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227 results on '"Girela, Daniel"'

2. Products of unbounded Bloch functions

Author

Girela, Daniel

Subjects
Mathematics - Complex Variables, 30D45, 30H30
Abstract

We give new constructions of pair of functions $(f, g)$, analytic in the unit disc, with $g\in H^\infty $ and $f$ an unbounded Bloch function, such that the product $g\cdot f$ is not a Bloch function.

Published
2019

3. A radial integrability result concerning bounded functions in analytic Besov spaces with applications

Author

Domínguez, Salvador and Girela, Daniel

Subjects
Mathematics - Complex Variables
Abstract

We prove that for every $p\ge 1$ there exists a bounded function in the analytic Besov space $B^p$ whose derivative is "badly integrable", along every radius. We apply this result to study multipliers and weighted superposition operators acting on the spaces $B^p$.

Published
2019
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5. Multipliers and integration operators between conformally invariant spaces

Author

Girela, Daniel and Merchán, Noel

Subjects
Mathematics - Complex Variables, 30H25, 47B38
Abstract

In this paper we are concerned with two classes of conformally invariant spaces of analytic functions in the unit disc $\D$, the Besov spaces $B^p$ $(1\le p<\infty )$ and the $Q_s$ spaces $(0

Published
2019

6. Integral means inequalities, convolution, and univalent functions

Author

Girela, Daniel and González, Cristóbal

Subjects
Mathematics - Complex Variables, 30C55, 30H10
Abstract

We use the Baernstein star-function to investigate several questions about the integral means of the convolution of two analytic functions in the unit disc. The theory of univalent functions plays a basic role in our work., Comment: To appear in Journal of Function Spaces

Published
2019
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7. Sequences of zeros of analytic function spaces and weighted superposition operators

Author

Domínguez, Salvador and Girela, Daniel

Subjects
Mathematics - Complex Variables
Abstract

We use properties of the sequences of zeros of certain spaces of analytic functions in the unit disc $\mathbb D$ to study the question of characterizing the weighted superposition operators which map one of these spaces into another. We also prove that for a large class of Banach spaces of analytic functions in $\mathbb D$, $Y$, we have that if the superposition operator $S_\varphi $ associated to the entire function $\varphi $ is a bounded operator from $X$, a certain Banach space of analytic functions in $\mathbb D$, into $Y$, then the superposition operator $S_{\varphi ^\prime }$ maps $X$ into $Y$., Comment: To appear in Monatshefte f\"ur Mathematik

Published
2018
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8. Hankel matrices acting on the Hardy space $H^1$ and on Dirichlet spaces

Author

Girela, Daniel and Merchán, Noel

Subjects
Mathematics - Complex Variables, 47B35 (Primary), 30H10 (Secondary)
Abstract

If $\,\mu \,$ is a finite positive Borel measure on the interval $\,[0,1)$, we let $\,\mathcal H_\mu \,$ be the Hankel matrix $\,(\mu _{n, k})_{n,k\ge 0}\,$ with entries $\,\mu _{n, k}=\mu _{n+k}$, where, for $\,n\,=\,0, 1, 2, \dots $, $\mu_n\,$ denotes the moment of order $\,n\,$ of $\,\mu $. This matrix induces formally the operator $\,\mathcal{H}_\mu (f)(z)= \sum_{n=0}^{\infty}\left(\sum_{k=0}^{\infty} \mu_{n,k}{a_k}\right)z^n\,$ on the space of all analytic functions $\,f(z)=\sum_{k=0}^\infty a_kz^k\,$, in the unit disc $\,\mathbb D $. When $\,\mu \,$ is the Lebesgue measure on $\,[0,1)\,$ the operator $\,\mathcal H_\mu\,$ is the classical Hilbert operator $\,\mathcal H\,$ which is bounded on $\,H^p\,$ if $\,1

