There are large amount of cellulose accumulated in radioactive waste and radioactive pollution sites. It is difficult to clean up these cellulose. In general, waste treatment process can only proceed until the radiation decay to a safty level. Since most cellulolytic microorganisms could not survive in radioactive waste, the accumulation of cellulose in radioactive waste become a serious problem. Deinococcus radiodurans is highly resistant to radiation, UV light, and dryness. It is possible to use this bacterial strain in the bioremediation of radioactive waste. In this study, we found out that there was not much difference on the growth of this organism under radiation and UV light. Cellulose enzyme activity was inhibited by UV irradiation, but not by 32P radiation. The addition of D. radiodurans whole cells or its cell crude extracts could protect the cellulase from UV damage. We also successfully constructed two plasmids, that contained a cel A gene isolated from Thermotoga maritima. These two plasmids had been used to transform Escherichia coli BL21 and D. radiodurans. All transformed bacterial strains could express celA activity. The celA activities in these transformed D. radiodurans strains were not affect by UV irradiation. However, celA enzyme activity in the transformed E. coli was greatly inhibited by UV irradiation up to 78%. Hopefully these two transformed D. radiodurans bacterial strains can be applied to the bioremediation of radioactive waste.

Η μελέτη που πραγματοποιήθηκε, στα πλαίσια της παρούσας διπλωματικής εργασίας, επικεντρώθηκε στο οικοσύστημα της λιμνοθάλασσας Κορισσίων της Κέρκυρας, που αποτελεί έναν υγροβιότοπο ενταγμένο στο ευρωπαϊκό οικολογικό δίκτυο Natura 2000. Η Κορισσίων βρίσκεται υπό διπλό καθεστώς προστασίας, εφόσον έχει χαρακτηριστεί από το δίκτυο τόσο ως Ειδική Ζώνη Διατήρησης (ΕΖΔ), όσο και ως Ζώνη Ειδικής Προστασίας (ΖΕΠ). Στα πλαίσια της ΕΖΔ, προστατεύεται πλήθος ειδών πανίδας και χλωρίδας που απαντώνται στην περιοχή, καθώς και οι τύποι οικοτόπων που αναπτύσσονται περιφερειακά της, ενώ στα πλαίσια της ΖΕΠ, προστατεύονται πολλά είδη ορνιθοπανίδας που απαντώνται εκεί. Επίσης, λόγω των σημαντικών ειδών της ορνιθοπανίδας, έχει χαρακτηριστεί ως Σημαντική Περιοχή για τα Πουλιά της Ελλάδας (Σ.Π.Π.Ε). Κατά τη μελέτη μας, συλλέχθηκαν και παρατηρήθηκαν στην περιοχή διάφορα φυτικά δείγματα, τα οποία συγκεντρώθηκαν σε χλωριδικό κατάλογο. Συνολικά, καταγράφηκαν 162 διαφορετικά φυτικά taxa, τα 91 εκ των οποίων αποτελούν νέες αναφορές για την περιοχή και τα οποία κατανέμονται σε 46 διαφορετικές οικογένειες. Μία από τις οικογένειες ανήκει στην ομάδα των Γυμνόσπερμων, ενώ οι υπόλοιπες 45 στην ομάδα των Αγγειοσπέρμων και, συγκεκριμένα, οι 36 ανήκουν στην ομάδα των Δικοτυληδόνων και οι 9 στην ομάδα των Μονοκοτυληδόνων. Οι οικογένειες με τα περισσότερα taxa είναι οι ακόλουθες: Fabaceae με 23 taxa, Asteracecae με 16, Poaceae με 14, Orchidaceae με 7, Apiaceae με 6, Lamiaceae με 6 και Liliaceae με 6 taxa. Κυρίαρχη βιομορφή είναι αυτή των Θεροφύτων (Τ), με ποσοστό 39,1%, γεγονός που δεν αποτελεί έκπληξη, αφού τα Θερόφυτα είναι η βιομορφή που κυριαρχεί σε περιοχές με θερινή καταπόνηση. Στη συνέχεια, ακολουθούν τα Ημικρυπτόφυτα (Η) με ποσοστό 21%, τα Γεώφυτα (G) με 19,1%, τα Χαμαίφυτα (Ch) με 10,5% και στην τελευταία θέση βρίσκονται τα Φανερόφυτα (P) με ποσοστό 9,9%. Η πλειοψηφία των φυτικών taxa που αναγνωρίστηκαν στην περιοχή μελέτης, ποσοστό 56%, ανήκει στη Μεσογειακή χωρολογική ενότητα. Στη συνέχεια, ακολουθούν η Κοσμοπολιτική-Υποκοσμοπολιτική και Μεσογειακή-Εξωμεσογειακή ενότητα, με ποσοστό 13% και 10% αντίστοιχα. Με χαμηλότερα ποσοστά εμφανίζονται η Εύκρατη ενότητα με 7% και η Ευρασιατική με 7% επίσης. Τις τελευταίες θέσεις καταλαμβάνουν η Βόρεια και η Τροπική-Υποτροπική ενότητα με 2%, τα ενδημικά taxa με 2% επίσης, και η Ευρωπαϊκή χωρολογική ενότητα με ποσοστό 1%. Το χαμηλό ποσοστό ενδημισμού που προκύπτει (2%) θεωρείται αξιόλογο για την περιοχή μελέτης, λαμβάνοντας υπόψη τη σχετικά φτωχή χλωριδική σύνθεση των παράκτιων οικοσυστημάτων, όπως οι λιμνοθάλασσες. Τα ενδημικά είδη που καταγράφηκαν είναι 3 στον αριθμό. Συγκεκριμένα, συλλέχθηκαν τα Crocus boryi (οικογένεια Iridaceae), Limonium brevipetiolatum (οικογένεια Plumbaginaceae) και Petrorhagia graminea (οικογένεια Caryophyllaceae). Από αυτά, τα Crocus boryi και Petrorhagia graminea είναι ενδημικά της δυτικής και νοτίου Ελλάδας και καταγράφονται για πρώτη φορά στην περιοχή μελέτης, ενώ το Limonium brevipetiolatum αποτελεί ενδημικό των Ιονίων Νήσων και της δυτικής Πελοποννήσου, και έχει καταγραφεί στη λιμνοθάλασσα Κορισσίων και παλαιότερα. Ειδικά για την Petrorhagia graminea, η εύρεσή της στην περιοχή αποτελεί νέα αναφορά για την Κέρκυρα. Και τα τρία αυτά ενδημικά είδη συλλέχθηκαν στο δάσος της μακκίας που σχηματίζεται στην περιοχή, στις ζώνες δειγματοληψιών