767 research outputs found
B CELL CHANGES IN AGING
No full textThe aging of the immune system is a gradual and dynamic process that modifies some immunological functions. These changes are known as “immunosenescence” that have a great impact on immune performance in late life, contributing to the decreased ability of the elderly people to respond to emerging pathogens and to the decreased responsiveness to vaccinations. It is known that the adaptive immune functions are affected in the aged. In particular, with aging, the acquired compartment of the immune system shows significant modifications in both T and B cell branches. Thus, the adaptive immune response of elderly people is qualitatively and quantitatively reduced when compared to that observed in young people. Lifelong and chronic antigenic load are the major driving forces of this process that is associated with a general increase in the production of pro-inflammatory cytokines and other inflammatory molecules that render elderly people prone to frailty and susceptible to major age-related diseases, such as Alzheimer’s disease (AD). On the other hand, centenarians represent an example of successful aging because they have delayed diseases that normally cause mortality in the general population. The aim of this thesis is to study changes in immune system with age, also focusing on people genetically advantaged for healthy ageing (Centenarian Offspring) or unsuccessfully aged patients (Alzheimer’s Disease), paying attention principally on the naïve/memory B cell compartments. The presented data suggest that the study of naïve/memory B and T cell compartments may be relevant in the evaluation of biological ageing of the immune system
Recent research results in Composite Materials and Adhesive Applications for Vehicle Lightweight
No full textVehicle weight reduction (and in turn reduction of fuel consumption, noxious gas and greenhouse gas emissions), manufacturing costs and riding comfort are pushing toward relevant growth the amount of polymeric materials employed in modern cars. At the same time the main performance of the car (and in particular safety and NVH comfort) should be maintained. In order to pursue this trend, it is important to carry out research and innovation on new polymer-based materials, with a high structural performance to weight ratio to replace standard materials, such as mild steel, for structural components. The base costs of composite materials are still relatively too high, therefore research activities are needed to reduce manufacturing costs of composite components. On the other hand the use of composites offer advantages not only in terms of lightweight but also in terms of parts integration, TTM reduction, etc. Innovative components can take advantage from new materials but need for proper design rules and proper manufacturing technologies.
Cycle times and production volumes are key factors. The production value chain and the research have to work in order to overtake some technological limits (joining technologies, recyclability, repairing, safety, costs, ...) for a wider employment of lightweight materials.
This paper is presenting some recent results in the design of vehicle components with composite materials and is also presenting some recent achievements in the use of thermoplastic adhesives, nanomodified by ferromagnetic particles, sensitive to the electromagnetic field finalized to speed up both the manufacturing and the dismounting processes
A Comparative Study On Composites Based On Polyamide Matrices Reinforced With Carbon Fibres
No full textDesign Optimization and Implementation of Composite and Recyclable Thermoplastic Materials for Automotive Bumper
No full textTesting of Compounds in Models of Pulmonary Emphysema
No full textThere is a pressing need for the development of new therapies for emphysema, particularly as no existing treatment has been shown to reduce disease progression. Compounds with a potential activity against the pathological mechanisms postulated to play a role in the development and progression of emphysema should be tested in vivo in animal models of this disease. The choice of the model is of capital importance. While models of elastase-induced emphysema are relatively easy to execute, require low personnel capacity and provide fast results, they also have a limited clinical relevance. On the other hand, models of chronic smoke exposure are time-consuming, expensive and require high personnel capacity but have a high clinical relevance. Presently, mainly two pharmacological approaches are being considered and investigated in experimental studies. The first approach consists of pharmacological interventions designed to slow down the rate at which alveolar wall is lost in emphysema. In this approach we find anti-inflammatory agents, protease inhibitors and antioxidants. The attempt to reduce lung inflammatory cell infiltration is most appealing since such an effect would also reduce the lung burden of both proteases and oxidants. The second approach is an attempt to reverse the process of alveolar loss by inducing alveolar growth. To our knowledge here only the effects of retinoids and/or retinoid receptor agonists have been investigated. This report presents a selected review of the literature of animal studies using these pharmacological approaches
Implementation of Composite and Recyclable Thermoplastic Materials for Automotive Bumper Subsystem
No full textIn order not only to meet the current targets in terms of safety, but also in terms of lightweight that means lower polluting gas emissions and fuel consumption, for a newly developed vehicle it is necessary to perform a number of component based tests. This kind of experimental tests is time consuming and very expensive. Therefore, it is recommended to develop cost effective design methodology and analysis using existing finite element methods in order to evaluate the performance of different design solutions under various loading, material and environmental conditions, since from the earliest stages of the design activity.
