Seeing Through the Noise: Seismic Reflection Profiling in Urban Areas

Studies for urban hazard or resource assessment often take place in densely populated areas characterized by considerable cultural noise. These site conditions can severely compromise seismic reflection data quality. We have collected vibroseis and hammer (weight drop) seismic reflection data in a range of geologic conditions to image stratigraphy and structures in the upper one km along regional highways, city streets,and power line access roads. In addition to the challenges of safety and outreach, acquisition efforts along busy streets and highways often encounter poor receiver coupling and large-amplitude coherent noise from traffic and power lines. Although higher quality seismic reflection data may be obtained by simply choosing alternate sites with less cultural noise, modifications to the acquisition and processing step scan minimize the effects of cultural noise and poor coupling where profiling is most relevant. Flagging crews, flyers and public announcements assist with outreach and safety concerns, and the local news media are often enthusiastic about publicizing geologic studies. Recording long-record vibroseis data reduces the effects of noise by itself,but data quality can be further optimized by recording uncorrelated,unstacked data and applying precorrelation amplitude adjustments and filters. Recording individual hammer shots likewise allows gains or mutes to normalize or remove traffic noise prior to vertical stacking. Large numbers of receiver channels allow attenuation of random noise and velocity filtering to remove coherent noise. Because ground roll and normal moveout (NMO) corrections minimize near-surface coverage, asymmetric source-receiver geometry allows for additional near-surface fold while muting large amplitude ground rolland NMO stretch. Source and geophone coupling on road shoulder scan degrade signal quality due to variable materials and topography,but these problems are often addressed with static corrections. Our experience is that high-quality seismic data can be obtained in noisy urban areas, but many recorded channels and a careful attention to acquisition and processing procedures can significantly improve the results

Are the impacts of land use on warming underestimated in climate policy?

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Research Letters 12 (2017): 094016, doi:10.1088/1748-9326/aa836d.While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing. In this study we compute time series of global surface temperature change separately for LULCC and non-LULCC sources (primarily fossil fuel burning), and show that because of the extra warming associated with the co-emission of methane and nitrous oxide with LULCC carbon dioxide emissions, and a co-emission of cooling aerosols with non-LULCC emissions of carbon dioxide, the linear relationship between cumulative carbon dioxide emissions and temperature has a two-fold higher slope for LULCC than for non-LULCC activities. Moreover, projections used in the Intergovernmental Panel on Climate Change (IPCC) for the rate of tropical land conversion in the future are relatively low compared to contemporary observations, suggesting that the future projections of land conversion used in the IPCC may underestimate potential impacts of LULCC. By including a ‘business as usual’ future LULCC scenario for tropical deforestation, we find that even if all non-LULCC emissions are switched off in 2015, it is likely that 1.5 ◦C of warming relative to the preindustrial era will occur by 2100. Thus, policies to reduce LULCC emissions must remain a high priority if we are to achieve the low to medium temperature change targets proposed as a part of the Paris Agreement. Future studies using integrated assessment models and other climate simulations should include more realistic deforestation rates and the integration of policy that would reduce LULCC emissions.We would like to acknowledge the support from grants NSF-ATM1049033, NSF-CCF-1522054, NSFAGS- 1048827 and DOE-SC0016362, DOE Office of Science Biogeochemical Cycles Feedbacks and ACME Science Focus Areas as well as assistance from the Atkinson Center for a Sustainable Futur

War and the Reelection Motive: Examining the Effect of Term Limits

This article investigates the relationship between term limits and international conflict. Theories of political survival and diversionary war both imply term limits should play a role in international relations, whereas “permanent referendum theory,” largely motivated by work in American politics, suggests otherwise. Drawing on these theories, we formulate and test competing hypotheses regarding term limits and international crises. Using dyadic militarized interstate disputes data and information on forty-eight democracies with term limits, we uncover strong evidence to support the claim that leaders reaching final terms in office are more likely to initiate conflict than those still subject to reelection. Moreover, we find that the likelihood of conflict initiation is significantly higher during times of recession, but only in the absence of binding term limits. While binding electoral terms and economic downturns are both independently associated with increased levels of conflict initiation, in concert their conditional effects actually counteract each other

