A return toward equilibrium in a 2D Rayleigh–Taylor instability for compressible fluids with a multidomain adaptive Chebyshev method

We numerically simulate a single-mode Rayleigh–Taylor instability between compressible miscible fluids with a highly accurate self-adaptive pseudospectral Chebyshev multidomain method in two two-dimensional boxes at small aspect ratios. The simulations are started from rest and pursued until the return toward mechanical equilibrium of the mixing. Four regimes—linear and weakly nonlinear, nonlinear steady bubble rise, return toward equilibrium, and finally a system of acoustic waves—can be identified. We show that this one-dimensional system of stationary acoustic waves is damped by the physical viscosity. This provides a reference solution.      

Structure and dynamics of a bidimensional pattern of liquid columns

We report an experimental study of the structure and dynamics of a bidimensional array of liquid columns. This pattern is formed below a flat porous plate continuously supplied with liquid. It exhibits a marked hexagonal tendency. Its typical wavelength is close to that of the most dangerous mode of the Rayleigh–Taylor instability of a thin viscous layer hanging below a plate, defined by the competition between gravity and surface tension. Collective dynamical behaviors are also evidenced, involving oscillations of the column positions, columns migrations, coalescences and nucleations. Quantitative comparisons are presented with the equivalent one-dimensional pattern formed below the perimeter of an overflowing dish (circular fountain experiment).

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Characterization of a non-isothermal water spray by global rainbow thermometry

The paper shows that the global rainbow thermometry (GRT) technique is a non-intrusive measurement technique, which provides the entire size distribution and the mean temperature of an ensemble of liquid droplets suspended in a gaseous phase. In this aim a non-isothermal flat-fan water spray is characterized by means of the GRT and the results obtained, both for temperature and for size, are in agreement with predictions already done by other authors. Moreover, it is shown that the main source of uncertainty for the GRT measurements is due to the systematic error committed in the determination of the GRT reference angle.     

A connectionist study on the role of pitch in infant-directed speech

Infant-directed speech (IDS) is believed to facilitate language learning. However, the benefit may be either due to clearer acoustic correlates to linguistic structures, or simply increased attention from infants induced by IDS exaggerated prosody. This study investigated the pure effect of IDS pitch on lexical tone learning, with attentional/affective factors removed by using artificial neural networks. Following training with the pitch of Mandarin tones in IDS versus adult-directed speech, the networks yielded equal tonal categorization for both registers. IDS pitch produced no additional linguistic support. IDS pitch appears to strictly play the non-linguistic role of attention/affect, which may indirectly benefit learning.     

Long‐Lived Circularly Polarized Phosphorescence in Helicene‐NHC Rhenium(I) Complexes: The Influence of Helicene,Halogen, and Stereochemistry on Emission Properties

The first enantiopure chiral‐at‐rhenium complexes of the form fac‐ReX(CO)₃(:C^N) have been prepared, where :C^N is a helicene‐N‐heterocyclic carbene (NHC) ligand and X=Cl or I. These have complexes show strong changes in the emission characteristics, notably strongly enhanced phosphorescence lifetimes (reaching 0.7 ms) and increased circularly polarized emission (CPL) activity, as compared to their parent chiral models lacking the helicene unit. The halogen along with its position within the dissymmetric stereochemical environment strongly affect the photophysics of the complexes, particularly the phosphorescence quantum yield and lifetime. These results give fresh insight into fine tuning of photophysical and chiroptical properties of Re‐NHC systems.     

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Synthesis of antifungal glucan synthase inhibitors from enfumafungin

An efficient, new, and scalable semisynthesis of glucan synthase inhibitors 1 and 2 from the fermentation product enfumafungin 3 is described. The highlights of the synthesis include a high-yielding ether bond-forming reaction between a bulky sulfamidate 17 and alcohol 4 and a remarkably chemoselective, improved palladium(II)-mediated Corey-Yu allylic oxidation at the highly congested C-12 position of the enfumafungin core. Multi-hundred gram quantities of the target drug candidates 1 and 2 were prepared, in 12 linear steps with 25% isolated yield and 13 linear steps with 22% isolated yield, respectively.