Gabriela Ulloa Contador | Pontificia Universidad Catolica de Chile (original) (raw)

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Papers by Gabriela Ulloa Contador

Research paper thumbnail of Analysis of prevalence and sociodemographic conditions among women in labor with and without COVID-19 in public hospitals in Chile

Journal of Perinatal Medicine

Objectives The SARS-CoV-2 virus continues wreaking worldwide havoc on health and between March an... more Objectives The SARS-CoV-2 virus continues wreaking worldwide havoc on health and between March and August 2020, the first outbreak of COVID-19 hit Chile. The pregnant population is especially vulnerable to infection. Studies have been published that associate socioeconomic status, overcrowding, and poverty with a higher prevalence of SARS-CoV-2 infection. There are few studies about the development of this pandemic in Latin American countries so far. This study seeks to show the prevalence and sociodemographic and perinatal characteristics in pregnant women at the time of delivery, comparing both groups with positive and negative COVID-19 PCR results. Methods A prospective, cross-sectional study of pregnant women who delivered at the San Juan de Dios Hospital in Santiago between April 15, 2020 and June 15, 2020. Analysis of epidemiological, sociodemographic, obstetric, perinatal and sociodemographic data of patients with positive and negative COVID-19 PCR results. Results There were...

Research paper thumbnail of Impacto de la migración haitiana en un hábitat de vivienda social en Santiago (Chile), desde la percepción de sus residentes

Población & Sociedad, 2020

In 2019, an exploratory qualitative study was carried out in a social housing neighborhood locate... more In 2019, an exploratory qualitative study was carried out in a social housing neighborhood located on the outskirts of the city of Santiago, Chile whose purpose was to understand the perception of its Chilean residents regarding the massive arrival of Haitian migrants to the place. The results show not only their dissimilar and ambivalent perceptions regarding the impact of the arrival of this new population to their residential habitat but also a greater precariousness in both groups living conditions.

Research paper thumbnail of Testing of the SIBERIA landscape evolution model using the Tin Camp Creek, Northern Territory, Australia, field catchment

Earth Surface Processes …, Jan 1, 2002

Research paper thumbnail of Modelling the formation and evolution of soils, towards an initial synthesis

Geoderma, Jan 1, 2008

We present a literature review of the different approaches in deterministic modelling of pedogene... more We present a literature review of the different approaches in deterministic modelling of pedogenesis, as well as of models developed in other scientific fields that might be adapted to pedogenetic problems. We distinguish two types of modelling, deriving from a so-called classic soil-science approach based exclusively on the analysis of the soil solid phase, and deriving from other scientific fields – in particular environmental and mining – that also integrate circulating water. The advantages and limitations of each approach are discussed. Models based on the analysis of the soil solid phases provide a good understanding of how present-day soils were formed. Nevertheless, the time factor is, at best, only represented through a single exponential law, which does not allow a transcription of the commonly observed rate changes in soil evolution. Models which couple geochemistry, water and solute, transfers must be adapted to the specific problems of pedogenesis: (1) the transfer module must by necessity be able to simulate an unsaturated environment; (2) the databases of the geochemical module must be compatible with the soil minerals; (3) any interactions and feedback between the solid and liquid phases must be integrated; and (4) the ‘nested’ organization of soils must be accounted for. Certain processes are still poorly or not at all accounted for in this type of modelling, in particular the leaching of clays and most biological processes. Even so, this type of modelling seems to be quite attractive, as it permits the explicit consideration of variations in soil-water contents over time.

Research paper thumbnail of Evolution model of progressive failure of landslides

Journal of geotechnical and …, Jan 1, 1999

... ABSTRACT: An evolution model considering rheologic effects is proposed to describe the progre... more ... ABSTRACT: An evolution model considering rheologic effects is proposed to describe the progressive failure process of soil slopes. ... CONCLUSIONS This paper presents an evolution model considering rheo-logic effects to describe the progressive failure process of soil slopes. ...

