We have isolated by DDRT-PCR (differential-display reverse-transcription polymerase chain reaction) and cDNA library screening a 1.3 kb cDNA corresponding to a strongly ozone-inducible transcript from birch (Betula pendula Roth). Nucleotide sequence analysis suggests that it encodes a mitochondrial phosphate translocator protein (Pic), the first one isolated from plants. The isolated birch mitochondrial phosphate translocator cDNA (designated Mpt1) contains an open reading frame of 1092 bases encoding a 364 amino acid polypeptide. The deduced protein is 66% similar to bovine Pic isoform B. Comparison of the N-terminal amino acid sequence to known mammalian Pic proteins and the existence of an in-frame stop codon upstream of the initiation codon suggest that the isolated cDNA is full-length. Southern hybridization analysis of birch genomic DNA shows that Mpt1 is a single-copy gene. Accumulation of Mpt1 mRNA during oxidative stress imposed by ozone is detectable already at 2 h and it is at maximum ca. 12 h after the beginning of an 8 h ozone exposure (150 ppb). A second O3 peak at 48-56 h did not increase transcript levels further. O3 exposure for 2 h was sufficient for Mpt1 induction. Birch Mpt1 transcript levels remain at moderately low level during leaf development and is lower in roots and leaves when compared to young shoots undergoing wood formation and lignification.

A new class of partially coherent model sources is introduced on the basis of the second-order coherence theory of nonstationary optical fields. These model sources are spatially fully coherent at each frequency but can have broadband spectra and variable spectral coherence properties, which lead to reduced spatiotemporal coherence in the time domain. The source model is motivated by the spectral coherence properties of supercontinuum pulse trains generated in single-spatial-mode optical fibers. We demonstrate that such broadband light is highly (but not completely) spatially coherent, even though the spectral and temporal coherence properties may vary over a wide range. The model sources introduced here are convenient in assessing the spatiotemporal coherence of broadband pulses in optical systems.

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We describe the second-order coherence functions of supercontinuum (SC) in terms of elementary fields that can be obtained from measurable average quantities. The representation is based on the partition of the second-order correlation functions of SC into quasi-coherent and quasi-stationary contributions. Numerical simulations of statistical ensembles of SC pulses with different coherence properties are used to illustrate the elementary field model. Comparison with the SC coherent-mode expansion is presented, and we also simulate the propagation of the elementary fields in a dispersive fiber to demonstrate the benefits of the model.

We present wide-band resonance waveguide refl ectors at the visible wavelengths providing nearly 100 % refl ectance over a range of several tens of nanometres. The refl ectors are based on multilayer designs consisting of layers of high and low index materials with a binary grating etched through the stack. We also fabricated an example structure and discuss the fabrication aspects of these elements.