Determining how stable network oscillations arise from neuronal and synaptic mechanisms

Many animal behaviors involve the generation of rhythmic patterns and movements. These rhythmic patterns are commonly mediated by neural networks that produce an oscillatory activity pattern, where different neurons maintain a relative phase relationship. This thesis examines the relationships between the cellular and synaptic properties that give rise to stable activity in the form of phase maintenance, across different frequencies in a well-suited model system, the pyloric network of the crab Cancer borealis. The pyloric network has endogenously oscillating ‘pacemaker’ neurons that inhibit ‘follower’ neurons, which in turn feed back onto the pacemaker neurons. The focus of this thesis was to determine the methods by which phase maintenance is achieved in an oscillatory network. This thesis examines the idea that phase maintenance occurs through the actions of intrinsic properties of isolated neurons or through the dynamics of their synaptic connections or both. A combination of pharmacological and electrophysiological techniques a used to show how identified membrane properties and short-term synaptic plasticity are involved with phase maintenance over a range of biologically relevant oscillation frequencies. To examine whether network stability is due to the characteristic stable activity of the identified pyloric neuron types, the hypothesis that phase maintenance is an inherent property of synaptically-isolated individual neurons in the pyloric network was first tested. A set of parameters were determined (frequency-dependent activity profile) to define the response of each isolated pyloric neuron to sinusoidal input at different frequencies. The parameters that define the activity profile are: burst onset phase, burst end phase, resonance frequency and intra-burst spike frequency. Each pyloric neuron type was found to possess a unique activity profile, indicating that the individual neuron types are tuned to produce a particular activity pattern at different frequencies depending on their role in the network. To elucidate the biophysical properties underlying the frequency-dependent activity profiles of the neurons, the hyperpolarization activated current (Ih) was measured and found to possess frequency-dependent properties. This implies that Ih has a different influence on the activity phase of pyloric neurons at different frequencies. Additionally, it was found that the Ih contribution to the burst onset phase depends on the neuron type: in the pacemaker group neurons (PD) it had no influence on the burst onset phase at any frequency whereas in follower neurons it acted to advance the onset phase in one neuron type (LP) and, paradoxically, to delay it in a different neuron type (PY). The results from this part of the study provided evidence that stability is due in part to the intrinsic neuronal properties but that these intrinsic properties do not fully explain network stability. To address the contribution of pyloric synapses to network stability, the mechanisms by which synapses promote phase maintenance were investigated. An artificial synapse that mimicked the feedforward PD to LP synapse, was used so that the synaptic parameters could be varied in a controlled manner in order to examine the influence of the properties of this synapse on the postsynaptic LP neuron. It was found that a static synapse with fixed parameters (such as strength and peak phase) across frequencies cannot result in a constant activity phase in the LP neuron. However, if the synaptic strength decreases and the peak phase is delayed as a function of frequency, the LP neuron can maintain a constant activity phase across a large range of frequencies. These dynamic changes in the strength and peak phase of the PD to LP synapse are consistent with the short-term plasticity properties previously reported for this synapse. In the pyloric network, the follower neuron LP provides the sole transmitter-mediated feedback to the pacemaker neurons. To understand the role of this synapse in network stability, this synapse was blocked and replaced by an artificial synapse using the dynamic clamp technique. Different parameters of the artificial synapse, including strength, peak phase, duration and onset phase were found to affect the pyloric cycle period. The most effective parameters that influence cycle period were the synaptic duration and its onset phase. Overall this study demonstrated that both the intrinsic properties of individual neurons and the dynamic properties of the synapses are essential in producing stable activity phases in this oscillatory network. The insight obtained from this thesis can provide a general understanding of the contribution of intrinsic properties to neuronal activity phase and how short-term synaptic dynamics can act to promote phase maintenance in oscillatory networks

THE APPLICATION OF LANGUAGE LEARNING STRATEGIES USED BY STUDENTS OF GENERAL ENGLISH CLASS OF INTERNATIONAL LANGUAGE PROGRAMS (ILP) KEDIRI AND THEIR CORRELATION WITH ACADEMIC ACHIEVEMENT