Published
2018

9. Products of Unbounded Bloch Functions

Author

Girela, Daniel, Gohberg, Israel, Founding Editor, Ball, Joseph A., Series Editor, Böttcher, Albrecht, Series Editor, Dym, Harry, Series Editor, Langer, Heinz, Series Editor, Tretter, Christiane, Series Editor, Bastos, M. Amélia, editor, Castro, Luís, editor, and Karlovich, Alexei Yu., editor

Published
2021
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10. A Hankel matrix acting on spaces of analytic functions

Author

Girela, Daniel and Merchán, Noel

Subjects
Mathematics - Complex Variables, 47B35, 30H10
Abstract

If $\mu $ is a positive Borel measure on the interval $[0, 1)$ we let $\mathcal H_\mu $ be the Hankel matrix $\mathcal H_\mu =(\mu _{n, k})_{n,k\ge 0}$ with entries $\mu _{n, k}=\mu _{n+k}$, where, for $n\,=\,0, 1, 2, \dots $, $\mu_n$ denotes the moment of order $n$ of $\mu $. This matrix induces formally the operator $$\mathcal{H}_\mu (f)(z)= \sum_{n=0}^{\infty}\left(\sum_{k=0}^{\infty} \mu_{n,k}{a_k}\right)z^n$$ on the space of all analytic functions $f(z)=\sum_{k=0}^\infty a_kz^k$, in the unit disc $\mathbb D $. This is a natural generalization of the classical Hilbert operator. In this paper we improve the results obtained in some recent papers concerning the action of the operators $H_\mu $ on Hardy spaces and on M\"obius invariant spaces., Comment: arXiv admin note: text overlap with arXiv:1612.08304

Published
2017
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11. A generalized Hilbert operator acting on conformally invariant spaces

Author

Girela, Daniel and Merchán, Noel

Subjects
Mathematics - Complex Variables, 47B35, 30H10
Abstract

If $\mu $ is a positive Borel measure on the interval $[0, 1)$ we let $\mathcal H_\mu $ be the Hankel matrix $\mathcal H_\mu =(\mu_{n, k})_{n,k\ge 0}$ with entries $\mu_{n, k}=\mu_{n+k}$, where, for $n\,=\,0, 1, 2, \dots $, $\mu_n$ denotes the moment of orden $n$ of $\mu $. This matrix induces formally the operator $$\mathcal{H}_\mu (f)(z)= \sum_{n=0}^{\infty}\left(\sum_{k=0}^{\infty} \mu_{n,k}{a_k}\right)z^n$$ on the space of all analytic functions $f(z)=\sum_{k=0}^\infty a_kz^k$, in the unit disc $\D $. This is a natural generalization of the classical Hilbert operator. The action of the operators $H_{\mu }$ on Hardy spaces has been recently studied. This paper is devoted to study the operators $H_\mu $ acting on certain conformally invariant spaces of analytic functions on the disc such as the Bloch space, $BMOA$, the analytic Besov spaces, and the $Q_s$ spaces., Comment: 24 pages

Published
2016
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12. Superposition operators, Hardy spaces, and Dirichlet type spaces

Author

Galanopoulos, Petros, Girela, Daniel, and Márquez, María Auxiliadora

Subjects
Mathematics - Complex Variables, Primary 47B35, Secondary 30H10
Abstract

For $0-1$ the space of Dirichlet type $\mathcal D^p_\alpha $ consists of those functions $f$ which are analytic in the unit disc $\mathbb D$ and satisfy $\int_{\mathbb D}(1-| z| )^\alpha| f^\prime (z)| ^p\,dA(z)<\infty $. The space $\Dp$ is the closest one to the Hardy space $H^p$ among all the $\mathcal D^p_\alpha $. Our main object in this paper is studying similarities and differences between the spaces $H^p$ and $\Dp$ ($0

Published
2016
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14. Radial growth of the derivatives of analytic functions in Besov spaces

Author

Domínguez Salvador and Girela Daniel

Subjects
besov spaces, radial behaviour, multipliers, 30h25, 47b38, Mathematics, QA1-939
Abstract

For 1 < p < ∞, the Besov space Bp consists of those functions f which are analytic in the unit disc 𝔻 = {z ∈ 𝔺 : |z| < 1} and satisfy ∫𝔻(1 − |z|2)p−2|f ′(z)|p dA(z) < ∞. The space B2 reduces to the classical Dirichlet space 𝒟. It is known that if f ∈ 𝒟then |f ′(reiθ)| = o[(1 − r)−1/2], for almost every ∈ [0, 2π]. Hallenbeck and Samotij proved that this result is sharp in a very strong sense. We obtain substitutes of the above results valid for the spaces Bp (1 < p < ∞) an we give also an application of our them to questions concerning multipliers between Besov spaces.

Published
2020
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15. Nutritional Status, Dietary Habits, and Physical Activity in Older Adults from Manta, Manabí

Author

Arencibia Moreno Ricardo, Hernández Gallardo Damaris, Linares Girela Daniel, and Linares Manrique Marta

Subjects
older adults, dietary habits, nutritional status, physical activity, healthy eating index, Chemical technology, TP1-1185
Abstract

Defining the nutritional status and physical activity level of older adults makes it possible to guide them toward healthy lifestyles. Objective: The aim of this study was to evaluate dietary habits, nutritional status, and physical activity engagement in older adults living in the city of Manta, Manabí. Methods: An observational, descriptive, and cross-sectional study of 130 older adults was conducted to determine nutritional status via anthropometry, self-reported frequency of the consumption of foodstuffs, calculation of the healthy eating index (IAS), and physical activity patterns. Results: Average age was 71.62 ± 4.34 years, whilst 83.07% of participants were at nutritional risk due to being overweight or obese. Dietary habits in males were characterized by the consumption of three meals a day, as well as greater intake of cereals, roots, tubers, and milk and its derivatives, whilst females consumed more fruits and vegetables. Meat was widely consumed, although females consumed more fish and seafood than males. Eggs were hugely popular foods, in contrast to legumes. Pasta was a dietary staple in females. Visible fats and luncheon meats were consumed little. IAS values reflected the “need to change”, whilst physical activity engagement was found to be low. Conclusions: The nutritional status of the present study population was characterized by a tendency toward increasing overweight, particularly amongst females, with the predominance of class 1 obesity, low physical activity, and a healthy eating index requiring change toward more healthy habits.

Published
2022
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16. Pointwise multipliers between spaces of analytic functions.

Author

Girela, Daniel and Merchán, Noel

Subjects
*ANALYTIC spaces, *ANALYTIC functions, *FUNCTION spaces, *BANACH spaces, *HOLOMORPHIC functions
Abstract

A Banach space X of analytic function in , the unit disc in , is said to be admissible if it contains the polynomials and convergence in X implies uniform convergence in compact subsets of. If X and Y are two admissible Banach spaces of analytic functions in and g is a holomorphic function in , g is said to be a multiplier from X to Y if g ·f ∈ Y for every f ∈ X. The space of all multipliers from X to Y is denoted M (X, Y), and M (X) will stand for M (X, X). The closed graph theorem shows that if g ∈ M (X, Y) then the multiplication operator Mg, defined by Mg (f) = g · f, is a bounded operator from X into Y. It is known that M (X) ⊂ H∞ and that if g ∈ M (X), then ∥g∥H∞ ≤ ||Mg||. Clearly, this implies that M (X, Y) ⊂ H∞ if Y ⊂ X. If Y ⊄ X, the inclusion M (X, Y) ⊂ H∞ may not be true. In this paper we start presenting a number of conditions on the spaces X and Y which imply that the inclusion M (X, Y) ⊂ H∞ holds. Next, we concentrate our attention on multipliers acting an BMOA and some related spaces, namely, the Qs-spaces (0

Published
2024
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17. A generalized Hilbert matrix acting on Hardy spaces

Author

Chatzifountas, Christos, Girela, Daniel, and Pelaez, Jose Angel

Subjects
Mathematics - Functional Analysis, Mathematics - Complex Variables
Abstract