Γ₁ και Γ₂. Ιδιαίτερη οικολογική αξία στην περιοχή, προσδίδει επίσης το φυτικό είδος Crucianella maritima, που εμφανίζει μια στενομεσογειακή γεωγραφική εξάπλωση, κυρίως στη δυτική Μεσόγειο, και είναι σπάνιο για τον ελληνικό χώρο. Η Crucianella maritima καταλαμβάνει μεγάλη από την έκταση της παραλίας του Χαλικούνα, όπου μαζί με τα οικοσυστήματα των αμμοθινών, σχηματίζει τον τύπο οικοτόπου «Σταθερές θίνες της Crucianellion maritimae» με κωδικό 2210. Η έκταση που καταλαμβάνει ο οικότοπος αυτός στην περιοχή, αλλά και η πολύ καλή κατάσταση διατήρησής του, αποτελούν αξιοσημείωτο γεγονός τόσο για την Ελλάδα, όσο και τη Βαλκανική, όπου δεν έχουν περιγραφεί έως τώρα παρόμοια διατηρημένες διαπλάσεις. Επίσης, στην περιοχή καταγράφηκαν 7 taxa άγριων ορχιδεών προστατευόμενων από την ευρωπαϊκή νομοθεσία, μέσω της Σύμβαση CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) για το «Διεθνές Εμπόριο των Ειδών της Άγριας Πανίδας και Χλωρίδας που Κινδυνεύουν με Εξαφάνιση», η οποία βασίζεται στον κανονισμό της Ευρωπαϊκής ένωσης 338/97. Σε εθνικό επίπεδο, τα είδη αυτά προστατεύονται επίσης από το Προεδρικό ∆ιάταγµα 67/1981 «Περί προστασίας της αυτοφυούς χλωρίδας και Αγρίας Πανίδος και καθορισµού διαδικασίας συντονισµού και Ελέγχου της Ερεύνης επ΄ αυτών». Συγκεκριμένα, συλλέχθηκαν τα: Anacamptis laxiflora (Οrchis laxiflora), A. morio (Ο. morio), A. palustris subsp. palustris, A. pyramidalis, Serapias lingua, S. parviflora και Spiranthes spiralis. Ειδικά η Anacamptis palustris subsp. palustris, περιλαμβάνεται επίσης στην Κόκκινη Λίστα των Απειλούμενων Ειδών, της Διεθνούς Ένωσης για τη Διατήρηση της Φύσης IUCN (International Union for Conservation of Nature). Στη λιμνοθάλασσα Κορισσίων, στα πλαίσια του δικτύου Natura 2000, καταγράφηκαν δώδεκα (12) διαφορετικοί τύποι οικοτόπων, τρεις από τους οποίους αποτελούν οικοτόπους προτεραιότητας. Συγκεκριμένα, οι οικότοποι αυτοί είναι: 1. Παράκτιες λιμνοθάλασσες, κωδικός Natura 1150 2. Μεσογειακά αλίπεδα (Juncetalia maritimi), κωδικός Natura 1410 3. Μεσογειακές θερμοατλαντικές αλόφιλες λόχμες, κωδικός Natura 1420 4. Υποτυπώδεις κινούμενες θίνες, κωδικός Natura 2110 5. Κινούμενες θίνες της ακτογραμής με Ammophila arenaria, κωδικός Natura 2120 6. Σταθερές θίνες της Crucianellion maritimae, κωδικός Natura 2210 7. Θίνες των παραλιών με Juniperus ssp., κωδικός Natura 2250 8. Υγροί μεσογειακοί λειμώνες με υψηλές πόες από Molinio Holoschoenion, κωδικός Natura 6420 9. Ασβεστούχα έλη με Cladium mariscus και είδη του Caricion davallianae, κωδικός Natura 7210 10. Καλαμώνες, κωδικός Natura 72Α0 11. Στοές με Salix alba και Populus alba, κωδικός Natura 92Α0 12. Ελληνικά δάση πρίνου, κωδικός Natura 934A Χαρακτηρισμένοι ως οικότοποι προτεραιότητας είναι: οι Παράκτιες λιμνοθάλασσες με κωδικό Natura 1150, οι Θίνες των παραλιών με Juniperus ssp., με κωδικό Natura 2250 και τα Ασβεστούχα έλη με Cladium mariscus και είδη του Caricion davallianae, με κωδικό Natura 7210. Εκτός από τους υπάρχοντες τύπους οικοτόπων, κατά τις επισκέψεις μας στην περιοχή μελέτης, καταγράφηκαν δύο επιπλέον οικότοποι. Ο τύπος οικοτόπου «Μονοετής βλάστηση μεταξύ ορίων πλημμυρίδας και άμπωτης» με κωδικό 1210 και ο τύπος οικοτόπου «Μονοετής βλάστηση με Salicornia και άλλα είδη λασπωδών και αμμωδών ζωνών» με κωδικό 1310. Όσον αφορά την πανίδα της περιοχής, από τα νομικά πλαίσια που αναφέρθηκαν παραπάνω, προστατεύονται 3 είδη θηλαστικών, 3 είδη ψαριών, 8 είδη πεταλούδων, 16 είδη ερπετών, στα οποία συμπεριλαμβάνονται και 3 είδη σπάνιων χελωνών, και ένα είδος αμφιβίου. Από τα προστατευόμενα αυτά είδη, η Βίδρα (Lutra lutra) και το ψαράκι των υφάλμυρων νερών Valencia letourneuxi χαρακτηρίζονται ως πολύ σπάνια. Επιπλέον, προστατεύονται συνολικά 148 είδη ορνιθοπανίδας, πολλά από τα οποία είναι επίσης σπάνια είδη. Κατά τη διεξαγωγή της μελέτης, παρατηρήθηκαν διάφορες μορφές υποβάθμισης του οικοσυστήματος, με κυριότερες από αυτές την όλο και αυξανόμενη ανοικοδόμηση και τουριστική ανάπτυξη, την ανεξέλεγκτη θήρευση των πουλιών, τη χρήση φυτοφαρμάκων και την έντονη παρουσία των παραθεριστών αλλά και των αυτοκινήτων. Επίσης, ελλοχεύει ο κίνδυνος υποβάθμισης μεγάλου μέρους της έκτασης της περιοχής, λόγω της ενδεχόμενης πώλησης 1,8 εκατομμυρίων τετραγωνικών μέτρων στην νοτιοανατολική της πλευρά (παραλία Ίσσος), για τα οποία υπάρχει σχέδιο αξιοποίησης, που περιλαμβάνει τη δημιουργία γηπέδου γκολφ και αθλητικών εγκαταστάσεων. Η μεγάλη οικολογική αξία της λιμνοθάλασσας Κορισσίων αποτελεί το κύριο συμπέρασμα που προκύπτει από τη διεξαγωγή της παρούσας εργασίας. Ολόκληρη η έκταση περιφερειακά της, αλλά και η ίδια η λεκάνη της λιμνοθάλασσας, φιλοξενούν πλήθος σπάνιων και προστατευόμενων μορφών ζωής. Η πλούσια χλωριδική σύσταση με 162 φυτικά taxa, τα πολυάριθμα και σπάνια είδη χλωρίδας και πανίδας, καθώς και οι τύποι οικοτόπων προτεραιότητας συνθέτουν ένα ιδιαίτερου φυσικού