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4. Localized holes and delocalized electrons in photoexcited inorganic perovskites: Watching each atomic actor by picosecond X-ray absorption spectroscopy

Author

Santomauro, Fabio G., Grilj, Jakob, Mewes, Lars, Nedelcu, Georgian, Yakunin, Sergii, Rossi, Thomas, Capano, Gloria, Haddad, André Al, Budarz, James, Kinschel, Dominik, Ferreira, Dario S., Rossi, Giacomo, Tovar, Mario Gutierrez, Grolimund, Daniel, Samson, Valerie, Nachtegaal, Maarten, Smolentsev, Grigory, Kovalenko, Maksym V., and Chergui, Majed

Subjects
Condensed Matter - Materials Science
Abstract

We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals (NCs) in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes are observed at the Cs L2-edge. The results at the Br and Pb edges suggest the existence of a weakly localized exciton, while the absence of signatures at the Cs edge indicates that the Cs+ cation plays no role in the charge transport, at least beyond 80 ps. These results can explain the rather modest charge carrier mobilities in these materials., Comment: 19 pages, 3 figures

Published
2016

11. Bi-additive models for extremes.

Author

Antunes, Patrícia, Ferreira, Sandra S., Ferreira, Dário, and Mexia, João T.

Subjects
CUMULANTS, ELLIPSOIDS
Abstract

To widen the application field of mixed models we introduce bi-additive models. These models are given by the sum of a fixed term X 0 β and independent random effects terms X i Z i , i = 1 , ... , w. Vectors Z 1 , ... , Z w , will have c 1 , ... , c w , i. i. d. components with r − th order cumulants χ r , 1 , ... , χ r , w. We now consider the case in which the distributions of these components are distributed as Gumbel, Fréchet and Weibull types, estimating their cumulants and parameters. We then obtain 1 − p confidence ellipsoids with [approximate] probability of containing realizations of the model. These ellipsoids can be used to, trough duality, test hypothesis on the fixed effects part X 0 β of the models. Moreover matrices X 0 , X 1 , ... , X w , contain in their columns values of controlled variables and, for given values of the controlled variables, prediction intervals are obtained, containing future observations, with 1 − p [approximate] probability. Three simulations studies, one for each distribution type, and an application to the Tagus river floods are included. We thus show how bi-additive models may be introduced in the important field of extreme value. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Editorial Summary: Mathematical Models and Methods in Various Sciences.

Author

Ferreira, Dário

Subjects
*PROPORTIONAL hazards models, *QUALITY control charts, *MATHEMATICAL models, *WIENER processes, *PROPORTIONAL representation, *GARCH model
Abstract

The Special Issue of Symmetry titled "Mathematical Models and Methods in Various Sciences" brings together innovative papers on the theory, methodology, and applications of symmetric/asymmetric mathematical models and methods in various areas of science. The published papers cover a wide range of topics, including estimation methods for mismeasured covariates, empirical models for data analysis, computational approaches for heat transport, investment and pricing strategies, memory-type control charts for monitoring operations, estimation of volatility function in GARCH models, novel weighted distributions, degradation modeling, queueing systems, bivariate proportional hazard models, proportional representation in elections, bounded rational decision-making models, and reliability estimation using a Wiener process. The papers demonstrate the adaptability and capabilities of mathematical modeling in resolving complex issues across diverse scientific fields. [Extracted from the article]

Published
2023
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19. Confidence intervals and ellipsoids for estimable functions and estimable vectors in models with orthogonal block structure.

Author

Ferreira, Sandra S., Ferreira, Dário, Nunes, Célia, and Mexia, João T.

Subjects
*CONFIDENCE intervals, *VECTOR valued functions, *ORTHOGONAL functions, *CONFIDENCE regions (Mathematics), *PARAMETERS (Statistics), *SPACE-time block codes
Abstract

Sub‐models of mixed linear models are considered. The independence of these sub‐models leads to sufficient statistics for the parameters relevant for their densities. Using pivot variables, confidence regions are obtained as well hypothesis testing for variance components, estimable functions, and estimable vectors. In addition, to compare the estimators and the models, we present the histograms with the empirical joint densities for positive and negative parts of the estimators. The figures, for the two‐dimensional charts, contain the corresponding UMVUE and are all unimodal with the UMVUE near the mode. The nearness of the estimators and the modes validates the presented methodology and allows the safe use of induced densities. A numerical example applied to real data is presented. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Orthogonal mixed models and prime basis factorials.

Author

Ferreira, Dário, Ferreira, Sandra S., Nunes, Célia, and Mexia, João T.

