Geometrical and kinematic properties of interfacial waves in stratified oil-water flow in inclined pipe

The stratified oil-water flow pattern is common in the petroleum industry, especially in offshore directional wells and pipelines. Previous studies have shown that the phenomenon of flow pattern transition in stratified flow can be related to the interfacial wave structure (problem of hydrodynamic instability). The study of the wavy stratified flow pattern requires the characterization of the interfacial wave properties, i.e., average shape, celerity and geometric properties (amplitude and wavelength) as a function of holdup, inclination angle and phases' relative velocity. However, the data available in the literature on wavy stratified flow is scanty, especially in inclined pipes and when oil is viscous. This paper presents new geometric and kinematic interfacial wave properties as a function of a proposed two-phase Froude number in the wavy-stratified liquid-liquid flow. The experimental work was conducted in a glass test line of 12 m and 0.026 m id., oil (density and viscosity of 828 kg/m(3) and 0.3 Pa s at 20 degrees C, respectively) and water as the working fluids at several inclinations from horizontal (-20 degrees, -10 degrees, 0 degrees, 10 degrees, 20 degrees). The results suggest a physical relation between wave shape and the hydrodynamic stability of the stratified liquid-liquid flow pattern. (C) 2011 Elsevier Inc. All rights reserved.

ALDH1A2 (RALDH2) genetic variation in human congenital heart disease

Abstract Background Signaling by the vitamin A-derived morphogen retinoic acid (RA) is required at multiple steps of cardiac development. Since conversion of retinaldehyde to RA by retinaldehyde dehydrogenase type II (ALDH1A2, a.k.a RALDH2) is critical for cardiac development, we screened patients with congenital heart disease (CHDs) for genetic variation at the ALDH1A2 locus. Methods One-hundred and thirty-three CHD patients were screened for genetic variation at the ALDH1A2 locus through bi-directional sequencing. In addition, six SNPs (rs2704188, rs1441815, rs3784259, rs1530293, rs1899430) at the same locus were studied using a TDT-based association approach in 101 CHD trios. Observed mutations were modeled through molecular mechanics (MM) simulations using the AMBER 9 package, Sander and Pmemd programs. Sequence conservation of observed mutations was evaluated through phylogenetic tree construction from ungapped alignments containing ALDH8 s, ALDH1Ls, ALDH1 s and ALDH2 s. Trees were generated by the Neighbor Joining method. Variations potentially affecting splicing mechanisms were cloned and functional assays were designed to test splicing alterations using the pSPL3 splicing assay. Results We describe in Tetralogy of Fallot (TOF) the mutations Ala151Ser and Ile157Thr that change non-polar to polar residues at exon 4. Exon 4 encodes part of the highly-conserved tetramerization domain, a structural motif required for ALDH oligomerization. Molecular mechanics simulation studies of the two mutations indicate that they hinder tetramerization. We determined that the SNP rs16939660, previously associated with spina bifida and observed in patients with TOF, does not affect splicing. Moreover, association studies performed with classical models and with the transmission disequilibrium test (TDT) design using single marker genotype, or haplotype information do not show differences between cases and controls. Conclusion In summary, our screen indicates that ALDH1A2 genetic variation is present in TOF patients, suggesting a possible causal role for this gene in rare cases of human CHD, but does not support the hypothesis that variation at the ALDH1A2 locus is a significant modifier of the risk for CHD in humans.

A graph-theoretical approach in brain functional networks. Possible implications in EEG studies

