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Abstract We report on the tunable and enhanced dielectric properties of tungsten (W) incorporated gallium oxide (Ga2O3) polycrystalline electroceramics for energy and power electronic device applications. The W‐incorporated Ga2O3(Ga2−2xWxO3, 0.00 ≤ x ≤ 0.20; GWO) compounds were synthesized by the high‐temperature solid‐state chemical reaction method by varying the W‐content. The fundamental aspects of the dielectric properties in correlation with the crystal structure, phase, and microstructure of the GWO polycrystalline compounds has been investigated in detail. A detailed study performed ascertains the W‐induced changes in the dielectric constant, loss tangent (tanδ) and ac conductivity. It was found that the dielectric constant increases with addition of W in the system as a function of temperature (25°C‐500°C). Frequency dependence (102‐106 Hz) of the dielectric constant follows the modified Debye model with a relaxation time of ∼20 to 90 μs and a spreading factor of 0.39 to 0.65. The dielectric constant of GWO is temperature independent almost until ∼300°C, and then increases rapidly in the range of 300°C to 500°C. W‐induced enhancement in the dielectric constant of GWO is fully evident in the frequency and temperature dependent dielectric studies. The frequency and temperature dependent tanδreveals the typical behavior of relaxation loses in GWO. Small polaron hopping mechanism is evident in the frequency dependent electrical transport properties of GWO. The remarkable effect of W‐incorporation on the dielectric and electrical transport properties of Ga2O3is explained by a two‐layer heterogeneous model consisting of thick grains separated by very thin grain boundaries along with the formation of a Ga2O3‐WO3composite was able to account for the observed temperature and frequency dependent electrical properties in GWO. The results demonstrate that the structure, electrical and dielectric properties can be tailored by tuning W‐content in the GWO compounds.
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Comparison of spectrophotometric and electrochemical pH measurements for calculating freshwater pCO2
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Abstract Freshwater snails of the genusBiomphalariaserve as intermediate hosts for the digenetic trematodeSchistosoma mansoni, the etiological agent for the most widespread form of intestinal schistosomiasis. As neuropeptide signaling in host snails can be altered by trematode infection, a neural transcriptomics approach was undertaken to identify peptide precursors inBiomphalaria glabrata, the major intermediate host forS.mansoniin the Western Hemisphere. Three transcripts that encode peptides belonging to the FMRF‐NH2‐related peptide (FaRP) family were identified inB.glabrata. One transcript encoded a precursor polypeptide (Bgl‐FaRP1; 292 amino acids) that included eight copies of the tetrapeptide FMRF‐NH2and single copies of FIRF‐NH2, FLRF‐NH2, and pQFYRI‐NH2. The second transcript encoded a precursor (Bgl‐FaRP2;347amino acids) that comprised 14 copies of the heptapeptide GDPFLRF‐NH2and 1 copy of SKPYMRF‐NH2. The precursor encoded by the third transcript (Bgl‐FaRP3; 287 amino acids) recapitulatedBgl‐FaRP2but lacked the full SKPYMRF‐NH2peptide. The three precursors shared a common signal peptide, suggesting a genomic organization described previously in gastropods. Immunohistochemical studies were performed on the nervous systems ofB.glabrataandB.alexandrina, a major intermediate host forS.mansoniin Egypt. FMRF‐NH2‐like immunoreactive (FMRF‐NH2‐li) neurons were located in regions of the central nervous system associated with reproduction, feeding, and cardiorespiration. Antisera raised against non‐FMRF‐NH2peptides present in the tetrapeptide and heptapeptide precursors labeled independent subsets of the FMRF‐NH2‐li neurons. This study supports the participation of FMRF‐NH2‐related neuropeptides in the regulation of vital physiological and behavioral systems that are altered by parasitism inBiomphalaria.more » « less
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Accepted Manuscript1.0
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- https://doi.org/10.1002/lom3.10501
