AN EXAMINATION OF HYDROXYL RADICAL: OUR CURRENT UNDERSTANDING OF THE OXIDATIVE CAPACITY OF THE TROPOSPHERE THROUGH EMPIRICAL, BOX, AND GLOBAL MODELING APPROACHES

Hydroxyl radical (OH) is the primary oxidant in the troposphere, initiating the removal of numerous atmospheric species including greenhouse gases, pollutants that are detrimental to human health, and ozone-depleting substances. Because of the complexity of OH chemistry, models vary widely in their OH chemistry schemes and resulting methane (CH4) lifetimes. The current state of knowledge concerning global OH abundances is often contradictory. This body of work encompasses three projects that investigate tropospheric OH from a modeling perspective, with the goal of improving the tropospheric community’s knowledge of the atmospheric lifetime of CH4. First, measurements taken during the airborne CONvective TRansport of Active Species in the Tropics (CONTRAST) field campaign are used to evaluate OH in global models. A box model constrained to measured variables is utilized to infer concentrations of OH along the flight track. Results are used to evaluate global model performance, suggest against the existence of a proposed “OH Hole” in the tropical Western Pacific, and investigate implications of high O3/low H2O filaments on chemical transport to the stratosphere. While methyl chloroform-based estimates of global mean OH suggest that models are overestimating OH, we report evidence that these models are actually underestimating OH in the tropical Western Pacific. The second project examines OH within global models to diagnose differences in CH4 lifetime. I developed an approach to quantify the roles of OH precursor field differences (O3, H2O, CO, NOx, etc.) using a neural network method. This technique enables us to approximate the change in CH4 lifetime resulting from variations in individual precursor fields. The dominant factors driving CH4 lifetime differences between models are O3, CO, and J(O3-O1D). My third project evaluates the effect of climate change on global fields of OH using an empirical model. Observations of H2O and O3 from satellite instruments are combined with a simulation of tropical expansion to derive changes in global mean OH over the past 25 years. We find that increasing H2O and increasing width of the tropics tend to increase global mean OH, countering the increasing CH4 sink and resulting in well-buffered global tropospheric OH concentrations.

Geochemistry and mineralogy of a silica chimney from an inactive seafloor hydrothermal field (East Pacific Rise, 18°S)

An inactive vent field comprised of dead chimneys was discovered on the ultrafast East Pacific Rise (EPR) at 18°S during the research campaign NAUDUR with the R/V Le Nadir in December 1993. One of these chimneys was sampled, studied and found to be largely composed of silica-mineralized bacterial-like filaments. The filaments are inferred to be the result of microbial activity leading to silica (± Fe-oxyhydroxide) precipitation. The chimney grew from the most external layer (precipitated 226 ± 4 yr. B.P.) towards the central chimney conduit. Hydrothermal activity ceased 154 ± 13 yr. B.P. and the chimney conduit was completely sealed. Mixing between an end-member hydrothermal fluid and seawater explains the Sr–Nd isotopic composition of the chimney. Seawater was the major source of Sr to the chimney, whereas the dominant Nd source was the local mid-ocean ridge basalt (MORB) leached by the hydrothermal fluids. The mixing scenarios point to a dynamic hydrothermal system with fluctuating fluid compositions. The proportion of seawater within the venting fluid responsible for the precipitation of the silica chimney layers varied between 94 and 85%. Pb-isotope data indicates that all of the Pb in the chimney was derived from the underlying MORB. The precipitation temperatures of the chimney layers varied between 55 and 71 °C, and were a function of the seawater/end-member hydrothermal fluid mixing ratio. δ30Si correlates with the temperature of precipitation implying that temperature is one of the major controls of the Si-isotope composition of the chimney. Concentrations of elements across the chimney wall were a function of this mixing ratio and the composition of the end-member hydrothermal fluid. The inward growth of the chimney wall and accompanying decrease in wall permeability resulted in an inward decrease in the seawater/hydrothermal fluid mixing ratio, which in turn exerted a control on the concentrations of the elements supplied mainly by the hydrothermal fluids. The silica chimney is significantly enriched in U, likely a result of bacterial concentration of U from the seawater-dominated vent fluid. The chimney is poor in rare earth elements (REE). It inherited its REE distribution patterns from the parent end-member hydrothermal fluids. The dilution of the hydrothermal fluid with over 85% seawater could not obliterate the particular REE features (positive Eu anomaly) of the hydrothermal fluids.