If $\mu $ is a positive Borel measure on the interval $[0, 1)$, the Hankel matrix $\mathcal H_\mu =(\mu_{n,k})_{n,k\ge 0}$ with entries $\mu_{n,k}=\int_{[0,1)}t^{n+k}\,d\mu(t)$ induces formally the operator $$\mathcal{H}_\mu (f)(z)=\sum_{n=0}^{\infty}\left(\sum_{k=0}^{\infty}\mu_{n,k}{a_k}\right)z^n$$ on the space of all analytic functions $f(z)=\sum_{k=0}^\infty a_kz^k$, in the unit disc $\mathbb{D} $. In this paper we describe those measures $\mu$ for which $\mathcal{H}_\mu $ is a bounded (compact) operator from $H^p$ into $H^q$, $0

Published
2013

22. Generalized Hilbert Operators

Author

Galanopoulos, Petros, Girela, Daniel, Peláez, José Ángel, and Siskakis, Aristomenis

Subjects
Mathematics - Complex Variables, Mathematics - Functional Analysis, 47B35, 30H10
Abstract

If $g$ is an analytic function in the unit disc $\D $ we consider the generalized Hilbert operator $\hg$ defined by {equation*}\label{H-g} \mathcal{H}_g(f)(z)=\int_0^1f(t)g'(tz)\,dt. {equation*} We study these operators acting on classical spaces of analytic functions in $\D $. More precisely, we address the question of characterizing the functions $g$ for which the operator $\hg $ is bounded (compact) on the Hardy spaces $H^p$, on the weighted Bergman spaces $A^p_\alpha $ or on the spaces of Dirichlet type $\mathcal D^p_\alpha $.

Published
2012
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47. Influence of the nutritional status based on physiological parameters of physical performance in teenager soccer player, Ecuador

Author

Hernández Gallardo, Damaris, Linares Girela, Daniel|||0000-0002-9910-9019, and Linares Manrique, Marta

Subjects
Rendimiento físico, Estado nutricional, Potencia Anaeróbica Máxima, VO2 máx, Futbolistas adolescentes
Abstract

Objetivo: determinar la influencia del estado nutricional sobre parámetros fisiológicos de rendimiento físico en adolescentes futbolistas, Ecuador. Materiales y métodos: Se presenta un estudio correlacional descriptivo y corte trasversal, ex post facto con medición de grupo único, sobre 126 futbolistas adolescentes masculinos sub 16 en preparación física general, explorando mediante procedimientos validados internacionalmente la composición corporal, la ingesta alimentaria y el gasto de energía en 24 horas, así como el uso de los test de Cooper y Matsudo en función de medir la capacidad aeróbica y anaeróbica lactácida según parámetros como el VO2máx y Potencia anaeróbica Máxima. Resultados: los sujetos muestran talla y masa corporal de los sujetos en valores respectivos de 1,68(0,05) m y 57,69(5,94) kg, IMC normopeso, complexión pequeña, mientras que el contenido graso de 6,57(1,03) kg, masa muscular de 34,26(4,28) kg, masa ósea de 14,78(1,41) kg y residual en 2,09(0,69) kg, el gasto energético no es compatible con la ingesta energética alimentaria, además de presentar un VO2máx de 2,87(0,52) lt/kg/min y Potencia Anaeróbica Lactácida de 403,11(44,02). Conclusiones: el estado nutricional de los deportistas en estudio no es propicio al despliegue del rendimiento físico, no favorece el desarrollo de la capacidad de resistencia, aunque en potencialidad de acciones motrices de gran deuda de oxígeno. Objective: To determine the influence of nutritional status on physiological parameters of physical performance in teenager soccer players, Ecuador. Materials and methods: a cross-sectional descriptive and cross-sectional study, ex post facto with single group measurement, is presented on 126 under 16 male teenager soccer players in general physical preparation, exploring by means of procedures the body composition valid internationally, the alimentary intake and the expense of energy in around 24 hours, as well as the use of the Cooper and Matsudo tests in order to measure the aerobic and anaerobic lactacid capacity, all of these according to parameters such as VO2max and maximal aerobic power. Results: The subjects showed size and body mass of the subjects in respective values of 1, 68 (0, 05) m and 57, 69 (5,94) kg BMI normal weight, small complexion, while fat content is 6.57 (1.03) kg. Muscle mass is 34.26 (4.28) kg bone mass is 14.78 (1.41) kg and residual in 2.09 (0.69) kg, energy expenditure is not compatible with food energy intake, in addition to presenting a VO2max of 2.87 (0.52) lt / kg / min and lactate anaerobic potency of 403.11 (42.02). Conclusions: the nutritional status of the athletes under study is not conducive to the deployment of physical performance, it does not even favor the development of resilience, although potentially motor actions of high oxygen are in debt.