Abstract Background Recently, it was realized that the functional connectivity networks estimated from actual brain-imaging technologies (MEG, fMRI and EEG) can be analyzed by means of the graph theory, that is a mathematical representation of a network, which is essentially reduced to nodes and connections between them. Methods We used high-resolution EEG technology to enhance the poor spatial information of the EEG activity on the scalp and it gives a measure of the electrical activity on the cortical surface. Afterwards, we used the Directed Transfer Function (DTF) that is a multivariate spectral measure for the estimation of the directional influences between any given pair of channels in a multivariate dataset. Finally, a graph theoretical approach was used to model the brain networks as graphs. These methods were used to analyze the structure of cortical connectivity during the attempt to move a paralyzed limb in a group (N=5) of spinal cord injured patients and during the movement execution in a group (N=5) of healthy subjects. Results Analysis performed on the cortical networks estimated from the group of normal and SCI patients revealed that both groups present few nodes with a high out-degree value (i.e. outgoing links). This property is valid in the networks estimated for all the frequency bands investigated. In particular, cingulate motor areas (CMAs) ROIs act as ‘‘hubs’’ for the outflow of information in both groups, SCI and healthy. Results also suggest that spinal cord injuries affect the functional architecture of the cortical network sub-serving the volition of motor acts mainly in its local feature property. In particular, a higher local efficiency El can be observed in the SCI patients for three frequency bands, theta (3-6 Hz), alpha (7-12 Hz) and beta (13-29 Hz). By taking into account all the possible pathways between different ROI couples, we were able to separate clearly the network properties of the SCI group from the CTRL group. In particular, we report a sort of compensatory mechanism in the SCI patients for the Theta (3-6 Hz) frequency band, indicating a higher level of “activation” Ω within the cortical network during the motor task. The activation index is directly related to diffusion, a type of dynamics that underlies several biological systems including possible spreading of neuronal activation across several cortical regions. Conclusions The present study aims at demonstrating the possible applications of graph theoretical approaches in the analyses of brain functional connectivity from EEG signals. In particular, the methodological aspects of the i) cortical activity from scalp EEG signals, ii) functional connectivity estimations iii) graph theoretical indexes are emphasized in the present paper to show their impact in a real application.

Selection of compositions with high glass forming ability in the Ni-Nb-B alloy system

A combination of an extension of the topological instability "λ criterion" and the "average electronegativity" has been recently reported in the literature to predict compositions with high glass-forming ability (GFA). In the present work, both criteria have been applied to select the Ni61.0Nb36.0B3 alloy with a high glass-forming ability. Ingots were prepared by arc-melting and were used to produce ribbons processed by the melt-spinning technique further characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Ni61.0Nb36.0B3 alloy revealed a complete amorphization and supercooled liquid region ΔTx = 68 K. In addition, wedge-shaped samples were prepared using copper mold casting in order to determine the critical thickness for amorphous formation. Scanning electron microscopy (SEM) revealed that fully amorphous samples could be obtained, reaching up to ~800 µm in thickness.

Valutazione del comportamento differito di una trave inflessa realizzata in due fasi

La presente tesi analizza il comportamento differito in una prova di flessione su quattro punti su una trave prefabbricata con getto di soletta integrativa in opera. Sono riportati i risultati della prova di carico e di rottura sulla trave. Le prove sono state eseguite presso il Laboratorio di Prove Strutture (DISTART) dell'Università di Bologna. La trave è composta di due tipi di calcestreuzzo, realizzati in tempi diversi e con proprietà meccaniche diverse. L'obiettivo della campagna sperimentale è studiare l'effetto delle fasi di costruzione sull'evoluzione delle tensioni e delle deformazioni nel tempo e sulla resistenza ultima della trave. Il comportamento sperimentale è stato confrontato con i risultati numerici ottenuti con un modello a fibre in grado di cogliere anche i fenomeni legati al creep.

