Υπολογιστική Μελέτη από Πρώτες Αρχές του υπεραγωγού Y Ba 2 Cu 3 O 7-x(YBCO)

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Μικροσυστήματα και Νανοδιατάξεις

Διερεύνηση της σύλληψης ηλεκτρονίου σε κρούσεις ταχέων C4+ (1s2s 3S) ιόντων με αέριους στόχους, χρησιμοποιώντας τη διάταξη φασματοσκοπίας Auger ηλεκτρονίων ιόντων στις 0 μοίρες που κατασκευάστηκε με τη γραμμή L45 στον 5.5 MV tandem επιταχυντή του ΕΚΕΦΕ "Δημόκριτος"

This thesis focuses primarily on the investigation of the collision process:C4+(1s2s 3S) + T->C3+ (1s2s2p 4P, 2P±) + T+, in which a highly-charged (He-like) beam of C4+ ions in the long-lived metastable state (1s2s 3S energetically collide with gas targets (He, H2). In the collision an electron from the target is captured by the 2p orbital of the carbon ion (a process known as electron transfer) in the process giving rise to the production of Li-like doubly-excited states 1s2s2p 4P (a spin quartet), 1s2s2p 2P- (for short as 2P-) and 1s2s2p 2P+ (for short as 2P+), both spin doublets, as well as many other levels to be discussed later. This collision process can be readily investigated experimentally since the initial, 1s2s 3S, ionic core is metastable and therefore naturally found mixed-in with the 1s2 ground state ions as provided by accelerators. One of the main interests in the aforementioned process has to do with the question of whether the similarly configured 1s2s2p 4P and 2P± states are populated in the collision according to spin statistics, i.e. in the ratio R of their spin degeneracies of quartets to doublets. The concept of spin statistics is of fundamental interest since most collision processes are assumed to obey spin statistics. In fact, the above process was found not to obey spin statistics as first exposed in 2004 for fluorine He-like ions (F7+) leading to controversial claims and results. In this thesis, the SDCS Δσ/ΔΩ is determined for each of these 1s2s2p produced levels using the high resolution projectile Auger electron spectroscopy technique known as ZAPS, i.e. where the emitted projectile Auger electron eA is observed at the angle of 0 degrees with respect to the beam direction. Towards this purpose, a new, dedicated beam line (L45), together with a unique, state-of-the-art ZAPS experimental setup was built from scratch, at the only heavy ion research accelerator in Greece, the 5.5 MV tandem Van de Graaff accelerator (for short tandem), operated since 1972 by the INPP of the NCSR "Demokritos", in Athens. Furthermore, this new Atomic Physics initiative involved non-trivial changes to the existing hardware and mode of operation of the tandem accelerator itself, used primarily for Nuclear Physics investigations involving mostly proton beams. Experimental results utilizing the ZAPS technique, regarding relative populations of quartet and doublet states were found to be in agreement with earlier corrected measurements. At the same time, ab initio dynamical calculations have been performed by the theory group of Prof. Alain Dubois - UPMC-Sorbone and CNRS Paris, involving for the first time three active electrons. These presented results, resolve the previously existing disagreement between theory and experiment and draw attention to the limited predictive power of the frozen core approximation as regards to spin statistics in highly correlated dynamical atomic systems.