NO3- selective mini-electrodes as a tool to investigate the NO3- traffic in Chlamydomonas reinhardtii D.

Ion selective NO3- mini-electrodes were used to measure the external NO3- concentration in C. reinhardtii liquid cultures. Electrodes were prepared using glass capillaries (1.5 mm external diameter). Capillaries were cut in 10 cm long pieces, dehydrated for 45 minutes in an oven and silanized by addition of dimethyldichlorosilane in bencene 0.1% (V/V). Once silanized, the capillaries were baked again for 30 minutes. Once cold the capillaries were backfilled with the NO3- ionophore (Fluka: 72549), which contains PVC (5.75% w/w) dissolved in tetrahydrofurane. Then, the NO3- mini-electrodes were stored in dark in a desiccator until tetrahydrofurane gets evaporated. Before use, NO3- selective mini-electrodes were backfilled with 0.1 M NaNO3 and 0.1 M KCl and connected to a high-impedance differential amplifier (WPI FD223). Mini-electrodes were calibrated in N-free Beijerinck medium, which contains 0.1 mM Cl-. In those conditions, electrodes calibration slope was 54 mV/p NO3- in the range 1 - 1000 µM NO3-. The mini-electrodes were used to continuous monitoring of the external NO3- concentration in liquid culture of different C. reinhardtii strains, incubated in N-free Beijerinck medium supplemented with 100 µM NO3Na. Previous to the assays, strains were N starved for 6 days. In the light, wild type strain uptakes NO3- at a rate of 15 nmol NO3-·106 cells-1·h-1, in the dark this rate was one third of this figure. After 5 h, the external NO3- levelled off at 10 µM in the light and around 30 µM in the dark. C. reinhardtii cells cultured in the presence of 2 mM NO3NH4 do not show significant NO3- uptake nor a mutant strain, defective in nitrate transport and having an active nitrate reductase. However, a mutant strain lacking the nitrate reductase shows an enhanced NO3- uptake rate, compared with the value obtained for the wild type in the light.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Strengthening the process of learning the quadratic function in the framework of the van ice model using GeoGebra in the ninth grade students of the Los Patios Municipal Technical Institute