κάλλους, εύθραυστο οικοσύστημα, το οποίο απειλείται με υποβάθμιση και περισσότερο από κάθε άλλη φορά, είναι αναγκαίες ενέργειες για την αειφόρο διατήρησή του. Τα στοιχειώδη μέτρα προστασίας που θωρούμε πως είναι αναγκαίο να εφαρμοστούν, έτσι ώστε να διατηρηθεί αναλλοίωτο το φυσικό περιβάλλον της λιμνοθάλασσας και να διασφαλιστεί η βιωσιμότητα των ειδών άγριας χλωρίδας και πανίδας που φιλοξενεί είναι τα εξής: 5. Δημιουργία Φορέα Διαχείρισης, ο οποίος θα είναι υπεύθυνος για τη συνεχή παρακολούθηση της περιοχής και θα λαμβάνει τα απαραίτητα μέτρα για την εξασφάλιση του καλού επιπέδου διατήρησής της. 6. Τοποθέτηση παρατηρητηρίων ορνιθοπανίδας, τα οποία θα εξασφαλίζουν την ομαλή διεξαγωγή του κυνηγιού και την αποτροπή λαθροθηρίας των προστατευόμενων ειδών, εφόσον το κυνήγι στης περιοχές Natura 2000 επιτρέπεται υπό όρους (Πηγή: Ευρωπαϊκή επιτροπή http://ec.europa.eu/). 7. Καταγραφή των ειδών χλωρίδας και πανίδας που προστατεύονται από το Natura 2000, έτσι ώστε να αξιολογηθεί η κατάσταση των πληθυσμών τους και να ληφθούν τα απαραίτητα μέτρα προστασίας τους, όπου χρειάζεται. 8. Εκ νέου καταγραφή και αξιολόγηση των τύπων οικοτόπων που προστατεύονται από το Natura 2000, έτσι ώστε να συγκριθεί η κατάσταση διατήρησής τους με αυτήν που καταγράφηκε από το δίκτυο Natura 2000, την περίοδο 1998 με 2000 και να ληφθούν τα απαραίτητα μέτρα προστασίας τους, όπου χρειάζεται. Επίσης η ανάπτυξη του οικοτουρισμού θα μπορούσε να αναδείξει την περιβαλλοντική ομορφιά και μοναδικότητα του τόπου μας και θα έδινε το κίνητρο στους ντόπιους κατοίκους να προστατεύσουν και να διατηρήσουν αναλλοίωτο το οικοσύστημα της λιμνοθάλασσας. Οικοτουριστική ανάπτυξη θα μπορούσε να επιτευχθεί με τη διεξαγωγή εκδρομών ενημέρωσης για την άγρια ζωή στην περιοχή, τη διάνοιξη μονοπατιών περιφερειακά της, τις παρακολουθήσεις των μεταναστευτικών πουλιών κλπ. Τέλος, η ευαισθητοποίηση των μικρότερων ηλικιών σε θέματα που αφορούν την προστασία του περιβάλλοντος, αλλά και η δημιουργία περιβαλλοντικής συνείδησης στους μικρούς και όχι μόνο μαθητές, είναι αυτή που θα διασφαλίσει ότι το οικοσύστημα της λιμνοθάλασσας Κορισσίων δεν θα καταστραφεί και θα αποτελέσει φυσική κληρονομιά των επόμενων γενεών. / -

Uppsatsen syftar till att analysera de förmågor som den maritima säkerheten i Sveriges närområde kräver. Dessa behov har sedan jämförts med aktuella maritima resurser genom en avslutande diskussion. Utgångspunkt har tagits i Regeringens havs –och utrikespolitik med inriktning på den maritima säkerheten.I uppsatsen motsvaras begreppet ”maritima enheter” av Kustbevakningen och marinen. Hoten mot den maritima säkerheten har identifierats utifrån de uppsatta mål som de maritima enheterna arbetar mot. Dessa har fördelats över Geoffrey Tills fem underkategorier för maritim säkerhet.Begreppet maritim säkerhet har sedan brutits ned till handlingsvägar och medel, det vill säga förmågor. Handlingsvägarna och medlen leder fram till målet, som är just maritim säkerhet.Resultatet från uppsatsen visar att Sverige som småstat ständigt måste kompromissa för att optimera sina maritima enheters förmågor för att uppnå målet maritim säkerhet. Vidare dras slutsatsen att internationella samarbeten spelar en viktig roll för Sverige i detta sammanhang. Slutligen konstateras att det finns brister i de maritima enheternas förmågor och att ett fortsatt aktivt prioriterings –och förbättringsarbete är mycket viktigt för att bibehålla nödvändiga, grundläggande förmågor inom den maritima arenan. / The aim of the report is to analyze the abilities that maritime security in thesurroundings of Sweden demands. These needs are then compared to maritimeresources in a finishing discussion.The Swedish government´s foreign policy and policy for the sea, with focus onmaritime security, has been used as a starting point.In this report, the concept “maritime units” is represented by the Swedish coastguard and the Swedish navy. The threats against the maritime security have beenidentified from the goals that the maritime units are working against. Thesethreats have been divided into Geoffrey Till´s five subcategories for maritimesecurity. The concept maritime security is then broken down into ways of actionand means, in this case abilities. The ways of action and the means lead up to thegoal, that is maritime security.The result from the report shows that Sweden as a small country always need tocompromise to optimize the abilities of its maritime units to achieve the goal ofmaritime security. Henceforth is the conclusion that international cooperationplays an important role for Sweden in this context. Finally it is established that theabilities of the maritime units contain flaws and that continuing work ofimprovement and continuing to prioritize is very important to sustain thenecessary and fundamental abilities within the maritime arena.

