Upper limits of auditory rotational motion perception

Three experiments are reported, which investigated the auditory velocity thresholds beyond which listeners are no longer able to perceptually resolve a smooth circular trajectory. These thresholds were measured for band-limited noises, white noise, and harmonic sounds (HS), and in different acoustical environments. Experiments 1 and 2 were conducted in an acoustically dry laboratory. Observed thresholds varied as a function of stimulus type and spectral content. Thresholds for band-limited noises were unaffected by center frequency and equal to that of white noise. For HS, however, thresholds decreased as the fundamental frequency of the stimulus increased. The third experiment was a replication of the second in a reverberant concert hall, which produced qualitatively similar results except that thresholds were significantly higher than in the acoustically dry laboratory.     

Micro-spectrometry in the visible range with full-field optical coherence tomography for single absorbing layers

A time-domain full-field OCT adapted to the visible range and with an original configuration using an interferometric objective, that minimizes mechanical vibrations and some settings and that performs imaging without moving the sample, is presented. This setup achieves micrometer scale imaging, 1.5 μm in the axial direction and 1.2 μm in the lateral one. The principle of micro-spectrometry from OCT data by Fourier transform is described and the influence of some key data processing parameters is simulated and discussed. The experimental spectra reconstruction from tomographic data is validated by comparison with transmittance spectra. Imaging and spectra of dyes at a micrometer scale are obtained from the same data volume.     

Turbulent Scalar Mixing in a Skewed Jet in Crossflow: Experiments and Modeling

Turbulent mixing of an inclined, skewed jet injected into a crossflow is investigated using MRI-based experiments and a high-fidelity LES of the same configuration. The MRI technique provides three-dimensional fields of mean velocity and mean jet concentration. The 30° skew of the jet relative to the crossflow produces a single dominant vortex which introduces spanwise asymmetries to the velocity and concentration fields. The turbulent scalar transport of the skewed jet is investigated in further detail using the LES, which is validated against the experimental measurements. Mixing is found to be highly anisotropic throughout the jet region. Isotropic turbulent diffusivity and viscosity are used to calculate an optimal value of the turbulent Schmidt number, which varies widely over the jet region and lies mostly outside of the typically accepted range 0.7 ≤ S c _t ≤ 0.9. Finally, three common scalar flux models of increasing complexity are evaluated based on their ability to capture the anisotropy and predict the scalar concentration field of the present configuration. The higher order models are shown to better represent the turbulent scalar flux vector, leading to more accurate calculations of the concentration field. While more complex models are better able to capture the turbulent mixing, optimization of model constants is shown to significantly affect the results.     

Double-hybrid density-functional theory made rigorous

We provide a rigorous derivation of a class of double-hybrid approximations, combining Hartree-Fock exchange and second-order M?ller-Plesset correlation with a semilocal exchange-correlation density functional. These double-hybrid approximations contain only one empirical parameter and use a density-scaled correlation energy functional. Neglecting density scaling leads to a one-parameter version of the standard double-hybrid approximations. We assess the performance of these double-hybrid schemes on representative test sets of atomization energies and reaction barrier heights, and we compare to other hybrid approximations, including range-separated hybrids. Our best one-parameter double-hybrid approximation, called 1DH-BLYP, roughly reproduces the two parameters of the standard B2-PLYP or B2GP-PLYP double-hybrid approximations, which shows that these methods are not only empirically close to an optimum for general chemical applications but are also theoretically supported.     

Tiling Groupoids and Bratteli Diagrams

Let T be an aperiodic and repetitive tiling of ${{\mathbb R}^d}$ with finite local complexity. Let Ω be its tiling space with canonical transversal ${\Xi}$ . The tiling equivalence relation ${R_\Xi}$ is the set of pairs of tilings in ${\Xi}$ which are translates of each others, with a certain (étale) topology. In this paper ${R_\Xi}$ is reconstructed as a generalized “tail equivalence” on a Bratteli diagram, with its standard AF -relation as a subequivalence relation. Using a generalization of the Anderson–Putnam complex (Bellissard et al. in Commun. Math. Phys. 261:1–41, 2006) Ω is identified with the inverse limit of a sequence of finite CW-complexes. A Bratteli diagram ${{\mathcal B}}$ is built from this sequence, and its set of infinite paths ${\partial {\mathcal B}}$ is homeomorphic to ${\Xi}$ . The diagram ${{\mathcal B}}$ is endowed with a horizontal structure: additional edges that encode the adjacencies of patches in T. This allows to define an étale equivalence relation ${R_{\mathcal B}}$ on ${\partial {\mathcal B}}$ which is homeomorphic to ${R_\Xi}$ , and contains the AF-relation of “tail equivalence”.     

Integrated terahertz source based on three-wave mixing of whispering-gallery modes

We propose an integrated terahertz emitter operating at room temperature between 2.4 and 6 THz. Based on difference-frequency generation in a triply resonant Au/AlAs/GaAs/AlAs/Au microcylinder, this nonlinear source is pumped by two near-IR whispering-gallery modes that are excited by InAs quantum dots embedded in the resonator. In the vertical direction, these pump modes are due to total internal reflection at GaAs/AlAs interfaces, while the terahertz mode is confined between the metallic layers. This parametric source offers potential advantages with respect to existing terahertz sources for spectroscopic applications, such as room-temperature operation and electrical pumping.     

Single resonance monolithic Fabry-Perot filters formed by volume Bragg gratings and multilayer dielectric mirrors

A new class of Fabry-Perot filters produced by a multilayer dielectric mirror deposited on top of a reflecting volume Bragg grating is described. The first fabricated prototype for the 852 nm region demonstrates a 30 pm bandwidth, 90+% transmission at resonance, and a good agreement with theoretical simulation.     

Efficient synthesis of 3-aminocyclobut-2-en-1-ones: squaramide surrogates as potent VLA-4 antagonists

A novel series of uniquely functionalized 3-aminocyclobut-2-en-1-ones has been prepared by facile condensation of a variety of cyclobuta-1,3-diones with a phenylalanine-derived primary amine. These systems subsequently lend themselves to substitution at C-2 by reaction with a variety of electrophilic reagents including N-halosuccinimides, sulfenyl chlorides, and Eschenmoser's salt. Compounds from this novel series are potent antagonists of VLA-4. [reaction: see text]     

First zeolite carbon replica with a well resolved X-ray diffraction pattern

The present study demonstrates that for the nanocasting process with zeolites, a careful choice of the zeolite structure type (EMT) allows the formation of faithful carbon replica exhibiting up to three well resolved XRD peaks.