Abstract Brillouin light scattering (BLS), a non-destructive and non-contact technique, offers a powerful tool for probing the micromechanical properties of biological tissues. However, the inherent ...heterogeneity of biological tissues can pose significant challenges in interpreting BLS spectra. In this study, we introduce a novel method that harnesses the intensity information within a single BLS spectrum to directly estimate the Voigt average of the longitudinal modulus. Additionally, we use a method to determine the ratio of the squared Pockels coefficients for photoelastically heterogeneous samples, based on global analysis of a 2D BLS map. This method is shown to effectively determine the photoelastic ratio of soft and hard components of human bone tissues, enabling the calculation of the average elastic moduli. Furthermore, it has the remarkable ability to generate maps of the filling factor of the scattering volume, shedding valuable light on the intricate structure and topography of rough surfaces under BLS mapping.
Recent studies propose dry reforming as a potential alternative to steam reforming. A number of advantages come mainly from the substitution of steam with CO2, representing a potential strategy for ...CO2 and waste heat reuse in both carbon-intensive industry (e.g. steel) and power generation applications (e.g. dry reforming coupling to solid oxide fuel cells).
The objective of this study is the development, by means of an ultrasound assisted synthesis technique, of a novel 15%Ni -6%ZrO2 –3%CaO -Al2O3 catalyst with high surface area and metal dispersion, to achieve high values of methane conversion and stable performance, obtained by significantly limiting carbon deposition at temperature in the range 700–750 °C. In this range, compatible with the dry reformer-SOFC thermal integration, conventional catalysts seriously suffer from coking tolerance issues.
The catalyst exhibited very promising results with high methane conversion rates of 93% at 750 °C and 1.25 CO2/CH4 ratio at the reactor inlet (dilution: in SiC 4:1 in volume), stable over 450 h of operation, with no significant changes in outlet gas composition and relevant modifications on material structure as revealed by SEM/EDX, XRD and Raman, analysis.
•Ni–5%CaO–5%ZrO2/Al2O3with high Ni dispertion thanks to US-assisted synthesis.•High Methane conversion.•Long time stability in the range at 750 °C.•Low carbon coke deposition due to effects of CaO and ZrO2.•System integration between a dry reforming reactor and a SOFC system.
Bone has a sophisticated architecture characterized by a hierarchical organization, starting at the sub-micrometre level. Thus, the analysis of the mechanical and structural properties of bone at ...this scale is essential to understand the relationship between its physiology, physical properties and chemical composition. Here, we unveil the potential of Brillouin-Raman microspectroscopy (BRaMS), an emerging correlative optical approach that can simultaneously assess bone mechanics and chemistry with micrometric resolution. Correlative hyperspectral imaging, performed on a human diaphyseal ring, reveals a complex microarchitecture that is reflected in extremely rich and informative spectra. An innovative method for mechanical properties analysis is proposed, mapping the intermixing of soft and hard tissue areas and revealing the coexistence of regions involved in remodelling processes, nutrient transportation and structural support. The mineralized regions appear elastically inhomogeneous, resembling the pattern of the osteons' lamellae, while Raman and energy-dispersive X-ray images through scanning electron microscopy show an overall uniform distribution of the mineral content, suggesting that other structural factors are responsible for lamellar micromechanical heterogeneity. These results, besides giving an important insight into cortical bone tissue properties, highlight the potential of BRaMS to access the origin of anisotropic mechanical properties, which are almost ubiquitous in other biological tissues.
Nonlinear bistable systems have proven to be advantageous for energy harvesting of random and real ambient vibrations. One simple way of implementing a bistable transducer is setting a piezoelectric ...beam in a post-buckled configuration by axial compression. Besides, hinged or clamped-clamped type of boundary conditions correspond to two different post-buckled shape functions. Here we study, through theoretical analysis and numerical simulations, the efficiency of a hinged and clamped-clamped piezoelectric bridge under band-limited random noise with progressive axial load. Clamped configuration results to harvest 26% more power than hinged around an optimal axial load of 0.05%, while, in the intra-well trapped situation, above 0.1%, the two configurations present no substantial difference. Nevertheless, simulations confirm the advantage of exploiting inter-well oscillations in bistable regime.
