Caratteristiche anatomiche e neurochimiche della formazione ippocampale di cane

Nei Roditori e nei Primati, studi di immunoistochimica condotti sulla formazione ippocampale hanno dimostrato che le proteine leganti il calcio (parvalbumina, calbindina-D28k e calretinina) sono dei marker che consentono di identificare differenti sottopopolazioni di neuroni. Nel presente studio è stata analizzata la distribuzione di queste proteine nella formazione ippocampale di cane. L’immunoreattività per la parvalbumina è stata localizzata in neuroni multipolari presenti nello strato polimorfo e nei campi CA3-CA1, così come in alcuni neuroni presumibilmente inibitori localizzati nel campo CA1 e nel subicolo. I granuli e le fibre muschiate presentavano una forte immunoreattività per la calbindina-D28k. Tale immunoreattività era evidente anche nei neuroni piramidali del campo CA1 e del subicolo ed in alcuni interneuroni, presumibilmente inibitori, distribuiti nella formazione ippocampale. L’immunoreatività per la calretinina era relativamente bassa in tutta la formazione ippocampale. Le analisi immunoistochimiche hanno evidenziato, nel giro dentato e nel campo CA1, una riduzione età-dipendente dell’immunoreattività per la parvalbumina e la calretinina. Le analisi condotte mediante risonanza magnetica hanno inoltre dimostrato una riduzione volumetrica età-dipendente della formazione ippocampale di cane.

Design of a new harrow type wool transport mechanism to reduce fibre entanglement

The wool is entangled at several stages of its processing. In the conventional scouring machines, the prongs or the rakes agitate the wool and lead the fiber entanglement. Several scouring systems have been commercialized in order to reduce the fiber entanglement. In spite of the existing technologies, the conventional scouring machines are widely used in wool processing. In this thesis, a new approach for the harrow type wool transport mechanism has been introduced. The proposed mechanism has been designed based on the motion of the conventional harrow type wool transport mechanism by exploiting new synthesis concepts. The developed structure has been synthesized based on the Hrones and Nelson's "Atlas of four bar linkages". The four bar linkage has been applied for the desired trajectory of the developed wool transport mechanism. The prongs of the developed mechanism immerse the wool into the scouring liquor and gently propel forward toward the end of the machine with approximately straight line motion in a certain length instead of circular or elliptical motion typical of the conventional machines.

Experimental and numerical investigation on short and long term performance of macro-synthetic fibre reinforced concrete materials

Fibre Reinforced Concretes are innovative composite materials whose applications are growing considerably nowadays. Being composite materials, their performance depends on the mechanical properties of both components, fibre and matrix and, above all, on the interface. The variables to account for the mechanical characterization of the material, could be proper of the material itself, i.e. fibre and concrete type, or external factors, i.e. environmental conditions. The first part of the research presented is focused on the experimental and numerical characterization of the interface properties and short term response of fibre reinforced concretes with macro-synthetic fibers. The experimental database produced represents the starting point for numerical models calibration and validation with two principal purposes: the calibration of a local constitutive law and calibration and validation of a model predictive of the whole material response. In the perspective of the design of sustainable admixtures, the optimization of the matrix of cement-based fibre reinforced composites is realized with partial substitution of the cement amount. In the second part of the research, the effect of time dependent phenomena on MSFRCs response is studied. An extended experimental campaign of creep tests is performed analysing the effect of time and temperature variations in different loading conditions. On the results achieved, a numerical model able to account for the viscoelastic nature of both concrete and reinforcement, together with the environmental conditions, is calibrated with the LDPM theory. Different type of regression models are also elaborated correlating the mechanical properties investigated, bond strength and residual flexural behaviour, regarding the short term analysis and creep coefficient on time, for the time dependent behaviour, with the variable investigated. The experimental studies carried out emphasize the several aspects influencing the material mechanical performance allowing also the identification of those properties that the numerical approach should consider in order to be reliable.

Theoretical and experimental study of novel hybrid composite and metal-composites interfaces

The growing demand for lightweight solutions in every field of engineering is driving the industry to seek new technological solutions to exploit the full potential of different materials. The combination of dissimilar materials with distinct property ranges embodies a transparent allocation of component functions while allowing an optimal mix of their characteristics. From both technological and design perspectives, the interaction between dissimilar materials can lead to severe defects that compromise a multi-material hybrid component's performance and its structural integrity. This thesis aims to develop methodologies for designing, manufacturing, and monitoring of hybrid metal-composite joints and hybrid composite components. In Chapter 1, a methodology for designing and manufacturing hybrid aluminum/composite co-cured tubes is assessed. In Chapter 2, a full-field methodology for fiber misalignment detection and stiffness prediction for hybrid, long fiber reinforced composite systems is shown and demonstrated. Chapter 3 reports the development of a novel technology for joining short fiber systems and metals in a one-step co-curing process using lattice structures. Chapter 4 is dedicated to a novel analytical framework for the design optimization of two lattice architectures.