APP RERMS enriched matrix as an adhesion substrate for neuritic outgrowth

Specific domains can determine protein structural functional relationships. For the Alzheimer’s Amyloid Precursor Protein (APP) several domains have been described, both in its intracellular and extracellular fragments. Many functions have been attributed to APP including an important role in cell adhesion and cell to cell recognition. This places APP at key biological responses, including synaptic transmission. To fulfil these functions, extracellular domains take on added significance. The APP extracellular domain RERMS is in fact a likely candidate to be involved in the aforementioned physiological processes. A multidisciplinary approach was employed to address the role of RERMS. The peptide RERMS was crosslinked to PEG (Polyethylene glycol) and the reaction validated by FTIR (Fourier transform infrared spectrometry). FTIR proved to be the most efficient at validating this reaction because it requires only a drop of sample, and it gives information about the reactions occurred in a mixture. The data obtained consist in an infrared spectra of the sample, where peaks positions give information about the structure of the molecules, and the intensity of peaks is related to the concentration of the molecules. Subsequently substrates of PEG impregnated with RERMS were prepared and SH-SY5Y (human neuroblastoma cell line) cells were plated and differentiated on the latter. Several morphological alterations were clearly evident. The RERMS peptide provoked cells to take on a flatter appearance and the cytoskeletal architecture changed, with the appearance of stress fibres, a clear indicator of actin reorganization. Given that focal adhesions play a key role in determining cellular structure the latter were directly investigated. Focal adhesion kinase (FAK) is one of the most highly expressed proteins in the CNS (central nervous system) during development. It has been described to be crucial for radial migration of neurons. FAK can be localized in growth cones and mediated the response to attractive and repulsive cues during migration. One of the mechanisms by which FAK becomes active is by auto phosphorylation at tyrosine 397. It became clearly evident that in the presence of the RERMS peptide pFAK staining at focal adhesions intensified and more focal adhesions became apparent. Furthermore speckled structures in the nucleus, putatively corresponding to increased expression activity, also increased with RERMS. Taken together these results indicate that the RERMS domain in APP plays a critical role in determining cellular physiological responses. Here is suggested a model by which RERMS domain is recognized by integrins and mediate intracellular responses involving FAK, talin, actin filaments and vinculin. This mechanism probably is responsible for mediating cell adhesion and neurite outgrowth on neurons.

Stenosis triggers spread of helical Pseudomonas biofilms in cylindrical flow systems

Biofilms are multicellular bacterial structures that adhere to surfaces and often endow the bacterial population with tolerance to antibiotics and other environmental insults. Biofilms frequently colonize the tubing of medical devices through mechanisms that are poorly understood. Here we studied the helicoidal spread of Pseudomonas putida biofilms through cylindrical conduits of varied diameters in slow laminar flow regimes. Numerical simulations of such flows reveal vortical motion at stenoses and junctions, which enhances bacterial adhesion and fosters formation of filamentous structures. Formation of long, downstream-flowing bacterial threads that stem from narrowings and connections was detected experimentally, as predicted by our model. Accumulation of bacterial biomass makes the resulting filaments undergo a helical instability. These incipient helices then coarsened until constrained by the tubing walls, and spread along the whole tube length without obstructing the flow. A three-dimensional discrete filament model supports this coarsening mechanism and yields simulations of helix dynamics in accordance with our experimental observations. These findings describe an unanticipated mechanism for bacterial spreading in tubing networks which might be involved in some hospital-acquired infections and bacterial contamination of catheters.

