bluuebunny/crossref_metadata_2025 huggingface dataset:
MAVEN observations of tail current sheet flapping at Mars
Authors: DiBraccio Gina A. , Dann Julian , Espley Jared R. , Gruesbeck Jacob R. , Soobiah Yasir , Connerney John E. P. , Halekas Jasper S. , Harada Yuki , Bowers Charles F. , Brain David A. , Ruhunusiri Suranga , Hara Takuya , Jakosky Bruce M.
Published: March 2017

The Martian magnetotail is a complex regime through which atmospheric particles are lost to space. Our current understanding of Mars' tail continues to develop with the comprehensive particle and field data collected by Mars Atmosphere and Volatile EvolutioN (MAVEN). In this work, we identify periods when MAVEN encounters multiple current sheet crossings through a single tail traversal in order to understand tail dynamics. We apply an analysis technique that has been developed and validated by using multipoint measurements in order to separate the spatial and temporal properties associated with current sheet flapping. Events are classified into periods of steady flapping, due to a global motion of the current sheet, and kink‐like flapping, resulting from localized wave propagation along the tail current sheet. Out of 106 periods during which multiple current sheet crossings were observed, 20 were due to steady flapping and 10 from kink‐like flapping. A majority of the kink‐like events resulted from waves propagating in the opposite direction of the solar wind convection electric field, regardless of their location in the tail, unlike at Earth and Venus. This finding suggests that possible magnetosphere energy sources, whereby plasma is accelerated and removed from the Martian environment, are not located in the central magnetotail; rather, these waves may be driven by a source located at the tail flank based on the direction of the solar wind electric field. Therefore, by identifying potential sources of impulsive energy release in the tail, we may better understand mechanisms that drive atmospheric loss at Mars.
Temperature responses to the 11 year solar cycle in the mesosphere from the 31 year (1979–2010) extended Canadian Middle Atmosphere Model simulations and a comparison with the 14 year (2002–2015) TIMED/SABER observations
Authors: Gan Quan , Du Jian , Fomichev Victor I. , Ward William E. , Beagley Stephen R. , Zhang Shaodong , Yue Jia
Published: March 2017

A recent 31 year simulation (1979–2010) by extended Canadian Middle Atmosphere Model (eCMAM30) and the 14 year (2002–2015) observation by the Thermosphere Ionosphere Mesosphere and Dynamics/Sounding of the Atmosphere using Broadband Emssion Radiometry (TIMED/SABER) are utilized to investigate the temperature response to the 11 year solar cycle on the mesosphere. Overall, the zonal mean responses tend to increase with height, and the amplitudes are on the order of 1–2 K/100 solar flux unit (1 sfu = 10−22 W m−2 Hz−1) below 80 km and 2–4 K/100 sfu in the mesopause region (80–100 km) from the eCMAM30, comparatively weaker than those from the SABER except in the midlatitude lower mesosphere. A pretty good consistence takes place at around 75–80 km with a response of ~1.5 K/100 sfu within 10°S/N. Also, a symmetric pattern of the responses about the equator agrees reasonably well between the two. It is noteworthy that the eCMAM30 displays an alternate structure with the upper stratospheric cooling and the lower mesospheric warming at midlatitudes of the winter hemisphere, in favor of the long‐term Rayleigh lidar observation reported by the previous studies. Through diagnosing multiple dynamical parameters, it is manifested that this localized feature is induced by the anomalous residual circulation as a consequence of the wave‐mean flow interaction during the solar maximum year.
Effects of solar wind ultralow‐frequency fluctuations on plasma sheet electron temperature: Regression analysis with support vector machine
Authors: Wang Chih‐Ping , Kim Hee‐Jeong , Yue Chao , Weygand James M. , Hsu Tung‐Shin , Chu Xiangning
Published: March 2017

To investigate whether ultralow‐frequency (ULF) fluctuations from 0.5 to 8.3 mHz in the solar wind and interplanetary magnetic field (IMF) can affect the plasma sheet electron temperature (Te) near geosynchronous distances, we use a support vector regression machine technique to decouple the effects from different solar wind parameters and their ULF fluctuation power. Te in this region varies from ~0.1 to 10 keV with a median of 1.3 keV. We find that when the solar wind ULF power is weak, Te increases with increasing southward IMF Bz and solar wind speed, while it varies weakly with solar wind density. As the ULF power becomes stronger during weak IMF Bz (~0) or northward IMF, Te becomes significantly enhanced, by a factor of up to 10. We also find that mesoscale disturbances in a time scale of a few to tens of minutes as indicated by AE during substorm expansion and recovery phases are more enhanced when the ULF power is stronger. The effect of ULF powers may be explained by stronger inward radial diffusion resulting from stronger mesoscale disturbances under higher ULF powers, which can bring high‐energy plasma sheet electrons further toward geosynchronous distance. This effect of ULF powers is particularly important during weak southward IMF or northward IMF when convection electric drift is weak.
Automated detection and cataloging of global explosive volcanism using the International Monitoring System infrasound network
Authors: Matoza Robin S. , Green David N. , Le Pichon Alexis , Shearer Peter M. , Fee David , Mialle Pierrick , Ceranna Lars
Published: March 2017

