Search

We study a slender filament beating in a viscous fluid with novel curvature-dependent bending stiffness. Our numerical and experimental investigations reveal that such differential stiffness can sustain planar bending waves far along flexible filaments, in stark contrast to the uniform-stiffness case which requires more sophisticated control. In particular, we establish basal actuation as a viable, parsimonious mechanism for generating high-amplitude planar bending waves. Moreover, the resulting beat patterns closely resemble the power-and-recovery strokes of propulsive biological filaments such as cilia, suggesting extensive applications in robotic and engineered systems.

Abstract Background Attitudes and behaviors towards mask wearing may influence the ability to reduce transmission of COVID-19 and other diseases. Methods University students, staff, and faculty (N = 9653) responded to an email invitation to complete electronic surveys (November 2021 and April 2022). Surveys included 19 items measuring attitudes and behaviors towards mask wearing from the Understanding America Study. Linear mixed models including variables for sex, age group, division, race and ethnicity, political affiliation, and history of COVID-19, were used to estimate the mean difference of the mean score for attitudes and behavior between Time 1 (November 2021) and Time 2 (April 2022). Results Participants were mostly female (62.1%), students (70.6%), White (39.5%) and Asian (34.7%). More than half identified their political affiliation as Democrat (65.5%). Characteristic variable-by-time interactions for difference in mean mask attitude scores difference were significant at Time 1 (T1) and Time 2 (T2) between Black and White participants (B = 0.18 (0.05), 95% CI: 0.07, 0.28, p = 0.001), Asian and White participants (B = 0.07 (0.02), 95% CI: 0.03–0.12, p = 0.001), participants with self-reported history of COVID-19 and no history of COVID-19 (B= -0.13 (0.02), 95% CI: -0.07, -0.18, p

Abstract Background Mistrust in science and scientists may adversely influence the rate of COVID-19 vaccination and undermine public health initiatives to reduce virus transmission. Methods Students, staff and faculty responded to an email invitation to complete an electronic survey. Surveys included 21-items from the Trust in Science and Scientists Inventory questionnaire. Responses were coded so higher scores indicated a higher trust in science and scientists, A linear regression model including sex, age group, division, race and ethnicity, political affiliation, and history of COVID-19, was used to determine variables significantly associated with trust in science and scientists scores at the p

Insects are good examples of ground locomotion because they can adapt their gait pattern to propel them in any direction, over uneven terrain, in a stable manner. Nevertheless, replicating such locomotion skills to a legged robot is not a straightforward task. Different approaches have been proposed to synthesize the gait patterns for these robots; each approach exhibits different restrictions, advantages, and priorities. For the purpose of this document, we have classified gait pattern generators for multi-legged robots into three categories: precomputed, heuristic, and bio-inspired approaches. Precomputed approaches rely on a set of precalculated motion patterns obtained from geometric and/or kinematic models that are performed repeatedly whenever necessary and that cannot be modified on-the-fly to adapt to the terrain changes. On the other hand, heuristic and bio-inspired approaches offer on-line adaptability, but parameter-tuning and heading control can be difficult. In this document, we present the K3P algorithm, a real-time kinematic gait pattern generator conceived to command a legged robot. In contrast to other approaches, K3P enables the robot to adapt its gait to follow an arbitrary trajectory, at an arbitrary speed, over uneven terrain. No precomputed motions for the legs are required; instead, K3P modifies the motion of all mechanical joints to propel the body of the robot in the desired direction, maintaining a tripod stability at all times. In this paper, all the specific details of the aforementioned algorithm are presented, as well as different simulation results that validate its characteristics.

