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Search Results: 1 - 10 of 18658 matches for " Alberto Bacci "
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Assortment of GABAergic Plasticity in the Cortical Interneuron Melting Pot
Pablo Méndez,Alberto Bacci
Neural Plasticity , 2011, DOI: 10.1155/2011/976856
Abstract: Cortical structures of the adult mammalian brain are characterized by a spectacular diversity of inhibitory interneurons, which use GABA as neurotransmitter. GABAergic neurotransmission is fundamental for integrating and filtering incoming information and dictating postsynaptic neuronal spike timing, therefore providing a tight temporal code used by each neuron, or ensemble of neurons, to perform sophisticated computational operations. However, the heterogeneity of cortical GABAergic cells is associated to equally diverse properties governing intrinsic excitability as well as strength, dynamic range, spatial extent, anatomical localization, and molecular components of inhibitory synaptic connections that they form with pyramidal neurons. Recent studies showed that similarly to their excitatory (glutamatergic) counterparts, also inhibitory synapses can undergo activity-dependent changes in their strength. Here, some aspects related to plasticity and modulation of adult cortical and hippocampal GABAergic synaptic transmission will be reviewed, aiming at providing a fresh perspective towards the elucidation of the role played by specific cellular elements of cortical microcircuits during both physiological and pathological operations. 1. Introduction The cerebral cortex (which includes the hippocampus, the entorhinal cortex, the piriform cortex, and the neocortex) is the origin of the most sophisticated cognitive functions and complex behaviors. Indeed, the constant computation of incoming sensory information is dynamically integrated to provide a coherent representation of the world, elaborate the past, predict the future, and ultimately develop a consciousness and the self. In particular, the specific activity states of intricate cortical networks often produce a wide range of rhythmic activities, believed to provide the computational substrate for different aspects of cognition and various behaviors [1, 2]. Cortical oscillations range from slow-wave activity (<1?Hz) to ultrafast oscillations (>100?Hz), with several intermediate rhythms (e.g., theta, beta gamma), each of which is considered to underlie specific cognitive aspects, such as non-REM sleep (slow-waves), sensory integration (gamma), working memory (theta), and motor planning (beta) [1]. Importantly, inhibitory neurons were proposed to play a fundamental role in the genesis of most of these rhythms [3–13] through the specialized activity of their GABAergic synapses [7–10]. In fact, it is noteworthy that malfunctioning of specific GABAergic circuits is often indicated as a leading
Avalia??o de superfícies usinadas por diferentes fluidos dielétricos no processo de usinagem por eletroeros?o
Arantes, Luciano José;Silva, Márcio Bacci da;Silva, Evaldo Malaquias da;Raslan, Alberto Arnaldo;
Rem: Revista Escola de Minas , 2003, DOI: 10.1590/S0370-44672003000200005
Abstract: the electrical discharge machining process is very useful while machining very hard materials, which are very difficult to be machined by traditional process, while can make complex geometries and minimum dimensions. one of the materials that are very used in this process is high-speed steel (abnt m2), which is very hard and has a high mechanical resistance. this work has as main objective the study of performance of different dielectric fluids used in edm in tree different pre chosen set-ups of work in terms or metal removal rate (mmr) and wear ratio (wr), roughness parameter (ra), then discuss and analyze the most important factors that can produce different performance when machining with this process. have been done five tests with different types of dielectric fluids using a cooper tool. can be noticed that occurred very important different performance between the fluids, which all the other conditions of operation were unchanged. when using such a fluid the workpiece presented less roughness and a higher mmr in some cases. in other cases, a higher mmr produced in the other hand a recast layer less uniform. however, the most important conclusion of this work is about kerosene, which costs 3 times less than the specific dielectric fluids for edm, presented worst finishing surfaces and not too high mmr as expected, despite all the risks for the operator.
