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Brain Cholinergic Mechanisms

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197149 Year: Pages: 127 DOI: 10.3389/978-2-88919-714-9 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-04-07 11:22:02
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Much of our understanding of brain physiology has focused on what one might call, first order processes. These essentially include the primary synaptic mechanisms underlying excitation (mainly glutamate) and inhibition (mainly GABA). Our attention has focused on how the balance of excitation and inhibition regulates the timing, patterns, and extent of information flow across various circuits. A lot less is understood regarding second order processes that sculpt and modify these primary interactions. One such modulatory transmitter in the brain is acetylcholine (ACh). The importance of ACh in modulating various behaviors related to learning, memory, and attention has been recognized over the last four decades as has its involvement in various neurodegenerative and psychiatric disorders. However, our understanding of the mechanistic bases for these actions is at its infancy, at best and much remains to be understood. The array of receptor subtypes for nicotinic and muscarinic receptors, their different locations, and complex signal transduction mechanisms remain a puzzle. Transmitter (ACh) release sites and their relationship to receptor loci are poorly understood. Overall, we lack a unifying framework for conceptualizing how disparate actions of the transmitter on receptors lead to circuit modulation and, eventually, influences on cognition. By its very nature, reports on cholinergic signaling are quite scattered, presented in journals across sub-disciplines and in the context of the systems they modulate. Hence, there is need for consolidation of these studies under a single cover that would allow one to compare and contrast the effects of this transmitter across systems and contexts. This special issue represents one such compilation. The issue addresses cholinergic modulation of defined circuits that lead to specific behaviors and consists of a judicious mixture of review articles and primary papers. The articles focus on three aspects of the system: 1) Cellular targets of cholinergic signaling. 2) Receptor mechanisms. 3) Endogenous transmitter distribution and action. While no common mechanism emerges that can explain cholinergic actions on brain functions, on can postulate that the transmitter system is dynamic, modulating the balance of excitation and inhibition in various circuits. This modulation sets up timed network oscillations and it is tempting to speculate that these oscillations form a template for better encoding of afferent inputs. One can broadly envision the role of the cholinergic system as facilitating processes that allow for more efficient acquisition of learning and engraving of memories. Thus, understanding the mechanisms underlying tonic and stimulus-dependent release of ACh and how it alters firing templates of neuronal networks would be the first step towards elucidating its role in learning and memory. This special topics edition provides clues to some of the actions of ACh. It is hoped that the articles allow the reader to extract common themes and potential mechanisms of cholinergic regulation that will lead to elucidation of general principles governing the actions of this important neuromodulator.

Synaptic Assembly and Neural Circuit Development

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889456307 Year: Pages: 191 DOI: 10.3389/978-2-88945-630-7 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2019-01-23 14:53:43
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Synapses are fundamental signaling units of the central nervous system that mediate communication between individual neurons, participate in the computation of neuronal networks, and process information through long-term modification of their strength and structure. The normal function of the central nervous system critically depends on the establishment of ‘precise’ synaptic connections between neurons and specific target cells. During synaptogenesis, synapses form, mature, stabilize, and are eliminated through processes that require intimate communication between pre- and postsynaptic partners. The sequential and/or parallel processes dictate the wiring of neural circuits in a rapid and dynamic fashion. Accumulating evidence suggests that activity-dependent synaptic and circuit plasticity reflects the assembly and disassembly of diverse synapses that occur in a distinctive manner in specific neuron types.In this Research Topic, our purpose is to compile the latest developments in our understanding of molecular and cellular mechanisms underlying pre- and postsynaptic assembly, specification of synaptic adhesion pathways, presynaptic neurotransmitter release and postsynaptic receptor trafficking. In addition, non-neuronal cell processes involved in dismantling and eliminating synapses and relevant neural circuits will be covered. Clinical implications of this research topic will be considered, emphasizing the importance of these basic neuroscience research activities for translational and therapeutic applications. This includes literature describing recent methodologies for probing key issues regarding assembly/disassembly of synapses and circuits as well as primary research articles that provide critical insights into these fundamental questions in various model systems and experimental preparations.

