Mitochondrial inheritance and germ line determination in a bivalve species with Doubly Uniparental Inheritance (DUI)

Mitochondria are inherited maternally in most metazoans. However, in some bivalves, two mitochondrial lineages are present: one transmitted through eggs (F), the other through sperm (M). This is called Doubly Uniparental Inheritance (DUI). During male embryo development, spermatozoon mitochondria aggregate and end up in the primordial germ cells, while they are dispersed in female embryos. The molecular mechanisms of segregation patterns are still unknown. In the DUI species Ruditapes philippinarum, I examined sperm mitochondria distribution by MitoTracker, microtubule staining and TEM, and I localized germ line determinants with immunocytochemical analysis. I also analyzed the gonad transcriptome, searching for genes involved in reproduction and sex determination. Moreover, I analyzed an M-type specific open reading frame that could be responsible for maintenance/degradation of M mitochondria during embryo development. These transcripts were also localized in tissues using in situ hybridization. As in Mytilus, two distribution patterns of M mitochondria were detected in R. philippinarum, supporting that they are related to DUI. Moreover, the first division midbody concurs in positioning aggregated M mitochondria on the animal-vegetal axis of the male embryo: in organisms with spiral segmentation this zone is not involved in further cleavages, so aggregation is maintained. Moreover, sperm mitochondria reach the same embryonic area where germ plasm is transferred, suggesting their contribution in male germ line formation. The finding of reproduction and ubiquitination transcripts led to formulate a model in which ubiquitination genes stored in female oocytes during gametogenesis would activate sex-gene expression in the early embryonic developmental stages (preformation). Only gametogenetic cells were labeled by in situ hybridization, proving their specific transcription in developing gametes. Other than having a role in sex determination, some ubiquination factors could also be involved in mitochondrial inheritance, and their differential expression could be responsible for the different fate of sperm mitochondria in the two sexes.

Virtual Compton scattering in baryon chiral perturbation theory

This thesis is concerned with the calculation of virtual Compton scattering (VCS) in manifestly Lorentz-invariant baryon chiral perturbation theory to fourth order in the momentum and quark-mass expansion. In the one-photon-exchange approximation, the VCS process is experimentally accessible in photon electro-production and has been measured at the MAMI facility in Mainz, at MIT-Bates, and at Jefferson Lab. Through VCS one gains new information on the nucleon structure beyond its static properties, such as charge, magnetic moments, or form factors. The nucleon response to an incident electromagnetic field is parameterized in terms of 2 spin-independent (scalar) and 4 spin-dependent (vector) generalized polarizabilities (GP). In analogy to classical electrodynamics the two scalar GPs represent the induced electric and magnetic dipole polarizability of a medium. For the vector GPs, a classical interpretation is less straightforward. They are derived from a multipole expansion of the VCS amplitude. This thesis describes the first calculation of all GPs within the framework of manifestly Lorentz-invariant baryon chiral perturbation theory. Because of the comparatively large number of diagrams - 100 one-loop diagrams need to be calculated - several computer programs were developed dealing with different aspects of Feynman diagram calculations. One can distinguish between two areas of development, the first concerning the algebraic manipulations of large expressions, and the second dealing with numerical instabilities in the calculation of one-loop integrals. In this thesis we describe our approach using Mathematica and FORM for algebraic tasks, and C for the numerical evaluations. We use our results for real Compton scattering to fix the two unknown low-energy constants emerging at fourth order. Furthermore, we present the results for the differential cross sections and the generalized polarizabilities of VCS off the proton.

Grid Connected Doubly Fed Induction Generator Based Wind Turbine under LVRT

This project concentrates on the Low Voltage Ride Through (LVRT) capability of Doubly Fed Induction Generator (DFIG) wind turbine. The main attention in the project is, therefore, drawn to the control of the DFIG wind turbine and of its power converter and to the ability to protect itself without disconnection during grid faults. It provides also an overview on the interaction between variable speed DFIG wind turbines and the power system subjected to disturbances, such as short circuit faults. The dynamic model of DFIG wind turbine includes models for both mechanical components as well as for all electrical components, controllers and for the protection device of DFIG necessary during grid faults. The viewpoint of this project is to carry out different simulations to provide insight and understanding of the grid fault impact on both DFIG wind turbines and on the power system itself. The dynamic behavior of DFIG wind turbines during grid faults is simulated and assessed by using a transmission power system generic model developed and delivered by Transmission System Operator in the power system simulation toolbox Digsilent, Matlab/Simulink and PLECS.