Avalia o de superfícies usinadas por diferentes fluidos dielétricos no processo de usinagem por eletroeros o
Arantes Luciano José,Silva Márcio Bacci da,Silva Evaldo Malaquias da,Raslan Alberto Arnaldo
Rem: Revista Escola de Minas , 2003,
Abstract: O processo de Usinagem por Descargas Elétricas é muito utilizado na usinagem de materiais de elevada dureza, difíceis de serem usinados por processos convencionais, além de permitir a confec o de geometrias bem complexas e de dimens es diminutas. O objetivo principal desse trabalho é o estudo das superfícies usinadas pelo processo EDM com diferentes tipos de fluidos dielétricos em três regimes de usinagem. Os diversos fluidos dielétricos utilizados possibilitam diferentes condi es de usinagem e muito pouco se sabe sobre qual o fluido mais indicado para opera es de acabamento ou desbaste. Foram feitos ensaios com cinco tipos diferentes de fluidos dielétricos e com uma ferramenta cilíndrica vazada de cobre eletrolítico. Verificou-se que há diferen as importantes quando usina-se com fluidos diferentes, mantendo-se constantes todas as demais condi es de opera o, embora todos os fluidos, com exce o do querosene, s o vendidos como se fossem exatamente iguais entre si, o que se mostrou falso. Porém a maior conclus o desse trabalho foi a de que o querosene, apesar de ser até três vezes mais barato que os demais fluidos, apresentou piores acabamentos superficiais com grande forma o de bolhas durante o processo, pois sua menor densidade confere também excessiva evapora o durante a usinagem, o que acabou por conferir uma superfície muito irregular e com muita porosidade e presen a de microtrincas, além de maiores riscos ao operador.
Desynchronization of Neocortical Networks by Asynchronous Release of GABA at Autaptic and Synaptic Contacts from Fast-Spiking Interneurons
Frédéric Manseau,Silvia Marinelli,Pablo Méndez,Beat Schwaller,David A. Prince,John R. Huguenard,Alberto Bacci
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000492
Abstract: Networks of specific inhibitory interneurons regulate principal cell firing in several forms of neocortical activity. Fast-spiking (FS) interneurons are potently self-inhibited by GABAergic autaptic transmission, allowing them to precisely control their own firing dynamics and timing. Here we show that in FS interneurons, high-frequency trains of action potentials can generate a delayed and prolonged GABAergic self-inhibition due to sustained asynchronous release at FS-cell autapses. Asynchronous release of GABA is simultaneously recorded in connected pyramidal (P) neurons. Asynchronous and synchronous autaptic release show differential presynaptic Ca2+ sensitivity, suggesting that they rely on different Ca2+ sensors and/or involve distinct pools of vesicles. In addition, asynchronous release is modulated by the endogenous Ca2+ buffer parvalbumin. Functionally, asynchronous release decreases FS-cell spike reliability and reduces the ability of P neurons to integrate incoming stimuli into precise firing. Since each FS cell contacts many P neurons, asynchronous release from a single interneuron may desynchronize a large portion of the local network and disrupt cortical information processing.
Root Zone Sensors for Irrigation Management in Intensive Agriculture
Alberto Pardossi,Luca Incrocci,Giorgio Incrocci,Fernando Malorgio,Piero Battista,Laura Bacci,Bernardo Rapi,Paolo Marzialetti,Jochen Hemming,Jos Balendonck
Sensors , 2009, DOI: 10.3390/s90402809
Abstract: Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy.
Desynchronization of Neocortical Networks by Asynchronous Release of GABA at Autaptic and Synaptic Contacts from Fast-Spiking Interneurons
Frédéric Manseau,Silvia Marinelli,Pablo Méndez,Beat Schwaller,David A. Prince,John R. Huguenard,Alberto Bacci
PLOS Biology , 2010, DOI: 10.1371/journal.pbio.1000492
Abstract: Networks of specific inhibitory interneurons regulate principal cell firing in several forms of neocortical activity. Fast-spiking (FS) interneurons are potently self-inhibited by GABAergic autaptic transmission, allowing them to precisely control their own firing dynamics and timing. Here we show that in FS interneurons, high-frequency trains of action potentials can generate a delayed and prolonged GABAergic self-inhibition due to sustained asynchronous release at FS-cell autapses. Asynchronous release of GABA is simultaneously recorded in connected pyramidal (P) neurons. Asynchronous and synchronous autaptic release show differential presynaptic Ca2+ sensitivity, suggesting that they rely on different Ca2+ sensors and/or involve distinct pools of vesicles. In addition, asynchronous release is modulated by the endogenous Ca2+ buffer parvalbumin. Functionally, asynchronous release decreases FS-cell spike reliability and reduces the ability of P neurons to integrate incoming stimuli into precise firing. Since each FS cell contacts many P neurons, asynchronous release from a single interneuron may desynchronize a large portion of the local network and disrupt cortical information processing.
