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For a rapid energy transition to renewable energy, green hydrogen is increasingly considered a solution to a myriad of challenges: climate neutrality, clean energy supply, and decoupling of growth and carbon emissions. However, whether the global hydrogen transition will indeed be a just transition is far from certain. This paper introduces the concept of hydrogen justice as an analytical toolkit to help examining justice challenges of the global hydrogen transition. Placing hydrogen justice at the nexus of energy, water and climate justice, and incorporating crucial insights from political ecology and decolonial studies we highlight potential hydrogen injustices and suggest a six-dimensional concept of hydrogen justice: procedural, distributive, restorative, relational, recognitional and epistemological justice. Our research explores socio-ecological, political and economic conditions in hydrogen target countries and examines emerging hydrogen projects and partnerships. Hydrogen injustices may manifest around issues of energy access in countries with high rates of energy poverty, water access in arid regions, as well as forced displacements, impairments of Indigenous livelihoods and the strengthening of authoritarian rule. We conclude that hydrogen injustices result from the interplay of global hydrogen governance and local conditions in producing countries. We illustrate this with examples from transnational hydrogen projects situated in Morocco and Namibia. Finally, we suggest strategies for redressing hydrogen injustices by integrating justice principles at all scales of hydrogen governance.

The regenerative potential of mammalian peripheral nervous system neurons after injury is critically limited by their slow axonal regenerative rate 1 . Regenerative ability is influenced by both injury-dependent and injury-independent mechanisms 2 . Among the latter, environmental factors such as exercise and environmental enrichment have been shown to affect signalling pathways that promote axonal regeneration 3 . Several of these pathways, including modifications in gene transcription and protein synthesis, mitochondrial metabolism and the release of neurotrophins, can be activated by intermittent fasting (IF) 4 , 5 . However, whether IF influences the axonal regenerative ability remains to be investigated. Here we show that IF promotes axonal regeneration after sciatic nerve crush in mice through an unexpected mechanism that relies on the gram-positive gut microbiome and an increase in the gut bacteria-derived metabolite indole-3-propionic acid (IPA) in the serum. IPA production by Clostridium sporogenes is required for efficient axonal regeneration, and delivery of IPA after sciatic injury significantly enhances axonal regeneration, accelerating the recovery of sensory function. Mechanistically, RNA sequencing analysis from sciatic dorsal root ganglia suggested a role for neutrophil chemotaxis in the IPA-dependent regenerative phenotype, which was confirmed by inhibition of neutrophil chemotaxis. Our results demonstrate the ability of a microbiome-derived metabolite, such as IPA, to facilitate regeneration and functional recovery of sensory axons through an immune-mediated mechanism.

Furan fatty acids (FuFAs) are valuable minor compounds in our food with excellent antioxidant properties. Naturally occurring FuFAs are characterised by a central furan moiety with one or two methyl groups in β-/β’-position of the heterocycle (monomethyl- or M-FuFAs and dimethyl- or D-FuFAs). Comparably high concentrations of D-/M-FuFAs were reported in soybeans, but soy is often consumed as a processed product, such as full-fat soy flour and flakes, soy drink, tofu and texturised soy protein (TSP). Due to the chemical lability of D-/M-FuFAs, e.g. in the presence of light or oxygen, a degradation during the processing is possible. For this purpose, freshly harvested soybeans (n = 4) and differently processed soybean products (n = 22) were analysed on FuFAs. Three FuFAs, i.e. 11-(3,4-dimethyl-5-pentylfuran-2-yl)-undecanoic acid (11D5), 9-(3,4-dimethyl-5-pentylfuran-2-yl)-nonanoic acid (9D5), and 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5), were identified and quantified in all fresh soybeans and most of the processed soy products (n = 20). A trend towards lower D-/M-FuFA contents in higher processed products was observable. Lower FuFA concentrations were usually accompanied with a decrease of the share of the less stable D-FuFAs (9D5, 11D5) in favour of the M-FuFA 9M5. Furthermore, one or two 3,4-nonmethylated furan fatty acids (N-FuFAs), i.e. 8-(5-hexylfuran-2-yl)-octanoic acid (8F6) and partly 7-(5-heptylfuran-2-yl)-heptanoic acid (7F7), were detected in all processed products, but not in the freshly harvested soybeans. Our results indicate that D-/M-/N-FuFAs may serve as suitable markers for both, careful manufacturing processes and adequate storage conditions of soy products.

