Showing papers by "Giuseppe Coppola published in 2007"

Phase map retrieval in digital holography: avoiding the undersampling effect by a lateral shear approach.

Abstract: In digital holography (DH) the numerical reconstruction of the whole wavefront allows one to extract the wrapped phase map mod, 2π. It can occur that the reconstructed wrapped phase map in the image plane is undersampled because of the limited pixel size in that plane. In such a case the phase distribution cannot be retrieved correctly by the usual unwrapping procedures. We show that the use of the digital lateral-shearing interferometry approach in DH provides the correct reconstruction of the phase map in the image plane, even in extreme cases where the phase profile changes very rapidly. We demonstrate the effectiveness of the method in a particular case where the profile of a highly curved silicon microelectromechanical system membrane has to be reconstructed.

Telomere length status of somatic cell sheep clones and their offspring.

Abstract: This study was carried out to determine the telomere length status of sheep clones and their offspring, and to examine telomere dynamics and chromosomal abnormalities in culture propagated donor cells. Skin samples were collected from somatic cell nuclear transfer-derived sheep clones, and three of their progeny generated by natural mating. Samples were collected from control animals (n = 35), spanning in age from 1 month to 36 months of age. Genomic DNA was extracted from cell/tissue samples and their telomere lengths were assessed by terminal restriction fragment (TRF) analysis. Results revealed: that (a) sheep clones derived from cultured somatic cells have shortened telomere lengths compared to age-matched controls; (b) the offspring derived from natural mating between clones had normal telomere lengths compared to their age-matched counterparts; and donor cell cultures beyond 20 population doublings had significantly (P < 0.05) shortened telomeres and exhibited a higher numerical and structural chromosomal abnormalities.

Use of cross-species in-situ hybridization (ZOO-FISH) to assess chromosome abnormalities in day-6 in-vivo- or in-vitro-produced sheep embryos.

Abstract: Causes of chromosomal differences such as mosaicism between embryos developed in vivo and in vitro may be resolved using animal models to compare embryos generated in vivo with those generated by different production systems. The aims of this study were: (1) to test a ZOO-FISH approach (using bovine painting probes) to detect abnormal chromosome make-up in the sheep embryo model, and (2) to examine the extent of chromosome deviation in sheep embryos derived in vivo and in vitro. Cytogenetic analysis was performed on day 6 in-vivo and in-vitro derived sheep embryos using commercially available bovine chromosome painting probes for sex chromosomes X–Y and autosomes 1–29. A total of 8631 interphase and metaphase nuclei were analyzed from 49 in-vitro-derived and 51 in-vivo-derived embryos. The extent of deviation from normal ovine chromosome make-up was higher (p < 0.05) in in-vitro-produced embryos relative to in-vivo-derived embryos (65.3% vs. 19.6% respectively) mainly due to diploid–polyploid mosaicism. Polyploid cells ranged from 3n to 8n with tetraploids most predominant among non-diploid cells. The proportions of polyploid cells per mixoploid embryo in in-vitro-produced embryos ranged from 1.4% to 30.3%, in contrast to less than 10% among the in-vivo-derived embryos. It was concluded that in-vitro-derived embryos are vulnerable to ploidy change compared to their in-vivo counterparts. The application of ZOO-FISH to domestic animal embryos is an effective approach to study the chromosome complement of species for which DNA probes are unavailable.

A Nondestructive Dynamic Characterization of a Microheater Through Digital Holographic Microscopy

Abstract: This paper describes the possibility of employing a digital holographic microscope (DHM) to carry out a noncontact and nondestructive characterization of a microheater integrated on a silicon nitride membrane and subjected to a high thermal load. Microheaters can be affected by the presence of the residual stress due to the technological processes appearing in the form of undesired bowing of the membrane. Moreover, when the temperature of the microheater increases, a further warpage of the structure can be induced. A DHM allows for evaluation, with high accuracy, the deformations due to the residual stress and how these deformations are affected by the thermal loads due to the microheater operating mode. In particular, this dynamic analysis is made possible by measuring the unwanted longitudinal displacement induced by the thermal expansion of both the device and its mechanical support. Taking into account this displacement, it is possible to have a continuous monitoring of profile deformation induced by the working condition of the microheater.

Fiber optic sensors system for high temperature monitoring of aerospace structures

Abstract: The study and development of Structural Health Monitoring (SHM) systems for aerospace applications is one of the best challenges for the research in the field of fiber optic (FO) sensors. The harsh environments in which these aerospace structures have to work are the major limit for the employment of standard fiber optic sensors for the thermo-mechanical monitoring processes. Thermal loads which act on these structures do not allow using standard fiber optic sensors used for classic avionics application. In fact, many aerospace structures can be exposed to temperatures up to 1000°C, higher than the operation temperature of the standard fiber optic sensors. In this paper a new fiber optic system for structural analysis of ultra high temperature ceramic (UHTC) materials is proposed. A tunable laser source is used to easily measure the spectral response of different fiber optic sensors. Moreover the employment of an in-fiber optical circulator and TLC 1x4 optical switch, allows to perform a multi-sensor interrogation, to analyse many physical parameters, such as: temperature, strain, pressure, etc.. In particular the monitoring system has been used to test high temperature resistant Fiber Bragg Grating sensors. The first tests at high temperature, up to 600°C, have shown a good response in terms of: sensitivity, resolution, repeatability and dynamic range of the measurement. At last, the flexibility of the electro-optical system developed for the interrogation of the fiber optic sensors, allows the extension of the instruments to mechanical stress analysis, using custom fiber optic strain sensors currently under development.

