Search results for " overtones"

showing 2 items of 2 documents

Enhancing the sound absorption of small-scale 3D printed acoustic metamaterials based on Helmholtz resonators

2018

Acoustic metamaterials have recently become of interest for their ability to attenuate sound by breaking the mass-density law. In this paper, acoustic metamaterials based on Helmholtz resonators and capable of attenuating sound up to 30 dB are fabricated for sound absorption applications in the small scale. The proposed metamaterials are subwavelength at a factor of $\lambda /12$ with respect to the lateral dimension of the units. The directional response due to the position of the acoustic source on the sound attenuation provided by the metamaterial is investigated by controlling the location of a loudspeaker with a robot arm. To enhance and broaden the absorption bands, structural modific…

0209 industrial biotechnologyAbsorption (acoustics)AcousticsTKPhysics::Optics02 engineering and technology01 natural scienceslaw.inventionResonatorsymbols.namesake020901 industrial engineering & automationlawElectrical and Electronic EngineeringInstrumentationStereolithographyPhysicsAttenuation010401 analytical chemistryMetamaterial0104 chemical sciencesComputer Science::SoundHelmholtz free energy3D printing Acoustic metamaterials Helmholtz resonators membranes overtones sound absorption stop bandssymbolsLoudspeakerAcoustic attenuation
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Retinal Vibrations in Bacteriorhodopsin are Mechanically Harmonic but Electrically Anharmonic: Evidence From Overtone and Combination Bands

2021

Fundamental vibrations of the chromophore in the membrane protein bacteriorhodopsin (BR), a protonated Schiff base retinal, have been studied for decades, both by resonance Raman and by infrared (IR) difference spectroscopy. Such studies started comparing vibrational changes between the initial BR state (all-trans retinal) and the K intermediate (13-cis retinal), being later extended to the rest of intermediates. They contributed to our understanding of the proton-pumping mechanism of BR by exploiting the sensitivity of fundamental vibrational transitions of the retinal to its conformation. Here, we report on new bands in the 2,500 to 1,800 cm−1 region of the K-BR difference FT-IR spectrum.…

bacteriorhodopsinQH301-705.5anharmonicityFTIR—spectroscopymicrobial rhodopsinscombinations and overtonesBiochemistry Genetics and Molecular Biology (miscellaneous)Biochemistryretinalanharmonic vibrational calculationsvibrational quasi-degenerate perturbation theoryMolecular BiosciencesBiology (General)Molecular BiologyOriginal ResearchFrontiers in Molecular Biosciences
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