En este trabajo se describe un estudio de investigación cualitativa con metodología investigación-acción, acerca de la función cuadrática en el marco del modelo de Van Hiele utilizando el software Geogebra para fortalecer el proceso de aprendizaje de los estudiantes del grado noveno del Instituto Técnico Municipal Los Patios. El desarrollo de la propuesta se hizo en tres proyectos pedagógicos de aula: acercamiento al concepto de función, la función cuadrática y la ecuación cuadrática. Estos fueron planteados, en primer lugar con situaciones de variación como la trayectoria parabólica, la caída libre y situaciones de área, que sirvieron para que los participantes abordaran el objeto de estudio en situaciones de la vida cotidiana y en segundo lugar desde diferentes registros de representación de la función como el simbólico algebraico, el cartesiano y el registro tabular y la traducción entre estos. Esta propuesta se diseñó para mejorar el componente numérico variacional, ya que en el análisis de los resultados de los estudiantes en las pruebas saber de los años 2015 y 2016 se evidenciaron debilidades y se constituyeron en una gran oportunidad para implementar acciones pedagógicas de mejoramiento. El análisis de la información se realizó a través de diferentes fuentes de recolección de la información como el diario pedagógico, fotografías, la observación directa, videos, pre-test y pos-test. En conclusión se obtuvo que los niveles de razonamiento de Van Hiele y el software Geogebra fueron apropiados para mejorar los aprendizajes de los estudiantes en el estudio de la función cuadrática, porque permitió desde situaciones específicas generar habilidades como análisis de gráficos, evaluación de expresiones algebraicas y dominio de un sistema de representación a otro todo dentro de un ambiente dinámico e interactivo.Introducción 17 1. Contextualización de la Investigación 19 1.1 Situación Problémica 21 1.1.1 Descripción del problema 21 1.1.2 Formulación del problema 25 1.1.3 Objetivos 25 1.1.3.1 Objetivo general 25 1.1.3.2 Objetivos específicos 25 1.2 Justificación 26 1.3 Contexto 31 1.3.1 Contexto local 31 1.3.2 Contexto institucional 31 1.3.3 Filosofía de la institución 33 1.3.4 Visión 33 1.3.5 Misión 33 1.3.6 Principios institucionales 33 2. Marco Referencial 35 2.1 Antecedentes Investigativos 35 2.1.1 Antecedentes internacionales 35 2.1.2 Antecedentes nacionales 38 2.1.3 Antecedentes locales 41 2.2 Marco Teórico 43 2.2.1 Proceso de Aprendizaje 43 2.2.1.1 El aprendizaje como proceso de desarrollo cognitivo 43 2.2.1.2 El aprendizaje en el constructivismo 45 2.2.1.3 Aprendizaje significativo 46 2.2.1.4 El proceso de aprendizaje de los estudiantes 48 2.2.2 Modelo de Van Hiele 49 2.2.2.1 Niveles de razonamientos 50 2.2.2.2 Fases de aprendizaje 54 2.2.2.3 Evaluación en el modelo de Van Hiele 54 2.2.2.4 El modelo de Van Hiele y la enseñanza-aprendizaje de las matemáticas 55 2.2.3 Pensamiento variacional y sistemas algebraicos 57 2.2.3.1 La función 58 2.2.3.1.1 Desarrollo histórico de la función en los siglos XIX y XX 59 2.2.3.1.2 Sistemas de representación de la función 60 2.2.3.1.3 La definición de función y sus elementos 63 2.2.3.2 La función cuadrática como objeto de conocimiento 67 2.2.3.2.1 Revisión histórica de la función cuadrática 67 2.2.3.2.2 Sistemas de representación de la función cuadrática 70 2.2.3.2.3 Definición y elementos de la función cuadrática 72 2.2.4 Las Tic en la educación 79 2.2.4.1 GeoGebra (GeoGebra - Dynamic Mathematics for Everyone) 80 2.3 Marco Legal 83 3. Diseño Metodológico 86 3.1 Tipo de Investigación 86 3.2 Proceso de Investigación 88 3.2.1 Observación en el aula 88 3.2.2 Exploración de estrategias 90 3.2.3 Proceso de aplicación de estrategias 91 3.2.3.1 Fase 1 91 3.2.3.2 Fase 2 97 3.2.3.2.1 Proyecto I: Acercamiento al concepto de función 99 3.2.3.2.2 Proyecto II - Tipos de función: la función cuadrática 101 3.2.3.2.3 proyecto de aula III: la ecuación cuadrática 104 3.3 Población y Muestra 106 3.4 Instrumentos para la Recolección 110 3.4.1 Diario pedagógico 111 3.4.2 Datos fotográficos 112 3.4.3 La observación directa 112 3.4.4 grabaciones de videos 112 3.4.5 Pre-test 113 3.4.6 Pos-test 113 3.5 Validación de los Instrumentos 113 3.6 Resultados y Discusión 114 3.6.1 Análisis de resultados fase I: año 2016 118 3.6.1.1 Resultados de la fase 1 118 3.6.2 Resultados y discusión de la fase 2 (propuesta ajustada en el año 2017) 133 3.6.2.1 Análisis del diagnóstico de la propuesta de intervención 133 3.6.2.2 Análisis de la Exploración de las herramientas del software de uso libre GeoGebra 137 3.6.2.3 Análisis proyecto de aula 1: acercamiento del concepto de función 139 3.6.2.4 Análisis proyecto de aula 2: la función cuadrática 155 3.6.2.5 Análisis de la evaluación del proyecto de aula I y II 177 3.6.2.6 Análisis y discusión del proyecto de aula III: La ecuación cuadrática 185 3.6.2.7 Mapa de relaciones y red de relaciones entre categorías 189 3.7 Principios Éticos 192 4. Propuesta Pedagógica 193 4.1 Presentación de la Propuesta 193 4.2 Justificación 195 4.3 Objetivos 196 4.3.1 Objetivo general 197 4.3.2 Objetivos específicos 197 4.4 Competencias y Aprendizajes a Desarrollar 197 4.5 Metodología 199 4.6 Fundamentos Pedagógicos 200 4.7 Diseño de Actividades 2011 4.8 Cierre de la Propuesta Pedagógica 282 5. Conclusiones 283 6. Recomendaciones 286 Referencias Bibliográficas 287 Anexos 295MaestríaThis paper describes a qualitative research study with research-action methodology, about the quadratic function in the framework of the Van Hiele model using Geogebra software to strengthen the learning process of the ninth grade students of the Instituto Técnico Municipal Los Patios. The development of the proposal was done in three pedagogical projects of classroom: approach to the concept of function, the quadratic function and the quadratic equation. These were first raised with situations of variation such as the parabolic trajectory, free fall and area situations, which served for the participants to approach the object of study in situations of daily life and secondly with different records of representation of the function as the algebraic symbolic, the Cartesian and the tabular register and the translation between them. This proposal was designed to improve the variational numerical component, since in the analysis of the students' results in the knowledge tests of the years 2015 and 2016 weaknesses were evidenced and they were a great opportunity to implement pedagogical improvement actions The analysis of the information was made through different sources of information collection such as the pedagogical journal, photographs, direct observation, videos, pre-test and post-test. In conclusion it was obtained that the levels of Van Hiele reasoning and the software Geogebra were appropriate to improve the learning of the students in the study of the quadratic function, because it allowed specific situations to generate skills such as analysis of graphics, evaluation of algebraic expressions and mastery of one system of representation to another all within a dynamic and interactive environment

