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Osteomyelitis (OM) and periprosthetic joint infections (PJIs) are major public health concerns in Western countries due to increased life expectancy. Infections usually occur due to bacterial spread through fractures, implants, or blood-borne transmission. The pathogens trigger an inflammatory response that hinders bone tissue regeneration. Treatment requires surgical intervention, which involves the precise removal of infected tissue, wound cleansing, and local and systemic antibiotic administration. Staphylococcus aureus (SA) is one of the most common pathogens causing infection-induced OM and PJIs. It forms antimicrobial-resistant biofilms and is frequently found in healthcare settings. In this proof-of-concept, we present an approach based on multiple spectroscopic techniques aimed at investigating the effects of SA infection on bone tissue, as well as identifying specific markers useful to detect early bacterial colonization on the tissue surface. A cross-section of a human femoral diaphysis, with negative-culture results, was divided into three parts, and the cortical and trabecular regions were separated from each other. Two portions of each bone tissue type were infected with SA for one and seven days, respectively. Multiple techniques were used to investigate the impact of the infection on bone tissue, Brillouin–Raman microspectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were employed to assess and develop a new noninvasive diagnostic method to detect SA by targeting the bone of the host. The results indicate that exposure to SA infection significantly alters the bone structure, especially in the case of the trabecular type, even after just one day. Moreover, Raman spectral markers of the tissue damage were identified, indicating that this technique can detect the effect of the pathogens' presence in bone biopsies and pave the way for potential application during surgery, due to its nondestructive and contactless nature. [ABSTRACT FROM AUTHOR]

The densification mechanisms of silicate melts under high pressure are of key interest in understanding the evolution of the early Earth and its present‐day internal structure. Here, we report Brillouin spectroscopy‐derived transverse acoustic wave velocities VS $\left({V}_{S}\right)$ from a basaltic glass at high pressures up to 163 GPa and ambient temperature to provide insight into pressure‐induced changes in its elasticity and, by extension, its density. We find that the pressure dependence of VS ${V}_{S}$ below 110–140 GPa follows a trend nearly tantamount to those of pyrolite and Fe‐ and (Fe,Al)‐bearing MgSiO3 glasses, indicating that the large compositional differences among these glasses do not exert variable acoustic wave velocity trends. However, at higher pressures we observe a small departure from the VS ${V}_{S}$ profiles of the Al‐poor compositions toward higher acoustic wave velocities to eventually become stiffer. This pressure‐induced steepening in VS ${V}_{S}$ is comparable to that of (Mg, Fe, Al)(Si, Al)O3 glass, and suggests a possible structural change toward a denser state caused by more rapidly changing Al–O coordination in network‐forming Al. Coupled with the high Fe content in basalt, this may render basaltic melt denser than surrounding minerals in the deep lower mantle, and may provide an additional mechanism for the existence of ultralow‐velocity zones. Plain Language Summary: Silicate melts are subject to different densification mechanisms from the counterpart solids. Although less dense at ambient/low pressures and for most of the mantle, it has long been speculated that at high enough pressures a density inversion may take place, where melts may become denser than the corresponding solids. This would have profound implications for the present‐day structure and dynamics of the Earth and its evolution through geological history. We have experimentally measured the sound wave velocities of a basaltic glass, which serves as a laboratory analogue to melt, up to 163 GPa. Through comparison of our sound wave velocity‐pressure profile to other glass compositions we observe a slight deviation in steepness above 110–140 GPa to a potentially stiffer and denser state. This pressure‐induced change may be the result of changes in the Al–O coordination environment. Extrapolated onto expected melt compositions in the lower mantle, which are enriched in both Al and heavy Fe, this may render dense pools of silicate melt gravitationally stable at the bottom of the mantle. Key Points: We have carried out acoustic wave velocity measurements of a basaltic glass up to 163 GPaThe VS‐pressure profile of basalt shows close similarities to other, more depolymerized glasses up to 110–140 GPa, where it becomes steeperThis anomaly is likely induced by changes in Al–O coordination [ABSTRACT FROM AUTHOR]

Humite-group minerals play a crucial role in transporting water and fluorine to the Earth's deep mantle through slab sinking. In this study, we have used Brillouin scattering to determine the single-crystal elastic constants of four natural humite-group minerals with varying H2O and fluorite contents under ambient conditions, including one chondrodite [Mg4.88Si1.94O8(OH0.78F1.22)] (F61-Chn), one humite [Mg7.03Si3.07O12(OH1.26F0.74)] (F37-Hu), and two clinohumite [Mg8.85Ti0.19Si3.93O16(OH1.11F0.89) and Mg8.63Fe0.10Ti0.24Si3.97O16(OH1.84F0.16)] (F45-Chu and F8-Chu) samples. The adiabatic bulk (KS0) and shear (G0) moduli calculated from the elastic constants using Voigt-Reuss-Hill averages are: KS0 = 120.4(3) GPa and G0 = 74.1(5) GPa for F61-Chn, KS0 = 122.4(3) GPa and G0 = 78.4(2) GPa for F37-Hu, KS0 = 126.2(3) GPa and G0 = 79.7(2) GPa for F45-Chu, and KS0 = 120.5(3) GPa and G0 = 76.8(2) GPa for F8-Chu. Our results indicate that the addition of F leads to a noticeable increase in the elasticity of clinohumite and chondrodite, which is in contrast to the effect of H2O. Although Fe has a negligible effect on the bulk modulus of clinohumite, it can produce a substantial decrease in the shear modulus. These results provide important insights into the influence of humite-group minerals on the mantle velocity structure. Furthermore, we have investigated the effects of composition on the elasticity and sound velocities of minerals along the forsterite-brucite join in the MgO-SiO2-H2O system, confirming previous observations. Increasing H2O content along the forsterite-brucite join leads to apparent reductions in the elasticity and sound velocities. The influence of Fe on the elasticity and sound velocities of these minerals has also been evaluated. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the numerical and experimental research of the spin-wave transport in a structure composed of a gallium arsenide (GaAs) stripe lattice interfaced to an yttrium iron garnet layer. We show that this structure can be considered as an array of an infinite number of laterally coupled ferrite-semiconductor waveguides. We show that the surface wave properties for colinear propagation along the semiconductor stripes are similar to the waves in magnetic films with partial metallization. In addition, the properties of these surface waves depend on the electron concentration of the GaAs and thus may be tuned. With regard to the wave propagation at a certain angle to the GaAs stripe lattice, the Bragg resonance forms and the corresponding band gap depend on the angle between the wave to the stripes and on the GaAs electron density. The Brillouin light scattering technique was used to experimentally observe the spin-wave beam transformation, and microwave measurements support the numerical data and reveal the mechanism of the dip formation and widening of the frequency range in the spin-wave transmission. The proposed structure could be used as a reconfigurable metasurface and magnonic beam separation unit. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic lead halide perovskites (LHPs) have emerged as a highly significant class of materials due to their tunable and adaptable properties, which make them suitable for a wide range of applications. One of the strategies for tuning and optimizing LHP-based devices is the substitution of cations and/or anions in LHPs. The impact of Cs substitution at the A site on the structural, vibrational, and elastic properties of MAxCs1−xPbCl3-mixed single crystals was investigated using X-ray diffraction (XRD) and Raman and Brillouin light scattering techniques. The XRD results confirmed the successful synthesis of impurity-free single crystals, which exhibited a phase coexistence of dominant cubic and minor orthorhombic symmetries. Raman spectroscopy was used to analyze the vibrational modes associated with the PbCl6 octahedra and the A-site cation movements, thereby revealing the influence of cesium incorporation on the lattice dynamics. Brillouin spectroscopy was employed to investigate the changes in elastic properties resulting from the Cs substitution. The incorporation of Cs cations induced lattice distortions within the inorganic framework, disrupting the hydrogen bonding between the MA cations and PbCl6 octahedra, which in turn affected the elastic constants and the sound velocities. The substitution of the MA cations with smaller Cs cations resulted in a stiffer lattice structure, with the two elastic constants increasing up to a Cs content of 30%. The current findings facilitate a fundamental understanding of mixed lead chloride perovskite materials, providing valuable insights into their structural and vibrational properties. [ABSTRACT FROM AUTHOR]

