bluuebunny/crossref_metadata_2025 huggingface dataset:
Southern Ocean Origin of Multidecadal Variability in the North Brazil Current
Authors: van Westen René M. , Dijkstra Henk A.
Published: October 2017

Analysis of model data from a long (200 years) simulation of a high‐resolution version of the Parallel Ocean Program indicates a connection between a mode of multidecadal variability in the Southern Ocean, the so‐called Southern Ocean Mode, and multidecadal variability in the North Brazil Current. The multidecadal sea surface height variability in the Southern Ocean propagates northward and submerges at about 40°S. Northward propagating anomalies in ocean heat content are found between 5° and 40°S at depths down to 1 km and affect the North Brazil Current. Similar variability and connections between Southern Ocean and North Brazil Current are also found in a (200 years) simulation of a high‐resolution global version of the Community Earth System Model. The results provide a new mechanism for the low‐frequency variability of the North Brazil Current.
How Might Recharge Change Under Projected Climate Change in the Western U.S.?
Authors: Niraula R. , Meixner T. , Dominguez F. , Bhattarai N. , Rodell M. , Ajami H. , Gochis D. , Castro C.
Published: October 2017

Although groundwater is a major water resource in the western U.S., little research has been done on the impacts of climate change on groundwater storage and recharge in the West. Here we assess the impact of projected changes in climate on groundwater recharge in the near (2021–2050) and far (2071–2100) future across the western U.S. Variable Infiltration Capacity model was run with RCP 6.0 forcing from 11 global climate models and “subsurface runoff” output was considered as recharge. Recharge is expected to decrease in the West (−5.8 ± 14.3%) and Southwest (−4.0 ± 6.7%) regions in the near future and in the South region (−9.5 ± 24.3%) in the far future. The Northern Rockies region is expected to get more recharge in the near (+5.3 ± 9.2%) and far (+11.8 ± 12.3%) future. Overall, southern portions of the western U.S. are expected to get less recharge in the future and northern portions will get more. Climate change interacts with land surface properties to affect the amount of recharge that occurs in the future. Effects on recharge due to change in vegetation response from projected changes in climate and CO2 concentration, though important, are not considered in this study.
State‐Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity
Authors: Pfister Patrik L. , Stocker Thomas F.
Published: October 2017

Growing evidence from general circulation models (GCMs) indicates that the equilibrium climate sensitivity (ECS) depends on the magnitude of forcing, which is commonly referred to as state‐dependence. We present a comprehensive assessment of ECS state‐dependence in Earth system models of intermediate complexity (EMICs) by analyzing millennial simulations with sustained 2×CO2 and 4×CO2 forcings. We compare different extrapolation methods and show that ECS is smaller in the higher‐forcing scenario in 12 out of 15 EMICs, in contrast to the opposite behavior reported from GCMs. In one such EMIC, the Bern3D‐LPX model, this state‐dependence is mainly due to the weakening sea ice‐albedo feedback in the Southern Ocean, which depends on model configuration. Due to ocean‐mixing adjustments, state‐dependence is only detected hundreds of years after the abrupt forcing, highlighting the need for long model integrations. Adjustments to feedback parametrizations of EMICs may be necessary if GCM intercomparisons confirm an opposite state‐dependence.
Is the Dst Index Sufficient to Define All Geospace Storms?
Authors: Borovsky Joseph E. , Shprits Yuri Y.
Published: October 2017

The purpose of this commentary is (1) to raise awareness about some shortcomings of the use of the Dst index to identify storms, to gauge storm intensity, and to represent storm time space‐weather phenomena and (2) to initiate discussions about different types of storms and about improved identifiers for different types of storms.
Modeling Dynamic Helium Release as a Tracer of Rock Deformation
Authors: Gardner W. Payton , Bauer Stephen J. , Kuhlman Kristopher L. , Heath Jason E.
Published: October 2017

We use helium released during mechanical deformation of shales as a signal to explore the effects of deformation and failure on material transport properties. A dynamic dual‐permeability model with evolving pore and fracture networks is used to simulate gases released from shale during deformation and failure. Changes in material properties required to reproduce experimentally observed gas signals are explored. We model two different experiments of 4He flow rate measured from shale undergoing mechanical deformation, a core parallel to bedding and a core perpendicular to bedding. We find that the helium signal is sensitive to fracture development and evolution as well as changes in the matrix transport properties. We constrain the timing and effective fracture aperture, as well as the increase in matrix porosity and permeability. Increases in matrix permeability are required to explain gas flow prior to macroscopic failure, and the short‐term gas flow postfailure. Increased matrix porosity is required to match the long‐term, postfailure gas flow. Our model provides the first quantitative interpretation of helium release as a result of mechanical deformation. The sensitivity of this model to changes in the fracture network, as well as to matrix properties during deformation, indicates that helium release can be used as a quantitative tool to evaluate the state of stress and strain in earth materials.
Lakes as a Source of Short‐Period (0.5–2 s) Microseisms
Authors: Xu Yan , Koper Keith D. , Burlacu Relu
Published: October 2017

