Universidad Andrés Bello
Recent publications
The objective of this study is to explore how a populated territory of wooden construction on water and peculiar buildings, consolidate a unique vernacular architecture. Chiloé Island in southern Chile has been selected as a case study, due to (1) it has a vernacular architecture (2) it has a geographic morphology that has allowed from its genesis as a city to build in wood and sustainable materials; (3) it is an island at the end of the world with a high Jesuit presence and presence of religious architecture in larch, cypress, coihue and mañio wood. The methodology is developed through the analysis of a complete palafito from the constructive and architectural point of view. It is concluded that a populated territory of wooden construction on the water and peculiar buildings, can be consolidated with a unique vernacular architecture, which contributes to the heritage and development of the place.
This paper outlines the role of intermolecular interactions involving group 4 transition metals in stabilizing the N-NO2 trigger bonds. Minimising sensitivity is the foremost priority in designing energetic compounds. The anomalies arising from the strong depletion of negative charge distribution of RDX and HMX have been evidenced using a quantitative analysis of Molecular Electrostatic Potential (MEP). The EDA-NOCV results reveal that the electrostatic and orbital contributions are the dominant factors driving the assembly of the M = {Ti,Zr,Hf}-based complexes. Sensitivity of the N-NO2 trigger bonds is investigated by using the Quantum Theory of Atoms in Molecules (QTAIM). The QTAIM topological analysis showed that the O · · ·M = {Ti,Zr,Hf} interaction strengthens these trigger bonds, revealing an increased stability to decomposition. This effect is more marked in the Hf– and Zr–based complexes. Finally, the IRI-based results are fully consistent with those generated from QTAIM analysis.
Transcription and processing of 45S rRNAs in the nucleolus are keystones of ribosome biogenesis. While these processes are severely impacted by stress conditions in multiple species, primarily upon heat exposure, we lack information about the molecular mechanisms allowing sessile organisms without a temperature-control system, like plants, to cope with such circumstances. We show that heat stress disturbs nucleolar structure, inhibits pre-rRNA processing and provokes imbalanced ribosome profiles in Arabidopsis thaliana plants. Notably, the accuracy of transcription initiation and cleavage at the primary P site in the 5'ETS (5' External Transcribed Spacer) are not affected but the levels of primary 45S and 35S transcripts are, respectively, increased and reduced. In contrast, precursors of 18S, 5.8S and 25S RNAs are rapidly undetectable upon heat stress. Remarkably, nucleolar structure, pre-rRNAs from major ITS1 processing pathway and ribosome profiles are restored after returning to optimal conditions, shedding light on the extreme plasticity of nucleolar functions in plant cells. Further genetic and molecular analysis to identify molecular clues implicated in these nucleolar responses indicate that cleavage rate at P site and nucleolin protein expression can act as a checkpoint control towards a productive pre-rRNA processing pathway.
Background: Mechanical power is a composite variable for energy transmitted to the respiratory system over time that may better capture risk for ventilator-induced lung injury than individual ventilator management components. We sought to evaluate if mechanical ventilation management with a high mechanical power is associated with fewer ventilator-free days (VFD) in children with pediatric acute respiratory distress syndrome (PARDS). Methods: Retrospective analysis of a prospective observational international cohort study. Results: There were 306 children from 55 pediatric intensive care units included. High mechanical power was associated with younger age, higher oxygenation index, a comorbid condition of bronchopulmonary dysplasia, higher tidal volume, higher delta pressure (peak inspiratory pressure-positive end-expiratory pressure), and higher respiratory rate. Higher mechanical power was associated with fewer 28-day VFD after controlling for confounding variables (per 0.1 J·min-1·Kg-1 Subdistribution Hazard Ratio (SHR) 0.93 (0.87, 0.98), p = 0.013). Higher mechanical power was not associated with higher intensive care unit mortality in multivariable analysis in the entire cohort (per 0.1 J·min-1·Kg-1 OR 1.12 [0.94, 1.32], p = 0.20). But was associated with higher mortality when excluding children who died due to neurologic reasons (per 0.1 J·min-1·Kg-1 OR 1.22 [1.01, 1.46], p = 0.036). In subgroup analyses by age, the association between higher mechanical power and fewer 28-day VFD remained only in children < 2-years-old (per 0.1 J·min-1·Kg-1 SHR 0.89 (0.82, 0.96), p = 0.005). Younger children were managed with lower tidal volume, higher delta pressure, higher respiratory rate, lower positive end-expiratory pressure, and higher PCO2 than older children. No individual ventilator management component mediated the effect of mechanical power on 28-day VFD. Conclusions: Higher mechanical power is associated with fewer 28-day VFDs in children with PARDS. This association is strongest in children < 2-years-old in whom there are notable differences in mechanical ventilation management. While further validation is needed, these data highlight that ventilator management is associated with outcome in children with PARDS, and there may be subgroups of children with higher potential benefit from strategies to improve lung-protective ventilation. Take home message: Higher mechanical power is associated with fewer 28-day ventilator-free days in children with pediatric acute respiratory distress syndrome. This association is strongest in children <2-years-old in whom there are notable differences in mechanical ventilation management.