Research paper thumbnail of Progressive and regressive pedogenesis and complex soil evolution

Quaternary Research, Jan 1, 1993

Research paper thumbnail of Soil chronosequences, soil development, and soil evolution: a critical review

Research paper thumbnail of The soil-evolution model as a framework for evaluating pedoturbation in archaeological site formation

Archaeological geology of North America, Jan 1, 1990

Research paper thumbnail of The mARM3D spatially distributed soil evolution model: Three-dimensional model framework and analysis of hillslope and landform responses

Journal of Geophysical Research, Jan 1, 2010

Research paper thumbnail of Conceptual models in pedogenesis: can soil-forming functions be solved?

Geoderma, Jan 1, 1975

Quantitative solutions of the univariant soil-forming functions are reviewed. Lithofunctions are ... more Quantitative solutions of the univariant soil-forming functions are reviewed. Lithofunctions are essentially of a comparative nature. Numerical solutions are possible if a coding of the parent material or its properties is made. The number of solutions of topofunctions and climofunctions is already considerable, though too few generally valid equations have been derived. These are required for the further development of the general solutions. Numerical solutions of true biotic functions are likely to remain exceptional and the biotic attributes are best considered as a dependent variable and property of the soil-ecosystem, like any of the soil properties.Several chronofunctions have been obtained for the initial stages of soil formation, and good graphical summaries for long-term soil development functions have been constructed, but strict numerical chronofunctions are rare because the difficulties in isolating and dating properly controlled sites. Runge's energy model uses incongruous terms whilst it essentially follows the tenets of the factorial system, but neglects the parent material (capacity) factor. Chesworth's weathering trend line does not disprove the absence of the steady state and his inference from this and his criticism of the state factor equation are essentially invalid.Because the number of degrees of freedom in the solution of the general soil formation function is rather large, the best way for advancing the solution of the state equation is by increasing the solutions of the univariant functions. It is suggested that the next step should be the preparation of a family of topofunctions, graphically or numerically, showing their change with time and on different parent materials or under different macroclimates. Computerized simulation models of such multivariate functions can then be prepared and compared with real data for further refinement and for pinpointing univariant functions or equations which are needed for the improvement of the solutions already obtained.Whereas the relevance of the univariant and multivariant functions of the state factors is in deriving the significant or major causal relationships, and thus explain or predict the distribution of soils in space and time, the computer simulation strategy can advance the quantification of the process-oriented models of soil dynamics.

Research paper thumbnail of Towards the quantitative modeling of pedogenesis—a review

Geoderma, Jan 1, 1992

The historical development of our pedogenetic model is reviewed, and trends or directions toward ... more The historical development of our pedogenetic model is reviewed, and trends or directions toward the future are discussed. Pedogenetic models are characterized with respect to relative degree of computation, complexity, and level of organization. These three characteristics are used as a framework for classification. Early qualitative models have well served the purpose of soil survey to describe the distribution of soils in landscapes. Further development of qualitative models will contribute to the understanding of soil genesis in areas where soil surveys are not completed. In the developed countries, however, the scientific questions have changed dramatically. Greater interest lies in understanding the physical and chemical processes of soil formation acting within relatively short time frames and assessing the interactions between natural processes and environmental change or anthropogenic impacts. Quantification of pedogenetic processes is a life-line to other environmental disciplines, and a mechanistic understanding would, in an ideal situation, describe and predict the behavior of a system for a limited number of years under changing environmental conditions.A proposed approach to mathematical simulation of the dynamic pedogenetic processes is to integrate soil physical, chemical, and other ecological system models into a quantitative pedogenetic model. Models may be developed as research tools in data-intensive studies at the pedon or horizon level, or for the purpose of simulating a soil system at the catena or soil region level. Specific kinds of pedogenetic models have specific implications with respect to the availability and spatial variability of the data needed for development and testing.

Research paper thumbnail of Evolution model of pedogenesis

Soil Science, Jan 1, 1987

Advertisement. Soil Science. Wolters Kluwer Health Logo. All Issues. ...