We identify and document microseisms produced by wave action in six lakes: The Great Slave Lake, Lake Ontario, Yellowstone Lake, Dianchi Lake, Fuxian Lake, and Erhai Lake. The lakes span more than 2 orders of magnitude in size (areas of 210–27,000 km2) and sample a range of climatic and tectonic regimes in Canada, the U.S., and China. Lake‐generated microseisms create spectral peaks at periods near 1 s and are often polarized as Rayleigh waves propagating away from the lake. In contrast to ocean‐generated microseisms, lake‐generated microseisms are only observed within about 25–30 km of the shoreline. This is consistent with the well‐known high attenuation of short‐period Rayleigh waves (Rg). It is unclear if lake‐generated microseisms are produced by a linear shoaling process, analogous to primary ocean microseisms, or a nonlinear wave‐wave interaction process, analogous to secondary ocean microseisms. If they are mainly produced by shoaling, lake‐generated microseisms might provide a spatially integrated measure of shoreline erosion. Regardless of the source mechanism, lake‐generated microseisms appear to provide a record of ice phenology for lakes that freeze in the winter. Such data could contribute to assessing the effects of climate change on high‐latitude lakes in remote areas. Finally, it is likely that lake‐generated microseisms are useful for imaging the geological structure of the shallow crust, information that is important for quantifying seismic hazard and can be difficult to obtain in urban areas where active source imaging is not feasible.
Observations of Tidal Straining Within Two Different Ocean Environments in the East China Sea: Stratification and Near‐Bottom Turbulence
Authors: Yang Wei , Wei Hao , Zhao Liang
Published: October 2017

Tidal straining describes the straining effect induced by the vertical shear of oscillatory tidal currents that act on horizontal density gradients. It tends to create tidal periodic stratification and modulate the turbulence in the bottom boundary layer (BBL). Here, we present observations of current, hydrology and turbulence obtained at two mooring stations that are characterized by two typical hydrological environments in the East China Sea (ECS). One is located adjacent to the Changjiang River's mouth, and the other is located over a sloping shelf which is far from the freshwater sources. Tidal straining induces a semidiurnal switching between stable and unstable stratification at both stations. Near‐bottom high‐frequency velocity measurements further reveal that the dissipation rate of turbulent kinetic energy (TKE) is highly elevated during periods when unstable stratification occurs. A comparison between the TKE dissipation rate (
) and the shear production (
) further reveals that the near‐bottom mixing is locally shear‐induced most of the time except during the unstable stratification period. Within this period, the magnitude of dissipation exceeds the expected value based on the law of the wall by an order of magnitude. The buoyancy flux that calculated by the balance method is too small to compensate for the existing discrepancy between the dissipation and shear production. Another plausible candidate is the advection of TKE, which may play an important role in the TKE budget during the unstable stratification period.
Calibrating a Viscoelastic Sea Ice Model for Wave Propagation in the Arctic Fall Marginal Ice Zone
Authors: Cheng Sukun , Rogers W. Erick , Thomson Jim , Smith Madison , Doble Martin J. , Wadhams Peter , Kohout Alison L. , Lund Björn , Persson Ola P.G. , Collins Clarence O. , Ackley Stephen F. , Montiel Fabien , Shen Hayley H.
Published: October 2017

This paper presents a wave‐in‐ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region. Wavenumbers are measured in one of these experiments. Forcing parameters are obtained from simultaneous in‐situ and remote sensing observations, as well as forecast/hindcast models. Cases from three wave experiments are used to calibrate a viscoelastic model for wave attenuation/dispersion in ice cover. The calibration is done by minimizing the difference between modeled and measured complex wavenumber, using a multi‐objective genetic algorithm. The calibrated results are validated using two methods. One is to directly apply the calibrated viscoelastic parameters to one of the wave experiments not used in the calibration and then compare the attenuation from the model with measured data. The other is to use the calibrated viscoelastic model in WAVEWATCH III® over the entire western Beaufort Sea and then compare the wave spectra at two remote sites not used in the calibration. Both validations show reasonable agreement between the model and the measured data. The completed viscoelastic model is believed to be applicable to the fall marginal ice zone dominated by pancake ice.
Uncertainty Quantification in Scale‐Dependent Models of Flow in Porous Media
Authors: Tartakovsky A. M. , Panzeri M. , Tartakovsky G. D. , Guadagnini A.
Published: October 2017

Equations governing flow and transport in randomly heterogeneous porous media are stochastic and scale dependent. In the moment equation (ME) method, exact deterministic equations for the leading moments of state variables are obtained at the same support scale as the governing equations. Computable approximations of the MEs can be derived via perturbation expansion in orders of the standard deviation of the random model parameters. As such, their convergence is guaranteed only for standard deviation smaller than one. Here, we consider steady‐state saturated flow in a porous medium with random second‐order stationary conductivity field. We show it is possible to identify a support scale
, where the typically employed approximate formulations of MEs yield accurate (statistical) moments of a target state variable. Therefore, at support scale
and larger, MEs present an attractive alternative to slowly convergent Monte Carlo (MC) methods whenever lead‐order statistical moments of a target state variable are needed. We also demonstrate that a surrogate model for statistical moments can be constructed from MC simulations at larger support scales and be used to accurately estimate moments at smaller scales, where MC simulations are expensive and the ME method is not applicable.
The NorWeST Summer Stream Temperature Model and Scenarios for the Western U.S.: A Crowd‐Sourced Database and New Geospatial Tools Foster a User Community and Predict Broad Climate Warming of Rivers and Streams
Authors: Isaak Daniel J. , Wenger Seth J. , Peterson Erin E. , Ver Hoef Jay M. , Nagel David E. , Luce Charles H. , Hostetler Steven W. , Dunham Jason B. , Roper Brett B. , Wollrab Sherry P. , Chandler Gwynne L. , Horan Dona L. , Parkes‐Payne Sharon
Published: October 2017

