425 research outputs found
The effect of residential urban greenness on allergic respiratory diseases in youth: A narrative review
Background: Environmental exposures across the life course may be a contributor to the increased worldwide prevalence of respiratory and allergic diseases occurring in the last decades. Asthma and rhinoconjunctivitis especially contribute to the global burden of disease. Greenness has been suggested to have beneficial effects in terms of reduction of occurrence of allergic respiratory diseases. However, the available evidence of a relationship between urban greenness and childhood health outcomes is not yet conclusive. The current review aimed at investigating the current state of evidence, exploring the relationship between children's exposure to residential urban greenness and development of allergic respiratory diseases, jointly considering health outcomes and study design. Methods: The search strategy was designed to identify studies linking urban greenness exposure to asthma, rhinoconjunctivitis, and lung function in children and adolescents. This was a narrative review of literature following PRISMA guidelines performed using electronic search in databases of PubMed and Embase (Ovid) from the date of inception to December 2018. Results: Our search strategy identified 2315 articles; after exclusion of duplicates (n = 701), 1614 articles were screened. Following review of titles and abstracts, 162 articles were identified as potentially eligible. Of these, 148 were excluded following full-text evaluation, and 14 were included in this review. Different methods for assessing greenness exposure were found; the most used was Normalized Difference Vegetation Index. Asthma, wheezing, bronchitis, rhinoconjunctivitis, allergic symptoms, lung function, and allergic sensitization were the outcomes assessed in the identified studies; among them, asthma was the one most frequently investigated. Conclusions: The present review showed inconsistencies in the results mainly due to differences in study design, population, exposure assessment, geographic region, and ascertainment of outcome. Overall, there is a suggestion of an association between urban greenness in early life and the occurrence of allergic respiratory diseases during childhood, although the evidence is still inconsistent. It is therefore hard to draw a conclusive interpretation, so that the understanding of the impact of greenness on allergic respiratory diseases in children and adolescents remains difficult
Application of chemical geothermometers to a low temperature thermal system
The Tiermas geothermal system is one of the areas with the greatest geothermal potential in Aragón, however, its hydrogeological and geochemical features are still poorly known. In this study, the main hydrochemical features of these waters are presented and the reservoir temperature is approached by applying chemical geothermometers. These waters have a sulphate chloride sodium affinity, with nearly 40 ºC of spring temperature and an approximate flow rate of 200 l/s. The most likely aquifer seems to be located in the Paleocene and Eocene carbonates. However, due to the structural complexity of the area, the waters would also interact with the evaporitic facies present in the Eocene–Oligocene boundary. Two different hydrochemical groups have been distinguished based on their salinity, Na/Cl ratios, SO4 concentrations and TDS values. Despite the compositional variations detected in the springs, the geothermometric calculations allow to infer a reservoir temperature of 85 ± 17 °C. Good consistency has been obtained with the cationic geothermometers, which is an unusual situation for a geothermal system in carbonate–evaporitic materialsEl sistema geotermal de Tiermas representa una de las zonas con mayor potencial geotérmico de Aragón y, sin embargo, se sabe todavÃa poco acerca de sus caracterÃsticas hidrológicas y geoquÃmicas. En este trabajo se presentan los principales rasgos hidroquÃmicos de estas aguas y se determina su temperatura en profundidad mediante la aplicación de geotermómetros quÃmicos. Estas aguas tienen una afinidad clorurada sulfatada sódica, una temperatura de surgencia de casi 40 °C y un caudal de unos 200 l/s. El acuÃfero más probable se localizarÃa en los carbonatos del Paleoceno y Eoceno, pero debido a la complejidad estructural de la zona, las aguas entrarÃan en contacto con la facies evaporÃtica del tránsito Eoceno–Oligoceno, adquiriendo asà dicha afinidad. Se han distinguido dos grupos hidroquÃmicos con una diferente salinidad, relación Na/Cl y concentraciones de SO4 y TSD. A pesar de las variaciones composicionales detectadas en las surgencias, los cálculos geotermométricos realizados permiten establecer un rango de temperaturas en el reservorio de 85 ± 17 °C, habiéndose obtenido buenos resultados con los geotermómetros catiónicos, situación poco habitual en sistemas termales instalados en materiales carbonatados – evaporÃtico
