The complexity of the human brain creates a spectrum of sophisticated behavioral repertoires, such as language, tool use, self-awareness, symbolic thought, cultural learning, and consciousness. Understanding how the human brain achieves that has been a longstanding challenge for neuroscientists and may bring insights into the evolution of human cognition and disease states. Human pluripotent stem cells could differentiate into specialized cell types and tissues in vitro. From this pluripotent state, it is possible to generate models of the human brain, such as brain organoids. The recent observation that brain organoids can spontaneously develop complex neural network activity in a dish can help one understand how neural network oscillations evolve and vary between normal and disease states. Moreover, this finding can be leveraged to other applications outside medicine, including engineering and artificial intelligence. However, as the brain model technology becomes more complex, it raises a series of ethical and moral dilemmas. This article discusses the status of this technology, some of its current limitations, and a vision of the future.

This paper presents bimodal mobility actuated by inertial forces with elastic bodies for an exploration robot in a microgravity environment. The proposed bimodal locomotion mechanism can selectively achieve vibration propulsion or rotational hopping mode based on centrifugal force and reaction torque exerted by the control of a single eccentric motor, where the rotational hopping is the primary locomotion mode for practical applications. The bimodal mobility performance under microgravity is experimentally examined using an air-floating testbed. Furthermore, we also present theoretical modeling of the bimodal mobility system, and the model is verified by comparison with the experiments.

The unique environment of space is characterized by several stress factors, including intense radiation, microgravity, high vacuum and extreme temperatures, among others. These stress conditions individually or in-combination influence genetics and gene regulation and bring potential evolutionary changes in organisms that would not occur under the Earth's gravity regime (1 × g). Thus, space can be explored to support the emergence of new varieties of microbes and plants, that when selected for, can exhibit increased growth and yield, improved resistance to pathogens, enhanced tolerance to drought, low nutrient and disease, produce new metabolites and others. These properties may be more difficult to achieve using other approaches under 1 × g. This review provides an overview of the space microgravity and ionizing radiation conditions that significantly influence organisms. Changes in the genomics, physiology, phenotype, growth and metabolites of organisms in real and simulated microgravity and radiation conditions are illustrated. Results of space biological experiments show that the space environment has significant scientific, technological and commercial potential. Combined these potentials can help address the future of life on Earth, part of goal e of astrobiology.

Astronauts who spend significant time in space may experience intracranial hypertension (pressure inside the skull), which often does not normalize upon return to Earth. This type of intracranial pressure can cause vision problems, headaches, glaucoma, and other serious health problems, making it a significant obstacle to long-duration space exploration missions. NASA is hoping that a better understanding of how central nervous system stem cells divide in microgravity will help lead to ways to protect astronauts from problems with intracranial pressure and to design adequate preventive measures. These studies examine cell growth and division of neural stem cells that experienced microgravity on the International Space Station and were returned to normal gravity prior to live-cell imaging studies to determine cell changes.

Since the beginning of the era of space travel, there have been mentions of related health effects. Various studies have described the effect of space travel and microgravity on health. Some of these studies involved short and extended follow-ups of the effect of microgravity on the head and neck of astronauts. Therefore, we aimed to analyse the oral and maxillofacial health effects associated with this sophisticated mission. It is essential to identify relevant problems and address microgravity complications. Humans have long dreamed of flying and in recent years, the dream has evolved to exploring space and creating new habitats on other planets such as Mars. This led to an increase in the need for dental treatment of the flight crew members, which led to the creation of aviation dentistry for the screening and treatment of the oral cavity of the flight crew. We are moving towards a more conservative approach than before, such as removing pulpless teeth in aircrew patients or extracting roots that had a fracture or incomplete extraction. With all the advancements in aerospace knowledge, the aviation dentistry has rarely or briefly been discussed in dental textbooks. Dentists must screen each flight crew member thoroughly and impose flight restrictions and ground them if necessary; the reasons will be discussed later within this paper. It is the duty of dentists and surgeons to notify their patients (aircrew members) about the postoperative flight consequences and restrictions.

