The influence of dopants (Cr, Co, Fe, Ni, Y, Er, Tb, Gd, Pr and La) on the crystal structure of barium titanate was studied at room temperature and at 250°C using X-ray diffraction. Fine BaTiO
3 ...powders (Ba/Ti=1.02, size ≈30 nm) have been doped with 1 at% of the foreign element and annealed for 14 and 62 h at two different temperatures: 950 and 1350°C. The room temperature structure of doped BaTiO
3 was in any case tetragonal with c/a ratio lower than in the undoped perovskite, but dependent on dopant nature and particle size. For powders calcined at 1350°C, the particle size was in the range 1–5 μm and the decrease in tetragonality was mainly determined by dopant incorporation. Powders treated at 950°C had particles more than one order of magnitude finer (0.1–0.2 μm) and a systematic lowering of the c/a ratio in comparison to the samples annealed at higher temperature was observed. Comparison of the experimental variations of the unit cell edge of cubic BaTiO
3 (250°C) with the results of atomistic computer simulations gives indication on the preferential incorporation site of the dopant. In particular, La
3+ and Pr
3+ prefer to substitute at the Ba site, whereas Tb
3+ and Gd
3+ give partial substitution at the Ti site. For Er
3+ and Y
3+ preferential substitution at the Ti site is predicted. For transition metal ions, substitution at the Ti site with oxygen vacancy compensation is confirmed, although their behaviour is less accurately reproduced.
La investigación fue realizada con el objetivo de caracterizar la expresión de la inteligencia emocional (en lo sucesivo IE) en preadolescentes con bajo rendimiento académico, de la escuela “4 de ...Abril”, de la provincia de Huambo, Angola. Se asumió un paradigma mixto, predominantemente cuantitativo, con un diseño no experimental, transversal y un tipo de estudio exploratorio. Se efectuó un muestreo no probabilístico, se seleccionó una muestra de 60 preadolescentes, 30 con bajo rendimiento (en lo sucesivo GE) y 30 con rendimiento medio (en lo sucesivo GC). Para la recogida de los datos se aplicó el Trait Meta-Mood Scale, Informe escolar, conflicto de diálogo y composición. La Inteligencia Emocional mostró resultados diferentes en ambos grupos de preadolescentes, en términos de percepción, comprensión y facilitación, siendo mejores en el grupo de desempeño académico medio. Se reveló que las mayores dificultades fueron apreciadas en la regulación emocional.
Solid solutions Mg
0.1Al
1.8Ti
1.1O
5 and Mg
0.5AlTi
1.5O
5 were obtained by reaction sintering of mixtures of the binary oxides at 1350–1600 °C using different precursor powders. For the composition ...Mg
0.1Al
1.8Ti
1.1O
5, ceramics sintered at 1400–1500 °C have high relative density (⩾90%), reduced grain size (2–6 μm), low thermal expansion (−0.8 to 0.3×10
−6 K
−1 in the range 200–1000 °C) and reproducible expansion behaviour. At higher temperature, grain size rapidly increases owing to anisotropic and exaggerated grain growth (EGG) resulting in severe microcracking. Microstructure evolution is affected by the nature of the starting oxides, in particular for what concerns the onset temperature of EGG, the size and the fraction of abnormal grains. For the composition Mg
0.5AlTi
1.5O
5, EGG already takes place at 1350 °C and materials with grain size < 5 μm are difficult to obtain by conventional reaction sintering. Large grained samples (>10 μm) of both compositions show a reduced hysteresis and complex thermal expansion behaviour. In particular, heating to 1000 °C results in a significant increase in specimen size on return to room temperature. Repeated thermal cycling leads to an increase of the hysteresis.
The present work deals with \(e^+\)-\(e^-\) pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one in the context of a state-of-the-art approach to ...nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory (\(\chi\)EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross section for such a process. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The ab initio calculations use exact hyperspherical-harmonics methods to describe the bound state and low-energy spectrum of the \(A\,\)=\(\,4\) continuum, and fully account for initial state interaction effects in the \(3+1\) clusters. While electromagnetic interactions are treated to high orders in the chiral expansion, the interactions of the hypothetical boson with nucleons are modeled in leading-order \(\chi\)EFT (albeit, in some instances, selected subleading contributions are also accounted for). We also provide an overview of possible future experiments probing pair production in the \(A\,\)=\(\,4\) system at a number of candidate facilities.facilities.