Seismic tomography has shown that the shear wave velocities (Vs) under continents, especially under cratons, are extremely fast at 100–200 km depth, which is difficult to explain by low temperatures or high Mg#. Alternatively, delaminated eclogitic lower continental crust has been proposed to account for these fast seismic anomalies. However, the thermoelastic properties of jadeite which constitutes up to 60–80 mol% of clinopyroxene in the potentially delaminated lower continental crust are not well constrained. In this study, we measured the single‐crystal elasticity of jadeite by Brillouin spectroscopy under simultaneous high pressure and temperature conditions for the first time. We found that the temperature dependence of Vs of jadeite is extremely small if not negligible. The seismic velocities of the potentially delaminated lower continental crusts were subsequently modeled and found to match the widely observed fast seismic anomalies under cratons between 100 and 200 km depth. Plain Language Summary: The seismic wave velocity variation images show the potential composition and temperature heterogeneities inside the Earth. Fast shear wave velocities (∼7% higher than the global average) have been observed under continents at 100–200 km depths. A candidate explanation of this fast shear wave velocity anomaly is the existence of delaminated eclogitic lower continental crust. However, due to the lack of knowledge of the thermoelastic properties of clinopyroxene, which is the dominant mineral phase (up to 60 vol%) in delaminated eclogitic lower continental crust, evaluation of this hypothesis is difficult. Clinopyroxene in the potentially delaminated lower continental crust is jadeite‐rich (up to 60–80 mol%) due to its high Na content (2.5–3.5 wt%). In this study, we report single‐crystal elasticity of jadeite at high pressure‐temperature conditions. We found the Vs of jadeite is much higher than all the other major upper mantle minerals under upper mantle conditions. The calculated seismic velocities of the potentially delaminated lower continental crusts could easily account for the fast shear wave anomalies observed under cratons. Key Points: High pressure‐temperature single‐crystal elasticity measurements of jadeite are conducted by Brillouin spectroscopyJadeite is among the seismically fastest phases in the Earth's upper mantleDelaminated lower crust can help explain the fast seismic anomalies under cratons [ABSTRACT FROM AUTHOR]

Metasomatized mantle xenoliths containing hydrous minerals, such as amphiboles, serpentine, and phlogopite, likely represent the potential mineralogical compositions of the metasomatized upper mantle, where low seismic velocities are commonly observed. This study presents the first experimentally determined single‐crystal elasticity model of an Fe‐free near Ca, Mg‐endmember amphibole tremolite at high pressure and/or temperature conditions (maximum pressure 7.3(1) GPa, maximum temperature 700 K) using Brillouin spectroscopy. We found that sound velocities of amphiboles strongly depend on the Fe content. We then calculated the sound velocities of 441 hydrous‐mineral‐bearing mantle xenoliths collected around the globe, and quantitatively evaluated the roles that amphiboles, phlogopite and serpentine played in producing the low velocity anomalies in the metasomatized upper mantle. Plain Language Summary: Amphiboles are the most widely distributed hydrous minerals resulting from metasomatism in the upper most mantle. We measured sound velocities of tremolite (Ca, Mg endmember of the amphibole series) at high pressures and high temperatures by Brillouin spectroscopy. Based on global hydrous‐mineral‐bearing mantle xenoliths record, we quantitively evaluated the contributions of amphiboles, serpentine, and phlogopite to low velocity anomalies and water storage in the upper most mantle. We found the existence of hydrous minerals (amphiboles, serpentine, and phlogopite) remains a viable explanation for the low velocity anomalies in the upper most mantle (e.g., mid‐lithosphere discontinuity). Compared to serpentine and phlogopite, although the amount of velocity reduction caused by amphibolization is moderate, the formation of amphiboles does not require K, Al, Si‐rich environments like phlogopite, or exceedingly water‐rich environments like serpentine. Key Points: The single‐crystal elasticity of tremolite is determined by Brillouin spectroscopy up to 7.3 GPa and 700 KSound velocities of uppermost mantle amphiboles mainly depend on Fe contentHydrous minerals (amphiboles, serpentine, phlogopite) are plausible causes of the low velocity anomalies in the uppermost mantle [ABSTRACT FROM AUTHOR]

The gigahertz longitudinal elastic modulus of hydrated gelatin films as a function of water content was studied using Brillouin spectroscopy. It was found that the elastic modulus increases with increasing protein concentration. Two ranges can be distinguished with different concentration behavior, which are associated with different proportions of bonded water molecules. The addition of glutaraldehyde has very little effect on the elastic modulus of hydrated gelatin films. [ABSTRACT FROM AUTHOR]

