A.R. Davies

Molecular cloning of human GATA-6 DNA binding protein: high levels of expression in heart and gut

Human GATA-6 has been cloned from foetal heart by a combination of PCR-based methods and cDNA library screening. The 3.8 kbp cDNA has a coding sequence of 1347 bp the 449 aa protein is virtually identical in the two zinc-finger binding domains to other human GATA sequences, but varies considerably in the amino and carboxy terminal regions. The sequence shows greatest similarity to GATA-6-like sequences from rat, mouse, chicken and Xenopus. Northern analysis and in situ hybridisation show that GATA-6 is expressed at high levels in human adult and foetal heart as well as in gut derivatives. It is postulated that GATA-6, in concert with GATA-4, plays a crucial role in the regulation of cardiac differentiation.

Uncooled DBR laser directly Modulated at 3.125 gb/s as athermal transmitter for low-cost WDM systems

An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A /spl plusmn/0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70/spl deg/C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20/spl deg/C-70/spl deg/C temperature range, with wavelength variation of as low as /spl plusmn/0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source.

Nanometer scale thermal drift of 4 Gbit/s uncooled laser for tight-channel-spacing low-cost WDM

A 4 Gbit/s directly modulated DBR laser is demonstrated with nanometre scale thermal tuning over an extended 20-70/spl deg/C temperature range. >40 dB side mode suppression over the entire temperature range is achieved.

Gain-clamped SOA with 1-11 dB variable gain based on a three-contact tunable DBR laser

We report variable gain gain-clamped SOA operation using a tunable laser based device. Variation of the clamped gain from 1-11 dB is achieved together with a noise figure of 7.9 dB and flat spectral performance over 25 nm.