPIN-II results, integrated over the same period, and showed a reasonable agreement, confirming the presence of pulsed neutron radiation in the proximity of the DRACO ion source. These results demonstrate for the first time that this kind of radiation can be monitored, in terms of H*(10) on a single-shot basis by using the LUPIN-II neutron REM counter.

Application experiments with laser plasma-based accelerators (LPA) for protons have to cope with the inherent fluctuations of the proton source. This creates a demand for non-destructive and online spectral characterization of the proton pulses, which are for application experiments mostly spectrally filtered and transported by a beamline. Here, we present a scintillator-based time-of-flight (ToF) beam monitoring system (BMS) for the recording of single-pulse proton energy spectra. The setup’s capabilities are showcased by characterizing the spectral stability for the transport of LPA protons for two beamline application cases. For the two beamline settings monitored, data of 122 and 144 proton pulses collected over multiple days were evaluated, respectively. A relative energy uncertainty of 5.5% (1 σ ) is reached for the ToF BMS, allowing for a Monte-Carlo based prediction of depth dose distributions, also used for the calibration of the device. Finally, online spectral monitoring combined with the prediction of the corresponding depth dose distribution in the irradiated samples is demonstrated to enhance applicability of plasma sources in dose-critical scenarios.

Due to the non-linear nature of relativistic laser induced plasma processes, the development of laser-plasma accelerators requires precise numerical modeling. Especially high intensity laser-solid interactions are sensitive to the temporal laser rising edge and the predictive capability of simulations suffers from incomplete information on the plasma state at the onset of the relativistic interaction. Experimental diagnostics utilizing ultra-fast optical backlighters can help to ease this challenge by providing temporally resolved inside into the plasma density evolution. We present the successful implementation of an off-harmonic optical probe laser setup to investigate the interaction of a high-intensity laser at 5.4 × 10 21 W/cm 2 peak intensity with a solid-density cylindrical cryogenic hydrogen jet target of 5 μ m diameter as a target test bed. The temporal synchronization of pump and probe laser, spectral filtering and spectrally resolved data of the parasitic plasma self-emission are discussed. The probing technique mitigates detector saturation by self-emission and allowed to record a temporal scan of shadowgraphy data revealing details of the target ionization and expansion dynamics that were so far not accessible for the given laser intensity. Plasma expansion speeds of up to ( 2.3 ± 0.4 ) × 10 7 m/s followed by full target transparency at 1.4 ps after the high intensity laser peak are observed. A three dimensional particle-in-cell simulation initiated with the diagnosed target pre-expansion at - 0.2 ps and post processed by ray tracing simulations supports the experimental observations and demonstrates the capability of time resolved optical diagnostics to provide quantitative input and feedback to the numerical treatment within the time frame of the relativistic laser-plasma interaction.

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens’ principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BEAT is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches.

A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 10 8 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E 0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches.