198 research outputs found
Interpretation of HINODE SOT/SP asymmetric Stokes profiles observed in quiet Sun network and internetwork
We present the first interpretation of the Stokes profile asymmetries
measured in the FeI 630 nm lines by SOT/SP, in both quiet Sun internetwork (IN)
and network regions. The inversion is carried out under the hypothesis of
MISMA, where the unresolved structure is assumed to be optically thin. We
analyze a 29.52"x31.70" subfield carefully selected to be representative of the
properties of a 302"x162" quiet Sun field-of-view at disk center. The inversion
code is able to reproduce the observed asymmetries in a very satisfactory way.
The inversion code interprets 25% of inverted profiles as emerging from pixels
in which both positive and negative polarities coexist. kG field strengths are
found at the base of the photosphere in both network and IN; in the case of the
latter, both kG fields and hG fields are admixed. When considering the magnetic
properties at the mid photosphere most kG fields are gone, and the statistics
is dominated by hG fields. We constrain the magnetic field of only 4.5% of the
analyzed photosphere (and this percentage reduces to 1.3% when referred to all
pixels, including those with low polarization not analyzed). The rest of the
plasma is consistent with the presence of weak fields not contributing to the
detected polarization signals. The average flux densities derived in the full
subfield and in IN regions are higher than the ones derived from the same
dataset by Milne-Eddington inversion. The existence of large asymmetries in
SOT/SP polarization profiles is uncovered. These are not negligible in quiet
Sun data. The MISMA inversion code reproduces them in a satisfactory way, and
provides a statistical description of the magnetized IN and network which
partly differs and complements the results obtained so far. From this it
follows the importance of having a complete interpretation of the line profile
shapes.Comment: 11 pages, 9 figures, 1 table - Accepted for publication on A&
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
Optimizing the clinical utility of PCA3 to diagnose prostate cancer in initial prostate biopsy
Background: PCA3 has been included in a nomogram outperforming previous clinical models for the prediction of any prostate cancer (PCa) and high grade PCa (HGPCa) at the initial prostate biopsy (IBx). Our objective is to validate such IBx-specific PCA3-based nomogram. We also aim to optimize the use of this nomogram in clinical practice through the definition of risk groups.
Methods: Independent external validation. Clinical and biopsy data from a contemporary cohort of 401 men with the same inclusion criteria to those used to build up the reference’s nomogram in IBx. The predictive value of the nomogram was assessed by means of calibration curves and discrimination ability through the area under the curve (AUC). Clinical utility of the nomogram was analyzed by choosing thresholds points that minimize the overlapping between probability density functions (PDF) in PCa and no PCa and HGPCa and no HGPCa groups, and net benefit was assessed by decision curves.
Results: We detect 28 % of PCa and 11 % of HGPCa in IBx, contrasting to the 46 and 20 % at the reference series. Due to this, there is an overestimation of the nomogram probabilities shown in the calibration curve for PCa. The AUC values are 0.736 for PCa (C.I.95 %:0.68–0.79) and 0.786 for HGPCa (C.I.95 %:0.71–0.87) showing an adequate discrimination ability. PDF show differences in the distributions of nomogram probabilities in PCa and not PCa patient groups. A minimization of the overlapping between these curves confirms the threshold probability of harboring PCa >30 % proposed by Hansen is useful to indicate a IBx, but a cut-off > 40 % could be better in series of opportunistic screening like ours. Similar results appear in HGPCa analysis. The decision curve also shows a net benefit of 6.31 % for the threshold probability of 40 %.
Conclusions: PCA3 is an useful tool to select patients for IBx. Patients with a calculated probability of having PCa over 40 % should be counseled to undergo an IBx if opportunistic screening is required
High cadence spectropolarimetry of moving magnetic features observed around a pore
Moving magnetic features (MMFs) are small-size magnetic elements that are
seen to stream out from sunspots, generally during their decay phase. Several
observational results presented in the literature suggest them to be closely
related to magnetic filaments that extend from the penumbra of the parent spot.
Nevertheless, few observations of MMFs streaming out from spots without
penumbra have been reported. The literature still lacks of analyses of the
physical properties of these features.
We investigate physical properties of monopolar MMFs observed around a small
pore that had developed penumbra in the days preceding our observations and
compare our results with those reported in the literature for features observed
around sunspots. We analyzed NOAA 11005 during its decay phase with data
acquired at the Dunn Solar Telescope in the FeI 617.3
nm spectral lines with IBIS, and in the G-band. The field of view showed
monopolar MMFs of both polarities streaming out from the leading negative
polarity pore of the observed active region. Combining different analyses of
the data, we investigated the temporal evolution of the relevant physical
quantities associated with the MMFs as well as the photospheric and
chromospheric signatures of these features.
We show that the characteristics of the investigated MMFs agree with those
reported in the literature for MMFs that stream out from spots with penumbrae.
Moreover, observations of at least two of the observed features suggest them to
be manifestations of emerging magnetic arches.Comment: Accepted by A&
Stokes Diagnostis of 2D MHD-simulated Solar Magnetogranulation
We study the properties of solar magnetic fields on scales less than the
spatial resolution of solar telescopes. A synthetic infrared
spectropolarimetric diagnostics based on a 2D MHD simulation of
magnetoconvection is used for this. We analyze two time sequences of snapshots
that likely represent two regions of the network fields with their immediate
surrounding on the solar surface with the unsigned magnetic flux density of 300
and 140 G. In the first region we find from probability density functions of
the magnetic field strength that the most probable field strength at logtau_5=0
is equal to 250 G. Weak fields (B < 500 G) occupy about 70% of the surface,
while stronger fields (B 1000 G) occupy only 9.7% of the surface. The magnetic
flux is -28 G and its imbalance is -0.04. In the second region, these
parameters are correspondingly equal to 150 G, 93.3 %, 0.3 %, -40 G, and -0.10.
