479 results on '"Jaime Gomez"'
Search Results
2. Urban-rural disparities in COVID-19 hospitalisations and mortality: A population-based study on national surveillance data from Germany and Italy.
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Simona Bignami-Van Assche, Federico Ferraccioli, Nicola Riccetti, Jaime Gomez-Ramirez, Daniela Ghio, and Nikolaos I Stilianakis
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Medicine ,Science - Abstract
PurposeRecent literature has highlighted the overlapping contribution of demographic characteristics and spatial factors to urban-rural disparities in SARS-CoV-2 transmission and outcomes. Yet the interplay between individual characteristics, hospitalisation, and spatial factors for urban-rural disparities in COVID-19 mortality have received limited attention.MethodsTo fill this gap, we use national surveillance data collected by the European Centre for Disease Prevention and Control and we fit a generalized linear model to estimate the association between COVID-19 mortality and the individuals' age, sex, hospitalisation status, population density, share of the population over the age of 60, and pandemic wave across urban, intermediate and rural territories.FindingsWe find that in what type of territory individuals live (urban-intermediate-rural) accounts for a significant difference in their probability of dying given SARS-COV-2 infection. Hospitalisation has a large and positive effect on the probability of dying given SARS-CoV-2 infection, but with a gradient across urban, intermediate and rural territories. For those living in rural areas, the risk of dying is lower than in urban areas but only if hospitalisation was not needed; while for those who were hospitalised in rural areas the risk of dying was higher than in urban areas.ConclusionsTogether with individuals' demographic characteristics (notably age), hospitalisation has the largest effect on urban-rural disparities in COVID-19 mortality net of other individual and regional characteristics, including population density and the share of the population over 60.
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- 2024
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3. An epidemiological model for mosquito host selection and temperature-dependent transmission of West Nile virus
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Augusto Fasano, Nicola Riccetti, Anastasia Angelou, Jaime Gomez-Ramirez, Federico Ferraccioli, Ioannis Kioutsioukis, and Nikolaos I. Stilianakis
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Medicine ,Science - Abstract
Abstract We extend a previously developed epidemiological model for West Nile virus (WNV) infection in humans in Greece, employing laboratory-confirmed WNV cases and mosquito-specific characteristics of transmission, such as host selection and temperature-dependent transmission of the virus. Host selection was defined by bird host selection and human host selection, the latter accounting only for the fraction of humans that develop symptoms after the virus is acquired. To model the role of temperature on virus transmission, we considered five temperature intervals (≤ 19.25 °C; > 19.25 and 26.75 °C). The capacity of the new model to fit human cases and the week of first case occurrence was compared with the original model and showed improved performance. The model was also used to infer further quantities of interest, such as the force of infection for different temperatures as well as mosquito and bird abundances. Our results indicate that the inclusion of mosquito-specific characteristics in epidemiological models of mosquito-borne diseases leads to improved modelling capacity.
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- 2022
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4. O-25 ASSESSMENT OF MODELS FOR PREDICTING RESPONSE TO CORTICOIDS TREATMENT IN ALCOHOL-ASSOCIATED HEPATITIS: A GLOBAL COHORT STUDY
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Francisco Idalsoaga, Luis Antonio Díaz, Gustavo Ayares, Jorge Arnold, Winston Dunn, Yanming Li, Ashwani Singal, Doug Simonetto, María Ayala-Valverde, Diego Perez, Jaime Gomez, Rodrigo Escarate, Eduardo Fuentes-López, Carolina A Ramirez, Dalia Morales-Arraez, Wei Zhang, Steve Qian, Joseph Ahn, Seth Buryska, Heer Mehta, Muhammad Waleed, Horia Stefanescu, Adelina Horhat, Andreea Bumbu, Bashar Attar, Rohit Grawal, Joaquín Cabezas, Inés García-Carrera, Berta Cuyàs, Maria Poca, German Soriano Pastor, Shiv K Sarin, Rakhi Maiwall, Prasun K Jalal, María Fátima Higuera-De La Tijera, Anand Kulkarni, Nagaraja Rao P, Patricia Guerra Salazar, Lubomir Skladaný, Natália Bystrianska, Veronica Prado, Ana Clemente-Sanchez, Diego Rincón, Tehseen Haider, Kristina R Chacko, Gustavo A Romero, Florencia D Pollarsky, Juan Carlos Restrepo, Luis G Toro, Pamela Yaquich, Manuel Mendizabal, Maria Laura Garrido, Sebastian Marciano, Melisa Dirchwolf, Victor Vargas, Cesar Jimenez, Guadalupe García-Tsao, Guillermo Ortiz, Juan G Abraldes, Patrick Kamath, Marco Arrese, Vijay Shah, Ramon Bataller, and Juan Pablo Arab
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Specialties of internal medicine ,RC581-951 - Abstract
Introduction and Objectives: Alcohol-associated hepatitis (AH) is a severe entity associated with high mortality. Corticosteroids might be used in cases with severe disease and several dynamic models can predict mortality and response to corticosteroids in AH patients. However, there is no consensus on the best of them. This study aimed to evaluate dynamic models to predict response to corticosteroid treatment based on short-term mortality in patients with severe AH based on a worldwide cohort. Materials and Methods: A retrospective cohort study of patients with severe AH (between 2009 – 2019). We included patients who received corticosteroid treatment and calculated the Lille model of day 4 (Lille-4), day 7 (Lille-7) (cut-off value ≥0.45), and the Trajectory of Serum Bilirubin (TSB)(cut-off value ≥0.8 of the ratio between bilirubin at admission and day 7) to predict mortality. We estimated up to 30-day survival using Kaplan-Meier curves, and we performed multivariable analyzes using Cox regression. Specifically, we constructed two models to compare Lille-4 vs. TSB and Lille-7 vs. TSB, adjusting by well-known clinical variables associated with higher mortality in AH (age, sex, and creatinine at admission). Results: 1,066 patients were included (30 centers, 10 countries), age 47.7 ± 10.9 years, 30% women. The MELD score on admission was 25 [21-30]. Responders were considered by Lille-4 49.1%, Lille-7 46.6%, and TSB 55.4%. In the first Cox regression, we observed that Lille-4 and TSB predicted 30-day mortality (HR 3.0, 95%CI: 1.7-5.1; p
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- 2023
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5. OP-5 ALCOHOL-ASSOCIATED HEPATITIS IN LATIN AMERICA: RESULTS FROM THE AH-LATIN STUDY
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Luis Antonio Díaz, Jorge Arnold, Francisco Idalsoaga, Gustavo Ayares, María Ayala-Valverde, Diego Perez, Jaime Gomez, Rodrigo Escarate, Juan Pablo Roblero, Blanca Norero, José Antonio Velarde, Janett Jacobo, Jesús Varela, Scherezada Mejía Loza, Jacqueline Córdova, Rita Silva, Cristina Melo Rocha, Roberta C. Araujo, Gustavo Henrique Pereira, Claudia Couto, Fernando Bessone, Mario Tanno, Gustavo Romero, Manuel Mendizabal, Sebastián Marciano, Melisa Dirchwolf, Pedro Montes, Patricia Guerra Salazar, Geraldine Ramos, Juan Carlos Restrepo, Gabriel Díaz, Luis Guillermo Toro, Enrique Carrera, Brahmania Mayur, Singal Ashwani, Bataller Ramon, Shah Vijay, Kamath Patrick S., Marco Arrese, and Juan Pablo Arab
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Specialties of internal medicine ,RC581-951 - Abstract
Introduction and Objectives: Severe alcohol-associated hepatitis (AH) is an entity with high morbidity and mortality; however, data in Latin America is limited. We aimed to characterize patients hospitalized for AH in a multinational cohort in Latin America. Materials and Methods: Multicenter prospective cohort study. We included patients admitted with severe AH between 2015-2022. Sociodemographic and clinical information was recorded. The analysis included survival analysis using Kaplan-Meier curves. This study was approved by the institutional ethics committee. Results: 470 patients from 24 centers (8 countries: Mexico, Chile, Argentina, Brazil, Peru, Bolivia, Colombia, and Ecuador) were included. Age 49.8 ± 10.6 years, 85.6% of men and 45% had a previous diagnosis of cirrhosis. Median MELD at admission was 26.9 [22-32] points. 26.5% met SIRS criteria and 34.3% had an acute kidney injury (AKI) on admission. Only 36.8% of patients were treated with corticosteroids. Survival at 30 days was 75.0% (95%CI: 70.1-79.3%) and 62.8% (95%CI: 57.1-68.0%) at 90 days. A total of 191 (45.8%) patients presented infections, 31.4% at admission and 24.9% during hospitalization. The most frequent locations of community-acquired infections were respiratory (33.5%), urinary (32.1%), spontaneous bacterial peritonitis (14.9%), and skin (10.5%), while the most frequent pathogens were Escherichia coli (40%), Klebsiella pneumoniae (12%), and Enterococcus (6%). The presence of infection at admission was associated with a decreased survival at 90-days (66.9% versus 48.1%, p=0.0002). AKI at admission was also associated with decreased survival at 90-days (86.8% versus 51.3%, p
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- 2023
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6. Improving Human Activity Recognition Integrating LSTM With Different Data Sources: Features, Object Detection and Skeleton Tracking
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Jaime Duque Domingo, Jaime Gomez-Garcia-Bermejo, and Eduardo Zalama
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Human activity recognition ,HAR ,recurrent neural network ,LSTM ,YOLO ,OpenPose ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
Over the past few years, technologies in the field of computer vision have greatly advanced. The use of deep neural networks, together with the development of computing capabilities, has made it possible to solve problems of great interest to society. In this work, we focus on one such problem that has seen a great development, the recognition of actions in live videos. Although the problem has been oriented in different ways in the literature, we have focused on indoor residential environments, such as a house or a nursing home. Our system can be used to understand what actions a person or group of people are carrying out. Two of the approaches used to solve the problem have been 3D convolution networks and recurrent networks. In our case, we have created a model that accurately combines several recurrent networks with processed data from different techniques: image feature extraction, object detection and people’s skeletons. The need to integrate these three techniques arises from the search to improve the detection of certain actions by taking advantage of the best recognition offered by each of the methods. In a complete experimentation, where several techniques have been evaluated against different datasets, the classification of the actions has been improved with respect to the existing models.