Published
2020

48. Influencia del estado nutricional sobre parámetros fisiológicos de rendimiento físico en adolescentes futbolistas, Ecuador

Author

Hernández Gallardo, Damaris, Linares Girela, Daniel, and Linares Manrique, Marta

Subjects
Rendimiento físico, Estado nutricional, Potencia Anaeróbica Máxima, VO2 máx, Futbolistas adolescentes
Abstract

Objetivo: determinar la influencia del estado nutricional sobre parámetros fisiológicos de rendimiento físico en adolescentes futbolistas, Ecuador. Materiales y métodos: Se presenta un estudio correlacional descriptivo y corte trasversal, ex post facto con medición de grupo único, sobre 126 futbolistas adolescentes masculinos sub 16 en preparación física general, explorando mediante procedimientos validados internacionalmente la composición corporal, la ingesta alimentaria y el gasto de energía en 24 horas, así como el uso de los test de Cooper y Matsudo en función de medir la capacidad aeróbica y anaeróbica lactácida según parámetros como el VO2máx y Potencia anaeróbica Máxima. Resultados: los sujetos muestran talla y masa corporal de los sujetos en valores respectivos de 1,68(0,05) m y 57,69(5,94) kg, IMC normopeso, complexión pequeña, mientras que el contenido graso de 6,57(1,03) kg, masa muscular de 34,26(4,28) kg, masa ósea de 14,78(1,41) kg y residual en 2,09(0,69) kg, el gasto energético no es compatible con la ingesta energética alimentaria, además de presentar un VO2máx de 2,87(0,52) lt/kg/min y Potencia Anaeróbica Lactácida de 403,11(44,02). Conclusiones: el estado nutricional de los deportistas en estudio no es propicio al despliegue del rendimiento físico, no favorece el desarrollo de la capacidad de resistencia, aunque en potencialidad de acciones motrices de gran deuda de oxígeno., Objective: To determine the influence of nutritional status on physiological parameters of physical performance in teenager soccer players, Ecuador. Materials and methods: a cross-sectional descriptive and cross-sectional study, ex post facto with single group measurement, is presented on 126 under 16 male teenager soccer players in general physical preparation, exploring by means of procedures the body composition valid internationally, the alimentary intake and the expense of energy in around 24 hours, as well as the use of the Cooper and Matsudo tests in order to measure the aerobic and anaerobic lactacid capacity, all of these according to parameters such as VO2max and maximal aerobic power. Results: The subjects showed size and body mass of the subjects in respective values of 1, 68 (0, 05) m and 57, 69 (5,94) kg BMI normal weight, small complexion, while fat content is 6.57 (1.03) kg. Muscle mass is 34.26 (4.28) kg bone mass is 14.78 (1.41) kg and residual in 2.09 (0.69) kg, energy expenditure is not compatible with food energy intake, in addition to presenting a VO2max of 2.87 (0.52) lt / kg / min and lactate anaerobic potency of 403.11 (42.02). Conclusions: the nutritional status of the athletes under study is not conducive to the deployment of physical performance, it does not even favor the development of resilience, although potentially motor actions of high oxygen are in debt.

Published
2020

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