Browsing by Autor "Daniel Ruíz"

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Climate extremes increase dengue risk along elevation and socio-economic gradients in Colombia
(2024) Pallavi A. Kache; Daniel Ruíz; Rachel Lowe; Anna M. Stewart‐Ibarra; Karen C. Seto; Maria Diuk-Wasser; Mauricio Santos‐Vega
Abstract Globally, urban settlements face increases in the frequency, magnitude, and duration of extreme climate events and shifts in their timing and spatial extent. Variation in temperature and rainfall conditions affect the temporal onset of dengue transmission. However, there is a need to understand how climate-related patterns and disease transmission mechanisms vary by location, particularly for topographically complex landscapes. In this investigation, we used dengue cases from 1,120 municipalities and five regions across Colombia during 2008–2019, and analyzed associations with extreme climate covariates generated from fine-scale, daily-level meteorological data, accounting for varying landscape and socio-economic properties. Using Bayesian spatio-temporal hierarchical models, we determined that high-intensity warm spells (with positive temperature anomalies of 8–12°C above mean monthly conditions) resulted in an earlier onset of dengue transmission risk in high-elevation settlements compared to low- elevation settlements. Furthermore, the risk of dengue transmission after extremely dry conditions was greater and extended for a longer duration in highly urbanized municipalities compared to those with a low urban population. Our findings highlight that meteorological hazards affect disease transmission in urban settlements differently based on elevation and socio-economic conditions. Additionally, our analysis adds to increasing evidence of the vulnerability of mountainous urban communities to extreme weather and vector-borne diseases. Overall, we emphasize the need for monitoring and forecasting the occurrence and intensity of meteorological hazards and associations with emerging climate-sensitive disease threats.
Ensayos dinámicos de resistencia en paneles del sistema royalco (64 mm) para la construcción de muros en vivienda
(Universidad de Los Andes, 2002) Daniel Ruíz; Luis E. Yamín; Camilo Phillips; Juan Carlos Reyes
Ensayos Dinamicos De Resistencia En Paneles Del Sistema Royalco (64 Mm) Para La Construccion De Muros En Vivienda
Matching Dendrochronological Dates with the Southern Hemisphere <sup>14</sup>C Bomb Curve to Confirm Annual Tree Rings in <i>Pseudolmedia rigida</i> from Bolivia
(Cambridge University Press, 2015) Laia Andreu‐Hayles; Guaciara M. Santos; David Herrera‐Ramírez; Javier Martin-Fernández; Daniel Ruíz; Tatiana Erika Boza Espinoza; A C.; Peter M J⊘rgensen
This study used high-precision radiocarbon bomb-pulse dating of selected wood rings to provide an independent validation of the tree growth periodicity of Pseudolmedia rigida (Klotzsch & H. Karst) Cuatrec. from the Moraceae family, collected in the Madidi National Park in Bolivia. 14 C content was measured by accelerator mass spectrometry (AMS) in 10 samples from a single tree covering over 70 yr from 1939 to 2011. These preliminary calendar dates were determined by dendrochronological techniques and were also used to select the samples for 14 C AMS. In order to validate these preliminary dates using the established Southern Hemisphere (SH) 14 C atmospheric concentration data set, the targeted rings were selected to be formed during periods before and after the 14 C bomb spike nuclear tests (i.e. 1950s–1960s). The excellent agreement of the dendrochronological dates and the 14 C signatures in tree rings associated with the same dates provided by the bomb-pulse 14 C atmospheric values for the SH (SHCal zone 1–2) confirms the annual periodicity of the observed growth layers, and thus the high potential of this species for tree-ring analysis. The lack of discrepancies between both data sets also suggests that there are no significant latitudinal differences between the 14 C SHCal zone 1–2 curve and the 14 C values obtained from the selected tree rings at this geographic location (14°33′S, 68°49′W) in South America. The annual resolution of P. rigida tree rings opens the possibility of broader applications of dendrochronological analysis for ecological and paleoclimatic studies in the Bolivian tropics, as well as the possibility of using wood samples from some tree species from this region to improve the quality of the bomb-pulse 14 C SHCal curve at this latitude.
Radial growth decline in a tropical Andean treeline in Bolivia
(2025) Rose Oelkers; Laia Andreu‐Hayles; Rosanne D’Arrigo; Arturo Pacheco-Solana; Milagros Rodríguez‐Catón; M. Eugenia Ferrero; Ernesto Tejedor; A C.; Carla Maldonado; Daniel Ruíz
Abstract. Relative to research efforts in higher latitiudes, the impact of climate shifts in the tropical treeline remains understudied. Little is known about the tree growth dynamics and climate response at this treeline over the past few centuries, and at present under a rapidly changing environment. Here we provide information on recent changes in tree-ring patterns of Polylepis pepei BB.Simpson, a tropical tree species that grows in a monospecific forest at the elevational treeline in the Andes-Amazon ecotone of Bolivia and identify factors that limit its radial growth. We first developed a ring width (RW) chronology spanning 1867–2018 C.E. using dendrochronological methods and independently verified annual periodicity with radiocarbon dating. The RW chronology indicates a significant (p < 0.01) radial growth decline in P. pepei since 1997, a trend that mirrors a decrease reported in other Polylepis species from the drier central Andes of South America. P. pepei tree-ring width (RW) was mostly limited by mean, minimum, and maximum temperature and precipitation during austral summer (November–January). Over the instrumental period (1981–2019) prior-year temperatures negatively affected current-year tree growth (p < 0.05), while prior-year wet conditions were associated with higher growth (p < 0.05). Gridded temperature records (1901–2019) showed a significant increase in minimum temperatures and a decline in the diurnal temperature range since 1967, which may reduce orographic convection and water availability at higher elevations where our forest is located. In situ daily measurements from dataloggers in the forest recorded higher temperatures and lower relative humidity values when data was available. Our results suggest less moisture availability associated with warming conditions was related to the observed tree-growth decline. If temperature continues to rise at current rates, one of the highest-elevation tree species on the globe, P. pepei, could face severe consequences. This work provides insights into the past and historical trends of a tropical Andean treeline, which shows a recent decline also observed in other high-elevation forests (4657–4800 m.a.s.l.) of tropical South America (>17° S).