This review surveys Infrared, Raman/SERS and Brillouin spectroscopies for medical diagnostics and detection of biomarkers in biofluids, that include urine, blood, saliva and other biofluids. These optical sensing techniques are non-contact, noninvasive and relatively rapid, accurate, label-free and affordable. However, those techniques still have to overcome some challenges to be widely adopted in routine clinical diagnostics. This review summarizes and provides insights on recent advancements in research within the field of vibrational spectroscopy for medical diagnostics and its use in detection of many health conditions such as kidney injury, cancers, cardiovascular and infectious diseases. The six comprehensive tables in the review and four tables in summarize a few dozen experimental papers in terms of such analytical parameters as limit of detection, range, diagnostic sensitivity and specificity, and other figures of merits. Critical comparison between SERS and FTIR methods of analysis reveals that on average the reported sensitivity for biomarkers in biofluids for SERS vs FTIR is about 103 to 105 times higher, since LOD SERS are lower than LOD FTIR by about this factor. High sensitivity gives SERS an edge in detection of many biomarkers present in biofluids at low concentration (nM and sub nM), which can be particularly advantageous for example in early diagnostics of cancer or viral infections. Raman, Infrared spectroscopies use low volume of biofluidic samples, little sample preparation, fast time of analysis and relatively inexpensive instrumentation. Applications of SERS may be a bit more complicated than applications of FTIR (e.g., limited shelf life for nanoparticles and substrates, etc.), but this can be generously compensated by much higher (by several order of magnitude) sensitivity in comparison to FTIR. High sensitivity makes SERS a noninvasive analytical method of choice for detection, quantification and diagnostics of many health conditions, metabolites, and drugs, particularly in diagnostics of cancer, including diagnostics of its early stages. FTIR, particularly ATR-FTIR can be a method of choice for efficient sensing of many biomarkers, present in urine, blood and other biofluids at sufficiently high concentrations (mM and even a few µM) Brillouin scattering spectroscopy detecting visco-elastic properties of probed liquid medium, may also find application in clinical analysis of some biofluids, such as cerebrospinal fluid and urine. [ABSTRACT FROM AUTHOR]

In recent years, there have been intense studies on hybrid organic–inorganic compounds (HOIPs) due to their tunable and adaptable features. This present study reports the vibrational, structural, and elastic properties of mixed halide single crystals of MAxFA1-xPbCl3 at room temperature by introducing the FA cation at the A-site of the perovskite crystal structure. Powder X-ray diffraction analysis confirmed that its cubic crystal symmetry is similar to that of MAPbCl3 and FAPbCl3 with no secondary phases, indicating a successful synthesis of the MAxFA1-xPbCl3 mixed halide single crystals. Structural analysis confirmed that the FA substitution increases the lattice constant with increasing FA concentration. Raman spectroscopy provided insight into the vibrational modes, revealing the successful incorporation of the FA cation into the system. Brillouin spectroscopy was used to investigate the changes in the elastic properties induced via the FA substitution. A monotonic decrease in the sound velocity and the elastic constant suggests that the incorporation of large FA cations causes distortion within the inorganic framework, altering bond lengths and angles and ultimately resulting in decreased elastic constants. An analysis of the absorption coefficient revealed lower attenuation coefficients as the FA content increased, indicating reduced damping effects and internal friction. The current findings can facilitate the fundamental understanding of mixed lead chloride perovskite materials and pave the way for future investigations to exploit the unique properties of mixed halide perovskites for advanced optoelectronic applications. [ABSTRACT FROM AUTHOR]

The single-crystal elastic moduli of three natural aragonites, CaCO3, have been determined at ambient conditions by Brillouin spectroscopy. The samples contain different amounts of Sr ranging from 0.1 mol% to 1.5 mol% and cover the majority of the compositional range of natural aragonites. Brillouin spectroscopy can resolve changes in elasticity produced by small differences in the Sr content in aragonite, however, these changes are at the limit of the resolving power of our measurements. Our results are in good agreement with the full tensor of a Sr-bearing natural aragonite determined by Brillouin spectroscopy and with the tensor obtained by DFT calculations. The decrease we measured of the aggregate adiabatic bulk modulus, K S , with increasing Sr content is qualitatively in good agreement with the softening observed in previously measured isothermal bulk modulus, K T , of synthetic CaCO3-SrCO3 solid solutions and with the value of K S determined for SrCO3. Our study provides the first full tensor on nominally pure (end-member) aragonite and places contraints on its dependence on Ca/Sr substitutions at levels observed in natural samples. Furthermore, we compare the elastic tensor of aragonite and calcite, the two main CaCO3 polymorphs observed at ambient conditions, and describe their differences based on the arrangement of the polyhedral structural units of the two polymorphs. In particular, the different arrangement of the Ca-O polyhedra leads to a smaller compressibility of aragonite along the c-axis, higher compressibilities along the a- and b-axes and an overall lower bulk modulus (- 9.7%) with respect to that of the less dense calcite. [ABSTRACT FROM AUTHOR]

We have carried out in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to pressures of 155 GPa, which confirmed a distinct pressure‐induced trend change in the transverse acoustic velocity (VS) profile around 98 GPa, likely caused by the Si‐O coordination number (CN) change from 6 to 6+. Although it has been reported that the substitution of Fe2+ in MgSiO3 glass induces almost linear velocity reduction up to ∼160 GPa, we revealed that the VS profile of (Fe2+, Al)‐bearing MgSiO3 becomes anomalously steeper above ∼100 GPa and eventually came to be equivalent to MgSiO3 glass above ∼125 GPa. This implies the incorporation of Al into Fe‐bearing MgSiO3 glass significantly facilitates making it far elastically stiffer and thus the densification under pressures well within the Earth's lower mantle. Our results indicate the possible presence of stiff and highly dense silicate melts in deep MOs in the rocky terrestrial planets. Plain Language Summary: Since the terrestrial planets are thought to have gone through multiple episodes of magma ocean (MO) in their formation processes, clarifying the structure and physical properties of silicate melts under relevant deep MO conditions is crucial to understanding the internal structure and evolution of the terrestrial planets. Our in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass, used as a structural analog of silicate melts, shows both Al and Fe2+ are very effective to reduce the pressure corresponding to the Si‐O CN change from 6 to 6+. In addition, a few percentages of Al incorporation could make the Fe‐bearing MgSiO3 glass significantly far elastically stiff and thus dense with 6+ CN in Si‐O in the deep terrestrial interiors. The presence of stiff and highly dense silicate melts in deep MOs in the terrestrial planets would offer essential insights into the MO convection, gravitational stability of silicate melts in the course of MO crystallization, and the mantle stratification of the terrestrial planets. Key Points: We have carried out acoustic wave velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to 155 GPaVS profile displays a change at 98 GPa induced by the Si‐O coordination number change from 6 to 6+ followed by anomalously steeper trendResults indicate the possible presence of highly dense Al, Fe2+‐bearing Si‐rich melts in the deep terrestrial magma oceans [ABSTRACT FROM AUTHOR]

