bluuebunny/crossref_metadata_2025 huggingface dataset:
Inspiring a Broader Socio‐Hydrological Negotiation Approach With Interdisciplinary Field‐Based Experience
Authors: Massuel S. , Riaux J. , Molle F. , Kuper M. , Ogilvie A. , Collard A‐L. , Leduc C. , Barreteau O.
Published: March 2018

Socio‐hydrology advanced the field of hydrology by considering humans and their activities as part of the water cycle, rather than as external drivers. Models are used to infer reproducible trends in human interactions with water resources. However, defining and handling water problems in this way may restrict the scope of such modeling approaches. We propose an interdisciplinary socio‐hydrological approach to overcome this limit and complement modeling approaches. It starts from concrete field‐based situations, combines disciplinary as well as local knowledge on water‐society relationships, with the aim of broadening the hydrocentric analysis and modeling of water systems. The paper argues that an analysis of social dynamics linked to water is highly complementary to traditional hydrological tools but requires a negotiated and contextualized interdisciplinary approach to the representation and analysis of socio‐hydro systems. This reflection emerged from experience gained in the field where a water‐budget modeling framework failed to adequately incorporate the multiplicity of (nonhydrological) factors that determine the volumes of withdrawals for irrigation. The pathway subsequently explored was to move away from the hydrologic view of the phenomena and, in collaboration with social scientists, to produce a shared conceptualization of a coupled human‐water system through a negotiated approach. This approach changed the way hydrological research issues were addressed and limited the number of strong assumptions needed for simplification in modeling. The proposed socio‐hydrological approach led to a deeper understanding of the mechanisms behind local water‐related problems and to debates on the interactions between social and political decisions and the dynamics of these problems.
How Does Snow Persistence Relate to Annual Streamflow in Mountain Watersheds of the Western U.S. With Wet Maritime and Dry Continental Climates?
Authors: Hammond John C. , Saavedra Freddy A. , Kampf Stephanie K.
Published: March 2018

With climate warming, many regions are experiencing changes in snow accumulation and persistence. These changes are known to affect streamflow volume, but the magnitude of the effect varies between regions. This research evaluates whether variables derived from remotely sensed snow cover can be used to estimate annual streamflow at the small watershed scale across the western U.S., a region with a wide range of climate types. We compared snow cover variables derived from MODIS, snow persistence (SP), and snow season (SS), to more commonly utilized metrics, snow fraction (fraction of precipitation falling as snow, SF), and peak snow water equivalent (SWE). Each variable represents different information about snow, and this comparison assesses similarities and differences between the snow metrics. Next, we evaluated how two snow variables, SP and SWE, related to annual streamflow (Q) for 119 USGS reference watersheds and examined whether these relationships varied for wet/warm (precipitation surplus) and dry/cold (precipitation deficit) watersheds. Results showed high correlations between all snow variables, but the slopes of these relationships differed between climates, with wet/warm watersheds displaying lower SF and higher SWE for the same SP. In dry/cold watersheds, both SP and SNODAS SWE correlated with Q spatially across all watersheds and over time within individual watersheds. We conclude that SP can be used to map spatial patterns of annual streamflow generation in dry/cold parts of the region. Applying this approach to the Upper Colorado River Basin demonstrates that 50% of streamflow comes from areas >3,000 masl. If the relationship between SP and Q is similar in other dry/cold regions, this approach could be used to estimate annual streamflow in ungauged basins.
On the Sensitivity of Annual Streamflow to Air Temperature
Authors: Milly P. C. D. , Kam J. , Dunne Krista A.
Published: March 2018

Although interannual streamflow variability is primarily a result of precipitation variability, temperature also plays a role. The relative weakness of the temperature effect at the annual time scale hinders understanding, but may belie substantial importance on climatic time scales. Here we develop and evaluate a simple theory relating variations of streamflow and evapotranspiration (E) to those of precipitation (P) and temperature. The theory is based on extensions of the Budyko water‐balance hypothesis, the Priestley‐Taylor theory for potential evapotranspiration (
), and a linear model of interannual basin storage. The theory implies that the temperature affects streamflow by modifying evapotranspiration through a Clausius‐Clapeyron‐like relation and through the sensitivity of net radiation to temperature. We apply and test (1) a previously introduced “strong” extension of the Budyko hypothesis, which requires that the function linking temporal variations of the evapotranspiration ratio (E/P) and the index of dryness (
/P) at an annual time scale is identical to that linking interbasin variations of the corresponding long‐term means, and (2) a “weak” extension, which requires only that the annual evapotranspiration ratio depends uniquely on the annual index of dryness, and that the form of that dependence need not be known a priori nor be identical across basins. In application of the weak extension, the readily observed sensitivity of streamflow to precipitation contains crucial information about the sensitivity to potential evapotranspiration and, thence, to temperature. Implementation of the strong extension is problematic, whereas the weak extension appears to capture essential controls of the temperature effect efficiently.
Predicting Hydrologic Function With Aquatic Gene Fragments
Authors: Good S. P. , URycki D. R. , Crump B. C.
Published: March 2018