Candida lusitaniae and C. guilliermondii are perfect model organisms for the study of Candida genera behaviour in various conditions. Both of them are rare pathogens capable to cause candidiasis in the patients with weakened immune system and can undergo morphology switches related to the increased antifungal drug resistance. Candida genera yeasts are able to inhabit diverse range of ecological niches including space ships and space stations. During the long-term expeditions, astronauts are affected by various factors that can change the state immune system. In such conditions, the commensal usually non-pathogenic microorganisms can spread through the body of the host and cause infections. Weakened immune system and limited use of drugs in spaceships promote the search of the alternative methods for the biocontrol of microorganisms. Several studies demonstrate that microorganisms are altering their gene expression, physiology, morphology, pathogenicity and evolving resistance to the antifungals under microgravity conditions. Our research indicated that switch to the pseudohyphae morphology leads up 30-fold increased resistance to amphotericin B in C. lusitaniae and C. guilliermondii. Cultivation of yeasts in rotary cell culture system (RCCS) is related to the altered cell growth and resistance to the antifungal treatment. Our results showed that growth in the RCCS led to the extreme increase in cell resistance to amphotericin B as compared with the standard growth conditions. In our research, we applied electroporation for the biocontrol of two Candida species. C. lusitaniae and C. guilliermondii cells grown in RCCS exhibited significantly increased survivability after pulsed electric field (PEF) treatment in comparison with cells grown under routine conditions. We have shown that PEF bursts of 2.5–25 kV cm−1 of 100 µs × 8 duration display a dose-dependent permeabilization of both studied Candida species. Our research indicated that budding cells and pseudohyphae morphology cells, with increased resistance to amphotericin B, can be effectively inactivated after applying PEF higher than 15 kV cm−1.

Space represents a rather hostile environment for the human body, with the bone loss being one of the most important consequences. Autophagy is a complex cellular process contributing to several cellular processes including recycling, nutrition, apoptosis and response to stressful environments. Recent reports have indicated that autophagy is a process that increases under microgravity conditions. In particular, this was shown to be true in skeletal cells such as the osteoclasts. Suppression of autophagy results in downregulation of osteoclastogenesis, making autophagy a quite tempting therapeutic target for preventing bone loss during space flights. The present work attempts to review the literature on the topic of autophagy role in osteoclastogenesis under microgravity conditions.

In this paper, we describe the development of an International Space Station experiment, BioRock. The purpose of this experiment is to investigate biofilm formation and microbe–mineral interactions in space. The latter research has application in areas as diverse as regolith amelioration and extraterrestrial mining. We describe the design of a prototype biomining reactor for use in space experimentation and investigations on in situ Resource Use and we describe the results of pre-flight tests.

Microgravity has a profound impact on the physiology of pathogenic microbes; however, its effects on mutualistic microbes are relatively unknown. To examine the effects of microgravity on those beneficial microbes that associate with animal tissues, we used the symbiosis between the bobtail squid Euprymna scolopes and a motile, luminescent bacterium, Vibrio fischeri as a model system. Specifically, we examined the role of Hfq, an RNA-binding protein known to be an important global regulator under space flight conditions, in the squid–vibrio symbiosis under simulated microgravity. To mimic a reduced gravity environment, the symbiotic partners were co-incubated in high-aspect-ratio rotating wall vessel bioreactors and examined at various stages of development. Results indicated that under simulated microgravity, hfq expression was down-regulated in V. fischeri. A mutant strain defective in hfq showed no colonization phenotype, indicating that Hfq was not required to initiate the symbiosis with the host squid. However, the hfq mutant showed attenuated levels of apoptotic cell death, a key symbiosis phenotype, within the host light organ suggesting that Hfq does contribute to normal light organ morphogenesis. Results also indicated that simulated microgravity conditions accelerated the onset of cell death in wild-type cells but not in the hfq mutant strains. These data suggest that Hfq plays an important role in the mutualism between V. fischeri and its animal host and that its expression can be negatively impacted by simulated microgravity conditions.

The kinetics of granular gases, including both freely cooling and steadily driven systems, is studied experimentally in quasi-two-dimensional cells. Under microgravity conditions achieved inside an aircraft flying parabolic trajectories, the frictional force is reduced. In both the freely cooling and steadily driven systems, we confirm that the velocity distribution function has the form exp(−α|v|β). The value of exponent β is close to 1.5 for the driven system in a highly excited case, which is consistent with theory derived under the assumption of the existence of the white-noise thermostat (van Noije & Ernst, Gran. Mat., vol. 1, 1998, p. 5764). In the freely cooling system, the value of β evolves from 1.5 to 1 as the cooling proceeds, and the system's energy decays algebraically (Tg = T0(1 + t/τ)−2), agreeing with Haff's law (Haff, J. Fluid Mech., vol. 134, 1983, p. 401430).

