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Morphology control and optical properties of ZnO nanostructures grown by ultrasonic synthesis
Morales-Flores, N.,Galeazzi, R.,Rosendo, E.,Diaz1d, T.,Velumani, S.,Pal, U. Techno-Press 2013 Advances in nano research Vol.1 No.1
ZnO nanostructures of rod-like, faceted bar, cup-end bars, and spindle shaped morphologies could be grown by a low power ultrasonic synthesis process. pH of the reaction mixture seems to plays an important role for defining the final morphology of ZnO nanostructures. While the solution pH as low as 7 produces long, uniform rod-like nanostructures of mixed phase (ZnO and $Zn(OH)_2$), higher pH of the reaction mixture produces ZnO nanostructures of different morphologies in pure hexagonal wurtzite phase. pH of the reaction as high as 10 produces bar shaped uniform nanostructures with lower specific surface area and lower surface and lattice defects, reducing the defect emissions of ZnO in the visible region of their photoluminescence spectra.
Diaz, Edgar A.,Chung, Yeonseung,Papapostolou, Vasileios,Lawrence, Joy,Long, Mark S.,Hatakeyama, Vivian,Gomes, Brenno,Calil, Yasser,Sato, Rodrigo,Koutrakis, Petros,Godleski, John J. Informa Healthcare 2012 Inhalation toxicology Vol.24 No.5
<P>The study presented here is a laboratory pilot study using diluted car exhaust from a single vehicle to assess differences in toxicological response between primary emissions and secondary products resulting from atmospheric photochemical reactions of gas phase compounds with O<SUB>3</SUB>, OH and other radicals. Sprague Dawley rats were exposed for 5 h to either filtered room air (sham) or one of two different atmospheres: (i) diluted car exhaust (P)+Mt. Saint Helens Ash (MSHA); (ii) P+MSHA+secondary organic aerosol (SOA, formed during simulated photochemical aging of diluted exhaust). Primary and secondary gases were removed using a nonselective diffusion denuder. Continuous respiratory data was collected during the exposure, and bronchoalveolar lavage (BAL) and complete blood counts (CBC) were performed 24 h after exposure. ANOVA models were used to assess the exposure effect and to compare those effects across different exposure types. Total average exposures were 363 ± 66 μg/m<SUP>3</SUP> P+MSHA and 212 ± 95 µg/m<SUP>3</SUP> P+MSHA+SOA. For both exposures, we observed decreases in breathing rate, tidal and minute volumes (TV, MV) and peak and median flows (PIF, PEF and EF50) along with increases in breathing cycle times (Ti, Te) compared to sham. These results indicate that the animals are changing their breathing pattern with these test atmospheres. Exposure to P+MSHA+SOA produced significant increases in total cells, macrophages and neutrophils in the BAL and <I>in vivo</I> chemiluminescence of the lung. There were no significant differences in CBC parameters. Our data suggest that simulated atmospheric photochemistry, producing SOA in the P+MSHA+SOA exposures, enhanced the toxicity of vehicular emissions.</P>
Invariant operators, orthogonal bases and correlators in general tensor models
Diaz, Pablo,Rey, Soo-Jong Elsevier 2018 Nuclear Physics, Section B Vol.932 No.-
<P><B>Abstract</B></P> <P>We study invariant operators in general tensor models. We show that representation theory provides an efficient framework to count and classify invariants in tensor models of (gauge) symmetry <SUB> G d </SUB> = U ( <SUB> N 1 </SUB> ) ⊗ ⋯ ⊗ U ( <SUB> N d </SUB> ) . As a continuation and completion of our earlier work, we present two natural ways of counting invariants, one for arbitrary <SUB> G d </SUB> and another valid for large rank of <SUB> G d </SUB> . We construct bases of invariant operators based on the counting, and compute correlators of their elements. The basis associated with finite rank of <SUB> G d </SUB> diagonalizes the two-point function of the free theory. It is analogous to the restricted Schur basis used in matrix models. We show that the constructions get almost identical as we swap the Littlewood–Richardson numbers in multi-matrix models with Kronecker coefficients in general tensor models. We explore the parallelism between matrix model and tensor model in depth from the perspective of representation theory and comment on several ideas for future investigation.</P>
Diaz-Pescador E.,Schäfer F.,Kliem S. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9
This paper provides an assessment of fluid transport and mixing processes inside the primary circuit of the test facility ROCOM through the numerical simulation of Test 2.1 with the system code ATHLET. The experiment represents an asymmetric injection of cold and non-borated water into the reactor coolant system (RCS) of a pressurized water reactor (PWR) to restore core cooling, an emergency procedure which may subsequently trigger a core re-criticality. The injection takes place at low velocity under single-phase subcooled conditions and presents a major challenge for the simulation in lumped parameter codes, due to multidimensional effects in horizontal piping and vessel arising from density gradients and gravity forces. Aiming at further validating ATHLET 3-D capabilities against horizontal geometries, the experiment conditions are applied to a ROCOM model, which includes a newly developed horizontal pipe object to enhance code prediction inside coolant loops. The obtained results show code strong simulation capabilities to represent multidimensional flows. Enhanced prediction is observed at the vessel inlet compared to traditional 1-D approach, whereas mixing overprediction from the descending denser plume is observed at the upper-half downcomer region, which leads to eventual deviations at the core inlet.
Solvent effect on the UV/Vis absorption and fluorescence spectroscopic properties of berberine
Diaz, Marta Susana,Freile, Monica Liliana,Gutierrez, Maria Isela Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.7
Spectral and photophysical properties of the alkaloid berberine (B) were studied in solvents with different solvent parameters, using UV/Vis absorption, emission and excitation spectroscopy. The absorption and emission maxima were found to be between 421-431 nm and 514-555 nm, respectively, leading to Stokes' shifts between 4099 and $5735cm^{-1}$. The fluorescence quantum yields varied between $10^{-2}-10^{-4}$, depending on the solvent. Different solvent scales have been used to study the solvatochromism of B. Linear solvation energy relationships (LSER) proposed by Kamlet-Taft suggest that B is a molecule attractive as a probe for solvent polarity and hydrogen bonding properties.