Development of hydroxyapatite-based nanomaterials to enhance biological response of osteoblast cells for clinical application

Purpose: To develop a novel chitosan/gelatin-hydroxyapatite (CGHaP) microspheres for evaluating the biological response of pre-osteoblast cells. Methods: The microsphere was prepared by water-in-oil emulsion method. Cell proliferation was studied using AlamarBlue colorimetric assay and DAPI staining while alkaline phosphatase assay was carried out by colorimetric assay method. Chitosan microspheres as well as chitosan-hydroxyapatite microspheres was prepared and tested for biological response from MC3T3-E1 cell line. Results: The results showed that CGHaP promotes MC3T3-E1 cell proliferation and spread on the surface of microspheres. The cells were clustered with more actin filaments and well-linked with neighbouring cells or adjacent cells when cultured in CGHaP microspheres whereas fewer cells were spread on chitosan (CH) microspheres. CGHaP microspheres significantly (p < 0.05) promoted cell attachment, proliferation and extracellular matrix mineralization. CGHaP microspheres presented significantly (p < 0.02) higher calcium deposition (0.5 ng) than CH microspheres (0.28 ng). Specifically, CGHaP microspheres exhibited high ALP activity (8 units; 2-fold) compared to CH with 3 units, after 7 days of incubation. The results suggest that CGHaP possesses a great ability to facilitate bone ingrowth formation and possibility of good osteointegration in vivo. Conclusion: The nanomaterial enhances the proliferation of pre-osteoblast cells in tissue engineering microspheres. The outcome of this study may have a major impact on the development of novel nanomaterials for bone tissue engineering.

Ecologia do fitoplâncton em áreas de cultivo de Tilápia do Nilo, Oreochromis niloticus, em tanques-rede no açude Ministro João Alves, Parelhas, Rio Grande do Norte

The dams are limnic ecosystems of great importance for its multiple uses, among them, water supply for the public and to culture of artisanal fish are most relevant. The aim of the present study is to evaluate the physical-chemical characteristics and the phytoplankton community in two chosen sites (Point 1 littoral zone of point source; Point 2 pelagic zone of non-point source) of the Minister João Alves dam, which is also known as Boqueirão de Parelhas/RN. This represents the spatial distribution of the phytoplankton species in order to understand any possible alterations of the water quality and the phytoplankton composition in relation to the water quality originating from the impact of the tilapia, Oreochromis niloticus, culture. The study period also encompasses temporal variations exhibited in two seasons of an annual cycle, one during the dry season (Oct, Nov and Dec of 2008 and Jan of 2009), and the other rainy season (Mar, Apr, May and June of 2008) to extend the observation. The physicalchemical parameters, such as pH, temperature, electrical conductivity, concentration of dissolved oxygen were measured in situ and the values of the inorganic nutrients (nitrate, ammonium and orto-phosfato) and chlorophyll in the laboratory. The quali-quantitative analyses of the phytoplankton had been carried through sedimentation technique and the enumeration of the random of 400 cells, colonies and filaments counted using Sedgwick-Rafter counting chamber. The results of pH varied widely from the acidic to alkaline range with the minimum of 5.8 (± 0.8) and the maximum of 9.2 (± 0.7-0.8), at point 1 and 2. The dissolved oxygen content was higher in the rainy period than that in the dry period. The maximum electrical conductivity was of 1409 μScm-1 in point 1 and 431 minim of μScm-1, in point 2. There was a considerable alteration in the levels of inorganic nutrients such as nitrate-nitrogen, ammoniacal nitrogen and orthophosphate during the two cycles of study period. Phytoplankton assemblages presented a picture of alternate dominance among species Cyanobacteria, Bacillariophyceae and Chlorophyceae. The trophic state index diagnosed to the category of mesotrophic, which is based on the values of chlorophyll, total phosphorus and Secchi-disc measurements. The wind driven turbulence of the water column and the fresh inflow of water (flushing and dilution) during rainy season acted as constraint and did-not allow an exaggerated growth of the species of cyanobacteria. On the basis of the present we conclude that the culture of tilapias in cage-culture fails to produce pollution load that could compromise the quality of the water of the dam, probably be due to small dimension of the culture in relation to the size, volume of the water and the reservoir capacity support its own environment

Caractérisation des structures de septines hautement organisées chez la drosophile et leur interaction avec le cytosquelette d’actine

