Multiscale modeling of synthetic and biological supramolecular systems.

In this thesis, we exploited the synergistic combination of multiscale molecular modeling, molecular dynamics (MD), and enhanced sampling to tackle two complex systems. In the first case study, we investigated the intrinsic dynamic behavior of a Benzene 1,3,5-TricarboxAmide (BTA) supramolecular polymer in water. In the second case study, we inquired about the effect of functionalized amphiphilic gold nanoparticles (Au NPs) on the phase behavior of a multi-component lipid membrane. Through our simulations, we gained a deeper understanding of the structure and dynamics of a class of supramolecular polymers. Additionally, we identified the factors that control the exchange of monomers between the different fibers, which can be used to inform the design of novel supramolecular materials in the future. Our simulations provided insights into the mechanisms underlying the interaction between functionalized nanoparticles and lipid membranes, extrapolating the factors that influence the stability of the membrane phase separation. The acquired knowledge can be applied in drug delivery systems or to create new hybrid materials containing ordered two-dimensional NP lattices. In particular, it is worth noting that in both studies, using coarse-grained models with the proper (sub-molecular) resolution was crucial to overcoming the limitations of classic all-atom force fields while maintaining the needed chemical specificity. Overall, the results of these studies have broad implications for materials science and biophysics and demonstrate the potential of computational modeling to inform the design of novel materials and systems

Structural and Dynamical Properties of Galaxies in a Hierarchical Universe: Sizes and Specific Angular Momenta

We use a state-of-the-art semi-analytic model to study the size and the specific angular momentum of galaxies. Our model includes a specific treatment for the angular momentum exchange between different galactic components. Disk scale radii are estimated from the angular momentum of the gaseous/stellar disk, while bulge sizes are estimated assuming energy conservation. The predicted size--mass and angular momentum--mass relations are in fair agreement with observational measurements in the local Universe, provided a treatment for gas dissipation during major mergers is included. Our treatment for disk instability leads to unrealistically small radii of bulges formed through this channel, and predicts an offset between the size--mass relations of central and satellite early-type galaxies, that is not observed. The model reproduces the observed dependence of the size--mass relation on morphology, and predicts a strong correlation between specific angular momentum and cold gas content. This correlation is a natural consequence of galaxy evolution: gas-rich galaxies reside in smaller halos, and form stars gradually until present day, while gas-poor ones reside in massive halos, that formed most of their stars at early epochs, when the angular momentum of their parent halos is low. The dynamical and structural properties of galaxies can be strongly affected by a different treatment for stellar feedback, as this would modify their star formation history. A higher angular momentum for gas accreted through rapid mode does not affect significantly the properties of massive galaxies today, but has a more important effect on low-mass galaxies at higher redshift.Comment: 26 pages, 14 figures, 4 appendices. Accepted for publication in MNRA

The Evolution of Sizes and Specific Angular Momenta in Hierarchical Models of Galaxy Formation and Evolution

We extend our previous work focused at $z\sim0$, studying the redshift evolution of galaxy dynamical properties using the state-of-the-art semi-analytic model GAEA: we show that the predicted size-mass relation for disky/star forming and quiescent galaxies is in good agreement with observational estimates, up to $z\sim2$. Bulge dominated galaxies have sizes that are offset low with respect to observational estimates, mainly due to our implementation of disk instability at high redshift. At large masses, both quiescent and bulge dominated galaxies have sizes smaller than observed. We interpret this as a consequence of our most massive galaxies having larger gas masses than observed, and therefore being more affected by dissipation. We argue that a proper treatment of quasar driven winds is needed to alleviate this problem. Our model compact galaxies have number densities in agreement with observational estimates and they form most of their stars in small and low angular momentum high-$z$ halos. GAEA predicts that a significant fraction of compact galaxies forming at high-$z$ is bound to merge with larger structures at lower redshifts: therefore they are not the progenitors of normal-size passive galaxies at $z=0$. Our model also predicts a stellar-halo size relation that is in good agreement with observational estimates. The ratio between stellar size and halo size is proportional to the halo spin and does not depend on stellar mass but for the most massive galaxies, where AGN feedback leads to a significant decrease of the retention factor (from about 80 per cent to 20 per cent).Comment: Accepted for publication in MNRAS, 17 pages, 11 figure

Counteraction of HCV-induced oxidative stress concurs to establish chronic infection in liver cell cultures