The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
Cystic Echinococcosis (CE), a zoonotic parasitic disease, is caused by the cestode Echinococcus granulosus sensu lato. CE inflicts severe damage in cattle, sheep, and human hosts worldwide. Fertile CE cysts are characterized by the presence of viable protoscoleces. These parasite forms are studied with minimal contamination with host molecules. Hosts, cattle and sheep, show differences in their CE cyst fertility. The effect of the host in protoscolex transcriptome is not known. We genotyped and performed transcriptomic analysis on sheep protoscoleces obtained from liver and lung CE cysts. The transcriptomic data of Echinococcus granulosus sensu stricto protoscoleces from 6 lung CE cysts and 6 liver CE cysts were Collected. For host comparison analysis, 4 raw data files belonging to Echinococcus granulosus sensu stricto protoscoleces from cattle liver CE cysts were obtained from the NCBI SRA database. Principal component and differential expression analysis did not reveal any statistical differences between protoscoleces obtained from liver or lung cysts, either within the same sheep or different sheep hosts. Conversely, there are significant differences between cattle and sheep protoscolex samples. We found differential expression of immune-related genes. In cattle, 7 genes were upregulated in protoscoleces from liver cysts. In sheep, 3 genes were upregulated in protoscoleces from liver and lung CE cysts. Noteworthy, are the differential expression of antigen B, tegument antigen, and arginase-2 in samples obtained from sheep CE cysts, and basigin in samples from cattle CE cysts. These findings suggest that the host species is an important factor involved in the differential expression of immune related genes, which in turn is possibly related to the fertility of Echinococcus granulosus sensu stricto cysts.
Background Salmonella Typhimurium is a Gram-negative pathogen that causes a systemic disease in mice resembling typhoid fever. During its infective cycle, S. Typhimurium is phagocytized by macrophages and proliferates inside a Salmonella -containing vacuole where Salmonella is exposed and survives oxidative stress induced by H 2 O 2 through modulation of gene expression. After exposure of Salmonella to H 2 O 2 , the expression of the porin-encoding gene ompX increases, as previously shown by microarray analysis. Expression of ompX mRNA is regulated at a post-transcriptional level by MicA and CyaR sRNAs in aerobiosis. In addition, sequence analysis predicts a site for OxyS sRNA in ompX mRNA. Results In this work we sought to evaluate the transcriptional and post-transcriptional regulation of ompX under H 2 O 2 stress. We demonstrate that ompX expression is induced at the transcriptional level in S . Typhimurium under such conditions. Unexpectedly, an increase in ompX gene transcript and promoter activity after challenges with H 2 O 2 does not translate into increased protein levels in the wild-type strain, suggesting that ompX mRNA is also regulated at a post-transcriptional level, at least under oxidative stress. In silico gene sequence analysis predicted that sRNAs CyaR, MicA, and OxyS could regulate ompX mRNA levels. Using rifampicin to inhibit mRNA expression, we show that the sRNAs (MicA, CyaR and OxyS) and the sRNA:mRNA chaperone Hfq positively modulate ompX mRNA levels under H 2 O 2 -induced stress in Salmonella during the exponential growth phase in Lennox broth. Conclusions Our results demonstrate that ompX mRNA is regulated in response to H 2 O 2 by the sRNAs CyaR, MicA and OxyS is Salmonella Typhimurium.
