12 research outputs found
Histology and symplasmic tracer distribution during development of barley androgenic embryos
The present study concerns three aspects of barley androgenesis: (1) the morphology and histology of the embryos during their development, (2) the time course of fluorescent symplasmic tracersâ distribution, and (3) the correlation between symplasmic communication and cell differentiation. The results indicate that barley embryos, which are developing via an androgenic pathway, resemble their zygotic counterparts with respect to their developmental stages, morphology and histology. Analysis of the distribution of the symplasmic tracers, HPTS, and uncaged fluorescein indicates the symplasmic isolation of (1) the protodermis from the underlying cells of the late globular stage onwards, and (2) the embryonic organs at the mature stage of development
GRB 050822: Detailed analysis of an XRF observed by Swift
We report on the temporal and spectral characteristics of the early X-ray
emission from the GRB 050822 as observed by Swift. This burst is likely to be
an XRF showing major X-ray flares in its XRT light-curve. The quality of the
data allows a detailed spectral analysis of the early afterglow in the X-ray
band. During the X-ray flares, a positive correlation between the count rate
and the spectral hardness (i.e. the higher the count rate, the harder the
spectrum) is clearly seen for the X-ray flares. This behaviour, similar to that
seen for Gamma-ray pulses, indicates that the energy peak of the spectrum is in
the XRT energy band and it moves towards lower energies with time. We show
evidence for the possible detection of the emergence of the forward-shock
emission, produced at a radius larger than 4x10^16 cm in the case of a CBM
afterglow model (a formation region clearly different from that producing the
prompt emission). Finally, we show that the null detection of a jet break up to
T_0 + 4x10^6 s in the X-ray light curve of this XRF can be understood: i) if
the jet seen on-axis is uniform with a large opening angle theta > 20 degrees);
or ii) if the jet is a structured Gaussian-like jet with the line-of-sight
outside the bright Gaussian core.Comment: Now accepted for publication in A&
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