L’emergere del periurbano: il caso di Bologna

The rationale behind this piece of research is to study the movement of people from Bologna city centre to its outskirts and to find out what type of people are subject to move and the reasons for this: are they forced into or do they choose to do so? The present study will also consider how people commute from home to the city centre and the effect this has on them. For the purpose of this work, attention will be drawn to the possibility of these outer areas to develop in such a way that people will no longer need to commute to the city in order to recreate the advantages this offers to them (e.g. shops, job opportunities, ext). The theoretical framework this doctorial work is based upon concerns historical, urbanist, sociological and demographic approaches, along with the fact that the hegemony of the city centre has been benefiting has decreased. Historical centres and the central poles of metropolitan systems have lost their functional and symbolic relevance. More specifically, the Bologna Area is undergoing two tendencies: the first one is a process of residential decentralization from the capital town, capable of involving a plurality of social groups, which caused an enrichment of the social composition of "suburban" population. The second process is a partial substitution of the population in the city centre with new groups: this not only occurred with directional groups, but it has also interested new parts of the “service worker” class and members of metropolitan underclass, causing, consequentially, a growing complexity in central areas of the metropolitan system. The need to increase knowledge of Bologna territory has become more and more relevant, since the 70’s, when a series of important environmental transformations favoured a research interest that did not exclusively stopped within the city centre boarders, but rather encouraged the exploration of Bologna outer/suburban areas. Finally, in the urban/suburban discourse, this piece of research has highlighted how the search for a better quality of life (financial reasons, larger spaces, possibility to buy/rent for a better price, environmental issues) determines the choice to leave the centre of the city in favour of outer areas. The tendency that this doctorial work has brought to surface is the need to match a more manageable standard of living to the proximity to the city, despite the fact that this results in the stress caused to commuting and the lack of those cultural and entertaining facilities offered by the city. The new suburban inhabitants do not regret leaving the city, but, at the same time, do not feel emotionally attached to the new location at a community level: what they seem to look for is a more comfortable environment where to live in.

Supramolecular functional assemblies with photo or chemical addressability

Supramolecular self-assembly represents a key technology for the spontaneous construction of nanoarchitectures and for the fabrication of materials with enhanced physical and chemical properties. In addition, a significant asset of supramolecular self-assemblies rests on their reversible formation, thanks to the kinetic lability of their non-covalent interactions. This dynamic nature can be exploited for the development of “self-healing” and “smart” materials towards the tuning of their functional properties upon various external factors. One particular intriguing objective in the field is to reach a high level of control over the shape and size of the supramolecular architectures, in order to produce well-defined functional nanostructures by rational design. In this direction, many investigations have been pursued toward the construction of self-assembled objects from numerous low-molecular weight scaffolds, for instance by exploiting multiple directional hydrogen-bonding interactions. In particular, nucleobases have been used as supramolecular synthons as a result of their efficiency to code for non-covalent interaction motifs. Among nucleobases, guanine represents the most versatile one, because of its different H-bond donor and acceptor sites which display self-complementary patterns of interactions. Interestingly, and depending on the environmental conditions, guanosine derivatives can form various types of structures. Most of the supramolecular architectures reported in this Thesis from guanosine derivatives require the presence of a cation which stabilizes, via dipole-ion interactions, the macrocyclic G-quartet that can, in turn, stack in columnar G-quadruplex arrangements. In addition, in absence of cations, guanosine can polymerize via hydrogen bonding to give a variety of supramolecular networks including linear ribbons. This complex supramolecular behavior confers to the guanine-guanine interactions their upper interest among all the homonucleobases studied. They have been subjected to intense investigations in various areas ranging from structural biology and medicinal chemistry – guanine-rich sequences are abundant in telomeric ends of chromosomes and promoter regions of DNA, and are capable of forming G-quartet based structures– to material science and nanotechnology. This Thesis, organized into five Chapters, describes mainly some recent advances in the form and function provided by self-assembly of guanine based systems. More generally, Chapter 4 will focus on the construction of supramolecular self-assemblies whose self-assembling process and self-assembled architectures can be controlled by light as external stimulus. Chapter 1 will describe some of the many recent studies of G-quartets in the general area of nanoscience. Natural G- quadruplexes can be useful motifs to build new structures and biomaterials such as self-assembled nanomachines, biosensors, therapeutic aptamer and catalysts. In Chapters 2-4 it is pointed out the core concept held in this PhD Thesis, i.e. the supramolecular organization of lipophilic guanosine derivatives with photo or chemical addressability. Chapter 2 will mainly focus on the use of cation-templated guanosine derivatives as a potential scaffold for designing functional materials with tailored physical properties, showing a new way to control the bottom-up realization of well-defined nanoarchitectures. In section 2.6.7, the self-assembly properties of compound 28a may be considered an example of open-shell moieties ordered by a supramolecular guanosine architecture showing a new (magnetic) property. Chapter 3 will report on ribbon-like structures, supramolecular architectures formed by guanosine derivatives that may be of interest for the fabrication of molecular nanowires within the framework of future molecular electronic applications. In section 3.4 we investigate the supramolecular polymerizations of derivatives dG 1 and G 30 by light scattering technique and TEM experiments. The obtained data reveal the presence of several levels of organization due to the hierarchical self-assembly of the guanosine units in ribbons that in turn aggregate in fibrillar or lamellar soft structures. The elucidation of these structures furnishes an explanation to the physical behaviour of guanosine units which display organogelator properties. Chapter 4 will describe photoresponsive self-assembling systems. Numerous research examples have demonstrated that the use of photochromic molecules in supramolecular self-assemblies is the most reasonable method to noninvasively manipulate their degree of aggregation and supramolecular architectures. In section 4.4 we report on the photocontrolled self-assembly of modified guanosine nucleobase E-42: by the introduction of a photoactive moiety at C8 it is possible to operate a photocontrol over the self-assembly of the molecule, where the existence of G-quartets can be alternately switched on and off. In section 4.5 we focus on the use of cyclodextrins as photoresponsive host-guest assemblies: αCD–azobenzene conjugates 47-48 (section 4.5.3) are synthesized in order to obtain a photoresponsive system exhibiting a fine photocontrollable degree of aggregation and self-assembled architecture. Finally, Chapter 5 contains the experimental protocols used for the research described in Chapters 2-4.