Thermal regimes are fundamental determinants of aquatic ecosystems, which makes description and prediction of temperatures critical during a period of rapid global change. The advent of inexpensive temperature sensors dramatically increased monitoring in recent decades, and although most monitoring is done by individuals for agency‐specific purposes, collectively these efforts constitute a massive distributed sensing array that generates an untapped wealth of data. Using the framework provided by the National Hydrography Dataset, we organized temperature records from dozens of agencies in the western U.S. to create the NorWeST database that hosts >220,000,000 temperature recordings from >22,700 stream and river sites. Spatial‐stream‐network models were fit to a subset of those data that described mean August water temperatures (AugTw) during 63,641 monitoring site‐years to develop accurate temperature models (r2 = 0.91; RMSPE = 1.10°C; MAPE = 0.72°C), assess covariate effects, and make predictions at 1 km intervals to create summer climate scenarios. AugTw averaged 14.2°C (SD = 4.0°C) during the baseline period of 1993–2011 in 343,000 km of western perennial streams but trend reconstructions also indicated warming had occurred at the rate of 0.17°C/decade (SD = 0.067°C/decade) during the 40 year period of 1976–2015. Future scenarios suggest continued warming, although variation will occur within and among river networks due to differences in local climate forcing and stream responsiveness. NorWeST scenarios and data are available online in user‐friendly digital formats and are widely used to coordinate monitoring efforts among agencies, for new research, and for conservation planning.
Exploring the Role of Social Media and Individual Behaviors in Flood Evacuation Processes: An Agent‐Based Modeling Approach
Authors: Du Erhu , Cai Ximing , Sun Zhiyong , Minsker Barbara
Published: October 2017

Flood warnings from various information sources are important for individuals to make evacuation decisions during a flood event. In this study, we develop a general opinion dynamics model to simulate how individuals update their flood hazard awareness when exposed to multiple information sources, including global broadcast, social media, and observations of neighbors' actions. The opinion dynamics model is coupled with a traffic model to simulate the evacuation processes of a residential community with a given transportation network. Through various scenarios, we investigate how social media affect the opinion dynamics and evacuation processes. We find that stronger social media can make evacuation processes more sensitive to the change of global broadcast and neighbor observations, and thus, impose larger uncertainty on evacuation rates (i.e., a large range of evacuation rates corresponding to sources of information). For instance, evacuation rates are lower when social media become more influential and individuals have less trust in global broadcast. Stubborn individuals can significantly affect the opinion dynamics and reduce evacuation rates. In addition, evacuation rates respond to the percentage of stubborn agents in a nonlinear manner, i.e., above a threshold, the impact of stubborn agents will be intensified by stronger social media. These results highlight the role of social media in flood evacuation processes and the need to monitor social media so that misinformation can be corrected in a timely manner. The joint impacts of social media, quality of flood warnings, and transportation capacity on evacuation rates are also discussed.
High Reversible Pseudocapacity in Mesoporous Yolk–Shell Anatase TiO2/TiO2(B) Microspheres Used as Anodes for Li‐Ion Batteries
Authors: Wei Hao , Rodriguez Erwin F. , Hollenkamp Anthony F. , Bhatt Anand I. , Chen Dehong , Caruso Rachel A.
Published: October 2017

As an anode material for lithium‐ion batteries, titanium dioxide (TiO2) shows good gravimetric performance (336 mAh g−1 for LiTiO2) and excellent cyclability. To address the poor rate behavior, slow lithium‐ion (Li+) diffusion, and high irreversible capacity decay, TiO2 nanomaterials with tuned phase compositions and morphologies are being investigated. Here, a promising material is prepared that comprises a mesoporous “yolk–shell” spherical morphology in which the core is anatase TiO2 and the shell is TiO2(B). The preparation employs a NaCl‐assisted solvothermal process and the electrochemical results indicate that the mesoporous yolk–shell microspheres have high specific reversible capacity at moderate current (330.0 mAh g−1 at C/5), excellent rate performance (181.8 mAh g−1 at 40C), and impressive cyclability (98% capacity retention after 500 cycles). The superior properties are attributed to the TiO2(B) nanosheet shell, which provides additional active area to stabilize the pseudocapacity. In addition, the open mesoporous morphology improves diffusion of electrolyte throughout the electrode, thereby contributing directly to greatly improved rate capacity.
Nanoparticle‐Based Therapeutics for Brain Injury
Authors: Bharadwaj Vimala N. , Nguyen Duong T. , Kodibagkar Vikram D. , Stabenfeldt Sarah E.
Published: October 2017

Brain injuries affect a large patient population with major physical and emotional suffering for patients and their relatives; at a significant cost to the society. Effective diagnostic and therapeutic options available for brain injuries are limited by the complex brain injury pathology involving blood–brain barrier (BBB). Brain injuries, including ischemic stroke and brain trauma, initiate BBB opening for a short period of time, which is followed by a second reopening for an extended time. The leaky BBB and/or the alterations in the receptor expression on BBB may provide opportunities for therapeutic delivery via nanoparticles (NPs). The approaches for therapeutic interventions via NP delivery are aimed at salvaging the pericontusional/penumbra area for possible neuroprotection and neurovascular unit preservation. The focus of this progress report is to provide a survey of NP strategies employed in cerebral ischemia and brain trauma and finally provide insights for improved NP‐based diagnostic/treatment approaches.
Modern Therapeutic Approaches for Noninfectious Ocular Diseases Involving Inflammation
Authors: Ratay Michelle L. , Bellotti Elena , Gottardi Riccardo , Little Steven R.
Published: October 2017

