Conflicts of interest improve collective computation of adaptive social structures Sci. Adv. Pub Date : 2018-01-01 Eleanor R. Brush, David C. Krakauer, Jessica C. Flack
In many biological systems, the functional behavior of a group is collectively computed by the system’s individual components. An example is the brain’s ability to make decisions via the activity of billions of neurons. A long-standing puzzle is how the components’ decisions combine to produce beneficial group-level outputs, despite conflicts of interest and imperfect information. We derive a theoretical model of collective computation from mechanistic first principles, using results from previous work on the computation of power structure in a primate model system. Collective computation has two phases: an information accumulation phase, in which (in this study) pairs of individuals gather information about their fighting abilities and make decisions about their dominance relationships, and an information aggregation phase, in which these decisions are combined to produce a collective computation. To model information accumulation, we extend a stochastic decision-making model—the leaky integrator model used to study neural decision-making—to a multiagent game-theoretic framework. We then test alternative algorithms for aggregating information—in this study, decisions about dominance resulting from the stochastic model—and measure the mutual information between the resultant power structure and the “true” fighting abilities. We find that conflicts of interest can improve accuracy to the benefit of all agents. We also find that the computation can be tuned to produce different power structures by changing the cost of waiting for a decision. The successful application of a similar stochastic decision-making model in neural and social contexts suggests general principles of collective computation across substrates and scales.
Changes in seasonal snow water equivalent distribution in High Mountain Asia (1987 to 2009) Sci. Adv. Pub Date : 2018-01-01 Taylor Smith, Bodo Bookhagen
Snow meltwaters account for most of the yearly water budgets of many catchments in High Mountain Asia (HMA). We examine trends in snow water equivalent (SWE) using passive microwave data (1987 to 2009). We find an overall decrease in SWE in HMA, despite regions of increased SWE in the Pamir, Kunlun Shan, Eastern Himalaya, and Eastern Tien Shan. Although the average decline in annual SWE across HMA (contributing area, 2641 × 103 km2) is low (average, −0.3%), annual SWE losses conceal distinct seasonal and spatial heterogeneities across the study region. For example, the Tien Shan has seen both strong increases in winter SWE and sharp declines in spring and summer SWE. In the majority of catchments, the most negative SWE trends are found in mid-elevation zones, which often correspond to the regions of highest snow-water storage and are somewhat distinct from glaciated areas. Negative changes in SWE storage in these mid-elevation zones have strong implications for downstream water availability.
Late formation of silicon carbide in type II supernovae Sci. Adv. Pub Date : 2018-01-01 Nan Liu, Larry R. Nittler, Conel M. O’D. Alexander, Jianhua Wang
We have found that individual presolar silicon carbide (SiC) dust grains from supernovae show a positive correlation between 49Ti and 28Si excesses, which is attributed to the radioactive decay of the short-lived (t½ = 330 days) 49V to 49Ti in the inner highly 28Si-rich Si/S zone. The 49V-49Ti chronometer shows that these supernova SiC dust grains formed at least 2 years after their parent stars exploded. This result supports recent dust condensation calculations that predict a delayed formation of carbonaceous and SiC grains in supernovae. The astronomical observation of continuous buildup of dust in supernovae over several years can, therefore, be interpreted as a growing addition of C-rich dust to the dust reservoir in supernovae.
Saigas on the brink: Multidisciplinary analysis of the factors influencing mass mortality events Sci. Adv. Pub Date : 2018-01-01 Richard A. Kock, Mukhit Orynbayev, Sarah Robinson, Steffen Zuther, Navinder J. Singh, Wendy Beauvais, Eric R. Morgan, Aslan Kerimbayev, Sergei Khomenko, Henny M. Martineau, Rashida Rystaeva, Zamira Omarova, Sara Wolfs, Florent Hawotte, Julien Radoux, Eleanor J. Milner-Gulland
In 2015, more than 200,000 saiga antelopes died in 3 weeks in central Kazakhstan. The proximate cause of death is confirmed as hemorrhagic septicemia caused by the bacterium Pasteurella multocida type B, based on multiple strands of evidence. Statistical modeling suggests that there was unusually high relative humidity and temperature in the days leading up to the mortality event; temperature and humidity anomalies were also observed in two previous similar events in the same region. The modeled influence of environmental covariates is consistent with known drivers of hemorrhagic septicemia. Given the saiga population’s vulnerability to mass mortality and the likely exacerbation of climate-related and environmental stressors in the future, management of risks to population viability such as poaching and viral livestock disease is urgently needed, as well as robust ongoing veterinary surveillance. A multidisciplinary approach is needed to research mass mortality events under rapid environmental change.
Limited contribution of ancient methane to surface waters of the U.S. Beaufort Sea shelf Sci. Adv. Pub Date : 2018-01-01 Katy J. Sparrow, John D. Kessler, John R. Southon, Fenix Garcia-Tigreros, Kathryn M. Schreiner, Carolyn D. Ruppel, John B. Miller, Scott J. Lehman, Xiaomei Xu
In response to warming climate, methane can be released to Arctic Ocean sediment and waters from thawing subsea permafrost and decomposing methane hydrates. However, it is unknown whether methane derived from this sediment storehouse of frozen ancient carbon reaches the atmosphere. We quantified the fraction of methane derived from ancient sources in shelf waters of the U.S. Beaufort Sea, a region that has both permafrost and methane hydrates and is experiencing significant warming. Although the radiocarbon-methane analyses indicate that ancient carbon is being mobilized and emitted as methane into shelf bottom waters, surprisingly, we find that methane in surface waters is principally derived from modern-aged carbon. We report that at and beyond approximately the 30-m isobath, ancient sources that dominate in deep waters contribute, at most, 10 ± 3% of the surface water methane. These results suggest that even if there is a heightened liberation of ancient carbon–sourced methane as climate change proceeds, oceanic oxidation and dispersion processes can strongly limit its emission to the atmosphere.
Tensile forces drive a reversible fibroblast-to-myofibroblast transition during tissue growth in engineered clefts Sci. Adv. Pub Date : 2018-01-01 Philip Kollmannsberger, Cécile M. Bidan, John W. C. Dunlop, Peter Fratzl, Viola Vogel
Myofibroblasts orchestrate wound healing processes, and if they remain activated, they drive disease progression such as fibrosis and cancer. Besides growth factor signaling, the local extracellular matrix (ECM) and its mechanical properties are central regulators of these processes. It remains unknown whether transforming growth factor–β (TGF-β) and tensile forces work synergistically in up-regulating the transition of fibroblasts into myofibroblasts and whether myofibroblasts undergo apoptosis or become deactivated by other means once tissue homeostasis is reached. We used three-dimensional microtissues grown in vitro from fibroblasts in macroscopically engineered clefts for several weeks and found that fibroblasts transitioned into myofibroblasts at the highly tensed growth front as the microtissue progressively closed the cleft, in analogy to closing a wound site. Proliferation was up-regulated at the growth front, and new highly stretched fibronectin fibers were deposited, as revealed by fibronectin fluorescence resonance energy transfer probes. As the tissue was growing, the ECM underneath matured into a collagen-rich tissue containing mostly fibroblasts instead of myofibroblasts, and the fibronectin fibers were under reduced tension. This correlated with a progressive rounding of cells from the growth front inward, with decreased α–smooth muscle actin expression, YAP nuclear translocation, and cell proliferation. Together, this suggests that the myofibroblast phenotype is stabilized at the growth front by tensile forces, even in the absence of endogenously supplemented TGF-β, and reverts into a quiescent fibroblast phenotype already 10 μm behind the growth front, thus giving rise to a myofibroblast-to-fibroblast transition. This is the hallmark of reaching prohealing homeostasis.
The accuracy, fairness, and limits of predicting recidivism Sci. Adv. Pub Date : 2018-01-01 Julia Dressel, Hany Farid
Algorithms for predicting recidivism are commonly used to assess a criminal defendant’s likelihood of committing a crime. These predictions are used in pretrial, parole, and sentencing decisions. Proponents of these systems argue that big data and advanced machine learning make these analyses more accurate and less biased than humans. We show, however, that the widely used commercial risk assessment software COMPAS is no more accurate or fair than predictions made by people with little or no criminal justice expertise. We further show that a simple linear predictor provided with only two features is nearly equivalent to COMPAS with its 137 features.
Membrane insertion of—and membrane potential sensing by—semiconductor voltage nanosensors: Feasibility demonstration Sci. Adv. Pub Date : 2018-01-01 Kyoungwon Park, Yung Kuo, Volodymyr Shvadchak, Antonino Ingargiola, Xinghong Dai, Lawrence Hsiung, Wookyeom Kim, Hong Zhou, Peng Zou, Alex J. Levine, Jack Li, Shimon Weiss
We developed membrane voltage nanosensors that are based on inorganic semiconductor nanoparticles. We provide here a feasibility study for their utilization. We use a rationally designed peptide to functionalize the nanosensors, imparting them with the ability to self-insert into a lipid membrane with a desired orientation. Once inserted, these nanosensors could sense membrane potential via the quantum confined Stark effect, with a single-particle sensitivity. With further improvements, these nanosensors could potentially be used for simultaneous recording of action potentials from multiple neurons in a large field of view over a long duration and for recording electrical signals on the nanoscale, such as across one synapse.