Untersuchungen zur Verfestigungskinetik in Suspensionen kolloidaler Partikel

Kolloidale Suspensionen, bei denen man die kolloidalen Teilchen als "Makroatome" in einem Kontinuum aus Lösungsmittelmolekülen auffaßt, stellen ein geeignetes Modellsystem zur Untersuchung von Verfestigungsvorgängen dar. Auf Grund der typischen beteiligten Längen- und Zeitskalen können Phasenübergänge bequem mit optischen Verfahren studiert werden. In der vorliegenden Arbeit wurde die Kinetik der Kristallisation in drei kolloidalen Systemen unterschiedlicher Teilchen-Teilchen-Wechselwirkung mit Lichtstreu- und mikroskopischen Methoden untersucht. Zur Untersuchung von Suspensionen aus sterisch stabilisierten PMMA-Teilchen, die in guter Näherung wie harte Kugeln wechselwirken, wurde ein neuartiges Laserlichtstreuexperiment aufgebaut, das die gleichzeitige Detektion von Bragg- und Kleinwinkelstreuung an einer Probe erlaubt. Damit konnte der zeitliche Verlauf der Kristallisation verfolgt sowie u.a. Nukleationsraten und erstmals auch Wachstumsgeschwindigkeiten bestimmt werden; diese wurden mit klassischer Nukleationstheorie sowie Wilson-Frenkel-Wachstum verglichen. In beiden Fällen konnte sehr gute Übereinstimmung mit der Theorie festgestellt werden. In Systemen geladener Partikel wurden mit Bragg-Mikroskopie die Wachstumsgeschwindigkeiten heterogener, an der Wand der Probenzelle aufwachsender Kristalle untersucht. Die Anpassung eines Wilson-Frenkel-Wachstumsgesetzes gelingt auch hier, wenn man die dazu eingeführte reskalierte Energiedichte auf den Schmelzpunkt bezieht. Geeignete Reskalierung der Daten erlaubt den Vergleich mit den Hartkugelsystemen. Zum ersten Mal wurde die Kristallisationskinetik in zwei verschiedenen kolloidalen binären Mischungen bestimmt und ausgewertet: In Beimischungen einer nichtkristallisierenden Teilchensorte zu einer kristallisierenden Suspension konnten die Daten mit einem modifizierten Wilson-Frenkel-Gesetz beschrieben werden, während in Mischungen aus zwei kristallisierenden Partikelsystemen eine unerwartet hohe Abnahme der Wachstumsgeschwindigkeiten beobachtet wurde. Kolloidale Suspensionen hartkugelähnlicher Mikrogel-Partikel konnten mit Hilfe des Lichtstreuaufbaues ebenfalls zum ersten Mal untersucht werden. Es wurde eine ähnliche Kristallisationskinetik wie in den PMMA-Systemen gefunden, jedoch auch einige wichtige Unterschiede, die insbesondere den Streumechanismus im Kleinwinkelbereich betrafen. Hier wurden verschiedene Interpretationsvorschläge diskutiert.

