Zeolite Synthesis in FluorideMedia: Structure Directiontoward ITW by Small Methylimidazolium Cations

Rojas, Alex,Martí,nez-Morales, Evangelina,Zicovich-Wilson, Claudio M.,Camblor, Miguel A. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.4

<P>Pure silica ITW zeolite can be synthesized using 1,2,3-trimethylimidazoliumand 1,3-dimethylimidazolium cations and fluoride anions as structure-directingagents (SDAs). Similarly to the previously reported 1,3,4-trimethylimidazolium,the dimethyl cation can also produce the zeolite TON, but this higherframework density phase finally transforms <I>in situ</I> into ITW. The structures of the as-made and calcined phases preparedwith the new cations show a unit cell doubling along <I>z</I>, and the refined structures are reported. Periodic Density FunctionalTheory calculations provide the energies of the six SDA-ITW and SDA-TONzeolites, and their relative stabilities fully agree with the experimentalobservations. Structure-direction in this system is discussed fromexperimental and theoretical results that give strong support to theidea that strained silica frameworks are made possible in fluoridemedia by decreasing the covalent character of the Si–O bond.This decreased covalency is enhanced with the 1,2,3-trimethyl isomer,which is shown to be the strongest SDA for ITW and, at the same time,is the more hydrophilic of the three SDAs tested. Our observationswith the three SDAs agree with the so-called Villaescusa’srule, i.e., the low framework density phase is favored at higher concentrations,but at the same time question the supersaturation hypothesis thathas been proposed to explain this rule, since here the low-densityphase is the most stable one.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-4/ja209832y/production/images/medium/ja-2011-09832y_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja209832y'>ACS Electronic Supporting Info</A></P>

Glycolate Oxidase Modulates Reactive Oxygen Species-Mediated Signal Transduction during Nonhost Resistance in Nicotiana benthamiana and Arabidopsis

Rojas, C.M.,Senthil-Kumar, M.,Wang, K.,Ryu, C.-M.,Kaundal, A.,Mysore, K.S. AMERICAN SOCIETY OF PLANT BIOLOGISTS 2012 The Plant cell Vol.24 No.1

Acute and Repeated 28-Day Oral Dose Toxicity Studies of Thymus vulgaris L. Essential Oil in Rats

Rojas-Armas, Juan,Arroyo-Acevedo, Jorge,Ortiz-Sanchez, Manuel,Palomino-Pacheco, Miriam,Castro-Luna, Americo,Ramos-Cevallos, Norma,Justil-Guerrero, Hugo,Hilario-Vargas, Julio,Herrera-Calderon, Oscar Korean Society of ToxicologyKorea Environmental Mu 2019 Toxicological Research Vol.35 No.3

Thymus vulgaris L. is widely used as an ingredient in cooking and in herbal medicine. However, there is little information about its toxicity. The present study was performed to evaluate the acute and repeated 28-day oral dose toxicity of thyme essential oil in rats. For the acute toxicity test, two groups of three rats were used. The rats received a single dose of essential oil: 300 or 2,000 mg/kg of body weight (bw). The rats were observed individually during the first four hours, and then daily until day 14. For the toxicity test with repeated doses, four groups of 10 rats were used. Doses of 100, 250, and 500 mg/kg/day were tested for 28 days. At the end of the experiment, blood was collected and the animals were sacrificed. Histopathological examination showed that in the lungs of rats given the 2,000 mg/kg bw dose, polymorph nuclear infiltrates, hemosiderin macrophages, and interstitial space thickening were present. In the repeated dose study, all rats survived the 28-day treatment period and apparently showed no signs of toxicity. The hematological and biochemical parameters were not altered. The histopathological study of the organs showed severe changes in the lung, with the dose of 500 mg/kg/day; in the other organs, no alterations were observed or the changes were slight. The body weight was only altered in male rats given the 500 mg/kg dose. The relative weight of the organs did not show any significant changes. Our studies revealed that the essential oil of Thymus vulgaris has moderate oral toxicity according to the results of the acute test, whereas the results of the 28-day oral toxicity test suggest that the no-observed-adverse effect level (NOAEL) is greater than 250 mg/kg/day.

스페인 정치선전에 언어학전 연구 (1977-1986)

Rojas, Eva Gomez,Eva Gomez Rojas 한국외국어대학교 1988 한국외국어대학교 논문집 Vol.21 No.1

Design of isolated footings of circular form using a new model

Rojas, Arnulfo Luevanos Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4

This paper presents the design of reinforced concrete circular footings subjected to axial load and bending in two directions using a new model. The new model considers the soil real pressure acting on contact surface of the circular footings and these are different, with a linear variation in the contact area, these pressures are presented in terms of the axial load, moments around the axis "X" and the axis "Y". The classical model takes into account only the maximum pressure of the soil for design of footings and it is considered uniform at all points of contact area. Also, a comparison is presented in terms of the materials used (steel and concrete) between the two models shown in table, being greater the classical model with respect the new model. Therefore, the new model is the most appropriate, since it is more economic and also is adjusted to real conditions.

