26 results on '"Claudio Contreras"'
Search Results
2. La memoria obstinada de Ranguelmo: vida y patrimonio en torno al ferrocarril y el ramal entre Ñuble y Biobío
- Author
-
Claudio Contreras, Nelson Alarcón Medina, Germán González Jara, and Carmen Hernández Zamorano
- Subjects
General Medicine - Abstract
En la localidad de Ranguelmo, comuna de Coelemu, Región de Ñuble, existe una memoria oral y tácita asociada al pasado ferroviario del sector y una remembranza hacia las formas de construcción cotidiana y social que esta generaba. Vivencias y materialidades que se plasman en la reproducción de una memoria histórica que se traspasa entre generaciones del sector. No obstante, en la actualidad, la memoria y oralidad colectiva de Ranguelmo resiste con dificultades ante los embates del tiempo y los cambios sociales. Las vivencias y relatos de las épocas de gloria del ferrocarril se apagan, desapareciendo sin dejar registros ni testimonios que permitan heredar debi-damente las memorias de las experiencias pasadas a las nuevas generaciones, que bien perciben el importante rol del ramal de Rucapequén y su estación principal Ranguelmo en sus identidades y patrimonio local. El presente artículo busca presentar los resultados y experiencia asociada a una investigación patrimonial participativa con la comunidad de la localidad de Ranguelmo. En particular se propone identificar, socializar y poner en valor el patrimonio material e inmaterial relacionado al ramal de trenes de Ranguelmo, por medio de la conjunción de metodologías cualitativas y participativas que permiten un importante rescate de la memoria histórica y patrimonio material e inmaterial asociado al ramal, revitalizando la memoria y oralidad que vienen a reforzar la identidad de Ranguelmo.
- Published
- 2022
- Full Text
- View/download PDF
3. The Influence of Magma Storage and Ascent Conditions on Laguna del Maule Rhyolite Eruptions
- Author
-
Claudio Contreras, Katharine V Cashman, Alison Rust, and Marcelo Cortés
- Subjects
Geophysics ,Geochemistry and Petrology - Abstract
The scarcity of historical rhyolite eruptions means that volcanological and petrological studies of past eruptions are a key tool for assessing the potential for future hazardous activity and improving interpretations of unrest signals. For the last 18 ky, the Laguna del Maule (LdM) volcanic complex in Chile has erupted primarily rhyolites but with differing magma compositions, eruption styles and eruptive volumes. Rapid surface uplift and episodic seismic activity at LdM over the last two decades has emphasized the need to understand both the recent evolution of the magmatic system and the most likely future eruption scenarios. Using mineral composition, geothermobarometry and MELTS modeling, we assess the influence of the magma storage and ascent conditions on the magnitude and styles of three LdM rhyolites. Magmas of the first and largest Plinian-ignimbrite eruption (LdM: rdm; >17 km3 DRE) form a distinct mineral assemblage with An28–60 plagioclase, amphibole and quartz derived from a magma plumbing system over a large pressure range (90–350 MPa). We suggest that the rdm eruption was triggered by magma recharge and overpressure within a ~ 90 MPa magma chamber of high-silica (>76.5 wt.% SiO2) rhyolitic melt. The rdm eruption appears to have reset the LdM storage conditions, such that subsequent rhyolite eruptions have been smaller (
- Published
- 2022
- Full Text
- View/download PDF
4. Effect of carbon support and functionalization on the synthesis of rhenium carbide and its use on HDO of guaiacol
- Author
-
Elodie Blanco, Paula Cabeza, Verónica Naharro Ovejero, Claudio Contreras, Ana Belén Dongil, I. Tyrone Ghampson, and Néstor Escalona
- Subjects
General Chemistry ,Catalysis - Published
- 2023
- Full Text
- View/download PDF
5. Modified Technique of Porcelain Laminate Veneer in Premolars with Abfraction Lesions: Three-Dimensional Finite Element Analysis (FEA)
- Author
-
Renata Marques de Melo, Lisseth Patricia Claudio Contreras, Alexandre Luiz Souto Borges, João Paulo Mendes Tribst, and Larissa Marcia Martins Alves
- Subjects
Orthodontics ,Physics ,0303 health sciences ,Abfraction ,Resin composite ,medicine.medical_treatment ,Modified technique ,030311 toxicology ,medicine.disease ,03 medical and health sciences ,Homogeneous ,medicine ,Porcelain laminate veneer ,Principal stress ,Veneer ,Dental veneers - Abstract
The incidence of non-carious cervical lesions (NCCLs) has increased as populations are aging, and teeth are increasingly retained for life. Several materials are available to treat these lesions. This study aimed to evaluate the stress distribution of maxillary premolars with NCCLs using three-dimensional (3D) finite element analysis (FEA) according to different restorative techniques. A 3D FEA mathematical model simulating a sound premolar was initially modeled and replicated in 6 more models simulating a tooth with abfraction: G.1 tooth with abfraction; G.2 tooth with abfraction + composite resin restoration; G.3 tooth with abfraction + glass-ionomer cement restoration; G.4 tooth with abfraction + resin composite restoration + porcelain laminate veneers; G.5 tooth with abfraction + glass-ionomer cement + porcelain laminate veneers; and G.6 modified porcelain laminate veneers filling the lesion. All materials and structures were considered linear, elastic, homogeneous and isotropic and the results were expressed as maximum principal stress. Lower stress concentration in dentin was calculated when the tooth was restored with composite resin and glass-ionomer cement. Regarding the veneer techniques, no difference was found to dentin stress among the groups, but the modified veneer concentrated less stress in the restoration than other the techniques. The control