This paper intends to address such design aspects and method of analysis with particular reference to the application of composite and recyclable thermoplastic materials to automotive front bumper design. Major constraints that have been dealt with are bumper crash resistance, absorbed energy and stiffness with particular reference to the existing bumper standards.
Finally, the results predicted by the finite element analysis are evaluated and interpreted to insight the effectiveness of the proposed solution
Per il «Doligamus» di Adolfo di Vienna: le “fabulae” VIII e IX, ovvero alcune variazioni sul tema
No full textIl «Doligamus», opera latina in 342 distici elegiaci e 7 esametri leonini degli inizi del sec. XIV (1315), si inserisce pienamente nel filone di poesia misogina di origine clericale che ebbe grande diffusione durante il Medioevo. Il suo autore, Adolfo di Vienna, attinge alla tradizione degli "exempla" e del materiale favolistico per condannare, in nove "fabulae", il comportamento deplorevole delle donne, siano esse mogli infedeli o vecchie diaboliche. In questo lavoro, dopo una presentazione generale dell’autore e dell’opera, ci si sofferma sulle ultime due "fabulae" del «Doligamus», la VIII e la IX, delle quali vengono studiati e analizzati la trama, i modelli, lo stile, la lingua e, soprattutto, le diverse “variazioni sul tema” nell’ambito della produzione novellistica ed esemplare dei secc. XIII e XIV.The «Doligamus», a latin work of 342 elegiac couplets and 7 leonine hexameters of the beginnings of XIVth century (1315), is strictly inserted in the misogynous clerical poetry which had a big diffusion during the Middle Ages. His author, Adolph of Vienna, draws from the tradition of "exempla" and "fabulae" for condemning, in his nine "fabulae", the dreadful manners of women, adulterous wives or diabolic old females. This paper, after a general presentation on the author and the work, offers an analysis of the lost two "fabulae" of the «Doligamus» (fab. VIIIth and IXth), in his plot, sources, style, language and, expecially, in the several “variations on the theme” in the literary production of short stories and "exempla" between XIIIth and XIVth centuries
Iron-based reversible adhesives: Effect of particles size on mechanical properties
No full text A hot melt adhesive – mainly used for bonding plastic component in automotive field – was modified with different iron-based particles to give it a reversible behaviour. Mechanical and physical properties of these reversible adhesives were experimentally assessed in the work. The modified adhesives, coupled with electromagnetic induction, are able to guarantee separation of the joints without any damage to the substrates for recycling, reuse or repairing of components. Single lap joint specimens were prepared using epoxy/glass fibres substrates and tests were carried out on neat and modified adhesive with 5% weight of iron and iron oxide. Three different Fe particles size were tested: 450 µm, 60 µm and 1–6 µm. The particles size of iron oxide was 50 nm. Separation was studied using single lap joint specimens under electro-magnetic induction. Experimental results showed that the maximum peak load decreases when the average particles sizes increase. The peak loads of the smallest particles were equal to the ones of the pristine adhesive. The elongation of the adhesives increases when the adhesive is modified with both iron and iron oxide particles. Finally, experimental tests on single lap joints coupled with electro-magnetic induction showed that separation of the substrates is possible using iron oxide particles. Electro-magnetic tests conducted on particles alone, helped to understand that bigger particles are able to overcome the melting temperature of the adhesive but hot-melt adhesives modified with these particles are not able to reach the melting. These tests showed that the number of particles into the adhesive matrix is very important for this kind of tests. </jats:p
Progressive damage analysis of a rate-dependent hybrid composite beam
No full textA hybrid beam combined of a molded woven fabric beam and over injected or compressive molded short fiber composite material, are manufactured and three point bending tests with different loading rates and two different boundary conditions are performed. Since the experimental results demonstrate a rate dependent behavior of the beam, then to predict its mechanical behavior under different loading velocities two strain rate sensitive progressive damage models have been developed based on Continuum Damage Mechanics approach. For internal reinforcing constituent of the beam which dominated by matrix, the matrix failure index of Hashin-Rotem's failure criterion was chosen and for outer part which governed by fibers the maximum stress theory is considered as damage initiation indicator. For both models Lapczyk-Hurtado's approach is followed to capture damage propagation. To account for rate-dependent material properties, where is needed, equations derived from a logarithmic formula, are utilized. The models are applied on the commercial finite element software of ABAQUS using user-written subroutine based on explicit numerical method. The numerical results are verified by the bending tests and it is shown that the numerical results of the proposed models have shown better agreement with experimental results of compressive molding technology than back injected on
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