Shedding Light on Diatom Photonics by means of Digital Holography

Diatoms are among the dominant phytoplankters in the worl's ocean, and their external silica investments, resembling artificial photonics crystal, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light. The data were discussed in the light of living cell behavior in response to their environment

Van der Waals Coefficients of Atoms and Molecules from a Simple Approximation for the Polarizability

A simple and computationally efficient scheme to calculate approximate imaginary-frequency dependent polarizability, hence asymptotic van der Waals coefficient, within density functional theory is proposed. The dynamical dipolar polarizabilities of atoms and molecules are calculated starting from the Thomas-Fermi-von Weizs\"acker (TFvW) approximation for the independent-electron kinetic energy functional. The van der Waals coefficients for a number of closed-shell ions and a few molecules are hence calculated and compared with available values obtained by fully first-principles calculations. The success in these test cases shows the potential of the proposed TFvW approximate response function in capturing the essence of long range correlations and may give useful information for constructing a functional which naturally includes van der Waals interactions.Comment: 6 pages, 4 figures. To appear in Phys. Rev.

Interlaminar Response of LSI-Produced C/SiC Ceramic Matrix Composites: Experiments and Modelling

This work investigates the interlaminar properties of a C/SiC composite produced by Liquid Silicon Infiltration, combining experiments based on Double Cantilever Beam tests and numerical analyses. Experimentally, a method to obtain pre-cracks with sharp tips at precise locations is proposed, and specimens with different thickness are used to investigate the effects of bending stress states in the delamination process. The properties of tri-linear Cohesive Zone Models for the modelling of delamination are identified numerically, by using automatic regression techniques without requiring additional assumptions or testing. Fiber bridging effects were observed and modelled, including the evaluation of the process zone lengths with different experimental, analytical, and numerical methods. Overall, the work provides a qualitative insight in the delamination process of long fiber reinforced C/SiC laminates produced with a cost-affordable technique and proposes an experimental and numerical protocol to characterize and model delamination phenomena, taking into account the scattering of material properties

A critical analysis of Popper's experiment

An experiment which could decide against the Copenhagen interpretation of quantum mechanics has been proposed by K. Popper and, subsequently, it has been criticized by M.J. Collett and R. Loudon. Here we show that both the above mentioned arguments are not correct because they are based on a misuse of basic quantum rules.Comment: 12 pages, 3 figures, RevTex; to be published on PR

{\it Ab initio} 27Al^{27}Al NMR chemical shifts and quadrupolar parameters for Al2O3Al_2O_3 phases and their precursors

The Gauge-Including Projector Augmented Wave (GIPAW) method, within the Density Functional Theory (DFT) Generalized Gradient Approximation (GGA) framework, is applied to compute solid state NMR parameters for $^{27}Al$ in the $\alpha$, $\theta$, and $\kappa$ aluminium oxide phases and their gibbsite and boehmite precursors. The results for well-established crystalline phases compare very well with available experimental data and provide confidence in the accuracy of the method. For $\gamma$-alumina, four structural models proposed in the literature are discussed in terms of their ability to reproduce the experimental spectra also reported in the literature. Among the considered models, the $Fd\bar{3}m$ structure proposed by Paglia {\it et al.} [Phys. Rev. B {\bf 71}, 224115 (2005)] shows the best agreement. We attempt to link the theoretical NMR parameters to the local geometry. Chemical shifts depend on coordination number but no further correlation is found with geometrical parameters. Instead our calculations reveal that, within a given coordination number, a linear correlation exists between chemical shifts and Born effective charges

RELATIONSHIP BETWEEN EARLY SOMANTIC, RADIOLOGICAL, CONGNITIVE AND PSYCHOSOCIAL FINDINGS AND OUTCOME DURING A ONE-YEAR FOLLOW-UP IN 117 PATIENTS SUFFERING FROM COMMON WHIPLASH

To analyse the significance of the interply between somatic and psychosocial factors in influencing the course of recovery a non-selected well defined group of 117 whiplash patients was investigated. Initial examination was performed, on average, 7.2±4.2 days after trauma and follo-ups were carried out at 3, 6 and 12 months. At the initial investigation all patients were given a neurological examination, congnitive and psychosocial factor assessment and cervical spine X-rays. At each follow-up stepwise regression was performed to evaluted the relationship between inital findings and the course of recovery. Fifty-one (44%), 36(31%) and 28(24%) patients were symptomatic at 3, 6 and 12 months respectively. Poor improvement at all examiniation was significntly correlated with factors associated with severity of injury such as intial symptoms of radicular irritation and intensity of neck pain. Moreover, results indicate that poor recovery is realted to severity of injury in addition to some pre-traumatic factors(previously history of head trauma and headache). However, Psychosocial factors did not prove predictive at any follow-up examination. These results indiacte that synmptoms suggesting a more severe neck injury appear to be particularly related to delayed recovery from common whiplash. Moreover these results may be of value in the objective evalutuion of potentially difficult claims compensation, which may in some cases be falsely base

Correlation between generalised joint hypermobility and temporomandibular joint disc displacement in adolescent patients: Magnetic Resonance Imaging study

Aim: Temporomandibular disorders (TMD), in particular disc displacement, are recognised to have a multifactorial aetiology. Ligamentous laxity has been suggested as a potential risk factor for TMD. Ligamentous laxity can lead to generalised joint hypermobility (GJH) involving multiple joints, including the temporomandibular joint (TMJ). The aim of this work is to evaluate the correlation between GJH and disc displacement (DD) assessed on magnetic resonance images (MRI) of the TMJ in adolescent patients. Materials: The study was included 40 adolescent patients (10-16 years), divided into two groups, a Study Group (SG), composed of 20 subjects with GJH, and a Control Group (CG), composed of 20 subjects without GJH. The GJH was assessed by the Beighton test with a threshold value of ≥ 4. The severity of the TMD was determined using the Fonseca Questionnaire and a clinical evaluation of the type of TMD. The condylar-discal relationship and the condylar mobility of the TMJ were evaluated by MRI. Pearson's χ2 Test was performed for the analysis of the statistical correlation. Conclusion: This study suggests that adolescents with GJH have a greater risk of developing TMJ disc displacement, especially disc displacement without reduction