Dry eye disease, age‐related macular degeneration, and uveitis are ocular diseases that significantly affect the quality of life of millions of people each year. In these diseases, the action of chemokines, proinflammatory cytokines, and immune cells drives a local inflammatory response that results in ocular tissue damage. Multiple therapeutic strategies are developed to either address the symptoms or abate the underlying cause of these diseases. Herein, the challenges to deliver drugs to the relevant location in the eye for each of these diseases are reviewed along with current and innovative therapeutic approaches that attempt to restore homeostasis within the ocular microenvironment.
Flexible Aqueous Li‐Ion Battery with High Energy and Power Densities
Authors: Yang Chongyin , Ji Xiao , Fan Xiulin , Gao Tao , Suo Liumin , Wang Fei , Sun Wei , Chen Ji , Chen Long , Han Fudong , Miao Ling , Xu Kang , Gerasopoulos Konstantinos , Wang Chunsheng
Published: October 2017

A flexible and wearable aqueous symmetrical lithium‐ion battery is developed using a single LiVPO4F material as both cathode and anode in a “water‐in‐salt” gel polymer electrolyte. The symmetric lithium‐ion chemistry exhibits high energy and power density and long cycle life, due to the formation of a robust solid electrolyte interphase consisting of Li2CO3‐LiF, which enables fast Li‐ion transport. Energy densities of 141 Wh kg−1, power densities of 20 600 W kg−1, and output voltage of 2.4 V can be delivered during >4000 cycles, which is far superior to reported aqueous energy storage devices at the same power level. Moreover, the full cell shows unprecedented tolerance to mechanical stress such as bending and cutting, where it not only does not catastrophically fail, as most nonaqueous cells would, but also maintains cell performance and continues to operate in ambient environment, a unique feature apparently derived from the high stability of the “water‐in‐salt” gel polymer electrolyte.
Improving the Power Efficiency of Solution‐Processed Phosphorescent WOLEDs with a Self‐Host Blue Iridium Dendrimer
Authors: Wang Shumeng , Yang Qingqing , Zhang Baohua , Zhao Lei , Xia Debin , Ding Junqiao , Xie Zhiyuan , Wang Lixiang
Published: October 2017

Solution‐processed phosphorescent white organic light‐emitting diodes (WOLEDs) with improved power efficiency are reported by simply blending a yellow phosphor Ir(Flpy‐CF3)3 into a self‐host blue Ir dendrimer B‐G2. Attributable to the elimination of the host‐induced power efficiency losses existed in the traditional host‐based devices, a state‐of‐the‐art total power efficiency as high as 48.8–62.8 lm W−1 is achieved at a practical luminance of 1000 cd m−2. Moreover, without considerably sacrificing the power efficiency, the related correlated color temperature and Commission Internationale de L'Eclairage coordinates can be well tuned to satisfy different illumination requirements. The results clearly demonstrate that the adoption of a self‐host blue phosphorescent dendrimer instead of the traditional host‐based device structure is a superior and promising strategy to realize power‐efficient white‐light emitting devices.
Metal‐Free Radical‐Triggered Selenosulfonation of 1,7‐Enynes for the Rapid Synthesis of 3,4‐Dihydroquinolin‐2(1H)‐ones in Batch and Flow
Authors: Qiu Jiang‐Kai , Shan Cheng , Wang De‐Cai , Wei Ping , Jiang Bo , Tu Shu‐Jiang , Li Guigen , Guo Kai
Published: October 2017

A novel three‐component selenosulfonation of 1,7‐enynes with sulfinic acids and diphenyl diselenides for the formation of multifunctional 3,4‐dihydroquinolin‐2(1H)‐ones was developed in batch and flow. This room‐temperature protocol provides a highly efficient approach to diverse selenosulfones in moderate to excellent yields and with a broad scope of substrates. It should provide a potential synthesis method for the construction of diverse and meaningful 3,4‐dihydroquinolin‐2(1H)‐ones derivatives in the fields of pharmaceutical and biological chemistry. Additionally, an obvious acceleration (20 h to 43 s) was obtained under micro flow conditions.

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Atomic‐Scale Monitoring of Electrode Materials in Lithium‐Ion Batteries using In Situ Transmission Electron Microscopy
Authors: Shang Tongtong , Wen Yuren , Xiao Dongdong , Gu Lin , Hu Yong‐Sheng , Li Hong
Published: October 2017

Lithium‐ion batteries (LIBs) are energy storage devices that have received much attention because of their high energy density, high power capacity, and long lifetime. However, even though they are used widely in daily life, their cycling life and safety need further improvement. Understanding the reaction mechanisms and the structural degradation during the lithiation/delithiation process is a prerequisite to further improve the performance of LIBs. In situ transmission electron microscopy (TEM) allows one to monitor structural evolution at the atomic scale in real time, thus providing an unprecedented opportunity to characterize the lithiation reaction pathway in a nonequilibrium state during battery cycling. In this article, the recent advances with respect to elucidating the relationships of dynamic structural evolution, reaction kinetics, and performance of different nanostructured electrode materials at the atomic scale using in situ TEM, based on three representative reaction mechanisms, are described. Specifically, the three systems are intercalation reaction, conversion reaction, and alloying reaction. Based on the advances that have been made, it is expected that in situ TEM will play an indispensable role on future design of LIBs electrode materials.
Efficient Solar Cells Based on Light‐Harvesting Antimony Sulfoiodide
Authors: Nie Riming , Yun Hyun‐sung , Paik Min‐Jae , Mehta Aarti , Park Byung‐wook , Choi Yong Chan , Seok Sang Il
Published: October 2017