Eksplicitna regulacija sile robotskog manipulatora aktivnim prigušenjem brzine

This paper presents a new interaction control structure that generates a family of explicit force regulators for robot manipulators. The proposed structure includes a term of a class of proportional-type functions in terms of force error; the force error is defined as the difference between a desired force and the actual force measured with a force sensor located at the end-effector. Also, the structure includes a generalized active velocity damping term in order to have a control of the energy dissipation, and a term used to compensate the gravity forces of the links. The stability analysis is performed in Lyapunov sense. An experimental comparison of two new explicit force regulators and the linear proportional structure, on a three degree-of-freedom, direct-drive robot, is presented. Also, proofs of the most important properties of the Cartesian dynamic model, are presented.Ovaj rad predstavlja novu interakcijsku kontrolnu strukturu koja predstavlja skupinu exsplicitnih regulatora sile za robotske manipulatore. Predložena struktura uključuje član klase funkcija proporcionalnog tipa u smilsu pogreške sile; pogreška sile se definira kao razlika između željene sile i stvarne sile koju mjere senzori postavljeni na kraju manipulatora. Također, struktura uključuje član za generalizirano aktvino prigušenje brzine kako bi se omogućila kontrola disipacije energije i član kojim se kompenzira utjecaj sile gravitacije na članke manipulatora. Analiza stabilnosti je napravljena u smislu Lyapunova. Prikazana je eksperimentalna usporedba dva nova eksplicitna regulatora sile i linearno-proporcionalne strukture na robotu s direktnim pogonom i tri stupnja slobode. Također su prikazani dokazi najvažnijih svojstava kartezijskog dinamičnog modela

Neograničeni regulatori s promijenjivim pojačanjem za upravljanje robotskim manipulatorima s direktnim pogonom

