Novel spatial domain integral equation formulation for the analysis of rectangular waveguide steps close to arbitrarily shaped dielectric and/or conducting posts

[EN] In this paper, a novel integral equation formulation expressed in the spatial domain is proposed for the analysis of rectangular waveguide step discontinuities. The important novelty of the proposed formulation is that which allows to easily take into account the electrical influence of a given number of arbitrarily shaped conducting and dielectric posts placed close to the waveguide discontinuity. For the sake of simplicity, and without loss of generality, the presented integral equation has been particularized and solved for inductive rectangular waveguide geometry. In this case, the integral equation mixed-potentials kernel is written in terms of parallel plate Green¿s functions with an additional ground plane located on the waveguide step. Therefore, the unknowns of the problem are reduced to an equivalent magnetic surface current on the step aperture and equivalent magnetic and electric surface currents on the dielectric and conducting posts close to the discontinuity. The numerical solution of the final integral equation is efficiently computed after the application of acceleration techniques for the slowly convergent series representing the Green¿s functions of the problem. The numerical method has been validated through several simulation examples of practical microwave devices, including compact size band-pass cavity filters and coupled dielectric resonators filters. The results have been compared to those provided by commercial full-wave electromagnetic simulation software packages, showing in all cases a very good agreement, and with substantially enhanced numerical efficiencies.This research work has been financially supported by the Spanish Ministerio de Economia y Competitividad in the frame of the projects "Demostradores Tecnologicos de Filtros y Multiplexores con Respuestas Selectivas y Sintonizables en Nuevas Guias Compactas para Aplicaciones Espaciales (COMPASSES)" with Ref. TEC2016-75934-C4-1-R, and "Analisis y Diseno de Nuevos Componentes en Microondas y Milimetricas para Comunicaciones por Satelite (MILISAT)" with Ref. TEC2016-75934-C4-4-R. As an additional financial source we thank the regional agency Fundacion Seneca from Region de Murcia under the research project "Desarrollo de Antenas y Componentes Pasivos de Microondas para Sistemas Avanzados de Comunicaciones" with Ref. 19494/PI/14 and Ref. 20147/EE/17, and the PhD scholarship granted by the Spanish national Ministerio de Educacion, Cultura y Deporte with Ref. FPU15/02883. All results of this paper can be reproduced by using the data and information contained in the drawings and in the captions of the figures included in the paper.Quesada Pereira, FD.; Gomez Molina, C.; Alvarez Melcon, A.; Boria Esbert, VE.; Guglielmi, M. (2018). Novel spatial domain integral equation formulation for the analysis of rectangular waveguide steps close to arbitrarily shaped dielectric and/or conducting posts. 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D., Cañete Rebenaque, D., Pascual-García, J., & Alvarez-Melcon, A. (2007). Efficient integral equation formulation for inductive waveguide components with posts touching the waveguide walls. Radio Science, 42(6). doi:10.1029/2006rs003591POGGIO, A. J., & MILLER, E. K. (1973). Integral Equation Solutions of Three-dimensional Scattering Problems. Computer Techniques for Electromagnetics, 159-264. doi:10.1016/b978-0-08-016888-3.50008-8Quesada Pereira , F. Boria , V. E. Gimeno , B. Cañete Rebenaque , D. Pascual Garcia , J. Alvarez Melcon , A. 2006 Investigation of multipaction phenomena in inductively coupled passive waveguide components for space applications IEEE MTT-S International Microwave Symposium Digest 246 249 San Francisco, CAPereira, F. D. Q., Esbert, V. E. B., Garcia, J. P., Ana Vidal Pantaleoni, Melcon, A. A., Tornero, J. L. G., & Gimeno, B. (2007). Efficient Analysis of Arbitrarily Shaped Inductive Obstacles in Rectangular Waveguides Using a Surface Integral-Equation Formulation. IEEE Transactions on Microwave Theory and Techniques, 55(4), 715-721. doi:10.1109/tmtt.2007.893673Quesada Pereira, F. D., Vera Castejón, P., Álvarez Melcón, A., Gimeno, B., & Boria Esbert, V. E. (2011). An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits. Radio Science, 46(2), n/a-n/a. doi:10.1029/2010rs004458Stumpf, M., & Leone, M. (2009). Efficient 2-D Integral Equation Approach for the Analysis of Power Bus Structures With Arbitrary Shape. IEEE Transactions on Electromagnetic Compatibility, 51(1), 38-45. doi:10.1109/temc.2008.2009223Wei, X.-C., Li, E.-P., Liu, E.-X., & Cui, X. (2008). Efficient Modeling of Rerouted Return Currents in Multilayered Power-Ground Planes by Using Integral Equation. IEEE Transactions on Electromagnetic Compatibility, 50(3), 740-743. doi:10.1109/temc.2008.924392Huapeng Zhao, En-Xiao Liu, Jun Hu, & Er-Ping Li. (2014). Fast Contour Integral Equation Method for Wideband Power Integrity Analysis. IEEE Transactions on Components, Packaging and Manufacturing Technology, 4(8), 1317-1324. doi:10.1109/tcpmt.2014.232724

