Tuning the reaction products of ruthenium and ciprofloxacin for studies of DNA interactions

This work presents two potential metallo-drugs, the ionic (C17H19FN3O3)(3)[RuCl6]center dot 3H(2)O (1) and the coordination [Ru(C17H17FN3O3)(3)]center dot 4H(2)O (2) compounds, obtained by the combination of ruthenium(III) and ciprofloxacin in different synthetic conditions. The ESI MS spectrum of 1 displayed a main peak at m/z = 994.6, assigned to the gaseous phase adduct (ciprofloxacin)(3)center dot H+, while 2 featured peaks at m/z 1093.3 and 547.1 ascribed to [Ru(C17H17FN3O3)(3)center dot H+-4H(2)O](+) and [Ru(C17H17FN3O3)(3)center dot 2H(+)-4H(2)O](2+). Thermal analysis corroborated the proposed water content for both complexes. Absorption spectra of the compounds in aqueous medium are dominated by ciprofloxacin transitions in the UV region but displayed weak bands in the visible region, assigned to ligand field transitions. The cyclic voltammograms of 2 exhibited a quasi-reversible process ascribed to the Ru(II)/(III) redox pair at -0.25V (vs. SHE) while 1 displayed this process at -0.11 V, showing that the central ruthenium ion is stabilized in the (III) oxidation state by the coordination to the hard oxygen atoms of ciprofloxacin. The solubility of 1 is pH dependent (as well as free ciprofloxacin) while 2 is fully water soluble and stable under physiological pH for at least 48 h. The compounds are also stable under incubation conditions (stomach pH and 37 degrees C) without significant pH lowering. An interaction study of 2 with ct-DNA showed a value of K-b = 2.47 (+/- 0.89) x 10(4) mol(-1) L for the intrinsic binding constant.

Shape resonance spectrum of cytosine-guanine pairs.

Single and double strand breaks in DNA can be caused by low-energy electrons, the most abundant secondary products of the interaction of ionizing radiation to the biological matter. Attachment of these electrons to biomolecules lead to the formation of transient negative ions (TNIs) [1], often referred to as resonances, a process that may lead to significant vibrational excitation and dissociation. In the present study, we employ the parallel version [2] of the Schwinger Multichannel Method implemented with pseudopotentials [3] to obtain the shape resonance spectrum of cytosine-guanine (CG) pairs, with special attention to π* transient anion states. Recent experimental studies pointed out a quasi-continuum vibrational excitation spectrum for electron collisions against formic acid dimers [4], suggesting that electron attachment into π* valence orbitals could induce proton transfer in these dimers. In addition, our previous studies on the shape resonance spectra of the hydrogen-bonded complexes comprising formic acid and formamide units indicated interesting electron delocalization (localization) effects arising from the presence (absence) of inversion symmetry centers in the complexes [5]. In the present work, we extend the studies on hydrogen-bonded complexes to the CG pair, where localization of ¼¤ anions would be expected, based on the previous results. References [1]. B. Boudaïffa, P. Cloutier, D. Hunting, M. A. Huels, L. Sanche, Science 287, 1658 (2000). [2]. J. S. dos Santos, R. F. da Costa , M. T. do N. Varella, J. Chem. Phys. 136, 084307 (2012). [3]. M. H. F. Bettega, L. G. Ferreira, M. A. P. Lima, Phys. Rev. A 47, 1111 (1993). [4]. M. Allan, Phys. Rev. Lett. 98, 123201 (2007). [5]. T. C. Freitas, S. dA. Sanchez, M. T. do N. Varella, M. H. F. Bettega, Phys. Rev. A 84, 062714 (2011).

Potential vorticity conserving flows and vortex-wave interaction : the role of vertical velocity and isopycnal diffusion on plankton heterogeneity

Programa de doctorado de oceanografía

Impatto di rifaximina sul microbiota intestinale: selezione di bifidobatteri antibiotico resistenti