Hepatitis C virus (HCV) is a blood-borne pathogen causing acute and chronic hepatitis. A significant number of people chronically infected with HCV develop cirrhosis and/or liver cancer. The pathophysiologic mechanisms of hepatocyte damage associated with chronic HCV infection are not fully understood yet, mainly due to the lack of an in vitro system able to recapitulate the stages of infection in vivo. Several studies underline that HCV virus replication depends on redox-sensitive cellular pathways; in addition, it is known that virus itself induces alterations of the cellular redox state. However, the exact interplay between HCV replication and oxidative stress has not been elucidated. In particular, the role of reduced glutathione (GSH) in HCV replication and infection is still not clear. We set up an in vitro system, based on low m.o.i. of Huh7.5 cell line with a HCV infectious clone (J6/JFH1), that reproduced the acute and persistent phases of HCV infection up to 76 days of culture. We demonstrated that the acute phase of HCV infection is characterized by the elevated levels of reactive oxygen species (ROS) associated in part with an increase of NADPH-oxidase transcripts and activity and a depletion of GSH accompanied by high rates of viral replication and apoptotic cell death. Conversely, the chronic phase is characterized by a reestablishment of reduced environment due to a decreased ROS production and increased GSH content in infected cells that might concur to the establishment of viral persistence. Treatment with the prooxidant auranofin of the persistently infected cultures induced the increase of viral RNA titer, suggesting that a prooxidant state could favor the reactivation of HCV viral replication that in turn caused cell damage and death. Our results suggest that targeting the redox-sensitive host-cells pathways essential for viral replication and/or persistence may represent a promising option for contrasting HCV infection

The historical evolution of school integration in Italy: Some witnesses and considerations

AbstractIn Italy, the policy of 'integration' that has been implemented since the 1970s, is based on a welcoming culture in the common school context, and represents a particular phase, both politically and socially, of Italian history. It is based on a system of relations around the person with a disability and on the reciprocal enrichment that allows the other students to understand a different way of learning which is concerned with living together. School integration allows the students to share a new understanding of education which is underpinned by the principle that by living together all students can acquire new ways of learning and new kinds of knowledge. The purpose of this article is not to describe the model and the process of integration in Italy – that can be the subject of further and more specific works – but to focus on the historical evolution and the reference points represented by some authors who discuss the principles, and most meaningful aspects, on which the idea of integrazione scolastica11Italian "integrazione scolastica" is focused on interaction and on reciprocal change, on context organisation and on integrated didactic strategies. is based. The historical analysis is developed through references to some of the key scholars and witnesses who have worked to develop the organizational framework for the development of the inclusive school in Italy

On the shape and evolution of a cosmic ray regulated galaxy-wide stellar initial mass function

In this paper, we present a new derivation of the shape and evolution of the integrated galaxy-wide initial mass function (IGIMF), incorporating explicitly the effects of cosmic rays (CRs) as regulators of the chemical and thermal state of the gas in the dense cores of molecular clouds. We predict the shape of the IGIMF as a function of star formation rate (SFR) and CR density, and show that it can be significantly different with respect to local estimates. In particular, we focus on the physical conditions corresponding to IGIMF shapes that are simultaneously shallower at high-mass end and steeper at the low-mass end than a Kroupa IMF. These solutions can explain both the levels of $\alpha$-enrichment and the excess of low-mass stars as a function of stellar mass, observed for local spheroidal galaxies. As a preliminary test of our scenario, we use idealized star formation histories to estimate the mean IMF shape for galaxies of different $z=0$ stellar mass. We show that the fraction of low-mass stars as a function of galaxy stellar mass predicted by these mean IMFs agrees with the values derived from high-resolution spectroscopic surveys.Comment: 8 pages, 5 figures, MNRAS accepte

Stellar Ages and Metallicities of Central and Satellite Galaxies: Implications for Galaxy Formation and Evolution

Using a large SDSS galaxy group catalogue, we study how the stellar ages and metallicities of central and satellite galaxies depend on stellar mass and halo mass. We find that satellites are older and metal-richer than centrals of the same stellar mass. In addition, the slopes of the age-stellar mass and metallicity-stellar mass relations are found to become shallower in denser environments. This is due to the fact that the average age and metallicity of low mass satellite galaxies increase with the mass of the halo in which they reside. A comparison with the semi-analytical model of Wang et al. (2008) shows that it succesfully reproduces the fact that satellites are older than centrals of the same stellar mass and that the age difference increases with the halo mass of the satellite. This is a consequence of strangulation, which leaves the stellar populations of satellites to evolve passively, while the prolonged star formation activity of centrals keeps their average ages younger. The resulting age offset is larger in more massive environments because their satellites were accreted earlier. The model fails, however, in reproducing the halo mass dependence of the metallicities of low mass satellites, yields metallicity-stellar mass and age-stellar mass relations that are too shallow, and predicts that satellite galaxies have the same metallicities as centrals of the same stellar mass, in disagreement with the data. We argue that these discrepancies are likely to indicate the need to (i) modify the recipes of both supernova feedback and AGN feedback, (ii) use a more realistic description of strangulation, and (iii) include a proper treatment of the tidal stripping, heating and destruction of satellite galaxies. [Abridged]Comment: 20 pages, 12 figures, submitted for publication in MNRA

Rice husk and thermal comfort: Design and evaluation of indoor modular green walls

