background: the aim of this study was to estimate the conversion rate from radiologically isolated syndrome (ris) to definite multiple sclerosis (ms). methods: during a mean (standard deviation [sd]) follow-up period of 17.4 (5.4) (range 8-29) months, 25 subjects with ris and without neurological symptom aged 22-45 year from a single-center have been examined for the occurrence of definite ms. ...

We demonstrate highly efficient generation of coherent 420 nm light via up-conversion of near-infrared lasers in a hot rubidium vapor cell. By optimizing pump polarizations and frequencies we achieve a single-pass conversion efficiency of 260% per Watt, significantly higher than in previous experiments. A full exploration of the coherent light generation and fluorescence as a function of both p...

Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequenc...

Continued progress in quantum communication and optical approaches to quantum computation, requires the development of enabling technologies for photonic quantum information processing [1]. Such resources include high efficiency single photon detectors, high-fidelity single-photon sources, high brightness sources of entanglement, and multiple microsecond optical quantum memories. Here we discus...

Up conversion is an Anti-Stokes luminescent process by which photons of low energy are piled up to generate light at a higher energy. Here we show that the addition of fluoride anions to a D2O solution of a macrocyclic erbium complex leads to the formation of a supramolecular [(ErL)2F](+) assembly in which fluoride is sandwiched between two complexes, held together by the synergistic interactio...

We give a short survey on computational techniques which can be used to solve the representation conversion problem for polyhedra up to symmetries. We in particular discuss decomposition methods, which reduce the problem to a number of lower dimensional subproblems. These methods have been successfully used by different authors in special contexts. Moreover, we sketch an incremental method, whi...