Η παρούσα διατριβή εστιάζει ως επί το πλείστον στην μελέτη της παρακάτω διεργασίας κρούσης: C4+(1s2s 3S) + T->C3+ (1s2s2p 4P, 2P±) + T+, κατά την οποία μια υψηλά φορτισμένη δέσμη ηλιοειδών ιόντων C4+ στη μακρόβια, μετασταθή κατάσταση 1s2s 3S συγκρούεται με αέριους στόχους (He, H2). Κατά τη κρούση αυτή, ένα ηλεκτρόνιο από τον στόχο δεσμεύεται στο 2p τροχιακο του ιόντος άνθρακα (ένας μηχανισμός γνωστός ως σύλληψη/ηλεκτρονίου), οδηγώντας στην παραγωγή των διπλά διεγερμένων λιθιοειδών καταστάσεων 1s2s2p 4P (quartet), 1s2s2p 2P- (εν συντομία 2P- ) και 1s2s2p 2P+ (εν συντομία 2P+), (doublet), μεταξύ άλλων που θα συζητηθούν μετέπειτα στο κείμενο. Αυτή η διεργασία κρούσης μπορεί εύκολα να διερευνηθεί πειραματικά, καθώς ο αρχικός 1s2s 3S, ιοντικός σχηματισμός είναι μετασταθής και ως εκ τούτου, συνυπάρχει σε διάφορες αναλογίες με τα 1s2 ιόντα στη θεμελιώδη κατάσταση κατά τη παραγωγή της δέσμης από τον επιταχυντή.Το βασικό ενδιαφέρον στη παραπάνω διεργασία έγκειται στο ερώτημα του αν οι καταστάσεις 4P και 2P± με παρόμοια 1s2s2p ηλεκτρονιακή διάταξη εποικίζονται κατά την 2p σύλληψη σύμφωνα με τη στατιστική των σπιν, δηλαδή κατά τον λόγο R των εκφυλισμών των spin για την quartet προς τις doublets. Η έννοια της εποίκισης σύμφωνα με τη στατιστική των σπιν είναι βασικού ενδιαφέροντος, καθώς οι περισσότεροι μηχανισμοί κατά τη διάρκεια ατομικών κρούσεων θεωρείται ότι ακολουθούν αυτή τη στατιστική. Πιο συγκεκριμένα, έχει βρεθεί ότι στη παραπάνω διεργασία δεν ακολουθεί αυτή τη στατιστική, όπως πρωτοπαρουσιάστηκε το 2004 για ηλιοειδή ιόντα φθορίου (F7+) οδηγώντας σε αμφιλεγόμενα συμπεράσματα. Σε αυτή τη διατριβή, οι διαφορικές ενεργείς διατομές Δσ/ΔΩ προσδιορίζονται για κάθε ένα από τα παραγώμενα 1s2s2p επίπεδα, χρησιμοποιώντας την υψηλής διακριτικής ικανότητας φασματογραφία Auger ηλεκτρονίων ιόντων δέσμης γνωστή ως ZAPS, όπου το παραγόμενο Auger ηλεκτρόνιο eA μετράται στις 0 μοίρες σε σχέση με τη κατεύθυνση της δέσμης. Προς αυτό το σκοπό, μια νέα πειραματική γραμμή L45, μαζί με μια μοναδική, υπερσύγχρονη πειραματική εγκατάσταση δημιουργήθηκε από το μηδέν, στον μοναδικό ερευνητικό επιταχυντή βαρέων ιόντων στην Ελλάδα, τον 5.5 MV tandem Van ded Graaff επιταχυντή (για συντομία tandem), που λειτουργεί από το 1972 στο Ινστιτούτο Πυρηνικής και Σωματιδιακής Φυσικής του Εθνικού Κέντρου Έρευνας Φυσικών Επιστημών "ΔΗΜΟΚΡΙΤΟΣ", στην Αθήνα. Επιπλέον, αυτή η νέα πρωτοβουλία ατομικής φυσικής περιλαμβάνει ουσιώδεις αλλαγές στο υπάρχον υλικό και τρόπο λειτουργίας του επιταχυντή tandem, που χρησιμοποιείται κυρίως για πειράματα πυρηνικής φυσικής με τη πλειονότητα των πειραμάτων να αφορά τη χρήση δεσμών πρωτονίων. Τα πειραματικά αποτελέσματα, με τη χρήση της μεθόδου ZAPS, όσων αφορά τους σχετικούς πληθυσμούς των quartet και doublet καταστάσεων, είναι σε συμφωνία με παλιότερες, διορθωμένες μετρήσεις. Ταυτόχρονα, έγιναν υπολογισμοί από πρώτες αρχές από την ομάδα θεωρητικών του καθ. Alain Dubois - UPMC-Sorbone και CNRS Paris, οι οποίοι περιλαμβάνουν για πρώτη φορά 3 ενεργά ηλεκτρόνια. Αυτά τα παρουσιασμένα αποτελέσματα, επιλύουν την προϋπάρχουσα διαφωνία μεταξύ θεωρίας και πειράματος και εφιστούν την προσοχή στην περιορισμένη προγνωστική ισχύ της frozen core προσέγγισης όσον αφορά την σπιν στατιστική σε ιδιαιτέρως συσχετισμένα δυναμικά ατομικά συστήματα

