Impact of optical tissue clearing on the Brillouin signal from biological tissue samples

Brillouin spectroscopy is a well-established technology in condensed matter physics to characterize the mechanical properties of inert materials, and it has been extended very recently to the study of biological samples. Transparency is beneficial for samples to be properly analyzed by Brillouin spectroscopy. Here, we explored the efficacy of optical tissue clearing techniques to improve the acquisition of Brillouin spectra from biological tissues in order to analyze their biomechanical properties. We describe the first application of Brillouin scattering to optically cleared biological tissues with CUBIC protocol. We conclude that, within the range of error, tissue clearing does not modify the mechanical properties of the studied biological tissues.Ministerio de Ciencia, Innovación y Universidades, the Pro CNIC Foundation, Severo Ochoa Center of Excellence (SEV-2015-0505); ISCIII-FIS grants PI18/00462 co-financed by ERDF, European Union (FEDER) Funds from the European Commission, European Union, “A way of making Europe”; MINECO/FEDER (MAT2015-65356-C3-1-R); Comunidad de Madrid Vol. 10, No. 6 | 1 Jun 2019 | BIOMEDICAL OPTICS EXPRESS 2681 (PHAMA 2.0-CM S2013/MIT-2740); CIBER de Salud Mental (CIBERSAM) and COSTaction CA16124

Two-Level Systems and Boson Peak Remain Stable in 110-Million-Year-Old Amber Glass

The two most prominent and ubiquitous features of glasses at low temperatures, namely the presence of tunneling two-level systems and the so-called boson peak in the reduced vibrational density of states, are shown to persist essentially unchanged in highly stabilized glasses, contrary to what was usually envisaged. Specifically, we have measured the specific heat of 110 million-year-old amber samples from El Soplao (Spain), both at very low temperatures and around the glass transition Tg. In particular, the amount of two-level systems, assessed at the lowest temperatures, was surprisingly found to be exactly the same for the pristine hyperaged amber as for the, subsequently, partially and fully rejuvenated samples.Comment: 22 pages, 9 figures, 2 tables (including Supplementary Material

Low-temperature thermal and elastoacoustic properties of butanol glasses: Study of position isomerism effects around the boson peak

We have concurrently measured the specific heat, the thermal conductivity, and the longitudinal and transverse sound velocities at low temperature of glasses from different isomers of butanol (n-butanol, sec-butanol and isobutanol), as well as the low-temperature specific heat for the crystals of n-butanol, isobutanol and tert-butanol. Whereas the elastic constants both for crystals and glasses are found to be almost independent of the position of the hydrogen bonds, the thermal properties at low temperatures of these glasses at a few kelvin (around the boson peak in the reduced specific heat or around the plateau in the thermal conductivity) are found to vary strongly. Our experiments clearly contradict other works or models claiming a Debye scaling of the boson peak, and hence of the excess low-temperature specific heat of glasses. Data analysis based upon the soft-potential model and its extensions allows us to estimate the Ioffe-Regel limit in these and other alcohol glasses, finding a correlation with the boson-peak position in agreement with that previously reported by other groupsWe acknowledge financial support by the Spanish Ministry of Science within program CONSOLIDER Nanociencia Molecular CSD2007-00010 and by the Comunidad de Madrid through the project NANOBIOMAGNET S2009/MAT-1726

Surface acoustic wave velocity and elastic constants of cubic GaN

We present high-resolution surface Brillouin scattering measurements on cubic GaN layers grown on GaAs substrate. By using a suitable scattering geometry, scattering by surface acoustic waves is recorded for different azimuthal angles, and the surface acoustic wave velocities are determined. A comparison of experimental results with numerical simulations of the azimuthal dependence of the surface wave velocity shows good agreement and allows a consistent set of elastic constants for c-GaN to be determined

Assessment of myocardial viscoelasticity with Brillouin spectroscopy in myocardial infarction and aortic stenosis models.

