University of Bío-Bío
  • Concepción, Chile
Recent publications
Background We examined the influence of superoxide dismutase 3 (SOD3) Arg213Gly and Peroxisome Proliferator-Activated α-Receptor (PPARα) 7G/C polymorphisms to a single dose of purple grape juice supplementation on time-to-exhaustion running test, redox balance and muscle damage in recreational runners. Methods Forty-seven male recreational runners performed a running test until exhaustion after supplementation with grape juice or a control drink. Serum total antioxidant capacity (TAC), malondialdehyde (MDA), plasma nitrite (NO), creatine kinase (CK) and lactate dehydrogenase (LDH) were measured pre and post exercise. Also, polymorphisms were analyzed in DNA extracted from the oral mucosa. Results Grape juice improved the time-to-exhaustion. When analyzed by genotype, the recreational runners with GG+CG genotypes of the SOD3 gene had greater time-to-exhaustion than the CC genotype, but was no different for the PAPRα gene. A slight difference was noted in TAC, since the CC genotype of the SOD3 gene showed higher TAC values in the post-exercise compared to the baseline and with pre-exercise, but these values did not increase compared to the CG+GG group, respectively. The SOD3 and PPARα genes were similar at all times for the other biochemical variables. Conclusion The ergogenic effect of grape juice was genotype-dependent for SOD3 Arg213Gly. However, biochemical redox balance markers did not explain this difference.
Solar protections are often designed as passive strategies in buildings, both for thermal and lighting performance. In this sense, the importance of the balance between these two parameters could be crucial in the early stages of design. The purpose of this research is to compare the variation solar protection strategies (glazing with solar protection, and the length of overhangs) have on energy and lighting, using as reference, the value defined by the Modified Solar Factor (MSF), used in some countries like Spain and Chile, to restrict solar contributions. Simulations were carried out to understand the potential of solar protections with the same MSF and the implications on thermal and lighting performance. The case study is a classroom located in Talca, in central-southern Chile, with a climate of marked seasons, including cold winters and hot summers. The results showed that the use of solar protection strategies with the same and similar MSF values do not provide comparable energy performance. Specifically, the differences in energy consumption are 0.62 kWh (East (E) - MSF 0.14) for heating, in cooling 42.28 kWh (Northeast (NE) - MSF 0.47), in lighting 5.30 kWh (Northwest (NW) - MSF 0.11), and 39.77 kWh in the total consumption (Northeast (NE) - MSF 0.47). According to the results obtained, suitable solar protection requires evaluating different alternatives that allow balancing both performances, while attaining significant energy savings.
The use of qualitative algorithms in images with dynamic speckle allows generating a three-dimensional intensity map, which correlates with the sample activity. Samples in an evaporation state will present temporary mobility related to their volume, which allows characterizing their topography. However, the quality of the topographic characterization depends on the illumination profile and the number of images or frames used. In this paper, a review of various qualitative processing algorithms is carried out in order to evaluate their robustness to the number of frames and their dependence on the beam profile, evaluating the characterization of topography hidden by a layer of paint in process of drying. We use an aluminum structure with perforations of different diameters and depths as a sample. Among the algorithms used, we highlight the results obtained by the normalized DJC method, which characterizes the topography of our sample with a correlation of 0.98 and presents stability to the number of frames used. Thus, with these results we validate the use of dynamic speckle in the characterization of a surface covered with paint.
Garretón’s “Una teoría cibernética de la ciudad y su sistema” (A cybernetic theory of the city and its system) was published in 1975 by Nueva Visión publishing house in Buenos Aires, a moment when the seminal criticisms against the modernist urban theory of the sixties led by Team 10 were becoming concrete proposals for updating and eventually overcoming its shortcomings. Yet, despite remaining unpublished in English and hence relatively unknown worldwide, few publications in the field compare in scope to Garreton’s cybernetic theory. The reason is straightforward: like Shannon’s mathematical theory, this work amounts to a general theory of the city. Thoroughly informed by system thinking, whose trademark rule of thumb was described by Luhmann as “drawing distinctions” to guarantee the autopoiesis of a determined system, Garretón’s chief objective was to draw distinctions that would guarantee the autopoiesis of the urban system. In doing so, he discovered three fundamental urban laws, namely: the law of urban communication, the law of urban attraction, and the law of urban circulation. This, in turn, allowed him to clearly distinguish a universe that had thus far remained undetected by urbanists and that he called the non-city Universe: the human-made universe that nevertheless does not belong in the urban universe. This paper argues that this allowed him to rediscover and update the ancient and lost art of city-making: not an art of making buildings, roads, and infrastructure in general but rather, the art of building, knitting, fostering, and sustaining communities and whole societies by means of or with the aid of buildings.