Although antimony sulfoiodide (SbSI) exhibits very interesting properties including high photoconductivity, ferroelectricity, and piezoelectricity, it is not applied to solar cells. Meanwhile, SbSI is predominantly prepared as a powder using a high‐temperature, high‐pressure system. Herein, the fabrication of solar cells utilizing SbSI as light harvesters is reported for the first time to the best of knowledge. SbSI is prepared by solution processing, followed by annealing under mild temperature conditions by a reaction between antimony trisulfide, which is deposited by chemical bath deposition on a mesoporous TiO2 electrode and antimony triiodide, under air at a low temperature (90 °C) without any external pressure. The solar cells fabricated using SbSI exhibit a power conversion efficiency of 3.05% under standard illumination conditions of 100 mW cm−2.
Near‐Infrared Light‐Driven Hydrogen Evolution from Water Using a Polypyridyl Triruthenium Photosensitizer
Authors: Tsuji Yutaro , Yamamoto Keiya , Yamauchi Kosei , Sakai Ken
Published: October 2017

In order to realize artificial photosynthetic devices for splitting water to H2 and O2 (2 H2O+hν→2 H2+O2), it is desirable to use a wider wavelength range of light that extends to a lower energy region of the solar spectrum. Here we report a triruthenium photosensitizer [Ru3(dmbpy)6(μ‐HAT)]6+ (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine, HAT=1,4,5,8,9,12‐hexaazatriphenylene), which absorbs near‐infrared light up to 800 nm based on its metal‐to‐ligand charge transfer (1MLCT) transition. Importantly, [Ru3(dmbpy)6(μ‐HAT)]6+ is found to be the first example of a photosensitizer which can drive H2 evolution under the illumination of near‐infrared light above 700 nm. The electrochemical and photochemical studies reveal that the reductive quenching within the ion‐pair adducts of [Ru3(dmbpy)6(μ‐HAT)]6+ and ascorbate anions affords a singly reduced form of [Ru3(dmbpy)6(μ‐HAT)]6+, which is used as a reducing equivalent in the subsequent water reduction process.
Silicon Wafers with Facet‐Dependent Electrical Conductivity Properties
Authors: Tan Chih‐Shan , Hsieh Pei‐Lun , Chen Lih‐Juann , Huang Michael H.
Published: October 2017

By breaking intrinsic Si (100) and (111) wafers to expose sharp {111} and {112} facets, electrical conductivity measurements on single and different silicon crystal faces were performed through contacts with two tungsten probes. While Si {100} and {110} faces are barely conductive at low applied voltages, as expected, the Si {112} surface is highly conductive and Si {111} surface also shows good conductivity. Asymmetrical I–V curves have been recorded for the {111}/{112}, {111}/{110}, and {112}/{110} facet combinations because of different degrees of conduction band bending at these crystal surfaces presenting different barrier heights to current flow. In particular, the {111}/{110} and {112}/{110} facet combinations give I–V curves resembling those of p–n junctions, suggesting a novel field effect transistor design is possible capitalizing on the pronounced facet‐dependent electrical conductivity properties of silicon.
Regio‐ und stereoselektive Synthese α,β‐disubstituierter Enamide durch Voraktivierung von Inamiden
Authors: Baldassari Lucas L. , de la Torre Aurélien , Li Jing , Lüdtke Diogo S. , Maulide Nuno
Published: October 2017

Eine neue Strategie der Voraktivierung von Inamiden ermöglicht die Verwendung ansonsten inkompatibler Reagenzien und erlaubt somit die Herstellung α,β‐disubstituierter Enamide mit hoher Regio‐ und Stereoselektivität. Mechanistische Analysen deuten auf die intermediäre Bildung einer Triflat‐gebundenen Spezies hin, die als Reservoir für hochreaktive Keteniminiumionen fungiert und so die nachfolgende Addition metallorganischer Reagenzien ermöglicht.
Enantioselective Copper‐Catalyzed Alkylation of Quinoline N‐Oxides with Vinylarenes
Authors: Yu Songjie , Sang Hui Leng , Ge Shaozhong
Published: October 2017

An asymmetric copper‐catalyzed alkylation of quinoline N‐oxides with chiral Cu–alkyl species, generated by migratory insertion of a vinylarene into a chiral Cu−H complex, is reported. A variety of quinoline N‐oxides and vinylarenes underwent this Cu‐catalyzed enantioselective alkylation reaction, affording the corresponding chiral alkylated N‐heteroarenes in high yield with high‐to‐excellent enantioselectivity. This enantioselective protocol represents the first general and practical approach to access a wide range of chiral alkylated quinolines.
Pd‐catalyzed Desulfitative reaction of Aryltrifluoroborates with sodium Arenesulfinates in water
Authors: Chang Sheng , Sun Yong Bing , Zhang Xiu Rong , Dong Lin Lin , Zhu He Yun , Lai Hong Wei , Wang Dan
Published: October 2017

An efficient procedure for the synthesis of biaryls was catalyzed by Pd(CH3CN)4(BF4)2 is reported. This Pd‐catalyzed cross‐coupling reaction of aryltrifluoroborates with sodium arenesulfinates was developed under mild and environmentally benign conditions, in water without any ligand or additive. The reaction gave a range of structurally diverse unsymmetrical bi‐aryl molecules with excellent yields, in which the byproduct was sulfur dioxide. It is worth noting that this protocol is also applicable to many heterocyclic aromatics such as thiophene, furan, pyridine, quinoline, isoquinoline and indole.
Synthesis and catalytic evaluation of Fe3O4/MWCNTs nanozyme as recyclable peroxidase mimetics: Biochemical and physicochemical characterization
Authors: Salarizadeh Navvabeh , Sadri Minoo , Sajedi Reza H.
Published: October 2017