group had the highest concentration of stress in the lesion. All techniques decreased the stress concentration inside the NCCLs and the indirect veneer filling the lesion presented better biomechanical behavior than the veneer cemented above direct restorations. Keywords: Finite Element Analysis. Dental Veneers. Ceramics. Bicuspid. Resumo A incidência de lesões cervicais não-cariosas (LCNC) tem aumentado, uma vez que a população tem envelhecido com uma menor perda de elementos dentários. Diferentes materiais estão disponíveis para tratar dessas lesões. Este estudo objetivou avaliar a distribuição de tensão de pré-molares superiores com LCNC por meio da análise tridimensional (3D) de elementos finitos (FEA) de acordo com diferentes técnicas restauradoras. Um modelo matemático 3D FEA simulando um pré-molar íntegro foi modelado e replicado em mais 6 modelos simulando um dente com abfração: G.1 dente com abfração; G.2 dente com abfração + resina composta; G.3 dente com abfração + cimento de ionômero de vidro; G.4 dente com abfração + resina composta + faceta; G.5 dente com abfração + cimento de ionômero de vidro + faceta cerâmica e G.6 com faceta cerâmica modificada, preenchendo a lesão. Todos os materiais e estruturas foram considerados lineares, elásticos, homogêneos e isotrópicos e os resultados foram expressos como máxima tensão principal. Menor concentração de tensão na dentina foi calculada quando o dente foi restaurado com resina composta ou cimento de ionômero de vidro. Dentre os grupos com laminados, não houve diferença para a dentina, entretanto a faceta modificada apresentou menor concentração de tensão na restauração. O grupo controle apresentou a maior concentração de tensão na lesão. Todas as técnicas restauradoras diminuíram a concentração de tensão no interior das LCNCs e dentre as técnicas com laminados a faceta modificada apresentou o melhor comportamento biomecânico. Palavras-chave: Análise de Elementos Finitos. Facetas Dentárias. Cerâmica. Dente Pré-Molar.
- Published
- 2020
- Full Text
- View/download PDF
6. Sobre fogones y semáforos: Percepciones y analogías de dos geografías desencontradas. El caso del volcán Callaqui en la geografía ancestral pehuenche de Alto Biobío
- Author
-
Claudio Contreras Véliz
- Subjects
geografía ,pehuenches ,lcsh:AZ20-999 ,lcsh:H1-99 ,desencuentro y ancestralidad ,lcsh:Social sciences (General) ,territorio ,lcsh:History of scholarship and learning. The humanities - Abstract
En Alto Biobío, área cordillerana del centro sur de Chile, habita parte del pueblo originario Pehuenche, cuyas comunidades o lob mapu, se emplazan alrededor del volcán Callaqui (‘Callavquen’ en la lengua local, que significa ‘celoso de los hombres’). El volcán en el último tiempo ha sido monitoreado por la institucionalidad vulcanológica y de emergencias del país (SERNAGEOMIN, ONEMI y Universidades), que busca generar planes y acciones para gestionar la alarma de una posible erupción, y advertir a través de un semáforo y escalas de riesgos, la peligrosidad que representa para la población local. No obstante, los pehuenches, habitantes ancestrales del área de influencia del volcán, han convivido con él de una manera intrínseca por generaciones, y le han asociado gran parte de sus actividades económicas, sociales y culturales, otorgándole un sentido protector desde sus propias percepciones respecto del macizo montañoso. El presente artículo tiene como objetivo dar cuenta de dos visiones diferentes respecto a la presencia y relación de la población local con el volcán Callaqui, en el territorio del pueblo originario Pehuenche en la comuna de Alto Biobío. Éste se basa en un extenso trabajo etnográfico, y expone el desencuentro en la valorización y apropiación de la geografía local, entre la percepción de la cultura de las comunidades que la habitan, y de la institucionalidad y la normativa de emergencia que la intervienen.
- Published
- 2020
7. Contrasting Sources and Conditions of Shallow Reservoirs of the Fui Group Small Eruptive Centres Associated with the Liquiñe-Ofqui Fault Zone (Chilean Andes)
- Author
-
Francisca Mallea-Lillo, Miguel Ángel Parada, Eduardo Morgado, Claudio Contreras, and Darío Hübner
- Published
- 2022
- Full Text
- View/download PDF
8. Molecular Dynamics Simulation of a Model Brain Membrane with and without a 14-3-3 tau Protein
- Author
-
Angel David Reyes-Figueroa, Fernando Favela-Rosales, Pavel Castro-Villarreal, Jorge Alfonso Arvayo-Zatarain, and Claudio Contreras-Aburto
- Subjects
Molecular dynamics ,Order (biology) ,Membrane ,biology ,Brain model ,Chemistry ,Diffusion ,Tau protein ,biology.protein ,Biophysics ,Transmembrane protein - Abstract
An unbalanced composition of lipids and proteins in brain membranes is related to the appearance neurodegenrative diseases and recent investigations show that the 14-3-3 tau protein might relate to some of these diseases. This article reports results from a coarse-grained model brain membrane with and without a 14-3-3 τ/θ protein inside the membrane. We investigated the symmetrized partial density, thickness, diffusion coefficients, and deuterium order parameters of the membrane with and without protein. We observe a slight increase in heads and linkers in the symmetrized partial density of the membrane with the protein inserted and higher values of the deuterium order parameters for the brain model membrane with protein. We observe a reduction in the diffusion coefficient of the fluid membrane in the presence of the transmembrane tau protein. Our findings show that the protein can modify the structural and dynamical properties of the membrane. This work will serve as a guide for future investigations on the interactions of tau proteins with brain membrane models and their relation to neurodegenerative diseases.
