Size and environment: The effect of phonon localization on micro-Brillouin imaging.

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.

Brillouin-Raman microspectroscopy for the morpho-mechanical imaging of human lamellar bone.

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.

On the actual spatial resolution of Brillouin Imaging.

Brillouin imaging is an emerging optical elastography technique that is able to generate maps of the mechanical properties at microscale with great potential in biophysical and biomedical fields. A key parameter is its spatial resolution, which is usually identified with that of the confocal microscope coupled to the Brillouin interferometer. Conversely, here we demonstrate that the mean free path of acoustic phonons plays a major role in defining the resolution, especially for high numerical aperture confocal setups. Surprisingly, the resolution of elastography maps may even deteriorate when decreasing the scattering volume.

Stress effects on the elastic properties of amorphous polymeric materials.

Brillouin light scattering measurements have been used to study the stress induced modification in the elastic properties of two glass forming polymers: polybutadiene and epoxy-amine resin, prototypes of linear and network polymers, respectively. Following the usual thermodynamic path to the glass transition, polybutadiene has been studied as a function of temperature from the liquid well into the glassy phase. In the epoxy resin, the experiments took advantage of the system ability to reach the glass both via the chemical vitrification route, i.e., by increasing the number of covalent bonds among the constituent molecules, as well as via the physical thermal route, i.e., by decreasing the temperature. Independently from the particular way chosen to reach the glassy phase, the measurements reveal the signature of long range tensile stresses development in the glass. The stress presence modifies both the value of the sound velocities and their mutual relationship, so as to break the generalized Cauchy-like relation. In particular, when long range stresses, by improvise sample cracking, are released, the frequency of longitudinal acoustic modes increases more than 10% in polybutadiene and ∼4% in the epoxy resin. The data analysis suggests the presence of at least two different mechanisms acting on different length scales which strongly affect the overall elastic behaviour of the systems: (i) the development of tensile stress acting as a negative pressure and (ii) the development of anisotropy which increases its importance deeper and deeper in the glassy state.

Phononic crystals of spherical particles: a tight binding approach.

The vibrational dynamics of a fcc phononic crystal of spheres is studied and compared with that of a single free sphere, modelled either by a continuous homogeneous medium or by a finite cluster of atoms. For weak interaction among the spheres, the vibrational dynamics of the phononic crystal is described by shallow bands, with low degree of dispersion, corresponding to the acoustic spheroidal and torsional modes of the single sphere. The phonon displacements are therefore related to the vibrations of a sphere, as the electron wave functions in a crystal are related to the atomic wave functions in a tight binding model. Important dispersion is found for the two lowest phonon bands, which correspond to zero frequency free translation and rotation of a free sphere. Brillouin scattering spectra are calculated at some values of the exchanged wavevectors of the light, and compared with those of a single sphere. With weak interaction between particles, given the high acoustic impedance mismatch in dry systems, the density of phonon states consist of sharp bands separated by large gaps, which can be well accounted for by a single particle model. Based on the width of the frequency gaps, tunable with the particle size, and on the small number of dispersive acoustic phonons, such systems may provide excellent materials for application as sound or heat filters.

Structural and optical characterization of the local environment of Er3+ ions in PbO-ZnO tellurite glasses.

Erbium activated PbO-ZnO tellurite glasses ((70TeO(2)-(30-x)ZnO-xPbO)(0.99)-(Er(2)O(3))(0.01) (TZPE), (x = 5, 10, 15, 20)) were prepared by a melt quenching process and studied by optical absorption, luminescence, Raman and x-ray absorption spectroscopy measurements as a function of the PbO/ZnO ratio. The glass structure, as monitored by Raman scattering, shows important changes with the PbO/ZnO ratio, attributed to a glass former action of PbO. The local environment of Er(3+) ions, as measured by extended x-ray absorption spectroscopy, does not appreciably change as regards the first oxygen shell. However, the intensity of the optical transitions is quite sensitive to the PbO/ZnO ratio, indicating a progressive increase of the site symmetry with the PbO content. The emission probability and radiative lifetime of several excited states of Er(3+) ions were calculated using Judd-Ofelt analysis.

[An example of the evaluation of risks of repeated movements in pottery plants located in western Liguria]. / Un esempio di valutazione del rischio da movimenti ripetuti in aziende del comparto ceramico del ponente ligure.

Pottery manufacturing is typical in western Liguria and it represents one of the most important economical resources of this area. The major part of manufacturers are handicrafts, although some bigger firms have developed industrialized production cycles. Both types of productions, however, require hand work at almost all levels of processing. Most workers are women and a significant part of these are affected by Carpal Tunnel Syndrome. INAIL (Direzione Regionale Liguria) carries on a dedicated program for employers' insurance and Health & Safety implementation but--in order to do so--INAIL needs to achieve more knowledge about risk factors in this field. The aim of this study was to assess CTD risk in two pottery industries located in Albisola: in particular, two productions Cycles equipped with assembly lines have been investigated. The method used for risk assessment was OCRA Index (OCcupational Repetitive Actions), adapted to be applied to pottery industries.

Land-use planning in the vicinity of chemical sites: risk-informed decision making at a local community level.

Land-use planning with respect to major accident hazards is one of the new requirements of the 'Seveso II Directive'. On top of this requirement, but also recognising the importance of the issue for the control of major accidents, the various European Member States have developed or are developing adequate procedures, approaches and criteria for the acceptability of hazards or risk. At a national level, various criteria are in use based either on 'generic distances', or on the level of consequences, or on the level of risk. At a regional and local level, however, local particularities and the presence of multiple and usually conflicting objectives - such as reduction of risk with simultaneous increase of the benefit from exploitation of land - seem to be of great importance in decision making. The paper focuses especially on the local level and it presents a methodological framework to take these conflicting objectives into account. Furthermore, it discusses the application of this methodology in an interesting case study and it demonstrates the useful insights and the substantial aid with which local planners can be provided.