Learning English as a foreign language is not as easy as learning the first and the second language since there are some differences among foreign language, first language, and second language that may cause problems in learning process. In learning foreign language, it needs some strategies to help learners. By applying the strategies, it will make the learning process becomes more effective. Since the goals of English course students are to enhance their English competence by practicing English, this study is aimed to examine the language learning strategies applied by students of General English class of ILP Kediri, and the correlation between the application of language learning strategies and academic achievement.This study used descriptive quantitative approach and survey related to correlation study. The subjects of this study were 46 students out of 201 students of General English class of International Language Programs Kediri taken by random sampling. The data were taken from Strategy Inventory for Language Learning (SILL) questionnaire completed by the students and their academic score at the end of the level.The results show that the use of overall language learning strategies falls into medium level, meaning that the students sometimes used those strategies. In particular, metacognitive strategies are found as the most frequently used strategies, followed by social, affective, compensation, cognitive, and memory strategies. There is a positive low significant correlation among metacognitive and social strategies and academic achievement. The possible reason of low correlation is caused by the context of English use since English is considered as a foreign language in Indonesia.In suggestion, it is expected that the teachers can introduce and emphasize the application of language learning strategies to the students, especially metacognitive and social strategies intended for the better academic achievement.Keywords: language learning strategies, English course students, Strategy Inventory for Language Learning (SILL) questionnair

Mutant-based model of two independent pathways for carotenoid-mediated chloroplast biogenesis in Arabidopsis embryos

Chloroplasts are essential for autonomous plant growth, and their biogenesis is a complex process requiring both plastid and nuclear genome. One of the essential factors required for chloroplast biogenesis are carotenoids. Carotenoids are synthesized in plastids, and it was shown that plastid localized methylerythritol 4-phosphate (MEP) pathway provides substrates for their biosynthesis. Here, we propose a model, using results of our own mutant analysis combined with the results of others, that a MEP-independent pathway, likely a mevalonate (MVA)-dependent pathway, provides intermediates for chloroplast biogenesis in Arabidopsis embryos. The pattern of this chloroplast biogenesis differs from the MEP-dependent chloroplast biogenesis. In MEP-dependent chloroplast biogenesis, chloroplasts are formed rather uniformly in the whole embryo, with stronger chlorophyll accumulation in cotyledons. In a MEP-independent pathway, chloroplasts are formed predominantly in the hypocotyl and in the embryonic root. We also show that this pattern of chlorophyll accumulation is common to MEP pathway mutants as well as to the mutant lacking geranylgeranyl diphosphate synthase 11 (GGPPS11) activity in plastids but expressing it in the cytosol (GGPPS11cyt). It was recently described that shorter GGPPS11 transcripts are present in Arabidopsis, and they can be translated into active cytosolic proteins. We therefore propose that the MEP-independent pathway for chloroplast biogenesis in Arabidopsis embryos is an MVA pathway that provides substrates for the synthesis of GGPP via GGPPS11cyt and this is then transported to plastids, where it is used for carotenoid biosynthesis and subsequently for chloroplast biogenesis mainly in the hypocotyl and in the embryonic root

The Application of Language Learning Strategies Used by Students of General English Class of International Language Programs (Ilp) Kediri and Their Correlation with Academic Achievement

Learning English as a foreign language is not as easy as learning the first and the second language since there are some differences among foreign language, first language, and second language that may cause problems in learning process. In learning foreign language, it needs some strategies to help learners. By applying the strategies, it will make the learning process becomes more effective. Since the goals of English course students are to enhance their English competence by practicing English, this study is aimed to examine the language learning strategies applied by students of General English class of ILP Kediri, and the correlation between the application of language learning strategies and academic achievement.This study used descriptive quantitative approach and survey related to correlation study. The subjects of this study were 46 students out of 201 students of General English class of International Language Programs Kediri taken by random sampling. The data were taken from Strategy Inventory for Language Learning (SILL) questionnaire completed by the students and their academic score at the end of the level.The results show that the use of overall language learning strategies falls into medium level, meaning that the students sometimes used those strategies. In particular, metacognitive strategies are found as the most frequently used strategies, followed by social, affective, compensation, cognitive, and memory strategies. There is a positive low significant correlation among metacognitive and social strategies and academic achievement. The possible reason of low correlation is caused by the context of English use since English is considered as a foreign language in Indonesia.In suggestion, it is expected that the teachers can introduce and emphasize the application of language learning strategies to the students, especially metacognitive and social strategies intended for the better academic achievement