- Published
- 2021
- Full Text
- View/download PDF
9. Contrasting sources and conditions of shallow magmatic reservoirs of the Fui Group small eruptive centres associated with the Liquiñe-Ofqui Fault Zone (Chilean Andes)
- Author
-
Francisca Mallea-Lillo, Miguel A. Parada, Eduardo Morgado, Claudio Contreras, and Darío Hübner
- Subjects
Geology ,Earth-Surface Processes - Published
- 2022
- Full Text
- View/download PDF
10. Single file diffusion meets Feynman path integral
- Author
-
Idrish Huet-Hernández, Oscar Vázquez-Rodríguez, Sendic Estrada-Jiménez, Claudio Contreras-Aburto, and Pavel Castro-Villarreal
- Subjects
Statistics and Probability ,Physics ,Particle system ,Statistical Mechanics (cond-mat.stat-mech) ,Smoluchowski coagulation equation ,FOS: Physical sciences ,Statistical and Nonlinear Physics ,Harmonic (mathematics) ,Condensed Matter - Soft Condensed Matter ,Langevin equation ,symbols.namesake ,Classical mechanics ,Path integral formulation ,Thermodynamic limit ,symbols ,Soft Condensed Matter (cond-mat.soft) ,Statistics, Probability and Uncertainty ,Diffusion (business) ,Brownian motion ,Condensed Matter - Statistical Mechanics - Abstract
The path-integral representation of Smoluchowski equation is exploited to explore the stochastic dynamics of a tagged Brownian particle within an interacting system where hydrodynamic effects are neglected. In particular, this formalism is applied to a particle system confined to a one-dimensional infinite line aiming to investigate the single-file diffusion phenomenon in this scenario. In particular, the path-integral method is contrasted against the standard many-particle Langevin equation for a system of interacting Brownian particles in a harmonic chain model, exhibiting excellent agreement; in this case of study a formula defined on the whole time-scale for the mean-square displacement, in the thermodynamic limit, is found for the tracer particle in terms of Bessel functions, recovering also the single-file regime. Additionally, a Brownian particle system with paramagnetic interactions is considered near crystallization where the total interaction potential is roughly a harmonic potential. Taking advantage of the path-integral formalism a simple perturbation treatment is carried out to investigate the single file diffusion behavior when temperature is increased away from the crystal phase., 27 pages, 2 figures
- Published
- 2021
11. Raymond Aron y la tradicion del realismo politico
- Author
-
Campi, Alessandro, Jeronimo, Molina, Pier Paolo Portinaro, Marco, Cesa, Angelo, Pabenianco, Alessandro, Vitale, Gianfranco, Miglio, Oro Tapia, Luis R., Armando, Zerolo, and Claudio, Contreras
- Subjects
Raymond Aron ,Raymond Aron, Realismo Politico, Scienza Poliica ,Realismo Politico ,Scienza Poliica - Published
- 2021
12. 'Qaralamaxat Qarma’ – Nuestros lugares', toponimia y oralidad como medio de reivindicación territorial en el Chaco argentino
- Author
-
Claudio Contreras Véliz
- Subjects
lcsh:G1-922 ,General Medicine ,lcsh:Geography (General) - Abstract
El presente artículo nos aproxima a la cuestión de la reivindicación territorial y el imaginario del lugar propio, teniendo en la toponimia, una instancia de valorización del espacio perdido y/o transformado, y que da cuenta de las particulares formas de aprehenderlo, en este caso, por parte del pueblo originario Qom en la localidad de Pampa del Indio, Provincia del Chaco, Argentina. Región afectada por profundo cambio ambiental, cultural y territorial en las últimas décadas, debido principalmente a la agresiva expansión de la industria agropecuaria y forestal, además de los procesos de colonización de población extranjera y de expulsión de la población nativa.De esta manera, el trabajo aborda dicho contexto de transformación, a partir de la memoria y praxis reivindicatoria de un grupo de mujeres del pueblo Qom, las “Madres cuidadoras de la cultura Qom”, que desarrollan un trabajo de preservación y reclamación cultural como territorial. En este caso, a través de la construcción y difusión de mapas toponímicos del territorio por ellos habitados por generaciones, el cual fue planteado como una herramienta de reclamación, entendiendo a través del mapa, la dinámica de conflicto entre la territorialidad indígena y la tierra productiva del blanco.Palabras claves: toponimia, reivindicación territorial, Chaco, Qom.
- Published
- 2018
- Full Text
- View/download PDF
13. Effects of Manufacturing and Finishing Techniques of Feldspathic Ceramics on Surface Topography, Biofilm Formation, and Cell Viability for Human Gingival Fibroblasts
- Author
-
Antonio Olavo Cardoso Jorge, Lilian Costa Anami, Samira Esteves Afonso Camargo, Amanda Maria de Oliveira Dal Piva, Lisseth Patricia Claudio Contreras, Felipe de Camargo Ribeiro, and Marco Antonio Bottino
- Subjects
Ceramics ,Materials science ,Cell Survival ,Surface Properties ,Gingiva ,Polishing ,02 engineering and technology ,In Vitro Techniques ,Streptococcus mutans ,03 medical and health sciences ,0302 clinical medicine ,Candida albicans ,Materials Testing ,Humans ,Ceramic ,Viability assay ,General Dentistry ,Stem Cells ,Biofilm ,030206 dentistry ,Adhesion ,Fibroblasts ,021001 nanoscience & nanotechnology ,Dental Porcelain ,Surface energy ,Dental Polishing ,Dental Veneers ,Chemical engineering ,Biofilms ,visual_art ,Microscopy, Electron, Scanning ,visual_art.visual_art_medium ,Computer-Aided Design ,Streptococcus sanguis ,0210 nano-technology - Abstract
SUMMARY Purpose: Feldspathic ceramic restorations can be obtained by different techniques (stratification or computer-aided design/computer-aided manufacturing [CAD/CAM] blocks) and finishing procedures (polishing or glaze application). This study evaluated the effects of techniques and finishing procedures on surface properties, biofilm formation, and viability of human gingival fibroblasts (FMM-1) in contact with these materials. Methods and Materials: Ceramic specimens were obtained through a stratification technique (Vita VM9) and from CAD/CAM blocks (Vita Blocs Mark II; both Vita Zahnfabrik) and their surfaces were finished by polishing (ceramisté diamond rubbers + polishing paste; “p” subgroups) or glaze spray application + sintering (“g” subgroups). Roughness (Ra and RSm parameters) and surface free energy (SFE) were measured. Early biofilm formation of Streptococcus mutans, Streptococcus sanguinis, and Candida albicans was evaluated by counting colony-forming units (CFU). MTT (3-[4.5-dimethyl-thiazol-2-yl-]-2.5-diphenyl tetrazolium bromide) cytotoxicity test evaluated cellular viability for the growth of FMM-1 after 24 hours and seven days of contact. Scanning electron microscopy (SEM) and three-dimensional optical profilometry were performed to qualitatively analyze the surface. Data were analyzed by analysis of variance, Tukey test, and t-test (all α=0.05). Results: Polished samples presented lower roughness (Ra, p=0.015; RSm, p=0.049) and higher SFE (p=0.00). Streptococci had higher CFU in all groups, but the CFU of C albicans was lower for polished samples. Biofilm formation was influenced by the interaction of all factors (p=0.018), and the materials showed no cytotoxicity to FMM-1 growth. Conclusions: Polishing resulted in the lowest values for surface roughness and higher SFE values. Polished ceramics showed less C albicans adherence while the adherence of Streptococci was greater than C albicans in all conditions.
