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•Hydrothermal treatment of Coal fly produce cancrinite and analcime zeolite.•Cancrinite zeolite exhibits ferrimagnetic signature.•Adsorption of blue methylene is described by ...Freundlich and Langmuir models.
Coal fly ash (CFA) was obtained from the Sochagota TermoPaipa IV power plant in Boyacá Colombia. CFA was subjected to a hydrothermal activation with NaOH. Morphology, elemental and mineralogical composition and magnetic properties of the obtained products were studied by means of SEM-EDX, XRD and VSM.
Activation with NaOH (4–5 M) between 80 and 150 °C for 24 h produced cancrinite zeolite; activation with NaOH at 2 and 3 M at 95 °C produced analcime zeolite. It was found out, that the synthesized zeolites exhibit a ferrimagnetic behavior due to iron coming from CFA. The magnetic response of the obtained products allows the use of these materials to environmental applications in aqueous medium. Adsorption test for methylene blue was performed for an analcime and cancrinite zeolite, the results show that equilibrium is reached after 60 min. The data of adsorption isotherms for analcime and cancrinite zeolite were fitted to Freundlich and Langmuir model, respectively. The synthesized zeolites from CFA were successfully used to remove methylene blue from aqueous solution.
Study of fly ash based zeolite by using slow positrons Supelano, G.I.; Palacio, C.A.; Weber, M. ...
Materials science & engineering. B, Solid-state materials for advanced technology,
January 2021, 2021-01-00, 20210101, Letnik:
263
Journal Article
Recenzirano
•Zeolites like materials were synthesized from fly ash by hydrothermal method.•Positron annihilation measurements show that increasing of NaOH increases porosity.•The increasing of synthesis ...temperature diminishes porosity.
After coal fly ash activation with alkaline NaOH solution by the hydrothermal method, it was possible to synthesize the zeolites type Cancrinite and Analcime. Slow positron beam experiments have been performed on two set of samples. One in which the NaOH concentration was varied and another one in which the synthesis temperature range was varied. The mineralogical composition was determined by X ray diffraction, the morphology of one of the zeolite samples as compared with the coal fly ash was observed by 3D X-ray imaging. Positron results suggest that increasing the NaOH concentration produces an increase in open volume and/or defects while increasing the temperature in the sample preparation diminishes it.
•Phlebotomine sand fly species of medical importance persist in the peridomestic environment of rural Mayan communities of Yucatan.•The rural scape heterogeneity around the dwellings increases the ...diversity and abundance of anthropophilic sand fly species.•Our results suggest that the change in land use in the peridomicile of human dwellings could increase the entomological risk in rural Mayan communities of Yucatan.
In the Yucatan Peninsula, tropical preserved forests harbor a high diversity of phlebotomine sand fly species, potential vectors of Leishmania. As a result, a significant risk of contracting localized cutaneous leishmaniasis (LCL) is associated with entry into these forest ecosystems. However, with the current trajectory of land use in the region, communities now live within modified landscapes which could increase their risk of contact with vectors. In this study, we characterized the sand fly fauna and its relationship with the characteristics of peridomestic habitats in two rural communities in Yucatan characterized by contrasting records of leishmaniasis. Five human dwellings in each community were randomly selected and the peridomestic landscape was characterized (i.e., type and percentage of land use). For the collection of sand flies, CDC traps were deployed in both the intra and peridomicile. Differences in alpha and beta diversity between communities and ecotopes were estimated considering three separate groups, all species together, zoophilic species, and anthropophilic species. In total, 1, 241 sand flies represented by eight species were collected from November 2021-March 2022. Both communities registered the presence of sand flies in the intra and peridomicile, and females were more abundant than males. However, the greatest diversity of species was recorded in the peridomicile of the community with the highest composition of land uses. Our study demonstrates that the transformation of the forest around the communities favors the abundance and richness of sand flies in the peridomestic environment. We discuss the limitations and implications of our findings regarding the potential risk of the emergence of peri‑rural cycles of leishmaniasis in the region.