Stable organic thin-film transistors Sci. Adv. Pub Date : 2018-01-01 Xiaojia Jia, Canek Fuentes-Hernandez, Cheng-Yin Wang, Youngrak Park, Bernard Kippelen
Organic thin-film transistors (OTFTs) can be fabricated at moderate temperatures and through cost-effective solution-based processes on a wide range of low-cost flexible and deformable substrates. Although the charge mobility of state-of-the-art OTFTs is superior to that of amorphous silicon and approaches that of amorphous oxide thin-film transistors (TFTs), their operational stability generally remains inferior and a point of concern for their commercial deployment. We report on an exhaustive characterization of OTFTs with an ultrathin bilayer gate dielectric comprising the amorphous fluoropolymer CYTOP and an Al2O3:HfO2 nanolaminate. Threshold voltage shifts measured at room temperature over time periods up to 5.9 × 105 s do not vary monotonically and remain below 0.2 V in microcrystalline OTFTs (μc-OTFTs) with field-effect carrier mobility values up to 1.6 cm2 V−1 s−1. Modeling of these shifts as a function of time with a double stretched-exponential (DSE) function suggests that two compensating aging mechanisms are at play and responsible for this high stability. The measured threshold voltage shifts at temperatures up to 75°C represent at least a one-order-of-magnitude improvement in the operational stability over previous reports, bringing OTFT technologies to a performance level comparable to that reported in the scientific literature for other commercial TFTs technologies.
Localized concentration reversal of lithium during intercalation into nanoparticles Sci. Adv. Pub Date : 2018-01-01 Wei Zhang, Hui-Chia Yu, Lijun Wu, Hao Liu, Aziz Abdellahi, Bao Qiu, Jianming Bai, Bernardo Orvananos, Fiona C. Strobridge, Xufeng Zhou, Zhaoping Liu, Gerbrand Ceder, Yimei Zhu, Katsuyo Thornton, Clare P. Grey, Feng Wang
Nanoparticulate electrodes, such as LixFePO4, have unique advantages over their microparticulate counterparts for the applications in Li-ion batteries because of the shortened diffusion path and access to nonequilibrium routes for fast Li incorporation, thus radically boosting power density of the electrodes. However, how Li intercalation occurs locally in a single nanoparticle of such materials remains unresolved because real-time observation at such a fine scale is still lacking. We report visualization of local Li intercalation via solid-solution transformation in individual LixFePO4 nanoparticles, enabled by probing sub-angstrom changes in the lattice spacing in situ. The real-time observation reveals inhomogeneous intercalation, accompanied with an unexpected reversal of Li concentration at the nanometer scale. The origin of the reversal phenomenon is elucidated through phase-field simulations, and it is attributed to the presence of structurally different regions that have distinct chemical potential functions. The findings from this study provide a new perspective on the local intercalation dynamics in battery electrodes.
Highly mobile charge-transfer excitons in two-dimensional WS2/tetracene heterostructures Sci. Adv. Pub Date : 2018-01-01 Tong Zhu, Long Yuan, Yan Zhao, Mingwei Zhou, Yan Wan, Jianguo Mei, Libai Huang
Charge-transfer (CT) excitons at heterointerfaces play a critical role in light to electricity conversion using organic and nanostructured materials. However, how CT excitons migrate at these interfaces is poorly understood. We investigate the formation and transport of CT excitons in two-dimensional WS2/tetracene van der Waals heterostructures. Electron and hole transfer occurs on the time scale of a few picoseconds, and emission of interlayer CT excitons with a binding energy of ~0.3 eV has been observed. Transport of the CT excitons is directly measured by transient absorption microscopy, revealing coexistence of delocalized and localized states. Trapping-detrapping dynamics between the delocalized and localized states leads to stretched-exponential photoluminescence decay with an average lifetime of ~2 ns. The delocalized CT excitons are remarkably mobile with a diffusion constant of ~1 cm2 s−1. These highly mobile CT excitons could have important implications in achieving efficient charge separation.
Direct measurements of DOCO isomers in the kinetics of OD + CO Sci. Adv. Pub Date : 2018-01-01 Thinh Q. Bui, Bryce J. Bjork, P. Bryan Changala, Thanh L. Nguyen, John F. Stanton, Mitchio Okumura, Jun Ye
Quantitative and mechanistically detailed kinetics of the reaction of hydroxyl radical (OH) with carbon monoxide (CO) have been a longstanding goal of contemporary chemical kinetics. This fundamental prototype reaction plays an important role in atmospheric and combustion chemistry, motivating studies for accurate determination of the reaction rate coefficient and its pressure and temperature dependence at thermal reaction conditions. This intricate dependence can be traced directly to details of the underlying dynamics (formation, isomerization, and dissociation) involving the reactive intermediates cis- and trans-HOCO, which can only be observed transiently. Using time-resolved frequency comb spectroscopy, comprehensive mechanistic elucidation of the kinetics of the isotopic analog deuteroxyl radical (OD) with CO has been realized. By monitoring the concentrations of reactants, intermediates, and products in real time, the branching and isomerization kinetics and absolute yields of all species in the OD + CO reaction are quantified as a function of pressure and collision partner.
Emergence of Kondo lattice behavior in a van der Waals itinerant ferromagnet, Fe3GeTe2 Sci. Adv. Pub Date : 2018-01-01 Yun Zhang, Haiyan Lu, Xiegang Zhu, Shiyong Tan, Wei Feng, Qin Liu, Wen Zhang, Qiuyun Chen, Yi Liu, Xuebing Luo, Donghua Xie, Lizhu Luo, Zhengjun Zhang, Xinchun Lai
Searching for heavy fermion (HF) states in non–f-electron systems becomes an interesting issue, especially in the presence of magnetism, and can help explain the physics of complex compounds. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy, physical properties measurements, and the first-principles calculations, we observe the HF state in a 3d-electron van der Waals ferromagnet, Fe3GeTe2. Upon entering the ferromagnetic state, a massive spectral weight transfer occurs, which results from the exchange splitting. Meanwhile, the Fermi surface volume and effective electron mass are both enhanced. When the temperature drops below a characteristic temperature T*, heavy electrons gradually emerge with further enhanced effective electron mass. The coexistence of ferromagnetism and HF state can be well interpreted by the dual properties (itinerant and localized) of 3d electrons. This work expands the limit of ferromagnetic HF materials from f- to d-electron systems and illustrates the positive correlation between ferromagnetism and HF state in the 3d-electron material, which is quite different from the f-electron systems.
Pressure-induced shear and interlayer expansion in Ti3C2 MXene in the presence of water Sci. Adv. Pub Date : 2018-01-01 Michael Ghidiu, Sankalp Kota, Vadym Drozd, Michel W. Barsoum
Pseudo-negative compressibility in layered materials is a phenomenon typically limited to in situ high-pressure experiments in some clay minerals and carbon-based materials. We show that the MXene Ti3C2Tx expands along its crystallographic c direction when compressed in the presence of H2O. This expansive effect occurs when a mixture of powders and excess water is quasi-hydrostatically compressed in a diamond anvil cell; it also occurs to a much larger extent when powders are pressed uniaxially into discs and, notably, persists after pressure is released. We attribute the expansion to the insertion of H2O molecules and have identified shear-induced slipping of the nanosheets comprising multilayered MXene particles as a possible cause of this behavior in the latter case. This both has implications for the processing of MXenes and contributes to the field of materials with pseudo-negative compressibility by adding a new member for further investigation.
Fast, noise-free memory for photon synchronization at room temperature Sci. Adv. Pub Date : 2018-01-01 Ran Finkelstein, Eilon Poem, Ohad Michel, Ohr Lahad, Ofer Firstenberg
Future quantum photonic networks require coherent optical memories for synchronizing quantum sources and gates of probabilistic nature. We demonstrate a fast ladder memory (FLAME) mapping the optical field onto the superposition between electronic orbitals of rubidium vapor. Using a ladder-level system of orbital transitions with nearly degenerate frequencies simultaneously enables high bandwidth, low noise, and long memory lifetime. We store and retrieve 1.7-ns-long pulses, containing 0.5 photons on average, and observe short-time external efficiency of 25%, memory lifetime (1/e) of 86 ns, and below 10−4 added noise photons. Consequently, coupling this memory to a probabilistic source would enhance the on-demand photon generation probability by a factor of 12, the highest number yet reported for a noise-free, room temperature memory. This paves the way toward the controlled production of large quantum states of light from probabilistic photon sources.