The ideal approach for the long term treatment of intestinal disorders, such as inflammatory bowel disease (IBD), is represented by a safe and well tolerated therapy able to reduce mucosal inflammation and maintain homeostasis of the intestinal microbiota. A combined therapy with antimicrobial agents, to reduce antigenic load, and immunomodulators, to ameliorate the dysregulated responses, followed by probiotic supplementation has been proposed. Because of the complementary mechanisms of action of antibiotics and probiotics, a combined therapeutic approach would give advantages in terms of enlargement of the antimicrobial spectrum, due to the barrier effect of probiotic bacteria, and limitation of some side effects of traditional chemiotherapy (i.e. indiscriminate decrease of aggressive and protective intestinal bacteria, altered absorption of nutrient elements, allergic and inflammatory reactions). Rifaximin (4-deoxy-4’-methylpyrido[1’,2’-1,2]imidazo[5,4-c]rifamycin SV) is a product of synthesis experiments designed to modify the parent compound, rifamycin, in order to achieve low gastrointestinal absorption while retaining good antibacterial activity. Both experimental and clinical pharmacology clearly show that this compound is a non systemic antibiotic with a broad spectrum of antibacterial action, covering Gram-positive and Gram-negative organisms, both aerobes and anaerobes. Being virtually non absorbed, its bioavailability within the gastrointestinal tract is rather high with intraluminal and faecal drug concentrations that largely exceed the MIC values observed in vitro against a wide range of pathogenic microorganisms. The gastrointestinal tract represents therefore the primary therapeutic target and gastrointestinal infections the main indication. The little value of rifaximin outside the enteric area minimizes both antimicrobial resistance and systemic adverse events. Fermented dairy products enriched with probiotic bacteria have developed into one of the most successful categories of functional foods. Probiotics are defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” (FAO/WHO, 2002), and mainly include Lactobacillus and Bifidobacterium species. Probiotic bacteria exert a direct effect on the intestinal microbiota of the host and contribute to organoleptic, rheological and nutritional properties of food. Administration of pharmaceutical probiotic formula has been associated with therapeutic effects in treatment of diarrhoea, constipation, flatulence, enteropathogens colonization, gastroenteritis, hypercholesterolemia, IBD, such as ulcerative colitis (UC), Crohn’s disease, pouchitis and irritable bowel syndrome. Prerequisites for probiotics are to be effective and safe. The characteristics of an effective probiotic for gastrointestinal tract disorders are tolerance to upper gastrointestinal environment (resistance to digestion by enteric or pancreatic enzymes, gastric acid and bile), adhesion on intestinal surface to lengthen the retention time, ability to prevent the adherence, establishment and/or replication of pathogens, production of antimicrobial substances, degradation of toxic catabolites by bacterial detoxifying enzymatic activities, and modulation of the host immune responses. This study was carried out using a validated three-stage fermentative continuous system and it is aimed to investigate the effect of rifaximin on the colonic microbial flora of a healthy individual, in terms of bacterial composition and production of fermentative metabolic end products. Moreover, this is the first study that investigates in vitro the impact of the simultaneous administration of the antibiotic rifaximin and the probiotic B. lactis BI07 on the intestinal microbiota. Bacterial groups of interest were evaluated using culture-based methods and molecular culture-independent techniques (FISH, PCR-DGGE). Metabolic outputs in terms of SCFA profiles were determined by HPLC analysis. Collected data demonstrated that rifaximin as well as antibiotic and probiotic treatment did not change drastically the intestinal microflora, whereas bacteria belonging to Bifidobacterium and Lactobacillus significantly increase over the course of the treatment, suggesting a spontaneous upsurge of rifaximin resistance. These results are in agreement with a previous study, in which it has been demonstrated that rifaximin administration in patients with UC, affects the host with minor variations of the intestinal microflora, and that the microbiota is restored over a wash-out period. In particular, several Bifidobacterium rifaximin resistant mutants could be isolated during the antibiotic treatment, but they disappeared after the antibiotic suspension. Furthermore, bacteria belonging to Atopobium spp. and E. rectale/Clostridium cluster XIVa increased significantly after rifaximin and probiotic treatment. Atopobium genus and E. rectale/Clostridium cluster XIVa are saccharolytic, butyrate-producing bacteria, and for these characteristics they are widely considered health-promoting microorganisms. The absence of major variations in the intestinal microflora of a healthy individual and the significant increase in probiotic and health-promoting bacteria concentrations support the rationale of the administration of rifaximin as efficacious and non-dysbiosis promoting therapy and suggest the efficacy of an antibiotic/probiotic combined treatment in several gut pathologies, such as IBD. To assess the use of an antibiotic/probiotic combination for clinical management of intestinal disorders, genetic, proteomic and physiologic approaches were employed to elucidate molecular mechanisms determining rifaximin resistance in Bifidobacterium, and the expected interactions occurring in the gut between these bacteria and the drug. The ability of an antimicrobial agent to select resistance is a relevant factor that affects its usefulness and may diminish its useful life. Rifaximin resistance phenotype was easily acquired by all bifidobacteria analyzed [type strains of the most representative intestinal bifidobacterial species (B. infantis, B. breve, B. longum, B. adolescentis and B. bifidum) and three bifidobacteria included in a pharmaceutical probiotic preparation (B. lactis BI07, B. breve BBSF and B. longum BL04)] and persisted for more than 400 bacterial generations in the absence of selective pressure. Exclusion of any reversion phenomenon suggested two hypotheses: (i) stable and immobile genetic elements encode resistance; (ii) the drug moiety does not act as an inducer of the resistance phenotype, but enables selection of resistant mutants. Since point mutations in rpoB have been indicated as representing the principal factor determining rifampicin resistance in E. coli and M. tuberculosis, whether a similar mechanism also occurs in Bifidobacterium was verified. The analysis of a 129 bp rpoB core region of several wild-type and resistant bifidobacteria revealed five different types of miss-sense mutations in codons 513, 516, 522 and 529. Position 529 was a novel mutation site, not previously described, and position 522 appeared interesting for both the double point substitutions and the heterogeneous profile of nucleotide changes. The sequence heterogeneity of codon 522 in Bifidobacterium leads to hypothesize an indirect role of its encoded amino acid in the binding with the rifaximin moiety. These results demonstrated the chromosomal nature of rifaximin resistance in Bifidobacterium, minimizing risk factors for horizontal transmission of resistance elements between intestinal microbial species. Further proteomic and physiologic investigations were carried out using B. lactis BI07, component of a pharmaceutical probiotic preparation, as a model strain. The choice of this strain was determined based on the following elements: (i) B. lactis BI07 is able to survive and persist in the gut; (ii) a proteomic overview of this strain has been recently reported. The involvement of metabolic changes associated with rifaximin resistance was investigated by proteomic analysis performed with two-dimensional electrophoresis and mass spectrometry. Comparative proteomic mapping of BI07-wt and BI07-res revealed that most differences in protein expression patterns were genetically encoded rather than induced by antibiotic exposure. In particular, rifaximin resistance phenotype was characterized by increased expression levels of stress proteins. Overexpression of stress proteins was expected, as they represent a common non specific response by bacteria when stimulated by different shock conditions, including exposure to toxic agents like heavy metals, oxidants, acids, bile salts and antibiotics. Also, positive transcription regulators were found to be overexpressed in BI07-res, suggesting that bacteria could activate compensatory mechanisms to assist the transcription process in the presence of RNA polymerase inhibitors. Other differences in expression profiles were related to proteins involved in central metabolism; these modifications suggest metabolic disadvantages of resistant mutants in comparison with sensitive bifidobacteria in the gut environment, without selective pressure, explaining their disappearance from faeces of patients with UC after interruption of antibiotic treatment. The differences observed between BI07-wt e BI07-res proteomic patterns, as well as the high frequency of silent mutations reported for resistant mutants of Bifidobacterium could be the consequences of an increased mutation rate, mechanism which may lead to persistence of resistant bacteria in the population. However, the in vivo disappearance of resistant mutants in absence of selective pressure, allows excluding the upsurge of compensatory mutations without loss of resistance. Furthermore, the proteomic characterization of the resistant phenotype suggests that rifaximin resistance is associated with a reduced bacterial fitness in B. lactis BI07-res, supporting the hypothesis of a biological cost of antibiotic resistance in Bifidobacterium. The hypothesis of rifaximin inactivation by bacterial enzymatic activities was verified by using liquid chromatography coupled with tandem mass spectrometry. Neither chemical modifications nor degradation derivatives of the rifaximin moiety were detected. The exclusion of a biodegradation pattern for the drug was further supported by the quantitative recovery in BI07-res culture fractions of the total rifaximin amount (100 μg/ml) added to the culture medium. To confirm the main role of the mutation on the β chain of RNA polymerase in rifaximin resistance acquisition, transcription activity of crude enzymatic extracts of BI07-res cells was evaluated. Although the inhibition effects of rifaximin on in vitro transcription were definitely higher for BI07-wt than for BI07-res, a partial resistance of the mutated RNA polymerase at rifaximin concentrations > 10 μg/ml was supposed, on the basis of the calculated differences in inhibition percentages between BI07-wt and BI07-res. By considering the resistance of entire BI07-res cells to rifaximin concentrations > 100 μg/ml, supplementary resistance mechanisms may take place in vivo. A barrier for the rifaximin uptake in BI07-res cells was suggested in this study, on the basis of the major portion of the antibiotic found to be bound to the cellular pellet respect to the portion recovered in the cellular lysate. Related to this finding, a resistance mechanism involving changes of membrane permeability was supposed. A previous study supports this hypothesis, demonstrating the involvement of surface properties and permeability in natural resistance to rifampicin in mycobacteria, isolated from cases of human infection, which possessed a rifampicin-susceptible RNA polymerase. To understand the mechanism of membrane barrier, variations in percentage of saturated and unsaturated FAs and their methylation products in BI07-wt and BI07-res membranes were investigated. While saturated FAs confer rigidity to membrane and resistance to stress agents, such as antibiotics, a high level of lipid unsaturation is associated with high fluidity and susceptibility to stresses. Thus, the higher percentage of saturated FAs during the stationary phase of BI07-res could represent a defence mechanism of mutant cells to prevent the antibiotic uptake. Furthermore, the increase of CFAs such as dihydrosterculic acid during the stationary phase of BI07-res suggests that this CFA could be more suitable than its isomer lactobacillic acid to interact with and prevent the penetration of exogenous molecules including rifaximin. Finally, the impact of rifaximin on immune regulatory functions of the gut was evaluated. It has been suggested a potential anti-inflammatory effect of rifaximin, with reduced secretion of IFN-γ in a rodent model of colitis. Analogously, it has been reported a significant decrease in IL-8, MCP-1, MCP-3 e IL-10 levels in patients affected by pouchitis, treated with a combined therapy of rifaximin and ciprofloxacin. Since rifaximin enables in vivo and in vitro selection of Bifidobacterium resistant mutants with high frequency, the immunomodulation activities of rifaximin associated with a B. lactis resistant mutant were also taken into account. Data obtained from PBMC stimulation experiments suggest the following conclusions: (i) rifaximin does not exert any effect on production of IL-1β, IL-6 and IL-10, whereas it weakly stimulates production of TNF-α; (ii) B. lactis appears as a good inducer of IL-1β, IL-6 and TNF-α; (iii) combination of BI07-res and rifaximin exhibits a lower stimulation effect than BI07-res alone, especially for IL-6. These results confirm the potential anti-inflammatory effect of rifaximin, and are in agreement with several studies that report a transient pro-inflammatory response associated with probiotic administration. The understanding of the molecular factors determining rifaximin resistance in the genus Bifidobacterium assumes an applicative significance at pharmaceutical and medical level, as it represents the scientific basis to justify the simultaneous use of the antibiotic rifaximin and probiotic bifidobacteria in the clinical treatment of intestinal disorders.

