Functional renormalization group study of the Anderson--Holstein model

We present a comprehensive study of the spectral and transport properties in the Anderson--Holstein model both in and out of equilibrium using the functional renormalization group (FRG). We show how the previously established machinery of Matsubara and Keldysh FRG can be extended to include the local phonon mode. Based on the analysis of spectral properties in equilibrium we identify different regimes depending on the strength of the electron--phonon interaction and the frequency of the phonon mode. We supplement these considerations with analytical results from the Kondo model. We also calculate the non-linear differential conductance through the Anderson--Holstein quantum dot and find clear signatures of the presence of the phonon mode.Comment: 19 pages, 8 figure

Symmetry breaking in the female germline cyst.

In mammals and flies, only one cell in a multicellular female germline cyst becomes an oocyte, but how symmetry is broken to select the oocyte is unknown. Here, we show that the microtubule (MT) minus end-stabilizing protein Patronin/CAMSAP marks the future Drosophila oocyte and is required for oocyte specification. The spectraplakin Shot recruits Patronin to the fusome, a branched structure extending into all cyst cells. Patronin stabilizes more MTs in the cell with the most fusome material. Our data suggest that this weak asymmetry is amplified by Dynein-dependent transport of Patronin-stabilized MTs. This forms a polarized MT network, along which Dynein transports oocyte determinants into the presumptive oocyte. Thus, Patronin amplifies a weak fusome anisotropy to break symmetry and select one cell to become the oocyte

The oxidation status of Mic19 regulates MICOS assembly.

The function of mitochondria depends on the proper organization of mitochondrial membranes. The morphology of the inner membrane is regulated by the recently identified mitochondrial contact site and cristae organizing system (MICOS) complex. MICOS mutants exhibit alterations in crista formation, leading to mitochondrial dysfunction. However, the mechanisms that underlie MICOS regulation remain poorly understood. MIC19, a peripheral protein of the inner membrane and component of the MICOS complex, was previously reported to be required for the proper function of MICOS in maintaining the architecture of the inner membrane. Here, we show that human and yeast MIC19 proteins undergo oxidation in mitochondria and require the mitochondrial intermembrane space assembly (MIA) pathway, which couples the oxidation and import of mitochondrial intermembrane space proteins for mitochondrial localization. Detailed analyses identified yeast Mic19 in two different redox forms. The form that contains an intramolecular disulfide bond is bound to Mic60 of the MICOS complex. Mic19 oxidation is not essential for its integration into the MICOS complex but plays a role in MICOS assembly and the maintenance of proper inner membrane morphology. These findings suggest that Mic19 is a redox-dependent regulator of MICOS function

Mitochondrial protein abundance gradients require the distribution of separated mitochondria

Mitochondria are highly dynamic organelles that interchange their contents mediated by fission and fusion. However, it has previously been shown that the mitochondria of cultured human epithelial cells exhibit a gradient in the relative abundance of several proteins, with the perinuclear mitochondria generally exhibiting a higher protein abundance than the peripheral mitochondria. The molecular mechanisms that are required for the establishment and the maintenance of such inner-cellular mitochondrial protein abundance gradients are unknown. We verified the existence of inner-cellular gradients in the abundance of clusters of the mitochondrial outer membrane protein Tom20 in the mitochondria of kidney epithelial cells from an African green monkey (Vero cells) using STED nanoscopy and confocal microscopy. We found that the Tom20 gradients are established immediately after cell division and require the presence of microtubules. Furthermore, the gradients are abrogated in hyperfused mitochondrial networks. Our results suggest that inner-cellular protein abundance gradients from the perinuclear to the peripheral mitochondria are established by the trafficking of individual mitochondria to their respective cellular destination

The process gg -> WW as a background to the Higgs signal at the LHC

The production of W pairs from the one-loop gluon fusion process is studied. Formulas are presented for the helicity amplitudes keeping the top mass finite, but all other quark masses zero. The correlations among the leptons coming from the W bosons are kept. The contribution of this background to the Higgs boson search in the WW decay mode at the LHC is estimated by applying the cuts foreseen in experimental searches using the PYTHIA Monte Carlo program. Kinematic distributions for the final state leptons are compared to those of the Higgs boson signal and of the q qbar -> WW background. After applying final cuts, the gg background is found to be large, at the level of 35% of the q qbar background.The characteristics of the gg background are very similar to those of the signal. Therefore, an experimental normalization of this background component appears to be very difficult and the uncertainty must largely be determined by theory. As a result, the significance of a Higgs signal in the gg -> H -> WW mode at the LHC is reduced.Comment: 24 pages, 4 figure

