Browsing by Author "Gonzalez, Jorge"

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    A Bayesian Nonparametric Multiple Testing Procedure for Comparing Several Treatments Against a Control
    (2019) Gutierrez, Luis; Barrientos, Andres F.; Gonzalez, Jorge; Taylor-Rodriguez, Daniel
    We propose a Bayesian nonparametric strategy to test for differences between a control group and several treatment regimes. Most of the existing tests for this type of comparison are based on the differences between location parameters. In contrast, our approach identifies differences across the entire distribution, avoids strong modeling assumptions over the distributions for each treatment, and accounts for multiple testing through the prior distribution on the space of hypotheses. The proposal is compared to other commonly used hypothesis testing procedures under simulated scenarios. Two real applications are also analyzed with the proposed methodology.
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    A Double-Structure Structural Equation Model for Three-Mode Data
    (AMER PSYCHOLOGICAL ASSOC, 2008) Gonzalez, Jorge; De Boeck, Paul; Tuerlinckx, Francis
    Structural equation models are commonly used to analyze 2-mode data sets, in which a set of objects is measured on a set of variables. The underlying structure within the object mode is evaluated using latent variables, which are measured by indicators coming from the variable mode. Additionally, when the objects are measured under different conditions, 3-mode data arise, and with this, the simultaneous study of the correlational structure of 2 modes may be of interest. In this article the authors present a model with a simultaneous latent structure for 2 of the 3 modes of such a data set. They present an empirical illustration of the method using a 3-mode data set (person by situation by response) exploring the structure of anger and irritation across different interpersonal situations as well as across persons.
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    Analyses of the Factor Structure and Item Measurement Bias of a School Climate Scale in Chilean Students
    (FRONTIERS MEDIA SA, 2021) Calderon, Francisca; Gonzalez, Jorge
    School Climate is an essential aspect in every school community. It relates to perceptions of the school environment experienced by various members of the educational system. Research has shown that an appropriate school climate impacts not only on the quality of life of all members in the educational system, but also on learning outcomes and education improvements. This study aims to explore a measure of School Climate on Chilean students. A sample of 176,126 10th grade students was used to investigate the factor structure of the items composing the School Climate construct, and to evaluate the potential presence of Differential Item Functioning between male and female groups. Both explanatory and confirmatory factor analysis as well as Rasch models were used to analyze the scale. Differential item functioning between male and female groups was investigated using the Langer-improved Wald test. The results indicated a multidimensional structure of the School Climate construct and that measurement bias for male and female groups exist in some of the items measuring the construct.
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    Effect of acute on chronic liver failure over post-transplant survival
    (2023) Benitez, Carlos; Arnold, Jorge; Cambindo, Veronica; Schoenfeldt, Fernanda; Cancino, Alejandra; Ibanez, Samuel; Grandy, Catalina; Hunfan, Paola; Gonzalez, Jorge; Guerra, Catalina; Godoy, Esteban; Araneda, Veronica; Mollo, Constanza; Poniachik, Jaime; Urzua, Alvaro; Cattaneo, Maximo; Roblero, Juan Pablo; Oppenheimer, Ilan; Pizarro, Vicente
    Introduction and Objectives: Acute-on-chronic liver failure (ACLF) is associated with reduced short-term sur-vival, and liver transplantation is frequently the only therapeutic option. Nonetheless, the post-transplanta-tion prognosis seems to be worse in ACLF patients.Materials and Methods: The databases of two university centers were retrospectively evaluated, and adult patients with cirrhosis who underwent transplantation between 2013 and 2020 were included. One-year survival of patients with ACLF was compared to that of patients without ACLF. Variables associated with mor-tality were identified.Results: A total of 428 patients were evaluated, and 303 met the inclusion criteria; 57.1% were male, the mean age was 57.1 +/- 10.2 years, 75 patients had ACLF, and 228 did not. The main etiologies of ACLF were NASH (36.6%), alcoholic liver disease (13.9%), primary biliary cholangitis (8.6%) and autoimmune hepatitis (7.9%). Mechanical ventilation, renal replacement therapy, the use of vasopressors and the requirement of blood product transfusion during liver transplantation were significantly more frequent in ACLF patients. Among those recipients without and with ACLF, survival at 1, 3 and 5 years was 91.2% vs. 74.7%, 89.1% vs. 72.6% and 88.3% vs. 72.6%, respectively (p=0.001). Among pre-transplantation variables, only the presence of ACLF was independently associated with survival (HR 3.2, 95% CI: 1.46-7.11). Post-transplantation variables indepen-dently associated with survival were renal replacement therapy (HR 2.8, 95% CI: 1.1-6.8) and fungal infec-tions (HR 3.26, 95% CI: 1.07-9.9).Conclusions: ACLF is an independent predictor of one-year post-transplantation survival. Importantly, trans-plant recipients with ACLF require the use of more resources than patients without ACLF. (c) 2023 Fundacion Clinica Medica Sur, A.C. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
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    Identifiability analysis of the fixed-effects one-parameter logistic positive exponent model
    (2024) Gonzalez, Jorge; Bazan, Jorge; Curi, Mariana
    In addition to the usual slope and location parameters included in a regular two-parameter logistic model (2PL), the logistic positive exponent (LPE) model incorporates an item parameter that leads to asymmetric item characteristic curves, which have recently been shown to be useful in some contexts. Although this model has been used in some empirical studies, an identifiability analysis (i.e., checking the (un)identified status of a model and searching for identifiablity restrictions to make an unidentified model identified) has not yet been established. In this paper, we formalize the unidentified status of a large class of fixed-effects item response theory models that includes the LPE model and related versions of it. In addition, we conduct an identifiability analysis of a particular version of the LPE model that is based on the fixed-effects one-parameter logistic model (1PL), which we call the 1PL-LPE model. The main result indicates that the 1PL-LPE model is not identifiable. Ways to make the 1PL-LPE useful in practice and how different strategies for identifiability analyses may affect other versions of the model are also discussed.