Capillary force-induced structural instability in liquid infiltrated elastic circular tubes
The capillary-induced structural instability of an elastic circular tube
partially filled by a liquid is studied by combining theoretical analysis and
molecular dynamics simulations. The analysis shows that, associated with the
instability, there is a well-defined length scale (elasto-capillary length),
which exhibits a scaling relationship with the characteristic length of the
tube, regardless of the interaction details. We validate this scaling
relationship for a carbon nanotube partially filled by liquid iron. The
capillary-induced structural transformation could have potential applications
for nano-devices
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Real time imaging of two-dimensional iron oxide spherulite nanostructure formation
The formation of complex hierarchical nanostructures has attracted a lot of attention from both the fundamental science and potential applications point of view. Spherulite structures with radial fibrillar branches have been found in various solids; however, their growth mechanisms remain poorly understood. Here, we report real time imaging of the formation of two-dimensional (2D) iron oxide spherulite nanostructures in a liquid cell using transmission electron microscopy (TEM). By tracking the growth trajectories, we show the characteristics of the reaction front and growth kinetics. Our observations reveal that the tip of a growing branch splits as the width exceeds certain sizes (5.5–8.5 nm). The radius of a spherulite nanostructure increases linearly with time at the early stage, transitioning to nonlinear growth at the later stage. Furthermore, a thin layer of solid is accumulated at the tip and nanoparticles from secondary nucleation also appear at the growing front which later develop into fibrillar branches. The spherulite nanostructure is polycrystalline with the co-existence of ferrihydrite and Fe3O4 through-out the growth. A growth model is further established, which provides rational explanations on the linear growth at the early stage and the nonlinearity at the later stage of growth. [Figure not available: see fulltext.]
Using bond-length dependent transferable force constants to predict vibrational entropies in Au-Cu, Au-Pd, and Cu-Pd alloys
A model is tested to rapidly evaluate the vibrational properties of alloys
with site disorder. It is shown that length-dependent transferable force
constants exist, and can be used to accurately predict the vibrational entropy
of substitutionally ordered and disordered structures in Au-Cu, Au-Pd, and
Cu-Pd. For each relevant force constant, a length- dependent function is
determined and fitted to force constants obtained from first-principles
pseudopotential calculations. We show that these transferable force constants
can accurately predict vibrational entropies of L1-ordered and disordered
phases in CuAu, AuPd, PdAu, CuPd, and PdAu. In
addition, we calculate the vibrational entropy difference between
L1-ordered and disordered phases of AuCu and CuPt.Comment: 9 pages, 6 figures, 3 table
Weisskopf-Wigner model for wave packet excitation
We consider a laser induced molecular excitation process as a decay of a
single energy state into a continuum. The analytic results based on
Weisskopf-Wigner approach and perturbation calculations are compared with
numerical wave packet results. We find that the decay model describes the
excitation process well within the expected parameter region.Comment: 14 pages, Latex2.09, 9 Postscript figures embedded using psfig, see
also http://www.physics.helsinki.fi/~kasuomin
Nucleation of Al3Zr and Al3Sc in aluminum alloys: from kinetic Monte Carlo simulations to classical theory
Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and
Al3Sc which for low supersaturations of the solid solution have the L12
structure. The aim of the present study is to model at an atomic scale this
kinetics of precipitation and to build a mesoscopic model based on classical
nucleation theory so as to extend the field of supersaturations and annealing
times that can be simulated. We use some ab-initio calculations and
experimental data to fit an Ising model describing thermodynamics of the Al-Zr
and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy
exchange mechanism. This allows us to simulate with a kinetic Monte Carlo
algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then
used to test the classical nucleation theory. In this purpose, we deduce from
our atomic model an isotropic interface free energy which is consistent with
the one deduced from experimental kinetics and a nucleation free energy. We
test di erent mean-field approximations (Bragg-Williams approximation as well
as Cluster Variation Method) for these parameters. The classical nucleation
theory is coherent with the kinetic Monte Carlo simulations only when CVM is
used: it manages to reproduce the cluster size distribution in the metastable
solid solution and its evolution as well as the steady-state nucleation rate.
