Artículos de Revistas

URI permanente para esta colección

https://repositorio.uft.cl/handle/20.500.12254/2436

Examinar

Mostrando 1 - 8 de 8

Design of an EEG analytical methodology for the analysis and interpretation of cerebral connectivity signals
(Elsevier, 2022-02-20) Córdova, Felisa M.; Cifuentes, Hugo F.; Díaz, Hernán A.; Yanine, Fernando; Pereira, Robertino
The objective of this study is to design an Electroencephalographic (EEG) analytic methodology that allows to develop a variety of analysis and interpretations of brain signals. The initial phase considers the acquisition and filtering of EEG signals, the division into bands in data ranges, and the storage of EEG signals in a cloud data base. Then, an analytical phase considering descriptive, predictive and prescriptive analysis is accomplished. A sequence of analytic intermediate processing steps is done in order to render a graphic visualization of significant correlations between pairs of EEG channels. Pearson correlation is utilized to detect synchronic connectivity through the brain areas. Time series in nearly instantaneous time lapses are treated by using Hilbert Huang Transform. An experimental design by submitting a set of students to an abbreviated version Raven visual test is made providing results in correlation maps of cerebral connectivity
On a pickup to delivery drone routing problem: models and algorithms
(Elsevier, 2022-09-06) Gómez-Lagos, Javier; Rojas-Espinoza, Benjamín; Candia-Véjar, Alfredo
A new variant of the Pickup and Delivery Routing problem is presented. Given a set of customers, facilities, a depot, and a homogeneous fleet of drones, the Pickup to Delivery Drone Routing Problem (PDDRP) aims to find a drone scheduling such that a drone serves the customer’s order from a set of available facilities. Each drone starts in the depot, flies to pickup the customer’s order in a facility, and continues its flight to deliver the parcel to a customer. Then, the drone begins another service, and once its last service is completed, it returns to the depot. The objective is to minimize the makespan associated with the drone fleet. The layer of facilities forcing drones to visit one of them to pickup the parcel makes the problem different from traditional pickup and delivery routing problems. Three mixed-linear programming models are presented to obtain optimal solutions for the problem. The first model is related to the multiple Traveling Salesman Problem (m-TSP), the second is associated with the Parallel Machine Scheduling Problem (PMS), and the third was developed specifically for the new problem. Given the high computational complexity of the PDDRP, a Greedy Randomized Adaptive Search Procedure (GRASP) was designed to find near-optimal solutions when exact approaches cannot achieve (near) optimal solutions. Computational experiments show that a commercial solver could solve only small problem instances. GRASP can find reasonable solutions in a short time when medium and large instance sizes need to be solved. Finally, is shown that some routing problems for delivery, allowing truck-drone collaboration, could be formulated as an extension of PMS.
ML models for severity classification and length-of-stay forecasting in emergency units
(Elsevier, 2023-03-02) Candia-Véjar, Alfredo; Moya-Carvajal, Jonathan; Pérez-Galarce, Francisco; Taramasco, Carla; Astudillo, César A.
Length-of-stay (LoS) prediction and severity classification for patients in emergency units in a clinic or hospital are crucial problems for public and private health networks. An accurate estimation of these parameters is essential for better planning resources, which are usually scarce. Although it is possible to find several works that propose traditional Machine Learning (ML) models to face these challenges, few works have exploited advances in Natural Language Processing (NLP) on Spanish raw-text vector representations. Consequently, we take advantage of those advances, incorporating sentence embeddings in traditional ML models to improve predictions. Moreover, we apply a strategy based on SHapley Additive exPlanations (SHAP) values to provide explanations for these predictions. The results of our case study demonstrate an increase in the accuracy of the predictions using raw text with a minimum preprocessing. The precision increased by up to 2% in the classification of the patient’s post-care destination and by up to 8% in the prediction of LoS in the hospital. This evidence encourages practitioners to use available text to anticipate the patient’s need for hospitalization more accurately at the earliest stage of the care process.
Photophysical characterization of tetrahydroxyphenyl porphyrin Zn(II) and V(IV) complexes: experimental and DFT study
(Springer Nature, 2023-06-21) Diaz-Uribe, Carlos; Rangel, Daily; Vallejo, William; Valle, Roger; Hidago-Rosa, Yoan; Zarate, Ximena; Schott, Eduardo
Photodynamic therapy (PDT) is a promising technique for the treatment of various diseases. In this sense, the singlet oxygen quantum yield (Φ∆) is a physical–chemical property that allows to stablish the applicability of a potential photosensitizers (PS) as a drug for PDT. In the herein report, the Φ∆ of three photosensitizers was determined: metal-free tetrahydroxyphenyl porphyrin (THPP), THPP-Zn and the THPP-V metal complexes. Their biological application was also evaluated. Therefore, the in vitro study was carried out to assess their biological activity against Escherichia coli. The metal-porphyrin complexes exhibited highest activities against the bacterial strain Escherichia coli. at the highest concentration (175 μg/mL) and show better activity than the free base ligand (salts and blank solution). Results indicated a relation between Φ∆ and the inhibitory activity against Escherichia coli, thus, whereas higher is the Φ∆, higher is the inhibitory activity. The values of the Φ∆ and the inhibitory activity follows the tendency THPP-Zn > THPP > THPP-V. Furthermore, quantum chemical calculations allowed to gain deep insight into the electronic and optical properties of THPP-Zn macrocycle, which let to verify the most probable energy transfer pathway involved in the singlet oxygen generation.
Exploring the adsorption of five emerging pollutants on activated carbon: a theoretical approach