Desde o início das investigações sobre o fundo do mar, considerável progresso no entendimento do ambiente marinho foi conquistado. A tecnologia e as ferramentas de mapeamento e análise desenvolvidas para estudar o fundo oceânico permitem que se descreva, com um certo grau de detalhamento, o relevo e, até mesmo, estruturas internas de camadas de sedimentos de diferentes tamanhos, que estão lá no fundo do mar, depositados ao longo de milhões de anos de história do planeta. O grande mistério, que até os dias de hoje ainda não foi completamente explicado, é o modo como esses sedimentos são transportados para o fundo do mar e geram depósitos no fundo oceânico, a centenas de quilômetros da costa? Acredita-se que os canyons que existem no fundo do mar sejam as vias expressas de transporte de boa parte desses sedimentos, já que se constata a existência de um grande volume de material depositado na parte terminal dos sistemas canalizados. A proposta dessa investigação experimental partiu de reprodução, em laboratório, dos processos que poderiam estar envolvidos na formação dos canyons. A teoria mais aceita existente na literatura, atribui a atuação de correntes de densidade durante as regressões do nível do mar como sendo o principal fator que desencadeou a formação dos canyons. A hipótese desse trabalho inclui, além da atuação das correntes de densidade, a atuação de um fluxo de aquífero mais intenso aflorando na região do talude. O fluxo de aquífero mais intenso é justificado pela ocorrência de um aumento de gradiente hidráulico, produzido durante o rebaixamento do nível do mar, durante as fazes de regressão. A simulação física é uma ferramenta poderosa e robusta, utilizada há mais de um século no dimensionamento de aviões, foguetes, pontes, torres, descarregadores de barragens, vertedores e muitos outros tipos de estruturas. A mesma ferramenta pode ser utilizada para gerar modelos do processo de transporte sedimentar em escala reduzida. Esse tipo de estudo parte do conhecimento dos elementos envolvidos no fenômeno investigado – no caso específico, o fundo do mar, a água e os sedimentos – e dos processos aos quais esses elementos possivelmente estão sujeitos no ambiente natural. Esta pesquisa, fundamentada na modelagem física, tentou reproduzir um fluxo de aquífero que aflora no talude e, concomitantemente, a atuação de correntes de densidade, produzindo assim em laboratório um ambiente análogo ao natural durante as fases de regressão do nível do mar, com base em teorias da bibliografia. A metodologia experimental adotada partiu da construção de um depósito cuja geometria representa um V talude com cerca de 1,5 metro de largura, 0,6 metro de comprimento e 0,25 metro de altura. O talude possui rampas com declividades entre 15 e 30 graus. Os sedimentos utilizados foram carvão mineral com fração de areia grossa, areia grossa de origem siliciclástica e calcário com frações de silte e argila. Os sedimentos de frações de areia foram utilizados na construção dos taludes testados, e o calcário, na produção das correntes de densidade. Os experimentos simularam escoamentos em meio poroso dentro do talude, reproduzindo um fluxo de água subterrânea de sistema aquífero que aflorou na região do declive, tendo sido medidas as vazões do aquífero e os respectivos gradientes hidráulicos. Foram também simuladas correntes de densidade com diferentes concentrações e intensidades, bem como obtidos valores médios de espessuras, velocidades e concentrações de sedimentos. Através da simulação, foram produzidas sequências de processos de erosão do talude, que iniciaram com escorregamentos – gerados a partir do aumento da vazão dentro do aquífero reproduzido – e terminaram com a geração de canyons – através da atuação simultânea de correntes de densidade. Os resultados mostraram que existe um significativo elo de ligação entre esses dois processos – fluxo de água subterrânea de sistema aquífero e correntes de densidade –, de tal modo que ambos são necessários para que ocorra a formação dos canyons e para que um grande volume de material seja efetivamente erodido e transportado. As correntes de densidade sozinhas, dentro da escala de simulação, não possuem capacidade de erosão e transporte de sedimentos muito significativa. O sistema de transporte via correntes só é efetivo quando existe um fluxo de aquífero atuando concomitantemente. A observação dos processos de erosão e deposição durante os experimentos, bem como análise do banco de imagens obtidas permitiram a construção de um modelo de formação e evolução de canyons. A formação passa por sequências ordenadas, onde o desenvolvimento de um knickpoint desencadeia um processo de erosão remontante, escavando um sulco que evolui para um canyon formado por uma cabeceira conectada a plataforma bem como depósitos associados. Os dados gerados na simulação física foram comparados com dados do ambiente natural, descritos em trabalhos acadêmicos publicados, e logrou-se provar que os parâmetros medidos estão dentro de valores passíveis de ser encontrados no ambiente natural. Além disso, o cálculo de extrapolação permitiu identificar canyons naturais análogos aos produzidos em laboratório. Os parâmetros dinâmicos das correntes de densidade, bem com as concentrações volumétricas de sedimentos e as faixas de tamanhos de grãos extrapolados estão também dentro de escalas medidas em protótipos análogos. As escalas encontradas seriam de 1:5000 na vertical (com exagero de 2 a 3 vezes) e 1:10000 e VI 1:15000 na horizontal. Assim, é possível que os resultados obtidos neste trabalho venham a elucidar um pouco as dúvidas que estão pendentes há muito tempo acerca do objeto de estudo. / Since the beginning of the deep sea research, considerable progress has been achieved in understanding the marine environment. The technology and tools developed for mapping and analyzing the ocean floor allow a detailed description of the relief and even the internal structures of sediment layers of different sizes that are there, in the bottom of the sea, deposited over millions of years of planetary history. The great mystery, which to this day has not yet been fully explained, is the way these sediments are transported to the seabed. How do sediments of varying sizes reach distances hundreds of miles beyond the coastline and generate deposits on the ocean floor? It is believed that the canyons that exist on the seabed are the express ways through which the transport of a good part of these sediments occurs, given that there is a great volume of material deposited in the terminal parts of these channeled systems. Thus, the focus of speculation and interest has been directed to canyons and density currents, which serve, respectively, as the pathway and the vehicle for sediments. The major obstacle to investigating the role of canyons and currents in the sediment transfer process is the difficulty in observing and measuring phenomena in the natural environment. Besides the scale problem, there is also the rarity of occurrence of events. In fact, it is practically impossible to predict when and where a density current will occur. And if it were possible to predict, how could it be measured? With what equipment? Physical simulation is a powerful and robust tool, used for more than a century in the scaling of aircraft, rockets, bridges, towers, dams, spillways and many other structures. The same tool can be used to generate small scale models of the sediment transport process. This type of study is based on the knowledge of the elements involved in the phenomenon investigated – in this case, the seabed, water and sediments – and the processes to which these elements are possibly subject in the natural environment. This research, based on physical modeling, allowed to reproduce in a laboratory, in a reduced scale, processes similar to those that possibly occur in the seabed. The experimental methodology adopted was based on the construction of a deposit whose geometry represents a slope about 1.5 meters wide, 0.6 meters long and 0.25 meters high. The slope has declivities between 15 and 30 degrees. The sediments used were mineral coal of a coarse sand fraction, coarse sand of siliciclastic origin and limestone with fractions of silt and clay. The sediments of sand fractions were used in the construction of the experimental slopes, and the limestone, in the production of the density currents. The experiments simulated water flows in porous medium within the slope, reproducing an VIII aquifer flow. Density currents were also simulated, since they are generally considered as an important mechanism of sediment transport in the natural environment. began with slides – generated from an increasing flow rate within the simulated aquifer – and ended with the generation of canyons – through the simultaneous action of density currents. The results show that there is a significant link between these two processes – aquifer flow and density currents –, in such a way that both are necessary for the formation of canyons to occur and for a large volume of material to be effectively eroded and transported. Density currents alone, within the simulation scale, do not have very significant sediment transport capacity. The density currents transport system is only effective when there is an aquifer flow acting concomitantly. The observation of the erosion and deposition processes during the experiments, as well as the analysis of the bank of images obtained allowed the construction of a model of formation and evolution of canyons. The formation passes through ordered sequences, where the development of a knickpoint triggers a process of erosion remontante, digging a groove that evolves to a canyon formed by a bedside connected to the platform as well as associated deposits. The data generated in the physical simulation were compared with data from the natural environment, described in published academic papers, which proved that the measured parameters are within the value range that can be found in the natural environment. In addition, the upscaling of the results allowed the identification of natural canyons analogous to those produced in the laboratory. The dynamic parameters of the density streams as well as the volumetric sediment concentrations and the extrapolated grain size ranges are also within scales measured in similar prototypes. The scales found would be 1: 5000 vertically and 1: 10000 and 1: 15000 horizontally. Thus, it is possible that the results obtained in this work will elucidate some doubts that have long been pending about the object of study.

