4982 research outputs found
Sort by
Propiedades psicométricas del Drive for Muscularity Scale (DMS) en una muestra de hombres y mujeres jóvenes chilenos
No full textLa obsesión por la musculatura, si bien suele presentarse mayormente en hombres, también la experimentan muje-res. Es importante contar con instrumentos para medir este constructo, por lo que el objetivo de este estudio fue evaluar las propiedades psicométricas del Drive for Muscularity Scale (DMS) en una muestra chilena de adolescentes y jóvenes (n = 602). Se administró el DMS y el SATAQ-4. El análisis factorial confirmatorio arrojó dos factores, uno de actitudes y otro de conduc-tas, además de un factor de segundo orden. Esta estructura tuvo un buen ajuste para ambos sexos, aunque en las mujeres fue necesario eliminar dos ítems. En cuanto al sexo, los hombres presentan mayor puntuación y, respecto a la edad, los adolescen-tes manifiestan mayor obsesión. Se observó una correlación positiva entre DMS y la escala de internalización del ideal atlético/corporal. Estos resultados constatan que la versión chilena del DMS presenta adecuadas propiedades psicométricas
Durability of geopolymer concrete exposed to acidic environment – a review
Get PDFAcids attack concrete by dissolving both hydrated and unhydrated cement compounds as well as calcareous aggregates and the subsequent chemical reaction forms water soluble calcium compounds which are then leached away. The aggressiveness of the reaction depends on the pH of the acidic medium and the types of salts formed. Concrete pipes made of ordinary portland cement (OPC) carrying sewage water have always the presence acidic solutions in it. They deteriorate and service life of the pipes is affected along with the increased maintenance costs and that process cause environmental impacts. Geopolymer binders are novel binders that relies on alumina silicate rather calcium silicate bonds for structural integrity so they have been reported as being acid resistant. Those could be produced by the chemical action between alumino-silicate material such as fly ash(FA), granulated blast furnaces slag (GGBS), metakaoline or silica fume with alkaline solutions like sodium silicate or sodium hydroxide. Geopolymers showsuperior performance in terms of corrosion and fire resistance due to the absence of water and calcium in their structure.Utilizationof waste materials like FA and GGBS makes geopolymer concrete (GPC) an environment friendly construction material. This review paper looks in to the effect of various acids such as sulphuric acid, acetic acid, nitric acids on durability properties of OPC specimens, GPC specimens and GPC composite specimens when immersed in acidic solutions for certain period. The performance of geopolymer is analysed by the visual inspection and studying the parameters like weight loss, loss in compressive strength and maximum depth of penetration.Los ácidos atacan el hormigón disolviendo los compuestos de cemento hidratados y no hidratados, así como los agregados calcáreos, y la reacción química subsiguiente forma compuestos de calcio solubles en agua que luego se lixivian. La agresividad de la reacción depende del pH del medio ácido y de los tipos de sales formadas. Las tuberías de hormigón hechas de cemento Portland ordinario (OPC) que transportan aguas residuales siempre tienen la presencia de soluciones ácidas. Se deterioran y la vida útil de las tuberías se ve afectada junto con el aumento de los costos de mantenimiento y ese proceso genera impactos ambientales. Los ligantes de geopolímero son ligantes novedosos que se basan en enlaces de silicato de alúmina en lugar de silicato de calcio para su integridad estructural, por lo que se ha informado que son resistentes a los ácidos. Aquellos podrían ser producidos por la acción química entre material de aluminosilicato como cenizas volantes (FA), escoria granulada de altos hornos (GGBS), metacaolinao humo de sílice con soluciones alcalinas como silicato de sodio o hidróxido de sodio. Los geopolímeros muestran un rendimiento superior en términos de resistencia a la corrosión y al fuego debido a la ausencia de agua y calcio en su estructura. La utilización de materiales de desecho como FA y GGBS hace que el concreto geopolímero (GPC) sea un material de construcción amigable con el medio ambiente. Este artículo de revisión analiza el efecto de varios ácidos como el ácido sulfúrico, el ácido acético, losácidos nítricos en las propiedades de durabilidad de las muestras de OPC, muestras de GPC y muestras compuestas de GPC cuando se sumergen en soluciones ácidas durante cierto período. El desempeño del geopolímero es analizado por inspección visual y estudiando parámetros como pérdida de peso, pérdida de resistencia a la compresión y profundidad máxima de penetración
Association between body mass index and functional outcomes in elderly patients with distal radius fracture. A prospective observational study
No full textIntroduction: The association between body mass index (BMI) and functional outcomes is unknown in elderly individuals with distal radius fracture (DRF).