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- 2022
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7. Host selection and forage ratio in West Nile virus-transmitting Culex mosquitoes: Challenges and knowledge gaps.
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Nicola Riccetti, Augusto Fasano, Federico Ferraccioli, Jaime Gomez-Ramirez, and Nikolaos I Stilianakis
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Arctic medicine. Tropical medicine ,RC955-962 ,Public aspects of medicine ,RA1-1270 - Abstract
BackgroundTo date, no specific therapy or vaccination is available for West Nile virus (WNV) infections in humans; preventive strategies represent the only possibility to control transmission. To focus these strategies, detailed knowledge of the virus dynamics is of paramount importance. However, several aspects of WNV transmission are still unclear, especially regarding the role of potential vertebrate host species. Whereas mosquitoes' intrinsic characteristics cause them to favour certain hosts (host preference), absolute selection is impossible in natural settings. Conversely, the selection carried out among available hosts and influenced from hosts' availability and other ecological/environmental factors is defined as host selection.Methodology/principal findingsIn July 2022, we searched PubMed database for original articles exploring host selection among WNV-transmitting Culex mosquitoes, the main WNV vector. We considered only original field studies estimating and reporting forage ratio. This index results from the ratio between the proportion of blood meals taken by mosquitoes on potential host species and the hosts' relative abundance. From the originally retrieved 585 articles, 9 matched the inclusion criteria and were included in this review. All but one of the included studies were conducted in the Americas, six in the United States, and one each in Mexico and Colombia. The remaining study was conducted in Italy. American Robin, Northern Cardinal, and House Finch were the most significantly preferred birds in the Americas, Common Blackbird in Italy.Conclusions/significanceAlthough ornithophilic, all observed WNV-transmitting mosquitoes presented opportunistic feeding behaviour. All the observed species showed potential to act as bridges for zoonotic diseases, feeding also on humans. All the observed mosquitoes presented host selection patterns and did not feed on hosts as expected by chance alone. The articles observe different species of mosquitoes in different environments. In addition, the way the relative host abundance was determined differed. Finally, this review is not systematic. Therefore, the translation of our results to different settings should be conducted cautiously.
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- 2022
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8. Resistive Metal Oxide Combined with Optical Gas Sensor in an Electro-optical Nose for Odour Monitoring
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Felix Melendez, Patricia Arroyo, Jaime Gomez-Suarez, José Pedro Santos, and Jesus Lozano
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Chemical engineering ,TP155-156 ,Computer engineering. Computer hardware ,TK7885-7895 - Abstract
This paper describes a prototype of artificial olfactory system or electro-optical nose (NEONOSE) containing commercially available MOX and optical (NDIR) gas sensors, forming an array of a total of 13 sensors (six MOX and seven NDIR sensors). The advantage of this configuration is to combine non-specific (MOX) and specific (NDIR) sensors to obtain an orthogonal array of sensors with a wider spectrum of responses. All the electronic circuits have been designed for this application. The prototype consists of two boards (containing different type of sensors) with two microcontrollers that communicates each other by using a digital interface. The Main Board is responsible for collecting the measurements from all the sensors and transmitting them via Bluetooth to a Smartphone. All the sensors that transmit data via I2C bus, which are all the MOX sensors and one of the optical sensors, are located on this board (main). The Secondary Board contains other NDIR sensors and is responsible for processing and sending this data to the Main Board via SPI communication. All the sensors of the Secondary Board are NDIR type. Some of them return the values in analog format, requiring the use of operational amplifiers for signal processing and analog-to-digital converters for data generation. The pre-processed data of all the sensors are sent via Bluetooth to an Android smartphone, where they are collected and stored using an own-developed application. Some measurements with different industrial gases have been done for testing the device. Keywords: metal-oxide sensors (MOX), optical sensors, electronic nose, smartphone, gas sensors.
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- 2022
9. Portable Instrumental Odour Monitoring System for Air Quality Monitoring by Citizens in Outdoor Environments
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Sergio Palomeque-Mangut, Felix Melendez, Jaime Gomez-Suarez, Patricia Arroyo, José Pedro Santos, and Jesus Lozano
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Chemical engineering ,TP155-156 ,Computer engineering. Computer hardware ,TK7885-7895 - Abstract
Air pollution is a major contributor to the global disease burden. Scientific literature has been consistent for the past decades, exposing the dangers behind hazardous air quality in both indoor and outdoor environments, and its impact on human health and ecosystems. Conventional monitoring stations are expensive and bulky, limiting the spatiotemporal resolution of the provided data. For this reason, administrations are interested in adding low-cost sensors to the monitoring network, and thus obtaining measures from multiple sources to enhance the network’s density and coverage. In this work, we present a portable Instrumental Odour Monitoring System (IOMS) consisting of an electronic device with an array of metal oxide semiconductor (MOS) gas and Particle Matter sensors connected through Bluetooth with a smartphone with our own developed app that gathers data and sends it to a cloud. We tested the device in two different experimental setups, the first with laboratory-controlled conditions and the second in field, creating a network with the help of volunteers in the city of Barcelona.
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- 2022
10. Enhanced hydrogenation catalyst synthesized by Desulfovibrio desulfuricans exposed to a radio frequency magnetic field
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Lynne E. Macaskie, John Collins, Iryna P. Mikheenko, Jaime Gomez‐Bolivar, Mohamed L. Merroun, and James A. Bennett
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Biotechnology ,TP248.13-248.65 - Abstract
Summary Desulfovibrio desulfuricans reduces Pd(II) to Pd(0)‐nanoparticles (Pd‐NPs) which are catalytically active in 2‐pentyne hydrogenation. To make Pd‐NPs, resting cells are challenged with Pd(II) ions (uptake), followed by addition of electron donor to promote bioreduction of cell‐bound Pd(II) to Pd(0) (bio‐Pd). Application of radiofrequency (RF) radiation to prepared 5 wt% bio‐Pd catalyst (60 W power, 60 min) increased the hydrogenation rate by 70% with no adverse impact on selectivity to cis‐2‐pentene. Such treatment of a 5 wt% Pd/carbon commercial catalyst did not affect the conversion rate but reduced the selectivity. Lower‐dose RF radiation (2–8 W power, 20 min) was applied to the bacteria at various stages before and during synthesis of the bio‐scaffolded Pd‐NPs. The reaction rate (μ mol 2‐pentyne converted s‐1) was increased by ~threefold by treatment during bacterial catalyst synthesis. Application of RF radiation (2 or 4 W power) to resting cells prior to Pd(II) exposure affected the catalyst made subsequently, increasing the reaction rate by 50% as compared to untreated cells, while nearly doubling selectivity for cis 2‐pentene. The results are discussed with respect to published and related work which shows altered dispersion of the Pd‐NPs made following or during RF exposure.
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- 2021
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11. Three new species of the sea fan genus Leptogorgia (Octocorallia, Gorgoniidae) from the Gulf of California, Mexico
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Osvaldo Hernández, Jaime Gomez-Gutiérrez, and Carlos Sánchez
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Zoology ,QL1-991 - Abstract
Three new sea fan species of Leptogorgia were discovered during multiple scuba diving expeditions along the Gulf of California coast and islands. Leptogorgia iridis sp. nov. is distributed in the southern region of the gulf (Mexican Province), inhabiting tropical rocky reefs of the Islas Marías Archipelago (Nayarit) and Bahía Banderas (Jalisco). This species has small colonies (< 7 cm height) with at least five clearly distinct chromotypes. Leptogorgia martirensis sp. nov. was found exclusively on the rocky reefs of San Pedro Mártir and San Esteban Islands located in the northern region of the Gulf of California (northern region of Cortez Province). Leptogorgia enrici sp. nov. is distributed from the south to the northern region of the Gulf of California (Cortez Province), inhabiting substrates of rocky reefs, sandy and pebbly sea floors. Comprehensive ecological diving expeditions to identify and classify octocorals in the Mexican Pacific (1995–2019) indicate that L. iridis sp. nov. and L. martirensis sp. nov. are likely to be micro-endemics and L. enrici sp. nov. is endemic to the Gulf of California, which defines their currently known biogeographic distribution ranges.
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- 2021
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12. A Deep Learning Image System for Classifying High Oleic Sunflower Seed Varieties
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Mikel Barrio-Conde, Marco Antonio Zanella, Javier Manuel Aguiar-Perez, Ruben Ruiz-Gonzalez, and Jaime Gomez-Gil
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classification system ,convolutional neural network ,high oleic sunflower seed ,Chemical technology ,TP1-1185 - Abstract
Sunflower seeds, one of the main oilseeds produced around the world, are widely used in the food industry. Mixtures of seed varieties can occur throughout the supply chain. Intermediaries and the food industry need to identify the varieties to produce high-quality products. Considering that high oleic oilseed varieties are similar, a computer-based system to classify varieties could be useful to the food industry. The objective of our study is to examine the capacity of deep learning (DL) algorithms to classify sunflower seeds. An image acquisition system, with controlled lighting and a Nikon camera in a fixed position, was constructed to take photos of 6000 seeds of six sunflower seed varieties. Images were used to create datasets for training, validation, and testing of the system. A CNN AlexNet model was implemented to perform variety classification, specifically classifying from two to six varieties. The classification model reached an accuracy value of 100% for two classes and 89.5% for the six classes. These values can be considered acceptable, because the varieties classified are very similar, and they can hardly be classified with the naked eye. This result proves that DL algorithms can be useful for classifying high oleic sunflower seeds.