Computational analyses on the structure-function relation in ion channels

Ion channels are protein molecules, embedded in the lipid bilayer of the cell membranes. They act as powerful sensing elements switching chemicalphysical stimuli into ion-fluxes. At a glance, ion channels are water-filled pores, which can open and close in response to different stimuli (gating), and one once open select the permeating ion species (selectivity). They play a crucial role in several physiological functions, like nerve transmission, muscular contraction, and secretion. Besides, ion channels can be used in technological applications for different purpose (sensing of organic molecules, DNA sequencing). As a result, there is remarkable interest in understanding the molecular determinants of the channel functioning. Nowadays, both the functional and the structural characteristics of ion channels can be experimentally solved. The purpose of this thesis was to investigate the structure-function relation in ion channels, by computational techniques. Most of the analyses focused on the mechanisms of ion conduction, and the numerical methodologies to compute the channel conductance. The standard techniques for atomistic simulation of complex molecular systems (Molecular Dynamics) cannot be routinely used to calculate ion fluxes in membrane channels, because of the high computational resources needed. The main step forward of the PhD research activity was the development of a computational algorithm for the calculation of ion fluxes in protein channels. The algorithm - based on the electrodiffusion theory - is computational inexpensive, and was used for an extensive analysis on the molecular determinants of the channel conductance. The first record of ion-fluxes through a single protein channel dates back to 1976, and since then measuring the single channel conductance has become a standard experimental procedure. Chapter 1 introduces ion channels, and the experimental techniques used to measure the channel currents. The abundance of functional data (channel currents) does not match with an equal abundance of structural data. The bacterial potassium channel KcsA was the first selective ion channels to be experimentally solved (1998), and after KcsA the structures of four different potassium channels were revealed. These experimental data inspired a new era in ion channel modeling. Once the atomic structures of channels are known, it is possible to define mathematical models based on physical descriptions of the molecular systems. These physically based models can provide an atomic description of ion channel functioning, and predict the effect of structural changes. Chapter 2 introduces the computation methods used throughout the thesis to model ion channels functioning at the atomic level. In Chapter 3 and Chapter 4 the ion conduction through potassium channels is analyzed, by an approach based on the Poisson-Nernst-Planck electrodiffusion theory. In the electrodiffusion theory ion conduction is modeled by the drift-diffusion equations, thus describing the ion distributions by continuum functions. The numerical solver of the Poisson- Nernst-Planck equations was tested in the KcsA potassium channel (Chapter 3), and then used to analyze how the atomic structure of the intracellular vestibule of potassium channels affects the conductance (Chapter 4). As a major result, a correlation between the channel conductance and the potassium concentration in the intracellular vestibule emerged. The atomic structure of the channel modulates the potassium concentration in the vestibule, thus its conductance. This mechanism explains the phenotype of the BK potassium channels, a sub-family of potassium channels with high single channel conductance. The functional role of the intracellular vestibule is also the subject of Chapter 5, where the affinity of the potassium channels hEag1 (involved in tumour-cell proliferation) and hErg (important in the cardiac cycle) for several pharmaceutical drugs was compared. Both experimental measurements and molecular modeling were used in order to identify differences in the blocking mechanism of the two channels, which could be exploited in the synthesis of selective blockers. The experimental data pointed out the different role of residue mutations in the blockage of hEag1 and hErg, and the molecular modeling provided a possible explanation based on different binding sites in the intracellular vestibule. Modeling ion channels at the molecular levels relates the functioning of a channel to its atomic structure (Chapters 3-5), and can also be useful to predict the structure of ion channels (Chapter 6-7). In Chapter 6 the structure of the KcsA potassium channel depleted from potassium ions is analyzed by molecular dynamics simulations. Recently, a surprisingly high osmotic permeability of the KcsA channel was experimentally measured. All the available crystallographic structure of KcsA refers to a channel occupied by potassium ions. To conduct water molecules potassium ions must be expelled from KcsA. The structure of the potassium-depleted KcsA channel and the mechanism of water permeation are still unknown, and have been investigated by numerical simulations. Molecular dynamics of KcsA identified a possible atomic structure of the potassium-depleted KcsA channel, and a mechanism for water permeation. The depletion from potassium ions is an extreme situation for potassium channels, unlikely in physiological conditions. However, the simulation of such an extreme condition could help to identify the structural conformations, so the functional states, accessible to potassium ion channels. The last chapter of the thesis deals with the atomic structure of the !- Hemolysin channel. !-Hemolysin is the major determinant of the Staphylococcus Aureus toxicity, and is also the prototype channel for a possible usage in technological applications. The atomic structure of !- Hemolysin was revealed by X-Ray crystallography, but several experimental evidences suggest the presence of an alternative atomic structure. This alternative structure was predicted, combining experimental measurements of single channel currents and numerical simulations. This thesis is organized in two parts, in the first part an overview on ion channels and on the numerical methods adopted throughout the thesis is provided, while the second part describes the research projects tackled in the course of the PhD programme. The aim of the research activity was to relate the functional characteristics of ion channels to their atomic structure. In presenting the different research projects, the role of numerical simulations to analyze the structure-function relation in ion channels is highlighted.