This paper addresses the position-control problem with variable gains for robot manipulators. We present a new regulator based on a hyperbolic-sine structure with tuning rules for control gains. It is demonstrated that the equilibrium point of the closed-loop system is globally, asymptotically stable according to Lyapunov theory. By using a similar methodology, this concept can be extended to other unbounded controllers such as PD and PID. In order to show the usefulness of the proposed scheme and with the purpose of validating its asymptotical stability property, an experimental comparison involving constant gains controllers, for example: simple PD, PID and hyperbolic-tangent schemes vs variable-gains hyperbolic-sine and PD control schemes, was performed by using a three degree-of-freedom, direct-drive robot manipulator.Ovaj rad se bavi problemom kontrole pozicije s promjenjivim pojačanjem robotskog manipulatora. U radu je predstavljen novi regulator baziran na hiperbolično-sinusnoj stukturi s pravilima ugađanja upravljačkih pojačanja. Pokazano je da je točka ravnoteže sustava u zatvorenoj petlji globalno i asimptotski stabilna prema Lzapunovljevoj teoriji stabilnosti. Korištenjem slilčne metodologije, predstavljeni koncept se može primijeniti na ostale neograničene kontrolere, npr. PD i PID. Kako bi pokazali korisnost predložene sheme i s ciljem provjere asimptotske stabilnosti, provedena je eksperimentalna usporedba između kontolera s konstantnim pojačanjem (npr. jednostavni PD, PID i hiperbolični-tangencijalna shema) i hiperbolično-sinusnih i PD upravljačkih shema s promjenjivim pojačanjem korištenjem robotskog manipulatora s direktnim pogonom i tri stupnja slobode

Variable-Angle Phase-Shifted PWM for Multilevel Three-Cell Cascaded H-bridge Converters

Multilevel cascaded H-bridge converters have become a mature technology for applications where high-power medium ac voltages are required. Normal operation of multilevel cascaded H-bridge converters assumes that all power cells have the same dc voltage, and each power cell generates the same voltage averaged over a sampling period using a conventional phase-shifted pulse width modulation (PWM) technique. However, this modulation method does not achieve good results under unbalanced operation per H-bridge in the power converter, which may happen in grid-connected applications such as photovoltaic or battery energy storage systems. In the paper, a simplified mathematical analysis of the phase-shifted PWM technique is presented. In addition, a modification of this conventional modulation method using variable shift angles between the power cells is introduced. This modification leads to the elimination of harmonic distortion of low-order harmonics due to the switching (triangular carrier frequency and its multiples) even under unbalanced operational conditions. The analysis is particularized for a three-cell cascaded H-bridge converter, and experimental results are presented to demonstrate the good performance of the proposed modulation method

Algae-Bacteria Consortia as a Strategy to Enhance H2 Production

Biological hydrogen production by microalgae is a potential sustainable, renewable and clean source of energy. However, many barriers limiting photohydrogen production in these microorganisms remain unsolved. In order to explore this potential and make biohydrogen industrially affordable, the unicellular microalga Chlamydomonas reinhardtii is used as a model system to solve barriers and identify new approaches that can improve hydrogen production. Recently, Chlamydomonas–bacteria consortia have opened a new window to improve biohydrogen production. In this study, we review the different consortia that have been successfully employed and analyze the factors that could be behind the improved H2 production

Role of Nitrate Reductase in NO Production in Photosynthetic Eukaryotes

Nitric oxide is a gaseous secondary messenger that is critical for proper cell signaling and plant survival when exposed to stress. Nitric oxide (NO) synthesis in plants, under standard phototrophic oxygenic conditions, has long been a very controversial issue. A few algal strains contain NO synthase (NOS), which appears to be absent in all other algae and land plants. The experimental data have led to the hypothesis that molybdoenzyme nitrate reductase (NR) is the main enzyme responsible for NO production in most plants. Recently, NR was found to be a necessary partner in a dual system that also includes another molybdoenzyme, which was renamed NO-forming nitrite reductase (NOFNiR). This enzyme produces NO independently of the molybdenum center of NR and depends on the NR electron transport chain from NAD(P)H to heme. Under the circumstances in which NR is not present or active, the existence of another NO-forming system that is similar to the NOS system would account for NO production and NO effects. PII protein, which senses and integrates the signals of the C–N balance in the cell, likely has an important role in organizing cell responses. Here, we critically analyze these topics