Recent advances in microbiology techniques, such as genetic sequencing, allow for rapid and cost‐effective collection of large quantities of genetic information carried within water samples. Here we posit that the unique composition of aquatic DNA material within a water sample contains relevant information about hydrologic function at multiple temporal scales. In this study, machine learning was used to develop discharge prediction models trained on the relative abundance of bacterial taxa classified into operational taxonomic units (OTUs) based on 16S rRNA gene sequences from six large arctic rivers. We term this approach “genohydrology,” and show that OTU relative abundances can be used to predict river discharge at monthly and longer timescales. Based on a single DNA sample from each river, the average Nash‐Sutcliffe efficiency (NSE) for predicted mean monthly discharge values throughout the year was 0.84, while the NSE for predicted discharge values across different return intervals was 0.67. These are considerable improvements over predictions based only on the area‐scaled mean specific discharge of five similar rivers, which had average NSE values of 0.64 and −0.32 for seasonal and recurrence interval discharge values, respectively. The genohydrology approach demonstrates that genetic diversity within the aquatic microbiome is a large and underutilized data resource with benefits for prediction of hydrologic function.
On Permeability Prediction From Complex Conductivity Measurements Using Polarization Magnitude and Relaxation Time
Authors: Robinson Judith , Slater Lee , Weller Andreas , Keating Kristina , Robinson Tonian , Rose Carla , Parker Beth
Published: March 2018

Geophysical length scales determined from complex conductivity (CC) measurements can be used to estimate permeability
when the electrical formation factor F is known. Two geophysical length scales have been proposed: (1) the specific polarizability
normalized by the imaginary conductivity
and (2) the time constant
multiplied by a diffusion coefficient
. The parameters
and
account for the control of fluid chemistry and/or varying minerology on the geophysical length scale. We evaluated the predictive capability of two CC permeability models: (1) an empirical formulation based on
or normalized chargeability
and (2) a mechanistic formulation based on
. The performance of the CC models was evaluated against measured
; and further compared against that of well‐established
estimation equations that use geometric length scales. Both CC models predict permeability within one order of magnitude for a database of 58 sandstone samples, with the exception of samples characterized by high pore volume normalized surface area
. Variations in
and
likely contribute to the poor model performance for the high
samples, which contain significant dolomite. Two observations favor the implementation of the
‐based model over the
‐based model for field‐scale
estimation: (1) a limited range of variation in
relative to
and (2)
field measurements are less time consuming to acquire relative to
. The need for a reliable field‐estimate of
limits application of either model, in particular the
model due to a high power law exponent associated with
.
Stochastic Scenario Evaluation in Evolutionary Algorithms Used for Robust Scenario‐Based Optimization
Authors: Sankary Nathan , Ostfeld Avi
Published: March 2018

This paper focuses on evaluating a scenario‐based multiobjective evolutionary algorithm for real‐world design problems in which the environment where a system will operate is dynamic, and uncertain. Subsequently, the performance of a stochastic scenario selection scheme, inspired by methods to reduce overfitting in genetic programming, is investigated for scenario‐based optimization. Using a scenario‐based scheme to address uncertainty in a real‐world system's operational environment, system designs are developed via aggregating the performance of a solution evaluated across many scenarios. Within each generation of the evolutionary algorithm the evaluation suite is resampled and evaluated by the current generation's solutions. This scheme is evaluated on two historical noisy test problems and two real‐world water resources design problem instances. For each case, the stochastic scenario selection scheme is compared to a static selection scheme at various evaluation suite sizes. Results show the proposed scenario selection scheme to outperform static sampling schemes and increase efficiency of a multiobjective evolutionary algorithm for robust optimization objectives.
A Model for Mass Transport Across the Sediment‐Water Interface
Authors: Voermans Joey J. , Ghisalberti Marco , Ivey Gregory N.
Published: March 2018

Molecular diffusion, dispersion, and turbulent diffusion can all contribute to the transport of mass across the sediment‐water interface (SWI). Flow observations across the SWI are critical in the description of these transport processes but are currently very limited as the sediment bed is inaccessible in most experimental approaches. We overcome this constraint by combining refractive‐index matching (RIM) with particle‐tracking velocimetry (PTV). Using measurements of the flow dynamics across the SWI, we propose a mechanistic model that describes the interfacial mass transport over a wide and relevant parameter space. We show there are three transport regimes where molecular, dispersive, or turbulent transport dominates the mass flux of a passive tracer across the SWI. Transitions between these regimes are defined by the permeability Reynolds number, whereKis the sediment permeability,is the shear velocity, andνis the fluid viscosity. In the molecular regime (), mass transport is described by the molecular diffusion coefficient (D). In both the dispersive () and turbulent regimes (), the mass diffusivity is directly proportional to. The model is strongly supported by an extensive data set of published interfacial mass flux observations and provides a tool for describing fluxes across the SWI in aquatic system models.
Blue Water Trade‐Offs With Vegetation in a CO2‐Enriched Climate
Authors: Mankin Justin S. , Seager Richard , Smerdon Jason E. , Cook Benjamin I. , Williams A. Park , Horton Radley M.
Published: March 2018

