Search results for " boson peak"

showing 3 items of 3 documents

Supercooled Water Confined in a Silica Xerogel: Temperature and Pressure Dependence of Boson Peak and of Mean Square Displacements

2013

A silica xerogel can be obtained from an alcoxide precursor (TMOS, tetramethylortosilcate) via the sol-gel method: TMOS hydrolysis and subsequent polycondensation yields a solid, disordered, porous SiO2 matrix (average pore dimensions ~20Å). Inside the pores water is trapped and the hydration level h=gr[H2O]/gr[SiO2] can be easily controlled. The presence and temperature dependence of the boson peak (BP) in xerogel confined supercooled water was studied with inelastic neutron scattering (spectrometer IN6 at ILL, Grenoble) in xerogel samples having h=0.4 and h=0.2. After careful subtraction of the contributions arising from the matrix and from quasi-elastic scattering, the BP contribution wa…

silica xerogel boson peak inelastic neutron scattering excess density of states LDL->HDL transition mean square displacements elastic neutron scattering protein dynamical transitionSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)
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Sound attenuation and anharmonic damping in solids with correlated disorder

2010

We study via self-consistent Born approximation a model for sound waves in a disordered environment, in which the local fluctuations of the shear modulus G are spatially correlated with a certain correlation length The theory predicts an enhancement of the density of states over Debye's omega(2) law (boson peak) whose intensity increases for increasing correlation length, and whose frequency position is shifted downwards as lg. Moreover, the predicted disorder-induced sound attenuation coefficient r(k) obeys a universal scaling law F(k) = f (ke) for a given variance of G. Finally, the inclusion of the lowest-order contribution to the anharmonic sound damping into the theory allows us to rec…

Physicssound attenuation; anharmonic interactions; vibrational properties of disordered solids; boson peakPhysics and Astronomy (miscellaneous)Condensed matter physicsvibrational properties of disordered solidsAnharmonicity02 engineering and technology021001 nanoscience & nanotechnologyCondensed Matter Physics01 natural sciencessound attenuationlcsh:QC1-999boson peakAmorphous solidPosition (vector)0103 physical sciencesBoson peak010306 general physics0210 nano-technologylcsh:PhysicsAcoustic attenuationanharmonic interactionsCondensed Matter Physics
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The Boson Peak of Amyloid Fibrils: Probing the Softness of Protein Aggregates by Inelastic Neutron Scattering

2014

Proteins and polypeptides are characterized by low-frequency vibrations in the terahertz regime responsible for the so-called "boson peak". The shape and position of this peak are related to the mechanical properties of peptide chains. Amyloid fibrils are ordered macromolecular assemblies, spontaneously formed in nature, characterized by unique biological and nanomechanical properties. In this work, we investigate the effects of the amyloid state and its polymorphism on the boson peak. We used inelastic neutron scattering to probe low-frequency vibrations of the glucagon polypeptide in the native state and in two different amyloid morphologies in both dry and hydrated sample states. The dat…

AmyloidPhysics::Biological PhysicsQuantitative Biology::BiomoleculesChemistryProtein dynamicsNeutron diffractionNeutron scatteringProtein aggregationFibrilVibrationAmyloid Protein dynamics collective motions boson peakInelastic neutron scatteringSurfaces Coatings and FilmsNeutron DiffractionMicroscopy Electron TransmissionChemical physicsMolecular vibrationSpectroscopy Fourier Transform InfraredMaterials ChemistryNative statePhysical and Theoretical ChemistryAtomic physics
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