Subjects
*SUM of squares, *CARDIOVASCULAR system, *FACTORIALS, *NUMBER theory
Abstract

Prime basis factorial models have the advantage of allowing the simultaneous study of a larger number of interactions compared to classical approaches. However, the procedures for obtaining the sums of squares can be somewhat cumbersome. In this work, we present a recurrence method for obtaining the sums of squares in prime basis factorial models. Nevertheless, this recurrence procedure may be applied in cases with any number of factors and levels, even when it is neither a prime nor a power of a prime. We illustrate the method with an application to real data, where the percentage of total deaths due to cancer, diabetes, and any circulatory system disease in three European countries, in 3 years, is compared. We compare the results with the ones obtained using ANOVA. [ABSTRACT FROM AUTHOR]

Published
2022
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22. Multiple additive models

Author

Antunes, Patrícia, Ferreira, Sandra S., Ferreira, Dário, Mexia, João T., and uBibliorum

Subjects
Mixed Models, Statistics and Probability, Combinatorics, Mixed model, ANOVA, Cumulants, Additive model, Base (exponentiation), Mathematics
Abstract

The models constituting a multiple model will correspond to d treatments of a base design. Using a classic result on cumulant generation function we show how to obtain least square estimators for cumulants and generalized least squares estimators for vectors \beta, l=1,...,d, in the individual models. Next we carry out ANOVA-like analysis for the action of the factors in the base design. This is possible since the estimators \tilde{\beta }(l) of \beta (l). l=1,...,d, have, approximately, the same covariance matrix. The eigenvectors of that matrix will give the principal estimable functions \epsilon_{i}^{\top} \beta (l) i=1,...,k, l=1,...,d, for the individual models. The ANOVA-like analysis will consider homologue components on principal estimable functions. To apply our results we assume the factors in the base design to have fixed effects. Moreover if w=1, and Z(1) has covariance matrix \sigma^{2} \m I_{n}, our treatment generalizes that previously given for multiple regression designs. In them we have a linear regression for each treatment of a base design. We then study the action of the factors on that design on the vectors \beta(l), l=1,...,d. An example of application of the proposed methodology is given.

Published
2020

23. Caracterização das tentativas de suicídio no Serviço de Urgência do Hospital Sousa Martins, Unidade Local de Saúde da Guarda, EPE

Author

Santos, Mário J., Nunes, Juliana, Ferreira, Dário, and Pissarra da Costa, António

Subjects
Psychiatry, Suicide, RC435-571, Psychology, Emergency Department, Suicídio, Attempted suicide, Tentativa de suicídio, humanities, Serviço de Urgência, BF1-990
Abstract

Introduction: Suicide is a complex public health problem resulting from the interaction between biological, psychological and sociocultural factors. Annually, according to the World Health Organization, about one million individuals commit suicide worldwide. That number corresponds to half of all violent deaths recorded and the tendency is to increase. Attempted suicide is defined as an act carried out by an individual who seeks his own death, but for various reasons, usually unrelated to the individual, results frustrated. The most important predictive factor of suicide is attempted suicide. It is considered that for every person who commits suicide, 20 or more make an attempt. Aims: To analyze the profile of the patient who resorts to the Emergency Department of Sousa Martins Hospital, ULS Guarda, E.P.E., for attempted suicide. Methods: Study, of retrospective basis, of the period between 1 January 2010 and 31 December 2014. We based it on the statistical survey of data from medical records of the individuals over 18 who resorted to the Emergency Department of Sousa Martins Hospital, ULS Guarda, E.P.E., for whom it was deemed an attempted suicide event, prior to clinical evaluation. Results and Conclusions: We conclude that the typical profile of the person who resorts, for suicide attempt, to the studied Emergency Department is female, at the beginning of middle age (approximately, at age 45), married, have a history of depressive disorder, use as a method of attempt drug ingestion and point out the existence of relational problems as a triggering factor. In addition, these individuals tend to resort to the Emergency Department, especially, in the last eight hours of the day., Introdução: O suicídio é um complexo problema de saúde pública, resultante da interação entre fatores biológicos, psicológicos e socioculturais. Suicidam-se anualmente, em todo o mundo, segundo a Organização Mundial de Saúde, cerca de um milhão de indivíduos, o que corresponde a metade de todas as mortes violentas registadas, tendo esse número tendência a aumentar. A tentativa de suicídio é definida como um ato levado a cabo por um indivíduo que visa a sua morte, mas que, por razões diversas, geralmente alheias ao indivíduo, resulta frustrado. O fator de predição mais importante do suicídio é a tentativa de suicídio. Considera-se que, por cada pessoa que se suicida, 20 ou mais cometem uma tentativa de suicídio. Objetivos: Analisar o perfil do doente que recorre ao Serviço de Urgência do Hospital Sousa Martins, ULS da Guarda, E.P.E., por tentativa de suicídio. Métodos: Estudo, de carácter retrospetivo, do período compreendido entre 1 de janeiro de 2010 e 31 de dezembro de 2014. Executámos o levantamento estatístico e análise dos dados dos processos clínicos dos indivíduos maiores de 18 anos que recorreram ao Serviço de Urgência do Hospital Sousa Martins, ULS da Guarda, E.P.E., para os quais foi presumido, antes da avaliação clínica, um evento de tentativa de suicídio. Resultados e Conclusões: Concluímos que o perfil típico do indivíduo que recorre por tentativa de suicídio, ao Serviço de Urgência estudado, é ser do sexo feminino, estar no início da meia-idade (por volta dos 45 anos), ser casado/a, ter antecedentes de perturbação depressiva, utilizar como método da tentativa a ingestão medicamentosa e apontar como motivo desencadeante a existência de problemas relacionais. Além disto, estes indivíduos tendem a recorrer ao Serviço de Urgência, principalmente, nas últimas oito horas do dia.