Study of Different Variants of Mo Enzyme crARC and the Interaction with Its Partners crCytb5-R and crCytb5-1

The mARC (mitochondrial Amidoxime Reducing Component) proteins are recently discovered molybdenum (Mo) Cofactor containing enzymes. They are involved in the reduction of several N-hydroxylated compounds (NHC) and nitrite. Some NHC are prodrugs containing an amidoxime structure or mutagens such as 6-hydroxylaminopurine (HAP). We have studied this protein in the green alga Chlamydomonas reinhardtii (crARC). Interestingly, all the ARC proteins need the reducing power supplied by other proteins. It is known that crARC requires a cytochrome b5 (crCytb5-1) and a cytochrome b5 reductase (crCytb5-R) that form an electron transport chain from NADH to the substrates. Here, we have investigated NHC reduction by crARC, the interaction with its partners and the function of important conserved amino acids. Interactions among crARC, crCytb5-1 and crCytb5-R have been studied by size-exclusion chromatography. A protein complex between crARC, crCytb5-1 and crCytb5-R was identified. Twelve conserved crARC amino acids have been substituted by alanine by in vitro mutagenesis. We have determined that the amino acids D182, F210 and R276 are essential for NHC reduction activity, R276 is important and F210 is critical for the Mo Cofactor chelation. Finally, the crARC C-termini were shown to be involved in protein aggregation or oligomerizatio

Nitrate Reductase Regulates Plant Nitric Oxide Homeostasis

Nitrate reductase (NR) is a key enzyme for nitrogen acquisition by plants, algae, yeasts, and fungi. Nitrate, its main substrate, is required for signaling and is widely distributed in diverse tissues in plants. In addition, NR has been proposed as an important enzymatic source of nitric oxide (NO). Recently, NR has been shown to play a role in NO homeostasis by supplying electrons from NAD(P)H through its diaphorase/dehydrogenase domain both to a truncated hemoglobin THB1, which scavenges NO by its dioxygenase activity, and to the molybdoenzyme NO-forming nitrite reductase (NOFNiR) that is responsible for NO synthesis from nitrite. We review how NR may play a central role in plant biology by controlling the amounts of NO, a key signaling molecule in plant cells

Identification of the MAPK Cascade and its Relationship with Nitrogen Metabolism in the Green Alga Chlamydomonasreinhardtii

The mitogen activated protein kinases (MAPKs) form part of a signaling cascade through phosphorylation reactions conserved in all eukaryotic organisms. The MAPK cascades are mainly composed by threeproteins, MAPKKKs, MAPKKs and MAPKs. Some signals induce MAPKKK-mediated phosphorylation and activation of MAPKK that phosphorylate and activate MAPK. Afterward, MAPKs can act either in the cytoplasm or be imported into the nucleus to activate other proteins or transcription factors. In the green microalga Chlamydomonasreinhardtii the pathway for nitrogen (N) assimilation is well characterized, yet its regulation still has many unknown features. Nitric oxide (NO) is a fundamental signal molecule for N regulation, where nitrate reductase (NR) plays a central role in its synthesis. The MAPK cascades could be regulating N assimilation, since it has been described that the phosphorylation of NR by MAPK6 promotes NO production in Arabidopsis thaliana. We have identified the proteins involved in the MAPK cascades in Chlamydomonasreinhardtii, finding 17 MAPKs, 2 MAPKKs and 108 MAPKKKs (11 MEKK-, 94 RAF- and 3 ZIK-type) that have been structurally and phylogenetically characterized. The genetic expressions of MAPKs and the MAPKK were slightly regulated by N. However, the genetic expressions of MAPKKKs RAF14 and RAF79 showed a very strong repression by ammonium, which suggests that they may have a key role in the regulation of N assimilation, encouraging to further analyze in detail the role of MAPK cascades in the regulation of N metabolism