We experiment with a new method to search systematically through multiyear data from the International Monitoring System (IMS) infrasound network to identify explosive volcanic eruption signals originating anywhere on Earth. Detecting, quantifying, and cataloging the global occurrence of explosive volcanism helps toward several goals in Earth sciences and has direct applications in volcanic hazard mitigation. We combine infrasound signal association across multiple stations with source location using a brute‐force, grid‐search, cross‐bearings approach. The algorithm corrects for a background prior rate of coherent unwanted infrasound signals (clutter) in a global grid, without needing to screen array processing detection lists from individual stations prior to association. We develop the algorithm using case studies of explosive eruptions: 2008 Kasatochi, Alaska; 2009 Sarychev Peak, Kurile Islands; and 2010 Eyjafjallajökull, Iceland. We apply the method to global IMS infrasound data from 2005–2010 to construct a preliminary acoustic catalog that emphasizes sustained explosive volcanic activity (long‐duration signals or sequences of impulsive transients lasting hours to days). This work represents a step toward the goal of integrating IMS infrasound data products into global volcanic eruption early warning and notification systems. Additionally, a better understanding of volcanic signal detection and location with the IMS helps improve operational event detection, discrimination, and association capabilities.
Upscaling pore pressure‐dependent gas permeability in shales
Authors: Ghanbarian Behzad , Javadpour Farzam
Published: March 2017

Upscaling pore pressure dependence of shale gas permeability is of great importance and interest in the investigation of gas production in unconventional reservoirs. In this study, we apply the Effective Medium Approximation, an upscaling technique from statistical physics, and modify the Doyen model for unconventional rocks. We develop an upscaling model to estimate the pore pressure‐dependent gas permeability from pore throat size distribution, pore connectivity, tortuosity, porosity, and gas characteristics. We compare our adapted model with six data sets: three experiments, one pore‐network model, and two lattice‐Boltzmann simulations. Results showed that the proposed model estimated the gas permeability within a factor of 3 of the measurements/simulations in all data sets except the Eagle Ford experiment for which we discuss plausible sources of discrepancies.
Bio‐optical anomalies in the world's oceans: An investigation on the diffuse attenuation coefficients for downward irradiance derived from Biogeochemical Argo float measurements
Authors: Organelli Emanuele , Claustre Hervé , Bricaud Annick , Barbieux Marie , Uitz Julia , D'Ortenzio Fabrizio , Dall'Olmo Giorgio
Published: March 2017

Identification of oceanic regions characterized by particular optical properties is extremely important for ocean color applications. The departure from globally established bio‐optical models (i.e., anomaly) introduces uncertainties in the retrieval of biogeochemical quantities from satellite observations. Thanks to an array of 105 Biogeochemical Argo floats acquiring almost daily downward irradiance measurements at selected wavelengths in the UV and blue region of the spectrum, we reexamined the natural variability of the spectral diffuse attenuation coefficients, Kd(λ), among the world's oceans and compared them to previously established bio‐optical models. The analysis of 2847 measurements of Kd(λ) at 380 and 490 nm, within the first optical depth, provided a classification of the examined regions into three groups. The first one included the Black Sea, a water body characterized by a very high content of colored dissolved organic matter (CDOM). The second group was essentially composed by the subtropical gyres (Atlantic and Pacific Oceans), with optical properties consistent with previous models (i.e., no anomalies). High latitude (North Atlantic and Southern oceans) and temperate (Mediterranean Sea) seas formed the third group, in which optical properties departed from existing bio‐optical models. Annual climatologies of the Kd(380)/Kd(490) ratio evidenced a persistent anomaly in the Mediterranean Sea, that we attributed to a higher‐than‐average CDOM contribution to total light absorption. In the North Atlantic subpolar gyre, anomalies were observed only in wintertime and were also attributed to high CDOM concentrations. In the Southern Ocean, the anomaly was likely related to high phytoplankton pigment packaging rather than to CDOM.
Ecosystem function in complex mountain terrain: Combining models and long‐term observations to advance process‐based understanding
Authors: Wieder William R. , Knowles John F. , Blanken Peter D. , Swenson Sean C. , Suding Katharine N.
Published: March 2017

Abiotic factors structure plant community composition and ecosystem function across many different spatial scales. Often, such variation is considered at regional or global scales, but here we ask whether ecosystem‐scale simulations can be used to better understand landscape‐level variation that might be particularly important in complex terrain, such as high‐elevation mountains. We performed ecosystem‐scale simulations by using the Community Land Model (CLM) version 4.5 to better understand how the increased length of growing seasons may impact carbon, water, and energy fluxes in an alpine tundra landscape. The model was forced with meteorological data and validated with observations from the Niwot Ridge Long Term Ecological Research Program site. Our results demonstrate that CLM is capable of reproducing the observed carbon, water, and energy fluxes for discrete vegetation patches across this heterogeneous ecosystem. We subsequently accelerated snowmelt and increased spring and summer air temperatures in order to simulate potential effects of climate change in this region. We found that vegetation communities that were characterized by different snow accumulation dynamics showed divergent biogeochemical responses to a longer growing season. Contrary to expectations, wet meadow ecosystems showed the strongest decreases in plant productivity under extended summer scenarios because of disruptions in hydrologic connectivity. These findings illustrate how Earth system models such as CLM can be used to generate testable hypotheses about the shifting nature of energy, water, and nutrient limitations across space and through time in heterogeneous landscapes; these hypotheses may ultimately guide further experimental work and model development.
Application of an improved spectral decomposition method to examine earthquake source scaling in Southern California
Authors: Trugman Daniel T. , Shearer Peter M.
Published: March 2017