Despite the efficacy and widespread availability of COVID-19 vaccines, vaccine uptake has been relatively low in U.S. Hispanic communities, especially among adolescents. This study examined vaccination status among 444 high school students in predominantly Hispanic neighborhoods of Los Angeles County, California in May-June 2022 (mean age = 15.74 years, 55% female, 93% Hispanic). Guided by Protection Motivation Theory, we hypothesized that the odds of being fully vaccinated (at least 2 vaccine doses) would be significantly associated with higher levels of perceived severity, perceived vulnerability, response efficacy, and self-efficacy. 79% of the respondents were fully vaccinated. Binary logistic regression analyses found that response efficacy (belief in the effectiveness of the COVID-19 vaccine) and self-efficacy to get vaccinated were significantly associated with the likelihood of being fully vaccinated. Perceived severity of COVID-19 and perceived vulnerability to COVID-19 were not associated with the likelihood of being fully vaccinated. Results indicate that health communications are needed to convince Hispanic adolescents and their parents that the COVID-19 vaccine is effective, and outreach efforts are needed to remove barriers to vaccination among this population.

IntroductionSevere acute respiratory syndrome virus 2 (SARS-CoV-2) has caused over million deaths worldwide, with more than 61,000 deaths in Chile. The Chilean government has implemented a vaccination program against SARS-CoV-2, with over 17.7 million people receiving a complete vaccination scheme. The final target is 18 million individuals. The most common vaccines used in Chile are CoronaVac (Sinovac) and BNT162b2 (Pfizer-Biotech). Given the global need for vaccine boosters to combat the impact of emerging virus variants, studying the immune response to SARS-CoV-2 is crucial. In this study, we characterize the humoral immune response in inoculated volunteers from Chile who received vaccination schemes consisting of two doses of CoronaVac [CoronaVac (2x)], two doses of CoronaVac plus one dose of BNT162b2 [CoronaVac (2x) + BNT162b2 (1x)], and three doses of BNT162b2 [BNT162b2 (3x)].MethodsWe recruited 469 participants from Clínica Dávila in Santiago and the Health Center Víctor Manuel Fernández in the city of Concepción, Chile. Additionally, we included participants who had recovered from COVID-19 but were not vaccinated (RCN). We analyzed antibodies, including anti-N, anti-S1-RBD, and neutralizing antibodies against SARS-CoV-2.ResultsWe found that antibodies against the SARS-CoV-2 nucleoprotein were significantly higher in the CoronaVac (2x) and RCN groups compared to the CoronaVac (2x) + BNT162b2 (1x) or BNT162b2 (3x) groups. However, the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups exhibited a higher concentration of S1-RBD antibodies than the CoronaVac (2x) group and RCN group. There were no significant differences in S1-RBD antibody titers between the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups. Finally, the group immunized with BNT162b2 (3x) had higher levels of neutralizing antibodies compared to the RCN group, as well as the CoronaVac (2x) and CoronaVac (2x) + BNT162b2 (1x) groups.DiscussionThese findings suggest that vaccination induces the secretion of antibodies against SARS-CoV-2, and a booster dose of BNT162b2 is necessary to generate a protective immune response. In the current state of the pandemic, these data support the Ministry of Health of the Government of Chile’s decision to promote heterologous vaccination as they indicate that a significant portion of the Chilean population has neutralizing antibodies against SARS-CoV-2.

Terrain irregularities in natural environments present mobility challenges for autonomous robots and vehicles. Loosely consolidated sandy slopes flow unpredictably when perturbed, often leading to locomotion failure. Systematic experiments with various robot morphologies on flowable terrains feature open‐loop quasistatic gait strategies that remodel the terrain to aid locomotor kinematics. On a sloped terrain of granular media near the critical angle, a laboratory‐scale rover robot induces a flow via a localized fluidization gait to remodel local terrain and succeed in locomotion. A Bayesian optimization machine learning approach that modulates this gait strategy then finds a pattern of selectively fluidizing and solidifying terrain to climb slopes rapidly. In a biped walker robot, a cleated foot design dynamically manipulates the stress fields of flowable slopes. The deeply submerged cleats remodel the shear response of the material by creating jammed regions behind them which then improve forward progression by reducing slip when compared to a flat foot. The “robophysics” approach of systematic experiments exploring terrain reconfiguration combined with future machine learning models of flowable terrain evolution can augment gait discovery for future robots.

