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Inference of magnetic fields in the very quiet Sun
Martí,nez Gonzá,lez, M. J.,Pastor Yabar, A.,Lagg, A.,Asensio Ramos, A.,Collados, M.,Solanki, S. K.,Balthasar, H.,Berkefeld, T.,Denker, C.,Doerr, H. P.,Feller, A.,Franz, M.,Gonzá,lez EDP Sciences 2016 Astronomy and astrophysics Vol.596 No.-
Mechanosynthesis of graphene nanoribbons from waste zinc–carbon batteries
Martínez-González J.,Reyes-Contreras D.,Vigueras-Santiago Enrique,Patiño-Carachure C.,Reyes-Esqueda J. A.,Castrejón-Sánchez V. H.,García-Orozco I. 한국탄소학회 2022 Carbon Letters Vol.32 No.2
The mechanosynthesis route is a physical top–down strategy to produce different nanomaterials. Here, we report the formation of graphene nanoribbons (GNRs) through this route using carbon bars recovered from discarded alkaline batteries as raw material. The mechanosynthesis time (milling time) is shown to have an influence on different features of the GNRs such as their width and edges features. TEM revealed the presence of GNRs with widths of 15.26, 8.8, and 23.55 nm for the milling times of 6, 12, and 18 h, respectively. Additionally, the carbon bars evolved from poorly shaped GNRs for the shortest milling time (6 h) to well-shaped GNRs of oriented sheets forming for the longest milling time. Besides GNRs, graphene sheets (GNS) of different sizes were also observed. The Raman analysis of the 2D bands identified the GNS signal and confirmed the GNRs nature. ID/IG values of 0.21, 0.32, and 0.40 revealed the degree of disorder for each sample. The in-plane sp2 crystallite sizes (La) of graphite decreased to 91, 60, and 48 nm with increasing peeling time. The RBLM band at 288 cm−1 confirmed the formation of the GNRs. Mechanosynthesis is a complex process and the formation of the GNRs is discussed in terms of a mechanical exfoliation, formation of graphene sheets and its fragmentation to reach GNR-like shapes. It is shown that the synthesis of GNRs through the mechanosynthesis route, besides the use of recycled materials, is an alternative for obtaining self-sustaining materials.
UNNOTICED MAGNETIC FIELD OSCILLATIONS IN THE VERY QUIET SUN REVEALED BY SUNRISE/IMaX
Martí,nez Gonzá,lez, M. J.,Asensio Ramos, A.,Manso Sainz, R.,Khomenko, E.,Martí,nez Pillet, V.,Solanki, S. K.,Ló,pez Ariste, A.,Schmidt, W.,Barthol, P.,Gandorfer, A. IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.730 No.2
<P>We present observational evidence for oscillations of magnetic flux density in the quiet areas of the Sun. The majority of magnetic fields on the solar surface have strengths of the order of or lower than the equipartition field (300-500 G). This results in a myriad of magnetic fields whose evolution is largely determined by the turbulent plasma motions. When granules evolve they squash the magnetic field lines together or pull them apart. Here, we report on the periodic deformation of the shapes of features in circular polarization observed at high resolution with SUNRISE. In particular, we note that the area of patches with a constant magnetic flux oscillates with time, which implies that the apparent magnetic field intensity oscillates in antiphase. The periods associated with this oscillatory pattern are compatible with the granular lifetime and change abruptly, which suggests that these oscillations might not correspond to characteristic oscillatory modes of magnetic structures, but to the forcing by granular motions. In one particular case, we find three patches around the same granule oscillating in phase, which means that the spatial coherence of these oscillations can reach 1600 km. Interestingly, the same kind of oscillatory phenomenon is also found in the upper photosphere.</P>
Dynamic Response of Low-Aspect-Ratio Cantilever NACA0012 Airfoil at Low-To-Moderate Reynolds Numbers
S. Martínez-Aranda,A. García-González,L. Parras,J. F. Velazquez-Navarro,C. del Pino 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.3
The influence of the angle of attack (AoA) and the chord based Reynolds number (Rec) on the lift and drag coefficients has been analyzed experimentally in a low-aspect-ratio NACA0012 airfoil, AR = 2. Results are shown for chord based Reynolds numbers in the range 3.33 × 104 ≤ Rec ≤ 1.33 × 105 and AoA between 0º and +35º, the stall angle being close to 12º. The aerodynamic characteristics show an increase and decrease of lift and drag force fluctuations for AoA greater than the stall angle. The explanation of how these aerodynamic variations appear has been reported numerically and it is based on two-dimensional effects which are mainly the unstable laminar separation bubble (LSB) and the subsequent downstream propagation of leading edge vortex (LEV) as AoA increases. In addition, the dynamic response of the wing has been studied using frequency analysis. We compute the power spectral density (PSD) from the temporal evolution of the net force exerted over the wing, showing that the main response of the wing is the presence of two natural frequencies of the wing-base system. The mean PSD suddenly increases for Rec ≈ 1 × 105, particularly at AoA exceeding the critical point that corresponds to the stall angle. Finally, and despite from the fact that our model is rigid, we find PSD peaks at very low and high frequencies in agreement with other authors’ results which correspond to energetic modes in the wingtip vortex and the formation and emission of coherent turbulent structures behind the airfoil, respectively.
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.
A parametric study of optimum tall piers for railway bridge viaducts
Francisco J. Martínez-Martín,Fernando González-Vidosa,Antonio Hospitaler,Víctor Yepes 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.6
This paper presents a parametric study of reinforced concrete bridge tall piers with hollow, rectangular sections. Such piers are typically used in railway construction of prestressed concrete viaducts. Twenty one different piers have been studied with seven column heights of 40, 50, 60, 70, 80, 90 and 100 m and three types of 10-span continuous viaducts, whose main span lengths are 40, 50 and 60 m. The piers studied are intermediate columns placed in the middle of the viaducts. The total number of optimization design variables varies from 139 for piers with column height of 40 m to 307 for piers with column height of 100 m. Further, the results presented are of much value for the preliminary design of the piers of prestressed concrete viaducts of high speed railway lines.
A novel approach for the rigid body guidance synthesis of planar RRPR linkages
Selma J. Rodríguez-González,Henry A. Suárez-Velásquez,J. Jesús Cervantes-Sánchez,José M. Rico-Martínez 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
This paper demonstrates that the maximum number of poses that can be exactly reached by a planar RRPR linkage is four, while the design for five poses requires the relaxation of displacement constraints at one prescribed pose. To this end, a novel and explicit condition for the synthesis of RP dyads with five prescribed poses is correspondingly introduced. It leads to a new and efficient approach to synthesize planar RRPR linkages, which is equipped with a branching identification procedure. Two successful case studies are provided to validate the applicability of the proposed synthesis approach.
Puente-Martínez D. E.,Díaz-Guillén J. A.,González-García K. A.,Montemayor S. M.,Díaz-Guillén J. C.,Burciaga-Díaz O.,Bazaldúa-Medellín M. E.,Padmasree K. P. 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.5
This research reports the synthesis, characterization, and electrical properties of the systems EryCe1−yO2−δ (y = 0.05, 0.1, and 0.15), and the effect of the incorporation of sintering aids (2 wt.% of CaO, MgO, and TiO2) on the electrical properties of the composition Er0.1Ce0.9O1.95, to be used as ceramic solid electrolytes in low-temperature solid oxide fuel cells (LT-SOFC). All EryCe1−yO2−δ samples were obtained by mechanochemistry (20 h of milling) and characterized by XRD. The morphology of the pure sintered compositions and with the incorporation of sintering aids (sintered at 1200 °C) was evaluated by FE-SEM. Electrical properties as a function of temperature (200–650 °C) and frequency (100 Hz–1 MHz) were evaluated by impedance spectroscopy. It reveals an increase of bulk ionic conductivity for higher contents of Er, as the number of oxygen vacancies increases. The higher value of conductivity (6.7 × 10–3 S cm−1) at 650 °C was for the composition Er0.15Ce0.85O1.925, while the ionic conductivity of Er0.1Ce0.9O1.95 at 650 °C increased from 2.68 × 10–3 S cm−1 to a maximum of 1.54 × 10–2 S cm−1 with the incorporation of CaO as additive. These improvements in bulk ionic conductivities can contribute to the development of more efficient electrolytes for the LT-SOFC technology.
del Carmen Velázquez-Martínez Guadalupe,González-Hernández Héctor,Equihua-Martínez Armando,Refugio Lomeli-Flores J.,Rojas Julio C.,Lopez-Collado Jose 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.1
Avocado production in Mexico represents an income of more than $3.2 billion dollars per year in foreign ex change. Unfortunately, several factors can limit the export of this fruit. One of such limiting factor is the avocado seed moth, Stenoma catenifer; however, its population dynamics is barely known. Therefore, is relevant to study the environmental factors affecting population changes, aimed to improve its management. In this study, we monitored the population fluctuations of S. catenifer males and explored its relationship with temperature and relative humidity by using pheromone-baited traps in Hass avocado orchards in the state of Colima, Mexico. From June 2018 to June 2019, a total of 6,836 males of the avocado seed moth were collected, with two population peaks. The first in June-August, during the fruiting stage, and the second in December-January, coinciding with the end of fruiting and flowering stages. Fruit infestation ranged from 0.0 to 65.0% in the or chards examined. Cluster analysis and principal coordinate analysis indicated that sampling time and relative humidity group together but differ from temperature. The effect of relative humidity and temperature on catches was analyzed by relating non-parametric bivariate distributions. The highest male catches were recorded at temperatures greater than 15.8 ◦ C and relative humidity greater than 60% while low relative humidity did not favor moth catches. These results may be useful to predict bioecological conditions for the occurrence of pop ulations of this pest.
Jorge Chávez,Omar Jiménez Alemán,Martín Flores Martínez,Héctor J. Vergara‑Hernández,Luis Olmos,Pedro Garnica‑González,Didier Bouvard 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.2
The design and fabrication of a bilayer Ti6Al4V–Ti6Al4V/30Ta component were performed by using the powder metallurgyprocess and solid-state sintering as the consolidation step. Phase change and sintering densifcation of the component werestudied by dilatometry. The addition of 30 vol% of Ta to the Ti6Al4V matrix had a noticeable efect over the microstructuraland mechanical properties of the alloy, which showed decrements of up to 12.2 and 21.5% in nano-hardness and elastic modulus, respectively. The decrement of these properties strongly afected the wear and corrosion performance of the component. Special attention was focused on the intermediate zone between layers denoted by a transition zone, which presented betterwear response because of the properties and microstructure caused by the gradient difusion of Ta. Ti6Al4V/30Ta alloyshowed an improved corrosion behaviour compared to Ti6Al4V alloy, decreasing 2.4 times their susceptibility to corrosionand about two orders of magnitude their corrosion rate. The bilayer component in this study is proposed as an alternative todecrease the consumption of expensive materials with improved properties.