Maremoti in bacini limitati

The work of my thesis is focused on the impact of tsunami waves in limited basins. By limited basins I mean here those basins capable of modifying significantly the tsunami signal with respect to the surrounding open sea. Based on this definition, we consider limited basins not only harbours but also straits, channels, seamounts and oceanic shelves. I have considered two different examples, one dealing with the Seychelles Island platform in the Indian Ocean, the second focussing on the Messina Strait and the harbour of the Messina city itself (Italy). The Seychelles platform is differentiated at bathymetric level from the surrounding ocean, with rapid changes from 2 km to 70 meters over short horizontal distances. The study of the platform response to the tsunami propagation is based on the simulation of the mega-event occurred on 26 December 2004. Based on a hypothesis for the earthquake causative fault, the ensuing tsunami has been numerically simulated. I analysed synthetic tide gauge records at several virtual tide gauges aligned along the direction going from the source to the platform. A substantial uniformity of tsunami signals in all calculated open ocean tide-gauge records is observed, while the signals calculated in two points of the Seychelles platform show different features both in terms of amplitude and period of the perturbation. To better understand the content in frequency of different calculated marigrams, a spectral analysis was carried out. In particular the ratio between the calculated tide-gauge records spectrum on the platform and the average tide-gauge records in the open ocean was considered. The main result is that, while in the average spectrum in the open ocean the fundamental peak is related to the source, the platform introduces further peaks linked both to the bathymetric configuration and to coastal geometry. The Messina Strait represents an interesting case because it consists in a sort of a channel open both in the north and in the south and furthermore contains the limited basin of the Messina harbour. In this case the study has been carried out in a different way with respect to the Seychelles case. The basin was forced along a boundary of the computational domain with sinusoidal functions having different periods within the typical tsunami frequencies. The tsunami has been simulated numerically and in particular the tide-gauge records were calculated for every forcing function in different points both externally and internally of the channel and of the Messina harbour. Apart from the tide-gauge records in the source region that almost immediately reach stationarity, all the computed signals in the channel and in the Messina harbour present a transient variable amplitude followed by a stationary part. Based exclusively on this last part, I calculated the amplification curves for each site. I found that the maximum amplification is obtained for forcing periods of approximately 10 minutes.

Grenzflächenspannung und Morphologie fließender zweiphasiger Polymermischungen

In der vorliegenden Arbeit wurde die Morphologie von zweiphasigen Polymermischungen unter Scherung in situ mit Hilfe einer Kombination aus optischer Scherzelle, Durchlichtmikroskop und computergestützten CCD-Kamera untersucht. Als Modellblends dienten die unverträglichen, bei Raumtemperatur flüssigen Polymersysteme Polyisobutylen (PIB)/Polydimethylsiloxan (PDMS) (I) und Poly(dimethyl-co-methylphenyl)siloxan/PDMS (II). Alle Komponenten verhalten sich bei den verwendeten Scherraten newtonisch.Eine der wichtigsten Einflussgrößen für die Blendmorphologie ist die Grenzflächenspannung gamma 12. Sie wurde für I und II mit Hilfe der Methode der Tropfenrelaxation (dynamisch) als Funktion der Zeit bestimmt. Diese Methode erlaubt die Messung von gamma 12 für Tropfen der Phase A in B sowie von Tropfen B in A. Bei der Methode des hängenden Tropfens (statisch) muss der Tropfen aus der Phase mit der höheren Dichte bestehen. Wo der Vergleich der beiden Methoden möglich ist, stimmen die Ergebnisse für beide Systeme sehr gut überein. Bei II sind die aus der Tropfenrelaxation erhaltenen gamma 12-Werte der beiden komplementären Zusammensetzungen im Rahmen des Fehlers gleich, bei I zeigt ein PIB-Tropfen in PDMS einen um 40 % niedrigeren Wert als ein PDMS-Tropfen in PIB, dies wird auf die Diffusion von kurzkettigen Anteilen des PDMS in die Grenzschicht zurückgeführt. Die Grenzflächenspannung hängt also unter Umständen auch bei binären Systemen deutlich von der Zusammensetzung ab.Für II wurde die Blendmorphologie über den gesamten Zusammensetzungsbereich untersucht. Die häufig beobachteten cokontinuierlichen Strukturen treten bei keiner Zusammensetzung auf. Die Phaseninversion erkennt man in einer sprunghaften Änderung der Tropfengröße zwischen phiPDMS <= 0,400 und 0,500; zudem lässt sich die Zeitabhängigkeit der Radien durch Auftragung gegen das Produkt aus der Deformation und dem Quadrat des Volumenbruchs der Tropfenphase für 0 <= phiPDMS <= 0,400 sowie 0,500 <= phiPDMS <= 1 normieren. Für I und II wurde die Morphologieentwicklung bei 25 °C nach Vorscherung bei 100 bzw. 50 s-1 und anschließendem Sprung der Scherrate auf deutlich niedrigere Werte als Funktion der Zeit verfolgt. Hierbei erhält man bei genügend langer Messdauer (mindestens 200 000-300 000 Schereinheiten) konstante Tropfengrößen. Zum einen handelt es sich dabei um pseudo-stationäre Werte, die nur durch Koaleszenz bestimmt sind, zum anderen um echte stationäre Radien, die durch gleichzeitig ablaufende Koaleszenz und Zerteilung entstehen. Für I liegen die stationären Mittelwerte auf der Zerteilungskurve, für II hingegen auf der Koaleszenzkurve.Der Einfluss eines grenzflächenwirksamen Additivs wurde anhand von I durch Zugabe des Blockcopolymer PIB-b-PDMS zu PIB untersucht. Der Vergleich des zeitlichen Verlaufs von gamma 12 mit der Morphologieentwicklung zeigt, dass das Additiv eine Stabilisierung der feinen Tropfen/Matrix-Struktur des Blends durch Hinderung der Koaleszenz und nicht durch Reduktion der Grenzflächenspannung bewirkt.