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- 2023
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13. Prediction of concrete compressive strength through artificial neural networks
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Pablo Neira, Leonardo Bennun, Mauricio Pradena, and Jaime Gomez
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concrete mix design ,compressive strength ,laboratory tests ,artificial neural networks ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Concrete properties, including its compressive strength, are in general highly nonlinear functions of its components. Concrete mix design methods are basically simulations that require costly and time consuming adjustments in laboratory. A useful support tool based on artificial neural networks, using a multilayer perceptron network, is proposed in this paper as a means to predict compressive strength of concrete mixes. The developed models are useful for reducing the quantity of laboratory tests required for concrete mix design adjustments.
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- 2020
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14. Coupled Biohydrogen Production and Bio-Nanocatalysis for Dual Energy from Cellulose: Towards Cellulosic Waste Up-Conversion into Biofuels
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Jaime Gomez-Bolivar, Rafael L. Orozco, Alan J. Stephen, Iryna P. Mikheenko, Gary A. Leeke, Mohamed L. Merroun, and Lynne E. Macaskie
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biohydrogen ,cellulose ,hot compressed water hydrolysis ,5-hydroxymethyl furfural up-valorisation ,2,5-dimethyl furan ,liquid fuel ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Hydrogen, an emergent alternative energy vector to fossil fuels, can be produced sustainably by fermentation of cellulose following hydrolysis. Fermentation feedstock was produced hydrolytically using hot compressed water. The addition of CO2 enhanced hydrolysis by ~26% between 240 and 260 °C with comparable hydrolysis products as obtained under N2 but at a 10 °C lower temperature. Co-production of inhibitory 5-hydromethyl furfural was mitigated via activated carbon sorption, facilitating fermentative biohydrogen production from the hydrolysate by Escherichia coli. Post-fermentation E. coli cells were recycled to biomanufacture supported Pd/Ru nanocatalyst to up-convert liquid-extracted 5-HMF to 2,5-dimethyl furan, a precursor of ‘drop in’ liquid fuel, in a one-pot reaction. This side stream up-valorisation mitigates against the high ‘parasitic’ energy demand of cellulose bioenergy, potentially increasing process viability via the coupled generation of two biofuels. This is discussed with respect to example data obtained via a hydrogen biotechnology with catalytic side stream up-conversion from cellulose feedstock.
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- 2022
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15. Polaritonic Chemistry Enabled by Non-Local Metasurfaces
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Verdelli, Francesco, Wei, Yu-Chen, Joseph, Kripa, Abdelkhalik, Mohamed S., Masoumeh, Goudarzi, Askes, Sven H. C., Baldi, Andrea, Meijer, E. W., and Rivas, Jaime Gómez
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Physics - Chemical Physics ,Physics - Optics - Abstract
Vibrational strong coupling can modify chemical reaction pathways in unconventional ways. Thus far, Fabry-Perot cavities formed by pairs of facing mirrors have been mostly utilized to achieve vibrational strong coupling. In this study, we demonstrate the application of plasmonic microparticle arrays defining non-local metasurfaces that can sustain surface lattice resonances as a novel tool to enable chemical reactions under vibrational strong coupling. We show that the solvolysis kinetics of \textit{para}-nitrophenyl acetate can be accelerated by a factor of 2.7 by strong coupling to the carbonyl bond of the solvent and the solute with a surface lattice resonance. Our work introduces a new platform to investigate and control polaritonic chemical reactions. In contrast to Fabry-Perot cavities, metasurfaces define open optical cavities with single surfaces, which removes alignment hurdles, facilitating polaritonic chemistry across large areas.
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- 2024
16. Performance Evaluation of Biomass Blends with Additives Treated by Hydrothermal Carbonization
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Fidel Vallejo, Luis A. Diaz-Robles, Francisco Cubillos, Ricardo Vega, Jaime Gomez, Ernesto Pino-Cortes, Bastian Bascunan, Paulina Carcamo, Francisca Parra, Ana Urzua, and Samuel Carrasco
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Chemical engineering ,TP155-156 ,Computer engineering. Computer hardware ,TK7885-7895 - Abstract
Hydrothermal carbonization (HTC) is a thermochemical technology of biomass conversion that has some advantages: lower operating temperature than other technologies, ability to process biomass with high moisture content and generation of a final product with a higher calorific value than the original biomass and with hydrophobic characteristics. This study evaluated the influence of temperature, time, biomass blend, nature and dose of additive in the HTC process. The response variables were mass yield (MY) and higher heating value (HHV), generating a total of 128 experiments that were grouped in 8 complete factorial designs (24). Pressed olive (OLV), oat husks (AV), Pinus radiata sawdust (AS), and raps seeds (RPS) were used as raw biomass. MY and HHV had an R2 above 0.90 using the response equations of Experimental Design. Results indicate that temperature was the main effect in both responses, since it produced a decrease of MY between 5 and 10 %, and an increase of HHV between 1.5 and 2.2 MJ / kg. Use of additives did not significantly improve the energy yield. On the other hand, addition of a ‘more reactive’ biomass with increasing temperature achieved an important improvement in the HHV value. It is a positive fact because the studied biomass presents strong seasonal and geographical availability.
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- 2019
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17. Synthesis of Pd/Ru Bimetallic Nanoparticles by Escherichia coli and Potential as a Catalyst for Upgrading 5-Hydroxymethyl Furfural Into Liquid Fuel Precursors
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Jaime Gomez-Bolivar, Iryna P. Mikheenko, Rafael L. Orozco, Surbhi Sharma, Dipanjan Banerjee, Marc Walker, Rachel A. Hand, Mohamed L. Merroun, and Lynne E. Macaskie
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ruthenium bionanoparticles ,Pd/Ru core-shells ,5-hydroxymethyl furfural conversion ,2,5-dimethyl furan synthesis ,cellulose conversion ,Microbiology ,QR1-502 - Abstract
Escherichia coli cells support the nucleation and growth of ruthenium and ruthenium-palladium nanoparticles (Bio-Ru and Bio-Pd/Ru NPs). We report a method for the synthesis of these monometallic and bimetallic NPs and their application in the catalytic upgrading of 5-hydroxymethyl furfural (5-HMF) to 2,5 dimethylfuran (DMF). Examination using high resolution transmission electron microscopy with energy dispersive X-ray microanalysis (EDX) and high angle annular dark field (HAADF) showed Ru NPs located mainly at the cell surface using Ru(III) alone but small intracellular Ru-NPs (size ∼1–2 nm) were visible only in cells that had been pre-“seeded” with Pd(0) (5 wt%) and loaded with equimolar Ru. Pd(0) NPs were distributed between the cytoplasm and cell surface. Cells bearing 5% Pd/5% Ru showed some co-localization of Pd and Ru but chance associations were not ruled out. Cells loaded to 5 wt% Pd/20 wt% Ru showed evidence of core-shell structures (Ru core, Pd shell). Examination of this cell surface material using X-ray photoelectron spectroscopy (XPS) showed Pd(0) and Pd(II) and Ru(IV) and Ru(III), with confirmation by analysis of bulk material using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses. Both Bio-Ru NPs and Bio-Pd/Ru NPs were active in the conversion of 5-HMF into 2,5-DMF but commercial Ru on carbon catalyst outperformed 5 wt% bio-Ru by fourfold. While 5 wt% Pd/20 wt% Ru achieved 20% yield of DMF the performance of the 5 wt% Pd/5 wt% Ru bio-catalyst was higher and comparable to the commercial 5 wt% Ru/C catalyst in a test reaction using commercial 5-HMF (>50% selectivity). 5-HMF was prepared by thermochemical hydrolysis of starch and cellulose with solvent extraction of 5-HMF into methyltetrahydrofuran (MTHF). Here, with MTHF as the reaction solvent the commercial Ru/C catalyst had little activity (100% conversion, negligible selectivity to DMF) whereas the 5 wt% Pd/5 wt% Ru bio-bimetallic gave 100% conversion and 14% selectivity to DMF from material extracted from hydrolyzates. The results indicate a potential green method for realizing increased energy potential from biomass wastes as well as showing a bio-based pathway to manufacturing a scarcely described bimetallic material.