- Published
- 2018
- Full Text
- View/download PDF
14. Massive hemoptysis following Rasmussen’s aneurysm. A case report
- Author
-
Hernan Quintana, Antonio Fabian Cabezas, Claudio Contreras, Fernando Andrés Lillo, Felipe Aedo, and Juan Manuel Zapata
- Subjects
Thorax ,lcsh:R5-920 ,medicine.medical_specialty ,Rasmussen's aneurysm ,medicine.diagnostic_test ,business.industry ,medicine.medical_treatment ,lcsh:Surgery ,lcsh:RD1-811 ,rasmussen’s aneurysm ,medicine.disease ,hemoptysis ,Surgery ,Pneumonia ,Pseudoaneurysm ,Aneurysm ,tuberculosis ,medicine.artery ,Pulmonary artery ,medicine ,Embolization ,lcsh:Medicine (General) ,Chest radiograph ,business - Abstract
Rasmussen’s aneurysm (RA) is a pseudoaneurysm of a pulmonary artery (AP), adjacent to or within a tuberculous cavity, appearing in 5% of these lesions. Its rupture might provoke massive hemoptysis (MH) with a near 50% mortality. The aim of this article is to report a case of massive hemoptysis following Rasmussen’s aneurysm. 52-year-old man with recent history of hospitalization due to pneumonia associated to influenza A and decompensated hyperthyroidism, presents outpatient chest radiograph with signs of hyperinflation and scarring apical opacities, the patient returned to the hospital due to sharp pain of left hemi thorax during inspiration accompanied with bloody sputum, asthenia and non-quantified weight loss. He evolves to frank MH, requiring endotracheal intubation managed in the intensive care unit (ICU). Chest computed tomography (CT) reported ground-glass opacity, nodules with a tendency to cavitation, tree-inbud pattern in agreement with inflammation and infection, active TB is considered, and truncus of PA with vascular lesion suggestive of aneurysm dependent on pulmonary circulation, possibly RA. Fibrobronchoscopy reported signs of old and recent bleeding of left bronchial tree, probably of the lingula, blood clots in right bronchial tree. Molecular study and TB cultures was negative. Endovascular procedure with arteriography was carried out, revealing amputation of left distal segmental PA carrying the pseudoaneurysm with complete regression, discarding embolization RA It must be considered among the differential diagnoses of MH, especially on patients with pulmonary TB complications, such as the reported case. Due to its associated increased mortality, once RA is identified, it must be either endovascularly or surgically eradicated.
- Published
- 2019
- Full Text
- View/download PDF
15. In vitro wear of a zirconium-reinforced lithium silicate ceramic against different restorative materials
- Author
-
Luiz Felipe Valandro, Renata Marques de Melo, Marco Antonio Bottino, Tiago Moreira Bastos Campos, Lisseth Patricia Claudio Contreras, Larissa Marcia Martins Alves, Universidade Estadual Paulista (Unesp), Physics department, and Universidade Federal de Sergipe (UFS)
- Subjects
Dental Stress Analysis ,Ceramics ,Materials science ,Dental materials ,Scanning electron microscope ,Surface Properties ,Biomedical Engineering ,chemistry.chemical_element ,02 engineering and technology ,Surface finish ,In Vitro Techniques ,Lithium ,Dental Restoration Wear ,Biomaterials ,03 medical and health sciences ,0302 clinical medicine ,Hardness ,Materials Testing ,Cubic zirconia ,Ceramic ,Composite material ,Acrylic resin ,Zirconium ,Silicates ,030206 dentistry ,021001 nanoscience & nanotechnology ,Silicon Dioxide ,Dental Porcelain ,Resins, Synthetic ,chemistry ,Distilled water ,Mechanics of Materials ,Dental restoration wear ,visual_art ,visual_art.visual_art_medium ,Microscopy, Electron, Scanning ,0210 nano-technology ,Magnesium Oxide - Abstract
Made available in DSpace on 2019-10-06T16:47:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 It is important to predict the wear behavior of a material as well as its potential to wear antagonized restorative materials. Thus, this study investigated the performance of zirconia-reinforced lithium silicate (ZLS) after wear with different antagonists. Thirty discs of ZLS were made and divided into three groups according to the antagonist (n = 10). Ten cylinders of each antagonist were also made. The parameters for the simulation of wear were: 30N, horizontal movement of 6 mm, and 1.7 Hz, totaling 300,000 cycles, in distilled water. Wear measurements (volume losses (mm3)) on the ZLS and antagonists were performed by digital optical profilometry or an analytical balance. Hardness of all materials was also measured, whereas roughness and Scanning Electron Microscopy (SEM) were only accessed for the ZLS. The wear and hardness values were subjected to one-way ANOVA and the Tukey Test (95%), while the roughness data was analyzed with paired T-test (95%). The hardness means of all materials were statistically different (zirconia > steatite = ZLS > acrylic resin) (p = 0.0001). Zirconia and steatite severely worn ZLS and only acrylic resin worn surfaces could be measured for roughness, which was significantly higher after wear (p = 0.007). SEM showed the ZLS's wear tracks when worn by steatite and zirconia. It was possible to observe differences of ZLS wear patterns depending on the antagonist and quantify the volumes worn with steatite (17.61 ± 2.65) and zirconia (41.98 ± 