Background: The Atacama salt flat is located in northern Chile, at 2300 m above sea level, and has a high concentration of lithium, being one of the main extraction sites in the world. The effect of lithium on microorganism communities inhabiting environments with high concentrations of this metal has been scarcely studied. A few works have studied the microorganisms present in lithium-rich salt flats (Uyuni and Hombre Muerto in Bolivia and Argentina, respectively). Nanocrystals formation through biological mineralization has been described as an alternative for microorganisms living in metal-rich environments to cope with metal ions. However, bacterial lithium biomineralization of lithium nanostructures has not been published to date. In the present work, we studied lithium-rich soils of the Atacama salt flat and reported for the first time the biological synthesis of Li nanoparticles. Results: Bacterial communities were evaluated and a high abundance of Cellulomonas, Arcticibacter, Mucilaginibacter, and Pseudomonas were determined. Three lithium resistant strains corresponding to Pseudomonas rodhesiae, Planomicrobium koreense, and Pseudomonas sp. were isolated (MIC > 700 mM). High levels of S²− were detected in the headspace of P. rodhesiae and Pseudomonas sp. cultures exposed to cysteine. Accordingly, biomineralization of lithium sulfide-containing nanomaterials was determined in P. rodhesiae exposed to lithium salts and cysteine. Transmission electron microscopy (TEM) analysis of ultrathin sections of P. rodhesiae cells biomineralizing lithium revealed the presence of nanometric materials. Lithium sulfide-containing nanomaterials were purified, and their size and shape determined by dynamic light scattering and TEM. Spherical nanoparticles with an average size < 40 nm and a hydro-dynamic size ~ 44.62 nm were determined. Conclusions: We characterized the bacterial communities inhabiting Li-rich extreme environments and reported for the first time the biomineralization of Li-containing nanomaterials by Li-resistant bacteria. The biosynthesis method described in this report could be used to recover lithium from waste batteries and thus provide a solution to the accumulation of batteries.
The study of the stress responses in bacteria has given us a wealth of information regarding the mechanisms employed by these bacteria in aggressive or even non-optimal living conditions. This information has been applied by several researchers to identify molecular targets related to pathogeny, virulence, and survival, among others, and to design new prophylactic or therapeutic strategies against them. In this study, our knowledge of these mechanisms has been summarized with emphasis on some aquatic pathogenic bacteria of relevance to the health and productive aspects of Chilean salmon farming ( Piscirickettsia salmonis, Tenacibaculum spp., Renibacterium salmoninarum, and Yersinia ruckeri ). This study will aid further investigations aimed at shedding more light on possible lines of action for these pathogens in the coming years.
The analogue of Hadwiger’s conjecture for the immersion order states that every graph G contains Kχ(G) as an immersion. If true, this would imply that every graph with n vertices and independence number α contains K⌈nα⌉ as an immersion. The best currently known bound for this conjecture is due to Gauthier, Le and Wollan, who recently proved that every graph G contains an immersion of a clique on ⌈χ(G)−43.54⌉ vertices. Their result implies that every n-vertex graph with independence number α contains an immersion of a clique on ⌈n3.54α−1.13⌉ vertices. We improve on this result for all α≥3, by showing that every n-vertex graph with independence number α≥3 contains an immersion of a clique on ⌊n2.25α−f(α)⌋−1 vertices, where f is a nonnegative function.
