University of La Serena
  • La Serena, Region de Coquimbo, Chile
Recent publications
Enzyme biocatalysis has a fundamental role in the transition to sustainable chemical industry. Biocatalyst design (as immobilized enzymes) is an enabling technology to facilitate enzyme application in multiple areas. The primary function of enzyme immobilization is simplifying the enzyme handling and allowing reuse or continuous use. Additionally, enzyme immobilization allows the modulation of functional properties by applying the immobilization updated knowledge. The design of a practical and suitable enzyme-immobilized biocatalyst involves a multiparameter process. Different aspects mastered by diverse scientific and technological disciplines must be jointly applied. In this book chapter, an overview of these aspects related to the enzyme, the material support, and the chemistry is given. We describe the early applications of enzyme immobilization, the current trends, and the biocatalyst design at the edge of the new demands and opportunities. Integrated design is needed where protein engineering, materials sciences, enzyme catalysis, and process engineering are considered in their synergic interdependency.
Gender plays an important role in human–wildlife coexistence. Women have their own distinct form of environmental knowledge; women shape attitudes and perceptions related to wildlife and influence the use of natural spaces and the nature of human–wildlife interactions. Being a female farmer or practitioner involved in human–wildlife conflict mitigation poses a variety of obstacles and benefits. The way conservation conflicts are perceived and managed is gendered, and this needs to be taken into account when working with local communities to achieve effective and fluent dialogue, planning, implementation, and evaluation. The existing body of evidence is focused mainly in Africa and Asia and suggests that the sharing of landscapes between humans and wildlife has different implications for men and women with respect to their attitudes toward wildlife and how they are impacted by it. Although extensive research has been done in relation to gender, conservation, and natural resource management, the gender perspective of human–wildlife coexistence is underreported. Feminist political ecology emphasizes that gender differences originate in the need to overcome existing social and political barriers and is highlighting the importance of en-gendering research. In Chile, work in the rural sector poses various challenges, especially for women. Rural landscapes are, in general, dominated by men, with low female participation in decision-making spaces. Nonetheless, this appears to be silently changing. In this perspective, we contrast three undocumented experiences of our work as female researchers and facilitators of human–wildlife coexistence (northern case, central case, and southern case). The aim of this perspective piece is to expose current findings for the role of women in human–wildlife coexistence, contrast these with our reports, and propose future directions.
We devote this paper to study semi-stable nonconstant radial solutions of $S_k(D^2u)=w(\left \vert x \right \vert )g(u)$ on the Euclidean space $\mathbb {R}^n$ . We establish pointwise estimates and necessary conditions for the existence of such solutions (not necessarily bounded) for this equation. For bounded solutions we estimate their asymptotic behaviour at infinity. All the estimates are given in terms of the spatial dimension $n$ , the values of $k$ and the behaviour at infinity of the growth rate function of $w$ .
The estimation of physical parameters from data analyses is a crucial process for the description and modeling of many complex systems. Based on Ré nyi α-Gaussian distribution and patched Green's function (PGF) techniques, we propose a robust framework for data inversion using a wave-equation based methodology named full-waveform inversion (FWI). From the assumption that the residual seismic data (the difference between the mod-eled and observed data) obeys the Ré nyi α-Gaussian probability distribution, we introduce an outlier-resistant criterion to deal with erratic measures in the FWI context, in which the classical FWI based on l 2-norm is a particular case. The new misfit function arises from the probabilistic maximum-likelihood method associated with the α-Gaussian distribution. The PGF technique works on the forward modeling process by dividing the computational domain into outside target area and target area, where the wave equation is solved only once on the outside target (before FWI). During the FWI processing, Green's functions related only to the target area are computed instead of the entire computational domain, saving computational efforts. We show the effectiveness of our proposed approach by considering two distinct realistic P-wave velocity models, in which the first one is inspired in the Kwanza Basin in Angola and the second in a region of great economic interest in the Brazilian pre-salt field. We call our proposal by the abbreviation α-PGF-FWI. The results reveal that the α-PGF-FWI is robust against additive Gaussian noise and non-Gaussian noise with outliers in the limit α ! 2/3, being α the Ré nyi entropic index.
Galactic haloes in a Λ-CDM universe are predicted to host today a swarm of debris resulting from cannibalised dwarf galaxies. The chemo-dynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ; (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way; (iii) the chemistry of Arjuna, LMS-1, and I’itoi is indistinguishable from that of GES, suggesting a possible common origin; (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion; (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures.