Les septines sont des GTPases conservées dérégulées dans le cancer et les maladies neurodégénératives. Elles servent de protéines d’échafaudage et forment une barrière de diffusion à la membrane plasmique et au corps central lors de la cytokinèse. Elles interagissent avec l’actine et s’organisent en complexes qui polymérisent et forment des structures hautement organisées (anneaux et filaments). Leur dynamique d’assemblage et leur rôle dans la cellule restent à être élucidés. La Drosophile est un modèle simple pour l’étude des septines puisqu’on n’y retrouve que 5 gènes (sep1, sep2, sep4, sep5, peanut) comparativement aux 13 gènes chez l’humain. À l’aide d’un anticorps contre Pnut, nous avons identifié des structures tubulaires dans 30% des cellules S2 de Drosophile. Mon projet a comme but de caractériser ces tubes en élucidant leurs constituants, leur comportement et leurs propriétés pour mieux clarifier le mécanisme par lequel les septines forment des structures hautement organisées et interagissent avec le cytosquelette d’actine. Par immunofluorescence, j’ai pu démontrer que ces tubes sont cytoplasmiques, en mitose ou interphase, ce qui suggère qu’ils ne sont pas régulés par le cycle cellulaire. Pour investiguer la composition et les propriétés dynamiques de ces tubes, j’ai généré une lignée cellulaire exprimant Sep2-GFP qui se localise aux tubes et des ARNi contre les cinq septines. Trois septines sont importantes pour la formation de ces tubes et anneaux notamment Sep1, Sep2 et Pnut. La déplétion de Sep1 cause la dispersion du signal GFP en flocons, tandis que la déplétion de Sep2 ou de Pnut mène à la dispersion du signal GFP uniformément dans la cellule. Des expériences de FRAP sur la lignée Sep2-GFP révèlent un signal de retour très lent, ce qui indique que ces structures sont très stables. J’ai aussi démontré une relation entre l’actine et les septines. Le traitement avec la Latrunculin A (un inhibiteur de la polymérisation de l’actine) ou la Jasplakinolide (un stabilisateur des filaments d’actine) mène à la dépolymérisation rapide (< 30 min) des tubes en anneaux flottants dans le cytoplasme, même si ces tubes ne sont pas reconnus suite à un marquage de la F-actine. L’Actin05C-mCherry se localise aux tubes, tandis que le mutant déficient de la polymérisation, Actin05C-R62D-mCherry perd cette localisation. On observe aussi que la déplétion de la Cofiline et de l’AIP1 (ce qui déstabilise l’actine) mène au même phénotype que le traitement avec la Latrunculine A ou la Jasplakinolide. Alors on peut conclure qu’un cytosquelette d’actine dynamique est nécessaire pour la formation et le maintien des tubes de septines. Les futures études auront comme but de mieux comprendre l’organisation des septines en structures hautement organisées et leur relation avec l’actine. Ceci sera utile pour l’élaboration du réseau d’interactions des septines qui pourra servir à expliquer leur dérégulation dans le cancer et les maladies neurodégénératives.

Mathematical models for cellular aggregation: the chemotactic instability and clustering formation

In this thesis we present a mathematical formulation of the interaction between microorganisms such as bacteria or amoebae and chemicals, often produced by the organisms themselves. This interaction is called chemotaxis and leads to cellular aggregation. We derive some models to describe chemotaxis. The first is the pioneristic Keller-Segel parabolic-parabolic model and it is derived by two different frameworks: a macroscopic perspective and a microscopic perspective, in which we start with a stochastic differential equation and we perform a mean-field approximation. This parabolic model may be generalized by the introduction of a degenerate diffusion parameter, which depends on the density itself via a power law. Then we derive a model for chemotaxis based on Cattaneo's law of heat propagation with finite speed, which is a hyperbolic model. The last model proposed here is a hydrodynamic model, which takes into account the inertia of the system by a friction force. In the limit of strong friction, the model reduces to the parabolic model, whereas in the limit of weak friction, we recover a hyperbolic model. Finally, we analyze the instability condition, which is the condition that leads to aggregation, and we describe the different kinds of aggregates we may obtain: the parabolic models lead to clusters or peaks whereas the hyperbolic models lead to the formation of network patterns or filaments. Moreover, we discuss the analogy between bacterial colonies and self gravitating systems by comparing the chemotactic collapse and the gravitational collapse (Jeans instability).

