LOWER MANTLE TEMPERATURE AND COMPOSITION

We evaluate the thermo-chemical state of the lower mantle by analysing the differences in the pattern of heterogeneity between shear and compressional velocity variations and the S−to−P heterogeneity ratio ( RS/P=δlnVS/δlnVP) as mapped in our model SPani and in alternative joint models. Robust structural differences between VP and VS evidence the presence of compositional heterogeneity within the two Large Low Shear Velocity Provinces (LLSVPs). We find also an increasing decorrelation with depth that can be associated with compositional layering of the LLSVPs. In addition, our model shows heterogeneity in the transition zone and mid mantle by complex morphology of subducting slabs and further differences between VP and VS that point to an unexpected heterogeneous lower mantle. Precise estimates of compositional heterogeneities are not yet affordable because of the difficulty to provide quantitative measure of RS/P, making it difficult to use this ratio to evaluate chemical heterogeneity. For instance, RS/P global median value ( ) drops from ∼2.8 to ∼1.9, at 2500 km depth when the VP component of SPani is replaced by a VP model resulting from a differently regularized inversion and obtaining an equally good data fit. An increase of 20% of the SPani VP anomalies also drastically reduces without significantly degrading the data fit. Noise in model parameters also leads to overestimate RS/P in the two LLSVPs as we show with synthetic tests. Additional mineral physics uncertainties for compositional effects on RS/P and for the conversion of δlnVS and δlnVP into density further complicates a precise chemical interpretation

Seismic waveform sensitivity to global boundary topography

We investigate the implications of lateral variations in the topography of global seismic discontinuities, in the framework of high-resolution forward modelling and seismic imaging. We run 3-D wave-propagation simulations accurate at periods of 10 s and longer, with Earth models including core-mantle boundary topography anomalies of ∼1000 km spatial wavelength and up to 10 km height. We obtain very different waveform signatures for PcP (reflected) and Pdiff (diffracted) phases, supporting the theoretical expectation that the latter are sensitive primarily to large-scale structure, whereas the former only to small scale, where large and small are relative to the frequency. PcP at 10 s seems to be well suited to map such a small-scale perturbation, whereas Pdiff at the same frequency carries faint signatures that do not allow any tomographic reconstruction. Only at higher frequency, the signature becomes stronger. We present a new algorithm to compute sensitivity kernels relating seismic traveltimes (measured by cross-correlation of observed and theoretical seismograms) to the topography of seismic discontinuities at any depth in the Earth using full 3-D wave propagation. Calculation of accurate finite-frequency sensitivity kernels is notoriously expensive, but we reduce computational costs drastically by limiting ourselves to spherically symmetric reference models, and exploiting the axial symmetry of the resulting propagating wavefield that collapses to a 2-D numerical domain. We compute and analyse a suite of kernels for upper and lower mantle discontinuities that can be used for finite-frequency waveform inversion. The PcP and Pdiff sensitivity footprints are in good agreement with the result obtained cross-correlating perturbed and unperturbed seismogram, validating our approach against full 3-D modelling to invert for such structure

Seismic waveform inversion for core-mantle boundary topography

The topography of the core-mantle boundary (CMB) is directly linked to the dynamics of both the mantle and the outer core, although it is poorly constrained and understood. Recent studies have produced topography models with mutual agreement up to degree 2. A broad-band waveform inversion strategy is introduced and applied here, with relatively low computational cost and based on a first-order Born approximation. Its performance is validated using synthetic waveforms calculated in theoretical earth models that include different topography patterns with varying lateral wavelengths, from 600 to 2500 km, and magnitudes (∼10 km peak-to-peak). The source-receiver geometry focuses mainly on the Pdiff, PKP, PcP and ScS phases. The results show that PKP branches, PcP and ScS generally perform well and in a similar fashion, while Pdiff yields unsatisfactory results. We investigate also how 3-D mantle correction influences the output models, and find that despite the disturbance introduced, the models recovered do not appear to be biased, provided that the 3-D model is correct. Using cross-correlated traveltimes, we derive new topography models from both P and S waves. The static corrections used to remove the mantle effect are likely to affect the inversion, compromising the agreement between models derived from P and S data. By modelling traveltime residuals starting from sensitivity kernels, we show how the simultaneous use of volumetric and boundary kernels can reduce the bias coming from mantle structures. The joint inversion approach should be the only reliable method to invert for CMB topography using absolute cross-correlation traveltime

