Silver nanoparticles incorporated into Na₂Ti6O13 microfibers

V. Rodríguez-González,I. Juárez-Ramírez,R. Zanella,M.E. Zarazúa,L.M. Torres-Martínez 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6

This research is concerned with novel semiconductor composites of sodium hexatitanate oxide (Na2Ti6O13), and silver metallic nanoparticles. The Na2Ti6O13 was prepared by two methods, a sol-gel process and a solid state reaction. The silver nanoparticles were incorporated into the titanate by a deposition-precipitation technique, using NaOH as precipitation agent in the dark. Ag/Na2Ti6O13 microfibers were obtained by the sol-gel method, meanwhile octagonal microbar agglomerates were the product of the solid state reaction. The SEM-TEM observations showed silver particles with a nanometric size (5-7 nm); and fibrillar structures in the sol-gel sodium titanates. The UV-Vis-RD spectroscopy showed a blue shift Eg from 3.3 to 3.4 nm; and a plasmon surface resonance in the visible region. These materials are proposed as potential photocatalysts for contaminated water purification. This research is concerned with novel semiconductor composites of sodium hexatitanate oxide (Na2Ti6O13), and silver metallic nanoparticles. The Na2Ti6O13 was prepared by two methods, a sol-gel process and a solid state reaction. The silver nanoparticles were incorporated into the titanate by a deposition-precipitation technique, using NaOH as precipitation agent in the dark. Ag/Na2Ti6O13 microfibers were obtained by the sol-gel method, meanwhile octagonal microbar agglomerates were the product of the solid state reaction. The SEM-TEM observations showed silver particles with a nanometric size (5-7 nm); and fibrillar structures in the sol-gel sodium titanates. The UV-Vis-RD spectroscopy showed a blue shift Eg from 3.3 to 3.4 nm; and a plasmon surface resonance in the visible region. These materials are proposed as potential photocatalysts for contaminated water purification.

PLASMON RESONANCE AND RAMAN MODES IN Pb NANOPARTICLES OBTAINED IN EXTRACT OF OPUNTIA FICUS-INDICA PLANT

L. P. RAMÍREZ-RODRÍGUEZ,M. CORTEZ-VALADEZ,H. ARIZPE-CH AVEZ,J.-G. BOCARANDO-CHACON,R. RAMÍREZ-BON,S. VELUMANI,M. FLORES-ACOSTA 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.6

Colloidal nanoparticles were obtained by green synthesis, embedded in the Opuntia ¯cus-indicaplant extract. Optical measurements allowed us to detect two absorption bands centered in230 nm and 298 nm. Agglomerates of Pb nanoparticles have size in the range 2 – 8 nm. The ef-fective absorption cross section of spherical Pb nanoparticles was calculated by applying the Mietheory for colloidal systems and compared to optical absorption measurements of Pb nano-particles. The Raman spectrum of the samples after the reduction of Pb, shows a band at lowwavenumbers centered at 116 cm? 1 . Similar bands have been assigned to small Pb and Agclusters in other experimental results. Additionally, we used the density functional theory (DFT)as well as semi-empirical methods to assign this band to radial breathing modes of Pb metalnanoparticles.

On the Ultimate Uniform Bounded-stabilization for a Class of Perturbed Time Delay System via Sub-optimal Robust Control

Omar Santos,Miguel Ramírez,Carlos Cuvas,Liliam Rodríguez-Guerrero,Hugo Romero,Patricio Ordaz 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.11

This paper deals with the robust control design for a class of time delay systems subject to unmatched disturbances and/or uncertain dynamics. For this, a specific Lyapunov-Krasovskii functional, the so called Attractive Ellipsoid concept and the dynamic programming algorithm for optimal control, are summarized to design the sub-optimal robust control law. Thus, the Lyapunov-Krasovskii candidate functional associated with specific Linear Matrix Inequality solution is aimed to guarantee the so called Ultimate Uniform Bounded-Stabilization. Furthermore, the sub-optimal robust control is achieved by minimizing a Hamilton-Jacobi-Bellman like equation, related to Lyapunov-Krasovskii type functional, respect to the admissible control. Hence, the robust and exponential stabilization is concluded for a perturbed and unperturbed time delay system, respectively. The theoretical results are illustrated on two numerical systems.

Properties of Thermoplastic Corn Starch Based Green Composites Reinforced with Barley (Hordeum vulgare L.) Straw Particles Obtained by Thermal Compression

José Antonio Silva-Guzmán,Raúl Rodríguez Anda,Francisco Javier Fuentes-Talavera,Ricardo Manríquez-González,María Guadalupe Lomelí-Ramírez 한국섬유공학회 2018 Fibers and polymers Vol.19 No.9

Currently, greater environmental awareness promotes research and development advances in biodegradable materials; they represent an alternative that decreases the environmental impact caused by traditional synthetic plastics. This study consists of the development and characterization of thermoplastic corn starch-based composites, reinforced with barley straw particles made by thermal compression. The study materials were prepared by using three particle concentrations (5, 10, and 15 %), while the matrix (0 %) was used as a reference. A mechanical evaluation of all samples was carried out, as well as that of their water absorption properties. They were also characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and flammability tests. The inclusion of straw in the thermoplastic matrix increased water absorption and quickened carbon formation, although it also increased its tensile strength (7 MPa) and the Young’s modulus of activity (MOE) (420 MPa) with a 15 % reinforcement. The FTIR analysis highlights the presence of a carbonyl signal (1720 cm-1) caused by a thermal breakdown (caramelization) linked to barley particles. Moreover, X-ray diffraction demonstrated a VA-type crystallinity pattern (anhydrous) within the biocomposites and an increase of the crystallinity index, through incorporating barley particles in the thermoplastic corn starch-based matrix.