A comparative study for design of boundary combined footings of trapezoidal and rectangular forms using new models

Luevanos-Rojas, Arnulfo,Barquero-Cabrero, Jose Daniel,Lopez-Chavarria, Sandra,Medina-Elizondo, Manuel Techno-Press 2017 Coupled systems mechanics Vol.6 No.4

This paper shows a comparative study for design of reinforced concrete boundary combined footings of trapezoidal and rectangular forms supporting two columns and each column transmits an axial load and a moment around of the axis X (transverse axis of the footing) and other moment around of the axis Y (longitudinal axis of the footing) to foundation to obtain the most economical combined footing. The real soil pressure acting on the contact surface of the footings is assumed as a linear variation. Methodology used to obtain the dimensions of the footings for the two models consider that the axis X of the footing is located in the same position of the resultant, i.e., the dimensions is obtained from the position of the resultant. The main part of this research is to present the differences between the two models. Results show that the trapezoidal combined footing is more economical compared to the rectangular combined footing. Therefore, the new model for the design of trapezoidal combined footings should be used, and complies with real conditions.

Adaptive force/position control of robot manipulators with bounded inputs

Lina Rojas-García,Isela Bonilla-Gutiérrez,Marco Mendoza-Gutiérrez,César Chávez-Olivares 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

In various automated industrial, medical, or service applications using robotic systems it is required to regulate both robot movement and contact force. In order to address this control problem, this paper presents a force/position control structure that has two characteristics that are very relevant in robot-environment interaction tasks. First, the structure of the controller is based on the use of generalized saturation functions, and this makes it possible to ensure that the robot actuators operate within a safe region without exceeding their torque limits. On the other hand, an adaptable term is included within the structure that allows to compensate for parametric uncertainty related to gravitational forces and the stiffness of the environment on which the robot operates. The validity and correct performance of the proposed control structure is based on a rigorous stability analysis, as well as numerical simulations using a three-degree-of-freedom robot manipulator.

A new model for T-shaped combined footings part II: Mathematical model for design

Luevanos-Rojas, Arnulfo,Lopez-Chavarria, Sandra,Medina-Elizondo, Manuel Techno-Press 2018 Geomechanics & engineering Vol.14 No.1

The first part shows the optimal contact surface for T-shaped combined footings to obtain the most economical dimensioning on the soil (optimal area). This paper presents the second part of a new model for T-shaped combined footings, this part shows a the mathematical model for design of such foundations subject to axial load and moments in two directions to each column considering the soil real pressure acting on the contact surface of the footing with one or two property lines restricted, the pressure is presented in terms of an axial load, moment around the axis "X" and moment around the axis "Y" to each column, and the methodology is developed using the principle that the derived of the moment is the shear force. The classic model considers an axial load and a moment around the axis "X" (transverse axis) applied to each column, i.e., the resultant force from the applied loads is located on the axis "Y" (longitudinal axis), and its position must match with the geometric center of the footing, and when the axial load and moments in two directions are presented, the maximum pressure and uniform applied throughout the contact surface of the footing is considered the same. To illustrate the validity of the new model, a numerical example is presented to obtain the design for T-shaped combined footings subjected to an axial load and moments in two directions applied to each column. The mathematical approach suggested in this paper produces results that have a tangible accuracy for all problems.

Multiferroic effect of multilayer low-distorted doped bismuth ferrite thin films as a function of sputtering power and crystallographic texture

G. Rojas-George,A. Concha-Balderrama,H. Esparza-Ponce,J.J. Gervacio-Arciniega,M.P. Cruz,V. Orozco-Carmona,A. Reyes-Rojas 한국물리학회 2017 Current Applied Physics Vol.17 No.6

Low-distortion rhombohedral multilayer barium-nickel co-doped BiFeO3 (Bi0.75Ba0.25Fe0.975Ni0.025O3) multiferroic thin films were grown on Pt/TiO2/SiO2/Si substrates by reactive RF magnetron sputtering, as a function of sputtering power. X-ray diffraction showed that Bi0.75Ba0.25Fe0.975Ni0.025O3 multilayer films have a pseudocubic-type structure. Piezoresponse force microscopy demonstrated polarization switching in all films at room temperature. Scanning electron microscopy showed different morphologies depending on the sputtering power used during the deposition process and that the thickness of the film decreases from about 142 nm to 72 nm as the sputtering power decreases. Magnetization results showed that as the thickness of the film decreases, the magnetization of the film increases. Thus, there is a direct relation between the sputtering power, thickness and the magnetization of the film. A direct relation between in-plane residual stress and thin film thickness has been obtained. This causes the main axe of the BO6 octahedra to be tilted from 90 to 45 (from thin-film surface) by a texture crystal volume of 29 and 18% in the (012) and (110) crystallographic planes respectively.

A new model for T-shaped combined footings part I: Optimal dimensioning

Luevanos-Rojas, Arnulfo,Lopez-Chavarria, Sandra,Medina-Elizondo, Manuel Techno-Press 2018 Geomechanics & engineering Vol.14 No.1

The foundations are classified into shallow and deep, which have important differences: in terms of geometry, the behavior of the soil, its structural functionality, and its constructive systems. The shallow foundations may be of various types according to their function; isolated footings, combined footings, strip footings, and slabs foundation. The isolated footings are of the type rectangular, square and circular. The combined footing may be rectangular, trapezoidal or T-shaped in plan. This paper presents a new model for T-shaped combined footings to obtain the most economical contact surface on the soil (optimal dimensioning) to support an axial load and moment in two directions to each column. The new model considers the soil real pressure, i.e., the pressure varies linearly. The classical model uses the technique of test and error, i.e., a dimension is proposed, and subsequently, the equation of the biaxial bending is used to obtain the stresses acting on each vertex of the T-shaped combined footing, which must meet the conditions following: The minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity that can withstand the soil. To illustrate the validity of the new model, numerical examples are presented to obtain the minimum area of the contact surface on the soil for T-shaped combined footings subjected to an axial load and moments in two directions applied to each column.