Earthquake source spectra contain fundamental information about the dynamics of earthquake rupture. However, the inherent tradeoffs in separating source and path effects, when combined with limitations in recorded signal bandwidth, make it challenging to obtain reliable source spectral estimates for large earthquake data sets. We present here a stable and statistically robust spectral decomposition method that iteratively partitions the observed waveform spectra into source, receiver, and path terms. Unlike previous methods of its kind, our new approach provides formal uncertainty estimates and does not assume self‐similar scaling in earthquake source properties. Its computational efficiency allows us to examine large data sets (tens of thousands of earthquakes) that would be impractical to analyze using standard empirical Green's function‐based approaches. We apply the spectral decomposition technique to P wave spectra from five areas of active contemporary seismicity in Southern California: the Yuha Desert, the San Jacinto Fault, and the Big Bear, Landers, and Hector Mine regions of the Mojave Desert. We show that the source spectra are generally consistent with an increase in median Brune‐type stress drop with seismic moment but that this observed deviation from self‐similar scaling is both model dependent and varies in strength from region to region. We also present evidence for significant variations in median stress drop and stress drop variability on regional and local length scales. These results both contribute to our current understanding of earthquake source physics and have practical implications for the next generation of ground motion prediction assessments.
A downslope propagating thermal front over the continental slope
Authors: van Haren Hans , Hosegood Phil J.
Published: March 2017

In the ocean, internal frontal bores above sloping topography have many appearances, depending on the local density stratification, and on the angle and source of generation of the carrier wave. However, their common characteristics are a backward breaking wave, strong sediment resuspension, and relatively cool (denser) water moving more or less upslope underneath warm (less dense) water. In this paper, we present a rare example of a downslope moving front of cold water moving over near‐bottom warm water. Large backscatter is observed in the downslope moving front's trailing edge, rather than the leading edge as is common in upslope moving fronts. Time series observations have been made during a fortnight in summer, using a 101 m long array of high‐resolution temperature sensors moored with an acoustic Doppler current profiler at 396 m depth in near‐homogeneous waters, near a small canyon in the continental slope off the Malin shelf (West‐Scotland, UK). Occurring between fronts that propagate upslope with tidal periodicity, the rare downslope propagating one resembles a gravity current and includes strong convective turbulence coming from the interior rather than the more usual frictionally generated turbulence arising from interaction with the seabed. Its turbulence is 3–10 times larger than that of more common upslope propagating fronts. As the main turbulence is in the interior with a thin stratified layer close to the bottom, little sediment is resuspended by a downslope propagating front. The downslope propagating front is suggested to be generated by oblique propagation of internal (tidal) waves and flow over a nearby upstream promontory.
Infiltration of Cellular Silicon by Molten Magnesium Alloys
Authors: Matz Alexander Martin , Mocker Bettina Stefanie , Heimann Johann , Jost Norbert
Published: March 2017

Open‐pore cellular Si structures are manufactured by investment casting and, subsequently, infiltrated with molten Mg(‐Sn), representing the initial state for a formation of the intermetallic compound Mg2Si1–xSnx. The processing parameters which govern the evolution of microstructure after the infiltration process are studied in the alloy systems Mg‐Si and Mg‐Si‐Sn. The resulting microstructures are analyzed using SEM and EDS. It is found that an initial diffusion layer is already formed after infiltration. Its thickness can slightly be increased by raising the infiltration temperature of the Mg(‐Sn) melt. A variation in mold temperature does not show a noticeable impact. The comparison of the diffusion layer formed in the systems Mg‐Si and Mg‐Si‐Sn showed that a lower Sn content resulted in thicker layers.
Polymer Derived Ceramics with β‐Eucryptite Fillers: Filler‐Matrix Interactions
Authors: Fedorova Anna , Betke Ulf , Scheffler Michael
Published: March 2017

Polymer derived ceramics with ß‐eucryptite are manufactured and filler‐matrix interactions in the temperature range between 800 and 1 100 °C are investigated. Pyrolysis temperatures above 1 000 °C led to changes of the β‐eucryptite phase, due to a significant SiO2 amount in the polymer derived ceramic matrix. A new phase, β‐spodumene, is formed; this is, confirmed by calculations of the lattice parameters. Scanning electron microscopy and energy dispersive x‐ray spectroscopy of the microstructure allow to localize spots on the matrix‐filler interface, where the described processes appear.
Stretchable Capacitive Sensors of Torsion, Strain, and Touch Using Double Helix Liquid Metal Fibers
Authors: Cooper Christopher B. , Arutselvan Kuralamudhan , Liu Ying , Armstrong Daniel , Lin Yiliang , Khan Mohammad Rashed , Genzer Jan , Dickey Michael D.
Published: March 2017