A Triassic-Jurassic window into the evolution of Lepidoptera Sci. Adv. Pub Date : 2018-01-01 Timo J. B. van Eldijk, Torsten Wappler, Paul K. Strother, Carolien M. H. van der Weijst, Hossein Rajaei, Henk Visscher, Bas van de Schootbrugge
On the basis of an assemblage of fossilized wing scales recovered from latest Triassic and earliest Jurassic sediments from northern Germany, we provide the earliest evidence for Lepidoptera (moths and butterflies). The diverse scales confirm a (Late) Triassic radiation of lepidopteran lineages, including the divergence of the Glossata, the clade that comprises the vast multitude of extant moths and butterflies that have a sucking proboscis. The microfossils extend the minimum calibrated age of glossatan moths by ca. 70 million years, refuting ancestral association of the group with flowering plants. Development of the proboscis may be regarded as an adaptive innovation to sucking free liquids for maintaining the insect’s water balance under arid conditions. Pollination drops secreted by a variety of Mesozoic gymnosperms may have been non-mutualistically exploited as a high-energy liquid source. The early evolution of the Lepidoptera was probably not severely interrupted by the end-Triassic biotic crisis.
Unlocking data sets by calibrating populations of models to data density: A study in atrial electrophysiology Sci. Adv. Pub Date : 2018-01-01 Brodie A. J. Lawson, Christopher C. Drovandi, Nicole Cusimano, Pamela Burrage, Blanca Rodriguez, Kevin Burrage
The understanding of complex physical or biological systems nearly always requires a characterization of the variability that underpins these processes. In addition, the data used to calibrate these models may also often exhibit considerable variability. A recent approach to deal with these issues has been to calibrate populations of models (POMs), multiple copies of a single mathematical model but with different parameter values, in response to experimental data. To date, this calibration has been largely limited to selecting models that produce outputs that fall within the ranges of the data set, ignoring any trends that might be present in the data. We present here a novel and general methodology for calibrating POMs to the distributions of a set of measured values in a data set. We demonstrate our technique using a data set from a cardiac electrophysiology study based on the differences in atrial action potential readings between patients exhibiting sinus rhythm (SR) or chronic atrial fibrillation (cAF) and the Courtemanche-Ramirez-Nattel model for human atrial action potentials. Not only does our approach accurately capture the variability inherent in the experimental population, but we also demonstrate how the POMs that it produces may be used to extract additional information from the data used for calibration, including improved identification of the differences underlying stratified data. We also show how our approach allows different hypotheses regarding the variability in complex systems to be quantitatively compared.
Adaptation required to preserve future high-end river flood risk at present levels Sci. Adv. Pub Date : 2018-01-01 Sven N. Willner, Anders Levermann, Fang Zhao, Katja Frieler
Earth’s surface temperature will continue to rise for another 20 to 30 years even with the strongest carbon emission reduction currently considered. The associated changes in rainfall patterns can result in an increased flood risk worldwide. We compute the required increase in flood protection to keep high-end fluvial flood risk at present levels. The analysis is carried out worldwide for subnational administrative units. Most of the United States, Central Europe, and Northeast and West Africa, as well as large parts of India and Indonesia, require the strongest adaptation effort. More than half of the United States needs to at least double their protection within the next two decades. Thus, the need for adaptation to increased river flood is a global problem affecting industrialized regions as much as developing countries.
Organic matter in extraterrestrial water-bearing salt crystals Sci. Adv. Pub Date : 2018-01-01 Queenie H. S. Chan, Michael E. Zolensky, Yoko Kebukawa, Marc Fries, Motoo Ito, Andrew Steele, Zia Rahman, Aiko Nakato, A. L. David Kilcoyne, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Kazuhiko Mase
Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body. Associated with these trapped brines are organic compounds exhibiting wide chemical variations representing organic precursors, intermediates, and reaction products that make up life’s precursor molecules such as amino acids. The organic compounds also contain a mixture of C-, O-, and N-bearing macromolecular carbon materials exhibiting a wide range of structural order, as well as aromatic, ketone, imine, and/or imidazole compounds. The enrichment in 15N is comparable to the organic matter in pristine Renazzo-type carbonaceous chondrites, which reflects the sources of interstellar 15N, such as ammonia and amino acids. The amino acid content of the Zag halite deviates from the meteorite matrix, supporting an exogenic origin of the halite, and therefore, the Zag meteorite contains organics synthesized on two distinct parent bodies. Our study suggests that the asteroidal parent body where the halite precipitated, potentially asteroid 1 Ceres, shows evidence for a complex combination of biologically and prebiologically relevant molecules.
Use of an Autonomous Surface Vehicle reveals small-scale diel vertical migrations of zooplankton and susceptibility to light pollution under low solar irradiance Sci. Adv. Pub Date : 2018-01-01 Martin Ludvigsen, Jørgen Berge, Maxime Geoffroy, Jonathan H. Cohen, Pedro R. De La Torre, Stein M. Nornes, Hanumant Singh, Asgeir J. Sørensen, Malin Daase, Geir Johnsen
Light is a major cue for nearly all life on Earth. However, most of our knowledge concerning the importance of light is based on organisms’ response to light during daytime, including the dusk and dawn phase. When it is dark, light is most often considered as pollution, with increasing appreciation of its negative ecological effects. Using an Autonomous Surface Vehicle fitted with a hyperspectral irradiance sensor and an acoustic profiler, we detected and quantified the behavior of zooplankton in an unpolluted light environment in the high Arctic polar night and compared the results with that from a light-polluted environment close to our research vessels. First, in environments free of light pollution, the zooplankton community is intimately connected to the ambient light regime and performs synchronized diel vertical migrations in the upper 30 m despite the sun never rising above the horizon. Second, the vast majority of the pelagic community exhibits a strong light-escape response in the presence of artificial light, observed down to 100 m. We conclude that artificial light from traditional sampling platforms affects the zooplankton community to a degree where it is impossible to examine its abundance and natural rhythms within the upper 100 m. This study underscores the need to adjust sampling platforms, particularly in dim-light conditions, to capture relevant physical and biological data for ecological studies. It also highlights a previously unchartered susceptibility to light pollution in a region destined to see significant changes in light climate due to a reduced ice cover and an increased anthropogenic activity.
The largest deep-ocean silicic volcanic eruption of the past century Sci. Adv. Pub Date : 2018-01-01 Rebecca Carey, S. Adam Soule, Michael Manga, James White, Jocelyn McPhie, Richard Wysoczanski, Martin Jutzeler, Kenichiro Tani, Dana Yoerger, Daniel Fornari, Fabio Caratori-Tontini, Bruce Houghton, Samuel Mitchell, Fumihiko Ikegami, Chris Conway, Arran Murch, Kristen Fauria, Meghan Jones, Ryan Cahalan, Warren McKenzie
The 2012 submarine eruption of Havre volcano in the Kermadec arc, New Zealand, is the largest deep-ocean eruption in history and one of very few recorded submarine eruptions involving rhyolite magma. It was recognized from a gigantic 400-km2 pumice raft seen in satellite imagery, but the complexity of this event was concealed beneath the sea surface. Mapping, observations, and sampling by submersibles have provided an exceptionally high fidelity record of the seafloor products, which included lava sourced from 14 vents at water depths of 900 to 1220 m, and fragmental deposits including giant pumice clasts up to 9 m in diameter. Most (>75%) of the total erupted volume was partitioned into the pumice raft and transported far from the volcano. The geological record on submarine volcanic edifices in volcanic arcs does not faithfully archive eruption size or magma production.
Experimenter gender and replicability in science Sci. Adv. Pub Date : 2018-01-01 Colin D. Chapman, Christian Benedict, Helgi B. Schiöth
There is a replication crisis spreading through the annals of scientific inquiry. Although some work has been carried out to uncover the roots of this issue, much remains unanswered. With this in mind, this paper investigates how the gender of the experimenter may affect experimental findings. Clinical trials are regularly carried out without any report of the experimenter’s gender and with dubious knowledge of its influence. Consequently, significant biases caused by the experimenter’s gender may lead researchers to conclude that therapeutics or other interventions are either overtreating or undertreating a variety of conditions. Bearing this in mind, this policy paper emphasizes the importance of reporting and controlling for experimenter gender in future research. As backdrop, it explores what we know about the role of experimenter gender in influencing laboratory results, suggests possible mechanisms, and suggests future areas of inquiry.
Monitoring reservoir response to earthquakes and fluid extraction, Salton Sea geothermal field, California Sci. Adv. Pub Date : 2018-01-01 Taka’aki Taira, Avinash Nayak, Florent Brenguier, Michael Manga
Continuous monitoring of in situ reservoir responses to stress transients provides insights into the evolution of geothermal reservoirs. By exploiting the stress dependence of seismic velocity changes, we investigate the temporal evolution of the reservoir stress state of the Salton Sea geothermal field (SSGF), California. We find that the SSGF experienced a number of sudden velocity reductions (~0.035 to 0.25%) that are most likely caused by openings of fractures due to dynamic stress transients (as small as 0.08 MPa and up to 0.45 MPa) from local and regional earthquakes. Depths of velocity changes are estimated to be about 0.5 to 1.5 km, similar to the depths of the injection and production wells. We derive an empirical in situ stress sensitivity of seismic velocity changes by relating velocity changes to dynamic stresses. We also observe systematic velocity reductions (0.04 to 0.05%) during earthquake swarms in mid-November 2009 and late-December 2010. On the basis of volumetric static and dynamic stress changes, the expected velocity reductions from the largest earthquakes with magnitude ranging from 3 to 4 in these swarms are less than 0.02%, which suggests that these earthquakes are likely not responsible for the velocity changes observed during the swarms. Instead, we argue that velocity reductions may have been induced by poroelastic opening of fractures due to aseismic deformation. We also observe a long-term velocity increase (~0.04%/year) that is most likely due to poroelastic contraction caused by the geothermal production. Our observations demonstrate that seismic interferometry provides insights into in situ reservoir response to stress changes.
