Developing the NASA food system for long-duration missions

Even though significant development has transformed the space food system over the last 5 decades to attain more appealing dietary fare for low-orbit space crews, the advances do not meet the need for crews that might travel to Mars and beyond. It is estimated that a food system for a long-duration mission must maintain organoleptic acceptability, nutritional efficacy, and safety for a 3- to 5-y period to be viable. In addition, the current mass and subsequent waste of the food system must decrease significantly to accord with the allowable volume and payload limits of the proposed future space vehicles. Failure to provide the appropriate food or to optimize resource utilization introduces the risk that an inadequate food system will hamper mission success and/or threaten crew performance. Investigators for the National Aeronautics and Space Administration (NASA) Advanced Food Technology (AFT) consider identified concerns and work to mitigate the risks to ensure that any new food system is adequate for the mission. Yet, even with carefully planned research, some technological gaps remain. NASA needs research advances to develop food that is nutrient-dense and long-lasting at ambient conditions, partial gravity cooking processes, methods to deliver prescribed nutrients over time, and food packaging that meets the mass, barrier, and processing requirements of NASA. This article provides a brief review of research in each area, details the past AFT research efforts, and describes the remaining gaps that present barriers to achieving a food system for long exploration missions.     

Exploiting social partners in robot learning

Social learning in robotics has largely focused on imitation learning. Here we take a broader view and are interested in the multifaceted ways that a social partner can influence the learning process. We implement four social learning mechanisms on a robot: stimulus enhancement, emulation, mimicking, and imitation, and illustrate the computational benefits of each. In particular, we illustrate that some strategies are about directing the attention of the learner to objects and others are about actions. Taken together these strategies form a rich repertoire allowing social learners to use a social partner to greatly impact their learning process. We demonstrate these results in simulation and with physical robot ‘playmates’.     

Effect of the CaO sintering on the calcination rate of CaCO3 under atmospheres containing CO2

For the calcination of CaCO₃ under CO₂‐containing atmospheres, a mathematical model taking into account the CO₂‐catalyzed sintering of the CaO product layer is developed. In this model, a modified shrinking core model is coupled with a population balance‐based sintering model. By comparing model predictions with experimental data, it is found that CO₂ strongly affects the overall calcination rate both at high temperature and CO₂ partial pressure, since under these conditions CaO densification considerably reduces the effective diffusivity of CO₂ within product layer. It is observed that for large particles, the CO₂‐catalyzed sintering of CaO can produce the “die off” phenomenon, which takes place when the reaction stops due to the blockage of pores within product layer. Finally, it was determined that limestone impurities do not significantly affect the calcination reaction under atmospheres containing CO₂, because CO₂ causes a much greater increase of the CaO sintering rate than limestone impurities do. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3638–3648, 2018     

An Automatic Diagnosis of an Inverter IGBT Open-Circuit Fault Based on HHT-ANN

Abstract

The main objective of this paper is to propose a method that contributes to the automatic diagnosis of the IGBT open-circuit fault of an inverter for detecting and localizing the fault using the stator current spectral analysis technique. The proposal focusses on the use of the combination of signal processing and artificial intelligence techniques for the detection and localization of the fault. The proposed diagnosis method begins first by using the Hilbert-Huang transform (HHT) to detect the harmonic characterizing the fault based on the complete empirical ensemble mode decomposition (CEEMD) of the three-stator currents (i_as, i_bs, i_cs ). The CEEMD provides the intrinsic mode function (IMF) which contains information of the IGBT open-circuit fault. For the exact choice of the IMF, a statistical study based on the calculation of the root mean square values (RMS) is carried out for each IMF. The IMF choice depends on the condition that the RMS values of the inverter upper IGBTs are always lower than the RMS values of the complementary ones. The results obtained can be seen to respond well to the RMS condition and the spectral envelope of the IMF₁ makes it possible to detect the harmonic characterizing the inverter IGBT open-circuit fault. The proposed diagnosis method then moves to the use of the artificial neural network (ANN) to localize the faulty IGBT. The results obtained using the proposed method are validated experimentally and demonstrate well their effectiveness with a very high classification rate.     

