Cysteine transport through excitatory amino acid transporter 3 (EAAT3)

Excitatory amino acid transporters (EAATs) limit glutamatergic signaling and maintain extracellular glutamate concentrations below neurotoxic levels. Of the five known EAAT isoforms (EAATs 1-5), only the neuronal isoform, EAAT3 (EAAC1), can efficiently transport the uncharged amino acid L-cysteine. EAAT3-mediated cysteine transport has been proposed to be a primary mechanism used by neurons to obtain cysteine for the synthesis of glutathione, a key molecule in preventing oxidative stress and neuronal toxicity. The molecular mechanisms underlying the selective transport of cysteine by EAAT3 have not been elucidated. Here we propose that the transport of cysteine through EAAT3 requires formation of the thiolate form of cysteine in the binding site. Using Xenopus oocytes and HEK293 cells expressing EAAT2 and EAAT3, we assessed the transport kinetics of different substrates and measured transporter-associated currents electrophysiologically. Our results show that L-selenocysteine, a cysteine analog that forms a negatively-charged selenolate ion at physiological pH, is efficiently transported by EAATs 1-3 and has a much higher apparent affinity for transport when compared to cysteine. Using a membrane tethered GFP variant to monitor intracellular pH changes associated with transport activity, we observed that transport of either L-glutamate or L-selenocysteine by EAAT3 decreased intracellular pH, whereas transport of cysteine resulted in cytoplasmic alkalinization. No change in pH was observed when cysteine was applied to cells expressing EAAT2, which displays negligible transport of cysteine. Under conditions that favor release of intracellular substrates through EAAT3 we observed release of labeled intracellular glutamate but did not detect cysteine release. Our results support a model whereby cysteine transport through EAAT3 is facilitated through cysteine de-protonation and that once inside, the thiolate is rapidly re-protonated. Moreover, these findings suggest that cysteine transport is predominantly unidirectional and that reverse transport does not contribute to depletion of intracellular cysteine pools

Diseño un controlador robusto basado en observador para el modelo lineal de un helicóptero de un grado de libertad (VTOL)

Este artículo propone un controlador basado en observador para un modelo de helicóptero tipo VTOL de un grado de libertad. El objetivo de control es mantener la posición del VTOL en un punto de operación, a pesar de las incertidumbres ocasionadas por inexactitud en el modelo y ruido en las mediciones. El controlador y el observador son diseñados con base en algoritmos que inducen modos deslizantes en el sistema en lazo cerrado, ofreciendo características de robustez y convergencia en tiempo finito. Los resultados de simulación muestran un buen desempeño del esquema propuesto tanto en condiciones de ausencia de ruido como cuando se consideran mediciones ruidosas.Universidad Nacional de ColombiaCinvestavColcienciasBanco Mundia

Problem solving strategy in the teaching and learning processes of quantitative reasoning

The study presents an analysis of Polya's problem-solving strategy used in the training processes of quantitative reasoning competence in students of the Universidad Simón Bolívar, San José de Cúcuta, Colombia. The research was based on a descriptive design and had an intentional sample of 58 students who were studying the sciences and general competencies elective. For the collection of information, a diagnostic test (pre-test) and a final test (post-test) were applied, in order to check the incidence of the applied strategy. The results showed a significant improvement in the final results obtained by the students in each of the processes formed: interpretation, representation and modeling, and argumentation

Trans-complexity: a management fad or a mathematical construct

Trans–complex organizations concept has been introduced in the management science, even becoming an object of study. In the global context, definitions, concepts, research and philosophical or practical proposals have emerged for the understanding of organizations from a trans-complex perspective. In this work, a critical position of trans-complexity is presented as a historical discovery that associates a new characterization of phenomena: for example, in exchange for trans–complex organizations, a trans-complex epistemic vision of social organizations is proposed. Thus, the trans-complexity is ratified not as a quality, but as a requirement of epistemic order of scientific research. From this perspective, that complex organization can be explained through elements such as uncertainty, chaos and self-organization, with an epistemological explanation of systems theory, decision theory and dynamic systems theory. This paper shows the trans-complexity more than a management fad, an analysis model or a management topic, as an element to be incorporated by researchers in the construction of theoretical frameworks and methodical designs of their researches in order to purpose significant contributions to science, and to the organization itself, based on such important mathematical theories

Testing GeoGebra as an effective tool to improve the understanding of the concept of limit on engineering students

The impact GeoGebra on the teaching of the concept of limit was analyzed. Two groups of engineering students, studying differential calculus, served as control and test groups. The traditional teaching, based on examples solved by hand, was given to the control group while a series of activities involving the usage of the mathematical software GeoGebra were applied in an attempt of improving the degree of assimilation on the concept of limits