Anderson localizations and photonic band-tail states observed in compositionally disordered platform Sci. Adv. Pub Date : 2018-01-01 Myungjae Lee, Jeongkug Lee, Sunghwan Kim, Ségolène Callard, Christian Seassal, Heonsu Jeon
Anderson localization in random structures is an intriguing physical phenomenon, for which experimental verifications are far behind theoretical predictions. We report the first experimental confirmations of photonic band-tail states and a complete transition of Anderson localization. An optically activated photonic crystal alloy platform enables the acquisition of extensive experimental data exclusively on pure eigenstates, revealing direct evidence of band-tail states and Anderson localization transition within the band-tail states. Analyses of both experimental and simulated data lead to a comprehensive picture of photon localization that is highly consistent with theories by Anderson and others. We believe that our results provide a strong experimental foundation upon which both the fundamental understandings and application possibility of Anderson localization can be promoted significantly.
Heralded quantum steering over a high-loss channel Sci. Adv. Pub Date : 2018-01-01 Morgan M. Weston, Sergei Slussarenko, Helen M. Chrzanowski, Sabine Wollmann, Lynden K. Shalm, Varun B. Verma, Michael S. Allman, Sae Woo Nam, Geoff J. Pryde
Entanglement is the key resource for many long-range quantum information tasks, including secure communication and fundamental tests of quantum physics. These tasks require robust verification of shared entanglement, but performing it over long distances is presently technologically intractable because the loss through an optical fiber or free-space channel opens up a detection loophole. We design and experimentally demonstrate a scheme that verifies entanglement in the presence of at least 14.8 ± 0.1 dB of added loss, equivalent to approximately 80 km of telecommunication fiber. Our protocol relies on entanglement swapping to herald the presence of a photon after the lossy channel, enabling event-ready implementation of quantum steering. This result overcomes the key barrier in device-independent communication under realistic high-loss scenarios and in the realization of a quantum repeater.
Ultrafast rotation of magnetically levitated macroscopic steel spheres Sci. Adv. Pub Date : 2018-01-01 Marcel Schuck, Daniel Steinert, Thomas Nussbaumer, Johann W. Kolar
Our world is increasingly powered by electricity, which is largely converted to or from mechanical energy using electric motors. Several applications have driven the miniaturization of these machines, resulting in high rotational speeds. Although speeds of several hundred thousand revolutions per minute have been used industrially, we report the realization of an electrical motor reaching 40 million rpm to explore the underlying physical boundaries. Millimeter-scale steel spheres, which are levitated and accelerated by magnetic fields inside a vacuum, are used as a rotor. Circumferential speeds exceeding 1000 m/s and centrifugal accelerations of more than 4 × 108 times gravity were reached. The results open up new research possibilities, such as the testing of materials under extreme centrifugal load, and provide insights into the development of future electric drive systems.
Nanometer-precision linear sorting with synchronized optofluidic dual barriers Sci. Adv. Pub Date : 2018-01-01 Yuzhi Shi, Sha Xiong, Lip Ket Chin, Jingbo Zhang, Wee Ser, Jiuhui Wu, Tianning Chen, Zhenchuan Yang, Yilong Hao, Bo Liedberg, Peng Huat Yap, Din Ping Tsai, Cheng-Wei Qiu, Ai Qun Liu
The past two decades have witnessed the revolutionary development of optical trapping of nanoparticles, most of which deal with trapping stiffness larger than 10−8 N/m. In this conventional regime, however, it remains a formidable challenge to sort out sub–50-nm nanoparticles with single-nanometer precision, isolating us from a rich flatland with advanced applications of micromanipulation. With an insightfully established roadmap of damping, the synchronization between optical force and flow drag force can be coordinated to attempt the loosely overdamped realm (stiffness, 10−10 to 10−8 N/m), which has been challenging. This paper intuitively demonstrates the remarkable functionality to sort out single gold nanoparticles with radii ranging from 30 to 50 nm, as well as 100- and 150-nm polystyrene nanoparticles, with single nanometer precision. The quasi-Bessel optical profile and the loosely overdamped potential wells in the microchannel enable those aforementioned nanoparticles to be separated, positioned, and microscopically oscillated. This work reveals an unprecedentedly meaningful damping scenario that enriches our fundamental understanding of particle kinetics in intriguing optical systems, and offers new opportunities for tumor targeting, intracellular imaging, and sorting small particles such as viruses and DNA.
Electrically switchable metadevices via graphene Sci. Adv. Pub Date : 2018-01-01 Osman Balci, Nurbek Kakenov, Ertugrul Karademir, Sinan Balci, Semih Cakmakyapan, Emre O. Polat, Humeyra Caglayan, Ekmel Özbay, Coskun Kocabas
Metamaterials bring subwavelength resonating structures together to overcome the limitations of conventional materials. The realization of active metadevices has been an outstanding challenge that requires electrically reconfigurable components operating over a broad spectrum with a wide dynamic range. However, the existing capability of metamaterials is not sufficient to realize this goal. By integrating passive metamaterials with active graphene devices, we demonstrate a new class of electrically controlled active metadevices working in microwave frequencies. The fabricated active metadevices enable efficient control of both amplitude (>50 dB) and phase (>90°) of electromagnetic waves. In this hybrid system, graphene operates as a tunable Drude metal that controls the radiation of the passive metamaterials. Furthermore, by integrating individually addressable arrays of metadevices, we demonstrate a new class of spatially varying digital metasurfaces where the local dielectric constant can be reconfigured with applied bias voltages. In addition, we reconfigure resonance frequency of split-ring resonators without changing its amplitude by damping one of the two coupled metasurfaces via graphene. Our approach is general enough to implement various metamaterial systems that could yield new applications ranging from electrically switchable cloaking devices to adaptive camouflage systems.
Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators Sci. Adv. Pub Date : 2018-01-01 Lifan Zhou, Hongkang Song, Kai Liu, Zhongzhi Luan, Peng Wang, Lei Sun, Shengwei Jiang, Hongjun Xiang, Yanbin Chen, Jun Du, Haifeng Ding, Ke Xia, Jiang Xiao, Di Wu
A magnetoresistance (MR) effect induced by the Rashba spin-orbit interaction was predicted, but not yet observed, in bilayers consisting of normal metal and ferromagnetic insulator. We present an experimental observation of this new type of spin-orbit MR (SOMR) effect in the Cu[Pt]/Y3Fe5O12 (YIG) bilayer structure, where the Cu/YIG interface is decorated with nanosize Pt islands. This new MR is apparently not caused by the bulk spin-orbit interaction because of the negligible spin-orbit interaction in Cu and the discontinuity of the Pt islands. This SOMR disappears when the Pt islands are absent or located away from the Cu/YIG interface; therefore, we can unambiguously ascribe it to the Rashba spin-orbit interaction at the interface enhanced by the Pt decoration. The numerical Boltzmann simulations are consistent with the experimental SOMR results in the angular dependence of magnetic field and the Cu thickness dependence. Our finding demonstrates the realization of the spin manipulation by interface engineering.
Low-threshold parametric oscillation in organically modified microcavities Sci. Adv. Pub Date : 2018-01-01 Xiaoqin Shen, Rigoberto Castro Beltran, Vinh M. Diep, Soheil Soltani, Andrea M. Armani
Coherent frequency generators are an enabling platform in basic science and applied technology. Originally reliant on high-power lasers, recently comb generation has been demonstrated in ultrahigh-Q microcavities. The large circulating intensity within the cavity results in strong light-matter interaction, giving rise to Kerr parametric oscillations for comb generation. However, the comb generation threshold is limited by competing nonlinear effects within the cavity material and low intrinsic material Kerr coefficients. We report a new strategy to fabricate near-infrared frequency combs based on combining high-Q microcavities with monomolecular layers of highly nonlinear small molecules. The functionalized microcavities demonstrate high-efficiency parametric oscillation in the near-IR and generate primary frequency combs with 0.88-mW thresholds, improving optical parametric oscillation generation over nonfunctionalized devices by three orders of magnitude. This organic-inorganic approach enables otherwise unattainable performance and will inspire the next generation of integrated photonic device platforms.