Objective: The aim of this study is to evaluate if there is association between BMI and functional outcomes in patients older than 60 years with DRF treated conservatively.
Materials and methods: A prospective observational study was performed. A total of 228 patients with extra-articular DRF were prospectively recruited. All patients were categorized by their BMI as normal, overweight, or obese. Functional outcomes were assessed after cast removal and at 1-year follow-up. The Disabilities of the Arm, Shoulder and Hand Outcome Measure (DASH), and Patient-Rated Wrist Evaluation (PRWE) questionnaires were used to assess upper limb and wrist/hand function, respectively, while the Jamar Dynamometer was used to assess grip strength.
Results: Of the total number of patients, 184 were female (80.7%), 87 were overweight (38.2%), and 111 were obese (48.7%). After cast removal, the correlations between BMI and functional outcomes were DASH 0.06 (p = 0.578), PRWE 0.04 (p = 0.692), and grip strength - 0.02 (p = 0.763). At 1-year follow-up, the correlations were DASH 0.55 (p = 0.036), PRWE 0.32 (p = 0.041), and grip strength - 0.21 (p = 0.043).
Conclusion: This study suggests that at 1-year follow-up, there was a low-to-moderate association between BMI and poor functional outcomes in elderly patients with extra-articular DRF treated conservatively.
Level of evidence: Level IV, observational prospective study.Introducción: Se desconoce la asociación entre el índice de masa corporal (IMC) y los resultados funcionales en ancianos con fractura de radio distal (DRF).
Objetivo: El objetivo de este estudio es evaluar si existe asociación entre el IMC y los resultados funcionales en pacientes mayores de 60 años con DRF tratados de forma conservadora.
Materiales y métodos: Se realizó un estudio observacional prospectivo. Se reclutó prospectivamente a un total de 228 pacientes con DRF extraarticular. Todos los pacientes fueron categorizados por su IMC como normales, con sobrepeso u obesos. Los resultados funcionales se evaluaron después de la extracción del yeso y al año de seguimiento. Se utilizaron los cuestionarios Disabilities of the Arm, Shoulder and Hand Outcome Measure (DASH), y Patient-Rated Wrist Evaluation (PRWE) para evaluar la función de la extremidad superior y la muñeca / mano, respectivamente, mientras que el dinamómetro Jamar se utilizó para evaluar la fuerza de agarre.
Resultados: Del total de pacientes, 184 eran mujeres (80,7%), 87 tenían sobrepeso (38,2%) y 111 eran obesos (48,7%). Después de retirar el yeso, las correlaciones entre el IMC y los resultados funcionales fueron DASH 0.06 ( p = 0.578), PRWE 0.04 ( p = 0.692) y fuerza de agarre - 0.02 ( p = 0.763). Al año de seguimiento, las correlaciones fueron DASH 0.55 ( p = 0.036), PRWE 0.32 ( p = 0.041) y fuerza de agarre - 0.21 ( p = 0.043).
Conclusión: Este estudio sugiere que en el seguimiento de 1 año, hubo una asociación de baja a moderada entre el IMC y los resultados funcionales deficientes en pacientes ancianos con DRF extraarticular tratados de manera conservadora.
Nivel de evidencia: Nivel IV, estudio prospectivo observacional
Moderate-severity silvicultural methods generate better forest reorganization than other silvicultural methods in temperate rainforests four decades after implementation
No full textSilvicultural regeneration methods promote regeneration of new tree cohorts following the harvest of mature trees and include a gradient of options from cutting all (clearcuts) or some (selection cuts) trees resulting in evenor uneven-aged forests. For forest managers and landowners, it is essential to have the best possible information on how forests reorganize following these different methods. Forest development, composition and growth are dependent on site quality and harvest type. In this study we evaluated two even-aged (clearcut (CC), seed-tree cut (STC)), one two-aged cut (extended irregular shelterwood (ISC)), one uneven-aged (single-tree selection cut (SC)), and an unmanaged control (CON), four decades after harvest implementation in old-growth Evergreen temperate rainforests above 500 m a.s.l. in the Coastal Range of south-central Chile. These forests grow on poorquality sites due to old and shallow soil conditions and were dominated by late-successional species and a thick understory with the bamboo Chusquea machrostachya at the time of harvest implementation. Compositional and structural conditions reflected the type of harvests, with even- and two-aged methods largely similar to one another and the SC and the OG having very similar characteristics, which is likely a consequence of the very light severity of the SC. Tree species composition in even-aged harvests was dominated by shade midtolerant species of high timber value, although short-lived pioneer species of the Proteaceae family were also abundant, especially in ISC. The ISC had the greatest homogeneity in all stand variables (tree density, basal area, volume, and quadratic stand diameter), and since it was a two-layered forest, had basal areas and volumes close to the SC and OG, and a rotated-sigmoid diameter distribution (different to all other treatments). Height of the new cohort in the ISC was significantly taller than in the CC and the STC for most species' groups, suggesting that the cut plus the residual canopy of ISC diminished the initial cover of the bamboo C. macrostachya and competition for regeneration. Only diameter growth of trees of all shade tolerances was lower in ISC, but diameter growth patterns were similar to CC and STC, with increasing growth during the first two-three decades followed by a decline. Based on these findings, we conclude that silvicultural methods of intermediate harvesting severity, especially ISC, provide the best ecological and economic option in these poor-quality sites given rapid reorganization following their implementation, while maintaining a relatively complex vertical structure, high tree species diversity, and a growing stock dominated by tree species of high timber value
