Dynamical evolution of heavy quarkonia in a deconfined medium

We investigate some consequences of the possibility that heavy quarkonia in a quark-gluon plasma possess different (quasi-) bound states, between which transitions are possible. In particular, we show that the time-evolution eigenstates in the medium are mixtures of the vacuum eigenstates. This leads to abundance ratios of quarkonia that differ from those predicted in statistical models or in the sequential-melting picture.Comment: 5 pages, 3 figure

Relaxation dynamics in covalently bonded organic monolayers on silicon

We study the dynamic electrical response of a silicon-molecular monolayer-metal junctions and we observe two contributions in the admittance spectroscopy data. These contributions are related to dipolar relaxation and molecular organization in the monolayer in one hand, and the presence of defects at the silicon/molecule interface in the other hand. We propose a small signal equivalent circuit suitable for the simulations of these molecular devices in commercial device simulators. Our results concern monolayers of alkyl chains considered as a model system but can be extended to other molecular monolayers. These results open door to a better control and optimization of molecular devices.Comment: 1 pdf file including text, figures and tables. Phys. Rev. B, in pres

Arrows of power at the dawn of metallurgy, from Brittany to Denmark (2500-1700 BC).

This article presents a comparative study of the arrowheads found in graves dating to between 2500 BC and 1700 BC in north-west France, southern Britain and Denmark. The aim is to characterize their modes of production and functions during a period which successively sees the introduction of copper then bronze metallurgy, the former accompanying the appearance of Bell Beaker pottery and associated practices in these areas. Several modes of production are proposed, from individual manufacture by Bell Beaker-using warriors to specialist production for elite use during the Early Bronze Age. Over and above their function as weapons - arguably associated more with interpersonal combat than with hunting -, arrowheads served to portray and emphasise the social status of the individuals. In the case of the Early Bronze Age Armorican arrowheads, they should be regarded as ‘sacred’ objects, made for display and enhancing the power of the chiefs. Lastly, arrows are placed in the broader perspective of major trends affecting Europe during the Bell Beaker period and then the Early Bronze Age, while the distribution of arrowheads with slanted barbs suggests the operation of an Atlantic cultural complex

The production and use of archery-related items as reflects of social changes during the Late Neolithic and the Early Bronze Age in Europe

Dates ranging from 2500 to 1700 BCE are a period of major social and economic change in western and central Europe, with the spreading of the Bell Beaker Culture and the introduction or the development of metalworking (copper then bronze). At that time, archery-related items became peculiarly significant for the Bell Beaker and some Early Bronze Age communities. They include especially specific types of arrowheads and an original item, the stone bracer, thought to have adorned organic wristguards. Technological studies point to the objects that were more or less easily made during the Bell Beaker period, suggesting that each warrior was able to shape his own set, while during the Early Bronze Age, the level of know-how as well the context of production suggests that these items were manufactured by craftsmen for the elite. Use-wear analysis shows that these objects might be commonly worn. During the Bell Beaker period, part of the arrowhead and, to a lesser extent, some bracers were used for shooting. However, in some regions during the Early Bronze Age, these objects were intended for display only. These two types of production and uses of archery-related items illustrate a shift from the object-signs of the Bell Beaker warriors towards items alienated from their primary function or sacred objects of the Early Bronze Age elites. Finally, the wide distribution of Bell Beaker arrowheads and bracers allow considering the relevance of the circulation of ideas, objects and individuals in adopting a European fashion

Evaluation of a gate capacitance in the sub-aF range for a chemical field-effect transistor with a silicon nanowire channel

An evaluation of the gate capacitance of a field-effect transitor (FET) whose channel length and width are several ten nanometer, is a key point for sensors applications. However, experimental and precise evaluation of capacitance in the aF range or less has been extremely difficult. Here, we report an extraction of the capacitance down to 0.55 aF for a silicon FET with a nanoscale wire channel whose width and length are 15 and 50 nm, respectively. The extraction can be achieved by using a combination of four kinds of measurements: current characteristics modulated by double gates, random-telegraph-signal noise induced by trapping and detrapping of a single electron, dielectric polarization noise, and current characteristics showing Coulomb blockade at low temperature. The extraction of such a small gate capacitance enables us to evaluate electron mobility in a nanoscale wire using a classical model of current characteristics of a FET.Comment: To be published in IEEE Trans. Nanotechno

Environmental NGOs : Channels of democracy for the European Union

The notion of democratic deficit has been at the centre of many debates on the European Union for the last 30 years. The reason is, to a certain degree, linked to the lack of legitimacy of the European Commission, which is not elected and remote from the European citizens. However, the Commission seems to have found a positive way to increase its legitimacy by the inclusion of civil-society in the decision-making process. The interaction between the Commission and two Environmental NGOs will therefore be analysed in order to make a constructive contribution to the debate. The present paper does not limit itself to normative statements on reality and considers that there is more to socio-political relations than “true” verifiable facts. Therefore, it is not limited to the formal decision-making process, and goes deeper into the socialisation process at play between the different actors. The outcome is that the Environmental NGOs studied appears as valuable models for the implementation of new democratic channels for the representation and participation of European citizens

Armorican Arrowheads Biographies : Production and Function of an Early Bronze Age prestige good from Brittany (France)

Brittany can pride itself on the Armorican arrowheads found in Early Bronze Age graves (2150-1700 BC). In the present state of knowledge, these are the only specialized craft products in knapped flint produced in this region at the western edge of continental Europe. Admired since the 19th century, these flint arrowheads have never really been studied. Due to the wealth of graves and gravegoods, a relatively precise study can be undertaken of the development of these craft products, despite the low number of reliable radiocarbon dates. These arrowheads are characterized by a well-defined type (pointed tang and oblique barbs) most often combined with ogival form. Raw materials show the selection of a high quality yellow translucent flint, of which the origin has to be sought at more than 400 kilometers (Lower Turonian flint from Cher Valley). From a technical point of view, Armorican arrowheads reveal a great mastery of retouch by pressure-flaking. This skill is written in stone by the perfection of forms, the extreme thinness (until 2,5 mm thick) and very long barbs (until 25 mm long). Such work could not have been done without the use of copper, even bronze, awls. Moreover, some marks may testify to the implication of these tools. On 549 arrowheads that have reached to us, none of them presents diagnostical impact features. However, use-wear analysis indicates that most of them were hafted (adhesive traces, bright spots, blunt edges). These facts suggest that they are less functional arrowheads than objects for the show. In the graves, Armorican arrowheads are frequently set down carefully in wooden boxes taking the shaft off. The Armorican arrowheads with their exotic raw materials, their high-degree of technicality, and their absence of use, have all features of a prestige good. They have been discovered by dozens in few graves under barrows with very rich funeral items (bronze daggers decorated with golden pins, precious bracers, silver beakers, etc.). According to these obvious facts, they symbolize the power of the elites. The genesis of Armorican arrowheads are in all likelihood explained by a climate of increasing social competition, which express itself in Brittany by an individualization of burial rites, a development of metalworking and a reorganization of territories. In this article, we will stress on raw materials selection, technology and know-how, as well as use-wear analyses. All these approaches will help us to trace the biographies of the Armorican arrowheads