Optical study of the ferroelastic Sb_5O_7I with Raman spectroscopy

126 σ.Ο κρύσταλλος Sb_5O_7I εμφανίζει μια δομική αλλαγή φάσης στη θερμοκρασία των 481Κ. Σε θερμοκρασίες χαμηλότερες των 481Κ ο κρύσταλλος εμφανίζει σιδηροελαστικές ιδιότητες, οι οποίες χάνονται όταν η θερμοκρασία ξεπεράσει τη θερμοκρασία μετάβασης. Σκοπός της παρούσα διπλωματικής είναι η μελέτη της Αλλαγής Φάσης που παρουσιάζεται στους 481Κ, με χρήση φασματοσκοπίας Raman. Διενεργήθηκαν μετρήσεις Raman με γεωμετρία οπισθοσκέδασης σε z(xx)z και z(xy)z διάταξη. Ο προσανατολισμός του κρυστάλλου έγινε με την εύρεση της Γωνίας Οπτικής Εξάλειψης. Τα αποτελέσματα συγκρίθηκαν με παλαιότερες μελέτες, έγινε επιβεβαίωση αυτών με μεθόδους Θεωρίας Ομάδων, καθώς και με μετρήσεις Διαφορικής Θερμιδομετρίας. Βρέθηκε και μελετήθηκε μια νέα κορυφή στο φάσμα η οποία παρουσιάζει συμπεριφορά Παράμετρου Τάξης. Τέλος, έγινε ποσοτική μελέτη στο Μαλακό Τρόπο Ταλάντωσης.Τhe Sb_5O_7I crystal displays a phase transition at a temperature of 481K. For temperatures lower than 481K, the crystal exhibits a ferroelastic behavior, which behaviour vanishes above the transition temperature. The purpose of this thesis is the study of the Phase Transition that occurs at 481K with the use of Raman spectroscopy. Raman spectra were acquired with backscattering geometry in z(xx)z και z(xy)z polarizations. The orientation of the crystal was determined by finding the Optical Extinction Angle. The results were compared with older studies and were confirmed with Group Theory Methods, along with DSC (Differential Scanning Calorimetry) measurements. A new peak was found in the spectrum that exhibits Order Parameter behavior. Finally, the already found Soft Mode was studied.Ιωάννης Μ. Μαδέση

Metataxonomic Analysis of Bacteria Entrapped in a Stalactite’s Core and Their Possible Environmental Origins

Much is known about microbes originally identified in caves, but little is known about the entrapment of microbes (bacteria) in stalactites and their possible environmental origins. This study presents data regarding the significant environmental distribution of prokaryotic bacterial taxa of a Greek stalactite core. We investigated the involvement of those bacteria communities in stalactites using a metataxonomic analysis approach of partial 16S rRNA genes. The metataxonomic analysis of stalactite core material revealed an exceptionally broad ecological spectrum of bacteria classified as members of Proteobacteria, Actinobacteria, Firmicutes, Verrucomicrobia, and other unclassified bacteria. We concluded that (i) the bacterial transport process is possible through water movement from the upper ground cave environment, forming cave speleothems such as stalactites, (ii) bacterial genera such as Polaromonas, Thioprofundum, and phylum Verrucomicrobia trapped inside the stalactite support the paleoecology, paleomicrobiology, and paleoclimate variations, (iii) the entrapment of certain bacteria taxa associated with water, soil, animals, and plants such as Micrococcales, Propionibacteriales, Acidimicrobiales, Pseudonocardiales, and α-, β-, and γ-Proteobacteria

Metataxonomic Analysis of Bacteria Entrapped in a Stalactite’s Core and Their Possible Environmental Origins

