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The majority of rail vehicles worldwide use diesel as a primary fuel source. Diesel engine carbon emissions harm the environment and human health. Although railway electrification can reduce emissions, it is not always the most economical option, especially on routes with low vehicle demand. As a result, interest in hydrogen-powered trains as a way to reduce greenhouse gas (GHG) emissions has steadily grown in recent years. In this paper, we discuss advancements made in hydrogen-powered freight and commuter trains, as well as the technology used in some aspects of hydrogen-powered vehicles. It was observed that hydrogen-powered trains are already in use in Europe and Asia, unlike most developing countries in Africa. Commuter trains have received most of the research and development (R&D) attention, but interest in hydrogen-powered freight trains has recently picked up momentum. Despite the availability and use of gray and blue hydrogen, green hydrogen is still the preferred fuel for decarbonizing the rail transport sector.

Abstract: Life Support Systems (LSS) are essential for human spaceflight. They are the key element for humans to survive, to live and to work in space. Ambitious goals of human space exploration in the next 40 years like a permanently crewed surface habitat on Moon or a manned mission to Mars require technologies which allow for a reduction of system and resupply mass. Enhancements of existing technologies, new technological developments and synergetic components integration help to close the oxygen, water and carbon loops. In order to design the most efficient LSS architecture for a given mission scenario, it is important to follow a dedicated design process: definition of requirements, selection of candidate technologies, development of possible LSS architectures and characterisation of LSS architectures by system drivers and evaluation of the LSS architectures. This paper focuses on the approach of a synergetic integration of Polymer Electrolyte Membrane Fuel Cells (PEFC) and microalgae cultivated in photobioreactors (PBR). LSS architectures and their benefits for selected mission scenarios are demonstrated. Experiments on critical processes and interfaces were conducted and result in engineering models for a PEFC and PBR system which fulfil the requirements of a synergetic integrative environment. The PEFC system (about 1kW) can be operated with cabin air enriched by stored or biologically generated oxygen instead of pure oxygen. This offers further advantages with regard to thermal control as high oxygen concentrations effect a dense heat production. The PBR system consists of an illuminated cultivation chamber (about 5 l), a nutrients supply and harvesting and analytics units. Especially the chamber enables a microgravity adapted cultivation of microalgae. However, the peripheral units still have to be adapted in order to allow for a continuous and automated cultivation and harvesting. These automation processes will be tested and evaluated by means of a parabolic flight experiment. Both engineering models are being specified in dimensions, components, mass and energy flows. They will serve as a platform for getting operational experience, reliability data and identifying technical problems before the next step is to be realized: in-orbit verification in a spaceflight experiment. [Copyright &y& Elsevier]

Abstract: The aim of this study was to understand the enhancement mechanism of H2 photoproduction in Chlorella protothecoides under simultaneous nitrogen limitation and sulfur deprivation (LNS). Nitrogen limitation (LN) rather than sulfur deprivation significantly inhibited relative variable fluorescence at K-step (W K) and J-step (V J), photochemical efficiency of PSII (photosystem II), F v/F m, during the process of incubation in the light. Under such conditions, photosynthetic O2 evolution decreased and the anaerobiosis was established after 12 h of incubation. The algae generated large amounts of H2 under nitrogen limitation but generated only trace amounts under sulfur deprivation. Obviously, nitrogen limitation rather than sulfur deprivation was the decisive factor that induced H2 photoproduction in C. protothecoides under LNS. The LNS culture generated much more H2 than the LN culture in the presence of DCMU during incubation, suggesting that a PSII-independent electron source contributed many more electrons for transfer to hydrogenase in the LNS culture. PSII electron transport includes linear electron flow (LEF) and cyclic electron flow (CEF) of PSII in C. protothecoides. In the PSII-dependent electron source for H2 photoproduction, PSII supplies electrons to hydrogenase through the LEF. The LNS culture showed much higher LEF and lower CEF than the LN culture during the H2 photoproduction phase, as indicated by the large lower quantum yield of PSII electron transport (Φ PSII) in the LNS culture in the presence of DCMU. Therefore, compared with nitrogen limitation, simultaneous nitrogen limitation and sulfur deprivation enhanced H2 photoproduction in C. protothecoides mainly due to enhanced PSII-dependent and -independent electron sources. [Copyright &y& Elsevier]

Highlights: [•] Comprehensive review of neuroprotective gases for multiple neural diseases. [•] Summary of underlying mechanisms for their neuroprotective effects. [•] Possible limitations hindering clinical translation of neuroprotective gases. [ABSTRACT FROM AUTHOR]