Study of the Performance of Propulsion Units with Nitrogen-Jet Thrusters for Astronaut Extravehicular Activities’ (EVAs)

The future plans of the space agencies all across the globe, mainly focus on the advance of the Extravehicular Activities (EVAs) that are orientated in the repair and maintenance of the space vehicles. This thesis presents a brief history of the space suits (EMU, Orlan-M) utilized in space applications and the propulsion units (Hand-Held Maneuvering Unit, Manned Maneuvering Unit and the Simplified Aid for Extravehicular Activity Rescue-SAFER which is currently being used for performing self-rescue maneuvers, in the case the EVA crew member becomes untethered from the orbiter) that have been used during the space activities. After introducing the space environment and the critical conditions that surround the astronaut during these activities, the fundamentals of the Cold Gas Propulsion Systems on which the function of the SAFER propulsion unit is based, are presented. The aim of this thesis is to perform a performance analysis of the SAFER propulsion unit, with the extraction of the basic space propulsion concepts, i.e. thrust, specific impulse, etc. and the verification of the produced results with the technical characteristics of the unit. The orbital dynamics applying on the astronaut during an EVA are also being studied in this thesis, starting from the scenario where the crew member becomes untethered and floats freely in the vacuum of space and at the same time, examining the case where the SAFER propulsion unit is being activated for the performance of the self-rescue maneuver, and the return of the astronaut to the orbiter

Life cycle assessment of a high-tech vertical decoupled aquaponic system for sustainable greenhouse production

IntroductionAquaponics provide multiple benefits due to the simultaneous yield of vegetables and fish, however they are characterized by increased greenhouse gas emissions owing to intensive production system. The most appropriate method for quantifying the environmental effects of these systems is Life Cycle Assessment with which the identification of hotspots and the suggestion of improved production plans can be achieved. The purpose of the present study was to evaluate the environmental impact of a pilot high-tech aquaponic system utilized for the simultaneous production of baby lettuce and rocket as well as rainbow trout, in indicators such as Global Warming Potential.Materials and methodsTo achieve this goal, data on inputs and outputs were collected from 12 case studies that were implemented, combining different fertilizer treatments, substrate choices, plant species cultivated and water source provision. Life Cycle Assessment was performed using SimaPro v.9.4.0.2 software.ResultsThe results showcase that the optimal case studies include the cultivation of baby lettuce and rocket in perlite substrate using wastewater from fish and partial use of synthetic fertilizers. Indicatively, Global Warming Potential of these cases was calculated at 21.18 and 40.59 kg CO2-eq/kg of vegetable respectively. The parameter with the greatest impact on most of the environmental indicators was electricity consumption for the operation of the oxygen supply pump for the fish tanks, while greenhouse infrastructure had the greatest impact in Abiotic Depletion and Human Toxicity impact categories. In an alternative production scenario tested where renewable energy sources were used, system impacts were reduced by up to 50% for Global Warming Potential and 86% for Eutrophication impact. The results of this study aspire to constitute a significant milestone in environmental impact assessments of aquaponic production systems and the adoption of more sustainable farming practices

The state of soils in Europe

This report delves into the intricate interplay between drivers, pressures and impacts on soil in the 32 Member States of the European Environment Agency (EEA), along with six cooperating countries from the West Balkans, Ukraine and UK, shedding light on the multifaceted challenges facing soil conservation efforts. Our analysis shows the complex interactions among various factors, both anthropogenic and natural, shaping soil degradation processes and their subsequent consequences. We highlight key findings, including the significant impacts of soil degradation on agriculture, ecosystem resilience, water quality, biodiversity, and human health, underscoring the urgent need for comprehensive soil management strategies. Moreover, our examination of citizen science initiatives underlines the importance of engaging the public in soil monitoring and conservation efforts. This work emphasises the policy relevance of promoting sustainable soil governance frameworks, supported by research, innovation, and robust soil monitoring schemes, to safeguard soil health and ensure the long-term resilience of ecosystems.JRC.D.3 - Land Resources and Supply Chain Assessment

The Effect of Botanicals with Nematicidal Activity on the Structural and Functional Characteristics of the Soil Nematode Community

We investigated the effects of three botanicals with nematicidal properties (anise-Pimpinella anisum, parsley-Petroselinum crispum, and rocket-Eruca sativa) on the soil nematode community, in terms of trophic structure and nematode genera composition. We compared effects with those of fluopyram (synthetic nematicide) and Nemagold (bionematicide). We assessed the role of time, by sampling 15 and 45 days after treatments and analyzing nematode genera and microbial phospholipid fatty acid biomarkers (PLFA). Soil incorporation of botanicals reduced plant parasitic nematodes, increased bacterivores, especially the enrichment opportunists and among them Rhabditis, having no effect on fungivores and non-parasitic plant feeders. Neither the number nor the composition and dominance hierarchy of nematode genera were affected. Nemagold did not induce any significant change, while fluopyram decreased both free-living and parasitic nematodes, but with no uniform effect against all genera. The least affected genus was the fungivorous Aphelenchus. While most microbial PLFAs increased with time, the abundances of nematode genera did not change, except the Meloidogyne incognita second stage juveniles, which emerged in soil only 45 days after treatments. The low enrichment index and high channel index values of the fluopyram soil samples indicated a stressful environment. The opposite was observed in the botanical treatments, especially parsley and rocket

