2,073 research outputs found
Oxygen transport in nanostructured lanthanum manganites
Methods and models describing oxygen diffusion and desorption in oxides have been developed for
slightly defective and well crystallised bulky materials. Does nanostructuring change the mechanism of
oxygen mobility? In such a case, models should be properly checked and adapted to take into account
new material properties. In order to do so, temperature programmed oxygen desorption and
thermogravimetric analysis, either in isothermal or ramp mode, have been used to investigate some
nanostructured La1\u2013xAxMnO3 d samples (A = Sr and Ce, 20\u201360 nm particle size) with perovskite-like
structure. The experimental data have been elaborated by means of different models to define a set of
kinetic parameters able to describe oxygen release properties and oxygen diffusion through the bulk.
Different rate-determining steps have been identified, depending on the temperature range and
oxygen depletion of the material. In particular, oxygen diffusion was shown to be rate-limiting at low
temperature and at low defect concentration, whereas oxygen recombination at the surface seems to
be the rate-controlling step at high temperature. However, the oxygen recombination step is characterised
by an activation energy much lower than that for diffusion. In the present paper oxygen transport
in nanosized materials is quantified by making use of widely diffused experimental techniques and
by critically adapting to nanoparticles suitably chosen models developed for bulk materials
The developmental pathways of preschool children with acute lymphoblastic leukemia: communicative and social sequelae one year after treatment
Early childhood is considered to be a period of rapid development, with the acquisition
of abilities predicting future positive school competences. Motor, cognitive, and social diculties
related to cancer therapies heavily impact the development of children with cancer. This study
focused on two main aims: To assess the developmental pathways of preschool children with
acute lymphoblastic leukemia one year post-treatment and to compare these abilities both with
those of a control group of healthy peers and with Italian norms. Forty-four children and their
families, recruited through the Hematology-Oncologic Clinic of the Department of Child andWoman
Health (University of Padua), agreed to participate in this study. The children\u2019s mean age was
4.52 years (SD = 0.94, range = 2.5\u20136 years), equally distributed by gender, all diagnosed with acute
lymphoblastic leukemia. Matched healthy peers were recruited through pediatricians\u2019 ambulatories.
Each family was interviewed adopting the Vineland adaptive behavior scales. Paired sampleWilcoxon
tests revealed that children were reported to have significantly more developmental diculties than
their healthy peers. When compared with Italian norms, they scored particularly low in verbal
competence, social, and coping skills. No significant association was found between treatment
variables and developmental abilities. These findings suggest that the creation of specialized
interventions, both for parents and children, may fill the possible delays in children\u2019s development
probably due to stress, lack of adequate stimulation, or dicult adaptation
The Overlooked Potential of Generalized Linear Models in Astronomy - I: Binomial Regression
Revealing hidden patterns in astronomical data is often the path to
fundamental scientific breakthroughs; meanwhile the complexity of scientific
inquiry increases as more subtle relationships are sought. Contemporary data
analysis problems often elude the capabilities of classical statistical
techniques, suggesting the use of cutting edge statistical methods. In this
light, astronomers have overlooked a whole family of statistical techniques for
exploratory data analysis and robust regression, the so-called Generalized
Linear Models (GLMs). In this paper -- the first in a series aimed at
illustrating the power of these methods in astronomical applications -- we
elucidate the potential of a particular class of GLMs for handling
binary/binomial data, the so-called logit and probit regression techniques,
from both a maximum likelihood and a Bayesian perspective. As a case in point,
we present the use of these GLMs to explore the conditions of star formation
activity and metal enrichment in primordial minihaloes from cosmological
hydro-simulations including detailed chemistry, gas physics, and stellar
feedback. We predict that for a dark mini-halo with metallicity , an increase of in the gas
molecular fraction, increases the probability of star formation occurrence by a
factor of 75%. Finally, we highlight the use of receiver operating
characteristic curves as a diagnostic for binary classifiers, and ultimately we
use these to demonstrate the competitive predictive performance of GLMs against
the popular technique of artificial neural networks.Comment: 20 pages, 10 figures, 3 tables, accepted for publication in Astronomy
and Computin
Phase Transformations in the CeO2-Sm2O3System : A Multiscale Powder Diffraction Investigation
The structure evolution in the CeO2-Sm2O3system is revisited by combining high resolution synchrotron powder diffraction with pair distribution function (PDF) to inquire about local, mesoscopic, and average structure. The CeO2fluorite structure undergoes two phase transformations by Sm doping, first to a cubic (C-type) and then to a monoclinic (B-type) phase. Whereas the C to B-phase separation occurs completely and on a long-range scale, no miscibility gap is detected between fluorite and C-type phases. The transformation rather occurs by growth of C-type nanodomains embedded in the fluorite matrix, without any long-range phase separation. A side effect of this mechanism is the ordering of the oxygen vacancies, which is detrimental for the application of doped ceria as an electrolyte in fuel cells. The results are discussed in the framework of other Y and Gd dopants, and the relationship between nanostructuring and the above equilibria is also investigated