First doubly polarised photoproduction on 3 He at the photon beam of MAMI

Im Juli 2009 wurde am Mainzer Mikrotron (MAMI) erstmal ein Experiment durchgeführt, bei dem ein polarisiertes 3He Target mit Photonen im Energiebereich von 200 bis 800 MeV untersucht wurde. Das Ziel dieses Experiments war die Überprüfung der Gerasimov-Drell-Hearn Summenregel am Neutron. Die Verwendung der Messdaten welche mit dem polarisierten 3He Target gewonnen wurden, geben - im Vergleich mit den bereits existieren Daten vom Deuteron - aufgrund der Spin-Struktur des 3He einen komplementären und direkteren Zugang zum Neutron. Die Messung des totalen helizitätsabhängigen Photoabsorptions-Wirkungsquerschnitts wurde mittels eines energiemarkierten Strahls von zirkular polarisierten Photonen, welcher auf das longitudinal polarisierte 3He Target trifft, durchgeführt. Als Produktdetektoren kamen der Crystal Ball (4π Raumabdeckung), TAPS (als ”Vorwärtswand”) sowie ein Schwellen-Cherenkov-Detektor (online Veto zur Reduktion von elektromagnetischen Ereignissen) zum Einsatz. Planung und Aufbau der verschiedenen komponenten Teile des 3He Experimentaufbaus war ein entscheidender Teil dieser Dissertation und wird detailliert in der vorliegenden Arbeit beschrieben. Das Detektorsystem als auch die Analyse-Methoden wurden durch die Messung des unpolarisierten, totalen und inklusiven Photoabsoprtions-Wirkungsquerschnitts an flüssigem Wasserstoff getestet. Hierbei zeigten die Ergebnisse eine gute Übereinstimmung mit bereits zuvor publizierten Daten. Vorläufige Ergebnisse des unpolarisierten totalen Photoabsorptions-Wirkungsquerschnitts sowie der helizitätsabhängige Unterschied zwischen Photoabsorptions-Wirkungsquerschnitten an 3He im Vergleich zu verschiedenen theoretischen Modellen werden vorgestellt.

Characterization of mitochondrial genomes in bivalve species with doubly uniparental inheritance of mitochondria

Many bivalve species possess two distinct mtDNA lineages, called F and M, respectively inherited maternally and paternally: this system is called doubly uniparental inheritance (DUI). The main experimental project of my PhD was the quantification of the two mtDNAs during the development of the DUI species Ruditapes philippinarum, from early embryos to sub-adults, using Real-Time qPCR. I identified the time interval in which M mtDNA is lost from female individuals, while it is retained in males (which are heteroplasmic through all of their life cycle). The results also suggested absence of mtDNA replication during early embryogenesis, a process constituting a bottleneck that highly reduces the copy number of mtDNA molecules in cells of developing larvae. In males this bottleneck may produce cells homoplasmic for M mtDNA, and could be considered as a first step of the segregation of M in the male germ line. Another finding was the characterization, in young clams approaching the first reproductive season, of a significant boost in copy number of F mtDNA in females and of M in males. Given the age of animals in which this mtDNA-specific growth was observed, the finding could probably be the outcome of the first round of gonads and gametes production. Other lines of research included the characterization of the unassigned regions in mt genomes of DUI bivalves. These regions can harbor signals involved in the control of replication and/or transcription of the mtDNA molecule, as well as additional open reading frames (ORFs) not related to oxidative phosphorylation. These features in DUI species could be associated to the maintenance of separate inheritance routes for the two mtDNAs. Additional ORFs are also found in other animal mt genomes: I summarized the presence of gene duplications as a co-author in a review focusing on animal mt genomes with unusual gene content.

Doubly-charged ethane ions: Solution to the dilemma of stability predicted by theory and instability observed in experiment

Potential energy curves have been computed for [C2H6]2+ ions and the results used to interpret the conspicuous absence of these ions in 2E mass spectra and in charge-stripping experiments. The energies and structures of geometry-optimized ground-state singlet and excited-state triplet [C2H6]2+ ions have been determined along with energies for different decomposition barriers and dissociation asymptotes. Although singlet and triplet [C2H6]2+ ions can exist as stable entities, they possess low energy barriers to decomposition. Vertical Franck-Condon transitions, involving electron impact ionization of ethane as well as charge-stripping collisions of [C2H6]+ ions, produce [C2H6]2+ ions which promptly dissociate since they are formed with energies in excess of various decomposition barriers. Appearance energies computed for doubly-charged ethane fragment ions are in accordance with experimental values.

Doubly charged ion mass spectra of alkyl-substituted furans and pyrroles

Doubly charged ion mass spectra of alkyl-substituted furans and pyrroles were obtained using a double-focusing magnetic mass spectrometer operated at 3.2 kV accelerating voltage. Molecular ions were the dominant species found in doubly charged spectra of lower molecular weight heterocydic compounds, whereas the spectra of the higher weight homologues were typified by abundant fragment ions from extensive decomposition. Measured doubly charged ionization and appearance energies ranged from 22.8 to 47.9 eV. Ionization energies were correlated with values calculated using self-consistent field–molecular orbital techniques. A multichannel diabatic curve-crossing model was developed to investigate the fundamental organic ion reactions responsible for development of doubly charged ion mass spectra. Probabilities for Landau–Zener type transitions between reactant and product curves were determined and used in the collision model to predict charge-transfer cross-sections, which compared favorably with experimental cross-sections obtained using time-of-flight techniques.

Doubly-charged gas phase cations

Unique features of doubly-charged stable organic ions are examined and the results correlated with experimental observations. Self-consistent field molecular orbital methods are used to compute structures and stabilities of CnH 2 2+ (n=2–9) ions which are prominent in electron impact ionization of hydrocarbon molecules. A simple curve crossing model is employed to rationalize charge transfer reactions of these ions.

Competition between single and double electron transfer in collisions of doubly charged molecular pyrrole ions with neutral pyrrole molecules

Cross-sections have been determined for one- and two-electron transfer channels in the collisions of keV gas-phase doubly charged pyrrole ions with pyrrole molecules. Measured single and double electron transfer total cross-sections approximate 45 Å2 and 15 Å2, respectively. A combination of symmetric resonance charge exchange and multistate curve-crossing models has been invoked to describe these reactions.