Strahlungsbegleitete Pion-Photoproduktion am Proton

Im Jahre 1997 wurden von Tatischeff et al. bei der Reaktion p p -> X p pi+ resonanzartige Zustände im Spektrum der invarianten Masse des fehlenden Nukleons X bei M = 1004, 1044 und 1094 MeV gefunden. In einem zweiten Experiment von Filkov et al. beobachtete man bei der Reaktion p d -> p p X Resonanzstrukturen bei M = 966, 986 und 1003 MeV. Solche exotischen Resonanzen widersprechen etablierten Nukleonenmodellen, die die Delta(1232)-Resonanz als ersten Anregungszustand beschreiben. Zur Deutung der beobachteten Strukturen wurden Quarkcluster-Modelle mit und ohne Farb-Magnet-Wechselwirkungen entwickelt. Lvov et al. zweifelten die experimentellen Ergebnisse an, da keine Strukturen in den Daten zur reellen Comptonstreuung gefunden wurden. Als Gegenargument wurde von Kobushkin vorgeschlagen, dass diese Resonanzen eine total-antisymmetrische Spin-Flavour-Wellenfunktion haben und nur der N-2Gamma-Zerfall erlaubt wäre. In dieser Arbeit wurde die Reaktion g p -> X pi+ -> n g g pi+ zur Suche nach diesen exotischen Resonanzen verwendet. Die Daten wurden parallel zur Messung der Pion-Polarisierbarkeiten am Mainzer Beschleuniger MAMI genommen. Durch Bremsstrahlung der Elektronen an einer Radiatorfolie wurden reelle Photonen erzeugt, deren Energie von der A2-Photonenmarkierungsanlage (Glasgow-Tagger) bestimmt wurde. Als Protontarget wurde ein 10 cm langes Flüssigwasserstoff-Target verwendet. Geladene Reaktionsprodukte wurden unter Vorwärtswinkeln Theta < 20 Grad bezüglich der Strahlachse in einer Vieldraht-Proportionalkammer nachgewiesen, während Photonen im Spektrometer TAPS mit 526 BaF2-Kristallen unter Polarwinkeln Theta > 60 Grad detektiert wurden. Zum Nachweis von Neutronen stand ein Flugzeitdetektor mit insgesamt 111 Einzelmodulen zur Verfügung. Zum Test der Analysesoftware und des experimentellen Aufbaus wurden zusätzlich die Reaktionskanäle g p -> p pi0 und g p -> n pi0 pi+ ausgewertet. Für die Ein-Pion-Produktion wurden differentielle Wirkungsquerschnitte unter Rückwärtswinkeln bestimmt und mit theoretischen Modellen und experimentellen Werten verglichen. Für den Kanal g p -> n pi0 pi+ wurden Spektren invarianter Massen für verschiedene Teilchenkombinationen ermittelt und mit einer Simulation verglichen. Die Daten legen nahe, dass die Reaktion hauptsächlich über eine Anregung der Delta0(1232)-Resonanz verläuft. Bei der Suche nach exotischen Resonanzen wurden keine statistisch signifikanten Strukturen gefunden. Es wurden Obergrenzen für den differentiellen Wirkungsquerschnitt ermittelt.

Der Einsatz elektrochemischer Methoden für die Untersuchung superschwerer Elemente

Das Hauptziel der vorliegenden Arbeit war die Entwicklung eines Experimentaufbaus für die elektrochemische Abscheidung von Transactiniden mit anschließender Detektion. Zu diesem Zweck wurden Experimente mit den Homologen dieser Elemente durchgeführt. Die Elektrodeposition von Tracermengen an Fremdelektroden führt zu einer Elektrodenbedeckung von weniger als einer Monolage. Die erforderlichen Abscheidepotentiale sind häufig positiver, als nach der Nernst’schen Gleichung zu erwarten ist. Dieses Phänomen nennt man Unterpotentialabscheidung. In zahlreichen Versuchen mit Radiotracern wurde die Abscheideausbeute als Funktion des Elektrodenpotentials bestimmt, wobei abzuscheidendes Ion, Elektrodenmaterial und Elektrolyt variiert wurden. Es wurden kritische Potentiale, bei denen eine nennenswerte Abscheidung gerade begann, ermittelt sowie Potentiale für die Abscheidung von 50 % der in der Lösung befindlichen Atome. Diese Werte wurden mit theoretisch vorhergesagten Potentialen und Werten aus der Literatur verglichen. Die Abscheidung von Pb als Homologem von Element 114 funktionierte sehr gut an Elektroden aus Palladium oder palladinierten Nickelelektroden unter Verwendung von 0,1 M HCl als Elektrolyt. Zur Charakterisierung der Unterpotentialabscheidung wurde neben der Radiotracer-Methode auch die Cyclovoltammetrie eingesetzt. Hier findet die Abscheidung der ersten Monolage auf der Elektrode ebenfalls häufig bei positiveren Potentialen statt, als die der Hauptmenge. Die mit beiden Methoden ermittelten Werte wurden einander gegenübergestellt. Die Elektrodeposition von kurzlebigen Isotopen muss sehr schnell erfolgen. Es konnte gezeigt werden, dass eine hohe Temperatur und damit verbunden eine niedrige Viskosität des Elektrolyten die Abscheidung beschleunigt. Ebenfalls wichtig ist ein gutes Rühren der Lösung, um eine kleine Nernst’sche Diffusionsschichtdicke zu erzielen. Das Verhältnis von Elektrodenfläche zu Elektrolytvolumen muss möglichst groß sein. Auf der Grundlage dieser Ergebnisse wurde eine für schnelle Elektrolysen optimierte Elektrolysezelle entwickelt. Unter Einsatz dieser Zelle wurden die Abscheidegeschwindigkeiten für verschiedene Ionen- und Elektrodenkombinationen gemessen. Es wurden Experimente zur Kopplung von Gasjet und Elektrolysezelle durchgeführt, dabei wurde sowohl mit am Reaktor erzeugten Spaltprodukten, mit Pb-Isotopen aus einer emanierenden Quelle und mit am Beschleuniger erzeugten Isotopen gearbeitet. Mit den dort gewonnenen Erkenntnissen wurde ein Experimentaufbau für die kontinuierliche Abscheidung und Detektion von kurzlebigen Isotopen realisiert. Am Beschleuniger wurden u. a. kurzlebige Hg- und Pb-Isotope erzeugt und mit einem Gasjet aus der Targetkammer zum ALOHA-System transportiert. Dort wurden sie in einem quasi-kontinuierlichen Prozess in die wässrige Phase überführt und zu einer Elektrolyszelle transportiert. In dieser erfolgte die Elektrodeposition auf eine bandförmige Elektrode aus Nickel oder palladiniertem Nickel. Nach der Abscheidung wurde das Band zu einer Detektorphalanx gezogen, wo der -Zerfall der neutronenarmen Isotope registriert wurde. Es wurden charakteristische Größen wie die Abscheidegeschwindigkeit und die Gesamtausbeute der Elektrolyse ermittelt. Das System wurde im Dauerbetrieb getestet. Es konnte gezeigt werden, dass der gewählte Aufbau prinzipiell für die Abscheidung von kurzlebigen, am Beschleuniger erzeugten Isotopen geeignet ist. Damit ist eine wichtige Voraussetzung für den zukünftigen Einsatz der Methode zum Studium der chemischen Eigenschaften der superschweren Elemente geschaffen.