Soft and stretchable sensors have the potential to be incorporated into soft robotics and conformal electronics. Liquid metals represent a promising class of materials for creating these sensors because they can undergo large deformations while retaining electrical continuity. Incorporating liquid metal into hollow elastomeric capillaries results in fibers that can integrate with textiles, comply with complex surfaces, and be mass produced at high speeds. Liquid metal is injected into the core of hollow and extremely stretchable elastomeric fibers and the resulting fibers are intertwined into a helix to fabricate capacitive sensors of torsion, strain, and touch. Twisting or elongating the fibers changes the geometry and, thus, the capacitance between the fibers in a predictable way. These sensors offer a simple mechanism to measure torsion up to 800 rad m−1—two orders of magnitude higher than current torsion sensors. These intertwined fibers can also sense strain capacitively. In a complementary embodiment, the fibers are injected with different lengths of liquid metal to create sensors capable of distinguishing touch along the length of a small bundle of fibers via self‐capacitance. The three capacitive‐based modes of sensing described here may enable new sensing applications that employ the unique attributes of stretchable fibers.
Extended Solution Gate OFET‐Based Biosensor for Label‐Free Glial Fibrillary Acidic Protein Detection with Polyethylene Glycol‐Containing Bioreceptor Layer
Authors: Song Jian , Dailey Jennifer , Li Hui , Jang Hyun‐June , Zhang Pengfei , Wang Jeff Tza‐Huei , Everett Allen D. , Katz Howard E.
Published: March 2017

A novel organic field effect transistor (OFET)‐based biosensor is described for label‐free glial fibrillary acidic protein detection. This study reports the first use of an extended solution gate structure where the sensing area and the organic semiconductor are separated, and a reference electrode is not needed. Different molecular weight polyethylene glycols (PEGs) are mixed into the bioreceptor layer to help extend the Debye screening length. The drain current change is significantly increased with the help of higher molecular weight PEGs, as they are known to reduce the dielectric constant. This study also investigates the sensing performance under different gate voltage (V
g). The sensitivity increases after the V
g is decreased from −5 to −2 V because the lower V
g is much closer to the OFET threshold voltage and the influence of attached negatively charged proteins becomes more apparent. Finally, the selectivity experiments toward different interferents are performed. The stability and selectivity are promising for clinical applications.
Membrane‐Based Strategy for Efficient Ionic Liquids/Water Separation Assisted by Superwettability
Authors: Zhang Jiajing , Liu Hongliang , Jiang Lei
Published: March 2017

Ionic liquids (ILs) acting as new functional solvents have significant impact in both synthetic and materials chemistry. However, the usage of volatile organic solvents in both synthesis and recycling of ILs usually imposes environmental issues. In this study, according to intrinsic wetting threshold theory, a membrane‐based approach assisted by superwettability is developed for efficient, convenient, and economical purification of water‐immiscible ILs. By precisely tailoring surface energy, the porous membrane is capable of hydrophobicity and superILphilicity (defined as IL contact angle close to zero), selectively allowing ILs to pass through. This kind of functional membrane can not only separate IL/water mixtures, but also IL/water systems containing inorganic salts, organic compounds, amino acids, and proteins.
Atomic Layer Deposited Non‐Noble Metal Oxide Catalyst for Sodium–Air Batteries: Tuning the Morphologies and Compositions of Discharge Product
Authors: Sun Qian , Liu Jian , Li Xia , Wang Biqiong , Yadegari Hossein , Lushington Andrew , Banis Mohammad N. , Zhao Yang , Xiao Wei , Chen Ning , Wang Jian , Sham Tsun‐Kong , Sun Xueliang
Published: March 2017

Catalysts can play a critical role in the development of sodium–air batteries (SABs). Atomic layer deposition (ALD) technology enables rational design and atomic utilization of catalyst by homogenously distributing catalytically active material on a variety of substrates. Here, a novel hierarchical nanostructured Co3O4 is decorated on carbon nanotubes by ALD (CNT@Co3O4) and used as a catalyst for SABs. CNT@Co3O4 demonstrates better performance and longer cycle life than a mechanically mixed CNT/Co3O4 nanocomposite. Well‐dispersed ALD Co3O4 catalyst on CNTs, which serves as functionalized active sites, enables rapid electron exchange and high oxygen reduction/evolution activities. Synchrotron‐based X‐ray analysis including X‐ray absorption near edge structure, extended X‐ray absorption fine structure, and scanning transmission X‐ray microscopy characterization techniques have been employed to elucidate the activity of Co3O4 and to investigate the nanoscale discharge product distribution found in SABs. This analysis reveals that Co3O4 catalyst can promote the electrochemical decomposition of sodium peroxide, superoxide, and carbonates. The role of the catalyst in SABs is clarified and discussed in detail.
Rationally Engineered Electrodes for a High‐Performance Solid‐State Cable‐Type Supercapacitor
Authors: Vellacheri Ranjith , Zhao Huaping , Mühlstädt Mike , Al‐Haddad Ahmed , Jandt Klaus D. , Lei Yong
Published: March 2017

Wire‐shaped electrodes for solid‐state cable‐type supercapacitors (SSCTS) with high device capacitance and ultrahigh rate capability are prepared by depositing poly(3,4‐ethylenedioxythiophene) onto self‐doped TiO2 nanotubes (D‐TiO2) aligned on Ti wire via a well‐controlled electrochemical process. The large surface area, short ion diffusion path, and high electrical conductivity of these rationally engineered electrodes all contribute to the energy storage performance of SSCTS. The cyclic voltammetric studies show the good energy storage ability of the SSCTS even at an ultrahigh scan rate of 1000 V s−1, which reveals the excellent instantaneous power characteristics of the device. The capacitance of 1.1 V SSCTS obtained from the charge–discharge measurements is 208.36 µF cm−1 at a discharge current of 100 µA cm−1 and 152.36 µF cm−1 at a discharge current of 2000 µA cm−1, respectively, indicating the ultrahigh rate capability. Furthermore, the SSCTS shows superior cyclic stability during long‐term (20 000 cycles) cycling, and also maintains excellent performance when it is subjected to bending and succeeding straightening process.
Transdermal Protein Delivery Using Choline and Geranate (CAGE) Deep Eutectic Solvent
Authors: Banerjee Amrita , Ibsen Kelly , Iwao Yasunori , Zakrewsky Michael , Mitragotri Samir
Published: March 2017