19.45), which were significantly different (p = 0.001). Acrylic resin promoted a superficial wear on ZLS that could not be quantified. In terms of the antagonists' materials, zirconia presented significantly different less volume loss compared to acrylic resin and steatite (p = 0.000). It can be concluded that zirconia caused more wear on ZLS than steatite and acrylic resin. São Paulo State University (Unesp) Institute of Science and Technology at São José dos Campos Department of Dental Materials and Prosthodontics Technological Institute of Aeronautics Physics department, Praça Marechal Eduardo Gomes 50 Federal University of Santa Maria (UFSM) Restorative Dentistry Department, Marechal Floriano 1184 São Paulo State University (Unesp) Institute of Science and Technology at São José dos Campos Department of Dental Materials and Prosthodontics
- Published
- 2019
16. The Wear Performance of Glazed and Polished Full Contour Zirconia
- Author
-
Larissa Alves, Lisseth Patricia Claudio Contreras, Tiago Campos, Marcia Carneiro Valera, Renata Marinho, Renata Melo, Mirian Bueno, Eduardo Bresciani, Universidade Estadual Paulista (Unesp), and ITA-Instituto Tecnológico de Aeronáutica
- Subjects
Ceramics ,Materials science ,Enamel paint ,Dental materials ,Scanning electron microscope ,Surface Properties ,030206 dentistry ,Surface finish ,Dental Porcelain ,Dental Restoration Wear ,Dental Polishing ,Contact angle ,03 medical and health sciences ,0302 clinical medicine ,Dental restoration wear ,visual_art ,Materials Testing ,visual_art.visual_art_medium ,Cubic zirconia ,030212 general & internal medicine ,Profilometer ,Wetting ,Zirconium ,Composite material ,General Dentistry - Abstract
This study evaluated the influence of zirconia surface finishes on the wear of an enamel analogue. 40 zirconia discs were divided into four groups: control (without finish); glazed; polished; polished and glazed. All samples were subjected to wear against steatite antagonists. The specimens underwent roughness, topographic, scanning electron microscopy (SEM) and wettability analyses. Quantitative wear measurements were performed on both steatites and discs. To measure wear of steatites the weight before and after the test and the diameter after the test were used. Profilometer measurements were performed to determine the wear on discs. Roughness, volumetric wear and mass loss were analyzed using the Kruskal-Wallis and Dunn tests (5%), while contact angle values were analyzed with One-way ANOVA and Tukey tests (5%). The polished group had the lowest roughness means, being statistically different from the other groups (p-value=0.0001). The glazed group presented the lowest steatite volumetric wear (p-value=0.0001), but not statistically different from the polished and glazed group, whereas these groups presented the highest zirconia volumetric wear, with statistically different (p-value=0.0002) compared to the others. SEM showed irregularities on the control groups surface, grooves on the polished group, and a homogeneous surface for the glazed group with a few pores. All groups presented contact angles lower than 90 degrees, characterizing hydrophilic surfaces. It can be concluded that just glazed zirconia caused less wear on the antagonist when compared to no finish and polished zirconia. Resumo Este estudo avaliou a influência dos acabamentos superficiais da zircônia no desgaste de um análogo de esmalte. 40 discos de zircônia foram divididos em quatro grupos: controle (sem acabamento); glazeado; polido; polido e glazeado. Todas as amostras foram submetidas ao desgaste contra antagonistas de esteatita. Os espécimes foram submetidos à análise de rugosidade, topografia, microscopia eletrônica de varredura (MEV) e análise de molhabilidade. Medidas quantitativas de desgaste foram realizadas nos antagonistas e nos discos de zircônia. Para medir o desgaste das esteatitas, foi mensurado o peso antes e depois do desgaste e o diâmetro após o teste. A análise de perfilometria mensurou o desgaste dos discos. Rugosidade, desgaste volumétrico e perda de massa foram analisados pelos testes de Kruskal-Wallis e Dunn (5%), enquanto os valores de ângulo de contato foram analisados com os testes One-way ANOVA e Tukey (5%). O grupo polido apresentou as menores médias de rugosidade, sendo estatisticamente diferente dos demais grupos (p-valor=0,0001). O grupo glazeado apresentou o menor desgaste volumétrico do antagonista (p-valor=0,0001), mas não foi estatisticamente diferente do grupo polido e glazeado, enquanto que esses grupos apresentaram o maior desgaste volumétrico da zircônia, com diferença estatisticamente diferente (p-valor=0,0002) em comparação com os outros. MEV mostrou irregularidades na superfície do grupo controle, sulcos no grupo polido e uma superfície homogênea para o grupo glazeado, com poucos poros. Todos os grupos apresentaram ângulos de contato menores que 90 graus, caracterizando superfícies hidrofílicas. Dentro das limitações deste estudo in vitro, é possível concluir que zircônia glazeada causou menos desgaste ao antagonista quando comparada a zircônia sem tratamento ou polida. Além disso, não foi encontrada diferença no desgaste do antagonista para os grupos de zirconia polida e controle.