Grating coupled surface plasmon enhanced fluorescence spectroscopy

Over the last three decades, sensors based on the phenomenon of surface plasmon resonance have proven particularly suitable for real time thin film characterization, gas detection, biomolecular interaction examination and to supplement electrochemical methods. Systems based on prism coupling have been combined with fluorescence detection under the name of surface plasmon fluorescence spectroscopy to increase sensitivity even further. Alternatively, metal gratings can be employed to match photons for plasmon resonance. The real time monitoring of binding reactions not yet been reported in the combination of fluorescence detection and grating coupling. Grating-based systems promise more competitive products, because of reduced operating costs, and offer benefits for device engineering. This thesis is comprised of a comprehensive study of the suitability of grating coupling for fluorescence based analyte detection. Fundamental properties of grating coupled surface plasmon fluorescence spectroscopy are described, as well as issues related to the commercial realization of the method. Several new experimental techniques are introduced and demonstrated in order to optimize performance in certain areas and improve upon capabilities in respect to prism-based systems. Holographically fabricated gratings are characterized by atomic force microscopy and optical methods, aided by simulations and profile parameters responsible for efficient coupling are analyzed. The directional emission of fluorophores immobilized on a grating surface is studied in detail, including the magnitude and geometry of the fluorescence emission pattern for different grating constants and polarizations. Additionally, the separation between the minimum of the reflected intensity and the maximum fluorescence excitation position is examined. One of the key requirements for the commercial feasibility of grating coupling is the cheap and faithful mass production of disposable samples from a given master grating. The replication of gratings is demonstrated by a simple hot embossing method with good reproducibility to address this matter. The in-situ fluorescence detection of analyte immobilization and affinity measurements using grating coupling are described for the first time. The physical factors related to the sensitivity of the technique are assessed and the lower limit of detection of the technique is determined for an exemplary assay. Particular attention is paid to the contribution of bulk fluorophores to the total signal in terms of magnitude and polarization of incident and emitted light. Emission from the bulk can be a limiting factor for experiments with certain assay formats. For that reason, a novel optical method, based on the modulation of both polarization and intensity of the incident beam, is introduced and demonstrated to be capable of eliminating this contribution.

Eigenschaftskorrelationen in kolloidalen Festkörpern und Fluiden aus optischen Experimenten