In this work, we combine the semi-analytic model of galaxy formation and evolution sag with the 102 relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that ∼85 per cent of the current population of quenched galaxies located inside the clusters are ancient infallers with low or null content of hot and cold gas. The fraction of quenched ancient infallers increases strongly between the first and second pericentric passage, due to the removal of hot gas by the action of ram-pressure stripping (RPS). The majority of them quenches after the first pericentric passage, but a non-negligible fraction needs a second passage, specially galaxies with M⋆ ≤ 1010.5 M⊙. Recent infallers represent ∼15 per cent of the quenched galaxies located inside the cluster and, on average, they contain a high proportion of hot and cold gas; moreover, pre-processing effects are the responsible for quenching the recent infallers prior to infall onto the main cluster progenitor. The ∼65 per cent of quenched galaxies located around clusters are backsplash galaxies, for which the combination of RPS acting during a pre-processing stage and inside the cluster is necessary for the suppression of SF in this population.
A man in his 80s presents with multiple yellowish to erythematous papules and verrucous cobblestone-like plaques on the mucosal surface on both sides of his tongue. What is your diagnosis?
PURPOSE Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype. The purpose of this study was to evaluate the clinical features, prognostic factors, and results of DLBCL that was treated in the cancer centers of the public health system in Chile and compare cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) with rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). PATIENTS AND METHODS Patients age > 15 years who were treated in 18 cancer centers in the country between 2001 and 2017 were included. The Kaplan-Meier method was used to calculate overall survival (OS), and Cox proportional hazard regression modeling was used to evaluate the effect of the addition of rituximab to CHOP on OS. RESULTS A total of 1,807 patients were evaluated. The median age at diagnosis was 62 (range, 15-95) years, with a female predominance (53%). Half of the patients were age ≥ 60 years. Serology for HIV infection was positive in 5% of cases (96 cases). International Prognostic Index scores were available for 90% of patients, of which 45% had low-risk, 25% low-intermediate-risk, 18% high-intermediate-risk, and 11% high-risk scores. CHOP was administered to 986 patients (55%; median follow-up, 13.2 years) and R-CHOP to 821 patients (45%; median follow-up, 8.4 years). R-CHOP was associated with superior OS compared with CHOP (5-year 66% v 48%, and 10-year 53% v 35%; P < .001). CONCLUSION Rituximab improved the survival of patients with DLBCL diagnosed and treated in Chile. The benefit was sustained over time, with curative rates of > 50%. This intervention shows that the inclusion of this biological drug justified the expenses incurred by the Ministry of Health in the National Lymphoma Protocols in Chile.
Lactose‐free milk is rising in popularity among consumers due to its claim to be a better digestible product compared to regular fluid milk. For that reason, concentrating on this food is a good alternative for increasing its versatility and usability in different dairy industry segments. Block freeze concentration (BFC) is a simple technology used to concentrate liquid foods through ice crystal formation and subsequent removal of water. Thus, this work aimed to test two variants of the BFC technique on lactose‐free milk concentration. In the first approach, it was investigated the centrifugation‐assisted BFC of skim lactose‐free milk by applying a factorial experimental design. Temperature, time, and rotation speed were the factors, and the response variables included the concentrate yield, concentration index, and efficiency of the process. Concentrate yield and concentration index were mainly affected by the centrifugation temperature. On the other hand, individual factors did not have a significant effect on the efficiency, only their interactions. In the case of centrifugation‐assisted BFC in a single step, the condition at 40°C, 70 min, and 4500 rpm was considered the best, given the highest values of efficiency and concentrate yield (80.87 and 67.02, respectively), and still an excellent value for concentration index (2.05). Conversely, the condition at 30°C, 45 min, and 3500 rpm was chosen to integrate a freeze concentration process in two stage. Then, the ice obtained from the first cycle was subjected to the vacuum‐assisted BFC, which consisted in the second cycle. The concentrate obtained from the vacuum‐assisted BFC presented contents of total solids, carbohydrates, and protein 2.95, 3.00, and 2.91 times more than the initial lactose‐free milk, respectively. Therefore, we believe that the concentrates obtained can be used for the development of innovative lactose‐free dairy products. Using concentration processes in the dairy industry can significantly contribute to enhancing the overall efficiency of milk processing since huge quantities of water from milk can be reduced, increasing the total solids content. In turn, dairy products that provide a high amount of solids (especially protein) are gaining in popularity among consumers, with consequent interest from researchers. In addition, milk concentration shows advantages in terms of processing, packaging, transportation, and handling. Since most changes occur in an aqueous environment, the removal of some parts of water results in the preservation of milk. It is noteworthy that dairy industries are concerned principally with food preservation, green technologies, and the production of high‐quality products. Thus, concentration processes could favor the development of milk products rich in proteins to meet certain demands on functional and nutritional properties, for example in beverages and formulated food.