- Published
- 2019
17. MÉTODOS DE SIMULACIÓN COMPUTACIONAL EN BIOLOGÍA
- Author
-
Amir Darío Maldonado Arce, Claudio Contreras Aburto, Jorge Alfonso Arvayo Zatarain, Fernando Favela Rosales, and Efraín Urrutia Bañuelos
- Subjects
Simulación computacional ,proteínas ,lcsh:T ,lcsh:Q ,lcsh:Science ,lcsh:Technology ,biofísica ,membranas biológicas - Abstract
Las técnicas de simulación computacional se usan extensivamente para estudiar sistemas biológicos, y en general, materiales sólidos y blandos. Debido a la complejidad de los fenómenos biológicos, y a la imposibilidad de estudiar teóricamente el comportamiento de sistemas tales como proteínas y membranas, la simulación computacional se utiliza para estudiar la estructura y dinámica de estos sistemas en diferentes escalas temporales. En este artículo describiremos brevemente algunas de las técnicas de simulación computacional más utilizadas en Biología: la Dinámica Molecular, la Dinámica Browniana y el Método de Monte Carlo. Nuestra intención es proporcionar un panorama introductorio de la utilidad de los métodos de simulación molecular en Biología.
- Published
- 2016
- Full Text
- View/download PDF
18. Assessment of the Wolf method using the Stillinger–Lovett sum rules: From strong electrolytes to weakly charged colloidal dispersions
- Author
-
Carlos Avendaño, Mayra Lara-Peña, Marco Heinen, Ramón Castañeda-Priego, José Marcos Falcón-González, Alejandro Gil-Villegas, and Claudio Contreras-Aburto
- Subjects
Physics ,010304 chemical physics ,General Physics and Astronomy ,Charge (physics) ,010402 general chemistry ,Electrostatics ,01 natural sciences ,Integral equation ,0104 chemical sciences ,Strong electrolyte ,Chain (algebraic topology) ,Simple (abstract algebra) ,0103 physical sciences ,Moment (physics) ,Statistical physics ,Physical and Theoretical Chemistry ,Wolf summation - Abstract
The Ewald method has been the cornerstone in molecular simulations for modeling electrostatic interactions of charge-stabilized many-body systems. In the late 1990s, Wolf and collaborators developed an alternative route to describe the long-range nature of electrostatic interactions; from a computational perspective, this method provides a more efficient and straightforward way to implement long-range electrostatic interactions than the Ewald method. Despite these advantages, the validity of the Wolf potential to account for the electrostatic contribution in charged fluids remains controversial. To alleviate this situation, in this contribution, we implement the Wolf summation method to both electrolyte solutions and charged colloids with moderate size and charge asymmetries in order to assess the accuracy and validity of the method. To this end, we verify that the proper selection of parameters within the Wolf method leads to results that are in good agreement with those obtained through the standard Ewald method and the theory of integral equations of simple liquids within the so-called hypernetted chain approximation. Furthermore, we show that the results obtained with the original Wolf method do satisfy the moment conditions described by the Stillinger-Lovett sum rules, which are directly related to the local electroneutrality condition and the electrostatic screening in the Debye-Hückel regime. Hence, the fact that the solution provided by the Wolf method satisfies the first and second moments of Stillinger-Lovett proves, for the first time, the reliability of the method to correctly incorporate the electrostatic contribution in charge-stabilized fluids. This makes the Wolf method a powerful alternative compared to more demanding computational approaches.
- Published
- 2020
- Full Text
- View/download PDF
19. Hayek y Böhm: dos lecturas del Estado de derecho neoliberal
- Author
-
Claudio Contreras
- Subjects
lcsh:K1-7720 ,administración ,estado de derecho ,lcsh:Law ,lcsh:Law in general. Comparative and uniform law. Jurisprudence ,Constitución ,planificación ,lcsh:K - Abstract
Muchas son las lecturas del neoliberalismo en términos de las reformas a nivel macro-económico que su doctrina implica, comprendiendo a la misma como una reacción frente al dirigismo de tipo keynesiano, tal como lo formulaba François Bilger. Otra lectura, menos frecuente, analiza a la doctrina neoliberal en términos de una racionalidad de gobierno, expuesta por Foucault. Hay, sin embargo, un tercer aspecto esbozado en tales lecturas que aun no fue desarrollado a fondo: se trata de analizar el problema neoliberal en términos de su concepto jurídico del Estado de derecho, Rechtsstaat o Rule of law. En vistas a determinar el estatuto del mismo es preciso situar las dos formulaciones neoliberales del concepto del Estado de derecho, aquella de Hayek y aquella de Böhm, en un punto de ruptura en la historia del concepto: se trata de la crisis de Weimar y la irrupción de los Estados totalitarios.
