David Villalobos | University of Nigeria, Nsukka (original) (raw)
Papers by David Villalobos
ABSTRACTThe severe acute respiratory syndrome Coronavirus 2 (SARS COV-2) caused a global pandemic... more ABSTRACTThe severe acute respiratory syndrome Coronavirus 2 (SARS COV-2) caused a global pandemic of COVID-19. Most of people affected are admitted to hospital with various grades of ADRS. A small proportion of these patients requires intensive care unit management and treatment. However not all of them survive. This study aims to describe the epidemiological and clinical characteristics of patients admitted to the intensive care units in Panama main hospital in the first six months of pandemic with available information. Special focus has been oriented to blood and respiratory biomarkers to correlate with survivors and non-survivors. Our results show that patients between 56-75 years old, with hypertension, obesity, and diabetes comorbid conditions are more likely to die in intensive care units. Regarding the PaFi ratio, we observed a greater proportion of non-survivor with values less than 200. The triglycerides, urea nitrogen, creatinine and procalcitonin levels resulted signific...
One of the challenging aspects of fuzzy systems is characterizing Fuzzy Membership Functions (FMF... more One of the challenging aspects of fuzzy systems is characterizing Fuzzy Membership Functions (FMF). In this paper we are trying to present a flexible framework which can be applied in different contexts for deriving individuals' FMFs from their genealogical factors. At first, we refer to the important role of genealogical factors in forming the conception of a linguistic variable and consequently in forming the FMF. Then, we discuss the fact that these factors are not crisp variables. Finally, it is discussed that the derived FMF from genealogical linguistic variable should be a strip of FMFs to contain as many FMFs as possible. Having derived this strip, the total membership degree of each point is measured through an appropriate mathematical operation.
![Research paper thumbnail of Reviewer's comment concerning "Lumbar total disc replacement: predictors for 8-year outcome" (by H. Furunes et al. [2017] Eur Spine J)](https://attachments.academia-assets.com/88293759/thumbnails/1.jpg)
](European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, Jan 23, 2017
Outre-Terre, 2017
Resumo-A evolução da forma do tronco de Araucaria angustifolia (Bertol.) Kuntze foi estudada por ... more Resumo-A evolução da forma do tronco de Araucaria angustifolia (Bertol.) Kuntze foi estudada por meio de funções de afilamento e fatores de forma. Os dados utilizados foram obtidos por análise de tronco e por cubagem rigorosa de árvores em pé em povoamentos estabelecidos na região Centro-Sul do Paraná, com uma amostra de 45 árvores. Foram ajustadas quatro funções de afilamento para o conjunto total de dados e para os dados estratificados em classes de idade, sendo construídas as curvas de afilamento para diferentes classes de idade. Foi realizado teste de identidade de modelos para comparar modelos completos com o modelo reduzido. Para avaliar a evolução dos fatores de forma naturais e artificiais, os mesmos foram calculados para o conjunto de dados em diferentes idades, iniciando aos 5 anos. A função de afilamento selecionada foi o polinômio de Schöpfer. Foram observadas diferenças significativas entre o modelo reduzido e os modelos completos, com ligeira vantagem com o uso de equações ajustadas por classes de idade, além de expressiva melhoria na forma do tronco com o aumento da idade, que também foi constatada pela estabilização dos valores de fator de forma aos 22 anos.
Chemosphere, 2017
Removal of triazines and chlorpyrifos in biomixture, bioaugmented biomixture and soil Final remov... more Removal of triazines and chlorpyrifos in biomixture, bioaugmented biomixture and soil Final removal (60 d) was similar in soil and biomixture, but faster in the latter Fungal bioaugmentation of the biomixture delayed pesticide removal and detoxification Fast detoxification in soil and biomixture according to tests on Daphnia magna Unclear detoxification patterns (phytotoxicity) despite high herbicide removal
Plant Genetics and Genomics: Crops and Models, 2015
The root systems of land plants mine the soil for water and essential edaphic nutrients that are ... more The root systems of land plants mine the soil for water and essential edaphic nutrients that are needed for the vegetative and reproductive phases of shoot growth. Different root system architectures exist across the angiosperms, and while there are many variants, two principal layouts are associated with the monocotyledon-dicotyledon divide: whereas a primary taproot and its branch roots typically dominate dicotyledon root systems, monocotyledon root systems appear overall more complex and are typically dominated by post-embryonic shoot-borne roots. Brachypodium distachyon (Brachypodium) displays all the characteristics of a monocotyledon root system; however its complexity is minimal as compared to many other monocotyledon species, notably crops. Together with its relatively small size, this makes the Brachypodium root system a tractable model for monocotyledon root development that can be easily investigated in tissue culture but also in soil. First molecular genetic and physiological studies already point to distinct regulatory mechanisms and environmental responses in Brachypodium as compared to well-characterized dicotyledon model species. These results highlight the worthwhileness of studying the Brachypodium root system and its value as a credible model to decipher major evolutionary-developmental facets of angiosperm root system diversity. Moreover, the fact that Brachypodium is a wild plant that has not undergone human selection contrasts with the crops that serve as key monocotyledon models so far. Therefore, analysis of Brachypodium can be instructive with respect to root traits that have been modified or lost during crop domestication, especially in the closely related temperate cereals, barley, rye and wheat. Combined with natural germplasm collections, Brachypodium is thus an ideal model to investigate ecological, evolutionary and developmental aspects of monocotyledon root systems and their relation to crop performance.
The Plant Cell, 2016
The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elo... more The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots.
Revista Estomatológica Herediana, 2014
Se reporta el caso de un paciente varón de 27 años con antecedente de exodoncia compleja de la te... more Se reporta el caso de un paciente varón de 27 años con antecedente de exodoncia compleja de la tercera molar mandibular inferior derecha que presentaba una tumefacción circunscrita dolorosa en la región submandibular ipsilateral. En el estudio imaginológico, la radiografía panorámica presentaba un proceso osteolítico periapical e interradicular con un patrón osteogénico circundante por lo que se utilizó como complemento una tomografía cone beam, en donde se evidenció compromiso desde la rama mandibular derecha hasta la sínfisis mandibular. Las lesiones a nivel de tejidos blandos y tejidos duros fueron diagnosticadas y manejadas como una actinomicosis cervicofacial y osteomielitis crónica supurativa respectivamente. El conocimientode las diferentes infecciones bacterianas, un adecuado análisis clínico y estudio imaginológico nos darán la pauta para la correcta terapéutica de las distintas patologías maxilofaciales.
Caribbean Journal of Science, 2013
Mastozoologia Neotropical
Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto
Acta Mechanica, 2014
Physical experiments can characterize the elastic response of granular materials in terms of macr... more Physical experiments can characterize the elastic response of granular materials in terms of macroscopic state variables, namely volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here, by means of numerical simulations, we analyze dense, frictionless granular assemblies with the final goal to relate the elastic moduli to the fabric state, i.e., to microstructural averaged contact network features as contact number density and anisotropy. The particle samples are first isotropically compressed and then quasi-statically sheared under constant volume (undrained conditions). From various static, relaxed configurations at different shear strains, infinitesimal strain steps are applied to "measure" the effective elastic response; we quantify the strain needed so that no contact and structure rearrangements, i.e. plasticity, happen. Because of the anisotropy induced by shear, volumetric and deviatoric stresses and strains are cross-coupled via a single anisotropy modulus, which is proportional to the product of deviatoric fabric and bulk modulus (i.e., the isotropic fabric). Interestingly, the shear modulus of the material depends also on the actual deviatoric stress state, along with the contact configuration anisotropy. Finally, a constitutive model based on incremental evolution equations for stress and fabric is introduced. By using the previously measured dependence of the stiffness tensor (elastic moduli) on the microstructure, the theory is able to predict with good agreement the evolution of pressure, shear stress and deviatoric fabric (anisotropy) for an independent undrained cyclic shear test, including the response to reversal of strain.