Melt viscosity is one of the most critical physical properties controlling magma transport dynamics and eruptive style. Although viscosity measurements are widely used to study and model the flow behavior of magmas, recent research has revealed that nanocrystallization of Fe–Ti-oxides can compromise the reliability of viscosity data. This phenomenon can occur during laboratory measurements around the glass transition temperature (Tg) and lead to the depletion of iron and titanium in the residual melt phase, with a significant increase in viscosity. Accurate viscosity measurements play a crucial role in determining the reliability of empirical models for magma viscosity, which are used to evaluate eruptive scenarios in hazardous areas. Here, we quantify the reliability of empirical models by elaborating a new viscosity model of Stromboli basalt that relies exclusively on viscosity data obtained from nanocrystal-free samples. We show that empirical models so far used to estimate melt viscosity at eruptive conditions overestimate Stromboli viscosity by a factor ranging between 2 and 5. In the context of numerical modelling of magmatic processes at Stromboli volcano, we analyse and interpret this finding. Based on our findings, we draw the conclusion that Stromboli basalt is anticipated to ascend from the storage area to the vent at a faster rate than previously hypothesized. [ABSTRACT FROM AUTHOR]

The expanded uncertainty of the measured Brillouin scattering shift frequencies is essential in assessing the measurements of parameters of various materials. We describe the general operation principles of a Brillouin light scattering (BLS) spectrometer with a high-power laser and a scanning tandem Fabry–Pérot interferometer (TFPI) for material characterization. Various uncertainty components have been analyzed for the BLS spectrometer following the Guide to the Expression of Uncertainty in Measurement (GUM). The expanded relative uncertainty in the measured Brillouin frequency shift of 15.70 GHz for polymethyl methacrylate (PMMA) was estimated to be 0.26%. The calculated Brillouin frequency shift (based on material properties of PMMA) was determined to be 15.44 GHz with expanded relative uncertainty of 2.13%. It was shown that the measured and calculated Brillouin frequency shifts for PMMA agree within their expanded uncertainties. The TFPI-based BLS spectrometer can be used to measure the longitudinal modulus of materials with an expanded uncertainty of 1.9%, which is smaller than that of the ultrasonic velocity-based method (estimated to be 2.9%). [ABSTRACT FROM AUTHOR]

The relationship between halogen content and the elastic/vibrational properties of MAPbBr3−xClx mixed crystals (x = 1.5, 2, 2.5, and 3) with MA = CH3NH3+ has been studied using Brillouin and Raman spectroscopy at room temperature. The longitudinal and transverse sound velocities, the absorption coefficients and the two elastic constants C11 and C44 could be obtained and compared for the four mixed-halide perovskites. In particular, the elastic constants of the mixed crystals have been determined for the first time. A quasi-linear increase in the sound velocity and the elastic constant C11 with increasing chlorine content was observed for the longitudinal acoustic waves. C44 was insensitive to the Cl content and very low, indicating a low elasticity to shear stress in mixed perovskites regardless of the Cl content. The acoustic absorption of the LA mode increased with increasing heterogeneity in the mixed system, especially for the intermediate composition where the Br and Cl ratio was 1:1. In addition, a significant decrease in the Raman-mode frequency of the low-frequency lattice modes and the rotational and torsional modes of the MA cations was observed with decreasing Cl content. It clearly showed that the changes in the elastic properties as the halide composition changes were correlated with the lattice vibrations. The present findings may facilitate a deeper understanding of the complex interplay between halogen substitution, vibrational spectra and elastic properties, and may also pave the way for optimizing the operation of perovskite-based photovoltaic and optoelectronic devices by tailoring their chemical composition. [ABSTRACT FROM AUTHOR]

• Halide mixing suppresses phase transitions in FAPbBr 1.5 Cl 1.5 perovskites. • Low shear rigidity observed in FAPbBr 1.5 Cl 1.5 compared to MA perovskites. • Local disorder stabilizes cubic phase down to 83 K. Halide mixing effects on the elastic and vibrational properties were investigated for FAPbBr 1.5 Cl 1.5 single crystals. The elastic and vibrational characteristics of the synthesized single crystal were examined using temperature-dependent Brillouin and Raman spectroscopies. Elastic constants C 11 and C 44 were derived from the longitudinal and transverse sound velocities, respectively. The softening and subsequent hardening of the elastic constants upon cooling was accompanied by substantial increase of the acoustic damping peaks indicating significant interaction between the acoustic waves and reorientational dynamics of the FA cations. Especially, FAPbBr 1.5 Cl 1.5 exhibited extremely low shear rigidity compared to other MA-based perovskites. Raman spectroscopy was used to study the vibrational modes of the PbX 6 octahedral lattice and the internal motions of FA cations. Raman modes did not reveal any drastic changes within the investigated temperature range. The combined elastic and vibrational properties showed that the structural phase transitions observed from pure compounds were suppressed in FAPbBr 1.5 Cl 1.5 due to the local heterogeneous environment for the FA cations caused by random substitution of two halogen ions. These findings are expected to enhance the understanding of the material's behavior under varying thermal conditions, which is crucial for optimizing the performance of perovskite-based devices. [ABSTRACT FROM AUTHOR]

Abstract Interglacial periods are characterised by thick accumulations of halite units in the Dead Sea Basin. During these intervals, small water droplets (fluid inclusions, FIs) were entrapped in the halite crystals which serve as windows to estimate the chemistry and physical properties of the primary lake water conditions. Brillouin spectroscopy is used here to reconstruct annual resolution temperatures from a halite core section in the Dead Sea Basin during the onset of Marine Isotope Stage 5e (ca 130 ka) of the Last Interglacial. Lake bottom temperatures can be inferred based on the occurrence of coarse/fine halite facies, as observed today with the formation of equivalent halite facies during winter/summer seasons in the Dead Sea. A recurring increase in lake bottom temperatures is found along the direction of coarse halite layers in three successive years. Moreover, low FI entrapment temperatures were detected in layers of fine (cumulate) halite facies. These results imply a twofold stronger seasonality in the Dead Sea Basin compared to today, with colder winters at the onset of Marine Isotope Stage 5e. The results therefore highlight the potential of using cyclic salt deposits to reconstruct seasonal temperature variability for numerous evaporitic environments in the geological record.

