Two Words, One Meaning: Evidence of Automatic Co-Activation of Translation Equivalents

Research on the processing of translations offers important insights on how bilinguals negotiate the representation of words from two languages in one mind and one brain. Evidence so far has shown that translation equivalents effectively activate each other as well as their shared concept even when translations lack of any formal overlap (i.e., non-cognates) and even when one of them is presented subliminally, namely under masked priming conditions. In the lexical decision studies testing masked translation priming effects with unbalanced bilinguals a remarkably stable pattern emerges: larger effects in the dominant (L1) to the non-dominant (L2) translation direction, than vice versa. Interestingly, this asymmetry vanishes when simultaneous and balanced bilinguals are tested, suggesting that the linguistic profile of the bilinguals could be determining the pattern of cross-language lexico-semantic activation across the L2 learning trajectory. The present study aims to detect whether L2 proficiency is the critical variable rendering the otherwise asymmetric cross-language activation of translations obtained in the lexical decision task into symmetric. Non-cognate masked translation priming effects were examined with three groups of Greek (L1)–English (L2) unbalanced bilinguals, differing exclusively at their level of L2 proficiency. Although increased L2 proficiency led to improved overall L2 performance, masked translation priming effects were virtually identical across the three groups, yielding in all cases significant but asymmetric effects (i.e., larger effects in the L1 → L2 than in the L2 → L1 translation direction). These findings show that proficiency does not modulate masked translation priming effects at intermediate levels, and that a native-like level of L2 proficiency is needed for symmetric effects to emerge. They furthermore, pose important constraints on the operation of the mechanisms underlying the development of cross-language lexico-semantic links

Space Charge Formation and its Modified Electric Field under Applied Voltage Reversal and Temperature Gradient in XLPE Cable

The results of space charge evolution in cross-linked polyethylene power cables under dc electrical field at a uniform temperature and during external voltage polarity reversal are presented in the paper. A mirror image charge distribution was observed in the steady state, but the pre-existing field altered the way in which the steady state charge distribution was formed from that obtaining when the cable was first polarized. Polarity reversing charge was generated in the middle of the insulation and moved towards the appropriate electrodes under the influence of a field in excess of the maximum applied field. Our results show that the mirror effect is a steady state effect that is due to crossinterface currents that depend only on the interface field and not its polarity. Measurements on cable sections with an elevated mean temperature and temperature gradient show that the interface currents are temperature dependent, and that differences between the activation energies of the interface and bulk currents can eliminate and possibly even invert the polarity of the space charge distributio

Aging mechanisms of polymeric materials under DC electrical stress: A new approach and similarities to mechanical aging

The main fundamental mechanisms proposed for the aging of polymeric insulation to breakdown at the DC design field are reviewed. A correlation between the action of static mechanical stress affecting the whole insulation volume, and DC electric-mechanical stress providing local strain large enough to bring the polymer to plastic deformation is hypothesized. With the corollary that local plastic deformation leads to the formation of cavities, or crazes, of size large enough to trigger highly energetic phenomena and bring about insulation failure, an inter-relationship between mechanical and electrical life models can be obtained and supported by calculation and fitting to experimental results. The influence of space charge is discussed and it is argued that it would play a central role in DC ageing even if its presence is not a precondition

The role of group polarization in the formation of fast charge pulses in polyethylene

Recent calculations on the small charge pulses observed to move in millimetre thick polymeric insulation at high speeds have suggested that the charges may take the unusual form of electron pairs bound together by local lattice deformation. Here we show how the global lattice deformation generated around such a pulse can produce a potential well in which local electron paired states are the most stable form for the carriers and in which they are bound together such that in an electric field they must transport together as a single unit

The hidden threat to HVDC polymeric insulation at design field: Solitonic conduction

While HVDC assets are impetuously expanding worldwide, the design of HVDC polymeric insulation systems still contains unknowns. It has been ascertained that space charge plays a fundamental role in DC insulation reliability because of modifications it may induce in the (Poissonian) electric field distribution, especially when heterocharge is formed during voltage application. Heterocharge (charge close to an electrode of opposite polarity to that of the electrode) can increase the electric field at the interface between electrode and polymer, thereby enhancing injection from the electrode. This can cause so large a field concentration as to increase the conductivity abruptly and lead to insulation failure due to the electrical discharge process called, usually, thermal instability breakdow

Effect of mechanical stress on fast pulse-like conduction in XLPE based materials

The aim of this paper is to investigate the relationship between mechanical stress and a new conduction mechanism discovered recently, that is conduction through fast charge pulses in insulting polymers. Theories and experimental data suggested that such pulses constitute charge solitons moving in the insulation bulk thanks to the induced compressive force applied to the natural relaxation of the polymer chains. This paper supports such picture. Experimental tests carried out under mechanical stress, in fact, show that charge pulse transport is significantly affected by insulation compression. In particular, charge pulse amplitude decreases and positive pulses disappear as mechanical stress is increased. On the contrary, negative pulse mobility increases with the applied stress

High mobility conduction in insulating polymers through fast soliton-like charge pulses

We present evidence for the existence of a new form of charge transport in insulating polymers which takes the form of charge pulses that move exceptionally quickly across the insulation in comparison to the charge carrier mobility typical of such materials. This phenomenon could be associated with electromechanical compression of the polymer (a minimum amount of charge is needed for this to occur) that triggers a discontinuous injection of charge at the electrodes and allows transport inside the bulk through chain displacement modes. These pulses behave as charged solitary waves, or solitons, with a speed that corresponds to a mobility of some orders of magnitude higher than that of independent carriers

Ultra-fast space charge packets in nanostructured epoxy-based materials

This paper reports observations of charge packets in nanostructured epoxy flat specimens with a filler content of 3% and 5%. These packets, behaving as solitons, accumulate very quickly close to the counter electrodes as heterocharge, due to the partially-blocking effect of the specimen/electrode interfaces. The base material, on the contrary, behaves differently: no charge pulses cross the insulation, showing instead a significant homocharge build up. However applying a compression of about 300 kPa to the base material specimen allows a significant amount of heterocharge to begin to accumulate, meaning that the fast charge pulse transport mechanism described above has been incepted