151 research outputs found
Bibliografia di Tadeusz Stefan Zielinski
No full textBibliografia critica dell'opera di T. Zielinski, preceduta da un breve profilo biografic
L'ultimo mito. Storie della storia del mondo. Greche e barbare di Laura Orvieto
No full textEdizione critica e analisi del testo della Storia di Ercole e di Filottete pubblicata da Laura Orvieto ne «La Settimana dei Ragazzi» (III, 7, 16 febbraio 1947, p. 3), a confronto con gli altri scritti per ragazzi di argomento mitologico dell’autrice.Critical edition and analysis of the Storia di Ercole e di Filottete, published by Laura Orvieto in «La Settimana dei Ragazzi» (III, 7, 16 febbraio 1947, p. 3), compared to the other writings for children on classical mythology by the same author
Laura Orvieto and the Classical Heritage in Italy before the Second World War
No full textStudio della narrativa per l'infanzia di Laura Orvieto di argomento mitologico: fonti classiche e contesto culturale.Laura Orvieto (1876-1953) is a Jewish-Italian author of several books for children: her masterpiece is Storie della storia del mondo. Greche e barbare, which was published in Florence in 1910 for the first time, was translated into many languages, and is still reprinted and read throughout the world. The subject of this book is the Trojan War: the Classical world appears very frequently in Laura’s writings. It was argued that her writings on Classical Antiquity were inspired by English literature for children (Nathaniel Hawthorne, Charles Kingsley, Andrew Lang): this paper reconsiders Laura’s references to the Classical culture found in her writings within the cultural background of her family (with a special attention to her husband Angiolo Orvieto’s education and interests) and of Florence at the beginning of the 20th century. Moreover, a close analysis of Laura’s published and unpublished writings reveals her effort of drawing from the ancient sources. On the other side, some handwritten notes in Laura’s manuscript of Storie della storia del mondo. Greche e barbare – published for the first time here – can be recognised as written by the classical philologist and papyrologist Girolamo Vitelli: the texts of two letters – published for the first time here, too – sent to Laura by Vitelli confirm that Vitelli read this book before publication upon Laura’s request. The Appendix includes the edition of an unpublished chapter of Storie della storia del mondo. Greche e barbare
DEVELOPMENT AND FINITE ELEMENTS ASSESSMENT OF STACKING SEQUENCES FOR INTERLAMINAR FRACTURE TOUGHNESS TESTING OF ANGLE-PLY INTERFACES
No full textInterlaminar fracture toughness of laminated composites may be characterised using standard test procedures (see, e.g., for mode I testing, [1]). All existing standards, however, recommend the use of unidirectional (UD) layups. This restricts the characterisation to 0°/0° delamination interfaces, while structures are typically built using multidirectional (MD) layups and delamination may appear in any interlaminar layer. Since fracture toughness may depend upon layers orientations, it is clear that its characterisation in angle-ply interfaces is of paramount importance. However, as confirmed by relevant literature, a certain number of problems emerges when multidirectional layups are used. Most of these problems are related to additional damage mechanisms that may appear during experimental tests and to the coupled nature of MD specimens.
Mechanical couplings of the stacking sequences used to fabricate specimens may cause thermal residual stresses that may appear during the curing phase and that may considerably affect fracture toughness values obtained experimentally. Furthermore, pure modes delamination tests require that the considered mode be the dominant one, while others be null or negligible; if mechanical couplings exist in the specimen, they affect the kinematics of the specimen and may induce parasite modes contributions during tests. Lastly, data reduction techniques adopted to obtain fracture toughness from tests are usually based on 2D models: while this may be an acceptable hypothesis for UD specimen, it is to be questioned in the case of MD ones. For these reasons, characterisation of interlaminar fracture toughness in angle-ply interfaces is still an open problem and layups able to prevent such issues are sought.
The present study describes the conception of a novel type of specimen for testing interlaminar fracture toughness in angle-ply interfaces of laminated composite materials.
