1,513 research outputs found
A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere
We report on spectropolarimetric observations of a near-IR line of Mn I
located at 15262.702 A whose intensity and polarization profiles are very
sensitive to the presence of hyperfine structure. A theoretical investigation
of the magnetic sensitivity of this line to the magnetic field uncovers several
interesting properties. The most important one is that the presence of strong
Paschen-Back perturbations due to the hyperfine structure produces an intensity
line profile whose shape changes according to the absolute value of the
magnetic field strength. A line ratio technique is developed from the intrinsic
variations of the line profile. This line ratio technique is applied to
spectropolarimetric observations of the quiet solar photosphere in order to
explore the probability distribution function of the magnetic field strength.
Particular attention is given to the quietest area of the observed field of
view, which was encircled by an enhanced network region. A detailed theoretical
investigation shows that the inferred distribution yields information on the
average magnetic field strength and the spatial scale at which the magnetic
field is organized. A first estimation gives ~250 G for the mean field strength
and a tentative value of ~0.45" for the spatial scale at which the observed
magnetic field is horizontally organized.Comment: 42 pages, 17 figures, accepted for publication in the Astrophysical
Journal. Figures 1 and 9 are in JPG forma
Aberrant innate immune sensing leads to the rapid progression of idiopathic pulmonary fibrosis
Novel approaches are needed to define subgroups of patients with Idiopathic pulmonary fibrosis (IPF) at risk for acute exacerbations and/or accelerated progression of this generally fatal disease. Progression of disease is an integral component of IPF with a median survival of 3 to 5 years. Conversely, a high degree of variability in disease progression has been reported among series. The characteristics of patients at risk of earlier death predominantly rely on baseline HRCT appearance, but this concept that has been challenged. Disparate physiological approaches have also been taken to identify patients at risk of mortality, with varying results. We hypothesized that the rapid decline in lung function in IPF may be a consequence of an abnormal host response to pathogen-associated molecular patterns (PAMPs), leading to aberrant activation in fibroblasts and fibrosis. Analysis of upper and lower lobe surgical lung biopsies (SLBs) indicated that TLR9, a hypomethylated CpG DNA receptor, is prominently expressed at the transcript and protein level, most notably in biopsies from rapidly progressive IPF patients. Surprisingly, fibroblasts appeared to be a major cellular source of TLR9 expression in IPF biopsies from this group of progressors. Further, CpG DNA promoted profibrotic cytokine and chemokine synthesis in isolated human IPF fibroblasts, most markedly again in cells from patients with the rapidly progressive IPF phenotype, in a TLR9-dependent manner. Finally, CpG DNA exacerbated fibrosis in an in vivo model initiated by the adoptive transfer of primary fibroblasts derived from patients who exhibited rapidly progressing fibrosis. Together, these data suggested that TLR9 activation via hypomethylated DNA might be an important mechanism in promoting fibrosis particularly in patients prone to rapidly progressing IPF
Entropy based parametrization of soils: Models and Tools
Particle-size distribution (PSD) is a fundamental soil physical property. The PSD is commonly reported in terms of the mass percentages of sand, silt and clay present
Deep Absorption Line Studies of Quiescent Galaxies at z~2: The Dynamical Mass-Size Relation, and First Constraints on the Fundamental plane
We present dynamical and structural scaling relations of quiescent galaxies
at z=2, including the dynamical mass-size relation and the first constraints on
the fundamental plane (FP). The backbone of the analysis is a new, very deep
VLT/X-shooter spectrum of a massive, compact, quiescent galaxy at z=2.0389. We
detect the continuum between 3700-22000A and several strong absorption features
(Balmer series, Ca H+K, G-band), from which we derive a stellar velocity
dispersion of 318 +/- 53 km/s. We perform detailed modeling of the continuum
emission and line indices and derive strong simultaneous constraints on the
age, metallicity, and stellar mass. The galaxy is a dusty (A_V=0.77
(+0.36,-0.32)) solar metallicity (log(Z/Zsun) = 0.02 (+0.20,-0.41)) post
starburst galaxy, with a mean luminosity weighted log(age/yr) of 8.9 +/- 0.1.
The galaxy formed the majority of its stars at z>3 and currently has little or
no ongoing star formation. We compile a sample of three other z~2 quiescent
galaxies with measured velocity dispersions, two of which are also post
starburst like. Their dynamical mass-size relation is offset significantly less
than the stellar mass-size relation from the local early type relations, which
we attribute to a lower central dark matter fraction. Recent cosmological
merger simulations qualitatively agree with the data, but can not fully account
for the evolution in the dark matter fraction. The z~2 FP requires additional
evolution beyond passive stellar aging, to be in agreement with the local FP.
