Climate change Social divisions in belief and behaviour

As a global problem, climate change affects everyone. But within Britain opinion is divided. This chapter asks to what extent people in Britain believe humans cause climate change, think it is a problem, and feel that citizens and governments are likely to be able to reduce it. Also, what are the main social divisions in attitudes to climate change, and how much does opinion differ between supporters of different political parties

Observation of fine one-dimensionally disordered layers in silicon carbide

The improved resolution of synchrotron edge-topography is enabling thinner (less than 100 microns), silicon carbide crystals to be studied, and is providing a more detailed and wider database on polytype depth profiles. Fine long-period and one-dimensionally-disordered layers, 5-25 microns thick, can now be confidently resolved and are found to be very common features, often in association with high-defect density bands. These features are illustrated in this paper using three examples. A new long period polytype LPP (152H/456R) has been discovered and reported here for the first time

Research impact evaluation, a wider context: Findings from a research impact pilot

In the face of increasing pressure to demonstrate the socio-economic impact of funded research, whether it is funded directly by research councils or indirectly by governmental research block grants, institutions have to tackle the complexity of understanding, tracking, collecting, and analysing the impact of all their research activities. This paper attempts to encapsulate the wider context of research impact by delineating a broad definition of what might be classified as impact. It also suggests a number of different dimensions that can help in the development of a systematic research impact assessment framework. The paper then proceeds to indicate how boundaries and criteria around the definition of impact and these dimensions can be used to refine the impact assessment framework in order to focus on the objectives of the assessor. A pilot project, run at Brunel University, was used to test the validity of the approach and possible consequences. A tool specifically developed for the pilot, the Brunel Research Impact Device for Evaluation (BRIDE), is used for the analysis of research impact collected during the pilot. The paper reports on the findings of the analysis produced by BRIDE and confirms how a number of areas might be greatly affected by the boundaries set on definition and dimensions of research impact. The pilot project shows that useful information on impacts can be generated and it also provides a way to identify areas of work from each unit of assessment for which it would be worth developing narrative case studies. The pilot project has illustrated that it is feasible to make progress in terms of assessing impact, but that there are many difficulties to be addressed before impact assessment can be incorporated into a system of assessing the impact from the university sector as a whole. The paper concludes with an institutional perspective of the value of the approach and highlights possible applications. It also confirms the intention to expand the pilot and introduce new lines of investigation

HIV-1 reverse transcriptase mutations that confer decreased in vitro susceptibility to anti-RT DNA aptamer RT1t49 confer cross resistance to other anti-RT aptamers but not to standard RT inhibitors

RNA and DNA aptamers specific for HIV-1 reverse transcriptase (RT) can inhibit reverse transcription in vitro. RNA aptamers have been shown to potently block HIV-1 replication in culture. We previously reported mutants of HIV-1 RT with substitutions N255D or N265D that display resistance to the DNA aptamer RT1t49. Variant viruses bearing these mutations singly or in combination were compromised for replication. In order to address the wider applicability of such aptamers, HIV-1 RT variants containing the N255D, N265D or both (Dbl) were tested for the extent of their cross-resistance to other DNA/RNA aptamers as well as to other RT inhibitors. Both N265D and Dbl RTs were resistant to most aptamers tested. N255D mutant displayed mild resistance to two of the DNA aptamers, little change in sensitivity to three and hypersensitivity to one. Although all mutants displayed wild type-like ribonuclease H activity, their activity was compromised under conditions that prevent re-binding. This suggests that the processivity defect caused by these mutations can also affect RNase H function thus contributing further to the replication defect in mutant viruses. These results indicate that mutants conferring resistance to anti-RT aptamers significantly affect many HIV-1 RT enzymatic activities, which could contribute to preventing the development of resistance in vivo. If such mutations were to arise in vivo, our results suggest that variant viruses should remain susceptible to many existing anti-RT inhibitors. This result was tempered by the observation that NRTI-resistance mutations such as K65R can confer resistance to some anti-RT aptamers