Numerical and experimental analysis of 3D printed smart structures and systems

Three dimensional (3D) printers of continuous fiber reinforced composites, such as MarkTwo (MT) by Markforged, can be used to manufacture such structures. To date, research works devoted to the study and application of flexible elements and CMs realized with MT printer are only a few and very recent. A good numerical and/or analytical tool for the mechanical behavior analysis of the new composites is still missing. In addition, there is still a gap in obtaining the material properties used (e.g. elastic modulus) as it is usually unknown and sensitive to printing parameters used (e.g. infill density), making the numerical simulation inaccurate. Consequently, the aim of this thesis is to present several work developed. The first is a preliminary investigation on the tensile and flexural response of Straight Beam Flexures (SBF) realized with MT printer and featuring different interlayer fiber volume-fraction and orientation, as well as different laminate position within the sample. The second is to develop a numerical analysis within the Carrera' s Unified Formulation (CUF) framework, based on component-wise (CW) approach, including a novel preprocessing tool that has been developed to account all regions printed in an easy and time efficient way. Among its benefits, the CUF-CW approach enables building an accurate database for collecting first natural frequencies modes results, then predicting Young' s modulus based on an inverse problem formulation. To validate the tool, the numerical results are compared to the experimental natural frequencies evaluated using a digital image correlation method. Further, we take the CUF-CW model and use static condensation to analyze smart structures which can be decomposed into a large number of similar components. Third, the potentiality of MT in combination with topology optimization and compliant joints design (CJD) is investigated for the realization of automated machinery mechanisms subjected to inertial loads.

Innovative electrospun nanofibers for improving delamination resistance and damping of CFRP laminates

Carbon Fiber Reinforced Polymers (CFRPs) are well renowned for their excellent mechanical properties, superior strength-to-weight characteristics, low thermal expansion coefficient, and fatigue resistance over any conventional polymer or metal. Due to the high stiffness of carbon fibers and thermosetting matrix, CFRP laminates may display some drawbacks, limiting their use in specific applications. Indeed, the overall laminate stiffness may lead to structural problems arising from their laminar structure, which makes them susceptible to structural failure by delamination. Moreover, such stiffness given by the constituents makes them poor at damping vibration, making the component more sensitive to noise and leading, at times, to delamination triggering. Nanofibrous mat interleaving is a smart way to increase the interlaminar fracture toughness: the use of thermoplastic polymers, such as poly(ε- caprolactone) (PCL) and polyamides (Nylons), as nonwovens are common and well established. Here, in this PhD thesis, a new method for the production of rubber-rich nanofibrous mats is presented. The use of rubbery nanofibers blended with PCL, widely reported in the literature, was used as matrix tougheners, processing DCB test results by evaluating Acoustic Emissions (AE). Moreover, water-soluble electrospun polyethylene oxide (PEO) nanofibers were proposed as an innovative method for reinforcing layers and hindering delamination in epoxy-based CFRP laminates. A nano-modified CFRP was then aged in water for 1 month and its delamination behaviour compared with the ones of the commercial laminate. A comprehensive study on the use of nanofibers with high rubber content, blended with a crystalline counterpart, as enhancers of the interlaminar properties were then investigated. Finally, PEO, PCL, and Nylon 66 nanofibers, plain or reinforced with Graphene (G), were integrated into epoxy-matrix CFRP to evaluate the effect of polymers and polymers + G on the laminate mechanical properties.

Mechanical behaviour and durability assessment of Fibre Reinforced Cementitious Matrix (FRCM) strengthening systems.

In recent years, the seismic vulnerability of existing masonry buildings has been underscored by the destructive impacts of earthquakes. Therefore, Fibre Reinforced Cementitious Matrix (FRCM) retrofitting systems have gained prominence due to their high strength-to-weight ratio, compatibility with substrates, and potential reversibility. However, concerns linger regarding the durability of these systems when subjected to long-term environmental conditions. This doctoral dissertation addressed these concerns by studying the effects of mild temperature variations on three FRCM systems, featuring basalt, glass, and aramid fibre textiles with lime-based mortar matrices. The study subjected various specimens, including mortar triplets, bare textile specimens, FRCM coupons, and single-lap direct shear wallets, to thermal exposure. A novel approach utilizing embedded thermocouple sensors facilitated efficient monitoring and active control of the conditioning process. A shift in the failure modes was obtained in the single lap-direct shear tests, alongside a significant impact on tensile capacity for both textiles and FRCM coupons. Subsequently, bond tests results were used to indirectly calibrate an analytical approach based on mode-II fracture mechanics. A comparison between Cohesive Material Law (CML) functions at various temperatures was conducted for each of the three systems, demonstrating a good agreement between the analytical model and experimental curves. Furthermore, the durability in alkaline environment of two additional FRCM systems, characterized by basalt and glass fibre textiles with lime-based mortars, was studied through an extensive experimental campaign. Tests conducted on single yarn and textile specimens after exposure at different durations and temperatures revealed a significant impact on tensile capacity. Additionally, FRCM coupons manufactured with conditioned textile were tested to understand the influence of aged textile and curing environment on the final tensile behavior. These results contributed significantly to the existing knowledge on FRCM systems and could be used to develop a standardized alkaline testing protocol, still lacking in the scientific literature.