Proteolysis of the receptor for advanced glycation end products by matrix metalloproteinases

RAGE mediates diverse physiological and pathological effects by binding a variety of ligands. Despite incomplete understanding of RAGE-mediated disorders soluble RAGE (sRAGE) has been identified as a potential biomarker for RAGE-related diseases and possibly represents a hopeful pharmaceutical against RAGE-mediated disorders. Nevertheless, the source of sRAGE remains poorly investigated. Currently sRAGE is thought to be derived exclusively from alternative splicing of mRNA. In this thesis it was investigated whether sRAGE can also be released as a result of ectodomain shedding of full-length RAGE. Using cells overexpressing RAGE as a model system, it was demonstrated clearly that RAGE undergoes ectodomain shedding in both constitutive and regulated manner. Several stimuli including PMA, AMPA, calcium and chelerythrine stimulated the release of sRAGE into cell culture medium. Moreover, possible mechanisms that regulate ectodomain shedding of RAGE were investigated and it was found that shedding of RAGE is likely independent from PKC and MAPK pathways. By using gain of function and loss of function approaches MMP9 but not ADAM10, ADAM17 or MT1-MMP was characterized as the metalloproteinase that mediates shedding of RAGE. Furthermore, it was shown that cytoplasmic domain of RAGE is not essential for shedding of RAGE. In addition, the potential cleavage site of RAGE by MMP9 was investigated and a lack of sequence specificity for the RAGE processing proteinase was demonstrated by mutation analysis. Finally the physiopathological significance of shedding of RAGE is discussed. In conclusion, for the first time ectodomain shedding of human RAGE and the underlying regulatory mechanisms were investigated. The data open a new field for modulation of RAGE shedding as a novel intervention approach against RAGE-mediated diseases.

Fluidodinamica biomedica computazionale del flusso sanguigno in presenza di affezioni strumentali e/o patologiche

La tesi di Dottorato studia il flusso sanguigno tramite un codice agli elementi finiti (COMSOL Multiphysics). Nell’arteria è presente un catetere Doppler (in posizione concentrica o decentrata rispetto all’asse di simmetria) o di stenosi di varia forma ed estensione. Le arterie sono solidi cilindrici rigidi, elastici o iperelastici. Le arterie hanno diametri di 6 mm, 5 mm, 4 mm e 2 mm. Il flusso ematico è in regime laminare stazionario e transitorio, ed il sangue è un fluido non-Newtoniano di Casson, modificato secondo la formulazione di Gonzales & Moraga. Le analisi numeriche sono realizzate in domini tridimensionali e bidimensionali, in quest’ultimo caso analizzando l’interazione fluido-strutturale. Nei casi tridimensionali, le arterie (simulazioni fluidodinamiche) sono infinitamente rigide: ricavato il campo di pressione si procede quindi all’analisi strutturale, per determinare le variazioni di sezione e la permanenza del disturbo sul flusso. La portata sanguigna è determinata nei casi tridimensionali con catetere individuando tre valori (massimo, minimo e medio); mentre per i casi 2D e tridimensionali con arterie stenotiche la legge di pressione riproduce l’impulso ematico. La mesh è triangolare (2D) o tetraedrica (3D), infittita alla parete ed a valle dell’ostacolo, per catturare le ricircolazioni. Alla tesi sono allegate due appendici, che studiano con codici CFD la trasmissione del calore in microcanali e l’ evaporazione di gocce d’acqua in sistemi non confinati. La fluidodinamica nei microcanali è analoga all’emodinamica nei capillari. Il metodo Euleriano-Lagrangiano (simulazioni dell’evaporazione) schematizza la natura mista del sangue. La parte inerente ai microcanali analizza il transitorio a seguito dell’applicazione di un flusso termico variabile nel tempo, variando velocità in ingresso e dimensioni del microcanale. L’indagine sull’evaporazione di gocce è un’analisi parametrica in 3D, che esamina il peso del singolo parametro (temperatura esterna, diametro iniziale, umidità relativa, velocità iniziale, coefficiente di diffusione) per individuare quello che influenza maggiormente il fenomeno.