In this research, the nanocomposite of multiwalled carbon nanotubes and magnetic metal oxide nanoparticles (Fe3O4/MWCNTs), as enzyme mimetic, was synthesized using an in situ chemical reduction method. The structure, composition and morphology of the prepared Fe3O4/MWCNT nanocomposite materials were characterized using X‐ray diffraction, FT‐IR and scanning electron microscopy with energy dispersive X‐ray spectroscopy, respectively. The magnetic properties of the nanocomposite were investigated by the vibrating sample magnetometer. A colorimetric system involving nanozyme, phenol/4‐aminoantipyrine and H2O2 was utilized for the determination of peroxidase mimetic catalytic assay. The obtained results confirmed that the synthesis of Fe3O4/MWCNTs nanostructures was successful. It was found that Fe3O4/MWCNTs nanohybrid exhibited peroxidase‐like activity without any pH limitation. Colorimetric data demonstrated that the prepared nanocatalyst had higher catalytic activity toward H2O2 than MWCNTs. The kinetic parameters of the nanozyme, Km and Vmax, were estimated to be 8.3 mm and 1.4 mm min−1, respectively. The Fe3O4/MWCNTs nanostructures were also successfully applied for glucose detection. In addition, peroxidase‐like activity of the nanozyme increased in the presence of butyl‐imidazolium bromide ionic liquid. These biomimetic catalysts have some advantages, such as simplicity, stability, reusability and cost effectiveness, which makes them great candidates to be used in various fields of biotechnology applications.
Supported ruthenium hydride catalysts for direct conversion of alcohols to carboxylic acids using styrene oxide as oxidant
Authors: Ghafouri Moloud , Moghadam Majid , Mehrani Kheirollah , Daneshvar Anahita
Published: October 2017

In the present work, the ability of two ruthenium hydride catalysts supported on multiwall carbon nanotubes, [Ru–H@EDT–MWCNT], and gold nanoparticles cored triazine dendrimer, [Ru–H@AuNPs–TD], in the direct conversion of alcohols to carboxylic acids via transfer hydrogenation using styrene oxide as oxidant is reported. Different alcohols were successfully converted to their corresponding carboxylic acids. The results showed that these two heterogeneous catalysts are more efficient than the homogeneous counterpart. In addition, the catalysts were reused several times.
Six‐coordinated vanadium(IV) complexes with tridentate task‐specific ionic liquid Schiff base ligands: Synthesis, characterization and effect of ionic nature on catalytic activity
Authors: Talouki Somayeh Azizi , Grivani Gholamhossein , Khalaji Aliakbar Dehno
Published: October 2017

By reaction of 5‐(chloromethyl)salicylaldehyde with triphenylphosphine and N‐methylimidazole in two separate reactions, salicylaldehydetriphenylphosphonium chloride (S2) and salicylaldehydemethylimidazolinium chloride (S3) were prepared. Reaction of 2‐(aminomethyl)pyridine with these aldehydes resulted in the task‐specific ionic liquid Schiff base ligands L1 and L2, respectively. Then six‐coordinated vanadium(IV) Schiff base complexes of VO(acac)L1–4 were synthesized by reactions of these tridentate Schiff base ligands and VO(acac)2 in 1:1 stoichiometry. The aldehydes, ligands and VO(acac)L1–4 complexes were characterized using infrared, 1H NMR, 13C NMR, 31P NMR, UV–visible and mass spectroscopies, as well as elemental analysis. Paramagnetic property of the complexes was also studied using magnetic susceptibility measurements. The complexes were used as catalysts in epoxidation of cyclooctene and oxidation of methylphenyl sulfide and the reaction parameters were optimized. The effect of the ionic nature of the complexes was investigated in these oxidation reactions. The catalytic activity of the complexes could be varied by changing the ionic (cationic or anionic) character of VO(acac)L1–4 catalysts in which counter anion variation showed a greater effect than cationic moiety variation.
Effect of surface modification with various thiol compounds on colloidal stability of gold nanoparticles
Authors: Mazloomi‐Rezvani Mahsa , Salami‐Kalajahi Mehdi , Roghani‐Mamaqani Hossein , Pirayesh Amin
Published: October 2017

Gold nanoparticles (AuNPs) are attractive materials due to their special optical and electronic properties. However, they tend to aggregate particularly in the presence of thiol‐containing compounds. In this study, to investigate the effect of surface conjugation with thiol‐containing compounds on colloidal stability, thiol compounds with various structures as modifying agents were used. To this end, AuNPs were synthesized and stabilized by trisodium citrate in aqueous solution, and then modified with thiol‐containing compounds, namely cysteamine hydrochloride (MEA, containing primary amine groups), 2‐mercaptoethanol (BME, containing hydroxyl groups), 1‐dodecanthiol (LCA, containing long‐chain alkyl groups) and thioglycolic acid (TGA, containing carboxylic acid groups). We studied the effect of thiol ligands on solution stability of colloidal AuNPs and on the formation of aggregates originating from the modification process using UV–visible spectroscopy, dynamic light scattering, field emission scanning electron microscopy and transmission electron microscopy. Results showed that surface modification with MEA, BME and LCA led to the formation of aggregates. However, conjugation with TGA showed a concentration‐dependent behaviour: surface modification with low concentration resulted in the formation of aggregates whereas that with high concentration of TGA did not disturb the colloidal stability of AuNPs. Finally, the effect of surface modification on temperature increase of solutions originating from infrared light irradiation was studied, where the temperature increase depends on the surface‐modifying compound.
HPA decorated Halloysite Nanoclay: An efficient catalyst for the green synthesis of Spirooxindole derivatives
Authors: Sadjadi Samahe , Heravi Majid M. , Malmir Masoumeh , Masoumi Baharak
Published: October 2017