Transdermal delivery of peptides and other biological macromolecules is limited due to skin's inherent low permeability. Here, the authors report the use of a deep eutectic solvent, choline and geranate (CAGE), to enhance topical delivery of proteins such as bovine serum albumin (BSA, molecular weight: ≈66 kDa), ovalbumin (OVA, molecular weight: ≈45 kDa) and insulin (INS, molecular weight: 5.8 kDa). CAGE enhances permeation of BSA, OVA, and insulin into porcine skin ex vivo, penetrating deep into the epidermis and dermis. Studies using tritium‐labeled BSA and fluorescein isothiocyanate labeled insulin show significantly enhanced delivery of proteins into and across porcine skin, penetrating the skin in a time‐dependent manner. Fourier transform IR spectra of porcine stratum corneum (SC) samples before and after incubation in CAGE show a reduction in peak area attributed to SC lipid content, suggesting lipid extraction from the SC. Circular dichroism confirms that CAGE does not affect insulin's secondary conformation. In vivo studies in rats show that topical application of 10 U insulin dispersed in CAGE (25 U kg−1 insulin dose) leads to a highly significant 40% drop in blood glucose levels in 4 h that is relatively sustained for 12 h. Taken together, these studies demonstrate that CAGE is a promising vehicle for transdermal delivery of therapeutic proteins; specifically, as a noninvasive delivery alternative to injectable insulin for the treatment of diabetes.
Remote Control of Cellular Functions: The Role of Smart Nanomaterials in the Medicine of the Future
Authors: Genchi Giada Graziana , Marino Attilio , Grillone Agostina , Pezzini Ilaria , Ciofani Gianni
Published: March 2017

The remote control of cellular functions through smart nanomaterials represents a biomanipulation approach with unprecedented potential applications in many fields of medicine, ranging from cancer therapy to tissue engineering. By actively responding to external stimuli, smart nanomaterials act as real nanotransducers able to mediate and/or convert different forms of energy into both physical and chemical cues, fostering specific cell behaviors. This report describes those classes of nanomaterials that have mostly paved the way to a “wireless” control of biological phenomena, focusing the discussion on some examples close to the clinical practice. In particular, magnetic fields, light irradiation, ultrasound, and pH will be presented as means to manipulate the cellular fate, due to the peculiar physical/chemical properties of some smart nanoparticles, thus providing realistic examples of “nanorobots” approaching the visionary ideas of Richard Feynman.
Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides
Authors: Vardi Naor , Anouchi Elihu , Yamin Tony , Middey Srimanta , Kareev Michael , Chakhalian Jak , Dubi Yonatan , Sharoni Amos
Published: March 2017

Transition metal oxides are complex electronic systems that exhibit a multitude of collective phenomena. Two archetypal examples are VO2 and NdNiO3, which undergo a metal–insulator phase transition (MIT), the origin of which is still under debate. Here this study reports the discovery of a memory effect in both systems, manifested through an increase of resistance at a specific temperature, which is set by reversing the temperature ramp from heating to cooling during the MIT. The characteristics of this ramp‐reversal memory effect do not coincide with any previously reported history or memory effects in manganites, electron‐glass or magnetic systems. From a broad range of experimental features, supported by theoretical modelling, it is found that the main ingredients for the effect to arise are the spatial phase separation of metallic and insulating regions during the MIT and the coupling of lattice strain to the local transition temperature of the phase transition. We conclude that the emergent memory effect originates from phase boundaries at the reversal temperature leaving “scars” in the underlying lattice structure, giving rise to a local increase in the transition temperature. The universality and robustness of the effect shed new light on the MIT in complex oxides.
Engineering Ultrathin Polyaniline in Micro/Mesoporous Carbon Supercapacitor Electrodes Using Oxidative Chemical Vapor Deposition
Authors: Smolin Yuriy Y. , Van Aken Katherine L. , Boota Muhammad , Soroush Masoud , Gogotsi Yury , Lau Kenneth K. S.
Published: March 2017

In this work, oxidative chemical vapor deposition (oCVD) is demonstrated to enable the integration of nanometer‐thin polyaniline (PANI) that significantly improves charge storage capacity of supercapacitors utilizing carbide‐derived carbon (CDC) with a bimodal (micro/mesoporous) pore size distribution. To our knowledge, this work is the first reported synthesis of PANI via oCVD. The oCVD process allows for the integration of PANI into pores as small as 1.7 nm, and resulting CDC/PANI electrodes have a gravimetric capacitance more than twice that of bare CDC (136 F g−1 for 11 wt% of PANI in the CDC electrode versus 60 F g−1 for bare Mo2C‐CDC at 10 mV s−1). This yields a PANI‐only gravimetric capacitance of ≈690 F g−1, which is close to the theoretical value of 750 F g−1. The coating preserves the native electrode surface area and pore size distribution, while improving capacitance due to the faradaic redox reactions of PANI. Even at high scan rates of over 100 mV s−1, the added pseudocapacitance from PANI remains evident. The composite electrode exhibits good cyclability, decreasing to 90% of the initial value (≈100 F g−1) after 10 000 cycles.
Impact of White Light Illumination on the Electronic and Chemical Structures of Mixed Halide and Single Crystal Perovskites
Authors: Zu Feng‐Shuo , Amsalem Patrick , Salzmann Ingo , Wang Rong‐Bin , Ralaiarisoa Maryline , Kowarik Stefan , Duhm Steffen , Koch Norbert
Published: March 2017

