A system model for ultrasonic NDT based on the Physical Theory of Diffraction (PTD).

Simulation of ultrasonic Non Destructive Testing (NDT) is helpful for evaluating performances of inspection techniques and requires the modelling of waves scattered by defects. Two classical flaw scattering models have been previously usually employed and evaluated to deal with inspection of planar defects, the Kirchhoff approximation (KA) for simulating reflection and the Geometrical Theory of Diffraction (GTD) for simulating diffraction. Combining them so as to retain advantages of both, the Physical Theory of Diffraction (PTD) initially developed in electromagnetism has been recently extended to elastodynamics. In this paper a PTD-based system model is proposed for simulating the ultrasonic response of crack-like defects. It is also extended to provide good description of regions surrounding critical rays where the shear diffracted waves and head waves interfere. Both numerical and experimental validation of the PTD model is carried out in various practical NDT configurations, such as pulse echo and Time of Flight Diffraction (TOFD), involving both crack tip and corner echoes. Numerical validation involves comparison of this model with KA and GTD as well as the Finite-Element Method (FEM).

Identification and localisation of SERCA 2 isoforms in mammalian sperm.

Upon binding to the egg's zona pellucida, capacitated spermatozoa will undergo a calcium-dependent exocytotic event called acrosome reaction. During this process, Ca2+ depletion from internal stores is followed by an important rise in [Ca2+]i due to a massive Ca2+ influx. Previous reports have shown that the acrosome can act as a Ca2+ store and that depletion of thapsigargin-sensitive stores induces acrosome exocytosis in capacitated spermatozoa from different mammalian species. The effect of thapsigargin, a specific inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCAs), suggests the presence and implication of SERCA in the active Ca2+ uptake during mammalian sperm capacitation. Although the presence of a thapsigargin-sensitive Ca2+-ATPase has been debated, the aim of this study was to clearly determine whether SERCAs are present in mammalian spermatozoa. Using three different anti-SERCA 2 antibodies, mono- and polyclonal, which recognised the same protein, we successfully identified and localised SERCA 2 in human, mouse and bovine sperm. Western blot analysis suggests that more than one SERCA 2 splice variant are present, one detected in the fraction containing the outer acrosomal membranes and another one present in the subcellular fraction containing the sperm midpiece. These results were confirmed by indirect immunofluorescence where SERCA 2 was observed in the acrosome and midpiece regions of human sperm. SERCA 2 immunohistochemical studies on human testis and PCR-amplification of mRNA encoding for each SERCA 2 splice variant in spermatogenic cells support the presence of this Ca2+-ATPase family in mature spermatozoa. In this paper, we clearly demonstrate, for the first time, the presence of SERCA 2 in mammalian sperm.

Characterization of an 80-kilodalton bull sperm protein identified as PH-20.

This paper presents the partial characterization and the identification of an 80-kDa protein detected in bull spermatozoa using a monoclonal antibody directed against a 16-amino acid long peptide from the N-terminal domain of the protooncogene p60(src) from the Rous Sarcoma Virus When subjected to two-dimensional electrophoresis, this 80-kDa protein migrated as several isoforms, with an isoelectric point ranging from 7.4 to 8.2. Amino acid sequence analysis of a peptide obtained following trypsin digestion of the bull sperm protein showed homology to the PH-20/hyaluronidase precursor sperm protein. As for PH-20, this bull sperm 80-kDa protein is located at the plasma membrane surface in the postacrosomal region of the head. An increased immunolabeling in the anterior head region of fixed/permeabilized spermatozoa was observed when these cells were incubated under capacitating conditions, whereas most sperm cells challenged with the calcium ionophore A23187 to acrosome react lost their labeling almost completely. As for the PH-20 protein, the 80-kDa bull sperm protein possesses a hyaluronidase activity that is higher at pH 7.0 than at pH 4.0 in an in-gel assay. Unlike what has been observed in the guinea pig, mouse, and human PH-20, this 80-kDa protein was not released from the surface of bull spermatozoa by treatment with phosphatidylinositol-specific phospholipase C or with trypsin. However, this protein was not sedimented by a 100,000 x g centrifugation after nitrogen cavitation, which suggests that the 80-kDa protein is loosely attached to the sperm membrane by a yet-unknown mechanism. These results suggest that the 80-kDa bull sperm protein shares many homologies with the sperm PH-20 protein reported in the literature and, most likely, is the bull sperm homologue of the PH-20.