Reforzamiento estructural de edificaciones patrimoniales en tierra de 1 y 2 pisos: aplicación de la normativa AIS-610-EP-2017
(Spanish National Research Council, 2023) Daniel Ruíz; Paula Rossana Galindo Jaramillo; Anyi Lizeth Hernández Niño; Juan Carlos Reyez Ortiz; Manuela Restrepo; Natalia Barrera; José Gustavo Martínez Murcia; Cecilia Teresa López Pérez
Los españoles que conquistaron la zona andina latinoamericana construyeron edificios en adobe y tapia apisonada. Por esta razón, el 90% de los edificios patrimoniales en Colombia están construidos en tierra; la mayoría ubicados en zonas de amenaza sísmica intermedia y alta. Considerando que estas edificaciones son sísmicamente vulnerables, en 2019 se incluyó la norma AIS-610-EP-2017 en la reglamentación sismo-resistente del país (norma para reforzamiento sísmico de edificios patrimoniales en tierra). Utilizando esta norma, se analizaron dos edificios construidos en el siglo XVI. Los muros fueron reforzados con placas de acero (o de madera). Los resultados indican que para cargas sísmicas solo el 24% de los muros sin refuerzo tendrían tensiones menores que la resistencia a la tracción de la tierra, mientras que en los muros reforzados este porcentaje es del 98%. Asimismo, las tensiones en los elementos de refuerzo (acero y madera) se mantienen por debajo de los límites permisibles.
Seismic Performance of a 1:4 Scale Two-Story Rammed-Earth Model Reinforced with Steel Strips Tested on a Bi-Axial Shaking Table
(2023) Natalia Barrera; Daniel Ruíz; Juan C. Reyes; Yezid A. Alvarado; Daniela Carrasco-Beltrán
During the 16th and 17th centuries, Latin American cities adopted earthen construction techniques from European colonizers. As a result, rammed earth (RE) buildings now occupy an important place in Latin America&#039;s cultural heritage. However, earthquakes around the world have shown that unreinforced earthen constructions are highly vulnerable. For several years, researchers in northern South America have been proposing a technique that consists of installing confining steel plates (or wooden elements) on both sides of the RE walls forming a grid. This system has shown excellent performance in controlling seismic damage and increasing strength and ductility capacity. Although researchers have tested full-scale one- and two-story earthen walls under pseudo-static loading in the laboratory, and one- and two-story earthen walls at 1:1 and 1:2 scale on uniaxial and biaxial shaking tables, the behavior of a complete reinforced module (one- or two-story) on a shaking table has never been assessed. The present study presents the results of shaking table tests performed on two-story RE modules at 1:4 scale. The experimental data indicate that the retrofit system with confining steel strips was effective in reducing the seismic damage of earthen constructions. In addition, the comparison of the results of the 1:4 scale tests with the 1:2 and 1:1 scale tests previously conducted by the researchers, shows that the acceleration levels of the equivalent prototypes are in the same order of magnitude for the three scales.
Seismic Vulnerability of Bridges in Colombia and Rehabilitation Strategies
(2002) Luis E. Yamín; Daniel Ruíz
A general diagnosis is presented on the seismic vulnerability of bridges of the main public road network in Colombia based on approximate evaluations and inspection of bridges. For the bridges identified as critical, a methodology is proposed to carry a detailed evaluation of seismic vulnerability considering simultaneously the live load capacity of the structure and the residual useful life of the bridge. The methodology includes the compilation of information (structural, geotechnical and foundation details), the evaluation of the properties of materials of the main structure, the evaluation of the behavior and characteristics of the bridge such as deflections and internal forces on elements under known loads, and registration and interpretation of environmental and forced vibrations. Based on the information the evaluation of seismic vulnerability of the bridge is established through capacity/demand ratios for the different elements and possible types of failure of the structure. General criteria are established to define intervention alternatives. Two case studies are presented of the proposed methodology for bridges of the public road network of Colombia.
Vulnerabilidad sísmica de puentes en Colombia y estrategias para rehabilitación
(Universidad de Los Andes, 2001) Luis E. Yamín; Daniel Ruíz
A general diagnosis concerning the seismic vulnerability of the bridges in the main Network of Roads in Colombia is presented based upon approximate appraisals. For those bridges identified as critical in this appraisal, a detailed methodology is presented to evaluate the seismic vulnerability considering simultaneously the problems of load capacity and residual useful life of the bridges due to the large increase of truckload in relation with the original design loads. General criteria are given to define alternatives of rehabilitation and/or reinforcement as well as general guidelines in order to choose the best solution.