Phase-field Crystals with Elastic Interactions

We report on a novel extension of the recent phase-field crystal (PFC) method introduced in [Elder et al., Phys. Rev. Lett., Vol. 88, 245701:1-4 (2002)], which incorporates elastic interactions as well as crystal plasticity and diffusive dynamics. In our model, elastic interactions are mediated through wave modes that propagate on time scales many orders of magnitude slower than atomic vibrations but still much faster than diffusive times scales. This allows us to preserve the quintessential advantage of the PFC model: the ability to simulate atomic-scale interactions and dynamics on time scales many orders of magnitude longer than characteristic vibrational time scales. We demonstrate the two different modes of propagation in our model and show that simulations of grain growth and elasto-plastic deformation are consistent with the microstructural properties of nanocrystals.Comment: 4 pages, 6 figure

A Comparative Study of Reservoir Computing for Temporal Signal Processing

Reservoir computing (RC) is a novel approach to time series prediction using recurrent neural networks. In RC, an input signal perturbs the intrinsic dynamics of a medium called a reservoir. A readout layer is then trained to reconstruct a target output from the reservoir's state. The multitude of RC architectures and evaluation metrics poses a challenge to both practitioners and theorists who study the task-solving performance and computational power of RC. In addition, in contrast to traditional computation models, the reservoir is a dynamical system in which computation and memory are inseparable, and therefore hard to analyze. Here, we compare echo state networks (ESN), a popular RC architecture, with tapped-delay lines (DL) and nonlinear autoregressive exogenous (NARX) networks, which we use to model systems with limited computation and limited memory respectively. We compare the performance of the three systems while computing three common benchmark time series: H{\'e}non Map, NARMA10, and NARMA20. We find that the role of the reservoir in the reservoir computing paradigm goes beyond providing a memory of the past inputs. The DL and the NARX network have higher memorization capability, but fall short of the generalization power of the ESN

Отношения правителя и знати в Северо­Восточной Руси

RésuméLes relations entre le prince et la noblesse en Russie du Nord-Est (xive-début du xvie s.) : le baiser sur la croix comme serment de fidélité ?Au Moyen žge, les nobles russes qui entraient au service d’un prince lui juraient-ils fidélité ? Répondre à cette question est essentiel pour comprendre l’idéologie et le rituel des relations entre le prince et la noblesse. Malgré quelques voix discordantes, la majorité des historiens considèrent qu'en Russie du Nord-Est le serment de fidélité prenait la forme d’un baiser sur la croix. L’article examine les sources attestant que les nobles baisaient la croix en signe de fidélité au grand-prince de Moscou. Il s’agit des chartes dites krestoceloval´nye, conservées depuis la seconde moitié du xve siècle. Or, ces documents n’avaient pas pour but de s’assurer de la fidélité de tous les nobles mais seulement de ceux qui étaient soupçonnés de vouloir fuir à l’étranger. Il faut remarquer également qu’à ces actes étaient jointes des chartes de caution, par lesquelles des nobles et des prélats se portaient garants de leurs pairs suspectés, s’engageant à verser des sommes importantes si ceux-ci manquaient à leur parole. L’auteur conclut que le baiser sur la croix comme serment de fidélité d’un noble à son prince n’est apparu qu’à la fin du xive siècle, en raison de la rivalité entre Moscou et la grande-principauté de Lituanie, qui toutes deux cherchaient à réunir les territoires russes à leur profit. Une autre pratique fut introduite parallèlement : lorsqu’un nouveau prince accédait au trône, la noblesse dans son ensemble devait lui prêter serment. Il s’agissait d’un serment obligatoire, public et collectif qui revêtait notamment la forme d’un baiser sur la croix. Ces deux pratiques de baiser sur la croix n’ont rien de commun avec les rituels de vassalité en Europe occidentale. Elles sont liées à la formation de la monarchie moscovite centralisée.AbstractRelations between the prince and the gentry in northeastern Russia between the fourteenth and early sixteenth centuries : was kissing the cross used as an oath of allegiance ?In the Middle Ages, did members of the gentry who entered the service of a prince pledge loyalty to him ? The answer to this question is crucial for understanding the ideology and ritual involved in the relationship between the prince and the gentry. With few exceptions, most historians agree that the oath of allegiance in northeastern Russia consisted in kissing the cross. This article examines sources attesting that the gentry kissed the cross as a sign of loyalty to the grand prince of Moscow. These are the krestotseloval´nye charters, which date back to the second half of the fifteenth century. They were not meant to ascertain the loyalty of all the members of the gentry, but only of those who were suspected of possible defection abroad. Mention must also be made that these charters were accompanied by documents in which noblemen and prelates stood security for their suspected peers and committed themselves to paying large sums of money if they failed to keep their word. The author concludes that kissing the cross as an oath of allegiance appeared as late as the end of the fourteenth century because of the rivalry opposing Moscow and the grand princedom of Lithuania in the gathering of Russian lands. A new practice was also introduced then : when a new prince acceded to the throne, the whole gentry had to pledge allegiance. This was obligatory, public, and collective, and involved kissing the cross. These two practices have nothing in common with the vassalage rituals of Western Europe. They are related to the formation of the centralized Muscovite monarchy