Caractérisation des structures de septines hautement organisées chez la drosophile et leur interaction avec le cytosquelette d’actine

Les septines sont des GTPases conservées dérégulées dans le cancer et les maladies neurodégénératives. Elles servent de protéines d’échafaudage et forment une barrière de diffusion à la membrane plasmique et au corps central lors de la cytokinèse. Elles interagissent avec l’actine et s’organisent en complexes qui polymérisent et forment des structures hautement organisées (anneaux et filaments). Leur dynamique d’assemblage et leur rôle dans la cellule restent à être élucidés. La Drosophile est un modèle simple pour l’étude des septines puisqu’on n’y retrouve que 5 gènes (sep1, sep2, sep4, sep5, peanut) comparativement aux 13 gènes chez l’humain. À l’aide d’un anticorps contre Pnut, nous avons identifié des structures tubulaires dans 30% des cellules S2 de Drosophile. Mon projet a comme but de caractériser ces tubes en élucidant leurs constituants, leur comportement et leurs propriétés pour mieux clarifier le mécanisme par lequel les septines forment des structures hautement organisées et interagissent avec le cytosquelette d’actine. Par immunofluorescence, j’ai pu démontrer que ces tubes sont cytoplasmiques, en mitose ou interphase, ce qui suggère qu’ils ne sont pas régulés par le cycle cellulaire. Pour investiguer la composition et les propriétés dynamiques de ces tubes, j’ai généré une lignée cellulaire exprimant Sep2-GFP qui se localise aux tubes et des ARNi contre les cinq septines. Trois septines sont importantes pour la formation de ces tubes et anneaux notamment Sep1, Sep2 et Pnut. La déplétion de Sep1 cause la dispersion du signal GFP en flocons, tandis que la déplétion de Sep2 ou de Pnut mène à la dispersion du signal GFP uniformément dans la cellule. Des expériences de FRAP sur la lignée Sep2-GFP révèlent un signal de retour très lent, ce qui indique que ces structures sont très stables. J’ai aussi démontré une relation entre l’actine et les septines. Le traitement avec la Latrunculin A (un inhibiteur de la polymérisation de l’actine) ou la Jasplakinolide (un stabilisateur des filaments d’actine) mène à la dépolymérisation rapide (< 30 min) des tubes en anneaux flottants dans le cytoplasme, même si ces tubes ne sont pas reconnus suite à un marquage de la F-actine. L’Actin05C-mCherry se localise aux tubes, tandis que le mutant déficient de la polymérisation, Actin05C-R62D-mCherry perd cette localisation. On observe aussi que la déplétion de la Cofiline et de l’AIP1 (ce qui déstabilise l’actine) mène au même phénotype que le traitement avec la Latrunculine A ou la Jasplakinolide. Alors on peut conclure qu’un cytosquelette d’actine dynamique est nécessaire pour la formation et le maintien des tubes de septines. Les futures études auront comme but de mieux comprendre l’organisation des septines en structures hautement organisées et leur relation avec l’actine. Ceci sera utile pour l’élaboration du réseau d’interactions des septines qui pourra servir à expliquer leur dérégulation dans le cancer et les maladies neurodégénératives.

Evaluation of recycled carbon fibers as PLA reinforcement for additive manufacturing applications

The increased exploitation of carbon fiber reinforced polymers (CFRP) is inevitably bringing about an increase in production scraps and end-of-life components, resulting in a sharp increase in CFRP waste. Therefore, it is of paramount importance to find efficient ways to reintroduce waste into the manufacturing cycle. At present, several recycling methods for treating CFRPs are available, even if all of them still have to be optimized. The step after CFRP recycling, and also the key to build a solid and sustainable CFRP recycling market, is represented by the utilization of Re-CFs. The smartest way to utilize recovered carbon fibers is through the manufacturing of recycled CFRPs, that can be done by re-impregnating the recovered fibers with a new polymeric matrix. Fused Filament Fabrication (FFF) is one of the most widely used additive manufacturing (3D printing) techniques that fabricates parts with a polymeric filament deposition process that allows to produce parts adding material layer-by-layer, only where it is needed, saving energy, raw material cost, and waste. The filament can also contain fillers or reinforcements such as recycled short carbon fibers and this makes it perfectly compliant with the re-application of the shortened recycled CF. Therefore, in this thesis work recycled and virgin carbon fiber reinforced PLA filaments have been initially produced using 5% and 10% of CFs load. Properties and characteristics of the filaments have been determined conducting different analysis (TGA, DMA, DSC). Subsequently the 5%wt. Re-CFs filament has been used to 3D print specimens for mechanical characterization (DMA, tensile test and CTE), in order to evaluate properties of printed PLA composites containing Re-CFs and evaluate the feasibility of Re-CFs in 3D printing application.