Low Wavenumber Raman Modes and Plasmon Resonance in Cd Nanoparticles Obtained in Extract of Opuntia ficus-indica Plant

M. Cortez-Valadez,L. P. Ramírez-Rodríguez,J.-G. Bocarando-Chacon,M. FLORES-ACOSTA,S. VELUMANI,R. Ramírez-Bon 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.7

"Cadmium colloidal crystalline nanoparticles were obtained by a simple green synthesis method employing the plant extract of Opuntia ficus-indica. The plant extract reduces the Cd ions and stabilizes the size of cadmium colloidal particles at the nanometric level. The size and morphology of agglomerates of nanoparticles of about 100 nm were analyzed by field-emission scanning electron microscopy (FESEM). The size, shape and crystalline structure of the Cd nanoparticles were determined from TEM analysis. The results show that Cd nanoparticles with hexagonal crystalline structure and average size 2–3 nm were obtained by this green synthesis method. The optical absorption spectrum of the colloidal solution containing the cadmium nanoparticles displays an optical absorption band centered at 236 nm, which was attributed to the plasmon resonance of the Cd colloidal nanoparticles. Mie theory for colloidal systems was applied to reproduce theoretically the plasmon resonance absorption data of the Cd colloidal nanoparticles. Furthermore, the Raman spectrum of powder from dried samples after reduction of cadmium ions, displays a low wavenumber vibration mode centered at 114 cm-1, assigned to the Cd nanoparticles. Density functional theory (DFT) calculations at local spin density approximation (LSDA) level were performed to determine the structure and vibrational properties of small clusters of cadmium consisting of 3–10 atoms. Radial breathing modes with frequencies between 90 cm-1 and 120 cm-1 were found to be the most active Raman modes of the low-energy Cdn clusters."

A pH/Temperature-Sensitive s-IPN Based on Poly(vinyl alcohol), Poly(vinyl methyl ether-alt-maleic acid) and Poly(vinyl methyl ether) Prepared by Autoclaving

Karla F. García-Verdugo,Andya J. Ramírez-Irigoyen,Mónica Castillo-Ortega,Dora E. Rodríguez-Félix,Jesús M. Quiroz-Castillo,Judith Tánori-Córdova,Francisco Rodríguez-Félix,Antonio Ledezma-Pérez,Teresa d 한국고분자학회 2022 Macromolecular Research Vol.30 No.6

A novel semi-interpenetrating polymer network (s-IPN) based on the entrapment of a thermosensitive polymer, the poly(vinyl methyl ether) (PVME), within a crosslinked 3D structure of poly(vinyl alcohol) (PVA) and poly(vinyl methyl etheralt- maleic acid) (COP) was synthesized by an autoclaving process. The preparation method avoids the use of toxic crosslinkers and allows the simultaneous sterilization of material. The PVA/COP/PVME hydrogel were characterized by Fourier transform infrared spectroscopy, thermal techniques, swelling kinetic measurements, scanning electron microscopy, and rheological analysis. The entrapment of PVME within the hydrated polymer framework significantly modified its transition temperature at pH 7.4 and pH 3 conditions. The swelling kinetics of the s-IPN were dependent on pH (7.4, 3 and 1), and temperature (25 and 37℃). The interpenetrated polymer chains reduced the internal pore sizes of crosslinked network without altering its elastic, solid-like behavior. The loading and in vitro release of 5-fluorouracil, a chemotherapeutic agent, from hydrogel systems were studied at different temperature and pH values. The hydrogels showed a sustained drug release up to 5 h at 37℃, in different pH media. The s-IPN exhibited a promising performance for a range of biomedical applications, in particular, for the controlled drug delivery in response to the pH and temperature conditions.

Fractional Sliding Mode Control of Underwater ROVs subject to Non-differentiable Disturbances

Aldo-Jonathan Muñoz-Vázquez,Heriberto Ramírez-Rodríguez,Vicente Parra-Vega,Anand Sánchez-Orta 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

Some hydrodynamic phenomena of an underwater Remotely Operated Vehicle (ROV), such as turbulence,cavitation, and multi-phase fluidic regimes, are associated to continuous but nowhere differentiable functions. These disturbances stand as complex forces potentially influencing the ROVs during typical navigation tasks. In thispaper, the tracking control of a ROV subject to nonsmooth Hölder disturbances is proposed based on a fractionalorderrobust controller that ensures exponential tracking. Notably, the controller gives rise to a closed-loop systemwith the following characteristics: a) continuous control signal that alleviates chattering effects; b) the fractionalsliding motion is substantiated on a proposed resetting memory principle; c) the control is robust to model uncertainties;and d) exact rejection of Hölder disturbances in finite-time. A representative simulation study reveals thefeasibility of the proposed scheme.