Discovery of slow magnetic fluctuations and critical slowing down in the pseudogap phase of YBa2Cu3Oy Sci. Adv. Pub Date : 2018-01-01 Jian Zhang, Zhaofeng Ding, Cheng Tan, Kevin Huang, Oscar O. Bernal, Pei-Chun Ho, Gerald D. Morris, Adrian D. Hillier, Pabitra K. Biswas, Stephen P. Cottrell, Hui Xiang, Xin Yao, Douglas E. MacLaughlin, Lei Shu
The origin of the pseudogap region below a temperature T* is at the heart of the mysteries of cuprate high-temperature superconductors. Unusual properties of the pseudogap phase, such as broken time-reversal and inversion symmetry are observed in several symmetry-sensitive experiments: polarized neutron diffraction, optical birefringence, dichroic angle-resolved photoemission spectroscopy, second harmonic generation, and polar Kerr effect. These properties suggest that the pseudogap region is a genuine thermodynamic phase and are predicted by theories invoking ordered loop currents or other forms of intra-unit-cell (IUC) magnetic order. However, muon spin rotation (μSR) and nuclear magnetic resonance (NMR) experiments do not see the static local fields expected for magnetic order, leaving room for skepticism. The magnetic resonance probes have much longer time scales, however, over which local fields could be averaged by fluctuations. The observable effect of the fluctuations in magnetic resonance is then dynamic relaxation. We have measured dynamic muon spin relaxation rates in single crystals of YBa2Cu3Oy (6.72 < y < 6.95) and have discovered “slow” fluctuating magnetic fields with magnitudes and fluctuation rates of the expected orders of magnitude that set in consistently at temperatures Tmag ≈ T*. The absence of any static field (to which μSR would be linearly sensitive) is consistent with the finite correlation length from neutron diffraction. Equally important, these fluctuations exhibit the critical slowing down at Tmag expected near a time-reversal symmetry breaking transition. Our results explain the absence of static magnetism and provide support for the existence of IUC magnetic order in the pseudogap phase.
Using parahydrogen to hyperpolarize amines, amides, carboxylic acids, alcohols, phosphates, and carbonates Sci. Adv. Pub Date : 2018-01-01 Wissam Iali, Peter J. Rayner, Simon B. Duckett
Hyperpolarization turns weak nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) responses into strong signals, so normally impractical measurements are possible. We use parahydrogen to rapidly hyperpolarize appropriate 1H, 13C, 15N, and 31P responses of analytes (such as NH3) and important amines (such as phenylethylamine), amides (such as acetamide, urea, and methacrylamide), alcohols spanning methanol through octanol and glucose, the sodium salts of carboxylic acids (such as acetic acid and pyruvic acid), sodium phosphate, disodium adenosine 5′-triphosphate, and sodium hydrogen carbonate. The associated signal gains are used to demonstrate that it is possible to collect informative single-shot NMR spectra of these analytes in seconds at the micromole level in a 9.4-T observation field. To achieve these wide-ranging signal gains, we first use the signal amplification by reversible exchange (SABRE) process to hyperpolarize an amine or ammonia and then use their exchangeable NH protons to relay polarization into the analyte without changing its identity. We found that the 1H signal gains reach as high as 650-fold per proton, whereas for 13C, the corresponding signal gains achieved in a 1H-13C refocused insensitive nuclei enhanced by polarization transfer (INEPT) experiment exceed 570-fold and those in a direct-detected 13C measurement exceed 400-fold. Thirty-one examples are described to demonstrate the applicability of this technique.
Document co-citation analysis to enhance transdisciplinary research Sci. Adv. Pub Date : 2018-01-01 Caleb M. Trujillo, Tammy M. Long
Specialized and emerging fields of research infrequently cross disciplinary boundaries and would benefit from frameworks, methods, and materials informed by other fields. Document co-citation analysis, a method developed by bibliometric research, is demonstrated as a way to help identify key literature for cross-disciplinary ideas. To illustrate the method in a useful context, we mapped peer-recognized scholarship related to systems thinking. In addition, three procedures for validation of co-citation networks are proposed and implemented. This method may be useful for strategically selecting information that can build consilience about ideas and constructs that are relevant across a range of disciplines.
Identifying the substrate proteins of U-box E3s E4B and CHIP by orthogonal ubiquitin transfer Sci. Adv. Pub Date : 2018-01-01 Karan Bhuripanyo, Yiyang Wang, Xianpeng Liu, Li Zhou, Ruochuan Liu, Duc Duong, Bo Zhao, Yingtao Bi, Han Zhou, Geng Chen, Nicholas T. Seyfried, Walter J. Chazin, Hiroaki Kiyokawa, Jun Yin
E3 ubiquitin (UB) ligases E4B and carboxyl terminus of Hsc70-interacting protein (CHIP) use a common U-box motif to transfer UB from E1 and E2 enzymes to their substrate proteins and regulate diverse cellular processes. To profile their ubiquitination targets in the cell, we used phage display to engineer E2-E4B and E2-CHIP pairs that were free of cross-reactivity with the native UB transfer cascades. We then used the engineered E2-E3 pairs to construct “orthogonal UB transfer (OUT)” cascades so that a mutant UB (xUB) could be exclusively used by the engineered E4B or CHIP to label their substrate proteins. Purification of xUB-conjugated proteins followed by proteomics analysis enabled the identification of hundreds of potential substrates of E4B and CHIP in human embryonic kidney 293 cells. Kinase MAPK3 (mitogen-activated protein kinase 3), methyltransferase PRMT1 (protein arginineN-methyltransferase 1), and phosphatase PPP3CA (protein phosphatase 3 catalytic subunit alpha) were identified as the shared substrates of the two E3s. Phosphatase PGAM5 (phosphoglycerate mutase 5) and deubiquitinase OTUB1 (ovarian tumor domain containing ubiquitin aldehyde binding protein 1) were confirmed as E4B substrates, and β-catenin and CDK4 (cyclin-dependent kinase 4) were confirmed as CHIP substrates. On the basis of the CHIP-CDK4 circuit identified by OUT, we revealed that CHIP signals CDK4 degradation in response to endoplasmic reticulum stress.
Seismic signature of active intrusions in mountain chains Sci. Adv. Pub Date : 2018-01-01 Francesca Di Luccio, Giovanni Chiodini, Stefano Caliro, Carlo Cardellini, Vincenzo Convertito, Nicola Alessandro Pino, Cristiano Tolomei, Guido Ventura
Intrusions are a ubiquitous component of mountain chains and testify to the emplacement of magma at depth. Understanding the emplacement and growth mechanisms of intrusions, such as diapiric or dike-like ascent, is critical to constrain the evolution and structure of the crust. Petrological and geological data allow us to reconstruct magma pathways and long-term magma differentiation and assembly processes. However, our ability to detect and reconstruct the short-term dynamics related to active intrusive episodes in mountain chains is embryonic, lacking recognized geophysical signals. We analyze an anomalously deep seismic sequence (maximum magnitude 5) characterized by low-frequency bursts of earthquakes that occurred in 2013 in the Apennine chain in Italy. We provide seismic evidences of fluid involvement in the earthquake nucleation process and identify a thermal anomaly in aquifers where CO2of magmatic origin dissolves. We show that the intrusion of dike-like bodies in mountain chains may trigger earthquakes with magnitudes that may be relevant to seismic hazard assessment. These findings provide a new perspective on the emplacement mechanisms of intrusive bodies and the interpretation of the seismicity in mountain chains.
Increased fluxes of shelf-derived materials to the central Arctic Ocean Sci. Adv. Pub Date : 2018-01-01 Lauren E. Kipp, Matthew A. Charette, Willard S. Moore, Paul B. Henderson, Ignatius G. Rigor
Rising temperatures in the Arctic Ocean region are responsible for changes such as reduced ice cover, permafrost thawing, and increased river discharge, which, together, alter nutrient and carbon cycles over the vast Arctic continental shelf. We show that the concentration of radium-228, sourced to seawater through sediment-water exchange processes, has increased substantially in surface waters of the central Arctic Ocean over the past decade. A mass balance model for228Ra suggests that this increase is due to an intensification of shelf-derived material inputs to the central basin, a source that would also carry elevated concentrations of dissolved organic carbon and nutrients. Therefore, we suggest that significant changes in the nutrient, carbon, and trace metal balances of the Arctic Ocean are underway, with the potential to affect biological productivity and species assemblages in Arctic surface waters.
Detecting reciprocity at a global scale Sci. Adv. Pub Date : 2018-01-01 Morgan R. Frank, Nick Obradovich, Lijun Sun, Wei Lee Woon, Brad L. LeVeck, Iyad Rahwan
Reciprocity stabilizes cooperation from the level of microbes all the way up to humans interacting in small groups, but does reciprocity also underlie stable cooperation between larger human agglomerations, such as nation states? Famously, evolutionary models show that reciprocity could emerge as a widespread strategy for achieving international cooperation. However, existing studies have only detected reciprocity-driven cooperation in a small number of country pairs. We apply a new method for detecting mutual influence in dynamical systems to a new large-scale data set that records state interactions with high temporal resolution. Doing so, we detect reciprocity between many country pairs in the international system and find that these reciprocating country pairs exhibit qualitatively different cooperative dynamics when compared to nonreciprocating pairs. Consistent with evolutionary theories of cooperation, reciprocating country pairs exhibit higher levels of stable cooperation and are more likely to punish instances of noncooperation. However, countries in reciprocity-based relationships are also quicker to forgive single acts of noncooperation by eventually returning to previous levels of mutual cooperation. By contrast, nonreciprocating pairs are more likely to exploit each other’s cooperation via higher rates of defection. Together, these findings provide the strongest evidence to date that reciprocity is a widespread mechanism for achieving international cooperation.
