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1,977 results on '"Fernández, Carmen"'

1. Iterates of composition operators on global spaces of ultradifferentiable functions

Author

Ariza, Héctor, Fernández, Carmen, and Galbis, Antonio

Subjects
Mathematics - Functional Analysis
Abstract

We analyze the behavior of the iterates of composition operators defined by polynomials acting on global classes of ultradifferentiable functions of Beurling type and being invariant under Fourier transform. We characterize the polynomials $\psi$ for which the sequence of iterates is equicontinuous between two different Gelfand-Shilov spaces. For the particular case in which the weight $\omega$ is equivalent to a power of the logarithm, the result obtained characterizes the polynomials $\psi$ for which the composition operator $C_\psi$ is power bounded in ${\mathcal S}_\omega({\mathbb R}).$ Unlike the composition operators in Schwartz class, the Waelbroek spectrum of an operator $C_\psi$, being $\psi$ a polynomial of degree greater than one lacking fixed points is never compact. We focus on the problem of convergence of Neumann series. We deduce the continuity of the resolvent operator between two different Gelfand-Shilov classes for polynomials $\psi$ lacking fixed points. Concerning polynomials of second degree the most interesting case is the one in which the polynomial only has one fixed point: we provide some restrictions on the indices $d, d'$ that are necessary for the resolvent operator to be continuous between the Gelfand-Shilov classes $\Sigma_d$ and $\Sigma_{d'}.$

Published
2024

2. Detecting quasicrystals with quadratic time-frequency distributions

Author

Boggiatto, Paolo, Fernández, Carmen, Galbis, Antonio, and Oliaro, Alessandro

Subjects
Mathematics - Functional Analysis
Abstract

The usefulness of time-frequency analysis methods in the study of quasicrystals was pointed out in a previous paper, where we proved that a tempered distribution $\mu$ on ${\mathbb R}^d$ whose Wigner transform is a measure supported on the cartesian product of two uniformly discrete sets in ${\mathbb R}^d$ is a Fourier quasicrystal. In this paper we go further in this direction using the matrix-Wigner transforms to detect quasicrystal structures. The results presented here cover essentially all the most important quadratic time-frequency distributions, and are obtained considering two different (disjoint) classes of matrix-Wigner transforms, discussed respectively in Theorems 1 and 2. The transforms considered in Theorem 1 include the classical Wigner transform, as well as all the time-frequency representations of matrix-Wigner type belonging to the Cohen class. On the other hand Theorem 2, which does not apply to the classical Wigner, has, as main example, the Ambiguity function. In this second case we only suppose that the support of the matrix-Wigner transform of $\mu$ is contained in the cartesian product of two discrete sets, obtaining that both the support and the spectrum of $\mu$ are uniformly discrete.

Published
2024

6. Composition operators on Gelfand-Shilov classes

Author

Ariza, Héctor, Fernández, Carmen, and Galbis, Antonio

Subjects
Mathematics - Functional Analysis, 47B33, 46F05
Abstract

We study composition operators on global classes of ultradifferentiable functions of Beurling type invariant under Fourier transform. In particular, for the classical Gelfand-Shilov classes $\Sigma_d,\ d > 1,$ we prove that a necessary condition for the composition operator $f\mapsto f\circ \psi$ to be well defined is the boundedness of $\psi'.$ We find the optimal index $d'$ for which $C_\psi(\Sigma_d({\mathbb R}))\subset \Sigma_{d'}({\mathbb R})$ holds for any non-constant polynomial $\psi.$

Published
2023

14. Early cortical atrophy in REM sleep behavior disorder

Author

Abenza Abildua, María José, Lanz Santos, Elvira, Moreno Domínguez, Luis, Mata Álvarez-Santullano, Marina, Borrue Fernández, Carmen, Palmí Cortés, Itziar, Lobato Rodríguez, Ricardo, Navacerrada Barrero, Francisco José, Martínez Ubierna, Sonia, Gómez Aceña A, Ángeles, Suárez Gisbert, Eugenio, Lores Gutiérrez, Vanesa, Gómez de la Riva, Álvaro, Pérez López, Carlos, and Novo Aparicio, Susana