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- 2019
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18. Upconversion of Cellulosic Waste Into a Potential 'Drop in Fuel' via Novel Catalyst Generated Using Desulfovibrio desulfuricans and a Consortium of Acidophilic Sulfidogens
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Iryna P. Mikheenko, Jaime Gomez-Bolivar, Mohamed L. Merroun, Lynne E. Macaskie, Surbhi Sharma, Marc Walker, Rachel A. Hand, Barry M. Grail, David Barrie Johnson, and Rafael L. Orozco
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5-hydroxymethylfurfural upgrade ,5-HMF upgrade ,PdRu catalyst ,Desulfovibrio desulfuricans ,waste sulfidogenic bacteria ,Microbiology ,QR1-502 - Abstract
Biogas-energy is marginally profitable against the “parasitic” energy demands of processing biomass. Biogas involves microbial fermentation of feedstock hydrolyzate generated enzymatically or thermochemically. The latter also produces 5-hydroxymethyl furfural (5-HMF) which can be catalytically upgraded to 2, 5-dimethyl furan (DMF), a “drop in fuel.” An integrated process is proposed with side-stream upgrading into DMF to mitigate the “parasitic” energy demand. 5-HMF was upgraded using bacterially-supported Pd/Ru catalysts. Purpose-growth of bacteria adds additional process costs; Pd/Ru catalysts biofabricated using the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans were compared to those generated from a waste consortium of acidophilic sulfidogens (CAS). Methyl tetrahydrofuran (MTHF) was used as the extraction-reaction solvent to compare the use of bio-metallic Pd/Ru catalysts to upgrade 5-HMF to DMF from starch and cellulose hydrolyzates. MTHF extracted up to 65% of the 5-HMF, delivering solutions, respectively, containing 8.8 and 2.2 g 5-HMF/L MTHF. Commercial 5% (wt/wt) Ru-carbon catalyst upgraded 5-HMF from pure solution but it was ineffective against the hydrolyzates. Both types of bacterial catalyst (5wt%Pd/3-5wt% Ru) achieved this, bio-Pd/Ru on the CAS delivering the highest conversion yields. The yield of 5-HMF from starch-cellulose thermal treatment to 2,5 DMF was 224 and 127 g DMF/kg extracted 5-HMF, respectively, for CAS and D. desulfuricans catalysts, which would provide additional energy of 2.1 and 1.2 kWh/kg extracted 5-HMF. The CAS comprised a mixed population with three patterns of metallic nanoparticle (NP) deposition. Types I and II showed cell surface-localization of the Pd/Ru while type III localized NPs throughout the cell surface and cytoplasm. No metallic patterning in the NPs was shown via elemental mapping using energy dispersive X-ray microanalysis but co-localization with sulfur was observed. Analysis of the cell surfaces of the bulk populations by X-ray photoelectron spectroscopy confirmed the higher S content of the CAS bacteria as compared to D. desulfuricans and also the presence of Pd-S as well as Ru-S compounds and hence a mixed deposit of PdS, Pd(0), and Ru in the form of various +3, +4, and +6 oxidation states. The results are discussed in the context of recently-reported controlled palladium sulfide ensembles for an improved hydrogenation catalyst.
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- 2019
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19. Application of Composite Spectrum in Agricultural Machines
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Fernando Feijoo, Francisco Javier Gomez-Gil, and Jaime Gomez-Gil
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composite spectrum ,monitoring ,vibrations ,coherent ,non-coherent ,poly-coherent ,Chemical technology ,TP1-1185 - Abstract
Composite spectrum (CS) is a data-fusion technique that reduces the number of spectra to be analyzed, simplifying the analysis process for machine monitoring and fault detection. In this work, vibration signals from five components of a combine harvester (thresher, chopper, straw walkers, sieve box, and engine) are obtained by placing four accelerometers along the combine-harvester chassis in non-optimal locations. Four individual spectra (one from each accelerometer) and three CS (non-coherent, coherent and poly-coherent spectra) from 18 cases are analyzed. The different cases result from the combination of three working conditions of the components—deactivated (off), balanced (healthy), and unbalanced (faulty)—and two speeds—idle and maximum revolutions per minute (RPM). The results showed that (i) the peaks can be identified in the four individual spectra that correspond to the rotational speeds of the five components in the analysis; (ii) the three formulations of the CS retain the relevant information from the individual spectra, thereby reducing the number of spectra required for monitoring and detecting rotating unbalances within a combine harvester; and, (iii) data noise reduction is observed in coherent and poly-coherent CS with respect to the non-coherent CS and the individual spectra. This study demonstrates that the rotating unbalances of various components within agricultural machines, can be detected with a reduced number of accelerometers located in non-optimal positions, and that it is feasible to simplify the monitoring with CS. Overall, the coherent CS may be the best composite spectra formulation in order to monitor and detect rotating unbalances in agricultural machines.
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- 2020
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20. The Bioreduction of Selenite under Anaerobic and Alkaline Conditions Analogous to Those Expected for a Deep Geological Repository System
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Miguel Angel Ruiz-Fresneda, Jaime Gomez-Bolivar, Josemaria Delgado-Martin, Maria del Mar Abad-Ortega, Isabel Guerra-Tschuschke, and Mohamed Larbi Merroun
- Subjects
stenotrophomonas bentonitica ,selenite ,reduction ,alkaline ,anaerobic ,disposal ,Organic chemistry ,QD241-441 - Abstract
The environmental conditions for the planned geological disposal of radioactive waste —including hyper-alkaline pH, radiation or anoxia—are expected to be extremely harsh for microbial activity. However, it is thought that microbial communities will develop in these repositories, and this would have implications for geodisposal integrity and the control of radionuclide migration through the surrounding environment. Nuclear waste contains radioactive isotopes of selenium (Se) such as 79Se, which has been identified as one of the main radionuclides in a geodisposal system. Here, we use the bacterial species Stenotrophomonas bentonitica, isolated from bentonites serving as an artificial barrier reference material in repositories, to study the reduction of selenite (SeIV) under simulated geodisposal conditions. This bacterium is able to reduce toxic SeIV anaerobically from a neutral to alkaline initial pH (up to pH 10), thereby producing elemental selenium (Se0) nanospheres and nanowires. A transformation process from amorphous Se (a-Se) nanospheres to trigonal Se (t-Se) nanowires, through the formation of monoclinic Se (m-Se) aggregates as an intermediate step, is proposed. The lesser solubility of Se0 and t-Se makes S. bentonitica a potential candidate to positively influence the security of a geodisposal system, most probably with lower efficiency rates than those obtained aerobically.
- Published
- 2019
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21. Leaf and canopy reflectance spectrometry applied to the estimation of angular leaf spot disease severity of common bean crops.
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Víctor Martínez-Martínez, Jaime Gomez-Gil, Marley L Machado, and Francisco A C Pinto
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Medicine ,Science - Abstract
This study is aimed at (i) estimating the angular leaf spot (ALS) disease severity in common beans crops in Brazil, caused by the fungus Pseudocercospora griseola, employing leaf and canopy spectral reflectance data, (ii) evaluating the informative spectral regions in the detection, and (iii) comparing the estimation accuracy when the reflectance or the first derivative reflectance (FDR) is employed. Three data sets of useful spectral reflectance measurements in the 440 to 850 nm range were employed; measurements were taken over the leaves and canopy of bean crops with different levels of disease. A system based in Principal Component Analysis (PCA) and Artificial Neural Networks (ANN) was developed to estimate the disease severity from leaf and canopy hyperspectral reflectance spectra. Levels of disease to be taken as true reference were determined from the proportion of the total leaf surface covered by necrotic lesions on RGB images. When estimating ALS disease severity in bean crops by using hyperspectral reflectance spectrometry, this study suggests that (i) successful estimations with coefficients of determination up to 0.87 can be achieved if the spectra is acquired by the spectroradiometer in contact with the leaves, (ii) unsuccessful estimations are obtained when the spectra are acquired by the spectroradiometer from one or more meters above the crop, (iii) the red to near-infrared spectral region (630-850 nm) offers the same precision in the estimation as the blue to near-infrared spectral region (440-850), and (iv) neither significant improvements nor significant detriments are achieved when the input data to the estimation processing system are the FDR spectra, instead of the reflectance spectra.
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- 2018
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22. An SVM-Based Classifier for Estimating the State of Various Rotating Components in Agro-Industrial Machinery with a Vibration Signal Acquired from a Single Point on the Machine Chassis
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Ruben Ruiz-Gonzalez, Jaime Gomez-Gil, Francisco Javier Gomez-Gil, and Víctor Martínez-Martínez
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Support Vector Machine (SVM) ,predictive maintenance (PdM) ,agricultural machinery ,condition monitoring ,fault diagnosis ,vibration analysis ,feature extraction and selection ,pattern recognition ,Chemical technology ,TP1-1185 - Abstract
The goal of this article is to assess the feasibility of estimating the state of various rotating components in agro-industrial machinery by employing just one vibration signal acquired from a single point on the machine chassis. To do so, a Support Vector Machine (SVM)-based system is employed. Experimental tests evaluated this system by acquiring vibration data from a single point of an agricultural harvester, while varying several of its working conditions. The whole process included two major steps. Initially, the vibration data were preprocessed through twelve feature extraction algorithms, after which the Exhaustive Search method selected the most suitable features. Secondly, the SVM-based system accuracy was evaluated by using Leave-One-Out cross-validation, with the selected features as the input data. The results of this study provide evidence that (i) accurate estimation of the status of various rotating components in agro-industrial machinery is possible by processing the vibration signal acquired from a single point on the machine structure; (ii) the vibration signal can be acquired with a uniaxial accelerometer, the orientation of which does not significantly affect the classification accuracy; and, (iii) when using an SVM classifier, an 85% mean cross-validation accuracy can be reached, which only requires a maximum of seven features as its input, and no significant improvements are noted between the use of either nonlinear or linear kernels.
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- 2014
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23. The Influence of Tractor-Seat Height above the Ground on Lateral Vibrations
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Jaime Gomez-Gil, Francisco Javier Gomez-Gil, and Rebeca Martin-de-Leon
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tractor ,vibration ,whole-body vibration ,comfort ,shock ,dose ,suspension ,terrain ,health ,low-back pain ,cab ,agriculture ,Chemical technology ,TP1-1185 - Abstract
Farmers experience whole-body vibrations when they drive tractors. Among the various factors that influence the vibrations to which the driver is exposed are terrain roughness, tractor speed, tire type and pressure, rear axle width, and tractor seat height above the ground. In this paper the influence of tractor seat height above the ground on the lateral vibrations to which the tractor driver is exposed is studied by means of a geometrical and an experimental analysis. Both analyses show that: (i) lateral vibrations experienced by a tractor driver increase linearly with tractor-seat height above the ground; (ii) lateral vibrations to which the tractor driver is exposed can equal or exceed vertical vibrations; (iii) in medium-size tractors, a feasible 30 cm reduction in the height of the tractor seat, which represents only 15% of its current height, will reduce the lateral vibrations by around 20%; and (iv) vertical vibrations are scarcely influenced by tractor-seat height above the ground. The results suggest that manufacturers could increase the comfort of tractors by lowering tractor-seat height above the ground, which will reduce lateral vibrations.
