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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.
Sergio Martínez-García,César I. Ortiz-García,Marisa Cruz-Aguilar,Juan Carlos Zenteno,José Martin Murrieta-Coxca,Sonia Mayra Pérez-Tapia,Sandra Rodríguez-Martínez,Mario E. Cancino-Diaz,Juan C. Cancino- 한국미생물학회 2019 The journal of microbiology Vol.57 No.2
Staphylococci have quorum-sensing (QS) systems that enable cell-to-cell communication, as well as the regulation of numerous colonization and virulence factors. The accessory gene regulator (Agr) operon is one of the Staphylococcus genus QS systems. Three groups (I, II, and III) are present in Staphylococcus epidermidis Agr operon. To date, it is unknown whether Agr groups can interact symbiotically during biofilm development. This study analyzed a symbiotic association among Agr groups during biofilm formation in clinical and commensal isolates. Different combinations among Agr group isolates was used to study biofilm formation in vitro and in vivo (using a mouse catheter-infection model). The analysis of Agr groups were also performed from samples of human skin (head, armpits, and nostrils). Different predominant coexistence was found within biofilms, suggesting symbiosis type. In vitro, Agr I had a competition with Agr II and Agr III. Agr II had a competition with Agr III, and Agr II was an antagonist to Agr I and III when the three strains were combined. In vivo, Agr II had a competition to Agr I, but Agr I and II were antagonists to Agr III. The associations found in vitro and in vivo were also found in different sites of the skin. Besides, other associations were observed: Agr III antagonized Agr I and II, and Agr III competed with Agr I and Agr II. These results suggest that, in S. epidermidis, a symbiotic association of competition and antagonism occurs among different Agr groups during biofilm formation.
First-principles study on structural, electronic and ferroelectric properties of Bi2VO5.5 compound
Hmok HLinh,Martínez-Aguilar E.,Alanis Javier,Mendoza M.E. 한국물리학회 2022 Current Applied Physics Vol.44 No.-
A first-principles investigation of the origin of ferroelectricity in the Aurivillius compound Bi2VO5.5 is presented. Calculations with the density functional theory, in conjunction with the modern theory of polarization, allowed us to study the structural, electronic, and polar properties of two configurations built with oxygen vacancies, causing a charge imbalance and a subsequent displacement of the ions, generating two maximum polarizations, one of 14.75 μC/cm2 and one of 4.31 μC/cm2 along [011] direction. Electron localization function schemes were used to identify the asymmetry of charges in (001), (010) and (100) planes. The results obtained in this study establish that the origin of ferroelectricity is due to the displacement of the ions caused by oxygen vacancies and the asymmetric distribution of the isolated pair of Bi ions. On the other hand, the bandgap calculations and the results of Ps establish that Bi2VO5.5 is a candidate ferro-photovoltaic material.
C. G. Garay-Reyes,S. E. Hernández-Martínez,J. L. Hernández-Rivera,J. J. Cruz-Rivera,E. J. Gutiérrez-Castañeda,H. J. Dorantes-Rosales,J. Aguilar-Santillan,R. Martínez-Sánchez 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2
According to Lifshitz, Slyozov, and Wagner (LSW) and Trans-Interface Diffusion-Controlled (TICD) theoreticalmodels, this paper reports the microstructure and its coarsening behavior of γ' metastable-coherentprecipitates in concentration gradient of Ni-13.75Ti (at%)/Ni generated by diffusion couple. The coarseningof precipitates was evaluated in two different Ti contents (R1-11.4Ti (at%) and R2-13Ti (at%)) generated alongthe concentration gradient and includes average size, size distributions and growth rate. The solvus andmetastable-coherent bimodal lines as determined at 850 °C of 9.16 (at%) and 9.92Ti (at%) respectively byscanning electron microscopy. This paper suggests that elastic strains produced by the matrix/precipitate latticemismatch caused significant deviations between the experimental results and those predicted by the LSW or TIDCtheories. Activation energies for TIDC (Qi) and LSW (Qr) are Qr: 219.69 and 172.61 kJ mol-1for R1 and R2regions, respectively, and Qi: 218.46 and 164.56 kJmol-1for R1 and R2 regions, respectively. A concentration gradientallows the study of various alloys with different concentration and volume-fraction in a single sample.
C.J. González-Pérez1,I. Vargas-Arispuro,E. Aispuro-Hernández,C.L. Aguilar-Gil,Y.E. Aguirre-Guzmán,A. Castillo,A. Hernández-Mendoza,J.F. Ayala-Zavala,M.A. Martínez-Téllez1 한국미생물·생명공학회 2019 한국미생물·생명공학회지 Vol.47 No.2
The consumption of fresh vegetables has been related to recurrent outbreaks of foodborne diseases (FBD) worldwide. Therefore, the development of effective alternative technologies is necessary to improve the safety of these products. This study aimed to isolate and identify epiphytic lactic acid bacteria (LAB) from fresh fruits and leafy vegetables and characterize their antagonistic capacity due to their ability to produce bacteriocins or antibacterial compounds. For this, 92 LAB isolates from fruits and leafy vegetables were screened for antagonistic activity. Two strains with the highest and broadest antagonistic activities were selected for further characterization; one from cantaloupe melon (strain CM175) and one from cilantro leaves (strain C15). The cell-free supernatants (CFS) of CM175 and C15 were found to exhibit antagonistic activity against FBD-causing pathogens. The CM175 and C15 strains were identified as Pediococcus pentosaceus and Lactobacillus graminis, respectively. Notably, the P. pentosaceus CM175 CFS stopped the growth of Salmonella Typhimurium, Salmonella Saintpaul, Staphylococcus aureus, and Listeria monocytogenes, and delayed Escherichia coli O157:H7 growth. Moreover, L. graminis C15 CFS delayed the growth of all indicator pathogens, but did not completely stop it. Organic acids and bacteriocin-like molecules were determined to be possibly exerting the observed antagonistic activity of the identified LAB strains. Thus, application of the antagonistic compounds produced by Pediococcus pentosaceus and Lactobacillus graminis could be a novel and ecological strategy in developing antimicrobial biopreservatives for the food industry and mitigating FBD by reducing the biological contamination in fruit and vegetable orchards, mainly via their potential in controlling both gram-negative and gram-positive pathogenic bacteria.
Hmok H´Linh,Betancourt I.,Martínez-Aguilar E. 한국물리학회 2023 Current Applied Physics Vol.45 No.-
This theoretical work presents magnetic, electronic and optical properties of SrFe12-xAlxO19 (x = 0.5; 1; 1.5) solid solutions using first-principles calculations based on density functional theory. A decrease in the magnetic properties of SrFe12O19 is predicted when doped with the Al ions. It was found that the Al ions preferentially replace Fe ions at 2a and 12k sites. On the other hand, SrFe11.5Al0.5O19 and SrFe11Al1O19 solid solutions behave like a semiconductor, while SrFe10.5Al1.5O19 solid solution showed a metallic response. From the optical analysis, incorporating the Al ions can benefit the polarizability of the medium. For the SrFe11.5Al0.5O19 (Al[2a]) and SrFe11Al1O19 (Al[2a-2a]) solid solutions, the incorporation of Aluminum ions results in the reduction of the gap, making it a more useful material for catalytic applications.