Super resolution imaging of genetically labeled synapses in drosophila brain tissue

Understanding synaptic connectivity and plasticity within brain circuits and their relationship to learning and behavior is a fundamental quest in neuroscience. Visualizing the fine details of synapses using optical microscopy remains however a major technical challenge. Super resolution microscopy opens the possibility to reveal molecular features of synapses beyond the diffraction limit. With direct stochastic optical reconstruction microscopy, dSTORM, we image synaptic proteins in the brain tissue of the fruit fly, Drosophila melanogaster. Super resolution imaging of brain tissue harbors difficulties due to light scattering and the density of signals. In order to reduce out of focus signal, we take advantage of the genetic tools available in the Drosophila and have fluorescently tagged synaptic proteins expressed in only a small number of neurons. These neurons form synapses within the calyx of the mushroom body, a distinct brain region involved in associative memory formation. Our results show that super resolution microscopy, in combination with genetically labeled synaptic proteins, is a powerful tool to investigate synapses in a quantitative fashion providing an entry point for studies on synaptic plasticity during learning and memory formation

Semiconductor saturable absorber mirror structures with low saturation fluence

We present two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation fluence than classical SESAM devices. Design considerations and characterization data are presented. These devices are particularly suited for passively mode-locked lasers with ultra-high repetition rate

Influence of the 6^1S_0-6^3P_1 Resonance on Continuous Lyman-alpha Generation in Mercury

Continuous coherent radiation in the vacuum-ultraviolet at 122 nm (Lyman-alpha) can be generated using sum-frequency mixing of three fundamental laser beams in mercury vapour. One of the fundamental beams is at 254 nm wavelength, which is close to the 6^1S_0-6^3P_1 resonance in mercury. Experiments have been performed to investigate the effect of this one-photon resonance on phasematching, absorption and the nonlinear yield. The efficiency of continuous Lyman-alpha generation has been improved by a factor of 4.5.Comment: 8 pages, 7 figure

Outlook for inverse design in nanophotonics

Recent advancements in computational inverse design have begun to reshape the landscape of structures and techniques available to nanophotonics. Here, we outline a cross section of key developments at the intersection of these two fields: moving from a recap of foundational results to motivation of emerging applications in nonlinear, topological, near-field and on-chip optics.Comment: 13 pages, 6 figure

Do oaks Quercus spp., dead wood and fruiting common ivy Hedera helix affect habitat selection of the middle spotted woodpecker Dendrocopos medius?

Over the past centuries, many forests in Europe have undergone massive changes resulting in loss, fragmentation and degradation of habitats and a decline in biodiversity. Due to their habitat needs, woodpeckers are generally considered to be excellent indicators of forest habitat quality and biodiversity. In the EU and in Switzerland, the middle spotted woodpecker Dendrocopos medius acts as a flagship species for nature conservation in forests. After several decades of decline, the population of this indicator species more than doubled between 2002 and 2012 in the Canton of Zurich, northern Switzerland. The reasons for this positive trend are unknown. A new hypothesis states that the availability of ivy berries Hedera helix, sometimes eaten by the middle spotted woodpecker, has increased over the same time period and could have contributed to the population growth. Based on the population monitoring in the Canton of Zurich from 2012, the availability of trees with ivy at sites with and without presence of the middle spotted woodpecker was examined in eight forests. At the same time, differences in the availability of oaks Quercus sp. and standing dead trees were studied, two habitat factors well known to be important for the middle spotted woodpecker. As proxy for the availability of these three habitat factors, distances from playback points with and without woodpecker presence to the closest representatives of those resources were measured. Additionally, the distance to the closest living tree was recorded. Results revealed a significantly shorter average distance to the closest oak and, as a tendency, to the closest standing dead tree, respectively, at points with middle spotted woodpecker presence than at points without observations of the species. In contrast, neither the mean distance to the closest tree with ivy nor the mean distance to the closest living tree differed between playback points with and without response from the middle spotted woodpecker. Counting annual rings on cross-sections of 10 ivy stems revealed an average age of 23 years, suggesting that availability of ivy on trees might have increased over the last two decade. This study confirmed that large oaks and standing dead trees are important for the occurrence of the middle spotted woodpecker, whereas the availability of trees with fruiting ivy did not contribute significantly to explaining the presence or absence of the species

Passively mode-locked 40-GHz Er : Yb : glass laser

ISSN:0946-2171ISSN:1432-0649ISSN:0721-7269ISSN:0340-379

Practical low-noise stretched-pulse Yb³⁺ doped fiber laser

We report on the development of what we consider to be a practical and highly stable stretched-pulse laser based on Yb3+-doped silica fiber. The Fabry Perot cavity uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting and incorporates a diffraction grating pair to compensate for the normal dispersion of the fiber. Use of a single-mode grating-stabilized telecommunications-qualified pump laser diode ensures reliable, low-noise operation ( 0.05 amplitude fluctuations at 10-Hz measurement bandwidth). The laser generates high-quality, 60-pJ pulses of 110 fs duration at a repetition rate of 54 MHz (3-mW average power)