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- 2014
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24. Multimodal Semi-analytical Model for Bound States in the Continuum and Unidirectional Guided Resonances in a Photonic Crystal
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Delplace, Thomas, van Loon, Tom, Liang, Minpeng, Rivas, Jaime Gómez, Maes, Bjorn, Witzens, Jeremy, editor, Poon, Joyce, editor, Zimmermann, Lars, editor, and Freude, Wolfgang, editor
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- 2024
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25. Listeriolysin S Is a Streptolysin S-Like Virulence Factor That Targets Exclusively Prokaryotic Cells In Vivo
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Juan J. Quereda, Marie A. Nahori, Jazmín Meza-Torres, Martin Sachse, Patricia Titos-Jiménez, Jaime Gomez-Laguna, Olivier Dussurget, Pascale Cossart, and Javier Pizarro-Cerdá
- Subjects
Listeria ,listeriolysin S ,streptolysin S ,cytotoxin ,epidemics ,infection ,Microbiology ,QR1-502 - Abstract
ABSTRACT Streptolysin S (SLS)-like virulence factors from clinically relevant Gram-positive pathogens have been proposed to behave as potent cytotoxins, playing key roles in tissue infection. Listeriolysin S (LLS) is an SLS-like hemolysin/bacteriocin present among Listeria monocytogenes strains responsible for human listeriosis outbreaks. As LLS cytotoxic activity has been associated with virulence, we investigated the LLS-specific contribution to host tissue infection. Surprisingly, we first show that LLS causes only weak red blood cell (RBC) hemolysis in vitro and neither confers resistance to phagocytic killing nor favors survival of L. monocytogenes within the blood cells or in the extracellular space (in the plasma). We reveal that LLS does not elicit specific immune responses, is not cytotoxic for eukaryotic cells, and does not impact cell infection by L. monocytogenes. Using in vitro cell infection systems and a murine intravenous infection model, we actually demonstrate that LLS expression is undetectable during infection of cells and murine inner organs. Importantly, upon intravenous animal inoculation, L. monocytogenes is found in the gastrointestinal system, and only in this environment LLS expression is detected in vivo. Finally, we confirm that LLS production is associated with destruction of target bacteria. Our results demonstrate therefore that LLS does not contribute to L. monocytogenes tissue injury and virulence in inner host organs as previously reported. Moreover, we describe that LlsB, a putative posttranslational modification enzyme encoded in the LLS operon, is necessary for murine inner organ colonization. Overall, we demonstrate that LLS is the first SLS-like virulence factor targeting exclusively prokaryotic cells during in vivo infections. IMPORTANCE The most severe human listeriosis outbreaks are caused by L. monocytogenes strains harboring listeriolysin S (LLS), previously described as a cytotoxin that plays a critical role in host inner tissue infection. Cytotoxic activities have been proposed as a general mode of action for streptolysin S (SLS)-like toxins, including clostridiolysin S and LLS. We now challenge this dogma by demonstrating that LLS does not contribute to virulence in vivo once the intestinal barrier has been crossed. Importantly, we show that intravenous L. monocytogenes inoculation leads to bacterial translocation to the gastrointestinal system, where LLS is specifically expressed, targeting the host gut microbiota. Our study highlights the heterogeneous modes of action of SLS-like toxins, and we demonstrate for the first time a further level of complexity for SLS-like biosynthetic clusters as we reveal that the putative posttranslational modification enzyme LlsB is actually required for inner organ colonization, independently of the LLS activity.
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- 2017
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26. Hallazgos endoscópicos y patológicos en pacientes con VIH y síntomas digestivos de un hospital universitario
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Luis Laguado, Reynaldo Rodríguez Amaya, Jaime Gomez, Rómulo Bonilla, and Gonzalo Rojas
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Sistema digestivo ,endoscopia ,infecciones por VIH ,enteropatía por HIV ,Diseases of the digestive system. Gastroenterology ,RC799-869 - Abstract
Introducción: el tracto gastrointestinal es un sitio frecuentemente afectado por el VIH; sin embargo, en la práctica clínica algunos hallazgos normales en la endoscopia pueden no serlo, lo cual conlleva a estos pacientes a no recibir tratamiento oportuno para patologías gastrointestinales. Métodos: estudio observacional descriptivo en pacientes con VIH que consultaron por síntomas digestivos y que requirieron endoscopia y/o colonoscopia durante el año 2014 en el Hospital Universitario de Santander. Se tomaron datos sociodemográficos, clínicos y paraclínicos. Se realizaron 41 endoscopias altas y 29 colonoscopias en 54 pacientes. A todo estudio se le practicó biopsia. Resultados: la edad promedio fue de 39 años, la sintomatología digestiva con mayor reporte fue la diarrea y las lesiones orales; 87% tenían conteo menor a 200 CD4, solo 24% reciben actualmente TARAE. Los diagnósticos más frecuentes por anatomía patológica diferentes a normalidad fueron: Candidiasis (17%) en esófago, gastritis crónica moderada (26,7%) en estómago y colitis crónica inespecífica moderada tanto en colon izquierdo (44,8%) como en colon derecho (51,7%). Conclusiones: los hallazgos endoscópicos y patológicos concuerdan con la frecuencia de presentaciones reportadas en la literatura, aunque no se encontraron neoplasias ni agentes infecciosos como micobacterias. Los oportunistas más frecuentes fueron la cándida y el citomegalovirus. Al confrontar el diagnóstico de normalidad entre el endoscopista y la anatomía patológica, solamente en esófago había una concordancia aceptable, a diferencia del estómago y el colon, donde la disparidad es evidente. Por lo anterior, en pacientes con VIH/ SIDA que requieran endoscopia sería importante siempre considerar la toma biopsias de manera protocolizada
- Published
- 2017
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27. Room Temperature Exciton-Polariton Condensation in Silicon Metasurfaces Emerging from Bound States in the Continuum
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Berghuis, Anton Matthijs, Castellanos, Gabriel W., Murai, Shunsuke, Pura, Jose Luis, Abujetas, Diego R., van Heijst, Erik, Ramezani, Mohammad, Sánchez-Gil, José A., and Rivas, Jaime Gómez
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We show the first experimental demonstration of room-temperature exciton-polariton (EP) condensation from a bound state in the continuum (BIC). This demonstration is achieved by strongly coupling stable excitons in an organic perylene dye with the extremely long-lived BIC in a dielectric metasurface of silicon nanoparticles. The long lifetime of the BIC, mainly due to the suppression of radiation leakage, allows for EP thermalization to the ground state before decaying. This property results in a condensation threshold of less than 5 \mu J cm^{-2}, one order of magnitude lower that the lasing threshold reported in similar systems in the weak coupling limit.
- Published
- 2023
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28. Koszulity and Point Modules of Finitely Semi-Graded Rings and Algebras
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Oswaldo Lezama and Jaime Gomez
- Subjects
graded algebras ,distributive lattices ,Koszul algebras ,Hilbert and Poincaré series ,Yoneda algebra ,point modules ,point functor ,Zariski topology ,skew PBW extensions ,Mathematics ,QA1-939 - Abstract
In this paper, we investigate the Koszul behavior of finitely semi-graded algebras by the distributivity of some associated lattice of ideals. The Hilbert series, the Poincaré series, and the Yoneda algebra are defined for this class of algebras. Moreover, the point modules and the point functor are introduced for finitely semi-graded rings. Finitely semi-graded algebras and rings include many important examples of non- N -graded algebras coming from mathematical physics that play a very important role in mirror symmetry problems, and for these concrete examples, the Koszulity will be established, as well as the explicit computation of its Hilbert and Poincaré series.
- Published
- 2019
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29. Characterization of Palladium Nanoparticles Produced by Healthy and Microwave-Injured Cells of Desulfovibrio desulfuricans and Escherichia coli
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Jaime Gomez-Bolivar, Iryna P. Mikheenko, Lynne E. Macaskie, and Mohamed L. Merroun
- Subjects
palladium nanoparticles ,microwave injured cells ,microwave energy ,Escherichia coli ,Desulfovibrio desulfuricans ,Chemistry ,QD1-999 - Abstract
Numerous studies have focused on the bacterial synthesis of palladium nanoparticles (bio-Pd NPs), via uptake of Pd (II) ions and their enzymatically-mediated reduction to Pd (0). Cells of Desulfovibrio desulfuricans (obligate anaerobe) and Escherichia coli (facultative anaerobe, grown anaerobically) were exposed to low-dose radiofrequency (RF) radiation(microwave (MW) energy) and the biosynthesized Pd NPs were compared. Resting cells were exposed to microwave energy before Pd (II)-challenge. MW-injured Pd (II)-treated cells (and non MW-treated controls) were contacted with H2 to promote Pd(II) reduction. By using scanning transmission electron microscopy (STEM) associated with a high-angle annular dark field (HAADF) detector and energy dispersive X-ray (EDX) spectrometry, the respective Pd NPs were compared with respect to their mean sizes, size distribution, location, composition, and structure. Differences were observed following MWinjury prior to Pd(II) exposure versus uninjured controls. With D. desulfuricans the bio-Pd NPs formed post-injury showed two NP populations with different sizes and morphologies. The first, mainly periplasmically-located, showed polycrystalline Pd nano-branches with different crystal orientations and sizes ranging between 20 and 30 nm. The second NPpopulation, mainly located intracellularly, comprised single crystals with sizes between 1 and 5 nm. Bio-Pd NPs were produced mainly intracellularly by injured cells of E. coli and comprised single crystals with a size distribution between 1 and 3 nm. The polydispersity index was reduced in the bio-Pd made by injured cells of E. coli and D. desulfuricans to 32% and 39%, respectively, of the values of uninjured controls, indicating an increase in NP homogeneity of 30−40% as a result of the prior MWinjury. The observations are discussed with respect to the different locations of Pd(II)-reducing hydrogenases in the two organisms and with respect to potential implications for the catalytic activity of the produced NPs following injury-associated altered NP patterning.