Investigación Agraria: Sistemas y Recursos Forestales, 2008
Para poder conocer la estructura y organización de los genomas vegetales es necesario la clonació... more Para poder conocer la estructura y organización de los genomas vegetales es necesario la clonación molecular de grandes fragmentos de secuencias genómicas para construir genotecas representativas. La construcción de genotecas genómicas en cromosomas artificiales de bacterias (BAC) es una de las herramientas más utilizadas con este fin y la estrategia elegida en este trabajo. Pero cuando se trabaja con especies que presentan genomas muy grandes, como el pino, realizar este tipo de genotecas es muy laborioso y costoso. En este estudio se describe un método para, a partir de cotiledones de P. pinaster, construir genotecas BAC en grupos de células, lo que disminuye drásticamente el coste, el espacio y el tiempo requerido. La genoteca BAC consta de 83 grupos de células con una media de 4000 clones por grupo y representa por ahora un 0,8 X del genoma de P. pinaster. También se demuestra que se puede realizar por PCR (reacción en cadena de la ADNpolimerasa) con rapidez la identificación del grupo que contiene un BAC de interés. Se ha identificado un grupo de células que contiene un clon BAC que porta una secuencia codificante similar a una quitinasa de clase I de Picea abies, y otro clon BAC en otro grupo que contiene secuencia homóloga a un ARNm desconocido de P. taeda. Esta estrategia permitirá rastrear y almacenar genotecas de organismos con grandes genomas y localizar en ella genes de interés con rapidez, describiéndose el método en detalle.
Advances in Soft Computing, 2007
Many Expressed Sequence Tags (EST) sequencing projects produce thousands of sequences that must b... more Many Expressed Sequence Tags (EST) sequencing projects produce thousands of sequences that must be cleaned and annotated. Here it is presented Full-Lengther, an algorithm that can find out full-length cDNA sequences from EST data. To accomplish this task, Full-Lenther is based on a BLAST report using a protein database such as UniProt. Blast alignments will guide to locate protein coding regions, mainly the start codon. Full-Lengther contains an ORF prediction algorithm for those cases that do not deploy any alignment in the BLAST output. The algorithm is implemented as a web tool to simplify its use and portability. This can be worldwide accessible via http://castanea.ac.uma.es/genuma/full-lengther/.
ABSTRACTThe severe acute respiratory syndrome Coronavirus 2 (SARS COV-2) caused a global pandemic... more ABSTRACTThe severe acute respiratory syndrome Coronavirus 2 (SARS COV-2) caused a global pandemic of COVID-19. Most of people affected are admitted to hospital with various grades of ADRS. A small proportion of these patients requires intensive care unit management and treatment. However not all of them survive. This study aims to describe the epidemiological and clinical characteristics of patients admitted to the intensive care units in Panama main hospital in the first six months of pandemic with available information. Special focus has been oriented to blood and respiratory biomarkers to correlate with survivors and non-survivors. Our results show that patients between 56-75 years old, with hypertension, obesity, and diabetes comorbid conditions are more likely to die in intensive care units. Regarding the PaFi ratio, we observed a greater proportion of non-survivor with values less than 200. The triglycerides, urea nitrogen, creatinine and procalcitonin levels resulted signific...
One of the challenging aspects of fuzzy systems is characterizing Fuzzy Membership Functions (FMF... more One of the challenging aspects of fuzzy systems is characterizing Fuzzy Membership Functions (FMF). In this paper we are trying to present a flexible framework which can be applied in different contexts for deriving individuals' FMFs from their genealogical factors. At first, we refer to the important role of genealogical factors in forming the conception of a linguistic variable and consequently in forming the FMF. Then, we discuss the fact that these factors are not crisp variables. Finally, it is discussed that the derived FMF from genealogical linguistic variable should be a strip of FMFs to contain as many FMFs as possible. Having derived this strip, the total membership degree of each point is measured through an appropriate mathematical operation.
