Showing papers by "Giuseppe Coppola published in 2002"

The Kallmann syndrome gene homolog in C. elegans is involved in epidermal morphogenesis and neurite branching.

Abstract: Kallmann syndrome is an inherited disorder defined by the association of anosmia and hypogonadism, owing to impaired targeting and migration of olfactory axons and gonadotropin-releasing hormone secreting neurons. The gene responsible for the X-linked form of Kallmann syndrome, KAL-1, encodes a secreted protein of still elusive function. It has been proposed that KAL-1 might be involved in some aspects of olfactory axon guidance. However, the unavailability of a mouse model, and the difficulties in studying cellular and axonal migration in vertebrates have hampered an understanding of its function. We have identified the C. elegans homolog, kal-1, and document its function in vivo. We show that kal-1 is part of a mechanism by which neurons influence migration and adhesion of epidermal cells undergoing morphogenesis during ventral enclosure and male tail formation. We also show that kal-1 affects neurite outgrowth in vivo by modulating branching. Finally, we find that human KAL-1 cDNA can compensate for the loss of worm kal-1 and that overexpression of worm or human KAL-1 cDNAs in the nematode results in the same phenotypes. These data indicate functional conservation between the human and nematode proteins and establish C. elegans as a powerful animal in which to investigate KAL function in vivo. Our findings add a new player to the set of molecules, which appear to underlie both morphogenesis and axonal/neuronal navigation in vertebrates and invertebrates.

Electro-optical switch and continuously tunable filter based on a Bragg grating in a planar waveguide with a liquid crystal overlayer

Abstract: The possibility of using smectic liquid crystals in active wave- guide devices is explored through the analysis of both an integrated electro-optic switch and a continuously tunable filter. The two devices are based on a Bragg grating in planar waveguide with a liquid crystal over- layer, which enables changing the spectral behavior of the device. The fast and bistable switching of smectic C* in the surface-stabilized liquid crystal structure is used to investigate the possibility of realizing an inte- grated electro-optical switch. The principal advantage of this device is its spectral signature, which enables us to overcome the problems of inten- sity dependent devices. The soft-mode of smectic A* liquid crystals, enabling a continuous modulation of extraordinary refractive index, is used to design an integrated wavelength filter in the wavelength range of interest for optical communications. The principal advantages of such device include fast tuning speed, wide tuning range, low power dissipa- tion, and low cost. © 2002 Society of Photo-Optical Instrumentation Engineers.

Digital holography for characterization and testing of MEMS structures

Abstract: Digital holography is proposed as a non-contact method for the inspection and characterization of MEMS. The method can be useful for assessing the fabrication process and the functionality as well as the reliability of micromachined structures.

Onset and sequence of RBA-band replication on the inactive X-chromosomes of cattle (Bos taurus L.), river buffalo (Bubalus bubalis L.) and goat (Capra hircus L.).

Abstract: This study was undertaken to provide cytogenetic information about onset and sequence of RBA-band replication on the inactive X-chromosomes of cattle, river buffalo and goat. Blood cultures were synchronized overnight with thymidine after 48 hours of growth. The cell block was released with fresh medium and the cells allowed to grow in the presence of BrdU and H33258 for 1, 2, 4, 6, 8, 10, 12 and 14 hours, including 20 minutes colcemide. Results show that: (a) the onset of RBA-banding replication was 12 hours before mitosis in cattle and river buffalo, 14 hours in the goat; (b) the replication process was still ‘on’ in cattle and river buffalo one hour before mitosis, whereas it was ‘off’ in the goat; consequently the length of the G2 phase was less than one hour in cattle and river buffalo and one hour or slightly longer in the goat; (c) the first band undergoing replication was identified as band Xq31 in cattle, homologous to band Xq34-36 in river buffalo and Xq24 in the goat; (d) the second replicating band was the Xp22 in cattle, homologous to band Xq21 in river buffalo and Xq34 in the goat, respectively; (e) the sequence of RBA-band replication was quite similar between cattle and river buffalo, but reversed in the goat, due to the wide chromosomal rearrangements which differentiated the X-chromosome of Caprinae from that of Bovinae.

A simple bi-polished silicon sample to detect vibrations by Fiber Bragg sensor

Abstract: Describes a simple method for interrogating fiber Bragg grating sensors by a bi-polished silicon sample acting like a Fabry-Perot filter. Thus, Bragg wavelength shift is converted into a variation of the light intensity.

Design, fabrication and testing of an integrated Si-based light modulator: experimental evidence of plasma redistribution

Abstract: The implementation of efficient Si-based optical functions has attracted a considerable interest in the last years since it would allow the use of the Si technology for the realization of integrated optoelectronic devices. We have fabricated and characterized a novel Si-based light modulator working at the standard communication wavelength of 1.54 micrometers . It consists of a three terminal Bipolar Mode Field Effect Transistor integrated with a silicon RIB waveguide on epitaxial Si wafers. The optical channel of the modulator is embodied within its vertical electrical channel. Light modulation is obtained through the formation of a plasma of carriers, inside the optical channel, that produces an increase of the absorption coefficient. Fast modulation is achieved by moving the plasma inside and outside the optical channel by properly biasing the control electrode. The devices have been fabricated using clean room processing. Detailed electrical characterization and device simulation confirm that strong conductivity modulation and plasma formations in the channel are achieved. The plasma distribution in the device under different bias conditions has been directly derived from Emission Microscopy analysis. The expected device performances in terms of modulation depth and speed will be presented and discussed.