Renewable energy has made significant inroads in addressing growing energy demands on the African continent. However, progress towards SDG 7 is still limited and difficult to trace. Furthermore, the results-oriented rationale of the SDGs means that both policy change and the dimension of environmental justice are not covered properly. We argue that the energy justice concept may provide a powerful tool to offset looming trade-offs and enhance the co-benefits of SDG 7 within broader transition endeavours. In doing so, we assess African energy transition processes based on a comparative mapping of African renewable energy policies in 34 countries. We investigate the scope of policy frameworks in order to analyse their contribution to greater energy justice along different justice dimensions. We then identify four transition scenarios, which reflect the challenges of integrating the justice dimension into renewable energy policies. In comparing these scenarios, we argue that SDG 7 tracking needs to consider the justice dimension to arrive at a more holistic implementation that is in line with socio-ecological justice and takes account of people’s energy needs.

Forests play a crucial role in the Earth System, providing essential ecosystem services and sustaining biological diversity. However, forest ecosystems are increasingly impacted by disturbances, which are often integral to their dynamics but have been exacerbated by climate change. Despite the growing concern about these trends, the lack of consistent and temporally continuous data on forest disturbances at large spatial scales hinders our ability to accurately characterize changes in disturbance regimes and respond to these changes. In this study, we evaluate the consistency in spatial distribution and extent, disturbance timing and causal agent (when available), of five forest disturbance datasets available for the conterminous United States, to identify advantages as well potential shortcomings and inaccuracies of different mapping approaches. Consistency refers to the extent to which different forest disturbance datasets report similar timings and causal agents for overlapping disturbance events, reflecting their level of agreement. Specifically, we compare data from the Forest Inventory and Assessment (FIA), the Insect Disease Survey (IDS), both regularly conducted by the U.S. Department of Agriculture (USDA), the literature survey by the International Tree Mortality Network (ITMN) and two satellite-based datasets, the Global Forest Change (GFC) and North American Forest Dynamics Forest Loss Attribution (NAFD). All datasets report disturbance timing with a temporal granularity of one year, FIA and ITMN are point-based, and IDS, GFC and NAFD are spatially explicit. FIA, IDS, ITMN and NAFD report on disturbance agent, with different classification groupings. We find a moderate spatial agreement between the spatially explicit datasets and the point-based ones, with IDS, GFC and NAFD overlapping with 24 %, 58 % and 42 % of FIA disturbed patches, and on average 35 % of the ITMN reported mortality events. The datasets show similar trends in total disturbed extent over conterminous USA (CONUS) for the common period of 2001–2010, but with more pronounced differences at smaller scales, and when accounting for disturbance agents. The datasets agree well in disturbance timing: the mean difference is less than one year, while the variability in differences ranges from about 1 to 4 years. For FIA, we find better agreement with other datasets when the disturbance timing coincides with the inventory year, compared to disturbances reported as occurring in years between inventories. The satellite-based datasets tend to show an earlier detection of disturbance events, compared to the other datasets, possibly due to the inconsistent revisiting times of the inventory datasets (FIA and IDS). Our results show that although the datasets exhibit reasonably good agreement in disturbance timing, their spatial correspondence is considerably lower. Furthermore, the datasets show low agreement in terms of disturbance agent, which results from differences in grouping but also potentially on the methodology used to report causes. Our findings thus underscore the importance of careful data quality assessment and consideration of their inherent uncertainty when using single forest disturbance datasets for further applications. Specifically, for smaller scales and for disturbance agent attribution, we recommend careful comparison of more than a single dataset. Our study further highlights the need for improved data integration to advance the understanding of changes in forest disturbance regimes and their drivers.

