3,388 research outputs found
Hormonal regulation of testicular functions in reptiles
No full textTesticular functions are controlled by important multifactors: environmental, hypothalamic-pituitary, and paracrine factors secreted by testicular cells. The existence of different gonadotropins and their role in testicular functions are have been described. In chelonians and crocodilians, two distinct pituitary gonadotropins similar to mammalian follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate two functions, respectively: spermatogenesis and steroidogenesis. In contrast, in squamates, has been purified and characterized a single gonadotropin that controls both testicular functions. Regarding steroids, androgens differentially regulate spermatogenesis, depending on reproductive stages, while estrogens are implicated at low concentrations in the control of spermiogenesis and at high levels in testicular regression. In addition, several paracrine factors such as neuropeptides from testicular cells, and other molecules secreted by macrophages and mast cells of Leydig and Sertoli cells, play critical roles in the regulation of spermatogenesis, steroidogenesis, and testicular immune responses
Proprietà meccaniche e comportamento flessionale di elementi di vetro alle alte temperature
No full textProgressive damage and fracture of laminated glass beams
No full textThe use of laminated glass is increasing due to the realization of transparent load-bearing elements for
architectural glazing applications. In laminated glass, two or more layers of glass are bonded to thin thermoplastic
interlayers to improve the post-breakage characteristics of the glass. After breakage, the residual load-carrying capacity of the laminate depends on the mechanical properties of the laminate constituents. Three-point bending tests are presented on laminated glass specimens, made with an internal float glass and two external equal tempered glass panels. The laminated glass specimens, of equal cross section, were characterized by three different combinations of annealed float and fully thermally tempered glass plies. In addition, two sets of specimens were constructed with two different interlayers having significantly different mechanical properties. The flexural load was applied parallel to the lamination plane (in-plane loading) and the tests were conducted at room temperature. The post-failure response and the failure mechanisms detected are presented and discussed
Influence of steel microfibers ad microsilica on behaviour of high performance cement based composites
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Overall structural behavior of strength concrete specimens
No full textThe effects of steel micro-fibre on the complete load-displacement response of a high
performance concrete in tension and compression were examined from tests performed on
specimens composed of high strength concrete under controlled strain through a closed-loop
system. The concrete had a maximum aggregate size of 3 mm, an aggregate to binder ratio of
two, silica fume to binder ratio of 0.2, water to binder ratio of 0.225 and randomly dispersed steel
micro-fibres of 0%, 2%, 4% and 6% by volume. Uniaxial tensile tests, bending tests and uniaxial
compressional tests were conducted and analyzed in order to provide a mechanical
characterization of the materials. Moduli of elasticity and fracture energies were evaluated and
compared
Delamination tests on CFRP-reinforced masonry pillars: Optical monitoring and mechanical modeling
No full textIn this methodological study, delamination phenomena of Carbon Fiber Reinforced Polymer (CFRP) strips
from masonry pillars were investigated on the basis of single-lap shear tests. The masonry pillar considered
in this case was constituted of three historical bricks, derived from a XVII century rural building. The
bricks were bonded by a high strength mortar recently proposed for the restoration process. To follow
the specimen response up to collapse, the test was controlled by a clip gauge located at the anchorage
of the reinforcement strip. The conventional experimental information, concerning the overall reaction
force and relative displacements provided by point sensors (LVDTs and clip gauge), were herein enriched
with no-contact, kinematic full-field measurements provided by 2D Digital Image Correlation (2D DIC).
Special care was devoted to improve the precision of the optical measurement, which included correction
of the effects owing to the lens distortion and to lack of coplanarity between the camera sensor and the
monitored flat surface. The overall accuracy was assessed through laboratory benchmarking tests.
Moreover, an advanced three-dimensional mechanical model based on nonlinear finite elements was
developed under the simplifying assumption of perfect adhesion. This model was adopted to describe
bulk damage inside the heterogeneous specimen and to correlate it to the macroscopic response and
surface measurements. Coherence between the above mentioned sources of information and the
predictions provided by the advanced finite element model were critically discussed
Production and mechanical characterization of very high performance fiber-reinforced concrete beams
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