On the mechanical properties and auxetic potential of various organic networked polymers

We simulate and analyse three types of two-dimensional networked polymers which have been predicted to exhibit on-axis auxetic behaviour (negative Poisson's ratio), namely (1) polyphenylacetylene networks that behave like flexing re-entrant honeycombs, commonly referred to as ‘reflexynes’, (2) polyphenylacetylene networks that mimic the behaviour of rotating triangles, commonly referred to as ‘polytriangles’ and (3) networked polymers built from calix[4]arene units. More specifically, we compute and compare their in-plane off-axis mechanical behaviour, in particular their off-axis Poisson's ratios and show that in some cases, the sign and magnitude of the Poisson's ratio are dependent on the direction of loading. We propose two functions that can provide a measure for the extent of auxeticity for such anisotropic materials and show that the polytriangles are predicted as the most auxetic when compared with the other networks with the reflexyne re-entrant networks being the least auxetic.peer-reviewe

Diffraction-free pulsed optical beams via space-time correlations

Diffraction places a fundamental limitation on the distance an optical beam propagates before its size increases and spatial details blur. We show here that imposing a judicious correlation between spatial and spectral degrees of freedom of a pulsed beam can render its transverse spatial profile independent of location along the propagation axis, thereby arresting the spread of the time-averaged beam. Such correlation introduced into a beam with arbitrary spatial profile enables spatio-temporal dispersion to compensate for purely spatial dispersion that underlies diffraction. As a result, the spatio-temporal profile in the local time-frame of the pulsed beam remains invariant at all positions along the propagation axis. One-dimensional diffraction-free space-time beams are described - including non-accelerating Airy beams, despite the well-known fact that cosine waves and accelerating Airy beams are the only one-dimensional diffraction-free solutions to the monochromatic Helmholtz equation

Traumatic brain injury : integrated approaches to improve prevention, clinical care, and research

Rahul Raj on työryhmän InTBIR Participants Investigators jäsen.Peer reviewe

Reclamo al CICR- commento all'art.9 TUB

Il reclamo al CICR resta apparentemente immutato come reclamo nazionale avverso i provvedimenti di vigilanza, mentre gli assetti dei poteri di vigilanza bancaria sono da tempo profondamente riconfigurati e incentrati sulla BCE. Nel nuovo sistema di vigilanza è previsto un diverso procediento di reclamo. Si affronta, quindi, principalmente il problema della convivenza dei due rimedi