Use of somatic cell nuclear transfer to study meiosis in female cattle carrying a sex-dependent fertility-impairing X-chromosome abnormality.

Abstract: Animal models have played an important part in establishing our knowledge base on reproduction, development, and the occurrence and impact of chromosome abnormalities. Translocations involving the X chromosome and an autosome are unique in that they elicit sex-dependent infertility, with male carriers rendered sterile by synaptic anomalies during meiosis, whereas female carriers conceive but repeatedly abort. Until now the limited access to relevant fetal oocytes has precluded direct study of meiotic events in female carriers. Because somatic cell nuclear transfer (SCNT) circumvents meiotic problems associated with fertility disturbances in translocation carriers, we used SCNT to generate embryos, fetuses, and calves from a cell line derived from a deceased subfertile X-autosome translocation carrier cow to study the meiotic configurations in carrier oocytes. Data from 33 replicates involving 2470 oocyte-donor-cell complexes were assessed for blastocyst development and of these, 42 blastocysts were transferred to 21 recipients. Fourteen pregnancies were detected on day 35 of gestation. One of these was sacrificed for ovary retrieval on day 94 and three went to term. Features of oocytes from the fetal ovary and from the newborn ovaries were examined. Of the pachytene spreads analyzed, 16%, 82%, and 1.5% exhibited quadrivalent, trivalent/univalent, and bivalent/univalent/univalent structures, respectively, whereas among the diakinesis/metaphase I spreads, 16% ring, 75% chain, and 8.3% bivalent/bivalent configurations were noted, suggesting that the low fertility among female carriers may be related to synaptic errors in a predominant proportion of oocytes. Our results indicate that fibroblasts carrying the X-autosome translocation can be used for SCNT to produce embryos, fetuses, and newborn clones to study such basic aspects of development as meiosis and to generate carriers that cannot easily be reproduced by conventional breeding.

Analysis of a planar silicon opto-electronic modulator based on the waveguide-vanishing effect

Abstract: Silicon is the most diffused material for microelectronic industry and, in recent times, it is becoming more and more widespread in integrated optic and optoelectronic fields. We present the thermo-electro-optical analysis of an integrated waveguide-vanishing-based optical modulator based on free-carrier dispersion effect, realizable on standard SOI wafer. The optical behavior is based on the vanishing of the lateral confinement in the rib region, and consequent cut-off of the propagating mode. Results show that an optical modulation depth close to 100% can be reached with a bandwidth of about 154 MHz. Smart electrical driving, that is an injection overdrive of a few volts for a very short time, allows to reach total ON-OFF switching time of about 860 ps. For that bias scheme the fall transient is then limiting the whole dynamic and the resulting bit rate in a pure digital modulation scheme is about 1.2 Gb/s.

Mapping fragile-sites in the standard karyotype of River Buffalo (Bubalus bubalis, 2n=50)

Abstract: A fragile-site map has been preliminarily established in the standard karyotype of river buffalo (Bubalus bubalis, 2n=50) with the aim of unmasking ‘weak’ chromosomal regions in the karyotype of the species. The majority of the breakages took place in the RBA/RBG-negative bands or at the band-interband regions. The most fragile chromosomes were identified as the inactive X, chromosomes 9 and 8, and the active X, with 42, 32, 31 and 30 breakages, respectively. The 400 breakages were distributed in 106 breaksites (BS), with an average intensity of 4 breaks per chromosomal site; (b) the most fragile bands of the river buffalo karyotype were identified as 9q213 with 24 breaks, band 19q21 with 16; inacXq24 with 15; bands 15q23 and 17q21 with 13; band 13q23 with 12, and so on. Preliminary gene mapping analysis revealed that the closest loci to these fragile sites contain genes such as RASA1 and CAST (9q214), NPR3 and C9 (19q19), OarCP09 (15q24), PLP and BTK (Xq24-q25) and EDNRB (13q22), whose mutations are responsible for severe phenotypic malformations and immunodeficiency in humans and mice, and meat quality in pigs. Further cytogenetic and molecular studies are needed to fully exploit the biological significance of the fragile sites in the karyotypes of domestic animals and their relationships with productive and reproductive efficiency.

