Beyond the hashtags: #Ferguson, #Blacklivesmatter, and the online struggle for offline justice

In 2014, a dedicated activist movement--Black Lives Matter (BLM)--ignited an urgent national conversation about police killings of unarmed Black citizens. Online tools have been anecdotally credited as critical in this effort, but researchers are only beginning to evaluate this claim. This research report examines the movement's uses of online media in 2014 and 2015. To do so, we analyze three types of data: 40.8 million tweets, over 100,000 web links, and 40 interviews of BLM activists and allies

Universal magnetic and structural behaviors in the iron arsenides

Commonalities among the order parameters of the ubiquitous antiferromagnetism present in the parent compounds of the iron arsenide high temperature superconductors are explored. Additionally, comparison is made between the well established two-dimensional Heisenberg-Ising magnet, K$_2$NiF$_4$ and iron arsenide systems residing at a critical point whose structural and magnetic phase transitions coincide. In particular, analysis is presented regarding two distinct classes of phase transition behavior reflected in the development of antiferromagnetic and structural order in the three main classes of iron arsenide superconductors. Two distinct universality classes are mirrored in their magnetic phase transitions which empirically are determined by the proximity of the coupled structural and magnetic phase transitions in these materials.Comment: 6 pages, 4 figure

How Black Twitter and Other Social Media Communities Interact With Mainstream News

People have been forming communities using digital communication technologies since long before the web as we know it today. Social media are only the latest in a long series of digital forums that have enabled global conversations and connections around nearly any topic imaginable. With its emphasis on public accessibility and real-time content production, Twitter has become a major hub for communities of all types and sizes. The issues and voices of people of color and women have attracted much attention from professional journalists over the past few years.1 Yet many such individuals have criticized journalists’ portrayals and coverage of issues that are important to them. In response, some participants have assumed the role of news creators and distributors, focusing on their communities’ particular concerns.2 Understanding these emerging social subcultures will allow more accurate portrayals of diverse communities and yield insights for better journalistic engagement in the digital age

Zn-induced spin dynamics in overdoped La2−x_{2-x}Srx_xCu1−y_{1-y}Zny_yO4_4

Spin fluctuations and the local spin susceptibility in isovalently Zn-substituted La$_{2-x}$Sr$_{x}$Cu$_{1-y}$Zn$_y$O$_4$ ($x=0.25$, $y\approx0.01$) are measured via inelastic neutron scattering techniques. As Zn$^{2+}$ is substituted onto the Cu$^{2+}$-sites, an anomalous enhancement of the local spin susceptibility $\chi^{\prime\prime}(\omega)$ appears due to the emergence of a commensurate antiferromagnetic excitation centered at wave vector \textbf{Q}$=(\pi, \pi, 0)$ that coexists with the known incommensurate SDW excitations at \textbf{Q}$_{HK}=(\pi\pm\delta,\pi), (\pi,\pi\pm\delta)$. Our results support a picture of Zn-induced antiferromagnetic (AF) fluctuations appearing through a local staggered polarization of Cu$^{2+}$-spins, and the simultaneous suppression of T$_c$ as AF fluctuations are slowed in proximity to Zn-impurities suggests the continued importance of high energy AF fluctuations at the far overdoped edge of superconductivity in the cuprates.Comment: 10 pages, 8 figure

Antiferromagnetic Critical Fluctuations in BaFe2_2As2_2

Magnetic correlations near the magneto-structural phase transition in the bilayer iron pnictide parent compound, BaFe$_2$As$_2$, are measured. In close proximity to the antiferromagnetic phase transition in BaFe$_2$As$_2$, a crossover to three dimensional critical behavior is anticipated and has been preliminarily observed. Here we report complementary measurements of two-dimensional magnetic fluctuations over a broad temperature range about T$_N$. The potential role of two-dimensional critical fluctuations in the magnetic phase behavior of BaFe$_2$As$_2$ and their evolution near the anticipated crossover to three dimensional critical behavior and long-range order are discussed.Comment: 6 pages, 4 figures; Accepted for publication in Physical Review

The nature of the magnetic and structural phase transitions in BaFe2_{2}As2_{2}

We present the results of an investigation of both the magnetic and structural phase transitions in a high quality single crystalline sample of the undoped, iron pnictide compound BaFe$_2$As$_2$. Both phase transitions are characterized via neutron diffraction measurements which reveal simultaneous, continuous magnetic and structural orderings with no evidence of hysteresis, consistent with a single second order phase transition. The onset of long-range antiferromagnetic order can be described by a simple power law dependence $\phi(T)^2\propto(1-\frac{T}{T_N})^{2\beta}$ with $\beta=0.103\pm0.018$; a value near the $\beta=0.125$ expected for a two-dimensional Ising system. Biquadratic coupling between the structural and magnetic order parameters is also inferred along with evidence of three-dimensional critical scattering in this system.Comment: New figure and discussion added. Length: 11 pages, 7 figure

Heat capacity study of BaFe2_{2}As2_{2}: effects of annealing

Heat-capacity, X-ray diffraction, and resistivity measurements on a high-quality BaFe$_{2}$As$_{2}$ sample show an evolution of the magneto-structural transition with successive annealing periods. After a 30-day anneal the resistivity in the (ab) plane decreases by more than an order of magnitude, to 12 $\mu\Omega$cm, with a residual resistance ratio $\sim$36; the heat-capacity anomaly at the transition sharpens, to an overall width of less than K, and shifts from 135.4 to 140.2 K. The heat-capacity anomaly in both the as-grown sample and after the 30-day anneal shows a hysteresis of $\sim$0.15 K, and is unchanged in a magnetic field $\mu_{0}$H = 14 T. The X-ray and heat-capacity data combined suggest that there is a first order jump in the structural order parameter. The entropy of the transition is reported

A hashtag worth a thousand words: Discursive strategies around #JeNeSuisPasCharlie after the 2015 Charlie Hebdo shooting

Following a shooting attack by two self-proclaimed Islamist gunmen at the offices of French satirical weekly Charlie Hebdo on 7 January 2015, there emerged the hashtag #JeSuisCharlie on Twitter as an expression of solidarity and support for the magazine’s right to free speech. Almost simultaneously, however, there was also #JeNeSuisPasCharlie explicitly countering the former, affirmative hashtag. Based on a multimethod analysis of 74,047 tweets containing #JeNeSuisPasCharlie posted between 7 and 11 January, this article reveals that users of the hashtag under study employed various discursive strategies and tactics to challenge the mainstream framing of the shooting as the universal value of freedom of expression being threatened by religious extremism, while protecting themselves from the risk of being viewed as disrespecting victims or endorsing the violence committed. The significance of this study is twofold. First, it extends the literature on strategic speech acts by examining how such acts take place in a social media context. Second, it highlights the need for a multidimensional and reflective methodology when dealing with data mined from social media

Examining user comments for deliberative democracy: a corpus-driven analysis of the climate change debate online

The public perception of climate change is characterized by heterogeneity, even polarization. Deliberative discussion is regarded by some as key to overcoming polarization and engaging various publics with the complex issue of climate change. In this context, online engagement with news stories is seen as a space for a new “deliberative democratic potential” to emerge. This article examines aspects of deliberation in user comment threads in response to articles on climate change taken from the Guardian. “Deliberation” is understood through the concepts “reciprocity”, “topicality”, and “argumentation”. We demonstrate how corpus analysis can be used to examine the ways in which online debates around climate change may create or deny opportunities for multiple voices and deliberation. Results show that whilst some aspects of online discourse discourage alternative viewpoints and demonstrate “incivility”, user comments also show potential for engaging in dialog, and for high levels of interaction