Semi-engineered earthquake-resistant structures: one-storey buildings built up with gabion-box walls

This thesis studies the static and seismic behavior of simple structures made with gabion box walls. The analysis was performed considering a one-story building with standard dimensions in plan (6m x 5m) and a lightweight timber roof. The main focus of the present investigation is to find the principals aspects of the seismic behavior of a one story building made with gabion box walls, in order to prevent a failure due to seismic actions and in this way help to reduce the seismic risk of developing countries where this natural disaster have a significant intensity. Regarding the gabion box wall, it has been performed some calculations and analysis in order to understand the static and dynamic behavior. From the static point of view, it has been performed a verification of the normal stress computing the normal stress that arrives at the base of the gabion wall and the corresponding capacity of the ground. Moreover, regarding the seismic analysis, it has been studied the in-plane and out-of-plane behavior. The most critical aspect was discovered to be the out-of-plane behavior, for which have been developed models considering the “rigid- no tension model” for masonry, finding a kinematically admissible multiplier that will create a collapse mechanism for the structure. Furthermore, it has been performed a FEM and DEM models to find the maximum displacement at the center of the wall, maximum tension stresses needed for calculating the steel connectors for joining consecutive gabions and the dimensions (length of the wall and distance between orthogonal walls or buttresses) of a geometrical configuration for the standard modulus of the structure, in order to ensure an adequate safety margin for earthquakes with a PGA around 0.4-0.5g. Using the results obtained before, it has been created some rules of thumb, that have to be satisfy in order to ensure a good behavior of these structure.

Heavily obscured AGN: an ideal laboratory to study the early co-evolution of galaxies and black holes

Obscured AGN are a crucial ingredient to understand the full growth history of super massive black holes and the coevolution with their host galaxies, since they constitute the bulk of the BH accretion. In the distant Universe, many of them are hosted by submillimeter galaxies (SMGs), characterized by a high production of stars and a very fast consumption of gas. Therefore, the analysis of this class of objects is fundamental to investigate the role of the ISM in the early coevolution of galaxies and black holes. We present a multiwavelength study of a sample of six obscured X-ray selected AGN at z>2.5 in the CDF-S, detected in the far-IR/submm bands. We performed the X-ray spectral analysis based on the 7Ms Chandra dataset, which provides the best X-ray spectral information currently available for distant AGN. We were able to place constraints on the obscuring column densities and the intrinsic luminosities of our targets. Moreover, we built up the UV to FIR spectral energy distributions (SEDs) by combining the broad-band photometry from CANDELS and the Herschel catalogs, and analyzed them by means of an SED decomposition technique. Therefore, we derived important physical parameters of both the host galaxy and the AGN. In addition, we obtained, through an empirical calibration, the gas mass in the host galaxy and assessed the galaxy sizes in order to estimate the column density associated with the host ISM. The comparison of the ISM column densities with the values measured from the X-ray spectral analysis pointed out that the contribution of the host ISM to the obscuration of the AGN emission can be substantial, ranging from ~10% up to ~100% of the value derived from the X-ray spectra. The absorption may occur at different physical scales in these sources and, in particular, the medium in the host galaxy is an ingredient that should be taken into account, since it may have a relevant role in driving the early co-evolution of galaxies with their black holes.

Dithienopyrrole-based materials: development of new polymeric derivatives

The possibility to control molar mass and termination of the growing chain is fundamental to create well-defined, reproducible materials. For this reason, in order to apply polydithienopyrrole (PDTP) as organic conjugated polymer, the possibility of controlled polymerization needs to be verified. Another aspect that is still not completely explored is bound to the optical activity of the PDTP, which bearing appropriate substituents may adopt a helical conformation. The configuration of the helix, built up from achiral co-monomers, can be established in an enantiopure way by using only a small percentage of the chiral monomer co-polymerized with achiral co-monomer. The effect, called “sergeants and soldiers effect”, is expressed by the nonlinear increase of the chiral response vs the ratio of the chiral co-monomer used for the polymerization. To date, this effect is still not completely explored for PDTP. In this framework the project will investigate, firstly, the possibility to obtain a controlled polymerization of PDTP. Then, monomers with different side chains and organometallic functions will be screened for a CTCP-type polymerization. Also a Lewis-acid based cationic polymerization will be performed. Moreover the chemical derivatization of dithienopyrrole DTP is explored: the research is going to concern also block copolymers, built up by DTP and monomers of different nature. The research will be extended also to the investigation of optically active derivates of PDTP, using a chiral monomer for the synthesis. The possibility to develop a supramolecular distribution of the polymeric chains, together with the “sergeants and soldiers effect” will be checked investigating a series of polymers with increasing amounts of chiral monomer.

Jeans modeling of massive early-type galaxies with observed stellar kinematic profiles up to 2-3 effective radii

A recent integral-field spectroscopic (IFS) survey, the MASSIVE survey (Ma et al. 2014), observed the 116 most massive (MK < −25.3 mag, stellar mass M∗ > 10^11.6 M⊙) early-type galaxies (ETGs) within 108 Mpc, out to radii as large as 40 kpc, that correspond to ∼ 2 − 3 effective radii (Re). One of the major findings of the MASSIVE survey is that the galaxy sample is split nearly equally among three groups showing three different velocity dispersion profiles σ(R) outer of a radius ∼ 5 kpc (falling, flat and rising with radius). The purpose of this thesis is to model the kinematic profiles of six ETGs included in the MASSIVE survey and representative of the three observed σ(R) shapes, with the aim of investigating their dynamical structure. Models for the chosen galaxies are built using the numerical code JASMINE (Posacki, Pellegrini, and Ciotti 2013). The code produces models of axisymmetric galaxies, based on the solution of the Jeans equations for a multicomponent gravitational potential (supermassive black hole, stars and dark matter halo). With the aim of having a good agreement between the kinematics obtained from the Jeans equations, and the observed σ and rotation velocity V of MASSIVE (Veale et al. 2016, 2018), I derived constraints on the dark matter distribution and orbital anisotropy. This work suggests a trend of the dark matter amount and distribution with the shape of the velocity dispersion profiles in the outer regions: the models of galaxies with flat or rising velocity dispersion profiles show higher dark matter fractions fDM both within 1 Re and 5 Re. Orbital anisotropy alone cannot account for the different observed trends of σ(R) and has a minor effect compared to variations of the mass profile. Galaxies with similar stellar mass M∗ that show different velocity dispersion profiles (from falling to rising) are successfully modelled with a variation of the halo mass Mh.