Published
2021

24. Inference in nonorthogonal mixed models.

Author

Ferreira, Dário, Ferreira, Sandra S., Nunes, Célia, and Mexia, João T.

Subjects
*CONFIDENCE regions (Mathematics), *LEAST squares, *BAYESIAN analysis, *CONFIDENCE intervals, *ANALYSIS of variance
Abstract

This paper presents an estimation method for the random effect parameters and the variance components in linear mixed models. These models may be orthogonal or nonorthogonal. In particular, least squares estimators and the corresponding confidence regions, based on the estimation of quantiles, are considered. As to the random effects parameters, it is only assumed that they have null mean vectors and distributions with known dispersion parameters and second order moments. So, it is not necessary that they are normally distributed. A numerical example considering the normal and the gamma distributions is included, where a comparison with the analysis of variance and a Bayesian estimation based method is provided. [ABSTRACT FROM AUTHOR]

Published
2022
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29. Multiple additive models.

Author

Antunes, Patrícia, Ferreira, Sandra S., Ferreira, Dário, and Mexia, João T.

Subjects
LEAST squares, FACTOR analysis, CUMULANTS, EIGENVECTORS, FIXED effects model
Abstract

The models constituting a multiple model will correspond to d treatments of a base design. When we have individual additive models Y (l) = X 0 β (l) + ∑ i = 1 w X i Z i (l) , l = 1 , ... , d , with Z 1 (l) , ... , Z w (l) , independent, with c 1 , ... , c w independent components, with χ r , 1 , ... , χ r , w , the r − th order cumulants, r = 2 , 3 , 4 , the multiple model will be additive. Using a classic result on cumulant generation function we show how to obtain least square estimators for cumulants and generalized least squares estimators for vectors β , l = 1 , ... , d , in the individual models. Next we carry out ANOVA-like analysis for the action of the factors in the base design. This is possible since the estimators β ˜ (l) of β (l) l = 1 , ... , d , have, approximately, the same covariance matrix. The eigenvectors of that matrix will give the principal estimable functions ϵ i ⊤ β (l) i = 1 , ... , k , l = 1 , ... , d , for the individual models. The ANOVA-like analysis will consider homolog components on principal estimable functions. To apply our results we assume the factors in the base design to have fixed effects. Moreover if w = 1 , and Z (1) has covariance matrix σ 2 I n , our treatment generalizes that previously given for multiple regression designs. In them we have a linear regression for each treatment of a base design. We then study the action of the factors on that design on the vectors β (l) , l = 1 , ... , d. An example of application of the proposed methodology is given. [ABSTRACT FROM AUTHOR]

Published
2021
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30. Limit distributions for asymptotically linear statistics with spherical error

Author

Nunes, Célia, Ferreira, Dário, Ferreira, Sandra S., Mexia, João T., and uBibliorum

