339 research outputs found
The Role of Expansins A in Petunia Development
Expansins, a diverse set of proteins found in plants and some other organ-
isms, appear to play a key regulatory role in cell expansion, thereby serving critical
functions in plant morphogenesis, development, and adaptation to stress. We have
isolated a number of expansin genes from Petunia. Their ongoing functional analysis
provides evidence for their involvement in cell wall functions, including cellulose
metabolism, disruption of noncovalent cellulose/glycan bonds, and separation of the
cell wall matrix during cell expansion
Near-infrared thermal emissivity from ground based atmospheric dust measurements at ORM
We present an analysis of the atmospheric content of aerosols measured at
Observatorio del Roque de los Muchachos (ORM; Canary Islands). Using a laser
diode particle counter located at the Telescopio Nazionale Galileo (TNG) we
have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 um size. The
seasonal behavior of the dust content in the atmosphere is calculated. The
Spring has been found to be dustier than the Summer, but dusty conditions may
also occur in Winter. A method to estimate the contribution of the aerosols
emissivity to the sky brightness in the near-infrared (NIR) is presented. The
contribution of dust emission to the sky background in the NIR has been found
to be negligible comparable to the airglow, with a maximum contribution of
about 8-10% in the Ks band in the dusty days.Comment: 6 pages, 3 figures, 6 tables, accepted for publication in MNRA
A Corona Australis cloud filament seen in NIR scattered light II: Comparison with sub-millimeter data
We study a northern part of the Corona Australis molecular cloud that
consists of a filament and a dense sub-millimetre core inside the filament. Our
aim is to measure dust temperature and sub-mm emissivity within the region. We
also look for confirmation that near-infrared (NIR) surface brightness can be
used to study the structure of even very dense clouds. We extend our previous
NIR mapping south of the filament. The dust colour temperatures are estimated
using Spitzer 160um and APEX/Laboca 870um maps. The column densities derived
based on the reddening of background stars, NIR surface brightness, and thermal
sub-mm dust emission are compared. A three dimensional toy model of the
filament is used to study the effect of anisotropic illumination on
near-infrared surface brightness and the reliability of dust temperature
determination. Relative to visual extinction, the estimated emissivity at 870um
is kappa(870) = (1.3 +- 0.4) x 10^{-5} 1/mag. This is similar to the values
found in diffuse medium. A significant increase in the sub-millimetre
emissivity seems to be excluded. In spite of saturation, NIR surface brightness
was able to accurately pinpoint, and better than measurements of the colour
excesses of background stars, the exact location of the column density maximum.
Both near- and far-infrared data show that the intensity of the radiation field
is higher south of the filament.Comment: 9 pages, 9 figures, accepted to A&
A southern hemisphere survey of the 5780 and 6284 {\AA} diffuse interstellar bands: correlation with the extinction
We present a new database of 5780.5 and 6283.8 {\AA} DIB measurements and
also study their correlation with the reddening. The database is based on
high-resolution, high-quality spectra of early-type nearby stars located in the
southern hemisphere at an average distance of 300 pc. Equivalent widths of the
two DIBs were determined by means of a realistic continuum fitting and
synthetic atmospheric transmissions. For all stars that possess a precise
measurement of their color excess, we compare the DIBs and the extinction. We
find average linear relationships of the DIBS and the color excess that agree
well with those of a previous survey of northern hemisphere stars closer than
550 pc. This similarity shows that there is no significant spatial dependence
of the average relationship in the solar neighborhood within 600 pc. A
noticeably different result is our higher degree of correlation of the two DIBs
with the extinction. We demonstrate that it is simply due to the lower
temperature and intrinsic luminosity of our targets. Using cooler target stars
reduces the number of outliers, especially for nearby stars, confirming that
the radiation field of UV bright stars has a significant influence on the DIB
strength. We have used the cleanest data to compute updated DIB shapes.Comment: Astronomy & Astrophysics (in press
Integrative Taxonomy of Armeria arenaria (Plumbaginaceae), with a Special Focus on the Putative Subspecies Endemic to the Apennines
Three subspecies of Armeria arenaria are reported from Italy, two of which are considered endemic to the Apennines. The taxonomic value of these two taxa (A. arenaria subsp. marginata and A. arenaria subsp. apennina) is unclear. Moreover, the relationships between A. arenaria subsp. praecox and Northern Italian populations—currently ascribed to A. arenaria subsp. arenaria—have never been addressed. Accordingly, we used an integrated taxonomic approach, including morphometry, seed morpho–colorimetry, karyology, molecular systematics (psbA–trnH, trnQ–rps16, trnF–trnL, trnL–rpl32, and ITS region), and comparative niche analysis. According to our results, French–Northern Italian populations are clearly distinct from Apennine populations. In the first group, there is evidence which allows the recognition of A. arenaria s.str. (not occurring in Italy) and A. arenaria subsp. praecox. In the second group, the two putative taxa endemic to the Northern Apennines cannot be separated, so a single subspecies is here recognized: A. arenaria subsp. marginata
Did the ancient egyptians record the period of the eclipsing binary Algol - the Raging one?
The eclipses in binary stars give precise information of orbital period
changes. Goodricke discovered the 2.867 days period in the eclipses of Algol in
the year 1783. The irregular orbital period changes of this longest known
eclipsing binary continue to puzzle astronomers. The mass transfer between the
two members of this binary should cause a long-term increase of the orbital
period, but observations over two centuries have not confirmed this effect.
Here, we present evidence indicating that the period of Algol was 2.850 days
three millenia ago. For religious reasons, the ancient Egyptians have recorded
this period into the Cairo Calendar, which describes the repetitive changes of
the Raging one. Cairo Calendar may be the oldest preserved historical document
of the discovery of a variable star.Comment: 26 pages, 5 figures, 11 table
Novel (Hetero)arylalkenyl propargylamine compounds are protective in toxin-induced models of Parkinson's disease
Background: Mitochondrial dysfunction, oxidative stress and their interplay are core pathological features of Parkinson's disease. In dopaminergic neurons, monoamines and their metabolites provide an additional source of reactive free radicals during their breakdown by monoamine oxidase or auto-oxidation. Moreover, mitochondrial dysfunction and oxidative stress have a supraadditive impact on the pathological, cytoplasmic accumulation of dopamine and its subsequent release. Here we report the effects of a novel series of potent and selective MAO-B inhibitory (hetero)arylalkenylpropargylamine compounds having protective properties against the supraadditive effect of mitochondrial dysfunction and oxidative stress. Results: The (hetero)arylalkenylpropargylamines were tested in vitro, on acute rat striatal slices, pretreated with the complex I inhibitor rotenone and in vivo, using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced acute, subchronic, and chronic experimental models of Parkinson's disease in mice. The compounds exhibited consistent protective effects against i) in vitro oxidative stress induced pathological dopamine release and the formation of toxic dopamine quinone in the rat striatum and rescued tyrosine hydroxylase positive neurons in the substantia nigra after rotenone treatment; ii) in vivo MPTP-induced striatal dopamine depletion and motor dysfunction in mice using acute and subchronic, delayed application protocols. One compound (SZV558) was also examined and proved to be protective in a chronic mouse model of MPTP plus probenecid (MPTPp) administration, which induces a progressive loss of nigrostriatal dopaminergic neurons. Conclusions: Simultaneous inhibition of MAO-B and oxidative stress induced pathological dopamine release by the novel propargylamines is protective in animal models and seems a plausible strategy to combat Parkinson's disease
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