Present and future freshwater availability and drought risks are physically tied to the responses of surface vegetation to increasing CO2. A single‐model large ensemble identifies the occurrence of colocated warming‐ and CO2‐induced leaf area index increases with summer soil moisture declines. This pattern of “greening” and “drying,” which occurs over 42% of global vegetated land area, is largely attributable to changes in the partitioning of precipitation at the land surface away from runoff and toward terrestrial vegetation ecosystems. Changes in runoff and ecosystem partitioning are inversely related, with changes in runoff partitioning being governed by changes in precipitation (mean and extremes) and ecosystem partitioning being governed by ecosystem water use and surface resistance to evapotranspiration (ET). Projections show that warming‐influenced and CO2‐enriched terrestrial vegetation ecosystems use water that historically would have been partitioned to runoff over 48% of global vegetated land areas, largely in Western North America, the Amazon, and Europe, many of the same regions with colocated greening and drying. These results have implications for how water available for people will change in response to anthropogenic warming and raise important questions about model representations of vegetation water responses to high CO2.
On Mars's Atmospheric Sputtering After MAVEN's First Martian Year of Measurements
Authors: Leblanc F. , Martinez A. , Chaufray J. Y. , Modolo R. , Hara T. , Luhmann J. , Lillis R. , Curry S. , McFadden J. , Halekas J. , Jakosky B.
Published: March 2018

Mars likely lost a significant part of its atmosphere to space during its history. The sputtering of the atmosphere, by precipitating planetary heavy pickup ions accelerated by the solar wind, is one of the processes that could have significantly contributed to this atmospheric escape, in particular since the cessation of its global magnetic field, 4.0–4.1 Gyr ago. We present a 2 year baseline analysis of Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of the precipitating flux. We use this measurement to model the expected escape rate and exospheric structure induced by this precipitation. We conclude that sputtering signatures in the dayside exosphere will be difficult to identify by MAVEN, and the induced atmospheric escape of O atoms remains orders of magnitude smaller than the expected rate induced by dissociative recombination of O2+ in Mars's ionosphere. On the contrary, deep in the nightside, Mars's sputtering might be the main source of the nonthermal part of the exospheric density profiles of species with mass larger or equal to Ar.
Tracking an Oil Tanker Collision and Spilled Oils in the East China Sea Using Multisensor Day and Night Satellite Imagery
Authors: Sun Shaojie , Lu Yingcheng , Liu Yongxue , Wang Mengqiu , Hu Chuanmin
Published: March 2018

Satellite remote sensing is well known to play a critical role in monitoring marine accidents such as oil spills, yet the recent SANCHI oil tanker collision event in January 2018 in the East China Sea indicates that traditional techniques using synthetic aperture radar or daytime optical imagery could not provide timely and adequate coverage. In this study, we show the unprecedented value of Visible Infrared Imaging Radiometer Suite (VIIRS) Nightfire product and Day/Night Band data in tracking the oil tanker's drifting pathway and locations when all other means are not as effective for the same purpose. Such pathway and locations can also be reproduced with a numerical model, with root‐mean‐square error of <15 km. While high‐resolution optical imagery after 4 days of the tanker's sinking reveals much larger oil spill area (>350 km2) than previous reports, the impact of the spilled condensate oil on the marine environment requires further research.
Thermospheric Expansion Associated With Dust Increase in the Lower Atmosphere on Mars Observed by MAVEN/NGIMS
Authors: Liu Guiping , England Scott L. , Lillis Robert J. , Withers Paul , Mahaffy Paul R. , Rowland Douglas E. , Elrod Meredith , Benna Mehdi , Kass David M. , Janches Diego , Jakosky Bruce
Published: March 2018

We present for the first time the dramatic variations in atmospheric composition and density at high altitudes from 170 to 220 km in Mars' neutral thermosphere in response to dust increases in the lower atmosphere, observed by the in situ Neutral Gas Ion Mass Spectrometer onboard the Mars Atmosphere and Volatile EvolutioN satellite. The observations reveal that CO2, Ar, N2, CO, and O densities all increase up to ~200% compared to the longer‐term running median densities. The density increases are seen throughout this altitude region, and the relative variations are seen to be stronger at higher altitudes. Density increases indicating the solar extreme ultraviolet influence are also seen. This study is consistent with that during increased dust load, the whole atmosphere expands and rises, and other processes may also be involved. The results agree with the general circulation model predictions, providing observational evidence for how dust increases affect different atmospheric species in the thermosphere.
The Reprise Special Collection for the 2001 Space Weather Monograph
Authors: Knipp Delores J.
Published: March 2018

This manuscript introduces the Special Collection of articles that reprise and update those in the 2001 AGU Monograph on Space Weather.
Who victimizes whom and who defends whom? A multivariate social network analysis of victimization, aggression, and defending in early childhood
Authors: Huitsing Gijs , Monks Claire P.
Published: March 2018