Die Arbeit beschäftigt sich mit ein- und zweikomponentigen, geladenen Kolloidsystemen, die in vollentsalzten wässrigen und organischen Dispersionen kristalline Strukturen ausbilden. Im ersten Teil der Arbeit wird die Wechselwirkung der Kolloide mit verschiedenen Methoden charakterisiert. Dabei zeigten sich quantitative Übereinstimmungen zwischen den Resultaten aus Zellenmodellrechnungen und aus elektrokinetischen Messungen einerseits und Messungen des Phasenverhaltens und der Elastizität andererseits. Diese nunmehr gut gesicherten Diskrepanzen und Korrelationen bedürfen des theoretischen Verständnisses. Im zweiten Teil der Arbeit wurde das Erstarrungsverhalten kolloidaler Scherschmelzen in den kristallinen Zustand mit (zeitaufgelöster) statischer Lichtstreuung und mikroskopischen Methoden untersucht. Dies erlaubte zunächst die kritische Überprüfung klassischer Modelle zur Kristallisationskinetik (Wilson- Frenkel- Gesetz, klassische Nukleationstheorie, Kolmogorov- Johnson- Mehl- Avrami (KJMA)- Modell). Es zeigte sich, dass diese Modelle gut geeignet sind die Verfestigung auch geladener kolloidaler Schmelzen zu beschreiben, wenn die diffusive Einteilchendynamik korrekt berücksichtigt wird. Erstmals wurden Oberflächenspannungen zwischen Kristallkeim und Schmelze für geladene Systeme bestimmt, die im Gegensatz zu Hartkugel- Systemen eine lineare Zunahme mit der Partikelkonzentration aufweisen. Der Methodenpark und die Auswerteverfahren wurden sodann auf binäre kolloidale Mischungen übertragen. Entsprechend den Einzelkomponenten kristallisieren alle Mischungen in einer kubischen Struktur. Leitfähigkeitsmessungen und Elastizität stehen meist im Einklang mit der Nukleation zufallsgeordneter Substitutionskristalle. Für mehrere Proben mit unterschiedlichen Größenverhältnissen wurde mit statischer Lichtstreuung der Einfluss der Komposition und der Partikelkonzentration auf das Nukleationsverhalten untersucht. Im Allgemeinen wurde das Nukleationsszenario einkomponentiger Systeme mit einigen unerwarteten, quantitativen Unterschieden reproduziert. Für eine Probe, die eine Kompositionsordnung andeutet, wurden interessante Korrelationen zwischen der Nukleationskinetik und den Eigenschaften des resultierenden Festkörpers gefunden.

Computation of direction selectivity in retinal starburst amacrine cell dendrites – studied using electrophysiological recordings and two-photon imaging

Neuronal circuits in the retina analyze images according to qualitative aspects such as color or motion, before the information is transmitted to higher visual areas of the brain. One example, studied for over the last four decades, is the detection of motion direction in ‘direction selective’ neurons. Recently, the starburst amacrine cell, one type of retinal interneuron, has emerged as an essential player in the computation of direction selectivity. In this study the mechanisms underlying the computation of direction selective calcium signals in starburst cell dendrites were investigated using whole-cell electrical recordings and two-photon calcium imaging. Analysis of the somatic electrical responses to visual stimulation and pharmacological agents indicated that the directional signal (i) is not computed presynaptically to starburst cells or by inhibitory network interactions. It is thus computed via a cell-intrinsic mechanism, which (ii) depends upon the differential, i.e. direction selective, activation of voltage-gated channels. Optically measuring dendritic calcium signals as a function of somatic voltage suggests (iii) a difference in resting membrane potential between the starburst cell’s soma and its distal dendrites. In conclusion, it is proposed that the mechanism underlying direction selectivity in starburst cell dendrites relies on intrinsic properties of the cell, particularly on the interaction of spatio-temporally structured synaptic inputs with voltage-gated channels, and their differential activation due to a somato-dendritic difference in membrane potential.

The impact of polymorphisms in P-gp, DNA repair and folic acid metabolism genes in newly diagnosed multiple myeloma patients treated with thalidomide plus dexamethasone, with or without bortezomib

The principle aim of this study was to investigate biological predictors of response and resistance to multiple myeloma treatment. Two hypothesis had been proposed as responsible of responsiveness: SNPs in DNA repair and Folate pathway, and P-gp dependent efflux. As a first objective, panel of SNPs in DNA repair and Folate pathway genes, were analyzed. It was a retrospective study in a group of 454, previously untreated, MM patients enrolled in a randomized phase III open-label study. Results show that some SNPs in Folate pathway are correlated with response to MM treatment. MTR genotype was associated with favorable response in the overall population of MM patients. However, this relation, disappear after adjustment for treatment response. When poor responder includes very good partial response, partial response and stable/progressive disease MTFHR rs1801131 genotype was associated with poor response to therapy. This relation - unlike in MTR – was still significant after adjustment for treatment response. Identification of this genetic variant in MM patients could be used as an independent prognostic factor for therapeutic outcome in the clinical practice. In the second objective, basic disposition characteristics of bortezomib was investigated. We demonstrated that bortezomib is a P-gp substrate in a bi-directional transport study. We obtain apparent permeability rate values that together with solubility values can have a crucial implication in better understanding of bortezomib pharmacokinetics with respect to the importance of membrane transporters. Subsequently, in view of the importance of P-gp for bortezomib responsiveness a panel of SNPs in ABCB1 gene - coding for P-gp - were analyzed. In particular we analyzed five SNPs, none of them however correlated with treatment responsiveness. However, we found a significant association between ABCB1 variants and cytogenetic abnormalities. In particular, deletion of chromosome 17 and t(4;14) translocation were present in patients harboring rs60023214 and rs2038502 variants respectively.