While maintaining standard geometric characteristics (see, e.g., [1]), the novelty of the specimen lies in its stacking sequence. Such sequence is developed using Quasi-Trivial (QT) solutions [2,3]. They are a particular class of sequences satisfying the condition for membrane-bending uncoupling and/or homogeneity (i.e. equal normalised membrane and bending stiffness matrices) of a laminate, in the framework of Classical Laminated Plate Theory (CLPT). In more detail, QT quasi-homogeneous solutions (that is satisfying both membrane-bending uncoupling and homogeneity) are used for each of the two arms of a typical DCB delamination specimen. Additionally, such sequences are designed in order to have null in-plane couplings and bending-torsion coupling: thus, each arm of the specimen is a specially orthotropic laminate. Furthermore, sequences for the two arms are chosen in order to comply with superposition rules for QT solutions presented in [4]. As a result, the stacking sequence of the entire specimen is a QT quasi-homogeneous solution too. It has null in-plane and bending-torsion coupling terms: thus, the entire specimen is a specially orthotropic laminate, too. To sum up, such a specimen avoids all coupling problems, for both its arms and for its entire sequence.
It’s worth mentioning that QT solutions are defined solely by specification of orientations positions in the sequence, regardless of orientations values. In other words, orientations values can be chosen freely without affecting the quasi-triviality of the sequence. Hence, from a unique QT solution multiple sequences, with different orientations, may be generated. Moreover, many different QT solutions may be used with the approach described. This allows generation of MD specimens with all kind of delamination interfaces (and maintaining all the described properties).
To validate the proposed approach, a sequence with a 0°/45° delamination interface has been developed and compared to other sequences taken from relevant literature and having the same delamination interface [5]. A Finite Elements (FE) model of the DCB test [1] has been developed and a revised VCCT formulation [6] has been used to evaluate ERR partition and distributions at the initial straight delamination front. Results obtained show that the proposed design strategy could allow fabrication of delamination specimen having significantly reduced parasite modes contributions during delamination tests.
Eventually, other sequences have been developed and studied by means of FE analysis in order to investigate some effects of stacking sequence on ERR modal partition and distribution.
REFERENCES
[1] A. D5528-13, Standard test method for mode I interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites, ASTM, International West Conshohocken (PA), URL: www.astm.org.
[2] P. Vannucci, G. Verchery, A special class of uncoupled and quasi-homogeneous laminates, Composites Science and Technology, 61, 2011, p. 1465-1473.
[3] T. Garulli, A. Catapano, M. Montemurro, J. Jumel, D. Fanteria, Quasi-trivial solutions for uncoupled, homogeneous and quasi-homogeneous laminates with high number of plies, in: R. Owen, de Borst, Pearce (Eds.), ECCM VI, International Center for Numerical Methods in Engineering (CIMNE), pp. 255-265.
[4] T. Garulli, A. Catapano, M. Montemurro, J. Jumel, D. Fanteria, Quasi-trivial stacking sequences for the design of thick laminates, Composite Structures 200, 2018, 614-623.
[5] T. Garulli, A. Catapano, D. Fanteria, J. Jumel, E. Martin, Design and finite element assessment of a Fully-Uncoupled Multi-Directional (FUMD) specimen for delamination tests, Composites Part B, paper submitted.
[6] P. S. Valvo, A revised virtual crack closure technique for physically consistent fracture mode partitioning, International Journal of Fracture 173 (1), 2012, p. 1-20
Primary CD8+ T-cell response to soluble ovalbumin is improved by chloroquine treatment in vivo
No full textThe efficiency of cross-presentation of exogenous antigens by dendritic cells (DCs) would seem to be related to the level of antigen escape from massive degradation mediated by lysosomal proteases in an acidic environment. Here, we demonstrate that a short course of treatment with chloroquine in mice during primary immunization with soluble antigens improved the cross-priming of naïve CD8+ T lymphocytes in vivo. More specifically, priming of chloroquine-treated mice with soluble ovalbumin (OVA), OVA associated with alum, or OVA pulsed on DCs was more effective in inducing OVA-specific CD8 + T lymphocytes than was priming of untreated mice. We conclude that chloroquine treatment improves the cross-presentation capacity of DCs and thus the size of effector and memory CD8+ T cells during vaccination. Copyright © 2008, American Society for Microbiology. All Rights Reserved
A novel bio-inspired microstructure for improved compressive performance of multidirectional CFRP laminates
No full textIn this work, we design, manufacture, test and discuss the first bio-inspired microstructural concept to enhance longitudinal compressive performance of multidirectional (MD) Carbon Fibre Reinforced Polymer (CFRP) laminates. To do so, we take inspiration from biologically occurring layered materials; one remarkable example being the anchoring spicula of the deep-sea glass sponge Monoraphis chuni. We designed numerically various concepts and then devised a strategy to reproduce, in a MD CFRP laminate, the characteristic alternation of stiff and soft regions observed in this material, followed by a bespoke procedure to manufacture the laminate. We evaluated their performances by means of small-scale notched compression tests and direct comparison with an industrially relevant baseline laminate. Our results show that the proposed concept led to a statistically significant increase in the failure load and in the average ligament specific stress at failure. Furthermore, the designed microstructure showed potential to delay damage initiation from a stress concentration and to arrest damage propagation. We conclude that the presented microstructural concept is potentially of great value for the design of lightweight structures undergoing compression loading
EXPERIMENTAL STUDY OF THE EFFECTS OF LAYERS ORIENTATION ON MODE I INTERLAMINAR FRACTURE TOUGHNESS USING FULLY UNCOUPLED MULTIDIRECTIONAL SPECIMENS
No full textNowadays, composite materials are used for a variety of applications, including safety-critical structures, whose design requires a damage tolerance approach. For laminated composites, delamination is one of the most critical damage modes.