Green walls are vertical greening structures where varied plant species grow. They are conceived as a form of urban landscape and have numerous environmental, social and economic benefits. In fact, these structures have positive effects on air quality, thermal and acoustic insulation, microclimate, psychophysical well-being and urban design. In the framework of thermal comfort, several studies demonstrated the potential of green walls to improve indoor thermal comfort and reduce heat flows through the wall of buildings. This research evaluates the thermal efficiency of two modular green walls that present an alternative substrate as growing medium. This substrate is composed of loam soil and rice husk, an agricultural organic waste derived from the rice milling process. The choice of rice husk is inspired by principles of circular economy in order to reduce the environmental impact and costs of the substrate used in greening applications. The alternative substrate was compared with expanded clay aggregate, used for plant cultivation in living walls, and the analysis was divided into two phases. Firstly, field experiments were carried out on three plant species (Chlorophytum, Dieffenbachia and Spathiphyllum) to evaluate the efficacy of these substrates to grow plants. The efficacy of the substrate was evaluated through the measurement of the concentration of chlorophyll, the determination of the growth index of plants and a qualitative observation of the root development. Secondly, two modular green walls with varied substrates and plants were designed and tested from the point of view of the thermal comfort, using the open source software TerMus-G. After the transmittance value was obtained as output for each green wall module, the heat flow and the relative variation were calculated and compared to the indoor supporting walls. This article presents a valid methodology approach to evaluate the efficiency of green walls substrate and its thermal performance. This methodology differs from those found in scientific literature and represents a valid alternative. The present research demonstrates the ability of designed modules and, more generally, of indoor green walls to increase thermal insulation without causing condensation. Furthermore, the investigation shows a positive contribution both in winter and in summer. Finally, the use of this undervalue by-product rice husk mixed with loam soil shows to be appropriate for green wall application, providing better performance than the expanded clay in terms of thermal comfort and plant growth rate. Moreover, its use as substrates should further improve the ecological footprint of green vertical structures and reduce costs

How subjective and non-physical parameters affect occupants’ environmental comfort perception

Employees’ wellbeing and comfort perception demonstrated to largely influence their productivity and tolerability of slight thermal discomfort conditions in the working spaces. Their whole comfort perception indeed depends on several parameters related to physical boundary conditions but also to the adaptation capability of occupants themselves and other personal, difficult to measure, variables. According to the available standards and regulations, only physical and measurable environmental parameters must be considered to evaluate occupants’ comfort conditions. Therefore, non-measurable factors such as socio-psychological, physiological, medical ones are currently not systematically considered. The present work aims to identify possible benefits in terms of occupants’ comfort perception due to non-physical strategies aimed at improving the work-environment quality and livability. To this aim, the environmental multi-physics and multi-domain performance of a mixed industry-office building is investigated through coupled in-field microclimate monitoring and questionnaires campaigns. The experimental microclimate monitoring and survey campaign were carried out to understand (i) the realistic indoor environmental conditions in terms of physical and measurable parameters and (ii) the personal perceptions and attitudes of the occupants with respect to those same ambient parameters, including also acoustic, lighting and medical investigation. Moreover, the collected experimental data were used to determine occupants’ comfort level through the classic comfort models, to be compared to the identified role of non-physical parameters on occupants’ final perception about the indoor environment. The main results show that non-measurable factors induced by virtuous company policy to improve employees’ working environment are effectively able to positively influence their whole-comfort perception even if the majority of workers do not have the opportunity to control their working environment. In fact, the consolidated comfort theories underestimate people satisfaction, as demonstrated by more than the 80% employees, who declared to be positively influenced by the pleasant aesthetics and livability of the workplace. The year-round experimental campaign demonstrated the need to further investigate the key role of non-physical parameters for possible incorporation into whole-comfort prediction models and standards. The role of such strategies could therefore be realistically considered as energy saving opportunities since they make building occupants much more open to tolerate slight uncomfortable conditions

La scuola inclusiva: ruoli e figure professionali

The international scenery is moving towards an inclusive school. In Italy, this reality has already been established since many years but the transformations and the international comparison raisenew questions and critical reflections. We are paying a close attention on the key factor of the integration and inclusion processes that is teacher training, as has been affirmed during the International Conference of UNESCO (2013): a new tool to develop learning paths for all the students.We are calling into question the teaching method, from individual to collective. In brief, we are going to analyze our Italian system in pedagogical terms, starting from didactic, with its methodand methodology, passing through the importance of the nets and the collaboration to finally take into account teachers’ role and, particularly, support teacher’s role, claiming its importance. Thestorytelling about “Best practices”, the research, the comparison. The specificity of the actions, based on historical sense of our past, motivations, relationships, feelings to improve the creativityand the expressivity.The international scenery is moving towards an inclusive school. In Italy, this reality has already been established since many years but the transformations and the international comparison raisenew questions and critical reflections. We are paying a close attention on the key factor of the integration and inclusion processes that is teacher training, as has been affirmed during the International Conference of UNESCO (2013): a new tool to develop learning paths for all the students.We are calling into question the teaching method, from individual to collective. In brief, we are going to analyze our Italian system in pedagogical terms, starting from didactic, with its methodand methodology, passing through the importance of the nets and the collaboration to finally take into account teachers’ role and, particularly, support teacher’s role, claiming its importance. Thestorytelling about “Best practices”, the research, the comparison. The specificity of the actions, based on historical sense of our past, motivations, relationships, feelings to improve the creativityand the expressivity