Subjects
Statistics and Probability, Asymptotically linear, Work (thermodynamics), Control and Optimization, Asymptotic linearity, Normal distribution, Spherical densities, Asymptotic linearity, Limit distributions, Normal distribution, Spherical densities, Cylinder volume, Artificial Intelligence, Homoscedasticity, Signal Processing, Statistics, Limit distributions, Cylinder, Cylinder volume, Computer Vision and Pattern Recognition, Limit (mathematics), lcsh:Probabilities. Mathematical statistics, Statistics, Probability and Uncertainty, lcsh:QA273-280, Information Systems, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T17:46:37Z No. of bitstreams: 1 2018 - Limit Distributions for Asymptotically Linear Statistics with Spherical Error.pdf: 109442 bytes, checksum: fea755ae8a80328f562c7b498bfe0926 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T14:29:51Z (GMT) No. of bitstreams: 1 2018 - Limit Distributions for Asymptotically Linear Statistics with Spherical Error.pdf: 109442 bytes, checksum: fea755ae8a80328f562c7b498bfe0926 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T14:36:35Z (GMT) No. of bitstreams: 1 2018 - Limit Distributions for Asymptotically Linear Statistics with Spherical Error.pdf: 109442 bytes, checksum: fea755ae8a80328f562c7b498bfe0926 (MD5) Made available in DSpace on 2020-02-06T14:36:35Z (GMT). No. of bitstreams: 1 2018 - Limit Distributions for Asymptotically Linear Statistics with Spherical Error.pdf: 109442 bytes, checksum: fea755ae8a80328f562c7b498bfe0926 (MD5) Previous issue date: 2018 info:eu-repo/semantics/publishedVersion

Published
2018

31. Estimation of variance components in models with positive commutativity orthogonal block structure

Author

Ferreira, Sandra S., Ferreira, Dário, Nunes, Célia, Mexia, João T., and uBibliorum

Subjects
Estimation, Block structure, Simple (abstract algebra), Numerical analysis, Linear model, Orthogonal block structure, Applied mathematics, Variance components, Estimator, Linear models, Commutative property, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T18:56:40Z No. of bitstreams: 1 2018 - Estimation of Variance Components in Models with Positive Commutativity Orthogonal Block Structure.pdf: 516997 bytes, checksum: e0d2abf568b9f1cc9e4ce1cda0c2365f (MD5) Rejected by Pessoa (pfep@ubi.pt), reason: Agregar os nomes ao OCID e/ou Ciência Vitae Colocar resumos e palavras chave Colocar código de financiamento FCT Consultar : https://www.ubi.pt/Ficheiros/Sites/7/Documentos/1375/Instruções%20para%20Auto%20depósito%20de%20documentos.pdf Após corrigir é só submeter de novo. Obrigado on 2020-02-06T15:57:05Z (GMT) Submitted by FERREIRA (dario@ubi.pt) on 2020-02-07T10:07:13Z No. of bitstreams: 1 2018 - Estimation of Variance Components in Models with Positive Commutativity Orthogonal Block Structure.pdf: 516997 bytes, checksum: e0d2abf568b9f1cc9e4ce1cda0c2365f (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T15:13:25Z (GMT) No. of bitstreams: 1 2018 - Estimation of Variance Components in Models with Positive Commutativity Orthogonal Block Structure.pdf: 516997 bytes, checksum: e0d2abf568b9f1cc9e4ce1cda0c2365f (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T15:14:30Z (GMT) No. of bitstreams: 1 2018 - Estimation of Variance Components in Models with Positive Commutativity Orthogonal Block Structure.pdf: 516997 bytes, checksum: e0d2abf568b9f1cc9e4ce1cda0c2365f (MD5) Made available in DSpace on 2020-02-07T15:14:30Z (GMT). No. of bitstreams: 1 2018 - Estimation of Variance Components in Models with Positive Commutativity Orthogonal Block Structure.pdf: 516997 bytes, checksum: e0d2abf568b9f1cc9e4ce1cda0c2365f (MD5) Previous issue date: 2018 info:eu-repo/semantics/publishedVersion

Published
2018

34. Considering the sample sizes as truncated Poisson random variables in mixed effects models.

Author

Nunes, Célia, Moreira, Elsa, Ferreira, Sandra S., Ferreira, Dário, and Mexia, João T.

Subjects
POISSON processes, POISSON distribution, ANALYSIS of variance, HOSPITAL patients, RANDOM variables, CANCER patients, SAMPLING (Process)
Abstract

When applying analysis of variance, the sample sizes may not be previously known, so it is more appropriate to consider them as realizations of random variables. A motivating example is the collection of observations during a fixed time span in a study comparing, for example, several pathologies of patients arriving at a hospital. This paper extends the theory of analysis of variance to those situations considering mixed effects models. We will assume that the occurrences of observations correspond to a counting process and the sample dimensions have Poisson distribution. The proposed approach is applied to a study of cancer patients. [ABSTRACT FROM AUTHOR]

Published
2020
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35. Tests and relevancies for the hypotheses of an orthogonal family in a model with orthogonal block structure.

Author

Ferreira, Dário, Ferreira, Sandra S., Nunes, Célia, and Mexia, João T.