Applications of remote sensing and geographic information systems in geomorphological studies: Safaga - El Quseir area, Red Sea coast, Egypt as an example

In den letzten drei Jahrzehnten sind Fernerkundung und GIS in den Geowissenschaften zunehmend wichtiger geworden, um die konventionellen Methoden von Datensammlung und zur Herstellung von Landkarten zu verbessern. Die vorliegende Arbeit befasst sich mit der Anwendung von Fernerkundung und geographischen Informationssystemen (GIS) für geomorphologische Untersuchungen. Durch die Kombination beider Techniken ist es vor allem möglich geworden, geomorphologische Formen im Überblick und dennoch detailliert zu erfassen. Als Grundlagen werden in dieser Arbeit topographische und geologische Karten, Satellitenbilder und Klimadaten benutzt. Die Arbeit besteht aus 6 Kapiteln. Das erste Kapitel gibt einen allgemeinen Überblick über den Untersuchungsraum. Dieser umfasst folgende morphologische Einheiten, klimatischen Verhältnisse, insbesondere die Ariditätsindizes der Küsten- und Gebirgslandschaft sowie das Siedlungsmuster beschrieben. Kapitel 2 befasst sich mit der regionalen Geologie und Stratigraphie des Untersuchungsraumes. Es wird versucht, die Hauptformationen mit Hilfe von ETM-Satellitenbildern zu identifizieren. Angewandt werden hierzu folgende Methoden: Colour Band Composite, Image Rationing und die sog. überwachte Klassifikation. Kapitel 3 enthält eine Beschreibung der strukturell bedingten Oberflächenformen, um die Wechselwirkung zwischen Tektonik und geomorphologischen Prozessen aufzuklären. Es geht es um die vielfältigen Methoden, zum Beispiel das sog. Image Processing, um die im Gebirgskörper vorhandenen Lineamente einwandfrei zu deuten. Spezielle Filtermethoden werden angewandt, um die wichtigsten Lineamente zu kartieren. Kapitel 4 stellt den Versuch dar, mit Hilfe von aufbereiteten SRTM-Satellitenbildern eine automatisierte Erfassung des Gewässernetzes. Es wird ausführlich diskutiert, inwieweit bei diesen Arbeitsschritten die Qualität kleinmaßstäbiger SRTM-Satellitenbilder mit großmaßstäbigen topographischen Karten vergleichbar ist. Weiterhin werden hydrologische Parameter über eine qualitative und quantitative Analyse des Abflussregimes einzelner Wadis erfasst. Der Ursprung von Entwässerungssystemen wird auf der Basis geomorphologischer und geologischer Befunde interpretiert. Kapitel 5 befasst sich mit der Abschätzung der Gefahr episodischer Wadifluten. Die Wahrscheinlichkeit ihres jährlichen Auftretens bzw. des Auftretens starker Fluten im Abstand mehrerer Jahre wird in einer historischen Betrachtung bis 1921 zurückverfolgt. Die Bedeutung von Regentiefs, die sich über dem Roten Meer entwickeln, und die für eine Abflussbildung in Frage kommen, wird mit Hilfe der IDW-Methode (Inverse Distance Weighted) untersucht. Betrachtet werden außerdem weitere, regenbringende Wetterlagen mit Hilfe von Meteosat Infrarotbildern. Genauer betrachtet wird die Periode 1990-1997, in der kräftige, Wadifluten auslösende Regenfälle auftraten. Flutereignisse und Fluthöhe werden anhand von hydrographischen Daten (Pegelmessungen) ermittelt. Auch die Landnutzung und Siedlungsstruktur im Einzugsgebiet eines Wadis wird berücksichtigt. In Kapitel 6 geht es um die unterschiedlichen Küstenformen auf der Westseite des Roten Meeres zum Beispiel die Erosionsformen, Aufbauformen, untergetauchte Formen. Im abschließenden Teil geht es um die Stratigraphie und zeitliche Zuordnung von submarinen Terrassen auf Korallenriffen sowie den Vergleich mit anderen solcher Terrassen an der ägyptischen Rotmeerküste westlich und östlich der Sinai-Halbinsel.