Albornoz, Tenorio y Rojas: las empresas artísticas de tres arzobispos de Toledo en la Baja Edad Media: Estado de la cuestión

Los obispos se constituyeron como uno de los grupos de promotores más importantes del panorama artístico bajomedieval castellano. El objetivo de este estudio es ofrecer una visión de conjunto sobre la promoción artística de tres importantes prelados de la sede toledana: Gil de Albornoz, Pedro Tenorio y Sancho de Rojas. Para ello, se ofrece una visión actualizada del conocimiento de los encargos de cada prelado en la que se ha tratado de resaltar las aportaciones más relevantes, además de destacar los aspectos que merecen un estudio específico

Comparison of the Effects of Sensorimotor Rhythm and Slow Cortical Potential Neurofeedback in Epilepsy

Current conventional epilepsy treatments do not always aim to improve epilepsy comorbidities. For a treatment to be effective, is not necessary for it to keep the patient seizure-free; it is sufficient to show improvement in functions to help people who suffer from epilepsy to become more independent and productive in life. There is an urgent need to explore non- pharmaceutical/non-invasive interventions that can help in that regard. The earlier patients are treated with this condition, the more likely it is to prevent severe disabilities over time. Neurofeedback is a self-modulatory brain activity oscillatory intervention that previous researchers have found to reduce seizure frequency in patients with epilepsy. The aim of this work was to compare two Neurofeedback techniques that have shown some efficacy in improving symptoms in epilepsy. The novelty of this study is to explore further and included clinical, neurophysiological and cognitive outcomes in order to assess in more detail the effectiveness of epilepsy comorbidities. Forty-four patients, between the ages of 12 and 18 years, and diagnosed with focal epilepsy, divided randomly into three groups: sensorimotor rhythm (SMR) training, slow cortical potential (SCP) training, and control. The patients completed 25 sessions of intervention. The results showed that the SMR group training had an advantage in improving reaction time compared with SCP and control. Regression analysis revealed a significant correlation between the patients who learned to modify their brain activity in the SMR group and improving reaction time in two different tasks. In addition, the quality of life scale significantly improved in all three groups. The study supplies preliminary data to support that SMR neurofeedback training as an intervention should further be explored as a therapeutic option for children who suffer from focal epilepsy.CONACYT (Mexican Council of science and technology

DIAGNÓSTICO SOCIOECONÓMICO Y ESTRATEGIAS DE DESARROLLO DEL MUNICIPIO DE MALINALCO, 2007-2015

El primer capítulo titulado; marco conceptual jurídico, donde se abordan temas como los principios de la planeación, surgimiento de las políticas públicas, el sistema de planeación municipal en México, su estructura y organización, para conocer en teoría como debiera funcionar y estructurarse una política pública en la planeación municipal. En el segundo capítulo citado: estudio físico geográfico, económico y social se describe las características de localización, físico-geográficas, su estructura social y económica apoyado de cifras de población, abastecimiento de servicios públicos, empleo, finanzas públicas etc., con el propósito de obtener un panorama de la situación en la que vive cada uno de los habitantes del municipio. En el capítulo 3 se detallan los objetivos, metas y estrategias de una planeación municipal adecuada para lograr un crecimiento en el municipio. Para finalizar se muestran las conclusiones obtenidas de la presente investigación

Feasibility of EB Welded Hastelloy X and Combination of Refractory Metals

As NASA continues to expand its horizon, exploration and discovery creates the need of advancement in technology. The Jupiter Icy Moon Orbiter's (JIMO) mission to explore and document the outer surfaces, rate the possibility of holding potential life forms, etc. within the three moons (Callisto, Ganymede, and Europa) proves to be challenging. The orbiter itself consists of many sections including: the nuclear reactor and the power conversion system, the radiator panels, and the thrusters and antenna. The nuclear reactor serves as a power source, and if successfully developed, can operate for extended periods. During the duration of my tenure at NASA Glenn Research Center's (NASA GRC) Advanced Metallics Branch, I was assigned to assist Frank J. Ritzert on analyzing the feasibility of the Electron Beam Welded Hastelloy X (HX), a nickel-based superalloy, to Niobium- 1 %Zirconium (Nb-1 Zr) and other refractory metals/alloys including Tantalum, Molybdenum, Tungsten, and Rhenium alloys. This welding technique is going to be used for the nuclear reactor within JIMO