Outdoor bronze conservation: assessment of protective treatments by accelerated aging and of treatment removal procedures by laser cleaning

Outdoor bronzes exposed to the environment form naturally a layer called patina, which may be able to protect the metallic substrate. However, since the last century, with the appearance of acid rains, a strong change in the nature and properties of the copper based patinas occurred [1]. Studies and general observations have established that bronze corrosion patinas created by acid rain are not only disfiguring in terms of loss of detail and homogeneity, but are also unstable [2]. The unstable patina is partially leached away by rainwater. This leaching is represented by green streaking on bronze monuments [3]. Because of the instability of the patina, conservation techniques are usually required. On a bronze object exposed to the outdoor environment, there are different actions of the rainfall and other atmospheric agents as a function of the monument shape. In fact, we recognize sheltered and unsheltered areas as regards exposure to rainwater [4]. As a consequence of these different actions, two main patina types are formed on monuments exposed to the outdoor environment. These patinas have different electrochemical, morphological and compositional characteristics [1]. In the case of sheltered areas, the patina contains mainly copper products, stratified above a layer strongly enriched in insoluble Sn oxides, located at the interface with the uncorroded metal. Moreover, different colors of the patina result from the exposure geometry. The surface color may be pale green for unsheltered areas, and green and mat black for sheltered areas [4]. Thus, in real outdoor bronze monuments, the corrosion behavior is strongly influenced by the exposure geometry. This must be taken into account when designing conservation procedures, since the patina is in most cases the support on which corrosion inhibitors are applied. Presently, for protecting outdoor bronzes against atmospheric corrosion, inhibitors and protective treatments are used. BTA and its derivatives, which are the most common inhibitors used for copper and its alloy, were found to be toxic for the environment and human health [5, 6]. Moreover, it has been demonstrated that BTA is efficient when applied on bare copper but not as efficient when applied on bare bronze [7]. Thus it was necessary to find alternative compounds. Silane-based inhibitors (already successfully tested on copper and other metallic substrates [8]), were taken into consideration as a non-toxic, environmentally friendly alternative to BTA derivatives for bronze protection. The purpose of this thesis was based on the assessment of the efficiency of a selected compound, to protect the bronze against corrosion, which is the 3-mercapto-propyl-trimethoxy-silane (PropS-SH). It was selected thanks to the collaboration with the Corrosion Studies Centre “Aldo Daccò” at the Università di Ferrara. Since previous studies [9, 10, 11] demonstrated that the addition of nanoparticles to silane-based inhibitors leads to an increase of the protective efficiency, we also wanted to evaluate the influence of the addition of CeO2, La2O3, TiO2 nanoparticles on the protective efficiency of 3-mercapto-propyl-trimethoxy-silane, applied on pre-patinated bronze surfaces. This study is the first section of the thesis. Since restorers have to work on patinated bronzes and not on bare metal (except for contemporary art), it is important to be able to recreate the patina, under laboratory conditions, either in sheltered or unsheltered conditions to test the coating and to obtain reliable results. Therefore, at the University of Bologna, different devices have been designed to simulate the real outdoor conditions and to create a patina which is representative of real application conditions of inhibitor or protective treatments. In particular, accelerated ageing devices by wet & dry (simulating the action of stagnant rain in sheltered areas [12]) and by dropping (simulating the leaching action of the rain in unsheltered areas [1]) tests were used. In the present work, we used the dropping test as a method to produce pre-patinated bronze surfaces for the application of a candidate inhibitor as well as for evaluating its protective efficiency on aged bronze (unsheltered areas). In this thesis, gilded bronzes were also studied. When they are exposed to the outside environment, a corrosion phenomenon appears which is due to the electrochemical couple gold/copper where copper is the anode. In the presence of an electrolyte, this phenomenon results in the formation of corrosion products than will cause a blistering of the gold (or a break-up and loss of the film in some cases). Moreover, because of the diffusion of the copper salts to the surface, aggregates and a greenish film will be formed on the surface of the sample [13]. By coating gilded samples with PropS-SH and PropS-SH containing nano-particles and carrying out accelerated ageing by the dropping test, a discussion is possible on the effectiveness of this coating, either with nano-particles or not, against the corrosion process. This part is the section 2 of this thesis. Finally, a discussion about laser treatment aiming at the assessment of reversibility/re-applicability of the PropS-SH coating can be found in section 3 of this thesis. Because the protective layer loses its efficiency with time, it is necessary to find a way of removing the silane layer, before applying a new one on the “bare” patina. One request is to minimize the damages that a laser treatment would create on the patina. Therefore, different laser fluences (energy/surface) were applied on the sample surface during the treatment process in order to find the best range of fluence. In particular, we made a characterization of surfaces before and after removal of PropS-SH (applied on a naturally patinated surface, and subsequently aged by natural exposure) with laser methods. The laser removal treatment was done by the CNR Institute of Applied Physics “Nello Carrara” of Sesto Fiorentino in Florence. In all the three sections of the thesis, a range of non-destructive spectroscopic methods (Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), μ-Raman spectroscopy, X-Ray diffractometry (XRD)) were used for characterizing the corroded surfaces. AAS (Atomic Absorption Spectroscopy) was used to analyze the ageing solutions from the dropping test in sections 1 and 2.

Investigation of the dipole response of nickel isotopes in the presence of a high-frequency electromagnetic field

The electric dipole response of neutron-rich nickel isotopes has been investigated using the LAND setup at GSI in Darmstadt (Germany). Relativistic secondary beams of 56−57Ni and 67−72Ni at approximately 500 AMeV have been generated using projectile fragmentation of stable ions on a 4 g/cm2 Be target and subsequent separation in the magnetic dipole fields of the FRagment Separator (FRS). After reaching the LAND setup in Cave C, the radioactive ions were excited electromagnetically in the electric field of a Pb target. The decay products have been measured in inverse kinematics using various detectors. Neutron-rich 67−69Ni isotopes decay by the emission of neutrons, which are detected in the LAND detector. The present analysis concentrates on the (gamma,n) and (gamma,2n) channels in these nuclei, since the proton and three-neutron thresholds are unlikely to be reached considering the virtual photon spectrum for nickel ions at 500 AMeV. A measurement of the stable 58Ni isotope is used as a benchmark to check the accuracy of the present results with previously published data. The measured (gamma,n) and (gamma,np) channels are compared with an inclusive photoneutron measurement by Fultz and coworkers, which are consistent within the respective errors. The measured excitation energy distributions of 67−69Ni contain a large portion of the Giant Dipole Resonance (GDR) strength predicted by the Thomas-Reiche-Kuhn energy-weighted sum rule, as well as a significant amount of low-lying E1 strength, that cannot be attributed to the GDR alone. The GDR distribution parameters are calculated using well-established semi-empirical systematic models, providing the peak energies and widths. The GDR strength is extracted from the chi-square minimization of the model GDR to the measured data of the (gamma,2n) channel, thereby excluding any influence of eventual low-lying strength. The subtraction of the obtained GDR distribution from the total measured E1 strength provides the low-lying E1 strength distribution, which is attributed to the Pygmy Dipole Resonance (PDR). The extraction of the peak energy, width and strength is performed using a Gaussian function. The minimization of trial Gaussian distributions to the data does not converge towards a sharp minimum. Therefore, the results are presented by a chi-square distribution as a function of all three Gaussian parameters. Various predictions of PDR distributions exist, as well as a recent measurement of the 68Ni pygmy dipole-resonance obtained by virtual photon scattering, to which the present pygmy dipole-resonance distribution is also compared.