Dual Stem Cell Therapy Improves the Myocardial Recovery Post-Infarction through Reciprocal Modulation of Cell Functions

Mesenchymal stromal cells (MSC) are promising candidates for regenerative therapy of the infarcted heart. However, poor cell retention within the transplantation site limits their potential. We hypothesized that MSC benefits could be enhanced through a dual-cell approach using jointly endothelial colony forming cells (ECFC) and MSC. To assess this, we comparatively evaluated the effects of the therapy with MSC and ECFC versus MSC-only in a mouse model of myocardial infarction. Heart function was assessed by echocardiography, and the molecular crosstalk between MSC and ECFC was evaluated in vitro through direct or indirect co-culture systems. We found that dual-cell therapy improved cardiac function in terms of ejection fraction and stroke volume. In vitro experiments showed that ECFC augmented MSC effector properties by increasing Connexin 43 and Integrin alpha-5 and the secretion of healing-associated molecules. Moreover, MSC prompted the organization of ECFC into vascular networks. This indicated a reciprocal modulation in the functionality of MSC and ECFC. In conclusion, the crosstalk between MSC and ECFC augments the therapeutic properties of MSC and enhances the angiogenic properties of ECFC. Our data consolidate the dual-cell therapy as a step forward for the development of effective treatments for patients affected by myocardial infarction.     

Effect of Drying Methods on the Quality Characteristics of Fenugreek (Trigonella foenum-graecum) Greens

Different drying methods were investigated for efficient dehydration of fenugreek (Trigonella foenum-graecum) greens for optimal retention of color and its constituents. Accordingly, hot air (HA, 40°C, 58–63% RH), low humidity air (LHA, 40°C and 28–30% RH), and radiofrequency (RF, 40°C, 56–60% RH) were explored for efficient drying of fenugreek greens. The three single-layer drying models (Exponential, Page, and Modified Page) tested showed excellent fit (R² = 0.92–0.99) for all three drying methods. The time required for drying with LHA and RF was less (～27%), as compared to HA drying. LHA-dried fenugreek had superior green color and a more porous and uniform structure than those obtained from RF and HA drying. Aqueous methanolic (60:40) extract of fenugreek greens dehydrated by LHA exhibited the highest radical scavenging activity. Dehydrated fenugreek greens showed good consumer acceptance as well as shelf life.     

Melt‐spun polylactic acid fibers: Effect of cellulose nanowhiskers on processing and properties

Bio‐based continuous fibers were processed from polylactic acid (PLA) and cellulose nanowhiskers (CNWs) by melt spinning. Melt compounding of master batches of PLA with 10 wt % CNWs and pure PLA was carried out using a twin‐screw extruder in which compounded pellets containing 1 and 3 wt % of CNWs were generated for subsequent melt spinning. The microscopy studies showed that the fiber diameters were in the range of 90‐95 µm, and an increased surface roughness and aggregations in the fibers containing CNWs could be detected. The addition of the CNWs restricted the drawability of the fibers to a factor of 2 and did not affect the fiber stiffness or strength, but resulted in a significantly lower strain and slightly increased crystallinity. Furthermore, CNWs increased the thermal stability, creep resistance and reduction in thermal shrinkage of PLA fibers, possibly indicating a restriction of the polymer chain mobility due to the nanoscale additives. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Screening and Profiling of Hydrocarbon Components and Squalene in Developing Tunisian Cultivars and Wild Arachis hypogaea L. Species

Total hydrocarbon composition and content of whole peanuts from three Tunisian varieties of peanut (two cultivars: AraC (Virginia type), AraT (Valencia type) and a wild one: AraA) were investigated during maturation. The results show that 30 hydrocarbons were identified from the wild AraA species, while only 27 hydrocarbon were detected in the cultivar ones. The hydrocarbon fraction is essentially composed of squalene, n-alkenes especially nC₁₄₌, nC₁₆₌, nC₁₈₌, nC₂₀₌ and nC₂₂₌, n-alkanes such as nC₁₆, nC₁₇, nC₁₈, nC₂₅, nC₂₆ and nC₂₇, and branched saturated hydrocarbon noted (HC₁, HC₂ and HC₃). Among the hydrocarbon components, generally the wild variety AraA presents the highest content of phytochemical squalene during maturation, whereas a maximum was detected from cultivar AraT at 12 days after podding (815.45 mg/100 g of oil). At maturity, the maximum level is reached at about 346.74 mg/100 g of oil for AraA. During maturity, wild AraA is considered to be an excellent source of squalene like olive and pumpkin oil.     

Application of natural hydroxyapatite in the treatment of polluted water: Utilization of dromedary bone as bioadsorbent

In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis X-ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo-second-order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.     

On the Effect of Poor Metals (Al, Ga, In) on the NO x Conversion in Ethanol Selective Catalytic Reduction

Alumina-supported indium and gallium oxide catalysts were prepared by excess solvent impregnation, characterized and tested for the reduction of NO _x by ethanol in Lean Burn Conditions. The promotion of alumina by “poor” metals showed an interesting ability to selectively reduce NO _x to N₂.