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, Jan 23, 2017
Outre-Terre, 2017
Resumo-A evolução da forma do tronco de Araucaria angustifolia (Bertol.) Kuntze foi estudada por ... more Resumo-A evolução da forma do tronco de Araucaria angustifolia (Bertol.) Kuntze foi estudada por meio de funções de afilamento e fatores de forma. Os dados utilizados foram obtidos por análise de tronco e por cubagem rigorosa de árvores em pé em povoamentos estabelecidos na região Centro-Sul do Paraná, com uma amostra de 45 árvores. Foram ajustadas quatro funções de afilamento para o conjunto total de dados e para os dados estratificados em classes de idade, sendo construídas as curvas de afilamento para diferentes classes de idade. Foi realizado teste de identidade de modelos para comparar modelos completos com o modelo reduzido. Para avaliar a evolução dos fatores de forma naturais e artificiais, os mesmos foram calculados para o conjunto de dados em diferentes idades, iniciando aos 5 anos. A função de afilamento selecionada foi o polinômio de Schöpfer. Foram observadas diferenças significativas entre o modelo reduzido e os modelos completos, com ligeira vantagem com o uso de equações ajustadas por classes de idade, além de expressiva melhoria na forma do tronco com o aumento da idade, que também foi constatada pela estabilização dos valores de fator de forma aos 22 anos.
Chemosphere, 2017
Removal of triazines and chlorpyrifos in biomixture, bioaugmented biomixture and soil Final remov... more Removal of triazines and chlorpyrifos in biomixture, bioaugmented biomixture and soil Final removal (60 d) was similar in soil and biomixture, but faster in the latter Fungal bioaugmentation of the biomixture delayed pesticide removal and detoxification Fast detoxification in soil and biomixture according to tests on Daphnia magna Unclear detoxification patterns (phytotoxicity) despite high herbicide removal
Plant Genetics and Genomics: Crops and Models, 2015
The root systems of land plants mine the soil for water and essential edaphic nutrients that are ... more The root systems of land plants mine the soil for water and essential edaphic nutrients that are needed for the vegetative and reproductive phases of shoot growth. Different root system architectures exist across the angiosperms, and while there are many variants, two principal layouts are associated with the monocotyledon-dicotyledon divide: whereas a primary taproot and its branch roots typically dominate dicotyledon root systems, monocotyledon root systems appear overall more complex and are typically dominated by post-embryonic shoot-borne roots. Brachypodium distachyon (Brachypodium) displays all the characteristics of a monocotyledon root system; however its complexity is minimal as compared to many other monocotyledon species, notably crops. Together with its relatively small size, this makes the Brachypodium root system a tractable model for monocotyledon root development that can be easily investigated in tissue culture but also in soil. First molecular genetic and physiological studies already point to distinct regulatory mechanisms and environmental responses in Brachypodium as compared to well-characterized dicotyledon model species. These results highlight the worthwhileness of studying the Brachypodium root system and its value as a credible model to decipher major evolutionary-developmental facets of angiosperm root system diversity. Moreover, the fact that Brachypodium is a wild plant that has not undergone human selection contrasts with the crops that serve as key monocotyledon models so far. Therefore, analysis of Brachypodium can be instructive with respect to root traits that have been modified or lost during crop domestication, especially in the closely related temperate cereals, barley, rye and wheat. Combined with natural germplasm collections, Brachypodium is thus an ideal model to investigate ecological, evolutionary and developmental aspects of monocotyledon root systems and their relation to crop performance.
The Plant Cell, 2016
The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elo... more The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots.
Revista Estomatológica Herediana, 2014
Se reporta el caso de un paciente varón de 27 años con antecedente de exodoncia compleja de la te... more Se reporta el caso de un paciente varón de 27 años con antecedente de exodoncia compleja de la tercera molar mandibular inferior derecha que presentaba una tumefacción circunscrita dolorosa en la región submandibular ipsilateral. En el estudio imaginológico, la radiografía panorámica presentaba un proceso osteolítico periapical e interradicular con un patrón osteogénico circundante por lo que se utilizó como complemento una tomografía cone beam, en donde se evidenció compromiso desde la rama mandibular derecha hasta la sínfisis mandibular. Las lesiones a nivel de tejidos blandos y tejidos duros fueron diagnosticadas y manejadas como una actinomicosis cervicofacial y osteomielitis crónica supurativa respectivamente. El conocimientode las diferentes infecciones bacterianas, un adecuado análisis clínico y estudio imaginológico nos darán la pauta para la correcta terapéutica de las distintas patologías maxilofaciales.