- Published
- 2018
20. Molecular dynamics simulation study of the effect of halothane on mixed DPPC/DPPE phospholipid membranes
- Author
-
Amir Maldonado, Jorge Alfonso Arvayo-Zatarain, Fernando Favela-Rosales, Efraín Urrutia-Bañuelos, and Claudio Contreras-Aburto
- Subjects
1,2-Dipalmitoylphosphatidylcholine ,Lipid Bilayers ,Phospholipid ,Molecular Dynamics Simulation ,010402 general chemistry ,01 natural sciences ,Catalysis ,Inorganic Chemistry ,Molecular dynamics ,chemistry.chemical_compound ,0103 physical sciences ,medicine ,Molecule ,Lipid molecule ,Physical and Theoretical Chemistry ,010304 chemical physics ,Chemistry ,Bilayer ,Phosphatidylethanolamines ,Organic Chemistry ,technology, industry, and agriculture ,0104 chemical sciences ,Computer Science Applications ,Crystallography ,Membrane ,Computational Theory and Mathematics ,Anesthetic ,Anesthetics, Inhalation ,lipids (amino acids, peptides, and proteins) ,Halothane ,Hydrophobic and Hydrophilic Interactions ,medicine.drug - Abstract
We report results of a molecular dynamics simulation study of the effect of one general anesthetic, halothane, on some properties of mixed DPPC/DPPE phospholipid membranes. This is a suitable model for the study of simple, two-phospholipid membrane systems. From the simulation runs, we determined several membrane properties for five different molecular proportions of DPPC/DPPE. The effect of halothane on the studied membrane properties (area per lipid molecule, density of membrane, order parameter, etc.) was rather small. The distribution of halothane is not uniform through the bilayer thickness. Instead, there is a maximum of anesthetic concentration around 1.2 nm from the center of the membrane. The anesthetic molecule is located close to the phospholipid headgroups. The position of the halothane density maximum depends slightly on the DPPC/DPPE molar proportion. Snapshots taken over the plane of the membrane, as well as calculated two-dimensional radial distribution functions show that the anesthetic has no preference for either phospholipid (DPPC or DPPE). Our results indicate that this anesthetic molecule has only small effects on DPPC/DPPE mixed membranes. In addition, halothane displays no preferential location around DPPC or DPPE. This is probably due to the hydrophobic nature of halothane and to the fact that the chosen phospholipids have the same hydrophobic tails.
- Published
- 2018
21. Litigio y apelación: aportes para un análisis procedimental del Estado de derecho
- Author
-
Claudio Contreras
- Subjects
ley ,regla ,lcsh:K1-7720 ,estado de derecho ,autoridad ,lcsh:Law ,lcsh:Law in general. Comparative and uniform law. Jurisprudence ,sociedad civil ,lcsh:K - Abstract
En el artículo presente vamos a analizar los antecedentes del concepto del Estado de derecho que operó durante el siglo XIX en términos de una reflexión retrospectiva. Para ello vamos a establecer una discusión crítica con los métodos de la historia y análisis conceptual en vistas de formular un problema procedimental: la cuestión del pasaje del conflicto civil al litigio a través del recurso de apelación a la autoridad. Los antecedentes procedimentales del Estado de derecho son los siguientes: el Árbitro en el contractualismo (Hobbes), el Juez en la sociedad civil (Locke), la Personalidad en el Estado constitucional (Hegel). A partir de los problemas derivados de estos antecedentes, por último, vamos a referir de un modo sumario el modo en que la cuestión es formulada por la tratadística del siglo XIX en torno al Estado de derecho: en ella se devela una crisis del concepto jurídico de la autoridad.
- Published
- 2017
22. A unifying mode-coupling theory for transport properties of electrolyte solutions. II. Results for equal-sized ions electrolytes
- Author
-
Gerhard Nägele and Claudio Contreras Aburto
- Subjects
Ions ,Aqueous solution ,Chemistry ,Analytical chemistry ,Solvation ,General Physics and Astronomy ,Molar conductivity ,Thermodynamics ,Biological Transport ,Electrolyte ,Thermal diffusivity ,Models, Biological ,Condensed Matter::Soft Condensed Matter ,Solutions ,Viscosity ,Electrolytes ,Solvation shell ,Ionic strength ,ddc:540 ,Hydrodynamics ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Particle Size - Abstract
On the basis of a versatile mode-coupling theory (MCT) method developed in Paper I [C. Contreras Aburto and G. Nagele, J. Chem. Phys. 139, 134109 (2013)], we investigate the concentration dependence of conduction-diffusion linear transport properties for a symmetric binary electrolyte solution. The ions are treated in this method as charged Brownian spheres, and the solvent-mediated ion-ion hydrodynamic interactions are accounted for also in the ion atmosphere relaxation effect. By means of a simplified solution scheme, convenient semi-analytic MCT expressions are derived for the electrophoretic mobilities, and the molar conductivity, of an electrolyte mixture with equal-sized ions. These expressions reduce to the classical Debye-Falkenhagen-Onsager-Fuoss results in the limit of very low ion concentration. The MCT expressions are numerically evaluated for a binary electrolyte, and compared to experimental data and results by another theoretical method. Our analysis encloses, in addition, the electrolyte viscosity. To analyze the dynamic influence of the hydration shell, the significance of mixed slip-stick hydrodynamic surface boundary conditions, and the effect of solvent permeability are explored. For the stick boundary condition employed in the hydrodynamic diffusivity tensors, our theoretical results for the molar conductivity and viscosity of an aqueous 1:1 electrolyte are in good overall agreement with reported experimental data for aqueous NaCl solutions, for concentrations extending even up to two molar.
- Published
- 2013
- Full Text
- View/download PDF
23. A unifying mode-coupling theory for transport properties of electrolyte solutions. I. General scheme and limiting laws
- Author
-
Claudio Contreras Aburto and Gerhard Nägele
- Subjects
Self-diffusion ,Chemistry ,General Physics and Astronomy ,Thermodynamics ,Electrolyte ,Viscoelasticity ,Condensed Matter::Soft Condensed Matter ,Strong electrolyte ,Viscosity ,Law ,Mode coupling ,ddc:540 ,Relaxation (physics) ,Physical and Theoretical Chemistry ,Brownian motion - Abstract
We develop a general method for calculating conduction-diffusion transport properties of strong electrolyte mixtures, including specific conductivities, steady-state electrophoretic mobilities, and self-diffusion coefficients. The ions are described as charged Brownian spheres, and the solvent-mediated hydrodynamic interactions (HIs) are also accounted for in the non-instantaneous ion atmosphere relaxation effect. A linear response expression relating long-time partial mobilities to associated dynamic structure factors is employed in our derivation of a general mode coupling theory (MCT) method for the conduction-diffusion properties. A simplified solution scheme for the MCT method is discussed. Analytic results are obtained for transport coefficients of pointlike ions which, for very low ion concentrations, reduce to the Deby-Falkenhagen-Onsager-Fuoss limiting law expressions. As an application, an unusual non-monotonic concentration dependence of the polyion electrophoretic mobility in a mixture of two binary electrolytes is discussed. In addition, leading-order extensions of the limiting law results are derived with HIs included. The present method complements a related MCT method by the authors for the electrolyte viscosity and shear relaxation function [C. Contreras-Aburto and G. Nagele, J. Phys.: Condens. Matter 24, 464108 (2012)], so that a unifying scheme for conduction-diffusion and viscoelastic properties is obtained. We present here the general framework of the method, illustrating its versatility for conditions where fully analytic results are obtainable. Numerical results for conduction-diffusion properties and the viscosity of concentrated electrolytes are presented in Paper II [C. Contreras Aburto and G. Nagele, J. Chem. Phys. 139, 134110 (2013)].