Models and Simulations of Diamond-like Carbon for large-area high voltage power diodes

Silicon-based discrete high-power devices need to be designed with optimal performance up to several thousand volts and amperes to reach power ratings ranging from few kWs to beyond the 1 GW mark. To this purpose, a key element is the improvement of the junction termination (JT) since it allows to drastically reduce surface electric field peaks which may lead to an earlier device failure. This thesis will be mostly focused on the negative bevel termination which from several years constitutes a standard processing step in bipolar production lines. A simple methodology to realize its counterpart, a planar JT with variation of the lateral doping concentration (VLD) will be also described. On the JT a thin layer of a semi insulating material is usually deposited, which acts as passivation layer reducing the interface defects and contributing to increase the device reliability. A thorough understanding of how the passivation layer properties affect the breakdown voltage and the leakage current of a fast-recovery diode is fundamental to preserve the ideal termination effect and provide a stable blocking capability. More recently, amorphous carbon, also called diamond-like carbon (DLC), has been used as a robust surface passivation material. By using a commercial TCAD tool, a detailed physical explanation of DLC electrostatic and transport properties has been provided. The proposed approach is able to predict the breakdown voltage and the leakage current of a negative beveled power diode passivated with DLC as confirmed by the successfully validation against the available experiments. In addition, the VLD JT proposed to overcome the limitation of the negative bevel architecture has been simulated showing a breakdown voltage very close to the ideal one with a much smaller area consumption. Finally, the effect of a low junction depth on the formation of current filaments has been analyzed by performing reverse-recovery simulations.

Production and characterization of novel thermoplastic (nano)composite materials for additive manufacturing applications

The increasing environmental global regulations have directed scientific research towards more sustainable materials, even in the field of composite materials for additive manufacturing. In this context, the presented research is devoted to the development of thermoplastic composites for FDM application with a low environmental impact, focusing on the possibility to use wastes from different industrial processes as filler for the production of composite filaments for FDM 3D printing. In particular carbon fibers recycled by pyro-gasification process of CFRP scraps were used as reinforcing agent for PLA, a biobased polymeric matrix. Since the high value of CFs, the ability to re-use recycled CFs, replacing virgin ones, seems to be a promising option in terms of sustainability and circular economy. Moreover, wastes from different agricultural industries, i.e. wheat and rice production processes, were valorised and used as biofillers for the production of PLA-biocomposites. The integration of these agricultural wastes into PLA bioplastic allowed to obtain biocomposites with improved eco-sustainability, biodegradability, lightweight, and lower cost. Finally, the study of novel composites for FDM was extended towards elastomeric nanocomposite materials, in particular TPU reinforced with graphene. The research procedure of all projects involves the optimization of production methods of composite filaments with a particular attention on the possible degradation of polymeric matrices. Then, main thermal properties of 3D printed object are evaluated by TGA, DSC characterization. Additionally, specific heat capacity (CP) and Coefficient of Linear Thermal Expansion (CLTE) measurements are useful to estimate the attitude of composites for the prevention of typical FDM issues, i.e. shrinkage and warping. Finally, the mechanical properties of 3D printed composites and their anisotropy are investigated by tensile test using distinct kinds of specimens with different printing angles with respect to the testing direction.