Objective: This study examined characteristics associated with being unvaccinated among a sample of university staff and faculty prior to university campus reopening for in-person learning in 2021. Methods: Staff and faculty responded to an email invitation to complete an online survey. Survey questions included demographic data (race/ethnicity, age, sex), COVID-19 knowledge and behaviors, employment specific data including division and subdivision (healthcare vs. non-healthcare related division); and self-reported vaccination status. A multivariable logistic regression analysis was performed to determine significant characteristics associated with the likelihood of being unvaccinated for COVID-19. Results: Participants identifying as Asian and Asian American (aOR = 1.44, 95% CI: 1.06, 1.96), Hispanic/Latinx (aOR = 1.73, 95% CI: 1.21, 2.49) or Multicultural/Other (aOR = 1.72, 95% CI: 1.24, 2.38) had greater odds of being unvaccinated compared to Non-Hispanic White participants. Other characteristics associated with greater likelihood of being unvaccinated included working as a university staff member (vs. faculty) (aOR = 1.69, 95% CI: 1.24. 2.30), decrease in income (aOR = 1.34, 95% CI:1.05, 1.71), inability to work remotely (aOR = 1.48, 95% CI:1.13, 1.93) and not traveling outside of the Los Angeles area (aOR = 1.46, 95% CI: 1.16, 1.83). Political affiliation as an Independent (aOR = 1.39, 95% CI:1.04, 1.85) or as something else (aOR = 3.84, 95% CI: 2.72, 5.41) were more likely to be unvaccinated compared to participants identifying as Democrat. Conclusions: Several factors associated with racial and social disparities may delay the uptake of COVID-19 vaccination. This study highlights the need for targeted educational interventions to promote vaccination among university staff and faculty.

Forest structure depends both on extrinsic factors such as climate and on intrinsic properties such as community composition and diversity. Here, the authors use a dataset of stand structural complexity based on LiDAR measurements to build a global map of structural complexity for primary forests, and find that precipitation variables best explain global patterns of forest structural complexity.

Accurate temperature measurements are needed to monitor and reduce energy use and greenhouse gas emissions in building, industrial, and other processes. This paper describes a temperature sensor instrument, named TempSense, developed for classroom demonstrations of thermal phenomena. The instrument can monitor, record, and visualize data from multiple temperature sensors using a K-type amplifier and thermocouples. It has an accuracy of ±2 deg C from -200 to +700 deg C and an accuracy of ±6 deg C from –270 to +1372 deg C. The instrument uses a USB bridge and the Python language to interface with open-source thermocouple amplifiers without the need for byte-level programming. Its design allows novice experimenters to inspect the build and operation and even customize it to their needs. TempSense can be extended via Python libraries to provide internet communication, visualization, and analysis.

This article states that human rights have evolved from an state’s responsibility focused on the safekeeping of the public sphere to a preoccupation to safeguard the private space. This essay develops the discussion about the relevance of an international regulation to certify of given entrepreneurial processes and how they could help stability and international peace. It points out that many private enterprises and companies related to security issues, make relevant investments in fragile governability or in undergoing armed conflict zones, and the fact that their intervention may foster or diminish conflicts. The war scenarios present the most complex problems due to the general complexity of observing the International Humanitarian Law, as well as for the difficulty to repair damages due to private companies actions. Finally the article summarize the juridical discussion around “mercenarism” and the dilemma set by the regulation or the prohibition of the private military and security enterprises.

This article describes that the military right comes from the constitutional regulation of the use of force. This regulation imposes a particular duty of obedience to the military, that is guarded at the same time, by the military disciplinary right and the military penal code. It informs that although military justice is not forbidden by the international right of the Human Rights, is considered as a regulation of restricted application. Also details, the valid requisites presented by the international right for the military justice, and how jurisprudence of the Inter American system had influenced the reform of the military penal jurisdiction in the continent.