Conservative Constraints on Dark Matter from the Fermi-LAT Isotropic Diffuse Gamma-Ray Background Spectrum

We examine the constraints on final state radiation from Weakly Interacting Massive Particle (WIMP) dark matter candidates annihilating into various standard model final states, as imposed by the measurement of the isotropic diffuse gamma-ray background by the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark matter annihilation has contributions from the local Milky Way (MW) as well as from extragalactic dark matter. The signal from the MW is very insensitive to the adopted dark matter profile of the halos, and dominates the signal from extragalactic halos, which is sensitive to the low mass cut-off of the halo mass function. We adopt a conservative model for both the low halo mass survival cut-off and the substructure boost factor of the Galactic and extragalactic components, and only consider the primary final state radiation. This provides robust constraints which reach the thermal production cross-section for low mass WIMPs annihilating into hadronic modes. We also reanalyze limits from HESS observations of the Galactic Ridge region using a conservative model for the dark matter halo profile. When combined with the HESS constraint, the isotropic diffuse spectrum rules out all interpretations of the PAMELA positron excess based on dark matter annihilation into two lepton final states. Annihilation into four leptons through new intermediate states, although constrained by the data, is not excluded.Comment: 11 pages, 5 figures. v3: minor revisions, matches version to appear in JCA

Sex-Based Differences in Outcomes Following Peripheral Artery Revascularization: Insights From VOYAGER PAD.

Background Despite high female prevalence of peripheral artery disease (PAD), little is known about sex-based outcomes after lower extremity revascularization (LER) for symptomatic PAD. The effects of rivaroxaban according to sex following LER have not been fully reported. Methods and Results In VOYAGER PAD (Vascular Outcomes Study of ASA [acetylsalicylic acid] Along with Rivaroxaban in Endovascular or Surgical Limb Revascularization for Peripheral Artery Disease), low-dose rivaroxaban versus placebo on a background of aspirin reduced the composite primary efficacy outcome of cardiovascular and limb events in patients with PAD undergoing LER. Unplanned index limb revascularization was prespecified and prospectively ascertained. The primary safety outcome was Thrombolysis in Myocardial Infarction major bleeding. Analyses of outcomes and treatment effects by sex were performed using Cox proportional hazards models. Among 6564 randomly assigned patients followed for a median of 28 months, 1704 (26.0%) were women. Among patients administered placebo, women were at similar risk for the primary efficacy outcome (hazard ratio [HR], 0.90; [95% CI, 0.74-1.09]; P=0.29) as men, while female sex was associated with a trend toward higher risk of unplanned index limb revascularization (HR, 1.18; [95% CI, 1.00-1.40]; P=0.0499). Irrespective of sex, effects of rivaroxaban were consistent for the primary efficacy outcome (P-interaction=0.22), unplanned index limb revascularization (P-interaction=0.64), and bleeding (P-interaction=0.61). Women were more likely than men to discontinue study treatment (HR, 1.13; [95% CI, 1.03-1.25]; P=0.0099). Conclusions Among >1700 women with PAD undergoing LER, women and men were at similar risk for the primary outcome, but a trend for greater risk of unplanned index limb revascularization among women was observed. Effects of rivaroxaban were consistent by sex, though women more often discontinued treatment. Better understanding of sex-based outcomes and treatment adherence following LER is needed. Registration URL: http://clinicaltrials.gov; Unique identifier: NCT02504216