Cool Core Clusters from Cosmological Simulations
We present results obtained from a set of cosmological hydrodynamic
simulations of galaxy clusters, aimed at comparing predictions with
observational data on the diversity between cool-core (CC) and non-cool-core
(NCC) clusters. Our simulations include the effects of stellar and AGN feedback
and are based on an improved version of the smoothed particle hydrodynamics
code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical
instabilities by including a suitable artificial thermal diffusion. In this
Letter, we focus our analysis on the entropy profiles, the primary diagnostic
we used to classify the degree of cool-coreness of clusters, and on the iron
profiles. In keeping with observations, our simulated clusters display a
variety of behaviors in entropy profiles: they range from steadily decreasing
profiles at small radii, characteristic of cool-core systems, to nearly flat
core isentropic profiles, characteristic of non-cool-core systems. Using
observational criteria to distinguish between the two classes of objects, we
find that they occur in similar proportions in both simulations and in
observations. Furthermore, we also find that simulated cool-core clusters have
profiles of iron abundance that are steeper than those of NCC clusters, which
is also in agreement with observational results. We show that the capability of
our simulations to generate a realistic cool-core structure in the cluster
population is due to AGN feedback and artificial thermal diffusion: their
combined action allows us to naturally distribute the energy extracted from
super-massive black holes and to compensate for the radiative losses of
low-entropy gas with short cooling time residing in the cluster core.Comment: 6 pages, 4 figures, accepted in ApJL, v2 contains some modifications
on the text (results unchanged
5kWe+5kWt reformer-PEMFC energy generator from bioethanol first data on the fuel processor from a demonstrative project
A power unit constituted by a reformer section, a H 2 purification section and a fuel cell stack is being tested c/o the Dept. of Physical Chemistry and Electrochemistry of Universit\ue0 degli Studi di Milano, on the basis of a collaboration with HELBIO S.A. Hydrogen and Energy Production Systems, Patras (Greece), supplier of the unit, and some sponsors (Linea Energia S.p.A., Parco Tecnologico Padano and Provincia di Lodi, Italy). The system size allows to co-generate 5 kW e (220 V, 50 Hz a.c.) + 5 kW t (hot water at 65\ub0C) as peak output. Bioethanol, obtainable by different non-food-competitive biomass, is transformed into syngas by a pre-reforming and reforming reactors couple and the reformate is purified from CO to a concentration below 20 ppmv, suitable to feed a proton exchange membrane fuel cell (PEMFC) stack that will be integrated in the fuel processor in a second step of the experimentation. This result is achieved by feeding the reformate to two water gas shift reactors, connected in series and operating at high and low temperature, respectively. CO concentration in the outcoming gas is ca. 0.4 vol% and the final CO removal to meet the specifications is accomplished by two methanation reactors in series. The second methanation step acts merely as a guard, since ca. 15 ppmv of CO are obtained already after the first reactor. The goals of the present project are to test the integrated fuel processor, to check the effectiveness of the proposed technology and to suggest possible adequate improvements
Beta-blocker treatment guided by head-up tilt test in neurally mediated syncope
This study was an open-label, uncontrolled, dose-escalation trial of beta-blockers in patients with a history of syncope without warning or syncope resulting in trauma (malignant vasovagal syncope) who had positive head-up tilt test (HUT) responses, with or without isoproterenol infusion. Thirty patients (mean age, 37 +/- 21 years) with recurrent syncopal and near-syncopal episodes of unexplained origin in the previous year (6 +/- 14 syncopal episodes and 17 +/- 3 near-syncopes) underwent HUT for diagnostic purposes and for guiding prophylactic treatment. After patients were given a 10-minute rest in a recumbent position, rye performed an WT at 70 degrees for 25 minutes; if indicated, isoproterenol testing was performed at incremental dosages (dye steps at 10-minute intervals at 80 degrees), AU patients experienced syncope during HUT, 15 (50%) at baseline HUT and 15 (50%) during isoproterenol infusion (1 to 3 mu g/min; mean, 1.6 mu g/min). Sixteen syncopes were of vasodepressor type, 10 were mixed, and 4 were of cardioinhibitory type. After baseline HUT, betablocking drugs were prescribed to all patients as follows: 1 patient was given propranolol (160 mg daily), and 29 patients were given metoprolol (246 +/- 49 mg daily), with a dose titration period of 14 days. HUT was repeated after 3 weeks, and 24 patients (80%) had negative results (no syncope or anomalous responses). After further dosage adjustment of beta-blockers in nonresponders, a negative HUT was obtained in 28 patients (93%). Overall mean metoprolol daily dose was 262 +/- 60 mg (29 patients), and propranolol was administered at 160 mg daily in 1 patient. Thirteen patients (43%) reported side effects, none of which required drug withdrawal. At an average follow-up of 16 +/- 4 months, none of the patients experienced syncope, a statistically significant reduction. Moreover, a statistically significant reduction in the number of near-syncopal episodes was observed in comparison to the previous year. None of the patients discontinued treatment because of long-term side effects. Beta-blockers were well tolerated and achieved a high rate of efficacy, even in cardioinhibitory syncopes. In conclusion, in selected patients with malignant vasovagal syncope, treatment with metoprolol or propranolol at relatively high doses is feasible and, if guided by HUT results, is associated with a favorable outcome in terms of freedom from syncopal recurrences. Appropriate titration to achieve the full beta-blocking effect appears to be advisable
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