Nejire/dCBP-mediated control of H3 acetylation and transcriptional regulation by testis-specific Plus3 domain proteins during Drosophila spermatogenesis

Spermatogenesis describes the development from germ line stem cells to highly specialized sperm. Drosophila melanogaster spermatogenesis is a good model system for chromatin remodelling processes as many of these processes are similar in mammals and in flies. Histone modifications are a prerequisite for the exchange of histones by protamines during these chromatin remodelling processes but also transcription processes in earlier germ cell stages can be compared. In this thesis, the histone acetyltransferase Nejire/dCBP has been characterised as being responsible for the modification of histone H3 at lysine 18 and lysine 27 during post-meiotic germ cell development as well as in the spermatocyte stage. An RNAi-mediated knock-down revealed that the function of Nejire/dCBP is essential for fertility of male flies. Efficient mRNA synthesis of postmeiotic chromatin components depends on Nejire/dCBP whereas incorporation of protamines into the chromatin does not seem to depend on Nejire/dCBP function. Drosophila spermatogenesis is featured by a special regulation of transcription and translation. While most transcripts are synthesised in spermatocytes, a large portion has to be translationally repressed until required in later stages of germ cell development. Transcriptional regulation is supported by testis-specific variants of the general transcription machinery. This includes among others the tTAFs, the tMAC complex and bromodomain proteins. Bromodomain proteins are able to recognise and bind acetylated lysine residues on N-terminal histone chains. The bromodomain proteins tBRD-1 and tBRD-2 are expressed in spermatocytes and can interact with tTAFs, this might facilitate recruitment of the TFIID complex to certain chromatin areas. Further testis-specific variants of ubiquitously expressed proteins are the Plus3 domain proteins. Here, the expression and function of the testis-enriched proteins tPlus3a and tPlus3b have been examined. Both proteins share the conserved Plus3 domain of Rtf1. RNAseq analysis using RNA from mutant testes revealed that tPlus3a and tPlus3b likely contribute to the regulation of transcription in spermatocytes. Furthermore, genes which also depend on tBRD-1 function were identified. We hypothesise that tPlus3a and tPlus3b regulate a group of genes overlapping with tBRD-1-depending genes but not with genes depending on tTAFs. tPlus3a and tPlus3b might therefore contribute to diversification of transcriptional regulation in spermatocytes

Analyticity of extremisers to the Airy Strichartz inequality

We prove that there exists an extremal function to the Airy Strichartz inequality, $e^{-t\partial_x^3}: L^2(\mathbb{R})\to L^8_{t,x}(\mathbb{R}^2)$ by using the linear profile decomposition. Furthermore we show that, if $f$ is an extremiser, then $f$ is extremely fast decaying in Fourier space and so $f$ can be extended to be an entire function on the whole complex domain. The rapid decay of the Fourier transform of extremisers is established with a bootstrap argument which relies on a refined bilinear Airy Strichartz estimate and a weighted Strichartz inequality.Comment: 18 page

Polarimetry microlensing of close-in planetary systems

A close-in giant planetary (CGP) system has a net polarization signal whose value varies depending on the orbital phase of the planet. This polarization signal is either caused by the stellar occultation or by reflected starlight from the surface of the orbiting planet. When the CGP system is located in the Galactic bulge, its polarization signal becomes too weak to be measured directly. One method for detecting and characterizing these weak polarization signatures due to distant CGP systems is gravitational microlensing. In this work, we focus on potential polarimetric observations of highly-magnified microlensing events of CGP systems. When the lens is passing directly in front of the source star with its planetary companion, the polarimetric signature caused by the transiting planet is magnified. As a result some distinct features in the polarimetry and light curves are produced. In the same way microlensing amplifies the reflection-induced polarization signal. While the planet-induced perturbations are magnified, whenever these polarimetric or photometric deviations vanish for a moment the corresponding magnification factor or the polarization component(s) is equal to the related one due to the planet itself. In order to evaluate the observability of such systems through polarimetric or photometric observations of high-magnification microlensing events, we simulate these events by considering confirmed CGP systems as their source stars and conclude that the efficiency for detecting the planet-induced signal with the state-of-the-art polarimetric instrument (FORS2/VLT) is less than 0.1 %. Consequently, these planet-induced polarimetry perturbations can likely be detected under favorable conditions by high-resolution and short-cadence polarimeters of the next generation.Comment: 9 pages, 7 figures, one tabl

Power Supply Options for a Naval Railgun

Large railguns require powerful power supply units. At the French-German Research Institute of Saint-Louis (ISL) most experimental railguns are driven by power supply units based on capacitors. Recent investigations at ISL explore the possibility to use coil based systems to increase the energy density of the power supply. In this study an electrical circuit simulation is used to investigate the difference for railgun operation in between a capacitor and a coil based power supply with respect to current amplitude behavior and projectile velocity. For this a scenario of a 25 MJ muzzle energy railgun is simulated with two different power supply options, replacing capacitors by coils and using a range of circuit resistances. The resistance determines to a large part the losses of the system and defines therefore the efficiency of the launch and the size of the power supply. The interpretation of the results of the performed simulations leads to the conclusion that the capacitor based system "naturally" pro- duces a favorable current pulse trace with respect to launching a mechanical delicate payload. Further simulations show that the disadvantage of the inductor based supply can be mitigated by increasing the power supply unit subdivision into smaller units.Comment: Submitted to IEEE Transactions on Plasma Physic

Reflection symmetries and absence of eigenvalues for one-dimensional Schrödinger operators

We prove a criterion for absence of decaying solutions for one-dimensional Schrödinger operators. As necessary input, we require infinitely many centers of local reflection symmetry and upper and lower bounds for the traces of the associated transfer matrices

Exponential decay of eigenfunctions and generalized eigenfunctions of a non self-adjoint matrix Schr\"odinger operator related to NLS

We study the decay of eigenfunctions of the non self-adjoint matrix operator \calH = (\begin{smallmatrix} -\Delta +\mu+U & W \W & \Delta -\mu -U \end{smallmatrix}), for $\mu>0$, corresponding to eigenvalues in the strip -\mu<\re E <\mu.Comment: 16 page