In literature, delamination is studied using Linear Elastic Fracture Mechanics (LEFM) concepts, and interlaminar fracture toughness of a material is determined, in pure mode and mixed-mode conditions, by means of standard test procedures [1-3]. However, the validity of such standards is restricted to unidirectional (UD) specimens in which all layers have fibres oriented along the longitudinal direction of the specimen (0°). Real structures, instead, are built using multidirectional (MD) layups and delaminations may occur at any interface. Hence, characterisation of interlaminar fracture toughness of the interface between plies oriented at different angles is required.
Unluckily, experimental characterisation of interlaminar fracture toughness in such interfaces is still an open problem due to the following issues:
• During delamination, additional damage mechanisms may appear such as intra-ply matrix cracking within off-axis plies; this may cause the delamination to jump to another interlaminar plane.
• MD laminates show a complex coupled mechanical behaviour. Due to couplings, thermal residual stresses may appear during curing and they affect fracture toughness evaluation; additionally, couplings induce displacement and strain fields that may introduce undesired parasite modes contributions2.
• Most data reduction techniques are based on 2-dimensional theoretical formulations, whose validity for MD laminates is not granted
To overcome such problems, a special class of stacking sequences, called Fully-Uncoupled Multi-Directional (FUMD), has been developed and presented in [4]. These sequences are conceived to have null coupling terms, in the framework of Classic Laminated Plate Theory (CLPT), for the entire sequence itself and for its upper and lower halves, which form the arms of a typical standard delamination specimen [1-3].
In this study, for the first time, FUMD stacking sequences were used to design Double Cantilever Beam (DCB) specimens for mode I interlaminar fracture toughness characterisation. Five FUMD specimen sets were fabricated with different delamination interfaces (indicated by a double slash):
1. FUMD 0°//0°;
2. FUMD 0°//15°;
3. FUMD 0°//30°;
4. FUMD 0°//45°;
5. FUMD -45°//45°;
where orientation 0° is aligned with the longitudinal direction of the DCB specimen. In addition, standard UD specimens (thus having 0°//0° delamination interface) were fabricated as well.
A glass/epoxy prepreg fabric with 10% fibres in the fill direction was used, as this is expected to reduce matrix cracking problems in off-axis plies and hence prevent delamination jump phenomena.
Sequences FUMD 0//0 and UD have the same delamination interface but different global stiffness: results from their tests allow to assess if, for a fixed delamination interface, global stiffness of the specimen play a relevant role in fracture toughness evaluation, as some authors suggest. On the other hand, sequences FUMD 0//0, FUMD 0//45 and FUMD -45//45 have different delamination interfaces, but identical global stiffness: their tests allow to observe whether fracture toughness is affected by local effects, such as orientation of plies embedding the delamination plane and of adjacent plies at most.
Results show that global stiffness has not relevant effects, while layers orientations plays a major role in changing interlaminar fracture toughness of the interface.
REFERENCES
[1] ASTM-D5528-13, Standard Test Method for Mode I Interlaminar FractureToughness of unidirectional Fiber-Reinforced Polymer Matrix Composites, ASTM Interntional, West Conshohocken, PA.
[2] ASTM D7905/7905M-14, Standard Test Method for Determination of the Mode II Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer, ASTM Interntional, West Conshohocken, PA.
[3] ASTM 6671/D 6671M-06, Standard Test Method for Mixed Mode I-Mode II Interlaminar Fracture Toughness of Unidirectional Fiber Reinforced Polymer Matrix Composites, ASTM International, West Conshohocken, PA.
