Observation of condensed phases of quasi-planar core-softened colloids

We experimentally study the condensed phases of repelling core-softened spheres in two dimensions. The dipolar pair repulsion between superparamagnetic spheres trapped in a thin cell is induced by a transverse magnetic field and softened by suitably adjusting the cell thickness. We scan a broad density range and we materialize a large part of the theoretically predicted phases in systems of core-softened particles, including expanded and close-packed hexagonal, square, chain-like, stripe/labyrinthine, and honeycomb phase. Further insight into their structure is provided by Monte Carlo simulations

Electro-optically tunable microring resonators in lithium niobate

Optical microresonators have recently attracted a growing attention in the photonics community. Their applications range from quantum electro-dynamics to sensors and filtering devices for optical telecommunication systems, where they are likely to become an essential building block. The integration of nonlinear and electro-optical properties in the resonators represents a very stimulating challenge, as it would incorporate new and more advanced functionality. Lithium niobate is an excellent candidate material, being an established choice for electro-optic and nonlinear optical applications. Here we report on the first realization of optical microring resonators in submicrometric thin films of lithium niobate. The high index contrast films are produced by an improved crystal ion slicing and bonding technique using benzocyclobutene. The rings have radius R=100 um and their transmission spectrum has been tuned using the electro-optic effect. These results open new perspectives for the use of lithium niobate in chip-scale integrated optical devices and nonlinear optical microcavities.Comment: 15 pages, 8 figure

Climate Scenarios for Switzerland CH2018 – Approach and Implications

To make sound decisions in the face of climate change, government agencies, policymakers and private stakeholders require suitable climate information on local to regional scales. In Switzerland, the development of climate change scenarios is strongly linked to the climate adaptation strategy of the Confederation. The current climate scenarios for Switzerland CH2018 - released in form of six user-oriented products - were the result of an intensive collaboration between academia and administration under the umbrella of the National Centre for Climate Services (NCCS), accounting for user needs and stakeholder dialogues from the beginning. A rigorous scientific concept ensured consistency throughout the various analysis steps of the EURO-CORDEX projections and a common procedure on how to extract robust results and deal with associated uncertainties. The main results show that Switzerland’s climate will face dry summers, heavy precipitation, more hot days and snow-scarce winters. Approximately half of these changes could be alleviated by mid-century through strong global mitigation efforts. A comprehensive communication concept ensured that the results were rolled out and distilled in specific user-oriented communication measures to increase their uptake and to make them actionable. A narrative approach with four fictitious persons was used to communicate the key messages to the general public. Three years after the release, the climate scenarios have proven to be an indispensable information basis for users in climate adaptation and for downstream applications. Potential for extensions and updates has been identified since then and will shape the concept and planning of the next scenario generation in Switzerland

Finite-wavevector Jahn-Teller-pairing and superconductivity in the cuprat es

A model interaction is proposed in which pairing is caused by a non-local Jahn-Teller (JT) -like instability due to the coupling between planar O states and knot equal to 0 phonons. Apart from pairing, the interaction is found to naturally allow metallic stripe formation. The consequences of the model for superconductivity in the cuprates are discussed. The model is shown to be consistent with numerous sets of experimental data in quite some detail.Comment: 20 pages, 6 ps figure

Reconciliation of halogen-induced ozone loss with the total-column ozone record

The observed depletion of the ozone layer from the 1980s onwards is attributed to halogen source gases emitted by human activities. However, the precision of this attribution is complicated by year-to-year variations in meteorology, that is, dynamical variability, and by changes in tropospheric ozone concentrations. As such, key aspects of the total-column ozone record, which combines changes in both tropospheric and stratospheric ozone, remain unexplained, such as the apparent absence of a decline in total-column ozone levels before 1980, and of any long-term decline in total-column ozone levels in the tropics. Here we use a chemistry–climate model to estimate changes in halogen-induced ozone loss between 1960 and 2010; the model is constrained by observed meteorology to remove the effects of dynamical variability, and driven by emissions of tropospheric ozone precursors to separate out changes in tropospheric ozone. We show that halogen-induced ozone loss closely followed stratospheric halogen loading over the studied period. Pronounced enhancements in ozone loss were apparent in both hemispheres following the volcanic eruptions of El Chichon and, in particular, Mount Pinatubo, which significantly enhanced stratospheric aerosol loads. We further show that approximately 40% of the long-term non-volcanic ozone loss occurred before 1980, and that long-term ozone loss also occurred in the tropical stratosphere. Finally, we show that halogen-induced ozone loss has declined by over 10% since stratospheric halogen loading peaked in the late 1990s, indicating that the recovery of the ozone layer is well underway

Stochastic resonance in colloidal systems

We investigate the dynamical properties of a colloidal particle in a double-well potential which is periodically modulated in time. In case of the modulation corresponding to a tilt of the potential (asymmetric modulation), stochastic resonance is observed when the modulation frequency vΩ matches one half of the Kramers frequency of the unperturbed potential. In contrast, when only the potential barrier height is modulated (symmetric modulation), no synchronization between the modulation and the particle dynamics is observed as demonstrated by the lack of a peak in the power spectrum at vΩpublishe

Stochastic resonance in colloidal systems

We investigate the dynamical properties of a colloidal particle in a double-well potential which is periodically modulated in time. In case of the modulation corresponding to a tilt of the potential (asymmetric modulation), stochastic resonance is observed when the modulation frequency $\nu_{\Omega}$ matches one half of the Kramers frequency of the unperturbed potential. In contrast, when only the potential barrier height is modulated (symmetric modulation), no synchronization between the modulation and the particle dynamics is observed as demonstrated by the lack of a peak in the power spectrum at $\nu_{\Omega}$

Nematic colloidal assemblies: towards photonic crystals and metamaterials - art. no. 69110C

Colloidal structures assembled in confined nematic liquid crystals are examined. Theoretical predictions based on Landau-type approaches are complemented with the latest studies of laser assisted colloidal assembling. Effective colloidal interactions are particularly sensitive to the confinement and external fields. Their complexity leads to numerous stable or metastable colloidal superstructures not present in isotropic solvents. Particularly important are colloidal structures coupled by entangled disclinations. Such a string-like coupling is very robust and opens new routes to assemble new photonic materials