Subjects
*ORTHOGRAPHIC projection, *COVARIANCE matrices, *HYPOTHESIS, *RELEVANCE, *RANDOM effects model
Abstract

A model has an orthogonal block structure if it has, as covariance matrix, a linear combination of pairwise orthogonal projection matrices, that add up to the identity matrix. The range space of these matrices are associated to hypotheses of an orthogonal family. In this paper we show how to obtain tests for these hypotheses when normality is assumed and how to consider their relevance when normality is discarded. Besides the notion of relevance, we formulate hypotheses in a general way that may be applied to models with orthogonal block structure, whose factors may have fixed and/or random effects. The results are applied to prime basis factorial models and an example is presented. [ABSTRACT FROM AUTHOR]

Published
2020
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39. F-tests with a rare pathology

Author

Nunes, Célia, Ferreira, Dário, Ferreira, Sandra S., Mexia, João T., and uBibliorum

Subjects
Statistics and Probability, Sample selection, Pathology, medicine.medical_specialty, Degrees of freedom (statistics), Rare pathology, Sample (statistics), Truncation error, F-tests, Sample size determination, Statistics, Econometrics, medicine, Statistics, Probability and Uncertainty, Random degrees of freedom, Random non-centrality parameters, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T18:11:05Z No. of bitstreams: 1 2012 - F-tests with a rare pathology.pdf: 298944 bytes, checksum: 141b337662eb720fee546d7c60f67b36 (MD5) Rejected by Pessoa (pfep@ubi.pt), reason: Agregar os nomes ao OCID e/ou Ciência Vitae Colocar resumos e palavras chave Colocar código de financiamento FCT Consultar : https://www.ubi.pt/Ficheiros/Sites/7/Documentos/1375/Instruções%20para%20Auto%20depósito%20de%20documentos.pdf on 2020-02-06T15:53:33Z (GMT) Submitted by FERREIRA (dario@ubi.pt) on 2020-02-07T00:02:11Z No. of bitstreams: 1 2012 - F-tests with a rare pathology.pdf: 298944 bytes, checksum: 141b337662eb720fee546d7c60f67b36 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T14:50:05Z (GMT) No. of bitstreams: 1 2012 - F-tests with a rare pathology.pdf: 298944 bytes, checksum: 141b337662eb720fee546d7c60f67b36 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T14:50:50Z (GMT) No. of bitstreams: 1 2012 - F-tests with a rare pathology.pdf: 298944 bytes, checksum: 141b337662eb720fee546d7c60f67b36 (MD5) Made available in DSpace on 2020-02-07T14:50:50Z (GMT). No. of bitstreams: 1 2012 - F-tests with a rare pathology.pdf: 298944 bytes, checksum: 141b337662eb720fee546d7c60f67b36 (MD5) Previous issue date: 2012 info:eu-repo/semantics/publishedVersion

Published
2012

40. Binding of Dengue Virus Particles and Dengue Proteins onto Solid Surfaces

Author

Rafael F. O. França, Benedito Antonio Lopes da Fonseca, Edla M. A. Pereira, Aline Ferreira Dário, and Denise Freitas Siqueira Petri

Subjects
Surface Properties, viruses, Hemagglutinin (influenza), Biocompatible Materials, Dengue virus, medicine.disease_cause, Styrene, Viral Proteins, chemistry.chemical_compound, Adsorption, Materials Testing, medicine, General Materials Science, biology, Chemistry, LECTINAS, Virion, Dengue Virus, Surface energy, Crystallography, Concanavalin A, Jacalin, biology.protein, Polystyrene, Protein Binding
Abstract

The interaction between dengue virus particles (DENV), sedimentation hemagglutinin particles (SHA), dengue virus envelope protein (Eprot), and solid surfaces was investigated by means of ellipsometry and atomic force microscopy (AFM). The surfaces chosen are bare Si/SiO2 wafers and Si/SiO2 wafers covered with concanavalin A (ConA), jacalin (Jac), polystyrene (PS), or poly(styrene sulfonate) (PSS) films. Adsorption experiments at pH 7.2 and pH 3 onto all surfaces revealed that (i) adsorption of DENV particles took place only onto ConA under pH 7.2, because of specific recognition between glycans on DENV surface and ConA binding site; (ii) DENV particles did not attach to any of the surfaces at pH 3, suggesting the presence of positive charges on DENV surface at this pH, which repel the positively charged lectin surfaces; (iii) SHA particles are positively charged at pH 7.2 and pH 3 because they adhered to negatively charged surfaces at pH 7.2 and repelled positively charged layers at pH 3; and (iv) SHA particles carry polar groups on the surface because they attached to silanol surfaces at pH 3 and avoided hydrophobic PS films at pH 3 and pH 7.2. The adsorption behavior of Eprot at pH 7.2 revealed affinity for ConAJacPSSPS≈bare Si/SiO2 layers. These findings indicate that selectivity of the Eprot adsorption is higher when it is part of virus structure than when it is free in solution. The correlation between surface energy values determined by means of contact angle measurements and DENV, SHA, or Eprot adsorption behavior was used to understand the intermolecular forces at the interfaces. A direct correlation was not found because the contributions from surface energy were probably surpassed by specific contributions.