•We documented the highest infective rate by Leishmania in anthropophilic sand flies so far reported in Mexico.•Based on the biting rate and the infective biting rate of Phlebotomine sandflies, the ...potential increase in entomological and epidemiological exposure to L. (L.) mexicana continues to be associated primarily with conserved forests.•Our study also detected that, albeit to a lesser extent, human exposure to Leishmania is occurring in environments with intermediate and high disturbance.•Change in land use did not influence the pattern of nocturnal exposition to anthropophilic Phlebotomine sand fly.•Although temperature and humidity vary between sites with different land uses, these variables are not related to the biting rate or the infective biting rate of Phlebotomine sand flies.
Could tropical forest conversion shape sand fly (Diptera: Phlebotominae) biting rhythms and Leishmania infection rates? Using a Shannon trap, we estimated the bite rate and infection prevalence among anthropophilic sand flies at sites with different land use in southern Mexico. We estimated the expected monthly infection rate of the Leishmania parasite along the gradient and generated information on the biting rhythm of sand flies in a poorly characterized cutaneous leishmaniasis endemic region. We used generalized mixed linear and mixed additives models to evaluate differences in the biting rate, nocturnal activity, and inoculation rate of female sand flies, as well as their relationship with the loss of forest cover and environmental disparities recorded throughout the study area. Our results show that the loss of forest cover influences the biting rhythm of sand fly species and the potential number of infectious bites with Leishmania, but the greatest entomological and potential epidemiological risk continues to be associated with sylvatic areas (amplification events). Despite this, we detected that the effect of forest cover (%) on the entomological exposure seems to be also dependent on the sand fly species, and that, albeit to a lesser extent, Leishmania parasite is circulating in disturbed landscapes through generalist and competent sand fly vector species. We also found that land use change did not affect the nocturnal activity, however we detected that important vector species were active most of the time. Contrary to our expectation, temperature and humidity did not shape the biting rhythm of sand fly species. We discuss the limitations and epidemiological implications of our findings regarding the risk of contracting leishmaniasis in southern Mexico.
We report on a search for nuclear recoil signals from solar B-8 neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 to 1.6 keV. We develop a ...variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant B-8 neutrinolike excess is found in an exposure of 0.6 t x y. For the first time, we use the nondetection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as nonstandard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 and 11 GeV c(-2) by as much as an order of magnitude.
In this paper, the formation and transformation of Magnéli phases (Ti
n
O
2n-1
) during manufacturing of flame-sprayed coatings from two powders consisting of anatase nanoparticles and submicrometric ...particles with Magnéli phases is analyzed, respectively. These powders were thermally sprayed on a ceramic substrate through oxidizing and neutral flame. Crystalline phases in powders and coatings were identified by x-ray diffraction and quantified by the Rietveld method, verifying the presence of identified crystalline phases in coatings by x-ray photoelectron spectroscopy. Finally, the electrical conductance of coatings was measured by the four-point probe method. Results indicate that Magnéli phases are produced from anatase nanoparticles sprayed using both the oxidizing and neutral flames, and when the neutral flame and finest particles are used, a high quantity of Ti
4
O
7
and Ti
5
O
9
, recognized thanks to their high electrical conductivity, is obtained. In contrast, when the coatings were fabricated from the powder containing Magnéli phases, they were oxidized as much in oxidizing as in neutral flame, producing a partial transformation from Ti
4
O
7
and Ti
5
O
9
to both the rutile phase and TiO in low quantity. In spite of this partial transformation, the coatings maintain high electrical conductivity thanks to Ti
4
O
7
and Ti
5
O
9
Magnéli phases remaining and the TiO produced.
Some previously described environmental associations for atopic eczema may be due to reverse causation. We explored the role of reverse causation by comparing individual- and school-level results for ...multiple atopic eczema risk factors. The International Study of Asthma and Allergies in Childhood (i.e, ISAAC) Phase Three surveyed children in schools (the sampling unit) regarding atopic eczema symptoms and potential risk factors. We assessed the effect of these risk factors on atopic eczema symptoms using mixed-effect logistic regression models, first with individual-level exposure data and second with school-level exposure prevalence. Overall, 546,348 children from 53 countries were included. At ages 6–7 years, the strongest individual-level associations were with current paracetamol use (odds ratio OR = 1.45, 95% confidence interval CI = 1.37–1.54), which persisted at school-level (OR = 1.55, 95% CI = 1.10–2.21), early-life antibiotics (OR = 1.41, 95% CI = 1.34–1.48), and early-life paracetamol use (OR = 1.28, 95% CI = 1.21–1.36), with the former persisting at the school level, whereas the latter was no longer observed (OR = 1.35, 95% CI = 1.00–1.82 and OR = 0.94, 95% CI = 0.69–1.28, respectively). At ages 13–14 years, the strongest associations at the individual level were with current paracetamol use (OR = 1.57, 95% CI = 1.51–1.63) and open-fire cooking (OR = 1.46, 95% CI = 1.33–1.62); both were stronger at the school level (OR = 2.57, 95% CI = 1.84–3.59 and OR = 2.38, 95% CI = 1.52–3.73, respectively). Association with exposure to heavy traffic (OR = 1.31, 95% CI = 1.27–1.36) also persisted at the school level (OR = 1.40, 95% CI = 1.07–1.82). Most individual- and school-level effects were consistent, tending to exclude reverse causation.