This article delimits the borders de of the associative crime, by using as the main study case the Tarantino’s film “Pulp Fiction” (1994). By means of the analysis and cinematographic interpretation, the main characteristics that shape the “organized crime” are described and illustrated: the existence of a solid organization, the criminal profitable ends and the employment of violence as a criminal method.

Introduction A broad range of stakeholders have called for randomised evidence on the potential clinical benefits and harms of proton therapy, a type of radiation therapy, for patients with breast cancer. Radiation therapy is an important component of curative treatment, reducing cancer recurrence and extending survival. Compared with photon therapy, the international treatment standard, proton therapy reduces incidental radiation to the heart. Our overall objective is to evaluate whether the differences between proton and photon therapy cardiac radiation dose distributions lead to meaningful reductions in cardiac morbidity and mortality after treatment for breast cancer.Methods We are conducting a large scale, multicentre pragmatic randomised clinical trial for patients with breast cancer who will be followed longitudinally for cardiovascular morbidity and mortality, health-related quality of life and cancer control outcomes. A total of 1278 patients with non-metastatic breast cancer will be randomly allocated to receive either photon or proton therapy. The primary outcomes are major cardiovascular events, defined as myocardial infarction, coronary revascularisation, cardiovascular death or hospitalisation for unstable angina, heart failure, valvular disease, arrhythmia or pericardial disease. Secondary endpoints are urgent or unanticipated outpatient or emergency room visits for heart failure, arrhythmia, valvular disease or pericardial disease. The Radiotherapy Comparative Effectiveness (RadComp) Clinical Events Centre will conduct centralised, blinded adjudication of primary outcome events.Ethics and dissemination The RadComp trial has been approved by the institutional review boards of all participating sites. Recruitment began in February 2016. Current version of the protocol is A3, dated 08 November 2018. Dissemination plans include presentations at scientific conferences, scientific publications, stakeholder engagement efforts and presentation to the public via lay media outlets.Trial registration number NCT02603341

The human respiratory syncytial virus (hRSV) is the main etiologic agent of severe lower respiratory tract infections that affect young children throughout the world, associated with significant morbidity and mortality, becoming a serious public health problem globally. Up to date, no licensed vaccines are available to prevent severe hRSV-induced disease, and the generation of safe-effective vaccines has been a challenging task, requiring constant biomedical research aimed to overcome this ailment. Among the difficulties presented by the study of this pathogen, it arises the fact that there is no single animal model that resembles all aspects of the human pathology, which is due to the specificity that this pathogen has for the human host. Thus, for the study of hRSV, different animal models might be employed, depending on the goal of the study. Of all the existing models, the murine model has been the most frequent model of choice for biomedical studies worldwide and has been of great importance at contributing to the development and understanding of vaccines and therapies against hRSV. The most notable use of the murine model is that it is very useful as a first approach in the development of vaccines or therapies such as monoclonal antibodies, suggesting in this way the direction that research could have in other preclinical models that have higher maintenance costs and more complex requirements in its management. However, several additional different models for studying hRSV, such as other rodents, mustelids, ruminants, and non-human primates, have been explored, offering advantages over the murine model. In this review, we discuss the various applications of animal models to the study of hRSV-induced disease and the advantages and disadvantages of each model, highlighting the potential of each model to elucidate different features of the pathology caused by the hRSV infection.

Genomic analysis of the kelp fly Fucellia costalis (Family Anthomyiidae) from Asilomar beach, Pacific Grove, California, resulted in the assembly of its complete mitogenome. The mitogenome is 16,175 bp in length, A + T biased (78.1%), contains 37 genes, a large 1356 bp control region, and has a high-level of gene synteny to other Muscoidea. Phylogenetic analysis of F. costalis fully resolves it in a clade with two members of the Anthomyiidae, Delia platura (8.2% pairwise genetic distance) and D. antiqua (9.2% distance), in a sister position to Scathophaga stercoraria (7.8% distance) from the Scathophagidae. The phylogenetic position and genetic distances of F. costalis support the continued recognition of the subfamily Fucellinae. This identification and data extends the distributional range of F. costalis northward from California to Vancouver Island, Canada.