Urban coastal wetlands are fragile ecosystems that provide important ecosystemic services. However, these ecosystems are subject to considerable external pressures from urban development, which leads to serious disturbances in their structure, functioning, and diversity as a result of the advancement of urban, agricultural, foraging, and drainage activities, as well as displacement of endemic species by invasive ones. Within the biological communities of these ecosystems, arthropods play an important trophic and ecological role as food resource, pollinating agents, biological controllers, organic matter decomposers, and nutrient cyclers. In this paper we characterize the taxonomic richness and abundance of the terrestrial arthropod fauna of the Aguada de La Chimba urban coastal wetland (Antofagasta Region, Chile) using various methods. From a total of 1,874 specimens, we identified 109 terrestrial arthropod species, where Insecta was the most represented taxon, with 85 species, 47 families, and 15 orders. The estimated species richness values were higher than the observed values for the different groups under study, and insects showed the highest species values in all estimators. Based on their origin, the communities identified included native (24%), naturalized (22%), and to a lesser extent, endemic species. We also characterize the major threats to this urban wetland and discuss the importance of building public–private partnerships with the local community for the success of biodiversity conservation programs in coastal ecosystems.
In this work, the influence of the position of salmon in a cooling cavity on heat transfer, freezing rate and local exergy destruction was investigated using mathematical modeling and numerical simulation. The predicted temperature evolution in the food during freezing by turbulent heat convection in air inside a cooling chamber was validated with experimental results. The conjugate turbulent model in three dimensions included the natural heat convection and the unsteady heat diffusion with the phase change of water to ice in the food meat. Three positions of the block of salmon in the freezer were studied: bottom-left, bottom-center, and center of the freezer. The local exergy destruction was calculated to quantify the contribution of viscous dissipation and heat transfer during the salmon freezing process. The unsteady description of air velocity, temperature, and freezing rate were analyzed. The highest cooling rate calculated was for the food at the bottom left, and the lowest when located at the center of the cooling cavity. The exergy destruction analysis determined the useful energy lost during the freezing process.
Seabirds are top predators in coastal and pelagic ecosystems that forage at sea but return to land regularly during the breeding season (i.e., central place foragers). This unique life history strategy is directly related to their biological traits and helps define their role as top predators in marine systems. We analysed the effects of physiographic characteristics of nesting islands (area, elevation, and distance from the continent, as predicted by the General Dynamic Model of Oceanic Island Biogeography) and oceanographic variables from waters surrounding nesting islands that tend to be characterised by steep gradients (temperature, salinity, and primary productivity) on the trait diversity of nesting seabird assemblages on islands of the southeastern Pacific Ocean. Four biological traits related to species' life history and feeding strategy were used to calculate two indices, the Functional Richness and Rao's Quadratic entropy. We used fourth-corner and RLQ analysis to determine the relationship between biological traits and environmental variables. Island physiography and primary productivity in the waters surrounding nesting islands significantly affected seabird trait diversity, which gradually decreased from Chilean coastal islands to the distant Polynesian Islands. The traits for body mass and clutch size showed a significant positive relationship with primary productivity. We identified three assemblages of seabirds that had contrasting trait structures. These were defined as the Galapagos, Coastal Chile, and southeastern Oceanic islands assemblages, and reflected the adaptations of three different species pools to Frontiers in Marine Science specific oceanographic conditions. Our results suggest that food-related constraints might be one of the most critical environmental filters that shaped the current trait structure of nesting seabird assemblages on the islands in the eastern South Pacific Ocean.