Brillouin spectroscopy has recently attracted attention as a powerful tool for the characterization of the mechanical properties of heterogeneous materials, particularly in the biological and biomedical domains. This study investigates the procedure to use Brillouin data to provide relevant morphological parameters of micro-structured samples. When acquiring Brillouin spectra at the interface between two regions of the sample, the spectrum shows signatures of both regions. This feature can be used to precisely identify the position of the interfaces by analyzing the evolution of the fitting parameters of the Brillouin spectra acquired by performing a linear scan across the interface. This concept has been demonstrated by measuring the thickness of adherent HEK293T cells. The results are validated using fluorescence microscopy, showing an excellent agreement. The present analysis showcases the wealth of information present in the Brillouin spectrum and the potentiality of Brillouin spectroscopy not only for mechanical characterization but also for label-free, high-resolution imaging of sample morphology. The study introduces the possibility of correlating mechanical properties and shape of biological samples using a single technique.

We report non-contact laser-based Brillouin light-scattering (BLS) spectroscopy measurements of the viscoelastic properties of hyperthermally radiofrequency (RF)-heated and ablated bovine liver and chicken flesh tissues with embedded gold nanoparticles (AuNPs). The spatial lateral profile of the local surface temperature in the flesh samples during their hyperthermia was measured through optical backscattering reflectometry (OBR) using Mg–silica-NP-doped sensing fibers distributed with an RF applicator and correlated with viscoelastic variations in heat-affected and ablated tissues. Substantial changes in the tissue stiffness after heating and ablation were directly related to their heat-induced structural modifications. The main proteins responsible for muscle elasticity were denatured and irreversibly aggregated during the RF ablation. At T > 100 °C, the proteins constituting the flesh further shrank and became disorganized, leading to substantial plastic deformation of biotissues. Their uniform destruction with larger thermal lesions and a more viscoelastic network was attained via AuNP-mediated RF hyperthermal ablation. The results demonstrated here pave the way for simultaneous real-time hybrid optical sensing of viscoelasticity and local temperature in biotissues during their denaturation and gelation during hyperthermia for future applications that involve mechanical- and thermal-property-controlled theranostics. [ABSTRACT FROM AUTHOR]

Multicomponent lipid bilayers are used as models for searching the origin of spatial heterogeneities in biomembranes called lipid rafts, implying the coexistence of domains of different phases and compositions within the lipid bilayer. The spatial organization of multicomponent lipid bilayers on a scale of a hundred nanometers remains unknown. Brillouin spectroscopy providing information about the acoustic phonons with the wavelength of several hundred nanometers has an unexplored potential for this problem. Here, we applied Brillouin spectroscopy for three binary bilayers composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC), and cholesterol. The Brillouin experiment for the oriented planar multibilayers was realized for two scattering geometries involving phonons for the lateral and normal directions of the propagation. The DPPC–DOPC mixtures known for the coexistence of the solid-ordered and liquid-disordered phases had bimodal Brillouin peaks, revealing the phase domains with sizes more than a hundred nanometers. Analysis of the Brillouin data for the binary mixtures concluded that the lateral phonons are preferable for testing the lateral homogeneity of the bilayers, while the phonons spreading across the bilayers are sensitive to the layered packing at the mesoscopic scale. Graphical Abstract [ABSTRACT FROM AUTHOR]

The expanded uncertainty of the measured Brillouin scattering shift frequencies is essential in assessing the measurements of parameters of various materials. We describe the general operation principles of a Brillouin light scattering (BLS) spectrometer with a high-power laser and a scanning tandem Fabry–Pérot interferometer (TFPI) for material characterization. Various uncertainty components have been analyzed for the BLS spectrometer following the Guide to the Expression of Uncertainty in Measurement (GUM). The expanded relative uncertainty in the measured Brillouin frequency shift of 15.70 GHz for polymethyl methacrylate (PMMA) was estimated to be 0.26%. The calculated Brillouin frequency shift (based on material properties of PMMA) was determined to be 15.44 GHz with expanded relative uncertainty of 2.13%. It was shown that the measured and calculated Brillouin frequency shifts for PMMA agree within their expanded uncertainties. The TFPI-based BLS spectrometer can be used to measure the longitudinal modulus of materials with an expanded uncertainty of 1.9%, which is smaller than that of the ultrasonic velocity-based method (estimated to be 2.9%).

[Display omitted] • Brillouin spectroscopy characterizes high-frequency elastic modulus of tissues used for cardiac bioimplants. • Diepoxide cross-linking of hydrated pericardium or vein wall weakly change Brillouin frequency. • Treatment-induced changes in the protein scaffold are manifested in the Brillouin frequency of dried tissues. • Treatment-induced effects on vein collagen and elastin can be simultaneously studied using the Brillouin spectrum. • Brillouin elastic modulus of tissue has no one-to-one correspondence to Young's modulus from tensile tests. There is the rapid growth in application of Brillouin scattering spectroscopy to biomedical objects in order to characterize their mechanoelastic properties in this way. However, the possibilities and limitations of the method when applied to tissues have not yet been clarified. Here, applicability of Brillouin spectroscopy for testing the elastic response of medically relevant tissues of bovine jugular vein and pericardium was considered. Parameters of the Brillouin peak were studied for samples untreated, diepoxide-fixed, and preserved after treatment in alcohol solutions. It was found that diepoxide cross-linking resulted to a slight tendency to increase the Brillouin position for hydrated tissues. The variations in the position and width of the Brillouin peaks, associated with local fluctuations in water concentration, were reduced after diepoxide treatment in the case of the pericardium, but not in the case of the vein wall. To obtain more information about the elastic response of the protein scaffold without the participation of water, dried samples were also studied. Brillouin spectra of the dried pericardium and vein wall revealed a significant increase in the Brillouin peak position (elastic modulus) after conservation in alcohol. In the case of the vein wall, this effect was found for both collagen and elastin-related peaks, which were identified in the Brillouin spectrum. This result corresponds to a denser packing of fibrous proteins after preservation in alcohol solutions. The ability of Brillouin spectroscopy to independently characterize the effect of treatment on the instantaneous elastic modulus of various tissue components is also attractive for its application in the development of new materials for bioimplants. A comparison of the Brillouin longitudinal and Young's elastic moduli determined for the hydrated samples of the vein and pericardium showed that there is no clear correspondence between these material parameters. The usefulness of using both experimental methods to obtain new information about the elastic response of the material is discussed. [ABSTRACT FROM AUTHOR]