- Published
- 2019
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30. A Kalman Filter Implementation for Precision Improvement in Low-Cost GPS Positioning of Tractors
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Francisco Javier Gomez-Gil, Jaime Gomez-Gil, Sergio Alonso-Garcia, and Ruben Ruiz-Gonzalez
- Subjects
Kalman filter ,agricultural vehicle ,Global Positioning System (GPS) ,vehicle guidance ,sensor data fusion ,autonomous navigation ,Chemical technology ,TP1-1185 - Abstract
Low-cost GPS receivers provide geodetic positioning information using the NMEA protocol, usually with eight digits for latitude and nine digits for longitude. When these geodetic coordinates are converted into Cartesian coordinates, the positions fit in a quantization grid of some decimeters in size, the dimensions of which vary depending on the point of the terrestrial surface. The aim of this study is to reduce the quantization errors of some low-cost GPS receivers by using a Kalman filter. Kinematic tractor model equations were employed to particularize the filter, which was tuned by applying Monte Carlo techniques to eighteen straight trajectories, to select the covariance matrices that produced the lowest Root Mean Square Error in these trajectories. Filter performance was tested by using straight tractor paths, which were either simulated or real trajectories acquired by a GPS receiver. The results show that the filter can reduce the quantization error in distance by around 43%. Moreover, it reduces the standard deviation of the heading by 75%. Data suggest that the proposed filter can satisfactorily preprocess the low-cost GPS receiver data when used in an assistance guidance GPS system for tractors. It could also be useful to smooth tractor GPS trajectories that are sharpened when the tractor moves over rough terrain.
- Published
- 2013
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31. Artificial neural network based model to calculate the environmental variables of the tobacco drying process; Modelo basado en redes neuronales artificiales para el cálculo de parámetros ambientales en el proceso de curado del tabaco
- Author
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Víctor Martínez-Martínez, Carlos Baladron, Jaime Gomez-Gil, Gonzalo Ruiz-Ruiz, Luis M Navas-Gracia, Javier M Aguiar, and Belen Carro
- Subjects
flue-cured tobacco ,process modeling ,neural networks ,estimation ,prediction. ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Technology (General) ,T1-995 - Abstract
This paper presents an Artificial Neural Network (ANN) based model for environmental variables related to the tobacco drying process. A fitting ANN was used to estimate and predict temperature and relative humidity inside the tobacco dryer: the estimation consists of calculating the value of these variables in different locations of the dryer and the prediction consists of forecasting the value of these variables with different time horizons. The proposed model has been validated with temperature and relative humidity data obtained from a real tobacco dryer using a Wireless Sensor Network (WSN). On the one hand, an error under 2% was achieved, obtaining temperature as a function of temperature and relative humidity in other locations in the estimation task. Besides, an error around 1.5 times lower than the one obtained with an interpolation method was achieved in the prediction task when the temperature inside the tobacco mass was predicted with time horizons over 2.5 hours as a function of its present and past values. These results show that ANN-based models can be used to improve the tobacco drying process because with these types of models the value of environmental variables can be predicted in the near future and can be estimated in other locations with low errors.
- Published
- 2013
32. Temperature and Relative Humidity Estimation and Prediction in the Tobacco Drying Process Using Artificial Neural Networks
- Author
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Belén Carro, Gonzalo Ruiz-Ruiz, Jaime Gomez-Gil, Javier M. Aguiar, Luis M. Navas-Gracia, Víctor Martínez-Martínez, and Carlos Baladrón
- Subjects
estimation ,prediction ,Artificial Neural Networks (ANN) ,tobacco drying process ,signal processing ,Chemical technology ,TP1-1185 - Abstract
This paper presents a system based on an Artificial Neural Network (ANN) for estimating and predicting environmental variables related to tobacco drying processes. This system has been validated with temperature and relative humidity data obtained from a real tobacco dryer with a Wireless Sensor Network (WSN). A fitting ANN was used to estimate temperature and relative humidity in different locations inside the tobacco dryer and to predict them with different time horizons. An error under 2% can be achieved when estimating temperature as a function of temperature and relative humidity in other locations. Moreover, an error around 1.5 times lower than that obtained with an interpolation method can be achieved when predicting the temperature inside the tobacco mass as a function of its present and past values with time horizons over 150 minutes. These results show that the tobacco drying process can be improved taking into account the predicted future value of the monitored variables and the estimated actual value of other variables using a fitting ANN as proposed.
- Published
- 2012
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33. Genetic markers of inflammation may not contribute to metabolic traits in Mexican children
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Neeti Vashi, Carolina Stryjecki, Jesus Peralta-Romero, Fernando Suarez, Jaime Gomez-Zamudio, Ana I. Burguete-Garcia, Miguel Cruz, and David Meyre
- Subjects
Genetic epidemiology ,Inflammation ,Obesity ,Cardio-metabolic complications ,Childhood ,Mexico ,Medicine ,Biology (General) ,QH301-705.5 - Abstract
Background: Low-grade chronic inflammation is a common feature of obesity and its cardio-metabolic complications. However, little is known about a possible causal role of inflammation in metabolic disorders. Mexico is among the countries with the highest obesity rates in the world and the admixed Mexican population is a relevant sample due to high levels of genetic diversity. Methods: Here, we studied 1,462 Mexican children recruited from Mexico City. Six genetic variants in five inflammation-related genes were genotyped: rs1137101 (leptin receptor (LEPR)), rs7305618 (hepatocyte nuclear factor 1 alpha (HNF1A)), rs1800629 (tumor necrosis factor alpha (TNFA)), rs1800896, rs1800871 (interleukin-10 (IL-10)), rs1862513 (resistin (RETN)). Ten continuous and eight binary traits were assessed. Linear and logistic regression models were used adjusting for age, sex, and recruitment centre. Results: We found that one SNP displayed a nominal evidence of association with a continuous trait: rs1800871 (IL-10) with LDL (beta = −0.068 ± 1.006, P = 0.01). Subsequently, we found one nominal association with a binary trait: rs7305618 (HNF1A) with family history of hypertension (odds-ratio = 1.389 [1.054–1.829], P = 0.02). However, no P-value passed the Bonferroni correction for multiple testing. Discussion: Our data in a Mexican children population are consistent with previous reports in European adults in failing to demonstrate an association between inflammation-associated single nucleotide polymorphisms (SNPs) and metabolic traits.
- Published
- 2016
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34. Brain Computer Interfaces, a Review
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Luis Fernando Nicolas-Alonso and Jaime Gomez-Gil
- Subjects
brain-computer interface (BCI) ,electroencephalography (EEG) ,rehabilitation ,artifact ,neuroimaging ,brain-machine interface ,collaborative sensor system ,Chemical technology ,TP1-1185 - Abstract
A brain-computer interface (BCI) is a hardware and software communications system that permits cerebral activity alone to control computers or external devices. The immediate goal of BCI research is to provide communications capabilities to severely disabled people who are totally paralyzed or ‘locked in’ by neurological neuromuscular disorders, such as amyotrophic lateral sclerosis, brain stem stroke, or spinal cord injury. Here, we review the state-of-the-art of BCIs, looking at the different steps that form a standard BCI: signal acquisition, preprocessing or signal enhancement, feature extraction, classification and the control interface. We discuss their advantages, drawbacks, and latest advances, and we survey the numerous technologies reported in the scientific literature to design each step of a BCI. First, the review examines the neuroimaging modalities used in the signal acquisition step, each of which monitors a different functional brain activity such as electrical, magnetic or metabolic activity. Second, the review discusses different electrophysiological control signals that determine user intentions, which can be detected in brain activity. Third, the review includes some techniques used in the signal enhancement step to deal with the artifacts in the control signals and improve the performance. Fourth, the review studies some mathematic algorithms used in the feature extraction and classification steps which translate the information in the control signals into commands that operate a computer or other device. Finally, the review provides an overview of various BCI applications that control a range of devices.
- Published
- 2012
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35. Steering a Tractor by Means of an EMG-Based Human-Machine Interface
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Sergio Alonso-Garcia, Luis Fernando Nicolas-Alonso, Israel San-Jose-Gonzalez, and Jaime Gomez-Gil
- Subjects
agricultural vehicles ,human-machine interface (HMI) ,human-computer interface (HCI) ,brain-computer interface (BCI) ,electroencephalography (EEG) ,control ,global positioning system (GPS) ,tractor, guidance ,Chemical technology ,TP1-1185 - Abstract
An electromiographic (EMG)-based human-machine interface (HMI) is a communication pathway between a human and a machine that operates by means of the acquisition and processing of EMG signals. This article explores the use of EMG-based HMIs in the steering of farm tractors. An EPOC, a low-cost human-computer interface (HCI) from the Emotiv Company, was employed. This device, by means of 14 saline sensors, measures and processes EMG and electroencephalographic (EEG) signals from the scalp of the driver. In our tests, the HMI took into account only the detection of four trained muscular events on the driver’s scalp: eyes looking to the right and jaw opened, eyes looking to the right and jaw closed, eyes looking to the left and jaw opened, and eyes looking to the left and jaw closed. The EMG-based HMI guidance was compared with manual guidance and with autonomous GPS guidance. A driver tested these three guidance systems along three different trajectories: a straight line, a step, and a circumference. The accuracy of the EMG-based HMI guidance was lower than the accuracy obtained by manual guidance, which was lower in turn than the accuracy obtained by the autonomous GPS guidance; the computed standard deviations of error to the desired trajectory in the straight line were 16 cm, 9 cm, and 4 cm, respectively. Since the standard deviation between the manual guidance and the EMG-based HMI guidance differed only 7 cm, and this difference is not relevant in agricultural steering, it can be concluded that it is possible to steer a tractor by an EMG-based HMI with almost the same accuracy as with manual steering.