Alternative Fermented Soy-Based Beverage: Impact of Inulin on the Growth of Probiotic Strains and Starter Culture
No full textThe number of people with dietary restrictions on dairy products has increased significantly due to lactose intolerance/allergy or adoption of vegan diets. Organic acid-producing probiotics have been used in fermented beverages, such as those based on soy, with good results. Such molecules have in fact been described for their role in sensory analyses and benefits to human health. Therefore, this study suggested the evaluation of an alternative soy extract-based beverage that could act as a functional food. For this purpose, products and biomass concentrations were monitored throughout soy extract fermentation through acidification kinetics and cell count. The effect of inulin on the growth of the probiotic strains Bifidobacterium longum and Lactobacillus acidophilus in co-culture with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was evaluated (technical replicates). It was observed that the addition of inulin reduced the time of fermentation by L. acidophilus, while no statistically significant effect was observed in the post-acidification period. In B. longum fermentation, the process did not change in the presence of inulin, but there was a significant increase in viability and survival in the post-acidification period. Therefore, it can be concluded that the strains studied can be used in the formulation of soy-based drinks and that inulin positively influenced the viability of both probiotics in fermented drinks tested
Noticeable Shifts in Soil Physicochemical and Biological Properties after Contrasting Tillage Management in Crop Rotations of Bean, Maize, and Amaranth in Ecuadorian Highland Soils
No full textSoil biological properties are sensitive indicators of soil quality changes due to perturbations occurred under agricultural management. The effects of contrasting tillage, increasing nitrogen fertilization doses, and crop rotations [e.g., bean, maize, bean (BMB) and bean, amaranth, bean (BAB)] on soil physicochemical and biological properties in an Andean soil from Ecuadorian highlands were evaluated in this study. Acid phosphatase, beta-Glucosidase, fluorescein diacetate hydrolysis, microbial biomass carbon (Cmic), soil basal respiration (BR), arbuscular mycorrhizal fungi (AMF) spore density, total glomalin content (TGRSP), and soil physicochemical properties were analyzed. Conventional tillage (CT) and crop rotation showed significant effects on soil physicochemical and biological properties. Towards the final crop rotations, no-tillage (NT) promoted BR, TGRSP, and higher AMF spore density in both crop rotations; the Cmic kept stable along time in BMB and BAB, while BR doubled its value when compared to CT. Results indicated that the AMF spore density increased by 308% at the end of the BMB, and 461% at the end of the BAB, while TGRSP increased by 18% and 32% at the end of BMB and BAB, respectively. Biological traits demonstrated to be strongly associated to the organic matter accumulation originated from crop residues under the NT post-harvest which improved soil moisture, biological activity, and AMF interaction. The conservative soil management system has definitively improved general soil properties when compared to soil conditions under the intensive soil management system in this research
Association between low vitamin D levels and cognitive impairment in Chilean older adults: findings of the National Health Survey 2016-2017
No full textIntroduction: Recent studies have shown that low vitamin D levels constitute a potential risk factor for the development of cognitive impairment. The present study aimed to investigate the association between vitamin D levels and the suspicion of cognitive impairment in Chilean older adults. Material and Method: We performed a cross-sectional study, including 1,287 participants >= 65 years (56.8% were women, age range 65 to 97 years) from the Chilean National Health Survey. Cognitive impairment was assessed using the Mini Mental State Examination (MMSE). Participants were classified into three groups according to their vitamin D levels (> 29 ng/ml sufficient, 12-29 ng/ ml deficit, and < 12 ng/ml severe deficit). The association between vitamin D levels and cognitive impairment was explored using logistic regression analysis, adjusted for confounding factors. Results: The prevalence of vitamin D deficit and vitamin D severe deficit was 37.7% and 21.0%, respectively. Compared to older adults with sufficient levels of vitamin D, those with severe deficits had a 94% (OR: 1.94 [95% IC: 1.27; 1.66], p = 0.002) higher odds of cognitive impairment (unadjusted model). Adjusting according to sociodemographic factors, lifestyle, adiposity, sunlight exposure, and multimorbidity slightly attenuated the association to 61% (OR: 1.61 [95%IC: 1.03; 2.19], p = 0.046), but remain significant. Conclusion: A severe deficit of vitamin D was associated with higher odds of cognitive impairment in Chilean older adults independent of major confounding factors. Future studies are needed to provide causal evidence between vitamin D and the suspicion of cognitive impairment