Dye-Perfused Human Placenta for Simulation in a Microsurgery Laboratory for Plastic Surgeons

Zambrano-Jerez Laura C.,Díaz-Santamaría Karen D.,Rodríguez-Santos María A.,Alarcón-Ariza Diego F.,Meléndez-Flórez Genny L.,Ramírez-Blanco Mónica A. 대한성형외과학회 2023 Archives of Plastic Surgery Vol.50 No.6

In recent decades, a number of simulation models for microsurgical training have been published. The human placenta has received extensive validation in microneurosurgery and is a useful instrument to facilitate learning in microvascular repair techniques as an alternative to using live animals. This study uses a straightforward, step-by-step procedure for instructing the creation of simulators with dynamic flow to characterize the placental vascular tree and assess its relevance for plastic surgery departments. Measurements of the placental vasculature and morphological characterization of 18 placentas were made. After the model was used in a basic microsurgery training laboratory session, a survey was given to nine plastic surgery residents, two microsurgeons, and one hand surgeon. In all divisions, venous diameters were larger than arterial diameters, with minimum diameters of 0.8 and 0.6 mm, respectively. The majority of the participants considered that the model faithfully reproduces a real microsurgical scenario; the consistency of the vessels and their dissection are similar in in vivo tissue. Furthermore, all the participants considered that this model could improve their surgical technique and would propose it for microsurgical training. As some of the model's disadvantages, an abundantly thick adventitia, a thin tunica media, and higher adherence to the underlying tissue were identified. The color-perfused placenta is an excellent tool for microsurgical training in plastic surgery. It can faithfully reproduce a microsurgical scenario, offering an abundance of vasculature with varying sizes similar to tissue in vivo, enhancing technical proficiency, and lowering patient error.

Carbon Storage Regulator A (csrA) Gene Regulates Motility and Growth of Bacillus licheniformis in the Presence of Hydrocarbons

Laura Iztacihuatl Serrano Ángel,Daniel Segura,Jeiry Toribio Jiménez,Miguel Ángel Rodríguez Barrera,Carlos Ortuño Pineda,Yanet Romero Ramírez 한국미생물·생명공학회 2020 한국미생물·생명공학회지 Vol.48 No.2

The global carbon storage regulator (Csr) system is conserved in bacteria and functions as a regulator in the exponential and stationary phases of growth in batch culture. The Csr system plays a role in the central carbon metabolism, virulence, motility, resistance to oxidative stress, and biofilm formation. Although the Csr was extensively studied in Gram negative bacteria, it has been reported only in the control of motility in Bacillus subtilis among Gram positive bacteria. The goal of this study was to explore the role of the csrA gene of Bacillus licheniformis M2-7 on motility and the bacterial ability to use hydrocarbons as carbon source. We deleted the csrA gene of B. licheniformis M2-7 using the plasmid pCsr-L, harboring the spectinomycin cassette obtained from the plasmid pHP45-omega2. Mutants were grown on culture medium supplemented with 2% glucose or 0.1% gasoline and motility was assessed by electron microscopy. We observed that CsrA negatively regulates motility by controlling the expression of the hag gene and the synthesis of flagellin. Notably, we showed the ability of B. licheniformis to use gasoline as a unique carbon source. Our results demonstrated that CsrA is an indispensable regulator for the growth of B. licheniformis M2-7 on gasoline.

Brucella melitensis omp31 Mutant Is Attenuated and Confers Protection Against Virulent Brucella melitensis Challenge in BALB/c Mice

L Verdiguel-Fernández,R Oropeza-Navarro,Adolfo Ortiz,MG Robles-Pesina,J Ramírez-Lezama,A Castañeda-Ramírez,A Verdugo-Rodríguez 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.4

For control of brucellosis in small ruminants, attenuated B. melitensis Rev1 is used but it can be virulent for animals and human. Based on these aspects, it is essential to identify potential immunogens to avoid these problems in prevention of brucellosis. The majority of OMPs in the Omp25/31 family have been studied because these proteins are relevant in maintaining the integrity of the outer membrane but their implication in the virulence of the different species of this genus is not clearly described. Therefore, in this work we studied the role of Omp31 on virulence by determining the residual virulence and detecting lesions in spleen and testis of mice inoculated with the B. melitensis LVM31 mutant strain. In addition, we evaluated the conferred protection in mice immunized with the mutant strain against the challenge with the B. melitensis Bm133 virulent strain. Our results showed that the mutation of omp31 caused a decrease in splenic colonization without generating apparent lesions or histopathological changes apparent in both organs in comparison with the control strains and that the mutant strain conferred similar protection as the B. melitensis Rev1 vaccine strain against the challenge with B. melitensis Bm133 virulent strain. These results allow us to conclude that Omp31 plays an important role on the virulence of B. melitensis in the murine model, and due to the attenuation shown by the strain, it could be considered a vaccine candidate for the prevention of goat brucellosis.