In this work, we construct the exact propagator for Dirac fermions in graphene-like systems immersed in external static magnetic fields with non-trivial spatial dependence. Such field profiles are generated within a first-order supersymmetric framework departing from much simpler (seed) magnetic field examples. The propagator is spanned on the basis of the Ritus eigenfunctions, corresponding to the Dirac fermion asymptotic states in the non-trivial magnetic field background which nevertheless admits a simple diagonal form in momentum space. This strategy enlarges the number of magnetic field profiles in which the fermion propagator can be expressed in a closed-form. Electric charge and current densities are found directly from the corresponding propagator and compared against similar findings derived from other methods.
The aim of this work is to prove analytically the existence of symmetric periodic solutions of the family of Hamiltonian systems with Hamiltonian function H(q1,q2,p1,p2)=12(q12+p12)+12(q22+p22)+aq14+bq12q22+cq24$$ H\left({q}_1,{q}_2,{p}_1,{p}_2\right)=\frac{1}{2}\left({q}_1^2+{p}_1^2\right)+\frac{1}{2}\left({q}_2^2+{p}_2^2\right)+a\kern0.1em {q}_1^4+b\kern0.1em {q}_1^2{q}_2^2+c\kern0.1em {q}_2^4 $$ with three real parameters a,b$$ a,b $$, and c$$ c $$. Moreover, we characterize the stability of these periodic solutions as a function of the parameters. Also, we find a first‐order analytical approach of these symmetric periodic solutions. We emphasize that these families of periodic solutions are different from those that exist in the literature.
Resting metabolic rate (RMR) depends on body fat-free mass (FFM) and fat mass (FM), whereas abdominal fat distribution is an aspect that has yet to be adequately studied. The objective of the present study was to analyze the influence of waist circumference (WC) in predicting RMR and propose a specific estimation equation for older Chilean women. This is an analytical cross-sectional study with a sample of 45 women between the ages of 60 and 85 years. Weight, height, body mass index (BMI), and WC were evaluated. RMR was measured by indirect calorimetry (IC) and %FM using the Siri equation. Adequacy (90% to 110%), overestimation (>110%), and underestimation (<90%) of the FAO/WHO/UNU, Harris–Benedict, Mifflin-St Jeor, and Carrasco equations, as well as those of the proposed equation, were evaluated in relation to RMR as measured by IC. Normal distribution was determined according to the Shapiro–Wilk test. The relationship of body composition and WC with RMR IC was analyzed by multiple linear regression analysis. The RMR IC was 1083.6 ± 171.9 kcal/day, which was significantly and positively correlated with FFM, body weight, WC, and FM and inversely correlated with age (p < 0.001). Among the investigated equations, our proposed equation showed the best adequacy and lowest overestimation. The predictive formulae that consider WC improve RMR prediction, thus preventing overestimation in older women.
Preeclampsia is a maternal syndrome characterized by the new onset of hypertension and proteinuria after 20 weeks of gestation associated with multisystemic complications, including brain alterations. Indeed, brain complications associated with preeclampsia are the leading direct causes of fetal and maternal morbidity and mortality, especially in low- and middle-income countries. In addition to the well-recognized long-term adverse cardiovascular effects of preeclampsia, women who have had preeclampsia have higher risk of stroke, dementia, intracerebral white matter lesions, epilepsy, and perhaps also cognitive decline postpartum. Furthermore, increasing evidence has also associated preeclampsia with similar cognitive and cerebral disorders in the offspring. However, the mechanistic links between these associations remain unresolved. This article summarizes the current knowledge about the cerebrovascular complications elicited by preeclampsia and the potential pathophysiological mechanisms involved, emphasizing the impaired brain vascular function in the mother and their offspring.
This article examines the connection between household poverty and natural disasters in Chile using a multidimensional analysis of poverty. Rather than using household income as a single poverty indicator, we implement a multidimensional poverty index, which measures poverty in four dimensions: work and social security, housing, health and education. This study helps reduce the limited knowledge of the impact of the 2010 earthquake and tsunami on household poverty in Chile, separating those events as different but related shocks. Using data from the National Socioeconomic Survey, we applied a difference-in-difference methodology to estimate the effect of the earthquake and tsunami on multidimensional poverty for two population groups in the short- and long-term. The treatment group was fisher-households located in the areas affected by both shocks with at least one member working in the artisanal sector. The control group included the rest of the Chilean population. Results show that after both disasters, fishers have a greater lack in the “work and social security” dimension of poverty than the overall population in both the short- and long-term. They are less likely, though, to be poor in the housing dimension compared to non-fishers. Moreover, after the shocks, both groups decreased their likelihood to be poor in health in the short and long-term when controlling for territorial and time effects, whereas only the overall population was more likely to decrease in educational poverty. Some policy guidelines include: promoting faster labor capital-recovery, designing a participatory post-disaster strategy and preparing a well-established emergency response in high-risk localities.