Fucus spiralis L. is a broadly distributed monoecious intertidal seaweed. The specific status of F. spiralis however is debatable. Here, we contribute to the bioinformatics and systematics of F. spiralis by analysing the complete mitochondrial and plastid genomes of a specimen from California, U.S.A. The F. spiralis mitogenome is 36,396 base pairs (bp) in length and contains 67 genes, and the plastid genome is 125,066 bp in length and contains 171 genes. The F. spiralis genomes are 99.7% and 99.8% similar in nucleotide sequence to F. vesiculosus, and support the revised classification of F. spiralis to Fucus vesiculosus var. spiralis.

Durante las primeras décadas del siglo XX, la minería de altura cobró importancia en la cordillera andina de Arica, estableciéndose una serie de azufreras en los faldeos de los volcanes Tacora y Taapaca. Dichas actividades extractivas incorporaron como mano de obra a comuneros aymaras, como jornaleros para las faenas de las compañías mineras del azufre, producción que activó la economía regional. Los obreros indígenas, en su mayoría de origen boliviano, participaron de un proceso de proletarización que fue regulado por la producción industrial, por los dispositivos legales del Estado chileno y por las diferentes formas de organización social, como los sindicatos. Sobre la base de un corpus de antecedentes documentales, este artículo describe y analiza dichos procesos, intentado relevar a la población indígena andina que se incorporó en el trabajo asalariado de las azufreras, y cómo interactuaron con las autoridades chilenas y con los industriales en un ambiente de tradición y modernidad. Abstract During the first decades of the twentieth century, mining at high altitude became important in the Andes of Arica, establishing a series of sulfur mines on the slopes of volcanoes Tacora and Taapaca. Such Extractive activities incorporated Aymara villagers as laborers for work on sulfur mining companies, production that triggered the regional economy. Indigenous workers, mostly of Bolivian origin, part of a process of proletarianisation which was regulated by industrial production, the legal provisions of the Chilean State and the different forms of social organization and trade unions. Based on a corpus of documentary background, this article describes and analyzes these processes, trying to relieve the Andean indigenous population that was incorporated into the wage labor of the sulfur mines and how they interacted with the Chilean authorities and with the industry in an environment of tradition and modernity.

