Search

Although we have sent humans into space for more than 50 years crucial questions regarding kidney physiology, volume regulation and osmoregulation remain unanswered. The complex interactions between the renin-angiotensin-aldosterone system, the sympathetic nervous system, osmoregulatory responses, glomerular function, tubular function, and environmental factors such as sodium and water intake, motion sickness and ambient temperature make it difficult to establish the exact effect of microgravity and the subsequent fluid shifts and muscle mass loss on these parameters. Unfortunately, not all responses to actual microgravity can be reproduced with head-down tilt bed rest studies, which complicates research on Earth. Better understanding of the effects of microgravity on kidney function, volume regulation and osmoregulation are needed with the advent of long-term deep space missions and planetary surface explorations during which orthostatic intolerance complaints or kidney stone formation can be life-threatening for astronauts. Galactic cosmic radiation may be a new threat to kidney function. In this review, we summarise and highlight the current understandings of the effects of microgravity on kidney function, volume regulation and osmoregulation and discuss knowledge gaps that future studies should address.

The Helmholtz-Zentrum Potsdam GFZ German Research Centre for Geosciences is one of the Associate Analysis Centers of the International Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Service (IDS). In the framework of a recent reprocessing campaign for the International Terrestrial Reference Frame (ITRF) the suite of DORIS-derived satellite products was extended and improved with respect to reference frame determination. Among others the Copernicus Sentinel-3A/3B and 6A Michael Freilich (MF) satellites were used for this purpose. The orbits were generated based on DORIS-only and on the combination of DORIS and Satellite Laser Ranging (SLR) observations, and attempts were made to optimize their accuracy. Also for these satellites, GFZ generates Global Positioning System (GPS) based orbits within the Copernicus Precise Orbit Determination (CPOD) quality working group (CPOD-QWG). The GPS orbits contribute to a combined CPOD orbit solution, which is assumed to have superior absolute accuracy and minimal residual systematic errors. The DORIS-only, the combined DORIS and SLR, and the GPS-only orbits are compared to the CPOD combined solution serving as reference solution. The accuracy of the orbits shows up in radial direction for all techniques and combinations with values of 0.60 to 0.82 cm. In transverse and normal direction the RMS values achieved with GPS are up to around 50% lower as with DORIS, which sizes at around 1.5-2 cm. Subsequently the reference points of the observation techniques were estimated. With a multi-technique approach, a center-of-mass deviation according to Montenbruck et al. (2017) could be reproduced for Sentinel-3A. In addition, for both Sentinel-3 satellites the DORIS reference point values show a deviation in normal direction of 8-9 mm and a drift in radial direction of about 3mm/year with respect to manufacturer’s data, reference point values for Sentinel-6A (MF) show a good agreement. With the confidence gained on the DORIS-only orbit solutions, weekly local reference frames are computed for each of the three satellites as well as a combined solution and evaluated in terms of the reference frame defining parameters, i.e. origin, scale, and orientation. The accuracy achieved here is in the range of a few mm to cm region. The scale remains stable, except for Sentinel-3A, which shows a scale drift of about -1.5 , whose cause is not clear yet. Standard deviations of station coordinate residuals (North, East, Up) are in the range of 2-4 mm, 5-9 mm and 5-7 mm respectively.