Desde o início das investigações sobre o fundo do mar, considerável progresso no entendimento do ambiente marinho foi conquistado. A tecnologia e as ferramentas de mapeamento e análise desenvolvidas para estudar o fundo oceânico permitem que se descreva, com um certo grau de detalhamento, o relevo e, até mesmo, estruturas internas de camadas de sedimentos de diferentes tamanhos, que estão lá no fundo do mar, depositados ao longo de milhões de anos de história do planeta. O grande mistério, que até os dias de hoje ainda não foi completamente explicado, é o modo como esses sedimentos são transportados para o fundo do mar e geram depósitos no fundo oceânico, a centenas de quilômetros da costa? Acredita-se que os canyons que existem no fundo do mar sejam as vias expressas de transporte de boa parte desses sedimentos, já que se constata a existência de um grande volume de material depositado na parte terminal dos sistemas canalizados. A proposta dessa investigação experimental partiu de reprodução, em laboratório, dos processos que poderiam estar envolvidos na formação dos canyons. A teoria mais aceita existente na literatura, atribui a atuação de correntes de densidade durante as regressões do nível do mar como sendo o principal fator que desencadeou a formação dos canyons. A hipótese desse trabalho inclui, além da atuação das correntes de densidade, a atuação de um fluxo de aquífero mais intenso aflorando na região do talude. O fluxo de aquífero mais intenso é justificado pela ocorrência de um aumento de gradiente hidráulico, produzido durante o rebaixamento do nível do mar, durante as fazes de regressão. A simulação física é uma ferramenta poderosa e robusta, utilizada há mais de um século no dimensionamento de aviões, foguetes, pontes, torres, descarregadores de barragens, vertedores e muitos outros tipos de estruturas. A mesma ferramenta pode ser utilizada para gerar modelos do processo de transporte sedimentar em escala reduzida. Esse tipo de estudo parte do conhecimento dos elementos envolvidos no fenômeno investigado – no caso específico, o fundo do mar, a água e os sedimentos – e dos processos aos quais esses elementos possivelmente estão sujeitos no ambiente natural. Esta pesquisa, fundamentada na modelagem física, tentou reproduzir um fluxo de aquífero que aflora no talude e, concomitantemente, a atuação de correntes de densidade, produzindo assim em laboratório um ambiente análogo ao natural durante as fases de regressão do nível do mar, com base em teorias da bibliografia. A metodologia experimental adotada partiu da construção de um depósito cuja geometria representa um V talude com cerca de 1,5 metro de largura, 0,6 metro de comprimento e 0,25 metro de altura. O talude possui rampas com declividades entre 15 e 30 graus. Os sedimentos utilizados foram carvão mineral com fração de areia grossa, areia grossa de origem siliciclástica e calcário com frações de silte e argila. Os sedimentos de frações de areia foram utilizados na construção dos taludes testados, e o calcário, na produção das correntes de densidade. Os experimentos simularam escoamentos em meio poroso dentro do talude, reproduzindo um fluxo de água subterrânea de sistema aquífero que aflorou na região do declive, tendo sido medidas as vazões do aquífero e os respectivos gradientes hidráulicos. Foram também simuladas correntes de densidade com diferentes concentrações e intensidades, bem como obtidos valores médios de espessuras, velocidades e concentrações de sedimentos. Através da simulação, foram produzidas sequências de processos de erosão do talude, que iniciaram com escorregamentos – gerados a partir do aumento da vazão dentro do aquífero reproduzido – e terminaram com a geração de canyons – através da atuação simultânea de correntes de densidade. Os resultados mostraram que existe um significativo elo de ligação entre esses dois processos – fluxo de água subterrânea de sistema aquífero e correntes de densidade –, de tal modo que ambos são necessários para que ocorra a formação dos canyons e para que um grande volume de material seja efetivamente erodido e transportado. As correntes de densidade sozinhas, dentro da escala de simulação, não possuem capacidade de erosão e transporte de sedimentos muito significativa. O sistema de transporte via correntes só é efetivo quando existe um fluxo de aquífero atuando concomitantemente. A observação dos processos de erosão e deposição durante os experimentos, bem como análise do banco de imagens obtidas permitiram a construção de um modelo de formação e evolução de canyons. A formação passa por sequências ordenadas, onde o desenvolvimento de um knickpoint desencadeia um processo de erosão remontante, escavando um sulco que evolui para um canyon formado por uma cabeceira conectada a plataforma bem como depósitos associados. Os dados gerados na simulação física foram comparados com dados do ambiente natural, descritos em trabalhos acadêmicos publicados, e logrou-se provar que os parâmetros medidos estão dentro de valores passíveis de ser encontrados no ambiente natural. Além disso, o cálculo de extrapolação permitiu identificar canyons naturais análogos aos produzidos em laboratório. Os parâmetros dinâmicos das correntes de densidade, bem com as concentrações volumétricas de sedimentos e as faixas de tamanhos de grãos extrapolados estão também dentro de escalas medidas em protótipos análogos. As escalas encontradas seriam de 1:5000 na vertical (com exagero de 2 a 3 vezes) e 1:10000 e VI 1:15000 na horizontal. Assim, é possível que os resultados obtidos neste trabalho venham a elucidar um pouco as dúvidas que estão pendentes há muito tempo acerca do objeto de estudo. / Since the beginning of the deep sea research, considerable progress has been achieved in understanding the marine environment. The technology and tools developed for mapping and analyzing the ocean floor allow a detailed description of the relief and even the internal structures of sediment layers of different sizes that are there, in the bottom of the sea, deposited over millions of years of planetary history. The great mystery, which to this day has not yet been fully explained, is the way these sediments are transported to the seabed. How do sediments of varying sizes reach distances hundreds of miles beyond the coastline and generate deposits on the ocean floor? It is believed that the canyons that exist on the seabed are the express ways through which the transport of a good part of these sediments occurs, given that there is a great volume of material deposited in the terminal parts of these channeled systems. Thus, the focus of speculation and interest has been directed to canyons and density currents, which serve, respectively, as the pathway and the vehicle for sediments. The major obstacle to investigating the role of canyons and currents in the sediment transfer process is the difficulty in observing and measuring phenomena in the natural environment. Besides the scale problem, there is also the rarity of occurrence of events. In fact, it is practically impossible