The aim of this research was to investigate the interplay between victim‐aggressor relationships and defending relationships in early childhood to test the proposition that young aggressors are less selective than older children in their choice of vulnerable targets. Cross‐sectional multivariate statistical social network analyses (Exponential Random Graph Models) for a sample of 177 preschoolers from seven classes, 5‐ to 7‐years‐old, revealed that boys were more aggressive than girls, toward both boys and girls, whereas defending relationships were most often same‐sex. There was significant reciprocity in aggression, indicating that it was more often bidirectional rather than unidirectional. In addition, aggressors clearly defended each other when they shared their targets of aggression, whereas a marginally significant trend appeared for defending between victims who were victimized by the same aggressors. Furthermore, teacher‐rated dominance was positively associated with children's involvement in both aggression and victimization, and teacher‐rated insecurity was associated with less aggression, but not with victimization. These findings suggest that those who are reported as being victimized may retaliate, or be aggressive themselves, and do not display some of the vulnerabilities reported among older groups of victims. The findings are in line with the proposition that young aggressors are less strategic than older children in targeting vulnerable victims. The network approach to peer victimization and defending contributes to understanding the social processes facilitating the development of aggression in early childhood.
Amino Acid Composition Determines Peptide Activity Spectrum and Hot‐Spot‐Based Design of Merecidin
Authors: Wang Xiuqing , Mishra Biswajit , Lushnikova Tamara , Narayana Jayaram Lakshmaiah , Wang Guangshun
Published: March 2018

There is a great interest in developing the only human cathelicidin into therapeutic molecules. The major antimicrobial region of human LL‐37 corresponds to residues 17–32. The resultant peptide GF‐17 shows a broad spectrum of antimicrobial activity against both Gram‐positive and Gram‐negative bacteria. By reducing the hydrophobic content, converting the broad‐spectrum GF‐17 to two narrow‐spectrum peptides (GF‐17d3 and KR‐12) with activity against Gram‐negative bacteria is successful. This study demonstrates that substitution of multiple basic amino acids by hydrophobic alanines makes a broad‐spectrum peptide 17BIPHE2 (designed based on GF‐17d3) active against Staphylococcal pathogens but not other bacteria tested. Taken together, the results reveal distinct charge and hydrophobic requirements for peptides to kill Gram‐positive or Gram‐negative bacteria. This finding is in line with the bioinformatics analysis of the peptides in the Antimicrobial Peptide Database (http://aps.unmc.edu/AP). In addition, a hot‐spot arginine is identified and used to design merecidin with reduced toxicity to human cells. Merecidin protects wax moth larvae (Galleria mellonella) from the infection of methicillin‐resistant Staphylococcus aureus USA300. These new selective peptides constitute interesting candidates for future development.
The Challenge of Reversing Theories to Hybridize Structures with Fiber Metal Laminate Design Concepts
Authors: Alderliesten René
Published: March 2018

To further optimize aeronautical structures, an increased level of material hybridization is required. Optimization efforts aim to identify optimal design solutions that satisfy prescribed requirements. However, this demands reversal of currently available knowledge on hybrid structural technologies, which are often formulated as theories predicting performance based on known load cases and selected material configurations. After briefly reviewing the available fundamental theories for strength, fatigue, and damage tolerance of hybrid structures, this paper discusses the challenges in reversing these theories. Solutions are proposed in which theories can be approximated to significantly reduce the computational time while maintaining the required level of accuracy.
Metallic Adhesive Layers for Ag‐Based First Surface Mirrors
Authors: James Robin A. , Stapleton Andrew J. , Hughes Adam , Charrault Eric , Zuber Kamil , Switalska Eliza , Evans Drew , Murphy Peter , Llusca Marta
Published: March 2018

Metallic thin films have been evaluated as adhesive layers for first surface mirrors. Thin films (0.5–4 nm thick) of Cr, Cu, Ge, Sn, and Ni, capped with an over layer of 100 nm of Ag have been deposited by means of ion assisted electron beam evaporation onto glass substrates. The specular reflectance, conductivity, morphology, adhesion, and abrasion resistance of the mirrors have been assessed and compared. This work demonstrates the superior Ni and Ge adhesion and abrasion resistance to Ag thin films, while Cr and again Ni are the best candidates in terms of reflectance enhancement. In particular, 4 nm of Ni increases the Ag reflectance from 95.7% to 96.7%, exhibits the strongest adhesion as determined by the cross hatch tape test and the lowest loss of material after the different abrasion tests is just 50% in comparison to 100% for Ag‐coated glass substrates.
Synergistic Effects of B4C and Sn on the Coupled Growth Pattern and Mechanical Properties of Mg–Y–Zn–Mn Alloy Containing LPSO and W Phases
Authors: Li Yi , Zhang Zhe , Zhang Jinshan , Ma Yanbin , Zhang Yatong , Xu Chunxiang
Published: March 2018

The effect of boron carbide (B4C) particles and Sn on the microstructure and mechanical properties of Mg94Y2.5Zn2.5Mn1 alloy is mainly studied in this work. The results show that separated addition of B4C and Sn could not achieve very good results. The separated addition of Sn significantly promotes the formation of LPSO phase, but it cannot change the growth pattern of LPSO phase and W phase. Adding B4C changes the growth pattern of LPSO phase, but cannot effectively promote the formation of LPSO phase. The addition of B4C and Sn in combination achieves the growth pattern transformation of α‐Mg from irregular dendrite to equiaxed dendrite and refines the grain size, which makes LPSO phase and W phase no longer grow by coupled growth. When 0.02 wt% B4C and 0.35 wt% Sn is added, the Mg94Y2.5Zn2.5Mn1 alloy's growth pattern is changed and grains are refined, and thus exhibit superior mechanical properties. (Ultimate tensile strength of 255 MPa and elongation of 8.8%).
Graphene Platelets and Their Polymer Composites: Fabrication, Structure, Properties, and Applications
Authors: Shi Ge , Araby Sherif , Gibson Christopher T. , Meng Qingshi , Zhu Shenmin , Ma Jun
Published: March 2018

