Generation of all-fiber ultrafast pulses at 2 µm by soliton self-frequency shift in highly nonlinear silica fiber

An efficient and straightforward method to obtain all-fiber pulsed sources at 2 μm is presented and experimentally demonstrated. It is based on the soliton self-frequency shift effect in a highly nonlinear fiber. The output power of a supercontinuum source is previously increased by an optimized homemade thulium-doped fiber amplifier. By coupling the amplified output power in a highly nonlinear fiber, the spectrum is shifted toward 130 nm and the spectral peak is located at 2014 nm. The power conversion factor reaches values as high as 0.93, without employing additional amplifiers. The mean spectral power of the 2 μm source reaches −4.6 dBm nm−1 (0.35 mW nm−1), its output power is 38 mW and the peak power of each pulse is higher than 27 kW

Effect of long range spatial correlations on the lifetime statistics of an emitter in a two-dimensional disordered lattice

The effect of spatial correlations on the Purcell effect in a bidimensional dispersion of resonant nanoparticles is analyzed. We perform extensive calculations on the fluorescence decay rate of a point emitter embedded in a system of nanoparticles statistically distributed according to a simple 2D lattice-gas model near the critical point. For short-range correlations (high temperature thermalization) the Purcell factors present a long-tailed statistic which evolves towards a bimodal distribution when approaching the critical point where the spatial correlation length diverges. Our results suggest long-range correlations as a possible origin of the large fluctuations of experimental decay rates in disordered metal films.Comment: 6 pages, 5 figure

Phase-transitions in spin-crossover thin films probed by graphene transport measurements

Future multi-functional hybrid devices might combine switchable molecules and 2D material-based devices. Spin-crossover compounds are of particular interest in this context since they exhibit bistability and memory effects at room temperature while responding to numerous external stimuli. Atomically-thin 2D materials such as graphene attract a lot of attention for their fascinating electrical, optical, and mechanical properties, but also for their reliability for room-temperature operations. Here, we demonstrate that thermally-induced spin-state switching of spin-crossover nanoparticle thin films can be monitored through the electrical transport properties of graphene lying underneath the films. Model calculations indicate that the charge carrier scattering mechanism in graphene is sensitive to the spin-state dependence of the relative dielectric constants of the spin-crossover nanoparticles. This graphene sensor approach can be applied to a wide class of (molecular) systems with tunable electronic polarizabilities.Comment: main text: 13 pages, 5 figures ; SI: 14 pages, 12 figure

Vortex solutions in the noncommutative torus

Vortex configurations in the two-dimensional torus are considered in noncommutative space. We analyze the BPS equations of the Abelian Higgs model. Numerical solutions are constructed for the self-dual and anti-self dual cases by extending an algorithm originally developed for ordinary commutative space. We work within the Fock space approach to noncommutative theories and the Moyal-Weyl connection is used in the final stage to express the solutions in configuration space.Comment: 18 pages, 5 figure

Crown ether-functionalized complex emulsions as an artificial adaptive material platform

Responsive materials capable of autonomously regulating and adapting to molecular recognition-induced chemical events hold great promise in the design of artificial chemo-intelligent life-like soft material platforms. In this context, the design of a synthetically minimal artificial emulsion platform that, regulated by interfacial supramolecular recognition events, is capable to autonomously and reversibly adapt to its chemical environment is reported. The systems exhibit programmed up- and down-regulating capabilities that are realized via selective assembly of synthesized crown ether surfactants onto one hemisphere of anisotropic biphasic emulsion droplets. Dynamic and reversible interfacial host–guest complexation of, for example, metal and ammonium ions or amino acids transduce into interface-triggered morphological reconfigurations of the complex emulsion droplets, which mediate their ability to selectively present, hide, or expand liquid–liquid interfaces. The separate responsive modalities are then used to showcase the utility of such adaptive soft material platforms for a self-regulated uptake and release of metal ions or phase-transfer catalysts, a biomimetic recognition of biomolecules including amino acids, carbohydrates, and antibodies, and for triggered surface-encoded payload release applications

Grafitos sobre Terra Sigillata Hispánica hallados en un vertedero del siglo I en la casa de Hippolytus (Complutum)

Presentamos en este estudio un conjunto de materiales inéditos del yacimiento romano de "hippolytus". Estos grafitos, presentes en la mayoría de los establecimientos romanos, no han recibido, en algunas ocasiones, la debida atención por parte de los investigadores. Su análisis pormenorizado, junto a la evidente ventaja de provenir de un contexto arqueológico cerrado y bien definido, nos acerca al conocimiento de las relaciones sociales, parentesco y origen de los moradores de este nuevo enclave altoimperial complutense

Dominant Color Extraction with K-Means for Camera Characterization in Cultural Heritage Documentation

The camera characterization procedure has been recognized as a convenient methodology to correct color recordings in cultural heritage documentation and preservation tasks. Instead of using a whole color checker as a training sample set, in this paper, we introduce a novel framework named the Patch Adaptive Selection with K-Means (P-ASK) to extract a subset of dominant colors from a digital image and automatically identify their corresponding chips in the color chart used as characterizing colorimetric reference. We tested the methodology on a set of rock art painting images captured with a number of digital cameras. The characterization approach based on the P-ASK framework allows the reduction of the training sample size and a better color adjustment to the chromatic range of the input scene. In addition, the computing time required for model training is less than in the regular approach with all color chips, and obtained average color differences ΔE∗ab lower than two CIELAB units. Furthermore, the graphic and numeric results obtained for the characterized images are encouraging and confirms that the P-ASK framework based on the K-means algorithm is suitable for automatic patch selection for camera characterization purposes