Specifically designed samples have been analyzed to test the ability of Brillouin spectroscopy to provide reliable mechanical characterization of micro and nano-objects. The selected samples are ...polymeric films, whose transversal sizes from hundreds of nano- to some micro-meters cover the entire range of length-scales relevant in Brillouin scattering process. The experimental data highlight how, the size of the extended collective oscillation (acoustic phonons, in brief) is the lowest spatial resolution reachable in Brillouin mechanical characterization. Conversely, in the limit condition of phonon confinement, the technique provides the mechanical properties of nano-objects whose characteristic size is comparable with the phonon wavelength (⁓300 nm). Investigating acoustically heterogeneous materials, both size of heterogeneity and acoustic mismatch between adjacent regions are shown to be relevant in shaping the Brillouin response. In particular, a transition from a confined to a non-confined condition is obtained modulating the acoustic mismatch between the micro-objects and their local environment. The provided results and the derived analytic models for the data analysis will guide the interpretation of Brillouin spectra acquired in complex nano-structured samples such as cells, tissues or biomimetic materials. Our analysis can therefore generate new insights to tackle fundamental problems in mechanobiology or to characterize new bioengineered materials.
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•Thin films of different traversals size are investigated as biomaterials models.•Brillouin spectroscopy measures the mechanical properties of micro and nano-objects.•Phonon confinement increases the spatial resolution of Brillouin spectroscopy.•Size and acoustic mismatch of heterogeneities alters Brillouin elastography.
This study concerns those crystallographic and microstructural features that can provide indications on the actual origin of red pigments based on hematite (Fe2O3). The main features of natural and ...artificial hematite are recalled and used to discuss the results obtained from the characterization of red‐ochre samples coming from the Palaeolithic site of Riparo Dalmeri, a rock‐shelter located in northeastern Italy, dated to 13 000 cal. bp, and notorious for the presence, among the other finds, of red‐painted calcareous stones. Painting and the treatment of leather and hides obtained from the intensive hunting activity were the main uses of the hematite‐based red‐ochres at Riparo Dalmeri. It turns out that hematite was mostly obtained from the thermal treatment of goethite, which, unlike hematite, was and still is widely available in the neighbourhood of the site.
Sol–gel processing was used to obtain monosized silica spheres of 270
nm in diameter. Starting from these spheres, two different systems have been fabricated: (i) 3D Photonic Crystals by means of ...vertical deposition and evaporation-assisted sedimentation deposition methods; (ii) core-shell-like Er
3+-activated silica spheres, where the core is the silica sphere and the shell is an Er
2O
3–SiO
2 coating. Optical and spectroscopic assessment, as well as morphological and structural characterization of the systems, have been performed.
Erbium doped tellurite glasses (TPE), having composition (70TeO2–(30−x)ZnO–xPbO)0.99–(Er2O3)0.01 (x=5, 10, 15, and 20), were prepared by melt quenching technique and characterized by density ...measurements, Raman and optical spectroscopies and extended X-ray absorption fine structure (EXAFS) experiments. The main structural modifications of glasses as a function of the PbO/ZnO ratio are monitored by Raman scattering. EXAFS analysis shows almost unchanged short range environment around Er3+ ions for all glasses. Absorption and luminescence spectra evidence a significant decrease of the asymmetry of crystal field at the Er3+ ion site as the PbO content increases.
•Structural variations and optical properties were studied as a function of PbO.•Raman spectra evident the network forming capability of PbO (Te–O–Pb).•EXAFS analysis reveals that there are no appreciable changes in the average Er3+ ion environment.•Predominant decrease of intensities in the hypersensitive transitions was observed.•Asymmetric crystal field at Er3+ ion sites decreases as the PbO content increases.
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