(Elsevier, 2024-06-06) González-Rodríguez, Lisdelys; Yáñez, Osvaldo; Mena-Ulecia, Karel; Hidalgo-Rosa, Yoan; García-Carmona, Ximena; Ulloa-Tesser, Claudia
The identification and management of contaminants of emerging concern (CECs) in water systems is crucial for protecting public and environmental health. This paper reports a theoretical approach to studying the adsorption of five CECs: Atrazine (ATZ), Caffeine (CAF), Carbamazepine (CBZ), Sulfamethoxazole (SMX), and Ibuprofen (IBU) - onto Activated Carbon (AC). A set of computational methods, including electrostatic molecular potential maps, conceptual density functional theory, Fukui functions, thermodynamic analysis, and tight-binding molecular dynamics simulations, were employed to analyze the electronic/energetic interactions and mechanisms involved in the adsorption of CECs on AC. The theoretical methodology offered valuable predictions on reactivity sites, stability, and binding mechanisms. Results showed that adsorption primarily occurred through non-covalent interactions like π-π electron donor-acceptor interactions, van der Waals forces, and hydrophobic interactions. Thermodynamic properties suggested the adsorption process was spontaneous and exothermic. However, for the AC/SMX system, the Gibbs free energy reveals that adsorption may be unfavorably compared to the other study systems. Molecular dynamics simulations validated the kinetic stability in the following order CAF (0.13 Å)>CBZ (0.23 Å)>ATZ (0.75 Å)> IBU (1.28 Å)>SMX (1.54 Å). This exploratory theoretical study provides a deep understanding of the interactions between AC and five CECs, aiding in the rational design and optimization of AC-based treatment systems for environmental and industrial applications.
UiO-66(Zr) as drug delivery system for non-steroidal anti-inflammatory drugs
(Elsevier, 2024-06-06) Salazar, Javier; Hidalgo-Rosa, Yoan; Burboa, Pia C.; Escalona, Néstor; Leiva, Angel; Zarate, Ximena; Schott, Eduardo
The toxicity for the human body of non-steroidal anti-inflammatory drugs (NSAIDs) overdoses is a consequence of their low water solubility, high doses, and facile accessibility to the population. New drug delivery systems (DDS) are necessary to overcome the bioavailability and toxicity related to NSAIDs. In this context, UiO-66(Zr) metal-organic framework (MOF) shows high porosity, stability, and load capacity, thus being a promising DDS. However, the adsorption and release capability for different NSAIDs is scarcely described. In this work, the biocompatible UiO-66(Zr) MOF was used to study the adsorption and release conditions of ibuprofen, naproxen, and diclofenac using a theoretical and experimental approximation. DFT results showed that the MOF-drug interaction was due to an intermolecular hydrogen bond between protons of the groups in the defect sites, (μ3 − OH, and − OH2) and a lone pair of oxygen carboxyl functional group of the NSAIDs. Also, the experimental results suggest that the solvent where the drug is dissolved affects the adsorption process. The adsorption kinetics are similar between the drugs, but the maximum load capacity differs for each drug. The release kinetics assay showed a solvent dependence kinetics whose maximum liberation capacity is affected by the interaction between the drug and the material. Finally, the biological assays show that none of the systems studied are cytotoxic for HMVEC. Additionally, the wound healing assay suggests that the UiO-66(Zr) material has potential application on the wound healing process. However, further studies should be done.
Furfural adsorption on V2O5 surface: A combined experimental-theoretical study
(Elsevier, 2024-06-16) Lizana, Ignacio; Schott , Eduardo; Saavedra-Torres, Mario; Hidalgo-Rosa, Yoan; Pecchi, Gina; Karelovic, Alejandro; Zarate, Ximena;
The adsorption of furfural on the V2O5 surface was investigated using experimental and theoretical methods. In situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy results show the presence of physi- and chemi-sorption phenomena, where trans-furfural is mostly chemisorbed at the beginning of the adsorption process. These results are in agreement with theoretical DFT results, as the most thermodynamically favored configurations corresponds to the chemisorbed trans-furfural (T1) and cis-furfural (C1) with binding energies of −1.83 and −2.05 eV.
Synthesis, physicochemical characterization, and antimicrobial evaluation of halogen-substituted non-metal pyridine schiff bases
(MDPI, 2024-10-06) Carreño, Alexander; Morales-Guevara, Rosaly; Cepeda-Plaza, Marjorie; Páez-Hernández, Dayán; Preite, Marcelo; Polanco, Rubén; Barrera, Boris; Fuentes, Ignacio; Marchant, Pedro; Fuentes, Juan A.
Four synthetic Schiff bases (PSB1 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-dibromophenol], PSB2 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-diiodophenol], PSB3 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-iodophenol], and PSB4 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-chloro-6-iodophenol]) were fully characterized. These compounds exhibit an intramolecular hydrogen bond between the hydroxyl group of the phenolic ring and the nitrogen of the azomethine group, contributing to their stability. Their antimicrobial activity was evaluated against various Gram-negative and Gram-positive bacteria, and it was found that the synthetic pyridine Schiff bases, as well as their precursors, showed no discernible antimicrobial effect on Gram-negative bacteria, including Salmonella Typhi (and mutant derivatives), Salmonella Typhimurium, Escherichia coli, and Morganella morganii. In contrast, a more pronounced biocidal effect against Gram-positive bacteria was found, including Bacillus subtilis, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus haemolyticus. Among the tested compounds, PSB1 and PSB2 were identified as the most effective against Gram-positive bacteria, with PSB2 showing the most potent biocidal effects. Although the presence of reactive oxygen species (ROS) was noted after treatment with PSB2, the primary mode of action for PSB2 does not appear to involve ROS generation. This conclusion is supported by the observation that antioxidant treatment with vitamin C only partially mitigated bacterial inhibition, indicating an alternative biocidal mechanism.

Examinar

Examinando Artículos de Revistas por Fecha de publicación

Resultados por página

Opciones de ordenación