1,721,015 research outputs found
Filogeneomica comparata tra Primati e Scandentia: il mappaggio delle sonde cromosomiche umane su Tupaia minor (Scandentia)
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Modelling of Damaged Laminated and Sandwich Shell Structures by means of Higher-order Shear Deformation Theories
No full textThe main aim of the current research is the development of a mathematical formulation for the modelling of damage in laminated and sandwich composite shells. For this purpose, the damage of some areas of the structures can be seen as concentrated decays of the mechanical properties of the elastic constituents. In general, several kinds of damage can affect the mechanical behavior of a generic laminated structure, such as microcracking, debonding, fiber ruptures, and transverse matrix cracking, as specified in [1].
Without investigating the causes of the damage, the current approach suggests to introduce peculiar functions that multiply directly the mechanical properties of the elastic media, expressed in terms of engineering constants. To this aim, the Gaussian function and an ellipse shaped law are used to model a quick variation of the mechanical properties within the whole structural domain. By setting properly the parameters that characterize these distributions, it is possible to control the intensity of the deterioration and the width of the damaged areas, as well as the point of applications.
The present approach is employed to characterize the damage in some doubly-curved shells characterized by different radii of curvature. The difficulties related to the description of these curved surfaces are overcome by means of an analytical formulation based on differential geometry [2]. As far as the mechanical properties are concerned, several constituents are considered and combined.
The theoretical framework is based on a formulation that allows to develop easily different kinematic models and expansions in a unified manner. Thus, several Higher-order Shear Deformation Theories, which can include also the zig-zag effect, are employed. In fact, it has been proven that peculiar mechanical configurations require an enriched structural model, since lower-order theories could be inadequate to capture the effective mechanical behavior.
Finally, a numerical technique able to solve the strong form of the governing equations is used. For this purpose, the partial derivatives that appear in the fundamental system are directly approximated through the Generalized Differential Quadrature method due to its accuracy [3].
References
[1] Tornabene, F., Fantuzzi, N., Bacciocchi, M., “Linear Static Behavior of Damaged Laminated Composite Plates and Shells”, Materials, 10, 811, 1-52 (2017).
[2] Tornabene, F., Fantuzzi, N., Bacciocchi, M., and E. Viola, Laminated Composite Doubly-Curved Shell Structures. Differential Geometry. Higher-order Structural Theories, Esculapio, Bologna (2016).
[3] Tornabene, F., Fantuzzi, N., Ubertini, F., Viola, E., “Strong Formulation Finite Element Method Based on Differential Quadrature: A Survey”, Applied Mechanics Reviews, 67, 020801-1-55
Modelling of Damaged Laminated and Sandwich Shell Structures by means of Higher-order Shear Deformation Theories
No full textThe main aim of the current research is the development of a mathematical formulation for the modelling of damage in laminated and sandwich composite shells. For this purpose, the damage of some areas of the structures can be seen as concentrated decays of the mechanical properties of the elastic constituents. In general, several kinds of damage can affect the mechanical behavior of a generic laminated structure, such as microcracking, debonding, fiber ruptures, and transverse matrix cracking, as specified in [1].
Without investigating the causes of the damage, the current approach suggests to introduce peculiar functions that multiply directly the mechanical properties of the elastic media, expressed in terms of engineering constants. To this aim, the Gaussian function and an ellipse shaped law are used to model a quick variation of the mechanical properties within the whole structural domain. By setting properly the parameters that characterize these distributions, it is possible to control the intensity of the deterioration and the width of the damaged areas, as well as the point of applications.
The present approach is employed to characterize the damage in some doubly-curved shells characterized by different radii of curvature. The difficulties related to the description of these curved surfaces are overcome by means of an analytical formulation based on differential geometry [2]. As far as the mechanical properties are concerned, several constituents are considered and combined.
The theoretical framework is based on a formulation that allows to develop easily different kinematic models and expansions in a unified manner. Thus, several Higher-order Shear Deformation Theories, which can include also the zig-zag effect, are employed. In fact, it has been proven that peculiar mechanical configurations require an enriched structural model, since lower-order theories could be inadequate to capture the effective mechanical behavior.