Sensitivity analysis of a parabolic-elliptic problem

We consider the heat flux through a domain with subregions in which the thermal capacity approaches zero. In these subregions the parabolic heat equation degenerates to an elliptic one. We show the well-posedness of such parabolic-elliptic differential equations for general non-negative L-infinity-capacities and study the continuity of the solutions with respect to the capacity, thus giving a rigorous justification for modeling a small thermal capacity by setting it to zero. We also characterize weak directional derivatives of the temperature with respect to capacity as solutions of related parabolic-elliptic problems.

Electronic transport in the heavy fermion superconductors UPd 2 Al 3 and UNi 2 Al 3

This work addresses the electronical properties of the superconductors UPd2Al3 and UNi2Al3 on the basis of thin film experiments. These isotructural compounds are ideal candiates to study the interplay of magnetism and superconductivity due to the differences of their magnetically ordered states, as well as the experimental evidence for a magnetic pairing mechanism in UPd2Al3. Epitaxial thin film samples of UPd2Al3 and UNi2Al3 were prepared using UHV Molecular Beam Epitaxy (MBE). For UPd2Al3, the change of the growth direction from the intrinsic (001) to epitaxial (100) was predicted and sucessfully demonstrated using LaAlO3 substrates cut in (110) direction. With optimized deposition process parameters for UPd2Al3 (100) on LaAlO3 (110) superconducting samples with critical temperatures up to Tc = 1.75K were obtained. UPd2Al3-AlOx-Ag mesa junctions with superconducting base electrode were prepared and shown to be in the tunneling regime. However, no signatures of a superconducting density of states were observed in the tunneling spectra. The resistive superconducting transition was probed for a possible dependence on the current direction. In contrast to UNi2Al3, the existence of such feature was excluded in UPd2Al3 (100) thin films. The second focus of this work is the dependence of the resisitive transition in UNi2Al3 (100) thin films on the current direction. The experimental fact that the resisitive transition occurs at slightly higher temperatures for I║a than for I║c can be explained within a model of two weakly coupled superconducting bands. Evidence is presented for the key assumption of the two-band model, namely that transport in and out of the ab-plane is generated on different, weakly coupled parts of the Fermi surface. Main indications are the angle dependence of the superconducting transition and the dependence of the upper critical field Bc2 on current and field orientation. Additionally, several possible alternative explanations for the directional splitting of the transition are excluded in this work. An origin due to scattering on crystal defects or impurities is ruled out, likewise a relation to ohmic heating or vortex dynamics. The shift of the transition temperature as function of the current density was found to behave as predicted by the Ginzburg-Landau theory for critical current depairing, which plays a significant role in the two-band model. In conclusion, the directional splitting of the resisitive transition has to be regarded an intrinsic and unique property of UNi2Al3 up to now. Therefore, UNi2Al3 is proposed as a role model for weakly coupled multiband superconductivity. Magnetoresistance in the normalconducting state was measured for UPd2Al3 and UNi2Al3. For UNi2Al3, a negative contribution was observed close to the antiferromagnetic ordering temperature TN only for I║a, which can be associated to reduced spin-disorder scattering. In agreement with previous results it is concluded that the magnetic moments have to be attributed to the same part of the Fermi surface which generates transport in the ab-plane.