Much is known about microbes originally identified in caves, but little is known about the entrapment of microbes (bacteria) in stalactites and their possible environmental origins. This study presents data regarding the significant environmental distribution of prokaryotic bacterial taxa of a Greek stalactite core. We investigated the involvement of those bacteria communities in stalactites using a metataxonomic analysis approach of partial 16S rRNA genes. The metataxonomic analysis of stalactite core material revealed an exceptionally broad ecological spectrum of bacteria classified as members of Proteobacteria, Actinobacteria, Firmicutes, Verrucomicrobia, and other unclassified bacteria. We concluded that (i) the bacterial transport process is possible through water movement from the upper ground cave environment, forming cave speleothems such as stalactites, (ii) bacterial genera such as Polaromonas, Thioprofundum, and phylum Verrucomicrobia trapped inside the stalactite support the paleoecology, paleomicrobiology, and paleoclimate variations, (iii) the entrapment of certain bacteria taxa associated with water, soil, animals, and plants such as Micrococcales, Propionibacteriales, Acidimicrobiales, Pseudonocardiales, and α-, β-, and γ-Proteobacteria

Protective Effects of Systiva^® Seed Treatment Fungicide for the Control of Winter Wheat Foliar Diseases Caused at Early Stages Due to Climate Change

Foliar fungal diseases are a serious threat to winter wheat production and climate change appears to favor pathogens associated with leaf blotch and tan spot symptoms in the Mediterranean area. The present work aimed to highlight these risks and propose appropriate disease management strategies by evaluating the seed treatment with the Systiva® (BASF) fungicide as a means to protect the crop against foliar fungal infections during the early growing stages. Towards that aim, plant tissue symptoms affected by the pathogens Pyrenophora tritici-repentis and Septoria spp. were systematically recorded in a study field in the region of Larissa, central Greece for three years (2016–2018), and the findings were associated with the monthly weather anomalies. Consequently, for the growing period of 2021–2022, a field experiment was established in the same disease prone field, comparing different doses of the seed treatment with Systiva® fungicide against leaf blotch and tan spot diseases. The evaluation was made by visual disease assessments, remote sensing with an unmanned aerial vehicle (UAV) and metagenomics analysis. Parallel measurements on straw residues were also made to characterize the plant residues perithecia (pseudothecia). Visual leaf disease assessments and UAV remote sensing data showed that Systiva® treatments at doses of 125 cc and 150 cc per 100 kg of wheat seed can reduce the percentage of infected wheat plants caused by foliar fungal pathogens at wheat growth stages GS23-25 and GS30-31. Moreover, the metagenomics analyses performed on the microbial communities revealed that Systiva® can decrease the degree of infection by P. tritici-repentis and Z. tritici but do not provide sufficient protection against P. nodorum. Foliar diseases were influenced by the soil surface area covered with straw residue with a high proportion of natural inoculum (pseudothecia/ascospores)

HRM and 16S rRNA gene sequencing reveal the cultivable microbiota of the European sea bass during ice storage

The total cultivable microbiota of the ice-stored European sea bass (Dicentrarchus labrax), the most important commercial fish species of the Mediterranean aquaculture, was determined using 16S rRNA gene sequence analysis. High Resolution Melting (HRM) curve profiles and sequencing analysis (V3–V4 region of the 16S rRNA gene) were used respectively for the differentiation and identification of the collected isolates from six time intervals (day 0, 4, 8, 12, 14 and 16) while fish were stored in ice. HRM analysis differentiated the unknown microbiota in ten groups (208 isolates) and in two single isolates based on their HRM curve profiles. The isolates with HRM profiles which were >91% similar within each group were found to belong to the same species using sequencing analysis. Thus, the ten groups consist of representatives of Psychrobacter glacincola, Ps. alimentarius, Ps. cryohalolentis, Ps. maritimus, Ps. fozii, Pseudomonas sp., Paeniglutamicibacter sp., Carnobacterium sp., Leucobacter aridicolis and Bacillus thuringiensis. Based on this approach, Ps. cryohalolentis was found to be the most dominant phylotype at the beginning of fish shelf-life compared to other species. The abundance of this bacterium decreased throughout storage, while Ps. glacincola increased and dominated at the time of the sensory minimum acceptability (day 14) and rejection (day 16). To conclude, HRM could be used for the rapid determination of sea bass microbiota, using the representatives of each group as reference bacterial strains, in order for scientists to solve rapidly stakeholders problems related with microbial quality or safety of fish

ITS Metabarcoding Reveals the Effects of Oregano Essential Oil on <i>Fusarium oxysporum</i> and Other Fungal Species in Soil Samples