By means of the Interaction Region Indicator (IRI) and Quantum Theory of Atoms in Molecules (QTAIM), the influence exerted by NH2 (amino) and CN (cyano) as electron donor and electron acceptor substituent groups, respectively, located at para–positions of axial and equatorial pyridine rings of derivatized complexes coming from the [(PY5Me2)MoO]+ complex during the hydrogen molecular release in the gas phase was analyzed. In any case, a H–H covalent bond is forming at the transition state, with a strengthening of the electron density of 5.5% when the substituent group involved is NH2 at the para–position of the axial pyridine ring. However, there was no difference between NH2 and CN when these substituent groups are located at the para–positions of the equatorial pyridine rings. The topological properties of electron densities from the QTAIM are not perturbed by the electron donor and electron acceptor nature of the substituents, even when these substituent groups are located at the axial or equatorial pyridine rings of the Mo–based complex.
Human-robot collaboration strategies for agricultural applications are still a challenging research topic that is in its early stages of development. The analysis of the production and physical workload measures during the harvesting process can be useful to obtain relevant information to improve production and farm management. In this work, it is presented the assessment of the avocado harvesting process under different scenarios. For this purpose, two simulation environments were created and compared based on the obtained information from a Chilean farm. The first scenario uses only a human-based workforce to perform all the avocado harvesting-related tasks, whilst the second scenario is based on a human-robot cooperative strategy proposed to improve the harvesting procedure. A total of 41 different tests for each simulated scenario was performed, and then a comparison of them in terms of production and expected human physical workload was obtained. The results showed that the use of a cooperative strategy during harvesting tasks can increase the production measured from the cargo zone from 15% to 80%, as well as the total harvested production from 23% to 85%, whilst the human workload only increases from 1% to 16%. These results enclose the possibility of using production and workload measures as metrics for a human–machine interaction cooperative approach design, in benefit of the harvesting process management and decision making.
The influence of artificial light at night (ALAN) is becoming evident in marine sandy beaches. These habitats are dominated by species reliant on natural daylight/night regimes, making the identification of biological indicators a priority. We assessed the applicability of hemocyanin, an oxygen-transport protein in the hemolymph of many invertebrates, as an indicator of ALAN-related stress. Unlike total proteins, hemocyanins signal metabolic function and stress, so we expected them to increase in response to ALAN. We adapted spectrophotometry protocols to describe spatial variation in hemocyanins and total proteins in four populations of the talitroid amphipod Americorchestia longicornis. Then, a two-week experiment tested for changes in response to ALAN. Hemocyanin levels increased by 17 % and 40 % with respect to experimental controls after 7 and 14 d, respectively, and were higher than any measurements conducted in the field. These results suggest good prospects for hemocyanin as an indicator of ALAN effects.
We assess the role of direct and indirect effects of coastal environmental drivers (including the parameters of the carbonate system) on energy expenditure (MR) and body mass (M) of the intertidal mussel, Perumytilus purpuratus, across 10 populations distributed over 2800 km along the Southern Eastern Pacific (SEP) coast. We find biogeographic and local variation in carbonate system variables mediates the effects of latitude and temperature on metabolic rate allometry along the SEP coast. Also, the fitted Piecewise Structural Equation models (PSEM) have greater predictive ability (conditional R² = 0.95) relative to the allometric scaling model (R² = 0.35). The largest standardized coefficients for MR and M were determined by the influence of temperature and latitude, followed by pCO2, pH, total alkalinity, and salinity. Thus, physiological diversity of P. purpuratus along the SEP coast emerges as the result of direct and indirect effects of biogeographic and local environmental variables.