Theoretical investigation of a miniature microwave driven plasma jet

Microwave and radio frequency driven plasmas jets play an important role in many technical applications. They are usually operated in a capacitive mode known as E-mode. As a new plasma source the MMWICP (Miniature Micro Wave ICP) has been proposed, a small scale plasma jet with inductive coupling based on a specially designed resonator that acts as an LC-resonance circuit. This work presents a theoretical model of the new device, based on a series representation of the electromagnetic field in the resonator and the volume integrated (global) model for the loss processes within the plasma. An infinite number of modes can be found ordered by the azimuthal wave number m. These modes essentially determine the electromagnetic behavior of the system and differ from ordinary cavity modes. The mode m=0 can be identified with the inductive mode and is called H-mode, the mode m=1 is the capacitive mode and is called E-mode. Both modes refer to different operating regimes, which are separated by different values of the plasma parameters. In a second step the matching network and its characteristics are taken into account in order to find stable equilibrium points and possible hysteresis effects. As main result, the feasibility of inductive power coupling for the MMWICP resonator is shown

Oophorectomy Reduces Estradiol Levels and Long-Term Spontaneous Neurovascular Recovery in a Female Rat Model of Focal Ischemic Stroke

Although epidemiological evidence suggests significant sex and gender-based differences in stroke risk and recovery, females have been widely under-represented in preclinical stroke research. The neurovascular sequelae of brain ischemia in females, in particular, are largely uncertain. We set out to address this gap by a multimodal in vivo study of neurovascular recovery from endothelin-1 model of cortical focal-stroke in sham vs. ovariectomized female rats. Three weeks post ischemic insult, sham operated females recapitulated the phenotype previously reported in male rats in this model, of normalized resting perfusion but sustained peri-lesional cerebrovascular hyperreactivity. In contrast, ovariectomized (Ovx) females showed reduced peri-lesional resting blood flow, and elevated cerebrovascular responsivity to hypercapnia in the peri-lesional and contra-lateral cortices. Electrophysiological recordings showed an attenuation of theta to low-gamma phase-amplitude coupling in the peri-lesional tissue of Ovx animals, despite relative preservation of neuronal power. Further, this chronic stage neuronal network dysfunction was inversely correlated with serum estradiol concentration. Our pioneering data demonstrate dramatic differences in spontaneous recovery in the neurovascular unit between Ovx and Sham females in the chronic stage of stroke, underscoring the importance of considering hormonal-dependent aspects of the ischemic sequelae in the development of novel therapeutic approaches and patient recruitment in clinical trials

Targeting cyclic nucleotide phosphodiesterase 5 (PDE5) in brain: Toward the development of a PET radioligand labeled with fluorine-18

International audienceWith the aim to develop a specific radioligand for imaging the cyclic nucleotide phosphodiesterase 5 (PDE5) in brain by positron emission tomography (PET), seven new fluorinated inhibitors (3-9) were synthesized on the basis of a quinoline core. The inhibitory activity for PDE5 together with a panel of other PDEs was determined in vitro and two derivatives were selected for IC50 value determination. The most promising compound 7 (IC50 = 5.92 nM for PDE5A), containing a 3-fluoroazetidine moiety, was further radiolabeled by aliphatic nucleophilic substitution of two different leaving groups (nosylate and tosylate) using [18F]fluoride. The use of the nosylate precursor and tetra-n-butyl ammonium [18F]fluoride ([18F]TBAF) in 3-methyl-3-pentanol combined with the addition of a small amount of water proved to be the best radiolabeling conditions achieving a RCY of 4.9 ± 1.5% in an automated procedure. Preliminary biological investigations in vitro and in vivo were performed to characterize this new PDE5 radioligand. Metabolism studies of [18F]7 in mice revealed a fast metabolic degradation with the formation of radiometabolites which have been detected in the brain