The organic glass-forming dibutyl phthalate (DBP) has been studied applying low-frequency Raman and Brillouin spectroscopy in the temperature range from 90 K to 200 K, covering glassy and liquid states. Spectra of fast relaxation in the GHz-THz frequency range were determined from the inelastic light scattering spectra. The line width and position of the Brillouin peak were used to determine the Q-1 -factor, which is inversely proportional to susceptibility at the Brillouin peak frequency. It was discovered that the temperature evolution of the fast relaxation susceptibility and the Q-1 -factor agree well with a mobility parameter from pulse EPR experiment. The findings show that peculiarities in the temperature dependence the EPR data found early for DBP have are accompanied by a redistribution of the relaxation times. [ABSTRACT FROM AUTHOR]

The subduction of serpentinized slabs is the dominant process to transport "water" into Earth's mantle, and plays a pivotal role for subduction dynamics. Antigorite, the most abundant serpentine mineral in subduction settings, may imprint a seismic signature on serpentinized slabs, making them seismically distinguishable from the dry, non‐serpentinized ones. However, the complete single‐crystal elasticity of antigorite has not been experimentally constrained at high pressures, hindering the use of seismological approaches to detect serpentinization in subducting slabs. Here, we report the full elastic stiffness tensor of antigorite by single‐crystal Brillouin spectroscopy and X‐ray diffraction up to 7.71(5) GPa. We use our results to model seismic properties of antigorite‐bearing rocks and show that their seismological detectability depends on the geometrical relation between seismic wave paths and foliation of serpentinized rocks. In particular, we demonstrate that seismic shear anisotropy shows low sensitivity to serpentinization for a range of relevant geometries. Plain Language Summary: The subduction of serpentinized slabs plays a key role in the deep recycling of water into the Earth's interior. Antigorite is the main serpentine mineral in subducting slabs, and the most important carrier of water. Antigorite‐bearing rocks are predicted to have a distinct seismic signature, potentially allowing them to be detected with seismological approaches. However, our current knowledge on seismic properties of antigorite‐bearing rocks is limited, mostly hampered by a lack of experimental constraints on single‐crystal elasticity of antigorite at relevant pressures. In this study, state‐of‐the‐art techniques were employed to produce the first experimental description of the complete high‐pressure elasticity of antigorite single crystals. Our experimental data set was implemented in the modeling of seismic properties of antigorite‐bearing rocks at pressures relevant for subduction. Our results were used to discuss the relation between seismic wave path and shear wave anisotropy in serpentinized slabs, and challenge the use of shear wave splitting as a proxy for serpentinization in slabs. Key Points: Single‐crystal elasticity of antigorite at high pressures is determined by Brillouin spectroscopy and X‐ray diffraction experimentsSeismic signature of serpentinized slabs is constrained in a relevant composition‐pressure spaceSerpentinization in slabs may be undetectable through shear wave anisotropy [ABSTRACT FROM AUTHOR]

In MgSiO SB 3 sb glass, the average Mg-O bond length is more-or-less constant with pressure up to ~10 GPa [from 2.051(30) at 0 GPa to 2.062(30) at 9.8 GPa] and then turns downward with further pressure increases. Keywords: MgSiO3 glass; high pressure; structural modification; Raman spectroscopy; Brillouin spectroscopy; X-ray scattering EN MgSiO3 glass high pressure structural modification Raman spectroscopy Brillouin spectroscopy X-ray scattering 1313 1324 12 07/05/22 20220701 NES 220701 Introduction The present day Earth possesses a crust composed of low-density minerals enriched in incompatible lithophile elements and a high-density metallic core beneath the rocky mantle, indicating that our planet is a well-differentiated body. Indeed, between 10 and 30 GPa, the average Mg-O distances in MgSiO SB 3 sb and Mg SB 2 sb SiO SB 4 sb glasses follow roughly the same trend, with r SB (Mg-O) sb in MgSiO SB 3 sb glass somewhat larger, suggesting that at the same pressure Mg-O polyhedra in Mg SB 2 sb SiO SB 4 sb glass are under more compression. The initial compression ( I K i SB T sb 0) is dominated by the response of Mg-O polyhedra, which, at >15 GPa, help transmit pressure onto the SiO SB 4 sb tetrahedra, causing the Si-O coordination number to increase at a similar rate to that in SiO SB 2 sb glass, with significantly increased rigidity. Figure 2a summarizes the structural modifications by compression based on Raman mode changes: (1) a discontinuity of Raman peaks at ~900 and ~512 cm SP -1 sp at ~8 GPa; (2) the emergence of a new peak at ~600 cm SP -1 sp at ~8 GPa; (3) a discontinuity of the 1096 cm SP -1 sp peak at ~20 GPa; (4) the emergence of a new peak at ~360 cm SP -1 sp at 20 GPa; and (5) the emergence of a new peak at 860 cm SP -1 sp at 40 GPa. [Extracted from the article]

Interglacial periods are characterised by thick accumulations of halite units in the Dead Sea Basin. During these intervals, small water droplets (fluid inclusions, FIs) were entrapped in the halite crystals which serve as windows to estimate the chemistry and physical properties of the primary lake water conditions. Brillouin spectroscopy is used here to reconstruct annual resolution temperatures from a halite core section in the Dead Sea Basin during the onset of Marine Isotope Stage 5e (ca 130 ka) of the Last Interglacial. Lake bottom temperatures can be inferred based on the occurrence of coarse/fine halite facies, as observed today with the formation of equivalent halite facies during winter/summer seasons in the Dead Sea. A recurring increase in lake bottom temperatures is found along the direction of coarse halite layers in three successive years. Moreover, low FI entrapment temperatures were detected in layers of fine (cumulate) halite facies. These results imply a twofold stronger seasonality in the Dead Sea Basin compared to today, with colder winters at the onset of Marine Isotope Stage 5e. The results therefore highlight the potential of using cyclic salt deposits to reconstruct seasonal temperature variability for numerous evaporitic environments in the geological record. [ABSTRACT FROM AUTHOR]