We estimate the distribution of line-of-sight velocities on the surface of log
tau_5=-1. The mean velocity is equal to 0.4 km/s in the first simulated region.
The averaged velocity in the granules is -1.2 km/s and in the intergranules is
2.5 km/s. In the second region, the corresponding values of the mean velocities
are equal to 0, -1.8, 1.5 km/s. In addition we analyze the asymmetry of
synthetic Stokes-V profiles of the Fe I 1564.8 nm line. The mean values of the
amplitude and area asymmetry do not exceed 1%. The spatially smoothed amplitude
asymmetry is increased to 10% while the area asymmetry is only slightly varied.Comment: 24 pages, 12 figure
Targets, mechanisms and cytotoxicity of half-sandwich Ir(III) complexes are modulated by structural modifications on the benzazole ancillary ligand
Cancers are driven by multiple genetic mutations but evolve to evade treatments targeting specific mutations. Nonetheless, cancers cannot evade a treatment that targets mitochondria, which are essential for tumor progression. Iridium complexes have shown anticancer properties, but they lack specificity for their intracellular targets, leading to undesirable side effects. Herein we present a systematic study on structure-activity relationships of eight arylbenzazole-based Iridium(III) complexes of type [IrCl(Cp*)], that have revealed the role of each atom of the ancillary ligand in the physical chemistry properties, cytotoxicity and mechanism of biological action. Neutral complexes, especially those bearing phenylbenzimidazole (HL1 and HL2), restrict the binding to DNA and albumin. One of them, complex 1[C,NH-Cl], is the most selective one, does not bind DNA, targets exclusively the mitochondria, disturbs the mitochondria membrane permeability inducing proton leak and increases ROS levels, triggering the molecular machinery of regulated cell death. In mice with orthotopic lung tumors, the administration of complex 1[C,NH-Cl] reduced the tumor burden. Cancers are more vulnerable than normal tissues to a treatment that harnesses mitochondrial dysfunction. Thus, complex 1[C,NH-Cl] characterization opens the way to the development of new compounds to exploit this vulnerability
Collective Particle Flow through Random Media
A simple model for the nonlinear collective transport of interacting
particles in a random medium with strong disorder is introduced and analyzed. A
finite threshold for the driving force divides the behavior into two regimes
characterized by the presence or absence of a steady-state particle current.
Below this threshold, transient motion is found in response to an increase in
the force, while above threshold the flow approaches a steady state with motion
only on a network of channels which is sparse near threshold. Some of the
critical behavior near threshold is analyzed via mean field theory, and
analytic results on the statistics of the moving phase are derived. Many of the
results should apply, at least qualitatively, to the motion of magnetic bubble
arrays and to the driven motion of vortices in thin film superconductors when
the randomness is strong enough to destroy the tendencies to lattice order even
on short length scales. Various history dependent phenomena are also discussed.Comment: 63 preprint pages plus 6 figures. Submitted to Phys Rev
The Imaging Magnetograph eXperiment (IMaX) for the Sunrise balloon-borne solar observatory
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by
four institutions in Spain that flew on board the Sunrise balloon-borne
telesocope in June 2009 for almost six days over the Arctic Circle. As a
polarimeter IMaX uses fast polarization modulation (based on the use of two
liquid crystal retarders), real-time image accumulation, and dual beam
polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the
instrument uses a LiNbO3 etalon in double pass and a narrow band pre-filter to
achieve a spectral resolution of 85 mAA. IMaX uses the high Zeeman sensitive
line of Fe I at 5250.2 AA and observes all four Stokes parameters at various
points inside the spectral line. This allows vector magnetograms, Dopplergrams,
and intensity frames to be produced that, after reconstruction, reach spatial
resolutions in the 0.15-0.18 arcsec range over a 50x50 arcsec FOV. Time
cadences vary between ten and 33 seconds, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in various ways
depending on the applied observing mode, from just two points inside the line
to 11 of them. All observing modes include one extra wavelength point in the
nearby continuum. Gauss equivalent sensitivities are four Gauss for
longitudinal fields and 80 Gauss for transverse fields per wavelength sample.
The LOS velocities are estimated with statistical errors of the order of 5-40
m/s. The design, calibration and integration phases of the instrument, together
with the implemented data reduction scheme are described in some detail.Comment: 17 figure
Modeling the Subsurface Structure of Sunspots
While sunspots are easily observed at the solar surface, determining their
subsurface structure is not trivial. There are two main hypotheses for the
subsurface structure of sunspots: the monolithic model and the cluster model.
Local helioseismology is the only means by which we can investigate
subphotospheric structure. However, as current linear inversion techniques do
not yet allow helioseismology to probe the internal structure with sufficient
confidence to distinguish between the monolith and cluster models, the
development of physically realistic sunspot models are a priority for
helioseismologists. This is because they are not only important indicators of
the variety of physical effects that may influence helioseismic inferences in
active regions, but they also enable detailed assessments of the validity of
helioseismic interpretations through numerical forward modeling. In this paper,
we provide a critical review of the existing sunspot models and an overview of
numerical methods employed to model wave propagation through model sunspots. We
then carry out an helioseismic analysis of the sunspot in Active Region 9787
and address the serious inconsistencies uncovered by
\citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find
that this sunspot is most probably associated with a shallow, positive
wave-speed perturbation (unlike the traditional two-layer model) and that
travel-time measurements are consistent with a horizontal outflow in the
surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic
Las yeserías del Patio del Sol del Real Alcázar de Sevilla: Caracterización y cronología
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