El presente trabajo describe petrográfica y genéticamente, una serie de hallazgos de peperitas como ejemplos de coexistencia espacial y temporal del magmatismo con la sedimentación en Costa Rica. Los casos se presentan en complejos ígneos básicos (ofiolitas) variando desde mezclas incompletas (megabloques de radiolaritas con diabasas en el Complejo de Nicoya) hasta mezclas completas en varios grados de calizas pelágicas del Maastrictiano-Paleoceno (Formación Golfito) o del Paleoceno con basaltos (Subcomplejo Quepos o Formación Tulín) para dar peperitas brechoides y bulbosas. Dentro del arco Oligo-Mioceno, se tienen ejemplos a lo largo de la cordillera de Talamanca y sus estribaciones, así como en las llanuras de Sarapiquí, representados por peperitas brechoides, fluidales y bulbosas en cuerpos de lava latiandesíticos (Formación Pacacua) o chimeneas peperíticas brechoides en ignimbritas (Miembro Mata de Limón), o posibles peperitas brechoides en los depósitos de flujos de lava del prospecto minero de Crucitas (Formación Cureña), o simples posibles peperitas brechoides en flujos de lava andesíticas (Formación Pacacua en Talamanca), o como brechas hidroclásticas con fragmentos de composición dacítica de Carbonal en Guanacaste, justamente entre las playas Cabuyal y Naranjo. Todas ellas serían los equivalentes proximales del vulcanismo explosivo, efusivo y subvolcánico (domos endógenos y criptodomos) y su concomitancia con la sedimentación fluvial. En el Cuaternario, un ejemplo se da en la base de la Formación Tiribí al contacto con el lacustre de Palmares. Se incluyen en el presente trabajo, además, casos posibles o potenciales. Se espera que la descripción e interpretación de este tipo de rocas ayude a su identificación en otras regiones de Costa Rica y Centroamérica en general, así como una fuente potencial para la prospección de metales valiosos.This paper describes petrographically and genetically, a number of peperites, as examples of spatial and temporal coexistence of magmatism and sedimentation in Costa Rica. The cases are presented in basic igneous complexes (ophiolites), mixtures varying from incomplete (megablocks of radiolarite with diabase in the Nicoya Complex) to complete mixes in various stages of Maastrichtian-Paleocene (Golfito Formation) or Paleocene pelagic limestones with basalts (Quepos Subcomplex or Tulín Formation) to form brechoid and pillowed peperites. Within the Oligo-Miocene arc, there are examples extended along the Talamanca range and its foothills, as well as Sarapiquí’s plains represented for brechoid and bulbous (fluidal) peperites in latiandesitic lavas (Pacacua Formation) or brechoid peperitic pipes in ignimbrites (Mata de Limón Member) or possible brechoid peperites in lavas in the Crucitas mining prospect (Cureña Formation), or simple brechoid peperites in andesitic flow (Pacacua Formation, in Talamanca) or as hydroclastic breccias with fragments of dacitic composition in lava flow deposits of Carbonal Guanacaste, just between the beaches Cabuyal and Naranjo. All these rocks represented proximal equivalents of the explosive, effusive and subvolcanic volcanism (endogenous domes and criptodomes) and his concomitance with the fluvial sedimentation. In Quaternary period, we have a sample in the base of Tiribí Formation in contact with Palmares Lacustrine. Also this paper included possible and potential cases. It hopes that the description and interpretation of this type of rocks helps to its identification in other regions of Costa Rica and Central America in general, as well as a potential source for the exploration of valuable metals.

BackgroundTobacco use prevalence rates are high among Spanish adolescents. Programming to counteract tobacco use is needed.Methods and findingsThe current study provides a one-year follow-up outcome evaluation of Project EX, an eight-session classroom-based curriculum. The intervention was tested using a randomized controlled trial with 1,546 Spanish students, involving three program and three control schools. Compared to the control condition, the program condition revealed a greater reduction in nicotine dependence (p < .05) and CO ppm levels (p < .001), and lower consumption of cigarettes at last month (p = .03).ConclusionsLong-term outcomes of the Project EX classroom-based program are promising for adolescent prevention and possibly cessation in Spain.

OBJECTIVE:This study explores the presence and actions of an electronic cigarette (e-cigarette) brand, Blu, on Twitter to observe how marketing messages are sent and diffused through the retweet (i.e., message forwarding) functionality. Retweet networks enable messages to reach additional Twitter users beyond the sender's local network. We follow messages from their origin through multiple retweets to identify which messages have more reach, and the different users who are exposed. METHODS:We collected three months of publicly available data from Twitter. A combination of techniques in social network analysis and content analysis were applied to determine the various networks of users who are exposed to e-cigarette messages and how the retweet network can affect which messages spread. RESULTS:The Blu retweet network expanded during the study period. Analysis of user profiles combined with network cluster analysis showed that messages of certain topics were only circulated within a community of e-cigarette supporters, while other topics spread further, reaching more general Twitter users who may not support or use e-cigarettes. CONCLUSIONS:Retweet networks can serve as proxy filters for marketing messages, as Twitter users decide which messages they will continue to diffuse among their followers. As certain e-cigarette messages extend beyond their point of origin, the audience being exposed expands beyond the e-cigarette community. Potential implications for health education campaigns include utilizing Twitter and targeting important gatekeepers or hubs that would maximize message diffusion.

