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Comesana-Gandara, B.,Hernandez, A.,de la Campa, J.G.,de Abajo, J.,Lozano, A.E.,Lee, Y.M. Elsevier Scientific Pub. Co 2015 Journal of membrane science Vol.493 No.-
Ortho-hydroxypolyimides (HPIs) undergo thermal rearrangement processes in a solid state at high temperatures to produce thermally rearranged polybenzoxazoles (TR-PBOs), which are promising materials for gas separation membranes due to their exceptional permeability-selectivity performance. The strong dependence between the structure of HPIs and the final properties of the TR-PBOs and the high cost of the HPI precursors are considered excellent reasons for their continued study. In this work, a set of low-cost HPIs were synthetized via the reaction of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) with 2,4-diaminophenol dihydrochloride (DAP-Cl) and 4,6-diaminoresorcinol dihydrochloride (DAR-Cl). The polyimide made from 6FDA and m-phenylene diamine (MPD) was also obtained for comparison purposes. The polyimide precursors and the corresponding TR-PBOs, which were tested as films, were thoroughly characterized. The glass transition temperature of these precursor polyimides was shown to be a function of the number of hydroxyl groups such that the lowest value corresponded to the polyimide from MPD and the highest value corresponded to that derived from DAR. The conversion rate of HPIs to PBO at different processing temperatures was determined, and the highest conversion rate matched the DAP derived polyimide. With respect to their gas separation properties after thermal treatment at 450<SUP>o</SUP>C, these HPIs gave rise to TR-PBOs with very high permeability and satisfactory permselectivity values for several gas pairs.
Hernandez, J.M.,Lim, D.H.,Nguyen, H.V.P.,Yoon, S.P.,Han, J.,Nam, S.W.,Yoon, C.W.,Kim, S.K.,Ham, H.C. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.23
Spin-polarized density functional theory studies of hydrogen sulfide (H<SUB>2</SUB>S) adsorption and decomposition on Ni(100) and Ni<SUB>3</SUB>Al(100) surfaces were conducted to understand the aluminum (Al) alloying effect on H<SUB>2</SUB>S dissociation. For such purpose, we first determined the near surface structure of fully ordered Ni<SUB>3</SUB>Al alloy along the [100] direction by calculating the Al segregation energy to the surface and then examined the adsorption energies of the adsorbates (H<SUB>2</SUB>S, HS, S, and H) and the activation barriers for the H<SUB>2</SUB>S and HS decomposition by using Climbing Image-Nudged Elastic Band method. We found that regardless of the way to terminate the surface, Al atom in bimetallic Ni<SUB>3</SUB>Al(100) tends to exist in the first surface layer, rather than in the second or third layer, and the Ni<SUB>3</SUB>Al(100) surface can substantially retard the H<SUB>2</SUB>S decomposition by reducing the adsorption energy of sulfur compounds compared to the pure Ni(100) case. Finally, we presented how the Al in Ni<SUB>3</SUB>Al modifies the activity of surface Ni atoms toward the sulfur compounds by calculating the local density of states and charge distribution in alloying components. This work hints the importance of knowing how to properly tailor the reactivity of Ni based materials to enhance the resistance for sulfur poisoning.
M.E. Rivas-Aguilar,N. Hernandez-Como,G. Gutierrez-Heredia,A. Sánchez-Martínez,M. Mireles Ramirez,M.A. Quevedo-López 한국물리학회 2018 Current Applied Physics Vol.18 No.7
In this work, the specific contact resistance (ρc) between amorphous indium-gallium-zinc-oxide (IGZO) semiconductor and different contact electrodes was obtained from thin film transistors (TFTs). Ti/Au (10/100 nm), aluminum doped zinc oxide (AZO, 100 nm) and indium tin oxide (ITO, 100 nm) were used as source/drain electrodes to fabricate IGZO TFTs. Chemical states of the contacts/semiconductor interfaces were examined by depth profile X-ray photoelectron spectroscopy (XPS) analysis to explain the origin of the differences on specific contact resistance. The lowest ρc achieved using Ti/Au was related to the formation of a TiOx interlayer due to oxygen atoms diffusing out from the semiconductor under layer, increasing the carrier concentration of IGZO at the interface and lowering the ρc. On the contrary, no interfacial reactions were observed between IGZO and AZO or ITO source/drain. However, IGZO resistivity increased with ITO contacts likely due to oxygen vacancies filling during ITO deposition. This fact seems to be the origin of the high contact resistance between IGZO and ITO, compared to IGZO-AZO and IGZO-Ti/Au interfaces.
