Co-precipitation synthesis of Nd:YAG nano-powders: the effect of Nd dopant addition with thermal treatment

Nanopowders of Yttrium Aluminium Garnet doped with neodymium ions were obtained by the co-precipitation method from the reaction of aluminium, yttrium and neodymium nitrate with ammonia. The amount of neodymium was selected in order to produce samples of nominal stoichiometry Nd_XY_(3–X)Al₅O₁₂ (where X = 0.006, 0.012, 0.024, 0.048, 0.081, 0.096, 0.17, 0.19, 0.38, 0.54, and 0.72, respectively). After washing and drying, the hydroxide precursors were subjected to Thermo-Gravimetry and Differential Thermal Analysis experiments from room temperature up to 1500 °C, which showed the presence of exothermal events accompanying phase transformation phenomena. X-ray diffraction investigations conducted with a high-resolution powder diffractometer on the specimens arrested at selected temperature of the thermograms, evidenced the amorphous-to-crystalline transformation phenomena leading to the garnet phase as the main product. On increasing the concentration of Nd, the presence of the monoclinic Y₄Al₂O₉ phase was also detected together with a variable amount of a metastable hexagonal YAlO₃ phase. Precise determination of the cubic garnet lattice parameters as a function of the neodymium content according to the Rietveld method shows a change from the value of 12.016 (±2) Å when X = 0 up to 12.128 (±2) Å for X = 0.720 with two distinctive regimes of increase. The line broadening analysis of X-ray profiles after correction for instrumental factors indicates that the average crystallite size is in the range 50–80 nm. Field-Emission Gun-Scanning Electron Microscopy observations showed the presence of aggregation features in the powders with a rounded morphology and a relatively uniform and narrow particle size distribution, with the average size figures in substantial agreement with the diffraction analyses.     

Applicability of diffusive gradients in thin films for measuring Mn in soils and freshwater sediments

Manganese (Mn) is an essential plant nutrient, receiving increased attention due to significant deficiency problems in modern crop production. In aquatic sediments, Mn plays an important role in controlling the mobility of other elements due to its high redox sensitivity. Diffusive gradients in thin films (DGT) is recognized as one of the most promising techniques to assess plant availability of nutrients in soils and mobility in sediments. However, the appropriate conditions where DGT can be used to measure Mn in soils and sediments have not been thoroughly investigated. We deployed DGTs in soil, sediment, and solution to investigate the effect of pH and competition from Ca and Fe ions. We found that by using DGT it is possible to accurately measure Mn in soils at pH levels and Ca and Fe concentrations resembling those of normal and fertile agricultural soils. However, in acid soils at pH below 5.5, Mn measurements might be biased due to potential competition effects caused by Ca. Soil deployments showed that changes in soil redox conditions were closely reflected by the DGT based Mn measurements. This might enable a novel approach of using DGT to predict Mn mobility and plant availability in soils. In reducing aquatic sediments, high concentrations of ferrous ions can displace Mn from the resin-gel of the DGT device. We found this to be a significant problem with longer deployment times.     

Oscillations of heart rate and respiration synchronize during affective visual stimulation

The objective of this study is to investigate the synchronization between breathing patterns and heart rate during emotional visual elicitation, that is, using sets of images gathered from the international affective picture system having five levels of arousal and five levels of valence, including a neutral reference level. Thirty-five healthy volunteers were emotionally elicited in agreement with a bidimensional spatial localization of affective states, i.e., arousal/valence plane, while two peripheral physiological signals, ECG and Respiration activity, were acquired simultaneously. The synchronization was then quantified by applying the concept of phase synchronization of chaotic oscillators, i.e., the cardio-respiratory synchrogram. This technique allowed us to estimate the synchronization ratio m:n as the attendance of n heartbeats in each m respiratory cycle, even for noisy and nonstationary data. We found a stronger evidence of cardiorespiratory synchronization during arousal than during neutral states.     

Stable isotope techniques for assessing labile Cu in soils: development of an L-value procedure, its application, and reconciliation with E values

Isotopic techniques have become a valuable tool for assessing the lability or potential availability of elements in soil. Until now, work on soil Cu has been limited to E-value methods where soil solution extracts are obtained by physical means due to the very short (12.4 h) half-life of the radio isotope 64Cu. However, a stable isotope method has recently been developed for determining soil Cu E values that utilizes enhancement of the 65Cu isotope in soil and measurement of the subsequent ratio with 63Cu. We have developed an L-value technique for soil Cu, where plants are used to sample the soil solution and therefore give a direct measure of the plant available Cu. The L-value technique developed was then compared, and found to be equivalent, with E values using equilibration periods up to and including the growth period of plants in the L-value method.     

Dynamic Characteristics of a Curved Cable-stayed Bridge:Operational Modal Testing and FE Modeling

This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequen...     

Antimicrobial residues in animal waste and water resources proximal to large-scale swine and poultry feeding operations

Serum selenium (Se) levels and glutathione peroxidase (GSH-Px) activity in erythrocytes have been determined for a healthy Lower Silesian population. The results have been analysed in relation to smoking and alcohol consumption habits. The mean concentration of serum Se for the group is within the lower range and appears to be significantly lower in the group of smokers that was studied (smoking over 20 cigarettes/day, mean concentration value = 50.8 microg/l), compared to non-smokers (mean value = 78.8 microg/l). For men that smoke, the concentration is lower than that found for smoking women, however, the difference is without statistical significance. Regarding GSH-Px activity, no difference between the smoking and non-smoking groups has been found (mean values = 19.84 and 20.92 U/gHb, respectively). From the group of people examined, we have selected those who drink an equivalent of 50 g or more of pure ethanol per week. For this group the serum Se level has been found to be lower compared to the group that does not consume that much alcohol. However, the difference is without statistical significance. We have found no correlation between age and the parameters studied (serum Se concentration and GSH-Px activity).