A novel heterogeneous catalyst, HPA@HNTs‐IMI‐SO3H, was designed and synthesized based on functionalization of halloysite nanotubes with ionic liquid and subsequent incorporation of heteropolyacid. The structure of the catalyst was studied and confirmed by using SEM/EDX, FTIR, XRD, ICP‐AES, TGA, DTGA and BET. Moreover, the catalytic activity of HPA@HNTs‐IMI‐SO3H was investigated for promoting ultrasonic‐assisted three‐component reaction of isatines, malononitrile or cyanoacetic esters and 1,3‐dicarbonyl compounds to afford corresponding spirooxindole in high yields and short reaction time. The reusability of the catalyst was also studied. Notably, the catalyst could be recovered and reused for three reaction runs. However, reusing for fourth reaction runs led to the decrease of the catalytic activity. Considering leaching test results, that observation was attributed to the leaching of heteropolyacids, which can be induced by ultrasonic irradiation.
Fabrication of nanoporous polymeric crystalline TiO2 composite for photocatalytic degradation of aqueous organic pollutants under visible light irradiation
Authors: Gao Dasheng , Liu Ningning , Li Weiwei , Han Yide
Published: October 2017

A nanoporous polymeric crystalline TiO2 composite (TiO2/PDVB‐MA) has been successfully synthesized through an in situ synthesis method using divinylbenzene (DVB), methacrylic acid (MA) and tetrabutyl titanate. The experimental results showed that TiO2 nanoparticles composed of the mixture phases of anatase and rutile were homogeneously dispersed into the PDVB‐MA support. The TiO2/PDVB‐MA composite was used as photocatalyst for Rhodamine B (RhB), bisphenol A and 2,4,6‐trichlorophenol degradation under visible light irradiation. More interestingly, the excellent photocatalytic performance of the composite was observed with regard to RhB and bisphenol A, which might be ascribed to the synergistic effect between TiO2 nanoparticles and PDVB‐MA. Moreover, TiO2/PDVB‐MA composite could be recycled at least four times in the removal of RhB, suggesting that it is a promising photocatalyst to catalyze the degradation of organic pollutants under visible light irradiation.
Electrochemical transformations and evaluation of antioxidant activity of some Schiff bases containing ferrocenyl and (thio‐)phenol, catechol fragments
Authors: Smolyaninov I.V. , Poddel'sky A.I. , Baryshnikova S.V. , Kuzmin V.V. , Korchagina E.O. , Arsenyev M.V. , Smolyaninova S.A. , Berberova N.T.
Published: October 2017

Electrochemical transformations and antioxidant activity of some Schiff bases 1–5 containing ferrocenyl group and (thio‐)phenol, catechol fragments were investigated. Compounds under investigation are: 2‐(ferrocenylmethylene)amino)phenol (1), 2‐((ferrocenylmethylene)amino)‐4,6‐di‐tert‐butylphenol (2), 2‐((ferrocenylmethylene)amino)‐thiophenol (3), 3‐((ferrocenylmethylene)hydrazonomethyl)‐4,6‐di‐tert‐butylcatechol (4) and 2‐((3,5‐di‐tert‐butyl‐4‐hydroxybenzylidene)amino)thiophenol (5).

In a case of compounds 1–3 it has shown that the sequence of electrochemical transformations leads to the products of intramolecular cyclization – 2‐ferrocenylbenzoxazole (benzothiazole). o‐Quinone formation occurs during the electrochemical oxidation of catechol‐ferrocene 4 at the first anode stage. Electrochemical oxidation of the redox‐active fragments in Schiff bases 1–4 can be achieved indirectly at a lower potential corresponding to the oxidation of ferrocenyl moiety, consequently these substances can reveal more pronounced antioxidant properties. The antioxidant activities of the compounds were evaluated using 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) assay, the reaction of 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the oxidative damage of the DNA, the process of lipid peroxidation of rat (Wistar) brain homogenates in vitro. The compounds 1–4 in the antioxidant assays show effectiveness comparable with standard antioxidants (vitamin E, Trolox) and in some parameters superior to them. In the reaction of AAPH with the glutathione compounds 2–5 have a more pronounced protective activity than Trolox. Compounds 1–5 inhibit AAPH induced oxidation damage of the DNA. The more effective inhibitors of the lipid peroxidation process in vitro are molecules containing the bulky tert‐butyl groups: 2 and 4 and Schiff base 3.
A versatile supported silver for heterogeneously catalysed processes: Synthesis of 3‐Acyloxylindolines solvent‐free conditions
Authors: Sadeghzadeh Seyed Mohsen , Zhiani Rahele , Emrani Shokufe
Published: October 2017