The near-complete in vitro reconstitution of the mitotic spindle assembly checkpoint reveals how the assembly of its effector, the mitotic checkpoint complex, is catalysed. Assembly of the mitotic checkpoint complex During mitotic cell division, chromatids attach to the spindle microtubules through protein structures called kinetochores. If even one kinetochore remains unattached, the spindle assembly checkpoint (SAC) is activated to prevent the progress of mitosis. In cells, the SAC response is established within minutes. In vitro , however, the process (activation of the SAC effector protein MAD2 through conformational change to allow the assembly of the mitotic checkpoint complex) takes hours. Andrea Musacchio and colleagues now resolve this discrepancy by reconstituting a near-complete SAC signalling system and analysing it using real-time sensors. Their observations offer a mechanistic explanation for the accelerated and spontaneous conversion of MAD2 in cells. In mitosis, for each daughter cell to inherit an accurate copy of the genome from the mother cell, sister chromatids in the mother cell must attach to microtubules emanating from opposite poles of the mitotic spindle, a process known as bi-orientation. A surveillance mechanism, termed the spindle assembly checkpoint (SAC), monitors the microtubule attachment process and can temporarily halt the separation of sister chromatids and the completion of mitosis until bi-orientation is complete 1 . SAC failure results in abnormal chromosome numbers, termed aneuploidy, in the daughter cells, a hallmark of many tumours. The HORMA-domain-containing protein mitotic arrest deficient 2 (MAD2) is a subunit of the SAC effector mitotic checkpoint complex (MCC). Structural conversion from the open to the closed conformation of MAD2 is required for MAD2 to be incorporated into the MCC 1 . In vitro , MAD2 conversion and MCC assembly take several hours 2 , 3 , 4 , but in cells the SAC response is established in a few minutes 5 , 6 , 7 . Here, to address this discrepancy, we reconstituted a near-complete SAC signalling system with purified components and monitored assembly of the MCC in real time. A marked acceleration in MAD2 conversion and MCC assembly was observed when monopolar spindle 1 (MPS1) kinase phosphorylated the MAD1–MAD2 complex, triggering it to act as the template for MAD2 conversion and therefore contributing to the establishment of a physical platform for MCC assembly. Thus, catalytic activation of the SAC depends on regulated protein–protein interactions that accelerate the spontaneous but rate-limiting conversion of MAD2 required for MCC assembly.

Clean energy is going transnational. Following the COP21 UN Climate Change Conference in December 2015, a roll-out of clean energy schemes in the global South is fostering a global energy transition. One such case is South Africa, where a policy innovation - the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) - was introduced in 2011. While REIPPPP seems to be a success story in terms of renewable energy capacity, it is unclear how the instrument is shaping the overall course of South Africa's green transformation regarding the influence of transnational actors, participation in local ownership, and socio-economic benefits. Based on expert interviews and empirical process tracing of the renewable energy projects during the five bidding rounds of REIPPPP (2011-2016), the article analyses the design and effects of REIPPPP and discusses its implications for transition strategies, such as a 'just transition'.

Cell division is spatiotemporally precisely regulated, but the underlying mechanisms are incompletely understood. In the social bacterium Myxococcus xanthus , the PomX/PomY/PomZ proteins form a single megadalton-sized complex that directly positions and stimulates cytokinetic ring formation by the tubulin homolog FtsZ. Here, we study the structure and mechanism of this complex in vitro and in vivo. We demonstrate that PomY forms liquid-like biomolecular condensates by phase separation, while PomX self-assembles into filaments generating a single large cellular structure. The PomX structure enriches PomY, thereby guaranteeing the formation of precisely one PomY condensate per cell through surface-assisted condensation. In vitro, PomY condensates selectively enrich FtsZ and nucleate GTP-dependent FtsZ polymerization and bundle FtsZ filaments, suggesting a cell division site positioning mechanism in which the single PomY condensate enriches FtsZ to guide FtsZ-ring formation and division. This mechanism shares features with microtubule nucleation by biomolecular condensates in eukaryotes, supporting this mechanism’s ancient origin. How cell division is regulated with spatiotemporal precision is not fully understood. Here the authors show that a bacterial protein undergoes phase separation through surface-assisted condensation to enrich the tubulin homolog FtsZ in M. xanthus cell division.