Slow plasmon modes in polymeric salt solutions

The dynamics of polymeric salt solutions are presented. The salt consists of chains $\rm A$ and $\rm B$, which are chemically different and interact with a Flory-interaction parameter $\chi$, the $\rm A$ chain ends carry a positive charge whereas the $\rm B$ chain ends are modified by negative charges. The static structure factor shows a peak corresponding to a micro phase separation. At low momentum transfer, the interdiffusion mode is driven by electrostatics and is of the plasmon-type, but with an unusually low frequency, easily accessible by experiments. This is due to the polymer connectivity that introduces high friction and amplifies the charge scattering thus allowing for low charge densities. The interdiffusion mode shows a minimum (critical slowing down) at finite $k$ when the interaction parameter increases we find then a low $k$ frequency quasi-plateau.Comment: accepted in Europhys. Let

A simplified picture for Pi electrons in conjugated polymers : from PPP Hamiltonian to an effective molecular crystal approach

An excitonic method proper to study conjugated oligomers and polymers is described and its applicability tested on the ground state and first excited states of trans-polyacetylene, taken as a model. From the Pariser-Parr-Pople Hamiltonian, we derive an effective Hamiltonian based on a local description of the polymer in term of monomers; the relevant electronic configurations are build on a small number of pertinent local excitations. The intuitive and simple microscopic physical picture given by our model supplement recent results, such as the Rice and Garstein ones. Depending of the parameters, the linear absorption appears dominated by an intense excitonic peak.Comment: 41 Pages, 6 postscript figure

Experimental phase diagram of moving vortices

In the mixed state of type II superconductors, vortices penetrate the sample and form a correlated system due to the screening of supercurrents around them. Interestingly, we can study this correlated system as a function of density and driving force. The density, for instance, is controlled by the magnetic field, B, whereas a current density j acts as a driving force F=jxB on all vortices. The free motion of vortices is inhibited by the presence of an underlying potential, which tends to pin the vortices. Hence, to minimize the pinning strength we studied a superconducting glass in which the depinning current is 10 to 1000 times smaller than in previous studies, which enables us to map out the complete phase diagram in this new regime. The diagram is obtained as a function of B, driving current and temperature and led a remarkable set of new results, which includes a huge peak effect, an additional reentrant depinning phase and a driving force induced pinning phase.Comment: 4 page

An examination of the effects of self-regulatory focus on the perception of the media richness: the case of email

Communication is a key element in organizations’ business success. The media richness theory and the channel expansion theory are two of the most influential theories regarding the selection and use of communication media in organizations; however, literature has focused little on the effects of self-regulation by managers and employees in these theories. To analyze these topics, this study develops an empirical investigation by gathering data from 600 managers and employees using a questionnaire. The results suggest that the perception of media richness is positively affected when the individual shows a promotion focus or strategy.Peer ReviewedPostprint (author’s final draft

My character: enhancing future mindedness in young people: a feasibility study

The aim of the My Character project was to develop a better understanding of how interventions designed to develop character might enhance moral formation and futuremindedness in young people. Futuremindedness can be defined as an individual’s capacity to set goals and make plans to achieve them. Establishing goals requires considerable moral reflection, and the achievement of worthwhile aims requires character traits such as courage and the capacity to delay gratification. The research team developed two new educational interventions – a website and a hard-copy journal – with the specific aim of developing future-mindedness. After development, the website and journal were piloted over a one-year period by over 1,000 11–14 year olds in six schools across England. Various research methods, including group interviews and case studies, were implemented to assess impact. In addition, a pilot RCT was conducted to assess the feasibility of using experimental methods to measure character. The main findings from the research are that: - Students benefit from opportunities in school to think about future-mindedness; this can be successfully taught through character education. - Harnessing new technology, such as the Internet, offers exciting opportunities for character education. - It is beneficial to investigate the impact of new character education resources in order to bring greater clarity about ‘what works’. The most useful approach is a mixed methods one that allows for triangulation of evidence. - It is possible to run RCTs and other experimental research in schools to assess developmental projects of this kind, but applying the method in schools and creating suitable outcome measures present challenges for researchers. - A positive indicator of the success is that five out of the six pilot schools have embedded My Character into their curriculum. In addition, many new schools, both in Britain and internationally, have started to use the website and / or journal. This report describes the research, analyses the impact of My Character and concludes with recommendations for policy makers, practitioners and researchers embarking on similar projects. These recommendations include: i) advocating that schools create space in the curriculum to teach future-mindedness through character education; ii) enhancing traditional character education teaching methods with opportunities brought by Internet technologies; iii) evaluating character education interventions using triangulated evidence drawn from a mixture of research methods