Learning the concept of integral through the appropriation of the competence in Riemann sums

It is proposed that the difficulty of engineering students into understanding the concept of the integral, as a way for calculating the area under a curve, can be overcame if students are taught how to translate it into the problem of calculating a Riemann sum. A series of applied problems are proposed to provide a frame that required to calculate the area under a curve to two groups of students. For one of these groups, Geogebra was proposed as a tool that could be used to maintain the focus of students into the concepts, by providing ways to easily calculate and visualize the solutions, while the other group reached to the solutions by analytically making all the calculations. Evidence was found that, to a confidence level of 95%, Riemann sums calculated with Geogebra reduce the score difference in context problems requiring the calculation of integrals, helping students to reach a better understanding on the concept of the integral as the area under the curve of a given function

In vitro dissolution characteristics of patent, generic and similar brands of naproxen in various dissolution media

Purpose: To investigate the dissolution properties of various brands of naproxen in four dissolution media in order to forecast their biological availability. Methods: Dissolution tests were carried out in a dissolution tester with 48 tablets of different naproxen brands in 900 mL of 0.1 M phosphate buffer, pH 7.4. Subsequently, the medium was modified with 600 mL of buffer plus 300 mL of cola drink, grapefruit or milk. Each sample was taken and brought to a concentration approximating that of a reference solution. Absorbance at 332 nm was determined and the dissolution, Q, was calculated (Q values ≥ 80.0 ± 5 % were acceptable). Results: Dissolution in buffer was > 85 %. In cola drink, it was < 80 %, while in grapefruit juice, it was in the range of 7 - 68 %. Using 2-way ANOVA, these media and the three naproxen brands showed significant differences (F = 68.90, p = 0.0000; F = 23.18, p = 0.0000). With Fisher's LSD test, two of these media contributed consistently to dissolution, and the three drug brands showed statistically different dissolution profiles (p ≤ 0.05). Conclusion: Caution must be exercised cola drink, grapefruit juice and milk are used to administered naproxen as the biological availability of the drug may be altered

Life Project for Adolescents: A Concept Analysis

It is essential to identify protective factors during adolescence due to its high incidence on risk behaviors. One of these factors is to have a life project that influences adolescent decision-making. The concept of life project has mainly been linked to teen pregnancy, depression and suicide; however, some authors agree that the concept is not clearly defined. Therefore, the objective of this paper is to define the concept of adolescent life project, using the methodology developed by Walker and Avant for concept analysis. The following steps were followed are: select a concept, determining the purpose of analysis, identifying all uses of the concept, determining the defining attributes, identifying a model, a borderline and a contrary cases, identifying history and consequences of the concept, and finally defining empirical referents. After the analysis, the final definition of the concept of adolescent life project includes the set of desires, future plans and actions necessary to accomplish it that influence the adolescent decisions. Knowing the importance of this concept when working with adolescents may guide development more effective interventions

The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Angular clustering tomography and its cosmological implications

We investigate the cosmological implications of studying galaxy clustering using a tomographic approach applied to the final BOSS DR12 galaxy sample, including both auto- and cross-correlation functions between redshift shells. We model the signal of the full shape of the angular correlation function, $\omega(\theta)$, in redshift bins using state-of-the-art modelling of non-linearities, bias and redshift-space distortions. We present results on the redshift evolution of the linear bias of BOSS galaxies, which cannot be obtained with traditional methods for galaxy-clustering analysis. We also obtain constraints on cosmological parameters, combining this tomographic analysis with measurements of the cosmic microwave background (CMB) and type Ia supernova (SNIa). We explore a number of cosmological models, including the standard $\Lambda$CDM model and its most interesting extensions, such as deviations from w_\rm{DE} = -1, non-minimal neutrino masses, spatial curvature and deviations from general relativity using the growth-index $\gamma$ parametrisation. These results are, in general, comparable to the most precise present-day constraints on cosmological parameters, and show very good agreement with the standard model. In particular, combining CMB, $\omega(\theta)$ and SNIa, we find a value of w_\rm{DE} consistent with $-1$ to a precision better than 5\% when it is assumed to be constant in time, and better than 6\% when we also allow for a spatially-curved Universe.Comment: 21 pages, 18 figures, accepted for publication MNRAS. The data used in this analysis is publicly available at https://sdss3.org/science/boss_publications.ph

Enhancement of the sensitivity of a temperature sensor based on fiber Bragg gratings via weak value amplification