Research paper thumbnail of Analysis of prevalence and sociodemographic conditions among women in labor with and without COVID-19 in public hospitals in Chile

Journal of Perinatal Medicine

Objectives The SARS-CoV-2 virus continues wreaking worldwide havoc on health and between March an... more Objectives The SARS-CoV-2 virus continues wreaking worldwide havoc on health and between March and August 2020, the first outbreak of COVID-19 hit Chile. The pregnant population is especially vulnerable to infection. Studies have been published that associate socioeconomic status, overcrowding, and poverty with a higher prevalence of SARS-CoV-2 infection. There are few studies about the development of this pandemic in Latin American countries so far. This study seeks to show the prevalence and sociodemographic and perinatal characteristics in pregnant women at the time of delivery, comparing both groups with positive and negative COVID-19 PCR results. Methods A prospective, cross-sectional study of pregnant women who delivered at the San Juan de Dios Hospital in Santiago between April 15, 2020 and June 15, 2020. Analysis of epidemiological, sociodemographic, obstetric, perinatal and sociodemographic data of patients with positive and negative COVID-19 PCR results. Results There were...

Research paper thumbnail of Impacto de la migración haitiana en un hábitat de vivienda social en Santiago (Chile), desde la percepción de sus residentes

Población & Sociedad, 2020

In 2019, an exploratory qualitative study was carried out in a social housing neighborhood locate... more In 2019, an exploratory qualitative study was carried out in a social housing neighborhood located on the outskirts of the city of Santiago, Chile whose purpose was to understand the perception of its Chilean residents regarding the massive arrival of Haitian migrants to the place. The results show not only their dissimilar and ambivalent perceptions regarding the impact of the arrival of this new population to their residential habitat but also a greater precariousness in both groups living conditions.

Research paper thumbnail of Testing of the SIBERIA landscape evolution model using the Tin Camp Creek, Northern Territory, Australia, field catchment

Earth Surface Processes …, Jan 1, 2002

Research paper thumbnail of Modelling the formation and evolution of soils, towards an initial synthesis

Geoderma, Jan 1, 2008

We present a literature review of the different approaches in deterministic modelling of pedogene... more We present a literature review of the different approaches in deterministic modelling of pedogenesis, as well as of models developed in other scientific fields that might be adapted to pedogenetic problems. We distinguish two types of modelling, deriving from a so-called classic soil-science approach based exclusively on the analysis of the soil solid phase, and deriving from other scientific fields – in particular environmental and mining – that also integrate circulating water. The advantages and limitations of each approach are discussed. Models based on the analysis of the soil solid phases provide a good understanding of how present-day soils were formed. Nevertheless, the time factor is, at best, only represented through a single exponential law, which does not allow a transcription of the commonly observed rate changes in soil evolution. Models which couple geochemistry, water and solute, transfers must be adapted to the specific problems of pedogenesis: (1) the transfer module must by necessity be able to simulate an unsaturated environment; (2) the databases of the geochemical module must be compatible with the soil minerals; (3) any interactions and feedback between the solid and liquid phases must be integrated; and (4) the ‘nested’ organization of soils must be accounted for. Certain processes are still poorly or not at all accounted for in this type of modelling, in particular the leaching of clays and most biological processes. Even so, this type of modelling seems to be quite attractive, as it permits the explicit consideration of variations in soil-water contents over time.

Research paper thumbnail of Evolution model of progressive failure of landslides

Journal of geotechnical and …, Jan 1, 1999

... ABSTRACT: An evolution model considering rheologic effects is proposed to describe the progre... more ... ABSTRACT: An evolution model considering rheologic effects is proposed to describe the progressive failure process of soil slopes. ... CONCLUSIONS This paper presents an evolution model considering rheo-logic effects to describe the progressive failure process of soil slopes. ...