The structural evolution predicted by the cosmological simulations is
insufficient, suggesting that additional, possibly non-homologous structural
evolution is needed.Comment: Re-submitted to ApJ after implementing the comments of the refere
Urban green space: creating a triple win for environmental sustainability, health, and health equity through behavior change
Urbanization, costs of green space maintenance, and diminishing connection between people and nature all exert pressures on urban green space. This is regrettable as green space has the potential to create wins for environmental sustainability, health, and health equity. This paper explores this potential triple win and investigates how to increase the use of urban green space through behavior change. A narrative literature review was conducted and was supplemented with literature suggested by experts. Results show that creating well-designed green spaces and stimulating people to use them can indeed deliver this triple win. Providing accessible, attractive, well-maintained green space with room for socialization, and where people feel safe, may increase the opportunity and motivation of people to use it more often. Informing and educating people and organizing activities may increase capability (and motivation) to use green space. Since the use of green space depends on life stage, lifestyle factors and individual values, it is important to involve potential users in its design. We recommend a specific focus on those groups who may benefit most from the use of green space. More evaluation is needed to inform effective green space interventions and to assess related economic, social, and environmental benefits.info:eu-repo/semantics/publishedVersio
Evolution of Galactic Discs: Multiple Patterns, Radial Migration and Disc Outskirts
We investigate the evolution of galactic disks in N-body Tree-SPH
simulations. We find that disks, initially truncated at three scale-lengths,
can triple their radial extent, solely driven by secular evolution. Both Type I
(single exponential) and Type II (down-turning) observed disk
surface-brightness profiles can be explained by our findings. We relate these
results to the strong angular momentum outward transfer, resulting from torques
and radial migration associated with multiple patterns, such as central bars
and spiral waves of different multiplicity. We show that even for stars ending
up on cold orbits, the changes in angular momentum exhibit complex structure as
a function of radius, unlike the expected effect of transient spirals alone.
Focussing on one of our models, we find evidence for non-linear coupling among
m=1, 2, 3 and 4 density waves, where m is the pattern multiplicity. We suggest
that the naturally occurring larger resonance widths at galactic radii beyond
four scale-lengths may have profound consequences on the formation and location
of breaks in disk density profiles, provided spirals are present at such large
distances. We also consider the effect of gas inflow and show that when
in-plane smooth gas accretion of ~5 M_sun/yr is included, the outer disks
become more unstable, leading to a strong increase in the stellar velocity
dispersion. This, in turn, causes the formation of a Type III (up-turning)
profile in the old stellar population. We propose that observations of Type III
surface brightness profiles, combined with an up-turn in the stellar velocity
dispersions beyond the disk break, could be a signature of ongoing
gas-accretion. The results of this study suggest that disk outskirts comprised
of stars migrated from the inner disk would have relatively large radial
velocity dispersions, and significant thickness when seen edge-on. [Abridged]Comment: Replaced with accepted version. New Fig. 5 added, Section 10
decreased in size, old Fig. 17 removed. Conclusions remain the same.
High-resolution version can be found at http://www.ivanminchev.co
A Comprehensive Analysis of Choroideremia: From Genetic Characterization to Clinical Practice.
Choroideremia (CHM) is a rare X-linked disease leading to progressive retinal degeneration resulting in blindness. The disorder is caused by mutations in the CHM gene encoding REP-1 protein, an essential component of the Rab geranylgeranyltransferase (GGTase) complex. In the present study, we evaluated a multi-technique analysis algorithm to describe the mutational spectrum identified in a large cohort of cases and further correlate CHM variants with phenotypic characteristics and biochemical defects of choroideremia patients. Molecular genetic testing led to the characterization of 36 out of 45 unrelated CHM families (80%), allowing the clinical reclassification of four CHM families. Haplotype reconstruction showed independent origins for the recurrent p.Arg293* and p.Lys178Argfs*5 mutations, suggesting the presence of hotspots in CHM, as well as the identification of two different unrelated events involving exon 9 deletion. No certain genotype-phenotype correlation could be established. Furthermore, all the patients´ fibroblasts analyzed presented significantly increased levels of unprenylated Rabs proteins compared to control cells; however, this was not related to the genotype. This research demonstrates the major potential of the algorithm proposed for diagnosis. Our data enhance the importance of establish a differential diagnosis with other retinal dystrophies, supporting the idea of an underestimated prevalence of choroideremia. Moreover, they suggested that the severity of the disorder cannot be exclusively explained by the genotype
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