Treatment of Y-T Humeral Fractures with Polyaxial Locking Plate System (PAX) in 14 Dogs

The aim of this study is to report the results and to review the outcome of 14 cases of Y-T humeral fractures repair using paired polyaxial locking system (PAX) plates through a combined medial and lateral approach. Fourteen consecutive dogs, with traumatic humeral Y-T fractures, met the inclusion criteria. This study includes signalment, preoperative radiographs, type of implants, radiographic bone healing assessment, complications, range of motion (ROM) of the elbow and limb function evaluated at 120 days after surgery. Postoperative radiographs revealed adequate anatomic reconstruction, and in all cases, bone healing has been achieved. No implant failure was observed. Functional outcome was excellent in 7 dogs (no lameness and preserved ROM), good in 4 (slight lameness and moderate ROM reduction) and discrete in 2 (mild lameness and severe ROM reduction). Complications were encountered in 2/14 patients with implant-associated infection resolved after long-term antibiotic treatment and implant removal. The PAX system is shown to be a valid alternative for the treatment of Y-T humeral fractures, offering the benefit of polyaxial insertion of locking screws. The possibility of angle locking screws is helpful in the distal humeral bicondylar fractures, providing additional options for screw placement in juxtarticular fractures, avoiding fracture lines or other implants

On measuring surface wave phase velocity from station-station cross-correlation of ambient signal

We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one method involves the time-domain cross-correlation of signal recorded at different stations; the other is based on frequency-domain cross-correlation, and requires finding the zero-crossings of the real part of the cross-correlation spectrum. Furthermore, the time-domain method, as implemented here and in the literature, practically involves the important approximation that interstation distance be large compared to seismic wavelength. In both cases, cross-correlations are ensemble-averaged over a relatively long period of time (1 yr). We verify that the two algorithms give consistent results, and infer that phase velocity can be successfully measured through ensemble-averaging of seismic ambient noise, further validating earlier studies that had followed either approach. The description of our experiment and its results is accompanied by a detailed though simplifed derivation of ambient-noise theory, writing out explicitly the relationships between the surface wave Green's function, ambient-noise cross-correlation and phase and group velocitie

Hyaluronic acid-based nanocomplexes as an innovative therapeutic tool to treat myotonic dystrophy

Hyaluronic acid-based nanocomplexes have been synthesized and tested as an innovative therapeutic tool to treat myotonic dystroph

Optical imaging of Tc-99m-based tracers: in vitro and in vivo results.

It has been recently shown that optical imaging (OI) methods can be used to image the in vivo biodistribution of several radiopharmaceuticals labeled with beta or alpha emitters. In this work particular attention has been focused on investigating the weaker optical signal induced by an almost pure gamma emitter like Tc-99m. Visible light emission measurements of a water solution containing Tc-99m were performed using a small animal OI system. A sequence of images was acquired for 24 h in order to study the decay of the luminescence signal. The difference between the luminescence decay half life and well-known Tc-99m half life was equal to 1%. in vivo imaging was performed by injecting one control nude mice with Tc-99m-MDP. Optical images obtained with equipment designed for bioluminescence imaging showed that a visible light emission was distinguishable and correctly localized in the bladder region where a higher concentration of Tc-99m-MDP was expected. The bladder to background ratio was always greater than 1. We conclude that the experimental data presented in this paper show that it is possible to detect in vivo luminescence optical photons induced by Tc-99m. This is important especially considering the large number of Tc-99m-based radiopharmaceutical currently available