Research paper thumbnail of Progressive and regressive pedogenesis and complex soil evolution

Quaternary Research, Jan 1, 1993

Research paper thumbnail of Soil chronosequences, soil development, and soil evolution: a critical review

Research paper thumbnail of The soil-evolution model as a framework for evaluating pedoturbation in archaeological site formation

Archaeological geology of North America, Jan 1, 1990

Research paper thumbnail of The mARM3D spatially distributed soil evolution model: Three-dimensional model framework and analysis of hillslope and landform responses

Journal of Geophysical Research, Jan 1, 2010

Research paper thumbnail of Conceptual models in pedogenesis: can soil-forming functions be solved?

Geoderma, Jan 1, 1975

Quantitative solutions of the univariant soil-forming functions are reviewed. Lithofunctions are ... more Quantitative solutions of the univariant soil-forming functions are reviewed. Lithofunctions are essentially of a comparative nature. Numerical solutions are possible if a coding of the parent material or its properties is made. The number of solutions of topofunctions and climofunctions is already considerable, though too few generally valid equations have been derived. These are required for the further development of the general solutions. Numerical solutions of true biotic functions are likely to remain exceptional and the biotic attributes are best considered as a dependent variable and property of the soil-ecosystem, like any of the soil properties.Several chronofunctions have been obtained for the initial stages of soil formation, and good graphical summaries for long-term soil development functions have been constructed, but strict numerical chronofunctions are rare because the difficulties in isolating and dating properly controlled sites. Runge's energy model uses incongruous terms whilst it essentially follows the tenets of the factorial system, but neglects the parent material (capacity) factor. Chesworth's weathering trend line does not disprove the absence of the steady state and his inference from this and his criticism of the state factor equation are essentially invalid.Because the number of degrees of freedom in the solution of the general soil formation function is rather large, the best way for advancing the solution of the state equation is by increasing the solutions of the univariant functions. It is suggested that the next step should be the preparation of a family of topofunctions, graphically or numerically, showing their change with time and on different parent materials or under different macroclimates. Computerized simulation models of such multivariate functions can then be prepared and compared with real data for further refinement and for pinpointing univariant functions or equations which are needed for the improvement of the solutions already obtained.Whereas the relevance of the univariant and multivariant functions of the state factors is in deriving the significant or major causal relationships, and thus explain or predict the distribution of soils in space and time, the computer simulation strategy can advance the quantification of the process-oriented models of soil dynamics.

Research paper thumbnail of Towards the quantitative modeling of pedogenesis—a review

Geoderma, Jan 1, 1992

The historical development of our pedogenetic model is reviewed, and trends or directions toward ... more The historical development of our pedogenetic model is reviewed, and trends or directions toward the future are discussed. Pedogenetic models are characterized with respect to relative degree of computation, complexity, and level of organization. These three characteristics are used as a framework for classification. Early qualitative models have well served the purpose of soil survey to describe the distribution of soils in landscapes. Further development of qualitative models will contribute to the understanding of soil genesis in areas where soil surveys are not completed. In the developed countries, however, the scientific questions have changed dramatically. Greater interest lies in understanding the physical and chemical processes of soil formation acting within relatively short time frames and assessing the interactions between natural processes and environmental change or anthropogenic impacts. Quantification of pedogenetic processes is a life-line to other environmental disciplines, and a mechanistic understanding would, in an ideal situation, describe and predict the behavior of a system for a limited number of years under changing environmental conditions.A proposed approach to mathematical simulation of the dynamic pedogenetic processes is to integrate soil physical, chemical, and other ecological system models into a quantitative pedogenetic model. Models may be developed as research tools in data-intensive studies at the pedon or horizon level, or for the purpose of simulating a soil system at the catena or soil region level. Specific kinds of pedogenetic models have specific implications with respect to the availability and spatial variability of the data needed for development and testing.

Research paper thumbnail of Evolution model of pedogenesis

Soil Science, Jan 1, 1987

Advertisement. Soil Science. Wolters Kluwer Health Logo. All Issues. ...