Cet article décrit la stratégie expérimentale développée afin d'améliorer la modélisation des écoulements diphasiques liquide-vapeur présents lors de la mise en froid de moteurs-fusée par des fluides cryogéniques en micro pesanteur. Une analyse de similitude est faite afin de déterminer les nombres adimensionnels pertinents pour le dimensionnement d'une expérience similaire à ces écoulements. Une analyse bibliographique sur les expériences menées en micro pesanteur, la température de remouillage et le flux lors de l'ébullition en film montre le manque de modèles adaptés à la micro gravité. Des résultats de "quenching" d'un tube de pyrex par du FC72 lors de vols paraboliques sont présentés, en particulier l'impact du niveau de gravité et du sous refroidissement sur la température de remouillage et le flux lors de l'ébullition en film. Les résultats montrent une baisse du transfert thermique en micro pesanteur et une augmentation de la température de remouillage.

Since experimentation with plants began in space, a wide range of information has been gained regarding how this unique environment affects the biology of seeds. Seed biology experiments in this milieu have addressed aspects of seed storage, seed germination and metabolism, seedling orientation and seed production by flowering plants. Construction of hardware that provides a suitable growth environment in microgravity has been especially challenging because of the consequences posed by microgravity for fluid and gas distribution around the plant. Fluid shifting causes seed hydration kinetics to occur at a faster rate in microgravity than in 1 g; however, it also induces hypoxic metabolism during the seed germination process. In the absence of a detectable gravitational force, seedling roots grow according to their embryonic orientation and then initiate random walk movements. Light and oxygen gradients are the primary stimuli that orient root growth in this environment. For seed development to occur in spaceflight, well-ventilated growth chambers are necessary to support the carbohydrate supply needs of the developing embryos, and to provide the necessary humidity gradient for anthers to successfully dehisce and release pollen. The dry weight of seeds formed in space is lower than that in ground controls, and seed storage reserves are altered. Seed storage phenomena in spaceflight depend on whether or not oxygen and moisture are present – if not, viability exceeds that of seeds stored under comparable conditions on the ground. Because of the key role to be played by seeds in future advanced life support scenarios in space, more research is needed on the implications of this unique environment for seed biology.

Le besoin d'un critère d'inflammabilité des matériaux est avéré dès lorsque la sécurité-incendie des engins spatiaux habités est envisagée.Différentes limites du nombre de transfert de masse apparaissentessentielles pour définir ce critère. Cependant, l'estimationde l'indice de confiance en ce critère requiert la connaissance de l'incertitudeliée aux transferts radiatifs, encore mal connus en micropesanteur.Afin de découpler les phénomènes de pyrolyse et de dégagement dechaleur, une flamme non-prémélangée d'éthylène a été étudiée en micropesanteur.L'absorption radiative par la couche de suie formée représente la premièreétape de la caractérisation des phénomènes radiatifs. L'émission spontanéedes radicaux CH* précise alors la zone de réaction tridimensionnelle.Une mesure par extinction laser permet d'y corréler le champ d'absorption des suies.L'évolution spectrale de l'épaisseur optique de la couche de suie est ainsi déduite.

La séparation de particules de taille micronique par la technique dite de SPLITT a mis en évidence des effets de migrations transverses non spécifiques, qui limitent l'efficacité de cette séparation dans le cas d'un mélange de plusieurs espèces. Des expériences en micropesanteur ont montré le rôle important joué par la diffusion hydrodynamique induite par cisaillement dans cette migration anormale. Une nouvelle cellule a donc été mise au point : les particules sont injectées au centre du canal dans l'épaisseur de la cellule et peuvent être focalisées dans n'importe quelle position dans l'épaisseur. La focalisation hydrodynamique ainsi contrôlée permet d'éloigner les particules des parois, où le cisaillement est maximal, afin de minimiser les effets des forces de portance et de diffusion. Les premiers tests de séparation binaire réalisés avec cette cellule de focalisation sont très encourageants puisqu'ils montrent une augmentation notable de l'efficacité, en termes de pureté des échantillons, comparée à celle obtenue avec la cellule de SPLITT.