Seeing real-space dynamics of liquid water through inelastic x-ray scattering Sci. Adv. Pub Date : 2017-12-01 Takuya Iwashita, Bin Wu, Wei-Ren Chen, Satoshi Tsutsui, Alfred Q. R. Baron, Takeshi Egami
Water is ubiquitous on earth, but we know little about the real-space motion of molecules in liquid water. We demonstrate that high-resolution inelastic x-ray scattering measurement over a wide range of momentum and energy transfer makes it possible to probe real-space, real-time dynamics of water molecules through the so-called Van Hove function. Water molecules are found to be strongly correlated in space and time with coupling between the first and second nearest-neighbor molecules. The local dynamic correlation of molecules observed here is crucial to a fundamental understanding of the origin of the physical properties of water, including viscosity. The results also suggest that the quantum-mechanical nature of hydrogen bonds could influence its dynamics. The approach used here offers a powerful experimental method for investigating real-space dynamics of liquids.
Origin of the blueshift of water molecules at interfaces of hydrophilic cyclic compounds Sci. Adv. Pub Date : 2017-12-01 Katsufumi Tomobe, Eiji Yamamoto, Dušan Kojić, Yohei Sato, Masato Yasui, Kenji Yasuoka
Water molecules at interfaces of materials exhibit enigmatic properties. A variety of spectroscopic studies have observed a high-frequency motion in these water molecules, represented by a blueshift, at both hydrophobic and hydrophilic interfaces. However, the molecular mechanism behind this blueshift has remained unclear. Using Raman spectroscopy and ab initio molecular dynamics simulations, we reveal the molecular mechanism of the blueshift of water molecules around six monosaccharide isomers. In the first hydration shell, we found weak hydrogen-bonded water molecules that cannot have a stable tetrahedral water network. In the water molecules, the vibrational state of the OH bond oriented toward the bulk solvent strongly contributes to the observed blueshift. Our work suggests that the blueshift in various solutions originates from the vibrational motions of these observed water molecules.
Observation of the Mott insulator to superfluid crossover of a driven-dissipative Bose-Hubbard system Sci. Adv. Pub Date : 2017-12-01 Takafumi Tomita, Shuta Nakajima, Ippei Danshita, Yosuke Takasu, Yoshiro Takahashi
Dissipation is ubiquitous in nature and plays a crucial role in quantum systems such as causing decoherence of quantum states. Recently, much attention has been paid to an intriguing possibility of dissipation as an efficient tool for the preparation and manipulation of quantum states. We report the realization of successful demonstration of a novel role of dissipation in a quantum phase transition using cold atoms. We realize an engineered dissipative Bose-Hubbard system by introducing a controllable strength of two-body inelastic collision via photoassociation for ultracold bosons in a three-dimensional optical lattice. In the dynamics subjected to a slow ramp-down of the optical lattice, we find that strong on-site dissipation favors the Mott insulating state: The melting of the Mott insulator is delayed, and the growth of the phase coherence is suppressed. The controllability of the dissipation is highlighted by quenching the dissipation, providing a novel method for investigating a quantum many-body state and its nonequilibrium dynamics.
Quantum criticality in the spin-1/2 Heisenberg chain system copper pyrazine dinitrate Sci. Adv. Pub Date : 2017-12-01 Oliver Breunig, Markus Garst, Andreas Klümper, Jens Rohrkamp, Mark M. Turnbull, Thomas Lorenz
Low-dimensional quantum magnets promote strong correlations between magnetic moments that lead to fascinating quantum phenomena. A particularly interesting system is the antiferromagnetic spin-1/2 Heisenberg chain because it is exactly solvable by the Bethe-Ansatz method. It is approximately realized in the magnetic insulator copper pyrazine dinitrate, providing a unique opportunity for a quantitative comparison between theory and experiment. We investigate its thermodynamic properties with a particular focus on the field-induced quantum phase transition. Thermal expansion, magnetostriction, specific heat, magnetization, and magnetocaloric measurements are found to be in excellent agreement with exact Bethe-Ansatz predictions. Close to the critical field, thermodynamics obeys the expected quantum critical scaling behavior, and in particular, the magnetocaloric effect and the Grüneisen parameters diverge in a characteristic manner. Beyond its importance for quantum magnetism, our study establishes a paradigm of a quantum phase transition, which illustrates fundamental principles of quantum critical thermodynamics.
Prediction of a low-temperature N2 dissociation catalyst exploiting near-IR–to–visible light nanoplasmonics Sci. Adv. Pub Date : 2017-12-01 John Mark P. Martirez, Emily A. Carter
Despite more than a century of advances in catalyst and production plant design, the Haber-Bosch process for industrial ammonia (NH3) synthesis still requires energy-intensive high temperatures and pressures. We propose taking advantage of sunlight conversion into surface plasmon resonances in Au nanoparticles to enhance the rate of the N2dissociation reaction, which is the bottleneck in NH3production. We predict that this can be achieved through Mo doping of the Au surface based on embedded multireference correlated wave function calculations. The Au component serves as a light-harvesting antenna funneling energy onto the Mo active site, whereby excited-state channels (requiring 1.4 to 1.45 eV, near-infrared–to–visible plasmon resonances) may be accessed. This effectively lowers the energy barriers to 0.44 to 0.77 eV/N2(43 to 74 kJ/mol N2) from 3.5 eV/N2(335 kJ/mol N2) in the ground state. The overall process requires three successive surface excitation events, which could be facilitated by amplified resonance energy transfer due to plasmon local field enhancement.
Spatial charge inhomogeneity and defect states in topological Dirac semimetal thin films of Na3Bi Sci. Adv. Pub Date : 2017-12-01 Mark T. Edmonds, James L. Collins, Jack Hellerstedt, Indra Yudhistira, Lídia C. Gomes, João N. B. Rodrigues, Shaffique Adam, Michael S. Fuhrer
Topological Dirac semimetals (TDSs) are three-dimensional analogs of graphene, with carriers behaving like massless Dirac fermions in three dimensions. In graphene, substrate disorder drives fluctuations in Fermi energy, necessitating construction of heterostructures of graphene and hexagonal boron nitride (h-BN) to minimize the fluctuations. Three-dimensional TDSs obviate the substrate and should show reducedEFfluctuations due to better metallic screening and higher dielectric constants. We map the potential fluctuations in TDS Na3Bi using a scanning tunneling microscope. The rms potential fluctuations are significantly smaller than the thermal energy room temperature (ΔEF,rms= 4 to 6 meV = 40 to 70 K) and comparable to the highest-quality graphene on h-BN. Surface Na vacancies produce a novel resonance close to the Dirac point with surprisingly large spatial extent and provide a unique way to tune the surface density of states in a TDS thin-film material. Sparse defect clusters show bound states whose occupation may be changed by applying a bias to the scanning tunneling microscope tip, offering an opportunity to study a quantum dot connected to a TDS reservoir.
Impact of complex topology of porous media on phase separation of binary mixtures Sci. Adv. Pub Date : 2017-12-01 Ryotaro Shimizu, Hajime Tanaka
Porous materials, which are characterized by the large surface area and percolated nature crucial for transport, play an important role in many technological applications including battery, ion exchange, catalysis, microelectronics, medical diagnosis, and oil recovery. Phase separation of a mixture in such a porous structure should be strongly influenced by both surface wetting and strong geometrical confinement effects. Despite its fundamental and technological importance, however, this problem has remained elusive for a long time because of the difficulty associated with the complex geometry of pore structures. We overcome this by developing a novel phase-field model of two coupled order parameters, the composition field of a binary mixture and the density field of a porous structure. We find that demixing behavior in complex pore structures is severely affected by the topological characteristics of porous materials, contrary to the conventional belief that it can be inferred from the behavior in a simple cylindrical pore. Our finding not only reveals the physical mechanism of demixing in random porous structures but also has an impact on technological applications.
Aggregation-induced emission in lamellar solids of colloidal perovskite quantum wells Sci. Adv. Pub Date : 2017-12-01 Jakub Jagielski, Sudhir Kumar, Mingchao Wang, Declan Scullion, Robert Lawrence, Yen-Ting Li, Sergii Yakunin, Tian Tian, Maksym V. Kovalenko, Yu-Cheng Chiu, Elton J. G. Santos, Shangchao Lin, Chih-Jen Shih
The outstanding excitonic properties, including photoluminescence quantum yield (ηPL), of individual, quantum-confined semiconductor nanoparticles are often significantly quenched upon aggregation, representing the main obstacle toward scalable photonic devices. We report aggregation-induced emission phenomena in lamellar solids containing layer-controlled colloidal quantum wells (QWs) of hybrid organic-inorganic lead bromide perovskites, resulting in anomalously high solid-state ηPLof up to 94%. Upon forming the QW solids, we observe an inverse correlation between exciton lifetime and ηPL, distinct from that in typical quantum dot solid systems. Our multiscale theoretical analysis reveals that, in a lamellar solid, the collective motion of the surface organic cations is more restricted to orient along the  direction, thereby inducing a more direct bandgap that facilitates radiative recombination. Using the QW solids, we demonstrate ultrapure green emission by completely downconverting a blue gallium nitride light-emitting diode at room temperature, with a luminous efficacy higher than 90 lumen W−1at 5000 cd m−2, which has never been reached in any nanomaterial assemblies by far.