- Published
- 2011
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36. A Simple Method to Improve Autonomous GPS Positioning for Tractors
- Author
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Tim Stombaugh, Francisco Javier Gómez-Gil, Jaime Gomez-Gil, and Sergio Alonso-Garcia
- Subjects
agricultural vehicles ,control ,Global Positioning System (GPS) ,guidance ,Chemical technology ,TP1-1185 - Abstract
Error is always present in the GPS guidance of a tractor along a desired trajectory. One way to reduce GPS guidance error is by improving the tractor positioning. The most commonly used ways to do this are either by employing more precise GPS receivers and differential corrections or by employing GPS together with some other local positioning systems such as electronic compasses or Inertial Navigation Systems (INS). However, both are complex and expensive solutions. In contrast, this article presents a simple and low cost method to improve tractor positioning when only a GPS receiver is used as the positioning sensor. The method is based on placing the GPS receiver ahead of the tractor, and on applying kinematic laws of tractor movement, or a geometric approximation, to obtain the midpoint position and orientation of the tractor rear axle more precisely. This precision improvement is produced by the fusion of the GPS data with tractor kinematic control laws. Our results reveal that the proposed method effectively reduces the guidance GPS error along a straight trajectory.
- Published
- 2011
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37. Engineering bound states in the continuum at telecom wavelengths with non-Bravais lattices
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Murai, Shunsuke, Abujetas, Diego R., Liu, Libei, Castellanos, Gabriel W., Giannini, Vincenzo, Sánchez-Gil, José A., Tanaka, Katsuhisa, and Rivas, Jaime Gómez
- Subjects
Physics - Optics ,Physics - Applied Physics - Abstract
Various optical phenomena can be induced in periodic arrays of nanoparticles by the radiative coupling of the local dipoles in each particle. Probably the most impressive example is bound states in the continuum (BICs), which are electromagnetic modes with a dispersion inside the light cone but infinite lifetime, i.e., modes that cannot leak to the continuum. Symmetry-protected BICs appear at highly symmetric points in the dispersion of periodic systems. Although the addition of nonequivalent lattice points in a unit cell is an easy and straightforward way of tuning the symmetry, BICs in such particle lattice, i.e., non-Bravais lattice, are less explored among periodic systems. Starting from a periodic square lattice of Si nanodisks, we have prepared three non-Bravais lattices by detuning size and position of the second disk in the unit cell. Diffraction-induced coupling excites magnetic/electric dipoles in each nanodisk, producing two surface lattice resonances at the $\Gamma$ point with a band gap in between. %of $\sim$ 41 meV. The high/low energy branch becomes a BIC for the size/position-detuned array, respectively, while both branches are bright (or leaky) when both size and position are detuned simultaneously. The role of magnetic and electric resonances in dielectric nanoparticles and the change of BIC to bright character of the modes is explained by the two different origins of BICs in the detuned arrays, which is further discussed with the aid of a coupled electric and magnetic dipole model. This study gives a simple way of tuning BICs at telecom wavelengths in non-Bravais lattices, including both plasmonic and dielectric systems, thus scalable to a wide range of frequencies., Comment: 26 pages, 5 figures
- Published
- 2022
38. RBF-Neural Network Applied to the Quality Classification of Tempered 100Cr6 Steel Cams by the Multi-Frequency Nondestructive Eddy Current Testing
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Víctor Martínez-Martínez, Javier Garcia-Martin, and Jaime Gomez-Gil
- Subjects
nondestructive testing ,eddy current ,tempering process ,radial basis function neural network ,multi-frequency ,analysis of variance ,Mining engineering. Metallurgy ,TN1-997 - Abstract
This article proposes a Radial Basis Function Artificial Neural Network (RBF-ANN) to classify tempered steel cams as correctly or incorrectly treated pieces by using multi-frequency nondestructive eddy current testing. Impedances at five frequencies between 10 kHz and 300 kHz were employed to perform the binary sorting. The ANalysis Of VAriance (ANOVA) test was employed to check the significance of the differences between the impedance samples for the two classification groups. Afterwards, eleven classifiers were implemented and compared with one RBF-ANN classifier: ten linear discriminant analysis classifiers and one Euclidean distance classifier. When employing the proposed RBF-ANN, the best performance was achieved with a precision of 95% and an area under the Receiver Operating Characteristic (ROC) curve of 0.98. The obtained results suggest RBF-ANN classifiers processing multi-frequency impedance data could be employed to classify tempered steel DIN 100Cr6 cams with a better performance than other classical classifiers.
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- 2017
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39. A Novel Method for Sensorless Speed Detection of Brushed DC Motors
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Ernesto Vazquez-Sanchez, Joseph Sottile, and Jaime Gomez-Gil
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brushed dc motor ,sensorless ,speed observer ,spectral analysis ,current ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Many motor applications require accurate speed measurement. For brushed dc motors, speed can be measured with conventional observers or sensorless observers. Sensorless observers have the advantage of not requiring any external devices to be attached to the motor. Instead, voltage and/or current are measured and used to estimate the speed. The sensorless observers are usually divided into two groups: those based on the dynamic model, and those based on the ripple component. This paper proposes a method that measures the current of brushed dc motors and analyses the position of its spectral components. From these spectral components, the method estimates the motor speed. Three tests, performed each with the speeds ranging from 2000 to 3000 rpm either at constant-speed, at slowly changing speeds, or at rapidly changing speeds, showed that the average error was below 1 rpm and that the deviation error was below 1.5 rpm. The proposed method: (i) is a novel method that is not based on either the dynamic model or on the ripple component; (ii) requires only the measurement of the current for the speed estimation; (iii) can be used for brushed dc (direct current) motors with a large number of coils; and (iv) achieves a low error in the speed estimation.
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- 2016
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40. High expression of oleoyl-ACP hydrolase underpins life-threatening respiratory viral diseases
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Jia, Xiaoxiao, Crawford, Jeremy Chase, Gebregzabher, Deborah, Monson, Ebony A., Mettelman, Robert C., Wan, Yanmin, Ren, Yanqin, Chou, Janet, Novak, Tanya, McQuilten, Hayley A., Clarke, Michele, Bachem, Annabell, Foo, Isabelle J., Fritzlar, Svenja, Carrera Montoya, Julio, Trenerry, Alice M., Nie, Shuai, Leeming, Michael G., Nguyen, Thi H.O., Kedzierski, Lukasz, Littler, Dene R., Kueh, Andrew, Cardamone, Tina, Wong, Chinn Yi, Hensen, Luca, Cabug, Aira, Laguna, Jaime Gómez, Agrawal, Mona, Flerlage, Tim, Boyd, David F., Van de Velde, Lee-Ann, Habel, Jennifer R., Loh, Liyen, Koay, Hui-Fern, van de Sandt, Carolien E., Konstantinov, Igor E., Berzins, Stuart P., Flanagan, Katie L., Wakim, Linda M., Herold, Marco J., Green, Amanda M., Smallwood, Heather S., Rossjohn, Jamie, Thwaites, Ryan S., Chiu, Christopher, Scott, Nichollas E., Mackenzie, Jason M., Bedoui, Sammy, Reading, Patrick C., Londrigan, Sarah L., Helbig, Karla J., Randolph, Adrienne G., Thomas, Paul G., Xu, Jianqing, Wang, Zhongfang, Chua, Brendon Y., and Kedzierska, Katherine
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- 2024
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41. Unveiling Symmetry Protection of Bound States in the Continuum with Terahertz Near-field Imaging
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van Hoof, Niels J. J., Abujetas, Diego R., ter Huurne, Stan E. T., Verdelli, Francesco, Timmermans, Giel C. A., Sánchez-Gil, José A., and Rivas, Jaime Gómez
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Physics - Optics ,Physics - Instrumentation and Detectors - Abstract
Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered their direct observation. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field of BICs over extended areas, unveiling the field-symmetry protection that suppresses far-field radiation. This investigation, done for metasurfaces of dimer rod resonators, reveals the in-plane extension and formation of BICs with anti-symmetric phases, in agreement with coupled-dipole calculations. By displacing the rods, we demonstrate that mirror symmetry is not a necessary condition for BIC formation. Only $\pi$-rotation symmetry is required, making BICs exceptionally robust to structural changes. This work makes the local field of BICs experimentally accessible, which is crucial for the engineering of cavities with infinite lifetimes., Comment: 7 pages and 7 figures plus supplemental material (6 pages and 5 figures)
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- 2021
42. Collective Mie Exciton-Polaritons in an Atomically Thin Semiconductor
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Wang, Shaojun, Raziman, T. V., Murai, Shunsuke, Castellanos, Gabriel W., Bai, Ping, Berghuis, Anton Matthijs, Godiksen, Rasmus H., Curto, Alberto G., and Rivas, Jaime Gómez
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Physics - Optics - Abstract
Optically induced Mie resonances in dielectric nanoantennas feature low dissipative losses and large resonant enhancement of both electric and magnetic fields. They offer an alternative platform to plasmonic resonances to study light-matter interactions from the weak to the strong coupling regimes. Here, we experimentally demonstrate the strong coupling of bright excitons in monolayer WS$_2$ with Mie surface lattice resonances (Mie-SLRs). We resolve both electric and magnetic Mie-SLRs of a Si nanoparticle array in angular dispersion measurements. At the zero detuning condition, the dispersion of electric Mie-SLRs (e-SLRs) exhibits a clear anti-crossing and a Rabi-splitting of 32 meV between the upper and lower polariton bands. The magnetic Mie-SLRs (m-SLRs) nearly cross the energy band of excitons. These results suggest that the field of m-SLRs is dominated by out-of-plane components that do not efficiently couple with the in-plane excitonic dipoles of the monolayer WS$_2$. In contrast, e-SLRs in dielectric nanoparticle arrays with relatively high quality factors (Q $\sim$ 120) facilitate the formation of collective Mie exciton-polaritons, and may allow the development of novel polaritonic devices which can tailor the optoelectronic properties of atomically thin two-dimensional semiconductors., Comment: 27 pages, 7 figures
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- 2020
43. Exciton diffusion and annihilation in nanophotonic Purcell landscapes
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Raziman, T. V., Visser, C. Peter, Wang, Shaojun, Rivas, Jaime Gómez, and Curto, Alberto G.
