1,152 research outputs found
Granular-Scale Elementary Flux Emergence Episodes in a Solar Active Region
We analyze data from Hinode spacecraft taken over two 54-minute periods
during the emergence of AR 11024. We focus on small-scale portions within the
observed solar active region and discover the appearance of very distinctive
small-scale and short-lived dark features in Ca II H chromospheric filtergrams
and Stokes I images. The features appear in regions with close-to-zero
longitudinal magnetic field, and are observed to increase in length before they
eventually disappear. Energy release in the low chromospheric line is detected
while the dark features are fading. In time series of magnetograms a diverging
bipolar configuration is observed accompanying the appearance of the dark
features and the brightenings. The observed phenomena are explained as
evidencing elementary flux emergence in the solar atmosphere, i.e small-scale
arch filament systems rising up from the photosphere to the lower chromosphere
with a length scale of a few solar granules. Brightenings are explained as
being the signatures of chromospheric heating triggered by reconnection of the
rising loops (once they reached chromospheric heights) with pre-existing
magnetic fields as well as to reconnection/cancellation events in U-loop
segments of emerging serpentine fields. We study the temporal evolution and
dynamics of the events and compare them with the emergence of magnetic loops
detected in quiet sun regions and serpentine flux emergence signatures in
active regions. Incorporating the novel features of granular-scale flux
emergence presented in this study we advance the scenario for serpentine flux
emergence.Comment: 24 pages, 9 figures. Accepted for publication in Solar Physic
Plastid and nuclear DNA polymorphism reveals historical processes of isolation and reticulation in the olive tree complex (Olea europaea L.)
A set of primers for length and nucleotide-substitution polymorphism in chloroplastic DNA of Olea europaea L. (Oleaceae)
A set of primers for length and nucleotide-substitution polymorphism in chloroplastic DNA of Olea europaea L. (Oleaceae)
Chloroplastic DNA (cpDNA) variation at five microsatellite motifs, two insertion-deletion sites, and eight nucleotide substitution sites was investigated in the Olea europaea complex. Primers were designed for flanking regions of these sites to amplify short cpDNA regions. They provided polymorphism when polymerase chain reaction (PCR) products from a representative sample of 128 O. europaea individuals were either resolved by size into polyacrylamide gels (length polymorphism) or digested with restriction enzymes (nucleotide-substitution polymorphism). These polymorphisms serve to distinguish most of the cytoplasmic haplotypes previously recognized. Potential application of these markers in O. europaea includes phylogeography, conservation and germplasm identification, even when using poorly preserved material from herbarium specimens or forensic and archaeological materials.This work was supported by the project BIOD-IBERIA (A82).Peer Reviewe
Polyploidy in the Olive Complex (Olea europaea): Evidence from Flow Cytometry and Nuclear Microsatellite Analyses
Background Phylogenetic and phylogeographic investigations have been previously performed to study the evolution of the olive tree complex (Olea europaea). A particularly high genomic diversity has been found in north-west Africa. However, to date no exhaustive study has been addressed to infer putative polyploidization events and their evolutionary significance in the diversification of the olive tree and its relatives. Methods Representatives of the six olive subspecies were investigated using (a) flow cytometry to estimate genome content, and (b) six highly variable nuclear microsatellites to assess the presence of multiple alleles at co-dominant loci. In addition, nine individuals from a controlled cross between two individuals of O. europaea subsp. maroccana were characterized with microsatellites to check for chromosome inheritance. Key Results Based on flow cytometry and genetic analyses, strong evidence for polyploidy was obtained in subspp. cerasiformis (tetraploid) and maroccana (hexaploid), whereas the other subspecies appeared to be diploids. Agreement between flow cytometry and genetic analyses gives an alternative approach to chromosome counting to determine ploidy level of trees. Lastly, abnormalities in chromosomes inheritance leading to aneuploid formation were revealed using microsatellite analyses in the offspring from the controlled cross in subsp. maroccana. Conclusions This study constitutes the first report for multiple polyploidy in olive tree relatives. Formation of tetraploids and hexaploids may have played a major role in the diversification of the olive complex in north-west Africa. The fact that polyploidy is found in narrow endemic subspecies from Madeira (subsp. cerasiformis) and the Agadir Mountains (subsp. maroccana) suggests that polyploidization has been favoured to overcome inbreeding depression. Lastly, based on previous phylogenetic analyses, we hypothesize that subsp. cerasiformis resulted from hybridization between ancestors of subspp. guanchica and europae