There is limited knowledge concerning factors that affect non-exclusive breastfeeding (NEBF) practices in immigrant populations, especially in Latin America. The objective of the present study was to determine the association between maternal factors and the prevalence of NEBF in Haitian immigrant women in southern Chile. This was an analytical cross-sectional study. The probabilistic sample consisted of 173 Haitian women who gave informed consent. Sociodemographic and dietary-nutritional information was collected from all participants. Bivariate (χ2) and multivariate (logistic regression) inferential statistics were applied. All analyses were performed with the STATA 16.0 statistical software, and the significance level was established as α < 0.05. The prevalence of EBF at 6 mo was 54.3%. Maternal factors associated with a lower prevalence of EBF were not having permanent residency (OR: 2.34, CI: 2.18–2.83), residency <12 months (OR: 2.23, CI: 2.09–2.78), limited knowledge of breastfeeding (OR: 1.96; CI: 1.81–2.27), and low educational attainment (OR: 1.78; CI: 1.61–2.11). The protective factors were employment (OR: 0.36, CI: 0.28–0.40), access to basic services (OR: 0.32; CI: 0.22–0.48), and Spanish proficiency (OR: 0.29; CI: 0.20–0.51). Haitian immigrant women without legal residency, recently arrived, with low educational attainment, and poor knowledge of breastfeeding have more risk of not providing exclusive breastfeeding. Targeted interventions for mothers with these risk factors may help improve EBF rates.
Cyclopeptide alkaloids with different biological activities are present in plants of the family Rhamnaceae. Plants of this family grow in a symbiotic relationship with aerobic Gram-positive actinomycetes belonging to the genus Frankia . This goal of this research was a study of the comparative profile of alkaloids present in Discaria chacaye and to establish a connection between the presence or absence of Frankia sp. and the alkaloids. In addition, insecticidal activities of the alkaloidal extract were examined. A total of 24 alkaloids were identified, of which 12 have a benzylisoquinoline skeleton, 9 were cyclopeptides, 2 isoquinolines, and 1 an aporphine. The presence of cyclopeptide alkaloids is associated with Frankia nodules in the plant root. The alkaloid extracts showed insecticidal activity with mortality dose-dependence and LD 50 values between 44 to 71 µg/mL.
Purpose This study aims to assess environmentally three different alternatives related to the valorization of Dichrostachys cinerea tree (an invasive plant) as a feedstock for cogeneration facilities installed in the sugarcane industry in Cuba. Methods The Life Cycle Assessment (LCA) methodology was applied to three cogeneration alternatives: (A-1) Electric- ity generation using raw Dichrostachys cinerea (marabou) as fuel in a back-pressure steam turbine cycle, (A-2) Electricity generation using torrefied marabou as fuel in a back-pressure steam turbine cycle, and (A-3) Electricity generation using torrefied marabou as fuel in an extraction-condensing turbines cycle. The SimaPro software was used for the inventory modeling and the ReCiPe method (midpoint and endpoint approach) was applied to estimate the environmental impacts associated with each case. Results and Discussion The LCA results showed that the electricity generation from torrefied marabou using extraction- condensing turbines (A-3) reduces the environmental impacts as compared with A-1 and A-2. This performance is explained by a lower marabou relative consumption (1.85 kg marabou/kWh generated), which leads to lower emissions associated with harvesting, transportation, and pre-processing stages. Fine Particulate Matter Formation, Terrestrial Acidification, and Water Consumption accounted the worst performance for all the scenarios. Marine Ecotoxicity was the impact category with better environmental performance due to the substitution of synthetic mineral fertilizers by the ashes produced during com- bustion. The Human health damage category reached the higher impacts on the torrefaction subsystem in the A-3 scenario, representing over 94% of the total environmental burden of the process, causing injuries in respiratory systems. The highest beneficial impact of the cogeneration stage was associated with the consideration of residual steam as an avoided product. Conclusions The use of torrefied marabou in extraction-condensing steam turbines can be considered as an environmental- friendly technology in the Cuban context.
In this article, we use the Euler–Bernoulli model to study the vibrations of a beam composed of two components, one consisting of a thermoelastic material and the other of a simply elastic material that does not produce dissipation. Our main result is that the semigroup associated with this model is differentiable. In particular, our proof implies the following properties of the semigroup (1) It is of Gevrey class 12. (2) It is exponentially stable. (3) It possesses the property of linear stability and has a regularizing effect on the initial data.