On the potential vegetation feedbacks that enhance phosphorus availability – insights from a process-based model linking geological and ecological timescales

In old and heavily weathered soils, the availability of P might be so small that the primary production of plants is limited. However, plants have evolved several mechanisms to actively take up P from the soil or mine it to overcome this limitation. These mechanisms involve the active uptake of P mediated by mycorrhiza, biotic de-occlusion through root clusters, and the biotic enhancement of weathering through root exudation. The objective of this paper is to investigate how and where these processes contribute to alleviate P limitation on primary productivity. To do so, we propose a process-based model accounting for the major processes of the carbon, water, and P cycles including chemical weathering at the global scale. Implementing P limitation on biomass synthesis allows the assessment of the efficiencies of biomass production across different ecosystems. We use simulation experiments to assess the relative importance of the different uptake mechanisms to alleviate P limitation on biomass production. We find that active P uptake is an essential mechanism for sustaining P availability on long timescales, whereas biotic de-occlusion might serve as a buffer on timescales shorter than 10 000 yr. Although active P uptake is essential for reducing P losses by leaching, humid lowland soils reach P limitation after around 100 000 yr of soil evolution. Given the generalized modelling framework, our model results compare reasonably with observed or independently estimated patterns and ranges of P concentrations in soils and vegetation. Furthermore, our simulations suggest that P limitation might be an important driver of biomass production efficiency (the fraction of the gross primary productivity used for biomass growth), and that vegetation on old soils has a smaller biomass production rate when P becomes limiting. With this study, we provide a theoretical basis for investigating the responses of terrestrial ecosystems to P availability linking geological and ecological timescales under different environmental settings

Knightly virtues : enhancing virtue literacy through stories : research report

There is a growing consensus in Britain on the importance of character, and on the belief that the virtues that contribute to good character are part of the solution to many of the challenges facing modern society. Parents, teachers and schools understand the need to teach basic moral virtues to pupils, such as honesty, self-control, fairness, and respect, while fostering behaviour associated with such virtues today. However, until recently, the materials required to help deliver this ambition have been missing in Britain. The Knightly Virtues Programme, devised by the Jubilee Centre for Character and Virtues, aims to help solve this challenge. The programme, designed for 9 to 11 year olds, draws on selected classic stories to help teach moral character in schools. This approach has proved to be popular with children and teachers, with more than 5,000 pupils from one hundred schools having participated in the programme so far. Fifty-five of these schools (including thirty Catholic and Church of England) and 3,272 pupils (1,517 of which attended a Church school) were directly involved in different stages of the research. Based at the University of Birmingham, the Jubilee Centre houses leading academics dedicated to researching the various ways in which good character, which underpins the building blocks of society, can be developed. Recent research from the Centre has shown that the qualities that make up character can be learnt and taught, and suggests that we need a new emphasis on their importance in schools and in professional education. This report from the Centre into the use of classic literature within schools sets out the ways in which the Knightly Virtues Programme is able to develop the virtue literacy of school pupils, and the extent to which an understanding and awareness of good moral character can make positive changes to behaviour. The impact of the programme has been tested using several rigorous research methods, detailed in this report alongside their findings, which provide substantial empirical evidence for the effectiveness of using stories to develop virtue literacy

Second magnetization peak in flux lattices: the decoupling scenario

The second peak phenomena of flux lattices in layered superconductors is described in terms of a disorder induced layer decoupling transition. For weak disorder the tilt mudulus undergoes an apparent discontinuity which leads to an enhanced critical current and reduced domain size in the decoupled phase. The Josephson plasma frequency is reduced by decoupling and by Josephson glass pinning; in the liquid phase it varies as 1/[BT(T+T_0)] where T is temperature, B is field and T_0 is the disorder dependent temperature of the multicritical point.Comment: 5 pages, 1 eps figure, Revtex. Minor changes, new reference