Graphene oxide is extensively compounded with polymers toward a wide variety of applications. Less studied are few‐layer or multi‐layer highly crystalline graphene, both of which are herein named as graphene platelets. This article aims to provide the most recent advancements of graphene platelets and their polymer composites. A first focus lies on cost‐effective fabrication strategies of graphene platelets – intercalation and exfoliation – which work in a relative mass scale, e.g., 5.3 g h−1. As no heavy oxidization is involved, the platelets have high crystalline integrity, e.g., C:O ratio over 8.0, with thicknesses 2–4 nm and lateral dimension up to a few micrometers. Through carefully selecting the solvent for dispersion and the molecules for surface modification, graphene platelets can be liquid‐processable, enabling them to be printed, coated, or compounded with various polymers. A purpose‐designed experiment is undertaken to unravel the effect of reasonable ultrasonication time on the platelet thickness. Typical polymer/graphene platelet composites are critically examined for their preparation, structure, and applications such as thermal management and flexible/stretchable electronic devices. Perspectives on the limitations, current challenges, and future prospects for graphene platelets and their polymer composites are provided.
Molecular Diffusion–Driven Motion in 2D Graphene Film
Authors: Chang Jin , Sheng Lizhi , Wei Tong , Fan Zhuangjun
Published: March 2018

Here, a new mode for driving the motion of graphene films on water by organic molecular diffusion is reported. Because of ultralight weight, micro/nanochannels constructed by interlayered sheets, the hydrophobic nature of graphene, and the one‐way 2D diffusion of organic molecules into water induce force/torque for driving the movement of the film. It is worth mentioning that the rectangular film filled with ethanol (1 cm × 2 cm) shows a high rotational speed of 300 rpm on the water. Importantly, the continuous rotation of the graphene film can be realized by continuously adding the collected ethanol from the ethanol–water mixture under visible light irradiation. Moreover, the folded graphene film filled with ethanol can push a porcelain boat (12 g) on water with a velocity of 50 mm s−1. Thus, it is believed that this new driving mode can be applied in the fields of microflow reactors, electric generating device, minisensors, and actuators.
Piezophototronic Effect Enhanced Photoresponse of the Flexible Cu(In,Ga)Se2 (CIGS) Heterojunction Photodetectors
Authors: Qiao Shuang , Liu Jihong , Niu Xiaona , Liang Baolai , Fu Guangsheng , Li Zhiqiang , Wang Shufang , Ren Kailiang , Pan Caofeng
Published: March 2018

The Cu(In,Ga)Se2 (CIGS) heterojunction, as a mature and high efficiency thin‐film solar cell, is rarely studied as a photodetector, especially in flexible substrates. In this paper, the structure of an ITO/ZnO/CdS/CIGS/Mo heterojunction is grown on the polyimide (PI) substrate to form a flexible CIGS heterojunction photodetector. The photodetector can work in a very wide band ranging from 350 to 1200 nm with responsivity up to 1.18 A W−1 (808 nm), detectivity up to 6.56 × 1010 Jones (cmHz1/2 W−1), and response time of 70 (/88) ms, respectively. Moreover, the piezophototronic effect is first used to investigate performance modulation of this device by effectively controlling the separation and transport of carriers at the interface of CdS/ZnO. Interestingly, by externally applying a 0.763% tensile strain, the photoresponsivity and detectivity of the photodetector exhibit a decrease from 1.18 to 0.88 A W−1, and from 6.56 × 1010 to 4.81 × 1010 Jones, respectively, while under a –0.749% externally static compressive strain, the photoresponsivity could be enhanced by ≈75.4% with a maximum of 2.07 A W−1, and the detectivity is improved by ≈66.1% with its peak value up to 10.9 × 1010 Jones. Meanwhile, the response time can be modulated from 99(/116) to 41.3(/42.6) ms. This work suggests that the CIGS heterojunction has great potential in novel applications for piezophototronic sensors and also gives a hint to modulate the performance of other multilayer heterostructures via the piezotronic effect.
Dual Electrostatic Assembly of Graphene Encapsulated Nanosheet‐Assembled ZnO‐Mn‐C Hollow Microspheres as a Lithium Ion Battery Anode
Authors: Xie Qingshui , Liu Pengfei , Zeng Deqian , Xu Wanjie , Wang Laisen , Zhu Zi‐Zhong , Mai Liqiang , Peng Dong‐Liang
Published: March 2018