A hydrodynamical view on the mass accretion onto massive halos

This Thesis presents the results of my work on how galaxy clusters form by the accretion of sub-clumps and diffuse materials, and how the accreted energy is distributed in the X-ray emitting plasma. Indeed, on scales larger than tens of millions of light years, the Universe is self-organised by gravity into a spiderweb, the Cosmic Web. Galaxy clusters are the knots of this Cosmic Web, but a strong definition of filaments (which link different knots) and their physical proprieties, is still uncertain. Even if this pattern was determined by studying the spatial distribution of galaxies in the optical band, recently, also in the X-rays probes of filamentary structures around galaxy clusters were obtained. Therefore, given these observational facilities, the galaxy clusters’ outskirts are the best candidate regions to detect filaments and study their physical characteristics. However, from X-rays observations, we have only a few detections of cosmic filaments to date. On the other hand, it is crucial to understand how the accreted energy is dissipated in the baryon content of galaxy clusters and groups. Indeed, it is well known that in the central region of galaxy clusters and groups, the baryon fraction increases with the halo mass. On the outer region, the lack of X-rays constraints influences our understanding of the evolution of baryons in the halos volume. The standard assumption of “closed-box” system, for which the baryon fraction should approach the cosmological ratio Omega_bar/Omega_m, for galaxy clusters and groups seems to be too strong, especially for less massive objects. Moreover, a complete redshift evolution of baryons in galaxy clusters and groups is still missing.

Aberrant c-MET activation impairs perinuclear actin cap organization with YAP1 cytosolic relocation

Growing evidence indicates that cell and nuclear deformability plays a crucial role in the determination of cancer cells tumorigenic and metastatic potential. The perinuclear actin cap, by wrapping the nucleus with a functional network of actomyosin cables, can modulate nuclear architecture and consequently cell/nuclear elasticity. The hepatocyte growth factor receptor (MET) stands out among other membrane receptors as crucial player of the actin filaments organization, but no data are available on a specific role for MET in the actin cap assembly and the overall nuclear architecture organization. In a cell system characterized by MET hyperactivation, we observed a strong rearrangement of the cellular actin caps, with a complete dismantling of apical stress fibers and a strikingly enhanced nuclear height. CRISPR/Cas9 silencing of MET completely reverted the aberrant phenotype, resulting in flattened cells with perfectly aligned perinuclear actomyosin bundles, as well as decreased MAPK and PI3K/AKT signaling, cell proliferation rate and aggressiveness. Interestingly, MET ablated cells acquired a remarkably directed and polarized migratory phenotype, contrarily to cells with MET sustained activation showing meandering random walk. A pathway enrichment analysis comparing MET-activated and MET-KO cells RNAseq data, unveiled the contribution of multiple pathways associated with cytoskeleton remodeling, regulation of cell shape and response to mechanical stimuli. In line, the co-transcriptional activator YAP1, playing a major role in cell mechanosensing and focal adhesions/actin stabilization, appeared the culprit of the genetic reassembling of KO cells. Indeed, MET silencing was shown to induce YAP1 nuclear shuttling and increased co-transcriptional activity. Finally, we were able to induce in a normal epithelial model a phenotype closer to MET activated cancer cells only by introducing a constitutive fusion protein of MET. Taken together, our results demonstrate a new mechanism of MET-mediated actin remodeling responsible for a tumor-initiating capacity and meandering random migration, which requires YAP1 inactivation.

Constraints on the duty cycle of the remnant radio galaxy NGC 6086 in the galaxy group Abell 2162

Galaxy clusters and groups are the most massive bounded structures and the knots of the large-scale structure of the Universe. These structures reside in dark matter haloes, hosting tens to hundreds of galaxies and they are filled with hot and rarefied gas. Radio Galaxies are a peculiar class of galaxies with a luminosity in the radio band up to 10^46 erg/s between 10 MHz and 100 GHz. These galaxies are a subclass of AGN in which there is accretion on the Super Massive Black Hole. The accretion generates jets of relativistic particles and magnetic fields which lose energy through synchrotron radiation, best observable at radio frequencies. The study of the spectral ageing of the AGN plasma is fundamental to understand its evolution, interaction with the environment and to constrain the AGN duty cycle. n this thesis, we have investigated the duty cycle of the nearby remnant radio galaxy NGC 6086, located in the centre of the galaxy group Abell 2162. We have made major steps forward thanks to the new high-sensitivity interferometers in the low-frequency radio band. We have detected for the first time three filaments of emission and a second couple of lobes. We have performed an integrated and resolved analysis on the previously known inner lobes, the new filaments and the older outer lobes. We have performed an age estimate of the two pairs of lobes to give constraints on the duty cycle of the source and an estimate of its active time.