Quantum Effects and Broken Symmetries in Frustrated Antiferromagnets

We investigate the interplay between frustration and zero-point quantum fluctuations in the ground state of the triangular and $J_1{-}J_2$ Heisenberg antiferromagnets, using finite-size spin-wave theory, exact diagonalization, and quantum Monte Carlo methods. In the triangular Heisenberg antiferromagnet, by performing a systematic size-scaling analysis, we have obtained strong evidences for a gapless spectrum and a finite value of the thermodynamic order parameter, thus confirming the existence of long-range N\'eel order.The good agreement between the finite-size spin-wave results and the exact and quantum Monte Carlo data also supports the reliability of the spin-wave expansion to describe both the ground state and the low-energy spin excitations of the triangular Heisenberg antiferromagnet. In the $J_1{-}J_2$ Heisenberg model, our results indicate the opening of a finite gap in the thermodynamic excitation spectrum at $J_2/J_1 \simeq 0.4$, marking the melting of the antiferromagnetic N\'eel order and the onset of a non-magnetic ground state. In order to characterize the nature of the latter quantum-disordered phase we have computed the susceptibilities for the most important crystal symmetry breaking operators. In the ordered phase the effectiveness of the spin-wave theory in reproducing the low-energy excitation spectrum suggests that the uniform spin susceptibility of the model is very close to the linear spin-wave prediction.Comment: Review article, 44 pages, 18 figures. See also PRL 87, 097201 (2001

The Functions and Practices of a Television Network

An Iterative Learning Control disturbance rejection approach is considered and it is shown that iteration variant learning filters can asymptotically give the controlled variable zero error and zero variance. Convergence is achieved with the assumption that the relative model error is less than one. The transient response of the suggested ILC algorithm is also discussed using a simulation example

Jamming Percolation and Glass Transitions in Lattice Models

A new class of lattice gas models with trivial interactions but constrained dynamics are introduced. These are proven to exhibit a dynamical glass transition: above a critical density, rho_c, ergodicity is broken due to the appearance of an infinite spanning cluster of jammed particles. The fraction of jammed particles is discontinuous at the transition, while in the unjammed phase dynamical correlation lengths and timescales diverge as exp[C(rho_c-rho)^(-mu)]. Dynamic correlations display two-step relaxation similar to glass-formers and jamming systems.Comment: 4 pages, 2 figs. Final version accepted for publication in Phys. Rev. Let

Density Matrix Renormalization Group Method for the Random Quantum One-Dimensional Systems - Application to the Random Spin-1/2 Antiferromagnetic Heisenberg Chain -

The density matrix renormalization group method is generalized to one dimensional random systems. Using this method, the energy gap distribution of the spin-1/2 random antiferromagnetic Heisenberg chain is calculated. The results are consistent with the predictions of the renormalization group theory demonstrating the effectiveness of the present method in random systems. The possible application of the present method to other random systems is discussed.Comment: 13 pages, 3 figures upon reques

Modeling microevolution in a changing environment: The evolving quasispecies and the Diluted Champion Process

Several pathogens use evolvability as a survival strategy against acquired immunity of the host. Despite their high variability in time, some of them exhibit quite low variability within the population at any given time, a somehow paradoxical behavior often called the evolving quasispecies. In this paper we introduce a simplified model of an evolving viral population in which the effects of the acquired immunity of the host are represented by the decrease of the fitness of the corresponding viral strains, depending on the frequency of the strain in the viral population. The model exhibits evolving quasispecies behavior in a certain range of its parameters, ans suggests how punctuated evolution can be induced by a simple feedback mechanism.Comment: 15 pages, 12 figures. Figures redrawn, some additional clarifications in the text. To appear in Journal of Statistical Mechanics: Theory and Experimen

Evidence for realignment of the charge density wave state in ErTe3_3 and TmTe3_3 under uniaxial stress via elastocaloric and elastoresistivity measurements

We report the evolution of a charge density wave (CDW) state in the quasi-2D rare-earth tritellurides ($R$Te$_3$ for $R$=Er,Tm) as a function of in-plane uniaxial stress. Measurements of the elastocaloric effect, resistivity, and elastoresistivity allow us to demonstrate the importance of in-plane antisymmetric strain on the CDW and to establish a phase diagram. We show that modest tensile stress parallel to the in-plane $a$-axis can reversibly switch the direction of the ordering wavevector between the two in-plane directions. This work establishes $R$Te$_3$ as a promising model system for the study of strain-CDW interactions in a quasi-2D square lattice.Comment: 18 pages, 12 figure