We present the first observational infrared luminosity function (IRLF) measurement in the Epoch of Reionization (EoR) based on a ultraviolet (UV)-selected galaxy sample with the Atacama Large Millimeter Array (ALMA) spectroscopic observations. Our analysis is based on the ALMA large program Reionization Era Bright Emission Line Survey (REBELS), which targets 42 galaxies at z = 6.4–7.7 with [C ii] 158 $\rm{\mu m}$ line scans. 16 sources exhibit dust detection, 15 of which are also spectroscopically confirmed through the [C ii] line. The infrared (IR) luminosities of the sample range from log LIR/L⊙ = 11.4 to 12.2. Using the UV luminosity function as a proxy to derive the effective volume for each of our target sources, we derive IRLF estimates, both for detections and for the full sample including IR luminosity upper limits. The resulting IRLFs are well reproduced by a Schechter function with the characteristic luminosity of $\log L_{*}/\mathrm{ L}_\odot =11.6^{+0.2}_{-0.1}$ . Our observational results are in broad agreement with the average of predicted IRLFs from simulations at z ∼ 7. Conversely, our IRLFs lie significantly below lower redshift estimates, suggesting a rapid evolution from z ∼ 4 to z ∼ 7, into the reionization epoch. The IR obscured contribution to the cosmic star formation rate density at z ∼ 7 amounts to $\mathrm{log(SFRD/{\rm M}_{\odot }\,yr^{-1}\,Mpc^{-3}) = -2.66^{+0.17}_{-0.14} }$ that is at least ∼10 per cent of UV-based estimates. We conclude that the presence of dust is already abundant in the EoR and discuss the possibility of unveiling larger samples of dusty galaxies with future ALMA and JWST observations.

To self-consistently model galactic properties, reionization of the intergalactic medium, and the associated 21-cm signal, we have developed the algorithm polar by integrating the one-dimensional radiative transfer code grizzly with the semi-analytical galaxy formation code L-Galaxies 2020. Our proof-of-concept results are consistent with observations of the star formation rate history, UV luminosity function and the CMB Thomson scattering optical depth. We then investigate how different galaxy formation models affect UV luminosity functions and 21-cm power spectra, and find that while the former are most sensitive to the parameters describing the merger of halos, the latter have a stronger dependence on the supernovae feedback parameters, and both are affected by the escape fraction model., Comment: MNRAS accepted

Ionospheric effects degrade the quality of radar data, which are critical for the precision of the satellite ephemeris produced by space surveillance systems; this degradation is especially noticeable for radars such as GRAVES that operate in the very high frequency range. This article presents a simple and effective method to correct for ionospheric effects, with an evaluation on data obtained with GRAVES, the French space surveillance radar. This method relies on GPS data, and our evaluation relies on GRAVES and DORIS data. We found that the gain in terms of evaluated radial velocity can be as high as 1.76$\kappa$, where $\kappa$ is the typical root mean square of the noise on radial velocity measurements for GRAVES (excluding ionospheric effects): the error decreases from 2.60$\kappa$ to 0.83$\kappa$ for daytime satellite overhead passes. Our conclusion is that, while this method is very simple to implement, it has proven to be a good correction for ionospheric effects in practice., Comment: Accepted for publication in Advances in Space Research. 6 pages, 4 figures

The stability of polycyclic aromatic hydrocarbons (PAHs) upon soft X-ray absorption is of crucial relevance for PAH survival in X-ray dominated regions. PAH stability depends on molecular size but also on the degree of hydrogenation that is related to H2 formation in the interstellar medium. In this project, we intend to reveal the changes of electronic structure caused by hydrogenation and the impact of hydrogenation on the stability of the carbon backbone for cationic pyrene and its hydrogenated derivatives by analysis of near C K-edge soft X-ray photoions. In our experiments, the PAH cations were trapped in a cryogenic radiofrequency linear ion trap and exposed to monochromatic X-rays with energies from 279 to 300 eV. The photoproducts were mass-analysed by means of time-of-flight spectroscopy. Partial ion yields were then studied as a function of photon energy. X-ray absorption spectra computed by time-dependent density functional theory (TD-DFT) aided the interpretation of the experimental results. A very good agreement between experimental data and TD-DFT with short-range corrected functionals for all PAH ions was reached. The near-edge X-ray absorption mass spectra exhibit clear peaks due to C 1s transitions to singly occupied molecular orbitals and to low-lying unoccupied molecular orbitals. In contrast to coronene cations, where hydrogen attachment drastically increases photostability of coronene, the influence of hydrogenation on photostability is substantially weaker for pyrene cations. Here, hydrogen attachment even destabilizes the molecular structure. An astrophysical model describes the half-life of PAH ions in interstellar environments.