Microcirculation analysis of the brain cortex is challenging because surface perfusion varies rapidly in small space-time regions and is bone protected. The laser speckle contrast imaging (LSCI) technique allows analyzing in vivo brain vascular perfusion generating a large amount of data that requires sophisticated data analytics, making researchers invest much effort in processing. Our research question was whether the reduced placental perfusion model (RUPP) of preeclampsia (PE) was associated with impaired blood perfusion in the offspring's brains. We aimed to develop a robust numerical approach that mainly consisted of applying a signal-processing tool for calculating optimal segmentation and piece-wise fits of the offspring's brain perfusion signals obtained from the LSCI technique. We combined this tool with the usual statistical analysis, implementing both in Matlab software. We performed brain perfusion measurements from offspring (five days postnatal, P5) of control pregnant dams (sham, n = 13) and of RUPP dams (RUPP, n = 7) using the Pericam® PSI-HR system at a basal condition and after thermal stimuli (warm and cold). We found that pups of RUPP mice exhibited significant differences in perfusion and vascular response to thermal stimuli compared to the sham mice. These differences were associated with high data variability in the Sham group, while in the RUPP group, perfusion looks “stiffer.” Data also suggest sex-dimorphism in the vascular response since female pups in the Sham group but not male pups showed statistically significant differences in response to the warm stimulus. Again, this sex-related difference was absent in pups of RUPP mice. In conclusion, we present a robust quantitative approach for LSCI measurements that revealed anomalies in the brain blood flow in offspring of the RUPP model of PE.
Corporate social responsibility (CSR) initiatives are common in the mining industry and have the watchful eye of their stakeholders. However, limited attention has been given to the perceptions of the host communities regarding these initiatives. This paper seeks to explore the perceptions of a host community, located in the north of Chile, regarding the CSR initiatives of mining companies close to their community. Through a qualitative methodology, nine semi-structured interviews (to residents and workers of the host community) are conducted. The data are analyzed with the thematic analysis technique and, together with the theoretical lenses of the CSR pyramid and the stakeholder theory, the results are obtained. The main findings indicate that the host community perceives different responsibilities regarding the CSR initiatives of the mining industry. These dimensions comprise the level of importance perceived by the community, from the bottom (most important) to the top of the pyramid (least important), such as environmental responsibility, responsibility for health and safety well-being, ethical responsibility, economic responsibility, legal responsibility, and finally, philanthropic responsibility. The investigation contributes to the literature on CSR in the mining industry, generating practical implications for public policies, the management of mining companies and the leaders of the host community.
Nonlinearities, exponential trends, and Euler equations are three key features of standard dynamic volatility models of speculation, economic growth, or macroeconomic fluctuations with occasionally binding constraints and endogenous state-dependent volatility. A natural way to estimate a model with all such three features could be to use the observed nonstationary data in a single step without preliminary linearization, log-linearization, or preliminary detrending. Adoption of this natural strategy confronts a serious challenge that has been neither articulated nor solved: a dichotomy in the empirical model implied by the Euler equation. This leads to a discontinuity in the regression in the limit, rendering the approaches employed in available proofs of consistency inapplicable. We characterize the problem and develop a novel method of proof of consistency and asymptotic normality. Our methodological contribution establishes a foundation for consistent estimation and hypothesis testing of nonstationary models without resorting to preliminary detrending, an a priori assumption that any trend is exactly zero, linearization, or other restrictions on the model.
This work aims to understand how relevant properties of polymers lead to different adsorption modes on a quartz surface (1 0 1). For this purpose, six polymers were considered: polyacrylamide (PAM), hydrolyzed polyacrylamide (HPAM), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), polyacrylic acid (PAA), polyethylene oxide (PEO) and guar gum (GUAR). The reagents have diverse physicochemical properties, with differences in charge density, structure, and functional groups. Classical molecular dynamics (CMD) simulations were performed with the generalized Amber force field (GAFF). The results clearly distinguish the different behaviors of charged polymers with respect to neutral polymers and their relevance to the adsorption modes and the conformation of the polymer on the surface. The highest affinity was achieved in neutral polymers, this considering that quartz is weakly charged at pH 7. Charged polymers adsorb but in stretched conformations leaving the tails of the polymers away from the surface, which is beneficial to producing polymer bridges. Salinity can impair or benefit the adsorption of reagents, depending mainly on their electrical charge. This study helps to understand the critical factors of a flocculant in the search for new additives for mineral aggregation and dispersion applications, a topic of special relevance in solid-liquid separation operations in the mining indust
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
2,455 members
Cesar Salazar Espinoza
  • Department of Business Management
Cristian Duran-Faundez
  • Department of Electrical and Electronics Engineering
Guillermo Petzold
  • Department of Food Engineering
Serguei Alejandro Martín
  • Wood Engineering Department
collao 1202, 4051381, Concepción, Chile
+56 (41) 3111200