[4] T. Garulli, A. Catapano, D. Fanteria, J. Jumel, E. Martin, Design and finite element assessment of a Fully-Uncoupled Multi-Directional (FUMD) specimen for delamination tests, Composites Part B, paper submitted
Enhancement of T cell-mediated immune responses to whole inactivated influenza virus by chloroquine treatment in vivo
No full textCurrent influenza vaccines induce poor cross-reactive CD8+ T cell responses. Cellular immunity is generally specific for epitopes that are remarkably conserved among different subtypes, suggesting that strategies to improve the cross-presentation of viral antigens by dendritic cells (DC) could elicit a broadly protective immune response. Previous studies have shown that limited proteolysis within the endocytic pathway can favorably influence antigen processing and thus immune responses. Herein, we demonstrate that chloroquine improves the cross-presentation of non-replicating influenza virus in vitro and T cell responses in mice following a single administration of inactivated HI-X31 virus. CD8+ T cells were also recruited to lymph nodes draining the site of infection and able to reduce viral load following pulmonary challenge with the heterologous PR8 virus. These findings may have implications for vaccination strategies aimed at improving the cross-presentation capacity of DCs and thus the size of effector and memory CD8+ T cells against influenza vaccines
Recessioni gengivali ed autostima
No full textObbiettivi: crecare correlazioni fra autostima e recessioni gengivali. Razionale: è nota una correlazione positiva fra livelli di autostima ed elevate frequenze di spazzolamento (Regis et al. J Clin Periodontol 1994;21:7-12 Macgregor et al. J Clin Periodontol 1997; 24:335-339). Lo spazzolamento è riconosciuto quale fattore eziologico della recessione gengivale (Checchi et al. J Clin Periodontol 1999;26:276-280). Non sono a nostra conoscenza contributi attestanti relazioni fra recessioni gengivali ed autostima.
Materiali&Metodi: un campione di 42 pazienti afferenti al reparto di Parodontologia dell'Università di Bologna e presentanti recessioni gengivali sono stati esaminati. All'analisi clinica si è valutato: biotipo parodontale, sondaggio parodontale, numero delle recessioni gengivali. Sulla base della presenza/assenza di perdita d'attacco interprossimale e/o presenza/assenza di tasca patologica il campione è stato diviso in due gruppi: GNO (gruppo non parodontale) 19 pazienti, GP (gruppo parodontale) 23 pazienti. Al campione è stato sottoposto un questionario per definire il grado di autostima di ogni soggetto. Per dare un valore alla correlazione è stato utilizzato l'indice r di Bravais-Pearson. La probabilità di errore è stata calcolata con il test t di Student.
Risultati: nel GNP, presentante un biotipo sottile nel 68% dei soggetti, si è evidenziata una correlazione positiva fra autostima e numero delle recessioni (r=0,38; p<0,01). Nel GP, con biotipo sottile nel 96% dei casi, non si è evidenziata alcuna correlazione tra tali variabili.
Conclusioni: solamente nel GNP si evidenzia una correlazione positiva fra l'autostima e la presenza di recessioni. Da ciò è possibile ipotizzare un ruolo di tale variabile nell'induzione della recessione gengivale in soggetti parodontalmente sani
Quasi-trivial solutions for uncoupled, homogeneous and quasi-homogeneous laminates with high number of plies
No full textQuasi-trivial (QT) sequences are a class of lamination stacks for which, in the framework of Classical Laminate Theory (CLT), the properties of uncoupling and/or homogeneity are verified in a closed-form solution [1]. These sequences have received great attention from the scientific community as they have proved to be an extremely powerful tool for the design and optimization of composite laminates. Nevertheless, two main reasons limit their adoption: first, to find QT sequences, a complex algorithm is required; second, calculations become computationally intensive for long QT sequences, thus limiting the maximum number of plies attainable. This constrains the use of QT stacks to applications involving only thin laminates. In order to exploit QT stacks for thick laminates new tools are proposed. Firstly, a new and more efficient algorithm for finding QT stacking sequences is developed and an original procedure is devised to effectively code it. The proposed algorithm finds a greater number of QT solutions, with respect to those given in [1]. Additionally, analytical relationships to obtain new QT sequences by superposition of known QT sequences are presented in [2]. Thanks to this new class of closed-form solutions, laminates can be designed using QT stacking sequences without limitations on the maximum number of plies. The results presented in this work open new possibilities for the design and optimisation of thick laminates. In addition, laminates with special requirements may be designed by superposition of QT stacks, thus reaching specific design goals that cannot otherwise be met
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