Experiments on flux qubits with pi-shifters

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Book Series: Experimental Condensed Matter Physics / Karlsruher Institut für Technologie, Physikalisches Institut ISSN: 21919925 ISBN: 9783866446441 Year: Volume: 1 Pages: XI, 110 p. DOI: 10.5445/KSP/1000022237 Language: ENGLISH
Publisher: KIT Scientific Publishing
Subject: Physics (General)
Added to DOAB on : 2019-07-30 20:02:02
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The results of the research re-ported in this work show that tunable gap flux qubits have a potential for building quantum registers. Cavities coupled to flux qubits can be used for in-formation storage and transfer between qubits. SFS &#960;-shifters provide a simple approach to bias multi-qubit circuits. A possibility to change the qubit resonance frequency while preserving qubit coherence enables implementation of switchable coupling between qubits and cavities.

Synthetic Biology: Engineering complexity and refactoring cell capabilities

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196852 Year: Pages: 123 DOI: 10.3389/978-2-88919-685-2 Language: English
Publisher: Frontiers Media SA
Subject: Biotechnology --- General and Civil Engineering
Added to DOAB on : 2015-10-30 16:33:44
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One of the key features of biological systems is complexity, where the behavior of high level structures is more than the sum of the direct interactions between single components. Synthetic Biologists aim to use rational design to build new systems that do not already exist in nature and that exhibit useful biological functions with different levels of complexity. One such case is metabolic engineering, where, with the advent of genetic and protein engineering, by supplying cells with chemically synthesized non-natural amino acids and sugars as new building blocks, it is now becoming feasible to introduce novel physical and chemical functions and properties into biological entities. The rules of how complex behaviors arise, however, are not yet well understood. For instance, instead of considering cells as inert chassis in which synthetic devices could be easily operated to impart new functions, the presence of these systems may impact cell physiology with reported effects on transcription, translation, metabolic fitness and optimal resource allocation. The result of these changes in the chassis may be failure of the synthetic device, unexpected or reduced device behavior, or perhaps a more permissive environment in which the synthetic device is allowed to function. While new efforts have already been made to increase standardization and characterization of biological components in order to have well known parts as building blocks for the construction of more complex devices, also new strategies are emerging to better understand the biological dynamics underlying the phenomena we observe. For example, it has been shown that the features of single biological components [i.e. promoter strength, ribosome binding affinity, etc] change depending on the context where the sequences are allocated. Thus, new technical approaches have been adopted to preserve single components activity, as genomic insulation or the utilization of prediction algorithms able to take biological context into account. There have been noteworthy advances for synthetic biology in clinical technologies, biofuel production, and pharmaceuticals production; also, metabolic engineering combined with microbial selection/adaptation and fermentation processes allowed to make remarkable progress towards bio-products formation such as bioethanol, succinate, malate and, more interestingly, heterologous products or even non-natural metabolites. However, despite the many progresses, it is still clear that ad hoc trial and error predominates over purely bottom-up, rational design approaches in the synthetic biology community. In this scenario, modelling approaches are often used as a descriptive tool rather than for the prediction of complex behaviors. The initial confidence on a pure reductionist approach to the biological world has left space to a new and deeper investigation of the complexity of biological processes to gain new insights and broaden the categories of synthetic biology. In this Research Topic we host contributions that explore and address two areas of Synthetic Biology at the intersection between rational design and natural complexity: (1) the impact of synthetic devices on the host cell, or "chassis" and (2) the impact of context on the synthetic devices. Particular attention will be given to the application of these principles to the rewiring of cell metabolism in a bottom-up fashion to produce non-natural metabolites or chemicals that should eventually serve as a substitute for petrol-derived chemicals, and, on a long-term view, to provide economical, ecological and ethical solutions to today’s energetic and societal challenges.

Mechanisms of Neural Circuit Formation

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889194032 Year: Pages: 179 DOI: 10.3389/978-2-88919-403-2 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2015-12-10 11:59:06
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The formation of the proper pattern of neuronal circuits during development is critical for the normal function of the vertebrate brain and for the survival of the organism. Circuit tracing studies spanning the past 100 years have revealed the beauty and exquisite intricacy of this pattern, which represents the most complex biological system known. In humans, aberrant circuit formation is a likely underlying cause of a wide variety of birth defects and neurological disorders, including autism, intellectual disability, and schizophrenia. Furthermore, future therapeutic approaches to restoring the function of damaged neural circuits will require a better understanding of the developmental constraints under which those circuits were originally assembled. For these reasons, elucidating the molecular mechanisms of neural circuit formation is a major goal of neurobiology today.

