Random Changes of Accommodation Stimuli: An Automated Extension of the Flippers Accommodative Facility Test

Postprint (author's final draft

Cosolvent Effects of Ethanol and Dissolved Organic Matter on the Aqueous Solubility and Partitioning of Organochlorine Pesticides

In the effort to promote ethanol/gasoline blends as an alternative fuel, potential negative impacts on the environment have been overlooked. Ethanol is produced in the Midwest and transported to the coasts. With the increased usage and the long distances of transport, a spill is reported on the average of every two days. The Midwest is also a location of high pesticide usage. The coincidence of ethanol spills and high pesticide usage in agricultural watersheds raises the concern that ethanol might enhance the concentration of regulated organochlorine pesticides in surface waters. Thus, the objective of this research was to examine the aqueous solubility and partitioning behavior of organochlorine pesticides in the presence of ethanol. The work reported here showed increases in the aqueous solubility of the organochlorine pesticides, dieldrin, lindane, and chlorpyrifos of about 7.46, 3.31, and 6.61 orders of magnitude, respectively, as the ethanol mass fraction increased from 0.0 to 1.0. A two-part log-linear model, with the breakpoint occurring at an ethanol mass fraction of approximately 0.35 was adequate to describe the relationship between the aqueous solubility of these compounds and the ethanol mass fraction, for all the pesticides examined. The breakpoint seems to be independent of the solute and dependent only on the ethanol-water interactions. The increase in the aqueous solubility of pesticides in the presence of ethanol can affect the partitioning behavior of such compounds between an organic liquid phase (e.g. iso-octane and gasoline) and water. This research showed that, in a water/ethanol/organic liquid system, ethanol displays a high preference for the aqueous phase. The aqueous solubility of the organic liquid also increased by orders of magnitude, but its concentration was still considerably lower than that of ethanol. The high concentration of ethanol resulted in an increased concentration of the organochlorine pesticides in the aqueous phase, causing a decrease in the partition coefficient by 4.83, 2.03, and 4.82 orders of magnitude for dieldrin, lindane, and chlorpyrifos, respectively. A log-log relationship between the partition coefficient versus the aqueous solubility of the pesticide was observed, with a slope of -1 and a y-intercept independent of the specific pesticide. Additionally, river sediment contains organic matter that, if dissolved, can further increasing the aqueous solubility of the pesticides. This study showed that the presence of DOM can further increase the aqueous solubility of lindane by over one order of magnitude. The results suggest that both the composition and concentration of DOM are important factors in determining the extent of the impact on the aqueous solubility, with DOM extracted from contaminated river sediments, like that from the Anacostia River, having a greater effect relative to that extracted from natural soils dominated by humic materials. Moreover, the solute’s polarity compatibility with the DOM was an important factor. In particular, a greater enhancement was noted for lindane, since its smaller size and more symmetric configuration made it more compatible with the bonding structure of the DOM.PHDEnvironmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140813/1/oteromar_1.pd

The role of asynchronous and synchronous activities in university academic performance: A comparative study of traditional and inverted class methodologies

Purpose: The objective of this work is to investigate the effect of synchronous and asynchronous activities on the academic performance of university students. For this purpose, the academic results obtained and the involvement and motivation of the student and the teacher in the different learning methodologies involved are analyzed. Students’ perception of the effectiveness of the flipped class with the face-to-face classroom and online methodologies is compared to that of the traditional learning methodology. Design/methodology/approach: Data were collected from undergraduate students in three marketing courses and were analyzed through a quantitative descriptive, quasi-experimental and cross-sectional study. Academic performance with the different learning methodologies and the effect of synchronous and asynchronous activities on academic performance were compared using logistic regression on each course and methodology. Findings: The results showed that academic performance in synchronous and asynchronous activities was better in the flipped class, except for synchronous activities in the online flipped class. In addition, the best academic performance was obtained in the face-to-face inverted classes. The explanatory effect of asynchronous activities on academic performance was also identified. The greatest predictive capacity and the best prognosis were obtained in the online inverted classes. Students expect to obtain satisfactory results with the inverted class methodology and perceive it as effective, although they prefer a mixture of inverted classes and the traditional methodology. Originality/value: We contribute to theoretical and practical research with this new model to study the influence of the flipped learning methodology and asynchronous and synchronous activities on academic performance. We believe that these results, despite the specific and limited scope of the study, will be of great interest to the teaching community and contribute to improving the motivation and performance of students, which constitutes a main challenge in the higher education systemPeer Reviewe

Sensing and Tactile Artificial Muscles from Reactive Materials

Films of conducting polymers can be oxidized and reduced in a reversible way. Any intermediate oxidation state determines an electrochemical equilibrium. Chemical or physical variables acting on the film may modify the equilibrium potential, so that the film acts as a sensor of the variable. The working potential of polypyrrole/DBSA (Dodecylbenzenesulfonic acid) films, oxidized or reduced under constant currents, changes as a function of the working conditions: electrolyte concentration, temperature or mechanical stress. During oxidation, the reactive material is a sensor of the ambient, the consumed electrical energy being the sensing magnitude. Devices based on any of the electrochemical properties of conducting polymers must act simultaneously as sensors of the working conditions. Artificial muscles, as electrochemical actuators constituted by reactive materials, respond to the ambient conditions during actuation. In this way, they can be used as actuators, sensing the surrounding conditions during actuation. Actuating and sensing signals are simultaneously included by the same two connecting wires