to predict when and where a density current will occur. And if it were possible to predict, how could it be measured? With what equipment? Physical simulation is a powerful and robust tool, used for more than a century in the scaling of aircraft, rockets, bridges, towers, dams, spillways and many other structures. The same tool can be used to generate small scale models of the sediment transport process. This type of study is based on the knowledge of the elements involved in the phenomenon investigated – in this case, the seabed, water and sediments – and the processes to which these elements are possibly subject in the natural environment. This research, based on physical modeling, allowed to reproduce in a laboratory, in a reduced scale, processes similar to those that possibly occur in the seabed. The experimental methodology adopted was based on the construction of a deposit whose geometry represents a slope about 1.5 meters wide, 0.6 meters long and 0.25 meters high. The slope has declivities between 15 and 30 degrees. The sediments used were mineral coal of a coarse sand fraction, coarse sand of siliciclastic origin and limestone with fractions of silt and clay. The sediments of sand fractions were used in the construction of the experimental slopes, and the limestone, in the production of the density currents. The experiments simulated water flows in porous medium within the slope, reproducing an VIII aquifer flow. Density currents were also simulated, since they are generally considered as an important mechanism of sediment transport in the natural environment. began with slides – generated from an increasing flow rate within the simulated aquifer – and ended with the generation of canyons – through the simultaneous action of density currents. The results show that there is a significant link between these two processes – aquifer flow and density currents –, in such a way that both are necessary for the formation of canyons to occur and for a large volume of material to be effectively eroded and transported. Density currents alone, within the simulation scale, do not have very significant sediment transport capacity. The density currents transport system is only effective when there is an aquifer flow acting concomitantly. The observation of the erosion and deposition processes during the experiments, as well as the analysis of the bank of images obtained allowed the construction of a model of formation and evolution of canyons. The formation passes through ordered sequences, where the development of a knickpoint triggers a process of erosion remontante, digging a groove that evolves to a canyon formed by a bedside connected to the platform as well as associated deposits. The data generated in the physical simulation were compared with data from the natural environment, described in published academic papers, which proved that the measured parameters are within the value range that can be found in the natural environment. In addition, the upscaling of the results allowed the identification of natural canyons analogous to those produced in the laboratory. The dynamic parameters of the density streams as well as the volumetric sediment concentrations and the extrapolated grain size ranges are also within scales measured in similar prototypes. The scales found would be 1: 5000 vertically and 1: 10000 and 1: 15000 horizontally. Thus, it is possible that the results obtained in this work will elucidate some doubts that have long been pending about the object of study.

Desde o início das investigações sobre o fundo do mar, considerável progresso no entendimento do ambiente marinho foi conquistado. A tecnologia e as ferramentas de mapeamento e análise desenvolvidas para estudar o fundo oceânico permitem que se descreva, com um certo grau de detalhamento, o relevo e, até mesmo, estruturas internas de camadas de sedimentos de diferentes tamanhos, que estão lá no fundo do mar, depositados ao longo de milhões de anos de história do planeta. O grande mistério, que até os dias de hoje ainda não foi completamente explicado, é o modo como esses sedimentos são transportados para o fundo do mar e geram depósitos no fundo oceânico, a centenas de quilômetros da costa? Acredita-se que os canyons que existem no fundo do mar sejam as vias expressas de transporte de boa parte desses sedimentos, já que se constata a existência de um grande volume de material depositado na parte terminal dos sistemas canalizados. A proposta dessa investigação experimental partiu de reprodução, em laboratório, dos processos que poderiam estar envolvidos na formação dos canyons. A teoria mais aceita existente na literatura, atribui a atuação de correntes de densidade durante as regressões do nível do mar como sendo o principal fator que desencadeou a formação dos canyons. A hipótese desse trabalho inclui, além da atuação das correntes de densidade, a atuação de um fluxo de aquífero mais intenso aflorando na região do talude. O fluxo de aquífero mais intenso é justificado pela ocorrência de um aumento de gradiente hidráulico, produzido durante o rebaixamento do nível do mar, durante as fazes de regressão. A simulação física é uma ferramenta poderosa e robusta, utilizada há mais de um século no dimensionamento de aviões, foguetes, pontes, torres, descarregadores de barragens, vertedores e muitos outros tipos de estruturas. A mesma ferramenta pode ser utilizada para gerar modelos do processo de transporte sedimentar em escala reduzida. Esse tipo de estudo parte do conhecimento dos elementos envolvidos no fenômeno investigado – no caso específico, o fundo do mar, a água e os sedimentos – e dos processos aos quais esses elementos possivelmente estão sujeitos no ambiente natural. Esta pesquisa, fundamentada na modelagem física, tentou reproduzir um fluxo de aquífero que aflora no talude e, concomitantemente, a atuação de correntes de densidade, produzindo assim em laboratório um ambiente análogo ao natural durante as fases de regressão do nível do mar, com base em teorias da bibliografia. A metodologia experimental adotada partiu da construção de um depósito cuja geometria representa um V talude com cerca de 1,5 metro de largura, 0,6 metro de comprimento e 0,25 metro de altura. O talude possui rampas com declividades entre 15 e 30 graus. Os sedimentos utilizados foram carvão mineral com fração de areia grossa, areia grossa de origem siliciclástica e calcário com frações de silte e argila. Os sedimentos de frações de areia foram utilizados na construção dos taludes testados, e o calcário, na produção das correntes de densidade. Os experimentos simularam escoamentos em meio poroso dentro do talude, reproduzindo um fluxo de água subterrânea de sistema aquífero que aflorou na região do declive, tendo sido medidas as vazões do aquífero e os respectivos gradientes hidráulicos. Foram também simuladas correntes de densidade com diferentes concentrações e intensidades, bem como obtidos valores médios de espessuras, velocidades e concentrações de sedimentos. Através da simulação, foram produzidas sequências de processos de erosão do talude, que iniciaram com escorregamentos – gerados a partir do aumento da vazão dentro do aquífero reproduzido – e terminaram com a geração de canyons – através da atuação simultânea de correntes de densidade. Os resultados mostraram que existe um significativo elo de ligação entre esses dois processos – fluxo de água subterrânea de sistema aquífero e correntes de densidade –, de tal modo que ambos são necessários para que ocorra a formação dos canyons e para que um grande volume de material seja efetivamente erodido e transportado. As correntes de densidade sozinhas, dentro da escala de simulação, não possuem capacidade de erosão e transporte de sedimentos muito significativa. O sistema de transporte via correntes só é efetivo quando existe um fluxo de aquífero atuando concomitantemente. A observação dos processos de erosão e deposição durante os experimentos, bem como análise do banco de imagens obtidas permitiram a construção de um modelo de formação e evolução de canyons. A formação passa por sequências ordenadas, onde o desenvolvimento de um knickpoint desencadeia um processo de erosão remontante, escavando um sulco que evolui para um canyon formado por uma cabeceira conectada a plataforma bem como depósitos associados. Os dados gerados na simulação física foram comparados com dados do ambiente natural, descritos em trabalhos acadêmicos publicados, e logrou-se provar que os parâmetros medidos estão dentro de valores passíveis de ser encontrados no ambiente natural. Além disso, o cálculo de extrapolação permitiu identificar canyons naturais análogos aos produzidos em laboratório. Os parâmetros dinâmicos das correntes de densidade, bem com as concentrações volumétricas de sedimentos e as faixas de tamanhos de grãos extrapolados estão também dentro de escalas medidas em protótipos análogos. As escalas encontradas seriam de 1:5000 na vertical (com exagero de 2 a 3 vezes) e 1:10000 e VI 1:15000 na horizontal. Assim, é possível que os resultados obtidos neste trabalho venham a elucidar um pouco as dúvidas que estão pendentes há muito tempo acerca do objeto de estudo. / Since the beginning of the deep sea research, considerable progress has been achieved in understanding the marine environment. The technology and tools developed for mapping and analyzing the ocean floor allow a detailed description of the relief and even the internal structures of sediment layers of different sizes that are there, in the bottom of the sea, deposited over millions of years of planetary history. The great mystery, which to this day has not yet been fully explained, is the way these sediments are transported to the seabed. How do sediments of varying sizes reach distances hundreds of miles beyond the coastline and generate deposits on the ocean floor? It is believed that the canyons that exist on the seabed are the express ways through which the transport of a good part of these sediments occurs, given that there is a great volume of material deposited in the terminal parts of these channeled systems. Thus, the focus of speculation and interest has been directed to canyons and density currents, which serve, respectively, as the pathway and the vehicle for sediments. The major obstacle to investigating the role of canyons and currents in the sediment transfer process is the difficulty in observing and measuring phenomena in the natural environment. Besides the scale problem, there is also the rarity of occurrence of events. In fact, it is practically impossible to predict when and where a density current will occur. And if it were possible to predict, how could it be measured? With what equipment? Physical simulation is a powerful and robust tool, used for more than a century in the scaling of aircraft, rockets, bridges, towers, dams, spillways and many other structures. The same tool can be used to generate small scale models of the sediment transport process. This type of study is based on the knowledge of the elements involved in the phenomenon investigated – in this case, the seabed, water and sediments – and the processes to which these elements are possibly subject in the natural environment. This research, based on physical modeling, allowed to reproduce in a laboratory, in a reduced scale, processes similar to those that possibly occur in the seabed. The experimental methodology adopted was based on the construction of a deposit whose geometry represents a slope about 1.5 meters wide, 0.6 meters long and 0.25 meters high. The slope has declivities between 15 and 30 degrees. The sediments used were mineral coal of a coarse sand fraction, coarse sand of siliciclastic origin and limestone with fractions of silt and clay. The sediments of sand fractions were used in the construction of the experimental slopes, and the limestone, in the production of the density currents. The experiments simulated water flows in porous medium within the slope, reproducing an VIII aquifer flow. Density currents were also simulated, since they are generally considered as an important mechanism of sediment transport in the natural environment. began with slides – generated from an increasing flow rate within the simulated aquifer – and ended with the generation of canyons – through the simultaneous action of density currents. The results show that there is a significant link between these two processes – aquifer flow and density currents –, in such a way that both are necessary for the formation of canyons to occur and for a large volume of material to be effectively eroded and transported. Density currents alone, within the simulation scale, do not have very significant sediment transport capacity. The density currents transport system is only effective when there is an aquifer flow acting concomitantly. The observation of the erosion and deposition processes during the experiments, as well as the analysis of the bank of images obtained allowed the construction of a model of formation and evolution of canyons. The formation passes through ordered sequences, where the development of a knickpoint triggers a process of erosion remontante, digging a groove that evolves to a canyon formed by a bedside connected to the platform as well as associated deposits. The data generated in the physical simulation were compared with data from the natural environment, described in published academic papers, which proved that the measured parameters are within the value range that can be found in the natural environment. In addition, the upscaling of the results allowed the identification of natural canyons analogous to those produced in the laboratory. The dynamic parameters of the density streams as well as the volumetric sediment concentrations and the extrapolated grain size ranges are also within scales measured in similar prototypes. The scales found would be 1: 5000 vertically and 1: 10000 and 1: 15000 horizontally. Thus, it is possible that the results obtained in this work will elucidate some doubts that have long been pending about the object of study.