We also find that the capillary approximation used in the classical nucleation
theory works surprisingly well when compared to a direct calculation of the
free energy of formation for small L12 clusters.Comment: submitted to Physical Review B (2004
Stable encoding of visual cues in the mouse retrosplenial cortex
The rodent retrosplenial cortex (RSC) functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While RSC is reciprocally connected with the sensory cortex, the form in which sensory information is represented in the RSC and how it interacts with motor feedback is unclear and likely to be critical to computations involved in navigation such as path integration. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and locomotion evoked activity in RSC and compare it to primary visual cortex (V1). We observed stimulus position and orientation tuning, and a retinotopic organization. Locomotion modulation of activity of single neurons, both in darkness and light, was more pronounced in RSC than V1, and while locomotion modulation was strongest in RSC parvalbumin-positive neurons, visual-locomotion integration was found to be more supralinear in CaMKII neurons. Longitudinal measurements showed that response properties were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in RSC that are spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information
Early and mid-term results in patients undergoing primary CABG in comparison with patients with PCI prior to CABG
Aim: We evaluated the impact of prior percutaneous coronary intervention (PCI) on early and mid-term results in
patients undergoing coronary artery bypass grafting (CABG).
Methods: Between 2015 and 2020, 938 consecutive patients (mean age 67.4 ± 9.11 years) underwent CABG with
prior PCI (n = 121) or primary CABG (n = 817). The mean follow-up was 37 ± 25 (median 36) months. Kaplan-
Meier estimates were used to assess survival rates, while Logistic and Cox model analysis regressions assessed the
risk of prior PCI and other variables.
Results: Six-year survival including in-hospital mortality was 79% ± 6% in CABG with prior-PCI patients vs.
88% ± 2% in primary CABG (P = 0.002). As compared with primary CABG, in prior-PCI patients, clinical
presentation (acute coronary syndrome, reduced left ventricular ejection fraction, and previous myocardial
infarction, P ≤ 0.01, for all comparisons) was worse, comorbidity increased (Euroscore-2, severe chronic renal
dysfunction, P < 0.01), and in-hospital mortality was higher (6.6% or 8 patients vs. 1.6% or 13 patients, P < 0.001).
Prior PCI was found to be an independent predictor of mortality (HR = 4.23; P = 0.01). Six-year freedom from late
all-cause death and cardiac death were 84% ± 6% vs. 90% ± 2% (P = 0.2) and 96% ± 2% vs. 96% ± 1% (P = 0.5),
respectively. Independent predictors of all-cause death were advanced age at the operation (P < 0.0001), reduced left ventricular ejection fraction (P = 0.01), severe chronic renal dysfunction (P = 0.02), prior PCI (P = 0.03), and
Euroscore-2 (P = 0.05). Prior PCI did not negatively affect late cardiac death (P = 0.5).
Conclusion: Patients undergoing CABG after prior PCI have worse perioperative outcomes. Mid-term reduced
survival in the prior-PCI patients is mainly due to the concomitant presence of worse clinical presentation and
increased comorbidity. Freedom from cardiac death is comparable and satisfactory in both cohorts, highlighting the
positive protective effect of CABG over time
Monte Carlo simulation of subsurface ordering kinetics in an fcc-alloy model
Within the atom-vacancy exchange mechanism in a nearest-neighbor interaction
model we investigate the kinetics of surface-induced ordering processes close
to the (001) surface of an fcc A_3B-alloy. After a sudden quench into the
ordered phase with a final temperature above the ordering spinodal, T_f > T_sp,
the early time kinetics is dominated by a segregation front which propagates
into the bulk with nearly constant velocity. Below the spinodal, T_f < T_sp,
motion of the segregation wave reflects a coarsening process which appears to
be slower than predicted by the Lifschitz-Allen-Cahn law. In addition, in the
front-penetrated region lateral growth differs distinctly from perpendicular
growth, as a result of the special structure of antiphase boundaries near the
surface. Our results are compared with recent experiments on the subsurface
ordering kinetics at Cu_3Au (001).Comment: 10 pages, 9 figures, submitted to Phys. Rev. B, in prin
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