Non-Additive Interactions Unlock Small-Particle Mobility in Binary Colloidal Monolayers

We examine the organization and dynamics of binary colloidal monolayers composed of micron-scale silica particles interspersed with smaller-diameter silica particles that serve as minority component impurities. These binary monolayers are prepared at the surface of ionic liquid droplets over a range of size ratios ($\sigma=0.16-0.66$) and are studied with low-dose minimally perturbative scanning electron microscopy (SEM). The high resolution of SEM imaging provides direct tracking of all particle coordinates over time, enabling a complete description of the microscopic state. In these bidisperse size mixtures, particle interactions are non-additive because interfacial pinning to the droplet surface causes the equators of differently sized particles to lie in separate planes. By varying the size ratio we control the extent of non-additivity in order to achieve phase behavior inaccessible to strictly 2D systems. Across the range of size ratios we tune the system from a mobile small-particle phase ($\sigma<0.24$), to an interstitial solid ($0.240.33$). These distinct phase regimes are classified through measurements of hexagonal ordering of the large-particle host lattice and the lattice's capacity for small-particle transport. Altogether, we explain these structural and dynamic trends by considering the combined influence of interparticle interactions and the colloidal packing geometry. Our measurements are reproduced in molecular dynamics simulations of 2D non-additive hard disks, suggesting an efficient method for describing confined systems with reduced dimensionality representations.Comment: 12 pages, 7 figures, also see supplementary ancillary fil

Delivering the promise of Sendai framework for disaster risk reduction in fragile and conflict-affected contexts (FCAC): A case study of the NGO GOAL's response to the Syria conflict

The Sendai Framework for Disaster Risk Reduction (SFDRR) has helped to reduce global disaster risk, but there has been a lack of progress in disaster risk reduction (DRR) for people living in fragile and conflict affected contexts (FCAC). Given the mounting evidence that DRR cannot be implemented through conventional approaches in FCAC, serious efforts must be made to understand how to meet SFDRR's goals. This paper offers a case study of international non-governmental organization GOAL's programming that responds to the protracted crisis in Syria, with a critical discussion on SFDRR and how to adapt humanitarian relief and disaster resilience

Final-State-Interaction Simulation of T-Violation in the Top-Quark Semileptonic Decay

The standard electroweak final-state interaction induces a false T-odd correlation in the top-quark semileptonic decay. The correlation parameter is calculated in the standard model and found to be considerably larger than those that could be produced by genuine T-violation effects in a large class of theoretical models.Comment: 14 pages, 1 diagram (not included

Quantifying the Advantage of Looking Forward

We introduce a future orientation index to quantify the degree to which Internet users worldwide seek more information about years in the future than years in the past. We analyse Google logs and find a striking correlation between the country's GDP and the predisposition of its inhabitants to look forward

Evaluation of the U.S. EPA/OSWER Preliminary Remediation Goal for Perchlorate in Groundwater: Focus on Exposure to Nursing Infants

BACKGROUND: Perchlorate is a common contaminant of drinking water and food. It competes with iodide for uptake into the thyroid, thus interfering with thyroid hormone production. The U.S. Environmental Protection Agency’s Office of Solid Waste and Emergency Response (OSWER) set a groundwater preliminary remediation goal (PRG) of 24.5 μg/L to prevent exposure of pregnant women that would affect the fetus. This does not account for the greater exposure that is possible in nursing infants or for the relative source contribution (RSC), a factor normally used to lower the PRG due to nonwater exposures. OBJECTIVES: Our goal was to assess whether the OSWER PRG protects infants against exposures from breast-feeding, and to evaluate the perchlorate RSC. METHODS: We used Monte Carlo analysis to simulate nursing infant exposures associated with the OSWER PRG when combined with background perchlorate. RESULTS: The PRG can lead to a 7-fold increase in breast milk concentration, causing 90% of nursing infants to exceed the reference dose (RfD) (average exceedance, 2.8-fold). Drinking-water perchlorate must be < 6.9 μg/L to keep the median, and < 1.3 μg/L to keep the 90th-percentile nursing infant exposure below the RfD. This is 3.6- to 19-fold below the PRG. Analysis of biomonitoring data suggests an RSC of 0.7 for pregnant women and of 0.2 for nursing infants. Recent data from the Centers for Disease Control and Prevention (CDC) suggest that the RfD itself needs to be reevaluated because of hormonal effects in the general population. CONCLUSIONS: The OSWER PRG for perchlorate can be improved by considering infant exposures, by incorporating an RSC, and by being responsive to any changes in the RfD resulting from the new CDC data

Experiments on Multidimensional Solitons

This article presents an overview of experimental efforts in recent years related to multidimensional solitons in Bose-Einstein condensates. We discuss the techniques used to generate and observe multidimensional nonlinear waves in Bose-Einstein condensates with repulsive interactions. We further summarize observations of planar soliton fronts undergoing the snake instability, the formation of vortex rings, and the emergence of hybrid structures.Comment: review paper, to appear as Chapter 5b in "Emergent Nonlinear Phenomena in Bose-Einstein Condensates: Theory and Experiment," edited by P. G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez (Springer-Verlag

Informality, violence, and disaster risks: Coproducing inclusive early warning and response systems in urban informal settlements in Honduras

Anticipatory disaster risk reduction (DRR) is an essential human right for the ~1 billion people living in informal settlements who are disproportionately exposed to climate-related hazards due to their high vulnerability. Participatory approaches are recognized as being critical for effective and sustainable disaster prevention, mitigation, and preparation through to response, but research on how to coproduce anticipatory DRR with people living and working in informal settlements is scant. Their exclusion is even more pronounced in challenging contexts, such as those characterized by social-political fragility and violence. As a result, a significant portion of the global population is left behind in best practices tied to global DRR ambitions, with DRR actions working neither with nor for the people most at risk. The signal case of urban informal settlements controlled by territorial gangs in Tegucigalpa, Honduras, illustrates the need for new thinking on how to inclusively mitigate, prepare for, and respond to natural hazard-related disasters. Our research examines the coproduction of early warning systems linked with response capacities for floods and landslides through the case study of the international NGO GOAL's work across the city with a focus on nine urban informal settlements with high levels of territorial gang violence. We explore how GOAL navigated informality and violent conflict to support the early warning and response system as an inclusive social process rather than a technical exercise. We identify four cross-cutting strategies employed by GOAL in support of local vulnerability reduction and capacity building based on a local systems approach. This research breaks new ground in identifying how to bridge the gap between knowledge and action in designing inclusive and sustainable early warning and response systems together with the millions of people around the world affected by the intersection of informality, violence, and disaster risks

Resonant Two-Magnon Raman Scattering in Cuprate Antiferromagnetic Insulators

We present results of low-temperature two-magnon resonance Raman excitation profile measurements for single layer Sr_2CuO_2Cl_2 and bilayer YBa_2Cu_3O_{6 + \delta} antiferromagnets over the excitation region from 1.65 to 3.05 eV. These data reveal composite structure of the two-magnon line shape and strong nonmonotic dependence of the scattering intensity on excitation energy. We analyze these data using the triple resonance theory of Chubukov and Frenkel (Phys. Rev. Lett., 74, 3057 (1995)) and deduce information about magnetic interaction and band parameters in these materials.Comment: REVTeX, 4 pages + 2 PostScript (compressed) figure