Published
2010

41. Effect of solvent on the adsorption behavior and on the surface properties of Sterculia striata polysaccharide

Author

Denise Freitas Siqueira Petri, Haroldo C.B. Paula, Judith P.A. Feitosa, Aline Ferreira Dário, and Regina C.M. de Paula

Subjects
Polymers and Plastics, Organic Chemistry, food and beverages, POLISSACARÍDEOS, Surface energy, Solvent, Contact angle, chemistry.chemical_compound, Adsorption, chemistry, Ellipsometry, Ionic liquid, Monolayer, Materials Chemistry, Organic chemistry, Lysozyme, Nuclear chemistry
Abstract

Characterization of Sterculia striata polysaccharide (SSP) films adsorbed onto Si wafers from solutions prepared in ethyl methyl imidazolium acetate (EmimAc), water or NaOH 0.01 mol/L was systematically studied by means of ellipsometry, atomic force microscopy and contact angle measurements. SSP adsorbed from EmimAc onto Si wafer as homogeneous monolayers (∼0.5 nm thick), while from water or NaOH 0.01 mol/L SSP formed layers of ∼4.0 nm and ∼1.5 nm thick, respectively. Surface energy values found for SSP adsorbed from EmimAc or water were 68 ± 2 mJ/m 2 and 65 ± 2 mJ/m 2 , respectively, whereas from NaOH it amounted to 57 ± 3 mJ/m 2 . The immobilization of lysozyme (LYS) onto SSP films was also investigated. The mean thickness of LYS ( d LYS ) immobilized onto SSP films adsorbed from each solvent tended to increase with the decrease of γ S p and γ S total . However, the enzymatic activity of LYS molecules was higher when they were immobilized onto SSP films with higher γ S p and γ S total values.

Published
2010

43. One-way fixed effects ANOVA with missing observations

Author

Nunes, Célia, Capistrano, Gilberto, Ferreira, Dário, Ferreira, Sandra S., Mexia, João T., and uBibliorum

Subjects
Missing observations, ANOVA, Geography, Random sample sizes, Statistics, Econometrics, Cancer registries, Analysis of variance, Melanoma skin cancer
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T22:13:42Z No. of bitstreams: 1 2015 - One-way Fixed Effects ANOVA with Missing Observation.pdf: 117720 bytes, checksum: de2ba26831fe1a3a294cccc47175ccd1 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:13:27Z (GMT) No. of bitstreams: 1 2015 - One-way Fixed Effects ANOVA with Missing Observation.pdf: 117720 bytes, checksum: de2ba26831fe1a3a294cccc47175ccd1 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:15:38Z (GMT) No. of bitstreams: 1 2015 - One-way Fixed Effects ANOVA with Missing Observation.pdf: 117720 bytes, checksum: de2ba26831fe1a3a294cccc47175ccd1 (MD5) Made available in DSpace on 2020-02-06T16:15:39Z (GMT). No. of bitstreams: 1 2015 - One-way Fixed Effects ANOVA with Missing Observation.pdf: 117720 bytes, checksum: de2ba26831fe1a3a294cccc47175ccd1 (MD5) Previous issue date: 2015 info:eu-repo/semantics/publishedVersion

Published
2015

45. Estimación de lascomponentes de varianza en modelos lineales mixtos con estructura de bloques ortogonal conmutativa

Author

FERREIRA, SANDRA S., FERREIRA, DÁRIO, NUNES, CÉLIA, and T. MEXIA, JOÃO

Subjects
Mixed model, Variance components, Commutative Jordan algebra, álgebra conmutativa Jordan, modelo mixto, componentes de varianza
Abstract

Segregation and matching are techniques to estimate variance components in mixed models. A question arising is whether segregation can be applied in situations where matching does not apply. Our motivation for this research relies on the fact that we want an answer to that question and to explore this important class of models that can contribute to the development of mixed models. That is possible using the algebraic structure of mixed models. We present two examples showing that segregation can be applied in situations where matching does not apply. La segregación y el emparejamiento son técnicas para estimar las componentes de varianza en modelos mixtos. Una pregunta que ha surgido es si la segregación puede ser aplicada en situaciones en las que el emparejamiento no es aplicable. Nuestra motivación para esta investigación se basa en el hecho de que se quiere una respuesta a esta pregunta y se quiere explorar esta importante clase de modelos con el fin de contribuir al desarrollo de los modelos mixtos. Esto es posible utilizando la estructura algebraica de los modelos mixtos con estructura de bloques ortogonal conmutativa. Se presentan dos ejemplos que muestran que la segregación puede ser aplicada en situaciones donde el emparejamiento no es aplicable.