- Published
- 2013
- Full Text
- View/download PDF
24. A common neighbor analysis of crystallization kinetics and excess entropy of charged spherical colloids
- Author
-
Amir Darío Maldonado Arce, Efraín Urrutia Bañuelos, and Claudio Contreras Aburto
- Subjects
education.field_of_study ,Materials science ,Icosahedral symmetry ,Population ,General Physics and Astronomy ,Thermodynamics ,02 engineering and technology ,Colloidal crystal ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Condensed Matter::Soft Condensed Matter ,law ,Metastability ,0103 physical sciences ,Brownian dynamics ,Physical and Theoretical Chemistry ,Crystallization ,010306 general physics ,0210 nano-technology ,Structure factor ,education ,Brownian motion - Abstract
The topological analysis tool known as the common neighbor analysis (CNA) is used for the first time in this work to analyze crystallization kinetics and excess entropy of charge-stabilized colloidal suspensions. For this purpose, Brownian dynamics computer simulations are implemented to investigate the crystallization kinetics of homogeneously melted colloidal crystals that are composed of hard-core-screened-Coulomb interacting particles. The results are in agreement with recent static structure factor measurements that could indicate the presence of icosahedral units in the metastable melt, and with the fact that weakly screened charged colloids crystallize into body-centered-cubic (bcc) ordering. A two-step crystallization pathway is found, in which the population of bcc-subunit CNA-pairs satisfactorily obeys a Verhulst model. Moreover, the CNA helped to unveil that the excess entropy obeys a quasi-universal functional form, relating the behavior of colloidal, molecular, and metallic liquid systems. The work contributes to the scientific understanding of the crystallization pathway of charged colloids, and to the development of new ways to assess the degree of crystalline order, starting from the excess entropy.
- Published
- 2016
- Full Text
- View/download PDF
25. Long-time self-diffusion of charged spherical colloidal particles in parallel planar layers
- Author
-
César Alejandro Báez, Claudio Contreras-Aburto, Ramón Castañeda-Priego, and J. M. Méndez-Alcaraz
- Subjects
Self-diffusion ,Colloid ,Planar ,Classical mechanics ,Particle transfer ,Colloidal particle ,Chemistry ,Brownian dynamics ,General Physics and Astronomy ,Electric potential ,Physical and Theoretical Chemistry ,Static structure ,Molecular physics - Abstract
The long-time self-diffusion coefficient, D(L), of charged spherical colloidal particles in parallel planar layers is studied by means of Brownian dynamics computer simulations and mode-coupling theory. All particles (regardless which layer they are located on) interact with each other via the screened Coulomb potential and there is no particle transfer between layers. As a result of the geometrical constraint on particle positions, the simulation results show that D(L) is strongly controlled by the separation between layers. On the basis of the so-called contraction of the description formalism [C. Contreras-Aburto, J. M. Méndez-Alcaraz, and R. Castañeda-Priego, J. Chem. Phys. 132, 174111 (2010)], the effective potential between particles in a layer (the so-called observed layer) is obtained from integrating out the degrees of freedom of particles in the remaining layers. We have shown in a previous work that the effective potential performs well in describing the static structure of the observed layer (loc. cit.). In this work, we find that the D(L) values determined from the simulations of the observed layer, where the particles interact via the effective potential, do not agree with the exact values of D(L). Our findings confirm that even when an effective potential can perform well in describing the static properties, there is no guarantee that it will correctly describe the dynamic properties of colloidal systems.
- Published
- 2014
- Full Text
- View/download PDF
26. Corrigendum: Determination of suitable zones for apitourism using multi-criteria evaluation in geographic information systems: a case study in the O’Higgins Region, Chile
- Author
-
Gabriel Pantoja, Gloria Montenegro, Claudio Contreras, Lissette Grimau, and Miguel Gómez
- Subjects
Beekeeping ,Geography ,Geographic information system ,Work (electrical) ,business.industry ,Ecotourism ,Environmental protection ,Environmental resource management ,Production (economics) ,Vegetation ,business ,Tourism ,Decision analysis - Abstract
Beekeeping, which involves honey production and pollination of agricultural crops, has become a significant production activity. Linking beekeeping with ecotourism brings greater value to the beekeeping sector, thereby attracting the development of apitourism. Multi-criteria decision analysis is a set of techniques developed through Geographic Information Systems (GIS) focused on spatial decision making, which can be used to link beekeeping and tourism for the development of priority sites for shared activity. This work is based on the definition and weighting of factors used for evaluation of apitourism suitability in Chile, considering the opinion of beekeepers and professionals associated with the sector. The result is a map of apitouristic suitability that includes vegetation, tourism, precipitation, temperature, roads, rivers and genetically modified crops (GM crops), as well as three restrictions: soil use, highways and wild areas protected by the state. The model allowed the localization of priority sites for resources and efforts pertaining to the development of apitourism.
- Published
- 2010
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.