Finally, a numerical technique able to solve the strong form of the governing equations is used. For this purpose, the partial derivatives that appear in the fundamental system are directly approximated through the Generalized Differential Quadrature method due to its accuracy [3].
References
[1] Tornabene, F., Fantuzzi, N., Bacciocchi, M., “Linear Static Behavior of Damaged Laminated Composite Plates and Shells”, Materials, 10, 811, 1-52 (2017).
[2] Tornabene, F., Fantuzzi, N., Bacciocchi, M., and E. Viola, Laminated Composite Doubly-Curved Shell Structures. Differential Geometry. Higher-order Structural Theories, Esculapio, Bologna (2016).
[3] Tornabene, F., Fantuzzi, N., Ubertini, F., Viola, E., “Strong Formulation Finite Element Method Based on Differential Quadrature: A Survey”, Applied Mechanics Reviews, 67, 020801-1-55
Comparative molecular cytogenetics and genomics redefines phylogenetic and taxonomic relationship of new world monkeys.
No full textStudio delle relazioni filogenetiche nell’infraordine Plathyrrinae attraverso l’approccio del Multidirectional Painting
No full textMULTIDIRECTIONAL CHROMOSOME PAINTING REVEALS A REMARKABLE SYNTENIC HOMOLOGY BETWEEN THE GREATER GALAGOS AND THE SLOW LORIS
No full textWe report on the first reciprocal chromosome painting of lorisoids and humans. The chromosome painting showed a remarkable syntenic homology between Otolemur and Nycticebus. Eight derived syntenic associations of human segments are common to both Otolemur and Nycticebus, indicative of a considerable period of common evolution between the greater galago and the slow loris. Five additional Robertsonian translocations form the slow loris karyotype, while the remaining chromosomes are syntenically equivalent, although some differ in terms of centromere position and heterochromatin additions. Strikingly, the breakpoints of the human chromosomes found fragmented in these two species are apparently identical. Only fissions of homologs to human chromosomes 1 and 15 provide significant evidence of a cytogenetic link between Lemuriformes and Lorisiformes. The association of human chromosomes 7/16 in both lorisoids strongly suggests that this chromosome was present in the ancestral primate genome
Evolutionary molecular cytogenetics of catarrhine primates: past, present and future
No full textThe catarrhine primates were the first group of species studied
with comparative molecular cytogenetics. Many of the
fundamental techniques and principles of analysis were initially
applied to comparisons in these primates, including interspecific
chromosome painting, reciprocal chromosome
painting and the extensive use of cloned DNA probes for
evolutionary analysis. The definition and importance of
chromosome syntenies and associations for a correct cladistics
analysis of phylogenomic relationships were first applied
to catarrhines. These early chromosome painting studies
vividly illustrated a striking conservation of the genome
between humans and macaques. Contemporarily, it also revealed
profound differences between humans and gibbons,
a group of species more closely related to humans, making
it clear that chromosome evolution did not follow a molecular
clock. Chromosome painting has now been applied to
more that 60 primate species and the translocation history
has been mapped onto the major taxonomic divisions in the
tree of primate evolution. In situ hybridization of cloned DNA probes, primarily BAC-FISH, also made it possible to more
precisely map breakpoints with spanning and flanking BACs.
These studies established marker order and disclosed intrachromosomal
rearrangements. When applied comparatively
to a range of primate species, they led to the discovery of
evolutionary new centromeres as an important new category
of chromosome evolution. BAC-FISH studies are intimately
connected to genome sequencing, and probes can usually
be assigned to a precise location in the genome assembly.
This connection ties molecular cytogenetics securely to
genome sequencing, assuring that molecular cytogenetics
will continue to have a productive future in the multidisciplinary
science of phylogenomics
Reciprocal chromosome painting on C. argentata, C. pygmaea, C. goeldii, and S. sciureus strongly supports the molecular based Cebidae Family grouping
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