Published
2024
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15. Atrofia cortical precoz en el trastorno de conducta del sueño REM

Author

Abenza Abildua, María José, Lanz Santos, Elvira, Moreno Domínguez, Luis, Mata Álvarez-Santullano, Marina, Borrue Fernández, Carmen, Palmí Cortés, Itziar, Lobato Rodríguez, Ricardo, Navacerrada Barrero, Francisco José, Martínez Ubierna, Sonia, Gómez Aceña A, Ángeles, Suárez Gisbert, Eugenio, Lores Gutiérrez, Vanesa, Gómez de la Riva, Álvaro, Pérez López, Carlos, and Novo Aparicio, Susana

Published
2024
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18. Clinical characteristics associated with elevated levels of lipoprotein(a) in patients with vascular risk

Author

Rubio-Serrano Javier, Gullón Ojesto Alejandra, and Suárez Fernández Carmen

Subjects
cardiovascular disease, risk factors, familial hypercholesterolemia, lipoprotein(a), Medical technology, R855-855.5
Abstract

Lipoprotein(a) (Lp(a)) is increasingly used in the evaluation of patients with vascular risk due to its association with cardiovascular events. The purpose of this study was to identify the clinical characteristics of patients with elevated levels of Lp(a) attended in an outpatient vascular risk unit.

Published
2023
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19. Características clínicas asociadas a niveles elevados de lipoproteína(a) en pacientes atendidos por riesgo vascular

Author

Rubio-Serrano Javier, Gullón Ojesto Alejandra, and Suárez Fernández Carmen

Subjects
enfermedad cardiovascular, factores de riesgo, hipercolesterolemia familiar, lipoproteína(a), Medical technology, R855-855.5
Abstract

La lipoproteína(a) (Lp(a)) es cada vez más relevante en la evaluación de pacientes con riesgo vascular debido a su asociación con una mayor incidencia de eventos cardiovasculares. Este estudio tiene como objetivo identificar las características clínicas de los pacientes con niveles elevados de Lp(a) atendidos en consultas externas por riesgo vascular.

Published
2023
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24. Wigner transform and quasicrystals

Author

Boggiatto, Paolo, Fernández, Carmen, Galbis, Antonio, and Oliaro, Alessandro

Subjects
Mathematics - Functional Analysis
Abstract

Quasicrystals are tempered distributions $\mu$ which satisfy symmetric conditions on $\mu$ and $\widehat \mu$. This suggests that techniques from time-frequency analysis could possibly be useful tools in the study of such structures. In this paper we explore this direction considering quasicrystals type conditions on time-frequency representations instead of separately on the distribution and its Fourier transform. More precisely we prove that a tempered distribution $\mu$ on ${\mathbb R}^d$ whose Wigner transform, $W(\mu)$, is supported on a product of two uniformly discrete sets in ${\mathbb R}^d$ is a quasicrystal. This result is partially extended to a generalization of the Wigner transform, called matrix-Wigner transform which is defined in terms of the Wigner transform and a linear map $T$ on ${\mathbb R}^{2d}$.

Published
2021

25. Evaluation of School Climate Behaviors in the School Context: CONVIVE Questionnaire

Author

Ruiz-Hernández, José Antonio, Ruiz-Fernández, Carmen María, Pina López, David, Llor-Zaragoza, Laura, Pagán-Escribano, María, Jiménez-Barbero, José Antonio, and Puente-López, Esteban

Abstract

School climate research has traditionally been carried out by separating its two main components, prosocial and antisocial behaviors. This is often a partial view of the school climate. Hence, the goal of this study is to develop an evaluation instrument (CONVIVE) that takes into account both perspectives of the school climate through a dual-strategy design, psychometric and non-experimental, cross-sectional, and descriptive-comparative. The sample includes 600 Primary and Secondary Education students from a southeastern region of Spain. Exploratory and Confirmatory Factorial Analysis fit indices were used for the psychometric study. The result is a 26-item instrument (CONVIVE) made up of four scales that evaluate antisocial and prosocial behaviors, both performed toward others and received by peers: "Prosocial Behavior Actor," "Prosocial Behavior Receiver," "Antisocial Behavior Actor," and "Antisocial Behavior Receiver." These behaviors differ as a function of sex and the educational stage.