Researching underwater: a submerged study

This chapter explores the unknown territory of a lost project: an ethnography of a public swimming pool. The discussion is contextualised within my broader sociological theory of ‘nothing’, as a category of unmarked, negative social phenomena, including no-things, no-bodies, no-wheres, non-events and non-identities. These meaningful symbolic objects are constituted through social interaction, which can take two forms: acts of commission and acts of omission. I tell the story of how this project did not happen, through the things I did not do or that did not materialise, and how I consequently did not become a certain type of researcher. I identify three types of negative phenomena that I did not observe and document – invisible figures, silent voices and empty vessels – and, consequently, the knowledge I did not acquire. However, nothing is also productive, generating new symbolic objects as substitutes, alternatives and replacements: the somethings, somebodies and somewheres that are done or made instead. Thus finally, I reflect on how not doing this project led me to pursue others, cultivating a different research identity that would not otherwise have existed

A two-domain elevator mechanism for sodium/proton antiport

Sodium/proton (Na+/H+) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis1. In humans, their dysfunction has been linked to diseases, such as hypertension, heart failure and epilepsy, and they are well-established drug targets2. The best understood model system for Na+/H+ antiport is NhaA from Escherichia coli1, 3, for which both electron microscopy and crystal structures are available4, 5, 6. NhaA is made up of two distinct domains: a core domain and a dimerization domain. In the NhaA crystal structure a cavity is located between the two domains, providing access to the ion-binding site from the inward-facing surface of the protein1, 4. Like many Na+/H+ antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, at which point a conformational change is thought to occur7. The only reported NhaA crystal structure so far is of the low pH inactivated form4. Here we describe the active-state structure of a Na+/H+ antiporter, NapA from Thermus thermophilus, at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the core and dimerization domains are in different positions to those seen in NhaA, and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to coordinate ion binding1, 8, 9 directly, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the core domain, some 20° against the dimerization interface. We conclude that despite their fast transport rates of up to 1,500 ions per second3, Na+/H+ antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general

Global environmental implications of atmospheric methane removal through chlorine-mediated chemistry-climate interactions

Atmospheric methane is both a potent greenhouse gas and photochemically active, with approximately equal anthropogenic and natural sources. The addition of chlorine to the atmosphere has been proposed to mitigate global warming through methane reduction by increasing its chemical loss. However, the potential environmental impacts of such climate mitigation remain unexplored. Here, sensitivity studies are conducted to evaluate the possible effects of increasing reactive chlorine emissions on the methane budget, atmospheric composition and radiative forcing. Because of non-linear chemistry, in order to achieve a reduction in methane burden (instead of an increase), the chlorine atom burden needs to be a minimum of three times the estimated present-day burden. If the methane removal target is set to 20%, 45%, or 70% less global methane by 2050 compared to the levels in the Representative Concentration Pathway 8.5 scenario (RCP8.5), our modeling results suggest that additional chlorine fluxes of 630, 1250, and 1880 Tg Cl/year, respectively, are needed. The results show that increasing chlorine emissions also induces significant changes in other important climate forcers. Remarkably, the tropospheric ozone decrease is large enough that the magnitude of radiative forcing decrease is similar to that of methane. Adding 630, 1250, and 1880 Tg Cl/year to the RCP8.5 scenario, chosen to have the most consistent current-day trends of methane, will decrease the surface temperature by 0.2, 0.4, and 0.6 °C by 2050, respectively. The quantity and method in which the chlorine is added, its interactions with climate pathways, and the potential environmental impacts on air quality and ocean acidity, must be carefully considered before any action is taken

Digitizing localism: anticipating, assembling and animating a ‘space’ for UK hyperlocal media production

This paper presents an unconventional view of media production, not as the direct production of media content or forms, but the cultivation of spaces for media production taking place elsewhere. I draw on a close analysis of Destination Local, a program of UK charity Nesta, which focused on the implications of location-based technologies for the emergent field of ‘hyperlocal’ media. Although the first round of the program – the focus in this paper – funded 10 experimental projects alongside extensive research, my argument is that Destination Local was less a matter of enabling specific place-based hyperlocal media outlets. Rather, it was an attempt to anticipate, assemble and animate a broader UK hyperlocal media ‘space’, composed of both technical ecologies (e.g. data, devices, platforms, standards) and practical fields (e.g. journalism, software development, local government, community activism). This space, I argue, was anchored to a largely implicit political discourse of localism