We have found that fibrous nanosilica (KCC‐1) can used as a excellent support for the synthesis of highly sparse nanoparticles and has high surface area that was functionalized with Tetrathia‐azacyclopentadecane (TTACP) groups acting as the strong performers so that the Ag nanoparticles were well‐dispersed without aggregation on the fibers of the KCC‐1 microspheres (KCC‐1/TTACP/Ag). We enthusiasm to report one‐pot synthesis of 3‐Acyloxylindolines for first time from N‐tosyl‐2‐vinylaniline, and benzoic acid in the presence of KCC‐1/TTACP/Ag as a catalyst.
Preparations, properties, and formation mechanism of novel cellulose hydrogel membrane based on ionic liquid
Authors: Peng Huafeng , Wang Shaopeng , Xu Hongyao , Dai Guoliang
Published: October 2017

Cellulose hydrogel membranes were successfully produced by casting the cellulose/1‐butyl‐3‐methylimidazolium chloride (BmimCl) solution into assembling molds, and then coagulated in water. The morphological features and mechanical properties of the prepared hydrogel membranes were characterized by a series of techniques including X‐ray diffraction measurements, scanning electron microscopy measurements, UV–visible light absorption spectrum, and tensile testing. The formation mechanism and the effects of different pre‐gelation temperature, pre‐gelation time, and coagulation batch temperature on the morphology and property of prepared cellulose hydrogel membranes were explored. The result shows that the hydrogel membrane of cellulose with excellent performance can be prepared adopting novel ionic liquid (BmimCl) as solvent through suitable process; the prepared hydrogel membranes present good mechanical properties and excellent transparency. In addition, the model of the hydrogel formation is established. It is believed that this is a promising material in the application of biomedical engineering and medical material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45488.
Polymeric seal degradation in nuclear power plants: Determination of physical and mechanical properties
Authors: Porter Christopher P. , Bezzina James P. , Clegg Francis , Ogden Mark D.
Published: October 2017

To assess the suitability of different materials as polymeric seals in the Nuclear Industry three commercial samples of nitrile rubber at grades BA40, BA50, and BA60 have been tested. Differential scanning calorimetry was used to find the glass transition temperature (Tg) and a Lloyds Texture Analyser 500 (TA500) was used to find the ratio of energy returned during relaxation against energy applied during compression. The mechanical properties determined from these experiments were then compared against the materials infrared spectra to infer structural characteristics. These were in turn cross‐analyzed against the materials ability to swell in a liquid solvent and absorption behavior in a gaseous solvent. From this information, a statement could be made about each material's capacity to perform as a seal. It was thus found that the high energy retention and low absorption characteristics of BA40 made this material the best choice out of those studied for use as a polymeric seal in the nuclear industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45814.
Supercritical CO2 deposition and foaming process for fabrication of biopolyester–ZnO bone scaffolds
Authors: Ivanovic Jasna , Rezwan Kurosch , Kroll Stephen
Published: October 2017

Subsequent supercritical CO2‐assisted deposition and foaming process followed by in situ synthesis was used to fabricate functional polylactide (PLA) and polylactide–poly(ɛ‐caprolactone) (PLA–PCL) bone scaffolds. Deposition of zinc bis(2‐thenoyltrifluoroacetonate) as a ZnO precursor onto biopolyester substrates (30 MPa; 110 °C) was followed by fast depressurization to create cellular structure. Contact time was optimized regarding the deposition yield (2 h), while PCL content in PLA was varied (1–10 wt %). Scaffolds impregnated with the precursor were treated with hydrazine alcoholic solution to obtain biopolyester–ZnO composites. Precursor synthesis and deposition onto the scaffolds was confirmed by Fourier‐transform infrared. Processed scaffolds had micron‐sized pores (d50 ∼ 20 μm). High open porosity (69–77%) and compressive strength values (2.8–8.3 MPa) corresponded to those reported for trabecular bone. PLA blending with PCL positively affected precursor deposition, crystallization rate, and compressive strength of the scaffolds. It also improved PLA surface roughness and wettability which are relevant for cell adhesion. ZnO improved compressive strength of the PLA scaffolds without significant effect on thermal stability. Analysis of structural, thermal, and mechanical properties of biopolyester–ZnO scaffolds testified a great potential of the obtained platforms as bone scaffolds. Proposed processing route is straightforward and ecofriendly, fast, easy to control, and suitable for processing of thermosensitive polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45824.
Use of poly(3‐hydroxybutyrate)/niobium oxyhydroxide nanocomposites in photocatalysis: Effect of preparation methods
Authors: Heitmann Rodrigues Ana Pacheli , Rocha Italo Coura , Mottin Arthur Caron , Carlos Alves Oliveira Luiz , de Oliveira Patrício Patrícia Santiago
Published: October 2017

In this work, nanocomposites were obtained by the dispersion of niobium oxyhydroxide into a poly(3‐hydroxybutyrate) (PHB) matrix by different preparative methods. These methods led to changes in the polymer morphology and in their photocatalytic properties. Thermal and structural properties of the nanocomposites were investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR)–attenuated total reflection (ATR). Scanning electron microscopy images were analyzed in order to observe the different morphologies of nanocomposites as well as the distribution of niobium nanoparticles in the PHB matrix. The chemical interactions between the polymer and niobium nanoparticles were observed in the FTIR–ATR and thermal analyses. The results of TGA and DSC indicated an improvement in the thermal stability of the polymer and the action of inorganic nanoparticles as nucleating agents in the process of heterogeneous nucleation of PHB. The composites exhibited good catalytic activity for the removal of methylene blue dye from an aqueous medium (∼90%) during a photocatalytic process. The different morphologies of PHB/niobium oxyhydroxide composites directly influenced the catalytic activity of the material due to the difference in the dispersion of nanoparticles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45836.