Multiwavelength Observations of Small-Scale Reconnection Events triggered by Magnetic Flux Emergence in the Solar Atmosphere
The interaction between emerging magnetic flux and the pre-existing ambient
field has become a "hot" topic for both numerical simulations and
high-resolution observations of the solar atmosphere. The appearance of
brightenings and surges during episodes of flux emergence is believed to be a
signature of magnetic reconnection processes. We present an analysis of a
small-scale flux emergence event in NOAA 10971, observed simultaneously with
the Swedish 1-m Solar Telescope on La Palma and the \emph{Hinode} satellite
during a joint campaign in September 2007. Extremely high-resolution G-band,
H, and \ion{Ca}{2} H filtergrams, \ion{Fe}{1} and \ion{Na}{1}
magnetograms, EUV raster scans, and X-ray images show that the emerging region
was associated with chromospheric, transition region and coronal brightenings,
as well as with chromospheric surges. We suggest that these features were
caused by magnetic reconnection at low altitude in the atmosphere. To support
this idea, we perform potential and linear force-free field extrapolations
using the FROMAGE service. The extrapolations show that the emergence site is
cospatial with a 3D null point, from which a spine originates. This magnetic
configuration and the overall orientation of the field lines above the emerging
flux region are compatible with the structures observed in the different
atmospheric layers, and remain stable against variations of the force-free
field parameter. Our analysis supports the predictions of recent 3D numerical
simulations that energetic phenomena may result from the interaction between
emerging flux and the pre-existing chromospheric and coronal field.Comment: In press for Ap
Follow-up study on lead exposure in children living in a smelter community in northern Mexico
<p>Abstract</p> <p>Background</p> <p>To study the changes of children lead exposure in the city of Torreon during the last five years, after environmental and public health interventions, using the timeline of lead in blood concentration as the biomarker of exposure and its relation to lead in soil concentrations.</p> <p>Methods</p> <p>This follow-up study started in 2001 and consisted of 232 children living in nine neighborhoods in Torreon. Children were tested at 0, 6, 12 and 60 months. Lead in blood concentrations, Hemoglobin, Zinc-Protoporphyrin, anthropometric measures and socioeconomic status questionnaire was supplied to the parents.</p> <p>Results</p> <p>Median and range of lead in blood concentrations obtained at 0, 6, 12, 60 months were: 10.12 μg/dl (1.9 - 43.8), 8.75 μg/dl (1.85 - 41.45), 8.4 μg/dl (1.7 - 35.8) and 4.4 μg/dl (1.3 - 30.3), respectively. The decrease of lead in blood levels was significantly related to ages 0, 6, 12 and 60 months of the follow-up study. The timeline of B-Pb was associated with the timeline of lead in soil concentrations.</p> <p>Conclusions</p> <p>B-Pb levels have significantly decreased in the group of children studied. This could be explained by a) environmental interventions by authorities and the smelter companies, b) normal changes in hygienic habits as children age and c) lead redistribution from blood to hard tissues.</p
Magnetic field emergence in mesogranular-sized exploding granules observed with SUNRISE/IMaX data
We report on magnetic field emergences covering significant areas of
exploding granules. The balloon-borne mission SUNRISE provided high spatial and
temporal resolution images of the solar photosphere. Continuum images,
longitudinal and transverse magnetic field maps and Dopplergrams obtained by
IMaX onboard SUNRISE are analyzed by Local Correlation Traking (LCT),
divergence calculation and time slices, Stokes inversions and numerical
simulations are also employed. We characterize two mesogranular-scale exploding
granules where 10 Mx of magnetic flux emerges. The emergence of
weak unipolar longitudinal fields (100 G) start with a single visible
magnetic polarity, occupying their respective granules' top and following the
granular splitting. After a while, mixed polarities start appearing,
concentrated in downflow lanes. The events last around 20 min. LCT analyses
confirm mesogranular scale expansion, displaying a similar pattern for all the
physical properties, and divergence centers match between all of them. We found
a similar behaviour with the emergence events in a numerical MHD simulation.
Granule expansion velocities are around 1 \kms while magnetic patches expand at
0.65 \kms. One of the analyzed events evidences the emergence of a loop-like
structure. Advection of the emerging magnetic flux features is dominated by
convective motion resulting from the exploding granule due to the magnetic
field frozen in the granular plasma. Intensification of the magnetic field
occurs in the intergranular lanes, probably because of being directed by the
downflowing plasma.Comment: 7 pages, 6 figure
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