The effect of a selected number of parameters of the Low-Temperature Aqueous Synthesis (LTAS) on BaTiO
3 particle size was investigated by the statistical design of experiment approach. Different ...syntheses were carried out changing the value of six physico-chemical parameters involved in the process, following the scheme of a 2
6-2 fractional factorial design. The characterisation of the submicron powders produced shows variations of the average size in the range 30–55 nm, deduced from specific surface area measurements. The statistical analysis of experimental results, performed by the ANOVA method, allows to ascribe such variations to the effect of solutions concentration, stirring energy and precursors mixing conditions. The significance of such parameters, together with the apparent ineffectiveness of the ageing time, is discussed. Also the XRD measurement of barium carbonate amount is presented and its dependence on experimental conditions is discussed.
The universal behavior of a three-boson system close to the unitary limit is encoded in a simple dependence of many observables in terms of few parameters. For example the product of the three-body ...parameter \(\kappa_*\) and the two-body scattering length \(a\), \(\kappa_* a\) depends on the angle \(\xi\) defined by \(E_3/E_2=\tan^2\xi\). A similar dependence is observed in the ratio \(a_{AD}/a\) with \(a_{AD}\) the boson-dimer scattering length. We use a two-parameter potential to determine this simple behavior and, as an application, to compute \(a_{AD}\) for the case of three \(^4\)He atoms.
The aim of this study was the assessment of the efficacy of recombinant human activated protein C (rhAPC) in septic patients.
A continuous observational prospective study on ICU patients with severe ...sepsis and septic shock was carried out. Applying the inclusion criteria of a national trial on the use of rhAPC, 15 patients (12 males and 3 females) were enrolled, mean age was 65.9 (SD 9.6), APACHE II score was > or =25. The following variables were assessed on 7 time-points (T1-T7): overall SOFA score; organ-specific SOFA score; APACHE II score; PCR, APTT, INR, fibrinogen, platelet count. Wilcoxon's statistical test and Spearman's correlation test (rho coefficient) between the SOFA and APACHE II scores were used. Test results with a P value below 0.05 were deemed significant.
A significant correlation was identified between the APACHE II and SOFA scores. No significant change was found in Friedman's test and the respiratory, haematological and hepatic SOFA score, whereas cardiovascular, renal and neurological SOFA scores showed a significant trend between the ranks at the 7 time-points (chi2=14; df=6; P=0.029). During rhAPC treatment Friedman's test showed significant changes of PCR values over the 7 time-points (chi2=19.2; df=6; P=0.02). Wilcoxon's test indicated a significant decrease in the values recorded during the T2-T6 period. On day 28, 12 of the 15 patients originally enrolled were still alive. Mortality rate was therefore 20% (CI 95%).
RhAPC is the first biological agent approved for the treatment of severe sepsis and septic shock. Our experience is confined to patients with severe sepsis and septic shock, and some severity indexes showed a modulation of the inflammatory processes and haemostatic balance, 2 factors which play a key role in the evolution of sepsis and organ dysfunction.
In this work we investigate 1+2 reactions within the framework of the hyperspherical adiabatic expansion method. With this aim two integral relations, derived from the Kohn variational principle, are ...used. A detailed derivation of these relations is shown. The expressions derived are general, not restricted to relative s partial waves, and with applicability in multichannel reactions. The convergence of the K matrix in terms of the adiabatic potentials is investigated. Together with a simple model case used as a test for the method, we show results for the collision of a {sup 4}He atom on a {sup 4}He{sub 2} dimer (only the elastic channel open), and for collisions involving a {sup 6}Li and two {sup 4}He atoms (two channels open).
A case of cryptococcal meningoencephalitis, as presented by a hypertensive hydrocephalus, is described. To our knowledge, this is the 24th case described in Italy since 1953. The diagnosis was made ...with ventricular fluid examination: the patient was successfully treated with amphotericin B and 5-fluorocytosine, thus avoiding the risks of surgical treatment of hydrocephalus. Early diagnosis and proper therapy are necessary in order to decrease the high lethality of cryptococcosis.
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