Published
2013

46. Estimation of variance components in linear mixed models with commutative orthogonal block structure

Author

Ferreira, Sandra S., Ferreira, Dário, Nunes, Célia, Mexia, João T., and uBibliorum

Subjects
Variance Components, álgebra conmutativa Jordan, modelo mixto, componentes de varianza, Commutative Jordan Algebra, lcsh:Statistics, lcsh:HA1-4737, Mixed Model
Abstract

Submitted by FERREIRA (sandraf@ubi.pt) on 2020-02-07T10:21:53Z No. of bitstreams: 1 2013 - Estimation of Variance Components in Linear Mixed Models with Commutative Orthogonal Block Structure.pdf: 3621466 bytes, checksum: ef8ca603751caa42fdf33cb354af8a20 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T15:15:51Z (GMT) No. of bitstreams: 1 2013 - Estimation of Variance Components in Linear Mixed Models with Commutative Orthogonal Block Structure.pdf: 3621466 bytes, checksum: ef8ca603751caa42fdf33cb354af8a20 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T15:18:18Z (GMT) No. of bitstreams: 1 2013 - Estimation of Variance Components in Linear Mixed Models with Commutative Orthogonal Block Structure.pdf: 3621466 bytes, checksum: ef8ca603751caa42fdf33cb354af8a20 (MD5) Made available in DSpace on 2020-02-07T15:18:18Z (GMT). No. of bitstreams: 1 2013 - Estimation of Variance Components in Linear Mixed Models with Commutative Orthogonal Block Structure.pdf: 3621466 bytes, checksum: ef8ca603751caa42fdf33cb354af8a20 (MD5) Previous issue date: 2013 info:eu-repo/semantics/publishedVersion

Published
2013

47. Fixed effects ANOVA: an extension to samples with random size

Author

Nunes, Célia, Ferreira, Dário, Ferreira, Sandra S., Mexia, João T., and uBibliorum

Subjects
Statistics and Probability, Applied Mathematics, Extension (predicate logic), Critical values, Sample size determination, Random sample sizes, Modeling and Simulation, Orthogonal ANOVA, Statistics, Econometrics, Analysis of variance, Statistics, Probability and Uncertainty, Random degrees of freedom, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T18:00:21Z No. of bitstreams: 1 2014 - Fixed effects ANOVA_an extension to samples with random size.pdf: 187495 bytes, checksum: 1d0062d82fa0257a6473ed0dee3f1445 (MD5) Rejected by Pessoa (pfep@ubi.pt), reason: Agregar os nomes ao OCID e/ou Ciência Vitae Colocar resumos e palavras chave Colocar código de financiamento FCT Consultar : https://www.ubi.pt/Ficheiros/Sites/7/Documentos/1375/Instruções%20para%20Auto%20depósito%20de%20documentos.pdf on 2020-02-06T15:53:20Z (GMT) Submitted by FERREIRA (dario@ubi.pt) on 2020-02-06T23:38:09Z No. of bitstreams: 1 2014 - Fixed effects ANOVA_an extension to samples with random size.pdf: 187495 bytes, checksum: 1d0062d82fa0257a6473ed0dee3f1445 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T14:35:20Z (GMT) No. of bitstreams: 1 2014 - Fixed effects ANOVA_an extension to samples with random size.pdf: 187495 bytes, checksum: 1d0062d82fa0257a6473ed0dee3f1445 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-07T14:37:07Z (GMT) No. of bitstreams: 1 2014 - Fixed effects ANOVA_an extension to samples with random size.pdf: 187495 bytes, checksum: 1d0062d82fa0257a6473ed0dee3f1445 (MD5) Made available in DSpace on 2020-02-07T14:37:07Z (GMT). No. of bitstreams: 1 2014 - Fixed effects ANOVA_an extension to samples with random size.pdf: 187495 bytes, checksum: 1d0062d82fa0257a6473ed0dee3f1445 (MD5) Previous issue date: 2013 info:eu-repo/semantics/publishedVersion

