Controlling the chemoselectivity of Palladium catalysed cyclizations of (2-iodoanilino)-carbonyl compounds

The factors which control the chemoselectivity of palladium catalyzed cyclizations of (2- haloanilino) carbonylic compounds have been explored by an extensive experimental-computational (DFT) study. It was found that the selectivity of the process, i.e. the formation of fused six versus fivemembered rings, can be controlled by the proper selection of the initial reactant, reaction conditions and the additives. Thus, esters or amides produce ketones by a nucleophilic addition process, whereas the addition of PhO- leads to the formation of indolines by an α-arylation reaction. In contrast, the corresponding ketone reactants yield mixture of both reaction products in the presence of phenol whose ratio depends on the base used. The outcome of the processes can be explained by the formation of a common four-membered palladacycle intermediate from which the competitive nucleophilic addition and α-arylation reactions occur. The remarkable effect of phenol in the process, which makes the αarylation reaction easier, was found to favor the formation of enol-complexes which are stabilized by an intramolecular hydrogen bond between the hydroxyl group of the enol moiety and the oxygen atom of the phenoxy ligand. Moreover, the chemoselectivy of the process can be also controlled by the addition of bidendate ligands leading to the almost exclusive formation of indoles at expenses of the corresponding alcohols

3D Dynamic Modeling of the Head-Neck Complex for Fast Eye and Head Orientation Movements Research

A 3D dynamic computer model for the movement of the head-neck complex is presented. It incorporates anatomically correct information about the diverse elements forming the system. The skeleton is considered as a set of interconnected rigid 3D bodies following the Newton-Euler laws of movement. The muscles are modeled using Enderle's linear model, which shows equivalent dynamic characteristics to Loeb's virtual muscle model. The soft tissues, namely, the ligaments, intervertebral disks, and facet joints, are modeled considering their physiological roles and dynamics. In contrast with other head and neck models developed for safety research, the model is aimed to study the neural control of the complex during fast eye and head movements, such as saccades and gaze shifts. In particular, the time-optimal hypothesis and the feedback control ones are discussed

Effects of spike anticipation on the spiking dynamics of neural networks

Synchronization is one of the central phenomena involved in information processing in living systems. It is known that the nervous system requires the coordinated activity of both local and distant neural populations. Such an interplay allows to merge different information modalities in a whole processing supporting high-level mental skills as understanding, memory, abstraction, etc. Though, the biological processes underlying synchronization in the brain are not fully understood there have been reported a variety of mechanisms supporting different types of synchronization both at theoretical and experimental level. One of the more intriguing of these phenomena is the anticipating synchronization, which has been recently reported in a pair of unidirectionally coupled artificial neurons under simple conditions (Pyragiene and Pyragas, 2013), where the slave neuron is able to anticipate in time the behavior of the master one. In this paper, we explore the effect of spike anticipation over the information processing performed by a neural network at functional and structural level. We show that the introduction of intermediary neurons in the network enhances spike anticipation and analyse how these variations in spike anticipation can significantly change the firing regime of the neural network according to its functional and structural properties. In addition we show that the interspike interval (ISI), one of the main features of the neural response associated with the information coding, can be closely related to spike anticipation by each spike, and how synaptic plasticity can be modulated through that relationship. This study has been performed through numerical simulation of a coupled system of Hindmarsh–Rose neurons

Los usuarios en la grieta: retomas de lo político en los sitios "Choripan & Vino" y "Peronismo Intergaláctico"

El trabajo que presentamos pretende ser un aporte descriptivo sobre los modos en los que se produce la lectura de lo político y su circulación en las redes sociales. Fue realizado en el marco del proyecto de investigación UBACyT “Absorciones y retomas discursivas. El campo de los efectos” (directora: María Rosa Del Coto; co-directora: Graciela Varela). Es importante destacar que la noción de medio es utilizada para denominar también a las redes sociales, partiendo de la definición que propone Eliseo Verón: “El término (…), designa para mí no solamente un dispositivo tecnológico particular (por ejemplo, la producción de imágenes y de sonidos sobre un soporte magnético) sino la conjunción de un soporte y de un sistema de prácticas de utilización (producción/reconocimiento)” (Verón: 2004: 144). Dentro del proyecto en el cual se enmarca esta investigación se entiende como retoma a los conceptos habilitados a partir de la década del ´70 alrededor de la definición intertextual de la vida discursiva (Bajtín, 1985; Kristeva, 1978; Angenot, 1996). "Todo enunciado es un eslabón en la cadena, muy complejamente organizada, de otros enunciados" Bajtín (1985).Eje 13. Análisis del discurso y estudios del lenguajeFacultad de Periodismo y Comunicación Socia

Los usuarios en la grieta: retomas de lo político en los sitios "Choripan & Vino" y "Peronismo Intergaláctico"

