The Quasi-1D S=1/2 Antiferromagnet Cs2CuCl4 in a Magnetic Field

Magnetic excitations of the quasi-1D S=1/2 Heisenberg antiferromagnet (HAF) Cs2CuCl4 have been measured as a function of magnetic field using neutron scattering. For T<0.62 K and B=0 T the weak inter-chain coupling produces 3D incommensurate ordering. Fields greater than Bc =1.66 T, but less than the field (~8 T) required to fully align the spins, are observed to decouple the chains, and the system enters a disordered intermediate-field phase (IFP). The IFP excitations are in agreement with the predictions of Muller et al. for the 1D S=1/2 HAF, and Talstra and Haldane for the related 1/r^2 chain (the Haldane-Shastry model). This behaviour is inconsistent with linear spin-wave theory.Comment: 10 pages, 4 encapsulated postscript figures, LaTeX, to be published in PRL, e-mail comments to [email protected]

Civil Society, Conflict and Violence

This book is available as open access through the Bloomsbury Open Access programme and is available on www.bloomsburycollections.com. This book looks at the role that civil society organizations play in dealing with conflict and violence. The authors argue that in most of the prevalent conceptualizations the conflict dimension of civil society is either downplayed or inadequately addressed. They contend that the ability to deal with conflict is at the heart of organized civil society; in the political process, one of civil society's key functions is to express and mediate between different interests, thus contributing to political decision-making. The chapters draw on detailed, empirical data from the CIVICUS Civil Society Index - a unique comparative data-set drawn from 25 countries, which has not previously been made publicly available. It examines the different ways violence has been manifested in civil societies, the meaning of violent protest and the impact of security legislation that might hinder the mediating efforts of civil society. The book offers a sophisticated comparison between conflict and post-conflict countries and an analysis of the role of civil society in conflict resolution, reconciliation and transitional justice

Civil Society, Conflict and Violence

This book is available as open access through the Bloomsbury Open Access programme and is available on www.bloomsburycollections.com. This book looks at the role that civil society organizations play in dealing with conflict and violence. The authors argue that in most of the prevalent conceptualizations the conflict dimension of civil society is either downplayed or inadequately addressed. They contend that the ability to deal with conflict is at the heart of organized civil society; in the political process, one of civil society's key functions is to express and mediate between different interests, thus contributing to political decision-making. The chapters draw on detailed, empirical data from the CIVICUS Civil Society Index - a unique comparative data-set drawn from 25 countries, which has not previously been made publicly available. It examines the different ways violence has been manifested in civil societies, the meaning of violent protest and the impact of security legislation that might hinder the mediating efforts of civil society. The book offers a sophisticated comparison between conflict and post-conflict countries and an analysis of the role of civil society in conflict resolution, reconciliation and transitional justice

Still a Private Universe? Community College Students’ Understanding of Evolution

Background Measuring what students know and retain about evolution is essential to improving our understanding of how students learn evolution. The literature shows that college students appear to have a poor understanding of evolution, answering questions on various instruments correctly only about half of the time. There is little research regarding evolution understanding among community college students and so this study examines if those students who are enrolled in life science classes, who are assessed using questions based on grade eight standards, show a better understanding of evolutionary principles than younger students and if there are differences in knowledge based on course enrollment. The authors utilized a survey of 41 items of the Life Sciences Concept Inventory that were specifically designed to measure knowledge about various aspects of evolution that relate to the 5–8 grade science standards on evolution. They administered it to 191 adult students who were enrolled in nine sections across five life sciences courses at one community college in Southern California. Results Results indicated that the students in this study possessed a fair understanding of evolution, averaging scores of nearly 70%, higher than what other researchers have found (using different instruments). Students enrolled in biology major classes scored significantly higher than those enrolled in non/mixed-major courses. There was a strong relationship between item difficulty and discrimination as well as difficulty and misconception strength. When compared with the 5–8 grade student data, the community college students showed a lower level of difficulty and higher levels of item discrimination, but the proportion choosing the most popular wrong answer (the dominant misconception), was comparable. College students showed similar patterns to the grade 5–8 students in terms of which questions and which material were the most challenging, despite performing better overall. Conclusions In this study, students possessed fair understanding of evolution. However, they were assessed with an instrument designed for 5th through 8th grade students. The results of this study support the need for more research into how community college students understand evolution and which factors impact that understanding

