Measuring High-Energy Spectra with HAWC

The High-Altitude Water-Cherenkov (HAWC) experiment is a TeV $\gamma$-ray observatory located \unit[4100]{m} above sea level on the Sierra Negra mountain in Puebla, Mexico. The detector consists of 300 water-filled tanks, each instrumented with 4 photomultiplier tubes that utilize the water-Cherenkov technique to detect atmospheric air showers produced by cosmic $\gamma$ rays. Construction of HAWC was completed in March of 2015. The experiment's wide instantaneous field of view (\unit[2]{sr}) and high duty cycle (> 95\%) make it a powerful survey instrument sensitive to pulsars, supernova remnants, and other $\gamma$-ray sources. The mechanisms of particle acceleration at these sources can be studied by analyzing their high-energy spectra. To this end, we have developed an event-by-event energy-reconstruction algorithm using an artificial neural network to estimate energies of primary $\gamma$ rays at HAWC. We will present the details of this technique and its performance as well as the current progress toward using it to measure energy spectra of $\gamma$-ray sources.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution

Mr Casement goes to Washington: The Politics of the Putumayo Photographs

It is well-known that when Roger Casement left the Putumayo in November 1910, he took with him several Barbadian men, two Huitoto youths and a bundle of depositions documenting in extraordinary detail the atrocities committed by the Peruvian Amazon Company. What is far less known (and we have to thank Angus Mitchell for directing our attention to it in his publications) is that he also had with him a camera and several rolls of film waiting to be developed. Unfortunately only a handful of the photographs Casement had developed have survived. They lie in a box in the National Photographic Archive in Dublin, dormant and seemingly historically inert. Thankfully, the historicity of these images can be reconstructed, for in March 1912, when it looked asthough the American government was backsliding in its promise of putting political pressure on the Peruvian government to protect the Indians and to stop the brutal labour regime in the rubber lands of the Putumayo, Casement posted copies of a number of these photographs to George Young at the British Embassy in Washington to shock the American administration into action. All of these photographs (which are in the National Archives in Washington, DC) were personally annotated by Casement, in the manner of an atrocity narrative, and provide a rare insight into the political possibilities of the visual image.

Of rats and children : plague, malaria, and the early history of disease reservoirs (1898-1930)

Funding: Research leading to this article by Matheus Alves Duarte da Silva was funded by the Wellcome Trust [grant ID 217988/Z/19/Z] for the project “The Global War Against the Rat and the Epistemic Emergence of Zoonosis”.This article’s jumping-off point is the highly incisive but often-ignored claim by the French doctor, Louis-Jacques Tanon, in 1922 that rats acted as plague reservoirs in Paris; in other words, that they harboured the plague bacillus but were refractory to it. This claim partially reframed the fight against this disease in the French capital in the 1920s, which became more centred on surveilling the plague reservoir rather than on destroying rats. Drawing upon Tanon’s hypothesis, this article explores the emergence, evolution, and several iterations of the idea of disease reservoirs in the early twentieth century. On the one hand, it describes the crafting of a range of ideas with which Tanon was directly or indirectly dialoguing, namely, that rats could present a stage called chronic plague, which was especially developed in India; and that human populations, especially children, acted as sources or reservoirs of malaria in Sierra Leone and Algeria. On the other hand, this article shows how Tanon created original reasoning by combining and reformulating some of these ideas and applying them to Paris. Thus, this article contributes to the early history of reasoning in terms of disease reservoirs, as well as presenting a more dynamic history of microbiology by showing how concepts crafted in the “Rest” found their place in Europe.Peer reviewe

Interferometric weak value deflections: quantum and classical treatments

We derive the weak value deflection given in a paper by Dixon et al. (Phys. Rev. Lett. 102, 173601 (2009)) both quantum mechanically and classically. This paper is meant to cover some of the mathematical details omitted in that paper owing to space constraints

Brief mindfulness training enhances cognitive control in socioemotional contexts: Behavioral and neural evidence.

In social contexts, the dynamic nature of others' emotions places unique demands on attention and emotion regulation. Mindfulness, characterized by heightened and receptive moment-to-moment attending, may be well-suited to meet these demands. In particular, mindfulness may support more effective cognitive control in social situations via efficient deployment of top-down attention. To test this, a randomized controlled study examined effects of mindfulness training (MT) on behavioral and neural (event-related potentials [ERPs]) responses during an emotional go/no-go task that tested cognitive control in the context of emotional facial expressions that tend to elicit approach or avoidance behavior. Participants (N = 66) were randomly assigned to four brief (20 min) MT sessions or to structurally equivalent book learning control sessions. Relative to the control group, MT led to improved discrimination of facial expressions, as indexed by d-prime, as well as more efficient cognitive control, as indexed by response time and accuracy, and particularly for those evidencing poorer discrimination and cognitive control at baseline. MT also produced better conflict monitoring of behavioral goal-prepotent response tendencies, as indexed by larger No-Go N200 ERP amplitudes, and particularly so for those with smaller No-Go amplitude at baseline. Overall, findings are consistent with MT's potential to enhance deployment of early top-down attention to better meet the unique cognitive and emotional demands of socioemotional contexts, particularly for those with greater opportunity for change. Findings also suggest that early top-down attention deployment could be a cognitive mechanism correspondent to the present-oriented attention commonly used to explain regulatory benefits of mindfulness more broadly

Commit and Connect: VCU Goes Green

In alignment with Theme IV of VCU’s Quest for Distinction, this university volunteer project will help to commit and connect faculty, staff, students, and alumni with a community education partner to help launch a green or sustainable project while promoting, teaching and educating participants on the value of sustainable living

Three-dimensional simulations of inorganic aerosol distributions in east Asia during spring 2001

In this paper, aerosol composition and size distributions in east Asia are simulated using a comprehensive chemical transport model. Three-dimensional aerosol simulations for the TRACE-P and ACE-Asia periods are performed and used to help interpret actual observations. The regional chemical transport model, STEM-2K3, which includes the on-line gas-aerosol thermodynamic module SCAPE II, and explicitly considers chemical aging of dust, is used in the analysis. The model is found to represent many of the important observed features. The Asian outflow during March and April of 2001 is heavily polluted with high aerosol loadings. Under conditions of low dust loading, SO_2 condensation and gas phase ammonia distribution determine the nitrate size and gas-aerosol distributions along air mass trajectories, a situation that is analyzed in detail for two TRACE-P flights. Dust is predicted to alter the partitioning of the semivolatile components between the gas and aerosol phases as well as the size distributions of the secondary aerosol constituents. Calcium in the dust affects the gas-aerosol equilibrium by shifting the equilibrium balance to an anion-limited status, which benefits the uptake of sulfate and nitrate, but reduces the amount of aerosol ammonium. Surface reactions on dust provide an additional mechanism to produce aerosol nitrate and sulfate. The size distribution of dust is shown to be a critical factor in determining the size distribution of secondary aerosols. As much of the dust mass is found in the supermicron mode (70–90%), appreciable amounts of sulfate and nitrate are found in the supermicron particles. For sulfate the observations and the analysis indicate that 10–30% of sulfate is in the supermicron fraction during dust events; in the case of nitrate, more than 80% is found in the supermicron fraction