Enhancing Peach Tree Fertilization: Investigating Methylobacterium symbioticum SB23 as Game-Changing Agent

This study aims to evaluate the potential of a nitrogen-fixing endophyte, Methylobacterium symbioticum SB23, as a sustainable biofertilizer in peach (Prunus persica) cultivation. We compared three treatments: a control with soil application of ammonium sulfate (250 kg ha−1) and two endophyte foliar applications at different doses: a single high-dose application (M.SYM500 at 500 kg ha−1) and a split half-dose application (M.SYM250 at 250 kg ha−1 applied twice). The first application was made at the fruit stage’s appearance, and the second when the fruits were fully developed. Key assessments included chlorophyll content and shoot growth, which were evaluated at 52 and 100 days after application (DAA), with continued growth benefits observed through 193 DAA. Evaluations were conducted of fruit characteristics, amino acid profiles, and plant tissues of leaves for nitrogen and phosphorus at 107 DAA (harvest). The M.SYM500 treatment notably enhanced fruit weight and increased specific amino acids, such as glutamic acid, methionine, and phenylalanine, contributing to improved fruit quality and resistance properties. No significant differences in °Brix (total soluble solid) levels were observed among treatments, indicating that photosynthetic gains were likely directed towards biomass and structural growth rather than sugar accumulation. This study demonstrates that nitrogen-fixing endophytes can be effective in reducing reliance on synthetic fertilizers while sustaining or improving peach growth and fruit quality

Ensuring Plant Nutrition through Sustainable Soil Management Strategies: Assessing Research Progress and Challenges

The ‘Soil and Plant Nutrition’ section of Agronomy (ISSN 2073-4395) is dedicated to sharing high-quality research articles, reviews, and communications that explore the latest scientific trends and advancements in the field [...