Understanding the Strategies to Overcome Phosphorus‒Deficiency and Aluminum‒Toxicity by Ryegrass Endophytic and Rhizosphere Phosphobacteria
No full textPhosphobacteria, secreting organic acids and phosphatases, usually favor plant performance in acidic soils by increasing phosphorus (P) availability and aluminum (Al) complexing. However, it is not well-known how P-deficiency and Al-toxicity affect the phosphobacteria physiology. Since P and Al problems often co-occur in acidic soils, we have therefore proposed the evaluation of the single and combined effects of P-deficiency and Al-toxicity on growth, organic acids secretion, malate dehydrogenase (mdh) gene expression, and phosphatase activity of five Al-tolerant phosphobacteria previously isolated from ryegrass. These phosphobacteria were identified as Klebsiella sp. RC3, Stenotrophomona sp. RC5, Klebsiella sp. RCJ4, Serratia sp. RCJ6, and Enterobacter sp. RJAL6. The strains were cultivated in mineral media modified to obtain (i) high P in absence of Al-toxicity, (ii) high P in presence of Al-toxicity, (iii) low P in absence of Al-toxicity, and (iv) low P in presence of Al-toxicity. High and low P were obtained by adding KH2PO4 at final concentration of 1.4 and 0.05 mM, respectively. To avoid Al precipitation, AlCl3 × 6H2O was previously complexed to citric acid (sole carbon source) in concentrations of 10 mM. The secreted organic acids were identified and quantified by HPLC, relative mdh gene expression was determined by qRT-PCR and phosphatase activity was colorimetrically determined using p-nitrophenyl phosphate as substrate. Our results revealed that although a higher secretion of all organic acids was achieved under P-deficiency, the patterns of organic acids secretion were variable and dependent on treatment and strain. The organic acid secretion is exacerbated when Al was added into media, particularly in the form of malic and citric acid. The mdh gene expression was significantly up-regulated by the strains RC3, RC5, and RCJ6 under P-deficiency and Al-toxicity. In general, Al-tolerant phosphobacteria under P deficiency increased both acid and alkaline phosphatase activity with respect to the control, which was deepened when Al was present. The knowledge of this bacterial behavior in vitro is important to understand and predict the behavior of phosphobacteria in vivo. This knowledge is essential to generate smart and efficient biofertilizers, based in Al-tolerant phosphobacteria which could be expansively used in acidic soils
A new formulation of cracking in concrete structures based on lumped damage mechanics
No full textLumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre -localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post -localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber -reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks
A comparative study of a viscous froth lens in two and three dimensions
No full textThe two-dimensional (2D) viscous froth model was initially designed to capture the dynamic behavior of dry foams within a Hele-Shaw cell, characterized by two parallel covering plates separated by a small gap. However, due to its inherent 2D nature, this model does not explicitly account for the dimension across the gap. To address this limitation, we have opted for a three-dimensional (3D) version of the viscous froth model. In this 3D model, the dynamic effect is introduced through the motion of the surface Plateau borders, while the configurations of films in bulk are determined via surface energy minimization subject to specified bubble volumes and surface Plateau border locations. We use this 3D model to simulate the motion of a viscous froth lens within a straight channel. The steady states of the viscous froth lens in 3D are primarily influenced by the driving velocity-to-gap size ratio, particularly at relatively small values of this ratio. By contrast, as the ratio becomes relatively large, the gap size begins to play a significant role in influencing the behavior of the viscous froth lens in 3D. Differences are observed in the steady-state configurations of the viscous froth lens in 3D when compared to those in 2D. However, the behavior of the viscous froth lens in 2D can be better aligned with the results in 3D by treating the drag coefficient required in the 2D viscous froth model as a fitting parameter. A further quantitative analysis indicates that the drag coefficient needed in the 2D viscous froth model may not serve as a uniform parameter for the entire foam structure. Instead, it may depend on the specific location along the evolving foam films over time