Electric vehicle (EV) has been widely used in our life, one of the key technologies is the batteries, power accumulator battery test system (PABTS), which is initiated for evaluating the performance of the EV batteries, has been used in many battery-manufacture companies. The parallel operation of the PABTS forms a dc-microgrid, owing to the low inertia of the dc-link capacitance, the charging and discharging tests of the batteries can easily cause dc-bus voltage fluctuations, which may jeopardize the system stability. To increase the system inertia and achieve good system stability, a fractional-order model-predictive-control (FOMPC) and fractional-order virtual-inertia-control (FOVIC) strategy (namely, FOMPC-FOVIC method) is proposed for the bidirectional grid-connected converter. First, the fractional-order virtual inertial link is used to replace the integral-order virtual inertial link, which significantly improves the system stability. Second, combined with fractional-order model-predictive-control, virtual dc current compensation is proposed to further suppress the dc-bus voltage fluctuations. Finally, the fractional-order discrete state-space equation of the virtual inertial link is derived, and the cost function design and its optimal solution are elaborated. To demonstrate the effectiveness of the proposed FOMPC-FOVIC scheme, experimental results indicate that the proposed method is superior to the existing methods in terms of inertial support and dc-bus voltage regulation.
A fault-tolerant control (FTC) is proposed for enhancing the reliability of power electronic systems. The software-based FTC of parallel-connected three-level T-type converters (3LT2Cs) for suppressing zero-sequence circulating current (ZSCC) induced by a vertical switch open-circuit fault is investigated. A simplified sequential model predictive control (SSMPC)-based FTC technique is developed. Parallel-3LT2Cs and their prediction models are introduced, followed by an SSMPC for the no-fault condition. The model inaccuracies under vertical switch faults are elaborated. For the faulty 3LT2C, two fault-tolerant SSMPC (FT-SSMPC) methods are provided by creating a sequential predictive controller that considers ZSCC suppression and grid current tracking. The control policies for the ZSCC are changed from the standard feedback-free to feedback-based cost function (CF) optimization using the unimproved FT-SSMPC. Furthermore, an improved FT-SSMPC is proposed using a phase-deficient CF, which increases the accuracy of the mathematical relation of the fault condition. After fault diagnosis, the proposed method achieves neutral-point voltage balance and excellent point-of-common-coupling current, effectively suppresses the ZSCC, and increases the control reliability. Finally, experiments demonstrate the effectiveness of the proposed FT-SSMPC under various conditions.
Pinnipeds are sentinel species for marine pollution, but their role as vectors of trace elements (TEs) or rare earth elements (REEs) to ecosystems has been poorly studied. The present study tested pinniped feces for 61 elements, including REEs. Feces of adult seals (Mirounga leonina, Hydrurga leptonyx) from Fildes Bay, King George Island, Antarctica, were analyzed by ICP-MS. TEs varied by several orders of magnitude across the suite examined herein, with Fe, Al, Zn, Mn, HgII and Sr as the top six in both species. Of the REEs, Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sc, Sm, Tb, Y and Yb were found consistently in all samples and ranged from 0.935 to 0.006 μg g⁻¹ d.w. The results show that both species act as biovector organisms of TEs and REEs through feces in remote environments, whose actual impacts and long-term fate need further exploration.
The main purpose of this study is to elucidate some discrepancies already observed in the catalytic activity values of some zirconocene methyl cations. The EDA-NOCV scheme was employed for a theoretical description of the interactions between an ethylene molecule and five catalysts of zirconocene methyl cation. The nature of the chemical interactions has been elucidated through the QTAIM topological analysis. The steric hindrance due to the ligands was evaluated qualitatively by means of an IRI-based analysis and quantitively through Fisher information. The findings prove that the indenyl ligand seems to favor the orbital interaction between the ethylene molecule and the metal center of zirconocene methyl cation. Both electrostatic and orbital contributions play a crucial role in stabilising the studied complexes. Based on the NOCV deformation density contributions, the strongest orbital interaction is reached with the bis(indenyl)methyl zirconium cation, which is the only one exhibiting covalent interactions. Especially, the strong contribution of π-back donation (occurring from the occupied orbitals of the zirconium atom to the π * anti-bonding orbital of ethylene) may be a key to understand why this catalyst has a higher polymerisation yield than the other studied catalysts. This work suggests a perspective for predicting values of catalytic activity when theoretically designing novel catalysts of zirconocene type.
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Claudia Miranda-Castillo
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Sergey Kuleshov
  • Center for Theoretical and Experimental Particle Physics
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  • Faculty of Medicine
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José Rodríguez Pérez
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