The production and the structural and magnetic characterization of the Bi1-xYxFeO3 (x= 0, 0.25 and 0.3) system is reported in this work. The system was produced through the solid-state reaction ...technique. The morphological characterization obtained by scanning electron microscopy technique evidences the granular behavior. The structural properties were studied by means of X-ray diffraction technique. Magnetization measurements in function of temperature of the Bi1-xYxFeO3 (x= 0, 0.25 and 0.3) system were performed with the magnetometer VSM by means of the Zero Field Cooled-Field Cooled method. The results obtained from all the techniques evidence the effect of yttrium on the physical properties of BiFeO3.
This paper reports the production of YBa
2
Cu
3
-
x
Fe
x
O
7
-
δ
(0.05
≤
x
≤
0.12) superconducting system by using the standard solid-state reaction technique. A Rietveld refinement of the ...experimental X-ray diffraction patterns allows the determination of the lattice parameters and the phase composition of the studied system; the mean present phase shown is an orthorhombic phase Pmmm. Magnetic and transport properties are typical for superconducting samples. In this paper, magnetic susceptibility fluctuations are studied in the limit of weak magnetic fields. For each of the samples, the best fit of the experimental data of
Δ
χ
/T, in the limit of weak magnetic fields in function of the reduced temperature, allowed us to obtain the values of
A
s
(diamagnetism of Schmidt) and
B
LD
(LD parameter). The Lawrence–Doniach model (LD) has been used for the fluctuation analysis. It is demonstrated, by means of the analysis of the thermal fluctuations, that the YBa
2
Cu
3
-
x
Fe
x
O
7
-
δ
system has an excellent 2D scaling behavior (BLD).
Background
Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC) measured the global prevalence of symptoms of asthma in children. We undertook comprehensive analyses ...addressing risk factors for asthma symptoms in combination, at both the individual and the school level, to explore the potential role of reverse causation due to selective avoidance or confounding by indication.
Objective
To explore the role of reverse causation in risk factors of asthma symptoms.
Methods
We compared two sets of multilevel logistic regression analyses, using (a) individual level exposure data and (b) school level average exposure (ie prevalence), in two different age groups. In individual level analyses, reverse causation is a possible concern if individual level exposure statuses were changed as a result of asthma symptoms or diagnosis. School level analyses may suffer from ecologic confounding, but reverse causation is less of a concern because individual changes in exposure status as a result of asthma symptoms would only have a small effect on overall school exposure levels.
Results
There were 131 924 children aged 6‐7 years (2428 schools, 25 countries) with complete exposure, outcome and confounder data. The strongest associations in individual level analyses (fully adjusted) were for current paracetamol use (odds ratio = 2.06; 95% confidence interval 1.97‐2.16), early life antibiotic use (1.65; 1.58‐1.73) and open fire cooking (1.44; 1.26‐1.65). In school level analyses, these risk factors again showed increased risks.
There were 238 586 adolescents aged 13‐14 years (2072 schools, 42 countries) with complete exposure, outcome and confounder data. The strongest associations in individual level analyses (fully adjusted) were for current paracetamol use (1.80; 1.75‐1.86), cooking on an open fire (1.32; 1.22‐1.43) and maternal tobacco use (1.23; 1.18‐1.27). In school level analyses, these risk factors again showed increased risks.
Conclusions & clinical relevance
These analyses strengthen the potentially causal interpretation of previously reported individual level findings, by providing evidence against reverse causation.
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