Coronal--Temporal Correlations in GX339-4: Hysteresis, Possible Reflection Changes, and Implications for ADAFs

We present spectral fits and timing analysis of Rossi X-ray Timing Explorer observations of GX339-4. These observations were carried out over a span of more than two years and encompassed both the soft/high and hard/low states. Hysteresis in the soft state/hard state transition is observed. The hard state exhibits a possible anti-correlation between coronal compactness (i.e., spectral hardness) and the covering fraction of cold, reflecting material. The correlation between `reflection fraction' and soft X-ray flux, however, appears to be more universal. Furthermore, low flux, hard state observations - taken over a decline into quiescence- show that the Fe line, independent of `reflection fraction', remains broad and at a roughly constant equivalent width, counter to expectations from ADAF models. All power spectral densities (PSD) of the hard state X-ray lightcurves are describable as the sum of just a few broad, quasi-periodic features with frequencies that roughly scale as coronal compactness to the -3/2 power. Similar to observations of Cyg X-1, time lags between soft and hard variability anti-correlate with coronal compactness. A stronger correlation is seen between the time lags and the `reflection fraction'.Comment: 29 Pages, 17 Figures, 6 Tables. Accepted for Publication in MNRAS. (Abstract Abridged

Using data visualization in creativity workshops: a new tool in the designer's kit

Creativity workshops have proved effective in drawing out unexpected requirements and giving form to participants' novel ideas. Here, we introduce a new addition to the workshop designer's toolkit: interactive data visualization, used as stimuli to prompt insight and inspire creativity. We first describe a pilot study in which we compare the effectiveness of two different styles of data visualization. Here we found that a less ambiguous style was more effective in supporting idea generation. Following this, we report a case study in which we employ data visualization within a service design workshop, where participants gain insights that are later realized in design ideas

Dynamics from diffraction

A model-independent approach for the extraction of detailed lattice dynamical information from neutron powder diffraction data is described. The technique is based on a statistical analysis of atomistic configurations generated using reverse Monte Carlo structural refinement. Phonon dispersion curves extracted in this way are shown to reproduce many of the important features found in those determined independently using neutron triple-axis spectroscopy. The extent to which diffraction data are sensitive to lattice dynamics is explored in a range of materials. The prospect that such detailed dynamical information might be accessible using comparatively facile experiments such as neutron powder diffraction is incredibly valuable when studying systems for which established spectroscopic methods are prohibitive or inappropriate

An economic examination of state legal regimes within the U.S. system of federalism

This dissertation is a collection of essays, each of which studies certain aspects of and differences between state legal frameworks within the U.S. Specifically, I analyze how even marginal differences between laws across the states can lead to radically different outcomes and incentives for both public and private actors. The first chapter explores state antitrust enforcement, as carried out by each state\u27s attorney general, to empirically test the potential policy business cycle that is created during elections for that office and for those sitting attorneys general that simultaneously pursue a gubernatorial position within their respective state. The second chapter applies Schumpeter\u27s (1942) process of creative destruction in the light of its impact on legal formation and creation. In particular, this chapter explores how the process of entrepreneurial creative destruction creates a gap in existing law and legal precedent, which simultaneously sets in motion a process of legal creative destruction. In this framework, entrepreneurs, at the margin, will shed the legal risks they face by shifting their activities to those jurisdictions that will most predictably create new law or legal precedent to cope with the new entrepreneurial processes or discoveries. The third chapter explores the sovereign debt crisis that swept the U.S. between 1839 and 1842, the aftermath of which caused eight states and one territory to default on their debt obligations, five of them eventually repudiating all or part of those obligations. This chapter further empirically analyzes the post default period when many states passed constitutional constraints meant to prevent future state governments from pursuing similar behavior through time. I test whether financial markets considered those constitutional constraints to be both binding and credible. Overall, the results suggest that markets did in fact react positively to these constitutional constraints, which allowed state governments to reenter capital markets relatively rapidly and on relatively favorable terms, even after defaulting

First and second order magnetic and structural transitions in BaFe2(1−x)_{2(1-x)}Co2x_{2x}As2_{2}

We present here high resolution magnetization measurements on high-quality BaFe$_{2(1-x)}$Co$_{2x}$As$_{2}$, 0$\leq$x$\leq$0.046 as-grown single crystals. The results confirm the existence of a magnetic tricritical point in the ($x$,$T$) plane at x$^{m}_{tr}$$\approx$0.022 and reveal the emergence of the heat capacity anomaly associated with the onset of the structural transition at x$^{s}$$\approx$0.0064. We show that the samples with doping near x$^{m}_{tr}$ do not show superconductivity, but rather superconductivity emerges at a slightly higher cobalt doping, x$\approx$0.0315Comment: 4 pages, 5 figure