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    On the relationships between sum score based estimation and joint maximum likelihood estimation
    (2008) Del Pino, Guido; Martin, Ernesto San; Gonzalez, Jorge; De Boeck, Paul
    This paper analyzes the sum score based (SSB) formulation of the Rasch model, where items and sum scores of persons are considered as factors in a logit model. After reviewing the evolution leading to the equality between their maximum likelihood estimates, the SSB model is then discussed from the point of view of pseudo-likelihood and of misspecified models. This is then employed to provide new insights into the origin of the known inconsistency of the difficulty parameter estimates in the Rasch model. The main results consist of exact relationships between the estimated standard errors for both models; and, for the ability parameters, an upper bound for the estimated standard errors of the Rasch model in terms of those for the SSB model, which are more easily available.
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    Oral infectivity through carnivorism in murine model of Trypanosoma cruzi infection
    (2024) Torres, Victor; Contreras, Victor; Gutierrez, Bessy; San Francisco, Juan; Catalan, Alejandro; Vega, Jose Luis; Moon, Kyung-Mee; Foster, Leonard J.; de Almeida, Rafael F.; Kalergis, Alexis M.; Gonzalez, Jorge
    Introduction Oral transmission of T. cruzi is probably the most frequent transmission mechanism in wild animals. This observation led to the hypothesis that consuming raw or undercooked meat from animals infected with T. cruzi may be responsible for transmitting the infection. Therefore, the general objective of this study was to investigate host-pathogen interactions between the parasite and gastric mucosa and the role of meat consumption from infected animals in the oral transmission of T. cruzi. Methods Cell infectivity assays were performed on AGS cells in the presence or absence of mucin, and the roles of pepsin and acidic pH were determined. Moreover, groups of five female Balb/c mice were fed with muscle tissue obtained from mice in the acute phase of infection by the clone H510 C8C3 hvir of T. cruzi, and the infection of the fed mice was monitored by a parasitemia curve. Similarly, we assessed the infective capacity of T. cruzi trypomastigotes and amastigotes by infecting groups of five mice Balb/c females, which were infected orally using a nasogastric probe, and the infection was monitored by a parasitemia curve. Finally, different trypomastigote and amastigote inoculums were used to determine their infective capacities. Adhesion assays of T. cruzi proteins to AGS stomach cells were performed, and the adhered proteins were detected by western blotting using monoclonal or polyclonal antibodies and by LC-MS/MS and bioinformatics analysis. Results Trypomastigote migration in the presence of mucin was reduced by approximately 30%, whereas in the presence of mucin and pepsin at pH 3.5, only a small proportion of parasites were able to migrate (similar to 6%). Similarly, the ability of TCTs to infect AGS cells in the presence of mucin is reduced by approximately 20%. In all cases, 60-100% of the animals were fed meat from mice infected in the acute phase or infected with trypomastigotes or amastigotes developed high parasitemia, and 80% died around day 40 post-infection. The adhesion assay showed that cruzipain is a molecule of trypomastigotes and amastigotes that binds to AGS cells. LC-MS/MS and bioinformatics analysis, also confirmed that transialidase, cysteine proteinases, and gp63 may be involved in TCTs attachment or invasion of human stomach cells because they can potentially interact with different proteins in the human stomach mucosa. In addition, several human gastric mucins have cysteine protease cleavage sites. Discussion Then, under our experimental conditions, consuming meat from infected animals in the acute phase allows the T. cruzi infection. Similarly, trypomastigotes and amastigotes could infect mice when administered orally, whereas cysteinyl proteinases and trans-sialidase appear to be relevant molecules in this infective process.
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    The Use of an Identifiability-Based Strategy for the Interpretation of Parameters in the 1PL-G and Rasch Models
    (2019) Farina, Paula; Gonzalez, Jorge; San Martin, Ernesto
    Using the well-known strategy in which parameters are linked to the sampling distribution via an identification analysis, we offer an interpretation of the item parameters in the one-parameter logistic with guessing model (1PL-G) and the nested Rasch model. The interpretations are based on measures of informativeness that are defined in terms of odds of correctly answering the items. It is shown that the interpretation of what is called the difficulty parameter in the random-effects 1PL-G model differs from that of the item parameter in a random-effects Rasch model. It is also shown that the traditional interpretation of the guessing parameter in the 1PL-G model changes, depending on whether fixed-effects or random-effects versions of both models are considered.
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    Trypanosoma cruzi Infection Induces Pannexin-1 Channel Opening in Cardiac Myocytes
    (2018) Barria, Ivan; Guiza, Juan; Cifuentes, Fredi; Zamorano, Pedro; Sáez, Juan Carlos; Gonzalez, Jorge; Vega, Jose L.