"This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.40.003962. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law"We present a proof-of-concept experiment aimed at increasing the sensitivity of Fiber-Bragg-gratings temperature sensors by making use of a weak-value-amplification scheme. The technique requires only linear optics elements for its implementation and appears as a promising method for increasing the sensitivity than state-of the-art sensors can currently provide. The device implemented here is able to generate a shift of the centroid of the spectrum of a pulse of ∼0.035 nm∕°C, a nearly fourfold increase in sensitivity over the same fiber-Bragg-grating system interrogated using standard methods.Severo Ochoa program; Fundacio Privada Cellex, Barcelona; Research Excellency Award Program GVA PROMETEO 2013/012; Spanish MCINN (TEC2014-53727-C2-1-R).Salazar-Serrano, L.; Barrera Vilar, D.; Amaya Ocampo, WA.; Sales Maicas, S.; Pruneri, V.; Capmany Francoy, J.; Torres, J. (2015). Enhancement of the sensitivity of a temperature sensor based on fiber Bragg gratings via weak value amplification. Optics Letters. 40(17):3962-3965. https://doi.org/10.1364/OL.40.003962S396239654017Aharonov, Y., Albert, D. Z., & Vaidman, L. (1988). How the result of a measurement of a component of the spin of a spin-1/2particle can turn out to be 100. Physical Review Letters, 60(14), 1351-1354. doi:10.1103/physrevlett.60.1351Duck, I. M., Stevenson, P. M., & Sudarshan, E. C. G. (1989). The sense in which a «weak measurement» of a spin-½ particle’s spin component yields a value 100. Physical Review D, 40(6), 2112-2117. doi:10.1103/physrevd.40.2112Howell, J. C., Starling, D. J., Dixon, P. B., Vudyasetu, P. K., & Jordan, A. N. (2010). Interferometric weak value deflections: Quantum and classical treatments. Physical Review A, 81(3). doi:10.1103/physreva.81.033813Torres, J. P., Puentes, G., Hermosa, N., & Salazar-Serrano, L. J. (2012). Weak interference in the high-signal regime. Optics Express, 20(17), 18869. doi:10.1364/oe.20.018869Ritchie, N. W. M., Story, J. G., & Hulet, R. G. (1991). Realization of a measurement of a ‘‘weak value’’. Physical Review Letters, 66(9), 1107-1110. doi:10.1103/physrevlett.66.1107Hosten, O., & Kwiat, P. (2008). Observation of the Spin Hall Effect of Light via Weak Measurements. Science, 319(5864), 787-790. doi:10.1126/science.1152697Dixon, P. B., Starling, D. J., Jordan, A. N., & Howell, J. C. (2009). Ultrasensitive Beam Deflection Measurement via Interferometric Weak Value Amplification. Physical Review Letters, 102(17). doi:10.1103/physrevlett.102.173601Starling, D. J., Dixon, P. B., Jordan, A. N., & Howell, J. C. (2010). Precision frequency measurements with interferometric weak values. Physical Review A, 82(6). doi:10.1103/physreva.82.063822Xu, X.-Y., Kedem, Y., Sun, K., Vaidman, L., Li, C.-F., & Guo, G.-C. (2013). Phase Estimation with Weak Measurement Using a White Light Source. Physical Review Letters, 111(3). doi:10.1103/physrevlett.111.033604Salazar-Serrano, L. J., Janner, D., Brunner, N., Pruneri, V., & Torres, J. P. (2014). Measurement of sub-pulse-width temporal delays via spectral interference induced by weak value amplification. Physical Review A, 89(1). doi:10.1103/physreva.89.012126TAHIR, B. A., ALI, J., & ABDUL RAHMAN, R. (2009). FIBER BRAGG GRATING BASED SYSTEM FOR TEMPERATURE MEASUREMENTS. International Journal of Modern Physics B, 23(10), 2349-2356. doi:10.1142/s0217979209052091Ricchiuti, A. L., Barrera, D., Nonaka, K., & Sales, S. (2014). Temperature gradient sensor based on a long-fiber Bragg grating and time-frequency analysis. Optics Letters, 39(19), 5729. doi:10.1364/ol.39.005729Egan, P., & Stone, J. A. (2012). Weak-value thermostat with 02 mK precision. Optics Letters, 37(23), 4991. doi:10.1364/ol.37.004991Salazar-Serrano, L. J., Valencia, A., & Torres, J. P. (2014). Observation of spectral interference for any path difference in an interferometer. Optics Letters, 39(15), 4478. doi:10.1364/ol.39.00447