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Physics - Optics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Excitons spread through diffusion and interact through exciton-exciton annihilation. Nanophotonics can counteract the resulting decrease in light emission. However, conventional enhancement treats emitters as immobile and noninteracting. Here, we go beyond the localized Purcell effect to exploit exciton dynamics. As interacting excitons diffuse through optical hotspots, the balance of excitonic and nanophotonic properties leads to either enhanced or suppressed photoluminescence. We identify the dominant enhancement mechanisms in the limits of high and low diffusion and annihilation to turn their detrimental impact into additional emission. Our guidelines are relevant for efficient and high-power light-emitting diodes and lasers based on monolayer semiconductors, perovskites, or organic crystals.
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- 2020
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44. Impact of indirect transitions on valley polarization in WS$_2$ and WSe$_2$
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Godiksen, Rasmus H., Wang, Shaojun, Raziman, T. V., Rivas, Jaime Gómez, and Curto, Alberto G.
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Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Optics - Abstract
Controlling the momentum of carriers in semiconductors, known as valley polarization, is a new resource for optoelectronics and information technologies. Materials exhibiting high polarization are needed for valley-based devices. Few-layer WS$_2$ shows a remarkable spin-valley polarization above 90%, even at room temperature. In stark contrast, polarization is absent for few-layer WSe$_2$ despite the expected material similarities. Here, we explain the origin of valley polarization in both materials based on the interplay between two indirect optical transitions. We show that the relative energy minima at the $\Lambda$- and K-valleys in the conduction band determine the spin-valley polarization of the direct K-K transition. Polarization appears as the energy of the K-valley rises above the $\Lambda$-valley as a function of temperature and number of layers. Our results advance the understanding of the high spin-valley polarization in WS$_2$. This insight will impact the design of both passive and tunable valleytronic devices operating at room temperature., Comment: 36 pages, including supplementary information
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- 2020
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45. Enhanced light emission by magnetic and electric resonances in dielectric metasurfaces
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Murai, Shunsuke, Castellanos, Gabriel W., Raziman, T. V., Curto, Alberto. G., and Rivas, Jaime Gómez
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Physics - Optics - Abstract
We demonstrate an enhanced emission of high quantum yield molecules coupled to dielectric metasurfaces formed by periodic arrays of polycrystalline silicon nanoparticles. Radiative coupling of the nanoparticles, mediated by in-plane diffraction, leads to the formation of collective Mie scattering resonances or Mie surface lattice resonances (M-SLRs), with remarkable narrow line widths. These narrow line widths and the intrinsic electric and magnetic dipole moments of the individual Si nanoparticles allow to resolve electric and magnetic M-SLRs. Incidence angle- and polarization-dependent extinction measurements and high-accuracy surface integral simulations show unambiguously that magnetic M-SLRs arise from in- and out-of-plane magnetic dipoles, while electric M-SLRs are due to in-plane electric dipoles. Pronounced changes in the emission spectrum of the molecules are observed, with almost a 20-fold enhancement of the emission in defined directions of molecules coupled to electric M-SLRs, and a 5-fold enhancement of the emission of molecules coupled to magnetic M-SLRs. These measurements demonstrate the potential of dielectric metasurfaces for emission control and enhancement, and open new opportunities to induce asymmetric scattering and emission using collective electric and magnetic resonances., Comment: 27 pages with 9 figures
- Published
- 2020
46. Mapping steady-state groundwater levels in the Mediterranean region: The Iberian Peninsula as a benchmark
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Ben-Salem, Nahed, Reinecke, Robert, Copty, Nadim K., Jaime Gómez-Hernández, J., Varouchakis, Emmanouil A., Karatzas, George P., Rode, Michael, and Jomaa, Seifeddine
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- 2023
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47. Association of the rs5186 polymorphism of the AGTR1 gene with decreased eGFR in patients with type 2 diabetes from Mexico City
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Figueroa, Manuel Alejandro Contreras, Lujambio, Irene Mendoza, Gutiérrez, Teresa Alvarado, Hernández, María Fernanda Pérez, Ramírez, Evelyn Yazmín Estrada, Guzmán, Dominga Jiménez, Sánchez, María Fernanda Lucas, Morales, Hannia Fernanda González, Samudio, Héctor Jaime Gómez, Sánchez, Fernando Suarez, Flores, Margarita Díaz, Zamarripa, Carlos Alberto Jiménez, Mendoza, Claudia Camelia Calzada, Hernández, María Esther Ocharán, Velázquez, Cora Mariana Orozco, Flores, Mariana Soto, Orozco, Daniela Vicenta Hernández, Moreno, Gabriela Yanet Cortés, Cruz, Miguel, and de Jesús Peralta Romero, José
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- 2023
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48. Enhanced Delayed Fluorescence in Tetracene Crystals by Strong Light-Matter Coupling
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Berghuis, Matthijs, Halpin, Alexei, Le-Van, Quynh, Ramezani, Mohammad, Wang, Shaojun, Murai, Shunsuke, and Rivas, Jaime Gómez
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Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Chemical Physics ,Physics - Optics - Abstract
We demonstrate experimentally an enhanced delayed fluorescence in tetracene single crystals strongly coupled to optical modes in open cavities formed by arrays of plasmonic nanoparticles. Hybridization of singlet excitons with collective plasmonic resonances in the arrays leads to the splitting of the material dispersion into a lower and an upper polariton band. This splitting significantly modifies the dynamics of the photo-excited tetracene crystal, resulting in an increase of the delayed fluorescence by a factor of four. The enhanced delayed fluorescence is attributed to the emergence of an additional radiative decay channel, where the lower polariton band harvests long-lived triplet states. There is also an increase in total emission, which is wavelength dependent, and can be explained by the direct emission from the lower polariton band, the more effcient light out-coupling and the enhancement of the excitation intensity. The observed enhanced fluorescence opens the possibility of effcient radiative triplet harvesting in open optical cavities, to improve the performance of organic light emitting diodes.
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- 2019
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49. Strong coupling between weakly guided semiconductor nanowire modes and an organic dye
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Abujetas, Diego R., Feist, Johannes, García-Vidal, Francisco J., Rivas, Jaime Gómez, and Sánchez-Gil, José A.
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Physics - Optics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The light-matter coupling between electromagnetic modes guided by a semiconductor nanowire and excitonic states of molecules localized in its surrounding media is studied from both classical and quantum perspectives, with the aim of describing the strong coupling regime. Weakly guided modes (bare photonic modes) are found through a classical analysis, identifying those lowest-order modes presenting large electromagnetic fields spreading outside the nanowire, while preserving their robust guided behavior. Experimental fits of the dielectric permittivity of an organic dye that exhibits excitonic states are used for realistic scenarios. A quantum model properly confirms through an avoided mode crossing that the strong coupling regime can be achieved for this configuration, leading to Rabi splitting values above 100 meV. In addition, it is shown that the coupling strength depends on the fraction of energy spread outside the nanowire, rather than on the mode field localization. These results open up a new avenue towards strong coupling phenomenology involving propagating modes in non-absorbing media., Comment: 10 pages, 7 figures
- Published
- 2019
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50. From Fano resonances to bound states in the continuum in dipole arrays at THz frequencies
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Abujetas, Diego R., van Hoof, Niels, ter Huurne, Stan, Rivas, Jaime Gómez, and Sánchez-Gil, José A.
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Physics - Optics - Abstract
Fano resonances and bound states in the continuum (BICs) exhibit a rich phenomenology stemming from, respectively, their asymmetric line shapes and infinite quality factors. Here, we show experimentally and theoretically that rod dimer metasurfaces exhibit narrow (high-Q) Fano resonances at THz frequencies. These resonances evolve continuously into a BIC as the rods in each dimer become identical. We demonstrate analytically that this is a universal behavior occurring in arrays of dimers consisting of detuned resonant dipoles. Fano resonances arise as a result of the interference between broad and narrow lattice dipole resonances, with high-Q factors tending to infinity in the detuning parameter space as the narrow lattice resonance becomes a BIC for identical resonant dipoles. Similar configurations can be straightforwardly envisioned throughout the electromagnetic spectrum leading to ultrahigh-Q Fano resonances and BICs of interest in photonics applications such as sensing and lasing., Comment: 6 pages, 4 figures
- Published
- 2019
- Full Text
- View/download PDF
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