An analytical solution for spacecraft rendezvous within closed Keplerian orbits is presented using continuous radial thrust. The two spacecraft are assumed to be initially placed within the same closed orbit with arbitrary phase angle separation. The target spacecraft is assumed to always remain in the same initial orbit. The chaser vehicle, however, uses a judiciously designed maneuver sequence comprising constant-acceleration radial thrust phases interspersed with coast phases. Importantly, the proposed maneuver design is analytically characterized by one or two (depending on whether the parking orbit is circular or elliptical, respectively) nonlinear algebraic equations that determine the time intervals for the different phases. The set of initial conditions from which rendezvous is feasible is also characterized. Additionally, orbit rotation (that is, changing the orbit argument of periapsis in plane) is also demonstrated for the elliptical parking orbit case. Finally, the remarkable emergence of the golden and silver ratios, as well as their connections to Kepler’s triangle, is demonstrated for a specific sequence of thrust and coast arcs.

This research paper explores the role of women in the sports industry, with a focus on their experiences in leadership positions. The paper begins by examining the historical context of women's participation in sports, and how this has evolved over time. It then discusses the current state of women's representation in the industry, including the challenges they face in breaking through the glass ceiling. The paper also looks at the strategies and initiatives that have been put in place to promote gender diversity in sports leadership and evaluates their effectiveness. Finally, the paper concludes by offering recommendations for further research and action that can be taken to ensure greater gender equity in the sports industry.

For optimal decision making and collaborative task performance in multispacecraft missions, it is essential for each spacecraft to maintain a state estimate of all the spacecraft in the formation. However, especially in the case of large formation sizes, each spacecraft may not be able to track or communicate with all other spacecraft. Further, for formations deployed in deep space, the unavailability of the Global Navigation Satellite System makes inertial state estimation challenging. We propose the Distributed Absolute and Relative Estimation (DARE) algorithm for autonomous inertial estimation of spacecraft formations. The algorithm enables each spacecraft to maintain an accurate inertial estimate of the entire formation even in the presence of observability and communication constraints. Each spacecraft utilizes measurements of feature points (landmarks) for inertial localization and measurements of neighboring spacecraft for relative localization. The algorithm is distributed and scalable to any number of spacecraft in the formation. A modified version of the algorithm called the Sparse Distributed Absolute and Relative Estimation (SDARE) algorithm is also derived. This algorithm is computationally more efficient at the expense of estimation accuracy, making it suitable for implementation on nanosatellites where resources are limited. Numerical simulation results demonstrating the effectiveness and comparing the performance of both algorithms are provided.

The aim of this paper is to explore the relationship between marginal identities, bodies, and the performance of madness in the North African trance dance. It casts light on festive rituals where the illnesses of the soul are manifested through corporeal expressions that variably combine the religious, the spiritual, the socio-cultural, and the psychological aspects. Rather than being stigmatized or pathologized, madness is celebrated to grant a legitimate space and voice to the disadvantaged and marginalized individuals. It is hence posited to produce a counter-discourse that symbolically speaks out against the dictates of formal discourses that control the lives of men and women and shape their identities. By applying a qualitative research method, this study involves observing subjects' corporeal performances in trance from a practice-based perspective. The descriptive analysis of the night of trance (the Lila) takes insights from social semiotics and the concept of the 'meta-sign' to account for the minimal details of madness and the corporeal signs into play. There are stages to follow and intricate bodily moments that would drive the observer of madness to where the order of society comes to a standstill. However, the focus of interest is to assess the readiness of women and men to play other than their normative sociocultural roles in society. The varying dramatic scenes with musical melodies, colors, spirits, litanies, and personifications are overwhelmingly loaded with the passion to celebrate and the desire to transcend time and space. The participants are voluntarily involved in trance as an outlet for their collective endeavor to exteriorize their own mental anxieties and whims. Their sole intention is to defy the prevailing ideologies and the pressures their bodies suffer from. Dancing for them embodies the psychiatric that helps the patients to be dispossessed and hopefully be cured. These observed rites of trance are found to be intentionally performed to relieve individuals from different types of alienation suffered in a 21st century modern world that marginalizes, downgrades, and chains them to the rigidity of disciplinary powers.