The SrxBa1 –xNb2O6 crystals with x = 0.33, 0.5, 0.61, 0.75 were studied by Raman and Brillouin light scattering in a wide temperature range. The experimental temperature dependences of the central peak's integral intensity and the position and width of the longitudinal acoustic mode were plotted using derivative analysis. It is shown that the temperature at which the abnormal behavior begins (the so-called Burns temperature) is only slightly different for all the crystals under study, while the phase transition temperatures differ significantly. It allows asserting the identical microscopic nature of the Burns temperature in SrxBa1 –xNb2O6 crystals. [ABSTRACT FROM AUTHOR]

In recent decades, mechanobiology has emerged as a novel perspective in the context of basic biomedical research. It is now widely recognized that living cells respond not only to chemical stimuli (for example drugs), but they are also able to decipher mechanical cues, such as the rigidity of the underlying matrix or the presence of shear forces. Probing the viscoelastic properties of cells and their local microenvironment with sub-micrometer resolution is required to study this complex interplay and dig deeper into the mechanobiology of single cells. Current approaches to measure mechanical properties of adherent cells mainly rely on the exploitation of miniaturized indenters, to poke single cells while measuring the corresponding deformation. This method provides a neat implementation of the everyday approach to measure mechanical properties of a material, but it typically results in a very low throughput and invasive experimental protocol, poorly translatable towards three-dimensional living tissues and biological constructs. To overcome the main limitations of nanoindentation experiments, a radical paradigm change is foreseen, adopting next generation contact-less methods to measure mechanical properties of biological samples with sub-cell resolution. Here we briefly introduce the field of single cell mechanical characterization, and we concentrate on a promising high resolution optical elastography technique, Brillouin spectroscopy. This non-contact technique is rapidly emerging as a potential breakthrough innovation in biomechanics, but the application to single cells is still in its infancy. [ABSTRACT FROM AUTHOR]

Phase Egg and δ-AlOOH are two typical hydrous phases that might exist in the wet sedimentary layer of subducted slabs under mantle conditions. They are thus regarded as potential water carriers to Earth's deep mantle. In this report, we report the full elastic constants of both phases determined by Brillouin scattering and X-ray diffraction measurements under ambient conditions. Our results indicate that the hydrogen-bond configurations in the crystal structures of the two phases have a profound effect on their principal elastic constants. The adiabatic bulk modulus (KS) and shear modulus (G) calculated from the obtained elastic constants using the Voigt-Reuss-Hill averaging scheme are 158.3(201) GPa and 123.0(60) GPa for phase Egg and 162.9(31) GPa and 145.2(13) GPa for δ-AlOOH, respectively. These results allow us to evaluate elastic moduli and sound velocities of hydrous minerals in the Al2O3-H2O-SiO2 ternary system (simplified composition of subducted wet sedimentary layer) at ambient conditions, including the contrast of the acoustic velocities VP and VS for the reaction AlSi3OH = δ-AlOOH + SiO2 (stishovite) and the evolution in the elastic moduli and sound velocities of hydrous minerals as a function of density. [ABSTRACT FROM AUTHOR]

We propose and demonstrate, first on simulated spectra and then experimentally, a novel approach to correct the undesired background distortions in the Brillouin spectra caused by molecular filter's absorption, fluorescent emission, ambient room light or any other constant contaminant. The developed multi-wavelength excitation Brillouin spectroscopy method computationally reconstructs the pure Brillouin component of the signal from multiple Brillouin spectra acquired using different excitation wavelengths. By removing the baseline distortions, the approach improves the goodness of fit of the Brillouin peaks, enabling accurate Brillouin shift and linewidth measurements from a wide range of challenging samples. In the present report, we explain the principle behind the method on a set of simulated spectra and present experimental application on an intentionally strongly-distorted spectrum. Utilizing the multi-excitation Brillouin spectroscopy approach, we successfully reconstruct Brillouin spectra of a highly-scattering sample, initially rendered not analyzable by excessive iodine absorption and contamination by out-of-focus light. [ABSTRACT FROM AUTHOR]

Nondipolar magnetic fields exhibited at Uranus and Neptune may be derived from a unique geometry of their icy mantle with a thin convective layer on top of a stratified nonconvective layer. The presence of superionic H2O and NH3 has been thought as an explanation to stabilize such nonconvective regions. However, a lack of experimental data on the physical properties of those superionic phases has prevented the clarification of this matter. Here, our Brillouin measurements for NH3 show a two-stage reduction in longitudinal wave velocity (Vp) by ~9% and ~20% relative to the molecular solid in the temperature range of 1,500 K and 2,000 K above 47 GPa. While the first Vp reduction observed at the boundary to the superionic a phase was most likely due to the onset of the hydrogen diffusion, the further one was likely attributed to the transition to another superionic phase, denoted? phase, exhibiting the higher diffusivity. The reduction rate of Vp in the superionic? phase, comparable to that of the liquid, implies that this phase elastically behaves almost like a liquid. Our measurements show that superionic NH3 becomes convective and cannot contribute to the internal stratification. [ABSTRACT FROM AUTHOR]

The results of studying ferroelectric materials obtained at the Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences in 1973-2020 are reported. Mechanisms of the photovoltaic effect and photorefraction, emergence and role of polar regions in ferroelectric crystals, methods of detection of polar regions, and mechanisms of manifestation of the displacive and order-disorder phase transitions in various ferroelectrics are discussed. The results of experimental and theoretical investigations allow one to conclude that imperfections of a crystal structure play a key role in phenomena observed in ferroelectrics. [ABSTRACT FROM AUTHOR]