Fabrication and characterization of zinc oxide based rib waveguide

Abstract: In this work we investigate the possibility to use Zinc Oxide (ZnO) thin films, deposited by RF magnetron sputtering, for the realization of integrated optical structures working at 1550 nm. Structural properties of sputtered zinc oxide thin films were studied by means of X-ray Diffraction (XRD) measurements, while optical properties were investigated by spectrophotometry and Spectroscopic Ellipsometry (SE). In particular, ellipsometric measurements allowed to determine the dispersion law of the ZnO complex refractive index (see manuscript) = n - jk through the multilayer modeling using Tauc-Lorentz (TL) dispersion model. We have found a preferential c-axis growth of ZnO films, with slightly variable deposition rates from 2.5 to 3.8 a/s. Conversely, the refractive index exhibits, from UV to near IR, a considerable and almost linear variation when the oxygen flux value in the deposition chamber varies from 0 to 10 sccm. In order to realize a waveguide structure, a 3-mm-thick ZnO film was deposited onto silicon single crystal substrates, where a 0.5-mm-thick thermal SiO 2 buffer layer was previously realized, acting as lower cladding. Dry and wet chemical etching processes have been investigated to achieve controllable etching rate and step etching profile, with the aim to realize an optical rib waveguide. The etched surfaces were inspected using scanning electron microscopy (SEM) and optical microscopy. Moreover, we carried out the experimental measurements of the fringes pattern and Free Spectral Range (FSR) of an integrated Fabry- Perot etalon, obtained by cleaving of a single mode rib waveguide.

Development of a fiber optic health monitoring system for aerospace applications

Abstract: This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics (UHTC) materials up to 1000 °C. Commercially available optic devices can operate up to 550 °C. To raise temperature limit up to 1000 °C, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials.

DNA polymerase alpha inhibition by aphidicolin and fragile site expression in prometaphase chromosomes of the Italian Mediterranean River Buffalo (Bubalus bubalis, 2n=50)

Abstract: The present study reports on the expression and localization of “fragile sites” (FS) on prometaphase chromosomes of two groups of river buffaloes (Bubalus bubalis, 2n=50; Mediterranean Italian breed), reared in two different farms, with the aim to characterize chromosome fragility in this species. Totally, 400 aphidicolin induced breakages were identified and localized on the standardized ideogram of the river buffalo karyotype. Preliminary results can be synthesized as follows: (a) aphidicolin showed a remarkable decondensing effect on chromosome structure, enabling further studies at high resolution level; (b) the chromosomal expression of the breakages was not different in the two groups of animals; (c) the most fragile chromosomes were the inactive-X, chromosomes 9, 8 and active-X, showing 42, 32, 31 and 30 breakages, respectively; (d) the breaks were localized in the RBG-negative bands (corresponding to eterochromatic regions) or at the band-interband regions; (e) the chromosomal distribution of the break sites was not random and only partially related to chromosome length. The study is in progress to determine the relative incidence of the fragile sites at chromosomal band level, in order to construct a ‘fragile-site map’ of river buffalo, which could be utilized for genetic improvement programs of the species.

Photolithography by a tunable electro-optical lithium niobate phase array

Abstract: Photolithography experiments are performed by means of an optical phase mask with electrooptically tunable phase step. The phase mask consists of a 2-dimensional hexagonal lattice of inverted ferroelectric domains fabricated on a z-cut lithium niobate substrate. The electro-optically tunable phase step, between inverted domain, is obtained by the application of an external electric field along the z axis of the crystal via transparent electrodes. The collimated beam of an argon laser passes through the phase mask and the near field intensity patterns, at different planes of the Talbot length and for different values of the applied voltage, are used for photolithographic experiments. Preliminary results are shown and further applications are discussed.

Electro-Optic Modulated Phase Array in Hexagonally Poled Lithium Niobate for Flexible Array Illuminator Device

Abstract: We present an adaptive and dynamic hexagonal electro-optic phase array. The proposed device consists of a 2-dimensional hexagonal array of periodically inverted ferroelectric domains, along the z-axis, in lithium niobate crystals. The phase step is achieved via the application of an external electric field, along the z-axis, through transparent electrodes. Thanks to the electro-optic effect the phase step can changed with continuity over all the 0 to 2π by applying a variable voltage. In this way different patterns can be generated. In fact, one important property of this new proposed configuration of array iluminator is the intrinsic flexibility.

Cytogenetic screening of a canadian pig breeding unit

Abstract: A cytogenetic study was undertaken on the chromosomal makeup and breeding data of 29 boars housed in a Canadian pig farm. Blood cultures were made and chromosome spreads were examined, searching for carriers of chromosomal abnormalities. The investigation revealed that twenty-six individuals had a normal karyotype and 3 (10.3%) carried the following aberrations: (a) two 1/6 translocations in two - unrelated - individuals, (b) one reciprocal translocation rcp(10;13). The litter size of the two boars carrying the 1/6 translocation was, on average, 6.5 and 5.8, respectively. The mean size of the litter sired by the boar carrying the rcp(10;13) was 6.0. As compared with the average litter size (11.0) sired by the normal boars in the herd, the translocations described here seemed to be responsible for ~35% decrease in prolificacy.