Determination of the laser-induced damage threshold of polymer optical fibers

Investigating the properties of manufactured polymer optical fibers is essential to determine proper areas of application. Using pulsed laser radiation, especially with respect to laser activity in optical fibers, the maximum acceptable transmittable energy without inducing damage is of particular interest. Therefore, this work is related to laser-induced damage in polymer optical fibers at a wavelength of 532 nm and a pulse duration of 7.3 ns. In particular, the influence of the coupling condition on the transmittable pulse energy and the damage behavior applying an R-on-1 test procedure are analyzed in this study. The obtained results give information about the long-Term behavior and will be used to optimize the manufacturing process. © COPYRIGHT SPI

A renormalization group approach to time dependent transport through correlated quantum dots

We introduce a real time version of the functional renormalization group which allows to study correlation effects on nonequilibrium transport through quantum dots. Our method is equally capable to address (i) the relaxation out of a nonequilibrium initial state into a (potentially) steady state driven by a bias voltage and (ii) the dynamics governed by an explicitly time-dependent Hamiltonian. All time regimes from transient to asymptotic can be tackled; the only approximation is the consistent truncation of the flow equations at a given order. As an application we investigate the relaxation dynamics of the interacting resonant level model which describes a fermionic quantum dot dominated by charge fluctuations. Moreover, we study decoherence and relaxation phenomena within the ohmic spin-boson model by mapping the latter to the interacting resonant level model

Reproductive arrest and stress resistance in winter-acclimated Drosophila suzukii.

Overwintering insects must survive the multiple-stress environment of winter, which includes low temperatures, reduced food and water availability, and cold-active pathogens. Many insects overwinter in diapause, a developmental arrest associated with high stress tolerance. Drosophila suzukii (Diptera: Drosophilidae), spotted wing drosophila, is an invasive agricultural pest worldwide. Its ability to overwinter and therefore establish in temperate regions could have severe implications for fruit crop industries. We demonstrate here that laboratory populations of Canadian D. suzukii larvae reared under short-day, low temperature, conditions develop into dark \u27winter morph\u27 adults similar to those reported globally from field captures, and observed by us in southern Ontario, Canada. These winter-acclimated adults have delayed reproductive maturity, enhanced cold tolerance, and can remain active at low temperatures, although they do not have the increased desiccation tolerance or survival of fungal pathogen challenges that might be expected from a more heavily melanised cuticle. Winter-acclimated female D. suzukii have underdeveloped ovaries and altered transcript levels of several genes associated with reproduction and stress. While superficially indicative of reproductive diapause, the delayed reproductive maturity of winter-acclimated D. suzukii appears to be temperature-dependent, not regulated by photoperiod, and is thus unlikely to be \u27true\u27 diapause. The traits of this \u27winter morph\u27, however, likely facilitate overwintering in southern Canada, and have probably contributed to the global success of this fly as an invasive species

Laser-induced degradation and damage morphology in polymer optical fibers

The radiation of pulsed laser systems can generate changes in various materials. On the one hand, these modifications can be used for a variety of applications i.e. laser welding, cutting and many more [1]. The precision and quality depends on the material and laser parameters. On the other hand, material changes are not always desired in other applications. When using optical materials such as optical fibers as a light guide or as a sensor, laser-induced damage effects inside the fiber are to be prevented to ensure constant light guidance and the reliable monitoring of a desired parameter. Therefore, investigations for quality assurance need to be performed. For this reason, this work investigates laserinduced damage in polymer optical fibers (POF) using a nanosecond pulsed laser system at a wavelength of 532 nm. The impact of different laser and fiber parameters on the long-term degradation behavior is observed. In addition, the overall degradation behavior as well as the knowledge gained by analyzing the damage morphology and distribution will be used to obtain a better understanding of the damage mechanisms