Intermittent turbulence is key for understanding the stochastic nonlinear dynamics of space, astrophysical, and laboratory plasmas. We review the theory of deterministic and stochastic temporal chaos in plasmas and discuss its link to intermittent turbulence observed in space plasmas. First, we discuss the theory of chaos, intermittency, and complexity for nonlinear Alfvén waves, and parametric decay and modulational wave–wave interactions, in the absence/presence of noise. The transition from order to chaos is studied using the bifurcation diagram. The following two types of deterministic intermittent chaos in plasmas are considered: type-I Pomeau–Manneville intermittency and crisis-induced intermittency. The role of structures known as chaotic saddles in deterministic and stochastic chaos in plasmas is investigated. Alfvén complexity associated with noise-induced intermittency, in the presence of multistability, is studied. Next, we present evidence of magnetic reconnection and intermittent magnetic turbulence in coronal mass ejections in the solar corona and solar wind via remote and in situ observations. The signatures of turbulent magnetic reconnection, i.e., bifurcated current sheet, reconnecting jet, parallel/anti-parallel Alfvénic waves, and spiky dynamical pressure pulse, as well as fully developed turbulence, are detected at the leading edge of an interplanetary coronal mass ejection and the interface region of two merging interplanetary magnetic flux ropes. Methods for quantifying the degree of coherence, amplitude–phase synchronization, and multifractality of nonlinear multiscale fluctuations are discussed. The stochastic chaotic nature of Alfvénic intermittent structures driven by magnetic reconnection is determined by a complexity–entropy analysis. Finally, we discuss the relation of nonlinear dynamics and intermittent turbulence in space plasmas to similar phenomena observed in astrophysical and laboratory plasmas, e.g., coronal mass ejections and flares in the stellar-exoplanetary environment and Galactic Center, as well as chaos, magnetic reconnection, and intermittent turbulence in laser-plasma and nuclear fusion experiments.
We analyse the connection between the star formation quenching of galaxies and their location in the outskirts of clusters in the redshift range z = [0, 2] by estimating the fraction of red galaxies. More specifically, we focus on galaxies that infall isotropically from those that are infalling alongside filaments. We use a sample of galaxies obtained from the semi-analytic model of galaxy formation sag applied to the MultiDark simulation. mdpl2. In agreement with observational results, we find that the infall regions show levels of star formation that are intermediate between those of galaxies in clusters and in the field. Moreover, we show that, in the redshift range [0-0.85], the quenching of the star formation is stronger in the filamentary region than in the isotropic infall region. We also study the fraction of red galaxies as a function of the normalised distance to the cluster centre and find that, for radii R/R200 > 3, the fraction of red galaxies in the filamentary region is considerably larger than in the isotropic infall region. From the analysis of properties of the main progenitors of galaxies identified at z = 0, we find that they have different evolutionary behaviours depending on the stellar mass and environment. Our results confirm the observational findings that suggest that the infall regions of clusters play an important role in the pre-processing of galaxies along most of the evolutionary history of galaxies.
We present a new spectroscopic orbit of the O-type binary system HD 152147. We identify absorption lines in both components and use their radial velocities to determine the orbit, which results in a period of P = 50.2199 ± 0.0007 d, an eccentricity e = 0.738 ± 0.007, and a mean separation between the components of asin i = 151 ± 1 R⊙. Considering that the distance to the system is 1600 pc, this implies an angular separation of ∼0.44 mas, making it suitable for modern interferometric observations. In addition, we determine the fundamental stellar parameters of each component by means of a quantitative spectral analysis. We obtain Ma = 31.9−34.6 M⊙ and Ra = 17−24 R⊙ for the primary, and Mb = 14−15 M⊙ and Rb = 5−10 R⊙ for the secondary. We apply models with rotation to try to characterize the evolutionary status of the HD 152147 system. We find that the two components are compatible with a common age of 4.5 Myr. We also detect variations in the profile of Hα that are not modulated by the orbital cycle. Moreover, TESS photometry also presents intrinsic variability and was analysed for periodicities. We find a most relevant frequency of 20 times the orbital one, in a TESS data set that includes the periastron passage, and we interpret it as a tidally induced pulsation that seems to dissipate on a time-scale shorter than the orbital cycle because it is not present in another TESS data set that nearly covers the apoastron.
Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order μ, generating changes in General Relativity. Friedmann equations are modified, and the evolution of the species densities depends on μ and the age of the Universe tU. We estimate stringent constraints on μ using cosmic chronometers, Type Ia supernovae, and joint analysis. We obtain $\mu =2.839^{+0.117}_{-0.193}$ within the 1σ confidence level providing a non-standard cosmic acceleration at late times; consequently, the Universe would be older than the standard estimations. Additionally, we present a stability analysis for different μ values. This analysis identifies a late-time attractor corresponding to a power-law decelerated solution for μ < 2. Moreover, a non-relativistic critical point exists for μ > 1 and a sink for μ > 2. This solution is a decelerated power law if 1 < μ < 2 and an accelerated power-law solution if μ > 2, consistent with the mean values obtained from the observational analysis. Therefore, for both flat Friedmann–Lemaître–Robertson–Walker and Bianchi I metrics, the modified Friedmann equations provide a late cosmic acceleration under this paradigm without introducing a dark energy component. This approach could be a new path to tackling unsolved cosmological problems.