The world according to zebrafish: How neural circuits generate behaviour

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193288 Year: Pages: 367 DOI: 10.3389/978-2-88919-328-8 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-03-10 08:14:32
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Understanding how the brain functions is one of the most ambitious current scientific goals. This challenge will only be accomplish by a multidisciplinary approach involving genetics, molecular biology, optics, ethology, neurobiology and mathematics and using tractable model systems. The zebrafish larva is a transparent genetically tractable small vertebrate, ideal for the combination state-of-the- art imaging techniques (e.g. two-photon scanning microscopy, single-plane illumination microscopy, spatial light modulator microscopy and lightfield microscopy), bioluminiscence and optogenetics to monitor and manipulate neuronal activity from single specific neurons up to the entire brain, in an intact behaving organism. Furthermore, the zebrafish model offers large and increasing collection of mutant and transgenic lines modelling human brain diseases. With these advantages in hand, the zebrafish larva became in the recent years, a novel animal model to study neuronal circuits and behaviour, taking us closer than ever before to understand how the brain controls behaviour.

Compact Models for Integrated Circuit Design

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ISBN: 9781482240665 Year: Language: English
Publisher: Taylor & Francis Grant: Knowledge Unlatched - 102706
Subject: Agriculture (General)
Added to DOAB on : 2019-03-02 11:21:02
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This modern treatise on compact models for circuit computer-aided design (CAD) presents industry standard models for bipolar-junction transistors (BJTs), metal-oxide-semiconductor (MOS) field-effect-transistors (FETs), FinFETs, and tunnel field-effect transistors (TFETs), along with statistical MOS models. Featuring exercise problems at the end of each chapter and extensive references at the end of the book, the text supplies fundamental and practical knowledge necessary for efficient integrated circuit (IC) design using nanoscale devices. It ensures even those unfamiliar with semiconductor physics gain a solid grasp of compact modeling concepts.

Aktive Frequenzvervielfacher zur Signalerzeugung im Millimeter- und Submillimeterwellen Frequenzbereich

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Book Series: Karlsruher Forschungsberichte aus dem Institut für Hochfrequenztechnik und Elektronik ISSN: 18684696 ISBN: 9783731503545 Year: Volume: 79 Pages: XIII, 158 p. DOI: 10.5445/KSP/1000046156 Language: GERMAN
Publisher: KIT Scientific Publishing
Subject: Technology (General)
Added to DOAB on : 2019-07-30 20:01:57
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In this work a new transistor topology for frequency multiplication is developed, achieving relative bandwidths of complex and balanced structures with only four transistors. It enables the highest bandwidth in active multiplication beyond 110 GHz. Cascading techniques are shown enabling a cascaded frequency multiplier by eight with a frequency range of 220 to 320 GHz. For the first time an active frequency multiplier by six reaches output frequencies up to 670 GHz.

Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

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ISBN: 9781789237689 9781789237696 Year: Pages: 214 DOI: 10.5772/intechopen.72459 Language: English
Publisher: IntechOpen
Subject: Computer Science
Added to DOAB on : 2019-10-03 07:51:52

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Around 80% of electrical consumption in an industrialised society is used by machinery and electrical drives. Therefore, it is key to have reliable grids that feed these electrical assets. Consequently, it is necessary to carry out pre-commissioning tests of their insulation systems and, in some cases, to implement an online condition monitoring and trending analysis of key variables, such as partial discharges and temperature, among others. Because the tests carried out for analysing the dielectric behaviour of insulation systems are commonly standardised, it is of interest to have tools that simulate the real behaviour of those and their weaknesses to prevent electrical breakdowns. The aim of this book is to provide the reader with models for electrical insulation systems diagnosis.

Neurobiological circuit function and computation of the serotonergic and related systems

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193844 Year: Pages: 165 DOI: 10.3389/978-2-88919-384-4 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2015-12-03 13:02:24
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Serotonin is one of the oldest neurotransmitters in evolutionary terms, and the serotonergic system is complex and multifaceted. Serotonin-producing neurons in the raphe nuclei provide serotonin innervations throughout various parts of the brain, modulating cellular excitability and network properties of targeted brain areas, and regulating mood, cognition and behavior. Dysfunctions of the serotonergic system are implicated in neuropsychiatric disorders including depression, schizophrenia, and drug abuse. Although the system has been studied for many years, an integrative account of its functions and computational principles remains elusive. This is partly attributed to the high variability and heterogeneity in terms of neuronal properties and receptor types, and its extensive connections with other brain regions. This Frontiers Research Topic e-book is a collection of recent experimental and computational work and approaches at multiple scales that provide the latest information regarding the integrated functions of the serotonergic system. The contributed papers include a variety of experimental and computational work, and human clinical studies.

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