Search

FexCu100-x metastable alloys were prepared by pulsed electrodeposition for 550) are reminiscent of those observed in Fe–Cu alloys prepared by other methods. The Curie temperature decreases regularly with decreasing x. In the Fe-poor alloys (x≤30), the observed properties indicate that Fe-rich clusters form within a Cu-rich matrix. In the x=10 alloy, the Fe clusters are found to be superparamagnetic at room temperature, but a superferromagnetic order develops below a critical temperature of about 120 K. It is suggested that the intercluster coupling is mediated by Ruderman–Kittel–Kasuya–Yosida interactions which are predominantly positive due to the very short intercluster distances. [ABSTRACT FROM AUTHOR]

Even though the impact of COVID-19 in metropolitan areas has been extensively studied, the geographic spread to smaller cities is also of great concern. We conducted an ecological study aimed at identifying predictors of early introduction, incidence rates of COVID-19 and mortality (up to 8 May 2020) among 604 municipalities in inner São Paulo State, Brazil. Socio-demographic indexes, road distance to the state capital and a classification of regional relevance were included in predictive models for time to COVID-19 introduction (Cox regression), incidence and mortality rates (zero-inflated binomial negative regression). In multivariable analyses, greater demographic density and higher classification of regional relevance were associated with both early introduction and increased rates of COVID-19 incidence and mortality. Other predictive factors varied, but distance from the State Capital (São Paulo City) was negatively associated with time-to-introduction and with incidence rates of COVID-19. Our results reinforce the hypothesis of two patterns of geographical spread of SARS-Cov-2 infection: one that is spatial (from the metropolitan area into the inner state) and another which is hierarchical (from urban centres of regional relevance to smaller and less connected municipalities). Those findings may apply to other settings, especially in developing and highly heterogeneous countries, and point to a potential benefit from strengthening non-pharmaceutical control strategies in areas of greater risk. [ABSTRACT FROM AUTHOR]

Deals with a study which used the Rutherford backscattering technique to determine the range parameters of Bi ions implanted into AZ111 photoresist film at energies from ten to 400 keV. Experimental procedure and data analysis; Results and discussion; Conclusions.

Zooarchaeological collections from shell mounds in Rio de Janeiro (2,470-4,632 cal BP) contain a high prevalence of swollen fish bones belonging to the Atlantic spadefish ( Chaetodipterus faber), crevalle jack ( Caranx hippos) and fat snook ( Centropomus parallelus). Given the lack of knowledge of the bone degenerative process in senile fishes, this study analysed hyperostotic bone in zooarchaeological and modern specimens to obtain high-resolution morphology and microstructure reconstruction. We used micro CT as well as X-ray diffraction to characterize the crystallographic changes associated with fish senility. Our results showed that trabecular microstructures in hyperostotic bones were consistent with estimated values of the per cent bone volume-to-total volume ratio ( BV/ TV) and were greater than 60% in cortical bone. Hyperostotic bones indicated a high radiograph density, and X-ray diffractograms showed a decrease in hydroxyapatite [Ca10( PO4)6( OH)2] and calcite (Ca CO3) neocrystallization. These crystalline and density changes revealed an advanced stage of fish senile and indicate the vulnerability of ageing fish populations. [ABSTRACT FROM AUTHOR]

Biodiversity is commonly referred to as species diversity but in forest ecosystems variability in structural and functional characteristics can also be treated as measures of biodiversity. Small unmanned aerial vehicles (UAVs) provide a means for characterizing forest ecosystem with high spatial resolution, permitting measuring physical characteristics of a forest ecosystem from a viewpoint of biodiversity. The objective of this study is to examine the applicability of photogrammetric point clouds and hyperspectral imaging acquired with a small UAV helicopter in mapping biodiversity indicators, such as structural complexity as well as the amount of deciduous and dead trees at plot level in southern boreal forests. Standard deviation of tree heights within a sample plot, used as a proxy for structural complexity, was the most accurately derived biodiversity indicator resulting in a mean error of 0.5 m, with a standard deviation of 0.9 m. The volume predictions for deciduous and dead trees were underestimated by 32.4 m3/ha and 1.7 m3/ha, respectively, with standard deviation of 50.2 m3/ha for deciduous and 3.2 m3/ha for dead trees. The spectral features describing brightness (i.e. higher reflectance values) were prevailing in feature selection but several wavelengths were represented. Thus, it can be concluded that structural complexity can be predicted reliably but at the same time can be expected to be underestimated with photogrammetric point clouds obtained with a small UAV. Additionally, plot-level volume of dead trees can be predicted with small mean error whereas identifying deciduous species was more challenging at plot level. [ABSTRACT FROM AUTHOR]