In this paper, a cosmological model of the Universe is presented in $f(Q,T)$ gravity and the parameters are constrained by cosmological data sets. Initially, a generalised form of $f(Q,T)$ model is used as $f(Q,T)=-\lambda_{1} Q^{m}-\lambda_{2} T^2$, where $\lambda_{1}$, $\lambda_{2}$ and $m$ are model parameters. With some algebraic manipulation, the Hubble parameter is obtained in terms of redshift. Then, using MCMC analysis, the model parameters are constrained using the most current Hubble and Pantheon$^{+}$ data. The model parameters are also verified through the BAO data set. The model shows an early deceleration transitioning to an accelerating phase of the Universe. The $Om(z)$ diagnostics indicate a positive slope, favouring the model to be in a phantom field dominated phase., Comment: 14 pages, 9 figures

A sparse recurrent fuzzy neural network (SRFNN)-based dynamic flight envelope protection (FEP) method is proposed and integrated into an aircraft control system against possible failures. As a baseline of the aircraft control system, a fault-tolerant flight controller is used to compensate the uncertainties caused by failures, such as damaged wing. As an augmentation, the SRFNN-based dynamic FEP is employed to prevent damaged aircraft from breaking through the safe flight envelope bounds, which are updated adaptively with the help of the safety-critical information obtained by the SRFNN. Additionally, the performance of the fault-tolerant flight controller can be improved after the proposed dynamic FEP is integrated into the aircraft control system. The integrated aircraft control system not only can improve the performance of aircraft with some failures but also can prevent the damaged aircraft from getting out of control. Simulations are conducted to test and verify the effectiveness of the fault-tolerant flight controller and the SRFNN-based dynamic FEP. Simulation results show the efficacy of the proposed integrated aircraft control system.

Trajectory optimization of low-thrust perturbed orbit rendezvous is a crucial technology for space missions in low Earth orbits, which is difficult to solve due to its initial value sensitivity, especially when the transfer trajectory has many revolutions. This paper investigated the time-fixed perturbed orbit rendezvous between low-eccentricity orbits and proposed a priori quasi-optimal thrust strategy to simplify the problem into a parametric optimization problem, which significantly reduces the complexity. The optimal trajectory is divided into three stages including transfer to a certain intermediate orbit, thrust-off drifting and transfer from intermediate orbit to the target orbit. In the two transfer stages, the spacecraft is assumed to use a parametric law of thrust. Then, the optimization model can be then obtained using very few unknowns. Finally, a differential evolution algorithm is adopted to solve the simplified optimization model and an analytical correction process is proposed to eliminate the numerical errors. Simulation results and comparisons with previous methods proved this new method's efficiency and high precision for low-eccentricity orbits. The method can be well applied to premilitary analysis and high-precision trajectory optimization of missions such as in-orbit service and active debris removal in low Earth orbits.

Even in multidisciplinary aircraft design, most aspects of nonlinear controllability are only considered in later design phases. Hence, control considerations are not used to inform the overall design of the airframe. This paper presents a control-aware controller-agnostic design optimization framework that integrates nonlinear controllability constraints, which are informed by the solutions to optimal control problems, into the multidisciplinary design process. To implement the optimization, procedures to evaluate the sensitivity of the controllability constraint to variations in the design variables are defined. A supersonic aircraft case study illustrates the methodology and the steps involved in the process. The proposed approach enables the integration of control-related constraints into gradient-based design optimization.

