Acoustic analysis by spherical microphone array processing of room impulse responses

Spherical microphone arrays have been recently used for room acoustics analysis, to detect the direction-of-arrival of early room reflections, and compute directional room impulse responses and other spatial room acoustics parameters. Previous works presented methods for room acoustics analysis using spherical arrays that are based on beamforming, e.g., delay-and-sum, regular beamforming, and Dolph-Chebyshev beamforming. Although beamforming methods provide useful directional selectivity, optimal array processing methods can provide enhanced performance. However, these algorithms require an array cross-spectrum matrix with a full rank, while array data based on room impulse responses may not satisfy this condition due to the single frame data. This paper presents a smoothing technique for the cross-spectrum matrix in the frequency domain, designed for spherical microphone arrays, that can solve the problem of low rank when using room impulse response data, therefore facilitating the use of optimal array processing methods. Frequency smoothing is shown to be performed effectively using spherical arrays, due to the decoupling of frequency and angular components in the spherical harmonics domain. Experimental study with data measured in a real auditorium illustrates the performance of optimal array processing methods such as MUSIC and MVDR compared to beamforming.     

Light‐triggered stabilization of microgel aggregates

Supramolecular assembly holds great potential in many technological applications. Such structures, however, tend to destabilize in dynamic environments due to weak interactions between their constituent entities. We report on a highly modular and biofriendly chemistry for the stabilization of supramolecular microgel aggregates. Upon irradiation, these structures undergo intermolecular cross‐linking, providing an efficient mechanism for stabilization.     

Selective CH Functionalization of Methane,Ethane, and Propane by a Perfluoroarene Iodine(III) Complex

Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate esters is achieved by a homogeneous hypervalent iodine(III) complex in non‐superacidic (trifluoroacetic acid) solvent. The reaction is highly selective for ester formation (>99 %). In the case of ethane, greater than 0.5 M EtTFA can be achieved. Preliminary kinetic analysis and density functional calculations support a nonradical electrophilic CH activation and iodine alkyl functionalization mechanism.     

Coiled to diffuse: brownian motion of a helical bacterium

We employ real-time three-dimensional confocal microscopy to follow the Brownian motion of a fixed helically shaped Leptospira interrogans (LI) bacterium. We extract from our measurements the translational and the rotational diffusion coefficients of this bacterium. A simple theoretical model is suggested, perfectly reproducing the experimental diffusion coefficients, with no tunable parameters. An older theoretical model, where edge effects are neglected, dramatically underestimates the observed rates of translation. Interestingly, the coiling of LI increases its rotational diffusion coefficient by a factor of 5, compared to a (hypothetical) rectified bacterium of the same contour length. Moreover, the translational diffusion coefficients would have decreased by a factor of ～1.5, if LI were rectified. This suggests that the spiral shape of the spirochaete bacteria, in addition to being employed for their active twisting motion, may also increase the ability of these bacteria to explore the surrounding fluid by passive Brownian diffusion.     

The structure of vincarodine

The structure of vincarodine has been determined to be 1 by an investigation of its IR.-, UV.-, ¹H- and ¹³C-NMR.- and mass spectra. A ¹³C-NMR. analysis has been performed on the bases vincamine ( 2 ), epivincine ( 9 ), 14, 15-dehydrovincine ( 7 ) and its 16-epimer ( 8 ).     

A theoretical study of three and four proton donors on linear HX···BeH2···HX and bifurcate BeH2···2HX trimolecular dihydrogen-bonded complexes with X?=?CN and NC

The interaction phenomenon H^−δ···H^+δ between two hydrogen atoms binding each other is well-known in dihydrogen-bonded complexes. Either by experimental or theoretical viewpoint, dihydrogen bonds are often known as directional or bifurcate interactions. Regarding the beryllium hydride BeH₂, its capacity to form bimolecular complexes with proton donors has been demonstrated, but in some cases, trimolecular complexes are also characterized in a minimum of the potential energy surface. As such, in this work is presented a theoretical study about the formation of trimolecular dihydrogen complexes with three hydrogen centers. By taking into account the beryllium hydride BeH₂ as proton acceptor, two classical proton donors were chosen, HCN and HNC. The great goal of this work is the analysis of two dihydrogen complexes types: bifurcate BeH₂···2HX and linear HX···BeH₂···HX. In these systems, it is discussed the capacity of one hydride H^−δ (H–Be–H^−δ) to interact simultaneously with two proton donors, as well as when two hydrides H^−δ (^−δH–Be–H^−δ) form linear dihydrogen bonds. In this context, the analysis of the vibrational harmonic spectrum at B3LYP/6-311 ++G(3d,3p) level of theory and the interpretation of the topological parameters derived from Quantum Theory of Atoms in Molecules (QTAIM) aided us to determine which is the most stable trimolecular complex, either bifurcate or linear. Moreover, quantification of charge transfer measured by the QTAIM formalism as well as by ChelpG calculations also were used with the purpose to justify infrared effects, such as red-shift and blue-shift stretch modes on donors (HCN and HNC) and acceptors (BeH₂) of protons.     

On productively Lindelöf spaces

The class of spaces such that their product with every Lindelöf space is Lindelöf is not well-understood. We prove a number of new results concerning such productively Lindelöf spaces with some extra property, mainly assuming the Continuum Hypothesis.