Computing the Refined Compression Field Theory
Hernandez-Diaz, A.M.,Garcia-Roman, M.D. Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.2
In recent years, some modifications were introduced in the stress-strain relationship of the steel in order to develop a more efficient shear model for reinforced concrete members. The last contribution in this sense corresponding to the Refined Compression Field Theory (RCFT, 2009); this theory proposed a steel constitutive model that has account the tension stiffening area prescribed by technical codes, what simplifies all the design process. However, under certain design conditions supported by such codes, the RCFT model does not provide a real (non-complex) solution for the steel yield strain when the prescribed tension stiffening area is considered; then the load-strain response cannot be computed. In this technical note, the tension stiffening area is fixed in order to guarantee the application of the embedded steel constitutive model for all the standard design range.
Computing the Refined Compression Field Theory
A. M. Hernandez-Diaz,M. D. Garcia-Roman 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.2
In recent years, some modifications were introduced in the stress–strain relationship of the steel in order to develop a more efficient shear model for reinforced concrete members. The last contribution in this sense corresponding to the Refined Compression Field Theory (RCFT, 2009); this theory proposed a steel constitutive model that has account the tension stiffening area prescribed by technical codes, what simplifies all the design process. However, under certain design conditions supported by such codes, the RCFT model does not provide a real (non-complex) solution for the steel yield strain when the prescribed tension stiffening area is considered; then the load-strain response cannot be computed. In this technical note, the tension stiffening area is fixed in order to guarantee the application of the embedded steel constitutive model for all the standard design range.
Antiamoebic Activity of Petiveria alliacea Leaves and Their Main Component, Isoarborinol
( Lizeth M. Zavala-ocampo ),( Eva Aguirre-hernandez ),( Nury Perez-hernandez ),( Gildardo Rivera ),( Laurence A. Marchat ),( Esther Ramirez-moreno ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.8
Petiveria alliacea L. (Phytolacaceae) is a medicinal plant with a broad range of traditional therapeutic properties, including the treatment of dysentery and intestinal infections caused by protozoan parasites. However, its effects against Entamoeba histolytica have not been reported yet. We investigated the antiamoebic activity present in the leaves of P. alliacea Antiamoebic activity was evaluated in methanolic and aqueous extracts, as well as in the hexanic, methanolic, and EtOAc fractions. The P. alliacea methanolic extract showed a better antiamoebic activity than the aqueous extract with an IC<sub>50</sub> = 0.51 mg/ml. Likewise, the hexanic fraction was the most effective fraction, showing a dose-dependent activity against E. histolytica, with an IC<sub>50</sub> = 0.68 mg/ml. Hexanic subfraction 12-19 showed the highest antiamoebic activity at 0.8 mg/ml, producing 74.3% growth inhibition without any toxicity in mammal cells. A major component in subfraction 12-19 was identified as isoarborinol, which produced 51.4% E. histolytica growth inhibition at 0.05 mg/ml without affecting mammal cells. The P. alliacea leaf extract has antiamoebic activity that can be attributed to a major metabolite known as isoarborinol.
( Palao J. M. ),( Garcia-de-alcaraz A. ),( Hernandez-hernandez E. ),( Ortega E. ) 한국스포츠정책과학원(구 한국스포츠개발원) 2016 International Journal of Applied Sports Sciences Vol.28 No.2
The purpose of this study was to test a protocol for establishing collective technical and tactical performance goals in elite men`s volleyball. The participants were a professional volleyball team. The period of study was one entire season. A baseline was established in the first half of the season, and the intervention was carried out in the second half of the season. The intervention involved the use of seven collective performance goals for monitoring the team in competitions. The variables studied were: the achievement of the collective performance goals that were established; the game phase; the result of the set; and the players`, coaches`, and psychologist`s perception of the use of the performance goals and the poster. The team slightly increased the number of goals achieved per game in the intervention period. There was a significant reduction in serve errors and a significant increase in block contacts. The intervention increased the players` engagement with the team, although there were differences in opinion about the effect on the different players. The intervention improved the players` understanding of the match. The effects of the goal-setting and the poster were positively perceived, due to helping the players to understand their needs and the aspects to improve.