Published
2013

48. Nanostructures on spin-coated polymer films controlled by solvent composition and polymer molecular weight

Author

Denise Freitas Siqueira Petri, Aline Ferreira Dário, and Henrique B. Macia

Subjects
chemistry.chemical_classification, Spin coating, Materials science, Metals and Alloys, Ethyl acetate, FILMES FINOS, Surfaces and Interfaces, Polymer, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Solvent, chemistry.chemical_compound, chemistry, Chemical engineering, Ellipsometry, Polymer chemistry, Materials Chemistry, Acetone, Methyl methacrylate, Porosity
Abstract

In this study we systematically investigated how the solvent composition used for polymer dissolution affects the porous structures of spin-coated polymers films. Cellulose acetate butyrate (CAB) and poly(methyl methacrylate) with low (PMMA-L) and high (PMMA-H) molecular weights were dissolved in mixtures of acetone (AC) and ethyl acetate (EA) at constant polymer concentration of 10 g/L The films were spin-coated at a relative air humidity of 55 ± 5%, their thickness and index of refraction were determined by means of ellipsometry and their morphology was analyzed by atomic force microscopy. The dimensions and frequency of nanocavities on polymer films increased with the acetone content (φ AC ) in the solvent mixture and decreased with increasing polymer molecular weight. Consequently, as the void content increased in the films, their apparent thicknesses increased and their indices of refraction decreased, creating low-cost anti-reflection surface. The void depth was larger for PMMA-L than for CAB. This effect was attributed to different activities of EA and AC in CAB or PMMA-L solution, the larger mobility of chains and the lower polarity of PMMA-L in comparison to CAB.

Published
2012

49. Confidence regions for variance components using inducing pivot variables

Author

Ferreira, Dário, Ferreira, Sandra S., Nunes, Célia, and uBibliorum

Subjects
Variance components, Carry (arithmetic), Linear model, Inference, Confidence interval, Variable (computer science), Probability theory, Statistics, Econometrics, Pivot variables, Probability measure, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T22:24:20Z No. of bitstreams: 1 2012 - Confidence regions for variance components using inducing pivot variables.pdf: 130388 bytes, checksum: 667fb584893755a9e2eeb8bcf20f13bb (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:43:48Z (GMT) No. of bitstreams: 1 2012 - Confidence regions for variance components using inducing pivot variables.pdf: 130388 bytes, checksum: 667fb584893755a9e2eeb8bcf20f13bb (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:45:59Z (GMT) No. of bitstreams: 1 2012 - Confidence regions for variance components using inducing pivot variables.pdf: 130388 bytes, checksum: 667fb584893755a9e2eeb8bcf20f13bb (MD5) Made available in DSpace on 2020-02-06T16:45:59Z (GMT). No. of bitstreams: 1 2012 - Confidence regions for variance components using inducing pivot variables.pdf: 130388 bytes, checksum: 667fb584893755a9e2eeb8bcf20f13bb (MD5) Previous issue date: 2012 info:eu-repo/semantics/publishedVersion

Published
2012

50. Linear and quadratic sufficiency and commutativity

Author

Ferreira, Sandra S., Ferreira, Dário, Nunes, Célia, and uBibliorum

Subjects
Numerical linear algebra, Quadratic sufficiency, Orthogonal projection, Orthographic projection, Inverse, computer.software_genre, Space (mathematics), Combinatorics, Range (mathematics), Matrix (mathematics), Quadratic equation, Linear sufficiency, Linear completeness, computer, Commutative property, Mathematics
Abstract

Submitted by FERREIRA (dario@ubi.pt) on 2020-02-05T22:31:06Z No. of bitstreams: 1 2012 - Linear and quadratic sufficiency and commutativity.pdf: 363266 bytes, checksum: 474c3388e6bd0663b5eb13cdf516ffe2 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:48:34Z (GMT) No. of bitstreams: 1 2012 - Linear and quadratic sufficiency and commutativity.pdf: 363266 bytes, checksum: 474c3388e6bd0663b5eb13cdf516ffe2 (MD5) Approved for entry into archive by Pessoa (pfep@ubi.pt) on 2020-02-06T16:51:13Z (GMT) No. of bitstreams: 1 2012 - Linear and quadratic sufficiency and commutativity.pdf: 363266 bytes, checksum: 474c3388e6bd0663b5eb13cdf516ffe2 (MD5) Made available in DSpace on 2020-02-06T16:51:13Z (GMT). No. of bitstreams: 1 2012 - Linear and quadratic sufficiency and commutativity.pdf: 363266 bytes, checksum: 474c3388e6bd0663b5eb13cdf516ffe2 (MD5) Previous issue date: 2012 info:eu-repo/semantics/publishedVersion

Published
2012

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