El trabajo que presentamos pretende ser un aporte descriptivo sobre los modos en los que se produce la lectura de lo político y su circulación en las redes sociales. Fue realizado en el marco del proyecto de investigación UBACyT “Absorciones y retomas discursivas. El campo de los efectos” (directora: María Rosa Del Coto; co-directora: Graciela Varela). Es importante destacar que la noción de medio es utilizada para denominar también a las redes sociales, partiendo de la definición que propone Eliseo Verón: “El término (…), designa para mí no solamente un dispositivo tecnológico particular (por ejemplo, la producción de imágenes y de sonidos sobre un soporte magnético) sino la conjunción de un soporte y de un sistema de prácticas de utilización (producción/reconocimiento)” (Verón: 2004: 144). Dentro del proyecto en el cual se enmarca esta investigación se entiende como retoma a los conceptos habilitados a partir de la década del ´70 alrededor de la definición intertextual de la vida discursiva (Bajtín, 1985; Kristeva, 1978; Angenot, 1996). "Todo enunciado es un eslabón en la cadena, muy complejamente organizada, de otros enunciados" Bajtín (1985).Eje 13. Análisis del discurso y estudios del lenguajeFacultad de Periodismo y Comunicación Socia

Los usuarios en la grieta: retomas de lo político en los sitios "Choripan & Vino" y "Peronismo Intergaláctico"

El trabajo que presentamos pretende ser un aporte descriptivo sobre los modos en los que se produce la lectura de lo político y su circulación en las redes sociales. Fue realizado en el marco del proyecto de investigación UBACyT “Absorciones y retomas discursivas. El campo de los efectos” (directora: María Rosa Del Coto; co-directora: Graciela Varela). Es importante destacar que la noción de medio es utilizada para denominar también a las redes sociales, partiendo de la definición que propone Eliseo Verón: “El término (…), designa para mí no solamente un dispositivo tecnológico particular (por ejemplo, la producción de imágenes y de sonidos sobre un soporte magnético) sino la conjunción de un soporte y de un sistema de prácticas de utilización (producción/reconocimiento)” (Verón: 2004: 144). Dentro del proyecto en el cual se enmarca esta investigación se entiende como retoma a los conceptos habilitados a partir de la década del ´70 alrededor de la definición intertextual de la vida discursiva (Bajtín, 1985; Kristeva, 1978; Angenot, 1996). "Todo enunciado es un eslabón en la cadena, muy complejamente organizada, de otros enunciados" Bajtín (1985).Eje 13. Análisis del discurso y estudios del lenguajeFacultad de Periodismo y Comunicación Socia

Emergence of Small-World Anatomical Networks in Self-Organizing Clustered Neuronal Cultures

In vitro primary cultures of dissociated invertebrate neurons from locust ganglia are used to experimentally investigate the morphological evolution of assemblies of living neurons, as they self-organize from collections of separated cells into elaborated, clustered, networks. At all the different stages of the culture's development, identification of neurons' and neurites' location by means of a dedicated software allows to ultimately extract an adjacency matrix from each image of the culture. In turn, a systematic statistical analysis of a group of topological observables grants us the possibility of quantifying and tracking the progression of the main network's characteristics during the self-organization process of the culture. Our results point to the existence of a particular state corresponding to a small-world network configuration, in which several relevant graph's micro- and meso-scale properties emerge. Finally, we identify the main physical processes ruling the culture's morphological transformations, and embed them into a simplified growth model qualitatively reproducing the overall set of experimental observations

Recurrent Variational Approach to the Two-Leg Hubbard Ladder

We applied the Recurrent Variational Approach to the two-leg Hubbard ladder. At half-filling, our variational Ansatz was a generalization of the resonating valence bond state. At finite doping, hole pairs were allowed to move in the resonating valence bond background. The results obtained by the Recurrent Variational Approach were compared with results from Density Matrix Renormalization Group.Comment: 10 pages, 14 Postscript figure

Maximizing Soil Carbon Sequestration: Assessing Procedural Barriers to Carbon Management in Cultivated Tropical Perennial Grass Systems

The natural capacity of the terrestrial landscape to capture and store carbon from the atmosphere can be used in cultivated systems to maximize the climate change mitigation potential of agricultural regions. A combination of inherent soil carbon storage potential, conservation management, and rhizosphere inputs should be considered when making landscape‐level decisions about agriculture if climate change mitigation is an important goal. However, the ability to accurately predict soil organic carbon accumulation following management change in the tropics is currently limited by the commonly available tools developed in more temperate systems, a gap that must be addressed locally in order to facilitate these types of landscape‐level decisions. Here, we use a case study in Hawaii to demonstrate multiple approaches to measuring and simulating soil carbon changes after the implementation of zero‐tillage cultivation of perennial grasses following more than a century of intensive sugarcane cultivation. We identify advancements needed to overcome the barriers to potential monitoring and projection protocols for soil carbon storage at our site and other similar sites