Soil quality evaluation of organically cultivated fields

Τhe subject of this thesis concerns the organically and conventionally cultivated soils and the study of the possible differences of their physical, biochemical and morphometric parameters. We compared soil variables among fields with different duration of organic cultivation (2 (O2), 3(O3), 5 (O5) and 6 (O6) yrs) and between these fields and a conventional one (Σ). All fields were planted with a common perennial plant (Asparagus officinalis (L.)) and they were subject to the same seasonal management practices (fertilizing, crop harvest, incorporation of aboveground residues etc). All sampling fields were located in the same area (Kria Vrisi, Giannitsa) in order to ensure similar climatic conditions. Soil samples were collected four times throughout a year (September, March, May, December) corresponding to management practices applied on asparagus cultivation. Samples were also collected from the close to the cultivations (organic-conventional) hedgerows. Τhe thesis is divided in four chapters and their content is briefly presented in the following paragraphs. In the first chapter the questions that were explored were the following: (a) which factor exerts the greatest influence on soil variables; management type (organic vs conventional) –regarding as long-term disturbances- or management practices- considering as short-term disturbances- (b) do fields with different duration of organic cultivation were distinguishable in terms of their soil biochemical status and (c) the importance of variables in fields’ distinction relates to the specific management practice applied or not? The effect of seasonal management practices on soil biochemical status was much more pronounced than of management type. Among the sampling periods, December was characterized by greater heterogeneity on samples’ soil variables. A fact that could be attributed to laying of aboveground biomass on soil surface which stimulated the microbial community (MBC and MBN) with consequent changes in NH4, NO3, N-mineralization and C-mineralization rate. The importance of soil variables in fields distinction was related to the specific practice applied. The differences among fields, even in the cases of extractable P and N organic that were important classification factors across all samplings, were not systematic. In addition, 10% of samples of the oldest organic field (O6), shared common soil features with samples belonging to the newest organically cultivated field (O2). This high intra-variability showed that none of the examined fields has developed systematically different soil characteristics. Therefore, the idea that soil quality improves as the duration of organic cultivation increases was not supported by our data. In the second chapter was analyzed the data only from the December sampling as it was shown that in this period many soil parameters differ among the cultivations. Data referring to the bacterial functional diversity (Biolog) and the activity of enzymes of the N and P nutrient cycles were also analyzed. The general objectives of this chapter were: a) to see which of the tested soil parameters could be used as indicators reflecting differences in soil quality between organically and conventionally managed asparagus fields, b) how the duration of organic management affects soil parameters.Το αντικείμενο της συγκεκριμένης διδακτορικής διατριβής αφορά στη μελέτη των φυσικών, βιοχημικών και μορφομετρικών εδαφικών παραμέτρων σε οργανικά και συμβατικά καλλιεργούμενα εδάφη σπαραγγιού. Συγκρίναμε εδαφικές παραμέτρους σε καλλιέργειες με διαφορετικό χρόνο ένταξης σε καθεστώς οργανικής καλλιέργειας (δυο (ο2), τριών (ο3), πέντε (ο5) και έξι (ο6) ετών) όπως επίσης έγινε και σύγκριση μεταξύ αυτών των καλλιεργειών και μιας συμβατικής καλλιέργειας (Σ) του ιδίου είδους. Σε όλες τις δειγματοληπτικές θέσεις καλλιεργούνταν το είδος Asparagus officinalis (L.) (σπαράγγι) και όλες οι καλλιέργειες υπόκειντο στις ίδιες εποχιακές καλλιεργητικές πρακτικές (λίπανση, συλλογή σοδειάς,προσθήκη οργανικού υλικού). Οι καλλιέργειες βρίσκονταν στη περιοχή της Κρύας Βρύσης, Γιαννιτσών, πολύ κοντά η μία στην άλλη προκειμένου να χαρακτηρίζονται από τις ίδιες κλιματικές συνθήκες και να ανήκουν στον ίδιο εδαφικό τύπο. Εδαφικά δείγματα συλλέχθηκαν τέσσερις φορές κατά τη διάρκεια ενός έτους (Σεπτέμβριο, Μάρτιο, Μάϊο και #εκέμβριο) που αντιστοιχούν σε καλλιεργητικές πρακτικές που εφαρμόζονται στις καλλιέργιες σπαραγγιών. Επιπρόσθετα, συλλέχθηκαν δείγματα και από τους φυτοφράκτες, που συνιστούν εναπομείνανατα τμήματα φυσικής βλάστησης, που γειτνίαζαν με κάποιες οργανικές καθώς και με την συμβατική καλλιέργεια.συγκεκριμένη διατριβή αποτελείται απο τέσσερα κεφάλαια, το περιεχόμενο των οποίων παρουσιάζεται εν συντομία ακολούθως. Στο πρώτο κεφάλαιο διερευνώνται τα ακόλουθα ερωτήματα: α) ποιός παράγοντας ασκεί μεγαλύτερη επίδραση στις εδαφικές παραμέτρους, ο τρόπος καλλιέργειας (οργανική – συμβατική) ή οι εποχιακές καλλιεργητικές πρακτικές, β) οι περιοχές με διαφορετική διάρκεια ένταξης σε καθεστώς οργανικής καλλιέργειας ήταν διακριτές με βάση το επίπεδο των βιοχημικών τους παραμέτρων ώστε να αποτελούν έναν διαβαθμητή ποιότητας εδάφους και γ) η σημαντικότητα των παραμέτρων στη διάκριση των καλλιεργειών σχετίζεται με τη συγκεκριμένη πρακτική που εφαρμόζεται ή όχι? Οπως προέκυψε η επίδραση των εποχιακών καλλιεργητικών πρακτικών στις βιοχημικές παραμέτρους ήταν πολύ πιο έντονη σε σχέση με αυτό του τρόπου καλλιέργειας. Μεταξύ των δειγματοληπτικών περιόδων, τα δείγματα του #εκεμβρίου εμφάνισαν τη μεγαλύτερη διασπορά. Τον #εκέμβριο εναποτίθεται η υπέργεια βιομάζα στην επιφάνεια του εδάφους μετά το κόψιμό της, γεγονός που ενεργοποιεί τη μικροβιακή βιομάζα (μικροβιακό άνθρακα και μικροβιακό άζωτο) με αποτέλεσμα αλλαγές στις συγκεντρώσεις των αμμωνιακών και νιτρικών ιόντων, στους ρυθμούς ανοργανοποίησης του άνθρακα και του αζώτου. Η σημαντικότητατων εδαφικών παραμέτρων στη διάκριση των καλλιεργειών σχετίστηκε με τη συγκεκριμένη πρακτική που εφαρμόστηκε δηλαδή διαφοροποιήθηκε στις επιμέρους δειγματοληψίες. Οι διαφορές μεταξύ των καλλιεργειών ακόμα και στην περίπτωση του εκχυλίσιμου φωσφόρου και του οργανικού αζώτου που λειτούργησαν ως σημαντικοί παράμετροι διάκρισης στο σύνολο των δειγματοληψιών, δεν ήταν συστηματικές. Επιπρόσθετα, το 10% των δειγμάτων που προέρχονταν από την παλαιότερη οργανική καλλιέργεια ο6, εμφάνισαν κοινά εδαφικά χαρακτηριστικά με δείγματα της νεότερης οργανικής καλλιέργειας ο2. Αυτή η υψηλή εσωτερική ποικιλότητα έδειξε πως καμία από τις εξεταζόμενες καλλιέργειες δεν έχει αναπτύξει συστηματικά διαφορετικά εδαφικά χαρακτηριστικά. Επομένως η ιδέα πως η ποιότητα του εδάφους βελτιώνεται καθώς η διάρκεια της οργανικής καλλιέργειας αυξάνει δε φαίνεται να ενισχύεται από τα δεδομένα αυτά

Crop Yield and Soil Quality Are Partners in a Sustainable Agricultural System

Agricultural practices involving the excessive use of chemical fertilizers and pesticides pose major risks to the environment and human health [...]</jats:p