Resilience and efficiency in transportation networks Sci. Adv. Pub Date : 2017-12-01 Alexander A. Ganin, Maksim Kitsak, Dayton Marchese, Jeffrey M. Keisler, Thomas Seager, Igor Linkov
Urban transportation systems are vulnerable to congestion, accidents, weather, special events, and other costly delays. Whereas typical policy responses prioritize reduction of delays under normal conditions to improve the efficiency of urban road systems, analytic support for investments that improve resilience (defined as system recovery from additional disruptions) is still scarce. In this effort, we represent paved roads as a transportation network by mapping intersections to nodes and road segments between the intersections to links. We built road networks for 40 of the urban areas defined by the U.S. Census Bureau. We developed and calibrated a model to evaluate traffic delays using link loads. The loads may be regarded as traffic-based centrality measures, estimating the number of individuals using corresponding road segments. Efficiency was estimated as the average annual delay per peak-period auto commuter, and modeled results were found to be close to observed data, with the notable exception of New York City. Resilience was estimated as the change in efficiency resulting from roadway disruptions and was found to vary between cities, with increased delays due to a 5% random loss of road linkages ranging from 9.5% in Los Angeles to 56.0% in San Francisco. The results demonstrate that many urban road systems that operate inefficiently under normal conditions are nevertheless resilient to disruption, whereas some more efficient cities are more fragile. The implication is that resilience, not just efficiency, should be considered explicitly in roadway project selection and justify investment opportunities related to disaster and other disruptions.
Host susceptibility to snake fungal disease is highly dispersed across phylogenetic and functional trait space Sci. Adv. Pub Date : 2017-12-01 Frank T. Burbrink, Jeffrey M. Lorch, Karen R. Lips
Emerging infectious diseases (EIDs) reduce host population sizes, cause extinction, disassemble communities, and have indirect negative effects on human well-being. Fungal EIDs have reduced population abundances in amphibians and bats across many species over large areas. The recent emergence of snake fungal disease (SFD) may have caused declines in some snake populations in the Eastern United States (EUS), which is home to a phylogenetically and ecologically diverse assembly of 98 taxa. SFD has been documented in only 23 naturally occuring species, although this is likely an underestimate of the number of susceptible taxa. Using several novel methods, including artificial neural networks, we combine phylogenetic and trait-based community estimates from all taxa in this region to show that SFD hosts are both phylogenetically and ecologically randomly dispersed. This might indicate that other species of snakes in the EUS could be currently infected or susceptible to SFD. Our models also indicate that information about key traits that enhance susceptiblity is lacking. Surveillance should consider that all snake species and habitats likely harbor this pathogen.
Skin-like biosensor system via electrochemical channels for noninvasive blood glucose monitoring Sci. Adv. Pub Date : 2017-12-01 Yihao Chen, Siyuan Lu, Shasha Zhang, Yan Li, Zhe Qu, Ying Chen, Bingwei Lu, Xinyan Wang, Xue Feng
Currently, noninvasive glucose monitoring is not widely appreciated because of its uncertain measurement accuracy, weak blood glucose correlation, and inability to detect hyperglycemia/hypoglycemia during sleep. We present a strategy to design and fabricate a skin-like biosensor system for noninvasive, in situ, and highly accurate intravascular blood glucose monitoring. The system integrates an ultrathin skin-like biosensor with paper battery–powered electrochemical twin channels (ETCs). The designed subcutaneous ETCs drive intravascular blood glucose out of the vessel and transport it to the skin surface. The ultrathin (~3 μm) nanostructured biosensor, with high sensitivity (130.4 μA/mM), fully absorbs and measures the glucose, owing to its extreme conformability. We conducted in vivo human clinical trials. The noninvasive measurement results for intravascular blood glucose showed a high correlation (>0.9) with clinically measured blood glucose levels. The system opens up new prospects for clinical-grade noninvasive continuous glucose monitoring.
Rain-fed agriculture thrived despite climate degradation in the pre-Hispanic arid Andes Sci. Adv. Pub Date : 2017-12-01 Pablo Cruz, Thierry Winkel, Marie-Pierre Ledru, Cyril Bernard, Nancy Egan, Didier Swingedouw, Richard Joffre
Archaeological research suggests significant human occupation in the arid Andean highlands during the 13th to 15th centuries, whereas paleoclimatic studies reveal prolonged drier and colder conditions during that period. Which subsistence strategy supported local societies in this harsh environment? Our field and aerial surveys of archaeological dwelling sites, granaries, and croplands provide the first evidence of extended pre-Hispanic agriculture supporting dense human populations in the arid Andes of Bolivia. This unique agricultural system associated with quinoa cultivation was unirrigated, consisting of simple yet extensive landscape modifications. It relied on highly specific environmental knowledge and a set of water-saving practices, including microterracing and biennial fallowing. This intense agricultural activity developed during a period of unfavorable climatic change on a regional and global scale, illustrative of efficient adaptive strategies to cope with this climatic change.
Penetration mechanics of a beetle intromittent organ with bending stiffness gradient and a soft tip Sci. Adv. Pub Date : 2017-12-01 Yoko Matsumura, Alexander E. Kovalev, Stanislav N. Gorb
Hyper-elongated structures and their penetration are widespread among insects, for example, intromittent organs, ovipositors, and piercing-sucking mouthparts. The penetration of thin structures with high aspect ratio without buckling and rupturing is mechanically very challenging. However, this problem is economically solved in nature, and the solutions might be helpful for, for example, in the development of harmless catheters. We focus on the penetration process of a hyper-elongated structure of a cassidine beetle intromittent organ, termed a flagellum. We applied a three-point bending test for the flagellum to measure its bending stiffness along the entire flagellum. We demonstrated the bending stiffness gradient, in which the basal half is relatively stiff and the apical half is softer, whose good performance during copulation had been previously numerically demonstrated. The stiffness gradient is the result of the flagellum shape, which is cylindrical and tapered toward the tip. Moreover, the curved tip comprises a harder outer curve and a softer inner curve. Considering the findings of preceding studies, the flagellum works in the following way: (i) the bending stiffness gradient supports the flagellum, easily fitting to a shape of a highly coiled spermathecal duct, (ii) the stiffness property of the very tip may make the tip tougher, and (iii) the curled tip and homogeneously cylindrical shape of the organ help the very tip to fit the shape of the spermathecal duct of the female. Our study shows that the apparently simple flagellum penetration is achieved with numerous elaborate mechanical adaptations.
Denial of service to same-sex and interracial couples: Evidence from a national survey experiment Sci. Adv. Pub Date : 2017-12-01 Brian Powell, Landon Schnabel, Lauren Apgar
Legislatures and courts are debating whether businesses can deny services to same-sex couples for religious reasons. Yet, little is known about public views on this issue. In a national survey experiment, Americans (n= 2035) responded to an experimental vignette describing a gay or interracial couple refused service. Vignettes varied the reason for refusal (religion/nonreligious) and by business type (individual/corporation). Results confirm greater support of service refusal by the self-employed than by corporations and to gay couples than to interracial couples. However, religious reasons for refusal to gay couples elicit no more support than do nonreligious reasons. In the first national study to experimentally analyze views on service refusal to sexual minorities, we demonstrate that views vary by several factors but not by whether the refusal was for religious reasons.
Induced seismicity provides insight into why earthquake ruptures stop Sci. Adv. Pub Date : 2017-12-01 Martin Galis, Jean Paul Ampuero, P. Martin Mai, Frédéric Cappa
Injection-induced earthquakes pose a serious seismic hazard but also offer an opportunity to gain insight into earthquake physics. Currently used models relating the maximum magnitude of injection-induced earthquakes to injection parameters do not incorporate rupture physics. We develop theoretical estimates, validated by simulations, of the size of ruptures induced by localized pore-pressure perturbations and propagating on prestressed faults. Our model accounts for ruptures growing beyond the perturbed area and distinguishes self-arrested from runaway ruptures. We develop a theoretical scaling relation between the largest magnitude of self-arrested earthquakes and the injected volume and find it consistent with observed maximum magnitudes of injection-induced earthquakes over a broad range of injected volumes, suggesting that, although runaway ruptures are possible, most injection-induced events so far have been self-arrested ruptures.
