Vaporization of LaCrO3: Partial and Integral Thermodynamic Properties

The vaporization of LaCrO₃(s) and samples of the composition LaCrO₃+ La₂O₃ was investigated in the temperature range of 1887-2333 K by Knudsen effusion mass spectrometry using Knudsen cells made of tungsten lined completely with iridium. The species Cr(g), CrO(g ), CrO₂(g), and LaO(g) were identified in the vapor. Their partial pressures were determined by calibration with pure platinum solid. The thermodynamic activity of Cr₂O₃, a _cr2o₃ in LaCrO₃ for the Cr₂0₃-poor phase boundary of this phase was In a_Cr2o₃⁼ -(17953/T) - 0.485 (temperature T given in K) for the temperature range of the measurements with a probable overall error of ± 13%. The following values and temperature dependence of ΔG°_f,T resulted for the formation of LaCrO₃(s) according to the reaction 0.5Cr₂O₃(s) + 0.5La₂O₃(s) → LaCrO₃(s): ΔG°_f,2100= -78.9 ± 1.1 kj/mol, Δ H°_f,298= -76.8 ± 5.2 kj/mol, and ΔG°_r(kJ/mol) = -74.7 - 0.00202 T . Computations for the vaporization of LaCrO₃ were conducted to show the volatility of this material in different atmospheres at high temperatures.     

Learning continuous trajectories in recurrent neural networks withtime-dependent weights

The paper is concerned with a general learning (with arbitrary criterion and state-dependent constraints) of continuous trajectories by means of recurrent neural networks with time-varying weights. The learning process is transformed into an optimal control framework, where the weights to be found are treated as controls. A learning algorithm based on a variational formulation of Pontryagin's maximum principle is proposed. This algorithm is shown to converge, under reasonable conditions, to an optimal solution. The neural networks with time-dependent weights make it possible to efficiently find an admissible solution (i.e., initial weights satisfying state constraints) which then serves as an initial guess to carry out a proper minimization of a given criterion. The proposed methodology may be directly applicable to both classification of temporal sequences and to optimal tracking of nonlinear dynamic systems. Numerical examples are also given which demonstrate the efficiency of the approach presented.     

Mechanochemical synthesis,crystal structure and ion conduction in the Gd<Subscript>2</Subscript>Hf<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Ti<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>7</Subscript> system

This work describes the mechanochemical synthesis, structural characterization and electrical properties of an interesting group of novel ionic conductors, with general formula Gd₂(Hf_2?x Ti _x )₂O₇. Different compositions in this system (x = 0, 0.4, 0.8, 1.2, 1.6 and 2) were obtained at room temperature, via a mechanochemical reaction between the corresponding elemental oxides, and characterized by using XRD, Raman spectroscopy and SEM. The XRD structural analysis by the Rietveld method revealed that all the Hf-containing compositions show a disordered fluorite-like structure instead of the expected pyrochlore-like atomic ordering, and the cation size mismatch criteria for pyrochlore stability. Increasing Ti content promotes a phase transformation to the pyrochlore structure with post-milling thermal treatments, which takes place in all samples on annealing at 1200 °C, except for Gd₂Hf₂O₇. These results were confirmed by Raman spectroscopy, which also suggests that the x = 0.4 sample has the highest degree of oxygen disorder in the system and that this disorder decreases with increasing Ti⁴⁺ content. Finally, all samples show the pyrochlore structure on firing at 1500 °C. Activation energies E _dc for oxygen migration were determined by using impedance spectroscopy and found to be within the ~0.9–1.2 eV range, whereas conductivity σ _dc values at 700 °C vary from 1.12 × 10^?6 to 2.75 × 10^?4 S cm^?1, with decreasing conductivity as Ti⁴⁺ content increases.     