In this article, our aim was at first, to analyze the regional disparities and territorial inequalities of human development in Tunisia. The first part of the article was devoted to the Factorial components analysis. Moreover, the second part was centered on the progress of synthetic indicators of human development in every region, thanks to our approach based on the HDI (Human Development Index), the HPI ((Human poverty Indicator) and a synthetic indicator of human development in every region and governorate.

In this work, we have developed an FLRW type model of a universe which displays transition from deceleration in the past to the acceleration at the present. For this, we have considered field equations of $f(R,T)$ gravity and have taken $f(R,T) = R + 2 \lambda T$, $\lambda$ being an arbitrary constant. We have estimated the $\lambda$ parameter in such a way that the transition red shift is found similar in the deceleration parameter, pressure and the equation of state parameter $\omega$. The present value of Hubble parameter is estimated on the basis of the three types of observational data set: latest compilation of $46$ Hubble data set, SNe Ia $580$ data sets of distance modulus and $66$ Pantheon data set of apparent magnitude which comprised of 40 SN Ia binned and 26 high redshift data's in the range $0.014 \leq z \leq 2.26 $. These data are compared with theoretical results through the $ \chi^2 $ statistical test. Interestingly, the model satisfies all the three weak, strong and dominant energy conditions. The model fits well with observational findings. We have discussed some of the physical aspects of the model, in particular the age of the universe., Comment: 19 pages 15 figures 1 table

BioSentinel is the first biological CubeSat designed and developed for deep space. The main objectives of this NASA mission are to assess the effects of deep space radiation on biological systems and to engineer a CubeSat platform that can autonomously support and gather data from model organisms hundreds of thousands of kilometers from Earth. The articles in this special collection describe the extensive optimization of the biological payload system performed in preparation for this long-duration deep space mission. In this study, we briefly introduce BioSentinel and provide a glimpse into its technical and conceptual heritage by detailing the evolution of the science, subsystems, and capabilities of NASA's previous biological CubeSats. This introduction is not intended as an exhaustive review of CubeSat missions, but rather provides insight into the unique optimization parameters, science, and technology of those few that employ biological model systems.

Improved attitude control laws based on a feedback reshaping strategy using rotation matrices are proposed for attitude control of a single rigid body on [Formula: see text] and for multibody attitude synchronization on [Formula: see text]. For attitude control of a single body the proposed control law improves the closed-loop response for initial principal rotation angles near 180° while producing a globally continuous control torque. For the problem of multibody attitude synchronization, an alternative feedback reshaping strategy is proposed, which destabilizes nonconsensus equilibria and produces attitude synchronization with almost global stability and globally continuous control. Finally, a previously proposed bipartite consensus algorithm based on the concept of a structurally balanced graph with antagonistic interactions represented by negative edge weights is applied for the first time to rigid-body attitude consensus control with feedback reshaping in which the consensus attitudes and angular velocities are divided into two distinct groups. Simulations serve as illustrative examples of each of these problems and confirm the advantages of the proposed strategies. For multibody synchronization the focus is on ring graph topologies for which locally stable nonconsensus equilibria arise when using an existing attitude consensus control protocol in the literature.

This work investigates the identification of reduced-order state-space models from aeroelastic simulations of the interaction of a built-in structural finite element model and a linear aerodynamic model using unsteady potential theory. The objective is to propose and compare different new frequency-based identification methods operating on frequency response associated to the inputs and outputs of interest. The first methods considered are the Loewner interpolation method and a subspace algorithm. Subsequently, the paper introduces the possibility to apply stability constraints and to impose a certain number of poles estimated beforehand by the [Formula: see text] method in order to make the identified models closer to the true aeroelastic physics. To achieve this goal, new dedicated techniques are developed and subsequently validated on data generated by random state-space models of various orders, and on aeroelastic data obtained from structural and aerodynamic aircraft models.