Née avec les premiers vols habités, la recherche dans le domaine des sciences de la matière en micropesanteur est pratiquée aujourd'hui par une communauté nationale et internationale qui a appris à utiliser avec pertinence un outil qu'elle n'avait pas demandé et pour la mise en place duquel elle avait peu été consultée. L'étude à des fins scientifiques ou technologiques des phénomènes physiques en micropesanteur est devenue un élément de la recherche spatiale. Après avoir rappelé comment se manifeste l'ambiance de micropesanteur, nous montrons comment au cours des dernières années et pour se limiter à la communauté scientifique française, celle-ci a obtenu des résultats remarqués qu'il aurait été impossible d'obtenir au sol notamment dans le domaine de la solidification d'alliages métalliques et de la physique des fluides au voisinage du point critique. Nous présentons le bilan et les perspectives dans les cinq domaines principaux dans lesquels ont été classés les actions de recherche en micropesanteur pour lesquels nous présentons les éléments les plus significatifs: la solidification et la croissance cristalline, la combustion, les interfaces fluides, les objets lévités et les fluides critiques et supercritiques. Nous rappelons les liens importants qui existent entre ces travaux et la gestion des fluides en orbite. Nous présentons enfin un projet d'expérimentation dans la Station Spatiale Internationale qui est le plus représentatif de ceux qui sont à la fois pertinents et porteurs de résultats de premier plan, la formation des structures lors de la croissance d'alliages eutectiques modèles transparents.

Afin de contrôler la température des ergols cryogéniques dans les réservoirs des lanceurs spatiaux, il est nécessaire de maîtriser des phénomènes thermodynamiques complexes. Pour les lanceurs du futur, l'apparition de phases à microgravité augmente cette complexité et exige des approches numériques plus complètes. Une phase caractéristique qui interviendra en microgravité dans les futurs lanceurs spatiaux est analysée ici : la dépressurisation des réservoirs cryogéniques. De par les difficultés pour réaliser des essais à grande échelle incluant une phase de microgravité avec un liquide cryogénique, on valide nos méthodes numériques par des essais au sol. Ces essais ont été réalisés sur le site de la Division des Techniques Avancées d'Air Liquide dans le cadre du programme franco-allemand COMPERE.

La crise d'ébullition est une transition entre deux régimes d'ébullition :ébullition nucléée (la bulle se forme sur la surface chauffante) et ébullition en film (la surface chauffanteest couverte par un film continu de vapeur séparant la surface chauffante du liquide). Dans cettecommunication, nous présentons un modèle physique de la crise d'ébullition basé sur le concept de recul devapeur. Nos simulations numériques de croissance thermiquement contrôlée montrent comment une bulle attachéeà la surface chauffante commence soudainement à s'y étaler, formant le germe d'un film de vapeur. La force derecul de vapeur ne provoque pas seulement l'étalement de la bulle, elle crée également une forceadditionnelle d'adhérence qui empêche le départ de la bulle de la surface chauffante lors de sa croissance.Près du point critique liquide-vapeur, la croissance de la bulle est très lente. Si, de plus, des conditionsde microgravité sont remplies, la bulle garde la forme convexe et il est possible d'observerexpérimentalement une augmentation de l'angle apparent de contact ainsi que la croissance de la tache sèche.Ces observations confirment l'explication proposée.

L'expérimentation en microgravité (tours de chute libre, vols paraboliques, fusées sondes et stations orbitales) est intéressante pour certains problèmes de mécanique des fluides où les gradients de densité sont importants sans que la convection forcée ne soit trop grande. On peut y éclaircir certaines situations rendues trop complexes par la présence des forces d'Archimède, reproduire des conditions idéales correspondant à des problèmes types bien connus. En France, le CNES et le CNRS soutiennent ces études au travers de groupements de recherche depuis 1992. L'intérêt de l'expérimentation en micropesanteur et du soutien théorique et numérique associés est mis en évidence dans cet article, tant pour la recherche fondamentale que pour les applications. Les moyens de compenser la gravité terrestre sont présentés. Les considérations de base portent sur la convection naturelle, les effets d'interface, l'évaporation d'une goutte de fluide pur dans un mélange gazeux, la combustion d'une plaque. Les effets de la gravité résiduelle sont abordés à propos de la combustion de gouttes sous haute pression. Les résultats et les perspectives portent sur les points suivants : convection, solidification et croissance cristalline, combustion et phénomènes réactifs, interfaces fluides, milieux granulaires et polyphasiques, fluides critiques.

Electrochemical experiments in microgravity are essential for the optimum design of advanced life support systems and power storage systems in space. In the absence of gravity, the evolved gas bubbles will clog the electrode and slow the reaction. Here, a rotating cell concept is introduced as a plan for improving mass transfer and bubble removal in a microgravity environment. A primary experimental study of bubble behavior in rotating water electrolysis cells has been done in reduced gravity through KC-135 parabolic flight. The results show that the cell resistance decreases with increasing rotation rate. Without rotation, the bubbles stick on the electrode surface during reduced gravity period, thus, the cell efficiency degrades. Mass transfer enhanced by bubble generation is investigated in ground-based work at high rotation rate of test cells, so that gravitational effects are minimized.