Phenotypic variation in plants induced by biotic stressors can have cascading effects throughout arthropod communities. Habitat modifiers increase habitat complexity, which may promote species diversity and change arthropod species composition. A taxonomic approach to describe arthropod communities together with a trait-based approach might reveal mechanisms behind taxonomic changes and consequences for ecological processes. We previously found that the mistletoe Tristerix aphyllus induces susceptibility in the cactus Echinopsis chiloensis to the stem-borer beetle Xyletomerus sp., a habitat-modifier that drills brood chambers on cactus. Further, the community of arthropods that colonized chambers on parasitized cacti was more diverse and was different in composition compared to that found in chambers of non-parasitized cacti. We do not know whether the effects of brood chambers extend to the whole mistletoe-cactus system and how the arthropod community responds to seasonal phenology of mistletoe. Here we experimentally reduced the number of brood chambers and examined the effects on taxonomic and functional richness and composition, considering mistletoe seasonal phenology. We found a positive relationship between the number of chambers and arthropod species richness, abundance and functional richness. Arthropod taxonomic and functional richness were generally higher at mistletoe flowering compared to fruiting or mistletoe senescence/cactus flowering stages. Species composition varied with chamber number and changed with mistletoe seasonal phenology. Functional composition changed with mistletoe phenology. Functional richness and species richness were positively correlated, yet, functional redundancy is likely to occur. We conclude that cascading effects initiated by mistletoe extends beyond the chamber scale, up to the plant scale.
Prosopis chilensis and Prosopis tamarugo, two woody legumes adapted to the arid regions of Chile, have a declining distribution due to the lack of new seedling establishment. This study investigated the potential of both species to establish in soil collected from four locations in Chile, within and outside the species distribution, and to assess the role of the root-colonizing microbiome in seedling establishment and growth. Seedling survival, height, and water potential were measured to assess establishment success and growth. 16S and ITS2 amplicon sequencing was used to characterize the composition of microbial communities from the different soils and to assess the ability of both Prosopis species to recruit bacteria and fungi from the different soils. Both species were established on three of the four soils. P. tamarugo seedlings showed significantly higher survival in foreign soils and maintained significantly higher water potential in Mediterranean soils. Amplicon sequencing showed that the four soils harbored distinct microbial communities. Root-associated microbial composition indicated that P. chilensis preferentially recruited mycorrhizal fungal partners while P. tamarugo recruited abundant bacteria with known salt-protective functions. Our results suggest that a combination of edaphic properties and microbial soil legacy are potential factors mediating the Prosopis establishment success in different soils.
We identify and characterise a Milky Way-like realisation from the Auriga simulations with two consecutive massive mergers ∼2 Gyr apart at high redshift, comparable to the reported Kraken and Gaia-Sausage-Enceladus. The Kraken-like merger (z = 1.6, $M_{\rm Tot}=8\times 10^{10}\, \rm {M_{\odot }}$) is gas-rich, deposits most of its mass in the inner 10 kpc, and is largely isotropic. The Sausage-like merger (z = 1.14, $M_{\rm Tot}=1\times 10^{11}\, \rm {M_{\odot }}$) leaves a more extended mass distribution at higher energies, and has a radially anisotropic distribution. For the higher-redshift merger, the stellar mass ratio of the satellite to host galaxy is high (1:3). As a result, the chemistry of the remnant is indistinguishable from contemporaneous in-situ populations, making it challenging to identify through chemical abundances. This naturally explains why all abundance patterns attributed so far to Kraken are in fact fully consistent with the metal-poor in-situ so-called Aurora population and thick disc. However, our model makes a falsifiable prediction: if the Milky Way underwent a gas-rich double merger at high redshift, then this should be imprinted on its star formation history with bursts about ∼2 Gyrs apart. This may offer constraining power on the highest-redshift massive mergers.
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1,506 members
Claudia Bernal
  • Department of Food Engineering
Pablo J. Castro-Carrasco
  • Department of Psychology
Patricio Orellana
  • Department of Food Engineering
Ricardo Amorin
  • Department of Astronomy
Paulina Meza
  • Instituto de Investigación Multidisciplinario en Ciencia y Tecnología
Avenida Raul Bitran Nachary, La Serena, Region de Coquimbo, Chile
Head of institution
Dr. Ing. Nibaldo Avilés Pizarro
+56 51 2204000