Secondary Microseisms Characterization and Green’s Function Extraction at the Larderello-Travale Geothermal Field (Italy)

Over the past ten years, the cross-correlation of long-time series of ambient seismic noise (ASN) has been widely adopted to extract the surface-wave part of the Green’s Functions (GF). This stochastic procedure relies on the assumption that ASN wave-field is diffuse and stationary. At frequencies <1Hz, the ASN is mainly composed by surface-waves, whose origin is attributed to the sea-wave climate. Consequently, marked directional properties may be observed, which call for accurate investigation about location and temporal evolution of the ASN-sources before attempting any GF retrieval. Within this general context, this thesis is aimed at a thorough investigation about feasibility and robustness of the noise-based methods toward the imaging of complex geological structures at the local (∼10-50km) scale. The study focused on the analysis of an extended (11 months) seismological data set collected at the Larderello-Travale geothermal field (Italy), an area for which the underground geological structures are well-constrained thanks to decades of geothermal exploration. Focusing on the secondary microseism band (SM;f>0.1Hz), I first investigate the spectral features and the kinematic properties of the noise wavefield using beamforming analysis, highlighting a marked variability with time and frequency. For the 0.1-0.3Hz frequency band and during Spring- Summer-time, the SMs waves propagate with high apparent velocities and from well-defined directions, likely associated with ocean-storms in the south- ern hemisphere. Conversely, at frequencies >0.3Hz the distribution of back- azimuths is more scattered, thus indicating that this frequency-band is the most appropriate for the application of stochastic techniques. For this latter frequency interval, I tested two correlation-based methods, acting in the time (NCF) and frequency (modified-SPAC) domains, respectively yielding esti- mates of the group- and phase-velocity dispersions. Velocity data provided by the two methods are markedly discordant; comparison with independent geological and geophysical constraints suggests that NCF results are more robust and reliable.

Speziation von Plutonium bei der Sorption und Diffusion in Opalinuston

Die vorliegende Arbeit wurde im Rahmen des BMWi-Verbundprojektes Wechselwirkung und Transport von Aktiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika – Wechselwirkung von Neptunium und Plutonium mit natürlichem Tongestein“ durchgeführt. Um die langfristige Sicherheit der nuklearen Endlager beurteilen zu können, muss eine mögliche Migration der radiotoxischen Abfälle in die Umwelt betrachtet werden. Wegen seiner langen Halbwertszeit (24000 a) leistet Pu-239 einen wesentlichen Beitrag zur Radiotoxizität abgebrannter Kernbrennstoffe in einem Endlager. Das redox-sensitive Pu tritt in Lösung unter umweltrelevanten Bedingungen in den Oxidationsstufen +III bis +VI auf und kann nebeneinander in bis zu vier Oxidationsstufen vorliegen. Tonsteinformationen werden als mögliches Wirtsgestein für Endlager hoch-radioaktiver Abfälle betrachtet. Deshalb sind ausführliche Informationen zur Mobilisierung und Immobilisierung des Pu durch/in das Grundwasser aus einem Endlager von besonderer Bedeutung. In dieser Arbeit wurden neue Erkenntnisse über die Wechselwirkung zwischen Pu und dem natürlichen Tongestein Opalinuston (OPA, Mont Terri, Schweiz) mit Hinblick auf die Endlagerung wärmeentwickelnder radioaktiver Abfälle in einem geologischen Tiefenlager gewonnen.rnDer Fokus der Arbeit lag dabei auf der Bestimmung der Speziation von Pu an der Mineraloberfläche nach Sorptions- und Diffusionsprozessen mittels verschiedener synchrotronbasierter Methoden (µ-XRF, µ-XANES/EXAFS, µ-XRD, XANES/EXAFS). rnDie Wechselwirkung zwischen Pu und OPA wurde zunächst in Batch- und Diffusionsexperimenten in Abhängigkeit verschiedener experimenteller Parameter (u.a. pH, Pu-Oxidationsstufe) untersucht. In Sorptionsexperimenten konnte gezeigt werden, dass einige Parameter (z.B. Temperatur, Huminsäure) einen deutlichen Einfluss auf die Sorption von Pu haben.rnDie Speziationsuntersuchungen wurden zum einen an Pulverproben aus Batchexperimenten und zum anderen an OPA-Dünnschliffen bzw. Diffusionsproben in Abhängigkeit verschiedener experimenteller Parameter durchgeführt. Die EXAFS-Messungen an der Pu LIII-Kante der Pulverproben ergaben, dass eine innersphäriche Sorption von Pu(IV) an Tongestein unabhängig von dem Ausgangsoxidationszustand des Plutoniums in Lösung stattgefunden hat. Durch die Kombination der ortsaufgelösten Methoden wurde erstmalig mittels μ-XRF die Verteilung von Pu und anderen in OPA enthaltenen Elementen bestimmt. µ-XANES-Spektren an Pu-Anreicherungen auf OPA-Dünnschliffen und in Diffusionsproben bestätigen, dass das weniger mobile Pu(IV) die dominierende Spezies nach den Sorptions- und Diffusionsprozessen ist. Darüber hinaus wurde zum ersten Mal ein Diffusionsprofil von Pu in OPA mittels µ-XRF gemessen. Die Speziationsuntersuchungen mittels μ-XANES zeigten, dass das eingesetzte Pu(V) entlang seines Diffusionspfades zunehmend zu Pu(IV) reduziert wird. Mit µ-XRD wurde Illit als dominierende Umgebung, in der Pu angereichert wurde, identifiziert und Siderit als eine redoxaktive Phase auftreten kann. Die Ergebnisse dieser Arbeit zeigen, dass die Sicherheit von OPA als Wirtsgestein eines Endlagers hoch-radioaktiver Abfälle positiv zu bewerten ist. rn