Ensayos galénicos de formas sólidas orales de acción retardada: Revisión de técnicas y dispositivos

Se estudian los ensayos galénicos a que se someten las formas farmacéuticas de administración oral y acción retardada y, en especial, los de liberación de la sustancia activa "in vitro". Aunque la revisión de las distintas técnicas y dispositivos se realiza con cierto detalle, se presta especial atención a la descripción de un método original para el estudio de la disgregación-disolución de las formas antes aludidas, con un sistema de medida continuo y directo, ya utilizado en el ensayo de formas sólidas de dosificación convencional y aplicado posteriormente en trabajos experimentales a preparados de acción prolongada. Se mencionan asimismo, los ensayos "in vivo" y clínicos con el fin de ofrecer una visión de conjunto sobre el control de las preparaciones sólidas de acción retardada, facilitando el acceso a los trabajes experimentales que sobre el tema puedan desarrollarse

Biorefinery of biomass of agro-Industrial banana waste to obtain high-value biopolymers

On a worldwide scale, food demand is increasing as a consequence of global population growth. This makes companies push their food supply chains’ limits with a consequent increase in generation of large amounts of untreated waste that are considered of no value to them. Biorefinery technologies offer a suitable alternative for obtaining high-value products by using unconventional raw materials, such as agro-industrial waste. Currently, most biorefineries aim to take advantage of specific residues (by either chemical, biotechnological, or physical treatments) provided by agro-industry in order to develop high-value products for either in-house use or for sale purposes. This article reviews the currently explored possibilities to apply biorefinery-known processes to banana agro-industrial waste in order to generate high-value products out of this residual biomass source. Firstly, the Central and Latin American context regarding biomass and banana residues is presented, followed by advantages of using banana residues as raw materials for the production of distinct biofuels, nanocellulose fibers, different bioplastics, and other high-value products Lastly, additional uses of banana biomass residues are presented, including energy generation and water treatmen

Influence of the aqueous matrix on the degradation of cyanotoxins by CWPO: a study on the Iberian Peninsula freshwaters

The increasing occurrence of toxic cyanobacterial blooms worldwide represents a critical health and environmental risk. Catalytic wet peroxide oxidation (CWPO) has emerged as an efficient and environmentally friendly technology for the removal of cyanotoxins in water. Nevertheless, its effectiveness has just been demonstrated in deionized water or simple synthetic aqueous matrices. In this work, the effect of the different components of the aqueous matrix on the CWPO of cyanotoxins was deeply evaluated considering the widespread properties of the Iberian Peninsula freshwaters. The presence of Cl-, HCO3- and SO42- ions reduced the oxidation rate of cylindrospermopsin (CYN) up to 70–80% at the highest concentrations tested (2000, 250 and 500 mg L−1 for Cl-, HCO3- and SO42-, respectively) due to their hydroxyl radical scavenging capacity. The presence of natural organic matter (NOM) resulted in a similar outcome (oxidation rate reduction up to 90% at the highest concentration tested, 20 mg L−1), but in this case due to the consumption of hydroxyl radicals in competition with CYN oxidation. The presence of NO3- and H2PO4- did not show any significant effect on CYN oxidation. Similarly, the presence of cyanobacteria (Chrysosporum ovalisporum, 50 µg chlorophyll-a L−1) did not appreciably affect the CYN oxidation rate. These results were consistent with those obtained by evaluating the impact of real aqueous matrices from drinking water treatment plants (DWTPs) located in Castilla y León and Extremadura regions (Spain) on CWPO performance. This knowledge is key to the implementation of the technology for the treatment of surface waters affected by toxic cyanobacterial bloomsThis research has been supported by the CYTED Ibero-American Science and Technology Program for Development (CYTED-2019) through the project TALGENTOX (PCI2020–112013) and by Spanish Ministry for Science and Innovation (MICINN) through the project PID2019–105079RB-I00. D. Ortiz thanks the Spanish Ministry of Universities (MIU) for the FPU predoctoral grant (FPU19/04816). M. Munoz thanks the Spanish MINECO for the Ramon ´ y Cajal postdoctoral contract (RYC-2016–20648). We especially thank Aqualia for providing the water samples from DWTPs employed in this study, which was performed in the framework of Rewaise project (http://rewaise.eu

Magnetic domains on magnetite islands: from XMCD-PEEM to micromagnetism

Oral presentation given at the 13th European Conference on Surface Crystallography and Dynamics, held in Donostia-San Sebastián, Spain, on June 19-21th, 2017.Magnetite nanostructures and thin films have been grown in spintronic devices such as spin valves in order to take advantage of the high Curie temperature, stability, and predicted half-metal character. However, thin films present magnetic properties which are rather different from the properties of bulk magnetite: high coercive fields, high saturation fields, out-of-plane magnetization, superparamagnetism in ultrathin films, or unexpected easy-axes. An explanation for these effects are growth defects, among which antiphase domain boundaries (APBs) are the best example. In the present work, we study the magnetic domains on flat single-crystal magnetite and other mixed spinels grown on Ru(0001) by molecular beam epitaxy [1,2]. As each island grows from a single nucleus, there are expected to be free of APBs. We have measured with nanometer-resolution the 3D magnetization of the islands by combining x-ray magnetic circular dichroism images acquired in a photoemission electron microscope at different azimuthal angles. The 3D magnetization maps have been used as the initial magnetization configuration for micromagnetic simulations of islands with the same lateral and vertical dimensions as the experimental ones. The Mumax3 software has been used to perform the micromagnetic simulations. By comparing the evolution of the micromagnetic simulations with the experimental behavior of the islands after annealing, we seek to validate the material parameters that define their magnetic behavior and to identify cases where defects or other effects play a role

FeCo Nanowire-Strontium Ferrite Powder Composites for Permanent Magnets with High-Energy Products

Due to the issues associated with rare-earth elements, there arises a strong need for magnets with properties between those of ferrites and rare-earth magnets that could substitute the latter in selected applications. Here, we produce a high remanent magnetization composite bonded magnet by mixing FeCo nanowire powders with hexaferrite particles. In the first step, metallic nanowires with diameters between 30 and 100 nm and length of at least 2 {\mu}m are fabricated by electrodeposition. The oriented as-synthesized nanowires show remanence ratios above 0.76 and coercivities above 199 kA/m and resist core oxidation up to 300 {\deg}C due to the existence of a > 8 nm thin oxide passivating shell. In the second step, a composite powder is fabricated by mixing the nanowires with hexaferrite particles. After the optimal nanowire diameter and composite composition are selected, a bonded magnet is produced. The resulting magnet presents a 20% increase in remanence and an enhancement of the energy product of 48% with respect to a pure hexaferrite (strontium ferrite) magnet. These results put nanowire-ferrite composites at the forefront as candidate materials for alternative magnets for substitution of rare earths in applications that operate with moderate magnet performance

Origin, genomic diversity and microevolution of the clostridium difficile b1/nap1/rt027/st01 strain in costa rica, chile, honduras and mexico

Indexación: Scopus.Clostridium difficile B1/NAP1/RT027/ST01 has been responsible for outbreaks of antibiotic-associated diarrhoea in clinical settings worldwide and is associated with severe disease presentations and increased mortality rates. Two fluoroquinolone-resistant (FQR) lineages of the epidemic B1/NAP1/RT027/ST01 strain emerged in the USA in the early 1990s and disseminated trans continentally (FQR1 and FQR2). However, it is unclear when and from where they entered Latin America (LA) and whether isolates from LA exhibit unique genomic features when compared to B1/NAP1/RT027/ST01 isolates from other regions of the world. To answer the first issue we compared whole-genome sequences (WGS) of 25 clinical isolates typed as NAP1, RT027 or ST01 in Costa Rica (n=16), Chile (n=5), Honduras (n=3) and Mexico (n=1) to WGS of 129 global isolates from the same genotype using Bayesian phylogenomics. The second question was addressed through a detailed analysis of the number and type of mutations of the LA isolates and their mobile resistome. All but two B1/NAP1/RT027/ST01 isolates from LA belong to the FQR2 lineage (n=23, 92 %), confirming its widespread distribution. As indicated by analysis of a dataset composed of 154 WGS, the B1/NAP1/RT027/ST01 strain was introduced into the four LA countries analysed between 1998 and 2005 from North America (twice) and Europe (at least four times). These events occurred soon after the emergence of the FQR lineages and more than one decade before the first report of the detection of the B1/NAP1/RT027/ST01 in LA. A total of 552 SNPs were identified across all genomes examined (3.8–4.3 Mb) in pairwise comparisons to the R20291 reference genome. Moreover, pairwise SNP distances were among the smallest distances determined in this species so far (0 to 55). Despite this high level of genomic conservation, 39 unique SNPs (7 %) in genes that play roles in the infection process (i.e. slpA) or antibiotic resistance (i.e. rpoB, fusA) distinguished the LA isolates. In addition, isolates from Chile, Honduras and Mexico had twice as many antibiotic resistance genes (ARGs, n=4) than related isolates from other regions. Their unique set of ARGs includes a cfr-like gene and tetM, which were found as part of putative mobile genetic elements whose sequences resemble undescribed integrative and conjugative elements. These results show multiple, independent introductions of B1/NAP1/RT027/ ST01 isolates from the FQR1 and FQR2 lineages from different geographical sources into LA and a rather rapid accumulation of distinct mutations and acquired ARG by the LA isolates.https://www.microbiologyresearch.org/content/journal/mgen/10.1099/mgen.0.00035