Effect of Experimental Conditions in the Accommodation Response in Myopia

SIGNIFICANCE The accommodative response is more affected by the type of refractive error than the method of stimulation, field of view (FOV), or stimulus depth. PURPOSE This study aims to analyze the effect of stimulation method, stimulus depth, and FOV on the accommodation response (AR) for emmetropes (EMM), late-onset myopes (LOM), and early-onset myopes (EOM). METHODS Monocular AR was measured in 26 young observers (n = 9 EMM, n = 8 LOM, n = 9 EOM) under 60 different viewing conditions that were the result of permuting the following factors: (1) stimulation method (free space or Badal lens viewing), (2) stimulus depth (flat or volumetric), (3) FOV (2.5, 4, 8, 10, and 30°), and (4) accommodative stimulus (AS: 0.17, 2.50, and 5.00 diopters [D]). RESULTS Mixed analysis of variance for 2.50 D of AS resulted in a significant effect of refractive group (F = 6.77, P < .01) and FOV (F = 1.26, P = .04). There was also a significant interaction between stimulus depth and FOV (F = 2.73, P = .03) and among stimulation method, FOV, and refractive group (F = 2.42, P = .02). For AS of 5.00 D, there was a significant effect of refractive group (F = 13.88, P < .01) and stimulation method (F = 5.16, P = .03). There was also a significant interaction of stimulation method, stimulus depth, and refractive group (F = 4.08, P = .03). When controlling for all interactions, LOM showed larger lags than EMM and EOM; the AR did not significantly change for fields of 8, 10, and 30°, and it did not significantly differ for different stimulation methods or stimulus depth. CONCLUSIONS Previously reported differences in AR when using lens-based methods compared with free space viewing may be explained by the effect of other factors such as the FOV or the depth of the stimulus. Targets with an FOV of 8 or 10° may be optimal for accurate ARs.Preprin

An induction-aware parameterization for wind farms in the WRF mesoscale model

With the aim of assessing the potential impacts of wind farms on weather and regional climate, in this work an induction-aware modified version of the Wind Farm Parameterization implemented in the WRF model is presented. It uses the undisturbed wind speed, instead of the grid cell velocity, as reference to compute the corresponding momentum sink, source of TKE and power output. The relation between the reference and grid velocity is obtained from a previous calibration process. The modified parameterization is verified by simulating one single wind turbine, showing that the power output becomes independent of the selected horizontal resolution. Finally, the performance of the new parameterization is tested over an utility-scale wind farm. It is applied to compute the wind farm efficiency for different wind directions, under several resolutions and its results compared with former parameterizations.Fil: Mayol, María Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; ArgentinaFil: Navarro Diaz, Gonzalo Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; ArgentinaFil: Saulo, AC. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Otero, Alejandro Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentin

El concepto de familia en México: una revisión desde la mirada antropológica y demográfica

Dada la compleja configuración de la dinámica familiar actual, sus transformaciones y el impacto que estos cambios tiene en la vida social, se vuelve relevante. Pero para el análisis y entendimiento de estos procesos, el primer paso es discutir la forma en que la familia es conceptualizada desde las ciencias sociales. Este es el interés del documento: argumentar sobre la forma en que los cambios en la familia se han visto reflejados o no y en la forma en que se define esta dimensión analítica. Para ello se plantean perspectivas analíticas de la familia desde la antropología, la sociología, la demografía y la historia

Intracellular trafficking and cellular uptake mechanism of PHBV nanoparticles for targeted delivery in epithelial cell lines

Indexación: Web of Science; Scopus; Scielo.Background: Nanotechnology is a science that involves imaging, measurement, modeling and a manipulation of matter at the nanometric scale. One application of this technology is drug delivery systems based on nanoparticles obtained from natural or synthetic sources. An example of these systems is synthetized from poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which is a biodegradable, biocompatible and a low production cost polymer. The aim of this work was to investigate the uptake mechanism of PHBV nanoparticles in two different epithelial cell lines (HeLa and SKOV-3). Results: As a first step, we characterized size, shape and surface charge of nanoparticles using dynamic light scattering and transmission electron microscopy. Intracellular incorporation was evaluated through flow cytometry and fluorescence microscopy using intracellular markers. We concluded that cellular uptake mechanism is carried out in a time, concentration and energy dependent way. Our results showed that nanoparticle uptake displays a cell-specific pattern, since we have observed different colocalization in two different cell lines. In HeLa (Cervical cancer cells) this process may occur via classical endocytosis pathway and some internalization via caveolin-dependent was also observed, whereas in SKOV-3 (Ovarian cancer cells) these patterns were not observed. Rearrangement of actin filaments showed differential nanoparticle internalization patterns for HeLa and SKOV-3. Additionally, final fate of nanoparticles was also determined, showing that in both cell lines, nanoparticles ended up in lysosomes but at different times, where they are finally degraded, thereby releasing their contents. Conclusions: Our results, provide novel insight about PHBV nanoparticles internalization suggesting that for develop a proper drug delivery system is critical understand the uptake mechanism.https://jnanobiotechnology.biomedcentral.com/articles/10.1186/s12951-016-0241-

Stimulus Unpredictability in Time, Magnitude, and Direction on Accommodation

Postprint (author's final draft

Characterization of amorphous LixSi structures from ReaxFF via accelerated exploration of local minima

Motivated by the abundant experimental work in the area of Li-ion batteries, in the present work we characterize via computer simulations the structure of Si-Li amorphous alloys in a wide range of compositions. Using a reactive force field we propose a novel accelerated exploration of local minima to obtain amorphous structures close to equilibrium. The features of this system analyzed for different alloy compositions are the partial radial distribution functions g(r), the first and second nearest neighbour coordination numbers and the short-order structure. The complex structure of the second peak of the Si-Li g(r) is elucidated by a cluster-connection analysis.Fil: Fernandez, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Paz, Sergio Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Otero, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Barraco Diaz, Daniel Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Leiva, Ezequiel Pedro M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin