High frequency guided wave propagation in monocrystalline silicon wafers

Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. The cutting process can introduce micro-cracks in the thin wafers and lead to varying thickness. High frequency guided ultrasonic waves are considered for the structural monitoring of the wafers. The anisotropy of the monocrystalline silicon leads to variations of the wave characteristics, depending on the propagation direction relative to the crystal orientation. Full three-dimensional Finite Element simulations of the guided wave propagation were conducted to visualize and quantify these effects for a line source. The phase velocity (slowness) and skew angle of the two fundamental Lamb wave modes (first anti-symmetric mode A0 and first symmetric mode S0) for varying propagation directions relative to the crystal orientation were measured experimentally. Selective mode excitation was achieved using a contact piezoelectric transducer with a custom-made wedge and holder to achieve a controlled contact pressure. The out-of-plane component of the guided wave propagation was measured using a noncontact laser interferometer. Good agreement was found with the simulation results and theoretical predictions based on nominal material properties of the silicon wafe

Noise driven translocation of short polymers in crowded solutions

In this work we study the noise induced effects on the dynamics of short polymers crossing a potential barrier, in the presence of a metastable state. An improved version of the Rouse model for a flexible polymer has been adopted to mimic the molecular dynamics by taking into account both the interactions between adjacent monomers and introducing a Lennard-Jones potential between all beads. A bending recoil torque has also been included in our model. The polymer dynamics is simulated in a two-dimensional domain by numerically solving the Langevin equations of motion with a Gaussian uncorrelated noise. We find a nonmonotonic behaviour of the mean first passage time and the most probable translocation time, of the polymer centre of inertia, as a function of the polymer length at low noise intensity. We show how thermal fluctuations influence the motion of short polymers, by inducing two different regimes of translocation in the molecule transport dynamics. In this context, the role played by the length of the molecule in the translocation time is investigated.Comment: 11 pages, 3 figures, to appear in J. Stat. Mechanics: Theory and Experiment, 200

AM-PM facial image comparison for forensic human identification

The uniqueness of the face has been studied concerning its application for human identification. In particular, morphological facial comparison has been used to verify the identities of living individuals in forensic investigations and has received considerable attention, including validation studies and the development of international guidelines (FISWG, 2019a; Bacci et al., 2021b). At the same time, the application of morphological comparison in post-mortem identification has been recognised (Olivieri et al., 2018; Cappella et al., 2021), but remains understudied and require further validation. In light of this, this study investigates the reliability of morphological facial comparison using an unconstrained sample of ante-mortem (AM) and post-mortem (PM) images of recent deceased (N=29), and aims to develop a methodological protocol combining the structure of the living individual's guidelines and accounts for the early post-mortem changes that affect the face. The reliability of the morphological method for PM identification is investigated by performing the comparisons and documenting the process using the protocol, and by testing it with three observers on selected AM-PM pairs (N=15). The key findings suggest that AM-PM photographic comparison using the proposed protocol could help to narrow down the potential matches of a PM subject. Moreover, in some cases, it is also possible to provide a single correct AM target for a PM subject with a high level of confidence. While the validity of the protocol requires further investigation beyond this study, its design, which includes the addition of a stage for analysis of the decomposition changes affecting the PM subjects and a holistic preliminary analysis of AM-PM pairs to exclude the obvious non-matches, seems advantageous. The interobserver study results indicate that both absolute agreement (ICC=0.813) and agreement on the level of support (Kendal’s K=0.885) are satisfactory. Overall, the limitation of the study includes the small interobserver random sample (15 pairs), the absence of non-matching AM subjects in the sample pool tasks, and presence of a very limited number of PM subjects showing signs of post-mortem changes (e.g. facial bloating). This study could benefit forensic casework, in particular in the Disaster Victim identification (DVI) procedures, when other AM primary identifiers are scarce. Future studies should investigate the application of PM photographic facial comparison using a larger database simulating an open disaster scenario, while also further validating and testing the applicability of the developed method with different observers

Axonal T₂ estimation using the spherical variance of the strongly diffusion-weighted MRI signal.

In magnetic resonance imaging, the application of a strong diffusion weighting suppresses the signal contributions from the less diffusion-restricted constituents of the brain's white matter, thus enabling the estimation of the transverse relaxation time T <sub>2</sub> that arises from the more diffusion-restricted constituents such as the axons. However, the presence of cell nuclei and vacuoles can confound the estimation of the axonal T <sub>2</sub> , as diffusion within those structures is also restricted, causing the corresponding signal to survive the strong diffusion weighting. We devise an estimator of the axonal T <sub>2</sub> based on the directional spherical variance of the strongly diffusion-weighted signal. The spherical variance T <sub>2</sub> estimates are insensitive to the presence of isotropic contributions to the signal like those provided by cell nuclei and vacuoles. We show that with a strong diffusion weighting these estimates differ from those obtained using the directional spherical mean of the signal which contains both axonal and isotropically-restricted contributions. Our findings hint at the presence of an MRI-visible isotropically-restricted contribution to the signal in the white matter ex vivo fixed tissue (monkey) at 7T, and do not allow us to discard such a possibility also for in vivo human data collected with a clinical 3T system

Different responses to rivastigmine in subcortical vascular dementia and multi-infarct dementia.

Vascular dementia (VaD) is associated with a large amount of heterogeneity, as it groups together a broad category of patients in whom various manifestations of cognitive decline are attributed to cerebrovascular or cardiovascular disease. Thus, a study was designed to determine the effects of rivastigmine on cognitive function, global daily living performance, and behavioral disorders in VaD patients versus an active control (nimodipine), stratifying patients according to the type of VaD, subcortical vascular dementia (sVAD), and multi-infarct dementia (MID). The trial was a prospective study. This study shows that long-term treatment with rivastigmine, at dosages approved for therapeutic use in Alzheimer's disease, produces significant improvement in all behavioral symptoms in 2 forms of VaD, MID and sVaD, except delusions. It also suggests that rivastigmine may enable a reduction in concomitant neuroleptics and benzodiazepines in VaD, especially in MID. The results are discussed with an overview of the literature

Biofeedback for gait retraining based on real-time estimation of tibiofemoral joint contact forces

Biofeedback assisted rehabilitation and intervention technologies have the potential to modify clinically relevant biomechanics. Gait retraining has been used to reduce the knee adduction moment, a surrogate of medial tibiofemoral joint loading often used in knee osteoarthritis research. In this study we present an electromyogram-driven neuromusculoskeletal model of the lower-limb to estimate, in real-time, the tibiofemoral joint loads. The model included 34 musculotendon units spanning the hip, knee, and ankle joints. Full-body inverse kinematics, inverse dynamics, and musculotendon kinematics were solved in real-time from motion capture and force plate data to estimate the knee medial tibiofemoral contact force (MTFF). We analyzed 5 healthy subjects while they were walking on an instrumented treadmill with visual biofeedback of their MTFF. Each subject was asked to modify their gait in order to vary the magnitude of their MTFF. All subjects were able to increase their MTFF, whereas only 3 subjects could decrease it, and only after receiving verbal suggestions about possible gait modification strategies. Results indicate the important role of knee muscle activation patterns in modulating the MTFF. While this study focused on the knee, the technology can be extended to examine the musculoskeletal tissue loads at different sites of the human body