Caribbean Journal of Science, 2013
Mastozoologia Neotropical
Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto
Acta Mechanica, 2014
Physical experiments can characterize the elastic response of granular materials in terms of macr... more Physical experiments can characterize the elastic response of granular materials in terms of macroscopic state variables, namely volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here, by means of numerical simulations, we analyze dense, frictionless granular assemblies with the final goal to relate the elastic moduli to the fabric state, i.e., to microstructural averaged contact network features as contact number density and anisotropy. The particle samples are first isotropically compressed and then quasi-statically sheared under constant volume (undrained conditions). From various static, relaxed configurations at different shear strains, infinitesimal strain steps are applied to "measure" the effective elastic response; we quantify the strain needed so that no contact and structure rearrangements, i.e. plasticity, happen. Because of the anisotropy induced by shear, volumetric and deviatoric stresses and strains are cross-coupled via a single anisotropy modulus, which is proportional to the product of deviatoric fabric and bulk modulus (i.e., the isotropic fabric). Interestingly, the shear modulus of the material depends also on the actual deviatoric stress state, along with the contact configuration anisotropy. Finally, a constitutive model based on incremental evolution equations for stress and fabric is introduced. By using the previously measured dependence of the stiffness tensor (elastic moduli) on the microstructure, the theory is able to predict with good agreement the evolution of pressure, shear stress and deviatoric fabric (anisotropy) for an independent undrained cyclic shear test, including the response to reversal of strain.
Investigación Agraria: Sistemas y Recursos Forestales, 2008
Para poder conocer la estructura y organización de los genomas vegetales es necesario la clonació... more Para poder conocer la estructura y organización de los genomas vegetales es necesario la clonación molecular de grandes fragmentos de secuencias genómicas para construir genotecas representativas. La construcción de genotecas genómicas en cromosomas artificiales de bacterias (BAC) es una de las herramientas más utilizadas con este fin y la estrategia elegida en este trabajo. Pero cuando se trabaja con especies que presentan genomas muy grandes, como el pino, realizar este tipo de genotecas es muy laborioso y costoso. En este estudio se describe un método para, a partir de cotiledones de P. pinaster, construir genotecas BAC en grupos de células, lo que disminuye drásticamente el coste, el espacio y el tiempo requerido. La genoteca BAC consta de 83 grupos de células con una media de 4000 clones por grupo y representa por ahora un 0,8 X del genoma de P. pinaster. También se demuestra que se puede realizar por PCR (reacción en cadena de la ADNpolimerasa) con rapidez la identificación del grupo que contiene un BAC de interés. Se ha identificado un grupo de células que contiene un clon BAC que porta una secuencia codificante similar a una quitinasa de clase I de Picea abies, y otro clon BAC en otro grupo que contiene secuencia homóloga a un ARNm desconocido de P. taeda. Esta estrategia permitirá rastrear y almacenar genotecas de organismos con grandes genomas y localizar en ella genes de interés con rapidez, describiéndose el método en detalle.
Advances in Soft Computing, 2007
Many Expressed Sequence Tags (EST) sequencing projects produce thousands of sequences that must b... more Many Expressed Sequence Tags (EST) sequencing projects produce thousands of sequences that must be cleaned and annotated. Here it is presented Full-Lengther, an algorithm that can find out full-length cDNA sequences from EST data. To accomplish this task, Full-Lenther is based on a BLAST report using a protein database such as UniProt. Blast alignments will guide to locate protein coding regions, mainly the start codon. Full-Lengther contains an ORF prediction algorithm for those cases that do not deploy any alignment in the BLAST output. The algorithm is implemented as a web tool to simplify its use and portability. This can be worldwide accessible via http://castanea.ac.uma.es/genuma/full-lengther/.