The destructive effects of Fusarium wilts are known to affect the production of many crops. The control of Fusarium oxysporum and other soilborne pathogens was mainly based on soil fumigation (methyl bromide), which has long been prohibited and, nowadays, is based on a limited number of available fungicides due to legislation restrictions on residue tolerances and environmental impacts. Alternatively, natural and environmentally safe compounds, such as essential oils, are being investigated for their efficacy in the control of soilborne diseases. The great fungicidal ability of the oregano essential oil components (carvacrol and thymol) has been reported to inhibit the germination and the mycelial development of several fungal species, including F. oxysporum. The aim of our study was to demonstrate how the metabarcoding approach can provide valuable information about the positive or negative impacts of two different doses of oregano essential oil on Fusarium oxysporum and other fungal species which were present in the studied soil samples through the amplification of the ITS1 and ITS2 regions, which were analyzed on a MiSeq platform. A higher dose of oregano essential oil decreased the abundance of F. oxysporum, along with other fungal species, but also had negative effects on Trichoderma evansii and Mortierella chlamydospora, species with possible fungicidal properties. Soil properties, essential oil properties, the fungal composition, and interactions between fungal species should be considered as factors influencing the effectiveness of essential oils as biological control agents for soilborne pathogens

<i>Phaseolus coccineus</i> L. Landraces in Greece: Microsatellite Genotyping and Molecular Characterization for Landrace Authenticity and Discrimination

Phaseolus coccineus L. is a highly valuable crop for human consumption with a high protein content and other associated health benefits. Herein, 14 P. coccineus L. landraces were selected for genetic characterization: two Protected Geographical Indication (PGI) landraces from the Prespon area, namely “Gigantes” (“G”) and “Elephantes” (“E”), and 12 additional landraces from the Greek Gene Bank collection of beans (PC1–PC12). The genetic diversity among these landraces was assessed using capillary electrophoresis utilizing fluorescence-labeled Simple Sequence Repeat (SSR) and Expressed Sequence Tag (EST); Simple Sequence Repeat (SSR) is a molecular marker technology. The “G” and “E” Prespon landraces were clearly distinguished among them, as well as from the PC1 to PC12 landraces, indicating the unique genetic identity of the Prespon beans. Overall, the genetic characterization of the abundant Greek bean germplasm using molecular markers can aid in the genetic identification of “G” and “E” Prespon beans, thus preventing any form of fraudulent practices as well as supporting traceability management strategies for the identification of authenticity, and protection of the origin of local certified products

Protective Effects of Systiva&reg; Seed Treatment Fungicide for the Control of Winter Wheat Foliar Diseases Caused at Early Stages Due to Climate Change

Foliar fungal diseases are a serious threat to winter wheat production and climate change appears to favor pathogens associated with leaf blotch and tan spot symptoms in the Mediterranean area. The present work aimed to highlight these risks and propose appropriate disease management strategies by evaluating the seed treatment with the Systiva&reg; (BASF) fungicide as a means to protect the crop against foliar fungal infections during the early growing stages. Towards that aim, plant tissue symptoms affected by the pathogens Pyrenophora tritici-repentis and Septoria spp. were systematically recorded in a study field in the region of Larissa, central Greece for three years (2016&ndash;2018), and the findings were associated with the monthly weather anomalies. Consequently, for the growing period of 2021&ndash;2022, a field experiment was established in the same disease prone field, comparing different doses of the seed treatment with Systiva&reg; fungicide against leaf blotch and tan spot diseases. The evaluation was made by visual disease assessments, remote sensing with an unmanned aerial vehicle (UAV) and metagenomics analysis. Parallel measurements on straw residues were also made to characterize the plant residues perithecia (pseudothecia). Visual leaf disease assessments and UAV remote sensing data showed that Systiva&reg; treatments at doses of 125 cc and 150 cc per 100 kg of wheat seed can reduce the percentage of infected wheat plants caused by foliar fungal pathogens at wheat growth stages GS23-25 and GS30-31. Moreover, the metagenomics analyses performed on the microbial communities revealed that Systiva&reg; can decrease the degree of infection by P. tritici-repentis and Z. tritici but do not provide sufficient protection against P. nodorum. Foliar diseases were influenced by the soil surface area covered with straw residue with a high proportion of natural inoculum (pseudothecia/ascospores)