Published
2022
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31. One-year Outcomes after Discharge from Noncardiac Surgery and Association between Predischarge Complications and Death after Discharge: Analysis of the VISION Prospective Cohort Study

Author

Roshanov, Pavel S., Chan, Matthew T. V., Borges, Flavia K., Conen, David, Wang, C. Y., Xavier, Denis, Berwanger, Otavio, Marcucci, Maura, Sessler, Daniel I., Szczeklik, Wojciech, Spence, Jessica, Alonso-Coello, Pablo, Fernández, Carmen, Pearse, Rupert M., Malaga, German, Garg, Amit X., Srinathan, Sadeesh K., Jacka, Michael J., Tandon, Vikas, McGillion, Michael, Popova, Ekaterine, Sigamani, Alben, Abraham, Valsa, Biccard, Bruce M., Villar, Juan Carlos, Chow, Clara K., Polanczyk, Carísi A., Tiboni, Maria, Whitlock, Richard, Ackland, Gareth L., Panju, Mohamed, Lamy, André, Sapsford, Robert, Williams, Colin, Wu, William Ka Kei, Cortés, Olga L., MacNeil, S. Danielle, Patel, Ameen, Belley-Côté, Emilie P., Ofori, Sandra, McIntyre, William F., Leong, Darryl P., Heels-Ansdell, Diane, Gregus, Krysten, and Devereaux, P. J.

Published
2024
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33. MEGACOLON TÓXICO

Author

Litardo Fernández, Carmen Rosa, primary, Álvarez Cruz, Erika Yolanda, additional, Onofre Jacome, Juleysi Magerly, additional, and Allieri Fernández, José Guillermo, additional

Published
2023
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34. Apendicitis aguda en la niñez

Author

Litardo Fernández, Carmen Rosa, primary, Molina Villacrés, Matthew Leonardo, additional, Reyes Ruiz, Víctor Iván, additional, and Riera Chérrez, Bertha Fabiola, additional

Published
2023
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40. Feasibility of a screening algorithm for chronic thromboembolic pulmonary hypertension: The OSIRIS study

Author

Otero, Remedios, Lobo, José Luis, López, Raquel, Fernández, Carmen, Jiménez, David, Muriel, Alfonso, Alfonso, María, Ballaz, Aitor, Núñez-Ares, Ana, Rodríguez-Matute, Consolación, de Miguel-Díez, Javier, Rodríguez-Chiaradía, Diego Agustín, Alcalde, Mercedes, Elías, Teresa, Jara-Palomares, Luis, Rivas, Agustina, Alonso, Ángel, García-Ortega, Alberto, Sancho, Teresa, Morillo, Raquel, García-Bragado, Fernando, Hernández-Blasco, Luis, Uresandi, Fernando, Madridano, Olga, Agüero, Ramón, and Monreal, Manuel

Published
2023
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42. Characterizations of a class of Pilipovi{\'c} spaces by powers of harmonic oscillator

Author

Abdeljawad, Ahmed, Fernandez, Carmen, Galbis, Antonio, Toft, Joachim, and Üster, Rüya

Subjects
Mathematics - Functional Analysis
Abstract

We show that a smooth function $f$ on $\mathbf R^d$ belongs to the Pilipovi{\'c} space $\mathcal H_{\flat _\sigma}(\mathbf R^d)$ or the Pilipovi{\'c} space $\mathcal H_{0,\flat _\sigma}(\mathbf R^d)$, if and only if the $L^p$ norm of $H_d^Nf$ for $N\ge 0$, satisfy certain types of estimates. Here $H_d=|x|^2-\Delta _x$ is the harmonic oscillator., Comment: 13 pages. This is the third version. Some mathematical details have been clarified in this version compared to earlier versions