Quantum phase estimation with lossy interferometers

We give a detailed discussion of optimal quantum states for optical two-mode interferometry in the presence of photon losses. We derive analytical formulae for the precision of phase estimation obtainable using quantum states of light with a definite photon number and prove that maximization of the precision is a convex optimization problem. The corresponding optimal precision, i.e. the lowest possible uncertainty, is shown to beat the standard quantum limit thus outperforming classical interferometry. Furthermore, we discuss more general inputs: states with indefinite photon number and states with photons distributed between distinguishable time bins. We prove that neither of these is helpful in improving phase estimation precision.Comment: 12 pages, 5 figure

Broadband study of blazar 1ES 1959+650 during flaring state in 2016

Aim : The nearby TeV blazar 1ES 1959+650 (z=0.047) was reported to be in flaring state during June - July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We studied the spectral energy distributions (SEDs) in different states of the flare during MJD 57530 - 57589 using simultaneous multiwaveband data to understand the possible broadband emission scenario during the flare. Methods : The UV/optical and X-ray data from UVOT and XRT respectively on board Swift and high energy $\gamma$-ray data from Fermi-LAT are used to generate multiwaveband lightcurves as well as to obtain high flux states and quiescent state SEDs. The correlation and lag between different energy bands is quantified using discrete correlation function. The synchrotron self Compton (SSC) model was used to reproduce the observed SEDs during flaring and quiescent states of the source. Results : A decent correlation is seen between X-ray and high energy $\gamma$-ray fluxes. The spectral hardening with increase in the flux is seen in X-ray band. The powerlaw index vs flux plot in $\gamma$-ray band indicates the different emission regions for 0.1 - 3 GeV and 3-300 GeV energy photons. Two zone SSC model satisfactorily fits the observed broadband SEDs. The inner zone is mainly responsible for producing synchrotron peak and high energy $\gamma$-ray part of the SED in all states. The second zone is mainly required to produce less variable optical/UV and low energy $\gamma$-ray emission. Conclusions : Conventional single zone SSC model does not satisfactorily explain broadband emission during observation period considered. There is an indication of two emission zones in the jet which are responsible for producing broadband emission from optical to high energy $\gamma$-rays.Comment: 11 pages, 12 figures, Accepted in A&

Molecular frame photoelectron angular distribution for oxygen 1s photoemission from CO_2 molecules

We have measured photoelectron angular distributions in the molecular frame (MF-PADs) for O 1s photoemission from CO2, using photoelectron-O+–CO+ coincidence momentum imaging. Results for the molecular axis at 0, 45 and 90° to the electric vector of the light are reported. The major features of the MF-PADs are fairly well reproduced by calculations employing a relaxed-core Hartree–Fock approach. Weak asymmetric features are seen through a plane perpendicular to the molecular axis and attributed to symmetry lowering by anti-symmetric stretching motion

Quantum frequency estimation with trapped ions and atoms

We discuss strategies for quantum enhanced estimation of atomic transition frequencies with ions stored in Paul traps or neutral atoms trapped in optical lattices. We show that only marginal quantum improvements can be achieved using standard Ramsey interferometry in the presence of collective dephasing, which is the major source of noise in relevant experimental setups. We therefore analyze methods based on decoherence free subspaces and prove that quantum enhancement can readily be achieved even in the case of significantly imperfect state preparation and faulty detections.Comment: 5 pages + 6 pages appendices; published versio

Phonon Life-times from first principles self consistent lattice dynamics

Phonon lifetime calculations from first principles usually rely on time consuming molecular dynamics calculations, or density functional perturbation theory (DFPT) where the zero temperature crystal structure is assumed to be dynamically stable. Here a new and effective method for calculating phonon lifetimes from first principles is presented, not limited to crystal structures stable at 0 K, and potentially much more effective than most corresponding molecular dynamics calculations. The method is based on the recently developed self consistent lattice dynamical method and is here tested by calculating the bcc phase phonon lifetimes of Li, Na, Ti and Zr, as representative examples.Comment: 4 pages, 4 figur