Non-linear optical frequency conversion crystals for space applications

Reliable, long term operation of high-power laser systems in the Earth orbit is not a straightforward task as the space environment entails various risks for optical surfaces and bulk materials. The increased operational risk is, among others, due to the presence of high energy radiation penetrating the metallic shielding of satellites and inducing absorption centers in the bulk of optical components, and vacuum exposure which can deteriorate coating performance. Comprehensive testing for analyzing high-energy radiation effects and mitigation procedures were performed on a set of frequency conversion crystals and are discussed in this paper. In addition to a general resistance to space environmental effects, the frequency conversion crystals were subjected to a comparative analysis on optimum third harmonic efficiency, starting from pulsed 1064 nm laser radiation, with the goal of exceeding a value of 30 %. Concomitant modeling supported the selection of crystal parameters and the definition of crystal dimensions

Prefabricated Timber Frame Façade with Integrated Active Components for Minimal Invasive Renovations

AbstractThe objective of the EU-funded project iNSPiRe is to tackle the problem of high-energy consumption by producing systemic renovation packages that can be applied to residential and tertiary buildings. The renovation packages aim to reduce the primary energy consumption of a building to lower than 50 kWh/(m2 a) for ventilation, heating/cooling, domestic hot water and lighting. The packages need to be suitable for a various climates in Europe while ensuring optimum comfort for the building users. One major aspect of iNSPiRe is the development of multifunctional renovation kits that make use of innovative envelope technologies, energy generation (including RES integration) and energy distribution systems. The technologies and renovation approaches developed by the iNSPiRe project will be installed and tested in three demo buildings. In this work the development, testing and modelling of a timber frame façade with integrated mechanical ventilation with heat recovery (MVHR) and a micro- heat pump (μ-HP) is presented. Three functional models were built for testing in so-called PASSYS test cells for the assessment of the thermal performance and for testing in the acoustic test rig at UIBK. Experimental results are used to validate a physical heat pump and MVHR model. The μ-HP with MVHR is a cost-effective and compact solution for ventilation and heating/cooling for buildings with high standard such as PH or EnerPHit. The integration of active components such as the MVHR and μ-HP in a prefabricated façade enables minimized space use and reducing installation time and effort

Algebraic order and the Berezinskii-Kosterlitz-Thouless transition in an exciton-polariton gas

We observe quasi-long range coherence in a two-dimensional condensate of exciton-polaritons. Our measurements are the first to confirm that the spatial correlation algebraically decays with a slow power-law, whose exponent quantitatively behaves as predicted by the Berezinskii-Kosterlitz-Thouless theory. The exciton-polaritons are created by non-resonant optical pumping of a micro-cavity sample with embedded GaAs quantum-wells at liquid helium temperature. Michelson interference is used to measure the coherence of the photons emitted by decaying exciton-polaritons

Isolating key features in urban traffic dynamics and noise emission: a study on a signalized intersection and a roundabout

Urban planning and transport network are considered as major urban systems with great impact on the sound environment. Most of the work done in transport management and traffic design to improve the quality of both outdoor and indoor sound environment relies on conventional noise mapping software outcomes. This type of tool is based on macroscopic traffic modelling, considering traffic flow as a steady noise source. A commonly implemented practice intended to reduce noise in urban areas is the transformation of a signalised crossing into a roundabout. However, the individual vehicle behaviour becomes relevant in these decisions, where high time-pattern fluctuations are responsible for changes in the quality of the urban sound environment and of human activity. The present paper studies a set of indicators from isolated key features in these two road traffic configurations and their possible variations (acceleration, heavy vehicles, etc.). A VISSIM microscopic traffic simulation model combined with the CNOSSOS-EU noise emission model is used to test cases based on real situations, now in development stage. The approach presented aims to provide stronger basis in the reasoning behind why different road traffic configurations adopted in the urban planning practice give certain effects in relation to the urban sound environment

Background traffic noise synthesis

When planning the development of urban areas, it is important to assess the future acoustic environment. Currently, this evaluation is achieved with the help of acoustic indicators, but they do not suffice for a holistic description of the perceived sound environment. New indicators can be extracted through listening tests and analysis of different acoustic scenarios. However, generating such scenarios using auralisation models for outdoors sound propagation is often computationally highly demanding. Here, a simplified auralisation model is described, focusing on background traffic noise simulation on flat city scenarios. For computational efficiency, the proposed method partly relies on physical models for air attenuation, ground effects and spherical spreading. The doppler effect and the contribution of individual vehicle pass-bys are achieved with the help of modulation transfer functions, and spatial imagery is realised by both non-corellated phase spectra and modulation transfer functions. Power profiles from measurements are used to model rolling noise. The proposed model is assessed through listening tests against the LISTEN demonstrator on its perceived speed and distance from the listener. The perceived speed is matching better to the LISTEN between 70 kmph and 90 kmph, while above 300 m and up to 900 m from the source, the distance is more correctly guessed from the subjects

Flexibility of the N-Terminal mVDAC1 Segment Controls the Channel’s Gating Behavior

Since the solution of the molecular structures of members of the voltage dependent anion channels (VDACs), the N-terminal α-helix has been the main focus of attention, since its strategic location, in combination with its putative conformational flexibility, could define or control the channel’s gating characteristics. Through engineering of two double-cysteine mVDAC1 variants we achieved fixing of the N-terminal segment at the bottom and midpoint of the pore. Whilst cross-linking at the midpoint resulted in the channel remaining constitutively open, cross-linking at the base resulted in an “asymmetric” gating behavior, with closure only at one electric field´s orientation depending on the channel’s orientation in the lipid bilayer. Additionally, and while the native channel adopts several well-defined closed states (S1 and S2), the cross-linked variants showed upon closure a clear preference for the S2 state. With native-channel characteristics restored following reduction of the cysteines, it is evident that the conformational flexibility of the N-terminal segment plays indeed a major part in the control of the channel’s gating behavior

Bragg Scattering as a Probe of Atomic Wavefunctions and Quantum Phase Transitions in Optical Lattices

We have observed Bragg scattering of photons from quantum degenerate $^{87}$Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wavefunction whose position and momentum width is Heisenberg-limited. The spatial coherence of the wavefunction leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence.Comment: 5 pages, 4 figure

Investigating Low Frequency Sound from Traffic in a Living Room Lab

No abstract availabl