This study investigates the effect of white light illumination on the electronic and chemical properties of mixed halide perovskite (CH3NH3PbI3−xClx) thin films and CH3NH3PbI3 single crystals using photoelectron and absorption spectroscopy. The pristine materials' surfaces are found to be n‐type because of surface band bending due to the presence of donor levels, likely consisting of reduced lead (Pb0) that acts as surface traps. When illuminating the sample with white light (up to 1 sun), the valence features shifted to lower binding energy due to surface photovoltage, i.e., the bulk of the materials is much less n‐type. However, the surface photovoltage is only partially reversible and vanishes for prolonged illumination time. Concomitantly, a high concentration of metallic Pb0 is found, which induces strong Fermi‐level pinning and quenching of the surface photovoltage. This is accompanied also by the formation of PbI2 defects. Similar experiments on single crystals reveal the presence of a high concentration of reduced (metallic) Pb0 at the sample surface after cleaving. The present findings indicate that the chemical and electronic properties of perovskite films are very sensitive to white light illumination. Accounting for these light‐induced material changes is important to fully understand its photophysical properties and for improving the lifetime of perovskite‐based devices.
Evaluation of the effective forcespinning parameters controlling polyvinyl alcohol nanofibers diameter using artificial neural network
Authors: Naghibzadeh Majid , Adabi Mohsen , Rahmani Hamid Reza , Mirali Mohsen , Adabi Mahdi
Published: March 2017

In this research, the polyvinyl alcohol (PVA) nanofibers through forcespinning process were successfully produced and the effective parameters for predicting nanofibers diameter using artificial neural network (ANN) were investigated. The various parameters of forcespinning process including rotational speed, orifice, distance to the collector, and polymer concentration were designed to produce PVA nanofibers. Scanning electron microscopy (SEM) showed that the produced fibers diameter was in the range of 0.56–1.9 μm. The neural network with four input factors, three hidden layers with 5, 10, 1 nodes in each layers, respectively, and one output layer had the best performance in the testing sets. Moreover, the mean squared error (MSE) and linear regression (R) between observed and predicted nanofibers diameter were about 0.1077 and 0.9387, respectively, demonstrating a suitable performance for the prediction of nanofibers diameter using the selected neural network model.
Taking Stock of the Diversity and Sense of Community Debate
Authors: Neal Zachary P.
Published: March 2017

Over the past couple of years, a debate has played out in the pages of the American Journal of Community Psychology concerning the relationship between two of Community Psychology's core values: promoting diversity and promoting a sense of community. This special section is to continue a discussion about diversity and community, both among the debate's initial contributors (Alex Stivala, Greg Townley, and Zachary Neal), as well as among others whose own work has touched on these issues (Anne Brodsky, Richard Florida, Jean Hill, and Roderick Watts). In this essay, I address some broad questions that have emerged through this discussion. First, because much has been written on the relationship between diversity and community, both in community psychology and in other disciplines, what do we know, or at least think we know? Second, since the constructs of diversity and sense of community are complex and multi‐faceted, how can definitions get in the way and how can we avoid talking past one another in this discussion? Finally, looking across the original papers that initiated this discussion, as well as the contributions in this special section, what path(s) forward do we have?
Technical intelligence and culture: Nut cracking in humans and chimpanzees
Authors: Boesch Christophe , Bombjaková Daša , Boyette Adam , Meier Amelia
Published: March 2017

Objectives

According to the technical intelligence hypothesis, humans are superior to all other animal species in understanding and using tools. However, the vast majority of comparative studies between humans and chimpanzees, both proficient tool users, have not controlled for the effects of age, prior knowledge, past experience, rearing conditions, or differences in experimental procedures. We tested whether humans are superior to chimpanzees in selecting better tools, using them more dexteriously, achieving higher performance and gaining access to more resource as predicted under the technical intelligence hypothesis.

Materials and methods

Aka and Mbendjele hunter‐gatherers in the rainforest of Central African Republic and the Republic of Congo, respectively, and Taï chimpanzees in the rainforest of Côte d'Ivoire were observed cracking hardPanda oleosanuts with different tools, as well as the softCoula edulisandElaeis guinensisnuts. The nut‐cracking techniques, hammer material selection and two efficiency measures were compared.

Results

As predicted, the Aka and the Mbendjele were able to exploit more species of hard nuts in the forest than chimpanzees. However, the chimpanzees were sometimes more efficient than the humans. Social roles differed between the two species, with the Aka and especially the Mbendjele exhibiting cooperation between nut‐crackers whereas the chimpanzees were mainly individualistic.