Published
2019

46. Key Factors Associated With Pulmonary Sequelae in the Follow-Up of Critically Ill COVID-19 Patients

Author

Cabello, María Aguilar, Alcaraz-Serrano, Victoria, Aldecoa, Cesar, Alegre, Cynthia, Calderón, Ángela Algaba, Álvarez, Sergio, Ruiz, Antonio Álvarez, Andrea, Ruth, Aparicio, Maria de Alba, Arrieta, Marta, Ayestarán, J. Ignacio, Badia, Joan Ramon, Badía, Mariona, Pravia, Orville Báez, Mariño, Ana Balan, Balsera, Begoña, Barbena, Laura, Barbeta, Enric, Bardi, Tommaso, Segade, Patricia Barral, Barroso, Marta, García, José Ángel Berezo, Bermejo, Jesus, Bigas, Judit, Blancas, Rafael, Cortés, María Luisa Blasco, Saera, María Bodi, Bofill, Neus, Vieiro, María Teresa Bouza, Bueno, Leticia, Bustamante-Munguira, Juan, Martínez, Cecilia del Busto, Hermoso, David Campi, Fernández, Sandra Campos, Cano, Iosune, Canseco, Joan, Fernández, Pablo Cardinal, García, Laura Carrión, Carvalho, Sulamita, Castellà, Manuel, Castellví, Andrea, Castro, Pedro, Centelles-Serrano, María José, Ávila, Ramon Cicuendez, Cillóniz, Catia, Clar, Luisa, Climent, Cristina, Codina, Jordi, Conde, Pamela, Contreras, Sofía, Parra, Raul de Frutos, Sánchez, Raul de Pablo, Mendoza, Diego De, Díaz, Yolanda, Vilas, María Digna Rivas, Moreno, Cristina Dólera, Dot, Irene, Giraudo, Pedro Enríquez, Arijón, Inés Esmorís, Monjo, Teresa Farre, Fernández, Javier, Ferrando, Carlos, Figueras, Albert, Espina, Lorena Forcelledo, Franquesa, Enric, Furro, Àngels, Gabarrus, Albert, Galbán, Cristóbal, García, Felipe, García, Beatriz, Prieto, Emilio García, Redruello, Carlos García, Sagastume, Amaia García, Castillo, Maria Luisa Gascón, Gomà, Gemma, Casal, Vanesa Gómez, Gómez, Silvia, Gonzalez, Carmen Gómez, Gordo, Federico, Gracia, Maria Pilar, Fernández, María José Gutierrez, Herraiz, Alba, Herrán-Monge, Rubén, Ibarz, Mercedes, Iglesias, Silvia, Janer, Maria Teresa, Jiménez, Gabriel, Díaz, Mar Juan, Kiarostami, Karsa, Álvarez, Juan I. Lazo, León, Miguel, López-Gavín, Alexandre, Guerrero, Desiree Macias, Herrera, Nuria Mamolar, Mendiluce, Rafael Mañez, Mantellini, Cecilia L., Naya, Gregorio Marco, Barcos, Iris Marco, Marcos, Pilar, Peis, Enrique Marmol, Cuadrado, Marta Martín, Delgado, María Cruz Martin, Vicente, Paula Martín, Martínez, María, Fernández, Carmen Eulalia Martínez, Juan, Maria Dolores Martínez, Palacios, Basilisa Martínez, Jimenez, Juan Fernando Masa, Masclans, Joan Ramon, Maseda, Emilio, Fernández, Eva María Menor, Banderas, Priscila Metora, Minguez, Olga, Miralbés, Mar, Monclou, Josman, Montejo-González, Juan Carlos, Montserrat, Neus, Aznar, María Mora, Morales, Dulce, Cano, Sara Guadalupe Moreno, Rodríguez, David Mosquera, Muñoz-Bermúdez, Rosana, Nicolás, José María, Bou, Ramon Nogue, Salinas, Rafaela Nogueras, Ocón, Marta, Ortega, Ana, Ossa, Sergio, Pagliarani, Pablo, Parrilla, Francisco, Pedregosa-Díaz, José, Bastida, Leire Pérez, Pérez, Purificación, Pérez-García, Felipe, Planelles, Gloria Pérez, Rubio, Eva Pérez, Laguna, David Pestaña, Prados, Javier, Pujol, Andrés, Coll, Núria Ramon, Sanchez-Giron, Gloria Renedo, Roche-Campo, Ferran, Rodriguez, Laura, Castro, Felipe