• Digital technology in prosthetic practice uses milled PMMA discs. • DMA and Brillouin spectroscopy are innovative techniques in dentistry. • Tested materials exhibit better mechanical properties in frequency ranges used. • Tested materials have less cytotoxicity than traditional ones. To compare the mechanical and biological features of a polymethylmethacrylate (PMMA) disc for CAD/CAM prostheses (test samples, TG) with a traditional resin (control samples, CG). Mechanical analysis was performed using Dynamic Mechanical Analysis (DMA) and Brillouin's micro-spectroscopy. Human keratinocyte morphology and adhesion were analyzed by scanning electronic microscopy (SEM), cytotoxicity by the MTT assay, apoptosis by flow cytometry and p53, p21 and bcl2 gene expression by real time PCR. TG exhibited a higher elastic modulus than CG (range 5100–5500 ± 114.3 MPa vs 3000–3300 ± 99.97 MPa). The Brillouin frequency was found at ω B = (15.50 ± 0.05) GHz for TG and at ω B_1 = (15.50 ± 0.05) GHz and ω B_2 = (15.0 ± 0.1) GHz for CG where two peaks were always present independently of the sample point. SEM analysis revealed that keratinocytes on TG disks appeared to be flattened with lamellipodia. Keratinocytes on CG disks rose above the substrate with cytoplasmatic filaments. MTT viability data at 3 h and 24 h showed TG was significantly less cytotoxic than CG (p < 0.001). No significant differences emerged in apoptosis on CG and TG. Real-time PCR showed p53 expression increased after 3 h by about 9-fold in keratinocytes on TG (p < 0.001) and about 5-fold in those on CG (p < 0.001). High p53 expression persisted after 24 h on both disks. No significant variations were observed in p21 and bcl2 expression at any time-point. PMMA resins, as used in CAD/CAM technology, displayed suitable biocompatible and mechanical properties for removable prostheses. [ABSTRACT FROM AUTHOR]

Brillouin and Raman imaging are powerful techniques for the investigation of complex materials and they are widely used in material science and biophysics [1–7]. When dealing with microstructures, the results interpretation requires an accurate understanding of the interaction processes in presence of acoustic and chemical boundaries between different materials [8–15]. The data here reported are obtained while scanning with sub-micron resolution the sharp interfaces between vitreous-SiO2/Water and Polyethylene (PET)/Glycerol. Molecular and acoustic vibrations were observed by means of a recently developed micro-spectrometer, which acquires simultaneously Raman and Brillouin spectra on the same point with high spatial and spectral resolution [3]. Two external optic configurations were adopted in order to evidence the dependency of the measurements on the optical scattering volume. The evolution of the detected phonon modes, propagating and not propagating, is obtained by a direct observation of the raw data for the two interfaces, which present different acoustic mismatch. These experimental records can be exploited by researchers employing Raman and Brillouin imaging to discuss the resolution limit of the techniques and to compare the effect of different experimental set-ups. Moreover, thanks to their high spectral resolution they can be useful to researchers working on acoustic phonon transport at interfaces to model the dependency of transmission of long wavelength phonons on the acoustic mismatch.

In this work, we study the relaxation behavior of a densified sodium aluminoborate glass by means of coupled Raman spectroscopy, Brillouin spectroscopy, and differential scanning calorimetry analyses. First, we show that the changes in elastic properties upon densification are largely associated with structural modifications in the glass network at short- and medium-range orders. Then, the evolution of the structural and elastic properties of the densified glass has been monitored in situ in the coupled DSC-Brillouin-Raman setup during isothermal annealing at different temperatures below the glass transition temperature. The stretched exponential function is found to well describe the observed relaxation kinetics, however, the stretching factor β varies non-monotonically with temperature. In contrast, the Arrhenius behavior of the characteristic decay times is deduced by lifetime distribution analysis, revealing three different relaxation processes with typical activation energies of 170±25, 200±5, and 280±15 kJ/mol. The relative contributions of these processes to the overall relaxation kinetics are found to vary with the temperature as well as the type of parameter considered (structural, elastic, or thermal), and hence, the relaxation kinetics cannot be properly understood using the stretched exponent function. The possible origins of the different relaxation processes are discussed. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Halite traps inclusions of the mother fluid when precipitating. When unchanged, the density of these fluid inclusions (FIs) records the water temperature Tf at the time of crystal formation. As halite is ubiquitous on Earth and geological time, its FIs possess a high potential as temperature archives. However, the use of FIs in halite as an accurate palaeothermometer has been hampered due to limitations of microthermometry, the most commonly used analytical method. Here, we show how Brillouin spectroscopy in halite FIs bypasses these limitations and allows recovering Tf to within 1 °C or less. To demonstrate this, we measured samples synthesised at 24.6 ± 0.5 °C and 33 ± 1 °C, and obtained 24.8 ± 0.4 °C and 31.9 ± 0.4 °C, respectively. This novel approach thus provides an accurate palaeothermometer for lacustrine and marine environments. Moreover, Brillouin spectroscopy solves the long‐standing debate on damage of halite fluid inclusions through quantifying the acceptable temperature excursion for preserving elastic behaviour: [l/(1 µm)]−0.64 × (90 °C), where l is the FI size. This threshold is lower for FIs close to the surface of the host crystal or to another FI. We also list 'best practices' for applying both microthermometry and Brillouin thermometry. [ABSTRACT FROM AUTHOR]

We investigate the potential of Brillouin Light Scattering (BLS) Microspectroscopy for fast non-invasive all-optical assessment of the mechanical properties of viscose fibers and bleached softwood pulp. Using an optimized Brillouin spectrometer, we demonstrate fast spatial mapping of the complex longitudinal modulus over extended areas (> 100 µm). Our results reveal that while the softwood pulp has a relatively uniform moduli, the viscous fibers have significant spatial heterogeneous in the moduli. Specifically, the viscose fibers exhibited a regular pattern of increasing and decreasing modulus normal to the fiber axis. The potential influence of a locally changing refractive index is investigated by holographic phase microscopy and ruled out. We discuss our results in light of the anisotropic mechanical properties of the fibers and are able to estimate the relative difference between the modulus along the fiber axis and that perpendicular to it. Results are presented alongside reference measurements of the quasi-static mechanical properties transverse to the fiber axes obtained using AFM-nanoindentation which reveal a similar trend, hinting at the potential usefulness of BLS for mechanical characterization applications. However, more detailed investigations are called for to uncover all the factors influencing the measured high-frequency BLS modulus and its significance in relation to physical properties of the fiber that may be of practical interest. [ABSTRACT FROM AUTHOR]

In SrxBa1−xNb2O6 crystals (x = 0.33, 0.5, 0.61, and 0.75), temperature dependences of spontaneous polarization, strain, elastic modules, and second harmonic generation (SHG) signal are compared. It is revealed that SHG describes the temperature dependences of dipole moments in polar nanoregions in paraelectric phase. In the vicinity of the phase transition in paraelectric phase, SHG reflects the temperature behavior of relatively large and long-lived polar asymmetric regions as indicated by the presence of the intermediate temperature range on the temperature dependence of this nonlinear response. [ABSTRACT FROM AUTHOR]