Discussion

Observations of nut‐cracking by humans and chimpanzees only partially supported the technical intelligence hypothesis as higher degrees of flexibility in tool selection seen in chimpanzees compensated for use of less efficient tool material than in humans. Nut cracking was a stronger social undertaking in humans than in chimpanzees.
The generation and properties of new classes of multipartite entangled coherent squeezed states in a conducting cavity
Authors: Daneshmand R. , Tavassoly M. K.
Published: March 2017

Recently the quantum description of electromagnetic waves in conducting media has been performed. It has been deduced that, in particular situations the Hamiltonian of corresponding field can be expressed by the well‐known Caldirola‐Kanai Hamiltonian. In this paper, using the associated annihilation and creation operators of the above‐mentioned real physical system, a few schemes for the generation of some classes of time‐dependent multipartite entangled coherent squeezed states are proposed. To achieve the purpose, the interaction of a narrow bunch of two‐level atoms with such a quantized field in a conducting cavity and in the presence of a strong‐driving classical field is taken into account. The influence of the conductivity parameter on the degree of entanglement and atomic population inversion is studied, numerically. As will be clarified, the related physical quantities can be controlled by the conductivity parameter. In detail, it is shown that the entanglement reaches to its maximum value with smaller delay in the presence of larger values of conductivity. Also, it is observed that by increasing the conductivity, the time for occurring collapse‐revival in the atomic inversion is decreased.

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Steering On‐Surface Reactions by a Self‐Assembly Approach
Authors: Chen Qiwei , Cramer Jacob R. , Liu Jing , Jin Xin , Liao Peilin , Shao Xiang , Gothelf Kurt V. , Wu Kai
Published: March 2017

4,4′‐Bis(2,6‐difluoropyridin‐4‐yl)‐1,1′:4′,1′′‐terphenyl (BDFPTP) molecules underwent dehydrocyclization and covalent coupling reactions on Au(111) according to scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Self‐assembly of the reactants in well‐defined molecular domains prior to reaction could greatly enhance the regioselectivity of the dehydrocyclization reaction and suppress defluorinated coupling, demonstrating that self‐assembly can efficiently steer on‐surface reactions. Such a strategy could be of great importance in surface chemistry and widely applied to control on‐surface reactions.
Fast and Minimal‐Solvent Production of Superinsulating Silica Aerogel Granulate
Authors: Huber Lukas , Zhao Shanyu , Malfait Wim J. , Vares Sirje , Koebel Matthias M.
Published: March 2017

With their low thermal conductivity (λ), silica aerogels can reduce carbon emissions from heating and cooling demands, but their widespread adoption is limited by the high production cost. A one‐pot synthesis for silica aerogel granulate is presented that drastically reduces solvent use, production time, and global warming potential. The inclusion of the hydrophobization agent prior to gelation with a post‐gelation activation step, enables a complete production cycle of less than four hours at the lab scale for a solvent use close to the theoretical minimum, and limits the global warming potential. Importantly, the one‐pot aerogel granulate retains the exceptional properties associated with silica aerogel, mostly λ=14.4±1.0 mW m−1⋅K−1 for the pilot scale materials, about half that of standing air (26 mW m−1⋅K−1). The resource‐, time‐, and cost‐effective production will allow silica aerogels to break out of its niche into the mainstream building and industrial insulation markets.
Iron(II)‐Catalyzed Hydrophosphination of Isocyanates
Authors: Sharpe Helen R. , Geer Ana M. , Lewis William , Blake Alexander J. , Kays Deborah L.
Published: March 2017

The first transition metal catalyzed hydrophosphination of isocyanates is presented. The use of low‐coordinate iron(II) precatalysts leads to an unprecedented catalytic double insertion of isocyanates into the P−H bond of diphenylphosphine to yield phosphinodicarboxamides [Ph2PC(=O)N(R)C(=O)N(H)R], a new family of derivatized organophosphorus compounds. This remarkable result can be attributed to the low‐coordinate nature of the iron(II) centers whose inherent electron deficiency enables a Lewis‐acid mechanism in which a combination of the steric pocket of the metal center and substrate size determines the reaction products and regioselectivity.
Elemental Boron for Efficient Carbon Dioxide Reduction under Light Irradiation
Authors: Liu Guigao , Meng Xianguang , Zhang Huabin , Zhao Guixia , Pang Hong , Wang Tao , Li Peng , Kako Tetsuya , Ye Jinhua
Published: March 2017

The photoreduction of CO2 is attractive for the production of renewable fuels and the mitigation of global warming. Herein, we report an efficient method for CO2 reduction over elemental boron catalysts in the presence of only water and light irradiation through a photothermocatalytic process. Owing to its high solar‐light absorption and effective photothermal conversion, the illuminated boron catalyst experiences remarkable self‐heating. This process favors CO2 activation and also induces localized boron hydrolysis to in situ produce H2 as an active proton source and electron donor for CO2 reduction as well as boron oxides as promoters of CO2 adsorption. These synergistic effects, in combination with the unique catalytic properties of boron, are proposed to account for the efficiency of the CO2 reduction. This study highlights the promise of photothermocatalytic strategies for CO2 conversion and also opens new avenues towards the development of related solar‐energy utilization schemes.
Multi‐shelled Hollow Metal–Organic Frameworks
Authors: Liu Wenxian , Huang Jijiang , Yang Qiu , Wang Shiji , Sun Xiaoming , Zhang Weina , Liu Junfeng , Huo Fengwei
Published: March 2017