Presents information on a study that compared the profiles of bismuth, xenon, tin, krypton, gallium, iron, potassium, argon, phosphorus, sodium and fluorine implanted into the AZ111 photoresist with theoretical predictions. Experimental procedure; Results and discussion.

Presents information on a study which determined the depth distribution of ion-implanted [sup10]boron in AZ111 photoresist in the 30-150 kiloelectrovolts energy range. Aspects of ion-implanted and irradiated polymers; Experimental procedure; Results and discussion; Conclusions.

Nanostrucured europium oxide and hydroxide films were obtained by pulsed Nd:YAG (532 nm) laser ablation of a europium metallic target, in the presence of a 1 mbar helium buffer atmosphere. Both the produced film and the ambient plasma were characterized. The plasma was monitored by an electrostatic probe, for plume expansion in vacuum or in the presence of the buffer atmosphere. The time evolution of the ion saturation current was obtained for several probe to substrate distances. The results show the splitting of the plume into two velocity groups, being the lower velocity profile associated with metal cluster formation within the plume. The films were obtained in the presence of helium atmosphere, for several target-to-substrate distances. They were analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and atomic force microscopy, for as-deposited and 600 °C treated-in-air samples. The results show that the as-deposited samples are amorphous and have chemical composition compatible with europium hydroxide. The thermally treated samples show x-ray diffraction peaks of Eu2O3, with chemical composition showing excess oxygen. Film nanostructuring was shown to be strongly correlated with cluster formation, as shown by velocity splitting in probe current versus time plots. [ABSTRACT FROM AUTHOR]

The phenomenon of frequency upconversion (UC) is observed in Er3+:Yb3+:SrAl2O4 powders prepared by combustion synthesis. Strong UC emission at the green (bands peaked at 521, 538, 547, and 562 nm) and weak UC emission at the red (bands peaked at 659 and 682 nm) corresponding to 4f–4f transitions of Er3+ were observed when the samples were irradiated with near-infrared laser excitation at ∼980 nm. Saturation of UC emission is observed for concentrations of 1.5 wt.% of Er3+ and 1.5 wt.% of Yb3+. The green-to-red intensity ratio, on the other hand, increases linearly with Er3+ concentration (Er3+ concentration varying from 0.5 to 1.5 wt.%) while keeping Yb3+ concentration fixed (at 1.5 wt.%). The green UC decay time was measured and Er3+–Er3+ interaction was suggested as a possible mechanism to explain the luminescence quenching effect observed. [ABSTRACT FROM AUTHOR]

The phenomenon of frequency upconversion (UC) is observed in Er3+:Yb3+:SrAl2O4 powders prepared by combustion synthesis. Strong UC emission at the green (bands peaked at 521, 538, 547, and 562 nm) and weak UC emission at the red (bands peaked at 659 and 682 nm) corresponding to 4f–4f transitions of Er3+ were observed when the samples were irradiated with near-infrared laser excitation at ∼980 nm. Saturation of UC emission is observed for concentrations of 1.5 wt.% of Er3+ and 1.5 wt.% of Yb3+. The green-to-red intensity ratio, on the other hand, increases linearly with Er3+ concentration (Er3+ concentration varying from 0.5 to 1.5 wt.%) while keeping Yb3+ concentration fixed (at 1.5 wt.%). The green UC decay time was measured and Er3+–Er3+ interaction was suggested as a possible mechanism to explain the luminescence quenching effect observed. [ABSTRACT FROM AUTHOR]

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 °C had a predominance of vernier orthorhombic Y6O5F8 phase, while samples heat treated at 800 °C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu3+) in different concentrations (1-15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu3+:Y6O5F8 samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu3+:YOF samples. [ABSTRACT FROM AUTHOR]