Rodríguez de, Rodríguez, Silvia, Ruiz, Covadonga Rodríguez, Rubio, Jorge, López, Alberto Rubio, Ruiz-García, Ángela Leonor, Miralles, Miriam Ruiz, Murúa, Pablo Ryan, Paz, Eva Saborido, Degracia, Ana Salazar, Sanchez, Miguel, Sánchez, Ana, Chinesta, Susana Sancho, Santacoloma, Bitor, Sariñena, Maria Teresa, Pensado, Marta Segura, Serra, Lidia, Serra-Fortuny, Mireia, Lázaro, Ainhoa Serrano, Servià, Lluís, Soliva, Laura, Speziale, Carla, Tormos, Adrián, Torres, Mateu, Tranque-Liberal, Celia, Trefler, Sandra, Trujillano, Javier, Vaca, Rafaela, Val, Estela, Ruiz, Luis Valdivia, Vallverdú, Montserrat, Martin-Montalvo, Maria Van der Hofstadt, Adrio, Sabela Vara, Vázquez, Nil, Vengoechea, Javier, Vilà-Vilardel, Clara, Vilanova, Judit, Warrington, Tatiana Villada, Yang, Hua, Yang, Minlan, Zapatero, Ana, González, Jessica, de Batlle, Jordi, Benítez, Iván D., Torres, Gerard, Santisteve, Sally, Targa, Adriano D.S., Gort-Paniello, Clara, Moncusí-Moix, Anna, Aguilà, Maria, Seck, Fatty, Ceccato, Adrián, Ferrer, Ricard, Motos, Anna, Riera, Jordi, Fernández, Laia, Menéndez, Rosario, Lorente, José Ángel, Peñuelas, Oscar, Garcia-Gasulla, Dario, Peñasco, Yhivian, Ricart, Pilar, Abril Palomares, Elena, Aguilera, Luciano, Rodríguez, Alejandro, Boado Varela, Maria Victoria, Beteré, Belén, Pozo-Laderas, Juan Carlos, Solé-Violan, Jordi, Salvador-Adell, Inmaculada, Novo, Mariana Andrea, Barberán, José, Amaya Villar, Rosario, Garnacho-Montero, José, Gómez, José M., Blandino Ortiz, Aaron, Tamayo Lomas, Luis, Úbeda, Alejandro, Catalán-González, Mercedes, Sánchez-Miralles, Angel, Martínez Varela, Ignacio, Jorge García, Ruth Noemí, Franco, Nieves, Gumucio-Sanguino, Víctor D., Bustamante-Munguira, Elena, Valdivia, Luis Jorge, Caballero, Jesús, Gallego, Elena, Rodríguez, Covadonga, Castellanos-Ortega, Álvaro, Trenado, Josep, Marin-Corral, Judith, Albaiceta, Guillermo M., de la Torre, Maria del Carmen, Loza-Vázquez, Ana, Vidal, Pablo, Añón, Jose M., Carbajales Pérez, Cristina, Sagredo, Victor, Carbonell, Nieves, Socias, Lorenzo, Barberà, Carme, Estella, Angel, Diaz, Emili, de Gonzalo-Calvo, David, Torres, Antoni, and Barbé, Ferran

Published
2023
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47. Spectrum of composition operators on ${\mathcal S}({\mathbb R})$ with polynomial symbols

Author

Fernández, Carmen, Galbis, Antonio, and Jordá, Enrique

Subjects
Mathematics - Functional Analysis, 46E10 (Primary) 47B33, 47A10, 47A35 (Secondary)
Abstract

We study the spectrum of operators in the Schwartz space of rapidly decreasing functions which associate each function with its composition with a polynomial. In the case where this operator is mean ergodic we prove that its spectrum reduces to 0, while the spectrum of any non mean ergodic composition operator with a polynomial always contains the closed unit disc except perhaps the origen. We obtain a complete description of the spectrum of the composition operator with a quadratic polynomial or a cubic polynomial with positive leading coefficient.

Published
2018

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