Hollow metal–organic frameworks (MOFs) are promising materials with sophisticated structures, such as multiple shells, that cannot only enhance the properties of MOFs but also endow them with new functions. Herein, we show a rational strategy to fabricate multi‐shelled hollow chromium (III) terephthalate MOFs (MIL‐101) with single‐crystalline shells through step‐by‐step crystal growth and subsequent etching processes. This strategy relies on the creation of inhomogeneous MOF crystals in which the outer layer is chemically more robust than the inner layer and can be selectively etched by acetic acid. The regulation of MOF nucleation and crystallization allows the tailoring of the cavity size and shell thickness of each layer. The resultant multi‐shelled hollow MIL‐101 crystals show significantly enhanced catalytic activity during styrene oxidation. The insight gained from this systematic study will aid in the rational design and synthesis of other multi‐shelled hollow structures and the further expansion of their applications.
Hierarchical Corannulene‐Based Materials: Energy Transfer and Solid‐State Photophysics
Authors: Rice Allison M. , Fellows W. Brett , Dolgopolova Ekaterina A. , Greytak Andrew B. , Vannucci Aaron K. , Smith Mark D. , Karakalos Stavros G. , Krause Jeanette A. , Avdoshenko Stanislav M. , Popov Alexey A. , Shustova Natalia B.
Published: March 2017

We report the first example of a donor–acceptor corannulene‐containing hybrid material with rapid ligand‐to‐ligand energy transfer (ET). Additionally, we provide the first time‐resolved photoluminescence (PL) data for any corannulene‐based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand‐to‐ligand ET rate calculated using two models is comparable with that observed in fullerene‐containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π‐bowls, specifically corannulene derivatives, with the versatility of crystalline hybrid scaffolds, but could also foreshadow the engineering of a novel class of hierarchical corannulene‐based hybrid materials for optoelectronic devices.
Bioinspired Asymmetric Synthesis of Hispidanin A
Authors: Li Fuzhuo , Tu Qian , Chen Sijia , Zhu Lei , Lan Yu , Gong Jianxian , Yang Zhen
Published: March 2017

The first enantiospecific synthesis of hispidanin A (4), a dimeric diterpenoid from the rhizomes of Isodon hispida, was achieved with a longest linear sequence of 12 steps in 6.5 % overall yield. A key component is the use of the abundant and naturally occurring diterpenoids (+)‐sclareolide and (+)‐sclareol as starting materials, which enables the gram‐scale preparation of the key intermediates totarane (1) and s‐trans‐12E,14‐labdadien‐20,8β‐olide (2). Subsequently a thermal or an erbium‐catalyzed intermolecular Diels–Alder reaction of totarane (1) with labdadienolide (2) provide convergent and rapid access to the natural product hispidanin A (4). The synthetic studies have offered significant impetus for the efficient construction of these architecturally complex natural products.
Highly Branched Metal Alloy Networks with Superior Activities for the Methanol Oxidation Reaction
Authors: Cui Xun , Xiao Peng , Wang Jing , Zhou Ming , Guo Wenlong , Yang Yang , He Yanjie , Wang Zewei , Yang Yingkui , Zhang Yunhuai , Lin Zhiqun
Published: March 2017

Three‐dimensional (3D) interconnected metal alloy nanostructures possess superior catalytic performance owing to their advantageous characteristics, including improved catalytic activity, corrosion resistance, and stability. Hierarchically structured Ni‐Cu alloys composed of 3D network‐like microscopic branches with nanoscopic dendritic feelers on each branch were crafted by a facile and efficient hydrogen evolution‐assisted electrodeposition approach. They were subsequently exploited for methanol electrooxidation in alkaline media. Among three hierarchically structured Ni‐Cu alloys with different Ni/Cu ratios (Ni0.25Cu0.75, Ni0.50Cu0.50, and Ni0.75Cu0.25), the Ni0.75Cu0.25 electrode exhibited the fastest electrochemical response and highest electrocatalytic activity toward methanol oxidation. The markedly enhanced performance of Ni0.75Cu0.25 eletrocatalyst can be attributed to its alloyed structure with the proper Ni/Cu ratio and a large number of active sites on the surface of hierarchical structures.
Catalytic Asymmetric N‐Alkylation of Indoles and Carbazoles through 1,6‐Conjugate Addition of Aza‐para‐quinone Methides
Authors: Chen Min , Sun Jianwei
Published: March 2017

Catalytic asymmetric N‐alkylation of indoles and carbazoles represents a family of important but underdeveloped reactions. Herein, we describe a new organocatalytic strategy in which in situ generated aza‐para‐quinone methides are employed as the alkylating reagent. With the proper choice of a chiral phosphoric acid and an N‐protective group, the intermolecular C−N bond formation with various indole and carbazole nucleophiles proceeded efficiently under mild conditions with excellent enantioselectivity and functional‐group compatibility. Control experiments and kinetic studies provided important insight into the reaction mechanism.
Dopamine‐functionalized poly(vinyl alcohol) elastomer with melt processability and self‐healing properties
Authors: Li Fayong , Xia Hesheng
Published: March 2017

A dopamine‐functionalized poly(vinyl alcohol) (PVA) elastomer with melt processability and self‐healing properties was prepared by a new chemical route of graft modification, that is, PVA carboxylation and a carbodiimide reaction. The conventional modifier for PVA sacrificed the intrinsic hydrogen‐bonding interactions and dramatically decreased the mechanical strength. The modifier dopamine, as a catechol derivative, has two hydroxyl groups, which formed hydrogen bonds with the hydroxyl groups of PVA; it also has one benzene ring, which increased the thermal stability. We found that the introduction of dopamine into the PVA molecular structure lowered the melting point, improved the thermal stability, broke the crystalline structure, and enabled thermal processing. Moreover, the modified PVA possessed good mechanical properties, could be self‐healed, and is believed to have potential applications in many fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45072.