Dense strontium hexaferrite-based permanent magnet composites assisted by cold sintering process

[EN] The use of rare-earth-based permanent magnets is one of the critical points for the development of the current technology. On the one hand, industry of the rare-earths is highly polluting due to the negative environmental impact of their extraction and, on the other hand, the sector is potentially dependent on China. Therefore, investigation is required both in the development of rare-earth-free permanent magnets and in sintering processes that enable their greener fabrication with attractive magnetic properties at a more competitive price. This work presents the use of a cold sintering process (CSP) followed by a post-annealing at 1100 °C as a new way to sinter composite permanent magnets based on strontium ferrite (SFO). Composites that incorporate a percentage ≤ 10% of an additional magnetic phase have been prepared and the morphological, structural and magnetic properties have been evaluated after each stage of the process. CSP induces a phase transformation of SFO in the composites, which is partially recovered by the post-thermal treatment improving the relative density to 92% and the magnetic response of the final magnets with a coercivity of up to 3.0 kOe. Control of the magnetic properties is possible through the composition and the grain size in the sintered magnets. These attractive results show the potential of the sintering approach as an alternative to develop modern rare-earth-free composite permanent magnets.This work has been supported by the Ministerio Español de Ciencia e Innovación (MICINN), Spain, through the projects MAT2017-86540-C4-1-R and RTI2018-095303-A-C52, and by the European Commission through Project H2020 No. 720853 (Amphibian). C.G.-M. and A.Q. acknowledge financial support from MICINN through the “Juan de la Cierva” program (FJC2018-035532-I) and the “Ramón y Cajal” contract (RYC-2017-23320). S. R.-G. gratefully acknowledges the financial support of the Alexander von Humboldt foundation, Germany. A.S. acknowledges the financialsupport from the Comunidad de Madrid, Spain, for an “Atracción de Talento Investigador” contract (No. 2017-t2/IND5395)

Cfr(B), cfr(C), and a New cfr-Like Gene, cfr(E), in Clostridium difficile Strains Recovered across Latin America

Indexación: Scopus.Cfr is a radical S-adenosyl-L-methionine (SAM) enzyme that confers cross-resistance to antibiotics targeting the 23S rRNA through hypermethylation of nucleotide A2503. Three cfr-like genes implicated in antibiotic resistance have been described, two of which, cfr(B) and cfr(C), have been sporadically detected in Clostridium difficile. However, the methylase activity of Cfr(C) has not been confirmed. We found cfr(B), cfr(C), and a cfr-like gene that shows only 51 to 58% protein sequence identity to Cfr and Cfr-like enzymes in clinical C. difficile isolates recovered across nearly a decade in Mexico, Honduras, Costa Rica, and Chile. This new resistance gene was termed cfr(E). In agreement with the anticipated function of the cfrlike genes detected, all isolates exhibited high MIC values for several ribosome-targeting antibiotics. In addition, in vitro assays confirmed that Cfr(C) and Cfr(E) methylate Escherichia coli and, to a lesser extent, C. difficile 23S rRNA fragments at the expected positions. The analyzed isolates do not have mutations in 23S rRNA genes or genes encoding the ribosomal proteins L3 and L4 and lack poxtA, optrA, and pleuromutilin resistance genes. Moreover, these cfr-like genes were found in Tn6218-like transposons or integrative and conjugative elements (ICE) that could facilitate their transfer. These results indicate selection of potentially mobile cfr-like genes in C. difficile from Latin America and provide the first assessment of the methylation activity of Cfr(C) and Cfr(E), which belong to a cluster of Cfr-like proteins that does not include the functionally characterized enzymes Cfr, Cfr(B), and Cfr(D).https://journals.asm.org/doi/10.1128/AAC.01074-1

High accuracy 234U(n,f) cross section in the resonance energy region

New results are presented of the 234U neutron-induced fission cross section, obtained with high accuracy in the resonance region by means of two methods using the 235U(n,f) as reference. The recent evaluation of the 235U(n,f) obtained with SAMMY by L. C. Leal et al. (these Proceedings), based on previous n-TOF data [1], has been used to calculate the 234U(n,f) cross section through the 234U/235U ratio, being here compared with the results obtained by using the n-TOF neutron flux