Graphene encapsulated nanosheet‐assembled ZnO‐Mn‐C hierarchical hollow microspheres are produced through a simple yet effective dual electrostatic assembly strategy, followed by a heating treatment in inert atmosphere. The modification of graphene sheets, metal Mn, and in situ carbon leads to form 3D interconnected conductive framework as electron highways. The hollow structure and the open configuration of hierarchical microspheres guarantee good structural stability and rapid ionic transport. More importantly, according to the density functional theory calculations, the oxygen vacancies in the hierarchical microspheres would cause an imbalanced charge distribution and thus the formation of local in‐plane electric fields around oxygen vacancy sites, which is beneficial for the ionic/electronic transport during cycling. Due to this multiscale coordinated design, the as‐fabricated graphene encapsulated nanosheet‐assembled ZnO‐Mn‐C hierarchical hollow microspheres demonstrate good lithium storage properties in terms of high reversible capacity (1094 mA h g−1 at 100 mA g−1), outstanding high‐rate long‐term cycling stability (843 mA h g−1 after 1000 cycles at 2000 mA g−1), and remarkable rate capability (422 mA h g−1 after total 1600 cycles at 5000 mA g−1).
Smart Passivation Materials with a Liquid Metal Microcapsule as Self‐Healing Conductors for Sustainable and Flexible Perovskite Solar Cells
Authors: Chu Kunmo , Song Byong Gwon , Yang Hye‐In , Kim Dong‐Min , Lee Chang Seung , Park Minwoo , Chung Chan‐Moon
Published: March 2018

The electrical repair of device circuits has been considered a main issue in the area of electronic packaging. Demand for self‐healing conductors as cost‐effective and promising materials for prolonging the durability of devices has increased. Recently, diverse designs of self‐healing and deformable circuits have been introduced in virtue of their high stretchability and conductivity. However, encapsulating a liquid metal with a polymer in a micro‐size container is essential for real applications. In this work, core–shell‐structured liquid metal microcapsules (LMCs, diameter = 2–10 µm) are synthesized via in situ polymerization of urea‐formaldehyde onto liquid metal colloids. Passivation films comprising LMC/polymer composites are simply prepared using phase separation between the capsules and the liquid prepolymer. Capsules ruptured by cutting or pressing release and transport liquid metal to the damaged sites, leading to effective recovery of electrical pathways. Such self‐healing of the metal contacts shows the high potential of LMCs for smart passivation of electronic devices. As an example, flexible perovskite solar cells incorporated with the passivation film demonstrate perfect recovery of the photovoltaic parameters immediately after cutting the metal contact, exhibiting a power conversion efficiency (PCE) retention of 99% relative to the initial value (PCE = 15.07%).
Copper Sulfide (CuxS) Nanowire‐in‐Carbon Composites Formed from Direct Sulfurization of the Metal‐Organic Framework HKUST‐1 and Their Use as Li‐Ion Battery Cathodes
Authors: Foley Sarah , Geaney Hugh , Bree Gerard , Stokes Killian , Connolly Sinead , Zaworotko Michael J. , Ryan Kevin M.
Published: March 2018

Li‐ion batteries containing cost‐effective, environmentally benign cathode materials with high specific capacities are in critical demand to deliver the energy density requirements of electric vehicles and next‐generation electronic devices. Here, the phase‐controlled synthesis of copper sulfide (CuxS) composites by the temperature‐controlled sulfurization of a prototypal Cu metal‐organic framework (MOF), HKUST‐1 is reported. The tunable formation of different CuxS phases within a carbon network represents a simple method for the production of effective composite cathode materials for Li‐ion batteries. A direct link between the sulfurization temperature of the MOF and the resultant CuxS phase formed with more Cu‐rich phases favored at higher temperatures is further shown. The CuxS/C samples are characterized through X‐ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy, and energy dispersive X‐ray spectroscopy (EDX) in addition to testing as Li‐ion cathodes. It is shown that the performance is dependent on both the CuxS phase and the crystal morphology with the Cu1.8S/C‐500 material as a nanowire composite exhibiting the best performance, showing a specific capacity of 220 mAh g−1 after 200 charge/discharge cycles.
Correlation between Geometrically Induced Oxygen Octahedral Tilts and Multiferroic Behaviors in BiFeO3 Films
Authors: Lee Sung Su , Kim Young‐Min , Lee Hyun‐Jae , Seo Okkyun , Jeong Hu Young , He Qian , Borisevich Albina Y. , Kang Boyoun , Kwon Owoong , Kang Seunghun , Kim Yunseok , Koo Tae Yeong , Rhyee Jong‐Soo , Noh Do Young , Cho Beongki , Seo Ji Hui , Lee Jun Hee , Jo Ji Young
Published: March 2018

The equilibrium position of atoms in a unit cell is directly connected to crystal functionalities, e.g., ferroelectricity, ferromagnetism, and piezoelectricity. The artificial tuning of the energy landscape can involve repositioning atoms as well as manipulating the functionalities of perovskites (ABO3), which are good model systems to test this legacy. Mechanical energy from external sources accommodating various clamping substrates is utilized to perturb the energy state of perovskite materials fabricated on the substrates and consequently change their functionalities; however, this approach yields undesired complex behaviors of perovskite crystals, such as lattice distortion, displacement of B atoms, and/or tilting of oxygen octahedra. Owing to complimentary collaborations between experimental and theoretical studies, the effects of both lattice distortion and displacement of B atoms are well understood so far, which leaves us a simple question: Can we exclusively control the positions of oxygen atoms in perovskites for functionality manipulation? Here the artificial manipulation of oxygen octahedral tilt angles within multiferroic BiFeO3 thin films using strong oxygen octahedral coupling with bottom SrRuO3 layers is reported, which opens up new possibilities of oxygen octahedral engineering.
Large‐Scale Synthesis and Medical Applications of Uniform‐Sized Metal Oxide Nanoparticles
Authors: Kwon Hyek Jin , Shin Kwangsoo , Soh Min , Chang Hogeun , Kim Jonghoon , Lee Jisoo , Ko Giho , Kim Byung Hyo , Kim Dokyoon , Hyeon Taeghwan
Published: March 2018

