Roma Tre University

About: Roma Tre University is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 4434 authors who have published 15352 publications receiving 374888 citations. The organization is also known as: Universita degli Studi Roma Tre & RomaTre.

Dynamics of plate bending at the trench and slab-plate coupling

Abstract: [1] The bending strength of subducting lithosphere plays a critical role in the Earth's plate tectonics and mantle convection, modulating the amount of slab pull transmitted to the surface and setting the boundary conditions under which plates move and deform. However, it is the subject of a lively debate how much of the potential energy of the downgoing plate is consumed in bending the plate and how the lithospheric strength is defined during this process. We model the subduction of a viscoelastic lithosphere, driven solely by the downgoing plate's buoyancy, freely sinking in a passive mantle, represented by drag forces. To investigate the dynamics of bending, (1) we vary the density and the viscosity profile within the plate from isoviscous, where strength is distributed, to strongly layered, where strength is concentrated in a thin core, and (2) we map the stress, strain, and dissipation along the downgoing plate. The effective plate strength during bending is not a simple function of average plate viscosity but is affected by rheological layering and plate thinning. Earth-like layered plates allow for the transmission of large fractions of slab pull (∼75–80%) through the bend and yield a net slab pull of FSPnet = 1 to 6 × 1012 N m−1, which varies with the buoyancy of plates. In all models, only a minor portion of the energy is dissipated in the bending. Surprisingly, bending dissipation hardly varies with lithospheric viscosity because in our dynamic system, the plates minimize overall dissipation rate by adjusting their bending curvature. As a result, bending dissipation, ΦB, is mainly controlled by the bending moment work rate exerted by slab pull. We propose a new analytical formulation that includes a viscosity-dependent bending radius, which allows for assessment of the relative bending dissipation in the Earth's subduction zones using parameters from a recent global compilation. This yields estimates of ΦB/ΦTOT < 20%. These results suggest that plates on Earth weakly resist bending, yet are able to propagate a large amount of slab pull.

Microscopic mechanism of protein cryopreservation in an aqueous solution with trehalose

Abstract: In order to investigate the cryoprotective mechanism of trehalose on proteins, we use molecular dynamics computer simulations to study the microscopic dynamics of water upon cooling in an aqueous solution of lysozyme and trehalose. We find that the presence of trehalose causes global retardation of the dynamics of water. Comparing aqueous solutions of lysozyme with/without trehalose, we observe that the dynamics of water in the hydration layers close to the protein is dramatically slower when trehalose is present in the system. We also analyze the structure of water and trehalose around the lysozyme and find that the trehalose molecules form a cage surrounding the protein that contains very slow water molecules. We conclude that the transient cage of trehalose molecules that entraps and slows the water molecules prevents the crystallisation of protein hydration water upon cooling.

Out-of-plane seismic behaviour of rocking masonry walls

Abstract: SUMMARY The evaluation of the out-of-plane behaviour of unreinforced walls is one of the most debated topics in the seismic assessment of existing masonry buildings. The discontinuous nature of masonry and its interaction with the remainder of the building make the dynamic modelling of out-of-plane response troublesome. In this paper, the results of a shaking table laboratory campaign on a tuff masonry, natural scale, U-shaped assemblage (facade adjacent to transverse walls) are presented. The tests, excited by scaled natural accelerograms, replicate the behaviour of external walls in existing masonry buildings, from the beginning of rocking motion to overturning. Two approaches have been developed for modelling the out-of-plane seismic behaviour: the discrete element method and an SDOF analytic model. Both approaches are shown to be capable of reproducing the experimental behaviour in terms of maximum rotation and time history dynamic response. Finally, test results and numerical time history simulations have been compared with the Italian seismic code assessment procedures. Copyright © 2011 John Wiley & Sons, Ltd.

Observation of nuclear scaling in the A(e,e′) reaction at X B>1

Abstract: The ratios of inclusive electron scattering cross sections of ${}^{4}\mathrm{He},$ ${}^{12}\mathrm{C},$ and ${}^{56}\mathrm{Fe}$ to ${}^{3}\mathrm{He}$ have been measured for the first time. It is shown that these ratios are independent of ${x}_{B}$ at ${Q}^{2}g1.4{\mathrm{GeV}}^{2}$ for ${x}_{B}g1.5,$ where the inclusive cross section depends primarily on the high momentum components of the nuclear wave function. The observed scaling shows that the momentum distributions at high-momenta have the same shape for all nuclei and differ only by a scale factor. The observed onset of the scaling at ${Q}^{2}g1.4{\mathrm{GeV}}^{2}$ and ${x}_{B}g1.5$ is consistent with the kinematical expectation that two-nucleon short range correlations (SRC) dominate the nuclear wave function at ${p}_{m}\ensuremath{\gtrsim}300\mathrm{MeV}/c.$ The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with $Ag~3.$ Our data, combined with calculations and other measurements of the ${}^{3}\mathrm{H}\mathrm{e}/\mathrm{d}\mathrm{e}\mathrm{u}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{i}\mathrm{u}\mathrm{m}$ ratio, demonstrate that for nuclei with $Ag~12$ these probabilities are 4.9--5.9 times larger than in deuterium, while for ${}^{4}\mathrm{He}$ it is larger by a factor of about 3.8.