In vivo genome editing improves motor function and extends survival in a mouse model of ALS Sci. Adv. Pub Date : 2017-12-01 Thomas Gaj, David S. Ojala, Freja K. Ekman, Leah C. Byrne, Prajit Limsirichai, David V. Schaffer
Amyotrophic lateral sclerosis (ALS) is a fatal and incurable neurodegenerative disease characterized by the progressive loss of motor neurons in the spinal cord and brain. In particular, autosomal dominant mutations in the superoxide dismutase 1 (SOD1) gene are responsible for ~20% of all familial ALS cases. The clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated (Cas9) genome editing system holds the potential to treat autosomal dominant disorders by facilitating the introduction of frameshift-induced mutations that can disable mutant gene function. We demonstrate that CRISPR-Cas9 can be harnessed to disrupt mutant SOD1 expression in the G93A-SOD1 mouse model of ALS following in vivo delivery using an adeno-associated virus vector. Genome editing reduced mutant SOD1 protein by >2.5-fold in the lumbar and thoracic spinal cord, resulting in improved motor function and reduced muscle atrophy. Crucially, ALS mice treated by CRISPR-mediated genome editing had ~50% more motor neurons at end stage and displayed a ~37% delay in disease onset and a ~25% increase in survival compared to control animals. Thus, this study illustrates the potential for CRISPR-Cas9 to treat SOD1-linked forms of ALS and other central nervous system disorders caused by autosomal dominant mutations.
Unveiling massive numbers of cancer-related urinary-microRNA candidates via nanowires Sci. Adv. Pub Date : 2017-12-01 Takao Yasui, Takeshi Yanagida, Satoru Ito, Yuki Konakade, Daiki Takeshita, Tsuyoshi Naganawa, Kazuki Nagashima, Taisuke Shimada, Noritada Kaji, Yuta Nakamura, Ivan Adiyasa Thiodorus, Yong He, Sakon Rahong, Masaki Kanai, Hiroshi Yukawa, Takahiro Ochiya, Tomoji Kawai, Yoshinobu Baba
Analyzing microRNAs (miRNAs) within urine extracellular vesicles (EVs) is important for realizing miRNA-based, simple, and noninvasive early disease diagnoses and timely medical checkups. However, the inherent difficulty in collecting dilute concentrations of EVs (<0.01 volume %) from urine has hindered the development of these diagnoses and medical checkups. We propose a device composed of nanowires anchored into a microfluidic substrate. This device enables EV collections at high efficiency and in situ extractions of various miRNAs of different sequences (around 1000 types) that significantly exceed the number of species being extracted by the conventional ultracentrifugation method. The mechanical stability of nanowires anchored into substrates during buffer flow and the electrostatic collection of EVs onto the nanowires are the two key mechanisms that ensure the success of the proposed device. In addition, we use our methodology to identify urinary miRNAs that could potentially serve as biomarkers for cancer not only for urologic malignancies (bladder and prostate) but also for nonurologic ones (lung, pancreas, and liver). The present device concept will provide a foundation for work toward the long-term goal of urine-based early diagnoses and medical checkups for cancer.
Cryo-mediated exfoliation and fracturing of layered materials into 2D quantum dots Sci. Adv. Pub Date : 2017-12-01 Yan Wang, Yang Liu, Jianfang Zhang, Jingjie Wu, Hui Xu, Xiewen Wen, Xiang Zhang, Chandra Sekhar Tiwary, Wei Yang, Robert Vajtai, Yong Zhang, Nitin Chopra, Ihab Nizar Odeh, Yucheng Wu, Pulickel M. Ajayan
Atomically thin quantum dots from layered materials promise new science and applications, but their scalable synthesis and separation have been challenging. We demonstrate a universal approach for the preparation of quantum dots from a series of materials, such as graphite, MoS2, WS2, h-BN, TiS2, NbS2, Bi2Se3, MoTe2, Sb2Te3, etc., using a cryo-mediated liquid-phase exfoliation and fracturing process. The method relies on liquid nitrogen pretreatment of bulk layered materials before exfoliation and breakdown into atomically thin two-dimensional quantum dots of few-nanometer lateral dimensions, exhibiting size-confined optical properties. This process is efficient for a variety of common solvents with a wide range of surface tension parameters and eliminates the use of surfactants, resulting in pristine quantum dots without surfactant covering or chemical modification.
Real-space analysis of diffusion behavior and activation energy of individual monatomic ions in a liquid Sci. Adv. Pub Date : 2017-12-01 Tomohiro Miyata, Fumihiko Uesugi, Teruyasu Mizoguchi
Investigation of the local dynamic behavior of atoms and molecules in liquids is crucial for revealing the origin of macroscopic liquid properties. Therefore, direct imaging of single atoms to understand their motions in liquids is desirable. Ionic liquids have been studied for various applications, in which they are used as electrolytes or solvents. However, atomic-scale diffusion and relaxation processes in ionic liquids have never been observed experimentally. We directly observe the motion of individual monatomic ions in an ionic liquid using scanning transmission electron microscopy (STEM) and reveal that the ions diffuse by a cage-jump mechanism. Moreover, we estimate the diffusion coefficient and activation energy for the diffusive jumps from the STEM images, which connect the atomic-scale dynamics to macroscopic liquid properties. Our method is the only available means to observe the motion, reactions, and energy barriers of atoms/molecules in liquids.
Reactivity of prehydrated electrons toward nucleobases and nucleotides in aqueous solution Sci. Adv. Pub Date : 2017-12-01 Jun Ma, Furong Wang, Sergey A. Denisov, Amitava Adhikary, Mehran Mostafavi
DNA damage induced via dissociative attachment by low-energy electrons (0 to 20 eV) is well studied in both gas and condensed phases. However, the reactivity of ultrashort-lived prehydrated electrons () with DNA components in a biologically relevant environment has not been fully explored to date. The electron transfer processes ofto the DNA nucleobases G, A, C, and T and to nucleosides/nucleotides were investigated by using 7-ps electron pulse radiolysis coupled with pump-probe transient absorption spectroscopy in aqueous solutions. In contrast to previous results, obtained by using femtosecond laser pump-probe spectroscopy, we show that G and A cannot scavengeat concentrations of ≤50 mM. Observation of a substantial decrease of the initial yield of hydrated electrons () and formation of nucleobase/nucleotide anion radicals at increasing nucleobase/nucleotide concentrations present direct evidence for the earliest step in reductive DNA damage by ionizing radiation. Our results show thatis more reactive with pyrimidine than purine nucleobases/nucleotides with a reactivity order of T > C > A > G. In addition, analyses of transient signals show that the signal due to formation of the resulting anion radical directly correlates with the loss of the initialsignal. Therefore, our results do not agree with the previously proposed dissociation of transient negative ions in nucleobase/nucleotide solutions within the timescale of these experiments. Moreover, in a molecularly crowded medium (for example, in the presence of 6 M phosphate), the scavenging efficiency ofby G is significantly enhanced. This finding implies that reductive DNA damage by ionizing radiation depends on the microenvironment around.
Molecular behavior of zero-dimensional perovskites Sci. Adv. Pub Date : 2017-12-01 Jun Yin, Partha Maity, Michele De Bastiani, Ibrahim Dursun, Osman M. Bakr, Jean-Luc Brédas, Omar F. Mohammed
Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6(X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4−surrounded by Cs+cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them.
Chemical potential–electric double layer coupling in conjugated polymer–polyelectrolyte blends Sci. Adv. Pub Date : 2017-12-01 Klas Tybrandt, Igor V. Zozoulenko, Magnus Berggren
Conjugated polymer–polyelectrolyte blends combine and couple electronic semiconductor functionality with selective ionic transport, making them attractive as the active material in organic biosensors and bioelectronics, electrochromic displays, neuromorphic computing, and energy conversion and storage. Although extensively studied and explored, fundamental knowledge and accurate quantitative models of the coupled ion-electron functionality and transport are still lacking to predict the characteristics of electrodes and devices based on these blends. We report on a two-phase model, which couples the chemical potential of the holes, in the conjugated polymer, with the electric double layer residing at the conjugated polymer–polyelectrolyte interface. The model reproduces a wide range of experimental charging and transport data and provides a coherent theoretical framework for the system as well as local electrostatic potentials, energy levels, and charge carrier concentrations. This knowledge is crucial for future developments and optimizations of bioelectronic and energy devices based on the electronic-ionic interaction within these materials.
Nanoscale magnetic imaging using circularly polarized high-harmonic radiation Sci. Adv. Pub Date : 2017-12-01 Ofer Kfir, Sergey Zayko, Christina Nolte, Murat Sivis, Marcel Möller, Birgit Hebler, Sri Sai Phani Kanth Arekapudi, Daniel Steil, Sascha Schäfer, Manfred Albrecht, Oren Cohen, Stefan Mathias, Claus Ropers
This work demonstrates nanoscale magnetic imaging using bright circularly polarized high-harmonic radiation. We utilize the magneto-optical contrast of worm-like magnetic domains in a Co/Pd multilayer structure, obtaining quantitative amplitude and phase maps by lensless imaging. A diffraction-limited spatial resolution of 49 nm is achieved with iterative phase reconstruction enhanced by a holographic mask. Harnessing the exceptional coherence of high harmonics, this approach will facilitate quantitative, element-specific, and spatially resolved studies of ultrafast magnetization dynamics, advancing both fundamental and applied aspects of nanoscale magnetism.
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