Photofunctions in Hybrid Systems of Schiff Base Metal Complexes and Metal or Semiconductor (Nano)Materials

Composite materials very often provide new catalytic, optical or other physicochemical properties not observed for each component separately. Photofunctions in hybrid systems are an interesting topic of great importance for industry. This review presents the recent advances, trends and possible applications of photofunctions of hybrid systems composed of Schiff base metal complexes and metal or semiconductor (nano)materials. We focus on photocatalysis, sensitization in solar cells (DSSC—dye sensitized solar cell), ligand-induced chirality and applications in environmental protection for Cr(VI) to Cr(III) reduction, in cosmetology as sunscreens, in real-time visualization of cellular processes, in bio-labeling, and in light activated prodrug applications.     

Effect of Quercetin on mitoBKCa Channel and Mitochondrial Function in Human Bronchial Epithelial Cells Exposed to Particulate Matter

Particulate matter (PM) exposure increases reactive oxygen species (ROS) levels. It can lead to inflammatory responses and damage of the mitochondria thus inducing cell death. Recently, it has been shown that potassium channels (mitoK) located in the inner mitochondrial membrane are involved in cytoprotection, and one of the mechanisms involves ROS. To verify the cytoprotective role of mitoBK_Ca, we performed a series of experiments using a patch-clamp, transepithelial electrical resistance assessment (TEER), mitochondrial respiration measurements, fluorescence methods for the ROS level and mitochondrial membrane potential assessment, and cell viability measurements. In the human bronchial epithelial cell model (16HBE14σ), PM < 4 μm in diameter (SRM-PM4.0) was used. We observed that PM decreased TEER of HBE cell monolayers. The effect was partially abolished by quercetin, a mitoBK_Ca opener. Consequently, quercetin decreased the mitochondrial membrane potential and increased mitochondrial respiration. The reduction of PM-induced ROS level occurs both on cellular and mitochondrial level. Additionally, quercetin restores HBE cell viability after PM administration. The incubation of cells with PM substantially reduced the mitochondrial function. Isorhamnetin had no effect on TEER, the mitoBK_Ca activity, respiratory rate, or mitochondrial membrane potential. Obtained results indicate that PM has an adverse effect on HBE cells at the cellular and mitochondrial level. Quercetin is able to limit the deleterious effect of PM on barrier function of airway epithelial cells. We show that the effect in HBE cells involves mitoBK_Ca channel-activation. However, quercetin’s mechanism of action is not exclusively determined by modulation of the channel activity.     

Effect of spark timing and load on a DISI engine fuelled with 2,5-dimethylfuran

Currently, bioethanol leads the automotive fuel market as the main substitute for gasoline in spark-ignition engines. However, worldwide interest has been triggered in the potential of 2,5-dimethylfuran, known as DMF, since the discovery of improved production methods. Although the energy content of DMF is comparable to that of gasoline, little is known about its combustion characteristics and emissions. Therefore, this work examines the effect of DMF in a single cylinder direct-injection spark-ignition engine. The results are compared to ethanol and gasoline using the optimized spark timings for gasoline and the respective fuel. In summary, DMF produces competitive combustion and emissions qualities to gasoline, which, in some cases surpass ethanol. The two biofuels have a higher burning rate and lower initial combustion duration than gasoline. They also produce greater combustion efficiency, which helps to lower hydrocarbon and carbon monoxide emissions. These initial results highlight how DMF, which was originally only considered as an octane improver, has the potential to become a competitive renewable gasoline alternative.     

Data fusion for ballistic targets tracking using least squares

The paper deals with the problem of state estimation of continuous-time nonlinear system using discrete-time measurements from multiple sensors. In particular, the problem of multi-radar tracking of artillery ballistic objects is considered. A batch estimator based on the iterative least squares approach is developed using simplified and accurate models of ballistic flight. The estimator is applied to process the sequences of measurements from radars tracking the same ballistic target. Estimates of the target state over time are computed and their accuracy is compared to the estimates yielded by the extended Kalman filter. Partial estimates from multiple radars are combined using track fusion approach and propagated using the 3 degree of freedom model of ballistic flight. Accuracy of target's firing point estimation is also analysed with respect to the data rates and locations of the radars with respect to the target. Practical aspects of the proposed method are also discussed.     

An update on thoron exposure in Canada with simultaneous ²²²Rn and ²²⁰Rn measurements in Fredericton and Halifax

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ～8 % of the radiation dose due to indoor radon exposure in Canada.