Thanks to recent advances in the synthesis of high‐quality inorganic nanoparticles, more and more types of nanoparticles are becoming available for medical applications. Especially, metal oxide nanoparticles have drawn much attention due to their unique physicochemical properties and relatively inexpensive production costs. To further promote the development and clinical translation of these nanoparticle‐based agents, however, it is highly desirable to reduce unwanted interbatch variations of the nanoparticles because characterizing and refining each batch are costly, take a lot of effort, and, thus, are not productive. Large‐scale synthesis is a straightforward and economic pathway to minimize this issue. Here, the recent achievements in the large‐scale synthesis of uniform‐sized metal oxide nanoparticles and their biomedical applications are summarized, with a focus on nanoparticles of transition metal oxides and lanthanide oxides, and clarifying the underlying mechanism for the synthesis of uniform‐sized nanoparticles. Surface modification steps to endow hydrophobic nanoparticles with water dispersibility and biocompatibility are also briefly described. Finally, various medical applications of metal oxide nanoparticles, such as bioimaging, drug delivery, and therapy, are presented.
Nonnoble‐Metal‐Based Plasmonic Nanomaterials: Recent Advances and Future Perspectives
Authors: Kim Sungi , Kim Jae‐Myoung , Park Jeong‐Eun , Nam Jwa‐Min
Published: March 2018

The application scope of plasmonic nanostructures is rapidly expanding to keep pace with the ongoing development of various scientific findings and emerging technologies. However, most plasmonic nanostructures heavily depend on rare, expensive, and extensively studied noble metals such as Au and Ag, with the limited choice of elements hindering their broad and practical applications in a wide spectral range. Therefore, abundant and inexpensive nonnoble metals have attracted attention as new plasmonic nanomaterial components, allowing these nonnoble‐metal‐based materials to be used in areas such as photocatalysis, sensing, nanoantennas, metamaterials, and magnetoplasmonics with new compositions, structures, and properties. Furthermore, the use of nonnoble metal hybrids results in newly emerging or synergistic properties not observed from single‐metal component systems. Here, the synthetic strategies and recent advances in nonnoble‐metal‐based plasmonic nanostructures comprising Cu, Al, Mg, In, Ga, Pb, Ni, Co, Fe, and related hybrids are highlighted, and a discussion and perspectives in their synthesis, properties, applications, and challenges are presented.
Nanomaterial‐Based Plasmon‐Enhanced Infrared Spectroscopy
Authors: Yang Xiaoxia , Sun Zhipei , Low Tony , Hu Hai , Guo Xiangdong , García de Abajo F. Javier , Avouris Phaedon , Dai Qing
Published: March 2018

Surface‐enhanced infrared absorption (SEIRA) has attracted increasing attention due to the potential of infrared spectroscopy in applications such as molecular trace sensing of solids, polymers, and proteins, specifically fueled by recent substantial developments in infrared plasmonic materials and engineered nanostructures. Here, the significant progress achieved in the past decades is reviewed, along with the current state of the art of SEIRA. In particular, the plasmonic properties of a variety of nanomaterials are discussed (e.g., metals, semiconductors, and graphene) along with their use in the design of efficient SEIRA configurations. To conclude, perspectives on potential applications, including single‐molecule detection and in vivo bioassays, are presented.
Thermal Conductivity of Polymers and Their Nanocomposites
Authors: Xu Xiangfan , Chen Jie , Zhou Jun , Li Baowen
Published: March 2018

Polymers are usually considered as thermal insulators, and their applications are limited by their low thermal conductivity. However, recent studies have shown that certain polymers have surprisingly high thermal conductivity, some of which are comparable to that in poor metals or even silicon. Here, the experimental achievements and theoretical progress of thermal transport in polymers and their nanocomposites are outlined. The open questions and challenges of existing theories are discussed. Special attention is given to the mechanism of thermal transport, the enhancement of thermal conductivity in polymer nanocomposites/fibers, and their potential application as thermal interface materials.
Enrichment of Precious Metals from Wastewater with Core–Shell Nanoparticles of Iron
Authors: Ling Lan , Huang Xiao‐Yue , Zhang Wei‐Xian
Published: March 2018

Large‐scale deployment of zero‐valent iron nanoparticles for enrichment and recovery of gold from industrial wastewater is reported. Iron nanoparticles have a core–shell structure in which a metallic iron core is enclosed with a thin layer of iron oxides/hydroxides. The two nanocomponents offer synergistic functions for rapid separation, enrichment, and stabilization of metal ions such as Au, Ag, Ni, and Cu. Thanks to the advantages of small size, large surface area, and high reactivity, only a small amount of iron nanoparticles are needed. The recovered nanoparticles thus contain precious metals well above conventional metal ores (e.g., >100 g Au ton−1). Cost‐effective recovery of precious metals from trace‐level sources such as wastewater looks promising.
Intercalated Water and Organic Molecules for Electrode Materials of Rechargeable Batteries
Authors: Lee Hyeon Jeong , Shin Jaeho , Choi Jang Wook
Published: March 2018

