Leggett mode in a strong-coupling model of iron arsenide superconductors

Using a two-orbital model of the superconducting phase of the pnictides, we compute the spectrum of the Leggett mode -- a collective excitation of the phase of the superconducting gap known to exist in multi-gap superconductors -- for different possible symmetries of the superconducting order parameter. Specifically, we identify the small regions of parameter space where the Leggett mode lies below the two-particle continuum, and hence should be visible as a sharp resonance peak. We discuss the possible utility of the Leggett mode in distinguishing different momentum dependencies of the superconducting gap. We argue that the observation of a sharp Leggett mode would be consistent with the presence of strong electron-electron correlations in iron-based superconductors. We also emphasize the importance of the orbital character of the Leggett mode, which can result in an experimental observation of the mode in channels other than $A_{1g}$

A Protocol for Citizen Science Monitoring of Recently-Planted Urban Trees

In this article, we present a protocol for citizen science monitoring of planted urban trees. Informed by social-ecological systems, urban forestry, and tree physiology research, the Planted Tree Re-Inventory Protocol is designed to allow minimally-trained volunteers or citizen scientists to collect data about the factors that influence urban tree survival and growth. We consider characteristics of the tree, the biophysical environment, institutions and management, and the community as factors that influence urban forest outcomes. Here, we reflect on tree planting organizations and their desire and capacity for monitoring. Then we define citizen science and review its use in urban forestry to date. Next we discuss the measurement of urban tree outcomes (survival and growth), and summarize the literature on factors influencing tree success and urban forest outcomes. Finally we present an overview of the main categories of variables included the Protocol. The entire Protocol is available on the Bloomington Urban Forestry Research Group website (http://www.indiana.edu/~cipec/research/bufrg_protocol) and as an Appendix to this paper

Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer.Comment: 11 pages, 4 figures. To appear in APL, April 200

Legislative strengthening meets party support in international assistance: a closer relationship?

Recent reports recommend that international efforts to help strengthen legislatures in emerging democracies should work more closely with support for building stronger political parties and competitive party systems. This article locates the recommendations within international assistance more generally and reviews the arguments. It explores problems that must be addressed if the recommendations are to be implemented effectively. The article argues that an alternative, issue-based approach to strengthening legislatures and closer links with civil society could gain more traction. However, that is directed more centrally at promoting good governance for the purpose of furthering development than at democratisation goals sought by party aid and legislative strengtheners in the democracy assistance industry

NMR study of a bimesogenic liquid crystal with two nematic phases

Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independent Maier-Saupe terms is successful in fitting the observed dipolar couplings (order parameters) of para-, meta- and ortho-dichlorobenzene solutes in both the nematic phases of 39 wt% of 4-n-pentyl-4′-cyanobiphenyl (5CB) in α,ω-bis(4-4′-cyanobiphenyl)nonane (CB_C9_CB) to better than the 5% level. The derived liquid-crystal potential parameters G₁ and G₂ for each solute in the N and Ntb phases will be discussed. The most interesting observation is that G1 (associated with size and shape interactions) is almost constant in the Ntb phase, whereas G₂ (associated with longer-range electrostatic interactions) has large variation, even changing sign

Observation of the influence of centrifugal distortion of the methane molecule on nuclear spin relaxation in the gas.

The spin–lattice relaxation time T1 was measured in gaseous CH4 as a function of density at room temperature between 0.006 and 7.0 amagats. T1 was found to pass through a minimum near 0.04 amagats in agreement with previous, less precise measurements. The spin–rotation interaction is the dominant relaxation mechanism in gaseous CH4. Since the spin–rotation constants are accurately known for CH4, the relaxation experiments provide a check on the theory of spin–lattice relaxation for spherical top molecules. In the conventional theory, it is assumed that the correlation function of the spin–rotation interaction is a simple exponential function of time. These experiments show that this assumption is not true for CH4 gas. The observed fine structure in the plot of relaxation rate versus density is attributed to the influence of centrifugal distortion of the CH4molecule, which removes the degeneracy of rotational states having the same value of the quantum number J by an amount somewhat greater than the nuclear Larmor frequency of 30 MHz

Earth Observations Division version of the Laboratory for Applications of Remote Sensing System (EOD-LARSYS) user guide for the IBM 370/148. Volume 3: As-built documentation (sections 13-23)

There are no author-identified significant results in this report

Earth Observations Division version of the Laboratory for Applications of Remote Sensing system (EOD-LARSYS) user guide for the IBM 370/148. Volume 4: Program listings

There are no author-identified significant results in this report