Langerhan’s cell histiocytosis (LCH) results from the proliferation of immunophenotypically and functionally immature, morphologically rounded Langerhan’s cells along with eosinophils, macrophages, lymphocytes, and, commonly, multinucleated giant cells. Here we report a case in a 6-year-old boy of differential diagnoses including dermatopathic lymphadenitis (DL), parasitic infection, Kimura’s disease, hypersensitivity reactions, cat-scratch disease, sinus histiocytosis with massive lymphadenopathy (SHML), hyperplasic lymph nodes, and lymphoma.

Este artículo presenta un algoritmo de optimización de colonia de hormigas (Ant Colony Optimization – ACO) multiobjetivo. El algoritmo propuesto es aplicado al problema de la mochila multidimensional. El problema de la mochila multidimensional es un problema de optimización combinatoria que consiste en encontrar un subconjunto de objetos que maximicen el beneficio total mientras se satisfacen ciertas restricciones. Se muestra como el algoritmo propuesto obtiene mejores resultados comparado con un importante algoritmo en un conjunto de datos seleccionado

La computacion movil es un paradigma emergente que surge de la combinacion de tres tecnologias: terminales portatiles, comunicaciones inalambricas y redes de computadoras. En este articulo se introducen los conceptos mas relevantes de la computacion movil enfatizandose lo referente a las terminales portatiles. Ademas se señalan varios de los nuevos problemas que afronta la ingenieria de sistemas y el manejo de la movilidad en internet

SIN RESUMEN

SIN RESUMEN

Don Fernando Carboni E. fue una figura importante en la vida cultural e intelectual de la Universidad de Costa Rica en el ámbitode la Ingeniería, la Física y las Matemáticas. Su labor en esas disciplinas es desconocida para las nuevas generaciones deacadémicos y profesionales. La breve semblanza que presentamos tiene el propósito de dar a conocer su intensa y profunda vidaintelectual, dedicada a la enseñanza y la investigación.Don Fernando Carboni E. dejó de existir el 11 de setiembre del 2001 y su muerte ha dejado un gran vacío en el corazón de susamigos y compañeros de estudio y de trabajo, especialmente en los autores de esta semblanza.

SIN RESUMEN

Durante las primeras décadas del siglo XX, la minería de altura cobró importancia en la cordillera andina de Arica, estableciéndose una serie de azufreras en los faldeos de los volcanes Tacora y Taapaca. Dichas actividades extractivas incorporaron como mano de obra a comuneros aymaras, como jornaleros para las faenas de las compañías mineras del azufre, producción que activó la economía regional. Los obreros indígenas, en su mayoría de origen boliviano, participaron de un proceso de proletarización que fue regulado por la producción industrial, por los dispositivos legales del Estado chileno y por las diferentes formas de organización social, como los sindicatos. Sobre la base de un corpus de antecedentes documentales, este artículo describe y analiza dichos procesos, intentado relevar a la población indígena andina que se incorporó en el trabajo asalariado de las azufreras, y cómo interactuaron con las autoridades chilenas y con los industriales en un ambiente de tradición y modernidad.

This paper presents an agent-based model employing a stochastic optimization search that attempts to find an optimal solution to the online bicycle rebalancing problem for general bike-sharing systems. The algorithm receives the initial and final global state configuration of the system. The main objective of the study is to find the minimum cost path from the initial to the final state. Each agent of the model has four behavioral options that search the optimal configuration; at each iteration, it selects one of these options based on random thresholds and shares the temporary solution found with neighboring agents to improve their search process. The algorithm presents a high exploratory behavior of the search space, which helps to find an approximation away from the local optimal configuration. Additionally, the exchanges between agents allow a consensus on the solutions found. The algorithm has been tested with two different generated configurations using as a basis a real dataset extracted from a functional bike-sharing system collected in 2019. The results show a positive evolution originating from the emerging effect of stochastic selection and interaction between agents. [ABSTRACT FROM AUTHOR]