The intrinsic limitations of lithium‐ion batteries (LIBs) with regard to safety, cost, and the availability of raw materials have promoted research on so‐called “post‐LIBs”. The recent intense research of post‐LIBs provides an invaluable lesson that existing electrode materials used in LIBs may not perform as well in post‐LIBs, calling for new material designs compliant with emerging batteries based on new chemistries. One promising approach in this direction is the development of materials with intercalated water or organic molecules, as these materials demonstrate superior electrochemical performance in emerging battery systems. The enlarged ionic channel dimensions and effective shielding of the electrostatic interaction between carrier ions and the lattice host are the origins of the observed electrochemical performance. Moreover, these intercalants serve as interlayer pillars to sustain the framework for prolonged cycles. Representative examples of such intercalated materials applied to batteries based on Li+, Na+, Mg2+, and Zn2+ ions and supercapacitors are considered, along with their impact in materials research.
Self‐Powered Wearable Electronics Based on Moisture Enabled Electricity Generation
Authors: Shen Daozhi , Xiao Ming , Zou Guisheng , Liu Lei , Duley Walter W. , Zhou Y. Norman
Published: March 2018

Most state‐of‐the‐art electronic wearable sensors are powered by batteries that require regular charging and eventual replacement, which would cause environmental issues and complex management problems. Here, a device concept is reported that can break this paradigm in ambient moisture monitoring—a new class of simple sensors themselves can generate moisture‐dependent voltage that can be used to determine the ambient humidity level directly. It is demonstrated that a moisture‐driven electrical generator, based on the diffusive flow of water in titanium dioxide (TiO2) nanowire networks, can yield an output power density of up to 4 µW cm−2 when exposed to a highly moist environment. This performance is two orders of magnitude better than that reported for carbon‐black generators. The output voltage is strongly dependent on humidity of ambient environment. As a big breakthrough, this new type of device is successfully used as self‐powered wearable human‐breathing monitors and touch pads, which is not achievable by any existing moisture‐induced‐electricity technology. The availability of high‐output self‐powered electrical generators will facilitate the design and application of a wide range of new innovative flexible electronic devices.
Revealing the Contribution of Individual Factors to Hydrogen Evolution Reaction Catalytic Activity
Authors: Zhou Yu , Silva Jose Luis , Woods John M. , Pondick Joshua V. , Feng Qingliang , Liang Zhixiu , Liu Wen , Lin Li , Deng Bingchen , Brena Barbara , Xia Fengnian , Peng Hailin , Liu Zhongfan , Wang Hailiang , Araujo Carlos Moyses , Cha Judy J.
Published: March 2018

For the electrochemical hydrogen evolution reaction (HER), the electrical properties of catalysts can play an important role in influencing the overall catalytic activity. This is particularly important for semiconducting HER catalysts such as MoS2, which has been extensively studied over the last decade. Herein, on‐chip microreactors on two model catalysts, semiconducting MoS2 and semimetallic WTe2, are employed to extract the effects of individual factors and study their relations with the HER catalytic activity. It is shown that electron injection at the catalyst/current collector interface and intralayer and interlayer charge transport within the catalyst can be more important than thermodynamic energy considerations. For WTe2, the site‐dependent activities and the relations of the pure thermodynamics to the overall activity are measured and established, as the microreactors allow precise measurements of the type and area of the catalytic sites. The approach presents opportunities to study electrochemical reactions systematically to help establish rational design principles for future electrocatalysts.
A Universal Strategy for Intimately Coupled Carbon Nanosheets/MoM Nanocrystals (M = P, S, C, and O) Hierarchical Hollow Nanospheres for Hydrogen Evolution Catalysis and Sodium‐Ion Storage
Authors: Yang Yong , Luo Mingchuan , Xing Yi , Wang Shitong , Zhang Weiyu , Lv Fan , Li Yingjie , Zhang Yelong , Wang Wei , Guo Shaojun
Published: March 2018

Intimately coupled carbon/transition‐metal‐based hierarchical nanostructures are one of most interesting electrode materials for boosting energy conversion and storage applications owing to the strong synergistic effect between the two components and appealing structural stability. Herein, a universal method is reported for making hierarchical hollow carbon nanospheres (HCSs) with intimately coupled ultrathin carbon nanosheets and Mo‐based nanocrystals. The in situ and confined reaction of the synthetic strategy can not only allow the aggregation of the nanocrystals to be impeded, but also endows extremely intimate coupled interaction between the conductive carbon nanosheets and the nanocrystals MoM (M = P, S, C and O). As a proof of concept, the as‐prepared MoP/C HCSs exhibit extraordinary hydrogen evolution reaction electrocatalytic activity with small overpotential and robust durability in both acidic and alkaline solutions. In addition, the unique sheet‐on‐sheet MoS2/C HCSs as an anode demonstrate high capacity, great rate capabilities, and long‐term cycles for sodium‐ion batteries (SIBs). The capacity can be maintained at 410 mA h g−1 even after 1000 cycles even at a high current density of 4 A g−1, one of the best reported values for MoS2‐based electrode materials for SIBs. The present work highlights the importance of designing and fabricating functional strongly coupled hybrid materials for enhancing energy conversion and storage applications.