Non-associative Potentiation of Perisomatic Inhibition Alters the Temporal Coding of Neocortical Layer 5 Pyramidal Neurons
Joana Louren?o ,Simone Pacioni,Nelson Rebola,Geeske M. van Woerden,Silvia Marinelli,David DiGregorio,Alberto Bacci
PLOS Biology , 2014, DOI: 10.1371/journal.pbio.1001903
Abstract: In the neocortex, the coexistence of temporally locked excitation and inhibition governs complex network activity underlying cognitive functions, and is believed to be altered in several brain diseases. Here we show that this equilibrium can be unlocked by increased activity of layer 5 pyramidal neurons of the mouse neocortex. Somatic depolarization or short bursts of action potentials of layer 5 pyramidal neurons induced a selective long-term potentiation of GABAergic synapses (LTPi) without affecting glutamatergic inputs. Remarkably, LTPi was selective for perisomatic inhibition from parvalbumin basket cells, leaving dendritic inhibition intact. It relied on retrograde signaling of nitric oxide, which persistently altered presynaptic GABA release and diffused to inhibitory synapses impinging on adjacent pyramidal neurons. LTPi reduced the time window of synaptic summation and increased the temporal precision of spike generation. Thus, increases in single cortical pyramidal neuron activity can induce an interneuron-selective GABAergic plasticity effectively altering the computation of temporally coded information.
Las múltiples causas de la catástrofe: consideraciones teóricas y empíricas
Livi Bacci, Massimo
Revista de Indias , 2003,
Abstract: The aim of this article is to contribute to the analysis of the indigenous population decline, namely the weight, role and function of every one of the causes that originated it. It is argued that the attention given to epidemies and pathologies has entailed a simplification that may seriously distort the historical interpretation of the demographic catastrophe, and that other contributing factors must be analyzed. Special attention is given to two of these factors which weigh on reproductivity and, therefore, on the capacity of reaction to crisis and mortality, namely the displacement effect and the substraction effect –social displacement and taking away of the reproductive heritage. El objetivo de este estudio es contribuir a la difícil labor de analizar el peso, el papel y la función de cada una de las causas que originaron el declive demográfico de los pueblos indígenas. La importancia que se ha dado a las epidemias y patologías en el descenso de la población ha llevado a una simplificación que puede distorsionar gravemente la interpretación histórica de la catástrofe demográfica. Junto a las epidemias, deben analizarse otros factores que contribuyeron al descenso de dicha población. Dos de ellos merecen una especial atención, ya que afectan a la reproductividad y por consiguiente, a la capacidad de reacción frente a las crisis y a los episodios de mayor mortalidad; nos referimos al efecto de desplazamiento y al efecto de sustracción , desplazamiento social y sustracción del patrimonio reproductivo.
Measurable Stochastics for Brane Calculus
Giorgio Bacci,Marino Miculan
Electronic Proceedings in Theoretical Computer Science , 2010, DOI: 10.4204/eptcs.40.2
Abstract: We give a stochastic extension of the Brane Calculus, along the lines of recent work by Cardelli and Mardare. In this presentation, the semantics of a Brane process is a measure of the stochastic distribution of possible derivations. To this end, we first introduce a labelled transition system for Brane Calculus, proving its adequacy w.r.t. the usual reduction semantics. Then, brane systems are presented as Markov processes over the measurable space generated by terms up-to syntactic congruence, and where the measures are indexed by the actions of this new LTS. Finally, we provide a SOS presentation of this stochastic semantics, which is compositional and syntax-driven.
Europa y América en la revolución geodemográfica
Massimo Livi Bacci
Estudios Demográficos y Urbanos , 2005,
Abstract: El trabajo establece un parangón entre Europa y América tanto de sus vivencias demográficas en el pasado con el Nuevo Mundo, como de las repercusiones futuras de las demografías de ambas regiones en un mundo globalizado. Con diversos indicadores el autor ilustra las transiciones en Europa, donde sepasó de una sociedad con abundancia de recursos humanos a otra con escasez de ellos. En este marco cuantitativo cualitativo expone las particularidades y soluciones de la crisis del Estado social en el caso europeo y la viabilidad de la aplicación de las políticas para revertir las tendencias de la baja natalidad y las concernientes a la migración, mayoritariamente de ultramar.
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