Orientador: Margarida Maria de Carvalho / Resumo: Nesta pesquisa, propomo-nos a analisar a noção de paideia de Orígenes (aprox. 185 – aprox. 253 d.C.) e o espaço de atuação desse autor em Cesareia Marítima, uma cidade situada na província da Judeia, no Império Romano. Em uma de suas obras, o Contra Celso, percebemos que Orígenes utiliza Celso como figura de retórica para expor suas noções de paideia, contrárias àquelas evidenciadas pelo autor do Discurso Verdadeiro, obra refutada e preservada parcialmente por Orígenes em seu Contra Celso. Dissertando sobre temas como a origem de Jesus e das ideias cristãs, Celso centra boa parte de sua crítica nas noções de paideia apostólica. O Contra Celso, com base nisto, contrapõe Celso embasando-se, principalmente, em uma paideia apostólica, alicerçada em uma retórica divina fundamentada pelos evangelhos, contracenando uma retórica humana – greco-romana – ante uma divina – cristã. Pretendemos, isto posto, comparar estes discursos presentes em um momento de desenvolvimento do cristianismo, apresentando como essa paideia apostólica marcou a legitimação de um espaço físico de atuação de Orígenes em Cesareia Marítima. Articulando-o com a sua reconhecida biblioteca na cidade, buscamos atestar como o Contra Celso põe em voga métodos de conversão de audiências mistas, com a ajuda de verdades canônicas em construção, garantindo uma forma de paideia que se mostraria como mais efetiva, assegurando o reconhecimento de Cesareia Marítima como um dos bastiões intelectuais do cristianismo a partir de ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this research, we propose to analyze the notion of paideia of Origen (ca. 185 – ca. 253 A.D.) and the acting area of this author at Caesarea Maritima, a city located at the province of Judaea, in the Roman Empire. In one of his works, the Contra Celsum, we realized that Origen uses Celsus as a rhetorical figure to expose his notions of paideia, contrary to those evidenced by the author of the True Discourse, a work refuted and preserved partially by Origen in his Contra Celsum. Discoursing about themes like the origins of Jesus and of the Christian ideas, Celsus centers a good part of his criticism on the notions of Christian paideia. The Contra Celsum, based on this, counterposes Celsus mainly based on an apostolic paideia, supported in a divine rhetoric substantiated by the gospels, countering a human rhetoric – Greco-Roman – before a divine one – Christian. We intend, that said, to compare these discourses present in a moment of Christian development, presenting how that apostolic paideia marked the legitimation of an acting area of Origen at Caesarea Maritima. Articulating it with his acknowledged library in the city, we seek to show how the Contra Celsum puts in vogue conversion methods of mixed audiences, with the help of canonical truths in construction, assuring a form of paideia that would show itself as more effective, ensuring the recognition of Caesarea Maritima as one of the intellectual bastions of Christianity as of Origen. / Mestre

The site-specific cleavage of double-stranded (ds) RNA is a conserved early step in bacterial ribosomal RNA (rRNA) maturation that is carried out by ribonuclease III. Studies on the RNase III mechanism of dsRNA cleavage have focused mainly on the enzymes from mesophiles such as Escherichia coli. In contrast, little is known of the RNA processing pathways and the functions of associated ribonucleases in the hyperthermophiles. Therefore, structural and biochemical studies of proteins from hyperthermophilic bacteria are providing essential insight on the sources of biomolecular thermostability, and how enzymes function at high temperatures. The biochemical behavior of RNase III of the hyperthermophilic bacterium Thermotoga maritima is analyzed using purified recombinant enzyme and the cognate pre-ribosomal RNAs as substrates. The T. maritima genome encodes a ~5,000 nucleotide (nt) transcript, expressed from the single ribosomal RNA (rRNA) operon. RNase III processing sites are expected to form through base-pairing of complementary sequences that flank the 16S and 23S rRNAs. The Thermotoga pre-16S and pre-23S processing stems are synthesized in the form of small hairpins, and are efficiently and site-specifically cleaved by Tm-RNase III at sites consistent with an in vivo role of the enzyme in producing the immediate precursors to the mature rRNAs. T. maritima (Tm)-RNase III activity is dependent upon divalent metal ion, with Mg^2+ as the preferred species, at concentrations >= 1 mM. Mn^2+, Co^2+ and Ni^2+ also support activity, but with reduced efficiency. The enzyme activity is also supported by salt (Na^+, K^+, or NH4^+) in the 50-80 mM range, with an optimal pH of ~8. Catalytic activity exhibits a broad temperature maximum of ~40-70 deg C, with significant activity retained at 95 deg C. Comparison of the Charged-versus-Polar (C-vP) bias of the protein side chains indicates that Tm-RNase III thermostability is due to large C-vP bias. Analysis of pre-23S substrate variants reveals a dependence of reactivity on the base-pair (bp) sequence in the proximal box (pb), a site of protein contact that functions as a positive determinant of recognition of E. coli (Ec)-RNase III substrates. The pb sequence dependence of reactivity is similar to that observed with the Ec-RNase III pb. Moreover, Tm-RNase III cleaves an Ec-RNase III substrate with identical specificity, and is inhibited by pb antideterminants that also inhibit Ec-Rnase III. These studies reveal the conservation acrosss a broad phylogenetic distance of substrate reactivity epitopes, both the positive and negative determinants, among bacterial RNase III substrates. / Chemistry

Aquatic plants and submerged aquatic vegetation (SAV) are some of the most wide-ranging species and create important habitat for fish and wildlife in many ecosystems, including highly variable coastal ecotones. Mechanistically understanding factors controlling current distributions of these species is critical to project future distribution and abundance under increasing variability and climate change. I used a population-based approach to quantify the effects of spatial and temporal variability on life history transitions of the SAV Ruppia maritima L. (widgeongrass) in the highly dynamic Everglades-Florida Bay ecotone as a model to (1) examine which life history stages were most constrained by these conditions and (2) determine how management can promote life history development to enhance its distribution, an Everglades restoration target. Ruppia maritima life history transitions were quantified in a series of laboratory and field experiments encompassing a ra nge of abiotic and biotic factors known to affect seagrass and SAV (salinity, salinity variability, temperature, light and nutrients and seed bank recruitment and competition). These studies revealed that R. maritima life history varied east to west across the Everglades ecotone, driven by multiple gradients in abiotic factors that constrained different life history transitions in distinct ways. Based on this examination, persistence of SAV populations from dynamic coastal environments is highly dependent on large reproductive events that produce high propagule densities for recruitment. Large productive meadows of SAV also depend on high rates of clonal reproduction where vegetation completely regenerates in a short amount of time. Therefore, in hydrologically variable systems, maintenance or increases in SAV reproduction is required for population persistence through recruitment. However, SAV communities that do not experience high rates of sexual reproduction are dependent on successful seed germination, seedling and adult survival and clonal reproduction for biomass production and maintenance. Seedling survival and to a lesser extent, adult survival, are bottlenecks that can limit life history transitions under highly variable hydrological conditions. To ensure long-term survival in these communities, management activities that increase survival and successful life history development through these critical stages will be beneficial. If not, SAV populations may become highly reduced and ephemeral, providing less productive habitat. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

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