Heart diseases are associated with changes in the biomechanical properties of the myocardial wall. However, there is no modality available to assess myocardial stiffness directly. Brillouin microspectroscopy (mBS) is a consolidated mechanical characterization technique, applied to the study of the viscoelastic and elastic behavior of biological samples and may be a valuable tool for assessing the viscoelastic properties of the cardiac tissue. In this work, viscosity and elasticity were assessed using mBS in heart samples obtained from healthy and unhealthy mice (n = 6 per group). Speckle-tracking echocardiography (STE) was performed to evaluate heart deformation. We found that mBS was able to detect changes in stiffness in the ventricles in healthy myocardium. The right ventricle showed reduced stiffness, in agreement with its increased compliance. mBS measurements correlated strongly with STE data, highlighting the association between displacement and stiffness in myocardial regions. This correlation was lost in pathological conditions studied. The scar region in the infarcted heart presented changes in stiffness when compared to the rest of the heart, and the hypertrophied left ventricle showed increased stiffness following aortic stenosis, compared to the right ventricle. We demonstrate that mBS can be applied to determine myocardial stiffness, that measurements correlate with functional parameters and that they change with disease.post-print6652 K

Surface acoustic wave velocity and elastic constants of cubic GaN

We present high-resolution surface Brillouin scattering measurements on cubic GaN layers grown on GaAs substrate. By using a suitable scattering geometry, scattering by surface acoustic waves is recorded for different azimuthal angles, and the surface acoustic wave velocities are determined. A comparison of experimental results with numerical simulations of the azimuthal dependence of the surface wave velocity shows good agreement and allows a consistent set of elastic constants for c-GaN to be determined

Stress-mediated solution deposition method to stabilize ferroelectric BiFe1-xCrxO3 perovskite thin films with narrow bandgaps

Ferroelectric oxides with low bandgaps are mainly based on the BiFeO perovskite upon the partial substitution of iron with different cations. However, the structural stability of many of these perovskites is only possible by their processing at high pressures (HP, >1GPa) and high temperatures (HT, >700ºC). Preparation methods under these severe conditions are accessible to powders and bulk ceramics. However, transferring these conditions to the fabrication of thin films is a challenge, thus limiting their use in applications. Here, a chemical solution deposition method is devised, which overcomes many of these restrictions. It is based on the application of an external compressive-stress to the film sample during the thermal treatment required for the film crystallization, promoting the formation and stabilization of these HP perovskites. We demonstrate the concept on BiFeCrO (BFCO) thin films deposited on SrTiO (STO) substrates and with large chromium contents. The resulting BFCO perovskite films show narrow bandgaps (Eg∼2.57 eV) and an excellent ferroelectric response (remnant polarization, P∼ 40 μC cm). The polarized thin films under illumination present a large out-put power of ∼6.4 μW cm, demonstrating their potential for using in self-powered multifunctional devices. This stress-mediated solution deposition method can be extended to other perovskite films which are unviable under conventional deposition methods

Depletion of two-level systems in highly stable glasses with different molecular ordering

Abstract Recent findings of structural glasses with extremely high kinetic and thermodynamic stability have attracted much attention. The question has been raised as to whether the well-known, low-temperature “glassy anomalies” (attributed to the presence of two-level systems [TLS] and the “boson peak”) persist or not in these ultrastable glasses of much lower configurational entropy. To resolve previous contradictory results, we study a particular type of ultrastable glass, TPD, which can be prepared by physical vapor deposition in a highly-stable state with different degrees of layering and molecular orientation, and also as a conventional glass and in crystalline state. After a thorough characterization of the different samples prepared, we have measured their specific heat down to 0.4 K. Whereas the conventional glass exhibits the typical glassy behaviour and the crystal the expected Debye cubic dependence at very low temperatures, a strong depletion of the TLS contribution is found in both kinds of ultrastable glass, regardless of their layering and molecular ordering